Abstract:
The present invention relates to a device for expelling a predetermined quantity of medicament comprising driving means comprising an energy-accumulating member, a nut, and a driver for driving a pressure means; and activation means for activating said driving means wherein said pressure means comprises a movable wall part arranged inside a 2 container and a threaded plunger rod arranged to interact with said driving means for pushing said movable wall part forwardly, and wherein said activation means comprises a manually operated push button arranged on the front end of the device for promoting an ergonomic handling of the device and wherein said activation means are capable of interacting with said driving means in a stepwise mode; such that each time said push button is depressed said pressure means moves an step exerting pressure on the medicament inside the container and expelling a predetermined quantity of the medicament through the opening.

Description:
TECHNICAL FIELD 
     The present invention relates to a device for delivering medicament, and in particular in connection with medicament containing devices where the medicament is in a container and is exposed to pressure when the medicament is to be delivered in multiple predetermined quantities on multiple delivery sites in a stepwise mode. 
     BACKGROUND ART 
     Nowadays on the medical delivery device market, there are numerous devices for delivering medicament and also patented where the medicament is arranged in a container, such as a syringe, cartridge and the like, and wherein the medicament is exposed to pressure when it is to be delivered. The most common design is a generally tubular compartment having a stopper in one end of the compartment and a delivery opening e.g. a needle, attached to the opposite end of the compartment. 
     In order to deliver a quantity of medicament, the stopper is exposed to pressure, i.e. pushed into the compartment by a plunger rod, which could be done manually by a finger of a physician or trained person, which is the case for simple handheld hypodermic syringes. 
     In many instances it is desirable to be able to deliver multiple specified quantities of the medicament on multiple delivery sites in a stepwise mode. This is for example the case with manually operative mechanisms for moving a plunger rod as disclosed in the International Application Publication WO2006/020756 A2 and in the U.S. Pat. No. 4,512,767. The problem of said devices resides in the accuracy of the doses. If the actuation button is not fully depressed smaller doses cannot be delivered. Another example is the case with a multi-dose injection device, which is capable of delivering a number of specified, set doses until the compartment is empty, as disclosed in the European patent application No. 05104734.8 where specific doses can be set before injection. The injection device disclosed in said European patent application is arranged with spring means for exerting a pressure on the medicament for delivering a specific dose, i.e. pushing the plunger rod and thus the stopper into the container. The delivery of a dose requires a certain force from the spring means in order to overcome the friction between the somewhat resilient stopper and the inner surface of the container and also to be able to press the medicament in liquid form through a rather small passage in the needle, possibly within a predetermined time. 
     Typically, when a medicament/substance is to be delivered in multiple predetermined small quantities on multiple delivery sites in a stepwise mode, said medicament/substance quantities are injected manually, i.e. a normal type of syringe is used. In some treatments said medicament/substance has a high viscosity. Because of the rather large forces required for injecting said substances, and also due to the many small injections needed for a treatment, it is tiresome for the operator to use such a syringe during a treatment. The problem of the device disclosed in the European patent application resides in the degree of ergonomics when the medicament is to be delivered in multiple predetermined quantities on multiple delivery sites in a stepwise mode. 
     Moreover, a further example is the case with a multiple, metered dosage dispensing device as disclosed in the U.S. Pat. No. 4,659,327; wherein the device comprises an elongated body with an ampule containing material to be dispensed, a piston movable against the material to discharge from a nozzle, a ribbed plunger rod linearly movable by a pressure device against the piston to discharge material and an stop and release toothed unit movable intermediately of the ends of the body between a depressed and an undepressed position respectively to engage a pair of racks of teeth on the ribbed plunger rod. When said stop and release toothed unit is depressed, said unit allows the plunger and the piston to move linearly a predetermined increment, to stop said movement and to maintain the plunger in a stopped position until the unit is depressed again. The problem of the device disclosed in the U.S. Pat. No. 4,659,327, resides especially in the possibility of delivering accurately very small doses, as in the range of 0.01 ml.-0.005 ml., since the plunger rod, which is not adapted to be rotatable, and the stop and release toothed unit are designed having a gearing which is not adapted for such small doses. 
     There are thus a number of aspects that are addressed with the present invention. 
     DISCLOSURE OF INVENTION 
     The aim of the present invention is to remedy a number of drawbacks and problems associated with the state of the art devices of the above mentioned type and to provide improvements that facilitate the handling and accuracy of medical delivery devices, and especially when delivering multiple small predetermined quantities on multiple delivery sites in a stepwise mode. 
     This aim is achieved with a device according to claim  1 . Preferable embodiments of the present invention are subject of the dependent claims. 
     According to a main aspect of the present invention is characterized by a device for delivering medicament comprising a container arranged to contain medicament, which container further comprises an opening arranged to expel medicament from the container; pressure means arranged to exert pressure on the medicament inside the container for expelling a predetermined quantity of the medicament through the opening; driving means comprising an energy accumulating member, a nut, and a driver for driving said pressure means; and activation means for activating said driving means wherein said pressure means comprises a movable wall part arranged inside the container and a threaded plunger rod arranged to interact with said driving means for pushing said movable wall part forwardly, and wherein said activation means comprises a manually operated push button arranged on the front end of the device for promoting an ergonomic handling of the device and wherein said activation means are capable of interacting with said driving means in a stepwise mode; such that each time said push button is depressed said pressure means moves an step exerting pressure on the medicament inside the container and expelling a predetermined quantity of the medicament through the opening. 
     According to another aspect of the invention, said device comprises a tensioning knob arranged and designed to interact with said energy accumulating member such that when said tensioning knob is actuated, said energy accumulating member is tensioned. 
     Yet, according to another aspect of the invention, said energy accumulating member is arranged and designed to be in a pre-tensed state. 
     Further, said device is suitable for the use within the area of injecting cosmetic substances. 
     The advantages with the present invention are several. Accurate small doses each time the press button is actuated. Ergonomic handling of the device when a medicament/substance is to be delivered in multiple predetermined small quantities on multiple delivery sites in a stepwise mode, due to the position of the push button on the front end of the device. These and other aspects of and advantages with the present invention will become apparent from the following detailed description of the invention and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS 
       In the following detailed description of the invention, reference will be made to the accompanying drawings, of which 
         FIG. 1  shows an injection device according to the present invention, 
         FIG. 2  shows a first embodiment of an injection device according to the present invention, 
         FIG. 3  shows an exploded view of activation means of the injection device according to  FIG. 2 , 
         FIG. 4  shows a second embodiment of an injection device according to the present invention, 
         FIG. 5  shows an exploded view of the injection device according to  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a non-limiting example of a medicament delivery device of the present invention. The delivery device comprises a housing  10  designed to be held in one hand for delivering repeated small quantities of medicament step by step. Inside and at the front end of the housing a medicament containing container  12  is arranged having a front end onto which an opening  14  e.g. a needle, may be attached. Said medicament delivery device comprises pressure means including a movable wall part, hereafter called stopper, arranged inside the container; and a pressure member  18  as a plunger rod, arranged to push on the stopper forwardly. The front end of the plunger rod is preferably pointed against a spinner to minimize the friction between the plunger rod and the stopper. Said medicament delivery device also comprises driving means including an energy accumulating member  42 , a nut  20  and a driver  26 . 
     The Delivery Device of the Present Invention According to a First Embodiment 
       FIGS. 2 ,  3  refer to a first configuration of the delivery device wherein the energy accumulating member  42  has to be tensioned before medicament delivery. Further, the nut  20  is adapted to be in a non-rotating state due to two outwardly protruding pivoting pins  23  journalled in the housing, wherein said nut  20  has a through-going central bore  22  having corresponding threads as the plunger rod. The driver  26 ,  FIG. 3 , is hollow and further arranged around the plunger rod in a rotationally locked position. The driver has a lower, first cylindrical front portion  28  having a number of outwardly directed protrusions  30  evenly spaced around its circumference where the distance between two adjacent protrusions constitutes a certain predetermined dose quantity, and a second elongated cylindrical portion  32 . 
     Further the energy accumulating member  42 , e.g. a flat spring, is wound around the second portion of the driver having its inner end attached to the driver  26 . A tensioning knob  44  is arranged at the rear end of the delivery device, to which the outer end of the spring  42  is attached. 
     An activation mechanism  46 , as seen in  FIG. 3 , is also arranged on the delivery device. It comprises a push button  48  protruding through a slot on the front end of the housing for promoting an ergonomic handling of the device. The push button is attached to an arm  51  on a side of the container and plunger rod. Two outwardly protruding pivoting pins  54  are arranged on the arm, which pivoting pins are journalled in the housing. The rear end of the arm comprises a wing formed part  52  having slots  53 . An intermediate lever  100  partially arranged around the cylindrical portion  32  of the driver  26  comprises two outwardly protruding pivoting pins  101  positioned on the slots  53 , and a ledge  102  arranged to be in contact with one of the teeth  202  on a pinion  200 ; wherein said pinion also comprises pins  201  that are journalled in the housing, and teeth  203  evenly spaced around its circumference. 
     When the delivery device is adapted to be used, a needle is attached to the container by suitable means and a needle sheath is removed. The tensioning knob  44  is then actuated whereby the energy accumulating member  42  is tensioned. The driver is prevented from turning due to that one of the teeth  203  of the pinion  200  is in contact with one of the protrusions  30  of the driver, thereby holding the driver against rotation. 
     When an injection is to be performed, the needle is penetrated on a suitable location on the skin, and the push button  48  is pressed. The pressing of the push button causes the activation mechanism to pivot around the pivoting pins  54 . This in turn causes the ledge  102  of the intermediate lever  100  to move the pinion  200  whereby one of the tooth  203  of the pinion  200  that is in contact with one of the protrusions  30  comes out of contact and the driver rotates a certain increment distance until a further tooth  203  of the pinion  200  come into contact with a further protrusion  30  and thereby locking the drive wheel from rotation. 
     The rotation of the driver  26  causes the plunger rod  18  to rotate. Due to the force from the energy accumulating member  42  and the threaded engagement between the plunger rod and the nut  20 , the plunger rod moves forwardly pushing on the stopper whereby the medicament is expelled through the needle. 
     In this it is to be understood that the distance between the protrusions  30  of the driver, together with the pitch of the thread of the plunger rod constitutes a certain predetermined dose quantity. I.e. in order to set a specific dose, which is done during manufacture of the device, a certain distance is chosen between the protrusions as well as a certain pitch of the threads of the plunger rod. This gearing mechanism is adapted for delivering small doses, especially in the range of 0.01 ml.-0.005 ml. 
     Said first configuration is more suitable for medicaments or substances having high viscosity. 
     The Delivery Device of the Present Invention According to a Second Embodiment 
       FIGS. 4 ,  5  refer to a second configuration of the delivery device wherein the manufacturer of the device delivers the device with the energy accumulating member  42 ′ in a pre-tensed state. The driver  26 ′ of said second configuration is tube-shaped having a number of dose step protrusions  30 ′ equally distributed along its outer circumference and having longitudinally grooves  31 ′ equally distributed along its inner circumference. Moreover, the plunger rod  18 ′ of said second configuration has a threaded part  19 ′ and a non-threaded part  25 ′, wherein said parts are divided by a disc  21 ′. Further, said disc has protrusions  24 ′ along its circumference accommodated on said longitudinally grooves  31 ′ of said driver, such that the plunger rod extends through the driver in a rotationally locked, but in a slidable mode. The nut  20 ′ is adapted to be in a non-rotating state due to two outwardly protruding pivoting pins  23 ′ journalled in the housing. Said nut  20 ′ has also a through-going central bore  22 ′ having corresponding threads as the threaded part  19 ′ of the plunger rod. The energy accumulating member  42 ′ is arranged inside said driver  26 ′ between an inner surface of the distal end of said driver  26 ′ and the rear end of the disc  21 ′. 
     An activation mechanism  46 ′, as seen in  FIG. 5 , is also arranged on the delivery device, wherein said activation mechanism  46 ′ comprises a push button  48 ′ protruding through a slot on the front end of the housing for promoting an ergonomic handling of the device. The push button is attached to an arm  51 ′ on a side of the container and plunger rod. Two outwardly protruding pivoting pins  54 ′ are arranged on the arm, which pivoting pins are journalled in the housing. The rear end of the arm, comprises a wing formed part  52 ′ having slots  53 ′. An intermediate lever  100 ′ having a larger diameter than the outer diameter of the driver  26 ′, is arranged around the outer surface of said driver  26 ′. Further, said intermediate lever  100 ′ comprises two outwardly protruding pivoting pins  101 ′ positioned on the slots  53 ′, and a ledge  102 ′ arranged to be in contact with one of the teeth  202 ′ on a pinion  200 ′; wherein said pinion also comprises pins  201 ′ that are journalled in the housing, and teeth  203 ′ evenly spaced around its circumference. A resilient means  300 ′ e.g. a coil spring is arranged between a slot on the housing and a slot on the lever  100 ′, as seen in  FIG. 4 . 
     When the delivery device is adapted to be used, a needle is attached to the container by suitable means and a needle sheath is removed. The driver is prevented from turning due to that one of the teeth  203 ′ of the pinion  200 ′ is in contact with one of the protrusions  30 ′ of the driver, thereby holding the driver against rotation. 
     When an injection is to be performed, the needle is penetrated on a suitable location on the skin, and the push button  48 ′ is pressed. The pressing of the push button causes the activation mechanism to pivot around the pivoting pins  54 ′. This in turn causes the ledge  102 ′ of the intermediate lever  100 ′ to move the pinion  200 ′ whereby one of the teeth  203 ′ of the pinion  200 ′ that is in contact with one of the protrusions  30 ′ comes out of contact and the driver rotates a certain increment distance until a further tooth  203 ′ of the pinion  200 ′ come into contact with a further protrusion  30 ′ and thereby locking the drive wheel from rotation. 
     The rotation of the driver  26 ′ causes the plunger rod  18 ′ to rotate. Due to force from the energy accumulating member  42 ′ and the threaded engagement between the threaded part  19 ′ of the plunger rod and the nut  20 ′, the plunger rod moves forwardly pushing the stopper whereby the medicament is expelled through the needle. 
     In this it is to be understood that the distance between the protrusions  30 ′ of the driver, together with the pitch of the thread of threaded part  19 ′ of the plunger rod constitutes a certain predetermined dose quantity. I.e. in order to set a specific dose, which is done during manufacture of the device, a certain distance is chosen between the protrusions as well as a certain pitch of the threads of the plunger rod. 
     Said second configuration is more suitable for medicaments or substances having low viscosity. 
     Moreover, in the currently preferred designs, the dose increment steps are in the order of 0.01 ml-0.005 ml per step and one dose increment step of 0.01 ml corresponds to a clock-wise rotation of the drive wheel with 45°. 
     It is to be understood that the embodiments described above and shown on the drawings are to be regarded only as non-limiting examples of the invention and that it can be modified in many ways within the scope of the patent claims.