Injection device

Abstract

An injection device comprises a housing containing a syringe with a discharge nozzle. The syringe can be moved between a retracted position, in which the discharge nozzle is inside the housing, and an extended position, in which it protrudes from the housing. The syringe has a cap to protect the discharge nozzle. The cap is removed from the syringe by rotating it relative to the housing. A support integrated into the housing prevents the syringe from rotating relative to the housing when the cap is removed.

Description

Injection device Field of invention The present invention relates to an injection device of the type having a syringe that extends, discharges its contents, and then retracts it automatically. Background of the invention The known injection devices are shown in patents WO 95 / 35126 and EP-A-0516473 and tend to employ an actuating spring and some type of release mechanism that releases the syringe from the influence of the actuating spring once its contents are presumed to have been discharged, to allow it to retract by means of a return spring. Such injection devices are frequently required to function with sealed hypodermic syringes, which typically have a tightly sealed cover or "sheath" that protects the hypodermic needle and maintains the sterility of the syringe contents. Naturally, it is necessary to maintain the sterility of the syringe contents until the moment of administration, meaning that for devices designed to be disposable, the sheath must be removed with the syringe still inside the injection device. Generally, the required action removes the sheath from the syringe, which involves either pulling the sheath away from the syringe or twisting the sheath and, at the same time or subsequently, pulling the sheath away from the syringe. UK patent application no. 0412051.5 pending describes a cap for an injection device that connects to the syringe sleeve such that removal of the housing locking element from the housing causes the syringe sleeve to be removed. In certain types of syringes, such as a Bünder ReadyJect™ syringe, the sheath must be rotated to break a fragile seal before it can be removed. Because the syringe is contained within the housing and not directly held by a user, it must be rigidly supported in the housing so that rotating the sheath does not cause the syringe to rotate, which could prevent the sheath from being removed. This is particularly important when significant rotational force is required to remove the sheath and / or break the fragile seal. The cylindrical shape of a syringe does not allow it to resist rotation, especially since syringes used with injection devices of the type described in this document are frequently made of glass, which can break. Patent WO 2004 / 087242 A1 describes an injection device having a housing and having an energy storage spring to store energy for an injection operation. US patent 6575939 B1 describes a device for automatically injecting a dose of a medicinal product, comprising a two-part housing in which a syringe is housed. The two parts can undergo relative movement between two positions: a retracted rest position achieved naturally in the absence of an external force exerted on said parts, and a forward injection position achieved by means of a longitudinal force applied by a user. The device is provided with a basket for supporting the collar of the syringe piston rod. Summary of the invention The injection device of the present invention is designed to address the problems mentioned above. In view of the foregoing and according to the present invention, an injection device is provided comprising: a housing comprising a syringe having a syringe body and a discharge nozzle that is movable from a retracted position in which the discharge nozzle is contained within the housing to an extended position in which the discharge nozzle extends from the housing, and from the extended position in which the discharge nozzle extends from the housing to the retracted position in which the discharge nozzle is contained within the housing, such that the syringe returns to the retracted position and the injection cycle is complete; a syringe cap for enclosing the discharge nozzle and removing it from the syringe by rotating it relative to the syringe; a syringe holder adapted to restrict the rotation of the syringe relative to the housing when the cap is removed, the syringe holder comprising a sleeve surrounding the syringe body along its entire length and into which the syringe can be inserted from a distal end. Therefore, the syringe cap can be easily removed by twisting it with the syringe held firmly in the housing. In one embodiment of the present invention, the syringe holder comprises a grip adapted to restrict the rotation of the syringe relative to the housing. Preferably, the grip comprises at least one deformable rib. Therefore, a firm connection is formed between the syringe and the syringe holder when the syringe is inserted into the holder. Preferably, the syringe holder comprises a ring through which the syringe discharge nozzle extends, the ring including the grip on its inner circumference. In one embodiment of the present invention, the syringe comprises at least one tubular structure that protrudes radially from the syringe body and extends at least partly along the length of the syringe body. The grip may comprise at least one rib that can engage with at least one tubular structure of the syringe body. In this way, the rib and the tubular structure can interlock like teeth to form better resistance to rotation. At least one tubular structure may be located adjacent to the discharge nozzle. A housing cap can be releasably attached over a housing opening through which the discharge nozzle extends during use, wherein the housing cap is in communication with the syringe cap. Brief description of the drawings The invention will now be described by way of example with reference to the accompanying figures, in which: Figure 1 shows a cross-sectional view of an injection device according to the present invention; and Figure 2 shows an enlarged portion of the injection device shown in Figure 1. Figure 3 shows a perspective view of a syringe holder for use in the present invention from a first direction; Figure 4 shows a perspective view of the syringe holder of Figure 3 from a second direction; Figure 5 shows an enlarged cross-sectional view of the end of the syringe holder of Figures 3 and 4; Figure 6 shows a cross-sectional view of a syringe for use in the present invention; and Figure 7 shows a perspective view of the injection device of the present invention. Detailed description of the drawings Figures 1 and 2 show an injection device 110, which has an injection device housing 112. The end of the housing 112 has an outlet opening 128, from which the end of a sleeve 119 can emerge. Housing 112 contains a conventional hypodermic syringe 114, which includes a syringe body 116 defining a reservoir and terminating at one end in a hypodermic needle 118 and at the other in a flange 120. The syringe body 116 has a substantially constant diameter along the reservoir and a significantly smaller diameter near the end of the syringe terminating in the hypodermic needle. An actuating element 134 acts through the syringe stopper to discharge the contents of the syringe 114 through the needle 118. This actuating element 134 confines the delivery of a drug 124 within the reservoir defined by the syringe body 116. Although the illustrated syringe is of the hypodermic type, this need not be the case. Transcutaneous or dart syringes, as well as dermal and subcutaneous syringes, can also be used with the injection device of the present invention. As illustrated, the syringe is housed within a syringe holder 150. The syringe holder is best seen in Figures 3 and 4. The syringe holder 150 has a proximal end 151 through which the syringe needle 118 protrudes. The needle 118 is attached to the syringe body 116 by a needle subunit 172 having a reduced diameter. At the proximal end 151 of the syringe holder 150, there is a reduced-diameter section 173 that holds the syringe end 114 in its body 116. The syringe holder 150 also includes a pair of flexible projections 152. The pair of flexible projections 152 communicate with a corresponding pair of locking openings in a return spring holder 160, so that the syringe holder 150 cannot move relative to the return spring holder 160.The syringe holder 150 also comprises a bearing surface 153 near its second end, against which a corresponding bearing surface of the return spring holder 160 is pushed by a return spring 126. The return spring 126, through the return spring holder 160 and the syringe holder 150, pushes the syringe 114 from an extended position in which the needle 118 extends from the opening 128 in the housing 112 to a retracted position in which the needle 118 is contained within the housing 112. The syringe holder 150 comprises a sleeve 154 into which the syringe 114 can be inserted from a distal end 170. The syringe 114 is provided with a sleeve (not shown). If the syringe fails or breaks, the sleeve 154, which surrounds the syringe 114 along its length, would contain the broken pieces of the syringe and reduce the likelihood of them escaping from the injection device 110. The housing is further provided with a flexible engagement element 161 that is pushed into a position where it engages a locking surface 163 on the return spring support 160. Before engaging the locking surface 163, the engagement element 161 also extends through an engagement opening 165 in the sleeve 119. The engagement element 161 includes an inclined surface 167 on which an edge of the engagement opening 165 acts as a cam acting on a cam roller. The housing also includes an actuator, which here takes the form of a compression-driven spring 130. The drive from the drive spring 130 is transmitted via a multi-component drive to the syringe piston 114 to advance the syringe from its retracted to its extended position and discharge its contents through the needle 118. The drive achieves its purpose by acting directly on the drug 124 and the syringe 114. Static friction between the drive element 134 and the syringe body 116 initially ensures that they advance together, until the return spring 126 bottoms out or the syringe body 116 encounters some other obstruction (not shown) that slows its movement. The multi-component drive between the drive spring 130 and the syringe 114 consists of three main components.An actuating sleeve 131 receives the impulse from the actuating spring 130 and transmits it to a first actuating element 132. This, in turn, transmits the impulse to the actuating element 134 mentioned above. The actuating element 132 includes a hollow stem 140, the inner cavity of which forms a collection chamber 142 in communication with a vent 144 extending from the collection chamber through the end of the stem 140. The second actuating element 134 includes a blind bore 146 that is open at one end to receive the stem 140 and closed at the other. As can be seen, the bore 146 and the stem 140 define a fluid reservoir 148, within which a damping fluid is contained. A trigger (not shown) is provided in housing 112, located away from the outlet opening 128. When actuated, the trigger disengages the drive sleeve 131 from housing 112, allowing it to move relative to housing 112 under the influence of the drive spring 130. The device then operates as follows. Initially, the return spring support 152, and consequently the syringe support 150 and the syringe 114, are prevented from moving by the flexible locking element 161. When the sleeve 119 is moved in a direction toward the housing 112, the edge of the locking opening 165 comes into contact with the inclined surface 167 of the locking element 161, causing the locking element 161 to move outward and thus disengage from the return spring support 160. Once the locking element 161 has disengaged from the locking surface 163, the syringe can move freely. The actuator is then pressed and the actuating spring 130 is released. The actuating spring 130 moves the actuating sleeve 131, the actuating sleeve 131 moves the first actuating element 132, and the first actuating element 132 moves the second actuating element 134. The second actuating element 134 moves and, by virtue of static friction and hydrostatic forces acting through the drug 124 to be administered, moves the syringe body 114 against the action of the return spring 126. The syringe body 114 moves the syringe holder 150, which in turn moves the return spring holder 160 and compresses the return spring 126. The hypodermic needle 118 emerges from the outlet opening 128 of the housing 112. This continues until the return spring 126 bottoms out or until the syringe body 116 encounters some other obstruction (not shown) that impedes its movement. Due to static friction between the second actuating element 134 and the syringe body 116, and the hydrostatic forces acting through the drug 124 to be administered, which are insufficient to resist the full actuating force developed by the actuating spring 130, at this point the second actuating element 134 begins to move within the syringe body 116 and the drug 124 begins to be discharged.However, the dynamic friction between the second drive element 134 and the syringe body 116 and the hydrostatic and hydrodynamic forces now acting through the drug 124 to be administered are sufficient to retain the return spring 126 in its compressed state, so that the hypodermic needle 118 remains extended. Before the second actuating element 134 reaches the end of its travel within the syringe body 116, i.e., before the syringe contents have been completely discharged, the flexible coupling arms connecting the first and second actuating elements 132, 134 reach a constriction within the housing 112 formed by the arms 155 at the end of the syringe holder closest to the flange 120 of the syringe 114. This constriction moves the flexible coupling arms to a position such that they no longer couple the first actuating element 132 to the second actuating element 134. Once this occurs, the first actuating element 132 no longer acts on the second actuating element 134, allowing the first actuating element 132 to move relative to the second actuating element 134. Because the damping fluid is contained within a reservoir 148 defined between the end of the first actuating element 132 and the blind hole 146 in the second actuating element 134, the volume of the reservoir 146 will tend to decrease as the first actuating element 132 moves relative to the second actuating element 134 when the former is actuated by the actuating spring 130. As the reservoir 148 collapses, the damping fluid is forced through the vent 144 into the collection chamber 142.Therefore, once the flexible locking arms are released, part of the force exerted by the drive spring 130 acts on the damping fluid, causing it to flow through the constriction formed by the vent 144; the remainder acts hydrostatically through the fluid and through friction between the first and second drive elements 132, 134, and from there through the second drive element 134. Consequently, the second drive element 134 continues to move within the syringe body 116, and the drug 124 continues to be discharged. The losses associated with the flow of the damping fluid do not significantly reduce the force acting on the syringe body. Therefore, the return spring 126 remains compressed, and the hypodermic needle remains extended. After a time, the second drive element 134 completes its displacement within the syringe body 116 and can move no further. At this point, the contents of the syringe 114 are completely discharged, and the force exerted by the drive spring 130 acts to retain the second drive element 134 in its terminal position and continue to allow the damping fluid to flow through the vent 144, enabling the first drive element 132 to continue its movement. Before the fluid in reservoir 148 is exhausted, the flexible coupling arms that connect the drive sleeve 131 to the first drive element 132 reach another constriction within the housing 112. This constriction moves the flexible coupling arms so that they no longer couple the drive sleeve 131 to the first drive element 132. Once this occurs, the drive sleeve 131 no longer acts on the first drive element 132, allowing them to move relative to each other. At this point, the forces developed by the drive spring 130 are no longer transmitted to the syringe 114. The only force acting on the syringe is the return force of the return spring 126, which acts on the end of the syringe 114 closest to the needle 118 via the return spring support 160 and the syringe support 150.Therefore, the syringe returns to its retracted position and the injection cycle is completed. Figure 5 shows an enlarged cross-sectional view of the proximal end 151 of the syringe holder 150, and Figure 6 shows, in isolation, the syringe 116 with the syringe cap 180 over the discharge needle 118. The reduced cross-sectional area 173 of the syringe holder 150 can be seen in greater detail in Figure 5. A ring 185 is also provided at the proximal end 151 through which the syringe cap 180 and needle subunit 172 protrude when the syringe 114 is inserted into the syringe holder 150. On the inner circumference of the ring 185, a plurality of deformable ribs 190 are provided, which flexibly deform to provide a grip on the needle subunit 172 when the syringe 114 is inserted into the syringe holder 150. The grip provided by the deformable ribs 190 prevents the syringe 114 from rotating within the syringe holder 150. On the outer surface of the needle subunit 195 of syringe 114, there is a plurality of tubular structures 195 that protrude radially from the syringe body and extend along its length, at least in part, along the needle subunit 195 of syringe 114. In one embodiment of the invention, the tubular structures 195 and the ribs 190 can be arranged to mesh together like interlocking teeth, thereby providing better grip and resistance to rotation. Figure 7 shows the injection device with a housing cap 199 into which the syringe cap 180 is inserted during the manufacture of the injection device 110. The syringe cap 180 is rigidly held in the housing cap 199 so that, when the housing cap 199 is rotated, the syringe cap 180 also rotates (while the syringe 114 is held against rotation in the syringe holder 150), thereby breaking a fragile connection of the syringe cap 180 with the needle subunit 172. Of course, it will be understood that the present invention has been described above only by way of example and modifications of details may be made within the scope of the invention, which are defined in the appended claims.

Claims

1. An injection device (110) comprising: a housing (112) comprising a syringe (114) having a syringe body (116) and a discharge nozzle (118) that is movable from a retracted position in which the discharge nozzle is contained within the housing to an extended position in which the discharge nozzle extends from the housing, and from the extended position in which the discharge nozzle extends from the housing to the retracted position in which the discharge nozzle is contained within the housing such that the syringe returns to the retracted position and the injection cycle is complete; a syringe cap (180) for enclosing the discharge nozzle (118) and withdrawn from the syringe by rotation relative to the syringe; and a syringe holder (150) adapted to restrict the rotation of the syringe relative to the housing as the cap (180) is withdrawn.

1. The syringe holder comprises a sleeve (154) surrounding the syringe body (116) along its entire length and into which the syringe (114) can be inserted from a distal end (170).

2. The injection device of claim 1, wherein the syringe holder comprises a grip adapted to restrict rotation of the syringe relative to the housing.

3. The injection device of claim 2, wherein the grip comprises at least one deformable rib (190).

4. The injection device of claim 2 or claim 3, wherein the syringe holder comprises a ring (185) through which the syringe discharge nozzle extends, the ring including the grip on its inner circumference.

5. The injection device of claim 1,wherein the syringe comprises at least one tubular structure (195) projecting radially from the syringe body and extending at least partly along the length of the syringe body.

6. The injection device of claim 2, wherein the syringe comprises at least one tubular structure (195) projecting radially from the syringe body and extending at least partly along the length of the syringe body.

7. The injection device of claim 6, wherein the grip comprises at least one rib that can engage with the at least one tubular structure (195) on the syringe body.

8. The injection device of any one of claims 5 to 7, wherein the at least one tubular structure (195) is located adjacent to the discharge nozzle (118).

9. The injection device of any one of the preceding claims,further comprising a housing cap (199) releasably attached over an opening (128) in the housing through which the discharge nozzle extends during use, wherein the housing cap is in communication with the syringe cap (180).

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