Patent ID: 6810912
Filing Date: 2004-11-02
Classification: F15B,F16K,Y10T

Abstract:
A spool valve for switching hydraulic pressure supply to a hydraulic circuit, comprising:a valve body defining a slide hole therein and having a pair of load ports for connection to the hydraulic circuit, a supply port for supplying hydraulic fluid and at least one return port for discharging the hydraulic pressure fluid, said four ports being formed in said slide hole respectively; a spool received in said slide hole and having a pair of land portions and a concave portion between said land portions, said spool being movable in said slide hole to at least a first position where said land portions and concave portion cause said supply port to communicate with one of said load ports and cause the other load port to communicate with said return port; and a fluid force reducer provided in said concave portion, said reducer comprising a spool portion so formed as to, when the spool valve is actuated, let the hydraulic fluid along a surface of said concave portion flow smoothly from said supply port to one of the load ports to which the hydraulic pressure is to be supplied, thereby decreasing a fluid force acting against an operating force of the spool.