JP7782986B2 - writing implements - Google Patents

Description

The present invention relates to a writing instrument.

Two cylindrical components, such as a front and rear axle, are commonly connected 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 (see, for example, Patent Document 1). In Patent Document 1, the connection 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 formed on the outer peripheral surface of the front axle.

JP 2013-139135 A

If, after the rear axle is locked, excessive tightening is performed by further rotating the rear axle in one direction relative to the front axle, the engagement of the male and female threads causes elastic deformation, causing the rear axle to move forward, but this is 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, is subjected to axial compressive stress, while the rear end of the front axle, which is formed with a male thread, is subjected to axial tensile stress. As a result, the threads of the male and female threads move relative to each other in the axial direction, causing strong friction and the risk of breakage. Furthermore, as the male and female threads move relative to each other in the axial direction, the male thread may climb over the female thread. Furthermore, as the male thread climbs over the female thread, the front end of the outer rear axle expands radially outward, while the rear end of the inner front axle contracts radially inward, potentially resulting in breakage of the end of the front or rear axle.

The present invention aims to provide a writing instrument with two threadable cylindrical parts that prevents the male and female threads from climbing over each other and prevents damage to the cylindrical parts, even when the parts are tightened excessively.

One aspect of the present invention provides a writing instrument comprising: a first cylindrical part having a first locking portion, at least one second locking portion, and a male threaded portion having a male thread; and a second cylindrical part having a first locked portion, at least one second locked portion, and a female threaded portion having a female thread that meshes with the male thread; wherein the first locking portion of the first cylindrical part and the first locked portion of the second cylindrical part are configured to lock together when the first and second cylindrical parts are assembled; and 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 only when the parts are tightened after assembly is complete.

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 axially by 0.5 mm or less. 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 longitudinal 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.

This aspect of the present invention has the common effect of providing a writing instrument having two threadable cylindrical components that prevents the male and female threads from climbing over each other and prevents damage to the cylindrical components, even if the components are tightened excessively.

FIG. 1 is a vertical cross-sectional view of a writing instrument according to an embodiment of the present invention. FIG. 2 is an enlarged vertical cross-sectional view of the fitting portion of the front and rear axles shown in FIG. 3 is an enlarged vertical cross-sectional view of the rear end portion of the front axle shown in FIG. 1. FIG.

Embodiments of the present invention will be described in detail below with reference to the drawings. Corresponding components are designated by common reference symbols throughout the drawings.

Figure 1 is a vertical cross-sectional view of a writing instrument 1 according to an embodiment of the present invention. Writing instrument 1 is a knock-type writing instrument.

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

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 part. A cylindrical weight member made of metal, the weight body 11, is located within the barrel tube 5, particularly in the front half of the front barrel 2. The front end of the weight body 11 protrudes from the front end opening of the front barrel 2. The protruding front end of the weight body 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 located inside the weight body 11, and urges the refill 6 rearward.

By performing a knocking operation that presses the cover member 10 forward against the biasing 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 retracted into the barrel 5.

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 a male threaded portion 2a formed on the outer peripheral surface of the rear end. The rear axle 3 has a female threaded portion 3a formed 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 female threaded portion 3a, in the vertical cross-section shown in Figure 2, that is inclined with respect to the axial direction and has a contact surface 3c facing forward.

The front axle 2 and rear axle 3 are threaded together and assembly is completed 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 surface of the front axle 2, which is the first locked portion. Completion of assembly or threading 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 in exact contact with each other without the front axle 2 and rear axle 3 elastically deforming in the axial direction. In other words, when assembly of the front axle 2 and rear axle 3 is complete, the front axle 2 and rear axle 3 are fitted together in a positional relationship that is approximately consistent with the designed dimensions. When assembly of the front axle 2 and 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.

If, after the front axle 2 and rear axle 3 are assembled, the rear axle 3 is overtightened to rotate it 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, bringing the rear end 2c of the front axle 2 and the abutment surface 3c of the rear axle 3 closer together and locking together.

In other words, excessive tightening of the rear axle 3 relative to the front axle 2 is prevented not only by the engagement between the step 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 2c of the front axle 2 and the abutment face 3c of the rear axle 3. By engaging the front axle 2 and rear axle 3 at two axially spaced locations, excessive elastic deformation of the rear end of the front axle 2 and the front end 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, as well as damage to the ends of the front axle 2 or rear axle 3.

When the front axle 2 and rear axle 3 are fully assembled, the distance D between the rear end 2c of the front axle 2 (the second locking portion) and the abutment surface 3c of the rear axle 3 (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 threaded portion 2a and the female threaded portion 3a may cross over each other or that the front axle 2 and rear axle 3 may be damaged before the second locking portion and the second locked portion are locked together through further tightening.

While the above-described embodiment provides a single pair of second locking portions and second locked portions, additional second locking portions and second locked portions may be provided in additional locations. For example, in FIG. 2, a separate step may be provided as an additional second locking portion between the male threaded portion 2a and rear end portion 2c of the front axle 2, and a separate annular protrusion may be provided as an additional second locked portion between the female threaded portion 3a and annular protrusion 3d of the rear axle 3. In this case, the additional second locking portion and the additional second locked portion may be engaged simultaneously with, or 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 only during tightening after assembly is complete.

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. This prevents the effects of elastic deformation from affecting the male thread portion 2a or the female thread portion 3a.

In the above-described embodiment, the step 2b of the front axle 2 was the first locking portion, the front end surface 3b of the rear axle 3 was the first locked portion, the rear end 2c of the front axle 2 was the second locking portion, and the abutment surface 3c of the rear axle 3 was the second locked portion. However, the front axle 2 and 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 surface 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 longitudinal cross section. By making these slopes, the corresponding components that abut against the slopes are slightly elastically deformed radially inward or outward when locked, preventing damage. The first locking portion and first locked portion, and the second locking portion and second locked portion may be configured in any manner as long as they can be locked to each other.

However, because the weight 11 is made of metal and is located in the front half of the front barrel 2, i.e., relatively far forward relative to the barrel tube 5 as a whole, the center of gravity of the writing instrument 1 is located forward of more than half of the overall length of the writing instrument 1. Users typically write by holding the writing instrument 1 with their fingers at a portion forward of more than half of its overall length. The writing action is performed by a combination of circular and rocking movements centered near the portion of the writing instrument 1 held with the fingers. In this case, if the center of gravity of the writing instrument 1 is located in the middle of its overall length, the writing instrument may be unbalanced and unstable when writing, due to the position where it is held with the fingers, i.e., the grip portion.

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, even a small amount of force will cause the writing portion 6a to move significantly, resulting in a lack of stability. Therefore, a larger moment of inertia at the grip portion is preferable because it makes it easier to control the position of the writing portion 6a during writing. Furthermore, a larger weight distribution in the portion of the writing instrument 1 located forward of the grip portion, i.e., a lower center of gravity, is preferable because it enables a stable writing operation. Specifically, it is preferable that the moment of inertia around a position 35 mm from the tip of the writing instrument 1 is 30,000 gf· ^mm² or more, and that the weight of the portion of the writing instrument 1 located forward of 35 mm from the tip accounts for 25% or more of the entire writing instrument 1.

The effective center of gravity position and moment of inertia described above can be achieved by adjusting the size, shape, and weight of the weight 11. The 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. In particular, forming the weight 11 from brass not only provides a lower center of gravity and a more comfortable writing experience, but also enhances the design by making the front end of the weight 11 protruding from the front barrel 2 a distinctive feature due to its color and luster. In other words, by having the front end of the weight 11 protruding from the front barrel 2, it gives the viewer a sharper, smarter, and more luxurious impression, unlike conventional writing instruments made of resin. The weight 11 may be any shape; for example, the weight 11 may be a member with a C-shaped cross section rather than a cylindrical member.

In the above-described embodiment, the writing instrument was a knock-type writing instrument with an operating part provided at the rear end of the barrel, but any writing instrument may be used as long as the front and rear barrels are threaded together. For example, a writing instrument according to an embodiment of the present invention may be a knock-type writing instrument with 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 combination of a holder for an eraser or the like and a rotating sleeve, as long as the writing instrument comprises a first cylindrical part having a first locking part, at least one second locking part, and a male threaded part with a male thread, and a second cylindrical part having a first locked part, at least one second locked part, and a female threaded part with a female thread that threads together with the male thread.

In addition to ballpoint pen refills, the refill 6 may also be other types of refills such as marking pens, touch pens, erasers, etc. Furthermore, part or all of the cover member 10, which is the operating part, may be an erasing part that erases handwriting made with 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 with the knock-type writing instrument, or an erasing member may be provided on the knock member.

The refill 6 may be a ballpoint pen containing thermochromic ink. Here, 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 its 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, the friction member serving as the erasing part rubs against the writing surface on which the line was drawn, generating frictional heat, which changes the drawn line to colorless, i.e., erases it. Naturally, the second color may be a color other than colorless.

REFERENCE SIGNS LIST 1 Writing implement 2 Front barrel 2a Male threaded portion 3 Rear barrel 3a Female threaded portion 4 Inner barrel 5 Barrel barrel 6 Refill 7 Clip member 8 Return spring 9 Rotor 10 Cover member 11 Weight

Claims (1)

a first cylindrical part having a first locking portion, at least one second locking portion, and an externally threaded portion on which an external thread is formed;
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;
When the assembly of the first cylindrical part and the second cylindrical part is completed, the first locking portion of the first cylindrical part and the first locked portion of the second cylindrical part are configured to lock together,
The at least one second locking portion of the first cylindrical part and the at least one corresponding second locked portion of the second cylindrical part are configured to lock together only when the parts are tightened after assembly is completed ,
A writing implement characterized in that one of the cylindrical parts is a front shaft of a barrel, and the other cylindrical part is a rear shaft of the barrel .