Abstract:
In one aspect, a medical injector is provided herein which includes a body; a displaceable plunger disposed in the body; a spring disposed to advance the plunger; a releasable retainer for retaining the plunger in a first state against force of the spring; and, a sleeve disposed on the body, the sleeve being slidable relative to the body. Sliding movement of the sleeve over a predetermined extent relative to the body results in the releasable retainer releasing the plunger thereby allowing the spring to advance the plunger. Advantageously, the subject invention provides a medical injector having an automated plunger drive which is triggered upon sliding movement of the sleeve, thereby minimizing premature or failed activations.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to medical injectors, and, more particularly, to medical injectors having plunger drive mechanisms. 
       BACKGROUND OF THE INVENTION 
       [0002]    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 
       [0003]    In one aspect, a medical injector is provided herein which includes a body; a displaceable plunger disposed in the body; a spring disposed to advance the plunger; a releasable retainer for retaining the plunger in a first state against force of the spring; and, a sleeve disposed on the body, the sleeve being slidable relative to the body. Sliding movement of the sleeve over a predetermined extent relative to the body results in the releasable retainer releasing the plunger thereby allowing the spring to advance the plunger. Advantageously, the subject invention provides a medical injector having an automated plunger drive which is triggered upon sliding movement of the sleeve, thereby minimizing premature or failed activations. 
         [0004]    In a further aspect, a medical injector is provided herein which includes a body; a displaceable plunger disposed in the body, the plunger having at least one thread formed thereon; a stem disposed in the body, the stem having at least one thread formed thereon; a button fixed to the stem; a spring disposed to advance the button away from the body; and, a releasable retainer for releasably retaining the button against force of the spring. Upon a predetermined extent of relative movement between the plunger and the stem, the thread of the plunger threadably engages the thread of the stem such that the stem rotates, rotation of the stem causing the releasable retainer to release the button thereby allowing the spring to advance the button. Advantageously, the subject invention provides a medical injector with a fixed order of operation, whereby access to a plunger drive button is only provided at a desired phase of operation. 
         [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]      FIG. 1  shows a medical injector formed in accordance with the subject invention; 
           [0007]      FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
           [0008]      FIG. 3  is an exploded view of a medical injector formed in accordance with the subject invention; 
           [0009]      FIG. 4  is a schematic of a releasable retaining arrangement useable with the subject invention; 
           [0010]      FIGS. 5 and 6  are cross-sectional views showing the medical injector of  FIG. 1  in post-reconstitution and needle mounted states, respectively; 
           [0011]      FIG. 7  is a cross-sectional view of the dose knob taken along line  7 - 7  of  FIG. 3 ; 
           [0012]      FIGS. 8-10  show a first plunger portion useable with the subject invention; 
           [0013]      FIGS. 11-13  show a second plunger portion useable with the subject invention; 
           [0014]      FIG. 14  shows a stem useable with the subject invention; and. 
           [0015]      FIG. 15  shows an arrangement for releasably retaining the dose knob in selected positions. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    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. 
         [0017]    As shown in  FIG. 2 , the medical injector  10  includes a body  12  having an axially-displaceable plunger  14  disposed therein. With reference to  FIG. 3 , the body  12  may be formed of multiple components, such as body portions  12 A,  12 B. The plunger  14  preferably includes a first plunger portion  16  and a second plunger portion  18 . The plunger  14  may be formed as a single piece or by modular components, such as the first and second plunger portions  16 ,  18  being separate components. Where dose setting is utilized, as described below, the first and second plunger portions  16 ,  18  are formed separately. 
         [0018]    A spring  20  is also provided configured and positioned to advance the plunger  14  a predetermined distance. Preferably, the spring  20  is a compression or coil spring, but other biasing elements may likewise be utilized. Preferably, the spring  20  is disposed between a cross-piece  22  formed on the body  12  and the plunger  14 , particularly, the first plunger portion  16 . A shoulder  24  may be formed on the plunger  14  against which the spring  20  applies force. 
         [0019]    A releasable retainer  26  is provided which is configured and positioned to releasably retain the plunger  14  in an initial first state against the force of the spring  20 . The first state of the plunger  14  is shown in  FIG. 2 . The releasable retainer  26  is configured such that, upon activation, the releasable retainer  26  releases the plunger  14  thereby allowing the spring  20  to advance the plunger  14 , as shown in  FIG. 5 . 
         [0020]    It is preferred that the plunger  14  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. 
         [0021]    By way of non-limiting example, and with reference to  FIG. 4 , the releasable retainer  26  may include one or more deflectable locking arms  28  formed on the body  12 . The locking arms  28  each include a detent  30  formed to interferingly engage a portion of the plunger  14 , particularly the first plunger portion  16 , in retaining the plunger  14  in an initial first state prior to use. Preferably, the first plunger portion  16  includes one or more wings  32  which extend radially outwardly from the plunger  14 . The detents  30  are formed to interferingly engage the wings  32 , as shown in  FIG. 4 . 
         [0022]    The wings  32  are formed to slide along guide channels  34  formed in the body  12 . The guide channels  34  limit the wings  32  to straight-line motion. Thus, the first plunger portion  16  is maintained non-rotatable relative to the body  12 . Preferably, the locking arms  28  are axially aligned with the guide channels  34 . Accordingly, the guide channels  34  maintain the wings  32  in axial alignment with the locking arms  20 . 
         [0023]    To facilitate release of the plunger  14  from the releasable retainer  26 , a sleeve  36  is provided, the sleeve  36  being disposed on the body  12  formed for sliding movement relative thereto. The sleeve  36  preferably is located exteriorly of the body  12  for easy handling. The sleeve  36  includes one or more ramped activation surfaces  38  which are preferably tapered to face proximally and outwardly from the body  12 . 
         [0024]    In an initial state, the activation surfaces  38  are spaced from the detents  30 . To release the plunger  14 , the sleeve  36  is slid proximally relative to the body  12  with the activation surfaces  38  engaging the detents  30 . With sufficient proximal movement, the activation surfaces cause outward deflection of the detents  30  and, thus, release of the plunger  14  from the first state. Upon release, the plunger  14  is advanced distally under force of movement of the spring  20  with the wings  32  sliding along the guide channels  34 . The sleeve  36  and/or the body  14  may include a rib  45  formed to engage a cooperating channel  47  so as to limit relative rotation therebetween. In this manner, axial alignment of the activation surfaces  38  with the locking arms  28  may be maintained. 
         [0025]    The medical injector  10  includes a reservoir  46  disposed in the body  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  40  having a distal end  42 , formed for insertion into a patient, and a proximal end  44 . 
         [0027]    The reservoir  46  may be configured to accommodate multiple components which are mixable for reconstitution. For example, as shown in  FIG. 2 , the reservoir  46  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. 2 , 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, as shown in  FIG. 5 . 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 body  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  14  under force of the spring  20  may be used to achieve one or more objectives. The plunger  14  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 body  12  and forced thereout of under force of the spring  20  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  14  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  14  be driven a predetermined distance. A physical stop, such as interengagement between the wings  32  and a proximal end  78  of the reservoir  46  (e.g., proximal end of the barrel  50 ) or a portion of the body  12  or another component (such as the dose knob described below), may be employed to limit distal advancement of the plunger  14 . Under certain circumstances, as shown in  FIG. 5 , the plunger  14  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  ( FIG. 6 ), 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  14 . In this manner, the contents of the reservoir  46  may be maximally compressed under force of the spring  20 . 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  14 . This secondary distal advancement may assist in priming the needle  60  for use. 
         [0033]    To prevent inadvertent activation of the plunger  14 , a locking ring  80  may be rotatably disposed on the body  12  having one or more protrusions  82  extending radially inwardly therefrom ( FIG. 7 ). One or more notches  84  ( FIG. 3 ), corresponding to the protrusions  82 , may be formed on the sleeve  36 . In an initial state, the protrusions  82  are located in the notches  84  so as to prevent sliding movement of the sleeve  36  relative to the body  12 . Radial displacement of the locking ring  80  frees the notches  84  and, thus, permits sliding movement of the sleeve  36 , particularly proximal sliding movement. 
         [0034]    For dose setting, the locking ring  80  may be configured as a dose knob  86 . As shown in  FIG. 7 , the dose knob  86  includes a plurality of axially and radially spaced apart abutment surfaces  88  which represent different dose amounts. In addition, the dose knob  86  includes one or more stop ledges  90  corresponding to the wings  32 . The stop ledges  90  are configured to interferingly engage the wings  32  so as to limit distal advancement thereof. The stop ledges  90  are axially aligned with the guide channels  34  in all radial positions of the dose knob  86 . 
         [0035]    With dose setting, the first and second plunger portions  16 ,  18  are formed separately. The second plunger portion  18  is formed with tabs  92  formed to nest within pockets  94  formed in the wings  32 . With this arrangement, the first and second plunger portions  16 ,  18  move in concert under force of movement of the spring  20 . The tabs  92 , however, are formed to by-pass the stop ledges  90  so as to engage one of the abutment surfaces  88 . 
         [0036]    In use, the dose knob  86  is turned about the body  12  to select a dose. Indicia  96  may be provided on the dose knob  86  and/or the body  12  to indicate dosage settings. With dose setting, the abutment surfaces  88  corresponding to the selected dose amount are axially aligned with the tabs  92 . With release of the plunger  14  from the first state as described above, the first and second plunger portions  14 ,  16  are distally advanced under force of movement of the spring  20 . With eventual distal movement, the wings  32  engage the stop ledges  90 , thus being stopped from further distal advancement. With the spring  20  acting against the first plunger portion  16 , and the first plunger portion  16  being stopped from further distal movement, the second plunger portion  18  also stops at the same location. 
         [0037]    The second plunger portion  18  may be distally advanced separately from the first plunger portion  16  to engage the stopper  54  and cause distal advancement thereof. The movement of the stopper  54  causes administration of the injectable solution  48 . The selected abutment surfaces  88  limit the distal advancement and thus control dosage amount. 
         [0038]    Movement of the plunger  14  from the first state may cause movement of the stopper  54  and autoreconstitution of the first and second mixable components  66 ,  68 . Preferably, the stroke of the plunger  14  is selected to cause full autoreconstitution prior to the wings  32  engaging the stop ledges  90 . It is preferred that autoreconstitution be conducted without the needle  60  being mounted to the medical injector  10 . Thus, the reservoir  46  is not vented during autoreconstitution. As discussed above, the mounting of the needle  60  causes venting and purging of any trapped gases. Purging of trapped gases causes reduction in the volume entrapped in the reservoir. Reduction in volume permits the spring  20  to cause secondary distal advancement of the plunger  14 . It is preferred that the wings  32  engage the stop ledges  90  upon the secondary distal advancement of the plunger  14 . 
         [0039]    For dosage administration, the second plunger portion  18  may be advanced by stem  96  which is affixed to button  98 . The button  98  is accessible by a user to receive force for causing manual dose administration. The stem  96  may extend through the first plunger portion  16  to engage the second plunger portion  18  and cause movement thereof under force of movement of the button  98 . More particularly, as shown in  FIG. 2 , the stem  96  extends into tubular portion  100  of the second plunger portion  18  in the initial first state of the plunger  14 . The tubular portion  100  is sized to engage the stopper  54  and cause distal advancement thereof. In addition, the stem  96  has an enlarged head  102 . With distal movement of the second plunger portion  18  during autoreconstitution, the tubular portion  100  is sized to slide past the enlarged head  102 , as shown in  FIG. 5 . Inwardly extending tangs  104  are located at or in proximity to the proximal end of the tubular portion  100 . The tangs  104  are formed to by-pass the enlarged head  102  with sufficient distal movement of the second plunger portion  18  ( FIG. 6 ). Once by-passed, the tangs  104  are located to interferingly engage the enlarged head  102  with subsequent distal movement of the stem  96  relative to the second plunger portion  18 . Thus, distal displacement of the stem  96 , via force applied to the button  98 , is transmitted to the second plunger portion  18 . In turn, the second plunger portion  18  advances distally separately from the first plunger portion  16  which is stopped by the stop ledges  90 . The second plunger portion  18  advances the stopper  54  in causing dose administration. The length of stroke of movement of the second plunger portion  18  is defined by the distance the tabs  92  travel to interengage the selected abutment surfaces  88 . The greater the distance tabs  92  travel before engaging the selected abutment surfaces  88 , the greater the administered dose; conversely, the smaller the distance, the smaller the dose. 
         [0040]    The first plunger portion  16  may be formed with recess  106  at a distal end thereof to provide clearance to accommodate the enlarged head  102  prior to distal advancement of the stem  96 . 
         [0041]    The medical injector  10  may be of various types, including fixed dose or variable dose. Preferably, the medical injector  10  is a single, variable dose, autoreconstitution device. In addition, it is preferred that the medical injector  10  be configured to have a fixed order of operation: dose setting; autoreconstitution; and, manual drug administration. 
         [0042]    To obtain the fixed order of operation, the button  98 , as described below, is initially restricted from movement. In addition, the dose knob  86  and the sleeve  36  are provided with the protrusions  82  and the notches  84  described above. In this manner, a dose must be initially set to permit movement of the sleeve  36 . Thus, dose setting is required prior to activation of autoreconstitution. 
         [0043]    As shown in  FIG. 2 , the button  98  is preferably located in a first state in proximity to the cross-piece  22  which thus limits distal advancement of the button  98 . With this arrangement, the stem  96  cannot be advanced. A secondary spring  106  is disposed to urge the button  98  away from the body  12 , e.g., being disposed between the cross-piece  22  and the button  98 , with a second releasable retainer  108  releasably retaining the button  98  in the first state against force of movement of the secondary spring  106 . 
         [0044]    The second releasable retainer  108  includes at least one catch  110  extending from the stem  96  disposed to interferingly engage the cross-piece  22  and retain the button  98  in the first state. Rotation of the stem  96  causes the catch  110  to align with slot  111  ( FIG. 4 ) in the cross-piece  22  thereby releasing the catch  110  from the cross-piece  22 , thus, allowing advancement of the button  96 . To obtain rotation of the stem  96 , at least one thread  112  may be formed on the stem  96 . The first plunger portion  16  may also be provided with at least one thread  114  formed to threadedly cooperate with the thread  112 . With sufficient relative movement between the first plunger portion  16  and the stem  96 , the threads  112 ,  114  threadedly engage. With the first plunger portion  16  being non-rotatably held by the body  12 , the threaded engagement causes the stem  96  to rotate. With rotation, the catch  110  becomes clear of the cross-piece  22 , and the button  98  advances proximally away from the body  12  under force of movement of the spring  20 . Lips  116  may be formed on the cross-piece  22  and/or the stem  96  to limit proximal movement of the button  98 . The button  98  is moved to a ready state where depression of the button  98  results in distal advancement of the stem  96 . The extent of permissible movement of the button  98  defines the maximum stroke of the stem  96 . 
         [0045]    The button  98  is preferably released to the ready state during the autoreconstitution process. It is further preferred that the button  98  be released upon the secondary distal advancement of the plunger  14  obtained with venting of the reservoir  46 . In this manner, the button  98  is released to the ready state with the medical injector  10  being ready for use, the post-reconstitution, needle mounted state shown in  FIG. 6 . Dose administration, thus, can be made only achievable after dose setting and autoreconstitution. 
         [0046]    It is noted that proximal advancement of the button  98  also results in proximal movement of the enlarged head  102 . With this arrangement, the stem  96  and the tubular portion  100  should be positioned and configured to account not only for distal advancement of the second plunger portion  18  but also account for proximal movement of the enlarged head  102 . 
         [0047]    It is preferred that the dose knob  86  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 inadvertent rotation of the dose knob  86 , thus avoiding that an improper of the abutment surfaces  88  engage the tabs  92 . Such an arrangement is disclosed in U.S. Pat. No. 6,793,646. As shown in U.S. Pat. No. 6,793,646, with reference to  FIG. 15 , one or more locking tabs  116  may be formed on the body  12  which are selectively engageable with one or more ratchet teeth  118  formed on the dose knob  86 . The ratchet teeth  118  may be circumferentially spaced apart and positioned to represent dose settings corresponding to the abutment surfaces  88 . The tabs  116  nest in between the ratchet teeth  118  at given radial positions corresponding to different dose sizes. With turning of the dose knob  86 , the tabs  116  are caused to by-pass the ratchet teeth  118 . The ratchet teeth  118  maintain the radial position of the dose knob  86 .