Syringe

Flexible sleeve syringe and system

Abstract
A syringe having an elastic sleeve which defines a fluid chamber, and a plunger positioned within the elastic sleeve. The outer diameter of the plunger is greater than the inner diameter of the elastic sleeve such that the plunger elastically deforms the sleeve during use. A syringe pump system is also provided.

Claims
What I claim is:

1. A syringe, comprising: (a) an elastic sleeve defining a fluid chamber; and (b) a plunger positioned within said elastic sleeve, wherein the outer diameter of said plunger is greater than the inner diameter of said elastic sleeve such that said plunger elastically deforms said sleeve during use.

2. The syringe of claim 1, wherein said elastic sleeve comprises at least one semi-rigid sleeve member positioned within at least one elastomeric sleeve member such that, upon deformation of said elastic sleeve, said at least one elastomeric sleeve member will provide a restoring force against the semi-rigid sleeve member such that said at least one semi-rigid sleeve member will be returned to its original size and shape

3. The syringe of claim 1, wherein said elastic sleeve comprising a syringe sleeve and a surrounding sleeve, wherein said fluid chamber is defined by the interior of said syringe sleeve and said syringe sleeve is positioned within the interior of said surrounding sleeve.

4. The syringe of claim 3, wherein said surrounding sleeve comprises an elastomeric sleeve which provides a compressive force against the outer surface of said syringe sleeve upon deformation of said sleeve during use.

5. The syringe of claim 4, wherein said syringe sleeve comprises a semi-rigid thermoplastic material.

6. The syringe of claim 5, wherein said syringe sleeve comprises a fluoroplastic chosen from the groups consisting of: PTFE, PFA and FEP.

7. The syringe of claim 4, wherein said surrounding sleeve comprises silicone.

8. The syringe of claim 1, further comprising a housing which encloses said elastic sleeve.

9. The syringe of claim 8, wherein said housing comprises a first end cap located at the proximal end of said syringe sleeve, a second end cap positioned at the distal end of said syringe sleeve, and at least one sidewall extending between said end caps.

10. The syringe of claim 9, further comprising a rod which extends distally away from away from said plunger, and further wherein said first end cap has an opening through which said rod extends, and further wherein said second end cap has at least one fluid passageway in fluid communication with said fluid chamber.

11. The syringe of claim 9, wherein said at least one sidewall comprises a tube secured to said first and second end caps such that an annular space is provided between said tube and said elastic sleeve.

12. The syringe of claim 11, wherein the proximal end of said second end cap includes a chamber and further comprising an insert member configured for insertion into said chamber of said second end cap, and further wherein the distal end of said elastic sleeve is secured within said chamber between the wall of said chamber and said insert member.

13. A syringe pump system, comprising: (a) an elastic sleeve defining a fluid chamber; (b) a plunger positioned within said elastic sleeve, wherein the outer diameter of said plunger is greater than the inner diameter of said elastic sleeve such that said plunger elastically deforms said sleeve during use; (c) an intake conduit having a first check valve associated therewith and in fluid communication with said fluid chamber; and (d) an output conduit having a second check valve associated therewith and in fluid communication with said fluid chamber; wherein a fluid may be drawn into the syringe pump through said intake conduit and said first check valve, and thereafter expelled from said syringe pump through said output conduit and said second check valve upon reciprocation of said plunger.

Medical Supplies Patent

Description
RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Patent Application No. 60/516,459 which was filed on Nov. 3, 2003, and is incorporated herein by way of reference.

TECHNICAL FIELD

[0002] The present invention relates to syringes and, more particularly, to syringes having flexible components, including a flexible sleeve, that are adapted to maintain sealing and performance integrity under varying chemical, temperature, fatigue and pressure conditions.

BACKGROUND OF THE INVENTION

[0003] Syringes have long been used in various applications requiring precise, sterile or convenient pumping, extraction or delivery of liquids. As a result, many varieties of syringes exist in different forms suitable for different purposes.

[0004] In environments requiring precision and sterile handling of liquids for medical or industrial applications, it is necessary for syringes and their components to have high temperature and chemical resistance. Such applications may require high volume, continuous operation which, therefore, calls for designs and components capable of high cycle or fatigue resistance.

[0005] It is known to use syringes or syringe pumps having a glass sleeve and a PTFE (polytetrafluoroethylene) plunger, in which both materials are selected for their inert properties and high chemical and temperature resistance. A problem associated with such designs, however, is tendency for the PTFE plunger to set, particularly after a high number of cycles. The setting of the plunger, as a result of compressive forces from the liquid pumped and the rigid glass sleeve during use, causes leakage between the plunger and the sleeve.

[0006] One known solution to the problems associated with glass and PTFE systems is to over-size the PTFE plunger so that it is under greater compressive force when installed in the glass sleeve. This solution has drawbacks in that the onset of leakage is merely prolonged and the syringe will require more axial force to pump the liquid. The requirement of more axial force will subject associated components to greater wear and higher costs in design to handle the increased load. In situations where pumping through the syringe is continuous or high volume, the need for increased axial force will increase power input requirements and associated costs.

SUMMARY OF THE PRESENT INVENTION

[0007] Some embodiments of the present invention provide a syringe or syringe pump system that has superior resistance to leakage, chemicals, and heat, such as in high volume or continuous cycle environments, while also having low pumping force requirements.

[0008] The present invention is directed to a syringe and syringe pump system having a plunger and an elastic sleeve, wherein the sleeve and plunger are sized such that the outside diameter of the plunger is greater than the inside diameter of the sleeve, thereby causing elastic deformation of the sleeve during use.

[0009] One embodiment of the present invention provides a syringe, comprising an elastic sleeve defining a fluid chamber, and a plunger positioned within the elastic sleeve, wherein the outer diameter of the plunger is greater than the inner diameter of the elastic sleeve such that the plunger elastically deforms the sleeve during use. The elastic sleeve may comprise a syringe sleeve and a surrounding sleeve, wherein the fluid chamber is defined by the interior of the syringe sleeve and the syringe sleeve is positioned within the interior of the surrounding sleeve. The surrounding sleeve may comprise an elastomeric material which provides a compressive force against the outer surface of the syringe sleeve upon deformation of the sleeve during use. The syringe sleeve may comprise a semi-rigid thermoplastic material, such as a fluoroplastic chosen from the groups consisting of: PTFE, PFA and FEP. The surrounding sleeve may comprise, for example, silicone.

[0010] The syringe may further comprise a housing which encloses the elastic sleeve. The housing may include a first end cap located at the proximal end of the syringe sleeve, a second end cap positioned at the distal end of the syringe sleeve, and at least one sidewall extending between the end caps (e.g., a hollow tube secured to the first and second end caps such that an annular space is provided between the tube and the elastic sleeve). The syringe may further comprise a rod which extends distally away from away from the plunger, and the first end cap may include an opening through which the rod extends. The second end cap may include at least one fluid passageway in fluid communication with the fluid chamber. The proximal end of the second end cap may include a chamber, and an insert member configured for insertion into the chamber of the second end cap may also be provided. The distal end of the elastic sleeve may be secured within the chamber between the wall of the chamber and the insert member.

[0011] Another embodiment of the present invention provides a syringe pump system. This syringe pump system may include an elastic sleeve defining a fluid chamber, a plunger positioned within the elastic sleeve, wherein the outer diameter of the plunger is greater than the inner diameter of the elastic sleeve such that the plunger elastically deforms the sleeve during use, an intake conduit having a first check valve associated therewith and in fluid communication with the fluid chamber, and an output conduit having a second check valve associated therewith and in fluid communication with the fluid chamber. Fluid may be drawn into the syringe pump through the intake conduit and the first check valve, and thereafter expelled from the syringe pump through the output conduit and the second check valve upon reciprocation of the plunger.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a schematic, partially cross-sectional illustration of a syringe system according to one embodiment of the present invention;

[0013] FIG. 2 is a schematic, partially cross-sectional illustration of a syringe according to one embodiment of the present invention;

[0014] FIG. 3 is a schematic, cross-sectional, exploded illustration of the distal end cap and insert member of the syringe shown in FIG. 2; and

[0015] FIG. 4 is a schematic, cross-sectional illustration of the proximal end cap of the syringe shown in FIG. 2; and

[0016] FIG. 5 is a schematic, partially cross-sectional illustration of a plunger which may be used in an embodiment of the present invention.

DETAILED DESCRIPTION

[0017] Embodiments of the present invention provides syringes and syringe systems which provide reduced friction between the plunger and the wall of the fluid chamber, reduced wear on components such as the plunger, and/or simplified manufacturing due to an ability to compensate for misalignment and less stringent tolerances. With respect to the reduced friction feature, embodiments of the present invention have lower pumping force requirements. Thus, for example, when a syringe according to an embodiment of the present invention is motor driven (i.e., a motor causes reciprocal movement of the plunger), less power is needed. In fact, this can allow a single motor to drive multiple syringes.

[0018] According to embodiments of the present invention, a syringe is provided comprising an elastic sleeve defining the fluid chamber of the syringe, and a plunger positioned within the elastic sleeve. The outer diameter of the plunger is oversized (i.e., greater than the inner diameter of the elastic sleeve) such that the plunger (in particular, the distal head portion of the plunger) will elastically deform the sleeve during use. As used herein, this elastic deformation simply means that the portion of the elastic sleeve which is adjacent the plunger at any given time is forced outward--thus creating a bulge in the wall of the elastic sleeve at the location of the plunger (see FIG. 2). However, because this deformation is elastic, as the plunger is moved axially away from the deformed region of the sleeve and thus no longer applies an outward force against the interior wall of the sleeve, the deformed region of the elastic sleeve will return to its original size and shape. Oversizing the plunger in this manner will also reduce the risk of leakage (the interior walls of the elastic sleeve will essentially mold to the outer surface of the plunger). Furthermore, the materials used for the plunger and at least the portion of the elastic sleeve forming the wall of the fluid chamber in some embodiments comprise materials having low coefficients of friction (e.g., fluoroplastics), thus providing the friction reductions mentioned above even though the plunger is oversized.

[0019] In some embodiments, in order to provide desired properties such as chemical resistance and inertness, low coefficient of friction, reduced wear, and high temperature resistance for the portion of the sleeve providing the fluid chamber of the syringe, while also ensuring that the sleeve is elastic (i.e., resumes its original shape when not being deformed by the plunger), the elastic sleeve may be formed from two or more layers of materials having distinct properties. For example, the elastic sleeve may comprise at least one semi-rigid sleeve member positioned within at least one elastomeric sleeve member (i.e., concentric to one another) such that, upon deformation of the at least one semi-rigid sleeve member, the at least one elastomeric sleeve member will provide a restoring force against the semi-rigid sleeve member such that it is returned to its original size and shape. The term "semi-rigid" simply means that the sleeve may be readily deformed by the plunger (due to the over-sizing of the plunger), but a deformed portion of the sleeve would not fully return to its original shape without the application of a restoring force. In one particular embodiment of the present invention (e.g., FIGS. 1 and 2) a semi-rigid syringe sleeve is surrounded by an elastomeric surrounding sleeve (with the surrounding sleeve sized to fit snugly over the syringe sleeve). The elastomeric surrounding sleeve provides the necessary restoring force since it is deformed with the syringe sleeve yet has the necessary elastic properties to force the syringe sleeve back to its orginal shape.

[0020] A syringe system 10 according to one embodiment of the present invention is diagrammatically shown in partial cross-section in FIG. 1. A plunger 12 having a rod 14 which may be attached to the plunger or formed integrally therewith is movably coupled to a drive system 16 of any one of the type generally known to those skilled in the art in order to impart linear, reciprocal motion to the plunger 12 as indicated by the arrow 18. In the embodiment of FIG. 1, plunger 12 has a round profile when viewed from the top (not shown), though it could vary among a variety of geometrical configurations (see, e.g., FIG. 5).

[0021] A syringe sleeve 20 is shaped cylindrically to cooperate in sealing engagement with the plunger 12 which is positioned therein. However, sleeve 20 may be configured in any geometrical shape that cooperates with the plunger 12 for sealing engagement, though in the embodiment shown it has a round cross-section. The lateral dimension or inner diameter of the sleeve 20 is smaller than the lateral dimension or outer diameter of the plunger 12 in order to provide a compressive fit when the plunger 12 is positioned inside the sleeve 20.

[0022] By way of example, the plunger 12, may be made from a variety of materials such as PCTFE (polychlorotrifluoroethylene, e.g., Kel-F.RTM.) or another suitable plastic with similar properties relating to chemical. temperature and fatigue resistance, as well as resiliency, impermeability, and chemical inertness (e.g., other fluoroplastics). While a more rigid material may be used for plunger 12, including glass or metal, such rigid materials would cause greater wear on the sleeve 20. The selection of a fluoroplastic such as PCTFE provides an appropriate balance of strength, smoothness and limited elasticity. Depending on a particular application and its parameters, as well as the selection of material and dimension for the sleeve 20, another material may be selected for plunger 12, such as various thermoplastics (e.g., fluoroplastics such as PTFE, FEP, or PFA. As is known to those skilled in the art, it may also be desirable to avoid the use of an indentical material for plunger 12 and sleeve 20.

[0023] By way of example, the sleeve 20 may be made from PTFE (Teflon.RTM., for example) or another fluoroplastic, as fluoroplastics have high chemical and temperature resistance in addition to some elasticity. Fluoroplastics also have extremely low coefficients of friction--an advantageous property since, among other things, it will reduce the force required to reciprocate the plunger. Other suitable fluoroplastics include PFA (perfluoroalkoxy resin), and FEP. Sleeve 20 can comprise an extruded, thin-walled polymer tube.

[0024] The combination of materials used for the sleeve 20 and plunger 12 provides minimal frictional resistance in combination with sufficient sealing capability during pumping of a liquid.

[0025] The syringe chamber 22 is in fluid communication with an intake conduit 24 having a check valve 26, and an output conduit 28 having a check valve 30 (such fluid communication may be provided within end cap 36 described further herein). Of course any number and type of fluid outlets, conduits, valves, and connector elements may be provided. For example, the check valves could be replaced by one or more multi-port selection valves (e.g., a rotary selection valve), thus providing a syringe system for selectively delivering and/or extracting fluid by operation of the selection valve(s) and a drive system which reciprocates the plunger. In the embodiment shown in FIG. 1, the syringe system 10 is essentially a positive displacement pump which is operated merely by reciprocating plunger 12 (e.g., manually or using a drive system 16 which causes reciprocal movement of plunger rod 14 and hence plunger 12 within syringe sleeve 20.

[0026] As also shown in FIG. 1, a silicone sleeve 32 surrounds the syringe sleeve 20. Of course silicone is merely exemplary, as other elastomeric materials with sufficient elasticity and restoring energy for restoring syringe sleeve 20 may be used for the surrounding sleeve 32. A housing comprises a lower end cap 34, having an opening 36 and seals 38 for the rod 14 and other components; an upper end cap 36 cooperating with various seals 38 as shown; and a set of sidewalls 40. The sidewalls 40 may comprise of any number such as four, that encloses the other components and supports the end caps 34 and 36 or a single cylindrical sidewall (not shown) may be used. The seals 38 may be O-rings or other seals, including seal assemblies of the type known to those skilled in the art. The various components may also be affixed to one another using and adhesive (e.g., an epoxy glue), heat welding, ultrasonic welding, snap-fitttin, or other suitable means known to those skilled in the art. The gap 42 between the sidewalls 40 and the silicone sleeve 32 may be filed with a compressible medium such as, but not limited to, gel, liquid, air, or foam, in order to provide additional support to the surrounding sleeve 32 and the syringe sleeve 20. The drive mechanism 16 may have any one of various types of internal gearing such as rack and pinion and it may be adapted to simultaneously drive two or more syringe pumps made in accordance with the present invention and mounted to a bench or freestanding work station.

[0027] FIGS. 2-4 depict another embodiment of a syringe 110 according to the present invention. Syringe 110 once again includes a fluid chamber 122 defined by the interior of a flexible sleeve which is elastically deformed by plunger 112 during use (i.e., as plunger 112 moves in either or both of the directions indicated by arrow 118).

[0028] Plunger 112 can have any of a variety of shapes and configurations, and that shown in FIG. 2 is merely exemplary. FIG. 5 depicts an alternative embodiment for a plunger 212 and a plunger rod 214 attached thereto. Plunger 112 can be made from any of a variety of materials, particularly thermoplastics such as fluoroplastics. Exemplary materials include PTFE, PCTFE (e.g., Kel-F.RTM.), FEP and PFA.

[0029] As also seen in FIG. 2, a plunger rod 114 is attached to, and extends away from the proximal end of plunger 112. Plunger rod 114 may once again be attached to any suitable drive system 116, or may even be configured for manual use (e.g., by providing a handle or other device at the proximal end of plunger rod 114 in order to facilitate manual use of syringe 110). Plunger rod 114 may be made from any of a variety of materials, particularly rigid materials such as stainless steel.

[0030] Syringe 110 shown in FIG. 2 also includes a flexible, elastic sleeve which is elastically deformed by plunger 112, as shown in FIG. 2. (It should be noted that the thickness of the elastic sleeve components and the outer housing 140 in FIG. 2 have been exaggerated to more clearly depict the deformation of the elastic sleeve). The outer diameter of plunger 112 is greater than the inner diameter of the flexible sleeve of syringe 110 such that plunger 112 will urge the adjacent region of the elastic sleeve outwardly. Thus, the flexible sleeve will bulge outwardly in the region adjacent plunger 112, and the bulge thus created will travel along the sleeve as plunger 12 is moved in the directions shown by arrow 118. As the plunger moves away from a deformed region of the elastic sleeve, that region will return to its original size and shape, this ensuring a fluid tight fit between the plunger and the elastic sleeve even after repeated use of the syringe. While the elastic sleeve of syringe 110 may comprise a single, sleeve element, the embodiment of FIG. 2 once again includes a pair of sleeves which provide the elastic sleeve member of syringe 110.

[0031] In particular, syringe 110 includes a syringe sleeve 120 and an elastomeric surrounding sleeve 132 which surrounds syringe sleeve 120. Syringe sleeve 120 may be made from a thermoplastic material, such as a fluoroplastic. Exemplary materials include PTFE, FEP and PFA, all of which provide reduced friction, thereby minimizing the force needed to move plunger 112, as well as chemical resistance and inertness. The material used for syringe sleeve 120 may also provide a sleeve 120 which is semi-rigid so that sleeve 120 may be deformed by plunger 112, as shown. In the embodiment shown, syringe sleeve 120 is not itself formed from an elastomeric material, since elastomers tend to have less chemical resistance than thermoplastics such as PTFE, FEP or PFA. It should be pointed out that fluoroplastics (e.g., PTFE, FEP and PFA) and the like do have some elasticity, particularly when extruded into a thin-walled tube which is then deformed in the manner shown in FIG. 2. However, these materials will take a set (due to creep or cold flow)--meaning that they will not fully return to their original size and shape without the application of a restoring force. Therefore, in order to ensure that the walls of syringe sleeve 120 return to their original inside diameter after passage of plunger 112, elastomeric sleeve 132 surrounds syringe sleeve 120 such that elastomeric sleeve 132 will urge syringe sleeve 120 back to its original size and shape. Elastomeric sleeve 132 will be deformed in the region adjacent plunger 112, as shown, since it is formed from an elastomer. However, the deformed region of elastomeric sleeve 132 will return to its original shape once plunger 112 has moved to a new location (i.e., plunger 112 is no longer applying an outward force to the previously-deformed region). Because of this, sleeve 132 will also urge syringe sleeve 120 back to its original size and shape, thus ensuring a fluid-tight fit between plunger 112 and syringe sleeve 120, even after repeated use.

[0032] Syringe 110 shown in FIGS. 2-4 also includes a pair of end caps, namely proximal (or first) end cap 134 and distal (or second) end cap 136. Syringe sleeve 120 extends between end caps 134 and 136, as shown. Plunger rod 114 extends through a central bore 135 provided on proximal end cap 134, as shown in FIGS. 2 and 4. However, in this embodiment, central bore 135 is approximately equivalent in size to the outer diameter of syringe sleeve 120 such that plunger rod 114 will not contact bore 135 of proximal end cap 134. In this manner, plunger rod 114 is free to float with respect to proximal end cap 134. This not only simplifies manufacturing and assembly, but also eliminates the need for precise alignment of plunger rod 114 and drive system 116. In addition, this arrangement also reduces the force required to reciprocate plunger 112 since there is no frictional contact between plunger rod 114 and any component of syringe 110.

[0033] As best seen in FIG. 4, proximal end cap 134 essentially comprises a cylindrical ring having a shoulder 147 extending around the outer circumference thereof. As further discussed herein, the size (or depth) of shoulder 147 may be approximately equivalent to the wall thickness of outer sidewall (or tube) 140, such that outer tube 140 may be secured to proximal end cap 134 and abut against shoulder 147, thus providing a smooth transition between end cap 134 and outer tube 140 (see FIG. 2). As also seen in FIG. 2, the proximal end of syringe sleeve 120 may be secured to the interior wall of end cap 134, such as by use of an adhesive, heat welding, ultrasonic welding, snap fitting, or other known or suitable attachment means. However, in some embodiments, it may not be necessary to attach syringe sleeve 120 to end cap 134. Tube 140 may similarly be attached to the end caps by means of an adhesive (e.g., epoxy), heat welding, ultrasonic welding, snap fitting, or other known or suitable attachment means.

[0034] Syringe 110 also includes a distal end cap 136, as best seen in FIGS. 2 and 3. Like end cap 134, distal end cap 136 can be made from any of a variety of materials, particularly various types of thermoplastics. In the embodiment of FIG. 2, there is generally no fluid contact with end caps 134 and 136. Therefore, chemical resistance is not as significant of a factor with respect to these two components. One suitable material for end caps 134 and 136 is PEEK.

[0035] As best seen in FIG. 3, distal end cap 136 includes a hollow, cylindrical body 137 and a connection member 139 extending away from the distal end of body member 137. In the embodiment shown, connection member 139 merely comprises a hollow cylinder having a central passageway (or bore) 146 extending therethrough. However, connection member 139 may have any of a variety of shapes and configurations, and may be configured in order to facilitate attachment of the syringe to a variety of devices. For example, connection member 139 may alternatively comprise a male or female-threaded connector, a Luer connector, or any of a variety of other connecting elements known to those skilled in the art. A quick disconnect fitting may also be attached at the distal end of connection member 139 in order to facilitate attachment of syringe 110 to a valve structure, or other apparatus or device. It is even contemplated that a hypodermic needle may be attached to connection member 139 (particularly when connection member 139 comprises a Luer connector), thus allowing the syringe to be used for the injection or withdrawal of fluids from a patient and other similar uses.

[0036] Like end cap 134, cylindrical body 137 of distal end cap 136 includes a shoulder (or flange) 143 which extends about the outer circumference of body 137. Once again the depth of shoulder 143 may be approximately the same as the wall thickness of outer tube 140, and outer tube 140 may be attached to end cap 136 such that the distal end of outer tube 140 abuts against shoulder 143, as shown. Outer tube 140 may be attached to end cap 136 in the same manner as described previously.

[0037] As mentioned previously, cylindrical body member 137 is generally hollow in nature, thus providing a chamber 145 at the proximal end of end cap 136. The distal end of syringe sleeve 120 may be inserted into chamber 145. In order to ensure a fluid-tight connection between syringe sleeve 120 and end cap 136, an insert member 150 is also provided. Insert 150 includes a first cylindrical portion 151 and a second cylindrical portion 152 extending away from the distal end wall 153 of first cylindrical portion 151. A bore 155 extends through both first and second cylindrical portions 151 and 152. During assembly, the distal end of syringe sleeve 120 is inserted into chamber 145 of body member 137 of distal end cap 136, and thereafter insert 150 is inserted into chamber 145 such that second cylindrical portion 152 extends through bore 146 on end cap 136 and first cylindrical portion 151 is positioned within chamber 145. The distal end wall of silicone sleeve 120 will thus be positioned within chamber 145, between the outer circumferential surface of first cylindrical portion 151 of insert 150 and the interior sidewall of chamber 145. In addition, chamber 145 and insert 150 may be sized and configured such that distal end wall of syringe sleeve 120 will be compressed between chamber 145 and the outer circumferential surface of first cylindrical portion 151 of insert 150 in order to secure syringe sleeve 120 to end cap 136.

[0038] In the embodiment shown in FIG. 3, a ridge 144 extends around the inner circumference of the proximal end of chamber 145 of end cap 136. The distal end of syringe sleeve 120 is folded outwardly down over the outer surface of syringe sleeve 120, as best seen in FIG. 2. The folded portion of syringe sleeve 120 is positioned within the interior of body portion 137, distally of ridge 144. The height of ridge 144 is such that once the distal end of sleeve 120 is inserted into end cap 136 and insert 150 has been secured to end cap 136 as shown in FIG. 2, ridge 144 will ensure that the distal end of syringe sleeve 120 remains within the interior of end cap 136, secured between insert 150 and the interior sidewall of chamber 145. In fact, once insert 150 has been secured to end cap 136, it may not be necessary to bond or otherwise secure syringe sleeve 120 to either end cap 136 or insert 150. For example, insert member 150 may be press or snap-fit into end cap 136 (e.g., by appropriate sizing of cylindrical portion 152 with respect to bore 146 on end cap 136. Alternatively, insert member 150 may be adhesively bonded to end cap 136 or attached via heat welding, ultrasonic welding, or other attachment means. It is also contemplated that insert member 150, end cap 136 and the distal end portion of syringe sleeve 120 may be attached to one another in the same manner (e.g., by use of an adhesive applied within chamber 145 and, if desired within bore 146.

[0039] Since insert 150 will be in fluid contact, it will often be desirable to manufacturer insert 150 from a chemically-resistant and inert material. Such materials include any of a variety of thermoplastics, such as fluoroplastics, including PTFE, FEP, PCTFE or PFA.

[0040] As mentioned previously, syringe 110 also includes an outer tube 140. Outer tube 140 may simply comprise a clear plastic tube, and is principally intended to protect the flexible sleeve and plunger components of syringe 110 and provide an aesthetically pleasing appearance. Visible indicia may be provided on tube 150 in order to facilitate use of syringe 110, such as measurement lines imprinted on or molded into tube 140. Since the materials used to manufacturer the flexible sleeve components (i.e., syringe sleeve 120 and elastomeric sleeve 130) will often not provide a clear view of fluid chamber 122 and the position of plunger 112, measurement lines and the like may not necessarily provide a precise indication of fluid volume within syringe 110. However, the bulge in the flexible sleeve caused by plunger 112 will generally be visible through tube 140. One exemplary material for tube 140 is commercial grade acrylic resin, however, any of a variety of materials may be employed.

[0041] As also seen in FIG. 2, elastomeric sleeve 132 is shorter in length than syringe sleeve 120. In fact, once assembled, elastomeric sleeve 132 encircles syringe sleeve 120 and only extends between end caps 134 and 136. Elastomeric sleeve 132 may be made from any of a variety of elastomeric materials. In general, the composition and wall thickness of elastomeric sleeve 132 should be such that it provides sufficient compressive force against the exterior wall of syringe sleeve 120 in order to return syringe sleeve 120 to its original size and shape after passage of plunger 112 (i.e., to return a deformed region of sleeve 120 to its original size and shape once that deformed region is no long adjacent plunger 112). One particularly suitable material is silicone. In general, the inner diameter of elastomeric sleeve 132 may be equal to or slightly less than the outer diameter of syringe sleeve 120, thus not only ensuring that elastomeric sleeve 132 remains in place on syringe sleeve 120 (provides a snug fit), but also ensuring that elastomeric sleeve 132 will be able to fully restore syringe sleeve 120 to its original size and shape in regions to which plunger 112 is not adjacent.

[0042] As with the previous embodiment, the outer diameter of plunger 112 (defined as the maximum outer diameter of any portion of the plunger, particularly when non-cylindrical plungers such as plunger 212 in FIG. 5 are employed) is greater than the interior diameter of syringe sleeve 120. The difference in diameter should be sufficient to ensure a fluid-tight seal between the plunger and the syringe sleeve, to cause deformation of the syringe sleeve wall adjacent the location of the plunger, and allow the plunger to freely slide within the syringe sleeve with minimal force. In one exemplary embodiment, and by way of example only, a PTFE plunger 112 having an outer diameter of 0.578 inches may be employed with a cylindrical syringe sleeve made from FEP having an inner diameter of 0.575 inches and a wall thickness of 0.012 inches. In such an embodiment, the elastomeric sleeve may be a cylindrical silicone sleeve having an inner diameter of 0.599 inches and a wall thickness of 0.015 inches.

[0043] In some embodiments of the present invention, the elastic sleeve may be formed from one or more thin-walled tubes. In the case of the syringe sleeve, it may comprise an extruded, thin-walled thermoplastic tube, such as a fluoroplastic tube (e.g., PTFEF, FEP or PFA). By way of example, the wall thickness for the syringe sleeve may be between about 0.008 and about 0.062 inches. In the case of the surrounding sleeve (e.g., a thin-walled silicone tube) the wall thickness may be between about 0.008 and about 0.125 inches.

[0044] The embodiments described herein may used for a variety of tasks such as, but not limited to, metering, pumping in product mixing or packaging, and controlling flow in laboratory environments.

[0045] While the various embodiments of the present invention have been herein described, it is understood that various modifications can be made without departing from the scope of the invention.

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