GB2194074A

GB2194074A - Rotatable workpiece supports

Info

Publication number: GB2194074A
Application number: GB08718521A
Authority: GB
Inventors: John David Galpin; Paul Stanley Willsher
Original assignee: PHOTON CONTROL Ltd
Current assignee: PHOTON CONTROL Ltd
Priority date: 1986-08-14
Filing date: 1987-08-05
Publication date: 1988-02-24
Anticipated expiration: 2007-08-05
Also published as: GB8718521D0; GB2194074B

Abstract

A support for angular rotation of a workpiece, such as a chuck supporting a bundle of optical fibres, comprises a fixed member 20, a movable member 14, and a pair of links 16, 18 inclined towards each other. The movable member 14 carries a chuck 10 on an arm 12 at a position in space where the straight line projections of the links intersect, such that movement of the member 14 by means of a threaded screw 22 causes the chuck 10 to rotate through a small angle. By having three such support arrangements, the chuck 10 may be moved about three mutually perpendicular axes. The links may be re- entrant (Figs. 4 and 5), in which case they are preferably connected by a rigid control arm (130, Figs. 4 and 5). <IMAGE>

Description

SPECIFICATION Workpiece supports Field of the invention This invention is concerned with supports for workpieces which have to provide at least one axis of rotation.

Background to the invention Supports for workpieces capable of rotating the latter about one or more axes are known.

Thus a turret chuck may be used to carry an object to rotate the latter to present different facets thereof to a work station or to assist in the rotational alignment with another object to permit a jointing operation to be performed as by welding or brazing.

Very precise, small angular movements are often required, as for example in work associated with fibre optics, typically in joining optical fibres end to end. Such joints usually need to be made so as to maximise the transmission of light from one fibre to the next and not only is it important to be able to accurately rotate one fibre relative to the next (so as to maintain the integrity of the individual optical fibre path through the junction) but it is also usually necessary to adjust the axes of one fibre bundle relative to the other, so as to obtain precisely the correct angle between the two abutting ends of the two fibres, to assure optimum light transmission across the junction.

Rotatable supports, commonly referred to as goniometers, are known for providing such control but known devices tend to include rolling bearings and for precision work, such as associated with the joining of the ends of optical fibres as aforesaid, there should preferably be no frictional and stictional forces or rumble and "noise" which are characteristices of all rolling bearings.

A gimballed support in which the conventional bearings are replaced by flexable strips or hinges eliminates many of the problems associated with rolling and sliding bearings, but as with all gimballed systems, access to the point at which the axes of rotation intersect is very restricted and such devices do not lend themselves to workpiece supports such as chucks where it is usually desirable to provide the flattest possible access cone.

To this end it is an object of the present invention to provide a workpiece support in which a platform or chuck is supported by a novel mechanism which allows unrestricted access to a workpiece when supported therein, but which allows precise angular movements to be accommodated.

Summary of the invention According to the present invention there is provided a workpiece support comprising: a first 4-bar linkage set including a fixed member, a movable member, a pair of first links joining the fixed member and the movable member at points spaced apart by a greater distance on one member than on the other, and drive means effective to move the movable member relative to the fixed member; a workpiece holder; and mounting means for mounting the workpiece holder to said movable member so that movement thereof causes the workpiece holder to rotate about a first axis at a substantially fixed position in space remote from the links.

It is to be understood that said fixed position can only be assumed to be a single unique point in space for very small displacements of the movable member. However, for anglar movements of less than 100 the point only moves through a minute distance and can to a first approximation be assumed to be a fixed point in space.

Where the workpiece holder is a chuck, the drive means can be arranged to effect rotational movement of small angular displacement of the chuck about its natural axis, by arranging that said point in space coincides with the natural axis of the chuck.

In a typical embodiment of the invention, a workpiece holder is incrementally rotatable to the extent of +/- 100 about its mean position.

The drive means for each movable member may be manually adjustable or may be powered as by electrical or pneumatic means.

Typically piezoelectric or electrostrictive drive devices may be employed.

A device incorporating the invention may be used for positioning optical fibres relative to one another for interrogation analysis, inspection or joining by fusion splicing.

Two such workpiece support assemblies may be provided on opposite sides of a fusion splicing station to support and independently position each of two fibres which are to be joined or otherwise treated.

In a particular advantageous arrangement the or each 4-bar linkage set is of a re-entrant arrangement and the movable member thereof includes an intermediate member movably disposed between the fixed member and the movable member and having said pair of first links joined thereto, and a pair of second links joining the movable member and the intermediate member at points which are spaced apart by a greater distance on one member than the other, the resulting inclination of each of the second links being similar to that of the corresponding first links. The support may then further comprise a rigid control arm connecting the movable and intermediate members with the fixed member, in such a manner that the movement of the movable member is porportionally greater than that of the intermediate member.

The drive means may then act on the movable and/or the intermediate member. Particu larly where the drive means acts on the intermediate member, the control arm ensures that the movable member will be moved commen surately greater than the intermediate member.

Preferably said spacing apart of the first pair of links is greater at the movable member.

In a preferred arrangement of the workpiece support each of the first pair of links is in doubled, the double first links being mounted outboard of the respective second links. In this case the respective points at each side of the intermediate member at which the first and second pair of links are joined to the intermediate member may be coincident.

The pairs of links may each comprise flexure springs which are rigidly attached to said points on the movable member.

Alternatively the links may comprise rigid struts hingedly joined to the respective ends of the fixed and the first and second movable members.

The rigid control arm may also be an elongated rigid strut, and may be connected pivotally to the fixed and the intermediate and the movable members.

Conveniently the mounting means for the workpiece holder may be in the form of an actuating arm extending also in a direction opposite to the workpiece holder to provide a mounting point for the control arm.

Other features of the invention are defined in the appended claims.

Brief Description of the drawings The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an elevation of a first embodiment of a workpiece support, allowing rotation about a single axis and representing the invention in its simplest form; Figure 2 is a perspective view of a second workpiece support allowing a workpiece to be rotated by small angular increments about two orthogonal axes; Figure 3 is a perspective view of a third workpiece support allowing a workpiece to be rotated by small angular increments about three orthogonal axes; Figure 4 is a perspective view of another embodiment of a workpiece support device allowing rotation about a single axis; and Figure 5 is an elevation of a simplified embodiment of the device of Fig. 1.

Detailed description of the embodiments In Fig. 1 a workpiece holder 10 is carried at the end of an arm 12, the other end of which is attached to and extends perpendicularly from a platform or bridge 14. The latter is joined at the two ends to a pair of inclined flexure springs 16, 18, the other ends of which are attached to a rigid yoke 20. The members 14, 16 and 18 and the yoke 20 thus constitute a 4-bar linkage set.

The length of the arm 12 is chosen so as to position the workpiece holder 10 at the point in space at which imaginary lines drawn as extensions to the two flexure springs 16,18 would intersect; For such displacements of the bridge 14, the movement of the midpoint of the bridge 14 can be considered to describe an arc of a circle centred on the holder 10 so that such movements will produce a rotation of the holder 10 about an axis passing through the imaginary point of intersection of the extensions of the flexure springs 16, 18.

Displacement of the bridge 14 is effected by a manually adjustable drive comprising a threaded shank 22 secured in a threaded boss 24 carried in the yoke 20, and having a knurled knob 26 attached thereto, for rotating the shank 22. The end of the shank bearing against the one end of the bridge 14 is conveniently tapered to a pencil point to simulate point contact between the shank and the bridge.

A return spring 28 may be provided if desired. Alternatively the flexure springs 16, 18 may be adapted to provide for the return spring action.

In Fig. 2 the arm 12 is replaced by a second flexure spring assembly to allow for a second orthogonal axis of rotation. Thus the workpiece holder, now shown in more detail as a chuck 30, is carried by a tubular member 32, itself carried by a rigid arm 34 which extends from the midpoint of a first bridge 36.

The latter is attached to a pair of flexure springs 38, 40 the opposite ends of which are attached to a rigid link 42 (shorter than the bridge 36) and attached to an L-shaped bracket 44 which carries a first drive 46 for displacing the bridge 36 relative to the link 42.

The link 42 is itself attached via an Lshaped arm 48 to the midpoint of a second bridge 50 which, like the first bridge 36, is joined to a rigid link 52 by a pair of flexure springs 54,56.

The link 52 is supported at the outboard end of an L-shaped support 58 the other end of which is attached to a base 60.

A drive 62 for displacing the bridge 52 is shown, mounted in a support 64 which extends upwardly from and is attached to the base 60.

Operation of the drive 46 will effect rotation of the tubular support 32 and therefore the chuck 30 about the axis 66 whilst operation of the drive 62 will effect rotation of the chuck and tubular support, about an axis 68.

As shown the two axes 66,68 are perpendicular. However, by altering the angular relationship between the assembly (50,52,54,56) and the assembly (36,38,40,42) so the angle between the two axes can be altered to other than 90 . Essentially this may be achieved by altering the angle of the upright leg 70 to the other leg 72 by the L-shaped bracket 48.

If adjustment of the angle between the two axes is required, the member 44 is made adjustable by an externally operable drive.

Fig. 3 illustrates a development of the arrangement shown in Fig. 2, in which the support 58 for the link 52 is replaced by a further adjustable flexure support mechanism comprising a V-shaped bridge 71 (to enable the latter to be fitted more intimately relative to the link 52) attached at its two ends by flexure springs 73,74 to a rigid link 76 carried by a yoke 78. The yoke has a cross piece 80 to which the link 76 is attached, a first arm 82 which carries a rotatable drive 84 for moving the V-shaped bridge 74 relative to the link 76 (and therefore to the yoke 78), and a second arm 86 which is attached to a base 88.

Where parts of the device of Figs. 2 and 3 are common the same reference numerals have been employed.

Since the bridge is no longer movable relative to the base 88 (base 60 in Fig. 2) the drive 62 therefor is instead supported by an L-shaped bracket 90 which is carried by the rigid link 52 and extends from one end thereof.

The drive 46 thus controls rotation about the axis 92, the drive 62 about the axis 94, and the drive 84 about the axis 96.

As with Fig. 2 the axes 92,94,96 are orthogonal but can be made non-perpendicular by adjustment of the relative angular orientations of the three flexure spring assemblies. Thus for example axis 94 can be altered relative to 92 and 96 in the plane containing axis 92 by adjustment of the angle of the bracket 48, axis 96 (relative to 92,94 and in the plane of axis 92) by adjustment of the angle between the arm 70 of the bracket 48 and the link 42) and axis 92 can be altered (relative to axes 94,96 in the plane containing axis 94) by adjustment of the angle made by the arm 72 relative to the bridge 50.

It will be appreciated that many other angular adjustments as between one flexure spring assembly and another in the embodiment of Fig. 3 can be made to effect alteration of the angles between the axes 92,94,96, and the above are given by way of example only.

It is also to be appreciated that although manually adjustable drives have been shown, these could be replaced or supplemented by other drives such as electromagnetic, pneumatic, electrostrictive or piezoelectric drives.

As shown in Fig. 3, an optical fibre 98 can be introduced into the end of the tube 32 and pushed therethrough, to protrude from the chuck 30 where it can be clamped and rotated about any of the axes 92,94,96 by adjustment of the appropriate drives 46, 62 and 84.

Additionally, the positions of the axes relative to one another or to some other datum can be altered by adjusting the length of the arms such as 34, 72.

Referring next to the embodiment of Fig. 5, there is shown generally at 110 a fixed member forming part of the framework of the body of a workpiece support. Above the fixed member 110, as viewed in Fig. 5, is an intermediate movable member or platform 112 which is connected to the fixed me#mber by a pair of links 114 and 116 of equal length.

Also connected to the intermediate platform 112 about axes or points aligned with those of the links 114 and 116, are a pair of shorter links 118 and 120 which are connected to the ends of a further movable member or platform 122. This is known as a re-entrant arrangement.

Mounted perpendicularly across the platform 122 is an actuating arm 124 at one end of which is mounted a workpiece holder in the form of a chuck 126. Towards the other end of the arm 124 remote from the chuck 126 is an adjusting screw 128 engageable with the arm 124.

A rigid control arm 130 is pivotally mounted at one end to the fixed member 110, and at an intermediate position is pivotally mounted through a link 134 to one side of the intermediate platform 112 at a point which may be coincident with the connection points of the links 114 and 118. The other end of the control arm 130 is connected by a link 136 to the remote other end of the actuating arm 124.

The operation of the device of Fig. 5 so- far described is similar to that described above.

In this case the platforms are spring biased to the right against the adjusting screw 128 and in the position shown the adjusting screw 128 has been moved to the right to allow the spring bias to move the platforms to the right.

The resultant movement of the pairs of reentrant -links 114 to 120 causes the platform 122 to move into such a position that the end of the arm 124, bearing the chuck 126, rotates about a small angle A.

The overall length of the control arm L2 in relation to its length L1 from the fixed member 110 to the link 134, is so chosen that the movement on the intermediate platform 112 is proportionally smaller than the total movement of the further movable platform 122.

Reference will now be made to the embodiment shown in perspective in Fig. 4, in which the same reference numerals are used as for Fig. 5, where there are corresponding parts.

The fixed member 110 in Fig. 4 is mounted on a frame 140 including an upright wall 142 at one end and a channel section wall 144 at the other end. A wall 146 is positioned intermediate and has a hole 148 through which the adjusting screw 128 passes. The screw 128 is in threaded engagement with a boss 150 and carries a knurled knob 152 at its right-hand end.

The pair of links 114 an 116 are in this case doubled, each being in two parts 116a and 116b, and 114a and 114b, the lower part 114b being hidden. Inboard between the links 116a and 116b is the second link 120. The movable platform 122 is secured to (or may be integral with) a triangular member 154, which in turn is secured to the arm 124, shown partly broken away.

The links 134 and 136, joining the control arm 130 to the intermediate platform 112 and to the arm 124 respectively, are in this instance spring connections. The links 114 to 120 could similarly be flexure springs.

The link 120 is also formed with an opening 156, aligned with the hole 148, through which the adjusting screw 128 passes. For reasons of clarity the end of the arm 124 carrying the chuck 126 has been omitted from Fig. 4.

It will be observed from Fig. 4 that the width of the links 114 to 120 and of the control arm 130 is relatively great in comparison with the small movements which are performed by the arm 124. This enables the tortional stiffness of the device to remain high, preventing undesired lateral movement of the axis of the chuck (not shown).

Claims

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1, 5, 6 and 7 above have been de leted or textually amended. New or textually amended claims have been filed as follows: Claims 8 to 16 above have been re-numbered as 7 to 15 and their appendancies corrected. 1. A workpiece support comprising: a first 4-bar linkage set including a fixed member, a movable member, a pair of first links joining the fixed member and the movable member at points spaced apart by a greater distance on one member than on the other, and drive means effective to move the movable member relative to the fixed member; a workpiece holder; and mounting means for mounting the workpiece holder to said movable member so that movement thereof causes the workpiece holder to rotate about a first axis at a substantially fixed position in space remote from the links; wherein the or each 4-bar linkage set is of a re-entrant arrangement and the movable member thereof includes an intermediate member movably disposed between the fixed member and the movable member and having said pair of first links joined thereto, and a pair of second links joining the movable member and the intermediate member at points which are spaced apart by a greater distance on one member than the other, the resulting inclination of each of the second links being similar to that of the corresponding first links. 5. A workpiece support according to claim 1 further comprising a rigid control arm connecting the movable and intermediate members with the fixed member, in such a manner that the movement of the movable member is porportionally greater than that of the intermediate member. 6. A workpiece support according to any one preceding claim in which the drive means acts on the movable and/or the intermediate member. CLAIMS

1. A workpiece support comprising: a first 4-bar linkage set including a fixed member, a movable member, a pair of first links joining the fixed member and the movable member at points spaced apart by a greater distance on one member than on the other, and drive means effective to move the movable member relative to the fixed member; a workpiece holder; and mounting means for mounting the workpiece holder to said movable member so that movement thereof causes the workpiece holder to rotate about a first axis at a substantially fixed position in space remote from the links.

2. A workpiece support according to claim 1 in which said mounting means comprises a second 4-bar linkage set arranged perpendicular to said first 4-bar linkage set, so that movement thereof causes the workpiece holder to rotate about a second axis perpendicular to said first axis at substantially said same fixed position in space.

3. A workpiece support according to claim 2 in which said mounting means further comprises a third 4-bar linkage set arranged mutually perpendicular to said first and second 4bar linkage sets, so that movement thereof causes the workpiece holder to rotate about a third axis perpendicular to said first and second axis at substantially said same fixed position in space.

4. A workpiece support according to any one of claims 1 to 3 in which said spacing apart of the first pair of links is greater at the movable member.

5. A workpiece support according to any one of claims 1 to 4 in which the or each 4bar linkage set is of a re-entrant arrangement and the movable member thereof includes an intermediate member movably disposed between the fixed member and the movable member and having said pair of first links joined thereto, and a pair of second links joining the movable member and the intermediate member at points which are spaced apart by a greater distance on one member than the other, the resulting inclination of each of the second links being similar to that of the corresponding first links.

6. A workpiece support according to claim 5 further comprising a rigid control arm connecting the movable and intermediate members with the fixed member, in such a manner that the movement of the movable member is porportionally greater than that of the intermediate member.

7. A workpiece support according to claim 5 or claim 6 in which the drive means acts on the movable and/or the intermediate member.

8. A workpiece support according to any one preceding claim in which each of the first pair of links is doubled, the double first links being mounted outboard of the respective second links.

9. A workpiece support as claimed in claim 8 in which the respective points at each side of the intermediate member at which the first and second pair of links are joined to the intermediate member are coincident.

10. A workpiece support as claimed in any one of the preceding claims in which the pairs of links each comprise flexure springs which are rigidly attached to said spaced points on the movable member.

11. A workpiece support according to any one of the preceding claim in which the links comprise rigid struts hingedly joined to the respective ends of the fixed and the intermediate and the movable members.

12. A workpiece support according to any one of claims 6 to 11 in which the rigid control arm is an elongated rigid strut, being connected pivotally to the fixed member and to the intermediate and movable members.

13. A workpiece support according to any one of claims 6 to 12 in which the mounting means is in the form of an actuating arm extending also in a direction opposite to the workpiece holder to provide a mounting point for the control arm.

14. A workpiece support according to any one of the preceding claims in which the workpiece holder is incrementally rotatable to the extent of +/~10 about its mean position.

15. A workpiece support according to any one of the preceding claims in which the drive means for each movable member is manually adjustable or is powered by electrical or pneumatic means.

16. A workpiece support substantially as described with reference to, and as shown in, the accompanying drawings.