| 摘要 |
1344461 Temperature indicators LEYTONS (FOODS) Ltd 29 June 1971 [30 June 1970] 31651/70 Heading G1D A temperature indication device, e.g. for frozen foods, comprises a plunger 20 of magnetic material urged by a compressor spring 22 toward one end of a tube, the tube having an annular transparent window 16 defined between coloured rings 17 bounding an opaque material 14, e.g. paper or paint, positioned between two transparent plastics tubes 10, 12, the tube 12 containing a medium such as water or a water/ethylene glycol mixture which is normally in a frozen state and prevents movement of the plunger from a retracted position shown in Fig. 2; but when the device is subjected to a temperature above the melting point of the medium for a sufficient length of time melts to allow the plunger, which may be brightly coloured, to move to the end of the tube where it is visible through window 16. By making the plunger of magnetic material, e.g. soft iron, it may be reset into the retracted position magnetically, as for example by the apparatus of Fig. 3 (not shown). |
