Patent Description:
More particularly, the invention relates to a drug injection device of the type allowing a user to set a desired dose of a predetermined drug volume contained in a cartridge and to deliver the previously set desired dose to a injection site, the set and delivery operation being repeatable till the whole drug volume contained in the cartridge is delivered.

Examples of drug injection devices of the type discussed above are described in <CIT> and <CIT>. These devices are appreciated by the users as being compact and user-friendly.

<CIT>, <CIT> and <CIT> disclose drug injection devices which, in addition to comprising members configured to allow the user to set a desired dose before delivering such a dose, further comprise members configured to prevent the user to set a dose exceeding the dose volume remaining in the cartridge after having delivered one or more doses. In particular, in <CIT> such an exceeding dose is prevented to be set by an abutment between a stop member fixed to a piston rod and a stop member fixed to a nut member configured to move along the piston rod, whereas in <CIT> the abovementioned exceeding dose is prevented to be set by an abutment between a nut configured to move along a drive shaft and a worm gear fixed to an end of the drive shaft.

The Applicant has considered the benefit of preventing the user to be able to set a dose greater than the one currently available in the cartridge.

Accordingly, the Applicant has designed a drug injection device wherein this benefit is achieved by a technical solution different from those of the prior art.

Therefore, the present invention relates to a drug injection device according to claim <NUM>.

Throughout the present description and in the annexed claims, the term "axial" and the corresponding term "axially" are used to refer to a longitudinal direction of the injection device, which corresponds to the longitudinal direction of the cartridge housing, whereas the term "radial" and the corresponding term "radially" are used to refer to a any direction perpendicular to the abovementioned longitudinal direction. In particular, when referring to components which rotate about an axis, the terms "radial" and radially" are used to indicate any direction perpendicular to such an axis.

A longitudinal direction oriented from the hand of the user who handles the injection device during the injection operation toward the injection site (for example the skin of a patient) is herein also referred to with the term "distal direction", whereas a longitudinal direction oriented from the injection site toward the hand of the user who handles the injection device during the injection operation is herein also referred to with the term "proximal direction".

The term "correlated" is used to indicate a mutual dependency relationship between two parameters, like for example two linear dimensions or a linear dimension and a volume. This means that the amount or size or extent of a first parameter is a function of (or depends on) the amount or size or extent of a second parameter and/or vice versa.

The Applicant has perceived that the provision in the drug injection device of a pinion-rack coupling wherein, during each dose setting operation, the pinion is prevented to move axially with respect to the dose setting service element while being driven in rotation by the dose setting service element and the rack moves with respect to the cartridge housing due to the engagement with the pinion causes, during the first dose setting operation and any further dose setting operation subsequent to the first dose delivery operation, for the rack to travel a corresponding partial axial length which depends on the specific dose actually set and delivered each time, so that from the first dose setting and delivery operation to the last dose setting and delivery operation the rack travels a total axial length which depends on the maximum dispensable drug volume provided within the cartridge.

Consequently, the Applicant has though that the provision in the pinion and in the rack of respective abutment elements configured to abut with each other when the rack has travelled the abovementioned total axial length obstruct a further rotation of the pinion (and therefore of the dose setting service element) after having reached, during any further dose setting operation subsequent to the first dose delivery operation, a dose equal to the dose volume currently present in the cartridge, thus preventing the user to set a dose greater than the one still available.

Preferred features of the drug injection device of the invention are disclosed below, each of these features being provided individually or in combination with the other preferred features.

Preferably, the injection device is of the pen-type, so as to allow an easy portability, handling, storing and operation of the injection device by the user.

The injection device of the invention is compact irrespective of the provision of the last dose setting device. For example, the size of the injection device can be the same as that of the injection devices of <CIT> and <CIT>, which do not include any last dose setting devices.

The injection device can be of the re-usable or disposable type, whereas the disposable use is the most preferred one.

Preferably, during the drug dose setting the dose setting service element does not move along said longitudinal direction.

Preferably, the dose setting service element is configured to move along said longitudinal direction toward the cartridge housing (thus along the distal direction) during the drug dose delivery. Thus, the dose setting mechanism and the dose delivery mechanism share a same structural element (namely, the dose setting service element), to the benefit of the compactness of the injection device.

Preferably, during the drug dose delivery the dose setting service element does not rotate about said longitudinal axis.

The rotational movement of the dose setting service element only during the dose setting operation and the axial movement of the dose setting service element only during the dose delivery operation allow these two operations to be structurally and functionally separate from each other while sharing a same structural element, namely the dose setting service element.

Preferably, the rack has a predetermined axial dimension which is correlated to an axial length travelled by the dose setting service element for delivering the predetermined drug volume.

This specific provision allows to select the specific axial dimension of the rack depending on the specific drug volume contained in the cartridge to be used, thus ensuring an identical effective operation of the injection device when new cartridges having the same volume of drug are used.

Preferably, before setting a first drug dose the pinion is located at a first free end of the rack closer to the cartridge housing.

Preferably, after having set the last drug dose the pinion is located at a second free end of the rack opposite to said first free end of the rack.

In this way the axial length travelled by the rack from the first dose setting and delivery operation to the last dose setting and delivery operation is equal to the axial dimension of the rack.

Preferably, said mutual abutment elements comprise a first rotational end stop element associated with the pinion.

Preferably, said mutual abutment elements comprise a second rotational end stop element associated with the rack.

The term "rotational end stop element" is used herein to indicate an element which abuts against another element upon rotation of at least one of the two elements about a respective rotation axis.

In the injection device of the invention, the provision of rotational end stop elements allows an effective stop to the rotation of the pinion and, accordingly, to the axial movement of the rack during the last dose setting operation.

Preferably, the first rotational end stop element is associated with a face of the pinion located on the opposite side with respect to the cartridge housing.

Preferably, the second rotational end stop element is arranged at the second free end of the rack.

Preferably, the rack is slidingly coupled to an outer case of the drug injection device.

Preferably, the rack comprises an axial guide groove slidably coupled to an axial guide rail provided on an internal surface of the outer case of the drug injection device. This axial coupling allows an easy and precise mounting of the rack within the outer case as well as a self-centering feature that further promotes the axial movement of the rack with respect to the outer case.

Preferably, the pinion is arranged between the rack and at least one rib formed on the internal surface of the outer case on the opposite side with respect to the rack. Such a rib acts as a limiter for the radial movement of the pinion to avoid a disengagement of the pinion from the rack in case of shocks.

Preferably, two ribs are provided on the internal surface of the outer case on opposite sides with respect to a radial plane of the pinion coinciding with a longitudinal median plane of the rack. This provision allows a more effective contrast against any possible disengagement movement of the pinion with respect to the rack.

Preferably, the dose setting service element has at least one planar surface and the pinion has at least one planar profile portion coupled to the at least one planar surface of the dose setting service element. This allows an effective rotational coupling between pinion and dose setting service element during the dose setting operation as well as an effective sliding coupling between pinion and dose setting service element during the dose delivery operation.

In preferred embodiments, the dose setting service element is a piston rod extending along said longitudinal axis.

In these embodiments, preferably, the pinion has a central hole coupled with the piston rod and said at least one planar profile is defined by a surface portion of said central hole.

Further features and advantages of the present invention will become clearer from the following detailed description of preferred embodiments thereof, made with reference to the attached drawings and given for indicating and not limiting purposes. In such drawings:.

An embodiment of a drug injection device <NUM> according to the present invention is shown in <FIG> and <FIG>.

The injection device <NUM> is of the pen-type and extends along a central longitudinal axis X, shown in <FIG>.

The injection device <NUM> includes a main body <NUM> and a cap case <NUM> removably associated with the main body <NUM> at a first free end 12a of the main body <NUM>.

Both the main body <NUM> and the cap case <NUM> when the latter is coupled to the main body <NUM>, extend coaxially to the longitudinal axis X.

A cartridge housing <NUM> extending coaxially with the longitudinal axis X is removably coupled to the main body <NUM> at the first free end 12a so as to be housed within the cap case <NUM> when the latter is coupled to the main body <NUM>. The cartridge housing <NUM> is configured to house a cartridge <NUM> including a predetermined drug volume to be delivered.

The main body <NUM> comprises an outer case <NUM>, which preferably is substantially cylindrically-shaped.

A dose setting mechanism <NUM> and a dose delivery mechanism <NUM> are provided within the outer case <NUM>. The dose setting mechanism <NUM> is configured to allow a user to set a drug dose to be delivered out of the cartridge <NUM>, whereas the dose delivery mechanism <NUM> is configured to allow the user to deliver the drug dose set by the dose setting mechanism <NUM>.

As many different kinds of dose setting mechanism <NUM> and dose delivery mechanism <NUM> can be foreseen in the injection device <NUM> of the invention, they are not described in detail herein. For example, the dose setting mechanism <NUM> and dose delivery mechanism <NUM> can be of the same type as described in <CIT> and <CIT>. In this specific case and as it will be clearer from the description below, the dose delivery mechanism <NUM> of the injection device <NUM> differs from the one of the devices of these two prior art documents in that it further includes a last dose setting device <NUM>, shown in <FIG> and described in more details below with reference to <FIG>.

The dose setting mechanism <NUM> and the dose delivery mechanism <NUM> share a knob <NUM> provided at a second free end 12b of the main body <NUM> opposite the first free end 12a thereof and a dose setting service element arranged within the outer case <NUM> coaxially to the longitudinal axis X and having a free end operatively connected to the knob <NUM>.

In the embodiment herein shown, the abovementioned dose setting service element is a piston rod <NUM> extending coaxially to the longitudinal axis X.

The knob <NUM> is configured to be driven by the user in rotation clockwise and counterclockwise about the longitudinal axis X to drive the dose setting mechanism <NUM> and to be pushed by the user along a longitudinal (or distal) direction P parallel to the longitudinal axis X to drive the dose delivery mechanism <NUM>.

The rotation is herein intended as clockwise or counterclockwise when looking a right side view of the injection device <NUM> when the latter is positioned as shown in <FIG>, that is when looking at the knob <NUM> from a side opposite to the side where the cartridge <NUM> is provided.

A clutch device <NUM> is provided within the outer case <NUM> to switch the injection device <NUM> between a dose setting configuration wherein the clutch device <NUM> is operatively connected to the knob <NUM> and operatively connects the knob <NUM> to the dose setting mechanism <NUM>, and a dose delivery configuration wherein the clutch device <NUM> is operatively disconnected from the knob <NUM> and the latter is operatively connected to the dose delivery mechanism <NUM>.

In the dose setting configuration, the piston rod <NUM> rotates about the longitudinal axis X and is prevented to move along the longitudinal direction P, whereas in the dose delivery configuration the piston rod <NUM> moves along the longitudinal direction P and is prevented to rotate about the longitudinal axis X.

The piston rod <NUM> is coupled to a dose setting sleeve <NUM> which rotates about the longitudinal axis X both in the dose setting configuration and in the dose delivery configuration. In the dose setting configuration, the rotation of the dose setting sleeve <NUM> and of the piston rod <NUM> is driven by the clutch device <NUM> which in turn is driven by the rotation of the knob <NUM> about the longitudinal axis X, whereas in the dose delivery configuration the rotation of the dose setting sleeve <NUM> is caused by an axial thrust exerted by the user on the knob <NUM> along the longitudinal direction P.

The dose setting sleeve <NUM> comprises an outer surface <NUM> (shown in <FIG>) having a plurality of numbers (or generally indicia, not shown), each number being correlated to a respective dose of all the settable doses.

As shown in <FIG>, a display window 20a is formed in the outer case <NUM>.

The user rotates the knob <NUM> clockwise or counterclockwise till the number correlated to the desired dose to be set and delivered is displayed through at the display window 20a, thus providing the user with a visual indication about the dose actually set. Rotation in both directions during the dose setting operation allows the user to set the desired dose in case he/she initially sets a dose greater or lower than the desired dose.

Once the desired dose has been set, the user pushes the knob <NUM> along the longitudinal direction P to deliver such a dose. The axial movement of the knob <NUM> causes the clutch device <NUM> to switch the injection device <NUM> from the dose setting configuration to the dose delivery configuration. In the latter configuration the knob <NUM> is prevented to rotate.

A stopper <NUM> (shown in <FIG>) is coupled to the free end of the piston rod <NUM> opposite to the knob <NUM>. The stopper <NUM> is initially inserted within the cartridge <NUM>, provided within the cartridge housing <NUM>, at a free end of the cartridge <NUM> located at the free end 12a of the main body <NUM>. Due to the axial movement of the piston rod <NUM> caused by the axial movement of the knob <NUM> during the dose delivery operation, the stopper <NUM> axially moves within the cartridge <NUM> along the longitudinal direction P toward the opposite free end of the cartridge <NUM> thus forcing the desired dose to exit from the cartridge <NUM> at the opposite free end thereof.

A last dose setting device <NUM> is arranged between the dose setting sleeve <NUM> and the cartridge housing <NUM> in order to prevent the user to set a dose greater than the one remaining in the cartridge <NUM> after the previous dose delivery/ies.

As shown in <FIG>, the last dose setting device <NUM> comprises a pinion <NUM> coupled within the outer case <NUM> at a fixed axial position of the outer case <NUM> and a rack <NUM> engaged with the pinion <NUM> and slidingly coupled with an internal surface of the outer case <NUM>.

As shown in <FIG>, the fixed axial position of the pinion <NUM> within the outer case <NUM> is defined by positioning a collar 61a formed at a free end of a mandrel <NUM> of the pinion <NUM> in abutment against an abutment surface <NUM> projecting radially inwardly from the internal surface of the outer case <NUM> and by positioning a free end portion 61b (or the collar 61a) of the mandrel <NUM> in abutment against another abutment surface <NUM> projecting radially inwardly from the internal surface of the outer case <NUM>.

The pinion <NUM> is arranged coaxially to the longitudinal axis X and includes a central hole <NUM> coupled with the piston rod <NUM>.

The coupling between the pinion <NUM> and the piston rod <NUM> is such that during the dose setting operation the piston rod <NUM> drags in rotation the pinion <NUM> whereas during the dose delivery operation the piston rod <NUM> slides axially within the central hole <NUM>.

In order to allow the rotational coupling between the pinion <NUM> and the piston rod <NUM>, the piston rod <NUM> has a longitudinal planar surface <NUM> and the central hole <NUM> has a planar profile portion <NUM> coupled to the longitudinal planar surface <NUM>.

In order to prevent the pinion <NUM> from disengaging from the rack <NUM> in case of shocks, two ribs <NUM> (only one of which can be seen in <FIG>) are formed on the internal surface of the outer case <NUM> on a portion of the latter arranged on the opposite side of the rack <NUM>, so that the pinion <NUM> is arranged between the ribs <NUM> and the rack <NUM>. The ribs <NUM> are preferably located on the opposite sides with respect to a radial plane of the pinion <NUM> coinciding with a longitudinal median plane of the rack <NUM>.

Due to the fixed axial position of the pinion <NUM> within the outer case <NUM>, when the pinion <NUM> rotates the rack <NUM> moves along the longitudinal direction P. Preferably, a clockwise rotation of the pinion <NUM> causes an axial movement of the rack <NUM> toward the cartridge housing <NUM>, that is along the distal direction, whereas a counterclockwise rotation of the pinion <NUM> causes an axial movement of the rack <NUM> toward the dose setting sleeve <NUM>, that is along the proximal direction.

The axial movement of the rack <NUM> is obtained thanks to the sliding coupling between an axial guide groove <NUM> formed in the rack <NUM> and extending along the longitudinal direction X and an axial guide rail <NUM> provided on an internal surface of the outer case <NUM> and also extending along the longitudinal direction X.

The rack <NUM> is designed such that the axial length travelled by the rack <NUM> during all the dose setting operations performed in order to delivery the maximum dispensable drug volume initially contained in the cartridge <NUM> is correlated to such a whole drug volume.

The rack <NUM> comprises a free end 66a closer to the cartridge <NUM> and an opposite free end 66b, as shown in <FIG> and <FIG>.

In particular, the rack <NUM> has a predetermined axial dimension which is equal or proportional to an axial length travelled by the piston rod <NUM> for delivering the abovementioned whole drug volume.

As shown in <FIG>, a rotational end stop element <NUM> is provided in a face 62a of the pinion <NUM> faced toward the second free end 66b of the rack <NUM> and a corresponding rotational end stop element <NUM> is provided in the rack <NUM> at the second free end 66b thereof.

During the rotation of the pinion <NUM>, and consequently during the axial movement of the rack <NUM>, when the rotational end stop element <NUM> abuts to the rotational end stop element <NUM> further rotation of the pinion <NUM>, and consequently further axial movement of the rack <NUM>, is prevented.

In operation, the injection device <NUM> is initially in the dose setting configuration and the user rotates the knob <NUM> to set the desired dose to be delivered. During such a first dose setting operation the knob <NUM> moves axially along the proximal direction, while rotating. As shown in <FIG>, the rack <NUM> is initially arranged at a first position such that the pinion <NUM> is located at the free end 66a of the rack <NUM> and during the first dose setting operation the rack <NUM> moves from such a first position toward the cartridge <NUM> along the longitudinal direction P (that is the distal direction) travelling an axial length which depends on the specific dose actually set. Once the first dose setting operation is concluded, the rack <NUM> is at a second axial position closer to the cartridge <NUM>.

After such a first dose setting operation is concluded, the user pushes the knob <NUM> toward the cartridge <NUM> along the longitudinal direction P to deliver the dose previously set. During such a first dose delivery operation the rack <NUM> does not move from the second axial position previously reached.

After such a first dose delivery operation, when the user wishes to set a new desired dose to be delivered, the user rotates the knob <NUM> to set such a new desired dose. During such a new dose setting operation the piston rod <NUM> remains at the axial position reached at the end of the first dose delivery operation till the end of the new dose setting operation, while the rack <NUM> moves toward the cartridge <NUM> travelling a respective axial length which depends on the new desired dose actually set.

Once such a new dose setting operation is concluded, the rack <NUM> is at a new axial position closer to the cartridge <NUM> than the previously second axial position. An example of the new axial position reached by the rack <NUM> is shown in <FIG>.

The user can continue to perform the abovementioned dose setting operation and dose delivery operation till the whole drug volume initially contained in the cartridge <NUM> is delivered.

After one or more previous dose setting and delivery operations, when the new dose setting operation (herein referred to as last dose setting operation) is such that the dose to be set is the same or almost the same as the drug volume remaining in the cartridge <NUM>, the rack <NUM> reaches an axial position such that the pinion <NUM> is positioned at the second free end 66b of the rack <NUM> opposite to the first free end 66a. An example of such an axial position is shown in <FIG> and <FIG>.

Thus, from the first dose setting and delivery operation to the last dose setting and delivery operation the rack <NUM> travels a total axial length towards the cartridge <NUM> which depends on the whole drug volume initially provided within the cartridge <NUM>.

The user can set (and subsequently deliver) any desired dose till the rotational end stop element <NUM> of the pinion <NUM> and the rotational end stop element <NUM> of the rack <NUM> abut to each other. Such a situation is very close to the one shown in <FIG>. In particular, it is reached upon a further small rotation of the pinion <NUM>, and a consequent short axial movement of the rack <NUM>, with respect to the situation shown in <FIG>.

Should the user try to set a dose greater than the one currently and actually available drug volume in the cartridge <NUM>, the rotational end stop element <NUM> of the pinion <NUM> abuts against the rotational end stop element <NUM> of the rack <NUM>, thus preventing further relative movement between pinion <NUM> and rack <NUM> and therefore preventing the user to set such a dose.

Accordingly, the user can set as the last dose a dose which is equal to the currently and actually available drug volume in the cartridge <NUM>.

Of course, those skilled in the art can bring numerous modifications and changes to the invention described above in order to satisfy specific and contingent requirements, all of which are within the scope of protection defined by the following claims. volume initially provided within the cartridge <NUM>.

Claim 1:
Drug injection device (<NUM>) comprising:
- a cartridge housing (<NUM>) extending along a longitudinal axis (X) and configured to house a cartridge (<NUM>) including a predetermined drug volume;
- a dose setting mechanism (<NUM>) configured to set a drug dose to be delivered out of the cartridge (<NUM>);
- a dose delivery mechanism (<NUM>) configured to deliver the drug dose set by the dose setting mechanism (<NUM>);
wherein the dose setting mechanism (<NUM>) comprises:
- a dose setting service element (<NUM>) configured to rotate about said longitudinal axis (X) during the drug dose setting;
- a last dose setting device (<NUM>) configured to prevent a user to set a drug dose greater than the drug volume remaining in the cartridge (<NUM>) after at least one previous drug dose delivery, wherein the last dose setting device (<NUM>) comprises:
- a pinion (<NUM>) arranged coaxially to said longitudinal axis (X) at a fixed axial position with respect to the cartridge housing (<NUM>);
- a rack (<NUM>) engaged with the pinion (<NUM>) and movable along a longitudinal direction (P) parallel to the longitudinal axis (X) when the pinion (<NUM>) rotates;
characterized in that the pinion (<NUM>) is configured to rotate about the longitudinal axis (X) together with the dose setting service element (<NUM>) during the drug dose setting and in that the pinion (<NUM>) and the rack (<NUM>) have mutual abutment elements (<NUM>, <NUM>) configured to abut with each other and prevent further rotation of the pinion (<NUM>) after the rack (<NUM>) has travelled an axial length correlated to the predetermined drug volume.