Lead screw tip for autoinjector

Abstract

An autoinjector medical device may include a housing and a lead screw disposed within the housing. The lead screw can rotate in the shell and axially translate along the axis of the lead screw. The auto-injector medical device may also include a lead screw tip coupled to an end of the lead screw. The lead screw tip may include a first end having at least one extension extending from the first end in a direction parallel to a central axis of the lead screw tip. A tip of the lead screw coupled to the lead screw tip is rotatable within and relative to the lead screw tip.

Description

Cross Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 525,999, filed July 11, 2023, which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to an auto-injector medical device, and more particularly, to a lead screw tip for an auto-injector medical device. BACKGROUND

[0003] An auto-injector medical device is a device configured to inject a dose of a particular drug or medicament to a user. Auto-injectors are designed to overcome the hesitation associated with self-injecting a needle dose. Most auto-injectors use disposable syringes that are pre-filled with the drug to be injected. After the drug is injected, the syringe can be discarded and a new pre-filled syringe can be inserted into the auto-injector for the next dose. Since the disposable syringes used with auto-injectors result in waste, it is desirable to minimize the waste generated by the auto-injector and the disposable syringes whenever possible. SUMMARY

[0004] According to one aspect, an auto-injector medical device is disclosed. The auto-injector medical device can include a housing and a lead screw disposed within the housing. The lead screw is rotatable within the housing and axially translatable along its axis. The auto-injector medical device can also include a lead screw tip coupled to a distal end of the lead screw. The lead screw tip can include a first end having at least one extension extending from the first end in a direction parallel to a central axis of the lead screw tip. The distal end of the lead screw coupled to the lead screw tip is rotatable within and relative to the lead screw tip.

[0005] In one aspect, the auto-injector medical device can also include a cartridge disposed within the housing, the cartridge can include a syringe having a needle at one end thereof and a plunger disposed within the syringe, the plunger being axially translatable within the syringe along an axis of the syringe.

[0006] In one aspect, the lead screw tip is configured to engage the plunger to axially translate the plunger within the syringe.

[0007] In one aspect, the engagement between the lead screw tip and the plunger is a non-rotational engagement such that the lead screw tip is rotationally fixed relative to the plunger.

[0008] In one aspect, the axis of the lead screw is axially aligned with the central axis of the lead screw tip.

[0009] In one aspect, the lead screw tip is coupled to the distal end of the lead screw via a snap-fit connection.

[0010] In one aspect, the end of the lead screw coupled to the lead screw tip abuts against a stop disposed within the lead screw tip.

[0011] In one aspect, the stop is a protrusion extending from the first end of the lead screw tip to an interior of the lead screw tip, and the stop is axially aligned with a central axis of the lead screw tip.

[0012] In one aspect, the end of the lead screw coupled to the lead screw tip is disposed axially between the stop and the protrusion extending from the at least one extension.

[0013] In one aspect, an outer diameter of the lead screw tip is greater than an outer diameter of the lead screw.

[0014] According to another aspect, a lead screw tip is disclosed. The lead screw tip can include a first end and a second end, the second end being at an opposite end of the lead screw tip from the first end. At least one extension can extend from the first end to the second end in a direction parallel to a central axis of the lead screw tip. A stop can extend from the first end to an interior of the lead screw tip, the stop being axially aligned with the central axis of the lead screw tip. A protrusion can extend from each of the at least one extension toward the central axis of the lead screw tip.

[0015] In one aspect, the at least one extension includes a plurality of extensions extending from the first end to the second end.

[0016] In one aspect, each of the plurality of extensions is circumferentially connected at the first end, and each of the plurality of extensions is circumferentially separated at the second end.

[0017] In one aspect, each protrusion extending from each of the at least one extension is oriented perpendicular to the central axis.

[0018] In one aspect, each protrusion extending from each of the at least one extension includes a sloped surface disposed proximate the second end of the lead screw tip, the sloped surface being neither parallel nor perpendicular with respect to the central axis.

[0019] In one aspect, the first end of the lead screw tip has a generally circular cross-sectional shape with respect to the central axis.

[0020] In one aspect, the lead screw tip is made of a low-friction polymer material.

[0021] In one aspect, the lead screw tip is configured to couple to an end of a lead screw of an automatic injector medical device.

[0022] In one aspect, the end of the lead screw coupled to the lead screw tip is rotatable within and relative to the lead screw tip.

[0023] In one respect, the coefficient of friction between the tip of the lead screw and the end of the lead screw is between 0.1 and 0.4. Attached Figure Description

[0024] Reading the foregoing description and the following detailed description in conjunction with the accompanying drawings will help to better understand this disclosure, which illustrates preferred embodiments of the present disclosure. In the drawings: Figure 1 This is a cross-sectional view of a portion of the autoinjector medical device according to this disclosure.

[0025] Figure 2 This is a cross-sectional perspective view of a part of an autoinjector medical device.

[0026] Figure 3 This is a first perspective view of the lead screw tip of an autoinjector medical device.

[0027] Figure 4 This is a second three-dimensional view of the tip of the lead screw.

[0028] Figure 5 It is along Figure 3 A cross-sectional view of the tip of the lead screw taken by section line 5-5.

[0029] Figure 6 It is a cross-sectional view of the tip of the lead screw coupled to the lead screw of the autoinjector medical device.

[0030] Figure 7 It is a partial cross-sectional perspective view of the lead screw tip coupled to the lead screw. Detailed Implementation

[0031] Certain terms used in the following description are for convenience only and not for limitation. The terms “front,” “back,” “up,” and “down” specify the direction indicated in the accompanying drawings. The terms “inward” and “outward” refer to directions toward and away from the components referenced in the drawings. “Axial” refers to the direction along the axis of a shaft, shaft, pin, etc. References to a list of items designated as “at least one of a, b, and c” (where a, b, and c represent the listed items) mean that any single item or combination of items a, b, and c is included. The terms “about” and “approximately” cover + / - 10% of the indicated value unless otherwise specified. The term “approximately” in relation to radial direction covers + / - 25 degrees. Certain terms include those specifically mentioned above, their derivatives, and terms with similar meanings.

[0032] Figure 1 This is a cross-sectional view of a part of the autoinjector medical device 10. Figure 2 This is a cross-sectional perspective view of a part of an autoinjector medical device 10. Figures 1-2They will be discussed together. In the following text, the auto-injector medical device 10 will be referred to as "device 10," but it should be understood that auto-injector medical device 10 and device 10 refer to the same component. Device 10 is configured to deliver a dose of a specific drug or agent to a user, thereby facilitating self-injection of injectable drugs and agents. Furthermore, device 10 uses disposable cartridges 16 and syringes 18, which are pre-filled with the drug or agent to be delivered. After the drug or agent is administered, the cartridges 16 and syringes 18 can be discarded, and new pre-filled cartridges 16 and syringes 18 can be inserted into device 10 for the next administration.

[0033] Device 10 includes a housing 12, within which other components of device 10 are disposed. Although not shown, those skilled in the art will understand that device 10 may include a battery or power source for supplying electrical energy to a motor or actuator to cause drug dispensing when a user presses a button. More specifically, the motor or actuator may be connected to a lead screw 14 of device 10, and the motor or actuator may rotate the lead screw 14 about its axis AA, thereby causing the lead screw 14 to translate axially within housing 12 along its axis AA. Thus, in operation, a user may press a button or switch to activate the motor / actuator, thereby causing the lead screw 14 to rotate and translate along its axis AA to dispense and administer drugs or agents from device 10, as discussed further below.

[0034] The device 10 may also include a cartridge 16, which can be coupled and secured within the housing 12 of the device 10, and can be removed from the device 10 after drug administration. Thus, the cartridge 16 can be inserted and secured within the housing 12 for drug administration, and then, after drug administration, the cartridge 16 can be removed from the housing 12 and replaced with another cartridge 16 containing the drug to be administered or a measurement dose of the drug.

[0035] The cartridge 16 may include a syringe 18 positioned and coupled within the cartridge 16. The syringe 18 may be configured to contain and store a drug or agent to be administered or dispensed into a user. Furthermore, the syringe 18 may include a needle 20 disposed at and coupled to one end of the syringe 18, configured to be inserted into the body to dispense the drug or agent from the syringe 18 into the user. The syringe 18 may also include a plunger 22 disposed within the syringe 18, the plunger 22 being axially translatable within the syringe 18 along its axis. The plunger 22 may be made of a compressible material (e.g., rubber), and the outer diameter of the plunger 22 may be slightly larger than the inner diameter of the syringe 18. Therefore, when the plunger 22 is inserted into the syringe 18, the plunger 22 may be slightly radially compressed within the inner diameter of the syringe 18 to create a sealing effect, preventing the drug or agent from escaping from the end of the syringe 18 opposite the needle 20. Additionally, the plunger 22 may be forced to translate axially through the syringe 18, causing the drug or agent within the syringe 18 to be dispensed from the needle 20.

[0036] More specifically, the lead screw 14 can rotate, thereby translating the lead screw 14 axially toward the syringe 18 and plunger 22 of the cartridge 16. The lead screw 14 can translate toward the plunger 22 until the end of the lead screw 14 contacts the plunger 22 and forces the plunger 22 to translate axially through the syringe 18. One problem that may arise when the end of the lead screw 14 directly contacts the plunger 22 is that the rotation of the lead screw 14 and direct pressure on the plunger 22 can cause deformation of the plunger 22. More specifically, the friction between the rotating and pressing lead screw 14 and the plunger 22 can cause the plunger 22 to twist and deform, creating a gap or flow path that allows the drug or agent to leak and flow toward the lead screw 14, away from the needle 20. This is undesirable because it may cause the drug or agent to leak and spill into the device 10, resulting in incorrect dosage of the drug or agent, as well as other problems not specifically listed.

[0037] To address the aforementioned issues, a lead screw tip 24 may be included in the device 10. Specifically, the lead screw tip 24 may be coupled to the end of the lead screw 14, which is configured to press the plunger 22. In some embodiments, the lead screw tip 24 may be coupled to the end of the lead screw 14 via a snap-fit ​​connection. This snap-fit ​​connection allows the lead screw tip 24 to be coupled to the lead screw 14 without any additional fasteners or components to hold them together, thereby reducing the total number of components in the device 10. The lead screw tip 24 may be made of a low-friction material such that the end of the lead screw 14 coupled to the lead screw tip 24 can rotate within and relative to the lead screw tip 24 with minimal friction. In some embodiments, the lead screw tip 24 may be made of a low-friction polymer material. In a further embodiment, the lead screw tip 24 may be made of polyoxymethylene thermoplastic (also known as POM, acetal polymer, acetal, polyacetal, and polyoxymethylene).

[0038] Furthermore, it should be understood that the term "low friction" as used herein refers to the frictional force present between the end of the lead screw 14 and the tip 24 of the lead screw as the lead screw 14 rotates and presses against the tip 24. Therefore, the material of the lead screw 14 will affect the frictional force present between the end of the lead screw 14 and the tip 24. In some embodiments, the lead screw 14 may be made of steel, stainless steel, or other similar metallic materials. In such embodiments, the coefficient of friction between the end of the lead screw 14 and the tip 24 is preferably between 0.1 and 0.4. It has been determined that such a coefficient of friction value can minimize and / or eliminate deformation of the plunger 22 caused by the lead screw 14 during rotation and pressing of the contact plunger 22, as will be discussed further below.

[0039] Therefore, the device 10 of this disclosure includes a lead screw tip 24 coupled to the end of a lead screw 14. The lead screw tip 24 is located closest to the plunger 22 within the syringe 18, and is configured to engage the plunger 22, allowing the plunger 22 to translate axially through the syringe 18 while preventing deformation of the plunger 22. In other words, when the lead screw 14 rotates and translates axially toward the plunger 22, the end of the lead screw 14 coupled to the lead screw tip 24 is within the lead screw tip 24 and rotates relative to the lead screw tip 24. Furthermore, the lead screw tip 24 translates axially with the lead screw 14 and engages with the plunger 22. The engagement between the lead screw tip 24 and the plunger 22 is a non-rotational engagement, such that the lead screw tip 24 is rotated and fixed relative to the plunger 22. Therefore, the lead screw tip 24 acts as a buffer or intermediate component, preventing direct contact between the lead screw 14 and the plunger 22, thereby preventing the aforementioned undesirable deformation of the plunger 22.

[0040] As shown in the figure, the axis AA of the lead screw 14 is axially aligned with the central axis CA of the lead screw tip 24. Furthermore, the axes AA and CA of the lead screw 14 and the lead screw tip 24 can be axially aligned with the cartridge 16 and the plunger 22 in the syringe 18 of the cartridge 16, respectively. Therefore, the lead screw 14 can be axially translated into the syringe 18, and through contact with the lead screw tip 24, it forces the plunger 22 to move towards the needle 20, thereby dispensing the medication from the syringe 18 into the user's body. During the axial translation, only the lead screw tip 24 directly contacts the plunger 22, thus preventing any undesirable contact or friction and facilitating smooth and easy dispensing of the medication from the device 10. To achieve the above objective, the outer diameter of the lead screw tip 24 is preferably slightly smaller than the inner diameter of the syringe 18. Furthermore, in some embodiments, the outer diameter of the lead screw tip 24 can be larger than the outer diameter of the lead screw 14, so that the lead screw 14 does not directly contact the syringe 18. Additionally, the outer diameter of the lead screw tip 24 is preferably slightly smaller than the outer diameter of the plunger 22 to facilitate smooth translation within the syringe 18.

[0041] In operation, the user can press a button / switch to activate the motor / actuator, which in turn causes the lead screw 14 to rotate and translate along its axis AA toward the plunger 22. The lead screw 14 continues to translate toward the plunger 22 until the lead screw tip 24 contacts the plunger 22 and forces the plunger 22 to translate axially through the syringe 18. During the axial translation of the lead screw 14, the lead screw tip 24, and the plunger 22, the end of the lead screw 14 coupled to the lead screw tip 24 rotates within the lead screw tip 24, while the lead screw tip 24 and the plunger 22 remain rotated and fixed relative to each other. In other words, the lead screw tip 24 and the plunger 22 do not rotate relative to each other, but remain rotated and fixed during axial translation through the syringe 18. The plunger 22 is forced to translate axially through the syringe 18 until the correct / required amount or dose of drug or agent has been administered into the user's body from the needle 20. Details regarding the shape and structure of the lead screw tip 24 will be discussed in detail below.

[0042] Figure 3 This is a first perspective view of the lead screw tip 24 of device 10. Figure 4 This is the second stereoscopic view of the lead screw tip 24. Figure 5 It is along Figure 3 A cross-sectional view of the lead screw tip 24 taken from the middle section line 5-5. Figures 3-5 This will be discussed together. The lead screw tip 24 may include a generally cylindrical shape that corresponds to the internal shape and diameter of the syringe 18. The lead screw tip 24 may include a first end 26 and a second end 28, the second end 28 being located at the end of the lead screw tip 24 opposite to the first end 26. In some embodiments, as shown, the first end 26 of the lead screw tip 24 may have a generally circular cross-sectional shape (relative to the central axis CA of the lead screw tip 24). Furthermore, in some embodiments, the lead screw tip 24 may include at least one through-hole 30 extending through the first end 26 of the lead screw tip 24. At least one through-hole 30 may be included to aid in the manufacture of the lead screw tip 24. In other embodiments, depending on the manufacturing technique used to produce the lead screw tip 24, the at least one through-hole 30 may not be included.

[0043] Furthermore, the lead screw tip 24 may include at least one extension 32 extending from a first end 26 to a second end 28 of the lead screw tip 24 in a direction generally parallel to the central axis CA of the lead screw tip 24. In some embodiments, as shown, the lead screw tip 24 may include a plurality of extensions 32 extending from the first end 26 to the second end 28. In some specific embodiments, the lead screw tip 24 may include four extensions 32 extending from the first end 26 to the second end 28. In other embodiments, the lead screw tip 24 may include more or fewer than four extensions 32 extending from the first end 26 to the second end 28. The specific number of extensions 32 can be selected to achieve the desired clamping or snap-fit ​​connection between the lead screw tip 24 and the end of the lead screw 14. Furthermore, it should be understood that in some embodiments, the extensions 32 may also be referred to as “finger-like structures.” The plurality of extensions 32 are configured to facilitate coupling with the lead screw 14, and the outer surface of each extension 32 is configured to facilitate guiding the lead screw tip 24 within and through the syringe 18.

[0044] like Figures 3-4 Ideally, each extension 32 may be circumferentially connected at the first end 26 of the lead screw tip 24 via a circular first end 26 that extends between and connects each extension 32. Furthermore, due to the gap or space between each individual extension 32 at the second end 28, each extension 32 may be circumferentially separated or disconnected at the second end 28 of the lead screw tip 24. In other words, each extension 32 may be coupled to and extend from the first end 26, and each extension 32 may be cantilevered or freely suspended at the second end 28, such that the extensions 32 are not coupled or connected at the second end 28.

[0045] The shape of the described extensions 32 (finger-like structures) allows the screw tip 24 to couple to the end of the screw 14 without the need for additional fasteners or other components. Specifically, when the second end 28 of the screw tip 24 presses axially against the end of the screw 14, each extension 32 bends and flexes radially outward and away from the central axis CA of the screw tip 24, allowing the screw tip 24 to slide past the end of the screw 14. Each extension 32 can then return to its original position and snap radially inward onto the end of the screw 14, as discussed in more detail below. Thus, each extension 32 can have spring-like properties, allowing the extension to bend when inserted into the end of the screw 14, and then spring back or bend back to its original position when inserted sufficiently deep into the end of the screw 14. Although the foregoing disclosure indicates that each extension 32 bends and flexes during insertion, it should be understood that in other embodiments, only a portion of the extensions 32 bends and flexes during insertion. For example, in some embodiments, only the two extensions 32 may bend and flex when inserted into the lead screw 14, as will be discussed further below.

[0046] The lead screw tip 24 may further include a stop 34 extending from a first end 26 of the lead screw tip 24, the stop 34 extending in the same direction as each extension 32, into the interior of the lead screw tip 24. Furthermore, the stop 34 may be axially aligned with the central axis CA of the lead screw tip 24, such that the stop 34 is located at the axial center of one end of the lead screw tip 24, and the stop 34 may extend inward into the lead screw tip 24 and toward the second end 28. The stop 34 may be configured as a surface against which the distal end of the lead screw 14 abuts when the lead screw tip 24 is coupled to the lead screw 14, preventing the lead screw 14 from further penetrating into the interior of the lead screw tip 24, as will be discussed further below.

[0047] like Figure 5 As best shown, each extension 32 may include a protrusion 36 extending from the respective extension 32 toward the central axis CA of the lead screw tip 24. Specifically, each protrusion 36 extending from the respective extension 32 may extend from the extension 32 toward the interior of the lead screw tip 24 at a perpendicular angle to the central axis CA of the lead screw tip 24. More specifically, the inner edge or surface of each protrusion 36 closest to the stop 34 and the first end 26 may be oriented perpendicular to the central axis CA of the lead screw tip 24. Each protrusion 36 extending from the respective extension 32 may be configured to facilitate securing the lead screw tip 24 to the lead screw 14, as discussed further below. Although the foregoing disclosure indicates that each extension 32 may include a protrusion 36, it should be understood that in some embodiments, only a portion of the extensions may include a protrusion 36. For example, in some embodiments, only two extensions 32 may include a protrusion 36 extending from the extension 32 toward the central axis CA of the lead screw tip 24. Furthermore, in some embodiments, only the extension 32 including the protrusion 36 may bend and flex when inserted into the lead screw 14, which will be discussed further below.

[0048] Each protrusion 36 extending from the corresponding extension 32 may include an inclined surface 38 disposed near the second end 28 of the lead screw tip 24. Each inclined surface 38 may be at a non-parallel and non-perpendicular angle relative to the central axis CA of the lead screw tip 24. Furthermore, each inclined surface 38 may be oriented away from the stop 34 and the first end 26. The inclined surface 38 may be configured to facilitate securing and coupling the lead screw tip 24 to the lead screw 14. More specifically, the inclined surface 38 may be configured as a guide surface to facilitate insertion of the lead screw tip 24 onto the end of the lead screw 14, as discussed further below.

[0049] Figure 6 It is a cross-sectional view of the tip 24 of the lead screw 14 coupled to the device 10. Figure 7This is a partial cross-sectional perspective view of the lead screw tip 24 coupled to the lead screw 14. More specifically, in Figure 7 In the diagram, the lead screw tip 24 is shown in cross-section, while the lead screw 14 is not shown in cross-section, to help understand how the lead screw tip 24 is coupled to the lead screw 14. Figures 6-7 This will be discussed together. As previously stated, once the lead screw tip 24 is coupled to the end of the lead screw 14, the end of the lead screw 14 can rotate freely within and relative to the lead screw tip 24. Furthermore, after the lead screw tip 24 is coupled to the end of the lead screw 14, the lead screw tip 24 is intended to remain coupled to the lead screw 14 for the service life of the lead screw 14 and the entire device 10. Nevertheless, it should be understood that if the lead screw tip 24 is damaged, it can be removed from the end of the lead screw 14 and replaced with another lead screw tip 24.

[0050] To couple the lead screw tip 24 to the end 40 of the lead screw 14, the lead screw tip 24 is axially inserted toward the end 40 until the inclined surface 38 contacts the end 40 of the lead screw 14. The lead screw tip 24 is further forced to move axially toward the end 40, causing each extension 32 to bend radially outward away from the axis AA of the lead screw 14. The extensions 32 bend radially outward until the lead screw tip 24 is inserted sufficiently deep toward the end 40 such that the inner surface 42 of the end 40 passes through the innermost surface or edge of the protrusion 36. Furthermore, the lead screw tip 24 is inserted sufficiently deep into the end 40 such that the distal surface of the end 40 abuts against or contacts the stop 34 disposed inside the lead screw tip 24.

[0051] Therefore, the lead screw tip 24 is inserted into the end 40 of the lead screw 14 until the extension 32 springs back or otherwise returns to its original position, and the end 40 of the lead screw 14 is axially positioned between the stop 34 and the protrusion 36 (relative to the central axis CA of the lead screw tip 24). Because the end 40 of the lead screw 14 is axially positioned between the stop 34 and the protrusion 36 of the lead screw tip 24, the lead screw tip 24 is axially fixed to the lead screw 14, preventing axial translation of the lead screw tip 24 relative to the lead screw 14. However, due to the structure and connection between the lead screw 14 and the lead screw tip 24, the end 40 of the lead screw 14 can rotate about its axis AA relative to the lead screw tip 24.

[0052] The screw tip 24 allows the screw 14 to rotate and translate axially while preventing the screw 14 from directly contacting and causing deformation of the plunger 22. Therefore, the screw tip 24 is fixed by its own rotation relative to the plunger 22, while allowing the screw 14 to rotate within the screw tip 24, thereby preventing deformation of the plunger 22. Direct contact between the screw tip 24 and the plunger 22 prevents direct contact between the plunger 22 and the screw 14, ensuring that no drug or medication leaks around the plunger 22 at the end of the syringe 18 opposite the needle 20. Furthermore, as part of the non-disposable (i.e., not part of the disposable cartridge 16) component of the device 10, the screw tip 24 prevents excessive waste and saves overall costs based on the fact that it is not discarded after each administration. Other benefits provided by the screw tip 24 and the device 10 as a whole will be appreciated by those skilled in the art, although not specifically described.

[0053] The embodiments of the present invention have been described in such detail that it will be apparent to those skilled in the art that many physical changes can be made without altering the inventive concept and principles embodied therein, only a few of which are exemplified in the specific embodiments.

[0054] Similarly, it is understood that there may be numerous embodiments that only include some of the preferred embodiments, without altering the inventive concept and principles embodied therein. Therefore, these embodiments and optional configurations should be considered exemplary and / or illustrative rather than restrictive in all respects, and the scope of this disclosure is defined by the appended claims rather than the foregoing description, and all alternative embodiments and modifications thereof falling within the equivalent meaning and scope of the claims are therefore included.

Claims

1. An auto-injector medical device, comprising: shell; A lead screw, which is disposed within the housing and is capable of rotating within the housing and axially translating along the axis of the lead screw; as well as A lead screw tip coupled to the end of the lead screw, the lead screw tip including a first end having at least one extension extending from the first end in a direction parallel to the central axis of the lead screw tip, wherein the end of the lead screw coupled to the lead screw tip is rotatable within and relative to the lead screw tip.

2. The automatic injector medical device according to claim 1, further comprising a cartridge disposed within the housing, the cartridge comprising: A syringe, wherein a needle is provided at one end; as well as A plunger disposed within the syringe, the plunger being axially translatable within the syringe along its axis.

3. The auto-injector medical device according to claim 2, wherein, The tip of the lead screw is configured to engage the plunger, causing the plunger to translate axially within the syringe.

4. The auto-injector medical device according to claim 3, wherein, The engagement between the lead screw tip and the plunger is a non-rotational engagement, which allows the lead screw tip to be rotated and fixed relative to the plunger.

5. The auto-injector medical device according to claim 1, wherein, The axis of the lead screw is axially aligned with the central axis of the lead screw tip.

6. The auto-injector medical device according to claim 1, wherein, The tip of the lead screw is coupled to the end of the lead screw via a snap-fit ​​connection.

7. The auto-injector medical device according to claim 1, wherein, The end of the lead screw coupled to the tip of the lead screw abuts against a stop provided inside the tip of the lead screw.

8. The auto-injector medical device according to claim 7, wherein, The stop is a protrusion extending from the first end of the lead screw tip into the interior of the lead screw tip, and the stop is axially aligned with the central axis of the lead screw tip.

9. The auto-injector medical device according to claim 7, wherein, The end of the lead screw, coupled to the tip of the lead screw, is axially disposed between the stop and the protrusion extending from the at least one extension.

10. The auto-injector medical device according to claim 1, wherein, The outer diameter of the lead screw tip is larger than the outer diameter of the lead screw.

11. A lead screw tip, comprising: The first end and the second end, wherein the second end is located at the tip of the lead screw opposite to the first end; At least one extension extends from the first end to the second end in a direction parallel to the central axis of the lead screw tip; A stop member extends from the first end into the interior of the lead screw tip, and the stop member is axially aligned with the central axis of the lead screw tip; as well as A protrusion extending from each of the at least one extension toward the central axis of the lead screw tip.

12. The lead screw tip according to claim 11, wherein, The at least one extension includes a plurality of extensions extending from the first end to the second end.

13. The lead screw tip according to claim 12, wherein, Each of the plurality of extensions is circumferentially connected at the first end, and each of the plurality of extensions is circumferentially separated at the second end.

14. The lead screw tip according to claim 11, wherein, Each protrusion extending from the at least one extension is oriented perpendicular to the central axis.

15. The lead screw tip according to claim 11, wherein, Each protrusion extending from each of the at least one extension includes an inclined surface disposed near the second end of the lead screw tip, the inclined surface being neither parallel nor perpendicular to the central axis.

16. The lead screw tip according to claim 11, wherein, The first end of the lead screw tip has a generally circular cross-sectional shape relative to the central axis.

17. The lead screw tip according to claim 11, wherein, The lead screw tip is made of a low-friction polymer material.

18. The lead screw tip according to claim 11, wherein, The lead screw tip is configured to be coupled to the end of the lead screw of an autoinjector medical device.

19. The lead screw tip according to claim 18, wherein, The end of the lead screw coupled to the tip of the lead screw is capable of rotating within and relative to the tip of the lead screw.

20. The lead screw tip according to claim 18, wherein, The coefficient of friction between the tip of the lead screw and the end of the lead screw is between 0.1 and 0.4.

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