TITLE:
A RETRACTABLE NON-REUSABLE SYRTNGE
FIELD OF THE INVENTION
The present invention relates generally to syringes, and more particularly to a disposable, retractable, πon-reusabte syringe.
BACKGROUND OF THE INVENTION
The following discussion of the prior art is provided to enable the invention to be placed in an appropriate technical context and allow the advantages of it to be ote fully appreciated. However, statements about the prior art should not be construed as express or implied admissions that such art was widely known or formed part of common general knowledge in the relevant field at the priority date.
Disposable syringes have been known for some time. These are typically manufactured from relatively inexpensive plastics materials, and are adapted to be discarded after a single use to prevent cross-contamination, One problem with syringes of this type is that they are present a significant health risk because of the potential for accidental needle sticks, which may be suffered by medical personnel, sanitation employees, and others involved in the administration and disposal of such syringes. They also pose a risk to the general public when discarded carelessly or inappropriately, as often occurs in the context of illicit drug use. These issues have increased in significance with the proliferation of AIDS, hepatitis and other serious infectious diseases.
In an attempt to minimise these problems, retractable syringes have been developed. These typically incorporate some form of retraction mechanism whereby the needle is withdrawn into the body of the syringe after use, to minimise the risk of accidental needle sticks. These too, however, have suffered from disadvantages. In particular, the retraction mechanisms hitherto known have tended to be relatively complex and expensive. Cost in particular has been found to be a significant impediment to widespread adoption, in both mainstream medical practice and among drug users, Known retraction mechanisms have also tended to be unreliable. In some cases, they inadvertently allow the needle to remain protruding after use with the
consequential risk of contamination through needle sticks, or allow the syringe to be reused with the possibility of cross contamination. Some retraction designs also rely heavily on the user to initiate operation of the retraction mechanism. Illicit drug users can intentionally fail to activate the retraction mechanism, if a replacement syringe is not readily available, which is often the case. Another problem with some syringe designs of this nature is that a small and residual amount of liquid remains within the syringe after use, which again tends to act as a disincentive to use by drug addicts. A further problem with most known retraction mechanisms is that they do not adequately seal the needle during the retraction stage, which may be initiated, intentionally or otherwise, with the needle still in contact with the patient. This gives rise to the possibility of injection of air bubbles, with potential for medical complications for the recipient.
It is an object of the present invention to provide a retractable non-reusable syringe, which overcomes or substantially ameliorates one or more of the disadvantages of the prior art, or at least provides a useful alternative.
DISCLOSURE OF THE INVENTION
According to the invention there is provided retractable non-reusable syringe including an elongate tubular container, a needle assembly, releasable locking means for the needle assembly, resilient bias means operable on the needle assembly, and a plunger slidably disposed within the container, the container having an open front end, an open back end and an inner surface defining a chamber to contain a liquid to be injected, the needle assembly including a needle having a support end and a penetrating end, and a needle holder having a distal end adapted to support the needle and a proximal end, the needle assembly being movable between a projecting configuration wherein the penetrating end of the needle projects forwardly from the front end of the container and a retracted configuration wherein the penetrating end of the needle is enclosed within the chamber, the releasable locking means being adapted to retain the needle assembly in releasable locking engagement with the front end of the container in the projecting configuration and maintain sealed fluid communication between the needle and the chamber,
the resilient bias means being disposed to urge the needle assembly toward the retracted configuration, the plunger having a forward actuating end sealingly engageable with the inner surface of the container, and a rear end, the actuating end being adapted for sealing engagement with the proximal end of the needle holder and being adapted to disengage the releasable locking means, the syringe being sequentially operable in a drawing mode, an injection mode, a transition mode and a retraction mode, whereby in the drawing mode, liquid is drawn through the needle into the container in response to rearward withdrawal of the plunger, in the injection mode the holder is sealingly and releasably engaged with the front end of the container with the needle in the projecting configuration and in fluid communication with the chamber such that depression of the plunger progressively injects the liquid from the container, in the transition mode the actuating end of the plunger at a predetermined position of forward displacement seahngly engages the proximal end of the holder and disengages the locking means to release the holder, and in the retraction mode the resilient bias means effect withdrawal of the needle assembly into the retracted configuration within the container to prevent reuse, Preferably, in the transition mode the actuating end of the plunger engages the proximal end of the holder sealingly and lockingly such that in the retraction mode the supporting end of the needle is closed off and positively sealed.
Preferably also, during disengagement of the releasable locking means, the actuating end of the plunger breaks the needle holder. Also preferably, during disengagement of the releasable locking means the actuating end of the plunger breaks the needle holder.
Preferably, the plunger includes an internal cavity adapted to accommodate and captively retain the needle assembly in the retracted configuration. Even more preferably, the plunger includes a front wall including a first line of weakness disposed such that upon release of the needle holder, the bias means force the needle holder to break an opening in the front wall of the plunger defined by the first line of
weakness, so as to move the needle irreversibly into the retracted configuration within the cavity.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a cross-sectional side elevation showing a syringe, according to tlie invention; figure 2 is a partially cutaway view showing the tubular body of the syringe from figure 1; figure 3 is an end view of the tubular body shown in figure 2; figure 4 is a cross-sectional view of the tubular body taken along line A of figure 2; figure 5 is an enlarged cross-sectional view showing the front end of the tubular body of the syringe, from within line A of figure 2; figure 6 is an enlarged cross-sectional side view showing the syringe of figure
1 in the injection mode; figure 7 is an enlarged cross-sectional side view similar to figure 6, showing the syringe in the transition mode; figure 8 is an enlarged cross-sectional side view similar to figures 6 and 7, showing the syringe in tlie retraction mode; figure 9 is an enlarged perspective view showing the tip of the needle of the syringe; figure 10 is another enlarged view showing the tip of the needle, from an alternative perspective; figure 11 is a partially sectioned side elevation showing the plunger from the syringe of figure 1; figure 12 is an end view of the plunger shown in figure 11; figure 13 is an enlarged cross-sectional side view showing tlie actuating end of the plunger from within line "A" αf figure 11; figure 14 is an enlarged end view of the annular sealing member from the actuating end of the plunger;
figure 15 is a cross-sectional view of tl e sealing member taken along line 15- 15 of figure 14; figure 16 is an enlarged end view of the needle holder from the syringe shown in figure 1; figure 17 is a cross-section l side view of the needle holder, taken along line
17 7 offιgure l6; and figure 18 shows a further enlarged cross-sectional view of the remote end of the needle holder from within line "A" of figure 17.
PREFERRED EMBODIMENT OF THE INVENTION Referring to the drawings, the invention in broad overview provides a retractable non-reusable syringe 1 including an elongate container 2, a needle assembly 3, releasable locking means 4 for the needle assembly, resilient bias means 5 operable on the needle assembly, and a plunger 6 slidably disposed within the container. The container comprises a generally cylindrical body 7, a frustoconical front end 8, and a tubular nozzle 9 extending forwardly from the front-end, as best shown in figures 1 and 2. The back end 10 of the cylindrical body is open and adapted to receive the plunger 6, It also includes an abutment formation 11 to facilitate single- handed manipulation of the syringe. The inner surface 12 of the tubular body 7 defines a chamber 13 to contain a liquid (not shown), typically dawn from an ampule for injection, or drawn from a patient for testing.
The needle assembly 3 includes a needle 14 and a needle holder 15. As best shown in figures 6 to 8, the needle has a support end 16 and a penetrating end 17 adapted for penetrating the membrane of an ampoule or the body of the patient. The penetrating end terminates at a peripheral edge 18 defining a concave virtual surface at the outlet 19 of the needle, as best shown in figure 9. The peripheral edge is bevelled so as to define a chisel-like tip 20 at the extremity of the penetrating end of the needle. Tlie needle holder 15 has a distal end 21 for supporting the needle and a proximal end 22 adapted for engagement by the plunger as described in more detail below. An outer surface 23 on the needle holder and a mating inner surface 24 on the front end 8 of the container are correspondingly tapered to facilitate the sealing engagement between these components. The proximal flared end 22 of the needle
holder 15 includes a flared section 25, an outwardly directed peripheral gripping rim 26, a pair of elongate slots 27 extending axially along opposite sides, and a line of weakness in the form of a circular groove 28 linking the bases of the slots. These features facilitate engagement with the actuating end of the plunger 6, as described more fully below.
The needle assembly is movable between a projecting configuration, as best illustrated in figures 1 and 6, and a retracted configuration, as best illustrated in figure 8. I the projecting configuration, the needle holder 15 is disposed generally within the frustoconical end 8 of the container, and the penetrating end 17 of the needle projects forwardly from the tip 29 of the nozzle. In this configuration, the respective, correspondingly tapered engagement surfaces 23 and 24 on the needle holder and tlie container prevent leakage, while the support end of the needle is positionally stabilised and sealed by the nozzle, hi the retracted configuration, the needle assembly including the penetrating end of die needle is safely enclosed within the chamber 13,
The releasable locking mechanism 4 includes a forwardly and inwardly directed circumferential stopper flange 30 formed on the inner surface 12 of the container, and a complementary rearwardly and outwardly directed abutment shoulder 31 formed on an outer surface of the needle holder 15. The stopper flange and the abutment shoulder are releasably engageable to retain the needle assembly 3 in the projecting configuration.
The resilient bias means 5 take the form of a coil spring 32, which al least in the projecting configuration, is disposed concentrically around the needle 14 and coaxially between the tip of the nozzle and the remote end of the needle holder 15. The biasing force of the spring urges the needle assembly 3 toward the retracted configuration. The spring 32 is designed not to force the needle holder over the stopper flange 30 during normal injection.
The plunger 6 is best illustrated in figures 11 to 13. It includes a generally cylindrical body 33, a forward actuating end 34, and a rear end 35 incorporating a sealed closure element in tlie form of cap 36. The actuating end includes a frustoconical tongue 37 adapted for sealing engagement with the proximal end 22 of the needle holder, which is correspondingly flared for optimum sealing characteristics.
The actuating end 34 also includes an inwardly directed circumferential gripping jaw 38 disposed around the tongue and complementary to the peripheral gripping rim 26 on the proximal end of the needle holder 15, By this means, the gripping j w and the gripping rim are interengageable to apply an inwardly directed circumferential pressure to the proximal end of the needle holder sufficient to break it. The body of the plunger includes an internal cavity 39 adapted to accommodate and captively retain the needle assembly 3 in the retracted configuration.
The front wall 40 of the forward actuating end 34 of the plunger includes a peripheral groove 41 disposed to define a line of weakness along the periphery of the base of the sealing tongue 37. It should be appreciated that the line of weakness, defined here by a grooves, may alternatively be defined by series of indentations, a frangible membrane, or other suitable means.
The actuating end of the plunger further includes a peripheral locating groove 42 and a sealing member 43 mounted in the groove for sϋdable sealing engagement with the inner surface of the container. The sealing member includes two peripheral sealing lips 44, each with a concave outer bearing surface 45, as best shown in figures 14 and 15, The bearing surfaces on the respective sealing lips are oriented toward one another to facilitate smooth, leakage-free operation during axial displacement of the plunger in either direction. The base of the rear end 35 of the plunger includes a forwardly prcj ecting breakable tab 46 to prevent inadvertent engagement of the actuating end of the plunger with the needle holder.
Turning now to describe the operation of the syringe, in an initial storage configuration, the plunger is forwardly depressed into a position where the protecting tab abuts the projection on the back end of the tubular body of the syringe. This maintains a predetermined minimum distance between the actuating end of the plunger ό and the needle holder 15. In this configuration, the needle holder is sealingly and releasably engaged with the front end of the container, with the needle in the projecting configuration being in fluid communication with the chamber. The syringe is intended for use either to draw liquid from an ampoule for injection as medication into a patient, or to draw liquid such as blood from a patient for testing. The functionahty in both cases is substantially identical but will be described here
with reference to the former scenario, which involves use of tl e syringe sequentially in a drawing mode, an injection mode, a transition mode and a retraction mode.
In the drawing mode, the tip of tlie needle in the projecting configuration is used to penetrate the membrane of the ampoule (not shown), following which withdrawal of the plunger draws liquid from the ampoule through the needle into the chamber of the container 2, in conventional manner. The needle is then withdrawn from the ampoule, the air bubbles are removed, and the tip of the needle is inserted so as to penetrate the body tissue of me patient where required for the injection. During this process, the particular structure of tlie tip of the needle can substantially reduce the damage to the skin caused by insertion of the needle. This is because the chisel- like tip of the needle, as best illustrated in figures 9 and 10, cuts only a small section of skin ( not shown) which is then lifted to allow the penetration of the needle. Upon withdrawal of the needle this skin "flap" covers the damaged area to allow expeditious healing. In the subsequent injection mode, depression of the plunger progressively injects the liquid from the container into the patient. It is important to note here that the line of weakness defined by the peripheral groove 41 on the forward end of the plunger has a break point sufficiently high to withstand pressures well above those usually generated during the drawing or injection modes. At or near the end of the injection phase, the transition mode is approached at a predetermined position of forward displacement of the plunger. At this point, the protecting tab 46 on the plunger engages the abutment formation at the base of the tubular body of the syringe, to prevents inadvertent initiation of the transition mode. The tab must therefore be removed manually if this mode is required. Once the tab is removed, further forward displacement of the plunger triggers the transition mode. In this mode, as best shown in figure 7, the sealing tongue 37 at the actuating end of the plunger sealingly engages the correspondingly flared proximal end 22 of the needle holder. At the same time, the gripping jaw 38 engages the gripping rim 26 and applies an inwardly directed circumferential pressure to the proximal end of the needle holder. The line of weakness defined by the groove 41 has a breaking point such that the inwardly directed circumferential pressure applied at this stage is sufficient to break tl e holder. The abutment shoulder 31 of the bolder is
thereby moved out of supporting engagement with the stopper fiunge 30, as a result of which the locking mechanism is effectively released and the needle assembly disengaged from the front end of the tubular body of the syringe. The release of tlie needle assembly at the conclusion of the transition mode irreversibly and automatically actuates the retraction mode.
The sealing tongue and the actuating end generally are configured relative to the front end of the container such that at the point of maximum forward displacement of the plunger, substantially all liquid remaining in the syringe is expelled. Ideally, however, the configuration is such that the entire contents of tlie syringe cannot be expelled without initiation of the transition mode. For this reason, d g addicts and illicit drug users are unlikely to attempt to reuse the syringe by intentionally failing to activate the transition mode, because this would entail leaving some residual quantity of liquid, containing the active drug, within the syringe.
Upon commencement of the retraction mode, the proximal end 22 of the needle holder is engaged by the sealing tongue 37 on the actuating end of the plunger. Consequently, the support end 16 of the needle is sealed off from the surrounding volume in the container. However, the needle holder 15 has been released from locking engagement with the front end of the container and the entire force of the retraction spring is consequently applied to the sealing tongue 37. The line of weakness defined by the groove 41 in the actuating end of the plunger has a break point that is sufficiently low to insure that the bias force of the spring easily breaks an opening, defined by the line of weakness, in the front wall 40 of the plunger and then pushes the needle assembly into the cavity. The needle thereby adopts the retracted configuration with the lip safely concealed within the plunger, as best shown in figure 8, Importantly, during the transition and retraction modes, the support end of the needle remains positively sealed, so as to prevent air from penetrating the patient's body during the retraction. It will also be appreciated that because of the rupturing of both the needle holder 15 and the actuating end 34 during the transition mode, the retraction mode is irreversible, thereby ensuring that the syringe cannot be reused. The invention thus provides a simple, reliable and cost-effective form of retractable, non-reusable syringe that avoids the possibility of inadvertent needle sticks after use, and also avoids the possibility of reuse. These factors combine to
substantially reduce or eliminate the risk of cross-contamination. In these respects, the invention represents a practical and commercially significant improvement over the prior art.
Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.