GB2300651A - Workpiece pick-up device - Google Patents

Abstract

A pick-up device for use in association with an automatic sewing machine has a perforated surface which acts as a suction pad for adhesion to a flat workpiece, the perforated surface including at least two respectively different perforation configurations. A first tack area (102) of the perforated surface has a relatively close perforation configuration to ensure a resilient and strong adhesion of the workpiece and is surrounded by a support perforated area (104) of less closely spaced perforations and so less adhesion strength. The invention avoids the possibility of more than one workpiece being picked up at the same time.

Description

wOxEPIBCB PICK-UP D = DEVICE This invention is concerned with workpiece pick-up devices for picking up flat workpieces from a surface, and also with automatic sewing machines comprising automatic loading and/or unloading devices including such pick-up devices.

Pick-up devices for such purposes are well known comprising suction heads by which a workpiece can be engaged and picked up. Such pick-up devices work satisfactorily where firstly the position and orientation of the workpiece are known and secondly where the configuration of the workpiece is known, so that the suction heads are provided only where they will engage the workpiece; otherwise, either the suction heads will attempt to engage the surface supporting the workpiece or there will be a significant loss of suction in those regions where the suction heads do not engage the workpiece.In order to overcome this problem, it has been proposed to provide each suction head with a ball valve or the like whereby only those suction heads which engage the workpiece will be actuated, but such valves add to the expense of the suction heads and have not proved always to be reliable, especially when subjected to continuous use.

It is thus one of the various objects of the present invention to provide an improved workpiece pickup device for picking up flat workpieces from a surface, which device can operate satisfactorily regardless of the orientation and/or location of the workpiece and of the size and configuration thereof.

In accordance with the present invention there is provided a pick-up device for flat workpieces, the device including a perforated surface upon which in use a workpiece is drawn by a vacuum in order to provide adhesion between the perforated surface and the workpiece, the pick-up device furthermore including lift means in order to bring the perforated surface into contact with the workpieces, the device characterised in that the perforated surface has at least two distinct areas of respectively different perforation configuration, a first tack, perforated area having a close perforated configuration in order to provide a relatively strong adhesion force between the workpiece and the perforated surface and a second perforated area about said first perforated area having a perforation configuration to provide a relatively weaker adhesion force between the workpiece and the perforated surface and so ensure only one workpiece is picked up by the device.

Further in accordance with the present invention there is provided a pick-up device for flat workpieces, the device including a air suction element arranged to draw air from a housing having a perforated surface and so ensure when a workpiece is brought into contact with the perforated surface the workpiece adheres to the perforated surface characterised in that the perforated surface has a differential perforation pattern configured about an edge of the housing, the perforation pattern comprising at least two perforation areas with respectively different perforation configurations, a first perforation configuration designated a tack area having relatively closely spaced perforations in order to provide the most resilient adhesion strength between the workpiece and the perforated surface, said tack area being positioned to ensure said tack area impinges in the pick-up device upon the workpiece irrespective of its size.

Preferably, the tack area of the perforation pattern is rectangular.

Preferably, the perforations may be arranged in rows or concentric arcs or any other regular spacing within each area.

Preferably, all the perforations in respective areas are of the same size. The perforated surface may be flat or slightly curved. The perforated surface may be slightly inclined or bowed from front to back to facilitate edge alignment. The perforations may be simply round or oval or defined to draw the workpiece into position. The edge of the housing may have a lip substantially less than the thickness of a single expected workpiece. The perforated surface may include alternate additional adherent apparatus including provision for electro-adhesion, which may be activated for a larger workpiece size or as necessary. It will be understood that shuttering may be provided within the perforation surface in order to alter adhesion strength as necessary.

Alternatively, a pick-up device incorporating a perforated suction pad having differential perforation configurations in at least two areas of the pad in order to pick up only one flat workpiece.

For picking up a workpiece using the illustrative device, the housing is mounted for movement between a pick-up position, in which the workpieceengaging surface can engage a workpiece placed upon a support surface, and a release position, in which the drawing of air as aforesaid is discontinued. Moreover, it has been found particularly advantageous that the support surface is perforated, thereby enabling a satisfactory air flow to be drawn through the perforated workpiece-engaging surface even when said surface is in contact with the support surface. Similarly, the illustrative pick-up device may also comprise a further support surface onto which a workpiece can be released when the housing is in its release position; it will be appreciated that said further support surface need not be perforated.

In order to ensure rapid release of a workpiece by the pick-up device a baffle or butterfly type valve is provided in the suction pipe. Thus, the inherent build up and degradation of the vacuum when the vacuum pump is switched on and off respectively is eliminated.

The illustrative pick-up device has been found particularly suitable for use in an automatic sewing machine comprising a sewing head and workpiece supporting means for supporting the workpiece to be sewn, between which means and the sewing head relative movement can be effected along two co-ordinate axes to cause the workpiece to follow a desired path relative to the sewing head. Such a machine is hereinafter described in detail, to illustrate the present invention in its machine aspects, this illustrative machine comprising an automatic workpiece loading device and also an automatic workpiece unloading device, each of which includes a pick-up device of the type referred to above.

In the illustrative machine, furthermore, the further support surface onto which a workpiece to be sewn can be released by the pick-up device of the workpiece loading device, when in its release position, is provided by two plates one of which is retractable beneath the other but is resiliently urged so as to cause a portion thereof to project from beneath the other. In using such an arrangement, with a workpiece released on to said surface in such a manner that said workpiece is supported at least partially by the projecting portion of said one plate, when the support surface is advanced towards the workpiece supporting means, the advancing movement of the one plate is arrested by stop means (forming part of the workpiece supporting means) while the movement of the other plate continues. In this way the workpiece is reliably advanced onto the workpiece supporting means.

Preferably, moreover, said other plate has a highfriction workpiece-supporting surface, forming part of the said further support surface.

The illustrative machine is generally of a type as described in EP-A-0 500 862, in which the workpiece supporting means forms part of a workpiece clamping and feeding arrangement by which a workpiece can be fed relative to the sewing head along one of said co-ordinate axes, said arrangement also being mounted for bodily movement relative to the sewing head along the other of said axes. In such machine, moreover, the loading device is arranged at a workpiece feeding station at which the workpiece clamping and feeding arrangement can receive from said further support surface a workpiece released from the pick-up device of the loading device as aforesaid.It will of course be appreciated that by advancing the workpiece using the two-plate arrangement referred to above, the workpiece clamping and feeding arrangement can readily grip a leading portion of the workpiece and then feed it into an appropriate position for the start of a sewing operation.

More particularly as described in the aforementioned EP-A, furthermore, the illustrative machine comprises also a workpiece "recognition" station, at which a camera is provided by which the peripheral outline of the workpiece can be progressively detected as the workpiece is fed by the workpiece clamping and feeding arrangement across a back-lit aperture. Using such an arrangement, each workpiece can be recognised and its location and orientation thus be determined, prior to the workpiece clamping and feeding means being moved bodily relative to the sewing head to bring the workpiece to a start position for a sewing operation to be performed thereon.

The above and other of the various objects and several features of the present invention will become clearer from the following detailed description, to be read with reference to the accompanying drawings, of the illustrative device and the illustrative machine. It will of course be appreciated that the illustrative device and the illustrative machine have been selected for description merely by way of non-limiting example of the invention.

In the accompanying drawings: Fig. 1 is a plan view, with parts broken away, of the illustrative machine, showing a loading and an unloading device thereof, each comprising the illustrative pick-up device; Fig. 2 is a plan view of a perforated surface or suction pad in accordance with the present invention; Fig. 3 is a schematic graphical representation of probable variation in adherent strength S across the surface or pad illustrated in Fig. 1 at line AA; Fig. 4 is a schematic cross section illustrating a baffle valve position in accordance with an aspect of the present invention; and Fig. 5 is a schematic plan view of a section of an alternate perforated surface including a pickup enhancement layer.

The illustrative machine, which, as already mentioned, is generally similar, except as hereinafter described, to the machine described in EP-A-O 500 862, comprises a base 10 on which are supported, by means of four supports 12 arranged one at each corner of the base, two transverse carrier rods 14 on which is supported, for movement therealong, a carriage generally designated 16.

The carriage 16 comprises two end blocks 18 connected together by two racks 20 (one only shown in Fig. 1) each meshing with a drive gear 22 secured on the output drive shaft of a stepping motor 24 mounted on the base 10. The two stepping motors 24 are driven synchronously with one another and thus serve to drive the carriage 16 transversely along the carrier rods 14.

On a rearward extension 30 of the base is mounted a sewing machine generally designated 32; said machine is conventional and has an arm projecting forwardly over the path of the carriage 16 such that the path of a needle of the machine lies on a line which is parallel with the carrier rods 14 and disposed centrally thereof. The point at which the needle penetrates the path of the carriage is indicated by the letter N in Fig.

1 (hereinafter "the needle penetration point"). The machine is provided with a shaft encoder (not shown) by which movement of the carriage 16 under the control of the stepping motors 24 can be effected in timed relation with reciprocation of the needle.

The carriage 16 supports workpiece supporting means of the illustrative machine, said means forming part of a workpiece clamping and feeding arrangement comprising two sets of rollers 46, each set comprising four upper and four lower rollers. (In the aforementioned EP-A, the lower rollers are referred to by the reference numeral 40.) The lower rollers (not shown) of each set are mounted in the end blocks 18 for rotation therein, while the upper rollers of each set are supported in a lifting frame 48 for heightwise movement relative to the end blocks 18, and thus relative to the lower rollers, each of the upper rollers being independently mounted in a bearing block 50 spring-urged downwardly thus to urge each upper roller against its associated lower roller.For raising the lifting frame 48, furthermore, four piston-and-cylinder arrangements 52 are provided, operable synchronously with one another, said arrangements being mounted on the carriage 16 and connected with the lifting frame via pivoting levers 54.

The rollers 46 of the two sets are synchronously driven, each set by means of a stepping motor 60; the two motors are arranged diagonally opposite one another on the carriage 16. Each stepping motor 60 is operatively connected to its associated rollers 46 by timing belts and pulleys; the mounting of the stepping motors is such that heightwise movement of the lifting frame 48 does not affect the driving relationship between the motor and the various pulleys.

As can be seen from Fig. 1, an aperture 42 is provided between the two sets of rollers, said aperture extending parallel to the path of the carriage 16 and aligned with, and accommodating, the needle penetration point N. Also aligned with the aperture is a camera 70 (indicated in chain-dot line in Fig. 1) mounted above the carriage 16 and a lamp 72 arranged beneath the carriage, also in alignment with the aperture 42, thus to backlight it. The camera 70 comprises an array of cells by which, in a progressive linescan operation, the peripheral outline of a workpiece being fed across the aperture can be progressively detected.

Whereas in the illustrative machine, the workpiece clamping and feeding arrangement comprises two sets of rollers, it will be appreciated that each set of rollers may be replaced by a belt arrangement comprising two opposed belts between which a workpiece can be clamped and fed, or any other suitable clamping and feeding arrangement.

For feeding workpieces automatically to the workpiece clamping and feeding arrangement of the illustrative machine, and also for removing workpieces after they have been operated upon by the machine, the machine comprises an automatic workpiece loading device generally designated 60 and also an automatic unloading device generally designated 62, respectively. Each of these devices incorporates an illustrative pick-up device, the devices being generally of the same construction, and therefore one only, viz. the pick-up device of the automatic loading device 60, will now be described with reference to Figs. 1 and 2, although differences between the two devices 60,62 will also be indicated.

It will be appreciated that instead of rollers 46 a set of friction belts could be used.

The illustrative pick-up device comprises a housing 74 which is fixedly mounted by a bifurcated bracket 76 at the lower end of a piston rod 78 of a piston-and-cylinder arrangement 80 which is in turn supported by an arm 82. The housing is thus mounted for heightwise movement in relation to the arm 82. The arm 82 is in turn mounted on a column 84, for pivotal movement about the axis thereof, between a pick-up position (as shown in Fig. 1), in which it overlays a support plate 86 on which a workpiece to be picked up can be supported, and a release position in which the housing is in opposed relationship with a further support plate 88, details of which will be referred to hereinafter.

(In Fig. 1, the housing 74 of the pick-up device of the automatic unloading device 62 is shown in its release position, in which it is in opposed relationship with a further support plate 88A of said device, and is thus shown clear of its pick-up position, in which it can pick up a workpiece located on a support plate 86A of said device.) The column 84 is supported by a frame 90 which in turn is mounted on the base 30 of the machine. Any suitable means, e.g. a piston-and-cylinder arrangement (not shown) may be provided for effecting pivotal movement of the arm to move the housing 74 between its pick-up position and its release position.

Within the housing 74 is provided a chamber 92, a lower wall portion 94 of which is perforated and the outer surface of said wall provides a workpiece-engaging surface 96 of the pick-up device. It will be appreciated that suction pads incorporating perforated surfaces have been known before in pick-up devices, however, there is an inherent problem of ensuring that there is sufficient adhesive force provided by the vacuum created in the suction pad to lift a workpiece whilst also ensuring unless the pad is coupled to the whole of a workpiece that only one pad is picked up. In the shoe industry it is not uncommon for shoe upper components to have various shapes and sizes and thus if a pick-up device perforated surface is to have wide utility the pad must be significantly larger than some component sizes.With a single suction capacity across the whole pad area a problem is created in that there is a tendency to lift or attempt to lift several shoe components at once through the perforation not in contact with the flat workpiece or shoe component.

In the present invention as can be seen in Fig.

2 the problem of multiple component pick up is eliminated by providing differing perforation configurations in the perforated or suction pad surface 101. In a tack area 102 of the pick-up device there is provided a relatively high perforation density or close configuration spacing and thus there is a high vacuum adherence of a workpiece 103 indicated in outline. About the tack area 102 there is a second support pick-up area 104 having a looser perforation configuration or spacing and so lower adhesion strength. It will be understood that the tacking area 102 resiliently adheres a pick-up perforated surface 101 to the workpiece 103 whilst support for such pick-up is provided by the support area 104. However, the relatively strong and powerful vacuum adhesion created in the tack area 102 is limited in extent and for the most part is totally sealed by the workpiece 103.

Thus, the strong drawing or adhesive power available to lift workpieces from a stack below that contacted by the pick-up device is reduced and so the inherent possibility of multiple workpiece pick-up is reduced.

It has been found that perforations of 2mm diameter are appropriate with the perforations in the tack area 102 having a 12mm spacing and the perforations in the support area 104 having a spacing of 24mm.

However it will be understood that other configurations could be used dependent upon desired performance.

Fig. 3 shows a schematic graphical representation of expected adhesion strength S across the line AA illustrated in Fig. 2. It can be seen that the most powerful adhesion is provided in the tack area 102 whilst a proportionately lower adhesion strength is present in the support areas 104. It will be understood by variation of perforation size and spacing and shape that the relative strengths between the tacking area 102 and support area 104 can be varied as a matter of design choice. Thus, for example, if a workpiece of relatively high central density were to be picked up the adhesion strength could be maximised in that central region whilst lower adhesion strength could be affected in the surface 101 by suitable variation in the perforation configuration.

Typically, the vacuum or suction power of the pick-up device can be provided by an industrial vacuum cleaner such as the NILFISK c80GST. Such a vacuum cleaner would be coupled to the pick-up device using a flexible pipe. It has been found that for a pick-up perforated pad of 320mm by 240mm with perforations as defined above then a suction power of 165 W, airflow of 35 litres/sec and a vacuum of 18,500 Pascals is adequate.

It will be understood wherever vacuum pumps are used there is an inherent working up and working down when the vacuum pump is switched on or off due to the motor of the pump moving from a static non-rotating to a fully powered rotation speed. With a pick-up arrangement in accordance with the present invention such a working up and, more importantly, working down in vacuum created in the pick-up would be inconvenient for release of the workpiece as appropriate. Thus in accordance with the present invention and as illustrated in Fig. 4, a baffle valve 110 is provided in order to provide an almost instant release of the vacuum in the housing incorporating the perforated panel 101. Thus, the adhesion strength will disappear almost immediately and the workpiece can be released consistently.The valve 110 is simply a paddle mounted on a pivot coupled to the control system such that to release the vacuum the paddle is moved to the position shown in Fig. 4 and thus the volume 111 in the housing is no longer coupled to the vacuum pump 112 and so the unsealed perforations in the surface 111 rapidly equalized pressure between the volume 111 and the exterior of the housing and the workpiece is thus no longer held against the perforated surface 111.

In order to reconnect the vacuum pump 112 to the housing and thus the volume 111 the valve 110 is simply rotated about its pivot in order not to present any further sealing obstruction between the vacuum pump 112 and the housing. Thus, the volume 111 can again be evacuated and a partial vacuum created within the housing due to the limited air flow through the perforation particularly when partially sealed by a workpiece 103.

In order to ensure a clean pick-up of a workpiece from the support plate 86 (86A), the surface is provided by a perforated plate.

In the operation of the pick-up device the housing 74 is lowered towards the support surface 86 (86A) and a workpiece on said surface can then be picked up and held against the workpiece-engaging surface 96 by suction or vacuum. The housing 74 is then raised away from the surface 86 (86A) by operation of the piston-andcylinder arrangement 80 and then is swung to its release position, and, in said position, is lowered towards the further surface 88 (88A) at which time the vacuum is released. Thereafter the housing 74 is then once more raised and returned to its pick-up position in opposed relation with the surface 86 (86A).

In order to ensure that the workpiece placed upon the further surface 88 will be fed into the workpiece clamping and feeding arrangement of the machine reliably, the support surface 88 of the automatic loading device 60 is provided by two plates 108,110. The plate 108 is mounted on a block 112 which is supported on the output of a so-called rodless piston-and-cylinder arrangement 114 supported on a flange 116 mounted on the base plate 30. Thus, operation of the arrangement 114 is effective to move the plate 108 towards and away from the workpiece clamping and feeding means.

Mounted on the underside of the plate are two blocks 118 in which are captive two slide rods 120, on which in turn are mounted, for sliding movement, two blocks 122 secured to the underside of the plate 110.

Moreover, acting between the blocks 118 and 122 are springs 124 which thus serve to urge the plate 110 towards the workpiece clamping and feeding means. For guiding the plate 110 on the underside of the plate 108, furthermore, guide blocks 126 are mounted on the edges of the plate 110 and provide a groove which accommodates the edges of the plate 108.

When the support surface 88 is in its position shown in Fig. 1, the plate 110 projects from beneath the plate 108 to an extent determined by the spring 124.

When the surface is then moved towards the workpiece clamping and feeding means, the plates move together until a forward edge of the guide blocks 126 engage stop members 128 mounted on the work table 44, thereby arresting the movement of the plate 110. The movement of the plate 108 on the other hand continues until the stroke of the arrangement 114 is completed. By depositing a workpiece to be operated upon in a forward position in which it overlies both the projecting portion of the plate 110 and also part of the plate 108, upon retraction of the projecting portion of the plate 110 as aforesaid the workpiece is effectively urged forward into the workpiece clamping and feeding means and is thus reliably fed thereto.

For enhancing the feeding of the workpiece, moreover, and also to avoid the workpiece shifting on the support surface 88 e.g. by reason of any vibration of the machine, the portion of the support surface provided by the plate 108 is covered with a friction material, e.g. a sandpaper, emery cloth or the like.

The support surface 86A of the automatic unloading device 62 of the machine is mounted for movement in a similar manner to that just described, but in this case the support surface is provided by a single plate member. Moreover, since this plate is at the pickup station of the housing 74, it is of course perforated.

It will be understood that it is the inherent problem solved by the present pick-up device that a range of sizes and weights must be accommodated. Thus, to pick-up small but heavy pieces a high hole density is required, but if such density is located over the whole pick-up area then the high air flow through holes not covered by the picked-up work place breaks the holding vacuum. Consequently, more of the pick-up area has a low hole density which in association with a small high density hole area is sufficient for large pieces.

It has been found that there may be a whistle problem due to the flow through the holes so a layer of acoustic wadding 200 may be added to dampen such irritation. The depth of this wadding may be up to half the housing height.

Figure 5 shows a partial section of a pickup surface 101 in enhanced detail but similar to that shown in Figure 2. To further enhance the strength of suction adhesion between a workpiece 501 (shown in outline) and the surface 101, a resilient upper layer 52 of perforated material is provided. This layer 52 gives enhanced pickup strength and becomes slightly compressed as the workpiece is held upon the surface 101. This pickup enhancement layer 52 may be made of a range of resilient materials including synthetic rubbers.

In addition to being resilient, the layer 52 includes holes 53 larger than the underlying holes 102, 103. By provision of this air flow funnelling effect of holes 53 and holes 102 or 103 there is further enhancement of adhesion strength between the workpiece 501 and the surface 101. The workpiece 501 may distort into the holes 53.

Claims (12)

Claims:

1. A pick-up device for flat workpieces, the device including a perforated surface upon which in use a workpiece is drawn by a vacuum in order to provide adhesion between a perforated surface and the workpiece characterised in that the perforated surface has at least two distinct areas of respectively different perforation configuration, a first tack area having a relatively close perforation configuration in order to provide a strong adhesion force between the workpiece and the perforated surface and a second support perforated area about said first perforated area having a loose perforation configuration to provide a weaker adhesion force between the workpiece and the perforated surface and so ensure only one workpiece is picked up by the device.

2. A pick-up device for flat workpieces, the device including an air vacuum element arranged to draw air from a housing with a perforated surface and so ensure when a workpiece is brought into contact with the perforated surface it adheres to it and so may be picked up, the device characterised in that the perforated surface has a differential perforation pattern configured about an edge of the housing, the perforation pattern comprising at least two perforation areas with respectively different perforation configurations, a first tack perforation area having relatively closely spaced perforations to ensure a most resilient adhesion strength between the workpiece and the perforated surface, the said tack area being positioned within said perforated surface to ensure it impinges upon the workpiece irrespective of the workpiece size.

3. A pick-up device according to Claim 1 or Claim 2 wherein the tack area perforations have a spacing of half that of the other perforation areas of the perforated surface.

4. A pick-up device as claimed in Claim 1, 2 or 3 wherein the perforations are arranged in rows or concentric arcs throughout respective perforation areas of the perforated surface.

5 A pick-up device as claimed in any proceeding claim which the perforated surface has a resilient contact layer for contact wih workpieces.

6 A pick-up device as claimed in any proceeding claim when the perforated surface is coupled to an upper layer including holes larger than those in the perforated layer but in alignment with them.

7. An automatic sewing machine comprising a sewing head, workpiece supporting means for supporting a workpiece to be sewn, between which workpiece and the sewing head relative movement can be effected along two co-ordinate axes to cause the workpiece to follow a desired path relative to the sewing head, and an automatic workpiece loading device including a pick-up device according to any one of Claims 1 to 6, wherein the further support surface is provided on to which a workpiece to be sewn can be released by the pickup device when in its release position, said surface being provided by two plates one of which is retractable beneath the other but is resiliently urged so as to cause a portion thereof to project from beneath the other, the arrangement being such that, with a workpiece released on to said surface in such a manner that said workpiece is support at least partially by the projecting portion of said one plate, the plates are advanced together towards the workpiece supporting means, the latter comprising stop means by which such movement of the one plate is arrested while the movement of the other plate continues, whereby the workpiece is advanced on to the workpiece supporting means.

8. A machine according to Claim 7 wherein said other plate has a high-friction workpiece-supporting surface, forming part of the said further support surface.

9. A machine according to Claim 7 or Claim 8 wherein the workpiece supporting means forms part of a workpiece clamping and feeding arrangement by which a workpiece can be fed relative to the sewing head along one of said co-ordinate axes and which is mounted for bodily movement relative to the sewing head along the other of said axes, and wherein the loading device is arranged at a workpiece feeding station at which the workpiece clamping and feeding arrangement can receive from said further support surface a workpiece released from the pick-up device as aforesaid.

10. A machine according any one of Claims 7 to 9 also having an automatic workpiece unloading device including a pick-up device according to any one of Claims 1 to 6.

11. An automatic sewing machine comprising a sewing head, workpiece supporting means for supporting a workpiece to be sewn, between which workpiece and the sewing head relative movement can be effected along two co-ordinate axes to cause the workpiece to follow a desired path relative to the sewing head, and an automatic workpiece unloading device including a pick-up device according to any one of Claims 1 to 6.

12. An automatic sewing machine as claimed in any of Claims 7 through to 11 wherein a baffle valve is provided in order to ensure almost immediate release of a workpiece.