Patent Description:
In some situations, it is desirable for patients to be able to administer drugs and medicament by themselves, e.g., without the need for trained medical staff to administer the drugs. There are a number of different existing delivery devices with varying degrees of automatic functions. For instance, existing automatic injection devices provide a means for automatically propelling a plunger forward to eject medicament from the automatic injection device in response to activation of the device.

In existing devices, the means for automatically propelling the plunger forward to eject the medicament are often complex and expensive to manufacture. There is, therefore, a desire to reduce the cost of manufacturing automatic injection devices while maintaining the reliability of the injection device to eject the dose of medicament.

Further, for some types of medicaments, there is a desire to eject the medicament at a substantially constant force. However, certain existing devices for ejecting the medicament at a substantially constant force are complex and expensive to manufacture. There is a desire to reduce the cost of manufacturing automatic injection devices while maintaining the reliability of the injection device to eject the medicament at a substantially constant force. <CIT> and <CIT> disclose prior art drug delivery devices.

The invention is defined in the independent claim <NUM>, preferable embodiments are further defined in the dependent claims.

A drug delivery device configured to administer a dose of medicament is provided. In an example embodiment, the drug delivery device includes a main housing, a medicament container arranged in the main housing, and a pneumatic power pack arranged in the main housing. The medicament container holds a medicament. The pneumatic power pack includes: (i) a pressurized gas source storing pressurized gas; (ii) a valve for the pressurized gas source; (iii) a sleeve having an inner wall; and (iv) a plunger comprising an inner chamber and a pressure release valve configured to release pressure from the inner chamber when the pressure in the inner chamber reaches a threshold pressure level. The plunger is axially movable with respect to both the sleeve and the medicament container. Further, the plunger is in sliding gas-tight engagement with the inner wall of the sleeve. The sleeve and the inner chamber are configured to receive pressurized gas released from the pressurized gas source. The valve for the pressurized gas source is configured to release the pressurized gas upon activation of the valve. Further, the released pressurized gas flows into both the sleeve and inner chamber and propels the plunger in a distal direction with respect to the sleeve and the medicament container at a substantially constant force, so as to eject the medicament from the medicament container.

Exemplary embodiments are described herein with reference to the drawings, in which:.

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.

The methods and systems in accordance with the present disclosure beneficially provide improved methods and systems for propelling a plunger forward so as to eject the medicament from an automatic injection device. The disclosed methods and systems provide a reliable, intuitive, and user-friendly drug delivery device that uses a pressurized gas to eject a dose of medicament. Further, the disclosed methods and systems provide a cost effective means for propelling the plunger forward so as to eject the medicament and thus help to reduce the cost of manufacturing automatic injection devices.

In accordance with an example embodiment of the present disclosure, a drug delivery device includes a main housing, a syringe arranged in the main housing, and a pneumatic power pack arranged in the main housing. The syringe holds a dose of medicament. The pneumatic power pack includes a pressurized gas source storing pressurized gas, a valve for the pressurized gas source, a sleeve having an inner wall, and a plunger. The sleeve is in gas-tight engagement with the pressurized gas source and is configured to receive pressurized gas released from the pressurized gas source. The plunger is at least partly surrounded by the sleeve and is axially movable with respect to both the sleeve and the syringe. Further, the plunger is in sliding gas-tight engagement with the inner wall of the sleeve. Upon activation of the valve, the valve releases the pressurized gas. The released pressurized gas then flows into the sleeve and propels the plunger in a distal direction with respect to the sleeve and the syringe, so as to eject the medicament from the syringe.

In an example embodiment, the plunger includes an inner chamber for receiving the released pressurized gas. In this embodiment, upon activation of the valve, the released pressurized gas flows into both the sleeve and the inner chamber. This pressurized gas then propels the plunger in the distal direction with respect to the sleeve and the syringe, so as to eject the medicament from the syringe.

<FIG> generally illustrates an example drug delivery device that uses pressurized gas to deliver a dose of medicament. In particular, <FIG> illustrates a drug delivery device <NUM> in an initial state prior to injection. Further, <FIG> illustrates an exploded view of the components of the drug delivery device <NUM> in the initial state prior to injection.

As seen in <FIG> and <FIG>, drug delivery device <NUM> includes a main housing <NUM> and a syringe <NUM> arranged in the main housing <NUM>. Main housing <NUM> includes a first housing portion <NUM> and a second housing portion <NUM>. First and second housing portions <NUM>, <NUM> include corresponding engagement features for providing an engagement between the two housing portions <NUM>, <NUM>. In an example embodiment, during assembly of the drug delivery device <NUM>, the first and second housing portions are irreversibly attached to one another. Although main housing <NUM> is depicted as comprising first and second housing portions <NUM>, <NUM>, in other examples, main housing <NUM> may comprise more or fewer portions. For instance, in an example embodiment, the main housing <NUM> is of unitary construction.

With reference to <FIG>, the syringe <NUM> includes a syringe body <NUM> holding a medicament <NUM>, a needle <NUM>, and a needle cover <NUM> covering the needle <NUM>. A piston or stopper <NUM> is disposed in the syringe body <NUM>. The drug delivery device <NUM> further includes a pneumatic power pack <NUM> for ejecting the medicament from the syringe <NUM>. The pneumatic power pack <NUM> includes a pressurized gas source <NUM> storing pressurized gas <NUM>, a valve <NUM> for the pressurized gas source <NUM>, a sleeve <NUM>, and a plunger <NUM>.

The sleeve <NUM> is in gas-tight engagement with the pressurized gas source <NUM> and is configured to receive pressurized gas <NUM> released from the pressurized gas source <NUM>. As used herein, "gas-tight engagement" means an engagement providing a seal that prevents or substantially prevents leakage of gas through the seal during the dose delivery process. By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. In an example embodiment, the gas-tight engagement prevents or limits leakage of gas such that less than <NUM>% of the released pressurized gas <NUM> received in sleeve <NUM> is able to leak through the gas-tight engagement during the dose delivery process. In another example embodiment, the gas-tight engagement prevents or limits leakage of gas such that less than <NUM>% of the released pressurized gas <NUM> received in sleeve <NUM> is able to leak through the gas-tight engagement during the dose delivery process. In yet another example, the gas-tight engagement prevents or limits leakage of gas such that less than <NUM>% of the released pressurized gas <NUM> received in sleeve <NUM> is able to leak through the gas-tight engagement during the dose delivery process.

The sleeve <NUM> has an inner wall <NUM>, and the plunger <NUM> is in sliding gas-tight engagement with the inner wall <NUM> of the sleeve <NUM>. During an injection process of drug delivery device <NUM>, the pressurized gas <NUM> will axially move the plunger <NUM> with respect to the sleeve <NUM> and consequently with respect to the syringe <NUM>. In particular, upon activation of valve <NUM>, the valve <NUM> releases the pressurized gas <NUM>. The pressurized gas <NUM> then flows into the sleeve <NUM> and propels the plunger <NUM> in distal direction <NUM> with respect to the sleeve <NUM> and syringe <NUM>, so as to eject the medicament from the syringe <NUM> through needle <NUM>.

In general, the valve <NUM> may be activated by the drug delivery device <NUM> in any suitable manner. In the example embodiment of <FIG>, the needle cover <NUM> and the sleeve <NUM> interact with one another in order to activate the valve <NUM>. To initiate the injection process, the user places the drug delivery device <NUM> on an injection site, such as injection site <NUM> as shown in <FIG>. When the drug delivery device <NUM> is pressed onto the injection site <NUM> in distal direction <NUM>, the needle cover <NUM> moves in a proximal direction <NUM> relative to the main housing <NUM>. This retraction of the needle cover <NUM> exposes the needle <NUM> and the needle <NUM> is consequently inserted into the injection site <NUM>.

In addition to exposing needle <NUM>, this retraction of the needle cover <NUM> also serves to activate the valve <NUM> of the pneumatic power pack <NUM>. In particular, the axial movement of the needle cover <NUM> in the proximal direction <NUM> causes axial movement of the sleeve <NUM> in the proximal direction <NUM>. This axial movement of the sleeve <NUM> causes the sleeve <NUM> to interact with and activate the valve <NUM>. The needle shield <NUM> may interact with sleeve <NUM> in any suitable manner in order to move the sleeve <NUM> in order to activate the valve <NUM>. In the example shown in <FIG>, a coupling flange <NUM> is attached to the sleeve <NUM>. Axial movement of the needle shield <NUM> in the proximal direction <NUM> causes a proximal end <NUM> of the needle cover <NUM> to engage the coupling flange <NUM> and move the sleeve <NUM> in the proximal direction <NUM> to activate the valve <NUM>.

The sleeve <NUM> may interact with the valve <NUM> in any suitable manner in order to activate the valve <NUM>. In the example of <FIG>, valve <NUM> includes a push portion <NUM> configured to open the valve <NUM>. In particular, the valve <NUM> is configured to open when the push portion <NUM> is moved a threshold amount in the proximal direction <NUM>. Axial movement of the sleeve <NUM> in the proximal direction <NUM> causes the sleeve <NUM> to contact the push portion <NUM> and then move the push portion <NUM> the threshold amount in the proximal direction <NUM>. This movement opens the valve <NUM> and releases the pressurized gas <NUM>. In general, for such a push-activated valve, any suitable threshold amount of movement in the proximal direction <NUM> to activate the valve <NUM> is possible. In an example, the threshold amount is between <NUM> and <NUM> millimeters (mm). However, threshold amounts less than <NUM> and greater than <NUM> are possible as well.

Although the example of <FIG> depicts a push-activated valve <NUM>, in other example embodiments, the valve <NUM> may be activated in other suitable ways. For instance, the valve <NUM> may include a twist portion that is configured to open the valve <NUM> upon rotation. In such an example, the device <NUM> is configured such that movement of the sleeve <NUM> causes rotation of the twist portion to open the valve <NUM>. Other examples are possible as well.

After activation of the valve <NUM>, the pneumatic power pack <NUM> releases the pressurized gas <NUM> to automatically inject the dose of medicament <NUM>. The injection process is described in detail with reference to <FIG> and <FIG>. As mentioned above, <FIG> depicts the device <NUM> in an initial state prior to injection. Further, <FIG> depicts the pneumatic power pack <NUM> and syringe <NUM> during dose delivery. Still further, <FIG> depicts the pneumatic power pack <NUM> and syringe <NUM> at the end of dose delivery.

In the initial state (see <FIG>), a proximal end <NUM> of plunger <NUM> is positioned in a proximal end <NUM> of the sleeve <NUM>. When the valve <NUM> is activated, the valve <NUM> releases the pressurized gas <NUM>. The pressurized gas <NUM> then flows into the sleeve <NUM> as indicated by arrow <NUM> (see <FIG>) and propels the plunger <NUM> in distal direction <NUM> with respect to the sleeve <NUM> and syringe <NUM>, so as to eject the medicament from the syringe <NUM> through the needle <NUM>. Since sleeve <NUM> is in gas-tight engagement with the pressurized gas source <NUM> and the plunger <NUM> is in sliding gas-tight engagement with the inner wall of sleeve <NUM>, the released pressurized gas <NUM> flowing into the sleeve <NUM> creates a pressure sufficient to propel the plunger <NUM> in the distal direction <NUM> with respect to the sleeve <NUM>.

The pressurized gas <NUM> propels the plunger <NUM> in the distal direction <NUM> until the stopper <NUM> reaches a distal end <NUM> of the syringe body <NUM> (see <FIG>). When the stopper <NUM> reaches the distal end <NUM> of the syringe body <NUM>, the proximal end <NUM> of plunger <NUM> is positioned in a distal end <NUM> of sleeve <NUM>.

During the dose delivery, the sleeve <NUM>, syringe <NUM>, and gas source <NUM> may be axially fixed with respect to main housing <NUM>. As a result of these components being axially fixed during dose delivery, all or substantially all of the pressure from the released pressurized gas <NUM> will beneficially go towards propelling the plunger <NUM> in the distal direction <NUM>.

The plunger <NUM> includes an inner chamber configured to receive the pressurized gas <NUM>. <FIG> illustrates a perspective cross-sectional view of plunger <NUM>, which includes inner chamber <NUM>. During dispense, the pressurized gas <NUM> flowing into sleeve <NUM> will also flow into the inner chamber <NUM> of the plunger <NUM>. Beneficially, the plunger <NUM> including an inner chamber <NUM> may help to reduce the mass of the plunger <NUM>, and this may consequently reduce the force required to propel the plunger <NUM> forward during dose delivery.

As mentioned above, sleeve <NUM> is in gas-tight engagement with pressurized gas source <NUM> and plunger <NUM> is in sliding gas-tight engagement with the inner wall <NUM> of sleeve <NUM>. The gas-tight engagement between the sleeve <NUM> and gas source <NUM> may be provided in any suitable manner. For instance, the engagement between the sleeve <NUM> and gas source <NUM> may include at least one washer or O-ring to provide the gas-tight engagement. Similarly, the sliding gas-tight engagement may be provided in any suitable manner. For instance, at least one washer or O-ring may be attached to the plunger <NUM> to provide the sliding gas-tight engagement with the inner wall <NUM>. As seen in <FIG>, plunger <NUM> includes a first washer <NUM> and a second washer <NUM> attached at the proximal end <NUM> of the plunger <NUM>. The plunger <NUM> may include one or more ribs, such as ribs <NUM> and <NUM> (see <FIG>), to hold the washers <NUM>, <NUM> on the plunger <NUM>. The washers <NUM>, <NUM> placed around the plunger <NUM> ensure that the space between the plunger <NUM> and pressurized gas source <NUM> is substantially air-tight so that any gas leakage that would reduce the thrusting force is minimized or prevented. Other methods for providing the gas-tight engagement between the sleeve <NUM> and gas source <NUM> and for providing the slidable, gas-tight engagement with inner wall <NUM> are possible as well.

After injection is complete, the device <NUM> is removed from the injection site <NUM> and the needle cover <NUM> will extend outward and lock into place. This extension and locking may limit or prevent needle stick injuries. The needle cover <NUM> may extend outward and lock into place in any suitable manner. In an example embodiment, when the drug delivery device <NUM> is removed from the injection site <NUM>, the needle cover <NUM> automatically extends outward in the distal direction <NUM> under a force such as a spring force. As seen in <FIG>, drug delivery device <NUM> includes spring <NUM> positioned between syringe <NUM> and needle cover <NUM>. This spring <NUM> provides the force to automatically extend the needle cover <NUM> in the distal direction <NUM> after the user removes the drug delivery device <NUM> from the injection site <NUM>. Other ways of locking the needle cover <NUM> in an extended position are possible as well.

In an example embodiment, during dose delivery, the user can hear and/or feel an audible and/or tactile feedback (e.g., clicking) throughout the dose delivery. For instance, the device <NUM> may include a clicker than produces a clicking sound when the plunger <NUM> is being propelled forward in the distal direction <NUM>. The end of injection may be indicated by the audible/tactile clicking having stopped. Additionally or alternatively, the stopper <NUM> and plunger <NUM> may be visible in the main body window <NUM> (see <FIG>) when injection is complete. In such an example, the end of delivery may be indicated by the stopper <NUM> and plunger <NUM> having stopped moving. Other indications of dose delivery being complete are possible as well.

Pressurized gas source <NUM> may be any source of pressurized gas suitable to propel the plunger <NUM> forward to eject the medicament <NUM>. In an example embodiment, the pressurized gas is CO<NUM>, Argon, or Nitrogen. Other example pressurized gases are possible as well. Further, in an example embodiment, the pressurized gas source <NUM> contains a gas pressurized to a pressure of between <NUM>-<NUM> PSI. However, in other examples, the pressure may be less than <NUM> PSI or more than <NUM> PSI. For instance, in another example, the pressure is between <NUM>-<NUM> PSI. In yet another example, the pressure is between <NUM>-<NUM> PSI. Other example pressures are possible as well.

Additionally, even though a syringe <NUM> is described in this example embodiment of <FIG>, any suitable type of medicament container may be used in the disclosed drug delivery device <NUM>, such as a syringe, an ampoule, a cartridge, an enclosure, etc. Further, the medicament may be any suitable substance used for medical treatment. In an example embodiment, the medicament is epinephrine (commonly known as adrenaline).

In an example embodiment, the disclosed pneumatic power pack may be configured to propel the plunger with a constant or substantially constant force. An example drug delivery device having a pneumatic power pack configured to propel the plunger with a constant or substantially constant force is described with reference to <FIG>.

<FIG> depicts a drug delivery device <NUM>. The drug delivery device <NUM> operates in a similar fashion as drug delivery devices <NUM>; however, rather than including power pack <NUM>, drug delivery device <NUM> includes power pack <NUM> (see <FIG>). Other elements of drug delivery device <NUM> may be the same or substantially similar to the other elements drug delivery device <NUM>, and thus drug delivery device <NUM> is not described in as great of detail. It should be explicitly noted, however, that any possibilities and permutations described above with respect to drug delivery device <NUM> may equally apply to drug delivery device <NUM>, and vice versa. Further, throughout the description of <FIG>, elements in drug delivery device <NUM> that are the same as or substantially similar to elements in drug delivery device <NUM> are described with like reference numerals.

<FIG> depicts a cross-sectional view of power pack <NUM> of drug delivery device <NUM>. Power pack <NUM> is positioned in second housing portion <NUM>. Further, power pack <NUM> includes pressurized gas source <NUM> storing pressurized gas <NUM>, valve <NUM>, sleeve <NUM>, and plunger <NUM> having inner chamber <NUM>. Sleeve <NUM> is in gas-tight engagement with pressurized gas source <NUM> and plunger <NUM> is in sliding gas-tight engagement with an inner wall <NUM> of sleeve <NUM>. In order to propel the plunger <NUM> with a constant or substantially constant force, valve <NUM> is configured to release the pressurized gas <NUM> at a substantially constant rate, and plunger <NUM> is configured to release pressure when the pressurized gas <NUM> in the inner chamber <NUM> reaches a threshold pressure level.

With reference to <FIG>, valve <NUM> includes a flow control orifice <NUM>. Valve <NUM> also includes a gasket <NUM> configured to open and close the flow control orifice <NUM>. Flow control orifice <NUM> includes an opening <NUM> and an exit <NUM> and is sized to release pressurized gas <NUM> at a substantially constant rate regardless of the pressure at the opening <NUM> and the pressure at exit <NUM>. An example size of the flow control orifice <NUM> may be on the order of <NUM> to about <NUM> Microns.

The flow control orifice <NUM> may release the pressurized gas at any suitable substantially constant rate. As mentioned herein, by the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

In an example embodiment, the substantially constant rate at which the flow control orifice <NUM> releases the pressurized gas is any substantially constant rate. Further, as used herein, a substantially constant rate of X means any rate in the range of X +/- <NUM>*(X).

Plunger <NUM> includes a pressure release valve <NUM> that is configured to release pressure when the pressurized gas in the inner chamber <NUM> reaches a threshold pressure level. The pressure release valve <NUM> includes one or more release holes (such as release hole <NUM>), gasket <NUM>, and spring <NUM>. Gasket <NUM> and spring <NUM> are disposed in a distal end of inner chamber <NUM>. When the pressure level in the inner chamber <NUM> is below the threshold pressure level, the gasket <NUM> is positioned at a location proximal to a location of the release hole <NUM>, so as to prevent the pressurized gas <NUM> from reaching the release hole <NUM>. <FIG> illustrates the gasket <NUM> positioned at a location proximal to a location of the release hole <NUM>. On the other hand, when the pressure level in the inner chamber <NUM> is above the threshold level, the pressurized gas <NUM> urges the gasket <NUM> against the spring <NUM> in a distal direction <NUM> until the gasket <NUM> moves distally beyond at least a part of the release hole <NUM>, so as to allow the pressurized gas <NUM> to exit the release hole <NUM>. <FIG> depicts the gasket <NUM> positioned at a location distal of the release hole <NUM>.

In general, the threshold pressure level may be selected based on a desired force at which the plunger <NUM> is to be propelled. In an example embodiment, the threshold pressure level is a pressure level between <NUM> PSI and <NUM> PSI.

In the example shown in <FIG>, pneumatic power pack <NUM> includes a container <NUM> for holding the pressurized gas source <NUM>. The container <NUM> includes a needle <NUM> that punctures the pressurized gas source <NUM> during assembly of the power pack <NUM>. In this example embodiment, the valve <NUM> for the pressurized gas source <NUM> is provided by flow control orifice <NUM> in container <NUM> and gasket <NUM>. However, in other embodiments, the pressurized gas source <NUM> may be replaced by a gas source that already has a release valve, such as valve <NUM>.

During operation of the drug delivery device <NUM>, valve <NUM> may be activated in any suitable manner. In the example of <FIG>, the valve <NUM> is activated by rotation of the gasket <NUM> to uncover the flow control orifice <NUM>. Similar to drug delivery device <NUM>, movement of the needle cover <NUM> may act on the sleeve <NUM> to activate the valve <NUM>. For instance, axial movement of needle cover <NUM> acts on sleeve <NUM> in order to rotate the gasket <NUM> in a clockwise direction <NUM> (see <FIG>) to uncover the flow control orifice <NUM>. In one arrangement, the sleeve <NUM> and an inner housing portion enclosing the gasket <NUM> are coupled during assembly. The needle cover <NUM> may act on either the sleeve <NUM> or the inner housing portion, depending on the designs, and the gasket <NUM> will be rotated by the inner housing portion to open and active the valve <NUM>. In other words, the needle cover <NUM> can act either the sleeve <NUM> or the inner housing portion to active the valve <NUM>.

When the valve <NUM> is activated by the rotation of gasket <NUM> to uncover flow control orifice <NUM>, the pressurized gas <NUM> moves through flow control orifice <NUM> at a substantially constant flow rate as shown by arrow <NUM> (see <FIG>). The pressurized gas <NUM> then moves into sleeve <NUM> and inner chamber <NUM> as shown by arrow <NUM>. Since the plunger <NUM> is in sliding gas-tight engagement with the inner wall <NUM> of the sleeve <NUM>, the flow of gas shown by arrow <NUM> will increase the pressure in the sleeve <NUM> and inner chamber <NUM> to propel the plunger <NUM> forward in distal direction <NUM> so as to eject medicament <NUM>. The pressurized gas <NUM> propels the plunger <NUM> in the distal direction <NUM> with the substantially constant force until the stopper <NUM> reaches the distal end <NUM> of the syringe body <NUM>. When the plunger <NUM> reaches this final point, any remaining pressurized gas <NUM> will be released through the pressure release valve <NUM> until the pressurized gas source <NUM> is empty or substantially empty.

During the propelling of the plunger <NUM> in the distal direction <NUM>, if the pressure in the inner chamber <NUM> exceeds the threshold level, the pressurized gas <NUM> will get released through pressure release valve <NUM> (as shown by arrow <NUM>). This pressure release through pressure release valve <NUM> allows for effectively keeping the pressure in the inner chamber <NUM> at a substantially constant value. As a result of the pressure being regulated in this manner, the pneumatic power pack <NUM> is able to push the plunger <NUM> in the distal direction <NUM> with a substantially constant force produced by the pressure in the sleeve <NUM> and inner chamber <NUM>.

The pneumatic power pack <NUM> may propel the plunger <NUM> forward with any suitable substantially constant force. As mentioned herein, by the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

In an example embodiment, the substantially constant force at which the plunger <NUM> is propelled is any substantially constant force falling in the range of forces between 10N and 100N +- 15N. Further, as used herein, a substantially constant force of X Newtons means any force in the range of 10N and 100N +- 15N.

Beneficially, the disclosed pneumatic power pack provides a cost effective means for propelling a plunger forward in an automatic injection device. Further, embodiments of the disclosed pneumatic power pack also provide a low-cost means for propelling the plunger forward at a substantially constant force. Therefore, the disclosed pneumatic power pack may help to reduce the cost of manufacturing automatic injection devices.

In the examples shown in the Figures, the drug delivery devices <NUM> and <NUM> are configured to inject a non-variable dose of medicament. However, in other embodiments, the drug delivery device could be configured to allow the user to select a variable single dose. For instance, in an example embodiment, the user is able to select two different dose values, three different dose values, four different dose values, and so forth.

In the Figures, various engagement features for are shown for providing an engagement between one or more components of the drug delivery device. The engagement features may be any suitable connecting mechanism such as a snap lock, a snap fit, form fit, a bayonet, lure lock, threads or combination of these designs. Other designs are possible as well.

It should be understood that the illustrated components are intended as an example only. In other example embodiments, fewer components, additional components, and/or alternative components are possible as well. Further, it should be understood that the above described and shown embodiments of the present disclosure are to be regarded as nonlimiting examples and that they can be modified within the scope of the claims.

Claim 1:
A drug delivery device (<NUM>) comprising:
a main housing (<NUM>);
a medicament container (<NUM>) arranged in the main housing (<NUM>), wherein the medicament container (<NUM>) comprises a medicament (<NUM>); and
a pneumatic power pack (<NUM>) arranged in the main housing (<NUM>), wherein the pneumatic power pack (<NUM>) comprises:
(i) a pressurized gas source (<NUM>) storing pressurized gas (<NUM>);
(ii) a valve (<NUM>) for the pressurized gas source (<NUM>);
(iii) a sleeve (<NUM>) having an inner wall (<NUM>); and
(iv) a plunger (<NUM>) comprising an inner chamber (<NUM>) and a pressure release valve (<NUM>) configured to release pressure from the inner chamber (<NUM>) when the pressure in the inner chamber (<NUM>) reaches a threshold pressure level,
wherein the plunger (<NUM>) is axially movable with respect to both the sleeve (<NUM>) and the medicament container (<NUM>),
wherein the plunger (<NUM>) is in sliding gas-tight engagement with the inner wall (<NUM>) of the sleeve (<NUM>),
wherein the sleeve (<NUM>) and the inner chamber (<NUM>) are configured to receive pressurized gas (<NUM>) released from the pressurized gas source (<NUM>),
wherein the valve (<NUM>) is configured to release the pressurized gas (<NUM>) upon activation of the valve (<NUM>), and
wherein the released pressurized gas (<NUM>) flows into both the sleeve (<NUM>) and inner chamber (<NUM>) and propels the plunger (<NUM>) in a distal direction with respect to the sleeve (<NUM>) and the medicament container (<NUM>) at a substantially constant force, so as to eject the medicament (<NUM>) from the medicament container (<NUM>).