Pilot controlled valves

Abstract

A new pilot valve for spool-type valves and cartridge-type valves is disclosed. In both types of valve, the valve body (spool or cartridge) is provided with a cylindrical bore and first and second radial bores on opposite sides of a land on the valve body. The valve body is slidable within the axial bore of a valve housing. The valve housing is provided with a pressure inlet port, at least one service port, and usually at least one pressure return port, the ports being axially spaced apart. In a central position, a land of the valve body isolates the pressure inlet port from the pressure inlet port and/or the service port, one of the radial bores is in fluid communication with the pressure inlet port, and the other radial bore is in fluid communication with either a pressure return port or service port. A control rod is inserted in the cylindrical bore of the valve body and rotatable therein. The control rod is shaped to selectively open or close the radial bores to create a pressure imbalance across the valve body, thereby causing the valve body to shift in an axial direction. The control rod can be machined into different shapes to effect different degrees of control of the valve body movement (i.e. proportional versus directional control). The present invention is described for various types of spool valves and for a cartridge valve.