Emergency auto-injector

Abstract

An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to its forward end includes a housing element arranged along a longitudinal axis and having a forward end and a rearward end, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, a control unit configured to fixedly hold the syringe therein and configured to be fixedly connected to the housing element, and a plunger rod biased axially forwardly as urged by the at least one resilient element and configured to engage with the control unit in a retracted position, the plunger rod in said position being prevented from forward axial movement relative to the control unit as urged by the at least one resilient element, and when the needle guard moves axially rearward relative to the housing element, the plunger rod disengages from the control unit and is allowed to move axially forward relative to the control unit as urged by the at least one resilient element.

Description

[Technical Field]

[0001] REFERENCE TO RELATED APPLICATIONS Reference is made to U.S. Provisional Patent Application No. 63 / 414,043, entitled "EMERGENCY AUTOMATIC INJECTION DEVICE," filed October 7, 2022, the entire disclosure of which is incorporated herein by reference, and priority is claimed under U.S.C. Sections 1.78(a)(4) and (5)(i).

[0002] FIELD OF THE INVENTION The present invention relates generally to autoinjectors, and more particularly to autoinjectors adapted for parenteral administration of a substance (e.g., a drug) to a living organism (human or animal) by pressing the autoinjector against the injection site.

[0003] Background of the Invention A variety of auto-injectors are known that are activated by pressing the auto-injector against an injection site on a patient's skin. It is important to ensure that the needle is protected at all times before, during, and after the injection of medication. It is also necessary to ensure that the auto-injector is prevented from being inadvertently activated. Summary of the Invention

[0004] Summary of the Invention SUMMARY OF THE INVENTION The present invention aims to provide an emergency automatic injection device.

[0005] Thus, according to one embodiment or combination of embodiments of the present invention, there is provided an automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, the automatic injection device comprising: a housing element arranged along a longitudinal axis and having a forward end and a rearward end; at least one resilient element arranged to be positioned within the housing element; a needle guard slidably arrangeable relative to the housing element; a control unit configured to fixedly hold the syringe therein and configured to be fixedly connected to the housing element; and a plunger rod biased axially forwardly urged by the at least one resilient element and configured to engage with the control unit in a retracted configuration, the plunger rod in said configuration being prevented from forward axial movement relative to the control unit urged by the at least one resilient element, wherein rearward axial movement of the needle guard relative to the housing element disengages the plunger rod from the control unit and is allowed to move axially forwardly relative to the control unit urged by the at least one resilient element.

[0006] Preferably, the automatic injection device also includes a rear cover fixedly attached to the rear end of the housing element, a portion of which is configured to deflect radially upon rearward axial movement of the needle guard. More preferably, the automatic injection device also includes a safety cap releasably attached to the rear cover, which is configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover. Even more preferably, rearward axial movement of the needle guard is prevented by engagement between the needle guard and the rear cover. Even more preferably, rearward axial movement of the needle guard is permitted upon removal of the safety cap from the rear cover. Preferably, the safety cap includes a rigid rib and at least one resilient spring portion.

[0007] According to an embodiment of the present invention, the control unit has at least one locking portion, and the plunger rod is configured to engage with the at least one locking portion in the retracted position, and when the needle guard moves axially rearward relative to the housing element, the plunger rod is disengaged from the at least one locking portion.

[0008] Preferably, the at least one locking portion is radially deflectable. More preferably, the automatic injection device also includes a buffer element between the control unit and the syringe, which is configured to partially absorb forces occurring during relative movement between the plunger rod and the syringe. Still more preferably, the plunger rod includes at least one protrusion, which is supported forwardly against the at least one locking portion of the control unit in the retracted configuration, and the at least one locking portion is supported radially outwardly against a portion of the needle guard, thereby preventing the plunger rod from deflecting radially outward and releasing the plunger rod to be moved forward in the retracted configuration.

[0009] Even more preferably, at least one resilient spring portion is disposed within the opening in the rear cover, and inward deflection of a portion of the rear cover is prevented by a rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

[0010] According to an embodiment of the present invention, at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until sufficient axial force is exerted to permit deflection of the at least one resilient spring portion and removal of the safety cap.

[0011] Preferably, rearward axial movement of the needle guard relative to the housing element causes a portion of the rear cover to deflect radially inward toward the plunger rod. More preferably, movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold. Still more preferably, the needle guard has at least one aperture, and the at least one locking feature is radially supported by the needle guard in the retracted configuration, such that rearward axial movement of the needle guard relative to the housing element inserts the at least one locking feature into the at least one aperture in the needle guard, thereby actuating the automatic injection device and allowing forward axial movement of the plunger rod relative to the syringe.

[0012] Even more preferably, the plunger rod has at least one locking engagement portion, which is supported forwardly by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

[0013] According to an embodiment of the present invention, the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, wherein the needle guard engages a portion of the control unit to prevent the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element, and the plunger rod prevents disengagement of the control unit and the needle guard until axial forward movement of the plunger rod relative to the syringe.

[0014] Preferably, the automatic injection device also includes a needle shield remover configured to be releasably coupled to the housing element, such that the needle guard engages a portion of the needle shield remover in the retracted configuration, thereby preventing the needle guard from being moved axially forward relative to the housing element.

[0015] According to an embodiment of the present invention, an automatic injection device for use with a syringe including at least one syringe piston and a needle connected to its forward end includes a housing element disposed along a longitudinal axis and having a forward end and a rearward end, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, a control unit configured to fixedly retain the syringe therein and configured to be fixedly coupled to the housing element, and a plunger rod biased axially forwardly urged by the at least one resilient element and configured to engage the control unit in a retracted configuration, the plunger rod prevented from forward axial movement relative to the control unit urged by the at least one resilient element in said configuration, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

[0016] According to an embodiment of the present invention, an automatic injection device for use with a syringe including at least one syringe piston and a needle connected to its forward end includes a housing element disposed along a longitudinal axis and having a forward end and a rearward end, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, a control unit configured to fixedly retain the syringe therein and configured to be fixedly coupled to the housing element, a safety cap removably coupled to the automatic injection device and having a rigid portion and a resilient portion, and a plunger rod biased axially forwardly urged by the at least one resilient element and configured to engage the control unit in a retracted configuration in which the plunger rod is prevented from forward axial movement relative to the control unit urged by the at least one resilient element, and in which axial rearward movement of the needle guard relative to the housing element is prevented until the safety cap is removed from the automatic injection device.

[0017] According to an embodiment of the present invention, an automatic injection device for use with a syringe including at least one syringe piston and a needle connected to its forward end comprises a housing element disposed along a longitudinal axis and having a forward end and a rearward end, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, the needle guard having at least one opening, a control unit configured to be fixedly coupled to the housing element, the control unit having at least one locking portion, and a plunger rod biased axially forward by the urging of the at least one resilient element and configured to move the piston axially forward relative to the syringe upon actuation of the automatic injection device, wherein the locking portion is radially supported by the needle guard in a retracted position, and axial rearward movement of the needle guard relative to the housing element causes the at least one locking portion to be inserted into the at least one opening in the needle guard, thereby actuating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

[0018] According to an embodiment of the present invention, an automatic injection device for use with a syringe including at least one syringe piston and a needle connected to its forward end includes a housing element disposed along a longitudinal axis and having a forward end and a rearward end, a rear cover fixedly attached to the rearward end of the housing element, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, a control unit configured to fixedly hold the syringe therein and fixedly coupled to the housing element, and a plunger rod configured to be axially forwardly biased by the at least one resilient element and to move the piston axially forward relative to the syringe upon actuation of the automatic injection device, the plunger rod further configured to engage with the control unit in a retracted configuration, wherein rearward axial movement of the needle guard relative to the housing element radially deflects a portion of the rearward end, thereby allowing the plunger rod to disengage from the control unit and resulting in forward axial movement of the plunger rod relative to the syringe.

[0019] According to an embodiment of the present invention, an automatic injection device for use with a syringe including at least one syringe piston and a needle connected to its forward end includes a housing element arranged along a longitudinal axis and having a forward end and a rearward end, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, a control unit configured to be fixedly coupled to the housing element, the control unit having at least one locking portion, and a plunger rod having at least one locking engagement portion configured to be urged axially forward by the urging of the at least one resilient element and to move the piston axially forward relative to the syringe when the automatic injection device is actuated, the at least one locking engagement portion being forwardly supported by the at least one locking portion in a retracted position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby actuating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

[0020] According to an embodiment of the present invention, an automatic injection device for use with a syringe including at least one syringe piston and a needle coupled to its forward end includes a housing element disposed along a longitudinal axis and having a forward end and a rearward end, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, a needle shield remover configured to be releasably coupled to the housing element, a control unit configured to fixedly hold the syringe therein and configured to be fixedly coupled to the housing element, and a plunger rod biased axially forward urged by the at least one resilient element, wherein the needle guard engages a portion of the control unit thereby preventing the needle guard from being moved axially forward relative to the housing element after removal of the needle shield remover from the housing element, and the plunger rod prevents disengagement of the control unit and the needle guard until axial forward movement of the plunger rod relative to the syringe.

[0021] According to an embodiment of the present invention, an automatic injection device for use with a syringe including at least one syringe piston and a needle connected to its forward end includes a housing element disposed along a longitudinal axis and having a forward end and a rearward end, at least one resilient element arranged to be positioned within the housing element, a needle guard slidably positionable relative to the housing element, a needle shield remover configured to be releasably coupled to the housing element, a control unit configured to securely hold the syringe therein and configured to be securely coupled to the housing element, and a plunger rod biased axially forward urged by the at least one resilient element, wherein the needle guard engages a portion of the needle shield remover in a retracted configuration, thereby preventing the needle guard from being moved axially forward relative to the housing element.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood and appreciated from the following detailed description when considered in conjunction with the following drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1A, 1B, and 1C are respectively a simplified perspective view and two cross-sectional views of an automatic injection device constructed and operative in accordance with an embodiment of the present invention, the cross-sectional views showing cross-sections along lines BB and CC in FIG. 1A. [Figure 2] 2A and 2B are a schematic exploded view and a cross-sectional exploded view, respectively, of the automatic injection device of FIGS. 1A-1C, the cross-sectional view showing a cross section along line BB in FIG. 2A. [Figure 3] Figures 3A, 3B, 3C, 3D and 3E are respectively two simplified perspective views, a simplified side view, a simplified top view and a simplified cross-sectional view along line EE of Figure 3C of a needle shield remover forming part of the automatic injection device of Figures 1A to 1C. [Figure 4] 4A, 4B, 4C and 4D are respectively a schematic perspective view, a schematic side view and two cross-sectional views along orthogonal lines CC and DD in FIG. 4B of a housing element forming part of the automatic injection device of FIGS. 1A-1C. [Figure 5] Figures 5A, 5B, 5C, 5D, 5E and 5F respectively show two schematic perspective views, a schematic side view, a schematic top view and two schematic cross-sectional views along lines EE in Figure 5C and FF in Figure 5B of a needle guard forming part of the automatic injection device of Figures 1A to 1C. [Figure 6] Figures 6A, 6B, 6C, 6D and 6E are respectively two schematic perspective views, a schematic side view, a schematic top view and a schematic cross-sectional view along line EE in Figure 6C of a control unit forming part of the automatic injection device of Figures 1A to 1C. [Figure 7] 7A, 7B, 7C and 7D are respectively two schematic perspective views, a schematic side view and a schematic cross-sectional view along line DD in FIG. 7C of a syringe assembly forming part of the automatic injection device of FIGS. 1A-1C. [Figure 8]Figures 8A, 8B, 8C, 8D and 8E are respectively two schematic perspective views, a schematic side view, a schematic top view and a schematic cross-sectional view along line EE in Figure 8C of a plunger rod forming part of the automatic injection device of Figures 1A to 1C. [Figure 9] Figures 9A, 9B, 9C, 9D, 9E and 9F respectively show two schematic perspective views, a schematic side view, a schematic top view and two schematic cross-sectional views along the orthogonal lines EE and FF in Figure 9C of a rear cover forming part of the automatic injection device of Figures 1A to 1C. [Figure 10] 10A, 10B, 10C and 10D are respectively two schematic perspective views, a schematic side view and a schematic cross-sectional view along line DD in FIG. 10C of a safety cap forming part of the automatic injection device of FIGS. 1A to 1C. [Figure 11] 11A, 11B and 11C are schematic drawings of the automatic injection device of FIGS. 1A to 10D in a "storage" position, including a schematic perspective view and two cross-sectional views along orthogonal lines BB and CC in FIG. 11A. [Figure 12] Figures 12A, 12B and 12C are schematic drawings of the automatic injection device of Figures 1A to 10D in a position during needle shield removal, including a schematic perspective view and two cross-sectional views along orthogonal lines BB and CC in Figure 12A, and Figure 12C is a partially cut-away view to clearly show the internal components of the automatic injection device of Figures 1A to 10D. [Figure 13] Figures 13A and 13B are schematic drawings of the automatic injection device of Figures 1A to 10D at intermediate stages of positioning during a safety cap removal operation, including a schematic perspective view and a cross-sectional view along line BB in Figure 13A, and Figure 13B is a partially cut-away view to clearly show the internal components of the automatic injection device of Figures 1A to 10D. [Figure 14] Figures 14A, 14B and 14C are schematic drawings of the automatic injection device of Figures 1A to 10D in a position at the end of the safety cap removal operation, including a schematic perspective view and two cross-sectional views along orthogonal lines BB and CC in Figure 14A. [Figure 15]15A and 15B are schematic drawings of the automatic injection device of FIGS. 1A-10D in an operative position with the needle guard pressed against the injection site, including a schematic perspective view and a cross-sectional view along line BB in FIG. 15A. [Figure 16] 16A and 16B are schematic drawings of the automatic injection device of FIGS. 1A-10D in a needle insertion configuration, including a schematic perspective view and a cross-sectional view taken along line BB in FIG. 16A. [Figure 17] 17A and 17B are schematic drawings of the automatic injection device of FIGS. 1A-10D in an injection start position, including a schematic perspective view and a cross-sectional view taken along line BB in FIG. 17A. [Figure 18] 18A and 18B are schematic drawings of the automatic injection device of FIGS. 1A-10D in an injection configuration, including a schematic perspective view and a cross-sectional view taken along line BB in FIG. 18A. [Figure 19] 19A and 19B are schematic drawings of the automatic injection device of FIGS. 1A-10D in a configuration at the end of an injection operation, including a schematic perspective view and a cross-sectional view along line BB in FIG. 19A. [Figure 20] Figures 20A and 20B are schematic drawings of the automatic injection device of Figures 1A to 10D in a position during removal from the injection site, including a schematic perspective view and a cross-sectional view along line BB in Figure 20A, and Figure 20B is a partially cut-away view to clearly show the internal components of the automatic injection device of Figures 1A to 10D. [Figure 21] 21A and 21B are schematic drawings of the automatic injection device of FIGS. 1A to 10D in a needle protection configuration, including a schematic perspective view and a cross-sectional view along line BB in FIG. 21A, and FIG. 21B is a partially cut-away view to clearly show the internal components of the automatic injection device of FIGS. 1A to 10D. DETAILED DESCRIPTION OF THE INVENTION

[0024] Description of the Embodiments The principles, uses, and implementation of the teachings herein may be better understood with reference to the following description and accompanying drawings, which will enable those skilled in the art, having reference to the description and drawings, to practice the invention without undue effort or experimentation.

[0025] Before describing at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and combinations of components and / or methods set forth in the following description and / or depicted in the drawings and / or examples. The invention is capable of other embodiments and of being practiced or carried out in various ways. It is also understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0026] Some embodiments of the present invention are described herein with reference to the accompanying drawings. The description, together with the drawings, will make apparent to those skilled in the art how to practice some embodiments of the present invention. The drawings are for illustrative purposes and are not intended to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the present invention. For clarity, some objects depicted in the drawings may not be drawn to scale.

[0027] Reference is now made initially to Figures 1A, 1B, and 1C, which are respectively a simplified perspective view and two cross-sectional views of an automatic injection device constructed and operative in accordance with an embodiment of the present invention, the cross-sectional views being taken along lines BB and CC in Figure 1A. Reference is also made additionally to Figures 2A and 2B, which are respectively a simplified exploded view and a cross-sectional exploded view of the automatic injection device of Figures 1A-1C, the cross-sectional view being taken along line BB in Figure 2A.

[0028] 1A-2B, the automatic injection device 100 includes a housing element 102 and a rear cover 104, which are fixedly attached, preferably by a snap-fit ​​engagement or the like. It is noted that the housing element 102 and the rear cover 104 are disposed along a common longitudinal axis 107.

[0029] A needle guard 110 is provided that is disposed within a receptacle formed by the rear cover 104 and the housing element 102 and is aligned along the longitudinal axis 107. The needle guard 110 is partially received within the housing element 102 and extends forwardly therefrom, projecting forwardly therefrom. The needle guard 110 is biased forwardly under the force of a needle guard spring 112 that is supported between the needle guard 110 and the control unit 120. A particular feature of this embodiment of the present invention is that the control unit 120 is axially fixed relative to the housing element 102 in all operative positions of the automatic injection device 100.

[0030] Syringe assembly 130 is at least partially received within and fixedly mounted to control unit 120. Syringe assembly 130 preferably includes a syringe barrel 132 containing a medication concealed therein by a piston 134. Syringe barrel 132 has a generally circular flange 136 at its rear end and a needle 138 extending forwardly from and fixedly mounted to the forward end of syringe barrel 132, the needle preferably being covered by a needle shield 139. Cushioning element 140 is configured to be supported between syringe flange 136 and a portion of control unit 120.

[0031] Plunger rod 150 is at least partially inserted into syringe barrel 132 and partially received within control unit 120. A particular feature of this embodiment of the present invention is that engagement with a portion of control unit 120 prevents plunger rod 150 from moving axially forward along longitudinal axis 107. Plunger rod 150 is biased forward by an injection spring 160 that is at least partially received in a socket formed in plunger rod 150. Injection spring 160 is supported between a portion of plunger rod 150 and rear cover 104.

[0032] A particular feature of this embodiment of the present invention is that the safety cap 170 is at least partially received by, and preferably selectively coupled to, the rear cover 104. When the safety cap 170 is coupled to the rear cover 104, rearward axial movement of the needle guard 110 relative to the housing element 102 is prevented.

[0033] 1A-2B also show that needle shield remover 180 is selectably attached, preferably threadably, to housing element 102 and is configured to protect needle 138 during storage and to expose needle 138 by removing needle shield 139 covering needle 138 when needle shield remover 180 is removed from housing element 102.

[0034] The needle guard 110 is configured to be prevented from axially forward movement relative to the housing element 102 by engagement with the needle shield remover 180 in the initial retracted configuration of the automatic injection device 100 .

[0035] Reference is now made to Figures 3A, 3B, 3C, 3D and 3E, which are respectively two simplified perspective views, a simplified side view, a simplified top view and a simplified cross-sectional view taken along line EE of Figure 3C of a needle shield remover 180 forming part of the automatic injection device 100 of Figures 1A-1C.

[0036] Needle shield remover 180 is preferably a unitarily formed element, preferably made of injection molded plastic, disposed along a longitudinal axis of symmetry 107. Needle shield remover 180 has a generally cylindrical portion 190 having a closed forward end 200 and an open rearward end 202. Closed forward end 200 defines a rearward-facing surface 203. Internal threads 204 are formed on the interior surface of cylindrical portion 190 and are disposed generally adjacent rearward end 202.

[0037] The needle shield engaging portion 210 extends axially rearward from the forward end 200 of the cylindrical portion 190. The needle shield engaging portion 210 is concentrically disposed within the cylindrical portion 190 and aligned along a common longitudinal axis therewith. The needle shield engaging portion 210 preferably has a bore 212 including an enlarged bore portion 214 adjacent the forward end 200 of the cylindrical portion 190 and a generally narrower bore portion 216. A forward-facing shoulder 220 is formed between bore portions 214 and 216.

[0038] Reference is now made to Figures 4A, 4B, 4C and 4D, which respectively show a simplified perspective view, a simplified side view and two cross-sectional views along orthogonal lines CC and DD in Figure 4B of a housing element 102 forming part of the automatic injection device 100 of Figures 1A-1C.

[0039] The housing element 102 is preferably an integrally formed element, preferably made of injection molded plastic, and is arranged along a longitudinal axis of symmetry 107 .

[0040] The housing element 102 is preferably a hollow cylindrical element having an open rearward end 230 and an open forward end 232. External threads 240 are formed on the outer surface of the forward portion of the housing element 102 and are located generally adjacent the forward end 232. The external threads 240 are slightly smaller in diameter than the remainder of the housing element 102, so that a rearward-facing shoulder 242 is formed on the inner surface of the housing element 102 adjacent the forward end 232 that extends generally slightly radially inward from the inner surface of the housing element 102.

[0041] 4C and 4D particularly show that threaded portion 240 has at least one aperture 250 formed therethrough and located generally forward of rearward-facing shoulder 242. Additionally, a pair of diametrically opposed apertures 252 are typically formed at an intermediate location along the longitudinal extent of housing element 102.

[0042] Reference is now made to Figures 5A, 5B, 5C, 5D, 5E and 5F, which respectively show two simplified perspective views, a simplified side view, a simplified top view and two simplified cross-sectional views taken along lines EE in Figure 5C and FF in Figure 5B of a needle guard 110 forming part of the automatic injection device 100 of Figures 1A-1C.

[0043] Needle guard 110 is preferably an integrally formed element, preferably made of injection molded plastic, and preferably has a generally cylindrical configuration including a generally tubular forward portion 260 having a forward-facing body-engaging surface 262 with an opening 264 formed therethrough. An inner, rearward-facing, annular surface 266 is located opposite body-engaging surface 262 and serves as a spring seat for spring 112.

[0044] Typically, a pair of diametrically opposed snap portions 270 are formed in recesses rearwardly disposed from the forward-facing body-engagement surface 262 of the tubular forward portion 260. Each snap portion 270 has a pair of outwardly projecting fingers 272 and 274 at its rearward end, axially spaced from each other to form a longitudinal groove 276 therebetween. Finger 272 preferably has a rounded forward-facing surface 280 and a rounded rearward-facing surface 282. Finger 274 preferably has a forward-facing tapered surface 286 and a rearward-facing shoulder 288, extending generally transversely to the longitudinal axis 107. The snap portions 270 are configured to be inwardly deflectable. It is noted that the snap portions 270 are configured for operable engagement with the housing element 102.

[0045] Needle guard 110 has a pair of symmetrical mounting arms 300 having rearward-most ends 302 disposed symmetrically about longitudinal axis 107. Mounting arms 300 extend rearwardly of tubular portion 260 parallel to longitudinal axis 107. Together, mounting arms 300 form an imaginary cylinder having a diameter greater than that of tubular portion 260, thereby forming a forward-facing, annular shoulder 306 between tubular portion 260 and mounting arms 300. A pair of longitudinal grooves 310 are formed between the pair of mounting arms 300, and extend rearwardly, preferably from a location generally adjacent forward-facing shoulder 306, to the rearward-most ends 302 of mounting arms 300. Each of rearward-most ends 302 of mounting arms 300 has inward-facing protrusions 312 that extend into grooves 310 and have forward-facing, tapered edges 314.

[0046] A window 320 is formed in each of the mounting arms 300. The windows 320 face each other and are aligned with one another and adapted for operable engagement with a portion of the control unit 120 in a fixed configuration during operation of the automatic injection device 100.

[0047] Reference is now made to Figures 6A, 6B, 6C, 6D and 6E, which respectively show two simplified perspective views, a simplified side view, a simplified top view and a simplified cross-sectional view along line E-E in Figure 6C of a control unit 120 forming part of the automatic injection device 100 of Figures 1A-1C.

[0048] The control unit 120 is preferably an integrally formed element, preferably made of injection molded plastic, and is positioned along the longitudinal axis of symmetry 107 .

[0049] The control unit 120 includes a generally hollow cylindrical forward portion 340 terminating in a forward annular edge 342 and having an annular flange 344 formed at a midpoint along the longitudinal extent of the forward portion 340 and extending radially outward therefrom.

[0050] Bulkhead portion 350 is formed at the rearward end of forward portion 340 and is generally circular and has a diameter generally larger than that of forward portion 340, thereby forming a forward-facing shoulder 352 between forward portion 340 and bulkhead portion 350. Bulkhead portion 350 extends from forward-facing shoulder 352 to a generally wider, rearward-facing annular wall 360. Typically, two diametrically opposed locking elements 370 extend rearward from rearward annular wall 360 and terminate in inwardly radially extending fingers 372 that define a forward-facing surface 374 and a rearward-facing, tapered surface 380 that extend generally transverse to longitudinal axis 107.

[0051] Typically, a pair of diametrically opposed, radially spaced, longitudinal support ribs 390 extend rearward from the forward-facing shoulder 352 to a rearwardly tapered edge 394. The rearwardly tapered edge 394 of each of the pair of support ribs 390 preferably tapers in opposite directions. In each pair, the support ribs 390 are radially spaced from one another and have a connecting ridge 396 therebetween, with the connecting ridge 396 having a radially outwardly extending protrusion 398 formed thereon. The support ribs 390 extend radially outward from the bulkhead portion 350. Preferably, each pair of support ribs 390 is disposed between two locking elements 370.

[0052] 6E particularly illustrates that additionally, typically two diametrically opposed retainers 400 are disposed between the two support ribs 390 in each pair of support ribs 390. The retainers 400 extend rearwardly from the annular wall 360 and each preferably has an inwardly projecting finger 402 having a forwardly facing surface 404 and a rearwardly facing tapered surface 406. It is noted that the retainers 400 may alternatively be formed as a continuous ring with an inwardly projecting annular edge.

[0053] A socket 410 is formed through bulkhead portion 350 and annular wall 360 and defines a rearwardly facing shoulder 412. Socket 410 communicates with a throughbore 416 extending through forward portion 340.

[0054] Reference is now made to Figures 7A, 7B, 7C and 7D, which are respectively two simplified perspective views, a simplified side view and a simplified cross-sectional view along line DD in Figure 7C of a syringe assembly 130 forming part of the automatic injection device 100 of Figures 1A-1C.

[0055] 1A-2B, syringe assembly 130 preferably includes a syringe barrel 132 containing a medicament concealed therein by a piston 134. Syringe barrel 132 has a generally circular flange 136 at its rear end, and a needle 138 extends forwardly from the forward end of syringe barrel 132 and is fixedly attached thereto, with the needle preferably being covered by a needle shield 139. FIGS. 7A-7D show that a cushioning element 140 is mounted on syringe barrel 132 adjacent to and extending forwardly therefrom. Cushioning element 140 is preferably made of a resilient material such as, for example, TPE.

[0056] Reference is now made to Figures 8A, 8B, 8C, 8D and 8E, which respectively show two simplified perspective views, a simplified side view, a simplified top view and a simplified cross-sectional view along line E-E in Figure 8C of plunger rod 150 forming part of automatic injection device 100 of Figures 1A-1C.

[0057] Plunger rod 150 is preferably an integrally formed element, preferably made of injection molded plastic, and is disposed along longitudinal axis of symmetry 107 .

[0058] Plunger rod 150 preferably includes a generally hollow cylindrical shaft 440 disposed along longitudinal axis 107 and defining an internal bore 442. A forward shaft portion 450 defines a piston that extends axially forward from a forward end 452 of shaft 440 and engages a protrusion 454 at the forward end of forward shaft portion 450.

[0059] Typically, two generally diametrically opposed projections 460 extend radially outward from and are located generally adjacent the rear end of the shaft 440. Each projection 460 has a side surface 462.

[0060] 8A-8D also show that two, typically generally diametrically opposed, protrusions 470 extend radially outward from shaft 440 and are positioned generally adjacent its forward end 452. Protrusions 470 are generally radially spaced apart from protrusions 460. Protrusions 470 define a forward-facing, tapered surface 472 and a rearward-facing surface 474 that extend generally transverse to longitudinal axis 107.

[0061] Reference is now made to Figures 9A, 9B, 9C, 9D, 9E and 9F, which respectively show two simplified perspective views, a simplified side view, a simplified top view and two simplified cross-sectional views along orthogonal lines EE and FF in Figure 9C of a rear cover 104 forming part of the automatic injection device 100 of Figures 1A-1C.

[0062] The rear cover 104 is preferably an integrally formed element, preferably made of injection molded plastic, and is disposed along a longitudinal axis 107 .

[0063] Rear cover 104 has a generally circular rear portion 500 that defines a forward-facing surface 502 from which projects axially forwardly a hollow cylindrical shaft 504. A spring-receiving socket 510 is defined in shaft 504 and defines a forward-facing spring seat 512.

[0064] Typically, two arms 520 extend forward from the forward-facing surface 502 and are spaced radially outward from the shaft 504. The arms 520 are preferably diametrically opposed to one another. The arms 520 have fingers 522 extending radially outward at their forward ends. The fingers 522 include a tapered forward-facing surface 524 and a rearward-facing surface 526.

[0065] Typically, two diametrically opposed openings 530 are formed through the circular rear portion 500. Preferably, the openings 530 are arcuate in shape.

[0066] Reference is now made to Figures 10A, 10B, 10C and 10D, which are respectively two schematic perspective views, a schematic side view and a schematic cross-sectional view along line DD in Figure 10C of a safety cap 170 forming part of the automatic injection device 100 of Figures 1A-1C.

[0067] Safety cap 170 is preferably an integrally formed element, preferably made of injection molded plastic, and is disposed along longitudinal axis 107 .

[0068] The safety cap 170 has a generally circular rear portion 550 defining a forward-facing surface 552. Typically, two restraining arms 560 extend forward from the forward-facing surface 552 to a forward-most edge 561. The restraining arms 560 are preferably diametrically opposed to one another and preferably have a slightly arcuate shape. The restraining arms 560 extend about the longitudinal axis 107 and each include a central rib 562, which is preferably rigid, and a pair of leaf spring portions 564, which are preferably resilient and extend tangentially outward from the central rib 562 in two opposite directions. The leaf spring portions 564 have a triangular shape in accordance with an embodiment of the present invention, but may alternatively have other shapes that provide tangential resilience to the restraining arm 560 structure.

[0069] Leaf spring portions 564 are shown in a resting position in Figures 10A-10D and are adapted to deflect tangentially inwardly towards central rib 562 when a tangential compressive force is exerted thereon.

[0070] Reference is now made to Figures 11A, 11B, and 11C, which are schematic illustrations of the automatic injection device 100 of Figures 1A-10D in a "stowing" configuration, including a schematic perspective view and two cross-sectional views taken along orthogonal lines BB and CC of Figure 11A.

[0071] The automatic injection device 100 has a housing element 102 fixedly attached to a rear cover 104 , both of which are aligned along a common longitudinal axis 107 .

[0072] Disposed within the receptacle formed by rear cover 104 and housing element 102 is a needle guard 110 which is partially received within housing element 102 and projects forwardly therefrom.

[0073] FIG. 11C shows that the needle guard 110 is selectively attached to the housing element 102 in this retracted position by engagement of outwardly projecting fingers 272 of the snap portion 270 of the needle guard 110 with the opening 250 in the housing element 102.

[0074] Alternatively, the outwardly projecting fingers 272 of the needle guard 110 may be eliminated.

[0075] The control unit 120 is generally received within the needle guard 110. A further particular feature of this embodiment of the present invention is that the control unit 120 is fixedly attached to the housing element 102 in all operative configurations of the automatic injection device 100. An outwardly extending protrusion 398 of the control unit 120 is inserted into the opening 252 of the housing element 102, thereby preventing any movement of the control unit 120 relative to the housing element 102.

[0076] Syringe assembly 130 is fixedly received within control unit 120 to prevent axial movement between control unit 120 and syringe assembly 130 in all operative configurations of automatic injection device 100. Specifically, flange 136 of syringe barrel 132 is shown to be captured by retaining portion 400 of control unit 120. Specifically, FIG. 11B shows flange 136 captured between rear annular wall 360 and forward-facing surface 404 of retaining portion 400 of control unit 120.

[0077] Additionally, cushioning element 140 is shown mounted on syringe barrel 132 adjacent flange 136 and received within socket 410 of control unit 120, which is supported between syringe flange 136 and a rearward-facing shoulder 412 of control unit 120.

[0078] A particular feature of this embodiment of the present invention is that the cushioning element 140 projects slightly rearward from the rear annular wall 360 of the control unit 120, thereby partially absorbing forces generated during relative movement of the plunger rod 150 and the syringe barrel 132, as will be described in more detail below.

[0079] Needle guard spring 112 is supported between control unit 120 and needle guard 110 , specifically between annular flange 344 of control unit 120 and rearward-facing annular surface 266 of needle guard 110 .

[0080] The needle shield remover 180 is preferably threadably and removably coupled to the housing element 102, with the internal threads 204 of the needle shield remover 180 engaging the external threads 240 of the housing element 102. The needle shield 139 covering the needle 138 is shown partially received within the enlarged bore 214 of the needle shield engagement portion 210 of the needle shield remover 180, with a portion of the needle shield 139 positioned adjacent the forward-facing shoulder 220 of the needle shield remover 180. The needle 138 is protected by the needle shield 139 and the needle shield remover 180 in this retracted position.

[0081] Plunger rod 150 is at least partially inserted into syringe barrel 132 and partially received within control unit 120. In this retracted position, plunger rod 150 is not yet fully engaged with piston 134, such that piston-engaging protrusion 454 of plunger rod 150 is spaced slightly rearward from an inner socket formed within piston 134.

[0082] The plunger rod 150 is biased forward by the urging of an injection spring 160 that is at least partially received within an internal bore 442 formed in the plunger rod 150. The injection spring 160 is supported between a rearward-facing surface of the internal bore 442 of the plunger rod 150 and a forward-facing spring seat 512 on the shaft 504 of the rear cover 104.

[0083] A particular feature of this embodiment of the present invention is that, in this retracted configuration, plunger rod 150 is prevented from moving axially forward along longitudinal axis 107. Although plunger rod 150 is biased axially forward by the urging of injection spring 160, such axial forward movement is prevented by engagement with control unit 120. Specifically, forward-facing tapered surface 472 of protrusion 470 of plunger rod 150 is supported forwardly against rearward-facing tapered surface 380 of locking element 370 of control unit 120. Locking element 370 of control unit 120 is in turn supported radially outwardly against mounting arm 300 of needle guard 110, thereby preventing radial outward deflection and releasing plunger rod 150 for forward movement. As the control unit 120 is oriented relative to the housing element 102, in this retracted configuration the plunger rod 150 is also oriented relative to the housing element 102.

[0084] The opening 320 in the arm 300 of the needle guard 110 is spaced forwardly from the radially extending fingers 372 of the locking element 370 of the control unit 120 in this retracted configuration.

[0085] It is noted that in this retracted position, the forward end 452 of the shaft 440 of the plunger rod 150 is spaced rearwardly from the flange 136 of the syringe barrel 132, and the distance between the forward end 452 and the flange 136 determines the amount of medication expelled from the syringe barrel 132.

[0086] 11B and 11C, rearward axial movement of the needle guard 110 relative to the housing element 102 is prevented so long as the safety cap 170 is at least partially received within the rear cover 104. Specifically, when the leaf spring portions 564 of the restraining arms 560 are positioned forward relative to the openings 530 formed in the rear portion 500 of the rear cover 104, inward deflection of the arms 520 of the rear cover 104 is prevented by the fact that they are supported radially inward by the rigid central rib portion 562, which in turn is supported radially inward by the shaft 440 of the plunge rod 150, thereby preventing rearward axial movement of the needle guard 110. The leaf spring portion 564 is retained within the rear cover 104 to prevent inadvertent removal of the safety cap 170 from the rear cover 104 until sufficient axial force is exerted to deflect the leaf spring portion 564 and allow removal of the safety cap 170.

[0087] A further particular feature of this embodiment of the present invention is that, as particularly shown in Figure 11C, engagement of the needle guard 110 with the rear cover 104, which in turn is also engaged with the safety cap 170, prevents rearward axial movement of the needle guard 110 relative to the housing element 102. In particular, the rearmost ends 302 of the mounting arms 300 of the needle guard 110 are supported rearwardly against the forward-facing tapered surfaces 524 of the arms 520 of the rear cover 104. In this retracted configuration, the presence of the safety cap 170 within the automatic injection device 100 prevents inward deflection of the arms 520 of the rear cover 104, thereby preventing rearward axial movement of the needle guard 110 relative to the housing element 102. 11C , safety cap 170 is selectively coupled to rear cover 104 such that restraining arm 560 of safety cap 170 is received through and projects forwardly from opening 530 in rear cover 104. Restraining arm 560 of safety cap 170 is disposed radially outward of rear cover shaft 504 and shaft 440 of plunger rod 150 and radially inward of arms 520 of rear cover 104, thereby preventing inward deflection of arms 520 during axial rearward movement by needle guard 110. Leaf spring portion 564 of restraining arm 560 of safety cap 170 maintains coupling of safety cap 170 to rear cover 104 because leaf spring portion 564 is wider than opening 530 in rear cover 104. The ribs 562 of the restraining arms 560 exert a radial force against the shaft 440 of the plunger rod 150 to prevent inward deflection of the arms 520 of the rear cover 104 .

[0088] The needle guard 110 is biased to move axially forward by the force of the needle guard spring 112. Figures 11B and 11C show that in this retracted position, the engagement of the needle guard 110 with the needle shield remover 180, specifically, the engagement of the forward-facing body engagement surface 262 of the needle guard 110 with the rearward-facing surface 203 of the needle shield remover 180, prevents the needle guard 110 from moving axially forward.

[0089] A particular feature of this embodiment of the present invention is that the rear portion 550 of the safety cap 170 has a closed end with no aperture, and the front end 200 of the needle shield remover 180 also has a closed end with no aperture. The lack of an aperture at the front end of the automatic injection device 100 is beneficial from a convenience standpoint, as it may prevent a user from becoming confused and prematurely injecting before removing the needle shield remover 180.

[0090] Reference is now made to Figures 12A, 12B, and 12C, which are schematic drawings of the automatic injection device 100 of Figures 1A-10E in a needle shield removal configuration, including a schematic perspective view and two cross-sectional views taken along orthogonal lines BB and CC of Figure 12A. Figure 12C is a partially cut-away view to clearly show the internal components of the automatic injection device 100 of Figures 1A-10D.

[0091] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the retracted orientation illustrated in FIGS. 11A-11C are the same as described above, except for the following spatial relationships.

[0092] The user grasps the needle shield remover 180 and preferably removes it from the threadable housing element 102 by engaging the internal threads 204 of the needle shield remover 180 with the external threads 240 of the housing element 102, thereby removing the needle shield 139 and exposing the needle 138 of the syringe assembly 130.

[0093] Following removal of the needle shield remover 180, the forward-facing body-engaging surface 262 of the needle guard 110 is exposed and projects forwardly from the housing element 102 to a first longitudinal extent.

[0094] A particular feature of this embodiment of the present invention is that once the needle shield remover 180 is removed from the housing element 102, the needle guard 110 is biased axially forward by the needle guard spring 112 and is prevented from axially forward movement by engagement with a portion of the control unit 120, which in turn is prevented from deflection by engagement with a portion of the plunger rod 150. Specifically, Figures 12B and 12C show that the needle guard 110, in this needle shield removal configuration, is selectably attached to the housing element 102 by engagement of outwardly projecting fingers 272 on the snap portion 270 of the needle guard 110 with the opening 250 in the housing element 102. Alternatively, the outwardly projecting fingers 272 on the needle guard 110 may be eliminated.

[0095] Specifically, FIGS. 12B and 12C show that the groove 276 of the needle guard 110 is generally positioned in front of the rearward-facing shoulder 242 of the housing element 102, thereby positioning the outwardly projecting finger 272 in front of the rearward-facing shoulder 242 and positioning the outwardly projecting finger 274 behind the rearward-facing shoulder 242.

[0096] More specifically, FIG. 12C shows that the inward-facing protrusion 312 of the needle guard 110 is supported generally axially forward by a support rib 390 of the control unit 120, thereby preventing forward axial movement of the needle guard 110 relative to the housing element 102. As specifically shown in FIG. 12C , the protrusion 460 of the plunger rod 150 is received between each pair of support ribs 390 of the control unit 120, and the side surfaces 463 of the protrusion 460 of the plunger rod 150 engage with the support ribs 390 to act as a wedge between them and prevent them from bending inward, so that the forward-facing tapered edge 314 of the inward-facing protrusion 312 of the needle guard 110 is supported forward against the rearward tapered edges 394 of the two support ribs 390 of the control unit 120, preventing the two support ribs 390 of the control unit 120 from being biased axially forward against the needle guard 110 and bending inward toward each other.

[0097] Also shown in FIG. 12C is that the support ribs 390 of the control unit 120 are radially supported outward by the mounting arms 300 of the needle guard 110, which in turn are radially supported outward by the housing element 102.

[0098] A particular feature of this embodiment of the present invention is that rearward axial movement of the needle guard 110 relative to the housing element 102 is prevented so long as the safety cap 170 is at least partially received within the rear cover 104. Specifically, when the leaf spring portion 564 of the restraining arm 560 is positioned forward relative to the opening 530 formed in the rear portion 500 of the rear cover 104, inward deflection of the arm 520 of the rear cover 104 is prevented, thereby preventing rearward axial movement of the needle guard 110.

[0099] A further particular feature of this embodiment of the present invention is that, as particularly shown in Figure 12B, rearward axial movement of the needle guard 110 relative to the housing element 102 continues to be prevented in this needle shield removal configuration by engagement of the needle guard 110 with the rear cover 104, which in turn is also engaged with the safety cap 170. In particular, the rearmost ends 302 of the mounting arms 300 of the needle guard 110 are supported rearwardly against the forward-facing tapered surfaces 524 of the arms 520 of the rear cover 104. In this needle shield removal configuration, the presence of the safety cap 170 within the automatic injection device 100 continues to prevent inward deflection of the arms 520 of the rear cover 104, thereby preventing rearward axial movement of the needle guard 110 relative to the housing element 102. A particular feature of this embodiment of the present invention is that, as particularly shown in FIGURE 12B, safety cap 170 is selectively coupled to back cover 104 such that restraining arm 560 of safety cap 170 is received through and projects forwardly from opening 530 in back cover 104. Restraining arm 560 of safety cap 170 is disposed between shaft 440 of plunger rod 150 and arm 520 of back cover 104, thereby preventing inward deflection of arm 520 during axial rearward movement by needle guard 110. Leaf spring portion 564 of restraining arm 560 of safety cap 170 maintains coupling of safety cap 170 to back cover 104 because leaf spring portion 564 is wider than opening 530 in back cover 104.

[0100] Reference is now made to Figures 13A and 13B, which are schematic illustrations of the automatic injection device 100 of Figures 1A-10D at intermediate stages of deployment during a safety cap removal operation, including a schematic perspective view and a cross-sectional view taken along line BB in Figure 13A.

[0101] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the needle shield removal configuration illustrated in FIGS. 12A-12C are the same as described above, except for the following spatial relationships.

[0102] The user grasps the safety cap 170 and pulls it axially rearward relative to the housing element 102. When the safety cap 170 is pulled axially rearward, the leaf spring portion 564 squeezes tangentially through the opening 530 formed in the rear portion 500 of the rear cover 104, allowing the safety cap 170 to be removed from the automatic injection device 100.

[0103] 13A and 13B illustrate the momentary operating position that occurs during removal of the safety cap 170 from the automatic injection device 100. FIG.

[0104] Reference is now made to Figures 14A, 14B and 14C, which are schematic illustrations of the automatic injection device 100 of Figures 1A-10D in a configuration at the end of a safety cap removal operation, including a schematic perspective view and two cross-sectional views taken along orthogonal lines BB and CC of Figure 14A.

[0105] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the intermediate stages of the positioning during the safety cap removal operation illustrated in Figures 13A and 13B are the same as described above, except for the following spatial relationships.

[0106] The user then pulls the safety cap 170 axially rearward relative to the housing element 102. As the safety cap 170 is pulled axially rearward, a tangential force is exerted on the sides of the opening 530 formed in the rear portion 500 of the rear cover 104, causing the leaf spring portion 564 to further squeeze tangentially through the opening 530, allowing the safety cap 170 to be completely removed from the automatic injection device 100.

[0107] 14C shows that the needle guard 110 is selectively attached to the housing element 102 in this safety cap removal end action configuration by the outwardly projecting fingers 272 of the snap portion 270 of the needle guard 110 engaging the rearwardly facing shoulder 242 of the housing element 102. Alternatively, the outwardly projecting fingers 272 of the needle guard 110 may not be required.

[0108] A particular feature of this embodiment of the present invention is that once the safety cap 107 is completely removed from the rear cover 104, rearward axial movement of the needle guard 110 is permitted relative to the housing element 102. Specifically, when the safety cap 170 is removed from the rear cover 104, the arms 520 of the rear cover 104 are allowed to flex inward, thereby permitting rearward axial movement of the needle guard 110.

[0109] FIG. 14C shows that the rearmost ends 302 of the mounting arms 300 of the needle guard 110 are supported rearwardly against the forward-facing tapered surfaces 524 of the arms 520 of the rear cover 104 .

[0110] A particular feature of embodiments of the present invention is that the rear end of the automatic injection device 100 typically has two side openings, i.e., opening 530 in the rear cover 104, when the safety cap 170 is removed and the front end of the automatic injection device 100 has one central opening 264 configured for needle penetration therethrough. Different types of openings on either side of the automatic injection device 100 are beneficial from a convenience standpoint as they prevent user confusion and provide a clear indication of which side of the automatic injection device 100 to press against the skin for needle penetration therethrough.

[0111] Reference is now made to Figures 15A and 15B, which are schematic illustrations of the automatic injection device 100 of Figures 1A-10D in an operative position with the needle guard pressed against the injection site, including a schematic perspective view and a cross-sectional view taken along line BB of Figure 15A.

[0112] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the configuration at the end of the safety cap removal operation illustrated in Figures 14A-14C are the same as described above, except for the following spatial relationships.

[0113] The user presses the automatic injection device 100 against the injection site and moves the needle guard 110 axially rearward along the axis 107 relative to the rest of the automatic injection device 100, compressing the needle guard spring 112, thereby initiating manual insertion of the needle 138 into the injection site.

[0114] It is noted that the actuation configuration illustrated in FIGS. 15A and 15B is a momentary stage, showing the needle guard 110 during its axial rearward movement to initiate actuation of the automatic injection device 100.

[0115] FIG. 15B shows that the needle guard 110 has been moved slightly axially rearward relative to the housing element 102 so that the needle guard 110 is no longer engaged with the housing element 102 .

[0116] A particular feature of embodiments of the present invention is that a user must overcome a predetermined trigger force threshold to decouple the needle guard 110 from the housing element 102 and move the needle guard 110 axially rearward. The trigger force threshold is preferably in the range of 1 kgf to 3.5 kgf. This trigger force is advantageous in that it minimizes the possibility that the user will stop and not insert the needle into the injection site. The trigger force that the user must apply to move the needle guard 110 rearward preferably also simultaneously causes a sudden manual insertion of the needle into the injection site without an opportunity to stop before full needle penetration occurs.

[0117] It is noted that the trigger force is preferably greater than the force of the needle guard spring 112 combined with the force required for the outwardly projecting fingers 272 of the needle guard 110 to jump over the shoulder 242 of the housing element 102 to provide sufficient needle penetration depth for the needle 138 to inject the medication into the intramuscular tissue.

[0118] It is noted that in an alternative embodiment of the present invention, the outwardly protruding fingers 272 of the needle guard 110 may not be necessary, and therefore the needle guard 110 is not coupled to the housing element 102 at all. According to the alternative embodiment, the trigger force that the user must apply to move the needle guard 110 relative to the housing element 102 is created by friction between the inner surface of the needle guard 110 and the outer surface of the control unit 120, and additionally by friction created when the rearmost ends 302 of the mounting arms 300 of the needle guard 110 engage the tapered surfaces 524 of the arms 520 of the rear cover 104. The trigger force threshold is preferably in the range of 1 kgf to 3.5 kgf.

[0119] A particular feature of embodiments of the present invention is that the user preferably applies a substantially constant force until the needle is fully penetrated to the desired injection depth. This is achieved by frictional forces that exist between the needle guard 110 and the control unit 120 during the complete axial rearward movement of the needle guard 110 relative to the housing element 102. The trigger force that the user must apply to move the needle guard 110 rearward preferably simultaneously causes sudden manual insertion of the needle into the injection site without an opportunity to stop before full needle penetration occurs. The automatic injection device 100 is preferably used for emergency situations, such as for injection of epinephrine into intramuscular tissue, typically in the outer thigh of the body, possibly through layers of clothing. The substantially constant force profile of the automatic injection device's actuation is beneficial for forcing through layers of clothing and soft body tissue to reach the desired injection depth.

[0120] 15B particularly illustrates that during decoupling of the needle guard 110 from the housing element 102, the snap portion 270 of the needle guard 110 is deflected inwardly such that the outwardly projecting fingers 272 of the snap portion 270 of the needle guard 110 are no longer engaged with the openings 250 in the housing element 102. The outwardly projecting fingers 272 and 274 of the snap portion 270 of the needle guard 110 are now positioned generally rearwardly relative to the rearward-facing surface 242 of the housing element 102. Alternatively, the outwardly projecting fingers 272 of the needle guard 110 may be eliminated.

[0121] The needle guard spring 112 is partially compressed in its active position pressing the needle guard against the injection site.

[0122] A particular feature of this embodiment of the present invention is that, in this operative configuration to press the needle guard against the injection site, the plunger rod 150 remains prevented from axially forward movement along the longitudinal axis 107. The plunger rod 150 is biased axially forward as urged by the injection spring 160, but such axial forward movement is prevented by engagement with the control unit 120. Specifically, the forward-facing tapered surface 472 of the protrusion 470 of the plunger rod 150 is supported forwardly against the rearward-facing tapered surface 380 of the locking element 370 of the control unit 120. The locking element 370 of the control unit 120 is in turn supported radially outwardly against the mounting arm 300 of the needle guard 110, thereby preventing it from deflecting radially outward and releasing the plunger rod 150 from forward movement. As the control unit 120 is oriented relative to the housing element 102, the plunger rod 150 is also oriented relative to the housing element 102 in an operative configuration that presses the needle guard against the injection site.

[0123] The opening 320 in the arm 300 of the needle guard 110 remains spaced forward from the radially extending fingers 372 of the locking element 370 of the control unit 120 in the operative position pressing the needle guard against the injection site.

[0124] A particular feature of this embodiment of the present invention is that once the user overcomes the trigger force threshold and moves the needle guard 110 axially rearward relative to the housing element 102, the rearmost ends 302 of the mounting arms 300 of the needle guard 110 engage the forward-facing tapered surfaces 524 of the arms 520 of the rear cover 104, thereby translating the rearward axial movement of the needle guard 110 into an inward radial deflection of the arms 520 of the rear cover 104. Specifically, FIG. 15B shows that the arms 520 of the rear cover deflect radially inward toward the shaft 440 of the plunger rod 150 while in the active position pressing the needle guard against the injection site.

[0125] It is particularly shown that in this momentary actuation position of the needle guard against the injection site, the needle 138 remains protected within the needle guard 110.

[0126] Reference is now made to Figures 16A and 16B, which are schematic illustrations of the automatic injection device 100 of Figures 1A-10D in a needle insertion configuration, including a schematic perspective view and a cross-sectional view taken along line BB in Figure 16A.

[0127] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the positioning of the needle guard against the injection site as illustrated in Figures 15A and 15B are the same as described above, except for the following spatial relationships:

[0128] It is noted that as the user continues to press the automatic injection device 100 against the injection site, moving the needle guard 110 fully axially rearward along axis 107 relative to the remainder of the automatic injection device 100, fully compressing the needle guard spring 112, thereby manually puncturing the needle 138 into the injection site. The automatic injection device 100 is still in the actuation process, as illustrated in Figures 16A and 16B.

[0129] FIG. 16B shows that the needle guard 110 has been moved axially rearward relative to the housing element 102 so that the needle guard 110 is no longer engaged with the housing element 102 .

[0130] Figure 16B particularly shows that snap portion 270 of needle guard 110 is no longer deflected inward, but rather has returned to its home position. Outwardly projecting fingers 272 and 274 of snap portion 270 of needle guard 110 are now positioned generally more rearward relative to rearward-facing surface 242 of the housing, as compared to their respective positions illustrated in Figures 15A and 15B.

[0131] A particular feature of this embodiment of the present invention is that in this needle insertion configuration, radially extending fingers 372 of locking element 370 of control unit 120 are positioned in front of opening 320 in arm 300 of needle guard 110 and are therefore permitted to deflect radially outward under the urging of injection spring 160, which in turn biases the plunger rod axially forward. Notably, in the instantaneous needle insertion configuration of this figure, locking element 370 of control unit 120 is shown permitted to deflect radially outward, whereas in the views shown in Figures 16A and 16B, locking element 370 has not yet deflected radially outward.

[0132] FIG. 16B shows that the needle guard 110 is now fully axially retracted rearward, thereby causing the arms 520 of the rear cover 104 to deflect radially inward.

[0133] 16A and 16B show the momentary actuation configuration in which plunger rod 150 remains engaged with control unit 120 but has not yet been moved axially forward. Specifically, forward-facing tapered surface 472 of protrusion 470 of plunger rod 150 is supported forwardly against rearward-facing tapered surface 380 of locking element 370 of control unit 120. Locking element 370 of control unit 120 is not prevented from deflecting radially outward into opening 320 of mounting arm 300 of needle guard 110.

[0134] FIG. 16B shows that the needle guard 110 projects forward from the housing element 102 to a second longitudinal extent that is in the retracted position and is smaller than the first longitudinal extent shown in FIGS. 11A-11C.

[0135] Reference is now made to Figures 17A and 17B, which are schematic drawings of the automatic injection device of Figures 1A-10D in an injection start position, including a schematic perspective view and a cross-sectional view taken along line BB in Figure 17A.

[0136] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the needle insertion configuration illustrated in FIGS. 16A and 16B are the same as described above, except for the following spatial relationships.

[0137] The user continues to press the automatic injection device 100 against the injection site to begin expelling medication from the syringe barrel 132, through the needle 138, and into the injection site. The needle guard 110 remains fully retracted, and the needle 138 remains within the injection site. It is noted that the automatic injection device 100 is shown in the activated operative configuration, as illustrated in Figures 17A and 17B.

[0138] A particular feature of this embodiment of the present invention is that locking element 370 of control unit 120 now deflects radially outward into opening 320 in mounting arm 300 of needle guard 110, allowing plunger rod 150, biased by injection spring 160, to slide past locking element 370 of control unit 120 and move axially forward relative to syringe barrel 132, expelling the medication out of syringe barrel 132.

[0139] It is noted that the axial position of the opening 320 in the mounting arm 300 of the needle guard 110 along the longitudinal extent of the needle guard 100 determines when the automatic injection device 100 is activated, and thereby when an injection is initiated. Specifically, an injection is initiated only when the locking element 370 of the control unit 120 deflects outward and engages the opening 320 in the needle guard 110. The degree of rearward axial movement of the needle guard 110 relative to the housing element 102 required to allow for radial deflection of the locking element 370 can be utilized to adjust the depth of needle penetration at the start of an injection. For example, if the degree of rearward axial movement of the needle guard 110 relative to the housing element 102 is small, the depth of needle penetration will be small, and such a configuration may be more suitable for children. Alternatively, if the degree of rearward axial movement of the needle guard 110 relative to the housing element 102 is large, the depth of needle penetration will be large, and such a configuration may be more suitable for adults. The extent of rearward axial movement of needle guard 110 relative to housing element 102 that provides the initiation of an injection is defined by the longitudinal extent of opening 320 in needle guard 110 .

[0140] A particular feature of this embodiment of the present invention is that plunger rod 150 has now moved axially forward slightly into engagement with piston 134. Plunger rod 150 is now biased by injection spring 160 to move axially forward along longitudinal axis 107. Specifically, FIG. 17B shows that plunger 150 is no longer engaged with control unit 120 in this injection start position. Specifically, forward-facing tapered surface 472 of projection 470 of plunger rod 150 no longer rests against rearward-facing tapered surface 380 of locking element 370 of control unit 120.

[0141] FIG. 17B shows that the injection spring 160 is now in a partially released working position.

[0142] It is noted that in this injection start position, the forward end 452 of the shaft 440 of the plunger rod 150 is spaced slightly less rearward from the flange 136 of the syringe barrel 132 than its position in the retraction position illustrated in Figures 11A-11C, and that the distance between the forward end 452 and the flange 136 determines the amount of medicine expelled from the syringe barrel 132.

[0143] Reference is now made to Figures 18A and 18B, which are schematic illustrations of the automatic injection device 100 of Figures 1A-10D in an injection configuration, including a schematic perspective view and a cross-sectional view taken along line BB in Figure 18A.

[0144] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the injection triggering configuration illustrated in FIGS. 17A and 17B are the same as described above, except for the following spatial relationships.

[0145] The user continues to press the automatic injection device 100 against the injection site to begin expelling medication from the syringe barrel 132, through the needle 138, and into the injection site. The needle guard 110 remains fully retracted, and the needle 138 remains within the injection site. The plunger rod 150 continues its forward axial movement relative to the housing element 102 and relative to the syringe assembly 130, urged by the injection spring 160.

[0146] The locking element 370 of the control unit 120 is now returned to its rest position in front of the opening 320 in the mounting arm 300 of the needle guard 110 .

[0147] A particular feature of this embodiment of the present invention is that plunger rod 150 is now moved axially forward further along longitudinal axis 107 as compared to the injection start position illustrated in Figures 17A and 17B. Specifically, Figures 18A and 18B show that in this injection position, plunger 150 is no longer engaged with control unit 120. Specifically, forward-facing tapered surface 472 of projection 470 of plunger rod 150 is now spaced forwardly relative to rearward-facing tapered surface 380 of locking element 370 of control unit 120.

[0148] It is noted that in this injection configuration, the forward end 452 of the shaft 440 of the plunger rod 150 is spaced rearward less from the flange 136 of the syringe barrel 132 compared to its position in the injection start configuration shown in Figures 17A and 17B.

[0149] FIG. 18B shows that the injection spring 160 is now positioned in a more relaxed working position compared to its position at the start of injection as illustrated in FIGS. 17A and 17B.

[0150] Reference is now made to Figures 19A and 19B, which are schematic illustrations of the automatic injection device 100 of Figures 1A-10D in a configuration at the end of an injection operation, including a schematic perspective view and a cross-sectional view taken along line BB in Figure 19A.

[0151] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the injection configuration illustrated in FIGS. 18A and 18B are the same as described above, except for the following spatial relationships.

[0152] The user continues to press the automatic injection device 100 against the injection site to begin expelling medication from the syringe barrel 132, through the needle 138, and into the injection site. The needle guard 110 remains fully retracted, and the needle 138 remains within the injection site. Urged by the injection spring 160, the plunger rod 150 continues its forward axial movement relative to the housing element 102 and relative to the syringe assembly 130 until it expels the predetermined amount of medication from the syringe barrel 132.

[0153] A particular feature of this embodiment of the present invention is that in this end-of-injection configuration, plunger rod 150 has been moved axially forward more along longitudinal axis 107 to its forward-most position, specifically, until a portion of plunger rod 150 engages flange 136 of syringe barrel 132. Specifically, as shown in FIG. 19B, forward end 452 of shaft 440 of plunger rod 150 now abuts flange 136 of syringe barrel 132.

[0154] A particular feature of this embodiment of the present invention is that damping element 140 protrudes slightly rearward from rear annular wall 360 of control unit 120 to partially absorb forces generated during relative movement between plunger rod 150 and syringe barrel 132. Specifically, upon full forward axial movement of plunger rod 150 relative to housing element 102, forward end 452 of shaft 440 of plunger rod 150 engages flange 136 of syringe barrel 132. Damping element 140 protrudes slightly rearward from annular wall 360 of control unit 120 to partially absorb forces exerted on flange 136 of syringe barrel 132 while engaged with forward end 452 of plunger rod 150, thereby preventing or minimizing the risk of damage to flange 136.

[0155] FIG. 19B shows that the injection spring 160 is now positioned in a relaxed, working configuration.

[0156] Reference is now made to Figures 20A and 20B, which are schematic drawings of the automatic injection device 100 of Figures 1A-10D in a configuration during removal from an injection site, including a schematic perspective view and a cross-sectional view taken along line BB of Figure 20A, with Figure 20B being partially cut away to clearly show the internal components of the automatic injection device 100 of Figures 1A-10D.

[0157] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to the configuration at the end of the injection action illustrated in Figures 19A and 19B are the same as described above, except for the following spatial relationships.

[0158] When the user removes the automatic injection device 100 from the injection site, this prompts axial forward movement of the needle guard 110 relative to the housing element 102 to cover and protect the needle 138. In the operative configuration of this figure, the needle guard 110 is shown in a momentary position during its axial forward movement, when the needle guard 110 has not yet fully deployed over the needle 138.

[0159] Plunger rod 150 remains in its forward-most position when forward end 452 of shaft 440 of plunger rod 150 abuts flange 136 of syringe barrel 132 .

[0160] A particular feature of this embodiment of the present invention is that when the plunger rod 150 is disposed in its forward position, it no longer supports the two pairs of ribs 390 of the control unit 120, thereby allowing the ribs 390 to deflect inward toward each other, thereby allowing the needle guard 110 to move axially forward relative to the housing element 102, urged by the needle guard spring 112, once the user releases the automatic injection device 100 from the injection site.

[0161] Specifically, FIG. 20B shows that the forward-facing tapered edges 314 of the inward-facing protrusions 312 of the needle guard 110 abut the rearward tapered edges 394 of the two support ribs 390 of the control unit 120, and that the plunger rod 150 is now positioned axially forward with the protrusions 460, which prevent the support ribs 390 of the control unit 120 from deflecting inward due to the axial forward bias of the needle guard spring 112, thereby allowing the needle guard 110 to move axially forward relative to the housing element 102.

[0162] In this momentary actuation configuration of the figure, the needle guard 110 has not been moved fully axially forward, but the snap portions 270 of the needle guard 110 are shown beginning to deflect radially inward toward each other due to their engagement with the rearward-facing shoulders 242 of the housing element 102.

[0163] Reference is now made to Figures 21A and 21B, which are schematic drawings of the automatic injection device 100 of Figures 1A-10D in a needle protection configuration, including a schematic perspective view and a cross-sectional view taken along line BB of Figure 21A, with Figure 21B being partially cut away to clearly show the internal components of the automatic injection device 100 of Figures 1A-10D.

[0164] It will be understood that all spatial relationships between the various components of the automatic injection device 100 with respect to their position upon removal from the injection site illustrated in Figures 20A and 20B are the same as described above, except for the following spatial relationships.

[0165] When the user completely removes the automatic injection device 100 from the injection site, this prompts axial forward movement of the needle guard 110 relative to the housing element 102 to cover and protect the needle 138. In this operative configuration, the needle guard 110 is shown fully deployed to its forward-most position relative to the housing element 102, where it is locked relative to the housing element 102 and the needle 138 is protected.

[0166] It is noted that the needle guard 110 now projects forward from the housing element 102 to a second longitudinal extent that is greater than the first longitudinal extent mentioned with reference to Figures 11A to 11C, which illustrate the automatic injection device 100 in its retracted position.

[0167] A particular feature of this embodiment of the present invention is that when the plunger rod 150 is disposed in its forward position, it no longer supports the two pairs of ribs 390 of the control unit 120, thereby allowing the ribs 390 to deflect inward toward each other, thereby allowing the needle guard 110 to move further axially forward relative to the housing element 102, urged by the needle guard spring 112, once the user releases the automatic injection device 100 from the injection site.

[0168] Specifically, FIG. 21B shows that the forward-facing tapered edge 314 of the inward-facing protrusion 312 of the needle guard 110 is now spaced forward relative to the rearward tapered edges 394 of the two support ribs 390 of the control unit 120, which are biased axially forward against the needle guard 110 and deflect inward, thereby allowing the needle guard 110 to move further forward axially relative to the housing element 102.

[0169] A particular feature of this embodiment of the present invention is that in this needle protection configuration, the needle guard 110 is moved fully axially forward and locked relative to the housing element 102. Specifically, Figure 21B shows that the snap portion 270 of the needle guard 110 has slid over the rearward-facing shoulder 242 of the housing element 102 such that both outwardly projecting fingers 272 and 274 of the snap portion 270 of the needle guard 110 are now positioned within the opening 250 of the housing element 102, and the rearward-facing shoulder 288 of the outwardly projecting finger 274 is now supported rearwardly by the rearward-facing shoulder 242 of the housing element 102, preventing rearward axial movement of the needle guard 110 relative to the housing element 102 and exposing the needle 138 in this needle protection configuration.

[0170] It is noted that both the needle guard spring 112 and the injection spring 160 are disposed in their respective released states in this needle guard configuration.

[0171] This invention relates generally to automatic injection devices for the parenteral administration (e.g., dosing) of drugs to living organisms (human or animal). The dose may be delivered subcutaneously or into muscle.

[0172] According to an embodiment of the present invention, the medicine is contained in a pre-filled syringe, but it is understood that it can alternatively be used with other drug containers, such as vials or ampoules, in which case a vial adapter or ampoules adapter is used to reconstitute, mix and pump the medicine into the syringe before injection. The pre-filled syringe can be a conventional single-chamber pre-filled syringe containing a ready-to-inject liquid medicine, or a multi-chamber pre-filled syringe.

[0173] Those skilled in the art will appreciate that the present invention is not limited to what has been specifically set forth herein, but rather includes within its scope various combinations of the features described above and each of the combined features, as well as variations and modifications thereof that are not within the prior art.

Claims

1. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element; a control unit configured to fixedly hold the syringe therein and configured to be fixedly coupled to the housing element; a plunger rod biased axially forward by the urging of the at least one resilient element and configured to engage the control unit in a retracted configuration, the plunger rod being prevented from forward axial movement relative to the control unit urging the at least one resilient element, wherein rearward axial movement of the needle guard relative to the housing element disengages the plunger rod from the control unit and allows forward axial movement relative to the control unit urging the at least one resilient element. Automatic injection device.

2. 10. The automatic injection device of claim 1, also including a rear cover fixedly attached to the rearward end of the housing element, a portion of which is configured to deflect radially upon the rearward axial movement of the needle guard.

3. 3. The automatic injection device of claim 2, also including a safety cap releasably mounted on the rear cover, the safety cap configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

4. 3. The automatic injection device of claim 2, wherein the rearward axial movement of the needle guard is prevented by engagement of the needle guard with the rear cover.

5. 4. The automatic injection device of claim 3, wherein the rearward axial movement of the needle guard is permitted when a safety cap is removed from the rear cover.

6. 3. The automatic injection device of claim 2, wherein the safety cap has a rigid rib and at least one resilient spring portion.

7. 2. The automatic injection device of claim 1, wherein the control unit has at least one locking portion, the plunger rod is configured to engage with the at least one locking portion in the retracted position, and the plunger rod disengages from the at least one locking portion when the needle guard moves axially rearward relative to the housing element.

8. 8. The automatic injection device of claim 7, wherein the at least one locking portion is radially flexible.

9. 10. The automatic injection device of claim 1, wherein the automatic injection device also includes a buffer element between the control unit and the syringe, the buffer element being configured to partially absorb forces generated during relative movement between the plunger rod and the syringe.

10. 8. The automatic injection device of claim 7, wherein the plunger rod has at least one protrusion that is supported forward against the at least one locking portion of the control unit in the retracted position, and the at least one locking portion is supported radially outward against a portion of the needle guard, thereby preventing the plunger rod from bending radially outward and releasing the plunger rod to be moved forward in the retracted position.

11. 7. The automatic injection device of claim 6, wherein the at least one resilient spring portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

12. 7. The automatic injection device of claim 6, wherein the at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until a sufficient axial force is exerted to permit deflection of the at least one resilient spring portion and removal of the safety cap.

13. 7. The automatic injection device of claim 6, wherein rearward axial movement of the needle guard relative to the housing element causes the portion of the rear cover to deflect radially inward toward the plunger rod.

14. 10. The automatic injection device of claim 1, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

15. 8. The automatic injection device of claim 7, wherein the needle guard has at least one opening, and the at least one locking portion is radially supported by the needle guard in the retracted position, such that when the needle guard moves axially rearward relative to the housing element, the at least one locking portion is inserted into the at least one opening in the needle guard, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

16. 8. The automatic injection device of claim 7, wherein the plunger rod has at least one locking engagement portion, the at least one locking engagement portion being supported forward by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe.

17. 2. The automatic injection device of claim 1, wherein the automatic injection device also includes a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the control unit thereby preventing the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element, and the plunger rod preventing disengagement of the control unit from the needle guard until axial forward movement of the plunger rod relative to the syringe.

18. 2. The automatic injection device of claim 1, wherein the automatic injection device also includes a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the needle shield remover in a retracted position, thereby preventing the needle guard from being moved axially forward relative to the housing element.

19. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element; a control unit configured to fixedly hold the syringe therein and configured to be fixedly coupled to the housing element; a plunger rod biased axially forward by the at least one resilient element and configured to engage the control unit in a retracted configuration, the plunger rod prevented from moving axially forward relative to the control unit urged by the at least one resilient element in the retracted configuration; movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold; Automatic injection device.

20. 20. The automatic injection device of claim 19, wherein axial rearward movement of the needle guard relative to the housing element disengages the plunger rod from the control unit and allows the plunger rod to be axially forwardly moved relative to the control unit by the urging of the at least one resilient element.

21. 20. The automatic injection device of claim 19, wherein the trigger force is created by friction between an inner surface of the needle guard and an outer surface of the control unit, and additionally by friction created when a portion of the needle guard engages with a portion of a rear cover fixedly connected to the rear end of the housing element.

22. 22. The automatic injection device of claim 21, wherein a substantially constant force must be exerted on the needle shield during rearward axial movement of the needle shield relative to the housing element until the needle is fully penetrated to a desired injection depth.

23. 20. The automatic injection device of claim 19, also including a rear cover fixedly attached to the rearward end of the housing element, a portion of which is configured to deflect radially upon the rearward axial movement of the needle guard.

24. 24. The automatic injection device of claim 23, also including a safety cap releasably mounted on the rear cover, the safety cap configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

25. 24. The automatic injection device of claim 23, wherein the rearward axial movement of the needle guard is prevented by engagement of the needle guard with the rear cover.

26. 25. The automatic injection device of claim 24, wherein the rearward axial movement of the needle guard is permitted when a safety cap is removed from the rear cover.

27. 25. The automatic injection device of claim 24, wherein the safety cap has a rigid rib and at least one resilient spring portion.

28. 20. The automatic injection device of claim 19, wherein the control unit has at least one locking portion, the plunger rod is configured to engage with the at least one locking portion in the retracted position, and the plunger rod disengages from the at least one locking portion when the needle guard moves axially rearward relative to the housing element.

29. 30. The automatic injection device of claim 28, wherein the at least one locking portion is radially flexible.

30. 20. The automatic injection device of claim 19, wherein the automatic injection device also includes a buffer element between the control unit and the syringe, the buffer element being configured to partially absorb forces generated during relative movement between the plunger rod and the syringe.

31. 29. The automatic injection device of claim 28, wherein the plunger rod has at least one protrusion that is supported forward against the at least one locking portion of the control unit in the retracted position, and the at least one locking portion is supported radially outward against a portion of the needle guard, thereby preventing the plunger rod from bending radially outward and releasing the plunger rod to move forward in the retracted position.

32. 28. The automatic injection device of claim 27, wherein the at least one resilient spring portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

33. 28. The automatic injection device of claim 27, wherein the at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until a sufficient axial force is exerted to permit deflection of the at least one resilient spring portion and removal of the safety cap.

34. 24. The automatic injection device of claim 23, wherein rearward axial movement of the needle guard relative to the housing element causes the portion of the rear cover to deflect radially inward toward the plunger rod.

35. 29. The automatic injection device of claim 28, wherein the needle guard has at least one opening, and the at least one locking portion is radially supported by the needle guard in the storage position, such that when the needle guard moves axially rearward relative to the housing element, the at least one locking portion is inserted into the at least one opening in the needle guard, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

36. 29. The automatic injection device of claim 28, wherein the plunger rod has at least one locking engagement portion, the at least one locking engagement portion being supported forward by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe.

37. 20. The automatic injection device of claim 19, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the control unit thereby preventing the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element, and the plunger rod preventing disengagement of the control unit and the needle guard until axial forward movement of the plunger rod relative to the syringe.

38. 20. The automatic injection device of claim 19, wherein the automatic injection device also includes a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the needle shield remover in a retracted position, thereby preventing the needle guard from being moved axially forward relative to the housing element.

39. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element; a control unit configured to fixedly hold the syringe therein and configured to be fixedly coupled to the housing element; a safety cap removably coupled to the automatic injection device and having a rigid portion and a resilient portion; a plunger rod biased axially forward by the at least one resilient element and configured to engage the control unit in a retracted configuration, the plunger rod prevented from forward axial movement relative to the control unit urged by the at least one resilient element in said configuration, wherein rearward axial movement of the needle guard relative to the housing element is prevented until the safety cap is removed from the automatic injection device. Automatic injection device.

40. 40. The automatic injection device of claim 39, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

41. 40. The automatic injection device of claim 39, wherein when the needle guard moves axially rearward relative to the housing element, the plunger rod disengages from the control unit and is allowed to move axially forward relative to the control unit by the urging of the at least one resilient element.

42. 41. The automatic injection device of claim 40, wherein the trigger force is created by friction between an inner surface of the needle guard and an outer surface of the control unit, and additionally by friction created when a portion of the needle guard engages with a portion of a rear cover fixedly connected to the rear end of the housing element.

43. 43. The automatic injection device of claim 42, wherein a substantially constant force must be exerted on the needle shield during rearward axial movement of the needle shield relative to the housing element until the needle is fully penetrated to a desired injection depth.

44. 40. The automatic injection device of claim 39, also including a rear cover fixedly attached to the rearward end of the housing element, a portion of which is configured to deflect radially upon the rearward axial movement of the needle guard.

45. 45. The automatic injection device of claim 44, wherein the safety cap is releasably mounted on the rear cover and configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

46. 40. The automatic injection device of claim 39, wherein the rearward axial movement of the needle guard is prevented by engagement of the needle guard with the rear cover.

47. 40. The automatic injection device of claim 39, wherein the rearward axial movement of the needle guard is permitted when a safety cap is removed from the rear cover.

48. 40. The automatic injection device of claim 39, wherein the control unit has at least one locking portion, the plunger rod is configured to engage with the at least one locking portion in the retracted position, and the plunger rod is disengaged from the at least one locking portion when the needle guard moves axially rearward relative to the housing element.

49. 49. The automatic injection device of claim 48, wherein the at least one locking portion is radially flexible.

50. 40. The automatic injection device of claim 39, wherein the automatic injection device also includes a buffer element between the control unit and the syringe, the buffer element being configured to partially absorb forces generated during relative movement between the plunger rod and the syringe.

51. 49. The automatic injection device of claim 48, wherein the plunger rod has at least one protrusion which is supported forward against the at least one locking portion of the control unit in the retracted position, and the at least one locking portion is supported radially outward against a portion of the needle guard, thereby preventing the plunger rod from bending radially outward and releasing the plunger rod to move forward in the retracted position.

52. 45. The automatic injection device of claim 44, wherein the elastic portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid portion, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

53. 45. The automatic injection device of claim 44, wherein the resilient portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until sufficient axial force is exerted to permit deflection of the at least one resilient spring portion and removal of the safety cap.

54. 45. The automatic injection device of claim 44, wherein rearward axial movement of the needle guard relative to the housing element causes the portion of the rear cover to deflect radially inward toward the plunger rod.

55. 49. The automatic injection device of claim 48, wherein the needle guard has at least one opening, and the at least one locking portion is radially supported by the needle guard in the storage position, such that when the needle guard moves axially rearward relative to the housing element, the at least one locking portion is inserted into the at least one opening in the needle guard, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

56. 49. The automatic injection device of claim 48, wherein the plunger rod has at least one locking engagement portion, which is supported forward by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe.

57. 40. The automatic injection device of claim 39, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the control unit thereby preventing the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element, and the plunger rod preventing disengagement of the control unit from the needle guard until axial forward movement of the plunger rod relative to the syringe.

58. 40. The automatic injection device of claim 39, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, and wherein the needle guard engages with a portion of the needle shield remover in the retracted position, thereby preventing the needle guard from being moved axially forward relative to the housing element.

59. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element, the needle guard having at least one opening; a control unit configured to be fixedly coupled to the housing element, the control unit having at least one lock; a plunger rod that is biased axially forward by the urging of the at least one elastic element and configured to move the piston axially forward relative to the syringe when the automatic injection device is activated, wherein the locking portion is radially supported by the needle guard in a retracted position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion is inserted into the at least one opening in the needle guard, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe. Automatic injection device.

60. 60. The automatic injection device of claim 59, wherein the plunger rod is prevented from moving axially forward relative to the control unit urged by the at least one resilient element in the retracted configuration.

61. 60. The automatic injection device of claim 59, wherein when the needle guard moves axially rearward relative to the housing element, the plunger rod disengages from the control unit and is allowed to move axially forward relative to the control unit by the urging of the at least one resilient element.

62. 60. The automatic injection device of claim 59, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

63. 63. The automatic injection device of claim 62, wherein the trigger force is created by friction between an inner surface of the needle guard and an outer surface of the control unit, and additionally by friction created when a portion of the needle guard engages with a portion of a rear cover fixedly connected to the rear end of the housing element.

64. 60. The automatic injection device of claim 59, wherein a substantially constant force must be exerted on the needle shield during rearward axial movement of the needle shield relative to the housing element until the needle is fully penetrated to the desired injection depth.

65. 60. The automatic injection device of claim 59, also including a rear cover fixedly attached to the rearward end of the housing element, a portion of which is configured to deflect radially upon the axial rearward movement of the needle guard.

66. 66. The automatic injection device of claim 65, also including a safety cap releasably mounted on the rear cover, the safety cap configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

67. 66. The automatic injection device of claim 65, wherein the rearward axial movement of the needle guard is prevented by engagement of the needle guard with the rear cover.

68. 67. The automatic injection device of claim 66, wherein the rearward axial movement of the needle guard is permitted upon removal of the safety cap from the rear cover.

69. 67. The automatic injection device of claim 66, wherein the safety cap has a rigid rib and at least one resilient spring portion.

70. 60. The automatic injection device of claim 59, wherein the plunger rod is configured to engage with the at least one locking portion in the retracted position, and the plunger rod is disengaged from the at least one locking portion when the needle guard moves axially rearward relative to the housing element.

71. 60. The automatic injection device of claim 59, wherein the at least one locking portion is radially flexible.

72. 60. The automatic injection device of claim 59, wherein the automatic injection device also includes a buffer element between the control unit and the syringe, the buffer element being configured to partially absorb forces generated during relative movement between the plunger rod and the syringe.

73. 60. The automatic injection device of claim 59, wherein the plunger rod has at least one protrusion that is supported at its front end against the at least one locking portion of the control unit in the retracted position.

74. 70. The automatic injection device of claim 69, wherein the at least one elastic spring portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

75. 70. The automatic injection device of claim 69, wherein the at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until a sufficient axial force is exerted to permit deflection of the at least one resilient spring portion and removal of the safety cap.

76. 66. The automatic injection device of claim 65, wherein rearward axial movement of the needle guard relative to the housing element causes the portion of the rear cover to deflect radially inward toward the plunger rod.

77. 60. The automatic injection device of claim 59, wherein the plunger rod has at least one locking engagement portion, which is supported forward by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe.

78. 60. The automatic injection device of claim 59, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the control unit thereby preventing the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element, and the plunger rod preventing disengagement of the control unit from the needle guard until axial forward movement of the plunger rod relative to the syringe.

79. 60. The automatic injection device of claim 59, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, and wherein the needle guard engages with a portion of the needle shield remover in a retracted position, thereby preventing the needle guard from being moved axially forward relative to the housing element.

80. 60. The automatic injection device of claim 59, wherein the plunger rod engages with the locking portion of the control unit in the retracted position, and in this position the plunger rod is prevented from moving axially forward relative to the control unit as urged by the at least one elastic element, and when the needle guard moves axially rearward relative to the housing element, the plunger rod is disengaged from the locking portion of the control unit and is allowed to move axially forward relative to the control unit as urged by the at least one elastic element.

81. 60. The automatic injection device of claim 59, wherein the control unit is configured to securely hold the syringe therein.

82. 60. The automatic injection device of claim 59, wherein the at least one locking portion is capable of deflecting radially outward into the at least one opening upon sufficient axial rearward movement of the needle guard relative to the housing element.

83. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; a rear cover fixedly attached to the rear end of the housing element; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element; a control unit configured to fixedly hold the syringe therein and configured to be fixedly coupled to the housing element; a plunger rod configured to be biased axially forward by the at least one resilient element and to move the piston axially forward relative to the syringe upon actuation of the automatic injection device, the plunger rod further configured to engage the control unit in a retracted orientation; rearward axial movement of the needle guard relative to the housing element causes a portion of the rear cover to deflect radially, thereby allowing the plunger rod to disengage from the control unit and resulting in forward axial movement of the plunger rod relative to the syringe. Automatic injection device.

84. 84. The automatic injection device of claim 83, wherein the plunger rod is prevented from moving axially forward relative to the control unit urged by the at least one resilient element in the retracted configuration.

85. 84. The automatic injection device of claim 83, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

86. 86. The automatic injection device of claim 85, wherein the trigger force is created by friction between an inner surface of the needle guard and an outer surface of the control unit, and additionally by friction created when a portion of the needle guard engages with a portion of a rear cover fixedly connected to the rear end of the housing element.

87. 84. The automatic injection device of claim 83, wherein a substantially constant force must be exerted on the needle shield during rearward axial movement of the needle shield relative to the housing element until the needle is fully penetrated to the desired injection depth.

88. 90. The automatic injection device of claim 89, also including a safety cap releasably mounted on the rear cover, the safety cap configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

89. 66. The automatic injection device of claim 65, wherein the rearward axial movement of the needle guard is prevented by engagement of the needle guard with the rear cover in the retracted configuration.

90. 89. The automatic injection device of claim 88, wherein the rearward axial movement of the needle guard is permitted upon removal of the safety cap from the rear cover.

91. 89. The automatic injection device of claim 88, wherein the safety cap has a rigid rib and at least one resilient spring portion.

92. 84. The automatic injection device of claim 83, wherein the control unit has at least one locking portion, the plunger rod is configured to engage with the at least one locking portion in the retracted position, and the plunger rod is disengaged from the at least one locking portion when the needle guard moves axially rearward relative to the housing element.

93. 93. The automatic injection device of claim 92, wherein the at least one locking portion is radially flexible.

94. 84. The automatic injection device of claim 83, wherein the automatic injection device also includes a buffer element between the control unit and the syringe, the buffer element being configured to partially absorb forces generated during relative movement between the plunger rod and the syringe.

95. 93. The automatic injection device of claim 92, wherein the plunger rod has at least one protrusion that is supported at its front end against the at least one locking portion of the control unit in the retracted position.

96. 70. The automatic injection device of claim 69, wherein the at least one elastic spring portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

97. 92. The automatic injection device of claim 91, wherein the at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until a sufficient axial force is exerted to permit deflection of the at least one resilient spring portion and removal of the safety cap.

98. 94. The automatic injection device of claim 93, wherein the portion of the rear cover deflects radially inward toward the plunger rod upon axial rearward movement of the needle guard relative to the housing element.

99. 93. The automatic injection device of claim 92, wherein the plunger rod has at least one locking engagement portion, the at least one locking engagement portion being supported forward by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe.

100. 84. The automatic injection device of claim 83, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the control unit thereby preventing the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element, and the plunger rod preventing disengagement of the control unit from the needle guard until axial forward movement of the plunger rod relative to the syringe.

101. 84. The automatic injection device of claim 83, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, and wherein the needle guard engages with a portion of the needle shield remover in a retracted position, thereby preventing the needle guard from being moved axially forward relative to the housing element.

102. 93. The automatic injection device of claim 92, wherein the at least one locking portion is capable of deflecting radially outward into the at least one opening upon sufficient axial rearward movement of the needle guard relative to the housing element.

103. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element; a control unit having at least one locking portion configured to be fixedly coupled to the housing element; a plunger rod having at least one locking engagement portion that is biased axially forward by the urging of the at least one elastic element and configured to move the piston axially forward relative to the syringe when the automatic injection device is activated, wherein the at least one locking engagement portion is forwardly supported by the at least one locking portion in a retracted position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe. Automatic injection device.

104. 104. The automatic injection device of claim 103, also comprising a rear cover fixedly attached to the rear end of the housing element, a portion of which is configured to deflect radially upon the axial rearward movement of the needle guard.

105. 105. The automatic injection device of claim 104, also comprising a safety cap releasably mounted on the rear cover, the safety cap configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

106. 105. The automatic injection device of claim 104, wherein the rearward axial movement of the needle guard is prevented by engagement of the needle guard with the rear cover.

107. 106. The automatic injection device of claim 105, wherein the axial rearward movement of the needle guard is permitted when a safety cap is removed from the rear cover.

108. 106. The automatic injection device of claim 105, wherein the safety cap has a rigid rib and at least one resilient spring portion.

109. 104. The automatic injection device of claim 103, wherein the at least one locking portion is radially flexible.

110. 104. The automatic injection device of claim 103, wherein the automatic injection device also has a buffer element between the control unit and the syringe, which is configured to partially absorb forces that occur during relative movement between the plunger rod and the syringe.

111. The automatic injection device of claim 103, wherein the at least one locking portion is supported radially outward against a portion of the needle guard, thereby preventing it from bending radially outward and releasing the plunger rod to be moved forward in the retracted position.

112. 109. The automatic injection device of claim 108, wherein the at least one elastic spring portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

113. 109. The automatic injection device of claim 108, wherein the at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until a sufficient axial force is exerted to allow deflection of the at least one resilient spring portion and removal of the safety cap.

114. 105. The automatic injection device of claim 104, wherein the portion of the rear cover deflects radially inward toward the plunger rod upon axial rearward movement of the needle guard relative to the housing element.

115. 104. The automatic injection device of claim 103, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

116. The automatic injection device of claim 103, wherein the needle guard has at least one opening, and the at least one locking portion is radially supported by the needle guard in the storage position, such that when the needle guard moves axially rearward relative to the housing element, the at least one locking portion is inserted into the at least one opening in the needle guard, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

117. The automatic injection device of claim 103, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, the needle guard engaging a portion of the control unit thereby preventing the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element, and the plunger rod preventing disengagement of the control unit from the needle guard until axial forward movement of the plunger rod relative to the syringe.

118. 104. The automatic injection device of claim 103, wherein the automatic injection device also has a needle shield remover configured to be releasably coupled to the housing element, and wherein the needle guard engages with a portion of the needle shield remover in a retracted position, thereby preventing the needle guard from being moved axially forward relative to the housing element.

119. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element; a needle shield remover configured to be releasably coupled to the housing element; a control unit configured to fixedly hold the syringe therein and configured to be fixedly coupled to the housing element; a plunger rod biased axially forward by the urging of the at least one resilient element, wherein the needle guard engages a portion of the control unit to prevent the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element; and the plunger rod prevents disengagement of the control unit and the needle guard until axial forward movement of the plunger rod relative to the syringe. Automatic injection device.

120. 26. The automatic injection device of claim 25, wherein the plunger rod is configured to engage with the control unit in the retracted position, wherein the plunger rod is prevented from moving axially forward relative to the control unit urged by the at least one resilient element, and when the needle guard moves axially rearward relative to the housing element, the plunger rod is disengaged from the control unit and allowed to move axially forward relative to the control unit urged by the at least one resilient element.

121. 120. The automatic injection device of claim 119, also comprising a rear cover fixedly attached to the rear end of the housing element, a portion of which is configured to deflect radially upon the axial rearward movement of the needle guard.

122. 122. The automatic injection device of claim 121, also comprising a safety cap releasably mounted on the rear cover, the safety cap configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

123. 122. The automatic injection device of claim 121, wherein the rearward axial movement of the needle guard is prevented by engagement of the needle guard with the rear cover.

124. 123. The automatic injection device of claim 122, wherein the axial rearward movement of the needle guard is permitted when a safety cap is removed from the rear cover.

125. 123. The automatic injection device of claim 122, wherein the safety cap has a rigid rib and at least one resilient spring portion.

126. The automatic injection device of claim 119, wherein the control unit has at least one locking portion, the plunger rod is configured to engage with the at least one locking portion in the retracted position, and the plunger rod is disengaged from the at least one locking portion when the needle guard moves axially rearward relative to the housing element.

127. 127. The automatic injection device of claim 126, wherein the at least one locking portion is radially flexible.

128. 120. The automatic injection device of claim 119, wherein the automatic injection device also has a buffer element between the control unit and the syringe, which is configured to partially absorb forces that occur during relative movement between the plunger rod and the syringe.

129. The automatic injection device of claim 126, wherein the plunger rod has at least one protrusion which is supported forward against at least one locking portion of the control unit in the storage position, and the at least one locking portion is supported radially outward against a portion of the needle guard, thereby preventing the plunger rod from bending radially outward and releasing the plunger rod to move forward in the storage position.

130. 126. The automatic injection device of claim 125, wherein the at least one elastic spring portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

131. 126. The automatic injection device of claim 125, wherein the at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until a sufficient axial force is exerted to allow deflection of the at least one resilient spring portion and removal of the safety cap.

132. 122. The automatic injection device of claim 121, wherein the portion of the rear cover deflects radially inward toward the plunger rod upon axial rearward movement of the needle guard relative to the housing element.

133. 120. The automatic injection device of claim 119, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

134. The automatic injection device of claim 126, wherein the needle guard has at least one opening, and the at least one locking portion is radially supported by the needle guard in the storage position, such that when the needle guard moves axially rearward relative to the housing element, the at least one locking portion is inserted into the at least one opening in the needle guard, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

135. The automatic injection device of claim 126, wherein the plunger rod has at least one locking engagement portion, which is supported forward by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe.

136. 2. The automatic injection device of claim 1, wherein the needle guard engages a portion of the needle shield remover in a retracted configuration, thereby preventing the needle guard from being moved axially forward relative to the housing element.

137. 1. An automatic injection device for use with a syringe including at least one syringe piston and a needle connected to a forward end thereof, said automatic injection device comprising: a housing element disposed along a longitudinal axis and having a forward end and a rearward end; at least one elastic element arranged to be positioned within the housing element; a needle guard slidably positionable relative to the housing element; a needle shield remover configured to be releasably coupled to the housing element; a control unit configured to fixedly hold the syringe therein and configured to be fixedly coupled to the housing element; a plunger rod urged axially forward by the at least one resilient element, wherein the needle guard engages a portion of the needle shield remover in a retracted configuration, thereby preventing the needle guard from being moved axially forward relative to the housing element. Automatic injection device.

138. The automatic injection device of claim 137, wherein the plunger rod is configured to engage with the control unit in the retracted position, and in this position the plunger rod is prevented from moving axially forward relative to the control unit as urged by the at least one elastic element, and when the needle guard moves axially rearward relative to the housing element the plunger rod is disengaged from the control unit and allowed to move axially forward relative to the control unit as urged by the at least one elastic element.

139. 138. The automatic injection device of claim 137, also comprising a rear cover fixedly attached to the rear end of the housing element, a portion of which is configured to deflect radially upon the axial rearward movement of the needle guard.

140. 140. The automatic injection device of claim 139, also comprising a safety cap releasably mounted on the rear cover, the safety cap configured to prevent rearward axial movement of the needle guard until the safety cap is removed from the rear cover.

141. 140. The automatic injection device of claim 139, wherein the axial rearward movement of the needle guard is prevented by engagement of the needle guard with the rear cover.

142. 141. The automatic injection device of claim 140, wherein the axial rearward movement of the needle guard is permitted when a safety cap is removed from the rear cover.

143. 141. The automatic injection device of claim 140, wherein the safety cap has a rigid rib and at least one resilient spring portion.

144. The automatic injection device of claim 137, wherein the control unit has at least one locking portion, the plunger rod is configured to engage with the at least one locking portion in the retracted position, and the plunger rod is disengaged from the at least one locking portion when the needle guard moves axially rearward relative to the housing element.

145. 145. The automatic injection device of claim 144, wherein the at least one locking portion is radially flexible.

146. 138. The automatic injection device of claim 137, wherein the automatic injection device also has a buffer element between the control unit and the syringe, which is configured to partially absorb forces that occur during relative movement between the plunger rod and the syringe.

147. The automatic injection device of claim 144, wherein the plunger rod has at least one protrusion which is supported forward against at least one locking portion of the control unit in the storage position, and the at least one locking portion is supported radially outward against a portion of the needle guard, thereby preventing the plunger rod from bending radially outward and releasing the plunger rod to move forward in the storage position.

148. 144. The automatic injection device of claim 143, wherein the at least one elastic spring portion is disposed within an opening in the rear cover, and inward deflection of the portion of the rear cover is prevented by the rigid rib, which in turn is supported radially inward by the plunger rod, thereby preventing rearward axial movement of the needle guard.

149. 144. The automatic injection device of claim 143, wherein the at least one resilient spring portion is retained within the rear cover to prevent inadvertent removal of the safety cap from the rear cover until a sufficient axial force is exerted to allow deflection of the at least one resilient spring portion and removal of the safety cap.

150. 140. The automatic injection device of claim 139, wherein the portion of the rear cover deflects radially inward toward the plunger rod upon axial rearward movement of the needle guard relative to the housing element.

151. 138. The automatic injection device of claim 137, wherein movement of the needle guard relative to the housing element requires overcoming a predetermined trigger force threshold.

152. The automatic injection device of claim 144, wherein the needle guard has at least one opening, and the at least one locking portion is radially supported by the needle guard in the storage position, such that when the needle guard moves axially rearward relative to the housing element, the at least one locking portion is inserted into the at least one opening in the needle guard, thereby activating the automatic injection device and allowing axial forward movement of the plunger rod relative to the syringe.

153. The automatic injection device of claim 144, wherein the plunger rod has at least one locking engagement portion, which is supported forward by the at least one locking portion in the storage position, and when the needle guard moves axially rearward relative to the housing element, the at least one locking portion disengages from the at least one locking engagement portion, thereby activating the automatic injection device and allowing the plunger rod to move axially forward relative to the syringe.

154. the needle guard engages a portion of the control unit to prevent the needle guard from being moved axially forward relative to the housing element after the needle shield remover is removed from the housing element; and 138. The automatic injection device of claim 137, wherein the plunger rod prevents disengagement of the control unit from the needle guard until axial forward movement of the plunger rod relative to the syringe.

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