Patent GB-1407624-A (GB)
Title: Altitude compensating pressure regulator
IPC: A62B9/02
Filed: 1972-08-18
Abstract: 1407624 Fluid-pressure servomotor systems ROBERTSHAW CONTROLS CO 18 Aug 1972 [20 Aug 1971] 38719/72 Heading G3P [Also in Division A5] A pressure regulator for use in high altitude breathing apparatus has a control valve between an inlet 15 and an outlet 17 comprising a valve seat 21 defining a port communicating with the inlet 15 and a flexible diaphragm valve member 23 having the side remote from the seat exposed to a communication chamber 63 and of greater area than the cross-sectional area of the port, a reference chamber 41 communicating with the outlet 17 through a bleed port 39, the pressure in the reference chamber 41 being controlled by an aneroid 51 and a biasing means 49 so that, above a predetermined exterior pressure, the pressure in the communication chamber 63 decreases and the outlet pressure rises and below said predetermined exterior pressure the aneroid becomes ineffective, the reference chamber pressure being controlled only by the biasing means thus maintaining a substantially constant pressure at the outlet. The outlet 17, which has a Venturi fitting 75 and a filter 77, communicates through a passage 83 with a pilot valve chamber 31 bounded on one side by a diaphragm 35 having the bleed port 39 to the reference chamber 41. In response to inhalation, the diaphragm 35 moves to open a pilot valve 33 to relieve the pressure in the communication chamber 63 and a control chamber 27 and thus permit the diaphragm valve member 23 to be spaced further from the seat 21 and increase the outlet pressure. In response to exhalation the diaphragm 35 moves to close the pilot valve 33 so that a pressure build-up in the communication chamber 63 and the control chamber 27 causes the valve member 23 to close and decrease the outlet pressure. The aneroid 51 is connected at one end to a stud 53 slidable in the regulator housing and at the other end to a spring-biased reference valve poppet 47 which controls flow of gas from the reference chamber 41 through a flanged opening to the ambient atmosphere. At normal ambient pressures the aneroid resists the action of the spring 49 on the valve poppet 47 so that the reference valve is open. Movement of the diaphragm 35 to close the pilot valve 33 tends to increase the pressure in the reference chamber such increase being  relieved through the reference valve to the ambient atmosphere at normal ambient pressures. At lower ambient pressures above the predetermined value the aneroid expands to assist the spring bias on the reference valve poppet 47 to reduce the flow of gas to atmosphere through the valve 47 so that movement of the diaphragm 35 in pilot valve closing direction is slower, and the pressure in the control and communication chambers 63, 27 is relieved to a greater extent and the outlet pressure increases in proportion to the decrease in ambient pressure. At an ambient pressure below the predetermined value, the stud carrying the aneroid rises so that the valve poppet 47 is controlled only by the spring 49, the reference chamber is open to ambient pressure and the outlet pressure relative to the ambient pressure is substantially constant.