GB1302538A - - Google Patents

Abstract

1302538 Welding by pressure A I WELDERS Ltd 5 Nov 1970 [14 Nov 1969] 55895/69 Heading B3R In a method of and apparatus for friction welding, the parts to be welded are rotated in rubbing contact by power-drive means at least until a steady temperature is attained at the interface of the workpieces, the drive means are then effectively disconnected and rotation continues under the effect of energy stored in an inertial mass to complete the weld. In one embodiment, Fig. 2, an electric motor 33, hydraulic pump 32 and hydraulic motor 34 form a variable speed drive for a shaft 26 which carries the rotary work holder 15 and a selected number of inertial weights 28. Movement of the headstock 14 supporting the shaft 26 and workpiece 18 towards a stationary tailstock 16 with workpiece 19 is effected by fluid pressure rams 23. A sensing device 38 which may be a speed measuring meter or accelerometer is provided and arranged to co-operate with a stop 41 on the headstock, the sensing device 38 giving a signal when the steady temperature condition at the workpiece interface is reached (as indicated by a steady speed of the headstock 14 or nil acceleration). As an alternative to the sensing device 38 a torque meter may be provided, the required signal being produced at a constant torque condition. Control means for the hydraulic motor 34 may be actuated by the signal from the sensing device 38 to set the motor 34 so that power is no longer transmitted to the shaft 26 and rotation (to effect further plastic working of the workpiece interface) continues by reason of the stored inertial energy. The sensing device 38 preferably however co-operates with a switch 43 actuated by a stop 42 when a predetermined burn-off is achieved in order to control the final length of the bonded workpieces. The sensing device 38 may provide a warning signal if the actual value of the speed i.e. the rate of burn-off, lies outside predetermined satisfactory limits. The hydraulic drive may be controlled to provide a braking effect during the inertial-drive stage of the welding operation and this effect may be applied in discrete steps or progressively. Alternatively electrical or mechanical braking devices may be incorporated where the drive means is other than the hydraulic system of Fig. 2. In a second embodiment (Fig. 4, not shown) a clutch is provided between the inertia weights and the rotary workholder so that the inertia weights may be accelerated to require speed while loading and removal of the workpieces takes place. In a third embodiment (Fig. 6, not shown) in a vertically arranged machine a clutch is provided between the drive motor and the shaft with the inertia weights (which therefore rotate at all times with the shaft).