Automatic injection device

Abstract

The present disclosure relates to an automatic injection device comprising a body, a medical container having a barrel, a distal tip, and a stopper, a safety shield, a plunger rod with a proximal flange, a cam, and an activator, wherein in an initial position, the activator is spaced proximally from a flexible arm, and when the cam is in an unlocked position, the activator deflects the flexible arm outwardly to release the proximal flange of the plunger rod, thereby allowing the plunger rod to move distally to push the medical container.

Description

[Technical field]

[0001] In particular, the present invention relates to a medical device for the safe automatic injection of a product in an emergency. [Background technology]

[0002] Some illnesses require regular injections of medications or products, for example, daily. To simplify treatment, autoinjectors are provided to allow patients to administer their own injections.

[0003] Since patients are usually not nurses or people with knowledge of medical equipment, such autoinjectors must be very easy to use and also proven to be very safe. In particular, needle insertion must be performed at the correct depth, the correct amount of product must be injected, i.e., a complete injection must be performed, and the syringe must be deactivated after use before disposal. Preferably, the needle should not be exposed before and after use to prevent needlestick injuries.

[0004] Another important requirement of these self-injection devices is to prevent inadvertent activation of the device before the patient is ready to perform an injection, and in particular before the device has been properly applied to the correct injection site.

[0005] Some automatic injection devices include a safety shield that covers the needle tip when not injecting, and a button that the patient presses to initiate the injection.

[0006] Patent Document 1 discloses such an automatic injection device.

[0007] Prior to use, the safety shield and needle are covered with a cap and the button is locked to prevent accidental activation. The device includes a mechanism that unlocks the button when the safety shield is fully pressed into the patient's skin.

[0008] Thus, an injection requires three actions by the user: (1) Remove the cap. (2) Press the device firmly against the patient's skin to unlock the button, (3) Press the unlock button to activate the device and begin the injection.

[0009] However, when a patient needs to receive medication in an emergency, this three-step injection process may be too long or too complicated: for example, if a patient develops anaphylaxis, adrenaline must be administered very quickly to avoid the patient's death. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent Application Publication No. 2921191 Summary of the Invention [Problem to be solved by the invention]

[0011] There is therefore a need for an autoinjection device that can be activated with a minimum of steps without compromising the safety of the device, in particular, as discussed above, the device must not be activated inadvertently and must also avoid accidental needlestick injuries. [Means for solving the problem]

[0012] The present invention meets this need by proposing a device for automatically injecting a product at an injection site. This device is The main body, a medical container having a barrel containing an injectable product, a distal tip provided with an injection needle, and a stopper slidably engaged within the barrel, the medical container being slidably disposed within the body between a proximal position and a distal position; a safety shield slidably mounted within the body between a distal initial position and a proximal second position; a plunger rod slidably disposed within the body, the plunger rod including a proximal flange releasably locked in a proximal initial position by at least one flexible arm of the body, the plunger rod being movable in a distal direction when the proximal flange is unlocked to engage the stopper; a cam cooperating with the safety shield, such that movement of the safety shield from the distal initial position to the proximal second position rotates the cam within the body to an unlocked position; an activator slidably mounted to a proximal end of the body, the activator configured to cooperate with the cam such that rotation of the cam to an unlocked position moves the activator in the distal direction; Equipped with In an initial position, the activator is spaced proximally from the flexible arm, and when the cam is in the unlocked position, the activator deflects the flexible arm outwardly to release the proximal flange of the plunger rod, thereby allowing the plunger rod to move in the distal direction to push the medical container.

[0013] The cam and activator work together so that the user only needs to perform two actions to completely administer the injection: (1) remove the cap and (2) press the safety shield against the patient's skin.

[0014] Thus, the ergonomics of the device are improved, which is particularly beneficial in emergency situations, as it may simplify operation of the device and reduce the time required to inject the entire dose into the patient.

[0015] As used herein, the distal end of a component or device is understood to mean the end furthest from the user's hand, and the proximal end is understood to mean the end closest to the user's hand. Similarly, as used herein, the distal direction is understood to mean the direction of injection, and the proximal direction is understood to mean the direction opposite to the direction of injection.

[0016] In this specification, the term "axial" refers to a direction parallel to the injection direction (which also corresponds to the longitudinal axis of the injection device) and the term "radial" refers to a direction perpendicular to the injection direction.

[0017] In some preferred embodiments, it may be considered alone or in combination. Each flexible arm has an inclined inner surface tapering inward in the distal direction and at least one plunger retainer disposed distally from the inclined surface, the proximal flange of the plunger rod abutting the at least one retainer in the initial position. The activator includes at least one inner protrusion extending in the distal direction, the at least one protrusion being spaced proximally from the inclined surface of each flexible arm in the initial position, and the at least one inner protrusion engaging the respective inclined surface to bias the flexible arm outwardly when the cam is in the unlocked position. The activator has at least one leg extending in the distal direction, each leg having a tooth received in a third groove of the cam such that rotation of the cam to the unlocked position deflects the flexible arms outwardly, moving the activator in a distal direction to release the proximal flange of the plunger rod. The safety shield includes at least one lug received in a first groove of each of the cams, such that movement of the safety shield in a proximal direction rotates the cams. The first groove comprises an inclined first branch and an axial second branch connected to the first branch at a proximal end, and in the initial position, the lug is located at the distal end of the first branch and moves to the proximal end of the first branch when the safety shield moves from the initial position to the second position. The plunger rod is urged in the distal direction by a first spring. The first spring extends between a distal face of the at least one plunger retainer and a proximal face of a distal flange of the plunger rod. The safety shield is urged in the distal direction by a second spring. The ring is locked in the proximal portion of the second groove and moves along a ramp portion to the distal portion when the plunger rod pushes the medical container from the initial position to the injection position. An axial distance between the proximal portion of the second groove and the distal portion of the second groove is equal to a penetration depth of the needle within the patient's body. The at least one finger engages an axial groove in the body. Movement of the ring in the distal direction rotates the cam such that the lug of the safety shield engages the second branch of the first groove of the cam. [Brief description of the drawings]

[0018] Further features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.

[0019] [Figure 1] FIG. 2 is a perspective view of the body and cap of the injection device. [Diagram 2] FIG. [Diagram 3] FIG. 2 is an exploded view of the medical container and needle shield of the injection device. [Figure 4] FIG. 2 is an exploded view of the plunger rod and medical container. [Diagram 5]FIG. 2 is a perspective view of the cap and needle shield. [Figure 6] FIG. 2 is a perspective view of a medical container and a support ring. [Figure 7] FIG. 2 is a perspective view of a safety shield. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. 13 is a perspective view of a safety shield, cam and ring assembly. [Figure 11] FIG. 13 is a perspective view of the safety shield, cam, ring and activator assembly. [Figure 12] FIG. 2 is a cross-sectional view of the top of the injection device in the initial position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Unless otherwise specified, the components of the injection device are depicted in an initial position prior to use of the injection device. However, as described below, some of the components can be translated and / or rotationally moved relative to one another to perform an injection. Thus, the description will refer not only to the initial positions of the components, but also to one or more operating positions or phases reached during the injection process.

[0021] In summary, prior to use, the injection device body is closed by a cap which protects the interior of the injection device from the external environment.

[0022] In a first step, the cap is removed, so that the injection device is in an initial position, in which the injection needle and the medical container containing the injectable product are housed within the body of the injection device, and the plunger rod is immovably locked within the body, preventing exposure of the injection needle and injection of the product.

[0023] In a second step, to administer the injection, the safety shield is applied to the patient's skin at the injection site. The safety shield is moved proximally, causing rotation of a cam coupled to the safety shield until the activator is unlocked.

[0024] This unlocking of the activator unlocks the plunger rod and initiates the sequential injection phase which pushes the stopper distally, thereby moving the medical container, which is engaged with the stopper, distally, allowing the needle to pierce the patient's skin at the proper injection depth, and further expelling the product from the medical container into the patient's body due to the distal movement of the stopper within the medical container.

[0025] 1 and 2 show perspective and exploded views, respectively, of a body and cap of an automatic injection device according to an embodiment of the present disclosure.

[0026] The device comprises a housing 10 with an upper body 11 and a lower body 12 which may be rigidly connected to each other.

[0027] The housing 10 has an outer shape suitable for being held in a user's hand. In general, the outer surface of the housing 10 is intended to be grasped by the palm and fingers of a user's hand.

[0028] The connection between the upper and lower bodies may be a snap-fit ​​connection, a threaded connection, a bayonet connection, or other means for connecting the two parts in a non-releasable manner. If the device is of a disposable type, the means for connecting the upper and lower bodies is made out of reach of the user.

[0029] Cap 13 is removably connected to the distal end of housing 10. Cap 13 may be connected to lower body 12 by a snap-fit ​​connection or by other type of connection that allows cap 13 to be removed by axial movement in the distal direction.

[0030] A medical container 20 , such as a syringe, is received in at least one of the upper body 11 and the lower body 12 .

[0031] As shown in Figure 3, the medical container 20 has a radial flange 21 defined at an open proximal end and an injection needle 22 at a substantially closed distal end 23. A sidewall extends between the proximal and distal ends to define a barrel 24 sized and shaped to contain a predetermined amount of product for injection. The injection needle 22 can be fixed to the distal end 23 or removable therefrom, as a design choice. The injection needle 22 is in fluid communication with the barrel 24 and provides an exit port for the product of the medical container 20.

[0032] 3 and 4, a needle shield 30 is provided at the distal end of the medical container 20 to cover and protect the needle 22 prior to use of the device 1. The needle shield 30 also provides a means for sealing the distal end 23 of the medical container prior to use. To that end, the needle shield 30 may include an inner elastomeric shield 31 that sealingly engages the distal end of the medical container and an outer rigid cap 32 that surrounds the inner shield.

[0033] Prior to use (see FIG. 5), removal of cap 13 engages cap 13 with outer rigid cap 32 as inner elastomeric shield 31 and outer rigid cap 32 are simultaneously removed from the distal end of the medical container.

[0034] 3 and 4, a stopper 25 is provided within the container 20 and is slidably movable within the barrel 24. Distal movement of the stopper causes the product to be expelled from the medical container 20 through the injection needle 22 during injection of the product into a patient. The stopper is typically made of an elastomeric material. The inner surface of the barrel and / or the outer surface of the stopper may be lubricated to reduce the sliding force of the stopper within the barrel.

[0035] A plunger rod 40 is received within the proximal portion of upper body 11 for moving a stopper relative to medical container 20, as will be described below.

[0036] Plunger rod 40 includes a shaft 41 with a distal flange 42 and a distal tip 43 adapted to engage a stopper at an injection position. Shaft 41 also includes a proximal flange 44. Shaft 41 may include one or more axial ribs designed to increase stiffness.

[0037] Returning to Figures 1 and 2, the upper body 11 is generally cylindrical and open at both ends. The distal end is connected to the lower body 12. The upper body 11 further comprises an inner cylinder 14 that houses a plunger rod 40. The inner cylinder 14 comprises an axial wall parallel to the outer wall of the upper body and is connected to said outer wall by a radial wall. The inner cylinder 14 has an open distal end and a proximal end that comprises at least one flexible arm 140 with an inclined inner surface 16 tapering inwards in the distal direction and at least one plunger retainer 17 located distally from said inclined surface 16. Preferably, the proximal end comprises two diametrically opposed flexible arms 140 or two pairs of diametrically opposed flexible arms with adjacent arms spaced at an angle of 90°. For example, each plunger retainer 17 is in the form of a radially inwardly extending clip with a proximal surface perpendicular to the injection direction that engages a distal surface of the proximal flange 44 of the plunger rod in the initial position. Thus, in the initial position, the plunger rod 40 is prevented from moving distally by the plunger retainer 17 (see FIG. 12). As will be explained in more detail below, the flexible arms 140 are designed to be able to flex outwardly when a force is applied to the ramp surface 16 in the distal direction.

[0038] The activator 80 (see FIG. 8) is attached to the proximal portion of the upper body 11. The activator is prevented from moving proximally by a clip 85 that engages the upper body 11, but is allowed to slide distally. The activator substantially surrounds the proximal end of the inner cylinder 14.

[0039] The activator 80 includes an axial skirt 81 having a generally cylindrical shape with an open distal end and a closed proximal end. The activator includes at least one leg 83 extending distally from the skirt 81. Preferably, the activator includes two legs 83 diametrically opposed to one another. The distal end of each leg 83 is provided with teeth 82 extending radially outwardly therefrom.

[0040] The proximal end of the activator includes at least one inner protrusion 84 extending distally towards the flexible arms 140. In some embodiments, the protrusion may form a continuous annular rib. In other embodiments, at least two separate protrusions 84 are provided, each in angular alignment with a flexible arm 140, with the number of protrusions 84 equal to the number of flexible arms 140. In the initial position, the at least one protrusion 84 is spaced proximally from the angled surface 16 of each flexible arm 140.

[0041] As best seen in FIG. 12, a first spring 49 is disposed around the plunger rod shaft 41, with the distal end of the spring 49 abutting the proximal face of the plunger rod distal flange 42, and the proximal end of the spring 49 abutting the distal face of the plunger retainer 17. In the initial position, the spring is in a compressed state. As a result, the spring 49 pushes the plunger rod 40 in a distal direction. However, as previously described, in the initial position, the plunger rod is locked by the plunger retainer 17, thereby preventing distal movement.

[0042] As shown in Figure 6, the medical container 20 is attached to a support ring 50. The ring includes a distal rigid portion 51 and a proximal resilient portion 52. The barrel of the medical container is inserted into the support ring 50 such that the proximal flange 21 abuts the proximal surface of the proximal resilient portion 52. The medical container may be maintained in a fixed position relative to the ring by frictional engagement between the resilient portion 52 and the barrel.

[0043] The ring 50 comprises at least one finger 53 projecting radially from the rigid portion 51. Preferably, the ring comprises two fingers 53 located diametrically opposite one another.

[0044] The lower body forms a housing that at least partially receives the medical container 20 and the ring 50. As described below, the medical container 20 is movable relative to the lower body between an initial position in which the tip of the needle does not extend beyond the distal end of the lower body and an injection position spaced distally from the initial position in which the tip of the needle extends beyond the distal end of the lower body and is exposed a predetermined length.

[0045] The lower body 12 is generally cylindrical and open at both ends. The lower body 12 has a distal portion 12b and a proximal portion 12a, the diameter of which is greater than the diameter of the distal portion 12b. The proximal portion 12a and the distal portion 12b are joined by a radial wall 12c. The proximal surface of the radial wall 12c forms the abutment surface for the ring 50.

[0046] The lower body comprises at least one axial groove 15 for receiving a respective finger 53 of the ring 50. Preferably, the lower body has two axial grooves 15 diametrically opposite each other and the ring has two fingers respectively received in the respective axial grooves. As will be explained in more detail below, such axial groove serves as a guide for the axial movement of the ring (and the container) relative to the lower body. Advantageously, this groove is located in the proximal part of the lower body 12, which is covered by the upper body 11, so that the groove 15 and the fingers 53 are not accessible to the user from outside the injection device.

[0047] As shown in Figure 7, the injection device also includes a safety shield 60 that is at least partially received within the distal portion of the lower body. The safety shield 60 includes two opposing proximally extending tongues 61. Each tongue 61 includes a lug 62 extending radially outwardly.

[0048] The distal end of the safety shield 60 is advantageously provided with a radial flange 63 which forms a support surface for placing the injection device on the patient's skin, the width of the flange being selected to distribute the pressure over a sufficiently wide surface area so as not to injure the patient.

[0049] The safety shield is coupled to a cam 70 that is rotatably mounted to the lower body 12 .

[0050] As shown in Figures 9, 10 and 11, the cam 70 has a generally cylindrical shape and is open at both ends.

[0051] The cam 70 is provided with at least one first groove 71, and preferably two first grooves located diametrically opposite each other.

[0052] Each primary groove 71 includes an inclined (i.e. non-axial) first branch 71a and an axial second branch 71b connected to the first branch at the proximal end of both branches 71a, 71b. In other words, each primary groove has the shape of the number "1".

[0053] Each lug 62 of the safety shield slidingly engages a respective first groove 71 in the cam 70 .

[0054] In the initial position, the lug 62 is located at the distal end of the first branch 71a and moves toward the proximal end of the first branch 71a as the safety shield 60 moves from the initial position to the injection position. As a result, the proximal movement of the safety shield 60 rotates the cam at an angle that depends on the inclination of the first branch 71a and the stroke of the lug 62.

[0055] When lug 62 reaches the proximal end of first branch 71a and engages second branch 71b, activator 80 is unlocked, as described below.

[0056] The second spring 65 is disposed between the proximal end of the rigid portion of the ring 50 and the flange 64 of the safety shield. In an initial position, the second spring 65 is in a relaxed state, but proximal movement of the safety shield 60 compresses the second spring 65. As a result, when the user releases the pressure applied to the injection device, the second spring 65 urges the safety shield 60 in a distal direction.

[0057] The cam 70 further comprises at least one second groove 72 (preferably two second grooves 72 diametrically opposite each other). Each second groove 72 comprises a proximal portion 72a extending perpendicular to the injection direction, a distal portion 72c parallel to the proximal portion, and an inclined portion (i.e., non-axial) 72b connecting the proximal portion 72a to the distal portion 72c. In other words, the proximal portion 72a, the distal portion 72c of each second groove are spaced apart both axially and angularly. The axial distance between the proximal portion 72a and the distal portion 72c of the second groove 72 is equal to the penetration depth of the needle in the patient's body.

[0058] The ring 50 is at least partially received within the cam, with each finger 53 of the ring slidingly engaged within a respective second groove 72 .

[0059] In the initial position, each finger 53 of the ring is in a proximal portion 72 a of a respective second groove 72 .

[0060] The cam 70 further comprises at least one third groove 73 (preferably two third grooves 73 diametrically opposite each other). Each third groove 73 comprises an inclined (i.e. non-axial) portion 73a and a proximal portion 73b connected to the inclined portion 73a and extending perpendicular to the injection direction. Each tooth 82 of the activator 80 is slidably received in a respective third groove 73. In the initial position, the tooth 82 is located at the proximal end of the inclined portion 73a.

[0061] As the safety shield 60 pivots (as described above) by moving proximally along the first branch 71a of the first groove of the cam, the tooth 82 of the activator 80 slides along the angled portion 73a of the third groove 73, causing the activator 80 to move distally until the tooth 82 reaches the distal portion 73b of the third groove 73. The first and third grooves 71, 73 are designed such that the tooth 82 reaches the distal portion 73b of the third groove 73 (corresponding to the unlocked position of the cam) when the lug 62 reaches the junction between the first and second branches 71a, 71b of the first groove 71 (corresponding to the second position of the safety shield). However, such rotation of the cam 70 does not move the ring 50.

[0062] Next, the function of the injection device 1 will be described.

[0063] The injection device is provided to the user ready to use with a cap closing the distal end of the body.

[0064] The medical container is filled with a predetermined amount of injectable drug, preferably a single dose, so that a single-use or disposable injection device is provided.

[0065] Before use, the user removes the cap and the needle shield without rotating the needle shield, and the injection device is now in the initial position.

[0066] The user then places the safety shield against the skin at the injection site of a patient, who may be the user or another person.

[0067] When the device is pressed against the patient's skin, the safety shield moves proximally into the lower body.

[0068] Because of the safety features described above, the user cannot activate the device (i.e., move the container from the initial position to the injection position and the plunger presses the stopper within the barrel) until the safety shield has moved a predetermined distance in the proximal direction to allow the cam to unlock the activator.

[0069] When the device is pressed against the patient's skin and the safety shield is moved proximally from the initial position until the activator is unlocked, the device automatically activates to begin the injection.

[0070] The unlocking of the activator causes the plunger rod to unlock and push the stopper distally, which in turn moves the entire medical container distally from the initial position to the injection position to cause the needle to also pierce the patient's skin.

[0071] The plunger rod then continues to push distally against the stopper within the barrel to expel the injectable product from the container and onto the patient's skin.

[0072] It should be noted that once the activator is unlocked, the unlocking of the plunger rod, the movement of the stopper and the medical container occur during the sequential injection phase without further action by the user. Furthermore, the second position of the safety shield and the unlocked position of the cam are not stable positions but merely intermediate (temporary) positions reached during triggering of the injection device.

[0073] Once an injection is completed, the user removes the device from the injection site and the safety shield automatically extends from the lower body to cover the contaminated needle tip. Advantageously, even if the user removes the device from the injection site before completing the injection, the safety shield will automatically extend beyond the tip of the needle. Once the injection device is removed from the injection site and the safety shield extends beyond the tip of the needle, the shield is locked in place and cannot thereafter be moved proximally from the locked position to expose the needle tip. In this manner, the used injection device provides for safe handling and disposal.

[0074] Thus, after the cap has been removed, activation of the injection device requires only one action from the user.

[0075] Referring to the figure, when the user places the injection device against the injection site by the support surface 63 of the safety shield 60, a distal force is applied to the lower body 12, causing the safety shield 60 to move from an initial position relative to the lower body to a second position in which the cam unlocks the activator, and the second position of the safety shield is spaced proximally relative to the initial position.

[0076] As the safety shield 60 moves proximally to the second position, each lug 62 moves along the angled branch 71a of the cam 70, thereby rotating the cam 70 until it connects with the axial branch 71b, which corresponds to the unlocked position of the cam.

[0077] If the user releases the pushing force before reaching the second position, the compressed second spring 65 will urge the safety shield back to the distal position to protect the needle.

[0078] Rotation of cam 70 pulls activator 80 distally until, in the unlocked position, activator tooth 82 reaches distal portion 73b of third groove 73.

[0079] In the unlocked position, the inner projection 84 of the activator engages the ramp surface 16 to deflect the flexible arms 140 of the inner cylinder 14 outwardly, thereby disengaging the plunger retainer 17 from the proximal flange 44 of the plunger rod.

[0080] As a result, plunger rod 40 moves distally due to the distal force of spring 49 .

[0081] The distal end 43 of the plunger rod 40 engages the stopper and urges it distally, which causes the stopper, in frictional engagement with the barrel, to move the entire medical container distally.

[0082] As the medical container is supported by the ring 50, the ring 50 moves distally with the medical container. During this movement, the fingers 53 of the ring 50 move within the second grooves 72 of the cam. More precisely, each finger 53 engages with the angled portion 72b of the respective second groove 72 until the fingers 53 reach a distal portion 72c of the second groove, which prevents further distal movement of the ring 50 and the medical container. This movement of the ring 50 causes the cam 70 to rotate further to allow the lug 62 to engage the second branch 71b of the first groove 71.

[0083] The medical container has thus reached the injection position. In this position, the needle projects from the distal end of the lower body 12 and pierces the patient's skin. As previously mentioned, the axial stroke of the finger 53 between the proximal portion 72a of the second groove 72 of the cam 70 and the distal portion 72c of the second groove 72 of the cam 70 defines the penetration depth of the needle. This ensures that the product is injected at the appropriate depth between the patient's body.

[0084] The plunger rod continues to push against the stopper to expel product from the barrel through the needle until the stopper reaches the distal end of the barrel.

[0085] Once the injection is complete, the user withdraws the injection device from the patient's skin.

[0086] This withdrawal causes the second spring 65 to push the safety shield 60 distally, sliding the lug 62 within the second branch 71b of the first groove 71 of the cam 70, to a final position where the safety shield covers and protects the needle. In this final position, the safety shield is locked against proximal movement, thereby preventing unintended access to a contaminated needle.

[0087] The injection device is therefore very easy to use even in an emergency and very safe as it prevents accidental needle stick injuries even if the injection device is removed from the injection site before injection of the product is actually completed.

Claims

1. A housing (10), a medical container (20) having a barrel (24) containing an injectable product, a distal end (23) provided with an injection needle (22), and a stopper (25) slidingly engaged within the barrel, the medical container (20) being slidably disposed within the housing (10) between a proximal position and a distal position; a safety shield (60) slidably mounted within said housing (10) between a distal initial position and a proximal second position; a plunger rod (40) slidably disposed within the housing (10), the plunger rod (40) including a proximal flange (44) releasably locked in a proximal initial position by at least one flexible arm (140) of the housing (10), the proximal flange (44) being movable distally when unlocked to engage the stopper; a cam (70) cooperating with the safety shield (60), such that movement of the safety shield (60) from the distal initial position to the proximal second position causes the cam (70) to rotate within the housing (10) to an unlocked position; an activator (80) slidably mounted to the proximal end of the housing (10), the activator (80) configured to cooperate with the cam (70) such that rotation of the cam (70) to an unlocked position moves the activator (80) in the distal direction; Equipped with In an initial position, the activator (80) is spaced proximally from the flexible arm (140), and when the cam (70) is in the unlocked position, the activator (80) deflects the flexible arm (140) outward to release the proximal flange (44) of the plunger rod (40), thereby allowing the plunger rod (40) to move in the distal direction to push the medical container (20).

2. 2. The automatic injection device of claim 1, wherein each flexible arm (140) has an inclined inner surface (16) tapering inward in the distal direction and at least one plunger retainer (17) disposed distally from the inclined inner surface (16), and the proximal flange (44) of the plunger rod (40) abuts against the at least one plunger retainer (17) in the initial position.

3. 3. The automatic injection device of claim 2, wherein the activator (80) comprises at least one inner protrusion (84) extending in the distal direction, the at least one inner protrusion (84) being spaced proximally from the inclined inner surface (16) of each flexible arm (140) in the initial position, and the at least one inner protrusion (84) engages with each inclined inner surface (16) to deflect the flexible arms (140) outward when the cam (70) is in the unlocked position.

4. 2. The automatic injection device of claim 1, wherein the activator (80) comprises at least one leg (83) extending in the distal direction, each leg (83) comprising a tooth (82) received in a third groove of the cam (70) such that rotation of the cam (70) to the unlocked position deflects the flexible arm (140) outward and moves the activator (80) in a distal direction to release the proximal flange (44) of the plunger rod (40).

5. 2. The automatic injection device of claim 1, wherein the safety shield (60) comprises at least one lug (62) received in each first groove (71) of the cams (70), and movement of the safety shield (60) in a proximal direction rotates the cams (70).

6. 6. The automatic injection device of claim 5, wherein the first groove (71) comprises an inclined first branch (71a) and an axial second branch (71b) connected to the first branch at a proximal end, and wherein in the initial position, the lug (62) is located at the distal end of the first branch (71a) and moves to the proximal end of the first branch (71a) when the safety shield (60) moves from the initial position to the proximal second position.

7. 2. The automatic injection device of claim 1, wherein the plunger rod (40) is urged in the distal direction by a first spring (49).

8. Each flexible arm (140) has an inclined inner surface (16) tapering inward in the distal direction and at least one plunger retainer (17) disposed distally from the inclined inner surface (16), and the proximal flange (44) of the plunger rod (40) abuts against the at least one plunger retainer (17) in the initial position; 8. The automatic injection device of claim 7, wherein the first spring (49) extends between a distal surface of the at least one plunger retainer (17) and a proximal surface of a distal flange (42) of the plunger rod (40).

9. 2. The automatic injection device of claim 1, wherein the safety shield (60) is urged in the distal direction by a second spring (65).

10. a ring (50) supporting the medical container (20), the ring (50) having at least one finger (53) projecting radially outward; the cam (70) further having at least one second groove receiving each of the at least one finger (53), the at least one second groove (72) having a proximal portion (72a), a distal portion (72c), and an inclined portion (72b) connecting the proximal portion (72a) to the distal portion (72c); 2. The automatic injection device of claim 1, wherein the ring (50) is locked in the proximal portion (72a) of the second groove (72) and moves along the inclined portion (72b) to the distal portion (72c) when the plunger rod (40) pushes the medical container (20) from the initial position to the injection position.

11. 11. The automatic injection device of claim 10, wherein the axial distance between the proximal portion (72a) of the second groove (72) and the distal portion (72c) of the second groove (72) is equal to the penetration depth of the injection needle (22) within the patient's body.

12. 12. The automatic injection device of claim 11, wherein the at least one finger (53) engages an axial groove (15) in the patient's body.

13. The safety shield (60) comprises at least one lug (62) received in each first groove (71) of the cams (70), and movement of the safety shield (60) in a proximal direction rotates the cams (70), the first groove (71) comprises an inclined first branch (71 a) and an axial second branch (71 b) connected to the first branch at a proximal end, wherein in the initial position, the lug (62) is located at the distal end of the first branch (71 a) and moves to the proximal end of the first branch (71 a) when the safety shield (60) moves from the initial position to the proximal second position; 11. The automatic injection device of claim 10, wherein movement of the ring in the distal direction rotates the cam so that the lug of the safety shield engages the second branch of the first groove of the cam.

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