Patent Description:
The present invention relates generally to syringes for transferring (i.e., injecting or withdrawing) fluids. In particular, but not by way of limitation, embodiments of the present invention relate to low cost insulin injection syringes in which the low cost is achieved by separating the syringe into two types of components, namely, durable components that that do not contact the fluid path and can be reused, and disposable or single-use components that contact the fluid path and are not reused. Methods for making, using and packaging such syringes are also disclosed herein.

Most syringes in use today are of the disposable or single-use type. A typical disposable syringe is made primarily of plastic and has several key components. The largest, and the one containing the most material, is the plastic barrel. The scale printing on the barrel is a critical and costly assembly step that is needed to assure proper dosing by the user. Inside the barrel is a rubber stopper that is used to create a hermetic seal and displace the liquid medication or other fluid into and out of the barrel. A plastic plunger rod interfaces with the rubber stopper to move it back and forth under the user's control. A metal needle or cannula is usually attached to the distal end of the barrel to allow fluids to be injected into or removed from the body, although this is not always the case. For example, a syringe having a male Luer connector at its distal end can be attached to a female Luer connector on a catheter or IV line to inject or withdraw fluids without the use of a needle or cannula.

In the management of diabetes, disposable plastic syringes are often used to administer liquid insulin to a user several times a day. These single-use syringes typically have clear polymeric barrels with printed scale numbers that allow the user to draw up an accurate dose of insulin from a vial, and fine-gauge metal needles (usually about <NUM> to <NUM> in length) that inject the dose into the skin with minimal discomfort to the user. The needles may be detachably connected to the barrels using Luer-Lok™ or Luer slip connections, or they may be permanently attached or "staked" to the barrels during manufacture of the syringes. Insulin syringes usually have a capacity of <NUM> or less (with <NUM>, <NUM> and <NUM> barrel sizes being common), with scale markings on the barrel representing units of a specific type of insulin (e.g., U-<NUM> or U-<NUM> insulin). Insulin syringes may also be provided with safety features to prevent reuse of the syringe, to shield the used needle, or both. Because insulin syringes are used only once and a user usually requires several of them each day, they are commonly sold in boxes or bags containing multiple syringes.

In insulin syringes of the type described above, there are no durable (reusable) components. The entire syringe is disposed of after a single use, and none of the components are reused. While disposal of a single-use syringe is advantageous in ensuring sterility and preventing the spread of blood-borne diseases, the expense of providing all of the required syringe components and assembly steps for only a one-time use is higher than might be desired. Discarded syringes also create a disposal burden in hospitals and other medical facilities, since they cannot be mixed with other types of medical waste and must instead be placed in dedicated sharps disposal containers. Therefore, a need exists for a syringe in which the expense and disposal burden associated with one-time use is reduced, while preserving the sanitary advantages of a single-use syringe.

<CIT> discloses a measurement sleeve adapted for use with a medication syringe.

<CIT> discloses a safety hypodermic syringe with a detachable plunger.

The subject matter of the invention is defined by each of independent claims <NUM>, <NUM> and <NUM>.

In accordance with embodiments of the present invention, a low cost syringe is provided by separating the syringe into two types of components, namely, durable components that do not contact the fluid path and can be reused, and disposable or single-use components that contact the fluid path and are not reused. The ability to reuse the durable components reduces the effective per-unit cost of the syringe when multiple syringes are used. Since these components do not contact the fluid path, sterility is not affected. The disposal burden is also reduced because not all of the syringe components need to be disposed of each time a syringe is used.

Two different syringe components - a reusable outer sleeve containing scale markings for the syringe, and a reusable syringe plunger - are provided as durable components in embodiments of the present invention. Syringes manufactured according to the present invention can employ one or both of these durable components.

More specifically, one aspect of the present invention relates to a syringe comprising a barrel assembly having a disposable tubular insert and a reusable outer sleeve, the tubular insert forming a fluid reservoir and having a fluid opening at a distal end thereof, the reusable outer sleeve being detachably received on an outer surface of the tubular insert and having visible scale markings thereon; a stopper movably received in the tubular insert for sealing a proximal end of the tubular insert and for displacing fluid into or out of the tubular insert through the fluid opening upon movement of the stopper within the tubular insert; and a user-operable plunger coupled to the stopper for causing the stopper to move within the tubular insert and thereby displace fluid into or out of the tubular insert through the fluid opening under the control of the user.

In another aspect, the present invention relates to a syringe comprising a disposable portion including a fluid reservoir having a fluid opening at a distal end thereof and a stopper movably received in the fluid reservoir for sealing a proximal end of the fluid reservoir and for displacing fluid into or out of the fluid reservoir through the fluid opening upon movement of the stopper within the fluid reservoir; and a reusable portion comprising a user-operable plunger detachably coupled to the stopper for causing the stopper to move within the fluid reservoir and thereby displace fluid into or out of the fluid reservoir through the fluid passage under the control of the user.

Additional aspects of the invention relate syringe multipacks in which the durable and disposable components of the syringe are packaged for sale or use.

Aspects and advantages of embodiments of the invention will be more readily appreciated from the following detailed description, taken in conjunction with the accompanying drawings, in which:.

Reference will now be made in detail to embodiments of the present invention, which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments described and illustrated herein exemplify, but do not limit, the present invention, and the drawings are not necessarily to scale with respect to each other or with respect to actual physical embodiments. Further, it will be understood by one skilled in the art that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Unless limited otherwise, the terms "connected," "coupled," and "mounted," and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms "connected" and "coupled" and variations thereof are not restricted to physical or mechanical connections or couplings. Further, terms such as "up", "down", "bottom", "top", "distal" and "proximal" are relative, and are employed to aid illustration, but are not limiting.

<FIG> and <FIG> illustrate a syringe <NUM> according a first embodiment of the invention. The syringe <NUM> comprises a tubular barrel assembly that includes a disposable tubular insert <NUM> and a reusable outer sleeve <NUM> that is open at both ends and coaxially receives the insert <NUM>. The disposable tubular insert is preferably made of a plastic (polymeric) material, such as polypropylene, that can be inexpensively injection molded. The reusable outer sleeve <NUM> is preferably also made of a plastic material, such as polypropylene, polystyrene, polycarbonate or ABS, but can also be made of a metal such as stainless steel. In general, it is preferred that the reusable outer sleeve <NUM> be made from a relatively stiff and durable material, whereas the disposable insert <NUM> can be made from a thinner, less rigid material. The upper portion of the tubular insert <NUM> can be seen in the partially disassembled view of <FIG>. The lower portion of the tubular insert <NUM> is partially obscured by the outer sleeve <NUM> in <FIG>, but is visible through an elongated rectangular slot <NUM> formed lengthwise in the outer sleeve <NUM>. <FIG> shows the tubular insert <NUM> fully received in the outer sleeve <NUM> as would be the case during use of the syringe <NUM>.

The tubular insert <NUM>, which is shown alone in <FIG>, is designed to be disposable and forms a fluid reservoir for the fluid (not shown) that is to be injected or withdrawn by the syringe <NUM>. The volume of the fluid reservoir varies according to the position of a separate rubber stopper <NUM> which seals the proximal end of the insert <NUM>. The stopper <NUM> is movably received in the tubular insert <NUM> for displacing fluid into or out of the tubular insert <NUM> through a fluid opening <NUM> at the distal end of the tubular insert <NUM>.

A plastic plunger <NUM> (shown in <FIG> but omitted from <FIG> and <FIG>) having its distal end connected to the stopper <NUM> causes the stopper <NUM> to move up or down within the tubular insert <NUM> and thereby displace fluid into or out of the tubular insert <NUM> through the fluid opening <NUM> under the control of the user. A thumb press <NUM> integrally formed at the proximal end of the plunger <NUM> allows the user to pull or push on the plunger <NUM> as required. A flange <NUM> with opposed arms is integrally formed near the proximal end of the tubular insert <NUM> and can be held by a user's fingers when operating the plunger <NUM>. An annular collar <NUM> is integrally formed at the proximal end of the tubular insert <NUM>, above the flange <NUM>, to receive a removable sterile cap (not shown) that covers the proximal end of the syringe <NUM> before use. With the plunger <NUM> fully depressed, the thumb press <NUM> is slightly elevated above the collar <NUM> so that the thumb press <NUM> can be grasped to operate the plunger <NUM>.

In the embodiment shown, the fluid opening <NUM> is formed in a reduced diameter distal end portion <NUM> of the tubular insert <NUM> which is intended to receive a permanently attached or "staked" needle or cannula (not shown). The use of a staked needle can be advantageous in reducing fluid dead space within the insert <NUM>. Alternatively, the distal end portion <NUM> can be formed as a male Luer slip or Luer Lok™ connector which allows the tubular insert <NUM> to be affixed to a separately provided needle or cannula <NUM> via a hub <NUM>. The Luer connector can also be used to couple the syringe <NUM> directly to a female Luer connector on a catheter or IV line without the use of a needle or cannula. In the case of a Luer Lok™ connector, the tapered Luer tip can be formed integrally with the insert <NUM>, and the internally threaded locking collar can be formed integrally with the sleeve <NUM>. Alternatively, both portions can be formed integrally with the insert <NUM>. Another possibility is to provide a snap fit between the hub <NUM> and the reduced diameter distal end portion <NUM> of the tubular insert, in lieu of a Luer connection. Whether separate or permanently affixed, the needle or cannula may have a sharp tip for penetrating the skin or a pro re nata (PRN), or it may consist of a blunt cannula of the type used to access a needleless connector.

For cost reasons, the disposable tubular insert <NUM> is preferably devoid of any printed indicia that require separate manufacturing steps, including the printed scale markings that are typically needed for proper operation of the syringe <NUM>. Instead, the required scale markings <NUM> are provided on the outer sleeve <NUM>, which can be detached from the used syringe <NUM> and reused. The scale markings <NUM> on the outer sleeve <NUM> may take the form of a combination of lines and numerals representing milliliters or units of insulin, as shown in <FIG> and <FIG>, or any other suitable form as may be required for the specific application. The scale markings <NUM> may be ink-printed or laser-printed, embossed, engraved, laser-etched, or a combination of these (e.g., embossed with an ink-printed overlay for increased legibility). The embossing or engraving may be accomplished as part of the injection molding process that is used to manufacture the outer sleeve <NUM> (if it is made of plastic), with any desired ink-printing carried out during a separate manufacturing step.

The lengthwise slot <NUM> in the outer sleeve <NUM> allows the user to directly view the tubular insert <NUM>, which is transparent or translucent, so that the fluid level in the tubular insert <NUM> can be viewed and compared with the scale markings <NUM> on the outer sleeve <NUM>. Due to the presence of the slot <NUM>, the outer sleeve <NUM> can be made partially or completely opaque if desired, although it will normally be preferable to make the outer sleeve <NUM> transparent or translucent so that the fluid level can be seen to some extent through its walls (although perhaps less clearly than through the slot <NUM>). The slot <NUM> can be omitted if the outer sleeve <NUM> is made sufficiently transparent or translucent so that the fluid level in the tubular insert <NUM> can be seen through the walls of the outer sleeve <NUM> with enough precision for proper dosing. Alternatively, the slot <NUM> can be replaced by a transparent or translucent window in embodiments where the outer sleeve <NUM> is partially or completely opaque.

A detachable connection is provided between the disposable tubular insert <NUM> and the reusable outer sleeve <NUM> so that the two components can be coupled together and used in the same manner as a conventional syringe, and then separated to allow for reuse of the outer sleeve <NUM>. This connection can be a simple friction or press fit between all or portions of the cylindrical outer surface of the tubular insert <NUM> and the cylindrical inner surface of the outer sleeve <NUM>, or a clamshell connection if the sleeve <NUM> is split or hinged. However, given the importance of axially positioning the scale markings <NUM> in such a way that they accurately and consistently represent the correct fluid volume within the tubular insert <NUM>, a more precise and positive releasable locking arrangement will usually be desired. The locking function is primarily needed in the axial direction because that is the direction in which the fluid level is compared with the scale markings <NUM>, but in some applications rotational locking (i.e., prevention of relative rotation between the tubular insert <NUM> and the outer sleeve <NUM>) may also be needed or desired.

One axial locking arrangement, referred to as a collar lock, is shown in <FIG> and <FIG>. In this arrangement, the tubular insert <NUM> bottoms out on an annular lip <NUM> formed at the bottom of the sleeve <NUM> when it reaches its full insertion point within the sleeve. At this point a separate collar <NUM> with internal threads <NUM>, which is received on an externally threaded proximal end portion <NUM> of the sleeve <NUM>, is rotated so that it advances from a location <NUM> on the sleeve <NUM> to a slightly more proximal location <NUM>. The threaded end portion <NUM> has a slightly greater outside diameter at the location <NUM> than it does at the location <NUM>. Cuts or gaps <NUM> divide the proximal end portion <NUM> into three or more portions which are relatively flexible. When the collar <NUM> is rotated to the location <NUM>, the increasing diameter of the threaded end portion <NUM> causes these flexible portions to be squeezed inwardly to grip the insert <NUM> and thereby lock the sleeve <NUM> and the insert <NUM> to each other both axially and rotationally. In an alternative embodiment, the threaded end portion <NUM> has a slightly greater outside diameter at the location <NUM> than it does at the location <NUM>, and the collar <NUM> is rotated so that it advances from the location <NUM> to the location <NUM> to secure the sleeve <NUM> to the insert <NUM>.

The user initially receives the syringe <NUM> with the outer sleeve <NUM> either already attached or provided as a separate component which the user attaches to the insert <NUM> before use. If a needle or cannula <NUM> is required for the intended fluid transfer but is not pre-affixed or pre-attached to the insert <NUM>, the user also attaches the required needle or cannula. The user then performs the fluid transfer, which may consist of a fluid aspiration (e.g., of insulin from a vial), an injection of fluid into the body, a delivery of fluid into a catheter or IV line, or a withdrawal of fluid from the body (e.g., a blood sample), or some combination of these steps. In doing so, the user can observe the amount of fluid in the syringe <NUM> by comparing the fluid level that is visible through the slot <NUM> with the scale markings <NUM> on the outer sleeve <NUM>. When the fluid transfer is complete, the user removes the outer sleeve <NUM> by unscrewing the collar <NUM> and discards the remaining portion of the syringe <NUM>. The outer sleeve <NUM> and collar <NUM> can then be reused as part of another syringe <NUM> by attaching it to another insert <NUM> and repeating the steps above.

Several advantages of the disclosed syringe <NUM> will be apparent. For example, there is a reduction in the effective per-unit cost of the syringe (perhaps up to <NUM>%) because a labor intensive manufacturing step (printing of the scale markings) is performed on a component of the syringe <NUM> (the outer sleeve <NUM>) that can be used multiple times before being discarded. Such reuse does not compromise the sterility of the syringe because the outer sleeve <NUM> and collar <NUM> do not come into contact with body fluids or with the fluid being transferred by the syringe <NUM>. Another advantage is that the reusable outer sleeve <NUM> can be made of a sufficiently rigid material, such as polycarbonate or even metal, to reduce the rigidity required of the insert <NUM>. In other words, the walls of the insert <NUM> can be made thinner than would otherwise be required to withstand handling by the user and the internal fluid pressures generated by an injection, because the insert <NUM> is snugly received in a closely conforming sleeve <NUM> that can provide some of the required strength. This results in less waste of material when the insert <NUM> is discarded than would be the case for the barrel of a conventional single-use syringe.

<FIG> and <FIG> illustrate a syringe 20A according a second embodiment of the invention (the needle or cannula <NUM> is not shown in this or subsequent embodiments, but will typically be present). The syringe 20A is constructed in much the same manner as the syringe <NUM> of <FIG> and <FIG>, except that a different locking arrangement is provided between the disposable tubular insert 22A and the reusable outer sleeve 24A. In particular, the flange 36A of the insert 22A is received in the cavity of a correspondingly shaped receptacle <NUM> formed at the proximal end of the sleeve 24A. In use, the flange 36A and the adjoining receptacle <NUM> together form a combined flange that can be held by the user's fingers. The underside of the flange 36A has a distally facing cavity with a pair of shallow indents <NUM> (visible in <FIG>) that interface with a sleeve collar <NUM> (shown alone in <FIG>). The sleeve collar <NUM> is captured and affixed within the sleeve 24A and the receptacle <NUM>, and has two protruding, cantilevered, proximally extending arms <NUM> that are flexible and normally biased outwardly. One end <NUM> of each arm <NUM> engages a corresponding indent <NUM> of the flange 36A, while the other end protrudes through an aperture <NUM> (visible in <FIG>) in the sleeve 24A. The engagement of the ends <NUM> of the arms <NUM> with the indents <NUM> in the flange 36A locks the sleeve 24A and the insert 22A to each other both axially and rotationally. The sleeve 24A and the insert 22A can be separated from each other after the syringe 20A is used by squeezing the arms <NUM> inwardly to disengage the ends <NUM> of the arms from the indents <NUM>, and then pulling the sleeve 24A and insert 22A apart.

<FIG> and <FIG> illustrate a syringe 20B according a third embodiment of the invention. The syringe 20B is constructed in much the same manner as the syringes <NUM> and 20A of <FIG>, except that a different locking arrangement is provided between the disposable tubular insert 22B and the reusable outer sleeve 24B. In particular, the insert 22B is molded with a laterally extending lug or projection <NUM>, and a proximal portion of the reusable outer sleeve 24B has an open-ended, L-shaped bayonet slot for slidably receiving the projection <NUM> to detachably secure the sleeve 24B to the insert 22B by a combination of axial and rotational movement. The bayonet connection provides both axial and partial rotational locking between the sleeve 24B and the insert 22B, and can be released by rotating and axially displacing these two components in the reverse direction with respect to each other. This allows the sleeve 24B and the insert 22B to be separated from each other after the syringe 20B is used so that the sleeve 24B can be reused.

<FIG> illustrate a syringe 20C according a fourth embodiment of the invention. In this embodiment, the flange 36C of the insert 22C is received in the cavity of a correspondingly-shaped receptacle 52C formed at the proximal end of the sleeve 24C. The receptacle 52C has slots <NUM> in its front and rear sidewalls to receive the arms of the flange 36C when the insert 22C is rotated <NUM> degrees and depressed relative to the sleeve <NUM> from the position shown in <FIG> to the position shown in <FIG>. The receptacle 52C also has diagonally opposed side openings <NUM> in its front and rear walls to frictionally receive and retain the arms of the flange 36C when the insert 22C is rotated an additional <NUM> degrees relative to the sleeve <NUM> from the position shown in <FIG>. Top closures <NUM>, <NUM> are located over the side openings <NUM> to prevent the insert 22C from being axially withdrawn from the sleeve 24C following this second <NUM> degree rotation, and the closed sidewalls of the receptacle 22C prevent any further rotation of the insert 22C in the same direction. In this way, the insert 22C is locked both axially and rotationally within the sleeve 24C. The frictional engagement between the arms of the flange 36C and side openings and walls of the receptacle 52C can be augmented, if desired, by providing mating or interlocking structures (not shown) on these structures. The flange 36C and the adjoining receptacle 52C together form a combined flange that can be held by the user's fingers during use of the syringe 20C. The insert 22C and the sleeve 24C can be separated from each other after use of the syringe 20C by first rotating and then axially displacing them with respect to each other in the reverse directions. This allows the sleeve 24C to be reused and the remainder of the syringe 20C to be disposed of.

The embodiment of <FIG> is similar to that of <FIG>, except that the length of the flange 36D is reduced (truncated) to save additional material in the manufacture of the insert 22D. <FIG> shows the insert 22D of <FIG> removed from the outer sleeve 24D and more clearly illustrates the reduced length of the flange 36D. For comparison, <FIG> shows the insert 22C of <FIG> with the full length flange 36C. <FIG> are front and back views of the reusable outer sleeve 24C of <FIG> as it would appear when removed from the disposable insert 22C. The reusable outer sleeve 24D of <FIG> would have essentially the same appearance.

<FIG> and <FIG> illustrate a syringe 20E according a fifth embodiment of the invention. The syringe 20E is constructed in much the same manner as the syringes <NUM>-20D of <FIG>, except that a different locking arrangement is provided between the disposable tubular insert 22E and the reusable outer sleeve 24E. In particular, a proximal portion of the disposable tubular insert 22E has a pair of diametrically opposed lateral projections or studs <NUM>, <NUM>, and a proximal portion of the reusable outer sleeve 24E has an expandable section comprising a pair of opposing deflectable flaps <NUM>, <NUM> with channels <NUM> and holes <NUM> for receiving the projections <NUM>, <NUM>. When the outer sleeve 24E is advanced proximally over the outer surface of the tubular insert 22E during initial assembly of the syringe 20E, the projections <NUM>, <NUM> slide into the channels <NUM> and ultimately settle into the holes <NUM> to detachably secure the sleeve 24E to the insert 22E. This holds the sleeve 24E and insert 22E together in an axially and rotationally locked manner. The sleeve 24E and the insert 22E can be separated from each other after the syringe 20E is used by depressing the squeeze tabs <NUM>, which flexes the flaps <NUM>, <NUM> outward and disengages the holes <NUM> from the projections <NUM>, <NUM>. The sleeve 24E and the insert 22E can then be pulled apart.

<FIG> and <FIG> illustrate two different embodiments of a stopper and reusable plunger assembly <NUM>, <NUM>' for use in any of the previous syringe embodiments (i.e., in combination with a disposable insert <NUM> and a reusable outer sleeve <NUM>) or for use in a conventional single-use syringe with no other reusable components. In each of <FIG> and <FIG>, the plunger <NUM>, <NUM>' is a durable plastic component which can be separated from the rubber stopper <NUM>, <NUM>' after the syringe is used, and then reused as part of another syringe. Such reuse does not compromise the sterility of the syringe, because the plunger <NUM>, <NUM>' does not come into contact with body fluids or with the fluid being transferred by the syringe.

The separation of the plunger <NUM>, <NUM>' from the stopper <NUM>, <NUM>' can be initiated by the user in various ways, depending on the nature of the structural connection between these components. For example, if the distal end <NUM> of the plunger <NUM> is provided with external annular rings <NUM> that mate with internal annular grooves <NUM> in the stopper cavity <NUM> as illustrated in <FIG>, the separation can be achieved by forcefully pulling on the plunger <NUM> in the proximal direction while the stopper <NUM> is held in the insert <NUM> either by the user manually blocking the proximal opening of the insert <NUM> or by providing a constriction at the proximal opening of the insert <NUM> (the stopper <NUM> can be forced past this constriction during initial assembly). Alternatively, if the if the distal end <NUM>' of the plunger <NUM>' is provided on its outside surface with a raised helical screw thread <NUM> that mates with an internal helical groove <NUM> in the stopper cavity <NUM>' as illustrated in <FIG>, the separation can be achieved by simply unscrewing the plunger <NUM>' from the stopper <NUM>'. The friction of the stopper <NUM>' within the insert <NUM> will ordinarily provide enough resistance to rotation of the stopper <NUM>' to allow the plunger <NUM>' to be unscrewed from it, but if this is not the case, the user can apply manual pressure to the stopper <NUM>' through the walls of the insert <NUM> and/or sleeve <NUM> to increase the friction. Such application of pressure can also be used to assist in restraining the stopper <NUM> when the plunger <NUM> is removed by axial pulling in the embodiment of <FIG>.

In all of the embodiments described, the stopper <NUM> is preferably located at the most proximal end of the insert <NUM> prior to use. This positioning can be seen, for example, in <FIG>. The user can push the stopper <NUM> distally with the plunger tip where it bottoms out and engages with the plunger tip. Additionally, there may be lubricant on the inside of the insert <NUM> to aid the movement of the stopper <NUM>. Having the stopper <NUM> initially located at the proximal end of the insert <NUM> will aid lubricant migration within the insert as well.

<FIG> illustrates one possible way in which syringes <NUM> constructed in accordance with any of the foregoing embodiments may be packaged for use or sale. In the illustrated example, a plurality of inserts <NUM> (e.g., <NUM> inserts) having individual stoppers <NUM> but lacking some or all of the scale markings required for proper use of the syringes is packaged in a sealed plastic bag <NUM> along with a single reusable sleeve <NUM> and a single reusable plunger <NUM>. After opening the bag, the user couples the sleeve <NUM> and plunger <NUM> (and a separately provided needle or cannula, if required for the intended use) to one of the inserts <NUM> to form a first syringe <NUM>, uses the first syringe <NUM>, removes the sleeve <NUM> and plunger <NUM>, and discards the insert <NUM> (including the stopper <NUM>). The removed sleeve <NUM> and plunger <NUM> are then attached to another insert <NUM> to form a second syringe <NUM>, which is used and subsequently disassembled in the same way. This process is repeated until the supply of inserts <NUM> is exhausted, at which point the sleeve <NUM> and plunger <NUM> may also be discarded.

It will be apparent that variations are possible in which only one of the sleeve <NUM> and plunger <NUM> is reusable, in which case the other component is either provided separately for each insert <NUM> (as in the case where the plunger <NUM> is not reused) or is not provided at all (as in the case where the inserts <NUM> are provided with scale markings directly and do not require a separate outer sleeve <NUM>). It will also be apparent that variations are possible in which more than one reusable sleeve <NUM> and/or plunger <NUM> is provided in the bag <NUM> (e.g., two or more reusable outer sleeves <NUM> with different types of scale markings <NUM> for different types of insulin), and in which a box or other form of packaging is substituted for the bag <NUM>. The ratio of disposable to reusable components could be higher than <NUM>:<NUM> (e.g., <NUM>:<NUM>, <NUM>:<NUM> or higher), and the reusable components could also be packaged separately from the disposable components if desired.

Syringes <NUM> constructed in accordance with the present invention may be used in any application in which it is desired to inject, withdraw or otherwise transfer fluids. These applications include the administration of insulin and other liquid medications, the withdrawal of blood and other body fluids for sampling purposes, and the transfer of fluids for non-medical purposes.

Claim 1:
A syringe (<NUM>) comprising:
a barrel assembly comprising a disposable tubular insert (<NUM>) having a distally facing cavity and a reusable outer sleeve, the tubular insert (<NUM>) forming a fluid reservoir and having a fluid opening at a distal end thereof, the reusable outer sleeve (<NUM>) being detachably received on the tubular insert (<NUM>) and having visible scale markings thereon, wherein a proximal portion of the reusable outer sleeve (<NUM>) has a proximally facing attachments collar (<NUM>) for detachable insertion into and retention by the cavity;
a stopper (<NUM>) movably received in the tubular insert (<NUM>) for sealing a proximal end of the tubular insert (<NUM>) and for displacing fluid into or out of the tubular insert (<NUM>) through the fluid opening upon movement of the stopper (<NUM>) within the tubular insert (<NUM>); and
a user-operable plunger (<NUM>) coupled to the stopper (<NUM>) for causing the stopper (<NUM>) to move within the tubular insert (<NUM>) and thereby displace fluid into or out of the tubular insert (<NUM>) through the fluid opening under the control of the user.