FOUR-WAY VALVE WITH INTERNAL PILOT

摘要

A four-way valve for selectively controlling the application of fluid and exhaust pressures to opposite sides of a double acting cylinder utilizes a main valve spool that is axially movable in a valve housing defining ports respectively connected to opposite sides of the cylinder and to the pressured and inlet sides of a fluid pressure source. The spool valve is provided with an axial bore and a pilot spool is mounted in such axial bore. Radial passages are provided in the main valve spool connecting its exterior with the axial bore and external sealing portions on the pilot spool cooperate with the radial port so that in a neutral position of both the main valve spool and the pilot spool, no fluid flow occurs. Upon axial shifting of the pilot spool in either direction from the neutral position, fluid pressure is applied to opposite ends of the main valve spool to cause it to follow the pilot spool and thus effect a connection between the outlet and inlet ports of the fluid pressure source and the appropriate side of the double acting cylinder.