Drop rate sensing and regulating apparatus
First Claim
1. An apparatus for sensing and regulating the rate at which liquid drops fall along a predetermined vertical path, said apparatus comprising:
- A. an enclosure which defines a vertical drop path and which is formed with an indentation having a wall portion that projects directly into the drop path to be impinged by drops falling therealong;
B. a probe removably mounted on the exterior of said enclosure in said enclosure indentation and including an electrically conductive element located to contact the exterior surface of said indentation wall portion which is directly in the drop path, the conductivity of said element being significantly variable with its temperature, said indentation wall portion being of such thinness in the vicinity of said conductive element as not significantly to isolate said element from thermal gradients created by drops falling successively on said wall portion; and
C. means electrically connected to said conductive element for regulating the rate at which drops fall along the drop path in response to changes in conductivity of said element caused by thermal gradients created by drops falling on said indentation wall portion.
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Accused Products
Abstract
An apparatus, for example, an intravenous drop-feed apparatus for sensing the rate at which liquid drops fall along a predetermined vertical path and for regulating this drop rate to be substantially equal to a preselected drop rate includes a disposable drip chamber which defines a vertical drop path. The drip chamber is formed with an indentation having an upper wall that projects into the drop path to be impinged by drops falling on its interior surface. A probe is removably mounted on the outside of the chamber in interfitting engagement with the chamber indentation and includes an electrically conductive element located to contact the exterior surface of the upper indentation wall. The element, which is electrically but not thermally isolated from falling drops, exhibits conductivity that varies significantly with its temperature and, accordingly, generates pulses at a rate that corresponds to the periodic rate of the falling drops. These pulses are compared with the preselected rate, which may be adjustable, and any detected difference is used to regulate liquid back pressure in the chamber to, in turn, regulate the drop rate. A clamping assembly, which reduces the flow area of a tube which conducts liquid from the drip chamber, is controlled by a heat sensitive bimetallic element to regulate this back pressure.
33 Citations
21 Claims
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1. An apparatus for sensing and regulating the rate at which liquid drops fall along a predetermined vertical path, said apparatus comprising:
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A. an enclosure which defines a vertical drop path and which is formed with an indentation having a wall portion that projects directly into the drop path to be impinged by drops falling therealong; B. a probe removably mounted on the exterior of said enclosure in said enclosure indentation and including an electrically conductive element located to contact the exterior surface of said indentation wall portion which is directly in the drop path, the conductivity of said element being significantly variable with its temperature, said indentation wall portion being of such thinness in the vicinity of said conductive element as not significantly to isolate said element from thermal gradients created by drops falling successively on said wall portion; and C. means electrically connected to said conductive element for regulating the rate at which drops fall along the drop path in response to changes in conductivity of said element caused by thermal gradients created by drops falling on said indentation wall portion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for sensing the rate at which liquid drops fall along a predetermined vertical path and for regulating the drop rate to be substantially equal to a preselected drop rate, said apparatus comprising:
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A. an enclosure which defines a vertical drop path; B. an electrically conductive element associated with said enclosure and positioned directly in the drop path, the conductivity of said element being significantly variable with its temperature; C. means for insulating said conductive element and electrically isolating it from falling drops, without significantly isolating said element from thermal gradients created by drops falling on it, said conductive element thereby being thermally coupled to the falling drops to sense the drop rate; D. a flexible, pliable tube connected to the bottom of said enclosure for conducting liquid therefrom; and E. means for regulating liquid back pressure in said tube and said enclosure to thereby regulate the rate at which drops fall along the drop path, said regulating means comprising; - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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11. fixed support means for holding said tube;
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2. clamp means mounted for movement toward said support means to compress said tube, reduce its cross-sectional area and, the liquid flow therethrough; 3. means, for moving said clamp means toward said support means, comprising; a. a bimetallic strip which flexes to a degree related to the heat applied to it, said strip being operatively associated with said clamp means, and b. means for applying heat to said bemetallic strip; and 4. monitor means for comparing the drop rate sensed by said conductive element with the preselected drop rate and for controlling said heat applying means and, hence, said bimetallic strip to regulate back pressure to said enclosure until the sensed drop rate is substantially equal to the preselected drop rate.
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Specification