Reversible fluid pressure drive unit

摘要

The drive unit is reciprocated automatically by coupling the opposite ends of the cylinder through delivery conduits to a source of fluid pressure and exhaust through a switching valve in which a longitudinally reciprocative spool has a pair of passageways which reversibly couple one end of the cylinder to the source of fluid pressure and the other end of the cylinder to an exhaust conduit. The opposite ends of the switching valve contain shift pistons each of which engages an end of the spool through a coil spring. The shift pistons abut the opposite ends of an elongated rod which extends freely through a bore in the spool. Bypass conduits couple the opposite ends of the cylinder through the delivery conduits, one to each end of the valve body. Fluid pressure in one delivery conduit from the source is coupled to one end of the valve body while exhaust fluid pressure from the other delivery conduit is coupled to the other end of the valve body. The exhaust conduit communicates with a detent conduit in which a detent pin is moved by exhaust fluid pressure into a selected detent in the spool to secure the spool against movement. When the piston-cylinder unit is a high vol. drive unit, a secondary switching valve is interposed between the cylinder and the primary switching valve to supply high vol. fluid pressure to the cylinder by control from the primary switching valve.