Abstract: This invention provides a valving arrangement for a reciprocating engine in which there are two valve assemblies, each with a pressure responsive valve member. As the piston approaches the end of its stroke in either direction, the exhaust port is closed, such as by an extension on the piston, causing fluid pressure to build up in the end of the cylinder. This pressure is conducted to the valve assemblies through fluid lines, causing the pressure-responsive valve members to move in response to the pressure build-up in the end of the cylinder. These valve members control the inlet and exhaust connections to the cylinder so that the piston is caused to reciprocate by the working fluid as the valve members are moved pneumatically to open and close the lines.

Abstract: Compressed air fed into a directional control sleeve is alternatingly delivered to two cylinders via a directional control valve. Pistons within the respective cylinders are each provided with a rack gear moved by feeding compressed air into the cylinders. A grindstone attached to a second set of rack gears is reciprocated through pinion gears by movement of the first-mentioned rack gears. As the grindstone reciprocates, a valve operating arm pivotally supported by a pin is caused to rotate back and forth to switch the directional control valve, thereby switching the cylinder that receives the compressed air. The grinding machine is thus capable of performing grinding in continuous fashion.

Abstract: A hydraulically operated pump jack utilizing dual hydraulically operated piston and cylinder assemblies for pivoting the beam of the pump jack and including a unique control arrangement associated with a reversing valve for controlling operation of the piston and cylinder assemblies. The control arrangement includes a hydraulically operated holding valve incorporated into each of the conduits between the reversing valve and the hydraulically operated piston and cylinder assemblies combined with a control piston and cylinder assembly for controlling the operation of the holding valves. A manually operated valve assembly is also incorporated into each conduit to enable conversion of either or both of the piston and cylinder assemblies from double acting to single acting.

Abstract: A portable abrading tool having a cylinder body containing a double ended piston with a reduced dimension intermediate portion of the piston carrying two oppositely facing racks engageable with two gear units which in turn engage two additional oppositely facing racks on a shoe to cause reciprocation thereof. A valving mechanism may include a rotatably oscillatable gear sector containing a pocket recess loosely receiving a valve element in a lost motion relation. An aspirator may be provided for withdrawing air and abraded particles from the vicinity of a work surface.