GB448588A - Improvements in and relating to electrical brake pressure regulators for railway vehicles - Google Patents

Abstract

448,588. Railway brakes. SIEMENSSCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. June 18, 1935, No. 17561. Convention date, June 19, 1934. [Class 103 (i)] An electrical brake-pressure regulator for fluid-pressure brakes comprises contacts 12 operated by brake cylinder pressure in a cylinder 9 controlling an electrically-operated brake cylinder relief-valve 8 which is opened above a certain pressure and a relay operable in response to a certain speed of the vehicle which renders this control inoperative. The relief valve 8 is opened when its circuit is closed through contact I of relay 13, the circuit of which is closed through contact I of a relay 14 and contacts 12 when brake cylinder pressure is above a certain limit. An impulse transmitter 17 driven from the vehicle axle momentarily energizes a frequency relay 16 at 28 m.p.h. which establishes a circuit through the attraction winding of the relay 14 which opens its contact I and closes its contact IV and renders the circuit of the relay 13 and thus the relief valve inoperative. Contact III closes a holding winding for the relay 14 through the contact I of the relay 15 and through the impulse transmitter 17 and maintains the relay 14 energized until the speed drops to 12-15 m.p.h. When the brake is applied above 28 m.p.h. the relief valve is not opened even if the contacts 12 are closed because the contact I of relay 14 is open. When the speed falls to 28 m.p.h. and brake cylinder pressure is sufficient to close the contacts 12, the relay 16 closes a circuit through the relay 15 and contacts 12 and this relay holds itself energized by its second winding over its contact II and contacts 12. The relay 15 closes a circuit for the relief valve 8 thrugh its contact III which opens and remains open till brake cylinder pressure falls sufficiently to allow the contacts 12 to open. Opening of the contacts I of the relay 15 will release the relay 14 again. If the impulse transmitter drive fractures the relay 14 de-energizes the relay 13 energizes and opens the relief valve to limit the brake pressure. A lighting dynamo may be used instead of the impulse transmitter. A minimum pressure valve may be arranged between the brake cylinder and the relief valve 8 which ensures relief of the brake cylincter pressure even if the battery should fail. This minimum pressure relief valve connects the brake cylinder to the relief valve above a certain pressure.