CN114788910A - Dose setting assembly for medical injection device - Google Patents

Abstract

A dose setting assembly for a medical injection device, the medical injection device comprising: a cartridge defining a reservoir adapted to contain a medical injection fluid; an open proximal end and a distal end including a hub portion; a flange provided at a proximal end of the barrel; and an elongate plunger rod having a plunger flange at a proximal end and a stopper at a distal end, the plunger rod being slidably movable within the barrel, the dose setting assembly comprising: a rear stop attachable to a flange of the barrel; a distal dose setting member fixed on the back stop and configured to hold the plunger rod in a distal predetermined position, which is laterally removable from the back stop to allow the plunger rod to move towards and abut the back stop; and a proximal dose setting member fixed on the distal dose setting member and holding the plunger rod in a second predetermined position, which is laterally removable from the distal dose setting member to allow the plunger rod to move towards the distal dose setting member and abut on the distal dose setting member.

Description

Dose setting assembly for medical injection device

Technical Field

The present invention relates to a dose setting assembly for a medical injection device, such as a syringe, which is capable of dispensing an accurate dose of a medical injection fluid.

Background

As is known in the art, medical injection devices, such as syringes, are utilized to administer medical injection fluid in liquid form into a patient.

Syringes typically include a barrel adapted to hold a medical injection fluid. The plunger rod is inserted through the open distal end of the barrel. Through its engagement with an elastomeric or rubber-like stopper fitted in a fluid-tight manner inside the barrel, a user may apply manual force to the proximal end of the plunger to deliver a medical injection fluid through a fluid channel provided at the distal end of the barrel. A barrel flange in the form of a finger rest is typically provided around the open proximal end of the syringe barrel to facilitate user manipulation of the medical injection device, and a plunger flange is also provided at the proximal end of the plunger rod, on which a user can apply finger pressure. The medical injection fluid is then dispensed by moving the plunger forward through the barrel.

Accurate dispensing of precise volumes of medical injection fluids is critical in situations like injecting drugs in the eye. For this type of drug, it is common practice to inject 50 microliters to 1 milliliter.

To this end, the barrel is typically marked with graduation marks which determine the volume of medical injection fluid dispensed by the stroke of the plunger. The required dose is determined by the distance between the two graduation marks.

The graduations are typically closely spaced and may be difficult to read, thus making it difficult to dispense an accurate dose of medical injection fluid.

Furthermore, the disengagement force (static friction force) required to start the movement of the plunger is greater than the slip force (kinetic friction force) required once the plunger has started moving. Thus, the user is liable to exceed the desired dose setting when a precise movement is required.

Syringe priming can also result in the loss of precious medical fluid if it is not done very carefully.

Thus, when the user is not very careful, too little or too much medical injection fluid may be delivered to the patient.

Disclosure of Invention

In such circumstances, it is desirable to improve the accuracy of medical injection fluid dispensed from a medical injection device, such as a syringe.

This and other related problems are solved by a dose setting assembly for a medical injection device comprising: a cartridge defining a reservoir adapted to contain a medical injection fluid; an open proximal end and a distal end including a hub portion; a flange disposed at a proximal end of the barrel; and an elongate plunger rod having a plunger flange at a proximal end and a stopper at a distal end, the plunger rod being slidably movable within the barrel, the dose setting assembly comprising:

-a rear stop attachable to the flange of the barrel,

-a distal dose setting member fixed on the back-stop, the distal dose setting member being configured to keep the plunger rod in a distal predetermined position, the distal dose setting member being laterally removable from the back-stop to allow the plunger rod to move towards and abut on the back-stop, and

-a proximal dose setting member fixed on the distal dose setting member, the proximal dose setting member holding the plunger rod in a second predetermined position, the proximal dose setting member being laterally removable from the distal dose setting member to allow the plunger rod to move towards and abut on the distal dose setting member.

Other embodiments of the invention may include the following features, taken alone or in combination:

-the proximal dose setting member comprises a locking means configured to hold the plunger flange in a hidden locked position.

-the proximal dose setting member comprises a proximal wall and two lateral walls, each lateral wall having an inwardly directed intermediate rib defining a plunger flange locking cavity together with the proximal wall.

-the proximal dose setting member comprises two inwardly directed distal ribs defining two grooves.

-the proximal dose setting member comprises an aperture defined by the intermediate rib, the aperture being configured and dimensioned to allow passage of the plunger rod and to prevent passage of the plunger flange.

The distal dose setting member comprises two legs joined by a transverse portion, each leg having an external groove defined between a proximal flange and a distal flange.

-the leg and the transverse portion defining an aperture configured and dimensioned to allow passage of the plunger rod and to prevent passage of the plunger flange.

-the distal dose setting member comprises a pull tab.

-the rear stop comprises a transverse wall and two lateral walls, the lateral walls of the rear stop defining an aperture configured and dimensioned to allow passage of the plunger rod and to prevent passage of the plunger flange.

Each lateral wall of the rear stop comprises two inwardly projecting parallel flanges defining a distal groove.

Each lateral wall of the rear stop comprises two inwardly projecting parallel flanges defining a proximal groove.

Another aspect of the invention relates to a method of operating a medical injection device, the method comprising the steps of:

-providing a medical device having the above-mentioned dose setting assembly;

-removing the proximal dose setting member from the distal dose setting member;

-moving the plunger rod into the syringe barrel towards the distal dose setting member until the plunger rod abuts on the distal dose setting member;

-removing the distal dose setting member from the back stop;

-moving the plunger rod into the syringe barrel towards the back stop until the plunger rod abuts on the back stop.

The disclosure set forth herein is further defined by the following features:

a dose setting assembly for a medical injection device, the medical injection device comprising: a cartridge defining a reservoir adapted to contain a medical injection fluid; an open proximal end and a distal end including a hub portion; a flange disposed at a proximal end of the barrel; and an elongate plunger rod having a plunger flange at a proximal end and a stopper at a distal end, the plunger rod being slidably movable within the barrel. The dose setting assembly comprises:

-a rear stop attachable to the flange of the barrel; and

-a dose setting member removably fixed on said back stop, said dose setting member being configured to hold said plunger rod in a predetermined position, said dose setting member being laterally removable from said back stop to allow said plunger rod to move towards and abut on said back stop.

The present invention provides an add-on assembly that can be easily applied to conventional medical injection devices such as plastic or glass syringes. The present invention makes it possible to keep the syringe plunger rod in a predetermined position by means of the dose setting member. After removal of the dose setting member, the plunger is free to advance distally. Distal movement of the plunger is limited by a plunger flange abutting the rear stop. Thus, the stroke of the plunger is fully controlled and the volume of medical injection fluid dispensed accordingly is not dependent on the user reading the scale on the barrel.

In one embodiment of the invention, the dose setting assembly comprises a distal dose setting member fixed on the back stop, the distal dose setting member being configured to hold the plunger rod in a distal predetermined position, the distal dose setting member being laterally removable from the back stop to allow the plunger rod to move towards the back stop and abut on said counter-element, and

a proximal dose setting member fixed on the distal dose setting member, the proximal dose setting member holding the plunger rod in the second predetermined position, the proximal dose setting member being laterally removable from the distal dose setting member to allow the plunger rod to move towards and abut on the distal dose setting member. In this embodiment, the present invention makes it possible to precisely define the dose of drug injection fluid. It is also ensured that the priming of the injection device takes place in a controlled manner.

In one embodiment, the proximal dose setting member comprises at least one internal locking means configured to hold the plunger flange in a hidden locked position. This embodiment of the invention ensures that the plunger rod is not unintentionally moved during sterilization, storage and transportation.

Other embodiments of the invention may include the following features, taken alone or in combination:

the dose setting member comprises an elongated U-shaped wall defining a housing.

-the dose setting member comprises: a distal part provided with at least one external groove oriented perpendicular to the longitudinal axis of the dose setting member; and a proximal portion provided with at least one internal groove oriented perpendicular to the longitudinal axis of the dose setting member.

The dose setting member comprises an inner shoulder provided in the U-shaped wall and an outer shoulder provided in the U-shaped wall.

The outer groove of the distal part of the distal dose setting member is dimensioned and configured to fit into the inner groove of the proximal part of the proximal dose setting member.

The rear stop comprises a distal plate and a proximal funnel, each defining a longitudinal housing.

The rear stop comprises a distal groove adjacent to the distal plate and two arcuate portions provided on the distal plate.

The rear stop comprises a proximal groove provided in the proximal funnel.

The distal plate extends radially from the funnel.

Another aspect of the invention relates to a method of operating a medical injection device, comprising the steps of:

-providing a medical injection device having a dose setting assembly;

-removing at least one dose setting member from the medical injection device;

-moving the plunger rod into the syringe barrel towards the back stop until the flange of the barrel abuts the back stop.

In another embodiment, the method of operation may further comprise the steps of:

-providing a medical device having a dose setting assembly;

-removing the proximal dose setting member from the distal dose setting member;

-moving the plunger rod into the syringe barrel towards the distal dose setting member until the plunger rod abuts on the distal dose setting member;

-removing the distal dose setting member from the back stop;

-moving the plunger rod into the syringe barrel towards the rear stop until the plunger rod abuts on the rear stop.

In one embodiment of the invention, the dose setting member is laterally removed from the medical injection device.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.

Drawings

The invention will now be described in more detail with reference to the accompanying drawings, in which:

fig. 1 shows in perspective view a dose setting assembly according to an exemplary embodiment of the present invention mounted to a conventional syringe;

FIG. 2 is a side view of the embodiment shown in FIG. 1;

fig. 3 shows the back stop of the dose setting assembly of fig. 1 in a perspective view;

fig. 4 shows the dose setting member of the dose setting assembly of fig. 1 in a perspective view;

fig. 5 to 7 show the dose setting assembly of fig. 1 in operation;

fig. 8 shows in perspective view a dose setting assembly according to an exemplary embodiment of the present invention mounted to a conventional syringe;

fig. 9 shows the dose setting assembly of fig. 8 on an enlarged scale;

fig. 10 to 13 show the dose setting assembly of fig. 8 in operation;

fig. 14 shows the distal setting member comprised in the dose setting assembly of fig. 8 on an enlarged scale.

Detailed Description

As used herein, the term "proximal" and its derivatives refer to the end of an item or direction that is closest to the user during use of the invention. The term "distal" and its derivatives refer to the end of an item or direction that is toward the patient during use of the invention. As used herein, the term "medical injection fluid" and derivatives thereof refer to any substance intended for injection into a patient, including, but not limited to, drugs, vaccines, therapeutics, and the like. It will be apparent to those skilled in the art and from the disclosure provided herein that the present invention is not limited or otherwise defined by the type or class of substance to be administered using the dose setting assembly of the present invention.

In an exemplary embodiment of the present invention, as shown in fig. 1-7 and 8-13, the dose setting assembly 10, 100 comprises a back stop 11, 110, a distal dose setting member 12, 121 and a proximal dose setting member 12', 120.

The dose setting assembly 10, 100 is engaged with a conventional syringe 15 comprising a barrel 16 and an elongate plunger rod 17.

The barrel 16 includes an open proximal end having a flange 18 and a distal end including a tip having a channel 19.

The distal end of the barrel 16 may be attached to a connecting hub 20. In other embodiments, the needle assembly 21 may be attached to the distal end of the barrel 16.

A plunger rod 17 is inserted into the barrel 16 at the proximal end of the syringe 15. At the distal end of the plunger rod 17 is a stopper 22 for sealing the barrel 16 to form a reservoir 23 for medical injection fluid. The plunger rod 17 further comprises a plunger flange 25 at the proximal end of the plunger rod 17. A plunger flange 25 extends radially from the plunger rod 17. In the embodiment shown, the plunger flange 25 has a circular disc shape.

The dose setting assembly 10 is at the proximal end of the syringe 15.

Turning now more particularly to fig. 3, one embodiment of the dose setting member 12 has an elongated single U-shaped wall 24 defining a housing 26; the housing 26 includes a lateral opening 29 defined by the free end of the U-shaped wall 24. In the embodiment shown, the dose setting member 12 has a square cross-section. The dose setting member 12 may also have a substantially circular cross-section or any other shape of cross-section.

The dose setting member 12 comprises: a distal portion 27 sized and configured to connect to the rear stop 11; and a proximal portion 28 sized and configured to receive the proximal dose setting member 12', as will be explained in more detail below.

The distal portion 27 has a series of external grooves 30 formed on the outer surface of the U-shaped wall 24, while the proximal portion has a series of internal grooves 31 formed on the inner surface of the U-shaped wall 24. The outer groove 30 and the inner groove 31 are parallel and oriented perpendicular to the longitudinal axis of the dose setting member. The dose setting member 12 comprises a cross-sectional constriction which makes the distal portion 27 narrower than the proximal portion 28. The cross-sectional constriction comprises an inner shoulder 33 provided in the U-shaped wall 24 and an outer shoulder 34 provided in the U-shaped wall 24.

The internal groove 31 is configured and dimensioned to receive the plunger flange 25, as will be explained in greater detail below.

In order to allow insertion of the distal part 27 of the distal dose setting member 12 into the second set dose member 12', the outer groove 30 of the distal part 27 is sized and configured to fit into the inner groove 31 of the proximal part 28.

Turning now more particularly to FIG. 4, one embodiment of the backstop 11 has a distal panel 37 and a proximal funnel portion 38, both of which define a longitudinal housing 39. A distal plate 37 extends radially from the funnel portion 38. The housing 39 includes a longitudinal opening 40.

To allow the back stop 11 to be inserted onto the syringe 15, the inner wall of the back stop 11 is provided with a distal groove 41 adjacent to the distal plate 37, as will be explained in more detail below. The distal plate 37 also includes two arcuate portions 42.

To allow insertion of the distal part of the dose setting member 12, as will be explained in more detail below, the dose setting member 12 comprises a proximal groove 43 provided in the inner surface of the funnel 38.

Those skilled in the art will understand and appreciate that the rear stop 11 and the dose setting member 12 may be formed in any of the conventional manners, such as injection molding. It may be made of suitable medical grade plastics, hard rubber materials, glass, metal, etc.

Turning now more particularly to fig. 1 or 2, a dose setting assembly 10 according to the present invention is configured for mating with a syringe 15 via a syringe flange element 18. However, those skilled in the art will understand and appreciate that the dose setting assembly 10 according to the present invention may be applied to other medical delivery devices where it is desirable to deliver precise and repeatable doses of medical injection fluid.

Syringes may be sold in pre-filled form, wherein a set dose of medical injection fluid is provided in a reservoir. In this configuration, the plunger rod 17 extends from the barrel 16.

As shown in fig. 2, the dose setting assembly 10 comprises a rear stop 11 engaged to a barrel flange 18. The barrel flange 18 engages into the distal recess 41 and the barrel 16 rests on an arcuate portion 42 provided in the rear stop 11. The rear stopper 11 longitudinal opening 29 to the housing 26 forms a passage that allows mounting of the rear stopper 11 on the syringe flange 18 with the plunger rod 17 extending from the barrel 16.

The distal dose setting member 12 is engaged into the back stop 11. To this end, the distal part of the dose setting member 12 engages into a groove 43 provided in the funnel part 38 of the rear stop.

Although in fig. 2 the back stop 11 and the distal dose setting member 12 face opposite directions, it will be appreciated that the distal dose setting member 12 may be oriented differently with respect to the back stop 11 due to its square cross section.

The proximal dose setting member 12' is engaged into the distal dose setting member 12. To this end, the distal portion 27 'of the second setting member 12' is engaged into the proximal portion 28 of the distal dose setting member 12.

It will be appreciated that in the illustrated embodiment the distal dose setting member 12 and the proximal dose setting member 12' are identical.

The back stop 11 and the two dose setting members 12, 12' are attached to each other and to the barrel flange 18 by a friction fit. Thus, they can be fixed or removed by hand relative to the syringe 15 without any tools or equipment. Thus, operating the dose setting assembly 10 proves to be easy and intuitive.

The longitudinal openings 40, 40 'and 29, 29' provided in the rear stopper 11 and the two dose setting members 12, 12 'allow to place the rear stopper 11 and the two dose setting members 12, 12' around the plunger rod 17 extending from the barrel 16. When the back stop 11 and the two dose setting members 12, 12 'are approaching the syringe 15, the barrel plunger rod 17 is accommodated within the housing of the back stop 11 and the two dose setting members 12, 12'.

As shown in fig. 2, the plunger rod 17 is fixed in its extended position when the plunger flange 25 is enclosed in the internal recess 31 of the proximal dose setting member 12'. In the shown embodiment the proximal dose setting member 12 'comprises three internal grooves 31' providing three positions where the plunger flange 12 can be fixed.

Turning now more particularly to fig. 5-7, the dose setting assembly 10 is configured to control the standard operation of the syringe and, therefore, provide a first medical injection fluid delivery stroke of the plunger (allowing for precise pre-priming) and a second medical injection fluid delivery stroke of the plunger (allowing for precise dosage of medical injection fluid to be dispensed).

The syringe 15 may be pre-filled in its configuration of fig. 3 and may be placed in a sterile package (not shown) with the dose-setting assembly 10.

After removal of the packaging, the syringe 15 is ready for use. It may be noted that the plunger rod 17 is completely hidden within the proximal dose setting member 12', thus avoiding accidental or unintentional movement of the plunger rod 17. Thus, movement of the plunger stopper out of the sterile field during transport or storage of the syringe 15 is avoided. Furthermore, accidental or unintentional discharge of the medical product contained in the barrel 16 of the syringe 15 is avoided.

The proximal dose setting member 12' may be removed from the injection device 15. For this purpose the proximal dose setting member 12 'is pulled laterally, which has the effect of making accessible the plunger rod 17 previously hidden in the dose setting member 12'.

It will be appreciated that the distal plate 37 of the rear stop 11 forms a type of finger rest, allowing the user to easily manipulate the syringe 15 during use.

The user now advances the plunger rod 17 in the distal direction by applying finger pressure to the plunger flange 25. Distal movement of the plunger rod 17 is limited due to the contact of the plunger flange 25 with the proximal region of the distal dose setting member 12. Thus, upon movement of the plunger, a dose of medical injection fluid is expelled from the reservoir 23. This enables the syringe 15 to be pre-filled. In other words, the dose setting assembly allows a desired amount of medical injection fluid to be dispensed to pre-fill syringe 15 without over-dispensing the medical injection fluid. This makes it possible to expel potential air bubbles present in the medical injection fluid, thereby avoiding their injection into the patient.

The distal dose setting member 12 can now be removed from the back stop 11. To this end, the distal dose setting member 12 is pulled laterally, which has the effect of releasing the plunger rod 17 that previously abutted on the proximal area of the distal dose setting member 12.

Now, the user may advance the plunger rod 17 in the distal direction by applying finger pressure to the plunger flange 25. Distal movement of the plunger rod 17 is limited due to contact of the plunger flange 25 with the proximal region of the rear stop 11. Thus, upon movement of the plunger rod, a dose of medical injection fluid is expelled from the reservoir 23. Preferably, the second dose is sized to deliver a precise therapeutic dose.

Turning now to fig. 8 to 14, one embodiment of the present invention comprises a static back stop 110 and two removable dose setting members 120, 121. The two removable dose setting members 120, 121 define two controlled plunger rod strokes, which makes it possible to deliver two precise doses of medical fluid.

One embodiment of the backstop 110 has a U-shaped additional element comprising a retaining wall connected to two lateral walls.

The rear stop 110 comprises a transverse wall 111 and two lateral walls 112. An aperture 113 is defined between the transverse wall 111 and the lateral wall 112; the aperture 113 is sized to receive the passage of the syringe plunger 17. The width of the aperture 113 is configured to be larger than the diameter of the plunger rod 17 and configured to be smaller than the diameter of the plunger flange 25, as will be explained in more detail below.

The inner surface of the back stop 110 may be provided with an insertion distal groove 115 configured to removably connect the back stop 110 to the syringe flange 18 and an insertion proximal groove 116 configured to removably connect the distal dose setting member 121 to the back stop 110.

The distal recess 115 is formed between two parallel, stacked flanges 118, 119 projecting inwardly. The overlapping flanges 118, 119 may include angled insertion edges 124, 125.

The proximal recess 116 is formed between two parallel flanges 127, 126 projecting inwardly.

To enhance the locking retention of the rear stopper 110 on the syringe barrel 16, the rear stopper 110 may suitably include two lips 129 extending distally from the flange 119.

The rear stop 110 includes an outer step configuration that provides a finger rest surface 130.

Turning more particularly to fig. 14, the distal dose setting member 121 has a generally fork-shaped configuration defining an aperture 132. The proximal dose setting member 121 comprises two parallel legs 133 connected by a transverse portion 134. The aperture 132 is defined between the parallel legs 133 and the transverse portion 134; the aperture 132 is sized to receive the passage of the syringe plunger 16 and is sized so that the legs 133 and transverse portion 134 act as a resting surface for the plunger flange 25. To this end, the width of the aperture 132 is configured to be larger than the diameter of the plunger rod 17 and configured to be smaller than the diameter of the plunger flange 25.

Each leg 133 is provided with an outer insertion groove 136. The groove 136 is defined between a proximal flange 138 and an outwardly projecting distal flange 139.

The distal flange 139 is configured and dimensioned to removably engage the proximal groove 116 disposed in the rear stopper 110.

The proximal flange 138 is configured and dimensioned to protrude laterally outward from the back stop lateral wall 112 when the distal dose setting member 121 is engaged on the back stop 110.

The transverse portion 134 is provided with a pull tab 135 extending in a direction opposite to that of the leg 133. The pull tab 135 may suitably be provided with an outwardly directed arrow sign 131 and may comprise at least one protrusion 137 to allow easy gripping of said pull tab 135.

The proximal dose setting member 120 is configured to be removably connected to the back stop 110.

With continued reference to fig. 8-13, the proximal dose setting member 120 has a generally U-shaped configuration comprising a generally flat proximal wall 141 and two lateral stepped walls 143 comprising a shoulder 142. As best shown in fig. 9, the proximal wall may have an arrow mark 148.

The proximal dose setting member 120 comprises two inwardly protruding intermediate ribs 147. The two intermediate ribs 147 face each other and define an aperture 144 sized to receive the passage of the syringe plunger 17 and sized to serve as a resting surface for the plunger flange 18.

The internal dimension between the intermediate rib 147 and the proximal wall 141 may be sized to receive the plunger flange 18 such that the plunger flange 18 is locked within the locking cavity 149 formed between the proximal wall 141 and the intermediate rib 147. In other words, once engaged between the intermediate rib 147 and the proximal rib 134, the plunger flange 18 is locked and thus the plunger rod 17 cannot move.

The proximal dose setting member 120 may further comprise two inwardly directed distal ribs 145. The groove 146 defined between the middle rib 147 and the distal rib 145 is sized and configured to removably receive the proximal end flange 138 of the distal dose setting member 121.

Those skilled in the art will understand and appreciate that the rear stop 110, the proximal dose setting member 120 and the distal dose setting member 121 may be formed in any of the conventional ways, such as injection molding. It may be made of suitable medical grade plastics, hard rubber materials, glass, metal, etc.

Turning now more particularly to fig. 8 or 9, the dose setting assembly 10 according to the present invention is configured for engagement with a syringe 15 via a syringe flange element 18. However, those skilled in the art will understand and appreciate that the dose setting assembly 10 according to the present invention may be applied to other medical delivery devices where it is desirable to deliver precise and repeatable doses of a medical injection fluid.

Syringes may be sold in pre-filled form, wherein a set dose of medical injection fluid is provided in a reservoir. In this configuration, the plunger rod 17 extends from the barrel 16.

As shown in fig. 8, the rear stop 110 is engaged to the barrel flange 18. Barrel flange 18 engages into the rear stop distal groove 115.

The distal dose setting member 121 is in turn connected to the back stop 110; to this end, the distal flange 139 of the distal setting member 121 engages the proximal groove 116 of the rear stop 110.

The proximal dose setting member 120 is in turn connected to the distal dose setting member 121; to this end, the groove 146 of the proximal dose setting member 120 engages the proximal flange 138 of the distal dose setting member 121.

The back stop 110, the proximal dose setting member 121 and the distal dose setting member 121 are attached to each other and to the barrel flange 18 by a friction fit. Thus, they can be fixed or removed by hand relative to the syringe 15 without any tools or equipment. Thus, operating the dose setting assembly 100 proves to be easy and intuitive.

In the configuration of the present invention shown in fig. 8, the plunger flange 18 is enclosed within the space defined between the proximal dose setting member 120 and the distal dose setting member 121; this ensures that the plunger rod 17 is not pushed or pulled accidentally.

Turning now more particularly to fig. 10-13, the dose setting assembly 100 is configured to control the standard operation of the syringe and, thus, provide a first medical injection fluid delivery stroke of the plunger (allowing for precise pre-filling) and a second medical injection fluid delivery stroke of the plunger (allowing for precise dosage of medical injection fluid to be dispensed).

The syringe 15 in its configuration of fig. 8 may be pre-filled and placed in a sterile package (not shown) with the dose setting assembly 100.

After removal of the packaging, the syringe 15 is ready for use. It may be noted that the plunger flange 18 is enclosed within the space defined between the proximal dose setting member 120 and the distal dose setting member 121; thus, accidental or unintentional movement of the plunger rod 17 is avoided. Thus, movement of the plunger stopper out of the sterile field during transport or storage of the syringe 15 is avoided. Furthermore, accidental or unintentional discharge of the medical product contained in the barrel 16 of the syringe 15 is avoided.

The proximal dose setting member 120 may be removed from the syringe 15. To do so, the proximal dose setting member 120 is pulled laterally in the direction of arrow mark 148; this has the effect of making it possible to access the plunger flange 18 previously hidden within the proximal dose setting member 120.

The user now advances the plunger rod 17 in the distal direction by applying finger pressure to the plunger flange 25. Distal movement of the plunger rod 17 is limited due to the contact of the plunger flange 25 with the distal dose setting member 121. More specifically, the plunger flange 25 abuts the leg 133. Thus, upon movement of the plunger, a dose of medical injection fluid is expelled from the reservoir 23. This enables the syringe 15 to be pre-filled. In other words, the dose setting assembly 100 allows for dispensing a desired amount of medical injection fluid to pre-fill the syringe 15 without over-dispensing the medical injection fluid. This makes it possible to evacuate the potential air bubbles present in the medical injection fluid, thus avoiding their injection into the patient.

The distal dose setting member 121 can now be removed from the back stop 110. To this end, the user may grasp the pull tab 135 such that the distal dose setting member 121 is pulled laterally in the direction of the arrow mark 131. This has the effect of releasing the plunger flange 25 that previously rested on the leg 133 of the distal dose setting member 121.

The user may now advance the plunger rod 17 in the distal direction by applying finger pressure to the plunger flange 25. Distal movement of the plunger rod 17 is limited by the plunger flange 25 contacting the proximal flange 126 of the rear stopper 110. Thus, upon movement of the plunger rod, a dose of medical injection fluid is expelled from the reservoir 23. Preferably, the second dose is sized to deliver a precise therapeutic dose.

It will be appreciated that the invention is not limited to the embodiments described above and shown in the drawings; on the contrary, one of ordinary skill in the art appreciates that various changes and modifications can be made that are within the scope of the appended claims.

Claims (12)

1. A dose setting assembly (100) for a medical injection device, the medical injection device comprising: a cartridge (16) defining a reservoir (23) adapted to contain a medical injection fluid; an open proximal end and a distal end including a hub portion; a flange (18) disposed at the proximal end of the barrel (16); and an elongate plunger rod (17) having a plunger flange (25) at a proximal end and a stopper (22) at a distal end, the plunger rod (17) being slidably movable within the barrel (16), the dose setting assembly comprising:

-a rear stop (110) attachable to a flange (18) of the barrel (16),

-a distal dose setting member (121) fixed on the back stop (110) configured to keep the plunger rod (17) in a distal predetermined position, the distal dose setting member (121) being laterally removable from the back stop (110) to allow the plunger rod (17) to move towards and abut on the back stop (110), and

-a proximal dose setting member (120) fixed on the distal dose setting member (121), the proximal dose setting member holding the plunger rod (17) in a second predetermined position, the proximal dose setting member (120) being laterally removable from the distal dose setting member (121) to allow the plunger rod (17) to move towards the distal dose setting member (121) and abut on the distal dose setting member (121).

2. The dose setting assembly (100) of claim 1, wherein said proximal dose setting member (120) comprises a locking means configured to hold said plunger flange (25) in a hidden locked position.

3. The dose setting assembly (100) of claim 2 wherein the proximal dose setting member (120) comprises a proximal wall (141) and two lateral walls (143), each lateral wall having an inwardly directed intermediate rib (147), the intermediate ribs (147) defining with the proximal wall a plunger flange locking cavity (149).

4. The dose setting assembly (100) of claim 2 or 3, wherein the proximal dose setting member (120) comprises two inwardly directed distal ribs (145) defining two grooves (146).

5. The dose setting assembly (100) according to any of claims 1 to 4 wherein the proximal dose setting member (120) comprises an aperture (144) defined by the intermediate rib (147), the aperture (144) being configured and dimensioned to allow passage of the plunger rod (17) and to prevent passage of the plunger flange (25).

6. The dose setting assembly (100) according to any of claims 1 to 5, wherein the distal dose setting member (121) comprises two legs (133) joined by a transverse portion (134), each leg (133) having an external groove (100) defined between a proximal flange (138) and a distal flange (139).

7. The dose setting assembly (100) of claim 6 wherein the leg (133) and the transverse portion (134) define an aperture (132), the leg (133) and the transverse portion (134) defining the aperture (132) being configured and dimensioned to allow passage of the plunger rod (17) and prevent passage of the plunger flange (25).

8. The dose setting assembly (100) according to claim 6 or 7, wherein the distal dose setting member (121) comprises a pull tab (135).

9. The dose setting assembly (100) of any of claims 1 to 8, wherein the rear stopper (110) comprises a transverse wall (111) and two lateral walls (112), the lateral walls of the rear stopper defining an aperture (113), the aperture (113) defined by the lateral walls of the rear stopper being configured and dimensioned to allow passage of the plunger rod (17) and to prevent passage of the plunger flange (25).

10. The dose setting assembly (100) of claim 9, wherein each lateral wall (112) of the back stop comprises two inwardly projecting parallel flanges (118, 119) defining a distal groove (115).

11. The dose setting assembly (100) of claim 10 wherein the lateral wall (112) of the back stop comprises two inwardly projecting parallel flanges (126, 127) defining a proximal groove (116).

12. A method of operating a medical injection device, comprising the steps of:

-providing a medical device having a dose setting assembly according to claims 1 to 11;

-removing the proximal dose setting member (120) from the distal dose setting member (121);

-moving the plunger rod (17) into the syringe barrel (16) towards the distal dose setting member (121) until the plunger rod (17) abuts on the distal dose setting member (121);

-removing the distal dose setting member (121) from the back stop (110);

-moving the plunger rod (17) into the syringe barrel (16) towards the rear stopper (110) until the plunger rod (17) abuts on the rear stopper (11).

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