| 摘要 |
1471872 Fluid-pressure servomotor systems HANSON BDC (CHESTERFIELD) Ltd 4 July 1974 [30 July 1973] 36274/73 Addition to 1408394 Heading G3P The system for supplying gas to consumers through a main 40, described in the parent specification, in which a main pressure control valve 10 at an upstream part of the main is controlled by a pilot valve 12 in accordance with the pressures at spaced-apart points at the upstream part of the main, is modified in that the pressures at the spaced-apart points, one of which is downstream of the main valve 10, and the other of which is at the outlet of that valve, are applied through the two parts of conduit 32 to the opposite sides of the secondary controlling diaphragm 24 of the pilot valve, the primary controlling diaphragm 22 having the pressure at the upstream part of the main applied to it through conduits 25 and 68, and being exposed to the atmosphere on its other side. The arrangement is such that the direct pressure control of the pilot valve 12, and hence of the main valve 10, is modified in accordance with the flow in the main, i.e. with the collective demand of the consumers, so that when demand increases, the pressure will be increased to counter the pressure loss due to flow along the main. |
