Lead holding device and mechanical pencil equipped with this lead holding device

Abstract

To hold a shorter core firmly.SOLUTION: A core holding device 30 includes: a cylindrical core holding holder 31 through which a core X is inserted and guided forward; and an outer cylinder 32 that covers an outer peripheral surface of the core holding holder 31. On a front end side of the core holding holder 31, there are provided a core holding portion 31b whose inner peripheral surface is gradually reduced in diameter toward the front so as to hold an outer peripheral surface of the core X, and a notch portion 31d that separates the core holding portion 31b in a circumferential direction.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a core holding device that holds an inserted core from its outer peripheral side, and a sharp pencil provided with this core holding device.

Background Art

[0002] Conventionally, a sharp pencil, as described in, for example, Patent Document 1, includes a guide tube that inserts a core and guides it forward at a portion that feeds out the core on the frontmost end side. According to this conventional technique, for example, when the core is broken, it is possible to hold the rear end side of the broken core in the guide tube and project the front end side from the guide tube.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to the above conventional technique, since the holding force of the broken core by the guide tube is weak, the broken core may rotate when trying to write. Also, if the broken core is too short, there is a risk of easily coming out of the guide tube.

Means for Solving the Problems

[0005] In view of such problems, the present invention has the following configuration. A cylindrical core holding holder that inserts a core and guides it forward, and an outer cylinder that covers the outer peripheral surface of this core holding holder , the nozzle that secures this outer cylinder and are provided. On the front end side of the core holding holder, a core holding portion whose inner peripheral surface gradually decreases in diameter forward so as to hold the outer peripheral surface of the core, and a cut portion that separates the core holding portion in the circumferential direction are provided. The core holding portion is formed by gradually increasing the thickness of the peripheral wall of the core holding holder radially inward toward the front.A core holding device characterized by the following features. [Effects of the Invention]

[0006] As described above, the present invention is configured to securely hold shorter leads. [Brief explanation of the drawing]

[0007] [Figure 1] This is a side view showing a mechanical pencil equipped with an example of a lead-holding device according to the present invention. [Figure 2] This is a disassembled perspective view of the concentricity retention device. [Figure 3] This is an enlarged longitudinal cross-sectional view of the main part of the concentricity holding device. [Figure 4] This is a longitudinal cross-sectional view showing the core inserted into the concentricity retaining device. [Figure 5] This is a longitudinal cross-sectional view showing the leading core and the trailing core inserted into the concentricity holding device. [Figure 6] This is a perspective view showing another example of a lead holder. [Figure 7] This is an enlarged longitudinal cross-sectional view of a key part showing another example of a core holding device. [Figure 8] This is an enlarged longitudinal cross-sectional view of a key part showing another example of a core holding device. [Modes for carrying out the invention]

[0008] This embodiment discloses the following features: The first feature is that it comprises a cylindrical lead-holding holder through which the lead is inserted and guided forward, and an outer cylinder that covers the outer surface of the lead-holding holder. The front end of the lead-holding holder is provided with a lead-holding portion whose inner diameter gradually decreases towards the front to hold the outer surface of the lead, and a notch that separates the lead-holding portion in the circumferential direction (see Figures 1 to 5).

[0009] A second feature is that the core holding portion is formed by gradually increasing the thickness of the peripheral wall of the core holding holder radially inward toward the front (see Figures 7 and 8).

[0010] As a third feature, there is provided a diameter-expanded portion in which the inner peripheral surface gradually expands in diameter forward from the core holding portion while the wall thickness of the peripheral wall is thinned (see FIGS. 3 to 5).

[0011] As a fourth feature, the diameter-expanded portion is formed in a convex curved surface shape (see FIGS. 3 to 5).

[0012] As a fifth feature, the cut portion extends from the front end of the core holding holder to the rear side of the core holding portion.

[0013] As a sixth feature, the outer cylinder has a gap with the outer peripheral surface of the core holding holder, and this gap enables the radial deflection of the core holding holder (see FIGS. 3 to 5).

[0014] As a seventh feature, the core holding holder is provided with a diameter-reduced inclined portion in which the outer peripheral surface gradually reduces in diameter forward to the foremost end portion (see FIGS. 3 to 5).

[0015] As an eighth feature, a sharp pencil is configured with the above core holding device (see FIG. 1).

[0016] <Specific Embodiment> Next, a specific embodiment having the above features will be described in detail based on the drawings. In the following description, "front" means one axial side of the core holding holder 31 in the direction in which the core X protrudes, and "rear" means the opposite side to the one side.

[0017] FIG. 1 shows a sharp pencil provided with the core holding device according to the present invention. This Sharp pencil 1 includes a long shaft cylinder 10, a tip 20 connected to the front end side of the shaft cylinder 10, a core holding device 30 attached to the front end side of the tip 20, a knock part 40 protruding from the rear end of the shaft cylinder 10, and a core feeding mechanism and a core tank (not shown) housed in the shaft cylinder 10. By operating to advance and retreat the knock part 40, the core feeding mechanism feeds out the core X in the core tank, and inserts this core X into the tip 20 and the core holding device 30 and projects it to the outside.

[0018] According to the illustrated example, the shaft cylinder 10 is a single cylindrical member, but it is also possible to adopt a mode in which a plurality of cylindrical members are connected.

[0019] The tip 20 is a tapered cylindrical member and is detachably screwed and connected to the front end side of the shaft cylinder 10. The core holding device 30 described later is attached to the front end side of this tip 20. As another example, this tip 20 can also be a member integral with the shaft cylinder 10.

[0020] The core feeding mechanism is a well-known mechanism for feeding out the core X in the core tank. As another example, it is possible to adopt a mode in which the core is fed out by a rotation operation or a mode in which the core is fed out by a side knock operation.

[0021] The core holding device 30 includes a cylindrical core holding holder 31 that inserts and guides the core X forward, and an outer cylinder 32 that covers the outer peripheral surface of this core holding holder 31 (see FIGS. 4 and 5).

[0022] The core holding holder 31 is formed in a long, substantially cylindrical shape from a hard metal material. The rear end side portion of this core holding holder 31 is press-fitted into the tip 20, and thus is fixed concentrically with the tip 20 and the shaft cylinder 10. The material of the core holding holder 31 can be a material other than metal as long as it allows the core holding holder 31 to be deflected in the radial direction, such as a synthetic resin material (including cases where it is hard or soft). Furthermore, in addition to the press-fitting method described above, the means for fixing the core holder 31 to the tip 20 can also be adhesive, welding, crimping, fitting, etc.

[0023] The lead holder 31 is provided with a diameter-reducing inclined portion 31a, in which the outer surface gradually decreases in diameter towards the front end of the lead holder 31. Furthermore, the reduced diameter inclined portion 31a is provided with a core holding portion 31b whose inner circumferential surface is reduced in diameter to hold the outer circumferential surface of the core X, and an enlarged diameter portion 31c in which the inner circumferential surface is gradually enlarged in diameter from the core holding portion 31b toward the front while the thickness of the circumferential wall is thinned (see Figure 3). Furthermore, the core-holding holder 31 is provided with a notch 31d (see Figure 2) that extends in an elongated shape from the front end of its peripheral wall to the portion behind the core-holding portion 31b.

[0024] The diameter-reducing inclined portion 31a is, for example, a portion of a cylindrical metal member that serves as the raw material for the core-holding holder 31, where the outer surface is gradually reduced in diameter towards the front end (see Figure 3). This diameter-reducing inclined portion 31a can be formed, for example, by a drawing process using a mold. On the inner circumferential surface of the lead holding holder 31, the portion behind the diameter-reducing inclined portion 31a is formed to have a diameter slightly larger than the outer circumferential surface of the lead X. Furthermore, on the outer surface of the core holding holder 31, the portion behind the diameter-reducing inclined portion 31a is formed to have a diameter slightly smaller than the inner surface of the cylindrical portion 32a of the outer cylinder 32, which will be described later.

[0025] The core holding portion 31b is the part at the front end of the inner circumferential surface of the diameter-reducing inclined portion 31a where its inner diameter is smallest. This core holding portion 31b is formed with an inner diameter slightly smaller than the outer diameter of the core X so that it contacts the outer circumferential surface of the core X with an appropriate pressure.

[0026] The enlarged diameter portion 31c is located in front of the core holding portion 31b, and its inner circumferential surface gradually expands in diameter towards the front while the circumferential wall thickness decreases. More specifically, this enlarged diameter portion 31c is formed in a convex curved shape (or, in other words, a convex curved shape in its longitudinal cross-section) that gradually widens as it extends forward from the core holding portion 31b. In one example shown in Figure 3, the foremost end of this enlarged diameter portion 31c is located at the foremost end of the core holding holder 31.

[0027] Multiple notches 31d are provided on the peripheral wall of the core holding holder 31 at intervals in the circumferential direction (in the illustrated example, two are provided at equal intervals). Each notch 31d extends in a substantially straight line from the foremost end of the core holding holder 31 to the rear. In one example shown in Figures 4 and 5, the rear end of the notch 31d is positioned inside the tip 20. Each notch 31d separates the front portion of the lead holder 31, including the lead holding portion 31b, in the circumferential direction.

[0028] Furthermore, the outer cylinder 32 is formed from a hard metal material into a long, roughly cylindrical shape, and its rear end portion is press-fitted into the tip 20 in front of the press-fit portion at the rear end of the lead holding holder 31. The outer cylinder 32 is then fixed concentrically with the tip 20, the shaft 10, and the lead holding holder 31, etc. The outer cylinder 32 has a cylindrical portion 32a that is close to the outer circumferential surface of the core holding holder 31, and a reduced-diameter portion 32b that is reduced in diameter at the front end of the cylindrical portion 32a. In addition, other materials for the outer cylinder 32 include synthetic resin materials, for example, as long as they can ensure adequate strength, materials other than metal can be used. In addition to press-fitting, other means of fixing the outer cylinder 32 to the tip 20 include bonding, welding, crimping, fitting, etc.

[0029] The cylindrical portion 32a has a gap s1 between it and the outer surface of the core holding holder 31 so as to allow the core holding holder 31 to bend radially and to regulate the amount of bending. This gap s1 is continuous to the rear end of the cylindrical portion 32a. The radial dimension of the gap s1 is approximately constant behind the diameter-reducing inclined portion 31a in the core-holding holder 31, and increases towards the front in the portion of the diameter-reducing inclined portion 31a.

[0030] The reduced diameter portion 32b is an annular projection that protrudes radially inward from the front end of the cylindrical portion 32a. The inner diameter of this reduced-diameter portion 32b is smaller than the outer diameter of the front end of the core holding holder 31, and larger than the outer diameter of the core X.

[0031] Furthermore, the diameter-reducing portion 32b is located in front of the front end of the core holding holder 31 (see Figure 3). A gap s2 is secured between the inner circumferential surface of the diameter-reducing portion 32b and the outer circumferential surface of the core X that is inserted through it, so as to prevent the core X from coming into contact with the diameter-reducing portion 32b and being damaged.

[0032] Next, the effects and benefits of the mechanical pencil 1 with the above configuration will be explained in detail. When the knock mechanism 40 is operated and the lead X inside the barrel 10 moves forward, the lead X passes through the lead holding device 30 and protrudes forward from the front end of the lead holding device 30 (see Figure 4). In this state, when writing is performed and a radial force component due to writing pressure is applied to the front end of the lead X, the front end of the lead X will bend slightly in the radial direction. This bending is restricted by the front end of the lead holder 31 bending radially and contacting the inner surface of the outer cylinder 32, thereby preventing the lead X from breaking due to this bending or being damaged by being strongly pressed against the reduced diameter portion 32b.

[0033] Furthermore, as shown in Figure 5, when the leading core X1 and the trailing core X2, which contacts the leading core X1 from behind, are inserted into the core holding device 30, an elastic restoring force in the diameter reduction direction is generated on the circumferential wall of the core holding holder 31 having the notched portion 31d. As a result, the leading core X1 is pressed against and firmly held by the core holding portion 31b that is trying to reduce its diameter. Therefore, even when writing with a shortened lead X1, it is possible to prevent the lead X1 from rotating or coming out of the lead holder 31.

[0034] Furthermore, if a shortened lead X1 (for example, a broken lead) is attempted to be inserted into the lead holding device 30 from the front, the rear end of the lead X1 will not get caught on the front end of the lead holding holder 31, but will be guided by the enlarged diameter portion 31c and will move smoothly backward. Furthermore, the enlarged diameter portion 31c also serves to prevent damage to the lead X that is held by the lead holding portion 31b and protrudes forward.

[0035] Thus, according to the invention of this embodiment, by gradually thinning the peripheral wall thickness of the core holding holder 31 toward the front, the enlarged diameter portion 31c is positioned near the front end of the core holding holder 31, and the position of the core holding portion 31b can also be positioned relatively close to the front end. Therefore, it is possible to hold shorter cores.

[0036] <Variation> According to the above embodiment, the enlarged diameter portion 31c is formed in the convex curved shape described above, but this enlarged diameter portion 31c only needs to have a circumferential wall that gradually widens in diameter towards the front, while gradually widening in diameter. Other examples include a concave curved shape, a conical shape, an R-chamfered shape, a C-chamfered shape, etc.

[0037] Furthermore, although the notch 31d is made to extend rearward from the foremost end of the core holding holder 31 according to the above embodiment, the notch 31d only needs to separate the core holding holder 31 in the circumferential direction at least in the core holding portion 31b, making it easier to elastically deform in the radial direction. Therefore, for example, it is also possible to have a configuration that has an elongated slot-shaped notch 31d' extending in the front-to-back direction, as shown in Figure 6, for example, the core holding holder 31'.

[0038] Furthermore, in the above embodiment, the lead holder 31 is inserted into a cylindrical outer tube 32. However, in other examples, the outer tube 32 may be another part of the mechanical pencil 1. For example, a through hole is provided on the front end side of the tip 20, and this through hole functions as the inner circumferential surface of the outer tube 32, with a gap s1 secured within this through hole to accommodate the lead holder 31.

[0039] Furthermore, in the above embodiment of the core holding device 30, the thickness of the peripheral wall of the core holding holder 31 is gradually increased radially inward toward the front in order to form the core holding portion 31b. However, as an alternative example, the core holding portion 31b can be formed in the manner of the core holding device 30S1 shown in Figure 7. The core holding device 30S1 is the same as the core holding device 30, but with the core holding holder 31 replaced by the core holding holder 31S1. The core-holding holder 31S1 forms the core-holding portion 31b by gradually increasing the thickness of its peripheral wall at the front end towards the radially inward direction. According to the core holding device 30S1 shown in Figure 7, the core holding portion 31b can be positioned further forward, and consequently, a shorter broken core can be held.

[0040] Furthermore, another example is the core holding device 30S2 shown in Figure 8. This core holding device 30S2 is the same as the core holding device 30 described above, but with the core holding holder 31 replaced by the core holding holder 31S2. The core holding holder 31S2 has an enlarged diameter portion 31c in which the inner circumferential surface gradually widens while the circumferential wall thickness is reduced, as it moves forward from the core holding portion 31b, compared to the core holding holder 31S1. According to the core holding device 30S2 shown in Figure 8, the core holding portion 31b can hold the broken core at the front end, and the enlarged diameter portion 31c facilitates the insertion of the core X from the front and prevents damage to the core X.

[0041] The present invention is not limited to the embodiments described above and can be modified as appropriate without altering the essence of the invention. [Explanation of Symbols]

[0042] 1: Mechanical pencil 10: Shaft tube 20: Sakiguchi 30: Core holding device 31: Core holding holder 32: Outer cylinder 31a: Diameter reducing slope part 31b: Core holding part 31c: Expanded diameter part 31d: Cut section X: core s1, s2: gap

Claims

1. It comprises a cylindrical lead-holding holder through which the lead is inserted and guided forward, an outer cylinder covering the outer surface of the lead-holding holder, and a tip that secures the outer cylinder. The front end of the core-holding holder is provided with a core-holding portion whose inner diameter gradually decreases towards the front to hold the outer surface of the core, and a notch portion that separates the core-holding portion in the circumferential direction. The core holding portion is characterized by being formed by gradually increasing the thickness of the peripheral wall of the core holding holder radially inward toward the front.

2. The core holding device according to claim 1, characterized in that an enlarged diameter section is provided in which the inner circumferential surface gradually widens in diameter toward the front from the core holding section while the circumferential wall thickness is reduced.

3. The core holding device according to claim 2, characterized in that the enlarged diameter portion is formed in a convex curved shape.

4. The core holding device according to any one of claims 1 to 3, characterized in that the notched portion extends from the front end of the core holding holder to the rear side of the core holding portion.

5. The core holding device according to any one of claims 1 to 4, characterized in that the outer cylinder has a gap between it and the outer circumferential surface of the core holding holder, and this gap allows the core holding holder to bend radially.

6. The core holding device according to any one of claims 1 to 5, characterized in that the core holding holder is provided with a diameter-reducing inclined portion in which the outer circumferential surface gradually decreases in diameter toward the front end.

7. A mechanical pencil equipped with a lead-holding device according to any one of claims 1 to 6.

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