GB719294A - Improvements in or relating to control mechanisms for maintaining potential variables at desired values - Google Patents

Abstract

719,294. Fluid-pressure servomotor-control systems. ILFORD, Ltd. Oct. 10, 1951 [Oct. 25, 1950], No. 26055/50. Class 135 A system for automatically regulating the value of a variable includes a movable member, means for applying thereto a loading fluid pressure the magnitude of which is dependent, at least in part, on a time differential of the variable, and means actuated by the movement of the movable member to regulate a fluid pressure supply to provide an output pressure that is substantially proportional to such movement; and the movement of the movable member resulting on the loading dependent on the time differential of the variable is five times as big as the movement of the movable member resulting from the remaining net loading, such difference in the movements being independent of the ratio between the two loadings. In an embodiment, the variable is applied through a link 41 to one end of a floating lever 42 which pivots on a link 44 from a fixed point 43. Floating lever 42 carries a rod 62 which passes through a further lever 36 and constrains the latter to follow the movements of lever 42 unless the end of lever 36 is in contact with a nozzle 34. Lever 36 and nozzle 34 constitute a nozzle and pallet system producing, from a pressure fluid fed past a filter 32 and a restriction 33, a pressure which is regulated in accordance with the movements of lever 36. This regulated pressure is applied to a bellows 38 which acts on levers 36 in such manner that, when permitted by lever 36, it is capable of closing the pallet against the full supply pressure. The regulated pressure is also applied through an adjustable needle valve 50 to a bellows 48 and through an adjustable needle valve 64 to a bellows 49, these two bellows acting in opposition on a lever 46 connected by a link 45 to the other end of floating lever 42. Bellows 48 is connected to a bellows 58 which acts on a lever 59 constituting the " movable member " of the invention, and acting on the lever in opposition to bellows 58 is a bellows 57 which is connected to bellows 49 through restriction 64 and to the regulated pressure via a conduit 40. The pressure in bellows 57 comprises components substantially proportioned to the variable, the time integral of the variable, and the first time differential of the variable, and the pressure in bellows 58 comprises components proportional to the variable and the time integral of the variable. The respective distances of bellows 57, 58 from the pivot point 60 are in the ratio 10:9. The free end of lever 59 is connected through a link 22 to a lever and nozzle and pallet system similar to the one mentioned above with, however, the lever 24 being acted upon solely by a loading spring 27 and a bellows 26 subject to the regulated pressure produced in the nozzle chamber 14. This second lever and nozzle and pallet system produces a regulated pressure in conduit 28 which is proportional to the movement of link 22. In a modification, bellows 57, 58 act on the opposite ends of a floating lever carried on a pivoted arm. Specification 568,634 is referred to.