in the present detailed description , the terms “ front side ” or “ front ” and “ rear side ” or “ rear ” are used to define the direction of different components . in the following text , “ front side ” or “ front ” refer to the physical end of the invention where the medicament is delivered out from the device , and also constitutes the end where an external component can be connected onto the device . it could be an injection needle , which is screwed fitted or snap - locked onto the device , or a mouth piece which transforms the pressurized liquid medicament into a spray or an aerosol . it could also be another kind of orifice , as for example a component equipped with a hole , which is pressed against the skin , where the fluid pressure of the liquid medicament is sufficiently high to enable the liquid to penetrate the patient &# 39 ; s skin without using a penetrating needle , whereby the device in this embodiment constitutes a needle - free injector for medicament . in the following text , “ rear side ” or “ rear ” refer to the physical end of the invention which is equipped with a dose knob ( 4 ) which is illustrated by the figures . the device for distribution of liquid medicament which is illustrated by the figures , comprises a cover consisting of the rear cover ( 12 ) and the front cover ( 16 ). in the described embodiment these two covers ( 12 , 16 ) are joined together by snap - in closures . in other embodiments , the covers ( 12 , 16 ) could be ultrasonically welded , glued , heat staked , riveted or screw fitted together . it is convenient to mould these parts of plastic , as for example of polycarbonate , cycoloy ( trademark ) or abs but the covers could also be manufactured of metal , as for example of brass or steel . in the described embodiment the joint is further reinforced with a deep drawn piece of sheet metal shaped as a barrel ring ( 3 ) which also consists of a protrusion directed towards the rear side of the device . this piece of sheet metal , as for example stainless steel , can be replaced by a moulded feature made of plastic , as for example of lcp . the ring ( 3 ) does not only function as a reinforcement of the joint between the front cover ( 16 ) and the rear cover ( 12 ), it also hides the joint and furthermore guides the trigger button ( 2 ). the trigger button ( 2 ) serves two purposes , the main function is to act as a trigger , which implies that the user separates the stop features along the perimeter of the dose stop ( 20 ) by pushing the trigger button ( 2 ) towards the front end of the device , and by this allows the inner components to rotate freely . this phase is executed when the user intends to deliver the liquid medicament . it is preferable to manufacture the trigger button ( 2 ) of transparent plastic , as for example of transparent polycarbonate , as the rear protrusion of the trigger button ( 2 ) can be used as a window for numerical values which are placed along a helical track along the outer surface of the dose drum ( 13 ) which is shown by fig5 . the trigger button ( 2 ) could also be made of metal or of another plastic material . in this case the position of the numerical values placed on the dose drum ( 13 ) has to be shifted , either by shifting the trigger button ( 2 ) angularly referred to the longitudinal direction of the device so that the numerical value can be read at the side of the trigger button ( 2 ), or else the trigger button could be equipped with a hole in its rear protrusion , through which the user can read the numerical value . this hole could also in this case be equipped with a separate magnifying glass made of glass or transparent plastic . the trigger button ( 2 ) is shifted against its rear stop position in the non - active mode , and rotationally locks the dose stop ( 20 ) as long as the user doesn &# 39 ; t push the trigger button ( 2 ) ahead . the trigger button ( 2 ) is kept in place in its rear stop position by a trigger spring ( 21 ) which front end in the illustrated embodiment pushes against a surface in the rear cover ( 12 ) and which rear end pushes against a recessed surface in the trigger button ( 2 ). this way a force which is directed towards the rear is created , which is used to ensure that the dose stop ( 20 ) is locked . when delivering a dose the trigger button ( 2 ) is pushed forwardly whereby the dose stop ( 20 ) is released . in fig3 the dose stop ( 20 ) is shown from a front side view and a rear side view . the dose stop ( 20 ) is hollow in its longitudinal direction , with a diameter of the hole which exceeds the maximum diameter of the plunger rods cross - section . the dose stop ( 20 ) is equipped with a backward directed end of a shaft which is equipped with spline grooves in which the clutch ( 14 ) can move back and forth . furthermore the dose stop ( 20 is equipped with an outer ring which on its outer surface is equipped with evenly distributed stop features , which together with corresponding stop features on the front end of the trigger button ( 2 ) constitute a trigger function , or in other terms , a rotational lock which can be operated by the user . the rear cover ( 12 ), which is illustrated by fig2 , is equipped with one or more threaded tracks propagating on the inside in a spiral shaped pattern , and thus constitute an internal thread . the number of tracks depend on if the thread has one or more entrances . the dose drum ( 13 ) is equipped with corresponding external threads which correspond to the internal threads which are integrated in the rear cover ( 12 ). the dose drum ( 13 ) is guided by the threaded tracks and rotates backward when the dose knob ( 1 ) is turned manually until it finally hits the rear stop position , which in this embodiment is constituted by the dose knob ( 1 ). in the same way the dose drum ( 13 ) is free to move to a front stop position , which in this embodiment is constituted by the front end of the internal threads in the rear cover ( 12 ). this consequently constitute a front stop position for the forward movement of the dose drum ( 13 ). another way of creating a front end stop position for the dose drum ( 13 ) movement is to equip the rear cover ( 12 ) with a protruding feature or separation wall which also would constitute a stop . the dose drum ( 13 ) also rotates by a window , or a hole in the rear cover ( 12 ). as the dose drum ( 13 ) is equipped with pre - defined stable positions , which are synchronized to the stop positions in the clutch ( 14 ) the dose drum ( 13 ) can be equipped with numerical values along its outer surface . these numerical values are grouped along a spiral shaped imaginary curve with the same pitch as the external thread of the dose drum ( 13 ). this imply that a certain movement and synchronized backward turn of the dose drum ( 13 ) will always result in that a certain numerical value will be displayed in the window . this numerical value indicates the size of the dose of the liquid medicament which the user of the device intends to deliver . in another embodiment of the invention the inner wall of the rear cover ( 12 ) could be equipped with an external thread which in that case correspond to a recessed thread in the dose drum ( 13 ). the dose drum ( 13 ) is preferably made of plastic , as for example of abs , but it can also be made of metal , as for example of brass . the advantage by using plastic is that the material can be coloured , for example with white paint to increase the contrast between the background , consequently the outer surface of the dose drum ( 13 ), and the numerical values which either are printed , as for example by using tampon print , or consists of a decal applied on the outer surface , as for example by in - mould decoration or marked by using jet - printing technique or laser printing technique , should be as good as possible . this is important , particularly if a diabetic will use the device , who often suffer from impaired eyesight , as a consequence of the decease . the dose drum ( 13 ) is in its longitudinal direction equipped with a hole inside of which the drive shaft ( 10 ) can move freely in the longitudinal direction of the device . by designing the hole with a spline function , which in this embodiment imply longitudinally protruding grooves and equip the drive shaft ( 10 ) with corresponding longitudinal grooves , a torque can be transferred from the dose drum ( 13 ) to the drive shaft ( 10 ). the drive shaft ( 10 ) is hollow and has an internal diameter which exceeds the maximum diameter of the plunger rod ( 19 ). this implies that the plunger rod ( 19 ) can move freely along the longitudinal direction of the internal hole of the drive shaft ( 10 ). at the rear side of the drive shaft ( 10 ) the dose knob ( 1 ) is firmly attached . the dose knob ( 1 ) is operated by the user , in that way that the user turns the dose knob ( 1 ) until the correct numerical value is displayed in the window in the rear cover . in the illustrated embodiment the front portion of the dose knob ( 1 ) is equipped med snap - in closures . the dose knob ( 1 ) transfers a torque from the hand of the user to the drive shaft ( 10 ). as the mainspring ( 11 ) is preset , the dose is preset which implies that the dose knob ( 1 ) is not free to rotate in relation to the drive shaft ( 10 ). therefore , in the present embodiment of the invention the dose knob ( 1 ) is equipped with snap - in closures which together with corresponding holes in the rear portion of the drive shaft ( 10 ) locks the dose knob ( 1 ) in the longitudinal direction and simultaneously allows torque transmission to the drive shaft ( 10 ). alternative ways of locking the dose knob ( 1 ) against the drive shaft ( 10 ) is by joining them together by using ultrasonic welding , gluing or heat staking . these parts can also be press fitted , if one of these parts is equipped with small protruding edges , with the height fluctuating from 0 . 1 mm up to 0 . 3 mm and which will deform as the two parts are pressed together . when the user turns the dose knob ( 1 ) the mainspring ( 11 ) will accumulate the load and thereby store the force necessary for the device to be able to deliver the liquid medicament as the user pushes the trigger button ( 2 ) ahead and thereby releases the dose stop ( 20 ). in this embodiment of the invention the mainspring ( 11 ) is a regular spiral shaped compression spring with a round cross section profile of the spring wire . the cross section profile of the wire could also be rectangular or some another shape . the material used for the spring ( 11 ) could for example be resilient stainless steel or resilient regular steel . most of the automatic devices for delivering liquid medicament available on the market today use some type of spring unit to create the force needed to distribute liquid medicament . one example of the most common spring types are the clock springs either wound with distance between the coils or tightly wound and made of a flat helical sheet metal strip . another example is a compression spring which is used in the present invention as a source of energy . yet another example of a mainspring ( 11 ) is some type of torsion spring . these springs have in common that their force / compression curve for linear springs , and respectively the force / angular turning for radial springs can be regarded as more or less linear within the active operation interval for the spring . regarding automatic devices for distribution of liquid medicament , in all existing embodiments there are a number of factors which result in an inherent friction in all devices , and thereby a friction force which has to be exceeded by the mainspring . furthermore it is widely known within the pharmaceutical industry that plungers many times stick to the glass surface of the cartridge , which in some cases depend on that the surface pressure between the plunger and the glass in course of time presses away the silicon treatment which the glass surface has undergone . the force which has to be applied on the plunger , in order to start the movement at all is known as “ break - loose ” force . because of all the inner frictions the spring has to , provide at least a minimum force to the plunger rod under the entire distribution phase , or in other terms the dose delivery phase . if this force is less than that , the inherent friction forces will exceed the movement which causes the dose delivery to cease . by this reason all mainsprings are pre - set in such manner that they deliver sufficient force all the way until the dose delivery mechanism stops in the front stop position , which is needed in order to maintain the mainspring in a static pre - set state . from this static pre - set state the user increases the spring force as he / she turns the dose knob ( 1 ) to set the correct dose size . the drive shaft ( 10 ) performs a variety of tasks . its rear end is , as described above , shaped as a mechanical joint fitting to be able to attach it to the dose knob ( 1 ). the rear portion of the drive shaft ( 10 ) is equipped with splines for transfer of the torque from and to the dose drum ( 13 ). the drive shaft ( 10 ) is in its longitudinal direction hollow in order for the plunger rod ( 19 ) to run freely on the inside in the longitudinal direction and also be able to rotate freely inside of this hole . on its front end the drive shaft ( 10 ) is equipped with a toothed flange which composes a ratchet wheel . the teeth are shaped the same way as the teeth in a regular ratchet wheel , with the top of the teeth pointing ahead in this embodiment . the teeth are designed with one side sloping , which allow the corresponding teeth of the clutch to slide on top of its surface . the opposite side of the teeth are leaned approximately 90 degrees in the normal direction from the bottom of the teethed flange . this implies that the force transmission between the teeth of the drive shaft ( 10 ) and the teeth of the clutch ( 14 ) are normal to the plane , which imply that they are rotationally locked to each other in this direction . the drive shaft ( 10 ) could be manufactured of plastic , as for example of polycarbonate with additives such as glass and teflon , but it can also be made of metal , as for example of stainless steel or brass . it is important that the sun gear is rotationally locked to the drive shaft ( 10 ) in order to be able to transmit the torque from the drive shaft ( 10 ). when the user set the dose which he / she intend to distribute , each tooth in the ratchet wheel corresponds to a dose increment which is indicated as a numerical value in a window in the cover . a tooth corresponds to a certain angular turn , which is transformed to a certain plunger rod pitch by the mechanical parts . the torque created by the mainspring ( 11 ) is transferred through the clutch ( 14 ) to the dose stop ( 20 ) and its sun gear shaped front end via a spline arrangement . the dose stop ( 20 ) with it &# 39 ; s integrated sun gear constitutes the input shaft to a planetary gear mechanism . fig6 illustrates the schematic structure of the planetary gear mechanism . the input shaft is represented by the number 1 . the planet carrier ( 5 ) constitutes output shaft which also is represented by the letter c . a typical planetary gear mechanism consist of an input shaft , 1 , equipped with a sun gear , which is equipped with a number of teeth z 1 , furthermore a planetary gear mechanism includes of a planet carrier ( 5 ) which hub shaft also constitutes the output shaft from the planetary gear mechanism , c . one or more planet gears ( 4 ) are assembled on the planet carrier ( 5 ) on a certain distance from the hub axis , and they are equipped with a number of teeth z 3 . in the present invention the ring gear on the front cover ( 16 ) is kept locked in relation to the sun gear on the dose stop ( 20 ) and the planet gears ( 4 ). in the present embodiment this is accomplished by integrating the ring gear into the front cover ( 16 ). the ring gear is a gear with a number z 2 of teeth pointing toward the hub . furthermore , in this embodiment the hub hole in the planet carrier ( 5 ) is shaped as a nut which drives the plunger rod ( 19 ) ahead with a lower gear than the drive shaft ( 10 ). in order to attain a forwardly directed plunger rod ( 19 ) movement , instead of spinning along with the planet carrier ( 5 ), the plunger rod ( 19 ) has to be linearly guided either in front of or behind the planet carrier ( 5 ). this implies that the plunger rod ( 19 ) only has one degree of freedom and is only allowed to move ahead with a linear movement . the linear guide in this embodiment is constituted by a non - circular longitudinally protruding hub hole in the plunger rod clutch ( 6 ). the profile of this hole corresponds to a corresponding profile along the plunger rod ( 19 ) long sides . when observing the raw material of a plunger rod it is a threaded rod , with one or more entrances for threads . by removing material from this raw material a non - circular cross section profile can be achieved . the result of the plunger rod ( 19 ) movement will be a forward movement and the resulting force in the plunger rod ( 19 ) will be directed ahead . yet another embodiment of this invention is accomplished by shaping the hub hole in the plunger rod clutch ( 6 ) is equipped with internal threads , corresponding to the plunger rod threads . in this case the planet carrier ( 5 ) is equipped with a longitudinal protruding hub hole with a linear guide which corresponds to the cross section profile of the plunger rod ( 19 ). the difference is that in this case the torque is transferred from the planet carrier ( 5 ) to the flat recesses along the threaded long sides of the plunger rod ( 19 ). fig5 distinctly illustrates how the plunger rod ( 19 ) could be designed . in this embodiment the plunger rod ( 19 ) will rotate as it moves ahead . to prevent the plunger ( 8 ) from obstructing the plunger rod ( 19 ) rotation and thereby increase the resistance which restrains the desired linear movement ahead of the plunger rod a spinner ( 7 ) has been mounted in the front end of the plunger rod ( 19 ). it constitutes the front end bearing of the plunger rod ( 19 ). in the illustrated embodiment the spinner ( 19 ) is snapped onto a flanged shaft journal in the front end of the plunger rod ( 19 ). fig6 illustrates the input shaft , 1 , which rotates with the angular velocity ω 1 . this shaft propel the output shaft , c , which will rotate with an angular velocity ωc . the velocity of the rotation which the output shaft will get also depends on the number of teeth of which the included gears are equipped with , i . e . the number of teeth on the sun gear z 1 , the number of teeth on the planet gears z 3 , and the number of teeth on the fixed and outer ring gear with internal teeth z 2 with the angular velocity ω 2 which accordingly is equal to 0 . the relation between ω 1 and ωc is described by the formula : by gearing down the angular velocity several advantages can be obtained . one advantage compared to known technology within the pen injector field is that the today existing injectors , as for example the insulin pens , don &# 39 ; t have this type of gear box , which results in that the size of the teeth of the ratchet wheel used in almost all design solutions has to be smaller , if a single dose step is small , or in other terms if the plunger rod is expected to move a very short distance . this put demands on the manufacturing precision when shaping the teeth of the ratchet wheel . this also imply that the wear which takes place between the pawl and the ratchet wheel quickly will wear down the teeth and thereby limit the duration of existing injectors . by introducing a planetary gear mechanism the teeth can have a more heavy - duty shape as the angular speed is geared down , which in present case increases the robustness of the design . if , on the other hand , the fine resolution between the teeth remain about the same as in the now existing injectors , the user will have an opportunity to fine tune the dose volume , which in a concrete example implies that a diabetic , who by a very good understanding of the amount of insulin he / she should inject , will with present invention get the opportunity to further fine tune the dose . if a user today has the opportunity to adjust his / her dose in steps of 5 iu , the planetary gear will make it possible for the user to adjust the dose in steps of 2 . 5 iu . yet another embodiment of the invention is achieved by serially couple two or more planetary gear mechanisms where the outgoing shaft from the first planetary gear mechanism is equipped with a sun gear equal to the sun gear in the front end of the dose stop ( 20 ) in order to further gear down the angular velocity , which will enable to set doses as small as 1 iu or less with accuracy , or to achieve an even higher force acting on the plunger rod ( 19 ). the present invention has a great benefit , as the planetary gear mechanism takes up very little space . a device which delivers a fixed or adjustable dose of liquid medicament to a patient should not be bulky , on the contrary it should be easy to fit within the handbag or the jacket pocket . furthermore the international pen - injector standard iso 11608 - 1 states in a regulation that it should “ resemble a pen ”. yet another benefit which will be achieved by implementing a planetary gear mechanism is that the plunger rod ( 6 ), with unchanged mainspring force is able to deliver a significantly higher force directed ahead to the plunger ( 8 ). this implies that the present invention is suitable to use for high viscous liquid medicaments such as botox ® and zoladex ® which are high viscous medicaments , at the same time as it will not get bulky , as it doesn &# 39 ; t require an extra powerful mainspring . as future injection needles , which are described by the international standard iso 11608 - 2 , tend to get thinner and thinner the flow resistance in these needles will get higher than the present needles , if the length of the needle is kept constant , which in most cases is 12 mm . the reasons why the needles get thinner is that frequent users tend to develop scar tissue and damages on nerves at the injection site , and that the pain sensation decreases if the skin is penetrated by a thinner needle . yet another benefit by using a planetary gear mechanism is that the preset of the mainspring ( 11 ) can be reduced which results in that the technical life length of the present invention can be enhanced compared to today existing injectors which are equipped with mainsprings . a factor which often limits the theoretical life length of injectors is the creep behaviour of thermoplastics as they are exposed to static load , as for example by a preset mainspring . as a consequence of the presence of a planetary gear mechanism in the present invention , consequently a high fluid pressure can be achieved in the liquid medicament , and at the same time keep the outside measurement of the present invention small and handy , and thus be used to transform the liquid medicament to a vapour , also referred to as soft mist . in this field of application the present invention can be used to propel a medicament inhaler where the medicament is stored in the cartridge ( 9 ) in liquid state . finally , the present invention is , due to it &# 39 ; s capability of creating a high fluid pressure , usable for injecting medicament straight into the body tissue without the necessity of the use of any injection needle for penetrating the skin , and thus open up a fluid channel for transportation of medicament into the body tissue . automatic devices for distribution of liquid medicament , in particular insulin pens , are often divided in either disposable devices or reusable devices . disposable devices will be referred to as disposable devices , and reusable devices will be referred to as reusable device in the following text . a concrete example of a disposable device is a disposable insulin pen . a disposable insulin pen comprises , similar to a reusable insulin pen , a cartridge containing insulin . the cartridge many times contains about 3 milliliter of insulin , which depending of the dosage will last a number of insulin treatments . when the cartridge is emptied the entire insulin pen is disposed . regarding disposable devices the cartridge is either integrated in the insulin pen or assembled inside of the body of the insulin pen in such way that it can &# 39 ; t be disouterd unless breaking the disposable device . an example of alternative assembly methods are regular non - dismountable snap - in - closure , which is designed in such way it can &# 39 ; t be dismounted without breaking . another example is to glue or weld the cartridge housing , which in most cases is made of plastic , to the insulin pen cover . an often used argument why a disposable device is better than a reusable devise is that the user doesn &# 39 ; t have to get as much distressed about bacterial growth and that a disposable device can &# 39 ; t be filled with another medicament than what it is intended for . furthermore the mechanical platform can be simplified , as the plunger rod in almost all of these existing automatic devices for distribution of liquid drug can &# 39 ; t reverse as they aren &# 39 ; t equipped with a plunger rod clutch mechanism . consequently the plunger rod moves ahead step by step , or in other words , dose by dose until the plunger rod has pushed the plunger towards the front end of the cartridge , and thus emptied all the medicament of the cartridge . a reusable device is an automatic device for distribution of liquid medicament , where the cartridge ( 9 ) can be replaced when the medicament has run out . when the medicament has run out , the cartridge housing ( 18 ) is dismantled together with the empty cartridge ( 9 ) and it &# 39 ; s belonging plunger ( 8 ). the cartridge ( 9 ) with its belonging plunger ( 8 ) is then replaced with a new similar one which is filled with liquid medicament . in the present embodiment of the invention the cartridge housing ( 18 ) is equipped with a threaded interface , which correspond to threads in the front cover . the user commonly has to reverse the plunger rod ( 19 ) by hand , but in the present embodiment of the invention the device is equipped with another clutch mechanism , which in it &# 39 ; s front end is composed by teeth in the front cover ( 16 ) that correspond to teeth in the plunger rod clutch ( 6 ). as the cartridge housing ( 18 ) is screw fitted onto the front cover these teeth interlock each other and locks the plunger rod clutch ( 6 ). in case the cartridge housing ( 18 ) has been equipped with a new cartridge ( 9 ) and is about to be screw fitted to the front cover the plunger rod return spring ( 17 ) separates the teeth from each other whereby the plunger rod clutch ( 6 ) can rotate freely . as a result of that the plunger rod clutch ( 6 ) can rotate freely , the plunger rod ( 19 ) is allowed to be pushed backwards in a backward spinning movement which is guided by the threaded hub of the planet carrier ( 5 ), pushed back by the plunger ( 8 ) which as the liquid medicament is to be more or less regarded as incompressible , until the cartridge housing ( 18 ) is screw fitted on to the front cover ( 16 ) and the teeth of the plunger rod clutch ( 6 ) and the front cover ( 16 ) are interlocked to each other again .
the present invention relates to a device for delivering a fixed dose or an adjustable dose of liquid medicament to a patient . characterising for the present invention is that it is equipped with a planetary gear with the purpose of increasing the power needed to deliver liquid medicament out of this type of devices . on almost all of the devices of this type appearing on the market with the purpose of delivering a fixed dose or an adjustable dose of liquid medicament , the dose volume can be set in separated steps . with assistance of a planetary gear these steps , which each represent an increase of the volume of the medicament to be delivered , get smaller , which increases the possibility to set an optimum dose volume of the medicament . in its primary field of use the invention is intended to be used together with an injection needle . the invention facilitates to create high fluid pressure in the medicament and can be used to operate an inhaler or a needle free injector at the same time as the invention will keep a compact outside measurement .