GB2168030A

GB2168030A - Fluid-operated rotary mechanism

Info

Publication number: GB2168030A
Application number: GB08529506A
Authority: GB
Inventors: John Warrander Franklin
Original assignee: BRITANNIA TOOL Co Ltd
Current assignee: BRITANNIA TOOL Co Ltd
Priority date: 1984-12-01
Filing date: 1985-11-29
Publication date: 1986-06-11
Also published as: GB2168030B; GB8529506D0

Abstract

A fluid-operated rotary mechanism consists of two or more devices 10 assembled together, each having relatively rotational portions connected so that the second device rotates about the axis of the first device. The devices have intersecting axes of rotation to provide a multi-axis device which may find application as a robot wrist having a roll axis 12, a pitch axis 50 (Fig.4), a yaw axis 35 and a further roll axis 63 intersecting at the common intersection point 65. In the piston and cylinder device 10 the piston 17 and cylinder 15 are relatively rotatable about the longitudinal axis 12 upon the supply of fluid. The piston 17 includes a helical groove 24 engaged by a roller 32 carried on the cylinder. <IMAGE>

Description

SPECIFICATION Fluid-operated rotary mechanism This invention relates to a fluid-operated rotary mechanism.

The invention may find particular application in industrial robots and especially at the end of the arm of an industrial robot to act as a robotic wrist but it is not limited to this application.

An object of the invention is to provide an improved fluid-operated rotary mechanism.

According to one aspect the invention provides a fluid-operated rotary mechanism comprising at least two rotary members of which a first rotary member has a first axis of rotation and a second rotary member has a second axis of rotation extending transverse to the first axis and intersecting the first axis, each rotary member including two relatively rotatable portions which are rotated relative to one another by fluid-operated drive means, a rotatable portion of the first member being connected to the second member for rotation of the second member about said first axis and a rotatable portion of the second member being rotatable about the second axis.

Preferably the mechanism includes a third rotary member having a third axis of rotation intersecting the first and second axes, lying in the same plane as the second axis and extending at a right angle thereto, the third rotary member having fluid-operated drive means for effecting relative rotation between two portions of the member.

Conveniently the third rotary member is connected to the first or second rotary member for rotation of the first and/or second rotary member about said third axis.

The drive means for at least one of the rotary members may be located between the two relatively rotatable portions one of which is in the form of a cylinder and the other portion of which includes a piston, relative reciprocal movement between the piston and cylinder causing relative rotation of the two portions.

The piston and cylinder may include constraining means between the piston and cylinder whereby relative reciprocal movement between the piston and cylinder is constrained to effect relative rotational movement between the piston and cylinder.

Conveniently the piston includes a helical path formed in the piston and arranged to be engaged by a follower fixed relative to the cylinder so that relative axial movement between the piston and cylinder causes the follower to move along the helical path and cause relative rotation of the piston and cylinder, and the piston is carried on a shaft or rod and is movable axially relative to the rod but is constrained against rotation relative to the rod.

The invention may include a fourth rotary member having relatively rotatable portions rotatable about a fourth axis intersecting the three other axes at said common point.

According to a second aspect the invention provides a fluid-operated rotary mechanism comprising a rotary member having two relatively rotatable portions and fluid-operated drive means between the portions to effect relative rotation between the portions, one of the portions including a cylinder and the other of the portions including a piston, the fluid being admitted to the cylinder to drive the piston reciprocally relative to the cylinder, the piston and the cylinder between them defining constraining means whereby, upon relative reciprocal movement between the piston and cylinder, relative rotation of the piston and cylinder takes place.

Further features of the invention will appear from the following description of an embodiment of the invention given by way of example only and with reference to the drawings, in which: Figure 1 is a side elevation of a rotary mechanism according to the invention, Figure 2 is a plan view of the mechanism of Figure 1, Figure 3 is a longitudinal cross-section of a part of the rotary mechanism of Figure 1, Figure 4 is a longitudinal cross-section of another part of the rotary mechanism of Figure 1, Figure 5 is a longitudinal cross-section of a further part of the rotary mechanism of Figure 1.

Referring to the drawings, a robotic wrist mechanism is shown in Figures 1 and 2 which is fluid-operated and is intended for mounting on the end of an arm of an industrial robot (not shown). The mechanism is fixed to the arm by fixing means (not shown) attaching the arm to a body member 10, shown in detail in Figure 3, having a central longitudinal axis 12 which is normally in alignment with the longitudinal axis of the arm. The axis 12 is termed a roll axis of the device.

The body or roll member 10 has an end cover 13 fixed to an outer sleeve 14. The fixing means for attachment to the arm is secured in relation to the cover 13 and the sleeve 14.

A cylinder member 15 is flanged at 16 at one end and is located in the sleeve 14 for rotation relative to the sleeve and cover 13. Within the cylinder member 15 is located an annular piston 17 which, with the cylinder 15, defines a piston and cylinder device by which rotation of the cylinder 15 about the axis 12 is achieved.

The piston 17 is carried on a rod 19 which is secured to the cover 13 by a nut 20 so that the rod 19 is fixed relative to cover 13 and the sleeve 14.

The piston 17 is movable along the rod 19 but is restrained against rotation relative to the rod 19 by interengaging splines 21 on the rod and on the inner surface of the piston 17.

The cylinder 15 carries four equally and circumferentially spaced rollers 22 rotatable about axes at a right angle to the axis 12 and which project inwardly of the cylinder 15 and into a four-start helical groove 24 formed in the outer surface of the piston 17. Thus, as fluid is directed into the cylinder through port 25 or 26 at opposite ends of the cylinder, the piston 17 moves reciprocally along the cylinder 15 in one direction or the other. Due to the engagement of the rollers 22 with the groove 24 such movement causes the cylinder 15 to rotate about the axis 12 relative to the piston 17 and its associated rod 19.

Fluid is fed to the ports 25 and 26 from a source of pressure fluid, which may be hydraulic fluid or air, via circumferential grooves 27 and 28 in the outer surface of the cylinder 15. Further grooves 29 serve to provide passageways for leading fluid to other fluid-operated body members, to be described. The grooves 27, 28 and 29 are sealed from one another by intermediate sealing members 30 and by the sleeve 14. Further seals are provided, as shown, for preventing the egress of fluid from within the cylinder.

The cylinder 15, as shown, can roll through about 355" about the axis 12.

The cylinder member 15 is connected through a connecting member 31 to pitch and yaw body member 32 and 33 (Figure 4) which together rotate about the axis 12 when the member 10 is operated.

The pitch member 32 is connected at its ends to the connecting member 31 and the member 32 has a central longitudinal axis 50, termed the pitch axis.

The pitch member 32 has end members 51 to which is fixed, by caps 52, a rod 53. A body member 40 is located at its end rotatably in the end members 51, needle rollers 54 being located between the end members 51 and the body 40.

An annular piston 55 is carried on the rod 53 for axial movement relative to the rod but constrained against rotation about the rod by splines 56. About the outer surface of the piston 55 is located a fourstart helical groove 57 in which is engaged four rollers 58 equally spaced about the axis 50, the axes of the rollers lying parallel to said axis.

The rollers are carried by the body member 40 and as fluid is introduced into the body member 40, which defines a cylinder for the piston 55, the piston is moved in one direction or the other relative to the rod 53. Since the rod and hence the piston are fixed against rotation about the axis 50, the body member 40 is caused to rotate about the axis 50 as the rollers 58 move along the groove 57.

As shown the pitch member 32 can rotate about 1900 about the axis 50.

The yaw member 33 has a central longitudinal axis 35, termed the yaw axis. The yaw member 33 has end members 36 at opposite ends fixed to an operating member or a further roll member 60 through a connecting member 61 and each end member 36 has secured to it, by a nut 37, a rod 38.

The rods 38 extend through cylinders 39 defined by a body member 40A integral with the member 40 of the pitch member 32, and the end members 36 and the rods 38 rotate relative to the body member 40A about the axis 35. Within each cylinder 39 is an annular piston 41 movable reciprocally in the cylinder but constrained against rotation about the rod 38 by splines 42 on the piston 41 and on a sleeve 43 secured to the associated end member 36. Needle roller bearings 44 are located between the end members 36 and the outer surface of the body member 40A for relative rotation thereof.

The pistons 41 are each formed with a short helical groove 46 about their outer surface and the body member 40A carries a roller 47 which projects into the cylinder 39 to engage in the groove 46.

The rollers are arranged for rotation about axes parallel to the axis 35.

As the pistons 41 are moved in unison with each other upon introduction of fluid into the cylinder 39 and in the direction of the axis 35, the rollers 47 pass along the grooves 46. Since the pistons 41 are constrained against rotation relative to the axis 35 the end members 36 rotate during such movement about said axis.

As illustrated the end members 36 are connected through the connecting member 61 to the roll member 60 (Figure 5) but, instead, the connecting member 60 may support an operating member (not shown), the operating member including, for example, a workpiece or tool holding member. In the present case a further roll axis 63 is provided, the operating member (not shown) being attached to the roll member 61 by a flange 64.

The roll axis 63 passes through the common intersection point 65 of the axes 12, 35, 50 of the device.

The roll member 60 includes a cylinder member 67 which defines a cylinder 68 for an annular piston 69. The piston 69 is axially movable along a rod 70 and is constrained against rotation relative to the rod 70 by splines 71 on the rod and on the piston.

The outer surface of the piston 69 is formed with a four-start helical groove 72 in which is engaged rollers 73 mounted on the cylinder member 67.

The rod 70 is secured to a drive body 74 for rotation therewith upon operation of the roll member and the body 74 is located around the cylindrical member 67. Needle bearings 75 are interposed between the body 74 and the member 67.

The cylinder member 67 is secured to the connecting member 61 so that when fluid is introduced into the cylinder 68 the piston 69 moves along the cylinder. The engagement of the rollers 73 with the groove 72 causes the piston 69 to rotate with the rod 70 about the roll axis 63 and thereby cause the drive body 74 to rotate about the same axis.

As shown the roll member 60 is rotatable through 1800 or 355" about its axis.

Each of the roll members 10, the pitch member 32, the yaw member 33 and the further roll member 60 are provided with encoders whereby the relative rotational positions of the members are determined. Such encoders are shown at 80, 81, 82 and 83 in the drawings and may be in the form of optical incremental encoders or potentiometers, each driven by a gear coupled by a spline to the associated rods of the members Such encoders feed electrical signals to a computer by which the mechanism is controlled.

Although there is described a device having four similarly constructed fluid-operated members the device may include only two members, for example the pitch and yaw members, or three members, for example one of the roll members and the pitch and yaw members.

Moreover the members may find application as individual units.

For these purposes each fluid-operated member is formed as an individual module capable of assembly into any desired configuration.

Claims

1. A fluid-operated rotary mechanism comprising at least two rotary members of which a first rotary member has a first axis of rotation and a second rotary member has a second axis of rotation extending transverse to the first axis and intersecting the first axis, each rotary member including two relatively rotatable portions which are rotated relative to one another by fluid-operated drive means, a rotatable portion of the first member being connected to the second member for rotation of the second member about said first axis and a rotatable portion of the second member being rotatable about the second axis.

2. A mechanism according to claim 1 comprising a third rotary member having a third axis of rotation intersecting the first and second axes, lying in the same plane as the second axis and extending at a right angle thereto, the third rotary member having fluid-operated drive means for effecting relative rotation between two portions of the member.

3. A mechanism according to claim 2 wherein the third rotary member is connected to the first or second rotary member for rotation of the first and/ or second rotary member about said third axis.

4. A mechanism according to claim 1, 2 or 3 wherein the drive means for at least one of the rotary members is located between the two relatively rotatable portions one of which is in the form of a cylinder and the other portion of which includes a piston, relative reciprocal movement between the piston and cylinder causing relative rotation of the two portions.

5. A mechanism according to claim 4 wherein the piston and cylinder include constraining means between the piston and cylinder whereby relative reciprocal movement between the piston and cylinder is constrained to effect relative rotational movement between the piston and cylinder.

6. A mechanism according to claim 5 wherein the piston includes a helical path formed in the piston and arranged to be engaged by a follower fixed relative to the cylinder so that relative axial movement between the piston and cylinder causes the follower to move along the helical path and cause relative rotation of the piston and cylinder.

7. A mechanism according to claim 6 wherein the piston is carried on a shaft or rod and is movable axially relative to the rod but is constrained against rotation relative to the rod.

8. A mechanism according to any one of the preceding claims wherein the first rotary member is carried on a support to extend with its axis longitudinally of the support, the second rotary member is rotatable about said longitudinal axis, a third rotary member is carried by the second rotary member for rotation about the second axis, and the third rotary member carries an operating member which is rotatable about the axis of rotation of the third rotary member, the three axes intersecting at a common point.

9. A mechanism according to claim 8 wherein the operating member includes a fourth rotary member having relatively rotatable portions rotatable about a fourth axis intersecting the three other axes at said common point.

10. A mechanism according to claim 9 wherein one of the rotatable portions of the fourth rotary member is rotated about the other portion by fluidoperated drive means and is arranged to carry tool or workpiece holding means.

11. A mechanism according to any one of the preceding claims wherein each of the rotary members includes positional detectors whereby the positions of the relatively rotatable portions relative to another are detected.

12. A fluid-operated rotary mechanism comprising a rotary member having two relatively rotatable portions and fluid-operated drive means between the portions to effect relative rotation between the portions, one of the portions including a piston, the fluid being admitted to the cylinder to drive the piston reciprocally relative to the cylinder, the piston and the cylinder between them defining constraining means whereby, upon relative reciprocal movement between the piston and cylinder, relative rotation of the piston and cylinder takes place.

13. A mechanism according to claim 12 wherein the piston defines a helical path and the cylinder carries a follower fixed relative to the cylinder and extending into said helical path so that during relative axial movement between the piston and cylinder the piston and cylinder are constrained to rotate relative to one another.

14. A mechanism according to claim 13 wherein the piston is carried on a central longitudinal shaft or rod for movement axially relative to the rod but is constrained against rotational movement about the axis of the rod.

15. A mechanism according to claims 6, 13 or 14 wherein the helical path is a helical groove in the outer periphery of the piston and the follower is engaged between the side walls of the groove so that the follower moves along the groove during relative movement between the piston and cylinder.

16. A mechanism according to claim 15 wherein the helical path includes multistart helical grooves each of which is engaged by a follower, the follower being in the form of a roller rotatable about an axis parallel to the axis of the cylinder.

17. A fluid operated rotary mechanism substantially as described with reference to the drawings.