in the following the orientation of the different elements are described with help of the terms front and rear , respectively forwards and rearwards , denoting orientations toward left and right , respectively , in the figures . the term longitudinal is used with reference to the general longitudinal orientation of the shown syringe . the syringe shown in fig1 as seen from the outside comprises a longitudinal housing 10 with a first ( rear ) portion 11 and a second ( front ) portion 12 , the first portion comprising a first compartment with the dose setting device of the present invention and the second portion comprising a second compartment adapted to accommodate a medicine - containing ampoule or cartridge . in the shown embodiment the second portion is formed integrally with the first portion , however , the second portion is not part of the present invention and could , correspondingly , also be provided as a separate element which could be connected to the first portion by , for example , a threaded or bayonet connection . when removing the first portion , an empty cartridge ( not shown ) can be removed , the plunger ( to be described below ) can be returned to its initial position , and a new cartridge can be inserted where after the portions again can be connected to each other . in case the two portions are formed integrally , the foremost end of the first portion should be closed by an additional element ( not shown ) in order to provide a compartment for the ampoule . the syringe further comprises a latch or trigger member 90 and a dose setting knob 40 arranged at the rear end of the syringe . as shown in fig1 a a partition member 20 is arranged between the first and second portions , the partition member having an opening with an internal thread 21 , the partition thereby serving as a nut member , however ; the term nut does not imply that the thread has to be defined by a bore but could also be defined between two opposed members . a longitudinal plunger 30 serving as a piston drive member ( i . e . when the plunger is positioned with its foremost end against a piston in the ampoule ) is arranged through the opening , the plunger having an external thread 31 corresponding to the internal thread of the partition allowing the plunger to be threaded through the opening . the thread of the plunger / nut connection has a pitch angle exceeding the friction angle of the nut and plunger . thereby forward movement of the plunger can be obtained by simply pressing the plunger axially forwardly , this resulting in a rotative movement of the drive member in the forwards direction . such a thread is also known as non - locking . the plunger further comprises two opposed and parallelly arranged , planar side surfaces 32 , 33 providing a “ partial ” external thread , however , this has no functional influence on the thread connection as such . the purpose of the opposed surfaces will be apparent from the below . the dose setting knob 40 comprises an outer cap portion 41 to be gripped by a user and an inner forwardly projecting cup - like skirt portion 42 , the two portions being connected by a shaft 43 arranged through an opening 16 in the rear end wall 15 of the housing , whereby the knob is allowed to rotate but not to be axially displaced relative to the housing . the dose setting member 50 comprises a foremost end wall 51 and a rearwardly arranged skirt portion 52 . the end wall has an opening with an internal thread 53 , the end wall thereby serving as a second nut member through which the plunger 30 is arranged . the thread 53 corresponds to the internal thread 21 thus allowing non - locking rotation of the plunger . the end wall further comprises a rearwardly facing coupling surface 54 to be described below . the skirt portion 52 of the dose setting member comprises longitudinal grooves 55 on its inner surface engaging corresponding longitudinal tongue members 45 on the outer surface of the skirt portion 42 of the knob 40 , whereby the two skirt members are allowed to slide axially but not to rotate relative to each other . indeed , any suitable configuration could be used to provide this functional relation between the two skirt members . numbers ( not shown ) are printed along a helical line on the external surface of the skirt 52 which can be inspected through a window 17 ( see fig4 ) in the housing of the device , the window allowing only a portion , preferably only one , of the numbers on the sleeve to be inspected . the tubular coupling member 60 comprises a foremost extension 61 with a forwardly facing coupling surface 62 , as well as a rearwardly oriented tubular skirt portion 63 . the skirt portion and the extension is formed with two internal , opposed and parallelly arranged , planar surfaces 68 , 69 ( see fig7 ) corresponding to the opposed surfaces 32 , 33 on the plunger , whereby the coupling member and the plunger are allowed to slide axially but not to rotate relative to each other . indeed , any suitable configuration could be used to provide this functional relationship between the plunger and coupling member . a helical spring 70 is supported at its respective ends at an rearwardly facing surface 64 of the extension 61 and at an inner end surface 46 of the knob skirt , the spring thus providing a biasing force on the coupling member . the shown spring may be replaced by any suitable element which can store and release energy , for example a gas - filled member or a foam body , such structures being examples of spring means . the above - described coupling surfaces 54 , 62 on the dose setting member and the coupling member co - operate to provide a bi - directional coupling between the dose setting member and the coupling member . in the shown embodiment the coupling is provided by coupling parts having circular surfaces provided with sector shaped teeth 57 , 67 ( see fig5 and 7 respectively ) having ramp shaped edges , the surfaces being forced against each other by the spring 70 with the ramp shaped edges of the teeth on one surface abutting the ramp shaped edges of the teeth on the other surface . when the dose setting member is rotated in either a dose setting or an adjusting direction , the teeth on the coupling parts will slide with their ramp shaped parts over each other , whereby the dose setting member is axially displaced relative to the plunger ( due to the threaded connection ) against the force of the spring and will jump back each time a top of the teeth is reached . each jump back may be heard and sensed by the operator , and the pitch of the too thing may be chosen so that a jump back takes place each time the dose setting is increased by say one unit . a locking member 80 is provided on the plunger in order to prevent the plunger from rotating during the setting operation , i . e . during the rotation of the dose setting member on the plunger . the locking member is in the form of a wheel - like member comprising an opening 81 having opposed and parallelly arranged , planar surfaces 83 , 84 ( see fig9 ) corresponding to the opposed surfaces 32 , 33 on the plunger , whereby the tubular portion and the plunger are allowed to slide axially but not to rotate relative to each other . the locking member is arranged such that it is allowed to rotate but not move axially with respect to the housing . the locking member further comprises a forwardly projecting , circumferential skirt with a plurality of axially aligned detents 82 . a latch member 90 comprising an inner latch arm 91 is arranged in the housing wall , the latch member being moveable between a setting position in which the latch arm engages between the detents on the locking member thereby preventing the locking member and thus the plunger from rotating , and a dosing position in which the latch arm disengages the detents on the locking member thereby allowing the locking member and thus the plunger to rotate . preferably the latch member is biased towards its setting position . next operation of the dose setting and expelling device of the present invention will be described with reference to the figures . when a fresh medicine - containing ampoule equipped with a fine needle ( neither shown ) is loaded into the syringe device , the piston in the ampoule is in its rearmost position and the plunger is positioned with its foremost end against the piston . during use of the syringe the plunger moves the piston forwards thereby expelling the medicine . fig1 a and 1b show an intermediate position in which the plunger has been advanced approximately half the full stroke length and with the dose setting member in its “ initial ” position with a “ 0 ” showing in the window . when setting a dose , the user preferably grips the housing with one hand , using the other hand to select ( i . e . dial up ) a desirable dose by rotating the dose setting knob 40 . due to the groove and tongue arrangement 45 , 55 the dose setting member is rotated and threaded rearwardly relative to the plunger . during dose setting the user can control the setting by inspecting the numbers printed on the dose setting member as they pass the window , the numbers being indicative of the length the dose setting member has been rotated rearwards , and thus indicative of the subsequent stroke length for the plunger . if the dose is set too high , the user can simple adjust ( i . e . dial down ) the dose by turning the knob in the opposite direction until the number corresponding to the desired dose size shows up in the window . as the dose setting member is rotated in either a dose setting or an adjusting direction , the teeth on the coupling parts will slide with their ramp shaped parts over each other , whereby the dose setting member is axially displaced relative to the plunger ( due to the threaded connection ) against the force of the spring and will jump back each time a top of the teeth is reached . as the coupling member is moved rearwardly the spring is compressed thus storing energy for the subsequent dosing . this situation is illustrated in fig2 a and 2b . when the desired dose is set the user advances the needle through the skin and the syringe is ready to expel the set dose which is performed when the user depresses the latch member thus releasing the locking member 80 and thus the plunger which can now rotate freely . the axial force exerted by the spring 70 is transmitted to the plunger through the coupling member 60 and the dose setting member 50 ( corresponding to the threaded connection ) this resulting in a rotational forward movement of the plunger due to the non - locking thread connection between the plunger and the internal thread 21 . as the coupling member cannot rotate relative to the rotating plunger , the dose setting member also rotates together with the plunger , this bringing the dose setting member back to its initial rotational position with a “ 0 ” showing in the window . this situation is illustrated in fig3 a and 3b . an “ end of content ” function ( i . e . for the ampoule ) is provided by the dose setting member simply abutting the rearmost portion 34 of the plunger as the threaded portion ends . the maximum possible dose is set when the rearmost end of the dose setting member abuts the rear end of the housing . the dose setting member is prevented from rotating past its “ 0 ” position as it abuts the partition wall . the above - described device can either be provided for single use or for re - use in which case the dose setting mechanism will have to be reset , i . e . the plunger moved backwardly , in order to allow a new cartridge to be inserted into the syringe . the plunger is moved backwardly simply by rotating the plunger , however , as the plunger is normally positioned inside a front portion 12 of the housing , the front portion should either be removed in order to allow a user to properly grip the plunger , or the plunger should be rotated indirectly . the latter could be achieved by providing a housing having releasable front and rear portions 11 , 12 ( not shown ) in order to allow the portions to be rotated relative to each other . as the front housing is rotated relative to the rear housing and the dose setting member , the latched locking member 80 , in sliding non - rotational engagement with the plunger , provides rotation of the plunger 30 which is then treaded rearwardly through the internal threads 21 , 53 of the partition member 20 respectively the dose setting member . in order to prevent the dose setting member from rotating , the knob 40 should be gripped together with the rear housing in order to prevent relative rotation between these members . as the coupling member 60 is in sliding non - rotational engagement with the plunger , it is correspondingly rotated resulting in a “ clicking ” relative rotation between the two mutually cooperating coupling surfaces 54 , 62 . when the plunger is brought to its rearmost position , the front and rear portions are again locked to each other and the syringe is ready to be loaded with a new cartridge . the different members of the syringe and dose setting device shown in the drawings of fig1 - 3 have been described in detail with reference to these drawings , however , in order to provide an even better understanding of the present invention , some of the members are shown individually in fig4 - 9 , fig4 showing the housing , fig5 the dose setting member , fig6 the piston drive member , fig7 the coupling member , fig8 the latch member and fig9 the locking member . in all of fig4 - 9 the same reference numerals are used as in fig1 - 3 and broken lines are used to indicate structures hidden behind surfaces . next an embodiment according to the second aspect of the invention will be described with reference to fig1 which in partial shows a pen - like syringe with a dose setting device , comprising a drive member 102 and a dose setting mechanism which simultaneously sets a given dose and stores the energy necessary for a subsequently driving the drive member in order to expel a dose of medicine from the syringe apparatus . the syringe is generally pen - like , being of elongate cylindrical form , with a pen body 108 closed at its left - hand end in fig1 by a plunger guide 111 screwed into the pen body and having a cylindrical boss extending to the left and being externally threaded to accommodate a cartridge carrier 113 ( shown in partial only ). a cartridge of insulin ( not shown ) can be fitted into the cartridge carrier 113 before the cartridge carrier is screwed onto the boss on the plunger guide 111 . the guide 111 guides longitudinal movement of a drive plunger 102 progressively into the open end of the cartridge as insulin is injected through a needle ( not shown ) at the end of the carrier . the bore in the plunger guide has opposed flats for preventing rotation of the drive plunger 102 as it moves into the cartridge , the drive plunger having corresponding opposed flats . movement of the plunger 102 is achieved by energy stored in a helical spring 106 , which is twisted as a pre - set dose of insulin to be injected is set by rotation of a cap 107 which can turn about a graduated sleeve 112 at the right - hand end of the pen body 108 . the cap 107 has a window ( not shown ) through which graduations can be read to show the angle through which the cap has been turned . the cap is integral with a drive sleeve 101 which can turn in a plain bearing defined by the sleeve 112 and has an annular ring 125 projecting at its left - hand end and formed with a ring of ratchet teeth . the spring 106 is secured , respectively , at its ends to a flange ( not shown ) at the left - hand end of the drive sleeve 101 and a flange ( not shown ) on the sleeve 112 so that , as the cap is turned , the spring is strained by being partially wound up . the spring is a compression spring and both when strained torsionally and unstrained urges the teeth on the annular ring 125 of the drive sleeve into engagement with cooperating ratchet teeth 126 formed on a gear member 103 . the arrangement of the ratchet teeth is such that the cap and drive sleeve can be turned in relation to the ratchet gear in one direction only with turning being accompanied by a series of clicks , as each successive ratchet tooth is engaged , i . e . an one - way ratchet mechanism . the ratchet gear member 103 is normally held against rotation by engagement of external teeth on the gear member 103 with internal teeth on a latch member 109 . the latch member 109 has a leg which extend through slots in the housing to prevent rotation of the gear member in relation to the pen body , although the latch member can slide axially , as will be described later . when the pre - set or “ dialled up ” dose of insulin is to be injected , the latch member 109 is slid axially to the left out of engagement with the ratchet gear member 103 so that the gear can rotate driven by the torque of the spring 106 through the drive sleeve and the ratchet teeth . rotation continues until the cap has returned to its initial position defined by a positive stop between the cap and the pen body . the latch member is preferably biased towards its locked position by spring means ( not shown ). the ratchet gear member 3 is internally threaded with a quick pitch thread to cooperate with a corresponding external thread on the stern of the drive plunger 102 . rotation of the ratchet gear and drive tapers is accompanied by axial movement of the plunger along the quick pitch thread since the plunger stern cannot turn in the plunger guide 111 . thus , the plunger is driven into the cartridge , expelling the pre - set dose of insulin . when the cap stops turning on the pen body , the plunger remains part - way along the inside of the cartridge . according to the invention , a second latch or locking member 119 is provided which in its normal locked position slides on a rear surface of the annular ring 125 and thereby prevents the drive sleeve from moving rearwardly and thus to disengage from the gear member . however , if a dose is set too high a user may move the locking member to the right allowing the drive sleeve to be pulled backwards to thereby disengage the ratchet teeth from the gear member in which position it can be rotated backwardly to selectively adjust the set dose . as the drive sleeve is forced forwardly by the spring 106 , it can only rotate when gripped and pulled backwardly by the user . when the dose has been adjusted the locking member is moved to its locked position ( properly secured by any convenient means , either mechanically or by a spring means ) and the syringe is ready to be released for expelling a set dose . in an alternative embodiment no second latch member is provided , the ratchet gear members being held in engagement merely by spring means allowing the drive sleeve to be pulled backwardly and out of engagement by a user . proper engagement between the ratchet members when not pulled apart to re - adjust the device is provided by spring means , either by the spring 106 alone or by an additional spring means . in order to protect against unintended disengagement the teeth of the ratchet members could be “ under - cut ” such that the drive member has to be rotated slightly forwardly as it is pulled rearwardly in order to disengage . the procedure can be repeated until the cartridge is exhausted , after which the cartridge can be replaced by unscrewing the cartridge carrier 113 from the plunger guide 111 . while the present invention has been described in connection with the preferred embodiment shown in the various figures , it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating there from . for example , although the above disclosed coupling provides a preferred solution to desired dial up / dial down function , any coupling between the dose setting member and the coupling member allowing the dose setting member to be rotated in either direction , yet preventing the spring means to counter rotate the dose setting member could be used , this including a manually actuatable coupling such as described above with respect to fig1 . further , in the shown embodiment most elements are arranged coaxially , however , this can be changed wherever specific needs make this convenient for the skilled person . when it is described that two elements are acting together , this may imply that they are directly or indirectly connected as long as the desired action is achieved . therefore , the present invention should not be limited to any single embodiment , but rather construed in accordance with the appended claims .
the present invention relates to a dose setting and expelling device comprising a drive member and a dose setting mechanism which simultaneously sets a given dose and stores the energy necessary for a subsequently driving the drive member in order to expel a dose of medicine from an injection device . according to the invention the dose setting mechanism allows adjustment in both directions , such that a given set dose can be reduced or cancelled by reversing the input motion , typically by rotating a setting member backwardly , this in contrast to the known devices which either requires an additional release mechanism or which cannot be reversed at all .