| 摘要 |
1481100 Indicating thermal history of frozen products MINNESOTA MINING & MFG CO 23 Sept 1974 [24 Sept 1973 10 Oct 1973] 41357/74 Heading G1D [Also in Division G3] A device 10 for indicating elapsed time or thermal history e.g. of photographic materials or frozen food comprises a wick 20 capable of wicking a liquid which is absorbed in a pad 26 and means for indicating the presence of the liquid as it travels up or when it reaches a certain area of the wick. For elapsed time indication the wick and pad are separated, e.g. by a plastics sheet 24 which is removed to activate the device. The parts are held together by a clip 40 between impermeable covers 14, 28 and the device may be attached to a stored article by pressure-sensitive adhesive 36 after removing a sheet 38. In an alternative arrangement the wick and pad are initially held apart in a channel-shaped clip (102) Figs. 9, 10 (not shown), and are brought into contact, e.g. by deforming the clip, to initiate operation. In a thermal history device the material in the pad may initially be solid and liquefy only when the ambient temperature rises above a certain level, which may be above room temperature. The pad and wick are then held permanently in contact, and a device is described having a wick (80) Fig. 6 (not shown), with several branches each in contact with a respective pad. Each pad has a saturant which becomes liquid at a different temperature. The indication may be provided by the moving front of a coloured liquid along the wick which can be printed with a set of spaced time indicia. Alternatively the wick may be impregnated or coated, for example at portion 22 remote from the pad, with a chemical to react with the wicked liquid and produce a visible indication.
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