DRIVE DEVICE FOR INJECTION DEVICES

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of medical injection devices for administering liquid substances, in particular medications or medicinal substances such as insulin and hormone preparations. The invention relates to a space-saving drive device with a piston rod for advancing a stopper in a product container of an injection device. BACKGROUND

[0002] Injection devices or injection apparatuses for the simplified administration of a substance include, among others, so-called auto-injectors, which have an energy storage or drive element with which the dispensing can be carried out automatically, without any external force being applied or exerted by a user. The energy storage or drive element advantageously stores the entire energy required for automatic substance dispensing in mechanical form. Such an energy storage or drive element can, for example, be a spring, which is installed in the injection device in a tensioned state and can release energy when released. The energy is advantageously released to a piston rod or a pressure element, which can push a plug into a product container. Optionally, the energy storage or drive element can also be provided to automate the process of inserting an injection needle.Alternatively, a further separate drive element can be provided for this purpose, or the piercing process can be carried out manually, i.e. by a user, without using energy stored in the injection device.

[0003] The injection device can comprise a product container holder for receiving a product container, wherein the product container can be held fixedly, in particular axially and preferably rotationally fixed, in the product container holder. The product container holder can be connected axially and rotationally fixed to the housing of the injection device, or can be movable relative to the housing during a piercing and / or needle retraction process. The product container can be a carpule or a pre-filled syringe known from the prior art with an injection needle permanently connected thereto. The product container has a hollow cylindrical product container section that displaceably supports a piston or stopper. The piston can form a sealing gap with the inner circumference of the product container section and can be displaced in a distal direction by means of a piston rod in order to dispense product from the product container via the injection needle.

[0004] The injection device can have a needle protection sleeve which, after the injection has been completed, extends distally over the distal end of the injection needle or is moved into this position relative to the housing while a needle protection sleeve spring is released in order to prevent accidental access to the injection needle and thereby reduce the risk of injury. In an auto-injector, the needle protection sleeve can also serve as a trigger element for triggering the product dispensing, whereby the needle protection sleeve is moved in the proximal direction relative to the housing for this purpose. Alternatively, the auto-injector can be triggered by pressing a trigger button on the auto-injector, whereby the needle protection sleeve serves at least as a visual screen before use of the auto-injector.

[0005] Patent application EP 2781230 describes an auto-injector for automatically dispensing a medicinal substance by means of a pre-tensioned dispensing or injection spring, which presses a stopper into a pre-filled syringe via a piston rod. The injection device further comprises a needle shield that is longitudinally displaceable between a proximal and a distal position. The needle shield is coupled to a needle shield spring as a separate drive element, which pushes the needle shield into the distal position after the substance has been dispensed, in which position it laterally surrounds or shields the needle. A movable stop element, serving as a feedback device for generating an acoustic signal after a specific amount of substance has been dispensed, is accelerated toward a stop by the needle shield spring.A second feedback device with a stop element accelerated by the dispensing spring signals the start of substance delivery. The needle shield spring is located in a proximal part of the auto-injector and surrounds the piston rod in its initial position.

[0006] WO 2005 / 115514 A1 describes a drive element in the form of a piston rod with, at a distal end of the piston rod facing the stopper, a conical tip surrounded by an annular drive surface. The piston or stopper of a syringe has a central bore or recess with an internal thread on its proximal side, into which the tip of the piston rod protrudes during dispensing. The bore of the stopper is surrounded by an annular support surface which comes into contact with the drive surface of the piston rod during dispensing. A proximal, rotationally symmetrical opening of the syringe is funnel-shaped, its inner surface having a minimum radius in a plane encompassing the longitudinal axis.The combination of the plunger rod tip as a centering aid with the rounded inner shape of the syringe allows for the compensation or correction of any inadequate axial alignment of the plunger rod and syringe when inserting the latter into the proximal opening of the syringe. The maximum radial width of the annular drive surface is in any case less than one-fifth of the total diameter of the plunger rod.

[0007] DE 10 2007 013 838 A1 discloses an injection device with a product container and a functional sleeve arranged proximally thereto, which surrounds a piston rod for product dispensing. The piston rod has a sleeve-shaped part that surrounds a drive spring, wherein the drive spring is supported distally on the piston rod and proximally on a switching sleeve. During a triggering process, the switching sleeve is released, allowing the drive spring to partially relax, whereby the carpule, together with a carpule holder and the functional sleeve, is displaced in the injection direction. As a result, the injection needle is pushed out over the distal end of the injection device and penetrates the injection site.

[0008] WO 2016 / 205962 A1 discloses an autoinjector comprising a two-part piston rod, which includes an inner threaded rod and an outer sleeve-shaped propulsion member threadedly connected to the threaded rod. The threaded rod is connected to a preloaded coil spring that stores the energy necessary for product delivery.

[0009] WO 2016 / 042075 A1 discloses an electric auto-injector with an electric motor arranged within a sleeve-shaped piston rod. The piston rod has a flange at its distal end, which can displace a plug in the product container. During dispensing, the motor drives a drive wheel, which has a threaded segment on its outer side that is connected to an internal thread of the piston rod. The rotating drive wheel causes the piston rod to be displaced in the dispensing direction.

[0010] US 2016 / 0015901 A1 discloses an injection device with a piston rod having a button-shaped end at the distal end. This is connected to a flange during assembly. For this purpose, the flange has an opening in the center. The material around the opening is flexible, allowing the opening to be expanded to join the piston rod to the flange, allowing the button-shaped end to be guided through the opening.

[0011] The term "product," "medicine," or "medicinal substance" in this context encompasses any flowable medicinal formulation suitable for controlled administration via a cannula or hollow needle, for example, a liquid, a solution, a gel, or a fine suspension containing one or more medicinally active ingredients. A product or medicine can therefore be a composition containing a single active ingredient or a premixed or co-formulated composition containing multiple active ingredients from a single container. The term particularly includes medicinal products such as peptides (e.g., insulins, insulin-containing medications, GLP-1-containing and derived or analogous preparations), proteins and hormones, biologically derived or active ingredients, hormone- or gene-based active ingredients, nutritional formulations, enzymes, and other substances in both solid (suspended) and liquid form.The term also includes polysaccharides, vaccines, DNA or RNA or oligonucleotides, antibodies or parts of antibodies as well as suitable base, auxiliary and carrier substances.

[0012] The term "distal" refers to the direction in which the tip of the injection needle points, and the term "proximal" refers to the direction opposite the distal direction. PRESENTATION OF THE INVENTION

[0013] It is an object of the invention to provide an injection device with a reduced space requirement and a reliable drive with sufficiently homogeneous force application to a displaceable plug. This object is achieved by an injection device according to claim 1. Further advantageous embodiments are set out in the dependent claims.

[0014] An injection device according to the invention for administering a product comprises a housing for accommodating a product container with a product receiving space for receiving the product. A plug with a support surface for pouring the product out of the product receiving space is displaceable in the product container in the direction of a longitudinal axis of the injection device up to a plug end position. Proximal to the plug end position, at its narrowest point, the product container has a minimal product container cross-section in a plane perpendicular to the longitudinal axis. The injection device further comprises a drive for displacing the plug, comprising a piston rod with a piston rod cross-section perpendicular to the longitudinal axis and a plug-side drive surface for driving the plug through force-fitting contact with its support surface.The injection device also comprises a piston rod guide arranged proximal to the product container in the housing, having a guide cross-section perpendicular to the longitudinal axis for guiding movement of the piston rod in the direction of the longitudinal axis. The guide cross-section is adapted or matched to the piston rod cross-section and limits movement of the piston rod cross-section in all directions perpendicular to the longitudinal axis to a manufacturing minimum. The product container itself guides the movement of the piston rod in the direction of the longitudinal axis at most incompletely or asymmetrically, so that the piston rod cross-section is not hindered by the product container cross-section at least from a lateral movement in a first tilting direction perpendicular to the longitudinal axis.A piston rod centering aid is provided at a distal end of the piston rod to limit the movement of the piston rod cross-section in the first tilting direction or to limit the tilting of the piston rod. Thus, the piston rod centering aid also counteracts a rotationally asymmetrical drive force distribution across the support surface.

[0015] In an advantageous variant of the invention, a circular product container cross-section with a first diameter is assumed, whereby for other, for example oval, cross-sectional shapes, the geometric considerations regarding the longitudinal guidance of the piston rod would have to be adapted accordingly. Likewise, circular guide and piston rod cross-sections with a second or third diameter are advantageously assumed, whereby angular, coordinated cross-sectional shapes are also conceivable, at least as long as a smallest circle encompassing the piston rod cross-section can fit within the product container cross-section. With the aforementioned designations, the first diameter is larger than the second diameter, and this in turn is not smaller than the third diameter. Preferably, the first diameter is at least four or even seven percent larger than the third diameter.In another advantageous variant, the plug comprises a central recess within the support surface, preferably a circular bore with an optional internal thread. Accordingly, the support surface is advantageously a circular ring.

[0016] According to the invention, a piston rod with a maximum outer diameter is used, which is preferably at least four percent smaller than the diameter of the product container. The resulting loss of longitudinal guidance of the piston rod through the product container is compensated for by a centering aid at the piston rod tip, which counteracts inaccurate or inadequate alignment of the piston rod in the product container. In this way, space can be saved in the housing in the area of ​​the piston rod guide and the drive without the risk of an unforeseeable or even unsafe deviation of the alignment of the piston rod from the longitudinal axis. The piston rod centering aid is preferably made of the same inelastic material as the piston rod.

[0017] In a first preferred embodiment of the injection device, the piston rod centering aid comprises a centering flange for enlarging the piston rod cross-section. The centering flange thus has a maximum flange diameter that is larger than a maximum outer diameter of the piston rod and smaller than a minimum inner diameter of the product container. The centering flange is preferably arranged flush with the drive surface, so that the force transmission surface is also larger than with a piston rod distal end without a centering flange.

[0018] In a second embodiment of the injection device not according to the invention, the piston rod centering aid comprises only one centering truncated member, in particular a truncated cone or pyramid. The centering truncated member has a base diameter that is smaller than the diameter of the bore of the plug. The centering truncated member can be combined with the aforementioned centering flange in a further preferred embodiment according to the invention.

[0019] The invention also relates to a drive for an injection device and a piston rod for a drive for an injection device. Furthermore, further embodiments and configurations are directly and obviously recognizable to the person skilled in the art, which result from combinations of the described examples or combinations of the described examples with the general technical knowledge of the person skilled in the art. The original references of the dependent claims are not intended to exclude further combinations of claims or features. FIGURES

[0020] Preferred embodiments of the invention are described below in conjunction with the attached figures. These are intended to illustrate basic possibilities of the invention and are in no way to be interpreted as limiting. Fig. 1 shows a longitudinal sectional view of an injection device, Fig. 2 shows an oblique plan view of a first embodiment with a centering flange, Fig. 3 shows a longitudinal section of the first embodiment, Fig. 4 shows an oblique plan view of a second embodiment with a centering cone, Fig. 5 shows a longitudinal section of the second embodiment, Fig. 6 shows two longitudinal sectional views of an auto-injector in an initial state, and Fig. 7 shows two longitudinal sectional views of the auto-injector in a triggered state.

[0021] The reference symbols and their meanings are summarized in the list of reference symbols. In general, the same reference symbols refer to the same parts. FIGURE DESCRIPTION

[0022] Fig.1 shows a longitudinal sectional view of an injection device. The injection device comprises a sleeve-shaped, in particular cylindrical, housing 1, on which a product container holder 11 and an end cap 12 are arranged. The product container holder 11 and the end cap 12 can be latched, glued, welded, locked, or snapped to the housing 1, or can be individually or entirely formed as one piece with the housing 1. A product container 2 can be received in the product container holder 11 and held thereby. The product container comprises a hollow-cylindrical product receiving space 22 delimited by a plug 21 that can be displaced along a longitudinal axis of the product container 2.During start-up, the product receiving chamber 22 contains a product to be dispensed, which product can be displaced out of the product receiving chamber 22 by moving the plug 21 in a displacement direction from a plug start position to a plug end position. The plug 21 has, on a side facing away from the displacement direction, an annular bearing surface 211 surrounding a central bore 212 or recess with an optional internal thread. The injection device further comprises a drive with a piston rod 3 for moving the plug 21 of the product container 2 in the displacement direction. The piston rod 3 is guided outside the product container 2 by a piston rod guide 13 in the direction of the longitudinal axis. The piston rod guide 13 can in turn be displaceable in the direction of the longitudinal axis and comprise a sleeve surrounding the piston rod 3 and / or a mandrel surrounded by the piston rod 3.The piston rod guide 13 can simultaneously assume the function of a holding element, which prevents movement of the piston rod 3 in the dispensing direction and holds an injection spring 4 in its tensioned state. For this purpose, the piston rod guide 13 can have two flexible holding arms 6c with opposing engagement elements 6a, which initially engage in recesses 34 of the piston rod 3. After release, the piston rod 3 slides along the flexibly mounted engagement elements 6a, so that a linear extension D13 of the cross-section Q13 of the piston rod guide 13 is defined between the engagement elements 6a, which is equal to a linear extension D3 of a cross-section Q3 of the piston rod 3 in the same direction.

[0023] The Fig.1 The preferred product container shown is a pre-filled syringe 2 made of glass or plastic with a product receiving space 22, from which a product to be dispensed can be removed by moving the stopper 21 in the distal longitudinal direction of the pre-filled syringe 2 (in Fig.1 to the left) through an injection needle 23 firmly connected to the front of the pre-filled syringe 2. The injection needle 23 is in the Fig. 1 In the initial state shown, the needle protection cap 24 is surrounded, in which an elastic needle protection element, made of TPE or rubber, for example, is present. The needle protection cap 24 can be pulled off together with the needle protection element by means of a cap removal element 14 placed thereon in order to expose the injection needle 23. The injection needle 23 is further surrounded by a needle protection sleeve 15 which is mounted so as to be axially displaceable relative to the housing 1 and can be inserted into the housing 1. The needle protection sleeve 15 has a passage opening on its distal end face through which the injection needle 23 can pass during a relative movement of the needle protection sleeve and the injection needle. The needle protection sleeve 15 can also serve as a trigger element for triggering the dispensing of the product, wherein the needle protection sleeve is moved in the proximal direction relative to the housing under tension of a needle protection sleeve spring 16.At the proximal end of the pre-filled syringe 2 there is a flange 25, which is also called a finger flange.

[0024] The Fig.1 The drive shown further comprises an injection spring 4 or discharge spring in the form of a compression spring, serving as an energy storage or drive means. The injection spring 4 preferably stores at least the energy for a complete discharge of the product in the product receiving space 22 and is inserted into the injection device as a pre-tensioned spring. The injection spring 4 is arranged within the piston rod 3 and is supported against a front end element 31 of the piston rod. In the proximal direction, the injection spring 4 is held by a proximal base or plate element 41 and supported during the product discharge. Fig.1 The base element 41 is formed integrally with the piston rod guide 13 and is movable longitudinally to generate a start signal. Alternatively, the injection spring can take the form of a coil spring or torsion spring and / or be responsible for moving the product container holder 11 in addition to discharging the product.

[0025] Fig.5 shows, in connection with a second embodiment of the invention described later, a central section of Fig.1 in an enlarged view. The product receiving space 22 has an inner diameter D22, wherein the product container 2 shown has an optional minimum inner diameter D25 in the region of the flange 25, which is smaller than a diameter D22 of the product receiving space 22. The piston rod 3, in turn, has a cross-section with a maximum diameter D3, which is smaller than the minimum inner diameter D25 and thus also smaller than D22. The cross-section of the piston rod 3 can include corners, for example, be rectangular or triangular, but should fit within a circle whose diameter, corresponding to the maximum diameter D3, is smaller than the minimum inner diameter D25 of the product container. The piston rod cross-section preferably corresponds at least partially to an inner cross-section of the piston rod guide 13 (in Fig.5 not shown) in the proximal part of the housing. The product container 2 therefore has a smallest diameter in the area pushed through by the piston rod tip and located proximal to a stopper end position, which is at least four and preferably at least seven percent larger than the maximum diameter D3 and is therefore not suitable for precise longitudinal guidance of the piston rod. Instead, by selecting a slim piston rod in the proximal part of the housing adjoining the flange 25, space can be created for additional concentric components such as the needle protection sleeve spring 16, or existing components can also be designed with a smaller diameter, thus reducing the overall diameter of the device.

[0026] By exclusively guiding the piston rod outside the product container, inaccurate or inadequate axial alignment of the piston rod in the product container can no longer be completely ruled out. Any tilting or deviation from the longitudinal axis, which the piston rod can still suffer after being inserted into the product container and in contact with the plug, is limited to a few degrees due to the geometries involved. Nevertheless, due to the asymmetrical contact of the piston rod tip with the plug, the driving force is concentrated on a partial area of ​​the annular driving force transmission surface of the plug, thereby increasing it locally. Particularly in the case of high forces, for example with a highly viscous product to be dispensed, this can lead to one-sided compression, crushing or even jamming of the plug, or to the bore wall deflecting radially inwards, forming a bulge.Such uncertain and unpredictable situations can ultimately lead to an axially imprecisely defined end position of the piston rod. As a remedy, a centering aid is provided at the distal end of the piston rod to prevent the piston rod from moving in the tilting direction and to homogenize the drive force distribution across the support surface. The centering aid can be firmly locked, glued, welded, locked, or snapped to the piston rod, or it can be formed as a single piece or integrally with the piston rod.

[0027] Fig.2 und Fig.3 show an oblique top view and a longitudinal section of a first embodiment of the invention with a piston rod centering or guiding aid in the form of a centering flange 33a, which projects laterally or radially beyond the piston rod 3. A cross-section of the centering flange 33a perpendicular to the longitudinal axis has a maximum flange diameter D33a or greatest linear extension not greater than the minimum inside diameter D25 of the product container, but greater than the maximum diameter of the piston rod cross-section D3. The centering flange improves the guidance of the piston rod in the product container compared to a piston rod tip with an unchanged cross-section.

[0028] In a variant of the first embodiment, the centering flange is not completely circumferential for manufacturing reasons, but is divided into a number of bead-shaped segments distributed over the circumference with maximum radial extension. Fig.2 Four such flange segments 33a1 to 33a4 are shown, which are arranged offset by 90° from one another and also taper at their tangential ends in such a way that they fit into a square with a side length equal to the piston rod diameter D3. The drive surface 32 has the shape of a circular ring interrupted by a diagonal recess. The centering flange shown contributes to a radial enlargement of the drive surface 32; alternatively, it can also be set back a small distance from the drive surface 32 in the proximal direction without thereby losing its centering effect.

[0029] A slim piston rod without a guide in the product container is particularly important for product containers with a volume of more than 1 ml, and preferably at least 2.25 ml, and a correspondingly adjusted minimum inner diameter. For a pre-filled syringe with a volume of 2.25 ml, the inner diameter D22 is 8.65±0.1 mm and the minimum inner diameter D25 is at least 8.25 mm. With a piston rod diameter D3 of 7.65±0.1 mm and a flange ring width of 0.225 mm, this results in a flange diameter D33a of 8.1 mm, slightly smaller than the minimum diameter D25. The diameter D13 of the piston rod guide 13 is 7.9±0.1 mm and is thus significantly smaller than the minimum inner diameter D25 of the product container.

[0030] Fig.4 und Fig.5 show an oblique top view and a longitudinal section of a second embodiment of the piston rod centering aid in the form of a centering stub 33b. The centering stub 33b lies within the annular drive surface 32 and has a base diameter at its base which is smaller than the diameter D212 of the bore 212 of the plug 21. The centering stub 33b shown has the advantage over a pointed cone or taper that, if a minimum distance must be ensured between the plug (support surface 211) and the piston rod tip in the initial state, the piston rod does not have to be displaced as much in the proximal direction. For this purpose, the height of the centering stub is preferably less than half, in particular less than a quarter of the depth of the bore 212 of the plug. The centering stub has a stub diameter D33b at its tip of at least a quarter, preferably at least half, of the diameter D3 of the piston rod.

[0031] Instead of the illustrated truncated cone with a circular base, a truncated pyramid with an angular, especially at least quadrangular, base is also possible as the truncated center. The truncated center can also be divided into several segments, into Fig.4 For example, it is divided into two parts 33b1, 33b2 by a diagonal recess. Due to the limited deviation of a maximum of three degrees from the longitudinal axis, at which the piston rod can strike the plug after insertion into the product container, the flank pitch of the centering stub, which must not be less than the specified deviation, may also be correspondingly modest. The flank of the stub serves to center the piston rod upon initial contact with the edge of the plug bore, and the base of the stub subsequently serves to improve the guidance of the piston rod in the product container during product discharge.

[0032] In patent application WO2016 / 205962, Fig. 9 ff. describes an auto-injector comprising a housing with a longitudinal axis, a triggering device, and a product container arranged axially fixed in the housing, in particular in the form of a prefilled syringe or carpule. An axially displaceable plug is arranged in the product container, the displacement of which in the distal direction allows product to be dispensed from the product container. A torsion, spiral, or mainspring, in which energy for the automatic dispensing of product can be stored, is coupled to the triggering device, a first end of the torsion spring being connected to the housing, and a second end of the torsion spring being connected in a rotationally fixed manner to a threaded rod arranged coaxially to the longitudinal axis.A two-part or multi-part piston rod comprises at least one outer piston rod which does not rotate within the housing, which has the shape of a sleeve and, when displaced in the distal direction, moves the stopper of the product container in the distal direction. The two-part or multi-part piston rod further comprises at least one inner piston rod which is at least partially mounted within the outer piston rod and can transmit forces thereto in the distal direction. The inner piston rod has a guide element at its proximal end which can engage with a longitudinal guide or rib of the housing, and is connected to the threaded rod via a threaded connection, so that during pouring, a rotational movement of the threaded rod results in an axial movement of the inner piston rod.

[0033] The outer and inner piston rods together define a cavity with an inner volume that is at least partially filled with a thick or viscous fluid, or a gel-like or grease-like mass, such that upon relative rotation between the inner and outer piston rods, the thick fluid creates a displacement resistance. The inner volume of the cavity can be defined as a gap between a section of the outer surface of the inner piston rod and a section of the inner surface of the outer piston rod. Alternatively, the cavity can also be located at the distal end of the inner piston rod and have an approximately cylindrical shape. In both cases, oar-like fluid displacement structures that are rotationally fixedly connected at least to the inner piston rod can protrude into the cavity or into the thick fluid.

[0034] During dispensing, the inner piston rod is initially guided in a rotationally fixed and movable manner via the guide element. Only after the inner piston rod has been moved a certain distance in the distal direction is the guide element released by the longitudinal guide of the housing, and the inner piston rod begins to rotate under the effect of the torque of the threaded rod. The viscous fluid slows the rotation of the inner piston rod and any fluid displacement structures connected to it in a rotationally fixed manner and immersed in the viscous fluid. In particular, the rotation of these structures can cause the viscous fluid to force its way from a first chamber through an opening into a second chamber, generating pressure and friction and slowing the rotation.

[0035] At its proximal end, the inner piston rod has at least one radially projecting release structure, in particular at least one recess, which can release a structure to be released depending on its orientation relative to the longitudinal axis. As soon as the decelerated rotation of the inner piston rod has reached a predetermined orientation, the release structure is released, and a delayed end signal is produced.

[0036] Preferably, the proximal end of the inner piston rod forms an annular structure or a flange with an enlarged outer diameter. This annular structure is interrupted by one or more recesses or depressions, which function as a guide element to prevent rotation relative to the longitudinal guide of the housing and / or to release the holding element after product dispensing has been completed. The recesses distributed over the circumference of the annular structure can therefore be used twice, depending on the arrangement of the longitudinal guide and holding element and the delay properties of the viscous fluid. If, for example, the holding element is arranged in the held state somewhat distal to a distal end of the longitudinal guide and offset by 90° to this, the inner piston rod can perform a dampened quarter turn to delay the end signal.

[0037] The piston rod centering aid designed according to the invention can therefore also be the distal end of an outer piston rod, which, as part of a delay mechanism, defines a cavity on its inner side for receiving a viscous fluid as described above and disclosed in detail in WO2016 / 205962.

[0038] Fig.6a und Fig.6b show two longitudinal sectional views, offset by approximately 90°, of another embodiment of an auto-injector in a delivery or initial state. The auto-injector has a holding element 6 with two holding arms 6c, wherein a first engagement element 6a and a second engagement element 6b are arranged on each holding arm 6c. The first engagement element 6a points radially toward the longitudinal axis L, wherein the second engagement element 6b points radially away from the longitudinal axis L. The first engagement element 6a engages in a recess 34 formed by the piston rod 3, thereby preventing movement of the piston rod 3 relative to the holding element in the dispensing direction and holding an injection spring 4 or dispensing spring in the form of a torsion spring in its tensioned state.

[0039] The auto-injector has a switching module 8, 9, which has a switching sleeve 9 and a locking sleeve 8 that is axially movable relative to the switching sleeve 9 and at least partially surrounded by the switching sleeve 9. The switching module 8, 9 thus forms a telescopic mechanism with an outer telescopic sleeve 9 and an inner telescopic sleeve 8. In the delivery state of the device, the first engagement element 6a is held in engagement with the recess 34 by the inner circumference of the locking sleeve 8, which bears against the second engagement element 6b.

[0040] The switching sleeve 9 rests against a proximal end 15a of the needle protection sleeve 15. A needle protection spring 16, which preferably at least partially surrounds the switching sleeve 9 and the locking sleeve 8, rests with its distal end on the switching sleeve 9. A part of the switching sleeve 9 is thus arranged between the needle protection sleeve 15 and the distal end of the needle protection spring 16. The needle protection spring 16 is a metal spring designed as a compression spring and helical spring. The needle protection spring 16 rests with its proximal end on a projection 6e of the holding element, which engages in the housing 1 in an axially displaceable and rotationally fixed manner. The needle protection spring 16 thus also at least partially, preferably completely, surrounds a mechanism holder 5 that is rotationally and axially fixedly connected to the housing.

[0041] The switching sleeve 9 has a recess or opening 9a with an axial length or extension L9a, which is delimited in the axial direction by a distal and a proximal boundary in the form of an edge or a frame section. A sawtooth-shaped locking member 8b of the locking sleeve 8, directed radially outward from the longitudinal axis L, engages from the inside into the recess 9a. The locking member 8b is resiliently arranged on a preferably distally oriented locking arm 8a, which is formed by the locking sleeve 8 or whose preferably proximal end is axially fixedly connected to the locking sleeve 8. By moving the needle protection sleeve 15 into the actuated position, the switching sleeve 9 is pushed in the proximal direction; as a result, the locking sleeve 8 is also driven or pushed in the proximal direction via the engagement of the locking member 8b with a distal boundary of the recess 9a.The locking member 8b can move axially within and relative to the recess 9a between the distal and proximal boundaries by a maximum distance L9a. In the initial state, a localization recess or depression 5b in the mechanism holder 5 can ensure that a locking member 8d on an inner side of the locking arm 8a holds the locking member 8b within the recess 9a and thus the entire locking sleeve 8 in a desired axial position. The proximal boundary of this recess 5b is designed and, in particular, beveled such that the locking member 8d can slide thereon with little resistance during an actuating movement in the proximal direction. The localization recess 5b in . Fig.6 is axially extended in such a way that a movement of the locking sleeve 8 in the initial state is completely or unilaterally limited by the recess 9a in the switching sleeve 9 and the locking member 8b engaging therein, but not or at most unilaterally by the recess 5b in the mechanism holder 5. Alternatively, the locating recess 5b can have a minimal axial extension and locate the locking sleeve axially with pinpoint accuracy.

[0042] The locking sleeve 8 has a distal end 8c, which, when the auto-injector is actuated or attached, is brought into the position of the second engagement element 6b by moving the switching sleeve 9 by an actuation stroke greater than L9a along the longitudinal axis L. As a result, the first engagement element 6a is moved out of engagement with the piston rod 3 by a movement transverse to and away from the longitudinal axis L, with the second engagement element 6b simultaneously coming into engagement with the distal end 8c of the locking sleeve 8. As a result, the piston rod 3 is released for movement by the dispensing stroke in the dispensing direction. Once triggered, the mechanism holder 5 serves as a piston rod guide for guiding a movement of the piston rod 3 in the direction of the longitudinal axis.The rigid cross-section of the mechanism holder 5 is adapted or matched to the piston rod cross-section Q3 as a guide cross-section Q13 and is preferably slightly larger on all sides than the latter, and limits movement of the piston rod cross-section in all directions perpendicular to the longitudinal axis to a manufacturing minimum.

[0043] Since the axially fixed coupling between the piston rod 3 and the holding element 6 is now released, the holding element, which is movable at least partially relative to the housing 1 and along the longitudinal axis L, can be moved in the proximal direction by the needle protection spring 16. Through the engagement of the second engagement element 6b behind the distal end 8c of the locking sleeve 8, the latter is moved by the accelerating holding element by a start signal stroke until the locking sleeve 8 strikes a start signal stop 5a formed by the mechanism holder 5, thereby emitting an acoustic and / or tactile signal that signals to the user of the device that product dispensing has started. During this signal movement, the locking sleeve 8 is moved by less than the length L9a, so that the locking member 8b does not abut the proximal boundary of the recess 9a.

[0044] Fig.7a und Fig.7bshow two longitudinal sectional views, offset by 90°, of the further embodiment of an auto-injector in a state after the start signal has been given and with the needle guard activated. By displacing the locking sleeve 8 by the start signal stroke, the locking member 8d, which is attached to the locking arm 8a of the locking sleeve opposite the locking member 8b and projects radially inward or toward the longitudinal axis L in a sawtooth shape, is released for movement transversely and toward the longitudinal axis L and into a recess 5d of the mechanism holder 5. The locking member 8d can thus deflect into the recess 5d and snap into place shortly before the locking sleeve 8 impacts as a result of the corresponding pretension of the locking arm 8a, without the locking member 8b coming out of the recess 9a.As a result, the locking sleeve 8 is axially and firmly connected to the mechanism holder 5, preventing movement of the locking sleeve 8 in the distal direction relative to the housing 1 and activating a needle protection mechanism. In this position, the locking arm 8a is relaxed, i.e., radially tensioned neither inward nor outward.

[0045] Since the second engagement member 6b still rests against the distal end 8c of the locking sleeve 8, the holding element 6 is prevented from moving further in the proximal direction relative to the housing 1 or the locking sleeve 8. The second engagement member 6b is held in engagement with the locking sleeve 8 by the outer circumference of the piston rod 3 as long as the piston rod 3 is moved by its discharge stroke.

[0046] At the end of the dispensing stroke, the piston rod 3 releases the first engagement member 6a for movement, in particular toward the longitudinal axis L, whereby the second engagement member 6b is moved out of engagement with the locking sleeve 8, so that the needle protection spring 16 accelerates the holding element 6 against the dispensing direction, ie in the proximal direction, so that an acoustic and / or tactile signal is generated when the holding element 6 hits the end signal stop 5e.

[0047] By removing the auto-injector from the injection site, the needle protection spring 16 can move the switching sleeve 9 and the needle protection sleeve 15 from the actuated position to the needle protection position by the needle protection stroke, whereby the locking member 8a is pressed out of engagement with the recess 9a, whereby the switching sleeve 9 moves in the distal direction relative to the locking sleeve 8. When the needle protection sleeve 15 is in its needle protection position, the locking member 8a snaps into the switching sleeve 9, whereby the locking member 8a prevents the needle protection sleeve 15 from being pushed back into its actuated position. When attempting to push the needle protection sleeve 15 back from the needle protection position to the actuated position, the switching member 9 abuts the locking member 8a, which prevents the needle protection sleeve 15 from moving into the actuated position. For this purpose, the locking sleeve 8 is supported axially on the start signal stop 5a of the mechanism holder 5. LIST OF REFERENCE SYMBOLS

[0048] 1 Housing 11 Product container holder 12 End cap 13 Piston rod guide 14 Cap removal element 15 Needle shield 15a Proximal end 16 Needle shield spring 2 Product container 21 Plug 211 Support surface 212 Bore 22 Product receiving space 23 Injection needle 24 Needle shield 25 Flange 3 Piston rod 31 End element 32 Drive surface 33 Piston rod centering aid 33a Centering flange 33b Centering stump 34 Recess 4 Injection spring 41 Base element 42 Threaded rod 5 Mechanism holder 5a Start signal stop 5b Localization recess 5d Recess 5e End signal stop 6 Holding element 6a First engagement element 6b Second engagement element 6c Holding arm 6eProtrusion 8Locking sleeve 8aLocking arm 8bLocking link 8cdistal end 8dLocking link 9Switching sleeve 9aRecess

Claims

1. Injection device for administering a liquid product, comprising - a housing (1) for receiving a product container (2), in which a plug (21) having a support surface (211) for dispensing the product is displaceable in the direction of a longitudinal axis of the injection device up to a plug end position, and which has a minimum product container cross section Q25 proximal to the plug end position, - a drive for displacing the plug (21), comprising a piston rod (3) which has a drive surface (32) for contact with the support surface (211) and has a piston-rod cross section Q3, - a piston rod guide (13) outside the product container (2) for guiding a movement of the piston rod (3) in the direction of the longitudinal axis, which piston rod guide has a guide cross section Q13 matched to the piston-rod cross section Q3, - wherein the product container (2) guides the movement of the piston rod (3) in the direction of the longitudinal axis at most incompletely, so that the piston-rod cross section Q3 is at least not prevented from moving in a tilting direction by the minimum product container cross section Q25, and - wherein a piston-rod centering aid (33a, 33b) is provided at a distal end of the piston rod (3) to limit the movement of the piston rod in the tilting direction, and wherein the piston rod centering aid comprises a centering flange (33a) having a maximum flange diameter D33a greater than a maximum outer diameter D3 of the piston rod (3) and smaller than a minimum inner diameter D25 of the product container (2), and wherein the drive further comprises an injection spring (4) as the drive means and the piston rod guide (13) comprises a holding element (6) which is displaceable in the direction of the longitudinal axis, can prevent movement of the piston rod (3) in the dispensing direction, and can hold the injection spring (4) in a tensioned state.

2. Injection device according to claim 1, wherein the minimum product container cross section Q25 is a circle having a diameter D25, the piston-rod cross section Q3 is a circle having a diameter D3, and the guide cross section Q13 is a circle having a diameter D13, characterized in that D13 is smaller than D25 and greater than or equal to D3, and in that D25 is at least four percent greater than D3.

3. Injection device according to claim 2, wherein the support surface (211) of the plug (21) is annular and surrounds a bore (212) in the plug (21).

4. Injection device according to claims 1 to 3, characterized in that the centering flange is made of the same inflexible material as the piston rod.

5. Injection device according to claim 4, characterized in that the centering flange (33a) makes contact with the support surface (211).

6. Injection device according to claim 4 or 5, wherein the piston-rod cross section Q3 fits into a circle having a diameter D3, characterized in that the centering flange has a cross section that fits into a square having a side length D3.

7. Injection device according to claim 3, characterized in that the piston rod centering aid comprises a centering projection (33b).

8. Injection device according to any of claims 1 to 7, characterized in that the drive for displacing the plug (21) comprises as an energy store (4) a compression spring acting against a distal terminal element (31) of the piston rod (3).

9. Injection device according to any of claims 1 to 7, characterized in that the drive for displacing the plug (21) comprises a torsion spring which acts on a threaded rod (42) which is connected via a threaded connection to the piston rod (3) mounted in the housing (1) in a rotationally fixed manner.

10. Injection device according to claim 9, characterized in that the drive comprises an inner piston rod, which is connected via the threaded connection to the threaded rod (42), and an outer piston rod, which is mounted in the housing (1) in a rotationally fixed manner and has the centering means (33b), wherein the two piston rods form a cavity that can be filled with a viscous fluid to attenuate a rotational movement of the inner piston rod, which movement is allowed towards the end of the dispensing.

11. Injection device according to any of the preceding claims, characterized in that the piston rod guide (13) comprises a mechanism holder (5) which is connected to the housing (1) in an axially fixed manner.

12. Injection device according to any of the preceding claims, characterized in that the injection apparatus is an auto-injector and the product container is a pre-filled syringe having a fixed injection needle and a nominal filling volume of 2.25 ml.

13. Injection device according to any of the preceding claims, characterized in that the product has a high viscosity of at least 5, preferably at least 15 cP (0.015 kgm-1s-1).