Eraser, eraser manufacturing device, and eraser manufacturing method

Abstract

To provide an eraser increasable in corners when necessary, while keeping a general eraser shape, a manufacturing device of the eraser and a manufacturing method of the eraser.SOLUTION: A manufacturing device 10 of an eraser comprises a cylindrical part 12 having an inlet 12a formed at a base end part and an outlet 12b formed at a tip side with an inner part to be heated, a screw part 16 rotatably arranged inside the cylindrical part 12 and extruding a material charged from the inlet 12a and heated in the cylindrical part 12 to the outlet 12b while kneading, a mouthpiece 15 having a molding hole 15a, attached to the outlet 12b of the cylindrical part 12 and molded by passing the material extruded from the screw part 16 through the molding hole 15a, and a divided face forming member 14 arranged to divide the molding hole 15a between the cylindrical part 12 and the mouthpiece 15. An eraser 1 is manufactured by using the device with the same material. The eraser 1 has dividing faces dividable by a tensile force smaller than that of other parts in the eraser 1.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an eraser, a manufacturing apparatus for an eraser, and a manufacturing method for an eraser.

Background Art

[0002] The corners of an eraser are convenient for erasing fine characters and the like. However, with use, the corners become rounded, making it difficult to erase fine areas. By using a cutting tool such as a knife, the rounded part of the eraser can be cut to regenerate the corners. However, it is necessary to carry a cutting tool to form the corners, and there is also a risk associated with using the cutting tool. Therefore, usually, a rectangular eraser has eight corners, but there are also erasers provided with eight or more corners (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the number of corners increases, the shape of the eraser becomes complicated, its portability deteriorates, it becomes difficult to hold during use, it becomes difficult to form a sleeve that fits the shape, and furthermore, strength is required for the eraser material.

[0005] An object of the present invention is to provide an eraser, a manufacturing apparatus for an eraser, and a manufacturing method for an eraser that can increase the number of corners as needed while maintaining a general eraser shape.

Means for Solving the Problems

[0006] In order to solve the above problems, one aspect of the present invention provides an eraser made of the same material, the eraser having a dividing surface that can divide the eraser with a tensile force smaller than that of other parts of the eraser.

[0007] When a force of 0.027 kg / cm 2 to 6.67 kg / cm 2 is applied between one side and the other side sandwiching the dividing surface, it is preferably the surface that is divided.

[0008] Another aspect of the present invention provides an eraser manufacturing apparatus for manufacturing an eraser made of the same material, the eraser having a dividing surface that can be divided with a tensile force smaller than that of other parts of the eraser, the apparatus comprising: a material holding part having an internal space and provided with an inlet and an outlet for the material to the internal space; an extrusion part for extruding the material introduced into the internal space of the material holding part to the outside from the outlet; a die part having a molding hole, attached to the outlet of the material holding part, and molding the material extruded by the extrusion part by passing it through the molding hole; and a dividing surface forming member disposed between the material holding part and the die part so as to divide the molding hole.

[0009] The die part is a plate-like member provided with the molding hole penetrating therethrough, and it may be possible to attach die parts having different thicknesses.

[0010] Still another aspect of the present invention is to introduce a material into the internal space of a material holding part having an internal space and provided with an inlet and an outlet for the material to the internal space, push the material out to the outside from the outlet, and form the pushed-out material by passing it through a forming hole of a die part attached to the outlet of the material holding part. In the method for manufacturing an eraser, when the pushed-out material flows into the forming hole, the material is divided by a dividing surface forming member arranged so as to divide the forming hole between the material holding part and the die part, thereby manufacturing an eraser made of the same material and having a dividing surface that can be divided with a tensile force smaller than that of other parts of the eraser. A method for manufacturing an eraser is provided.

[0011] Still another aspect of the present invention provides a method for manufacturing an eraser made of the same material and having a dividing surface that can be divided with a tensile force smaller than that of other parts of the eraser, by manufacturing a plurality of plate-shaped eraser pieces, stacking and pressing the manufactured eraser pieces to join the plurality of eraser pieces.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide an eraser, an eraser manufacturing apparatus, and an eraser manufacturing method that can maintain a general eraser shape and increase the number of corners as needed.

Brief Description of the Drawings

[0013]

Figure 1

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Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described. The eraser 1 of the embodiment is substantially in the shape of a rectangular parallelepiped. The eraser 1 is manufactured entirely from the same material and has a split surface 2 that can split the eraser 1 with a tensile force smaller than that of other parts in the eraser 1. The same material means that different materials are not used for each part and the components of the material are substantially uniform.

[0015] FIG. 1 is a perspective view of the eraser 1 according to the embodiment, where (a) is a state where no predetermined tensile force is applied to the eraser 1, (b) is a state where a predetermined tensile force is applied and the eraser 1 is split at the split surface 2, and (c) is a diagram showing an example of splitting the eraser 1 at the split surface 2 with a force smaller than the predetermined tensile force. As shown in Fig. 1(a), the dividing surface 2 does not form cuts, grooves, slits, etc. on the outer surface of the eraser 1 in a state where no predetermined tensile force is applied. That is, the outer surface of the eraser 1, including the outer surface where the dividing surface 2 extends internally, is a flat surface on which cuts, grooves, slits, etc. are not formed.

[0016] (Material of the eraser 1) The eraser 1 is prepared by uniformly mixing a base material component such as rubbers, plastics, thermoplastic elastomers, etc. with a softening component such as a plasticizer or process oil, a filler, a stabilizer, and, if necessary, a coloring agent, etc., and then, for example, once cured by heating to form pellets or plates, and then reheated to be molded into the shape of an eraser.

[0017] (Base material component) The eraser 1 can be roughly classified according to the types of the following base material components, for example. These base material components can be used alone or in combination of two or more as necessary.

[0018] (1) Plastic erasers using a thermoplastic resin as the base material component Examples of the thermoplastic resin that is the base material component of the plastic eraser include vinyl chloride resins such as vinyl chloride resin, vinyl chloride-vinyl acetate resin, vinyl chloride-ethylene-vinyl acetate resin, and vinyl acetate resins such as ethylene-vinyl acetate resin. Among them, vinyl chloride resins, especially vinyl chloride resin, are suitable for obtaining the eraser 1 that is easily miscible with a plasticizer and has both high shape retention and high erasability.

[0019] (2) Rubber erasers using a rubber as the base material component Examples of the rubber that is the base material component of the rubber eraser include IIR (butyl rubber), IR (isoprene rubber), SBR (styrene-butadiene rubber), BR (butadiene rubber), EPM (ethylene propylene rubber), EPDM (ethylene propylene diene terpolymer), acrylic rubber, polyisobutylene, NR (polyisoprene, natural rubber), etc.

[0020] (3) Elastomer-based eraser in which an elastomer is used as the base material component Examples of the elastomer that is the base material component of the elastomer eraser include styrene-based, butadiene-based, isoprene-based, ethylene-propylene-based, nitrile-based, chloroprene-based, urethane-based, acrylic-based, polyester-based, and olefin-based elastomers.

[0021] (Softening component) The softening component is a plasticizer or a process oil. As the plasticizer, phthalate-based plasticizers such as dioctyl phthalate, diheptyl phthalate, and dibutyl phthalate, acetyl citrate-based plasticizers such as tributyl acetyl citrate, adipic acid ester-based plasticizers such as di-2-ethylhexyl adipate and adipic acid polyester, alkyl sulfonic acid ester-based plasticizers such as phenyl alkyl sulfonate, epoxy-based plasticizers, trimellitic acid-based plasticizers, and benzoic acid esters are preferably used. These plasticizers may be used alone or, if necessary, in combination of two or more of them. As the process oil, mineral oils such as paraffin-based process oil, naphthene-based process oil, and aromatic-based process oil, animal and vegetable oils, or oils derived from these are used.

[0022] (Filler) As the filler, calcium carbonate, magnesium carbonate, magnesium oxide, silica, talc, clay, diatomaceous earth, quartz powder, alumina, alumina silicate, mica, etc. are used.

[0023] (Dividing surface 2) In the embodiment, as shown in FIG. 1, the dividing surface 2 is a single plane capable of dividing the eraser 1, and when divided by the dividing surface 2, the eraser 1 is divided into two rectangular parallelepiped eraser pieces 1a and 1b. However, it is not limited to this. FIG. 2 is a diagram showing other forms of the dividing surface 2. As shown in FIG. 2(a), there may be a plurality of dividing surfaces 2. As shown in FIG. 2(b), the dividing surface 2 may be in a jigsaw puzzle shape including a curve with a partially curved cross section. As shown in FIG. 2(c), the dividing surface 2 may be in a cross-sectional zigzag shape including a plurality of planes. In addition, as shown in the figure, the dividing surface 2 is preferably formed in a direction along the direction perpendicular to the longitudinal direction of the eraser, which is the direction in which the eraser is used.

[0024] The dividing surface 2 is a surface that can divide the eraser 1 with a predetermined tensile force smaller than other parts of the eraser 1 as described above. The predetermined tensile force is the tensile force when one side of the eraser 1 is fixed across the dividing surface 2 and the other side is pulled, and the rubber pieces 1a and 1b are divided at the dividing surface 2. The eraser 1 of the embodiment has a size of 5 mm × 15 mm on one side surface. And the dividing surface 2 of the eraser 1 is 5 mm × 15 mm parallel to, of the same shape and the same size as that one side surface. When separating the 5 mm × 15 mm dividing surface 2 to divide the eraser 1 into the rubber pieces 1a and 1b, the tensile force is preferably a force of 0.02 kg to 5 kg, and more preferably a force of 1 kg to 4 kg. Note that when it is a force per 1 cm for 0.02 kg to 5 kg, it is 0.027 kg to 6.67 kg, and when it is a force per 1 cm for 1 kg to 4 kg 2 it is 1.33 kg to 5.33 kg. 2 According to the Yamagata Insurance Medical Research No. 18, 2015, "Relationship between Basal Metabolism and Grip Strength" for reference, the average of the force called pinch force pinched by fingers from the 20s to the 50s is 6.6 kg to 7.1 kg for the right hand and 5.8 kg to 6.4 kg for the left hand. Since the preferable range of the tensile force of the embodiment is a force below that, the user can easily divide the eraser 1 at the dividing surface 2.

[0025] In addition, as a result of conducting a load monitoring test during erasure using a general eraser, the average load during erasure for lower elementary school boys and girls was found to be a maximum of 2.085 kg, a minimum of 0.78 kg, and an average of 1.322 kg. Therefore, even the child with the smallest strength can easily divide the eraser 1 at the dividing surface 2. In addition, as shown in FIG. 1(c), it can be separated with a smaller force by peeling off the dividing surface 2 from one side.

[0026] (First Embodiment of the Manufacturing Method of the Eraser 1: Extrusion Molding Case) Hereinafter, a manufacturing method by extrusion molding as the first embodiment of the manufacturing method of the eraser 1 will be described. FIG. 3 is an exploded view of a manufacturing apparatus 10 for implementing the manufacturing method by extrusion molding as the first embodiment. FIG. 4 is a perspective view of the assembled state of the manufacturing apparatus 10. FIG. 5 is a cross-sectional view of the material extrusion part of the manufacturing apparatus 10. FIG. 6 is a front view of the material extrusion part of the manufacturing apparatus 10.

[0027] The manufacturing apparatus 10 includes a material input hopper 11, a cylinder part 12 which is a material holding part having a cylinder part 12A and a head part 12B, a screw part 16 which is an extrusion part arranged inside the cylinder part 12A, a dividing surface forming member 14, and a die part 15.

[0028] (Material Input Hopper 11) The material input hopper 11 has a material input port 11a and guides, for example, pellet-shaped materials input from the material input port 11a to the inlet 12a of the cylinder part 12.

[0029] (Cylinder Part 12) The cylinder part 12 has a cylinder part 12A and a head part 12B provided on the tip side of the cylinder part 12A. The cylinder part 12A is formed with an inlet 12a to which the material input hopper 11 is attached on the base end side, and a screw part 16 is arranged inside. The cylinder part 12A can further be heated inside by a heating device (not shown) to heat and melt the pellet-shaped materials input from the material input hopper 11.

[0030] (Screw part 16) The screw part 16 is disposed in the internal space of the cylinder part 12A and is rotationally driven by a drive part (not shown). The screw part 16 extrudes the material that has been put into the inside of the cylinder part 12A and heated and melted to the tip side of the cylinder part 12A while kneading it.

[0031] (Head part 12B) The head part 12B is attached to the tip side of the cylinder part 12A. An outlet 12b through which the material heated and melted and kneaded in the cylinder part 12A is extruded is formed on the tip side of the head part 12B.

[0032] (Base part 15) The base part 15 is a plate-like member with a predetermined thickness, and a molding hole 15a is provided at the center. The base part 15 is disposed on the front end surface of the head part 12B such that the outlet 12b of the head part 12B and the molding hole 15a overlap. The base part 15 molds the molten material extruded from the outlet 12b into the shape of the molding hole 15a by passing it through the molding hole 15a. The molding hole 15a has a rectangular shape, and the material extruded through the molding hole 15a is molded into a rod-shaped eraser material 1A having a rectangular cross-section that is the same shape as the molding hole 15a.

[0033] (Split surface forming member 14) In the embodiment, the split surface forming member 14 is a linear member that is a metal wire and extends in a direction orthogonal to the extrusion direction in which the molten material is extruded. The split surface forming member 14 is disposed on the flow path through which the material is extruded, where the outlet 12b of the head part 12B and the molding hole 15a of the base part 15 overlap, between the head part 12B and the base part 15. The split surface forming member 14 is disposed so as to bisect the rectangular molding hole 15a that serves as the flow path of the material.

[0034] In the embodiment, one dividing surface forming member 14 which is a linear member is arranged. However, as corresponding to Fig. 2(a), a plurality of dividing surface forming members 14 may be arranged. Further, in the embodiment, the dividing surface forming member 14 which is a linear member extends linearly. However, as corresponding to the dividing surfaces 2 in Figs. 2(b) and 2(c), it may be bent. Furthermore, the dividing surface forming member 14 may not be a linear member, and may be a belt-like member having a predetermined width in the extrusion direction of the material and extending in a direction orthogonal to the extrusion direction.

[0035] Next, a method for manufacturing the eraser 1 will be described. The inside of the cylinder part 12A is heated to a predetermined temperature by a heating device (not shown). Then, the screw part 16 in the cylinder part 12A is rotated by a drive part (not shown). In this state, the pellet-shaped material is put into the material charging hopper 11. The charged pellets naturally fall into the cylinder part 12A from the inlet 12a by their own weight and are supplied. In the cylinder part 12A, the pellets are heated and melted, and while being kneaded by the rotating screw part 16, they are sent to the tip part of the cylinder part 12A and are extruded from the outlet 12b provided in the head part 12B to the outside of the cylinder part 12.

[0036] The heated and melted material extruded from the outlet 12b flows into the molding holes 15a of the die part 15. At this time, however, the flow is divided into two by the dividing surface forming member 14. That is, a weld line is forcibly formed. The weld line is a vulnerable part formed at a place where the molten resin branches and then merges when flowing in the mold. When the material passes through the molding holes 15a of the die part 15 and solidifies, the material divided into two flows recombines again. However, the part of the recombined weld line becomes a dividing surface 2 that is easier to separate than other parts. Then, a continuous rod-shaped eraser material 1A having a rectangular cross section with the dividing surface 2 formed is extrusion-molded. The rod-shaped eraser material 1A is then cut to a predetermined length to manufacture the eraser 1.

[0037] Since the split surface 2 is the recombined part, it is easier to separate than other parts. However, it is bonded without applying a predetermined tensile force, and no cuts, grooves, slits, etc. are formed on the outer surface of the eraser 1. That is, the outer surface where the split surface 2 in the eraser 1 extends internally is flat.

[0038] Also, the predetermined tensile force for separating the split surface 2 can be changed by changing the thickness of the base part 15, that is, the time for the molten material to pass through the molding hole 15a of the base part 15. When the base part 15 is thick, the time for the molten material to pass through the molding hole 15a becomes long, so the bonding force of the split surface 2 becomes strong, and a strong tensile force is required to separate the split surface 2. When the base part 15 is thin, the time for the molten material to pass through the molding hole 15a becomes short, so the bonding force of the split surface 2 becomes weak, and the tensile force for separating the split surface 2 becomes weak.

[0039] Figure 7 is a table showing the results of manufacturing the vinyl chloride resin eraser 1 using the manufacturing apparatus 10 of the first embodiment and measuring the tensile force for separating its split surface 2. Example 1 and Example 2 are erasers 1 manufactured using the manufacturing apparatus 10 of the first embodiment, that is, the manufacturing apparatus 10 in which the split surface forming member 14 is arranged, and include the split surface 2. Example 1 used a base part 15 with a thickness of 1 mm, and Example 2 used a base part 15 with a thickness of 5 mm. Comparative Example 1 and Comparative Example 2 are erasers 1 manufactured using the manufacturing apparatus obtained by removing the split surface forming member 14 from the manufacturing apparatus 10 of the first embodiment, and do not include the split surface 2. Comparative Example 1 used a base part 15 with a thickness of 1 mm, and Comparative Example 2 used a base part 15 with a thickness of 5 mm.

[0040] Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are plastic erasers 1 with a vinyl chloride resin as the base material component. Specifically, it contains 24.95% by weight of vinyl chloride resin as the base material component, 49.95% by weight of phenyl alkyl sulfonate as the plasticizer, 24.95% by weight of calcium carbonate as the filler, and 0.15% by weight of additives.

[0041] Figure 8 is a table showing the results of manufacturing the non-chlorinated vinyl resin eraser 1 using the manufacturing apparatus 10 of the first embodiment and measuring the tensile force for separating the split surface 2 thereof. Examples 3 and 4 are erasers 1 manufactured using the manufacturing apparatus 10 of the first embodiment, that is, the manufacturing apparatus 10 in which the split surface forming member 14 is disposed, and include the split surface 2. For Example 3, a base portion 15 having a thickness of 1 mm was used, and for Example 4, a base portion 15 having a thickness of 5 mm was used. Comparative Examples 3 and 4 are erasers 1 manufactured using the manufacturing apparatus obtained by removing the split surface forming member 14 from the manufacturing apparatus 10 of the first embodiment, and do not include the split surface 2. For Comparative Example 3, a base portion 15 having a thickness of 1 mm was used, and for Comparative Example 4, a base portion 15 having a thickness of 5 mm was used.

[0042] Examples 3 and 4 and Comparative Examples 3 and 4 are elastomeric erasers 1 having a thermoplastic elastomer as a base material component. Specifically, it contains 30% by weight of a thermoplastic elastomer as a base material component, 60% by weight of silica particles as a filler, and 10% by weight of process oil as a softening component.

[0043] Figure 9 is a photograph showing the shapes of the test pieces of the examples and comparative examples for measuring the tensile force. The shape of the test piece is a small tensile test piece shape based on JIS K 7139 type CP. Figure 10 is a photograph showing the method for measuring the tensile force of the test pieces of the examples and comparative examples manufactured using the manufacturing apparatus 10.

[0044] The method for measuring the tensile force is as follows. In the examples, the eraser 1 manufactured by the manufacturing apparatus 10 and having a thickness of about 2 mm was punched into the shape of Figure 9 so that the split surface was in the middle of the constriction to produce a test piece. In the comparative examples, an eraser without a split surface manufactured by a manufacturing apparatus without a split surface forming member was processed in the same manner as in the examples to produce a test piece.

[0045] These test pieces were pulled at both ends using a universal material testing machine model 5566 (manufactured by Instron Corporation) based on JIS K 7161-1, and the force when they were fractured was taken as the tensile force as shown in Fig. 10. The average of five measurements was taken for each test piece. The test conditions were a test speed of 50 mm / min, a chuck distance of 30 mm, the number of measurements n = 5, a test chamber temperature of 23°C ± 2°C, and a test chamber relative humidity of 50% ± 10%.

[0046] The test pieces of Examples 1, 2, 3, and 4 that were fractured during the measurement of the tensile force all separated neatly along the split surface. The test pieces of Comparative Examples 1, 2, 3, and 4 were all fractured so as to tear at the constricted part, and the cross-section was rough and dirty with many irregularities.

[0047] As shown in Fig. 7, for the plastic eraser 1 using vinyl chloride resin, when the base thickness was 1 mm, the tensile force of the eraser of Example 1 was 2.56 kg / cm 2 and the tensile force of the eraser of Comparative Example 1 was 13.6 kg / cm 2 It was. That is, it was proved that the eraser of Example 1 provided with the split surface 2 could be split at a value 18.8% lower than that of the eraser of Comparative Example 1.

[0048] Also, for the plastic eraser 1 using vinyl chloride resin, when the base thickness was 5 mm, the tensile force of the eraser of Example 2 was 6.45 kg / cm 2 and the tensile force of the eraser of Comparative Example 2 was 13.6 kg / cm 2 It was. That is, it was shown that the eraser of Example 2 could be split at a value 47.4% lower than that of the eraser of Comparative Example 2 due to the split surface 2.

[0049] In addition, when the tensile force of the eraser of Example 1 was converted to the cross-sectional size of the eraser 1 of 5 mm × 15 mm, it became 1.92 kg, and when the tensile force of the eraser of Example 2 was converted to the cross-sectional size of the eraser 1 of 5 mm × 15 mm, it became 4.83 kg.

[0050] As shown in Fig. 8, in the elastomeric eraser 1 using a thermoplastic elastomer, when the die thickness is 1 mm, the tensile strength of the eraser of Example 3 is 3.21 kg / cm 2 and the tensile strength of the eraser of Comparative Example 3 is 39.6 kg / cm 2 . That is, it was shown that the eraser of Example 3 provided with the split surface 2 can be split at a value 8.1% lower than that of the eraser of Comparative Example 3.

[0051] Also, in the elastomeric eraser 1 using a thermoplastic elastomer, when the die thickness is 5 mm, the tensile strength of the eraser of Example 4 is 6.21 kg / cm 2 and the tensile strength of the eraser of Comparative Example 4 is 39.6 kg / cm 2 . That is, it was shown that the eraser of Example 4 provided with the split surface 2 can be split at a value 15.7% lower than that of the eraser of Comparative Example 4.

[0052] In addition, when the tensile strength of the eraser of Example 3 is converted to the cross-sectional size of the eraser 1 of 5 mm × 15 mm, it becomes 2.41 kg, and when the tensile strength of the eraser of Example 4 is converted to the cross-sectional size of the eraser 1 of 5 mm × 15 mm, it becomes 4.65 kg.

[0053] Thus, according to the manufacturing method of the embodiment, when the size of the split surface 2 of the eraser 1 is 5 mm × length 15 mm, when one side is fixed with the split surface 2 sandwiched and the other side is pulled, a force of 0.02 kg to 5 kg can be applied.

[0054] (Second Embodiment of the Manufacturing Method of the Eraser 1: In the Case of Press Molding) Fig. 11 is a diagram for explaining a manufacturing method by press molding as the second embodiment of the manufacturing method of the eraser 1. First, as shown in Fig. 11(a), a mixed material obtained by blending a base material component, a softening component such as a plasticizer or process oil, a filler, a stabilizer, and, if necessary, a coloring agent, etc., and uniformly mixing them is introduced into each of the concave portions 20a of two molds 20 each provided with a similarly shaped concave portion 20a. At this time, since the plasticizer is a liquid, the mixed material becomes liquid. When the mold 20 is heated, for example, the plasticizer is incorporated into the molecular chain of the base material component which is a vinyl chloride-based thermoplastic resin, resulting in a decrease in fluidity and solidification of the material. The two molds 20 each containing the solidified material in the concave portion 20a are faced so that the concave portions 20a face each other. In this state, the two molds 20 are pressed against each other and heated. Then, the materials in the respective concave portions 20a are joined, and the joint surface becomes a split surface 2 equivalent to a weld line. Thereby, an eraser 1 is manufactured which is made of the same material throughout and has a split surface 2 that can split the eraser 1 with a smaller tensile force than other parts of the eraser 1.

[0055] As described above, the eraser 1 of the embodiment forms the split surface 2 by intentionally generating a weld line which is regarded as a problem in normal resin molding. This split surface 2 is a surface that can split the eraser 1 with a smaller tensile force than other parts of the eraser 1 even though the eraser 1 is made of the same material throughout. On the other hand, before being split at the split surface 2, the eraser 1 has the shape of a normal rectangular parallelepiped eraser, and no cuts, grooves, slits, etc. are formed on the outer surface. That is, the outer surface of the eraser 1 where the split surface 2 extends inside is flat. Therefore, compared with an eraser having a special shape with increased corners, it has excellent portability, is easy to hold during use, and it is easy to form a sleeve that fits the shape. Furthermore, the eraser fabric may have normal strength. When the eraser 1 is used to erase fine parts using the corners, the corners become rounded. Here, since the eraser 1 of the embodiment has a splitting surface 2 that can split the eraser 1 with a tensile force smaller than that of other parts, it can be split by this splitting surface 2. The split eraser 1 can form new corners at the split parts and can further erase smaller parts.

[0056] As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto. For example, the eraser 1 may be manufactured by injection molding in which materials flow in from two lines respectively to form a splitting surface by a weld line. Also, in the embodiment, the screw part 16 that rotates and drives as an extrusion part to extrude the material input into the cylindrical part 12 is used, but the present invention is not limited thereto. That is, as the extrusion part, a pusher (stem) that advances and retreats in the axial direction of the cylindrical part to extrude the material input into the cylindrical part may be used.

Explanation of Reference Numerals

[0057] 1 Eraser 1a Rubber piece 1b Rubber piece 2 Splitting surface 10 Manufacturing apparatus 11 Material input hopper 11a Material input port 12 Cylindrical part (material holding part) 12A Cylinder part 12B Head part 12a Inlet 12b Outlet 14 Splitting surface forming member 15 Die head part 15a Molding hole 16 Screw part (extrusion part) 20 Mold 20a Recess 1

Claims

1. Erasers made of the same material, a dividing surface that allows the eraser to be divided by a smaller tensile force than other parts of the eraser; the dividing surface is bonded to the other surface on both sides of the dividing surface when the tensile force is not applied, eraser.

2. The dividing surface has a tensile force of 0.027 kg / cm between the two sides of the dividing surface. ２ ~6.67kg / cm ２ When a force of 0.05 mm is applied, the surface is divided.

2. The eraser according to claim 1.

3. a material holding portion having an internal space and provided with an inlet and an outlet for a material to the internal space; an extrusion section that extrudes the material introduced into the internal space of the material holding section to the outside through the outlet; a die portion having a molding hole, attached to the outlet of the material holding portion, and molding the material extruded by the extrusion portion by passing the material through the molding hole; a dividing surface forming member disposed between the material holding portion and the die portion so as to divide the molding hole, An eraser manufacturing device for manufacturing erasers made of the same material and having a dividing surface that can be divided with a smaller tensile force than other parts of the eraser.

4. The nozzle portion is a plate-like member through which the molding hole is provided, and the nozzle portion of different thicknesses can be attached.

4. An apparatus for manufacturing the eraser according to claim 3.

5. A material is introduced into an internal space of a material holding unit having an internal space and an inlet and an outlet for the material into the internal space; Extruding the material out through the outlet; In the method for manufacturing an eraser, the extruded material is molded by passing it through a molding hole of a nozzle part attached to the outlet of the material holding part, A method for manufacturing an eraser, in which, as the extruded material flows into the molding hole, the material is divided by a dividing surface forming member arranged between the material holding portion and the nozzle portion so as to divide the molding hole, thereby producing an eraser made of the same material and having a dividing surface that can be divided with a smaller tensile force than other parts of the eraser.

6. Manufacture multiple sheet-shaped eraser pieces, The produced eraser pieces are stacked and pressed together to bond multiple eraser pieces together, A method for manufacturing an eraser made of the same material and having a dividing surface that can be divided with a smaller tensile force than other parts of the eraser.

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