Air pilot operated directional control valve

Claim 1

A snap acting air pilot operated directional control valve for controlling a fluid connection between one normally open port and two selection ports, comprising a casing, a plunger which is arranged in the casing to move in the axial directions thereof in the casing and which moves in response to a pilot pressure, elastically deformable means for enabling the plunger to axially move, said elastically deformable means being connected to the casing and the plunger and being arranged to define a control chamber in the casing, said open port and the selection ports being connected to the control chamber to open into the control chamber, said selection ports having axial open ends which face in opposite axial directions with respect to the control chamber, said plunger being provided with valve seats to selectively close the axial open ends of the selection ports in accordance with the axial displacement of the plunger, each of said valve seats being rigidly attached to the plunger and being positioned in direct alignment with its corresponding selection port to receive energy of ejected air and cause quick axial movement of the plunger in the event that air is ejected from the respective selection port, and spring means for biasing the plunger in a direction opposite to a direction of the movement of the plunger by the pilot pressure, whereby the plunger moves in a snap action when the pilot pressure exceeds a predetermined valve, said elastically deformable means comprising three diaphragms consisting of two end diaphragms and one intermediate diaphragm between the end diaphragms, said three diaphragms being connected to the plunger so as to axially move together therewith, said control chamber being defined between and by one of the end diaphragms and the intermediate diaphragm.