GB2306332A

GB2306332A - A hypodermic syringe

Info

Publication number: GB2306332A
Application number: GB9522119A
Authority: GB
Inventors: Richard Warrington George
Original assignee: Fenson and Co Ltd
Current assignee: Fenson and Co Ltd
Priority date: 1995-10-28
Filing date: 1995-10-28
Publication date: 1997-05-07
Anticipated expiration: 2015-10-28
Also published as: GB9522119D0; GB2306332B

Abstract

A hypodermic syringe comprises a syringe barrel 10 having a hollow tip 11 at one end, a needle 16 extending through an aperture 18 at the free end of the hollow tip, a plunger 12 reciprocatable within the syringe barrel, means 17 engageable with the plunger when the plunger is moved fully into the syringe barrel for withdrawing the needle into the syringe barrel when the plunger is drawn outwards and means 26 for preventing the needle re-extending through the aperture 18 when the plunger is again moved fully into the syringe barrel.

Description

A HYPODERMIC SYRINGE This invention relates to a hypodermic syringe.

Accidental sticks with a used needle of a hypodermic syringe can transmit a disease. It is now well known to provide the needle with a shield which can be moved to cover the needle tip after the hypodermic syringe has been used. In order to move the shield, a user must move one hand beyond the syringe barrel towards the needle tip. Accidents can still happen.

The present invention seeks to provide a hypodermic syringe in which accidental needle stick is less likely.

According to the invention there is provided a hypodermic syringe comprising a syringe barrel having a hollow tip at one end, a needle extending through an aperture at the free end of the hollow tip, a plunger reciprocatable within the syringe barrel, means engageable with the plunger when the plunger is moved fully into the syringe barrel for withdrawing the needle into the syringe barrel when the plunger is drawn outwards and means for preventing the needle re-extending through the aperture when the plunger is again moved fully into the syringe barrel.

Preferred and/or optional features of the invention are set forth in claims 2 - 12, inclusive.

The invention will now be more particularly described with reference to the accompanying drawings, in which: Figure 1 is a sectional view of one embodiment of a hypodermic syringe according to the present invention showing the needle in an operative position, Figure 2 is a view similar to Figure 1 but showing the plunger extended and the needle withdrawn into the syringe barrel, Figure 3 is a view similar to Figure 2 but showing the plunger after it has again been moved fully into the syringe barrel, Figures 4 and 5 are plan and side views of one of the spring washers of the syringe shown in Figures 1 to 3, Figure 6 is a fragmentary sectional view showing a first modification to the syringe shown in Figures 1 to 5, and Figure 7 is a fragmentary sectional view showing a second modification to the syringe shown in Figures 1 to 5.

Referring to Figures 1 to 5 of the drawings, the hypodermic syringe shown therein has a syringe barrel 10 having at one end a hollow tip 11 which is permanently secured to a tapered nose 9 of the barrel 10 and which communicates with the interior of the barrel 10, and a plunger 12 reciprocatable within the barrel 10. The plunger 12 has a hollow cylindrical core 13, a plurality of guide fins 14 which extend radially outwards from the core 13 and which guide the plunger 12 within the barrel 10 and an elastomeric diaphragm 15 at the inner end of the plunger 12.

The hypodermic syringe also has a needle 16 which is supported by a plunger engageable member 17 and which extends through an aperture 18 in the free end of the tip 11.

The plunger engageable member 17 has a sleeve portion 19 which receives the needle 16 as a sliding fit, a tapered, barb-like, annular head 20, a cylindrical guide portion 21 which is slidable within the tip 11, a frustoconical portion 22 connecting the sleeve portion 19 to the guide portion 21, an annular locking portion 23 which is snap fittably engageable with an annular groove in the tip 11 and an annular stop portion 25 which is engageable with the inner end of the barrel 10.

The needle 16 has a head 16a at its inner end and this head 16a prevents the needle 16 from being withdrawn from the sleeve portion 19 in a direction towards the aperture 18.

The syringe has a first spring washer 26 which is an interference fit in the blind end of the hollow tip 11 and which grips the needle 16 in such a way as to permit movement of the needle 11 relative to the washer 26 only in a direction towards the plunger 12.

A second spring washer 27 is provided between the spring washer 26 and the plunger engageable member 17. This second spring washer 27 is held captive in a recess 28 defined by the frustoconical portion 22 and the guide portion 21 of the plunger engageable member 17, by an inwardly directed flange 29. In its unstressed condition, it does not grip the needle 16 and is a loose fit in the recess 28. However, when compressed between the washer 26 and the plunger engageable number 17, the washer 27 grips the needle 16 and prevents the needle sliding relative to the plunger engageable member 17 during use.

The barrel 10 has an internal inwardly directed, annular projection 30 at its outer end to prevent complete withdrawal of the plunger 12 from the barrel 10. The barrel also has a small inwardly directed step 31 at its inner end adjacent to the tip 11 to prevent the plunger from being unintentionally moved fully into the barrel 10. As an alternative to the step 31, the plunger 12 may have a sprung leg (or ring) 32 which is arranged to engage the outer end of the barrel 10 when the syringe is supplied to prevent the plunger 12 from being moved fully into the barrel 10 but which springs inwards as soon as the plunger 12 is pulled outwards to then allow the plunger to be moved fully into the barrel 10.

The barrel 10 may also have an annular guard ring 33 at its end adjacent the tip 11 to prevent a user's fingers from slipping off the barrel 10 towards the needle 16.

The syringe may also be provided with manually operable locking means (not shown) for preventing the plunger 12 from being drawn outwards after use.

The operation of the syringe will now be described.

The syringe is supplied in the condition shown in Figure 1. The needle 16 is supported by the plunger engageable member 17 and extends through the aperture 18 in the free end of the tip 11. The needle tip is protected by a removable cap (not shown) and the diaphragm 15 of the plunger 12 is in contact with the step 31.

The needle cap is removed and a drug to be injected is drawn into the barrel 10 in conventional manner. Having vented air from the syringe, the patient is given an injection in the normal way. At the end of the injection stroke, the plunger is forced fully into the barrel 10 and the barb-like, annular head 20 of the plunger engageable member 17 penetrates the centre of the diaphragm 15 and snap fittably engages behind an annular, radially inwardly directed flange 34 at the inner end of the cylindrical core 13 of the plunger 12. The needle 16 can then be withdrawn into the barrel 10 by pulling the plunger 12 outwards. As the plunger 12 is extended the frustoconical portion 22 of the plunger engageable member 17 flexes and the annular locking portion 23 of the plunger engageable member 17 is disengaged from the annular groove in the tip 11.The plunger 12 is shown in its outermost position in Figure 2 in which the plunger engageable member 17 and needle 16 are withdrawn from the tip 11 and into the main body of the barrel 10.

The plunger 12 may then be pushed into the barrel 10 once again, but when the tip of the needle 16 engages the washer 26, the washer 26 will grip the needle 16, and although the bevelled tip of the needle 16 may enter the aperture 18, as soon as the spring washer 26 engages the full circumferential surface of the needle 16 it will prevent further movement of the needle 16 and hence prevent the needle 16 from reextending through the aperture. A loosely fitting flat washer (not shown) may be provided between the spring washer 26 and the blind end of the tip 11 so that, when the needle 16 is withdrawn into the barrel 12, the flat washer moves out of alignment with the aperture 18 to prevent even the bevelled tip of the needle re-entering the aperture 18.On further inward movement of the plunger 12, the sleeve portion 19 of the plunger engageable member 17 will slide over the needle 16 until the stop portion 25 engages the inner end of the barrel 10 and the annular locking portion 23 of the plunger engageable member 17 will re-engage in the annular groove in the tip 11. The washer 27 will compress and grip the needle 16 to prevent the needle from falling out of the sleeve portion 19 and into the hollow cylindrical core 13 of the plunger 12.

The needle 16 is therefore held within the barrel 10 of the syringe as shown in Figure 3 and the syringe can be disposed of safely without risk of accidental needle stick.

If the hollow tip 11 of the barrel 10 is offset from the central axis of the barrel, the barrel 10 and plunger 12 can be provided with mutually co-operable means to prevent angular displacement of the plunger 12 relative to the barrel 10 and to ensure that the plunger 12 is correctly aligned with the plunger engageable member 17.

Also, a metal or plastics sleeve (not shown) may be placed over the needle stem to prevent the washers 26 and 27 from crushing the needle.

A typical example of the washer 26, 27 is shown in Figures 4 and 5. This is formed of metal and is of generally frustoconical shape with a central hole 35 and radially extending slits 36. However, the slits 36 could be omitted. Also, the washers 26, 27 could be moulded in plastics material and provided with an extended central collar to prevent crushing of the needle. In this case, the needle surface may be textured to improve grip.

Figure 6 shows a modification to the syringe described above in which the washer 27 is replaced by a frustoconical, elastomeric bush 37 which engages a frustoconical wall portion 38 of the tip 11' when the needle 16' and plunger engageable member 17' are in an operable position. In this condition, the bush 37 is compressed slightly to grip the needle 16' and to prevent the needle from sliding into the barrel 10 of the syringe during use. When the plunger engageable member 17' and the needle 16' are withdrawn by the plunger into the barrel, the bush 37 becomes uncompressed.

Figure 7 shows a modified diaphragm 15' having an integral cap 39 for receiving the head 20' of the plunger engageable member 17". This avoids the need for the head of the plunger engageable member to penetrate part of the diaphragm to engage behind a formation on the plunger itself. The cap 39 has a small aperture 40 to allow drugs to be injected into a patient to pass into the needle at the end of an injection stroke of the plunger.

In yet a further modification some means for capturing the head of the needle when in its fully withdrawn position may be provided in the core of the plunger as an additional safeguard against removal of a contaminated needle.

The embodiments described above are given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined by the appended claim.

Claims

1. A hypodermic syringe comprising a syringe barrel having a hollow tip at one end, a needle extending through an aperture at the free end of the hollow tip, a plunger reciprocatable within the syringe barrel, means engageable with the plunger when the plunger is moved fully into the syringe barrel for withdrawing the needle into the syringe barrel when the plunger is drawn outwards and means for preventing the needle re-extending through the aperture when the plunger is again moved fully into the syringe barrel.

2. A hypodermic syringe as claimed in claim 1, wherein said plunger engageable means is releasably engageable with said hollow tip.

3. A hypodermic syringe as claimed in claim 2, wherein the plunger engageable means is snap fittably engageable with said hollow tip.

4. A hypodermic syringe as claimed in any one of the preceding claims, wherein the needle is a slidable fit in the plunger engageable means but is held captive relative to the plunger engageable means so as not to be removable from the plunger engageable means in the direction in which the plunger is moved into the syringe barrel.

5. A hypodermic syringe as claimed in any one of the preceding claims, wherein the plunger engageable means has a tapered head which is engageable with a formation at the inner end of the plunger when the plunger is moved fully into the syringe barrel.

6. A hypodermic syringe as claimed in any one of the preceding claims, wherein the means for preventing the needle re-extending through the aperture comprises a spring washer which grips the needle when the needle is in its operative position in which it extends through said aperture and which only allows the needle to be withdrawn into the syringe barrel.

7. A hypodermic needle as claimed in claim 6, wherein the spring washer is an interference fit in the hollow tip of the syringe barrel.

8. A hypodermic syringe as claimed in claim 6 or claim 7, wherein the spring washer is disposed between the plunger engageable means and the free end of the hollow tip.

9. A hypodermic syringe as claimed in any one of the preceding claims, comprising needle retaining means which is compressed when the plunger engageable means is engaged with the hollow tip to grip the needle.

10. A hypodermic syringe as claimed in claim 9, wherein the needle retaining means comprises a further spring washer which is held captive relative to the plunger engageable means.

11. A hypodermic syringe as claimed in any one of the preceding claims, wherein the plunger and syringe barrel have means for preventing the plunger from being unintentionally moved fully into the syringe barrel.

12. A hypodermic syringe as claimed in any one of the preceding claims, wherein the syringe barrel has a guard to protect a user's fingers from sliding off the syringe barrel towards the needle.

13. A hypodermic syringe as claimed in any one of the preceding claims, further comprising manually operable locking means for preventing the plunger from being drawn outwards after use.

14. A hypodermic syringe substantially as hereinbefore described with reference to the accompanying drawings.