GB2121760A

GB2121760A - A workpiece transfer device

Info

Publication number: GB2121760A
Application number: GB08313186A
Authority: GB
Inventors: Christopher T S Stevenson
Original assignee: Litton Industrial Products Inc
Current assignee: Western Atlas Inc
Priority date: 1982-06-14
Filing date: 1983-05-13
Publication date: 1984-01-04
Also published as: JPS594987A; GB8313186D0

Abstract

Workpieces (W), which may have irregular and inconsistent outer peripheries, are located by a pin (15) and a block (16). Pairs of gripping jaws (22) engage a workpiece (W) without altering its orientation, and are locked in position by a clamping action exerted by two support members (20, 23) under the action of a hydraulic cylinder and piston unit (26). The workpiece (W) can then be transferred to, for example, the chuck of a friction welding machine, in a predetermined orientation regardless of the shape of the periphery of the workpiece. The jaws of each pair are biased to their closed position by a respective spring and a hydraulic cylinder (24) can move all of the pairs of jaws concurrently to their open positions. <IMAGE>

Description

SPECIFICATION A workpiece transfer device This invention relates to workpiece transfer devices, particularly, although not exclusively, loaders for friction welding machines.

A friction welding machine forcefully displaces a rotating or orbiting workpiece into a stationary workpiece to fuse the workpieces together by friction welding. While workpieces of various shapes and sizes may be selectively joined in this manner, precise orientation of the workpieces within respective chucks of the machine is required so that the workpieces may be accurately positioned with respect to one another to produce the desired weld.

A conventional loader includes jaws which close along a centerline to grip a symmetrical, machined surface of a workpiece for presenting the workpiece to the chuck of a friction welding machine. Some workpieces, however, do not have symmetrical, machined surfaces which may be gripped, and in such cases the centreline closing of the jaws will not accurately align the workpiece.

According to the present invention there is provided a workpiece transfer device comprising a workpiece gripper having a plurality of pairs of opposed jaws arranged in a stack, means being provided for pivoting the jaws of each pair between open and closed positions, the gripper being adapted to engage a workpiece, situated in a predetermined orientation at a first station, without altering the predetermined orientation, locking means being provided for locking the jaws in their closed positions engaging the workpiece, and displacement means being provided for displacing the jaws from the first station to a second station.

An embodiment in accordance with the present invention comprises a loader for a friction welding machine which properly presents a workpiece to the chuck of a friction loader although the loader grips the workpiece on unmachined surfaces.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 is a perspective view of a loader for a friction welding machine; Figure 2 is a top view of the loader; and Figure 3 is an exploded perspective view of the loader.

The loader shown in Figure 1 is generally indicated by the reference numeral 10 and includes a gripper assembly 12 mounted on one end of a displaceable arm 13. The arm 13 is effective to selectively displace the gripper assembly 12 from a pre-load station 14to the chuck of a friction welding machine (not shown) such as the chuck disclosed in our copending patent application entitled "A Chuck" (Agents ref: HL 26262). At the pre-load station, a workpiece W, such as a clevis, is accurately positioned by a locating pin 15 and a locating block 16 which respectively engage a bore 17 and an end 18 of the workpiece W. It will be appreciated that although the bore 17 and end 18 are accurately positioned at the pre-load station 14, the outer surface 19 of the workpiece, if unmachined, will be irregular with respect to the centerline CL of the workpiece.

The gripper assembly 12 comprises an upper support member 20 and a lower support member 23 which support a jaw module 21 comprising a stack of opposed jaws 22. The jaws 22 are normally biased to a closed position but may be forced to an open position by a hydraulic cylinder 24. A second hydraulic cylinder 26 is provided to lock the jaws 22 in a desired position, as more fully explained below.

As can be seen in Figure 2, when the jaws 22 close upon an irregular workpiece W positioned at the pre-load station 14, each jaw 22 independently engages the unmachined workpiece surface 19 rather than closing symmetrically about a centerline CL. The jaws are then locked in this gripping position while the loader arm 13 displaces the gripper assembly 12 to present the workpiece to a machine chuck (not shown). After the chuck has received the workpiece, the loader jaws 22 are unlocked and opened to release the workpiece W, so permitting the gripper assembly 12 to be returned to the pre-load station. Accordingly, the workpiece W is presented by the gripper to a machine chuck with the orientation of the bore 17 and end 18 of the workpiece determined by the pre-load station 14.

Turning now to Figure 3, it will be seen that the jaw module 21 comprises a pair of pivot sleeves 30 on which the jaws 22 are stacked for pivotable motion.

The jaws 22 are positioned between upper and lower pressure plates 31,32, all of which are maintained on the pivot sleeves 30 by retaining rings 33 (only top rings shown). Compression springs 34 are mounted upon telescopic rods 35 and bias the opposed jaws 22 towards their closed position, it being understood that three sets of the compression springs 34 and telescopic rods 35 are provided, one for each of the upper, middle, and lower pairs of opposed jaws 22.

A central sleeve 36 is positioned between the pressure plates 31,32 and serves to limit the inward movement of opposed jaws 22 towards each other.

A pair of bolts 40 which pass through the pivot sleeves 30 secure the jaw module 21 to the upper and lower support members 20 and 23 such that the spring biased ends of the jaws 22 are positioned between a pair of opposing actuator blocks 42. The first cylinder 24 forces the actuator blocks 42 together to engage the jaws 22 and pivot them to their fully open position defined by engagement of the actuator blocks 42 with respective abutment portions 41 and 43 of the support members 20 and 23. When the first cylinder 24 retracts the actuator blocks 42 to release the jaws 22, the springs 34 force the jaws to their fully closed position engaging the central sleeve 36 (Figure 3) or, as the case may be, into independent gripping engagement with a workpiece W positioned between the jaws (Figure 2).

A centrally mounted pin 44 extends through the jaw module 21 and includes a head 45 and a washer 46 on one end for bearing on the upper pressure plate 31 and threads 47 on its opposite end which engage with the piston 48 of the second hydraulic cylinder 26. The second cylinder 26 is suspended from the lower support member 23 by bolts 49 such that when it is actuated to retract the draw pin against the upper pressure plate 31, the cylinder housing 50 is raised against the lower pressure plate 32. In this way, the jaws 22, which are mounted between the pressure plates 31,32, are immobilized and locked in position by actuating the second cylinder 26 to squeeze the pressure plates 31 and 32 together.

Claims

1. A workpiece transfer device comprising a workpiece gripper having a plurality of pairs of opposed jaws arranged in a stack, means being provided for pivoting the jaws of each pair between open and closed positions, the gripper being adapted to engage a workpiece, situated in a predetermined orientation at a first station, without altering the predetermined orientation, locking means being provided for locking the jaws in their closed positions engaging the workpiece, and displacement means being provided for displacing the jaws from the first station to a second station.

2. A transfer device as claimed in claim 1, in which the means for moving the jaws comprises a respective resilient element for each pair of jaws, the resilient elements biassing the jaws closed.

3. A transfer device as claimed in claim 1 or 2, in which the means for moving the jaws comprises a hydraulic cylinder and piston unit for opening the jaws.

4. A transfer device as claimed in any one of the preceding claims, in which the locking means comprises a draw pin operated by a hydraulic cylinder and piston unit.

5. Atransferdevice as claimed in claim 4, in which the stack of pairs of jaws is disposed between two support members which are movable towards and away from each other, the draw pin being operable by its hydraulic cylinder and piston unit to bring the support members towards each other thereby to clamp the jaws between them to lock the jaws frictionally in position.

6. A transfer device as claimed in any one of the preceding claims, which is a loader for a friction welding machine.

7. A workpiece transfer device substantially as described herein with reference to, and as shown in, the accompanying drawings.