Patent GB-797456-A (GB)
Title: Improvements relating to the measurement of the speed of vehicles moving on railway track
IPC: B61L17/02
Filed: 1956-03-01
Abstract: 797,456. Railway retarders. WESTINGHOUSE AIR BRAKE CO. March 1, 1956 [March 4, 1955], No. 6426/56. Class 103 (1). Radar-operated means for measuring the speed of vehicles moving over a selected section in a stretch of railway track e.g. to obtain an average value of the acceleration as a factor in deriving the rolling resistance of a cut of wagons travelling under gravity over the selected section of a hump in a marshalling yard in order to set retarders accordingly, are rendered effective and ineffective respectively as the vehicle enters and leaves the section by controlling apparatus comprising: for marking the selected section, first and second light beams directed across the track in the path of the vehicles to influence light-sensitive cells which when so influenced operate associated vehicle detecting relays; a track relay circuit section preceding the selected section and controlling contacts to complete the energizing circuits of the beam light sources as a vehicle approaches and moves through the section; and a control circuit governed by the vehicle detecting relays arranged to render effective and ineffective the radar-operated means. When the vehicles or cuts pass through the section with little delay between one and the next, the radaroperated means is not cut out each time a vehicle passes the second beam, but is rendered incapable of registering or transmitting a result to the control means of dependent apparatus such as the retarders. The beams are preferably projected obliquely to the track both in the horizontal and vertical planes to prevent their passing between coupled vehicles in a cut. The inadvertent obstruction of a beam as by a person on the track is neutralized by the inclusion in the control circuit of slow-release relays which are arranged to operate an alarm when the obstructions of the beams do not occur in proper sequence or when the first is not followed in properly timed succession by the second. As shown, when a vehicle or cut CC enters the insulated track section AT of the track relay circuit, the track relay ATR falls off and at back contact a of relay ATR completes the light circuit for the lamp 10 producing the first beam 12 across the track to influence the light-sensitive cell P1 e.g. of the barrier layer type, to pick up the first vehicle detecting relay Z1. At back contact b of relay ATR, repeater relay ATP picks up and at front contact a of relay ATP completes the light circuit for the lamp 13 of the second beam 15 directed across the track to influence the light-sensitive cell P2 to pick up the second vehicle detecting relay Z2. As the cut leaves the section AT the lights 10 and 13 are extinguished. At front contact a of relay Z1 a holding circuit is completed for normally picked-up control relay ZP over its front contact a, to maintain the relay energized when its pick-up circuit is opened at back contact a of relay Z2. During the brief interval between the picking up of relay ATP and of relay Z2 a current impulse is supplied to the radar-operated means RRM over front contact b of relay ATP; back contact d of relay Z2 and front contact b of time element normally energized relay 2TER and wire 21, to prepare the radaroperated means. When the front end of the cut obstructs beam 12, relay Z1 falls off followed by release of relay ZP and at back contact c of relay ZP completes the control circuit for the means RRM over back contact c of relay ATR and wire 22 to render the means RRM effective for registering speed of the cut. As the front of the cut obstructs the beam 15, relay Z2 falls off and at back contact a of relay Z2, relay ZP is picked up and at back contact c of relay ZP the control circuit of the means RRM is interrupted and the means rendered ineffective to register the speed of the cut. As the section between beams 12, 15 is cleared relays Z1, Z2 pick up and relay ZP is maintained picked up all ready to function for a following cut. In the absence of a following cut relay ATR picks up and relay ATP drops off and lamps 10, 13 are extinguished. The slow release periods for time element relays 1TER, 2TER are as long as the time taken by a cut moving at the minimum permissible speed to move between the light beams 12, 15. If the light beam 12 is inadvertently obstructed, e.g. by a person walking through the beam, relay Z1 is released and shortly picked up, relay ZP releasing at front contact a of relay Z1 followed by relay 1TER at the end of its slow-release. period to pick up relay ZP at back contact b of relay 1TER over front contact a of relay Z1. An alarm circuit is also completed over back contact a of relay ITER and back contact b of relay ZP, wire 18 and back contact b of relay BCU to bell 19 or from wire 18 to lamp 20. Relay 1TER is picked up at front contact b of relay ZP. If beam 15 is inadvertently obstructed relay 2TER is de-energized at front contact b of relay Z2 and releases at the end of its delay period if the obstruction persists for this period, and the alarm circuit is completed at back contact a of relay 2TER. The alarm is also operated if lamps 10, 13 or the cells P1, P2 fail and the bell 19 can be silenced by operating a push button PB to pick up the relay BCU and open back contact b of relay BCU and at front contact a of relay BCU establish a.holding circuit for itself over back contacts c in parallel of relays Z1, Z2. If the section 12, 15 is not traversed and cleared during the release times of relays ITER, 2TER one or both these relays is or are released to complete the alarm circuit.