Pneumatic relay

A pneumatic relay responsive to an air input signal whose pressure represents a variable to produce an air output signal proportional thereto, said relay comprising:

• A. a structure defining an input chamber, an output chamber and a supply chamber;
• B. an elastomeric diaphragm interposed between the input and output chambers, said structure being constituted by a meter body provided with a central bore which is secured to a plate having a well formed therein to define said input chamber, said diaphragm being sandwiched between said plate and said body, whereby said outer face seals said input chamber and said inner face seals the output chamber which is defined in said bore, said bore being internally divided to further define said supply chamber;
• C. a supply port interposed between the output and supply chambers, said supply port having a valve seat and being operatively coupled to said diaphragm;
• D. means to feed air from a constant pressure source to said supply chamber;
• E. means to feed said input signal into said input chamber to deflect said diaphragm in one direction to cause said supply port to open to admit air from said supply chamber into said output chamber until the pressure in the output chamber is in equilibrium with the pressure in the input chamber;
• F. an exhaust port provided with a valve seat defined in the raised hub of a disc disposed centrally in said output chamber and bonded to the inner face of said diaphragm, said exhaust port valve seat being coupled by an open-ended elastomeric tube passing through a lateral passage in said hub to the atmosphere at opposing sides of the meter body, whereby when there is a change in input signal pressure resulting in an imbalance between said output pressure and the input pressure, the resultant diaphragm deflection in the reverse direction causes opening of the exhaust port to discharge air from the output chamber until equilibrium is restored;
• G. a helical spring disposed in a well in said plate, the upper end of the spring engaging the inner face of the diaphragm to apply a bias to said disc;
• and
• H. means to derive said output signal from said output chamber.