Abstract:
A needle assembly for an injection device comprising a needle cannula which is mounted in a hub connectable to an injection device, and a biasing shield which is telescopically guided relative to the hub between a position in which the needle cannula is covered and a position in which at least the sharp end of the needle cannula is exposed, such that an injection can be performed without visual contact with the needle cannula. Further releasable locking means is provided such that the user can lock or unlock the shield to perform the telescopi-cally movement. In order to release the shield, the injection device itself can be utilized as the key for unlocking.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. §371 national stage application of International Patent Application PCT/EP2007/062759 (published as WO 2008/077706), filed Nov. 23, 2007, which claimed priority of European Patent Application 06126970.0, filed Dec. 22, 2006; this application further claims priority under 35 U.S.C. §119 of U.S. Provisional Application 60/878,574, filed Jan. 4, 2007. 
    
    
     THE TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a needle assembly and especially to a needle having a shielded needle cannula. 
     DESCRIPTION OF RELATED ART 
     Needle assemblies are commonly used to either inject substances into or extract substances out of human or animal bodies. Such needle assemblies are typically disposable and are discarded after use. The problem presented by the disposal of a needle assembly, and indeed, by any handling of the needle assembly, is the potential risk of being injured by the sharp end of the needle cannula. This is particular dangerous when following after the penetration of a patients skin since the needle cannula then may be contaminated and therefore capable of spreading diseases such as hepatitis and HIV. 
     A great number of needle assemblies have been developed where the needle cannula is concealed by a spring loaded and telescopically movable shield during the injection. These needle assemblies can be divided into two different kinds of needles assemblies. 
     The first kind is often referred to as safety needles and has a spring loaded shield which covers the sharp end of the needle cannula both before injection, during injection and especially after injection. Such safety needle further has irreversible locking means locking the shield in the position covering the needle cannula after only one injection. Such safety needles are disclosed in e.g. WO 03/066141, EP 1.289.587 and in EP 1.448.256. 
     A second kind of shielded needle is disclosed in WO 99/25402 and in WO 01/76665. The shield disclosed is telescopically movable against the force of a spring located between the hub and the shield. This needle assembly has no irreversible lock and can therefore be used for multiple injections in the same way as a common non-shielded injection needle. 
     As it is apparent from WO 99/25402 such injection needle is ready for injection at any time, however the same kind of needle assembly which can be used for multiple injections can also be made in a way requiring the user to actively unlock the shield prior to each injection. Such needle assembly is disclosed in WO 01/76665. Here the locking element must be moved into a new axial track prior to each injection by applying an axial pressure on the shield. 
     Instead of attaching the shield to the hub as in the previous examples, WO05/035029 discloses an injection pen with a common non-shielded injection needle and an auxiliary shield-mechanism forming part of the injection pen. 
     It is henceforth a problem with injection needle assemblies that any person handling the needle is in a potential risk of being accidentally injured by the needle. For the second type of needle assemblies that do not lock after injection there is also a danger for persons handling the needle assembly after it has been discarded. 
     Thus, there is a need for a needle assembly that can provide a higher degree of safety against accidental needle stick injuries in more situations. 
     DESCRIPTION OF THE INVENTION 
     It is an object of the present invention to provide a needle assembly having a shielded needle cannula which can be locked or unlocked dependent on the situation of use. 
     The shield is constantly urged in the distal direction by the biasing means such that the tip of the needle cannula is covered. When the needle assembly is in its unlocked position it is possible to telescope the shield in the proximal direction which is preferably done by pressing the shield against the skin of the user during injection. In the locked position, the shield is prevented from telescoping. The releasable locking means cooperates with the connecting means such that the locking means are only released upon activation of the connecting means. When the locking means cooperates with the connecting means to be released when the connecting means are activated it is possible for a user to use the injection device to unlock the shield such that when a user connects the needle assembly to the injection device the needle assembly is automatically unlocked whereas when it is removed from the injection device it is automatically locked again. As a result of this the needle assembly is always locked when dismounted and unlocked when mounted. 
     It is however also possible to make it such that the needle assembly can be manually shifted between a locked and an unlocked mode when mounted, whereas it is always locked when dismounted. 
     The connecting means which is usually a thread connection or a bayonet coupling is normally located at the proximal end of the hub ready to be connected to an injection device. The releasable locking means is usually provided with a number of activating parts or extensions which protrudes into the area of the connecting means such that the activating parts are activated when an object such as an injection device enters into the connecting area and interfaces the connecting means. 
     Further a separate locking element can be provided. The activating means are preferably provided on the locking element which is moved from the locking to the unlocking position by activation from the injection device. The movement of the locking element can either be rotational or axial or a combination thereof. Preferably, a thread connection secures that the locking element is rotated when it is axially moved, in this way the locking element can be moved to a new rotational position as it is axially moved e.g. by the injection device. 
     The needle assembly and injection pen together forms a system were it is assured that the safety shield can only be telescoped once the needle assembly is mounted on the injection device, further it is also assured that when the needle assembly is dismounted the shield covering the needle cannula is locked such that a user can not come into contact with the sharp end on the needle cannula. 
     In addition to this an overriding locking mechanism can be provided such that the safety shield can be shifted between a locked and an unlocked position only when the needle assembly is mounted on an injection device. 
     DEFINITIONS 
     An “injection pen” is typically an injection apparatus having an oblong or elongated shape somewhat like a pen for writing. Although such pens usually have a tubular cross-section, they could easily have a different cross-section such as triangular, rectangular or square or any variation around these geometries. 
     As used herein, the term “drug” is meant to encompass any drug-containing flowable medicine capable of being passed through a delivery means such as a hollow needle in a controlled manner, such as a liquid, solution, gel or fine suspension. Representative drugs includes pharmaceuticals such as peptides, proteins (e.g. insulin, insulin analogues and C-peptide), and hormones, biologically derived or active agents, hormonal and gene based agents, nutritional formulas and other substances in both solid (dispensed) or liquid form. 
     Correspondingly, the term “subcutaneous” injection is meant to encompass any method of transcutaneous delivery to a subject. 
     Further the term “injection needle” defines a piercing member adapted to penetrate the skin of a subject for the purpose of delivering or removing a liquid. 
     The term “Needle Cannula” is used to describe the actual conduit performing the penetration of the skin during injection. A needle cannula is usually made from a metallic material and connected to a hub to form an injection needle. A needle cannula could however also be made from a polymeric material or a glass material. The hub which carries the connecting means for connecting the injection needle to an injection apparatus is usually moulded from a suitable thermoplastic material. 
     “Cartridge” is the term used to describe the container containing the insulin. Cartridges are usually made from glass but could also moulded from any suitable polymer. A cartridge or ampoule is preferably sealed at one end by a pierceable membrane which can be pierced e.g. by an injection needle. The opposite end is closed by a plunger or piston made from rubber or a suitable polymer. The plunger or piston can be slidable moved inside the cartridge. The space between the pierceable membrane and the movable plunger holds the insulin which is pressed out as the plunger decreased the volume of the space holding the insulin. 
     All references, including publications, patent applications, and patents, cited herein are incorporated by reference in their entirety and to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     All headings and sub-headings are used herein for convenience only and should not be constructed as limiting the invention in any way. 
     The use of any and all examples, or exemplary language (e.g. such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be constructed as indicating any non-claimed element as essential to the practice of the invention. The citation and incorporation of patent documents herein is done for convenience only and does not reflect any view of the validity, patentability, and/or enforceability of such patent documents. 
     This invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which: 
         FIG. 1  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 2  A-B Show a cross section of the hidden needle assembly of  FIG. 1 . 
         FIG. 3  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 4  A-C Show a cross section of the hidden needle assembly of  FIG. 3 . 
         FIG. 5  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 6  A-B Show a cross section of the hidden needle assembly of  FIG. 5 . 
         FIG. 7  Show an exploded view of an example of a hidden needle assembly 
         FIG. 8  A-C Show a cross section of the hidden needle assembly of  FIG. 6 . 
         FIG. 9  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 10  A-B Show a cross section of the hidden needle assembly of  FIG. 9 . 
         FIG. 11  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 12  Show an exploded view of the hidden needle assembly of  FIG. 11 . 
         FIG. 13  A-C Show a cross section of the hidden needle assembly of  FIGS. 11 and 12 . 
         FIG. 14  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 15  A-C Show a cross section of the hidden needle assembly of  FIG. 14 . 
         FIG. 16  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 17  A-C Show a cross section of the hidden needle assembly of  FIG. 16 . 
         FIG. 18  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 19  A-C Show a cross section of the hidden needle assembly of  FIG. 18 . 
         FIG. 20  A-B Show an exploded view of an example of a hidden needle assembly. 
         FIG. 21  A-C Show a cross section of the hidden needle assembly of  FIG. 20A . 
         FIG. 22  Show an exploded view of an example of a hidden needle assembly. 
         FIG. 23  A-C Show a cross section of the hidden needle assembly of  FIG. 22 . 
         FIG. 24  Show a side view of an example of a hidden needle assembly. 
         FIG. 25  A-B Show a view of a hidden needle assembly. 
         FIG. 26  A-B Show a view of a hidden needle assembly. 
     
    
    
     The figures are schematic and simplified for clarity, and they just show details, which are essential to the understanding of the invention, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts. 
     DETAILED DESCRIPTION OF EMBODIMENT 
     When in the following terms as “upper” and “lower”, “right” and “left”, “horizontal” and “vertical”, “clockwise” and “counter clockwise” or similar relative expressions are used, these only refer to the appended figures and not to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as there relative dimensions are intended to serve illustrative purposes only. 
     In that context it may be convenient to define that the term “distal end” in the appended figures is meant to refer to the end of the needle cannula penetrating the patient whereas the term “proximal end” is meant to refer to the opposite end pointing away from the patient in a situation of use. 
     Example 1 
     FIG.  1 - 2   
       FIGS. 1 and 2  discloses a hub  1  carrying a needle cannula  15 . In use the needle cannula  15  forms a conduit between the interior of a cartridge  25  secured in an injection device  20  and the subcutaneous layer of a user. The hub  1  is surrounded by an outer shield  30  which is permanently connected to the hub  1  e.g. by snapping, gluing or welding the two parts  1 ,  30  together, alternatively the two parts  1 ,  30  can be formed as one part during moulding. 
     The hub  1  is further provided with interior coupling means  2  such as a thread or one or more protrusions for a bayonet coupling as described in EP 1,536,854. These engagement means  2  co-operates with similar engaging means  21  on the distal end of the injection device  20  in order to secure the hub  1  to the injection device  20 . 
     Although the term “injection device” is used through out this application, a Penfill® equipped with an adapter top to fit into a Novo Nordisk pen system according to U.S. Pat. No. 5,693,027 or similar containers with drugs provided with connecting means for a needle assembly is also considered to fall under this term. 
     The needle cannula  15  has a distal end  16  with a sharp point for penetrating the skin of the user and a proximal end  17  for penetrating into the cartridge  25  holding the drug to be injected. 
     The outer shield  30  is provided with a rim  31  bordering an opening  32  at the distal end. A safety shield  40  which preferably is provided with a rib  41  is prevented from falling out the opening  32  due to the engagement between the rim  31  and the rib  41 . 
     A resilient element  50  such as a spring is located between the safety shield  40  and the hub  1 , urging the safety shield  40  in the distal direction whereby the safety shield  40  covers the distal end of the needle cannula  10 . 
     The hub  1  is on its distal side provided with a number of arms  3  extending in the distal direction. These arms  3  are secured to the remaining part of the hub  1  by film hinges  4  such that the arms  3  can move flexible in a radial direction. The arms  3  could also be provided on a separate element which could be attached to the hub  1  e.g. by snapping, gluing or welding. The most distal end of these arms  3  is preferably provided with a shoulder  5 . The proximal side of the film hinges  4  is further provided with a proximally pointing protrusion  6  located radically displaced to the axial axis of the arms  3 . 
     In the initial position shown in  FIG. 2A , the safety shield  40  is pressed forward by the spring  50  and the shoulder  5  on the arms  3  is positioned directly beneath the shield  40 . Due to the abutment between the shoulders  5  and the safety shield  40  it is not possible to telescope the safety shield  40  in the proximal direction. 
     When the injection device  20  is inserted into the hub  1  and secured in position as shown in  FIG. 2B , the distal end of the injection device  20  abuts the protrusions  6 . This distally working pressure on the protrusions  6  makes the flexible film hinge  4  flex whereby the arms  3  and its shoulders  5  are moved inwardly toward the centre of the needle assembly due to the dislocated position of the protrusions  6 . This radial movement of the arms  3  and its shoulders  5  removes the shoulders  5  from its abutment with the safety shield  40 , which is hereafter movable in its axial direction. 
     When the injection has been finalized and the needle hub  1  is removed from the injection device  20 , the pressure is released from the protrusions  6 . This will make the flexible film hinge  4  flex back to its initial position where the arms  3  once again will be situated right beneath the safety shield  40  preventing axial movement of the safety shield  40 . Due to this mechanism, the safety shield  40  is only axially movable when connected to the injection device  20 . 
     Example 2 
     FIG.  3 - 4   
     In a different example disclosed in  FIGS. 3 and 4  the hub  101  carrying the needle cannula  115  is connected with the outer shield or alternatively moulded as one piece. A spring  150  is located between the hub  101  and the safety shield  140  urging the safety shield  140  in the distal direction. The inside surface of the safety shield  140  is provided with a number of raised ribs  142  which extends in the longitudinal direction. These ribs  142  can be formed in a multitude of different ways e.g. as protrusions. 
     Similar ribs or protrusions  162  are formed on the exterior surface of a locking element  160 . The locking element  160  is located inside the hub  101  and abuts the hub  101  proximally. Also proximally, the locking element  160  is provided with a number of fingers  166  which extends into the connecting area  171  of the hub  101 . 
     The hub  101  is divided into two areas by a partition  107 . The first area being the safety shield guiding area  172  and the second area being the connecting area  171  which is provided with means  102  for coupling the hub  101  to an injection device  120 . The injection device  120  and the hub  101  could also be provided with combined thread  122  and bayonet  123  coupling as described in EP 1.536.854. As could a broad variety of different ways of mounting the needle assembly on the injection device  120  be foreseen e.g. different snap or click-on mechanisms. 
     In this embodiment the injection device  120  is preferably provided with a number of distally located knobs  124 . These knobs  124  interact with the fingers  166  of the locking element  160 . When the hub  101  is connected to the injection device  120 , the injection device  120  and the hub  101  is usually rotated relatively to each other, the extend of the rotation depends of the type of connection. A threaded connection demands several full rotations where a bayonet coupling usually demands less than one full rotation. The situation just before the knobs  124  on the injection device  120  encounters the fingers  166  on the locking element is disclosed in  FIG. 4B . At the end of the rotational movement between the hub  101  and the injection device  120  as depictured in  FIG. 4C , the knobs  124  engages the fingers  166  of the locking element  160  forcing the locking element  160  to rotate. In order for the knobs  124  to abut properly to the fingers  166  a bayonet coupling or a steep thread is preferred. 
     The longitudinal ribs or protrusions  142  of the safety shield  140  are in the initial position located aligned with the similar ribs or protrusions  162  on the locking element  160 . In this way the safety shield  140  is prevented from axial movement. When the locking element  160  is rotated the ribs or protrusion  142 ,  162  disengages and makes it possible to move the safety shield  140  in a telescopic movement as disclosed in  FIG. 4C . 
     Once the user releases the hub  101  from the injection device  120  by rotating in the opposite direction, the position of the knobs  124  on the injection device  120  and the fingers  166  on the locking element  160  is designed such that the fingers  166  and thereby the locking element  160  is returned to the initial and locked position. The injection device  120  could e.g. be equipped with four knobs  124  as disclosed. When mounting the needle assembly to the injection device, the forefront of the knops  124  in the rotational direction abuts the fingers  166 , whereas when the needle assembly is dismounted the backfront of the next knob  124  abuts the finger  166  at its opposite end. 
     In order to prevent unintentional rotational movement between the locking element  160  and the hub  101  e.g. during transportion, a reversible click-arm  165  could be guided in a not shown track inside the hub  101 . This could also serve the purpose of providing the user with a sound signal. 
     Example 3 
     FIG.  5 - 6   
     A similar embodiment is disclosed in  FIGS. 5 and 6 . The hub  201  is provided with an internal thread  202  for connecting the hub  201  carrying the needle cannula  215  to an injection device  220 . An outer shield  230  is attached to the hub  201  or alternatively moulded in one piece with the hub  201 . The hub  201  is further provided with a centrally located tower  209  inside which the needle cannula  215  is glued to the hub  201 . This tower  209  is provided with an external thread  210 . A locking element  260  having an internal thread  261  surrounds the tower  209  and is threadedly engaged with the external thread  210  on the tower  209 . Alternatively an internal thread could be provided on the inside surface of the outer shield  230  engaging an external thread provided on the outside surface of the locking element  260 . 
     The locking element  260  is further provided with a number of protrusions  266  which extends in a proximal direction through openings  208  in the base portion of the hub  201  and into the hollow part  271  of the hub  201  housing the internal threads  202 . All though internal threads  202  are disclosed in the figures they could be replaced by a bayonet coupling without interfering with the way of operating the disclosed needle assembly. 
     A resilient element disclosed as a spring  250  is interfaced between the locking element  260  and the shield  240  urging the shield  240  in the distal direction and urging the locking element  260  in the proximal direction such that the locking element  260  in the initial position disclosed in  FIG. 6A  abuts the hub  201 . 
     The locking element  260  is on its outside surface equipped with a number of axially extending ribs  262  and the shield  240  is on its inside surface provided with similar inwardly pointing ribs  242 . In the initial position the axially extending ribs  262  of the locking element  260  abuts the inwardly pointing rib  242  of the shield  240  thereby preventing the rib from telescoping relatively to the hub  201 . 
     When the hub  201  is attached to an injection device  220  having a cartridge  225  as disclosed in  FIG. 6B , the distal end of the injection device  220  will press the protrusions  266  on the locking element  260  through the holes  208  of the hub  201  and lift the locking element  260  out of abutment with the hub  201 . Due to the threaded connection  210 ,  261  between the locking element  260  and the tower  209  of the hub  201 , the locking element  260  will be rotated during its axial movement. This rotation will cause the axially extending ribs  262  on the locking element  260  to be dislocated in relation to the inwardly pointing ribs  242  on the shield  240  thereby allowing the shield  240  to move in an axial direction relatively to the hub  201 . 
     It is evident that the axial extending ribs  262  and the inwardly pointing ribs  242  could be formed in many different ways, The function that the two elements  242 ,  262  abuts each other in one position but are free of each other when rotated can be accomplished in many different ways e.g. by forming the ribs as protrusions or the like. 
     When the hub  201  is disconnected from the injection device, the spring  250  will urge the locking element  260  in the proximal direction which will cause the locking element  260  to be rotated back to the locked position. In this way the shield  240  is only allowed to telescope when the hub  201  is mounted on the injection device  220 . 
     Example 4 
     FIG.  7 - 8   
     In the embodiment depictured in  FIGS. 7 to 8 , the axial movement of the locking element  360  forces the arms  363  to move in a radial direction in and out of engagement with the safety shield  340 . 
     A spring  350  is mounted between the hub  301  and the safety shield  340 . In addition the spring  350  could apply pressure on the locking element  360  urging it in the proximal direction as explained below. 
     The locking element  360  has a number of arms  363  provided on a base  364  located in the connecting area  371  of the hub  301  having threads  302 , the arms  363  extends into the area distal to the hub  301  through openings  308  in the partition  307 . The geometry of the openings  308  in the partition  307  and the arms  363  is such that the arms  363  are forced to move in a radial direction when the locking element  360  is axially moved. 
     When the hub  301  carrying the needle cannula  315  is connected to the injection device the pressure applied on base  364  of the locking element  360  by the injection device  320  forces the locking element  360  to move in the distal direction which again forces the arms  363  to move in a radial direction towards the centre of the needle assembly thereby bringing the arms  363  out of engagement with the safety shield  340 . Once the arms  363  do no longer abut the safety shield  340 , the safety shield  340  can be moved telescopically in the proximal direction as disclosed in  FIG. 8  B-C making it possible to perform an injection. 
     When the hub  301  is removed form the injection device, the geometry and elasticity of the arms  363  and partitions  307  forces the locking element  360  back into its initial position whereby the arms  363  are moved radial outward to a position beneath the safety shield  340  thereby preventing further movement of the safety shield  340 . The returning of the locking element  360  could also be assisted by not-shown arms on the base  364  penetrating through openings in the hub  301 , which not-shown arms would then be acted upon by the spring  350 . 
     Example 5 
     FIG.  9 - 10   
     In the example disclosed in  FIG. 9-10 , the hub  401  carrying the needle cannula  415  is provided with a number of distally extending arms  403 . In-between the arms  403  open slots  411  are provided. Further the hub  401  is provided with suitable connecting means  402  for connecting the needle assembly to an injection device. 
     On the external surface of the hub  401  a rotational outer shield  430  is provided. This shield  430  can rotate relatively to the hub  401 , which is further provided with a number of click-arms  412  which engages a toothed track  434  on the inside surface of the outer shield  430  such that this can only rotate in one direction relatively to the hub  401 . 
     The outer shield  430  is further provided with a number of guiding slits  433  guiding similar guiding ribs  443  on the outside of the safety shield  440 . 
     A spring  450  is located between the hub  401  and the safety shield  440  urging the safety shield  440  in the distal direction. Protrusions  441  on the safety shield  440  interact with a rim  431  on the outer shield  430  thereby preventing the safety shield  440  from be pressed out the opening  432  of the outer shield  430 . 
     The safety shield  440  is further provided with a number of inwardly pointing ribs  442  on its inside surface. 
     In the initial position disclosed in  FIG. 10A  the ribs  442  on the inside surface of the safety shield  440  is positioned above the arms  403  provided on the hub  401 . This alignment prevents the safety shield  440  form axial movement. 
     When a user rotates the outer shield  430  relatively to the hub  401 , the safety shield  440  is forced to rotate due to the engagement between the guiding slits  433  on the outer shield  430  and the guiding ribs  443  on the outside of the safety shield  440 . This rotational movement rotates the inwardly pointing ribs  442  out of engagement with the arms  403  and into a position above the open slots  411  provided between the arms  403 . In this position the inwardly pointing ribs  442  of the safety shield  440  is free to move telescopically in the slots  411 . The click arms  412  and the toothed track  434  on the inside of the outer shield  430  control the rotational movement. When four arms  403  are present as disclosed in the  FIGS. 9-10 , then the rotational movement between locked on unlocked position would be 45 degrees, however a different number of arms  403  and inwardly pointing ribs  442  can be used. 
     In order to lock the safety shield  440 , the user simply rotates the outer shield  430  and the safety shield  440  to its next position in which the inwardly pointing ribs  403  once again is positioned aligned with the arms  403 . 
     In this way a user can shift the needle assembly between its locked and its unlocked mode simply by rotating the outer shield  430  relatively to the hub  401  no matter if the needle assembly is mounted on an injection device  420  or not. 
     Example 6 
     FIG.  11 - 13   
     An example very similar to the previous is disclosed in the  FIGS. 11-13 . Here the rotational outer shield  530  engages the safety shield  540  by the guiding slits  533  engaging the guiding ribs  543  on the outside surface of the safety shield  540 . 
     The arms  563  obstructing the telescopically movement of the safety shield  540  is provided on a separate locking element  560  which in the initial position disclosed in  FIG. 13A  prevents axial movement of the safety shield  540 . Longitudinal slots  569  are provided between the arms  563 . 
     The outer shield  530  is rotational mounted on the hub  501  carrying the needle cannula  510  by a groove  535  in the outer shielded  530  engaging a similar raised ring  513  on the hub  501 , and the rotational movement is controlled by the click arms  512  and the track  534  inside the outer shield  530 . The hub  501  is further provided with suitable connecting means  502  for connecting the needle assembly to an injection device  520 . However, when the needle assembly is not mounted on an injection device  520  the locking element  560  is urged by the spring  550  into a position where it abuts the hub  501 , and in this position depictured in  FIG. 13A  the inwardly pointing ribs  542  of the safety shield  540  is positioned above the arms  563  such that the safety shield  540  is prevented from telescopically movement. The interaction between the click arms  512  and the track  534  is such that when the outer shield  530  is moved into its next guided position the inwardly pointing ribs  542  move to a position above the next arm  563 . So no matter in which guided position the outer shield  530  (and the safety shield  540 ) is, no telescopically movement is allowed. 
     The locking element  560  is further provided with a number of fingers  566  which extend through openings  508  into the connecting area  571  such that the injection device  520  presses on the protrusion  566  when the needle assembly is mounted. 
     The locking element  560  is on its proximal side provided with cut-away parts  567  carrying a sloping edge  568 . This sloping edge  568  abuts a similar sloping protrusion  514  provided on the distal side of the hub  501 . 
     When a user mounts the needle assembly on an injection device  520  as depictured in  FIGS. 13B and 13C , the injection devices  520  presses the locking element  560  in the distal direction. Due to engagement between the sloping edge  568  of the locking element  560  and the sloping protrusion  514  on the hub  501 , the locking element  560  rotates relatively to the hub  501  as it is moved distally. 
     This rotation moves the arms  563  and the slots  569  to a new position in which the arms  563  is located such relatively to the inwardly pointing ribs  542  on the safety shield  540  that the safety shield  540  can be shifted from a position in which the arms  563  are aligned with the inwardly pointing ribs  542  and a position where the inwardly pointing ribs  542  is aligned with the slots  569 . This means that once the needle assembly is mounted on the injection device  520  the user can rotate the outer shield  530  guided by the click arms  512  and the track  534  such that the safety shield  540  shifts between a locked and an unlocked position. As disclosed in the  FIGS. 11 and 12  the slots  569  can be 90 degrees apart form each other in which case the outer shield  530  is moved 45 degrees in each rotation such that it shifts between locked and unlocked positions. However when the needle assembly is not mounted on an injection device  520  the inwardly pointing ribs  542  and the slots  569  are dislocated such that the inwardly pointing ribs  542  can never be in a position above a slot  569 . In this way it is secured that the position in which the safety shield  540  can telescope only can be obtained when the needle assembly is mounted on the injection device  520 . Once the needle assembly is dismounted the relative position between the arms  563  and the inwardly pointing ribs  542  are such that the safety shield  540  can never telescope, the inwardly pointing ribs  542  will be above an arm  563  no matter in which guided position the outer shield  530  (and the safety shield  540 ) is in. It is understood that the location of the shiftable positions in the track  534  and the relative location of the inwardly pointing ribs  542  inside the safety shield  540  and the arms  563  and slots  569  are decisive for this. 
     Example 7 
     FIG.  14 - 15   
     In the embodiment depictured in the  FIGS. 14-15  no spring element as such is included. The hub  601  carries the needle cannula  615 , and a separate locking element  660  is provided between the hub  601  and the safety shield  640  which parts are encapsulated in the outer shield  630 . 
     The locking element  660  is further provided with fingers  666  which protrude through holes  608  in the hub  601 . 
     When the hub  601  is mounted on an injection device  620 , the distal end of the injection device  620  presses on the fingers  666  which makes the arms  663  of the locking element  660  deflect inwardly allowing the safety shield  640  to axially pass the locking element  660  as depictured in  FIGS. 15B and 15C . 
     The safety shield  640  is internally provided with a plurality of conical flanges  644  which in use slides on the tower  609 . These conical flanges  644  replaces the spring member in the forgoing embodiments and works as the biasing means urging the safety shield  640  to the first position once the needle cannula  615  is retracted from the skin. In order to enhance the biasing force the tower  609  of the hub  601  slopes towards its distal end, further when the hub  601  is removed from the injection device  620  the flexibility of the base of the locking element  660  urges it back to its first position and the safety shield  640  is moved to its first position. 
     Example 8 
     FIG.  16 - 17   
     In the embodiment depictured in the  FIGS. 16 and 17 , the arms  763  on the locking element  760  deflect outwardly when the fingers  766  are activated by the injection device  720 . When the arms  763  are outwardly deflected as depictured in  FIG. 17B , the safety shield  740  is allowed to axially pass the locking element  760 . 
     Further the skirt of the safety shield  740  is divided into a plurality of skirt parts  745  which are pressed inwardly by the arms  763  of the locking element  760  when the safety shield  740  is moved to the position uncovering the needle cannula  715 . The arms  763  forms a conical sloping surface on the interior when deflected outwardly as depictured in the  FIGS. 17B and 17C . The inwardly pressing of the skirt parts  745  on the conical sloping surface operates as a biasing mean urging the safety shield  740  back to its secured position when the needle cannula  715  is removed from injection site, further when the hub  701  is removed from the injection device  720  the flexibility of the base of the locking element  760  urges it back to its first position and the safety shield  740  is moved to its first position. 
     Example 9 
     FIG.  18 - 19   
       FIGS. 18 and 19  discloses an embodiment in which the needle cannula  815  is attached to the hub  801 , further an outer shield  830  is attached to the hub  810 . Internally of the outer shield  830 , a safety shield  840  and a locking element  860  is provided with a spring  850  urging the two parts  840 ,  860  from each other, 
     The locking element is provided with a finger  866  stretching through a hole  808  in the hub  801  and into the connecting area  871  of the hub  801 . 
     The locking element  860  is provided with a number of arms  863  which forms an angle with the axial axis X of the needle assembly as depictured in  FIG. 19A . In this non-activated position, the safety shield  840  is prevented from axial movement by the arms  863  of the locking element  860 . When an injection device  820  is attached to the connecting area  871 , the finger  866  of the locking element  860  is activated and the locking element  860  is forced into a position in which the arms  863  is aligned with the axial axis X of the needle assembly as depictured in  FIG. 19B . In this position the safety shield  840  can move freely in the axial direction. 
     Example 10 
     FIG.  20 - 21   
     This embodiment discloses a similar needle assembly however, the locking element  960  is only provided with one arm  963 . Further, the spring element  950  can be replaced by an elastic sponge  950 A as disclosed in  FIG. 20A . In fact in any of the embodiments disclosed any element providing a biasing force can be used instead of a spring. 
     Example 11 
     FIG.  22 - 23   
     In this embodiment the locking element  1060  is provided with two arms  1063  which are deflected inwardly when the fingers  1066  are activated by the injection device attached to the needle assembly. 
     Example 12 
     FIG.  24   
     In all the embodiments the element forming the outer barrier such as the outer shield  30  could be provided with an opening such as a window  36  through which a user can visually see the safety shield  40  or an element moving with the safety shield  40 . In this way the user can visually follow the progress of the injection. The element forming the background in the window  40  e.g. the locking member, could be coloured in a different colour than the element passing the window  36  e.g. the safety shield  40  during injection to enhance the visibility of the element passing the window  36 . 
     Example 13 
     FIG.  25 - 26   
     In all the foregoing embodiments the needle assembly could be provided with a mechanism which provides the user with an audible, visual or tactile confirmation when the needle cannula is fully inserted. 
     An example of such audible mechanism is disclosed in  FIG. 25A-B . Here a mechanism  1180  carrying a click-arm  1181  is provided on the interior of the outer shield  1130 , the safety shield  1140  is at its proximal end provided with a peripheral rib  1141  which engages the click-arm  1181  once the safety shield  1140  is pressed fully back in order to provide a distinct sound informing the user that the needle cannula  1115  is fully inserted. This activation can be done in multiple ways e.g. as disclosed by having the click-arm  1181  carry a protrusion  1182  at the end, or the arm  1181  could carry more than one protrusion  1181 . The proximal end of the click-arm  1181  could e.g. be formed with a not-shown threaded portion providing a distinct sound as the rib  1141  slides over the threaded portion at the end of the needle insertion. In addition to providing a sound this would also provide a vibration of the needle assembly and the injection device to which it is attached thereby providing a tactile confirmation. 
     A further example of a visual and tactile indication is provided in the  FIGS. 26A-B . In this embodiment the click-arm  1181  is provided with an indicator  1183  e.g. a coloured indicator  1183  which is forced out of an opening  1136  in the outer shield  1130  once the shield reaches its proximal destination. This indicator  1183  could also be provided with a Braille-like indication. 
     Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject matter defined in the following claims, e.g. could a needle assembly as herein described be delivered to the user in a rigid and sterile container which further could be shaped as a tool for assisting the user in mounting the needle assembly on to the injection device.