GB1276575A - Improvements in or relating to clinical fluid warmers - Google Patents

Abstract

1276575 Electric liquid flow heaters THERMOLYNE CORP 22 Oct 1969 [27 March 1969] 51791/69 Headings F4 AN2A A clinical fluid warmer for warming refrigerated blood and other fluids to transfusion temperature at any flow-rate from zero to a maximum comprises first and second thermally conductive heater plates 21, 22 mounted for relative pivotal movement between a closed position in which the plates are closely spaced and parallel and an open position; a support, e.g. pins 15A-15D, for removably supporting a thin flat fluid containing sac 16 in a predetermined position on one of the heater plates 21, 22, the sac 16 having an inlet 18 and outlet 19 at opposite ends and having its opposite sides in contact with the heater plates 21, 22 respectively when they are closed and the sac is full of fluid; an electric heating element 25A, 25B associated with plate 21 and an electric heating element 26A, 26B associated with plate 22; and a thermal control device thermally connected to at least one plate and electrically connected to the heating elements for controlling their operation in accordance with the temperature of said at least one plate. Sac 16 has meander channels as shown and the heating elements are mounted in the plates 21, 22 which are of cast aluminium. The heating elements in each plate are made in two sections, e.g. 25A, 25B and 26A, 26B as shown, and each section is designed so that the heat supplied to its plate is reduced in an upward direction, i.e. from the inlet to the outlet end of the sac 16, in proportion to the diminishing rate of heat absorption of fluid flowing through the sac 16. As shown this requirement is met in each section by arranging successive parallel runs of the heating element section, e.g. 25A at the centre of increasing size areas A1-A4. Alternatively Fig. 5 (not shown) each of the heating element segments 25A, 25B, 26A, 26B can comprise equispaced parallel runs of resistance element of differing power output. The thermal control device comprises four thermostats 31, 32, 33, 34 mounted in a cover 14 on heater plate 22. Thermostat 31 controls heating element sections 25A, 26A by way of triac 36 and thermostat 32 operates an alarm 38 on failure of thermostat 31 and overheating. Thermostat 33 controls sections 25B, 26B directly and thermostat 34 operates alarm 38 on failure of thermostat 33 and overheating.