Patent GB-379088-A (GB)
Title: Improvements in or relating to railway crossing gates
IPC: B61L29/22
Filed: 1931-08-18
Abstract: 379,088. Operating levelcrossing barriers. POLAK, H., 6, Squires Avenue, Endicott, New York, U.S.A. Aug. 18, 1931, No. 23286. Convention date, Sept. 17, 1930. [Class 65 (i).] In electric motor-operated mechanism for railway level crossing gates or barriers, having a switch operated by an approaching train to close the motor circuit for lowering the gates, means for breaking the motor circuit when the gates are lowered, another switch operated by a train leaving the crossing to close the motor circuit to raise the gates, magnetic latch means to hold this second switch, and means to release the switch when the gates are raised, the train actuated switches comprise spring-controlled pivoted treadles, and one of the gates has a switch to break the motor circuit after the gates are lowered and another switch for controlling the latch means to release the treadle beyond the crossing to break the motor circuit after the gates are raised. Means are provided to prevent the gates from being raised by a train leaving the crossing on one track when another train is approaching on another track. In the construction shown in Fig. 3, the barriers are of the pole type, each barrier 5 being operated by sprocket and chain gear from a shaft 1 which runs across the tracks below the rails ; this shaft is driven by a motor M placed at the foot of the post carrying one of the barriers. The motor shaft carries a worm engaging a toothed wheel 12 which has internal and external sector gears 14, 16 each engaging a separate pinion, such as 15, on the shaft 1 ; the shaft 1 is therefore rotated alternately in opposite directions to lower and raise the barriers as the motor continues to rotate in the same direction. One barrier carries an arcuate contact-piece 41, which engages with two contacts 42 except when the barrier is lowered, and a contact 43, which engages a contact 44 and a similar contact 44<1>, Fig. 8, only when the barrier is raised. Each barrier also carries a lamp C, Fig. 8. The treadles operate spring- controlled pivoted switch arms 25 or 32, Fig. 8, each arm being permanently connected to the positive supply line a and being brought into engagement, when depressed, with a pair of contacts 28, 29 or 34, 35. The switch arms 25 of the treadles operated by trains approaching the crossing have holding solenoids 27 connected at one end to their cores, with which contact is made by the switch arm 25. The switch arm 32 of the treadles operated by trains leaving the crossing have latches 37 operated by solenoids 36<1>, 36<11>; as shown in Fig. 7, each latch comprises a core having a bevelled spring-pressed nose-piece 39, and a spring diaphragm 38 is provided to maintain the latch in the extended or retracted position until the solenoid 36<1> or 36<11> is energized to move it to the other position. The treadles are operated by a wheel, carried on a bracket on the locomotive, which may be moved to an inoperative position if desired. The circuit arrangement shown in Fig. 8 is for trains running on the right-hand track of the pair, i.e. left to right on track B and right to left on B<1>. A train approaching the barrier on either track will depress the switch arm 25 of the first treadle, and thus complete a circuit for the motor M through the holding coil 27 and barrier contacts 42 ; this circuit will be broken at contacts 42 when the barrier reaches its lowered position, and the switch arm will then be returned to its raised position by its spring, breaking all its contacts. While this switch arm remains down, it completes a circuit through contact 29 for latch winding 36<11> of the second treadle on the other track, thus ensuring that this latch is retracted ; a circuit from contact 29 is also completed for the latch winding 36<11> of the second treadle on the track on which the train is running, but this circuit includes barrier contacts 44 or 44<1> and 43 and is therefore broken as soon as the barrier commences to move ; contact 28 on the switch arm 25 closes a circuit for the latch coil 361 of the second treadle on the same track, and this circuit is maintained until the barrier is lowered, so that this latch is finally left in the extended position. When the train reaches the second treadle, the switch arm 32 will be depressed and will be held down by the extended latch 37, the nose-piece of which yields to allow the arm to pass downwards ; a circuit will be completed at contact 34 for the motor to resume its rotation and raise the barriers, and a circuit from contact 35 will be completed when the barrier reaches its raised position and closes contacts 43, 44, 44<1>, this circuit passing through these contacts to energize the coils 36<11> of the second treadles on both tracks. The latch of the treadle which has just been operated will therefore be withdrawn, and the switch arm 32 will therefore rise, breaking its contacts and thus opening the motor circuit. If, before the train reaches the second treadle, a second train, on the other track, approaches the crossing, the operation of the first treadle on this other track will cause withdrawal of the latch of the second treadle on the first track, so that when the first train operates this second treadle a momentary contact only will be made and the barriers will remain lowered until the second train operates the second treadle on its track.