WO2017138883A1

WO2017138883A1 - Gripping device comprising a core member and an iflatable gripping sleeve arranged around this core member

Info

Publication number: WO2017138883A1
Application number: PCT/SE2017/050133
Authority: WO
Inventors: Matilda BASTMAN; Sten BASTMAN
Original assignee: Morab Ab
Priority date: 2016-02-12
Filing date: 2017-02-13
Publication date: 2017-08-17
Also published as: SE1650191A1

Abstract

A gripping device (1) for a robot arm, having an inner end directed towards the robot arm and an outer end directed away from the robot arm, comprising an attachment part (8) coupled at an outer end to a core member (2), an inflatable gripping sleeve (3) arranged around, and detachably attached to, said core member (2) and a conically shaped guide member (4) at the outer end of the gripping device(l), said core member (2) defining a first axial passageway (20) in communication with the interior of said gripping sleeve (3) for provision of compressed air thereto wherein the conically shaped guide member (4) is, at its widest part, wider than the inflatable gripping sleeve (3) in an uninflated state.

Description

GRIPPING DEVICE COMPRISING A CORE MEMBER AND AN I FLATABLE GRIPPING SLEEVE ARRANGED AROUND THIS CORE MEMBER

TECHNICAL FIELD

The present invention relates to a gripping device comprising an attachment part, a core member, an inflatable gripping sleeve, a conically shaped guide member, said inflatable gripping sleeve being arranged around said core member, said core member defining a first passageway in communication with the interior of said gripping sleeve for provision of compressed air thereto. STATE OF THE ART

Inflatable gripping devices are used as an alternative to conventional multifingered claws and vacuum cups in robotic or mechanical pick-and-place systems (a process of picking parts up and placing them in new locations), particularly in so-called bin- picking. Bin-picking enables a robot to automatically move a number of randomly placed parts regardless of their orientation. It uses a plurality of sensors and cameras for stereoscopic vision. The standard application moves one part in any orientation whether loosely or tightly packed, either on the floor, conveyor, bin or container, the parts can be in any orientation. The inflatable gripping device is attached to the outer end of the robot arm and is inserted inside a product and inflated against the interior by means of friction and pressure from the sleeve against the interior of the goods, the object may be picked.

The document US 5449182 describes a universal substrate holding apparatus comprising: a first core member having a top end and a bottom end; a first inflatable tube disposed around the first core member; a first passageway defined by the first core member in communication with the interior surface of the first tube; a second core member having a top end and a bottom end, a portion of the second core member having a larger outer cross-sectional dimension than the first core member, wherein the top end of the first member is associated with the bottom end of the second member; a second inflatable tube disposed around the second core member, a portion of the second tube having a larger outer cross-sectional dimension than the first tube, and whereby the second tube is disposed in tandem with the first tube; and a second passageway defined by the second core member in communication with the interior surface of the second tube.

The document JP 2009-050993 describes a chucking device that comprises a base body and a rubber sleeve disposed on the outer periphery of the base body. The rubber sleeve is inflated by supplying air into an air tight chamber formed between the base body and the rubber sleeve. At both ends of the rubber sleeve, bead sections are formed to embed a bead wire around all circumferences, and on the base body bearing surfaces are formed so as to abut against all the circumferences of the bead sections.

Since a bin-picking system should be able to be unmanned for many hours the gripping device must be reliable and durable. Inflatable gripping devices available today are either too large and clumsy, or they last only a few hours because the sleeve becomes worn and breaks.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of the present invention to eliminate or at least minimize the above mentioned problems, which is achieved by means of a gripping device according to claim 1.

Thanks to the invention, a gripping device is provided where all or some of the parts easily and quickly may be replaced when they become worn or if the size needs to be changed. According to one aspect of the invention the gripping device comprises a core member that supports a gripping sleeve at both an outer and an inner end of the gripping sleeve which gives the advantage that the gripping sleeve will not be so quickly worn and thus may last longer in use, getting a longer lifetime. According to another aspect of the invention, the core member comprises an inner part and an outer part and said inner part comprises an inner cylindrical lip and said outer part comprises an outer cylindrical lip and the gripping sleeve is easily arranged around these lips. According to still another aspect of the invention the head of the core member comprises a concave portion provided with an outlet for compressed air. Thanks to the concave portion the weight of the core member is minimized. The risk of the core bumping into the objects to be picked during insertion and retraction is also minimized which in turn minimizes the wear of the sleeve. Furthermore, the outlet for compressed air being placed in the concave portion secures an efficient discharge of compressed air from the sealing room. According to another aspect of the invention, the gripping device comprises a guide member, which preferably is conically shaped and guides the gripping device into the goods to be picked and where the guide member is arranged in the outer end of the gripping device and gets into contact with the goods first, thereby protecting and preventing the gripping sleeve to get worn.

According to one aspect of the invention the gripping sleeve comprises an outer and an inner end, both ends comprising an annular portion extending radially inwards, towards a circular opening. Said annular portion comprises a cylindrical edge extending in an axial direction from the annular portion into the interior of the gripping sleeve. The gripping sleeve is arranged around the cylindrical lips of the core member. The annular portions and the cylindrical edges are dimensioned to have a snug fit around the cylindrical lips of the core member. When assembled, the diameter of the guide member is the same, but preferably larger, than the diameter of gripping sleeve in uninflated state in order to protect the gripping sleeve during insertion into the goods and in order to clamp the gripping sleeve against the head of the core member in a preferred way.

According to another aspect of the invention, the gripping device comprises a washer. When assembled, the diameter of the washer is the same, or slightly larger than the diameter of the gripping sleeve in uninflated state in order to protect the gripping sleeve during retraction out of the goods and in order to clamp the gripping sleeve against the head of the core member in a preferred way.

A core member for a gripping device is also provided.

BRIEF DESCRIPTION OF FIGURES

In the following, the invention will be described in greater detail with reference to the attached figures of the drawings, in which: Fig. 1 illustrates a side view of a gripping device according to the invention,

Fig. 2 illustrates an assembly drawing of the gripping device 1,

Fig. 3 illustrates a perspective view of a guide member according to the

invention,

Fig. 4 illustrates a perspective view of a core member according to the invention, Fig. 5 illustrates a cross sectional view of a core member according to the

invention, Fig. 6 illustrates a cross sectional view across the line B-B in figure 5, of a gripping device according to the invention,

Fig. 7 illustrates a perspective view of a sleeve according to the invention,

Fig. 8 illustrates a cross sectional view of a sleeve according to the invention, and

Fig. 9 illustrates a cross sectional view across the line A-A in figure 1, of a

gripping device according to the invention.

DETAILED DESCRIPTION OF FIGURES

The following detailed description, and the examples contained therein, are provided for the purpose of describing and illustrating certain embodiments of the invention only and are not intended to limit the scope of the invention in any way. By the term compressed air or air any kind of fluid suitable for the purpose is comprised, unless otherwise indicated. Parts that in the description are defined by the term "inner" are

directed/arranged/extending towards the attachment part of the robot while parts that are defined by the term "outer" are directed/arranged/extending outwardly, away from the attachment part of the robot. These terms are not intended to limit the scope of the invention in any way but are provided for a better understanding of the description. In the same manner and where appropriate the terms proximal and distal are used to describe the direction towards the robot arm (proximal) and away from the robot arm

(distal).

Figure 1 illustrates a side view of a gripping device 1 according to a preferred embodiment of the invention. The gripping device 1 comprises, from left to right in the figure, an attachment part 8, a washer 5, an inflatable gripping sleeve 3 and a guide member 4 which preferably is conically shaped. The dashed lines illustrate the interior of the gripping device 1 including a core member 2. The inflatable gripping sleeve 3 is arranged between the attachment part 8 and the conical guiding member 4. The attachment part 8 connects the core member 2 to a robot arm. The core member 2 is coupled to the outer end of the attachment part 8. As described above, outer in this respect relates simply to the direction distal to the robot arm. The guide member 4 is provided at the distal end, the outer end, of the device 1.

Figure 2 illustrates an assembly drawing of the gripping device 1. From left to right in the figure is seen the attachment part 8 having an inlet/radial bore 800 for provision of compressed air to internal air channels, see fig. 9. In an outer end face of the attachment part 8 attachment means are arranged which comprise a cylindrical recess 85 for coupling the core member 2 to the attachment part 8. At a bottom 900 in the recess 85, the outlet 84 for one of the air channels 80b is visible. Outside the face end of the attachment part is arranged the washer 5, a sealing 10 arranged in a groove 240 on the core member 2, the gripping sleeve 3 and the guide member 4. The core member is inserted into the washer 5 and further into the recess 85. The gripping sleeve 3 is arranged around the core member 2. A screw, see fig. 9, is used to attach the different parts to each other via an axial passageway 20 aligned with the longitudinal axis in the figure. The passageway 20 is formed by central bores in the attachment part 8, the core member 2 and the guide member 4. Figure 3 illustrates a perspective view of a guide member 4 according to the invention. In a preferred embodiment the guide member 4 comprises an inner end 40 and an outer end 42 and a peripheral surface forming a guiding portion 41 there between. The guiding portion 41 is gradually tapered towards the narrower outer end 42. Preferably, the guiding portion 41 is conical but the skilled person realize that the guiding portion 41 may have other tapered shapes. However, the shape is preferably symmetrical about the longitudinal axis. The peripheral surface forming the circumferential wall of the guide member 4 may be substantially flat and smooth. This aids the guiding effect of the guide member 4 in to the parts to be picked. The conical guide member 4 may also be adapted for receiving an attachment member 9. Figure 4 illustrates a perspective view of a core member 2 according to the invention. The core member 2 has a first end for connecting to the attachment part 8. The attachment part 8 provides compressed air to the first axial passageway 20 of the core member 2. The core member is connectable at a second end to the conical guiding member 4. When arranged together with the robot arm as part of a gripping device, the first end of the core member 2 is the proximal end, the second end of the core member 2 is the distal end. The core member 2 comprises a cylindrical pipe 241 having an outer head portion 25 and an inner arm portion 24, said pipe 241 defining a second portion 201 and a third portion 202 of the axial passageway 20. Radial channels 23 extend from the second passageway portion 201 to the outside of the head portion 25. The arm portion 24 is directed inwards and arranged to be attached to the attachment part 8 via the attachment means. The head portion 25 is directed outwards and arranged to hold the gripping sleeve 3 and the guide member 4. The gripping sleeve 3 is arranged around the head portion 25, see fig. 9. The head portion 25 comprise inner and outer cylindrical ends 252, 253 and a concave portion 250, 251 arranged there between. For cost reasons, the core member 2 is preferably made in metal although it may also be made in plastic. Metal is preferable also for strength reasons, in that machining is easier and in a better resistance to chemicals, among other reasons. The core member is preferably

manufactured as one integrated part for cost reasons, e.g. by turning, but may of course also be made of several parts.

Figure 5 illustrates a cross sectional view in the longitudinal direction of a core member 2 according to the invention. In the arm portion 24, the inner end 242 of the cylindrical pipe 241 comprises an outside circumferential groove 240, suitable for a seal 10, see Fig. 9, typically an O-ring or similar. The length of said arm portion 24 is adapted to the depth of the cylindrical recess 85 in the attachment part 8 and the thickness of the washer 5. As can be seen in fig. 9, the depth of the cylindrical recess 85 shall be sufficient for providing space for the seal 10 which acts against the inside wall of the cylindrical recess 85. The outer diameter D of the cylindrical pipe 241 is adapted to the diameter of the cylindrical recess 85 such that a snug fit is achieved upon entry of the cylindrical pipe 241 into the cylindrical recess 85 when the gripping device 1 is assembled. Hence, the core member 2 is supported by the cylindrical wall and positioned axially in the cylindrical recess 85. The outer diameter D of the arm portion 24 is in the interval 5-200 mm, preferably in the interval 10-150 mm and more preferred in the interval 20-90 mm.

In the head portion 25, the cylindrical pipe 241 comprises a protruding collar 256 at its outer end with a stepped axial recess which serves to hold the guide member 4 and which also forms an inlet 257 to the third passageway portion 202. The head portion 25 further comprises inner and outer cylindrical portions forming a respective protruding lip 252, 253 extending in the axial direction. A waist portion 254, formed by a first inwardly conical part 251 and a mirrored second outwardly conical part 250, extends there between. The waist portion is a tapered waist portion provided between the first and second ends of the core member 2. Discharge openings from the radial channels 23 are arranged in the waist portion. The core member may be provided with a plurality of discharge openings 23a provided at the waist portion of the core member 2. By providing the openings 23a in the waist portion of the core member 2 the flow of air from the radial channels in to the inflatable gripping sleeve 3 may be improved due to the volume present between the gripping sleeve 3 and the core member 2. The core member 2 has a greatest width W in the area of the inner and outer protruding lips 252, 253. The collar 256 extends outside the outer protruding lip 253 in a forward direction such that there is a level difference q between their end faces. Radially inside the respective protruding lips 252, 253 there is a circular groove 244, 255. The grooves 244, 255 encircle the cylindrical pipe 241 and the collar 256 respectively. The cylindrical lips and the grooves cooperate with the end portions of the gripping sleeve 3 such that the gripping sleeve is detachably fixed to the head portion in a firm and airtight manner, which will be further described in connection to fig. 8 and fig 9.

The second passageway portion 201 have a diameter di that is larger than the diameter d₂ of the third passageway portion 202. The diameter di of the second passageway portion 201 is also larger than the diameter d₄ of the screw 9 in order to create a gap 90 between the outer periphery of the screw 9 and the inner wall of the second passageway portion 201, best seen in Fig. 9. This gap 90 is arranged to let the compressed air flow to and from the air channels 80a, 80b in the attachment part 8, via the gap 90 along the screw 9 in the second passageway portion 201 and further via the radial channels 23 to the inflatable sealing room 36 for inflation and deflation of the gripping sleeve 3. The radial channels 23 are arranged in the waist portion 254 between the first conical part 251 and the second conical part 250. They extend radially between the gap 90 and the sealing room 36 which is arranged outside the head portion 25 of the core member, between the periphery of the core member 2 and the inside wall of the gripping sleeve 3. The inlet to the radial channels are preferably arranged in the zone where the second passageway portion 201 and the third passageway portion 202 meet although the inlet may be arranged elsewhere along the gap 90 in the head portion 25. The outlet of the radial channels 23 are preferably arranged in the very waist thus securing an efficient discharge of compressed air from the sealing room 36, best understood from figure 5. Figure 6 illustrates a cross sectional view of the core member 2 across the line B-B in figure 5 and shows the radial channels 23 which extend from the second passageway portion 201 to the waist portion outside of the head 25.

Figure 7 and 8 illustrates a gripping sleeve 3 in a preferred embodiment according to the invention. In the preferred embodiment the gripping sleeve 3 is symmetrical both in longitudinal and transversal direction. The gripping sleeve 3 is preferably made of an elastic material with adequate fatigue strength and wear resistance, in particular abrasive wear resistance. Examples of suitable materials are rubber, silicone or polyurethane. Normally, the gripping device is used at temperatures around room temperature but the skilled person understands that the sleeve material shall be adapted to the actual working temperature and selected in order to obtain the required properties. The gripping sleeve 3 comprises a cylindrical wall 31 with partially closed ends 32, 33 in the form of an outer annular portion 320 and an inner annular portion 330 extending radially inwards. Normally a gripping device of this type is used for picking small to medium sized objects, i.e. objects with a weight in the range of 0 - 30 kg or at least in the rage of 0 - 20 kg. Larger objects are normally easy to handle as they are larger and therefore easier to grip. For obvious reasons best performance is obtained if the size of the gripping sleeve 3 is adapted to the objects to be picked. The outer diameter H of the gripping sleeve 3 is in the interval 10-200 mm, preferably in the interval 15-150 mm and more preferred in the interval 20-100 mm. The cylindrical wall 31 has a thickness T in the interval 0.5-15 mm, preferably in the interval 1-10 mm and more preferred in the interval 1.5-5 mm. The outer annular portion 320 surrounds an outer circular opening 34. The wall thickness t of the outer annular portion 320 is at least as thick as the level difference q between the collar 256 and the outer cylindrical lip 253 of the core member's head 25, preferably somewhat thicker, in order to enable that the outer annular portion 320 is clamped between a back side 404 of the guide member 4 and the protruding lip 253 when assembled. In a preferred embodiment the outer annular portion 320 has an outer cylindrical edge 321 which protrudes toward the sleeve's interior. The outer cylindrical edge 321 extends from the annular portion 320 into the gripping sleeve 3 in an axial direction of said gripping sleeve 3. The opposite end of the gripping sleeve 3, i.e. the inner end 33, is reversed towards the outer end 32. The inner end 33 also comprises an inner annular portion 330 surrounding an inner circular opening 35. The inner annular portion 330 ends with an inner cylindrical edge 331 around the opening 35. The inner cylindrical edge 331 extends from the annular portion 330 into the gripping sleeve 3 in an axial direction of said gripping sleeve in reversed direction compared with the outer cylindrical edge 321 at the outer end 32. The inner end 33 of the gripping sleeve 3 is clamped between the washer 5 and the inner protruding lip 252 of the core member 2 when the screw 9 is tightened upon assembly of the gripping device. The gripping sleeve 3 may have a diameter that is smaller, larger than or as wide as the attachment part 8 but the diameter of the washer 5, the guide member 4 and the core member 2 follows the outer diameter H of the gripping sleeve 3. The guide member 4 may have a diameter W that is the same as the outer diameter H of the gripping sleeve 3 or wider. Preferably, the washer 5 has a diameter as wide or wider as the diameter H of the gripping sleeve 3. The greatest width W of the core member 2 is adapted to the thickness T of the gripping sleeve 3, such that the gripping sleeve 3 is supported from inside by the core member 2 but still obtains an overall diameter H in assembled state which is smaller than the diameter W of the guide member 4, typically in the order of a few millimeters smaller than the diameter W of the guide member 4.

Figure 9 illustrates a cross sectional view through the line A-A of the gripping device 1 in assembled state. The gripping device comprises an axial passageway 20 along a longitudinal axis B. The attachment part 8 comprises a hollow shaft defining a first portion 82 of an axial passageway 20. The core member 2 comprises second passageway portion 201 and third passageway portion 202. The guide member 4 comprises a fourth 401 and a fifth 402 portion of the axial passageway 20. The second to fifth portions of the passageway 20 form a mounting bore 6 arranged concentrically along the longitudinal axis B. The inner end of the attachment part 8, see fig 2, is arranged at a robot arm in a manner known per se and the outer end is provided with attachment means for attaching the other parts of the gripping device 1. It shall be understood that the attachment part 8 may be an integrated part of the outer end of the robot arm itself and need not be a separate part which is attached to the robot arm. The attachment means comprises a cylindrical recess 85 at the outer end face of the attachment part 8 for coupling, preferably demountable, the core member 2 to the attachment part. The cylindrical recess 85 is axially aligned with the first passageway portion 82. At its outer end, adjacent the cylindrical recess 85, the first passageway portion 82 is provided with a threaded portion 81. By providing a threaded portion within a central bore of the attachment part 8 the core member can be mounted and dismounted easily.

When the gripping device 1 is in assembled state the axial mounting bore 6 aligns with the first passageway portion 82 in the attachment part 8. The washer, core member and guide member 4 are detachably attached to the attachment part 8 and to each other by a screw 9, see Fig. 9, or other suitable fixing means, inserted into the mounting bore 6 and engaged with the threaded portion 81. The inflatable gripping sleeve 3 is arranged outside a head portion 25, see fig 5, of the core member 2 and clamped at its inner end between the core member 2 and the washer 5 and at its outer end between the core member 2 and the guide member 4. The first passageway portion 82 and the axial mounting bore 6 communicates with air channels 80a, 80b, 23 in the attachment part 8 and the core 2 respectively for provision of compressed air in the gripping device 1. As can be seen in Figure 9, the conical guiding member 4, core member 2 and attachment part 8 are detachably fixed by a single screw 9. The force of the screw 9 holding the conical guiding member 4 and core member 2 to the attachment part 8 may also provide a force holding the inflatable gripping sleeve 3 to the core member 2. Since the parts of the gripping device 1 are detachably attached to each other by the screw (or the like), it is easy to assemble or disassemble the gripping device 1, for instance if any part is worn and needs to be replaced. An improvement is also obtained in that it is convenient to substitute one gripping device (or parts thereof) for another in a different size if differently sized objects are to be picked up from different batches. The dimensions, and in particular the outer diameter of the core member 2, conical guiding member 4, and inflatable gripping sleeve are all replaceable if the size of the parts to be picked changes. When assembling the gripping device 1, the core member 2 is inserted into the gripping sleeve 3 and the inner cylindrical edge 331 is slipped around the inner protruding lip 252 and into the inner circular groove 244 of the core member and the outer cylindrical edge 321 is slipped around the outer protruding lip 253 and into the outer circular groove 255 of the core member so that the gripping sleeve 3 is arranged around the core member 2 in a snug fit. In a bridging area between the outer and inner cylindrical edge 321, 331 and the outer and inner annular portion 320, 330 respectively, an outside surface is formed with a right angled edge. The right angled edge is positioned where the cylindrical surface surrounding the opening 34, 35 and the radially extending surface of the outer and inner annular portion 320, 330 meet. The inside surface of the outer cylindrical edge 321 is preferably rounded. The outer cylindrical lip 253 preferably has a correspondingly rounded edge in order to reduce wear on the cylindrical edge 321. Letting the cylindrical edges 321, 331 extend into the circular grooves 244, 255 reduces the risk that the guide sleeve is pulled off the core in case the guide sleeve 3 is overinflated. This effect is pronounced due to the increased wall thickness in the bridging area. The washer 5 is slipped on to the arm portion 24 of the core member 2. A seal 10 is arranged in the circumferential outer groove 240 of the arm portion 24 and the arm is inserted into the recess 85 of the attachment part 8. The seal 10 ensures an airtight mounting so that no compressed air seeps out when the gripping sleeve 3 is inflated. In next step the guide member 4 is arranged at the head portion 25 of the core member 2 and the screw 9 is inserted into the common mounting bore 6 that extends through the guide member 4, the core member 2 and into the attachment part 8. The screw 9 is threaded into a threaded part 81 inside the attachment part 8 and tightened to a predetermined clamping force, for example by the aid of a torque wrench. Thereby, the sleeve is clamped between the inner protruding lip 252 and the washer 5 at the inner end and between the outer protruding lip 253 and the guide member's back side 404 at the outer end. As the skilled person will understand, the elasticity of gripping sleeve 3 can be varied and the pressure of the compressed air and the clamping force can be adapted accordingly. Thereby, objects with different weights may be handled while still maintaining an airtight clamping of the protruding lips 252,

253. The clamping force shall however not be so strong that the gripping sleeve 3 may explode in case of too high air pressure. Instead, the clamping force shall permit compressed air at a certain pressure to escape via the clamping gap 252a, 253a between the protruding lips 252, 253 and the washer 5 and back side 404 respectively. In order to be able to vary the clamping force the length of the arm portion 24 and/or the thickness of the washer 5 is chosen so that the end face of the arm portion 24 does not reach the bottom of the cylindrical recess 85. Thus, a gap 86 between the bottom surface 900 and the inner end face of the arm portion 24 is obtained which also serves as a

communication gap 86 for the compressed air.

The width W of the inner end 40 of the guide member 4 preferably is as wide as the gripping sleeve 3 in the uninflated state, or wider. In the preferred embodiment the width W is some few millimeters wider, typically 1-2 mm wider, than the width of the gripping sleeve 3 giving the advantage that the guide member 4 protects the gripping sleeve 3, and particularly the outer end 32 of the gripping sleeve, see Fig. 8, when the gripping device 1 is inserted into the interior of the object to be picked. The guiding portion 41 further makes it easier to insert the gripping device 1 into the interior of the goods to be picked /handled. The fourth 401 and fifth 402 passageway portions in the guide member 4 comprises a through bore 43 for the fastening screw 9. The fifth passageway portion 402 in the outer end of the through bore 43 forms a countersink 402 for the head 900 of the screw 9, thus avoiding the head 900 to extend outside the outer end 42 of the guide member 4. A stepped transition between the countersink 402 and the inner, narrower fourth passageway portion 401 of the through bore 43 forms an abutment surface 403 for the head 900 of the screw 9. The screw 9 extends from the outer end of the guide member 4, through the core member 2 and into engagement with the threaded portion 81 in the first passageway portion 82 in the attachment part 8. The screw 9 may be a general attachment member. For example, a bolt would also be suitable.

The guiding sleeve 405 engages with the collar 256 of the core member 2. The collar 256 forms a stepped axial recess into which a guiding sleeve 405 of the guide member 4 is inserted in a tight fit with respect to the width and preferably also with respect to the depth of the guiding sleeve 405. The stepped axial recess also forms an inlet 257 to the third passageway portion 202. The depth of the inlet 257 is adapted to the height of the guiding sleeve 405 such that the back side 404 of the guide member 4 abuts the outward facing end 258, which preferably is substantially flat, of the collar 256 when assembled. The guiding sleeve 405 acts like a guide for the guide member 4 in the radial direction when to be assembled with the core member 2. The guiding sleeve 405 extends around the opening of the fourth passageway portion 401 at the back of the guide member 4.

The back side 404 radially outside the guiding sleeve 405 is preferably substantially flat. The inner diameter d₃ of the guiding sleeve 405 is preferably the same as the inner diameter di of the third passageway portion 202. In order to prevent air leakage and axial alignment between these parts, the diameter d₄ of the screw 9 is preferably the same (theoretically) as the inner diameter di of the third passageway portion 202. A tolerance in the order of H6 or H7 between the two is desired. The third passageway portion 202 has a diameter that is less wide than the diameter of the inlet 257. The third passageway portion 202 has a diameter that is the same as the diameter on the screw 9. If desired, a seal, conventionally an O-ring, may be arranged at the bottom of the recess into which the guiding sleeve 405 of the guide member 4 is inserted for further increasing the safety against air leakage.

Thanks to this invention a gripping device 1 is provided where the guide member 4 guides the gripping device 1 into the piece to be picked up and where the guide member 4 gets into contact with the goods before the gripping sleeve 3 does, thereby preventing that the gripping sleeve 3 gets worn. The guide member 4 is, at the widest part that is arranged to abut the gripping sleeve 3, preferably as wide as the diameter H of the gripping sleeve 3 or wider giving the advantage that the guide member 4 instead of the gripping sleeve 3 strikes into the goods to be picked when the gripping device 1 is seeking its way into the goods. Thereby, the gripping sleeve 3 will get a longer lifetime. The same protecting principle applies also to the washer. The washer 5 is a standard circular washer with a diameter preferably as wide as the diameter H of the gripping sleeve 3 in order to clamp the gripping sleeve 3 against the core member 2 in an optimal way and to protect the inner edge of the gripping sleeve 3 when retracting the gripping device 1 from the device that has been handled. If the washer 5 has a wider diameter than the diameter H of the gripping sleeve 3 there is also a risk that the washer 5 gets hooked into details of the goods when inserting or retracting the gripping device 1 into or out from the goods, but it is a possible modification although not preferred. The gripping device 1 according to the invention provides a gripping sleeve 3 that is more protected against wear and the risk that the gripping sleeve 3 will be hooked into details of the goods is minimized. Also, the new configuration of the edges of the gripping sleeve and the head of the core member provides a new way of clamping the gripping sleeve to the core member resulting in less wear of the guiding sleeve upon inflation in the region where it is clamped to the core compared to bin-picking sleeves according to prior art which are subjected to sharp bending in the area where it is clamped when inflated. Thanks to the invention, the gripping sleeve 3 may also be easily replaced by a new one which will result in cost savings.

The gripping device 1 works in a conventional manner by inflation and deflation of the gripping sleeve 3. In this embodiment, compressed air is used to expand the gripping sleeve 3. For provision of compressed air to the gripping sleeve 3, the first passageway portion 82 may be used. Existing air used for maneuvering the robot arm may be provided for instance through a sealed coupling at the inner end of the attachment part 8. At least one but in this embodiment two air channels 80a, 80b are arranged, preferably diametrically, alongside the first passageway portion 82 in the wall of the shaft. The attachment part 8 further comprise a channel 83 between the first passageway portion 82 and the respective air channels 80a, 80b. For ease of manufacture, a radial bore 83 is made from one side of the shaft in order to join the first passageway portion 82 with the respective air channels 80a, 80b. The channel 83 runs through the shaft wall, through the closest air channel 80a, through the first passageway portion 82 and into the opposite air channel 80b and forms a radial channel 83 between them. The channel' s inlet 800 in the shaft wall is then plugged. From the first passageway portion 82 the compressed air flows, via the radial channel 83, into the two air channels. The air channels 80a, 80b has a respective outlet 84 for compressed air at the bottom of the cylindrical recess 85. The compressed air flows via the communication gap 86 into the gap 90 outside the screw 9 in the second passageway portion 201, through the radial channels 23 and into the sealing room 36 for inflation of the gripping sleeve 3. Upon deflation the compressed air flows the opposite way. As a safety measure in order to avoid rupture of the gripping sleeve and possible damage to the device to be picked, compressed air is allowed to escape via the inner clamping gap 252a where the inner cylindrical edge 331 is slipped around the inner protruding lip 252 and via the outer clamping gap 253a where the outer cylindrical edge 321 is slipped around the outer protruding lip 253 in case of overpressure in the sealing room 36.

ALTERNATIVE EMBODIMENTS

The invention is not limited by what has been described hereinabove, but can be varied within the scope of the following claims. For instance, it will be appreciated that the different parts in the gripping device may be manufactured in different dimensions depending on the goods that will be picked. The gripping device is controlled by means of pneumatics and by adjusting the pressure to the gripping sleeve the gripping force will be adjusted. The number of radial channels in the core member may of course vary and be both more and fewer in number than described in the description. The head of core member need not have a convex portion but may be cylindrical although the skilled person understands that the described benefits will not be obtained. Also, the radial channels in the head of the core member may be arranged differently. They may be fewer or more, they need not be evenly spaced or extend in radial direction. The circular grooves of the core member may be omitted or formed in another fashion. For provision of compressed air, it is also conceivable to arrange a nozzle from an external source of compressed air at the inlet of the channel. It is also conceivable to have radial bores from opposite sides of the shaft for provision of compressed air into the respective air channel in which case the radial bore/bores doesn't have to pass into the first passageway portion. The same goes for the embodiment with only one air channel in case the bore serves as an inlet for compressed air. The screw may be provided with a central bore and a radial channel/channels which communicates with the radial channels in the head portion of the core member.

Claims

1. A gripping device (1) for a robot arm, having an inner end directed towards the robot arm and an outer end directed away from the robot arm, comprising an attachment part (8) coupled at an outer end to a core member (2), an inflatable gripping sleeve (3) arranged around, and detachably attached to, said core member (2) and a conically shaped guide member (4) at the outer end of the gripping device (1), said core member (2) defining a first axial passageway (20) in communication with the interior of said gripping sleeve (3) for provision of compressed air thereto characterized in that the conically shaped guide member

(4) is, at its widest part, wider than the inflatable gripping sleeve in an uninflated state.

The gripping device (1) according to claim 1, characterized in that said core member (2) comprise an inner cylindrical end portion and an outer cylindrical end portion and a concave portion (250, 251, 254) there between.

The gripping device (1) according to claim 2, characterized in that said end portions comprise an inner and outer protruding lip (252, 253) which supports said sleeve (3) at an inner end (33) and an outer end (32) of said sleeve (3).

The gripping device (1) according to claim 3, characterized in an inner radial clamping gap (252a) between the inner protruding lip (252) and a washer (5) and an outer (253a) radial clamping gap between the outer protruding lip (253) and the guide member (4).

The gripping device (1) according to claim 4, characterized in that a clamping force acting upon the outer end (33) of said gripping sleeve (3) is exerted by an attachment screw (9) acting upon said guide member (4) and running in the axial passageway (20) through said core member (2) and further into the attachment part (8).

The gripping device (1) according to claim 5, characterized in that the attachment part (8) comprises a recess (85) arranged to receive an arm portion (24) of the core member (2). The gripping device (1) according to claim 6, characterized in that a length of the arm portion (24) and/or a thickness of the washer (5) is adapted to a depth of the recess (85) so that a communication gap (86) for an inflation medium is obtained between a bottom surface (900) of the recess (85) and an inner end face of the arm portion (24) upon tightening of the attachment screw (9) to a predetermined clamping force.

The gripping device (1) according to claim 7, characterized in that a second passageway portion (201) of said axial passageway (20) comprise a gap (90) for the inflation medium which gap (90) communicates with said communication gap (86) and at least one channel (23) having a discharge opening (23a) in the concave portion (250, 251, 254).

The gripping device (1) according to claim 8, characterized in that said air gap (90) is arranged alongside the attachment screw (9).

10. The gripping device (1) according to claim 1, wherein a first passageway portion of attachment part (8) is provided with a threaded portion (81), and wherein the core member (2), conical guiding member (4) and inflatable gripping sleeve (3) are fixed by a single attachment member (9) extending from the outer end of the gripping device (1) through the axial passageway (20).

A core member (2) for a gripping device (1), the core member (2) being connectable at a first end to an attachment part (8) for the provision of compressed air in to a first axial passageway (20) of the core member (2), the core member (2) being connectable at a second end to a conical guiding member (4), wherein the core member (2) is provided with a tapered waist portion arranged between the first and second ends, the tapered waist portion being provided with a plurality of discharge openings (23a).

The core member (2) according to claim 11, wherein an inflatable gripping sleeve (3) is detachably receivable around the core member (2).