GB743767A - Compressed air breathing apparatus - Google Patents

Abstract

743,767. Respiratory appliances. HAMPTON, T. A. Dec. 2, 1954 [Dec. 7, 1953; June 21, 1954], Nos. 34024/53 and 18198/54. Class 81(2). In a device for controlling the supply of air for breathing during diving, a reducing valve reduces the pressure to a low intermediate value and a demand-actuated low pressure valve controls the supply from this to a breathing chamber. Both valves avoid the use of mechanical linkage and are arranged to maintain the pressure in the breathing chamber equal to that of the surrounding medium. In the equipment shown, high pressure air enters a compartment 4 through a union 5 and thence passes to a low pressure compartment 6 through a reducing valve 8, which is controlled by a diaphragm 10 influenced by the low pressure air on one side and by the pressure in the breathing chamber 16 on the other. This chamber is closed by a flexible diaphragm 17, the outer face of which is subject to the pressure of the surrounding medium, and which tends to close the low pressure valve 21, between the low pressure chamber 6 and the breathing chamber 16. Air enters the breathing chamber until the pressure is equal to that of the surrounding medium, at which point the pressure of a spring 22 is just sufficient to hold the valve 21 closed. Either an inhalation by the user or an increase in ambient pressure will lift the low pressure valve off its seating and pass air to the breathing chamber 16 and any increase in pressure in the breathing chamber, resulting from the second cause, is communicated to the diaphragm 10 and thus raises the pressure in the chamber 6 accordingly. Other forms of low pressure valves, described with reference to Figs. 3 and 4 (not shown) comprise, in one case, a ball valve actuated by a flexible diaphragm and, in the other case, a tapered seating engaged by a conical boss formed on the diaphragm.