Patent GB-265001-A (GB)
Title: Improvements in or relating to fluid pressure brake apparatus for tramcars or other vehicles
IPC: B60T1/10
Filed: 1926-01-25
Abstract: 265,001. Peters &. Co., Ltd., G. D., and Rawlings, V. P. Jan. 25, 1926. Fluid - pressure. - Compressed air is used to release vehicle brakes by acting on the brake piston and to re-comnress into its reservoir the fluid which has been used to apply the brakes. In the construction shown in Fig. 1, the brake piston 10 is moved to apply the brakes by liquid from a reservoir 5 which also contains air under pressure. The flow of liquid is controlled by a service valve 8, which is held closed when its operating solenoid is energized, and also by an emergency valve 7, which is opened against the pressure in the reservoir 5 by a solenoid. The opposite side of the brake piston 10 is put into communication with the atmosphere by a solenoid-operated valve 4 or is supplied with compressed air from a compressor 11 driven by an electromotor 12 or from a reservoir 13. When the brakes are off and the vehicle is running, the solenoid of the service valve 8 is energized so as to hold the valve on its seat while the solenoid of the emergency valve 7 is de-energized but the valve is held on its seat by the pressure of the liquid; the solenoid of the exhaust valve 4 is then de-energized. The brakes are applied by (1) de-energizing the solenoid of the service valve 8 to allow the braking fluid to flow into the brake cylinder and (2) energizing the solenoid of the exhaust valve 4 to hold the valve open and avoid back pressure. To release the brakes, the exhaust valve solenoid is de-energized, so that the valve 4 may be closed by pressure of air, and air is supplied from the compressor 11 through the pipe 16 to the brake cylinder so as to return the brake piston 10 and recompress the air in the reservoir 5. The oil then flows backward through the valve 7. On the release being completed, the current to the motor 12 driving the compressor 11 is cut off and the compressed air in the brake cylinder is released through the groove 21 in the piston rod. The compressor 11 may supply air to the reservoir 5 through a hand-controlled valve 18 or to the reservoir 13 through a one-way valve 15. The brakes may be released by air from the reservoir 13, in the event of failure of the electric current, the supply of air being controlled by the hand-actuated valve 20. The valve 8 may then be held closed by hand. The piston 10 may be provided with two cup leathers 22 facing oppositely and the space between the two may be kept at atmospheric pressure by a connection to a hollow piston rod or, as shown in Fig. 6, by a port 26 in the cylinder wall, the piston 10 in this case being so long that the space between the cup leathers 22 always covers the port 26. The compressed air for release may be always supplied from the reservoir 13 as shown in Fig. 8. The exhaust valve 4 and an additional valve 31 are both operated by the same solenoid 35. When the valves are lowered, air passes from the reservoir 13 through the valve 31 and cock 20 to the brake cylinder 1 to release the brakes. When released, the valves are raised to put the brake cylinder into communication with the atmosphere. The cock 20 may be turned by hand to give a direct connection between the reservoir 13 and the brake cylinder. Modified arrangements of the combined valves 4, 31 are described. In the construction shown in Fig. 10, the brakes are controlled directly by hand-operated valves 47, 48 having three positions. In one position the valve 47 is opened and the valve 48 connects one end of the cylinder 1 to the atmosphere so that the brakes are applied. In another position the valve 47 is closed and the valve 48 connected to the compressor 11 so that the brakes are released and the brake-applying fluid is returned to the reservoir 5 through the one-way valve 46. In the third position the valve 48 reconnects the brake cylinder to the atmosphere, the valve 47 remaining closed. The emergency valve 7 of the form shown in Fig. 1 may be arranged to open upwards and an additional one-way valve opening downwards and closed by a spring may be provided. A differential brake piston may be employed, the oil acting on the smaller piston and the releasing air on the larger piston.