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Device for heating liquids contained in sealed plastics containers

  • US 4,164,645 A
  • Filed: 01/16/1978
  • Issued: 08/14/1979
  • Est. Priority Date: 10/14/1977
  • Status: Expired due to Term
First Claim
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1. A device for heating a liquid in a container of thermoplastics material hermetically sealed by means of a metal cover, the device comprising in combination:

  • support means for the container adapted to accommodate the container in an inverted position;

    an electrical resistive heater positioned in relation to the container support means to be in thermal contact substantially with the whole surface of the metal cover of the inverted container during heating of the liquid therein, said heater being of nominal power rating sufficient to heat the liquid in a short time while having the electrothermal characteristics of a positive temperature coefficient of resistance;

    support means for the heater adapted to keep the heater in contact with the cover of the container accommodated in the support means during the period of the heating of the liquid,a general switch, andan electronic control unit connectable to a power supply through said general switch, the control unit comprising;

    (a) input terminals for connection to a power supply,(b) a Wheatstone bridge having four arms a supply diagonal and a measuring diagonal, the supply diagonal being connected to the input terminals, and the resistive heater being included in one arm of said bridge, the measuring diagonal of which provides signal indicative of the temperature reached by the said resistive heater,(c) a regulator circuit arranged to regulate the current supply to supply diagonal of said Wheatstone bridge in dependence upon the said signal on the measuring diagonal of the bridge so that, after an initial transient phase, the temperature of the heater remains substantially within a predetermined range for the whole duration of the heating of the liquid, and(d) a timer arranged, after a predetermined interval timed from the moment of commencement of the heating, to switch off, by means of the regulator circuit, the current supply to the Wheatstone bridge and to open the general switch, disconnecting the control unit from the power supply.

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