GB2091196A - Apparatus for sequential displacement of a carrier - Google Patents

Abstract

A carrier (2) is required to be moved through a series of set positions for various operations to be performed on a workpiece on the carrier. The carrier may be on or part of a rotatable arm (1) or guided on a track, and it is connected by a cable (8) to a fixed but adjustable point. It is also urged by biasing means such as a spring (11) towards a start position, which keeps the cable taut. The other set positions are determined by devices which alter the cable path between the carrier and the fixed point, creating or accentuating bends or bights in the cable, which thus pulls the carrier against the bias. These devices may be rams (17, 18, 22) or solenoids which move pulleys (13, 14) around which the cable is led. <IMAGE>

Description

SPECIFICATION Apparatus for sequential displacement of a carrier In various industrial applications it is desired to move a workpiece between various stations at which separate operations may be carried out on the workpiece. There is therefore the requirement for a carrier which will move the workpiece sequentially between the various stations and locate the workpiece precisely at each station. For example, in a vacuum depositioning apparatus a workpiece needs to be moved on a carrier from a loading position into one or more vacuum chambers for deposition techniques to be applied to the workpiece and on to a discharge point for removal of the workpiece.

One method of operating the carrier is to cause it to rotate so that an arm forming part of the carrier will be moved to the various stations at points on the circumference of a circle swept by the carrier. The required stepped rotary movement of the carrier can be effected by means of a rotary motor which is designed to come to a halt at the required position.

Such rotary motors are relatively expensive, can be prone to breakdown unless they are very carefully looked after, and can slip out of true adjustment so that precise location of the carrier at each station is not achieved.

It is an object of this invention to provide apparatus for moving a carrier between fixed stations which will be accurate in operation and relatively inexpensive and easy to operate and adjust.

Accordingly, this invention provides apparatus for moving a carrier relative to a mounting between predetermined positions, comprising a cable having one end attached to the carrier and the other end connected at a datum point, a series of individual movement determining devices, each operable between two set positions to act on the cable so as to increase or decrease the cable path between the datum point and the carrier mounting, and biasing means tending to restore the carrier to a start position.

The individual movement determining devices may take many forms and can be constructed quite simply to achieve an accurate displacement of the cable resulting in correspondingly accurate movement of the carrier. For example, the movement determining device could comprise an arm movable between the two position and including means for releasbly securing the arm in the position where it acts to increase the cable path. Such an arm could be manually operable. It is preferred, however, that the movement determining devices should be automatic in operation and thus could comprise pneumatic or hydraulic rams or solenoids.

In the preferred arrangement the two set positions of each movement determining device are adjustable. This allows for the apparatus to be set up initially to ensure accurate displacement of the carrier or adjustment of the positions to which the carrier is moved if the working positions at which the workpiece is operated on are modified. For the latter purpose in particular it is also desirable that the stroke length of each movement determining device should be adjustable. Thus stop members may be provided to limit the stroke length of each movement determining device.

The carrier could be slidably mounted on or in the mounting, in which case the movement determining devices could act on the cable to displace it from an initial straigtht line condition between the datum point and the carrier. It is preferred, however, that the carrier should be rotatably mounted on the mounting, in which case the carrier will ideally include an arm rotatable about the mounting. The cable could then be wound around the part of the mounting and then operation of the movement determining devices would have the effect of unwinding the cable and thus rotating the carrier.

To enable the apparatus to be set up initially, it is preferred that the connection of the cable to the datum point should be adjustable. It may also be of advantage to be able to adjust the position of the datum point itself.

The biasing means may take many forms but conveniently will comprise a spring or a spring in combination with a cable attached between a fixed point and the carrier.

The invention may be performed in various ways and two preferred embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a plan view of part of an apparatus of this invention for moving a carrier between three positions; Figure 2 is a side view of the carrier and its mounting; Figure 3 is a side view of the part of the apparatus which is operated to rotate the carrier; Figures 4a and 4b are plan views of the left and right hand parts respectively of a further apparatus of this invention for moving a carrier between five positions; and Figure 5 illustrates in side view the part of the apparatus which causes the carrier to be rotated.

Figure 1 shows a carrier arm 1 which has at one end a mounting part 2 for receiving a workpiece, the other end of the arm being mounted for rotation about the axis of a shaft 3. It is desired that the arm should be moved from the position illustrated (position 1) through 90" so that the workpiece is positioned centrally of a chamber 4, where it will be subjected to a vacuum deposition process (position 2) and through a further 90" to a position where the workpiece will be unloaded (position 3). As can be seen from Figure 2, the shaft 3 extends through a base plate 5 and carries at its lower end a drive wheel 6 comprising a large drum 7 on which is wound a cable 8 and a smaller drum 9 on which is wound a wire 10 connected, via a spring 1 1,to a fixed position 12.As shown in Figure 3 the cable 8 leads round a pair of pulleys 13, 14 and is then fixed art a datum point 15 on a post 16. Each of the pulleys 13, 14 is connected to the piston of a respective ram 17, 18 by means of a clevis 19. A spacer 20 is screwthreadedly engaged on each piston 21 and can be adjusted to limit the extent of movement of the piston into the cylinder of the respective ram, thus determining the stroke of the ram. The fixing position of the cable 8 in the datum point 15 can also be adjusted.

In operation the two rams 17, 18 will initially be in their retracted positions so that the carrier arm 1 lies in position 1. When ram 17 is operated, the cable length between the datum point 15 and the shaft 3 will be increased as the cable unwinds from the drum 7 and the stroke of the rame 17 will be so chosen that the carrier arm 1 will rotate through 90" to position 2. Subsequent operation of the ram 18 will cause further increase in the path length of the cable resulting in an additional rotation of the arm 1 through a further 90" to position 3. Initial adjustments can be made to ensure that the arm is precisely positioned at position 1 when the two rams 17, 18 are retracted by modifying the fixing of the cable at the datum point 15.The stroke length of the two rams will also be adjusted by suitably rotating the spacers 20 to ensure precise 90" rotations of the arm upon operation of the rams 17 and 18.

Where a greater number of positions are required for the carrier arm 1 further rams, operating on the cable 8, may be employed and an arrangement using three rams providing five operating positions of the carrier arm 1 is illustrated in Figures 4 and 5.

The construction is basically as before except that there is a third ram 22. In this case the stroke of the ram 17 is chosen to be of four units of stroke length resulting in a 60 rotational movement of the carrier arm 1. Cylinder 18 provides six units of stroke length which causes the carrier arm 1 to rotate through 90" whilst cylinder 22 has a stroke length of three units resulting in a 45" rotation of the carrier arm 1.

With all the rams in the retracted position, the carrier arm 1 is in the rest position (position 1) wherein a workpiece may be mounted on the mounting 2. Operation of the ram 17 causes rotation of the arm 1 so as to position the workpiece centrally of a first chamber 23 where a first vacuum deposition procedure may be carried out. The next stage of operation is to retract the ram 17 and at the same time operate the ram 18 resulting in a further 30 rotation of the arm 1 sothattheworkpieceis centrally positioned within a second chamber 24 for a further stage in the vacuum deposition process.

Next the ram 22 is operated (ram 18 remains in the extended position) resulting in a further 45" rotation of the arm 1 so that the workpiece then is centrally positioned within a third chamber 25 where a final vacuum deposition procedure is applied to it. Lastly the ram 17 is additionally operated so that a further 60 rotation of the arm 1 carries the workpiece to a demounting position (position 5) where it can be removed.

It will be appreciated that the apparatus could be modified in various ways. For example, the hydraulic rams 17, 18 and 22 illustrated in the drawings could be replaced by solenoids or even by manually operable arms movable between two limiting positions. Furthermore, the carrier arm 1 could be replaced by a sliding carrier mounted on a track and having one end of the cable 8 secured thereto.

Operation of the rams would then cause the carrier to move to predetermined positions along the track.

Although the drawings illustrate positioning of the rams so that the cable follows a sinuous path, the rams could be positioned so that they all operate on the same side of the cable if desired. Also the datum point 15 could be a connection point on the end of the piston of a further ram.

Claims (13)

1. Apparatus for moving a carrier relative to a mounting between predetermined positions, comprising a cable having one end attached to the carrier and the other end connected at a datum point, a series of individual movement determining devices, each operable between two set positions to act on the cable so as to increase or decrease the cable path between the datum point and the carrier mounting, and biasing means tending to restore the carrier to a start position.

2. Apparatus according to claim 1, wherein the carrier is slidably mounted on or in the mounting.

3. Apparatus according to claim 1, wherein the carrier is rotatably mounted on the mounting.

4. Apparatus according to claim 3, wherein the carrier includes an arm rotatable about the mounting.

5. Apparatus according to any one of claims 1 to 4, wherein the position of the datum point is adjustable.

6. Apparatus according to any one of claims 1 to 5, wherein the connection of the cable to the datum point is adjustable.

7. Apparatus according to any one of claims 1 to 6, wherein the biasing means comprises a spring or a spring in combination with a cable attached between a fixed point and the carrier.

8. Apparatus according to any one of claims 1 to 7, wherein each movement determining device comprises an arm movable between the two positions and including means for releasably securing the arm in the position where it acts to increase the cable path.

9. Apparatus according to any one of claims 1 to 7, wherein each movement determining device comprises a pneumatic or hydraulic ram or a solenoid.

10. Apparatus according to any one of claims 1 to 9, wherein the two set positions of each movement determining device are adjustable.

11. Apparatus according to claims 8 and 10 or claims 9 and 10, wherein the stroke length of each movement determining device is adjustable.

12. Apparatus according to claim 11, wherein stop members are provided to limit the stroke length of each movement determining device.

13. Apparatus for moving a carrier according to claim 1 and substantially as herein described.