| 摘要 |
1,131,032. Hydraulic brakes; electromagnetically-released drum brakes; controlling clutches. BUTTERLEY CO. Ltd. and P. G. WESTMORELAND. 17 March, 1966 [5 April, 1965], No. 14453/65. Headings F2E, F2F and F2L. In an hydraulically-controlled brake or clutch mechanism incorporating a rotary member in the form of a brake drum 11, the speed of which is to be controlled, an hydraulic actuator 13 effects the engagement of the brake and a control pump being driven in a predetermined speed relationship to the brake drum 11 delivers hydraulic fluid to the hydraulic actuator 13 at a pressure determined by the speed of the brake drum 11 so that the latter achieves a desired speed. The pump 15 draws its supply of hydraulic fluid through a pipe line 15<SP>1</SP> from a tank 17 and delivers by way of pipe lines 18, 19 and 20 through a solenoid-operated valve 21 to the hydraulic actuator 13, the delivery of the pump 15 being proportional to the rotational speed of the brake drum 11 through the medium of a driving connection 16. At a predetermined rotational speed or " creep " of the brake drum 11, a predetermined volume of the output of the pump 15 is leaked to the tank through pressure-compensated flow control valves 22, 23. In the position shown the solenoid-operated valve 21 provided between the lines 19 and 20 such that the pump 15 is connected to the hydraulic actuator 13 and in the further position when the solenoid is energized both the pump and the hydraulic actuator are connected back to the tank 17. A relief valve 25 may be incorporated in the hydraulic system to prevent an excessive pressure build-up. A further solenoid-operated valve 24 controls operation of one of the valves 22. In order to provide a " fail-safe " feature the brake may be further actuated by spring means (not shown) and released by energization of an electro-magnetic actuator 14.
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