GB860524A - Improvements in and relating to overheated axle box detectors - Google Patents

Abstract

860,524. Detecting radiated heat. SERVO CORPORATION OF AMERICA. Nov. 4, 1958 [Nov. 8, 1957], No. 35438/58. Class 40 (3). [Also in Group XXX] In a system for detecting overheated axle boxes on railway vehicles, two heat detecting units, positioned on opposite sides of a railway track, are energized by heat from opposite axle boxes and an alarm and counter are operated when the difference between the received signals exceeds a predetermined value. The heat detector units 10 and 11, Fig. 3, each comprises two heat sensitive elements 14 and 15, e.g. thermistor flakes, which are mounted in a housing 20 and an optical system, including aperture 23, shutter 24 and lens 19, via which the element 14 is energized by heat received from a direction forming an angle α with the base of the housing. Element 15, which is shielded from heat entering the aperture, is connected in a bridge circuit with element 14 and acts to compensate for changes in ambient temperature. The units 10 and 11 are positioned on opposite sides of a track, Fig. 2 (10 only shown) and act in cooperation with electromagnetic wheel trips A, B and C, each of which produces an output pulse when a wheel flange passes through its magnetic air gap. Trips A and B are positioned apart at a distance equal to the wheel base of the vehicle being checked and trips B and C are positioned such that an axle box moves through the receive beam of the heat detector when its associated wheel moves from B to C. In operation, the moving vehicle produces a signal in trip A which energizes solenoids 25 via the storage circuit 30 to withdraw the shutters 24 protecting the elements 14 in the detector units 10 and 11, if the vehicle has the correct size of wheel base coincident signals are produced from the trips A and B which via a coincidence circuit 31 prepare a gate 26 for operation, additionally the gate is switched to its " on " position by the signal from trip B. The axle boxes, e.g. 22, Fig. 2, are then scanned by their respective detecting units and the signal produced in each unit is amplified and passed via the gate to the integrating circuits 40, 41 and 42, 43. The pulse from trip C switches off the gate and additionally operates relay 52 to discharge the integrating condensers 41 and 43 through the potentiometer 48. Each of the thyratron valves 55 and 56 is associated with one side of the track and is connected to a stepping relay which brings a new alarm and counter into operation each time the valve fires. The valves are normally held at cut-off and the potentiometer 48 is connected so that neither valve fires when the response from the detectors is equal, if, however, a difference exists, exceeding a predetermined value, one or other valve fires whereby an alarm is operated and the associated counter counts the number of pulses produced by the wheel trip C after the detection of the hot bearing. This count indicates the wheel position from the end of the train.