Automatic injection device for pre-filled syringes

Abstract

The utility model relates to an automatic injection device for prefilled syringe, wherein the automatic injection device for prefilled syringe comprises an outer pen shell, an excitation unlocking cylinder, a needle-retracting spring base and an injection cylinder; the fixed part of the needle-retracting spring base is connected with the outer sleeve through the excitation unlocking cylinder; the needle-retracting spring base is fixed in the outer sleeve; the upper part of the needle-retracting spring base is provided with a needle-retracting spring, and the injection cylinder is releasably installed. The utility model improves the structure of the needle-retracting spring base, so that the needle of the PFS can move downward together with the outer sleeve during the needle puncture process, and the puncture process is more controllable and reliable.

Description

Technical Field

[0001] This utility model relates to an automatic injection device for mounting a pre-filled syringe to form an automatic injection pen, belonging to the field of medical syringes. Background Technology

[0002] This utility model relates to an automatic injection pen with Chinese patent publication number CN116392673A, a locking and triggering mechanism and its automatic injection pen with Chinese patent publication number CN219558328U, and structural improvements of related products.

[0003] In the aforementioned published Chinese patent, when the pen cap is removed, the syringe needle remains hidden within the concealed needle sleeve. The locking mechanism is activated by the sleeve pressing against the skin at the injection site, releasing the push spring and propelling the syringe forward to insert the needle into the injection site. The spring then continues to act, pushing the medication in. In this structure, the depth of needle insertion into the patient's injection site is difficult to control. It relies on the initial release of the push spring, which provides a strong pushing force to fully penetrate the needle. However, this also results in a relatively strong puncture force during the injection process, potentially causing discomfort to the patient during self-injection, loosening of the grip, and injection failure, posing a certain risk.

[0004] Therefore, it is necessary to make appropriate improvements to the product structure in order to improve the reliability and controllability of needle puncture and enhance the safety of using the automatic injection device. Utility Model Content

[0005] The purpose of this invention is to provide an automatic injection device for a pre-filled syringe, which improves the internal structure so that during puncture, the needle of the PFS moves downward along with the outer sleeve to perform puncture, thereby improving the accuracy and controllability of needle puncture.

[0006] To achieve the above-mentioned utility model objectives, this utility model provides an automatic injection device for a pre-filled syringe, including an outer pen shell, an activation unlocking cylinder, a needle retraction spring base, and an injection cylinder;

[0007] The outer pen casing includes an outer sleeve and a detachable pen cap;

[0008] An activation unlocking cylinder is slidably installed inside the outer sleeve;

[0009] The fixing part of the needle retraction spring base passes through the trigger unlocking cylinder and connects to the outer sleeve; the needle retraction spring base is fixed inside the outer sleeve;

[0010] A needle retraction spring is installed on the upper part of the needle retraction spring base, and an syringe is releasably installed thereon.

[0011] The syringe consists of a PFS mounting sleeve and an injection spring sleeve connected together.

[0012] An injection spring is installed on the upper part of the injection spring sleeve; a push rod is sleeved inside the injection spring, and the top of the push rod can be releasably connected to the top of the injection spring sleeve.

[0013] The bottom of the trigger unlocking cylinder is equipped with an triggering part that can extend beyond the bottom of the outer sleeve;

[0014] The top of the trigger unlocking cylinder is equipped with an unlocking part that matches the release part on the top of the push rod to unlock the injection spring;

[0015] The push rod is equipped with an unlocking part that matches the release part at the needle take-off spring, thereby unlocking the needle take-off spring.

[0016] As a further improvement to this utility model, an installation part is provided on the inner side of the sleeve body of the outer sleeve;

[0017] The outer wall of the needle retraction spring base is provided with a mounting buckle;

[0018] The mounting part of the outer sleeve is combined with the mounting buckle of the take-off spring base to achieve the installation and fixation of the take-off spring base inside the outer sleeve.

[0019] Furthermore, the mounting portion of the outer sleeve includes a lower limiting platform and an upper limiting platform;

[0020] The mounting buckle of the needle retractor spring base includes a stop block and a latch;

[0021] The abutment block abuts against the lower limit platform;

[0022] The hook engages with the upper limit positioner.

[0023] The needle retraction spring base and the outer sleeve are fixed to the upper and lower axial limits.

[0024] Furthermore, there are two lower limit platforms and abutment blocks, with an upper limit platform and a hook in the middle;

[0025] The lower limit platforms and abutment blocks on both sides radially limit the upper limit platform and hook in the middle.

[0026] Furthermore, above the mounting portion of the outer sleeve, there are two axially extending guide bars located on both sides of the mounting portion;

[0027] The connecting cylinder of the needle retractor spring base is provided with a connecting buckle groove, which matches the guide bar to achieve radial limiting;

[0028] The mounting buckle has a retractable spring base inside the connecting buckle slot.

[0029] As a further improvement to this utility model, the upper part of the needle retraction spring base is provided with an elastic locking arm, the upper part of the elastic locking arm protrudes inward to form a needle retraction lock buckle, and the upper part of the needle retraction lock buckle is provided with a needle retraction activation slope.

[0030] The lower outer side of the PFS mounting sleeve is provided with a needle retraction locking hook, which matches the needle retraction lock buckle;

[0031] When the take-off lock and the take-off locking hook are engaged together, the take-off spring base is connected to the PFS mounting sleeve, and the take-off spring is in a compressed state.

[0032] The needle retraction latch disengages from the needle retraction locking hook, the needle retraction spring base and the PFS mounting sleeve can slide axially, and the needle retraction spring is in the unlocked and activated state, which can push the syringe barrel axially away from the needle retraction spring base.

[0033] Furthermore, the middle two sides of the push rod extend downward to form a pin-retracting unlocking part with a free end;

[0034] The free end of the needle release unlocking part matches the needle release activation slope of the needle release spring base.

[0035] This invention relates to an automatic injection device for a pre-filled syringe. By improving the structure of the needle retraction spring base, it ensures that the base is always fixedly connected to the outer sleeve of the pen shell. During needle puncture, the needle of the PFS moves downward along with the outer sleeve, simultaneously activating and unlocking the triggering cylinder to complete the puncture at the injection site. This makes the puncture process more controllable and reliable, resulting in higher patient acceptance. Subsequently, the automatic injection device utilizes an injection spring and a needle retraction spring to release the thrust, achieving fully automatic drug withdrawal and convenient needle retraction. Attached Figure Description

[0036] Figure 1 This is an overall external view of the automatic injection pen of this utility model before use;

[0037] Figure 2 for Figure 1 Internal structure diagram;

[0038] Figure 3 This is an exploded view of the components of the automatic injection pen of this utility model;

[0039] Among them, 1-PFS (Prefilled Syringe, also known as prefilled needle assembly, pre-filled syringe, or drug-loaded syringe), 10-Drug, 11-Instrument, 12-Flange (or flange), 13-Needle, 14-Piston, 15-Soft cap, 16-Hard cap; 21-Outer sleeve, 22-Top cap, 23-Pen cap; 31-Activation sleeve, 32-Unlocking sleeve; 4-Needle retraction spring base; 51-Needle retraction spring, 52-PFS mounting sleeve; 61-Injection spring, 62-Injection spring sleeve; 7-Push rod; 8-Buffer pad;

[0040] Figure 4 This is a schematic diagram of the outer sleeve structure of the present invention;

[0041] Figure 5 This is a schematic diagram of the internal structure of the outer sleeve of this utility model;

[0042] Figure 6 This is a schematic diagram of the external structure of the assembled trigger unlocking cylinder. Figure 1 ;

[0043] Figure 7 This is a schematic diagram of the external structure of the assembled trigger unlocking cylinder. Figure 2 ;

[0044] Figure 8 This is a schematic diagram of the external structure of the excitation sleeve of this utility model;

[0045] Figure 9 This is a schematic diagram of the external structure of the unlocking sleeve of this utility model;

[0046] Figure 10 for Figure 7 Internal structure diagram;

[0047] Figure 11 A schematic diagram illustrating the internal structure of the combination of the unlocking cylinder and the outer cylinder;

[0048] Figure 12 This is a schematic diagram of the external structure of the needle retraction spring base of this utility model;

[0049] Figure 13 This is a schematic diagram of the internal structure of the needle retraction spring base of this utility model;

[0050] Figure 14 This is a schematic diagram of the internal structure of the take-off spring base after it is installed inside the outer sleeve.

[0051] Figure 15 A schematic diagram of the fixing structure between the needle take-off spring base and the outer sleeve;

[0052] Figure 16A schematic diagram of the external structure of the PFS mounting sleeve and injection spring sleeve combination;

[0053] Figure 17 for Figure 16 Internal structure diagram;

[0054] Figure 18 This is a schematic diagram of the external structure of the push rod of this utility model. Figure 1 ;

[0055] Figure 19 This is a schematic diagram of the external structure of the push rod of this utility model. Figure 2 ;

[0056] Figure 20 A schematic diagram of the external structure of the push rod combined with the injection spring sleeve;

[0057] Figure 21 This is a cross-sectional view of the assembly of the push rod, injection spring, and injection spring sleeve.

[0058] Figure 22 for Figure 21 A schematic diagram of the internal structure of the component combined with the unlocking sleeve;

[0059] Figure 23 for Figure 22 Overall sectional view;

[0060] Figure 24 This is a structural diagram illustrating the first step of using the automatic injection pen of this utility model.

[0061] Figure 25 This is a structural diagram illustrating step two of using the automatic injection pen of this utility model.

[0062] Figure 26 for Figure 25 Overall sectional view;

[0063] Figure 27 This is a schematic diagram of the action structure for activating and unlocking the injection spring in step two of using the automatic injection pen of this utility model.

[0064] Figure 28 This is a structural diagram illustrating step three of using the automatic injection pen of this utility model.

[0065] Figure 29 for Figure 28 Overall sectional view;

[0066] Figure 30 This is a schematic diagram of the action structure of the unlocking and needle-retracting spring in step three of using the automatic injection pen of this utility model.

[0067] Figure 31This is a structural diagram illustrating step four of using the automatic injection pen of this utility model.

[0068] Figure 32 for Figure 31 Overall sectional view. Detailed Implementation

[0069] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0070] This utility model relates to an automatic injection device for a pre-filled syringe, the overall structure of which is basically equivalent to the automatic injection pen in the applicant's earlier application, Chinese Patent Publication No. CN116392673A. Figure 1 , Figure 2 , Figure 3 As shown, the automatic injection device for pre-filled syringes of this utility model consists of an outer sleeve 21 and a top cover 22 combined to form a pen holder for the installation of internal components and for the operator's hand to hold; a pen cap 23 is detachably connected to the lower part of the outer sleeve 21, which is used to seal the pen holder during storage and transportation; an excitation and unlocking sleeve formed by the combination of an excitation sleeve 31 and an unlocking sleeve 32 is slidably provided inside the outer sleeve 21; a needle retraction spring base 4 is fixedly installed at the lower part of the outer sleeve 21 (in the prior art, the lower spring sleeve (8) is slidably installed inside the pen tube body (21)); a needle retraction spring 51 is installed on the upper part of the needle retraction spring base 4, and a PFS mounting sleeve 52 is releasably installed; an injection spring sleeve 62 is connected and installed on the upper part of the PFS mounting sleeve 52; an injection spring 61 is installed on the upper part of the injection spring sleeve 62; a push rod 7 is sleeved inside the injection spring 61, and the top of the push rod 7 is releasably connected to the top of the injection spring sleeve 62.

[0071] The automatic injection pen developed using the pre-filled syringe automatic injection device of this utility model is based on the above-mentioned pre-filled syringe automatic injection device. PFS1 is installed in the PFS mounting sleeve 52. In particular, the main body of the syringe 11 passes through the PFS mounting sleeve 52 and extends into the needle retraction spring base 4. The puncture end of the needle 13 connected to the bottom of the syringe 11 passes through the bottom of the outer sleeve 21 and enters the activation end of the activation sleeve 31 (in the above-mentioned prior art, the needle (12) is located in the pen tube body (21) and the hidden needle sleeve (3) before the whole is activated and unlocked). The protective cap wrapped around the needle 13 generally includes a soft protective cap 15 and a hard protective cap 16, which are inserted into the pen cap 23 and combined with the pen cap 23. The flange 12 is fixedly installed in the PFS mounting sleeve 52 by the buffer pad 8. At the same time, the push end of the push rod 7 enters into the syringe 11 and approaches the piston 14 (in the above-mentioned prior art, the end of the piston assembly (4) is always connected to the piston (111)).

[0072] Outer sleeve 21, specific structure as follows Figure 4 , Figure 5 As shown, a sleeve body 211 with openings at both ends has a sleeve cavity 212 inside. The top of the sleeve body 211 is provided with a fixing part 213 for fixed connection with the top cover 22. The bottom of the sleeve body 211 is provided with a pen cap connecting part 214 for connecting or disconnecting with the pen cap 23. On the inner side of the sleeve body 211, i.e., on the wall of the sleeve cavity 212, a guide body 215 and a guide groove 2152 are provided along the axial direction to guide the axial movement of the trigger unlocking cylinder in the outer sleeve 21. The guide body 215 is located at the lower part and the guide groove 2152 is located at the upper part to realize the axial movement guidance at both the upper and lower parts. In the lower middle part of the inner side of the sleeve body 211, a mounting part is provided, including a lower limit platform 216 and an upper limit platform 217, for connection and fixation with the needle retracting spring base 4. At the same time, an axially extending guide strip 218 is also provided above the mounting part.

[0073] The activation unlocking cylinder has the following specific structure: Figure 6 , Figure 7 , Figure 10 As shown;

[0074] Excitation sleeve 31, please refer to the details. Figure 8 The bottom is an activation surface 311, which is used to press against the skin at the injection site; the middle of the activation surface 311 is a puncture hole 312, which allows the puncture end of the needle 13 to pass through and pierce the skin at the injection site; the lower part of the activation sleeve 31 is provided with a guide part 313, which is adapted to the guide body 215 to guide the axial movement of the lower part; the upper part of the activation sleeve 31 is provided with an opening 314 for other components to pass through; the top of the activation sleeve 31 is provided with a fixing part 315; the upper outer wall surface of the activation sleeve 31 is provided with a guide protrusion 316, which is adapted to the guide groove 2152 to guide the axial movement of the upper part.

[0075] Unlocking the 32mm socket; please refer to the details. Figure 9 The upper inner side is provided with an unlocking plate 321, and the unlocking plate 321 is provided with an unlocking slope 322; the middle of the two unlocking plates 321 is provided with a safety plug 323, and the top of the safety plug 323 is provided with a safety protrusion 324; the bottom of the unlocking sleeve 32 is provided with a fixing part 325, and the fixing part 315 of the excitation sleeve 31 and the fixing part 325 of the unlocking sleeve 32 are combined to realize the combination of the excitation sleeve 31 and the unlocking sleeve 32, forming an integrated excitation unlocking sleeve; furthermore, a fixing claw 326 is provided at the top of the unlocking sleeve 32.

[0076] like Figure 11 As shown, the trigger unlocking cylinder is installed inside the outer sleeve 21, the guide part 313 is adapted to the guide body 215, and the guide protrusion 316 is inserted into the guide groove 2152, so that the trigger unlocking cylinder can move axially along the outer sleeve 21.

[0077] The needle-retracting spring base 4 has the specific structure shown in 12. Figure 13 As shown, the lower middle part is a hollow guide cylinder 41; the bottom of the guide cylinder 41 protrudes inward to form an elastic limiting claw 412, which is used to position and buffer the bottom of the syringe 11; the bottom of the guide cylinder 31 protrudes outward to form a positioning claw 413, preferably four of which contact the guide body 215 of the outer sleeve 21 to achieve positioning. The upper part of the guide cylinder 41 forms a connecting structure, including a needle retraction spring lower limit 414 formed at the top of the guide cylinder 41, a PFS mounting sleeve engagement cavity 42 outside the needle retraction spring lower limit 414, and a connecting cylinder 43 on the outer side. The connecting cylinder 43 is symmetrically provided with connecting buckle grooves 45, which match the guide strip 218 to achieve radial limiting. A mounting buckle is provided on the lower inner side of the connecting buckle groove 45, which combines with the mounting part inside the outer sleeve 21 to achieve fixed installation of the needle retraction spring base 4 inside the outer sleeve 21. It includes a stop block 442 that abuts against the lower limit platform 216 and a hook 441 that engages with the upper limit platform 217, thereby achieving axial upper and lower limit fixation. On the upper inner side of the connecting buckle groove 45, a set of locks that can be opened from the inside out are also provided, including an elastic locking arm 46 that is slightly inclined inward in its natural state. The upper part of the elastic locking arm 46 protrudes inward to form a needle retraction lock 47. The upper part of the needle retraction lock 47 is provided with a needle retraction activation slope 48.

[0078] like Figure 14 , Figure 15 As shown, the needle retractor spring base 4 is fixedly installed by combining with the mounting part of the outer sleeve 21 through the mounting buckle.

[0079] The PFS mounting sleeve 52 and the injection spring sleeve 62 can be combined to form a mounting cavity for mounting the injection spring 61 and the push rod 7, as shown in the following configuration. Figure 16 , Figure 17 As shown.

[0080] The lower part of the PFS mounting sleeve 52 is a guide tube 521, which can be inserted into the PFS mounting sleeve engagement cavity 42 of the needle take-up spring base 4. The guide tube 521 is provided with a needle take-up sliding surface 5212 and a needle take-up locking hook 5213. The top of the guide tube 521 extends inward to form the upper limit position 522 of the needle take-up spring. The top of the guide tube 521 forms a platform, namely the PFS fixing platform 523. The upper part of the PFS fixing platform 523 is provided with an inwardly extending PFS fixing claw 524. The PFS fixing platform 523 and the PFS fixing claw 524 are combined to limit and fix the flange 12 of the PFS, thereby fixing the PFS1. The upper part of the PFS mounting sleeve 52 is provided with a connecting part, including a connecting groove 527 and a limiting surface 528, for fixed connection with the injection spring sleeve 62.

[0081] The top of the injection spring sleeve 62 is located in a through hole for the top of the push rod 7 to pass through. Below the top of the injection spring sleeve 62 is an upper limit stop 622 for the injection spring. Inside the through hole at the top of the injection spring sleeve 62, there is a push rod fixing bracket 623 and an anti-rotation groove 624 for connecting the top of the push rod 7 and preventing rotation. The lower part of the injection spring sleeve 62 has an axial slot, i.e., a guide groove 626. The lower part of the injection spring sleeve 62 has a connecting part, including a connecting hook 627 and a limiting platform 628, which respectively match the connecting groove 527 and the limiting surface 528 of the PFS mounting sleeve 52 to achieve a fixed connection.

[0082] Push rod 7, specific structure as follows Figure 18 , Figure 19 As shown; the lower part of the push rod 7 is the push rod part 71, and the bottom of the push rod part 71 is the push head 72; the upper part of the push rod 7 is provided with two fixed spring arms 73 that can be elastically deformed inward, and the bottom of the fixed spring arms 73 extends outward to form the lower limit 733 of the injection spring. The upper part of the fixed spring arm 73 is provided with a fixing structure and an unlocking structure. The fixing structure is a locking groove 74, with a locking hook 742 formed at the top of the locking groove 74, which matches the push rod fixing bracket 623. An anti-rotation clip 75 is provided between the two locking grooves 74, matching the anti-rotation groove 624. A safety groove is formed between the tops of the two fixed spring arms 73 to accommodate the safety insert plate 323. Furthermore, a safety cone groove 76 is formed on the inner side of the top of the two fixed spring arms 73. The safety cone groove 76 is tapered, narrow at the top and wide at the bottom, to accommodate the safety protrusion 324. When the safety protrusion 324 attempts to move upward, it is squeezed by the safety cone groove 76, generating greater force and making it less likely to detach, thus improving safety. Unlocking heads 77 are provided on both sides of the top of each fixed spring arm 73, which match the unlocking ramp 322 on the unlocking plate 321. The middle part of the push rod 7, that is, the lower part of the injection spring lower limit 733, extends downward on both sides to form the needle retraction unlocking part 78. The needle retraction unlocking part 78 is simultaneously engaged in the guide groove 626 to guide the axial movement of the push rod 7. The bottom plate of the needle unlocking part 78 preferably forms an unlocking slope 782, which contacts the needle retraction triggering slope 48 to achieve unlocking.

[0083] like Figure 20 , Figure 21 As shown in the diagram, the push rod 7 and the injection spring 61 are installed inside the injection spring sleeve 62. The locking hook 742 is engaged with the push rod fixing bracket 623, and the anti-rotation clip 75 is engaged in the anti-rotation groove 624. The injection spring 61 is in a compressed state, with its top abutting against the upper limit position 622 and its bottom abutting against the lower limit position 733. The needle retraction unlocking part 78 is located in the guide groove 626. The push rod part 71 extends downward, beyond the injection spring sleeve 62.

[0084] Furthermore, such as Figure 22, Figure 23 As shown, it is combined with the unlocking sleeve 32; the safety insert 323 is inserted into the safety groove in the middle of the top of the two fixed spring arms 73, in particular the safety protrusion 324 is inserted into the safety cone groove 76, so that the two fixed spring arms 73 cannot be elastically deformed inward, that is, they cannot be separated from the injection spring sleeve 62, thus making the injection spring 61 always in a compressed state; the unlocking slope 322 of the unlocking plate 321 is located below the unlocking head 77.

[0085] The automatic injection device for the pre-filled syringe of this utility model is assembled with PFS1 to form a structure as follows: Figure 1 , Figure 2 The automatic injection pen of this utility model shown has the activation and unlocking sleeves (activation sleeve 31 and unlocking sleeve 32) located at the bottom, and the pen cap 23 installed in place. The entire automatic injection pen is in a safe and sealed state and can be transported and stored.

[0086] The pre-filled syringe of this invention is formed into an automatic injection pen using an automatic injection device. When used, it includes the following steps:

[0087] Step 1, remove the pen cap 23, as follows Figure 24 As shown; the operator holds the outer sleeve 21 with one hand and the pen cap 23 with the other, and removes the pen cap 23 from the outer sleeve 21 by rotating and pulling; at the same time as the pen cap 23 is removed, the protective cap (soft protective cap 15, hard protective cap 16) wrapped on the needle 13 is also removed, so that the needle 13 is in a puncture-ready state; at this time, the lower part of the activation sleeve 31 extends beyond the outer sleeve 21 and wraps the puncture end of the needle 13, and is in a state of waiting to be activated.

[0088] Step two, wear stimulating hair, such as Figure 25 , Figure 26 As shown; the operator holds the main body of the automatic injection pen after removing the pen cap 23 in step one, and places the activating surface 311 of the activating sleeve 31 against the skin of the patient's injection site, and then applies a downward force, causing the outer sleeve 21 to move downward along with the internal components connected to it; from the perspective of the automatic injection pen, that is, the activating sleeve 31 moves upward relative to the outer sleeve 21; during this process, the needle 13 passes through the puncture hole 312, passes over the activating surface 311, and pierces into the injection site.

[0089] Compared to existing technologies (the applicant's earlier application, the automatic injection pen in Chinese Patent Publication No. CN116392673A), the needle 13 is located in the PFS1 and installed inside the PFS mounting sleeve 52, where it is engaged with the needle retraction spring base 4. The needle retraction spring base 4 is fixed inside the outer sleeve 21. Therefore, as the outer sleeve 21 presses downward, the needle 13 also moves downward. The depth to which the needle 13 can penetrate the injection site beyond the activation surface 311 is also controllable. Therefore, the automatic injection device for the pre-filled syringe and its automatic injection pen of this utility model can ensure that the same puncture depth is obtained every time during puncture, achieving the set depth of drug injection, which is more reliable. Moreover, the puncture process is manually operated by the operator, making the process more controllable and more acceptable to patients.

[0090] In this step, in addition to completing the puncture, as the activation sleeve 31 moves upward relative to the outer sleeve 21, the unlocking sleeve 32 also moves upward relative to the outer sleeve 21 simultaneously to perform activation. (Refer to...) Figure 27 :

[0091] (1) The safety protrusion 324 is dislodged from the safety cone groove 76 under force;

[0092] (2) The safety insert 323 is removed from the safety groove between the two fixed spring arms 73;

[0093] (3) As the unlocking head 77 moves down, it comes into contact with the unlocking ramp 322 of the unlocking plate 321. The unlocking head 77 is guided by the unlocking ramp 322, which causes the two fixed spring arms 73 to deform inward. Subsequently, the locking hook 742 of the locking groove 74 disengages from the push rod fixing bracket 623, and the anti-rotation card 75 disengages from the anti-rotation groove 624.

[0094] (4) Until the two fixed spring arms 73 are fully deformed inward, the locking groove 74 and anti-rotation clip 75 at the top are completely disengaged from the push rod fixing bracket 623 and anti-rotation groove 624 at the top of the injection spring sleeve 62, that is, the top of the push rod 7 is disengaged from the top of the injection spring sleeve 62; at this point, the injection spring 61 is unlocked and is in a releaseable state.

[0095] (5) The fixing claw 326 at the top of the unlocking sleeve 32 passes over the fixing inner claw 224 of the top cover 22 (the fixing outer claw 222 of the top cover 22 is combined with the fixing part 213 / fixing groove of the outer sleeve 21 to achieve the fixing between the top cover 22 and the outer sleeve 21), so that the unlocking sleeve 32 and the triggering sleeve 31 are fixed at the upper limit position inside the outer sleeve 21 after the unlocking and triggering actions are completed.

[0096] Once the injection spring 61 is unlocked, it unfolds and releases outward, pushing the push rod 7, and then proceeding to step three.

[0097] Step 3, injection, such as Figure 28 , Figure 29 As shown; the injection spring 61 unfolds and releases. The top of the injection spring 61 is fixed by the upper limit 622 of the injection spring sleeve 62, while the bottom of the injection spring 61 pushes the lower limit 733 of the injection spring of the push rod 7, causing the push rod 7 to move downward. The push head 72 at the bottom of the push rod 7 contacts the piston 14 in the PFS1, thereby pushing the piston 14 to move axially in the syringe 11, injecting the drug 10 in the syringe 11 from the needle 13 into the patient's body.

[0098] As the push rod 7 moves downward, the needle release unlocking parts 78 on both sides move downward as well. When the piston 14 is about to reach the bottom of the inner barrel of the syringe 11, the unlocking slope 782 of the needle release unlocking part 78 contacts the needle release activation slope 48. As the push rod 7 continues to move downward, the needle release unlocking part 78 opens the needle release activation slope 48 outward, so that the needle release lock 47 gradually disengages from the needle release locking hook 5213.

[0099] Until the piston 14 reaches the bottom of the inner barrel of the syringe 11, completely injecting the drug 10 into the syringe 11, the needle retraction lock 47 completely disengages from the needle retraction locking hook 5213, thus unlocking the needle retraction spring 51 between the PFS mounting sleeve 52 and the needle retraction spring base 4, placing it in a releaseable state. Figure 30 As shown, proceed to step four.

[0100] Step four, finish stitching, as follows: Figure 31 , Figure 32 As shown; since the needle retraction spring base 4 is fixed inside the outer sleeve 21, the bottom of the needle retraction spring 51 abuts against the lower limit 414 of the needle retraction spring base 4, while the top of the needle retraction spring 51 pushes the upper limit 522 of the needle retraction spring, thereby causing the PFS mounting sleeve 52 to move upward; the PFS mounting sleeve 52 then causes the buffer pad 8 and PFS1 connected to it to move upward together, and the upward movement of PFS1 causes the needle 13 to move upward, so that the needle 13 is pulled out from the injection site; at the same time, the PFS mounting sleeve 52 causes the injection spring sleeve 62 and the injection spring 61 and push rod 7 located inside the two to move upward together.

[0101] Until the top of the injection spring sleeve 62 is pressed against the top of the unlocking sleeve 32 to achieve a limit, at which point the needle 13 retracts from the puncture hole 312 and retracts into the lower part of the activation sleeve 31, or even into the lower part of the outer sleeve, away from the activation surface 311, thus meeting safety standards and achieving the effect of safety protection.

[0102] The preferred embodiments of this utility model have been described in detail above, but this utility model is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this utility model, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. An automatic injection device for a pre-filled syringe, characterized in that, Includes an outer pen casing, an activation unlocking cylinder, a needle retraction spring base, and an injection cartridge; The outer pen casing includes an outer sleeve and a detachable pen cap; An activation unlocking cylinder is slidably installed inside the outer sleeve; The fixing part of the needle retraction spring base passes through the trigger unlocking cylinder and connects to the outer sleeve; the needle retraction spring base is fixed inside the outer sleeve; A needle retraction spring is installed on the upper part of the needle retraction spring base, and a releasable syringe is also installed thereon. The syringe consists of a PFS mounting sleeve and an injection spring sleeve connected together. An injection spring is installed inside the injection spring sleeve; a push rod is fitted inside the injection spring, and the top of the push rod is releasable and connected to the top of the injection spring sleeve. The bottom of the trigger unlocking cylinder is equipped with an triggering part that can extend beyond the bottom of the outer sleeve; The top of the trigger unlocking cylinder is equipped with an unlocking part that matches the release part on the top of the push rod to unlock the injection spring; The push rod is equipped with an unlocking part that matches the release part at the needle take-off spring, thereby unlocking the needle take-off spring.

2. The automatic injection device for a pre-filled syringe as described in claim 1, characterized in that, The inner side of the sleeve body of the outer sleeve is provided with an installation part; The outer wall of the needle retraction spring base is provided with a mounting buckle; The mounting part of the outer sleeve is combined with the mounting buckle of the take-off spring base to achieve the installation and fixation of the take-off spring base inside the outer sleeve.

3. The automatic injection device for a pre-filled syringe as described in claim 2, characterized in that, The mounting portion of the outer sleeve includes a lower limiting platform and an upper limiting platform; The mounting buckle of the needle retractor spring base includes a stop block and a latch; The abutment block abuts against the lower limit platform; The hook engages with the upper limit positioner. The needle retraction spring base and the outer sleeve are fixed to the upper and lower axial limits.

4. The automatic injection device for a pre-filled syringe as described in claim 3, characterized in that, There are two lower limit platforms and abutment blocks, and an upper limit platform and a hook are provided in the middle. The lower limit platforms and abutment blocks on both sides radially limit the upper limit platform and hook in the middle.

5. The automatic injection device for a pre-filled syringe as described in claim 3, characterized in that, Above the mounting portion of the outer sleeve, there are two axially extending guide bars located on both sides of the mounting portion; The connecting cylinder of the needle retractor spring base is provided with a connecting buckle groove, which matches the guide bar to achieve radial limiting; The mounting buckle has a retractable spring base inside the connecting buckle slot.

6. The automatic injection device for a pre-filled syringe as described in claim 1 or 3, characterized in that, The upper part of the needle retraction spring base is provided with an elastic locking arm, the upper part of the elastic locking arm protrudes inward to form a needle retraction lock, and the upper part of the needle retraction lock is provided with a needle retraction activation slope. The lower outer side of the PFS mounting sleeve is provided with a needle retraction locking hook, which matches the needle retraction lock buckle; When the take-off lock and the take-off locking hook are engaged together, the take-off spring base is connected to the PFS mounting sleeve, and the take-off spring is in a compressed state. The needle retraction latch disengages from the needle retraction locking hook, the needle retraction spring base and the PFS mounting sleeve can slide axially, and the needle retraction spring is in the unlocked and activated state, which can push the syringe barrel axially away from the needle retraction spring base.

7. The automatic injection device for a pre-filled syringe as described in claim 6, characterized in that, The middle part of the push rod extends downward on both sides to form a pin-retracting unlocking part with a free end; The free end of the needle release unlocking part matches the needle release activation slope of the needle release spring base.

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