WO2008128274A1

WO2008128274A1 - Single use syringe

Info

Publication number: WO2008128274A1
Application number: PCT/AU2007/000971
Authority: WO
Inventors: Allan Walsh; Feiyan Tan
Original assignee: Morgan Meditech Inc
Priority date: 2007-04-24
Filing date: 2007-07-12
Publication date: 2008-10-30

Abstract

A single use syringe (20) having a first engagement formation (42) located on the plunger (28). A plunger stopper (50) is mounted to the plunger (28), the plunger stopper (50) having a second engagement formation (51) and a third engagement formation (56). A sleeve (70) is mounted within the barrel (22), having a fourth engagement formation (74). The syringe (20) includes a needle hub (90) having a fifth engagement formation (94) and a sixth engagement formation (96). In a pre-use position, the first engagement formation (42) is engaged with the second engagement formation (51), and the fourth engagement formation (74) is engaged with the fifth engagement formation (94). As the plunger (28) is displaced in an insertion direction, the first engagement formation (42) disengages from the second engagement formation (51), and the needle hub (90) and the plunger stopper (50) are retracted within the barrel (22).

Description

SINGLE USE SYRINGE

TECHNICAL FIELD

This present invention relates to a single use syringe. In particular the present invention relates to an auto retractable syringe in which the needle tip is retractable within the syringe barrel after completion of an injection.

BACKGROUND OF THE INVENTION

There are existing auto retractable syringes which permit the needle tip to be retracted within the syringe barrel after administering an injection for the purpose of minimising the risk of needle stick injuries. However, operation of some of the known auto retractable syringes results in blood splash. Blood splash is the unintentional production of a blood and air vapor when the needle retracts within the barrel after injection has taken place. Tests carried out in Australia have shown that there is the possibility of transmission of hepatitis and other air born infections that can be transmitted by blood vapor to the medical practitioner or other people in the vicinity of the infected recipient at the time of injection.

Many existing auto retractable syringes are complex in design. They are also generally more expensive to manufacture than simpler, manually retracting syringes, hi addition, existing auto retracting syringes are often not favoured by medical practitioners because the release action is known to often result in a jolting movement at the completion of injection which may be discomforting for the patient. Li addition, the rapid return of the needle hub into the plunger may be unnerving for the medical practitioner when the retraction mechanism impacts with the inside of the hollow plunger.

OBJECT OF THE INVENTION.

It is the object of the invention to substantially overcome or at least ameliorate one or more of the above disadvantages, or at least to provide a useful alternative.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a single use syringe having a leading end, a trailing end and a longitudinal axis, said syringe comprising: a longitudinally extending hollow barrel, a plunger mounted in said barrel, said plunger being longitudinally displaceable within said barrel between a pre-use position, an intermediate position and a post-use position, said plunger having a hollow longitudinally extending from an opening at a leading end of the plunger towards a trailing end of the plunger, said plunger having a first engagement formation located on an internal wall of said plunger defining said hollow, the leading end of said plunger having a forward facing projection; a plunger stopper mounted at the leading end of the plunger in said hollow, said plunger stopper having a second engagement formation and a third engagement formation; a sleeve mounted within said barrel toward a leading end of said barrel, said sleeve having a fourth engagement formation; a needle hub mounted within the sleeve and connected to and in fluid communication with a needle tip, said needle hub having a fifth engagement formation and a sixth engagement formation, a recess being formed in a trailing end of the needle hub; and a biasing member extending between a leading end of said needle hub and the leading end of said barrel, said biasing member adapted to bias the needle hub away from the leading end of the barrel, wherein when said plunger is in the pre-use position said first engagement formation is engaged with said second engagement formation inhibiting longitudinal movement of the plunger stopper relative to the plunger, and said fourth engagement formation is engaged with said fifth engagement formation inhibiting longitudinal movement of the needle hub relative to the sleeve, further wherein as the plunger is displaced in an insertion direction toward the leading end of said barrel from the pre-use position to the intermediate position, said forward facing projection enters between said sleeve and said needle hub, thereby disengaging the fourth engagement formation from the fifth engagement formation, a leading portion of said plunger stopper enters said recess creating a liquid tight seal between the needle hub and the plunger stopper, and said third engagement formation engages said sixth engagement formation, captively engaging said needle hub to said plunger stopper, further wherein as the plunger is displaced in an insertion direction toward said leading end of said barrel from the intermediate position to the post-use position, said first engagement formation disengages from said second engagement formation, and said biasing member longitudinally displaces said needle hub, said needle tip and said plunger stopper to a retracted position within said hollow. The first engagement formation preferably includes a projection formed on the internal wall of the plunger, and the second engagement formation includes a groove formed on the plunger stopper.

The fourth engagement formation preferably includes a radially inwardly facing projection formed on the sleeve and the fifth engagement formation includes a groove formed on the needle hub.

The plunger stopper preferably includes a body portion connected to a forwardly projecting head, the third engagement formation being defined by a neck located between the head and the body, and the sixth engagement formation being defined by a radially inwardly facing projection.

Preferably an air venting aperture is located at a trailing end of the plunger, the air venting aperture being in fluid communication with the hollow.

The recess is preferably cup shaped and the forwardly projecting head has a corresponding rounded projection. The sleeve is preferably elastically deformable and a trailing end of the sleeve has a reduced cross-sectional area when viewed in a plane extending perpendicular to the longitudinal axis, the region of reduced cross sectional area being defined by a step formed on a radially outer portion of the sleeve.

The sleeve preferably includes a truncated cone shaped guide surface, a large end of the cone being located at a trailing end of the sleeve, the guide surface being adapted to assist guiding of the forward facing projection between the sleeve and the needle hub.

The region of reduced cross sectional area preferably defines a space between the trailing end of the sleeve and an inner wall of the barrel, the trailing end of the sleeve being adapted to displace radially outwardly into the space when the forward facing projection is inserted between the sleeve and the needle hub.

In a second aspect, the present invention provides a method of assembling a syringe having a longitudinal axis, said method including the steps of: inserting a sleeve into an opening formed in a trailing end of a barrel of the syringe and pushing the sleeve to a seated position at a leading end of the barrel; inserting a loading tube into an aperture formed in a leading end of said barrel inserting a biasing member into said trailing end and pushing said biasing member toward said leading end until a circumferentially outer surface of said loading tube is located within said biasing member, inserting a needle hub having a needle tip connected thereto into the opening and pushing the needle hub toward the leading end of the barrel such that a leading end of said needle tip enters a passage formed within said loading tube; withdrawing the loading tube from the barrel as the needle hub moves toward the leading end and the biasing member compresses; moving the needle hub to a seated position within the sleeve, such that said needle hub engages said sleeve, thereby inhibiting longitudinal movement of the needle hub relative to the sleeve; inserting a plunger stopper into an opening formed in a leading end of a plunger, such that said plunger engages with said plunger stopper, thereby inhibiting longitudinal movement of the plunger stopper relative to the plunger; and inserting a leading end of the plunger into the trailing end of the barrel and pushing the plunger to a pre-use position.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is sectional view showing the syringe in a pre-use position;

Fig. 2 is a sectional view showing the syringe in a post-use position after an injection has been administered:

Fig. 3 is a partial sectional view showing the plunger of the syringe in isolation;

Fig. 4 is a sectional view of the barrel of the syringe in isolation;

Fig. 5 shows a sectional view of the displacement sleeve of the syringe in isolation; Fig. 6 is a sectional view of the plunger stopper of the syringe in isolation;

Fig. 7 is a sectional view of the needle and needle tip of the syringe in isolation;

Fig. 8 is a further sectional view showing a portion of the syringe in a post-use position;

Fig. 9 is a sectional view showing the plunger approaching the intermediate position;

Fig. 10 is a sectional view showing the plunger in the intermediate position; and

Fig. 11 is a schematic view showing a method of assembling a syringe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A single use retractable syringe 20 is depicted in the drawings. As seen in Fig. 1, the syringe 20 has a longitudinal axis X and a hollow barrel 22 made from a clear plastic material permitting the volume of liquid contained therein to be externally seen. The 5 barrel 22 has a leading end 26 and a trailing end 30.

The syringe 20 includes a plunger 28 mounted in the barrel. The plunger is shown in isolation in Fig. 3 which is insertable into an opening 21 formed in the trailing end 30 of the barrel 22. The plunger 28 includes a finger pad 32, which is formed at an end of the plunger 28 furthest from the leading end 26. A rubber piston seal 36 is seated IQ near the leading end 26 of the plunger 28 against a radially projecting shoulder 34 formed on the plunger 28. The piston seal 36 provides a liquid tight seal against the internal wall of the barrel 22.

The plunger 28 has a hollow 38 longitudinally extending from an opening 40 at a leading end of the plunger 28 toward a trailing end 30 of the plunger 28. The plunger 28 I₅ includes a first engagement formation 42 defined by an inwardly facing annular projection 42.

The leading end of the plunger 28 includes a forward facing projection 44. As seen in Fig. 3, the forwardly facing projection 44 defines the leading end of the plunger 28. The trailing end 30 of the plunger 28 includes one or more air venting apertures 460 which are in fluid communication with the hollow 38.

Fig. 6 shows a plunger stopper 50 which is mounted at the leading end of the plunger 28 within the hollow 38. The plunger stopper 50 is formed from an elastically deformable material such as a rubber. The plunger stopper 50 includes a body portion 52 connected to a forwardly facing head portion 54. The plunger stopper 50 includes a₅ second engagement formation 51 defined by a circumferential groove 51 formed in the body portion 52. The plunger stopper also 50 includes a third engagement formation 56 defined by a neck 56 formed between the body portion 52 and the head portion 54. The neck 56 has a locally reduced cross-sectional area when viewed in a plane extending perpendicular to the axis X, so as to define a circumferential groove around the plunger0 stopper 50. A leading end of the plunger stopper 50 has a rounded, forwardly facing projection 58. A cylindrical outer wall 60 of the body portion 52 is slidingly engageable with the inner wall of the plunger 28 defined by the hollow 38.

The syringe includes a sleeve 70 shown in isolation in Fig. 5. As shown in Fig. 1, the sleeve 70 is located with the barrel 22 and is seated upon a shoulder 72 located toward₅ the leading end 26 of the barrel 22. The sleeve 70 includes a fourth engagement formation 74 defined by a radially inwardly facing projection 74. The sleeve is elastically deformable and a trailing end 76 of the sleeve 70 has a region of reduced cross-sectional area 78 when viewed in a plane extending perpendicular to the longitudinal axis X. The region of reduced cross-sectional area 78 is defined by a step 80 formed on a radially outer portion of the sleeve 70. When seated within the barrel 22, the region of reduced cross-sectional area 78 defines a space 79 between the trailing end of the sleeve 70 and the inner barrel 22 wall. The trailing end 76 of the sleeve 70 includes a guide surface 82 defined by a truncated cone shaped portion 84. The large end of the truncated cone 84 is located at the trailing end 76 of the sleeve 70, and a small end of the truncated cone 84 projects into the inside of the sleeve 70 and defines the fourth engagement formation 74.

The syringe includes a needle hub 90 as shown in isolation in Fig. 7. The needle hub 90 is mounted within the sleeve 70 as shown in Fig. 1. The needle hub 90 is connected to and in fluid communication with a stainless steel needle tip 92. The needle hub 90 has a fifth engagement formation 94 defined by a circumferential groove 94 formed in an outer circumferential surface 95 of the needle hub 90 and a sixth engagement formation 96 defined by a radially inwardly facing projection such as an annular rib. A recess 98 is formed in the trailing end of the needle hub 90. The recess 98 corresponds in shape to the forwardly facing projection 58 of the plunger stopper 50.

As shown in Fig. 1, a first end of a biasing member 100, defined by a coil spring 100, is seated on a shoulder 102 at the leading end 26 of the barrel 22. The second end of the coil spring 100 is seated on a shoulder 104 formed on a circumferential outer wall 106 of the needle hub 90.

The spring 100 provides a force to urge the needle hub 90 toward the trailing end 30 of the barrel 22. The syringe 20 may include a back lock assembly 120. The back lock assembly

120 may include a finger 121 connected to a longitudinally extending web 122. The projection 121 is engageable with a corresponding locking formation formed in a locking bush or other such component fitted inside or integrally formed within the barrel 22. The back lock 120 assembly may be used to lock the plunger 28 relative to the barrel 22 at the completion of an inj ection, once the medication has been administered.

The assembly of the syringe 20 will now be described. The assembly operation is shown schematically in Fig. 11. The sleeve 70 is initially inserted into the opening 21 at the trailing end 30 of the barrel 22. The sleeve 70 is pushed toward the leading end 26 to a seated position on the shoulder 72. A loading tube 120 is then inserted into an aperture 122 located in the leading end 26 of the barrel 22. The spring 100 is then inserted into the opening 21 at the trailing end 30 of the barrel 22. The spring 100 is pushed toward the leading end 26, and the loading tube 120 enters the space within the spring 100, such that the loading tube 120 is within the spring 100. The spring 100 is pushed toward the leading end 26 the barrel 22 until it is seated on the shoulder 102.

5 The needle hub 90 is then the inserted into the opening 21 and pushed toward the leading end 26. The needle tip 92 enters the passage through the centre of the loading tube 120. As the needle hub 90 is further inserted, the shoulder 104 contacts the end of the spring 100 and compresses the spring 100. As the spring 100 is being compressed, the loading tube 120 is withdrawn from the aperture 122. At the end of the assembly process,Q the fourth engagement formation 74 formed on the sleeve 70 engages the fifth engagement formation 94 formed on the needle hub 90, thereby inhibiting longitudinal movement of the needle hub 90 relative to the sleeve 70. This prevents the needle hub 90 from retracting within the barrel 22 and keeps the spring 100 in a loaded, compressed state. s Given that the loading tube 120 has an outer diameter slightly larger than the needle tip 92, there is a slight clearance between the needle tip 92 and the aperture 122. The leading end of the needle hub 90 projects slightly from the end of the barrel into that clearance when the syringe 20 is in the assembled, pre-use position.

The plunger stopper 50 is then inserted into the opening 40 at the leading end ofQ the plunger 28, such that the first engagement formation 42 engages with the second engagement formation 51, thereby inhibiting longitudinal movement of the plunger stopper 50 relative to the plunger 28.

The plunger 28 is then inserted into the opening 21, and the finger pad 32 is pressed to displace the leading end of the plunger 28 and the plunger stopper 50 toward₅ the leading end 26 of the barrel 22, to the pre-use position of the plunger 28, as depicted in Fig. 1.

An advantage of using the loading tube 120 is that it prevents the needle tip 92 from coming into contact with the spring 100 during assembly, which can result in fouling of the needle tip 92. 0 A further advantage of the clearance between the aperture 122 and the needle tip

90 is that during retraction of the needle tip 90 within the barrel 22, there is a reduced likelihood of the needle tip touching the edge of the barrel defining the aperture 122, which may cause blood on the needle tip 90 to be transferred to the atmosphere in the form of a blood air vapor. The operation of the syringe 20 will now be described. When medication or an immunisation is to be administered, a medical practitioner removes the needle cap 110 which exposes the needle tip 92. The practitioner then applies a force with his/her thumb to the finger pad 32, to drive the plunger 28 in an insertion direction into the barrel 22, until the plunger stopper 50 approaches the end of its stroke.

The user then inserts the needle tip 92 into a vial of liquid (not shown) and subsequently retracts the finger pad 32 away from the leading end 26 end of the barrel 22, to draw a desired quantity of the liquid into the barrel 22. Markings on the side of the barrel 22 indicate the volume of the liquid contained therein, such that a desired dosage of liquid can be measured.

The user then holds the syringe 20 with the needle tip 24 facing upwardly and applies a further force with his/her thumb to the finger pad 32, to again drive the plunger 28 in an insertion direction into the barrel 22 toward the leading end 26. Any air present in the barrel 22 is then expelled from the needle tip 92, leaving only liquid within the barrel 22. At this stage, when the injection is ready to be administered, the plunger 28 is in the pre-use position depicted in Fig. 1.

The needle tip 92 is then inserted into a patient's tissue or a vein as required, and the contents of the barrel 22 are injected into the patient by applying further force to the finger pad 32 such that the plunger stopper 50 moves in the barrel 22 in an insertion direction towards the leading end 26 of the plunger 22. When the plunger stopper 50 approaches the end of its stroke, all of the liquid has been injected.

As noted above, in the assembled, pre-use position of the plunger 28, the first engagement formation 42 is engaged with the second engagement formation 51 thereby inhibiting longitudinal movement of the plunger stopper 50 relative to the plunger 28, and the fourth engagement formation 74 is engaged with the fifth engagement formation 94 thereby inhibiting longitudinal movement of the needle hub 90 relative to the sleeve 70.

Fig. 9 depicts the pre-use position. As the plunger 28 is longitudinally displaced in an insertion direction toward the leading end 26 from the pre-use position to the intermediate position, the forward facing projection 44 is inserted between the sleeve 70 and the needle hub 90. The projection 44 comes into contact with the guide surface 82, and this radially outwardly elastically deforms the trailing end 76 of the sleeve 70. The region of reduced cross-sectional area 78 is displaced into the space 79, hence causing the fourth engagement formation 74 to pull away from and disengage the fifth engagement formation 94. The forwardly facing projection 58 of the plunger stopper 50 enters the recess 98 in the trailing end of the needle hub 90, thereby creating a liquid tight seal between the needle hub 90 and the plunger stopper 50. This prevents any blood from being expelled from the needle tip 92, and hence the risk of blood splash is avoided. At this point the 5 third engagement formation 56 engages with the sixth engagement formation 96 thereby captively engaging the needle hub 90 with the plunger stopper 50. The syringe 20 is now in the intermediate position depicted in Fig. 10.

As the plunger 28 is further displaced in the insertion direction from the intermediate position to a post-use position (as depicted in Fig. 2), the first engagementQ formation 42 is forced to disengage from the second engagement formation 51, on account of the captive engagement between the third engagement formation 56 and the sixth engagement formation 96. Accordingly, the plunger stopper 50 is forced to slide within the piston 28, and once it is clear of contact with the first engagement formation 42, the spring 100 is permitted to longitudinally extend and displace the needle hub 90,s the needle tip 92 and the plunger stopper 50 to a retracted, post-use position within the hollow 38. The post use position is depicted in Fig. 8.

As the retraction of the plunger stopper 50 takes place, any air trapped in the hollow 38 behind the plunger stopper 50 is permitted to exit from the hollow 38 through the air venting apertures 46. This reduces the chance of the plunger stopper 50 beingQ blocked before complete retraction of the needle tip 92 within the barrel 22 has occurred. The plunger stopper 50 remains in sealing contact with the internal wall of the plunger during displacement through the hollow 38 toward the trailing end 30. This prevents the stopper from moving excessively quickly when urged by the spring 100.

At the end of the injection, the back lock assembly 120 permits captive5 engagement of the plunger 28 with the barrel 22. Accordingly, the plunger 28 cannot be withdrawn from the barrel 22 on account of the back lock assembly 120, and the needle tip 92 cannot project from the leading end 26 of the barrel 22 on account of the spring 100. At this point the syringe 20 is fully retracted and the chance of a needle stick injury is significantly reduced. The syringe 20 can now be disposed of in a sharps bin for0 subsequent destruction.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

Claims:

1. A single use syringe having a leading end, a trailing end and a longitudinal axis, said syringe comprising: a longitudinally extending hollow barrel, a plunger mounted in said barrel, said plunger being longitudinally displaceable within said barrel between a pre-use position, an intermediate position and a post-use position, said plunger having a hollow longitudinally extending from an opening at a leading end of the plunger towards a trailing end of the plunger, said plunger having a first engagement formation located on an internal wall of said plunger defining said hollow, the leading end of said plunger having a forward facing projection; a plunger stopper mounted at the leading end of the plunger in said hollow, said plunger stopper having a second engagement formation and a third engagement formation; a sleeve mounted within said barrel toward a leading end of said barrel, said sleeve having a fourth engagement formation; a needle hub mounted within the sleeve and connected to and in fluid communication with a needle tip, said needle hub having a fifth engagement formation and a sixth engagement formation, a recess being formed in a trailing end of the needle hub; and a biasing member extending between a leading end of said needle hub and the leading end of said barrel, said biasing member adapted to bias the needle hub away from the leading end of the barrel, wherein when said plunger is in the pre-use position said first engagement formation is engaged with said second engagement formation inhibiting longitudinal movement of the plunger stopper relative to the plunger, and said fourth engagement formation is engaged with said fifth engagement formation inhibiting longitudinal movement of the needle hub relative to the sleeve, further wherein as the plunger is displaced in an insertion direction toward the leading end of said barrel from the pre-use position to the intermediate position, said forward facing projection enters between said sleeve and said needle hub, thereby disengaging the fourth engagement formation from the fifth engagement formation, a leading portion of said plunger stopper enters said recess creating a liquid tight seal between the needle hub and the plunger stopper, and said third engagement formation engages said sixth engagement formation, captively engaging said needle hub to said plunger stopper, further wherein as the plunger is displaced in an insertion direction toward said leading end of said barrel from the intermediate position to the post-use position, said first engagement formation disengages from said second engagement formation, and said biasing member longitudinally displaces said needle hub, said needle tip and said plunger stopper to a retracted position within said hollow.

2. The syringe of claim 1, wherein said first engagement formation includes a projection formed on said internal wall of said plunger, and said second engagement formation includes a groove formed on said plunger stopper.

3. The syringe of claim 1, wherein said fourth engagement formation includes a radially inwardly facing projection formed on said sleeve and said fifth engagement formation includes a groove formed on said needle hub.

4. The syringe of claim I₃ wherein said plunger stopper includes a body portion connected to a forwardly projecting head, said third engagement formation being defined by a neck located between said head and said body, and said sixth engagement formation being defined by a radially inwardly facing proj ection.

5. The syringe of claim 1, including an air venting aperture located at a trailing end of the plunger, said air venting aperture being in fluid communication with said hollow.

6. The syringe of claim 4, wherein said recess is cup shaped and said forwardly projecting head has a corresponding rounded projection.

7. The syringe of claim 1, wherein said sleeve is elastically deformable and a trailing end of said sleeve has a reduced cross-sectional area when viewed in a plane extending perpendicular to the longitudinal axis, said region of reduced cross sectional area being defined by a step formed on a radially outer portion of said sleeve.

8. The syringe of claim 7, wherein said sleeve includes a truncated cone shaped guide surface, a large end of said cone being located at a trailing end of said sleeve, said guide surface being adapted to assist guiding of said forward facing projection between said sleeve and said needle hub.

9. The syringe of claim 8, wherein said region of reduced cross sectional area defines a space between the trailing end of said sleeve and an inner wall of said barrel, the trailing end of said sleeve being adapted to displace radially outwardly into said space when said forward facing projection is inserted between said sleeve and said needle hub.

10. A method of assembling a syringe having a longitudinal axis, said method including the steps of: inserting a sleeve into an opening formed in a trailing end of a barrel of the syringe and pushing the sleeve to a seated position at a leading end of the barrel; inserting a loading tube into an aperture formed in a leading end of said barrel inserting a biasing member into said trailing end and pushing said biasing member toward said leading end until a circumferentially outer surface of said loading tube is located within said biasing member, inserting a needle hub having a needle tip connected thereto into the opening and pushing the needle hub toward the leading end of the barrel such that a leading end of said needle tip enters a passage formed within said loading tube; withdrawing the loading tube from the barrel as the needle hub moves toward the leading end and the biasing member compresses; moving the needle hub to a seated position within the sleeve, such that said needle hub engages said sleeve, thereby inhibiting longitudinal movement of the needle hub relative to the sleeve; inserting a plunger stopper into an opening formed in a leading end of a plunger, such that said plunger engages with said plunger stopper, thereby inhibiting longitudinal movement of the plunger stopper relative to the plunger; and inserting a leading end of the plunger into the trailing end of the barrel and pushing the plunger to a pre-use position.