Unloader valve

An unloader valve comprising:

• a. valve housing means having aligned inlet and outlet ports and defining a straight-through first passageway connecting said ports;
• b. a one-way outlet check valve in said first passageway adjacent said outlet port;
• c. said housing means further defining, a bypass port, a second passageway connecting said bypass port with said first passageway, a valve seat at one end of said second passageway and at one side of said first passageway, and a cylindrical chamber axially aligned with said valve seat;
• d. a piston in said chamber dividing the chamber into an inner pressure chamber portion and an outer chamber portion open to the exterior of said housing means;
• e. said housing means further defining, an opening between said pressure chamber portion and said first passageway, and a third passageway communicating at one end with said first passageway between said outlet port and said check valve and at its other end with said pressure chamber portion;
• f. a bypass vlave element disposed in said first passageway and having a stem extending through said opening and connected to said piston, said bypass valve element being movable with said piston toward and away from valve closing engagement with said valve seat;
• g. yielding means in said outer chamber portion yieldingly urging said pistong and said bypass valve element in a valve closing direction, said yielding means comprising a plurality of resilient conical washers arranged in axial pairs to provide a stack of said washers, the washers of each pair having concave sides in face-to-face relationship;
• and
• h. a conical washer mounted on said bypass valve element stem and positioned to engage said housing means to cushion said bypass valve element during opening movement thereof.