Mechanical pencil

Abstract

To provide a mechanical pencil with a holding chuck that prevents the occurrence of improper installation.SOLUTION: The mechanical pencil includes a barrel 2, and a holding chuck 10 arranged inside the tip end of the barrel 2 and capable of holding a writing core 4. The holding chuck 10 has a fitting portion 11 that fits with a fitting surface 3a provided on the inner surface of the barrel 2 and a concave relief portion 13 provided on the outer surface of the fitting portion 11. A relief portion 13 is provided along the circumferential direction. Further, the relief portion 13 is provided over the entire circumference.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a mechanical pencil. [Background technology]

[0002] A mechanical pencil is configured such that a fixed amount of lead is dispensed from a tip member attached to the front end side of the barrel by performing a knocking operation that presses the operating part forward against the biasing force of a spring arranged inside the barrel. For example, the mechanical pencil described in Patent Document 1 has a chuck that moves forward while holding the lead as the operating part is pressed forward, and a holding chuck that applies resistance to the lead and holds the lead when the chuck retreats as the operating part is released from the pressure. An insertion hole for the lead is formed in the holding chuck, and the lead is held by being inserted into the insertion hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-082128 A Summary of the Invention [Problem to be solved by the invention]

[0004] The holding chuck is a minute cylindrical member made of an elastic material. The tip member is made of a material harder than the holding chuck, such as metal or hard plastic. The holding chuck is attached by fitting its outer surface into the inner surface of the tip member. In the process of attaching the holding chuck to the tip member during the manufacture of the mechanical pencil, the holding chuck may be damaged. This will be described with reference to Figures 9 to 11.

[0005] FIG. 9 is a partial cross-sectional view of a conventional holding chuck 100. In FIG. 9, the left side is the front end side of the mechanical pencil from which the writing lead protrudes, and the right side is the rear end side where the operation part is provided. The holding chuck 100 has a cylindrical fitting part 101 and a tapered part 102 formed in a tapered shape in front of the fitting part 101. The holding chuck 100 has an insertion hole 105 into which the writing lead is inserted formed along the central axis C. A tapered surface 106 is provided toward the front on the rear end side of the insertion hole 105, and a straight surface 107 is provided in front of the tapered surface 106. The writing lead inserted into the holding chuck 100 is clamped by the straight surface 107.

[0006] 10 is a diagram illustrating the process of attaching the holding chuck 100 to the tip member 110 of a mechanical pencil. Since the holding chuck 100 is a very small member, an insertion tool 120 is used to attach it to the tip member 110. The holding chuck 100 is set on the tip of the insertion tool 120, and the insertion tool 120 and the holding chuck 100 are inserted from the rear end side of the tip member 110 (FIG. 10(A)).

[0007] On the inner surface of the tip member 110, at the attachment position of the holding chuck 100, a cylindrical fitting surface 111 having an inner diameter slightly smaller than the outer diameter of the fitting portion 101 of the holding chuck 100 before fitting is provided. The holding chuck 100 set in the insertion tool 120 is press-fitted into the tip member 110, and the fitting portion 101 of the holding chuck 100 is elastically deformed radially inward at the fitting surface 111, thereby completing the attachment.

[0008] However, when the holding chuck 100 is pressed in by the insertion tool 120, the frictional resistance may be extremely large depending on the individual holding chuck 100 due to the relationship between the dimensional tolerance or surface roughness of the fitting portion 101 and the fitting surface 111. The increase in frictional resistance is particularly likely to occur because the outer surface of the cylindrical fitting portion 101 of the holding chuck 100 is in close contact with the cylindrical fitting surface 111 of the tip member 110 over the entire surface, as shown in the cross-sectional view of Fig. 11. Note that the holding chuck 100 is generally formed by compression molding, and is therefore cylindrical in shape in consideration of the manufacturing costs of the mold, etc.

[0009] If the frictional resistance is large, the outer surface portion of the fitting portion 101 may not follow the movement of the retaining chuck 100 by engaging with the fitting surface 111, and may be largely elastically deformed. At this time, the outer surface portion of the fitting portion 101 is stretched by the movement of the entire retaining chuck 100 (FIG. 10(B)), and as a result, the outer surface rear end portion S of the fitting portion 101 is sheared, i.e., cut, between the inner surface of the tip member 110. The retaining chuck 100 attached to the tip member 110 in this way cannot maintain a normal posture and position because the outer surface portion is missing, and therefore cannot hold the writing core correctly. For example, if the central axis of the retaining chuck 100 does not coincide with the central axis of the tip member 110, a writing core may not be advanced even when a knocking operation is performed, resulting in a poor advancement. In addition, since the retaining chuck 100 itself is a very small member, it is very difficult to discover that the outer surface rear end portion S of the fitting portion 101 has been sheared.

[0010] An object of the present invention is to provide a mechanical pencil equipped with a holding chuck that prevents installation failure. [Means for solving the problem]

[0011] According to one aspect of the present invention, there is provided a mechanical pencil comprising a barrel and a retaining chuck disposed inside the tip of the barrel and capable of holding a writing lead, wherein the retaining chuck has a fitting portion that fits with a fitting surface provided on the inner surface of the barrel, and a concave relief portion provided on the outer surface of the fitting portion.

[0012] The recess may be provided along the circumferential direction. The recess may be provided over the entire circumference. The recess may be provided at the rear end of the fitting portion. The recess may be formed to have a smaller diameter than the fitting portion. The recess may be formed in a tapered shape. The recess may be provided along the axial direction. The recess may be provided over the entire length of the fitting portion. A plurality of the recesses may be provided at intervals along the circumferential direction. Effect of the Invention

[0013] According to the aspects of the present invention, a common effect is achieved in that a mechanical pencil having a holding chuck that prevents the occurrence of installation failure is provided. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a partial cross-sectional view of a mechanical pencil. [Diagram 2] FIG. 2 is a front view of the holding chuck according to the first embodiment. [Diagram 3] FIG. 3 is a partial cross-sectional view showing a state in which the holding chuck is attached to the tip member. [Figure 4] FIG. 4 is a front view of the holding chuck according to the second embodiment. [Diagram 5] FIG. 5 is a front view of the holding chuck according to the third embodiment. [Figure 6] FIG. 6 is a cross-sectional view of a fitting portion showing the fitting of the holding chuck and the prong member according to the fourth embodiment. [Figure 7] FIG. 7 is a cross-sectional view of a fitting portion showing the fitting of the holding chuck and the prong member according to the fifth embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a fitting portion showing the fitting of the holding chuck and the prong member according to the sixth embodiment. [Figure 9] FIG. 9 is a partial cross-sectional view of a conventional holding chuck 100. [Figure 10] FIG. 10 is a view for explaining a process of attaching the holding chuck to the tip member. [Figure 11] FIG. 11 is a cross-sectional view of a fitting portion showing the fitting of the holding chuck and the prong member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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.

[0016] 1 is a partial cross-sectional view of a mechanical pencil 1. In this specification, in the axial direction of the mechanical pencil 1, the side from which the writing lead protrudes is defined as the "front" side, and the side opposite to the side from which the writing lead protrudes is defined as the "rear" side.

[0017] The mechanical pencil 1 has a barrel 2 and a tip member 3 attached to the front end of the barrel 2. The term "barrel" may include the tip member. A chuck 5 capable of gripping a writing core 4 is disposed inside the front end of the barrel 2. The chuck 5 has a through hole formed along its axis. The front end of the chuck 5 is divided in three directions, and the divided front ends are attached so as to be loosely fitted into a fastener 6 formed in a ring shape. The fastener 6 is attached to the inner surface of the front end of the barrel 2. The chuck 5 is biased backward by a coil spring 7. A tip pipe 8 that guides the writing core 4 is disposed at the front end of the tip member 3 so as to protrude from the front end. A holding chuck 10 having an insertion hole 14 formed along the axis is disposed inside the tip of the barrel 2, i.e., inside the tip member 3. An operating unit 9 is disposed at the rear end of the barrel 2. The operating unit 9 may be disposed on a side surface of the barrel 2, for example, other than the rear end of the barrel 2.

[0018] In the mechanical pencil 1, when the operating part 9 is pressed forward against the biasing force of the coil spring 7, a knocking operation is performed, and the chuck 5 advances together with the writing core 4, and the front end of the chuck 5 protrudes from the fastener 6, releasing the gripped state of the writing core 4. Next, when the pressure of the knocking operation is released, the chuck 5 retreats due to the biasing force of the coil spring 7. At this time, the writing core 4 is held in the insertion hole 14 formed in the holding chuck 10. In this state, only the chuck 5 retreats and the front end of the chuck 5 is housed in the fastener 6, and the writing core 4 is again in a gripped state. In other words, the writing core 4 is released and gripped by the back and forth movement of the chuck 5 due to repeated knocking operations of the operating part 9, and as a result, the writing core 4 is sequentially advanced forward from the chuck 5.

[0019] Fig. 2 is a front view of the holding chuck 10 according to the first embodiment, and Fig. 3 is a partial cross-sectional view showing the state in which the holding chuck 10 is attached to the tip member 3. The internal shape and structure of the holding chuck 10 are similar to those of the conventional holding chuck 100 shown in Fig. 9, and therefore description thereof will be omitted.

[0020] The holding chuck 10 has a cylindrical fitting portion 11 and a tapered portion 12 formed in a tapered shape in front of the fitting portion 11. A concave relief portion 13 is provided at the rear end of the outer surface of the fitting portion 11. The relief portion 13 is formed in a tapered shape and is provided around the entire circumference of the fitting portion 11 in the circumferential direction.

[0021] The holding chuck 10 is pressed into the jaw member 3 using, for example, an inserting tool, in the same manner as the conventional holding chuck 100 described with reference to Fig. 10. That is, on the inner surface of the jaw member 3, at the mounting position of the holding chuck 10, a cylindrical fitting surface 3a having an inner diameter slightly smaller than the outer diameter of the fitting portion 11 of the holding chuck 10 before fitting is provided. The holding chuck 10 set in the inserting tool is pressed into the jaw member 3, and the fitting portion 11 of the holding chuck 10 is elastically deformed radially inward at the fitting surface 3a, thereby completing the mounting.

[0022] As described above, the outer surface of the fitting portion 11 is elastically deformed so as to be stretched due to the frictional resistance during press-fitting, but is not sheared between the inner surface of the tip member 3. That is, even if the outer surface of the fitting portion 11 is elastically deformed, the part enters the recessed recess 13 and elastically deforms so as to fill the recess 13. When the holding chuck 10 is pressed into the mounting position, the fitting portion 11 recovers from the elastic deformation, and mounting of the holding chuck 10 is completed.

[0023] Fig. 4 is a front view of the holding chuck 20 according to the second embodiment, and Fig. 5 is a front view of the holding chuck 30 according to the third embodiment. The basic configurations and installation steps of the holding chuck 20 and the holding chuck 30 are similar to those of the holding chuck 10 according to the first embodiment, so only the differences will be described.

[0024] 4, in the holding chuck 20, a recessed relief portion 23 is provided at the rear end of the outer surface of the fitting portion 21. The relief portion 23 is formed in a cylindrical shape having a smaller diameter than the cylindrical fitting portion 21, and is provided along the circumferential direction of the fitting portion 21 over the entire circumference.

[0025] 5, in the holding chuck 30, a recessed relief portion 33 is provided at the rear end of the outer surface of the fitting portion 31. The relief portion 33 is formed in a cylindrical, tapered shape having a smaller diameter than the cylindrical fitting portion 31, and is provided along the entire circumferential direction of the fitting portion 31.

[0026] FIG. 6 is a cross-sectional view of a fitting portion 41 showing the fitting of the holding chuck 40 and the tip member 3 according to the fourth embodiment. The holding chuck 40 has a cylindrical fitting portion 41 and a tapered portion (not shown) formed in a tapered shape in front of the fitting portion 41. A concave relief portion 44 is provided on the outer surface of the fitting portion 41. The relief portion 44 is provided along the axial direction over the entire length of the fitting portion 41. A plurality of relief portions 44 are provided at intervals along the circumferential direction, four in this embodiment. The relief portion 44 has a flat surface 44a separated from the fitting surface 3a of the tip member 3. A protrusion 45 is provided between adjacent relief portions 44.

[0027] The holding chuck 40 is pressed into the tip member 3 using, for example, an inserting tool, in the same manner as the conventional holding chuck 100 described with reference to Fig. 10. That is, as described with reference to Fig. 3, a cylindrical fitting surface 3a having an inner diameter slightly smaller than the outer diameter of the fitting portion 41 of the holding chuck 40 before fitting, i.e., a circumscribing circle including the convex portion 45, is provided at the mounting position of the holding chuck 40 on the fitting surface 3a of the tip member 3. The holding chuck 40 set in the inserting tool is pressed into the tip member 3, and the fitting portion 41 of the holding chuck 40, particularly the convex portion 45, is elastically deformed radially inward on the fitting surface 3a, thereby completing the mounting.

[0028] As described above, the outer surface of the fitting portion 41, i.e., the convex portion 45, is elastically deformed due to the frictional resistance during press-fitting, but is not sheared between the inner surface of the tip member 3. That is, even if the convex portion 45 of the fitting portion 41 is elastically deformed, the convex portion 45 enters the recessed recess 44 and elastically deforms so as to fill the recess 44. When the holding chuck 40 is press-fitted to the attachment position, the convex portion 45 of the fitting portion 41 recovers from the elastic deformation, and the attachment of the holding chuck 40 is completed.

[0029] Fig. 7 is a cross-sectional view of a fitting portion 51 showing the fitting of the holding chuck 50 and the proboscis member 3 according to the fifth embodiment, and Fig. 8 is a cross-sectional view of a fitting portion 61 showing the fitting of the holding chuck 60 and the proboscis member 3 according to the sixth embodiment. The basic configurations and installation steps of the holding chuck 50 and the holding chuck 60 are the same as those of the holding chuck 40 according to the fourth embodiment, so only the differences will be described.

[0030] 7, in the holding chuck 50, a recessed recess 54 is provided on the outer surface of the fitting portion 51. The recess 54 is provided along the axial direction over the entire length of the fitting portion 51. A plurality of the recesses 54 are provided at intervals along the circumferential direction, four in this embodiment. The recess 54 has a cylindrical surface 54a that is spaced apart from the fitting surface 3a of the tip member 3 and is concentric with the tip member 3 and the insertion hole 14. A protrusion 55 having a substantially semicircular cross section is provided between adjacent recesses 54.

[0031] 8, in the holding chuck 60, a recessed recess 64 is provided on the outer surface of the fitting portion 61. The recess 64 is provided along the axial direction over the entire length of the fitting portion 61. A plurality of the recesses 64 are provided at intervals along the circumferential direction, four in this embodiment. The recess 64 has a curved surface 64a that is spaced apart from the fitting surface 3a of the tip member 3. A protrusion 65 is provided between adjacent recesses 64.

[0032] In the holding chucks according to the first to third embodiments, the recess is provided around the entire circumference of the rear end of the fitting portion along the circumferential direction. However, the recess does not have to be provided at the rear end of the fitting portion, and may be provided, for example, near the rear end. The recess does not have to be provided around the entire circumference of the fitting portion, and may be, for example, a plurality of recesses provided at intervals along the circumferential direction.

[0033] In the holding chucks according to the fourth to sixth embodiments, the recess is provided on the outer surface of the fitting portion along the axial direction over the entire length of the fitting portion. However, the recess does not have to be provided over the entire length of the fitting portion, and may be, for example, a plurality of recesses spaced apart along the axial direction. There does not have to be a plurality of recesses along the circumferential direction, and there may be only one recess.

[0034] A single holding chuck may be constructed by arbitrarily combining the configuration of the recess provided along the circumferential direction in the holding chuck according to the first to third embodiments and the configuration of the recess provided along the axial direction in the holding chuck according to the fourth to sixth embodiments.

[0035] The holding chuck according to the first to sixth embodiments is made of an elastic material such as a rubber material such as nitrile rubber. The holding chuck can be molded by compression molding, but may also be molded by other molding methods, such as injection molding. The shape and size of the relief portion may be set arbitrarily, taking into consideration the material properties of the holding chuck, particularly the elastic modulus, etc., as long as the outer surface portion of the fitting portion that is elastically deformed when the holding chuck is pressed in can enter. Furthermore, in the holding chuck according to the fourth to sixth embodiments, the shape and size of the relief portion may be set arbitrarily, taking into consideration the frictional resistance when the holding chuck is pressed in.

[0036] According to the holding chucks of the first to sixth embodiments, as described above, shearing of the outer surface of the fitting portion is prevented when the holding chuck is pressed in. As a result, the holding chuck can be placed in the correct position in the mechanical pencil with the correct posture, and installation failure can be prevented.

[0037] The holding chucks according to the fourth to sixth embodiments have the further effect of improving the ease of assembly. That is, compared to conventional holding chucks in which the outer surface of the fitting portion and the fitting surface of the tip member are in close contact with each other, a recessed relief portion is provided on the outer surface of the fitting portion, so that a partial clearance is provided between the outer surface of the fitting portion and the fitting surface of the tip member. Therefore, it is possible to reduce the frictional resistance when the holding chuck is pressed in, and it is possible to perform the press-in easily and reliably. [Explanation of symbols]

[0038] 1 mechanical pencil 2 shaft cylinder 3 Tip parts 3a Mating surface 4 writing lead 5 Chuck 6 Fasteners 7 Coil spring 8 Tip Pipe 9 Control section 10 Holding chuck 11 Fitting part 12 Tapered section 13 Relief

Claims

[Claim 1] A shaft cylinder, A holding chuck is disposed inside the tip of the barrel and capable of holding a writing lead. The holding chuck has a fitting portion that fits with a fitting surface provided on an inner surface of the barrel, and a recessed relief portion provided on an outer surface of the fitting portion, The holding chuck has an inner surface on a front end side thereof that is provided with a straight surface, and a tapered surface is provided from the straight surface to a rear end thereof, the recess is configured so that, when the holding chuck is press-fitted into the tip of the barrel, an outer surface portion of the fitting portion that is elastically deformed enters into the recess and fills the recess, The recess is provided along a circumferential direction at a rear end of the fitting portion, A mechanical pencil, characterized in that the relief portion is formed in a tapered shape.

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