GB799249A - Car retarder speed control apparatus - Google Patents

Abstract

799,249. Railway retarders. WESTING- HOUSE AIR BRAKE CO. June 27, 1956 [July 11, 1955], No..19890/56. Class 103 (1). In retarder systems for railway hump classification yards, it is usual for a predetermined initial pressure to be applied to the retarder bars before a, car enters the retarder, and then to reduce the initial pressure to a partial pressure as the speed of the car unit within the retarder is lowered to near the correct or desired leaving speed, the retarder bar pressure being completely released should the car's speed be reduced to the correct speed. The retarder bars, therefore, have to be moved from a closed to an open position, if a car should enter them, which is already moving at less than the required leaving speed and the invention aims at avoiding the pressure expended and the unnecessary wear of the retarder shoes in this operation. If a car should enter the retarder CR at less than the desired leaving speed of, for example 5 miles per hour, shunting of track relay 1T will set in operation, the relay counting chains, the time measuring means being permitted to operate to its limit so that the relays 4U and 6M are energized. The control relays 2PPR and 2SPR will be energized through the network since the increased speed of the car unit in section 1S is less than the selected leaving speed. The normal contact 140 for relay 2PPR will be closed to connect wire 160 to the terminal 138 of the network SP. The control circuits are thus conditioned to apply a positive voltage to the car retarder terminal XP should the control relay A be energized. When the leading wheels of the slow-moving car unit enter section 2S of the car retarder, the energization of control relay A merely transfers the positive energy supply to terminal XP from its back contact 168 and wire 169 to its front contact 159 and wire 160 to terminal XP so that the car retarder remains open as the car unit proceeds through the retarder. The operation of the control system as a whole is generally similar to that described in Specification 724,844 but an occupancy relay RR1 is provided which is energized only so long as a car is in the retarder and which through control relay A makes the retarder inoperative if no car is passing through.