WO2016185212A1

WO2016185212A1 - Disposable dental anaesthetic syringe

Info

Publication number: WO2016185212A1
Application number: PCT/GB2016/051440
Authority: WO
Inventors: Alan Julian Segal
Original assignee: Astek Innovations Ltd
Current assignee: Astek Innovations Ltd
Priority date: 2015-05-21
Filing date: 2016-05-19
Publication date: 2016-11-24
Anticipated expiration: 2017-11-21
Also published as: GB201508705D0; GB2538708A

Abstract

The present invention relates to a disposable dental safety-syringe comprising a barrel and a sleeve capable of exposing or sheathing a needle. The needle can be sheathed temporarily or permanently, or exposed in a release position, depending on the user's requirements. The sleeve comprises a lock which provides circumferentially offset cooperable configurations interengageable by rotation to move between the release position and a temporary lock position and to a permanent lock position. The circumferentially offset cooperable configurations comprise a number of inwardly extending formations provided in the form of multiple ramp surfaces and stop surfaces. The ramp and stop surfaces allow particular rotational and axial movements of the sleeve in order to attain a desired sleeve position on the barrel. Temporarily sheathing the needle between use greatly reduces the risk of needle-stick injury, especially if the syringe is being passed between users in order to, for example, insert new medication cartridges.

Description

DISPOSABLE DENTAL ANAESTHETIC SYRINGE

Technical Field of the Invention

The present invention relates to disposable dental syringes and in particular to disposable dental safety-syringes including means for preventing needle-stick injury. Background to the Invention

The risk of needle-stick injury is present for all healthcare workers. In the medical field there are a large number of safety- syringes on the market, however in the dental industry the requirements for the design of a safety syringe are significantly different due to the way the products are used. In particular dental syringes: are often used more than once on the same patient so need to be left ready for use in between inj ections; need to be compatible with standard anaesthetics cartridges which often need to be changed during use; must be compatible with a range of standard screw-on needles which must be removed after use; and often need to be passed between dentist and nurse.

Syringes used in the dental industry have traditionally been of the non-disposable type which require sterilisation by autoclave after each use. An example of a non- disposable i.e. reusable safety syringe is set out in EP1465690. For some dentists however the cost and inconvenience of autoclaving a traditional non-disposable syringe can be prohibitive. This is particularly true of those working in dental hospitals or schools where autoclaving is done by an external sub-contractor, or those working in the armed forces without easy access to sterilising equipment. In these instances there is a market for a completely disposable dental safety-syringe.

An example of an existing "semi-disposable" dental syringe is the Ultra Safety Plus syringe manufactured by Septodont. The syringe consists of reusable plunger assembly which fits onto a disposable body with a built-in needle. As shown in figure 1, the syringe body (1) has a plastic sleeve portion (2) which can be pulled forward to protect the needle (not shown) when not in use. The sleeve is operated by pulling it over features on the body so that it locks into place, it has two positions 'park' (for use in between injections), in which the sleeve is pulled over a bulge 3 in the barrel and 'permanent lock' (for use after final injection for disposal), in which the sleeve is pulled beyond the bulge, such that an inwardly extending circumferential rib 4 in the rear of the sleeve clips into a circumferential groove 5 in the barrel. This product has had some success and works fairly well; however there are 3 main limitations of the design: 1. The sleeve locking mechanism is not sufficiently positive. In the 'park' position it relies solely on friction along the axis of the syringe to keep the sleeve in place and can easily be dislodged if knocked, exposing the needle. Even in the 'permanent lock' position, testing has shown that the sleeve will release if moderate pressure is applied. 2. Although this is called a disposable syringe, it is really only semi-disposable as the plunger assembly is reusable so the inconvenience of autoclaving and also the risk of cross infection is not completely avoided.

3. The syringe has a built-in needle and, although this adds convenience, there are a wide variety of lengths and gauges of screw-on needles available to the dentists for use in different applications. By having the needle built-in, user choice and product flexibility is greatly reduced.

Summary of the Invention According to the present invention, there is provided a disposable dental safety syringe comprising a barrel to receive a cartridge of injectable liquid, said barrel having a forward end for connection to a needle and a rearward end for receiving a plunger; and a sleeve mounted relative to the barrel so as to be slidable towards a position at which it is retained on the barrel but extends beyond the forward end to sheath the needle; wherein a lock is provided, the lock comprising circumferentially offset cooperable configurations interengageable by rotation to move between a release position and a temporary lock position and to a permanent lock position; wherein: in the release position, axial movement of the sleeve relative to the barrel is possible; in the temporary lock position, axial movement of the sleeve relative to the barrel is restricted, but rotation back to the release position is possible; and in the permanent lock position both axial movement of the sleeve relative to the barrel and rotation back to the release position are restricted.

The provision of a rotatable lock, rather than the axial lock proposed in the prior art disposable dental syringe, creates a more positive lock, requiring two different motions, twisting and pushing axially to unsheathe the needle from the temporary position, making accidental unlocking much less likely. Moreover, the provision of a permanent locking position, in which rotation back to the release position is restricted, makes it significantly less likely that the needle will become unsheathed, even upon application of a large force. The temporary lock position is for use between injections and the permanent lock position is for use once the final inj ection has been administered, prior to disposal.

The circumferentially offset cooperable configurations may comprise one or more first cooperable configurations being a temporary lock and one or more second cooperable configurations being a permanent lock. The first cooperable configuration may comprise a first formation. The first formation may interengage with a rib. The first formation may be inwardly extending. The first formation may comprise a ramp surface. The first formation may comprise two ramp surfaces.

The rib may be provided on the barrel.

Alternatively the rib may be provided on the sleeve. In that case, the first formation may be outwardly extending.

A plurality of ribs may be provided. The or each rib may extend from the rear of the barrel, but be spaced from the front of the barrel.

The first formation may be semi-cylindrical or semi-spherical.

A plurality of first formations may be provided.

The second cooperable configuration may comprise a second formation. The second formation may interengages with a rib.

The second formation may extend inwardly. The second formation may comprise a ramp surface. The second formation may comprise a stop surface.

The height of the second formation may be higher than the height of the first formation. The height of the second formation may be at least twice as high as the height of the first formation.

A plurality of second formations may be provided.

The first and/or second formations may be formed in the sleeve. The first or second formations may be formed by cutouts in the sleeve.

The first and/or second formations may be formed on a collar.

The collar may be integral with the sleeve.

The lock may be provided at the rear end of the sleeve.

The lock may be rotatable about the axis of the barrel between the temporary lock and the release positions and to the permanent lock position.

Said positions may be limit positions.

The sleeve may have a main tubular body portion which is restrained against rotation around the barrel.

The sleeve may comprise one or more grooves, which are aligned with one or more ribs in the barrel in the release position.

The depth of the grooves may be substantially equal to the height of the second formations.

The lock may be arranged to lock the sleeve in the position at which it is retained on the barrel but extends beyond the forward end to sheath the needle. The syringe may comprise a plunger having an overmoulded rubber seal to allow aspiration of the syringe. The barrel, the sheath, and/or the plunger may be formed from a material which is not suitable for sterilisation by autoclaving.

Marks may be provided to show whether the lock is in the temporary lock, permanent lock, or release position.

The marks may comprise an indicator on the collar and corresponding markers on the barrel.

Detailed Description of the Invention

In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 shows a lateral cross section through a portion of a prior art safety syringe;

Figure 2a shows an isometric view of a syringe according to the invention with the sleeve pushed rearwards; Figure 2b shows an isometric view of the syringe of figure 2a with a needle attached;

Figure 2c shows an isometric view of the syringe of figure 2b with the sleeve pushed forwards and rotated to the temporary lock position, to sheath the needle; Figure 3 shows an exploded plan view of the syringe of figures 2a to 2c;

Figure 4 shows a cross section through the syringe of figures 2a and 2b looking down the barrel (forwards) from the forward end of the collar; Figure 5 a shows a cross section through the syringe of figures 2a and 2b looking down the barrel (forwards) from the rearward end of the collar, with the sleeve in the temporary lock position;

Figure 5b shows a cross section through the syringe of figures 2a and 2b looking down the barrel (forwards) from the rearward end of the collar, with the sleeve in the permanent lock position;

Figure 5 c shows a cross section through the syringe of figures 2a and 2b looking down the barrel (forwards) from the rearward end of the collar, with the sleeve in the release position;

Referring to figures 2a-c to figures 5a-c, a dental syringe has a barrel 10 in the form of a tube of generally circular cross section, which is open at its rear (distal) end and constricted at its forward (proximal) end and has diametrically opposed cut-out side openings 11. A pair of diametrically opposed, longitudinally extending ribs 16 are formed on the outside of the barrel between the side openings 11. The ribs 16 extend from the rear of the barrel, but are spaced from the front of the barrel.

The barrel 10 has a finger grip structure 12 formed at the rearward open end, with a plunger 13 extending through the finger grip structure 12, via a plunger guide 14. The plunger terminates at a forward free end with an enlarged head formed by an overmoulded rubber seal 21 and at a rearward end with a further finger grip 15.

At its constricted forward end, the barrel 10 has an integral end portion 17, having an annular front end wall having a forward central axially extending projection 19 with an external screw thread and an internal axial through bore 20. The barrel 10, including the finger grip structure 12, the plunger 13 and its guide 14 may all be formed from plastics and need not be capable of withstanding disinfection by autoclaving, or other techniques.

Around the barrel 10 is located a sleeve 22 comprising an open ended generally circular cross section tubular portion 23 having a slightly larger diameter than that of the barrel 10 and comprising a pair of diametrically opposed internal grooves 26, which slidably interfit with the ribs 16 fit. The tube may be transparent or may have transparent or cut-out side sections for viewing the plunger 13 or a cartridge 24 through the side opening 11 in the barrel 10. The sleeve 22 may also be formed from plastics that need not be capable of withstanding disinfection, since the syringe is intended to be disposed of.

The sleeve 22 can slide to a rearmost position (figures 2a and 2b) at which its rear end abuts or is close to the finger grip structure 15 and its front end is generally level with the forward end of the barrel 10. The sleeve 22 can slide to a forwards position (figure 2c) at which its rear end is slightly behind the front end of the barrel 22 and the sleeve extends forward beyond such front end.

The interengagement between the internal grooves 26 of the sleeve 22 and the ribs 16 permits easy sliding but prevents relative rotation of the tubular portion 23 of the sleeve 22 and the barrel 10.

At the rearward end of the tube 23 a locking member 25 is integrally formed in the form of an open ended collar of greater outer diameter than the tube 23. The internal grooves 26 extend into the forward end of the locking member 25, which has the same internal shape as the remainder of the sleeve 22, with grooves 26 which align with the ribs 16 and a generally circular cross section, following the shape of the remainder of the generally circular barrel 10.

However, as shown in figures 5a to 5c, cutouts of larger internal diameter are formed in the rearward end of the locking member 25, such that when the tubular portion 23 of the sleeve 22 is pulled right forward, to the un-ribbed region where the ribs are spaced from the front of the barrel 10, the rear ends of the grooves 26 are no longer situated over the ribs 16, and the sleeve 22 can be twisted, so as to bring the ribs 16 out of alignment with the grooves 26. These cutouts co-operate with the ribs 16 to form a lock. In particular, to one side of each diametrically opposed groove 26 (clockwise in the drawings), a first circumferentially offset cooperable configuration 27 is formed, which is a temporary (releasable) lock. Each of the two diametrically opposed first circumferentially offset cooperable configurations 27 consist of a rib-receiving recess 28 circumferentially offset from the groove 26 and separated therefrom by a radially inwardly extending formation 29 having two ramp-surfaces. The inwardly extending formation 29 extends inwardly by a first distance, so as to have a height of about half of the depth of the groove 26. Twisting the collar (clockwise) allows the ribs 16 to move up relatively easily over the first ramp surface of the cooperable configurations 27 and down the second ramp surface into the recess 28, to the position shown in figure 5a. This is the temporary lock position, as the formation 29 only extends slightly inwardly and, owing to the second ramp surface and the relatively small height of the inwardly extending formation 29, can be easily twisted (anticlockwise) back to the release position of figure 5c. In the temporary lock position of figure 5a, axial movement of the sleeve 22 relative to the barrel is restricted, because the rib 16 is out of alignment with the groove 26. Since the cut-outs are only formed in the rear part of the collar, not all the way along the length of the sleeve, the (forward) end of the ribs 16 is prevented from moving axially along the sleeve by stop faces 30.

To the other side of each diametrically opposed groove 26 (anticlockwise in the drawings), a second circumferentially offset cooperable configuration 31 is formed, which is a permanent (non-releasable) lock. Each of the two diametrically opposed second circumferentially offset cooperable configurations 31 consist of a rib-receiving recess 32 circumferentially offset from the groove 26 and separated therefrom by a radially inwardly extending permanent lock formation 33 having one ramp surface 34 and one stop surface 35. The ramp surface 34 of the permanent lock formation 33 is adjacent the groove 26. Thus, twisting the collar (anticlockwise) allows the ribs 16 to move up over the ramp surface 34 of the cooperable configuration 31 and over the stop surface 35 into the recess 32, to the position shown in figure 5b. This is the permanent lock position. The formation 31 extends significantly inwardly, being substantially the same height as the depth of the groove 26 and, owing to the stop surface 35, which is not ramped, twisting (clockwise) back to the release position of figure 5c is prevented.

In the permanent lock position of figure 5b, axial movement of the sleeve 22 relative to the barrel is restricted, because the rib 16 is out of alignment with the groove 26. Since the cut-outs are only formed in the rear part of the collar, not all the way along the length of the sleeve, the (forward) end of the ribs 16 is prevented from moving axially along the sleeve by stop faces 36. Moreover, rotation back to the release position is also restricted, since the ribs 16 cannot pass the stop faces 36 to move back into alignment with the groove 26.

A snap-fit finger 37 (figure 3) is formed near the front end of the barrel 10, with a radially outwardly extending lug, which can be depressed to allow the sleeve 22 to fit onto the barrel, but is arranged to interfere with a corresponding formation (not shown) in the sleeve 22, if it is pulled too far forwards, and thereby prevent the sleeve 22 from being entirely displaced off the barrel 10.

The syringe described is used with a conventional anaesthetic-filled cartridge 24, in the form of a glass tube sealed with a rearend bung and a front end membrane and a needle 38 (fig 3) comprising a stainless steel tube member 39 with an attached hub 40, in the form of an internally threaded cap, adjacent to, but spaced from its rear end. Various embodiments of the syringe are envisaged with the forward central axially extending projection 19 sized appropriately for different standard screw-on-needles 38.

In use, with the sleeve 22 in its forward position and the plunger 13 retracted, the cartridge 24 is inserted through the side opening 11 of the barrel 10.

The plunger head 21 can then be moved forward to engage the cartridge bung.

The needle hub 40 is screwed onto the end projection 19 with the sleeve 22 in its rearward position. This causes the rear end portion of the needle 39 to pass through the bore 20 so as to be directed into a position to penetrate the membrane at the front end of the cartridge 24.

The sleeve 22 can now be moved to its forward position, in which it completely covers the needle 38. The sleeve can be releasably held in this position by rotating the collar 25 such that the first circumferentially offset cooperable configurations 27 in the collar 25 and the ribs 16 interact. An indicator 41 formed on the outer surface of the collar 25 aligns with a marker 42 on the barrel 10 to show that the temporary lock position is engaged.

When required, the collar 25 can be rotated back to the release position (where the ribs 16 are aligned with the grooves 26) and the sleeve 22 can then be moved back to its rearward position. The needle 38 is thereby exposed for use.

After use, but before further use, the sleeve 22 is again moved to its forward position and rotated to the temporary lock position.

After final use, the sleeve 22 is brought to its forward position and the collar 25 is rotated in the opposite direction, such that the second circumferentially offset cooperable configurations 31 interact with the ribs 16, with the ribs 16 held against counter-rotation by the stop faces 36. This rotation brings the indicator 41 into alignment with a second marker 43 on the barrel 10 to show that the permanent lock position is engaged.

The entire disposable safety syringe can then be safely disposed of. The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

For example, ribs 16 having parallel sides have been disclosed, whereby one parallel side interacts with a parallel stop surface 35 in the permanent lock-position, and the other parallel side rides up a ramp to move out of the temporary lock position. However, the ribs need not have that shape and, if the side that rides up the ramp surface of the radially inwardly extending formation 29 was itself ramped, it could assist sliding up the ramped surface of the inwardly extending formation 29. Indeed, in that case, the inwardly extending formation 29 need not even be ramped.

Claims

1. A disposable dental safety syringe comprising a barrel to receive a cartridge of injectable liquid, said barrel having a forward end for connection to a needle and a rearward end for receiving a plunger; and a sleeve mounted relative to the barrel so as to be slidable towards a position at which it is retained on the barrel but extends beyond the forward end to sheath the needle; wherein a lock is provided, the lock comprising circumferentially offset cooperable configurations interengageable by rotation to move between a release position and a temporary lock position and to a permanent lock position; wherein: in the release position, axial movement of the sleeve relative to the barrel is possible; in the temporary lock position, axial movement of the sleeve relative to the barrel is restricted, but rotation back to the release position is possible; and in the permanent lock position both axial movement of the sleeve relative to the barrel and rotation back to the release position are restricted.

2. A disposable dental safety syringe according to claim 1 wherein the circumferentially offset cooperable configurations comprise one or more first cooperable configurations being a temporary lock and one or more second cooperable configurations being a permanent lock.

3. A disposable dental safety syringe according to claim 2 wherein the first cooperable configuration comprises a first formation.

4. A disposable dental safety syringe according to claim 3 wherein the first formation is inwardly extending.

5. A disposable dental safety syringe according to claim 3 or 4 wherein the first formation comprises a ramp surface.

6. A disposable dental safety syringe according to claim 5 wherein the first formation comprises two ramp surfaces.

7. A disposable dental safety syringe according to any of claims 3 to 6 wherein the first formation inter engages with a rib.

8. A disposable dental safety syringe according to claim 7 wherein the rib is provided on the barrel.

9. A disposable dental safety syringe according to claim 7 or 8 wherein the rib extends from the rear of the barrel, but is spaced from the front of the barrel.

10. A disposable dental safety syringe according to claim 7 wherein the rib is provided on the sleeve.

11. A disposable dental safety syringe according to claim 10 wherein the first formation is outwardly extending.

12. A disposable dental safety syringe according to any of claims 8 to 12 wherein a plurality of ribs are provided.

13. A disposable dental safety syringe according to any of claims 3 to 12 wherein the first formation is semi-cylindrical or semi-spherical.

14. A disposable dental safety syringe according to any of claims 3 to 13 wherein a plurality of first formations are provided.

15. A disposable dental safety syringe according to any of claims 2 to 14 wherein the second cooperable configuration comprises a second formation.

16. A disposable dental safety syringe according to claim 15 wherein the second formation inter engages with a rib.

17. A disposable dental safety syringe according to claim 15 or 16 wherein the second formation extends inwardly.

18. A disposable dental safety syringe according to any of claims 15 to 17 wherein the second formation comprises a ramp surface.

19. A disposable dental safety syringe according to any of claims 15 to 18 wherein the second formation comprises a stop surface.

20. A disposable dental safety syringe according to any of claims 15 to 19 when dependent on any of claims 3 to 14 wherein the height of the second formation is higher than the height of the first formation.

21. A disposable dental safety syringe according to claim 20 wherein the height of the second formation is at least twice as high as the height of the first formation.

22. A disposable dental safety syringe according to any of claims 15 to 21 wherein a plurality of second formations are provided.

23. A disposable dental safety syringe according to any of claims 3 to 22 wherein the first and/or second formations are formed in the sleeve.

24. A disposable dental safety syringe according to claim 23 wherein the first aand/or second formations are formed by cutouts in the sleeve.

25. A disposable dental safety syringe according to any of claims 3 to 24 wherein the first and/or second formations are formed on a collar.

26. A disposable dental safety syringe according to claim 25 wherein the collar is integral with the sleeve.

27. A disposable dental safety syringe according to any of the preceding claims wherein the lock is provided at the rear end of the sleeve.

28. A disposable dental safety syringe according to any of the preceding claims wherein the lock is rotatable about the axis of the barrel between the temporary lock and the release positions and from the release position to the permanent lock position.

29. A disposable dental safety syringe according to any of claims 1 to 28 wherein said positions are limit positions.

30. A disposable dental safety syringe according to any of the preceding claims wherein the sleeve has a main tubular body portion which is restrained against rotation around the barrel.

31. A disposable dental safety syringe according to any of the preceding claims wherein the sleeve comprises one or more grooves, which are aligned with one or more ribs in the barrel in the release position.

32. A disposable dental safety syringe according to claim 31 when dependent on any of claims 15 to 30 wherein the depth of the grooves may be substantially equal to the height of the second formations.

33. A disposable dental safety syringe according to any of the preceding claims wherein the lock is arranged to lock the sleeve in the position at which it is retained on the barrel but extends beyond the forward end to sheath the needle.

34. A disposable dental safety syringe according to any of the preceding claims wherein the syringe comprises a plunger having an overmoulded rubber seal.

35. A disposable dental safety syringe according to any of the preceding claims wherein the barrel, the sheath, and/or the plunger are formed from a material which is not suitable for sterilisation by autoclaving.

36. A disposable dental safety syringe according to any of the preceding claims wherein marks are provided to show whether the lock is in the temporary lock, permanent lock, or release position.

37. A disposable dental safety syringe according to claim 36 wherein the marks comprise an indicator on the collar and corresponding markers on the barrel.