Automatic injection device and method for using the same

Abstract

The present disclosure relates to an automatic injection device, comprising a first assembly for receiving a syringe, and a second assembly coupled with the first assembly. The second assembly includes: an outer casing; a driving mechanism placed within the outer casing and capable of being loaded and released, wherein when loaded, the driving mechanism stores energy, and when released, the driving mechanism drives the movable element of the syringe towards the injection site by releasing energy; a retaining mechanism placed within the outer casing, the retaining mechanism including a retaining position and a releasing position; and a trigger mechanism positioned at a first end of the outer casing and configured to move the retaining mechanism from the retaining position to the releasing position to release the loaded driving mechanism.

Description

AUTOMATIC INJECTION DEVICE AND METHOD FOR USING THE SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to Chinese Application No. 202311086267.2 entitled “Automatic Injection Device and Method for Using the Same” filed August 28, 2023, the disclosure of which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The present disclosure generally relates to reusable automatic injection devices and methods for using the same.Description of Related Art

[0003] Some diseases make it necessary to inject medications or products regularly (for example, on a daily basis). In order to simplify treatment, there have been some automatic injection devices (also called "self-injectors") to allow patients to inject by themselves.

[0004] Self-injection capacity has always been the crucial driving force for developing automatic injection devices. As patients typically have no special injection skills, these automatic injection devices must be simple and safe to use. For example, it is generally required that the automatic injection device shall ensure insertion of a needle into a correct depth and ensure injection of a correct dose of products (that is, complete injection is required), and that the needle shall not be exposed before and after use to prevent any accidental needle- stick injury, or the like.

[0005] In addition, for these automatic injection devices, they shall not be accidentally activated before a patient is ready for injection (especially before the automatic injection device is correctly placed at an appropriate injection site). Furthermore, it is expected that the automatic injection device can provide a constant driving force, thus producing a constant injection speed and avoiding giving patients an uncomfortable injection experience.

[0006] Therefore, there is a demand for an automatic injection device that can meet at least one of the above-mentioned requirements or other requirements not mentioned.

[0007] It should be noted that the subject matter claimed in the present application is not limited to the fields as described above, to only solving any shortcomings as mentioned above, and to embodiments that are only used or operated in the above-mentioned environments. Rather, this background is provided only to illustrate an exemplary technical field in which some embodiments described in the present application may be implemented.SUMMARY OF THE INVENTION

[0008] An object of the present disclosure is to solve one or more of the problems existed in the automatic injection devices in the prior art and realize other additional advantages.

[0009] In a first aspect of the present disclosure, an automatic injection device is provided for automatically injecting a fluid in a syringe into an injection site of a target. The syringe comprises a barrel containing the fluid, a needle disposed at a first end of the barrel, and a movable element movable within the barrel, the movable element capable of being driven from a second end of the barrel opposite to the first end to discharge the fluid through the needle. The automatic injection device comprises a first assembly for removably receiving the syringe; and a second assembly detachably coupled with the first assembly. The second assembly includes an outer casing including a first end far away from the first assembly and a second end close to the first assembly; a driving mechanism placed within the outer casing and capable of being loaded and released, wherein when loaded, the driving mechanism stores energy, and when released, the driving mechanism drives the movable element of the syringe towards the injection site by releasing its stored energy; a retaining mechanism placed within the outer casing, the retaining mechanism comprising a retaining position where the loaded driving mechanism is retained, and a releasing position where the loaded driving mechanism is released; and a trigger mechanism arranged at the first end of the outer casing, the trigger mechanism being configured to move the retaining mechanism from its retaining position to its releasing position to release the loaded driving mechanism, wherein the trigger mechanism is configured to rotate, when the driving mechanism is loaded, about a central axis of the outer casing under an action of a pushing element connected with the driving mechanism until it reaches a non-triggerable position where the trigger mechanism cannot be pressed down to move the retaining mechanism from its retaining position to its releasing position; and wherein the trigger mechanism is further configured to be manually rotatable about the central axis of the outer casing from the non-triggerable position to atriggerable position where the trigger mechanism can be pressed down to move the retaining mechanism from its retaining position to its releasing position to release the loaded driving mechanism.

[0010] According to an embodiment of the present disclosure, the trigger mechanism comprises a bottom wall and a side wall extending from the bottom wall, the side wall has a substantially circular-arc shaped cross section and includes a circumferential direction and an extending direction orthogonal to the circumferential direction, and an inner surface of the side wall is provided with a first groove and a second groove communicating with each other, wherein the first groove extends obliquely towards the bottom wall in the extending direction and has a starting end far away from the side wall and an ending end close to the side wall; the second groove extends from the ending end of the first groove along the circumferential direction of the side wall at a substantially same height with the first groove and has a starting end and an ending end; and wherein the pushing element is configured as a protrusion, which is capable of entering the first groove from the starting end of the first groove and rotating the trigger mechanism by pushing a groove sidewall of the first groove when the driving mechanism is loaded.

[0011] According to an embodiment of the present disclosure, a depth of the second groove gradually decreases to zero from the starting end of the second groove to the ending end of the second groove, so that the protrusion is capable of sliding out of the ending end of the second groove when the trigger mechanism is rotated from the non- triggerable position to the triggerable position.

[0012] According to an embodiment of the present disclosure, the side wall of the trigger mechanism comprises a first cylindrical portion having a substantially cylindrical shape and a second suspending portion suspended from the first cylindrical portion, the first groove and the second groove being disposed in an inner surface of the second suspending portion.

[0013] According to an embodiment of the present disclosure, the inner surface of the outer casing comprises a first stop, which stops the second suspending portion to prevent the trigger mechanism from being pressed down when the trigger mechanism is at the non-triggerable position, and which stays away from the second suspending portion so as not to prevent the trigger mechanism from being pressed down when the trigger mechanism is at the triggerable position.

[0014] According to an embodiment of the present disclosure, the trigger mechanism further comprises at least one finger, a free end of which comprises a hook, and the innersurface of the outer casing is provided with a second stop, which cooperates with the hook to prevent the trigger mechanism from being disengaged from the outer casing.

[0015] According to an embodiment of the present disclosure, the driving mechanism comprises a substantially cylindrical body with a closed first end and an opened second end, and the pushing element is connected with the second end of the body of the driving mechanism via a rod- shaped connector.

[0016] According to an embodiment of the present disclosure, the pushing element, the rod-shaped connector, and the body of the driving mechanism are integrally formed.

[0017] According to an embodiment of the present disclosure, the second assembly further comprises an annular protrusion placed within the outer casing; when the body of the driving mechanism moves past the annular protrusion in a direction towards the first assembly, a friction is generated between the annular protrusion and the outer surface of the body of the driving mechanism, and the friction decreases with an increase in the distance that the body of the driving mechanism moves in the direction towards the first assembly.

[0018] According to an embodiment of the present disclosure, the outer surface of the body of the driving mechanism includes at least one recess extending from the first end of the body to the second end of the body, and the recess has a width gradually increasing from the first end of the body to the second end of the body, so that when the body of the driving mechanism moves past the annular protrusion in the direction towards the first assembly, a contact area between the annular protrusion and the outer surface of the body of the driving mechanism gradually decreases, and thus the friction gradually decreases.

[0019] According to an embodiment of the present disclosure, the outer surface of the body of the driving mechanism has a gradually varying smoothness, and the smoothness gradually increases from the first end of the body towards the second end of the body, so that when the body of the driving mechanism moves past the annular protrusion in the direction towards the first assembly, the friction between the annular protrusion and the outer surface of the body of the driving mechanism gradually decreases.

[0020] According to an embodiment of the present disclosure, the second assembly further comprises an inner casing fixedly placed within the outer casing, and at least a portion of the inner casing extends out of the second end of the outer casing to be connected with the first assembly.

[0021] According to an embodiment of the present disclosure, the annular protrusion is disposed in an inner surface of the inner casing.

[0022] According to an embodiment of the present disclosure, the annular protrusion is formed of a rubber ring, which is removably positioned in an annular groove in the inner surface of the inner casing.

[0023] According to an embodiment of the present disclosure, the driving mechanism comprises a first spring element, which is compressed to store energy when the driving mechanism is loaded, and which is extended by releasing its stored energy when the driving mechanism is released.

[0024] According to an embodiment of the present disclosure, the retaining mechanism comprises a first retaining element fixedly connected with the driving mechanism and a second retaining element fixedly connected with the outer casing, the first retaining element and the second retaining element cooperating with each other to retain the loaded driving mechanism, and wherein the trigger mechanism comprises an unlocking element configured to unlock the retaining mechanism to release the loaded driving mechanism when the trigger mechanism is pressed down.

[0025] According to an embodiment of the present disclosure, the first retaining element and the second retaining element are in snap-fitted connection with each other to retain the loaded driving mechanism, the second retaining element is configured to be elastically deflectable outward, and wherein the unlocking element is configured to bias the second retaining element outwards to disconnect the second retaining element from the first retaining element when the trigger mechanism is pressed down.

[0026] According to an embodiment of the present disclosure, the outer surface of the outer casing is provided with a locking mark for indicating the non-triggerable position and an unlocking mark for indicating the triggerable position; and the outer surface of the trigger mechanism is provided with an indication line, which is aligned with the locking mark when the trigger mechanism is at the non-triggerable position, and which is aligned with the unlocking mark when the trigger mechanism is at the triggerable position.

[0027] According to an embodiment of the present disclosure, the first assembly comprises: an outer shell including a first end close to the second assembly and a second end far away from the second assembly; and a safety mechanism disposed at the second end of the outer shell of the first assembly, wherein the safety mechanism comprises a safety shield and a second spring element placed within the safety shield, wherein the safety shield is movable between a first position where the second spring element is extended to push a portion of the safety shield out of the outer shell of the first assembly to cover the needle, and a second position where the second spring element is compressedand said portion of the safety shield is pushed back into the outer shell of the first assembly to allow the needle to protrude out of the safety shield and penetrate into the injection site.

[0028] According to an embodiment of the present disclosure, the safety shield comprises a first end for contacting the injection site and a second end opposite to the first end of the safety shield, wherein the second end of the safety shield comprises a plurality of regulating portions for regulating a penetration depth of the needle, and distances between the regulating portions and the first end of the safety shield are different.

[0029] According to an embodiment of the present disclosure, the safety shield is configured to be rotatable relative to the outer shell of the first assembly to allow selection of a desired penetration depth by selecting one of the plurality of regulating portions.

[0030] According to an embodiment of the present disclosure, the outer surface of the outer shell of the first assembly is provided with a plurality of indication marks for indicating different penetration depths respectively, the outer surface of the safety shield is provided with an indication line, and a desired penetration depth is selected by aligning the indication line with one of the plurality of indication marks.

[0031] According to an embodiment of the present disclosure, the outer shell of the first assembly is provided therein with an abutting portion for cooperation with any one of the plurality of regulating portions.

[0032] According to an embodiment of the present disclosure, the abutting portion is configured as a rib.

[0033] According to an embodiment of the present disclosure, the first assembly further comprises a syringe retainer for retaining the syringe, and the syringe retainer comprises a third spring element which is extended in an initial state to retain the syringe within the first assembly, and which is compressed in an injection state to be capable of inserting the needle of the syringe into the injection site.

[0034] According to an embodiment of the present disclosure, the first assembly further comprises a cover for covering the second end of the outer shell of the first assembly, and the syringe comprises a cap for covering the needle, and wherein the cover comprises at least one finger, a free end of which comprises a hook, and the hook of the finger can be hooked on the cap of the syringe, so that when the cover is removed from the first assembly, the syringe is also removed.

[0035] In a second aspect of the present disclosure, a method for using the automatic injection device according to the present disclosure is provided, which includes anassembling step of assembling the automatic injection device and an injection step of performing automatic injection using the assembled automatic injection device.

[0036] The assembling step comprises: pushing the driving mechanism of the second assembly from the second end of the outer casing of the second assembly to load the driving mechanism until the retaining mechanism of the second assembly retains the loaded driving mechanism, at which time the trigger mechanism of the second assembly is at the non-triggerable position; receiving the syringe in the first assembly; and connecting the first assembly and the second assembly.

[0037] The injection step comprises: pressing the assembled automatic injection device against an injection site of a target; rotating the trigger mechanism from the non- triggerable position to the triggerable position; pressing the trigger mechanism to release the loaded driving mechanism; and automatically inserting the needle of the syringe into the injection site by means of the driving mechanism, and performing injection until the injection is completed.

[0038] The method according to the present disclosure can be used for non-therapeutic purposes, wherein the target may not include living human and animal bodies.

[0039] According to an embodiment of the present disclosure, the method further comprises: removing the automatic injection device from the injection site after the injection is completed; disconnecting the first assembly and the second assembly of the automatic injection device; removing the syringe from the first assembly and putting it into a recycling container.

[0040] According to an embodiment of the present disclosure, the assembling step further comprises selecting one of the plurality of regulating portions to select a desired penetration depth.

[0041] According to an embodiment of the present disclosure, the injection step may further comprise removing the cap of the syringe by removing the cover before pressing the assembled automatic injection device against the injection site of the target.

[0042] It should be noted that aspects of the present disclosure described for one embodiment can be included in other different embodiments, although they are not specifically described for the other different embodiments. In other words, all embodiments and / or features of any embodiment can be combined in any way and / or combination as long as they are not contradictory.BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to easily understand the above and other features and advantages of the present disclosure, the present disclosure will be described in more detail with reference to the specific embodiments shown in the attached drawings. These drawings depict only typical embodiments of the present disclosure and are therefore not to be considered as limiting the scope of the present disclosure, in which:

[0044] FIG. la is an exploded perspective view of an automatic injection device according to one embodiment of the present disclosure;

[0045] FIG. lb is a front view of the automatic injection device according to an embodiment of the present disclosure;

[0046] FIG. 1c is a sectional perspective view of the automatic injection device according to an embodiment of the present disclosure;

[0047] FIG. Id is a sectional front view of the automatic injection device according to an embodiment of the present disclosure;

[0048] FIG. 2a is a front view of a second assembly of the automatic injection device according to an embodiment of the present disclosure;

[0049] FIG. 2b is a sectional front view of the second assembly of the automatic injection device according to an embodiment of the present disclosure, in which the second assembly is cut from an angle;

[0050] FIG. 2c is a sectional perspective view of the second assembly of the automatic injection device according to an embodiment of the present disclosure, in which the second assembly is cut from another angle, and a driving mechanism of the second assembly is at an unloaded position;

[0051] FIG. 2d is a sectional perspective view of the second assembly of the automatic injection device according to an embodiment of the present disclosure, in which the second assembly is cut from another angle, and the driving mechanism of the second assembly is at a loaded and retained position;

[0052] FIG. 3 is a perspective view of a trigger mechanism of the second assembly of the automatic injection device according to an embodiment of the present disclosure;

[0053] FIG. 4 is a front view of the driving mechanism of the second assembly of the automatic injection device according to an embodiment of the present disclosure;

[0054] FIGS. 5a and 5b are sectional perspective views of the trigger mechanism and the driving mechanism of the second assembly of the automatic injection device according toan embodiment of the present disclosure, which show the cooperation between the driving mechanism and the trigger mechanism;

[0055] FIG. 6 is a schematic view of the trigger mechanism of the second assembly of the automatic injection device according to an embodiment of the present disclosure at a non- triggerable position, in which an indication line provided on an outer surface of the trigger mechanism and a locking mark and an unlocking mark provided on the outer surface of the outer casing of the second assembly are shown;

[0056] FIG. 7 is a schematic view of the trigger mechanism of the second assembly of the automatic injection device according to an embodiment of the present disclosure at a triggerable position;

[0057] FIG. 8a is a front view of a first assembly of the automatic injection device according to an embodiment of the present disclosure;

[0058] FIG. 8b is a sectional front view of the first assembly of the automatic injection device according to an embodiment of the present disclosure;

[0059] FIG. 8c is a sectional perspective view of the first assembly of the automatic injection device according to an embodiment of the present disclosure;

[0060] FIG. 9a is a perspective view of an inner shell of the first assembly of the automatic injection device according to an embodiment of the present disclosure;

[0061] FIG. 9b is a sectional perspective view of the inner shell of the first assembly of the automatic injection device according to an embodiment of the present disclosure;

[0062] FIG. 10 is a perspective view of a safety shield of a safety mechanism of the first assembly of the automatic injection device according to an embodiment of the present disclosure;

[0063] FIG. Ila is a schematic view of the safety mechanism of the first assembly of the automatic injection device according to an embodiment of the present disclosure at a position corresponding to a first penetration depth high penetration depth);

[0064] FIG. 11b is a schematic view of the safety mechanism of the first assembly of the automatic injection device according to an embodiment of the present disclosure at a position corresponding to a second penetration depth (low penetration depth);

[0065] FIG. 12 is a schematic view of a syringe for the automatic injection device according to an embodiment of the present disclosure;

[0066] FIG. 13a is a front view of the first assembly, mounted with a syringe, of the automatic injection device according to an embodiment of the present disclosure;

[0067] FIG. 13b is a sectional front view of the first assembly, mounted with a syringe, of the automatic injection device according to an embodiment of the present disclosure;

[0068] FIG. 14 is a flow chart of a method for using the automatic injection device according to an embodiment of the present disclosure;

[0069] FIG. 15a is a schematic view showing the state where the driving mechanism of the second assembly of the automatic injection device according to the present disclosure is loaded and retained, and the trigger mechanism is at a non-triggerable position.

[0070] FIG. 15b is a schematic view showing the state where the syringe is mounted in the first assembly of the automatic injection device according to the present disclosure;

[0071] FIG. 15c is a schematic view showing that the second assembly and the first assembly of the automatic injection device according to the present disclosure are connected together;

[0072] FIG. 15d is a schematic view showing the state where the cover of the first assembly of the automatic injection device according to the present disclosure is removed and the safety mechanism of the first assembly is regulated to the position corresponding to the first penetration depth;

[0073] FIG. 15e is a schematic view showing the state where the trigger mechanism of the second assembly of the automatic injection device according to the present disclosure is rotated to the triggerable position;

[0074] FIG. 15f is a schematic view showing the state where the automatic injection device according to the present disclosure is pressed against an injection site of a target;

[0075] FIG. 15g is a schematic view showing the state where the trigger mechanism of the second assembly of the automatic injection device according to the present disclosure is pressed down to release the driving mechanism;

[0076] FIG. 15h is a schematic view showing the state where the driving mechanism of the second assembly of the automatic injection device according to the present disclosure is released and pushes a plunger rod of the syringe to insert the needle of the syringe into the injection site.

[0077] FIG. 15i is a schematic view showing that the driving mechanism of the second assembly of the automatic injection device according to the present disclosure continues to push the plunger rod of the syringe to carry out injection;

[0078] FIG. 16 is a schematic view showing the variation in magnitude of the spring force applied by the driving mechanism and of the friction force applied to the drivingmechanism during movement of the driving mechanism of the second assembly of the automatic injection device according to the present disclosure.

[0079] It is to be understood that like numbers refer to like elements throughout. In the drawings, for the sake of clarity, the sizes of certain features may be modified and not drawn to scale.DESCRIPTION OF THE INVENTION

[0080] The present disclosure will be described below with reference to the drawings, in which several embodiments of the present disclosure are shown. It should be understood, however, that the present disclosure may be implemented in many different ways, and is not limited to the example embodiments described below. In fact, the embodiments described hereinafter are intended to make a more complete disclosure of the present disclosure and to adequately explain the scope of the present disclosure to a person skilled in the art. It should also be understood that, the embodiments disclosed herein can be combined in various ways to provide many additional embodiments.

[0081] It should be understood that, the wording in the specification is only used for describing particular embodiments and is not intended to define the present disclosure. All the terms used in the specification (including technical and scientific terms) have the meanings as normally understood by a person skilled in the art, unless otherwise defined. For the sake of conciseness and / or clarity, well-known functions or constructions may not be described in detail.

[0082] The singular forms “a / an” and “the” as used in the specification, unless clearly indicated, all contain the plural forms. The words “comprising”, “containing” and “including” used in the specification indicate the presence of the claimed features, but do not preclude the presence of one or more additional features. The wording “and / or” as used in the specification includes any and all combinations of one or more of the relevant items listed.

[0083] In the specification, when an element is referred to as being “on”, “attached” to, “connected” to, “coupled” with, or “contacting”, etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on”, “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present.

[0084] In the description, the terms "first", "second" or "third" are used only for convenience of description and are not intended to be limiting. Any technical features represented by "first", "second" or "third" are interchangeable.

[0085] In the specification, words describing spatial relationships such as “up”, “down”, “forth”, “back”, “top”, “bottom” and the like may describe a relation of one feature to another feature in the drawings. It should be understood that these terms also encompass different orientations of the apparatus in use or operation, in addition to encompassing the orientations shown in the drawings. For example, when the apparatus shown in the drawings is turned over, the features previously described as being “below” other features may be described to be “above” other features at this time. The apparatus may also be otherwise oriented (rotated 90 degrees or at other orientations) and the relative spatial relationships will be correspondingly altered.

[0086] Referring to FIGS, la to Id, an automatic injection device 100 according to an embodiment of the present disclosure is shown, which can be used to automatically inject a fluid (for example, a liquid medication or other fluids) into an injection site of a target 101 (for example, living patients such as humans or animals, or other inanimate injected objects). The automatic injection device 100 may include a first assembly 200, and a second assembly 300 detachably connected to the first assembly 200 (for example, by threaded connection, friction-fit connection, snap-fit connection, etc.).

[0087] The first assembly 200 is configured to removably receive a syringe 400. The syringe 400 may be a conventional syringe that is common in the life. The syringe 400 may be a pre-filled syringe that is pre-filled with fluids in advance, and may also be a syringe that is filled with fluids on site before use. As shown more clearly in FIG. 12, the syringe 400 may include a barrel 401 for containing a fluid, a needle 402 provided at a first end 411 of the barrel 401, and a movable element 403 movable within the barrel 401. The movable element 403 can be driven from a second end 412 of the barrel 401 to discharge the fluid contained in the barrel 401 via the needle 402. In the embodiment shown in FIG. 12, the movable element 403 of the syringe 400 may include a plunger rod 431 and a stopper 432 provided at an end of the plunger rod 431 (as shown in FIG. 13b). In other embodiments, the movable element 403 may include only the stopper 432 but does not include the plunger rod 431. The movable element 403 of the syringe 400 may be driven by a driving mechanism disposed in the second assembly 300, which will be described in detail below. The syringe 400 may further include a cap 404 for covering the needle 403 of the syringe 400 to prevent accidental needle- stick injury.

[0088] Referring to FIGS. 2a to 2d, the second assembly 300 of the automatic injection device 100 will be described first.

[0089] The second assembly 300 may include an outer casing 310. The outer casing 310 may be cylindrical and may have a first end 311 and a second end 312. The first end 311 and the second end 312 may be opened. When the automatic injection device 100 has been assembled, the first end 311 of the outer casing 310 may be far away from the first assembly 200, and the second end 312 of the outer casing 310 may be close to the first assembly 200.

[0090] The second assembly 300 may further include a driving mechanism 320, a retaining mechanism 330 and a trigger mechanism 340.

[0091] The driving mechanism 320 may be placed within the outer casing 310 to drive the movable element 403 of the syringe 400. The driving mechanism 320 can be loaded and released. When the driving mechanism 320 is loaded, the driving mechanism 320 stores energy, whereas when the driving mechanism 320 is released, the driving mechanism 320 drives the movable element 403 of the syringe 400 towards the injection site by releasing its stored energy.

[0092] In the embodiment shown in FIGS. 2a to 2d, the driving mechanism 320 is configured as a spring-loaded driving mechanism, which may include a driving element321 and a spring element 322 disposed at a side of the driving element 321. When the driving mechanism 320 is loaded (for example, when the driving element 321 is pushed from the second end 312 of the outer casing 310 towards the first end 311 of the outer casing 310, as shown in FIG. 5a), the spring element 322 may be compressed to store elastic potential energy. When the driving mechanism 320 is released, the spring element322 can release its stored elastic potential energy to extend from the first end 311 of the outer casing 310 toward the second end 312 of the outer casing 310, thereby driving the movable element 403 of the syringe 400 via the driving element 321. In an embodiment according to the present disclosure, the spring element 322 is configured as a compressible and extendable helical spring. However, the present disclosure is not limited to this. The spring element 322 may have any suitable form.

[0093] In other embodiments according to the present disclosure, the driving mechanism 320 may be configured to be loaded by other energy sources. For example, the energy sources of the driving mechanism 320 may include compressible gases or other energy conversion mechanisms.

[0094] Referring to FIG. 4, in an embodiment according to the present disclosure, the driving element 321 is configured to have a substantially cylindrical body with a closed first end 323 and an opened second end 324. The spring element 322 may extend into the interior of the driving element 321 via the opened second end 324 and abut against the closed first end 323 of the driving element 321. In some embodiments, one end of the spring element 322 may also be fixedly connected with the first end 323 of the driving element 321.

[0095] In other embodiments according to the present disclosure, the driving element 321 may include a body in other shapes. For example, the driving element 321 may include a rod-shaped body, and in this embodiment, the spring element 322 may be disposed around the rod-shaped body. The driving element 321 may also include a disc-shaped body, and in this embodiment, the spring element 322 may abut against or be fixedly connected to a surface of the disc-shaped body.

[0096] The retaining mechanism 330 may also be placed within the outer casing 310 to retain the loaded driving mechanism 320. The retaining mechanism 330 may include a retaining position, where the retaining mechanism 330 may retain the loaded driving mechanism 320 to prevent its stored energy from being released, and a releasing position, where the retaining mechanism 330 may release the loaded driving mechanism 320 to allow it to release the stored energy.

[0097] In the embodiment shown in FIGS. 2b to 2d, the retaining mechanism 330 includes a first retaining element 331 in fixed connection with the driving mechanism 320 and a second retaining element 332 in fixed connection with the outer casing 310. The retaining mechanism 330 retains the loaded driving mechanism 320 through mutual cooperation between the first retaining element 331 and the second retaining element 332. For example, as shown in FIGS. 2a to 2c, the first retaining element 331 may be configured as a rod-shaped member. One end of the rod-shaped member may be connected to the driving element 321 of the driving mechanism 320 and the other end of the rod-shaped member is provided with a hook. The second retaining element 332 may be configured as a plurality of fingers arranged around the first retaining element 331, and a free end of each finger may include a mating member mated with the hook of the first retaining element 331, which mating member can bring the first retaining element 331 and the second retaining element 332 into snap-fit connection to thereby retain the loaded driving mechanism 320 (as shown in FIG. 2d). In an embodiment according to the present disclosure, the mating member of the second retaining element 332 is configured as aprotrusion protruding inwardly. In another embodiment according to the present disclosure, the mating member of the second retaining element 332 may also be configured as an opening for receiving the first retaining element 331. In other embodiments according to the present disclosure, the first retaining element 331 and the second retaining element 332 may have other different mating structures, for example, the free end of the second retaining element 332 includes a protrusion protruding inwardly, while the end of the first retaining element 331 includes a slot, an opening or the like for receiving the protrusion.

[0098] The second retaining element 332 may also be configured to be elastically deflectable outward, such that it can be disconnected from the first retaining element 331 when necessary so as to release the loaded driving mechanism 320. When the second retaining element 332 is disconnected from the first retaining element 331 due to outward deflection, the retaining mechanism 330 is at its releasing position.

[0099] The trigger mechanism 340 is configured to move the retaining mechanism 330 from its retaining position to its releasing position when necessary to release the loaded driving mechanism 320. The trigger mechanism 340 may be disposed at the first end 311 of the outer casing 310. The trigger mechanism 340 may include an unlocking element 365 for unlocking the retaining mechanism 330 (i.e., moving or biasing the retaining mechanism 330 from its retaining position to its releasing position) when the trigger mechanism 340 is pressed, thereby releasing the loaded driving mechanism 320. The unlocking element 365 may be disposed at an appropriate position of the trigger mechanism 340 (for example, at its central position) and may have various appropriate configurations, as shown in FIGS. 2c and 2d.

[0100] In an embodiment according to the present disclosure, the trigger mechanism 340 is configured to have a function of preventing accidental triggering. For this purpose, the trigger mechanism 340 according to the present disclosure is configured to include a non- triggerable position, in which the trigger mechanism 340 cannot be pressed down to move the retaining mechanism 330 from its retaining position to its releasing position, and a triggerable position, in which the trigger mechanism 340 can be pressed down to move the retaining mechanism 330 from its retaining position to its releasing position.

[0101] In an embodiment according to the present disclosure, the trigger mechanism 340 is configured to rotate around the central axis of the outer casing 310 to reach the non- triggerable position when the driving mechanism 320 is loaded. Specifically, as shown in FIGS. 3 and 4, the trigger mechanism 340 may be configured in the form of a button. Thetrigger mechanism 340 may include a bottom wall 341 and a side wall 342 extending from the bottom wall 341. The side wall 342 may have a substantially circular-arc shaped cross section, and may include a circumferential direction and an extending direction orthogonal to the circumferential direction (in FIG. 3, the extending direction corresponds to the vertical direction). An inner surface of the side wall 342 may be provided with a first groove 343 and a second groove 344 communicating with each other. The first groove 343 may extend obliquely (for example, along a spiral line) from a bottom surface 345 of the side wall 342 towards the bottom wall 341 in the extending direction of the side wall342. The first groove 343 may have a starting end 346 and an ending end 347, wherein the starting end 346 may be located near the bottom surface 345 of the side wall 342. The second groove 344 extends along the circumferential direction of the side wall 342 from the ending end 347 of the first groove at a substantially same height with the first groove. The second groove 344 has a starting end 348 and an ending end 349. The starting end 348 of the second groove 344 and the ending end 347 of the first groove 343 may be smoothly connected via a transition portion. Additionally, the second assembly 300 may include a pushing element 360 connected with the driving mechanism 320. As shown in FIG. 4, the pushing element 360 may be configured as a protrusion, which may be connected with the driving mechanism 320 (for example, with a body of the driving element 321 of the driving mechanism 320) via a rod-shaped connector 351. In an embodiment according to the present disclosure, the pushing element 360, the rod-shaped connector 351 and the body of the driving element 321 of the driving mechanism 320 may be integrally connected.

[0102] When the driving mechanism 320 is loaded, the driving mechanism 320 moves from the second end 312 of the outer casing 310 towards the first end 311 of the outer casing 310 in an axial direction within the outer casing 310. At this time, the pushing element 360 moves with the driving mechanism 320 and can enter the first groove 343 from the starting end 346 of the first groove. When the pushing element 360 is moving, it abuts against and pushes a groove sidewall 350 of the first groove 343. As the groove sidewall 350 is oblique, the trigger mechanism 340 may be rotated under the pushing of the pushing element 360, which facilitates the pushing element 360 to move from the starting end 346 of the first groove 343 towards the ending end 347 of the first groove343. When the pushing element 360 reaches the ending end 347 of the first groove 343, the loaded driving mechanism 320 may be in a state where it is retained by the retaining mechanism 330, and the trigger mechanism 340 may be rotated to its non-triggerableposition. At this non-triggerable position, the bottom surface 345 of the side wall 342 of the trigger mechanism 340 can be stopped by a first stop 361 provided on the inner surface of the outer casing 310 (see FIG. 5b) so as not to allow the trigger mechanism 340 to be pressed down. The first stop 361 may be a ridge or rib provided on the inner surface of the outer casing 310, the length of which is configured not to stop the bottom surface 345 of the side wall 342 when the trigger mechanism 340 is at the triggerable position.

[0103] In embodiments according to the present disclosure, by configuring the trigger mechanism 340 to include a non-triggerable position, users can be effectively prevented from accidentally pressing down the trigger mechanism 340 to release the loaded driving mechanism 320 before being ready to use the automatic injection device 100. Further, the trigger mechanism 340 is configured to be automatically rotated to the non-triggerable position when the driving mechanism 320 is loaded, so the automatic injection device 100 according to the present disclosure does not require an additional step to move the trigger mechanism 340 to the non-triggerable position. This simplifies the operation of the automatic injection device 100 and avoids the adverse consequences caused by the users forgetting to take this additional step. Finally, the trigger mechanism 340 including the non-triggerable position eliminates the need for a separate interlock design to prevent accidental triggering for the automatic injection device 100 according to the present disclosure, which simplifies the structure of the automatic injection device 100.

[0104] In embodiments according to the present disclosure, the trigger mechanism 340 is also configured to be manually rotatable from the non-triggerable position to the triggerable position about the central axis of the outer casing 310, so that the loaded driving mechanism 320 can be released when necessary. At the triggerable position, as shown in FIG. 7, the bottom surface 345 of the side wall 342 of the trigger mechanism 340 is remote from the first stop 361, thus allowing the trigger mechanism 340 to be pressed down.

[0105] In order to allow the driving mechanism 320 to be completely released and enable the driving mechanism 320 to move automatically within the outer casing 310 when the trigger mechanism 340 is at the triggerable position, the depth of the second groove 344 is configured to gradually decrease to zero from the starting end 348 of the second groove to the ending end 349 of the second groove. In this way, when the trigger mechanism 340 is rotated from the non-triggerable position towards the triggerable position, the pushing element 360 can first enter the second groove 344 from the first groove 343 and then move from the starting end 348 of the second groove 344 towards the ending end 349 ofthe second groove 344, and move out of the ending end 349 of the second groove 344 when the trigger mechanism 340 reaches the triggerable position. At this time, the pushing element 360 is disconnected from the trigger mechanism 340 to allow the driving mechanism 320 to move automatically under the action of the spring element 322.

[0106] In other embodiments according to the present disclosure, the second groove 344 may also have a constant depth. In this embodiment, in order to allow the driving mechanism 320 to move automatically within the outer casing 310, the inner surface of the side wall 342 may further be provided with a third groove extending from the ending end 349 of the second groove 344 towards the bottom surface 345 of the side wall 342 along the extending direction of the side wall 342. After the driving mechanism 320 is released by the trigger mechanism 340, the pushing element 360 can move along the third groove without interfering with the automatic movement of the driving mechanism 320.

[0107] In the embodiment shown in FIG. 3, the side wall 342 of the trigger mechanism 340 is configured to include a first cylindrical portion 3421 having a substantially cylindrical shape, and a second suspending portion 3422 suspended from the first cylindrical portion 3421. The first groove 343, the second groove 344, and the optional third groove may be provided on the inner surface of the second suspending portion 3422. In other embodiments according to the present disclosure, the side wall 342 of the trigger mechanism 340 may also include only the second suspending portion 3422 directly connected with the bottom wall 341.

[0108] As shown in FIG. 3, in an embodiment according to the present disclosure, the trigger mechanism 340 may further include at least one finger 352, such as two fingers 352 as shown in FIG. 3. Free ends of the fingers 352 may include hooks 353. Correspondingly, the inner surface of the outer casing 310 may be provided with second stops 354 (as shown in FIGS. 2c and 2d) cooperating with the hooks 353. The second stops 354 are configured to prevent the trigger mechanism 340 from disengaging from the outer casing 310.

[0109] Referring to FIGS. 6 and 7, in an embodiment according to the present disclosure, in order to more clearly indicate the position of the trigger mechanism 340, an outer surface of the outer casing 310 may be provided with a locking mark 355 for indicating the non-triggerable position of the driving mechanism 320 and an unlocking mark 356 for indicating the triggerable position of the driving mechanism 320. Correspondingly, an outer surface of the trigger mechanism 340 may be provided with an indication line 357. When the trigger mechanism 340 is at the non-triggerable position, the indication line357 is aligned with the locking mark 355 (as shown in FIG. 6), and when the trigger mechanism 340 is at the triggerable position, the indication line 357 is aligned with the unlocking mark 356 (as shown in FIG. 7).

[0110] Referring to FIGS. 2c and 2d, FIG. 4 and FIG. 16, in order to endow the automatic injection device 100 with a constant injection force throughout the injection process, in an embodiment according to the present disclosure, the second assembly 300 may further include an annular protrusion 362 disposed within the outer casing 310. The annular protrusion 362 is configured to generate friction against the outer surface of the body of the driving mechanism 320 when the body of the driving mechanism 320 moves past the annular protrusion 362. This friction is designed to decrease with an increase in the distance L that the body of the driving mechanism 320 moves in a direction towards the first assembly 200.

[0111] As shown more clearly in FIG. 16, the driving force Fs of the driving mechanism 320 (for example, the elastic force of the spring element) may decrease with an increase in the distance L that the body of the driving mechanism 320 moves in the direction towards the first assembly. When the friction Ff is also designed to decrease with an increase in the distance that the body of the driving mechanism 320 moves in the direction towards the first assembly 200, the injection force applied by the driving mechanism 320 (which is a resultant force F of the driving force Fs and the spring force Ff and is equal to Fs minus Ff) can be kept constant throughout the injection process. Constant injection force can produce constant injection speed and can bring more comfortable injection experience to users.

[0112] In order to make the friction reduced with an increase in the distance that the body of the driving mechanism 320 moves in the direction towards the first assembly 200, in an embodiment according to the present disclosure, as shown in FIG. 4, an outer surface of the body of the driving mechanism 320 may be provided with at least one recess 325 extending from a first end 323 to a second end 324 of the body. The width of the recess 325 is configured to gradually increase from the first end 323 of the body towards the second end 324 of the body. As the annular protrusion 362 cannot contact a bottom of the recess 325, when the body of the driving mechanism 320 moves past the annular protrusion 362 in the direction towards the first assembly 200, the contact area between the annular protrusion 362 and the outer surface of the body of the driving mechanism 320 may gradually decrease, thus resulting in a gradual decrease in the friction Ff. In another embodiment according to the present disclosure, the outer surface of the body ofthe driving mechanism 320 may have a different configuration, for example, it may not include the recess 325. In this embodiment, the outer surface of the body of the driving mechanism 320 may have a gradually varying smoothness (the greater the smoothness, the smaller the generated friction Ff). For example, the smoothness may gradually increase from the first end 323 to the second end 324 of the body of the driving mechanism 320, so that when the body of the driving mechanism 320 moves past the annular protrusion 362 in the direction towards the first assembly 200, the friction Ff between the annular protrusion 362 and the outer surface of the body of the driving mechanism 320 gradually decreases.

[0113] In addition, as shown in FIGS. 2c and 2d, in an embodiment according to the present disclosure, the second assembly 300 may further include an inner casing 370. The inner casing 370 can facilitate assembling of the second assembly 300. The inner casing 370 can retain the driving mechanism 320 within the second assembly 300. The inner casing 370 may be fixedly disposed within the outer casing 310 (for example, by welding, screwed connection, etc.). At least a portion of the inner casing 370 may extend from the outer casing 310 to form a connecting portion for connecting with the first assembly 200. The connecting portion may be inserted into the first assembly 200 to connect the second assembly 300 with the first assembly 200. The connecting portion may be connected with the first assembly 200 in any suitable means (for example, by threaded connection, friction-fit connection, snap-fit connection, etc.). In an embodiment where the inner casing 370 is included, the annular protrusion 362 may be disposed on an inner surface of the inner casing 370. For example, the annular protrusion 362 may be integrally formed on the inner surface of the inner casing 370. The annular protrusion 362 may also be formed of a rubber ring. The rubber ring may be removably positioned in an annular groove in the inner surface of the inner casing 370.

[0114] Next, the first assembly 200 of the automatic injection device 100 will be described with reference to FIGS. 8a to 8c.

[0115] The first assembly 200 may include an outer shell 210. The outer shell 210 may be cylindrical and may include a first end 211 and a second end 212. The first end 211 and the second end 212 may be opened. When the automatic injection device 100 has been assembled, the first end 211 of the outer shell 210 may be close to the second assembly 300, and the second end 212 may be far away from the second assembly 300. The syringe 400 may be loaded into the outer shell 210 via the first end 211 of the outer shell 210.

[0116] The outer shell 210 of the first assembly 200 may be provided therein with a syringe retainer 220 for retaining the syringe 400. The syringe retainer 220 may include a first retainer 221 fixedly disposed within the outer shell 210, and a second retainer 222 floatable with respect to the first retainer 221. The syringe retainer 220 may further include a spring element 223 disposed between the first retainer 221 and the second retainer 222. The syringe 400 may extend through and be retained by the first retainer 221 and the second retainer 222. The spring element 223 is extended in an initial state to retain the syringe 400 within the first assembly 200, so that the needle 402 of the syringe 400 cannot protrude from the outer shell 210 of the first assembly 200. The spring element 223 is compressed in an injection state to enable the needle 402 of the syringe 400 to be inserted into an injection site of a target. The second retainer 222 may be configured to be retained within the outer shell 210 without being detached from the outer shell 210. For example, the second retainer 222 may include a hook 224, and the outer shell 210 may be provided with an opening 225 for engagement with the hook 224.

[0117] The first assembly 200 may include a safety mechanism 230 disposed at the second end 212 of the outer shell 210 of the first assembly 200. The safety mechanism 230 is configured to further cover the needle 402 of the syringe 400, such that the needle 402 is covered before use of the syringe 400 to prevent accidental needle-stick injury. The safety mechanism 230 may include a safety shield 231 and a spring element 232 disposed within the safety shield 231. The safety shield 231 is movable between a first position and a second position by means of the spring element 232. At the first position, the spring element 232 is extended to push a portion of the safety shield 231 out of the outer shell 210 of the first assembly 200 to cover the needle 402. At the second position, the spring element 232 is compressed and said portion of the safety shield 231 is pushed back into the outer shell 210 of the first assembly 200, allowing the needle 402 to protrude out of the safety shield 231 and penetrate into the injection site of a target 101.

[0118] Referring to FIG. 10, the safety shield 231 may be substantially cylindrical. The safety shield 231 may include a first end 2311 for contacting the injection site and a second end 2312 opposite to the first end 2311. In an embodiment according to the present disclosure, the second end 2312 of the safety shield 231 may include a plurality of regulating portions for regulating the penetration depth of the needle 402 into the injection site. The distances between the regulating portions and the first end 2311 of the safety shield 231 are different, so as to adjust the depth to which the safety shield 231 retracts into the outer shell 210 of the first assembly 200. For example, if the safety shield231 retracts into the outer shell 210 to a high depth, the needle 402 can be inserted deeper into the injection site (i.e., a high penetration depth); however, if the safety shield 231 retracts into the outer shell 210 of the first assembly 200 to a low depth, the needle 402 can be inserted into the injection site more shallowly (i.e., a low penetration depth). In the embodiment shown in FIG. 10, the second end 2312 of the safety shield 231 includes two regulating portions 2313 and 2314. However, the safety shield 231 may include more, for example, three, four, five, six, eight, etc., regulating portions.

[0119] The outer shell 210 of the first assembly 200 may be provided therein with an abutting portion 233 for cooperation with any one of the plurality of regulating portions. The abutting portion 233 may abut against the top of each regulating portion (for example, the regulating portions 2313 and 2314) to limit the depth to which the safety shield 231 is retracted into the outer shell 210. In the embodiment shown in FIG. 9b, the abutting portion 233 is configured as a rib. However, the abutting portion 233 may have various shapes, for example, the abutting portion 233 may be configured as a protrusion in any shape.

[0120] In an embodiment according to the present disclosure, in order to select different penetration depths, the safety shield 231 is configured to be rotatable relative to the outer shell of the first assembly 200 to allow selection of one of the plurality of regulating portions by rotating the safety shield 231. In addition, in order to identify the selected penetration depth more easily and intuitively, a plurality of indication marks for indicating different penetration depths may be arranged on the outer surface of the outer shell 210 of the first assembly 200. For example, as shown in FIGS. Ila and 11b, an indication mark "H" for indicating a high penetration depth and an indication mark "L" for indicating a low penetration depth may be provided on the outer surface of the outer shell 210 of the first assembly 200. Depending on the number of the regulating portions, more indication marks may be provided on the outer surface of the outer shell 210 of the first assembly 200. In addition, an indication line 2315 may be provided on the outer surface of the safety shield 231. A desired penetration depth can be obtained by rotating the indication line 2315 of the safety shield 231 to align with one of the indication marks.

[0121] Returning to FIGS. 9a and 9b, in an embodiment according to the present disclosure, the first assembly 200 may further include an inner shell 240 fixedly disposed within the outer shell 210. The aforementioned first retainer 221, opening 225 and abutting portion 233 may be disposed on the inner shell 240. However, the inner shell240 is not necessary. In some embodiments, the first assembly 200 may include only the outer shell 210, or has the outer shell 210 and the inner shell 240 integrally formed.

[0122] Referring to FIGS. 8a to 8c and FIGS. 13a to 13b, in an embodiment according to the present disclosure, the first assembly 200 may further include a cover 250 for covering the second end 212 of the outer shell 210 of the first assembly 200. The cover 250 may include at least one finger 251, for example, a plurality of the fingers 251 as shown in FIG. 8c. A free end of each finger 251 may include a hook 252, for example, a hook protruding towards the center of the outer shell 210 of the first assembly 200. After the syringe 400 including the cap 404 is loaded in the first assembly 200, the hook 252 of each finger 251 may be hooked on the cap 404 (for example, hooked on a tail edge of the cap 404), so that the cap 404 of the syringe 400 can also be removed when the cap 250 is removed from the first assembly 200. This can simplify the operation steps of the automatic injection device 100. When a plurality of fingers 251 are included, the plurality of fingers 251 may be arranged circumferentially about the central axis.

[0123] Next, a method 500 for using the automatic injection device 100 according to the present disclosure will be described with reference to FIGS. 14 to 15i.

[0124] The method 500 may include an assembling step 510 for assembling the automatic injection device. The assembling step 510 may include:

[0125] step 511, in which the driving mechanism 320 of the second assembly 300 is loaded by pushing from the second end 312 of the outer casing 310 of the second assembly 300 until the retaining mechanism 330 of the second assembly 300 retains the loaded driving mechanism 320, and at this time, the trigger mechanism 340 of the second assembly 300 is rotated to the non-triggerable position, as shown in FIG. 15a;

[0126] step 512, in which the syringe 400 is received in the first assembly 200, as shown in FIG. 15b;

[0127] step 513, in which the first assembly 200 and the second assembly 300 are connected to form the assembled automatic injection device 100, as shown in FIG. 15c;

[0128] After the automatic injection device 100 has been assembled, the method 500 may include an injection step 520 of automatically injecting using the assembled automatic injection device 100. The injection step 520 may include:

[0129] step 521, in which the cover 250 is removed in the case where the first assembly 200 includes the cover 250, and the cap 404 of the syringe 400 can be moved by removing the cover 250;

[0130] step 522, in which one of a plurality of regulating portions is selected to select a desired penetration depth, in the case where the safety shield 231 of the safety mechanism 230 of the first assembly 200 includes the plurality of regulating portions (as shown in FIG. 15d, where the regulating portion of the safety shield 231 is regulated to a deep insertion position);

[0131] step 523, in which the automatic injection device 100 with the regulated safety shield 231 is pressed against the injection site of the target 101, as shown in FIG. 15f;

[0132] step 524, in which the trigger mechanism 340 of the second assembly 300 is rotated from the non-triggerable position to the triggerable position, as shown in FIG. 15e;

[0133] step 525, in which the trigger mechanism 340 at the triggerable position is pressed down from the first end 311 of the outer casing 310 of the second assembly 300 to release the loaded driving mechanism 320, as shown in FIG. 15g;

[0134] step 526, in which the needle 402 of the syringe 400 is automatically inserted into the injection site of the target 101 by means of the driving mechanism 320 (as shown in FIG. 15h), and injection is performed (as shown in FIG. 15i) until the injection is completed.

[0135] After the injection is completed, the method 500 may further include:

[0136] step 530, in which the automatic injection device 100 is removed from the injection site;

[0137] step 531, in which the first assembly 200 and the second assembly 300 of the automatic injection device 100 are disassembled; and

[0138] step 532, in which the syringe 400 having finished injection is removed from the first assembly 200 and placed in a recycling container.

[0139] The automatic injection device 100 according to the present disclosure may be reusable. Therefore, the same automatic injection device 100 and a new syringe 400 may be used to repeat the above steps 510 to 532 to carry out injection. In addition, it should be noted that some of the above steps 510 to 532 can be omitted in some cases, and some of them may have their orders exchanged as required.

[0140] Although the automatic injection device 100 according to the present disclosure and a method for using the same have been described above in the context of drug injection, it should be noted that the automatic injection device 100 according to the present disclosure and a method for using the same can be applied to other technical fields. For example, the automatic injection device 100 according to the present disclosuremay be used in the industrial field to inject a desired process fluid into a desired industrial part; for another example, the automatic injection device 100 according to the present disclosure may be used to inject fluids such as pesticides into plants or other inanimate organisms, etc.. Therefore, the automatic injection device 100 according to the present disclosure can be used for non-therapeutic purposes.

[0141] Although the exemplary embodiments of the present disclosure have been described, those skilled in the art should understand that multiple changes and modifications may be made to the exemplary embodiments without substantively departing from the spirit and scope of the present disclosure. Accordingly, all the changes and modifications are encompassed within the protection scope of the present disclosure as defined by the claims. The present disclosure is defined by the appended claims, and equivalents of these claims are also included in the scope of the present disclosure.

Claims

WHAT IS CLAIMED IS:

1. An automatic injection device for automatically injecting a fluid in a syringe into an injection site of a target, the syringe comprising: a barrel containing the fluid, a needle disposed at a first end of the barrel, and a movable element movable within the barrel, the movable element capable of being driven from a second end of the barrel opposite to the first end to discharge the fluid through the needle, wherein the automatic injection device comprises: a first assembly for removably receiving the syringe; and a second assembly detachably coupled with the first assembly, the second assembly comprising: an outer casing including a first end far away from the first assembly and a second end close to the first assembly; a driving mechanism placed within the outer casing and capable of being loaded and released, wherein when loaded, the driving mechanism stores energy, and when released, the driving mechanism drives the movable element of the syringe towards the injection site by releasing its stored energy; a retaining mechanism placed within the outer casing, the retaining mechanism comprising a retaining position where the loaded driving mechanism is retained, and a releasing position where the loaded driving mechanism is released; and a trigger mechanism disposed at the first end of the outer casing, the trigger mechanism being configured to move the retaining mechanism from its retaining position to its releasing position to release the loaded driving mechanism, wherein the trigger mechanism is configured to rotate, when the driving mechanism is loaded, about a central axis of the outer casing under an action of a pushing element connected with the driving mechanism until it reaches a non-triggerable position where the trigger mechanism is unable to be pressed down to move the retaining mechanism from its retaining position to its releasing position; and wherein the trigger mechanism is further configured to be manually rotatable about the central axis of the outer casing from the non-triggerable position to a triggerable position where the trigger mechanism is capable of being pressed down to move the retaining mechanism from its retaining position to its releasing position to release the loaded driving mechanism.

2. The automatic injection device according to claim 1, wherein the trigger mechanism comprises a bottom wall and a side wall extending from the bottom wall, the side wall has a substantially circular-arc shaped cross section and includes a circumferential direction and an extending direction orthogonal to the circumferential direction, and an inner surface of the side wall is provided with a first groove and a second groove communicating with each other, wherein the first groove extends obliquely towards the bottom wall in the extending direction and has a starting end far away from the side wall and an ending end close to the side wall; the second groove extends from the ending end of the first groove along the circumferential direction of the side wall at a substantially same height with the first groove and has a starting end and an ending end; and wherein the pushing element is configured as a protrusion, which is capable of entering the first groove from the starting end of the first groove and rotating the trigger mechanism by pushing a groove sidewall of the first groove when the driving mechanism is loaded.

3. The automatic injection device according to claim 2, wherein a depth of the second groove gradually decreases to zero from the starting end of the second groove to the ending end of the second groove, so that the protrusion is capable of sliding out of the ending end of the second groove when the trigger mechanism is rotated from the non-triggerable position to the triggerable position.

4. The automatic injection device according to claim 2, wherein the side wall of the trigger mechanism comprises a first cylindrical portion having a substantially cylindrical shape and a second suspending portion suspended from the first cylindrical portion, the first groove and the second groove being disposed in an inner surface of the second suspending portion.

5. The automatic injection device according to claim 4, wherein an inner surface of the outer casing comprises a first stop, which stops the second suspending portion to prevent the trigger mechanism from being pressed down when the trigger mechanism is at the non- triggerable position, and which stays far from the second suspending portion so as not to prevent the trigger mechanism from being pressed down when the trigger mechanism is at the triggerable position.

6. The automatic injection device according to claim 2, wherein the trigger mechanism further comprises at least one finger, a free end of which includes a hook, and the inner surface of the outer casing is provided with a second stop for cooperation with the hook to prevent the trigger mechanism from being disengaged from the outer casing.

7. The automatic injection device according to claim 1, wherein the driving mechanism comprises a substantially cylindrical body with a closed first end and an opened second end, and the pushing element is connected with the second end of the body of the driving mechanism via a rod-shaped connector.

8. The automatic injection device according to claim 7, wherein the pushing element, the rod-shaped connector, and the body of the driving mechanism are integrally formed.

9. The automatic injection device according to claim 7, wherein the second assembly further comprises an annular protrusion placed within the outer casing; when the body of the driving mechanism moves past the annular protrusion in a direction towards the first assembly, a friction is generated between the annular protrusion and the outer surface of the body of the driving mechanism; and the friction decreases with an increase in the distance that the body of the driving mechanism moves in the direction towards the first assembly.

10. The automatic injection device according to claim 9, wherein the outer surface of the body of the driving mechanism includes at least one recess extending from the first end of the body to the second end of the body, and the recess has a width gradually increasing from the first end of the body to the second end of the body, so that when the body of the driving mechanism moves past the annular protrusion in the direction towards the first assembly, a contact area between the annular protrusion and the outer surface of the body of the driving mechanism gradually decreases, thus gradually reducing the friction.

11. The automatic injection device according to claim 9, wherein the outer surface of the body of the driving mechanism has a gradually varying smoothness, and the smoothness gradually increases from the first end of the body towards the second end of the body, so that when the body of the driving mechanism moves past the annular protrusion in the direction towards the first assembly, the friction between the annular protrusion and the outer surface of the body of the driving mechanism gradually decreases.

12. The automatic injection device according to claim 9, wherein the second assembly further comprises an inner casing fixedly placed within the outer casing, and at least a portion of the inner casing extends out of the second end of the outer casing to be connected with the first assembly.

13. The automatic injection device according to claim 12, wherein the annular protrusion is disposed on an inner surface of the inner casing.

14. The automatic injection device according to claim 12, wherein the annular protrusion is formed of a rubber ring, which is removably positioned in an annular groove in the inner surface of the inner casing.

15. The automatic injection device according to claim 1, wherein the driving mechanism comprises a first spring element, which is compressed to store energy when the driving mechanism is loaded, and which is extended by releasing its stored energy when the driving mechanism is released.

16. The automatic injection device according to claim 1, wherein the retaining mechanism comprises a first retaining element fixedly connected with the driving mechanism and a second retaining element fixedly connected with the outer casing, the first retaining element and the second retaining element cooperating with each other to retain the loaded driving mechanism, and wherein the trigger mechanism comprises an unlocking element configured to unlock the retaining mechanism to release the loaded driving mechanism when the trigger mechanism is pressed down.

17. The automatic injection device according to claim 16, wherein the first retaining element and the second retaining element are in snap-fitted connection with each other to retain the loaded driving mechanism, the second retaining element is configured to be elastically deflectable outward, and wherein the unlocking element is configured to bias the second retaining element outwards to disconnect the second retaining element from the first retaining element when the trigger mechanism is pressed down.

18. The automatic injection device according to claim 1, wherein the outer surface of the outer casing is provided with a locking mark for indicating the non-triggerable position and an unlocking mark for indicating the triggerable position; and the outer surface of the trigger mechanism is provided with an indication line, which is aligned with the locking mark when the trigger mechanism is at the non-triggerable position, and which is aligned with the unlocking mark when the trigger mechanism is at the triggerable position.

19. The automatic injection device according to claim 1, wherein the first assembly comprises: an outer shell including a first end close to the second assembly and a second end far away from the second assembly; and a safety mechanism disposed at the second end of the outer shell of the first assembly, wherein the safety mechanism comprises a safety shield and a second spring element placed within the safety shield, wherein the safety shield is movable between a first position where the second spring element is extended to push a portion of the safety shield out of the outer shell of the first assembly to cover the needle, and a second position where the second spring element is compressed and said portion of the safety shield is pushed back into the outer shell of the first assembly to enable the needle to protrude out of the safety shield and penetrate into the injection site.

20. The automatic injection device according to claim 19, wherein the safety shield comprises a first end for contacting the injection site and a second end opposite to the first end of the safety shield, wherein the second end of the safety shield comprises a plurality ofregulating portions for regulating a penetration depth of the needle, and distances between the regulating portions and the first end of the safety shield are different.

21. The automatic injection device according to claim 20, wherein the safety shield is configured to be rotatable relative to the outer shell of the first assembly to allow selection of a desired penetration depth by selecting one of the plurality of regulating portions.

22. The automatic injection device according to claim 20, wherein an outer surface of the outer shell of the first assembly is provided with a plurality of indication marks for indicating different penetration depths respectively, an outer surface of the safety shield is provided with an indication line, and a desired penetration depth is selected by aligning the indication line with one of the plurality of indication marks.

23. The automatic injection device according to claim 20, wherein the outer shell of the first assembly is provided therein with an abutting portion for cooperation with any one of the plurality of regulating portions.

24. The automatic injection device according to claim 23, wherein the abutting portion is configured as a rib.

25. The automatic injection device according to claim 1, wherein the first assembly further comprises a syringe retainer for retaining the syringe, and the syringe retainer comprises a third spring element which is extended in an initial state to retain the syringe within the first assembly, and which is compressed in an injection state to be capable of inserting the needle of the syringe into the injection site.

26. The automatic injection device according to claim 19, wherein the first assembly further comprises a cover for covering the second end of the outer shell of the first assembly, and the syringe comprises a cap for covering the needle, and wherein the cover comprises at least one finger, a free end of which comprises a hook, and the hook of the fingeris capable of being hooked on the cap of the syringe, so that when the cover is removed from the first assembly, the syringe is also removed.

27. A method for using the automatic injection device according to claim 1 , for non- therapeutic purposes, comprising: an assembling step of assembling the automatic injection device, the assembling step comprising: pushing the driving mechanism of the second assembly from the second end of the outer casing of the second assembly to load the driving mechanism until the retaining mechanism of the second assembly retains the loaded driving mechanism, at which time the trigger mechanism of the second assembly is at the non-triggerable position; receiving the syringe in the first assembly; and connecting the first assembly and the second assembly; an injection step of automatically injecting using the assembled automatic injection device, the injection step comprising, pressing the assembled automatic injection device against an injection site of a target, wherein the target does not include living human and animal bodies; rotating the trigger mechanism from the non-triggerable position to the triggerable position; pressing the trigger mechanism to release the loaded driving mechanism; and automatically inserting the needle of the syringe into the injection site by means of the driving mechanism, and performing injection until the injection is completed.

28. The method of claim 27, further comprising: removing the automatic injection device from the injection site after the injection is completed; disconnecting the first assembly and the second assembly of the automatic injection device; removing the syringe from the first assembly and putting it into a recycling container.

29. The method of claim 27, further comprising: when the automatic injection device is the automatic injection device according to any one of claims 20 to 24, the assembling step further comprises selecting one of the plurality of regulating portions to select a desired penetration depth.

30. The method of claim 27, further comprising: when the automatic injection device is the automatic injection device according to claim 26, the injection step further comprises removing the cap of the syringe by removing the cover before pressing the assembled automatic injection device against the injection site of the target.

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