Patent GB-601229-A (GB)
Title: Improvements in fluid pressure operated speed governing systems
IPC: G05D13/00
Filed: 1945-01-19
Abstract: 601,229. Fluid-pressured servomotor-control systems ; valves. MASSEY MACHINE CO. Jan. 19, 1945, No. 1613. Convention date. Jan. 19, 1944. [Class 135] [Also in Group XXVI] A governor mechanism comprises a regulator member 45 movable in a pressure chamber 43 in response to pressure changes therein and a pilot valve 16 which normally closes each of two passages 41, 42 connecting the opposite sides of the regulator member to a source of fluid pressure, the pilot valve being influenced by speed-responsive means 20 and by fluid pressure, the force exerted by the latter being the sole force balancing the force exerted by the speed-responsive means. In Fig. 1, a power piston 45 operates in a cylinder 43 and is controlled by a piston valve 16 which is subject to the action of the fly-weights 20 and the opposing action of the fluid pressure in a chamber 36 below the valve. The piston 45 through its piston-rod 46 operates on a shaft 11 controlling the engine throttle valve or other fuel control means. The chamber 36 is formed in the base of a hollow shaft 13 mounted in a support 14 and driven by the shaft 10, the speed of which is to be controlled. The flyweights 20 are pivoted at 22 on the shaft 13 and connected by links 23 to a head 19 on the valve 16. Passages are formed in the shaft 13 and the support 14 to admit pressure fluid selectively from a pipe 30 to either of conduits 41, 42. The rapidity with which the power piston responds to the control is adjustable by a valve 50 controlling conduits 41, 42. A similar valve 110 controls the rapidity of the response of a compensating piston 68 operating in a cylinder 67. The pipe 30 contains an accumulator 29 and is supplied by a pump 25 driven from the shaft 10. The pump 25 also supplies the chamber 36 through conduits 60 and 86 under the control of a valve 70 comprising a head 74 and a piston 73 with a notch 87 (Fig. 2). The notch co-operates with a trapezoidal port 85 in a sleeve 84 adjustable by means of a screw-operated rack to regulate the sensitivity of the governor mechanism. The valve 70 is moved axially by the power piston 45 through levers 94, 95 which have a pin-and-slot connection 96. The lever 94 has a pivotal support 97 and the lever 95 is pivoted to the compensating piston 68 and to a bracket 72 rigidly connected to the valve 70 and to a piston valve 71 controlling the supply and exhaust of pressure fluid to the two sides of the compensating piston from a port 82 in the conduit 60. The pressure in the chamber 36 and hence the setting of the governor may be adjusted by a leak-off valve 91 in the conduit 86, the valve 91 being operated by a handoperated arm 115 through links 112, 114 and a floating lever 113. The setting of the governor may also be adjusted in accordance with the prevailing load as reflected by the position of the shaft 11 by a lever 119 which has an adjustable fulcrum 120. The lever 119 is connected to the piston-rod 46 and to a link 118 also pivoted to the floating lever 113. For isochronous governing, the fulcrum 120 coincides with the pivotal connection of the lever 119 and the link 118. For governing with negative speed droop, the fulcrum is arranged to be moved to the right beyond the aforesaid pivotal connection. In the operation of the compensating means, the valve 70 is moved by the piston 45 in a direction to produce in the chamber 36 a change of pressure which will retard the prevailing movement of the valve 16. The same movement of the piston 45 also moves the valve 71 and starts movement of the compensating piston 68 which restores the valves 70, 71 to their initial positions so that at the end of a control cycle the valves 16, 70, 71 are all in their initial positions, but the power piston 45 and the compensating piston 68 occupy new positions. The mechanism is provided with adjustable maximum loadlimiting means comprising a lever 126 with an adjustable fulcrum 128, one end of which lever lies in the path of a projection 125 on the piston-rod 46. The projection 125 causes the lever 126 to operate a spring-loaded valve 131 which blocks the conduit 86 when the maximum load limit is reached. In a modified arrangement, the lever 126 is pivoted on the pistonrod 46 and acts at an intermediate point on the head 19 of the piston valve 16 when the load limit is reached. In a modified form of compensating valve, Fig. 4, the valve member 147 and a fixed sleeve 145 have oppositely tapered ports 148, 149 and the valve 147 is rotatably adjustable by means of an axially fixed screw 154 which reciprocates a slotted bracket 153 embracing a pin 151 on the valve stem. The complete system may be arranged in a single casing with external adjusting devices and dials for prevailing speed, load limit and speed droop. The base of the casing may form the sump 104. The governor mechanism is adapted for combined speed and fluid pressure regulation and may be used in marine service and in the control of engine-driven compressors and pumps. It may also be used to control the pitch of variable pitch propellers.