Abstract:
There is provided medicine delivery apparatus including a casing, a drive shaft which, in use, engages a medicine containing cartridge, an automatic driver, a user actuable trigger for causing the automatic driver to move the drive shaft through the casing, and a user actuable brake for allowing a user to control a rate of delivery of medicine.

Description:
TECHNICAL FIELD  
       [0001]    The present invention relates to an injection method and apparatus, and more particularly to an injection method and apparatus which provides for automatic medicine delivery and for variable dose setting. 
       BACKGROUND 
       [0002]    U.S. Pat. No. 5,743,889 and U.S. Pat. No. 6,899,698 describe a generally pen-like syringe that incorporates a dose metering device provided by a dose knob which is rotatable relative to the pen body to a position related to the dose of medicine to be injected. Within the body, there is a spring, a drum comprising a set of teeth and a grooved helical track, a drive rod arranged to push against a medicine cartridge and a lock that is arranged to releasably hold the drive rod. The lock includes a set of teeth arranged to engage with the drum teeth. The pen also includes a trigger that has a projecting cam follower. As the knob is rotated, the cam follower engages with the helical track and the drum undergoes rotational movement relative to the casing of the pen. This movement causes loading of the spring. The helical track ensures that the drum also undergoes axial movement along a main axis of the pen. The teeth of the drum move over the non-rotating teeth of the lock and disengage the lock from the drive rod as the lock teeth rise and fall during rotation. The axial movement of the lock corresponds to the axial movement of the drum. As the teeth are almost fully engaged between the lock and the drum, the lock grips the drive rod under the force of the spring. When the trigger is depressed, the cam follower is lifted out of engagement with the helical track, and the unwinding of the compressed spring pushes the lock and therefore the drive rod forward, thereby ejecting a dose of medicine. The front faces of the lock meet an internal stop fixed relative to the body. The drum and lock teeth are fully disengaged and the trigger cam follower can no longer engage with the helical track. A marking on the drum in this position is displayed through a window on the main body, which shows that the syringe is ready for further use. 
         [0003]    A problem with these types of pen syringe is that the user has no control over the rate of ejection. The dose is ejected at a rate determined by the unwinding force of the spring. For larger doses, users may prefer to be able to limit the speed of medicine delivery. 
       SUMMARY  
       [0004]    According to a first aspect of the present invention there is provided medicine delivery apparatus comprising:
       a casing;   a drive shaft which, in use, engages a medicine containing cartridge;   an automatic driver;   a user actuable trigger for causing the automatic driver to move the drive shaft through the casing; and   a user actuable brake for allowing a user to control a rate of delivery of medicine.       
 
         [0010]    By “automatic driver”, it is meant a driver that does not require a motive force directly from a user. An automatic driver may be moved by a spring, a pre-cocked spring, a pneumatic force, and so on, and is distinct from a driver in a syringe that is pushed directly by a user. 
         [0011]    It is preferred that the brake is disposed on the trigger, such that, in use, a pressure on the trigger operates the brake. 
         [0012]    Preferably, the apparatus further comprises:
       a dose setting knob;   driver teeth disposed on the driver;   a drum mounted in the casing and being rotatably coupled to the dose setting knob;   drum teeth disposed on the drum arranged to engage with the locking member teeth;   a helical track around an outer surface of the drum, the helical track arranged to engage with a cam follower disposed on the trigger; and   wherein, in use a rotation of the drum causes the drum teeth to move over the driver teeth, such that when the teeth are engaged the driver locks the drive shaft, and when the teeth are disengaged, the driver releases the drive shaft.       
 
         [0019]    The brake may be arranged to restrict movement of the drum, thereby restricting movement of the drive shaft. 
         [0020]    In order to facilitate moulding and assembly, the apparatus may further comprise a chassis located within the casing, the drum being partially located in and coaxial with the chassis, the chassis further comprising a projection arranged to contact the cam follower. In this instance it is preferred that the chassis comprises a chassis ramp disposed on the chassis and a drum ramp disposed on the drum, wherein, in use, a rotation of the drum relative to the chassis causes the ramps to co-operate to move the drum axially away from the chassis to a position in which the cam follower can engage with the helical track. 
         [0021]    The apparatus may comprise a locking disc fixed relative to the casing, the locking disc having an opening through which the drive shaft can pass, the locking disc further comprising inwardly pointing fingers arranged to grip the drive shaft, such that the locking disk permits movement of the drive shaft in one direction only. 
         [0022]    In order to allow the trigger to return to its original position after use, the apparatus may comprise an elastic overmoulding over the trigger, such that, in use, operation of the trigger deforms the overmoulding, and subsequent release of the trigger allows the overmoulding to revert to its original shape. Alternatively, the apparatus may comprise a leaf spring disposed between the trigger and the casing, the leaf spring biasing the trigger towards a rest position. Where a leaf spring is used, the brake may also act as the leaf spring. 
         [0023]    In order to reduce the necessity for “air shots” or storing the medicine cartridge under pressure, the apparatus may comprise an opening in the dose setting knob, through which a user may manipulate the drive member to ensure contact with the medicine containing member. 
         [0024]    According to a second aspect of the present invention, there is provided medicine delivery apparatus comprising:
       a casing;   a drive shaft which, in use, engages a medicine containing cartridge;   an automatic driver;   a user actuable trigger for causing the automatic driver to move the drive shaft through the casing;   a cam follower located on the trigger, the cam follower arranged to engage with a helical track associated with the driver; and   a projecting surface fixed relative to the casing and arranged to contact the cam follower.       
 
         [0031]    According to a third aspect of the invention, there is provided medicine delivery apparatus comprising:
       a casing;   a drum rotatable within the casing and having a helical track formed on a surface thereof;   a cam follower which is engageable with said track to allow the drum to be screwed through the casing;   a first ramp located on the drum;   a second ramp fixed relative to the casing;   wherein, during dose setting, a rotation of the drum relative to the casing causes the ramps to co-operate to move the drum longitudinally within the casing, thereby bringing the cam follower into engagement with the helical track.       
 
         [0038]    According to a fourth aspect of the present invention, there is provided medicine delivery apparatus comprising:
       a casing;   a drive member which, in use, engages a medicine containing cartridge;   an automatic driver;   a user actuable trigger for causing the automatic driver to move the drive shaft through the casing;   an opening in the medicine delivery apparatus, through which a user may manipulate the drive member to ensure contact with the medicine containing member.       
 
         [0044]    It is preferred that the opening is in a dose setting knob. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0045]    For a better understanding of the present invention and in order to show how the same may be carried into effect reference will now be made by way of example to the accompanying drawings in which: 
           [0046]      FIG. 1  shows schematically a pen-type injector; 
           [0047]      FIG. 2  shows a longitudinal cross-section through the injector of  FIG. 1 ; 
           [0048]      FIG. 3  shows an exploded perspective view of the injector of  FIG. 1 ; 
           [0049]      FIG. 4  is a perspective view of a dose knob of the injector of  FIG. 1 ; 
           [0050]      FIG. 5  is a perspective view of a lock of the injector of  FIG. 1 ; 
           [0051]      FIG. 6  is a perspective view of a drive rod of the injector of  FIG. 1 ; 
           [0052]      FIG. 7A  shows a longitudinal cross-section through a drum of the injector of  FIG. 1 ; 
           [0053]      FIG. 7B  is a perspective view of the drum of the injector of  FIG. 1 ; 
           [0054]      FIG. 8A  is a perspective view of a chassis of the injector of FIG.  1 ′ 
           [0055]      FIG. 8B  is a rear elevation view of the chassis of  FIG. 8   
           [0056]      FIG. 9  is a perspective view of a collar of the injector of  FIG. 1 ; 
           [0057]      FIG. 10A  is a side elevation view of a trigger and drum of the injector illustrating a first alternative braking mechanism; 
           [0058]      FIG. 10B  is a side elevation view of a trigger and drum of the injector illustrating a second alternative braking mechanism; and 
           [0059]      FIG. 10C  is a side elevation view of a trigger and drum of the injector illustrating the braking mechanism of the injector of  FIGS. 1 to 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0060]    There is illustrated in  FIGS. 1 to 9 , and  FIG. 10C , a pen-type injector having a user operable dose setting mechanism. It can be seen that the injector comprises a casing  1  and a cap  2 , which snap fit together. A dose knob  3  is disposed at one end of the casing. A trigger  4  is also disposed on an outer surface of the casing. A cartridge housing (not shown) is secured to the end of the casing  1  opposite to the dose knob. The cartridge housing is arranged to receive a disposable medicine filled cartridge (not shown). Such a cartridge has a rubber bung sealing one end of the cartridge, with the other end being arranged to receive a disposable needle. The cartridge is typically multi-use, that is to say each cartridge contained multiple doses of medicine. A user attaches a new needle to the cartridge for each injection, and disposes of the cartridge or the whole device after all of the doses have been used. 
         [0061]    The dose knob  3  comprises a gripping portion for a user to grip in order to rotate the dose knob. Extending from the gripping portion is a cylindrical portion having protruding splines  6 . The gripping portion protrudes from the casing  1 , whilst the cylindrical portion is located coaxially within the casing  1 . 
         [0062]    A compression spring  5  is located coaxially within the casing  1  and is arranged to provide the drive force for ejecting medicine from a loaded cartridge. The spring  5  abuts the dose knob  3  at one end, and its other end abuts a lock  7  located in the casing  1 . 
         [0063]    The lock  7  is located within and coaxial with the casing  1 , and cannot rotate relative thereto. The lock  7  comprises an annular body defining an opening. Three locking legs  8  extend from the annular body in the direction of the main axis of the casing. The annular body also comprises a set of lock teeth  9 . In this embodiment, three locking legs are provided, although it will be appreciated that any number of locking legs could be used. 
         [0064]    A drive rod  10  is located in the casing  1 . The drive rod  10  passes through the opening in the annular body of the lock  7 . The drive rod  10  further comprises three channels  11  running along its length. Each channel  11  receives a locking leg  8 , such that when the legs are in an unstressed state, the rod  10  can move freely through the lock  7 . The drive rod  10  further comprises flanges at either end to prevent the lock  7  from slipping off the drive rod  10 . At the end opposite the dose knob  3 , the drive rod  10  abuts the rubber bung of the cartridge. The flange at the end of the drive rod  10  opposite to the end that contacts the rubber bung has a sloped surface such that when the lock  7  is assembled over the drive rod, the cone shape pushes the legs  8  such that they flex outwards and pass over the flange. However, once the locking legs  8  have passed over the flange they are restricted from passing back over the flange. 
         [0065]    A drum  12  is also disposed coaxially within the main housing  1 . The drum comprises a drum cylinder portion  13  and a drum track portion  14 . The lock  7  is located coaxially within the drum  1 , with the drive rod  10  passing through the lock as described above. The drum cylinder portion  13  comprises a multiplicity of drum splines  15  on an inner surface (see  FIG. 7A ). The drum splines engage with the dose knob splines  6 , such that a rotation of the dose knob  3  causes a corresponding rotation of the drum  12 , whilst allowing the drum  12  and the dose knob  3  to move axially relative to one another. A series of drum teeth  16  are also disposed on an inner surface of the drum  12 , the drum teeth arranged to engage with the lock teeth  9 . When the drum teeth  16  and the lock teeth  9  are engaged, the locking legs  8  push against angled inner surface of the drum  12 , which stresses them and causes them to grip the drive rod  10 . When the dose knob  3  is rotated, the drum teeth  16  move over the lock teeth  9 , causing the lock  7  to move back and forward axially away from and towards the drum  12  and the locking legs  8  to release their friction grip on the drive rod  10 . In order to bias the locking legs  8  in a gripping position, a strained biasing spring is attached at one end to the lock  7  and at the other end to the drum  12 . This ensures that the lock  7  is urged towards the drum  12  and maintains a friction lock with the drive rod  10 . 
         [0066]    The drum cylinder portion  13  further comprises a series of numbers printed in a helical path along the outer surface of the cylinder. A window (not shown) in the casing  1  allows a user to see one of these numbers at a time. The numbers correspond to dose units of medicine that can be set by the user when turning the dose knob  3 . In addition to the series of numbers, a green band is also printed on the drum cylinder portion  13 . When the syringe is ready for use, and no dose has been set, the green band is visible through the window. When a dose is being set by rotating the dose knob  3 , the green band is replaced by the numbers. Of course, any colour or pattern could be used in place of a green band to indicate that the syringe is ready for use. 
         [0067]    The track portion  14  comprises a helical track  17  on its outer surface, and a projecting track ramp  18  at one end of the track portion  14 . The track portion is coaxial with and is located in a chassis  19 , formed as a separate component. The chassis  19  is a cylindrical component that is coaxial with and located within the casing  1  and cannot move relative thereto, and has an opening through which the drive rod  10  can move. The chassis  19  also comprises projections that engage with the drive rod channels  11 , thereby ensuring that the drive rod  10  cannot rotate relative to the housing  1 . The chassis  19  comprises a chassis ramp  20  arranged to co-operate with the track ramp  18 , such that when the two ramps meet during rotational movement of the drum  12  relative to the casing  1  (the chassis  19  being fixed), the ramps slide across one another and cause an axial movement of the drum  12  away from the chassis  19  relative to the casing  1 . The chassis further comprises a projecting reaction surface  21  arranged to engage with the trigger  4 . 
         [0068]    The trigger  4  allows the user to fire the dose of medicine. The trigger  4  co-operates with a lower trigger portion  22 . The lower trigger portion has a projecting cam follower  23  that projects into the casing  1 . The lower trigger portion  22  can move relative to the casing such that the cam follower  23  can move in and out of engagement with the helical track  17  of the drum  12 . The trigger  4  comprises a trigger brake  24  that projects from an underside of the trigger  4  towards the casing  1 . 
         [0069]    The trigger  4  may be provided with a soft plastics overmoulded cover (not shown). An advantage of such an overmoulding is that when the trigger  4  is depressed, the overmoulding at the rear portion  25  of the trigger  4  is compressed. When the trigger  4  is released, the elasticity of the overmoulding urges the trigger  4  back towards its rest position. Alternatively, a leaf spring may be provided to return the trigger  4  to its rest position. 
         [0070]    A collar  26  is provided attached to the end of the casing  1  from which the dose knob  3  protrudes. The collar  26  comprises an annular portion having an opening in which the dose knob  3  is located. The collar  26  further comprises a collar plate  27  which extends longitudinally within the casing  1  such that it is located between the trigger  4  and the drum cylinder  13 . 
         [0071]    When the pen syringe is assembled, the green band indicating zero dose can be seen through the window on the casing  1 , indicating that the device is ready for use. When the user rotates the dose knob  3  to set the required dose, the dose knob splines  6  engaged with the drum splines  15  ensure that the drum  12  rotates. The cam follower  23  sits on an outer surface of the drum cylinder  13 , and is not engaged with the helical track  17 . As the drum  12  rotates within the chassis  19 , the track ramp  18  moves around a base of the chassis. There is, however, no axial movement of the drum  12  relative to the chassis  19 , and so no dose is being set. The track ramp  18  moves around the base of the chassis with no audible clicks, and the green band remains visible in the window of the casing  1 . When the track ramp  18  comes into contact with the chassis ramp  20 , co-operation between the ramps  18 ,  20  causes the drum  12  to move axially away from the chassis  19 . The axial movement of the drum  12  away from the chassis  19  moves the helical track  17  such that the cam follower  23  of the lower trigger portion  22  drops into the helical track  17 . The axial movement also moves the green printed band on the drum cylinder  13  away from the window in the casing  1 , such that the first of the helically printed series of numbers is visible through the window. The use of the co-operating ramps  18 ,  20 , allows the green band to be printed around the entire circumference of the cylinder drum so that when the pen syringe is ready for another dose to be set the green band is always visible through the window, no matter what rotational angle the drum  12  is disposed at relative to the casing  1 . 
         [0072]    Further rotation of the dose knob  3  causes rotation of the drum  12 , and due to the engagement of the cam follower  23  with the helical track  17 , this rotational movement is accompanied by further axial movement of the drum  12  away from the chassis  19 , and consequent compression of the spring  5 . This axial movement is accommodated within the casing by further telescoping of the drum  12  into the dose knob cylinder. The user can view the numbers printed on the drum cylinder  13  through the window in the casing, and set the dose required. Each increment in number is accompanied by an audible click caused by the drum teeth  16  moving over the lock teeth  9 . If the user sets the dose too high, it can be reduced by counter-rotating the dose knob  3 . 
         [0073]    When the required dose has been set, the lock  7  locks the drive rod  10  in place relative to the drum  12 . The user then inserts the needle into skin and presses the trigger  4  with a force sufficient to cause the lower trigger portion  22  to pivot and raise the cam follower  23  out of engagement with the helical track  17 . The spring  5  unwinds and urges the lock  7  towards the chassis  19 , thereby urging the locking legs into tight engagement with the drive rod  10 . The drum  12 , lock  7  and drive rod  10  are urged towards the chassis  19 , thereby pushing the drive rod  10  against the rubber bung in the cartridge and causing ejection of the desired dose of medicine. 
         [0074]    In order to control the rate of ejection of the medicine, the user exerts an extra force on the trigger  4 , which pushes the trigger brake  24  against the collar plate  27 . The collar plate  27  in turn presses against the drum cylinder  13 . By varying the amount of force used to press the trigger  4 , the user varies the amount of friction force between the drum  12 , the collar plate  27  and the brake  24 , and therefore controls the speed with which the drum  12  and consequently the drive rod  10  are urged forward by the unwinding of the spring  5 . The collar plate  27  spreads the load of the force applied by the user over the drum, reducing wear on the components, and also reduces the risk that the numbers printed on the drum cylinder  13  are worn away. 
         [0075]    The reaction surface  21  disposed on the chassis is in contact with the cam follower  23  of the lower trigger portion  22  to resist any undesirable force applied by the trigger  4  to the drum  12 . The force of the spring  5  is borne by the reaction surface  21  rather than the pivots about which the trigger  4  moves, thereby reducing tolerance and wear problems. 
         [0076]    If the pen syringe is mishandled, the drive rod  10  may slip out of contact with the rubber bung in the cartridge. If this occurs, then a user may believe that he is setting a higher dose than will actually be delivered, as the drive rod  10  must move to come into contact with the rubber bung before a dose is ejected. In order to prevent this, a resilient annular disc  28  having inwardly pointing fingers is located at the chassis  19 . When the drive rod  10  is urged by the spring  5  to eject a dose of medicine, it passes through the centre of the resilient disc  28 , splaying the fingers outwards. The splayed fingers grip the drive rod  10 , thereby preventing any movement of the drive rod  10  back into the casing, that is to say the annular disc  28  forms a one-way “valve”. This also prevents re-use of the syringe. Of course, where re-use of the syringe is required then a releasable locking mechanism may be used in order to allow the drive rod  10  to move back into the casing  1 . 
         [0077]    When the pen syringe is assembled, it is assembled with a medicine cartridge in the cartridge housing. Due to the tolerances of parts, the end of the drive rod  10  may not engage the bung of the cartridge, and so the first dose ejected from the syringe will not be exactly the dose the user has set. The dose may either be too low, or the user may need to fire an “air shot” of a first dose of medicine to ensure that the drive rod is fully engaged with the rubber bung. Air shots are wasteful of expensive medicine, and if a user omits performing an air shot prior to the first dose, then the user may inject himself with an incorrect dose. One solution is to provide biasing means such as a spring to urge the drive rod onto the medicine cartridge. However, a pen syringe can be stored for periods of years before use, and it is not desirable to leave the cartridge under pressure for a long period of time. For this reason, the dose knob  3  is provided with an opening  29 . Once the pen has been assembled, an elongate tool is pushed through the dose knob opening  29  against the drive rod  10 , and the drive rod is pushed by the tool so as to be in contact with the cartridge. This ensures that the drive rod is at the base of the cartridge for the first dose to be ejected, but that the cartridge is not stored under pressure. Manufacturing tolerances are set to ensure that the drive rod  10  will not quite engage with the bung, rather than engaging with the bung to store the cartridge under pressure. 
         [0078]    In a second specific embodiment, a collar plate  27  is not required. Referring to  FIG. 10A , there is illustrated a trigger and a drum. The trigger is formed like a rocker switch having a peg  30  that is disposed over the helical track of the drum, by pressing the trigger such that the peg  30  comes into contact (but not engagement) with the helical track, the user can control the rate that the drum moves when ejecting a dose of medicine through friction between the peg  30  and the surface of the helical track. 
         [0079]    According to a third specific embodiment, an alternative syringe is provided that also does not require a collar plate. Referring to  FIG. 10B , a pad  31  is provided on the trigger which is larger than the width of the channel of the helical track  17 . When a user depresses the trigger to fire a dose, a further user-applied force causes the pad  31  to come into contact with the outer surface of the drum track  14 , and friction between the drum track  14  and the pad  31  reduces the speed at which the drum is urged forwards. 
         [0080]    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. For example, a leaf spring is referred to in the above description for returning the trigger to its rest position. A single part may be used to act as both the leaf spring and the brake. Furthermore, it will be appreciated that a chassis  19  is provided to assist in production and assembly, but as the chassis  19  is fixed relative to the casing  1 , the functional parts of the chassis  19  such as the chassis ramp  20  and the reaction surface  21  could be formed integrally with the casing  1 . 
         [0000]    
       
         
               
             
               
               
             
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 List of parts 
               
             
          
           
               
                 Number 
                 Part 
               
               
                   
               
             
          
           
               
                 1 
                 Casing 
               
               
                 2 
                 Cap 
               
               
                 3 
                 Dose knob 
               
               
                 4 
                 Trigger 
               
               
                 5 
                 Spring 
               
               
                 6 
                 Splines 
               
               
                 7 
                 Lock 
               
               
                 8 
                 Locking legs 
               
               
                 9 
                 Lock teeth 
               
               
                 10 
                 Drive rod 
               
               
                 11 
                 Drive rod channels 
               
               
                 12 
                 Drum 
               
               
                 13 
                 Drum cylinder 
               
               
                 14 
                 Drum track 
               
               
                 15 
                 Drum splines 
               
               
                 16 
                 Drum teeth 
               
               
                 17 
                 Helical track 
               
               
                 18 
                 Track ramp 
               
               
                 19 
                 Chassis 
               
               
                 20 
                 Chassis ramp 
               
               
                 21 
                 Reaction surface 
               
               
                 22 
                 Lower trigger portion 
               
               
                 23 
                 Cam follower 
               
               
                 24 
                 Trigger brake 
               
               
                 25 
                 Trigger rear portion 
               
               
                 26 
                 Collar 
               
               
                 27 
                 Collar plate 
               
               
                 28 
                 Resilient disc 
               
               
                 29 
                 Dose knob opening