Patent GB-572867-A (GB)
Title: Improvements in or relating to systems operated by liquid pressure
IPC: B60T13/16
Filed: 1943-08-09
Abstract: 572,867. Hydraulic machines. AUTOMOTIVE PRODUCTS CO., Ltd., and CHOUINGS, L. C. Aug. 9, 1943, No. 12867. [Class 69 (ii)] [Also in Group XXXIV] A hydraulic system for operating brakes, aircraft controls, &c., of the kind in which liquid is normally circulated idly by a pump and in which the operating pressure is built-up in the pressure outlet by obstructing the flow by closing a control valve, includes an accumulator which is charged to a chosen pressure by the pump and can be connected to the pressure outlet when the valve is closed. When the pump is driven from the transmission system or the wheels of a vehicle, prompt operation of the brakes is thus ensured even when the vehicle is travelling slowly. In the system shown, a plunger 69 slidable in -the body 19 and in a slidable sleeve 55 engages a member 47 carrying a valve 65 seating on the sleeve 55, and a valve 46 controlling a passage 45. A control valve is provided by a plunger 39 formed with a valve seat 78 for engagement with one end of the plunger 69 and operable by the pedal 17' through a floating lever 40 which is connected also to the piston 21 of a master cylinder. The chambers 27, 33 of this cylinder are connected respectively to the rear and front brakes 13, 15, the chamber 33 being connected also by the pressure outlet 34 to the passage 49. With the pump 10 inoperative and the accumulator 12 empty, the parts occupy the positions shown. Liquid supplied to chamber 51 when the pump is driven moves the sleeve 55 against the action of spring 85 to unseat the valve 65 and flows to the accumulator through passages 66, 67 until the pressure therein acting in passage 93 on a spring-urged ball-valve 86 is sufficient to unseat this valve. The accumulator pressure then acts through passage 92 on a piston 70 which moves the plunger 69 by a collar 84, thus displacing the valve 46 from the passage 45 to byepass the pump supply to the reservoir 11 through passages 49, 95, 79, 80, 81. The fall of pressure in the chamber 51 permits the sleeve 55 to seat on the valve 65 and thus to cut-off the accumulator. Operation of the pedal 17 seats the plunger 39 on the plunger 69, thus building up pressure by the pump in the passages 34, 49 and chamber 33 with consequent application of the front brakes 15, and movement of the master piston 21 operates the lever 40 to partly return the plunger 39, thus reducing the supply to chamber 33. If the pedal movement is sufficient to move the plunger 69, the valve 65 is unseated to permit supply from the accumulator 12 to chamber 33 through passages 67, 66, 49, 34. During operation of the brakes, the sleeve 55 is held in against shoulder 54 by the pressure acting in chamber 61 on its larger end face, the chamber 59 at the rear of this face being connected to reservoir 11 through passage 60 and the bore in plunger 69. The plunger and valve member 47 are balanced as regards the fluid pressure acting on them. The follow-up action may be dispensed with, the pedal being unconnected with the piston 21 and being connected to the plunger 39 through a spring against the action of which the fluid pressure tends to unseat the plunger 39. In a modification, Fig. 4, the motor cylinder unit 100 is of the form shown in Specification 545,667, [Group XXXIV], the main control valve and its seat 105, 106 being provided respectively on the master piston 102 and its operating plunger 111. A lever 131 connects the pedal 107 to this plunger and to the accumulator control valve which comprises differential pistons 125, 126 and a coaxial valve 124 which with the accumulator 118 uncharged and the brakes released is closed as shown. The pump 104 supplies the accumulator until the pressure therein acting on the pistons is sufficient to move them against the action of the spring 128 to close passage 134 and open passage 139, thus byepassing the pump supply to the reservoir 150 through passages 109, 113 and valve 105, 106. Operation of the pedal first closes the valve 105, 106, thus building up pressure by the pump in the chamber 103 behind the master piston 102 and then moves the piston valves 125, 126 further to the right to uncover the port 136 to connect the accumulator to the chamber 103, the pressure in which acts on a piston area 110 to react on the operator's foot.