Abstract:
A two-dose autoinjector for a medicament wherein the locking and releasing of the drive spring of the autoinjector is controlled through stepped guides with ramps for two successive slidings of slides operated by the spring and connected with the syringe and plunger. The guides and the slides are pivotable relative to one another and the sliding direction, while the syringe can only slide axially. To enable or disable the sliding of the slides within the guides an angularly angularly mobile arming member is provided formed with a guide track substantially equal to that of the stationary member where the guides are formed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is the US national stage of International Application PCT/IB2011/050985 filed on Mar. 9, 2011 which, in turn, claims priority to Italian Patent Application FI2010A000033 filed on Mar. 10, 2010. 
     FIELD OF THE INVENTION 
     the present application is the US national stage of International Application PCT/IB2011/050985 files on Mar. 9, 2011 which, in turn, claims priority to Italian Patent Application FI2010A000033 filed on Mar. 10,2010 
     The present invention relates generally to devices for the injection of medicaments and more precisely relates to a device for the automatic injection of medicaments especially a medicament for allergic emergencies, such as epinephrine or adrenaline, according to a requested time sequence. In particular, the invention refers to a device for the automatic injection of two doses of a medicament at two successive times. 
     BACKGROUND OF THE INVENTION 
     Many devices of the above mentioned type allowing a patient to self-administer one or more (generally two) doses of a medicament are known. U.S. Pat. No. 6,575,939 discloses an autoinjector device comprising a syringe housed in a casing formed by an inner part and an outer part capable of sliding in relation to each other. By pressing the end of the inner part (the needle outlet end) against the patient&#39;s skin at the injection site, the outer part slides forward along the inner part, thus unlocking a push-button. By depressing the button, the syringe and the relevant plunger are triggered to first thrust in the needle and then deliver the medicament. The needle retraction in the casing is obtained by stopping pressing the outer part end against the skin. This autoinjector allows a single dose of medicament to be administered. 
     An autoinjector device for automatic administering a single dose of a medicament is also known from U.S. Pat. No. 4,031,893. The autoinjector is equipped with an unlocking device with a deformable member for the driving device. The syringe plunger is axially connected to a rod comprising four flexible axial arms having a toothed end engaged on the edge of an opening formed on a cap placed at the end of the syringe housing. Cap sliding causes the arm ends to deform and their teeth to release from the opening edge. In this way the driving device is triggered. The autoinjector according to this document also comprises a safety device to prevent accidental deformation of the arm ends and triggering of the driving device, consisting of an insert centrally extending from the cap and capable of coming between the rod arms to prevent them from bending. 
     EP700307 discloses a two-dose autoinjector allowing the automatic delivering of a first dose of a medicament and the manual administration of a second dose. The autoinjector device according to this patent foresees the use of a syringe housed slidably in a tubular housing in two parts that can be separated to allow positioning of the syringe containing two doses of the medicament to be delivered and removal after use. The sliding of the syringe in the housing to penetrate the needle and inject the medicament is operated by an actuator movable between an armed position and an extended position. A releasable locking device is provided to limit the syringe plunger sliding to an extent corresponding to the volume of the first dose. The syringe is mounted in the tubular housing in a movable way to enable the locking device to be removed after the first dose is delivered and the plunger drive means to be armed again, if the second dose is to be automatically administered, or the syringe to be removed, if the second dose is to be manually administered. Furthermore the drive means is provided with a safety lock formed by a member engaging with a deformable pin of the drive means to keep it in a deformed condition, thereby preventing it to trigger. An autoinjector of this type is commercially available under the trade mark Twinject® and allows the first dose to be administered automatically, but the second dose must be manually administered. 
     The autoinjector according to EP651662 is designed to carry out a sequence of injections from a single syringe that is capable of performing a limited sliding movement in a tubular housing. The syringe has a plunger to deliver doses of a medicine through the needle and spring drive means engage with a piston rod and, once they are armed, retain the rod in a first position, while, when they are triggered, cause the rod to move forward and this causes first the syringe sliding and needle projection and then a controlled sliding of the plunger to deliver a medicine dose. Manual arming means are provided and means to trigger again the spring drive means. 
     The plunger rod has a toothed profile on which a catch of the drive means engages and the syringe is housed in a bushing capable of moving in a limited way in the tubular housing and provided with a further catch that is also engaged with the toothed profile of the rod. When the device is armed by the manual arming means, both the drive means and the bushing in which the syringe is placed are displaced toward the rear end of the tubular housing, the two catches engaging with the toothed profile of the rod. An axial groove connection between the bushing and the drive means allows a further sliding between the catch integral to the drive means and the toothed profile of an extent equal to the pitch of the profile. When the device is triggered, first the drive means cause the syringe bushing to slide up to a front stop and then the rod start sliding relative to the bushing catch for an extent corresponding to the profile pitch, whereby the displacement of a volume of medicine is enabled together with its deliver through the needle. 
     There is a strong need for an injector device for the automatic injection of a medicament in two successive doses which is user-friendly and is easier to manufacture as compared to the conventional devices. The object of the present invention is therefore to meet these requirements by providing a medicament autoinjector device capable of enabling the patient to self-administering two successive doses of a medicament in the easiest possible way, thus sparing the patient of performing potentially dangerous, complex dismounting/re-arming operations. 
     SUMMARY OF THE INVENTION 
     The basic idea of the invention is to control the locking and releasing of the drive spring of the autoinjector by providing stepped guide means with ramps for two successive slidings therealong of slide means operated by the spring and connected with the syringe and relevant plunger. The guide means and the slide means are pivotable relative to one another and the sliding direction, while the syringe can only slide axially, and the triggering control for each sliding is obtained by pressing a trigger, axially slidable relative to a stationary member, against the patient&#39;s skin to push the slide means first into one ramp and then into the other ramp of the guide means. 
     To enable or disable the sliding of the slide means within the guide means a angularly mobile arming member is provided formed with a guide track substantially equal to that of the stationary member where the guide means are formed. Following two subsequent angular arming displacements of the mobile member relative to the stationary member the ramps and the guide track are radially aligned to enable the slide means to slide under the action of the spring and therefore deliver the first dose and then the second dose. 
     According to one aspect of the invention, the injector device comprises a syringe assembly containing the medicament to deliver and arranged coaxially and slidably within an outer housing extending along a longitudinal axis and means for arming the device from a rest position to a first dose injecting armed position and a second dose injecting armed position, the device arming means being placed at one end of the outer housing. First elastic means that are in a compressed state when the device is in the rest position are provided between the syringe assembly and the device arming means. Device drive means are further provided for controlling the sliding of the syringe assembly from the armed positions to inject the syringe needle in an injection site and deriver the first dose and, if necessary, to deliver the second dose at a prefixed successive time. 
     The syringe assembly comprises a slide means engaged in stepped guide means inclined, but not incident, with respect to the direction of the longitudinal axis X and axially integral to the outer housing. The slide means and the guide means are pivotable relative to each other about the longitudinal axis and the drive means are axially slidable following separate and subsequent pressures against the injection site, thus causing a first relative displacement of the slide means from the first dose injecting armed position to a guide means alignment position, whereby the slide means is free to run therealong up to a first stop position, and a second relative displacement of the slide means from the second dose injecting armed position to a guide means alignment position, whereby the slide means is free to run therealong up to a second stop position. 
     In a preferred embodiment, the slide means is axially and pivotally mounted on the syringe assembly, the guide means are rotationally integral with the outer housing and the stepped guide means comprise an inner housing on which an inclined guide track with an intermediate land is formed, said land separating a first and a second inclined guide tract, and two end lands, on which the slide means rests in the first dose injecting armed position and, respectively, after delivering the second dose. 
     According to another aspect of the invention, the drive means comprise axial legs configured to act on the slide means to displace it from the first dose injecting armed position and, subsequently, from the second dose injecting armed position following corresponding axial movements of the drive means. In particular the drive means comprise a triggering slide movably arranged between the outer housing and the inner housing and projecting from the other end of the outer housing, and second elastic means are provided between the syringe assembly and the triggering slide to keep the latter projecting out of the outer housing. 
     Preferably, the triggering slide, comprises two diametrically opposed pairs of axial legs for causing the first displacement and, respectively, the second displacement of the slide means. In an embodiment of the invention the arms have a sloped profile and a length substantially equal to that of the first inclined tract and, respectively, the second inclined tract of the guide means. 
     Further features of the autoinjector device according to the invention are set forth in the attached claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the autoinjector device according to the invention will be apparent from the following description of an exemplifying, non-limiting embodiment thereof with reference to the attached drawings, in which: 
         FIG. 1  is an overall side view of the autoinjector device according to the invention, shown separated from its protective sheath; 
         FIG. 2  is a simplified, exploded view of the autoinjector device according to the invention; 
         FIG. 3  is a longitudinal sectional view of the autoinjector device according to the invention taken along lines III-Ill of  FIG. 1 ; 
         FIG. 4  is a longitudinal sectional view of the device for arming the autoinjector according to the invention; 
         FIG. 5  is an axial view in the direction of arrow A of  FIG. 4  (cap removed) of the autoinjector device according to the invention; 
         FIG. 6  is a perspective view of the syringe assembly mounted in the autoinjector device according to the invention; 
         FIG. 7  is a partial side view of the autoinjector device according to the invention with parts removed for clarity; 
         FIGS. 8   a  and  8   b  show, in two perspective views axially rotated by 90°, a tubular member of the autoinjector device according to the invention; 
         FIG. 9  is a perspective view of the syringe support of the autoinjector device according to the invention; 
         FIGS. 10   a ,  10   b  and  10   c  show, in two longitudinal views axially rotated by 90° and a perspective view, the inner housing of the autoinjector device according to the invention; 
         FIGS. 11 to 22  show the operational steps of the autoinjector device according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , the autoinjector device according to the invention comprises an outer housing  1 , having a tubular shape and equipped with a cap-shaped knob  3  at one end, while a tapered end of a trigger slide  30 , internal to the outer housing  1 , projects from the other end. The tapered end is closed by a needle cap  41  and an inner needle shield  42  sitting directly over the needle is housed in the needle cap  41 . Needle cap  41  and needle shield  42  are easily removable when the device is to be used in order to expose the needle ready for the first dose injection. The autoinjector is further provided with a protective sheath  40  sitting over the outer housing  1  when the device is in the storage state. 
     With reference also to  FIGS. 3 and 4 , the outer housing  1  extends over a longitudinal axis X between an open (or distal) end and a closed (or proximal) end, having a closure wall la, on which two diametrically opposed, arc grooves  2  (only one shown in  FIG. 5 ) are formed each having an angular extension of, for example, about 90°. The outer housing  1  further has an end portion  1   b  at its closed end with a lower diameter and defining a surface acting as a seat for the cap-shaped knob  3 . Two pins  4  engaging with grooves  2  extend from the bottom side of the knob  3 . The knob  3  is mounted coaxially to the outer housing  1  and is pivotable on the end portion  1   b  of the outer housing  1  and the extent of its clockwise or anticlockwise, angular displacement depends on the angular extension of the grooves  2 . 
     A rod  3   a  extends from knob  3  parallel to longitudinal axis X along the outer housing  1 . Rod  3   a  serves as pointer to indicate the actual operating condition of the autoinjector device (stored state, first triggerable state, i.e. ready for the first injection, second triggerable state, i.e. ready for the second injection) in combination to as many corresponding reference marks  5  (for instance consisting of reference numerals  0 ,  1 ,  2 ) arranged in a circumferential line on the surface of outer housing  1 . 
     A portion  1   c  of the outer housing  1 , extending from its open end, is formed with a greater inner diameter than the remaining part of the outer housing  1 , whereby a circular step  6  is formed between the two parts. Two diametrically opposed slots  7  are formed on the same portion  1   c  close to the step  6 , while two further diametrically opposed slots  8  are formed near the open end of the outer housing  1 . 
     The side wall of the end portion  1   b  of the outer housing  1  is formed with two diametrically opposed side grooves  9  and two tabs  10  projecting from the side surface of a tubular member  11  engage therewith. Tubular member  11  is open at its distal end and closed by a wall  11   a  at its proximal end. With reference also to  FIGS. 5 ,  8   a  and  8   b , the tubular member  11  is coaxially engaged within the tubular outer housing  1  and wall  11   a  is formed with two holes  12  for a fixed connection with the ends of the two knob pins  4  passing through the arc grooves  2 , whereby the tubular member  11  is integral to knob  3  and can angularly displace with it but cannot axially slide due to the bent-out tabs  10  engaging with the side grooves  9  of the outer housing  1 . 
     Two diametrically opposed, circumferential slots  13  are formed on the lateral surface of the tubular member  11  at an intermediate position and respective through guides  14  extend diagonally along the side surface of the tubular member  11  toward the distal end thereof, each with an angular extension of about 90°. The two through guides  14  have equal slope, but are symmetrically opposed relative to longitudinal axis X. 
     The two through guides  14  are formed each by a first and a second inclined tract  14   a  and  14   b  separated by an intermediate step  14   c  lying on a plane orthogonal to the longitudinal axis X and an end tract  14   d  extending longitudinally from the end of the second tract  14   b  to the open end of the tubular member  11 . 
     The first inclined tract  14   a  of the through guides  14  starts from an intermediate position of the respective circumferential slots  13  and defines in this way two slot parts  13   a  and  13   b  placed at the right side and at the left side of the first tract  14   a.  A flap  15 , the function of which will be explained later on, extends out from the lower side of the slot part  13   b  close to the first tract  14   a.    
     An inner housing  16  of tubular shape with open ends, shown in detail in  FIGS. 10   a ,  10   b  and  10   c , is coaxially housed in the tubular member  11 . Two diametrically opposed, longitudinal grooves  17  are formed on the inner housing  16  and at least a longitudinal cut  18 , serving as viewing window for the drug extends from the distal end thereof. Two radial teeth  19  extend outwardly from the inner housing  16  for engaging within the slots  7  of the outer housing  1 , preventing the inner housing  16  from moving linearly and rotationally relative to the outer housing  1 . A pair of radial projections  20  extend from inner housing  16  to rest against the step  6  (see  FIG. 4 ) of the outer housing  1  to further prevent any axial movement. 
     With reference to  FIG. 6 , a syringe assembly S is shown therein. The assembly comprises a syringe  21  with a needle  22  at its distal end. The syringe is housed in a tubular support  23 , also shown in  FIG. 9 , open at its ends and having an intermediate enlargement  23   c  fitting against the distal end of the inner housing  16 , wherein the tubular support  23  is partly housed. A window  23   d  is formed on tubular support  23  and is aligned to longitudinal cut  18  of inner housing  16  to make the syringe content visible from the outside. 
     The tubular support  23  is formed with bent-in edges  23   a  at its distal end against which the syringe distal end abuts, while two opposed radial projections  23   b  are formed at the other end on which a flange  21   a  of the syringe  21  rests. 
     The two radial projections  23   b  of the tubular support  23  are further configured to be slidably engaged within the longitudinal grooves  17  of the inner housing  16  to allow the tubular support  23  to axially move for a set extent, whereby the syringe housed therewith is correspondingly moved. 
     Two inclined guides  24  are formed on the wall of the inner housing  16  at diametrically opposed parts, said guides being inclined relative to the longitudinal axis X, but not incident thereto, because they are formed on the lateral surface of the inner housing  16 . In particular, as shown in  FIGS. 10   a  and  10   b , each inclined guide  24  comprises a first and a second ramp  24   a  and  24   b  separated by an intermediate land  24   c  and ending with two end lands  24   d  and  24   e  formed at the beginning of the first ramp  24   a  and, respectively, at the end of the second ramp  24   b.  The first ramp  24   a  has a length greater than the second ramp  24   b . The inclined guides  24  have equal inclination and a substantially equal extension of the through guides  14  of the tubular member  11 . 
     Inside the syringe  21  a plunger stopper  25  is slidably and sealingly housed and is connected to the end of a plunger  26  axially sliding within the inner housing  16 . In particular the plunger  26  has an enlarged intermediate portion  26   a  of a substantially cylindrical shape and diameter substantially equal to the inner diameter of the inner housing  16  in order to keep the plunger in axial alignment to the inner housing  16  when sliding therein. 
     As shown in  FIG. 6 , at the end opposed to that bearing the stopper  25  the plunger  26  has an axial stem  26   b  with an injection spring  27  arranged around it and placed between the wall  11   a  of the tubular member  11  and a cam plate  28  coaxially and slidably mounted on the stem  26   b  and placed close to the enlargement  26   a  of the plunger  26 . The injection spring  27  is mounted in a compressed state between the wall  11   a  and the cam plate  28  and therefore is pre-loaded when the device is in the rest or storage condition. 
     Two slide pins  29  extend radially from cam plate  28  at diametrically opposed sides thereof and are configured to rest on flaps  15  of the tubular member  11  when the device is in the rest or storage condition and to be able to slide in the respective inclined guide  24  of the inner housing  16 . 
     The inner housing  16 , which houses the syringe support  23  and the syringe  21  therein, both slidable in the axial direction, is arranged in the trigger slide  30  that is shaped with the tapered end from which the syringe needle  22  extends when the device is used. The syringe support  23  projects from the inner housing  16  starting from its intermediate enlargement  23   c,  which has an essentially cylindrical shape and a diameter substantially equal to the inner diameter of the trigger slide  30  to allow for the relative sliding while keeping the axial alignment. 
     A push-back spring  31  is placed between the intermediate enlargement  23   c  of the syringe support  23  and the tapered end of the trigger slide  30  in order to keep the syringe support  23  biased against the end of the inner housing  16 . From the trigger slide  30 , near its tapered end, there extend two diametrical teeth  32  (only one visible in  FIG. 1 ) which engage slidably in the slots  8  of the outer housing  1 , whereby the trigger slide  30  is enabled to slide axially over a distance equal to the length of the slots  8  relative to the outer housing  1 . 
     The other end (the proximal end) of the trigger slide  30 , which has a substantially tubular shape, is arranged between the outer housing  1  and the tubular member  11  and is configured in the shape of legs, which, in the present embodiment of the invention, are formed with sloped profile having substantially the same inclination as that of the inclined guides  24  formed on the inner housing  16 . In particular, as shown in  FIG. 7 , starting from said end the trigger slide  30  is formed with two diametrically opposed, longitudinal cuts  30   a  defining two portions of tubular surface each delimited by a first side coinciding with a generatrix of the tubular trigger slide and a second side inclined relative to said generatrix. The inclined side of each tubular surface portion is formed by a long leg  36 , starting from the proximal end of the trigger slide  30 , and a short leg  37  separated by a recess  38 . 
     When the autoinjector is operated, the slide pins  29  of cam plate  28  coaxial to stem  26   b  of plunger  26  slidingly engage, as said before, in the respective inclined guides  24  of the inner housing  16  passing through the through guides  14  of the tubular member  11  and abutting against the inclined profiles of the respective long and short legs  36  and  37  of the trigger slide  30 . 
     In summary, knob  3  and tubular member  11  are integral to each other and pivotable relative to the outer housing  1  and the tubular member  11  is unable to axially slide relative thereto. The inner housing  16  is fixed relative to the outer housing  1  and therefore is unable to move linearly and rotationally relative thereto. The trigger slide  30  is axially slidable relative to the outer housing  1 , but cannot rotate relative thereto, and the syringe support  23  is slidable axially in the inner housing  16  and in the trigger slide  30  against the push-back spring  31 . The plunger  26  is axially slidable in the inner housing  16  under the action of the injection spring  27  once it is triggered. Since the inner housing  16  is fixed to the outer housing  1 , the sliding of the slide pins  29  on the inclined profiles of the legs  36  and  37  and within the inclined guides  24  of the inner housing  16  causes the syringe support  23  and the plunger  26  to axially move. 
     The operation of the autoinjector device according to the invention is now described with reference to  FIGS. 11 to 22 . 
     In the stored condition, the injection spring  27  rests in a fully compressed state between the wall  11   a  of the tubular member  11  and the cam plate  28 , as shown in  FIG. 3 . The slide pins  29  of the cam plate  28  rest on the bent-out flaps  15  of the tubular member  11 , thereby securing the injection spring  27  in place ( FIG. 11 ). This to prevent creep of the mechanism over a medium to long-term storage period. The stem  26   a  of the plunger  26  also helps to prevent the compressed injection spring  27  from deflecting. The tubular member  11  is connected to the outer housing  1  through the projecting tabs  10  clipped in the grooves  9  to allow the rotation and prevent the translation of the tubular member  11  with respect to the outer housing  1 , when the knob  3  is rotated. 
     The inner housing  16  sits in the tubular member  11  and is fixed to the outer housing  1  by the teeth  19  and projections  20  preventing them from rotating and translating relative to each other. 
     The support  23  of the syringe  21  is seated in the trigger slide  30  and slidingly engages its radial projections  23   b  in the longitudinal grooves  17  of the inner housing  16 . The length of these grooves defines how far the syringe support  23  can move which ultimately sets the needle extension distance. 
     Once the protective sheath  40  is removed, to perform the first automatic injection the user must remove the needle cap  41  from the tapered end of the trigger slide  30 . In this step the needle is uncovered, but remains sub-flush within the tapered end of the trigger slide. 
     To arm the device for the first dose, the user must rotate the cap-shaped knob  3  by a set angle. Twisting the knob  3  from the position  0  (stored state) to position  1  (first dose armed state) causes the tubular member  11  to rotate a corresponding set angle, as it is integrally linked to the knob  3  ( FIG. 12 ), and the alignment of the first inclined tract  14   a  of the through guides  14  to the first ramp  24   a  of the inclined guides  24 . This action causes the slide pins  29  of the cam plate  28  to drop from the bent-out flaps  15  of the tubular member  11  onto the respective first lands  24   d  of the inclined guides  24  of the inner housing  16 , thereby allowing the injection spring  27  to decompress a small set distance. In this step no other components change position or orientation. The device is now armed and ready to be triggered by the user. 
     The device is triggered by the user pressing the tapered end of the trigger slide  30  against the injection site ( FIG. 13 ). Depressing the trigger slide  30  forces the component to move inside the outer housing  1  towards the opposite end. This causes the ends of the long legs  36  of the trigger slide  30  to exert a side force against the slide pins  29  of the cam plate  28 , which rotates around stem  26   b  to arrange the pins  29  into alignment to the first ramp  24   a  of the inclined guides  24  of the inner housing  16  ( FIG. 14 ), whereby these pins  29  are free to slide in the first ramp  24   a  under the action of the injection spring  27 . 
     Once triggered, the injection spring  27  is free to decompress and thereby forces the cam plate  28 , the plunger  26  and the syringe  21  forward, i.e. toward the distal end of the outer housing  1  ( FIG. 15 ). This movement also causes the syringe needle  22  to enter the injection site by a depth governed by the length of the longitudinal grooves  17  guiding the syringe support  23  on the inner housing  16 . In order that this movement can occur, the hydrostatic force required to expel the medicament from the syringe needle must be greater than the sum of the frictional forces to push the syringe assembly S forward to the specified needle injection depth. 
     Once the syringe needle  22  reaches the full injection depth ( FIG. 16 ), the injection spring  27  continues to decompress pushing the cam plate  28  and the plunger  26  forward with respect to the syringe barrel and causing the first dose of medicament to be expelled from the syringe. It is worth noting that the cam plate  28 , while axially moving, rotates around the stem  26   a  of the plunger  26 , as the slide pins  29  are constrained to slide in the inclined guides  24 . It is also worth noting that the length of the ramp  24   a  of the inclined guides  24  is such as to allow both the sliding of the syringe support  23 , to cause the needle to penetrate the skin, and the sliding of the plunger  26  to delivery the first drug dose. 
     The first dose delivery is complete once the slide pins  29  reach the intermediate land  24   c  of the inclined guides  24  on the inner housing  16  and the recess  38  of the trigger slide  30  ( FIG. 17 ). As the land  24   c  prevents the injection spring  27  from decompressing any further and the engagement in the recess  38  prevents the slide pins  29  from rotating any further, no more medicament will be expelled. 
     After delivery of the first dose, the user removes the device from the injection site. Since the pressure on the tapered end of the trigger slide  30  ceases, the push-back spring  31  moves forward the tapered end reducing the exposed needle length. Due to this sliding of the trigger slide  30 , the slide pins  29  come out from the respective recesses  38 , while being stopped on lands  24   c  of the guide  24 , as shown in  FIG. 18 . Then the user re-sheaths the device in the protective sheath  40  to avoid any needle damaging or injuries and waits for a prescribed time to decide if a second dose is necessary. 
     Should a second dose be required, the user must first remove the protective sheath  40  from the device in order to access the needle and then arm the device to prepare it for the second dose delivery. To this purpose the user must rotate the cap-shaped knob  3  by a prefixed angle. Rotating the knob  3  from position  1  to position  2  (second dose injecting armed state) causes the tubular member  11  to rotate a set angle. In this way the second inclined tract  14   b  of the through guides  14  is aligned to the ramp  24   b  of the inclined guides  24  and the slide pins  29  move along the intermediate land  24   c  up to reach a position ready to be triggered ( FIG. 19 ). 
     The device is triggered by the user pressing the tapered end of the trigger slide  30  against the injection site and causing the trigger slide to move toward the opposite end of the outer housing  1 . The end of short legs  37  of the trigger slide  30  comes into contact with the respective slide pin  29  and displaces it laterally on the intermediate land  24   c  up to bring it into alignment to the second ramp  24   b  of the inclined guide  24  on the inner housing  16 , thus allowing the slide pins  29  to freely move in the respective second ramps  24   b  ( FIG. 20 ) under the action of the injection spring  27  which depresses further. In this way a further sliding of the cam plate  28  and the piston  26  relative to the syringe barrel is caused to expel the medicament from the syringe, i.e. the delivery of the second dose. It is worth noting that, since the needle remains exposed from the first dose, there is no need to push the syringe assembly forward and therefore a lower length of the second ramp  24   b  with respect to the first ramp  24   a  is necessary. 
     The delivery of the second dose is complete once the slide pins  29  reach the end land  24   e  of the inclined guides  24  on the inner housing  16  ( FIG. 21 ). As the end land  24   e  prevents the injection spring  27  from decompressing any further, no more medicament will be expelled. 
     After delivery of the second dose, the user removes the device from the injection site. As the pressure on the tapered end of the trigger slide  30  ceases, the push-back spring  31  moves forward the tapered end ( FIG. 22 ). Finally, the user re-sheaths the device for its safe disposal. 
     The tubular member  11  is preferably made of metallic material to provide adequate protection to the syringe and to ensure a long-term storage of the device, as it is not prone to creep to the same extent that the other moulded device components would be. 
     The autoinjector device according to the invention is suitable to the delivery of medicaments in solution, especially epinephrine (also known as adrenaline). 
     In particular, the doses of epinephrine that can be administered with the device of the invention are preferably in the range of 0.05 mg to 0.5 mg for each delivered dose (from 0.1 mg to 1 mg if two doses are considered). 
     Preferred doses for each delivery are 0.05 mg, 0.10 mg, 0.15 mg, 0.30 mg and 0.50 mg. 
     The above doses are based on a concentration of the epinephrine solution preferably ranging from 0.05 mg/ml to 0.5 mg/ml, the concentrations 0.05 mg/ml, 0.1 mg/ml, 0.16 mg/ml, 0.3 mg/ml and 0.5 mg/ml being particularly preferred.