SYRINGES

Abstract: A syringe is provided comprising a barrel (10) open at one end, a piston (20) sealably located in the barrel and being partly formed by a membrane (23), a plunger (30) slidable into the barrel to engage and move the piston, and a needle (40) projecting through the plunger into and out of the barrel. A material to be dispensed is located between the barrel and piston, and plunger movement causes the needle to pierce the membrane and also causes the piston to move to eject material through the needle. Preferably a protective cap (50) is connected with the barrel to cover the plunger/needle projection. Typically the dispensed material is pharmaceutical and it can be maintained sterile by suitable sealing of the piston and/or cap with the barrel. The plunger can interlock with the piston to allow withdrawal movement useful in intravenous injection. Also the barrel closed end can include another membrane (62) allowing mixture of another material, such as a solvent or diluent liquid.

Description: - l - SYRINGES This invention concerns syringes and more particularly, but not exclusively, medical syringes. Modern medical syringes offer a variety of benefits such as disposability, sterility, economy, wide availability, etc. , but they can be regarded as inappropriate relative to a commonly occurring situation, namely, one requiring the administration of a drug in a standardised amount. The inappropriateness arises from the fact that the syringe body and its needle are usually separately wrapped and so must be unwrapped, suitably connected, and then filled, prior to use. The frequency of the situation in question is recognised insofar as most drugs are now available in standarised single dosage ampoules for syringe filling, but it is evident that a wastage is entailed in syringe/ampoule materials and also in the time of skilled drug-administration personnel. Some proposals have been made with a view to reducing this wastage, but they are also open to objection. One such proposal involves the use of a pressurised ampoule and attached needle, but is subject to variation in administered dose and may introduce air into tissue. Another proposal involves the pre-loading of a special ampoule directly ' into a syringe, but still involves material wastage. A pre-filled syringe of conventional form is also available but this requires special packaging to maintain sterility and to prevent inadvertent actuation. In these circumstances there is room for an improved, alternative parenteral drug delivery system of single dose, pre-packed form and to this end the present invention provides a syringe comprising: a barrel in the form of a tube closed at one end; a piston sealably and longitudinally slidably located in said barrel, said piston being formed in part as a membrane extending transversely across the interior of said barrel; a plunger located for longitudinal sliding movement into, said barrel to engage and urge said piston thereinto; and a needle projecting through said plunger into and out of said barrel. In use of the proposed syringe, material to be dispensed is pre-charged into the space defined between the closed end of the barrel and the piston, and movement of the plunger into the barrel first causes the needle to pierce the piston membrane to communicate with the material and thereafter the plunger urges the piston into the barrel to expel material through the needle. In a preferred form of the proposed syringe, a protective cap is located over the needle and other parts projecting from the barrel. This cap provides mechanical protection and can, when required, also ensure sterility prior to use. Another preferred feature of the proposed syringe comprises adaptation of the mutually facing surfaces of the piston and plunger/needle assembly to allow or to cause interlocking engagement therebetween. Such engagement enables the piston to be subjected to withdrawal as well as inward movement by the plunger. This is particularly appropriate for intravenous injections, when it is necessary to check that the needle is in a vein prior to injecting the contents of the barrel. Partial withdrawal of the plunger, with piston attached, will cause blood to be drawn into the barrel signifying the correct location of the needle. In order that the present invention may be clearly understood, the same will now be more fully described by way of example with reference to the accompanying drawings, in which:- Figure 1 schematically illustrates in longitudinal sectional view one embodiment of the present invention; and Figures 2 and 3 similarly illustrate, in part, respectively different modified forms of the embodiment of Figure 1. The syringe embodiment of Figure 1 is intended for medical use and comprises a barrel 10, a piston 20, a plunger 30, a needle 4θ, and a cap 50. The barrel 10 is of hollow substantially circular cylindrical form with a side wall 11 and one end wall 12, the other end being open. The side wall 11 is formed with a radially outwardly projecting flange 13 ' adjacent the open end of the barrel. The piston 20 comprises a main body part 21 of generally hollow cylindrical form with its outer surface shaped to define three, say, circumferential ribs 22 successively longitudinally spaced therealong and of such diameter as to allow slidable sealing location of the piston in the barrel. The end of the piston body part 21 nearer to the open end of the barrel is closed by a membrane 23. The plunger 0 also comprises a main body part 31 of generally cylindrical form and of such a diameter as to allow slidable location in the barrel. However in this instance the part 31 s of stepped form, with a portion 3 of larger diameter slidably located in the barrel, and a portion 33 of lesser diameter, the latter portion being located, prior to use, beyond the barrel as shown. The portion 32 is preferably fluted, or has polygonal or other circumferentially indented cross-sectional shape rather than one which seals in the barrel, and the portion 33 is formed with a radially outwardly projecting flange 3 adjacent its end further from the barrel. Also, the part 31 is coaxially extended from its portion J, > by an elongate portion 35 of further reduced diameter and which terminates at its free end in a divergently conical or other transversely enlarged portion 36, this last portion also being of lesser diameter than the part 31. The needle 4θ is longitudinally bored, chamfered at each end, longer than the plunger 30, and secured coaxially in the pl nger to project from both ends thereof. The cap 50* comprises a shell 51 of circular cylindrical form extending at one end into a closure which may be tapered as shown, with the other end being open. The shell may be formed as shown to the same diameter at its open end as the barrel to abut therewith, with the open end of the shell being continued into an expanded rim 52 having* an internal groove 53 to seat over the barrel flange 13 in a snap fit. In manufacture the barrel is suitably moulded from glass or plastics material, such as polystyrene or polypropylene, which is compatible with drugs containment, and the barrel will normally be non-opaque. The piston is suitably moulded from rubber or other elastomeric material to facilitate the desired sliding and sealing in the barrel, this being enhanced by the ribs 22. The piston material also is to be compatible with drugs containment. The plunger and cap are also suitably moulded from plastics material, which may be common to the barrel, although neither need be non-opaque. Lastly, the needle will normally be of metal and this may be secured in the plunger by moulding of the latter around the former, or by cementing or other appropriate technique. Use of the syringe of Figure 1 is largely self-evident from the foregoing description. A drug is contained in the space defined between the closed end portions of the barrel and the piston. The syringe is prepared for use simply by removing the cap, and then urging the plunger into the barrel so that the needle pierces the piston membrane, whereafter continuation of this plunger movement engages the plunger with the piston to urge the latter into the barrel and thereby to eject the drug by way of the needle. Various points should be noted in relation to this usage. Unintended operation of the plunger is prevented by the cap 50 OM - j - abutting against the barrel, thus stopping movement of the cap over the barrel and, of course, acting against impact on and damage to the needle by the cap. The snap fit connection of the cap on the barrel can provide a mechanical seal which maintains sterility by preventing air flow to and from the interior of the device, and this connection can be made secure by heat sealing at one or more points therearound with separation being initiated by rotation of the cap to break the heat sealed joints. Sterility of the capped syringe interior and its drugs content can alternatively, or additionally, be ensured by taping around the barrel-cap connection, and such a measure is beneficial in providing a visual indication that the seal has not been broken prior to use. The plunger portion 33 & nd its flange 34 afford an easy grip when applying the needle to a patient before plunger action. As an alternative, the plunger portions 35 and 36 can serve this same function and additionally serve to facilitate plunger actuation. This last function suitably involves location of two fingers around portion 35 to press on portion 33 in association with thumb-engagement of the barrel end wall 12 to urge the plunger into the barrel. The operator will know when the prescribed volume of drug has been administered as the plunger pushes the piston to the end wall 12 to limit movement, and in addition the drug containing space between the barrel end and piston can be seen to be emptied. The fluted or polygonal shape of the plunger body part 31 tracks the plunger in the barrel with a minimal engagement to afford low friction, while affording passageways for air movement to and from the adjoining space in the barrel. This feature also represents an economy in reducing the material content of the plunger. The piston, or at least its membrane, must be of such a nature as to seal around the needle when pierced thereby. Indeed the membrane preferably self-seals after withdrawal, for location of a needle through the membrane can be used to allow egress of air from the barrel when the piston is first inserted. Also, at the same time, or as a separate procedure, such a needle can be used to introduce the drug into the barrel through the membrane and at the same time to force the piston along the barrel, whereafter the plunger and cap can be assembled with the barrel. It is evident that the syringe just described can be pre-charged with a drug in an appropriate volume such that use with plunger movement within the barrel forces the piston to the end of the barrel causing delivery of a predetermined volumetric dose. Use for subcutaneous and intramuscular injections is appropriate. In either case the outer end of the needle is suitably inserted into the patient while gripping the appropriate portion of the plunger, but without urging the plunger into the barrel. In the case of intravascular injections, appropriate needle location is indicated by flash back of blood into the space between the plunger and piston. In this last case the plunger is preferably modified compared to that described above so that the portion 32 provides only capillary sized passageways between itself and the barrel to prevent spillage of blood during subsequent plunger actuation. The syringe can be pre-sterilised prior to assembly, or after assembly, by gamma radiation. The drug can be inserted through a needle as described above under sterile conditions at a later stage, or also be sterilised in situ by gamma radiation. Once the syringe including the cap has been assembled, the needle, plunger and space between the plunger and piston can be sterilised by ethylene oxide diffusing through the gap between the engaged cap and barrel, or by gamma radiation. The syringe then requires no preparation other than removal of the cap 50. ___ OMPI In the modification illustrated by Figure 2 the mutually facing surfaces of the piston 20 and plunger 0 are adapted to allow interlocking engagement therebetween. More specifically in the illustrated embodiment, the relevant inner end of the plunger includes a coaxial portion 37 of reduced diameter extending around and partway along the associated projecting end of the needle 40. This plunger portion 37 s formed with an external thread 38 complementary with an internal thread 24 formed within the nearer end of the hollow of piston 20. The membrane 23 is suitably relocated within the piston, or at the further end thereof, to allow inter-engagement of the threads 24 and 38. Use of this modified form of syringe is effectively self- evident in that, after removal of the cap, the plunger and/or barrel is rotated to inter-engage the threads 24 and 8 to cause penetration of the membrane by the needle. Thereafter, ejection of the syringe drug content is effected by inward translation of the plunger to push the piston, as before. A benefit of this modification is, as noted earlier above, that the piston can additionally be subjected to withdrawal movement by way of the plunger. Also, the inter-engagement of the plunger with the piston assists in more positively locating the former in the barrel. This is particularly beneficial in the case where the plunger is fluted, polygonal or of other such shaping. When this modification is employed, it may be appropriate to prevent movement of the plunger prior to use of the syringe, such as when transported. Various measures are available for this purpose. For example, the plunger can be heat sealed with the barrel at one or more points around their adjacent circumferences, as proposed above for the barrel and cap, with movement being initiated when required by a snap action. Alternatively, the rotation movement necessary to plunger-piston inter-engagement can be prevented by the provision of internal projections within the cap to locate in the concavities of the plunger when fluted or similarly shaped. In this last case, the cap should be prevented from rotation by an appropriate one of the security measures discussed earlier above- The essence of the modification of Figure 2 is, as already noted to allow interlocking engagement between the plunger and piston, and the thread adaptation of Figure 2 is but one way of attaining this functional result. For examples, alternative adaptations can involve the use of an impact adhesive, barbs on the needle or plunger, or inter-digitating formations on the piston and plunger. While the invention has been conceived primarily in relation to simple, single-dose administration, it is nevertheless capable of variation to cater for other requirements such as might be appropriate in the provision of a family of related syringe products. For example, the syringe barrel can be provided with scale markings to allow for dispensing of only part of its drug content. Equally such markings can be employed for the purpose of multiple dispensing. In thi-s last case it may be appropriate to allow for needle replacement and this can be accommodated by modification of the illustrated syringe to terminate the outer end of the needle, possibly within plunger portion 36. in a luer or other fitting for connection to conventional needles or other components. It will also be appropriate to modify the illustrated syringe for use with freeze-dried or like drugs which must be rendered liquid immediately before administration. Figure 3 shows one such modification in which the barrel end wall 12 is opened for co-operation with a rubber or other elastomeric plug 60 for closure of the wall after dried-drug charging of the barrel, possibly by way of the cavity 6l defined by the interior part of eft x N the plug, with the piston being located immediately adjacent to the plug. The plug 60 incorporates a membrane 62 to function in self-sealing manner relative to a needle, such as that of a syringe as illustrated in Figure 1, whereby a prescribed volume of solvent is applied to the drug to dissolve it, at the same time pushing the piston down the barrel. The plug is preferably housed behind an outer cover 63 connected to the end of the barrel, this cover having a central aperture to allow access of a needle and diluent to the plug membrane 62. Lastly, while the invention has been described in relation to drugs administration it is also applicable to other uses where precise and repeatable small volume liquid delivery is required with accurate location, such uses possibly involving epoxy resin mixes and other chemicals.

Claims: CLAIMS 1. A syringe comprising: a barrel in the form of a tube closed at one end; a piston sealably and longitudinally slidably located in said barrel, said piston being formed in part as a membrane extending transversely across the interior of said barrel; a plunger located for longitudinal sliding movement into said barrel to engage and urge said piston thereinto; and a needle projecting through said plunger into and out of said barrel, inward movement of said plunger causing said needle to pierce said membrane and to move said piston into said barrel. 2. A syringe according to aim 1 comprising a protective cap releasably connected with said barrel to cover the parts of said plunger and needle projecting from said barrel. 3. A syringe according to Claim 1 or 2 wherein said plunger has a circumferentially indented cross-sectional shape along its length compared to the corresponding shape of said barrel. 4. A syringe according to Claim 1, 2 or 3 wherein the mutually facing surfaces of said piston and plunger/needle assembly are adapted to allow or to cause interlocking engagement therebetween. 5. A syringe according to Claim 4 wherein said surfaces are adapted as aforesaid by the provision of respective complementary thread formations thereon to allow locking by screw action. 6. A syringe according to Claim 4 or 5 wherein said plunger is releasably secured to said barrel to inhibit said interlocking engagement. 7. A syringe according to Claims 2, 3 and 5 wherein said cap has an inwardly directed formation engaged with said plunger indented shape, and said cap is releasably secured to said barrel to inhibit rotation of said cap and said plunger relative to said barrel. 8. A syringe according to any preceding claim having a pharmaceutical composition housed in the space between said ___O .ywϊ barrel and said piston, said composition being maintained sterile by sealing of said piston within said barrel. 9. A syringe according to Claims 2 and 8 wherein said cap is connected with said barrel in sealed manner to maintain sterility in the space therebetween. 10. A syringe according to any preceding claim wherein said barrel closed end is partly defined by a further membrane. 11. A syringe according to Claim 10 wherein said further membrane is covered by a further protective cap releasably connected with said barrel.

Inventors: HOLMAN R, TURNER R
Applicants: HOLMAN R, NAT RES DEV, TURNER R, NAT RES DEV CORP
Application year: 1980
Main classification: A61M5
IPC codes: A61M5