Plunger assembly for patient infusion device

Field of the Invention

0001The present invention relates generally to medical devices and systems, and more particularly to small, low cost, portable infusion devices that are useable to achieve precise, sophisticated, and programmable flow patterns for the delivery of therapeutic liquids such as insulin to a mammalian patient. Even more particularly, the present invention is directed to a spring-driven plunger assembly for a fluid delivery device, that can utilize shape memory elements.

Background of the Invention

0002Today, there are numerous diseases and other physical ailments that are treated by various medicines including pharmaceuticals, nutritional formulas, biologically derived or active agents, hormonal and gene based material and other substances in both solid or liquid form. In the delivery of these medicines, it is often desirable to bypass the digestive system of a mammalian patient to avoid degradation of the active ingredients caused by the catalytic enzymes in the digestive tract and liver. Delivery of a medicine other than by way of the intestines is known as parenteral delivery. Parenteral delivery of various drugs in liquid form is often desired to enhance the effect of the substance being delivered, insuring that the unaltered medicine reaches its intended site at a significant concentration. Also, undesired side effects associated with other routes of delivery, such as systemic toxicity, can potentially be avoided.

0003Often, a medicine may only be available in a liquid form, or the liquid version may have desirable characteristics that cannot be achieved with solid or pill form. Delivery of liquid medicines may best be accomplished by infusing directly into the cardiovascular system via veins or arteries, into the subcutaneous tissue or directly into organs, tumors, cavities, bones or other site specific locations within the body.

0004Parenteral delivery of liquid medicines into the body is often accomplished by administering bolus injections using a needle and reservoir, or continuously by gravity driven dispensers or transdermal patch technologies. Bolus injections often imperfectly match the clinical needs of the patient, and usually require larger individual doses than are desired at the specific time they are given. Continuous delivery of medicine through gravity feed systems compromise the patient's mobility and lifestyle, and limit the therapy to simplistic flow rates and profiles. Transdermal patches have special requirements of the medicine being delivered, particularly as it relates to the molecular structure, and similar to gravity feed systems, the control of the drug administration is severely limited.

0005Ambulatory infusion pumps have been developed for delivering liquid medicaments to a patient. These infusion devices have the ability to offer sophisticated fluid delivery profiles accomplishing bolus requirements, continuous infusion and variable flow rate delivery. These infusion capabilities usually result in better efficacy of the drug and therapy and less toxicity to the patient's system. An example of a use of an ambulatory infusion pump is for the delivery of insulin for the treatment of diabetes mellitus. These pumps can deliver insulin on a continuous basal basis as well as a bolus basis as is disclosed in <patcit id="pcit0001" dnum="US4498843A"><text>U.S. Patent 4,498,843 to Schneider et al.</text></patcit>

0006The ambulatory pumps often work with a reservoir to contain the liquid medicine, such as a cartridge, a syringe or an IV bag, and use electro-mechanical pumping or metering technology to deliver the medication to the patient via tubing from the infusion device to a needle that is inserted transcutaneously, or through the skin of the patient. The devices allow control and programming via electromechanical buttons or switches located on the housing of the device, and accessed by the patient or clinician. The devices include visual feedback via text or graphic screens, such as liquid crystal displays known as LCD's, and may include alert or warning lights and audio or vibration signals and alarms. The device can be worn in a harness or pocket or strapped to the body of the patient.

0007Currently available ambulatory infusion devices are expensive, difficult to program and prepare for infusion, and tend to be bulky, heavy and very fragile. Filling these devices can be difficult and require the patient to carry both the intended medication as well as filling accessories. The devices require specialized care, maintenance, and cleaning to assure proper functionality and safety for their intended long term use. Due to the high cost of existing devices, healthcare providers limit the patient populations approved to use the devices and therapies for which the devices can be used.

0008Clearly, therefore, there was a need for a programmable and adjustable infusion system that is precise and reliable and can offer clinicians and patients a small, low cost, light-weight, easy-to-use alternative for parenteral delivery of liquid medicines.

0009In response, the applicant of the present application provided a small, low cost, light-weight, easy-to-use device for delivering liquid medicines to a patient. The device, which is described in detail in co-pending <patcit id="pcit0002" dnum="US94399201A" dnum-type="L"><text>U. S. application serial No. 09/943,992, filed on August 31,2001</text></patcit>, includes an exit port, a dispenser for causing fluid from a reservoir to flow to the exit port, a local processor programmed to cause a flow of fluid to the exit port based on flow instructions from a separate, remote control device, and a wireless receiver connected to the local processor for receiving the flow instructions. To reduce the size, complexity and costs of the device, the device is provided with a housing that is free of user input components, such as a keypad, for providing flow instructions to the local processor.

0010What are still desired are new and improved components, such as plunger assemblies and reservoirs, for a device for delivering fluid to a patient. Preferably, the components will be simple in design, and relatively compact, lightweight, easy to manufacture and inexpensive, such that the resulting fluid delivery device can be effective, yet inexpensive and disposable. <patcit id="pcit0003" dnum="US5222362A"><text>US-A-5 222 362</text></patcit> discloses a heat-activated fluid delivery system using thermal actuators in which energy is derived from the physical expansion of paraffin wax as it changes state from solid to liquid when heated.

Summary of the Invention

0011The present invention provides a device for delivering fluid, such as insulin for example, to a patient. The subject-matter of the invention in defined by claim 1. In addition, further advantageous embodiment follow from the dependent claims.

0012The invention together with additional features and advantages thereof may best be understood by reference to the following detailed descriptions and examples taken in connection with the accompanying illustrated drawings.

Brief Description of the Drawings

0013<figref idref="f0001">Fig. 1</figref> is a perspective view of a first exemplary embodiment of a fluid delivery device constructed in accordance with the present invention and shown secured on a patient, and a remote control device for use with the fluid delivery device (the remote control device being enlarged with respect to the patient and the fluid delivery device for purposes of illustration);

0014<figref idref="f0001">Fig. 2</figref> is a sectional side view of the fluid delivery device of <figref idref="f0001">Fig. 1</figref> showing an exemplary embodiment of a plunger assembly constructed in accordance with the present invention for causing fluid to be dispensed from the device;

0015<figref idref="f0002 f0003 f0004">Figs. 3a-3f</figref> are enlarged sectional side views illustrating operation of the plunger assembly of <figref idref="f0001">Fig. 2</figref>;

0016<figref idref="f0005">Fig. 4</figref> is a sectional side view of another exemplary embodiment of a reservoir and a plunger assembly constructed in accordance with the present invention for use with the fluid delivery device of <figref idref="f0001">Fig. 1</figref>;

0017<figref idref="f0005">Fig. 5</figref> is a top plan view of a longitudinal reference guide attached to the reservoir of <figref idref="f0005">Fig. 4</figref>;

0018<figref idref="f0006">Fig. 6</figref> is an enlarged sectional side view of the plunger assembly of <figref idref="f0005">Fig. 4</figref>;

0019<figref idref="f0006 f0007 f0008">Figs. 7a-7e</figref> are enlarged sectional side views illustrating operation of another exemplary embodiment of a plunger assembly constructed in accordance with the present invention for use with the fluid delivery device of <figref idref="f0001">Fig. 1</figref>;

0020<figref idref="f0009 f0010">Figs. 8a-8c</figref> are enlarged sectional side views illustrating operation of an exemplary plunger assembly not forming part of present invention for use with the fluid delivery device of <figref idref="f0001">Fig. 1</figref>; and

0021<figref idref="f0010">Fig. 9</figref> is a sectional side view of a fluid delivery device similar to the fluid delivery device of <figref idref="f0001">Fig. 2</figref> showing another exemplary embodiment of a reservoir and a plunger assembly constructed in accordance with the present invention for causing fluid to be dispensed from the device.

0022Like reference characters designate identical or corresponding components and units throughout the several views.

Detailed Description of Exemplary Embodiments

0023Referring first to <figref idref="f0001">Fig. 2</figref>, there is illustrated an exemplary embodiment of a fluid delivery device 10 including a dispenser in the form of a plunger assembly 40 constructed in accordance with the present invention. The plunger assembly 40 causes fluid flow from a reservoir 30 to an exit port assembly 70 during operation of the device 10. In general, the plunger assembly 40 is spring-driven and can use shape memory elements in accordance with the present invention to provide effective, yet simple and inexpensive fluid dispensing for fluid delivery devices.

0024The fluid delivery device 10 of <figref idref="f0001">Fig. 2</figref> can be used for the delivery of fluids to a person or animal. The types of liquids that can be delivered by the fluid delivery device 10 include, but are not limited to, insulin, antibiotics, nutritional fluids, total parenteral nutrition or TPN, analgesics, morphine, hormones or hormonal drugs, gene therapy drugs, anticoagulants, analgesics, cardiovascular medications, AZT or chemotherapeutics. The types of medical conditions that the fluid delivery device 10 might be used to treat include, but are not limited to, diabetes, cardiovascular disease, pain, chronic pain, cancer, AIDS, neurological diseases, Alzheimer's Disease, ALS, Hepatitis, Parkinson's Disease or spasticity. In addition, it should be understood that the plunger assembly 40 according to the present invention can be used with fluid delivery devices other than those used for the delivery of fluids to persons or animals.

0025The fluid delivery device 10 also includes a processor or electronic microcontroller (hereinafter referred to as the "local" processor) 50 connected to the plunger assembly 40. The local processor 50 is programmed to cause a flow of fluid to the exit port assembly 70 based on flow instructions from a separate, remote control device 100, an example of which is shown in <figref idref="f0001">Fig. 1</figref>. Referring also to <figref idref="f0001">Fig. 2</figref>, the fluid delivery device 10 further includes a wireless receiver 60 connected to the local processor 50 for receiving the flow instructions from the separate, remote control device 100 and delivering the flow instructions to the local processor. The device 10 also includes a housing 20 containing the exit port assembly 70, the reservoir 30, the plunger assembly 40, the local processor 50 and the wireless receiver 60.

0026As shown, the housing 20 of the fluid delivery device 10 is free of user input components for providing flow instructions to the local processor 50, such as electromechanical switches or buttons on an outer surface 21 of the housing, or interfaces otherwise accessible to a user to adjust the programmed flow rate through the local processor 50. The lack of user input components allows the size, complexity and costs of the device 10 to be substantially reduced so that the device 10 lends itself to being small and disposable in nature. Examples of such devices are disclosed in co-pending <patcit id="pcit0004" dnum="US94399201A" dnum-type="L"><text>U.S. patent application serial number 09/943,992, filed on August 31, 2001</text></patcit> (Atty. Docket No. INSL-110), and entitled DEVICES, SYSTEMS AND METHODS FOR PATIENT INFUSION, which is assigned to the assignee of the present application.

0027In order to program, adjust the programming of, or otherwise communicate user inputs to the local processor 50, the fluid delivery device 10 includes the wireless communication element, or receiver 60 for receiving the user inputs from the separate, remote control device 100 of <figref idref="f0001">Fig. 1</figref>. Signals can be sent via a communication element (not shown) of the remote control device 100, which can include or be connected to an antenna 130, shown in <figref idref="f0001">Fig. 1</figref> as being external to the device 100.

0028The remote control device 100 has user input components, including an array of electromechanical switches, such as the membrane keypad 120 shown. The control device 100 also includes user output components, including a visual display, such as a liquid crystal display (LCD) 110. Alternatively, the control device can be provided with a touch screen for both user input and output. Although not shown in <figref idref="f0001">Fig. 1</figref>, the remote control device 100 has its own processor (hereinafter referred to as the "remote" processor) connected to the membrane keypad 120 and the LCD 110. The remote processor receives the user inputs from the membrane keypad 120 and provides "flow" instructions for transmission to the fluid delivery device 10, and provides information to the LCD 110. Since the remote control device 100 also includes a visual display 110, the fluid delivery device 10 can be void of an information screen, further reducing the size, complexity and costs of the device 10.

0029The communication element 60 of the device 10 preferably receives electronic communication from the remote control device 100 using radio frequency or other wireless communication standards and protocols. In a preferred embodiment, the communication element 60 is a two-way communication element, including a receiver and a transmitter, for allowing the fluid delivery device 10 to send information back to the remote control device 100. In such an embodiment, the remote control device 100 also includes an integral communication element comprising a receiver and a transmitter, for allowing the remote control device 100 to receive the information sent by the fluid delivery device 10.

0030The local processor 50 of the device 10 contains all the computer programs and electronic circuitry needed to allow a user to program the desired flow patterns and adjust the program as necessary. Such circuitry can include one or more microprocessors, digital and analog integrated circuits, resistors, capacitors, transistors and other semiconductors and other electronic components known to those skilled in the art. The local processor 50 also includes programming, electronic circuitry and memory to properly activate the plunger assembly 40 at the needed time intervals.

0031In the exemplary embodiment of <figref idref="f0001">Fig. 2</figref>, the device 10 includes a power supply 80, such as a battery or capacitor, for supplying power to the local processor 50. The power supply 80 is preferably integrated into the fluid delivery device 10, but can be provided as replaceable, e.g., a replaceable battery.

0032Although not shown, the device 10 can include sensors or transducers such as a reservoir volume transducer or a reservoir pressure transducer, for transmitting information to the local processor 50 to indicate how and when to activate the plunger assembly 40, or to indicate other parameters determining flow, pump flow path prime condition, blockage in flow path, contact sensors, rotary motion or other motion indicators, as well as conditions such as the reservoir 30 being empty or leaking, or the dispensing of too much or too little fluid from the reservoir, etc.

0033The volume of the reservoir 30 is chosen to best suit the therapeutic application of the fluid delivery device 10 impacted by such factors as available concentrations of medicinal fluids to be delivered, acceptable times between refills or disposal of the fluid delivery device 10, size constraints and other factors. The reservoir 30 may be prefilled by the device manufacturer or a cooperating drug manufacturer, or may include external filling means, such as a fill port 90 having a needle insertion septum 92 as shown in <figref idref="f0001">Fig. 2</figref>, for example. In addition, or alternatively, the device 10 can be provided with a removable and replaceable reservoir.

0034Although not shown, the exit port assembly 70 can include elements to penetrate the skin of the patient, such that the entire volume of the flow path of the fluid delivery device 10 is predetermined. For example, a needle-connection tubing terminating in a skin penetrating cannula (not shown) can be provided as an integral part of the exit port assembly 70, with the skin penetrating cannula comprising a rigid member, such as a needle. The exit port assembly 70 can further be provided with injection means, such as a spring driven mechanism, to assist in penetrating the skin with the skin penetrating cannula. For example, if the cannula is a flexible tube, a rigid penetrator within the lumen of the tube can be driven through the skin by the injection means and then withdrawn, leaving the soft cannula in place in the subcutaneous tissue of the patient or other internal site. The injection means may be integral to the device 10, or removable soon after transcutaneous penetration.

0035Alternatively, the exit port assembly 70 can be adapted to connect, with a Luer connector for example, to a separate, standard infusion device that includes a skin penetrating cannula. In any event, the exit port assembly 70 can also be provided with a removable plug (not shown) for preventing leakage during storage and shipment if prefilled, and during priming if filled by user, and prior to use. It should be understood that, as used herein, the term "flow path" is meant to include all portions of the fluid delivery device 10 that contain therapeutic fluid for delivery to a patient, e.g., all portions between the fill port of the reservoir to the tip of the needle of the exit port assembly.

0036Although not shown, the device 10 can also be provided with an adhesive layer on the outer surface of the housing 20 for securing the device 10 directly to the skin of a patient. The adhesive layer is preferably provided in a continuous ring encircling the exit port assembly 70 in order to provide a protective seal around the penetrated skin. The housing 20 can be made from flexible material, or can be provided with flexible hinged sections that allow the fluid delivery device 10 to flex during patient movement to prevent detachment and aid in patient comfort.

0037Referring to <figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3a-3f</figref>, the present disclosure provides the plunger assembly 40 and the reservoir 30 for use with the fluid delivery device 10 of <figref idref="f0001">Figs. 1 and 2</figref>. The plunger assembly 40 is small and simple in design, and inexpensive and easy to manufacture, in order to further reduce the size, complexity and costs of the fluid delivery device 10, such that the device 10 continues to lend itself to being small and disposable in nature. In general, the device 10 is provided with a non-pressurized, syringe-like reservoir 30, and the plunger assembly 40 operates to cause flow from the reservoir 40 to the exit port assembly 70. The plunger assembly 40 is controlled by the local processor 50, which includes electronic programming, controls, and circuitry to allow sophisticated fluid delivery programming and control of the plunger assembly 40.

0038Referring to <figref idref="f0001">Fig. 2</figref>, the syringe-like reservoir 30 is provided with a side wall 32 extending along a longitudinal axis 33 between an open end and an end wall 34 of the reservoir. The end wall 34 includes an outlet, or an opening 36 that functions as an outlet and an inlet, connected through a first lumen 72 to the exit port assembly 70 and connected through a second lumen 94 to the fill port 90. The plunger assembly 40 is received in the reservoir 30 and is shaped and sized such that a fluid-tight seal is generally formed between at least a portion of the plunger assembly 40 and the side wall 32 of the reservoir so that movement of the plunger assembly 40 towards the end wall 34 of the reservoir 30 forces fluid through the outlet 36 to the exit port assembly 70.

0039The plunger assembly 40 is prevented from rotating with respect to the side wall 32. For example, the reservoir 30 and the plunger assembly 40 are provided with matching non-circular cross-sections, such as oval cross-sections. Alternatively, the plunger assembly 40 can be provided with at least one longitudinal channel and the side wall 32 of the reservoir 30 can be provided with at least one protrusion extending longitudinally along its length and received within the channel of the plunger assembly (or vice versa) to prevent rotation of the plunger assembly. In addition, the reservoir 30 and the plunger assembly 40 can alternatively be provided with other matching non-circular cross-sections, such as oval, square or rectangular, along at least a portion of their length to prevent rotation of the plunger assembly 40 with respect to the side wall 32, without the use of a protrusion and a channel. Such non-circular cross-sections can also include simply providing the side wall 32 and the plunger assembly 40 with mating flat portions in otherwise circular cross-sections. The side wall 32 and the end wall 34 of the reservoir are preferably made from a rigid material such as a suitable metal (e.g., stainless steel) or plastic. The plunger assembly 40, however, does not need to be prevented from rotating with respect to the side wall 32.

0040The plunger assembly 40 includes a first lateral segment 200 extending laterally with respect to the longitudinal axis 33 of the reservoir 30 and contacting the side wall 32 of the reservoir, and a second lateral segment 220 extending laterally with respect to the longitudinal axis 33 of the reservoir 30 and contacting the side wall 32 of the reservoir. The second lateral segment 220 is positioned between the first lateral segment 200 and the outlet 36 of the reservoir 30 and is longitudinally spaced from the first lateral segment 200. The plunger assembly 40 also includes a longitudinal segment 240 extending substantially parallel with respect to the longitudinal axis 33 of the reservoir and connecting the first and the second lateral segments 200, 220.

0041The longitudinal segment 240 includes a spring 242 biasing the first and the second lateral segments 200, 220 longitudinally apart, and an actuator 244 arranged to overcome the spring and bias the first and the second lateral segments 200, 220 longitudinally together upon actuation. In the exemplary embodiment shown, the spring comprises a helical (or coil) compression spring 242 that is made of a suitable material such as stainless steel or a plastic. The spring 242, however, can be provided in other forms for biasing the first and the second lateral segments 200, 220 longitudinally apart, such as buckling columns, spring washers, or Bellville spring washers for example.

0042In the exemplary embodiment of the plunger assembly 40 of the present invention as shown in <figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3a-3f</figref> the actuator is provided as a shape memory element 244 made of a shape memory material. Alternatively, the actuator can be provided in the form of a solenoid, a piezoelectric element, or another actuator capable of bringing the first and the second lateral segments 200, 220 together against the force of the spring 242 upon being actuated.

0043The application of an electrical current to the shape memory element 244 heats the material and results in molecular and crystalline restructuring of the shape memory material. If the shape memory material is in the shape of an elongated wire, for example, as the shape memory element 244 preferably is, this restructuring causes a decrease in length. Nitinol, a well-known alloy of nickel and titanium, is an example of such a so-called shape memory material and is preferred for use as the shape memory element 244.

0044In general, when the shape memory element 244 is in its martensitic form (i.e., low temperature state), it is easily deformed to an elongated shape by the spring. However, when the alloy is heated through its transformation temperatures, the shape memory element 244 reverts to its austenite form (ie., high temperature state) and recovers its shorter, original shape with great force. The temperature (or the level of electrical charge) at which the alloy remembers its high temperature form can be adjusted by slight changes in alloy composition and through heat treatment. In the nickel-titanium alloys, for instance, austenite temperature can be changed from above 100° C to below 100° C. The shape recovery process occurs over a range of just a few degrees and the start or finish of the transformation can be controlled to within a degree or two if necessary.

0045These unique alloys also show a superelastic behavior if deformed at a temperature which is slightly above their transformation temperatures. This effect is caused by the stress-induced formation of some martensite above its normal temperature. Because it has been formed above its normal temperature, the martensite reverts immediately to undeformed austenite as soon as the stress is removed. This process provides a very springy, "rubberlike" elasticity in these alloys. A one-way SME alloy can be deformed, then recover to retain permanently its original shape when heated to a certain temperature. A two-way alloy, however, holds its original shape at one temperature and takes on another shape at a different temperature. Two-way memory is unique in that the material "remembers" different high temperature and low temperature shapes.

0046The shape memory element 244 of the embodiment of the present invention comprises a one-way shape memory alloy. However, it should be understood that the shape memory element 244 of the longitudinal segment 240 can be provided as a two-way shape memory alloy if desired. As shown <figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3a-3f</figref>, the shape memory element 244 is secured between the first and the second lateral segments 200, 220 of the plunger assembly 40. As shown in <figref idref="f0001">Fig. 2</figref>, the fluid delivery device 10 includes wires 246 connecting opposite ends of the shape memory element 244 to the processor 50, such that the processor can apply electrical charges to the shape memory element 244 for controlling the longitudinal segment 240.

0047When a charge is applied to the elongated shape memory element 244 through the wires 246, the length of the shape memory element 244 decreases from an uncharged length to a charged length. The shape memory element 244 is arranged such that the changeable length of the shape memory element 244 decreasing from an uncharged length to a charged length causes the first and the second lateral segments 200, 220 to be drawn together against the force of the spring 242, as shown in <figref idref="f0003">Figs. 3c, 3d</figref> and <figref idref="f0004">3e</figref>. When the charge is removed from the elongated shape memory element 244, the spring 242 is allowed to bias the first and the second lateral segments 200, 220 apart and increase the length of the shape memory element 244 from the charged length to the uncharged length, as shown in <figref idref="f0004">Figs. 3f</figref>, <figref idref="f0002">3a and 3b</figref>.

0048The longitudinal segment 240 of the plunger assembly 40 also includes a rigid, longitudinally extending projection 248 that limits the smallest longitudinal distance that can be attained between the first and the second lateral segments 200, 220 upon actuation of the shape memory element 244 (i.e., when the first and the second lateral segments 200, 220 are pulled together by the charged shape memory element 244). The differences in lengths between the fully elongated and uncharged shape memory element 244 and the longitudinally extending projection 248 defines the distance traveled by the plunger assembly 40 during a cycle of charges, as described in greater detail below.

0049In the embodiment of <figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3a-3f</figref>, the first lateral segment 200 includes two blocks 208 laterally movable with respect to the longitudinal axis 33 of the reservoir 30, and a spring 202 biasing the two blocks 208 apart and laterally outwardly to frictionally engage the side wall 32 of the reservoir 30 and prevent longitudinal movement of the first lateral segment 200 within the reservoir 30. In the exemplary embodiment shown, the spring comprises a helical compression spring 202 but can be provided in other suitable forms for biasing the blocks 208 laterally apart. The blocks can be of various shapes including cylindrical pins, rectangular pins, wedge portions, partial rings, etc., and can be made from various rigid or semi-rigid materials. In any event, the frictional forces created between the blocks 208 and the side wall 32 must be greater than the force generated by the actuator 244 of the longitudinal segment 240.

0050The first lateral segment 200 also includes an actuator 204 arranged to overcome the spring 202 and bias the blocks 208 together laterally upon actuation. When biased together by the actuator 204, the blocks 208 disengage from the side wall 32 of the reservoir 30 to allow longitudinal movement of the first lateral segment 200 within the reservoir 30. The actuator of the first lateral segment 200 is provided as a shape memory element 204 made of a shape memory material. Alternatively, the actuator can be provided in the form of a solenoid, a piezoelectric element, or another actuator capable of bringing the blocks 208 together against the force of the spring 202 upon being actuated. The shape memory element 204 of the first lateral segment 200 comprises a one-way shape memory alloy. However, the shape memory element 204 can be provided as a two-way shape memory alloy. As shown <figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3a-3f</figref>, the elongated shape memory element 204 is secured at opposing ends between the two blocks 208 and is anchored to the first lateral segment 200 at a midpoint between the two blocks 208. As shown in <figref idref="f0001">Fig. 2</figref>, the fluid delivery device 10 includes wires 206 connecting the opposite ends of the shape memory element 204 to the processor 50 such that the processor can apply an electrical charge to the element 204.

0051When a charge is applied to the elongated shape memory element 204 of the first lateral segment 200, the length of the shape memory element 204 decreases from an uncharged length to a charged length. The shape memory element 204 of the first lateral segment 200 is arranged such that the changeable length of the shape memory element 204 decreasing from an uncharged length to a charged length causes the two blocks 208 to be drawn together against the force of the spring 202, as shown in <figref idref="f0002">Figs. 3b</figref> and <figref idref="f0003">3c</figref>. When the charge is removed from the elongated shape memory element 204, the spring 202 is allowed to bias the two blocks 208 apart and increase the length of the shape memory element 204 from the charged length to the uncharged length, as shown in <figref idref="f0002">Figs. 3a</figref> and <figref idref="f0002 f0003 f0004">3d-3f</figref>.

0052In the embodiment of <figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3a-3f</figref>, the second lateral segment 220 also includes two blocks 228 laterally movable with respect to the longitudinal axis 33 of the reservoir 30, and a spring 222 biasing the two blocks 228 apart and laterally outwardly to frictionally engage the side wall 32 of the reservoir 30 and prevent longitudinal movement of the second lateral segment 220 within the reservoir 30. In the exemplary embodiment shown, the spring comprises a helical compression spring 222 but can be provided in other suitable forms for biasing the blocks 228 laterally apart.

0053The second lateral segment 220 also includes an actuator 224 arranged to overcome the spring 222 and bias the blocks 228 together laterally upon actuation. When biased together by the actuator 224, the blocks 228 disengage from the side wall 32 of the reservoir 30 to allow longitudinal movement of the second lateral segment 220 within the reservoir 30. The actuator of the second lateral segment 220 is provided as a shape memory element 224 made of a shape memory material. Alternatively, the actuator 224 can be provided in the form of a solenoid, a piezoelectric element, or another type of actuator capable of bringing the blocks 228 together against the force of the spring 222 upon being actuated. The shape memory element 224 of the second lateral segment 220 comprises a one-way shape memory alloy. However, the shape memory element 224 can be provided as a two-way shape memory alloy. As shown <figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3a-3f</figref>, the elongated shape memory element 224 is secured at opposing ends between the two blocks 228 and anchored to the second lateral segment 220 at a midpoint between the two blocks 228. As shown in <figref idref="f0001">Fig. 2</figref>, the fluid delivery device 10 includes wires 226 connecting the opposite ends of the shape memory element 224 to the processor 50 such that the processor can apply an electrical charge to the element 224.

0054When a charge is applied to the elongated shape memory element 224, the length of the shape memory element 224 decreases from an uncharged length to a charged length. The shape memory element 224 of the second lateral segment 220 is arranged such that the changeable length of the shape memory element 224 decreasing from an uncharged length to a charged length causes the two blocks 228 to be drawn together against the force of the spring 222, as shown in <figref idref="f0004">Figs. 3e and 3f</figref>. The plunger assembly is adapted such that the fluid-tight seal between the second lateral segment 220 and the side wall 32 of the reservoir 30 is maintained. When the charge is removed from the elongated shape memory element 224, the spring 222 is allowed to bias the two blocks 228 apart and increase the length of the shape memory element 224 from the charged length to the uncharged length, as shown in <figref idref="f0002 f0003">Figs. 3a-3d</figref>.

0055<figref idref="f0001">Figs. 2</figref> and <figref idref="f0002 f0003 f0004">3</figref> show the plunger assembly 40 when no charges are applied to the actuators 204, 224, 244, The processor 50 is programmed to provide a predetermined cycle of charges to the actuators 204, 224, 244 of the plunger assembly 40 in order to cause longitudinal advancement of the plunger assembly 40 towards the outlet 36 of the reservoir 30.

0056For example, during operation of the plunger assembly 40, the actuator 204 of the first lateral segment 200 is charged to pull the blocks 208 of the first lateral segment 200 laterally inwardly away from the side wall 32 of the reservoir 30, as shown in <figref idref="f0002">Figs. 3b</figref> and <figref idref="f0003">3c</figref>, to allow longitudinal movement of the first lateral segment 200. Then the actuator 244 of the longitudinal segment 240 is charged to pull the first lateral segment 200 longitudinally within the reservoir 30 from an initial longitudinal position x1, as illustrated in <figref idref="f0002 f0003 f0004">Figs. 3a-3f</figref>, towards the second lateral segment 220 until the first lateral segment 200 is stopped by the longitudinally extending projection 248 of the longitudinal segment 240 at a second longitudinal position x1', as shown in <figref idref="f0003 f0004">Figs. 3c-3e</figref>.

0057The charge can then be removed from the actuator 204 of the first lateral segment 200 such that the spring 202 of the first lateral segment 200 is allowed to bias the blocks 208 against the side wall 32 and prevent further longitudinal movement of the first lateral segment 200 within the reservoir 30, as shown in <figref idref="f0003">Fig. 3d</figref>.

0058Then, the actuator 224 of the second lateral segment 220 is charged to pull the blocks 228 of the second lateral segment 220 laterally inwardly away from the side wall 32 of the reservoir 30, as shown in <figref idref="f0004">Figs. 3e and 3f</figref>, to allow longitudinal movement of the second lateral segment 220. The plunger assembly is adapted such that the fluid-tight seal between the second lateral segment 220 and the side wall 32 of the reservoir 30 is maintained during this longitudinal movement. The charge is then removed from the actuator 244 of the longitudinal segment 240 to allow the spring 242 of the longitudinal segment 240 to push the second lateral segment 220 longitudinally within the reservoir 30 from an initial longitudinal position x2, as illustrated in <figref idref="f0002 f0003 f0004">Figs. 3a-3f</figref>, away from the first lateral segment 200 to a second longitudinal position x2', as shown in <figref idref="f0004">Fig. 3f</figref>. This longitudinal movement of the second lateral segment 220 causes fluid to be dispensed from the reservoir. The charge can then be removed from the actuator 224 of the second lateral segment 220 such that the spring 222 of the second lateral segment 220 is allowed to bias the blocks 228 against the side wall 32 and prevent further longitudinal movement of the second lateral segment 220 within the reservoir 30, as shown in <figref idref="f0002">Fig. 3a</figref>.

0059The longitudinal difference between x2' and x2 is substantially equal to the longitudinal difference between x1' and x1, and substantially equal to the longitudinal difference between the length of the fully elongated and uncharged actuator 244 of the longitudinal segment 240 and the length of the longitudinally extending projection 248 of the longitudinal segment 240. Since both the length of the fully elongated and uncharged actuator 244 and the length of the longitudinally extending projection 248 of the longitudinal segment 240 are predetermined, the longitudinal difference between x2' and x2 is also predetermined.

0060The cycle of charges applied to the actuators 204, 224, 244 of the plunger assembly 40 as illustrated in <figref idref="f0002 f0003 f0004">Figs. 3b through 3f</figref> are successively repeated (through electrical charges provided by the local processor 50) to intermittently advance the plunger assembly 40 longitudinally within the reservoir 30 and produce pulse volumes of fluid flow from the reservoir 30. Thus, one cycle of charges is illustrated in <figref idref="f0002 f0003 f0004">Figs. 3b-3f</figref>, and produces a longitudinal displacement of fluid between the plunger assembly and the end wall of the reservoir equal to the longitudinal difference between x2' and x2.

0061Although not shown, the processor 50 can include capacitors for storing a charge received from the power source 80 for use in providing electrical charges to the actuators 204, 224, 244 of the plunger assembly 40. The fluid delivery device 10 can be calibrated so that a single cycle of charges from the processor 50 causes the dispensing of a predetermine volume of fluid, called a pulse volume (PV), from the reservoir 30. In general, the PV is substantially equal to the longitudinal difference between x2' and x2 multiplied by the cross-sectional area of the reservoir 30.

0062In this manner, a desired volume to be delivered by the fluid delivery device 10 is dispensed by the application of multiple cycles of charges over a predetermined period. PV's delivered by infusion devices are typically chosen to be small relative to what would be considered a clinically significant volume. For insulin applications at a concentration of one hundred units per microliter (100 units/ml), a PV of less than two microliters, and typically a half of a microliter, is appropriate. If the fluid delivery device 10 is programmed via the remote control device 100 to deliver two units an hour, the processor 50 will deliver forty cycles of charges an hour, or a cycle of charges every ninety seconds, to the actuators 204, 224, 244. Other drugs or concentrations may permit a much larger PV. Various flow rates are achieved by adjusting the time between the cycles of charges. To give a fixed volume or bolus, multiple cycles of charges are given in rapid succession until the bolus volume is reached.

0063Referring back to <figref idref="f0001">Fig. 2</figref>, the fluid delivery device 10 can be provided with the fill port 90 connected to the reservoir 30. In the embodiment shown, the fill port 90 includes the needle-pierceable septum 92. Although not shown, the device 10 can further include a sensor, such as a pressure switch, connected to the local processor 50 and adapted and arranged to provide a signal upon the presence of a needle in the fill port 90. The local processor 50, in-turn, can be programmed to apply a charge to the actuators 204, 224 of the first and the second lateral segments 200, 220 whenever it receives a signal from the fill port 90 sensor. Thus when a needle is positioned in the fill port 90, the plunger assembly 40 is disengaged from the side wall 32 of the reservoir 30 to allow the plunger assembly 40 to be moved longitudinally away from the inlet 36 upon fluid being added to the reservoir 30 through a needle inserted into the fill port 90. Alternatively, the device 400 can be provided with a manual actuator, such as a button for a user to push, for applying a charge to the actuators 204, 224 of the first and the second lateral segments 200, 220 during a filling process.

0064The plunger assembly 40 further includes a case 260 of resiliently flexible material enclosing the longitudinal segment 240 and the first and the second lateral segments 200, 220 in a fluid-tight manner. The case 260 includes a first portion 262 covering the first lateral segment 200, a second portion 264 covering the second lateral segment 220, and a collapsible bellows 266 covering the longitudinal segment 240 and connecting the first and the second portions 262, 264. The case 260 provides a fluid-tight seal between the outermost periphery of the second lateral segment 220 and the side wall 32 of the reservoir 30, such that fluid contained in the reservoir 30 cannot escape between the side wall 32 and the piston assembly 40 and can only exit the reservoir 30 from the outlet 36.

0065Another exemplary embodiment of a plunger assembly 340 constructed in accordance with the present invention is shown in <figref idref="f0005">Fig. 4</figref>. Elements of the plunger assembly 340 are similar to elements of the plunger assembly 40 of <figref idref="f0001 f0002 f0003 f0004">Figs. 2-3f</figref> such that similar elements have the same reference numeral. The plunger assembly 340 and the reservoir 30 of <figref idref="f0005">Fig. 4</figref>, however, further include a longitudinal position sensor assembly 350.

0066In particular, the longitudinal position sensor assembly 350 includes a barcode 352 secured to the side wall 32 of the reservoir 30 and an optical emitter/receiver 354 mounted in the plunger assembly 340 in alignment with the barcode 352. As shown in <figref idref="f0005">Fig. 5</figref>, the barcode 352 includes equally spaced alternating bars of reflective and non-reflective material. In the embodiment of the plunger assembly 340 shown in <figref idref="f0005">Figs. 4</figref> and <figref idref="f0006">6</figref>, the optical emitter/receiver 354 is mounted in the first lateral segment 200. The optical emitter/receiver 354 is connected to the processor 50 of the fluid delivery device and provides a signal whenever the optical emitter/receiver 354 is aligned with one of the reflective bars of the barcode 352. The processor 50 in turn is programmed to determine the relative longitudinal position of the plunger assembly 340 within the reservoir 30 based in part upon the number of signals received from the emitter/receiver 354 in the moving plunger assembly. Thus, the amount of fluid contained in the reservoir 30 can be determined by the processor 50 based on the relative position of the plunger assembly 340 within the reservoir. The processor 50 can also be programmed to determine the amount of fluid dispensed from the reservoir 30 (e.g., microliters) based upon the changing relative position of the plunger assembly 340 within the reservoir 30, and the rate of fluid dispensing (e.g., microliters per hour) based upon the change in the relative position of the plunger assembly 340 within the reservoir 30 and the period of time for that change.

0067It should be noted that a single row of dark and light bars can be used with single optical receiver/transmitter to detect magnitude of motion. The smaller the bars, the more resolution the motion detector provides. If two rows of offset dark and light bars are used, with a second optical receiver/transmitter, both the magnitude and the direction of motion can be detected (this direction feature can be important if the plunger assembly, for example, sticks and is on the cusp of a dark and light transition and causing a "chattering" back and force signal to the processor and thus false information of infusion).

0068An additional exemplary embodiment of a plunger assembly 440 constructed in accordance with the present invention is shown in <figref idref="f0006 f0007 f0008">Figs. 7a-7e</figref>. Elements of the plunger assembly 440 are similar to elements of the plunger assembly 40 of <figref idref="f0001 f0002 f0003 f0004">Figs. 2-3f</figref> such that similar elements have the same reference numeral. The plunger assembly 440 of <figref idref="f0006 f0007 f0008">Figs. 7a-7e</figref>, however, includes a second lateral segment 420 that does not includes laterally movable blocks, a spring or an actuator. Instead the second lateral segment 420 is simply sized and shaped to frictionally engage the side wall of the reservoir. Moreover, in the embodiment shown the second lateral segment 420 includes outer circumferential ridges 430 shaped and oriented to engage the side wall of the reservoir and substantially prevent movement of the second lateral segment away from the outlet of the reservoir.

0069During operation of the plunger assembly 40, the actuator 204 of the first lateral segment 200 is charged to pull the blocks 208 of the first lateral segment 200 laterally inwardly away from the side wall 32 of the reservoir 30, as shown in <figref idref="f0007">Figs. 7b and 7c</figref>, to allow longitudinal movement of the first lateral segment 200. Then the actuator 244 of the longitudinal segment 240 is charged to pull the first lateral segment 200 longitudinally within the reservoir 30 from an initial longitudinal position x1, as illustrated in <figref idref="f0006 f0007 f0008">Figs. 7a-7e</figref>, towards the second lateral segment 420 until the first lateral segment 200 is stopped by the longitudinally extending projection 248 of the longitudinal segment 240 at a second longitudinal position x1' as shown in <figref idref="f0007 f0008">Figs. 7c-7e</figref>.

0070The charge can then be removed from the actuator 204 of the first lateral segment 200 such that the spring 202 of the first lateral segment 200 is allowed to bias the blocks 208 against the side wall 32 and prevent further longitudinal movement of the first lateral segment 200 within the reservoir 30, as shown in <figref idref="f0008">Fig. 7d</figref>.

0071Then, the charge is removed from the actuator 244 of the longitudinal segment 240 to allow the spring 242 of the longitudinal segment 240 to push the second lateral segment 420 longitudinally within the reservoir 30 from an initial longitudinal position x2, as illustrated in <figref idref="f0006 f0007 f0008">Figs. 7a-7e</figref>, away from the first lateral segment 200 to a second longitudinal position x2', as shown in <figref idref="f0008">Fig. 7e</figref>.

0072The frictional engagement force of the second lateral segment 420 against the side wall 32 must be carefully designed to be slightly less than the force generated by the spring 242. Basically, the first lateral segment 200, with the blocks 208 withdrawn, should have a minimal frictional engagement force when compared to the frictional engagement force of the second lateral segment 420. When the longitudinal segment 240 is contracted, the first lateral segment 200 preferentially moves due to the lower frictional forces. After the first lateral segment 200 is locked in place with the release of its blocks 208, the second lateral segment 420 moves forward more slowly than the first lateral segment did due to the constant, higher frictional force acting on the second lateral segment 420.

0073The cycle of charges applied to the actuators 204, 244 of the plunger assembly 440 as illustrated in <figref idref="f0007 f0008">Figs. 7b through 7e</figref> are successively repeated (through electrical charges provided by the local processor 50) to intermittently advance the plunger assembly 440 longitudinally within the reservoir 30 and produce pulse volumes of fluid flow from the reservoir 30. Thus, one cycle of charges is illustrated in <figref idref="f0006 f0007 f0008">Figs. 7b-7e</figref>.

0074An exemplary plunger assembly 540 the present invention is shown in <figref idref="f0009 f0010">Figs. 8a-8c</figref>. Elements not forming part of of the plunger assembly 540 are similar to elements of the plunger assembly 40 of <figref idref="f0001 f0002 f0003 f0004">Figs. 2-3f</figref> such that similar elements have the same reference numeral. The plunger assembly 540 of <figref idref="f0009 f0010">Figs. 8a-8c</figref>, however, includes a second lateral segment 520 that does not includes laterally movable blocks, a spring or an actuator, and a first lateral segment 500 that does not includes laterally movable blocks, a spring or an actuator. Instead the first and the second lateral segment 500, 520 are simply sized and shaped to frictionally engage the side wall of the reservoir. Moreover, in the embodiment shown the lateral segment 500, 520 include outer circumferential ridges 530 shaped and oriented to engage the side wall of the reservoir and substantially prevent longitudinal movement of the lateral segments 500, 520 away from the outlet of the reservoir.

0075During operation of the plunger assembly 540, the actuator 244 of the longitudinal segment 240 is charged to pull the first lateral segment 500 longitudinally within the reservoir 30 from an initial longitudinal position x1, as illustrated in <figref idref="f0009 f0010">Figs. 8a-8c</figref>, towards the second lateral segment 520 until the first lateral segment 500 is stopped by the longitudinally extending projection 248 of the longitudinal segment 240 at a second longitudinal position x1', as shown in <figref idref="f0009 f0010">Figs. 8b-8c</figref>. The actuator 244 of the longitudinal segment 240 is adapted (e.g., sized) to be strong enough to overcome the frictional engagement between the first lateral segment and the side wall of reservoir. Since the circumferential ridges 530 of the second lateral segment 520 prevent longitudinal movement of the second lateral segment 520 away from the outlet of the reservoir, the actuator 244 of the longitudinal segment 240 pulls the first lateral segment 500 towards the second lateral segment 520 without moving the second lateral segment 520.

0076Then, the charge is removed from the actuator 244 of the longitudinal segment 240 to allow the spring 242 of the longitudinal segment 240 to push the second lateral segment 520 longitudinally within the reservoir 30 from an initial longitudinal position x2, as illustrated in <figref idref="f0009 f0010">Figs. 8a-8c</figref>, away from the first lateral segment 500 to a second longitudinal position x2', as shown in <figref idref="f0010">Fig. 8c</figref>. Since the circumferential ridges 530 of the first lateral segment 500 prevent longitudinal movement of the first lateral segment 500 away from the outlet of the reservoir, the spring 242 of the longitudinal segment 240 pushes the second lateral segment 520 longitudinally away the first lateral segment 500 without moving the first lateral segment 500.

0077Thus, the single charge applied to the actuator 244 of the plunger assembly 540 as illustrated in <figref idref="f0009 f0010">Figs. 8a-8c</figref> is successively repeated (through electrical charges provided by the local processor 50) to intermittently advance the plunger assembly 540 longitudinally within the reservoir 30 and produce pulse volumes of fluid flow from the reservoir 30. A single charge is illustrated in <figref idref="f0009 f0010">Figs. 8a-8c</figref>.

0078<figref idref="f0010">Fig. 9</figref> shows a fluid delivery device similar to the fluid delivery device of <figref idref="f0001">Fig. 2</figref>, but including another exemplary embodiment of a reservoir 630 and a plunger assembly 640 constructed in accordance with the present invention for causing fluid to be dispensed from the device. The reservoir 630 and the plunger assembly 640 are similar to the reservoir and the plunger assembly of <figref idref="f0001">Fig. 2</figref> such that similar elements have the same reference numerals.

0079The reservoir 630 is provided with a side wall 632 extending along a longitudinal axis 633 between an open end 635 and an end wall 634 of the reservoir. The end wall 634 includes an outlet, or an opening 636 that functions as an outlet and an inlet. The side wall 632 includes a first section 632a extending from the outlet 636, and a second section 632b extending from the first section 632a to the open end 635 (it should be noted that the reservoirs disclosed herein can be provided with closed ends if desired).

0080The plunger assembly 640 is received in the second section 632b of the side wall 632 of the reservoir 630. The plunger assembly 640 includes a strut 650 extending along the longitudinal axis 633 of the reservoir 630 and received in the first section 632a of the side wall 632 of the reservoir 630. The strut 650 is shaped and sized such that a fluid-tight seal is generally formed between the strut 650 and the first section 632a of the side wall 632 of the reservoir 630 so that movement of the plunger assembly 640 and the strut 650 towards the end wall 634 of the reservoir 630 forces fluid located between the strut 650 and the end wall 634 through the outlet 636 to the exit port assembly 70.

0081Features and advantages of the exemplary embodiments of the reservoir 630 and the plunger assembly 640 of <figref idref="f0010">Fig. 9</figref> include, but are not limited to, allowing the lateral segments 200, 220 of the plunger assembly 640 to have a cross-sectional dimensions that are different than the cross-sectional dimension of the strut 650, such that a desired pulse volume (PV) produced by the reservoir 630 and the plunger assembly 640 can be further refined. In the exemplary embodiment of <figref idref="f0010">Fig. 9</figref>, the lateral segments 200, 220 of the plunger assembly 640 are provided with cross-sectional dimensions that are larger than the cross-sectional dimension of the strut 650 (i.e., the first section 632a of the side wall 632 of the reservoir 630 has a cross-sectional dimension that is smaller than a cross-sectional dimension of the second section 632b of the side wall 632). However, the lateral segments 200, 220 of the plunger assembly 640 can be provided with cross-sectional dimensions that are smaller than the cross-sectional dimension of the strut 650 (i.e., the first section 632a of the side wall 632 of the reservoir 630 can be provided with a cross-sectional dimension that is larger than a cross-sectional dimension of the second section 632b of the side wall 632) if desired.

0082As illustrated by the above described exemplary embodiments, the present invention generally provides a device 10 for delivering fluid, such as insulin for example, to a patient. The device 10 includes an exit port assembly 70, and a reservoir 30 including an outlet 36 connected to the exit port assembly 70 and a side wall 32 extending along a longitudinal axis 33 towards the outlet 36. A plunger assembly (e.g., 40, 340, 440, 540) is received in the reservoir 30 and is movable along the longitudinal axis 33 of the reservoir 30 towards the outlet 36 of the reservoir in order to cause fluid to be dispensed from the reservoir to the exit port assembly 70.

0083In any event, it should be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make variations and modifications to the embodiments described without departing from the spirit and scope of the present invention. For example, some linear actuators have a limited contraction distances (i.e., small change in length). A shape memory element for example may be only able to contract approximately 5% of its length upon being charged. In applications where this small change in length is insufficient, various geometric design alternatives can be used to create sufficient linear motion based on the small change in length of the shape memory element. The simplest geometric design alternative, for example, may be to use a longer shape memory element connected back and forth multiple times between the two objects to be pulled together. Alternatively, the shape memory element can be attached to a shorter arm of a lever (or other length versus force exchange mechanism), utilizing the large forces generated by the shape memory element to "exchange" force for increased travel. In any event, all such equivalent variations and modifications are intended to be included within the scope of this invention as defined by the appended claims.