Abstract:
A drive sleeve is arranged within a body and coupled with a dose member by means of threads. Stop means inhibit a shift of the drive sleeve while allowing a rotation of the drive sleeve. A clutch is provided to lock the dose member rotationally to the body in a releasable manner when a force is exerted on the dose member in the distal direction, the clutch permitting a movement of the dose member in the distal direction with respect to the body.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a U.S. National Phase Application pursuant to 35 U.S.C. §371 of International Application No. PCT/EP2011/069963 filed Nov. 11, 2011, which claims priority to European Patent Application No. 10190942.2 filed Nov. 12, 2010. The entire disclosure contents of these applications are herewith incorporated by reference into the present application. 
     
    
     FIELD OF DISCLOSURE 
       [0002]    The present invention relates to a drive mechanism for a drug delivery device and a drug delivery device incorporating such a drive mechanism. 
       BACKGROUND 
       [0003]    Portable drug delivery devices are used for the administration of a drug that is suitable for self-administration by a patient. A drug delivery device is especially useful in the shape of a pen, which can be handled easily and kept everywhere available. A type of drug delivery device is constructed to be refillable and reusable many times. A drug is delivered by means of a drive mechanism, which may also serve to set the dose or amount to be delivered. 
         [0004]    DE 102 37 258 B4 describes a drug delivery device in the shape of an injection pen having a drive mechanism, which allows to deliver a plurality of different prescribed doses. The drive mechanism comprises elements which are rotated relatively to one another around a common axis. They are coupled by unidirectional gears. 
       SUMMARY 
       [0005]    It is an object of the present invention to disclose a new drive mechanism for a drug delivery device that allows to set a dose. 
         [0006]    This object is achieved by a drive mechanism according to claim  1 . Further objects are achieved by variants and embodiments according to the dependent claims. 
         [0007]    The drive mechanism for a drug delivery device comprises a body having a proximal end and a distal end, a dose member having a thread, and a drive sleeve. The drive sleeve is rotatable with respect to the body and has a thread which engages the thread of the dose member. Stop means restrict or inhibit a movement of the drive sleeve in the proximal direction and in the distal direction with respect to the body. A clutch is provided to lock the dose member rotationally to the body in a releasable manner when a force is exerted on the dose member in the distal direction, the clutch permitting a movement of the dose member in the distal direction with respect to the body. 
         [0008]    The body can be any housing or any component that forms part of a housing, for example. The body can also be some kind of an insert connected with an exterior housing. The body may be designed to enable the safe, correct, and/or easy handling of the device and/or to protect it from harmful liquids, dust or dirt. The body can be unitary or a multipart component of tubular or non-tubular shape. The body may house a cartridge, from which doses of a drug can be dispensed. The body can especially have the shape of an injection pen. The term “distal end” refers to a part of the body or housing which is intended to be arranged at a portion of the drug delivery device from which a drug is dispensed. The term “proximal end” refers to a part of the body or housing which is remote from the distal end. 
         [0009]    In an embodiment of the drive mechanism, the dose member has a cylindrical shape and partially surrounds the drive sleeve. 
         [0010]    In an embodiment of the drive mechanism, the stop means are provided by webs or interfaces of the body. 
         [0011]    Further embodiments comprise a clutch member, which is rotationally locked to the body. An axial coupling means and a rotational coupling means are provided at the clutch member and the dose member. The axial coupling means is provided to move the clutch member in the proximal direction when the dose member is moved in the proximal direction, and the rotational coupling means forms the clutch. 
         [0012]    In a further embodiment the rotational coupling means comprises a surface of the clutch member and a surface of the dose member, the surfaces being coupled by friction. 
         [0013]    In a further embodiment the rotational coupling means comprises a structured surface of the clutch member and a structured surface of the dose member, the structured surfaces mechanically engaging with one another. 
         [0014]    Further embodiments comprise a piston rod arranged within the body, the piston rod being movable in distal direction and in proximal direction. The drive sleeve is rotationally coupled to the piston rod. The term “piston rod” encompasses any element that is provided to transfer a movement to a piston, especially for the purpose of dispensing a drug. The piston rod may be flexible or not. It may be of unitary or multipart construction, and may especially be a simple rod, a lead-screw, a rack-and-pinion, a worm gear system, or the like. 
         [0015]    A further embodiment comprises a drive member rotationally locked to the piston rod and held in contact with the drive sleeve. The drive member permits the drive sleeve to rotate in one direction relatively to the piston rod and inhibits the drive sleeve from rotating in the opposite direction relatively to the piston rod. 
         [0016]    A further embodiment comprises a stop member rotationally locked to the body and held in contact with the drive member. The stop member permits the drive member to rotate in one direction relatively to the body and inhibits the drive member from rotating in the opposite direction relatively to the body. 
         [0017]    A further embodiment comprises a guide means coupled to the piston rod and restricting a relative movement of the piston rod with respect to the body to a helical movement. 
         [0018]    In a further embodiment of the drive mechanism, a set operation is performed by a helical movement of the dose member with respect to the body in the proximal direction, the helical movement being guided by the thread of the dose member and the thread of the drive sleeve, while the drive sleeve is stationary with respect to the body. 
         [0019]    In a further embodiment of the drive mechanism, a dispense operation is performed by a movement of the dose member with respect to the body in the distal direction. A rotation of the dose member with respect to the body is inhibited by the clutch, and a rotation of the drive sleeve with respect to the body is generated by the thread of the dose member and the thread of the drive sleeve. 
         [0020]    In a further embodiment of the drive mechanism, a correcting set operation is performed by a helical movement of the dose member with respect to the body in the distal direction, the helical movement being guided by the thread of the dose member and the thread of the drive sleeve, while the drive sleeve is stationary with respect to the body. 
         [0021]    The invention further relates to a drug delivery device with a drive mechanism according to one of the embodiments. The drug delivery device can especially have a body in the shape of an injection pen. 
         [0022]    The drug delivery device can be a disposable or re-usable device designed to dispense a dose of a drug, especially a liquid, which may be insulin, a growth hormone, a heparin, or an analogue and/or a derivative thereof, for example. The device can be configured to dispense fixed doses of the drug or variable doses. The drug may be administered by a needle, or the device may be needle-free. The device may be further designed to monitor physiological properties like blood glucose levels, for example. 
         [0023]    These and other features of the invention will become apparent from the following brief description of the drawings, detailed description and appended claims and drawings, in which similar or corresponding elements bear the same reference numerals. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0024]      FIG. 1  shows a cross-section of an injection pen comprising an embodiment of the drive mechanism. 
           [0025]      FIG. 2  shows a cross-section according to  FIG. 1  after the setting of a dose. 
           [0026]      FIG. 3  shows a cross-section according to  FIG. 1  after the delivery of several doses. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  shows a cross-section of a drug delivery device in the shape of an injection pen. The drug delivery device can have another suitable shape instead, according to the shape of a body or housing. The term “body” encompasses any exterior housing, like a main housing or shell, as well as an interior housing, like an insert or inner body arranged within an exterior housing. In the embodiment shown in  FIG. 1 , the body  1  is of elongated shape. It has a proximal end  2  and a distal end  3 . The body  1  can be composed of at least two attachable and separable parts enabling a refill of the device. 
         [0028]    The body  1  comprises a receptacle  4  for a drug. The receptacle  4  can be designed to be filled by means of a cartridge  5  containing the drug and being inserted in the receptacle  4 . A full cartridge  5  preferably contains a plurality of doses of the drug. When the cartridge  5  is empty, it can be removed and substituted with a new cartridge. 
         [0029]    The drug is dispensed through an opening of the receptacle  4  by means of a piston  6 , which is advanced in the receptacle  4 , particularly within the cartridge  5 , towards the distal end  3  by means of a piston rod  7 . The distal end  3  can be provided with a needle, not shown in  FIG. 1 , or with a needle unit, for instance. 
         [0030]    If the piston rod  7  is to be moved relatively to the piston  6 , a bearing, which is schematically shown in  FIG. 1 , can be arranged at the connection of the piston  6  with the piston rod  7  to reduce damages that may be caused by friction. The drive mechanism shown in  FIG. 1  can be operated by means of a dose button  20  at the proximal end  2 . The dose button  20  is located outside the body  1  and can be gripped by a user. 
         [0031]    The drive mechanism comprises a drive sleeve  11 , which is partially surrounded by a cylindrical dose member  12  provided with the dose button  20 . The drive sleeve  11  and the dose member  12  are coupled by means of a thread  15  of the dose member  12  engaging a corresponding thread  16  of the drive sleeve  11 . Because of the threads, the dose member  12  can be moved helically with respect to the drive sleeve  11 . The drive sleeve  11  can be rotated with respect to the body  1 , but a movement of the drive sleeve  11  in the distal direction or in the proximal direction is inhibited or at least restricted. To this purpose, the body  1  can be provided with stop means, which can be interfaces or webs  13 ,  14 , for instance, which stop a shift of the drive sleeve  11  in the distal direction and in the proximal direction. 
         [0032]    The movement of the piston rod  7  with respect to the body  1  is guided by a suitable guide means  17 . The guide means  17  can be an integral part of the body  1 , or it may be an element which is permanently or temporarily fastened to the body  1 , like a nut, for example. The piston rod  7  passes through an opening of the guide means  17 , which engages a thread of the piston rod  7  to restrict the movement of the piston rod  7  with respect to the body  1  to a helical movement. A rotation of the piston rod  7  with respect to the body  1  thus comprises a simultaneous shift of the piston rod  7  with respect to the body  1 . 
         [0033]    A clutch sleeve  18  comprising a clutch  19  is arranged between the body  1  and the dose member  12 . The clutch  19  can be formed by a surface area of the clutch sleeve  18  and a corresponding surface area of the dose member  12 , the surface areas touching each other when the dose member  12  is moved towards the distal end  3  and rotationally coupling the clutch sleeve  18  and the dose member  12  by means of friction. Instead, the clutch  19  can be formed by a structured surface area of the clutch sleeve  18  and a corresponding structured surface area of the dose member  12 . The surface structure may comprise teeth, for instance. When the dose member  12  is moved towards the distal end  3 , the structured surface areas engage with each other, thus coupling the clutch sleeve  18  and the dose member  12  rotationally. The clutch sleeve  18  is rotationally locked to the body  1 , which may be achieved by an axial groove or track and a corresponding element, like a track, pin, peg, hook, spike or lug, which is guided by the groove or track, for instance. 
         [0034]    The embodiment according to  FIG. 1  further comprises a spring  8 , a stop member  9 , and a drive member  10 , which can be substituted with other means to couple the piston rod  7  with the drive sleeve  11 . The drive member  10  and the drive sleeve  11  are rotationally coupled by a ratchet, and so are the drive member  10  and the stop member  9 . The stop member  9  is rotationally locked to the body  1 , but is allowed to perform a reciprocating motion enabling the ratchets to engage and disengage during a rotation in the permitted direction. The stop member  9 , the drive member  10 , and the drive sleeve  11  are held in contact by the action of the spring  8 , which is supported by the web  14  of the body  1 . 
         [0035]    The ratchets allow unidirectional rotations of the drive member  10  with respect to the stop member  9  and with respect to the drive sleeve  11 . In both of these relative movements, the drive member  10  rotates in the same sense of rotation with respect to the proximal direction. This means that, depending on the sense of rotation of the drive sleeve  11  with respect to the body  1 , either the drive sleeve  11  is rotationally locked to the drive member  10 , which rotates together with the drive sleeve  11  relatively to the body  1  and to the stop member  9 , or the drive sleeve  11  rotates relatively to the body  1  and to the drive member  10 , which is rotationally locked to the stop member  9 . 
         [0036]    The drive member  10  essentially stays at its position within the body  1  and is rotationally locked to the piston rod  7 , while the piston rod  7  is able to move axially with respect to the body  1  in the distal direction or in the proximal direction. Because of the guide means  17 , a rotation of the piston rod  7  by means of the drive member  10  generates a helical movement of the piston rod  7  relatively to the body  1 . The guide means  17  is provided to convert a rotation of the drive member  10  that is permitted by the stop member  9  into a helical movement of the piston rod  7  shifting the piston rod  7  in the distal direction. 
         [0037]    An operation to set a dose is performed by a helical movement of the dose member  12  with respect to the body  1  in the proximal direction. The dose member  12  can be rotated by turning the dose button  20 , the helical movement being guided by the thread of the dose member  12  engaging the thread of the drive sleeve  11 . The drive sleeve  11  is stationary with respect to the body  1 , because the drive sleeve  11  is in contact with the web  13  or with another suitable stop means of the body  1 , which inhibits a shift of the drive sleeve  11  in the proximal direction. A premature rotation of the drive sleeve  11  according to the rotation of the dose member  12  is preferably inhibited in view of dose accuracy. This can be achieved, for example, by means of the friction between the surfaces of the drive sleeve  11  and the web  13  which touch one another; instead, these surfaces may be provided with a structure engaging the drive sleeve  11  with the web  13  to inhibit a relative rotation. 
         [0038]      FIG. 2  shows a cross-section of the drive mechanism after the setting of a dose. Further to the dose button  20 , a portion of the dose member  12  now juts out of the body  1 . An axial coupling means highlighted at letter A in  FIG. 2  is provided to shift the clutch sleeve  18  in the proximal direction simultaneously with the dose member  12  to keep the clutch  19  ready for coupling the clutch sleeve  18  and the dose member  12 . The clutch  19  thus forms a rotational coupling means highlighted at letter B in  FIG. 2 . Since the clutch sleeve  18  is rotationally locked to the body  1 , the dose member  12  rotates relatively to the clutch sleeve  18  during the set operation. This is made possible by the clutch  19  not being engaged during the movement of the dose member  12  in the proximal direction. 
         [0039]    A correction of the set dose is easily possible by a helical movement of the dose member  12  with respect to the body  1  in the distal direction. This is achieved by turning the dose button  20  in the opposite direction until the desired position of the dose member  12  is obtained. The correct value of the set dose may be indicated by a scale or a numbering applied to the dose member  12  or dose button  20 . Audible and/or tactile means can also be provided to guide the user when setting a dose. When the dose member  12  is helically moved back in the distal direction, the helical movement of the dose member  12  with respect to the body  1  is again guided by the threads  15 ,  16  of the dose member  12  and the drive sleeve  11 . A rotation of the drive sleeve  11  according to the rotation of the dose member  12  can be inhibited, in the described embodiment for example, by the coupling between the surfaces of the drive sleeve  11  and the web  13 . A rotation of the drive sleeve  11  according to the rotation of the dose member  12  during the correction of the set dose may be allowed in embodiments comprising the arrangement of the spring  8 , the stop member  9 , and the drive member  10  as described above, because the stop member  9  inhibits an undesired rotation of the drive member  10  during the correction operation, even if the drive sleeve  11  rotates in the same sense as the dose member  12 . 
         [0040]    If the dose button  20  is not turned but pressed in the distal direction, the clutch  19  engages, and the dose member  12  and the clutch sleeve  18  are rotationally locked. This means that the dose member  12  cannot rotate with respect to the body  1 , because the clutch sleeve  18  is rotationally locked to the body  1 . The drive sleeve  11  is decoupled from the web  13  or other stop means and is free to rotate relatively to the body  1 . A distal movement of the drive sleeve  11  is inhibited or restricted by a further stop means, which can be the web  14  or the stop member  9  under the load of the spring  8 , for example. The shift of the dose member  12  with respect to the body  1  therefore requires a corresponding relative movement of the dose member  12  with respect to the drive sleeve  11 . This movement can only be a helical relative movement because of the threads  15 ,  16  coupling the dose member  12  and the drive sleeve  11 . The drive sleeve  11  is thus rotated with respect to the body  1 . If the device is provided with the arrangement of the stop member  9  and the drive member  10 , this rotation of the drive sleeve  11  locks the drive member  10  rotationally to the drive sleeve  11 , and the drive member  10  is permitted to rotate in this sense of rotation. The drive member  10  therefore rotates according to the drive sleeve  11  and rotates the piston rod  7 , which advances in the distal direction because of the guide means  17 . 
         [0041]      FIG. 3  shows a cross-section of the drive mechanism after the delivery of several doses. Apart from rotations, the dose member  12  is again in the position which it occupied when the device was in the initial state shown in  FIG. 1 . The position of the piston rod  7  is now changed, because the piston rod  7  was shifted several times in the distal direction in the course of delivery operations. The other components of the drive mechanism are arranged according to the state shown in  FIG. 1 , and a further set operation can be performed by turning the dose button  20  as described above. 
         [0042]    The drive mechanism is easily and reliably operated and is therefore especially appropriate for drug delivery devices that are designed for repeated setting of doses, particularly varying doses. The drive mechanism allows a correction of the set dose in an easy way by just reversing the setting operation. It is an advantage of the drive mechanism that the accuracy in setting the dose is not adversely affected by a correction of the set dose. The correct use of the device is therefore assured, thus helping the user to administer the medication correctly.