Patent Abstract:
The present invention relates to an injection device comprising a housing ( 10, 100 ), a container holder ( 12 ) arranged within said housing having a container ( 20 ) adapted to contain medicament to be delivered through a needle, plunger drive means ( 40 ), an energy accumulating member ( 80 ) adapted to accumulate and transfer energy to said plunger drive means wherein said device further comprises container driver means ( 30 ) arranged and designed to be connected to the plunger drive means and to the container holder for holding the container and its needle stationary within said housing before said energy is provided to the drive means and for urging the container towards the proximal end of the device when said energy is provided to the drive means whereby a needle penetration and respectively an injection are performed.

Full Description:
TECHNICAL FIELD 
     The present invention relates to an injection device having several automatic functions such as automatic penetration, automatic injection and automatic safety means for preventing from accidental needle sticks and in particular an injection device capable of handling medicament in fluid form having high viscosity. 
     BACKGROUND ART 
     The present invention relates to injection devices for injecting medicament in fluid form having high viscosity which means that these devices require high forces in order to press the fluid through a needle when injecting the medicament. 
     Auto-injectors, or pen-injectors have been on the market for many years. One of the first auto-injectors was developed for war-times, which was activated by pressing the injector against a body part for activating it. The main concern was to have the medicament injected as fast as possible, without much concern for the patient or for handling safety aspects. During the recent years some medicaments have been developed such that these have to be injected by the patients themselves. Therefore, depending on the intended use and type of medicament, it has also been developed injection devices having a varying degree of automatic functions to facilitate the injection of medicaments in a reliable and safe way for patients and even for trained personnel; e.g. physicians, nurses. 
     Auto-injector devices having an automated injection function often comprises a housing, a spirally wound compression spring acting on a plunger rod which in its turn acts on a stopper inside a medicament container for expelling the medicament through an attached needle to the container. Normally, one end of the spring is often abutting an inner end surface of the housing, which means that the housing has to be dimensioned to the force of the spring. When fluids with high viscosity are to be injected using an auto-injector, high forces are required to expel the medicament through a fine needle. Consequently, the spring becomes very large both regarding the diameter of the wound spring and also the diameter of the thread of the wire. The size of the spring means that the device becomes large, and for some applications and customers, such sizes of the devices are not acceptable. 
     A solution to said problem is disclosed in document EP 1 728 529 which discloses a medicament delivery device arranged with an energy accumulating member, e.g. a flat spiral spring, capable of providing an output torque to a plunger rod driving member which is adapted to engage a threaded plunger rod. The rotation of the plunger rod driving member due to the output torque of the spring rotates the plunger rod and allows said rod to be driven forwardly within a medicament container for expelling said medicament. When said device is used as an injection device; a user e.g. a patient, a physician or trained personal; has to penetrate the needle manually. Though, said device comprises a needle shield sleeve for activating the injection step and for covering the needle after the medicament has been injected, some users experience this manually penetration as an unpleasant step. 
     A solution to this problem is disclosed in document U.S. Pat. No. 5,104,380 which discloses an injection device having a rotatable dose metering cap which compresses a coil spring. When a dose is to be injected, a latch body is pressed against an injection site such that a compression spring can be decompressed for performing an auto-penetration. That action also brings a drive gear out of engagement permitting the coil spring to unwind and thereby rotating a drive plunger rod. Said rotational movement is accompanied by axial movement to cause medicament to be discharged from a cartridge and injected through a needle. This design cannot be utilised when larger forces for injecting a high viscous medicament are required. This design also requires an extra latch body comprising an extra spring for auto-penetration, which increases the physical size and manufacturing cost for such device. 
     DISCLOSURE OF THE INVENTION 
     The aim of the present invention is to provide injection device having several automatic functions as automatic penetration, automatic injection and automatic safety means for preventing accidental needle sticks and in particular an injection device capable of handling medicament in fluid form having high viscosity without increasing the size of the injector in any substantive way. 
     This aim is obtained with an injector according to the features of claim  1 . Preferable embodiments of the invention are the subject of the dependent claims. 
     According to a main aspect of the invention it is characterised by an injection device comprising a housing, a container holder arranged within said housing having a container adapted to contain medicament to be delivered through a needle attached to the container and a stopper sealingly and slidable arranged inside said container, an energy accumulating member arranged in the interior of the device and adapted to accumulate energy, plunger drive means comprising a plunger rod driving member connected to said energy accumulating member and threadly engaged to a plunger rod which is arranged with a proximal end in contact with said stopper, such that when said plunger rod driving member is rotated due to an output torque from the energy accumulating member, the plunger rod ( 40 ) is urged towards the proximal end of the device, characterized in that said device further comprises container driver means arranged and designed to be fixedly connected to the container holder and to be releasably connected to the plunger rod, such that when said plunger rod is urged towards the proximal end of the device, the container holder is moved a predetermined distance towards the proximal end of the device whereby a needle penetration is performed and whereupon the continuous movement of said plunger rod forces said container driver means to be released from said plunger rod whereby an injection is performed. 
     According to another aspect of the invention, said container driver means is connected to the plunger drive means in a snap-on fit manner for releasing said container driver means from said driver means and thereby said container holder from the force that urges it towards the proximal end of the device, directly after the needle penetration is performed. 
     According to yet another aspect of the invention, said container driver means comprises resilient members arranged in snap-on fit manner in an annular groove on said plunger rod for releasing said container driver from said plunger rod directly after the needle penetration is performed and for allowing said container driver to slide over said plunger rod when said plunger rod continues to be driven towards the proximal end of the device inside said container for expelling the medicament through said needle. 
     According to another aspect of the invention, said plunger drive means further comprises non-rotating means arranged and designed to be engaged to longitudinal guiding means on the plunger rod for urging the plunger rod to move linearly inside said container towards the proximal end of the device. 
     According to a further aspect of the invention, said device further comprises holding means capable of acting on said plunger drive means for holding said energy accumulating member in a loaded state. 
     According to yet another aspect of the invention, it further comprises actuating means capable of acting on said holding means for releasing said energy accumulating member and thereby said plunger drive means. 
     According to a further aspect of the invention, it further comprises a needle shield sleeve arranged slidable in said proximal housing capable of acting on said actuating means when said needle shield sleeve is pressed against an injection site. 
     According to yet an aspect of the invention, said actuating means further comprises a resilient means for urging said needle shield sleeve towards the proximal end of the device when said device is removed from the injection site. 
     According to yet an aspect of the invention, said device further comprises a locking means for locking said needle shield sleeve against moving towards the distal end of the device when said device is removed from the injection site. 
     The advantages with the present invention are several. Because the device is arranged with an energy accumulating member which provides a torque force, a large force can be obtained. The device is thus capable of handling liquid medicament having high viscosity, without the device having to be large and bulky, and thus not very attractive to users. 
     Also, the device requires only one energy accumulating member for performing both an automatic penetration and an injection function. 
     These and other aspects of and advantages with the present invention will become apparent from the following detailed description and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       In the following detailed description of the invention, reference will be made to the accompanying drawings, of which 
         FIG. 1  is a cross-sectional view of an injector according to the present invention in a state when delivered to a user, 
         FIG. 2  is a cross-sectional view of the injector of  FIG. 1  where penetration has been initiated, 
         FIG. 3  is a cross-sectional view of the injector of  FIG. 1  where penetration has been completed, 
         FIG. 4  is a cross-sectional view of the injector of  FIG. 1  where injection has been completed, 
         FIG. 5  is a cross-sectional view of the injector of  FIG. 1  where the injector has been withdrawn from the injection site, and 
         FIG. 6  is an exploded view of the injector of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the present application, when the term “distal part/end” is used, this refers to the part/end of the injection device, or the parts/ends of the members thereof, which under use of the injection device is located the furthest away from the medicament injection site of the patient. Correspondingly, when the term “proximal part/end” is used, this refers to the part/end of the injection device, or the parts/ends of the members thereof, which under use of the injection device is located closest to the medicament injection site of the patient. 
     The embodiment of the injector shown in the drawings comprises a housing having a proximal housing  10  and a distal housing  100 , an elongated needle shield sleeve  11 , a container driver  30 , a plunger rod  40 , a plunger rod driving member  50 , a helical spring  60 , an actuating sleeve  70  and an energy accumulating member  80 . The proximal housing  10  being an elongated tube-shaped comprising of two sections: a proximal section and a distal section, wherein the distal section has a diameter that is larger than the diameter of the proximal section. The elongated needle shield sleeve  11  comprises of three sections: a proximal section a middle section and a distal section, wherein the distal section has a diameter that is larger than the diameter of the middle section and the middle section has a diameter that is larger than the diameter of the proximal section, as seen in  FIG. 6 . Said elongated needle shield sleeve  11  is slidably arranged within said elongated housing, wherein a portion of the proximal end of said needle shield sleeve protrudes out of the proximal housing  10 , which is pressed against the injection site during use, as will be described below. Further said needle shield sleeve comprises in the circumference of its distal section resilient tongues  15 . 
     Inside the needle shield sleeve a medicament container holder  12  is arranged and inside the container holder a container  20 , e.g. a cartridge, a syringe or the like, is arranged containing medicament to be delivered through a needle  22  attached to the container and a stopper  23  sealingly and slidable arranged inside said container. Moreover, the distal part of the container holder is arranged with tongues  13  having inwardly directed ledges  14 , as seen in  FIG. 6 . 
     Between the tongues  13  of said medicament container holder  12 , a funnel-shaped annular member  30 , hereinafter called container driver, is arranged. Said container driver comprises in its proximal end and in its outer surface one outwardly directed annular ledge  31  which cooperates with the ledges  14  of the container holder creating a snap-on fit between these components. From the proximal end of said container driver extends at least two resilient members  32 , e.g. tongues, legs; towards the distal end, wherein each member  32  comprises an inwardly directed ledge  33 . 
     The plunger rod  40  is provided in the interior of the injection device, running along the longitudinal axis of said device. Said plunger rod comprises two of sections: a distal section  42  and a proximal section  41 , wherein the distal section has a diameter that is smaller than the diameter of the proximal section, wherein the distal section has a length that is larger than the length of the proximal section and wherein the distal section is threaded and comprises longitudinal guiding means  44 . Moreover, an annular groove  43  is arranged at the distal end of the proximal section  41  of said plunger rod  40  wherein said annular groove  43  cooperates with the ledges  33  of said container driver  30  creating a snap-on fit between these components. Further, the proximal end of the proximal section  41  is in contact with the stopper  23  in the medicament container. 
     The threaded distal section  42  of the plunger rod  40  is screw threaded in the interior of the plunger rod driving member  50 . Said driving member  50  comprises of two sections: a distal section  52  and a proximal section  51 , wherein the distal section  52  has a diameter that is smaller than the diameter of the proximal section  51  and a length than is larger than then length of the proximal section  51 . Further, the proximal section  51  comprises outwardly protruding flanges or teeth  53 , as seen in  FIG. 6 . 
     In a preferred embodiment, the distal housing  100  comprises of three housings: a first half distal housing  110 , a second half distal housing  120  and a third distal housing  130  adapted to house the plunger rod driving member  50 , a helical spring  60 , the actuating sleeve  70  and the energy accumulating member in the form of e.g. a flat spiral spring  80 , a helical torque spring. 
     Said first half distal housing  110  comprises of two sections: a distal section  112  and a proximal section  111 , wherein the distal section has a diameter that is larger than the diameter of the proximal section. The distal section  112  is divided from the proximal section  111  by a member, which comprises a disc-like part  114  in its distal end and a coaxially part  115  in its proximal end forming a cylindrical space, in which said helical spring  60  is arranged having its distal end supported against the disc-like part  114 . Said coaxially part  115  comprises outwardly protruding flanges  116  on its outer surface and a through going hole  117  adapted to house a portion of the distal  52  section of the plunger rod driving member  50 . At least two of said outwardly protruding flanges  116  have resilient arms  118 . 
     Said second half distal housing  120  comprises of two sections: a distal section  122  and a proximal section  121 , wherein the distal section  122  has a diameter that is larger than the diameter of the proximal section  121 . Further, said second half distal housing  120  also comprises a proximal end wall  123  having a two crescent apertures  124  and a through going hole  125  provided with non-rotating interior means (not shown) adapted to travel along the longitudinal guiding means  44  of the plunger rod  40 . 
     The third distal housing  130  also comprises a distal section  132  and a proximal section  131 , wherein the distal section  132  has an inner diameter that is smaller than the inner diameter of the proximal section  131 . The distal section  132  is thus adapted to house a portion of the distal  52  section of the plunger rod driving member  50  and the proximal section  131  is adapted to house the flat spiral spring  80 . Said flat spiral spring  26  is provided with outer holding means in order to be connected to the proximal section  131  of the third distal housing  130  and with inner holding means in order to be attached to the distal section  52  of the plunger rod driving member  50 . Moreover, in a preferred embodiment, the proximal section  131  of the third distal housing  130  is arranged to be manually rotatable between the distal sections  112  and  122 . 
     The actuating sleeve  70  comprises of two sections: a distal section  72  and a proximal section  71 , wherein the distal section  72  is a ring and the proximal section are two tongues  71 ′,  71 ″. Both sections  71 ,  72  arranged between the first half distal housing  110  and the second half distal housing  120 . The distal section  72  has an outer diameter that is smaller than the outer diameter of the proximal section  71  forming two support walls  74  where the proximal end of the helical spring  60  is supported. Said tongues  71 ′,  71 ″ extends towards the proximal end of the device through the crescent apertures  124  of the second half distal housing  120  and comprises on its outer surface some ledges that mates with resilient tongues  15  of the needle shield sleeve  11 . Further, said sections  71  and  72  comprises inwardly directed ledges forming slots  73 , as seen in  FIG. 6 , which mate the outwardly protruding flanges  53  of the plunger rod driving member  50  and the outwardly protruding flanges  116  of the first half distal housing  110 . 
     The device is intended to function as follows. When the device is delivered to a user, in a preferred embodiment, the flat spiral spring  80  has been already loaded at the manufacturing site. In another embodiment the flat spiral spring  80  is loaded by the user through rotating the third distal housing  130 . Further, a protective cap (not shown) is arranged at the proximal end of the device. The protective cap comprises a sheath (not shown) covering the needle in a sterile way. When the cap is removed, so is also the sheath. This also causes the needle shield sleeve  11  to move towards the proximal end of the device and protrude somewhat at the proximal end of the injector,  FIG. 1 . 
     The injector is now ready to use. The proximal end of the needle shield sleeve  11  is pressed against the injection site, whereby the needle shield sleeve is pushed towards the distal end of the device,  FIG. 2 . Since the needle shield sleeve is connected to the actuating sleeve  70 , the latter is also moved towards the distal end of the device, whereby the helical spring  60  is compressed and the inwardly directed ledges forming slots  73  of the actuation sleeve  70  and the outwardly protruding flanges  53  of the plunger rod driving member  50  are brought out of engagement whereby the plunger rod driving member  50  is released for rotation due to the energy accumulated in the flat spiral spring  80 . The rotation of the plunger rod driving member  50  will rotate the plunger rod  40 , and due to the non-rotating interior means provided in the through going hole  125  adapted to travel along the longitudinal guiding means  44  of the plunger rod  40 , the plunger rod is linearly urged towards the proximal end of the device without rotation. 
     When the plunger rod is linearly urged towards the proximal end of the device, the medicament container holder  12  is also urged towards the proximal end of the device, due to the engagements  14 ,  31 ,  32 ,  43  between the medicament container holder  12 , the container driver  30  and the plunger rod  40 . The movement of the medicament container holder  12  causes the automatic penetration of the needle  22  into the injection site. 
     The needle  22  is completely penetrated until the proximal end of the medicament container holder  12  comes into contact with the transition part between the proximal section and the middle section of the needle shield sleeve  11 . The torque force of the spring  80  will continue to drive the plunger rod further towards the proximal end of the device inside the container pressing the stopper  23  in order to start expelling the medicament through the passage of the needle  22 . Said movement takes out of contact the inwardly directed ledges  33  of the container driver  30  which cooperates with the annular groove  43  of the plunger rod  40  for releasing the container driver from the plunger rod and thereby the container/container holder from the force that urges it towards the proximal end of the device. The container driver slides over along the plunger rod as said plunger rod continues to move towards the proximal end of the device. The injection is completed when the stopper is at the proximal end of the container,  FIG. 4 . 
     The device may now be removed from the injection site. The spring  60  acting on the actuation sleeve  70  will cause the needle shield sleeve  11  to move forward,  FIG. 5 , since the needle shield sleeve is connected to the actuating sleeve, thereby covering the needle. The resilient arms  118  are thus free to flex out radially whereby they come into contact with the distal wall of the actuation sleeve  70  and thereby locking said needle shield sleeve  11  such that said needle shield sleeve  11  cannot be pushed again towards the distal end of the device. 
     The device is now ready to be discarded. 
     It is to be understood that the embodiment described above and shown in the drawings is to be regarded only as non-limiting examples of the present invention and that it may be modified within the scope of the patent claims.

Technology Classification (CPC): 0