CLINICAL FLUID WARMER
First Claim
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1. A dry heat clinical fluid warmer for use in warming refrigerated blood and other fluids to a safe usable transfusion temperature, at any flow rate from zero to a given maximum rate, comprising:
- a first thermally conductive heat plate;
a second thermally conductive heater plate;
mounting means mounting said first and second heater plates for pivotal movement, relative to each other, between a closed position in which said heater plates are disposed in closely spaced parallel relation to each other and an open position in which said heater plates are disposed at a relatively wide angle to each other;
a thin, flat, disposable fluid sac having inlet and outlet openings at opposite ends thereof;
support means for removably supporting said sac in predetermined position on one of said heater plates, when the heater plates are in open position, opposite sides of said sac contacting said first and second heater plates, respectively, when said heater plates are in closed position and said sac is filled with fluid;
first and second electrical heating elements, individually associated with said first and second heater plates, respectively, each of said heating elements being effectively tapered from the end thereof adjacent the sac inlet to the end adjacent the sac outlet so that the heat output of said heating elements gradually diminishes form the inlet end of said sac to the outlet end thereof in direct proportion to the diminishing rate of heat absorption by fluid moving from the sac inlet to the sac outlet, each heating element comprising at least two sections, arranged in sequence between the sac inlet and the sac outlet; and
precision thermal control means, thermally connected to at least one of said heater plates and electrically connected to said heating elements, for controlling operation of said heating elements in accordance with the temperature of said heater plate, said control means including separate thermostats for controlling the respective sections of each heating element.
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Abstract
A dry heat clinical blood warmer comprising first and second heater plates, pivotally mounted relative to each other; a thin, flat, channeled sac, having an inlet and an outlet spaced from each other, is mounted between the plates, the sac contacting both plates when the plates are closed. The electrical heater elements for the plates are effectively tapered, by positioning or by power relationships, from inlet end to outlet end, in proportion to the diminishing rate of heat absorption of blood or other fluid flowing through the sac.
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Citations
7 Claims
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1. A dry heat clinical fluid warmer for use in warming refrigerated blood and other fluids to a safe usable transfusion temperature, at any flow rate from zero to a given maximum rate, comprising:
- a first thermally conductive heat plate;
a second thermally conductive heater plate;
mounting means mounting said first and second heater plates for pivotal movement, relative to each other, between a closed position in which said heater plates are disposed in closely spaced parallel relation to each other and an open position in which said heater plates are disposed at a relatively wide angle to each other;
a thin, flat, disposable fluid sac having inlet and outlet openings at opposite ends thereof;
support means for removably supporting said sac in predetermined position on one of said heater plates, when the heater plates are in open position, opposite sides of said sac contacting said first and second heater plates, respectively, when said heater plates are in closed position and said sac is filled with fluid;
first and second electrical heating elements, individually associated with said first and second heater plates, respectively, each of said heating elements being effectively tapered from the end thereof adjacent the sac inlet to the end adjacent the sac outlet so that the heat output of said heating elements gradually diminishes form the inlet end of said sac to the outlet end thereof in direct proportion to the diminishing rate of heat absorption by fluid moving from the sac inlet to the sac outlet, each heating element comprising at least two sections, arranged in sequence between the sac inlet and the sac outlet; and
precision thermal control means, thermally connected to at least one of said heater plates and electrically connected to said heating elements, for controlling operation of said heating elements in accordance with the temperature of said heater plate, said control means including separate thermostats for controlling the respective sections of each heating element.
- a first thermally conductive heat plate;
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2. A dry heat clinical fluid warmer according to claim 1 in which said mounting means mounts said heater plates in vertical alignment with one of said heater plates pivotally movable about a vertical axis, in which the sections of each heating element are mounted one above the other, and in which the sac inlet is located at the bottom of the heater plates and the sac outlet is located at the top of the heater plate.
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3. A dry heat clinical fluid warmer according to claim 1 in which the taper of said heating elements is determined in accordance with the basic relationship where T fluid temperature at a given time To plate temperature above initial fluid temperature D thermal conductivity of sac A contact area of one plate D thickness of sac S maximum liquid flow rate P ratio of effective contact area to actual plate area all expressed in the c.g.s. system.
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4. A dry heat clinical fluid warmer according to claim 3 in which each of said heating elements comprises a series of n transverse segments each centered in a segmental area of its associated plate, from the sac inlet end of the plate to the sac outlet end, said segmental areas of said plates being determined in accordance with the series relationship:
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5. A dry heat clinical fluid warmer according to claim 4, in which said mounting means mounts said heater plates in vertical alignment, in which each electrical heating element comprises two sections, one above the other, with each heating element section distributed in accordance with said series relationship, and in which said precision thermal control means includes a first main thermostat for control of both of the lower heat element sections and a second main thermostat for control of both of the upper heating element sections.
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6. A dry heat clinical fluid warmer according to claim 3 in which each of said heating elements comprise a series of n transverse segments centered in nsegmental areas of equal size on its associated plate, from the sac inlet end of the plate to the sac outlet end, the power inputs to said heating element segments being determined in accordance with the series relationships W1 4.18 LST1, W2 4.18 LST2,... Wn 4.18 LSTn and T1 To M, T2 (To-T1) M,... Tn (To-T1-...Tn-1) M wherein and where T1...Tn fluid temperature rise in each segment L constant to compensate for low-line voltage and thermal losses W1...Wn power input for each segment all expressed in the c.g.s. system.
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7. A dry heat clinical fluid warmer according to claim 6, in which said mounting means mounts said heater plates in vertical alignment, in which each electrical heating element comprises tow sections, one above the other, with each heating element section distributed in accordance with said series relationships, and in which said precision thermal control means includes a first main thermostat for control of both of the lower heating element sections and a second main thermostat for control of both of the upper heating element sections.
Specification