Abstract:
An actuator is provided which is adapted, in conjunction with a cartridge, to form a needle-less injector, the cartridge being filled with a liquid to be injected in a subject, and having a liquid outlet and a free piston in contact with the liquid. The actuator comprises an impact member urged by a spring and temporarily restrained by a latch, the impact member being movable in a first direction under the force of the spring to first strike the free piston and then to continue to move the piston in the first direction to expel a dose of liquid through the liquid outlet, the spring providing a built-in energy store. A pressure pad surrounds the said liquid outlet and, in use, bears on the subject&#39;s skin. The actuator may be formed of two main housing components urged apart by an integral cantilever spring formed on one of them, a safety catch can be provided to prevent inadvertent actuation.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a medicament delivery device, and in particular, but not exclusively to a medicament delivery device such as an injector for self-administration of a medicament. Such injectors include those known as pen-type injectors.  
       BACKGROUND TO THE INVENTION  
       [0002]     In the past, it was known for those requiring regular injections of a medicament, such as those having diabetes requiring infections of insulin, to use a syringe to remove a required amount of medicament from a phial, and then use the syringe to inject the required amount of medicament. There are a number of drawbacks with this method. These include the fact that the loading of the syringe in this way is a delicate and somewhat skilled task, while those with, for example diabetes, tend to be infirm or have impaired vision, each of which increases the risk of inadvertent pricking by the syringe. In addition, the use of syringes in public places has increasingly become socially unacceptable. To overcome these difficulties pen-type injectors have been developed.  
         [0003]     Such injectors include within a main housing a medicament cartridge. The medicament cartridge is supplied loaded with a medicament. A user then selects a dosage and uses the pen-type injector to deliver the selected amount of medicament. The pen-type injectors are, as the name suggests, typically in the shape of a pen, though sometimes other forms are adopted. In each case, however, the appearance is non-descript so as not to draw attention to the device.  
         [0004]     Often, the medicament cartridge is replaceable to facilitate reuse of the injector. As noted above, those using such devices are often inform or have impaired vision. There is accordingly a demand for a medicament delivery device in which a medicament cartridge can be easily removed from the medicament delivery device and equally easily replaced with a replacement medicament cartridge.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     According to a first aspect of the present invention, in a medicament delivery device comprising a housing, a cartridge retainer having a bore for receiving a medicament cartridge, the cartridge retainer being adapted for pivoting movement between an open position angularly displaced form the houses and a closed position adjacent the housing, a drive means, in use, operating within the cartridge retainer to cause medicament to be expelled from a medicament cartridge and a latch for releasably retaining the cartridge retainer in the closed position.  
         [0006]     Preferably, the latch is moveable between a first advanced position and a second retracted position. More preferably, the drive means are adapted to move the latch from the first position to the second position. Even more preferably, the drive comprises a plunger having a head, the head engaging with the latch to move the latch from the first position to the second position.  
         [0007]     Alternatively, the latch is received within the housing and comprises spring means, and a body portion, the body portion further comprising a spring engaging portion, a downwardly extending part extending at an angle away from the spring engaging portion, a generally U-shaped portion extending from an end of the downwardly extending part remote from the spring engaging portion, a laterally extending tab extending from an end of the generally U-shaped portion remote from the downwardly extending part and a forwardly extending tab extending from a web of the generally U-shaped portion. Preferably the drive means comprises a plunger having a head, the head engaging with the laterally extending tab of the latch to move the latch from the first position to the second position. More preferably the cartridge retainer comprises a recess for mating engagement with the forwardly extending tab of the latch.  
         [0008]     Preferably the housing includes first and second elongated slots, the cartridge retainer comprises first and second tabs, each of the first and second tabs having fingers extending therefrom, in use the tabs extending through the slots and the open position is achieved when the fingers abut against a rear surface of the housing adjacent the slots. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention will now be described, by way of example only, with reference to the accompanying drawing, in which:  
         [0010]      FIG. 1  shows a sub assembly incorporating a housing, a cartridge retainer for a medicament cartridge and a latch in accordance with the present invention, with the cartridge retainer in an open position;  
         [0011]      FIG. 2  shows the sub-assembly of  FIG. 1 , with the cartridge retainer in a partially closed position;  
         [0012]      FIG. 3  shows the sub-assembly of  FIGS. 1 and 2 , with the cartridge retainer in a closed position;  
         [0013]      FIG. 4  shows the sub-assembly in the position shown in  FIG. 3 , but from a different angle;  
         [0014]      FIG. 5  shows an enlarged view of the latch;  
         [0015]      FIG. 6  shows a view of the housing without the cartridge retainer or latch;  
         [0016]      FIG. 7  shows a view of the cartridge without the housing or the latch;  
         [0017]      FIG. 8  shows a view of a second embodiment of the latch;  
         [0018]      FIG. 9  shows a view of a second embodiment of the housing for use with the latch shown in  FIG. 8 ;  
         [0019]      FIG. 10  shows a detail of a third embodiment of a sub-assembly incorporating a housing, a cartridge retainer for a medicament cartridge and a latch in accordance with the present invention; and  
         [0020]      FIG. 11  shows the sub-assembly of  FIG. 10  as a whole. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring first to FIGS.  1  to  4 , there may be seen a sub-assembly incorporating a housing  2 , a cartridge retainer  4  for a medicament cartridge and a latch  6 . A medicament delivery device will also typically comprise a number of further elements such as a cover, which may or may not be integrated with the housing, a drive means and a microprocessor to store information and to orate electrical aspects of the medicament delivery device such as a display or motor means for operation of the drive means. This will be understood by one skilled in the art. However, since such elements do not form part of the present invention they are not discussed further herein.  
         [0022]     The housing  2  (shown separately in  FIG. 5 ) comprises a generally elongate structure disposed along a first elongate axis having a first end and a second end. Intermediate the first end and the second end there is disposed a cut-away or recessed portion  8  extending from the second end towards the first end. First and second shoulders  10 ,  11  extend along the sides of the recessed portion  8 .  
         [0023]     At the first end of the recessed portion  8  of the housing  4  there are provided a first shaped grove  12  and a second shaped groove  14 . A projecting part  16  located adjacent the first shaped groove  12  extends within the recessed portion  8  from the first end of the housing  2  towards the second end of the housing  2 . The second shaped groove extends within the projecting part  16 . The projecting part is further provided with an opening  18  connecting the second shaped groove  14  with the recessed portion  8 . The recessed portion  8  is further provided with first and second elongate slots  20 , 22 .  
         [0024]     At the second end of the housing  2  there are provided two oppositely disposed projections  24 . Each of the projections  24  is provided with a through bore  26 .  
         [0025]     The cartridge retainer  4  comprises a body portion of generally elongate part-cylindrical configuration and is provided with an internal cylindrical bore (not shown), adapted in use, to receive a medicament cartridge (not shown). The cartridge retainer  4  is provided at a second end with a boss  30  having a thread  32  about an external portion thereof. In use, a needle unit (not shown) will be threadably engaged with the external thread  32  of the boss  30 .  
         [0026]     The cartridge retainer  4  (shown separately in  FIG. 7 ) is further provided with an outwardly directed flange  34  extending from one side of a body  28  of the cartridge retainer  4 . The flange  34  is located towards the second end of the cartridge retainer  4 . At an end remote from the body  28  of the cartridge retainer  4  the flange  34  is provided with a barrel portion  35  having a through bore. In use the through bore of the barrel portion  35  is aligned with the through bores  26  of the projections  24  formed at the second end of the housing  2  and pivot pin  36  passed through the aligned bores. In this way, the cartridge retainer  4  is adapted to pivot with respect to the housing  2 .  
         [0027]     The cartridge retainer  4  is further provided with first and second oppositely disposed tabs  38 ,  40 , each of the first and second tabs  38 ,  40  extending away from the body  28  of the cartridge retainer  4 . The first and second tabs  38 ,  40  are located approximately one third along the cartridge retainer  4  towards the second end of the cartridge retainer  4 . Each of the first and second tabs  38 , 40  is provided with an outwardly directed finger  42 ,  44  that is each finger is disposed in a direction away from the other of the first and second tabs  38 ,  40 .  
         [0028]     In use, each of the first and second tabs  38 , 40  is adapted to extend through a respective one of the first and second elongate slots  20 , 22  provided in the housing  2 . The outwardly directed fingers  42 , 44  will locate behind respective edges of the first and second elongate slots  20 , 22  to prevent pivotal movement of the cartridge retainer  2  with respect to the housing  2  beyond a predetermined position.  
         [0029]     At the first end of the cartridge retainer  2  there is provided a further outwardly directed flange  46 . The further flange  46  is provided with a ridge or projection  48  extending away from the further flange  46  in a direction generally parallel to the elongate axis of the cartridge retainer  4 . At the second end of the cartridge retainer  4 , between the bore of the cartridge retainer  4  and the further flange  46 , a recess  49  is formed within the body  28  of the cartridge retainer  4 .  
         [0030]     Within the first and second shaped grooves  12 , 14  of the housing  2  there is located a latch  6  (shown separately in  FIG. 5 ). The latch  6  comprises a means and a body portion  60 . The spring means illustrated in the Figures is a helical spring  50 . The spring means is located in a closed end of the first shaped groove  12 . It will be understood that in the presence of a cover (not shown) the first shaped groove will become a blind bore, thereby constraining operation of the spring  50 .  
         [0031]     The body portion  60  of the latch  6  is located within both the first and second shaped grooves  12 , 14 .  
         [0032]     The body portion  60  of the latch  6  comprises a spring engaging portion  62 , a downwardly extending part  64  extending at an angle away from the spring engaging portion  62 , a generally U-shaped portion  66  extending from an end of the downwardly extending part  64  remote from the spring engaging portion  62 , a laterally extending tab  68  extending from an end of the generally U-shaped portion  66  remote from the downwardly extending part  64  and a forwardly extending tab  70  extending from a web of the generally U-shaped portion  66 .  
         [0033]     In use, the spring engaging portion  62  is located within the first shaped groove  12  with the spring means. The generally U-shaped portion  66  is located about the projecting part  16  of the housing  2 , the laterally extending tab  68  being disposed generally parallel to a surface of the first end of the housing abutting a side surface  72  of the projecting part  16 . The body portion  60  is further provided with a protrusion (not shown) which is seated in and adapted to travel within the opening  18  in the projecting part  16 .  
         [0034]     Operation of the cartridge retainer  4  and the associated latch  6  will now be explained with principal reference to FIGS.  1  to  3 . In  FIG. 1 , the cartridge retainer  4  is at an extreme angular location with respect to the housing  2 . The cartridge retainer  4  is prevented from moving beyond this position by the restraining effect of the fingers  42 , 44  of the first and second tabs  38 , 40  abutting with the surfaces behind the respective first and second elongate slots  20 , 22  through which the first and second tabs  38 , 40  pass.  
         [0035]     In this position, the opening of the bore of the cartridge retainer  4  at the first end of the cartridge retainer  4  is clear of the housing  4  allowing a medicament cartridge easily to be inserted into or withdrawn from the cartridge retainer  4 . Preferably, the medicament cartridge should easily slide within the bore of the cartridge retainer  4  such that when the cartridge retainer  4  is in the position shown in  FIG. 1 , removal of a medicament cartridge may be effected simply by inverting the sub-assembly to allow the medicament cartridge to slide out due to gravity.  
         [0036]     It will be seen that in  FIG. 1  that the latch  6  is in an advanced position.  
         [0037]     In  FIG. 2 , the cartridge retainer  4  has been moved to an intermediate position in which the cartridge retainer  4  is at a reduced angular displacement with respect to the housing  2 . In particular, it will be noticed that the further flange  46  at the first end of the cartridge retainer  4  has pushed against the forwardly extending tab  70  of the latch  6  causing the latch  6  to be moved backwards against the spring  50  within the first shaped groove  12  in the housing  2 . As the latch  6  is moved backwards, the side surface  72  of the projecting part  16  acts as a guide wall for the laterally extending tab  68 .  
         [0038]     As the cartridge retainer moves from the position shown in  FIG. 1  through the position shown in  FIG. 2  and into the position shown in  FIG. 3 , the further flange  46  is received within that portion of the recessed portion  8  defined between the first and second shoulders  10 , 11 . During this movement, it will be seen that the further flange  46  acts as a camming surface displacing the latch  6  within the first and second shaped grooves  12 , 14 .  
         [0039]     When the cartridge retainer  4  is the position shown in  FIG. 3 , a closed position, the forwardly extending tab  70  moves from the further flange  46  into the recess  49 . It will be understood that the impact of the latch  6  (either the web of the U-shaped portion  6  or the forwardly extending tab  70 ) striking against the cartridge retainer  4  will provide an audible click, providing conformation to a user of the medicament deliver device that the cartridge retainer  4  is in a closed position against the housing  2 . The forwardly extending tab  70  is held within the recess  49  under the action of the spring  50 .  
         [0040]     In one embodiment (not shown), the latch  6  is provided with a tab that extends through a slot in the cover of the medicament delivery device. A user may then manipulate the tab to withdraw the forwardly extending tab  70  of the latch from the recess  49  of the cartridge retainer  4 , thereby to free the cartridge retainer  4  for pivoting movement away from the housing  2 .  
         [0041]     However, this arrangement has as a disadvantage that a user may free the cartridge retainer  4  in this way, while a drive means of the medicament delivery device is still operational within the bore of the cartridge retainer  4  to cause medicament to be expelled form the medicament cartridge. Attempting to move the cartridge retainer  4  at this time cause damage to the drive means rendering the medicament delivery device inoperative.  
         [0042]     In a preferred embodiment, the drive means comprises a headed plunger in which the head of the plunger is located ahead of the laterally extending tab  70 . When the cartridge retainer  4  is in the closed position of  FIG. 3 , the headed plunge is free to advance within the cartridge retainer  4 . When a medicament cartridge is present within the cartridge retainer  4 , this will cause medicament to be expelled from the medicament cartridge.  
         [0043]     When a user wishes to move the cartridge retainer  4  away from the housing  2 , the plunger is caused to be withdrawn from the cartridge retainer  4 . This has the effect of bringing the head of the plunger into contact with the laterally extending tab  70  of the latch  6 . Further movement of the plunger in this direction causes the laterally extending tab  68 , together with the latch  6 , to be withdrawn together with the plunger. Beyond a certain point, the forwardly extending tab  70  of the latch will be disengaged from the groove  49  in the cartridge retainer  4 . This point is chosen such that at this point the head of the plunger and the laterally extending tab  68  have both been withdrawn behind the path of movement of the cartridge retainer  4 . In this way, the cartridge retainer  4  cannot be moved away from the housing  2  until the drive means is clear of the cartridge retainer  4 .  
         [0044]     Turning now to  FIGS. 8 and 9 , there is shown a further embodiment of a latch and housing for use in a sub-assembly of a medicament delivery device in accordance with the present invention.  
         [0045]     The housing  102  of this embodiment is generally similar to the housing  2  of the previous embodiment. The principal differences lie at the first end of the housing  102 . The first end of a recessed portion  108  is provided with a single groove  112 . The single groove  112  is formed in a region of the housing  102  of reduced thickness. The housing  102  is provided with an opening  118  extending through the single groove  112 . A bore (not shown) is located in the housing  106  beneath the single groove  112 .  
         [0046]     The latch  106  comprises a spring means and a body portion  160 . The spring means is conveniently in the form of a helical spring  150 . In use, the spring means is located within the bore.  
         [0047]     The body portion  160  of the latch  106  comprises a spring engaging portion  162 , a web portion  163  connected across one end of the spring engaging portion  162 , a forwardly directed flange  165  connected to one end of the web portion  163 , a laterally extending tab  168  extending from an end of the forwardly directed flange  165  remote from the web portion  163 , a generally U-shaped portion  166  extending from a second end of the web portion  163 , and a forwardly extending tab  170  extending from a web of the generally U-shaped portion  166 . A locating tab  171  is provided on one limb of the generally U-shaped portion  166 . It can be seen that this limb is longer than the other limb of the generally U-shaped portion  166 .  
         [0048]     In use, the latch  106  is seated within the single groove  112 . The locating tab  171  is adapted to be seated within the opening  118 . The longer limb of the generally U-shaped portion  166  of the latch  106  is provided with a shoulder  172  which way in use abut a corresponding shoulder  173  provided on the housing  112  as part of the single groove  112 .  
         [0049]     The operation of this embodiment is essentially the same as for the previous embodiment in that as the cartridge retainer is moved to the closed position, the cartridge retainer abuts with the forwardly extending tab  170  to urge the latch  106  backwards within the single grove  112 . Similarly, the drive means may comprise a headed plunger in which the head of the plunger is located ahead of the laterally extending tab  168  in order the latch  106  may be drawn backwards under the action of the plunger to allow the cartridge retainer to be pivoted away from the housing  106  to facilitate removal and/or insertion of a medicament cartridge.  
         [0050]     Turning now to  FIGS. 10 and 11 , there is shown a third embodiment of a latch  206  and housing  202  for use in a sub-assembly of a medicament delivery device in accordance with the present invention.  
         [0051]     The housing  202  of this third embodiment is generally similar to the housing  2  of the first embodiment. The principal differences lie at the first end of the housing  202 .  
         [0052]     A slot  212  is located at a first end of the housing  202 . A region of the housing  202  adjacent the slot  212  takes the form of a generally cylindrical bore.  
         [0053]     The latch  206  comprises a spring means and a body portion  260 . The spring means is conveniently in the form of a helical spring  250 . In use, the spring means located within the bore. The helical spring  250  abuts against one end of the bore. This end of the bore includes an opening through which a drive means may in use extend.  
         [0054]     The body portion  260  is generally bowl-shaped having a central opening at a base  268  of the bowl. A forwardly extending tab  270  is located at a point on a rim of the bowl. In the illustrated embodiment, the slot  212  and the forwardly extending tab  270  are each repeated about an axis of the sub-assembly. In use, a headed plunger extends through the central opening such that a head  280  of the plunger is located ahead of the base  268  of the bowl.  
         [0055]     When the latch  206  is drawn backwards under the action of the plunger, the forwardly extending tab(s)  270  are fully retained within the slot(s)  212 , and a cartridge retainer  204  is free to be pivoted away from the housing  206  to facilitate removal and/or insertion of a medicament cartridge. When the cartridge retainer  204  is in position adjacent the housing  202  the latch  206  may be released and the forwardly extending tab(s)  270  will move forward under the action of the spring  250  to engage with recess(es)  249  provided in the cartridge retainer  204  for this purpose and thereby retain the cartridge retainer  204  in position.