Writing instrument

Abstract

To provide a writing instrument capable of preventing a male screw and a female screw from getting over each other and preventing a cylindrical component from being damaged even if excessive fastening is performed in the writing instrument having two cylindrical components which can be screwed together.SOLUTION: A writing instrument 1 includes a front shaft 2 having a first locking portion 2b, at least one second locking portion 2c, and a male screw portion 2a on which a male screw is formed, and a rear shaft 3 having a first locked portion 3b, at least one second locked portion 3c, and a female screw portion 3a on which a female screw to be screwed with the male screw is formed, and is configured such that the first locking portion 2b of the front shaft 2 and the first locked portion 3b of the rear shaft 3 are locked to each other in a state where assembly of the front shaft 2 and the rear shaft 3 is completed. At least one second locking part side 2c of the front shaft 2 and at least one corresponding second locked part side 3c of the rear shaft 3 are locked only in fastening after completion of assembly.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a writing instrument. [Background technology]

[0002] It is common practice to couple two cylindrical components, for example a front axle and a rear axle, by threading a male thread formed on the outer peripheral surface of the rear end of the front axle with a female thread formed on the inner peripheral surface of the front end of the rear axle (for example, Patent Document 1). In Patent Document 1, the coupling is completed by rotating the rear axle in one direction relative to the front axle until the front end face of the rear axle abuts and locks against a step provided on the outer peripheral surface of the front axle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-139135 Summary of the Invention [Problem to be solved by the invention]

[0004] If the rear axle is overtightened by further rotating it in one direction relative to the front axle after it has been locked, the engagement of the male and female threads will cause the rear axle to move forward while undergoing elastic deformation, but the forward movement will be prevented by the engagement with the stepped portion of the front axle. At this time, the front end of the rear axle, which is formed with a female thread, will be subjected to axial compressive stress, while the rear end of the front axle, which is formed with a male thread, will be subjected to axial tensile stress. As a result, the threads of the male and female threads will move relative to each other in the axial direction, causing strong friction and risk of breakage. Furthermore, when the male and female threads move relative to each other in the axial direction, the male thread may climb over the female thread. Furthermore, when the male thread climbs over the female thread, the front end of the rear axle, which is located on the outer side, will expand radially outward, and the rear end of the front axle, which is located further inward, will contract radially inward, potentially resulting in damage to the end of the front axle or rear axle.

[0005] The present invention aims to provide a writing instrument having two screwable cylindrical parts, which can prevent the male and female threads from climbing over each other and prevent damage to the cylindrical parts even if excessive tightening is performed. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a writing instrument comprising: a first cylindrical part having a first locking portion, at least one second locking portion, and an externally threaded portion having an external thread; and a second cylindrical part having a first locked portion, at least one second locked portion, and an internally threaded portion having an internal thread that threadably engages with the external thread; wherein, when the assembly of the first cylindrical part and the second cylindrical part is complete, the first locking portion of the first cylindrical part and the first locked portion of the second cylindrical part are configured to lock together; and, only when the first cylindrical part and the second cylindrical part are tightened after the assembly is complete, the at least one second locking portion of the first cylindrical part and the corresponding at least one second locked portion of the second cylindrical part are configured to lock together.

[0007] The first locking portion and the at least one second locking portion may be arranged on opposite sides of the male thread portion in the axial direction, and the first locked portion and the at least one second locked portion may be arranged on opposite sides of the female thread portion in the axial direction.When the first cylindrical part and the second cylindrical part are assembled, the at least one second locking portion of the first cylindrical part and the corresponding at least one second locked portion of the second cylindrical part may be separated from each other by 0.5 mm or less in the axial direction.At least one of the at least one second locking portion and the corresponding at least one second locked portion may be inclined with respect to the axial direction in a vertical cross section.One of the cylindrical parts may be a front axle of a barrel, and the other cylindrical part may be a rear axle of a barrel. [Effects of the Invention]

[0008] According to this aspect of the present invention, a common effect is achieved in that a writing instrument having two screwable cylindrical parts is provided that can prevent the male thread from climbing over the female thread and prevent damage to the cylindrical parts even if excessive tightening is performed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a vertical cross-sectional view of a writing instrument according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged vertical cross-sectional view of the fitting portion of the front and rear axles shown in FIG. [Figure 3] 3 is an enlarged vertical cross-sectional view of the rear end portion of the front axle shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Corresponding components throughout the drawings are designated by common reference numerals.

[0011] 1 is a vertical cross-sectional view of a writing instrument 1 according to an embodiment of the present invention. The writing instrument 1 is a knock-type writing instrument.

[0012] Writing instrument 1 has a barrel 5 including a front barrel 2 which is a first cylindrical member, a rear barrel 3 which is a second cylindrical member arranged behind front barrel 2, and an inner tube 4 arranged behind rear barrel 3. Writing instrument 1 also has a refill 6 which is a writing body arranged inside barrel 5 and has a writing portion 6a at one end. In this embodiment, refill 6 is a ballpoint pen refill. In this specification, in the axial direction of writing instrument 1, the side of writing portion 6a is defined as the "front" side, and the side opposite writing portion 6a is defined as the "rear" side.

[0013] A clip member 7 made of metal wire is attached to the inner tube 4 via a clip holder 4a. A return spring 8 that urges the refill 6 rearward and a rotor 9 located behind the refill 6 are located within the barrel tube 5. The rear of the rotor 9 is covered by a cover member 10, which serves as the operating section. A weight 11, a cylindrical weight member made of metal, is located within the barrel tube 5, particularly in the front half of the front barrel 2. The front end of the weight 11 protrudes from the front opening of the front barrel 2. The protruding front end of the weight 11 is tapered to be continuous with the tapered front end of the front barrel 2, providing a unified design. The return spring 8 is supported by its front end engaging with a step provided inside the weight 11, and urges the refill 6 rearward.

[0014] By performing a knocking operation that presses the cover member 10 forward against the force of the return spring 8, the rotor 9 switches between a writing state (not shown) in which the writing part 6a of the refill 6 protrudes from the tip of the barrel 5 and a non-writing state (Figure 1) in which the writing part 6a is sunk into the barrel 5.

[0015] Figure 2 is an enlarged vertical cross-sectional view of the mating portion of the front axle 2 and rear axle 3 shown in Figure 1. The front axle 2 has an externally threaded portion 2a on the outer peripheral surface of the rear end. The rear axle 3 has an internally threaded portion 3a on the inner peripheral surface of the front end. An annular protrusion 3d is formed on the inner peripheral surface of the rear axle 3 rearward of the internally threaded portion 3a, in the vertical cross-section shown in Figure 2, which is inclined with respect to the axial direction and has a contact surface 3c facing forward.

[0016] The front axle 2 and the rear axle 3 are screwed together and assembled by rotating the rear axle 3 in one direction relative to the front axle 2 until the front end surface 3b of the rear axle 3, which is the first locked portion, abuts and locks against the stepped portion 2b on the outer circumferential surface of the front axle 2, which is the first locked portion. Completion of assembly or screwing refers to a state in which the stepped portion 2b of the front axle 2 and the front end surface 3b of the rear axle 3 are just abutting against each other without elastic deformation of the front axle 2 and the rear axle 3 in the axial direction. In other words, when the assembly of the front axle 2 and the rear axle 3 is complete, the front axle 2 and the rear axle 3 are fitted together in a positional relationship that is approximately consistent with the designed dimensions. When the assembly of the front axle 2 and the rear axle 3 is complete, the rear end portion 2c of the front axle 2, which is the second locked portion, and the abutment surface 3c of the rear axle 3, which is the second locked portion, are separated by a distance D, as shown in Figure 3.

[0017] If, after the front axle 2 and rear axle 3 are assembled, the rear axle 3 is overtightened so that it rotates further in one direction relative to the front axle 2, the engagement of the male and female threads will cause the rear axle 3 to move forward, accompanied by elastic deformation. However, the relative forward movement of the rear axle 3 relative to the front axle 2 is prevented by the engagement between the front end face 3b of the rear axle 3 and the step 2b of the front axle 2. At this time, the end of the rear axle 3 where the female thread is formed is subjected to axial compressive stress, while the end of the front axle 2 where the male thread is formed is subjected to axial tensile stress. As a result, the rear end of the front axle 2 and the front end of the rear axle 3 elastically deform, causing the rear end 2c of the front axle 2 to approach the abutment surface 3c of the rear axle 3 and lock together.

[0018] In other words, forward movement of the rear axle 3 relative to the front axle 2 due to excessive tightening is prevented not only by the engagement between the stepped portion 2b of the front axle 2 and the front end face 3b of the rear axle 3, but also by the engagement between the rear end portion 2c of the front axle 2 and the abutment surface 3c of the rear axle 3. By engaging the front axle 2 and the rear axle 3 at two points spaced apart in the axial direction, excessive elastic deformation of the rear end portion of the front axle 2 and the front end portion of the rear axle 3 is suppressed. This prevents the male thread portion 2a from climbing over the female thread portion 3a, and further prevents damage to the male or female thread, and further prevents damage to the ends of the front axle 2 or rear axle 3.

[0019] When the assembly of the front axle 2 and the rear axle 3 is complete, the distance D between the rear end 2c of the front axle 2, which is the second locking portion, and the abutment surface 3c of the rear axle 3, which is the second locked portion, is preferably 0.5 mm or less. If the distance D is greater than 0.5 mm, there is a risk that the male thread portion 2a and the female thread portion 3a may cross over each other or that the front axle 2 and the rear axle 3 may be damaged before the second locking portion and the second locked portion are locked together through further tightening.

[0020] In the above-described embodiment, the second locking portion and the second locked portion are provided as a single pair. However, a second locking portion and a second locked portion may be provided at additional locations. For example, in FIG. 2, a separate step may be provided as a separate second locking portion between the male threaded portion 2a and the rear end portion 2c of the front axle 2, and a separate annular protrusion may be provided as a separate second locked portion between the female threaded portion 3a and the annular protrusion 3d of the rear axle 3. In this case, the separate second locking portion and the separate second locked portion may be engaged with each other simultaneously, before or after the engagement between the rear end portion 2c of the front axle 2 and the abutment surface 3c of the rear axle 3. Additional second locking portions and second locked portions may also be provided. In other words, a configuration may be adopted in which at least one second locking portion of the front axle 2 and at least one corresponding second locked portion of the rear axle 3 are engaged with each other only when the axle is tightened after assembly is complete.

[0021] In the above-described embodiment, the first locking portion and at least one second locking portion are arranged on opposite sides of the male thread portion 2a in the axial direction, and the first locked portion and at least one second locked portion are arranged on opposite sides of the female thread portion 3a in the axial direction, thereby preventing the influence of elastic deformation from reaching the male thread portion 2a or the female thread portion 3a.

[0022] In the above-described embodiment, the step 2b of the front axle 2 is the first locking portion, the front end face 3b of the rear axle 3 is the first locked portion, the rear end 2c of the front axle 2 is the second locking portion, and the abutment surface 3c of the rear axle 3 is the second locked portion. However, the front axle 2 and the rear axle 3 may be configured so that the rear end 2c of the front axle 2 is the first locking portion and the abutment surface 3c of the rear axle 3 is the first locked portion, and they abut when assembly is complete. In this case, the step 2b of the front axle 2 is the second locking portion, and the front end face 3b of the rear axle 3 is the second locked portion. One of the first locking portion and the first locked portion, or one of the second locking portion and the second locked portion, may be configured as a slope that is inclined relative to the axial direction in a vertical cross section. By making these slopes, the corresponding parts that abut against the slopes are slightly elastically deformed radially inward or outward when locked, preventing damage. The first locking portion and the first locked portion, and the second locking portion and the second locked portion may be configured in any manner as long as they can be locked to each other.

[0023] Meanwhile, weight 11 is made of a metal material and is located in the front half of front barrel 2, i.e., relatively forward relative to barrel tube 5 as a whole, so the center of gravity of writing instrument 1 is located forward of half the overall length of writing instrument 1. A user typically writes by holding writing instrument 1 with their fingers at a portion forward of half the overall length. The writing action is performed by a combination of circular motions and swinging motions centered near the portion of writing instrument 1 held with the fingers. In this case, if the center of gravity of writing instrument 1 is located in the center of the overall length of writing instrument 1, the position where it is held with the fingers, i.e., the grip portion, may cause the writing instrument to be unbalanced and unstable when writing.

[0024] The grip portion is generally located 35 mm from the tip of the writing instrument 1. If the moment of inertia at the grip portion is too small, the writing portion 6a will move significantly even with a small amount of force applied, resulting in a lack of stability. Therefore, a larger moment of inertia at the grip portion is preferable, as it makes it easier to control the position of the writing portion 6a during writing. Also, in the writing instrument 1, it is preferable that the weight distribution in the portion located forward of the grip portion, i.e., a low center of gravity, is greater, as this allows for a stable writing action. Specifically, if the moment of inertia around a position 35 mm from the tip of the writing instrument 1 is 30,000 gf·mm 2 In addition, it is preferable that the weight of the portion of the writing instrument 1 located more than 35 mm forward from the tip thereof accounts for 25% or more of the weight of the entire writing instrument 1.

[0025] The effective center of gravity position and moment of inertia described above can be achieved by adjusting the size, shape, and weight of weight 11. Weight 11 is formed from a metal material, such as brass, but may also be formed from any material, such as a mixture of metal and resin. Forming weight 11 from brass not only provides a low center of gravity and a more comfortable writing experience, but also enhances the design by allowing the front end of weight 11 protruding from front barrel 2 to become a distinctive feature, thanks to its color and luster. In other words, unlike conventional writing instruments made of resin, the protruding front end of weight 11 from front barrel 2 gives the viewer a sharper, smarter, and more luxurious impression. Weight 11 may have any shape. For example, weight 11 may be a member having a C-shaped cross section rather than a cylindrical member.

[0026] In the above-described embodiment, the writing instrument is a knock-type writing instrument having an operating part provided at the rear end of the barrel. However, any writing instrument may be used as long as the front and rear barrels are threaded together. For example, the writing instrument according to the embodiment of the present invention may be a knock-type writing instrument having an operating part provided on the side of the barrel, a multi-core writing instrument with multiple fillers, or a cap-type writing instrument. Furthermore, the present invention may be applied to other writing instrument components, such as a tip member and a front barrel, or a holder for an eraser or the like, and a rotating sleeve, as long as the writing instrument includes a first cylindrical part having a first locking part, at least one second locking part, and an externally threaded part having an external thread, and a second cylindrical part having a first locked part, at least one second locked part, and an internally threaded part having an internal thread that threads together with the external thread.

[0027] The refill 6 may be a ballpoint pen refill or other types of refills such as a marking pen, a touch pen, or an eraser. Also, part or all of the cover member 10, which is the operating part, may be an erasing part that erases handwriting made by the writing instrument 1. A knock member may be disposed between the rotor 9 and the cover member 10 as the operating part. In this case, part or all of the knock member may be an erasing part that erases handwriting made by the knock-type writing instrument, or the eraser may be provided on the knock member.

[0028] The refill 6 may be a ballpoint pen containing thermochromic ink. Thermochromic ink refers to ink that maintains a predetermined color (first color) at room temperature (e.g., 25°C), changes to a different color (second color) when heated to a predetermined temperature (e.g., 60°C), and then returns to the original color (first color) when cooled to a predetermined temperature (e.g., -5°C). In a thermochromic writing instrument using thermochromic ink, the second color is colorless, and "erasing" refers to heating a line drawn in the first color (e.g., red) to make it colorless. Therefore, a friction member, which serves as the erasing unit, rubs against the writing surface on which the line was drawn, generating frictional heat, thereby changing the drawn line to colorless, i.e., erasing it. Naturally, the second color may be a color other than colorless. [Explanation of symbols]

[0029] 1 writing implements 2 front axle 2a Male thread 3 rear axle 3a Female thread 4 Inner cylinder 5 shaft cylinder 6 refills 7 Clip member 8 Return spring 9 Rotor 10 Cover member 11 Pyramid

Claims

[Claim 1] The invention described in the specification.

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