Patent GB-249096-A (GB)
Title: Improvement in hydraulic brake mechanism for automotive vehicles
IPC: B60T13/16
Filed: 1926-02-24
Abstract: 249,096. Bragg, C. S., and Kliesrath, V. W. March 14, 1925, [Convention date]. Fluid-pressure.-Hydraulically actuated brake mechanism for motor vehicles comprises a pump driven by the motor or the road wheels so as normally to circulate liquid freely in a circuit to which one chamber of a piston cylinder is open, and a valve device the co-operating members of which are operated respectively by the usual operating pedal and by the piston whereby a graduated pressure may be established in the cylinder. The piston is adapted to force liquid contained in the other chamber of the cylinder into a series of cylinders connected to the several brakes of the vehicle. The operator may apply direct pressure to the piston by means of the valve rod. The system comprises a main cylinder 8 within the piston 12 of which are located valve members 30, 31 mounted on a tubular rod 20 connected at 36 to the usual operating pedal and sliding in the piston-rod 13. A gear wheel pump 52, driven directly from the motor of the vehicle or through the transmission gear, has its delivery and suction pipes 62, 54 connected respectively to a pipe 46 opening into the pistonrod 13 and to a pipe 33 opening into the valve rod 20. When that brakes are released, the piston 12 is disposed at the right-hand end of the cylinder and a spring 42, abutting against the piston-rod at 43 and against a disc 41 on the extension 20a of the valve rod, holds an abutment 40 on the valve rod against the stuffing-box 23 of the cylinder so that both the valve members 30, 31 are unseated and the liquid delivered by the pump circulates freely through the pipe 46, orifices 20b. 28 in the valve rod, past the valves 30, 31, orifices 29 in the valve rod, through this rod and the pipe 33 to the suction pipe 54 of the pump. To apply the brakes the valve rod 30 is moved to the left to seat the valve 31, thus causing the liquid delivered by the pump to be forced Into the chamber 12<1> of the cylinder by ports 49. The consequent movement of the piston 12 forces liquid in the other chamber 12<11> of the cylinder through pipes 50, 51 into a number of cylinders connected to the brakes on the several wheels of the vehicle. When the forward movement given to the valves and valve rod is stopped, the forward movement of the piston 12 continues and unseats the valve 31 to such an extent as to establish a pressure in the piston chamber 12<1> equal to the reaction of the brake, mechanism. When the closure of the valve 31 during the application of the brakes cuts off the cylinder from the suction side of the pump, liquid is delivered thereto from a reservoir 57 past a non-return sleeve 59. When the valve rod 20 is allowed to move to the right and release the brakes, the valve 30 is seated and the pump withdraws liquid from the cylinder chamber 12<1> through the ports 49, past the valve 31, and through the valve rod and pipe 33 and returns it to the reservoir 57 by way of a non-return valve 67 which is spring-loaded to the desired operating pressure. The piston 12 is thus returned and withdraws the liquid previously forced into the several brake cylinders through the pipe 50 to effect the release of the brakes. The non-return valve 59 is spring-loaded to about atmospheric pressure to prevent the pressure in the cylinder chamber 12<1> from being reduced below the valve. Direct pressure applied by the operator through the pedal, the valve rod and the valve member 31 to the piston may be added to that due to the fluid-pressure or may be substituted therefor when the pump is not working. In the latter case the liquid displaced by the piston 12 in the operation of the brakes is supplied from and returned to the reservoir 57 past non-return valves 66, 61. A non-return valve 71 may be disposed in the piston 12 to permit the supply of liquid from the chamber 12' to the chamber 12<11> and the brake cylinders to compensate for leakage, that may take place in this part of the system.