Pilot valve assembly

In a pilot valve assembly provided with four pistons arranged in parallel relationship with one another and spaced apart from one another at an equal distance so as to be in first and second pairs of respective two pistons opposite to each other, each piston being inserted into a main valve body slidably in its longitudinal direction parallel to the axis of said valve body and being urged upwardly by means of a compression spring interposed between a proximal end thereof and said main valve body so as to project its leading end outwardly of the valve body;

• a disc member whose lower surface comes into contact with respective leading ends of said pistons;
• a control lever connected to an upper central portion of said disc member, said lever being swayed in operation in such a back and forth direction, so as to cause to thrust through said disc member either one of said first pair of pistons and in such a direction transverse to said back and forth direction, so as to cause to thrust through said disc member either one of said second pair of pistons;
• a pressure-oil port formed within said main valve body at an approximately intermediate portion with respect to the axial direction of said valve body;
• four outlet ports formed within said main valve body in parallel relationship with one another and spaced apart from one another at an equal distance so as to be in first and second pairs of respective two outlet ports opposite to each other, each of said outlet ports extending downward in a substantially linear relationship with each of said pistons;
• and four spool valves provided in said main valve body and operatively connected to said four pistons, respectively, so as to selectively allow at least any one of said outlet ports to communicate with said pressure-oil port and, on the other hand, other outlet ports to interrupt the communication with said pressure-oil port;
• the improvement comprising:
• (a) a pair of first and second main outlet ports formed in said main valve body so as to selectively establish and block communication of said main outlet ports to communicate/discommunicate with said pairs of outlet ports, respectively;
• and
• (b) a spool valve slidably mounted in said main valve body of the pilot valve assembly so as to be movable between a first position, where one of said second pair of outlet ports and the other outlet port thereof are allowed to communicate with said first main outlet port and said second main outlet port, respectively, and a second position, where one of said second pair of outlet ports and the other outlet port thereof are allowed to communicate reversely with said second main outlet port and said first main outlet port, respectively;
• wherein said spool valve is moved in operation to said first position by the action of pressure oil introduced through one of said first pair of outlet ports from said pressure-oil port to one longitudinal end of said spool valve and, on the other hand, said spool valve is moved in operation to said second position by the action of pressure oil introduced through the other outlet port of said first pair of outlet ports from said pressure-oil port to the other longitudinal end of said spool valve.