EP1890847A2

EP1890847A2 - Support fixture for a gripping member of a manipulator robot

Info

Publication number: EP1890847A2
Application number: EP06744960A
Authority: EP
Inventors: Carlo Paletto
Original assignee: O L C I ENGINEERING Srl; Olci Engineering Srl
Current assignee: Cima Srl
Priority date: 2005-05-17
Filing date: 2006-05-17
Publication date: 2008-02-27
Also published as: RU2007146713A; ITTO20050337A1; WO2006123296A3; BRPI0613264A2; WO2006123296A2

Abstract

A support fixture comprises a fixing structure (16) to which at least one gripping member (18) is fixed and an attachment device (20) intended to connect the fixing structure (16) to a support beam which can be attached to an arm of the robot. The attachment device (20) includes a first connecting member (22) connected to the fixing structure (16), a second support member (26) intended to be mounted on the support beam (12) , and releasable coupling means (58, 76) able to connect stably the first and the second member (22, 26) and reversibly disconnect these members in the event of an impact of predetermined force on the fixing structure (16). The second support member (26) includes a first fixed part (28) and a second movable part (32) mounted rotatably on the first one about a first axis (X) and carrying the first connecting member (22) in such a manner that this latter can be oriented with respect to the first fixed part (28) about. the first axis (X) .

Description

Support fixture for a gripping member of a manipulator robot

The present invention relates to a support fixture for a gripping member of a manipulator robot, such as a robot for motor-vehicle body welding lines, as well as to a manipulator robot provided with such a support fixture.

As is known, manipulator robots comprise one or more gripping members, or grippers, for releasably gripping a work piece (for example, a part of a bodywork) to be transferred from one point to another in the working area. The gripping members are mounted on special support fixtures fixed to a mobile arm of the robot . These support fixtures allow the gripping members to be arranged in a given position and in a given direction with respect to the mobile arm of the robot depending on specific needs, for example depending on the shape and size of the parts to be gripped. The support fixture used hitherto, however, have proved to be not particularly resistant to impacts which may occur in particular during setting-up of the automated lines, due to the high speeds at which the parts are moved and the restricted space within which these parts must be moved. These fixtures are in fact formed as rigid structures, consisting of structural elements (such as steel tubes or aluminium sections) which are fixed together by means of welding or threaded connections . In order to avoid troublesome and costly interruptions in the production process in the event of breakage of a support fixture following an impact, the suppliers of automated lines are therefore required to provide each robot with a spare fixture for each of the support fixture provided on the robot, so that a spare part is always available for use in case of need. This obviously results in additional cost for the suppliers of automated lines. Moreover, the replacement of a support fixture damaged after an impact, with a spare fixture, results in a prolonged interruption in the production process and requires the assistance of specialised personnel .

The object of the present invention is therefore to provide a support fixture for a gripping member of a manipulator robot which is not affected by the drawback of the prior art described above.

This and other objects are achieved according to the invention by means of a support fixture for a gripping member of a manipulator robot having the characteristic defined in independent Claim 1. Further advantageous characteristics of the invention are specified in the dependent claims .

In short, the invention is based on the idea of providing a support fixture for a gripping member of a manipulator robot, comprising a support structure to which the gripping member is fixed and an attachment device intended to connect the fixing structure to an arm of the robot, the attachment device including : a first connecting member connected to the fixing structure, a second support member intended to be mounted on the robot arm, and releasable coupling means able to stably couple the connecting member to the support member and reversibly disconnect the two members when the support fixture is subject^" to an impact having a force such as to cause irreparable damage to the fixture. The main advantage of the invention therefore consists in the possibility of preventing damage to the support fixture in the event of an impact, since the attachment device automatically uncouples the fixing structure from the robot arm in the event of an impact having a predetermined force. It is therefore no longer necessary to replace the damaged support fixture with a spare fixture, but it is sufficient to mount again the fixture on the robot arm, coupling again the two members of the attachment device to one another. This obviously results in a considerable reduction in the costs arising from maintenance and interruption of production, since the operations needed to restore the operative condition of the robot are simple and quick to perform, without the need for assistance by specialised personnel . Moreover, it is no longer absolutely indispensable to provide a spare fixture on the machine, since the probability of causing permanent damage to the support fixture is significantly reduced.

Further characteristics and advantages of the invention will become clear from the detailed description which follows, provided purely by way of a non-limiting example with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of an end portion of a robot arm on which a pair of support fixture according to a preferred embodiment of the present invention are mounted;

Figure 2 is a perspective view which shows in detail a device for attaching one of the two support fixtures of Figure 1 ;

Figure 3 is a vertically sectioned view of the attachment device of Figure 2 ;

Figure 4 is an exploded view of the attachment device of Figure 2 ; and Figure 5 is an axially sectioned view of a variant of embodiment of an attachment device for a support fixture according to the invention.

With reference initially to Figure 1, a robot arm (known per se and not illustrated) carries at its free end an attachment plate 10 to which a support beam 12 is fixed, the beam being formed preferably as a metal section segment provided with a plurality of straight grooves 14 directed parallel to its longitudinal axis. A pair of fixing structures 16, of a type known per se, are mounted on the' support beam 12, a respective gripping member 18, also of a type known per se, being fixed to each of them. The fixing structures 16 are formed for example as a set of tubular elements connected together preferably by means of screw-type connecting members, so as to facilitate any variations in the spatial arrangement of these elements. Each fixing structure 16 is mounted on the support beam 12 by means of a disengageable attachment device, generally indicated 20. The assembly consisting of the fixing structure 16 and the attachment device 20 forms a support fixture according to the invention.

With reference now in particular to Figures 2 to 4, the attachment device 20 comprises a -connecting member 22 intended to be connected to an end of a tubular element 24 of the fixing structure 16 and a second support member 26 intended to be mounted on the support beam 12. The support member 26 includes a first fork-shaped part 28 connected to the support beam 12 by means of two or more screws 30, and a second part 32 movable with respect to the first one. The movable part 32 comprises an outer annular element 34, mounted rotatably on the support member 26 by means of a first pair of pins 35 and 35a so that it can be oriented about a first axis X, and a second inner annular element 36, mounted rotatably on the first annular element 34 by means of a second pair of pins 37 and 37a so that it can be oriented about a second axis Y perpendicular to the first one.

In the example of embodiment shown, the pins 35 and 37 each comprise a cylindrical shank 38 and a cylindrical head 40, while the pins 35a and 37a each comprise a cylindrical shank 38a and a hexagonal socket threaded cylindrical head 40a. The cylindrical shanks 38 and 38a of the first pair of pins 35 and 35a define the first axis of rotation X and are inserted into respective cylindrical holes 42 provided in a pair of opposite vertical walls 44 of the outer annular element 34. The cylindrical head 40 of the pin 35 is inserted into a hole 46 provided in a first vertical arm 48 of the fixed part 28 of the support member 26, while the cylindrical head 40a of the pin 35a is screwed into a threaded hole 46a provided in a second vertical arm 48a of the fixed part 28 opposite the first arm. Similarly, the cylindrical shanks 38 and 38a of the second pair of pins 37 and 37a define the second axis of rotation Y and are inserted into respective cylindrical holes 50 provided in a pair of opposite horizontal walls 52 of the inner annular element 36. The cylindrical head 40 of the pin 37 is inserted into a hole 54 provided in a first horizontal wall 56 of the outer annular element 34, while the cylindrical head 40a of the pin 37a is screwed into a threaded hole 54a provided in a second horizontal wall 56 of the outer annular element 34 opposite the first wall.

Owing to the use of the threaded pins 35a and 37a, once the orientation of the inner annular element 36 with respect to the fixed part 28 of the support member 26 about the two axes X and Y has been adjusted, it is -therefore possible to maintain stably this orientation by tightening the heads 40a of these pins inside the respective threaded holes 46a and 54a.

Preferably, as envisaged in the embodiment shown, each pair has only one pin provided with a threaded head, while the head of the other pin, namely the head 40 of the pin 35 and the head 40 of the pin 37, is inserted with play into the corresponding hole 46, 54. The shanks 38 of the non-threaded pins 35 and 37 are each connected for rotation with the associated movable element (namely, the outer annular element 34 in the case of the pin 35 and the inner annular element 36 in the case of the pin 37) by means of a respective lock pin 57. The heads 40 of these pins therefore rotate inside the respective holes 46 and 54 integrally with the associated movable elements 34 and 36. Advantageously, means for indicating the angular position, such as goniometric scales, are provided on the heads 40 of the pins 35 and 37 or on the arm 48 of the fixed part 28 of the support member 26 and on the first horizontal wall 56 of the outer annular element 34 so as to facilitate adjustment of the^* orientation about the two axes X and Y.

It is nevertheless possible to envisage that both the pins of each pair have a threaded head. In the same way it is possible to envisage other measures for stably maintaining the orientation of the inner annular element 36 with respect to the fixed part 28 of the support member 26 about the two axes X and Y.

The inner annular element 36 has a plurality of support inserts 58 (in the example of embodiment proposed three inserts arranged at 120°) , each comprising a shank 60 inserted into a corresponding hole 62 in the element 36 and a bearing plate 64 which projects towards the inner side of the element 36 and has centrally a conically shaped recess 66. According to the embodiment shown in Figures 3 and 4 , the shank 60 of one of the three support inserts 58 is threaded and has a hexagonal recess into which an Allen wrench can be inserted to allow the attachment device to be coupled again following an impact, as will be explained in detail further below. In the variant of embodiment of Figure 5, on the other hand, the shanks 60 of all the three support inserts 58 (only one of which can be seen) are inserted' with interference into the respective holes 62.

As shown in particular in the exploded view of Figure 4, the connecting member 22 of the attachment device 20 comprises, for example, a first component 68 carried by the inner annular element 36 of the movable part 32 of the support member 26 and a second component 70 firmly secured, for example by means of threaded connecting members (not shown) , to one end of the tubular element 24. The two components 68 and 70 of the connecting member 22 are joined together by means of screws 72. The first component 68 has a series of radial cylindrical cavities 74 corresponding in number to the number of the support inserts 58 of the inner annular element 36 (in the example shown, three cavities arranged at 120°) . Each cavity 74 receives a pin 76 provided with a spherical head 78 projecting externally from the side surface of the component 68 and intended to engage in the recess 66 of a corresponding insert 58. Each pin 76 is subject to a radial preload force which tends to expel it from the respective cavity 74 and is exerted by a respective spring assembly 80, formed for example by a series of Belleville springs (only one of which is shown in the exploded view of Figure 4) arranged in pack form on top of each other inside the cavity 74 about a stem 82 of the pin 76. For each pin 76 a locking plate 84 is envisaged which is fixed by means of screws 86 to the first component 68 of the connecting element 22 and has a circular through-hole 88 through which the spherical head 78 of the pin 76 passes. By co-operating with radial flanges 90 of the pins 76, the plates 84 prevent the pins from being expelled from the respective radial cavities 74.

Owing to the co-operation between the spherical-head pins 76 of the connecting member 22 and the support inserts 58 of the inner annular element 36 of the movable part 32 of the support member 26, the tubular element 24, forming part of the fixing structure 16 of the gripping member 18, is releasably connected to the support beam 12, and therefore to the arm of the robot. The release force of the attachment device 20 may obviously be adjusted as desired by setting the preload force exerted by the spring assembly 80. The use of packed Belleville springs allows the formation of spring assemblies 80 of compact dimensions, but are nevertheless capable of exerting high preload forces. The attachment device 20 must in fact not become disengaged during normal operation of the robot, but only in the event of impacts having a force such as to cause permanent damage to the support fixture and to require, therefore, replacement of the said fixture .

In order to couple again the connecting member 22 with the inner annular element 36 of the support member 26 after an impact, it is sufficient to unscrew the threaded shank 60 of one of the support inserts 58 so as to. move the bearing plate 64 radially away from the spherical head 78 of the respective pin 76. According to the variant of embodiment shown in Figure 5, on the other hand, a screw-type mechanism is envisaged, said mechanism allowing the preload force exerted by all the three spring assemblies 80 to be simultaneously adjusted. This mechanism includes a screw 92 which engages in an axial threaded hole 94 provided in the connecting device 22. The end of the shank of the screw 92 co-operates with three inclined surfaces 96 of three spring plates 98 (only one of which is shown in Figure 5) , each associated with a respective spring assembly 80. Each spring plate 98 is arranged slidably in the respective radial cavity 74 and can therefore be displaced radially by means of the screw 92 so as to increase or reduce the preload force exerted by the respective spring assembly 80. In order to restore the engaged condition of the attachment device 20 it is therefore sufficient to unscrew the adjusting screw 92 so as to reduce the preload force of the spring assemblies 80.

In the variant of embodiment of Figure 5, moreover, the connecting member 22 is formed as a single piece, instead of two separate components connected together by means of screws .

Owing to the fact that the connecting member 22 can be oriented with respect to the support member 26 about the two axes X and Y, positioning of the fixing structure 16 of the gripping member 18 is extremely simple, since it is defined solely by the two angles of rotation .about these axes. This therefore also results in simplification of the operations of setting-up and testing the movement cycle of the robot.

Naturally, the principle of the invention remaining unchanged, the embodiments and the constructional details may be widely varied with respect to those described and illustrated purely by way of a non-limiting example.

For example, the attachment device 20 may also not be provided with the mechanism for orienting the connecting member 22 (namely the gripping member 18 integral therewith) relative to the support member 26 (namely the robot arm) about the two axes X and Y. In this case, the connecting member 22 may be substantially identical to that previously described, while the support member 26 will have an annular element (corresponding to the inner annular element 36) provided with the support inserts 58.

Claims

1. Support fixture for a gripping member of a manipulator robot, comprising a support structure (16) to which at least one gripping member (18) can be fixed and an attachment device (20) intended to connect the fixing structure (16) to an arm of the robot, the attachment device (20) including: a first connecting member (22) connected to the fixing structure (16) , a second support member (26) intended to be mounted on the robot arm, and releasable coupling means (58, 76) , able to connect stably the first and the second member (22, 26) and reversibly disconnect these members in the event of an impact of predetermined force on the fixing structure (16) .

2. Support fixture according to Claim 1, in which said second support member (26) includes a first fixed part (28) and a second movable part (32) mounted rotatably on the first one about a first axis (X) and carrying said first connecting member (22) in such a way that the latter can be oriented with respect to said first fixed part (28) about at least said first axis (X) .

3. Support fixture according to Claim 2 , in which said second movable part (32) of the second support member (26) includes a first and a second element (34, 36) connected together rotatably about a second axis (Y) perpendicular to the first one (X) .

4. Support fixture according to Claim 3 , in which said first element (34) is an annular element mounted rotatably on the fixed part (28) of the support member (26) about said first axis (X) , and said second element (36) is an annular element mounted rotatably inside the first element (34) about said second axis (Y) .

5. Support fixture according to Claim 3 or 4, in which said first element (34) is mounted on the fixed part (28) of the support member (26) by means of a first pair of pins (35) defining said first axis of rotation (X) and in which said second element (36) is connected to the first one (34) by means of a second pair of pins (37) defining said second axis of rotation (Y) .

6. Support fixture according to Claim 1 , in which said coupling means (58, 76) include a plurality of support inserts (58) which form each a bearing surface (64) having a recess (66) and a corresponding plurality of spherical-head pins (76) preloaded resiliently so as 'to engage each in the recess (66) of a corresponding insert (58) .

7. Support fixture according to Claim 6 , in which said plurality of support inserts (58) comprises three inserts angularly equidistant and said corresponding plurality of spherical-head pins (76) comprises three angularly equidistant pins, in such a way that the pins (76) are preloaded resiliently in a radial direction against the bearing surfaces (64) of the respective inserts (58) .

8. Support fixture according to Claims 2 and 6, in which the support inserts (58) are mounted in said second movable part (32) and the spherical-head pins (76) are mounted in said first connecting member (22) .

9. Support fixture according to Claims 4 and 8, in which the support inserts (58) are mounted in the second annular element (36) of the second movable part (32) .

10. Support fixture according to Claim 9, in which the support inserts (58) each comprise a shank (60) inserted into a corresponding hole (62) of said second annular element (36) and a plate (64) which projects towards the inner side of the element (36) and forms said bearing surface.

11. Support fixture according to Claim 8, in which said first connecting member (22) has a corresponding plurality of radial cylindrical cavities (74) , each of which receives a spherical-head pin (76) and a spring assembly (80) able to exert a preload elastic force tending to push the spherical- head pin (76) against the bearing surface (64) of the corresponding support insert (58) .

12. Support fixture according to Claim 11, in which each spring assembly (80) comprises a series of Belleville springs arranged in pack form on top of one another inside the cavity (74) about a stem (82) of the pin (76) .

13. Support fixture according to Claim 12 , in which each radial cylindrical cavity (74) slidably receives a spring plate (98) able to vary the preload force of the respective spring assembly (80) .

14. Support fixture according to Claim 13 , in which the connecting member (22) includes a screw-type adjusting mechanism (92) able to vary the position of the spring plates

(98) of the spring assemblies (80) so as to vary the preload force of these latter.

15. Manipulator robot, comprising a support fixture according to any of the preceding claims .