Fluid delivery apparatus with shape-memory flow control element

• US 4,645,489 A
• Filed: 04/29/1985
• Issued: 02/24/1987
• Est. Priority Date: 11/30/1982
• Status: Expired due to Fees

• Current Assignee: Graseby Medical Limited
• Original Assignee: Molex LLC (KOCH Industries Incorporated)
• Inventors: Krumme, John F., Hodgson, Darel E.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/733,036
• Time in Patent Office: 666 Days
• Field of Search: 251/7-11, 604/34, 604/65-67, 604/250, 604/244
• US Class Current: 604/245
• CPC Class Codes: A61M 39/285 Cam clamps, e.g. roller clamps with eccentric axis
• CPC Class Codes: A61M 5/16813 by controlling the degree of opening of the flow line

Abstract

A unitary disposable conduit extends from the intravenous reservoir along a gravity-flow path to the patient, and incorporates a valve block containing an externally controlled flow-control valve. An electronic controller monitors the drop rate in a drop chamber which is an integral part of the disposable conduit, compares this rate with an operator-selected rate, and controls the valve by varying the current in a shape-memory actuator element whose movements, caused by the resultant Joule heating, are coupled to the valve to proportionally vary the flow rate in the conduit. The valve block is securely received within a recess in the controller, and is automatically coupled to the controller when inserted within this recess. The shape-memory actuator element may be incorporated within the disposable valve block, or may form a part of the controller, with a simple mechanical coupling to transmit its movements to the valve. The valve may be automatically or manually closed when the valve block is removed from the controller, or if power failure occurs.

Claims

1. An intravenous flow controller for use in a gravity-fed intravenous liquid dispensing apparatus designed for intravenous adminstration of nutrients and medicaments at a preselected flow rate from a liquid reservoir at an upstream end thereof, downwardly along a flow path bounded over a portion of its length by a flexible intravenous tube, to a point of exit therefrom, said flow controller comprising:

flow-rate monitor and control means for monitoring the flow rate along said flow path and for producing in response to said flow rate an electrical valve control signal directly related to the difference between said flow rate and said preselected flow rate;

valve means disposed along said flow path and connected to respond to said electrical valve control signal by varying said flow rate in response thereto in direct relation to the magnitude of said valve control signal, said valve means comprising;

means for biasing said valve means to a closed position to prevent flow of liquid through the flexible intravenous tube,

a shape-memory valve actuator element connected to actuate said valve means and made of a material which has the intrinsic property of shape memory and transits between two different crystalline phases whenever its temperature passes through a certain region of transition temperatures, said actuator element having a first physical shape defined by a first set of dimensions at temperatures above said transition temperature and a second physical shape defined by a second set of dimensions at temperatures below said transition temperature, and transiting through a region of shapes intermediate said first and second shapes as its temperature passes through said region of transition temperatures, and causing flow rate along said flow path to vary in response to said transiting through said region of transition temperatures;

means to cause heating of said actuator element to change its temperature in direct relation to the magnitude of said valve control signal, whereby changes in physical shape of said actuator and, hence, flow rate are caused by changes in said valve control signal;

said shape memory valve actuator overcoming said biasing means and causing opening of said valve means to permit flow of fluid only upon heating of said actuator above a prescribed minimum temperature.

3. The apparatus of claim 1 or 2 wherein said electrically operated valve means comprises occluding means coupled to said actuator element movement to compressively occlude said flexible tube over a certain region thereof in direct relation to the relative movement of said one portion of said actuator element to thereby control flow rate through said tube.

4. The apparatus of claim 3 wherein said actuator element is operatively connected to said occluding means to cause full occlusion of said tube when said actuator element is in one of its said phases, and to progressively withdraw said occluding means from full occlusion of said tube as said actuator element transits to the other of its said phases.

5. The apparatus of claim 1 or 2 wherein said means to cause heating in direct relation to the magnitude of said valve control signal includes means to cause an electric current to flow in said actuator element in direct relation to the magnitude of said valve control signal, to thereby cause Joule heating of said actuator element in direct relation to said valve control signal.

6. The apparatus of claim 1 or 2 wherein said electrically operated valve means comprises bias means connected to said actuator element to exert a force on said one portion thereof along the direction of relative movement of said one portion.

7. The apparatus of claim 6 wherein said force exerted by said bias means is in a direction to aid said relative movement when the temperature of said actuator element transits from above said transition temperature to below said transition temperature.

8. The apparatus of claim 1 or 2 wherein said shape-memory actuator element includes a shape-memory extensor element having a greater length at temperatures below a certain transition temperature range, and a lesser length at temperatures above said transition temperature range, and wherein said electrically operated valve means includes occluding means coupled to said extensor element to cause occlusion of said flexible tube in direct relation to the legnth of said extensor element, to fully occlude said tube at temperatures below said transition temperature range, and to progressively reduce the occlusion of said tube at temperatures above said transition temperature range.

9. The flow-regulating conduit of claim 8 wherein said occluding means comprises a spring-biased occluding element connnected to said extensor element, said spring-biased element being biased in a direction to occlude said tube, and being withdrawn from said occlusion upon transition of said extensor element from said greater to said lesser length.

2. A disposable flow-regulating conduit for use in a gravity-fed intravenous liquid dispensing apparatus designed for intravenous adminstration of nutrients and medicaments at a preselected flow rate from a liquid reservoir at an upstream end thereof, downwardly along a flow path bounded over a portion of its length by a flexible intravenous tube, to a point of exit therefrom, said apparatus including flow-rate monitoring and control means to monitor the flow of liquid downwardly along said flow path and to produce in response to the monitored flow rate an electrical control signal directly related to the difference between the monitored flow rate and the preselected flow rate, said flow-regulating conduit comprising;

a flexible tube of a length for extending generally from said reservoir to said point of exit;

reservoir attachment means at an upstream end of said conduit for attachment to said reservoir and for communicating fluid downstream therefrom through said flexible tube;

electrically operated valve means disposed along said flow path and electrically connected to response to said electrical control signal by varying said flow rate in response thereto in direct relation to the magnitude of said control signal, said electrically operated valve means comprising;

a valve having means for occluding said flexible tube to prevent liquid flow therethrough,

said valve having means to bias said valve to occlude said flexible tube,

a shape-memory valve actuator element connected to operate said means for occluding and made of a material which has the intrinsic property of shape memory and transits between two different crystalline phases whenever its temperature passes through a certain region of transition temperatues, said actuator element having a first physical shape defined by a first set of dimensions at temperatures above said transition temperature and a second physical shape defined by a second set of dimensions at temperatures below said transition temperature, and transiting through a region of shapes intermediate said first and second shapes as its temperature passes through said region of transition temperatures, and causing flow rate along said flow path to vary in response to said transiting through said region of transition temperatures;

means to cause heating of said actuator element to change its temperature in direct relation to the magnitude of said electrical control signal;

said shape-memory valve actuator opposing the force of said means to bias from its second physical shape to its first physical state.

10. A flow rate controller for use in gravity-fed liquid dispensing apparatus, comprising:

means defining a gravity feed flow path between a reservoir and a point of utilization of liquid;

a valve having a member movable between a first position locking flow of a liquid along said flow path and a second position permitting generally uninhibited flow of a fluid along said flow path;

means exerting a force for biasing said member to said first position; and

a shape-memory element of a material having the intrinsic property of shape-memory and which transits between two different shape defining a first shape at a first temperature and a second shape at a second temperature and transiting through all intermediate shapes over the temperature range between between said first and second temperatures, said shape-memory element overcoming said force of said biasing means upon transiting from the lower to the higher of said first and second temperatures.

11. A flow rate controller as in claim 10 wherein said means exerting a force comprises a spring member exerting a force on said movable member to close said flow path and wherein said shape-memory element comprises a thin wire connected between said movable member and a relatively fixed location.

12. A flow rate controller as in claim 11 wherein said spring member comprises a cantilevered spring having one end secured against movement and another end free to move, said movable member located adjacent said free end and said thin wire connected to said cantilevered spring adjacent to said free end.

13. A flow rate controller as in claim 12 further including means for applying a force to said cantilevered spring intermediate said secured and free ends of said cantilevered spring.