US20070246674A1 - Valve for use with a syringe and which prevents backflow - Google Patents

Abstract

A one-way valve assembly can be fitted to the end of a syringe to allow fluid to flow from the syringe and into a body cavity but to prevent backflow. The valve assembly is opened by insertion of the luer tip of the syringe into the assembly inlet. The valve has an internal elastic member that forms a variable volume internal chamber. This chamber expands upon insertion of the luer tip into the inlet and shrinks when the luer tip is removed from the assembly. The shrinking action creates a positive pressure in the valve assembly to prevent backflow.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of application Ser. No. 11/327,395 filed Jan. 9, 2006 (which is hereby incorporated by reference herein); which is a continuation of application Ser. No. 10/475,530, filed Oct. 30, 2003, now Pat. No. 6,991,215, issued Jan. 31, 2006; which is a National Stage filing of PCT/AU02/00861, filed Jul. 1, 2002; which claims priority of the following two applications: 1) Australian Application Number PR9444, filed Dec. 12, 2001; and 2) Australian Application Number 63598/01, filed Aug. 23, 2001.
FIELD OF THE INVENTION
• This invention is directed to a valve that can be attached to a catheter, a needle or any other type of injecting device and that has a particular configuration to prevent backflow. The invention is particularly directed to a needle free access valve for use in a needle free intravenous access system.
BACKGROUND ART
• A needle free access valve is one where the valve can be opened using a needleless syringe. A needleless syringe is a syringe where the needle has been removed such that the front of the syringe has only the luer taper or luer lock. Such valves are known but suffer from a number of disadvantages.
• A typical known valve has a body composed of two cylindrical containers. One container has a tubular opening into which the luer taper can be pressed. The other container has a tubular opening filled with a luer lock that allows the valve to be attached to various medical devices. Fluid flows through the luer taper upon depression of the syringe plunger and flows through the valve. The valve has a circular valve disk that can be forced open by the pressure of the fluid. When the fluid pressure stops, the valve returns to its closed position. This type of arrangement is entirely conventional. One disadvantage with this arrangement is that high levels of fluid flow can often not be obtained due to the design of the valve. That is, the valve itself is solid and fluid can flow only about the edge of the valve when the valve is opened. Another disadvantage is the lack of sterilization around the inlet part of the valve.
• A serious disadvantage with many existing one-way valves is that fluid can flow back into the valve from the body cavity or the body in which the needle etc has penetrated. This results in contamination, and a potential health hazard. Most valves are provided with some form of spring or bias to naturally bias the valve back into the closed position. Therefore, there would be a great advantage if it was possible to provide a one-way valve (for instance a needle free access valve) where there is little or no likelihood of backflow occurring upon removal or retraction of the syringe (or other device) to which the valve is attached.
• Other disadvantages with conventional valves are the production costs, the relatively large number of components making up the valve, the difficulty in mass production of the valve.
OBJECT OF THE INVENTION
• It is an object of the invention to provide a valve assembly for use in the medical field and which can reduce or entirely prevent the occurrence of backflow from the body cavity etc back into the valve assembly.
• It is further object of the invention to provide a valve assembly that may at least partially overcome the abovementioned disadvantages or provide the public with a useful or commercial choice.
• In one form, the invention resides in a valve assembly that comprises:
• 1. An inlet and an outlet,
• 2. A flow pathway that extends through the valve assembly from the inlet to the outlet,
• 3. A plunger that is positioned in the flow pathway and which can move between a forward open position where fluid can flow from the inlet to the outlet, and a retracted closed position where fluid is prevented from flowing from the inlet to the outlet, the plunger having a forward portion,
• 4. An at least partially elastic sock that has an outer end fixed to the valve assembly, and an inner portion which engages with the plunger such that reciprocation of the plunger from the retracted position to the forward position causes at least part of the sock to stretch, and
• 5. A variable volume chamber having walls defined by the plunger and the sock, the chamber forming part of the flow pathway, the chamber having smaller or nil volume when the plunger is in the retracted position, and a larger volume when the plunger is in the extended position, whereby upon retraction of the plunger, the variable volume chamber reduces in volume which results in a pumping action to pump fluid through the fluid pathway towards the outlet, thereby reducing or preventing backflow.
• With this arrangement, the apparatus can be attached to a syringe (or other device), and a needle, catheter or other body-injecting device can be attached to the apparatus. The contents of the syringe can then be passed through the apparatus and into the body by depressing the plunger into the forward (open) position. As the plunger moves towards the forward position, it stretches at least part of the sock and the variable volume chamber adopts the larger volume. However once the syringe is removed, or retracted, the sock retracts to its initial position, causing the plunger to be pushed back into the closed position and at the same time contracting the variable volume chamber. The contraction causes a positive pressure inside the apparatus that means that backflow does not occur. Indeed, it is found that the positive pressure is sufficient to at least partially “pump” any residual fluid in the apparatus through the outlet upon retraction of the plunger. This is in contrast to known devices where retraction of the plunger or closure of the valve often allows backflow of fluid through the outlet and into the valve apparatus.
• The valve assembly may have an outer body formed in two parts that are attached together. The two parts may comprise a top part, and a base part. The top part is substantially hollow and suitably contains an outer passageway of smaller diameter or cross-section, and an inner passageway of larger diameter or cross-section, the inner passageway forming part of an internal chamber. The outer passage way may contain longitudinal slots or recesses that comprise fluid ports the reason for which will be described in greater detail below.
• The base part may be substantially hollow and may contain a outer passageway of smaller diameter or cross-section, and an inner passageway of larger cross-section or diameter and which forms part of the internal chamber that is also defined by the top part. Thus, when the two parts are attached, there is provided a substantially central internal chamber. The outer passageway of the base part may be surrounded by attachments to allow the outlet to attach to a needle etc.
• The apparatus has a flow pathway that extends through the valve assembly from the inlet to the outlet, and typically through the central internal chamber described above.
• The apparatus has a plunger. The plunger is movable between a forward open position where the plunger moves more towards the outlet, and a retracted closed position where the plunger is more towards the inlet. The plunger typically slides or reciprocates between the two positions.
• The plunger has a forward portion which is typically a projecting nose portion. Suitably, the plunger also has a rear body portion. The nose portion and the body portion may be formed integrally. The plunger suitably has a fluid flow pathway extending at least partially therethrough. The fluid flow pathway may comprise an internal flow passageway extending through the nose portion which means that the nose portion may have an open outer end. Suitably, the internal flow passageway includes a transverse through bore in the rear body portion such that fluid can pass through the through bore and through the flow passageway that extends through the nose portion.
• The rear body portion of the plunger is typically configured and dimensioned to substantially fill the outer passageway in the top part of the valve assembly. Suitably, the rear body portion has an end face that is substantially flush with the end of the top part of the valve assembly that can make cleaning of this area quite easy. The rear body portion typically has a sealing face extending about the rear body adjacent the end face and which seals with the internal wall of the outer passageway.
• The plunger may an engagement means to engage with the elastic sock. The engagement means may comprise an annular step or shoulder portion on the plunger and which can catch against or engage with the elastic sock upon forward movement of the plunger. Alternatively, the plunger can push against the sock.
• The apparatus has an at least partially elastic sock. The sock may be formed of a rubbery elastic material having a good memory. In one form of the invention, the sock may be formed as a separate component. The elastic sock may comprise a substantially circular base portion, and an extending tubular wall portion. The base portion and the wall portion may be formed integrally. The wall portion may extend substantially about the nose portion of the plunger. The base portion may have a peripheral edge that is held against movement in the valve assembly. Suitably, the peripheral edge also comprises a sealing edge. Preferably, the base portion is elastic and can therefore be stretched upon forward movement of the plunger. Preferably, the tubular wall portion is compressible or is otherwise configured to allow it to be shortened in length, for instance by allowing the wall portion to buckle in a controlled manner. The wall portion may be provided with circumferential recesses that provide zones to allow a controlled buckling of the wall portion. The end of the tubular wall portion may be provided with a sealing lip or a sealing bead that seals against the base portion of the valve assembly.
• Alternatively, the sock may have a substantial disklike configuration without a tubular wall portion. In this embodiment, the sock may have an outer peripheral edge that is attached to the valve assembly in a manner similar to that described above. The sock may have an internal opening, which is typically a central opening and through which part of the plunger can pass, which is typically a nose portion of the plunger. If desired, the plunger may be provided with an annular recess to capture the wall of the internal opening. With this arrangement, the plunger may be provided with seals.
BRIEF DESCRIPTION OF THE DRAWINGS
• Embodiments of the invention will be described with reference to the following drawings in which:
• FIG. 1. Illustrates an exploded section view of the various components of the valve apparatus.
• FIG. 2. Illustrates the valve in the closed position with the plunger in the retracted position.
• FIG. 3. Illustrates the valve in the partially open position with the plunger moving to the forward position.
• FIG. 4. Illustrates the valve in the fully open position.
• FIG. 5. Illustrates a second embodiment of the invention having a slightly different sock arrangement that does not contain a tubular portion.
• FIG. 6. Illustrates the valve assembly ofFIG. 5 with the plunger in the retracted closed position and the sock in a substantially unstretched mode.
• FIG. 7. Illustrates the valve assembly ofFIG. 6 with the plunger has been pushed into the forward open position and the elastic sock is stretched.
• FIG. 8. Illustrates a third embodiment of the invention with the plunger in the closed position.
• FIG. 9. Illustrates the invention ofFIG. 8 in the open position.
BEST MODE
• Referring to the drawings, and initially toFIG. 1, there is illustrated a valve assembly which comprises aninlet10 and anoutlet11, a flow pathway that extends through the valve assembly frominlet10 tooutlet11, aplunger12 that is positioned in the flow pathway and which can reciprocate between a forward open position illustrated inFIG. 3, and a retracted closed position illustrated inFIG. 2, the plunger having an elongateforward nose portion13, anelastic sock14 which is adapted to extend at least partially about thenose portion13 ofplunger12, engagement means15 to engage the plunger to the sock, and avariable volume chamber16 best illustrated inFIG. 3 (where the chamber is of maximum volume), but also just visible inFIG. 2 (where the chamber is of minimal and almost having a zero volume).
• Referring to the parts in greater detail, the valve assembly in the embodiment comprises an outer body that is formed of two parts that are attached together, the two parts being atop part17 and abase part18. These parts are formed of plastic material and are joined together by any suitable method.Top part17 is best illustrated inFIG. 1 and is substantially hollow.Top part17 comprises anouter passageway19 which is circular and which has a smaller diameter, and aninner passageway20 which is also circular and which has a substantially larger diameter. Similarly,base part18 has aninner passageway21 that has a substantially larger diameter thanouter passageway22. When the two parts are joined as illustrated inFIG. 2 andFIG. 3, the two larger diameter passageways together form aninternal chamber23.Outer passageway22 terminates inoutlet11, whileouter passageway19 terminates ininlet10.
• Theouter passageway19 intop part17 contains a plurality of longitudinal open endedfluid ports24.Ports24 comprise recesses in the wall ofouter passageway19 and are open ended which means that the ports communicate withchamber16. Theports24 do not extend entirely along the wall ofpassageway19. Rather, the ports terminate partway along the wall such that asmooth wall portion25 extends between the end ofports24 andinlet10. The reason for this will be described in greater detail below.
• Base part18 contains a standard luer lock fitting26 which extends aboutpassageway22 and which functions to allow a needle etc to be attached to this part of the assembly. Of course, other types of attachments can also be used.
• Inner passageway21 has a diameter that is smaller thaninner passageway20. Thus, thewall27 ofinner passageway21 passes intoinner passageway20 this being best illustrated inFIG. 2. Moreover,wall27 has a length that results in thewall27 being spaced somewhat fromwall28 of top part17 (seeFIG. 2). This spacing facilitates the attachment of the elastic sock that will be described in greater detail below.
• Plunger12 is formed of plastic material and comprises a unitary body. The plunger has a particular configuration that provides anose portion13, and arear body portion29.Nose portion13 is slightly tapered and has a throughpassageway30 which passes through an openouter end31 and functions to allow fluid to flow through the valve assembly.Body portion29 is provided with a transverse throughbore32 through which fluid can pass.Body portion29 has a substantially cylindrical outer wall provided with a sealing area orcollar35. This is why thefluid ports24 inend wall25 terminate short ofinlet10 to also provide a smooth area which functions as a sealingzone36. Thus, when the plunger is in the closed position illustrated inFIG. 2, the sealingcollar35 seals against the sealingzone36 to provide seal against fluid flow.
• Whenplunger12 is pushed forwardly from the position illustrated inFIG. 2 to the position illustrated inFIG. 3 and4, the plunger only moves by a few mm, but this movement is sufficient to movecollar35 away from sealingzone36 and into the area of theflow ports24 and to allow fluid to pass along the outside wall ofbody portion29, through thefluid ports24, throughbore32 throughpassageway30 and throughoutlet11. Conversely, when the plunger is retracted from the position illustrated inFIG. 3 to the position illustrated inFIG. 2 the plunger again seals against passage of fluid frominlet10 throughoutlet11.
• Fluid only flows when theflow ports24 are opened bycollar35 moving past the outer most edge of the flow ports. At all other times a seal is maintained between theinternal wall25 andcollar35.
• The plunger is biased back to its retracted position by theelastic sock14 which also provide additional functions.Elastic sock14 is made of a rubbery elastic material having an excellent memory. The elastic sock has acircular base portion39 and an extendingtubular wall portion40. The elastic sock, when in the rest position, adopts the configuration illustrated inFIG. 1. The base portion is made of a stretchable and elastic material. The base portion has aperipheral edge41 that is thickened with respect to the thickness of the base portion immediately next to the peripheral edge.
• FIG. 2 illustrates attachment of the sock to the apparatus and shows how the thickenedperipheral edge41 is trapped betweenwall27 ofbase part18 and the inner wall oftop part17. The area of the base part between the peripheral edge and thetubular wall portion40 is quite elastic and can stretch.Peripheral edge41 also functions to seal the fluid pathway in the apparatus. The outer end oftubular wall portion40 is provided with anannular sealing lip45 that fits within anannular recess46 formed in base part18 (seeFIG. 2).
• Theplunger12 has an engagement means15 that comprises an annular shoulder extending from the base ofnose portion13. The annular shoulder sits behindbase portion39, this being best illustrated inFIG. 2. Thus, when theplunger12 is pushed forwardly from the position illustrated inFIG. 2 to the position illustrated inFIG. 3, the engagement means15 will pushbase portion39 forwardly. As theperipheral edge41 is trapped in place, the base portion will begin to stretch this being best illustrated inFIG. 3. As this occurs, a chamber16 (called the variable volume chamber) opens up from a very small or zero volume best illustrated inFIG. 2, to a larger volume best illustrated inFIGS. 3 and 4. Thischamber16 forms part of the fluid flow pathway that means that fluid fills or can at least partially fillchamber16. Of course, upon removal of the syringe tip (which pushes the plunger forwardly) from the apparatus, the plunger is pulled back into the retracted position by virtue of the stretchedbase portion39 shrinking back to its rest position. This action reduces the volume ofchamber16 and causes any fluid in the chamber to be “pumped” or squeezed throughflow passageway30 and throughoutlet11.
• The sock is designed such that when theplunger12 is in the retracted closed position, there is still some tension in the sock to keep the plunger in the retracted position.
• Thetubular wall portion40 of the sock has an array of spacedcircumferential grooves43 which are best illustrated inFIG. 1 andFIG. 2. These grooves facilitate a control buckling of thetubular wall portion40 from a substantially unbuckled position illustrated inFIG. 2, to a buckled position illustrated inFIG. 3. The buckling compensates for the stretching ofbase portion39. The tubular wall portion (also called the sock stem) has a natural position and memory to retain the position illustrated inFIG. 2. Thus, when the wall portion adopts the buckled position illustrated inFIG. 3, it also assists in pushing back to the plunger as soon as the syringe (or other type of device) is removed frominlet10.
• Referring toFIG. 4, when theplunger12 is in the fully open position, the plunger nose seals against annular sealinglip45.
• FIGS. 5-7 illustrate another embodiment of the invention, the primary difference being the configuration of the elastic sock on the plunger. Like parts have been given like numbers.
• In this embodiment,plunger47 is substantially similar to the plunger described above except that thenose portion48 contains aO ring seal49 which is in sliding engagement with the inside wall ofouter passageway22 thereby preventing fluid from flowing along the outside wall of thenose portion48. The plunger supports anelastic sock51 that is disklike in configuration, and differs from the elastic sock described above in that there is no tubular portion. Thesock51 again has an outer peripheral thickened sealingedge52 that is trapped in the valve housing as illustrated inFIG. 6 andFIG. 7.
• Asplunger47 moves from its retracted position illustrated inFIG. 6 to the extended position illustrated inFIG. 7, the movement causes theelastic sock51 to stretch. This stretching action increases the volume of thevariable volume chamber16. When the syringe tip (not illustrated) or other similar device is removed frominlet10,plunger47 will then be retracted back to the closed position illustrated inFIG. 6 by virtue of the bias provided by the stretched sock. Additionally, shrinking of the sock back to its initial position will reduce the volume ofchamber16 that provides the positive pressure to prevent backflow. A further0ring55 is positioned on the outer edge ofplunger47.
• In each embodiment, asmall air passageway56 is provided to allow air to pass intochamber23 upon shrinking of the sock and to allow air to pass out ofchamber23 upon stretching of the sock.
• The valve assembly prevents back flow of fluids by maintaining a positive pressure inchamber16.
• Referring toFIGS. 8 and 9 there is illustrated an anti-siphon means that can be fitted to a valve assembly which is described in Australian patent 736326 the specification of which is incorporated herein by cross reference. In this embodiment, the anti-siphon means includes asleeve64 which fits generally in abottom casing69 which is one part of a two part housing.Sleeve64 can be formed from an elastic material or a material that is elastic in the region where the sleevecontacts opening fingers74. Suitably, the sleeve is formed from SANTOPRENE or similar material.Sleeve64 has an inner portion which is dish shaped75 and anouter portion69 which is in the shape of a tube and which extends along the inside wall ofspigot71, and terminates in asmall lip72 which extends over the front end ofspigot71 to hold the sleeve in place.Inner portion75 of the sleeve is sealed to the innermostannular land portion65 ofbottom casing69. Thus, the sleeve can be positioned inbottom casing69 prior tobottom casing69 being attached totop casing62. A small annular thickenedportion66 is provided on the sleeve where the dish shapedportion75 joins or becomes part of theouter portion69. Suitably, the entire sleeve is formed from a single piece of material.
• The sleeve is designed to naturally adopt a position illustrated inFIG. 8 where it abuts against, or is closely spaced fromfingers74. In this position, the sleeve isolates the fluid pathway from the remainder ofchamber67. Whenvalve member61 is pushed forwardly, the arrangement adopts the position illustrated inFIG. 9. As valve member is pushed forwardly, it deforms or pushes apartfingers74.Fingers74 in turn push back/stretch sleeve64 intochamber67. This action causes air inchamber67 to be vented from the chamber through asmall vent opening68.Vent68 in the particular embodiment illustrated inFIG. 8 andFIG. 9 extends betweenchamber67 andoutlet73. Specifically, vent68 passes betweenchamber67 and thethreads70 in the internal passageway. An advantage in having the vent in this position is that it cannot be clogged by any cleaning/wiping of the exterior of the valve assembly. Of course, it is possible forvent68 to vent air fromchamber67 to any convenient outer part of the valve assembly.
• Whenvalve member plunger61 is pushed forwardly, fluid can now pass frominlet60 throughoutlet73. Whenvalve member61 is pushed back from the position illustrated inFIG. 9 to the position illustrated inFIG. 8, the stretchedsleeve64 will shrink back to the position illustrated inFIG. 8, and will stay abutting against or closely spaced from thefingers74/valve member61. As this occurs, air will pass throughvent68 and intochamber67 to equalise the pressure. Thus, air will pass through vent76 and not throughoutlet16. The effect of this is that asvalve member61 is retracted, fluid will not suck back throughoutlet73 as air will move preferentially intochamber67 throughvent68. The reason for this is thatoutlet73 will usually be connected to some form of needle assembly or body access means and it is much more difficult to suck fluid back throughoutlet73 then to have air passing throughvent68. Thus, the arrangement functions as an anti-siphon means to prevent body fluid (for instance blood) from being sucked back into the valve assembly.
• Another advantage with the arrangement is that possibly contaminated air is kept separate from the fluid flow pathway of the valve assembly by virtue of thesleeve64.
• It should be appreciated that various other changes and modifications can be made to the invention without departing from the spirit and scope of the invention.

Claims (38)

1. An intravenous valve assembly for providing a positive charge of intravenous fluid upon closure, the valve assembly comprising:

a valve body presenting an inlet and an outlet fixed relative to each other;

a flow pathway that extends through the valve body from the inlet to the outlet;

a plunger that is positioned in the valve body and which can move between a forward open position where fluid can flow from the inlet to the outlet, and a retracted closed position where fluid is prevented from flowing from the inlet to the outlet;

an at least partially elastic sock that has an outer end fixed to the valve body, and an inner portion which engages with the plunger such that reciprocation of the plunger from the retracted closed position to the forward open position causes at least part of the sock to stretch; and

a variable volume chamber having walls defined by the plunger and the sock, the chamber forming part of the flow pathway, said flow pathway having a smaller volume when the plunger is in the retracted closed position, and a larger volume when the plunger is in the forward open position, whereby upon retraction of the plunger, the variable volume chamber reduces in volume which results in a pumping action to pump fluid through the flow pathway out of the outlet, thereby reducing or preventing backflow.

2. The assembly ofclaim 1, wherein the valve body is formed in two parts that are attached together.

3. The assembly ofclaim 2, wherein one of the two parts comprises a top part having an outer passageway of smaller diameter or cross-section, and an inner passageway of larger diameter or cross-section, the inner passageway forming part of an internal chamber.

4. The assembly ofclaim 3, wherein the outer passageway contains at least one longitudinal slot or recess that comprise fluid ports.

5. The assembly ofclaim 3, wherein the other of the two parts comprises a base part which has an outer passageway of smaller diameter or cross-section, and an inner passageway of larger cross-section or diameter and which forms part of the internal chamber that is also defined by the top part.

6. The assembly ofclaim 5, said flow pathway extending through the internal chamber.

7. The assembly ofclaim 1, wherein the flow pathway extends at least partially through the plunger.

8. The assembly ofclaim 7, wherein the plunger has an engagement means to engage with the at least partially elastic sock.

9. The assembly ofclaim 8, wherein the engagement means comprises an annular step or shoulder portion on the plunger and which catches the at least partially elastic sock upon forward movement of the plunger.

10. The assembly ofclaim 1, wherein the sock has a substantially circular base portion, and an extending tubular wall portion.

11. The assembly ofclaim 10, said plunger including a forward portion wherein the extending tubular wall portion extends substantially about the forward portion of the plunger.

12. The assembly ofclaim 11, wherein the base portion has a peripheral edge that is held against movement in the valve body.

13. The assembly ofclaim 12, wherein the tubular wall portion includes an annular line of weakness and is thereby compressible and allowed to buckle in a controlled manner.

14. The assembly ofclaim 1, wherein the sock has a substantial disklike configuration.

15. The assembly ofclaim 14,

said plunger including a forward portion,

said sock having an outer peripheral edge that is attached to the valve body,

said sock presenting an internal opening through which the forward portion of the plunger extends.

16. An intravenous injection site valve assembly for providing a charge of injection fluid to reduce backflow from the patient, the injection site valve assembly comprising:

a valve body presenting an inlet, an outlet in a relatively spaced apart and fixed relationship to the inlet, and a hollow interior; and

a plunger shiftable progressively into and out of the hollow interior of the valve body,

said plunger and valve body cooperatively presenting a chamber access port which is sealable to prevent injection fluid flow therethrough, with an expandable injection fluid chamber being defined between the chamber access port and the outlet,

said plunger being shiftable between an inner closed position and an outer closed position, with the access port being sealed when the plunger is at and between the closed positions to thereby prevent injection fluid flow therethrough,

said injection fluid chamber becoming volumetrically smaller as the plunger shifts from the inner position to the outer position, with the valve assembly being thereby operable to pump the charge of injection fluid from the injection fluid chamber and out of the outlet.

17. The intravenous injection site valve assembly as claimed inclaim 16,

said plunger being shiftable between an open position where the access port is unsealed and the outer closed position, with the inner closed position being intermediate to the open and outer closed positions.

18. The intravenous injection site valve assembly as claimed inclaim 16; and

an elastic member operable to urge the plunger from the inner closed position to the outer closed position.

19. The intravenous injection site valve assembly as claimed inclaim 18,

said elastic member interconnecting the plunger and valve body.

20. The intravenous injection site valve assembly as claimed inclaim 19,

said elastic member being located within the hollow interior of the valve body.

21. The intravenous injection site valve assembly as claimed inclaim 19,

said elastic member partly defining the injection fluid chamber.

22. The intravenous injection site valve assembly as claimed inclaim 21,

said elastic member comprising an elastic sock,

said elastic sock including an outermost margin sealingly fixed to the valve body and an inner margin sealingly attached to the plunger.

23. The intravenous injection site valve assembly as claimed inclaim 22,

said elastic sock being stretched to a greater extent in the inner closed position than in the outer closed position so as to urge the plunger into the outer closed position.

24. The intravenous injection site valve assembly as claimed inclaim 22,

said inner margin defining a single opening in the elastic sock for receiving the plunger.

25. The intravenous injection site valve assembly as claimed inclaim 24,

said plunger presenting an internal fluid flow path that provides the only path for injection fluid to flow between sides of the elastic sock.

26. The intravenous injection site valve assembly as claimed inclaim 22,

said plunger and sock cooperatively preventing fluid communication between the injection fluid chamber and a remainder of the hollow interior.

27. The intravenous injection site valve assembly as claimed inclaim 26,

said valve body presenting an opening that permits the remainder of the hollow interior to fluidly communicate with ambient.

28. The intravenous injection site valve assembly as claimed inclaim 16,

said access port being spaced inwardly from the inlet.

29. The intravenous injection site valve assembly as claimed inclaim 16,

said plunger presenting an outer terminal plunger end,

said valve body presenting a sleeve portion that slidably receives the terminal plunger end, with the sleeve portion presenting an outer terminal sleeve end,

said terminal plunger and sleeve ends being flush with one another when the plunger is in the outer closed position.

30. An intravenous injection site valve assembly for providing a charge of injection fluid to reduce backflow from the patient, the injection site valve assembly comprising:

a valve body presenting an inlet, an outlet, and a hollow interior defined between the inlet and outlet; and

a plunger shiftable progressively into and out of the hollow interior of the valve body,

said plunger and valve body defining at least in part an injection fluid flow path extending between the inlet and outlet, with an expandable injection fluid chamber being defined along the fluid flow path and within the hollow interior,

said plunger and valve body defining at least in part an expandable compensating chamber within the hollow interior, with the compensating chamber being outside the fluid flow path and fluidly separated from the injection fluid chamber,

said injection fluid chamber becoming volumetrically larger and the compensating chamber becoming volumetrically smaller when the plunger shifts inwardly,

said injection fluid chamber becoming volumetrically smaller and the compensating chamber becoming volumetrically larger when the plunger shifts outwardly, with the valve assembly being thereby operable to pump the charge of injection fluid from the injection fluid chamber and out of the outlet.

31. The intravenous injection site valve assembly as claimed inclaim 30,

said injection fluid and compensating chambers changing volumetrically inversely proportionate to one another.

32. The intravenous injection site valve assembly as claimed inclaim 30,

said valve body including a vent communicating the compensating chamber to ambient.

33. A backflow-reducing method of injecting intravenous fluid into a patient,

the method comprising the steps of:

(a) fluidly connecting an intravenous fluid infusion component to the patient via a valve that fluidly communicates the component with the patient when open;

(b) injecting intravenous fluid from the component, through the valve, and into the patient at a pressure greater than the patient venous pressure;

(c) after the valve closes to fluidly disconnect the component from the patient, pumping a volume of fluid in a downstream direction from the valve into the patient to reduce any backflow from the patient.

34. A backflow-reducing method of injecting fluid as claimed inclaim 33,

step (c) being performed by removing the component from the valve.

35. The backflow-reducing method of injecting fluid as claimed inclaim 34,

said valve presenting an expandable valve chamber,

step (a) including the step of expanding the chamber by connecting the component to the valve, with the valve being configured to contain a charge of intravenous fluid when opened,

step (b) including the step of filling the valve chamber with the charge of fluid.

36. The backflow-reducing method of injecting fluid as claimed inclaim 35,

step (c) including the step of purging the charge of intravenous fluid from the valve chamber.

37. The backflow-reducing method of injecting fluid as claimed inclaim 36,

said valve including a shiftable plunger, with the expanding step occurring by inserting part of the component into the valve and displacing the plunger.

38. The backflow-reducing method of injecting fluid as claimed inclaim 37,

step (c) including the steps of sealing the valve inlet and then shifting the plunger from a first position to a second position to decrease the volume of the valve chamber.

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