Abstract:
A medical injector is provided herein which includes first and second body portions rotatably coupled together; a displaceable plunger disposed in at least one of the first and second body portions; a spring disposed to advance the plunger; and, a releasable retainer for retaining the plunger in a first portion against force of the spring. The releasable retainer releases the plunger upon a predetermined extent of relative rotation between the first and second body portions, thus allowing the spring to advance the plunger. Advantageously, the subject invention provides a medical injector having an automated plunger drive which is triggered upon rotation of injector body portions, thereby minimizing premature or failed activations.

Description:
FIELD OF THE INVENTION 
     This invention relates to medical injectors, and, more particularly, to medical injectors having plunger drive mechanisms. 
     BACKGROUND OF THE INVENTION 
     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 
     A medical injector is provided herein which includes first and second body portions rotatably coupled together; a displaceable plunger disposed in at least one of the first and second body portions; a spring disposed to advance the plunger; and, a releasable retainer for retaining the plunger in a first position against force of the spring. The releasable retainer releases the plunger upon a predetermined extent of relative rotation between the first and second body portions, thus allowing the spring to advance the plunger. Advantageously, the subject invention provides a medical injector having an automated plunger drive which is triggered upon rotation of injector body portions, thereby minimizing premature or failed activations. 
     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 
         FIG. 1  is a perspective view of a medical injector formed in accordance with the subject invention; 
         FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 1 ; 
         FIG. 4  is an exploded view of a medical injector formed in accordance with the subject invention; 
         FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 1 ; 
         FIG. 6  is a cross-sectional view of an interior sleeve useable with the subject invention; 
         FIG. 7  is a perspective view of a dose ring useable with the subject invention; and, 
         FIG. 8  is a schematic showing an arrangement for restricting radial motion. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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. 
     With reference to  FIG. 1 , the medical injector  10  includes rotatably coupled first and second body portions  12 ,  14 . The first and second body portions  12 ,  14  are complementarily formed so as to allow relative rotation therebetween, by movement of one or both of the components. 
     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 obtain rotatability, as shown in  FIG. 2 , a track  16  is formed in one of the first and second body portions  12 ,  14 , with one or more detents  18 , formed opposite the track  16 , being seated in the track  16  so as to lock the first and second body portions  12 ,  14  together once assembled. The detents  18  may be formed slidable along the track  16  so as to permit the first and second body portions  12 ,  14  to rotate relative to one another. One or more stops  15  may be located along the track  16  to limit the extent of relative rotation. 
     In a preferred arrangement, with reference to  FIGS. 2-4 , the second body portion  14  may include an interior sleeve  20  on which the detents  18  are formed. It is preferred the interior sleeve  20  be non-rotatably coupled to the first body portion  12 . The stops  15  may be provided on the first body portion  12  to prevent rotation. In addition, it is preferred that the interior sleeve  18  be coupled to the second body portion  14  in any known manner so as to permit rotation of the second body portion  14  thereabout such as through mating snap fingers  17  and engagement surface  19 . With the interior sleeve  18  being non-rotatably coupled to the first body portion  12 , the interior sleeve  18  is held fixed with the second body portion  14  being rotatable thereabout. Alternatively, the detents  18  may be formed directly on the second body portion  14 . 
     The medical injector  10  includes an axially-displaceable plunger  22 . The plunger  22  may be formed as a single piece or 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, at least a majority, if not the entirety, of the plunger  22  is initially located in the second body portion  14 . A spring  24  is also provided configured and positioned to advance the plunger  22  a predetermined distance. Preferably, the spring  24  is a compression or coil spring, but other biasing elements may likewise be utilized. Preferably, the spring  24  is positioned in the second body portion  14 . 
     A releasable retainer  26  is provided configured and positioned to releasably retain the plunger  22  in an initial first state against the force of the spring  24 . The releasable retainer  26  is configured such that, upon a predetermined extent of relative rotation between the first and second body portions  12 ,  14 , the releasable retainer  26  releases the plunger  22  thereby allowing the spring  24  to advance the plunger  22  the predetermined distance. As will be appreciated by those skilled in the art, various releasable retainers may be used with the subject invention. 
     It is preferred that the plunger  22  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. 
     By way of non-limiting example, the releasable retainer  26  may be one or more latches  28  formed on the plunger  22 , as shown in  FIGS. 2 ,  3  and  5 . One or more channels  30  are formed radially outwardly of the plunger  22  with each having a first portion  32 , that is disposed transversely to the plunger  22 , and a second portion  34 , that is disposed generally parallel to the plunger  22 . The number of the channels  30  corresponds to the number of the latches  28 . The channels  30  are formed to accommodate the latches  28 . The channels  30  are formed in the interior sleeve  20  and/or the second body portion  14 . 
     In an initial state, the latches  28  are located in the first portions  32  of the channels  30 , as shown in  FIGS. 2 and 3 . The interengagement of the latches  28  with ledges  36  defined adjacent to the first portions  32  of the channels  30  retains the plunger  22  in the first position against force of movement of the spring  24 . To release the plunger  22 , the latches  28  are displaced out of the first portions  32  of the channels  30  and into the second portions  34  of the channels  30 . In the second portions  34 , the latches  28  are free to translate the second portions  34 , and thus the spring  24  causes distal advancement of the plunger  22 . 
     The latches  28  may be caused to be displaced from the first portions of the channels  30  in various manners. Preferably, one of the channels  30  is formed in the interior sleeve  20  so as to extend through the interior sleeve  20 . As shown in  FIG. 5 , one of the latches  28  protrudes from the plunger  22  and through the interior sleeve  20 , e.g., via the channel  30 , so as to protrude from the interior sleeve  20 . A slot  40 , or other engaging member, may be formed and located on the second body portion  14  to engage the latch  28 . With rotation of the second body portion  14 , the latch  28  may be caused to rotate, thus causing rotation of the plunger  22 , and, thus, displacement of the latch  28  into the second portion  34  of the channel  30 . 
     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. 4 , 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, such as a needle adaptor fixed to the reservoir  46 . 
     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 . 
     The reservoir  46  may be configured to accommodate multiple components which are mixable for reconstitution. For example, as shown in  FIG. 4 , 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 . 
     One or more by-pass channels  76  are formed in the wall of the reservoir  46 . In an initial state, as shown in  FIG. 4 , 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. 
     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 . 
     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. 
     Distal advancement of the plunger  22  under force of the spring  24  may be used to achieve one or more objectives. The plunger  22  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 spring  24  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  22  may cause administration of the contents of the reservoir  46  through the injected needle. 
     Depending on the desired effect, the medical injector  10  may be configured to have the plunger  22  be driven a predetermined distance. A physical stop, such as interengagement between a portion of the plunger  22  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  22 . Under certain circumstances, the plunger  22  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  22 . In this manner, the contents of the reservoir  46  may be maximally compressed under force of the spring  24 . 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  22 . This secondary distal advancement may assist in priming the needle  60  for use. 
     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. 
     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 the figures, a dose ring  90  may be provided with a plurality of axially and radially spaced-apart abutment surfaces  92 . 
     The abutment surfaces  92  are axially alignable with an engagement surface  94  formed on the plunger  22  such that with sufficient distal displacement of the plunger  22  at least one of the abutment surfaces  92  will be caused to be engaged by the engagement surface  94  thus limiting the stroke of the plunger  22 . The engagement surface  94  may be defined on one or more of the latch tabs  28 . With this arrangement, a controlled amount of distal displacement of the plunger  22  may be transmitted to the stopper  54 . Stem  91  of the plunger  22  passes through opening  93  of the dose ring  90  to obtain proper alignment of the engagement surface  94  with the corresponding abutment surface  92  and so that the stem  91  may engage the stopper  54 . Moreover, stroke length corresponding to the movement of the plunger  22  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 greater dose that will be caused to be administered. Regardless of the selected dose amount, it is preferred that the plunger  22  having a fixed length of stroke for distal displacement during administration of an injection. The further abutment surfaces  92  have greater distal movement of the plunger  22 . The extent of movement of the plunger  22  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. The dose ring  90  is preferably stationary. A spring arm  120  may extend from the dose ring  90  to resiliently press against the plunger  22  and provide stability thereto. 
     The dose is selected by rotating the second body portion  14  which is fixed to the plunger  22  so as to rotate therewith. To prevent the second body portion  14  from setting a dose prior to proper preparation of the medical injector  10 , such as prior to mixing of the mixable components  66 ,  68 , rotation of the plunger  22  may be limited by interengagement of the latch  28  with the channel  30 . As shown in  FIG. 6 , open space  71  may be defined at the distal terminus of the second portion  34  of the channel  30  which extends radially to permit rotation of the latch  28  thereinto. In this manner, doses can be adjusted by rotating the plunger  22  to axially locate the engagement surface  94  with a desired of the abutment surfaces  92 . The channel  30  may be formed with one or more catches  73  which initially catch the latch  28  upon distally advancing the second portion  34  of the channel  30 . By permitting such radial adjustment at the terminus of the channels  30 , dose setting may be restricted to post-advancement of the plunger  22 . Optionally, the channel  30 , particularly at the second portion  34 , may be made with sufficient radial width to permit dose setting. Thus, dose setting can be achieved at any instance at the initiation of, during, or after advancement of the plunger  22 . 
     It is preferred that the second body portion  14  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 second body portion  14 , 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, with reference to  FIG. 8 , one or more tabs  110  may be formed on the interior sleeve  20  which are selectively engageable with one or more ratchet teeth  112  formed on the second body portion  14 . The ratchet teeth  112  may be circumferentially spaced apart and positioned to represent dose settings corresponding to the abutment surfaces  92 . The tabs  110  nest in between the ratchet teeth  112  at given radial positions of the plunger  22  corresponding to different dose sizes. With turning of the second body portion  14 , the tabs  110  are caused to by-pass the ratchet teeth  112 . The ratchet teeth  112  maintain the radial position of the second body portion  14 . 
     In addition, it is preferred that the plunger  22  be limited in axial movement so as to permit a fixed stroke length of distal advancement for dose administration. The stroke of an injection is defined by the extent of distal movement of the plunger  22 . The plunger  22  may be advanced in any known manner for injection, including under force of movement of the spring  24 . 
     Indicia  116  may be provided to represent doses. The indicia  116  may include numeral representations and a pointer or other indicator. The indicia  116  may be on both the first and second body portions  12 ,  14  to provide dose indications.