Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/20—Automatic syringes, e.g. with automatically actuated piston rod, with automatic needle injection, filling automatically
  • A61M5/2033—Spring-loaded one-shot injectors with or without automatic needle insertion
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/31—Details
  • A61M5/32—Needles; Details of needles pertaining to their connection with syringe or hub; Accessories for bringing the needle into, or holding the needle on, the body; Devices for protection of needles
  • A61M5/3202—Devices for protection of the needle before use, e.g. caps
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/31—Details
  • A61M5/32—Needles; Details of needles pertaining to their connection with syringe or hub; Accessories for bringing the needle into, or holding the needle on, the body; Devices for protection of needles
  • A61M5/3205—Apparatus for removing or disposing of used needles or syringes, e.g. containers; Means for protection against accidental injuries from used needles
  • A61M5/321—Means for protection against accidental injuries by used needles
  • A61M5/322—Retractable needles, i.e. disconnected from and withdrawn into the syringe barrel by the piston
  • A61M5/3232—Semi-automatic needle retraction, i.e. in which triggering of the needle retraction requires a deliberate action by the user, e.g. manual release of spring-biased retraction means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/20—Automatic syringes, e.g. with automatically actuated piston rod, with automatic needle injection, filling automatically
  • A61M2005/206—With automatic needle insertion
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/20—Automatic syringes, e.g. with automatically actuated piston rod, with automatic needle injection, filling automatically
  • A61M2005/2073—Automatic syringes, e.g. with automatically actuated piston rod, with automatic needle injection, filling automatically preventing premature release, e.g. by making use of a safety lock
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/31—Details
  • A61M5/32—Needles; Details of needles pertaining to their connection with syringe or hub; Accessories for bringing the needle into, or holding the needle on, the body; Devices for protection of needles
  • A61M5/3202—Devices for protection of the needle before use, e.g. caps
  • A61M5/3204—Needle cap remover, i.e. devices to dislodge protection cover from needle or needle hub, e.g. deshielding devices
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/31—Details
  • A61M5/32—Needles; Details of needles pertaining to their connection with syringe or hub; Accessories for bringing the needle into, or holding the needle on, the body; Devices for protection of needles
  • A61M5/3205—Apparatus for removing or disposing of used needles or syringes, e.g. containers; Means for protection against accidental injuries from used needles
  • A61M5/321—Means for protection against accidental injuries by used needles
  • A61M5/3243—Means for protection against accidental injuries by used needles being axially-extensible, e.g. protective sleeves coaxially slidable on the syringe barrel
  • A61M5/326—Fully automatic sleeve extension, i.e. in which triggering of the sleeve does not require a deliberate action by the user

Definitions

• the invention relates to an auto-injector for administering a dose of a liquid medicament according to the preamble of claim 1 .
• Injection devices i.e. devices capable of delivering medicaments from a medication container
• Injection devices typically fall into two categories - manual devices and auto-injectors.
• buttons / plunger that has to be continuously pressed by the user during the injection.
• Auto-injector devices aim to make self-administration of injected therapies easier for patients.
• Current therapies delivered by means of self-administered injections include drugs for diabetes (both insulin and newer GLP-1 class drugs), migraine, hormone therapies, anticoagulants etc.
• Auto-injectors are devices which completely or partially replace activities involved in parenteral drug delivery from standard syringes. These activities may include removal of a protective syringe cap, insertion of a needle into a patient's skin, injection of the medicament, removal of the needle, shielding of the needle and preventing reuse of the device.
• This overcomes many of the disadvantages of manual devices. Injection forces / button extension, hand-shaking and the likelihood of delivering an incomplete dose are reduced.
• Triggering may be performed by numerous means, for example a trigger button or the action of the needle reaching its injection depth. In some devices the energy to deliver the fluid is provided by a spring.
• US 2002/0095120 A1 discloses an automatic injection device which automatically injects a pre-measured quantity of fluid medicine when a tension spring is released.
• the tension spring moves an ampoule and the injection needle from a storage position to a deployed position when it is released.
• the content of the ampoule is thereafter expelled by the tension spring forcing a piston forward inside the ampoule.
• torsion stored in the tension spring is released and the injection needle is automatically retracted back to its original storage position.
• US 2007/01 12310 A1 discloses an injector being automatic in that the needle is inserted into the injection site (e.g., a patient's skin) with user or caregiver assistance, the delivery is automatically initiated upon needle insertion, and the needle is retracted automatically after the end of delivery.
• the needle is not seen by the user prior to, during or after injection. Prior to and after injection, the needle is hidden in the device so as to avoid any potential injury or health risk to the user or health care provider.
• the injector includes a housing and a shield arranged to slide relative to the housing and a driver moving during drug delivery. The housing and shield form a cartridge enclosure. The cartridge is shielded and locked after delivery is completed.
• a needle-locking mechanism can be used in any number of pen-like injectors or safety needles.
• US 5,267,963 discloses an automatic injection device which, upon activation by the user, automatically extends a syringe with needle, delivers medication through the needle, and retracts the needle, thus keeping the needle hidden from view. All motions are achieved by means of a tension spring and a cam profile.
• WO 2009/081 103 A1 discloses an auto-injector for a syringe that is suitable for use in the injected delivery of drug to a patient.
• the auto-injector comprises a housing defining a housing cavity arranged for receipt of a syringe; and a needle delivery aperture through which a needle tip of the syringe protrudes during dispensing of the liquid drug formulation.
• the auto-injector further comprises a barrel coupling element that couples to the barrel of the syringe and is movable in tandem therewith; a syringe advancer for moving the syringe and barrel coupling element in tandem therewith from a rest position, in which the hollow needle, is within the housing to a use position, in which the needle tip protrudes through the needle delivery aperture; a syringe actuator for actuating the syringe by plunging said plunger within the barrel of the syringe to dispense the liquid drug formulation; a syringe retractor for retracting the syringe and barrel coupling element in tandem therewith from the use position to a retract position, in which the hollow needle is within the housing; and a syringe lock for locking the barrel coupling element and syringe coupled thereto in the retract position.
• WO 2008/155377 discloses an inserter for an infusion set comprising an insertion needle and a spring unit assuring automatic insertion and automatic retraction of the insertion needle.
• the inserter for a medical device comprises - a housing, - a first body which is movable relative to the housing and comprising penetrating means pointing in the direction of insertion, - a second body which is also movable relative to the housing and - driving means which move respectively the first body and the second body relative to the housing wherein the driving means moves the first body in the direction of insertion and moves the second body in a direction different from the insertion direction.
• DE 10 2005 038 933 A1 discloses an inserter for an infusion set comprising an insertion needle and a spring unit assuring automatic insertion and automatic retraction of the insertion needle.
• the inserter for a medical device comprises - a housing, - a first body which is movable relative to the housing and comprising penetrating means pointing in the direction of insertion, - a second body which is also movable relative to the housing and - driving means which move respectively the first body and the second body relative to the housing wherein the driving means moves the first body in the direction of insertion and moves the second body in a direction different from the insertion direction.
• the object is achieved by an auto-injector according to claim 1 .
• an auto- injector for administering a dose of a liquid medicament comprises:
• an elongate housing arranged to contain a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, the housing having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the housing,
• the spring means is a single compression spring arranged to be grounded at a distal end in the housing for advancing the needle and for injecting the dose of medicament.
• the force of the compression spring is forwarded to the needle and/or the syringe via a plunger.
• the compression spring is arranged to have its ground in the housing switched to its proximal end for retracting the syringe when the injection of the medicament is at least nearly finished.
• the single compression spring is used for inserting the needle, fully emptying the syringe and retracting the syringe and needle to a safe position after injection.
• a second spring for withdrawing the syringe and needle which is a motion with an opposite sense compared to advancing the syringe and injecting the dose, is not required.
• the proximal end moves the syringe forward for inserting the needle and carries on to the injection by pushing on the stopper.
• the compression spring bottoms out at its proximal end resulting in the proximal end being grounded in the housing.
• the distal end of the compression spring is released from its ground in the housing.
• the compression spring is now pulling the syringe in the opposite direction.
• the auto-injector according to the invention has a particularly low part count compared to most conventional auto-injectors.
• the use of just one compression spring reduces the amount of metal needed and thus consequently reduces weight and manufacturing costs.
• a retraction sleeve is axially movable arranged in the housing. At least one latch is provided for axially fixing the retraction sleeve in a maximum proximal position.
• the compression spring is arranged inside the retraction sleeve with its distal end bearing against a distal end face of the retraction sleeve and with its proximal end bearing against a thrust face of a decoupling member.
• the decoupling member is arranged to decouple the latch when being moved in proximal direction nearly into a maximum proximal position. When decoupled the retraction sleeve is allowed to move in distal direction and retract the needle by means of the spring force which is no longer grounded at its distal end.
• the plunger is arranged for pushing the syringe and/or the stopper in proximal direction.
• At least two resilient decoupling arms are arranged at the decoupling member.
• the decoupling arms exhibit inner ramped surfaces bearing against a first shoulder of the plunger in proximal direction P.
• the resilient decoupling arms are supportable by an inner wall of the retraction sleeve in order to prevent the decoupling arms from being flexed outward and slip past the first shoulder. In this state the plunger may be pushed in proximal direction by the decoupling member pushing against the first shoulder in order to insert the needle and inject the dose.
• At least one aperture is arranged in the retraction sleeve allowing the decoupling arms to be flexed outward by the first shoulder thus allowing the first shoulder to slip through the decoupling arms in proximal direction. This may happen when the injection is at least nearly finished.
• the decoupled plunger allows the syringe and needle to be retracted since it is no longer bearing against the decoupling member.
• the syringe may be arranged for joint axial movement with a syringe holder which is slidably arranged in the retraction sleeve.
• the syringe holder is provided with at least two resilient syringe holder arms arranged distally, the syringe holder arms having a respective inclined surface for bearing against a second shoulder, which is arranged at the plunger proximally from the first shoulder.
• the syringe holder arms are supportable by an inner surface of the housing in order to prevent them from being flexed outward.
• a widened portion is provided in the housing for allowing the syringe holder arms to flex outwards when the syringe holder has nearly reached a maximum proximal position thus allowing the second shoulder to slip through the syringe holder arms and to switch load of the compression spring from the syringe to the stopper. This allows for defining the moment to start injecting the medicament.
• a stud may be arranged at the distal end of the plunger.
• the retraction sleeve may have two or more resilient arms distally from the end face for holding the stud.
• the stud and/or the resilient arms have ramp features.
• the activating means comprise a trigger button arranged at the distal end of the auto-injector.
• the trigger button is axially moveable and has at least two rigid retainers for preventing the resilient arms from being flexed outward when the trigger button is in a maximum distal position.
• the retainers are moved in proximal direction in a manner to allow the resilient arms to be flexed out by the stud biased by the compression spring in proximal direction.
• the stud is allowed to slip past the resilient arms in proximal direction under load of the compression spring in order to start a needle insertion/injection/retraction cycle.
• the main advantages of this trigger mechanism are its simplicity, the low part count and a high reliability.
• a safety button may be arranged laterally at the housing.
• the safety button has an interlock for preventing the trigger button from being pushed.
• the safety button is arranged to pull the interlock outward when operated thus allowing the trigger button to be pushed.
• the safety button may be pivoted in the housing or it may be cast in one piece with the housing in a manner to be pivoted somewhere in the middle so pushing one end inwards causes the other end to be pulled outwards.
• a delay box is arranged for slowing down the motion of the retraction sleeve.
• the latches are arranged to be disengaged by the decoupling member before the stopper has reached a maximum proximal position in the syringe.
• the apertures are arranged to meet the decoupling arms after the stopper has reached its maximum proximal position by means of the motion of the retraction sleeve.
• a gap is provided between a front face of the retraction sleeve and the syringe holder in their respective maximum proximal positions.
• the gap allows the retraction sleeve to travel a distance before retracting the syringe holder so the syringe holder is retracted after the decoupling arms met the apertures.
• Triggering the retraction when the stopper exactly reaches the end of its travel is a problem due to tolerances when manufacturing the syringe and stopper. Due to these tolerances the position of the stopper at the end of its travel is not repeatable.
• the stopper would prematurely bottom out so the retraction would not be triggered at all. In other cases the retraction would be triggered before the stopper bottomed so residual medicament would remain in the syringe.
• the delay box may comprise a circumferential outer wall with a back collar attached to the housing and a circumferential inner wall with a front collar attached to the retraction sleeve.
• a volume is defined between the outer wall and inner wall, the volume sealed by the back collar and front collar and filled with a viscous fluid.
• At least one hole is arranged in the delay box for allowing the viscous fluid to be pushed out as the volume decreases due to motion of the retraction sleeve. This is a particularly simple and cost- efficient way to damp the backward motion of the retraction sleeve.
• the hollow needle is equipped with a protective needle shield for keeping the needle sterile and preventing it from being mechanically damaged.
• the protective needle shield is attached to the needle when the auto-injector or the syringe is assembled.
• a cap is provided at the proximal end of the housing.
• a sheet metal clip is attached to the cap for joint axial movement and independent rotation.
• the sheet metal clip is arranged to extend through an orifice into the housing when the cap is attached to the housing.
• the sheet metal clip comprises at least two barbs snapped into a circumferential notch or behind a shoulder of the protective needle shield. This allows for automatically engaging the sheet metal clip with the protective needle shield during assembly.
• the protective needle shield is reliably removed without exposing the user too high a risk to injure themselves.
• the cap may be attachable to the housing by a screw connection. This allows for a low force removal of the protective needle shield.
• the housing may have at least one viewing window for inspecting the syringe.
• the auto-injector may preferably be used for subcutaneous or intra-muscular injection, particularly for delivering one of an analgetic, an anticoagulant, insulin, an insulin derivate, heparin, Lovenox, a vaccine, a growth hormone, a peptide hormone, a proteine, antibodies and complex carbohydrates.
• ..medicament means a pharmaceutical formulation containing at least one pharmaceutically active compound, wherein in one embodiment the pharmaceutically active compound has a molecular weight up to 1500 Da and/or is a peptide, a proteine, a polysaccharide, a vaccine, a DNA, a RNA, a antibody, an enzyme, an antibody, a hormone or an oligonucleotide, or a mixture of the above-mentioned pharmaceutically active compound, wherein in a further embodiment the pharmaceutically active compound is useful for the treatment and/or prophylaxis of diabetes mellitus or complications associated with diabetes mellitus such as diabetic retinopathy, thromboembolism disorders such as deep vein or pulmonary thromboembolism, acute coronary syndrome (ACS), angina, myocardial infarction, cancer, macular degeneration, inflammation, hay fever, atherosclerosis and/or rheumatoid arthritis, wherein in a further embodiment the pharmaceutically
• Insulin analogues are for example Gly(A21 ), Arg(B31 ), Arg(B32) human insulin; Lys(B3), Glu(B29) human insulin; Lys(B28), Pro(B29) human insulin; Asp(B28) human insulin; human insulin, wherein proline in position B28 is replaced by Asp, Lys, Leu, Val or Ala and wherein in position B29 Lys may be replaced by Pro; Ala(B26) human insulin; Des(B28-B30) human insulin; Des(B27) human insulin and Des(B30) human insulin.
• Insulin derivates are for example B29-N-myristoyl-des(B30) human insulin; B29-N- palmitoyl-des(B30) human insulin; B29-N-myristoyl human insulin; B29-N-palmitoyl human insulin; B28-N-myristoyl LysB28ProB29 human insulin; B28-N-palmitoyl- LysB28ProB29 human insulin; B30-N-myristoyl-ThrB29LysB30 human insulin; B30-N- palmitoyl- ThrB29LysB30 human insulin; B29-N-(N-palmitoyl-Y-glutamyl)-des(B30) human insulin; B29-N-(N-lithocholyl-Y-glutamyl)-des(B30) human insulin; ⁇ 29- ⁇ -( ⁇ - carboxyheptadecanoyl)-des(B30) human insulin and B29-N-( -carboxy
• Exendin-4 for example means Exendin-4(1 -39), a peptide of the sequence H-His-Gly- Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Lys-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe- lle-Glu-Trp-Leu-Lys-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-NH2.
• Exendin-4 derivatives are for example selected from the following list of compounds:
• Hormones are for example hypophysis hormones or hypothalamus hormones or regulatory active peptides and their antagonists as listed in Rote Liste, ed. 2008, Chapter 50, such as Gonadotropine (Follitropin, Lutropin, Choriongonadotropin, Menotropin), Somatropine (Somatropin), Desmopressin, Terlipressin, Gonadorelin, Triptorelin, Leuprorelin, Buserelin, Nafarelin, Goserelin.
• Gonadotropine Follitropin, Lutropin, Choriongonadotropin, Menotropin
• Somatropine Somatropin
• Desmopressin Terlipressin
• Gonadorelin Triptorelin
• Leuprorelin Buserelin
• Nafarelin Goserelin.
• a polysaccharide is for example a glucosanninoglycane, a hyaluronic acid, a heparin, a low molecular weight heparin or an ultra low molecular weight heparin or a derivative thereof, or a sulphated, e.g. a poly-sulphated form of the above-mentioned polysaccharides, and/or a pharmaceutically acceptable salt thereof.
• An example of a pharmaceutically acceptable salt of a poly-sulphated low molecular weight heparin is enoxaparin sodium.
• Pharmaceutically acceptable salts are for example acid addition salts and basic salts. Acid addition salts are e.g. HCI or HBr salts.
• Basic salts are e.g. salts having a cation selected from alkali or alkaline, e.g. Na+, or K+, or Ca2+, or an ammonium ion N+(R1 )(R2)(R3)(R4), wherein R1 to R4 independently of each other mean: hydrogen, an optionally substituted C1 -C6-alkyl group, an optionally substituted C2-C6-alkenyl group, an optionally substituted C6-C10-aryl group, or an optionally substituted C6-C10- heteroaryl group.
• R1 to R4 independently of each other mean: hydrogen, an optionally substituted C1 -C6-alkyl group, an optionally substituted C2-C6-alkenyl group, an optionally substituted C6-C10-aryl group, or an optionally substituted C6-C10- heteroaryl group.
• R1 to R4 independently of each other mean: hydrogen, an optionally substituted C1 -C
• solvates are for example hydrates.
• the delay box may be employed with other types of auto-injectors.
• the cap with the sheet metal spring may also be applied with other auto-injectors and injection devices.
• Figure 1 are two longitudinal sections of an auto-injector with a single
• Figure 2 are two longitudinal sections of the auto-injector with the syringe and needle advanced and the dose expelled from the syringe,
• Figure 3 is a perspective sectional view of the auto-injector in the initial state of figure 1 ,
• Figure 4 is another perspective sectional view of the auto-injector of figure 3.
• Figure 5 is a detail view of the distal end of the auto-injector with a delay box
• Figure 6 is a detailed view of the proximal end of the autoinjector showing the cap and needle shield remover.
• FIG. 1 shows two longitudinal sections in different section planes of an auto-injector 1 , the different section planes approximately 90° rotated to each other.
• the auto-injector 1 comprises an elongate housing 2.
• a syringe 3, e.g. a Hypak syringe, with a hollow needle 4 is arranged in a proximal part of the auto-injector 1 .
• a protective needle shield 5 is attached to the needle 4.
• a stopper 6 is arranged for sealing the syringe 3 distally and for displacing a liquid medicament M through the hollow needle 4.
• the syringe 3 is held in a tubular syringe carrier 7 and supported at its proximal end therein.
• a single compression spring 8 is arranged in a distal part of the auto-injector 1 .
• a plunger 9 is arranged for forwarding the spring force of the compression spring 8.
• a retraction sleeve 10 is slidably arranged inside the housing 2 .
• the retraction sleeve 10 Before the injection is triggered as shown in figure 1 the retraction sleeve 10 is in a maximum proximal position and prevented from moving in distal direction D by means of stops 1 1 caught behind latches 12 in the housing 2.
• a distal end of the compression spring 8 bears against an end face 13 of the retraction sleeve 10. Due to the stops 1 1 and latches 12 the force of the compression spring 8 is thus reacted into the housing 2.
• the proximal end of the compression spring 8 bears against a decoupling member 14 arranged around the plunger 9.
• the retraction sleeve Distally from the end face 13 the retraction sleeve has two or more resilient arms 15 for holding a stud 16 and keeping it from being moved in proximal direction P.
• the stud 16 is arranged at the distal end of the plunger 9.
• the stud 16 and the resilient arms 15 have corresponding ramp features for pushing the resilient arms 15 apart in order to allow the stud 16 and the plunger 9 to move in proximal direction P.
• the decoupling member 14 comprises a thrust face 17 for bearing against a proximal end of the compression spring 8. Proximally from the thrust face 17 two or more resilient decoupling arms 18 are provided at the decoupling member 14, the decoupling arms 18 having inner ramped surfaces bearing against a first shoulder 19 in the plunger 9 in proximal direction P.
• the resilient decoupling arms 18 are supported by an inner wall of the retraction sleeve 10 in this situation so they cannot flex outward and slip past the first shoulder 19.
• a trigger button 20 is arranged at the distal end D of the auto-injector 1 .
• the trigger button 20 may be pushed in proximal direction P in order to start an injection. As long as the trigger button 20 is not pushed the resilient arms 15 are caught between two or more retainers 21 arranged at the trigger button 20 so the resilient arms 15 cannot flex outward and the stud 16 although proximally biased by the compression spring 8 cannot slip through.
• the syringe carrier 7 is engaged for joint axial movement with a syringe holder 22 which is slidably arranged in the retraction sleeve 10.
• the syringe holder 22 is provided with two or more resilient syringe holder arms 23 arranged distally.
• the syringe holder arms 23 have a respective inclined surface for bearing against a second shoulder 24 in the plunger 9 arranged proximally from the first shoulder 19. In the initial position shown in figure 1 the syringe holder arms 23 are supported by an inner surface of the housing 2 so they cannot flex outward and the second shoulder 24 cannot slip through.
• a respective number of apertures are provided in the retraction sleeve 10.
• Figure 1 shows the auto-injector 1 as-delivered with a cap 25 screwed onto to the proximal end P of the auto-injector 1 .
• Figure 6 shows details of the proximal end P with the cap 25.
• the cap 25 comprises a sheet metal clip 26 with two or more barbs 27 extending through an orifice into the proximal end P of the auto-injector 1 .
• the sheet metal clip 26 is mounted to the cap 25 for joint axial movement with respect to a longitudinal axis of the auto-injector 1 . However, the sheet metal clip 26 may rotate independently from the cap 25.
• the cap 25 is screwed onto the proximal P end of the auto-injector 1 the barbs 27 are pushed down the protective needle shield 5 and snap into a
• a safety button 29 is arranged laterally at the distal part of the housing 2.
• the safety button 29 serves for interlocking with the trigger button 20 in a manner to prevent the trigger button 20 from being inadvertently operated without the safety button 29 being released from a first blocking position. Consequently, in order to operate the trigger button 20 the safety button 29 has to be pushed transversally with respect to the longitudinal axis against the force of a spring element 30 which is formed in the safety button 29.
• the safety button 29 is pivoted in the middle so pushing the proximal end of the safety button 29 inward pulls an interlock 31 at its proximal end obstructing the trigger button 20 outward so the trigger button 20 can be pushed.
• the retainers 21 are pushed in proximal direction P so the resilient arms 15 are allowed to flex outward.
• Under load of the compression spring 8 the inclined surfaces of the stud 16 force the resilient arms 15 apart until the stud 16 can slip through.
• the second shoulder 24 pushes the syringe holder 22, syringe carrier 7 and syringe 3 forward while no load is exerted onto the stopper 6.
• the hollow needle 4 appears from the proximal end P and is inserted into an injection site, e.g. a patient's skin.
• decoupling member 14 has reached a position where it pushes against the latches 12 in a manner to decouple the retraction sleeve 10 from the housing 2, so the retraction sleeve 10 may slide in distal direction D.
• the compression spring 8 is no longer grounded with its distal end in the housing 2. Instead, as soon as the decoupling member 14 has bottomed out at a second abutment 33 the proximal end of the compression spring 8 gets grounded in the housing while the distal end is pulling the retraction sleeve 10 in distal direction D.
• the decoupling arms 18 reach an aperture 34 in the retraction sleeve 10 (see fig. 4) so they are no longer kept from being flexed outward.
• the decoupling arms 18 are thus pushed outward by the first shoulder 19 pushing against its ramped surfaces so the first shoulder 19 slips through in distal direction as soon as the decoupling member 14 has hit the second abutment 33.
• the syringe holder 22 is taken along in distal direction D by the retraction sleeve 10, e.g. by a front face 35.
• the syringe 3 and needle 4 are retracted into a safe position inside the housing 2, e.g. into the initial position.
• the plunger 9, no longer bearing against the decoupling arms 18 is pulled back too.
• the delay box 36 comprises a circumferential outer wall 37 with a back collar
• a viscous fluid such as silicon grease.
• a viscous fluid such as silicon grease.
• the inner wall 39 glides along the outer wall 37 wherein the back collar 38 and front collar 40 increasingly reduce the volume.
• One or more holes provided in a part of the delay box 36 allow the viscous fluid to be pushed out as the volume decreases. The force required to do this slows down the motion of the retraction sleeve 10.
• the retraction sleeve 10 is released by the decoupling member 14 from the housing 2 a certain amount of time or travel before the stopper 6 bottoms out in the syringe 3 and the distal motion of the retraction sleeve 10 begins.
• the motion of the retraction sleeve 10 is slowed down by the delay box 36. Due to a gap 41 between the front face 35 and the syringe holder 22 the retraction sleeve 10 is not yet dragging the syringe back in distal direction D.
• the plunger 9 is still pushing against the stopper 6 and expelling residual medicament M.
• the cap 25 and the delay box 36 are not restricted to be used with the auto-injector 1 shown in the embodiments. Instead the cap 25 may be combined with any kind of auto- injector with the needle hidden in the housing prior to an injection.
• the delay box may be combined with any kind of auto-injector for ensuring full delivery of the syringe's contents and reliable triggering of the retraction, irrespective of the spring means or driving means used in the respective auto-injector.
• the housing 2 may have at least one viewing window for inspecting the syringe 3.
• the auto-injector 1 may preferably be used for subcutaneous or intra-muscular injection, particularly for delivering one of an analgetic, an anticoagulant, insulin, an insulin derivate, heparin, Lovenox, a vaccine, a growth hormone, a peptide hormone, a proteine, antibodies and complex carbohydrates.
• the aforementioned arrangement for coupling the plunger (9) to either, the syringe (3) or the stopper (6), may be applied in any auto-injector having a plunger for forwarding a force of a drive means to a syringe with a stopper.
• the primary advantage of this arrangement ensures the load from the drive means is not transferred directly to the stopper until the needle is inserted in the patient, thus avoiding a wet injection.
• the arrangement comprises the syringe holder (22) and associated syringe holder arms (23), a shoulder (e.g.
• the spring means or other drive means the ability to retract the syringe or to forward a needle shroud after injection and other features described herein are not required for the prevention of a wet injection.

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