Air distributing units

Claim 1

A PRESSURE-RESPONSIVE VALVE FOR USE IN A CONTROL SYSTEM FOR AN AIR DISTRIBUTING UNIT INCLUDING A CONTROL FLUID CHAMBER, COMPRISING A FIRST CHAMBER ADAPTED TO BE PLACED IN COMMUNICATION WITH THE CONTROL FLUID CHAMBER, MEANS ADAPTED TO PLACE THE FIRST CHAMBER INTO COMMUNICATION WITH THE CONTROL CHAMBER, A SECOND CHAMBER LOCATED ADJACENT SAID FIRST CHAMBER AND BEING IN COMMUNICATION THEREWITH BY MEANS OF AN ORIFICE, A PISTON RECIPROCATINGLY MOUNTED WITHIN SAID SECOND CHAMBER AND SEPARATING THE SECOND CHAMBER INTO A FIRST PORTION AND A SECOND PORTION TO METER SAID ORIFICE, THE SECOND PORTION BEING IN COMMUNICATION WITH THE FIRST CHAMBER THROUGH SAID ORIFICE TO APPLY PRESSURE AGAINST ONE END FACE OF THE PISTON, MEANS ADAPTED TO PLACE THE FIRST PORTION INTO COMMUNICATION WITH A SOURCE OF PRESSURE SUBSTANTIALLY EQUAL TO THE PRESSURE OF AIR SUPPLIED THE AIR DISTRIBUTING UNIT TO APPLY SAID LAST NAMED PRESSURE TO THE OPPOSITE END FACE OF SAID PISTON, MOVEMENT OF SAID PISTON SERVING TO VARY THE SIZE OF THE ORIFICE PLACING THE FIRST CHAMBER INTO COMMUNICATION WITH THE SECOND PORTION THEREBY VARYING PRESSURE IN THE SECOND PORTION, MEANS FOR BIASING THE PISTON IN A DIRECTION OPPOSITE THE DIRECTION OF MOVEMENT CAUSED BY THE PRESSURE SUPPLIED TO THE FIRST PORTION, SAID BIASING MEANS BEING LOCATED IN THE SECOND PORTION, AND SAID SECOND PORTION HAVING AN EXHAUST PORT.