WO2003033061A1

WO2003033061A1 - Single-use syringe assembly

Info

Publication number: WO2003033061A1
Application number: PCT/GB2002/004600
Authority: WO
Inventors: Filippo Filippi; James Love
Original assignee: Plastic Medical (Supplies) Ltd
Priority date: 2001-10-12
Filing date: 2002-10-10
Publication date: 2003-04-24
Also published as: GB2380680A; GB0124585D0

Abstract

There is described a retractable needle syringe assembly wherein sealing of the grommet (21) is improved by a thinwalled neck (2) surrounding a plunger head (18). A sealing grommet with no penetrating bore is also described, and means for preventing reuse of the syringe by causing breakage (43,44) of parts (1,10) during disassembly is disclosed.

Description

Single-use syringe assembly

The present invention relates to hypodermic syringes and particularly relates to a single-use syringe with a retractable needle.

Two important considerations in the manufacture of disposable syringes are the prevention of re-using the syringe, and preventing "needle-stick" from accidentally injuring a user of the syringe. The hypodermic syringe assembly of EP0636381 has a first resilient latching means operable between a needle hub and a syringe body to prevent retraction of the needle until the plunger is pushed to its forward most position. In this position the stem of the plunger engages the latching elements of the hub to release the first latch and engage a second latch which attaches the needle hub to the plunger. Withdrawal of the plunger draws the needle inside the syringe body, thus preventing needle-stick injury. The stem of the plunger is then broken off, preventing re-use of the syringe.

The principal disadvantage of this structure is that, if the first user fails to break off the plunger stem, the plunger may be withdrawn from the syringe with the needle attached, and the parts subsequently re- assembled to provide a hypodermic syringe capable of re- use. Since the protective sleeve provided over the needle prior to first use may not be disposed of with the remaining parts, the reassembled syringe presents both needle-stick risk and contamination risk. A further disadvantage of this structure is that the attachment of the needle hub directly to the plunger stem requires a central through-bore to penetrate the sealing grommet. The sealing grommet therefore has to effect a fluid-tight seal not only with the internal wall of the bore of the syringe, but also with the central latching element which extends from the stem through the grommet to engage the needle hub. An ineffective seal at this central part of the grommet will lead to the fluid passing through the syringe body to exit from the trailing end. The volume of the dose is therefore not assured, and contamination of the contents of the syringe may occur .

The present invention seeks to provide an improved sealing arrangement for a retractable needle syringe having a sealing grommet.

A yet further objective of the present invention is to provide a retractable needle syringe wherein fluid- tightness of the sealing grommet is not compromised by any bore extending through the grommet. A further objective of the present invention is to provide a single-use syringe assembly wherein even if the syringe is incompletely disposed of after first use, the components cannot be reconfigured for a subsequent use. A yet further objective of the present invention is to provide a disposable syringe construction wherein the needle is withdrawn inside the syringe by using very simple and mechanically reliable means.

Another object of the present invention is to provide a disposable syringe construction which can be made using very simple component elements and may include components common to non-retracting syringes .

Yet another object of the invention is to provide a disposable syringe assembly which is very reliable and safe in operation. According to one aspect of the present invention, there is provided a syringe assembly comprising a needle having a penetrating leading end and a needle hub at its trailing end, a syringe body having a leading end for engaging the needle hub and a hollow tubular body with an open trailing end, a plunger assembly comprising a stem movable within the syringe body a grommet fixed to an end of the stem and sealingly engaging the interior of the syringe body and wherein the plunger includes a latching element extending through a central bore in the sealing grommet, wherein first latching means are operable between the needle hub and the syringe body to resist rearward movement of the needle, and wherein the sealing grommet includes an internal cavity for accepting a retaining flange of the plunger, and wherein a face of the internal cavity remote from the stem of the plunger is undercut to provide a thin-walled tubular sealing neck to surround the latching element of the plunger.

A second aspect of the present invention provides a syringe assembly comprising a plunger, a sealing grommet, a syringe body, and a needle mounted to a needle hub, wherein the needle hub and the grommet are engageable to release said first latching means and engage second latching means operable to fix the needle hub to the grommet so that rearward movement of the grommet draws the needle into the interior of the syringe body. This aspect of the invention also provides a sealing grommet for a retractable-needle syringe wherein the grommet has first engaging means at its trailing end for engagement with a plunger of the syringe, and second engagement means at its leading end for engaging a needle hub to draw the needle into the syringe when the grommet is moved rearwardly in the syringe body. In a preferred embodiment of this aspect of the invention, the grommet includes a blind cavity at its leading end having an undercut opening, the undercut surface being engageable with latching elements of the needle hub.

In order for the needle to be retained within the syringe body after retraction, the engagement between the needle hub and the grommet is arranged so that, when the needle tip is within the syringe body, the needle tip is urged sideways to incline the needle to the syringe axis and thus prevent forward movement of the plunger from advancing the needle out through the neck of the syringe. The present invention provides, in a third aspect, for the resilient engagement between the needle hub and the grommet to produce a force urging the needle out of axial alignment with the grommet and the syringe body. The grommet and/or the needle hub are provided, in this aspect, with cooperating surfaces which lie in a plane oblique to the axis of the grommet and the needle, respectively. Most preferably, the engagement surfaces of the grommet are inclined to the axis of the syringe so that engagement urges the needle hub to lie at an angle to the syringe axis. A fourth aspect of the invention provides a syringe assembly comprising a plunger, a sealing grommet, a syringe body, a needle holder, and a needle mounted to a needle hub, the needle holder being sealingly fixable to a leading end of the syringe body and adapted to releasably sealingly support the needle hub, and frangible means being provided in the assembly to prevent disassembly and re-use of the syringe by causing breakage of at least one component of the assembly during disassembly. In a preferred embodiment of this aspect of the invention, the removal of the needle holder intact from the syringe body is prevented by a frangible section in the needle holder and/or in the neck of the syringe body.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 is an exploded sectional view of the retractable syringe assembly of the prior art;

Figure 2 is a sectional view, to an enlarged scale, of the grommet and stem of a syringe embodying the first aspect of the invention;

Figure 3 is a sectional view of the stem, grommet, needle hub and needle of a syringe embodying the second and third aspects of the present invention; Figure 4 is a sectional view showing an alternative embodiment of a grommet and needle hub embodying the second and third aspects of the present invention;

Figure 5 is a partial sectional view of a first embodiment of the fourth aspect of the invention; Figure 6 is a partial sectional view of a second embodiment of the fourth aspect of the invention; and

Figure 7 is a view showing the syringe of Figure 6 after partial retraction of the needle.

Referring now to the drawings, Figure 1 shows a longitudinal sectional view of the components of the retractable syringe of the prior art. The syringe comprises a tubular body 1 having a neck 2 at its leading end. The internal surface of the neck 2 is formed with a ridge 3 whose purpose will be described later. At the trailing end of the tubular body 1, grip portions 4 extend radially outwardly from the tubular body.

The needle assembly for the syringe comprises a needle holder 5, a needle protector 6, and a needle 7 having a needle hub 8 at its trailing end. The needle holder 5 has a tubular configuration, with a first bore

9 engageable with the outer surface of the neck 2 of the tubular body 1 to make a fluid-tight seal. A second bore

10 within the needle holder 5 is sealingly engageable by the outer surface of the needle hub 8, to retain the needle hub 8 within the needle holder 5. The needle hub 8 is provided with a central bore 11 penetrating the needle hub 8 axially, and communicating with the lumen of the needle 7.

The trailing end of the needle hub 8 is formed with a pair of latching arms 12 and 13. The latching arms 12 and 13 have at their ends remote from the needle hub 8 detent surfaces 14 facing towards the needle hub 8. Intermediate the lengths of the latching arms 12 and 13, second detent surfaces 15 are provided, facing away from the needle hub 8.

The needle protector 6 is a tubular component having a closed leading end 16 and an external circumferential flange 17 at its trailing end. The needle protector 6 is so dimensioned as to fit over the external surface of the needle holder 5 with a slight interference.

Slidably receivable within the tubular body 1 is a plunger 18 comprising a stem 19 and a plunger head 20.

A sealing grommet 21 is mounted on the plunger head 20.

The plunger head 20 extends axially from the leading end of the stem 19, and has an external flange 22 intermediate its axial length. The end of the plunger head 20 remote from the stem comprises an axially-facing opening 23 leading into an enlarged cavity 24. The radial enlargement of the cavity 24 provides abutment surfaces 25 within the cavity 24 surrounding the opening 23.

To operate the syringe of Figure 1 , the neck 2 of the tubular body 1 is introduced into the first bore 9 of the needle holder 5, so that the latching arms 12 and 13 of the needle hub 8 enter the neck 2. The detent surfaces 14 at the ends of the latching arms pass the ridge 3 within the neck 2, but the second detent surfaces 15 of the latching arms 12 and 13 engage the ridge 3 to prevent further movement of the needle hub towards the interior of the tubular body 1. The needle protector 6 is then removed from the needle holder 5, exposing the needle 7.

The liquid to be injected is drawn up by advancing the plunger assembly 18 so that the sealing grommet 21 approaches the leading end of the tubular body 1, and then placing the exposed tip of the needle 7 into the liquid to be injected and retracting the plunger 18. The fluid-tight seals between the needle holder 5 and the neck 2 and between the needle hub 8 and the second bore 10 of the needle holder 5 ensure that the liquid is properly drawn up.

Any air within the syringe is expelled in the conventional way by holding the syringe needle-upwards, and advancing the plunger 18. The injection is then administered by inserting the needle 7 into the patient and advancing the plunger 18 to the leading end of the tubular body 1.

As the plunger 18 approaches the end of its travel, the latching arms 12 and 13 enter the opening 23 in the leading end of the plunger 18, compressing the latching arms 12 and 13 together by the action of converging cam surfaces 26 at the tips of the latching arms 12 and 13 and the sides of the opening 23. When the detent surfaces 14 have passed through the opening 23, the latching arms 12 and 13 spring apart so that the detent surfaces 14 engage the abutment 25 within the cavity 24. The latching arms 12 and 13 are held sufficiently close together by the edges of the opening 23 to release the engagement between the second detent surfaces 15 and the ridge 3 within the neck 2.

The syringe is then removed from the patient, and the plunger 18 is drawn back along the tubular body 1. The engagement between the detent surfaces 14 and the abutment 25 ensures that the needle hub 8 and needle 7 are drawn back with the plunger 18, positioning the needle 7 wholly within the tubular body 1 of the syringe. Weakened sections 27 in the stem 18 enable the stem 18 to be snapped off in this position, preventing re-use of the syringe and preventing removal of the needle from within the tubular body 1.

As will be appreciated, the sealing grommet 21 of the syringe described above has a penetrating central bore to accommodate the plunger head 20. Leakage of liquid from within the tubular body 1 between the sealing grommet 21 and the plunger head 20 can occur during use of the syringe, rendering the dosing of the syringe inaccurate. In order to avoid such leakage, the present invention provides an alternative structure for the plunger 18 and sealing grommet 21, which is illustrated in Figure 2.

Referring now to Figure 2, there is shown an enlarged scale the leading end of the stem 19 of the plunger assembly 18, together with a sealing grommet 21 according to a first aspect of the invention. Elements having counterparts in Figure 1 and described above are given like reference numerals.

The stem 19 and plunger head 20 of the plunger 18 are substantially identical to those shown in Figure 1, the plunger head 20 comprising an outwardly-extending flange 22 midway along its axial length to retain the grommet 21. The grommet 21 has a cavity 28 which communicates with the rear surface 29 of the grommet via a tapered opening 30, and communicates with the conical front surface 31 of the grommet via a bore 32. The bore 32 closely surrounds the forward part of the plunger head 20.

Where the bore 32 meets the cavity 28, the front surface 33 of the cavity is cut away to leave a thin- wall tubular extension 34 protruding into the cavity 28. The axial end surface 35 of this tubular extension 34 lies against the flange 22 of the plunger head 20.

The extension 34 assists in the sealing of the grommet to the plunger head, particularly when pressure is applied to the plunger to expel liquid from the syringe. The hydrostatic pressure acting on the front surface 31 of the grommet causes the end surface 35 of the extension 34 to be pressed into close engagement with the flange 22 of the plunger head, ensuring a fluid tight seal at this point. Leakage of liquid from the syringe through the bore 32 into the cavity 28 and thence through the bore 30 is thus prevented by the sealing engagement of the tubular extension 34 with the flange 22 of the plunger head.

A second aspect of the invention is illustrated in Figures 3 and 4. In Figure 3, there is shown a sectional view of the plunger assembly comprising the stem 19, plunger head 20 and grommet 21. Again, corresponding parts have been given the same reference numerals as in the above description. In Figure 3, the plunger head 20 comprises a short axial shank 36, terminating at its leading end in a radially-enlarged flange 37. The shank 36 and flange 37 are closely received in a blind cavity 28 formed in the rear surface 29 of the grommet 21. In the conical front surface 31 of the grommet 21 a further blind cavity 38 is formed. The cavity 38 has an opening 39 and an undercut surface 40 surrounding the opening 39 within the cavity 38.

The grommet of Figure 3 also embodies the third aspect of the invention, in that the undercut surface 40 within the cavity 38 is set at a slight angle to the axis of the grommet, for reasons to be explained below. The undercut surface 40 may alternatively be set in a plane perpendicular to the axis of the sealing grommet 21. The operation of the syringe incorporating the grommet shown in Figure 3 is substantially the same as for the syringe as described in relation to Figure 1. As the plunger assembly is advanced toward the leading end of the syringe, the latching arms 12 and 13 of the needle hub 8 enter the cavity 38 via the opening 39. The arms 12 and 13 are compressed together as they pass through the opening 39, and spring apart so that the detent surfaces 14 of the arms may engage the undercut surface 40 within the cavity 38. Retraction of the plunger assembly then draws the needle hub 8 and needle 7 through the neck 2 of the syringe. The oblique orientation of the undercut surface 40 causes the needle to be rotated when the tip of the needle is within the syringe body, so that the needle hub and needle lie obliquely in relation to the axis of the syringe, preventing forward movement of the plunger from extending the needle back through the neck 2 of the syringe. Since the cavity 28 in the rear surface 29 of the grommet is not in fluid communication with the cavity 38 formed in the front surface 31 of the grommet 21, no leakage of liquid can occur through the centre of the grommet. The leakage problem is thus solved, according to this second aspect of the invention, by providing a latching engagement between the grommet 21 and the needle hub 8, rather than a latching engagement between a plunger head 20 mounted on the stem 19 and the needle hub 8.

An alternative embodiment of the second and third aspects of the invention is shown in Figure 4 , which shows only the grommet and needle hub of this embodiment. In the embodiment shown in Figure 4, the cavity 38 formed in the front surface 31 of the grommet is substantially spherical, and the opening 39 leading into this cavity is set at a slight angle to the axis of the grommet 21. The latching arms 12 and 13 of the needle hub 8 are formed at their free ends with substantially hemispherical enlargements 41, which are capable of passing through the opening 39 and into the cavity 28 of the grommet to substantially fill the cavity. Resilient deformation of the grommet allows the enlargements 41 to pass through the opening 39. When the plunger assembly 18 is withdrawn, engagement between the enlargements 41 and the cavity 38 withdraws the needle hub 8 and needle 7 through the neck 2 of the syringe, and as the tip of the needle 7 passes through the neck, the resilience of the grommet causes the needle hub 8 and needle 7 to rotate about the ball and socket joint formed by the hemispherical enlargements 41 and the cavity 38, so that the needle lies obliquely within the syringe body and cannot be advanced forward again through the neck 2. In alternative embodiments of the third aspect of the invention, the cavity 38 may be formed in the grommet by a simple axial bore extending from the front surface 31, and a radially inwardly extending annular rib may be formed within this bore. The annular rib may be in a plane perpendicular to the axis of the bore, or may be inclined thereto. Likewise, the axis of the bore may be parallel with the grommet axis or may be slightly inclined thereto so that the latching arms 12 and 13 are slightly flexed as they enter the bore, and can straighten when the needle tip is within the syringe body to place the needle at an angle to the syringe axis. In yet further alternative embodiments of the third aspect of the invention, the detent surfaces 14 of the respective latching arms 12, 13 of the needle hub 8 may be set in planes spaced in, or inclined to, the axial direction of the needle, and the undercut surface 40 within the cavity 38 of the grommet may be aligned perpendicularly to the grommet axis, so that retraction of the needle by the grommet causes an asymmetric tension force on the needle to rotate the needle as it enters the syringe body.

Re-use of the syringe is effectively prevented by the fourth aspect of the invention, embodiments of which are illustrated in Figures 5 to 7. Figure 5 shows in transverse section the leading end of a syringe body 1, with a needle holder 5 attached to the neck 2 of the syringe body and a needle hub 8 and needle 7 positioned within the needle holder and having the latching arms 12 and 13 protruding through the neck 2 into the interior of the syringe body 1. In this embodiment, latching barbs 42 formed on the external surface of the neck 2 of the syringe engage with cooperating grooves in the interior surface of the needle holder 5, to prevent the needle holder 5 from being removed from the neck 2 after it has been snap-engaged onto the neck 2. Adjacent its junction with the syringe body, the neck 2 is formed with a weakened section 43, in this case a circumferential groove in the outer surface of the neck. The groove may have a sharp "V" cross-section to concentrate stress. In this embodiment, once the needle 7 and needle hub 8 have been retracted into the syringe, any attempt to remove the needle holder 5 from the neck 2 of the syringe will result in the neck 2 of the syringe breaking at the weakened section 43, rendering the syringe unusable. The size and shaping of the barbs 42 is so arranged that the force required to remove the needle holder 5 over the barbs 42 is significantly greater than that required to break the neck 2 of the syringe at the weakened section 43. Figures 6 and 7 show an alternative embodiment of this aspect of the invention. In this embodiment, the needle hub 8 is provided with a circumferential groove 44, and the portion 8a of the needle hub between the groove 44 and the leading end of the needle hub is arranged to be freely slidable on the needle 7. When the syringe is assembled as shown in Figure 6, fluid-tight seals are produced between the portion 8a of the needle hub and the bore 10 in the needle holder 5, and between the needle holder 5 and the external surface of the neck 2. The groove 44 is so arranged that, when the latching arms 12 and 13 are engaged and the needle hub and needle are retracted into the syringe, the needle hub 8 breaks at the groove 44 leaving the portion 8a of the needle hub trapped within the needle holder 5. Latching means may be provided on the needle holder 5 to engage the groove 44 and retain the portion 8a of the needle hub positively within the bore 10 of the needle holder 5.

Even if the parts are recovered and the syringe is reassembled, breakage of the needle hub 8 prevents the reuse of the needle as the fluid-tightness of the syringe assembly is destroyed. A leakage path is created between the needle 7 and the portion 8a of the needle hub, via the broken surfaces of the groove 44. The needle thus cannot be reused. The frangible needle hub shown in Figures 6 and 7 may be provided either as an alternative to, or in combination with the frangible syringe neck illustrated in Figure 5.

In an alternative embodiment to that shown in Figure 5, the frangible section 43 may be provided in the needle holder 5 between the sealing surfaces of the bores 9 and 10. With such an arrangement, any attempt to remove the needle holder 5 results in its breakage and the fluid- tightness of the syringe is destroyed, preventing reuse.

Claims

1. A syringe assembly comprising a needle having a penetrating leading end and a needle hub at its trailing end, a syringe body having a leading end for engaging the needle hub and a hollow tubular body with an open trailing end, a plunger assembly comprising a stem movable within the syringe body a grommet fixed to an end of the stem and sealingly engaging the interior of the syringe body and wherein the plunger includes a latching element extending through a central bore in the sealing grommet, wherein first latching means are operable between the needle hub and the syringe body to resist rearward movement of the needle, and wherein the sealing grommet includes an internal cavity for accepting a retaining flange of the plunger, and wherein a face of the internal cavity remote from the stem of the plunger is undercut to provide a thin-walled tubular sealing neck to surround the latching element of the plunger.

2. A syringe assembly comprising a needle having a penetrating leading end and a needle hub at its trailing end, a syringe body having a leading end for engaging the needle hub and a hollow tubular body with an open trailing end, a plunger assembly comprising a stem movable within the syringe body a grommet fixed to an end of the stem and sealingly engaging the interior of the syringe body wherein first latching means are operable between the needle hub and the syringe body to resist rearward movement of the needle, wherein the needle hub and the grommet are engageable to release said first latching means and engage second latching means operable to fix the needle hub to the grommet so that rearward movement of the grommet draws the needle into the interior of the syringe body.

3. A syringe assembly comprising a needle having a penetrating leading end and a needle hub at its trailing end, a syringe body having a leading end for engaging the needle hub and a hollow tubular body with an open trailing end, a plunger assembly comprising a stem movable within the syringe body a grommet fixed to an end of the stem and sealingly engaging the interior of the syringe body, wherein the grommet has first engaging means at its trailing end for engagement with the plunger of the syringe, and second engagement means at its leading end for engaging the needle hub to draw the needle into the syringe when the grommet is moved rearwardly in the syringe body.

4. A syringe assembly according to claim 3, wherein the first engaging means comprises a blind cavity formed n the trailing surface of the grommet, and the second engaging means comprises a second blind cavity formed in the leading surface of the grommet.

5. A syringe assembly according to claim 4, wherein the second blind cavity includes an undercut surface inclined to the axis of the grommet.

6. A syringe assembly comprising a needle having a penetrating leading end and a needle hub at its trailing end, a syringe body having a leading end for engaging the needle hub and a hollow tubular body with an open trailing end, a plunger assembly comprising a stem movable within the syringe body a grommet fixed to an end of the stem and sealingly engaging the interior of the syringe body and wherein the plunger includes a latching element extending through a central bore in the sealing grommet, wherein first latching means are operable between the needle hub and the syringe body to resist rearward movement of the needle wherein the latching means of the plunger is engageable with the needle hub to release said first latching means and engage second latching means operable to fix the needle hub to the plunger so that rearward movement of the grommet draws the needle into the interior of the syringe body, and wherein the second latching means comprise first and second cooperating surfaces on the needle hub and the plunger respectively, cooperable to transmit tensile force, and at least one of said surfaces being in a plane inclined to the axis of the syringe assembly.

7. A syringe assembly comprising a plunger, a sealing grommet, a syringe body, a needle holder, and a needle mounted to a needle hub, the needle holder being sealingly fixable to a leading end of the syringe body and adapted to releasably sealingly support the needle hub, and frangible means being provided in the assembly to prevent disassembly and re-use of the syringe by causing breakage of at least one component of the assembly during disassembly.

8. A syringe according to claim 7 wherein the frangible section is between the syringe body and the leading end of the syringe body.

9. A syringe according to claim 7 wherein the frangible section is between two sealing portions of the needle holder.

10. A syringe according to claim 7 wherein the frangible section is between a sealing portion of the needle hub and a remaining portion of the needle hub.

11. A syringe assembly substantially as herein described with reference to Figures 2, 3, 4, 5 or 6 and 7 of the accompanying drawings.