| 摘要 |
<p>871,250. Fluid-pressure servomotor control systems; valves. FARRIS FLEXIBLE VALVE CORPORATION. Oct. 24, 1957 [May 29, 1957], No. 33268/57. Class 135. A fluid flow-control valve comprises a flowcontrolling mechanism and a throttling mechanism for actuating the first mechanism interconnected by a first light and second heavy prestressed loading means, wherein the first loading means is effective for a preselected valve flow capacity range and is ineffective when the second loading means becomes effective for valve capacities outside the range. The pinchcock 25 is compressed between plates 27, 28 connected by chains 31, 32 passing over sprockets 33, 34, plate 27 being moved by pressure in chamber 36 above a diaphragm 16. The valve capacity or that fluid flow through the valve is to be kept constant for a valve opening within a range of 10% to 40% of the full opening stroke of the valve which range corresponds to 10% to 90% of the valve capacity. Air under a pressure setting a given valve capacity is supplied to passage 61 up to closed valve 60, the stem 62 of which forms a seat closed by a valve member 56 in diaphragm 24 controlling flow to atmospheric port 55, while a control air pressure responsive fluid flow through the valve is fed to passage 66 and chamber 51 between large diaphragm 22 and small diaphragm 23, both connected to valve member 56. Member 56 is connected to the valve operating diaphragm 16 via a first spring 45 in series with a heavier spring 43 prestressed between cup 42 and cup 44 abutting operating stem 29 and plunger 40 slidable in the stem. If control pressure at 66 increases, due to increased flow detected by e.g. an electric flow meter, diaphragms 22-24 move upward with stem 62 to open valve 60 allowing pressure air at 61 to pass via passage 54 to chamber 36 and act on diaphragm 16 to close valve 25, this pressure also acting downward on diaphragm 24 against spring 45 to reseat valve 60. A decrease in control pressure opens the exhaust valve 62, 56 to vent pressure in chamber 36 to atmosphere at 55 so that valve 25 opens and spring 45 recloses the exhaust valve. When diaphragm 16 is moved in an opening direction more than 40% of its maximum stroke, cup 42 abuts housing 14 so that spring 45 is compressed a maximum amount and no longer exerts any control and pressure in valve 25 opens the valve against the loading of spring 43, stem 29 and cup 44 sliding upward over plunger 40. The control part of the device is thus protected from overloading. Manual adjustment is effected via screw 63 acting on spring 57.</p> |
