Fluid level detector
AssigneeBourns Medical Systems, Inc.
InventorHarold U. Bartels
Life of this patent
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Abstract
Fluid level detection means utilizing a thermally conductive element in the general shape of a cone, in one embodiment, in direct contact with fluid whose level is to be detected. A portion of the element, excluding the apex, is directly heated. A thermal sensor is bonded to the apex. When the fluid depletes such that the apex is exposed to air, the temperature in the immediate vicinity of the apex rises to a new point of equilibrium. The sensor converts this elevated temperature into a signal recognized by electronic circuitry as a flow fluid level. This signal may subsequently be used to provide visual or audible alarm.
Claims9
A device for detecting when the level of fluid in a vessel decreases below a predetermined fluid level, said device comprising:
- a thermally conductive cover element covering at least part of the bottom of the vessel and having a raised portion rising to the predetermined fluid level;
- heating means for directly heating conductively substantially all of said cover element except for said raised portion;
- heat sensitive means, attached to the interior of said cover element in said raised portion for producing an output signal which varies in amplitude as a function of the temperature sensed in said raised portion, said output signal varying around a first level when said raised portion is submerged below the surface of said fluid and varying around a second level when said raised portion is exposed to air;
- and
- a control circuit for (a) regulating the temperature of said fluid below the boiling point thereof by controlling the application of electric power to said heating means as a function of the amplitude of said output signal when said output signal varies around said first level, and (b) producing a warning signal when the output signal is varying around the second level.
A device for detecting a predetermined level of fluid in a vessel, comprising:
- a thermally conductive cover element attached to the bottom of said vessel, and having an interior surface with first and second areas, said cover element having a shape which permits exposure to air of substantially only said second area when said fluid in said vessel is at said predetermined level;
- heat-sensitive means attached to and in thermal communication with said second area, for producing an electrical output signal having an amplitude which varies around a first level in response to the temperature of said second area when said second area is below the surface of said fluid, and around a second level in response to the temperature of said second area when said second area is exposed to air;
- means attached to said first area of said cover element for heating said first area of said cover element;
- and
- a control circuit for (a) regulating the temperature of said fluid below the boiling point thereof by controlling the application of electric power to said heating means as a function of the amplitude of said electrical output signal when said output signal is varying around said first level, and (b) producing a warning signal when said electrical output signal is varying around said second level.
Dependencies are inferred from the claim text.