Pencil

Abstract

To provide a pencil capable of suppressing deterioration in the surface quality of the pencil after cutting, even when an air-dry specific gravity of the wood of a shaft body is less than 0.6.SOLUTION: A pencil 10 includes a lead 14, and a shaft body 12 covering the lead 14, the shaft body 12 having wood with an air-dry specific gravity of less than 0.6 and a machinability improver that is added to the wood to improve machinability during cutting.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a pencil having a wooden shaft. [Background technology]

[0002] Patent Document 1 discloses that by adding at least a naturally occurring filler and a naturally occurring binder to the shaft material composition that forms the shaft of a pencil, the shaft can be given the same ease of sharpening as a conventional wooden shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-059431 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have discovered that if the air-dry specific gravity of the wood of the shaft is less than 0.6, the cutting resistance of the shaft becomes relatively high when the pencil is sharpened to sharpen the lead, and as a result, the inner lead covered by the shaft becomes more likely to break. In other words, if the air-dry specific gravity of the wood of the shaft is less than 0.6, the surface quality of the pencil after cutting deteriorates. In this regard, Patent Document 1 does not consider any technology for reducing the cutting resistance of the shaft when sharpening a pencil made of wood with an air-dry specific gravity of less than 0.6.

[0005] The present disclosure has been made in consideration of the above, and provides a pencil that can suppress deterioration in the surface quality of the pencil after cutting, even if the air-dry specific gravity of the wood of the shaft is less than 0.6. [Means for solving the problem]

[0006] The aspects of the present disclosure are as follows.

[0007] <Aspect 1> The core and a shaft covering the core, the shaft comprising wood having an air-dry specific gravity of less than 0.6 and a machinability improver added to the wood to improve machinability during cutting; A pencil.

[0008] In the first aspect, the cutting resistance of the shaft can be reduced by the machinability improver.

[0009] <Aspect 2> The machinability improver comprises paraffin. 2. The pencil of embodiment 1.

[0010] In embodiment 2, the machinability enhancer can be realized by paraffin.

[0011] <Aspect 3> The ratio of the paraffin to the mass of the wood of the shaft is 5.0% or more. 3. The pencil of embodiment 2.

[0012] In the third aspect, the machinability can be further improved compared to when the ratio of paraffin to the mass of the wood of the shaft is less than 5.0%.

[0013] <Aspect 4> The machinability improver includes a polyglycerol fatty acid ester. 2. The pencil of embodiment 1.

[0014] In embodiment 4, the machinability improver can be realized by a glycerin fatty acid ester.

[0015] <Aspect 5> The ratio of the volume of the shaft to the whole is less than 90%. A pencil according to any one of aspects 1 to 4.

[0016] In the fifth embodiment, the cutting resistance is reduced by the amount of cutting volume of the wood of the shaft. [Effects of the Invention]

[0017] According to the present disclosure, a pencil can be provided that can suppress deterioration in the pencil surface quality after cutting, even when the air-dry specific gravity of the wood of the shaft is less than 0.6. This is particularly effective when used with cedar and cypress, which are widely planted in Japan. [Brief explanation of the drawings]

[0018] [Figure 1] Figure 1(A) is a front view illustrating a pencil according to this embodiment, having a hexagonal cross-sectional shape; Figure 1(B) is a side view illustrating a pencil according to this embodiment; Figure 1(C) is a cross-sectional view taken along line 1C-1C in Figure 1(A); Figure 1(D) is a front view illustrating a pencil having a circular cross-sectional shape as another example of this embodiment; and Figure 1(E) is a side view illustrating a pencil according to another example of this embodiment. [Figure 2] FIG. 1C is a cross-sectional view illustrating a pencil according to a modified example taken along the same line as line 1C-1C in FIG. 1A. [Figure 3] 1 is a photograph illustrating the state of the tip of a pencil according to Example 1 and a pencil according to a comparative example after cutting. [Figure 4] 10 is a graph illustrating the cutting torque of the pencil according to Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] Embodiments of the present disclosure will be described below with reference to Figures 1 to 4. In the following description of the drawings, identical or similar parts are designated by the same or similar reference numerals. However, the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each device or component, etc., differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following explanation. Furthermore, parts with different dimensional relationships and ratios are included between the drawings. Furthermore, unless otherwise specified in the specification, the number of each component element of the present disclosure is not limited to one, and multiple elements may be present.

[0020] <Pencil structure> (overview) First, an overview of a pencil 10 according to this embodiment will be described. As shown in Figures 1(A) and 1(B), the pencil 10 has a lead 14 and a shaft 12 that covers the lead 14.

[0021] (shaft body) The shaft 12 is made of wood. As shown in Fig. 1(C), a hollow portion 13 extending along the axial direction (the vertical direction in Fig. 1(C)) is formed inside the shaft 12 for arranging a core 14. The hollow portion 13 is tubular and passes through the shaft 12 in the axial direction.

[0022] As shown in Fig. 1(B), the cross-sectional shape of the shaft 12 of the pencil 10 according to this embodiment is, for example, hexagonal. Fig. 1(B) illustrates the diameter RC of the lead 14, the diameter RA of an imaginary circumscribing circle of the hexagonal shaft 12 in side view, and the inter-face distance W between the opposing outer surfaces of the hexagonal shaft.

[0023] In the present disclosure, the cross-sectional shape of the shaft may be any shape, such as a circle, an ellipse, a rectangle, etc. Figures 1(D) and 1(E) illustrate a pencil 10A having a circular shaft 12A as an example of a pencil having a different cross-sectional shape. Figure 1(E) illustrates the diameter RB of the circular shaft 12A in a side view.

[0024] (Modification of shaft body) In this embodiment, the length of the lead 14 is the same as the entire length of the barrel, but the present disclosure is not limited to this. The length of the lead may be shorter than the entire length of the barrel. For example, the length of the lead may be a length corresponding to a portion of the entire length of the barrel, such as about two-thirds of the entire length of the barrel. By shortening the length of the lead to a length corresponding to a portion of the entire length of the barrel, it is possible to form a pencil in which there is no lead inside the barrel when the lead is completely used up.

[0025] In other words, once the lead is used up, no lead material remains inside the pencil. Therefore, when disposing of or recycling a pencil, there is no need to separate the shaft from the lead, which is made of a different material from the shaft. As a result, it contributes to environmental protection.

[0026] (core) The lead 14 can be arbitrarily set to an ink lead, a color lead, an eraser lead, a cosmetic lead, etc. The lead 14 is disposed in the hollow portion 13 of the shaft body 12.

[0027] [Variations] Next, an overview of a pencil 10B according to a modified example will be described. As shown in Fig. 2, the pencil 10B according to the modified example has a shaft 12B, a lead 14B, a conductive core 16, and a conductive contact portion 18. The pencil 10B according to the modified example functions as an input pen used to input information into an electronic device such as a tablet terminal.

[0028] (shaft body) As in the present embodiment, shaft body 12 is made of wood. Inside shaft body 12, hollow portion 13 is formed extending along the axial direction (the vertical direction in FIG. 2) for arranging core 14 and conductive core 16.

[0029] (core) The lead 14B is a non-conductive lead that does not have electrical conductivity. The lead 14B is arranged in series with the conductive lead 16 in the hollow portion 13 of the shaft 12. The lead 14B is arranged on the opposite side of the conductive lead 16 from the conductive contact portion 18. In other words, in the pencil 10B, the lead 14B is arranged at the tip end, and the conductive contact portion 18 is arranged at the rear end. The conductive lead 16 is arranged between the lead 14B and the conductive contact portion 18. The lead 14B and the conductive lead 16 butt against each other inside the pencil 10B, like the red and blue leads of a vermilion pencil, for example.

[0030] (conductive core) The conductive core 16 is conductive. The conductive core 16 is disposed in the hollow portion 13 of the shaft 12. The conductive core 16 is a non-writing core electrically connected to the conductive contact portion 18. The conductive core 16 is made of, for example, a conductive resin. The rear end of the conductive core 16 is in contact with the conductive contact portion 18. In the axial direction of the pencil 10B, the sum of the length of the conductive contact portion 18 and the length of the conductive core 16 is, for example, 20 mm or more and less than 90 mm.

[0031] (Conductive contact part) The conductive contact portion 18 is provided at one end of the shaft body 12. The conductive contact portion 18 is, for example, a soft contact plug that is conductive. The conductive contact portion 18 is fixed to the shaft body 12 by a fixing member 22. The fixing member is a cylindrical crimping member (ferrule) made of conductive metal or resin. The fixing member is, for example, crimped to the shaft body 12 and the conductive contact portion 18, thereby connecting the shaft body 12 and the conductive contact portion 18.

[0032] Other configurations of the pencil 10B according to the modified example are the same as the configurations of the components with the same names in the pencil 10 according to the present embodiment, and therefore redundant explanations will be omitted. Also, the configuration of the pencil 10B according to the modified example is the same as the configuration of the input pen illustrated in Figure 1 of JP 2023-031218 A, for example.

[0033] <Details of the shaft body of this embodiment> Next, the configuration of the wooden shaft of the present disclosure will be described in detail using shaft 12 of the present embodiment in Figures 1(A) to 1(C) as a representative example. Note that the configuration of shaft 12A in Figure 1(D) and the configuration of modified shaft 12B in Figure 2 are also similar to that of shaft 12 of the present embodiment.

[0034] (volume ratio of shaft body) In this embodiment, the ratio of the volume of the shaft 12 to the entire pencil 10 is set to less than 90% in order to further reduce cutting resistance. However, in the present disclosure, the ratio of the volume of the shaft 12 to the entire pencil 10 may be 90% or more.

[0035] (wood) The air-dry specific gravity of the wood of the shaft 12 is less than 0.6. Specifically, domestic wood such as cedar, cypress, red pine, camphor tree, and ginkgo can be used for the shaft 12. The specific gravity of the wood of the shaft 12 in this embodiment is about 0.4 or more. The shaft 12 may be made of solid wood or laminated wood.

[0036] (machinability improver) The shaft 12 contains a machinability improver added to wood. The machinability improver improves the machinability of the pencil 10 during cutting. Examples of machinability improvers that can be used in this embodiment include glycerin fatty acid esters and paraffin. Glycerin fatty acid esters include esterification reaction products obtained by esterifying fatty acids with glycerin, and triglycerides, which are oils and fats extracted from natural plants and animals. Examples of glycerin fatty acid esters that can be used include myristate esters, palmitate esters, and stearates. Stearic acid esters are preferred for improving machinability. Furthermore, the glycerin fatty acid esters can be dissolved in an organic solvent and then immersed in the shaft 12. Propylene glycol monomethyl ether (PGM) is preferred as the organic solvent, as this allows the shaft 12 to be uniformly immersed in the machinability improver. Note that the machinability improver used in this disclosure is not limited to these, and any material that can improve the machinability of the wood of the shaft 12 can be used as appropriate.

[0037] (Method of adding machinability improver) To add the machinability improver to the shaft 12, for example, a liquid tank filled with an impregnation liquid of a glycerin fatty acid ester as the machinability improver is prepared. Then, each piece of wood for the shaft 12 or a piece of wood such as a slat for the shaft 12 is immersed in the prepared liquid tank for a predetermined time or more.

[0038] When paraffin is used as the machinability improver, the paraffin is melted to form a liquid solution, and a liquid tank filled with the solution is prepared. For example, a solution of paraffinic hydrocarbons in which solid paraffin is dissolved in an organic solvent may be used. Examples of paraffin that can be used include liquid paraffin, which can be used as a food additive, and paraffin wax, which is solid at room temperature.

[0039] The impregnation process allows the glycerin fatty acid ester to penetrate deep into the structure of the shaft 12. The impregnation process of the machinability improver in the solution may be carried out under normal pressure or under reduced pressure. When the addition process is carried out under reduced pressure, the concentration of the machinability improver added will be higher than when the addition process is carried out under normal pressure, even if the impregnation time is the same. In the present disclosure, the method of adding the machinability improver is not limited to impregnation. For example, methods such as applying or spraying onto the surface of the wood are also not excluded.

[0040] Then, each piece of wood for the shaft 12 or the slats for the shaft 12 is removed from the liquid bath and dried. If slats for the shaft 12 are used, for example, cores are placed in the pre-formed hollows of the slats, and the slat with the core 14 placed therein is joined to another slat that corresponds to the slat. When joining, an adhesive can be placed between the shaft 12 and the core 14.

[0041] The pencil 10 according to this embodiment can then be manufactured by carrying out a predetermined process, such as cutting, on the pair of joined slats. Furthermore, by using naturally occurring materials such as vinyl acetate, starch, and other natural materials as the adhesive between the shaft 12 and the lead 14, a pencil with reduced environmental impact can be provided. [Example]

[0042] (Example 1: Relationship between machinability improver and cutting resistance) Next, the relationship between the machinability improver and cutting resistance in the pencil 10 according to this embodiment will be explained using Example 1. In Example 1, a plurality of solid wood pieces and a plurality of laminated wood pieces were prepared as wood pieces for the shaft 12. The laminated wood pieces were made using the solid wood pieces according to this embodiment as raw materials.

[0043] Specifically, as shown in Table 1, two groups of solid wood and two groups of laminated wood were prepared. Each group contained eight different pieces of wood. Samples were taken at random positions from each piece of wood to which paraffin had been added as a machinability improver to measure the ratio of the machinability improver. The ratio of the machinability improver to the mass of the wood in the taken-out sample was then measured.

[0044] [Table 1]

[0045] The right side of Table 1 shows the measured ratio of the machinability improver to the mass of the wood. Note that the "difference" in Table 1 refers to the difference between the "mass of wood after addition" and the "mass of wood before addition," both of which are listed to the left of the "difference." This means the mass of the solution containing the machinability improver. The values ​​in the "difference" column in Table 1 are rounded to one decimal place. As shown in the "Amount of components in solution" column in Table 1, the concentration of the machinability improver in the solutions used in Example 1 was 8%.

[0046] As shown in Table 1, in Example 1, in groups 1 and 2 of solid wood and groups 1 and 2 of laminated wood, shaft bodies 12 were obtained in which the ratio of the machinability improver to the mass of the wood in the samples was 5.0% or more.

[0047] In the present disclosure, the ratio of the machinability improver to the mass of the wood may be less than 5.0%, however, when the ratio of the machinability improver to the mass of the wood is 5.0% or more, the machinability improving effect can be improved more than when the ratio is less than 5.0%.

[0048] Furthermore, as shown in Table 1, in Groups 1 and 2 of solid wood, the ratio of machinability improver to wood mass was approximately 5.5% to approximately 9.5%, while in Groups 1 and 2 of laminated wood, the ratio of machinability improver to wood mass was approximately 6.4% to approximately 7.8%. In other words, the ratio of machinability improver to wood mass was less variable in laminated wood than in solid wood. This is because the internal structure of solid wood is less uniform than that of laminated wood, and the fact that samples were taken from the wood at random positions had a significant impact.

[0049] Two types of wood, cypress and cedar, were prepared, and a machinability improver was added to each of the two types of wood by impregnation in a solution in a ratio of 5.0% or more relative to the mass of the wood, to produce shafts 12 according to Example 1. Pencils were then manufactured using each of the produced shafts 12. Each pencil was then sharpened using a pocket sharpener, which is a portable manual pencil sharpener, and the cutting torque during cutting was measured.

[0050] The pocket sharpener has a conical insertion hole and a straight blade fixed inside the insertion hole. Examples of the pocket sharpener that can be used include the manual pencil sharpener disclosed in JP 2015-083355 A and the pocket sharpener disclosed in JP 2010-82868 A.

[0051] As shown in FIG. 3, no lead breakage occurred in the pencil of Example 1 on the left, which uses a cypress shaft 12, and the pencil of Example 1 on the right, which uses a cedar shaft 12. On the other hand, two types of comparative pencils, one made of cypress and one made of cedar, were manufactured using shafts 12 made only of the same wood as in Example 1, without adding a shaving improver. The other configurations of the comparative pencils are the same as those of Example 1. The comparative pencils were then cut under the same conditions as in Example 1.

[0052] As shown in Figure 3, lead breakage occurred in both the comparative pencil on the left, which uses a cypress shaft 12, and the comparative pencil on the right, which uses a cedar shaft 12. In the comparative pencil using a cypress shaft 12, the wood surface of the shaft 12 was relatively less roughened, but the lead broke inside the shaft 12. In particular, in the comparative example using a cypress shaft 12, the cutting resistance during cutting caused the shaft 12 to shift up and down and left and right relative to the fulcrum of the lead 14 inside the insertion hole of the pocket sharpener (i.e., bending and twisting occurred), and the bending and twisting caused a relatively large load to be applied to the tip of the lead.

[0053] Furthermore, as shown in Figure 3, the comparative example of the cedar shaft 12 had relatively large amounts of rough wood grain on the shaft 12. As a result, similar to the cypress shaft 12, the core broke inside the shaft 12 due to the cutting resistance during cutting.

[0054] (Example 2: Relationship between machinability improver concentration and cutting torque) Next, the relationship between the concentration of the machinability improver and the cutting torque in the pencil 10 according to this embodiment will be explained using Example 2. The concentration of the machinability improver in the solution used in Example 1 was 8%, but in Example 2, two types of solutions were prepared: one with a 40% concentration and one with a 50% concentration. The addition of the machinability improver was carried out under normal pressure.

[0055] Then, as shown in FIG. 4, pencils were manufactured using shafts 12 in which the concentration of the machinability improver in the solution was 40% and shafts 12 in which the concentration was 50%. Three pencils were manufactured for each concentration. Then, as in Example 1, the cutting torque was measured when each pencil was sharpened using a pocket sharpener. The measurement conditions for each pencil in Example 2 were all the same.

[0056] In Figure 4, three examples (A) to (C) are shown for when the concentration of the machinability improver in the solution is 40%, and three examples (D) to (F) are shown for when the concentration is 50%. Each example in Figure 4 also shows the maximum value among multiple cutting torque measurements taken during cutting, and the average value of multiple cutting torque measurements.

[0057] As shown in Figure 4, when the concentration of the machinability improver in the solution was 40%, the maximum cutting torque could be kept below 14 cN·m, and the average cutting torque could be kept below 8 cN·m. Furthermore, when visually inspecting for lead breakage during cutting, in the three examples (A) to (C), although some pencils had partially broken leads, no pencils had completely broken leads.

[0058] Furthermore, when the concentration of the machinability improver in the solution was 50%, the maximum cutting torque could be suppressed to 11 [cN·m] or less, and the average cutting torque could be suppressed to 7 [cN·m] or less. Furthermore, when visually inspecting the lead during cutting, in the three examples (D) to (F), while some pencils had partially broken lead, not only were no pencils with completely broken lead obtained, but pencils with no broken lead at all were also obtained.

[0059] That is, in this embodiment, even when the addition work is performed under normal pressure (i.e., normal pressure impregnation), it was found that a solution with a machinability improver concentration of 40% or more can effectively suppress lead breakage during cutting using a pocket sharpener. It was also found that when the concentration is 50%, the cutting torque can be reduced compared to when the concentration is 40%.

[0060] Furthermore, impregnation under vacuum can expedite the introduction of the solution compared to impregnation under normal pressure, so even if the concentration of the machinability improver in the solution is around 5% to 10%, it is possible to obtain the same effect as when the concentration of the machinability improver in the solution is 40%.

[0061] (Example 3: Relationship between lead diameter and degree of breakage) Next, the relationship between the lead diameter and the degree of breakage in the pencil 10 according to this embodiment will be described using Example 3.

[0062] Here, the larger the core diameter, the larger the polar section modulus, i.e., the greater the resistance to twisting. Also, the larger the core diameter, the larger the polar moment of inertia, i.e., the greater the resistance to twisting.

[0063] [Table 2]

[0064] Table 2 shows the magnitude of the breakage load for each lead diameter obtained in a bending strength test in accordance with Japanese Industrial Standard JIS S 6006 (2020). Twenty samples were used for each lead diameter. The hardness of the sample leads was 2B.

[0065] As shown in Table 2, the larger the core diameter, the greater the load required to break the core in the bending strength test. For example, when the core diameter is 2.595 mm, the load required to break the core is 7.97 [N].

[0066] Meanwhile, in manual sharpeners with handles currently available on the market from several manufacturers, the blade member used to sharpen pencils has multiple grooved blades. The inside of the sharpener also has a guide hole that supports the pencil lead inserted from the outside. When the handle is turned during sharpening, the blade member itself rotates, and the blade member rotates around the pencil, sharpening the supported lead and shaft inside.

[0067] In a manual sharpener with a handle, the diameter of the guide hole opening is generally 2.6 mm or more. If the diameter of the pencil lead exceeds the diameter of the guide hole opening, the broken lead is likely to fit tightly into the guide hole opening, i.e., the lead is likely to get clogged.

[0068] For this reason, in this embodiment, the diameter of the lead 14 is preferably enlarged to an upper limit of approximately 2.6 mm. When the lead diameter is approximately 2.6 mm, the diameter of the circumscribed circle of the shaft 12 can be designed to be, for example, approximately 8 mm. In this embodiment, the addition of a machinability improver reduces the cutting resistance of the shaft 12, and by setting the upper limit of the lead diameter to approximately 2.6 mm, the occurrence of lead clogging in a manual sharpener can be further suppressed.

[0069] (Action and effect) In the pencil 10 according to this embodiment, a machinability improver is added to the wood of the shaft 12 to improve machinability during cutting. This reduces the cutting resistance of the shaft 12, preventing deterioration in the pencil's surface quality after cutting, even when the wood of the shaft 12 has an air-dry specific gravity of less than 0.6. This is particularly effective when used with cedar and cypress, which are widely planted in Japan. Furthermore, in this embodiment, the addition of the machinability improver reduces the cutting torque when using a pocket sharpener, which is subject to significant bending and twisting loads. As a result, the cutting surface condition of the wood of the shaft 12 is improved, as shown in Figure 3.

[0070] Furthermore, in this embodiment, in addition to being able to improve the condition of the cutting surface of the wood of the shaft 12, the core diameter can be expanded to about 2.6 mm, which reduces the amount of wood that is cut from the shaft 12 during cutting. It also reduces core breakage during cutting. Furthermore, in this embodiment, domestic wood can be used as the wood for the shaft 12, which promotes the use of domestic wood.

[0071] In this embodiment, the machinability improver contains paraffin, and therefore, the machinability improver can be realized by paraffin.

[0072] In this embodiment, the ratio of paraffin in the machinability improver to the mass of the wood of the shaft 12 is 5.0% or more, which improves machinability more than when the ratio is less than 5.0%.

[0073] In this embodiment, the machinability improver may include a polyglycerin fatty acid ester, and thus the machinability improver can be realized by the glycerin fatty acid ester.

[0074] In this embodiment, the volume ratio of the shaft 12 to the entire pencil 10 is less than 90%. The amount of wood cutting volume of the shaft 12 is reduced, and the cutting resistance is reduced accordingly.

[0075] <Other embodiments> Although the present disclosure has been described using the above disclosed embodiments, the descriptions and drawings that form part of this disclosure should not be understood to limit the present disclosure. For example, the present disclosure can be configured by partially combining the configurations illustrated in the multiple examples disclosed in the specification. The present disclosure includes various embodiments not described above, and the technical scope of the present disclosure is defined only by the invention-specific matters in the scope of the claims that are appropriate from the above description. [Explanation of symbols]

[0076] 10,10A,10B Pencil 12,12A,12B Shaft 13 Hollow part 14,14B Core 16 Conductive core 18 Conductive contact part 22 Diameter of fixing member RC core RA: Diameter of the circumscribed circle of the hexagonal shaft RB: Diameter of the circular shaft W: Distance between faces of hexagonal shaft

Claims

1. The core and a shaft covering the core, the shaft comprising wood having an air-dry specific gravity of less than 0.6 and a machinability improver added to the wood to improve machinability during cutting; A pencil.

2. The machinability improver comprises paraffin.

2. The pencil of claim 1.

3. The ratio of the paraffin to the mass of the wood of the shaft is 5.0% or more.

3. The pencil of claim 2.

4. The machinability improver includes a polyglycerol fatty acid ester.

2. The pencil of claim 1.

5. The ratio of the volume of the shaft to the whole is less than 90%. The pencil according to any one of claims 1 to 4.

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