Heater-scale for heating fluids for injection into a patient
First Claim
1. A heat-scale comprising:
- means for supporting a selected contained volume of fluid to be weighed and heated including a first generally horizontal concave supporting surface for receiving the contained volume of fluid with said heating means affixed to a second, spaced apart, surface thereof and including temperature sensing means extending through said first and second surfaces toward the contained volume so as to be in contact with the contained volume of fluid;
distributed means affixed to a selected surface of said supporting means for evenly heating the volume of fluid in response to an electrical signal applied thereto;
means for sensing the temperature of the contained volume of fluid and for comparing the sensed temperature to a predetermined temperature;
means for switching the electrical signal to said heating means on and off for selected, time intervals which vary nonlinearly with respect to the comparison between the sensed temperature and the predetermined temperature to evenly heat the contained volume of fluid to said predetermined temperature without overshoot and to maintain said volume at the predetermined temperature;
means for comparing an electrical signal corresponding to a sensed initial weight of the contained volume of fluid to a first predetermined threshold and for enabling said switching means provided said sensed initial weight exceeds said first threshold; and
means for continuously monitoring said electrical signal applied to said heating means and for interrupting said switching on of said signal in response to sensing a selected condition.
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Accused Products
Abstract
A heater-scale having a curved supporting member upon which a bag of fluid to be heated can be placed, has a distributed two-dimensional heating element affixed to a lower surface thereof. The curved member is supported by a load cell for generating an electrical signal proportional to the weight of the bag on the heater member, a thermistor is in contact with the fluid whose temperature is to be maintained, a thermistor is affixed to the heater member, and a control system senses the weight and temperature of the bag of fluid as well as the temperature of the heater member for the purpose of nonlinearly adjusting the electrical current supplied to the heater element as fluid is removed from or variable temperature fluid is added to the bag so as to maintain the bag at a predetermined temperature.
88 Citations
15 Claims
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1. A heat-scale comprising:
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means for supporting a selected contained volume of fluid to be weighed and heated including a first generally horizontal concave supporting surface for receiving the contained volume of fluid with said heating means affixed to a second, spaced apart, surface thereof and including temperature sensing means extending through said first and second surfaces toward the contained volume so as to be in contact with the contained volume of fluid; distributed means affixed to a selected surface of said supporting means for evenly heating the volume of fluid in response to an electrical signal applied thereto; means for sensing the temperature of the contained volume of fluid and for comparing the sensed temperature to a predetermined temperature; means for switching the electrical signal to said heating means on and off for selected, time intervals which vary nonlinearly with respect to the comparison between the sensed temperature and the predetermined temperature to evenly heat the contained volume of fluid to said predetermined temperature without overshoot and to maintain said volume at the predetermined temperature; means for comparing an electrical signal corresponding to a sensed initial weight of the contained volume of fluid to a first predetermined threshold and for enabling said switching means provided said sensed initial weight exceeds said first threshold; and means for continuously monitoring said electrical signal applied to said heating means and for interrupting said switching on of said signal in response to sensing a selected condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of controlling heat to be applied to a contained volume of fluid so as to heat the fluid to a predetermined value without temperature overshoot comprising the steps of:
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supporting the contained volume of fluid on a supporting surface; continuously monitoring the temperature of the fluid; comparing a predetermined set-point value to the monitored fluid temperature; forming a first time interval; forming a second time interval, shorter than the first time interval, and non-linearly related to a positive difference between the set-point value and the monitored fluid temperature; and applying heat to the fluid only during the second time interval; sensing the weight of the contained volume of fluid; sampling the temperature of the supporting surface; and providing electrical power to the electrical heater only during the second time interval, provided the sensed fluid weight exceeds a predetermined threshold and the temperature of the supporting surface does not exceed a predetermined value. - View Dependent Claims (14, 15)
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Specification