Sicherheitsventil

摘要

1,251,280. Fluid-pressure servomotor systems. LUCEAT. Dec.18, 1969 [Dec.20, 1968], No.61652/69. Heading G3P. A relief valve 10, which may be used to relieve either excess pressure or excess vacuum within its inlet A, has connected thereto a pressure pilot valve 12 and a vacuum pilot valve 14, the two pilot valves being of identical construction and being responsive respectively, to excess pressure or excess vacuum at the inlet A. Up to a predetermined excess inlet pressure, such inlet pressure is transmitted to a diaphragm chamber C of the pilot valve 12, and from chamber C is communicated through a check-valvecontrolled passage 114, chambers F and E, and a passage 136 to relief valve control chamber B, such communication being possible as long as the inlet pressure acting within chamber C does not overcome the force of spring 96 and hence pilot valve member 70 remains remote from a seat surrounding a duct between chambers E and F but seated on a seat surrounding a duct between chambers D and E, the former of which is vented to atmosphere via port 81. Upon the pressure rising, the diaphragm of chamber C moves upwardly as does closure member 70. As a result the inlet pressure ceases to be communicated to chamber E, the pressure within chamber B is relieved to atmosphere via passage 136 chambers E and D and port 81, and hence the relief valve opens. The pressure at which relief occurs is adjustable by varying the loading on spring 96. Upon the inlet pressure exceeding a certain level of vacuum, pilot valve 12 becomes inoperative on account of the check valve in passage 114. Instead, vacuum is communicated to chamber D' of vacuum pilot valve 14 with such vacuum acting on a diaphragm 66' the other side of which may be exposed to positive or negative pressure. Upon the degree of vacuum reaching a limit predetermined by springs 96', diaphragm 66' moves in opposition to spring 96' and hence valve member 70' moves upwardly. Accordingly, vacuum supplied to chamber D' from inlet A is communicated to chamber E', and thence, via duct 136', to chamber B as a result of which relief valve 10 opens, the degree of vacuum at which relief occurs is adjustable by varying the loading of spring 96'. Alternatively, valve 14 may be omitted and the check valve in passage 114 of valve 12 removed. In such an arrangement, transmission of vacuum from chamber C to chamber F is no longer impeded and pilot valve 12 serves to actuate relief valve 10 under both excess pressure and excess vacuum conditions.