GB1081172A - Pneumatic controller - Google Patents

Abstract

1,081,172. Fluid-pressure servomotor systems. MAGNETROL Inc. March 5, 1965, No. 9551/65. Heading G3P. Variations in liquid level in a container 10 are sensed by a float 11 connected to a magnetic armature 15 which co-operates with a magnet 17 carried on a pivoted lever 18 to cause rotation of a cam 25 to thereby displace a flapper 27 relative to a nozzle 26 supplied with air from a conduit 31 via a restriction 32. Consequent pressure changes in conduit 30 actuate a diaphragm 34 connected to a valve member 40 to cause corresponding pressure changes in a conduit 37 which communicates with a control device for correction of the liquid level. The conduit 37 also communicates with bellows 38, 41, the latter via an adjustable restriction 39, mounted on a lever 42 pivoted at 43 and having an extension 50 which provides a pivot for a lever 45 engaging the upper ends of the bellows. A spring 48, the rate of which is adjustable, also engages lever 45 which abuts a pin 47 carried by a beam 28 pivoted at 29 and carrying both the flapper and the nozzle. The arrangement is such that a movement of the flapper first causes bellows 38 to rotate lever 45 and beam 28 to thereby cause the nozzle to move relative to the flapper, and then, as the bellows 41 responds, the lever 45 is moved in the opposite direction to return the nozzle towards the steady state position, which position can be varied by means of screw 44. The operating range is varied by adjusting the stiffness of spring 48. The controller may also control fluid-flow or the like.