DEVICE AND METHOD FOR DRAWING METAL TUBE

Abstract

A device for drawing a metal tube capable of sufficiently applying a lubricating oil to an inner surface of a tube at the time of drawing and preventing occurrence of seizures is provided. The device for drawing a metal tube in which drawing is performed by making a metal blank tube 2 pass through between a die 10 for forming an outer surface and a plug 11 for forming an inner surface includes a control unit 31 configured to: measure an elapsed time from a time at which supplying of a lubricating oil L to a surface of the plug 11 is stopped until the metal blank tube 2 is set at a drawing position between the die 10 and the plug 11 and becomes ready to be drawn; control to not perform drawing of the metal blank tube 2 when the measured elapsed time exceeds a preset elapsed time; and control to initiate drawing of the metal blank tube 2 when the measured elapsed time is within a preset allowed time.

Description

TECHNICAL FIELD

The present invention relates to a device and a method for drawing a metal tube, capable of producing a drawn tube excellent in dimensional accuracy suitably used as a substrate for an OPC photosensitive drum for use in, for example, an electrophotographic device such as a copying machine, a laser beam printer, a facsimile device, etc.

In the description of this specification, the language of “rear” in the drawing method and the drawing device is used to include the meaning of the direction toward the blank tube side with respect to the drawn tube, and the language of “front” means the direction toward the toward tube side with respect to the blank tube.

TECHNICAL BACKGROUND

In recent years, as an OPC photosensitive drum substrate for use in, for example, an electrophotographic device such as a copying machine, a laser beam printer, a facsimile device, etc., uncut tubes suitable for mass production has been used widely. As one of uncut tubes, there is an ED tube obtained by drawing an aluminum extruded blank tube. Such an ED tube is suitable for mass production in that a plurality of tube products can be produced in a single drawing process, and the method has attracted attention as a method which can meet the need of mass consumption caused by market expansion.

Such an ED tube is manufactured by initially obtaining an aluminum extruded blank tube by extruding an aluminum billet, cutting the extruded blank tube into a predetermined length, then drawing the cut tube in one or two or more passes by a die and a plug to obtain an aluminum tube having a predetermined shape (outer diameter, inner diameter, and wall thickness), thereafter cutting the aluminum tube, chamfering the cut edge portions thereof, cleaning, and inspecting the dimension and appearance.

In a drawing process of such an aluminum tube for a photosensitive drum substrate, for supplying a lubricating oil onto an outer surface of a blank tube, it is easy to apply a lubricating oil in advance or make a lubricating oil flow down during the drawing process as necessary. However, when supplying a lubricating oil to an inner surface of a blank tube, especially in the case of an ED tube in which a blank tube is continuously drawn at a high speed for two or passes, it is difficult to provide a lubricating oil onto an inner surface of a blank tube in advance. Therefore, there is no other choice other than applying a lubricating oil to a plug, inserting the plug into a blank tube, and then performing a drawing process as it is. Therefore, contrary to an outer surface of a blank tube to which a lubricating oil can be supplied as necessary, on an inner surface of a blank tube, a lubricating oil tends to become insufficient during the drawing, causing occurrence of seizures, which results in deterioration of the drawn tube swing accuracy.

To solve these problems, the applicant proposed drawing devices in which an opening portion is formed in a peripheral wall of a hollow rod supporting a plug to eject a lubricating oil supplied from a rear end portion of the rod to an inside of the rod through the opening portion so that the lubricating oil can be supplied as necessary to an inner surface of the blank tube. In these drawing devices, a core for evenly spreading the lubricating oil adhered to the inner surface of the blank tube is attached to the rod (Patent Documents 1 and 2).

PRIOR ART DOCUMENTS

Patent Document

Patent Document 1: Japanese Unexamined Laid-opened Patent Application Publication No. 2009-22982

Patent Document 2: Japanese Unexamined Laid-opened Patent Application Publication No. 2009-45663

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In the technologies as described in the aforementioned Patent Documents 1 and 2, however, a large amount of lubricating oil adheres to portions (e.g., a core) other than the plug when supplying the lubricating oil to the inner surface of the blank tube, thereby increasing the amount of lubricating oil which remains inside the tube. This caused an increased amount of consumption of lubricating oil.

Also, as explained above, in a drawing method in which a plug to which a lubricating oil was applied is inserted into a blank tube, seizures sometimes occur due to insufficient lubricating oil on the inner surface of the blank tube. Occurrence of such seizures not only causes scrapes but also provides cause of deterioration of dimensional accuracy by processing heat. Shortage of lubricating oil more likely occurs when the length of the blank tube is longer and the drawing rate is faster. Therefore, in order to increase the productivity of an ED tube by drawing a long blank tube at a high drawing rate, the problem of the inner surface seizures must be overcome. In addition, shortage of lubricating oil on an inner surface of a blank tube when applying a lubricating oil on a plug is especially notable when drawing in a horizontal direction (that is, when drawing in a horizontal direction, the lubricating oil especially on the upper side of the inner surface of the blank tube tends to become insufficient).

The present invention was made in view of the aforementioned technical background, and aims to provide a drawing device and a drawing method for a metal tube capable of sufficiently applying a lubricating oil to an inner surface of the tube at the time of drawing to prevent occurrence of seizures.

Means for Solving the Problems

To achieve the aforementioned objects, the present invention provides the following means.

[1] A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

measure an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured elapsed time exceeds a preset allowed time; and

control to initiate drawing when the measured elapsed time is within a preset allowed time.

[2] A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

initiate a measurement of an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of the device when a measuring elapsed time exceeds a preset allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to initiate drawing when the measuring elapsed time is within the preset allowed time at a time at which the metal blank tube is set at the pulling position between the die and the plug and becomes ready to be drawn.

[3] A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of the device when the measured first elapsed time exceeds a preset first allowed time; and

control to continue an operation of the device when the measured first elapsed time is within the preset first allowed time,

wherein the control unit is configured to:

• • also measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second allowed time; and

control to initiate drawing when the measured second elapsed time is within the preset second allowed time.

[4] A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of the device when the measured first elapsed time exceeds a preset first allowed time; and

control to continue an operation of the device when the measured first elapsed time is within the preset first allowed time,

wherein the control unit is configured to:

measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to initiate drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a pulling position between the die and the plug and becomes ready to be drawn.

[5] A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

initiate a measurement of a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of the device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from an initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted; and

control to continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube,

wherein the control unit is configured to:

also measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second elapsed time; and

control to initiate drawing when the measured second elapsed time is within the second allowed time.

[6] A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

initiate a measurement of a first elapsed time from a period of time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of the device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted; and

control to continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube,

wherein the control unit is configured to:

initiate a measurement of a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to initiate drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a pulling position between the die and the plug and becomes ready to be drawn.

[7] A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping the supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

measure an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn is measured;

control to not perform drawing of the metal blank tube when the measured elapsed time exceeds a preset allowed time; and

control to perform drawing of the metal blank tube when the measured elapsed time is within a preset allowed time.

[8] A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping the supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is controlled to:

initiate a measurement of an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of a device when a measuring elapsed time exceeds a preset allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to perform drawing when the measuring elapsed time is within the preset allowed time at a time at which the metal blank tube is set at a pulling position between the die and the plug and becomes ready to be drawn.

[9] A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of a device when the measured first elapsed time exceeds a preset first allowed time; and

control to continue the operation of the device when the measured first elapsed time is within the preset first allowed time,

measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second allowed time; and

control to perform drawing when the measured second elapsed time is within a preset second allowed time.

[10] A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of a device when the measured first elapsed time exceeds a preset first allowed time;

control to continue an operation of the device when the measured first elapsed time is within the preset first allowed time;

initiate a measurement of a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

perform drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn.

[11] A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

initiate a measurement of a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of a device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted;

continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube;

measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second allowed time; and

perform drawing when the measured second elapsed time is within the second allowed time.

[12] A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug,

wherein it is configured to:

initiate a measurement of a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of a device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted;

continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube;

initiate a measurement of a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

perform drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn.

[13] The method for drawing a metal tube as recited in any one of the aforementioned Items 7 to 12, wherein the application step, the insertion step, and the setting step are performed in this order.

[14] A method for producing a metal tube by performing drawing by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug,

wherein it is configured to:

measure an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured elapsed time exceeds a preset allowed time; and

perform drawing of the metal blank tube when the measured elapsed time is within a preset allowed time.

[15] The method for producing a metal tube as recited in the aforementioned Item 14, wherein the application step, the insertion step, and the setting step are performed in this order.

Effects of the Invention

In the following explanation of the effects of the invention, the effects in the case of performing a drawing process by drawing a metal blank tube in a horizontal direction are explained for an easy understanding of the effects of the invention (that is, the effects are explained by focusing on whether or not an amount of a lubricating oil is enough on an upper side of an inner surface of a blank tube). However, the present invention is not especially limited to the case in which a drawing process is performed by drawing in a horizontal direction.

In the invention [1], a control unit is provided. The control unit is configured to: measure an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn; control to not perform drawing of the metal blank tube when the measured elapsed time exceeds a preset elapsed time; and control to initiate the drawing when the measured elapsed time is within a preset allowed time.

Therefore, for a blank tube in a state in which the amount of the lubricating oil on the upper side of the inner surface of the blank tube has decreased since it took time (it exceeded the allowed time) until it becomes ready to be drawn, it can be controlled to not perform drawing. Further, for a blank tube in which the elapsed time until it becomes ready to be drawn is within the allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface of the blank tube, it can be controlled to perform drawing. Therefore, it is possible to produce a drawn tube having no seizures (a drawn tube having seizures will not be produced).

In the invention [2], a control unit is provided. The control unit is configured to: initiate a measurement of an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped; control to stop an operation of the drawing device when a measuring elapsed time exceeds a preset allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn or at a time at which it becomes ready to be drawn; and control to initiate drawing when the measuring elapsed time is within the preset allowed time at a time at which the metal blank tube is set at a pulling position between the die and the plug and becomes ready to be drawn.

Therefore, the operation of the device is stopped when the elapsed time exceeds the allowed time during a period of time until it becomes ready to be drawn, or at a time at which it becomes ready to be drawn. Further, drawing is performed for a blank tube in which the elapsed time until it becomes ready to be drawn is within the allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface of the blank tube.

Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [3], a control unit is provided. The control unit is configured to: measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube; control to stop an operation of the drawing device when the measured first elapsed time exceeds a preset first allowed time; and control to continue an operation of the drawing device when the measured first elapsed time is within the preset first allowed time.

Therefore, the operation of the device can be stopped when an amount of the lubricating oil carried into the metal blank tube from the plug is not sufficiently secured, and the operation of the device can be continued as it is when an amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured.

Further, the control unit is configured to: also measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or at a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn; control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second allowed time; and control to initiate drawing when the measured second elapsed time is within a preset second allowed time.

Therefore, for a blank tube in a state in which the mount of the lubricating oil on the upper side of the inner surface of the blank tube has decreased since it took time (it exceeded the second allowed time) until it becomes ready to be drawn, it can be controlled to not perform drawing. Further, for a blank tube in which the second elapsed time until it becomes ready to be drawn is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface of the blank tube, it can be controlled to perform drawing.

Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be produced).

In the invention [4], the operation of the device can be stopped when an amount of the lubricating oil carried into the metal blank tube from the plug is not sufficiently secured, and the operation of the device can be continued as it is when an amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured.

Further, when it exceeds the second allowed time during a period of time until it becomes ready to be drawn, or at a time at which it becomes ready to be drawn, the amount of the lubricating oil on the upper side of the inner side of the blank tube is insufficient. Therefore, the operation of the device is stopped to not perform drawing of the blank tube. For a blank tube in which the second elapsed time until it becomes ready to be drawn is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface thereof, drawing is performed. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [5], the operation of the device can be stopped when it exceeds the first allowed time during a period of time until the plug is inserted into the blank tube or at a time at which the plug is inserted into the blank tube and therefore an amount of the lubricating oil carried into the metal blank tube from the plug cannot not be sufficiently secured. When an amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured, the operation of the device can be continued as it is.

Further, for a blank tube in a state in which it took time (it exceeded the second allowed time) until it becomes ready to be drawn and an amount of the lubricating oil on the upper side of the inner surface thereof has decreased, it is possible to not perform drawing. For a blank tube in which the second elapsed time until it becomes ready to be drawn is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface thereof, it is possible to perform drawing. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [6], when it exceeds the first allowed time during a period of time until the plug is inserted into the blank tube or at a time at which the plug is inserted into the blank tube and an amount of the lubricating oil carried into the metal blank tube from the plug cannot be sufficiently secured, the operation of the device can be stopped. When an amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured, the operation of the device can be continued as it is.

Further, when it exceeds the second allowed time during a period of time until it becomes ready to be drawn or at a time at which it becomes ready to be drawn, the amount of the lubricating oil on the upper side of the inner side of the blank tube is insufficient. Therefore, the operation of the device is stopped to not perform drawing. For a blank tube in which the second elapsed time until it becomes ready to be drawn is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface thereof, drawing is performed. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [7], an elapsed time is measured from a time at which supplying of the lubricating oil to the surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, it is controlled to not perform drawing of the metal blank tube when the measured elapsed time exceeds the preset allowed time, and drawing is performed when the measured elapsed time is within the preset allowed time. Therefore, for a blank tube in a state in which it took time (it exceeded the allowed time) until it becomes ready to be drawn and the amount of the lubricating oil on the upper side of the inner surface of the blank tube has decreased, it is possible to not perform drawing. For a blank tube in which the elapsed time until it becomes ready to be drawn is within the allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface of the blank tube, drawing is performed. Therefore, it is possible to produce a drawn tube having no seizures (a drawn tube having seizures will not be produced).

In the invention [8], a measurement of an elapsed time is initiated from a time at which supplying of the lubricating oil to the surface of the plug is stopped, it is controlled to stop the operation of the device when the measuring elapsed time exceeds the preset allowed time during a period of time from the initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn. Drawing is performed when the measuring elapsed time is within the preset allowed time at a time at which the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn. Therefore, the operation of the device is stopped when the allowed time has exceeded during a period of time until it becomes ready to be drawn, or at a time at which it becomes ready to be drawn. For a blank tube in which the elapsed time until it becomes ready to be drawn is within the allowed time and there exists a sufficient amount of lubricating oil on the upper surface of the inner surface of the blank, drawing is performed. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [9], a first elapsed time is measured from a time at which supplying of the lubricating oil to the surface of the plug is stopped until the plug is inserted into the metal blank tube, and it is controlled to stop the operation of the device when the measured first elapsed time exceeds the preset first allowed time, and the operation of the device is continued when the measured first elapsed time is within the first allowed time. Therefore, the operation of the device can be stopped when the amount of the lubricating oil carried into the metal blank tube from the plug is not sufficiently secured, and the operation of the device can be continued as it is when the amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured.

Further, for a blank tube in a state in which it took time (it exceeded the second allowed time) until it becomes ready to be drawn and the amount of the lubricating oil on the upper side of the inner surface thereof has decreased, it is possible to not perform drawing. For a blank tube in which the second elapsed time until it becomes ready to be drawn is within the second allowed time and there exist a sufficient amount of the lubricating oil on the upper side of the inner surface thereof, drawing is performed. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [10], the operation of the device can be stopped when the amount of the lubricating oil carried into the metal blank tube from the plug is not sufficiently secured. And the operation of the device can be continued as it is when the amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured.

Further, when the measuring second elapsed time exceeds the second allowed time during a period of time until it becomes ready to be drawn, or at a time at which it becomes ready to be drawn, the amount of the lubricating oil on the upper side of the inner side of the blank tube becomes insufficient. Therefore, the operation of the device is stopped to not perform drawing of the blank tube. For a blank tube in which the measuring second elapsed time is within the second allowed time and there exists a sufficient amount of the lubricating oil on the upper side of the inner surface thereof at a time at which the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, drawing is performed. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [11], the operation of the device can be stopped when it exceeds the first allowed time during a period of time until the plug is inserted into the blank tube or at a time at which the plug is inserted into the blank tube, and the amount of the lubricating oil carried into the metal blank tube from the plug cannot be sufficiently secured. And the operation of the device can be continued as it is when the amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured.

Further, for a blank tube in a state in which it took time (it exceeded the second allowed time) until it becomes ready to be drawn and the amount of the lubricating oil on the upper side of the inner surface thereof has decreased, it is possible to not perform drawing. For a blank tube in which the second elapsed time until it becomes ready to be drawn is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface thereof, drawing is performed. Therefore a drawn tube having no seizures can be produced (a drawn tubes having seizures will not be formed).

In the invention [12], when it exceeds the first allowed time during a period of time until the plug is inserted into the blank tube or at a time at which the plug is inserted into the blank tube, the operation of the device can be stopped. When the amount of the lubricating oil carried into the metal blank tube from the plug is sufficiently secured, the operation of the device can be continued as it is.

Further, when the measuring second elapsed time exceeds the second allowed time during a period of time until it becomes ready to be drawn or at a time at which the tube becomes ready to be drawn, since the amount of the lubricating oil on the upper side of the inner side of the blank tube is insufficient, drawing is not performed. For a blank tube in which the measuring second elapsed time is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface thereof at a time at which the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, drawing is performed. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [13], since the application step, the insertion step, and the setting step are performed in this order, seizures of the tube at the time of drawing can be sufficiently prevented from being occurred, which enables a production of a high quality drawn tube having no seizures.

In the invention [14], a metal tube is produced by measuring an elapsed time from a time at which supplying of the lubricating oil to the surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, controlling to not perform drawing the metal blank tube when the measured elapsed time exceeds the preset allowed time, and performing drawing when the measured elapsed time is within the preset allowed time. Therefore, for a blank tube in a state in which it took time (it exceeded the allowed time) and becomes ready to be drawn and the mount of the lubricating oil on the upper side of the inner surface of the blank tube has decreased, it is possible to not perform drawing. For a blank tube in which the elapsed time until it becomes ready to be drawn is within the allowed time and there exists a sufficient amount of the lubricating oil on the upper side of the inner surface of the blank tube, drawing is performed. Therefore, a drawn tube having no seizures can be produced (a drawn tube having seizures will not be formed).

In the invention [15], since the application step, the insertion step, and the setting step are performed in this order, seizures of the tubes at the time of drawing can be sufficiently prevented from being occurred, which enables a production of a high quality drawn tube having no seizures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front vertical cross-sectional view showing a portion of an embodiment of a drawing device according to the present invention.

FIG. 2 (a) is a cross-sectional view showing a state in which a lubricating oil is being applied to a surface of a plug, FIG. 2 (b) a cross-sectional view showing a state in which supplying of the lubricating oil to the surface of the plug is stopped, and FIG. 2 (c) a cross-sectional view showing a state in which an insertion of the plug into the metal blank tube is initiated.

FIG. 3 (a) is a cross-sectional view showing a state in which the insertion and the arrangement of the plug into the metal blank tube is finished, and FIG. 3 (b) is a cross-sectional view showing a state in which the metal blank tube is set at a drawing position between the die and the plug, the front end of the blank tube is chucked, and the tube has become available to be drawn.

FIG. 4 is a flow chart showing an example of a drawing method.

FIG. 5 is a flow chart showing another example of a drawing method.

FIG. 6 is a flow chart showing still another example of a drawing method.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic view shown by a vertical cross-section and showing a portion of an example of a drawing device 1 for carrying out a drawing method for a metal tube according to the present invention (schematic view showing a state in which the tube is being drawn). The drawing method and the drawing device 1 according to this embodiment perform a drawing process by drawing a metal blank tube 2 in a horizontal direction, but not especially limited to such an embodiment, and can perform a drawing process by drawing in a vertical direction, for example.

The drawing device 1 includes a die 10 for forming an outer surface of a metal blank tube 2, a plug 11 for forming an inner surface of the metal blank tube 2, a nozzle portion 18 for applying a lubricating oil L, a chucking unit 21 for holding a front end portion of the metal blank tube 2, a pulling unit 24 for pulling the chucking unit 21, and a control unit 31 (see FIG. 1).

The die 10 is equipped with a die main body 13 fitted in a die case 12, and the die main body 13 includes an approach portion 14 formed on an inner circumferential surface of a central die hole and a bearing portion 15 continued from a front side of the approach portion 14.

The plug 11 is attached to and supported by the front end of a rod 20 made of a hollow tube. The plug 11 has, on its outer peripheral surface, an approach portion 16 and a bearing portion 17 continued from the approach portion 16 toward the front side thereof.

The chucking unit 21 includes a pair of chuck fingers 22 and 22 for chucking the front end portion (pointing portion) of the metal blank tube 2 in cooperation with each other, and a chuck finger holder 23 for holding the chuck fingers 22 and 22. During a drawing process, the chucking unit 21 is pulled in the right direction of the figure by the pulling unit 24, and in this way, the drawing of the metal blank tube 2 is performed. That is, by drawing the metal blank tube 2 in a horizontal direction with the tube 2 inserted between the die 10 and the plug 11, the outer surface of the tube is formed by the bearing portion 15 of the die main body 13, and the inner surface of the tube is formed by the bearing portion 17 of the plug 11. Thus, a drawn tube 3 is produced.

The nozzle portion 18 is arranged at a rear upper portion of the die 10 (see FIG. 1). A lubricating oil L is ejected from the nozzle portion 18. The nozzle portion 18 is used for supplying (applying) the lubricating oil L to the surface of the plug 11 and supplying (applying) the lubricating oil L to the outer surface of the metal blank tube 2.

The control unit 31 is configured to: measure an elapsed time T from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped until the metal blank tube 2 is set at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the tube becomes ready to be drawn; control to not perform drawing of the metal blank tube 2 when the measured elapsed time T exceeds a preset allowed time; and control to initiate drawing when the measured elapsed time T is within the preset allowed time (see FIG. 4).

The preset allowed time T is not especially limited, but can be 120 seconds, for example.

The control unit 31 is configured to control to not move the pulling unit 24 when drawing is not performed (stop control) and control to move the pulling unit 24 when drawing is initiated.

Next, the drawing method of a metal tube using the drawing device 1 will be explained with reference to the flow chart of FIG. 4. In the flow charts of FIGS. 4 to 6, “step” is abbreviated as “S” for simplification.

First, as shown in FIG. 2 (a), the plug 11 is arranged at a lower position of the nozzle portion 18, and the supplying (application) of the lubricating oil L to the surface of the plug 11 from the nozzle portion 18 is initiated (S01).

After applying the lubricating oil L to the surface of the plug 11 for a predetermined time (predetermined amount), the supplying (application) of the lubricating oil L to the surface of the plug 11 is stopped (S02), as shown in FIG. 2(b). Simultaneously with the stopping, a measurement of the elapsed time T is initiated. That is, the measurement of the elapsed time T is initiated from the time at which the supplying of the lubricating oil L to the surface of the plug 11 is stopped. The lubricating oil L adhered to the upper portion of the outer surface of the plug 11 is supplied to the entire circumference of the outer surface of the plug 11 along the outer surface, and the excessive lubricating oil L flows down as time passes.

After that, as shown in FIG. 2(c), the insertion of the plug to which the lubricating oil L was applied into the metal blank tube 2 is initiated, and as shown in FIG. 3(a), the plug 11 to which the lubricating oil L was applied is inserted and arranged inside (at a predetermined position) the metal blank tube 2 (S03).

Next, as shown in FIG. 3(b), these plug 11 and metal blank tube 2 are inserted into the die 10 and set at a drawing position (arranged). That is, the metal blank tube 2 is set at a drawing position between the die 10 and the plug 11 (S04). Simultaneously with setting (arranging) the tube at the drawing position, supplying of the lubricating oil L to the outer surface of the metal blank tube 2 from the nozzle portion 18 is initiated (see FIG. 3(b)).

Next, as shown in FIG. 3(b), the front end portion (pointing portion) of the metal blank tube 2 is chucked (sandwiched and fastened) by a pair of chuck fingers 22 and 22 (S05). The measurement of the elapsed time T is terminated when the blank tube 2 becomes in a drawable state by completion of sandwiching and fastening the blank tube 2 by the chucking unit 21.

The control unit 31 determines whether or not the elapsed time T (the elapsed time T from a time at which supplying of the lubricating oil to the surface of the plug is stopped until the tube becomes ready to be drawn) is within a preset allowed time (S06).

When the measured elapsed time T exceeds the preset allowed time (when the judgment result is NO), the drawing of the metal blank tube 2 is not initiated (drawing is not performed) and an alarm is sounded (S10). Next, the plug 11 is moved backwards (moved back in a direction separating from the die 10) (S11). Thereafter, the metal blank tube 2 set at the drawing position is pulled out (removed) (S12) to prepare for a drawing process for the next new metal blank tube 2.

On the other hand, when the measured elapsed time T is within the preset allowed time (when the judgment result is YES), drawing is initiated (S07). That is, as shown in FIG. 1, the metal blank tube 2 is subjected to a drawing process by making the tube pass through between the die 10 and the plug 11 to obtain a drawn tube 3 by pulling the front end portion of the blank tube 2 by the chucking unit 21 while applying the lubricating oil L on the outer surface of the metal blank tube 2 from the nozzle portion 18 (S08). Then, the plug 11 is moved backwards (moved back in a direction separating from the die 10) (S09) to prepare for a drawing process for the next new metal blank tube 2.

In the aforementioned drawing method, for a blank tube 2 in a state in which the amount of the lubricating oil on the upper side of the inner surface of the blank tube 2 has decrease since it took time (it exceeded the allowed time) until it become ready to be drawn, it is possible to not perform drawing (drawing operation can be cancelled). Also, for a blank in which the elapsed time T until it becomes ready to be drawn is within the allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface of the blank tube 2, drawing is performed. Therefore, a drawn tube 3 having no seizures can be produced (a drawn tube having seizures is not formed).

Further, in the aforementioned first embodiment, the control unit 31 (control method) can be configured as follows. That is, in the first embodiment, the control unit 31 can be configured to have a structure (control method) as follows:

the measurement of the elapsed time is initiated from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped;

it is controlled to stop the operation of the device 1 when the measuring elapsed time T exceeds a preset allowed time during a period of time from the initiation of the measurement until the metal blank tube 2 is set (arranged) at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the tube becomes ready to be drawn, or at the time at which the tube becomes ready to be drawn; and

it is controlled to initiate drawing when the measuring elapsed time T is within the preset allowed time at a time at which the metal blank tube 2 is set (arranged) at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the tube becomes ready to be drawn.

Another embodiment (second embodiment) of a drawing device 1 according to the present invention will be explained. The structure of the drawing device 1 of this second embodiment is as shown in FIG. 1. Although the structure of the control unit 31 (control method) is different from the aforementioned first embodiment, the other structures are the same as those of the first embodiment.

That is, in this second embodiment, the control unit 31 is configured to: measure a first elapsed time T1 from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped until the plug 11 is inserted into the metal blank tube 2; control to stop the operation of the drawing device 1 when the measured first elapsed time T1 exceeds the preset first allowed time; and control to continue the operation of the drawing device 1 when the measured first elapsed time T1 is within the first allowed time (see FIG. 5).

Further, the control unit 31 is configured to: measure a second elapsed time T2 from at time at which the plug is inserted into the metal blank tube 2 until the metal blank tube 2 is set at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the tube becomes ready to be drawn; control to not perform drawing of the metal blank tube 2 when the measured second elapsed time T2 exceeds a preset second allowed time; and control to initiate drawing when the measured second elapsed time T2 is within the preset second allowed time (see FIG. 5).

In this second embodiment, the preset first allowed time T1 is not especially limited, but can be 30 seconds, for example. Also, the preset second allowed time T2 is not especially limited, but can be 90 seconds, for example.

Next, a drawing method of a metal tube using the drawing device 1 according to the second embodiment will be explained with reference to the flow chart of FIG. 5.

First, as shown in FIG. 2(a), the plug 11 is arranged at a lower position of the nozzle portion 18, and supplying (application) of the lubricating oil L to the surface of the plug 11 from the nozzle portion 18 is initiated (S21).

After applying the lubricating oil L to the surface of the plug 11 for a predetermined time (predetermined amount), as shown in FIG. 2(b), the supplying (application) of the lubricating oil L to the surface of the plug 11 is stopped (S22). Simultaneously with the stopping, a measurement of the first elapsed time T1 is initiated. That is, the measurement of the first elapsed time T1 is initiated from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped. The lubricating oil L adhered to the upper portion of the outer surface of the plug 11 is supplied to the entire periphery of the outer surface of the plug 11 along the outer surface, and the excessive lubricating oil L flows down as time passes.

Thereafter, as shown in FIG. 2(c), the insertion of the plug to which the lubricating oil L was applied into the metal blank tube 2 is initiated, and as shown in FIG. 3(a), the plug 11 to which the lubricating oil L was applied is inserted and arranged inside (at a predetermined position) the metal blank tube 2 (S23). At this time, as shown in FIG. 2(c), the measurement of the first elapsed time T1 is terminated at a time at which the plug 11 is inserted into the metal blank tube 2, and at the same time, the measurement of the second elapsed time T2 is initiated (see FIG. 5).

The control unit 31 determines whether or not the measured first elapsed time T1 (the first elapsed time T from a time at which supplying of the lubricating oil to the surface of the plug is stopped until the plug is inserted into the metal blank tube 2) is within a preset first allowed time (S24).

When the measured first elapsed time T1 exceeds the preset first allowed time (when the judgment result is NO), the operation of the drawing device 1 is stopped and an alarm is sounded (S34).

On the other hand, when the measured first elapsed time T1 is within the preset first allowed time (when the judgment result is YES), as shown in FIG. 3(b), the plug 11 and the metal blank tube 2 are inserted into the die 10 and set (arranged) at the drawing positions. That is, the metal blank tube 2 is set (arranged) at a drawing position between the die 10 and the plug 11 (S25). Simultaneously with the setting (arranging) of the tube at the drawing position, supplying of the lubricating oil L to the outer surface of the metal blank tube 2 from the nozzle portion 18 is initiated (see FIG. 3(b)).

Next, as shown in FIG. 3(b), the front end portion (pointing portion) of the metal blank tube 2 is chucked (sandwiched and fastened) by a pair of chuck fingers 22 and 22 (S26). The measurement of the second elapsed time T2 is terminated when the sandwiching and fastening of the blank tube 2 by the chucking unit 21 is completed and the tube becomes in a drawable state (see FIG. 5).

The control unit 31 determines whether or not the second elapsed time T2 (the elapsed time T2 from a time at which the plug 11 is inserted into the metal blank tube 2 until the tube becomes ready to be drawn) is within a preset second allowed time (S27).

When the measured second elapsed time T2 exceeds the preset second allowed time (when the judgment result is NO), drawing of the metal blank tube 2 is not initiated (drawing is not performed) and an alarm is sounded (S31). Next, the plug 11 is moved backwards (moved back in a direction separating from the die 10) (S32). Thereafter, the metal blank tube 2 set at the drawing position is pulled out (removed) (S33) to prepare for a drawing process for the next new metal blank tube 2.

On the other hand, when the measured second elapsed time T2 is within the preset second allowed time (when the judgment result is YES), drawing is initiated (S28). That is, as shown in FIG. 1, a drawing process is performed by making the metal blank tube 2 pass through between the die 10 and the plug 11 by pulling the front end portion of the blank tube 2 by the chucking unit 21 while applying the lubricating oil L on the outer surface of the metal blank tube 2 from the nozzle portion 18 (S29) to obtain a drawn tube 3 and complete the drawing. Thereafter, the plug 11 is moved backwards (moved back in a direction separating from the die 10) (S30) to prepare for a drawing process for the next new metal blank tube 2.

In the aforementioned drawing method, in the judgment in S24, when the measured first elapsed time T1 exceeds the preset first allowed time and a sufficient amount of the lubricating oil carried into the metal blank tube 2 from the plug 11 is not secured, the operation of the device 1 can be stopped; and when the measured first elapsed time T1 is within the preset first allowed time, and a sufficient amount of the lubricating oil carried into the metal blank tube 2 from the plug 11 is secured, the operation of the device 1 can be continued as it is. Further, through the judgment in S27, for a blank tube in a state in which the amount of the lubricating oil on the upper side of the inner surface thereof has decreased since it took time (the second elapsed time T2 exceeded the second allowed time), it can be configured to not perform drawing. For a blank tube 2 in which the second elapsed time T2 until it becomes ready to be drawn is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface of the blank tube 2, drawing is performed. Therefore, a drawn tubes 3 having no seizures can be produced (a drawn tube having seizures will not be formed).

Further, in the aforementioned second embodiment, the structure of the control unit 31 (control method) can be changed into the following structure. That is, in the second embodiment, as for the measurement of the first elapsed time T1 and the judgment in S24, the control unit 31 can be configured to have a structure (control method) as follows: the measurement of the first elapsed time T1 is initiated from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped; it is controlled to stop the operation of the device 1 when the measuring first elapsed time T1 exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug 11 is inserted into the metal blank tube 2, or at a time at which the plug 11 is inserted; and it is controlled to continue the operation of the device 1 when the measuring first elapsed time T1 is within a preset first allowed time at a time at which the plug 11 is inserted into the metal blank tube 2. Further, in the second embodiment, as for the measurement of the second elapsed time T2 and the judgment in S27, the control unit 31 can be configured to have a structure (control method) as follows: the measurement of the second elapsed time T2 is initiated from a time at which the plug 11 is inserted into the metal blank tube 2; it is controlled to stop the operation of the device 1 when the measuring second elapsed time T2 exceeds a preset second allowed time during a period of time from the initiation of the measurement until the metal blank tube 2 is set (arranged) at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the tube becomes ready to be drawn, or at the time at which the pipe becomes ready to be drawn; and it is controlled to initiate drawing when the measuring second elapsed time T2 is within the preset second allowed time at a time at which the metal blank tube 2 is set (arranged) at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the pipe becomes ready to be drawn.

Still another embodiment (third embodiment) of a drawing device 1 according to the present invention will be explained. The structure of the drawing device 1 of this third embodiment is as shown in FIG. 1. Although the structure of the control unit 31 (control method) is different from the aforementioned first embodiment, the other structures are the same as those of the aforementioned first embodiment.

That is, in this third embodiment, the control unit 31 is configured to: measure a first elapsed time T1 from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped until the plug 11 is inserted into the metal blank tube 2; control to stop the operation of the drawing device 1 when the measured first elapsed time T1 exceeds the preset first allowed time; and control to continue the operation of the drawing device 1 when the measured first elapsed time T1 is within the first allowed time (see FIG. 6).

Further, the control unit 31 is configured to: measure a second elapsed time T from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped until the metal blank tube 2 is set at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the tube becomes ready to be drawn; control to not perform drawing of the metal blank tube 2 when the measured second elapsed time T exceeds the preset second allowed time; and control to initiate drawing when the measured second elapsed time T is within the preset second allowed time (see FIG. 6).

In this third embodiment, the preset first allowed time T1 is not especially limited, but can be 30 seconds, for example. Also, the preset second allowed time T is not especially limited, but can be 90 seconds, for example.

Next, a flowchart of a drawing method of a metal tube using the drawing device 1 according to the aforementioned third embodiment is shown in FIG. 6. It is different from the drawing method of a metal tube using the drawing device 1 according to the aforementioned second embodiment (see FIG. 5) in that the initiation of the measurement of the second elapsed time T in the control unit 31 is set to “a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped.” The other methods are the same as those of the aforementioned second embodiment.

In the drawing method according to this third embodiment, in the judgment in S24, when the measured first elapsed time T1 exceeds the preset first allowed time and a sufficient amount of the lubricating oil carried into the metal blank tube 2 from the plug 11 is not secured, the operation of the device 1 can be stopped; and when the measured first elapsed time T1 is within the preset first allowed time and a sufficient amount of the lubricating oil carried into the metal blank tube 2 from the plug 11 is secured, the operation of the device 1 can be continued as it is. Further, through the judgment in S27, for a blank tube in a state in which the amount of the lubricating oil on the upper side of the inner surface thereof has decreased since it took time (the second elapsed time T exceeded the second allowed time), it can be configured to not perform drawing; and for a blank tube 2 in which the second elapsed time T until it becomes ready to be drawn is within the second allowed time and there exists a sufficient amount of lubricating oil on the upper side of the inner surface of the blank tube 2, drawing is performed. Therefore, a drawn tubes 3 having no seizures can be produced (a drawn tube having seizures will not be formed).

Further, in the aforementioned third embodiment, the structure of the control unit 31 (control method) can be changed into the following structure. That is, in the third embodiment, as for the measurement of the first elapsed time T1 and the judgment in S24, the control unit 31 can be configured to have a structure (control method) as follows:

the measurement of the first elapsed time T1 is initiated from a time at which supplying of the lubricating oil L to the surface of the plug 11 is stopped;

it is controlled to stop the operation of the device 1 when the measuring first elapsed time T1 exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug 11 is inserted into the metal blank tube 2, or at a time at which the plug 11 is inserted; and

it is controlled to continue the operation of the device 1 when the measuring first elapsed time T1 is within a preset first allowed time at a time at which the plug 11 is inserted into the metal blank tube 2.

Further, in the third embodiment, as for the measurement of the second elapsed time T and the judgment in S27, the control unit 31 can be configured to have a structure (control method) as follows:

the measurement of the second elapsed time T is initiated from a time at which supplying of lubricating oil L to a surface of the plug 11 is stopped;

it is controlled to stop the operation of the device 1 when the measuring second elapsed time T exceeds a preset second allowed time during a period of time from the initiation of the measurement until the metal blank tube 2 is set (arranged) at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the tube becomes ready to be drawn, or at the time at which the pipe becomes ready to be drawn; and

it is controlled to initiate drawing when the measuring second elapsed time T is within the preset second allowed time at a time at which the metal blank tube 2 is set (arranged) at a drawing position between the die 10 and the plug 11, the front end portion of the metal blank tube 2 is held by the chucking unit 21 and the pipe becomes ready to be drawn.

Further, in the first embodiment, the initiation point of the measurement of the elapsed time T is set to the time at which “supplying of the lubricating oil to the surface of the plug is stopped” (see FIG. 4), and in the second embodiment, the initiation point of the measurement of the first elapsed time T1 is set to the time at which “supplying of the lubricating oil to the surface of the plug is stopped” (see FIG. 5), and furthermore, in the third embodiment, the initiation point of the measurement of the first elapsed time T1 and the second elapsed time T are set to the time at which “supplying of the lubricating oil to the surface of the plug is stopped” (see FIG. 6). However, for example, if the supplying time (application time) of the lubricating oil L is set to be constant, the initiation points of these measurements can be set to “initiation of supplying of the lubricating oil to the surface of the plug” (they are essentially the same).

Also, in the aforementioned first to third embodiments, alarms are sounded to notify an operator when the judgment result in S06, S24, and S27 is NO, but not especially limited to that. For example, when the judgment result is NO, a revolving light (red, etc) can be turned on or blinked to notify an operator.

Furthermore, in the aforementioned first to third embodiments, when drawing is not initiated (S10, S31), an operation to pull out (eject) the set blank tube is performed afterwards (S11, S32). The ejecting operation of the blank tube can be performed by hand, or performed automatically by an ejecting device. Further, a blank tube ejected in this way can be disposed, or reused in the aforementioned drawing method.

In the present invention, the length of the metal blank tube 2 which is an object to be drawn is not limited. Since shortage of lubricating oil more likely occurs for longer metal blank tubes, the present invention is preferably applied to drawing of a longer blank tube. Specifically, significant effects can be obtained for a blank tube 2 m or longer, especially 2.5 m or longer.

In the present invention, the material of the metal blank tube 2 which is an object to be drawn (type of metal) is not especially limited, but can be, for example, aluminum, iron, copper, or alloys thereof. Since significant effects can be obtained when drawing a longer blank tube, the present invention is suited for a production of an aluminum tube for a photosensitive drum substrate.

EXAMPLES

Next, specific examples of the present invention will be explained, but the present invention is not especially limited to these examples.

Example 1

A metal blank tube 2 was drawn using the drawing device 1 according to the first embodiment having the structure shown in FIG. 1 (see the flowchart of FIG. 4). A billet made of an aluminum alloy (Mn: 1.12 mass %, Si: 0.11 mass %, Fe: 0.39 mass %, Cu: 0.16 mass %, Zn: 0.01 mass %, Mg: 0.02 mass %, and the balance being aluminum and inevitable impurities) was extruded under the condition of an extrusion temperature of 520° C. and an extrusion rate of 5 m/min to obtain a cylindrical tube having an outer diameter of 32 mm and a thickness of 1.5 mm, and cut into 2.2 m in length, which was used as a metal blank tube 2.

In the drawing device 1, the approach angle of the approach portion 14 of the die 10 was 15°, the bearing length of the bearing portion 15 of the die 10 was 15 mm, the approach angle of the approach portion 16 of the plug 11 was 7°, and the bearing length of the bearing portion 17 of the plug 11 was 2 mm.

Applying of a lubricating oil L ejected from the nozzle portion 18 to the surface of the plug 11 was initiated as shown in FIG. 2(a) (S01), and the application was stopped after applying for 10 seconds (S02) (see FIG. 2(b)). The measurement of the elapsed time T was initiated from a time at which the application was stopped. Next, as shown in FIG. 3(a), the plug 11 to which the lubricating oil L was applied was inserted and arranged inside the metal blank tube 2 (S03). Then, as shown in FIG. 3(b), the metal blank tube 2 was set at the drawing position between the die 10 and the plug 11 (S04). Simultaneously with the setting to the drawing position, the application of the lubricating oil L to the outer surface of the metal blank tube 2 from the nozzle portion 18 was initiated. Next, as shown in FIG. 3(b), the front end portion (pointing portion) of the metal blank tube 2 was chucked by a pair of chuck fingers 22 and 22 (which became in a drawable state) (S05). The measurement of the elapsed time T was terminated when the sandwiching and fastening of the blank tube 2 by the chucking unit 21 was completed and the tube became in a drawable state.

It was determined by the control unit 31 whether or not the elapsed time T (the elapsed time T from a time at which supplying of the lubricating oil to the surface of the plug is stopped until the tube becomes ready to be drawn) was within a preset allowed time (200 seconds)(S06). In Example 1, the elapsed time T was 60 seconds, which was within the allowed time (200 seconds), so the judgment result was YES and therefore, drawing was initiated as it is (S07). That is, as shown in FIG. 1, the metal blank tube 2 was drawn by making the tube pass through between the die 10 and the plug 11 by pulling the front end portion of the blank tube 2 by the chucking unit 21 while applying the lubricating oil L onto the outer surface of the metal blank tube 2 from the nozzle portion 18 to obtain a drawn tube 3, and the drawing was completed (S08). A drawn tube 3 was obtained by performing the drawing at a drawing rate of 30 m/min, an outer diameter reduction rate of 16%, and a cross-sectional area reduction rate of 32%. As the lubricating oil L, a lubricating oil named “Stroll ES150” produced by Kyoueiyuka Co. was used.

The obtained drawn tube 3 was transferred to a transfer conveyer from the drawing device 1 and cooled at room temperature (around 25° C.) and cut into 260 mm length.

Example 2

After performing to S06 in the same manner as in Example 1, it was judged in S06. In Example 2, the elapsed time T was 120 seconds, which was within the allowed time (200 seconds), so the judgment result was YES and therefore, drawing was initiated as it is (S07). That is, a drawn tube 3 was obtained by performing the drawing in the same manner as in Example 1.

Example 3

After performing to S06 in the same manner as in Example 1, it was judged in S06. In Example 3, the elapsed time T was 180 seconds, which was within the allowed time (200 seconds), so the judgment result was YES and therefore, drawing was initiated as it is (S07). That is, a drawn tube 3 was obtained by performing the drawing in the same manner as in Example 1.

Example 4

After performing to S06 in the same manner as in Example 1, it was judged in S06. In Example 4, the elapsed time T was 240 seconds, which exceeded the allowed time (200 seconds), so the judgment result was NO and therefore, drawing was not initiated (S10). After moving the plug 11 backwards (in the direction separating from the die 10) (S11), the metal blank tube 2 set at the drawing position was pulled out (S12) to prepare for the drawing of the next new metal blank tube 2.

Example 5

After performing to S06 in the same manner as in Example 1, it was judged in S06. In Example 5, the elapsed time T was 300 seconds, which exceeded the allowed time (200 seconds), so the judgment result was NO and therefore, drawing was not initiated (drawing was not performed) (S10). After moving the plug 11 backwards (in the direction separating from the die 10) (S11), the metal blank tube 2 set at the drawing position was pulled out (S12) to prepare for the drawing process of the next new metal blank tube 2.

Comparative Example 1

After performing to S06 in the same manner as in Example 1, it was judged in S06. In Example 4, the elapsed time T was 240 seconds, which exceeded the allowed time (200 seconds), so the judgment result was NO. But, ignoring the judgment, drawing was performed in the same manner as in Example 1 to obtain a drawn tube 3.

Comparative Example 2

After performing to S06 in the same manner as in Example 1, it was judged in S06. In Example 4, the elapsed time T was 300 seconds, which exceeded the allowed time (200 seconds), so the judgment result was NO. But, ignoring the judgment, drawing was performed in the same manner as in Example 1 to obtain a drawn tube 3.

	TABLE 1
		Seizure resistance
	Elapsed Time T (sec)	evaluation
Example 1	60	◯
Example 2	120	◯
Example 3	180	◯
Comparative Example 1	240	Δ
Comparative Example 2	300	X

The existence of seizures and the states of the drawn tubes 3 of Example 1 to 3 and Comparative Examples 1 and 2 obtained in the aforementioned manner were examined, and the seizure resistances were evaluated based on the following decision criterion. These evaluation results are shown in Table 1.

(Decision Criterion)

“◯” . . . seizures did not occur at all in the drawn tube
“Δ” . . . seizures occurred in the rear half region of the drawn tube
“X” . . . seizures occurred in all regions in the lengthwise direction of the drawn tube

As it is clear from Table 1, according to the drawing methods of the present invention (Examples 1 to 3), drawn tubes not having seizures could be produced. Also, according to the drawing methods of the present invention (Examples 4 and 5), production of drawn tubes having seizures could be prevented by not performing drawing considering the judgment in S06 (“NO” judgment).

On the other hand, in Comparative Examples 1 and 2, obtained drawn tubes had seizures.

The present invention claims priority to Japanese Patent Application No. 2011-186790 filed on Aug. 30, 2011, the entire disclosure of which is incorporated herein by reference in its entirety.

The terms and descriptions used herein are used only for explanatory purposes and the present invention is not limited to them. The present invention allows various design-changes falling within the claimed scope of the present invention unless it deviates from the spirits of the invention.

INDUSTRIAL APPLICABILITY

The device and method for drawing a metal tube according to the present invention are suited for a production of aluminum tubes for use in a photosensitive drum substrate since it is possible to make a sufficient amount of lubricating oil adhere to an inner surface of a metal blank tube in a continuous drawing of a plurality of blank tubes.

DESCRIPTION OF THE REFERENCE NUMERALS

• 1 . . . drawing device
• 2 . . . metal blank tube
• 3 . . . drawn tube
• 10 . . . die
• 11 . . . plug
• 18 . . . nozzle portion
• 21 . . . chucking unit
• 24 . . . pulling unit
• 31 . . . control unit
• L . . . lubricating oil

Claims

1. A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

measure an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured elapsed time exceeds a preset allowed time; and

control to initiate drawing when the measured elapsed time is within a preset allowed time.

2. A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

initiate a measurement of an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of the device when a measuring elapsed time exceeds a preset allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to initiate drawing when the measuring elapsed time is within the preset allowed time at a time at which the metal blank tube is set at the pulling position between the die and the plug and becomes ready to be drawn.

3. A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of the device when the measured first elapsed time exceeds a preset first allowed time; and

control to continue an operation of the device when the measured first elapsed time is within the preset first allowed time,

wherein the control unit is configured to:

also measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second allowed time; and

control to initiate drawing when the measured second elapsed time is within the preset second allowed time.

4. A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of the device when the measured first elapsed time exceeds a preset first allowed time; and

control to continue an operation of the device when the measured first elapsed time is within the preset first allowed time,

wherein the control unit is configured to:

measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to initiate drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a pulling position between the die and the plug and becomes ready to be drawn.

5. A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

initiate a measurement of a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of the device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from an initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted; and

control to continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube,

wherein the control unit is configured to:

also measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second elapsed time; and

control to initiate drawing when the measured second elapsed time is within the second allowed time.

6. A device for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising a control unit configured to:

initiate a measurement of a first elapsed time from a period of time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of the device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted; and

control to continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube,

wherein the control unit is configured to:

initiate a measurement of a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to initiate drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a pulling position between the die and the plug and becomes ready to be drawn.

7. A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping the supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

measure an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn is measured;

control to not perform drawing of the metal blank tube when the measured elapsed time exceeds a preset allowed time; and

control to perform drawing of the metal blank tube when the measured elapsed time is within a preset allowed time.

8. A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping the supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is controlled to:

initiate a measurement of an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of a device when a measuring elapsed time exceeds a preset allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

control to perform drawing when the measuring elapsed time is within the preset allowed time at a time at which the metal blank tube is set at a pulling position between the die and the plug and becomes ready to be drawn.

9. A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of a device when the measured first elapsed time exceeds a preset first allowed time; and

control to continue the operation of the device when the measured first elapsed time is within the preset first allowed time,

measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second allowed time; and

control to perform drawing when the measured second elapsed time is within a preset second allowed time.

10. A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

measure a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the plug is inserted into the metal blank tube;

control to stop an operation of a device when the measured first elapsed time exceeds a preset first allowed time;

control to continue an operation of the device when the measured first elapsed time is within the preset first allowed time;

initiate a measurement of a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

perform drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn.

11. A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug;

wherein it is configured to:

initiate a measurement of a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of a device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted;

continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube;

measure a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured second elapsed time exceeds a preset second allowed time; and

perform drawing when the measured second elapsed time is within the second allowed time.

12. A method for drawing a metal tube in which drawing is performed by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug,

wherein it is configured to:

initiate a measurement of a first elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped;

control to stop an operation of a device when the measuring first elapsed time exceeds a preset first allowed time during a period of time from the initiation of the measurement until the plug is inserted into the metal blank tube, or at a time at which the plug is inserted;

continue the operation of the device when the measuring first elapsed time is within the preset first allowed time at a time at which the plug is inserted into the metal blank tube;

initiate a measurement of a second elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped or from a time at which the plug is inserted into the metal blank tube;

control to stop the operation of the device when the measuring second elapsed time exceeds a preset second allowed time during a period of time from an initiation of the measurement until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn, or at a time at which it becomes ready to be drawn; and

perform drawing when the measuring second elapsed time is within the preset second allowed time at a time at which the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn.

13. The method for drawing a metal tube as recited in claim 7, wherein the application step, the insertion step, and the setting step are performed in this order.

14. A method for producing a metal tube by performing drawing by making a metal blank tube pass through between a die for forming an outer surface and a plug for forming an inner surface, comprising:

an application step for applying a lubricating oil to a surface of the plug and then stopping supplying of the lubricating oil;

an insertion step for inserting and placing the plug to which the lubricating oil was applied into the metal blank tube; and

a setting step for setting the metal blank tube at a drawing position between the die and the plug,

wherein it is configured to:

measure an elapsed time from a time at which supplying of a lubricating oil to a surface of the plug is stopped until the metal blank tube is set at a drawing position between the die and the plug and becomes ready to be drawn;

control to not perform drawing of the metal blank tube when the measured elapsed time exceeds a preset elapsed time; and

perform drawing of the metal blank tube when the measured elapsed time is within a preset allowed time.

15. The method for producing a metal tube as recited in claim 14, wherein the application step, the insertion step, and the setting step are performed in this order.

16. The method for drawing a metal tube as recited in claim 8,

wherein the application step, the insertion step, and the setting step are performed in this order.

17. The method for drawing a metal tube as recited in claim 9, wherein the application step, the insertion step, and the setting step are performed in this order.

18. The method for drawing a metal tube as recited in claim 10, wherein the application step, the insertion step, and the setting step are performed in this order.

19. The method for drawing a metal tube as recited in claim 11, wherein the application step, the insertion step, and the setting step are performed in this order.

20. The method for drawing a metal tube as recited in claim 12, wherein the application step, the insertion step, and the setting step are performed in this order.