MXPA99011902A - Dose setting device - Google Patents

Abstract

By a dose setting device for a delivery system wherein a piston rod (6, 9) succesively presses a piston (2) into a cylinder ampoule (1) a dose is set by rotating a second part (9) of the piston rod (6, 9) in relation to a first part (6) which parts are connected by mating threads so that the total length of the piston rod (6, 9) is increased proportionally with the rotation and a point (18) on the second part is moved away from a stop position fixedin relation to a housing (5). The set dose is delivered when said point (18) is moved back to the stop position. The first part (6) can be axially displaced but not rotated in the housing (5), and the second part (9) can be as well rotated as axially displaced. The first part (6) is maintained in abutment with the piston (2) and the second part (9) is coupled to be rotated by a dose setting wheel (20). An injection push button (10) is movable between a projecting position and a pressed home position and has elements (13) acting on the second part (9) to press this part to its stop position.

Description

; DEVICE FOR DOSE ADJUSTMENT "Description of the invention and The invention is concerned with a device which adjusts the dose for a drug delivery system of the kind in which one end of a piston rod comprises a first part and a second part is pressed successively to a first end of a cylinder ampule containing a medication to press a piston which closes the first end of the vial to the vial in such a way that the medicament is expelled through a mounted delivery element In an extreme Indo of the bulb, the dose adjustment is provided by rotating the second part of the piston rod in relation to the first piston rod part, the parts are joined by the coupling of internal and external threads that are they find in the respective parts, in such a way that the total length of the piston rod is increased by a distance that is proportional nal with the extension of the rotation of the second part in relation to the first part and by which rotation of the second A part of a tip on this second part of the piston rod is ejected from a fixed retention position in relation to a ca, so that the adjusted dose is supplied when the tip is moved back to the position of retention, the first part of the and ~ ref; 32236 piston is guided in the box in such a way that it can be - i i. t axially displaced but not rotated and the second part of the piston rod remote from the piston is mounted in such a way that it can rotate, as well as move axially. EP 327 910 discloses a device by means of which doses can be adjusted by increasing the total length of the rod of a piston, which is connected to a piston of a bulb in the device and an extension of the piston rod that it is found, by means of a threaded connection, coupled to the piston rod. The increase is obtained by rotating the extension of the piston rod relative to the piston rod by rotating an element that adjusts the dose that can be rotated relative to the housing and consequently in relation to the piston rod. . A connection between the element that adjusts the dose and the extension of the piston rod makes the extension of the piston rod follow the rotation of the dose adjustment element. By the resulting increase in the total length of the piston rod and its extension, the outer end of the extension of the piston rod that was previously leveled with the end of the box is passed out through the end of the box. The prominent end of the piston rod extension is used as an injection button that can be depressed until it is again level with the box. By this, the piston is pressed to the bulb by a distance - i i? corresponding to the established increase in the total length of the piston rod and the extension of the piston rod. This process of adjustment and injection can be repeated until the vial is empty and the piston rod and its extension have reached a maximum length, time in which the entire device is discarded. ^ Similar dose-adjusting devices are used in durable devices where only the -f ampoule is replaced by a new one when it is empty. Before a new bulb can be mounted on the device, it is necessary to screw the two parts of the piston rod together to reduce the total length of the piston rod, including its extension to the original length it had before. the length was increased by means of repeated dose adjustments. As mentioned, the two parts have to be screwed together manually or the threading can be done with a separation, by which the friction angle for the material of the piston rod is exceeded, "in such a way that the parts, if allowed, will rotate one in relation to the other and in this way can be screwed between each other. When the parts are pressed axially towards each other, the threads can also be formed in such a way that they can be ejected from their mutual coupling when they are pressed towards each other.This axial compression or compression I can result by the movement of a part of the layer of the device in order to gain access to the space accommodating the bulb.With the device described in EP 327 910 the end of the piston rod emerges above the end of a syringe by a distance corresponding to the adjustment of In small doses this distance can be - t I be very small, less than 1 millimeter. It may be desired that the injection button has to be moved by the same distance regardless of the dose to be injected. A device in which that desire is satisfied is described in EP 245 312. In this device, an injection button with a push rod reciprocates between fixed end positions. The vast thrust -go has a length that allows it to join with the piston in the bulb when the injection button is pressed. If the length of the piston rod is increased by a distance corresponding to a set dose when the rod is in its retracted position, the next time the injection button is pressed I back press the piston to the bulb for a distance corresponding to lengthening provided by adjusting the dose. After injection the piston rod f _ i will again be removed from the piston. When the vial is empty, the push rod has been lengthened to approximately twice its original length and before a new bulb can be mounted on the device, the push rod must be screwed to its original length. A disadvantage of this device is that the push rod is ejected from the piston when the injection is finished and the injection button is no longer depressed, since the piston due to its elasticity and due to the pressure in the bulb can move towards back in the vial by which, also as the newly injected dose as the subsequent one becomes imprecise. While injection devices have so far had the form of a fountain pen, a trend now points toward shorter devices than, rather than having the shape of a small pack of cigarettes or slightly larger. One reason for this development may be that the bulbs with a "higher content, 3 milliliters instead of the previous 1.5 milliliters, demand a pen diameter that makes it impossible to maintain the fountain pen shape." * "While the device agrees With the EP 327 910 it could be provided with a rod of the flexible piston I to adapt it to a short device, the device according to EP 245 312 is not suitable for such adaptation since the piston rod complete and its extension they have to be moved alternately in a guide that fits the flexible rod, while the resistance against the movement of a flexible piston rod by means of a guide of the piston rod can serve as a barrier against the rearward movement of the piston rod. of the piston, it will be unacceptable if the piston rod I were to move alternately since such reciprocating movement is conditioned by a spring of restoration that can overcome resistance. When an injection is made, the injection button must be pressed with a force that also exceeds the resistance in the guide, the force of the spring and the force necessary to expel a liquid from the vial and inject it. It is an object of the invention to provide a device that adjusts the dose that is appropriate for short devices. This is obtained by means of a device as described in the introduction to this application, which device according to the invention is characterized in that the first part of the piston rod is held in abutment or butt connection with the piston in the bulb, the The second part of the piston is coupled to gear teeth which are engaged with gear teeth on a dose adjustment drum, to rotate the second part of the piston rod when the dose adjustment drum is rotated and a Injection mechanism Ique 1- f comprises an injection button that can be moved between a projection position and an original position depressed and r which injection mechanism has elements acting t on the second part of the piston rod to make this move second part, such that the tip of the second part is moved to its position of retention when the retention button is pressed to its original position. In one embodiment of the device according to the invention, the threads can and can not be self-locking, the gears that engage with the teeth of the dose adjustment drum must be locked against unintentional rotation t relative to the box and the holding position can be defined by an end position by a surface of a lifting element forming part of the injection mechanism, which lifting element can be reciprocated ^ between fixed end positions and the tip of the second part The piston rod can be defined as an end tip at the end of this second part of the piston rod, which tip of the end, spliced with the surface, forms a pivot around which the second part of the piston rod can turn when it is not blocked against such rotation.

When the threads joining the two parts of the piston rod are not self-locking, the two parts can be pressed together if they are allowed to rotate one relative to the other. However, the first part does not '? i can rotate in relation to the box and since the second part \ carries a gear that engages the teeth of a serrated dose adjustment drum which is again locked against unintentional rotation relative to the box, both parts can not be rotated together, unless special precautions are taken. Movement of the injection element by a constant distance each time an injection button is depressed is ensured by the provision of an injection element that can be moved alternately between fixed end positions. When this element is in its end position defined by the "fact that an injection button is pressed to its original position, a surface of the element defines the holding position at which a point of the second part of the piston rod is moved when the injection button is pressed to its original position, the fact that the tip is a tip of the end at the outer end of the second part of the piston rod, which ends at the end of the piston rod. in splice with the surface forms a pivot around which f [the second part of the piston rod can rotate when not > "| it is locked against such a relationship, ensures that the piston rod will either transmit axial forces from one end of the piston rod to the other or its parts will rotate in such a way that the two parts are screwed together and the active piston rod is shortened. If the dose adjustment drum is rotated voluntarily to -! setting or setting a dose, the second part of the piston rod is rotated in relation to the first part to change the length of the piston rod according to the relative rotation as the rotation of the dose adjustment drum is rotated voluntarily To set a dose to be set, the second part of the piston rod is rotated relative to the first part to change the length of the piston rod according to the relative rotation as the rotation of the drum that adjusts the dose is transmitted to the second part of the piston rod by means of the gear. According to one embodiment of a device according to the invention, a connection of a cap covering the ampoule can eject the piston rod away from the piston, unblock the drum that adjusts the dose for its rotation and move the second one. part of the rod of the piston towards the surface of the lifting element to make the tip of the end of that second part spliced with the surface when the part is open. When the first part of the piston rod is moved away from the piston the nut element will be pressed towards the surface of the lifting element and because the threads are not self-locking and because the second part of the piston rod is freely rotating the element of nut will induce a rotation of the second part of the piston rod . - \ piston and in this way will be moved to the other end of the second part of the piston rod to be separated for a series of new adjustments and dose injections. In a preferred embodiment of a device 1 according to the invention the threads can be self-locking, the holding position can be defined by a fixed arm or lever in the box, which lever can be connected by a fixed element to the second part ^ The piston rod and the nut element can be directed in such a way that their threads can be freely coupled from their engagement with the threads of the second part of the piston rod. _ i ~ Self-locking threads may have a smaller spacing than threads that do not. { they are self-locking and a threading with smaller spacing: i provides a more precise adjustment of the dose. With the rotation of the self-locking or self-locking threads of the second part of the piston rod, it is not possible to depend on i when the nut element is to be moved along the length of the piston rod. ~~ i is apart and the nut element has to be coupled In the piston, the nut element is incunably mounted to the first part of the piston rod so that the threaded bore is concentric with the second part of the piston rod during the adjustment or injection of the dose and is tilted by the connection acting on the nut element to bring the smooth perforation to a concentric position with the second part of the piston during the removal of the piston rod. __ In the following, the invention will be described in further detail with reference to the drawings, wherein: r Figure 1 shows schematically a syringe with a dose adjustment mechanism according to the invention in a condition prepared for the adjustment of the I I dose. Fig. 2 shows the syringe of Fig. 1 in a condition at the end of an injection, Fig. 3 shows the syringe of Fig. 1 in FIG.

Z- ^ 'a condition in which the vial is freshly emptied, Figure 4 shows the syringe of figure 1 in a' condition where it is open for the replacement of an empty vial, Figure 5 shows schematically a detail of - f Another embodiment of the dose adjusting mechanism, Figure 6 shows a sectional view along the line VI-VI of Figure 5, Figure 7 shows a sectional view of an incunable nut element with two perforations in FIG. a position wherein the threaded bore is concentric with a threaded spindle and Fig. 8 shows the nut element of Fig. 7 inclined to a position where its smooth bore is concentric with the spindle. In figure 1, a bulb 1, which is located at one end closed by a piston 2 and at the other end I closed by a rubber or rubber membrane not shown to receive a center or hub 3 of needle with a needle 4 of injection, is contained in the box 5 of an injection device, the box 5 is indicated by a frame of broken lines. The piston is driven by a long-lasting flexible piston consisting of a first flexible part 6 which can be, for example, constructed as a coil and hermetically sealed propeller of resilient steel. One end of the flexible part 6 acts on the piston 2 by means of a shoe 7 of the piston rod while the other end piece is flexed by a guide not shown 180 ° from the first end and is provided with a nut element has an internally threaded opening. An externally threaded spindle 9 is carried in this opening with its thread which engages with the internal threading of the opening of the nut element 8. This spindle forms a second part of the piston rod. By rotating the spindle 9 in which the nut element 8, the total length of the piston rod can be changed by varying the part of the second piston rod part that lies in the extension of the first part 6. An injection mechanism comprises an injection button 10 at the end of an articulated bar 11, a gear 12 and a lifting element 13 having an articulated arm, the joints of the bar 11 and the h articulations of the arm of the lifting element 13 are located on diametrically opposed sides coupled by the gear 12 that can rotate around a fine bolt to the housing whereby a downward movement of the injection button 10 and the bar 11 is converted to an upward movement of the element of rising 13, that can! the outer end of the spindle 9 is pressed and by this the piston rod is pressed in an axial direction, so that its piston rod drives the piston 2 II further to the bulb 1. When the device is ready for injection, a The spring not shown will push the injection button 10 to the projection position shown in relation to the box and the lifting element to a lower position. By injection the injection button 10 can be depressed to its original position to join the box 10 where the splice parts 14 are indicated. Seals not shown define the extreme positions of the parts of the injection mechanism. These I extreme positions are indicated by lines 15 and 16 that indicate the position more ^ lower and uppermost i respectively, of a surface 17 of the lifting element 13. The distance _ between lines 15 and 16 is marked with the letter D. | ? In Figure 1, the tip 18 of the outer end of the spindle 9 falls on a line 16 depressed to this position l by the lifting element the last time the injection button 10 was pressed to its original position to engage with the box. A dose can now be _ 1 i set or adjusted by screwing the spindle 9 outwardly into the nut member 8 to cause its tip 18 on the end to fall between the lines 15 and 16. The size of the! dose is defined by the distance between point 18 of the! and the line 16 as the tip of the end 18 moves back to this line when the injection button 10 is depressed to its original position. The spindle is provided. { with a gear 19 which engages internal teeth on a drum 20 for adjusting the dose. The drum has a background 21 with radial knurls which engage with corresponding radial knurls on a disk 22 which is pressed by a spring 23 against the bottom 21 of the drum 20, the knurls are designed in such a way that they move with audible clicks on each other every time the drum 20 is rotated by a certain angle, for example corresponding to the alteration of the dose adjustment by one unit. A dose can be adjusted by rotating the drum 20. This rotation will be transmitted to the spindle which is bolted out on the nut member 8 by a distance corresponding to the rotation of the drum 20 of the dose adjustment. It should be noted that too large a dose can be reduced by rotating the drum 20 in the opposite direction. The rotation of the dose adjusting drum 20 is detected electronically and transmitted to an indicator, whereby the size of the figures on the screen is independent of the physical size of the dose setting drum 20 and all other advantages obtained through adjustments and electronic screens are obtained. Figure 2 shows a-l device with the button! 10 of injection pressed to its original position to splice with the box as it appears after a dose has been injected. A ! lock not shown is provided which keeps the injection button 10 in this position until it is released again, for example when the dose adjustment drum 20 is put into operation. Also, when the apparatus is stored until the next injection, the injection button is kept in its original depressed position. * • Figure 3 shows the device in the same condition as figure 2 but in figure 3 the ampoule -i is "empty and a new element 24 is shown.This element consists of an extraction element of the piston rod which is Attached to an extraction element wherein the bulb is retained Figure 4 shows how the element 24 moves the nut element towards the surface 17: - t of the "lifting element when the bulb 1 is removed to be changed. As the injection button is locked in the original pressed position the tip 18 of the end of the spindle is connected to the surface 17 of the lifting element which is consequently locked in its shown position. Surface 17 and ^ t tip 18 forms a pivot around which the spindle can rotate, if allowed. When the vial box is opened, the disc 22 is initially withdrawn at a distance from the bottom 21 of the drum 20 by dose adjustment and in this way the dose adjustment drum 20 is free to stop rotating. A condition that must be satisfied is that the threads of coupling of the spindle 9 and the element 8 of and 1 nut are not self-locking, that is, that the angle of inclination for the threading is greater than the angle of friction for the threaded materials. Figure 5 shows a detail of another embodiment of a dose adjustment mechanism according to the invention.

In this embodiment, a spindle 25 forming the second part of the piston rod has an axial bore, the inner wall of which is provided with a variety of longitudinal grooves 26. The spindle 25 is screwed i by means of a nut element 27 at the end of the first flexible part 6 of the piston rod by means of which "the spindle 25 is divided into a protruding part forming an extension of the first part 6 of the piston rod and a part falling behind the element 27. of nut f The part behind the nut element 27 is rotatably guided and axially displaceable in a The opening in a lower arm or lever 29 of a fixed E-shaped construction in the box. A flange 28 at the end of the spindle 25 limits the axial movement of the spindle and thus is also rotatable as the spindle 25 will advance to its engagement with the nut member 27 which will be displaced longitudinally when it is rotated until the flange 28 splices either with the middle arm r of the E-shaped construction or the lower arm 29 of this construction. 1 ! A mainly cylindrical carrier 31 is inserted at the end projecting from the end of the - ^ L spindle. The carrier has on its outer cylindrical wall longitudinal grooves 37 which engage with the longitudinal grooves 26 in the internal wall of the bore in the spindle 25 as seen in Figure 6, in such a way that the rotational movement of the carrier 31 is transmitted. to the spindle 25 while the carrier 31 can be moved axially to the spindle 25. On its surface of the outer end II, the carrier 31 is knurled to engage with corresponding knurls in the gear element 32 which has teeth that engage a flange inner teeth 33 in the drum 20 that adjusts the dose. A bolt 35 running through the axial bores in the gear element 32 and the carrier 31 is at its end and projects through the gear element 32 terminated by a disk 36 secured to the bolt. The bolt extends through the bore of the spindle 25 and through a bore in a counting member 38 mounted on a mainly cylindrical rod I inserted at the end of the spindle 25 that carries the flange 28. The outer cylindrical wall of the This rod provides grooves 40 which engage the slots 26 in the spindle 25, so that the rod can be displaced axially but the rotation of the spindle 25 must follow. The counting element is placed between the middle arm 30 and an upper arm 41 of the E-shaped construction and has on its external wall means f not shown to activate contacts or detectors not shown fixed in the box to verify the extension of rotation of the counting element 38 and consequently of the spindle 25 which The counting element is limited to follow The bolt extends through the rod 39, the counting element 38 and the ex co ta the respective ends of the spindle 25, this is the carrier 31 and the rod 39, are separated by pressure by a spring 42 positioned in the bore of the spindle 25. By this the knurls of the carrier 31 are pressed in engagement with the knurls of the gear element 32 and a wall in e ' The end of the counting element is pressed or pressed in engagement with a surface of the upper arm 41 of the I construction in the form of an E. The surface of the upper arm - it 41 which provides with engaging protrusions 43 Icon coupling depressions 44_ on the end wall of the counting element. When setting or adjusting a dose by rotating the dose adjustment drum 20, the flange The toothed 33 of this drum will rotationally urge the gear element 32 from which rotation will be transmitted via the carrier 31 to the spindle 25 unless this spindle t is in a position where its flange 28 is connected with the lower half rockers. 29 or 30 respectively and the rotation is in a direction that causes the flange to move further towards the arm in question, in which case the coupling formed by the knurled surfaces of the gear element 32 and the carrier will be released when the knurls slide one over the other. the other as the carrier 31 can be pressed away from the gear element against the force of the spring 42. In this way the transmission of rotational forces which could be damaging to the device is prevented. By injection "I will be moved to join with the middle arm 30 of the E-shaped construction. From this position a dose is adjusted by screwing the flange away from the intermediate arm 30. The size of an established dose is determined by the distance established between the flange 28 and the * middle arm 30 and a limit to the dose that can be set is determined by the rotation necessary to cause the flange to be connected to the inner arm 29 of the E-shaped construction. " When the spindle 25 is rotated, the rod 39 of the counting element 38 will follow this rotation and the protuberances 43 on the upper arm 41 will slide out of the depressions 44 by pressing the counting element 38 away against the force of the spring 42 until the projections find new depressions to fit. The protuberances and depressions may be provided with a circumferential spacing which makes the number of clicks provided by the successive couplings indicative of the size of an established dose. When a dose is adjusted and the flange is thereby separated from the intermediate arm 30 of the E-shaped construction, injection can be carried out by depressing the injection button of the device t to pull pin 35 towards the end of the stem of the device. piston. The spindle 25 forming the second part of the piston rod is driven by a shoulder 45 which is located on the gear element which is connected to a t end surface 46 of the spindle 25. A play between the shoulder 45 and the end surface 46 ensure that the! The gear element 32 is ejected from engagement with the toothed flange 33 before or at an earlier stage of the injection. In this way the dose adjustment drum I is released in such a way that the size of the dose can not be ; [influenced during the injection. It should be noted that the injection button must have a sufficient stroke to allow the lifting element to lift the free engagement element 32 from the toothed flange 33 and to make it move ~~ l the spindle at a distance corresponding to the maximum dose that can be adjusted. The coupling threads of the nut element 27 and spindle 25 are self-locking. This allows a smaller separation of the threads and ensures a more accurate dosage. However, care must be taken to ensure that the threading of the nut element 27 can be removed from engagement with the threads of the spindle in such a way that the nut element can be moved from one end of this spindle to the other. without rotating the spindle, when the piston rod is removed to be space for a new filled vial when an empty vial is removed to be replaced. Figures 7 and 8 show a nut element 27 That has a first and a second perforation, the use of which intersects when forming an acute angle to each other, the first perforation has a diameter corresponding to the end diameter of the rod 25 of the threaded spindle and the second perforation has a internal thread that engages r - - j. with the external threading 47 of the piston rod only in part of this second bore which are not depressed by the first bore ^, -During the adjustment of "the dose and injection, the nut element 27 is in the position shown in FIG. Figure 7 with its second coaxial perforation with the spindle 25 and the threading 48 in this hole that engages with the threading 47 of the spindle 25. When the spindle is screwed down in the nut element 27 to adjust a dose or is raised up to inject an established dose will attempt to rotate the nut member in the direction of the arrow 49 about a pivot pin not shown at the end of the first part of the piston rod which pivot pin engages a stump 50 i fixed on the nut element 27. When the element = - f of nut by a withdrawal element of the piston rod is driven to an edge diametrically opposite the pivot pin as indicated by the arrow 51 of the nut member 27 is inclined around the pivot pin to bring the first bore to a position wherein it is coaxial with the spindle 25. Since the piston rod due to its resistance against withdrawal acts on the nut member 27 in the direction of the arrow 52 of the nut member 27 it will be held in its inclined position - I where it can be slid on top of the threading 47 on the spindle 2b during the separation of the ~ _ ~ i piston rod. In figures 7 and 8 the dotted lines l indicate the direction of the perforation non-coaxial with the spindle. It is noted that, in relation to this date, the best method known by the applicant to carry out the aforementioned invention is the conventional one for the manufacture of the objects to which it refers.

Claims (6)

1. CLAIMS ii Having described the invention as above, the content of the following claims is claimed as property: 1. A device that adjusts the dose for a drug delivery system of the kind wherein one end of a piston rod comprising a first part of a second part is successively pressed to a first end of a cylindrical vial containing a medicament for pressing a piston that closes the first end of the vial to the vial in such a way that the medicament is expelled through a supply element mounted on the second end of the bulb, dose adjustment is provided by rotating the second part of the piston rod in relation to the first part of the piston rod, the parts are joined by internal threading engagement and which are in the respective parts in such a way that the total length of the piston rod is increased the distance is proportional to the extent of rotation of the second part "in relation to the first part and by means of which rotation of the second part, a tip on this second part of the piston rod is ejected from a holding position fixed in relation to a box, in such a way that the established dose is administered when the tip is moved back to the holding position, the first part of the piston rod is guided in the box in such a way that - l can be moved axially but not rotated in the second part of the piston rod remote from the piston, which is mounted in such a way that it will be rotated and displaced t I axially, characterized in that: the first part of the piston rod is maintained in splicing with the piston in the bulb, the second part of the piston is coupled to a gear that engages with gear teeth on a 1 'dose adjusting drum ^ to rotate the second part of the piston rod when the drum which adjusts the dose is rotated and an injection mechanism is provided which comprises a push button which can be moved between a projection position and a pressed original position and which injection mechanism has elements acting on the second part of the rod of the piston to move this second part, in such a way "that the tip in the part is moved to its detent position when the push button is oppressed to its original position. I
2. 2. The device that adjusts the dose according to claim 1, characterized in that the threads are not self-locking, "the gear that engages with the teeth of the dose adjustment drum is blocked against unintentional rotation I in relation to the box, and the holding position is defined by "an I" - 1 position of the end of a surface of a lifting element that forms part of the injection mechanism, which lifting element can be moved I alternately between end positions fixed if the tip of the second part of the piston rod can be defined as an end tip or end of this second part of the piston rod, which tip of the end in splice with the "surface forms a pivot around of which the second part of the piston rod can be rotated when it is not blocked against such rotation
3. 3. A device that adjusts the dose according to the reivi 2, characterized in that a connection of a cap covering the ampoule pushes the piston rod I away from the piston, unlocks the drum that adjusts the dose for rotation and moves the second part of the piston rod towards the piston. surface of the 1 \ lift element to make the tip of the end of this second part splice into the "surface when the lid is opened.
4. 4. A device that adjusts the dose according to claim 1, characterized in that the coupling thread is self-locking, the holding position is defined by a fixed arm in the box, which arm is connected by a fixed flange to the second Part of the I piston rod and the nut element is designed in such a way that its threading can be coupled coupling free with the threading of the second part of the piston rod. - __ i of the piston.
5. 5. A device according to claim 1, characterized in that the nut element I has two perforations that form an angle between each other and of which "a perforation has an internal thread that engages with the external thread of the second part". of the piston rod and the other bore is smooth and slidably fits over the threading of the second part of the piston, the nut element is mounted incunable to the piston rod part in such a way that the threaded bore is concentric with the second part of the piston rod during dose adjustment and injection and is inclined when the nut member is actuated to bring the smooth perforation to a concentric position with the second part of the piston.
6. 6. A device according to claim 5 , characterized in that a connection of one - '* f cap "" that covers the bulb drives the piston rod to ^ - I away from the piston when acting on the nut element that inclines this element to bring the smooth perforation to a concentric position with the second part of the piston rod during the opening of the lid.