Injection Device

Abstract

An injection device is described. The injection device includes a housing, a dose indicator, and a release mechanism. The dose indicator is positioned within the internal space of the housing. The dose indicator includes a number of engaging members at least one thereof being configured to contact multiple of distinct ratchet features in course of a helical or screwing movement in distinct positions, wherein the contact is configured to provide a user with a tactile indexing appearance in the way of an increased or decreased dwelling torque at each of the multiple distinct positions. The release mechanism is connected to the dose indicator. The release mechanism is configured to, when activated during dose dispense, urge the engaging members away from the distant position and against the force of the resilient bias thereby suspending the indexing ratchet appearance at least for a subset of the multiple distinct positions.

Claims

1-15. (canceled)

16. An injection device comprising: a housing defining an internal space with an inner surface, the inner surface being provided with a thread feature and multiple distinct ratchet features spread along a helical path; a dose indicator positioned within the internal space of the housing, the dose indicator having an external surface configured to mesh or engage with the thread feature for restricting a motional freedom of the dose indicator within the housing to follow a helical or screwing movement during a dose dialing and a dose dispensing, the dose indicator further comprising a number of engaging members, at least one of the engaging members being configured to contact the multiple distinct ratchet features in distinct positions during the helical or screwing movement, wherein the contact is configured to provide a user with a tactile feedback by increasing or decreasing a dwelling torque at each of the distinct positions, and wherein the engaging members are resiliently biased towards a distant position; and a release mechanism connected to the dose indicator, the release mechanism being configured to, when activated during the dose dispensing, urge the engaging members away from the distant position and against a force of the resilient bias thereby suspending the tactile feedback at least for a subset of the multiple distinct positions.

17. The injection device of claim 16, wherein the thread feature is a helical thread, and the multiple distinct ratchet features are integrated with the helical thread.

18. The injection device of claim 17, wherein the multiple distinct ratchet features are integrated with the helical thread as a profiled crest line or as a shoulder of the helical thread.

19. The injection device of claim 16, wherein the multiple distinct ratchet features are provided as a series of teeth, notches or detent features that are arranged along a helical path on the internal surface or integrated with the helical path of the thread feature.

20. The injection device of claim 16, wherein the resilient bias of the engaging members towards the distant position is appropriate for contacting the multiple distinct ratchet features.

21. The injection device of claim 16, wherein the resilient bias of the engaging members is achieved by elasticity of multiple live hinges integrated with each of the engaging members.

22. The injection device of claim 16, wherein the tactile feedback is suspended by reducing the dwelling torque to a uniform lower value.

23. The injection device of claim 16, wherein the release mechanism is integrated with a drive member, the drive member being located within the dose indicator and comprising a first sleeve-like element that is axially displaceable relative to the dose indicator during the dose dispensing.

24. The injection device of claim 23, wherein the dose indicator further comprises at least one slider member, wherein a pivotable member is adapted to support the first sleeve-like element during axial displacement of the first sleeve-like element relative to the dose indicator.

25. The injection device of claim 23, wherein during the dose dispensing, the dose indicator is rotatably fixed with regard to the first sleeve-like element, wherein the drive member comprises a second sleeve-like element positioned within the first sleeve-like element, wherein the second sleeve-like element is splined to a lead screw, and wherein the first sleeve-like element is coupled to the second sleeve-like element by a connection comprising a pin and a groove, wherein the pin moves along the groove during the dose dialing and the dose dispensing.

26. The injection device of claim 25, wherein the groove provides a first pitch along a first section of the groove and a second pitch along a second section of the groove, wherein the first pitch is different from the second pitch.

27. The injection device of claim 25, wherein the lead screw is rotatably coupled with the housing during the dose dispensing and is axially and rotatably fixed with regard to the housing during the dose dialing.

28. The injection device of claim 23, wherein the drive member effects a change in a transformation ratio between a rotation and a longitudinal shift of the dose indicator with regard to the housing such that within a first rotation angle section the rotation of the dose indicator is transformed with a first transformation ratio and within at least a second rotation angle section the rotation of the dose indicator is transformed with a second transformation ratio.

29. The injection device of claim 23, further comprising an injection button coupled to a proximal end of the dose indicator, wherein the injection button is adapted to be pressed into a distal direction for the dose dispensing thereby axially displacing the first sleeve-like element relative to the dose indicator.

30. The injection device of claim 23, wherein at least of the engaging members has a wing-like form, and wherein a sloping surface at a proximal end of the wing-like form is adapted such that a corresponding sloping surface at a distal end of the first sleeve-like element engages the sloping surface of the wing-like form during the dose dispensing and after an axial displacement of the first sleeve-like element thereby urging the engaging member away from the distant position.

31. The injection device of claim 16, wherein at least of the engaging members has a wing-like form with a wing-like portion, wherein: the wing-like portion is integrated with the dose indicator thereby defining a live hinge with a pivot axis located at the live hinge, or a side surface of the wing-like form is oriented radially outwards is adapted to engage with the multiple ratchet features.

32. The injection device of claim 16, wherein the multiple distinct ratchet features include a first subset of ratchet features having a first profile form and a second subset of ratchet features having a second profile form, wherein the first profile form is different from the second profile form.

33. The injection device of claim 16, wherein the dose indicator comprises a scale at its outer surface showing a dialed dose to the user through a window or an opening within the housing.

34. The injection device according to claim 33, wherein the drive member effects a change in a transformation ratio between a rotation and a longitudinal shift of the dose indicator with regard to the housing such that within a first rotation angle section the rotation of the dose indicator is transformed with a first transformation ratio and within at least a second rotation angle section the rotation of the dose indicator is transformed with a second transformation ratio, and wherein the scale comprises a first scale section corresponding to the first rotation angle section and a second scale section corresponding to the second rotation angle section, wherein a graduation of the first scale section is different from a graduation of the second rotation angle section.

35. The injection device of claim 16, further comprising a cartridge containing a liquid medicament.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0046] Non-limiting, exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0047] FIG. 1A shows a side view of a first embodiment of an injection device with a cap;

[0048] FIG. 1B shows a side view of the injection device of FIG. 1 without cap;

[0049] FIG. 2 shows an exploded view of the components of the injection device of FIG. 1;

[0050] FIG. 2A depicts a longitudinal section of the proximal end of the injection device of FIG. 1 during dose dialing;

[0051] FIG. 2B shows a cross section of the injection device of FIG. 1 during dose dialing (see A-A in FIG. 2A);

[0052] FIG. 2C shows an enlarged section of FIG. 2A;

[0053] FIG. 2D depicts a longitudinal section of the proximal end of the injection device of FIG. 1 during dose dispensing;

[0054] FIG. 2E shows a cross section of the injection device of FIG. 1 during dose dispensing (see A-A in FIG. 2D);

[0055] FIG. 3 shows a cross section of the drive member of the injection device of a second embodiment of an injection device (see A-A in FIG. 4);

[0056] FIG. 4 depicts a partly cut away side view of the drive member of FIG. 3; and

[0057] FIG. 5 shows the unrolled surface of one element of the drive member of FIG. 3.

DETAILED DESCRIPTION

[0058] FIGS. 1A and 1B show a first embodiment of an injection device (drug delivery device) in the form of an injection pen. The device has a distal end (lower end in FIGS. 1A and 1B) and a proximal end (upper end in FIGS. 1A and B). The component parts of the injection device are shown in FIG. 2. All components are located concentrically about a common principal axis (longitudinal axis) of the mechanism. The drug delivery device comprises a body or housing 1, a cartridge holder 2, a cartridge 3, a cap 4, a lead screw (piston rod) 6, an insert 40, a drive member which is a unit consisting of two elements, namely a bushing (first sleeve-like element) 82 and a driver tube (second sleeve-like element) 85, a dose indicator (number sleeve) 80, a dial grip 81, and an injection button 88.

[0059] A needle arrangement (not shown) with a needle hub and a needle cover may be provided as additional components, which can be exchanged as explained above. The needle arrangement may be attached to the distal end of the cartridge holder 2, for example by a thread 5 (see FIGS. 1B and 2).

[0060] The removable cap 4 fits over the cartridge holder 2 and is retained via clip features to the cartridge holder 2 or the housing 1 (see FIG. 1A).

[0061] The housing 1 is a generally tubular component which provides location for the liquid medication cartridge 3 and the cartridge holder 2 which is attached to the housing 1 or integral with it. The cartridge holder 2 receives cartridge 3. A slot or window 2a is provided through which the cartridge 3 can be viewed.

[0062] One window (through going opening) 18 is provided extending in the longitudinal direction of the housing 1. Through window 18 the dose number N of a scale provided on the outer surface of the dose indicator 80 can be viewed. In one embodiment, the window 18 may be covered by a transparent layer or may comprise a transparent lens in order to magnify the shown dose number N.

[0063] The lead screw 6 has an external thread 7 and is rotationally constrained to driver tube 85 via a splined interface. When rotated, the lead screw 6 is forced to move axially relative to the housing 1, through its threaded interface with the insert 40 using thread 7 of the lead screw 6. The lead screw 6 acts on a bung within the liquid medicament cartridge 3 such that the medicament is driven out of the cartridge 3.

[0064] The insert 40 is axially and rotationally fixedly attached to the housing 1, for example within the distal end of the housing 1.

[0065] The tubular bushing 82 having a flange 83 at its proximal end fits into the dose indicator 80 and over the driver tube 85. The bushing 82 has, for example, two pins 101 projecting from its inner wall engaging grooves 100 of the driver tube 85 whereby the bushing 82 and the driver tube 85 are coupled to each other so that rotation is transmitted between said two elements based on the form of the groove 100 as explained in detail below. Providing only one pin 101 or three or more pins 101 is possible as well.

[0066] The driver tube 85 is a tubular element which comprises, for example, two grooves 100 running in axial (longitudinal) direction at its outer surface. The number of grooves 100 corresponds to the number of pins 101 of the bushing 82.

[0067] The dial grip 81 is splined to the dose indicator 80, for example by teeth, when in the dialing condition. Alternatively, as shown in FIGS. 2A and 2D the dial grip 81 is one-piece with the dose indicator 80, for example formed by injection molding.

[0068] The motional freedom between the dose indicator 80 and the housing 1 is constrained to follow a helical or screwing movement. This is achieved by corresponding mechanical features provided on the dose indicator 80 on one hand side and the inner surface 11 of the housing 1 on the other hand side that mate to form a threaded connection. In the specific situation, the inner surface of the housing is provided with a thread feature in the way of an extended helical rib 12. In the specific situation, the corresponding configuration on the dose indicator for mating with the tread feature on the housing inner surface 11 is a helical groove 79, located at the outer surface of the dose indicator 80. The helical path 79 may have rotational hard stops (not shown) at the respective ends forming a zero dose abutment and a maximum dose abutment for the dose dialed within one dialing step. The dose indicator 80 is marked with a sequence of numbers N in form of a scale at its outer surface, which are visible through the window 18 in the housing 1, to denote the dialed dose of medicament.

[0069] The injection button 88 may be formed a plate-like element which is rotatably mounted with a pivot pin 94 journaled in an end wall of the bushing 82. Alternatively, as shown in FIGS. 2A and 2D, the injection button 88 is rotatably coupled to the bushing 82 by means of a bearing 95, for example, a ball bearing. During dose dialing, the injection button 88 moves axially together with the bushing 82 in proximal direction. During dose expelling, the button 88 is pressed by the user's finger axially in distal direction and moves driven by the force of the users finger into the distal direction and does not rotate, wherein the bushing 82 rotates together with the dose indicator 80, the driver tube 85 and the lead screw 6 helically with respect to the housing 1. The bearing 95 allows the rotation of the bushing 82 relative to the injection button 88.

[0070] As depicted in FIGS. 2A to 2E a the crest line 12a of the projecting helical thread 12 comprises at least along a predefined section a toothing 112, for example gear teeth or saw teeth. Other pointed or rounded toothing forms are possible, as well. In the specific example, the teething is of a regular kind in the sense that the teeth or features are placed adjacently and without suspension, for example by intermittent un-contoured regions. The purpose of the teething 112 is to provide a mechanical interface with a multiple of distinct ratchet features that serve for contact areas in an interacting or meshing engangement with one or more engaging members located in essentially fixed relation to the dose indicator 80. This engagement, in general, is configured to cause a modulation in the dwell torque or frictional counter torque it acts against a relative rotation of the dose indicator 80 and the housing 1. The modulation, at a distinct position, may be in the way of an increase or decrease in the dwell torque that promotes or counteracts a user induced rotation of the aforementioned parts. In instances, the perception of the modulation can provide a user with a tactile indexing feedback. In instances, the indexing feedback may be such that it allows the user to understand where distinct preferred dialing positions are located. In other situations, as shown in the figures, the feedback may be rather designed to give the user a tactile impression when performing a stepwise increase or decrease in dose dialing. The feedback may be provided for convenience reasons but, in instances, the feedback may also be designed to increase safety. In particular, an appropriately defined dose increment overhaul torque may help to prevent unintended changes in dose setting. Unintended dose setting changes could be cause by incautious handling of the dialed injection device during subsequent steps before drug administration. It is not hard to imagine that unexperienced users might touch the injection device at the dose indicator 80 when screwing a needle (not shown) onto the flange, namely thread 5.

[0071] It should be apparent, that perceivable indexing appearance requires some torque input. It might therefore be a consideration to provide switchable indexing appearance. This may help to reduce an indexing caused loss in torque output during dose delivery. It should be noted that the torque required for rotating the lead screw has to be created by conversion of the linear user input force along the threaded engagement between the dose indicator and the housing. In the shown embodiment, switching of the indexing is achieved by means of one engaging member 84a which is pivotable hinged to the dose indicator 80 in a live hinge or similar bendable structure. In particular, the live hinge is configured to provide a biasing force to the engaging member 84a in a radially outward direction. This biasing is configured to urge the engaging member 84a into engagement with a teeth (cog) of the teething 112. Accordingly, this contact occurs at the side surface 184a of the engaging member 84 which is oriented radially outwards against the crest line of the teething 112 of the thread 12. This is shown in FIGS. 2A, 2B and 2C. The engaging member 84a is attached by a neck portion 284a located at the distal end of the engaging member 84a to the dose indicator 80, wherein the neck portion 284a is, for example, pivotably attached to a front surface of a distal end flange of the dose indicator 80 as shown in FIGS. 2A, 2C and 2D. In the specific embodiment, the engaging member 84a has a wing-like form with a proximal end and a sloping surface 384a extending from the proximal end of the wing-like form.

[0072] In the specific embodiment, the dose indicator 80 further comprises at least one second pivotable member 84b which is located, as shown, radially opposite to the slider member 84a. Very similar to the engaging member 84a, the slider member 84b has a wing-like form In difference to the engaging member 84a, the slider member 84b does not engage with the teething 112 of the thread 12 but rather abuts against a cylindrically shaped portion of the inner surface 11. The contact region of the slider member 84b may be provided as a slightly rounded side surface 184b projecting radially outwards. This is shown in FIGS. 2A to 2C. In the outlined situation, the slider member 84b is expected to produce approximately the opposite radial reaction force to the dose indicator 80 as the engaging member 84a produces to thereby maintain the dose indicator 80 in a center axis balanced force situation. The second pivotable member 84b is attached to the front surface of the distal end flange of the dose indicator 80 by a second live hinge 284b. Both, namely the engaging member 84a and the slider member 84b have tapered rounded heads defining protruding distally into the interior space of a teethed bore 86 in the dose indicator 80. The rounded heads define two radially outward facing sloping surfaces 384a, 384b that allow contact of a tapered surface to deflect the members 84a, 84b radially inwards.

[0073] Additionally, the dose indicator 80 comprises a compression spring 89 located between the front surface of the distal end flange of the dose indicator 80 at its distal end and an opposite distal front surface of the bushing 82 and presses the flange 83 of the bushing 82 and/or an outer flange 88a of the injection button 88 against a flange 80a projecting from the inner surface of the dial grip 81 or the dose indicator 80.

[0074] Alternatively or additionally, a biasing element, for example at least two Belleville spring washer, may be provided between a flange 80b at the housing (see FIGS. 2A and 2D) and the flange 83 of the bushing 82 (not shown).

[0075] The bushing 82 comprises at its distal end a sloping surface 82a forming a cone-like surface (see FIG. 2C). Further, the outer surface of the bushing 82 comprises at its distal end longitudinal grooves 82b (see FIGS. 2C and 2D).

[0076] With the device in the “at rest” condition, the dose indicator 80 is positioned at its initial position, for example with its zero dose abutment against the zero dose abutment of the housing 1 and the injection button 88 is not depressed, i.e. in the position shown in FIG. 1A. Dose marking (number) ‘0’ on the dose indicator 80 is visible through the window 18 of the housing 1.

[0077] The user selects a variable dose of the medicament by rotating the dial grip 81 clockwise, which generates an identical rotation of the dose indicator 80 by the connection to the housing 1 via thread 12 and helical path 79. The dose indicator 80 with the dial grip 81, the injection button 88 screws out and the bushing 82 is thereby lifted away from the proximal end of the housing 1 (see FIG. 1B), wherein the axial distance moved by the bushing 82 into proximal direction corresponds to the axial distance over which the dose indicator is screwed out.

[0078] As the dose indicator 80 rotates, each projecting pin 101 of the bushing 82 translates along the respective longitudinal groove 100 of the driver tube 85 into proximal direction taken along by the axial force of the compression spring 89, wherein the driver tube 85 is locked against clockwise rotation by radial protrusions at a clicker arm 85a which are biased toward the inner side wall of the insert 40. Neither the driver tube 85 nor the lead screw 6 undergo any type of motion relative to the housing during dose dialing.

[0079] If a set dose is reduced by rotating the dose setting button 81 in an anti-clockwise direction the pawl mechanism working between the driver tube 85 and the housing 1 (radial protrusion at clicker arm 85a) is sufficient reluctant to rotate in its non-blocking direction to prevent the bushing 82 and driver tube 85 from following this anti-clockwise rotation. As in this situation each pin 101 of bushing 82 travels along the groove 100 into distal direction the movement of the dose indicator 80 and the bushing 82 is reversed from the movement described above.

[0080] By the rotation of the dose setting button 81 in any direction the cog or tooth on the side surface 184a of the pivotable engaging member 84a of the dose indicator 80 clicks from one recess between two of the teeth of the teething 112 at the thread 12 to the next one, the recesses may be so spaced that one click corresponds to a pre-defined change of the set dose, e.g. one unit or one half unit. As the user rotates the dial grip 81 sufficiently to increment the mechanism by one increment, the dose indicator 80 rotates relative to the housing 1 by one recess. At this point the protrusion (cog or tooth on the side surface 184 of the engaging member 84a) re-engage into the next settled position. Depending on the shape of the teething 112 and the engaging member 84a, an audible click may be generated by the tooth overhaul, and tactile feedback is given by the change in torque input.

[0081] The user may further increase the selected dose by continuing to rotate the dial grip 81 in the clockwise direction. The process of overhauling the teeth of the teething 112 is repeated for each dose increment. If the user continues to increase the selected dose until the maximum dose limit for one selected medicament dose (not shown) is reached, the dose indicator 80 may reach the maximum dose abutment when provided on the housing 1 and thereby prevent further rotation of the dose indicator 80 in this direction.

[0082] The compression spring 89 may be attached to the dose indicator 80 and slides with its proximal end along the distal front surface of the bushing 82 during dose dialing. Alternatively, the compression spring 89 is attached to the bushing 82 and slides along the dose indicator 80 during dose dialing. It is a purpose of the compression spring 89 to maintain the bushing 82 in a distally retracted position relative to the dose indicator 80 wherein no engagement of the internal teeth 86 in the bore of the dose indicator 80 and on the external teeth 82b on bushing occurs and the dose indicator 80 is allowed to rotate without driving the bushing 82.

[0083] With the mechanism in a state in which a dose has been selected, the user is able to deselect any number of increments from this dose. Deselecting a dose is achieved by the user rotating the dial grip 81 anti-clockwise.

[0084] When the injection button 88 is pressed to inject (dispense) the set dose the bushing 82 will follow the anti-clockwise rotation of the dial grip 81 which is induced by the thread engagement between the helical path 79 of the dose indicator 80 and the thread feature 12 at the inner side of the housing 1 when the dose indicator 80 is pressed back into the housing 1. Before this rotation starts, a splined connection is created between the dose indicator 80 and the bushing 82 to cause the bushing 82 for rotating together with the dose indicator 80. In the embodiment, the splined connection is provided by the grooves 82b of the bushing 82 engaging the teeth between two neighboring grooves 86 at the inner wall of the dose indicator 89 (see FIG. 2D). In view of this aforementioned switching in the drivetrain configuration it is useful to understand that the spring 89 may be configured such as to allow engagement of the splined connection before the dose indicator 80 starts rotating. This can, for example, be achieved by making the spring rate and bias such that the linear force required for overcoming the spring 89 until splined engagement occurs is not sufficient, when converted into a torque, for rotating the dose indicator 80 away from the presently settled index engagement between the teething 12 and the engaging member 84a. In a more elaborated variant with intermittent teething 112 the forces may be arranged such as to create the above locking effect only in a position of the dose indicator 80 where a ratchet feature 112 engagement occurs. In the intermittent positions the dose indicator 80 would be driven towards the next ratchet feature 112 engagement without driving the bushing 82 to this extent. At the ratchet feature engagement, the mechanism would behave as explained before, namely by engaging the splined connection between dose indicator 80 and bushing 82 before subsequent rotation takes place.

[0085] By pressing the injection button 88 the injection button 88 and with it the bushing 82 move into distal direction relative to the dose indicator 80 against the force of the compression spring 89 until the flange 83 of the bushing and/or the flange 88a of the injection button 88 abuts the second flange 80b of the dose indicator 80 (see FIG. 2D). By the displacement of the bushing 82 the engaging member 84a and the slider member 84b are deflected radially inwards by abutment of the sloping surface 82a of the bushing 82 against the sloping surfaces 384a, 384b of the engaging member 84a and the slider member 84b. The deflection of the engaging member 84a causes disengagement of the engaging member 84 from the teething 112. The slider member 84b is deflected, as well, thereby maintaining the balance in reaction forces on the bushing 82 and thereby avoiding creation of any tilting torque on the bushing 82 relative to the dose indicator 80 (see FIGS. 2D and 2E). The deflection axis are configured to extend, for example, essentially perpendicular to the longitudinal axis of the injection device. Further, the displacement of the bushing 82 into distal direction causes an engagement of the grooves 82b at the outer surface of the bushing 82 and the teeth forming the grooves 86 at the inner surface of the dose indicator 80 thereby coupling the dose indicator 80 and the bushing 82 so that both elements rotate together. In one embodiment the longitudinal force necessary to compress the compression spring 89 is configured such that first the grooves 82b at the outer surface of the bushing 82 engage the teeth forming the grooves 86 at the inner surface of the dose indicator 80 and after engagement the longitudinal force provided by the user to the injection button 88 is transmitted via the dose indicator 80, the bushing 82, the driver tube 85 to the lead screw 6 in order to inject the dialed medicament dose.

[0086] Tactile feedback during dose dispense may be provided via compliant cantilever clicker arm 85a integrated into the distal end of the driver tube 85 as shown in FIG. 2. This arm 85a interfaces radially with ratchet features on the inner surface of the insert 40, whereby the ratchet tooth spacing corresponds to the dose indicator 80 rotation required for a single increment dispense. During dispense, as the driver tube 85 rotates, the ratchet feature engages with the clicker arm 85a to produce an audible click with each dose increment delivered. The clicker arm 85a is further adapted such that it prevents rotation of the lead screw during dose dialing.

[0087] Delivery of a dose continues via the mechanical interactions described above while the user continues to depress the injection button 88. If the user releases the injection button 88, the delivery of a dose is halted.

[0088] Once the delivery of a dose is stopped, by the dose indicator 80 returning to the zero dose abutment within the housing 1, the user may release the injection button 88. The mechanism is now returned to the “at rest” condition, in particular the dose indicator 80 is returned to its initial position (zero position, see FIG. 1A).

[0089] In one embodiment at the end of dose, additional audible feedback may be provided in the form of a “click”, distinct from the “clicks” provided during dispense, to inform the user that the device has returned to its zero position.

[0090] In a second embodiment shown in FIGS. 3 to 5 corresponds to the embodiment shown in FIGS. 1A to 2D but each groove 100 of the driver tube 85 has a first section 100a at its distal end and a second section 100b at its proximal end, wherein the second section 100b is a straight groove traveling parallel to the longitudinal axis of the device. The first section 100a of the groove 100 is a helical groove providing a half revolution with the same handedness as a helical path 79 of the dose indicator 80. Concerning the embodiment shown in FIGS. 1A to 2D the helical path 79 of the dose indicator 80 and the first section 100a of the groove 100 both are left-handed. To some extent the groove 100 forms a two-start-thread but a one-start-thread or a three-start-thread is possible as well depending on the number of pins 101 of the bushing 82.

[0091] Correspondingly, as one can derive from FIG. 5, the second embodiment of the injection device comprises a scale with numbers N having a first section 99a of the scale covering the numbers 0 to 19 and a second section 99b of the scale covering the numbers 20 to 100. The numbers of the first section of the scale are shown through window 18 of the housing 1 during the first revolution of the dose indicator 80 (i.e. the first 360° of the rotation, the first rotation angle section) and the numbers of the second section of the scale are shown during the second and the third revolution of the dose indicator 80 (i.e. >360° to 1080° of the rotation, the second rotation angle section). Accordingly, during the first rotation angle section of the dose indicator 80 the dose can be dialed with the double resolution compared with the second rotation angle section of the dose indicator 80.

[0092] As the dose indicator 80 rotates, each projecting pin 101 of the bushing 82 translates along the respective longitudinal groove 100 of the driver tube 85 into proximal direction taken along by the projecting flange 83, wherein the groove 100 comprises the first section 100a and the second section 100b. The pitch of the first groove section 100a is approximately 45°, whereas the pitch of the second groove section 100b is 0°.

[0093] During the first revolution of the dose indicator 80, i.e. in this embodiment the first rotation angle section of 360° from the initial position (zero position), the full revolution of the dose indicator 80 is transformed into a half revolution of the bushing 82 backwards caused by the helical groove section 100a and the axial (helical) translation of the dose indicator 80 with the length I/2 compared with the lead I of the helical thread 79 of the dose indicator 80. To some extend the first helical groove section 100a thereby provides a loss angle of 180° or a half revolution (see FIG. 3). Accordingly, the transformation ratio increases from the first rotation angle section to the second rotation angle section. This allows a higher resolution for dose dialing during the first rotation angle section of—in this embodiment—360° using the dose indicator 80. During dialing within the first rotation angle section of the dose indicator 80 the numbers N of the first scale section 99a are shown within window 18.

[0094] After the first revolution (full turn) of the dose indicator 80 each pin 101 arrives at the second section 100b of the groove 100. In this section the bushing 82 is kept non-rotated with regard to the driver tube 85 due to its coupling to the driver tube 85 by the straight axial second section 100b of the groove 100. Accordingly, during the second rotation angle section covering the range >360° to 1080° the axial (helical) translation of the dose indicator corresponds to the lead I of the helical thread 79 of the dose indicator 80. Hence, the resolution for dose dialing is half of the resolution provided during the first rotation angle section of the dose indicator 80. During dialing within the second rotation angle section of the dose indicator 80 the numbers N of the second scale section 99b are shown within window 18.

[0095] During dose injection, each pin 101 travels along its corresponding groove 100 into opposite (distal) direction compared with dose dialing. Accordingly, when passing the first groove section 100a only half of the dose per one revolution is dispensed due to the helical form of the groove compared with the second groove section 100b.

[0096] With higher pitch angle the pin 101 is not sufficiently supported by the rim of the groove 100. This is demonstrated in FIG. 5. The resulting sliding force depicted by arrow 102 is almost parallel to the rim of the groove 100 within the first groove section 100a. The force fraction normal to the rim of the groove 100 is higher within the second groove section 100b having a smaller pitch. However, the accuracy of dose dialing is provided by the ratchet engagement of the teething 112 of the thread 12 at the housing 1 and the engaging member 84a.

[0097] With regard to the second embodiment, the inner toothing at the insert 40 has smaller teeth with a pitch of half of the pitch in the first embodiment explained above. The ratchet teething at the insert is thereby able to match with the increased resolution of the mechanism during high-resolution dose expelling, namely when the pin 101 travels along the helical first section 100a of the groove 100.

[0098] For the first and second embodiments the form of the teething 112 of the thread 12 may be adapted to a different dose amount per rotation angle of the dial grip 81 or different mechanism behavior at different rotation angle. Accordingly, the teeth form may be adapted to the dialed (and dispensed) dose for each (absolute) rotation angle section. This adequate feedback improves dose dialing for the user.

REFERENCE NUMBERS

[0099] 1 housing

[0100] 2 cartridge holder

[0101] 2a window in cartridge holder 2

[0102] 3 cartridge

[0103] 4 cap

[0104] 5 thread

[0105] 6 lead screw

[0106] 7 thread of the lead screw 6

[0107] 11 inner surface of housing 1

[0108] 12 thread projecting from inner surface 11 of housing 1

[0109] 12a front surface of thread 12

[0110] 18 window of the housing 1

[0111] 40 insert

[0112] 79 helical path

[0113] 80 dose indicator

[0114] 80a first flange

[0115] 80b second flange

[0116] 81 dial grip

[0117] 82 bushing

[0118] 82a sloping surface of bushing 82

[0119] 82b groove

[0120] 83 flange of bushing 82

[0121] 84a engaging member

[0122] 84b slider member

[0123] 85 driver tube

[0124] 85a clicker arm

[0125] 86 groove

[0126] 87 radial protrusion

[0127] 88 injection button

[0128] 88a flange

[0129] 89 compression spring

[0130] 94 pivot pin

[0131] 95 bearing

[0132] 99a first scale section

[0133] 99b second scale section

[0134] 100 groove

[0135] 100a first groove section

[0136] 100b second groove section

[0137] 101 pin

[0138] 102 arrow

[0139] 112 toothing

[0140] 184a side surface of engaging member 84a

[0141] 184b side surface of slider member 84b

[0142] 284a side surface of engaging member 84a

[0143] 284b side surface of slider member 84b

[0144] 384a sloping surface of engaging member 84a

[0145] 384b sloping surface of slider member 84b

[0146] N number of the scale