GB953755A - A minimum pressure delivery valve assembly - Google Patents

Abstract

953,755. Regulating compressors. ATLAS COPCO A. B. May 23, 1961 [May 23, 1960], No. 18542/61. Heading F1N. [Also in Division F2] A non-return delivery valve assembly which opens only at a predetermined minimum pressure in a compressor discharge duct 29 comprises a main check valve 3 of the disc type controlling an opening 31 in the valve casing 6 and connecting duct 29 to a delivery duct 16 and biased to its closed position by a weak spring 28 and by a spring-biased differential piston valve 10 against which the spring 28 bears; the valve 10 having an auxiliary check valve 21 in the bone of its stem 11 controlling a passage 19 in the valve 3. On starting the compressor and assuming atmospheric pressure throughout the system, valves 3, 10, 21 remain in the positions shown until a predetermined minimum pressure is attained in duct 29 whereon valve 21 is raised and compressed air gains access to a pilot chamber 20, a passage 27 in valve 10, a chamber 15 and a restricted orifice 14 leading to duct 16. A further pressure rise to an intermediate level in duct 29 results in valves 3, 10 being lifted in unison and a still further increase in pressure to the working level displaces valve 10 to its other seat 18 to allow valve 3 to half open and allow flow of compressed air from duct 29 to duct 16 with substantially no pressure drop. When air consumption is stopped the compressor is automatically stopped or unloaded by conventional means where on valves 3, 21 are closed by springs 28, 23 thereby preventing back flow of air, but valve 10 remains open until the pressure in conduit 16 falls to below said intermediate pressure after which the valves assume the position shown.