WO1991003269A1

WO1991003269A1 - Safety syringe

Info

Publication number: WO1991003269A1
Application number: PCT/AU1990/000377
Authority: WO
Inventors: James Dunstone Townsend
Original assignee: Townsend Controls Pty. Ltd.
Priority date: 1989-08-28
Filing date: 1990-08-28
Publication date: 1991-03-21

Abstract

A syringe including a syringe barrel (1) and a plunger (2) which by continued pressure on the plunger after the injecting stroke an end piece (5) and an attached cannula needle (8) are released from the barrel of the syringe (3) and is automatically and substantially irreversible withdrawn into the plunger such that none of the needle is left external of the syringe barrel. Withdrawal means may include springs (21) or a vacuum. The needle assembly (5, 8) is held in place by a reverse star washer (13).

Description

SAFETY SYRINGE

This invention relates to syringes of a type useful as hyperdermic syringes.

Hitherto syringes have usually been of simple construction in which a piston is able to reciprocate within a cylinder. The assembly is completed by mounting a needle appropriate to the purpose onto the distal end of the cylinder or barrel.

The construction has the advantage of ease of construction and cheapness, but it does little or nothing to protect the user or those in the vicinity of the user, or those involved in the removal of waste materials including used syringes and/or used needles from accidents in which non-intentional penetration of the skin of an unintended person occurs following use of the syringe or needle thus exposing such accidentally "pricked" persons to the risk of cross-infection or contamination with the AIDS virus.

The serial use of syringe/needle combinations in certain (usually non-medical) situations is and has resulted in a high incidence of cross-infection with AIDS, hepatitis B and other diseases among such user groups.

Patent specification AU-A-14189/88 describes a single use hypodermic syringe whereby following the injection of injectate the needle can be allowed under a resilient pressure to be withdrawn into the cylinder of the syringe and the piston is prevented from further movement. The mechanism for this action involves a series of cams, flexible levers and latches,. The actual cylinder in which the piston slides is a tensioned elastic bladder which after the injecting stroke provides a resilient retraction pressure which can however be resisted by the operator simply not reducing pressure on the piston.

It is an object of this invention to provide a safety syringe in which there is an improved and safer way to effect needle retraction.

Thus there is provided according to this invention a syringe which includes a barrel, a piston operable in the barrel and needle support means adapted to support a hollow needle at an end of the barrel, the needle support means being separable from the barrel, means adapted to assist such release being effected by relative positioning of the piston to the barrel, resilient means adapted to effect a withdrawal pressure on the needle support means and any attached needle there with with respect to the barrel, and an inner piston within the piston and an inner chamber also within the piston and into which the inner piston with ensnared needle support means are adapted to be moved under the said resilient withdrawal pressure.

In preference the invention is further characterised in that the resilient means are provided by means establishing a gaseous pressure differential between the inner chamber and an environment external to but within which the syringe is located, or alternatively the resilient means are a tensioned spring.

The significant advantage of this arrangement is that health workers who are consistently using needles may be more persuaded to continue the injection stroke so that the syringe with its attached needle will be rendered fully safe against further accidental needle strike.

In the circumstances that will often apply when a health worker is giving an injection such as a very disturbed patient or the need for great urgency, it is well known that hypodermic syringes with their attached needles have to be used in all manner of ways and there is the continuing potential for accidental needle strike with a contaminated needle.

It has been previously proposed by others that there be a technique by which after use, the syringe is rendered non-operable but this does not avoid the problem that the needle itself is still accessible in a very easy way and this does nothing to avoid needle strike potential.

In an alternate arrangement, there has been proposed that the needle be withdrawn into the barrel by subsequent withdrawal of the plunger but the difficulty here is that in urgent situations, there will be many occasions when health workers will simply not have the time or the inclination to perform the extended step of capturing and fully withdrawing on a manual basis the needle.

The advantage of the present proposal therefore is firstly that there can be designed an arrangement using this concept whereby with a minimal extra continuing pressure after full usage has been made of the syringe, the needle will be effectively withdrawn and rendered totally safe and further, the plunger will be in a completely depressed position so rendering the waste volume of the then disposal syringe somewhat less than might have to be the case if the plunger is withdrawn as a method of making it safe. A first of these is that the inner piston is retained with respect to the plunger by positive means with respect to its forward and aft relative position.

The point here is that the inner piston needs to first of all provide an effective seal with the plunger which provides an inner cylindrical shape but at the same time, the inner piston must be retained positively against quite high hydraulic pressures firstly to ensure that there is no accidental release of the piston during uptake of injectate and at the same time, the piston must be able to resist the strong hydraulic pressure during almost all of the stroke while the plunger is directed inwardly to force the injectate through the narrow hollow needle and of course into the patient.

It must also be remembered that what is being proposed is an additional continual pressure on the inner piston relative to the plunger so that upon release, this will have sufficient force applied to retract both the piston, and the captured needle.

The difficulty has been however to propose an arrangement by which, recalling that there must be positive securement of the inner piston with respect to the plunger, that there can be a totally reliable arrangement to effect a release at the completion of the injecting stroke and if possible such that such final release will not add significantly to pressure requirements for an operator.

A number of attempts have been made to try to solve this particular problem for instance by providing breakaway tabs with plastic deformation being used as the criteria for release pressure.

The problem with this approach has been that if the pressure of a rather energetic health worker could be somewhat high, then accidental release of the inner piston could be most awkward and of course could be quite dangerous in a situation where there is limited access to the material to be injected.

After considerable investigation, it has been realised that such release cannot effectively be acceptable if it is pressure dependent and there has been therefore provided a position dependent release technique.

This is in preference achieved by providing that there is a divertable finger which by reason of the position of the inner piston with respect to the barrel will be caused to divert to an extent that at a selected position of the plunger, the inner piston will be released from specific interlocking with the plunger of itself.

In order to be effective however it is important that the inner piston can effectively capture and take with it on an extraction step, the needle and to the extent necessary, the base to which the needle is attached.

Once again, the capture step that is an interlocking of the inner piston with a base to which the needle is attached also needs to be attached on a basis which is not dependent upon excessive pressures and in preference is also attachable simply by reason of relative positioning.

Finally, there is the mechanism by which the needle is attached to the barrel and in preference, the needle is attached to a base which is separably secured to the barrel and is releasable once again by reason of a relative positioning of the plunger with respect to the barrel.

Several mechanisms are potentially available in order to achieve this but a first mechanism that has been found to be primarily effective and is therefore a preferable technique provides that the base is securable within the end of the barrel by reason of a jamming of the two parts together with relatively located frusto-conical shapes and there is a breakaway mechanism activated by movement of the plunger as a final positioning step with respect to the barrel.

For a better understanding of this invention it will now be described with respect to two preferred embodiments. The first utilises a spring to retract the needle and the second uses a vacuum.

The first embodiment is now described with the assistance of drawings in which:

FIGURE 1 is a side cross section view showing the syringe prior to use;

FIGURE 2 is a side cross section showing the plunger in a first position which is a position in which the plunger has been moved to a first capture position between the inner piston and the base,

FIGURE 3 is the same view as in Figure 2 with the plunger being moved slightly more forward so that the release tongue is being diverted by the base into a release position, FIGURE 4 is a cross-sectional view along the lines through 4 in Figure 3,

FIGURE 5 is the same view as in Figures 2 and 3 with the plunger having been pushed further forward providing the effective release of the base which has been captured by the inner piston,

FIGURE 6 is the same cross-sectional view as in Figures 2, 3 and 5 subsequent to the release of the base showing the retractive effect of the spring pulling both the inner piston and the base with the attached needle into a encapsulated position within the plunger,

FIGURE 7 is a plan view of the reverse star washer used to assist in affecting a release of the base from a gripping position relative to the barrel, and finally

FIGURE 8 is an enlarged view of the forward section of the plunger,

FIGURE 9 shows a cross sectional side view of a syringe according to the second prefered embodiment which will be described hereafter prior to use,

FIGURE 10 shows the syringe of Figure 9 in more detail just at the end of the injecting stroke,

FIGURE 11 shows the syringe of Figure 9 just as the needle is about to be retracted into the plunger,

FIGURE 12 shows the reverse star washer in plan view used to release the needle, and finally

FIGURE 13 shows the needle of the syringe of Figure 9 retracted into the plunger.

Now referring to the drawings in detail, there is a barrel 1 which is generally of cylindrical shape providing an innermost cylinder within which a plunger 2 is shown which can be slidably operated. At the inner end of the barrel 1 is an end 3 which provides an innermost frusto- conical shape at 4 into which a base 5 can be fitted with gripping force at the same time providing coincidence in the alignment of feed conduits 6 and within the base feed conduit 7.

There is a needle 8 with a boss 9 fitted to an outlet end of the base 5.

At the further end of the barrel 1 there is a finger grip 10.

Adapted to slidably move through the inner piston shape of the barrel 1 is plunger 2 which has at its end seals at 11 and an innermost abutting edge 12 adapted to engage the outer edge of a reverse star washer 13.

Adapted to operate within the plunger 2 and to be slidably retainable along the length of the plunger is inner piston 14.

The inner piston 14 has seals 15 and includes around its forward perimeter respectively three release tongues as shown typically at 16 and offset by 60° from these three capture fingers 17.

Adapted to operating cooperation with respectively the release tongues 16 and the capture fingers 17 is the outwardly facing dish shaped part of the base 5 at 18.

Around an outer edge the perimeter of this part 18 is a barb shape at 19 and the inner side of this dish shape at 20 is adapted to appropriately engage with the release tongue 16 so as to cause this to come into a release position relative to abutting face 20 on the plunger 2.

There is a helical stainless spring at 22 which is shown in Figures 1 , 2 ,3 and 5 as under tension so that this is adapted to keep a retraction pressure on the inner piston 14 when this is in the location as shown in Figures 1 , 2, 3 and 5.

The rear end of the spring 22 is captured at 23 by thumb pressure member 24.

An aperture 25 is located in this whereby the inner piston can be pushed into a position from first location within the plunger 2 to a position as shown in Figures 1 , 2, 3 and 5. It will now be seen how the arrangement works and the advantages of the arrangement shown.

As a first item, as a syringe, the device will work in the conventionally normal manner in so far that the inner piston 14 is captured and will provide an effective seal at the end of the plunger 2 so the plunger 2 can be used in the conventional way to withdraw fluid through the needle 8 and subsequently inject this.

At the end of an injection stroke however the operator may continue the injection step by continued pressure on the pressure member 24 so that by reason of the innermost position of the plunger 2 and through this the inner piston 14, the inner piston is first brought to a position so that its capture finger 17 engages over the other side of the barb shape 19.

With continued depression, plunger 2 then reaches the stage where the release tongue 16 is pushed inwardly to a sufficient extent to release its interlocking with the abutting face 21 where upon the inner piston 14 is free to move and will do so under pressure of the helical spring 22 to the extent allowed by the capture finger 17 in relation to its engagement with the barb shape 19.

From this point on, the inner piston is simply held in position by reason of the barb shape and the capture finger so that the final release exercise is to continue the pressure of the plunger which in turn then presses against the external edges of the reverse star washer 13 which pivots around its support point with the barrel 1 providing with significant mechanical advantage a release pressure for the base 5.

As soon as the base is released from ripping pressure this will allow the inner piston 14 with its captured base and attached needle to retract to the position shown at Figure 6.

The second prefered embodiment will now be described with the aid of Figures 9,10, 11 12,and 13

Now refering to the last mentioned Figures it can be seen that the syringe comprises a barrel 26 into which is a plunger 27. The plunger 27 is slidably operable within the barrel 26 by means of pressure being applied to the thumb piece 28 whilst the barrel 26 is held relatively in place by use of the finger piece 29. Inserted into the barrel 26 is a base end 30 which is held therein by a friction, that is the base end 30 and the barrel 26 form a friction fit.

Attached to the base end 30 is a hollow needle 31.

The base end 31 has side communicating ducts 32 and a central communicating duct 33. The barrel 26 has side communicating ducts 34 which, prior to retraction of the needle, align with the communicating ducts 32. By means of the communicating ducts 32, 33 and 34 a passage is formed though which a injectant can by drawn into the space 35 and then injected therefrom via the hollow needle 31.

An abutment is provided in the shape of the barrel at 36. Between the barrel 26 and the end piece 30 at 36 a reverse star washer 37 is placed.

Between the plunger 27 and the barrel 26 are sealing means 38 effecting a seal between the two so enabling and injectant to be drawn into and ejected from the space 35.

Within the plunger 27 is hollow and an inner piston 39 which is sealed by a second sealing means 40 to the inside of the plunger 27. The inner piston extends only partly into the plunger 27, the rest of the cavity within the hollow plunger 27 is evacuated.

The inner piston 39 is characterised by being cup shaped with a base furthest from the needle 31 and tapered side walls. Attached to the inner piston 39 is the second sealing means 40 and a member 41 made of plastics material. The member 41 is adapted to sit part way into the inner piston 39 and has a periphery adapted to sit upon the periphery of the plunger 39 and also on a recessed face 42 of the plunger 27. The member 41 is adapted to prevent the retraction of the inner piston 39 under the influence of the vacuum within the evacuated hollow portion of the plunger 26.

Upon the member 41 is fixed a disk like member 43 which has a hole cut out of the central portion.

The end piece 30 has a protruding section 44 characterised by captivating means 45. Having described the parts of the syringe exhibiting the second prefered embodiment now the operation of the syringe will be described. Figure 9 shows the syringe prior to use and ready to be filled with an injectant.

When the syringe is used, the plunge 27 is pushed into the barrel 26 forcing the injectant out of the space 35. Towards the end of the plunger 27 travel, disk member 43 is pushed over the protruding portion 44 of the end piece 30 and the disk member 43 is held captive of the protruding portion 44 by captivating means 45. This stage is illustrated in Figure 10.

Further movement of the plunger 27 into the barrel 26 results in the reverse star washer 36 being deformed. The deformation of the reverse star washer 36 causes the end piece 30 to be released from its friction fit, and it and the attached needle start to be withdrawn into the barrel 26. The movement of the plunger 27 causes the face 46 of the plunger 27 to seal the ducts 34 and also causes the member 41 to deform so releasing the inner piston 39 to be retracted into the plunger 27. The movement of the inner piston 39 retracts the attached end piece 30 and needle 31 into the barrel of the syringe.

This then describes in a general sense how the concept described at the initial part of the specification can be put into practice in two prefered embodiments. It can be appreciated that, whilst two prefered embodiments are described in detail herein, there many variations on the theme which would occur to a person skilled in the art.

For instance, the capture finger can be rearranged to capture the inside of the dish shape of the base with the appropriate barb its shape being located there.

Likewise, there can be two rather than three capture fingers and equivalent^ two instead of three release tongues.

This then describes the invention from which it will be seen that there can be provided a very effective method of providing for an automatic retraction of a needle by reason only of a continuing depression relative to the barrel of a plunger in respect of a hypodermic syringe.

Claims

CLAIMS :

1. A syringe which includes a barrel, a piston operable in the barrel and needle support means adapted to support a hollow needle at an end of the barrel, the needle support means being separable from the barrel, means adapted to assist such release being effected by relative positioning of the piston to the barrel, resilient means adapted to effect a withdrawal pressure on the needle support means and any attached needle there with with respect to the barrel, and an inner piston within the piston and an inner chamber also within the piston and into which the inner piston with ensnared needle support means are adapted to be moved under the said resilient withdrawal pressure.

2. A syringe as in claim 1 in which the resilient means are a tensioned spring.

3. A syringe as in claim 1 further characterised in that the resilient means are provided by means establishing a gaseous pressure differential between the inner chamber and an environment external to but within which the syringe is located.

4. A syringe which includes a barrel, a piston operable in the barrel and needle support means adapted to support a hollow needle at an end of the barrel, said piston comprising a hollow plunger and including an inner piston, the arrangement being adapted such that a selected position of the plunger relative to the barrel will be caused to effect a release of the needle support means and any needle attached thereto, and adapted to allow the needle support means and any needle attached thereto to be withdrawn into the hollow plunger.

5. A syringe as in claim 4 further characterised in that there are means adapted to effect the attachment of the inner piston to the needle support means, and resilient means effective between the inner piston and the plunger to effect the substantial withdrawal of the needle support means and any needle attached thereto into the plunger.

6. A syringe as in claim 5 in which there are means to form a seal between the inner piston and the plunger, means to form a seal between the barrel and the plunger, the needle support means comprises an end piece adapted to be held into a substantially frusto-conical orifice through the barrel adapted for that purpose, the end piece being further characterised by being adapted to have a needle attached thereto and at least one duct within the end piece adapted to communicate with the inside of the hollow needle to enable a continuous ducting between inside the barrel and outside the barrel to be formed.

7. A syringe which includes a barrel, a piston operable in the barrel, a needle support means comprising an end piece adapted to be held into a substantially frusto-conical orifice through the barrel adapted for that purpose, the end piece being further characterised by being coaxial with the barrel and adapted to have a needle attached thereto and also at least one duct within the end piece adapted to communicate with the inside of the hollow needle to enable a continuous ducting between the inside the barrel and outside the barrel to be formed, said piston comprising a hollow plunger supporting an inner piston, the arrangement being adapted such that a selected position of the plunger relative to the barrel will be caused to effect a release of the needle support means and any needle attached thereto, the arrangement being adapted to allow the needle support means and any needle attached thereto to be withdrawn into the hollow plunger, a seal between the inner piston and the plunger, means to form a seal between the barrel and the plunger, and the syringe is further characterised by a release member being adapted to fit in part between the end piece and the barrel and protrude into a space within the barrel and adjacent to the end piece.

8. A syringe as in claim 7 further characterised by end piece having at least one catch means and at least one release means adapted to cooperate with the inner piston.

9. A syringe which includes a barrel, a piston operable in the barrel, a needle support means comprising an end piece adapted to be held into a substantially frusto-conical orifice through the barrel adapted for that purpose, the end piece being further characterised by being coaxial with the barrel and adapted to have a needle attached thereto and also at least one duct within the end piece adapted to communicate with the inside of the hollow needle to enable a continuous ducting between the inside the barrel and outside the barrel to be formed, said piston comprising a hollow plunger supporting an inner piston, the arrangement being adapted such that a selected position of the plunger relative to the barrel will be caused to effect a release of the needle support means and any needle attached thereto, the arrangement being adapted to allow the needle support means and any needle attached thereto to be withdrawn into the hollow plunger, a seal between the inner piston and the plunger, means to form a seal between the barrel and the plunger, a release member being adapted to fit in part between the end piece and the barrel and protrude into a space within the barrel and adjacent to the end piece, the end piece having at least one catch means and at least one release means adapted to cooperate with the inner piston, the inner piston having at least one catch member, and at least one releaseable catch means adapted to mate with a corresponding portion of the plunger, the plunger being further characterised by at least one member adapted to cooperate with the release member so that during the last of the travel of the plunger when the plunger is forced into the barrel the release member is caused to release the end piece from being held to the barrel.

10. A syringe as in claims 6, 8 or 9 wherein the end piece is held in place to the barrel by a friction fit, the inner piston is attached to a tensioned spring within the plunger which is also attached at the distal end to the plunger, the plunger has a hole coaxial with the longitudinal axis of the plunger and distal from the inner piston, and the end piece has a catch member adapted to capture another catch member attached to the inner piston.

11. A syringe which includes a barrel, a piston operable in the barrel, a needle support means comprising an end piece adapted to be held into a substantially frusto-conical orifice through the barrel adapted for that purpose, the end piece being coaxial with the barrel and adapted to have a needle attached thereto and also at least one duct within the end piece adapted to communicate with the inside of the hollow needle to enable a continuous ducting between the inside of the barrel and outside of the barrel to be formed, said piston comprising a plunger supporting an inner piston, the arrangement being adapted such that a selected position of the plunger relative to the barrel will be caused to effect a release of the needle support means and any needle attached thereto, the arrangement being adapted to allow the needle support means and any needle attached thereto to be withdrawn into the hollow plunger, a seal between the inner piston and the plunger, means to form a seal between the barrel and the plunger, means to form a seal between the barrel and the plunger, further characterised by a release member being adapted to fit in part between the end piece and the barrel, and protrude into the space within the barrel, and the cavity of the hollow plunger is substantially evacuated to produce a substantial pressure difference between inside the plunger and outside the plunger.

12. A syringe as in any of the preceding claims in which the syringe has a hollow needle attached thereto.

13. A syringe as in any of the preceding claims in which the syringe is adapted so that when the plunger is fully pressed into the barrel and the needle support and any needl attached thereto is withdrawn into the plunger there is none of the needle external to the barrel.

14. A syringe substantially as described herein with or without reference to the accompanying Figures or as illustrated in the accompanying Figures.