Safe injection needle head

Abstract

A safe injection needle head, comprising a needle hub (1), a first protective sleeve (2), a second protective sleeve (3), and a spring (4). A rear end of the second protective sleeve (3) is positioned between the first protective sleeve (2) and the needle hub (1), and a front end of the second protective sleeve (3) is provided with a second opening (31) and extends outward from a first opening (21). A transmission ring (6) is disposed between a rear port of the second protective sleeve (3) and the needle hub (1). At least one first protrusion (61) is provided circumferentially on an outer wall of the transmission ring (6), and at least one second protrusion (62) is provided circumferentially on an inner wall of the transmission ring (6). An inner wall of the second protective sleeve (3) is provided with a blocking guide surface (33) corresponding to the first protrusion (61), and the blocking guide surface (33) comprises a planar guide segment (331) and an inclined guide segment (332). One end of the planar guide segment (331) is set as an initial position (A), the other end of the planar guide segment is connected to one end of the inclined guide segment (332), and the other end of the inclined guide segment (332) is set as a terminal position (B). The outer periphery of the needle hub (1) is provided with an axially extending guide groove (13) corresponding to the second protrusion (62), and a front end of one side of the guide groove (13) is provided with a front-facing locking surface (134). Thus, the safe injection needle head prevents secondary use, while exhibiting high operational stability, a relatively simple structure, and convenient assembly.

Description

A safety injection needle Technical Field

[0001] The present invention relates to the technical field of medical supplies, in particular to a safety injection needle, which is a disposable needle. Background Art

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

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

[0004] In the prior art, a representative structure can be found in Chinese patent CN116942966A, which discloses an invention patent application named "Disposable Injection Needle". The disclosed injection needle has a basic structure comprising a needle seat, a first sheath, a second sheath, an inner core and a spring; the needle seat is provided with a needle tube extending axially therethrough; the first sheath is placed on the needle seat, its rear end is fixedly connected to the needle seat, and its front end is provided with a first opening, the needle tube of the needle seat extends from the first opening to form an accommodating space between the first sheath and the needle seat; the rear end of the second sheath is located in the accommodating space, the front end of the second sheath has a second opening and extends from the first opening, and the second sheath is axially slidably connected relative to the first sheath; the inner core is located between the second sheath and the needle seat, and is rotatable relative to the circumferential direction of the needle seat; the outer wall of the inner core is provided with a limiting guide groove that cooperates with the blocking member on the inner wall of the second sheath, the rear end of the inner core is provided with an inner core guide portion that cooperates with the guide matching portion on the needle seat, and the guide matching portion includes a flat guide portion and an inclined guide portion; the spring is When the needle is used, the second sheath is no longer subjected to external force and the second sheath is reset and popped out under the action of the spring. When the second sheath moves to the point where its blocking member is separated from the limiting guide groove of the inner core, the inner core slides along the inclined guide portion of the needle seat under the action of the spring until the inner core guide portion contacts the limiting plane of the needle seat. At this time, the sheath blocking surface of the inner core has rotated to a position opposite to the blocking member of the second sheath, so that the second sheath can no longer be retracted into the accommodating space, so that the needle head will not be exposed a second time, thereby achieving the effect of only one use.

[0005] Although the above-mentioned prior art has achieved the function of disposable use, it is found in actual application that its operational reliability is still insufficient: its inner core is a core component that needs to rotate circumferentially, and both a limiting guide groove and an inner core guide portion are provided on the inner core. Especially when the second sheath is retracted due to external force when the needle is used, the blocking member on the second sheath is pressed against the limiting guide groove of the inner core, so that the limiting guide groove moves to promote the rotation of the inner core. The action here is not smooth and is easy to get stuck; and, since one end of the spring is pressed against the second sheath and the other end is pressed against the rear end of the inner core, the second sheath needs to be telescopically moved axially during use, and the inner core needs to rotate. For the spring, both ends need to move, especially when the injection needle is used, the spring force needs to reset the second sheath and eject it, and the inner core guide portion of the inner core needs to slide along the inclined guide portion of the needle seat to the limiting plane. At this time, the spring is prone to deviation or incomplete reset, and the inner core may not rotate into place, so the single-use protection function is invalid, which is easy to cause accidents. Summary of the Invention

[0006] The present invention provides a safety injection needle to improve the reliability of disposable protection.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A safety injection needle comprises a needle seat, a first shield, a second shield, and a spring; an axially extending needle tube is disposed on the needle seat; the first shield is placed on the needle seat, with its rear end fixedly connected to the needle seat and a first opening defined at its front end; the needle tube of the needle seat extends through the first opening, and a receiving space is formed between the first shield and the needle seat; the rear end of the second shield is located within the receiving space, and its front end has a second opening and extends from the first opening; the second shield is axially slidably connected relative to the first shield;

[0009] A transmission ring is provided between the rear port of the second sheath and the needle seat, and at least one first protrusion is provided on the circumference of the outer wall of the transmission ring, and at least one second protrusion is provided on the circumference of the inner wall of the transmission ring;

[0010] A blocking guide surface is provided on the inner wall of the second sheath corresponding to the first protrusion, the blocking guide surface including a planar guide section and an inclined guide section, one end of the planar guide section is set to an initial position, and the other end thereof is connected to one end of the inclined guide section, and the inclined guide section is inclined toward the front end of the second sheath, and the other end of the inclined guide section is set to an end position;

[0011] A guide groove extending in the axial direction is provided on the outer circumference of the needle seat corresponding to the second protrusion, the guide groove comprising a front guide groove portion and a rear guide groove portion, the front guide groove portion being larger in the circumferential direction than the rear guide groove portion, a side wall of the front guide groove portion and the same side wall of the rear guide groove portion being transitionally connected by an oblique guide surface, and a locking surface facing forward is provided on the front end of the other side of the front guide groove portion;

[0012] The spring is sleeved on the needle seat, and a spring mounting surface is provided on the needle seat corresponding to the rear end of the spring, and the front end of the spring abuts against the transmission ring;

[0013] In the initial state before use, the first protrusion of the transmission ring is located at the initial position of the blocking guide surface, and the second protrusion is opposite to the side wall of the front end guide groove portion of the needle seat close to the oblique 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 to push the transmission ring backward, and the second protrusion slides into the front end guide groove portion, and through the cooperation of the second protrusion and the oblique guide surface, the transmission ring is pushed to rotate circumferentially; when the second sheath moves backward to the limit, the first protrusion slides to the oblique guide section of the blocking guide surface, and the second protrusion slides to the rear end of the rear end guide groove portion; after use, the second sheath and the transmission ring extend and reset under the action of the spring, and the second protrusion slides to the front end of the front end guide groove portion. Under the sliding cooperation of the first protrusion and the oblique guide section, the second protrusion rotates to be opposite to the locking surface, so that the second sheath cannot retract again due to the blocking of the locking surface.

[0014] In the above scheme, the locking surface corresponds to the end point of the inclined guide section, and the circumferential width of the locking surface is greater than the circumferential width of the end point of the inclined guide section, so that after the first protrusion slides into the end point, the second sleeve is pressed again to ensure that the second protrusion is opposite to the locking surface, so that the second sleeve cannot retract again due to the obstruction of the locking surface.

[0015] In the above solution, a protrusion is provided at the junction of the locking surface and the front guide groove portion, so that the locking surface is concave.

[0016] In the above embodiment, 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 back to its limit, the first projection abuts against the axial transition surface. This transition surface acts as a stop, preventing the first projection from sliding back toward the planar guide section during upward movement of the transmission ring under the action of the spring, thereby failing to achieve the anti-reuse function.

[0017] In the above solution, a circumferential annular protrusion is provided on the rear end of the needle seat, and a corresponding snap-fitting portion is provided on the inner wall of the rear end of the first sheath. The first sheath and the needle seat are connected by the snap-fitting portion and the annular protrusion.

[0018] In the above solution, the second sheath is provided with 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 from the transparent portion of the second sheath to be exposed from the first opening of the first sheath, so as to distinguish it from an unused state.

[0019] In the above solution, the axial lengths of the front guide groove portion and the oblique guide surface are both greater than the axial length of the rear guide groove portion, so that the pressing trigger stage has a larger stroke. Even if it is accidentally touched (not pressed to near the 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 an anti-accidental touch function.

[0020] The present invention provides a guide groove on a stationary needle seat, and provides a blocking guide surface on a second sheath that only moves axially. As a core component that achieves locking through circumferential rotation, only a first protrusion and a second protrusion are provided on the transmission ring. During the operation, the first protrusion cooperates with the blocking guide surface, and the second protrusion cooperates with the guide groove, both in the form of the protrusion sliding on the guide surface. The guide surface is stationary, and it is the protrusion that moves, so that the transmission ring rotates smoothly; and the rear end of the spring is against the completely stationary rear end of the needle seat, so that the reset action of the spring is also stable, will not deviate, and the rotation of the transmission ring is not blocked; thereby, the action is more reliable and stable; after use, even if the second sheath is pressed again, the second sheath moves backward and drives 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 being exposed. After releasing the second sheath, under the reset action of the spring, the transmission ring moves to the end position of the inclined guide section of the second sheath, so that the transmission ring is exposed from the first sheath, which is different from before use. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic diagram of the overall three-dimensional appearance of an embodiment of the present invention;

[0022] FIG2 is an exploded schematic diagram of an embodiment of the present invention;

[0023] FIG3 is a perspective schematic diagram of a second sheath according to an embodiment of the present invention;

[0024] FIG4 is a perspective schematic diagram of a first sheath according to an embodiment of the present invention;

[0025] FIG5 is a perspective schematic diagram of a transmission ring according to an embodiment of the present invention;

[0026] FIG6 is a perspective schematic diagram of a needle holder according to an embodiment of the present invention;

[0027] FIG7 is a cross-sectional view of an embodiment of the present invention in an initial state before use, with the outer shell and the first sheath removed;

[0028] FIG8 is a schematic perspective view of a radial section of an embodiment of the present invention in an initial state before use, with the outer shell removed;

[0029] FIG9 is a partially cutaway perspective view of an embodiment of the present invention in its initial state before use, with the outer shell removed;

[0030] FIG10 is a second partially cutaway perspective view of an embodiment of the present invention in an initial state before use, with the outer shell and the second sheath removed;

[0031] FIG11 is a schematic diagram of the relative positions of the transmission ring and the second sheath in an initial state before use according to an embodiment of the present invention;

[0032] FIG12 is a schematic diagram of the relative positions of the transmission ring and the needle seat in an initial state before use according to an embodiment of the present invention;

[0033] FIG13 is a cross-sectional view of the embodiment of the present invention when the second sheath is moved back to the limit state during use, with the outer shell removed;

[0034] FIG14 is a partially cutaway perspective view of the embodiment of the present invention when the second sheath is moved back to the limit state, with the outer shell removed;

[0035] FIG15 is a schematic diagram of the relative positions of the transmission ring and the second sheath when the second sheath is moved back to the limit state in use according to an embodiment of the present invention;

[0036] FIG16 is a schematic diagram showing the relative positions of the transmission ring and the needle seat when the second sheath is moved back to the limit state during use of the embodiment of the present invention;

[0037] FIG17 is a cross-sectional view of the second sheath in a restored state after use according to an embodiment of the present invention, with the outer shell removed;

[0038] FIG18 is a partially cutaway perspective view of the second sheath in a reset state during use of the embodiment of the present invention, with the outer shell removed;

[0039] FIG19 is a schematic diagram of the relative positions of the transmission ring and the second sheath in the reset state of the second sheath when in use according to an embodiment of the present invention;

[0040] FIG20 is a schematic diagram of the relative positions of the transmission ring and the needle seat in the reset state of the second sheath during use of an embodiment of the present invention;

[0041] FIG21 is a cross-sectional view of a state where the second sheath is pressed down again after the second sheath is reset after use according to an embodiment of the present invention, with the outer shell removed;

[0042] FIG22 is a partially cutaway perspective view of a state where the second sheath is pressed down again after the second sheath is reset after use according to an embodiment of the present invention, with the outer shell removed;

[0043] FIG23 is a schematic diagram of the relative positions of the transmission ring and the second sheath in a state where the second sheath is pressed down again after the second sheath is reset after use according to an embodiment of the present invention;

[0044] 24 is a schematic diagram of the relative positions of the transmission ring and the needle seat in a state where the second sheath is pressed down again after the second sheath is reset after use according to an embodiment of the present invention.

[0045] In the above figure:

[0046] 1. Needle seat; 11. Needle tube; 12. Annular protrusion; 13. Guide groove; 131. Front guide groove portion; 132. Rear guide groove portion; 133. Oblique guide surface; 134. Locking surface; 1341. Front protrusion; 14. Spring mounting surface;

[0047] 2. First sheath; 21. First opening; 22. Guide rib; 23. Snap-fit ​​portion;

[0048] 3. Second sheath; 31. Second opening; 32. Guide groove; 33. Blocking guide surface; 331. Plane guide section; 332. Inclined guide section; 333. Transition surface; A. Initial position; B. End position;

[0049] 4. Spring;

[0050] 5. Shell;

[0051] 6. Transmission ring; 61. First protrusion; 62. Second protrusion;

[0052] R, accommodation space; DETAILED DESCRIPTION

[0053] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0054] Example: See Figure 1-24:

[0055] A safety injection needle, as shown in FIG2 , comprises a needle seat 1 , a first sheath 2 , a second sheath 3 , a housing 5 , a spring 4 and a transmission ring 6 .

[0056] 2 , the needle seat 1 is provided with an axially extending needle tube 11 , with the needle tube head pointing in the forward direction and the reverse direction pointing in the backward direction.

[0057] Referring to Figures 7, 9 and 13, the first sheath 2 is placed on the needle seat 1, with its rear end fixedly connected to the needle seat 1 and a first opening 21 provided at its front end; the needle tube 11 of the needle seat 1 extends from the first opening 21, forming an accommodating space R between the first sheath 2 and the needle seat 1; the rear end of the second sheath 3 is located in the accommodating space R, and its front end has a second opening 31 and extends from the first opening 21, and the second sheath 3 is axially slidably connected relative to the first sheath 2.

[0058] Specifically, the preferred sliding connection between the second sheath 3 and the first sheath 2 is as follows: as shown in Figures 3, 4 and 8, a guide rib 22 extending axially is provided on the inner wall of the first sheath 2, and a guide groove 32 is provided on the outer wall of the second sheath 3 corresponding to the guide rib 22. The first sheath 2 and the second sheath 3 achieve sliding connection through the guiding cooperation of the guide rib 22 and the guide groove 32.

[0059] Referring to Figures 2, 6, 13, 17 and 21, specifically, a circumferential annular protrusion 12 is provided on the rear end of the needle seat 1, and a corresponding snap-fitting portion 23 is provided on the inner wall of the rear end of the first sheath 2. The first sheath 2 and the needle seat 1 are connected by the snap-fitting portion 23 and the annular protrusion 12.

[0060] Referring to Figures 5, 7, and 8, the transmission ring 6 is positioned between the inner wall of the rear port of the second sheath 3 and the needle hub 1. The transmission ring 6 has at least one (preferably two, as shown) first protrusion 61 circumferentially disposed on its outer wall, and at least one (preferably two, as shown) second protrusion 62 circumferentially disposed on its inner wall. The first protrusion 61 protrudes radially outward from the transmission ring 6, with its forward-facing end surface serving as an active surface. The second protrusion 62 protrudes radially inward from the transmission ring 6, with its side surfaces and rearward-facing end surface serving as active surfaces.

[0061] Referring to Figures 3 and 15 , a blocking guide surface 33 is provided on the inner wall of the second sheath 3, 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 on the axial cross-section of the second sheath 3 is essentially a straight line perpendicular to the axial direction, while the projection of the inclined guide section 332 on the axial cross-section of the second sheath 3 is an oblique line at an angle to the axial direction. One end of the planar guide section 331 is set to the initial position A, and its other end is connected to one end of the inclined guide section 332. The other end of the inclined guide section 332 is set to the terminal position B. The inclined guide section 332 is inclined from the planar guide section 331 toward the front end of the second sheath 3.

[0062] 6 and 12 , a guide groove 13 extending in the axial direction is provided on the outer circumference of the needle seat 1 corresponding to the second protrusion 66. As shown in FIG6 , the guide groove 13 includes a front end guide groove portion 131 and a rear end guide groove portion 132. The front end guide groove portion 131 is larger in the circumferential direction than the rear end guide groove portion 132. One side wall of the front end guide groove portion 131 and the same side wall of the rear end guide groove portion are transitionally connected by an oblique guide surface 133. A locking surface 134 facing the front side is provided on the front end of the other side of the front end guide groove portion.

[0063] As shown in Figure 7, the spring 4 is sleeved on the needle seat 1, and a spring mounting surface 14 is provided on the needle seat 1 corresponding to the rear end of the spring 4, and 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.

[0064] The locking surface 134 corresponds to the end point B of the inclined guide section 332, and the circumferential width of the locking surface 134 is greater than the circumferential width of the end point B of the inclined guide section 332, so that after the first protrusion 61 slides into the end point, it presses the second sheath 3 again to ensure that the second protrusion 62 is opposite to the locking surface 134, so that the second sheath 3 cannot retract again due to the obstruction of the locking surface 134.

[0065] In the initial state before use, the first protrusion 61 of the transmission ring 6 is located at the initial position A blocking the guide surface 33, see Figures 9 and 11, and the second protrusion 62 is opposite to the side wall of the oblique guide surface 133 of the front end guide groove portion 131 of the needle seat 1, see Figure 12.

[0066] During use, the outer shell 5 is removed, and the second shield 3 is moved backward by external force (i.e., the injection needle is pressed toward the human skin for puncture). Its blocking guide surface 33 engages with the first protrusion 61, pushing the transmission ring 6 backward as well. The second protrusion 62 slides into the front guide groove 131. The engagement of the second protrusion 62 with the inclined guide surface 133 (see Figure 16) causes the transmission ring 6 to rotate circumferentially. Finally, when the second shield 3 reaches its rearward limit, as shown in Figures 13, 14, 15, and 16, 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 point, the front end of the second shield 3 is substantially flush with the front end of the first shield 2, allowing the needle tube 11 to penetrate the human skin over its maximum distance.

[0067] After use, the second sheath 3 and the transmission ring 6 are extended forward and reset under the action of the spring 4 (that is, the injection is completed and the needle is moved away from the skin). The second protrusion 62 reaches the front end of the front guide groove portion 131 and is free 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 is rotated to be opposite to the locking surface 134. At this time, referring to Figures 17, 18, 19 and 20, the second protrusion 62 of the transmission ring 6 is located in front of the locking surface 134 and the two are opposite to each other. The first protrusion 61 reaches the end position B of the inclined guide section 332, that is, the use is completed.

[0068] If the second sheath 3 is pressed again, the second sheath 3 moves backward and abuts against the locking surface 134. It cannot retract again due to the obstruction of the locking surface 134. The state at this time is shown in Figures 21, 22, 23 and 24. The second sheath 3 always covers the tip of the needle tube 11, achieving the protection function of prohibiting secondary use.

[0069] 20 , a front protrusion 1341 is provided at the junction of the locking surface 134 and the front guide groove portion 131 , so that the locking surface 134 is concave, making the locking surface 134 more stable in restricting the positioning of the second protrusion 62 .

[0070] As shown in Figure 3 , 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. This allows the first protrusion 61 to abut against the axial transition surface 333 when the second sheath 3 moves rearward to its limit. This transition surface 333 acts as a stop, preventing the first protrusion 61 from sliding back toward the planar guide section 331 during upward movement of the transmission ring 6 under the action of the spring, thereby preventing secondary use and ensuring more reliable operation.

[0071] As shown in FIG3 , the initial position A of the blocking guide surface 33 is also designed to be slightly concave, which makes it easier to position and facilitate assembly during initial assembly.

[0072] As shown in FIG6 , the axial lengths of the front guide groove portion 131 and the oblique guide surface 133 are both greater than the axial length of the rear guide groove portion 132, so that the pressing trigger stage has a larger stroke. Even if it is accidentally touched (not pressed to near the 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 an anti-accidental touch function.

[0073] Specifically, the second sheath 3 is entirely made of a transparent material or has a transparent portion thereon. After use, when the second sheath 3 and transmission ring 6 are extended and reset by the spring, and the first protrusion 61 reaches the end point B of the inclined guide section, the transmission ring 6 can be seen through the transparent portion of the second sheath 3, emerging from the first opening 21 of the first sheath 2, as shown in FIG17 , thereby distinguishing the second sheath 3 from an unused injection needle.

[0074] This embodiment has the following advantages:

[0075] 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. Subsequently, the second sheath 3 cannot move backward again, thus protecting the tip of the needle tube 11 and achieving the protection function of preventing secondary use;

[0076] 2. Good working stability and high safety;

[0077] 3. The structure is relatively simple;

[0078] 4. Easy to assemble and can be automated;

[0079] 5. It feels better and more comfortable when used.

[0080] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the present invention and implement it accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications based on the spirit and essence of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A safety injection needle, comprising a needle hub, a first shield, a second shield, and a spring; an axially extending needle tube is disposed on the needle hub; the first shield is positioned over the needle hub, with its rear end fixedly connected to the needle hub and a first opening defined at its front end; the needle tube of the needle hub extends through the first opening, with a receiving space formed between the first shield and the needle hub; the rear end of the second shield is positioned within the receiving space, with its front end having a second opening and extending from the first opening; the second shield is axially slidably connected relative to the first shield; and characterized in that: A transmission ring is provided between the rear port of the second sheath and the needle seat, and at least one first protrusion is provided on the circumference of the outer wall of the transmission ring, and at least one second protrusion is provided on the circumference of the inner wall of the transmission ring; A blocking guide surface is provided on the inner wall of the second sheath corresponding to the first protrusion, the blocking guide surface including a planar guide section and an inclined guide section, one end of the planar guide section is set to an initial position, and the other end thereof is connected to one end of the inclined guide section, and the inclined guide section is inclined toward the front end of the second sheath, and the other end of the inclined guide section is set to an end position; A guide groove extending in the axial direction is provided on the outer circumference of the needle seat corresponding to the second protrusion, the guide groove comprising a front guide groove portion and a rear guide groove portion, the front guide groove portion being larger in the circumferential direction than the rear guide groove portion, a side wall of the front guide groove portion and the same side wall of the rear guide groove portion being transitionally connected by an oblique guide surface, and a locking surface facing forward is provided on the front end of the other side of the front guide groove portion; The spring is sleeved on the needle seat, and a spring mounting surface is provided on the needle seat corresponding to the rear end of the spring, and 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 at the initial position of the blocking guide surface, and the second protrusion is opposite to the side wall of the front end guide groove portion of the needle seat close to the oblique 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 to push the transmission ring backward, and the second protrusion slides into the front end guide groove portion, and through the cooperation of the second protrusion and the oblique guide surface, the transmission ring is pushed to rotate circumferentially; when the second sheath moves backward to the limit, the first protrusion slides to the oblique guide section of the blocking guide surface, and the second protrusion slides to the rear end of the rear end guide groove portion; after use, the second sheath and the transmission ring extend and reset under the action of the spring, and the second protrusion slides to the front end of the front end guide groove portion. Under the sliding cooperation of the first protrusion and the oblique guide section, the second protrusion rotates to be opposite to 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 surface 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 surface guide section in the circumferential direction.

3. The safety injection needle according to claim 2, characterized in that: A front protrusion is provided at the junction of the locking surface and the front guide groove portion, 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 plane guide section and the inclined guide section of the blocking guide surface, so that when the second sheath moves backward to the limit, the first protrusion abuts against the axial transition surface.

5. The safety injection needle according to claim 1, characterized in that: A circumferential annular protrusion is provided on the rear end of the needle seat, and a corresponding snap-fitting portion is provided on the inner wall of the rear end of the first sheath. The first sheath and the needle seat are connected by the snap-fitting portion and the annular protrusion.

6. The safety injection needle according to claim 1, characterized in that: The second sheath is provided with 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 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 lengths of the front end guide groove portion and the oblique guide surface are both greater than the axial length of the rear end guide groove portion.

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