A low pressure warning alarm

摘要

947,489. Respiratory appliances. E. H. REPLOGIE. Oct. 20, 1960 [Feb. 1, 1960], No. 35955/60. Heading A5T. [Also in Division G1] A pressure alarm arranged in the supply line to breathing equipment comprises a chamber 25 supplied with pressure fluid from pipes 18, 19 through filter 20 (Figs. 1 and 3) and passage 22 and containing a diaphragm 63 with holes 71 naturally biased as shown in Figs. 3 and 4 so that a resilient pad 64 closes a restricted orifice 33. If the pressure in chamber 25 drops below a predetermined level a spring 75 urges a plunger 28 against an inclined surface 69 to bias the diaphragm 63 as shown in Fig. 7 and thus allows pressure fluid to pass through a restricted orifice 33 into a chamber 25. When pressure in chamber 25 is sufficiently high it displaces a pad 55 fixed to a piston 51 to open a passage 34. The pressure fluid then acts on the whole of the end of piston 51 causing it to move quickly outwards opening exhaust ports 58 in communication through apertures 60 with atmosphere and also causes piston 51 to strike a bell 61. As the air escapes through ports 58 a spring 52 urges piston 51 inwards until pressure has again built up sufficiently high in chamber 25 and the bell striking operation is repeated. The pressure at which the bell first strikes can be varied by altering the force of spring 75 with retainer 78.