Patent Publication Number: US-11642467-B2

Title: Drive assembly for moving piston within container

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/080,130, filed Aug. 27, 2018, which is the National Stage of International Application No. PCT/US2017/022259, filed Mar. 14, 2017, which claims priority and the benefit of U.S. provisional patent application Ser. No. 62/310,961, filed on Mar. 21, 2016 entitled MEDICAL DELIVERY DEVICE WITH AXIALLY EXPANDABLE DRIVE MEMBER, the disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to medical delivery devices such as injection devices. 
     Conventional injection devices are often used to inject a medicament into a patient. 
     For example, injection pens that receive disposable cartridges containing insulin are often used by diabetes patients. Such pens generally include an elongate rod that acts on a piston within the cartridge. As the rod advances the piston, the medicament within the cartridge is dispensed through a needle and into the patient. 
     The rod must project outwardly from the cartridge to engage a driving mechanism within the pen throughout the injection process including when the rod has reached the limit of forward advancement into the cartridge. The rod must also be accommodated within the pen when it is has been fully retracted so that the rod may be inserted into a fresh cartridge that is filled with medicament. As a result, conventional injection pens are generally elongate and thin with the length of the injection pen being more than twice the length of the cartridge barrel in which the medicament is contained. Similarly, for non-pen-shaped refillable injection devices, the length of the device is generally more than twice the length of the cartridge barrel in which the medicament is contained. 
     When such injection devices are used to self-administer the medicament at different times throughout the day, it is desirable for the injection device to be readily carried by the user. For example, diabetes patients often self-administer insulin using injection devices and carry the devices with them throughout the day. While conventional injection pens and similar devices are sufficiently small to be portable, the length of such devices often makes transport of the devices awkward. 
     SUMMARY 
     In one embodiment, a drive assembly for a device for use with a container is disclosed. The container has a container body and a slidable piston therein. The drive assembly includes a drive ribbon movable between an axially retracted configuration and an axially extended configuration to advance said piston axially within the container body. The drive ribbon includes a proximal edge section and a distal edge section. During movement of the drive ribbon, a retracted portion of the drive ribbon defines a spiral about a drive axis, and an extended portion of the drive ribbon defines a helical column about said drive axis in which the proximal edge section of the drive ribbon is in engaged with the distal edge section that is adjacent to the proximal edge section. The extended portion defines a distal end of the drive ribbon that is disposed within the container body to advance said piston. 
     In another embodiment, a medical delivery device is disclosed, including an axially expandable drive assembly, and a container having a container body and a slidable piston therein. The axially expandable drive assembly includes a drive ribbon movable between an axially retracted configuration and an axially extended configuration to advance said piston axially within the container body. The drive ribbon includes a proximal edge section and a distal edge section. During movement of the drive ribbon, a retracted portion of the drive ribbon defines a spiral about a drive axis, and an extended portion of the drive ribbon defines a helical column about said drive axis in which the proximal edge section of the drive ribbon is in engaged with the distal edge section that is adjacent to the proximal edge section. The extended portion defines a distal end of the drive ribbon that is disposed within the container body to advance said piston. 
     In yet another embodiment, a medical delivery device is disclosed, including a mechanical drive, an axially expandable drive assembly, and a container having a container body and a slidable piston therein. The axially expandable drive assembly includes a drive ribbon movable between an axially retracted configuration and an axially extended configuration to advance said piston axially within the container body. The drive ribbon includes a proximal edge section and a distal edge section. During movement of the drive ribbon, a retracted portion of the drive ribbon defines a spiral about a drive axis, and an extended portion of the drive ribbon defines a helical column about said drive axis in which the proximal edge section of the drive ribbon is interlockable with the distal edge section that is adjacent to the proximal edge section. The extended portion defines a distal end of the drive ribbon that is disposed within the container body and contactable with said piston. The mechanical drive is operably coupled with the drive ribbon to move the drive ribbon from the axially retracted configuration to the axially extended configuration. 
     It is noted that several different features of the delivery device are disclosed herein and these features may be combined in various different configurations. While several different combinations of such features are described herein, the person having ordinary skill in the art will realize that further such combinations not explicitly described herein are also possible and enabled by the present disclosure and are within the scope of the present application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG.  1 A  is a side view of a first embodiment of a delivery device. 
         FIG.  1 B  is an end view of the first embodiment. 
         FIG.  1 C  is another end view of the first embodiment. 
         FIG.  1 D  is side view of the first embodiment with the cap removed and a needle assembly attached. 
         FIG.  1 E  is an end view of the embodiment of  FIG.  1 D . 
         FIG.  1 F  is a perspective view of the first embodiment. 
         FIG.  2 A  is a side view of a prior art delivery device. 
         FIG.  2 B  is an end view of the prior art device. 
         FIG.  2 C  is another end view of the prior art device. 
         FIG.  2 D  is side view of the prior art device with the cap removed and a needle assembly attached. 
         FIG.  2 E  is an end view of the prior art device of  FIG.  2 D . 
         FIG.  2 F  is a perspective view of the prior art device. 
         FIG.  3 A  is a side view of a second embodiment of a delivery device. 
         FIG.  3 B  is an end view of the second embodiment. 
         FIG.  3 C  is another end view of the second embodiment. 
         FIG.  3 D  is side view of the second embodiment with the cap removed and a needle assembly attached. 
         FIG.  3 E  is an end view of the embodiment of  FIG.  3 D . 
         FIG.  3 F  is a perspective view of the second embodiment. 
         FIG.  4    is a partial schematic perspective view of the drive assembly. 
         FIG.  5    is a partial perspective view of the drive ribbon. 
         FIG.  6    is another perspective view of the drive ribbon. 
         FIG.  7    is another partial perspective view of the drive ribbon. 
         FIG.  8    is a detail partial perspective view of the drive ribbon. 
         FIG.  9    is another detail partial perspective view of the drive ribbon. 
         FIG.  10    is another detail partial perspective view of the drive ribbon. 
         FIG.  11    is a schematic perspective view showing an extended portion of the drive ribbon. 
         FIG.  12    is a perspective view of a ribbon thrust member. 
         FIG.  13    is a schematic perspective view showing a ribbon bearing assembly around a drive ribbon. 
         FIG.  14    is a schematic perspective view showing a mechanical drive assembly for engaging the drive ribbon. 
         FIG.  15    is a schematic perspective view of an alternative mechanical drive assembly. 
         FIG.  16    is a schematic perspective view of a drive ribbon and a storage bobbin. 
         FIG.  17    is a schematic view of the first embodiment. 
         FIG.  18    is partial perspective view showing the drive assembly and a medicament container. 
         FIG.  19    is another partial perspective view showing the drive assembly and a medicament container. 
         FIG.  20    is a partial perspective view of the drive assembly. 
         FIG.  21    is a side view of another embodiment. 
         FIG.  22    is a partial exploded view of the embodiment of  FIG.  21   . 
         FIG.  23    is a cross sectional view taken along line  23 - 23  of  FIG.  26   . 
         FIG.  24    is a top view of the drive ribbon of the embodiment of  FIG.  21   . 
         FIG.  25    is a view of detail D 25  in  FIG.  24   . 
         FIG.  25 A  is an end view of the drive ribbon of  FIG.  24   . 
         FIG.  26    is a side view of a portion of the embodiment of  FIG.  21    with the housing removed. 
         FIG.  27    is a cross sectional view taken along line  27 - 27  of  FIG.  26    and also showing the ribbon bearing member. 
         FIG.  28    is a side view of the embodiment of  FIG.  21    with the housing removed. 
         FIG.  29    is an end view of the embodiment of  FIG.  21    with the housing removed. 
         FIG.  30    is a side view of another embodiment with the housing removed. 
         FIG.  31    is an end view of the embodiment of  FIG.  30    with the housing removed. 
         FIG.  32    is a perspective view of the embodiment of  FIG.  30    with the housing removed. 
         FIG.  33    is an exploded view of the embodiment of  FIG.  30    without the housing. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, in one form, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed. 
     DETAILED DESCRIPTION 
     A first embodiment of a compact medical delivery device  20  is shown in  FIGS.  1 A- 1 F  while a second embodiment of a compact medical delivery device  20 A is illustrated in  FIGS.  3 A- 3 F . One conventional prior art medical delivery device  21  is shown in  FIGS.  2 A- 2 F . The device  21  illustrated in  FIGS.  2 A- 2 F  is a Kwikpen injector commercially available from Eli Lilly and Company which has headquarters in Indianapolis, Ind. and has a length of approximately 145 mm. As can be seen in a comparison of  FIGS.  1 A,  2 A and  3 A , the compact medical delivery devices  20 ,  20 A are considerably shorter in length than the conventional device  21 . The conventional device  21  is, however, thinner than compact devices  20 ,  20 A as can be seen with reference to  FIGS.  1 B,  1 C,  2 B,  2 C,  3 B and  3 C . 
     Medical delivery device  20  receives a medicament container  22 . As schematically depicted in  FIG.  17   , medicament container  22  includes a container body  24  holding a medicament  25 , for example, insulin, inside its cylindrical barrel. A piston  26  is disposed within body  24  and advancement of piston  26  within container body  24  expels medicament  25  through outlet  28 . In the illustrated embodiment, outlet  28  is an injection needle having one end that pierces a septum of the container and an opposite end that can be inserted into a patient to inject the medicament  25 . 
     Device  20  also includes a support structure  30  that is adapted to support medicament container  22 . Support structure  30  also functions as a device housing in the illustrated embodiment and is also referred to herein as a housing. Housing  30  also supports a drive assembly  32  for advancing piston  26  and is adapted to be held in a human hand. Device  20  and device  20 A are generally similar but do have different housings with housing  30 A of device  20 A being slightly larger than housing  30 . 
     Both housings  30 ,  30 A include a removable cap  31 ,  31 A which are releasably securable to housings  30 ,  30 A and cover outlet/needle  28  when the device is not being used.  FIGS.  1 D and  3 D  illustrate devices  20 ,  20 A with caps  30 ,  30 A removed while  FIGS.  1 A and  3 A  show caps  31 ,  31 A installed on housings  30 ,  30 A. As can be seen in  FIGS.  1 D and  3 D , the caps  30 ,  30 A are used to cover a standard needle that also has a removable, cylindrical inner needle shield  29 . 
     As can be seen with reference to  FIGS.  3 A and  3 D , removal of cap  31 A exposes nearly the entire longitudinal length of container body  24 . Generally, container body  24  will be formed out of glass or other transparent material. By exposing this length of container body  24 , the user can visually determine the quantity of medicament  25  remaining in cartridge body  24 . In contrast, housing  30  only exposes the end of medicament container  22  near outlet  28  and provides an open slot  42  in housing  30  to allow the user to visually determine the quantity of medicament  25  remaining in container body  24 . A transparent material can be used to form a window instead of using an open slot  42  to allow for such visual inspection. 
     Housing  30  includes a control knob  44  for controlling the setting of a dosage, a button  45  for initiating an injection and an electronic display  46  located on the end of housing  30 . For example, knob  44  can be rotated to set the injection dosage and central button  45  depressed to initiate the injection process. Housing  30 A includes controls  44 A and an electronic display  46 A on the side of housing  30 A. Controls  44 A are used to set an injection dosage while control button  45 A on the end of housing  30 A is used to initiate the injection procedure. While the illustrated embodiments have actuators located on the end of the housing for initiating an injection other locations on the housing for such a feature may also be employed. For example, the thicker body of the housing relative to conventional pens may cause some people to grasp the device differently and an actuator which initiates the injection procedure may alternatively be deployed on the side of housing. The grip of the patient may also depend upon where on the patient&#39;s body the injection will occur and it may also be desirable in some embodiments to include multiple actuators on the housing to facilitate various gripping scenarios. 
     Medicament container  22  has a storage volume of at least 3 mL and is shown in the form of a conventional medicament cartridge. Support structure  30  may define an axial length of no more than 110 mm, or even an axial length of no more than 100 mm. The axial length of support structures  30 ,  30 A are indicated by reference numbers  48 ,  48 A respectively in  FIGS.  1 A and  3 A . As evident from  FIGS.  1 A and  3 A , the axial length of the support structure as referred to herein includes the removable caps. In the illustrated embodiments, the capped axial lengths  48 ,  48 A are both 105 mm. In the illustrated embodiment, the axial length  48 ,  48 A of devices  20 ,  20 A is less than twice the axial length  49  of container  22  (not including needle  28 ). A standard 3 mL medicament cartridge used for insulin has an axial length of 64 mm and a plunger travel of approximately 43 mm. 
     It is the use of a drive assembly  32  having a drive ribbon  40  which allows devices  20 ,  20 A to have relatively short axial lengths  48 ,  48 A.  FIG.  17    provides a schematic overall view of device  20  showing how container  22  is positioned in support structure  30  relative to drive assembly  32 . Drive assembly  32  includes a mechanical drive  38  coupled with drive ribbon  40 . Drive ribbon  40  is incrementally moveable between a retracted configuration and an extended configuration. With a medicament container  22  installed in device  20 , the movement of drive ribbon from a retracted configuration to an extended configuration extends drive ribbon  40  and causes the advancement of piston  26  and the consequent discharge of medicament through outlet  28 . 
     Selective rotation of drive ribbon  40  by mechanical drive  38  causes either the retraction or extension of drive ribbon  40 . In the illustrated embodiment, mechanical drive  38  includes a DC electric motor  34  and a battery  36 , e.g., a single AAA battery or rechargeable lithium ion cell, for powering motor  34 . Alternative arrangement could employ an external electrical power source or an alternative form of torque supply. For example, a torque spring or other arrangement could be manually tensioned with the selective release of such tension providing the torque necessary to drive the operation of drive assembly  32 . 
     Mechanical drive  38  is selectively coupled with the drive ribbon to rotate ribbon  40  about a drive axis  50  in either rotational direction. In a first rotational direction it causes drive ribbon  40  to extend axially, in the opposite second rotational direction it causes the retraction of drive ribbon  40 . Rotation of drive ribbon  40  shifts the ribbon between spiral and helical configurations. When drive ribbon  40  is fully extended, the majority, if not all, of drive ribbon  40  will be in a helical configuration. When drive ribbon  40  is fully retracted, the majority, if not all, of drive ribbon  40  will be in a spiral configuration. In most axial positions, an extended portion  52  of drive ribbon  40  will define a helix while a retracted portion  54  of drive ribbon  40  will define a spiral. Rotation of drive ribbon  40  causes the ribbon to incrementally shift between the two configurations. 
       FIGS.  5 - 11    provide detailed views of drive ribbon  40 .  FIG.  6    illustrates ribbon  40  in a configuration wherein ribbon  40  is partially extended. In  FIG.  6   , retracted portion  54  defines a spiral while extended portion  52  defines a helix. In retracted portion  54 , the axial end surface of distal edge section  56  of ribbon  40  for each of the spiral wraps lie in a common plane  110 , similarly, the axial end surface of proximal edge section  58  of each of the spiral wraps also lie in a common plane  112 . This spiral arrangement allows the retracted portion  54  of ribbon  40  to be stored in a minimal axial space that is approximately equal to the width of ribbon  40 . In the extended portion  52  of drive ribbon  40 , proximal edge section  56  is directly bearingly engaged with an adjacent portion of the distal edge section  58 . 
     It is noted that  FIGS.  6  and  11    show helical extended portion  52  with engaged edges while  FIGS.  5  and  7    show an exploded view of drive ribbon  40 .  FIGS.  5  and  7    are provided for purposes of explaining and showing the details of ribbon  40 . In use, drive ribbon  40  would not assume the exploded configuration shown in  FIGS.  5  and  7   . 
     One of the proximal  58  and distal  56  edge sections of ribbon  40  define a radially extending lip  60  to directly and bearing engage the other one of the proximal  58  and distal  56  edge sections. As can be seen in  FIG.  8   , in the illustrated embodiment, it is distal edge section  56  that includes a radially extending lip  60  and that the illustrated lip  60  extends radially inward. Lip  60  includes an axially facing surface  62  that is generally perpendicular to axis  50  which engages opposing proximal edge  58  to allow for the transfer of axially compressive forces. Ribbon  40  also provides for the transfer of torque forces. One of the proximal  58  and distal  56  edge sections of ribbon  40  defines a plurality of projections  64  with the other one of the proximal  58  and distal  56  edge sections defining a plurality of cooperating recesses  66 . The interfitting of projections  64  with recesses  66  allow for the transfer of torque and help keep the proximal  58  and distal  56  edge sections interlocked as ribbon  40  is rotated. As can be seen in  FIGS.  8  and  9   , in the illustrated embodiment, it is distal edge section  56  that defines the plurality of recesses  66  and it is proximal edge section  58  that defines the plurality of projections  64 . It is noted that it is the engagement of sidewall surfaces  68  of recesses  66  with sidewall surfaces  70  of projections  64  that allow for the transfer of torque. Sidewall surfaces  68  and  70  both define planar surfaces that are oriented substantially radially relative to axis  50 . This radial orientation of the engaged sidewall surfaces resists shear forces along the joint and thus torsion in the column formed by the extended ribbon  40 . Various other arrangements and configurations of the cooperating projections  64  and recesses  66  can be used. For example, recesses  66  could form openings that extend through the full thickness of ribbon  40 . As a result of the resistance to shear forces along joint formed by the engaged edges, the resulting column carries torsional loads preventing one end from rotating relative to the opposite end. It also resists the twisting and uncoiling of the column formed by extended portion  52  of ribbon  40 . 
     Distal  56  and proximal  58  edge sections also include radially extending flanges  72 ,  74  respectively. Flange  72  on distal edge section  56  extends radially inwardly while flange  74  on proximal edge section  58  extends radially outwardly. When the distal and proximal edge sections  56 ,  58  are engaged, radially outwardly extending flange  74  is seated in groove  76  defined by lip  60  and flange  72 . Engagement of flanges  72 ,  74  provides resistance to axially acting tensile forces and prevents the engaged distal and proximal edge sections  56 ,  58  from axially separating when subjected to axially acting tensile forces. 
     When deployed the ribbon  40  is formed into a helix to form an interlocked rigid cylindrical column. Interlocking of the distal  56  and proximal  58  edge sections gives the column axial and torsional rigidity and strength as described above. The ribbon edge sections  56 ,  58  mechanically engage one another in a detachable and re-attachable manner. The deployment process, discussed below, is continuous, enabling a smooth and accurate injection process. 
     The column formed by extended portion  52  of ribbon  40  acts as a continuous tubular structure and will primarily carry compressive axial loads which correspond to the force necessary to expel medicament from container  22 . It will also carry some torsional loads generated by the rotation of ribbon  40  as ribbon  40  is extended and retracted. Although no axial tensile loads are generally applied to ribbon  40 , the use of interfitting flanges  72 ,  74  provides resistance to axial tensile loads and thereby prevents the engaged edges of ribbon  40  from axial separation during use and enhances the reliability of ribbon  40 . 
     Drive ribbon  40  also defines a plurality of gear teeth  76  that are engageable with mechanical drive  38  whereby mechanical drive  38  can rotate drive ribbon  40  by transmitting a rotational force through the plurality of gear teeth  76 . As can be seen in  FIGS.  8  and  9   , gear teeth  76  are disposed on the radially inward facing surface of ribbon  40 . While gear teeth  76  are disposed on the inner face of ribbon  40 , an alternative arrangement may utilize gear teeth on the radially exterior surface of ribbon  40 .  FIG.  10    illustrates a set of gear teeth  78  on the exterior surface of ribbon  40  that are formed by a series of recesses. Either internal  76  or external  78  gear teeth can be used to rotate ribbon  40 . Still other variations are also possible, for example, gear teeth could be employed on the proximal edge of ribbon  40  or both internal and external gear teeth could be employed on the same ribbon. Engagement and rotation of ribbon  40  by mechanical drive  38  is discussed in greater detail below. 
     The illustrated embodiments of drive ribbon  40  utilize a flexible polymeric ribbon that has been machined to define the various features of the ribbon. Nylon, polypropylene and high density polyethylene are examples of suitable polymeric materials that may be used to form ribbon  40 . While the illustrated embodiments are machined, alternative embodiments could use a molding process to form a polymeric ribbon  40  with all of its edge features. It is envisioned that molding the ribbon in a flat arrangement and then rolling the ribbon into a spiral configuration will be the most efficient manufacturing method of forming a ribbon  40 . 
     Other materials may also be used to form ribbon  40 . For example, thin metal strip could be used to form ribbon  40 . Photo etching, laser etching or other suitable micro machining methods could be used to form the individual features of ribbon  40 . Alternatively, a metal ribbon could be formed by diffusion bonding two half-thickness layers instead of using a single metal strip. 
     Still other ribbon embodiments might take the form of an overmolded metal strip. The metal strip would be provided with the distal edge features and the overmolded plastic portion of the ribbon would form the proximal edge features. This approach combines the desirable stiffness, elasticity and creep resistance of metal with the low friction and manufacturing ease of forming small features in molded plastic. For all embodiments of ribbon  40 , it is desirable for ribbon  40  to be flexible so that ribbon  40  can be extended and retracted, and undergo concomitant elastic strains, without permanent deformation. 
     The distal end of ribbon  40  must exert axial forces on piston  26 . To enable such a transfer of force, a bearing member  80  is supported on drive ribbon  40  proximate distal end  81  of drive ribbon  40  and is adapted to exert an axial force on piston  26 . The column formed by ribbon  40  will rotate as it extends, however, piston  26  of container  22  does not rotate. A rotational bearing  82  is provided at the distal end  81  of ribbon  40  to account for the relative rotational motion and allow relative rotational movement between drive ribbon  40  and piston  26  about drive axis  50 . In the illustrated embodiment, rotational bearing  82  is a jewel bearing located on bearing member  80 . In the illustrated embodiment, bearing member  80  is shown as an integral part of drive ribbon  40 , but the two can also be separate parts with a suitable joint therebetween. As can be seen in  FIG.  10   , a transfer member  84  acts on piston  26  or other intermediate part and includes a projecting member  86  that rotates within jewel bearing  82 . Transfer member  84  pushes against and advances piston  26  and does not rotate relative to piston  26  as ribbon  40  is advanced. As ribbon  40  advances and ribbon  40  rotates relative to piston  26 , projecting member  86  rotates within rotational bearing  82 . Since loads are predominantly axial and minimizing frictional losses is desirable, the revolute joint at this location may be a low-friction jewel bearing, however, other arrangements allowing for relative rotation of ribbon  40  and piston  26  may also be used. 
     A thrust member  88  ( FIG.  12   ) is operably disposed between support structure  30  and drive ribbon  40 . Thrust member  88  is engaged with a portion of proximal edge  58  of ribbon  40  when drive ribbon  40  is at least partially extended. More specifically, thrust member  88  engages ribbon  40  where ribbon  40  transitions between a spiral configuration and a helical configuration and also bears axial compressive forces acting on ribbon  40 . In the illustrated embodiment, drive ribbon  40  is a one-piece unitary ribbon and all axial forces transferred between bearing member  80  and thrust member  88  when the drive ribbon  40  is at least partially extended are transferred by the unitary one-piece ribbon  40 . The axial compressive load created by bearing on piston  26  is transmitted to the support structure  30  through bearing surface  91  on the axial end of thrust member  88  opposite ramp  90 . In this regard, it is noted that some of the axial compressive force acting on ribbon  40  will act on the medicament in container  22  causing the ejection of the medicament through outlet  28 . 
     It is also noted that the axial force exerted by the transfer member  84  on piston  26  is at least partially transmitted to support structure  30  through the medicament container  22  otherwise, container  22  would simply move axially together with ribbon  40  as ribbon  40  was extended. If container  22  is held within device  20 ,  20 A by a friction fit within support structure  30 , this friction fit may be sufficient to hold container  22  in place and absorb the axially compressive forces acting on container. Alternatively, a structural retainer could be used to retain container  22  in support structure  30 .  FIG.  18    schematically depicts how shoulder surface  128  of container  22  could be engaged by sliding a retainer with bearing surface  130  into engagement with shoulder  128 . Compressive forces would be transferred from shoulder  128  to surface  130  and, thus, to the retainer which is a part of support structure  30 . 
     Thrust member  88  is rotationally fixed relative to housing  30  and defines a helical ramp  90  that engages proximal edge  58  of ribbon  40 . Compressive axial forces are transferred between ribbon  40  and thrust member  88  at helical ramp  90 . Helical ramp  90  also guides the transition of ribbon  40  between its spiral and helical configurations. 
     When the drive ribbon is rotated in a first direction so that the proximal edge  58  engaged with ramp  90  is sliding upward and in a distal direction, a transition portion  53  of ribbon  40  that is engaged with helical ramp  90  is guided by ramp  90  into a helical arrangement and is transitioned from the retracted (spiral) configuration  54  to the extended (helical) configuration  52 . Similarly, when ribbon  40  is rotated in a second, opposite, direction, transition portion  53  of the ribbon  40  engaging the helical ramp  90  slides down ramp  90  and transitions from the extended (helical) configuration  52  to the retracted (spiral) configuration  54 . 
     Due to the limited area of contact between proximal edge section  58  and ramp  90 , the friction resisting sliding movement is relatively small. To further limit frictional resistance to sliding along ramp  90 , thrust member  88  may be formed out of a lubricious polymeric material such as acetal. Proximal edge section  58  may form a continuous surface and avoid recesses or interruptions in the portion of proximal edge section  58  that engages ramp  90  to avoid the increased resistance and greater wear that such irregular surfaces are likely to cause. 
     Alternative thrust support surfaces may also be used. For example, instead of using a sliding surface, small rollers could be arranged in helical pattern along the outer perimeter of the thrust member. Due to the small scale and small forces generally anticipated when using ribbon  40  to inject a medicament, the greater manufacturing difficulties and expense that such rollers would require will generally not be warranted. 
     An axially extending wall  92  is located on the radially inner edge of helical ramp  90  and extends in the distal direction. Wall  92  prevents proximal edge section  58  from being biased radially inward out of engagement with ramp  90  by ribbon bearing member  100 . Ribbon bearing member  100  circumscribes thrust member  88  and exerts a radially inward bearing force on drive ribbon  40  proximate helical ramp  90 . Ribbon bearing member  100  includes a sleeve  102  that surrounds thrust member  88  and a plurality of rollers  94  mounted within sleeve  102 . Rollers  94  are engageable with drive ribbon  40  and exert a radially inward force and bias drive ribbon  40  onto helical ramp  90  as drive ribbon  40  is rotated. Rollers  94  include a cylindrical disk  96  which engages ribbon  40  and axle stubs  98  extending from opposite sides of disk  96  which are rotatably mounted on the inner surface of sleeve  102 . 
     Ribbon  40  is fed onto helical ramp  90  from the retracted portion  54  of ribbon  40  which is stored within bobbin  104  in a spiral configuration as can be seen in  FIG.  16   . The proximal end  106  of ribbon  40  is secured to bobbin  104  and as ribbon  40  is rotated, bobbin  104  rotates with ribbon  40 . In the illustrated embodiment, bobbin  104  is a cylindrical storage bobbin and is rotatably mounted on thrust member  88 . In the illustrated embodiment, bobbin  104  includes an axially extending slot  108  in which proximal end  106  of ribbon  40  is secured. Various other methods may also be used to secure proximal end  106  to bobbin  104 . Both ribbon  40  and bobbin  106  rotate about axis  50 . 
     As can be seen in  FIG.  16   , for the retracted portion  54  of drive ribbon  40  disposed within bobbin  104 , the axial end surface of distal edge section  56  of drive ribbon  40  lies in a first plane  110  oriented perpendicular to drive axis  50  and the axial end surface of proximal edge section  58  of drive ribbon  40  lies in a second plane  112  oriented perpendicular to drive axis  50 . This spiral configuration allows ribbon  40  to be stored in a minimal amount of space and is particularly useful for reducing the axial length of the storage space required to store ribbon  40 . The distance between planes  110 ,  112  is equivalent to the width of ribbon  40 , i.e., the shortest distance between the opposing axial end surfaces defined by distal and proximal edge sections  56 ,  58  of ribbon  40 . 
     As can also be seen in  FIG.  16   , the retracted portion  54  of ribbon  40  fills storage bobbin  104  from the radially outermost location within bobbin  104  inwardly with the innermost portions of the stored ribbon  40  still defining a larger radius than the radius of helical ramp  90 . This facilitates the movement of ribbon  40  from the stored spiral configuration of retracted portion  54  to the extended helical configuration of extended portion  52  by engagement of ribbon  40  with ribbon bearing member  100 . 
     It is desirable for ribbon  40  to naturally assume a coiled shape having a radius larger than the inner diameter of bobbin  104  so that ribbon  40  will expand to engage the inner surface of bobbin  104  when it is stored therein. Some plastic materials tend to creep and take on their stored dimensions. The use of a metal ribbon or an overmolded metal ribbon will minimize the risk of having the ribbon fail to expand and fill the radially outermost portions of bobbin  104 . 
     While the illustrated embodiment utilizes a cylindrical storage bobbin  104  for ribbon  40 , alternative embodiments are also possible. For example, a plurality of abutments within housing  30  may be sufficient for some embodiments, or, if ribbon  40  has the appropriate physical properties, it might naturally assume a spiral configuration when disengaged from an adjacent turn of the ribbon and thereby avoiding the use of a storage bobbin. 
     The size of storage bobbin  104  is chosen so that it will be adequate when ribbon  40  is fully retracted. When fully retracted, ribbon  40  has a minimum radius that is larger than the radius of ramp  90  which corresponds to the radius of the helical extended portion  52  of ribbon  40 . When ribbon  40  is rotated in a direction that feeds stored ribbon  40  from storage bobbin  104  onto helical ramp  90 , each additional coil of the ribbon transitions from the inside of the storage spiral onto the column formed by extended portion  52 . The transition portion  53  of ribbon  40  gets radially smaller as it moves from its stored configuration in bobbin  104  onto ramp  90  and it becomes tangent to the helical column formed by extended portion  52  at the point where the ribbon  40  joins the helical column of extended portion  52 . As the ribbon is moved radially inward along this helical path, the features along the distal edge section  56  of the transition portion  53  of ribbon  40  engage the features of the proximal edge section  58  of the lowermost turn of the extended portion  52  of ribbon  40 . 
     The position where the radial lay-in and ribbon edge engagement occurs remains fixed within the device and fixed relative to thrust member  88 . Distally from this point of engagement the ribbon is a helical column forming the extended portion  52 ; proximally from this point of engagement the ribbon relaxes through the transition helical spiral (transition portion  53 ), into the spiral arrangement (retracted portion  54 ) contained within storage bobbin  104 . 
     All of the coils of ribbon  40  distal of the engagement location, i.e., the extended portion  52  of ribbon  40 , are kept engaged with each other by the ribbon coil proximally below them. At the point of engagement, the proximal edge of the ribbon coil being engaged is still un-engaged and is biased radially inward by ribbon bearing member  100  so that the ribbon coil being engaged does not expand radially outward and fail to engage. At the same time, ribbon  40  must be maintained in a position encircling axis  50 . These tasks are accomplished by external bearing  100  which surrounds roughly one full helical coil of ribbon  40 . Relative to this fixed bearing  100 , ribbon  40  both rotates and translates as ribbon  40  advances (or retracts) along its helical path. 
     As discussed above, the illustrated embodiment utilizes a ribbon bearing member  100  that includes a plurality of rollers  94 . In this arrangement, each of the rollers  94  is tangent to the cylinder defined by ribbon  40  and tilted at the helix angle. Rollers  94  roll rather than slide along the cylinder defined by ribbon  40 . The position of the rollers  94  establish and then maintain the engagement of the ribbon edge sections  56 ,  58  while keeping the overall helical structure of the engaged ribbon edges supported both radially and axially. While the disclosed rollers  94  are effective, alternative arrangements that are simpler and which can be more cost-effectively manufactured may be suitable for some applications. For example, small ball bearings disposed in a groove similar to a conventional ball bearing or that found in a ball screw may be suitable for some applications. A simple bushing formed out of a lubricious polymeric material may also be adequate for some applications. 
       FIG.  4    provides a partially transparent view of drive assembly  32  and views of alternate drive assemblies are provided in  FIGS.  14  and  15   . In the illustrated embodiments, drive assembly  32  includes a battery powered electrical motor  34  and a mechanical drive  38 . Mechanical drive  38  includes motor shaft  114  which is driven by motor  34  and includes a gearing arrangement  116  for transferring torque generated by motor  34 . The transfer of torque from motor  34  to ribbon  40  allows ribbon  40  to perform mechanical work, i.e., forcibly rotate and advance ribbon  40  to thereby advance piston  26 , or, when rotated in the opposite direction, retract ribbon  40  and wind it into a spiral in bobbin  104 . 
     Small electrical motor  34  provides the power to operate the extension and retraction of ribbon  40 . Typically, motors of this size utilize a mechanical gear reduction. Motor shaft angle sensing can be used to control advancement of ribbon  40  and thus the dose delivered. 
       FIGS.  14  and  15    illustrate two different arrangements by which torque may be transferred from motor  34  to ribbon  40 . Various other torque transfer arrangements and modifications to the illustrated arrangements may also be employed with drive ribbon  40 . 
     In the embodiment of  FIG.  14   , ribbon  40  includes gear teeth  76  on the interior surface of ribbon  40 . A gear member  124  having gear teeth  126  that meshes with gear teeth  76  is used to rotate ribbon  40 . Gear member  124  includes a shaft (not shown) extending through opening  93  in thrust member  88 . The shaft includes another gear arrangement that meshes with a transfer gear member which is also engaged with gearing arrangement  116  on motor shaft  114  whereby torque from motor  34  is transferred to ribbon  40 . 
     In the internal gear drive arrangement depicted in  FIG.  14   , teeth  76  on the inner wall of ribbon  40  engage a gear inside the helical column formed by extended portion  52 . As gear  124  rotates it causes ribbon  40  to rotate and either extend or retract. In the illustrated embodiment, the rotational axis of gear  124  is parallel to axis  50  and slightly offset. This offset arrangement together with gear  124  having an outside diameter less than the inner diameter of ribbon  40  at the location of gear  124  allows gear  124  to engage ribbon  40  at one location only instead of along the entire perimeter of gear  124 . Gear teeth pitches are selected to establish conventional meshed engagement. With a straight-toothed gear, the internal teeth  76  on ribbon  40  are tilted by the helix angle (relative to the ribbon edge) to ensure correct meshing. Since ribbon  40  is extending (or retracting) as it rotates, the gear teeth slide axially along one another as ribbon  40  is rotated. 
     Drive gear  124  can also have helical teeth if the helical teeth are tilted to match the helix angle of extended portion  52 . In such an application, ribbon teeth  76  can be perpendicular to the ribbon edge. Other relative angles between gear teeth  76  and ribbon edges  56 ,  58  are also possible. Various other arrangements are also possible, for example, alternative axis orientations are possible (for example, the gear could be arranged to be tangent to the helix). 
     The use of an internally positioned gear can be effective. For some applications, however, it does pose drawbacks. For example, it will generally require that some mechanical elements such as a gear train to rotate internal gear  124  be disposed at the proximal axial end of thrust member  88 . This can add additional axial length to the overall device. This arrangement also requires that a sufficiently radially rigid mechanical structure hold the external ribbon bearing member  100  in place. 
       FIG.  15    illustrates an embodiment wherein ribbon  40  includes a gearing arrangement  78  on the exterior surface of ribbon  40 . In this embodiment, two transfer gear members  118  transfer torque from motor shaft  114  to ribbon  40 . More specifically, transfer gear members  118  each include a first gearing arrangement  120  that engages with gear arrangement  116  on shaft  114  and a worm gear  122  engaged with ribbon  40 . 
     The external drive system shown in  FIG.  15    uses a worm gear  122  enmeshed with external-facing slots  78  on ribbon  40 . The worm  122  may be chosen to have a helix angle that matches the helix angle of extended portion  52  of ribbon  40  to thereby allow the slots  78  cut into ribbon  40  to be arranged perpendicular to the ribbon edge. Although two worm gears  122  are shown in  FIG.  15   , a single worm gear  122  could alternatively be used. As the worm(s) rotate they advance or retract the ribbon. 
     The use of an external worm drive such as transfer gear members  118  places the transfer gear member  118  on the side of ribbon  40  and therefore adds no axial length to the device. Additionally, transfer gear members  118  can reduce the number of rollers  94  because transfer gear members  118  provide radial support to ribbon  40 . 
     The illustrated container  22  is a replaceable cartridge. To facilitate the convenient replacement of container  22  upon its depletion, a cartridge retainer may be used. Such retainers are well known in the art and typically utilize a threaded joint or bayonet joint, however, other suitable mechanical retention devices may also be used. 
     Another consideration regarding the replacement of container  22  is avoidance of user contact with extension portion  52  of ribbon  40 . While contact with extension portion  52  will not necessarily cause damage, rough handling of ribbon  40  has the potential to impair the operability of ribbon  40 , e.g., disengaging edge sections  56 ,  58  of extended portion  52 . Various approaches can be used to inhibit or prevent such contact. For example, if the full length of extended portion  52  would be exposed upon removal of container  22 , a mechanical interlock can be provided so that ribbon  40  is retracted prior to removal of container  22 . If only the distal end of container  22  is exposed and extended portion  52  is shielded from contact by housing  30 , an electrical interlock can command retraction of ribbon  40  when removal of container  22  is detected. 
     It is also noted that while the illustrated embodiments discussed herein utilize replaceable containers  22  to allow for the re-use of devices  20  and  20 A- 20 C alternative embodiments could take the form of prefilled disposable devices or use a medicament container that is re-filled instead of discarded and replaced. 
     Another embodiment, device  20 B, is shown in  FIGS.  21 - 29   . Device  20 B is generally similar to devices  20 ,  20 A but has several modifications. The overall length of device  20 B as shown in  FIG.  21    is less than 110 mm. Device  20 B dispenses medicament from a container  22  having a needle  28 . A removable cap  31 B covers needle  28  when device  20 B is not in use and has sufficient space to allow for the use of an inner needle shield  29 . Support structure  30 B provides a housing for drive assembly  32 B. A cartridge sleeve  140  receives container  22  and has an opening  142  through which needle  28  can be extended. Cartridge sleeve  140  is best seen in  FIG.  33    and includes a threaded portion  144  adjacent opening  142 . A securement cap  146  engages threaded portion  144  and is used to secure needle  28  to cartridge sleeve  140 . A set of rear threads  148  secures cartridge sleeve  140  to the device. In the illustrated embodiments, rear threads  148  engage corresponding threads on an extension of the ribbon bearing member. The illustrated cartridge sleeve  140  also includes an axially extending opening  150  that functions as a window allowing a user to view the container  22  to see the quantity of medicament remaining therein without having to remove container  22 . Cartridge sleeve  140  also provides a bearing surface which functions the same as surface  130  and may be formed by an internal shoulder contacting the narrowing portion of container  22 . Various other means for securing container  22  within the device may alternatively be used. 
       FIG.  22    illustrates the main components of drive assembly  32 B. Drive assembly  32 B includes a DC motor  34 B having an output shaft  114 B on which a first gear  116 B is secured. Gear member  116 B engages gear members  120 B located on two transfer gears  118 B. Gear members  116 B,  120 B are cross axis involute helical gears. Worm gears  122 B on transfer gears  118 B engage gear teeth  78 B on the exterior of drive ribbon  40 B to rotatably drive ribbon  40 B. 
     The worm gear pitch, gear ratio and pitch of gear slots  78 B in ribbon  40 B are all selected to work together. In this regard, it is noted that the selection of an integer number of ribbon teeth per half turn of the extended ribbon is a significant factor in determining appropriate values for these pitches and gear ratios. 
     Drive ribbon  40 B differs from the drive ribbon of devices  20 ,  20 A. Drive ribbon  40 B includes a recessed area  152  along the proximal edge section  58 B of ribbon  40 B that receives an adjacent portion of the distal edge section  56 B of ribbon  40 B when ribbon  40 B is extended and forms a helix. Recessed portion  152  does not, however, receive the full thickness of distal edge section  56 B and a portion of both the distal and proximal edge sections project radially in opposite directions as a result. 
     A plurality of pegs  154  are located in recess  152  and engage a corresponding plurality of holes  156 . In the illustrated embodiment, pegs  154  are located on the proximal edge section  58 B with holes  156  being located on the distal edge section  56 B. These positions, however, could be reversed. As drive ribbon  40 B is extended and formed into a helix, the engagement of proximal edge section  58 B with an adjacent portion of distal edge section  56 B includes the engagement of pegs  154  with holes  156 . In the illustrated embodiment, pegs  154  have a chamfered surface  155  that facilitates the entry and removal of pegs  154  from holes  156 . 
     The engagement of pegs  154  with holes  156  secures the adjacent portions of drive ribbon  40 B together axially. The engagement of pegs  154  and holes  156  also provides for the transfer of torque between adjacent portions of the extended ribbon and maintains the stability of the column formed by the extended ribbon. 
     In the illustrated embodiment, drive ribbon  40 B has a first major surface  158  and a second major surface  160  on the opposite side of drive ribbon  40 B. A plurality of gear teeth  78 B are formed in first major surface  158 . Gear teeth  78 B are engaged by gear members  122 B whereby drive assembly  32 B can rotate drive ribbon  40 B by transmitting a rotational force to drive ribbon  40 B. 
     The configuration of drive ribbon  40 B may take on a variety of different forms. In the illustrated embodiment, the plurality of pegs  154 , recess  152 , plurality of holes  156  and gear teeth  78 B are all expressed on the first major surface  158 . In this regard, it is noted that it is the opening of holes  156  on the second major surface  160  that receives pegs  154 . While it is not necessary for the proper functioning of holes  156  for holes  156  to extend all the way to the first major surface  158 , by extending holes  156  to the first major surface the manufacture of ribbon  40 B is facilitated. More specifically, it allows for the manufacture of a flat ribbon having two flat planar surfaces and a subsequent machining or milling operation that forms the plurality of pegs  154 , recess  152 , plurality of holes  156  and gear teeth  78 B to be performed from the side of the first major surface  158  and without requiring any such operation to be performed on the second major surface  160  forming the opposite side of ribbon  40 B. This reduces the handling of ribbon  40 B during manufacture and thereby improves efficiency and reduces cost. Ribbon  40 B may be formed out of ABS (acrylonitrile butadiene styrene) or other suitable material. For example, while ABS is a relatively flexible material, other relatively stiffer material such as polycarbonate and metal ribbons may alternatively be used. When employing a relatively stiff material, it may be advantageous to use a plurality of perforations along the length of the ribbon to enhance the flexibility of the ribbon. 
     Prior to machining these features in ribbon  40 B, it is a flat ribbon having two planar surfaces which are parallel to each other and without any features formed in the planar surface. As a result, after forming pegs  154 , recess  152 , holes  156  and gear teeth slots  78 B, the outermost portions of the first and second major surfaces  158 ,  160  define planes  159 ,  161  which are parallel with each other and the distance  162  between these two planes  159 ,  161  defined by the first and second major surfaces defines the greatest thickness of drive ribbon  40 B. 
     As mentioned above, the proximal edge section  58 B of drive ribbon  40 B includes a recess  152  that extends for all or substantially all of the length of drive ribbon  40 B and a plurality of pegs  154  located within recess  152 . Proximal edge section  58 B defines a proximal edge surface  164  having a first axially facing lengthwise portion  166  and a second axially facing lengthwise portion  168 . Distal edge section  56 B includes a plurality of holes  156  and defines a distal edge surface  170  having a third axially facing lengthwise portion  172  and a fourth axially facing lengthwise portion  174 . First and second axially facing surface portions  166 ,  168  face in an axial direction that is opposite than the axial direction faced by third and fourth axially facing surface portions  172 ,  174 . 
       FIG.  24    shows ribbon  40 B in an unrolled condition and detail D 25  is shown in  FIG.  25   . Another view of ribbon  40 B is shown in  FIG.  25 A . As can be understood with reference to  FIGS.  24 ,  25  and  25 A , proximal edge surface  164  and distal edge surface  170  extend between first and second major surfaces  158 ,  160  and, when ribbon  40 B forms a helix, are axially facing in opposite directions. First surface portion  166  extends lengthwise relative to ribbon  40 B and is proximate second major surface  160  while second surface portion  168  extends lengthwise relative to ribbon  40 B and is proximate first major surface  158 . 
     In the illustrated embodiment, first portion  166  and second portion  168  are axially separated by recess  152 . Third surface portion  172  extends lengthwise relative to ribbon  40 B and is proximate second major surface  160  while fourth surface portion  174  extends lengthwise relative to ribbon  40 B and is proximate first major surface  158 . In the illustrated embodiment, third and fourth surface portions  172 ,  174  are coplanar. It is further noted that in the illustrated ribbon  40 B, both the first and second major surfaces  158 ,  160  are parallel with the plane defined by drive ribbon  40 B and the axially facing portions  166 ,  168 ,  172  and  174  of the proximal and distal edge surfaces  164 ,  170  are oriented perpendicular to the first and second major surfaces  172 ,  174 . 
     As best understood with reference to  FIGS.  26  and  27   , in the extended portion of drive ribbon  40 B that forms a helix, proximal edge section  58 B is engaged with an adjacent portion of distal edge section  56 B with the second axially facing lengthwise portion  168  of proximal edge surface  164  being engaged with the third axially facing lengthwise portion  172  of distal edge surface  170 . The first axially facing lengthwise portion  166  of proximal edge surface  164  and the fourth axially facing lengthwise portion  174  of distal edge surface  170  extend radially outwardly in opposite directions. In the illustrated embodiment, the first axially facing lengthwise portion  166  extends radially inwardly while the fourth axially facing lengthwise portion  174  projects radially outwardly. 
     Thrust member  88 B includes a helical thread  176  which is engaged with first axially facing lengthwise portion  166  of proximal edge surface  164 . Helical thread  176  can engage surface  166  of drive ribbon  40 B in the transition portion of drive ribbon  40 B disposed between the retracted portion  54 B defining a spiral and the extended portion  52 B defining a helix of drive ribbon  40 B. Because surface  166  projects radially and is still exposed in the extended portion  52 B of drive ribbon  40 B, helical thread  176  may also engage surface  166  in the helical extended portion  52 B of drive ribbon  40 B. Moreover, this arrangement also allows the helical thread  176  to engage surface  166  for more than 360 degrees about drive axis  50 B. In the illustrated embodiment, helical thread  176  extends for greater than 360 degrees about axis  50 B. 
     The ability of helical thread  176  to engage surface  166  after the engagement of the proximal edge section  58 B with distal edge section  56 B allows thread  176  to bear axial loads in the extended helical portion of the drive ribbon and thereby allow pegs  154  to mesh with holes  156  at a location where no axial load is being carried by drive ribbon  40 B. 
     A ribbon bearing member  100 B circumscribes the drive ribbon and defines a second helical thread  178  engageable with the fourth lengthwise portion  174  of distal edge surface  170 . Thread  178  can engage surface portion  174  in the transition portion of drive ribbon  40 B. However, because surface  174  projects radially and is still exposed in the extended portion  52 B of drive ribbon  40 B, helical thread  178  may also engage surface  174  in the helical extended portion  52 B of drive ribbon  40 B. This arrangement also allows helical thread  178  to engage surface  174  for more than 360 degrees about drive axis  50 B. In the illustrated embodiment helical thread  178  extends for more than 360 degrees about drive axis  50 B and circumscribes drive ribbon  40 B proximate thrust member  88 B. Ribbon bearing member  100 B also supports gear members  118 B and may be machined out of polyoxymethylene (POM), also known as acetal, polyacetal and polyformaldehyde or and sold under various tradenames such as Delrin, or formed using other suitable materials and methods. 
     By providing helical threads  176  and  178  which extend for more than 360 degrees about drive axis  50 B and positioning the threads proximate each other, a short section of drive ribbon  40 B is simultaneously constrained by both threads  176  and  178  thereby firmly controlling the axial position of the drive ribbon to facilitate the engagement of drive ribbon  40 B with itself. The use of a helical thread  176  on thrust member  88 B that extends for more than 360 degrees about drive axis  50 B also increases the surface area over which compressive axial forces can be transferred between drive ribbon  40 B and thrust member  88 B. 
     Both thrust member  88 B and ribbon bearing member  100 B remain stationary relative to each other and support structure  30 B while drive ribbon  40 B rotates about drive axis  50 B relative to these parts when drive ribbon  40 B is being extended and retracted. Helical thread  176  on thrust member  88 B bears against ribbon  40 B to thereby bear axial compressive forces acting on the extended portion of drive ribbon  40 B such as those generated when drive ribbon  40 B axially pushes a piston  26  in a container  22 . Helical thread  178  is engageable with portion  174  of distal edge surface  170  and thereby resists tensile forces acting on the drive ribbon  40 B which would act to axially pull drive ribbon  40 B away from thrust member  88 B. Helical threads  176 ,  178  also axially align the drive ribbon with itself as the proximal edge section is engaged with an adjacent portion of the distal edge section as drive ribbon  40 B is extended. 
     With regard to axially compressive forces, it is noted that the illustrated drive ribbon  40 B is a unitary one-piece ribbon and all axial forces transferred between bearing member  80 B and thrust member  88 B when the drive ribbon is at least partially extended are transferred by the unitary one-piece drive ribbon  40 B. Bearing member  80 B includes two securement pegs  180  that are disposed in openings  182  in ribbon  40 B. A transfer member  84 B is rotatably mounted on bearing member  80 B and engages piston  26  when using device  20 B. 
     Bearing member  80 B transfers axial forces to drive ribbon  40 B through the engagement of pegs  180  with openings  182  and through an overlapping lip that engages distal end surface  171  of the distal end of drive ribbon  40 B. The engagement of pegs  180  with openings  182  prevents the rotation of bearing member  80 B relative to drive ribbon  40 B. As drive ribbon  40 B is extended, bearing member  80 B will exert an axial force on piston  26  to thereby cause the discharge of medicament from container  22 . In this regard, it is noted that bearing member  80 B exerts this axial force on piston  26  through transfer member  84 B which can rotate relative to bearing member  80 B. Thus, during discharge of a medicament, transfer member  84 B will bear on piston  26  and will not rotate relative to piston  26  but will rotate relative to bearing member  80 B. 
     Axial compressive forces are transferred through ribbon  40 B from bearing member  80 B to thrust member  88 B through the engagement of the second lengthwise portion of the proximal edge surface  168  with the third lengthwise portion of distal edge surface  172 . Although the engagement of pegs  154  with holes  156  does not transfer compressive forces in the illustrated embodiment, alternative embodiments could utilize pegs and holes for this purpose. The engagement of the pegs  154  with holes  156  in the illustrated embodiment does, however, resist axially directed tensile forces acting on ribbon  40 B and thereby resists the separation of extended ribbon. 
     A bobbin  104 B is rotatable relative to thrust member  88 B and the retracted portion  54 B of drive ribbon  40 B is stored in bobbin  40 B. Bobbin  40 B rotates along with drive ribbon  40 B due to frictional engagement of drive ribbon  40 B with bobbin  104 B. In the illustrated embodiment, ribbon  40 B is not attached to bobbin  104 B. By not attaching ribbon  40 B to bobbin  104 B, the short length of ribbon that would be necessary to extend to and be secured with the bobbin when the drive ribbon is fully extended can be omitted. Various methods can be used to prevent the unsecured end of drive ribbon  40 B from being overextended and having drive ribbon  40 B escape from the drive mechanism. For example, the gear slots  78 B can be terminated on the drive ribbon  40 B at a location that will limit the extension of ribbon  40 B. A stop in the form of a hook or other catch type member could alternatively or additionally be secured at the end of the drive ribbon that would prevent it from being moved through the gap between thrust member  88 B and ribbon bearing member  100 B. Alternatively, a controller which governs operation of the motor in a manner that limits the extension of drive ribbon  40 B and prevents escape of the ribbon can be employed. 
     The use of a rotating bobbin  104 B helps prevent friction lock of the retracted portion of the drive ribbon during extension and retraction of the drive ribbon. Alternative methods of preventing such friction lock, such as the use of a lubricous material to form the drive ribbon may alternatively be used and the rotating bobbin omitted. 
     In the illustrated version of drive ribbon  40 B, a portion of the proximal edge surface projects radially inward while a portion of the distal edge surface projects radially outward. It is noted that other arrangements may also be used. For example, a portion of the proximal edge surface could project radially outward and a portion of the distal edge surface could project radially inward. In such an alternative embodiment, the helical thread engaging the proximal edge surface and bearing axially compressive forces would be positioned radially outward of the drive ribbon and the thread member engaging a portion of the distal edge surface and positioned to resist axial tensile forces would be positioned radially inward of the drive ribbon. 
     The offset arrangement of the edge surfaces causes one of the edge surfaces to have a longer length per unit length of drive ribbon. In the illustrated embodiment, it is the distal edge that has a relatively longer length. When drive ribbon  40 B is unrolled and positioned in a plane as depicted in  FIG.  24   , drive ribbon  40 B defines an arc with proximal edge section  58 B positioned radially inward of distal edge section  56 B. In embodiments where the proximal edge projects radially outward, the proximal edge section will be positioned radially outward of the distal edge section when the ribbon is positioned in a plane to define an arc. 
     Another embodiment  20 C similar to device  20 B but having a slightly slimmer profile is shown in  FIGS.  30 - 33   . Device  20 C differs from device  20 B by employing several sheet metal parts that allow for a reduction in the size of housing support structure. More specifically, a metal base plate  184 , a metal skirt  186  and a metal support bracket  188  are utilized in device  20 C. 
     As most easily seen in  FIG.  33   , the motor, gearing, drive ribbon and bobbin are the same as those used in device  20 B. Ribbon bearing member  100 C has a slightly different shape but functions in the same manner as ribbon bearing member  100 B. As can be seen in  FIG.  33   , ribbon bearing member  100 C includes threads  190  for engaging threads  148  of cartridge sleeve  140 . Although not shown in the figures for purposes of graphical clarity, ribbon bearing member  100 B includes similar threads for engaging cartridge sleeve  140 . Thrust member  88 C includes a post  192 . A key  194  on post  192  engages a keyway  196  on baseplate  184  and prevents relative rotation of post  192  and the support structure of which baseplate  184  is a part. Bobbin  104 C is rotatably disposed on post  192  and a washer  198  encircling post  192  is located between baseplate  184  and bobbin  104 C to separate bobbin  104 C from baseplate  184 . 
     Devices  20  and  20 A- 20 C can be provided with or without what is generally referred to as force feedback. Force feedback determines the force acting on piston  26  and thereby allows the device to know the state of container  22  and/or position of piston  26 . 
     If the user is relied upon for priming and otherwise confirming the state of the device, force feedback is not needed. In a device without force feedback, motor speed and current can be monitored to determine the state of the system and avoid applying excessive torque to ribbon  40  and hence excessive force to piston  26 . It may be possible that the current-sensing signal-to-noise ratio will be sufficient to detect contact between distal end of the drive ribbon and piston  26 . Generally, the system will initiate and complete each dose with the system open to atmospheric pressure through outlet  28 . In such a system, sensing the force on piston  26 , i.e., force feedback, is not necessary for dosing accuracy. 
     If a force feedback system is used, the device will know when the distal end of transfer member  84  contacts piston  26 . This will allow some user steps, such as priming, to be fully or partially automated. A simple force feedback system could employ a contact switch that triggers at a low force. Such a switch could be located at the distal end  81  of the drive ribbon and coupled with bearing member  80  or rotational bearing  82 . Electrical conductors could be disposed on the drive ribbon to provide electrical communication between the contact switch and a processor within the housing. Proportional force sensing is also possible by using a force-sensing component such as a force sensitive resistor instead of a contact switch. The conductors disposed on the drive ribbon could terminate in or on the storage bobbin. If a rotating bobbin is used, a continuous connection to the device frame can be provided by slip rings or other appropriate contacts. 
     The illustrated embodiments are electro-mechanical and controlled by a processor, microcontroller or microcomputer. The use of a processor allows numerous interaction points and additional functions to be incorporated in the device. For example, the user can interact with the device using a touchscreen, a multiple-button interface, or specific touch points (such as a dose-setting wheel). If desired, such controls could mimic the interaction behaviors of conventional injection devices. 
     The device could also display a variety of different information such as current dose setting, last dose, reminders and use cues or any other useful information. The displays may take the form of a liquid crystal display (LCD), organic light-emitting diode (OLED), electronic paper display (EPD), or other suitable display. 
     The device can also be provided with connectivity allowing it to connect to and interact with other devices (e.g. smart phones) using either wired or wireless communication techniques. These interactions can be used to exchange information in either direction, allowing (for instance) a health care practitioner to change device settings or download dosing history. 
     While this invention has been described as having an exemplary design, the present invention may 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 invention using its general principles.