Pneumatic function generator

摘要

1,016,932. Fluid-pressure servomotor systems. ROBERTSHAW CONTROLS CO. June 19, 1963 [Aug. 17, 1962], No. 24455/63. Heading G3P A pneumatic force balance device for producing an output pressure as a function of a number of input pressures comprises a pair of balance levers 60, 62, Figs. 2 and 6 (not shown), acted upon by four flexible diaphragms 98 and having fulcrum points constituted by rollers 63, 66 on a carriage 68 which is movable by a spring-loaded diaphragm motor 34 in response to changes of pressure in a chamber 52 connected by a port 124 with a valve member 126 movable by the lever 60 relatively to a nozzle (not shown). Further rollers 76, 78 on the carriage engage tracks on a plate 72 but do not engage the levers 60, 62, whilst the fulcrum rollers 64, 66 do not make contact with the plate 72. The diaphragms 98, which are free portions of a single flexible sheet clamped between apertured plates 94, 100 have button assemblies at their centres with pins 108, 110 engaging the levers, and three of the diaphragms, which have loading springs 142, define chambers A, B, D which have inlets 90 for input pressures. The fourth diaphragm, loaded by an adjustable leaf spring 150, defines a chamber C in which the output pressure is established. In operation, any change in pressure in the chamber A or B will result in actuation of the valve member 126 to cause the diaphragm motor 34 to move until the fulcrum roller 64 is positioned such that the lever 60 is rebalanced. The accompanying movement of the roller 66 will throw the lever 62 out of balance so that the pressure in chamber C is altered, by lifting a valve member 144 from a seat in a partition 146 to admit pressure from a supply port PM or by lifting a seat 148 away from-the valve member to open an exhaust E to atmosphere, whereby the lever 62 is brought back into balance. The output pressure C will be a function of the product of the input pressures A, D divided by the input pressure B. If the pressure B. If the pressure D is maintained equal to the pressure A and the pressure B is constant the output pressure will be proportional to the square of A, and if B is maintained equal to C and D is a constant the output pressure will be proportional to the square root of A. The surfaces of the levers 60, 62 engaged by the rollers 64, 66 may be curved to give non-linear action. In a modification, the diaphragm motor 34 moves only the fulcrum roller for the lever 60, that for the lever 62 being adjusted by a second diaphragm motor controlled by a valve influenced by the position of the motor 34 through its loading spring 54.