Air conditioning control equipment

Claim 1

A pressure control for controlling the air flow in a duct of an air conditioning system comprising: a first pair of plenum chambers; a first diaphragm forming a common wall between the chambers of the first pair for developing a force proportional to the pressure differential between the chambers; a second pair of plenum chambers; a second diaphragm forming a common wall between the chambers of the second pair for developing a force proportional to the pressure differential between the chambers; mechanical means coupling the diaphragms together for combining the forces; spring means coupled to said mechanical means for opposing the combined force of the diaphragms; electrical switch means coupled to the mechanical means for controlling an electrical circuit in response to the position of the mechanical means; means coupled to the first pair of plenum chambers for applying to the first diaphragm a pressure differential which is a parameter of the static pressure in the duct, means coupled to the second pair of plenum chambers for applying to the second diaphragm a pressure differential which is a parameter of the air velocity in the duct with the two pressure differentials connected in opposition to each other by the mechanical means, and control means connected to the electrical switch means for altering fluid flow in the duct responsive to operation of the switch.