Abstract:
A housing for a dispensing apparatus. The housing comprising a main housing and a dose dial sleeve. The dose dial sleeve comprising a helical groove configured to engage a threading provided by the housing. A dose knob is disposed near a proximal end of the dose dial sleeve and a piston rod is provided within the housing. The piston rod is non-rotatable during a dose setting step. A driver comprises an internal threading near a distal portion of the driver and is adapted to engage an external thread of the piston rod. A tubular clutch is located adjacent a distal end of the dose knob and operatively coupled to the dose knob. The dose dial sleeve may extend circumferentially around at least a portion of the tubular clutch.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. patent application Ser. No. 12/944,544, filed Nov. 11, 2010, entitled “Pen-Type Injector”, which is a continuation application of U.S. patent application Ser. No. 11/483,546, filed Jul. 11, 2006, now U.S. Pat. No. 7,918,833, which is a continuation application of U.S. patent application Ser. No. 10/790,225, filed Mar. 2, 2004, abandoned, and claims priority to GB Patent Application No. 0304822.0, filed Mar. 3, 2003, the entire contents of each of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Improvements in and Relating to a Pen-Type Injector 
     The present invention relates to pen-type injectors, that is to injectors of the kind that provide for administration by injection of medicinal products from a multidose cartridge. In particular, the present invention relates to such injectors where a user may set the dose. 
     Such injectors have application where regular injection by persons without formal medical training occurs. This is increasingly common amongst those having diabetes where self-treatment enables such persons to conduct effective management of their diabetes. 
     These circumstances set a number of requirements for pen-type injectors of this kind. The injector must be robust in construction, yet easy to use both in terms of the manipulation of the parts and understanding by a user of its operation. In the case of those with diabetes, many users will be physically infirm and may also have impaired vision. Where the injector is to be disposable rather than reusable, the injector should be cheap to manufacture and easy to dispose of (preferably being suitable for recycling). 
     OVERVIEW 
     It is an advantage of the present invention that an improved pen-type injector is provided. 
     According to a first aspect of the present invention, a pen-type injector comprises a housing; 
     a piston rod adapted to operate through the housing; 
     a dose dial sleeve located between the housing and the piston rod, the dose dial sleeve having a helical thread of first lead; 
     a drive sleeve located between the dose dial sleeve and the piston rod, the drive sleeve having a helical groove of second lead; 
     characterized in that the first lead of the helical thread and the second lead of the helical groove are the same. 
     Preferably, the piston rod has a first threaded portion at a first end and a second threaded portion at a second end; 
     an insert or radially inwardly extending flange is located in the housing and through which the first threaded portion of the piston rod may rotate; 
     the dose dial sleeve being rotatable with respect to the housing and the insert; 
     the drive sleeve being releasably connected to the dose dial sleeve and connected to the piston rod for rotation with respect thereto along the second threaded portion of the piston rod; 
     a button is located on the dose dial sleeve and rotatable with respect to the dose dial sleeve; and 
     clutch means are provided which upon depression of the button permit rotation between the dose dial sleeve and the drive sleeve. 
     Preferably, the injector further comprises a nut which is rotatable with respect to the drive sleeve and axially displaceable but not rotatable with respect to the housing. 
     More preferably, the drive sleeve is provided at a first end with first and second flanges with an intermediate thread between the first and second flanges, the nut being disposed between the first and second flanges and keyed to the housing by spline means. Additionally, a first radial stop may be provided on a second face of the nut and a second radial stop may be provided on a first face of the second flange. 
     Preferably, the first thread of the piston rod is oppositely disposed to the second thread of the piston rod. 
     Preferably, a second end of the clutch is provided with a plurality of dog teeth adapted to engage with a second end of the dose dial sleeve. 
     Preferably, the pen-type injector further includes clicker means disposed between the clutch means and spline means provided on the housing. 
     More preferably, the clicker means comprises a sleeve provided at a first end with a helically extending arm, a free end of the arm having a toothed member, and at a second end with a plurality of circumferentially directed saw teeth adapted to engage a corresponding plurality of circumferentially saw teeth provided on the clutch means. 
     Alternatively, the clicker means comprises a sleeve provided at a first end with at least one helically extending arm and at least one spring member, a free end of the arm having a toothed member, and at a second end with a plurality of circumferentially directed saw teeth adapted to engage a corresponding plurality of circumferentially directed saw teeth provided on the clutch means. 
     Preferably, the main housing is provided with a plurality of maximum dose stops adapted to be abutted by a radial stop provided on the dose dial sleeve. More preferably, at least one of the maximum dose stops comprises a radial stop located between a helical rib and spline means provided at a second end of the housing. Alternatively, at least one of the maximum dose stops comprises a part of a raised window portion provided at a second end of the housing. 
     Preferably, the dose dial sleeve is provided with a plurality of radially extending members adapted to abut a corresponding plurality of radial stops provided at a second end of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the accompanying drawings, in which: 
         FIG. 1  shows a sectional view of a pen-type injector in accordance with the present invention in a first, cartridge full, position; 
         FIG. 2  shows a sectional view of the pen-type injector of  FIG. 1  in a second, maximum first dose dialed, position; 
         FIG. 3  shows a sectional view of the pen-type injector of  FIG. 1  in a third, first maximum first dose dispensed, position; 
         FIG. 4  shows a sectional view of the pen-type injector of  FIG. 1  in a fourth, final dose dialed, position; 
         FIG. 5  shows a sectional view of the pen-type injector of  FIG. 1  in a fifth, final dose dispensed, position; 
         FIG. 6  shows a cut-away view of a first detail of the pen-type injector of  FIG. 1 ; 
         FIG. 7  shows a partially cut-away view of a second detail of the pen-type injector of  FIG. 1 ; 
         FIG. 8  shows a partially cut-away view of a third detail of the pen-type injector of  FIG. 1 ; 
         FIG. 9  shows the relative movement of parts of the pen-type injector shown in  FIG. 1  during dialing up of a dose; 
         FIG. 10  shows the relative movement of parts of the pen-type injector shown in  FIG. 1  during dialing down of a dose; 
         FIG. 11  shows the relative movement of parts of the pen-type injector shown in  FIG. 1  during dispensing of a dose; 
         FIG. 12  shows a partially cut-away view of the pen-type injector of  FIG. 1  in the second, maximum first dose dialed, position; 
         FIG. 13  shows a partially cut-away view of the pen-type injector of  FIG. 1  in the fourth, final dose dialed, position; 
         FIG. 14  shows a partially cut-away view of the pen-type injector of  FIG. 1  in one of the first, third or fifth positions; 
         FIG. 15  shows a cut-away view of a first part of a main housing of the pen-type injector of  FIG. 1 ; and 
         FIG. 16  shows a cut-away view of a second part of the main housing of the pen-type injector of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIGS. 1 to 5 , there may be seen a pen-type injector in accordance with the present invention in a number of positions. 
     The pen-type injector comprises a housing having a first cartridge retaining part  2 , and second main housing part  4 . A first end of the cartridge retaining means  2  and a second end of the main housing  4  are secured together by retaining features  6 . In the illustrated embodiment, the cartridge retaining means  2  is secured within the second end of the main housing  4 . 
     A cartridge  8  from which a number of doses of medicinal product may be dispensed is provided in the cartridge retaining part  2 . A piston  10  is retained in a first end of the cartridge  8 . 
     A removable cap  12  is releasably retained over a second end of the cartridge retaining part  2 . In use the removable cap  12  can be replaced by a user with a suitable needle unit (not shown). A replaceable cap  14  is used to cover the cartridge retaining part  2  extending from the main housing  4 . Preferably, the outer dimensions of the replaceable cap  14  are similar or identical to the outer dimensions of the main housing  4  to provide the impression of a unitary whole when the replaceable cap  14  is in position covering the cartridge retaining part  2 . 
     In the illustrated embodiment, an insert  16  is provided at a first end of the main housing  4 . The insert  16  is secured against rotational or longitudinal motion. The insert  16  is provided with a threaded circular opening  18  extending therethrough. Alternatively, the insert may be formed integrally with the main housing  4  the form of a radially inwardly directed flange having an internal thread. 
     A first thread  19  extends from a first end of a piston rod  20 . The piston rod  20  is of generally circular section. The first end of the piston rod  20  extends through the threaded opening  18  in the insert  16 . A pressure foot  22  is located at the first end of the piston rod  20 . The pressure foot  22  is disposed to abut a second end of the cartridge piston  10 . A second thread  24  extends from a second end of the piston rod  20 . In the illustrated embodiment the second thread  24  comprises a series of part threads rather than a complete thread. The illustrated embodiment is easier to manufacture and helps reduce the overall force required for a user to cause medicinal product to be dispensed. 
     The first thread  19  and the second thread  24  are oppositely disposed. The second end of the piston rod  20  is provided with a receiving recess  26 . 
     A drive sleeve  30  extends about the piston rod  20 . The drive sleeve  30  is generally cylindrical. The drive sleeve  30  is provided at a first end with a first radially extending flange  32 . A second radially extending flange  34  is provided spaced a distance along the drive sleeve  30  from the first flange  32 . An intermediate thread  36  is provided on an outer part of the drive sleeve  30  extending between the first flange  32  and the second flange  34 . A helical groove  38  extends along the internal surface of the drive sleeve  30 . The second thread  24  of the piston rod  20  is adapted to work within the helical groove  38 . 
     A first end of the first flange  32  is adapted to conform to a second side of the insert  16 . 
     A nut  40  is located between the drive sleeve  30  and the main housing  2 , disposed between the first flange  32  and the second flange  34 . In the illustrated embodiment the nut  40  is a half-nut. This assists in the assembly of the injector. The nut  40  has an internal thread matching the intermediate thread  36 . The outer surface of the nut  40  and an internal surface of the main housing  4  are keyed together by splines  42  (see  FIGS. 10 ,  11 ,  15  and  16 ) to prevent relative rotation between the nut  40  and the main housing  4 , while allowing relative longitudinal movement therebetween. 
     A shoulder  37  is formed between a second end of the drive sleeve  30  and an extension  38  provided at the second end of the drive sleeve  30 . The extension  38  has reduced inner and outer diameters in comparison to the remainder of the drive sleeve  30 . A second end of the extension  38  is provided with a radially outwardly directed flange  39 . 
     A clicker  50  and a clutch  60  are disposed about the drive sleeve  30 , between the drive sleeve  30  and a dose dial sleeve  70  (to be described below). 
     The clicker  50  is located adjacent the second flange  34  of the drive sleeve  30 . The clicker  50  is generally cylindrical and is provided at a first end with a flexible helically extending arm  52  (shown most clearly in  FIG. 6 ). A free end of the arm  52  is provided with a radially directed toothed member  54 . A second end of the clicker  50  is provided with a series of circumferentially directed saw teeth  56  (cf  FIG. 7 ). Each saw tooth comprises a longitudinally directed surface and an inclined surface. 
     In an alternative embodiment (not shown) the clicker means further includes at least one spring member. The at least one spring member assists in the resetting of the clutch means  60  following dispense. 
     The clutch means  60  is located adjacent the second end of the drive sleeve  30 . The clutch means  60  is generally cylindrical and is provided at a first end with a series of circumferentially directed saw teeth  66  (see  FIG. 7 ). Each saw tooth comprises a longitudinally directed surface and an inclined surface. Towards the second end  64  of the clutch means  60  there is located a radially inwardly directed flange  62 . The flange  62  of the clutch means  60  is disposed between the shoulder  37  of the drive sleeve  30  and the radially outwardly directed flange  39  of the extension  38 . The second end of the clutch means  60  is provided with a plurality of dog teeth  65  ( FIG. 8 ). The clutch  60  is keyed to the drive sleeve  30  by way of splines (not shown) to prevent relative rotation between the clutch  60  and the drive sleeve  30 . 
     In the illustrated embodiment, the clicker  50  and the clutch  60  each extend approximately half the length of the drive sleeve  30 . However, it will be understood that other arrangements regarding the relative lengths of these parts are possible. 
     The clicker  50  and the clutch means  60  are normally engaged, that is as shown in  FIG. 7 . 
     A dose dial sleeve  70  is provided outside of the clicker  50  and clutch means  60  and radially inward of the main housing  4 . A helical groove  74  is provided about an outer surface of the dose dial sleeve  70 . 
     The main housing  4  is provided with a window  44  through which a part of the outer surface of the dose dial sleeve may be seen. The main housing  4  is further provided with a helical rib  46 , adapted to be seated in the helical groove  74  on the outer surface of the dose dial sleeve  70 . The helical rib  46  extends for a single sweep of the inner surface of the main housing  4 . A first stop  100  is provided between the splines  42  and the helical rib  46  ( FIG. 15 ). A second stop  102 , disposed at an angle of 180° to the first stop  100  is formed by a frame surrounding the window  44  in the main housing  4  ( FIG. 16 ). 
     Conveniently, a visual indication of the dose that may be dialed, for example reference numerals (not shown), is provided on the outer surface of the dose dial sleeve  70 . The window  44  conveniently only allows to be viewed a visual indication of the dose currently dialed. 
     A second end of the dose dial sleeve  70  is provided with an inwardly directed flange in the form of number of radially extending members  75 . A dose dial grip  76  is disposed about an outer surface of the second end of the dose dial sleeve  70 . An outer diameter of the dose dial grip  76  preferably corresponds to the outer diameter of the main housing  4 . The dose dial grip  76  is secured to the dose dial sleeve  70  to prevent relative movement therebetween. The dose dial grip  76  is provided with a central opening  78 . An annular recess  80  located in the second end of the dose dial grip  76  extends around the opening  78 . 
     A button  82  of generally ‘T’ section is provided at a second end of the pen-type injector. A stem  84  of the button  82  may extend through the opening  78  in the dose dial grip  76 , through the inner diameter of the extension  38  of the drive sleeve  30  and into the receiving recess  26  of the piston rod  20 . The stem  84  is retained for limited axial movement in the drive sleeve  30  and against rotation with respect thereto. A head  85  of the button  82  is generally circular. A skirt  86  depends from a periphery of the head  85 . The skirt  86  is adapted to be seated in the annular recess  80  of the dose dial grip  76 . 
     Operation of the pen-type injector in accordance with the present invention will now be described. In  FIGS. 9 ,  10  and  11  arrows A, B, C, D, E, F and G represent the respective movements of the button  82 , the dose dial grip  76 , the dose dial sleeve  70 , the drive sleeve  30 , the clutch means  60 , the clicker  50  and the nut  40 . 
     To dial a dose ( FIG. 9 ) a user rotates the dose dial grip  76  (arrow A). With the clicker  50  and clutch means  60  engaged, the drive sleeve  30 , the clicker  50 , the clutch means  60  and the dose dial sleeve  70  rotate with the dose dial grip  76 . 
     Audible and tactile feedback of the dose being dialed is provided by the clicker  50  and the clutch means  60 . Torque is transmitted through the saw teeth  56 , 66  between the clicker  50  and the clutch means  60 . The flexible arm  52  deforms and drags the toothed member  54  over the splines  42  to produce a click. Preferably, the splines  42  are disposed such that each click corresponds to a unit dose. 
     The helical groove  74  on the dose dial sleeve  70  and the helical groove  38  in the drive sleeve  30  have the same lead. This allows the dose dial sleeve  70  (arrow C) to extend from the main housing  4  and the drive sleeve  30  (arrow D) to climb the piston rod  20  at the same rate. At the limit of travel, a radial stop  104  on the dose dial sleeve  70  engages either the first stop  100  or the second stop  102  provided on the main housing  4  to prevent further movement. Rotation of the piston rod  20  is prevented due to the opposing directions of the overhauled and driven threads on the piston rod  20 . 
     The nut  40 , keyed to the main housing  4 , is advanced along the intermediate thread  36  by the rotation of the drive sleeve  30  (arrow D). When the final dose dispensed position ( FIGS. 4 ,  5  and  13 ) is reached, a radial stop  106  formed on a second surface of the nut  40  abuts a radial stop  108  on a first surface of the second flange  34  of the drive sleeve  30 , preventing both the nut  40  and the drive sleeve  30  from rotating further. 
     In an alternative embodiment (not shown) a first surface of the nut  40  is provided with a radial stop for abutment with a radial stop provided on a second surface of the first flange  32 . This aids location of the nut  40  at the cartridge full position during assembly of the pen-type injector. 
     Should a user inadvertently dial beyond the desired dosage, the pen-type injector allows the dosage to be dialed down without dispense of medicinal product from the cartridge ( FIG. 10 ). The dose dial grip  76  is counter rotated. This causes the system to act in reverse. The flexible arm  52  now acts as a ratchet preventing the clicker from rotating. The torque transmitted through the clutch means  60  causes the saw teeth  56 ,  66  to ride over one another to create the clicks corresponding to dialed dose reduction. Preferable the saw teeth  56 ,  66  are so disposed that the circumferential extent of each saw tooth corresponds to a unit dose. 
     When the desired dose has been dialed, the user may then dispense this dose by depressing the button  82  ( FIG. 11 ). This displaces the clutch means  60  axially with respect to the dose dial sleeve  70  causing the dog teeth  65  to disengage. However the clutch means  60  remains keyed in rotation to the drive sleeve  30 . The dose dial sleeve  70  and associated dose dial grip  76  are now free to rotate (guided by the helical rib  46  located in helical groove  74 ). 
     The axial movement deforms the flexible arm  52  of the clicker  50  to ensure the saw teeth  56 , 66  cannot be overhauled during dispense. This prevents the drive sleeve  30  from rotating with respect to the main housing  4  though it is still free to move axially with respect thereto. This deformation is subsequently used to urge the clicker  50 , and the clutch  60 , back along the drive sleeve  30  to restore the connection between the clutch  60  and the dose dial sleeve  70  when pressure is removed from the button  82 . 
     The longitudinal axial movement of the drive sleeve  30  causes the piston rod  20  to rotate though the opening  18  in the insert  16 , thereby to advance the piston  10  in the cartridge  8 . Once the dialed dose has been dispensed, the dose dial sleeve  70  is prevented from further rotation by contact of a plurality of members  110  ( FIG. 14 ) extending from the dose dial grip  76  with a corresponding plurality of stops  112  formed in the main housing  4  ( FIGS. 15 and 16 ). In the illustrated embodiment, the members  110  extend axially from the dose dial grip  76  and have an inclined end surface. The zero dose position is determined by the abutment of one of the axially extending edges of the members  110  with a corresponding stop  112 .