Patent GB-762549-A (GB)
Title: Improvements in or relating to fluid pressure operated relays
IPC: G05B11/48
Filed: 1954-10-11
Abstract: 762,549. Fluid-pressure servomotor-control systems. BAILEY METERS & CONTROLS, Ltd. Oct. 11, 1954 [Oct. 14, 1953], No. 29215/54. Addition to 736,731. Class 135. In the fluid pressure-operated relay described in the parent Specification, the element of the nozzle-baffle couple which is actuated by the output pressure acting on a pressure-responsive device such as the bellows 53, Fig. 3, is given a swinging movement against a resilient means such as the constant rate spring 24, Fig. 5, and the other element of the couple is moved transversely of the direction of swing of the first mentioned element by a control device responsive to a variable condition, the edge or surface of that part of the baffle element which controls the flow from the nozzle element being straight and being maintained parallel to itself in its movement to control the flow from the nozzle element. This arrangement enables a movement of the second mentioned element which is proportional to the square of a variable quantity to be converted into an output pressure which is proportional to the variable quantity itself. Thus in Fig. 1, the differential pressure across an orifice plate 2 in a conduit 1 is measured by a mercury manometer 5 and applied as an angular movement to the input shaft 9 of a relay 10 according to the invention and the resulting output pressure in the pipe 11 is used to operate an indicator 12, a recordei 14, and a flow control valve 13. The pressure in the pipe 11 is proportional to the flow in the conduit 1. The relay 10, Fig. 5, has a baffle 91 with a straight upper edge adapted to cooperate with opposed nozzles in a member 92 carried by an arm 93. The baffle 91 is carried on an arm 90 having a pivot 71 at one end and an adjustment screw 74 at the other. The movements of the shaft 9 are communicated to the screw end of the arm 90 by a link 73. The movements of the baffle 91 about the pivot 71 are so small that the baffle moves substantially in a vertical plane without fouling the nozzle member 92. The arm 93 has a horizontal - pivot 94 about which it is moved in a plane at right-angles to the arm 90 by a bellows 53 subject internally to the output pressure of the relay through a pipe 52. The bellows 53 operates against the constant rate spring 24. The nozzle member 92 is supplied through a flexible pipe 40. The movements of the arm 93. are communicated through a suitable linkage to a pointer 80 movable over a linear scale 81. In a modification, the nozzle element is carried by a pivoted arm similar to the arm 90 and the baffle is arranged horizontally above the nozzle and suspended from parallel pivoted links, one of which is directly connected to the bellows 53 and the constant rate spring. In either case the nozzle-baffle couple operates to control the output pressure in the pipes 11, 51 and the bellows 53 by an arrangement similar to that described in the parent Specification. Thus, in Fig. 3 the baffle 21 and nozzle 20 control the pressure in a chamber 31 supplied with pressure fluid through a restricted orifice 39. The pressure in the chamber 31 acts on a spring-loaded bellows 41 connected to a lever 44 pivotally supported by a diaphragm 45. The lever 44 is connected by a link, 46 to a parallel tubular member 37 pivotally supported by a diaphragm 38 and supplied with pressure fluid from a chamber 32. The tubular member 37 operates rigidly connected valves 48, 49 controlling the inlet and exhaust of pressure fluid to a chamber 30 connected to the output line 51.