Pneumatic servo-positioner unit

摘要

966,720. Fluid-pressure servomotor systems. WORTHINGTON CORPORATION. Feb. 19, 1962 [July 21, 1961],No. 6280/62. Heading G3P. A pneumatic servomechanism for positioning a member such as a valve, a rheostat or a graphic recorder pen in accordance with variations of a signal pressure, e.g. a pressure derived from a fluid flow, comprises a pair of diaphragms 19, 20, Fig. 3, to a space 24 between which the signal pressure is applied to produce a net upward force due to the larger area of the diaphragm 19, a flexible valve member 40 fixed to a post 50 and moveable by a flanged member 34 secured to the diaphragms to vary the degree of obstruction offered to a nozzle 54, and a spring-loaded actuator diaphragm (not shown) for positioning the controlled member and responsive to the pressure between the nozzle and a restriction 53 which pressure is communicated to the diaphragm through passages 56, 41. Movement of the diaphragm is transmitted through a rod 12 and spring abutment 39 adjustably fixed thereto to a spring 38 bearing on the member 34, the arrangement being such that the change in spring force applied to the member 34 opposes the deflection of the diaphragms 19, 20. The rod is slidable in the member 34 and in a sealing device 57. The unit, including the actuator diaphragm, may be connected at either end to the controlled member so that the latter can be operated in either sense in response to a given change of signal pressure. In a modification, the flexible valve member is replaced by a shuttle lift valve controlling supply and exhaust connections to and from the actuator diaphragm. In a further modification, the nozzle 52c, Fig. 12, controlled by the flexible valve member 40c, is externally mounted, the actuator diaphragm 65c and the signal-pressure responsive diaphragms 19c, 20c share a common loading spring 38c, and the rod 12c operates a rheostat 89 through a rack and pinion 86, 87. For operating a recording pen each end of the rod 12c is connected to an end of a steel wire which passes over pulleys and carries the pen intermediate its ends.