Abstract:
A medical injector is provided herein which includes first and second body portions each having a longitudinal axis and configured to couple at a coupling. The medical injector also includes an axially-displaceable plunger; biasing element for advancing the plunger a predetermined distance; and, a releasable retainer for releasably retaining the plunger in a first state against the force of the biasing element. In an initial state, the axes of the first and second body portions are not aligned and the plunger is in the first state. In a coupled state, the axes of the first and second body portions are axially aligned, and the releasable retainer releases the plunger, thereby allowing the biasing element to advance the plunger the predetermined distance. Advantageously, the subject invention provides a medical injector having an automated plunger drive which is triggered upon assembly of the pen injector, thereby minimizing premature or failed activations.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/063,806, filed on May 3, 2011, now allowed, which is a National Stage Application under 35 U.S.C. §371 of PCT/US2009/057446, filed on Sep. 18, 2009, which claims the benefit of priority to U.S. Provisional Application No. 61/192,465, filed on Sep. 18, 2008, the entire contents of these applications being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to medical injectors, and, more particularly, to medical injectors having plunger drive mechanisms. 
       BACKGROUND OF THE INVENTION 
       [0003]    Medical injectors are well known in the prior art, including injectors which have internal drive mechanisms for plunger advancement. Plunger advancement may be utilized to conduct automated reconstitution of a two-or more part medicament and/or to cause automated injection. More specifically, the automation of plunger advancement may be utilized to cause combination of a multiple part (e.g., wet/dry) medicament. In addition, or alternatively, the automated advancement of the plunger may cause a needle to be advanced for injection and/or medicament to be driven through the needle during injection. Such automated action requires a trigger mechanism. Concerns exist over premature or failed trigger activation. 
       SUMMARY OF THE INVENTION 
       [0004]    A medical injector is provided herein which includes first and second body portions each having a longitudinal axis and configured to couple at a coupling. The first and second body portions are complementarily formed so as to be movable about the coupling. The medical injector also includes an axially-displaceable plunger; biasing element for advancing the plunger a predetermined distance; and, a releasable retainer for releasably retaining the plunger in a first state against the force of the biasing element. In an initial state, the axes of the first and second body portions are not aligned and the plunger is in the first state. In a coupled state, the axes of the first and second body portions are axially aligned, and the releasable retainer releases the plunger, thereby allowing the biasing element to advance the plunger the predetermined distance. Advantageously, the subject invention provides a medical injector having an automated plunger drive which is triggered upon assembly of the pen injector, thereby minimizing premature or failed activations. 
         [0005]    These and other features of the subject invention will be better understood through a study of the following detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIGS. 1 and 2  show a medical injector formed in accordance with the subject in pre-assembled and assembled states, respectively; 
           [0007]      FIGS. 3 and 4  are cross-sectional views of a medical injector formed in accordance with the subject invention; 
           [0008]      FIG. 5  is a schematic of a releasable retainer useable with the subject invention; 
           [0009]      FIG. 6  is a cross-sectional view of a medical injector formed in accordance with the subject invention having a reservoir configured for reconstitution; 
           [0010]      FIGS. 7 and 8  show an arrangement for achieving relative movement of components; 
           [0011]      FIG. 9  is an exploded view of components useable with the subject invention; 
           [0012]      FIG. 10  is a cross-sectional view taken along line  10 - 10  of  FIG. 9 ; 
           [0013]      FIG. 11  is a perspective view of a dose knob useable with the subject invention; 
           [0014]      FIG. 12  is an exploded view of the subject invention; 
           [0015]      FIGS. 13-16  show operation of a medical injector formed in accordance with the subject invention; and 
           [0016]      FIGS. 17-20  show cap configurations useable with the subject invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    With reference to the figures, a medical injector is shown and generally designated with the reference numeral  10 . The medical injector  10  may be of various types, but preferably is of the pen injector type. The medical injector  10  may be used to administer various injectable liquids, particularly medicaments. 
         [0018]    With reference to  FIG. 1 , the medical injector  10  includes first and second body portions  12 ,  14  which are connected through a movement relative to coupling  16 . Preferably, the coupling  16  is a hinged connection. The first and second body portions  12 ,  14  are complementarily formed so as to be assembled together with sufficient movement, e.g., rotation, about the coupling  16 . As shown in  FIG. 1 , longitudinal axes L 1 , L 2  of the first and second body portions  12 ,  14  are not axially (not collinearly) aligned in an initial state of the medical injector  10 . The assembled state of the medical injector  10  is shown in  FIG. 2  where the longitudinal axes L 1 , L 2  are axially aligned. 
         [0019]    The first and second body portions  12 ,  14  are preferably formed of rigid material and to varying extents accommodate different portions of the medical injector  10 . Preferably, to facilitate assembly, as shown in  FIG. 3 , a reduced diameter portion  18  is formed on one of the first and second body portions  12 ,  14  with a corresponding telescoping portion  20  being formed on the other of the first and second body portions  12 ,  14 . In this manner, the first and second body portions  12 ,  14  may be assembled with the telescoping portion  20  being disposed over the reduced diameter portion  18 . In addition, cooperating locking elements  22 , such as cooperating detent and groove, meshing teeth, and/or other snap-together locking features, may be provided to lock the first and second body portions  12 ,  14  together once assembled. 
         [0020]    As shown in the figures, particularly  FIGS. 7 and 8 , the coupling  16  may be a pin hinge where brackets  24  are provided on the first and second body portions  12 ,  14  which are joined together to rotate about a central pin  26 . As will be appreciated by those skilled in the art, a living hinge may also be used for the coupling  16 . The coupling  16  is positioned and formed to allow proper movement, e.g., rotation, thereabout in allowing the first and second body portions  12 ,  14  to come together and form the medical injector  10 . 
         [0021]    The medical injector  10  includes an axially-displaceable plunger  28 . The plunger  28  may be formed as a single piece or by modular components. The modular components may be fixed to one another or located adjacently, but not connected, so as to move together. In a preferred embodiment, the plunger  28  is initially located in the second body portion  14 . A biasing element  30  is also provided configured and positioned to advance the plunger  28  a predetermined distance. Preferably, the biasing element  30  is a compression or coil spring, but other biasing elements may likewise be utilized. Preferably, the biasing element  30  is positioned in the second body portion  14 . 
         [0022]    A releasable retainer  32  is provided configured and positioned to releasably retain the plunger  28  in an initial first state against the force of the biasing element  30 . The releasable retainer  32  is configured such that, upon assembly of the first and second body portions  12 ,  14 , the releasable retainer  32  releases the plunger  28  thereby allowing the biasing element  30  to advance the plunger  28  the predetermined distance. As will be appreciated by those skilled in the art, various releasable retainers may be used with the subject invention. 
         [0023]    It is preferred that the plunger  28  be advanced in a distal direction. As used herein, distal refers to a direction towards a patient during use, while proximal refers to a direction away from a patient during use. 
         [0024]    By way of non-limiting example, the releasable retainer  32  may be a displaceable cam member  34 , as shown in  FIGS. 3-5 . As shown in  FIGS. 3 and 4 , upon assembly of the first and second body portions  12 ,  14 , a cam arm  36  may be displaced, such as by interfering engagement with a portion or component of the first body portion  12 , thus causing displacement of the cam member  34 . The cam member  34  may include a protruding stop member  38  formed to interferingly engage a portion of the plunger  28 , such as shoulder  40 , in causing retention thereof in an initial, first state, before use. With displacement of the cam member  34 , the cam member  34  releases the shoulder  40  thus allowing the biasing element  30  to drive the plunger  28  distally. It is preferred that the cam member  34  be pivotally connected to the second body portion  14 , so as to be rotatable relative thereto. Displacement of the cam member  34  may be achieved by interengagement of ramped surface  42  of the cam arm  36  acting against engagement surface  44  of the cam member  34  under movement of the cam arm  36  resulting in sufficient rotation of the cam member  34  to clear the stop member  38  from the shoulder  40 . 
         [0025]    The medical injector  10  includes a reservoir  46  disposed in the first body portion  12  formed to accommodate medicament or other substance  48  for injection into a patient. As shown in  FIG. 3 , the reservoir  46  may be a single chamber disposed in a barrel  50  sealed at a proximal end by a septum  52  and sealed at a distal end by a stopper  54  which is formed to be slidable through the barrel  50  for urging the substance  48  therefrom, as known in the art. The medical injector  10  also includes a needle mounting surface  56  having features  58  formed thereon for mounting a needle  60  thereto. The needle  60  may include a hub  62  having mounting features  64  provided thereon for cooperative engagement with the features  58  in mounting the needle  60  to the needle mounting surface  56 . The features  58  and the mounting features  64  may be of any known cooperating elements which permit a mechanical connection therebetween, such as threads or bayonet lock, and/or a frictional interengagement, such as a Luer mounting. The needle mounting surface  56  may be formed on the first body portion  12  or a component thereof. 
         [0026]    The needle  60  also includes a needle cannula  61  having a distal end  63 , formed for insertion into a patient, and a proximal end  65 . 
         [0027]    The reservoir  46  may be configured to accommodate multiple components which are mixable for reconstitution. For example, as shown in  FIG. 6 , the reservoir may accommodate first and second mixable components  66 ,  68 . The stopper  54  may be associated with the reservoir  46  such that distal advancement of the stopper  54  over a predetermined distance shall cause mixing of the first and second mixable components  66 ,  68 . Any known arrangement for allowing such mixing may be utilized. By way of non-limiting example, the first and second mixable components  66 ,  68  may be separated by a secondary stopper  70 . The secondary stopper  70  divides the reservoir  46  into first and second chambers  72 ,  74 , respectively, accommodating the first and second mixable components  66 ,  68 . The septum  52  seals off the distal end of the first chamber  72 , while the stopper  54  is positioned to seal off the proximal end of the second chamber  74 . Preferably, if a dry component is used as one of the mixable components, the dry mixable component is located in the first chamber  72 . 
         [0028]    One or more by-pass channels  76  are formed in the wall of the reservoir  46 . In an initial state, as shown in  FIG. 6 , the secondary stopper  70  is located at least partially proximally of the by-pass channels  76  so as to define a seal between the first and second chambers  72 ,  74  and to define a seal between the second chamber  74  and the by-pass channels  76 . With distal advancement of the stopper  54 , and with the second mixable component  68  being wet and generally incompressible, force of movement of the stopper  54  is transmitted to the secondary stopper  70  through the second mixable component  68 . With sufficient distal movement of the secondary stopper  70 , the second chamber  74  comes into communication with the by-pass channels  76 , thus allowing the second mixable component  68  to be urged into the first chamber  72  with further distal movement of the stopper  54 . With sufficient distal advancement of the stopper  54 , the second chamber  74  is collapsed with none or substantially none of the second mixable component  68  remaining therein. In addition, the secondary stopper  70  is located so as to define a seal between the first chamber  72  and the by-pass channels  76 . The first and second mixable components  66 ,  68  are mixed within the first chamber  72 , such as through agitation of the medical injector  10 , so as to produce the injectable substance  48 , ready for injection. 
         [0029]    The barrel  50  of the reservoir  46  may be the barrel of a separate drug cartridge, as shown in the figures, or a portion of the medical injector  10 , particularly the first body portion  12 . 
         [0030]    As will be recognized by those skilled in the art, other arrangements for permitting reconstitution may be utilized. In addition, more than two-part systems, such as three-part and so forth, systems may be utilized. Active medical ingredients may be included in one or both of the first and second mixable components  66 ,  68 . The first mixable component  66  may be dry (e.g., a powder or granular substance) and/or a liquid (e.g., flowable (slurry or liquid)). As mentioned above, the second mixable component  70  is preferably only a wet flowable component, such as a liquid or slurry. 
         [0031]    Distal advancement of the plunger  28  under force of the biasing element  30  may be used to achieve one or more objectives. The plunger  28  is configured to act against the stopper  54  and cause displacement thereof. With the reservoir  46  being configured for reconstitution, autoreconstitution of the contents of the reservoir  46  may be achieved. In addition, or alternatively, the medical injector  10  may be configured to be an autoinjector, where the needle  60  is initially housed within the first body portion  12  and forced thereout of under force of the biasing element  30  so as to pierce a patient&#39;s skin, e.g., with forward movement of the reservoir  46 , as known in the art. In addition, or alternatively, distal advancement of the plunger  28  may cause administration of the contents of the reservoir  46  through the injected needle. 
         [0032]    Depending on the desired effect, the medical injector  10  may be configured to have the plunger  28  be driven a predetermined distance. A physical stop, such as interengagement between the shoulder  40  and a proximal end  78  of the reservoir  46  (e.g., proximal end of the barrel  50 ), may be employed to limit distal advancement of the plunger  28 . Under certain circumstances, the plunger  28  may be distally advanced without the needle  60  being mounted to the medical injector  10 . Thus, the reservoir  46  is not vented during such action. With the needle  60  being subsequently mounted to the reservoir  46 , any residual gases trapped in the reservoir  46  are purged through the needle  60 . It may be preferred to not provide a physical stop to the distal advancement of the plunger  28 . In this manner, the contents of the reservoir  46  may be maximally compressed under force of the biasing element  30 . With subsequent mounting of the needle  60  onto the medical injector  10 , the reservoir  46  is vented thus permitting further distal advancement of the plunger  28 . This secondary distal advancement may assist in priming the needle  60  for use. 
         [0033]      FIG. 6  shows the medical injector  10  in a state prior to use. As shown therein, the reservoir  46  may be a drug cartridge which is separable from the first body portion  12 . One or more cartridge retaining hooks  80  may be provided to act against the barrel  50  in holding the barrel  50  in the first body portion  12 . It is preferred that the cartridge retaining hooks  80  be resilient so as to permit outward deflection in loading the reservoir  46  into the first body portion  12 . 
         [0034]    It is preferred that a cartridge retaining element  82  be provided which includes a sleeve  84  into which the reservoir  46  is disposed. In addition, it is preferred that the needle mounting surface  56  and the cartridge retaining hooks  80  be formed on the cartridge retaining element  82 . The cartridge retaining element  82  may be retained in the first body portion  12  through any known fixing arrangement, such as a mechanical connection, e.g., snap engagement or frictional connections, and/or chemical or adhesive connections, such as fusion, welding or gluing. 
         [0035]    Movement of one or more of the components relative to the first and/or second body portions  12 ,  14  may be desired. To obtain such relative movement, with reference to  FIGS. 7 and 8 , a pinion  86  may be mounted to one of the first and second body portions  12 ,  14  with a corresponding rack  88  being mounted to the component intended for relative movement. As shown in the Figures, the cartridge retaining element  82  may be configured for movement relative to the first body portion  12 . To this end, the cartridge retaining element  82  may be nested within the first body portion  12  with the rack  88  being located thereon. The pinion  86  and the rack  88  are formed with teeth  87 ,  89  formed for cooperating meshing engagement. With movement about the coupling  16 , the pinion  86  rotates and causes linear translation of the rack  88 , thus causing the cartridge retaining element  82  to translate relative to the first body portion  12 . This linear translation permits for various axial adjustments of the reservoir  46 , or other components. The needle mounting surface  56  may be formed on the cartridge retaining element  82  and caused to be initially hidden in the first body portion  12  ( FIG. 1 ) with subsequent distal advancement through translation of the cartridge retaining element  82  causing the needle mounting surface  56  to become exposed ( FIG. 2 ). In this manner, control can be established over proper timing of the needle mounting surface  56  during sequence of preparation of the medical injector  10 . In particular, it may be desired to expose the needle mounting surface  56  only after reconstituting, if reconstitution is utilized. 
         [0036]    The medical injector  10  may be a fixed dose injector configured to administer single or multiple fixed doses. In addition, the medical injector  10  may be configured to permit dose setting for either a single or multiple doses. In a preferred embodiment, the medical injector  10  is a single, variable-dose autoreconstitution injector. 
         [0037]    As will be appreciated by those skilled in the art, various configurations to permit dose setting may be utilized. By way of non-limiting example, and with reference to  FIGS. 9  and  10 , a knob stem  90  may be provided with a plurality of axially and radially spaced-apart abutment surfaces  92 . 
         [0038]    The abutment surfaces  92  are axially alignable with an engagement surface  94  formed on the plunger  28  such that with sufficient distal displacement of the knob stem  90  at least one of the abutment surfaces  92  will be caused to engage the engagement surface  94  and transmit force of movement to the plunger  28 . In this manner, distal displacement of the knob stem  90  may be transmitted to the plunger  28 . Moreover, stroke length corresponding to the movement of the plunger  28  may be adjusted depending on the abutment surface  92  which is in engagement with the engagement surface  94 . The greater the initial distance of the abutment surfaces  92  from the engagement surface  94 , the corresponding smaller dose that will be caused to be administered. Regardless of the selected dose amount, it is preferred that the knob stem  90  having a fixed length of stroke for distal displacement during administration of an injection. The further abutment surfaces  92  have greater lost motion with distal movement of the knob stem  90  and, thus, less distance engaging the engagement surface  94 . The extent of movement of the plunger  28  dictates the extent of movement of the stopper  54  and, thus, dictates the amount of the injectable solution  48  to be driven from the reservoir  46  in an injected dose. 
         [0039]    The dose is selected by rotating a dose knob  96  which is fixed to the knob stem  90  so as to rotate therewith. The dose knob  96  and the knob stem  90  can be connected through any known manner, including through cooperating mechanical elements. To prevent the dose knob  96  from being inadvertently turned prior to proper preparation of the medical injector  10 , such as prior to mixing of the mixable components  66 ,  68 , assembly of the first and second body portions  12 ,  14 , and so forth, the knob stem  90  may be coupled to the plunger  28  so as to prevent relative rotation therebetween with the plunger  28  being non-rotatably coupled to the second body portion  14 . With reference to  FIG. 9 , the plunger  28  may have one or more lobes  98  formed to nest in corresponding channels  100  formed in the second body portion  14 . The plunger  28  may slide along the channels  100  without rotating relative thereto. In turn, the plunger  28  may have one or more internal slots  102  in which are initially nested corresponding splines  104  protruding from the plunger  28 . With distal advancement of the plunger  28 , the plunger  28  may decouple from the knob stem  90  so as to permit relative rotation therebetween. 
         [0040]    In addition, with reference to  FIGS. 9 and 10 , a groove  106  may be formed in the knob stem  90  corresponding to a rib  108  formed on the plunger  28 . In an initial state, the rib  108  nests within the groove  106  so as to prevent relative rotation between the plunger  28  and the knob stem  90 . With distal advancement of the plunger  28  being completed, such as with completed reconstitution, the plunger  28  may be advanced so as to have the rib  108  removed from the groove  106  and to have the spline  104  removed from the internal slot  102 . The knob stem  90  is then free to rotate in setting a dose. Alternatively, the rib  108  may still be partially nested in the groove  106  even after distal advancement of the plunger  28 , such as to a post-reconstituted state. With this configuration, the knob stem  90  may be proximally displaced to have the rib  108  removed from the groove  106  thus permitting subsequent dose setting. The dose is administered by causing distal advancement of the knob  90  once the dose has been properly set. 
         [0041]    It is noted that the engagement surface  94  may be located at a proximal end  110  of the rib  108 . 
         [0042]    It is preferred that the dose knob  96  be releasably retained in positions corresponding to the various dose settings. In this manner, it is preferred that once a dose has been set, there is no rotation of the dose knob  96  during distal displacement thereof, thus avoiding that an improper of the abutment surfaces  92  engage the engagement surface  94 . Such an arrangement is disclosed in U.S. Pat. No. 6,793,646. As shown in U.S. Pat. No. 6,793,646, and with reference to  FIGS. 11 and 12 , one or more tabs  110  may be formed on the dose knob  96  which are selectively engageable with one or more positioning channels  112  formed on the second body portion  14 . The positioning channels  112  may be circumferentially spaced apart and positioned to represent dose settings corresponding to the abutment surfaces  92 . The tabs  110  nest in the positioning channels  112  at given radial positions of the dose knob  96  corresponding to different dose sizes. With turning of the dose knob  96 , the tabs  110  are caused to by-pass the dose positioning channels  112 . The positioning channels  112  maintain the radial position of the dose knob  96 . 
         [0043]    In addition, it is preferred that the dose knob  96  be limited in axial movement so as to permit a fixed stroke length of distal advancement for dose administration. The second body portion  14  may be provided with a reduced diameter opening  116  sized and positioned to interferingly engage the knob stem  90  upon a predetermined extent of proximal movement. The stroke of an injection is defined by the extent of proximal movement of the knob stem  90 . 
         [0044]    For use, the medical injector  10  is initially presented in the state shown in  FIG. 1 , where the first and second body portions  12 ,  14  are separated. To prepare for use, the first and second body portions  12 ,  14  are moved about the coupling  16  so as to come to the assembled state shown in  FIG. 2 . It is preferred that no needle be mounted to the medical injector  10  prior to assembly. With assembly, the plunger  28  is caused to be distally advanced under force of movement by the biasing element  30 . Reconstitution and/or other effects are achieved through this automated movement. Thereafter, the needle  60  is mounted to the medical injector  10  as shown in  FIG. 13 . The needle  60  may be provided with a cap or shield  60 A. Any gases trapped in the reservoir  46  are purged through the needle  60  and the needle  60  may be primed for use. 
         [0045]    With reference to  FIGS. 14 and 15 , a dose may be selected by proximally withdrawing the dose knob  96 . Proximal withdrawal of the dose knob  96  is limited, as described above. Once withdrawn, the dose knob  96  may be rotated to a desired setting. Indicia  116  may be provided to represent doses. The indicia  116  may include numeral representations and a pointer or other indicator. With reference to  FIG. 16 , the needle  60  is caused to pierce the skin of a patient and the dose knob  96  is then depressed to cause the knob stem  90  to advance distally. Interengagement between the selected of the abutment surfaces  92  and the engagement surface  94  causes the plunger  28  to drive the stopper  54  in administering an injection. 
         [0046]    With the pre-use assembly of the medical injector  10 , a cap  118  may be provided to cover at least partially the first and second body portions  12 ,  14 , particularly about the coupling  16  as shown in  FIGS. 17-20 . 
         [0047]    The cap  118  may be formed of a rigid material with a general cup shape. A loading aperture  120  may be formed in the cap  118  positioned over the first body portion  12  so as to allow the reservoir  46  to pass therethrough and be loaded into the first body portion  12 . In this manner, a medical injector  10  may be stored without the reservoir  46  being located therein. The reservoir  46  may be loaded into the medical injector  10  without the cap  118  having to be removed therefrom. In addition, the cap  118  may be formed to accommodate one or more of the needles  60  therein. To maintain a clean and sterile environment within the cap  118 , a sterility barrier  122 , such as a removable film, is preferably provided to cover the loading aperture  120 . The cap  118  may also be configured to form a tight seal about the medical injector  10 . A complimentary compartment  124  may be provided with the cap  118  to wholly enclose the medical injector  10 .