Fluid delivery apparatus with shape-memory flow control element

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.

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.