Patent Description:
Medicament delivery devices such as injectors are sometimes provided with functions where a specific dose can be set by the user, which dose may be varied within a range.

Quite often this dose setting function is performed by turning a knob or wheel at the distal end of the device whereby it is moved in the distal direction. When performing a subsequent injection, the knob is pushed linearly in the proximal direction. One such injector is disclosed in the document <CIT> in which the distal dose knob of the injector is threaded out of a rod barrel tube as a dose is set. Thus the distance the knob is moved in the distal direction is directly related to the dose quantity to be delivered. <CIT> also discloses a similar dose setting mechanism for a medicament delivery device as defined in the preamble of claim1.

One drawback with that type of solution is that if larger doses are to be delivered, the dose knob has to be moved quite a long distance in the distal direction, which means that it might be difficult for a user to push the dose knob in the proximal direction during injection.

The aim of the present invention is to remedy the drawbacks of the state of the art medicament delivery devices and to provide a device by which it is possible to set a desired or required dose in a simple and intuitive way.

This aim is obtained by a medicament delivery device according to the features of the independent patent claim. Preferable embodiments of the invention are subject of the dependent patent claims.

Another aim of the present invention is to provide a dose injection button locking feature that reliably releases the dose button to an activated state when a user is ready to set a second and/or subsequent doses for injection. Failure to unlock the dose button, and concurrently the lead screw, reliably each time a dose is to be set will present a potentially dangerous situation in that a user may not be able to set and administer needed subsequent doses of medicament from the drug delivery device. The drug delivery device must be reliably unlocked after each administered dose by dialling the dose setting knob to an initial start position or to a zero dose setting causing the dose button to pop out rearwardly in the distal direction away from the outer housing of the delivery device.

According to a main aspect of the invention it is characterised by a medicament delivery device comprising a housing having opposite distal and proximal ends; a medicament container holder releasably connected to said housing; a medicament container arranged inside said medicament container holder; a threaded plunger rod arranged to pass through a first inner wall of the housing and arranged to act on a stopper in the medicament container; a lead screw member coaxially connected to the threaded plunger rod by co-acting first slidably-androtatably-locked means; wherein said device further comprises a nut coaxially connected to the threaded plunger rod by a treaded engagement between them, connected to the lead screw member by co-acting non-slidable-and-rotatable means, and connected to the housing by coacting second slidably-and-rotatably-locked means; a primary dose member coaxially rotatable on the lead screw member when the device is in a non-activated state and connected to the lead screw member by co-acting third slidably-and-rotatably-locked means when the device is in an activated state; a locking member fixedly connected to the housing and releasably connected to the lead screw member by co-acting locking means; a first spring force means arranged between the first inner wall of the housing and the nut, wherein the first spring force means is in a pre- tensioned state when said locking means are engaged and the device is in the non-activated state; a secondary dose member rotatably connected to said primary dose member via a pinion gear; dose setting means connected to the primary dose member by co-acting fourth slidably-androtatably-locked means, such that when the device is to be set from the non-activated state to the activated state, he dose setting means are manually manipulated in a pre-determined direction, whereby the locking means are released and the lead screw member is distally moved a predetermined distance by the first spring force means independent of the size of a dose to be set.

According to a further aspect of the invention, said primary and said secondary dose members are provided with indicia.

According to another aspect of the invention, the locking means comprises a proximally pointing and radial flexible lever arranged on the locking member, an annular ledge on the circumferential surface of the lead crew member, and the circumferential inner surface of the secondary dose member; such that when the first spring force means is in a pre-tensioned state, the circumferential inner surface of the secondary dose member forces the flexible lever radial inwardly in contact with the ledge; and when the dose setting means are manually manipulated, the secondary dose member is rotated to a position wherein the flexible lever is radial outwardly flexed into a longitudinal groove on the inner circumferential surface of the secondary dose member.

According to yet a further aspect of the invention, the locking member comprises on its distal circumferential surface a distally pointing stop member, and wherein the secondary dose member comprises on its proximal circumferential surface a first and a second proximally pointing stop members arranged to interact with the stop member of the locking member.

According to yet another aspect of the invention, the non-slidable-and-rotatable means comprises ratchet arms and radial inwardly directed arms on the nut, grooves on the outer circumference of wheels on the proximal end of the lead screw member, and an annular groove between the wheels, wherein the ratchet arms cooperate with the grooves for giving an audible signal when the lead screw member is rotated; and wherein the radial inwardly directed arms cooperate with the annular groove such that the lead screw member and the nut are slidably locked and rotatable in relation to each other.

According to a further aspect of the invention, the first slidably-and-rotatably locked means comprises radial inwardly directed ledges on the inner surface of the proximal end of the lead screw member, and longitudinally extending grooves on the plunger rod, wherein the grooves cooperate with the radial inwardly directed ledges such that the lead screw member and the plunger rod are rotationally locked and slidable in relation to each other.

According to another aspect of the invention, the second slidably-and-rotatably locked means comprises grooves on the outer circumferential side surface of the nut, and longitudinal ribs on the inner surface of the housing, wherein the grooves cooperate with the longitudinal ribs such that the nut and the housing are rotationally locked and slidable in relation to each other.

According to yet a further aspect of the invention, the third slidably-and-rotatably locked means comprises splines on the outer circumferential surface of the lead screw member, and corresponding splines arranged on the inner circumferential surface of the primary dose member, wherein the splines cooperate with corresponding splines such that the lead screw member and the primary dose member are rotationally locked and slidable in relation to each other.

According to yet another aspect of the invention, the dose setting means comprises a clutch plate provided with a first annular ratchet, a dose setting knob provided with a second annular ratchet, and a second spring force means arranged between a second inner wall of the housing and a proximal surface of the clutch plate, such that clutch plate is distally urged and the first and the second ratchet are abutting each other, and which dose setting knob protrudes through the distal end of the housing.

According to a further aspect of the invention, the fourth slidably-and-rotatably locked means comprises longitudinally extending grooves on the outer circumferential surface of the primary dose member, and radial inwardly directed protrusions on the inner surface of the clutch plate, wherein the longitudinally extending grooves cooperate with radial inwardly directed protrusions such that the primary dose member and the clutch plate are rotationally locked and slidable in relation to each other.

According to another aspect of the invention, the plunger rod is arranged to be proximally moved a distance corresponding to a set dose to be delivered by manually manipulating the dose setting knob when the device is in the activated state.

Yet another aspect of the invention relates to reliably unlocking the dose injection button and lead screw when the dose setting mechanism transitions from a non-activated to an activated state. The dose setting mechanism includes a housing having a longitudinal axis, a lead screw positioned with the housing, and a locking member rotationally and slidably fixed to the housing, the locking member comprising a locking slot. A dose member assembly is included in the housing having a biasing element, an inner sleeve and an outer sleeve, where the dose member assembly is arranged coaxially around the locking member and the lead screw, the biasing element is operatively engaged with the locking member and the inner sleeve, and where the inner sleeve has a radially projecting key configured to travel in the locking slot to engage the lead screw to prevent axial movement of the lead screw when the dose setting mechanism is in the non-activated state. Preferably, the locking slot maybe L-shape.

The biasing element may be a spring, preferably a torsional spring, that exerts a rotational force on the inner sleeve. The key on the inner sleeve can be configured to disengage from the lead screw when the dose setting mechanism transitions from the non-activated state to an activated state thereby releasing or unlocking the dose injection button.

In one particular advantageous embodiment of the dose setting mechanism, the key comprises a chamfer projecting distally and configured to engage a proximal edge of an axial rib positioned on an outer surface the lead screw such that axial movement of the lead screw in a proximal direction causes rotation of the inner sleeve. Additionally the inner sleeve may include a radially projecting protrusion on its outer surface that engages a radially projecting rib located on an inner surface of the outer sleeve such that rotation of the outer sleeve causes rotation of the inner sleeve.

There are a number of advantages with the present invention. Because the lead screw, e.g. the manually operating delivery means, protrudes outside the housing with the same length independent of the set dose quantity the manual dose delivery operation is the same independent of set dose, i.e. the lead screw member has always the same position when a dose has been set.

Compared to the state of the art medicament delivery devices, this solution is a great advantage for the user or patient who suffers of dexterity problems. Also when not in use, the lead screw member is inside the medicament delivery device and locked. The unlocking of the lead screw member is performed when said dose setting knob is turned to an initial position, preferably a zero-dose position.

These and other features and advantages will become apparent from the detailed description and from the accompanying drawings.

In the detailed description reference will be made to the accompanying drawings in which.

In the present application, when the term "distal part/end" is used, this refers to the part/end of the injection device, or the parts/ends of the members thereof, which under use of the injection device is located the furthest away from the medicament injection site of the patient. Correspondingly, when the term "proximal part/end" is used, this refers to the part/end of the injection device, or the parts/ends of the members thereof, which under use of the injection device is located closest to the medicament injection site of the patient.

The medicament delivery device <NUM> according to the drawings comprises a generally elongated housing <NUM> having opposite distal and proximal ends. The elongated housing <NUM> being e.g. divided in a proximal 12a and a distal part 12b. The proximal end of the housing <NUM> is arranged with fastening means such as e.g. threads <NUM> on its inner surface, which fastening means cooperate with corresponding fastening means such as outwardly threads <NUM> on a distal end of a medicament container holder <NUM>, providing a releasable connection. Inside the medicament container holder <NUM> a medicament container <NUM> can be placed. The proximal end of the medicament container holder <NUM> is arranged with a threaded neck <NUM> for connection of a medicament delivery member such as an injection needle <NUM>, a mouthpiece, a nozzle or the like, <FIG>.

When received by a user, the medicament delivery device IO is provided with a releasably attachable protective cap <NUM>. At the distal end of the medicament container holder <NUM> a sleeve-shaped container support <NUM> is inserted for holding and supporting the medicament container <NUM> when inserted, <FIG>. At the proximal end of the housing <NUM> a first inner wall <NUM> is arranged, which wall is provided with a central passage <NUM>, <FIG>. The central passage <NUM> is arranged with a distally directed tubular flange <NUM>, <FIG> A threaded plunger rod <NUM> extends in the longitudinal direction through the central passage <NUM> with a proximal end adjacent a stopper <NUM> inside said medicament container <NUM>, <FIG>. The proximal end of the plunger rod <NUM> is further arranged with a plunger rod tip <NUM>, <FIG>.

The device further comprises a lead screw member <NUM> coaxially connected to the threaded plunger rod <NUM> by co-acting first slidably-and-rotatably-locked means; and a nut <NUM> coaxially connected to the threaded plunger rod <NUM> by a treaded engagement between them. The nut <NUM> also being connected to the lead screw member <NUM> by co-acting non-slidable-and-rotatable means, and to the housing by co-acting second slidably-and-rotatably-locked means.

The first slidably-and-rotatably-locked means comprises radial inwardly directed ledges <NUM> on the inner surface of the proximal end of the lead screw member <NUM>, and longitudinally extending grooves <NUM> on the plunger rod <NUM>, <FIG>, wherein the grooves <NUM> cooperate with the radial inwardly directed ledges <NUM> such that the lead screw member <NUM> and the plunger rod <NUM> are rotationally locked and slidable in relation to each other.

The non-slidable-and-rotatable means comprises ratchet arms <NUM> and radial inwardly directed arms <NUM> on the nut <NUM>, grooves <NUM> on the outer circumference of wheels <NUM> on the proximal end of the lead screw member <NUM>, and an annular groove <NUM> between the wheels <NUM>, wherein the ratchet arms <NUM> cooperate with the grooves <NUM> for giving an audible signal when the lead screw member <NUM> is rotated; and wherein the radial inwardly directed arms <NUM> cooperate with the annular groove <NUM> such that the lead screw member <NUM> and the nut <NUM> are slidably locked and rotatable in relation to each other, <FIG>.

The second slidably-and-rotatably-locked means comprises grooves <NUM> on the outer circumferential side surface of the nut <NUM>, <FIG>, and longitudinal ribs on the inner surface of the housing (not shown), wherein the grooves <NUM> cooperate with the longitudinal ribs such that the nut and the housing are rotationally locked and slidable in relation to each other.

The nut <NUM> comprises a threaded central passage <NUM> which cooperates with the threads of the plunger rod <NUM>, <FIG>, thereby forming the threaded engagement between them.

The device also comprises a primary dose member <NUM> coaxially rotatable on the lead screw member <NUM> when the device is in a non-activated state and connected to the lead screw member <NUM> by co-acting third slidably-and-rotatably-locked means when the device is in an activated state. The third slidably-and-rotatably-locked means comprises splines <NUM> on the outer circumferential surface of the lead screw member <NUM>; and corresponding splines <NUM> arranged on the inner circumferential surface of the primary dose member <NUM>, wherein the splines <NUM> cooperate with corresponding splines <NUM> such that the lead screw member <NUM> and the primary dose member <NUM> are rotationally locked and slidable in relation to each other, <FIG> and <FIG>.

The device further comprises: - a locking member <NUM> fixedly connected to the housing <NUM> and releasably connected to the lead screw member <NUM> by co-acting locking means; - a first spring force means <NUM> arranged between the first inner wall <NUM> of the housing <NUM> and the nut <NUM>, wherein the first spring force means is in a pre-tensioned state when said locking means are engaged and the device is in the non-activated state; and - a secondary dose member <NUM> rotatably connected to said primary dose member <NUM> via a pinion gear <NUM>, <FIG>.

The device also comprises dose setting means connected to the primary dose member <NUM> by co-acting fourth slidably-and-rotatably-locked means, such that when the device is to be set from the non-activated state to the activated state, the dose setting means are manually manipulated in a pre-determined direction, whereby the locking means are released and the lead screw member <NUM> is distally moved a pre-determined distance by the first spring force means <NUM> independent of the size of a dose to be set.

The dose setting means comprises a clutch plate <NUM> provided with a first annular ratchet <NUM>, a dose setting knob <NUM> provided with a second annular ratchet <NUM>, and a second spring force means <NUM> arranged between a second annular inner wall <NUM> of the housing and a proximal surface of the clutch plate <NUM>, such that clutch plate <NUM> is distally urged and the first and the second ratchet <NUM>, <NUM> are abutting each other, and which dose setting knob <NUM> protrudes through the distal end of the housing <NUM>, Figs. la and <NUM>. The fourth slidably-and-rotatably-locked means comprises longitudinally extending grooves <NUM> on the outer circumferential surface of the primary dose member <NUM>, and radial inwardly directed protrusions <NUM> on the inner surface of the clutch plate <NUM>, wherein the longitudinally extending grooves <NUM> cooperate with radial inwardly directed protrusions <NUM> such that the primary dose member <NUM> and the clutch plate <NUM> are rotationally locked and slidable in relation to each other, <FIG> and <FIG>. The distal end of the lead screw member <NUM> protrudes through the dose setting knob <NUM>, and is at its distal end arranged with a dose injection button <NUM>, <FIG> and <FIG>. Outside the dose injection button <NUM> a spin ring <NUM> is rotatably arranged, <FIG>.

The locking means comprises: - a proximally pointing and radial flexible lever <NUM> arranged on the locking member <NUM>, - an annular ledge <NUM> on the circumferential surface of the lead crew member <NUM>, and - the circumferential inner surface of the secondary dose member, <FIG>. The secondary dose member <NUM> is also arranged with teeth <NUM> arranged around its circumference, which teeth cooperate with teeth <NUM> on the pinion gear <NUM>, which is journalled in the housing as well as the locking member <NUM> via a locking lever bracket, <FIG>. Further the primary dose member <NUM> is arranged with a gear segment <NUM>, which also cooperate with the pinion gear <NUM>, <FIG>. A certain part of the lead screw member <NUM> is arranged with the splines <NUM> on its outer circumferential surface, <FIG>; which splines <NUM> have a lesser diameter than the proximal part of the lead screw member <NUM>, thereby creating the annular ledge <NUM>, <FIG>. The locking member <NUM> also comprises on its distal circumferential surface a distally pointing stop member <NUM>, and the secondary dose member <NUM> comprises on its proximal circumferential surface a first <NUM> and a second <NUM> proximally pointing stop member <NUM> arranged to interact with the stop member <NUM> of the locking member, <FIG>.

The proximal part of the primary dose member <NUM> and the secondary dose member <NUM> are arranged with a circumferential band containing numbers or indicia <NUM> which are used to indicate dose size through a dose window on the housing, as will be explained below, <FIG>.

The device is intended to function as follows. When delivered to the user, the device is in the non-activated state wherein a medicament container <NUM> has been inserted in the medicament container holder <NUM> in the proximal end of the device, <FIG>, the first spring force means <NUM> is in a pre-tensioned state and said locking means are engaged, wherein the circumferential inner surface of the secondary dose member <NUM> forces the flexible lever <NUM> radial inwardly in contact with the ledge <NUM>.

When the device is to be used the protective cap <NUM> is removed and the dose setting means are manually manipulated for setting the device from the non-activated state to the activated state by rotating the dose setting knob <NUM> counter clockwise until activating indicia as e.g. two zeros are visible through the window of the housing <NUM>. The rotation of the dose setting knob <NUM> causes the clutch plate <NUM> and thereby the primary dose member <NUM> to rotate due to the engagement between the co-acting fourth slidably-and-rotatably-locked means, and due to the connection between the first <NUM> and the second <NUM> ratchets. However, the lead screw member <NUM> is not rotated since the third slidably-and-rotatably-locked means <NUM>, <NUM> are not in engagement, i.e. the splines <NUM> on the outer circumferential surface of the lead screw member <NUM> and the corresponding splines <NUM> arranged on the inner circumferential surface of the primary dose member <NUM> are not in engagement. The secondary dose member <NUM> also rotates due to the connection between the gear segment <NUM> of the primary dose member <NUM> and the teeth <NUM> of the secondary dose member <NUM> through the pinion gear <NUM>. The rotation of the secondary dose member <NUM> is stopped when its second proximally pointing stop member <NUM> abuts the distally pointing stop member <NUM>. This causes a longitudinal groove on the inner circumferential surface (not shown) of the secondary dose member <NUM> to be aligned with the flexible lever <NUM> whereby the flexible lever <NUM> is radial outwardly flexed into the groove and thereby moved out of contact with the ledge <NUM> of the lead screw member <NUM>. This causes the lead screw member <NUM> to move a pre-determined distance in the distal direction due to the force of the spring <NUM> acting on the nut <NUM>, which in turn is attached to the lead screw member <NUM>. The splines <NUM> on the outer circumferential surface of the lead screw member <NUM> and the corresponding splines <NUM> arranged on the inner circumferential surface of the primary dose member <NUM> are then engaged to each other. Because of the movement of the nut <NUM>, the plunger rod <NUM> is also moved. The distal end of the lead screw member <NUM> and its dose injection button <NUM> now protrude distally out of the housing said predetermined distance and independent of the size of the dose to be set.

The device is now in the activated state and ready for setting a required dose of medicament, <FIG>.

When setting a dose, the plunger rod <NUM> is arranged to be proximally moved a distance corresponding to a set dose to be delivered by manually manipulating the dose setting knob <NUM>. The dose setting knob <NUM> is rotated in the clockwise direction which also rotates the primary dose member <NUM> clockwise indicating the dose that is being dialled. At the same time the primary dose member <NUM> rotates the lead screw member <NUM> clockwise due to the engagement between the co-acting third slidably-and-rotatably-locked means <NUM>, <NUM>; and the lead screw member <NUM> rotates the plunger rod <NUM> due to the engagement between the co-acting first slidably-and-rotatably-locked means, driving the plunger rod <NUM> through the nut <NUM> because of the threaded engagement between them, thereby moving the plunger rod <NUM> proximally. The secondary dose member <NUM> also rotates due to the connection between the gear segment <NUM> of the primary dose member <NUM> and the teeth <NUM> of the secondary dose member <NUM> through the pinion gear <NUM>. The rotation of the secondary dose member <NUM> is stopped when its first proximally pointing stop member <NUM> abuts the distally pointing stop member <NUM>, which indicates the maximum dose the device can deliver e.g. two indicia as e.g. a seven and a zero are visible through the dose window. In any case, the set dose is visible through the dose window of the housing. At this point the device is ready for an injection.

Moreover, if the user attempts to dial past the maximum dose the device can deliver or if the user attempts to dial pass the activating indicia, the connection between the first annular ratchet <NUM> and the second annular ratchet will function as a clutch.

When the dose is set, a medicament delivery member <NUM> is attached to the proximal end of the device, such as e.g. an injection needle. It is however to be understood that other types of medicament delivery members may be used in order to deliver a dose of medicament. The medicament delivery member <NUM> is then placed at the delivery site and the user presses the dose injection button <NUM> in the proximal direction the predetermined distance that the distal end of the lead screw member <NUM> and its dose injection button <NUM> protrudes distally out of the housing and which said predetermined distance is independent of the size of the dose to be delivered. This causes the lead screw member <NUM> to move in the proximal direction as well as the nut <NUM> and the plunger rod <NUM>. This proximal movement of the plunger rod <NUM> causes it to act on the stopper <NUM> of the medicament container <NUM> whereby a dose of medicament is expelled through the medicament delivery member <NUM>. When the lead screw member <NUM> has reached a certain distance inside the housing, the flexible lever <NUM> of the locking member <NUM> is again moved in contact with the ledge <NUM> of the lead screw member <NUM>, <FIG>. The medicament delivery member may now be removed and discarded.

When a subsequent dose is to be performed, the above described procedure is performed and can be repeated until the medicament container is emptied.

Another embodiment of the invention is presented in <FIG>. This embodiment <NUM> differs slightly in structure and operation from that of the above-described embodiments in that this version of the device allows a user to set only one pre-set, pre-selected or pre-determined dose setting. For example, the device <NUM> could be manufactured such that a single fixed dose of <NUM> units or <NUM> units is preselected and the user would not be able to dial a dose greater than or less than the one single dose. In other words, the device does not have <NUM> variable dose setting functionality, instead this type of device is referred to as a fixed dose device.

In one possible embodiment of the fixed dose design, device <NUM> has a dose setting mechanism <NUM> shown in <FIG> and in more detail in <FIG>. The distal part 12a of the elongated housing <NUM> contains a window <NUM> that allows a user to view and/or feel indicia <NUM> printed or otherwise located on the outer surface 66a of the dose member <NUM>. As illustrated in the figures, an arrow can be used to provide the user with a visual clue or prompt as to what direction to rotate dose setting knob <NUM> when the dose setting mechanism is in the activated state. The activated state is achieved when the user rotates the dose setting knob to the zero dose position, which as exemplified in the figures can be seen as the arrow or as a "<NUM>" or any other desired indicia to indicate the starting position.

In the non-activated state, the flexible lever <NUM> of locking member <NUM> is engaged with ledge <NUM> on lead screw <NUM>. This is best shown in <FIG> where the upper figure illustrates the activated state where the dose button is moved distally outward (so-called "popped out") from the dose setting knob <NUM> and housing 12a as a result of the axial movement in the distal direction of lead screw <NUM> by the biasing force exerted by biasing member <NUM>, shown as a compression spring. <FIG> illustrates indicia <NUM> and <NUM> being aligned when the device is in the activated state with the button <NUM> "popped out. " The lower figure of <FIG> illustrates the dose setting mechanism <NUM> in the non-activated state where spring <NUM> is compressed (pre-tensioned) by the forward or proximal movement of lead screw <NUM> during dose delivery. The lead screw <NUM> is prevented from moving distally by the engagement of lever <NUM> with ledge <NUM>, where the lever <NUM> is biased radially inward by the dose member <NUM> and in particular by the cam surface <NUM> on the inside surface of dose member <NUM>. This is best shown in <FIG>. This cam surface <NUM> acts as a bearing surface against the outside surface of lever <NUM> to deflect the lever <NUM> inwardly so that it remains engaged with ledge <NUM>.

<FIG> shows the relationship of locking member <NUM>, dose member <NUM> and distal housing 12a. As mentioned, locking member <NUM> is rotationally and axially fixed relative to the housing 12a. This fixation is a result of the engagement of radially projecting ribs <NUM> on locking member <NUM> that engages corresponding slots <NUM> on the inside surface of housing 12a. Dose member <NUM> has two rotational stops <NUM> and <NUM> that engage corresponding stops <NUM> and <NUM> on the distal side of locking member <NUM> (see <FIG> illustrates axial ribs <NUM> that engage with slots <NUM> on dose member <NUM> when the device is in the activated state. This engagement rotationally fixes the dose member <NUM> to the lead screw <NUM> such that rotation of the dose setting knob <NUM> causes the dose member <NUM> to rotate as well as lead screw <NUM>. <FIG> illustrates the relationship of the plunger rod <NUM> to the lead screw <NUM>. In the particular embodiment shown the plunger rod <NUM> is shown with a non-circular cross-section having a pair of opposed flat surfaces 36b with threaded segments 36a between each flat portion 36b. The proximal through hole <NUM> of lead screw <NUM> is configured to match the non-circular cross-sectional shape of plunger rod <NUM> such that the plunger rod is rotationally fixed to the lead screw <NUM>, but can move or slide axially relative to the lead screw.

The plunger rod <NUM> is threadedly engaged with nut <NUM> through threaded through hole <NUM> (see <FIG> & <FIG>). Nut <NUM> is rotational fixed to the housing by the engagement of radially extending ribs <NUM> that cooperate with corresponding slots on the inside of the housing. These slots are longitudinal in length and are configured to allow the nut <NUM> to slide axially relative to the housing. The nut <NUM> is fixed to the proximal end of lead screw <NUM> through the engagement of finger <NUM> in radial groove <NUM> at the proximal end of lead screw <NUM>. This groove <NUM> is sized with sufficient axial width such that the lead screw <NUM> and the distal face of the nut <NUM> can move axially relative to each other during dose setting. During dose setting the lead screw <NUM> is rotated relative to nut <NUM>, which is rotationally fixed to the housing. The spring <NUM> exerts a biasing force in the proximal direction against the proximal face of the nut <NUM> causing two opposed distally projecting ratchet teeth <NUM> to engage complimentary proximally projecting ratchet teeth <NUM> located at the proximal end of the lead screw <NUM>. As the lead screw <NUM> is rotated the ratchet teeth <NUM> rotate relative to the stationary ratchet teeth <NUM> causing the teeth <NUM> to ride up and over teeth <NUM>. This riding up and over motion moves the lead screw axially back and forth within groove <NUM>. The nut is held in the groove by finger <NUM> (see <FIG>).

<FIG> illustrates the sequence of operation of device <NUM>. The top figure shows the device in a non-activated state, for example, immediately after dose delivery. Here the dose button is pushed in (i.e., not "popped out") and the spring is in the pre-tensioned compressed state being held in this compressed state by the engagement of the flexible lever on the locking member locked with the ledge on the lead screw. The next figure shows the device in the activated state when the dose setting knob is rotated to the zero dose or starting position, e.g., where the arrow is shown in the housing window. The transition from the non-activated to the activated state causes the lead screw, plunger rod and nut to all move distally by the biasing force exerted by the spring. The spring moves these three components because the dose setting knob and dose member were rotated such that the dose member no longer biases the flexible lever inward and thus it disengages from the ledge on the lead screw. The distance these three components move is always the same distance distally as indicated by the distance between lines <NUM> and <NUM>. This moves the plunger rod off of and away from cartridge piston 20a by the same distance. At this point, when the device is in the activated state, a dose can be set by rotating the dose setting knob. Since the plunger rod was moved distally off the cartridge piston when the zero dose position was obtained, the axial movement of plunger rod in the proximal direction does not move (or contact) the bung.

Setting a dose also rotates the dose member, which then biases the flexible lever inwardly. The third figure in <FIG> represents the device with a dose set. Setting the dose caused the plunger rod to screw through the nut moving proximally a distance X. To deliver the set dose the user pushes the dose button proximally which pushes the lead screw, nut and plunger rod proximally as well. These three components move proximally and as the lead screw is pushed forward proximally, the flexible levers on the locking member that is axially fixed relative to the housing, flex over the ledge on the outside of the lead screw and causes the lead screw to be locked in the original most forward or proximal position, i.e., the non-activated state. As the lever re-engages the ledge on the lead screw, the spring is returned to the pre-tensioned state. As illustrated in the bottom figure of <FIG>, the plunger rod moves an additional distance X representing and proportional to the dose set. This in turn moves the cartridge piston the same distance X and thus expels that amount of medicament from the proximal end of the cartridge through the injection needle <NUM>.

An alternative to locking member <NUM> and dose member <NUM> as described above is presented in <FIG>, where an alternative design of the locking member 96a is operatively engaged with dose member 66a to provide a lock mechanism that reliably unlocks the dose injection button and the lead screw <NUM> so subsequent doses can be set, as will be further described below. Dose member assembly 66a comprises at least three components, a biasing element <NUM>, an inner sleeve <NUM> and an outer sleeve <NUM>. The biasing element is shown as a torsional spring, however, other types or designs of springs may be used. Likewise, a non-spring component could be used, for example, flexible fingers, spring washers, and the like materials can be used to provide the required rotation forces necessary to bias the key <NUM> to stay within the transverse portion 430b of the locking slot <NUM>.

The inner and outer sleeves, <NUM> and <NUM>, preferably have a circular cross-section and are concentrically positioned with respect to each other such that the outer sleeve <NUM> is coaxially arranged and covers the inner sleeve <NUM>. The outer sleeve <NUM> has an outer surface <NUM> that may contain indicia <NUM> as earlier described. The outer sleeve <NUM> also has an inner surface <NUM> that contains at least one radially projecting rib <NUM> positioned longitudinally along the inner surface <NUM>. This rib <NUM> is configured to interact with protrusion <NUM> on the outer surface <NUM> of inner sleeve <NUM> when the dose setting knob <NUM> is rotated to set a dose of medicament, which also causes outer sleeve <NUM> to rotate.

Inner sleeve <NUM> has an inner surface <NUM> that contains a radially projecting key <NUM> having a proximally facing stop face <NUM>. This stop face <NUM> is configured to abut the distal facing ledge <NUM> on lead screw <NUM> (see <FIG>) when the dose setting mechanism is in the non-activated state and the dose button <NUM> is locked in the retracted or proximal-most position. As the outer sleeve <NUM> is rotated to a zero dose or initial position i.e., where the indicia arrow shown in <FIG> is moved to be visible in window <NUM> (see <FIG>) the inner sleeve <NUM> and key <NUM> are simultaneously rotated, which moves the stop face <NUM> from abutment with ledge <NUM> thus allowing spring <NUM> to move the lead screw <NUM> distally to the activated position where the dose button is popped out in the distal direction rearwardly relative to the housing 12a and the dose setting knob <NUM>. Key <NUM> also has a chamfer <NUM> (see <FIG>) that faces distally and is configured with a sloping or camming surface that will operatively engage with a proximal projecting end face <NUM> (see <FIG>) in manner where axial movement of the lead screw <NUM> in the proximal direction, when the dose button is pushed to deliver a set dose of medicament, causes the inner sleeve <NUM> and key <NUM> to rotate against a biasing force of biasing element <NUM>, as described in more detail below.

Key <NUM> is configured and designed to travel within a locking slot <NUM> during rotational movement caused by both the rotation of outer sleeve <NUM> and the engagement with end face <NUM> of the lead screw <NUM>. Inner sleeve <NUM> is axially fixed relative to housing 12a and also has a connector <NUM>, shown as a hole <NUM>, or indentation, that fixedly attaches a proximal end of the biasing element <NUM>. Biasing element <NUM> is illustrated in the embodiment in <FIG> and <FIG> as a spring with opposing anchor posts <NUM> and <NUM>. Connector <NUM> is configured to accept and retain post <NUM> to prevent rotational movement of spring <NUM>. Post <NUM> is configured to attach to a similar connector <NUM> located in locking member 96a. Because locking member 96a is rotationally fixed to the outer housing 12a of the dose setting mechanism, the biasing element <NUM> exerts a rotational spring force on inner sleeve <NUM> such that the key <NUM> is biased in the locking position within the transverse portion 430b of locking slot <NUM>. Locking member 96a also has stops <NUM>, <NUM>, and <NUM>. The stops work collectively as a device to limit the rotation of the radially projecting rib <NUM> to certain degrees of rotation. The degree of rotation depends on the spacing between the neighbouring two stops and can be adjusted according to design needs.

The interaction of the key <NUM> with the locking slot <NUM> will now be described. In the non-activated state of the dose setting mechanism the key <NUM> is positioned within the transvers portion 430b of the locking member 96a, which itself is axially fixed relative to the dose member assembly 66a and housing 12a. In this position the lead screw is blocked by the key <NUM> from moving axially in the distal direction. The indicia on the outer sleeve <NUM> will display a dose number (as opposed to the arrow or a "<NUM>") in the window of the housing. To activate the dose setting mechanism, a user will rotate the dose setting knob to an initial or start position in order to display the arrow or a "<NUM>". This rotational force overcomes the rotational biasing force exerted by biasing member <NUM> on the inner sleeve <NUM>. Biasing element <NUM> exerts a biasing spring force to maintain key <NUM> against end wall 430c of the transverse portion 430b. Rotation of the outer sleeve causes the key <NUM> to rotate against the biasing spring force causing the key <NUM> to travel in the transverse portion 430b of locking lot <NUM> disengaging the key <NUM> from the ledge <NUM> of the lead screw <NUM>. Spring <NUM> expands and pushes the lead screw <NUM> axially in the distal direction relative to the locking member 96a and the dose member assembly 66a. The lead screw <NUM> has now moved distally relative the key <NUM> such that the end face <NUM> of the lead screw <NUM> is positioned distally from the chamfer <NUM>. This movement of the lead screw <NUM> causes the dose button to pop out of the distal end of the housing 12a relative to the dose setting knob placing the device in an activated state. At this point the dose setting knob can be rotated to set a fixed predetermined dose medicament, which also causes rotation of the lead screw relative to plunger rod <NUM>. This rotation of the dose setting knob also rotates the outer and inner sleeves <NUM>, <NUM> and returns the key <NUM> to abutment with end wall 430c of the locking slot <NUM>. This rotation further causes end face <NUM> to align axially with chamfer <NUM>. The device is now ready to deliver a dose.

To deliver the set dose the user pushes the dose button in the proximal direction causing the lead screw to move with it axially, thus engaging end face <NUM> with chamfer <NUM> causing rotation of the inner sleeve <NUM> to move key <NUM> away from end wall 430c against the biasing force of biasing element <NUM>. As the axial rib <NUM> of the lead screw <NUM> moves past the key <NUM> it holds inner sleeve <NUM> from rotating back in response to the biasing force exerted by biasing element <NUM>. Once the rib <NUM> moves proximally out of engagement with key <NUM> the inner sleeve <NUM> is then free to rotate back to end wall 430c in response to the biasing force of biasing element <NUM>. At the end of the proximal travel of the lead screw the set dose of medicament has now been delivered. As a result of the resetting of the key <NUM> to abut end wall 430c, the device is now locked or in a non-activated state with the last set dose number shown in the housing window. To set another or subsequent dose, the user repeats the process of first unlocking the key from engagement with the lead screw and then rotating the dose setting knob to set a dose.

Claim 1:
A dose setting mechanism (<NUM>) for a medicament delivery device comprising,
a housing (<NUM>) having a longitudinal axis;
a lead screw (<NUM>) positioned with the housing (<NUM>);
a locking member (<NUM>) rotationally and slidably fixed to the housing (<NUM>), the locking member (<NUM>) comprising a locking slot (<NUM>);
a dose member assembly (66a) comprising a biasing element (<NUM>), an inner sleeve (<NUM>) and an outer sleeve (<NUM>), where the dose member assembly (66a) is arranged coaxially around the locking member (<NUM>) and the lead screw (<NUM>), the biasing element (<NUM>) is operatively engaged with the locking member (<NUM>) and the inner sleeve (<NUM>), and
characterized in that the inner sleeve (<NUM>) has a radially projecting key (<NUM>) configured to travel in the locking slot (<NUM>) to engage the lead screw (<NUM>) to prevent axial movement of the lead screw (<NUM>) when the dose setting mechanism (<NUM>) is in a non-activated state.