SPRING-POWERED INFUSION PUMP

Abstract: A spring-powered infusion pump (10) includes a syringe barrel (20) having two opposing openings (30, 55) forming two chambers (80, 90) between the first opening (30) and the plunger (40); and the second opening (55), and the plunger (40). The dispenser opening (30) has a duck-bill valve (35) to selectively release fluid retained within the first chamber (80). The second opening (55) is capped, a spring (60) is compressed between the plunger (40), and syringe cap (50) within the second chamber (90). The spring (60) applies a force to the plunger (40) in the direction of the first opening (30). However, the duck-bill valve (35) retains the fluid within the first chamber (80), despite the force applied to the plunger (40), until a tubing set (70) equipped with an infuser connector (75) is attached to the dispenser opening (30) of the syringe barrel (20). The infuser connector (75) is inserted through the duck-bill valve (35) and thus provides a passageway for the fluid retained within the first chamber (80) of the syringe barrel (20).

Description: SPRING-POWERED INFUSION PUMP BACKGROUND OF THE INVENTION 1. Field of the Invention. The present invention relates generally to the field of spring-powered infusion pumps. More specifically, the present invention discloses a single-dose spring- powered infusion pump. 2. Statement of the Problem. Syringe-type infusers typically require the user to manually dispense the fluid contents (e.g., by pressing the syringe plunger). Thus, it is difficult to deliver a constant flow over time, especially when there is a large amount of fluid to be dispensed over a period of time. Spring-powered infusers, on the other hand, deliver fluid at a constant rate, but require elaborate mechanisms, caps or clips to retain the fluid within the syringe because the plunger is under pressure. Conventional spring-loaded infusers are initially loaded under pressure. Therefore, a secondary problem is created when the infuser is disconnected from the syringe barrel. If tubing is not immediately attached or the connection is not otherwise capped or clipped, the pressurized liquid will be lost, thus making the amount delivered inaccurate. Syringe type infusers used in the past include the following: Inventor Patent No. Issue Date Calhoun 1 ,123,990 Jan. 5, 1915 Bessesen 1 ,476,946 Dec. 11 , 1923 Kollsman 2,605,765 Aug. 5, 1952 Jinotti 3,565,292 Feb. 23, 1971 Magoon, et al. 4,312,347 Jan. 26, 1982 Genese 4,381 ,006 Apr. 26, 1983 Vaillancourt 4,813,937 Mar. 21 , 1989 Chang 4,991 ,742 Feb. 12, 1991 LeFevre 4,997,420 Mar. 5, 1991 Reese 5,078,679 Jan. 7, 1992 Vaillancourt 5,100,389 Mar. 31 , 1992 Zdeb 5,135,500 Aug. 4, 1992 Ishikawa 5,178,609 Jan. 12, 1993 Elson 5,346,476 Sep. 13, 1994 Chang teaches an automatic drip bottle set. A cover and basin connect to hold a spring in the basin. The spring provides pressure urging the basin downward and applying uniform pressure on an expansion drip bottle. LeFevre discloses a portable drug delivery device for delivering a drug in liquid form at a constant and self-regulated rate. A syringe having a spring-loaded piston in a cylinder forces the liquid out through a tubing having a restrictor in the length of tubing to impede flow and achieve a desired flow rate. Zdeb teaches a self-driven pump device for delivering fluid at a relatively constant, controlled rate. A vacuum power means collapses under atmospheric pressure and drives a plunger to deliver fluid from the fluid storage means. The fluid storage means is filled by attaching a male luer opening to a female luer opening associated with the fluid storage means. As the male luer is pushed into the duck-bill valve, the tapered end portion opens to allow fluid to pass through the valve and into the fluid storage means. Fluid can then be delivered from the fluid storage means as the plunger moves under atmospheric pressure. A generally similar vacuum-powered infusion pump has been marketed by McKinley Medical, LLLP, of Wheat Ridge, Colorado, as the Outbound" disposable syringe infuser. Calhoun discloses a type of syringe for dosing or inoculating animals. The syringe automatically discharges the contents when the user forces a small plunger inward, permitting a spring to draw a piston into the syringe barrel, thus forcing the contents out in a controlled manner. Bessesen discloses a fluid-pressure device. When the aperture is closed and the barrel filled with fluid, pressure is created in the barrel by turning the handle to release the spring. When the barrel is emptied, the piston is retracted by turning the handle the opposite direction. Kollsman teaches an automatic syringe. After removing a release cap from the end of the piston guide rod, a spring expands moving the piston toward a partition plug against the resistance of a viscous liquid in chamber 33. The liquid flows slowly through a capillary passage 36 into a chamber 32, which moves a piston 15 displacing fluid from the chamber 14 through an injection needle over a predetermined time. Jinotti discloses an apparatus for holding a blood bag and causing the blood to be fed out of the bag. A piston is retracted by turning a handle to the desired position and then released so that the piston is under pressure created by the spring, which in turn forces blood out of the bag gradually and constantly. Magoon et al. teach a positive-pressure drug releasing device. A chamber is filled with a liquid drug and placed under continuous positive pressure by a spring and plunger device. Fluid diffuses at a predetermined rate through a membrane opposite the plunger. Genese discloses a continuous low flow rate fluid dispenser. Two spiral coiled springs move the driver member toward the abutment member, forcing the plunger stopper toward the nozzle portion expelling fluid from the syringe barrel at a slow and steady rate. Vaillancourt ('937) teaches an ambulatory disposable infusion delivery system. Inflow of a fluid causes an elastomeric member attached to a piston to stretch, which pushes the fluid out of the bore when the tubing line is opened. The housing is provided with a discharge fluid conduit and a restrictor controlling the rate of flow. Reese discloses a method of administering anesthesia directly to the surgical site. The plunger of a spring-loaded syringe creates pressure thus causing the medication to flow through a cannula and catheter into the wound. Flow of the medication is regulated by the micro-bore cannula to ensure delivery at very small rates. Vaillancourt ('389) teaches an ambulatory infusion pump with a preloaded spring having a fixed spring constant. The preloaded spring is released by a tab and biases the piston of the pump. The biasing force of the spring and the stroke of the piston are coordinated to maintain pressure on the fluid and dispense the fluid at a slow rate. Ishikawa discloses a medical liquid injector for continuous transfusion. A syringe is fitted with a piston and a cap having an elastic pressing device for continuously pressing the piston to force the liquid from the syringe. Flow is controlled using a flow rate control tube having a given inner diameter. Elson discloses a fluid delivery system having a bladder enclosed in a cap and drive mechanism. A piston driven by a constant force spring delivers the fluid at a predetermined rate based on the spring design. 3. Solution to the Problem. None of the prior art references discussed above show a spring-powered infusion pump having a duck-bill valve for retaining the fluid within the dispenser while under pressure from a spring. The spring compressed between the syringe plunger and the syringe cap provides pressure to the plunger so that the fluid contained within the syringe barrel can be released automatically at a constant flow and the user does not have to manually dispense the fluid contents. A duck-bill valve retains the fluid within the syringe barrel against the pressure on the plunger from the spring. By inserting an infuser connector through the duck-bill valve, the fluid retained within the dispenser can be selectively released. SUMMARY OF THE INVENTION The present invention is a spring-powered infusion pump. The spring-powered infusion pump has a syringe barrel with two opposing openings and a plunger disposed between the openings within the syringe barrel. Thus, two chambers are formed between the first opening and the plunger, and the second opening and the plunger. The first opening is fitted with a duck-bill valve to selectively release fluid retained within the first chamber. The second opening is capped, and a spring is biased between the plunger and syringe cap within the second chamber. The spring applies a force to the plunger in the direction of the first opening. However, the duck-bill valve retains the fluid within the first chamber, despite the force applied to the plunger, until a tubing set equipped with an infuser connector is attached to the first opening of the syringe barrel. The infuser connector is insertable through the duck-bill valve and thus provides a passageway for the fluid retained within the first chamber of the syringe barrel. Once attached, the force exerted by the spring causes the plunger to move toward the first opening, thereby dispensing the fluid from the first chamber through the infuser connector and duck-bill valve into the tubing set. A primary object of the present invention is to provide a single predetermined dose of fluid at a constant rate of flow. Inconsistencies in the flow rate associated with manual operation of the syringe plunger are largely eliminated by the spring-powered syringe of the present invention. Another object of the present invention is to provide a sterile, disposable device for dispensing predetermined amounts of fluid. The syringe barrel of the present invention can be prefilled in a sterile environment so that the fluid is not contaminated prior to being dispensed. Yet another object of the present invention is to retain the fluid within the syringe barrel prior to being dispensed without the need for caps, clips or other stoppers. When caps or other stoppers are removed, the fluid immediately is released from the syringe barrel, and if tubing is not immediately attached, this fluid is lost and the amount delivered is thus inaccurate. In addition, caps and clips can easily be lost. Fluid is retained within the syringe barrel of the present invention by the duck-bill valve and released only when an infuser connector fitted within the tubing, is connected to the dispenser. Therefore, when the duck-bill valve is opened, fluid flows immediately into the tubing and none is lost. These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS The present invention can be more readily understood in conjunction with the accompanying drawings, in which: FIG. 1 is an exploded perspective view of the spring-powered infusion pump. FIG. 2 is a cross-sectional view of the assembled infusion pump. FIG. 3 is a detail cross-sectional view showing an infusion connector penetrating the duck-bill valve. FIG. 4 is a detail cross-sectional view corresponding to FIG. 3 after the infuser connector has been completely attached the infusion pump. DETAILED DESCRIPTION OF THE INVENTION Turning to FIG. 1 , the spring-powered infusion pump 10 has a syringe barrel 20 with two opposing openings 30 and 55. The bottom portion of the syringe barrel 20 is tapered to form a dispenser opening 30. Opposite the dispenser opening 30, the syringe barrel 20 forms a top opening 55 that is substantially the same diameter as the syringe barrel 20. A plunger 40 can thus be inserted into, and slidable within, the syringe barrel 20 through the top opening 55. The plunger 40 is surrounded by an o-ring 45 to form a seal between the plunger 40 and the inside surface of the syringe barrel 20. As shown in FIG. 2, a fluid chamber 80 is formed within the lower portion of the syringe barrel 20 between the dispenser opening 30 and the plunger 40. Similarly, a spring chamber 90 is formed in the upper portion of the syringe barrel 20 between the top opening 55, which is covered by a cap 50, and the plunger 40. Before the cap 50 is secured over the top opening 55, a spring 60 is compressed within the spring chamber 90 to exert a force against the plunger 40 in the direction of arrow 65 shown in figure 2. Although in the preferred embodiment, the syringe barrel 20 is cylindrical, it is to be expressly understood that the syringe barrel 20, and hence the plunger 40 can be any suitable shape. It is only important that a sealed fluid chamber and a separate spring chamber be formed adjacent one another. In the preferred embodiment, the syringe barrel 20, plunger 40, and cap 50 are made from a hard plastic, such as polyurethane, so that these parts can be disposed or recycled after use. However, other materials such as metal or glass can also be used for the various components. In addition, the terms "dispenser opening" and "top opening" are intended only to differentiate the two openings, and not to limit the present invention to its orientation. FIG. 2 shows the present infusion pump after it has been assembled. As depicted in FIG. 1 , a series of barrel tabs 200 are formed on the outside of the syringe barrel 20,. The cap 50 includes a lip 210 that fits over the top opening 55 of the syringe barrel 20. A series of cap tabs 215 are formed within the lip 210 of the cap 50, which can be snapped over the barrel tabs 200 to securely hold the cap 50 over the top opening 55 of the syringe barrel 20. In the preferred embodiment, the cap 50 is separate from the barrel 20 to simplify manufacturing and assembly of the present invention. The cap 50 readily fits over the top opening of the barrel 20 and is locked in place. Thus it is difficult to remove the cap 50 once it is assembled to prevent the cap 50 from popping off due to pressure from the spring 60. In the preferred embodiment of the present invention, there are more cap tabs 215 than barrel tabs 200 so that the cap 50 and barrel 20 do not have to be perfectly aligned, and so that the cap 50 does not come off under pressure from the spring 60 in the event that cap 50 is rotated. However, it is to be expressly understood that the number and placement of cap tabs 215 and barrel tabs 200 are not important to the present invention so long as the cap 50 can be securely fitted to top opening 55. Likewise, the cap 50 can be secured over the top opening 55 of the syringe barrel 20 in any suitable manner, including but not limited to: permanently bonding the plastic cap to the syringe barrel 20, mechanical latches, or any other suitable design for retaining the cap 50 on the syringe barrel 20 under pressure from the spring 60. Figures 3 and 4 show the details of the duck-bill valve 35. The duck-bill valve 35 is securely fitted within the dispenser opening 30. The duck-bill valve 35 typically is formed by two "duck-bills" 310 made of a soft, sealable plastic or rubber having an opening between the duck-bills 310. In its normal position shown, the duck-bill valve 35 is in a closed position (e.g., the duck-bills 310 are collapsed against one another by fluid pressure) so that the fluid is retained within the fluid chamber 80. The dispenser opening 30 includes threads 300 so that the threaded connector 305 of the tubing 70 can be secured to the dispenser opening 30. As the threaded end of tubing 70 is threaded onto the dispenser opening 30, a tubular portion 315 of the infuser connector 75 is inserted between the duck-bills 310, thus spreading duck-bills 310 and forming a conduit from the fluid chamber 80 through the dispenser opening 30 (via the duck-bill valve 35) and through the infuser connector 75 (via the needle-like portion 315) and into the tubing 70. Thus, fluid retained within fluid chamber 80 is allowed to flow, under the force of the spring 60, into the tubing 70 to be dispensed (e.g., as an IV into a patient). In the preferred embodiment, the dispenser opening 30 and the tubing connector 305 are threaded. However, any suitable means for securely attaching the tubing 70 to the dispenser opening 30 can be used without departing from the scope of the present invention. For instance, the dispenser opening 30 may be ribbed to receive the tubing 70, or any other suitable design may be used so long as the tubing 70 is held securely to the dispenser opening 30 when the infuser connector 75 opens the duck-bill valve 35. Design considerations will determine the rate at which fluid is dispensed from the syringe barrel 20. For instance, the diameter of the dispenser opening 30, the size of the opening created by the duck-bill valve 35 and the infuser connector 75, the diameter of the tubing 70, and the spring constant of the spring 60 can be selected to achieve the desired flow characteristics. Flow restrictor elements attached to the tubing 70 can also serve to regulate the flow. Likewise, the amount of pressure exerted by the spring 60 will determine the characteristics of the duck-bill valve 35 required to retain the fluid within the fluid chamber 80. Markings on the syringe barrel can be used to indicate the amount of fluid retained in the fluid chamber 80. The fluid chamber 80 of the present invention is preferably filled by the manufacturer or the health care provider. The device is assembled with the plunger 40 disposed within the syringe barrel 20 and the spring 60 compressed between the plunger 40 and the cap 50. The health care provider then connects tubing 70 with an infuser connector 75 for penetrating the duck-bill valve 35 into the fluid chamber 80. Pressurized fluid is fed through the tubing 70 into the fluid chamber 80 with sufficient pressure to overcome the force of the spring 60. Once the fluid chamber 80 is filled to a predetermined level, the tubing 70 and infuser connector 75 are removed and the duck-bills 310 of the duck-bill valve 35 return to their sealed position to retain the fluid within the fluid chamber 80. The fluid is retained by the duck-bill valve 35 until the spring-powered infusion pump is ready for use, at which time, tubing 70 having an infuser connector 75 is connected to the dispenser opening 30, and the fluid is allowed to flow from the fluid chamber 80 as described above. It is to be expressly understood that the spring-powered infusion pump 10 of the present invention can be filled by the manufacturer and disposed of after use, or the present invention may be refilled for repeated use. Alternatively, the infusion pump can be shipped empty and filled by the healthcare provider before use. The preferred embodiment offers the advantage of accurate filling and sterility. The above disclosure sets forth a number of embodiments of the present invention. Other arrangements or embodiments, not precisely set forth, could be practiced under the teachings of the present invention and as set forth in the following claims.

Claims: I CLAIM: 1. A spring-powered infusion pump comprising: a syringe barrel having a dispenser opening on one end for dispensing a liquid contained in said syringe barrel; a duck-bill valve at said dispenser opening for retaining said liquid within said syringe barrel, and a top opening opposite said dispenser opening; a plunger slidably disposed within said syringe barrel through said top opening forming a fluid chamber within said syringe barrel between said plunger and said dispenser opening for receiving a liquid through said duck-bill valve; a cap attached to said top opening of said syringe barrel, forming a spring chamber adjacent to said fluid chamber within said syringe barrel between said cap and said plunger; and a spring compressed between said plunger and said cap within said spring chamber, said spring applying a force to said plunger in the direction of said dispenser opening. 2. The spring-powered infusion pump of claim 1 further comprising: a tubing set; and an infuser connector attached to said tubing set, said infuser connector insertable through said duck-bill valve to form a conduit for liquid flow from said fluid chamber into said tubing set. 3. The spring-powered infusion pump of claim 2 wherein liquid is released only after said infuser connector is inserted through said duck-bill valve. 4. The spring-powered infusion pump of claim 3 wherein said liquid is released at a constant flow rate. 5. The spring-powered infusion pump of claim 1 wherein said liquid is a predetermined dose. 6. The spring-powered infusion pump of claim 1 wherein said syringe barrel is pre-filled with said liquid. 7. The spring-powered infusion pump of claim 1 wherein said dispenser opening is threaded. 8. The spring-powered infusion pump of claim 1 further having: a cap tab on said cap; and a barrel tab on said syringe barrel, said cap tab and said barrel tab interlocking to attach said cap to said syringe barrel. 9. A spring-powered infusion pump comprising: a syringe barrel having a dispenser opening on one end and a top opening opposite said dispenser opening; a duck-bill valve at said dispenser opening for retaining said liquid in said syringe barrel; a plunger movable along said syringe barrel; a fluid chamber formed within said syringe barrel between said plunger and said dispenser opening, said fluid chamber retaining a liquid therein; a cap secured to a top opening of said syringe barrel by interlocking tabs; a spring chamber within said syringe barrel between said cap and said plunger; and a spring compressed between said plunger and said cap within said spring chamber, said spring applying a force to said plunger in the direction of said dispenser opening.

Inventors: SKINKLE DAVID W, SKINKLE, DAVID, W.
Applicants: MCKINLEY MEDICAL LLP, SKINKLE DAVID W, MCKINLEY MEDICAL, LLP, SKINKLE, DAVID, W.
Application year: 1999
Main classification: A61M5
IPC codes: A61M5, A61M39