A dosage limiting device for an injection pen

Abstract

This utility model proposes a metering limiting device for an injection pen, including a housing, with a proximal end at the front end and a distal end at the rear end. The proximal end of the housing is equipped with a screw injection mechanism, and the distal end is equipped with a fixed end cap. A screw sleeve is fitted inside the housing, passing sequentially through the fixed end cap, an adjustment knob, and an injection button. The adjustment knob is connected to the distal end of the housing. The screw injection mechanism includes a threaded screw, with a push block connected to the end of the screw near the proximal end and a limiting block connected to the end of the screw near the distal end. The screw itself is fitted with a metering limiting mechanism, the outer periphery of which is fitted and radially connected to the inner wall of the screw sleeve. The metering limiting mechanism has a hollow cylindrical structure, with a helix on its inner wall. The screw rotates in conjunction with the helix. The limiting block abuts against the metering limiting mechanism, restricting its rotation.

Description

Technical Field

[0001] This utility model relates to the field of adjustable dosage injection device technology, and more specifically, to a dosage limiting device for an injection pen. Background Technology

[0002] The adjustable dosing injection device comprises a dosing adjustment and injection mechanism and a cartridge retaining mechanism. When adjusting the dosing, the user rotates a dosing adjustment element on the dosing pouring mechanism; the force applied by the user is stored in a torsion spring for subsequent dispensing. To dispensing the adjusted dose, the user presses a dispensing button on the proximal end of the syringe; the torsional force accumulated in the torsion spring is then delivered to the drive element to propel the liquid out of the injection device.

[0003] A Chinese invention patent with publication number CN118490935A discloses a dosage limiting device for an injection pen, including a housing. The front end of the housing is a proximal end, and the rear end of the housing is a distal end. The distal end of the housing is provided with a fixed end cap, which is sleeved with a screw support 141. One end of the screw support 141 passes through the fixed end cap and is connected to a dosage setting element. A dosage display bracket is sleeved on the outer periphery of the screw support 141, and the dosage display bracket and the fixed end cap are engaged by ratchet teeth with beveled ends, so that the screw support 141 can only move back and forth along the axial direction relative to the dosage setting element and the dosage display bracket. The dosage setting element is connected to the distal end of the housing, so that the dosage setting element can only rotate relative to the housing. A torsion spring is provided between the screw support 141 and the dosage display bracket. One end of the torsion spring is connected to the proximal end of the dosage display bracket near the housing, and the other end is connected to the fixed end cap.

[0004] However, existing patents may have issues with the torsion spring releasing energy for injection. Excessive spring force could exceed the maximum set dosage, resulting in inaccurate administration of the last injection. Therefore, setting an accurate maximum injection dosage has become a problem that needs to be solved. Utility Model Content

[0005] In view of this, the present invention proposes a measurement limiting device for an injection pen, comprising a housing 10, the front end of which is the proximal end and the rear end of which is the distal end. The proximal end of the housing 10 is provided with a screw injection mechanism 14, and the distal end of the housing 10 is provided with a fixed end cap 20. A screw sleeve 30 is fitted inside the housing 10, and the screw sleeve 30 passes sequentially through the fixed end cap 20, an adjusting knob 50, and an injection button 80. The adjusting knob 50 is connected to the distal end of the housing 10. The screw injection mechanism 14 includes a threaded screw 142, and a pusher block 1 is connected to the end of the screw 142 near the proximal end. 47. A limiting block 148 is connected to the end of the screw 142 near its distal end. The screw 142 itself is fitted with a metering limiting mechanism 149. The outer periphery of the metering limiting mechanism 149 is fitted with and radially connected to the inner wall of the screw sleeve 30. The metering limiting mechanism 149 has a hollow cylindrical structure. The inner wall of the metering limiting mechanism 149 is provided with a spiral. The screw 142 rotates in cooperation with the spiral. The limiting block 148 abuts against the metering limiting mechanism 149 to limit the rotation of the metering limiting mechanism 149. The metering setting is completed to prevent the maximum amount of medicine in the cartridge from being exceeded during the metering setting, which would cause inaccurate metering of the last injection.

[0006] A metering limiting device for an injection pen includes a housing 10, with a proximal end at the front end and a distal end at the rear end. A screw injection mechanism 14 is provided at the proximal end of the housing 10. A screw sleeve 30 is fitted inside the housing 10. The screw injection mechanism 14 includes a threaded screw 142. A push block 147 is connected to the end of the screw 142 near the proximal end, and a limiting block 148 is connected to the end of the screw 142 near the distal end. A metering device is fitted onto the screw 142 itself. The metering limiting mechanism 149 is fitted around the inner wall of the screw sleeve 30 and radially connected. The metering limiting mechanism 149 has a hollow cylindrical structure and a spiral line on its inner wall. The screw 142 rotates in cooperation with the spiral line. The limiting block 148 abuts against the metering limiting mechanism 149 to limit its rotation. The metering setting is completed to prevent the maximum amount of medicine in the cartridge from being exceeded during the metering setting, which would cause inaccurate metering during the last injection.

[0007] Furthermore, the end face of the metering limiting mechanism 149 near the distal end is the locking top surface, and the end face of the limiting block 148 near the proximal end is the limiting surface. The distance between the limiting surface and the locking top surface is the remaining maximum dose travel distance of the screw 142.

[0008] Furthermore, the inner wall of the screw sleeve 30 is provided with a fourth groove 33, and the corresponding position of the outer periphery of the metering limiting mechanism 149 is provided with a fourth rib 1491. The fourth groove 33 and the fourth rib 1491 are matched and connected, so that the metering limiting mechanism 149 can only move back and forth along the axial direction relative to the screw sleeve 30. By adjusting the back and forth position of the metering limiting mechanism 149 relative to the screw sleeve 30, the displacement of the screw 142 is limited, thereby limiting the maximum injection volume of the injection pen.

[0009] In some embodiments, a fixed end cap 20 is provided at the distal end of the housing 10. A screw sleeve 30 is fitted inside the housing 10. The screw sleeve 30 passes sequentially through the fixed end cap 20, an adjusting knob 50, and an injection button 80. The adjusting knob 50 is connected to the distal end of the housing 10 and can only rotate relative to the housing 10. A torsion spring 70, a dose scale bracket 60, and a dose display element 90 are sequentially fitted around the outer periphery of the screw sleeve 30 from the inside to the outside. The dose display element 90 is helically connected to the housing 10. One end of the torsion spring 70 is connected to the proximal end of the dose scale bracket 60 near the housing 10, and the other end is connected to the fixed end cap 20. When adjusting the dosage, the forward selection knob 50 drives the screw sleeve 30, the dosage scale support 60, and the dosage display element 90 to rotate synchronously, and stores energy in the torsion spring 70. The dosage display element 90 moves closer to the body along the thread of the housing 10. When injecting, the screw sleeve 30 disengages from the injection button 80. The screw sleeve 30 moves closer to the body until it engages with the screw injection mechanism 14 for injection. The torsion spring 70 releases energy, and the screw sleeve 30, the dosage scale support 60, the dosage display element 90, and the adjustment knob 50 rotate in opposite directions. The dosage display element 90 moves further to the body along the thread of the housing 10.

[0010] In some embodiments, the outer periphery of the fixed end cap 20 is provided with a plurality of first hooks 21, and the corresponding position of the distal end of the housing 10 is provided with a first slot 11 that is engaged with it, and the first hooks 21 and the first slots 11 are matched and engaged.

[0011] Furthermore, the outer periphery of the fixed end cap 20 is provided with a first protrusion 22, and the corresponding position of the distal end of the housing 10 is provided with a first notch 12. When the housing 10 and the fixed end cap 20 are matched and installed, the first protrusion 22 is engaged with the first notch 12, thereby enhancing the connection between the fixed end cap 20 and the housing 10.

[0012] Furthermore, a first torsion spring mounting seat 23 is provided on the inner wall of the fixed end cover 20 for fixing one end of the torsion spring.

[0013] In some embodiments, the outer periphery of the dose scale support 60 is provided with a plurality of parallel first ribs 61 arranged at intervals along the axial direction, which are used to match and connect with the first groove on the inner wall of the dose display element 90. The dose display element 90 is rotatably connected to the inner wall of the housing 10, so that the dose display element 90 can only move back and forth along the axial direction relative to the dose scale support 60. The housing 10 is provided with a dose display window, which cooperates with the dose display element 90 to display the required injection dose and the injection volume during the injection process.

[0014] In some embodiments, the inner wall of the dose scale support 60 is provided with a second groove 63 near the proximal end of the housing 10, and the screw sleeve 30 is provided with a second rib 31 at the corresponding position. The second groove 63 and the second rib 31 are matched and connected, so that the screw sleeve 30 can only move back and forth along the axial direction relative to the dose scale support 60.

[0015] In some embodiments, the screw sleeve 30 is provided with a third rib 32 at the distal end near the housing 10, and the inner wall of the adjusting knob 50 is provided with a third groove at a corresponding position. The third groove is matched and connected with the third rib 32, so that the screw sleeve 30 can only move back and forth along the axial direction relative to the adjusting knob 50.

[0016] In some embodiments, the screw injection mechanism 14 includes a screw support 141, which is sleeved on a screw 142. The screw 142 passes through the screw support 141 and is sleeved on its lower anti-reverse mechanism 143. The anti-reverse mechanism 143 has a through hole 144 at its center to prevent axial rotation. The cross-section of the screw 142 is the through hole to prevent axial rotation, so that the rotation of the anti-reverse mechanism 143 can drive the screw 142 to rotate. When injection begins... At this time, the lower part of the anti-reverse mechanism 143 engages with the screw sleeve 30, and the screw sleeve 30 drives the anti-reverse mechanism 143 to rotate, thereby driving the screw 142 to rotate. Meanwhile, since the inner ring of the screw support 141 is a hollow structure and the inner wall of the inner ring is provided with internal threads, the inner ring is threadedly connected to the screw 142, and the outer periphery of the screw support 141 cooperates with the inner wall of the housing 10, so that when the screw 142 rotates, it can move towards the end near the body under the action of the inner ring thread.

[0017] Furthermore, the anti-reverse mechanism 143 is provided with a spring arm 145 around its outer periphery, and the free end of the spring arm 145 is provided with an outwardly protruding pawl 146. The inner wall of the housing 10 is provided with evenly spaced pawl blocks corresponding to the position of the anti-reverse mechanism 143. The anti-reverse mechanism 143 can only drive the pawl 146 to rotate in the forward direction, but cannot rotate in the reverse direction.

[0018] Working principle: During assembly, the distance between the locking surface of the metering limiting mechanism 149 and the limiting surface of the screw 142 is pre-set according to the amount of medicine in the matching cartridge bottle, i.e., the maximum stroke, to prevent the maximum amount of medicine in the cartridge bottle from being exceeded during metering setting, resulting in inaccurate dosage for the last injection. When the adjustment knob 50 adjusts the metering, the fourth groove 33 and the fourth rib 1491 inside the screw 142 sleeve cooperate to drive the screw 142 sleeve to rotate. The spiral of the metering limiting mechanism 149 rotates in coordination with the spiral of the screw 142 sleeve. When there is not much medicine left in the cartridge bottle, it ensures that the dosage display element 90 can only rotate to the remaining dosage number. The locking surface of the metering limiting mechanism 149 contacts the limiting surface of the screw 142, restricting the rotation of the metering limiting mechanism 149, thereby restricting the rotation of the screw 142 sleeve and the adjustment knob 50, ensuring that the dosage display element 90 can only rotate to the remaining dosage number.

[0019] The beneficial effects of this utility model are as follows: This utility model proposes a metering limiting device for an injection pen, including a housing 10. The front end of the housing 10 is a proximal end, and the rear end of the housing 10 is a distal end. The proximal end of the housing 10 is provided with a screw injection mechanism 14, and the distal end of the housing 10 is provided with a fixed end cap 20. A screw sleeve 30 is fitted inside the housing 10. The screw injection mechanism 14 includes a threaded screw 142. The end of the screw 142 near the proximal end is connected to a push block 147, and the end of the screw 142 near the distal end is connected to a limiting block 1. 48. The screw 142 itself is fitted with a metering limiting mechanism 149. The outer periphery of the metering limiting mechanism 149 is fitted with the inner wall of the screw sleeve 30 and radially connected. The metering limiting mechanism 149 is a hollow cylindrical structure. The inner wall of the metering limiting mechanism 149 is provided with a spiral. The screw 142 rotates in cooperation with the spiral. The limiting block 148 abuts against the metering limiting mechanism 149 to limit the rotation of the metering limiting mechanism 149. The metering setting is completed to prevent the maximum amount of medicine in the cartridge from being exceeded during the metering setting, which would cause inaccurate metering of the last injection. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of the injection pen of this utility model.

[0021] Figure 2 This is an exploded view of the overall metering limiting device of the injection pen of this utility model.

[0022] Figure 3 This diagram shows the connection between the anti-reverse mechanism and the screw of the metering limiting device for the injection pen of this invention.

[0023] Figure 4 This is a structural diagram of the anti-reverse mechanism of the metering limiting device for the injection pen of this utility model.

[0024] Figure 5 This is a cross-sectional view showing the connection between the metering limiting mechanism and the screw in the metering limiting device of the injection pen of this utility model.

[0025] Figure 6 This is a structural diagram showing the connection between the metering limiting mechanism and the screw in the metering limiting device of the injection pen of this utility model.

[0026] Figure 7 This is a structural diagram of the fixed end cap of the metering limiting device for the injection pen of this utility model.

[0027] Figure 8 This is a structural diagram of the dosage scale support of the dosage limiting device for the injection pen of this utility model.

[0028] Figure 9 This is a structural diagram of the screw sleeve of the metering limiting device for the injection pen of this utility model.

[0029] Explanation of main component symbols

[0030] Housing 10; First slot 11; First notch 12; Screw injection mechanism 14; Screw support 141; Screw 142; Anti-reverse mechanism 143; Through hole 144 to prevent axial rotation; Spring arm 145; Pawl 146; Push block 147; Limit block 148; Metering limiting mechanism 149; Fourth rib 1491; Fixed end cap 20; First hook 21; First protrusion 22; First torsion spring mounting seat 23; Screw sleeve 30; Second rib 31; Third rib 32; Fourth groove 33; Adjustment knob 50; Dosage scale support 60; First rib 61; Second groove 63; Torsion spring 70; Injection button 80; Dosage display element 90.

[0031] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this utility model. Detailed Implementation Example 1

[0032] like Figure 1 , Figure 2 , Figure 5 and Figure 6As shown, a metering limiting device for an injection pen includes a housing 10, with a proximal end and a distal end. The proximal end of the housing 10 is provided with a screw injection mechanism 14. A screw sleeve 30 is fitted inside the housing 10. The screw injection mechanism 14 includes a threaded screw 142. A push block 147 is connected to the end of the screw 142 near the proximal end, and a limiting block 148 is connected to the end of the screw 142 near the distal end. A metering device is fitted onto the screw 142 itself. The metering limiting mechanism 149 is radially connected to the inner wall of the screw sleeve 30, and has a hollow cylindrical structure. The inner wall of the metering limiting mechanism 149 is provided with a spiral line. The screw 142 rotates in cooperation with the spiral line. The limiting block 148 abuts against the metering limiting mechanism 149 to limit its rotation. The metering setting is completed to prevent the maximum amount of medicine in the cartridge from being exceeded during the metering setting, which would cause inaccurate metering during the last injection.

[0033] The end face of the metering limiting mechanism 149 near the distal end is the locking top surface, and the end face of the limiting block 148 near the proximal end is the limiting surface. The distance between the limiting surface and the locking top surface is the remaining maximum dose travel distance of the screw 142.

[0034] like Figure 5 and Figure 9 As shown, the inner wall of the screw sleeve 30 is provided with a fourth groove 33, and the corresponding position of the outer periphery of the metering limiting mechanism 149 is provided with a fourth rib 1491. The fourth groove 33 and the fourth rib 1491 are matched and connected, so that the metering limiting mechanism 149 can only move back and forth along the axial direction relative to the screw sleeve 30. By adjusting the back and forth position of the metering limiting mechanism 149 relative to the screw sleeve 30, the displacement of the screw 142 is limited, thereby limiting the maximum injection volume of the injection pen.

[0035] like Figure 1 , Figure 2 and Figure 8 As shown,

[0036] The distal end of the housing 10 is provided with a fixed end cap 20. A screw sleeve 30 is fitted inside the housing 10. The screw sleeve 30 passes sequentially through the fixed end cap 20, the adjusting knob 50, and the injection button 80. The adjusting knob 50 is connected to the distal end of the housing 10 and can only rotate relative to the housing 10. From the inside to the outside, a torsion spring 70, a dose scale bracket 60, and a dose display element 90 are sequentially fitted around the outer periphery of the screw sleeve 30. The dose display element 90 is spirally connected to the housing 10. One end of the torsion spring 70 is connected to the proximal end of the dose scale bracket 60 near the housing 10, and the other end is connected to the fixed end cap 20. When injection... When adjusting the dosage, the forward selection knob 50 drives the screw sleeve 30, the dosage scale support 60, and the dosage display element 90 to rotate synchronously, and stores energy in the torsion spring 70. The dosage display element 90 moves towards the proximal end along the thread of the housing 10. When injection is performed, the screw sleeve 30 disengages from the injection button 80. The screw sleeve 30 moves towards the proximal end until it engages with the screw injection mechanism 14 for injection. The torsion spring 70 releases energy, and the screw sleeve 30, the dosage scale support 60, the dosage display element 90, and the adjustment knob 50 rotate in opposite directions. The dosage display element 90 moves towards the distal end along the thread of the housing 10.

[0037] The fixed end cap 20 has a plurality of first hooks 21 on its outer periphery. The corresponding position of the distal end of the housing 10 has a first slot 11 that engages with it. The first hooks 21 and the first slots 11 are matched and engaged. The fixed end cap 20 also has a first protrusion 22 on its outer periphery. The corresponding position of the distal end of the housing 10 has a first notch 12. When the housing 10 and the fixed end cap 20 are matched and installed, the first protrusion 22 engages with the first notch 12 to enhance the connection between the fixed end cap 20 and the housing 10. The inner wall of the fixed end cap 20 has a first torsion spring mounting seat 23 for fixing one end of the torsion spring.

[0038] like Figure 1 , Figure 2 and Figure 8As shown, the outer periphery of the dose scale support 60 is provided with multiple parallel first ribs 61 arranged at intervals along the axial direction, which are used to match and connect with the first groove on the inner wall of the dose display element 90. The dose display element 90 is rotatably connected to the inner wall of the housing 10, so that the dose display element 90 can only move back and forth along the axial direction relative to the dose scale support 60. The housing 10 is provided with a dose display window, which cooperates with the dose display element 90 to display the required injection dose and the injection volume during the injection process. The inner wall of the dose scale support 60 is provided with a second groove 63 near the proximal end of the housing 10, and the screw sleeve 30 is provided with a second rib 31 at the corresponding position. The second groove 63 and the second rib 31 are matched and connected, so that the screw sleeve 30 can only move back and forth along the axial direction relative to the dose scale support 60.

[0039] like Figure 1 , Figure 2 As shown, the screw sleeve 30 is provided with a third rib 32 at the far end near the housing 10, and the inner wall of the adjusting knob 50 is provided with a third groove at the corresponding position. The third groove is matched and connected with the third rib 32, so that the screw sleeve 30 can only move back and forth along the axial direction relative to the adjusting knob 50.

[0040] like Figure 3 , Figure 4 As shown, the screw injection mechanism 14 includes a screw support 141, which is sleeved with a screw 142. The screw 142 passes through the screw support 141 and is sleeved with an anti-reverse mechanism 143 at its lower part. The anti-reverse mechanism 143 has a through hole 144 at its center to prevent axial rotation. The cross-section of the screw 142 body is the through hole to prevent axial rotation, so that the rotation of the anti-reverse mechanism 143 can drive the screw 142 to rotate. When injection begins, the lower part of the anti-reverse mechanism 143 engages with the screw sleeve 30, and the screw sleeve 30 drives the anti-reverse mechanism 143 to rotate, thereby driving the screw 142 to rotate. Meanwhile, since the inner ring of the screw support 141 is a hollow structure and the inner wall of the inner ring is provided with internal threads, the inner ring is threadedly connected to the screw 142, and the outer periphery of the screw support 141 cooperates with the inner wall of the housing 10, so that when the screw 142 rotates, it can move towards the end under the action of the inner ring threads. The outer periphery of the anti-reverse mechanism 143 is provided with a spring arm 145, and the free end of the spring arm 145 is provided with an outwardly protruding pawl 146. The inner wall of the housing 10 is provided with evenly spaced ratchet blocks corresponding to the position of the anti-reverse mechanism 143. The anti-reverse mechanism 143 can only drive the pawl 146 to rotate in the forward direction and cannot rotate in the reverse direction.

[0041] Working principle: During assembly, the distance between the locking surface of the metering limiting mechanism 149 and the limiting surface of the screw 142 is pre-set according to the amount of medicine in the matching cartridge bottle, i.e., the maximum stroke, to prevent the maximum amount of medicine in the cartridge bottle from being exceeded during metering setting, resulting in inaccurate dosage for the last injection. When the adjustment knob 50 adjusts the metering, the fourth groove 33 and the fourth rib 1491 inside the screw 142 sleeve cooperate to drive the screw 142 sleeve to rotate. The spiral of the metering limiting mechanism 149 rotates in coordination with the spiral of the screw 142 sleeve. When there is not much medicine left in the cartridge bottle, it ensures that the dosage display element 90 can only rotate to the remaining dosage number. The locking surface of the metering limiting mechanism 149 contacts the limiting surface of the screw 142, restricting the rotation of the metering limiting mechanism 149, thereby restricting the rotation of the screw 142 sleeve and the adjustment knob 50, ensuring that the dosage display element 90 can only rotate to the remaining dosage number.

[0042] The beneficial effects of this utility model are as follows: This utility model proposes a metering limiting device for an injection pen, including a housing 10. The front end of the housing 10 is a proximal end, and the rear end of the housing 10 is a distal end. The proximal end of the housing 10 is provided with a screw injection mechanism 14, and the distal end of the housing 10 is provided with a fixed end cap 20. A screw sleeve 30 is fitted inside the housing 10. The screw injection mechanism 14 includes a threaded screw 142. The end of the screw 142 near the proximal end is connected to a push block 147, and the end of the screw 142 near the distal end is connected to a limiting block 1. 48. The screw 142 itself is fitted with a metering limiting mechanism 149. The outer periphery of the metering limiting mechanism 149 is fitted with the inner wall of the screw sleeve 30 and radially connected. The metering limiting mechanism 149 is a hollow cylindrical structure. The inner wall of the metering limiting mechanism 149 is provided with a spiral. The screw 142 rotates in cooperation with the spiral. The limiting block 148 abuts against the metering limiting mechanism 149 to limit the rotation of the metering limiting mechanism 149. The metering setting is completed to prevent the maximum amount of medicine in the cartridge from being exceeded during the metering setting, which would cause inaccurate metering of the last injection.

[0043] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A dose limiting device for an injection pen, comprising a housing (10), the proximal end of the housing (10) being the front end, the distal end of the housing (10) being the rear end, the proximal end of the housing (10) being provided with a screw injection mechanism (14), a screw sleeve (30) being sleeved in the housing (10), characterized in that: The screw injection mechanism (14) includes a threaded screw (142). A push block (147) is connected to the end of the screw (142) near the proximal end, and a limiting block (148) is connected to the end of the screw (142) near the distal end. A metering limiting mechanism (149) is sleeved on the screw (142). The outer periphery of the metering limiting mechanism (149) is sleeved with the inner wall of the screw sleeve (30) and radially connected. The metering limiting mechanism (149) is a hollow cylindrical structure. A spiral is provided on the inner wall of the metering limiting mechanism (149). The screw (142) rotates in cooperation with the spiral. The limiting block (148) abuts against the metering limiting mechanism (149) to limit the rotation of the metering limiting mechanism (149). The metering setting is completed to prevent the maximum amount of medicine in the cartridge from being exceeded during the metering setting, which would cause inaccurate metering of the last injection.

2. The dosage limiting device for the injection pen as described in claim 1, characterized in that: The end face of the metering limiting mechanism (149) near the distal end is the locking top surface, and the end face of the limiting block (148) near the proximal end is the limiting surface. The distance between the limiting surface and the locking top surface is the remaining maximum dose of the screw (142) moving distance.

3. The dosage limiting device for the injection pen as described in claim 2, characterized in that: The inner wall of the screw sleeve (30) is provided with a fourth groove (33), and the corresponding position of the outer periphery of the metering limiting mechanism (149) is provided with a fourth rib (1491). The fourth groove (33) and the fourth rib (1491) are matched and connected, so that the metering limiting mechanism (149) can only move back and forth along the axial direction relative to the screw sleeve (30). By adjusting the back and forth position of the metering limiting mechanism (149) relative to the screw sleeve (30), the displacement of the screw (142) is limited, thereby limiting the maximum injection volume of the injection pen.

4. The dosage limiting device for the injection pen as described in claim 1, characterized in that: The housing (10) has a fixed end cap (20) at its distal end. The fixed end cap (20) has a plurality of first hooks (21) on its outer periphery. The housing (10) has a corresponding first slot (11) at the corresponding position at its distal end. The first hooks (21) and the first slots (11) are matched and engaged.

5. The dosage limiting device for the injection pen as described in claim 4, characterized in that: The outer periphery of the fixed end cap (20) is also provided with a first protrusion (22), and the corresponding position of the far end of the housing (10) is provided with a first notch (12). When the housing (10) and the fixed end cap (20) are matched and installed, the first protrusion (22) is just engaged with the first notch (12), thereby enhancing the connection between the fixed end cap (20) and the housing (10).

6. The dosage limiting device for the injection pen as described in claim 5, characterized in that: The inner wall of the fixed end cap (20) is provided with a first torsion spring mounting seat (23) for fixing one end of the torsion spring.

7. The dosage limiting device for the injection pen as described in claim 6, characterized in that: The outer periphery of the screw sleeve (30) is sequentially fitted with a torsion spring (70), a dose scale bracket (60), and a dose display element (90) from the inside to the outside. The outer periphery of the dose scale bracket (60) is provided with multiple parallel first ribs (61) arranged at intervals along the axial direction, which are used to match and connect with the first groove on the inner wall of the dose display element (90). The dose display element (90) is rotatably connected to the inner wall of the housing (10), so that the dose display element (90) can only move back and forth along the axial direction relative to the dose scale bracket (60). The housing (10) is provided with a dose display window, which cooperates with the dose display element (90) to display the required injection dose and the injection volume during the injection process.

8. The dosage limiting device for the injection pen as described in claim 7, characterized in that: The inner wall of the dose scale support (60) near the end of the housing (10) is provided with a second groove (63), and the screw sleeve (30) is provided with a second rib (31) at the corresponding position. The second groove (63) and the second rib (31) are matched and connected, so that the screw sleeve (30) can only move back and forth along the axial direction relative to the dose scale support (60).

9. The dosage limiting device for the injection pen as described in claim 8, characterized in that: The screw sleeve (30) passes through the fixed end cap (20), the adjusting knob (50) and the injection button (80) in sequence. The adjusting knob (50) is connected to the distal end of the housing (10). The adjusting knob (50) can only rotate relative to the housing (10). The screw sleeve (30) is provided with a third rib (32) near the distal end of the housing (10). The inner wall of the adjusting knob (50) is provided with a third groove at the corresponding position. The third groove and the third rib (32) are matched and connected, so that the screw sleeve (30) can only move back and forth along the axial direction relative to the adjusting knob (50).

10. The dosage limiting device for the injection pen as described in claim 9, characterized in that: The screw injection mechanism (14) includes a screw support (141), which is sleeved with a screw (142). The screw (142) passes through the screw support (141) and is sleeved with an anti-reverse mechanism (143) at its lower part. The anti-reverse mechanism (143) has a through hole (144) at its center to prevent axial rotation. The cross-section of the screw (142) is the through hole to prevent axial rotation, so that the rotation of the anti-reverse mechanism (143) can drive the screw (142) to rotate. When injection begins, The lower part of the anti-reverse mechanism (143) is engaged with the screw sleeve (30). The screw sleeve (30) drives the anti-reverse mechanism (143) to rotate, thereby driving the screw (142) to rotate. At the same time, since the inner ring of the screw support (141) is a hollow structure, the inner wall of the inner ring is provided with internal threads. The inner ring is threadedly connected to the screw (142). The outer periphery of the screw support (141) cooperates with the inner wall of the housing (10), so that when the screw (142) rotates, it can move towards the near end under the action of the inner ring thread.

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