Winding core and method for manufacturing winding core

Abstract

The core is designed so that the outer diameter of the wound sheet-like material is uniform in the axial direction. [Solution] In a winding core around which a sheet-like material 2 is wound, the winding core comprises a core material 10 with a circular cross-section and a covering material 20 made of a material softer than the core material 10 that covers the entire circumference around the axis of the core material 10. The core material 10 has a recess 11 that is recessed in the inner diameter direction over at least a portion of its circumference in the axial direction, and the covering material 20 covers the recess 11 and has portions with different thicknesses along the axial direction, and the outer surface of the covering material 20 is formed so that the outer diameter is constant over the entire length in the axial direction.

Description

Technical Field

[0001] The present invention relates to a winding core for winding sheet-like materials such as films and sheets, and a method for manufacturing the same.

Background Art

[0002] Films and sheets made of flexible materials (hereinafter referred to as sheet-like materials) are stored and transported in a state wound around a winding core, and then used in various manufacturing processes. When a sheet-like material is wound around a winding core, step marks may occur on the sheet-like material. Step marks are generated when a step is formed on the sheet-like material by a double-sided tape attached to fix the starting end of the sheet-like material to the winding core or the edge of the sheet-like material, and this step leaves marks on the sheet-like material wound thereafter. When step marks occur, the portion of the sheet-like material with such marks has to be discarded, leading to the problem of so-called film loss.

[0003] In particular, in recent years, sheet-like materials used for display materials of televisions and smartphones have been increasingly thinned for the purpose of weight reduction. Even a slight step generated at the start of winding the sheet-like material easily causes step marks on the surface of the sheet-like material wound thereon.

[0004] Accordingly, the winding core described in Patent Document 1 has been proposed. The winding core described in Patent Document 1 includes a core material having a circular cross section and a urethane lining coated over the entire circumference around the axis of the core material. The outer peripheral surface of the urethane lining is formed such that the outer diameter is constant over the entire axial length. Since this winding core is provided with a urethane lining on the surface of the core, it is stated that the elasticity of the urethane lining absorbs the step, and can suppress the occurrence of step marks on the sheet-like material caused by the step.

Prior Art Literature

Patent Literature

[0005]

Patent Document 1

[0006] Incidentally, the inventors of this application have found that when a sheet-like material is wound onto a core, the load applied from the sheet-like material in the inner diameter direction to the core is not uniform along the axial direction of the core. The core described in Patent Document 1 has a core material with a constant outer diameter along the entire axial direction, and is lined with urethane. If the load applied from the sheet-like material to the urethane lining is uniform along the axial direction of the core, the amount of deformation of the urethane lining is uniform along the entire axial direction. However, as described above, if the load applied from the sheet-like material is not uniform along the axial direction of the core, the amount of deformation of the urethane lining in the inner diameter direction will not be uniform along the entire axial direction, and the outer diameter of the wound sheet-like material may not be uniform in the axial direction. If the outer diameter of the wound sheet-like material is not uniform, it can cause wrinkles in the film, which is undesirable.

[0007] The problem that this invention aims to solve is to provide a winding core in which the outer diameter of the wound sheet-like material is uniform in the axial direction. [Means for solving the problem]

[0008] To solve the above problems, this invention provides a winding core with the following configuration. [Configuration 1] In a core around which a sheet-like material is wound, The system comprises a core material with a circular cross-section and a covering material made of a material softer than the core material that covers the entire circumference around the axis of the core material. The core material has a recess formed in the inner diameter direction over its entire circumference, at least in part of its axial direction. The covering material covers the recess and has portions with different thicknesses along the axial direction. The outer surface of the covering material is formed such that the outer diameter is constant along the entire length in the axial direction.

[0009] [Configuration 2] The winding core according to configuration 1, wherein the covering material is provided across the recess and another portion adjacent to the recess in the axial direction, and the thickness of the covering material differs between the recess and the other portion.

[0010] [Configuration 3] The winding core according to configuration 1 or 2, wherein a second recess is formed in the axial center of the aforementioned recess, extending in the axial direction and in the axial direction over its entire circumference.

[0011] [Structure 4] The covering material is a core according to any one of configurations 1 to 3, wherein the covering material is a material containing polyurethane.

[0012] [Composition 5] The core material is made of a hard resin, as described in any of configurations 1 to 4.

[0013] [Composition 6] In the method for manufacturing a winding core described in any one of configurations 1 to 5, A recess forming step in which the recess is formed in the core material, After the recess formation step, the core material is positioned in the center of the mold, After the arrangement step, a filling step is performed in which the covering material is filled between the core material and the mold, A method for manufacturing a winding core, comprising the filling step followed by a curing step of curing the filled coating material.

[0014] [Composition 7] The method for manufacturing a winding core according to configuration 6, wherein the recess is formed by grinding in the recess formation step. [Effects of the Invention]

[0015] According to the present invention, the covering material has portions with different thicknesses in the axial direction of the winding core, and the portion with a larger thickness of the covering material has a larger amount of deformation against a load in the inner diameter direction than the portion with a smaller thickness. Therefore, even when the magnitude of a load expected from a wound sheet-shaped material on the covering material is not uniform along the axial direction, generation of film wrinkles can be suppressed by adjusting the thickness of the covering material to make the amount of deformation of the covering material in the inner diameter direction approach uniformity over the entire axial length. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [Figure 1] Partial cross-sectional view of a winding core according to an embodiment of the present invention [Figure 2] Figure showing the state before forming the covering material of the winding core of Figure 1 [Figure 3] Partial enlarged view of Figure 1 [Figure 4] Figure showing a state of forming a covering material on the core material of the winding core of Figure 1 [Figure 5] Figure showing a modified example of the winding core of Figure 1 [Figure 6] Figure showing another modified example of the winding core of Figure 1 DESCRIPTION OF EMBODIMENTS

[0017] Hereinafter, embodiments of the present invention will be described based on the drawings. As shown in Figure 1, the winding core 1 according to the present embodiment, onto which a sheet-shaped material 2 is wound, is composed of a core material 10 and a covering material 20 covering the outer circumference of the core material 10. The sheet-shaped material 2 is, for example, an elongated sheet member or an elongated film member. The sheet-shaped material 2 is made of a flexible material. Specifically, it includes various functional films, metal foils, special paper, and the like. In this embodiment, a plastic film used for display materials of televisions, smartphones and other devices is employed as the sheet-shaped material 2.

[0018] As shown in Figure 2, the core material 10 is a longitudinal member with a circular cross-section. The core material 10 is made of a rigid resin. Fiber-reinforced plastic (FRP) can be used as the rigid resin. The core material 10 has an axial length of 1 to 2 m, an outer diameter of 100 to 200 mm, and a cylindrical thickness of 3 to 15 mm. In this embodiment, the core material 10 is cylindrical, but this does not preclude the core material 10 from being a solid shaft.

[0019] The core material 10 has a first recess 11a (recess 11) formed therein that is recessed in the radial direction over its entire circumference in at least a portion of its axial direction. Furthermore, within the first recess 11a, a second recess 11b (recess 11) is formed that is recessed in the radial direction over its entire circumference and extends in the axial direction.

[0020] The first recess 11a is located in the axial center of the core material 10. The first recess 11a is formed over a range of 80-95% of the axial length of the core material 10. The bottom of the first recess 11a is a circumferential surface with a constant outer diameter over its entire axial length. In this embodiment, the outer diameter (diameter) of the bottom of the first recess 11a is set to be 1-5 mm smaller than the outermost diameter of the core material 10 (the diameter of the outermost part at the axial end).

[0021] The second recess 11b is located in the axial center of the first recess 11a. The second recess 11b is formed over a range of 80-95% of the axial length of the first recess 11a. The bottom of the second recess 11b is a circumferential surface with a constant outer diameter throughout the entire axial direction. The outer diameter (diameter) of the bottom of the second recess 11b is set to be 1-5 mm smaller than the outer diameter of the bottom of the first recess 11a.

[0022] As shown in Figure 3, the entire circumference of the core material 10 around its axis is covered with a covering material 20 made of a material softer than the core material 10. Polyurethane can be used as the material for the covering material 20. In addition, the material for the covering material 20 is not limited to polyurethane; elastic and soft resin materials such as polyethylene and Teflon, as well as various other soft resins and rubbers can be used. The covering material 20 covers the recess 11 and has portions with different thicknesses along the axial direction.

[0023] In this embodiment, the covering material 20 is provided spanning the first recess 11a and the second recess 11b. The covering material 20 is also filled into the entire recess 11 (the entirety of the first recess 11a and the entirety of the second recess 11b). The outer circumferential surface of the covering material 20 is formed so that its outer diameter is constant along its entire axial length.

[0024] The manufacturing method for this core 1 will now be described. First, as shown in Figure 2, a recess formation step is performed to form the recesses 11. In the recess formation step, recesses 11 (the first recess 11a and the second recess 11b) are formed on the outer surface of a cylindrical material that has not been processed on its outer surface by grinding, thereby manufacturing the core material 10. At this time, grinding is used to efficiently produce a uniform processed surface. However, the processing method is not limited to grinding and may also be cutting. Alternatively, the core material 10 may be molded to have the recesses 11 during the resin molding stage.

[0025] After the recess formation process, as shown in Figure 4, a placement process is performed to position the core material 10 at the center of the mold 30. Here, the inner surface of the mold 30 is formed in a cylindrical shape and the bottom is closed. The inner circumferential surface of the bottom of the mold 30 is set to a size that matches the outermost diameter portion 12 (outer circumferential surface of the end) of the core material 10 so that it can guide the outermost diameter portion 12 (outer circumferential surface of the end) of the core material 10. The core material 10 is positioned coaxially with the space inside the mold 30 while being guided by the mold 30, and in this state, a certain gap is provided between the outer circumferential surface of the core material 10 and the inner circumferential surface of the mold 30.

[0026] After the placement process, a filling process is performed for casting the coating material 20. In the filling process, liquid coating material 20 (liquid polyurethane 20) is filled into the gap between the outer surface of the core material 10 and the inner surface of the mold 30 through the opening of the mold 30. The liquid polyurethane 20 is filled so as to cover the entire recess 11.

[0027] After the filling process, a curing process is performed in which the filled liquid (uncured) polyurethane 20 is left to cure. When leaving the liquid polyurethane 20 to cure, it is also possible to heat it to a certain temperature to accelerate the curing process.

[0028] In this embodiment, the winding core 1 may cause a step at the beginning of winding the sheet material 2 onto the winding core 1 due to the double-sided tape used to attach the starting end of the sheet material 2 to the winding core 1, or the thickness of the sheet material 2 itself, which may cause a step mark on the sheet material 2 wound thereafter. However, since the material of the covering material 20 in this embodiment is polyurethane, the elasticity of the covering material 20 absorbs the step and prevents the occurrence of a step mark on the covering material 20.

[0029] Furthermore, when winding the sheet-like material 2 onto the core 1, the load applied from the sheet-like material 2 in the inner diameter direction to the core 1 may not be uniform along the axial direction of the core 1. However, with the core 1 of this embodiment, when a recess 11 is provided at any position in the axial direction of the core 1, the thickness of the portion of the covering material 20 that is covered by the recess 11 becomes larger than the thickness of the portion that is not covered by the recess 11, and the amount of deformation in response to the load in the inner diameter direction becomes larger. As a result, even if the magnitude of the load expected to be applied to the covering material 20 from the wound sheet-like material 2 is not uniform along the axial direction, by providing the recess 11 in such a way that the thickness of the covering material 20 is thinner in the portion with a large load and thicker in the portion with a small load, the amount of deformation of the covering material 20 in the inner diameter direction can be made to be more uniform along the entire axial length. Therefore, the sheet-like material 2 can be wound onto the core 1 so that the outer diameter of the sheet-like material 2 is uniform in the axial direction, and the occurrence of film wrinkles can be suppressed.

[0030] Furthermore, since the core material 10 is made of hard resin, it has high strength. It is also lightweight, making transportation easy. If FRP is used as the material for the core material 10, the strength can be further increased.

[0031] Furthermore, in the above embodiment, as shown in Figure 3, the recess 11 is provided in the axial center of the core material 10, but the recess 11 can be set at any position depending on the axial load conditions applied from the sheet-like material 2 to the covering material 20. For example, as shown in Figure 5, the recess 11 can be provided as a recess 11c that is recessed in the inner diameter direction at the axial end of the core material 10. In Figure 5, a recess 11d that is recessed in the inner diameter direction is provided at the end of the recess 11c. In this case, the covering material 20 is provided spanning the recess 11c and the outermost diameter portion 12, which is the adjacent portion axially inward of the recess 11c. The covering material 20 is also provided spanning the recess 11c and the recess 11d.

[0032] Furthermore, as shown in Figure 6, the recesses 11 can be provided at multiple locations along the axial direction. In this case, the covering material 20 is provided across the recesses 11 and the outermost diameter portion 12, which is adjacent to them in the axial direction.

[0033] In this embodiment, the recess 11 is formed from a first recess 11a and a second recess 11b. However, as a variation, the second recess 11b may not be formed, and only the first recess 11a may be formed. When only the first recess 11a is formed, the covering material 20 is provided spanning the first recess 11a (recess 11) and the outermost diameter portion 12, which is the adjacent portion on its axially outer side. Alternatively, the covering material 20 may be provided spanning the first recess 11a and the second recess 11b, as well as spanning the first recess 11a and the outermost diameter portion 12, which is the adjacent portion on its axially outer side.

[0034] Furthermore, although the manufacturing method of the above embodiment employs casting molding as the method for molding the covering material 20 onto the core material 10, other molding methods may also be used. For example, injection molding can be used.

[0035] In the above embodiment, the structure of this invention was described using a plastic film used as a display material for televisions and smartphones as an example of the sheet-like material 2. However, this invention can also be applied to sheet-like materials used for substrates, electrodes, various other electronic components, machine parts, building materials, daily necessities, and various other applications.

[0036] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0037] 2. Sheet-like material 10 Core material 11 recess 11b Second recess 20 Covering material 30 molds

Claims

1. In a core around which a sheet-like material (2) is wound, The device comprises a core material (10) with a circular cross-section, and a covering material (20) made of a material softer than the core material (10) that covers the entire circumference around the axis of the core material (10). The core material (10) has a recess (11) formed therein that is recessed in the radial direction over its entire circumference, at least in part with respect to its axial direction. The covering material (20) covers the recess (11) and has portions with different thicknesses along the axial direction. The outer surface of the covering material (20) is formed such that the outer diameter is constant along the entire length in the axial direction.

2. The winding core according to claim 1, wherein the covering material (20) is provided across the recess (11) and another portion adjacent to the recess (11) in the axial direction, and the thickness of the covering material differs between the recess (11) and the other portion.

3. The winding core according to claim 2, wherein a second recess (11b) is formed in the axial center of the recess (11), extending in the axial direction and concave in the axial direction over the entire circumference.

4. The winding core according to claim 1, wherein the covering material (20) is a material containing polyurethane.

5. The core material (10) is made of a hard resin, as described in claim 1.

6. In the method for manufacturing a winding core according to any one of claims 1 to 5, A recess forming step in which the recess (11) is formed in the core material (10), After the recess formation step, the arrangement step is to place the core material (10) in the center of the mold (30), After the arrangement step, a filling step is performed in which the covering material (20) is filled between the core material (10) and the mold (30), A method for manufacturing a winding core, comprising the filling step followed by a curing step of curing the filled coating material (20).

7. The method for manufacturing a winding core according to claim 6, wherein the recess (11) is formed by grinding in the recess formation step.

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