Automatic retraction pen
By using magnetic suction components and elastic parts in the automatic retracting pen, the refill automatically retracts the pen holder when not in use, solving the problems of easy damage to the pen tip and harming the human body in the prior art, and providing automated Protection mechanism.
Patent Information
- Application Number
- CN202421067307.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-15
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2034-05-15
AI Technical Summary
The existing automatic anti-fall pen only starts the retracted structure after the pen falls, which cannot protect the pen tip in time, and the pen tip is still open when it has not fallen on the desktop, making it susceptible to collision damage or damage to the human body.
Design an automatic retracting pen, using magnetic suction components and elastic parts, the refill automatically retracts into the pen holder when not in use. Through the cooperation of buttons and magnetic suction components, the refill is made by the action of gravity and elastic parts to make the refill when placed. Automatically retract to avoid exposure of the pen tip.
Automatic retraction of the pen tip can be achieved without manual operation, protecting the pen tip from damage and accidental collisions, avoiding the pen tip from harming the human body, ensuring that the pen tip is always in a contracted state, and extending the service life.
Smart Images
Figure CN222271672U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of stationery, and more specifically to an automatic retractable pen. Background Art
[0002] The pen is the most commonly used writing tool for people to write. The current pen is mainly composed of a pen barrel and a pen core. The pen core is installed in the pen barrel, and the tip of the pen core extends out of one end of the pen barrel. When a person writes, he holds the pen barrel and makes the pen tip touch the pen tip. The ink in the pen core can flow to the paper through the pen tip to complete the writing. In this process, the pen tip is in an open state. The pen tip in an open state is easily hit, and the pen tip after the collision is prone to water shortage, ink leakage and other faults, causing the pen core to be unable to continue to be used. The general technical solution is to protect the pen tip by setting a pen cap to cover the pen tip or by pressing a button to retract the pen tip into the pen barrel. However, in actual use, after finishing writing, the user often puts the pen on the desktop casually, forgets to cover the pen cap or press the button to retract the pen tip into the pen barrel, so that the pen tip is still in an open state. In order to facilitate holding, the pen barrel is generally set to a cylindrical shape. Therefore, the pen placed on the desktop is easily affected by the outside world and causes rolling. When the pen rolls off the table and falls to the ground, it will be hit and impacted, causing damage to the pen tip. At the same time, if the pen tip is kept open, it may collide with other objects, causing damage to the pen tip. If the pen tip accidentally touches the surface of other objects, the pen tip is sharp and may cause accidental injury to the human body.
[0003] There is a Chinese utility model with application number CN202223320590.5, which discloses a weightlessness-sensing anti-drop pen, and relates to an anti-drop pen. It includes a pen barrel, a refill seat is slidably arranged in the pen barrel, a magnetic structure is also arranged in the pen barrel, the magnetic structure adsorbs the refill seat, and a retraction structure is also arranged between the refill seat and the pen barrel. When the refill touches the ground, the refill seat retracts the refill back into the pen barrel through the retraction structure. The beneficial effect of the utility model is that the refill seat can be kept relatively fixed with the pen barrel by arranging the magnetic structure, and at the same time, the retraction structure can be arranged to limit the upward movement of the refill seat after it moves downward, so as to ensure writing, and the upward movement restriction of the refill seat can be cancelled when the pen falls, so that the refill can be smoothly retracted into the pen barrel after touching the ground, avoiding damage to the pen tip on the refill.
[0004] However, in this technical solution, the retraction structure can only be activated after the pen falls down and enters a weightless state, which causes the problem that the pen tip cannot be retracted in time. Moreover, when the pen is placed on the desktop and does not fall, the retraction structure cannot be activated, and the pen tip is still in an open state, which cannot protect the pen tip from collision on the desktop, and the pen tip is easy to scratch objects on the desktop, and solve the problem that the pen tip is sharp and easy to cause harm to the human body. Utility Model Content
[0005] In order to solve the above problems, the utility model provides an automatic retracting pen. Only by placing the pen flat on the table, the pen tip can be automatically retracted into the pen barrel, thereby protecting the pen tip. No manual operation is required, thus avoiding the problems of pen tip being damaged due to forgotten operation, the pen tip scratching other objects, and the sharp pen tip easily causing harm to the human body.
[0006] In order to solve the above technical problems, the technical solution adopted by the utility model is: an automatic retractable pen, including a pen barrel, a refill, a button, a magnetic attraction component and an elastic member, the refill is installed in the pen barrel, and an elastic member is installed at the tip of the refill, and the two ends of the elastic member are respectively abutted against the pen barrel and the refill; the button is slidably installed on the pen barrel perpendicular to the length direction of the pen barrel, the magnetic attraction component includes a first body fixedly installed in the pen barrel and a second body that can be attracted to the first body, the button has an inserting portion inserted into the connecting surface of the first body and the second body and an abutting portion for abutting against the refill, the abutting portion is located below the inserting portion, and a receiving groove for receiving part of the second body is formed on the abutting portion; a limiting groove for accommodating part of the second body is also connected in the pen barrel, and the second body is located in the limiting groove and the receiving groove to lock the button.
[0007] In the present technical scheme, the pen core is arranged in the pen barrel, which plays a protective role for the pen core. When the pen is not in use, the pen core shrinks in the pen barrel and cannot be written. The button is slidably installed on the pen barrel perpendicular to the length direction of the pen barrel, and the button includes an abutment portion and an insertion portion, wherein the abutment portion abuts against the pen core. When the pen needs to be used, the button is pressed, and the abutment portion of the button pushes the pen core to move, so that the tip of the pen core protrudes from the pen barrel. A magnetic suction component is also arranged in the pen barrel, and the magnetic suction component includes a first body and a second body, wherein the first body is fixed at one end of the pen barrel away from the pen core, and the second body is adsorbed by the first body. When the user uses the pen, after lifting the pen, the second body is affected by gravity, and the adsorption force between the second body and the first body is offset. At the same time, the button is pressed, and the insertion portion of the button is inserted between the first body and the second body, and the insertion portion pushes the second body to move so that the first body and the second body are separated. A limit groove is also arranged in the pen barrel, and a receiving groove is arranged on the abutment portion of the button. After the second body is separated from the first body, it falls into the limiting groove and the receiving groove, fixing the relative position between the limiting groove and the button. The limiting groove is a fixed structure that cannot be moved, thereby achieving the locking of the button position, ensuring that the tip of the pen core will not be retracted into the pen barrel due to the sliding of the button during use, affecting normal writing. The pen core is installed in the pen barrel, and an elastic member is installed at the tip of the pen core, and the two ends of the elastic member are respectively in contact with the pen barrel and the pen core. The elastic member provides a restoring force for the pen core to be retracted into the pen barrel. When the pen is not needed, the user puts the pen down, and the gravity on the second body cannot offset the adsorption force of the first body on the second body due to the change in direction. The first body sucks the second body out of the receiving groove, releasing the lock on the movement of the button. The pen core moves toward the inside of the pen barrel under the action of the elastic member, and at the same time the button is pushed back to the initial position by the pen core, and the pen tip of the pen core retracts into the pen barrel, thereby preventing the pen tip from being continuously exposed outside the pen barrel to scratch other objects, the pen tip being sharp and easily causing harm to the human body, and the pen tip being damaged due to the pen rolling off the ground.
[0008] Preferably, the button further comprises a connecting portion, the connecting portion is located outside the pen barrel, and a side of the connecting portion close to the pen barrel is connected to an end of the inserting portion extending out of the pen barrel and an end of the abutting portion extending out of the pen barrel.
[0009] Preferably, the plug-in portion is slidably connected to the pen holder, and the lower surface of the plug-in portion is an inclined surface that slopes downward from the end of the plug-in portion that is inserted into the pen holder.
[0010] Preferably, the upper surface of the plug-in portion is parallel to the bottom surface of the first body.
[0011] Preferably, the abutment portion is slidably connected to the pen holder, the lower surface of the abutment portion is a second inclined surface that is inclined downward from the end of the abutment portion inserted into the pen holder, and the accommodating groove is arranged on the upper surface of the abutment portion.
[0012] Preferably, a first through hole and a second through hole are formed on the outer wall surface of the end of the pen barrel away from the pen tip, the first through hole is located above the second through hole, the first through hole is slidably connected to the plug-in portion, and the second through hole is slidably connected to the abutment portion.
[0013] Preferably, a connecting piece is provided in the pen barrel, the connecting piece has a limiting groove with open upper and lower ends, the connecting piece is aligned with the second body, and the second body can be inserted into the connecting piece.
[0014] Preferably, a limiting structure is further provided in the pen barrel, and the limiting structure is slidably connected to the tube wall of the pen core.
[0015] Preferably, a cylindrical structure with two open ends is provided in the center of the limiting structure, and the pen core passes through the cylindrical structure.
[0016] Preferably, a second abutment portion is provided at the tip of the pen core, the diameter of the second abutment portion is larger than the diameter of the pen tip, a side of the second abutment portion close to the pen tip abuts against one end of the elastic member, and the other end of the elastic member abuts against the inner wall surface of the lower end of the pen barrel.
[0017] Compared with the prior art, the utility model has the following beneficial effects: the pen tip can be retracted into the pen barrel by simply laying the pen flat, without any manual operation, thus avoiding the possibility of forgetting to retract the pen tip due to forgetfulness. The second body can be inserted into the button, and the button position can be fixed to ensure that the pen tip can always protrude from the pen barrel during normal writing and will not be accidentally retracted. The button is provided with a plug-in connector and an abutment, both of which are provided with a sharp angle structure, so that the plug-in connector and the abutment are easier to insert between the first body and the second body and push the pen core to move. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a half-section diagram of the nib of the automatic retractable pen of the utility model in an extended state;
[0019] Figure 2 It is a half-section diagram of the nib of the automatic retractable pen of the utility model in a retracted state.
[0020] In the accompanying drawings: 1. pen holder; 2. pen core; 3. button; 4. magnetic attraction component; 5. elastic member; 11. first through hole; 12. second through hole; 21. second abutting portion; 31. connecting portion; 32. plug-in portion; 33. abutting portion; 41. first body; 42. second body; 321. inclined surface; 331. accommodating groove; 332. second inclined surface. DETAILED DESCRIPTION
[0021] The drawings are only for illustrative purposes and cannot be construed as limiting the present invention. To better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are only for illustrative purposes and cannot be construed as limiting the present invention.
[0022] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "long", "short" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.
[0023] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings:
[0024] Example 1
[0025] like Figure 1As shown, an automatic retractable pen comprises a pen barrel 1, a pen core 2, a button 3, a magnetic attraction component 4 and an elastic member 5, the pen core 2 is installed in the pen barrel 1, and the elastic member 5 is installed at the tip of the pen core 2, and the two ends of the elastic member 5 are respectively abutted against the pen barrel 1 and the pen core 2; the button 3 is slidably installed on the pen barrel 1 perpendicular to the length direction of the pen barrel 1, the magnetic attraction component 4 comprises a first body 41 fixedly installed in the pen barrel 1 and a second body 42 that can be attracted to the first body 41, the button 3 has an inserting portion 32 inserted into the connecting surface of the first body 41 and the second body 42 and an abutting portion 33 for abutting against the pen core 22, the abutting portion 33 is located below the inserting portion 32, and a receiving groove 331 for receiving part of the second body 42 is formed on the abutting portion 33; a limiting groove 6 for accommodating part of the second body 42 is also connected in the pen barrel 11, and the second body 42 is located in the limiting groove 6 and the receiving groove 331 to lock the button 33. The pen core 2 is arranged in the pen barrel 1, which plays a protective role for the pen core 2. When the pen is not in use, the pen core 2 shrinks in the pen barrel 1 and cannot be written. The button 3 is slidably installed on the pen barrel 1 perpendicular to the length direction of the pen barrel 1. The button 3 includes an abutment portion 33 and an insertion portion 32, wherein the abutment portion 33 abuts against the pen core 2. When the pen needs to be used, the button 3 is pressed, and the abutment portion 33 of the button 3 pushes the pen core 2 to move, so that the tip of the pen core 2 protrudes from the pen barrel 1. A magnetic suction component 4 is also arranged in the pen barrel 1. The magnetic suction component 4 includes a first body 41 and a second body 42, wherein the first body 41 is fixed at one end of the pen barrel 1 away from the pen core 2, and the second body 42 is adsorbed by the first body 41. When the user uses the pen, after lifting the pen, the second body 42 is affected by gravity, and the adsorption force between the second body 42 and the first body 41 is offset. At the same time, the button 3 is pressed, and the plug-in portion 32 of the button 3 is inserted between the first body 41 and the second body 42. The plug-in portion 32 pushes the second body 42 to move so that the first body 41 is separated from the second body 42. A limiting groove 6 is also provided in the pen barrel 1, and a receiving groove 331 is provided on the abutting portion 33 of the button 3. After the second body 42 is separated from the first body 41, it falls into the limiting groove 6 and the receiving groove 331, fixing the relative position between the limiting groove 6 and the button 3. The limiting groove 6 is a fixed structure that cannot be moved, thereby locking the position of the button 3, ensuring that the pen tip of the pen core 2 will not be retracted into the pen barrel 1 due to the sliding of the button 3 during use, affecting normal writing. The pen core 2 is installed in the pen barrel 1, and an elastic member 5 is installed at the pen tip of the pen core 2, and the two ends of the elastic member 5 are respectively abutted against the pen barrel 1 and the pen core 2. The elastic member 5 provides a restoring force for the pen core 2 to retract into the pen barrel 1. When the pen is not needed, the user puts the pen down. The gravity on the second body 42 cannot offset the adsorption force of the first body 41 on the second body 42 due to the change in direction. The first body 41 sucks the second body 42 out of the accommodating groove 331, thereby releasing the lock on the movement of the button 3.The refill 2 moves toward the inside of the pen barrel 1 under the action of the elastic member 5, and at the same time, the button 3 is pushed back to the initial position by the refill 2, and the tip of the refill 2 retracts into the pen barrel 1, thereby preventing the tip of the pen from being continuously exposed outside the pen barrel 1 and scratching other objects, the sharp pen tip being easily harmful to the human body, and the pen tip being damaged due to the pen rolling off the ground.
[0026] like Figure 1 As shown, the button 3 also includes a connecting portion 31, which is located outside the pen barrel 1. The side of the connecting portion 31 close to the pen barrel 1 is connected to the end of the plug-in portion 32 extending out of the pen barrel 1 and the end of the abutting portion 33 extending out of the pen barrel 1. The connecting portion 31 connects the plug-in portion 32 and the abutting portion 33. When the pen needs to be used, it is only necessary to press the connecting portion 31, and the connecting portion 31 can drive the plug-in portion 32 and the abutting portion 33 to move together to push the tip of the pen core 2 out of the pen barrel 1. When the pen is not needed, the restoring force provided by the elastic member 5 acts on the abutting portion 33 through the pen core 2, and the abutting portion 33 transmits the movement to the plug-in portion 32 through the connecting portion 31, so that the abutting portion 33, the connecting portion 31 and the plug-in portion 32 move together to restore to the initial position.
[0027] like Figure 1 As shown, the plug-in portion 32 is slidably connected to the pen holder 1, and the lower surface of the plug-in portion 32 is an inclined surface 321 that is inclined downward from the end of the plug-in portion 32 inserted into the pen holder 1. The lower surface of the plug-in portion 32 is the inclined surface 321, which together with the upper surface of the plug-in portion 32 forms a wedge-shaped structure, making it easier for the plug-in portion 32 to be inserted between the first body 41 and the second body 42. At the same time, as the inclined surface 321 is gradually inserted, the contact between the inclined surface 321 and the second body 42 moves along the inclined direction of the inclined surface 321, and finally pushes the second body 42 to the direction where the pen core 2 is located.
[0028] like Figure 1 As shown, the upper surface of the plug-in portion 32 is parallel to the bottom surface of the first body 41. The first component 41 is fixed in the pen holder 1 and cannot move, so the upper surface of the plug-in portion 32 in contact with the first component 41 should remain parallel to the bottom surface of the first body 41 to avoid the button 3 being unable to be pressed into the pen holder 1 due to interference with the first component 41.
[0029] The abutment portion 33 is slidably connected to the pen barrel 1, and the lower surface of the abutment portion 33 is a second inclined surface 332 that is inclined downward from the end of the abutment portion 33 inserted into the pen barrel 1, and the receiving groove 331 is provided on the upper surface of the abutment portion 33. The lower surface of the abutment portion 33 is the second inclined surface 332, which together with the upper surface of the abutment portion 33 forms a wedge-shaped structure, making it easier for the abutment portion 33 to be inserted above the pen core 2. At the same time, as the second inclined surface 332 is gradually inserted, the contact between the second inclined surface 332 and the pen core 2 moves along the inclined direction of the second inclined surface 332, and finally the tip of the pen core 2 is pushed out of the pen barrel 1. The upper surface of the abutment member 33 faces the direction of the second body 42, so the receiving groove 331 for being inserted by the second body 42 is provided on the upper surface of the abutment member 33.
[0030] Example 2
[0031] This embodiment is similar to the above-mentioned embodiment 1, except that: Figure 1 As shown, a first through hole 11 and a second through hole 12 are provided on the outer wall surface of the end of the pen barrel 1 away from the pen tip, the first through hole 11 is located above the second through hole 12, the first through hole 11 is slidably connected to the plug-in portion 32, and the second through hole 12 is slidably connected to the abutment portion 33. The first through hole 11 and the second through hole 12 provide a space for the button 3 to extend from the pen barrel 1, so that the operator only needs to press the connection portion 31 of the button 3 located outside the pen barrel 1 to control the movement of the button 3 inside the pen barrel 1. At the same time, the first through hole 11 and the second through hole 12 constitute a two-point fixation for the button 3, so that the button 3 only slides along the direction where the first through hole 11 and the second through hole 12 are located, and is not easily deflected.
[0032] like Figure 2 As shown, a connecting member 13 is provided in the pen holder 1, and the connecting member 13 has a limiting groove 6 opened at both ends, and the connecting member 13 is aligned with the second body 42, and the second body 42 can be inserted into the connecting member 13. The second body 42 can only move along the opening direction of the connecting member 13, so that the movement trajectory of the second body 42 is determined, ensuring that the second body 42 can be accurately inserted into the limiting groove 6 and the accommodating groove 331, and at the same time providing a support force for the second body 42 to prevent the second body 42 from being offset.
[0033] like Figure 1 As shown, a limiting structure 14 is also provided in the pen barrel 1, and the limiting structure is slidably connected to the tube wall of the pen core 2. The limiting structure 14 is used to support the position of the pen core 2, ensuring that the pen core 2 is located at the center of the pen barrel 1.
[0034] like Figure 1As shown, a cylindrical structure with two open ends is provided in the center of the limiting structure 14, and the pen core 2 passes through the cylindrical structure. The cylindrical structure with two open ends increases the contact area between the limiting structure 14 and the pen core 2 without affecting the normal movement of the pen core 2, and has a better supporting effect on the pen core 2.
[0035] Example 3
[0036] This embodiment is similar to the above-mentioned embodiment 1, except that: Figure 1 As shown, the tip of the pen core 2 is provided with a second abutment 21, the diameter of the second abutment 21 is larger than the diameter of the pen tip, the side of the second abutment 21 close to the pen tip abuts against one end of the elastic member 5, and the other end of the elastic member 5 abuts against the inner wall surface of the lower end of the pen barrel 1. When the button 3 is contacted and locked, the compressed elastic member 5 stretches, pushes the second abutment 21, and then drives the pen core 2 to move inside the pen barrel 1, and pushes the button 3 to return to the initial position. Finally, the elastic member 5 is fully stretched, so that the tip of the pen core 2 retracts into the pen barrel 1.
[0037] Obviously, the above embodiments of the utility model are only examples for clearly explaining the utility model, and are not intended to limit the implementation methods of the utility model. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the utility model should be included in the protection scope of the claims of the utility model.
Claims
1. An automatic retractable pen, characterized in that: The invention comprises a pen barrel (1), a pen core (2), a button (3), a magnetic attraction component (4) and an elastic member (5); the pen core (2) is installed in the pen barrel (1); the elastic member (5) is installed at the tip of the pen core (2); the two ends of the elastic member (5) are respectively in contact with the pen barrel (1) and the pen core (2); the button (3) is slidably installed on the pen barrel (1) perpendicular to the length direction of the pen barrel (1); the magnetic attraction component (4) comprises a first body (41) fixedly installed in the pen barrel (1) and a second body (42) that can be attracted to the first body (41); the button (3) is installed on the pen barrel (1) and the magnetic attraction component (4) is installed on ... The button (3) comprises an inserting portion (32) inserted into the connecting surface of the first body (41) and the second body (42) and an abutting portion (33) for abutting against the pen core (2); the abutting portion (33) is located below the inserting portion (32); a receiving groove (331) for receiving part of the second body (42) is formed on the abutting portion (33); a limiting groove (6) for accommodating part of the second body (42) is also connected to the pen barrel (1); the second body (42) is located in the limiting groove (6) and the receiving groove (331) to lock the button (3).
2. An automatic retractable pen according to claim 1, characterized in that: The button (3) further comprises a connecting portion (31), wherein the connecting portion (31) is located outside the pen barrel (1), and a surface of the connecting portion (31) close to the pen barrel (1) is connected to an end of the plug-in portion (32) extending out of the pen barrel (1) and an end of the abutting portion (33) extending out of the pen barrel (1).
3. An automatic retractable pen according to claim 1, characterized in that: The plug-in portion (32) is slidably connected to the pen holder (1), and the lower surface of the plug-in portion (32) is an inclined surface (321) that is inclined downward from one end of the plug-in portion (32) inserted into the pen holder (1).
4. An automatic retractable pen according to claim 2, characterized in that: The upper surface of the plug-in portion (32) is parallel to the bottom surface of the first body (41).
5. The automatic retractable pen according to claim 1, characterized in that: The abutment portion (33) is slidably connected to the pen holder (1); the lower surface of the abutment portion (33) is a second inclined surface (332) that is inclined downward from one end of the abutment portion (33) inserted into the pen holder (1); and the accommodating groove (331) is arranged on the upper surface of the abutment portion (33).
6. The automatic retractable pen according to claim 1, characterized in that: A first through hole (11) and a second through hole (12) are provided on the outer wall surface of the end of the pen barrel (1) away from the pen tip, the first through hole (11) is located above the second through hole (12), the first through hole (11) is slidably connected to the plug-in portion (32), and the second through hole (12) is slidably connected to the abutting portion (33).
7. The automatic retractable pen according to claim 1, characterized in that: A connecting piece (13) is arranged inside the pen holder (1), and the connecting piece (13) has the limiting groove (6) which is open at both ends. The connecting piece (13) is aligned with the second body (42), and the second body (42) can be inserted into the connecting piece (13).
8. The automatic retractable pen according to claim 1, characterized in that: A limiting structure (14) is also provided in the pen barrel (1), and the limiting structure is slidably connected to the tube wall of the pen core (2).
9. An automatic retractable pen according to claim 8, characterized in that: A tubular structure with two open ends is arranged in the center of the limiting structure (14), and the pen core (2) passes through the tubular structure.
10. The automatic retractable pen according to claim 1, characterized in that: A second abutting portion (21) is provided at the tip of the pen core (2); the diameter of the second abutting portion (21) is greater than the diameter of the pen tip; a surface of the second abutting portion (21) close to the pen tip abuts against one end of the elastic member (5); and the other end of the elastic member (5) abuts against the inner wall surface of the lower end of the pen barrel (1).