HK1092084B - Improvements in and relating to drive mechanisms suitable for use in drug delivery devices - Google Patents

Description

Improvements in and relating to drive mechanisms suitable for use in drug delivery devices

Technical Field

The present invention relates to a drive mechanism suitable for use in a drug delivery device, in particular a pen injector, having dose setting means to enable the administration of a drug from a multiple dose cartridge. In particular, the present invention relates to a drug delivery device in which a user can set a dose.

Background

Such drug delivery devices are used in applications where regular injections are administered by persons without formal medical training, i.e. patients. This is increasingly common in patients with diabetes where self-treatment allows such personnel to effectively administer their diabetes.

These circumstances set a number of requirements for such drug delivery devices. The structure of such a device must be robust and easy to use in terms of the manipulation of the components and the understanding of the user of its operation and the delivery of the required dose of medicament. The dose setting must be easy and unambiguous. In the case of users with diabetes, many users are physically weak and may also have impaired vision, which requires that the drive mechanism has a low dispensing force and that the dose setting display is easy to read. Where the device is disposable rather than reusable, the device should be inexpensive to manufacture and easy to dispose of (preferably being suitable for recycling). To meet these requirements, the number of parts required to assemble the device and the number of types of materials from which the device is made need to be kept to a minimum.

User operated drug delivery devices comprising a telescopic piston rod are well known in the medical field.

WO9114467 a1 discloses a dispensing device comprising a drive mechanism with a telescopic piston rod consisting of first and second threaded members having equally spaced threaded sections and between the sections non-threaded sections. The device further comprises a dose setting sleeve which surrounds the coupled second threaded member for rotation and is in threaded engagement with the housing of the device. The leads of the threads of these three said elements are the same. The design of this device requires a ratio of body length to plunger length of about 1: 1 so that larger doses can be dispensed. However, the problem of simple and safe correction of a set overdose without dispensing the set amount of fluid nor disassembling the cartridge has not been solved.

Surprisingly, it has been found that the drive mechanism according to the invention provides a valuable solution for the design of a compact drive mechanism which requires less force to actuate and which also has the advantage that dose dial setting and dispensing can be performed safely. Furthermore, the drive mechanism according to the invention has the advantage of being intuitive and easy to use for correcting a set dose.

Disclosure of Invention

According to a first aspect of the present invention there is provided a drive mechanism for a drug delivery device comprising:

a housing;

a dose dial sleeve having a helical thread, the thread having a first lead; and

two-part piston rods; it is characterized in that the preparation method is characterized in that,

the piston rod comprises an outer part comprising an external helical thread having a second lead and an inner part comprising an external helical thread having a third lead, wherein the first lead of the thread of the dose dial sleeve is equal to the sum of the second lead of the thread of the outer part of the piston rod and the third lead of the thread of the inner part of the piston rod.

The term "drug delivery device" according to instant invention refers to a single-dose or multi-dose, disposable or reusable device designed to dispense a selected dose, preferably a plurality of selected doses, of a medicinal product, such as insulin, growth hormone, low molecular weight heparin, their analogs and/or derivatives, and the like. The device may be of any type, for example a small or pen type. Dose delivery may be achieved by a mechanical (optionally manual) or electrical drive mechanism or a stored energy drive mechanism such as a spring or the like. Dose selection may be achieved by a manual mechanism or an electronic mechanism. In addition, the device may include elements designed to monitor physiological characteristics such as blood glucose levels, etc. Also, the device may include a needle or be needle-free. In particular, the term "drug delivery device" refers to disposable, multi-dose pen-type devices having mechanical and manual dose delivery and dose selection mechanisms, which are designed to be used regularly by persons without formal medical training, such as patients. Preferably, the drug delivery device is of the syringe type.

The term "housing" according to instant invention preferably refers to any external housing ("main housing", "body", "housing") or internal housing ("insert element", "inner body"). The housing is designed such that the drug delivery device or any mechanism thereof can be safely, correctly and comfortably handled. Typically, the housing is designed to house, secure, protect, guide and/or engage any internal components of the drug delivery device (e.g. drive mechanism, cartridge, piston rod) by limiting exposure to contaminants such as liquid, dust, dirt etc. In general, the housing may be a tubular or non-tubular integral or multipart element. Typically, the outer housing is used to house a cartridge from which a plurality of doses of a medicinal product may be dispensed.

In other embodiments of the invention, the outer housing, the dose dial sleeve and/or the drive sleeve are each provided with one or more maximum dose stops adapted to be abutted by a corresponding radial stop provided on each corresponding engagement element.

The term "engaged" according to instant invention especially refers to an interlocking of two or more elements of the drive mechanism/drug delivery device, such as a spline connection or a threaded connection, preferably an interlocking of helical threads of the elements ("threaded engagement").

The term "helical thread" according to instant invention preferably refers to a full or partial thread on the inner and/or outer surface of an element of a drug delivery device, e.g. a cylindrical helical rib/groove, which is substantially triangular or square or circular in cross-section and designed to allow continuous free rotational and/or axial movement between the elements. Optionally, the threads may also be designed to prevent rotational or axial movement of a particular element in one direction.

The term "dose dial sleeve" according to instant invention refers to a substantially tubular element of substantially circular cross-section comprising:

a) internal and external screw threads, or

b) Internal screw threads, or

c) The external thread is provided with a screw thread,

preferably, the dose dial sleeve according to the present invention comprises a helical thread having a lead close to and preferably equal to the sum of the leads of the helical threads of the inner and outer parts of the two split piston rods. In another preferred embodiment of the invention the dose dial sleeve is threadedly engaged with the housing and, in a particular embodiment, the dose dial sleeve comprises a first portion having a first diameter and a second portion having a second diameter, wherein the outer surface of the first portion of the dose dial sleeve is threadedly engaged with the housing. In a further preferred embodiment, the dose dial sleeve is designed to indicate a selected dose of a dispensable drug. This may be achieved by using, for example, markings, symbols, numbers or the like printed on the outer surface of the dose dial sleeve or a range finder or the like.

The term "lead" according to instant invention preferably refers to the axial distance the nut advances when it rotates one full revolution; preferably, the "lead" refers to the axial distance travelled by a helically threaded element of the drive mechanism, i.e. the dose dial sleeve, the drive sleeve, the piston rod, etc. during one rotation. The lead is thus related to the pitch of the thread of the associated element.

The term "pitch" according to instant invention preferably refers to the distance between successive profiles on a helical thread measured parallel to the axis of the helical thread.

Optionally, the drive mechanism of the present invention further comprises a drive sleeve, wherein the term "drive sleeve" according to the present invention refers to any substantially tubular element of substantially circular cross-section which is engaged with the dose dial sleeve and more preferably also with the piston rod. In a particular embodiment of the invention, the drive sleeve includes a helical thread extending from the first end of the drive sleeve along an inner surface toward an internal shoulder (land) having a radially inwardly directed flange.

The term "releasably connected" according to instant invention preferably means that two elements of the inventive mechanism or device are reversibly connected to each other, for example by means of a clutch, which makes it possible to engage and disengage.

The term "piston rod" according to instant invention shall mean any two-part element adapted to operate through/within the housing, which element is designed for transferring axial movement through/within the drug delivery device, preferably from the drive sleeve to the piston, for expelling/dispensing an injectable product. The "two-part piston rod" of the present invention further refers to an element that is circular or non-circular in cross-section. It may be made of any suitable material known to those skilled in the art. The term "two-part piston rod" according to instant invention comprises an outer element and an inner element ("outer part" and "inner part") and at least two helical threads, preferably an outer helical thread on the outer part and an outer helical thread on the inner part. In other preferred embodiments of the invention the sum of the leads of said threads of the inner and outer parts of the "two part piston rod" is equal to the lead of the thread of the dose dial sleeve. The meaning of the term "equal" according to instant invention includes a value close to, substantially the same or the same as the lead of the thread, whereby the function of the above-mentioned threaded engagement of the threaded element is substantially maintained. Optionally, the leads of the threads of the inner and outer parts of the piston rod are oppositely arranged. One of the threads may be designed to engage the drive sleeve. In a further preferred embodiment of the invention, the inner and outer parts of the piston rod are adapted to move longitudinally relative to each other, but are restricted from relative rotation.

In another preferred embodiment of the invention, the outer part of the piston rod is adapted to move only longitudinally relative to the housing, e.g. by a ratchet arrangement. In a particular embodiment of the invention, the ratchet means is in the form of barbs (barb) or protrusions extending from the housing.

The term "first end" according to instant invention refers to the proximal end. The proximal end of the device or an element of the device refers to the end closest to the dispensing end of the device.

The term "second end" according to instant invention refers to a distal end. The distal end of the device or an element of the device refers to the end furthest from the dispensing end of the device.

Optionally, the drive mechanism of the invention further comprises a clutch device, wherein the term "clutch device" according to the invention means any such clutch: the clutch releasably connects the dose dial sleeve and the inner part of said piston rod and is arranged to allow the dose dial sleeve and the inner part of said piston rod to rotate relative to the housing when the dose dial sleeve and the inner part of said piston rod are coupled. In particular, the clutch means couples the inner part of the piston rod to the dose dial sleeve, thereby preventing rotation between the inner part of the piston rod and the dose dial sleeve when they are coupled. Preferably, the clutch means is located between the dose dial sleeve and the piston rod, in particular the inner part of the piston rod.

Thus, the term "clutch means" refers to any clutch that is engaged in order to reversibly lock two elements against (relative) rotation, for example by using an axial force to engage a set of surface teeth (saw teeth, dog teeth, crown teeth) or any other suitable friction surface.

In a particular embodiment of the invention, the clutch means comprises a plurality of radially extending longitudinally directed teeth provided on the dose dial sleeve and a disc connected to the inner part of the piston rod respectively.

In a further embodiment of the invention the drive mechanism comprises clicker means, for example provided between the clutch means and the dose dial sleeve, between the inner and outer parts of the piston rod, or any applicable position.

Optionally, the clicker means comprises an insert element having an upper portion and a lower portion depending therefrom, the upper portion of the insert element having a plurality of circumferentially spaced longitudinally extending teeth on an inner surface, the lower portion of the insert element comprising a flexible toothed member arranged to align with a plurality of circumferentially arranged longitudinally directed teeth provided on the inner surface of the dose dial sleeve, and the inner surface of the upper portion of the insert element having a plurality of circumferentially arranged longitudinally extending teeth arranged to align with a flexible toothed member provided on the clutch means such that relative rotation between the dose dial sleeve and the clutch means causes one of the flexible toothed members to pass the corresponding longitudinally directed teeth to produce a series of clicks.

A second aspect of the invention provides an assembly for a drug delivery device comprising a drive mechanism according to the invention.

A third aspect of the invention provides a drug delivery device comprising a drive mechanism or assembly according to the invention.

A fourth aspect of the invention provides a method of assembling a drug delivery device comprising the step of providing a drive mechanism or assembly according to the invention.

A fifth aspect of the present invention is the use of a drug delivery device according to the present invention for dispensing a pharmaceutical product, preferably a pharmaceutical formulation (e.g. solution, suspension, etc.) comprising an active compound selected from the group consisting of insulin, growth hormone, low molecular weight heparin, and analogues and/or derivatives thereof.

Drawings

The invention will be described in more detail, but not by way of limitation, with reference to a preferred embodiment and with reference to the accompanying drawings, in which:

fig. 1 shows a cross-sectional view of an embodiment of a drug delivery device according to the invention in a first position in which the cartridge is full;

fig. 2 shows a cross-sectional view of the drug delivery device of fig. 1 in a second position in which a maximum first dose is set;

FIG. 3 shows a cross-sectional view of the drug delivery device of FIG. 1 in a third position where a maximum first dose is dispensed;

fig. 4 shows a cross-sectional view of the drug delivery device of fig. 1 in a fourth position in which a final dose is set;

fig. 5 shows a cross-sectional view of the drug delivery device of fig. 1 in a fifth position where a final dose is dispensed.

Detailed Description

Referring first to fig. 1, a drug delivery device according to the present invention can be seen. The device comprises a housing 2 in which a cartridge 4 containing a medicinal product is arranged, means for selecting or setting a dose of medicinal product to be expelled, and means for expelling the selected dose of medicinal product. The housing 2 is generally cylindrical and is divided into two chambers by a web 6, which will be described in more detail below. The cartridge 4 is located in a first end of the housing 2 and the dose setting means and the means for expelling a selected dose of a medicinal product are located in a second end of the housing 2.

The cartridge 4 may be secured in place within the first end of the housing 2 by any suitable means. In the embodiment shown, the cartridge holder 12 is secured on a first side of the web by any suitable means for holding the cartridge in place. A needle assembly (not shown) may be secured to the first end of the cartridge holder 12. The cartridge 4 further comprises a movable piston 10. Pushing this piston 10 towards the first end of the cartridge 4 causes the medicinal product to be expelled from the cartridge 4 through the needle assembly. A cap may be provided to cover the needle assembly when the device is not in use.

The web 6 of the partition housing 2 extends radially inwardly from the cylindrical housing to define an opening 8. The piston rod 14 extends through the opening 8 in the connecting plate 6. The piston rod 14 comprises a first inner portion 16 and a second outer portion 18. The inner and outer portions 16, 18 of the piston rod are interconnected or engaged by a one-way ratchet for longitudinal movement therebetween, thereby limiting rotation between the inner and outer portions of the piston rod 14 in a first direction. In the shown embodiment the inner part 16 is connected to the outer part 18 by at least one radially extending flexible barb 17, which barb 17 extends from the inner part 16, which inner part 16 runs in a longitudinally extending groove 19 on the inner surface of the outer part 18 of the piston rod 14. In the embodiment shown, two diametrically opposed flexible barbs 17 are used, only one of which is visible in each figure, the other being hidden.

The first inner portion 16 of the piston rod 14 has a threaded portion 22 along the second end. The second outer portion 18 of the piston rod 14 has a helical rib (thread) 24 on its outer surface along the second end.

The ratchet 20 is provided in the form of a plurality of barbs or tangs extending from the housing. The ratchet 20 prevents relative rotation between the outer part 18 of the piston rod 14 and the housing 2. The ratchet 20 also prevents the outer part 18 of the piston rod 14 from retracting anticlockwise into the main housing 4, i.e. away from the piston 10 of the cartridge.

The dose setting means and the means for expelling a selected dose of a medicinal product will be described in more detail below.

A drive sleeve 30 is located at the second end of the piston rod 14. The drive sleeve 30 is cylindrical. A helical groove (thread) 32 extends along the inner surface of the drive sleeve 30 from the first end of the drive sleeve 30 toward an internal shoulder 34. Shoulder 34 also has a second thread 36 for engaging threaded portion 22 on inner portion 16 of piston rod 14.

The helical groove 32 and the helical rib 24 engage to allow relative rotation between the outer portion 18 of the piston rod 14 and the drive sleeve 30. The second thread 36 runs within the threaded portion 22 of the inner part 16 of the piston rod 14 to allow relative rotation between the drive sleeve 30 and the inner part 16 of the piston rod 14.

The helical rib 24 and the second thread 36 are oppositely manipulated.

The generally cylindrical dose dial sleeve 40 comprises a first portion having a first diameter and a second portion having a second diameter. The first part is located between the drive sleeve 30 and the housing 2. Both the outer surface of the first part and the inner surface of the housing 2 have inter-engaging features to form a helical thread 41 between the housing 2 and the dose dial sleeve 40. This allows the dose dial sleeve 40 to rotate around and along the housing 2. The outer surface of the dose dial sleeve 40 has numerals or other indicia (not shown) of the dose that may be dialed. The housing has a window (not shown) through which numerals or other indicia representing a user selected dose may be displayed.

The dose dial sleeve 40 and the drive sleeve 30 are splined together. The inner surface of the dose dial sleeve 40 and the outer surface of the drive sleeve 30 are keyed together to allow only longitudinal movement therebetween.

The outer diameter of the second part of the dose dial sleeve 40 is the same as the housing 2. Within the dose dial sleeve 40 there is a shoulder 42 between the first part of the dose dial sleeve 40 and the second part of the dose dial sleeve 40. The inner surface of the shoulder 42 has a plurality of radially extending longitudinally oriented teeth. The inner surface of the second part of the dose dial sleeve 40 has a plurality of circumferentially spaced longitudinally extending serrations 54. Each serration has a radially oriented surface and an inclined surface.

The second part of the dose dial sleeve 40 comprises a first recessed region in which the clutch 48 is retained and another region in which the button 50 is retained. The button 50 is free to rotate within the second portion of the dose dial sleeve 40 and is axially connected to the clutch 48. The button 50 is generally a "T" shaped structure with the stem thereof retained within a circumferential recess provided in the clutch 48. The stem of the button 50 has a circumferential flange which is retained within the circumferential recess, the button 50 being free to rotate relative to the clutch and dose dial sleeve 40 but still being retained axially within the clutch 48.

The clutch includes a disc having a plurality of radially extending longitudinally oriented teeth. The clutch 48 is retained on the first inner portion 16 of the piston rod 14 so that no relative rotation occurs therebetween. When the dose dial sleeve 40 and the clutch 48 are not forcibly engaged together, their respective teeth will ride over each other. Preferably, the radial spacing of each tooth corresponds to a unit dose. The clutch 48 is connected to the inner portion 16 of the piston rod 14 so as to prevent relative rotation therebetween.

A clicker is also provided between the clutch 48 and the second portion of the dose dial sleeve 40. In the illustrated embodiment, the second section of the dose dial sleeve 40 has an insert element 44 having an upper portion and a lower portion depending therefrom. The upper portion of the insert member 44 is provided with a plurality of circumferentially spaced longitudinally extending serrations on an inner surface. Each serration has a radially oriented surface and an inclined surface. The clutch 48 supports a flexible toothed member 52 around an upper region of the clutch 48, which member is aligned with the upper portion of the male member 44.

The lower portion of the insertion element 44 is in the form of a flexible toothed member that is biased in a generally radially outward direction. The lower part of the insert 44 is generally aligned with the teeth 54 provided on the inner surface of the second part of the dose dial sleeve 40.

The radial spacing of the teeth on each of the dose dial sleeve 40 and the inserted component 44 preferably corresponds to a unit dose.

Relative rotation between the dose dial sleeve 40 and the clutch 48 in a first direction will cause the flexible toothed member 52 to pass the inclined surfaces of the serrations on the inserted component 44, thereby creating a series of clicks. Conversely, relative rotation between the dose dial sleeve 40 and the clutch 48 in a second direction opposite to the first direction will cause the flexible toothed member 52 to abut against the radial surface of one of the serrations of the upper portion of the inserted component and urge the inserted component 44 in the second direction. However, this will cause the lower part of the inserted component 44 to pass over the inclined surface of the serrations 54 on the dose dial sleeve 40, thereby creating a series of clicks.

The first direction may be selected to represent a direction of increasing or decreasing a set dose and the second direction is the opposite case of a dial setting with a suitable arrangement of the flexible member and the longitudinally extending teeth.

In fig. 1, the device has a pre-filled cartridge 4. To operate the device, the user first has to select a dose. To set a dose, the second part of the dose dial sleeve 40 is rotated relative to the housing 2 outwardly from the housing 2. Since the drive sleeve 30 cannot rotate relative to the dose dial sleeve 40, this rotates out of the initial position by an amount corresponding to the required dose. Thus, the drive sleeve 30 rotates around the helical rib 24 of the outer part 18 of the piston rod. The second thread 36 of the drive sleeve 30 thus also runs within the threaded portion 22 of the inner part 16 of the piston rod 14, thereby withdrawing the inner part 16 of the piston rod 14 from the outer part 18 a distance related to the dose selected by the user. When a dose has been dialled, the drive sleeve 30 is lowered down the inner part 16 of the piston rod a distance equal to the distance required to move the piston 10 of the cartridge in order to expel the selected dose of the medicinal product.

In the illustrated embodiment, when a dose is incrementally set, relative rotation between the dose dial sleeve 40 and the clutch 48 (fixed against rotation relative to the inner portion 16 of the piston rod 14) causes the flexible toothed member of the inserted component 44 to pass the teeth 54 on the dose dial sleeve 40, thereby creating a series of clicks. This is an audible confirmation that the dose is set with a scale. In reducing the dose setting, the inserted component 44 locks onto the dose dial sleeve and the flexible member 52 acts on the teeth of the inserted component 44. In this way, a voice confirmation of the action set by the user with the scale is generated.

The user may rotate the dose dial sleeve 40 to increase or decrease the selected dose to be delivered. Advantageously, the first portion of the dose dial sleeve 40 has a marked scale which, together with the associated parts of the housing, enables the user to determine the selected dose to be delivered. The relevant parts of the housing 2 may comprise a window formed in the housing 2 or markings on the housing 2 for alignment with the marked scale.

Once the required dose has been set (as shown in fig. 2), to deliver the dose, the user depresses the button 50 to advance the button 50 and associated clutch 48 towards the first end of the housing 2. When the button 50 is depressed, the clutch 48 is pushed into the second part of the dose dial sleeve 40 to prevent relative rotation of the dose dial sleeve 40 and the inner part 16 of the piston rod 14. The button 50 is still rotatable relative to the dose dial sleeve and the drive sleeve 30. Further longitudinal movement of the button 50 causes the dose dial sleeve 40 (together with the drive sleeve 30) to rotate towards the first end of the device. As the dose dial sleeve 40 travels into the housing 2, rotation of the drive sleeve 30 (keyed to the dose dial sleeve 40) forces the outer part 18 of the piston rod 14 to move axially relative to the housing 2.

Rotation of the inner portion 16 of the piston rod 14 within the outer portion 18 of the piston rod 14 as the button is advanced towards the first end of the housing 2 causes the barbs 17 to ride over the grooves 19 to provide tactile and audible feedback as each unit of medicine is dispensed. It can be seen that the angular spacing of the grooves 19 preferably corresponds to a unit dose.

The outer part 18 of the piston rod 14 continues to advance until the dose dial sleeve 40 has returned to its initial position relative to the housing and the drive sleeve has returned to its initial position relative to the outer part 18 of the piston rod 14 (figure 3).

Other doses may also be delivered as desired. Figure 4 shows an example of a subsequently selected dose. It is noted that the drive sleeve 30 has been advanced further along the threaded portion 22 of the inner portion 16 of the piston rod 14. The position of the drive sleeve 30 along this threaded portion 22 corresponds to the amount of medicament remaining in the cartridge 4, and therefore, when the drive sleeve 30 reaches the end of the threaded portion 22 and cannot be rotated further, this corresponds to no medicament remaining in the cartridge 4. It will be seen that if the amount of medicine the user intends to select is greater than the amount remaining in the cartridge 4, this will not be achieved because the dose dial sleeve 40 is prevented from continuing to rotate and set a larger dose when the drive sleeve 30 stops rotating.

Fig. 5 shows a device according to the invention in which the entire medicinal product in the cartridge 4 has been discharged.

Claims (10)

1. A drive mechanism for a drug delivery device comprising:

a housing;

a dose dial sleeve having a helical thread, the thread having a first lead; and

two piston rods are divided; it is characterized in that the preparation method is characterized in that,

the two part piston rod comprises an outer part comprising a helical thread having a second lead and an inner part comprising a helical thread having a third lead, wherein the first lead of the thread of the dose dial sleeve is equal to the sum of the second lead of the thread of the outer part of the piston rod and the third lead of the thread of the inner part of the piston rod.

2. An assembly for a drug delivery device comprising the drive mechanism of claim 1.

3. A drug delivery device comprising the drive mechanism of claim 1 or the assembly of claim 2.

4. A drug delivery device according to claim 3, characterized in that the device is a pen-type device.

5. A drug delivery device according to claim 3, characterized in that the device is a syringe type device.

6. A drug delivery device according to claim 3, characterised in that the device comprises a needle.

7. A drug delivery device according to claim 3, characterized in that the device is a device which does not comprise a needle.

8. The drug delivery device of claim 3, wherein the drug delivery device is for dispensing a drug.

9. The drug delivery device according to claim 8, characterized in that it is used for dispensing pharmaceutical formulations comprising active compounds selected from the group consisting of insulin, growth hormone, low molecular weight heparin, their analogues and derivatives.

10. A method of manufacturing or assembling a drug delivery device, the method comprising the step of providing a drive mechanism as claimed in claim 1 or an assembly as claimed in claim 2.