A safety injection needle

Abstract

A safe injection needle comprises a needle seat, a first sheath, a second sheath and a spring; the rear end of the second sheath is located between the first sheath and the needle seat, the front end of the second sheath has a second opening and extends from the first opening; a transmission ring is arranged between the rear end of the second sheath and the needle seat, the outer wall of the transmission ring is provided with at least one first protrusion in the circumferential direction, and the inner wall of the transmission ring is provided with at least one second protrusion in the circumferential direction; the inner wall of the second sheath is provided with a blocking guide surface corresponding to the first protrusion, the blocking guide surface comprises a planar guide segment and an inclined guide segment, one end of the planar guide segment is provided with an initial position, and the other end of the inclined guide segment is provided with a terminal position; the outer periphery of the needle seat is provided with a guide groove extending in the axial direction corresponding to the second protrusion, and the front end of one side of the guide groove is provided with a locking surface facing the front side. The present application can prohibit secondary use, has high working stability, a relatively simple structure and is convenient to assemble.

Description

Technical Field

[0001] This invention relates to the field of medical supplies technology, specifically to a safe injection needle, which is a disposable needle. Background Technology

[0002] Diabetes is a metabolic disease characterized by high blood sugar. There is currently no cure, but injecting insulin can effectively control the condition.

[0003] There are various types of insulin injection tools. The insulin injection needle described in this invention is an injection tool used in conjunction with an insulin pen. The insulin pen carries a specified amount of insulin liquid medication and is reusable, while the injection needle is a disposable needle with a safety protection device.

[0004] A representative structure in the prior art can be found in Chinese Patent CN116942966A, which discloses an invention patent application entitled "Disposable Injection Needle". The disclosed injection needle has a basic structure including a needle hub, a first sheath, a second sheath, an inner core, and a spring. The needle hub has a needle tube extending axially through it. The first sheath is fitted onto the needle hub, its rear end is fixedly connected to the needle hub, and its front end has a first opening from which the needle tube of the needle hub extends, forming a receiving space between the first sheath and the needle hub. The rear end of the second sheath is located within the receiving space, and the front end of the second sheath has a second opening extending from the first opening. The second sheath is slidably connected relative to the first sheath along the axial direction. The inner core is located between the second sheath and the needle hub and is rotatable relative to the circumference of the needle hub. The outer wall of the inner core has a limiting guide groove that cooperates with a blocking element on the inner wall of the second sheath. The rear end of the inner core has an inner core guide portion that cooperates with a guide engagement portion on the needle hub. The guide engagement portion includes a planar guide portion and a sloped guide portion. The spring is... A compression spring rests at one end against the second sheath and at the other end against the rear end of the inner core. Thus, during use, the second sheath retracts into the receiving space under external force, allowing the needle tip to extend from the second opening of the second sheath. The cooperation between the blocking element and the limiting guide groove causes the inner core to rotate circumferentially, rotating the inner core guide from the flat guide to the inclined guide. After the injection needle is used, the second sheath is no longer subject to external force and returns to its original position under the action of the spring. When the second sheath moves to the point where its blocking element separates from the limiting guide groove of the inner core, the inner core, under the force of the spring, slides along the inclined guide of the needle holder until the inner core guide contacts the limiting plane of the needle holder. At this point, the sheath blocking surface of the inner core has rotated to a position opposite to the blocking element of the second sheath, preventing the second sheath from retracting into the receiving space and ensuring the needle tip is not exposed again, thus achieving the effect of single-use only.

[0005] While the aforementioned existing technology achieves the function of single-use, its reliability in practical application is still insufficient. The inner core, as the core component requiring circumferential rotation, has both a limiting guide groove and an inner core guide. Especially when the second sheath retracts due to external force during needle use, the blocking element on the second sheath abuts against the limiting guide groove of the inner core, causing the limiting guide groove to move and push the inner core to rotate. This movement is not smooth and prone to jamming. Furthermore, since one end of the spring rests on the second sheath and the other end on the rear end of the inner core, during use, the second sheath needs to extend and retract axially, and the inner core needs to rotate. For the spring, both ends must move. Especially after the injection needle is used, the spring force needs to reset and eject the second sheath while simultaneously sliding the inner core guide along the inclined guide of the needle holder to the limiting plane. At this time, the spring is prone to misalignment or incomplete reset, and the inner core may not rotate to its proper position. Thus, the single-use protection function fails, easily causing accidents. Summary of the Invention

[0006] This invention provides a safe injection needle to improve the reliability of single-use protection.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A safety injection needle includes a needle hub, a first sheath, a second sheath, and a spring; the needle hub is provided with an axially extending needle tube; the first sheath is fitted onto the needle hub, its rear end is fixedly connected to the needle hub, and its front end has a first opening; the needle tube of the needle hub extends out from the first opening, and a receiving space is formed between the first sheath and the needle hub; the rear end of the second sheath is located in the receiving space, its front end has a second opening and extends out from the first opening, and the second sheath is axially slidably connected to the first sheath. A transmission ring is provided between the rear port of the second sheath and the needle seat. The outer wall of the transmission ring is provided with at least one first protrusion in the circumferential direction, and the inner wall of the transmission ring is provided with at least one second protrusion in the circumferential direction. The inner wall of the second sheath is provided with a blocking guide surface corresponding to the first protrusion. The blocking guide surface includes a planar guide section and an inclined guide section. One end of the planar guide section is set as the initial position, and the other end is connected to one end of the inclined guide section. The inclined guide section is inclined towards the front end of the second sheath, and the other end of the inclined guide section is set as the end position. The outer periphery of the needle seat is provided with a guide groove extending in the axial direction corresponding to the second protrusion. The guide groove includes a front guide groove and a rear guide groove. The front guide groove is larger in the circumferential direction than the rear guide groove. One side wall of the front guide groove and the same side wall of the rear guide groove are connected by an oblique guide surface. The front end of the other side of the front guide groove is provided with a locking surface facing forward. The spring is sleeved on the needle holder, and the needle holder has a spring mounting surface that abuts against the rear end of the spring. The front end of the spring abuts against the transmission ring. In the initial state before use, the first protrusion of the transmission ring is located in the initial position of the blocking guide surface, while the second protrusion is directly opposite the side wall of the front guide groove of the needle seat near the inclined guide surface. During use, the second sheath moves backward under the action of external force, and its blocking guide surface cooperates with the first protrusion, pushing the transmission ring backward. The second protrusion slides into the front guide groove, and through the cooperation of the second protrusion and the inclined guide surface, it pushes the transmission ring to rotate circumferentially. When the second sheath moves backward to its limit, the first protrusion slides to the inclined guide section of the blocking guide surface, while the second protrusion slides to the rear end of the rear guide groove. After use, the second sheath and the transmission ring extend and reset under the action of the spring. The second protrusion slides to the front end of the front guide groove. Under the sliding cooperation of the first protrusion and the inclined guide section, the second protrusion rotates to face the locking surface, so that the second sheath cannot retract again due to the blocking of the locking surface.

[0008] In the above scheme, the locking surface corresponds to the end point of the inclined guide section, and the width of the locking surface in the circumferential direction is greater than the width of the end point of the inclined guide section in the circumferential direction, so that after the first protrusion slides into the end point, the second sheath is pressed again to ensure that the second protrusion is opposite to the locking surface, so that the second sheath cannot retract again due to the obstruction of the locking surface.

[0009] In the above scheme, a protruding part is provided at the junction of the locking surface and the front guide groove so that the locking surface is concave.

[0010] In the above scheme, an axial transition surface is provided between the planar guide section and the inclined guide section of the blocking guide surface, so that when the second sheath moves to its limit, the first protrusion abuts against the axial transition surface. This transition surface acts as a limit, preventing the first protrusion from sliding back to the planar guide section during the upward movement of the transmission ring under the action of the spring, thereby preventing the secondary use function from being achieved.

[0011] In the above scheme, the needle hub has a circumferential annular protrusion on its rear end, and the inner wall of the rear end of the first sheath has a corresponding locking part. The first sheath and the needle hub are connected by the locking part and the annular protrusion.

[0012] In the above scheme, the second sheath has a transparent part; after use, when the second sheath and the transmission ring extend and reset under the action of the spring, and the first protrusion reaches the end position of the inclined guide section, the transmission ring can be observed from the first opening of the first sheath through the transparent part of the second sheath, so as to distinguish it from the unused state.

[0013] In the above solution, the length of the front guide groove and the oblique guide surface in the axial direction is greater than that of the rear guide groove in the axial direction, which makes the press triggering stage have a large stroke. Even if it is accidentally pressed (not pressed to the near limit position), the second sheath can rebound under the action of the spring, so that the entire safety injection needle can be reused and has the function of preventing accidental touch.

[0014] This invention places the guide groove on the fixed needle holder and the blocking guide surface on the second sleeve, which only moves axially. The core component, the transmission ring, which achieves locking through circumferential rotation, has only a first and a second protrusion. During operation, the first protrusion engages with the blocking guide surface, and the second protrusion engages with the guide groove, both by sliding on the guide surface. The guide surface remains stationary while the protrusion moves, allowing the transmission ring to rotate smoothly. Furthermore, the rear end of the spring rests against the completely stationary rear end of the needle holder, ensuring stable spring return and preventing offset, thus preventing the transmission ring from jamming. This makes the operation more reliable and stable. After use, even if the second sleeve is pressed again, the second sleeve moves backward, causing the transmission ring to move backward. The second protrusion of the transmission ring contacts the locking surface and cannot move backward again, preventing the needle tip from protruding. After releasing the second sleeve, under the spring's return action, the transmission ring moves to the end point of the inclined guide section of the second sleeve, causing the transmission ring to protrude from the first sleeve, different from before use. Attached Figure Description

[0015] Figure 1 This is a three-dimensional overall shape diagram of an embodiment of the present invention; Figure 2 This is an exploded view of the components according to an embodiment of the present invention; Figure 3 This is a perspective view of the second sheath according to an embodiment of the present invention; Figure 4 This is a three-dimensional schematic diagram of the first sheath according to an embodiment of the present invention; Figure 5 This is a three-dimensional schematic diagram of the transmission ring according to an embodiment of the present invention; Figure 6 This is a three-dimensional schematic diagram of the needle holder according to an embodiment of the present invention; Figure 7 This is a cross-sectional view of the initial state before use according to an embodiment of the present invention, with the outer shell and the first sheath removed from the figure; Figure 8 This is a radially sectional perspective view of the initial state before use according to an embodiment of the present invention, with the outer shell removed. Figure 9 This is a partial cross-sectional view of the initial state before use in an embodiment of the present invention. Figure 1 The outer shell has been removed from the image; Figure 10This is a partial cross-sectional view of the initial state before use in an embodiment of the present invention. Figure 2 The outer shell and second sheath have been removed from the image. Figure 11 This is a schematic diagram showing the relative positions of the transmission ring and the second sheath in their initial state before use, according to an embodiment of the present invention. Figure 12 This is a schematic diagram showing the relative positions of the transmission ring and the needle seat in their initial state before use, according to an embodiment of the present invention. Figure 13 This is a cross-sectional view of the second sheath being moved to its limit state during use according to an embodiment of the present invention, with the outer shell removed from the figure; Figure 14 This is a partial cross-sectional perspective view of the second sheath being moved to its extreme state during use according to an embodiment of the present invention, with the outer shell removed from the figure; Figure 15 This is a schematic diagram showing the relative positions of the transmission ring and the second sheath when the second sheath is moved to its limit state during use according to an embodiment of the present invention. Figure 16 This is a schematic diagram showing the relative positions of the transmission ring and the needle seat when the second sheath is moved to its limit state during use according to an embodiment of the present invention; Figure 17 This is a cross-sectional view of the second sheath in its reset state after use according to an embodiment of the present invention; the outer shell has been removed from the figure. Figure 18 This is a partial cross-sectional perspective view of the second sheath in its reset state during use according to an embodiment of the present invention, with the outer shell removed from the figure; Figure 19 This is a schematic diagram showing the relative positions of the transmission ring and the second sheath in the reset state during use according to an embodiment of the present invention. Figure 20 This is a schematic diagram showing the relative positions of the transmission ring and the needle seat in the reset state of the second sheath during use according to an embodiment of the present invention; Figure 21 This is a cross-sectional view of the state after the second sheath has been reset and then pressed down again in an embodiment of the present invention. The outer shell has been removed from the figure. Figure 22 This is a partial cross-sectional perspective view of the state of the second sheath being pressed down again after being reset following use in an embodiment of the present invention. The outer shell has been removed from the figure. Figure 23 This is a schematic diagram showing the relative positions of the transmission ring and the second sheath after the second sheath has been reset and then pressed down again, according to an embodiment of the present invention. Figure 24 This is a schematic diagram showing the relative positions of the transmission ring and the needle seat after the second sheath has been reset and then pressed down again, according to an embodiment of the present invention.

[0016] In the above figure: 1. Needle base; 11. Needle tube; 12. Annular protrusion; 13. Guide groove; 131. Front guide groove; 132. Rear guide groove; 133. Angled guide surface; 134. Locking surface; 1341. Forward protrusion; 14. Spring mounting surface; 2. First sheath; 21. First opening; 22. Guide rib; 23. Fitting part; 3. Second sheath; 31. Second opening; 32. Guide groove; 33. Blocking guide surface; 331. Planar guide section; 332. Sloping guide section; 333. Transition surface; A. Initial position; B. End position; 4. Spring; 5. Outer casing; 6. Transmission ring; 61. First protrusion; 62. Second protrusion; R, storage space; Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments: Example: See Figure 1-24 As shown: A safe injection needle, see Figure 2 It includes a needle holder 1, a first sheath 2, a second sheath 3, a housing 5, a spring 4, and a transmission ring 6.

[0018] See Figure 2 The needle holder 1 is provided with an axially extending needle tube 11, with the head of the needle tube pointing forward and backward.

[0019] See Figure 7 , Figure 9 , Figure 13 The first sheath 2 is placed on the needle holder 1, and its rear end is fixedly connected to the needle holder 1. Its front end has a first opening 21. The needle tube 11 of the needle holder 1 extends out from the first opening 21, forming a receiving space R between the first sheath 2 and the needle holder 1. The rear end of the second sheath 3 is located in the receiving space R. Its front end has a second opening 31 and extends out from the first opening 21. The second sheath 3 is slidably connected to the first sheath 2 along the axial direction.

[0020] Specifically, the preferred sliding connection between the second sheath 3 and the first sheath 2 is as follows: See Figure 3 , Figure 4 and Figure 8 As shown, the inner wall of the first sheath 2 is provided with a guide rib 22 extending axially, and the outer wall of the second sheath 3 is provided with a guide groove 32 corresponding to the guide rib 22. The first sheath 2 and the second sheath 3 achieve a sliding connection through the guiding cooperation of the guide rib 22 and the guide groove 32.

[0021] See Figure 2 , Figure 6 , Figure 13 , Figure 17 and Figure 21 Specifically, the needle holder 1 has a circumferential annular protrusion 12 on its rear end, and the inner wall of the rear end of the first sheath 2 has a corresponding locking part 23. The first sheath 2 and the needle holder 1 are connected by the locking part 23 and the annular protrusion 12.

[0022] See Figure 5 , Figure 7 and Figure 8 The transmission ring 6 is located between the inner wall of the rear port of the second sheath 3 and the needle seat 1. At least one (preferably two) first protrusion 61 is provided circumferentially on the outer wall of the transmission ring 6, and at least one (preferably two) second protrusion 62 is provided circumferentially on the inner wall of the transmission ring 6. The first protrusion 61 protrudes outward in the radial direction of the transmission ring 6, and its forward-facing end face serves as the working surface. The second protrusion 62 protrudes inward in the radial direction of the transmission ring 6, and its two sides and rearward-facing end face serve as the working surface.

[0023] See Figure 3 and Figure 15 The inner wall of the second sheath 3 is provided with a blocking guide surface 33 corresponding to the first protrusion 61. This blocking guide surface 33 faces rearward and specifically includes a planar guide section 331 and an inclined guide section 332. The projection of the planar guide section 331 onto the axial section of the second sheath 3 is essentially a straight line perpendicular to the axial direction. The projection of the inclined guide section 332 onto the axial section of the second sheath 3 is an oblique line forming an angle with the axial direction. One end of the planar guide section 331 is designated as the initial position A, and its other end is connected to one end of the inclined guide section 332, which is designated as the endpoint position B. The inclined guide section 332 slopes from the planar guide section 331 towards the front end of the second sheath 3.

[0024] See Figure 6 and Figure 12 As shown, the outer periphery of the needle seat 1 is provided with a guide groove 13 extending axially corresponding to the second protrusion 66. Figure 6 The guide groove 13 includes a front guide groove portion 131 and a rear guide groove portion 132. The front guide groove portion 131 is larger in circumferential dimension than the rear guide groove portion 132. One side wall of the front guide groove portion 131 and the same side wall of the rear guide groove portion are connected by an inclined guide surface 133. A locking surface 134 facing forward is provided on the front end of the other side of the front guide groove portion.

[0025] See Figure 7As shown, the spring 4 is sleeved on the needle seat 1, and the needle seat 1 has a spring mounting surface 14 that abuts against the rear end of the spring 4. The front end of the spring 4 abuts against the rear end of the transmission ring 6, and the spring force pushes the transmission ring 6 forward.

[0026] The locking surface 134 corresponds to the end point B of the inclined guide section 332, and the width of the locking surface 134 in the circumferential direction is greater than the width of the end point B of the inclined guide section 332 in the circumferential direction, so that after the first protrusion 61 slides into the end point, the second sleeve 3 is pressed again to ensure that the second protrusion 62 is opposite to the locking surface 134, so that the second sleeve 3 cannot retract again due to the obstruction of the locking surface 134.

[0027] In the initial state before use, the first protrusion 61 of the transmission ring 6 is located at the initial position A of the blocking guide surface 33, see... Figure 9 and Figure 11 The second protrusion 62 is directly opposite the sidewall of the oblique guide surface 133 of the front guide groove portion 131 of the pin seat 1, see Figure 12 .

[0028] In use, remove the outer shell 5. The second sheath 3 moves backward under external force (i.e., the injection needle is pressed and punctured into the skin). Its blocking guide surface 33 cooperates with the first protrusion 61, pushing the transmission ring 6 to move backward as well. The second protrusion 62 slides into the front guide groove 131. Through the cooperation of the second protrusion 62 and the oblique guide surface 133, see... Figure 16 This drives the transmission ring 6 to rotate circumferentially. Finally, when the second sheath 3 moves to its limit, [the following is observed]. Figure 13 , Figure 14 , Figure 15 and Figure 16 As shown, the first protrusion 61 slides onto the inclined guide section 332 of the blocking guide surface 33, while the second protrusion 62 slides to the rear end of the rear guide groove 132. At this time, the front end of the second sheath 3 is basically flush with the front end of the first sheath 2, allowing the needle 11 to penetrate the human skin at its longest distance.

[0029] After use, the second sheath 3 and the transmission ring 6 extend forward and reset under the action of the spring 4 (i.e., the process of moving the needle away from the skin after injection). The second protrusion 62 reaches the front end of the front guide groove 131, disengaging from the restriction of the guide groove 13. Under the sliding cooperation of the first protrusion 61 and the inclined guide section 332, the second protrusion 62 of the transmission ring 6 rotates to face the locking surface 134. At this time, see Figure 17 , Figure 18 , Figure 19 and Figure 20 The second protrusion 62 of the transmission ring 6 is located at the front of the locking surface 134 and the two are opposite each other. The first protrusion 61 reaches the end position B of the inclined guide section 332, that is, the use is completed.

[0030] If the second sheath 3 is pressed again, it will move backward and abut against the locking surface 134. Due to the obstruction of the locking surface 134, it cannot retract further. The state at this point is shown in the image. Figure 21 , Figure 22 , Figure 23 and Figure 24 The second sheath 3 covers the tip of the syringe 11, thus preventing it from being reused.

[0031] See Figure 20 As shown, a protruding part 1341 is provided at the junction of the locking surface 134 and the front guide groove 131, so that the locking surface 134 is concave, making the locking surface 134 more stable in restricting and positioning the second protrusion 62.

[0032] See Figure 3 As shown, an axial transition surface 333 is provided between the planar guide section 331 and the inclined guide section 332 of the blocking guide surface 33, so that when the second sheath 3 moves backward to its limit, the first protrusion 61 can abut against the axial transition surface 333. The transition surface 333 acts as a limit, preventing the first protrusion 61 from sliding back to the planar guide section 331 during the upward movement of the transmission ring 6 under the action of the spring, thereby ensuring that it will not be reused and making the operation more reliable.

[0033] See Figure 3 As shown, the initial position A of the blocking guide surface 33 is also designed to be slightly concave, which makes it easier to position and assemble during initial assembly.

[0034] See Figure 6 As shown, the lengths of the front guide groove 131 and the oblique guide surface 133 in the axial direction are both greater than the length of the rear guide groove 132 in the axial direction, which makes the press triggering stage have a large stroke. Even if it is accidentally pressed (not pressed to the near limit position), the second sheath 3 can rebound under the action of the spring, so that the entire safety injection needle can be reused and has the function of preventing accidental touch.

[0035] Specifically, the second sheath 3 is made entirely of transparent material or has a transparent portion. After use, when the second sheath 3 and the transmission ring 6 extend and reset under the action of the spring, and the first protrusion 61 reaches the end position B of the inclined guide section, the transmission ring 6 can be observed from the transparent portion of the second sheath 3 protruding from the first opening 21 of the first sheath 2. Figure 17 As shown, this is to distinguish it from an unused injection needle.

[0036] This embodiment has the following advantages: 1. After the second sheath 3 is reset after one use, the second protrusion 62 of the transmission ring rotates to face the locking surface 134. Due to the blocking of the second protrusion 62 by the locking surface 134, the transmission ring 6 cannot move backward again. The first protrusion 61 of the transmission ring 6 blocks the second sheath 3, and the second sheath 3 also cannot move backward again, thus protecting the tip of the needle tube 11 and achieving the protection function of prohibiting secondary use. 2. Excellent operational stability and high safety; 3. The structure is relatively simple; 4. Easy to assemble and can be automated; 5. It feels better and more comfortable to use.

[0037] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A safety injection needle, comprising a needle hub, a first sheath, a second sheath, and a spring; the needle hub is provided with an axially extending needle tube; the first sheath is fitted onto the needle hub, its rear end is fixedly connected to the needle hub, and its front end has a first opening; the needle tube of the needle hub extends out from the first opening, and a receiving space is formed between the first sheath and the needle hub; the rear end of the second sheath is located within the receiving space, its front end has a second opening and extends out from the first opening, and the second sheath is axially slidably connected relative to the first sheath; characterized in that: A transmission ring is provided between the rear port of the second sheath and the needle seat. The outer wall of the transmission ring is provided with at least one first protrusion in the circumferential direction, and the inner wall of the transmission ring is provided with at least one second protrusion in the circumferential direction. The inner wall of the second sheath is provided with a blocking guide surface corresponding to the first protrusion. The blocking guide surface includes a planar guide section and an inclined guide section. One end of the planar guide section is set as the initial position, and the other end is connected to one end of the inclined guide section. The inclined guide section is inclined towards the front end of the second sheath, and the other end of the inclined guide section is set as the end position. The outer periphery of the needle seat is provided with a guide groove extending in the axial direction corresponding to the second protrusion. The guide groove includes a front guide groove and a rear guide groove. The front guide groove is larger in the circumferential direction than the rear guide groove. One side wall of the front guide groove and the same side wall of the rear guide groove are connected by an oblique guide surface. The front end of the other side of the front guide groove is provided with a locking surface facing forward. The spring is sleeved on the needle holder, and the needle holder has a spring mounting surface that abuts against the rear end of the spring. The front end of the spring abuts against the transmission ring. In the initial state before use, the first protrusion of the transmission ring is located in the initial position of the blocking guide surface, while the second protrusion is directly opposite the side wall of the front guide groove of the needle seat near the inclined guide surface. During use, the second sheath moves backward under the action of external force, and its blocking guide surface cooperates with the first protrusion, pushing the transmission ring backward. The second protrusion slides into the front guide groove, and through the cooperation of the second protrusion and the inclined guide surface, it pushes the transmission ring to rotate circumferentially. When the second sheath moves backward to its limit, the first protrusion slides to the inclined guide section of the blocking guide surface, while the second protrusion slides to the rear end of the rear guide groove. After use, the second sheath and the transmission ring extend and reset under the action of the spring. The second protrusion slides to the front end of the front guide groove. Under the sliding cooperation of the first protrusion and the inclined guide section, the second protrusion rotates to face the locking surface, so that the second sheath cannot retract again due to the blocking of the locking surface.

2. The safety injection needle according to claim 1, characterized in that: The locking surface corresponds to the end point of the inclined guide section, and the width of the locking surface in the circumferential direction is greater than the width of the end point of the inclined guide section in the circumferential direction.

3. The safety injection needle according to claim 2, characterized in that: The locking surface is provided with a protruding part at the junction with the front guide groove so that the locking surface is concave.

4. The safety injection needle according to claim 1, characterized in that: An axial transition surface is provided between the planar guide section and the inclined guide section of the blocking guide surface, so that when the second sheath moves to its limit, the first protrusion abuts against the axial transition surface.

5. The safety injection needle according to claim 1, characterized in that: The needle hub has a circumferential annular protrusion at its rear end, and a corresponding locking part is provided on the inner wall of the rear end of the first sheath. The first sheath and the needle hub are connected by the locking part and the annular protrusion.

6. The safety injection needle according to claim 1, characterized in that: The second sheath has a transparent portion; after use, when the second sheath and the transmission ring extend and reset under the action of the spring, and the first protrusion reaches the end position of the inclined guide section, the transmission ring can be observed to be exposed from the first opening of the first sheath through the transparent portion of the second sheath.

7. The safety injection needle according to claim 1, characterized in that: The axial length of both the front guide groove and the oblique guide surface is greater than the axial length of the rear guide groove.

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