Patent GB-754487-A (GB)
Title: Improvements in or relating to fluid pressure operated relays
IPC: G05D7/03
Filed: 1954-05-07
Abstract: 754,487. Fluid-pressure servomotor-control systems. BAILEY METERS & CONTROLS, Ltd. May 7, 1954 [May 8, 1953], No. 13481/54. Addition to 736,731. Class 135. The fluid-pressure operated relay described in the parent Specification is provided with a baffle element 29 which is profiled 'to effect a desired relationship between the output pressure of the relay and the value of a variable to which the control device of the relay responds. In Fig. 1, the structure 10 which includes the invention is utilized to convert the pressure drop which occurs across a restricted orifice 2 in a fluid flow conduit 1 and is proportional to the square of the flow through the conduit into an output pressure directly proportional to the flow. The pressure drop across the orifice 2 is applied to a mercury manometer 5, the float 7. of which is connected to rotate a spindle 9 in the counterclockwise direction shown for an increase of fluid flow. The spindle 9 passes into the structure 10 which for convenience is shown in Fig. 1, laterally displaced from the manometer 5. The baffle 29 is pivotally mounted on a shaft 30, Fig. 2, and operated from the spindle 9 by a link 31. The baffle 29 moves between opposed outlet orifices 28<SP>1</SP> in a bifurcated nozzle element 28. 'The nozzle element 28 is adjustably mounted on a beam or lever 23 supported by a flexible pivot 24 and subject to the opposed actions of an adjustable tension spring 26 and a bellows 25 subject to the output pressure of the structure 10. The structure 10 includes a relay 20, Fig. 5, having form chambers 40, 41, 42, 43 of which the chamber 41 is open to the atmosphere, the chamber 43 is connected through a restriction 49 with a conduit 11<SP>1</SP> supplying air under pressure, the chamber 40 is connected to an output pressure pipe 11, and the chamber 42 is connected directly to the air supply pipe 11<SP>1</SP>. The chamber 42 is separated from the chambers 40, 41 by flexible diaphragms 48, 55 which carry respectively a tubular member 46 and an arm or lever 54. The member 46 and the arm 54 are connected by a link 56, and the arm 54 is connected to a spring-loaded bellows 51 separating the chambers 41, 43. The tubular member 46 has an orifice controlled by an inlet valve 58. The inlet valve 58 is rigidly connected to an exhaust valve 59 controlling an orifice in the outer wall of the chamber 40. The nozzle element is connected to the chamber 43 by a pipe 21 and the bellows 25 is connected to the output pressure pipe 11 by a pipe 22. Thus an increase in flow in the conduit results in a decrease in pressure in the chamber 43 and an increase in pressure in the chamber 40 and therefore in the output pressure pipe 11. The pipe 11 is connected to a remote indicator 12 to a recorder 14 and to a control valve 13. The baffle 29 is connected to rotate with a pointer 32 which moves over a scale 33 in a non-linear fashion with respect to the flow rate. The beam 23 is connected by a link 35 with a further pointer 34 which since it enjoys movements in accordance with the output pressure moves over the scale 34 in a linear manner with respect to the flow rate.