Grinding machine with belts

Claim 1

A belt grinding machine comprising a grinding belt, a flexible pressure member for pressing an operative portion of said belt from a normally maintained inactive position downwardly against a workpiece conveyed in a first direction beneath said operative portion of said belt, said pressure member extending transversely of said first direction entirely across the width of the surface of the workpiece to be ground, a plurality of double acting, fluid pressure motors each having a first and a second internal chamber divided from each other by a piston having a rod projecting from the first chamber end of sad motor, the rods of said motors being connected to said pressure member at spaced locations transversely of said first direction and operable upon actuation of the associated motor to raise or lower the section of said pressure member connected thereto, a first pressure source commonly connected to all of said first chambers to urge said pistons and the connected pressure member toward a position of maximum elevation wherein said grinding belt is in said inactive position, a second pressure source maintained at a pressure higher than that of said first source, valve means on each motor operable to selectively connect the second chamber of the motor to said second source or to vent, and delayed action control means associated with each motor engageable with a workpiece surface at a location upstream of the direction of movement of the workpiece from each motor for actuating said valve means to position the grinding belt beneath the associated motor at a position corresponding to the position of the control means when the engaged portion of the workpiece subsequently arrives in operative relationship with the grinding belt.