Finishing machine

Claim 1

In a workpiece surface finishing apparatus comprising a base supporting a workpiece carrying table motivated to reciprocate workpieces relative to a finishing roll, said finishing roll being mounted for movement toward and away from the plane of reciprocation of said workpiece when supported by said table, and a control system regulating movements of said finishing roll toward and away from said table, the improvement wherein said control system produces substantially uniform working pressure relationships between said finishing roll and the variously profiled surface portions of the workpiece and comprises in combination: a fluid cylinder; a piston movable relatively within said cylinder, one of said cylinder and piston being fixed to said base and the other thereof being coupled to said finishing roll to effect movement thereof; a counter balance circuit for applying air at relatively high pressure tending to move said piston relatively towards one end of said cylinder whereby the weight of said finishing roll is counter balanced and said finishing roll is moved away from said workpiece; a finishing roll pressure control circuit for selectively applying air at relatively low pressure to said one end of said cylinder, said low pressure partially counterbalancing said high pressure such as to permit movement of said finishing roll under the influence of gravity towards said workpiece, the difference between said high and low pressures determining the pressure of said finishing roll on said workpiece; a reduce force circuit for decreasing said low pressure applied to said one end of said cylinder; and means to control operation of said reduce force circuit in accordance with changes in profile of said workpiece surface.