Toggle-type die clamping unit of an injection molding machine

Abstract

A toggle mechanism is supported at the front face of the housing and a forward end of the toggle mechanism is connected to a back face of the movable platen. Upon the closing and opening of dies, the toggle mechanism is stretched and contracted to move the movable platen forward and backward along the tie bars. An automatic control device calculates, before the dies are mounted, from a die thickness input and the kind of the dies input, such a stop position for the link housing as impart a target value to the stretching/contraction amount that the toggle mechanism has when the dies are in closed state, and calculates, from the kind of the dies input, an appropriate contraction amount greater than the target value, and the automatic controlling device moves the link housing to the stop position calculated and the toggle mechanism by the appropriate contraction amount calculated.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-029831, filed Feb. 6, 2002, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a toggle-type die clamping unit of an injection molding machine and, in particular, to the function of, before mounting operation of dies, automatically stopping a link housing and movable platen to their appropriate positions.

[0004] 2. Description of the Related Art

[0005] In an electric injection molding machine, a toggle mechanism has been widely used as a die clamping unit. A primary section of the toggle-type die clamping unit comprises a base, a stationary platen, a movable platen, a link housing, a toggle mechanism, etc. The stationary platen is fixed on the base and retains a stationary die in place. The movable platen is arranged opposite to the stationary platen and configured to retain the movable die and supported on the base to be movable in forward and backward directions. The link housing is arranged behind the movable platen and can adjust the forward and backward positions on the base. The toggle mechanism is mounted on a front face of the linked housing and its forward end is connected to a back face of the movable platen. Upon closing and opening of the dies, a stretching/contraction amount of the toggle mechanism is controlled to move the movable platen forward and backward.

[0006] Since, in the toggle-type die clamping unit, in order to effectively utilize clamping force raising function of the toggle mechanism, it is necessary that the position of the link housing be initially adjusted so as to allow the stretching/contraction amount of the toggle mechanism to reach a predetermined target value with the dies in a closed state. If, therefore, the die thickness (a total thickness of the stationary and movable dies in a closed state) varies, it is necessary to adjust the stop position of the link housing each time.

[0007] At a start of a die mounting operation in a conventional injecting machine, the operator has initially adjusted the stop positions of the link housing and movable platen as will be described later, while operating push buttons on an operation panel in a manual mode. That is, with associated dies not in a mounted state, the stretching/contraction amount of the toggle mechanism is adjusted and then it is stopped in a state to be contracted to some extent for example, about 10 to 20 mm from a supposed position at a die clamping time. Then, while confirming the distance between the stationary platen and the movable platen by the eyes of the observer, the position of the link housing is adjusted in accordance with the thickness of the dies and, in a supposed state allowing the insertion of the dies, the link housing is stopped.

[0008] After, in this way, the stop positions of the link housing and movable platen have been initially adjusted, the stationary and movable dies are attached to the stationary and movable platens, respectively. Then the stop position of the link housing is finally fine-adjusted by clamping the dies by a predetermined die clamping force and, in this state, bringing the stretching/contraction amount of the toggle mechanism up to a predetermined target value.

[0009] (Problem of the Conventional Die Clamping Unit)

[0010] In the conventional die clamping unit, as set out above, when, prior to the die mounting operation, the stop position of the link housing is initially adjusted so as to meet the thickness of the dies used, the operator has confirmed, by the eyes, the distance between the stationary platen and movable platen. For this reason, it is not easy to accurately align the stop position of the link housing with the appropriate position. It also needs a cumbersome operation and it takes a lot of time to do so.

[0011] In the case where no accurate preliminary adjustment is performed, in a final adjustment subsequent to the mounting of the dies, more steps are required so as to fine-adjust the stop position of the link housing. And more time is needed in the final adjustment operation.

BRIEF SUMMARY OF THE INVENTION

[0012] The present invention has been achieved in view of the problem encountered in the conventional toggle-type die clamping unit and it is accordingly the object of the present invention to provide a die clamping unit which can accurately and efficiently perform a preliminary adjusting operation of a link housing's position which has to be done prior to the mounting of the dies.

[0013] A toggle-type die clamping unit of an injection molding machine according to the present invention comprises a base; a stationary platen fixed on the base and configured to retain a stationary die; a movable platen arranged opposite to the stationary platen and configured to retain a movable die, the movable platen being configured to be supported on the base in such a state as to be movable in forward and backward directions; a link housing arranged on the base behind the movable platen and adjustable in position in the forward and backward directions; a toggle mechanism mounted to a front face of the link housing and having a forward end which is connected to a back face of the movable platen, the toggle mechanism being configured to have its stretching/contraction amount controlled so as to move the movable platen forward and backward to close and open the dies; a detector configured to detect a position of the link housing on the base and an automatic controlling device configured to control a stop position of the link housing, wherein, before the dies are mounted, the automatic controlling device calculates, from a die thickness input, such a stop position for the link housing as impart a target value to the stretching/contraction amount that the toggle mechanism has when the dies are in closed state, and the automatic controlling device moves the link housing to the stop position calculated.

[0014] It is to be noted that the target value for the stretching/contraction amount of the toggle mechanism is so set that the die clamping force raising function by the toggle mechanism becomes a maximal value, or its near value, when the dies are in closed state.

[0015] Preferably, a toggle-type die clamping unit of an injection molding machine according to the present invention has, in addition to the detector (first detector) configured to detect the position of the link housing on the base, a second detector configured to detect the stretching/contraction amount of the toggle mechanism, in which, before the dies are mounted, the above-mentioned automatic controlling device calculates, from a die thickness input and the kind of the dies input, such a stop position for the link housing as impart a target value to the stretching/contraction amount that the toggle mechanism has when the dies are in closed state, and calculates, from the kind of the dies input, an appropriate contraction amount greater than the target value, and the automatic controlling device moves the link housing to the stop position calculated and the toggle mechanism by the appropriate contraction amount calculated.

[0016] It is to be noted that the above-mentioned appropriate contraction amount for the toggle mechanism is so set in accordance with the kind of the dies as to allow the distance between the stationary platen and the movable platen to become a value corresponding to the thickness of the dies plus a gap necessary to the insertion of the dies.

[0017] In the case where, for example, spring-incorporated-type dies (dies incorporating springs to open the dies) are used, the above-mentioned automatic controlling device is so configured as to, when the spring-incorporated-type dies are inputted as the kind of dies, calculate the above-mentioned appropriate contraction amount on the basis of the opening amount of dies opened by the spring. That is, the above-mentioned appropriate contraction amount is so set as to allow the distance between the stationary platen and the movable platen to become a value corresponding to the thickness of the dies opened by springs plus a gap necessary to the insertion of the dies.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0018] FIG. 1 is a view of a structure diagrammatically showing a toggle-type die clamping unit according to the present invention; and

[0019] FIG. 2 is a flow chart showing one method for preliminarily adjusting the positions of a link housing and movable platen before the mounting of dies in the toggle-type die clamping unit of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] FIG. 1 shows a structure diagrammatically showing a toggle-type die clamping unit of an injection molding machine according to the present invention.

[0021] In the Figure, reference numeral 1 shows a stationary platen; 2, a movable plate; 3, a link housing; 4, a toggle mechanism; 5, tie bars; 6, a stationary die; 7, a movable die; 10, a base; 11, an encoder (a second detector); and 12, a displacement detector (a first detector).

[0022] The stationary platen 1 and link housing 3 are arranged to face each other on a base 10. The stationary platen 1 is fixed on the base 10. The stationary platen 1 and link housing 3 are coupled to each other by four tie bars 5. A threaded portion is provided at an area of the tie bar where it extends through the link housing 3. A nut 17 on the threaded portion of each tie bar 17 is attached to the link housing 3. By driving the nut 17, a positional adjustment of the link housing 3 is made in forward and backward (right and left) directions on the base 10. The position of the link housing 3 is detected by means of the displacement detector 12 mounted on the base 10.

[0023] The movable platen 2 is arranged between the stationary platen 1 and the link housing 3. The tie bars 5 pass through the four corner portions of the movable platen 2, respectively. The movable platen 2 can be moved back and forth on the base 10. The stationary die 6 is attached to the front surface (to the left in the Figure) of the stationary platen while the movable die 7 is attached to the front surface (to the right in the Figure) of the movable platen 2.

[0024] The toggle mechanism 4 is attached to the front face of the link housing 3. The forward end of the toggle mechanism 4 is connected to a back face of the movable platen 2. Upon closing and opening of the dies, the stretching/contraction amount of the toggle mechanism 4 is controlled to allow the movable platen to be moved forward and backward along the tie bars 5. The stretching/contraction amount is controlled by driving a ball screw 21 through a pulley 18, a timing belt 20 and pulley 19 with the use of a servomotor 16 and, by doing so, moving a crosshead 22 forward and backward along the tie bars 5. The stretching/contraction amount of the toggle mechanism 4 is detected by the encoder 11 attached to the servomotor 16.

[0025] In connection with this toggle-type die clamping unit, an explanation will be made below about one method for preliminarily adjusting the positions of the link housing 3 and movable platen 2 before the mounting of the dies. FIG. 2 shows a flow chart of the preliminary adjustment in supposing the case of mounting a spring-incorporated-type dies, that is, the dies with springs incorporated to open the dies. It is to be noted that, in FIG. 2, “LH” denotes the link housing and “MP” denotes the movable platen.

[0026] Before mounting the dies 6 and 7, an unit operator selects a “die mounting” mode on an operation panel and then inputs the die thickness and springing amount (a die opening amount by the springs) as input data. Then, the operator depresses an “automatic die thickness adjustment” button. By doing so, the input data is conformed and a corresponding LED starts to be flashed on and off.

[0027] An automatic control device, not shown, of the die clamping unit determines a stop position (XSL12L in the Figure) of the link housing 3 based on the inputted die thickness and springing amount so that the stretching/contraction amount of the toggle mechanism 4 in a die-closed state reaches a predetermined target value. On the other hand, an appropriate value (XSL12 in the Figure) of the stretching/contraction amount of the toggle mechanism 4 before the mounting of the dies is so determined that a distance between the stationary platen 1 and the movable platen 2 becomes a value corresponding to the thickness of the dies opened by the springs plus a gap necessary to insertion of the dies.

[0028] When the operator again depresses the “automatic die thickness adjustment” button, the corresponding LED is lighted and the link housing 3 and movable platen 2 start to be moved. The automatic control device of the die clamping unit, while detecting the position of the link housing 3 by the displacement sensor 12, moves the link housing 3 to the appropriate position (XSL12L) set out above. At the same time, it moves the movable platen 2 to the above-mentioned appropriate position (XSL 12) while detecting the stretching/contraction amount of the toggle mechanism 4 by the encoder 11.

[0029] After the link housing 3 and movable platen 2 have been brought to their appropriate positions and stopped there, the LED is turned OFF and the preliminary position adjusting operation of the link housing 3 and movable platen 2 has been completed.

[0030] Although, in the above-mentioned example, it is supposed that the spring-incorporated-type dies are mounted, if normal-type dies (dies not incorporating springs to open the dies) are mounted, it is not necessary to consider the opening amount by the springs. That is, the appropriate value (XSL12) of the stretching/contraction amount of the toggle mechanism 4 before the mounting of the dies is determined such that the distance between the stationary platen 1 and the movable platen 2 becomes a value corresponding to the thickness of the dies in a closed state plus a gap necessary to the insertion of the dies.

[0031] According to the toggle-type die clamping unit of the injection molding machine according to the present invention, it is possible to accurately and efficiently make an adjusting operation of preliminarily adjusting the positions of the link housing and movable platen before the mounting of the dies.

Claims

1. A toggle-type die clamping unit of an injection molding machine comprising:

a base;

a stationary platen fixed on the base and configured to retain a stationary die;

a movable platen arranged opposite to the stationary platen and configured to retain a movable die, the movable platen being configured to be supported on the base in such a state as to be movable in forward and backward directions;

a link housing arranged on the base behind the movable platen and adjustable in position in the forward and backward directions;

a toggle mechanism mounted to a front face of the link housing and having a forward end which is connected to a back face of the movable platen, the toggle mechanism being configured to have its stretching/contraction amount controlled so as to move the movable platen forward and backward to close and open the dies;

a detector configured to detect a position of the link housing on the base and

an automatic controlling device configured to control a stop position of the link housing,

wherein, before the dies are mounted, the automatic controlling device calculates, from a die thickness input, such a stop position for the link housing as impart a target value to the stretching/contraction amount that the toggle mechanism has when the dies are in closed state, and the automatic controlling device moves the link housing to the stop position calculated.

2. A toggle-type die clamping unit of an injection molding machine comprising:

a base;

a stationary platen fixed on the base and configured to retain a stationary die;

a movable platen arranged opposite to the stationary platen and configured to retain a movable die, the movable platen being configured to be supported on the base in such a state as to be movable in forward and backward directions;

a link housing arranged on the base behind the movable platen and adjustable in position in the forward and backward directions;

a toggle mechanism mounted to a front face of the link housing and having a forward end which is connected to a back face of the movable platen, the toggle mechanism being configured to have its stretching/contraction amount controlled so as to move the movable platen forward and backward to close and open the dies;

a first detector configured to detect a position of the link housing on the base;

a second detector configured to detect the stretching/contraction amount of the toggle mechanism; and

an automatic controlling device configured to control a stop position of the link housing and the stretching/contraction amount of the toggle mechanism,

wherein, before the dies are mounted, the automatic controlling device calculates, from a die thickness input and the kind of the dies input, such a stop position for the link housing as impart a target value to the stretching/contraction amount that the toggle mechanism has when the dies are in closed state, and calculates, from the kind of the dies input, an appropriate contraction amount greater than said target value, and the automatic controlling device moves the link housing to the stop position calculated and the toggle mechanism by the appropriate contraction amount calculated.

3. A toggle-type die clamping unit according to claim 2, wherein the automatic control device calculates the appropriate contraction amount when the type of dies input designates spring-incorporated-type dies incorporating springs, said appropriate contraction amount being corresponding to an opening amount of the dies opened by the springs.