Wrist Device, Industrial Robot And Method

Abstract

A wrist device for an industrial robot, the wrist device including a wrist housing; a first member; a second member; a first pinion rotatable about a first pinion axis; a first crown wheel for driving the first member, the first crown wheel meshing with the first pinion; a second pinion rotatable about a second pinion axis; a second crown wheel for driving the second member, the second crown wheel meshing with the second pinion; and an integral pinion housing fixedly attached to the wrist housing, the pinion housing supporting the first pinion for rotation about the first pinion axis and supporting the second pinion for rotation about the second pinion axis. An industrial robot including a wrist device, and a method of assembling a wrist device for an industrial robot, are also provided.

Claims

1. A wrist device for an industrial robot, the wrist device comprising: a wrist housing; a first member movable relative to the wrist housing; a second member movable relative to the wrist housing and relative to the first member; a first pinion rotatable about a first pinion axis; a first crown wheel for driving the first member, the first crown wheel meshing with the first pinion; a second pinion rotatable about a second pinion axis; a second crown wheel for driving the second member, the second crown wheel meshing with the second pinion; and an integral pinion housing fixedly attached to the wrist housing, the pinion housing supporting the first pinion for rotation about the first pinion axis and supporting the second pinion for rotation about the second pinion axis.

2. The wrist device according to claim 1, wherein the first crown wheel is arranged to rotate about a first axis, and wherein the first pinion and the second pinion are offset in a direction parallel with the first axis.

3. The wrist device according to claim 1, further comprising at least one first bearing rotationally supporting the first pinion inside the pinion housing for rotation about the first pinion axis, and at least one second bearing rotationally supporting the second pinion inside the pinion housing for rotation about the second pinion axis.

4. The wrist device according to claim 3, wherein the pinion housing comprises a first opening and a second opening, and wherein one of the at least one first bearing is arranged in the first opening and one of the at least one second bearing is arranged in the second opening.

5. The wrist device according to claim 1, wherein the pinion housing comprises a first through hole and a second through hole, wherein the first pinion passes through the first through hole and wherein the second pinion passes through the second through hole.

6. The wrist device according to claim 1, wherein the pinion housing is fixedly attached to the wrist housing by means of a fastening arrangement.

7. The wrist device according to claim 1, wherein the pinion housing is formed in one piece.

8. The wrist device according to claim 1, wherein the first pinion axis and the second pinion axis are parallel.

9. The wrist device according to claim 1, wherein the first crown wheel is arranged to rotate about a first axis, and wherein the first member and the first crown wheel are fixed with respect to each other.

10. The wrist device according to claim 1, wherein each of the first crown wheel and the second crown wheel is arranged to rotate about a first axis.

11. The wrist device according to claim 1, wherein the first crown wheel is arranged to rotate about a first axis, and wherein the second member is arranged to rotate about a second axis perpendicular to the first axis.

12. An industrial robot comprising a wrist device having: a wrist housing; a first member movable relative to the wrist housing; a second member movable relative to the wrist housing and relative to the first member; a first pinion rotatable about a first pinion axis; a first crown wheel for driving the first member, the first crown wheel meshing with the first pinion; a second pinion rotatable about a second pinion axis; a second crown wheel for driving the second member, the second crown wheel meshing with the second pinion; and an integral pinion housing fixedly attached to the wrist housing, the pinion housing supporting the first pinion for rotation about the first pinion axis and supporting the second pinion for rotation about the second pinion axis.

13. A method of assembling a wrist device for an industrial robot, the method comprising: providing a wrist housing having a first crown wheel and a second crown wheel; Page 6 providing an integral pinion housing rotationally supporting a first pinion and rotationally supporting a second pinion; and fixedly attaching the pinion housing to the wrist housing such that the first pinion meshes with the first crown wheel and the second pinion meshes with the second crown wheel.

14. The method according to claim 13, further comprising translationally moving the pinion housing such that the first pinion meshes with the first crown wheel and the second pinion meshes with the second crown wheel prior to fixedly attaching the pinion housing to the wrist housing.

15. The method according to claim 13, further comprising rotating the pinion housing such that the first pinion meshes with the first crown wheel and the second pinion meshes with the second crown wheel prior to fixedly attaching the pinion housing to the wrist housing.

16. The wrist device according to claim 2, further comprising at least one first bearing rotationally supporting the first pinion inside the pinion housing for rotation about the first pinion axis, and at least one second bearing rotationally supporting the second pinion inside the pinion housing for rotation about the second pinion axis.

17. The method according to claim 14, further comprising rotating the pinion housing such that the first pinion meshes with the first crown wheel and the second pinion meshes with the second crown wheel prior to fixedly attaching the pinion housing to the wrist housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

[0049] FIG. 1: schematically represents a side view of an industrial robot comprising a wrist device;

[0050] FIG. 2: schematically represents a cross-sectional side view of the wrist device;

[0051] FIG. 3: schematically represents a perspective view of the wrist device; and FIG. 4: schematically represents a cross-sectional top view of the wrist device.

DETAILED DESCRIPTION

[0052] In the following, a wrist device for an industrial robot, an industrial robot comprising a wrist device, and a method of assembling a wrist device for an industrial robot, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

[0053] FIG. 1 schematically represents a side view of an industrial robot 10. The industrial robot 10 is here exemplified as a six-axis industrial robot but the present disclosure is not limited to this type of industrial robot. An industrial robot according to the present disclosure may comprise a manipulator movable in at least three axes.

[0054] The industrial robot 10 of this example comprises a base member 12, a tool 14, and a control system 16, such as a robot controller. The industrial robot 10 further comprises a link member 18 distal of the base member 12 and rotatable around a vertical axis 20a relative to the base member 12, a link member 22 distal of the link member 18 and rotatable around a horizontal axis 20b relative to the link member 18, a link member 24 distal of the link member 22 and rotatable around a horizontal axis 20c relative to the link member 22, a link member 26 distal of the link member 24 and rotatable around an axis 20d relative to the link member 24, a link member 28 distal of the link member 26 and rotatable around an axis 20e relative to the link member 26, and a link member 30 distal of the link member 28 and rotatable around an axis 20f relative to the link member 28. The link member 30 comprises an interface (not denoted) to which the tool 14 is attached.

[0055] The industrial robot 10 comprises a wrist device 32. The wrist device 32 of this example comprises a wrist housing 34, the link member 28 and the link member 30. The wrist housing 34 is fixed with respect to the link member 26.

[0056] In the following, the link member 28 will be referred to as a first member 28, the link member 30 will be referred to as a second member 30, although the first member 28 is provided at the fifth axis and the second member 30 is provided at the sixth axis. Correspondingly, the axis 20e will be referred to as a first axis 20e and the axis 20f will be referred to as a second axis 20f. The wrist housing 34, the first member 28 and the second member 30 may however be provided at different link members of the industrial robot 10. In any case, the first member 28 is proximal of the second member 30.

[0057] The industrial robot 10 of this example is a welding robot. The tool 14 is thus a weld tool. The industrial robot 10 of this example further comprises a cable harness 36. The cable harness 36 may for example comprise electric power cables, electric signal cables, hoses for compressed air and coolant etc. The cable harness 36 extends from the link member 26, outside of the wrist housing 34, and to the first member 28.

[0058] In FIG. 1, the wrist housing 34 is a tilt housing. The first member 28 is rotatable relative to the wrist housing 34 about the first axis 20e. The second member 30 is rotatable relative to the first member 28, and also relative to the wrist housing 34, about the second axis 20f. In this example, the axis 20d and the first axis 20e cross each other at right angles. Furthermore, the axis 20d and the second axis 20f are arranged in the same plane. Consequently, the first axis 20e and the second axis 20f intersect and are perpendicular to each other.

[0059] FIG. 2 schematically represents a cross-sectional side view of the wrist device 32. As shown in FIG. 2, the wrist device 32 comprises a first pinion 38 and a second pinion 40. The first pinion 38 is rotatable about a first pinion axis 42. The second pinion 40 is rotatable about a second pinion axis 44. In this example, the first pinion axis 42 and the second pinion axis 44 are parallel.

[0060] The wrist device 32 further comprises a first crown wheel 46. The first pinion 38 meshes with the first crown wheel 46. The first crown wheel 46 is arranged to drive the first member 28 relative to the wrist housing 34. In this example, the first crown wheel 46 is fixed with respect to the first member 28 such that the first crown wheel 46 and the first member 28 rotate in common about the first axis 20e. The first pinion 38 and the first crown wheel 46 form a first hypoid gear.

[0061] The wrist device 32 further comprises a second crown wheel 70 (see FIG. 4). The second pinion 40 meshes with the second crown wheel 70. The second crown wheel 70 is arranged to drive the second member 30 relative to the first member 28, and relative to the wrist housing 34. The second pinion 40 and the second crown wheel 70 form a second hypoid gear.

[0062] The wrist device 32 further comprises an integral pinion housing 48. The pinion housing 48 is fixedly attached to the wrist housing 34. In this example, the pinion housing 48 is fixedly attached to the wrist housing 34 by means of a fastening arrangement, here exemplified as screws 50. Both the first pinion 38 and the second pinion 40 extend through the same pinion housing 48. The pinion housing 48 is thus a common pinion housing 48 for both the first pinion 38 and the second pinion 40. Furthermore, the pinion housing 48, the first pinion 38 and the second pinion 40 are arranged inside the wrist housing 34.

[0063] The pinion housing 48 rotationally supports the first pinion 38 for rotation about the first pinion axis 42. The pinion housing 48 further rotationally supports the second pinion 40 for rotation about the second pinion axis 44. To this end, the pinion housing 48 of this example comprises two first bearings 52, 54 and two second bearings 56, 58. The two first bearings 52, 54 and the two second bearings 56, 58 are arranged inside the pinion housing 48.

[0064] The two first bearings 52, 54 rotationally support the first pinion 38 for rotation about the first pinion axis 42. The two first bearings 52, 54 are here exemplified as a primary first bearing 52 and a secondary first bearing 54. The primary first bearing 52 is an angular contact ball bearing and the secondary first bearing 54 is a needle roller bearing. The primary first bearing 52 takes both axial and radial loads (with respect to the first pinion axis 42) and the secondary first bearing 54 takes radial loads (with respect to the first pinion axis 42). As shown in FIG. 2, the secondary first bearing 54 is arranged between the primary first bearing 52 and the first axis 20e.

[0065] The two second bearings 56, 58 rotationally support the second pinion 40 for rotation about the second axis 20f. The two second bearings 56, 58 are here exemplified as a primary second bearing 56 and a secondary second bearing 58. In this example, the primary second bearing 56 is an angular contact ball bearing and the secondary second bearing 58 is a needle roller bearing. The primary second bearing 56 takes both axial and radial loads (with respect to the second pinion axis 44) and the secondary second bearing 58 takes radial loads (with respect to the second pinion axis 44). As shown in FIG. 2, the secondary second bearing 58 is arranged between the primary second bearing 56 and the first axis 20e.

[0066] The pinion housing 48 further comprises a first opening 60 and a second opening 62. The primary first bearing 52 is accommodated inside the first opening 60 and the primary second bearing 56 is accommodated inside the second opening 62. Due to the integrity of the pinion housing 48, only a very small material thickness is provided between the first opening 60 and the second opening 62.

[0067] The pinion housing 48 further comprises a first through hole 64 and a second through hole 66. As shown in FIG. 2, the first through hole 64 has a smaller diameter than the first opening 60 and the second through hole 66 has a smaller diameter than the second opening 62. Thereby, more material is provided in the pinion housing 48 between the first through hole 64 and the second through hole 66 than between the first opening 60 and the second opening 62.

[0068] The first through hole 64 extends from the first opening 60 to the opposite side of the pinion housing 48. The secondary first bearing 54 is accommodated inside the first through hole 64. The secondary first bearing 54 rotationally supports the first pinion 38 for rotation about the first pinion axis 42.

[0069] The second through hole 66 extends from the second opening 62 to the opposite side of the pinion housing 48. The secondary second bearing 58 is accommodated inside the second through hole 66. The secondary second bearing 58 rotationally supports the second pinion 40 for rotation about the second pinion axis 44.

[0070] The pinion housing 48 further comprises a plurality of slots 68. Each slot 68 extends through the pinion housing 48, in FIG. 2 generally parallel with the first pinion axis 42 and the second pinion axis 44. Each slot 68 is arranged to receive a shaft of the screw 50. Each slot 68 is however larger than the shaft of the screw 50. Thereby, if the screws 50 are loosened slightly, the position of the pinion housing 48 can be adjusted relative to the wrist housing 34 while the screws 50 are maintained in engagement with the wrist housing 34. That is, the pinion housing 48 can be adjusted by rotation and/or translation relative to the wrist housing 34 in a plane perpendicular to the first pinion axis 42 and the second pinion axis 44.

[0071] The industrial robot 10 further comprises a first drive unit (not shown) and a second drive unit (not shown). The first drive unit is arranged to rotationally drive the first pinion 38 and the second drive unit is arranged to rotationally drive the second pinion 40.

[0072] FIG. 3 schematically represents a perspective view of the wrist device 32. In FIG. 3, it can be seen that the first pinion 38 and the second pinion 40 are offset in a direction parallel with the first axis 20e.

[0073] The first pinion 38 and the second pinion 40 can be rotationally arranged in the pinion housing 48 at a site remote from the remaining industrial robot 10. The pinion housing 48 together with the first pinion 38 and the second pinion 40 can then be brought as one package into the wrist housing 34, e.g. linearly in a direction parallel with the second axis 20f in FIG. 3. The screws 50 can then be slightly screwed into the wrist housing 34. Prior to tightening the screws 50, the pinion housing 48 can be manually moved, e.g. rotated and translated, until both a backlash between the first pinion 38 and the first crown wheel 46, and a backlash between the second pinion 40 and the second crown wheel 70, are eliminated. The pinion housing 48 is then fixedly attached to the wrist housing 34 by tightening the screws 50. An operator can now manually rotate the first pinion 38 and the second pinion 40 and feel the response in the respective crown wheel to confirm that the backlash has been eliminated. Should backlash still prevail, the screws 50 can be slightly loosened and the pinion housing 48 adjusted once more.

[0074] As shown in FIG. 3, the primary first bearing 52 and the primary second bearing 56 are compactly arranged inside the pinion housing 48. Only a very thin piece of material is provided between the primary first bearing 52 and the primary second bearing 56.

[0075] Furthermore, since the pinion housing 48 encloses both the first pinion 38 and the second pinion 40, a largest distance between two screws 50 (over both the first pinion 38 and the second pinion 40) is relatively large. The pinion housing 48 can thereby provide large counter torques, despite the compact design of the wrist device 32.

[0076] FIG. 4 schematically represents a cross-sectional top view of the wrist device 32. In FIG. 4, the second crown wheel 70 can be seen. In this example, both the first crown wheel 46 and the second crown wheel 70 are arranged to rotate about the first axis 20e. The first crown wheel 46 has a larger diameter than the second crown wheel 70. An offset distance between the first pinion 38 and the first axis 20e is different than an offset distance between the second pinion 40 and the first axis 20e.

[0077] As shown in FIG. 4, the first pinion 38 and the second pinion 40 are arranged between the first crown wheel 46 and the second crown wheel 70. As can be gathered from FIG. 4, the first pinion 38 can be brought into meshing engagement with the first crown wheel 46 without backlash and the second pinion 40 can be brought into meshing engagement with the second crown wheel 70 without backlash by means of a single rotation of the pinion housing 48. FIG. 4 further shows that an offset distance between the first pinion 38 and the second pinion 40 in the direction parallel with the first axis 20e is relatively small. Thus, the wrist device 32 has a very compact design.

[0078] The wrist device 32 of this example further comprises a third bevel gear (not visible) for transmitting rotation of the second crown wheel 70 to a rotation of the second member 30 about the second axis 20f.

[0079] While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.