Patent GB-257234-A (GB)
Title: Improvement in hydraulically actuated brake mechanism
IPC: B60T13/24
Filed: 1926-07-14
Abstract: 257,234. Bragg, C. S., and Kliesrath, V. W. Aug. 20, 1925, [Convention date]. Fluid-pressure. - In a hydraulic brake system, the main hydraulic cylinder 5, Fig. 2, is provided with one or more venting and filling ports 14 adjacent to the position of the piston 9 when retracted and communicating with an oil reservoir 8 above the cylinder so as to provide a large body of oil into which occluded air may pass to escape at its surface, the movement of the piston being controlled by the operator and the cylinder 5 being connected by a pipe 6 and branch pipes 7, Fig. 1, to one or more actuating cylinders 3 with pistons for operating one or more brakes. The cylinder 5 is preferably inclined downwards towards the pipe 6 and is mounted above the actuating pistons so that the ports 14 are at the highest point of the fluid system. The reservoir 8 has a removable cover plate 11 with a filling aperture and cap 13 provided with a baffle plate 13<a> to prevent oil from splashing through vent holes 13b in the cap. A pipe 16 with a check valve 17 and a hand-operated cut-off valve 18 connects the resevoir to the pipe 6 and is used in filling and bleeding the system from the reservoir oil being forced into the system by the piston 9 during its outward stroke and drawn from the reservoir through the pipe 16 into the cylinder 5 during the return stroke of the piston. The valve 18 may be dispensed with when the pipe 16 and ports 14 are connected to a common reservoir. The piston 9 may be operated by a foot or hand lever or by power. As shown, a power actuator is employed operated by power supplied from the intake manifold of a vehicle engine, and provision is made whereby the operator may actuate the brakes on failure of power. The power actuator comprises a cylinder 20 closed at both ends by heads 21, of which one has an extension 22 screwed to the cylinder 5. A piston 24 in the cylinder 20 has a hollow hub 34 with a hollow piston rod 35 which extends through a stuffing-box 36 and is connected to the piston 9 by a stud 37. The other end of the hub 34 has a hollow sleeve 38 extending through a stuffing-box 39 in the adjacent head 21. A hollow valve rod 44 is movable within the sleeve 38 and piston rod 35 and is connected at 56 by a link 58 to a brake pedal 57 provided with a retracting spring 59. The rod 44 has slidable thereon two pairs of valves 40, 41 and 42, 43 cooperating with seats in the hub 34, the valves of each pair being yieldingly pressed in opposite directions by cushioning devices 50, and secured to the rod 44 are collars adapted to abut against and operate the valves and the sleeve 38 and piston rod 35. The hollow rod 44 is connected by a suction pipe 55 containing an adjustable regulating valve 60 and a check valve 61 to the intake manifold of the engine, and the spaces between the rod 44 and the sleeve 38 and piston rod 35 communicate with the atmosphere through ports 45<a> and 52, 53 respectively, while the interior of the rod 44 is in communication through ports 47 with the space 25 in the hub 34. In the brake-off position shown, the valves 40, 43 are closed and the valves 41, 42 are open, so that both sides of the piston 24 are in communication with the suction pipe 55 through ports 26, 27, the space 25, ports 47, and the hollow rod 44 thus maintaining a partial vacuum in the cylinder 20. Pressure on the pedal 57 causes the rod 44 to move to the right, open the valve 40, and close the valve 41, thus admitting air to the left of the piston 24 and causing the brakes to be applied. Since a partial vacuum existed in the cylinder 20, movement of the piston 24 will not withdraw any material quantity of air from the cylinder, and the operation of the engine will not be affected. Any occluded air in the cylinder 5 will be expelled to the reservoir 8 through the ports 14. The piston 24 overtakes the rod 44 when the rod stops and the valve 40 is closed and the valve 41 opened, thus restoring the actuator to a balanced condition. When the pedal is released and retracted by its spring, the rod 44 returns, closing the valve 42 and opening the valve 43 to admit air to the right of the piston, while the left of the piston is connected to the suction pipe so that the piston 24 is returned to its initial position, the air withdrawn through the pipe 55 being distributed gradually into the intake manifold by the regulating valve 60 so as not to interfere with the engine. In the event of failure of power, the operator can actuate the piston 9 directly through the end of the rod 44 abutting against a shoulder 63 in the stud 37, withdrawal being effected through co-operating collars or rings 62, 65 on the rod 44 and within the stud 37 respectively. Specification 226.514 is referred to.