Sliding plate-type directional control valve

Claim 1

A rotary plate-type directional control valve comprising a housing defining a valve bore therein, a rotary member rotatably disposed in said valve bore and adapted to change over the fluid supply from one line to another, a floating plate disposed in said valve bore in plane contact with said rotary member, and a port member hermetically attached to said housing to seal said valve bore with sealing members and springs interposed therebetween, said rotary member having at least one fluid passage formed therein and being rotated freely by a rotary shaft extending through the wall of said housing, said floating plate being held between said rotary member and said port member in such a manner that it is slidable axially but not rotatable about its axis, the floating plate having at least two through-holes that is, one through-hole which is always communicated with a pressure port in said port member and the other through-hole which is always communicated with a cylinder port and/or a tank port, the openings of said through-holes closer to the rotary member being arcuate in shape and the effective pressurereceiving area thereof being smaller than the area of said ports, said through-holes being brought into and out of communication with the fluid passage in said rotary member after the fluid supply changing-over operation, and said sealing members and said springs biasing said respective sealing members being mounted in said port member in which a fluid leakage through the gap between said floating plate and said port member is prevented simultaneously maintaining said floating plate in plane contact with said rotary member, under which condition said rotary shaft is rotated for effecting the fluid supply changing-over operation.