GB2507345A

GB2507345A - Injection device having sheath remover blocking the syringe carriage movement

Info

Publication number: GB2507345A
Application number: GB1219402.3A
Authority: GB
Inventors: Lee Lovelace
Original assignee: Owen Mumford Ltd
Current assignee: Owen Mumford Ltd
Priority date: 2012-10-29
Filing date: 2012-10-29
Publication date: 2014-04-30
Also published as: GB201219402D0

Abstract

An injection device comprising a housing 10, 20 for receiving a syringe 22 comprising a needle and protective sheath covering the needle, a carriage 11 located within the housing and facilitating movement of the syringe between a retracted position and an injection position in which the needle projects through an opening in the housing, and a sheath remover 13 attached to the housing and configured to capture the protective sheath upon loading of a syringe into the housing and to remove the protective sheath upon detachment from the housing, thereby exposing the needle. The device is configured such that a distal end of the sheath remover 13 is in close proximity with a proximal end of the syringe carriage 11 so as to substantially block movement of the carriage towards the opening whilst the sheath remover is connected to the housing. The needle sheath may comprise snap-in fingers 14 which engage behind the needle sheath, leaving only a small gap G between the syringe carrier 11 and the snap-in fingers 14.

Description

INJECTION DEVICE

Technical Field

The present invention relates to injection devices of the type used to inject medication into patients. In particular, the invention relates to the provision of an improved protective sheath remover for use with such injection devices.

Background

Spring driven injection devices are known and used to assist patients and medical professionals with the injection of medications held in conventional plunger driven syringes. Such injection devices typically comprise a housing for containing the syringe to which a needle is fixed, and a drive member attached to a relatively strong compression spring for driving the plunger into the syringe body to eject medication through the needle and into a patient.

By way of example, International patent application publication number W094121316 describes an injection device. The device is intended to completely eject all medication from a syringe, i.e. it has no mechanism for adjusting the ejected dose. The injection device comprises a distal housing part into which is screwed a proximal housing part (where the terms "distal" and proximal" are used here and in the following text to identify respectively locations distant from and close to a patient's skin when the device is in use). An adjustable needle shield is further screwed into a proximal end of the proximal housing part. A housing sleeve is slideably mounted on top of the distal housing part. The injection device comprises a trigger which projects through a window provided in the sleeve.

W020121098371 describes an improved injection device that comprises a damper to reduce the possibility of damage occurring on the syringe plunger or drive member caused by the impact of the drive member hitting the end plate ot the syringe plunger.

A cross section through a first part of the housing typically used in these injection devices is shown in Eigure 1. Figure 1 shows the proximal housing 1 which contains a carriage 2 that can hold a syringe and enables movement ot the syringe between a tirst position in which the needle is contained fully within the housing and a second position in which the needle projeots through an opening in the housing. A spring 3 is provided to keep the carriage 2 in the first position until a force is applied to it, via the syringe, whereby the carriage can slide through the housing to the second position.

Also shown in Figure 1 is a sheath remover 4 which projects into the opening at the end of the housing and has flexible snap-in fingers 5 that can engage with the protective sheath covering a syringe needle. During insertion of a syringe into the housing, the protective sheath pushes into the sheath remover, flexing the snap-in fingers outwards in the direction shown by the arrows A in Figure 1. Once the sheath has passed into the sheath remover, the snap-in fingers snap in behind the protective sheath between the protective sheath and the syringe body. When the sheath remover is subsequently detached from the housing, it removes the sheath from the end of the syringe, thus exposing the needle.

A problem observed in prior art devices such as that illustrated in Figure 1 arises from the syringe being inserted too far into the housing. As shown in Figure 2, the spring 3 biasing the carriage 2 into the first position can be compressed by the force applied when a syringe is inserted. The carriage is able to move towards the proximal end of the housing as shown by arrow B, resulting in the syringe being over-inserted, in turn resulting in the syringe body being pushed through the snap-in fingers of the sheath remover. It has been observed that having the syringe body pass through the snap-in fingers can cause them to over-flex and deform to the point that they cannot properly recover their shape. If this happens, the snap-in fingers may be splayed too far to properly engage in the gap between the sheath and the syringe body, and the sheath will not be removed when the sheath remover is detached from the housing.

Summary

It is an object of the present invention to overcome or at least mitigate the problems identified with known injection devices including the problem identified above. This object is achieved by having the sheath remover in close proximity to an edge of the carriage so as to substantially block movement of the carriage (and consequently the syringe) whilst the sheath remover is connected to the housing.

According to a first aspect of the invention there is provided an injection device comprising a housing for receiving a syringe comprising a needle and protective sheath covering the needle, a carriage located within the housing and facilitating movement of the syringe between a retracted position and an injection position in which the needle projects through an opening in the housing, and a sheath remover attached to the housing and configured to capture the protective sheath upon loading of a syringe into the housing and to remove the protective sheath upon detachment from the housing, thereby exposing the needle. The device is configured such that a distal end of the sheath remover is in close proximity with a proximal end of the carriage so as to substantially block movement of the carriage towards the opening whilst the sheath remover is connected to the housing.

Embodiments of the present invention may provide an improved injection device with a sheath remover that has a reduced the risk of being damaged when a syringe is inserted into the injection device.

The sheath remover may comprise one or more flexible snap-in fingers extending in a distal direction for capturing the protective sheath, wherein the carriage extends in a proximal direction towards the snap-in fingers, and movement of the carriage in the proximal direction causes it to engage the snap-in fingers before the body of the syringe comes into contact with the snap-in fingers. Alternatively, the sheath remover may comprise a sleeve extending around and beyond the snap-in fingers into close proximity with a proximal end of the carriage.

The injection device may comprise a spring biasing the carriage in the distal direction.

The housing may comprise at least two housing parts that are separable to facilitate insertion of a syringe into the housing. The device may further comprise one of a compression spring, torsion spring, constant force spring, and clock spring configured to apply an axial force to a syringe to drive the syringe and the carriage from said retracted position to said injection position and to subsequently eject medicine from the syringe. The sheath remover and the carriage may be contigured to prevent movement of the carriage towards the proximal end by more than 2mm and preferably no more than 1mm.

Brief Descrirjtion of the Drawings Further aspects, features and advantages of the invention will become apparent to the reader of the following description of specific embodiments of the invention, provided by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a cross section through a first part of the housing of a typical injection

device in the prior art;

Figure 2 shows the housing of Figure 1 in a second configuration; Figure 3 shows a cross section through a housing part of an improved injection device; Figure 4 shows a the housing part of Figure 3 with the sheath remover removed from the housing part; and Figure 5 shows an improved injection device comprising the housing part of Figures 3 and 4.

Detailed Description

As discussed above with reference to Figures 1 and 2, it is known with conventional injection devices for snap-in fingers of a sheath remover to be damaged as a result of over over-insertion of a syringe into the device during syringe loading, such that the snap-in fingers cannot properly engage a sheath during subsequent sheath removal.

A new injection device will now be described, with reference to Figures 3 to 5, that can overcome or at least mitigate this problem.

The terms distal" and proximal" as used below have the same meaning as the same terms used in the background -i.e. to identify respectively locations distant from (distal) and close to (proximal) a patient's skin when the device is in use.

Figure 3 shows a oross section through a first housing part 10 (the proximal housing part) of an improved injection device. The first housing part 10 contains a carriage 11 for receiving and holding a syringe (not shown), and a carriage spring 12 for biasing the carriage into a first position within the housing in which the needle is contained fully within the housing (Figure 3 shows the carriage in this first position). Also shown in Figure 3 is a sheath remover 13 that projects into the opening at the end of the first housing part, and which comprises flexible snap-in fingers 14 which can engage a protective sheath provided over the needle of a syringe. An adjustable needle shield is provided that can be lengthened or retracted, as required, and which covers the needle when the syringe is held in the first position within the housing by the carriage, such that none of the needle projects beyond the opening of the needle shield.

As shown in the inset of Figure 3, the gap G between carriage 11 and the sheath remover 13 is very small. Consequently, very little movement of the carriage is permitted as the sheath remover substantially blocks its movement. When a syringe is being inserted into the housing, a force will be generated that will try to move the carriage from the first position in the housing to the second position. However, the carriage will very quickly, and with little displacement, come into contact with the end of the sheath remover which provides an equal and opposite force, thus blocking any further movement of the carriage through the housing. By substantially blocking movement of the carriage in this way, the sheath remover prevents the syringe from being over-inserted into the device and therefore potentially damaging the snap-in fingers on the sheath remover as described above. Movement of the carriage will typically be blocked beyond 2mm, but preferably it would be substantially blocked beyond less than 1mm, and even more preferably less than 0.5mm.

Figure 4 shows the same first housing part 10 of Figure 3 once the sheath remover has been removed. Now that the sheath remover has been removed, there is no longer anything blocking the movement of the carriage 11 through the housing part 10, and so the carriage spring 12 has been compressed by the carriagel 1 moving from a first position to a second position in the direction of arrow C, the second position being such that the needle (not shown) projects through an opening in the housing.

Figure 5 shows an improved injection device 20 comprising the tirst (proximal) housing part 10 shown in Figures 3 and 4, connected to a second (distal) housing part 21. A sheath remover 13 is connected to the first (proximal) housing part 10. A syringe 22 has been inserted into the injection device 20 which is primed and ready for use. In position, the syringe body is held in place in the carriage 11, and the syringe plunger 23 extends into the second housing part 21. Typically the syringe will have a protective sheath covering the needle, but this is not shown in Figures. Snap-in fingers 14 on the sheath remover will engage behind the protective sheath (or with corresponding receiving portions provided on the protective sheath), and the protective sheath will be removed from the syringe when the sheath remover 13 is detached from the first housing part 10. As described br Figures 3 and 4, prior to the sheath remover being detached from the first housing part, the sheath remover projects into the opening at the proximal end of the first housing part such that the sheath remover is in close proximity to an adjacent edge of the carriage 11 (as shown in the inset of Figure 5) so as to substantially block movement of the carriage and syringe. This prevents the snap-in fingers 14 from being damaged due to the syringe being inserted too far into the device.

The second housing part 21 contains a drive member 24, which, when triggered, will be forced by a force applicator (for example a compression spring) to drive axially through the second housing, engaging the syringe plunger as it travels through the housing.

The force exerted by the force applicator pushes the drive member 24 forward and into engagement with the end plate 25 of the syringe plunger 23. At this stage in the operation of the device (i.e. once the sheath remover has been detached from the first housing part), the syringe body 22 and carriage 11 are relatively tree to move through the proximal housing part 10 such that the force exerted by the drive member 24 on the plunger end plate 25 causes the entire syringe 22 to move towards the proximal end of the injection device (the end through which the needle is to be projected). The wings formed on the end of the syringe body act on the carriage 11, causing the carriage to also move towards the proximal end of the device, compressing the relatively light carriage spring 12. Once this spring is bully compressed, further movement of the carriage 11 and therefore of the syringe body is prevented. Of course, during this preliminary phase, the needle is projected beyond the end of the needle shield and into the patient's skin. The extent to which the needle projects beyond the end of the needle shield 15 can be adjusted by screwing the shield into and out of the proximal end of the proximal housing part 10.

As the driver member 24 continues to exert a significant force on the plunger 25 after further movement of the carriage 11 and the syringe body has been prevented, the plunger 23 begins to move through the syringe body thereby ejecting medication through the needle.

The initial movement of the driver may be dampened in order to reduce the impact force felt by the plunger end plate 25, and therefore reduce the possibility of damage occurring to the plunger.

The carriage and sheath remover can be brought into close proximity in a number of ways. For example, as shown in the figures, the carriage body may extend further towards the proximal end of the first housing part. Alternatively, or in addition, the sheath remover may contain extended portions that extend towards the distal end of the first housing portion. Extended portions provided on a sheath remover can be the flexible snap-in fingers themselves (as shown in Figures 3 to 5), or could be extending portions that are distinct from the snap-in fingers themselves.

The snap-in fingers described herein could be replaced with any alternative that is suitable for engaging the protective sheath of a syringe. For example, instead of snap-in fingers, the sheath remover may be provided with an elastomeric ring that can expand over the protective sheath and then contract again behind it, between the sheath and the syringe body, in order to capture the sheath.

It will be appreciated by the person of skill in the art that various modifications may be made to the above described embodiments without departing from the scope of the present invention.

Claims

CLAIMS1. An injection device comprising: a housing for receiving a syringe comprising a needle and protective sheath covering the needle; a carriage located within the housing and facilitating movement of the syringe between a retracted position and an injection position in which the needle projects through an opening in the housing; a sheath remover attached to the housing and configured to capture the protective sheath upon loading of a syringe into the housing and to remove the protective sheath upon detachment from the housing, thereby exposing the needle, wherein a distal end of the sheath remover is in close proximity with a proximal end of the carriage so as to substantially block movement of the carriage towards the opening whilst the sheath remover is connected to the housing.
2. An injection device according to claim 1, wherein the sheath remover comprises one or more flexible snap-in fingers extending in a distal direction for capturing the protective sheath.
3. An injection device according to claim 2, wherein the carriage extends in a proximal direction towards the snap-in fingers, and movement of the carriage in the proximal direction causes it to engage the snap-in fingers before the body of the syringe comes into contact with the snap-in fingers.
4. An injection device according to claim 2, wherein the sheath remover comprises a sleeve extending around and beyond the snap-in fingers into close proximity with a proximal end of the carriage.
5. An injection device according to any one of the preceding claims and comprising a spring biasing the carriage in the distal direction.
6. An injection device according to any one of the preceding claims, wherein the housing comprises at least two housing parts that are separable to facilitate insertion of a syringe into the housing.
7. An injection device according to any one of the preceding claims and comprising one of a compression spring, torsion spring, constant force spring, and clock spring contigured to apply an axial force to a syringe to drive the syringe and the carriage from said retracted position to said injection position and to subsequently eject medicine from the syringe.
8. An injection device according to any one of the preceding claims, wherein the sheath remover and the carriage are configured to prevent movement of the carriage towards the proximal end by more than 2mm and preferably no more than 1mm.