Patent Publication Number: US-2022211945-A1

Title: Medication injection system

Description:
BACKGROUND 
     Aspects herein pertain to pharmaceutical injection devices, and, in particular, to automatic injection devices. 
     Patients suffering from a number of different diseases frequently must inject themselves with pharmaceuticals. A variety of devices have been proposed to facilitate these injections. One type of device is an automatic injection device. This type of device typically includes a trigger assembly that when operated by a user causes the device to automatically insert into the user a needle of a syringe that prior to triggering was disposed within the device housing, and then the device automatically injects a dose of medication through that inserted needle. The device may then automatically retract the syringe back into the device housing. 
     Some automatic injection devices include a syringe carrier that engages with a flange of a syringe. The syringe carrier may only support the flange or, in some cases, move the syringe between retracted and deployed positions. Some syringe carriers are of a single-piece construction. Some syringe carriers only partially surround the syringe, e.g. 270 degrees around the syringe, to leave an opening through which the syringe can be inserted radially. 
     Some automatic injection devices include retraction assemblies for auto-retraction of the syringe/needle combination. Retraction assemblies may include two components that slidably engage with one another. For example, to retract the syringe, one component rotatably slides against the other component. The inventors have recognized that such sliding contact can generate friction and/or friction variation along the sliding contact surfaces that may serve to impede retraction. Improvements to the syringe carrier and the retraction assemblies are described herein. 
     SUMMARY 
     In some embodiments, an automatic injection device includes a housing having a proximal end and a distal end, and a syringe including a needle, a syringe body and a plunger. The syringe is moveable within the housing from a first position to a second position that is distal to the first position to move the needle toward distal proximal end of the housing. The plunger is moveable relative to the syringe body to expel medication from the syringe body through the needle. The automatic injection device also includes a syringe carrier including two parts that are identical to one another, are discrete from one another, and are interlocked together. Each of the two parts has a proximal flange surface, a distal flange surface, a circumferential rounded wall between the proximal flange surface and the distal flange surface. A gap is located between the proximal flange surface, the distal flange surface, and the circumferential wall. A portion of the syringe body is received within the gap. 
     In another embodiment, an automatic injection device includes a housing, a syringe, and a syringe carrier. The housing includes a proximal end and a distal end. The syringe includes a needle, a syringe body and a plunger. The syringe body includes a syringe flange extending radially from the syringe body, and the plunger is moveable relative to the syringe body to expel medication from the syringe body through the needle. The syringe carrier includes a first part and a second part that are discrete from one another, and are interlockable together. Each of the first and second parts includes a proximal flange surface, a distal flange surface, a circumferential rounded wall extending between the proximal flange surface and the distal flange surface, a cushion disposed along a distal flange surface. The proximal flange surface and the distal flange surface having a greater material hardness than the cushion. A gap is defined by the proximal flange surface, the cushion, and the circumferential rounded wall, receiving a portion of the syringe flange. The cushions of each of the first and second parts together defining a ring shape to provide full circumferential support along the syringe flange. 
     In some embodiments, an automatic injection device includes a housing having a proximal end and a distal end, and a syringe including a needle, a syringe body and a plunger. The syringe is moveable within the housing from a first position to a second position that is distal to the first position to move the needle toward the distal end of the housing. The plunger is moveable relative to the syringe body to expel medication from the syringe body through the needle. The automatic injection device also includes a shuttle having a distal surface including a protrusion and a curvilinear surface. The curvilinear surface extends from the protrusion to define an undercut region. At least a portion of the distal surface is made of a lubricant-infused material. The automatic injection device also includes a follower having a follower body and a latch. The latch is moveable relative to the follower body and relative to the protrusion of the shuttle. The follower has a coupled configuration in which the latch is biasedly coupled over the protrusion. The follower also has a decoupled configuration in which the latch has cleared the protrusion and is in sliding engagement with the curvilinear surface, the follower is rotatable relative to the shuttle, and the shuttle is moveable toward the proximal end of the housing to retract the syringe. 
     These and other aspects will be apparent from the following description and claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Aspects of the invention are described below with reference to the following drawings in which like numerals reference like elements, and wherein: 
         FIG. 1  is a side view of an automatic injection device with a trigger assembly of according to one embodiment, which device is shown in a locked arrangement prior to use; 
         FIG. 2  is a longitudinal cross-sectional view of the automatic injection device of  FIG. 1  with the overcap removed; 
         FIG. 3  is a perspective view of a button shown separate from the other components of the device of  FIG. 1 ; 
         FIGS. 4 a , 4 b    are respectively a perspective view and a partial side view of a plunger element shown separate from the other device components; 
         FIG. 5 a    is an assembly including a syringe, syringe carrier, and plunger element, with the syringe shown in phantom; 
         FIG. 5 b    is the assembly of  FIG. 5 a    with one part of the syringe carrier hidden from view and the syringe shown in solid; 
         FIG. 5 c    is an enlarged view of a portion of  FIG. 5   b;    
         FIG. 6 a    is a perspective view of a syringe carrier separate from the other device components; 
         FIG. 6 b    is an exploded perspective view of the syringe carrier of  FIG. 6   a;    
         FIGS. 7 a , 7 b , 7 c , 7 d , 7 e  and 7 f    are respectively top right perspective, bottom right perspective, top, bottom, front, and rear views of one part of the syringe carrier of  FIG. 6   a;    
         FIG. 8  is a perspective view of another embodiment of a syringe carrier mated with a syringe, with one part of the syringe carrier hidden from view; 
         FIG. 9 a    is a perspective view of the part of the syringe carrier of  FIG. 8 ; 
         FIG. 9 b    is another perspective view of the part of the syringe carrier of  FIG. 8 ; 
         FIG. 10  is a perspective view of a proximal shuttle part shown separate from the other device components; 
         FIGS. 11 a , 11 b , 11 c , 11 d  and 11 e    are respectively perspective, first side, longitudinal cross-sectional, top and bottom views of a distal shuttle part shown separate from the other device components; 
         FIGS. 12 a , 12 b , 12 c , 12 d  and 12 e    are respectively first perspective, first side, second perspective, second side and longitudinal cross-sectional views of a follower shown separate from the other device components; 
         FIG. 13 a    is an assembly including a distal shuttle and a follower, the follower being shown in the coupled configuration; 
         FIG. 13 b    is a slightly rotated view of the assembly of  FIG. 13 b    to show the interaction between a latch of the follower with a protrusion of the distal shuttle; 
         FIG. 14  is an exploded view of the assembly of  FIG. 13   a;    
         FIG. 15 a    is a perspective view of a distal shuttle; 
         FIG. 15 b    is another perspective view of the distal shuttle of  FIG. 15   a;    
         FIGS. 16 a  and 16 b    are respectively perspective and side views of a grease collar shown separate from the other device components; 
         FIG. 17  is a longitudinal cross-sectional view of the automatic injection device in its ready to operate arrangement; 
         FIG. 18  is a longitudinal cross-sectional view of the automatic injection device after the automatic injection device has been triggered for injection. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIGS. 1 and 2 , there are shown different views of a first embodiment of an automatic injection device, generally designated  20 , with a trigger assembly. When the trigger assembly is operated, the needled syringe of the device  20  is automatically driven downward such that the injection needle projects beyond the distal end of the device housing to penetrate the user. The device may then proceed to inject automatically, that is without further user action, the medication contents of the syringe through the needle, after which the syringe is retracted automatically such that the needle is returned to within the housing. 
     It will be appreciated from the following description that device  20  is conceptually similar in various aspects to the devices disclosed in U.S. Pat. No. 8,734,394, filed Feb. 24, 2011, and U.S. Pat. No. 9,872,961, filed Oct. 11, 2013, the disclosures of which are incorporated by reference herein in their entireties. 
     In the illustrative embodiment shown in  FIG. 1 , device  20  includes an outer housing  22  in which are operationally disposed working components of the device. The outer housing  22  may include a sleeve  26  and a main body  24  that may together form the axial height of the outer housing. Sleeve  26  may be rotatable relative to the main body  24  by the user. The sleeve may include a protruding fin  93  to facilitate rotation by a user. The device may include a button  25  that is part of the trigger assembly and that protrudes in the axial direction from the proximal end  27  of the housing. In some embodiments, when properly rotationally oriented by rotation of sleeve  26 , the button  25  is unlocked such that the button can be depressed in the distal direction to start the automatic injection function of device  20 . As used herein, distal and proximal refer to axial locations relative to an injection site when the device is oriented for use at such site, whereby, for example, distal end of the housing refers to the housing end that is closest to such injection site. 
     Button  25  may be molded as a single piece from a suitably durable material, such as Lustran ABS  348 . As further shown in the illustrative embodiment of  FIG. 3 , button  25  may include a disc  35  with a skirt  37  extending distally from the outer periphery of disc  35 . End disc  35  may have a flat proximal face  38  upon which a force can be directly applied by a user to selectively plunge the button to trigger the device. A notch  40  may be formed in skirt  37  at the distal end of the skirt  37 , and may extend axially and form a slot which receives a rib of sleeve  26  so as to rotatably key together the button  25  and sleeve  26 . A set of three equally angularly spaced resilient fingers  42  that may each be provided with a detent on its radially inward face may be provided at the base of skirt  37  for locating the button  25  on shuttle  200 . Each finger  42  may be adjacent to one of three equally angularly spaced fingers  46  with inwardly angled stops  48  also provided in skirt  37  for attachment to shuttle  200 . 
     Tapered flange portion  52  may have a sloped surface that serves as an actuating element of the trigger which cams a prong of the trigger to unlatch it for the trigger assembly. Differently designed actuating elements, including one that is not ramp shaped, can be used to cam and thereby unlatch the prong in alternate embodiments. 
     In some embodiments, device  20  includes a medication-filled syringe. As shown in  FIG. 2 , the syringe, generally designated  130 , includes a barrel  132  with a flange  133 , and an injection needle  134  mounted at the distal end of the barrel and in fluid communication with the medication contents of the barrel. Although needle  134  is shown as a single needle and is generally expected to be sized for subcutaneous delivery, with adaptions the device could be equipped with a needle of various sizes or types known in the art, including, but not limited to, a needle formed of one or more shortened injection needles, including microneedle arrays, and which needle allows for injection at different depths, such as intradermal. 
     Device  20  in general, and more particularly the technology claimed in this application, may be utilized in injecting a variety of medications or therapeutics into a person in need thereof. Syringes of the devices or claimed technology can be filled with any of a number of therapeutics. Device  20  may further comprise a medication, such as for example, within a reservoir within barrel  132  of syringe body or cartridge. In another embodiment, a system may comprise one or more devices including device and a medication. The term “medication” refers to one or more therapeutic agents including but not limited to insulins, insulin analogs such as insulin lispro or insulin glargine, insulin derivatives, GLP-1 receptor agonists such as dulaglutide or liraglutide , glucagon, glucagon analogs, glucagon derivatives, gastric inhibitory polypeptide (GIP), GIP analogs, GIP derivatives, oxyntomodulin analogs, oxyntomodulin derivatives, therapeutic antibodies, such as, for example, but not limited to treatment of psoriasis, ulcerative colitis, Chrohn&#39;s disease, pain, migraine, and any therapeutic agent that is capable of delivery by the above device. The medication as used in the device may be formulated with one or more excipients. The device is operated in a manner generally as described above by a patient, caregiver or healthcare professional to deliver medication to a person. The device, or claimed technology of this application, may then be operated in a manner generally as described above with respect to device  20  to inject a person with such therapeutic in the syringe. 
     The plunger mechanism may include a plunger element, generally designated  136 , and an elastomeric sealing member or piston  138  that seals the medication within barrel  132 . 
     Plunger element  136  may be molded as a single piece of a lightweight but sturdy and sufficiently resilient material, such as DELRIN 311DP from Dupont Engineering Polymers. As further shown in  FIG. 4 a   , plunger element  136  includes a cylindrical foot  140  which may be hollowed so as to have a cruciform center  142 . The distal face  144  of foot  140  operationally abuts piston  138  during plunger advancement. A ribbed bar  146  may rigidly or inflexibly extend axially upward from the top of foot  140  to a disc-shaped flange  150  that has a larger diameter than foot  140 . A plunger arm  152  may be formed on the outer radial periphery of flange  150  and may extend axially and distally from flange  150  in spaced relationship with plunger bar  146 . 
     Four equally angularly spaced bosses  153  may upwardly project from the flange  150 . Bosses  153  may aid in centering the drive coil spring  155  shown in  FIG. 2  that acts on flange  150  to bias plunger element  136  distally within device  20 . 
     Plunger element  136  may include a resilient prong, generally designated  160 , that serves as part of the trigger assembly. The single prong  160  may latchably engage a shuttle in the shown embodiment until released by the plunging of button  25 , which release allows the spring  155  to bias the plunger element  136  distally to result in needle insertion and injection. In some embodiments, the plunger includes one and only one resilient prong. In other embodiments, however, the plunger may include more than one resilient prong. 
     Prong  160  may include an upstanding, tapering finger  162  that projects axially from the center of flange  150  so as to be centered on the axis of the housing  22 . Finger  162  may be flexible due to its construction to allow its bending movement when the prong is acted on for its release. As shown in  FIG. 4 b   , prong  160  may include a triangular projection  165  centered on the side to side width of finger  162 . Projection  165  may include a ramp surface  167  extending proximally and at an angle inward from the tip  169  of the projection  165  to form an outward facing ramp used in camming of the prong for release. Ramp surface  167  extends from tip  169  to a proximal end  168 . The distal face  170  of projection  165 , which face does not serve a latching function, is transverse to the axial direction. 
     A pair of latching surfaces  172  may be provided on the proximal-most portions  171  of extensions  174  of finger  162 . Latching surfaces  172  and extensions  174  flank either side of projection  165  and are spaced radially inward from the ramp surface  167  at the height of the latching surfaces along prong  160 . Latching surfaces  172  are provided generally in axial alignment with finger  162  and each may be formed with a slight undercut so as to slope slightly distally as it extends in the radial direction toward ramp surface  167 . Latching surfaces  172  are disposed at a height between the axial extent of ramp surface  167 , such as near the proximal end  168 . In this location, the contacting forces on the ramp surface may tend to produce a translational deflection of the latching element which may have a lower and more consistent unlatching force than would a rocking or pivoting motion, caused by the latching surfaces being substantially above or below the ramp surface, that would introduce extra deformation of prong  160  and make the unlatching motion less smooth. 
     The back surface of projection  165  may jut rearward beyond extensions  174  to define a safety protuberance  178 . Protuberance may be backed up by safety arm  72  when button  25  is in its locked orientation. 
     An assembly including the plunger element  136 , syringe carrier  185 , and syringe  130  is shown in  FIG. 5 a   . The plunger bar  146  of the plunger element  136  extends through an opening  158  in the syringe carrier  185  and into the syringe carrier. As shown in  FIGS. 5 b  and 5 c   , in which one part of the syringe carrier is hidden from view, the syringe carrier encloses a radial flange  133  of the syringe  130 . As also seen in  FIGS. 5 b  and 5 c   , the syringe carrier also encloses the foot  140  of the plunger element. The syringe carrier  185  may be configured to provide full, surrounding support of the syringe flange  133  of syringe  130 . While such syringe carrier may be desired, designs of the syringe carrier which allow for manufacturing and assembly is also desirable in high-volume manufacturing settings. 
     An illustrative embodiment of a fully assembled syringe carrier is shown in  FIG. 6 a   . The syringe carrier may be made up of a first part  156  that couples with a second part  157 . The parts  156 ,  157  may be coupled to one another by various attachment mechanisms, such as, for example, adhesives, such as bonding glue, ultrasonic welding, mechanical interlocking, and the like. An exploded view of the syringe carrier is shown in  FIG. 6 b   . The two halves of the syringe carrier combine to define a cavity  450  that receives syringe flange  133  during device assembly such that the syringe carrier  185  surrounds the flange  133 . 
     In some embodiments, the syringe carrier  185  is made up of two identical, interlocking parts. One embodiment of one of the parts is shown in  FIG. 7 a   . The part shown in  FIG. 7 a    is the first part  156  of the syringe carrier, but the second part  157  may also be identical to what is shown in  FIGS. 7 a -7 f    Having the first and second parts be identical may have the benefit of requiring manufacture of only one shape, and may facilitate assembly of the syringe carrier by avoiding the need for a particular part being oriented at a specific side of the syringe carrier. Other embodiments of the parts having at least some of the features described herein may include parts that are not identical and still provide interlocking and support to the flange. 
     The first part  156  may include a proximal flange surface  402 , a distal flange surface  404 , and a circumferential rounded wall  410  disposed between the proximal flange surface  402  and the distal flange surface  404 . An axial gap  460  is defined between the proximal flange surface  402  and the distal flange surface  404 . The gap  460  is sized to receive the axial thickness of flange  133  (see  FIG. 5 c   ) of the syringe. The proximal flange surface  402  may include a proximal flange extending from the wall, and the distal flange surface  404  may include a distal flange extending from the wall in parallel with the proximal flange. 
     In some embodiments, the syringe carrier  185  may include a cushion  187  that defines a distal boundary for the gap  460 . With reference to  FIG. 5 c   , the distal surface of flange  133  of the syringe may rest against and be supported by the proximal surface  187 A of cushion  187  when the flange is held by the syringe carrier. In some embodiments, the rest of the syringe carrier is made of a material having a greater hardness than that of cushion  187 . The cushion  187  may provide shock absorbance or other impact attenuation to, e.g., reduce the likelihood of breakage of the syringe during actuation of the automatic injection device, and/or to soften the impact sound of the syringe against the syringe carrier during movement of the syringe. The cushion may be made by overmolding a material onto the syringe carrier. The cushion may be formed of a compressible material, such as an elastomer or a closed cell foam. 
     In some embodiments, the cushion may be arc-shaped to fit with the shape of the circumferential rounded wall  410  and/or the shape of the distal flange surface  404 . In some embodiments, the cushion  187  segments are configured and shaped, such as in a ring shape, to provide full circumferential, that is  360  degrees, support to the entire flange  133  when the parts  156 ,  157  are coupled. To this end, in some embodiments, the parts are shaped around the flange so that the cushion  187  can provide this full support to the flange  133 , such as, for example, to withstand spring insertion drive forces. 
     In some embodiments, the syringe carrier  185  may include one or more protrusions extending radially inward, where the protrusions may facilitate centering of the syringe within the syringe carrier by contacting the syringe body underneath the syringe flange. In the embodiment shown in  FIG. 7 a   , the syringe carrier includes a protrusion  188  that extends from an inner radial surface  189  of the cushion  187 . The protrusion may be made from the same cushioning material as the cushion  187  and may be integrally formed with the cushion  187  as a single component. The protrusions may be radially compressed to a greater degree relative to any radial compression of the surface  189  by the syringe body. In the embodiment shown, the cushion  187  of each of the parts includes a pair of protrusions  188   a  and  188   b  (as shown in  FIG. 7 d   ) so that when the parts are coupled to one another the protrusions together help centering of the syringe at four points. In one example, the coupled parts define the four protrusions that are arranged spaced equally apart from one another. When parts are coupled, the number of protrusions provided can vary between two or more. In another embodiment, the one or more protrusions may optionally include the protrusion  191  that can be located along the inner radial surface  189  in closer proximity to a latch protrusion  430  than a prong  420 , and in some embodiments, adjacent to the end of the inner radial surface  189  next to the latch protrusion as shown in  FIG. 7 a   . In other embodiments, there may be a protrusion adjacent the end of the inner radial surface  189  next to the prong  420  in addition to, or instead of, the protrusion  191 . Protrusion  191  may be included to support the syringe during the snap engagement of the two parts of the syringe carrier together, when the portion of the part  156  or  157 , which includes the latch protrusions  430 , flexes radially outward when mating with the prongs  420  of the other part. After the snap engagement, the protrusion  191  may also provide additional support to the syringe at a location where when mated there may be a gap between the cushions. 
     The proximal flange surface  402  may provide supportive engagement for the proximal surface of foot  140  of the plunger element. 
     Each part of the syringe carrier may define an opening portion  45  defined by radial plunger facing walls that forms one part of the opening  158  of the fully assembled syringe carrier. Such opening portion  45  may be shaped and sized to receive the shape and size of the plunger element in a manner to provide sliding support to the plunger body. In the example shown, the opening portion  45  in each part has a U-shape with opposing parallel planar sides coupled to one another by a rounded side. 
     The edges  405 ,  407  of the proximal flange surface of one of the parts of the syringe carrier disposed lateral relative to the opening portion  45  may be complementarily shaped to mate with the edges of the other of the parts, such as shown in  FIG. 6 a   . The edges may have a planar shape. In the embodiment shown, each of the edges is non-linearly shaped including a protrusion and recess. 
     In some embodiments, each part of the syringe carrier  185  may include a first lateral wall end  411  and a second lateral wall end  412 , where the circumferential rounded wall  410  extends from the first lateral wall end  411  to the second lateral wall end. In the embodiment shown, the first lateral wall  411  is disposed recessed relative to the edge  407 , while the second lateral wall  412  is disposed protruding relative to the edge  405 . 
     The syringe carrier  185  may include interlocking components that interlock to form the fully assembled syringe carrier. In some embodiments, the interlocking components extend from the lateral wall ends of each part of the syringe carrier. In the embodiment shown in  FIGS. 7 a  and 7 b   , the interlocking components comprise prongs  420 , each having an indentation  421 , and latch protrusions  430 , each having an accompanying slot  432 . The prongs  420  may extend from one of the lateral walls, shown as the first lateral wall end  411 , and the protrusions  430  extend from the other of the lateral walls, shown as the second lateral wall end  412 . Each of the prong  420  and indentation  421  of the first part  156  of the syringe carrier are complementarily shaped and sized to mate with a corresponding protrusion  430  and slot  432  of the second part  157  of the syringe carrier to interlock the two parts of the syringe carrier together. 
     As seen from the top view in  FIG. 7 c    and the bottom view in  FIG. 7 d   , each part of the syringe carrier may be approximately C-shaped. As seen from the front view in  FIG. 7 e    and the front view in  FIG. 7 f   , the syringe carrier may include a window  490  that passes completely through the circumferential rounded wall  410  of the syringe carrier. 
     As best seen in  FIG. 5 a   , the syringe carrier  185  may fully surround an outer perimeter of the syringe body, i.e. 360 degrees around the syringe body. The proximal and distal flange surfaces  402 ,  404  of each of the parts together fully overlap the proximal surface  133 A and/or the distal surface  133 B of the syringe flange  133 , as shown in  FIG. 5 a   . This configuration of a syringe carrier completely surrounding and/or overlapping the syringe flange may be advantageous when higher spring forces for driving the plunger are used by the delivery device, such as, for example, due to larger volume of medication, such as 2 to 3 mL, and/or higher viscous medications. Such configuration can allow for distribution of the drive force over a greater area of the syringe flange, which may help to reduce the likelihood of breakage of the syringe flange that are typically made of glass. 
     It should be understood, however, that other configurations for the syringe carrier are possible. One alternative embodiment is shown in  FIG. 8 . In  FIG. 8 , one part of the syringe carrier  185 ′ is removed to better see the flange  133 ′ of the syringe interacting with the syringe carrier. The proximal flange surface  402 ′ and the distal flange surface  404 ′of both parts of the syringe carrier  185 ′ together may be configured to provide full  360  degree support to the syringe flange  133 ′. The syringe carrier may also include the cushion  440 , shown disposed along the proximal surface of the distal flange surface  404 ′. When employed, the flange  133 ′ would rest along the cushion in a position in between the cushion and the proximal flange surface  402 ′. 
     As seen in  FIGS. 9 a   - 9   b,  in this embodiment, the syringe carrier  185 ′ has a wall  410 ′ that does not extend laterally side to side as far as the embodiment shown in  FIG. 7 a   . This shortened wall  410 ′, relative to the longer circumferential extension of the proximal and distal flange surfaces  402 ′,  404 ′, allows for lateral spaces  495 ,  496  flanking the lateral ends of the wall  410 ′. In some embodiments, these spaces  495 ,  496  may be used to accommodate syringes having flanges with different shapes, such as the cut flange syringe shown in  FIG. 8 . 
     The syringe carrier may have interlocking components in the form of protrusions  425  and indentations  426 . The protrusions  425  of the first part of the syringe carrier interlock with the indentations  426  of the second part. These interlocking components may have other snap-fit configurations. Due to the shortened wall  410 ′, the interlocking features are shown defined by the respective flange surfaces  402 ′,  404 ′. Indeed, the protrusions  425  and indentations  426  are shown defined by the radially inward edges  405 ′,  407 ′of the corresponding flange surfaces  402 ′  404 ′. In one embodiment, the circumferential rounded wall  410 ′ partially surrounds an outer perimeter of the syringe flange  133 ′, and the proximal flange surface  402 ′of each of the parts together fully overlap a proximal surface  133 A′ of the syringe flange  133 ′. As shown in  FIG. 8 , the distal flange surface  404 ′ of each of the parts together fully overlap the proximal surface  133 B′ of the syringe flange  133 ′, with the cushion  440  disposed therebetween. 
     Device  20  may have a delay mechanism that includes a shuttle, generally designated  200 , a follower  250  that releasably latches with the shuttle  200 , and a dual functioning biasing member  275  acting between the shuttle and the follower. Shuttle  200  may be formed of a proximal shuttle  202  and a distal shuttle  204  further shown in  FIG. 10  and  FIGS. 11 a -11 e   , respectively, that are fixedly connected during manufacturing assembly. The interaction between the proximal shuttle  202  and the distal shuttle  204 , as well as the features of the proximal shuttle  202  are described in greater detail in U.S. Pat. No. 9,872,961. 
     Distal shuttle  204  includes distal region  270 , and the flange  272  that transitions from body  210  to region  270  is designed to engage syringe carrier  185 . When the distal shuttle  204  is moved proximally during retraction, the flange  272  abuts against a distal surface of the syringe carrier  185 , thus moving the syringe carrier  185  and syringe barrel  132  in the proximal direction with proximal movement of the distal shuttle  204 . Groove  280  in distal shuttle body  210  receives a housing key to rotatably fix shuttle  200  with a cavity in sleeve  26 . In some embodiments, the device includes a different drive system, where the syringe carrier  185  and syringe barrel may remain stationary (that is, is not proximally moved), and where the syringe carrier still provides a benefit to the syringe flange. 
     Tabs  282  and  284  radially project from distal region  270  and serve as latching elements or hooks to engage the follower. Notch  286  that leads to pocket  288  within tab  282  receives a proximal projection  289  of the biasing member  275 . 
     An angled, locking latch surface  290  is disposed distally of an opening  292  in line with an axially extending channel  294  formed in the interior surface of distal shuttle body  210 . Channel  294  accommodates plunger arm  152  that can project through opening  292  to unlock the locking mechanism described below. 
     Follower  250  is further shown in  FIGS. 12 a -12 e    and includes a proximal portion  298  with ledges  300  and  302  that serve as latching elements that engage shuttle latching tabs  282  and  284 . Channel  304  and opening  306  in proximal portion  298  allow axial movement of tabs  282  and  284  therein for manufacturing assembly and for shuttle release relative to the follower during device use. Opening  306  tapers to a slot-shaped portion  310  adapted to closely receive a radial projection  312  of biasing member  275 . 
     A radially projecting flange  316  may snap past snaps in the main body  24  during device assembly. The interior surface of follower portion  298  includes an inwardly projecting ring  318  with a spring centering lip  320 . A sleeve shaped distal portion  322  of follower  250  depends from follower portion  298  and has a lesser diameter. Slots  324  in the distal edge of portion  322  define four damping fins  326  of the follower. The slots  324  can be adjusted in size to create to differing delay times. A locking member for follower  250  to limit its rotation relative to the shuttle  200  is formed as a flexure arm  330  with an upwardly extending latch  332  at its end. 
     An exploded view of the distal shuttle  204 , biasing member  275 , and follower  250  is shown in  FIG. 14 . Biasing member  275  may function as both a torsion spring and a compression spring, with torsional preloading and an axial preloading accomplished during the manufacturing assembly of device  20 . Biasing member  275  is shown as a cylindrical spring formed of a helically coiled wire  311 , with a shuttle engaging tip in the form of a proximal projection  289 , and a follow engaging tip  312 . 
     An assembly of the distal shuttle  204  and follower  250  shown in a coupled configuration is shown in  FIGS. 13 a  and 13 b   . In the coupled configuration, the latch  332  of the follower is engaged with a protrusion  213  on a distal surface  211  of the distal shuttle  204 . 
     As shown in  FIGS. 15 a  and 15 b   , the distal surface  211  of the distal shuttle  204  has an undercut region  215  adjacent to the protrusion  213 . The undercut region  215  has a curvilinear shape. In some embodiments, the trailing surface  335  may be curved and the undercut region  215  may be curvilinear to facilitate sliding engagement between both. 
     As shown in  FIG. 12 d   , the latch  332  of the follower is axially moveable relative to the follower body  251  due to cantilevered flexure arm  330 , which is able to deflect relative to the follower body. The latch  332  may be comprised of a leading surface  333  and a trailing surface  335 . The sliding contact between the latch surfaces and the shuttle during rotation of the follower relative to the shuttle can generate friction variability that impede consistent rotation speed of the follower. The leading surface  333  engages with the protrusion  213  when the follower is in the coupled configuration in  FIG. 13 b   . The trailing surface  335  may slidingly engage with the undercut region  215  when the follower is in an uncoupled configuration and is rotating relative to the distal shuttle  204 . In the uncoupled configuration, the latch  332  is disengaged with the protrusion  213 . In some embodiments, the leading surface  333  may be a flat surface that engages in a confronting relationship a flat surface portion  214  of the protrusion  213 . At least one, or both, of the leading surface  333  and flat surface portion  214 , may be angled slightly to facilitate latching with and/or uncoupling from the protrusion  213 . In some embodiments, the trailing surface  335  may be curved to facilitate uncoupling of the latch from the protrusion, and/or facilitate sliding engagement with the undercut region  215 . 
     Distal shuttle  204  may include a lubricant-infused material to aide in the movement of the distal shuttle  204  within the device housing, particularly during the needle retraction operation. In one example, the entire distal shuttle includes lubricant-infused material. In some embodiments, at least the distal surface  211  of the distal shuttle is made of a lubricant-infused material. Such a material may aid in facilitating uncoupling of the latch  332  from the protrusion  213  and/or facilitating sliding engagement between the latch  332  and the undercut region  215  as the follower  250  rotates relative to the distal shuttle. In some embodiments, the lubricant-infused material may serve to decrease friction and/or friction variability between the distal shuttle and the latch during movement of the follower relative to the distal shuttle. The lubricant-infused material may also serve to lower friction and/or friction variability between the tabs  282 ,  284  with the ledges  300 ,  302 . In some embodiments, the material may be a silicone-infused material. In some embodiments, the material may be made of polycarbonate with infused silicone of 2%. In some embodiments, all of or at least a portion of the follower  250  may be made of a copolymer to decrease friction and/or friction variability between the distal shuttle and the follower. In some embodiments, at least one of at least the distal surface  211  of the distal shuttle is made of a lubricant-infused material, the trailing surface  335  may be curved, the undercut region  215  may be curvilinear, copolymer follower, or any combination thereof may be employed to provide a retraction assembly for an automatic injection device which can facilitate syringe retraction by decreasing the sliding engagement friction and/or by decreasing friction variation that is generated during retraction. Such embodiments may reduce any frictional delay variability in rotational speed and timing of the follower to a position to allow for shuttle/syringe retraction and/or and more consistent retraction speed and timing at the completion of the delivery cycle, which together may avoid factors contributing to stalled retraction. 
     The device may include a grease collar  340 , further shown in  FIGS. 16 a  and 16 b   , that provides a support surface for damping fluid as the follower  250  rotates relative to that support surface. Collar  340  includes an annular body  342  through which fits the syringe barrel. Collar  340  is axially supported within the housing  22 . Collar body  342  includes a generally U-shaped wall that defines an annular hollow  346 . 
     A damping compound  350  (shown in  FIG. 2 ), such as a silicone grease thickened with Teflon, may fill annular hollow  346 . Follower fins  326  fit within hollow  346  such that compound  350  is disposed both radially inward and outward of such fins  326 , as well as between adjacent fins  326  and as a film between the fin undersides and the base of the collar wall, resulting in a damping or delay effect as the follower fins  326  try to rotate relative to the collar. 
     The construction of device  20  will be further understood in view of a description of one illustrative embodiment of its operation after the end cap is removed in preparation for an injection. To arrange device  20  to inject, sleeve  26 , and thereby button  25 , is manually rotated by a user to an unlocked state in which the device is ready to inject. 
     A cross-sectional view of the device in the unlocked state is shown in  FIG. 17 . When a user subsequently applies a distal force on button  25 , button  25  starts to move downward into sleeve  26 , thereby driving flange surface  54  against ramp surface  167 . As button  25  continues to move further distally, with flange portion  52  inserting further into the shuttle opening, flange surface  54  slides along ramp surface  167 . During this sliding, flange portion  52  cams prong  160  radially outward because flange portion  52  is prevented from bending in the opposite radially outward direction due to the contact with the supportive collar surface  234 . Flange portion  52  is prevented from twisting due to contact with supportive surfaces on the proximal shuttle  202 . Prong  160  can be cammed outward as finger  162  bends until latching surfaces  172  disengage from latch surfaces on the proximal shuttle, at which point the proximal-most portion of plunger prong  160  passes downward through the shuttle due to spring  155  directly biasing the plunger element  136  downward to drive the plunger element and thereby the piston  138  distally, which driven motion shifts syringe barrel  132  and syringe carrier  185  distally relative to the shuttle and the housing to cause the tip of needle  134  to project beyond the housing distal end for penetrating a user&#39;s skin, and then forces the medication contents of the syringe through that needle for an injection. 
     As plunger element  136  moves distally during medication injection, the arm  152  abuts against the latch  332  of the follower  250 , causing flexure arm  330  to deflect distally, causing the leading surface  333  of the latch to slide distally past the protrusion  213  of the distal shuttle  204 , thus causing the latch  332  to clear the protrusion  213 . With the latch  332  disengaged from the protrusion  213  of the distal shuttle  204 , the follower  250  is in the uncoupled configuration, and the follower  250  is thus unlocked for rotation relative to the distal shuttle  204 .  FIG. 18  shows the arrangement of device  20  at this point of the use process. 
     Follower  250 , as urged by the torsional preloading of biasing member  275 , rotates against the damping effect of damping compound  350 , during which rotation remaining medication can be properly expelled from the syringe through the needle. When follower  250  has rotated such that shuttle tabs  282  and  284  are clear of ledges  300  and  302 , shuttle  200  and follower  250  are thereby unlatched so as to allow the compressively preloaded biasing member  275  to decompress, forcing shuttle  200  proximally to retract the syringe carrier  185  and the syringe barrel  132  along with the syringe carrier, thereby retracting the distal tip of the injection needle  134  to a protected, retracted position within the housing  22 . 
     While the automatic injection device described herein has been shown and described as having preferred designs, the present device may be modified within the spirit and scope of this disclosure. For example, while the biased element that the trigger assembly releases in the shown embodiment is the plunger that itself contacts the syringe piston, the trigger assembly could be used to release different biased elements in alternate embodiments, or elements that are biased with parts different than coiled springs. This application is therefore intended to cover any variations, uses or adaptations of the device using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this automatic injection device pertains. 
     Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only. 
     Various aspects are described in this disclosure, which include, but are not limited to, the following aspects: 
     1. An automatic injection device, including: a housing including a proximal end and a distal end; a syringe including a needle, a syringe body and a plunger, the syringe being moveable within the housing from a first position to a second position that is distal to the first position to move the needle toward the distal end of the housing, and the plunger being moveable relative to the syringe body to expel medication from the syringe body through the needle; a syringe carrier including a first part and a second part that are identical to one another, are discrete from one another, and are interlocked together, each of the first and second parts including: a proximal flange surface; a distal flange surface; a circumferential rounded wall between the proximal flange surface and the distal flange surface; and a gap located between the proximal flange surface, the distal flange surface and the circumferential rounded wall, wherein a portion of the syringe body is received within the gap. 
     2. The automatic injection device of aspect 1, wherein each of the first and second parts of the syringe carrier includes a protruding prong that interlocks with the other of the first and second parts. 
     3. The automatic injection device of any one of aspects 1-2, wherein the syringe carrier includes a cushion, the proximal flange surface and the distal flange surface having a greater material hardness than the cushion. 
     4. The automatic injection device of aspect 3, wherein the syringe body includes a syringe body flange, and the cushion is in contact with the syringe body flange. 
     5. The automatic injection device of aspect 3, wherein the cushion includes at least one radial protrusion extending from an inner radial surface of the cushion. 
     6. The automatic injection device of any one of aspects 1-5, wherein the syringe body includes a syringe body flange, wherein the circumferential rounded wall of the syringe carrier partially surrounds an outer perimeter of the syringe flange, and the proximal flange surface of each of the parts together fully overlap a proximal surface of the syringe flange. 
     7. The automatic injection device of any one of aspects 1-6, wherein the syringe body includes a syringe body flange, wherein the proximal flange surface of each of the parts together fully overlap a proximal surface of the syringe flange. 
     8. The automatic injection device of any one of aspects 1-7, wherein the syringe carrier fully surrounds an outer perimeter of the syringe body. 
     9. The automatic injection device of any one of aspects 1-8, wherein each of the first and second parts of the syringe carrier includes a first lateral wall end and a second lateral wall end, the circumferential rounded wall extending from the first lateral wall end to the second lateral wall end, the first lateral wall end having a prong, and the second lateral wall end having a latch protrusion, wherein the prong of the first part of the syringe carrier interlocks with the latch protrusion of the second part of the syringe carrier. 
     10. An automatic injection device, including: a housing including a proximal end and a distal end; a syringe including a needle, a syringe body and a plunger, the syringe body including a syringe flange extending radially from the syringe body, and the plunger being moveable relative to the syringe body to expel medication from the syringe body through the needle; a syringe carrier including a first part and a second part that are discrete from one another, and are interlocked together, each of the first and second parts including: a proximal flange surface; a distal flange surface; a circumferential rounded wall extending between the proximal flange surface and the distal flange surface; a cushion disposed along a distal flange surface, the proximal flange surface and the distal flange surface having a greater material hardness than the cushion; and a gap defined by the proximal flange surface, the cushion, and the circumferential rounded wall, receiving a portion of the syringe flange, wherein the cushions of each of the first and second parts together defining a ring shape to provide full circumferential support along the syringe flange. 
     11. The automatic injection device of aspect 10, wherein the cushion includes at least one protrusion contacting the syringe body underneath the syringe flange, flange, wherein the at least one protrusion is disposed adjacent to an end of an inner radial surface of the cushion of each of the first and second parts. 
     12. The automatic injection device of any one of aspects 10-11, wherein the first part and the second part are identical to one another, each of the first and second parts having interlocking elements configured to couple to one another, and walls defining together an opening surrounding the moveable plunger. 
     13. An automatic injection device, including: a housing including a proximal end and a distal end; a syringe including a needle, a syringe body and a plunger, the syringe being moveable within the housing from a first position to a second position that is distal to the first position to move the needle toward the distal end of the housing, and the plunger being moveable relative to the syringe body to expel medication from the syringe body through the needle; a shuttle having a distal surface including a protrusion and a curvilinear surface, the curvilinear surface extending from the protrusion to define an undercut region, at least a portion of the distal surface being made of a lubricant-infused material; and a follower having a follower body and a latch, the latch being moveable relative to the follower body and relative to the protrusion of the shuttle; wherein: the follower has a coupled configuration in which the latch is biasedly coupled over the protrusion, and the follower has a decoupled configuration in which the latch has cleared the protrusion and is in sliding engagement with the curvilinear surface, the follower is rotatable relative to the shuttle, and the shuttle is moveable toward the proximal end of the housing to retract the syringe. 
     14. The automatic injection device of aspect 13, wherein the latch includes a cantilevered arm with an end having a protrusion. 
     15. The automatic injection device of aspect 14, wherein the protrusion has a straight leading surface and a curved trailing surface, wherein the straight leading surface is in contact with the protrusion when the follower is in the coupled configuration, and the curved trailing surface is in contact with the curvilinear surface when the follower is in the decoupled configuration. 
     16. The automatic injection device of any one of aspects 13-15, wherein the lubricant-infused material includes silicone. 
     17. The automatic injection device of any one of aspects 13-16, wherein the entire shuttle is made of the lubricant-infused material. 
     18. The automatic injection device of any one of aspects 13-17, further including a spring that is compressed between the shuttle and the follower when the follower is in the coupled configuration. 
     19. The automatic injection device of aspect 18, wherein the spring is torsionally pre-loaded when the follower is in the coupled configuration. 
     20. The automatic injection device of any one of aspects 13-19, wherein the shuttle is moveable toward the proximal end of the housing after the follower has rotated through a predetermined angle of rotation. 
     21. The automatic injection device of aspects 1, 11 or 13, wherein the syringe body contains a medication. 
     22. The automatic injection device of aspects 1 and 11 may be combined together alone, or along with any other aspects described herein.