Drive mechanism for a drug delivery device and drug delivery device

The drive mechanism is suitable for a permanent delivery of a drug from a compact drug delivery device, which may be carried on the body. The drive mechanism comprises a flexible advance cable bearing a coupling feature of longitudinal extension. The advance cable is guided by a guide means. A drive means engages the coupling feature and thus enables an advancement of the advance cable according to the guide means. An end piece is provided to push a plug or bung of a cartridge containing a drug, and the end piece is driven by the advance cable. The drive means is permanently engaged with the coupling feature. This allows a permanent advancement of the plug or bung by means of the drive mechanism.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. National Phase Application pursuant to 35 U.S.C. §371 of International Application No. PCT/EP2012/054560 filed Mar. 15, 2012, which claims priority to European Patent Application No. 11158491.8 filed Mar. 16, 2011. The entire disclosure contents of these applications are herewith incorporated by reference into the present application.

FIELD OF DISCLOSURE

The present invention relates to a drive mechanism for a drug delivery device and to a drug delivery device that is provided with such a drive mechanism.

BACKGROUND

EP 1 372 768 B1 describes a drive mechanism for an injection device in which a semi-rigid belt with a track is used to drive a piston member. A belt drive means is provided to drive the belt a preselected way. It comprises a tooth for a selective engagement with the track and allows an advancement of the belt only in one direction.

SUMMARY

It is an object of the present invention to provide a new drive mechanism and a drug delivery device of compact dimensions.

This object is achieved with a drive mechanism and a drug delivery device according to the appended claims. Further objects are achieved with embodiments according to the dependent claims.

The term “drug”, as used herein, preferably means a pharmaceutical formulation containing at least one pharmaceutically active compound,

wherein in a further embodiment the pharmaceutically active compound comprises at least one human insulin or a human insulin analogue or derivative, glucagon-like peptide (GLP-1) or an analogue or derivative thereof, or exedin-3 or exedin-4 or an analogue or derivative of exedin-3 or exedin-4.

The housing of the drug delivery device can be an exterior housing or some kind of an insert connected with an exterior housing. The housing may enable the safe, correct, and/or easy handling of the device and/or may be provided to protect the device from harmful liquids, dust or dirt. The housing can be unitary or a multipart component and may house a cartridge, from which doses of a drug can be dispensed. The housing may be provided with a lid, so that it can be opened to insert a cartridge containing a drug. The drive mechanism can be used to expel a drug from a cartridge that is inserted in the housing. The drug delivery device can be a disposable or re-usable device. The drug may be administered by a needle, or the device may be needle-free.

The drive mechanism comprises a flexible advance cable bearing a coupling feature of longitudinal extension. The advance cable is guided by a guide means. A drive means engages the coupling feature and thus enables an advancement of the advance cable according to the guide means. An end piece is provided to push a plug or bung of a cartridge containing a drug, and the end piece is driven by the advance cable. The drive means is provided for a permanent engagement with the coupling feature. This allows a permanent advancement of the plug or bung by means of the drive mechanism.

In an embodiment of the drive mechanism, the advance cable has an outer diameter that corresponds to an inner diameter of the cartridge.

In a further embodiment of the drive mechanism, the advance cable is provided with beads or balls having an outer diameter that exceeds the outer diameter of the advance cable and corresponds to the inner diameter of the cartridge.

In a further embodiment of the drive mechanism, the advance cable is a plastics material, and the beads or balls are formed as integral parts of the advance cable.

In a further embodiment of the drive mechanism, the beads or balls are separate parts arranged according to the guide means, and the advance cable passes through the beads or balls.

In a further embodiment of the drive mechanism, the drive means is a worm or pinion, and the coupling feature is a screw thread.

In a further embodiment of the drive mechanism, the drive means is a worm or pinion, and the coupling feature is a sequence of annular protrusions.

In a further embodiment of the drive mechanism, the drive means is a worm or pinion, and the coupling feature is a rack.

In a further embodiment of the drive mechanism, the advance cable is a plastics material, and the end piece is formed as an integral part of the advance cable.

In a further embodiment of the drive mechanism, the end piece is applied to the advance cable as a separate part formed from a metal.

In a further embodiment of the drive mechanism, a piston rod is driven by the advance cable, and the end piece is provided on the piston rod.

In a further embodiment of the drive mechanism, the piston rod is driven parallel to the advance cable.

The drive mechanism is particularly suitable for a permanent delivery of a drug from a compact drug delivery device, which may be carried on the body.

The drug delivery device comprises a housing and a flexible advance cable bearing a coupling feature of longitudinal extension, which is arranged inside the housing. A guide means, which guides the advance cable, is formed inside the housing. A drive means engages the coupling feature and thus enables an advancement of the advance cable according to the guide means. An end piece is provided to push a plug or bung of a cartridge containing a drug and is driven by the advance cable. The drive means is provided for a permanent engagement with the coupling feature.

In an embodiment of the drug delivery device, the end piece is applied to the advance cable.

In a further embodiment of the drug delivery device, the end piece is located on a piston rod, and the piston rod is advanced by the advance cable.

The length of the advance cable may exceed the dimensions of the housing, and the advance cable may be bent to fit into the housing. This allows particularly compact dimensions of the drug delivery device.

In the following, examples and embodiments of the drive mechanism and the drug delivery device are described in detail in conjunction with the appended figures.

DETAILED DESCRIPTION

FIG. 1shows a perspective view of an embodiment of the drug delivery device in an opened state. A housing1contains a drive mechanism comprising a flexible advance cable2, which may be bent as shown in the figure. A guide means3, which may be formed by sidewalls, for instance, is provided inside the housing1to guide the advance cable2along a prescribed way within the housing1and to inhibit a lateral deviation of the advance cable2. Thus the advance cable2may be stored in a compact volume and operated as a driving agent.

A drive means4is also arranged in the housing1and is engaged with a coupling feature12on the surface of the advance cable2. The coupling feature12extends along a major portion of the longitudinal extension of the advance cable2in order to facilitate a permanent advancement of the advance cable2by means of the coupling feature12. The drive means4is represented inFIG. 1as a worm, and the coupling feature12is shown to be a screw thread, the worm and the screw thread forming a worm drive. Instead, the drive means4may be a pinion, a quill drive, or a similar device. Instead of a continuous screw thread, the coupling feature12may comprises a sequence of separate annular protrusions. The position of the drive means4may differ from the location shown inFIG. 1. The drive means4may be operated by a loaded spring or by an electric motor supplied with a battery, for example. These components, which are known per se, can be applied as desired according to individual requirements and are not represented in the figures.

The housing1can be opened, and a cartridge6containing a drug may then be inserted into an empty space19left in the housing1for this purpose. In the embodiment shown inFIG. 1the housing1comprises a lid11, which may be hinged and can be opened.FIG. 1shows the cartridge6outside the housing1, and the direction in which the cartridge6is arranged when properly inserted is indicated. An end piece5of the advance cable2is provided to push a plug7or bung of the cartridge6.

When the cartridge6is inserted and the drive mechanism is actuated, the advance cable2is being advanced and the end piece5is maintained in contact with the plug7or bung, which is consequently also permanently advanced. An outlet21at the other end of the cartridge6is arranged in or at an opening20of the housing1, so that the drug is being expelled from the cartridge6and may be injected, by means of a needle, for instance, into a patient's body.

The end piece5may be an integral part of the advance cable2, particularly if the advance cable2is moulded from a plastics material as one part including the end piece5. Instead, the end piece5may be formed from a metal, like steel, aluminum, brass or other, and may be arranged as a separate part between the advance cable2and the plug7or bung, or may be fastened to the advance cable2by pressing, hammering, forging, clipping or the like.

The outer diameter of the advance cable2preferably corresponds to the inner diameter of the cartridge6, at least approximately. The guide means3allows the drive means4to exert a longitudinal force on the advance cable2, without causing a lateral deviation of the flexible advance cable2from the intended longitudinal path.

FIG. 2shows another embodiment, in which the radius of curvature of the bent portion of the advance cable2is smaller, so that the arrangement is more compact than in the embodiment according toFIG. 1. The pitch of the screw thread may be adapted to provide the required flexibility of the advance cable2. InFIGS. 1 and 2similar elements and corresponding components are designated with the same reference numerals.

FIG. 3shows still another embodiment, in which the position of the drive means4is changed, the screw thread of the coupling feature12has a smaller pitch, and the end piece5is not directly applied to and in contact with the advance cable2. The end piece5is instead provided on a piston rod13, which is shifted within a compartment that is formed by an inner sidewall10of the housing1. The piston rod13is advanced by means of a transverse bar8protruding from the advance cable2. The guide means3guides a portion of the advance cable2parallel to the movement of the piston rod13. The advance cable2may be prevented from a rotation around its longitudinal axis by threads or spikes which may be formed on the surface of the advance cable2and may be guided in tracks9provided in the sidewalls10of the guide means3. The bar8, which may be formed resembling a sprig or cantilever, for example, passes through an opening formed by one of the tracks9and extends far enough to be able to push the piston rod13in the direction of the cartridge6.

FIG. 4shows another embodiment, in which the advance cable2is provided with beads14or balls having an outer diameter that exceeds the outer diameter of the advance cable2and preferably corresponds to the inner diameter of the cartridge6. The beads14or balls allow the use of a thinner and therefore more flexible advance cable2and keep the advance cable2in its proper longitudinal direction with respect to the intended path of advancement. If the advance cable2is formed from a plastics material, the beads14or balls may be moulded together with the advance cable2. Instead, the beads14or balls may be separate parts arranged in the compartment that is formed by the guide means3, and the advance cable2may pass through openings or channels formed in the beads14or balls.

The beads14or balls may provide the coupling feature12which is engaged by the drive means4. Instead, the beads14or balls may each comprise a recess formed in such a manner that the recesses uncover a longitudinal strip of the surface of the core of the advance cable2. The coupling feature12may be provided by a toothing on said longitudinal strip, for example. The drive means4may comprise a worm as shown or a pinion fitting the rack that is formed by the toothing.

FIG. 5shows a detailed view of a drive means4which is particularly suitable in conjunction with the beaded advance cable2of the embodiment according toFIG. 4. The drive means4comprises a pinion15engaging the coupling feature12on the core of the advance cable2within the recesses22of the beads14or balls. The axis23of rotation of the pinion15is orthogonal to the direction of longitudinal extension of the advance cable2, which is the direction normal to the plane of the drawing. As can be seen fromFIG. 5, the beads14or balls enlarge the outer diameter17of the advance cable2to the outer diameter18of the beads14or balls.

Grooves16may be formed in the beads14or balls as a means to prevent a rotation of the advance cable2around its longitudinal axis and to maintain the recesses22of the beads14or balls in the appropriate position with respect to the pinion15or other drive means4. The grooves16may be guided by corresponding threads running along the guide means3or along the inner sidewalls10of the housing1. The position and the realisation of the drive means4may vary and deviate from the examples shown in the figures.

The drive mechanism and the drug delivery device provided with the drive mechanism are especially useful for infusion devices like insulin pumps, which are used to inject the drug permanently.

Further, the drive mechanism and the drug delivery device provided with the drive mechanism may be used in an injection device, for example in an injection device for injecting insulin such as long or short acting insulin. Such an injection may take place once per day for long acting insulin, or several times a day, for example before or after a meal, for other types of insulin.