Patent GB-607409-A (GB)
Title: Improvements in automatic temperature alarm systems
IPC: G08B17/04
Filed: 1946-02-01
Abstract: 607,409. Fire alarms. TEGALEMIT. Feb. 1, 1946, Nos. 3341 and 3342. Convention dates, Sept. 17, 1942, and May 13, 1943. [Class 47 (i)] [Also in Group XXXVII] A temperature alarm apparatus of the kind in which expansion of fluid in a detector tubing located in the area to be supervised deforms a diaphragm so as to operate an alarm, and which is self-compensating for normal temperature variations in the area, comprises a detector in the form of outer and inner closed tubings 10, 9 and a diaphragm 13 which divides a closed casing 1 into chambers 11, 12 into which the tubings 10, 9 respectively open. Normal temperature variations affect the tubings equally. Sudden heating expands the fluid in tubing 10 and bulges the diaphragm away from a contact point 29. The latter is connected through a metal ring 22, plate 24 and contact 7 to the lead 4 of a relay circuit 15, 16, and the other lead 3 is connected to the casing 1 and diaphragm by a contact 6. Separation of the diaphragm 13 and point 29 opens the relay circuit to close an alarm circuit 17. The point 29 is adjustable by means of a screw 8 and the casing 1 is enclosed in an outer box 2. Means 14 for testing the detector consists of a chamber 37, Fig. 11, within which a terminal portion of the tubings 9, 10 is coiled, and a chamber 38 connected to the tubing 10. If the chamber 37 is slowly heated, the diaphragm will not be affected if the tubings are sound. If only chamber 38 is heated, the diaphragm will be bulged provided that tubing 10 is sound, but not if it is leaky. The diaphragm may actuate a mechanical instead of an electrical alarm. The tubing 9 may be shorter than the tubing 10 and communicate with it by a restricted vent for pressure equalization. If the detector tubing is exposed in a particular location to non-dangerous abnormal temperature variations, the tubing 9 may be carried outside the tubing 10 at this point to increase its compensating effect, Fig. 8 (not shown). At localized points where dangerous slow rises of temperature may occur, the tubing 10 may be enlarged, or the tubing 9 may be shortened, so as to reduce the compensating effect of the latter. To the same end, the tubing 9 may be carried outside the tubing 10 and provided with fusible plugs, which melt and relieve the pressure in chamber 12 if slow heating to a dangerous temperature occurs. To produce particular compensation effects, the tubings 9, 10 may be made of materials of differing thermal conductivities. In a modification, Fig. 13, a diaphragm casing 1 with detector tubings 9, 10 has its chamber 12 connected to the chamber 12b of a second casing 1b, to the chamber 11b of which is connected a detector tubing 11c having an expansion chamber 11d arranged adjacent a particular danger R. The tubing 9, 10 gives warning of sudden temperature rises in the whole enclosure, and the chamber 11d and diaphragm 13b give warning of any localized rise of temperature at R. The Specification as open to inspection under Sect. 91 describes also a modified apparatus, Fig. 14 (Cancelled), suitable for supervising two adjacent spaces e, e<SP>1</SP> in which differing temperature conditions may prevail, each space containing a diaphragm casing la or 1b and a detector in the form of a single tubing 5 or 5a. Each tubing is connected to the chamber 11 of its own casing and the chamber 12 of the other casing. With this arrangement, the system is balanced and the circuit of relay 15 closed, whatever mean temperature exists in the whole enclosure E. If, however, the temperature rises, at whatever rate, in either space e or e<SP>1</SP>, the diaphragm in that space will be bulged and the alarm 17 operated. One of the tubings 5 or 5a may be provided with fusible outlets to produce an alarm if the mean temperature in enclosure E should reach a dangerous point. If an enclosure is divided into more than two spaces, diaphragm casings are arranged in pairs on opposite sides of the partitions and are wired up to the relay in series. If small, permissible temperature differences may occur in the two spaces, the two detector tubings are inter-connected by a compensating device such as a restricted vent. It describes also a modified testing arrangement in which the outer ends of the tubings 9, 10 are reversely connected to a second, similar, diaphragm casing, and a modification of the apparatus shown in Fig. 13 in which single detector tubings are used and the diaphragm 13a has a restricted vent for pressure equalization. It states also that the tubings may be of different electrical conductivities and that the diaphragm casing may be removable as a unit from the box 2. This subject-matter does not appear in the Specification as accepted.