Notebook

Abstract

To provide a writing instrument and lead-holding structure that can easily and reliably hold a broken pencil lead, allowing for continuous use. [Solution] A writing instrument for holding a broken pencil lead has a pair of clamping pieces for holding the lead, an openable and closable clamping part, an elastic support part that biases the clamping pieces in the closing direction, a gripping part for the user to hold, and an opening and closing mechanism for opening and closing the clamping pieces, wherein the pair of clamping pieces are configured such that when the lead is not being held, their clamping surfaces come into contact with each other so that there is no substantial gap.

Description

[Technical Field]

[0001] The present invention relates to a writing instrument that enables reuse of broken pencil leads, and particularly relates to a lead holding structure that can reliably hold even short leads or leads with uneven diameters and enables continuous writing. [Background Art]

[0002] Pencils are widely used as writing instruments, but their leads often break during use, and shortened leads are generally discarded without being reused. On the other hand, mechanical pencils have a configuration in which thin-diameter leads are extended for use, and the thickness and shape of leads are standardized, so it has been difficult to use broken pencil leads directly as they are. For this reason, from the viewpoint of effective utilization of resources, structures and instruments that can easily reuse broken pencil leads have been demanded, but a sufficiently practical technique has not been established.

[0003] Non-Patent Document 1 describes that: "Attempts were made to produce a writing instrument by mixing graphite with wheat flour clay, reusing broken mechanical pencil leads and pencil leads that can no longer be used. Depending on the material ratio, firing method, and contrivance of the handle, the product reached a level practical as a simple writing instrument. This attempt is significant in that it demonstrates a new possibility for reducing environmental load and recycling." [Prior Art Document] [Non-Patent Literature]

[0004] [Non-Patent Document 1] Recycling of Unusable Broken Mechanical Pencil Leads, [online], Internet <URL,https: / / handa-h.jp / wp-content / uploads / 2026 / 03 / 25fd219a52387da412a3fed0db1b9652.pdf> [Brief Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Conventional writing instruments have lacked effective ways to utilize broken pencil leads, and short leads are often discarded because they are difficult to grip and write with. Furthermore, existing lead-holding mechanisms, such as those found in mechanical pencils, have standardized lead diameters and shapes, making it difficult to reliably hold irregularly shaped broken leads. Additionally, when multiple short leads are connected, insufficient strength at the connection point and lead misalignment are common, making it difficult to ensure stable writing performance. In view of these problems, the present invention aims to provide a writing instrument and lead-holding structure that can easily and reliably hold broken pencil leads, allowing for continuous use. In particular, the invention aims to provide a writing instrument and lead-holding structure capable of holding broken pencil leads of different diameters. [Means for solving the problem]

[0006] A writing instrument for holding a broken pencil lead, It has a pair of clamping pieces 1A that hold the core, and a clamping part 1 that can be opened and closed, A biasing part 3 that biases the clamping piece 1A in the closing direction, A gripping part 2 for the user to hold, An opening and closing mechanism for opening and closing the clamping piece 1A, Equipped with, A writing instrument characterized in that the pair of clamping pieces 1A are configured such that when the core is not being clamped, their clamping surfaces come into contact with each other so that there is virtually no gap. [Brief explanation of the drawing]

[0007] [Figure 1] This is a complete diagram of the writing instrument. [Figure 2] This is an internal diagram of a part of a writing instrument. [Figure 3] This is a diagram illustrating the opening and closing mechanism of a writing instrument. [Modes for carrying out the invention]

[0008] Figure 1 shows a writing instrument 10 for holding a broken pencil lead. This writing instrument 10 has a pair of clamping pieces 1A for holding the lead, and also has an openable and closable clamping part 1. The writing instrument 10 also has a gripping part 2 connected to the clamping part 1. Here, "clamping part 1" refers to a component that mechanically fixes the lead, and includes a pair of elastic clamping pieces 1A or a pair of clamping pieces 1A with a variable inner diameter. "Gripping part 2" is a shaft-shaped member that the user grips.

[0009] The clamping portion 1 has a pair of clamping pieces 1A that clamp the core. The clamping pieces 1A are configured such that when the core is not being clamped, their clamping surfaces are in contact with each other, so that there is virtually no gap. That is, the pair of clamping pieces 1A are biased by a biasing portion 3 that biases the clamping pieces 1A in the closing direction. This configuration makes it possible to securely hold even a small diameter core. The clamping pieces 1A may be made of an elastic material and may be able to be opened and closed by external force.

[0010] Furthermore, the clamping portion 1 may include a connecting member for connecting multiple cores. The connecting member has an inner circumferential surface formed in a funnel shape and an outer circumferential surface formed in a cylindrical shape. "Funnel shape" refers to a shape in which the opening diameter at one end is larger than the opening diameter at the other end. This configuration allows the ends of the broken cores to be guided and aligned coaxially.

[0011] The inner diameter of the connecting member can be configured such that the inner diameter at the tip is 1.0 mm or more and 2.0 mm or less, and the inner diameter at the end is 0.3 mm or more and 1.0 mm or less. In other words, by defining the range of the inner diameter at the tip and end, it is possible to accommodate various core diameters while ensuring the positioning accuracy of the core.

[0012] Furthermore, by combining the clamping portion 1 and the connecting member, it becomes possible to hold not only a single lead but also multiple leads in a connected state. This allows for continuous writing even when a lead becomes short by connecting a new lead.

[0013] One embodiment of the present invention is a writing instrument 10 equipped with a clothespin-shaped clamping part 1. This writing instrument 10 has a pair of clamping pieces 1A at its tip and a gripping part 2 extending toward the end. When in use, the broken lead is inserted by opening the clamping pieces 1A and then the lead is secured by closing the clamping pieces 1A. When a broken lead is not inserted, the clamping surface makes full contact, so there is no gap and even a thin lead can be prevented from slipping out.

[0014] The writing instrument 10 according to this embodiment is equipped with a so-called clothespin-shaped clamping part 1 and is configured for the purpose of easily holding a broken pencil lead. The writing instrument 10 mainly comprises a clamping part 1 located at the tip, a gripping part 2 extending to the end, and a biasing part 3 that allows the clamping part 1 to be opened and closed.

[0015] The clamping portion 1 has a pair of clamping pieces 1A, which are positioned opposite each other. The "clamping pieces 1A" are members that directly hold the core, and a clamping surface is formed on the inside thereof. The clamping surface is formed as a flat surface, or a surface with grooves or fine irregularities, and has the function of preventing the core from slipping by increasing the frictional force. The clamping surfaces of the clamping pieces 1A are in contact with each other when closed, so that there is virtually no gap. For this reason, even a small diameter core with a diameter of 0.3 mm or more and 1.0 mm or less can be securely clamped.

[0016] The biasing part 3, which biases the clamping piece 1A in the closing direction, is formed, for example, from an elastic material or a coil spring. This biasing part 3 has a restoring force that returns the clamping piece 1A to its original closed state when the external force is released, after it has been opened by an external force. When the user presses the push button 2A with their finger, the interlocking rod shown in Figure 2 moves toward the tip. The interlocking rod is connected to a link mechanism 4, which is an opening and closing mechanism that opens and closes the pair of clamping pieces 1A. The link mechanism 4 is also connected to the base ends of the pair of clamping pieces 1A. Therefore, when the interlocking rod moves toward the tip, the pair of clamping pieces 1A rotate around the rotation axis 4A in a direction away from each other. As a result, the tip side of the clamping part 1 opens, allowing the core to be inserted.

[0017] Subsequently, when the user releases their finger, the biasing portion 3 biases the interlocking rod, and the interlocking rod moves toward the distal end. Then, the pair of clamping pieces 1A rotate around the rotating shaft 4A in a direction approaching each other. Accordingly, the distal end side of the clamping portion 1 is closed, and the lead can be clamped.

[0018] The grip portion 2 is a shaft-shaped member connected to the rear of the link mechanism 4, and is a portion gripped by a user with a hand. The length of the grip portion 2 can be, for example, 50 mm or more and 150 mm or less. That is, the length of the grip portion 2 is set to a range of 50 mm or more and 150 mm or less. By setting this range, sufficient grip performance can be ensured even when a short lead is used.

[0019] Further, it is preferable that the distal end portion of the clamping piece 1A has a curved surface or a chamfered shape so as not to damage the lead. Furthermore, an elastic coating layer or a rubber pad can be provided on the clamping surface. In this case, the followability to variations in lead diameter is improved, and more stable holding can be achieved.

[0020] As the operation of the present embodiment, the user first opens the clamping piece 1A, inserts the broken lead, and then closes the clamping piece 1A to fix the lead. Here, since the clamping surfaces are configured to abut against each other so that no gap is formed, even a thin lead can be held without falling off. Further, when the lead becomes short, it can be continuously used by inserting and holding a new lead in the same manner.

[0021] Furthermore, since the present configuration is realized with a simple mechanical structure, it has the advantages that the number of parts is small, the manufacturing cost can be reduced, and the durability is also excellent. In addition, since it can be used without depending on the diameter or length of the lead, it can be applied to various types of broken leads, and contributes to effective utilization of resources.

[0022] As described above, the writing instrument 10 according to the present embodiment is useful in that it can reliably hold a broken pencil lead while having a simple structure.

[0023] The "clamping section 1" refers to a mechanism that includes a pair of clamping pieces 1A that are rotatable relative to each other via a rotating shaft 4A, and which clamps the pencil lead with the pair of clamping pieces 1A. The writing instrument 10 may be configured in the shape of a clothespin. The clamping section 1 of this writing instrument 10 consists of a pair of levers extending from the pair of clamping pieces 1A, a biasing section (torsion spring) connecting the pair of levers, and a gripping section that holds the pair of levers. When the user pinches the ends of the levers and applies force to narrow the gap between them, the gap between the pair of clamping pieces 1A opens with the central axis of the torsion spring as the fulcrum. Then, when the user releases the force from their fingers after clamping the broken lead, the pair of clamping pieces 1A, which are biased by the torsion spring, close, and the broken lead can be clamped. The torsion spring and levers function as an opening and closing mechanism for opening and closing the clamping pieces 1A.

[0024] The writing instrument 10 comprises a first clamping piece, a second clamping piece, a link mechanism 4 that rotatably supports the first and second clamping pieces, and a biasing part 3 that biases the first and second clamping pieces in the closing direction. The first and second clamping pieces each extend forward of the rotation axis 4A.

[0025] The inner surfaces of the first and second clamping pieces are formed with clamping surfaces that contact the pencil lead. When closed, the clamping surfaces approach or touch each other, pressing the broken pencil lead from both sides. As a result, even short leads or leads of uneven diameter are held in place by friction and clamping force. The clamping surfaces may be provided with grooves along the axial direction of the lead, fine irregularities, or a coating layer made of an elastic material. This prevents the lead from sliding back and forth or rotating circumferentially during writing.

[0026] The push button 2A is the part that the user presses with their finger. When the user presses the push button 2A, the first clamping piece and the second clamping piece move apart from each other around the rotation axis 4A, and the clamping part 1 opens. In this open state, the user can insert a broken pencil lead between the clamping surfaces. After that, when the user releases the pressure, the biasing force of the biasing part 3 brings the first clamping piece and the second clamping piece closer together, and the pencil lead is clamped.

[0027] As the biasing part 3, for example, a torsion coil spring, a leaf spring, or the elastically deformable part of the clamping piece 1A itself can be used. In particular, if the clamping piece 1A itself is made of an elastic member and a hinge is formed near the rotation axis 4A, the number of parts can be reduced.

[0028] Furthermore, it is preferable that the clamping portion 1 is configured such that the clamping surfaces abut each other in the closed state, without forming any substantial gaps. With this configuration, even when the core diameter is small, the core can be held without slipping between the clamping surfaces. Moreover, if the clamping surfaces are concave curved surfaces that conform to the outer circumference shape of the core, the contact area with the core increases, which can suppress breakage and detachment of the core.

[0029] With the above configuration, the clamping part 1 can detachably hold a broken pencil lead with a simple opening and closing operation, and can stably fix even a short lead to the tip of the writing instrument 10.

[0030] The "clamping part 1" refers to a mechanism that directly grips a broken pencil lead and stably maintains the lead's position during writing. The clamping part 1 in this invention has at least one pair of clamping pieces 1A and is configured to clamp the lead with opposing clamping surfaces.

[0031] The clamping piece 1A includes a clamping surface that contacts the core and a base on which the clamping surface is formed. The "clamping surface" is the portion that contacts the outer circumferential surface of the core and is formed in a planar, curved, or a combination thereof shape. In particular, the clamping surface is preferably a concave curved surface corresponding to the outer diameter of the core. In this case, the contact area with the core is increased, and a stable holding force can be obtained while suppressing localized stress concentration.

[0032] The clamping surfaces are configured to contact each other in the closed state, forming virtually no gaps. Here, "forming virtually no gaps" means that when the smallest diameter core to be clamped is held, the clamping surfaces are close enough or in contact to prevent the core from falling out from between them. This configuration makes it possible to securely hold cores with diameters of, for example, 0.3 mm or more and 1.0 mm or less.

[0033] Furthermore, the clamping surface may be provided with grooves along the axial direction of the lead, fine irregularities, or a coating layer made of an elastic material. The grooves assist in positioning the lead and suppress lateral displacement of the lead. The irregularities or elastic coating layer increase the coefficient of friction and improve the ability to follow variations in lead diameter. As a result, slippage or rotation of the lead during writing is suppressed, ensuring stable writing performance.

[0034] The clamping force of the clamping portion 1 is generated by the elastic force applied to the clamping piece 1A. It is desirable that this clamping force be set to ensure sufficient holding power without damaging the lead. For example, the clamping force should be set to such an extent that the lead does not slip against the axial pressure it receives when writing.

[0035] Furthermore, the tip shape of the clamping portion 1 can be tapered or chamfered to facilitate the insertion of the lead. This configuration allows the user to easily introduce the lead into the clamping portion 1, improving operability.

[0036] Furthermore, the clamping portion 1 may be made replaceable. In this case, by replacing the worn clamping surface, stable holding performance can be maintained over a long period of time.

[0037] As described above, the clamping portion 1 is an important component that ensures the stability of the lead during writing by reliably holding broken leads of uneven diameter and length, through the appropriate design of the shape, material, surface condition, and elastic properties of the clamping surface.

[0038] The "biasing part 3" refers to a component that generates a restoring force that biases the pair of clamping pieces 1A in the closing direction. In the present invention, the biasing part 3 constitutes the functional core of the clamping part 1 and is an important part that defines the opening and closing operation of the clamping pieces 1A and the holding force of the core.

[0039] The following are examples of modified versions of the biasing unit 3.

[0040] (1)Integrated type The clamping piece 1A has a thin-walled portion that serves as the biasing portion 3. The clamping piece 1A is made of, for example, an elastic material, and the thin-walled portion deforms to open and close. This clamping piece 1A allows for both durability to withstand repeated opening and closing and appropriate restoring force. This configuration reduces the number of parts and contributes to lower manufacturing costs.

[0041] (2) Type with added spring member This configuration uses a spring member separate from the clamping piece 1A. The spring member can be a torsion spring, a leaf spring, or the like. For example, a torsion spring is placed on the rotating shaft 4A, and its torque biases the clamping piece 1A in the closing direction. In this case, the spring constant is set within a range that securely holds the core while preventing damage to the core.

[0042] The elastic properties of the biasing part 3 directly affect the clamping force, and are therefore designed based on the material's modulus of elasticity, shape, dimensions, and deformation. For example, the opening and closing angle of the biasing part 3 can be 20 degrees or more and 45 degrees or less, from 0 degrees (closed state). That is, the opening and closing angle is 20 degrees or more and 45 degrees or less. By setting it within this range, sufficient clamping force can be ensured in the closed state while facilitating the core insertion process.

[0043] Furthermore, the biasing portion 3 is required to have fatigue characteristics that can withstand repeated use. For this reason, it is preferable to use a metal material. In addition, it is desirable to provide a curved shape or a fillet portion for the biasing portion 3 in order to alleviate stress concentration. This can suppress the occurrence of fracture and improve reliability during long-term use.

[0044] In this invention, the biasing part 3 allows the clamping piece 1A to easily open when the user presses the push button 2A, and to quickly return to the closed state when the pressure is released, thus enabling the attachment and detachment of the broken lead with simple operation. Furthermore, since a constant clamping force is always applied, stable retention is achieved even when there are variations in lead diameter.

[0045] As described above, the biasing portion 3 is an element that defines the opening and closing operation of the clamping portion 1, the generation of clamping force, and durability, and is an important component that supports the practicality of the present invention.

[0046] The "gripping portion 2" refers to the part that the user grips with their fingers to allow for stable operation of the entire writing instrument 10 during writing. In this invention, the gripping portion 2 extends behind the clamping portion 1 and the biasing portion 3 and is a component that contributes to the transmission of writing pressure.

[0047] The gripping portion 2 includes a main body portion that extends in an axial direction and a gripping surface 2B formed on the outer circumference of the main body portion. The "main body portion" is a member that extends along the longitudinal direction of the writing instrument 10 and is formed, for example, in the shape of a cylinder, elliptical column, or polygonal column. On the other hand, the "gripping surface 2B" refers to the outer surface that comes into contact with the user's fingers.

[0048] The length of the gripping portion 2 can be, for example, 50 mm or more and 150 mm or less. That is, the length of the gripping portion 2 is 50 mm or more and 150 mm or less. By setting it within this range, sufficient operability can be ensured even when using a short lead. The outer diameter can be, for example, 5 mm or more and 15 mm or less. That is, the outer diameter is 5 mm or more and 15 mm or less. By setting it within this range, appropriate gripping force can be ensured while reducing the burden on the fingers.

[0049] The gripping surface 2B may be provided with a structure to provide an anti-slip function. Specifically, this could include knurling, rib-like protrusions, or a coating with an elastomer layer. This improves gripping stability during writing and makes it easier to control the pressure applied to the lead.

[0050] Furthermore, it is desirable that the grip portion 2 be positioned approximately coaxially with the axial direction of the lead. This configuration allows writing pressure to be transmitted linearly to the lead, reducing the loss of force during writing. In addition, it is possible to provide a hollow structure inside the grip portion 2, which reduces weight and can be used as space to store spare leads as needed.

[0051] The gripping portion 2 may be formed separately from the biasing portion 3 and connected by fitting, screw connection, or the like. If they are separate components, the gripping portion 2 can be easily replaced or its material changed, improving customizability to suit different operating environments and applications.

[0052] A cap member may be provided at the rear end of the gripping portion 2. This cap member protects the gripping portion 1 when not in use and also enhances safety when carrying the device.

[0053] As described above, the gripping portion 2 is an important component that affects the operability, stability, and feel of use during operation, and the effects of the present invention can be further enhanced by appropriate dimensional setting and surface structure design.

[0054] As shown in Figure 2, the writing instrument 10 is equipped with a connecting part that connects the tip of the interlocking rod to the link mechanism 4. The interlocking rod and the like are housed in the internal space of the gripping part 2. When the push button 2A is pressed, the end portion of the interlocking rod that is in contact with the push button 2A is pushed toward the tip. Furthermore, a pad (rubber pad) is positioned inside the pair of clamping pieces 1A. This pad functions as a restricting part that restricts the movement of the lead toward the gripping part. For this purpose, the pad holds the end portion of the lead. This allows the lead to be held in place while writing. The restricting part may be a groove or unevenness formed on the clamping surface. The link mechanism 4 has a V-shaped groove, which contributes to weight reduction.

[0055] The present invention may further be a writing instrument 10 as described below. 1. The writing instrument 10 is characterized in that the biasing portion 3 includes an elastic hinge portion formed integrally with the clamping piece 1A. 2. The writing instrument 10 is characterized in that the biasing part 3 comprises a separate biasing part 3 including a torsion coil spring, a leaf spring, or a wire spring. 3. Further comprising a connecting member that connects multiple broken pencil leads coaxially, The writing instrument 10 is characterized in that the connecting member has an inner circumferential surface whose inner surface is formed in the shape of a funnel. 4. The writing instrument 10 is characterized in that the connecting member has an inner diameter of 1.0 mm or more and 2.0 mm or less at the tip end, and an inner diameter of 0.3 mm or more and 1.0 mm or less at the end end. 5. The writing instrument 10 is further characterized by comprising a cylindrical clamping portion 1 for housing the plurality of leads, and an extrusion mechanism for extending the leads in the axial direction. 6. The writing instrument 10 is characterized in that the extrusion mechanism is of the type of push-button, twist-action, or slide-action. 7. The writing instrument 10 is characterized in that the gripping portion 2 has a length of 50 mm or more and 150 mm or less, and an outer diameter of 5 mm or more and 15 mm or less. 8. The writing instrument 10 according to claim 1, characterized in that the clamping surface is formed in a shape that includes a concave curved surface corresponding to the outer circumference of the lead.

[0056] This invention was created using the "GPT-5(registered trademark).3 Instant model." The specific prompts entered and a summary of the output results are shown below. Furthermore, from input 4 onwards, the prompt "Explain the '○○ section' in detail" was entered.

[0057] Input 1: You are a brilliant inventor. You will be filing a patent application, so please propose several solutions to the problem of wasting broken pencil lead.

[0058] Output 1: Instead of focusing on "how to use a broken lead," the structure and function should be based on the premise of the broken state itself. We can't compete without focusing on this. Below are only practical, actionable ideas. 1. Modular interconnected core system (mechanical connection) Overview: Broken cores are joined together using a special miniature connector to create a single core. 2. Core regeneration holder (crushing → re-solidification) Overview: A portable device that crushes a broken core and then reshapes it into a rod. 3. Lead cartridge system (mechanical pencil for short lead only) Overview: A dedicated holder (with feeding mechanism) that allows you to use short lead directly. 4. Core alignment mechanism by magnetic / electrostatic adsorption Overview: Automatically aligns and sequentially supplies multiple short cores. 5. Changes in writing medium (from "using" the lead to "transferring") Overview: Broken pencil leads are shaved down into powder and used as transfer sheets or stamps. 6. Writing instruments with automatic refilling mechanism Summary: While writing, the subsequent lead is automatically connected to the front lead.

[0059] Input 2: Propose a method or device to solve the problem of "how to use it without making a mess," in a way that even elementary school students can understand.

[0060] Output 2: Instead of thinking "don't let the powder out," we should change our approach to "use the powder while keeping it contained." We need to come up with a proposal that even a primary school student can understand, but that is also patentable. 1. Spinning sponge pen (the most practical option) How it works: Put "black powder" inside the pen. Put a sponge around it. Make the tip a sponge as well. All the powder is trapped inside the sponge. 2. Rolling transfer roller (very inventive) How it works: A small roller with powder inside. The surface is made of rubber with a slightly rough texture. 3. Powder capsules that snap shut (a type that wins through its structure) Mechanism: A capsule containing powder. There is a fine mesh at the front. 4. Automatic rub-on transfer sheet (a slightly shifted version) Mechanism: The powder is trapped inside the sheet. When pressed from above, the powder is released only from that area.

[0061] Input 3: I think the powder won't come out easily, so please suggest an alternative method that even elementary school students can understand.

[0062] Output 3: "Dispensing the powder little by little" sounds good in theory, but in reality, it clogs, doesn't dispense properly, or is uneven. If you stick to this, you won't finish. So you need to change your approach. Stop "dispensing the powder." In other words, create a structure that "uses the powder as is without letting it out." Come up with a plan that even a primary school student can understand, but that is still competitive. 1. Clip-on pen (strongest) How it works: The tip of the pen has a "serrated claw" that clicks into place the broken lead. 2. Pens wrapped in rubber (won't slip or break) How it works: A core is placed inside a soft rubber. The rubber grips it tightly. 3.2 pens that connect (an evolved version of the linking pen) How it works: Two cores are placed inside a small part. They stick together snugly inside. 4. Stick it on like a sticker (a rather unconventional idea) Mechanism: The core is ground up to make a "thin sheet," like tape.

[0063] Input 4: Explain the structure of a clip-on pen in a way that even elementary school students can understand.

[0064] Output 4: It may look difficult, but what it does is very simple. "They're just gripping the lead tightly with their little hands." 1. There is a "small hand" inside. Inside the tip of the pen are these things: about three "claws" (like fingers), and a spring (the kind that springs back). These "claws" grip the lead. 2. It opens when you knock. When you press the end of the pen, a spring moves, the tabs open with a "snap," and the pen tip becomes ready to be inserted. 3. It closes when you release your finger. When you stop clicking, the spring returns to its original position. The claws close with a "squeeze," firmly gripping the lead. 4. Therefore, it can be used even if it's short. Regular mechanical pencils require long leads. But this one is fine even with short leads (because you can still grip it).

Claims

1. A writing instrument for holding a broken pencil lead, The clamping portion has a pair of clamping pieces that hold the core, and is openable and closable. A biasing part that biases the clamping piece in the closing direction, A gripping part for the user to hold, An opening and closing mechanism for opening and closing the clamping piece, Equipped with, A writing instrument characterized in that the pair of clamping pieces are configured such that, when the core is not being clamped, their clamping surfaces come into contact with each other so that there is virtually no gap.

2. The writing instrument according to claim 1, characterized in that it has at least one of the following as a restricting part for restricting the movement of the lead toward the gripping part: grooves or irregularities formed on the gripping surface, or a pad for holding the end of the lead.

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