Disposable injection pen

Abstract

This invention provides a disposable injection pen, comprising an upper pen shell assembly and a lower pen shell assembly that are assembled together. The lower pen shell assembly includes a pen cap and a protective shell fitted inside the pen cap. An injection bracket supporting a pre-filled syringe is arranged on the inner ring of the protective shell. The upper pen shell assembly includes an upper pen shell and a drive structure arranged within the upper pen shell. The drive structure is a driving part that pushes the pre-filled syringe to perform an injection action. A screw driven by the drive structure for rotational feeding is also provided within the upper pen shell. The upper pen shell provides double-end center positioning for the screw's rotational feeding motion at both axial ends. By forming a double-end center positioning structure for the screw's rotational feeding motion at both axial ends of the upper pen shell, the coaxiality and motion stability of the screw during the injection process of driving the pre-filled syringe are ensured.

Description

Technical Field

[0001] This invention relates to the field of injection pen technology, and more specifically, to a disposable injection pen. Background Technology

[0002] A disposable injection pen is a pen-shaped syringe pre-filled with medication, also known as a pre-filled injection pen. In one existing disposable automatic injection pen design, the pen contains a syringe assembly consisting of a pre-filled syringe, pre-filled liquid, and a rubber stopper.

[0003] When using the device, first remove the pen cap, which will bring out the pre-filled syringe needle cap. Then, press the protective shell to administer the subcutaneous injection. The injection is powered by a compression spring, torsion spring, or coil spring. The injection process is visible, as there is a viewing window near the needle on the protective shell. An injection completion beep will sound as the injection is nearing completion to remind the user. Stop pressing the protective shell; it will return to its pre-use position under the reaction force of the compression spring, locking in place. Pressing the protective shell again will prevent the needle tip from protruding, ensuring that the needle of the disposable auto-injector pen cannot extend after use and preventing puncture wounds.

[0004] In existing injection pen structures, during injection, the protective shell pushes a slider. When it reaches a certain stroke, the teeth disengage, and a protrusion inside the drive element engages with a groove on the screw. Under the reaction force of a torsion spring, the drive element drives the screw to rotate and advance, completing the injection. During injection, the propulsion element is prone to misalignment and impact with the side wall of the pre-filled syringe, leading to breakage. Simultaneously, the propulsion element experiences significant friction, resulting in uneven injection. After assembly, the flange of the pre-filled syringe is prone to deflection, and the protective shell may retract inward, causing the activation function to fail and ultimately leading to product failure. Summary of the Invention

[0005] In view of this, the present invention provides a disposable injection pen to ensure the stability of the injection pen during operation.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A disposable injection pen includes an upper pen shell assembly and a lower pen shell assembly that are assembled together. The lower pen shell assembly includes a pen cap and a protective shell that is snapped into the pen cap. The inner ring of the protective shell is provided with an injection bracket that supports a pre-filled syringe.

[0008] The upper pen shell assembly includes an upper pen shell and a drive structure arranged inside the upper pen shell. The drive structure is a drive part that pushes the pre-filled syringe to perform an injection action.

[0009] The upper pen housing is also provided with a screw that is driven by the drive structure to rotate and feed. The upper pen housing is positioned at both ends of the axial direction to center the rotation of the screw.

[0010] Preferably, in the above-mentioned disposable injection pen, the screw has a threaded section with a rectangular cross-section having a racetrack shape and double arc edges;

[0011] The upper pen shell is provided with a drive cover that is driven to rotate by the drive structure, and the drive cover has a racetrack-shaped through hole.

[0012] The screw is driven by the drive cover to rotate and feed.

[0013] Preferably, in the above-mentioned disposable injection pen, the drive cap has a rotating sleeve that is assembled into a single unit, and the screw is rotatably arranged inside the rotating sleeve.

[0014] Preferably, in the above-mentioned disposable injection pen, the screw also has a cylindrical screw tail, and the screw is rotatably supported by its screw tail and arranged in the rotating sleeve.

[0015] Preferably, in the above-mentioned disposable injection pen, the screw also has a connecting head that abuts against the pre-filled syringe, and the connecting head has a spherical circular feature.

[0016] Preferably, in the above-mentioned disposable injection pen, the rotating sleeve includes a sleeve portion that inserts into the drive cap and a guide sleeve portion that extends coaxially with the sleeve portion; the guide sleeve portion is a cylindrical structure with a circular guide hole, and the tail of the screw is arranged inside the guide sleeve portion.

[0017] Preferably, in the above-mentioned disposable injection pen, a fixing sleeve is installed on the upper pen shell, and the fixing sleeve has an internal through hole that aligns with the tail end of the guide cylinder.

[0018] Preferably, in the above-mentioned disposable injection pen, the inner ring of the upper pen shell is further provided with a bracket for rotating support of the closed end of the drive cover;

[0019] The drive cover has a first annular protrusion extending coaxially to its outer side, and the bracket has a second annular protrusion extending toward the drive cover in the middle.

[0020] The first annular boss and the second annular boss have an axial insertion fit structure.

[0021] Preferably, in the disposable injection pen described above, the second annular boss is inserted into the inner ring of the first annular boss, and the second annular boss abuts against the end face of the closed end of the drive cover.

[0022] Preferably, in the above-mentioned disposable injection pen, the inner ring of the upper pen shell is further provided with a nut, the nut having a central nut that is fitted into the inner circumferential side of the second annular boss;

[0023] The external thread of the screw and the threaded hole of the nut form a threaded transmission pair.

[0024] Preferably, in the above-mentioned disposable injection pen, the end of the upper pen shell has an insertion part, and the end of the lower pen shell has a receiving cavity;

[0025] The outer periphery of the insertion part has an outwardly protruding locking point, and the inner ring of the receiving cavity has an inwardly concave locking groove that engages with the outwardly protruding locking point.

[0026] The upper pen shell and the lower pen shell are connected by the insertion part and the receiving cavity.

[0027] Preferably, in the above-mentioned disposable injection pen, a clamping fin extends from the insertion part of the upper pen shell toward the lower pen shell side, and the protruding end of the clamping fin abuts against the flange part of the pre-filled syringe.

[0028] Preferably, in the above-mentioned disposable injection pen, the clamping fins extend from the end face of the bracket, and the clamping fins include one or more sets radially distributed along the inner circle of the internal through hole of the upper pen shell.

[0029] Preferably, in the above-mentioned disposable injection pen, the overhanging end of the clamping fin is bent radially inward to form a support foot, the support foot is pressed against the transition arc surface of the flange of the pre-filled syringe, and undergoes bending deformation under the guidance of axial clamping force.

[0030] Preferably, in the above-mentioned disposable injection pen, the nut has radially extending forked arms, and the forked structures of the forked arms form a U-shaped groove for the passage of the clamping fins.

[0031] Preferably, in the above-mentioned disposable injection pen, the injection holder has a flange support end, the flange support end has a flange portion for accommodating the flange portion, the flange portion has an annular arm plate structure, and the inner circle of the flange portion forms a groove for accommodating the flange portion.

[0032] Preferably, in the above-mentioned disposable injection pen, the flange portion has a racetrack-shaped flange feature, and the inner surface of the flange portion is provided with a conforming feature suitable for cooperating with the racetrack-shaped flange feature.

[0033] Preferably, in the above-mentioned disposable injection pen, the inner surface of the flange portion is provided with a recessed feature, which is adapted to provide a deformation space for accommodating the flange portion when the pre-filled syringe is inserted into the injection holder.

[0034] Preferably, in the above-mentioned disposable injection pen, the straight segment of the flange portion has a first recessed feature that is thinned along the wall thickness direction, and the arc segment of the flange portion has a second recessed feature that is thinned along the wall thickness direction. The first recessed feature and the second recessed feature make the flange portion have a wall plate structure with varying thickness.

[0035] Preferably, in the above-mentioned disposable injection pen, the flange portion causes the injection holder to form an annular groove, the bottom surface of the annular groove is recessed inward to form a secondary groove, and a central flange is formed between the secondary groove and the central through hole of the injection holder;

[0036] A plurality of support ribs are connected between the central flange and the flange portion to provide multi-point support for the flange portion.

[0037] Preferably, in the above-mentioned disposable injection pen, a protective shell is further arranged between the lower pen shell and the injection holder, and the protective shell has a pair of support arms arranged radially opposite each other; the pair of support arms are respectively located on both sides of the injection holder, and the inner side of the support arm is pressed against the straight segment of the flange portion.

[0038] Preferably, in the above-mentioned disposable injection pen, the inner side of the support arm is provided with a rib arranged along its extension direction, and the support arm is pressed against the flange portion by the rib to form a pressing fit.

[0039] Preferably, in the above-mentioned disposable injection pen, two ribs are arranged and symmetrically arranged on both sides of the arm plate structure extending from the support arm in the width direction.

[0040] Preferably, in the above-mentioned disposable injection pen, a fixed beam-type inner arm plate is provided between the flange portion of the injection holder and the end of the injection holder;

[0041] The inner arm plate is provided with guide protrusions, and the support arm of the protective shell is provided with guide grooves arranged along the axial direction. The guide protrusions are guided to slide within the guide grooves.

[0042] The disposable injection pen provided by this invention includes an upper pen shell assembly and a lower pen shell assembly that are assembled together. The lower pen shell assembly includes a pen cap and a protective shell that is fitted inside the pen cap. The inner ring of the protective shell has an injection bracket that supports the pre-filled syringe. The upper pen shell assembly includes an upper pen shell and a drive structure arranged inside the upper pen shell. The drive structure is a drive part that pushes the pre-filled syringe to perform an injection action. The upper pen shell also has a screw driven by the drive structure to rotate and feed. The upper pen shell is double-centered at both ends of its axial direction to support the rotational feed of the screw. By forming a double-centered positioning structure at both ends of the upper pen shell to support the rotational feed of the screw, the coaxiality and motion stability of the screw during the injection process of driving the pre-filled syringe are ensured. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 An exploded view of the first structure of the disposable injection pen provided in this application;

[0045] Figure 2 A cross-sectional view of the assembly structure of the disposable injection pen provided in this application;

[0046] Figure 3 for Figure 1 A schematic diagram of the internal structure of a locking slider;

[0047] Figure 4 for Figure 1 Schematic diagram of the internal structure of the drive cover;

[0048] Figure 5 A schematic diagram of the groove structure of the drive cover;

[0049] Figure 6 for Figure 1 Schematic diagram of the rotating sleeve;

[0050] Figure 7 This is a schematic diagram of the second direction structure of the rotating sleeve;

[0051] Figure 8 Figure 1 Schematic diagram of the middle screw;

[0052] Figure 9 for Figure 1 Schematic diagram of the middle nut structure;

[0053] Figure 10 This is a schematic diagram of the second-direction structure of the nut;

[0054] Figure 11 for Figure 1 Schematic diagram of the middle gasket structure;

[0055] Figure 12 for Figure 1 A schematic diagram of the bottom structure of the central drive cover;

[0056] Figure 13 for Figure 1 A schematic diagram of the internal structure of the upper and middle part of the pen casing;

[0057] Figure 14 This is a schematic diagram of the insertion part of the upper pen shell;

[0058] Figure 15 for Figure 1 Schematic diagram of the structure of the fixed sleeve;

[0059] Figure 16 for Figure 1 Schematic diagram of the insertion end structure of the injection tray;

[0060] Figure 17 This is a schematic diagram of the insertion end of the injection tray;

[0061] Figure 18 for Figure 1 Schematic diagram of the receiving cavity in the lower pen shell;

[0062] Figure 19 This is a schematic diagram of the second structure of the injection holder;

[0063] Figure 20 This is a schematic diagram of the flange structure of a pre-filled syringe;

[0064] Figure 21 for Figure 1 A schematic diagram of the structure of the protective shell. Detailed Implementation

[0065] This invention discloses a disposable injection pen that ensures stability during the operation of the injection pen.

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] like Figures 1-5 As shown, Figure 1An exploded view of the first structure of the disposable injection pen provided in this application; Figure 2 A cross-sectional view of the assembly structure of the disposable injection pen provided in this application; Figure 3 for Figure 1 A schematic diagram of the internal structure of a locking slider; Figure 4 for Figure 1 Schematic diagram of the internal structure of the drive cover; Figure 5 A schematic diagram of the groove structure of the drive cover; Figure 6 for Figure 1 Schematic diagram of the rotating sleeve; Figure 7 This is a schematic diagram of the second direction structure of the rotating sleeve.

[0068] This application provides a disposable injection pen, including an upper pen shell assembly and a lower pen shell assembly that are assembled and fitted together. The lower pen shell assembly includes a pen cap 001 and a protective shell 002 that is fitted inside the pen cap 001. An injection bracket 004 that supports a pre-filled syringe 005 is arranged in the inner circle of the protective shell 002. The pen cap 001 is provided with a claw extending towards the bracket, and the claw presses against the axial edge of the needle cap of the pre-filled syringe 005. The lower pen shell assembly supports the injection bracket 004 by the protective shell 002 installed inside the pen cap 001. The pre-filled syringe 005 can be fixedly installed in the injection bracket 004. The claw provided inside the pen cap 001 presses against the axial edge of the needle cap. By using the claw to lock onto the circumferential edge of the needle cap, the needle cap is subjected to an axial pull-out force. The locking structure is stable, ensuring that the needle cap can be easily pulled out.

[0069] The upper pen housing assembly is the driving part that actuates the pre-filled syringe 005 to perform the injection action. It includes an upper pen housing 008 and a driving structure disposed within the upper pen housing 008. The upper pen housing 008 and the lower pen housing 003 are inserted into each other, and the end of the upper pen housing 008 is sealed and protected by a rear cover 013.

[0070] Specifically, this embodiment achieves the injection driving function through 11 parts, including protective shell 002, locking slider 009, rotating slider 010, torsion spring 011, sound spring 015, rotating sleeve 017, torsion spring 018, drive cover 014, nut 007, screw 019, and washer 006.

[0071] Press the protective shell 002, and the protective shell 002 slides upward toward the pen shell 008. The protective shell 002 abuts against the locking slider 009, pushing the locking slider 009 to slide synchronously. The locking slider abuts against the rotating slider 010 in the axial direction, thereby pushing the rotating slider 010 to slide.

[0072] Locking slider 009 and rotating slider 010 are fitted onto the outer periphery of fixed sleeve 012. A guide groove is provided on the outer periphery of fixed sleeve 012, and a guide boss is provided on the inner ring of rotating slider 010 to abut against the groove on fixed sleeve 012. A torsion spring 011 is also fitted between rotating slider 010 and fixed sleeve 012. Correspondingly, the guide groove includes a vertical groove and a horizontal groove formed on the outer periphery of fixed sleeve 012. The vertical groove serves as an axial sliding guide, and the horizontal groove serves as a guide for rotating slider 010 to rotate circumferentially after sliding to a predetermined position, due to the torsional force accumulated by the torsion spring 011. A collision wall is provided at the bottom of the horizontal groove to collide with the guide boss. The collision between the guide boss and the collision wall produces a sound, serving as an audible indication that the protective shell 002 has axially slid into place.

[0073] The locking slider 009 and the rotating slider 010 are axially abutted together, and both can rotate freely. During the pressing process, the protective shell 002 first abuts against the shaft end of the locking slider 009, and then the locking slider 009 sequentially abuts against the shaft end of the rotating slider 010. As the protective shell 002, the locking slider 009, and the rotating slider 010 slide synchronously, the locking relationship between the locking slider 009 and the drive cover 014 is gradually released. When the rotating slider 010 moves from the vertical slide groove into the horizontal slide groove, the torsion spring 011 is compressed. After a certain displacement, a sliding completion indicator sound is emitted, and the locking relationship between the locking slider 009 and the drive cover 014 is simultaneously released. The drive cover 014 then enters an automatic rotation state, and the injection stage begins.

[0074] Specifically, the inner wall surface of the locking slider 009 is provided with internal protrusions 020. The locking slider 009 is an annular sleeve structure, and the internal protrusions 020 are strip-shaped bosses arranged on the inner wall surface of the locking slider 009. Correspondingly, the outer wall surface of the drive cover 014 is provided with external protrusions 021. During the axial sliding of the locking slider 009, the external protrusions 021 maintain abutting contact with the internal protrusions 020 in the circumferential direction. Due to the strip-shaped boss structure of the internal protrusions 020, the external protrusions 021 maintain abutting contact with the internal protrusions 020 as the locking slider 009 slides. When the external protrusions 021 slide to the end of the internal protrusions 020, the two separate. At this time, the locking slider 009 disengages from the drive cover 014, and the internal protrusions 020 are released from their constraint on the external protrusions 021.

[0075] The drive cover 014 is coaxially connected to the rotating sleeve 017. The drive cover 014 is a cylindrical structure. It is locked and positioned with the locking slider 009 through the external protrusion 021 on the outer wall surface, and enters a free rotation state after being unlocked from the locking slider 009.

[0076] The rotating sleeve 017 includes a sleeve portion 0171 that is inserted into the drive cover 014 and a guide sleeve portion 0172 that extends coaxially with the sleeve portion 0171. A screw 019 is arranged inside the rotating sleeve 017. The screw 019 is driven to rotate by the drive cover 014 through the sleeve portion 0171 and the rotational feed of the screw 019 is guided by the guide sleeve portion 0172. The sleeve portion 0171 of the rotating sleeve 017 is inserted into the inner ring of the drive cover 014. The drive cover 014 is arranged on the shaft end of the fixed sleeve 012. A torsion spring 018 is fixedly arranged on the inner ring of the fixed sleeve 012. The first end of the torsion spring 018 is fixed to the root of the fixed sleeve 012, and the second end is fixed to the sleeve portion 0171. The torsion spring 018 is pre-applied with torque. After the drive cover 014 is unlocked and released, the torque stored in the torsion spring 018 drives the drive cover 014 and the rotating sleeve 017 to rotate together, thereby driving the screw 019 to feed. Specifically, the inner ring of the drive cover 014 has a groove 022 extending through its wall thickness. Correspondingly, the outer ring of the rotating sleeve 017 has protruding protrusions 023. During the insertion of the rotating sleeve 017 into the inner ring of the drive cover, the protrusions 023 abut against the inner wall surface of the rotating sleeve 017 and fall into the groove 022 as the insertion depth increases. The protrusions 023 fall into the groove 022, thus achieving a fixed connection between the drive cover 014 and the rotating sleeve 017. Preferably, the groove 022 includes a pair arranged radially along the drive cover 014, and correspondingly, the protrusions 023 include a pair arranged radially along the rotating sleeve 017, thereby achieving a stable connection between the two.

[0077] Under the counter-rotating force of the torsion spring 018, the rotating sleeve 017 begins to rotate, further driving the drive cover 014 to rotate. The internal through hole 024 of the drive cover 014 matches the external shape feature 025 of the screw 019, thereby driving the screw 019 to rotate. The drive cover 014 also contains a sounding element 016 and a sounding spring 015, which are triggered during the screw 019's feeding process to emit an injection warning sound, indicating that the injection stage has begun.

[0078] like Figures 8-16 As shown, Figure 8 Figure 1 Schematic diagram of the middle screw; Figure 9 for Figure 1 Schematic diagram of the middle nut structure; Figure 10 This is a schematic diagram of the second-direction structure of the nut; Figure 11 for Figure 1 Schematic diagram of the middle gasket structure; Figure 12 for Figure 1 A schematic diagram of the bottom structure of the central drive cover; Figure 13 for Figure 1 A schematic diagram of the internal structure of the upper and middle part of the pen casing; Figure 14 This is a schematic diagram of the insertion part of the upper pen shell; Figure 15 for Figure 1Schematic diagram of the structure of the fixed sleeve; Figure 16 for Figure 1 A schematic diagram of the insertion end of the injection tray.

[0079] Specifically, in this embodiment, the rotation of the rotating sleeve 017 drives the screw 019 to rotate accordingly.

[0080] The rotating sleeve 017 and the drive cover 014 are assembled into a single structure. The rotation of the rotating sleeve 017 drives the screw 019 to follow. At the same time, the screw 019 needs to be axially fed during rotation so that it can push the pre-filled syringe 005 to perform the injection action.

[0081] During rotation, the screw 019 needs to be ensured to move only in the axial direction to avoid tipping over and causing jamming with the pre-filled syringe 005, which would affect injection. The axial feed of the screw 019 is achieved through the upper pen housing 008, the fixed sleeve 012, the rotating sleeve 017, and the drive cover 014; while the axial guiding function of the screw 019 to ensure positive orientation and prevent tilting is achieved by the nut 007 installed on the upper pen housing 008.

[0082] With the threaded section 026 of the screw 019 engaging with the threaded hole 027 of the nut 007, the screw 019 rotates forward. The circular feature 028 of the screw 019 engages with the through hole 029 of the washer 006, and the screw then pushes the washer 006 forward to complete the injection.

[0083] Specifically, the rotating sleeve 017 begins to rotate under the reversing force of the torsion spring 018, which further drives the drive cover 014 to rotate. The internal through hole 024 of the drive cover 014 matches the external shape feature 025 of the screw 019, thereby driving the drive cover 014 to drive the screw 019 to rotate.

[0084] The screw 019's external features 025 include a connecting head that abuts against the pre-filled syringe 005. The connecting head has a spherical circular feature 028. A gasket 006 is provided on the pre-filled syringe 005. The gasket 006 has a through hole 029. The circular feature 028 is inserted into the through hole 029 to drive the injection of the pre-filled syringe 005 through the gasket 006. The main body of the screw 019 is a threaded section 026, which consists of an arc surface structure and a straight section structure. From the cross-section of the screw 019, its cross-section is a racetrack shape with a rectangular structure with double arc edges. The thread of the screw 019 is opened on the double arc edge structure, so that the screw 019 can utilize its double arc surface structure and straight section external features 025 to simultaneously achieve follow-up rotation and axial feed with the rotating sleeve 017. The screw 019 also has a cylindrical screw tail.

[0085] Furthermore, the guide sleeve 0172 of the rotating sleeve 017 has a cylindrical structure with a circular guide hole. By utilizing the guide sleeve 0172 and the cylindrical screw tail, the feed guidance of the screw 019 can be realized during the feeding process, avoiding feed deviation problems such as tilting of the screw 019.

[0086] The inner ring of the drive cover 014 has a through hole 024, and the inner hole of the through hole 024 is also a racetrack-shaped structure. The threaded section 026 of the screw 019 is clearance-fitted with the through hole 024. During the rotation of the drive cover 014, the threaded section 026 is driven to rotate synchronously through the through hole 024, thereby causing the entire screw 019 and the drive cover 014 to rotate synchronously.

[0087] The rotation of the drive cover 014 causes the screw 019 to rotate accordingly. The axial feed of the screw 019 is provided by the nut 007 fixed on the upper pen shell 008.

[0088] Specifically, the upper pen shell 008 and the lower pen shell 003 are inserted into each other at the shaft end. The end of the upper pen shell 008 has an insertion part 0081, and the end of the lower pen shell 003 has a receiving cavity 0091. The outer periphery of the insertion part 0081 has an outward protruding locking point 0082, and the inner ring of the receiving cavity 0091 has an inwardly recessed locking groove 0092 that engages with the outwardly protruding locking point 0082. The two are connected by insertion through the insertion part 0081 and the receiving cavity 0091, and the outwardly protruding locking point 0082 falls into the inwardly recessed locking groove 0092, thus locking into place and completing the connection between the upper pen shell 008 and the lower pen shell 003.

[0089] The drive cover 014 has two axial ends, one open for insertion into the rotating sleeve 017, and the other closed. A hollow cylinder 0141 is nested inside the closed end, forming an annular cavity between the hollow cylinder 0141 and the drive cover 014. The hollow cylinder 0141 and the drive cover 014 are coaxially arranged, and the inner hole of the hollow cylinder 0141 is a through hole 024. The structural design of the hollow cylinder 0141 allows for a certain length of rigid contact with the screw 019, ensuring the stability of the rotating support structure. Simultaneously, the annular cavity structure between the hollow cylinder 0141 and the drive cover 014 provides axial sliding space for the sound-emitting component 016.

[0090] A first annular boss 0142 extends coaxially from the closed end of the drive cover 014, and an annular step structure is formed between the first annular boss 0142 and the closed end of the drive cover 014.

[0091] The inner ring of the upper pen shell 008 is also provided with a bracket 030 for rotating support of the closed end of the drive cover 014. The middle part of the bracket 030 is provided with a second annular boss 0083 extending towards the drive cover 014. The first annular boss 0142 and the second annular boss 0083 have an axial insertion fit structure and a radial clearance fit rotation limiting structure, so that during the rotation of the drive cover 014, the first annular boss 0142 and the second annular boss 0083 form a cylindrical sliding pair structure to ensure the rotational stability of the drive cover 014.

[0092] In the preferred structure, the second annular boss 0083 is inserted into the inner ring of the first annular boss 0142, and the second annular boss 0083 abuts against the end face of the closed end of the drive cover 014.

[0093] Furthermore, the inner ring of the insertion part 0081 is also provided with a nut 007. The nut 007 includes a central nut 038 with a cylindrical center. A mounting bracket extends from the outer periphery of the central nut 038, and a mounting protrusion 036 extends from the outer periphery of the mounting bracket. The inner ring of the insertion part 0081 is provided with a mounting groove 037 recessed along the wall thickness direction. The nut 007 is inserted into the insertion part 0081 axially and is engaged and limited within the mounting groove 037 by the mounting protrusion 036, thereby achieving a fixed connection between the nut 007 and the upper pen shell 008.

[0094] After nut 007 is installed, center nut 038 is fitted into the inner circumference of the second annular boss 0083. In the preferred structure, the outer circumferential surface of center nut 038 and the inner circumferential surface of the second annular boss 0083 are closely arranged, in an interference fit or tight fit state. Center nut 038 has a threaded hole 027 at its center, and the threaded section 026 of screw 019 and the threaded hole 027 of nut 007 form a threaded transmission pair; when screw 019 is driven to rotate around its central axis, since nut 007 is limited and fixed in the circumferential and axial directions, the threaded transmission pair converts the rotational motion of screw 019 into linear feed motion along the central axis, thereby realizing the axial displacement of screw 019 relative to nut 007.

[0095] In this embodiment, the drive cover 014 and the rotating sleeve 017 form a remote support structure for the screw 019; the fixed sleeve 012 and the upper pen shell 008 are assembled as a whole to rotate and position the guide sleeve 0172 end of the rotating sleeve 017; the upper pen shell 008 is inserted through the bracket 030 of its insertion part, and the bracket 030 is provided with a second annular boss 0083 in the middle. The outer ring of the second annular boss 0083 is rotatably engaged with the inner circumferential surface of the first annular boss 0142 on the drive cover 014, and the inner circumferential surface of the second annular boss 0083 is tightly engaged with the central nut 038 of the nut 007.

[0096] In summary, the fixed sleeves 012 / first annular boss 0142 and brackets 030 / second annular boss 0083 respectively set at both ends of the upper pen shell 008 in the axial direction constitute a double-end center positioning structure for the rotational feeding motion of the screw 019, ensuring the coaxiality and motion stability of the screw 019 in the process of driving the pre-filled syringe 005 to inject.

[0097] With the threaded section 026 of the screw 019 engaging with the threaded hole 027 of the nut 007, the screw 019 rotates forward. The circular feature 028 of the screw 019 engages with the through hole 029 of the washer 006, and the screw 019 further pushes the washer 006 of the pre-filled syringe 005 forward to complete the injection.

[0098] This embodiment uses four parts—upper pen shell 008, fixed sleeve 012, rotating sleeve 017, and drive cover 014—to maintain the alignment of nut 007 and screw 019 during the injection process.

[0099] Both the upper pen shell 008 and the drive cover 014 have a cylindrical structure. The bracket 030 of the upper pen shell 008 has an internal through hole. The bracket 030 has an internal through hole outer circle on its outer periphery through the boss structure of its second annular boss 0083. The internal through hole outer circle of the bracket 030 is aligned with the cylindrical feature 031 of the drive cover 014.

[0100] The rotating sleeve 017 is aligned by the tail end 032 of its guide sleeve 0172 engaging with the internal through hole 033 of the fixed sleeve 012;

[0101] The upper pen shell 008 and the fixing sleeve 012 are fixedly connected by the groove 034 of the upper pen shell 008 and the protrusion 035 of the fixing sleeve 012.

[0102] Nut 007 and upper pen shell 008 are fixedly engaged by mounting protrusion 036 of nut 007 and groove feature 037 of upper pen shell 008. Nut 007 and upper pen shell 008 are aligned by center nut 038 of cylindrical feature of nut 007 and inner circle 039 of internal through hole of upper pen shell 008. Using upper pen shell 008 as a guide reference, the screw 019 and nut 007 are guided during injection, keeping the injection stable.

[0103] like Figure 17-21 As shown, Figure 17 for Figure 1 Schematic diagram of the insertion end structure of the injection tray; Figure 18 for Figure 1 Schematic diagram of the receiving cavity in the lower pen shell; Figure 19 This is a schematic diagram of the second structure of the injection holder; Figure 20 This is a schematic diagram of the flange structure of a pre-filled syringe; Figure 21 for Figure 1A schematic diagram of the structure of the protective shell.

[0104] The disposable injection pen provided in this application includes an upper pen shell assembly and a lower pen shell assembly that are assembled together. The lower pen shell assembly is used to arrange a pre-filled syringe 005, and the upper pen shell assembly is used to arrange a driving device for driving the pre-filled syringe 005 to perform injection.

[0105] The lower pen housing assembly includes a pen cap 001 and a protective shell 002 that is snapped into the inner ring of the pen cap 001. The outer ring of the protective shell 002 further includes a lower pen housing 003, the first end of which is simultaneously installed inside the pen cap. The inner ring of the protective shell 002 further includes an injection holder 004, which is snapped into position with the protective shell 002. A pre-filled syringe 005 is installed within the injection holder 004. The needle cap 501 of the pre-filled syringe 005 extends into the pen cap 001 and is pressed against the axial edge of the needle cap 501 by claws arranged on the pen cap 001, so that the needle cap 501 is simultaneously removed during the removal of the pen cap 001.

[0106] In this embodiment, the pre-filled syringe 005 is placed and the protective shell 002 is retracted through the injection bracket 004.

[0107] The pre-filled syringe 005 includes a body, which protects the needle tip with a needle cap 501. The body also has an injection end with a flange 045. The flange 045 is a racetrack-shaped flange, which includes a double-arc edge structure and a straight edge structure. The straight edge structure and the arc edge structure are connected by a flange chamfer 046.

[0108] The injection bracket 004 fixes and supports the pre-filled syringe 005 on the injection end of the lower pen housing 003. The screw 019 abuts against the piston of the pre-filled syringe 005 through the gasket 006. Based on the above-mentioned structure that ensures the screw 019 is aligned during injection, the injection stability during the injection process is improved.

[0109] However, the pre-filled syringe 005 is assembled inside the injection holder 004, with its proximal end abutting against the end face of the injection holder 004 via a flange 045 to form an axial limit; its distal cylindrical body is arranged to form an interference fit or clearance fit with the through hole of the injection holder 004 to form a radial limit. This further ensures that during the injection process, the screw 019 precisely drives the axial ejection of the piston.

[0110] Considering that the consistency of the end face structure of the proximal flange of the pre-filled syringe 005 affects the stability of its end face contact with the injection holder 004, and thus affects the precise ejection of the piston, in a further structure, a clamping fin 0084 extends from the insertion part 0081 of the upper pen shell 008 to the side of the lower pen shell 003. After the upper pen shell 008 and the lower pen shell 003 are inserted into place, the protruding end of the clamping fin 0084 abuts against the flange part 045 to press the flange part 045 onto the injection holder.

[0111] Specifically, the clamping fins 0084 extend from the end face of the bracket 030, and the clamping fins include one or more sets radially distributed along the inner circle 039 of the internal through hole of the upper pen shell 008. In this embodiment, one set of clamping fins is preferably used.

[0112] In the preferred structure, the middle part of the flange 045 of the pre-filled syringe 005 is connected to the piston channel of the body through an arc transition. The overhanging end of the compression fin 0084 is bent radially inward to form a support foot. During the insertion of the upper pen shell 008 and the lower pen shell 003, the support foot abuts against the flange 045 and is pressed by the transition arc surface between the support foot and the flange. Under the guidance of the axial pressing force of the transition arc surface, the support foot undergoes bending deformation along the arc transition. The deformed outer side of the support foot is also set as a circular arc transition structure to press the transition arc surfaces on the flange 045 together.

[0113] In a preferred embodiment, the clamping fins include a radially arranged set, comprising two clamping fins. Correspondingly, since the insertion part 0081 needs to be fitted with a nut 007, to ensure the assembly stability of the nut 007 and to allow the clamping fins to pass, the nut 007 has a set of forked arms extending radially in the opposite direction. A U-shaped groove for the clamping fins to pass through is formed between the forked structures of each forked arm, and the mounting protrusion 036 is located at the overhanging end of the fork.

[0114] By setting a clamping fin structure, the injection end face of the flange 045 can be pressed against it, thereby pressing the injection back side of the flange 045 of the pre-filled syringe 005 onto the injection bracket 004. Due to the problem of hard contact between the injection back side of the flange 045 and the injection bracket 004, the contact end faces of the two are prone to tilting due to manufacturing errors, forming a clamping slope. Even if the clamping fins provide clamping to the flange 045, there may still be a deflection problem during the injection process.

[0115] In the preferred embodiment, the flange support end of the injection bracket 004 has a flange portion 040 for accommodating the flange portion 045. The flange portion 040 has an annular arm plate structure. The inner ring of the flange portion 040 forms a recess for accommodating the flange portion. The outer ring of the flange portion 040 has a protrusion 041. The inner wall surface of the receiving cavity 0091 of the lower pen shell 003 has a groove 042 recessed towards the wall thickness side. During the process of assembling the injection bracket 004 into the lower pen shell 003, the protrusion 041 falls into the groove 042 of the lower pen shell 003, thereby achieving a fixed connection between the two.

[0116] This design is applicable to flanges with a racetrack-shaped flange feature (flange part 045) and flanges with a chamfered angle (flange part 046) at the intersection of arc segments and straight segments (flange part 045). The inner surface of the flange portion 040 is provided with a contour feature, which is suitable for mating with the racetrack-shaped flange feature of the pre-filled syringe 005. This prevents the flange feature from deflecting during the process of accommodating the pre-filled syringe 005, which could cause the product to fail to start.

[0117] Meanwhile, the inner surface of the flange portion 040 is also provided with a contour feature at the intersection of the arc segment and the straight segment, which is suitable for matching with the flange chamfer 046 on the flange feature of the pre-filled syringe 005, and has sufficient deformation space to install the flange chamfer 046 with large deformation, thus having greater compatibility.

[0118] In a specific embodiment of this case, the inner surface of the flange portion 040 of the injection holder 004 is provided with a recessed feature 047, which is suitable for providing deformation space when the protrusion 041 of the injection holder 004 is assembled into the groove 042 of the lower pen shell 003, thus facilitating assembly. Specifically, the middle part of the straight segment of the flange portion 040 has a first recessed feature that is thinned along the wall thickness direction, and the middle part of the curved segment has a second recessed feature that is thinned along the wall thickness direction. The first and second recessed features make the flange portion 040 as a whole a wall plate structure with varying thickness. When the flange portion 040 and the flange portion 045 are pressed at the circumferential end face, the recessed feature 047 can form a deformation space, reserving deformation allowance and reducing assembly difficulty.

[0119] In a specific embodiment of this case, the flange portion 040 causes the flange support end of the injection bracket 004 to form an annular groove. The center of the injection bracket 004 is the through hole of the pre-filled syringe 005. A secondary groove is formed by recessing inward on the bottom surface of the annular groove. The annular groove and the secondary groove are connected. A central flange is formed between the secondary groove and the through hole of the pre-filled syringe 005. The central flange abuts against the injection back side of the flange portion 045.

[0120] Multiple support ribs connect the central flange and flange portion 040, and these ribs are evenly distributed around the central flange. The axial height of the support ribs is approximately flush with the height of the central flange. When flange portion 045 is assembled onto injection bracket 004, the end faces of the support ribs directly contact the injection back side of flange portion 045, thus constructing a multi-point support system between the injection back side of flange portion 045 and injection bracket 004. This multi-point support structure, formed by multiple support ribs, transforms the support for flange portion 045 of pre-filled syringe 005 from traditional surface contact to local line or point contact, significantly reducing the precision requirements for the flatness of the injection back side of flange portion 045. Even when the injection back side of flange portion 045 experiences surface flatness issues due to processing, resulting in microscopic unevenness or dimensional errors, multiple support ribs can still form a line or point support structure to ensure stable force transmission, thereby reducing contact stability issues caused by surface flatness problems on the injection back side and improving contact safety and reliability.

[0121] In one specific embodiment of this case, the injection holder 004 is mounted on the lower pen housing 003. After the injection holder 004 is assembled in place, the protrusion 041 on the flange portion 040 and the groove 042 on the lower pen housing 003 are engaged, and the positioning is completed by the protrusion 041 snapping into the groove 042. The protruding structure of the protrusion 041 is a trapezoidal cross-section protrusion with a gradually changing curvature or a hemispherical protrusion. Its top working surface is polished to reduce the coefficient of friction, thereby maintaining the structural strength and surface finish when it is squeezed into the groove 042.

[0122] A protective shell 002 is also arranged between the pen housing 003 and the injection holder 004. During injection, the protective shell 002 is pressed and retracts axially, sliding backward and pushing the rotating slider 010 and locking slider 009 to expose the needle and activate the injection function of the pen. After injection, the protective shell 002 automatically springs back to its original position, forming a rigid barrier to prevent punctures during reuse or disposal.

[0123] The protective shell 002 has a pair of radially opposite support arms 049, which extend axially from the protective shell 002. The pair of support arms 049 are located on both sides of the injection holder 004. Specifically, the inner side of the support arm 049 is pressed against the straight section of the flange portion 040. When the protective shell 002 slides axially, the flange portion 040 is always in contact with the inner side of the support arm 049 to maintain the extended state of the support arm 049 and prevent it from radially retracting, which would affect the working stability.

[0124] Furthermore, the inner side of the support arm 049 is provided with protruding ribs 050 arranged along its extension direction. The support arm 049 is pressed against the flange portion 040 by the protruding ribs 050 to form a pressing fit. The extended end of the support arm 049 is an arm plate structure with a certain width. Preferably, two protruding ribs 050 are arranged, and they are symmetrically arranged on both sides of the width direction of the extended arm plate structure of the support arm 049, so as to provide stable lateral support for the support arm 049.

[0125] By setting the flange portion 040 of the injection bracket 004 to a racetrack-shaped structure corresponding to the flange portion 045, the outer surface of the straight section of the flange portion 040 forms a sectional feature 048, which is suitable for cooperating with the rib 050 on the support arm 049 of the protective shell 002, preventing the support arm 049 of the protective shell 002 from shrinking inward during the injection process, thus preventing product failure.

[0126] The protective shell 002 and the injection holder 004 have an axial sliding fit. The telescopic structure of the protective shell 002 is supported by the support arm 049 and the flange portion 040 of the injection holder 004, preventing inward retraction. At the same time, the protective shell 002 needs to maintain a locking fit with the injection holder 004 during and after pressing to prevent the protective shell 002 from coming out of the lower pen shell 003.

[0127] In this embodiment, a fixed beam-type inner arm plate is installed between the flange portion 040 and the end of the injection bracket 004. This inner arm plate adopts a double-end fixed structure and preferably also has a central support point. The front end of the inner arm plate is rigidly connected to the flange portion 040, and the rear end is fixedly connected to the thickened end of the bracket, forming a fixed support structure with excellent mechanical properties. The inner arm plate and the flange portion 040 together form an anti-inward shrinkage structure that supports the inner end face of the support arm. This arrangement makes the inner arm plate exhibit the deformation characteristics of a fixed beam when subjected to lateral loads, effectively suppressing the warping deformation of the support plate of the protective shell 002 under inward shrinkage force.

[0128] The inner surface of the inner arm plate facing the central axis of the injection holder 004 remains flush with the inner wall of the holder to ensure smooth assembly of the vial. In a preferred structure, a support gap is provided between the injection holder 004 and the inner arm plate through a hole in the middle, and a guide protrusion 043 is formed on the outer surface of the inner arm plate. This guide protrusion 043 is preferably designed as a trapezoidal cross-section protrusion or a hemispherical protrusion with a gradually changing curvature, and its top working surface is polished to reduce the coefficient of friction. The height H of the protrusion is designed to be slightly greater than the wall thickness of the support arm 049 to form reliable mechanical interference after assembly. The inner arm plate is a set of two support arms corresponding to the protective shell 002.

[0129] A guide protrusion 043 is provided on the inner arm plate, and a guide groove 143 arranged axially is formed on the support arm 049 of the protective shell 002. The guide groove 143 is a through groove. When the protective shell 002 is pressed, the guide protrusion 043 slides within the guide groove 143. The guide groove 143 can slide and engage with the guide protrusion 043 in the width direction to form an open guide channel similar to a "slide rail". The width W of the guide groove 143 is designed to form a clearance fit with the maximum width of the guide protrusion 043.

[0130] During the pressing operation, when the user presses the protective shell 002 axially, the protective shell 002 slides axially relative to the injection tray 004. At this time, the guide protrusion 043 is embedded in the guide groove 143 and slides axially thereafter. Because the sidewall of the guide groove 143 forms a double-sided guiding constraint on the guide protrusion 043, it ensures that the protective shell 002 maintains precise axial alignment during axial reciprocating motion, avoiding jamming caused by misalignment. During this sliding process, the support arm 049 utilizes its cantilever beam characteristics to generate moderate elastic deformation, providing the necessary clearance space for the pressing stroke.

[0131] After the pressing is completed, the protective shell 002 returns to its original position under the elastic force. The guide protrusion 043 then abuts and limits the sliding out of the guide groove 143, preventing the protective shell 002 from sliding out between the lower pen shell 003 and the injection holder 004. When the user releases the pressing force, the protective shell 002 automatically returns to its original position under the force of the return spring on the upper pen shell. At this time, the guide protrusion 043 slides in the opposite direction relative to the guide groove 143 with the inner arm plate, moving to a position close to the end of the groove. The stop side of the guide protrusion 043 abuts and limits the movement of the end stop surface (or groove edge) of the guide groove 143. The root of the guide protrusion 043 is a stepped surface, which forms a rigid mechanical stop when it contacts or surfaces the edge of the guide groove 143. This type of contact limit effectively prevents the guide protrusion 043 from continuing to slide out of the groove, thereby limiting the axial displacement of the protective shell 002 within the predetermined stroke range and completely preventing the protective shell 002 from accidentally slipping out of the assembly gap between the lower pen shell 003 and the injection bracket 004.

[0132] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A disposable injection pen, characterized in that, The invention includes an upper pen shell assembly and a lower pen shell assembly that are assembled together. The lower pen shell assembly includes a pen cap and a protective shell that is fitted inside the pen cap. The inner ring of the protective shell is provided with an injection bracket that supports the pre-filled syringe. The upper pen shell assembly includes an upper pen shell and a drive structure arranged inside the upper pen shell. The drive structure is a drive part that pushes the pre-filled syringe to perform an injection action. The upper pen housing is also provided with a screw that is driven by the drive structure to rotate and feed. The upper pen housing is positioned at both ends of the axial direction to center the rotation of the screw.

2. The disposable injection pen according to claim 1, characterized in that, The screw has a threaded section with a rectangular cross-section that is racetrack-shaped and has double-arc edges; The upper pen shell is provided with a drive cover that is driven to rotate by the drive structure, and the drive cover has a racetrack-shaped through hole. The screw is driven by the drive cover to rotate and feed.

3. The disposable injection pen according to claim 2, characterized in that, The drive cover has a rotating sleeve that is assembled into a single unit, and the screw is rotatably arranged inside the rotating sleeve.

4. The disposable injection pen according to claim 3, characterized in that, The screw also has a cylindrical screw tail, which is rotatably supported by the screw tail and arranged inside the rotating sleeve.

5. The disposable injection pen according to claim 4, characterized in that, The screw also has a connecting head that abuts against the pre-filled syringe, the connecting head having a spherical circular feature.

6. The disposable injection pen according to claim 5, characterized in that, The rotating sleeve includes a sleeve portion that inserts into the drive cover and a guide sleeve portion that extends coaxially with the sleeve portion; the guide sleeve portion is a cylindrical structure with a circular guide hole, and the tail of the screw is arranged inside the guide sleeve portion.

7. The disposable injection pen according to claim 6, characterized in that, A fixing sleeve is installed on the upper pen shell, and the fixing sleeve has an internal through hole that aligns with the tail end of the guide cylinder.

8. The disposable injection pen according to claim 7, characterized in that, The inner ring of the upper pen shell is also provided with a bracket that provides rotational support for the closed end of the drive cover. The drive cover has a first annular protrusion extending coaxially to its outer side, and the bracket has a second annular protrusion extending toward the drive cover in the middle. The first annular boss and the second annular boss have an axial insertion fit structure.

9. The disposable injection pen according to claim 8, characterized in that, The second annular boss is inserted into the inner ring of the first annular boss, and the second annular boss abuts against the end face of the closed end of the drive cover.

10. The disposable injection pen according to claim 9, characterized in that, The inner ring of the upper pen shell is also provided with a nut, the nut having a central nut that is fitted into the inner circumferential side of the second annular boss; The external thread of the screw and the threaded hole of the nut form a threaded transmission pair.

11. The disposable injection pen according to claim 10, characterized in that, The upper pen shell has an insertion part at one end, and the lower pen shell has a receiving cavity at one end; The outer periphery of the insertion part has an outwardly protruding locking point, and the inner ring of the receiving cavity has an inwardly concave locking groove that engages with the outwardly protruding locking point. The upper pen shell and the lower pen shell are connected by the insertion part and the receiving cavity.

12. The disposable injection pen according to claim 11, characterized in that, A clamping fin extends from the insertion part of the upper pen shell toward the lower pen shell side, and the protruding end of the clamping fin abuts against the flange part of the pre-filled syringe.

13. The disposable injection pen according to claim 12, characterized in that, The clamping fins extend from the end face of the bracket, and the clamping fins include one or more sets radially distributed along the inner circle of the internal through hole of the upper pen shell.

14. The disposable injection pen according to claim 13, characterized in that, The overhanging end of the compression fin is bent radially inward to form a support foot. The support foot is pressed against the transition arc surface of the flange of the pre-filled syringe and undergoes bending deformation under the guidance of axial compression force.

15. The disposable injection pen according to claim 14, characterized in that, The nut has radially extending forked arms, and the forked structures of the forked arms form a U-shaped groove for the passage of the clamping fins.

16. The disposable injection pen according to claim 15, characterized in that, The injection bracket has a flange support end, which has a flange portion for accommodating the flange portion. The flange portion has an annular arm plate structure, and the inner ring of the flange portion forms a groove for accommodating the flange portion.

17. The disposable injection pen according to claim 16, characterized in that, The flange portion has a racetrack-shaped flange feature, and the inner surface of the flange portion is provided with a conforming feature suitable for engaging with the racetrack-shaped flange feature.

18. The disposable injection pen according to claim 17, characterized in that, The inner surface of the flange portion is provided with a recessed feature, which is adapted to provide a deformation space for accommodating the flange portion when the pre-filled syringe is inserted into the injection holder.

19. The disposable injection pen according to claim 18, characterized in that, The straight section of the flange portion has a first recessed feature that is thinned along the wall thickness direction, and the arc section of the flange portion has a second recessed feature that is thinned along the wall thickness direction. The first recessed feature and the second recessed feature make the flange portion have a wall panel structure with varying thickness.

20. The disposable injection pen according to claim 18, characterized in that, The flange portion causes the injection holder to form an annular groove, the bottom of the annular groove is recessed inward to form a secondary groove, and a central flange is formed between the secondary groove and the central through hole of the injection holder. A plurality of support ribs are connected between the central flange and the flange portion to provide multi-point support for the flange portion.

21. The disposable injection pen according to claim 20, characterized in that, A protective shell is also arranged between the lower pen housing and the injection holder. The protective shell has a pair of support arms arranged radially opposite each other. The pair of support arms are located on both sides of the injection holder, and the inner side of the support arm is pressed against the straight section of the flange portion.

22. The disposable injection pen according to claim 21, characterized in that, The inner side of the support arm is provided with protruding ribs arranged along its extension direction. The support arm is pressed against the flange portion by the protruding ribs to form a pressing fit.

23. The disposable injection pen according to claim 22, characterized in that, Two ribs are arranged, and they are symmetrically arranged on both sides of the arm plate structure extending from the support arm in the width direction.

24. The disposable injection pen according to claim 23, characterized in that, A fixed beam-type inner arm plate is installed between the flange portion of the injection bracket and the bracket end of the injection bracket. The inner arm plate is provided with guide protrusions, and the support arm of the protective shell is provided with guide grooves arranged along the axial direction. The guide protrusions are guided to slide within the guide grooves.

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