Patent GB-1044835-A (GB)
Title: Improvements in and relating to vehicle brakes
Inventor: CHOUINGS LESLIE CYRIL
IPC: B60T13/24
Filed: 1962-05-03
Abstract: 1,044,835. Fluid-pressure brakes. AUTOMOTIVE PRODUCTS CO. Ltd. April 30, 1963 [May 3, 1962], No. 17058/62. Headings F2E and F2F. In an hydraulic braking system for a vehicle including a servomotor having a valve operated, either directly through mechanical linkage or hydraulically, by a foot pedal, the valve is also operable through a mechanical connection by an operator control mounted on the hand brake. In one embodiment, Fig. 1, a pair of vacuum or pressure servomotors 9, 10 controlled by respective valves 11, 12 together act on a master cylinder 2 having separate outlets 3, 4 connected to brakes 6, 7 on the two vehicle axles, the master cylinder 2 also being subject to the pressure of fluid in a master cylinder 1, as described in Specification 975,259. The valves 11, 12 have a common operating rod 18 which is pivoted to one end of a balance beam 16, to the other end of which is pivoted the piston-rod 17 of master cylinder 1. A link 15 connects the beam 16 to a foot pedal 13 so that when the latter is operated the valves 11, 12 and master cylinder 1 are operated simultaneously to pressurize the brakes. Valves 11 12 are also operable by an operator control on the hand brake lever which may be the usual pawl-release lever 27 but, as shown, is preferably a separate lever 26 pivoted to the hand brake lever 25 together with the pawl-release lever 27 and coupled by the core 32 and sheath 33 of a flexible cable to a lever 35 pivoted to a bracket 37 on the valve assembly and forked to engage an enlargement 38 on the operating rod 18. In another embodiment (Figs. 3 and 4, not shown), the valves are modified for operation hydraulically by the pedal, and also for mounting one of a pair of separate master cylinders, both of which are controlled thereby to pressurize separate hydraulic systems for the two vehicle axles. In this embodiment, there is provided a three-part casing 39, 46, 47, secured together by bolts which also secure diaphragms 50. The centre part 39 of the casing is fastened by bolts 79 to a mounting 78 on master cylinder 76 to which servomotor 77 is also bolted, so that a vacuum chamber of the servomotor is at all times connected via passages 82, 83 to one of two chambers 49, and an enclosed space behind the piston of the master cylinder is at all times connected via passages 80, 63 with a corresponding one of two chambers formed between three normally contacting pistons 41, 42, 43 which are floating in a bore 40. The other chamber 49 is connected by a pipe 84 to the vacuum chamber of another servomotor associated with a separate master cylinder (not shown), the space behind the piston of which is connected to the other passage 63. The two outer pistons 41, 43 are recessed to receive projections 53 on bosses 51 secured to the diaphragms 50, the bosses normally being positioned such that vacuum is communicated via passages 54, 55 from each of the chambers 49 to chambers 48 on the opposite side of the respective diaphragm 50 and thence via pipes 81, 85 to the respective power chambers of the servomotors. In operation, as a servo for the foot pedal, depression of the pedal pressurizes two primary master cylinders (not shown), which are connected to the spaces behind the pistons of the master cylinders 76 so that the chambers between the pistons 41, 42, 43 are also pressurized. As a result, the bosses 51 are moved outwardly so that plungers 52 engage and lift spring-loaded valves 56, cutting-off communication between chambers 49 and chambers 48, and connecting the latter chambers to atmosphere via inlets 59, so that the servomotors are energized, the piston 42 taking up a position to balance the forces on the two bosses 51. By this arrangement both valves will still be operated if one of the primary master cylinders fails or a leak occurs in one hydraulic line. To provide for operation of the valves by the operator control on the hand brake lever, rocking-plates 61 are provided to move the bosses 51 when rocked by sliding- pins 66, 68 connected respectively with the core 65 and sheath 72 of a flexible operating cable, the other ends of which are connected as before with lever 26 on the hand brake lever 25. Alternatively, a pair of flexible cables may be used (Fig. 7, not shown), each connected directly with one of the bosses 51. In a simplified system employing only a single hydraulically-operated valve (Fig. 6, not shown), the operating stem 91 of the valve is arranged to be engaged by a forked end 95 of a lever secured to a shaft 94 which carries, externally of the valve casing, a lever 92 for connection to the operator control on the hand brake lever.