GB507219A - Device for signalling the presence of gas in inhabited premises - Google Patents

Abstract

507,219. Gas detectors; switches. MENOZZI, G. Dec. 10, 1937, No. 34264. Addition to 480,335. [Class 1 (i)] [Also in Group XXXVII] In the inflammable-gas detector of the parent Specification, which is of the type in which a differential gas thermometer having one bulb surrounded by a catalyst is provided with electric contacts operating a signalling circuit, one or more of the following further improvements is or are embodied. As the expansion medium in the bulbs there is used a saturated vapour, or a gas under pressure. The movement of the mercury to close the circuit is facilitated by a conical expansion of the capillary, Fig. 1, and/or by sealing the wires into the glass at a point remote from the point of contact, Fig. 11, to avoid distortion of the capillary. Instead of a straight tube a U-tube may be used provided that the mercury extends over only a small segment of the bend. The capillary may be extended into the bulbs or constricted-near its ends 5, Fig. 11, to prevent spilling of the mercury. The bulbs may be covered with a thin layer of heatconducting material. The heating of the non-catalytic bulb when the circuit is closed, in order to give an intermittent signal, may be effected by an internal resistance 2, Fig. 6, which may be regulated by a shunt 4, or by an external resistance wound found the bulb. Where there are equal lengths of wire in each bulb as shown in Fig. 11, that in the catalytic bulb may have a heat-insulating covering 4, or may be partly shunted by an external variable resistance.