Patent GB-447829-A (GB)
Title: Improvements in hydraulic brakes
IPC: B60T13/14
Filed: 1934-11-19
Abstract: 447,829. Hydraulic brakes. SOC. ANON. FRANCAISE DES FREINS HYDRAULIQUES LOCKHEED, 27, Rue Jules Verne, St. Ouen, Seine, France. Nov. 19, 1934, Nos. 33257, 33258, 33259, and 33260. Convention dates, Nov. 20, 1933, July 2, 1934, Aug. 24, 1934, and Oct. 16, 1934. [Class 103 (i)] [See also Group XXIX] In hydraulic brakes an initial pressure on the operating liquid is applied manually by the brake pedal and increased pressure is applied by liquid put under pressure by a pump and controlled by a valve moved to brake operative position through a spring by the brake pedal and returned to inoperative position by the pressure of the braking liquid. In the construction shown, brake pedal 2 operates master cylinder 1 of hydraulic transmission also valve 25 of pressure system which acts in a cylinder 6 on a piston 5 connected to the master piston by a rod 4. A pump 12 drawing from a reservoir 9, forces liquid into accumulator 15, and when a predetermined pressure is attained the output of the pump is byepassed by a conduit 16 containing a check valve. The cylindrical slide valve 25 in release position connects the cylinder 6 by a conduit 8 to the reservoir 9 and in application position closes this connection and connects the cylinder 6 by a pipe 11 to the liquid under pressure in the accumulator 15, which comprises a piston 18 engaging a lever 19 splined to a torsion spring 20 fixed by a bracket 22. The valve 25 is operated through a spring 28 and the pressure in the cylinder 6 acts below the valve in a chamber 25 so that the valve acts as a follow-up valve. An accumulator is shown comprising a compression coil spring and the piston operates a switch to break the circuit of the pump motor when a predetermined pressure is attained in the accumulator. The pump motor circuit may be controlled by a relay controlled by the ignition switch of a vehicle engine. In a further modification in which the liquid from the pump is admitted under control of the valve 25 directly to the outlet of the master cylinder and so to the brakes a check valve in the master piston opens at a predetermined pressure to connect the master cylinder with the reservoir in which it is contained so that the master piston moves freely and allows the pedal to operate the valve 25, the movement of which is regulated by a dash-pot. A check valve prevents liquid from the pump entering the master cylinder. In a further modification of this arrangement a piston is in communication with the master cylinder and bears against a spring which yields at a predetermined pressure so that further braking pressure is supplied solely by the pump. In another arrangement the pressure applied by the master cylinder is limited by a spring in the connection between the pedal and the master piston. In a further modification the pump normally circulates liquid through the pipe 11, 8, the connection between which is close by a valve which causes liquid to be forced to the brakes, the brake liquid acting on the valve tending to open it. In a further modification the brake pedal operates a switch to bring the pump motor into action when the brake is applied. Specifications 280,502, [Class 103 (i)], 349,786, and 356,491, are referred to.