Patent GB-427681-A (GB)
Title: Improvements in the detection of rises of temperature
IPC: G08B17/06
Filed: 1934-05-04
Abstract: 427,681. Temperature - alarms. VILLIERS, C., BOURDON, R. E., ROUSSELET, P. F., COMPAGNIE D'ELECTRICITE DE L'OUEST PARISIEN (OUEST LUMIERE), and ETABLISSEMENTS SOULAT FRERES, 3, Quai National, Puteaux, Seine, France. May 4, 1934, No. 13533. Convention date, May 5, 1933. [Class 47 (i)] [See also Group XXXVIII] Automatic means for detecting increased temperature and giving warning thereof, comprises a conducting wire formed of alternate sections 1, 3 and 2, 4 of different metals which, in combination, form thermo-couples at the joints 5-9. The sections are joined by a low melting-point solder. Alternate joints 5, 7, 9, are covered with heat insulation 10. Thus, slow heating affects all the thermo-couples equally, so that zero E.M.F. results. Under rapid heating, however, a positive E.M.F. is generated at the joints 6, 8. Further, slow heating to a predetermined point breaks the conductor by fusion of the soldered joints. The conducting wire is carried around the wire 11 opposite in direction to the E.M.F. generated when the thermo-couples are subject to heat, and the coil 17 of a relay 16 is connected across its terminals 20, 21. The relay 16 is part of a normally-closed circuit 18 wired in parallel with a control circuit 22 which includes a battery 23, ammeters 56, 57, centralstation signal-receiving devices 27, 28, and a code-transmitter device 25 or 26 for each detector loop 11. Normally, the current flowing through the coil 17 is insufficient to operate the relay 16. Heat conditions, either by breaking a soldered joint or by causing a thermo-couple to generate a back E.M.F. in the loop 11, reduce the current flowing in the loop, thereby increasing the potential difference between 20 and 21, so that the relay 16 is actuated to break the circuit 18. The effect of this is to include the coil 44 of the corresponding code transmitter in the circuit 22, so that the transmitter is operated. The circuit 18 may be opened by a manual switch 58. Half loops 51, 52 connected to the midpoint of the battery 23 can be connected into the circuit 22, to maintain the installation operature if a break occurs in the circuit 22, by means of pairs of slow-release minimum relays 53, 54 distributed along the circuit. Each codetransmitter comprises a clock-work mechanism, of which the escapement mechanism 31, 32, 34, 35, 43, 46 is released when the coil 44 is energized. The code wheel 36 is then rotated by the spring 30, and sends a characteristic signal by make and break of the contact 38 in the circuit 22. A latch member 48 holds the escapement mechanism released until the wheel 36 has completed its stroke. At the end of its stroke, the wheel moves a slide 40 to allow switches 41 42, to close. Closure of switch 42 energizes a local alarm, not shown. Closure of space to be protected, preferably in a grid formation. The wire 11, Fig. 2, is connected through a resistance 19 to a source of constant current 14, 15, so that a current flows in the switch 41 short-circuits the coil 44. Each transmitter coil 44 is provided with a slowrelease coil 50 whereby the simultaneous operation of the transmitters is avoided.