Pneumatic relay

Abstract

A pneumatic relay, and more particularly a pneumatic reversing relay, wherein the output decreases with increasing signal pressure. The relay is of the rolling diaphragm type, each rolling diaphragm including a radially outer clamping flange, a radially inner clamping flange and an intermediate rolling wall. Means are provided for securing clamping flanges of the rolling diaphragms against pull-out, creep and relaxation of clamping forces. The valve has a freely floating valve stem having a high degree of pneumatic stability combined with low stem friction. The freely floating operation is obtained by means of an 'O' ring surrounding the valve stem and a baffle plate deforming the 'O' ring. The relay includes a bias spring whose bias is controlled by the deformation of a metal bonnet housing the bias spring. Spring retainer caps transmit the deformation of the bias spring in a precise and stable manner. The supply pressure port is connected to a pressure control chamber by a fluid passage including a valve element and a valve seat, the valve stem being surrounded by a helical compression spring positioned to obtain normally closed valve operation. The supply fluid flows past the movable valve element, the fixed supply seal, and along the stem and is then deviated to the pressure control chamber. The stem has a portion of increased diameter which cooperates as valve element with the seat of the exhaust valve. The seat of the supply valve is impact resistant and is affixed to the relay body without use of threads, or like fastener means subject to change of adjustment. The various components of the device are held together by a clamp ring having an opening or window for the admission of signal pressure. Anti-rotation pins are used to prevent relative rotary movement of the parts held together by the clamp ring.