GB826915A - Automatic hydraulic regulating apparatus - Google Patents

Abstract

826,915. Fluid-pressure servomotor-control systems. CURTISS-WRIGHT CORPORATION. Nov. 1, 1955, No. 31243/55. Addition to 825,048. Class 135. An hydraulic regulating apparatus comprises an hydraulic cylinder 53 containing a power piston movable in opposite directions under the control of a pilot valve 16 movable automatically to either side of a neutral position and directly connected with the movable wall 71 of fluid-pressure chamber 72 in free fluid communication with a compensating chamber 98 coaxial with the cylinder 53, the compensating chamber containing a movable wall 99 yieldably retained in a neutral position by resilient means, such as the springs 101, 102 which are adjusted to vary the neutral position of the wall 99 by a connecting rod 105 extending from the power piston 54. In the case of a speed governor the pilot valve 16 rotates with and is axially slidable within a sleeve 15 under the control of flyweights 20 movable outwardly against the action of an adjustable tension spring 30. The sleeve 15 is rotated by an engine-driven or other shaft 10 the speed of which is to be maintained constant. The shaft 10 through gears 37, 38 drives a pump 35 supplying fluid through a pipe 40 to the pilot valve 16. The latter has heads 17, 18 controlling outlet ports 49, 50 leading to opposite sides of the piston 54. The sleeve 15 also has inlet ports 42 and exhaust ports 60, 61. The chamber 72, and the compensating chamber, comprising a cylinder 98, are in free communication by a passage 85 which is also open to the interior of an outer reservoir or casing 32 through an adjustable needle valve 90. The springs 101, 102 act on opposite sides of the wall 99 which constitutes a compensating piston, the upper spring 101 abutting against the lower end of the rod 105 and the lower spring against the lower end of the compensating cylinder 98 which is open to the casing 32 through a port 96. In a modification, the rod 105 slides in a hole in the compensating piston and the springs abut collars on the rod at opposite sides of the compensating piston. Alternatively the resilient means may comprise a single spring which is neither in tension or compression in the neutral position. The compensating piston may be replaced by a diaphragm or by an expansible chamber member.