Vaccum-generating unit

Abstract

A main body comprises first to third block members composed of resin materials. A nozzle hole and a diffuser hole are integrally formed in the third block member. A suction passage is provided between the nozzle hole and the diffuser hole.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vacuum-generating unit capable of applying a negative pressure to a suction mechanism such as a suction pad.

2. Description of the Related Art

A vacuum supply apparatus has been hitherto utilized as a means for applying a negative pressure to a suction pad. Such a vacuum supply apparatus generally comprises: an ejector for generating a negative pressure; a vacuum port connected to and communicated with a suction mechanism such as a suction pad via a tube; a valve mechanism provided with a pressure fluid-supplying solenoid valve and a vacuum-breaking solenoid valve for feeding compressed air to the ejector and the vacuum port and cutting off the supply of the compressed air; and a vacuum switch for detecting the negative pressure generated in the vacuum port (see, for example, Japanese Laid-Open Utility Model Publication No. 61-9599).

In this arrangement, the ejector includes a nozzle and a diffuser which are formed as separate members respectively and which are coaxially assembled into a hole of a body respectively.

An explanation will be made schematically about an operation of such a conventional vacuum supply apparatus.

Compressed air is supplied to the ejector via the valve mechanism section to generate a negative pressure. The negative pressure generated in the ejector is applied to the suction pad via the tube connected to the vacuum port. The suction pad attracts and holds a workpiece in accordance with the action of the negative pressure generated in the suction pad. While the suction pad is attracting and holding the workpiece, a robot arm displaces the workpiece to transport the workpiece to a predetermined position.

Subsequently, in order to release the workpiece, compressed air (positive pressure) is supplied to the suction pad from the valve mechanism section via a passage communicated with the vacuum port, and thus an effect of the negative pressure of the suction pad is decreased and eliminated. As a result, the suction pad releases the workpiece to locate the workpiece to a desired position.

There has been hitherto a need to achieve a small size and a light weight as far as possible by reducing the outer diameter dimension, and to decrease the production cost by reducing the number of assembling steps. It is because, for example, when a plurality of vacuum supply apparatuses are provided in a row to construct a manifold, it is possible to obtain a solenoid valve manifold having an extremely small size and a light weight, and to effectively utilize the installation space by reducing the outer diameter dimension of the entire apparatus.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a vacuum-generating unit capable of achieving a small size and a light weight by reducing the outer diameter dimension of the entire apparatus and capable of reducing the production cost.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view illustrating a vacuum-generating unit according to an embodiment of the present invention;

FIG. 2 shows a side elevational view, partly cut away, taken in the axial direction of the vacuum-generating unit shown in FIG. 1;

FIG. 3 shows a fragmental longitudinal sectional view illustrating an ejector shown in FIG. 2;

FIG. 4 shows a fragmental side view, partly cut away, illustrating a state in which a pressure sensor is detachably installed to a tube joint;

FIG. 5 shows a fragmental longitudinal sectional view illustrating an ejector according to a modified embodiment of the present invention; and

FIG. 6 shows a fragmental longitudinal sectional view illustrating an ejector according to a comparative embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 and 2, reference numeral 10 indicates a vacuum-generating unit according to an embodiment of the present invention.

The vacuum-generating unit 10 comprises: a main body 20 including a first block member 12, a second block member 14, and a third block member 16 formed of resin materials and connected to each other in the longitudinal direction; a solenoid valve assembly 26 including a pressure fluid-supplying solenoid valve 22 and a vacuum-breaking solenoid valve 24 arranged on the upper portion of the main body 20; an ejector 32 including a nozzle hole 28 and a diffuser hole 30 (see FIG. 2) integrally formed (i.e., formed in a single component) in the third block member 16; and a detector 34 for detecting a negative pressure derived from a vacuum port as described later on.

The pressure fluid-supplying solenoid valve 22 and the vacuum-breaking solenoid valve 24 have the same components respectively, and they are closed in a normal state. The solenoid valves 22, 24 are not limited to the above normally closed type. The solenoid valves 22, 24 may be open in a normal state, self-retained, or timer-equipped, for example.

The first to third block members 12, 14, 16 have substantially the same width respectively, and they are formed to be thin-walled (see FIG. 1). The first block member 12 includes a compressed air supply port (pressure fluid supply port) 36 for supplying compressed air (positive pressure) to the ejector 32.

The second block member 14 includes a first ON/OFF valve 42 in a chamber 40 therein, and the first ON/OFF valve 42 is switched from an OFF state to an ON state by applying a pilot pressure thereto. The third block member 16 includes an unillustrated second ON/OFF valve in a chamber thereof, and the second ON/OFF valve is switched from an OFF state to an ON state by applying a pilot pressure thereto.

The compressed air supply port 36 communicates with the inside of the chamber 40 of the second block member 14 arranged with the first ON/OFF valve 42, via a first passage 48 having a substantially L-shaped bent form. An unillustrated second passage, which is branched from the first passage 48, is formed to communicate with the pressure fluid-supplying solenoid valve 22. An unillustrated third passage, which is branched from the first passage 48, is formed to communicate with the vacuum-breaking solenoid valve 24. An unillustrated fourth passage, which is branched from the first passage 48, is formed to communicate with the second ON/OFF valve (not shown).

As shown in FIG. 2, a first pilot passage 58 is formed between the pressure fluid-supplying solenoid valve 22 and the first ON/OFF valve 42. The solenoid valve 22 applies a pilot pressure to the first ON/OFF valve 42 through the first pilot passage 58 when energized to be in the ON state. A second pilot passage 60 is formed between the vacuum-breaking solenoid valve 24 and the unillustrated second ON/OFF valve. The solenoid valve 24 applies a pilot pressure to the second ON/OFF valve (not shown) through the second pilot passage 60 when energized to be in the ON state.

The ejector 32 is provided in the third block member 16 which is integrally formed, for example, by means of resin molding. As shown in FIG. 3, the ejector 32 includes the nozzle hole 28 and the diffuser hole 30, both of which are formed in an integrated manner in the third block member 16. The nozzle hole 28 and the diffuser hole 30 are arranged coaxially respectively. The nozzle hole 28 includes an orifice having a small diameter. On the other hand, the diffuser hole 30 includes a hole having a diameter larger than that of the nozzle hole 28 and a predetermined length in the axial direction.

A suction passage 64 is formed between the nozzle hole 28 and the diffuser hole 30 which constitute the ejector 32. The suction passage 64 is communicated with a vacuum port 62 and is bent in a substantially L-shaped form. A negative pressure generated in the ejector 32 is applied to a suction mechanism such as an unillustrated suction pad connected to a tube joint 65 via a tube, for example.

An exit end of the diffuser hole 30 is communicated with an exhaust port (discharge port) 66 formed in the third block member 16. The compressed air supplied to the ejector 32 is exhausted outside via a silencer 68 communicated with the exhaust port 66.

When the vacuum-breaking solenoid valve 24 is in the ON state, a pilot pressure is applied to the unillustrated second ON/OFF valve. When the pilot pressure is applied, the unillustrated second ON/OFF valve becomes the ON state, and a compressed air (positive pressure) is supplied to the suction passage 64 communicated with the vacuum port 62. Accordingly, an effect of the negative pressure is decreased and eliminated.

The first ON/OFF valve 42 and the unillustrated second ON/OFF valve have the same components respectively. Each of the valves includes: a valve plug 72 displaceable by a predetermined distance in a substantially horizontal direction; and a retainer 74 fixed in the chamber 40 and formed to be cylindrical so that the valve plug 72 is surrounded thereby (see FIG. 2).

A first ring member 78 is installed to the outer circumferential surface of the valve plug 72 on one end side. The first ring member 78 is seated on a seat section 76 of the retainer 74 to close the chamber 40. A second ring member 80 is installed to the outer circumferential surface of the valve plug 74 on the other end side. The second ring member 80 is slidable along the inner wall surface of the retainer 74. Each of the first and second ring members 78, 80 is made of an elastic material such as natural rubber and synthetic rubber.

When the first ON/OFF valve 42 is in the OFF state, the supply of the compressed air to the ejector 32 is stopped. When the first ON/OFF valve 42 is in the ON state, the compressed air is supplied to the ejector 32.

The detector 34 includes a pressure sensor 82 for detecting the negative pressure to be applied to the suction pad via an unillustrated communication passage communicated with the suction passage 64. As shown in FIG. 4, the pressure sensor 82 is detachably installed to a tube joint 84 connected to the third block member 16 by the aid of a screw portion. A detection signal outputted from the pressure sensor 82 is transmitted, for example, to an unillustrated external controller via a lead wire 86.

In this arrangement, since the pressure sensor 82 is detachably installed by the aid of the tube joint 84, it is possible to achieve a small size and a light weight of the entire apparatus as compared with an arrangement in which an unillustrated vacuum switch is installed. An operator can arbitrarily select a pressure sensor 82 corresponding to a negative pressure range of the negative pressure derived from the vacuum port 62. Further, it is possible to conveniently replace with another pressure sensor 82.

As shown in FIG. 2, a flow rate-adjusting screw 88 for adjusting a flow rate of a pressure fluid (i.e., pilot pressure) for breaking the vacuum is provided between the pressure fluid-supplying solenoid valve 22 and the vacuum-breaking solenoid valve 24. When a knob 88a of the flow rate-adjusting screw 88 is gripped and rotated in a predetermined direction, a tapered portion 88b, which faces the passage 60, can be displaced in the vertical direction by screwing the screw 88 with respect to a cylinder 90 to adjust the flow rate of the pressure fluid flowing through the passage 60.

The vacuum-generating unit 10 according to the embodiment of the present invention is basically constructed as described above. Next, its operations, functions, and effects will be explained. It is assumed that each of the pressure fluid-supplying solenoid valve 22 and the vacuum-breaking solenoid valve 24 is in the OFF state in the initial state.

Compressed air supplied from an unillustrated compressed air supply source is introduced into the first passage 48 via the compressed air supply port 36. The compressed air introduced into the first passage 48 is supplied into the chamber 40 of the first ON/OFF valve 42 communicated with the first passage 48. The valve plug 72 is displaced in the leftward direction in FIG. 2 under the action of the compressed air, but the first ON/OFF valve 42 is still in the OFF state.

In the above state, the unillustrated controller outputs an ON signal to the pressure fluid-supplying solenoid valve 22 to start a pressure fluid-supplying operation. In this situation, the vacuum-breaking solenoid valve 24 is still in the OFF state.

When the pressure fluid-supplying solenoid valve 22 becomes the ON state, a pilot pressure is applied to the first ON/OFF valve 42 via the first pilot passage 58. The valve plug 72 is displaced in the rightward direction in FIG. 2 under the pilot pressure, so that the first ON/OFF valve 42 becomes the ON state. When the first ON/OFF valve 42 is in the ON state, then the compressed air introduced into the first passage 48 passes through the first ON/OFF valve 42, and the compressed air is supplied to the ejector 32.

In the ejector 32, the compressed air is jetted from the nozzle hole 28 toward the diffuser hole 30 to generate a negative pressure. The negative pressure is applied to the unillustrated suction pad via the suction passage 64 and the tube connected to the vacuum port 62.

Therefore, the suction pad makes contact with the workpiece in accordance with the operation of the unillustrated robot arm. When the suction pad attracts and contacts the workpiece under the negative pressure, the negative pressure is further raised. The negative pressure is detected by the pressure sensor 82 of the detector 34. A detection signal is transmitted from the pressure sensor 82 to the unillustrated controller. When the controller receives the detection signal from the pressure sensor 82, it is confirmed that the suction pad reliably attracts and holds the workpiece.

Next, an explanation will be made about a situation in which the negative pressure of the suction pad is shut off to separate the workpiece therefrom at a predetermined position after moving the workpiece by a predetermined distance.

The unillustrated controller transmits an OFF signal to the pressure fluid-supplying solenoid valve 22. As a result, the solenoid valve 22 becomes the OFF state, and thus the first ON/OFF valve 42 becomes the OFF state. Accordingly, the supply of the compressed air to the ejector 32 is stopped, and thus the application of the negative pressure from the vacuum port 62 to the suction pad is stopped.

On the other hand, the unillustrated controller transmits an ON signal to the vacuum-breaking solenoid valve 24 so that the solenoid valve 24 is in the ON state. When the solenoid valve 24 is in the ON state, a pilot pressure is applied to the unillustrated second ON/OFF valve via the second pilot passage 60. The valve plug 72 of the second ON/OFF valve is displaced under the pilot pressure, and the second ON/OFF valve becomes the ON state. When the second ON/OFF valve is in the ON state, the compressed air introduced into the first passage 48 is supplied to the vacuum port 62 through the second ON/OFF valve. As a result, the compressed air supplied from the compressed air supply port 36 passes through the vacuum port 62, and the compressed air is supplied to the suction pad. The suction pad stops attracting the workpiece and separates the workpiece therefrom.

When the suction pad separates the workpiece therefrom, the pressure of the suction pad changes the negative pressure to an atmospheric pressure. The pressure sensor 82 detects the atmospheric pressure and transmits a detection signal to the unillustrated controller to indicate the fact that the workpiece is separated. When the controller receives the detection signal, it is confirmed that the suction pad separates the workpiece therefrom. Thus, it is possible to reliably separate the workpiece from the suction pad.

In the embodiment of the present invention, the nozzle hole 28 and the diffuser hole 30 are integrally formed or formed in a single component, for example, by using a mold for molding resin, in the third block member 16 of the main body 20. Accordingly, it is possible to realize a small size and a light weight of the entire apparatus. Therefore, it is possible to effectively utilize the space in which the vacuum-generating unit 10 is installed.

It is a matter of course that a plurality of the vacuum-generating units 10 according to the embodiment of the present invention are connected in a row to construct a manifold.

Next, an explanation will be made while making comparison between an ejector 100 according to a modified embodiment of the present invention shown in FIG. 5 and an ejector 200 concerning a comparative embodiment shown in FIG. 6.

In the ejector 100 according to the modified embodiment, a nozzle hole 104 and a diffuser hole 106 are formed coaxially in an integrated manner in a single block member 102 composed of a resin material. A suction port 108 is formed between the nozzle hole 104 and the diffuser hole 106. A supply port 110 for supplying a pressure fluid to the nozzle hole 104 is formed on one side of the block member 102. A discharge port 112 for discharging the pressure fluid derived from the diffuser hole 106 is formed on the opposite side of the block member 102.

The ejector 200 concerning the comparative embodiment comprises two members of a block member 203 having a diffuser hole 202 formed therein, and a nozzle 210 formed with a nozzle hole 208 and connected to the block member 203 in an air-tight manner by the aid of an O-ring 206 in an opening 204 of the block member 203. A supply port 212 and the nozzle hole 208 are formed integrally in the nozzle 210. The nozzle 210 is inserted into the opening 204 of the block member 203 by the aid of a screw portion 214.

The block member 203 is formed with a suction port 216 which is communicated with the opening 204, and a discharge port 218 which is communicated with the diffuser hole 202 respectively.

Therefore, in the ejector 100 according to the modified embodiment, the nozzle 210 and the O-ring 206 are unnecessary as compared with the ejector 200 concerning the comparative embodiment. The ejector 100 according to the modified embodiment can be constructed by only the single block member 102. Therefore, the number of parts is reduced, and it is unnecessary to perform the operation for assembling the nozzle 210 to the block member 203. As a result, the ejector 100 according to the modified embodiment makes it possible to reduce the production cost by reducing the number of parts and reducing the number of assembling steps.

While the invention has been particularly shown and described with reference to preferred embodiments, it will be understood that variations and modifications can be effected thereto by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A vacuum-generating unit comprising:

a main body provided with a pressure fluid supply port connected to a pressure fluid supply source, a vacuum port connected to a suction mechanism, and a discharge port for discharging a pressure fluid supplied from said pressure fluid supply port to the outside; and

an ejector for generating a negative pressure based on said pressure fluid supplied from said pressure fluid supply port,

said ejector including a nozzle hole and a diffuser hole which are formed integrally in said main body.

2. The vacuum-generating unit according to claim 1, wherein said main body includes a plurality of block members composed of resin materials, and said nozzle hole and said diffuser hole are integrally formed in one of said block members.

3. The vacuum-generating unit according to claim 1, further comprising a pressure sensor for detecting said negative pressure derived from said vacuum port, wherein said pressure sensor is detachably and exchangeably connected to said main body by the aid of a tube joint.

4. The vacuum-generating unit according to claim 1, wherein said nozzle hole and said diffuser hole are arranged coaxially respectively, said nozzle hole including an orifice, and said diffuser hole having a diameter larger than that of said nozzle hole and a predetermined length in an axial direction.

5. The vacuum-generating unit according to claim 4, wherein said discharge port is formed at an exit end of said diffuser hole, and a silencer is provided to discharge said pressure fluid supplied from said discharge port to the outside.

6. The vacuum-generating unit according to claim 1, wherein a suction passage is formed between said nozzle hole and said diffuser hole.

7. The vacuum-generating unit according to claim 1, wherein said vacuum-generating unit is connected in a row to another vacuum-generating unit to construct a manifold.