Patent Publication Number: US-11654248-B2

Title: Needle actuator assembly for drug delivery system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/616,212, filed Jun. 7, 2017, which claims priority to U.S. Provisional Application Ser. No. 62/347,921, filed Jun. 9, 2016, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Disclosure 
     The present disclosure relates generally to an injector device and method for delivering a fluid into the body of a patient by injection. 
     Description of the Related Art 
     Various types of automatic injection devices have been developed to allow drug solutions and other liquid therapeutic preparations to be administered by untrained personnel or to be self-injected. Generally, these devices include a reservoir that is pre-filled with the liquid therapeutic preparation, and some type of automatic needle-injection mechanism that can be triggered by the user. When the volume of fluid or drug to be administered is generally below a certain volume, such as 1 mL, an auto-injector is typically used, which typically has an injection time of about 10 to 15 seconds. When the volume of fluid or drug to be administered is above 1 mL, the injection time generally becomes longer resulting in difficulties for the patient to maintain contact between the device and the target area of the patient&#39;s skin. Further, as the volume of drug to be administered becomes larger, increasing the time period for injection becomes desirable. The traditional method for a drug to be injected slowly into a patient is to initiate an IV and inject the drug into the patient&#39;s body slowly. Such a procedure is typically performed in a hospital or outpatient setting. 
     Certain devices allow for self-injection in a home setting and are capable of gradually injecting a liquid therapeutic preparation into the skin of a patient. In some cases, these devices are small enough (both in height and in overall size) to allow them to be “worn” by a patient while the liquid therapeutic preparation is being infused into the patient. These devices typically include a pump or other type of discharge mechanism to force the liquid therapeutic preparation to flow out of a reservoir and into the injection needle. Such devices also typically include a valve or flow control mechanism to cause the liquid therapeutic preparation to begin to flow at the proper time and a triggering mechanism to initiate the injection. 
     SUMMARY OF THE INVENTION 
     In one aspect, a needle actuator assembly for a drug delivery system includes a needle actuator body having a guide surface, a needle shuttle having a cam surface, with the needle shuttle moveable along a vertical axis between a first position and a second position. The needle shuttle is configured to move between the first and second position through engagement between the guide surface of the needle actuator body and the cam surface of the needle shuttle. The assembly further including a needle received by the needle shuttle. 
     The needle shuttle may include a biasing member configured to move the needle shuttle from the first position to the second position with the guide surface of the needle actuator body disengaged from the cam surface of the needle shuttle. The assembly may include a guide post, where the needle shuttle moves along the guide post. The guide post may be linear. The cam surface of the needle shuttle may include a first cam member and a second cam member spaced from the first cam member, where the guide surface is non-linear and includes a first side and a second side positioned opposite from the first side. The second cam member of the needle shuttle may be configured to engage the second side of the guide surface to move the needle shuttle from the first position to the second position, where the first cam member of the needle shuttle is configured to engage the first side of the guide surface to move the needle shuttle from the second position to the first position. 
     In a further aspect, a drug delivery system for injecting a medicament includes a housing, a needle actuator assembly received within the housing, where the needle actuator assembly includes a needle actuator body having a guide surface, with the needle actuator body moveable between a first position and a second position, and a needle shuttle having a cam surface. The needle shuttle is moveable along a vertical axis between a first position and a second position, where the needle shuttle is configured to move between the first and second position through engagement between the guide surface of the needle actuator body and the cam surface of the needle shuttle. The needle actuator assembly also includes a needle received by the needle shuttle. The system further including a button actuator at least partially received by the housing, where movement of the button actuator is configured to move the needle actuator body from the first position to the second position, and where movement of the needle actuator body from the first position to the second position is configured to cause movement of the needle shuttle from the first position to the second position. 
     The needle shuttle may include a biasing member configured to move the needle shuttle from the first position to the second position with the guide surface of the needle actuator body disengaged from the cam surface of the needle shuttle. The system may include a guide post extending from the housing, where the needle shuttle moves along the guide post. The guide post may extend about perpendicular from the housing. 
     The system may include a pad configured to engage the needle when the needle actuator is in the second position. The pad may be received by a pad arm having a cam surface configured to engage a corresponding cam track on the housing to move the pad beneath the needle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following descriptions of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein: 
         FIG.  1    is a perspective view of a drug delivery system according to one aspect of the present invention. 
         FIG.  2    is a perspective, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention. 
         FIG.  3    is a front, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention. 
         FIG.  4    is a top view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a top portion of the housing removed and the drug delivery system in a pre-use position. 
         FIG.  5    is a top, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in a pre-use position. 
         FIG.  6    is a front, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in a pre-use position. 
         FIG.  7    is a top view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a top portion of the housing removed and the drug delivery system in an initial actuation position. 
         FIG.  8    is a top, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in an initial actuation position. 
         FIG.  9    is a front, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in an initial actuation position. 
         FIG.  10    is a top view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a top portion of the housing removed and the drug delivery system in a use position. 
         FIG.  11    is a top, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in a use position. 
         FIG.  12    is a front, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in a use position. 
         FIG.  13    is a top view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a top portion of the housing removed and the drug delivery system in a post-use position. 
         FIG.  14    is a top, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in a post-use position. 
         FIG.  15    is a front, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing the drug delivery system in a post-use position. 
         FIG.  15 A  is a front, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a pad with the drug delivery system in a pre-use position. 
         FIG.  15 B  is a perspective, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a pad with the drug delivery system in a pre-use position. 
         FIG.  15 C  is a perspective, cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a pad with the drug delivery system in a pre-use position. 
         FIG.  16    is a partial cross-sectional view of the drug delivery system of  FIG.  1    according to one aspect of the present invention, showing a valve assembly. 
         FIG.  17    is a perspective view of a drive assembly for a drug delivery system according to one aspect of the present invention. 
         FIG.  18    is a cross-sectional view of the drive assembly of  FIG.  17    according to one aspect of the present invention, showing a pre-use position of the drive assembly. 
         FIG.  19    is a cross-sectional view of the drive assembly of  FIG.  17    according to one aspect of the present invention, showing a use position of the drive assembly. 
         FIG.  20    is a cross-sectional view of the drive assembly of  FIG.  17    according to one aspect of the present invention, showing a post-use position of the drive assembly. 
         FIG.  21    is a perspective view of a plunger actuation member of the drive assembly of  FIG.  17    according to one aspect of the present invention. 
         FIG.  22    is a perspective view of a first plunger member of the drive assembly of  FIG.  17    according to one aspect of the present invention. 
         FIG.  23    is a perspective view of a plunger actuation member and first plunger member of the drive assembly of  FIG.  17    according to one aspect of the present invention, showing the plunger actuation member engaged with the first plunger member. 
         FIG.  24    is a perspective view of a plunger actuation member and first plunger member of the drive assembly of  FIG.  17    according to one aspect of the present invention, showing the plunger actuation member disengaged from the first plunger member. 
         FIG.  25    is a perspective view of a plunger actuation member and first plunger member of the drive assembly of  FIG.  17    according to one aspect of the present invention, showing the plunger actuation member disengaged from and axially displaced relative to the first plunger member. 
         FIG.  26    is a front view of a first plunger member and a second plunger member of the drive assembly of  FIG.  17    according to one aspect of the present invention. 
         FIG.  27    is a top view of a drive assembly for a drug delivery system according to a further aspect of the present invention. 
         FIG.  28    is a perspective view of the drive assembly of  FIG.  27    according to one aspect of the present invention. 
         FIG.  29    is a cross-sectional view of the drive assembly of  FIG.  27    according to one aspect of the present invention, showing a pre-use position of the drive assembly. 
         FIG.  30    is a perspective view of the drive assembly of  FIG.  27    according to one aspect of the present invention, showing the drive assembly received by a bottom portion of a housing. 
         FIG.  31    is a perspective view of the housing of  FIG.  30    according to one aspect of the present invention. 
         FIG.  32    is a top view of the drive assembly of  FIG.  27    according to one aspect of the present invention, showing engagement of the drive assembly with a portion of a needle actuator in an initial actuation position of the drive assembly. 
         FIG.  33    is an enlarged perspective view of the drive assembly of  FIG.  27    according to one aspect of the present invention, showing engagement of the drive assembly with a portion of a needle actuator in an initial actuation position of the drive assembly. 
         FIG.  34    is a front view of a needle actuator assembly according to one aspect of the present invention. 
         FIG.  35    is a left side perspective view of a needle shuttle of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention. 
         FIG.  36    is a right side perspective view of a needle shuttle of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention. 
         FIG.  37 A  is a front view of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in a pre-use position. 
         FIG.  37 B  is a front view of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in a use position. 
         FIG.  37 C  is a front view of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in an initial post-use position. 
         FIG.  37 D  is a front view of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in a post-use position. 
         FIG.  38 A  is a perspective view of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in a use position. 
         FIG.  38 B  is a perspective view of the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in an initial post-use position. 
         FIG.  39    is a perspective view of an actuator button and the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in an initial post-use position. 
         FIG.  40 A  is a cross-sectional view of an actuator button and the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in an initial post-use position. 
         FIG.  40 B  is a perspective view of an actuator button and the needle actuator assembly of  FIG.  34    according to one aspect of the present invention, showing the needle actuator assembly in a post-use position. 
         FIG.  41    is a perspective view of a drive assembly for a drug delivery system according to a further aspect of the present invention. 
         FIG.  42    is a perspective view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing a top portion of a housing removed. 
         FIG.  43    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention. 
         FIG.  44    is a perspective view of the drive assembly of  FIG.  41    according to one aspect of the present invention. 
         FIG.  45    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a pre-use position. 
         FIG.  46    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a pre-use position. 
         FIG.  47    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a pre-use position. 
         FIG.  48    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in an initial actuation position. 
         FIG.  49    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in an initial actuation position. 
         FIG.  50    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly an initial actuation position. 
         FIG.  51    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  52    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  53    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  54    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  55    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  56    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  57    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  58    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in an initial post-use position. 
         FIG.  59    is a perspective view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in an initial post-use position. 
         FIG.  60    is a top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a post-use position. 
         FIG.  61    top view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a post-use position. 
         FIG.  62    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a pre-use position. 
         FIG.  63    is a cross-sectional view of the drive assembly of  FIG.  41    according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  64    is a perspective view of a drive assembly according to a further aspect of the present invention. 
         FIG.  65 A  is a front view of a needle actuator assembly according to one aspect of the present invention, showing the needle actuator assembly in a use position. 
         FIG.  65 B  is a front view of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention, showing the needle actuator assembly in a use position. 
         FIG.  65 C  is a front view of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention, showing the needle actuator assembly in an initial post-use position. 
         FIG.  65 D  is a front view of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention, showing the needle actuator assembly in a post-use position. 
         FIG.  65 E  is a front view of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention, showing the needle actuator assembly in a pre-use position. 
         FIG.  65 F  is a cross-sectional view of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention, showing the needle actuator assembly in a pre-use position. 
         FIG.  65 G  is a front view of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention, showing the needle actuator assembly in a pre-use position with a button actuator axially displaced. 
         FIG.  65 H  is a cross-sectional view of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention, showing the needle actuator assembly in a pre-use position with a button actuator axially displaced. 
         FIG.  66    is a perspective view of a button spring of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention. 
         FIG.  67    is a perspective view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention. 
         FIG.  68    is a cross-sectional view of a button spring and actuator button of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention. 
         FIG.  68 A  is a perspective view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to a further aspect of the present invention. 
         FIG.  68 B  is a bottom view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to a further aspect of the present invention. 
         FIG.  68 C  is a front view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to a further aspect of the present invention. 
         FIG.  68 D  is a top view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to a further aspect of the present invention, showing the actuator button in a pre-use position 
         FIG.  68 E  is a front view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to a further aspect of the present invention, showing the actuator button in a pre-use position. 
         FIG.  68 F  is a top view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to a further aspect of the present invention, showing the actuator button in a use position. 
         FIG.  68 G  is a front view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to a further aspect of the present invention, showing the actuator button in a use position. 
         FIG.  69    is a top view of an actuator button of the needle actuator assembly of  FIG.  65 A  according to one aspect of the present invention. 
         FIG.  70 A  is a schematic view of a drive assembly according to one aspect of the present invention, showing the drive assembly in a pre-use position. 
         FIG.  70 B  is a schematic view of the drive assembly of  FIG.  70 A  according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  70 C  is a schematic view of the drive assembly of  FIG.  70 A  according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  70 D  is a schematic view of the drive assembly of  FIG.  70 A  according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  70 E  is a schematic view of the drive assembly of  FIG.  70 A  according to one aspect of the present invention, showing the drive assembly in a use position. 
         FIG.  70 F  is a schematic view of the drive assembly of  FIG.  70 A  according to one aspect of the present invention, showing the drive assembly in a post-use position. 
         FIG.  70 G  is a schematic view of the drive assembly of  FIG.  70 A  according to one aspect of the present invention, showing the drive assembly in a post-use position. 
         FIG.  71    is a perspective view of a spacer assembly for a drug delivery system according to one aspect of the present invention, showing an assembled, pre-use position of the spacer assembly. 
         FIG.  72    is a perspective view of the spacer assembly of  FIG.  71    according to one aspect of the present invention, showing a use position of the spacer assembly. 
         FIG.  73    is a perspective view of the spacer assembly of  FIG.  71    according to one aspect of the present invention, showing an initial post-use position of the spacer assembly. 
         FIG.  74    is a perspective view of a restriction member according to one aspect of the present invention. 
         FIG.  75    is a front view of a spacer assembly for a drug delivery system according to a further aspect of the present invention. 
         FIG.  76    is a top view of a spacer assembly for a drug delivery system according to one aspect of the present invention. 
         FIG.  77    is a perspective view of the spacer assembly of  FIG.  76    according to one aspect of the present invention. 
         FIG.  78    is a cross-sectional view of the spacer assembly of  FIG.  76    according to one aspect of the present invention. 
         FIG.  79    is a perspective view of a spacer assembly for a drug delivery system according to a further aspect of the present invention. 
         FIG.  80    is a perspective view of a spacer assembly for a drug delivery system according to another aspect of the present invention. 
         FIG.  81 A  is a cross-sectional view of the spacer assembly of  FIG.  80    according to one aspect of the present invention, showing a pre-assembly position of the spacer assembly. 
         FIG.  81 B  is a cross-sectional view of the spacer assembly of  FIG.  80    according to one aspect of the present invention, showing an assembled position of the spacer assembly. 
         FIG.  82    is a perspective view of a drive assembly for a drug delivery system according to one aspect of the present invention. 
         FIG.  83    is a perspective view of the drive assembly of  FIG.  82    according to one aspect of the present invention, showing a top portion of a housing removed. 
         FIG.  84    is a cross-sectional view of the drive assembly of  FIG.  82    according to one aspect of the present invention, showing a pre-use position of the drive assembly. 
         FIG.  85    is an enlarged cross-sectional view of the drive assembly of  FIG.  82    according to one aspect of the present invention, showing a pre-use position of the drive assembly. 
         FIG.  86    is a top view of a biasing member of the drive assembly of  FIG.  82    according to one aspect of the present invention. 
         FIG.  87    is a perspective view of the drive assembly of  FIG.  82    according to one aspect of the present invention, showing a restriction member engaged with the drive assembly. 
         FIG.  88    is a perspective view of a drive assembly for a drug delivery system according to one aspect of the present invention. 
         FIG.  89    is a perspective view of the drive assembly of  FIG.  88    according to one aspect of the present invention, showing a pre-use position of the drive assembly. 
         FIG.  90    is a cross-sectional view of the drive assembly of  FIG.  88    according to one aspect of the present invention. 
         FIG.  91    is a perspective view of the drive assembly of  FIG.  88    according to one aspect of the present invention, showing a post-use position of the drive assembly. 
         FIG.  92    is a cross-sectional view of the drive assembly of  FIG.  88    according to one aspect of the present invention, showing a pre-use position of the drive assembly. 
         FIG.  93    is a front view of the drive assembly of  FIG.  88    according to one aspect of the present invention, showing a use position of the drive assembly. 
         FIG.  94    is a perspective view of a spacer assembly for a drug delivery system according to one aspect of the present invention. 
         FIG.  95    is a front view of the spacer assembly of  FIG.  94    according to one aspect of the present invention. 
         FIG.  96    is a cross-sectional view of the spacer assembly of  FIG.  94    according to one aspect of the present invention. 
         FIG.  97    is a perspective view of the spacer assembly of  FIG.  94    according to one aspect of the present invention, showing a shim removed. 
         FIG.  98    is a perspective view of a fixed spacer of the spacer assembly of  FIG.  94    according to one aspect of the present invention. 
         FIG.  99    is a perspective view of an adjustable spacer of the spacer assembly of  FIG.  94    according to one aspect of the present invention. 
         FIG.  100    is a perspective view of a shim of the spacer assembly of  FIG.  94    according to one aspect of the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary aspects of the disclosure, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner. 
     DETAILED DESCRIPTION 
     The following description is provided to enable those skilled in the art to make and use the described embodiments contemplated for carrying out the invention. Various modifications, equivalents, variations, and alternatives, however, will remain readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the spirit and scope of the present invention. 
     For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal”, and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume various alternative variations, except where expressly specified to the contrary. It is also to be understood that the specific devices illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the invention. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting. 
     Referring to  FIGS.  1 - 16   , a drug delivery system  10  according to one aspect of the present invention includes a drive assembly  12 , a container  14 , a valve assembly  16 , and a needle actuator assembly  18 . The drive assembly  12 , the container  14 , the valve assembly  16 , and the needle actuator assembly  18  are at least partially positioned within a housing  20 . The housing  20  includes a top portion  22  and a bottom portion  24 , although other suitable arrangements for the housing  20  may be utilized. In one aspect, the drug delivery system  10  is an injector device configured to be worn or secured to a user and to deliver a predetermined dose of a medicament provided within the container  14  via injection into the user. The system  10  may be utilized to deliver a “bolus injection” where a medicament is delivered within a set time period. The medicament may be delivered over a time period of up to 45 minutes, although other suitable injection amounts and durations may be utilized. A bolus administration or delivery can be carried out with rate controlling or have no specific rate controlling. The system  10  may deliver the medicament at a fixed pressure to the user with the rate being variable. The general operation of the system  10  is described below in reference to  FIGS.  1 - 16    with the specifics of the drive assembly  12 , needle actuator assembly  18 , and other features of the system  10 , discussed below in connection with  FIGS.  17 - 93   . 
     Referring again to  FIGS.  1 - 16   , the system  10  is configured to operate through the engagement of an actuation button  26  by a user, which results in a needle  28  of the needle assembly  18  piercing the skin of a user, the actuation of the drive assembly  12  to place the needle  28  in fluid communication with the container  14  and to expel fluid or medicament from the container  14 , and the withdrawal of the needle  28  after injection of the medicament is complete. The general operation of a drug delivery system is shown and described in International Publication Nos. 2013/155153 and 2014/179774, which are hereby incorporated by reference in their entirety. The housing  20  of the system  10  includes an indicator window  30  for viewing an indicator arrangement  32  configured to provide an indication to a user on the status of the system  10  and a container window  31  for viewing the container  14 . The indicator window  30  may be a magnifying lens for providing a clear view of the indicator arrangement  32 . The indicator arrangement  32  moves along with the needle actuator assembly  18  during use of the system  10  to indicate a pre-use status, use status, and post-use status of the system  10 . The indicator arrangement  32  provides visual indicia regarding the status, although other suitable indicia, such an auditory or tactile, may be provided as an alternative or additional indicia. 
     Referring to  FIGS.  4 - 6   , during a pre-use position of the system  10 , the container  14  is spaced from the drive assembly  12  and the valve assembly  16  and the needle  28  is in a retracted position. During the initial actuation of the system  10 , as shown in  FIGS.  7 - 9   , the drive assembly  12  engages the container  14  to move the container  14  toward the valve assembly  16 , which is configured to pierce a closure  36  of the container  14  and place the medicament within the container  14  in fluid communication with the needle  28  via a tube (not shown) or other suitable arrangement. The drive assembly  12  is configured to engage a stopper  34  of the container  14 , which will initially move the entire container  14  into engagement with the valve assembly  16  due to the incompressibility of the fluid or medicament within the container  14 . The initial actuation of the system  10  is caused by engagement of the actuation button  26  by a user, which releases the needle actuator assembly  18  and the drive assembly  12  as discussed below in more detail. During the initial actuation, the needle  28  is still in the retracted position and about to move to the extended position to inject the user of the system  10 . 
     During the use position of the system  10 , as shown in  FIGS.  10 - 12   , the needle  28  is in the extended position at least partially outside of the housing  20  with the drive assembly  12  moving the stopper  34  within the container  14  to deliver the medicament from the container  14 , through the needle  28 , and to the user. In the use position, the valve assembly  16  has already pierced a closure  36  of the container  14  to place the container  14  in fluid communication with the needle  28 , which also allows the drive assembly  12  to move the stopper  34  relative to the container  14  since fluid is able to be dispensed from the container  14 . At the post-use position of the system  10 , shown in  FIGS.  13 - 15   , the needle  28  is in the retracted position and engaged with a pad  38  to seal the needle  28  and prevent any residual flow of fluid or medicament from the container  14 . The container  14  and valve assembly  16  may be the container  14  and valve assembly  16  shown and described in International Publication No. WO 2015/081337, which is hereby incorporated by reference in its entirety. 
     Referring to  FIGS.  15 A- 15 C , the pad  38  is biased into the pad as the needle actuator body  96  moves from the use position to the post-use position. In particular, the pad  38  is received by a pad arm  122  having a cam surface  124  that cooperates with a cam track  126  on the bottom portion  24  of the housing  20 . The pad arm  122  is connected to the needle actuator body  96  via a torsion bar  128 . The cam surface  124  is configured to engage the cam track  126  to deflect the pad arm  122  downwards thereby allowing the pad  38  to pass beneath the needle  28  before being biased upwards into the needle  28 . The torsion bar  128  allows the pad arm  122  to twist about a pivot of the needle actuator body  96 . The pad  38  may be press-fit into an opening of the pad arm  122 , although other suitable arrangements for securing the pad  38  may be utilized. 
     Referring to  FIGS.  1 - 33   , the drive assembly  12  according to one aspect of the present invention is shown. As discussed above, the drive assembly  12  is configured to move the container  14  to pierce the closure  36  of the container  14  and also to move the stopper  34  within the container  14  to dispense fluid or medicament from the container  14 . The drive assembly  12  shown in  FIGS.  17 - 33    is configured to engage and cooperate with a spacer assembly  40  received by the stopper  34  of the container  14 . The spacer assembly  40  includes a spacer  42  and a spacer holder  44 . The spacer holder  44  is received by the stopper  34  and the spacer  42  is received by the spacer holder  44 . The spacer holder  44  includes a first threaded portion  46  that engages a corresponding threaded portion of the stopper  34 , although other suitable arrangements may be utilized. The spacer  42  also includes a threaded portion  48  that engages a corresponding second threaded portion  50  of the spacer holder  44  for securing the spacer  42  to the spacer holder  44 , although other suitable arrangements may be utilized. The drive assembly  12  is configured to dispense a range of predetermined fill volumes of the container  14  while maintaining the functional features of the system  10  described above, including, but not limited to, retraction of the needle  28  after the end of the dose and providing an indication of the status of the system  10  while also minimizing abrupt engagement of the stopper  34  by the drive assembly  12 . The drive assembly  12  is configured to dispense a plurality of discrete fill volume ranges by utilizing a plurality of sizes of the spacers  42 . In one aspect, twelve fill volume ranges and twelve spacer  42  sizes are provided. In one aspect, the length of the spacer  42  is changed to accommodate different fill volumes in the container  14 . Alternatively, a single size spacer  42  may be utilized with a plurality of fill volumes in the container  14  accommodated by utilizing a plurality of shims that are received by the spacer  42 . 
     Referring to  FIGS.  17 - 26   , the drive assembly  12  includes a first plunger member  52 , a second plunger member  54  received by the first plunger member  52 , a first biasing member  56 , a second biasing member  58 , a plunger actuation member  60 , and an index member  62 . The first plunger member  52  is moveable from a pre-use position (shown in  FIG.  18   ), to a use position (shown in  FIG.  19   ), to a post-use position (shown in  FIG.  20   ) with the first plunger member  52  configured to engage the spacer assembly  40  and move the stopper  34  within the container  14  to dispense medicament from the container  14 . The first plunger member  52  is configured to move axially. The second plunger member  54  and the first plunger member  52  form a telescoping arrangement with the second plunger  54  configured to move axially after the first plunger member  52  moves a predetermined axial distance. The movement of the first and second plunger members  52 ,  54  is provided by the first and second biasing members  56 ,  58 , which are compression springs, although other suitable arrangements for the biasing members  56 ,  58  may be utilized. 
     The first biasing member  56  is received by the second plunger member  54  and is constrained between the plunger actuation member  60  (and index member  62 ) and a first spring seat  64  of the second plunger member  54 . The second biasing member  58  is positioned radially inward from the first biasing member  56  and received by the second plunger member  54 . The second biasing member  58  is constrained between a second spring seat  66  of the second plunger member  54  and the first plunger member  52 . The second biasing member  58  is configured to bias the first plunger  52  member towards the container  14  from the pre-use position, to the use position, and to the post-use position. The first biasing member  56  is configured to bias the second plunger member  54  towards the container  14 , which, in turn, biases the first plunger member  52  towards the container  14  from the pre-use position, to the use position, and to the post-use position. More specifically, the second biasing member  58  is configured to drive the first plunger member  52  against the spacer assembly  40  or stopper  34  to move the container  14  into engagement the valve assembly  16  thereby piercing the closure  36  of the container  14  and placing the container  14  in fluid communication with the needle  28 . The first biasing member  56  is configured to move the stopper  34  within the container  14  to dispense the medicament within the container  14 . The second biasing member  58  has a different spring constant than the first biasing member  56 . In particular, the second biasing  58  member is stiffer than the first biasing member  56  to provide a high force for piercing the closure  36  of the container  14  while the first biasing member  56  provides a lower force for dispensing as appropriate for the viscosity of the fluid or medicament within the container  14 . 
     Referring again to  FIGS.  17 - 26   , the plunger actuation member  60  has an annular portion  68  and a spindle portion  70 . The plunger actuation member  60  is rotationally moveable relative to the first plunger member  52  between a first rotational position and a second rotational position spaced from the first rotational position. The first rotational position may be 15 degrees from the second rotational position, although other suitable positions may be utilized. The annular portion  68  includes a drive surface  72  including a plurality of gears  74 , although other suitable arrangements may be utilized for the drive surface  72 . The spindle portion  70  includes an actuator locking surface  76  configured for engagement and release from a plunger locking surface  78  of the first plunger member  52 . The plunger locking surface  78  includes a plurality of projections  80  configured to be received by a plurality of slots or cutouts  81  defined by the actuator locking surface  76 . 
     As shown in  FIGS.  18  and  23   , in the first rotational position of the plunger actuation member  60 , the plurality of projections  80  and the plurality of slots or cutouts  81  are out of alignment such that the plunger actuation member  80  is engaged with the first plunger member  52  to prevent movement of the first and second plunger members  52 ,  54  with the first and second biasing members  56 ,  58  biasing the first and second plunger members  52 ,  54  away from the plunger actuation member  60 . As shown in  FIGS.  19  and  24   , in the second rotational position of the plunger actuation member  60 , the plurality of projections  80  and the plurality of slots or cutouts  81  are aligned with each other such that the plunger actuation member  60  is disengaged with the first plunger member  52  to allow movement of the first and second plunger members  52 ,  54  thereby starting the dispensing process from the container  14 . 
     Referring to  FIGS.  7  and  33   , the drive surface  72  of the plunger actuation member  60  is configured to be engaged by a portion of the needle actuator assembly  18 . After engagement of the actuator button  26  and release of the needle actuator assembly  18 , which is discussed in more detail below, the needle actuator assembly  18  moves within the housing  20  from the pre-use position, to the use position, and to the post-use position. During the initial movement of the needle actuator assembly  18 , a portion of the needle actuator assembly  18  engages the drive surface  72  of the plunger actuation member  60  to move the plunger actuation member  60  from the first rotational position to the second rotational position. As shown in  FIG.  33   , an angled blade portion  82  of the needle actuator assembly  18  engages the drive surface  72  of the plunger actuation member  60  to cause rotation of the plunger actuation member  60 . 
     Referring to  FIGS.  11 ,  13 , and  26   , the second plunger member  52  includes a plurality of coded projections  84  with a preselected one of the plurality of coded projections  84  configured to engage a restriction member  86  of the system  10 . As discussed in more detail below, the restriction member  86  cooperates with the needle actuation assembly  18  and restricts movement of the needle actuator assembly  18  from the use position to the post-use position until a predetermined end-of-dose position of the stopper  34  is reached. In one aspect, the restriction member  86  is configured to restrict axial movement of the needle actuation assembly  18  from the use position through engagement between the restriction member  86  and a portion of the needle actuation assembly  18 . Such engagement between the restriction member  86  and the needle actuation assembly  18  is released by rotation of the restriction member  86  when the stopper  34  reaches the end-of-dose position. During the use position of the needle actuator assembly  18 , the restriction member  86  is biased in a rotational direction with the rotation of the restriction member  86  being prevented through engagement between the restriction member  86  and one of the plurality of coded projections  84  of the second plunger member  54 . The plurality of coded projections  84  may be axial ribs of varying length, although other suitable arrangements may be utilized. Each coded projection  84  defines a point at which the restriction member  86  is able to rotate thereby releasing the needle actuator assembly  18 . The smooth portion of the second plunger member  52  may also provide a further “code” for determining when the system  10  transitions to the end-of-dose position. 
     As discussed above, the indicator arrangement  32  moves with different portions of the indicator arrangement  32  visible through the indicator window  30  as the system  10  moves from the pre-use, use, and post-use or end-of-dose positions. More specifically, the indicator arrangement  32  engages a portion of the restriction member  86  and moves along with the restriction member  86  through the various stages of the system  10  to provide an indication to the user regarding the state of the system  10 . 
     During assembly of the system  10 , the dosage of the container  14  is matched with a specific spacer  42  having a set length and a corresponding one of the plurality of coded projections  84  is aligned with the restriction member  86 . Accordingly, as discussed above, the container  14  may be provided with a plurality of dosage volumes with each volume corresponding to a specific spacer  42  and coded projection  84 . Thus, even for different dosage volumes, the system  10  is configured to inject the needle  28  into the user to deliver a dose of medicament from the container  14 , retract the needle  28  after the end of the dose, and provide an indication of the status of the system  10  while minimizing abrupt engagement of the stopper  34  by the drive assembly  12 . In particular, the size of the stopper  34  may be selected to minimize the distance between the first plunger member  52  and the spacer assembly  40  and does not require the use of damping. 
     Referring to  FIGS.  27 - 33   , a drive assembly  12 A according to a further aspect of the present invention is shown. The drive assembly  12 A shown in  FIGS.  27 - 33    is similar to and operates in the same manner as the drive assembly  12  shown in  FIGS.  17 - 26    and described above. In the drive assembly of  FIGS.  27 - 33   , however, the first plunger member  52  is received by the second plunger member  54  and extends from the second plunger member  54  during axial movement from the pre-use position to the use position. Further, the first plunger member  52  includes an extension portion  88  configured to engage the second plunger member  54  after the first plunger member  52  moves predetermined axial distance such that the first and second plunger members  52 ,  54  move together. The first and second biasing members  56 ,  58  engage and act on the first and second plunger members  52 ,  54  in the same manner as the drive assembly  12  of  FIGS.  17 - 26   . 
     Referring to  FIGS.  27 - 32   , the index member  62  is positioned about the first and second plunger members  52 ,  54  and includes a plurality of ratchet teeth  90  configured to engage a flexible tab  92  positioned on the bottom portion  24  of the housing  20 . When the drive assembly  12 ,  12 A is installed into the bottom portion  24  of the housing  20 , the engagement of the ratchet teeth  90  of the index member  62  with the flexible tab  92  of the housing  20  provide a one-way rotation of the index member  62 . The index member  62  is configured to rotate to align one of the coded projections  84  of the second plunger member  52  with the restriction member  86  based on the dosage volume and spacer  42  size as discussed above. The index member  62  may provide the drive assembly  12 ,  12 A with  24  rotational positions of which  12  may have unique dose values associated with them. 
     Referring to  FIGS.  1 - 16  and  34 - 40 B , the needle actuator assembly  18  according to one aspect of the present invention is shown. The needle actuator assembly  18  includes a needle actuator body  96  having guide surfaces  98 , a needle shuttle  102  having cam surfaces  104 , and the needle  28  received by the needle shuttle  102  and configured to be in fluid communication with the container  14  as discussed above. The needle actuator body  96  is generally rectangular with the guide surfaces  98  protruding radially inward. The needle shuttle  102  is received within the needle actuator body  96 . As described above, the needle actuator body  96  is moveable within the housing  20  from a pre-use position (shown in  FIGS.  4 - 6   ), an initial actuation position ( FIGS.  7 - 9   ), a use position ( FIGS.  10 - 12   ), and a post-use position ( FIGS.  13 - 15   ). The needle actuator body  96  is biased from the pre-use position to the post-use position via an extension spring  106 , although other suitable biasing arrangements may be utilized. The needle actuator body  96  is released and free to move from the pre-use position to the use position upon engagement of the actuator button  26 , which is discussed in more detail below. The needle actuator body  96  moves from the use position to the post-use position after rotation of the restriction member  86  as discussed above in connection with  FIGS.  17 - 33   . 
     Referring to  FIGS.  34 - 40 B , the needle shuttle  102  is moveable along a vertical axis between a retracted position where the needle  28  is positioned within the housing  20  and an extended position where at least a portion of the needle  28  extends out of the housing  20 . The needle shuttle  102  is configured to move between the retracted position and the extended position through engagement between the guide surfaces  98  of the needle actuator  96  and the cam surfaces  104  of the needle shuttle  102 . The cam surfaces  104  are provided by first and second cam members  108 ,  110 , with the first cam member  108  spaced from the second cam member  110 . The housing  20  includes a guide post  112  having recess configured to receive a T-shaped projection  114  on the needle shuttle  102 , although other shapes and configurations may be utilized for the guide post  112  and T-shaped projection  114 . The needle shuttle  102  moves along the guide post  112  between the retracted and extended positions. The guide post  112  is linear and extends about perpendicular from the housing  20 , although other suitable arrangements may be utilized. The guide surfaces  98  of the needle actuator body  86  are non-linear and each include a first side  116  and a second side  118  positioned opposite from the first side  116 . 
     As discussed below, the guide surfaces  98  of the needle actuator body  96  cooperate with the cam members  108 ,  110  of the needle shuttle  102  to move the needle shuttle  102  vertically between the retracted and extended positions as the needle actuator body  96  moves axially from the pre-use position to the post-use position. The needle shuttle  102  also includes a shuttle biasing member  120  configured to engage the housing  20  or the actuator button  26 . In particular, the shuttle biasing member  120  engages the housing  20  or actuator button  26  and provides a biasing force when the needle actuator body  96  is transitioning from the use position to the post-use position. When the needle actuator body  96  is fully transitioned to the post-use position, the cam members  108 ,  110  of the needle shuttle  102  are disengaged from the guide surfaces  98  of the needle actuator body  96  and the shuttle biasing member  120  biases the needle shuttle  102  downward such that the needle  28  engages the pad  38 , as discussed above. As discussed above in connection with  FIGS.  1 - 16   , however, the pad  38  may also be biased into the needle  28  rather than biasing the needle shuttle  102  downwards via the shuttle biasing member  120 . The needle actuator body  96  may interact with the actuator button  26  to prevent the actuator button  26  from popping back up until the post-use position is reached, which is discussed below in more detail. 
     Referring to  FIGS.  37 A- 40 B , in a pre-use position ( FIG.  37 A ), the needle shuttle  102  is in the retracted position with the cam members  108 ,  110  spaced from the guide surface  98  of the needle actuator body  96 . As the needle actuator body  96  moves to the use position ( FIGS.  37 B and  38 A ), the second cam member  110  of the needle shuttle  102  engages the second side  118  of the guide surfaces  98  to move the needle shuttle  102  from the retracted position to the extended position. During the transition from the use position to the post-use position of the needle actuator body  96  ( FIG.  37 C ), the first cam member  108  of the needle shuttle  102  is engaged with the first side  116  of the guide surfaces  98  to move the needle shuttle  102  from the second position to the first position. After the needle actuator body  96  is fully transitioned to the post-use position ( FIGS.  37 D and  38 B ), the shuttle biasing member  120  biases the needle shuttle  102  downward as the cam members  108 ,  110  disengage from the guide surfaces  98  of the needle actuator body  96  with the needle  28  engaging the pad  38 . The transition of the needle actuator body  96  and the corresponding position of the needle shuttle  102  is also shown in  FIGS.  39 - 40 B . The interaction between the actuator button  26  and the needle actuator body  96  is discussed in detail in connection with  FIGS.  65 A- 67   . Referring to  FIGS.  41 - 64   , a drug delivery system  200  according to a further embodiment is shown. The system  200  includes a housing  202  having an upper housing  204  and a lower housing  206 . The housing has a proximal end  205  and a distal end  207 . The upper housing  204  has a status view port  208  so that a user can view the operating status of the system  200 . The system  200  also includes a valve assembly  212 , a tube  214  fluidly connecting the valve assembly  214  with a patient needle  215  that is disposed in a proximal end of a needle arm  216 . A spring  218  biases a needle actuator  220  distally. 
     As shown in  FIGS.  42 - 46   , the system  200  additionally includes a container or medicament container  222  with a stopper  224  movably disposed therein, although the stopper  224  is omitted from various figures to aid clarity. Preferably, the distal end of the medicament container  222  has a septum assembly  228  that is spaced apart from the valve assembly  212  prior to actuation of the device  222 , as best shown in  FIG.  47   . 
     For manufacturing purposes, using one size for a medicament container is often desirable, even if multiple fill volumes or dosages are contemplated for use with the container. In such cases, when medicament containers are filled, the differing fill volumes result in different positions of the stopper. To accommodate such different stopper positions, as well as accommodate manufacturing differences of the stoppers, aspects of the present invention include a bespoke or custom spacer  226  disposed in a proximal end of the container  222 , proximal to the stopper  224 . In other words, the bespoke spacer  226  provides an option that allows dispensing of a range of manufacturer-set pre-defined fill volumes by selection of different spacers  226 , and reduces or eliminates the need for assembly configuration operations. The size of the spacer  226  can be employed to account for under-filled volumes of the container  222 , and provide a consistent bearing surface at the proximal end of the container. 
     The spacer  226  is selected from a plurality of different size spacers  226  to occupy space from a proximal end of the stopper  224  to a proximal end of the container  222 . According to one embodiment, as shown in  FIGS.  45 - 47   , the spacer  226  is selected to be substantially flush with the proximal end of the container  222 . Additionally, according to one embodiment, the spacer  226  has a “top hat” shape, which includes a central column  230  and a distal flange  232 , as best shown in  FIG.  45   . 
     Returning to  FIGS.  44 - 47   , the system  200  also includes a drive assembly  234  for displacing the container  222  distally to establish the fluid connection between the container  222  and the patient needle  215 , as well as dispensing the medicament from the container  222 . In more detail, the drive assembly  234  includes an inner spring  236  disposed within a central plunger  238 , an outer plunger  240 , an outer spring  242  disposed between the central plunger  238  and the outer plunger  240 , a telescoping member  244 , and a release gate  246 . 
     Preferably, the inner spring  236  has a greater spring constant than the outer spring  242 , and is therefore, stronger or stiffer than the outer spring  242 . The inner spring  236  is disposed inside the central plunger  238 , and pushes between a spring flange  248  in the lower housing (best shown in  FIG.  46   ) and the central plunger  238 , which bears directly on the proximal end of the spacer  226  subsequent to device activation. The outer spring  242  is disposed inside outer plunger  240 , and pushes between a proximal external flange  250  of the central plunger  238  and a distal internal flange  252  of the outer plunger  240 . Thus, the inner and outer springs  236  and  242  are nested, and can provide a more compact drive assembly (and thus, a more compact system  200 ) than employing a single spring. 
     According to one aspect, the inner spring  236  acts only to displace the container  222  to establish the fluid connection with the patient needle  215 , and the outer spring  242  acts only to subsequently dispense the medicament from the container  222 . According to another aspect, the inner spring  236  acts to displace the container  222  to establish the fluid connection with the patient needle  215 , and also acts to begin dispensing the medicament from the container  222 , and the outer spring  242  acts to complete dispensing the medicament. In a further aspect, the inner spring  236  causes the initial piercing of the container  222  with the outer spring  242  completing the piercing and dispensing of the medicament from the container  222 . 
     As shown in  FIGS.  44 - 47   , and as subsequently described in greater detail, the outer plunger  240  includes a pair of proximal flanges or feet  254  that each have a slanted surface that interacts with a corresponding slanted surface (or surfaces) on the release gate to retain and subsequently release the power module subsequent to actuation of the device  200 . 
     As best shown in  FIGS.  46  and  47   , as initially assembled, the container  222  is disposed in clearance from the drive assembly  234  and the valve assembly  212 . A lateral flange  256  on the needle actuator  220  axially retains the medicament container  222 , and the needle actuator  220  prevents the release gate  246  from displacing laterally. According to one embodiment, a spring (not shown) biases the needle actuator  220  distally, but the actuation button  210  (and/or its associated assembly) prevents distal displacement of the needle actuator  220  prior to actuation of the device  200 . A status bar  258  is disposed on the needle actuator  220 , and has a top surface that is visible through the status view port  208 . According to one embodiment, the top surface of the status bar has a plurality of colors or patterns, and when the device is in a pre-actuated state, a first color or pattern, such as yellow, is visible through the status view port  208 . 
       FIGS.  48 - 52    are top views of the system  200  illustrating the operation of events at and subsequent to actuation of the system  200 . In  FIG.  47   , a user slides the actuation button  210  proximally and then displaces the button  210  vertically into the housing  202 , thereby freeing the needle actuator  220  to displace distally under the influence of the spring (omitted for clarity). As shown in  FIG.  49   , as the needle actuator displaces distally, tracks  260  on the needle actuator  220  interact with lateral bosses  262  on the needle arm  216  to insert the patient needle  215 . Preferably at this stage, the proximal end of the needle actuator  220  has not yet cleared the release gate  246 , and thus, the drive assembly  234  has not yet been released. But the lateral flange  256  has displaced distally and therefore, the container  222  is unrestrained. 
     Subsequently, as shown in  FIGS.  50  and  51   , with continued distal displacement, the proximal end of the needle actuator  220  clears the release gate  246  (thereby releasing the drive assembly  234 ). The needle actuator  220  comes to temporarily rest against a feature on a rotatable release flipper  264 , driving the release flipper  264  against an outrigger  266  (best shown in  FIGS.  44  and  59   ) of the telescoping member  244 . The needle actuator  220  remains in this position until the medicament has been dispensed. In this position, preferably, a second color or pattern of the status bar  258 , such as green, is visible through the status view port  208 . 
     At this stage, the force of the springs  236  and  242  and the interaction of the angled surfaces of the proximal flanges or feet  254  with the corresponding angled surface (or surfaces) on the release gate  246  causes the release gate  246  to displace laterally, thereby freeing the outer plunger  240  from restraining interaction with the release gate  246 . Up to this point, the outer plunger  240  has been restraining the central plunger  238 . 
     Referring to  FIGS.  52  and  53    (the inner spring  236  is omitted from  FIG.  52    for clarity), the stiff inner spring  236  distally drives central plunger  238  to contact the spacer  226 . Because the medicament container  222  is filled with a substantially incompressible fluid, the continued distal displacement of the central plunger  238  distally displaces the spacer  226 , the stopper  224 , and the container  222  relative to the housing  202 . This distal displacement causes the septum assembly  228  to be pierced by the valve assembly  212 , establishing fluid communication between the container  222  and the patient needle  215 . The central plunger  238  travels distally until its proximal external flange  250  (best shown in  FIG.  59   ) contacts a flange on the lower housing  206 , thereby limiting the “piercing travel.” Preferably, another flange on the lower housing  206  and/or the lateral flange  256  of the needle actuator  220  limits distal travel of the container  222 . 
     Subsequently, because the inner spring  236  can no longer distally displace the central plunger  238 , the lighter outer spring  242  distally displaces the outer plunger  240  relative to the central plunger  238  to contact the distal flange  232  of the spacer  226 , as shown in  FIGS.  54  and  55   . As subsequently described in greater detail, preferably, the contact between the outer plunger  240  and the spacer  226  is damped to minimize the impact force. Further expansion of the outer spring  242  distally displaces the outer plunger  240  to dispense the medicament. 
     As shown in  FIGS.  56  and  57   , as the outer spring  242  continues to expand and distally displace the outer plunger  240 , upon a predetermined distal displacement of the outer plunger  240  relative to the telescoping member  244 , an external feature or flange  268  of the outer plunger  240  interacts with an internal distal feature or flange  270  of the telescoping member  244  to “pick up” the telescoping member  244 . This ensures that further distal displacement of the outer plunger  240  causes corresponding distal displacement of the telescoping member  244 . This paired distal displacement continues until the end of the medicament dispensing. 
     As previously noted, the outrigger  266  is disposed on the telescoping member  244 . The axial length of the outrigger and the distal travel of the telescoping member  144  controls the timing of the disengagement of the outrigger  266  with the release flipper  264 . As shown in  FIGS.  58  and  59   , at the end of medicament dispensing, the proximal end of the outrigger  266  bypasses the release flipper  264 . This allows the release flipper  264  to rotate out of engagement with the needle actuator  220  ( FIG.  60   ), and allows the needle actuator  220  to continue its distal displacement and withdraw the patient needle  215  ( FIG.  61   ). At this stage, another color or pattern of the status bar  258 , such as red, is visible through the status view port  208 , signifying that the device  200  has completed operation. 
     As previously noted, the contact between the outer plunger  240  and the spacer  226 , as illustrated in  FIGS.  62  and  63   , is preferably damped to minimize the impact force. The highest level of energy dissipation is desirable for under-filled syringes containing viscous fluid, as the outer spring  242  will be stiffer to provide desired dispense rates. The lowest level of energy dissipation is desirable for maximum-filled syringes containing low-viscosity fluid, as the outer spring can be less stiff to provide desired dispense rates. Various methods can be employed to adjust damping levels, such as air damping, or closed-cell foam damping. 
     As another method of damping the impact force,  FIG.  64    illustrates an embodiment of a spacer  226  in which one or more axial interface ribs  272  are circumferentially arrayed about the central column  230  of the spacer  226 . In this embodiment, the outer plunger  240  must drive past the interference ribs  272 , which provide frictional resistance to the distal displacement of the outer plunger  240  relative to the spacer  226 . The frictional force created by the interference between interference ribs  272  and the outer plunger  240  is independent of plunger speed. Preferably, the frictional force does not exceed the minimum dispense spring load, to avoid stalling weaker springs. The interference can be tuned to give the desired level of frictional resistance. For different fluid viscosities, there can be different sizing (axial and/or radial) of the interference ribs  272 . This could mean a bespoke or custom spacer for each viscosity and fill-level combination, or, depending on the number of springs required for a viscosity range, there can be a number of tined positions, whereby the spacer can be set to a particular position for a particular modular spring (the position have had the interference/damping tuned for that particular spring load/viscosity scenario). 
     Referring to  FIGS.  65 A- 69   , an actuator button arrangement  280  for actuating the system  10  according to one aspect of the present invention is shown. The actuator button arrangement  280  includes the actuator button  26 , a button spring  284 , and a needle actuator body  286 . The needle actuator body  286  may be similar to the needle actuator bodies  96 ,  220  discussed above and configured to move within the housing  20  to transition the needle shuttle  102  or needle  28  between retracted and extended positions. As shown in  FIG.  69   , the actuator button  26  includes a user interface portion  288  for interacting with a user. Preferably, the user interface portion  288  is about 22 mm long and about 10 mm wide, although other suitable dimensions may be utilized. The actuator button  26  includes two pairs of lockout arms  290 ,  292  that interact with button contacting surfaces  294 ,  296  on the needle actuator body  286  prior to device actuation to prevent the needle actuator body  286  from rocking upward. As shown in  FIG.  65 H , an overlap between the needle actuator body  286  and the housing  20  prevents premature actuation. Referring to  FIG.  66   , the button spring  284  includes a first bearing surface  298  and a second bearing surface  300  spaced from the first bearing surface  298 , and a cantilevered central spring arm  302  surrounded by a pair of outer arms  304  that are joined by the first bearing surface  298 . 
     The actuation button arrangement  280  is configured to provide one or more of the following features, which are discussed in more detail below: one-way axial displacement or sliding of the actuator button  26 ; transverse movement (raised and depressed positions) of the actuator button  26  where the actuator button  26  remains depressed during the use position of the needle actuator body  286 ; and lockout of the actuator button  26  in the post-use position of the needle actuator body  286  such that the button  26  is in the raised position and cannot be depressed by a user. 
     To actuate the system  10  using the actuator button  26 , the user first slides the user interface portion  288  in a first axial direction, shown as being to the right in  FIGS.  65 G and  65 H . The user may be required to slide the user interface portion  288  about 10 mm or about 8 mm, although other suitable distances may be utilized. Moving the actuator button  26  axially moves the lockout arms  290 ,  292  to clear the button contact surfaces  294 ,  296  on the needle actuator body  286  to allow movement of the actuator button  26  from the raised position to the depressed position. 
     As the user distally slides the user interface portion  288 , the central spring arm  302  of the button spring  284  rides over a spring arm  306  bearing surface on the housing  20  while the first and second bearing surfaces  298 ,  300  engage first and second bearing ramps  308 ,  310  on the housing  20 . The forces on the button spring  284  are balanced through the engagement with the spring arm bearing surface  306  and the first and second bearing ramps  308 ,  310  to provide a smooth axial displacement or sliding of the actuator button  26 . 
     As the actuator button  26  and the button spring  284  reach the end of their axial sliding travel, the central spring arm  302  and the first bearing surface  298  pass the end of a respective stops  312 ,  314  to prevent the actuator button  26  from sliding backward to its original position, as shown in  FIG.  65 H . Further, when the actuator button  26  and the button spring  284  reach the end of their axial sliding travel, the user engages the user interface portion  288  to move the actuator button  26  downward to its depressed position. The actuator button  26  may be depressed about 2 mm and the minimum force required to depress the actuator button  26  is about 3 N, and most preferably, about 2.8 N, although other suitable distances and minimum forces may be utilized. 
     As the user depresses the user interface portion  288 , shown in  FIGS.  65 A and  65 B , the actuator button  26  rotates the needle actuator body  286  to release the needle actuator body  286  thereby allowing the needle actuator body  286  to move from the pre-use position to the use position. As shown in  FIG.  65 B , as the needle actuator body  286  travels to the use position, the lockout arms  290 ,  292  run along the underside of the button contact surfaces  294 ,  296  to prevent the actuator button  26  springing upward. After the medicament has been delivered and as the needle actuator body  286  is transitioning from the use position to the post-use position, shown in  FIG.  65 C , the lockout arms  290 ,  292  are disengaged from the button contact surfaces  294 ,  296  allowing the actuator button  26  to spring back up under the influence of the button spring  284 . Once the needle actuator body  286  fully transitions to the post-use position, shown in  FIG.  65 D , the actuator button  26  has finished moving from the depressed position to the raised position due to the biasing force of the button spring  284 . When the needle actuator body  286  is in the post-use position, a spring arm  316  on the needle actuator body  286  engages the actuator button  26  to prevent the actuator button  26  from moving to the depressed position while axial movement is still restricted by the engagement of the spring arm  302  with the stops  312 ,  314 . Thus, the actuator button  26  is locked after delivery of the medicament is complete to provide a clear indication between a used system and an unused system. 
     Furthermore, if the user holds down the actuator button  26  during dispensing of the medicament, proper dosing and needle retraction will still complete, but the actuator button  26  will not spring back up to the raised position until the button  26  is released. 
     In one aspect, the button spring  284  is made of plastic. The button spring  284  may also be a pressed metal spring could be used instead, although any other suitable material may be utilized. 
     Referring to  FIGS.  68 A- 68 G , rather than providing a separate actuator button  26  and button spring  284 , the spring may be provided integrally with the button  26 . More specifically, an actuator button  320  according to a further aspect of the present invention includes an integral spring arm  322 . The actuator button  320  also includes lockout arms  324 , retention arms  326 , and a rear pivot  328 . As shown in  FIGS.  68 D and  68 E , the spring arm  322  engages prongs  330  in the top portion  22  of the housing  20 . During transition of the system  10  from the pre-use position to the use position, the spring arm  322  slides past a detent of the prongs  330  providing an axial spring force. The end of the spring arm  322  engages a portion of the top portion  22  of the housing  20  to provide the vertical spring force as the spring arm  322  deflects. The actuator button  320  is configured to a fluid motion between the sliding and depression movements of the button  320  even though two separate motions are occurring, which is similar to the operation of the button  26  discussed above. During transition between the pre-use position and the use position, the button  320  pivots about the rear pivot  328  with the retention arm  326  engaging a portion of the needle actuator body  286  thereby maintaining a depressed position of the button  320  until the end-of-dose position is reached in a similar manner as actuator button  26 . The lockout arms  324  deflect inwards and engages a portion of the needle actuator body  286  as the needle actuator body  286  moves to the end-of-dose position thereby preventing further movement of the actuator button  320  in a similar manner as the actuator button  26  discussed above. 
     Aspects of the present invention provide improvements over previous button designs. For example, the actuation button arrangement  280  provides multiple surfaces to hold the needle actuator body  286  in place against a needle actuator spring  106  prior to actuation, thereby reducing the likelihood of premature actuation during a drop impact. The actuation button arrangement  280  physically prevents the needle actuator body  286  from moving prior to actuation by holding it in a tilted (locked) state in such a way that the surfaces have no room to separate and pre-activate. 
     In addition, button slide forces of the actuation button arrangement  280  are controlled more precisely by utilizing a flexing arm rather than using a simple bump detent. This permits longer sliding strokes of the button  26  with better force control, resulting in a more ergonomically effective design. Further, the actuation button arrangement  280  causes the button  26  to pop back out at the end of injection, giving the user an additional visual, audible, and tactile indication that the medicament delivery is completed. 
     According to one aspect, the fluid delivery volume of the system  10  is determined by the end position of a plunger relative to a point inside the housing regardless of actual fill volume, container inner diameter, and stopper starting position and length. The dosing accuracy variability can be significant because the tolerances of the factors above can be quite large. Aspects of the present invention allow for the elimination of some or all of these tolerances from the dosing equation, resulting in a more precise and less variable injection volume of medicament. 
     Referring to  FIGS.  70 A- 70 G , a spacer assembly  400  for use in connection with a drive assembly according to one aspect of the present invention is shown. 
     Elements in a chain of tolerances in the stopper spacer assembly  400  include a thickness (A) of a flange  402  of an inner plunger  404 , an internal length (B) of an outer plunger  406  between an internal proximal end  408  and an internal shoulder  410 , and an initial offset distance (CO between the inner plunger flange  402  and the internal proximal end  408  of the outer plunger. This initial offset distance (CO is preferably greater than a gap distance (C 2 ) between outer plunger  406  and the proximal end of the medicament barrel  412 . The chain of tolerances in the stopper spacer assembly  400  also includes the internal barrel diameter (D). Once assembled, the stopper spacer  414  and the outer plunger  406  are unique for a given medicament volume. 
       FIGS.  70 B- 70 G  illustrate operation of the stopper spacer assembly  400 . As shown in  FIG.  70 B , when the system is actuated, the both inner and outer plungers  404  and  406  are released. An outer spring  416  pushes the outer plunger  406  into the barrel  412 , compressing damping material  418 , and an inner spring  420 . The stopper  422  does not yet mover relative to the barrel  412  due to the fluid column of medicament. 
     Next, as shown in  FIG.  70 C , the outer spring  416  distally displaces the outer plunger  406  and the barrel  412  to open a valve (not shown) at the distal end of the barrel  412  that establishes fluid communication with the needle (not shown). Due to the incompressibility of the liquid medicament, the stopper  422  cannot displace relative to the barrel  412  until the valve is opened and the fluid path to the patient needle is established. 
     Subsequently, as shown in  FIGS.  70 D and  70 E , the inner spring  420  displaces the inner plunger  404 , the stopper spacer  414 , and the stopper  422 , to dispense the fluid. 
       FIG.  70 F  illustrates the end of medicament delivery when the proximal flange  402  of the inner plunger  404  contacts the internal shoulder  410  of the outer plunger  406 , thereby ceasing displacement of the inner plunger  404  (and the stopper spacer  414  and stopper  422 ) relative to the medicament barrel  212  and stopping the flow of medicament. 
     According to one aspect, as shown in  FIG.  70 G , the cessation of displacement of the inner plunger  404  relative to the medicament barrel  412  triggers an end-of-dose indicator for the system. 
     Referring to  FIGS.  71  and  72   , a collapsible spacer assembly  430  includes a forward spacer portion  432  secured to a stopper  434 , an inner plunger  436 , a rear spacer portion  438 , and a rotating shuttle  440 . The inner plunger  436  can translate relative to the forward spacer portion  432 , but not rotate relative thereto. Similarly, the rear spacer portion  438  can also move axially relative to the forward spacer portion  432 , but not rotate relative to the forward spacer portion  432 . As subsequently described in greater detail, the rotating shuttle  440  first rotates, and subsequently translates. 
     According to one aspect, forward spacer portion  432  is fixedly secured to the stopper  434 . One skilled in the art will understand that many methods can be employed to secure the forward spacer portion  432  to the stopper  434 , for example, adhesive, mechanical fasteners, or any other suitable arrangement. Preferably, the forward spacer portion  432  includes threads that engage mating threads in the stopper  434 . 
     When the stopper spacer assembly  430  is screwed into the stopper  434 , an axial load is applied through access openings  442  in the rear spacer portion  438 . This force can be used to push the stopper  434  forward, applying pressure to the fluid medicament. This pressure causes the front (distal) face of the stopper  434  to deflect and press proximally, pushing back on the rear spacer portion  438  and rotating the rotating shuttle into its “as assembled” condition. In other words, when a medicament barrel is filled with medicament and the system&#39;s plunger is applying axial force to the medicament via the spacer assembly  430 , the distal face of the stopper  434  is deformed by the pressure of the medicament. During medicament delivery, pressure is applied by a drive assembly (via the plunger) to the rear spacer portion  438 , which in turn applies a rotational torque to the rotating shuttle  440  via helical faces  444  of the rear spacer portion  438 . But the stopper deformation from the medicament provides a rearward or proximal force on the inner plunger  436 , which prevents rotation of the rotating shuttle  440 . 
     According to one aspect, an axial reaction load on the inner plunger  436  can be increased by increasing the length of the inner plunger  436 . 
     Once the medicament delivery is complete, as shown in  FIG.  73   , the pressure on the stopper  434  decreases, thereby permitting the distal end of the inner plunger  436  to displace distally. This distal displacement permits the rotating shuttle  440  to rotate. The continued axial force applied by the drive assembly rotates and distally displaces the rotating shuttle  440  due to interaction of the helical faces  444  in the rear spacer portion  438  with corresponding cam-faced arms  446  of the rotating shuttle  440 . According to one aspect, this final movement of the rotating shuttle  440  causes the drive assembly to trigger needle retraction. 
     Referring to  FIGS.  74  and  75   , a restriction member  452  according to one aspect of the present invention is disposed with the drive assembly. The restriction member  452  governs the timing of the final displacement of the needle actuator bodies  96 ,  220  subsequent to the completion of the medicament dose. Instead of rotating about a fixed post, the restriction member  452  floats freely. Once a plunger displaces sufficiently distally for a gap to align with the restriction member  452  (as shown in  FIGS.  74  and  75   ), the restriction member  452  displaces laterally into the gap because of the force of the spring on the needle actuator  96 ,  220  and the angled face  454  on the rear of the arm of the restriction member  174  that engages the needle actuator body (best shown in  FIG.  75   ). Once the restriction member no longer retains the needle actuator body  96 ,  220 , the needle actuator body  96 ,  220  is free to complete the axial movement to the post-use position. Further, as shown in  FIG.  75   , the restriction member  452  is biased onto the rear of the barrel portion of the container  14 , which minimizes the tolerance chain of the various components and improves dose accuracy. 
     Referring to  FIGS.  76 - 78   , a spacer assembly  460  according to a further aspect of the present invention is shown. The spacer assembly  460  shown in  FIGS.  76 - 78    allows for the removal of the effect of manufacturing tolerance build up through adjustment of the spacer assembly thereby allowing each system to inject the same amount of medicament. 
     As shown in  FIG.  77   , the spacer assembly  460  includes a stopper  462  and a stopper spacer  464 . The stopper spacer  464  includes a fixed spacer piece or fixed spacer  466  that is fixedly connected with the stopper  462 , and an adjustable spacer piece or adjustable spacer  468  that is rotationally displaceable in one direction relative to the fixed spacer  466 . 
     One skilled in the art will understand that many methods can be employed to secure the fixed spacer  466  to the stopper  462 , for example, adhesive, mechanical fasteners, or any other suitable arrangement. Preferably, the fixed spacer  466  includes one or more external threads that engage one or more mating threads in the stopper  462 . According to one aspect, the adjustable spacer  468  has a distal stem with an external thread  470 . The distal stem thread  470  engages an internal thread  472  in the fixed spacer  466  (best shown in  FIG.  78   ) to rotationally control axial displacement of the adjustable spacer  468  relative to the fixed spacer  466 . 
     As shown in  FIGS.  76  and  77   , the fixed spacer  466  includes radially spaced detents  474  and the adjustable spacer  468  includes a spring detent arm  476 , the free end of which engages a selected one of the detents  474  to prevent rotation and axial displacement of the adjustable spacer  468  toward the fixed spacer  466 . The free end of the spring detent arm  476  is shaped to pass over the detents  474  in one direction, thereby permitting rotation and proximal axial displacement of the adjustable spacer  468  away from the fixed spacer  466 . 
     Despite variations in the dimensions of stoppers and containers, the adjustable spacer  468  can be adjusted relative to the fixed spacer  466  to provide a consistent axial length of the stopper assembly  460 . 
     As shown in  FIG.  78   , once the container is filled, an axial load, such as a load that would be encountered when installed in the system  10 ,  200 , can be applied to the adjustable spacer  468  (and thus, the fixed spacer  466  and the stopper  462 ). Once the axial load is applied, the adjustable spacer  468  can be proximally backed out to ensure a consistent gap  478  between the proximal end of a medicament barrel  480  and the proximal face of the adjustable spacer  468 , thereby accounting for variations in the medicament barrel glass and the compressibility of any entrapped air. In other words, the spacer assembly  460  allows the adjustable spacer  468  to have a predetermined set position relative to the container  14  independent of the variables of the container  14  and stopper length. Accordingly, the start position of the spacer assembly  460  is a predetermined distance from the container  14  and the end position of the spacer assembly  460  is also a predetermined distance from the container  14  such that the travel of the stopper  462  is defined by the effective length of the plungers  52 ,  54  of the drive assembly  12 . 
     Referring to  FIGS.  79  and  80   , a base column  482  and a cap  484  of an automatically adjusting spacer  486  according to one aspect of the present invention is shown. The base column  482  includes a base portion  488  and an axially extending column  490 . According to one embodiment, the base column  482  includes a plurality of columnar protrusions  491  that each have a plurality of ratchet teeth  492  disposed on a proximal portion thereof. A locking barb  493  is disposed at the proximal end of each of the plurality of ratchet teeth  492 . The cap  484  is hollow, and a distal end of the cap  484  includes one or more axial springs  494 . According to one aspect, the axial springs  494  are bent, cantilevered arms formed during molding of the cap  484 . According to another aspect, a separate biasing member, such as a compression spring can be employed in the automatically adjusting spacer  486 . When assembled with the base column  482 , the springs  494  engage the base portion  488  and maintain an initial spacing between the base column  482  and the cap  484 . According to one aspect, the springs  494  are omitted. The cap  484  also includes a plurality of flexible cantilevered arms or tabs  496 , which each have a free proximal portion with a plurality internal of ratchet teeth  497 . The proximal end of each flexible tab  496  includes a foot  498 . 
       FIG.  81 B  illustrates the cap of the automatically adjusting spacer deployed within a proximal recess of a stopper  494  at a proximal portion of a medicament barrel. The base column  482  is assembled into the hollow cap  484  with the base portion  482  engaging the stopper  494  and the feet  498  disposed outside the proximal end of the barrel. 
     In operation, as shown in  FIGS.  81 A and  81 B , the cap  484  displaces distally relative to the base column  482  (as well as the stopper  494  and the barrel) until the proximal end of the cap  484  is flush with the end of the medicament barrel. This action causes the feet  498  to engage the internal surface of the barrel and displace radially inward, thereby forcing the ratchet teeth  492  into locking engagement with the ratchet teeth  497 . The locking barb  493 , the engagement of the ratchet teeth  492  and  497 , and the engagement of the feet  498  with the internal surface of the barrel prevents the displacement of the cap  484  relative to the base column  482 . Thus, the automatically adjusting spacer  486  can accommodate differences in stoppers, barrel diameters, and medicament fill volumes, to automatically provide a bearing surface flush the proximal end of the medicament barrel. 
     One aspect of the present invention is a spacer assembly  486  that is situated against the stopper in the container within the system. The spacer design is such that its effective length can be adjusted in order to allow the dispensing of a precise quantity of medicament. The length adjustment is intended to compensate for manufacturing tolerances within the container, the fill volume, and especially the stopper length, which can add up to ⅓ of the variability in a delivered dose using a non-adjustable spacer. The spacer length can be adjusted through several techniques, depending on the specific aspect. The spacer length can be self adjusting based on its location to the back of the container, it can be adjusted by assembly equipment at the time of final assembly of the primary container into the subassembly, and it can be made an integral part of the stopper and adjusted as a subassembly prior to filling. The adjustable spacer  486  allows a more precise volume of fluid to be injected compared to a non-adjustable stopper. 
     Referring to  FIGS.  82 - 87   , a drive assembly  500  for a drug delivery system according to one aspect of the present invention is shown. The drive assembly  500  includes an actuation button  506 , a container  508 , a needle actuator assembly  510 , an actuation release or flipper  512 , a lead screw  514 , and a plunger  516 . The lead screw includes a drum portion  518  with external radially-protruding vanes  520 , and, as best shown in  FIGS.  84  and  85    and subsequently described in greater detail, a screw thread portion  522 . Prior to activation, as best shown in  FIGS.  83  and  86    one end  513  of the actuation release  512  engages one of the vanes  520  to prevent rotation of the lead screw  514 . 
     According to one aspect, as shown in  FIGS.  84 - 86   , the screw thread portion  522  of the lead screw  514  engages internal threads of a nut  524  connected with the plunger  516 . According to another aspect, the nut and its internal threads are integrally formed with the plunger as a unitary structure. Additionally, a constant force spring  526  is received within the drum portion  518  and biases the lead screw  514  in a rotational direction. According to one aspect, the spring  526  is secured to the base cover  504 . According to another aspect, as shown in  FIGS.  84 - 86   , a drive assembly housing  528  is disposed within the system and the spring  526  is secured to the power pack housing  528 . 
     Unlike a helical spring, such as a compression spring, which has a force profile proportional to its displacement, the constant force spring  526  and the like maintain a relatively flat or even force profile over a long working length. The even force profile advantageously provides an injection force that is proportional to the spring force. This will provide a flat or even injection force, and thus, a substantially constant injection rate for the medicament. Although the spring  526  is illustrated in  FIG.  86    as having only two turns of material, one skilled in the art will appreciate that fewer or greater numbers of turns can be employed. Preferably, an assembler winds the spring  526  when the drive assembly  500  is assembled, and the spring  526  is stored in the wound position until the time of actuation. 
     Upon actuation of the system, the needle actuator assembly  510  is released to axially displace (to the right in  FIGS.  82 - 85   ) from the pre-use position to the post-use position under the influence of a biasing member  530  (best shown in  FIG.  83   ). During this displacement, the needle actuator assembly  510  bears against a second end  532  of the actuation release  512  and rotates the release  512  counter-clockwise, as shown in  FIG.  87   . This counter-clockwise rotation of the actuation release  512  frees the first end  513  thereof from engagement with the vane  520 . Subsequent to the disengagement of the first end  513  from the vane  520 , the spring  526  unwinds and drives rotation of the lead screw  514 , which, in combination with the nut  524 , advances the plunger  514  to dispense the medicament. 
     As the lead screw  514  is rotating, the rotation of the drum portion  518  and the vanes  520  is visible through a window  534  in the housing. This window  534  indicates progress of the screw in a way that is much more apparent than viewing the linear movement of the stopper  536  in the container  508 . In fact, this rotational movement is many times more sensitive than the linear movement. One skilled in the art will appreciate that the exact amount of advantage or increase depends on the pitch of screw thread portion  522  of the lead screw  514 , the diameter of the drum portion  518 , and number of vanes  520  on the drum portion  518 . 
     Referring to  FIGS.  88 - 93   , a drive assembly  600  for a drug delivery system according to a further aspect of the present invention is shown. The drive assembly  600  acts to store a spring&#39;s mechanical energy and to activate it when triggered. The drive assembly  600  includes a medicament barrel  601 , a stopper  602  slidably disposed in the barrel  601 , a first valve plunger  603 , a second valve plunger  604 , a first revolve nut  605 , and a second revolve nut  606 . The drive assembly  600  also includes a rotary indicator  607 , a locking element  608 , a constant force spring  609  disposed within the rotary indicator  607 , and an actuation release or flipper  610 . The drive assembly  600  is at least partially disposed within a housing  611  that can be assembled into a drug delivery system. 
     The constant force spring  609  is contained between the housing  611  and the rotary indicator  607  within a drum portion  616  of the rotary indicator  607 . The drive assembly&#39;s inactive state is such that energy is applied by uncoiling the spring  609  and harnessing this energy geometrically with the housing  611 , rotary indicator  607 , and actuation release  610 . When the drive assembly  600  is deactivated, the spring recoils and translates the mechanical energy into rotational motion of the rotary indicator. 
     The telescoping multi-part plunger is oriented along a force axis between the medicament barrel  601  and the rotary indicator  607 . The rotary indicator  607  features a threaded shaft  618 . According to one aspect, the threads are dual lead, and are either square or rectangular in nature. The multi-part telescoping plunger includes a two-part threaded nut (first revolve nut  605  and second revolve nut  606 ) and a two-part plunger (first valve plunger  603  and second valve plunger  604 ). The second revolve nut  606  is a threaded shaft that mates with the rotary indicator  607  and first revolve nut  605  and features matching threads on its inner and outer surfaces (internal and external threads, respectively) to mate with them. The second revolve nut  606  also has a circular collar  620  (best shown in  FIG.  92   ) on its proximal end that bottoms down on the second valve plunger  604 . The second revolve nut  606  is free to spin along the force axis. The first revolve nut  605  is also a threaded shaft that features threads on its inner diameter corresponding to the external threads of the second revolve nut  606  to mate with the second revolve nut  606 . 
     According to one aspect, on one end, the first revolve nut  605  has a hexagonal collar that press fits on the first valve plunger  603  to fixedly connect the first valve plunger  603  with the first revolve nut  605 . In the drive assembly  600 , the first revolve nut is not free to rotate and will only translate when the power module subassembly is actuated. 
     The second valve plunger  604  is a hollow cylindrical component with a small collar  622  on its distal end, a large collar  624  on its proximal end, and an extended L-shaped arm  626  (best shown in  FIG.  93   ) protruding from the large proximal collar  624 . According to one embodiment, the small collar  622  is discontinuous and features four leaf cantilevered arms or leaf springs  623  that allow the collar to bend and mate with the first valve plunger  603 . The inner surface of the second valve plunger  604  has an undercut through its length terminating at its proximal end a radially inward protruding shelf  628  of the large collar  624 . The shelf  628  engages the second revolve nut  606  within the telescoping assembly. 
     The first valve plunger  603  attaches to the stopper  602  and is also a hollow cylindrical component that mates with the second valve plunger  604 . More specifically, the first valve plunger  603  features a cylindrical protrusion  630  on its distal end to mate with the stopper  602 . According to one aspect, as best shown in  FIG.  89   , four thru slots  632  are disposed on the proximal quadrants of the first valve plunger  603  to mate with the leaf springs or arms  623  and small collar portion  622  of the second valve plunger  604 . Both the first and second valve plungers  603  and  604  are free to slide. 
     Telescoping is achieved when the constant force spring  609  recoils and the rotary indicator  607  starts spinning. The threaded attachment between the rotary indicator  607  and the second revolve nut  606  causes second revolve nut  606  to rotate. But because the second revolve nut  606  is threaded to the first revolve nut  605 , which cannot rotate and experiences resistance to distal translation due to the pressure caused by medicament in the barrel  601 , the second revolve nut  606  will displace proximally and bottom out on the second valve plunger&#39;s radially inward protruding shelf  628 . The second valve plunger  604  is prevented from displacing proximally by the housing  611 . Subsequently, and with continued rotation of the rotary indicator  607 , because the second revolve nut  606  is threaded with the first revolve nut  605  (which cannot rotate) the first revolve nut  605  translates distally to push the first valve plunger  603  (and the stopper  602 ) to dispense medicament from the barrel  601 . 
     The first valve plunger  603  displaces distally relative to the second valve plunger  604  until the small collar sections  622  (respectively disposed on the distal ends of the leaf springs or arms  623  of the second valve plunger  604 ) engage the corresponding proximal ends of the slots  632  of the first valve plunger  603 . This locks the relative positon of the first and second valve plungers  603  and  604 , with continued rotation of the rotary indicator  607 , both valve plungers translate distally while also pushing the second revolve nut along (because of its proximal engagement with the shelf  624 ). 
     The initial and final positions of the telescoping plunger, and thus the medicament dose, are controlled by the rectangular thread form of the threaded shaft  618  of the rotary indicator  607 , a threaded shaft on the drum portion  616  of the rotary indicator  607 , and a stepped pin that acts as the locking element  608 . According to one aspect, threaded shaft on the drum portion  616  of the rotary indicator  607  is single lead, and because the rest of the components in the telescoping chain have dual lead threads, the axial travel of the other threaded components is twice the axial travel of the lock  608  relative to the rotary indicator. 
     According to one embodiment, the lock  608  is cylindrical and features a domed tip on one end and a cylindrical collar on the other. The threads on the exterior of the rotary indicator&#39;s drum portion  616  along with a slot and undercut  636  at the bottom of the housing  611  captures the lock  608  in place, allowing it to slide parallel to the force axis. Thus, as the spring  609  is released and the rotary indicator  607  turns, the lock  608  translates as well and creates a positive stop when the distal end of the thread on the exterior of the rotary indicator&#39;s drum portion  616  is reached. 
     One benefit of aspects of the drive assembly  600  include the use of a constant force spring  609 , the mechanical energy of which is converted into substantially constant linear force to the medicament in the barrel  601 . In turn, this creates a uniform medicament delivery rate. Another benefit is that employing the telescoping plunger driven by a thread form, the drive assembly can create in-line space savings of up to 0.75 inches compared to other plunger designs. Additionally, the drive assembly provides a controlled medicament dose through an initial and final mechanical constraint within the same component. 
     As previously noted, other drug delivery systems utilize a compressed coil spring, which exerts a maximum force at actuation that eventually decreases as the spring expands. A decreasing force at the plunger translates into variable medicament delivery time and medicament exit pressure. By using a constant force spring, the force exerted on the plunger is constant from the beginning to the end of the dosage. In addition, the distance a coil spring has to travel in addition to the length of a static plunger that needs translate inside the drug container can create a long assembly. In contrast, in embodiments of the present invention, the constant force spring is contained radially and does not require any additional space before or after activation. Furthermore, the aspects of the telescoping plunger allow that the plunger length of the can be significantly reduced in comparison to the length of a static plunger. 
     Previous drug delivery systems have variable dose accuracy performance because the mechanical components enabling the drug delivery create a geometric dependence by bottoming down on the container, which cannot be fabricated with tight tolerances. Some embodiments of the present invention create a control to the start and end times of the translating plunger via a thread form in the rotary indicator and the use of the constant force spring. 
     The drive assembly creates a space saving geometry in addition to well-controlled time, volume and pressure for the drug delivery device, which translates to a more attractively compact and precise drug delivery device. 
     Some aspects of the drive assembly implement three rotating threaded shafts to create a linear space savings of about 0.75 inch. In other aspects, the same concept can be employed using two rotating threaded shafts and result in a space savings of about 0.5 inch. Some aspects of the present invention convert the rotational energy of a constant force spring to a translational force motion of a plunger. 
     Referring to  FIGS.  94 - 100   , a spacer assembly  660  according to a further aspect of the present invention is shown. The spacer assembly  660  is similar to the spacer assembly  460  discussed above and shown in  FIGS.  76 - 78    and operates in a similar manner to achieve similar advantages. The spacer assembly  660  includes a fixed spacer  666  and an adjustable spacer  668 . The fixed spacer  666  is configured to be received by the stopper  462  with lugs  670  engaging the stopper  462  to secure the fixed spacer  666  within the stopper  462 , although other suitable securing arrangements, such as threads, may be utilized. The fixed spacer  666  includes interior threads  672  that receive exterior threads  678  of the adjustable spacer  668 . The fixed spacer  666  includes a plurality of detents  674  positioned on a helical portion of the fixed spacer  666 . The adjustable spacer  668  includes a spring detent arm  676  that engages one of the detents  674  to prevent rotation and axial displacement of the adjustable spacer  668  relative toward the fixed spacer  666 . The spring detent arm  676  is shaped and configured to pass over the detents  674  in one direction to allow rotation and axial displacement of the adjustable spacer  668  away from the fixed spacer  666 . The adjustable spacer  668  may be initially secured to the fixed spacer  666  via the threads  672 ,  678  by applying a force to the top of the spring detent arm  676 , which biases the spring detent arm  676  away from the detents  674  to allow the spacers  666 ,  668  to be secured to each other. Accordingly, in the same manner as discussed above in connection with spacer assembly  460 , the adjustable spacer is free to rotate in one axial direction to adjust the length of the spacer assembly  660 . 
     Referring again to  FIGS.  94 - 100   , the spacer assembly  660  further includes a shim  680  configured to be received and secured to the adjustable spacer  668 . Rather than providing a plurality of sizes of adjustable spacers  468 ,  668 , a plurality of shim  680  sizes can be provided to accommodate a plurality of different fill volumes within the container  14 . The shim  680  may be secured to the adjustable spacer  668  via a connector  682  extending from the shim  680  that is received by the adjustable spacer  668  using a snap-fit, although other suitable securing arrangements may be utilized. A center portion  684  of the fixed spacer  666  is configured to be engaged while the adjustable spacer  668  is rotated relative to the fixed spacer  666  to prevent rotation of the fixed spacer  666  along with the adjustable spacer  268 . The center portion  684  of the fixed spacer  666  is accessible through an opening in the shim  680 . 
     Elements of one disclosed aspect can be combined with elements of one or more other disclosed aspects to form different combinations, all of which are considered to be within the scope of the present invention. 
     While this disclosure has been described as having exemplary designs, the present disclosure can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure 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 disclosure pertains and which fall within the limits of the appended claims.