GB1459513A - Diaphragm member - Google Patents

Abstract

1459513 Fluid-pressure servomotor systems FRAM CORP 5 Feb 1974 [5 Feb 1973] 05326/74 Heading G3P [Also in Divisions F1 and F2] In a fluid-pressure controlled valve 10, a diaphragm closure member 80, controlling a seating on the end of a passage 58 in a tube 56, is combined with a differential pressure sensitive diaphragm 74 to form an integral diaphragm member 72. The closure member diaphragm 80 is essentially planar and the pressure sensitive diaphragm 74 flares outwardly from a central joining post 84 almost to its outer perimeter so as to be rigid over almost its entire operative area, which is considerably greater than that of the diaphragm 80. The diaphragm 80 closes a chamber 44 and is biased towards an open condition by a helical spring 102. The diaphragm 74 closes a chamber 24 and is subject to the over-riding influence of a piston 104 having a flexible wall 106 sealed to the valve housing to form a chamber 28. The piston is biased towards the diaphragm 74 by a spring 116 which is stronger than the spring 102. The two diaphragms form between them a chamber 88. A restricted bleed passage 86 is provided in the central post of the diaphragm member to connect the chambers 44 and 88. In use in a system, Fig. 6, for the control of exhaust gas re-circulation in an internal combustion engine, a valve 226 admits exhaust gas from a passageway 224 into the inlet manifold when vacuum from a reservoir 236 is admitted to a vacuum motor 228, controlling valve 226, as a result of the diaphragm 80 moving away from its seating to provide a connection between passages 58, 62 in tubes 56, 60 respectively. Chamber 24 is connected, via passage 36 in tube 34, to a Venturi 208 in a carburetter 204. Chamber 88 is connected via passage 54 in tube 52 with a point in the carburetter air intake between the carburetter and an air filter 212. Over-ride chamber 28 is connected via passage 40 in tube 38, with the inlet manifold 202 so that if there is insufficient vacuum in the inlet manifold 202 to overcome the biasing spring 116, the diaphragm member 72 is locked with the valve diaphragm 80 in the closed position. Vacuum reservoir 236 is connected to the inlet manifold 202 via a check-valve 238 which closes if pressure in the manifold rises above that in the reservoir. Provided the vacuum in the manifold is high enough to withdraw the over-ride piston 104, the diaphragm 74 will respond to the pressure differential between the air intake and the Venturi throat. Thus the degree of vacuum fed to the motor 228, and hence the degree of opening of the valve 226, is proportional to the rate of flow through the carburetter.