GB677889A - Improvements relating to hydraulic speed governors - Google Patents

Abstract

677,889. Fluid-pressure servomotor-control systems MASSEY MACHINE CO. Jan. 5, 1949, No. 333/49. Class 135. A speed governor comprises a shaft 10, Fig. 1, driven by the governed device, e.g. an engine, and driving a sleeve 15 supported in a housing 14, a piston valve 16 being slidable in the sleeve under the control of flyweights 20 pivoted to the sleeve at 22 and to the valve at 24, whereby increases in speed move the valve down and decreases up. The valve controls the supply of pressure fluid from a pump 25 to either side of a piston 44 which moves a lever 12 connected, e.g. to the engine throttle valve. A piston 61 moves with the pilot valve to vary the pressure in a chamber 62, and another piston 66 moves with the piston 44 to vary the pressure in a chamber 68, the chambers being interconnected by a bore 71 and having communication with the sump 60 through an adjustable orifice 73. Thus, movement of the valve in one direction causes movement of the pistons 44, 66 in the opposite direction, which latter movement recentres the valve at a rate dependent on the setting of the orifice 73, and causes a small adjustment of the speed of the engine. Further small adjustments will occur until the engine is again on speed. If the engine goes off speed by a sufficiently large amount, a passage 91 in the piston 61 aligns with a port 95 thus exhausting the chambers 62, 68 and enabling a large adjusting movement of the piston 44 to be made. Pressure fluid from the pump 25 may be supplied through an adjustable valve 91<SP>1</SP> to the chambers 62, 68, whereby a predetermined pressure may be maintained therein. For use with engines which respond quickly to the throttle, a chamber 80 may be incorporated in the bore 71, a piston 81 in the chamber being attached by a spring 82 to the bottom of the chamber, whereby changes in the volume of the chambers 62, 68 are partly absorbed by movement of the piston 81 enabling the piston 44 to move quickly. A proportioning chamber 200, Fig. 3, may be used in conjunction with, or as an alternative to, the chamber 80, and comprises a piston 202 acted on oppositely by similar springs 203, 204 jointly adjustable by a screw 207. Changes in volume of the chambers 62, 68 are absorbed by movement of the piston 202 which is limited by locking of the coils of the springs. In a modification, the proportioning chamber comprises a piston centred by a single adjustable spring and operating between adjustable stops. The governor may be provided with speed droop adjusting means of the kind shown in Specification 666,991.