GB1297798A - - Google Patents

Abstract

1297798 Thermometers INTERNATIONALER DIENST FUR BETRIEBSBERATLING LIND MARKTFORSCHLING GmbH 24 Dec 1969 62806/ 69 Heading G1D A thermometer comprises a sleeve 1 of clear plastics material and containing a capillary 5 and a bulb 2 of good heat conducting material e.g. aluminium, the bulb containing a thermometric filling substance 3 in the form of a mixture of several crystallic organic compounds with melting points close to each other, the expansion of this substance on melting being transmitted through the agency of a separating diaphragm 4 to an indicating liquid 6 which fills part of the bulb 2 and capillary 5. The sleeve 1 is preferably made from a polycarbonate or acrylic resin and the aluminium bulb 2 coated inside with carbon fluoride. The diaphragm 4 may be of polychloroprene or chlorosulphonated polyethylene, and the sleeve may be formed so as to magnify the capillary 5 and associated scale 8. A proposed composition for the thermometric substance is a mixture of cicosane, lencicosane and dicosane, and additives such as m-dinitrobenzene, ptoluidene, camphor, benzene, acetone, menthol, phenyl salycylate, cyanamide ethyl carbonate, dimethoxy-aniline, or o-terphenyl may be added to enlarge the melting range of the substance wherein the greatest expansion takes place. The indicating liquid 6 is preferably a dilute solution of methyl cellulose in water coloured with a dyestuff or a polyglycol ether also with added dyestuff, both with or without a fluorescent substance. In an alternative embodiment, Fig. 4, a plastics material hose 11 is coiled round an aluminium tube 10, the hose being filled with indicating liquid, sealed at one end and secured to the tube 10, the other end being pulled upwardly through the tube 10 to form the capillary for the thermometer, the coiled hose 11 being enclosed by an aluminium sleeve 12 containing the thermometric substance, and the upper end of the sleeve 12 being closed by a transparent plastics tube 14 with a stopper 15 provided with a bore for the tube 10. The crystalline organic compounds may be finely dispersed in a liquid with which they are immiscible.