A sealing member for a pen and a differential pressure self-locking airtight button pen

Abstract

The utility model discloses a kind of sealing parts for pen, including barrel portion and end head, end head is set to one end of barrel portion, the other end of barrel portion is open;End head is equipped with the self-closing notch for repeatedly inserting nib, the inside of end head is raised towards barrel portion inner cavity, and the wall thickness of end head gradually decreases from center to periphery, and the inside of end head, and the two side edges of self-closing notch respectively are equipped with a raised sealing lip, sealing lip extends with the contour of self-closing notch, and its two ends are connected with the inner wall of barrel portion respectively.Using utility model, it can solve the problem that the existing sealing part is poor in air tightness due to the rebounding misplacement of self-closing notch, the deformation displacement of repeatedly inserting nib.The utility model also discloses a differential pressure self-locking airtight key pen, by applying the sealing part for pen, and cooperating with additional sealing structure, form double-sealed closed cavity, completely seal the nib after retracting in cavity, prevent ink evaporation dry knot.

Description

Technical Field

[0001] This utility model relates to the field of writing stationery technology, specifically to a pen seal and a differential pressure self-locking airtight key pen using the seal, which is particularly suitable for fountain pens that require long-term storage and have high requirements for nib sealing. Background Technology

[0002] Fountain pens, as writing instruments primarily made of metal, play an important role in daily office work, study, and creative writing. Most existing push-button fountain pens employ a retractable nib mechanism, where the nib is extended by pressing and retracts into the barrel when not in use. However, this structure has a significant drawback: the nib remains exposed to the air after retraction. When not in use for extended periods, residual ink on the nib can dry and harden upon contact with air, clogging the ink outlet and resulting in uneven ink flow during subsequent writing, severely impacting the user experience.

[0003] To solve the above problems, users usually wipe the pen tip with a tissue to remove dried ink. If wiping still doesn't allow ink to flow properly, they need to gently shake the pen or squeeze the ink reservoir to force the ink to flow to the pen tip. However, during this process, ink is very likely to spill out of the pen, causing stubborn stains on clothing, desktops, and other items, and further affecting the continued use of the pen, causing great inconvenience to the user. Although the structure disclosed by the inventor in Chinese Patent ZL2023204029183 has initially solved the problem of ink drying when the pen tip retracts. However, the patented solution still has the following shortcomings in practical applications: First, the self-closing slit on the pen tip seal for pen tip insertion is prone to springback and misalignment after repeated use due to uneven stress distribution, which greatly reduces the reliability of the slit self-closing and makes it difficult to continuously achieve an effective sealing function. It cannot be airtight and self-locking when there are large differences in internal and external temperature and air pressure. Second, the pen tip seal and pen tip end cap are usually sealed by adhesive. However, if the pen tip is repeatedly inserted into the seal, it is easy to cause deformation and displacement of the seal, which will damage the original sealing structure, reduce airtightness, and make it impossible to guarantee the sealing effect for a long time.

[0004] Therefore, how to design a structure that can improve the reliability of the self-closing notch, avoid deformation and displacement of the seal, and achieve long-term sealing of the pen tip has become a key problem that urgently needs to be solved in the field of push-button fountain pen technology. Utility Model Content

[0005] The primary objective of this invention is to provide a pen seal that solves the problem of poor airtightness caused by the self-closing cut springback misalignment and the easy deformation and displacement due to repeated pen tip insertion, thereby improving the structural stability and self-closing reliability of the seal. Another objective of this invention is to provide a differential pressure self-locking airtight key pen. By applying the aforementioned pen seal and in conjunction with an additional sealing structure, a double-sealed closed cavity is formed, which completely seals the retracted pen tip within the cavity, effectively isolating it from air and preventing ink from drying out. At the same time, it avoids ink leakage during operation, thus improving the user experience.

[0006] To achieve the aforementioned primary objective, this utility model provides the following technical solution: A pen seal includes a cylindrical body and an end head. The end head is located at one end of the cylindrical body, and the other end of the cylindrical body is open. The end head has a self-closing slit for repeated insertion of a pen tip. The inner surface of the end head protrudes towards the inner cavity of the cylindrical body, and the wall thickness of the end head gradually decreases from the center to the periphery. On the inner surface of the end head, and close to the two sides of the self-closing slit, there are sealing lips that protrude towards the inner cavity of the cylindrical body. The sealing lips extend along the contour of the self-closing slit, and their two ends are respectively connected to the inner wall of the cylindrical body.

[0007] Furthermore, the inner surface of the end head is a spherical surface that protrudes into the inner cavity of the cylinder, and the surrounding area of ​​the outer surface of the end head is a plane, while the central area is an inwardly concave arc surface.

[0008] Furthermore, the outer wall surface of the cylindrical part is provided with a first sealing rib arranged along the circumferential direction of the cylindrical part; the first sealing rib is provided at least once and is arranged at intervals along the length direction of the cylindrical part; the inner wall surface of the cylindrical part is provided with a second sealing rib arranged along the circumferential direction of the cylindrical part; the second sealing rib is provided at least once and is arranged at intervals along the length direction of the cylindrical part.

[0009] Furthermore, a positioning block that protrudes outward along the axial direction of the cylinder portion is provided on the end face of the open end of the cylinder portion.

[0010] Furthermore, the outer periphery of the end head is provided with a toothed or wavy structure arranged along the circumferential direction of the end head.

[0011] Compared with the prior art, the pen seal of this utility model has the following advantages: (1) Improved springback reliability: The gradual wall thickness design at the end head optimizes the stress distribution, avoids local stress concentration, and ensures accurate alignment and stable closure when the cut springs back. (2) Enhanced sealing performance: The sealing lip can correct the rebound misalignment when the self-closing cut is closed, and at the same time directly enhance the sealing of the cut edge, prevent air from entering from the cut gap, and avoid the imbalance of internal and external pressure difference; (3) Achieve self-locking closure: The self-locking force is generated adaptively by the air pressure difference. The greater the pressure difference, the tighter the closure, effectively preventing ink leakage or overflow caused by excessive internal pressure; (4) Integrated design ensures stability: The sealing lip is seamlessly connected to the inner wall of the cylinder, avoiding structural weaknesses and leakage risks, and improving the overall durability and reliability of the structure; (5) Enhance the sealing effect with external assembly structure: Multiple sealing ribs are set on the outer and inner walls of the cylinder, which can form multiple seals with the inner or outer walls of the external assembly structure (such as the pen tip cap or the insertion tube inserted into the cylinder) during assembly, effectively improving the overall airtightness. (6) Smooth and effortless, with fast rebound response: The gap between the toothed structures provides the necessary "give way" space for the expansion and deformation of the seal, making it easier for the end head to be opened and the pressing action of the core to be smoother and less effortless; in addition, when the pen tip is retracted, the elasticity generated after the gap between the toothed structures closes can quickly retract to the original state, ensuring that the self-closing cut and sealing lip can restore the seal without delay.

[0012] To achieve the other objective mentioned above, this utility model provides the following technical solution: A differential pressure self-locking airtight key pen includes a pen barrel, a writing component disposed within the pen barrel, and a press-return component. The writing component includes a pen tip assembly and an ink storage component for supplying ink to the pen tip assembly. The pen tip assembly has a pen tip and a feed that cooperates with the pen tip. The press-return component includes a pressing head located at the rear end of the pen barrel and a spring for providing a rebound force. The pressing head is linked to the writing component through a transmission structure to realize the extension and retraction of the pen tip. The pen barrel is provided with a pen grip for the user to hold. The differential pressure self-locking airtight key pen also includes a first sealing structure and a second sealing structure. The first sealing structure includes the pen seal described above. The front end of the pen barrel is connected to a pen tip end cap, and the pen seal is embedded inside the pen tip end cap. The second sealing structure is disposed inside the pen barrel, and the position where the second sealing structure forms a sealing fit with the transmission structure is axially spaced a certain distance from the first seal. When the pen tip is retracted, the first sealing structure and the second sealing structure together form a closed cavity, sealing the pen tip within the closed cavity.

[0013] Furthermore, the inner wall surface of the pen tip cap is provided with an annular shoulder, which abuts against the outer side of the pen tip to form a first axial limiting structure; the front end face of the pen barrel abuts against the end face of the open end of the cylinder to form a second axial limiting structure; wherein, the annular shoulder is provided with a plurality of grooves spaced apart along its edge.

[0014] Furthermore, a positioning block protruding outward along the axial direction of the cylinder is provided on the end face of the open end of the cylinder part; a positioning groove recessed inward along the axial direction of the pen barrel is provided at the front end of the pen barrel; the positioning groove and the positioning block are complementary in shape to form an axial limiting structure.

[0015] Furthermore, the front end face of the pen barrel is provided with a insertion tube that protrudes outward along the axis of the pen barrel, and the insertion tube is inserted into the inner cavity of the cylindrical body; the inner wall surface of the cylindrical body is sealed to the outer wall surface of the insertion tube, and the outer wall surface of the cylindrical body is sealed to the inner wall surface of the pen tip end cap.

[0016] Compared with the prior art, the differential pressure self-locking airtight key pen of this utility model has the following advantages: (1) Long-lasting sealing and anti-drying: The first sealing structure and the second sealing structure form a double-sealed closed cavity, which completely isolates the pen tip from the air, effectively preventing ink from drying. At the same time, the pressure difference is used to achieve self-locking, ensuring the pressure balance inside and outside the ink reservoir, and avoiding the phenomenon of ink leakage and overflow caused by excessive internal pressure. (2) Easy assembly, reliable and precise positioning: The pen seal and the pen barrel and pen tip end cap adopt an inner and outer sleeve structure to achieve a quick and tight connection, and multiple sealing ribs between each contact surface enhance the reliability of the sealing fit of the assembly structure; at the same time, precise positioning is achieved through positioning blocks, positioning grooves, annular shoulders and other structures to avoid the sealing effect being affected by structural displacement during use.

[0017] (3) Smooth and effortless, and contains residual ink: The multiple grooves on the annular shoulder can work in conjunction with the toothed structure on the outer periphery of the aforementioned end head. These grooves provide clear escape and containment space for the expanding material, which makes the deformation of the seal smoother and more controllable, further reducing puncture resistance, making the hand feel lighter, and reducing stress fatigue of the material. In addition, these grooves can also contain and contain the trace amount of residual ink scraped off by the seal, effectively preventing it from overflowing, thereby ensuring the cleanliness of the pen tip and improving the quality of the product and user experience. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings of the embodiments will be briefly described below.

[0019] Figure 1 An isometric view of the pen seal provided in Embodiment 1 of this utility model; Figure 2 An isometric view of the pen seal provided in Embodiment 1 of this utility model from another perspective; Figure 3 This is an isometric view of the differential pressure self-locking airtight key pen provided in Embodiment 2 of this utility model; Figure 4 This is a cross-sectional view of the differential pressure self-locking airtight key pen provided in Embodiment 2 of this utility model; Figure 5 For Figure 4 A magnified view of region A in the structure shown; Figure 6 For Figure 4 One of the enlarged views of region B in the structure shown in the figure, which illustrates that the second sealing structure is achieved by a conical surface mating sealing method; Figure 7 This is a magnified view of a portion of the second sealing structure, which is achieved using an O-ring.

[0020] Marked in the image: Pen seal 10; cylinder 11; end head 12; sealing lip 13; spherical surface 14; flat surface 15; arc surface 16; first sealing rib 17; second sealing rib 18; positioning block 19; toothed or wavy structure 110; pen barrel 20; positioning groove 21; insertion tube 22; ink storage component (ink reservoir) 30; pen tip 40; pen feed 50; pressing head 60; spring 70; transmission structure 80; fixed component 81; moving component 82; stop ring 83; inner conical surface 84; outer conical surface 85; pen tip end cap 90; annular shoulder 91; groove 92; O-ring seal 100; first sealing structure I; second sealing structure II. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Example 1 like Figure 1 and Figure 2 As shown, Embodiment 1 of this utility model proposes a pen seal 10, including a cylindrical body 11 and an end head 12. The end head 12 is integrally formed at one end of the cylindrical body 11, and the other end of the cylindrical body 11 has an open structure for the pen tip 40 to extend or retract. A self-closing slit is provided at the center of the end head 12 for the pen tip 40 to repeatedly pass through. The self-closing slit is opened when the pen tip 40 extends and automatically closes when the pen tip 40 retracts, achieving a preliminary seal. In this embodiment, the self-closing slit can be either "straight" or "cross-shaped".

[0023] To improve the reliability and sealing effect of the self-closing slit, the inner surface of the end head 12 protrudes towards the inner cavity of the cylinder 11, and the wall thickness of the end head 12 gradually decreases from the center to the periphery. On the one hand, when the air pressure on the inner side of the end head 12 is greater than the air pressure on the outer side, the gradual wall thickness design of the end head 12 optimizes the stress distribution, avoids local stress concentration, and ensures accurate alignment and stable closure when the slit rebounds. On the other hand, when the ambient temperature rises or the pen is shaken during handling, the air pressure inside the pen increases. This gradual wall thickness structure can absorb some of the pressure and provide gap compensation, thereby achieving airtight sealing of the gaps and preventing the gas inside the pen from leaking out, thus preventing ink leakage and the problem of ink spillage in the fountain pen.

[0024] Meanwhile, on the inner surface of the end head 12, and close to the two sides of the self-closing cut, there are integrally formed sealing lips 13 protruding into the inner cavity of the cylinder part 11. The sealing lips 13 extend along the "I" or "cross" contour of the self-closing cut, and their two ends are seamlessly connected to the inner wall of the cylinder part 11. The sealing lips 13 protruding on both sides of the cut not only enhance the sealing performance at the cut and prevent air from entering from the cut gap, but their seamless connection structure with the inner wall of the cylinder part 11 also provides a clear guiding path when the end head rebounds, minimizing misalignment. At the same time, its arc-shaped protrusion structure can generate greater contact stress and self-locking effect under the action of air pressure difference.

[0025] In this embodiment, the pen seal 10 is integrally injection molded from silicone material, which has good elasticity and self-sealing properties.

[0026] For example, the inner surface of the end head 12 is designed as a spherical surface 14 protruding into the inner cavity of the cylinder portion 11, the outer surface has a plane 15 around its perimeter, and an inwardly concave arc surface 16 in its central region. The projection shape of the arc surface 16 along the axial direction of the cylinder portion 11 is elliptical, with the major axis of the ellipse located on the tangential surface of the self-closing notch. The spherical inner surface 14 can further optimize stress distribution, making the seal easier to rebound and reset. The special shape design of the outer surface facilitates the assembly and positioning of the seal with external structures (such as pen tip caps), while not affecting the normal rebound of the self-closing notch and effectively preventing rebound misalignment.

[0027] For example, to enhance the sealing fit between the cylindrical body 11 and external assembly structures (such as pen tip caps and insert pipes for pen barrel insertion into the cylindrical body 11), the outer wall surface of the cylindrical body 11 is provided with first sealing ribs 17 arranged along the circumference of the cylindrical body 11. At least one first sealing rib 17 is provided, and they are evenly spaced along the length of the cylindrical body 11. The inner wall surface of the cylindrical body 11 is provided with second sealing ribs 18 arranged along the circumference of the cylindrical body 11. At least one second sealing rib 18 is also provided, and they are evenly spaced along the length of the cylindrical body 11. Multiple sealing ribs can form multiple seals with the inner or outer wall of the external assembly structure during assembly, effectively improving the overall airtightness. For example, to achieve precise positioning of the seal during assembly and prevent circumferential rotation, a positioning block 19 protruding outward along the axis of the cylinder 11 is provided on the end face of the open end of the cylinder 11. Preferably, two positioning blocks 19 are provided, and the two positioning blocks 19 are arranged symmetrically at 180° with the axis of the cylinder 11 as the center. The positioning block 19 can cooperate with the positioning groove 21 on the external structure (such as the pen barrel 20) to achieve circumferential limiting and ensure that the position of the self-closing cut is precisely aligned with the movement trajectory of the pen tip 40. For example, the outer periphery of the tip 12 is provided with toothed or wavy structures 110 arranged along the circumferential direction of the tip 12. These toothed or wavy structures 110 form regular gaps with the inner wall of the pen tip cap. When the pen tip 40 pierces through the self-closing slit, the tip 12 expands radially under pressure. The gaps between the toothed or wavy structures 110 provide the necessary "give way" for this expansion, making it easier for the tip 12 to open. Because expansion is easier, the friction that the pen tip 40 needs to overcome when extending is greatly reduced, making the pressing action to eject the core smoother and less strenuous, improving the user experience. Furthermore, when the pen tip 40 retracts, due to the elasticity of the silicone, the gaps between the toothed or wavy structures 110 close, and the tip 12 can quickly retract to its original state, ensuring that the self-closing slit and sealing lip 13 can restore the seal without delay, without affecting the final sealing effect due to the presence of gaps.

[0028] Example 2 like Figures 1 to 5As shown, Embodiment 2 of this utility model proposes a pressure differential self-locking airtight key pen, including a pen barrel 20, a writing component disposed within the pen barrel 20, and a press-return component. The writing component includes a pen tip assembly and an ink storage component 30 (such as an ink cartridge) for supplying ink to the pen tip assembly. The pen tip assembly has a pen tip 40 and a pen tongue 50 that cooperates with the pen tip 40. The pen tongue 50 is used to guide the ink in the ink storage component 30 to the pen tip 40. The press-return component includes a pressing head 60 located at the rear end of the pen barrel 20 and a spring 70 for providing a rebound force. The pressing head 60 is linked to the writing component through a transmission structure 80 (such as the snap-fit ​​transmission mechanism in existing key pens). When the pressing head 60 is pressed, it can drive the writing component to move along the axis of the pen barrel 20, realizing the extension and retraction of the pen tip 40. The pen barrel 20 is provided with a pen grip for the user to hold. The pen grip is preferably made of a non-slip material to improve the grip comfort. The core improvement of this key pen lies in the inclusion of a first sealing structure I and a second sealing structure II. The first sealing structure I includes a pen seal 10 as described in any of the embodiments above. A pen tip cap 90 is detachably connected to the front end of the pen barrel 20. The pen seal 10 is embedded inside the pen tip cap 90, and the position of its self-closing cut is aligned with the movement trajectory of the pen tip 40, ensuring that the pen tip 40 can smoothly pass through the self-closing cut. The second sealing structure II is located inside the pen barrel 20, and the position where the second sealing structure II forms a sealing fit with the transmission structure 80 is axially separated from the first seal by a certain distance.

[0029] When the pen tip 40 retracts, the second sealing structure II and the transmission structure 80 fit tightly together, forming a sealed fit. At this time, the second sealing structure II and the first sealing structure I together form a closed cavity inside the pen barrel 20. The pen tip 40 is completely located within this closed cavity, isolating the pen tip 40 from the outside air and effectively preventing the ink from drying out. At the same time, due to the pressure difference between the air inside the closed cavity and the outside atmosphere, the sealing effect is further enhanced under the action of the pressure difference, achieving "pressure difference self-locking" and preventing air leakage from the closed cavity or the entry of outside air.

[0030] It is understandable that, such as Figure 6As shown, in this embodiment, the second sealing structure II can also be implemented using a conical surface sealing method. Specifically, the fixing component 81 of the transmission structure 80 is sealed to the inner wall of the pen barrel 20 by interference fit or glue fixation. The front end of the fixing component 81 of the transmission structure 80 is provided with an inner conical surface 84. Correspondingly, the movable component 82 of the transmission structure 80 is provided with a stop ring 83 that is axially opposite to the inner conical surface 84. The stop ring 83 has an outer conical surface 85 that seals with the inner conical surface 84. When the pen tip 40 is retracted, the movable component 82 of the transmission structure 80 retracts under the action of the spring 70, and the stop ring 83 moves accordingly and presses against the front end of the fixing component 81 of the transmission structure 80. At this time, the outer conical surface 85 on the stop ring 83 is tightly fitted with the inner conical surface 84 at the front end of the fixing component 81, thus achieving a seal.

[0031] like Figure 7 As shown, in another embodiment, the second sealing structure II can be implemented using an O-ring 100. Specifically, the fixing component 81 of the transmission structure 80 is sealed to the inner wall surface of the pen barrel 20 by interference fit or glue fixation, while the O-ring 100 is installed on the front end face of the fixing component 81 of the transmission structure 80 by glue fixation. Correspondingly, the movable component 82 of the transmission structure 80 is provided with a stop ring 83 that is axially opposite to the O-ring 100. When the pen tip 40 is retracted, the movable component 82 of the transmission structure 80 retracts under the action of the spring 70, and the stop ring 83 moves accordingly and presses against the O-ring 100 to achieve sealing.

[0032] For example, such as Figure 1 , Figure 2 and Figure 5 As shown, to ensure reliable positioning of the first sealing structure I within the pen tip end cap 90, the inner wall of the pen tip end cap 90 is provided with an annular shoulder 91. The annular shoulder 91 abuts against the outer periphery of the end head 12, forming a first axial limiting structure to restrict the pen seal 10 from moving out of the pen tip end cap 90. The front end face of the pen barrel 20 abuts against the end face of the open end of the cylinder 11, forming a second axial limiting structure to restrict the pen seal 10 from moving inward into the pen barrel 20. Through double axial limiting, it can be ensured that the seal does not shift axially during use.

[0033] For example, such as Figure 1 , Figure 2 and Figure 5As shown, in order to further improve the assembly and positioning accuracy of the first sealing structure I and the pen barrel 20, a positioning block 19 protruding outward along the axis of the cylinder 11 is provided on the end face of the open end of the cylinder 11, and a positioning groove 21 recessed inward along the axis of the pen barrel 20 is provided at the front end of the cylinder 20. The shapes of the positioning groove 21 and the positioning block 19 are complementary, and the two cooperate to form a circumferential limiting structure to prevent the sealing element from rotating circumferentially in the pen barrel 20, and ensure that the self-closing cut is always aligned with the movement trajectory of the pen tip 40.

[0034] For example, such as Figure 1 , Figure 2 and Figure 5 As shown, the annular shoulder 91 has multiple grooves 92 spaced apart along its edge. These grooves 92 work in conjunction with the toothed or wavy structure 110 on the outer periphery of the aforementioned end cap 12. When the pen tip 40 pierces the pen seal 10, the end cap 12 is compressed, and its material expands outwards. These grooves 92 provide clear escape and containment space for the expanding material, making the deformation of the seal smoother and more controllable, further reducing piercing resistance, making it lighter to hold, and reducing material stress fatigue. In addition, after multiple piercings, the trace amounts of ink carried on the surface of the pen tip may be scraped off and accumulate around the seal cut. Without these grooves, the excess ink would have nowhere to go and might seep out from the gaps in the pen tip end cap 90, causing contamination. However, these grooves 92 act as miniature "ink reservoirs," capable of containing and storing these scraped-off trace amounts of residual ink, effectively preventing them from overflowing, thus ensuring the cleanliness of the pen tip area and improving the product's quality and user experience.

[0035] For example, such as Figure 1 , Figure 2 and Figure 5 As shown, to enhance the sealing effect between the pen barrel 20 and the first sealing structure I, the front end face of the pen barrel 20 is provided with a plug tube 22 that protrudes outward along the axis of the pen barrel 20. The plug tube 22 is inserted into the inner cavity of the cylindrical body 11, and the inner wall surface of the cylindrical body 11 and the outer wall surface of the plug tube 22 form a tight sealing fit through the second sealing rib 18. The outer wall surface of the cylindrical body 11 and the inner wall surface of the pen tip end cap 90 form a tight sealing fit through the first sealing rib 17, thereby achieving multiple seals and further improving the overall airtightness.

[0036] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0037] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A pen seal, characterized in that, The device includes a cylindrical body and an end head. The end head is located at one end of the cylindrical body, and the other end of the cylindrical body is open. The end head has a self-closing slit that allows the pen tip to be repeatedly inserted. The inner surface of the end head protrudes towards the inner cavity of the cylindrical body, and the wall thickness of the end head gradually decreases from the center to the periphery. On the inner surface of the end head, and close to the two sides of the self-closing slit, there are sealing lips that protrude towards the inner cavity of the cylindrical body. The sealing lips extend along the contour of the self-closing slit, and their two ends are respectively connected to the inner wall of the cylindrical body.

2. The pen seal as described in claim 1, characterized in that, The inner surface of the end head is a spherical surface that protrudes into the inner cavity of the cylinder, and the outer surface of the end head has a planar area around it and an inwardly concave arc surface in the middle area.

3. The pen seal as described in claim 1, characterized in that, The outer wall surface of the cylindrical part is provided with a first sealing rib arranged along the circumference of the cylindrical part; the first sealing rib is provided at least once and is arranged at intervals along the length of the cylindrical part; the inner wall surface of the cylindrical part is provided with a second sealing rib arranged along the circumference of the cylindrical part; the second sealing rib is provided at least once and is arranged at intervals along the length of the cylindrical part.

4. The pen seal as described in claim 1, characterized in that, The end face of the open end of the cylindrical part is provided with a positioning block that protrudes outward along the axis of the cylindrical part.

5. The pen seal as described in claim 1, characterized in that, The outer periphery of the end head is provided with a toothed or wavy structure arranged along the circumferential direction of the end head.

6. A differential pressure self-locking airtight key pen, characterized in that, The pen includes a barrel, a writing component disposed within the barrel, and a press-and-return component. The writing component includes a pen tip assembly and an ink storage component for supplying ink to the pen tip assembly. The pen tip assembly has a pen tip and a feed that cooperates with the pen tip. The press-and-return component includes a pressing head located at the rear end of the barrel and a spring for providing a rebound force. The pressing head is linked to the writing component through a transmission structure to realize the extension and retraction of the pen tip. The pen is characterized by further including a first sealing structure and a second sealing structure. The first sealing structure includes a pen seal as described in any one of claims 1 to 5. A pen tip end cap is connected to the front end of the barrel, and the pen seal is embedded inside the pen tip end cap. The second sealing structure is disposed inside the barrel, and the position where the second sealing structure forms a sealing fit with the transmission structure is axially spaced a certain distance from the first seal. When the pen tip is retracted, the first sealing structure and the second sealing structure together form a closed cavity, sealing the pen tip within the closed cavity.

7. The differential pressure self-locking airtight key pen as described in claim 6, characterized in that, The inner wall of the pen tip cap is provided with an annular shoulder, which abuts against the outer side of the pen tip to form a first axial limiting structure; the front end face of the pen barrel abuts against the end face of the open end of the cylinder to form a second axial limiting structure; wherein, the annular shoulder is provided with a plurality of grooves spaced apart along its edge.

8. The differential pressure self-locking airtight key pen as described in claim 6, characterized in that, The end face of the open end of the cylindrical part is provided with a positioning block that protrudes outward along the axis of the cylindrical part; the front end of the pen barrel is provided with a positioning groove that is recessed inward along the axis of the pen barrel; the positioning groove and the positioning block are complementary in shape to form an axial limiting structure.

9. The differential pressure self-locking airtight key pen as described in claim 6, characterized in that, The pen barrel has a connector protruding outward along the pen barrel axis on its front end face. The connector is inserted into the inner cavity of the cylindrical body. The inner wall of the cylindrical body is sealed to the outer wall of the connector, and the outer wall of the cylindrical body is sealed to the inner wall of the pen tip cap.

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