Tube and core shaft for winding core shaft

Abstract

To further stabilize a posture of a tube which is wound in a spiral manner, in a winding core shaft for supporting a winding core.SOLUTION: A tube 3 comprises an elastic body wound around a cylindrical body 2 of a winding core shaft 1 in a spiral manner. On a cross section orthogonal to an axial direction of the tube 3, a cavity part 31 where a fluid passes has a shape flat in the longer direction X. A center 31a on the cross section of the cavity part 31 is at a position deviated to one Y1 side in the shorter direction Y of the flat shape of the cavity part 31 from a center 3a on the cross section of the tube 3. Thickness A2 on one side of the tube 3 has a portion 35a which is thinner than thickness A1 of an end 31b in the longer direction X of the flat shape of the cavity part 31.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a tube for a core shaft and a core shaft used for winding a sheet around a core or feeding a sheet out from a core in a manufacturing process of a manufacturer that manufactures products by processing sheets such as films, papers, and non-woven fabrics.

Background Art

[0002] In the manufacturing process of a manufacturer that manufactures products by processing sheets such as films, papers, and non-woven fabrics, there are processes of winding a sheet around a cylindrical core and feeding out the sheet wound around the core. In these processes, a core shaft is inserted into the core, and the core is rotatably supported by the core shaft. As an example of the core shaft, there is a paper tube shaft that fixes a paper tube by air pressure (see, for example, Patent Document 1).

[0003] FIGS. 6(A) and 6(B) are cross-sectional views showing the main part of the paper tube shaft 20 described in Patent Document 1, and the left-right direction in FIGS. 6(A) and 6(B) is the axial direction of the paper tube shaft 20. The paper tube shaft 20 described in Patent Document 1 includes a paper tube shaft cylinder 20', a spiral groove 21b formed on the outer peripheral surface of the paper tube shaft cylinder 20', and a tube 22 wound around the groove 21b. Compressed air is supplied to the tube 22. When the paper tube 36 (core) is inserted into the paper tube shaft 20, compressed air is not injected into the tube 22, and the tube 22 is in a contracted state. Therefore, when the paper tube 36 is inserted into the paper tube shaft 20, the paper tube 36 is not easily caught by the tube 22. Thus, the paper tube 36 can be smoothly attached to and detached from the paper tube shaft 20. When connecting the paper tube 36 to the paper tube shaft 20, compressed air is injected into the tube 22 in a state where the paper tube shaft cylinder 20' is inserted into the paper tube 36. Thereby, the tube 22 expands and the outer diameter of the tube 22 increases, and the tube 22 adheres closely to the paper tube 36. Thereby, the paper tube shaft 20 and the paper tube 36 are connected so as to be integrally rotatable.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Special Publication No. 57-24296 [Overview of the project] [Problems that the invention aims to solve]

[0005] The tube 22 has a thickened portion 23 in its outer diameter side that contacts the paper tube 36. On the other hand, the thickness of the inner diameter side of the tube 22 that contacts the groove 21b of the paper tube shaft 20' is thinner and more uniform than the thickness of the thickened portion 23. Due to this configuration, the direction of elastic deformation of the inner diameter side of the tube 22 due to external force is not fixed. Therefore, the amount of deformation at both ends of the tube 22 in the width direction cannot be kept constant due to uneven load balance when the tube 22 is wound around the paper tube shaft 20', and for example, as shown in Figure 6(B), the thickened portion 23 (outer diameter side of the tube 22) may be tilted relative to the paper tube shaft 20'. If compressed air is injected into the tube 22 in this position, the expansion of the outer diameter of the tube 22 due to the expansion of the tube 22 may not reach the desired value, and the bonding force between the tube 22 and the paper tube 36 may be weakened.

[0006] One of the purposes of this disclosure is to provide greater stability to the orientation of the spirally wound tube in a core shaft for supporting a core. [Means for solving the problem]

[0007] This disclosure primarily concerns the following core shaft tube and core shaft.

[0008] (1) A tube made of an elastic body that is wound spirally around the cylindrical body of a core shaft, In a cross-section perpendicular to the axial direction of the tube, the cavity through which the fluid passes is flattened in shape. The center of the cavity in the cross-section is located at a position displaced from the center of the tube in the cross-section to one side in the shorter direction of the flattened shape of the cavity. A tube for a winding core shaft, characterized in that the thickness of one side of the tube has a portion that is thinner than the thickness of the longitudinal end of the flattened shape of the cavity.

[0009] (2) The tube for a winding core shaft according to (1), characterized in that the outer shape of the tube is a flattened shape in which the longitudinal direction is the same as the longitudinal direction of the flattened shape of the hollow portion.

[0010] (3) The tube for a winding core shaft according to (1) or (2), characterized in that one side of the tube is convex in cross-section from the center outward.

[0011] (4) A cylindrical body and A winding core shaft characterized by comprising a tube according to any one of the above (1) to (3) which is wound spirally around the cylindrical body. [Effects of the Invention]

[0012] According to this disclosure, the orientation of the spirally wound tube can be made more stable in a core shaft for supporting a core. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a front view of the winding core shaft and winding core in one embodiment of the present disclosure, with a portion shown in cross-section. [Figure 2] Figure 2(A) is an enlarged view of a portion of the winding core shaft shown in Figure 1. Figure 2(B) shows the state in which the winding core is integrally connected to the winding core shaft shown in Figure 2(A) so as to be able to rotate together. [Figure 3] Figure 3 shows a single tube in a cross-section perpendicular to the axial direction of the tube. [Figure 4] Figures 4(A) and 4(B) are perpendicular cross-sectional views of the winding core shaft along the line IV-IV in Figure 1, with the tubes indicated by dashed lines. [Figure 5]FIG. 5(A) is a front view of the core shaft in the modified example, showing a part in cross section. FIG. 5(B) shows an enlarged view of a part in a state where the core is integrally rotatably connected to the core shaft shown in FIG. 5(A). [Figure 6] FIGS. 6(A) and 6(B) are cross-sectional views showing the main part of the paper tube shaft described in Patent Document 1.

Embodiments for Carrying out the Invention

[0014] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the drawings, substantially the same components are denoted by the same reference numerals, and redundant descriptions are omitted.

[0015] <Overall Configuration of the Core Shaft> FIG. 1 is a front view of the core shaft 1 and the core 100 in an embodiment of the present disclosure, showing a part in cross section. In FIG. 1, the core shaft 1 shows a state where the connection with the core 100 is released. FIG. 2(A) is an enlarged view of a part of the core shaft 1 in FIG. 1. FIG. 2(B) is a view showing a state where the core 100 is integrally rotatably connected to the core shaft 1 shown in FIG. 2(A).

[0016] As shown in FIGS. 1 to 2(B), the core shaft 1 is used to support the core 100. The total length of the core shaft 1 is not particularly limited, but an example of a total length suitable for supporting a core 100 having a total length of about 1.0 m to 1.5 m can be given. When pressurized fluid is supplied to the tube 3 of the core shaft 1 and the tube 3 expands, the core shaft 1 is connected (contacts) to the core 100. As a result, the core shaft 1 is connected to the core 100 so as to be able to transmit torque, and can rotate integrally with the core 100. On the other hand, when the pressurized fluid is discharged from the tube 3 and the tube 3 contracts, the connection between the core shaft 1 and the core 100 is released. As a result, the core 100 can be attached to and detached from the core shaft 1, and the core shaft 1 can be easily inserted into the core 100 and easily pulled out from the core 100.

[0017] The core 100 that is detachably attached to the core shaft 1 may be cylindrical. Examples of the core 100 include a core around which a sheet such as a film, paper, or non-woven fabric is wound. The inner diameter of the core 100 is substantially the same as the outer diameter of the core shaft 1 when the pressurized fluid is supplied to the tube 3 and expands. Examples of the fluid supplied to the tube 3 to expand the tube 3 include a gas such as air or nitrogen, and a liquid such as water. In the present embodiment, a form in which compressed air is supplied to the tube 3 will be described as an example.

[0018] The core shaft 1 includes a cylindrical body 2 and a tube 3 wound around the cylindrical body 2 in a spiral shape.

[0019] In addition to the above configuration, the core shaft 1 may further include a pair of end shafts 4 and 5, a pair of collars 6 and 7, and a cover 8.

[0020] <Cylindrical body> The cylindrical body 2 is preferably lightweight. For example, it is made of CFRP (Carbon Fiber Reinforced Plastics). Note that the cylindrical body 2 may be made of a synthetic resin other than CFRP, may be made of a non-ferrous metal such as an aluminum alloy, or may be made of iron. The outer peripheral surface 2a of the cylindrical body 2 is not formed with grooves such as spiral grooves and has a cylindrical shape. A pair of end shafts 4 and 5 are fixed to a pair of ends of the cylindrical body 2.

[0021] <End shaft> The end shafts 4 and 5 are portions supported by bearings (not shown). A part of each of the end shafts 4 and 5 protrudes from the cylindrical body 2, and this protruding part is supported by the bearing.

[0022] An air intake hole 4a is formed inside one end shaft 4. The air intake hole 4a is the part through which compressed air passes. In this embodiment, the air intake hole 4a is formed along the central axis of the end shaft 4 from the tip of the end shaft 4 (the left end in Figure 1) and opens to the outer circumferential surface of the end shaft 4. A plug 9 is attached to the tip portion of the end shaft 4. The plug 9 is connected to an air compressor via a hose (not shown), thereby introducing compressed air from the air compressor into the air intake hole 4a.

[0023] A joint 10 is attached to the portion of the air intake hole 4a that opens onto the outer surface of the end shaft 4. The joint 10 is a hollow member and is connected to one end of the tube 3. Compressed air from the air intake hole 4a is supplied to the hollow portion 31 of the tube 3 through the joint 10.

[0024] <Color> A cylindrical collar 6 is fixed to the outer surface of the end shaft 4. The collar 6 is positioned to surround the joint 10 and a portion of the tube 3. A cylindrical collar 7 is fixed to the outer surface of the short shaft 5.

[0025] <tube> Tube 3 is made of, for example, rubber and is an elastic material. Tube 3 can be any elastic material; its specific material is not limited. Examples of materials for Tube 3 other than rubber include thermoplastic elastomers such as thermoplastic urethane elastomers and thermoplastic polyester elastomers, as well as soft synthetic resins such as polyvinyl chloride resin and urethane resin. Tube 3 can be manufactured, for example, by extrusion molding or blow molding.

[0026] Tube 3 is spirally wound around the outer surface 2a of the cylindrical body 2, with adjacent portions facing each other in the longitudinal direction of the cylindrical body 2. In tube 3, adjacent portions facing each other in the longitudinal direction of the cylindrical body 2 may or may not be in contact. One end of tube 3 in the axial direction is fixed by a joint 10. The other end of tube 3 (not shown) in the axial direction is fixed by a plug fixed to the other end shaft 5, and the cavity 31 is sealed. Note that the other end of tube 3 (not shown) in the axial direction only needs to be fixed to the end shaft 5 and the cavity 31 sealed to prevent compressed air leakage, and the specific configuration is not limited. For example, the other end of tube 3 (not shown) in the axial direction may be configured to allow compressed air to be discharged by a valve or the like.

[0027] The tube 3 has a cavity 31 through which compressed air passes. When compressed air is supplied to the cavity 31, the tube 3 expands. The cavity 31 is formed along the entire axial length of the tube 3.

[0028] Figure 3 shows a cross-section of tube 3 perpendicular to its axial direction. Unless otherwise specified, the following explanation will be based on the free state in which no external force is applied to tube 3, as shown in Figure 3.

[0029] In a cross-section perpendicular to the axial direction of the tube 3, the cavity 31 is flattened. Hereafter, the cross-section perpendicular to the axial direction of the tube 3 will also be simply referred to as the "cross-section". In the cross-section, the longitudinal direction X of the cavity 31 is parallel to the longitudinal direction of the cylindrical body 2 (the direction in which the central axis 2b of the cylindrical body 2 extends) when the tube 3 is wound around the cylindrical body 2. In this case, "parallel" includes cases where the longitudinal direction X of the cavity 31 is tilted at an angle of a small error (a few degrees) with respect to the longitudinal direction of the cylindrical body 2 when the tube 3 is wound around the cylindrical body 2. In the cross-section, the cavity 31 is elongated in the longitudinal direction X and short in the transverse direction Y perpendicular to the longitudinal direction X. This elongated shape is formed by semicircular shapes at both ends in the longitudinal direction X, and a straight line connecting the two semicircular shapes in the middle of the longitudinal direction X. In this embodiment, the tube 3 is formed in a cross-sectional shape that is symmetrical in the longitudinal direction X (left-right symmetrical in Figure 3).

[0030] In the cross-section, the longitudinal direction X may be the direction in which the linear portion of the cavity 31 extends, or it may be the direction in which the straight line connecting the two furthest points (ends 31b, 31b) of the cavity 31 extends.

[0031] In the cross-section, the center 31a of the cavity 31 is located displaced from the center 3a of the tube 3 to one side Y1 in the short direction Y. One side Y1 in the short direction Y is the downward direction in Figures 2(A), 2(B), and 3, and is the direction from the tube 3 toward the cylindrical body 2 when the tube 3 is wound around the cylindrical body 2. The other side Y2 in the short direction Y is the upward direction in Figures 2(A), 2(B), and 3, and is the opposite direction to one side Y1 in the short direction Y. In the cross-section, the center 31a of the cavity 31 is the centroid of the cavity 31, and the center 3a of the tube 3 is the centroid of the region enclosed by the outer surface 32 of the tube 3. The outer surface 32 refers to the surface exposed to the outside of the tube 3 in the cross-section. In the cross-section, it is preferable that the position of the center 31a of the cavity 31 in the long direction X and the position of the center 3a of the tube 3 in the long direction X are aligned. Because they are aligned, the amount of expansion of tube 3 when it is expanded by compressed air can be made uniform in each part along the longitudinal direction X.

[0032] Due to the arrangement of the cavity 31 described above, in cross-section, the tube 3 has both ends 31b of the cavity 31, a portion 35 located on one side Y1 in the shorter direction Y beyond 31b (hereinafter also simply referred to as the one-side portion 35), and a portion 37 (thick-walled portion 37) located on the other side Y2 in the shorter direction Y beyond the cavity 31. The one-side portion 35 refers to the portion located on one side Y1 in the shorter direction Y beyond the dimension line indicating thickness A1 in Figure 3. The end 31b is located on the circumferential surface 31c.

[0033] In the cross-section, there is a portion of the tube 3 with a thickness A2 on one side Y1 in the shorter direction Y that is thinner than the thickness A1 of the end 31b in the longer direction X of the cavity 31. That is, there is a portion 35a where the thickness A2 of one side portion 35 is thinner than the thickness A1 of the end 31b in the longer direction X of the cavity 31. Here, thickness is defined as the minimum value measured from the outer surface 32 to the circumferential surface 31c of the cavity 31.

[0034] Thickness A2 refers to the thickness of the circumferential surface 31c of the cavity 31 in a cross-section, at any point on one side Y1 in the shorter direction Y, beyond the end 31b in the longer direction X. Minimum value of thickness A2: A2 min This is the thickness at the thin portion 35a including point 31d on the semicircular portion of the circumferential surface 31c of the cavity 31 in the cross-section. Thickness A1 > Thickness A2 min That is the case.

[0035] Thickness A2 min It is preferable that the thin portion 35a is not located outside the ends 31b, 31b of the cavity 31 in the longitudinal direction X. That is, in Figure 3, it is preferable that the entire thin portion 35a is located between the dashed lines 31e, 31e extending from the ends 31b, 31b of the cavity 31 towards one side Y1 in the short direction Y. With this preferred configuration, the portion of the tube 3 outside the region between the dashed lines 31e, 31e can be made thicker, and the expansion of the tube 3 in the longitudinal direction X when compressed air is supplied to the cavity 31 can be more reliably suppressed.

[0036] Next, we will describe the external shape of tube 3 in more detail.

[0037] The outer shape of tube 3 is a flattened shape, with its longitudinal direction being the same as the longitudinal direction X of the flattened shape of the cavity 31. In cross-section, the outer shape of tube 3 is formed by the outer surface 32 of tube 3.

[0038] The outer surface 32 of the tube 3 includes a flat surface 32a located in the thickened portion 37, a pair of arcuate surfaces 32b, 32b extending from the flat surface 32a toward one side Y1 in the short direction Y, a pair of side surfaces 32c, 32c extending from the pair of arcuate surfaces 32b, 32b toward one side Y1 in the short direction Y, and a curved surface 32d connecting the pair of side surfaces 32c, 32c.

[0039] The flat surface 32a is the part that directly contacts the cover 8. In cross-section, the flat surface 32a is formed in a straight line along the longitudinal direction X, and the longitudinal direction X can be considered as the direction parallel to the direction in which the flat surface 32a extends. In cross-section, the cavity 31 faces the flat surface 32a in the short direction Y. The pair of arcuate surfaces 32b, 32b are formed over an angular range of approximately 90 degrees in cross-section, but may be formed over an angular range other than 90 degrees. No cavity 31 is located between the pair of arcuate surfaces 32b, 32b that face each other in the longitudinal direction X. The pair of side surfaces 32c, 32c that face each other in the longitudinal direction X are the parts that face each other and contact each other in the longitudinal direction of the cylindrical body 2 when the tube 3 is helically wound around the cylindrical body 2. The pair of side surfaces 32c, 32c are formed in a straight line in the short direction Y in cross-section, but may include shapes that are not straight.

[0040] The curved surface 32d is the surface facing the outer circumferential surface 2a of the cylindrical body 2, and is the portion that contacts the outer circumferential surface 2a. In cross-section, the curved surface 32d is a convex shape that is convex in the direction away from the center 3a of the tube 3 in the short direction Y. As a result, one side portion 35 of the tube 3 is convex in cross-section in the direction outward from the center of the tube 3 in the long direction X. In cross-section, most of the curved surface 32d, including the portion facing the cavity 31 in the short direction Y, is formed in the shape of a circular arc with a predetermined first radius of curvature R1. Furthermore, the portion of the curved surface 32d between the portion with the first radius of curvature R1 and the pair of side surfaces 32c, 32c is formed in the shape of a circular arc with a second radius of curvature R2, which is smaller than the first radius of curvature R1. The second radius of curvature R2 may or may not be the same as the radius of curvature of the circular arc surface 32b. The ends 32f, 32f of the curved surface 32d in the cross-section are points on the outer surface 32 where the radius of curvature changes from the side surface 32c.

[0041] By forming it as described above, in the cross-section, the thickness of the tube 3 on one side Y1 in the shorter direction Y, relative to the center 31a of the cavity 31, becomes thinner as it moves from the center 32e of the curved surface 32d towards the end 32f, resulting in a minimum value A2 min The thin portion 35a is the thinnest part on the curved surface 32d, and is formed to become thicker thereafter.

[0042] In the case of the tube 3 having the above configuration, it is preferable that the tube 3 is wound around the cylindrical body 2 while tension (tensile load) is applied in the axial direction of the tube 3. Specifically, as shown in Figure 2(A), the tube 3 is wound around the cylindrical body 2 such that the curved surface 32d at the point where it is in contact with the outer surface 2a of the cylindrical body 2 becomes flat. When compressed air is not supplied and the air pressure inside the cavity 31 is atmospheric pressure and the tube 3 is in a contracted state, the tube 3 is elastically deformed such that the height of the cavity 31 in the short direction Y decreases, and is pressed towards the cylindrical body 2.

[0043] Figures 4(A) and 4(B) are perpendicular cross-sectional views of the winding core shaft 1 along the line IV-IV in Figure 1, with the tube 3 indicated by the dashed line. Figure 4(A) shows the contracted state of tube 3 when compressed air is not supplied to it, while Figure 4(B) shows the expanded state of tube 3 when compressed air is supplied to it, with a magnified view of a portion of tube 3.

[0044] <Cover> As shown in Figures 2(A), 2(B), 4(A), and 4(B), a cover 8 is attached to the tube 3. The cover 8 is the part that comes into direct contact with the core 100. The cover 8 comprises a plurality (four) of cover members 8a. Each cover member 8a has the same configuration and is arranged at 90-degree intervals in the circumferential direction of the cylindrical body 2. Each cover member 8a is positioned to cover the portion of the cylindrical body 2 where the collars 6 and 7 are not located, and is formed in an arc shape in a cross-section perpendicular to the axis. Each cover member 8a is made of a material harder than the tube 3, such as polyvinyl chloride (PVC), a synthetic resin such as polycarbonate, or metal. The middle portion of each cover member 8a in the circumferential direction of the cylindrical body 2 is fixed to the tube 3 by adhesive and is bonded to the flat surface 32a of the tube 3.

[0045] Of each cover member 8a, a notch 8b is formed on the outer circumferential surface of one end of the cylindrical body 2 in the circumferential direction, within a predetermined range along the circumferential direction. In addition, of each cover member 8a, a notch 8c is formed on the inner circumferential surface of the other end of the cylindrical body 2 in the circumferential direction, within a predetermined range along the circumferential direction.

[0046] When the tube 3 is in a contracted state, the portion of one cover member 8a where the notch 8b is formed and the portion of the other cover member 8a where the notch 8c is formed are arranged to overlap in the radial direction of the cylindrical body 2.

[0047] The above is a general overview of the winding core shaft 1.

[0048] <An example of the operation of the winding core shaft> The winding core shaft 1 is connected to and disconnected from the winding core 100 in the following manner.

[0049] When the tube 3 is in a contracted state, the outer diameter of the core shaft 1, i.e., the outer diameter of the cover 8, is less than the inner diameter of the core 100, and the core 100 can be attached to and detached from the core shaft 1.

[0050] On the other hand, when compressed air is injected into the tube 3 and the tube 3 expands, the space within the cavity 31 expands, and the thick-walled portion 37 of the tube 3 and each cover member 8a move radially outward from the cylindrical body 2. As a result, in two adjacent cover members 8a, relative movement occurs in the direction in which the notch 8b moves out of the notch 8c, while maintaining the overlap between the cover members 8a. Due to this operation, the outer diameter of the cover 8 increases without exposing the tube 3 between the cover members 8a, and the outer surface of the cover 8 and the inner surface of the winding core 100 are connected. As a result, the winding core shaft 1 and the winding core 100 are connected so that they can rotate together as a single unit. In this state, the winding core shaft 1, with its end shafts 4 and 5 supported by bearings (not shown), rotates together with the winding core 100, thereby winding the sheet onto the winding core 100 or unwinding the sheet from the winding core 100.

[0051] Then, when the core 100 is no longer in use, the compressed air is released from tube 3, causing tube 3 to contract. As a result, the outer diameter of cover 8 becomes less than the inner diameter of core 100, allowing core 100 to be removed from core shaft 1.

[0052] <Example of effect> As described above, according to this embodiment, in cross-section, the cavity 31 is flattened, the cavity 31 is offset to one side Y1 in the short direction Y, and furthermore, in one side portion 35 of the tube 3, there is a portion 35a where the thickness A2 is thinner than the thickness A1 of the end 31b in the longitudinal direction X of the cavity 31. With this configuration, when the tube 3 wound around the cylindrical body 2 changes between a contracted state and an expanded state, the thick-walled portion 37 and the portions on both sides of the cavity 31 in the longitudinal direction X hardly undergo elastic deformation, while the portions on one side Y1 in the short direction Y relative to the cavity 31, such as the thin portion 35a, mainly undergo elastic deformation. Thus, in the tube 3, the portion close to the cylindrical body 2 that supports the tube 3 undergoes elastic deformation, while the thick-walled portion 37 of the cavity 31 and the portions on both sides of the cavity 31 in the longitudinal direction X hardly undergo elastic deformation. Therefore, in cross-section, the flat surface 32a of the tube 3 is more likely to maintain a state parallel to the central axis 2b of the cylindrical body 2, and the tilting of the flat surface 32a with respect to the central axis 2b can be suppressed. As a result, the posture of the spirally wound tube 3 can be made more stable. Therefore, the deformation mode of the tube 3 when changing from either a contracted state or an expanded state to the other can be made to a more desired state. As a result, when the tube 3 is in an expanded state, the outer diameter of the cover 8 can be changed as designed, and the coupling force between the cover 8 and the winding core 100 can be made to the value designed.

[0053] Furthermore, according to this embodiment, the outer shape of the tube is a flattened shape in which the longitudinal direction X of the flattened shape of the cavity 31 is the same as the longitudinal direction X of the cavity 31. With this configuration, the length over which the tube 3 can contact the cylindrical body 2 and the length over which the tube 3 can contact the cover member 8a can be increased. As a result, the tilting of the longitudinal direction X with respect to the central axis 2b of the cylindrical body 2 can be suppressed, and the tube 3 is supported by the cylindrical body 2 in a stable position. In addition, the contact area between the tube 3 and the cover member 8a can be increased. As a result, the tube 3 can maintain the cover member 8a in a stable position even when expanded.

[0054] Furthermore, according to this embodiment, one side portion 35 has a convex shape in cross-section, extending outward from the center in the longitudinal direction X. With this configuration, when the tube 3 is in a contracted state, the convex portion is pressed against the outer surface 2a of the cylindrical body 2, allowing for significant elastic deformation, and thereby suppressing the elastic deformation of both sides of the cavity portion 31 in the tube 3 in the longitudinal direction X. As a result, the tube 3 can be positioned more stably relative to the cylindrical body 2.

[0055] Furthermore, according to this embodiment, in the tube 3, the elastic deformation in the longitudinal direction X is extremely small in both the contracted and expanded states of the portions on both sides of the cavity 31 in the longitudinal direction X. Therefore, even when the tube 3 is wound spirally around the cylindrical body 2 and adjacent portions of the tube 3 in the longitudinal direction X are in direct contact with each other, each portion of the tube 3 does not expand or contract in the longitudinal direction X, and gaps between adjacent portions of the tube 3 in the longitudinal direction X are suppressed. Thus, it is not necessary to leave space for the elastic deformation of the tube 3 between adjacent portions of the tube 3 in the longitudinal direction X, and the tube 3 can be wound more tightly, increasing the contact area between the tube 3 and the cover member 8a. Therefore, the bonding force between the tube 3 and the cover 8 can be increased.

[0056] Furthermore, according to this embodiment, when the tube 3 is tightly wound around the cylindrical body 2 under tension, one side portion 35 of the tube 3 is elastically deformed toward the other side Y2 in the short direction Y. When the tube 3 expands due to compressed air, the one side portion 35 of the tube 3 mainly elastically deforms, causing the tube 3 to return to its shape before tension was applied, thereby connecting it to the winding core 100 via the tube 3 cover 8. With this configuration, because tension is applied beforehand, even when the tube 3 changes from a contracted state to an expanded state, the tensile load acting in the short direction Y can be zero or a small value. Therefore, deterioration of the tube 3 due to this tensile load can be suppressed, the tube 3 can be repeatedly changed between a contracted state and an expanded state over a longer period of time, and the lifespan of the tube 3 can be extended.

[0057] As clearly shown in Figure 4(B), the edge 8d of the cover member 8a on the side where the notch 8b is formed is in contact with the thick-walled portion 37 of the tube 3. Therefore, the repeated expansion and contraction of the tube 3 causes friction on the tube 3 due to the load acting on the tube 3 from the edge 8d. As a result, the edge 8d of the cover member 8a exhibits a kneading behavior on the surface of the tube 3. In particular, when compressed air is used at low pressure, the portion of the tube 3 in contact with the cover member 8a expands relatively less near the edge 8d of the cover member 8a, while the portion not in contact with the cover member 8a expands relatively more. In this case, the frictional force from the edge 8d to the tube 3 due to the kneading behavior described above becomes stronger. This kneading behavior also exists in a winding core shaft that uses a conventional tube instead of the tube 3, that is, a winding core shaft that uses a conventional tube in which the thickness from the portion of the tube in contact with the resin cover to the cavity is the same as the thickness from the cavity to the portion in contact with the cylindrical body. In conventional winding shafts, the tube is thin in the area where it rubs against the edge of the cover material. Therefore, friction with the edge of the cover material caused by the aforementioned kneading motion can quickly cause damage to the tube, potentially leading to air leaking from the cavity to the outside of the tube through the damaged area.

[0058] On the other hand, according to this embodiment, the thick-walled portion 37 of the tube 3 that contacts the resin cover member 8a is made thicker. As a result, the tube 3 is less likely to be damaged by frictional contact with the flat surface 32a of the tube 3 due to the kneading behavior described above. Furthermore, even if damage occurs, because the thick-walled portion 37 is thick, the damage does not reach the cavity portion 31. Therefore, damage to the tube 3 and air leakage caused by sliding between the cover member 8a and the tube 3 can be reliably suppressed for a longer period of time. Moreover, as described above, in this embodiment, the tube 3 is tightly wound around the cylindrical body 2, applying tension and compressing it toward the cylindrical body 2. When the tube 3 expands due to compressed air, the thin portion 35a of one side portion 35 of the tube 3 mainly undergoes elastic deformation, causing the tube 3 to return to its shape before tension was applied, thereby connecting the tube 3 to the winding core 100 via the cover 8. With this configuration, the thickened portion 37, including the flat surface 32a, undergoes little or no shape change as the tube 3 contracts and expands, and the flat shape of the flat surface 32a can be maintained even when the tube 3 expands. This allows for a larger contact area between the edge 8d of the cover member 8a and the flat surface 32a of the tube 3, suppressing scratches caused by only a small portion of the flat surface 32a contacting the edge 8d. Furthermore, when the tube 3 changes from a contracted state to an expanded state under tension, the flat surface 32a, which is the outer diameter side surface of the tube 3, undergoes little or no shape change due to the expansion of the tube 3. Therefore, there is little or no friction between the edge 8d of the cover member 8a and the flat surface 32a of the tube 3, thus reducing the occurrence of scratches on the flat surface 32a. If, as with the conventional tube described above, the portion in contact with the cover member is thin, then when the tube is in an expanded state, it bulges in a convex arc shape towards the cover member in cross-section, and the edge 8d only contacts the tip of the convex part of the tube, making the tube prone to damage. Furthermore, in conventional tubes, when the tube changes state from a contracted state to an expanded state, the outer diameter surface of the tube undergoes a large change in shape due to the expansion of the tube, resulting in high friction with the edge of the cover member and making it prone to damage. On the other hand, in this embodiment, the occurrence of such damage can be suppressed more reliably.In particular, as in this embodiment, the synergistic effect of providing a thin portion 35a on one side Y1 of the short direction Y of the tube 3, providing a convex cross-sectional shape in this one-sided portion 35, and providing a thick-walled portion 37 and a flat surface 32a on the other side Y2 of the short direction Y, significantly reduces the occurrence of damage to the tube 3 caused by the aforementioned kneading behavior.

[0059] Embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. In the following, configurations different from those of the embodiments described above will be mainly described, and similar configurations will be denoted by the same reference numerals in the figures and their descriptions will be omitted.

[0060] <Variation> In the above-described embodiment, the tube 3 was explained as being connected to the core 100 via the cover 8. However, it is not necessary to follow this configuration.

[0061] Figure 5(A) is a front view of the winding core shaft 1A in a modified example, with a portion shown in cross-section. In Figure 5(A), the winding core shaft 1A is shown in a state where it is disconnected from the winding core 100. Figure 5(B) is a magnified view of a portion of the state in which the winding core 100 is integrally connected to the winding core shaft 1A shown in Figure 5(A).

[0062] As shown in Figures 5(A) and 5(B), the core shaft 1A differs from the core shaft 1 in that a helical groove 2d is formed on the outer surface 2aA of the cylindrical body 2A, the tube 3 is wound around this helical groove 2d, and the tube 3 is in direct contact with the core 100 because a cover 8 is not provided.

[0063] Because the tube 3 is wound around the helical groove 2d, portions of the tube 3 adjacent to the cylindrical body 2A in the longitudinal direction do not come into contact. Furthermore, in the contracted state, the flat surface 32a of the tube 3 is flush with the outer circumferential surface 2aA of the cylindrical body 2A, thereby preventing the tube 3 from accidentally coming into contact with components around the winding core shaft 1.

[0064] In the winding core shaft 1 having the above configuration, when compressed air is supplied to the cavity 31 of the contracted tube 3 shown in Figure 5(A), one side portion 35 of the tube 3 elastically deforms and expands as shown in Figure 5(B). As a result, a portion of the thick-walled portion 37, including the flat surface 32a, protrudes from the helical groove 2d and contacts the inner circumferential surface of the winding core 100, connecting the winding core shaft 1A to the winding core 100. Furthermore, when compressed air is discharged from the tube 3, the tube 3 returns from the expanded state shown in Figure 5(B) to the contracted state shown in Figure 5(A).

[0065] In this modified example, as clearly shown in Figure 5(B), when the tube 3 expands, the tube 3, which is positioned so that the longitudinal direction of the cylindrical body 2A and the longitudinal direction X of the tube 3 are parallel, expands perpendicular to the longitudinal direction of the cylindrical body 2A. As a result, almost the entire flat surface 32a can come into contact with the inner circumferential surface of the winding core 100, and as a result, the winding core shaft 1 is reliably connected to the winding core 100.

[0066] <Other variations> (1) In the embodiments and modifications described above, an example was given in which the cross-sectional shape of the outer surface of the tube 3 is a horizontally elongated, flattened shape that is elongated in the longitudinal direction X of the cavity 31. However, this is not required. The cross-sectional shape of the outer surface of the tube 3 may be an approximately square with the same length in the longitudinal direction X and the short direction Y of the cavity 31, or it may be a vertically elongated, flattened shape that is elongated in the short direction Y of the cavity 31.

[0067] (2) In the embodiments and modifications described above, the curved surface 32d is described as having one convex shape on one side of the tube 3 that extends outward from the center, but this is not required. In the cross-section, the curved surface 32d may have two or more convex shapes on one side of the tube 3 that extend outward from the center.

[0068] (3) In the embodiments and modifications described above, the cavity portion 31 was described as having an elongated hole shape in cross-section, but this is not required. In cross-section, the cavity portion 31 may have an elliptical shape that is flattened in the longitudinal direction X, or any shape that is flattened in the longitudinal direction X. [Industrial applicability]

[0069] This disclosure can be applied to a tube for a winding core shaft and a winding core shaft. [Explanation of symbols]

[0070] 1.1A core shaft 2,2A Cylindrical body 3 tubes 3a Center of the tube cross-section 31 Cavity 31a Center in the cross-section of the cavity 35a A portion of the cavity that is thinner than the thickness of the longitudinal end of the flattened shape. A1 Thickness of the longitudinal end of the flattened cavity X Longitudinal direction of the flattened shape of the cavity Y-shaped cavity, short side

Claims

1. A tube made of an elastic body that is spirally wound around the cylindrical body of a core shaft, In a cross-section perpendicular to the axial direction of the tube, the cavity through which the fluid passes is flattened in shape. The center of the cavity in the cross-section is located at a position displaced from the center of the tube in the cross-section to one side in the shorter direction of the flattened shape of the cavity. One of the aforementioned shorter directions is the direction from the tube toward the cylindrical body, A tube for a winding core shaft, characterized in that the thickness of one side of the tube has a portion that is thinner than the thickness of the longitudinal end of the flattened shape of the cavity.

2. The tube for a winding core shaft according to claim 1, characterized in that the outer shape of the tube is a flattened shape in which the longitudinal direction is the same as the longitudinal direction of the flattened shape of the hollow portion.

3. The tube for a winding core shaft according to claim 1 or claim 2, characterized in that one side of the tube is convex in cross-section from the center outward.

4. A cylindrical body and A winding core shaft characterized by comprising the tube described in claim 1, which is wound spirally around the cylindrical body.

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