Patent GB-742125-A (GB)
Title: Improvements in or relating to temperature alarm systems
IPC: B61K9/04
Filed: 1953-04-02
Abstract: 742,125. Temperature alarms. POITRAS, E. J. 'April 2, 1953. No. 9220/53. Class. 118(1) [Also in Group XXIX] A temperature alarm system for indicating the overheating of a railway-coach bearing comprises an air-pressure line 1 extending the length of the train, temperature-responsive means 19 associated with each bearing to be protected, and one or more relay devices 15 connected between the temperature-responsive devices and the air line and adapted to vent the air line in a predetermined manner in response to actuation by a temperature-sensitive device 19 due to overheating of a corresponding bearing, thus giving rise to a predetermined signal by a whistle 10 situated at a suitable point along the airpressure line. The control of the relay devices 15 by the temperature-responsive devices 19 may be pneumatic, in which case the actuation of the systemis wholly pneumatic or it may be electrical. Each relay device 15, upon actuation by a device 19, provides intermittent venting of an air line 1, thus causing the whistle 10 to emit intermittent blasts. The air-line 1 may also include a number of manually operable valves 11 used conventionally for normal signalling between members of the train crew and providing continuous blasts upon the whistle. Details of operation. In a first embodiment, the units 19 each comprise a fusible plug mounted in the bearing to be protected and closing the end of a pipe line 17 leading from the corresponding relay unit 15. A unit 15 is shown in greater detail in Fig. 2. A pipe 14 from the mainline 1 is connected with a chamber 22, and also connects via restricted passages 25, 26 with chambers 21 and 20, the latter communicating via pipe line 17 with the units 19. The chambers 20 and 21 are separated by a snap-acting diaphragm 24 which takes up either the position shown in full lines or that shown in broken lines in accordance with the pressure difference existing across it. The diaphragm is connected by a rod with a valve 30 which either closes a port or vents it to the atmosphere in accordance with the position of the diaphragm. Under normal conditions the diaphragm is in. its free line position and the pressure is the same at all points within the unit 15. However, upon a fusible plug at one of the units 19 melt. ing, the chamber 20 is vented to the atmo. sphere, thus causing the diaphragm to move to its broken-line position, under the action of the excess pressure in the chamber 21. The valve 30 is consequently lifted, releasing the pressure in the chamber 22 and thus causing the pressure in chamber 21 to fall comparatively slowly due to the restricted passages 25. This continues until the excess pressure within the chamber 21 is insufficient to overcome the spring 33 and the diaphragm 24 snaps back to its full-line position. The valve 30 closes, the pressure in chamber 21 builds up through the restriction 25 until it is once again sufficient to operate the diaphragm 24. the operation described above continuing so long as the tube 17 is connected directly to the atmosphere. The main pressure line 1 is consequently intermittently vented to the atmosphere through the line 14 and valve 30, thus causing a pressure difference to be produced intermittently across the restricted passage 8. Such pressure causes the spring- loaded valve 9 to be released thus permitting operation of the whistle 10. ' A test valve 13 may be provided to permit manual checking of the operation of the system. In the modified form of relay device 15 shown in Fig. 4, the chambers 21 and 22 are separated by a corrugated diaphragm 38, a separate auxiliary chamber 22a in communication with chamber 22 and separated from chamber 20 by a corrugated diaphragm 36, 38 being also provided, to compensate for the thrust on the diaphragm 38. Similarly the thrust on a piston 30a at one end of the rod 31 compensates for the thrust on the valve 30.. In the arrangement shown in Fig. 5 chambers 41, 42 are separated by a corrugated diaphragm. Upon pipe line 17 being vented to the atmosphere, the valve 46 opens and air flows through pipe 47 and restriction 49 to drive the motor 50. Attached to the motor shaft is a cam 51 which effects the periodic venting of the pipe 48. The restriction 49 is chosen to be so small that the air flowing through it is insufficient to actuate the whistle 10; thus rotation of the motor 50 causes an intermittent operation of the whistle. In an alternative embodiment of the invention, Fig. 7 (not shown), the air pressure line employed is that communicating with the pneumatically operated brakes. Means comprising a check-valve are provided to ensure that operation of a relay 15 does not affect the braking system and the brake valve is interconnected with the whistle to prevent sounding the latter during operation of the brake valve. In a third embodiment, Fig.' 8 (not shown), overheating of a bearing opens a thermostatic switch thereby causing, through a relay circuit a solenoid controlling a valve venting the pipe line 1 to be operated intermittently and so causing intermittent sounding of the whistle 10.