This invention is concerned with a retracting rocker unit.
Retracting rocker units are extensively used in, for example, the car industry in welding operations. A welding head is controlled by the rocker unit to move into position to effect a welding operation on say a panel and then to withdraw to allow the welded panel to be removed and a fresh panel substituted. The movement of the welding head in space is important as in the region of the panel it should be substantially perpendicular to the panel to ensure a good clamping force for welding while the main component of movement away from the panel should be at right angles to the previous movement so that the welding head clears the edge of the panel to allow the panel to be withdrawn and the new panel inserted.
A common retracting unit achieves this movement by mounting the welding head on a linkage system which incorporates a cam track in which a cam follower is moved by a pneumatic cylinder assembly, the intersection of the substantially linear movement of the follower and the shaped cam track producing the desired movement.
This arrangement does however have the disadvantage that the welding spatter tends to find its way onto the cam track and interferes with the movement of the cam follower.
Moreover there is heavy wear of the cam track because of the necessarily high angle of incidence of the thrust of the cam follower on the track.
It is an object of the present invention to provide an improved retracting rocker unit which obviates or mitigates these problems and produces a smooth controlled action.