Patent Document

TECHNICAL FIELD 
     The present invention relates to syringe sheath removers and to injection devices incorporating such removers. 
     BACKGROUND 
     Various types of injection devices are available for assisting with the injection of a medicament into a patient (human or animal), and which are configured to receive a standard, pre-filled glass or plastic syringe tipped with an injection needle. These devices may have a dose setting mechanism and a main drive spring for driving a plunger into the syringe so as to expel the medicament out through the needle. Injection devices may comprise a further spring for driving the needle out of the device housing and into the patient&#39;s skin, prior to activation of the main drive spring to expel the medicament. 
     In order to maintain sterility prior to use, and to avoid “sticking” injuries, the pre-filled syringe is supplied to the injection device assembler with a rubber or rubber and plastic cap, known as a “sheath” or “boot”, covering the needle. The sheath has an interior space for containing the needle, and a sealing end that abuts the adjacent end of the syringe body to seal that inner space. In some cases, the sheath may also comprise a solid piece into which the needle is pushed. Immediately prior to use, a user (e.g. healthcare professional or patient) must remove the sheath to uncover the needle. This is typically achieved using a sheath removal tool that is inserted by a user into the injecting end of the device. The tool comprises a set of sprung fingers that ride over and along the sheath as the tool is pushed into the device. The fingers then snap into the junction between the syringe end and the sheath. The user can then pull out the tool, bringing the cap with it. 
     Particularly in the case of expensive medicaments, it is extremely important to minimise the failure rate of assembled injection devices. Considering the sheath removal solution outlined in the previous paragraphs, it may be difficult to achieve exactly the right degree of flexibility in the fingers to ensure that they can ride over the sheath whilst still providing sufficient force to close over the junction at the rear of the sheath. 
     GB 2438593 (Cilag), US2006/0100588 A1 (Brunnberg et al), WO 2007/047200 A1 (Eli Lilly), US 2006/0270986 A1 (Hommann et al), WO 2006/063015 A2 (Washington Biotech Corp.) and US 2004/010234 A1 all describe devices for housing syringes and removing sheaths therefrom. 
     SUMMARY 
     It is an object of the present invention to provide a sheath removal mechanism that is both easy to use and reliable, reducing the failure rate of assembled injection devices. 
     According to a first aspect of the present invention there is provided apparatus for removing a sheath from a syringe, the sheath providing a sterile cover for a needle of the syringe, the apparatus comprising:
         a substantially cylindrical housing defining an opening for receiving a sheath attached to a syringe;   a driver mounted on the housing and being slideable along the housing between first and second axially displaced positions; and   a plurality of radially deflectable fingers mounted within said housing and being coupled to said driver for movement therewith, the fingers being configured such that movement of said driver from said first to said second position causes said fingers to slide over said sheath and engage with a formation on said sheath, and movement of the driver from said second position towards said first position causes said fingers to push the sheath off the syringe.       

     By coupling the fingers to a driver slideable on the housing, embodiments of the invention are provided with a greater level of control. Indeed, this arrangement allows the sheath to be easily removed in a smooth manner, thus preventing it from being inadvertently dropped on the floor, for instance. 
     In an embodiment of the invention, the formation on the sheath is an end of the sheath adjacent to a shoulder of the syringe body. Alternatively, the formation on the sheath may be a notch on the body of the sheath arranged to cooperate with the fingers of the apparatus. 
     The driver may comprise one or more corrugations or protrusions. These enable the user to grip the driver more easily, especially if the user is wearing latex gloves, for instance. 
     The driver may be in the form of a sleeve arranged coaxially about the housing over which it slides. For example, the driver may be substantially cylindrical. The driver may be formed from one or more, for instance two, cooperating parts that are snapped together around the outside of the housing. 
     The housing may define one or more axially extending slots through which the driver is coupled to the fingers, for instance by one or more arms, with the arm(s) being slideable along the slot(s) as the driver is moved between said first and second positions. 
     The apparatus may comprise a collar within the housing, said fingers depending from the collar. The fingers may be formed integrally with the fingers. Said arms may be formed integrally with said collar or with said driver. 
     The apparatus may comprise a driver return spring located within said housing and configured to bias said driver towards said first position. The driver return spring may be coupled at one end to said collar and at its other end to the housing. 
     According to a second aspect of the present invention there is provided an injection device for assisting with the injection of medicament from a syringe, the device comprising apparatus according to the above first aspect of the invention. In some embodiments, the injection device further comprises a pre-filled syringe having a needle and a sheath providing a sterile cover for the needle. 
     Said housing may be a main housing of the injection device arranged to receive a syringe. The injection device may further comprise a syringe return spring tending to push the syringe into the housing and away from an injecting end, such that once the sheath is removed and the driver released, the syringe and its needle are pushed back into the housing. The syringe return spring may be couple at one end to the housing and at another end to the syringe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a syringe with a sheath covering a syringe needle; 
         FIG. 2  illustrates a sheath remover for use with the syringe of  FIG. 1 ; 
         FIG. 3  illustrates an injection device comprising the sheath remover of  FIG. 2  and loaded with the syringe of  FIG. 1 ; 
         FIG. 4  illustrates a cross-section of the sheath remover of  FIG. 2 , partially exploded, and loaded with a syringe; 
         FIG. 5  illustrates, in a more detailed cross-section, the sheath remover of  FIG. 2 ; 
         FIG. 6  illustrates in cross-section a first intermediate assembly state of the sheath remover and syringe of  FIGS. 1 and 2 ; 
         FIG. 7  illustrates in cross-section an assembled state of the sheath remover of  FIG. 2 ; 
         FIG. 8  illustrates in cross-section the sheath remover and syringe of  FIG. 7  at a first intermediate stage of a sheath removal procedure; 
         FIG. 9  illustrates in cross-section the sheath remover and syringe of  FIG. 7  at a second intermediate stage of a sheath removal procedure; 
         FIG. 10  illustrates in cross-section the sheath remover and syringe of  FIG. 7  at a third intermediate stage of a sheath removal procedure; and 
         FIG. 11  illustrates in cross-section the remover and syringe of  FIG. 7 , with the sheath removed. 
     
    
    
     DETAILED DESCRIPTION 
     Apparatus will now be described that enables the easy and reliable removal of a sheath or cap covering a needle of a pre-filled syringe. As has already been outlined above, an assembler of injection devices (e.g. auto-injectors and the like) will typically obtain pre-filled syringes from a supplier. The assembler may have little or no influence over the design of the syringes including the sheaths, and may therefore have to ensure that its device design and assembly process is compatible with the syringe design. 
       FIG. 1  shows a conventional syringe  1 , comprising a body  2  containing the medicament, a plunger  3  located within the body and which may extend outwardly therefrom, an annular lip  4 , wings  5  and a hypodermic needle  6  coupled to the opposite end of the body. An essentially solid rubber or rubber and plastics sheath  7  covers the needle  6  and seals around a shoulder portion of the syringe body  2 . An additional sheath cover  33  is shown provided on the outside of the sheath  5 . At the junction between the shoulder  8  of the sheath  7  and the distal end of the body  2 , a small axial gap, channel or formation  9  exists. 
       FIG. 2  is a perspective view of an assembled sheath remover  10 . The remover comprises a generally cylindrical casing or housing  11 , defining an opening  12 . The housing  11  is provided with locating formations for retaining an inserted syringe  1  and is of a rigid plastics material. The sheath remover  10  further comprises a driver sleeve  13  which is slideable on the housing  11  back and forth between a first position  14  and a second position  15 , see arrows A and B in  FIG. 2 . The driver sleeve  13  cooperates with clamping fingers  16 , having ends  17 , such that the fingers also move in the direction of arrows A and B upon movement of the driver sleeve  13 . The sheath remover is described in more detail below. 
       FIG. 3  shows an injection device  18 . The injection device  18  comprises a casing  19  and a dose delivery mechanism  20  to inject the medicament (and insert the needle if this functionality is provided). The sheath remover of  FIG. 2  is connected to an end of the injection device  18  by complimentary screw threads. 
       FIG. 4  shows the syringe and, in more detail, a cross-section through the sheath remover  10 . The sheath remover comprises two components. A first of these components, the driver sleeve  13 , comprises a partially cylindrical body (shown as two separate pieces in this exploded view) which engages, through a pair of slots  21  in the housing  11 , with a collar  22  by means of a pair of respective depending arms  23 . As the driver sleeve  13  is slideable on the housing  11 , movement of the driver sleeve  13  leads to corresponding movement of the collar and the fingers, relative to the housing  11 . 
     The fingers  16  are resilient and depend from an end of the collar  22  towards the injecting end  24  of the device, the injecting end  24  accommodating the sheath  7  of the syringe. It will be appreciated that in the absence of an additional restraining force, the clamping fingers  16  exhibit a small degree of flexibility in a radial direction. 
     The fingers  16  are arranged for snap-engagement with the gap  9  between the sheath  7  and the syringe body  2 , as described further below. The fingers  16  are provided with ramps  25  on their inward facing sides for contacting the sheath  7 . The fingers  16  are also provided with ends  17  to abut the sheath  7  when the fingers are engaged in the gap  9 . 
     A driver return spring  26  acts at one end against the collar  22  and at its other end against a blocking member  27 . The driver return spring  26  thus urges the collar  22  and driver sleeve  13  towards the injecting end  24  of the device, namely towards the first position  14  in the direction of arrow A as shown in  FIG. 2 . 
     Referring to  FIG. 5 , the sheath remover  10  also comprises a syringe carrier  28  within the housing  11 . A carrier return spring  29  is positioned between, and acts upon, annular end point  30  of the housing  11  and the carrier  28 . The carrier return spring  29  thus urges the carrier  28  rearward (away from the injecting end  24 ). 
     The carrier  28  is adapted to contact and retain the wings  5 , described earlier with reference to  FIG. 1 , provided at the end of the syringe body  4 , once the syringe has been inserted into the device, as described below with reference to  FIG. 7 . The carrier  28  is itself slideable forwards (in the direction of injecting end  24 ) and rearwards (away from injecting end  24 ) within the housing. Forward and rearward protrusions  31  and  32  limit the extent of the movement of the carrier  28  by acting on the end point  30  on the housing  11 . The rearward protrusion  32  stops the carrier  28  at limit of its forward movement by abutting end point  30 . Similarly, forward protrusion  31  stops the carrier  28  at limit of its rearward movement by abutting end point  30 . 
     In the absence of the syringe, as shown in  FIG. 5 , the carrier  28  is urged rearwards (away from injecting end  24 ), so that forward protrusion  31  abuts end point  30 . At the same time, driver return spring  26  urges the collar  22 , and therefore also the driver sleeve  13  and fingers  16 , forwards (in the direction of injecting end  24 ).  FIG. 5  shows that both driver return spring  26  and, in particular, carrier return spring  29  are fully extended in the absence of the syringe. 
     The insertion of the syringe into the sheath remover will now be described.  FIGS. 6 and 7  illustrate assembly stages of the syringe and sheath remover  10  of  FIGS. 1 and 2 . As the syringe  1  is pushed into the housing  11  of the sheath remover  10 , the syringe body  2  passes through opening  12  until lip  4  and wings  5  engage with the carrier  28 . In this position, the carrier return spring is substantially in its extended state. 
     The proportions of the slots  21  and second position  15 , as well as fingers  16  and driver sleeve  13 , are such that the depending arm  23  of the driver sleeve  13  does not reach the ends of the slots  21 , distal from the injecting end  24 , before the fingers  16  have engaged the gap  9 , when the driver sleeve  13  is slid towards second position  15 . 
     Upon insertion of the syringe into the housing  11 , the sheath  7  will eventually come into contact with the ramps  25  formed on respective clamping fingers  16 , as shown in  FIG. 5 . At this point, the driver sleeve  13  is in the first position  14 , proximal to the injecting end  24 , due to the action of the driver return spring  26 . The driver return spring  26 , like the carrier return spring, is substantially in its extended state. 
     Once the syringe  1  and sheath  7  have been inserted into the housing  11  of the sheath remover  10 , other injection device components are inserted into the housing, behind the syringe, for instance by screwing the sheath remover  10  into casing  19 , as described above. This aids in locking the syringe in place. This is shown in  FIG. 7 . 
     Use of the sheath remover to remove the sheath will be described with reference to  FIGS. 8 to 11 . 
     To remove the sheath  7 , the user grips driver sleeve  13  and moves it from the first position  14 , along the housing  11 , towards the second position  15 , in the direction of arrow B in  FIG. 8 , thereby urging the ends  17  of the fingers  16  against the end of the sheath  7  distal to the syringe body  2 . 
     Due to the presence of the ramps  25 , the sheath  7  will deflect these fingers outward to a small extent, causing them to ride up and travel across the sheath as the driver sleeve  13  is moved towards second position  15 —see  FIGS. 8 and 9  which show intermediate stages of the sheath removal process. 
     Once the driver sleeve  13  has been moved to the second position  15  as shown in  FIG. 9 , the fingers  16  have been pulled the full length of the sheath  7 , such that the clamping fingers snap into the gap  9  formed at the junction between the sheath  7  and the syringe body  2 . 
     The user then grasps the housing  11  and the driver sleeve  13 , and pulls or pushes the latter back towards the injecting end  24 , from the second position  15  towards the first position  14 , as shown by arrow A in  FIG. 10 , representing the second stage of the sheath removal procedure. This causes the ends  17  of clamping fingers  16  to abut against the sheath  7  in the gap  9 . 
     Upon movement of the driver sleeve  13  towards the first position  14 , i.e. in the reverse direction, the syringe body  2  is retained within the housing  11  of the remover on the carrier  28 , by virtue of the lip  4  and the wings  5  on the syringe body  2 . However, the carrier  28  itself slides forwards (in the direction of arrow A in  FIG. 10 ). The carrier return spring  29  is thereby compressed between the carrier  28  and end point  30 , until further forward movement of the carrier is prevented by the contact of the rearward protrusion  32  against the end point  30 , as shown in  FIG. 10 . This contact prevents further forward motion of the carrier and, therefore, the syringe body. 
     At this point, further forward movement of the driver sleeve  13  in the direction of arrow A in  FIGS. 10 and 11  (and towards the first position  14 ), will continue to force the ends  17  of the fingers  16  against sheath  7 , thereby urging the sheath off the needle  6 . In the embodiment shown, the tip of the needle  6  protrudes beyond the injection end  24  of the sheath remover  10 . 
       FIG. 11 , being the third stage of the sheath removal process, shows how, by virtue of the restraint of the syringe body  2  and the abutment of the ends  17  of fingers  16  against the end of the sheath, further movement of the driver sleeve  13  in the direction of arrow A removes the sheath  7  from the needle  6 . 
     Once the sheath  7  has been removed, the fingers no longer exert a pull on the syringe and the carrier return spring  29  urges the carrier  28  rearwards away from the injecting end  24 , in the direction of arrow C in  FIG. 11 . In the embodiment shown, the exposed tip of the needle  6  is now retracted in the direction of arrow C. Thus, the tip of the needle  6  moves from an exposed position, beyond the injecting end  24 , back within the housing  11 . 
     It will be appreciated that, in some embodiments, the syringe carrier  28  is not required. 
     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 invention. For example, rather than being configured for attachment to an end of an injection device, the sheath remover may be a separate component that is either used directly with a sheathed syringe, or is adapted to be inserted into an end of an injection device and removed once the sheath has been removed.

Technology Category: 1