Rotary coupling device for a multi-axis manipulator

Abstract

A multi-axis manipulator in the form of a robotic arm includes a safety disc (41) and safety collar (42) at one or more of the pivoting joints (14, 17, 19, 21, 23) thereof. The disc and collar define a small running clearance in normal use, but make contact in the event of excessive wear or failure of the rotary bearing at the respective joint. An inspection window (48) permits the running clearance to be checked, and the collar may comprise a caliper brake.

Claims

1. A rotary device comprising an input member, an output member rotatable on said input member about an axis of rotation, and one or more rolling element support bearings between said input member and output member, said bearings being adapted to resist axial and cantilever loads of said output member in use, wherein one of said input and output members includes a rim having a circular periphery co-axial with said axis, and wherein the other of said input and output members includes a safety collar having an arcuate groove overlapping said rim with a running clearance, such that in the event of a loss of structural integrity in the one or more rolling element support bearings, the rim contacts the safety collar and prevents substantial movement of the output member with respect to the input member.

2. The rotary device according to claim 1, wherein the collar is substantially external to the rim.

3. The rotary device according to claim 2, wherein said collar includes an inspection aperture for viewing said running clearance.

4. The rotary device according to claim 1, wherein said rim is defined by a disc attachable to a stator.

5. The rotary device according to claim 1, wherein said collar comprises arcuate segments.

6. The rotary device according to claim 5, wherein said collar is directly attached to a rotor.

7. The rotary device according to claim 1, wherein said collar is circularly continuous in use.

8. The rotary device according to claim 1, wherein said one or more support bearings comprise opposed rolling element bearings at a separation along said axis.

9. The rotary device according to claim 1, wherein said running clearance is in the range 0.5-2.0 mm in the direction of said axis.

10. A multi-axis manipulator comprising one or more rotary devices, each rotary device comprising: an input member, an output member rotatable on said input member about an axis of rotation, and one or more rolling element support bearings between said input member and output member, said bearings being adapted to resist axial and cantilever loads of said output member in use; a stator connected to said input member, and a rotor connected to said output member, wherein one of said input and output members includes a rim having a circular periphery co-axial with said axis, and the other of said input and output members includes a safety collar having an arcuate groove overlapping said rim with a running clearance, defining a space that does not abut the one or more rolling element support bearings and such that in the event of a loss of structural integrity in the one or more rolling element support bearings, the rim contacts the safety collar and prevents substantial movement of the output member with respect to the input member.

11. The multi-axis manipulator according to claim 10, having a base mounting, the input member being closer to the base than the output member.

12. The multi-axis manipulator according to claim 10, comprising three or more axes of non-intersecting relative rotation, a rotary device of said one or more rotary devices being provided on each axis.

13. The multi-axis manipulator according to claim 10, comprising an amusement park ride.

14. The multi-axis manipulator according to claim 13, wherein said manipulator has a chair at the free end thereof.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Features of the invention will be apparent from the following description of an embodiment of the invention shown by way of example only in the accompanying drawings, in which:

(2) FIG. 1 is a perspective view of an exemplar multi-axis manipulator adapted to a fairground ride.

(3) FIG. 2 is a plan view of the manipulator of FIG. 1.

(4) FIG. 3 is an exploded view from one side of a multi-axis manipulator incorporating an embodiment of the invention.

(5) FIG. 4 corresponds to FIG. 3, and shows an exploded view from the other side.

(6) FIG. 5 is a perspective side elevation of a motor and turntable assembly incorporating an embodiment of the invention.

(7) FIG. 6 corresponds to FIG. 5 and shows a perspective view from one end.

(8) FIG. 7 is an exploded view of the assembly of FIGS. 5 and 6.

(9) FIG. 8 corresponds to FIG. 5 and illustrates in partial section a safety collar and disc of the invention.

(10) FIG. 9 is an enlarged view of the sectioned portion of FIG. 8.

DESCRIPTION OF AN EMBODIMENT

(11) FIGS. 1 and 2 illustrate a known kind of multi-axis manipulator 10 adapted to a fairground ride, and having a two-person chair 11 at the free end of a computer controlled robotic arm.

(12) The manipulator 10 comprises a base ring 12 anchored to a substrate (not shown) such as a wheeled vehicle or permanent foundation. A base cylinder 13 has a rotary coupling 14 in the form of a turntable rotatable about a vertical axis A-A.

(13) The turntable 14 has a short upwardly angled arm 15 defining a horizontal axis B-B at the free end, and about which a second arm 16 is pivotable via a rotary coupling 17.

(14) The second arm 16 defines at the free end a horizontal axis C-C about which a third arm 18 is pivotable via a rotary coupling 19.

(15) The third arm 18 has a rotary coupling 21 via which a fourth arm 22 is rotatable about an axis D. The fourth arm 22 defines at the free end a pivot axis E-E about which a chair 11 is pivotable via a rotary coupling 23.

(16) As illustrated, the chair carries two persons, and has suitable over-the-shoulder restraint mechanisms 24. The chair could be adapted to 3, 4 or more persons depending upon the load capacity of the manipulator.

(17) The manipulator of FIGS. 1 and 2 has five degrees of freedom and may be programmed to give an exciting high speed ride within the envelope defined by the reach of the arm. Each coupling 14, 17, 19, 21, 23 comprises typically a rolling element bearing assembly of known type, for example opposed ball or angular contact bearings suitable for supporting the axial and cantilever loads which may be expected in use.

(18) FIGS. 3-9 illustrate an embodiment of the invention. The manipulator of FIGS. 3 and 4 is of the same general kind as that illustrated in FIGS. 1 and 2, save that the coupling 21, arm 22, coupling 23 and seat 11 are omitted; other components are given the same reference numerals for ready reference. The rotary coupling 14 is rotatable via a co-axial motor 30, and the turntable arm 15 is constituted by parallel arms 15a, 15b, having respective eyes 31a, 31b on the pivot axis B.

(19) The invention is illustrated by reference to coupling 17 and comprises a stator 32 and a rotor 33.

(20) The stator 32 consists of an epicyclic gearbox 34 having a casing/annulus 35 connected to turntable arm 15a via a ring of threaded fasteners. A reversible motor 36 is coupled to the casing 35, and has rotatable armature 37 coupled to the sun gear of the epicyclic gearbox 34.

(21) The output of the epicyclic gearbox is via the planet carrier 38, which is rotatably coupled to a drive plate 39 and to the second arm 16 via respective circular arrays of threaded fasteners. The second arm comprises a rotor, though according to space and operational constraints such a rotor may move through only a restricted arcuate range.

(22) In such an arrangement back and forth rotation of the armature 37 results in relative bi-directional pivoting movement of the arm 16.

(23) The invention comprises a safety disc 41 and safety collar 42. The safety disc 41 comprises an annulus connected to the turntable arm 15b and surrounding the drive connection from the gearbox 34 to the second arm 16; connection is by a circular array of threaded fasteners, as illustrated.

(24) The safety disc 41 has a circular peripheral rim 43 of substantially fixed diameter and width.

(25) The safety collar 42 comprises semi-circular elements which substantially surround and enclose the rim 43 by virtue of an arcuate groove 44 (FIG. 9), and which are connected to the drive plate 39 by a circular array of threaded fasteners so as to be pivotable therewith. Additionally the safety collar 42 provides a convenient attachment location for a counterbalance strut 45 which applies in use a torque to the drive plate 39 in opposition to the gravitational torque acting on the arm 16.

(26) The safety collar 42 encloses the rim 43 with a small radial and axial running clearance 46, 47, so as to permit relative pivoting movement without contact. The conventional bearing arrangement for the arm 16 with respect to the turntable arms 15a, 15b, is relied upon to maintain the clearance 46, 47 in normal operation. However should this bearing arrangement fail, due to routine wear or catastrophic mechanical failure, relative tipping of the arm 16 will be arrested immediately by contact between the rim 43 and the safety collar 42, thus preventing potential separation of the arm 16 from the turntable.

(27) Contact between the rim 43 and collar 42 results in increased friction, which in turn requires additional drive torque from the motor to meet position and speed requirements of a control program. Such additional torque can be sensed by a conventional over-torque sensor of the motor, and utilized by a control system to safely bring the manipulator to a halt. Other means of sensing contact, for example by positional or acoustic sensors, may also be used.

(28) It will be understood that the additional friction of contact will also result in reduced speed of relative movement, and this may be enhanced by providing one or both of the rim 43 and groove 44 with a high friction surface or coating.

(29) One or both segments of the collar 42 may be provided with an inspection window 48 whereby the clearance 47 may be checked, for example by using a conventional feeler or go/no go gauge; by this means progressive deterioration of the bearing may be periodically assessed so that a scheduled maintenance programmed may be effected.

(30) The rim 43 and or groove 44 may also be provided with a coating, such as paint, whereby a witness mark is created upon the slightest contact. Such a mark may be easily observed when the manipulator is at rest and indicate to an unskilled machine minder that maintenance and/or adjustment may be required.

(31) The safety rim and safety collar of the invention may be applied, if desired, to each of the couplings 14, 17, 19, 21, 23 so as to obviate risk of separation of the rotor and stator components. It will also be understood that the rim and collar need not be produced as distinct components, but may be incorporated integrally with other components to which they are connected in use. However separate components facilitates repair, replacement and retro-fitting to existing manipulators.

(32) In a further alternative it will be understood that the collar may be functionally part of the stator, and the rim may be functionally part of the rotor. For example in the arrangement of FIG. 7, the planet carrier 38 might be connected to the disc 41 and in turn to the drive plate 39, whilst the safety collar 42 could be anchored to the turntable arm 15. In this case the counterbalance strut would be directly connected to the arm 16.

(33) It may also be desirable to, in some circumstances, to have the safety collar radially within the safety disc, in which case the disc may be constituted by segments for the purpose of assembly. Alternatively the male and female elements may be reversed, so that the safety collar includes a protruding circular rim, and the safety disc includes a peripheral groove to engage over such a rim.

(34) The female safety element, namely that component incorporating the groove 44, may also comprise a caliper brake for gripping the male element (the rim 43). Any suitable caliper brake may be appropriate, and it may act dynamically to bring the rotor element (e.g. arm 16) to a halt, or statically to act as a parking brake.