A ROBOT END EFFECTOR

Abstract: A robot end effector (10) for holding a fabric workpiece (64) against a working surface (74) has a rigid backing member (11), a facing strip material (13) arranged to contact the workpiece (64) around its periphery and a resilient intermediate layer (12) between the backing member (11) and the facing strip material (13), the width (w) of the facing strip material (13) being no greater than the thickness (t) of the intermediate layer (12).

Description: A robot end effector BACKGROUND OF THE INVENTION This invention relates to a rooot enα effector for Dressing flexible worκpιeces, e.g. of fadric, onto and moving such workpieces over, a flat working surface. A known robot end effector is shown in WO 86/03948 and comprises a sandwich construction consisting of a bacκιng sheet, a facing sheet for gripping tne workpiece ana a resilient intermediate layer for accommodating irregula*"- ities, sucn as seams or uneαual multi-plies cf faoπc parts in εuDassembl les and local imperfections in tne working surface. The Packing sheet is U-snapeα ans the resilient intermediate layer and facing sheet are similarly snaoed. In addition the thickness of the intermediate layer is less than the width of the facing sheet whicn nas a relatively large surface area. Altnougn tms known enc effector performs adequately for its Dreαetermineα task, i.e. gripping a workpiece during an unfolαing ooeration ana moving tne worKDiece along a αe÷ined patr.. its relative Du ' r renders it unsuitable for performing movements at tr.e mgneεt soeeαs reαuireα for moαern processing. It may be consiαered αesirab e fc r a sanαwicr, con¬ struction enα effector to have its packing sneet, facing sneet ana intermediate layer all of the same size as a workpiece to be manoeuvred. However, this may result m the end effector being too Dulky and having too high an inertia for effective, speedy manoeuveπng. Furthermore, such a "solid" construction will result in air αisturϋance as an end effector is moved down on to a workpiece whicn will cause the latter to be displaced prior to contact Detween the effector and workpiece if tne speed of movement of the enα effector is not to be reαuceσ to a slow ao- proach. Tne weight of an enα effector can Pe reαuced DY only contacting a worκpιece around its periphery. This is achieveα by employing peπpneral strips of facing sneet. When employing only strips of facing sheet the form of the resilient intermediate layer is important. Ideally it should be easily compressed, e.g. made of a soft foam material. However such easily compressed material tends to undergo shearing movement as the end effector moves a workpiece over a work surface. To some extent this tenden- cy cf the intermediate layer to undergo shearing movement can be counteracted by increasing the width cf the inter¬ mediate layer. Sucn a solution is shown in WO 86/0394-6 in which the width of each strip of intermediate layer is consiαerably greater than its tmckness. However this increased width of the strip-form intermeαiate layer increases the bulk of the end effector. The present invention seeks to provide an improve: form of robot end effector having a sanαwich construction. SUMMARY OF THE INVENTION According to tne present invention a ropot end effec¬ tor comprising a rigid bacκιng member. facing strip mater¬ ial arranged to contact a worKoiece around, or aα.iacent tc. the periphery cf the workpiece and a resilient intermediate layer petween the backing member and the facing stπc material, is characterised in that tne width cf the facing strip material is no greater than the thickness of tne intermediate layer. Conveniently the resilient intermeαiate layer requires a force of from 80 - 120 kg/ , to compress it 1mm. Typically the intermediate layer is a foam material, e.g. a polyurethane foam such as that marketed by Dunlopillo unαer the trade name "DHR 264 Dunloflex' - i.e. a high resilient grade polyurethane foam. Typically the resilient intermeαiate layer nas a thickness of from 20mm to 30mm, e.g. 25mm. Typically the facing strip material has a width of less than 20mm. e.g. 15mm. Suitably the width of the intermediate layer where it is adjoined to the backing plate is greater than tne width of the intermediate layer where it is adjoined to the facing strip material. Conveniently, for the peripheral lengths of facing strip material, the intermediate layer nas a cross-section such that its inwardly facing siαe is at an angle, e.g. 45° , tc the backing plate. If tne end effector is proviαed witn inner lengtns cf strip materia " i i.e. lengtns disposed inwardly of the peπonera lengths : cr outer lengths of strip material ι l .e. lengths αiεoosec outwardly of peripheral lengths positioned slightly * nwarα- ly of a worκpιece periphery), the intermeαiate layer may have a cross-section of trapezoidal form. the two faces Deir.g αisposed at eαual angles, e.g. 45° . tc tne packing o1ate. ^re^e a y the end effecto r is cc' ceo witn a c ura - -. > of wιnαow-lικe apertures. Conveniently the πgiα packing plate comprises a ' . ightweignt composite panel such as an aluminum noneycomP structure sanαwiched Detween facing sheets, e.g. of a u- minum. An example of such material is 0.5 men (12.5mm. 1 tmck "Aerolam". The packing plate material shoulα be cnosen for its rigidity and lightness. Tne facing sheet conveniently comprises an elect r ical¬ ly conductive sheet, e.g. electrically conductive rupber sneet, typically having a thickness of approximatel 1mm. Suitably weights are provided around tne of the enα effector. BRIEF DESCRIPTION OF THE DRAWINGS Emboαiments of the invention will now oe αeεcriped, DV way of example, with reference to the accompanying αraw- ings, in which Figure 1 is a schematic exploded view of a first embodiment of a robot end effector according to tne inven¬ tion attached to a robot arm. Figure . 2 is a view from below of a seconα emooαiment of a robot end effector accorαing to tne invention. Figure 3 is a sectional view, on an enlargeα scale, taken on the line III-III of Figure 2, Figure 4 is a view from below of a tmrα e ocdiment of a robot end effector according to the invention, Figure 5 is a view from below of a fourth emc-odiment of a robot end effector accorαing to the invention, Figure 6 is a view from Pelow of a fiftn emooαiment of a robot enα effector accorαing tc the invention. Figure 7 is plan of an attachment accorαing to anothe* ** aspect of the invention for an end effector for clamping a workpiece part to be sewn by means of a gripper pac, and Figure 8 is a view in the direction of arrow A in Figure 7. DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 shows one emboαiment cf a rocot end effector 1 accorαing to the invention attacneα to tne enα of a robot arm 2. Tne robot arm 2 can be rotateα anc moved in x, y. z ana θ airectionε. The ena effector i comprises c a πgiα backing member 3, facing strip material 4 for contacting a workpiece to slide it across a horizontal work surface and a resilient intermediate layer 5. Tne memoer 3 has window-like openings 6 formed therein to enable escape of ai r as the end effector 1 is lowereα onto a workpiece supported on a work surface. The width w of the strip material 4 is less than the thickness t of the intermediate layer 5. Figure 2 and 3 show the construction of another emoodiment of robot end effector 10 in greater detail. The end effector 10 is intended for handling or gripping tnree different sizes of waist slip faoπc having different waist perimeters but the same deptn or length. Tne end effector 10 comprises a lightweight, rigid oacκιng plate 11. a resilient intermediate layer 12 and a facing sneet 13 of strip like form bonded together to provide a sandwich construction. The backing plate 11 is typically 0.5 inch (12.5mm) thιcκ and of composite form comprising a cellular, e.g. honeycomb. structure 14 sarrdwicneα between facing sheets 15 anc 16. A suitable material for tne backing plate 11 s sole unαer the traαe name " Aerolam and con¬ sists of an aluminum noneycomo structure sandwiched Detween aluminum facing sheets. The resilient intermeαiate layer 12 suitably comprises a high resilient graαe polyuretnane foam typically having a thickness of from 20mm to 30mm, e.g. 25mm. A suitable foam material is marketed by Dun- lopillo unαer the traαe name "DHR 264 Dunloflex " . As can be seen from Figure 3, the intermeαiate layer 12 has a trapezoidal cross-section with its inwardly facing surface angled at an inclined angle (e.g. 45°) to the backing plate 11. The purpose of this angling is to increase the resis¬ tance of the layer 12 to withstand a shearing movement during traverse of the end effector 10 across a work surface. The facing sheet 13 is conveniently an electπ- cally conductive flexible sheet of friction material, e.g. a rubber sneet containing electrically conductive par¬ ticles. Ey using an electrically conductive sheet 12, static electricity is effectively discharged. The sneet 12 typically has a thickness of 1mm and eacn strip has a width (w) no more than 20mm, e.g. 15mm.. Thus the wiαth of each strip of the sheet 13 is no greater than the thickness (t) of the intermediate layer 12. The backing plate 11 has a plurality of window-like openings 18 formed therein to allow escape of air as tne end effector 10 is lowered towards a workpiece 64 supported on a flat working surface 74. A mounting hole 19 is also formed in the plate 11 to enable the end effector 10 to oe secured to the end of a robot arm (not shown. with tne aic of bolts (not shown, entered into holes 20. Tne intermeαiate layer 12 and facing sheet 13 are arranged stripwise around the entire periphery of the backing plate 11 along top and bottom regions 21 and 22, respectively, and along side regions 23 and 24. Two further strips are spaced inwardly of the side regions 23 and 24 along regions 25 and 26, respectively. In use tne regions 25 and 26 are used for manoeuvering a " small" size waist slip workpiece, the regions 23 ana 24 are useα for manoeuvering a "large" size waist slip workpiece ana regions 23 and 26 ( or regions 24 and 25.' a e used for manoeuvering a "medium" size waist slip. The end effector 10 has a weight of 2.2kg and the total surface area of the facing sheet 12 is 64200 mm". The extra load on the end effector 10 αue to the robot coupling is 0.2 kg. In order to obtain efficient workpiece control an extra load of 2.25 kg reαuires to be applied to the end effector 10. In theory this loading could be applied to the end effector by means of the robot arm. However "this centrally applied loadin'g would tend to benα the entire end effector. The preferred methoα of loading the enα effector 10 is therefore to apply weights 28 around the entire periphery of the upper surface of tne backing plate 11. With the weights 28 added, the load/unit area of ά tne facing sneet 13 is 72.4 kg/m " Otner designs of robot end effectors 3C , 40 and 50 for differently shaped workpieces are shown in Figures 4. 5 and 6, respectively. The end effectors 30, 40 and 5C are basically similar in construction to the end effector 10 and where appropriate similar parts have been identified by similar reference numerals. In the enα effector 40 window¬ like apertures are not shown and, in the end effector .50, window-like apertures and a mounting aperture are not shown. In practice, however, such apertures would be proviαeα. Tne main additional features of the enα effectors 30 ana 50 are the strips 31 - 38 in end effector 30 ana tne strips 51 and 52 in the end effector 50. These strips enable αifferent sizes of workpiece to be gπppeα. For example, with end effector 30, the strips 31 - 38 would be employeα to grip a workpiece at spaceα locations along side eαges of the workpiece. F igu* * es 7 and 8 show an attacnment αevice 50 wmch ma/ oe attached to an end effector 6 * . Tne αevice 6C comprises a gπpper pad 62 for gripping scal opeα lace 62 to oe sewn to a faoπc piece 64, the stitcn line ceing mαicated py reference numeral 65. The pad 62 is mounted at one end of a noπzontal arm 66 connecteα to a vertical shaft 67 journal led for sliαing and pivoting movement in a journal 68 attached to the end effector 61. Tne top of tne εnaft 67 is connected to a further horizontal arm 69 wmch, in the position snown in Figure 7, rests in a slot 70 forming part of a cam surface 71 of a cam member 72. A spring 73 urges the arm 69 into the full line position shown in Figure 7. In use, an upwardly sloping part in front of tne sewing head of a sewing machine (not shown) moves relatively to tne attachment device 60 along tne stitch line 65 and engages beneath the arm 66. As tne sewing macmne part advances, the sloping part thereof δ lifts the arm 66 so tnat the arm 69 is moved out of tne slot 70 and the pad 62 is raised clear of the lace 63. The sewing machine part, as it advances along the stitch line 65, pivots the arm 66 about the axis of the shaft 67 so that the pad 62 is swung clear of the stitcn line 65 and the arm 69 is moved along the cam surface 71. Finally the sewing machine part clears the arm 66 and the spring 73 pivots the arm back into the slot 70, the gπpper pad 62 swinging back over the lace 63 before finally dropping back down into contact with the lace in its original clamping position on. the now sewn-on lace. A number of sucn devices 61 would be proviαed on an end effector, the pads of the various end effectors being moved sequentially out of contact and then back into contact with the lace as the sewing progresses along tne lace. The attachment devices 60 may be provided on end effectors according to the present invention. The attachment αevice shown in Figures 7 and 8 can be used with any design of end effector or gripping device and not just one having the features set out in the following claim 1.

Claims: CLAIMS 1. A robot end effector comprising a rigid backing member, facing strip material arranged to contact a work- piece around, or adjacent to, the periphery of the work-" piece and a resilient intermediate layer between the backing member and the facing strip material, charac¬ terised in that the width of the facing strip material * is no greater than the thickness of the intermediate layer. • 2. A robot end effector according to claim 1, further characterised in that the resilient intermediate layer is maαe of a material which requires a force of from 80 to 120 2 kg/ , to compress it 1mm. 3. A rooot enα effector according to claim 1, further characterised in that the intermediate layer is maαe of a foam material . 4. A robot end effector according to claim 3, charac¬ terised in that the foam material is a high resilient grade of polyurethane foam. 5. A robot end effector accorαing to claim 1, cnarac- tensed in that the width of the intermediate layer where it is adjoined to the backing member is greater than tne width of the intermediate layer where it is adjoined to the facing strip material. 6. A robot end effector according to claim 5. further characterised in that the intermediate layer has a cross- sectional shape such that an inwardly facing side thereof is at an inclined angle to the backing plate. 7. A robot end effector accorαing to claim 5, further characterised in that the intermediate layer has a cross- section of trapezoidal form. 8. A robot end effector according to claim 1, charac¬ terised in that the backing member has at least one window¬ like aperture therein. 9. A robot end effector according to claim 1. charac- terised in that the rigid backing member comprises a light¬ weight composite panel. 10. A robot end effector according to claim 9, characterised in that the composite panel is of laminated construction having a honeycomb core. 11. A robot enα effector according to claim 1, charac¬ terised in that the facing strip material comprises an electrically conductive material. 12. A robot end effector according to claim 11, characterised in that tne facing strip material is maαe of a rubber containing electrically conductive particles. 13. A robot end effector accorαing to claim l. characterised in that the resilient intermediate layer nas a thickness of from 20 mm to 30 mm, and tne facing strip material has a width of less than 20 mm. 14. A robot end effector according to claim 13, characterised in that the facing strip material has a thickness of substantially 1mm. 15. A robot end effector for holding a workpiece against a working surface, said workpiece extending beyond the periphery of the effector, characterised in that at least one attachment device is supported on mounting means to project beyond said periphery of the effector, the mounting means being adapted to permit each attachment device to be lifted clear of the working surface while the workpiece remains held by the effector. 16. A robot end effector according to claim 15, characterised in that the mounting means includes a first arm which is mounted on, and extends radially from a shaft, a second arm being attached to the shaft, said second arm extending radially from said shaft and having a cam fol¬ lower means which co-operates with a cam so that, in use, arcuate movement of the second arm causes the cam follower to move the attachment device towards or away from the working surface.

Inventors: FLAVELL JOHN, JEFFCOAT KEITH, FLAVELL, JOHN, JEFFCOAT, KEITH
Applicants: COURTAULDS PLC
Application year: 1989
Main classification: A41H43
IPC codes: A41H43, B25J15, D05B33, D05B35