Double-seat electromagnetic valve

Claim 1

A double-seat electromagnetic valve comprising: a valve casing having first port adapted to be supplied with a pressure medium; a second port adapted to be connected to a load; and a third port for returning the pressure medium; a valve body in said valve casing and adapted to selectively assume a first seated position wherein said first port is closed and said second port is communicated with said third port, and a second seated position wherein said third port is closed and said second port is communicated with said first port; a valve spring chamber in said valve casing and permanently communicating only with said third port; a valve spring in said valve spring chamber and permanently urging said valve body toward said first seated position; a first valve bore communicating with said first port, said first valve bore having an end edge thereof provided with a first valve seat on which said valve body is to be seated when it assumes said first seated position; and a second valve bore communicating with said third port, said second valve bore having an end edge thereof provided with a second valve seat on which said valve body is to be seated when it assumes said second seated position; said first and second valve seats being disposed opposite each other; and said valve body being interposed between said first and second valve seats; a control plunger actuatable by an electromagnetic force to urge said valve body toward said second seated position, against the force of said valve spring; passage means coupled to said first port for always supplying pressure medium from said first port to only one end of said valve body through said first valve bore so that said pressure medium acts on only said one end of said valve body; and a plunger spring urging said control plunger toward said valve body; said valve spring having a urging force for urging said valve body, said urging force of said valve spring being set at a value slightly larger than the sum of pressure force of said pressure medium acting upon said valve body through said first valve bore and a force of said plunger spring urging said control plunger.