METHOD FOR MANUFACTURING FLAT CLOSURES, FLAT CLOSURE AND FORMING DEVICE

Abstract

A method for producing surface adhesive closures according to the present invention comprises at least one forming step involving the feeding of molten synthetic resin to a die wheel (11) and a stretching step involving a stretching process after the forming step. The method includes the use of the die wheel (11) in the forming step. The die wheel (11) comprises a sleeve (12, 13) with cavities. The sleeve (12, 13) has a circular cylindrical shape and is obtained from a thin metal plate (18) by bringing one end section and another end section of the thin plate (18) into contact in a first direction and joining the contacted end sections by welding.The one end section and the other end section that have been joined together form a welded part (12b, 13b). The welded part (12b, 13b) is inclined at an angle (θ) of 4° or more with respect to a second direction. The process enables the production of a surface bond (70) in which a section with transferred irregularities (56) is less noticeable even after the stretching process and in which the peel strength is less likely to vary.

Description

Technical area

[0001] The present invention relates to a method for producing surface fasteners, a surface fastener and a forming device. State of the art

[0002] Previously known surface fastener products include one in the form of a combination of a female surface fastener (hereinafter referred to as a loop member) having a plurality of loops and a male surface fastener that can be attached to and detached from the loop member. The male surface fastener comprises, for example, a flat base part and a plurality of engaging elements. The engaging elements protrude from the base part and are each shaped like a mushroom or the like.

[0003] Currently, surface fasteners are widely used in various products, including items that can be removably attached to any part of the body: for example, disposable diapers, infant diaper covers, braces for protecting limb joints, and the like, waist corsets (belts for lower back pain), gloves, and so on. An example surface fastener for disposable diapers and the like is disclosed in International Publication No. 2017 / 109902 (PTL 1).

[0004] The surface fastener disclosed in PTL 1 includes a base and a plurality of engaging elements protruding from the base. The engaging elements disclosed in PTL 1 each include a stem portion protruding from the base and a disc-shaped engaging head integrally provided with the upper end of the stem portion. The engaging head has a plurality of micro-fine pawl portions protruding from the outer peripheral edge of the engaging head.

[0005] In the surface fastener disclosed in Patent Application Publication 1, the micro-fine pawl portions on the engaging heads of the engaging elements facilitate the engagement of the loop links with the engaging elements and make it difficult for the loops to detach from the engaging elements after engagement. Thus, the loop link of the surface fastener is provided with increased peel strength (also referred to as engagement strength). Furthermore, according to Patent Application Publication 1, since the pawl portions that contribute to increasing peel strength are provided in micro-sized sizes on the outer peripheral edges of the engaging heads, the influence of the pawl portions on the feel of the surface fastener is reduced. As a result, a surface fastener with increased engagement strength and favorable feel is provided.

[0006] As in Fig.As shown in Fig. 8, the surface fastener disclosed in PTL 1 is manufactured using a manufacturing apparatus 80. The manufacturing apparatus 80 includes a forming device 81 configured to perform primary forming and a hot-pressing device 91 configured to perform secondary forming. The forming device 81 includes a die wheel 82 configured to rotate in one direction; a feed nozzle 86 facing the outer peripheral surface of the die wheel 82; and a doffer roller 87 provided on the downstream side relative to the feed nozzle 86 in the rotation direction of the die wheel 82.

[0007] The die wheel 82 includes a circular cylindrical outer sleeve 83 serving as a die; a circular cylindrical inner sleeve 84 on the inside of the outer sleeve 83 and in close contact therewith; and a rotatable drive roller 85 configured to rotate the outer sleeve 83 and the inner sleeve 84 in one direction. The outer sleeve 83 has a plurality of through holes, each penetrating the outer sleeve 83 from its outer peripheral surface to its inner peripheral surface. The inner sleeve 84 has a plurality of recesses in its outer peripheral surface.

[0008] The hot pressing device 91 comprises a pair of upper and lower press rolls (calender rolls) 92 and 93.

[0009] For the production of a surface fastener using the Fig.In the manufacturing apparatus 80 shown in Figure 8, a primary molding step is first performed in the molding device 81. In the primary molding step, molten thermoplastic resin is continuously supplied from the supply nozzle 86 onto the outer peripheral surface of the rotating die wheel 82, thereby obtaining a primary molded article comprising a base part and a plurality of primary elements provided on the base part.

[0010] Subsequently, the primary molded article thus obtained in the primary molding step is transported to the hot-pressing device 91. In the hot-pressing device 91, a secondary molding step is performed, in which secondary molding is performed on the primary molded article. In the secondary molding step, the primary molded article is inserted between the upper and lower press rollers 92 and 93, and the upper end portions of the primary elements are deformably pressed. Accordingly, engaging elements are obtained, each having an engaging head with primary pawl portions provided on its outer peripheral edge. In this way, the surface fastener disclosed in PTL 1 is manufactured.

[0011] The outer sleeve 83 and the inner sleeve 84 included in the die wheel 82 to be used in the primary forming step described above each have a circular cylindrical shape. Such a circular cylindrical outer sleeve 83 and inner sleeve 84 are generally manufactured as follows: A thin metal plate member having an elongated rectangular shape in plan view is bent into a circular cylindrical body so that one end portion and the other end portion of the thin plate member are brought into contact with each other, and the one end portion and the other end portion thus brought into contact with each other are joined by welding.

[0012] The thus-prepared circular cylindrical outer sleeve 83 and inner sleeve 84 are then joined together by inserting the inner sleeve 84 into the outer sleeve 83. The combined outer sleeve 83 and inner sleeve 84 is then fixed to the rotatable drive roller 85 while being moved in the axial direction of the rotatable drive roller 85 so as to cover the rotatable drive roller 85.

[0013] In this case, the inner sleeve 84 has an inner diameter smaller than the outer diameter of the rotary drive roller 85. Furthermore, the outer sleeve 83 and the inner sleeve 84 are fitted together such that the outer peripheral surface of the inner sleeve 84 contacts all or substantially all of the inner peripheral surface of the outer sleeve 83. Furthermore, when the outer sleeve 83 and the inner sleeve 84 are fixed to the rotary drive roller 85, air is forcefully blown radially outward from the outer peripheral surface of the rotary drive roller 85, thereby inflating the outer sleeve 83 and the inner sleeve 84, which are to be placed over the rotary drive roller 85, so that the diameters of their circular cylindrical bodies increase. Thus, the outer sleeve 83 and the inner sleeve 84 are easily movable in the axial direction of the rotary drive roller 85.

[0014] After the outer sleeve 83 and the inner sleeve 84 reach a predetermined position on the rotary drive roller 85, the air blown from the rotary drive roller 85 is shut off, causing the outer sleeve 83 and the inner sleeve 84 to contract and reduce their diameters. Thus, the outer sleeve 83 and the inner sleeve 84 are attached and secured to the rotary drive roller 85. List of patents

[0015] PTL 1: International Publication No. 2017 / 109902 Brief description of the inventionTechnical problem

[0016] As described above, the outer sleeve 83 and the inner sleeve 84 of the die wheel 82 are each formed by welding one end portion and the other end portion of a thin plate member together. Therefore, the outer sleeve 83 and the inner sleeve 84 each have a welded portion formed by welding one end portion and the other end portion of the thin plate member together. The welded portion extends rectilinearly parallel to the axial direction of the circular cylindrical body from the edge of one of the ends of the circular cylindrical body to the edge of the other end.

[0017] On the other hand, when attaching the outer sleeve 83 and the inner sleeve 84 to the rotary drive roller 85 of the die wheel 82, the air blown from the rotary drive roller 85 is used to first inflate the circular cylindrical bodies, and then the air is shut off to allow the circular cylindrical bodies to contract. That is, when the outer sleeve 83 and the inner sleeve 84, each having the welded part described above, are attached to the rotary drive roller 85, the welded part undergoes elastic deformation and plastic deformation.

[0018] Specifically, when the circular cylindrical bodies of the outer sleeve 83 and the inner sleeve 84 are inflated as described above with the air blown from the rotary drive roller 85, the welded parts of the outer sleeve 83 and the inner sleeve 84 undergo elastic deformation and plastic deformation to expand in the circumferential direction of their circular cylindrical bodies. Subsequently, when the air is shut off to allow the outer sleeve 83 and the inner sleeve 84 to contract, the expanded welded parts undergo elastic deformation and plastic deformation to protrude slightly radially outward.

[0019] Therefore, the outer peripheral surfaces of the outer sleeve 83 and the inner sleeve 84 thus fixed to the rotatable drive roller 85 each have a protrusion that projects slightly outward and extends linearly parallel to the axial direction of the outer sleeve 83 and the inner sleeve 84. Furthermore, the outer peripheral surface of the outer sleeve 83, which is joined to the outer side of the inner sleeve 84, has another protrusion due to the welded part of the inner sleeve 84, because the slight protrusion formed on the outer peripheral surface of the inner sleeve 84 is transferred to the outer peripheral surface of the outer sleeve 83. That is, the outer peripheral surface of the outer sleeve 83 fixed to the rotatable drive roller 85 has two linear protrusions due to the welded part of the inner sleeve 84 and the welded part of the outer sleeve 83.

[0020] In such a case, where the outer sleeve 83 has two protrusions on its outer peripheral surface, and the die wheel 82 is used with the outer sleeve 83 to manufacture a surface fastener, the shapes of the protrusions of the outer sleeve 83 are transferred to the base part of the surface fastener, which is elongated in the machining direction, leaving a plurality of imprints (also called transfer marks) with small concavities. In this case, the plurality of imprints each extend rectilinearly in the width direction of the base part and appear regularly in the longitudinal direction of the base part.

[0021] Despite a demand in recent years for reducing the thickness of the base part between its upper and lower surfaces in order to reduce the manufacturing cost of the surface fastener and increase the flexibility of the surface fastener, there is a limit to the thickness reduction of the base part in the primary forming step performed using the above-mentioned die wheel 82. Therefore, to reduce the thickness of the base part, a method is being studied and promoted for practical use, for example, in which a surface fastener obtained by the secondary forming step is supplied to a stretching device in which the base part of the surface fastener undergoes a stretching process to be stretched in the processing direction (transportation direction).

[0022] However, when a surface fastener having a plurality of imprints formed in its base portion and each extending in its width direction, as described above, is subjected to a stretching process to be stretched in the machine direction, the stretching process stretches the base portion more actively in the imprinted portions than in the non-imprinted portions. Therefore, the thickness of the surface fastener obtained by the stretching process is greatly reduced in the imprinted portions.

[0023] Accordingly, factors such as the thickness dimension of the base portion (hereinafter referred to as the thickness dimension) and the pitch of the formed engaging elements tend to fluctuate in the longitudinal direction of the surface fastener (machining direction), and such fluctuations may lead to fluctuations in the peel strength of the surface fastener (especially fluctuations in the longitudinal direction). Furthermore, since the imprints formed in the base portion, including concavities, are primarily stretched during the stretching process, the base portion may deform to the extent that the concavities protrude, affecting the appearance quality of the surface fastener.

[0024] The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing surface fasteners which enables production of a surface fastener in which transfer marks resulting from the transfer of a welded part of a sleeve are less conspicuous even after a stretching process is performed on a molded article obtained by a molding step, and in which peel strength is less likely to fluctuate, and also to provide a surface fastener produced by the production method and a molding device to be used in the production method. Solution to the problem

[0025] To achieve the above object, the present invention provides a method for manufacturing surface fasteners for producing a surface fastener made of synthetic resin and comprising a base part with a plurality of engaging elements, the method comprising at least a molding step of performing molding by supplying molten synthetic resin to a die wheel rotating in one direction, and a stretching step of performing a stretching process in a machining direction after the molding step. The manufacturing method is characterized in that it comprises using the die wheel in the molding step, the die wheel comprising at least one sleeve with cavities with which the engaging elements or precursor elements to be deformed into the engaging elements are to be formed.wherein the sleeve has a circular cylindrical shape and is obtained from a thin metal plate part by bringing one end portion and another end portion of the thin plate part into contact with each other in a first direction and joining the one end portion and the other end portion that have been brought into contact with each other by welding, wherein the one end portion and the other end portion that have been joined together form a welded part, wherein the welded part is inclined at an angle of 4° or more with respect to a second direction, wherein the second direction is perpendicular to the first direction and is arranged along an axial direction of the sleeve.

[0026] In the method for producing surface fasteners according to the present invention, it is preferable that the sleeve comprises an outer sleeve and an inner sleeve which is in close contact with an inner peripheral surface of the outer sleeve, wherein the outer sleeve has a plurality of through-holes penetrating the outer sleeve from an outer peripheral surface to the inner peripheral surface of the outer sleeve, the inner sleeve has a plurality of depressed portions provided in an outer peripheral surface of the inner sleeve, and an outer peripheral edge of at least one of the through-holes on the inner peripheral surface of the outer sleeve includes a portion which overlaps a depressed portion provided in the inner sleeve.

[0027] It is also preferable that the inner sleeve is made of a softer metal than the outer sleeve.

[0028] The present invention further provides a surface fastener made of synthetic resin and comprising a base member and a plurality of engaging elements, the base member having a first surface and a second surface facing away from each other, the engaging elements protruding from the first surface of the base member, the base member being configured as a thin plate elongated in a first direction.The surface fastener is characterized in that the base part has a thickness dimension between the first surface and the second surface of less than 90 µm, the first surface of the base part has a transferred asperity portion including a concave portion and a convex portion formed in the first surface, the transferred asperity portion is formed rectilinearly along a direction inclined at an angle of 4° or more with respect to a second direction perpendicular to the first direction, and an asperity height difference in the transferred asperity portion is 20 µm or less.

[0029] The present invention further provides a molding device for use in producing a surface fastener, wherein the surface fastener is made of synthetic resin and comprises a base part with a plurality of engaging elements. The molding device comprises a die wheel configured to rotate in one direction and a feed nozzle configured to feed molten synthetic resin toward the die wheel. The molding device is characterized in that the die wheel comprises at least one sleeve with cavities for forming the engaging elements or precursor elements to be formed into the engaging elements. The sleeve has a circular-cylindrical shape and is obtained from a thin metal plate part.by bringing one end portion and another end portion of the thin plate member into contact with each other in a first direction, and joining the one end portion and another end portion that have been brought into contact with each other by welding, and the one end portion and another end portion that have been joined together form a welded portion, the welded portion being inclined at an angle of 4° or more with respect to a second direction, the second direction being perpendicular to the first direction and arranged along an axial direction of the sleeve.

[0030] In the molding device according to the present invention, it is preferable that the sleeve comprises an outer sleeve and an inner sleeve that is in close contact with an inner peripheral surface of the outer sleeve, wherein the outer sleeve has a plurality of through-holes penetrating the outer sleeve from an outer peripheral surface to the inner peripheral surface of the outer sleeve, the inner sleeve has a plurality of depressed portions provided in an outer peripheral surface of the inner sleeve, and an outer peripheral edge of at least one of the through-holes on the inner peripheral surface of the outer sleeve includes a portion that overlaps a depressed portion provided in the inner sleeve.

[0031] It is also preferable that the inner sleeve is made of a softer metal than the outer sleeve. Advantageous effects of the invention

[0032] The manufacturing method according to the present invention provides a surface fastener in which transfer marks (portions with transferred unevenness) resulting from the transfer of a welded part of a sleeve are less conspicuous than in the prior art even after performing a stretching process on a molded article obtained by a molding step, and in which peel strength is less likely to fluctuate than in the prior art. Brief description of the drawings Fig. 1 is a schematic diagram of a manufacturing apparatus for use in a method for manufacturing surface fasteners according to an example of the present invention. Fig. Figure 2 is a schematic perspective view of an outer sleeve and an inner sleeve provided in a primary forming device shown in Fig. 1 shown manufacturing device. Fig. 3 is a schematic plan view of a thin metal plate part to be formed into the outer sleeve. Fig. 4 is a schematic sectional view of a die wheel included in the forming device. Fig. 5 is a schematic perspective view of a primary molded body to be molded in a primary molding step. Fig. 6 is a schematic sectional view of a relevant part of a pre-fastener body to be formed in a secondary forming step. Fig. 7 is a schematic perspective view of a surface fastener to be manufactured by the manufacturing method according to the example. Fig. Figure 8 is a schematic diagram of a known manufacturing apparatus for surface fasteners. Description of the embodiments

[0033] A preferred embodiment of the present invention will now be described in detail with reference to the drawings. The present invention is by no means limited to the following embodiment and may be modified in various ways as long as such modifications provide substantially the same configuration and produce the same advantageous effects as the present invention.

[0034] Fig. 1 is a schematic diagram of a manufacturing apparatus to be used in a method for manufacturing surface fasteners according to the present embodiment. Fig. 2 is a schematic perspective view of an outer sleeve and an inner sleeve provided in a primary forming device included in the manufacturing apparatus.

[0035] In the following description, a processing direction (an M direction or MD) is a direction in which a primary molded body, a pre-fastener body, and a surface fastener are to be transported in a process for manufacturing a surface fastener, and is also referred to as the front-to-back direction. The processing direction and the front-to-back direction are the longitudinal directions of the primary molded body, the pre-fastener body, and the surface fastener, respectively, which are formed into an elongated shape.

[0036] A transverse direction (a C-direction or CD) is a width direction perpendicular to the machining direction and located along the substantially flat top surface (first surface) of a base part or precursor base part, and is also referred to as the left-right direction. The transverse direction and the left-right direction are the width directions of the primary mold body, the pre-fastener body, and the surface fastener, respectively, which are each formed into an elongated shape.

[0037] A thickness direction is a direction that runs along a direction perpendicular to the substantially flat top surface of the base part and is also referred to as the up-down direction or height direction. The thickness direction and the up-down direction are each a direction perpendicular to both the machining direction and the transverse direction. With respect to the base part, a side toward which engaging elements protrude is referred to as the top surface, and a side opposite the top surface is referred to as the bottom surface.

[0038] The manufacturing method according to the present embodiment provides a surface fastener 70 made of synthetic resin, in which, as shown in Fig.7, a plurality of engaging elements 72 are formed integrally with a thin plate-shaped base part 71 on the upper side of the base part 71. The surface fastener 70 is in the processing direction MD of a manufacturing device 1, which is shown in Fig. 1 is shown, elongated.

[0039] The manufacturing device 1, which is designed to manufacture the surface fastener 70, will now be described with reference to Fig. 1 and Fig. 2 described.

[0040] The manufacturing apparatus 1 according to the present embodiment includes a primary forming device 10 configured to perform primary forming; a hot-pressing device (secondary forming device) 20 configured to form a pre-adhesive fastener body (secondary formed body) 60 formed in Fig. 6, by performing a secondary forming on a primary mold body 50 which is in Fig. 5 and formed by the primary forming device 10; and a stretching device 30 configured to perform a stretching process on the thus-obtained pre-fastener body 60. In the present invention, the pre-fastener body 60 refers to a molded body or part obtained in a case where the production of the surface fastener 70 includes a stretching process, and which has yet to undergo the stretching process.

[0041] The primary molding device 10 includes a die wheel 11 driven to rotate in one direction (counterclockwise in the drawing); a feed nozzle 15 facing the peripheral surface of the die wheel 11 and configured to continuously extrude or discharge a molten resin material; and a doffer roller 16 provided on the downstream side relative to the feed nozzle 15 in the rotation direction of the die wheel 11.

[0042] The die wheel 11 comprises a circular cylindrical outer sleeve 12 (also referred to as outer cylinder) serving as a die; a circular cylindrical inner sleeve 13 (also referred to as inner cylinder) provided on the inside of the outer sleeve 12 and in close contact therewith; and a rotatable drive roller 14 to which the outer sleeve 12 and the inner sleeve 13 are attached. The rotatable drive roller 14 is adapted to rotate the outer sleeve 12 and the inner sleeve 13, which are attached to the rotatable drive roller 14, in one direction (in Fig. 1 counterclockwise). The rotatable drive roller 14 is provided internally with a cooling jacket, which is not shown but allows the flow of cooling liquid.

[0043] The outer sleeve 12 has, as for example in Fig.2, a plurality of through-holes 12a extending through the outer sleeve 12 from the outer peripheral surface to the inner peripheral surface, each serving as a cavity for molding a part of the primary member 52 described below of the primary mold body 50. In the present embodiment, for example, synthetic resin is injected into the through-holes 12a of the outer sleeve 12, thereby molding the primary stem portions 53 of the primary members 52 described below.

[0044] In the present embodiment, the many through holes 12a are arranged corresponding to the positions at which the Fig.6 are to be formed. In the present embodiment, for example, the plurality of through holes 12a are regularly arranged at constant intervals in the machining direction MD (the circumferential direction of the outer sleeve 12) and are regularly arranged at constant intervals in the transverse direction CD (a direction parallel to the rotational axis of the outer sleeve 12).

[0045] The through holes 12a each have a substantially circular frustoconical shape, wherein a circle on the outer peripheral surface of the outer sleeve 12 is larger than a circle on the inner peripheral surface of the outer sleeve 12. In the present invention, no particular limits are placed on the positions, sizes, shapes, and other relevant factors of the plural through holes 12a provided in the outer sleeve 12.

[0046] The outer peripheral surface of the inner sleeve 13 has a plurality of recessed groove portions 13a, each serving as a cavity for molding portions of the primary member 52 (specifically, a rib portion 54 and protruding portions 55, which will be described later). The recessed groove portions 13a each extend rectilinearly in the transverse direction CD parallel to the rotational axis of the inner sleeve 13 and are each recessed to a size that allows the flow of molten resin.

[0047] The plurality of recessed groove portions 13a are arranged at regular intervals in the circumferential direction of the inner sleeve 13 (the machining direction MD). With the die wheel 11 mounted, at least a portion of each of the recessed groove portions 13a of the inner sleeve 13 intersects the outer peripheral edges of the corresponding through holes 12a on the inner peripheral surface of the outer sleeve 12. According to the present invention, the shape of the recessed portions formed in the outer peripheral surface of the inner sleeve is not limited to the rectilinear recessed groove portions 13a according to the present embodiment. The recessed portion according to the present invention includes, for example, a recessed groove portion curved in a zigzag shape and a recessed counterbore portion depressed in a three-dimensional, cuboid shape, or the like relative to the outer peripheral surface of the inner sleeve.

[0048] The outer sleeve 12 and the inner sleeve 13 according to the present embodiment are each manufactured through a sleeve manufacturing process including a welding process. Therefore, the thus-manufactured outer sleeve 12 and inner sleeve 13 each have welded portions 12b and 13b. The welded portions 12b and 13b are formed in the welding process and each extend linearly and continuously from one end edge (left side edge) to the other end edge (right side edge) of the outer sleeve 12 or the inner sleeve 13 in the transverse direction CD.

[0049] The welded part 12b formed in the outer sleeve 12 and the welded part 13b formed in the inner sleeve 13 are in positions rotated by 180° to each other when in a cross section ( Fig. 4) of the die wheel 11, which is taken perpendicular to the axis of rotation, as will be described below. While in Fig.2 the welded part 13b of the inner sleeve 13 is shown, the welded part 12b of the outer sleeve 12 is in Fig. 2 in a hidden position. In Fig. 4, the welded part 12b of the outer sleeve 12 and the welded part 13b of the inner sleeve 13 are intentionally shown by solid lines so that the locations of the welded parts 12b and 13b can be easily recognized.

[0050] The sleeve manufacturing process will now be described in more detail, in which the outer sleeve 12 is manufactured from a thin plate part 18.

[0051] To produce the outer sleeve 12, a thin plate part 18 is first prepared, which is formed as shown in Fig. 3. The thin plate part 18 is made of stainless steel. Stainless steel is a steel alloy consisting primarily of iron with carbon and chromium in respective mass concentrations of 1.2% or less and 10.5% or more (ISO standards).

[0052] In the present embodiment, for example, the multiple through-holes 12a of the outer sleeve 12 are formed by a punching process described below. Therefore, a hard stainless steel is preferable as the thin plate member 18 for the outer sleeve 12, because such stainless steel tends to have satisfactory strength even after the multiple through-holes 12a are formed therein. In the present invention, the outer sleeve 12 can be made of any metal other than stainless steel, but preferably of a metal harder than that for the inner sleeve 13 to achieve adequate strength.

[0053] The thin plate part 18 for the outer sleeve 12 has, seen from above, that is, in plan view ( Fig.3), the shape of a parallelogram. Alternatively, the thin plate part 18 may have a substantially parallelogram-like shape that is close to a parallelogram. The thin plate part 18 with a parallelogram-like shape has two pairs of sides 19 (namely, first pair sides 19a and second pair sides 19b), each pair of sides 19 being parallel to and opposite to each other. One of the two pairs, in particular the first pair sides 19a (the upper and lower sides 19 in Fig. 3), extends parallel to a first direction. The other of the two pairs, in particular the second pair sides 19b (the left and right sides 19 in Fig.3) extends in a direction inclined with respect to a second direction. The second direction is perpendicular to the first direction. In such a case, the first direction corresponds to the circumferential direction of the outer sleeve 12 or the machining direction MD, and the second direction corresponds to the rotational axis direction of the outer sleeve 12 or the transverse direction CD.

[0054] In the present embodiment, the inclination angle θ at which the second pair of sides 19b of the thin plate member 18 are inclined with respect to the second direction (transverse direction CD) is set to 4° or more. Setting the inclination angle θ in this manner makes it difficult for the outer sleeve 12 to experience elastic deformation and plastic deformation at the welded portion 12b when the outer sleeve 12 is attached to the rotatable drive roller 14, as described below. Consequently, the transferred asperity portions (transfer marks) 56 described below, which are to be formed in the surface fastener 70 due to the shape of the welded portion 12b, can be made difficult to notice, and the asperity height difference in the transferred asperity portions 56 can be reduced.In order to make the outer sleeve 12 less susceptible to elastic deformation and plastic deformation at the welded part 12b when the outer sleeve 12 is attached to the rotatable drive roller 14, the inclination angle θ of the second pair sides 19b may preferably be set to 45° or smaller.

[0055] In the present embodiment, the Fig.3 is bent after preparation so as to be rolled in the first direction, and the second pair of sides 19b of the bent thin plate part 18 (that is, one side edge and the other side edge of the thin plate part 18 in the first direction) are brought into contact with each other. Then, a welding process is performed on the thus-contacted second pair of sides 19b of the thin plate part 18, thereby bonding the second pair of sides 19b to each other. In this way, a circular cylinder having a space extending in the second direction inside is obtained. The circular cylinder has a welded part 12b formed on the bonded second pair of sides 19b. Note that the inclination angle θ of the second pair of sides 19b may preferably be set to 20° or less, particularly 15° or less.In this way, the length of the second pair of sides 19b is less likely to be larger than the dimension (the width dimension) of the thin plate part 18 in the second direction, and the simplicity of the welding process to be performed when forming the circular cylinder is increased.

[0056] After completion of the above welding process, the circular cylinder is subjected to a piercing process, thereby forming a plurality of through holes 12a. Thus, an outer sleeve 12 according to the present embodiment is obtained. In the present embodiment, the outer sleeve 12 may alternatively be manufactured by first performing the piercing process on the Fig. 3 to form a plurality of through holes 12a, and then the above welding process is performed on the thin plate part 18 having the through holes 12a.

[0057] To manufacture the inner sleeve 13, as in the case of the outer sleeve 12, a thin plate member made of stainless steel is prepared which has a parallelogram-like shape or a substantially parallelogram-like shape, as shown in Fig. 3. In the present embodiment, the thin plate member for the inner sleeve 13 is subjected to a groove forming process to form the recessed groove portions 13a. Therefore, stainless steel, which is softer and has better machinability than that for the outer sleeve 12, is preferably used for the inner sleeve 13. In the present invention, the inner sleeve 13 may alternatively be made of a metal other than stainless steel. Furthermore, the inner sleeve 13 may be made of a softer metal than the outer sleeve 12, but it is not required.

[0058] The thin plate member for the inner sleeve 13, as in the case of the outer sleeve 12, has first pair sides extending parallel to the first direction (machining direction MD) and second pair sides extending parallel to a direction inclined with respect to the second direction (transverse direction CD). The inclination angle θ of the second pair sides with respect to the second direction is set to 4° or more. The inclination angle θ of the second pair sides may preferably be set to 45° or less. In consideration of the simplicity of the welding process, the inclination angle θ may preferably be set to 20° or less, particularly 15° or less.

[0059] In the present embodiment, a groove forming process is performed on one surface (a first surface) of the thin plate member for the inner sleeve 13, thereby forming a plurality of recessed groove portions 13a parallel to the second direction. Subsequently, the thin plate member, now having the recessed groove portions 13a, is bent to be rolled in the first direction, and the second pair sides of the bent thin plate member are brought into contact with each other. A welding process is then performed on the thus-contacted second pair sides of the thin plate member, thereby joining the second pair sides to each other. Thus, an inner sleeve 13 according to the present embodiment is obtained, which has a circular cylindrical shape and has a welded portion 13b formed by joining the second pair sides to each other.

[0060] In the present embodiment, the inner sleeve 13 may alternatively be manufactured by performing a welding process on a thin plate part to obtain a circular cylinder, and then performing a groove-making process on the circular cylinder to form a plurality of depressed groove portions 13a. In the present embodiment, the welded parts 12b and 13b of the outer sleeve 12 and the inner sleeve 13 are both formed with an inclination angle θ of 4° or more with respect to the transverse direction CD. However, in the present invention, only at least one of the welded part of the outer sleeve and the welded part of the inner sleeve needs to be formed with an inclination angle θ of 4° or more with respect to the transverse direction CD, and the other welded part may be formed parallel to the transverse direction CD or with an inclination angle θ of less than 4° with respect to the transverse direction CD.

[0061] After the outer sleeve 12 and the inner sleeve 13 are manufactured from the respective thin plate members 18 as described above, the outer sleeve 12 and the inner sleeve 13 are attached to the rotary drive roller 14 so as to cover the rotary drive roller 14. In the present embodiment, a preferred method to be used when attaching the outer sleeve 12 and the inner sleeve 13 to the rotary drive roller 14 is to inflate the outer sleeve 12 and the inner sleeve 13 by strongly blowing air radially outward from the rotary drive roller 14. In such a case, the rotary drive roller 14 is configured to be capable of blowing air from the outer peripheral surface of the rotary drive roller 14. Furthermore, the rotary drive roller 14 is manufactured such that the outer diameter of the rotary drive roller 14 is slightly larger than the inner diameter of the inner sleeve 13.

[0062] Here, a method for attaching the outer sleeve 12 and the inner sleeve 13 to the rotatable drive roller 14 is described.

[0063] First, the inner sleeve 13 is inserted into the outer sleeve 12, and the outer sleeve 12 and the inner sleeve 13 are joined together such that the outer peripheral surface of the inner sleeve 13 is in contact with the entire or substantially entire inner peripheral surface of the outer sleeve 12.

[0064] In this case, the outer sleeve 12 and the inner sleeve 13 are joined to each other in a positional relationship of the outer sleeve 12 and the inner sleeve 13 in which at least a portion of the recessed groove portions 13a of the inner sleeve 13 overlaps the outer peripheral edge of at least one of the through holes 12a formed on the inner peripheral surface of the outer sleeve 12. In addition, the outer sleeve 12 and the inner sleeve 13 are joined to each other in such a way that the welded part 12b of the outer sleeve 12 and the welded part 13b of the inner sleeve 13 are arranged at positions rotated by 180° to each other when viewed in a cross section ( Fig.4), which is taken perpendicular to the rotational axis direction of the outer sleeve 12 and the inner sleeve 13. Alternatively, when joining the outer sleeve 12 and the inner sleeve 13, the welded parts 12b and 13b may be arranged at any positions other than 180° rotated from each other, as long as the welded parts 12b and 13b do not coincide with each other.

[0065] Subsequently, the thus joined outer sleeve 12 and inner sleeve 13 are fixed to the rotary drive roller 14. At this time, air is forcefully blown radially outward from the outer peripheral surface of the rotary drive roller 14. Meanwhile, the outer sleeve 12 and inner sleeve 13, which are fixed to each other, are brought close to the rotary drive roller 14, from which air is blown, and moved in the rotational axis direction of the rotary drive roller 14 so that they cover the rotary drive roller 14 (in other words, so that the rotary drive roller 14 is inserted into the inner sleeve 13).

[0066] Accordingly, the joined outer sleeve 12 and inner sleeve 13 receive the pressure of the air blown from the rotary drive roller 14 from the inner peripheral side of the inner sleeve 13 and are inflated to obtain enlarged diameters. Thus, the inner diameter of the inner sleeve 13 is made larger than the outer diameter of the rotary drive roller 14. Therefore, the outer sleeve 12 and the inner sleeve 13 can be easily moved along the rotary drive roller 14 to a predetermined fastening position.

[0067] In such a case, upon expansion of the outer sleeve 12 and the inner sleeve 13, the welded parts 12b and 13b of the outer sleeve 12 and the inner sleeve 13 each undergo elastic deformation and plastic deformation to expand in the circumferential direction of the outer sleeve 12 or the inner sleeve 13. However, according to the present embodiment, the welded parts 12b and 13b each extend in a direction inclined at an inclination angle θ of 4° or more with respect to the rotation axis direction of the outer sleeve 12 and the inner sleeve 13.Therefore, when comparing the welded parts 12b and 13b of the outer sleeve 12 and the inner sleeve 13 with, for example, the welded parts of the outer sleeve and the inner sleeve in the prior art, each extending in the rotation axis direction, the stress (tensile force) applied to the welded parts 12b and 13b when the outer sleeve 12 and the inner sleeve 13 are expanded is dispersed, thereby reducing the amount of elastic deformation and plastic deformation (the amount of deformation) of the welded parts 12b and 13b.

[0068] After the outer sleeve 12 and the inner sleeve 13 are moved relative to the rotary drive roller 14 to the predetermined fixing position, the air blown from the rotary drive roller 14 is stopped. Accordingly, the outer sleeve 12 and the inner sleeve 13, which have been inflated with the pressure of the air, contract in such a direction as to have reduced diameters and fix the rotary drive roller 14. Consequently, the outer sleeve 12 and the inner sleeve 13 are in close contact with each other at the inner peripheral surface of the outer sleeve 12 and the outer peripheral surface of the inner sleeve 13, and the inner peripheral surface of the inner sleeve 13 is in close contact with the rotary drive roller 14. Thus, the outer sleeve 12 and the inner sleeve 13 are fixed to the rotary drive roller 14 without a gap and are secured to the rotary drive roller 14 without displacement in the rotational direction.

[0069] At this time, because the welded parts 12b and 13b of the outer sleeve 12 and the inner sleeve 13 undergo elastic deformation and plastic deformation to expand in the circumferential direction upon expansion of the outer sleeve 12 and the inner sleeve 13, the welded parts 12b and 13b undergo elastic deformation and plastic deformation to protrude radially outward upon contraction of the outer sleeve 12 and the inner sleeve 13. However, in the present embodiment, since the amount of deformation in the elastic deformation and plastic deformation that the outer sleeve 12 and the inner sleeve 13 undergo upon expansion is small, the sizes of the protrusions (the heights of the protrusions) formed on the outer peripheral surfaces of the outer sleeve 12 and the inner sleeve 13 are smaller than, for example, in the case of the outer sleeve and the inner sleeve in the prior art.

[0070] Thus, in the die wheel 11 according to the present embodiment, in which the outer sleeve 12 and the inner sleeve 13 are fixed to the rotatable drive roller 14, the two protrusions formed on the outer peripheral surface of the outer sleeve 12 are smaller than in the prior art due to the elastic deformation and plastic deformation at the welded parts 12b and 13b of the outer sleeve 12 and the inner sleeve 13. Furthermore, in the present embodiment, the two small protrusions formed on the outer peripheral surface of the outer sleeve 12 are arranged in a symmetrical position rotated by 180° from each other, as described above.

[0071] The Fig.The doffer roller 16 shown in Figure 1 comprises a pair of an upper squeeze roller 16a and a lower squeeze roller 16b, which are configured to pinch the primary molded body 50 formed on the outer peripheral surface of the die wheel 11 from above and below and to pull the primary molded body 50. The upper squeeze roller 16a and the lower squeeze roller 16b each have a surface layer on their outer peripheral surface, which is not shown but is made of an elastomer, such as a polyurethane elastomer.

[0072] The hot-pressing device 20 includes a pair of upper and lower press rolls (calender rolls) 21 and 22 arranged downstream of the doffer roll 16. The upper press roll 21 and the lower press roll 22 are arranged to oppose each other with a predetermined gap therebetween. The gap between the upper press roll 21 and the lower press roll 22 is adjustable by means of a height adjustment device (not shown).

[0073] The upper press roller 21 includes a heat source (not shown). The surface temperature of the upper press roller 21 is set to a temperature that softens the resin to be molded into the surface fastener 70. In the present invention, there are no particular limitations on the configuration of the hot-pressing device 20, as long as the hot-pressing device 20 is capable of forming the engaging elements 72 by pressing at least a portion of the primary molded body 50, as described below.

[0074] As in Fig.1, the stretching device 30 is installed on the downstream side relative to the hot-pressing device 20 to perform at least one stretching process on the pre-fastener body (secondary molded body) 60 formed by the hot-pressing device 20. Although specific illustration is omitted, the stretching device 30 includes a feed unit configured to feed the pre-fastener body 60 into the stretching device 30, a discharge unit configured to discharge the surface fastener 70 obtained by the stretching process to the downstream side, and a plurality of rotatable rollers arranged between the feed unit and the discharge unit and along a transport path for a processing object (i.e., the pre-fastener body 60 or the surface fastener 70).

[0075] The rotating rollers are each configured to rotate while the workpiece is held in contact therebetween, allowing the workpiece to be transported toward the downstream side at a speed corresponding to their rotational speed. At least one of the rotating rollers is capable of heating the workpiece to a preset heating temperature while the workpiece is held in contact with the outer peripheral surface of the roller.

[0076] The rotatable rollers of the stretching device 30 include a heating roller configured to perform a heat treatment on the pre-fastener body 60, a stretching roller configured to perform a stretching process on the pre-fastener body 60 in cooperation with the heating roller, and a relaxation roller provided on the downstream side relative to the stretching roller. In such a case, the heating roller, the stretching roller, and the relaxation roller are arranged so that the transport path for the processing object runs up and down in a meandering manner.

[0077] The heating roller is configured to transport the pre-touch fastener body 60 by rotating it at a constant speed and to heat the pre-touch fastener body 60 while keeping the pre-touch fastener body 60 in contact with the roller surface. The heating roller is provided with a backup roller (nip roller) opposite the heating roller. The heating roller and the backup roller are configured to rotate at constant speeds while clamping and holding the pre-touch fastener body 60 between them from above and below. With the heating roller, the pre-touch fastener body 60, which is yet to be stretched, is heated to a temperature such that it becomes stretchable. In the present embodiment, there are no particular limitations on the means and methods for performing the heat treatment before the stretching process.

[0078] The stretching roller is controlled to rotate at a higher rotational speed than the heating roller, with the processing object kept in contact with the roller surface. In the present embodiment, the rotational speed of the stretching roller is set, for example, to 110% or more and 200% or less of the rotational speed of the heating roller. The heating temperature of the stretching roller is set higher than or equal to the heating temperature of the heating roller and lower than the melting point of the synthetic resin to be formed into the surface fastener 70. The above combination of the heating roller and the stretching roller enables the stretching process to be performed on the pre-fastener body 60. Through the stretching process, the precursor base part 51 of the pre-fastener body 60 described below is stretched in the machine direction MD, thereby obtaining the base part 71 of the surface fastener 70.

[0079] The relaxation roller is controlled to rotate at a lower rotational speed than the stretching roller, keeping the workpiece in contact with the roller surface. The heating temperature of the relaxation roller is set lower than the melting point of the resin to be formed into the surface fastener 70. This reduces the tension exerted on the surface fastener 70 between the stretching roller and the relaxation roller, thereby stabilizing the shape and dimensions of the surface fastener 70.

[0080] The configuration of the stretching device 30 according to the above embodiment is merely exemplary. In the present invention, there are no particular limitations on the configuration of the stretching device, as long as the stretching device is arranged on the downstream side relative to at least the forming device and is capable of stretching a formed body, such as the pre-fastener body 60, supplied from the primary forming device 10 or the hot-pressing device 20 in the machine direction MD.

[0081] A manufacturing method will now be described in which a surface fastener 70 is to be manufactured using the above-described manufacturing apparatus 1 comprising the primary forming device 10, the hot pressing device 20, and the stretching device 30.

[0082] The method for producing a surface fastener 70 according to the present embodiment comprises a primary molding step of forming a primary molded body 50, as shown, for example, in Fig. 5, using the primary forming device 10; a secondary forming step of forming a pre-fastener body 60 comprising a plurality of engaging elements 72, such as shown in Fig.6, in such a manner that portions of the primary molded body 50 are deformed using the hot-pressing device 20; and a stretching step for obtaining a surface fastener 70 through a stretching process performed on the pre-fastener body 60 in the machine direction MD using the stretching device 30. The method for producing a surface fastener 70 according to the present invention may further include one or more steps in each of which any other process or treatment other than the above-described primary molding step, secondary molding step, and stretching step is performed.

[0083] In the primary molding step, molten resin is continuously supplied from the supply nozzle 15 toward the outer peripheral surface of the die wheel 11. In the present embodiment, the resin to be molded into a surface fastener 70 is polypropylene, which is supplied in a molten state from the supply nozzle 15. In this way, a precursor base part 51 is continuously molded between the supply nozzle 15 and the die wheel 11. Furthermore, many primary elements 52 (precursor elements) are integrally molded with the precursor base part 51 by the outer sleeve 12 and the inner sleeve 13 of the die wheel 11.

[0084] In the present invention, there are no particular limitations on the type of resin to be molded into the surface fastener 70. The material for the surface fastener 70 may be, for example, a thermoplastic resin such as polypropylene, polyester, nylon, polybutylene terephthalate, or a copolymer of any of the aforementioned resins. The primary molding device 10 may alternatively be configured to, for example, supply a molten resin material from a supply nozzle toward a gap between two opposing die wheels. In such a configuration, the precursor base part is to be molded between the pair of die wheels, and the plurality of primary elements are to be molded by the outer sleeve and the inner sleeve of one of the die wheels.

[0085] Through the primary molding step according to the present embodiment, a primary molded body 50 is formed as shown in Fig.5. The primary mold body 50 includes the precursor base part 51, which is a thin plate having a top (first surface) and a bottom (second surface), and the plurality of primary elements 52 protruding from the top of the precursor base part 51.

[0086] The top and bottom surfaces of the precursor base part 51 are flat or substantially flat. The top surface of the precursor base part 51 takes the shapes of the above-described projections formed on the outer peripheral surface of the outer sleeve 12 of the die wheel 11, and thereby has portions with transferred unevennesses 56, such as the one shown in Fig. 5. In particular, the primary mold body 50 has a plurality of transferred asperity portions 56 formed at positions corresponding to the projections of the outer sleeve 12 and spaced apart from each other in the longitudinal direction.

[0087] The transferred asperity portions 56 of the primary mold body 50 are difficult to observe by direct visual observation, but are of a size that can be observed, for example, when measuring the top surface of the precursor base part 51 with a laser microscope. Like the projections of the outer sleeve 12, the transferred asperity portions 56 of the primary mold body 50 are each linear along a direction inclined at an inclination angle θ of 4° or more with respect to the transverse direction CD, and are formed continuously or discontinuously. Furthermore, the transferred asperity portions 56 may each include one concave portion and two convex portions formed at the front and rear sides of the concave portion, respectively.The one concave portion and the two convex portions are observable when measuring the upper surface of the precursor base part 51 in the machining direction MD through a laser microscope. Such a convex portion may protrude relative to the concave portion or the upper surface of the precursor base part 51, or may not necessarily protrude relative to the upper surface of the precursor base part 51. The convex portion may be formed only on one of the front and rear surfaces of the concave portion.

[0088] The primary elements 52 included in the primary mold body 50 are portions to be subjected to secondary forming (press forming) in the secondary forming step, thereby forming them into respective engaging elements 72. In the present embodiment, the plurality of primary elements 52 are regularly arranged on the upper surface of the precursor base part 51 in a lattice pattern in which the primary elements 52 are arranged in the machining direction MD and the transverse direction CD. Therefore, the plurality of engaging elements 72 formed from the primary elements 52 are also regularly arranged in a lattice pattern. With such a configuration, the primary elements 52 are arranged at regular intervals in the machining direction MD, thus forming element rows 57. Furthermore, the plurality of element rows 57 are arranged adjacent to one another at regular intervals in the transverse direction CD.

[0089] In the present invention, factors such as the number, size (width and height), arrangement pattern, and arrangement density of the primary elements and the engaging elements obtained from the primary elements are not particularly limited and can be varied. For example, the primary elements and the engaging elements may be arranged in a staggered pattern in which the primary elements or the engaging elements are arranged alternately or zigzag, with the element rows adjacent in the transverse direction CD being offset relative to each other by half the pitch of the primary elements or engaging elements in the machining direction MD.

[0090] In the present embodiment, the primary members 52 each include a primary stem portion 53 having a circular truncated cone shape and projecting from the precursor base member 51; a rod-shaped rib portion 54 that is a portion of the top surface of the primary stem portion 53 directed upward; and two projecting portions (primary pawl portions) 55 that are integrally formed with the rib portion 54 and project from two respective ends of the rib portion 54.

[0091] In the die wheel 11 according to the present embodiment, as described above, the outer peripheral edge of each of the through holes 12a formed on the inner peripheral surface of the outer sleeve 12 includes a portion overlapping at least one of the recessed groove portions 13a provided in the inner sleeve 13. Therefore, when the molten resin is supplied to the die wheel 11 in the primary molding step, it flows through the through holes 12a of the outer sleeve 12 into the recessed groove portions 13a of the inner sleeve 13 and spreads therein, thereby forming the rib portion 54 and the protruding portions 55 of each of the primary elements 52. Therefore, the rib portion 54 and the protruding portions 55 of each of the primary elements 52 are aligned in the transverse direction CD (the direction in which the recessed groove portions 13a extend).In addition, in a plan view of the primary member 52, the protruding portions 55 each protrude outward relative to the upper end surface of the primary stem portion 53.

[0092] In the primary molding step, the molten resin is conveyed from the outer peripheral surface of the die wheel 11 and undergoes a half rotation while cooling, thereby forming the above-described primary molded body 50. Subsequently, the primary molded body 50 is continuously peeled off the outer peripheral surface of the die wheel 11 by the stripping roller 16.

[0093] Subsequently, the primary molded body 50 peeled from the die wheel 11 is transported to the hot-pressing device 20 which is configured to perform the secondary molding step and is inserted between the upper press roller 21 and the lower press roller 22 of the hot-pressing device 20.

[0094] In the secondary forming step, the precursor base part 51 of the primary molded body 50 is supported from below by the lower press roll 22. Furthermore, at least the upper end portions of the primary elements 52 of the primary molded body 50 are heated to be softened and pressed from above by the upper press roll 21. In this way, a pre-adhesive fastener body (secondary molded body) 60 as shown in FIG. Fig. 7, in which a plurality of engaging elements 72 are molded integrally with the upper surface of the precursor base part 51. In the present invention, the pre-fastener body is a molded body that has yet to undergo the stretching process and includes a base part (precursor base part) thicker than that of the surface fastener and a plurality of engaging elements.

[0095] The engaging elements 72 of the pre-fastener body 60 each include a stem portion 73 having a substantially truncated circular cone shape and projecting from the precursor base part 51; an engaging head 74 formed integrally with the upper end portion of the stem portion 73; and two microfine pawl portions (engaging pawl portions) 75 each projecting outwardly from the outer peripheral edge of the engaging head 74.

[0096] The engaging head 74 extends over the entire upper end portion (distal end portion) of the stem portion 73 and perpendicular to the thickness direction. In a plan view (not shown) of the engaging element 72 viewed from above, the two pawl portions 75 each protrude in the transverse direction CD from the engaging head 74. In the present invention, there are no particular limits on the shape and size of the engaging elements. For example, factors such as the shape of the fastening head, the shape of the pawl portions, the number of pawl portions, and the direction in which the pawl portions protrude from the engaging head can be changed to form the engaging elements. Furthermore, a single surface fastener can include engaging elements of different types with different shapes.

[0097] After the secondary forming step, the pre-adhesive fastener body 60 supplied from the hot-pressing device 20 is transported to the stretching device 30 (see Fig. 1). At the stretching device 30, the pre-adhesive fastener body 60 is fed into the stretching device 30 from the feed unit (not shown) and is subjected, in this order, to a heat treatment (heating step) performed by the heating roller, a stretching process (stretching step) performed between the heating roller and the stretching roller, and a relaxation treatment (relaxing step) performed after the stretching process.

[0098] Specifically, during the heat treatment, the pre-adhesive fastener body 60 is brought into contact with the roller surface of the heating roller, whereby the pre-adhesive fastener body 60 is heated to a temperature such that it becomes stretchable.

[0099] The pre-touch fastener body 60, which has passed through the heating roller, is then subjected to the stretching process (uniaxial stretching process), in which the pre-touch fastener body 60 is stretched in the machine direction MD between the heating roller and the stretching roller, which rotates at a higher rotational speed than the heating roller. In the stretching process, the precursor base part 51 of the pre-touch fastener body 60 is stretched in the machine direction MD into a base part 71. Furthermore, the base part 71 to be obtained in the stretching process has a thickness between its top and bottom surfaces that is smaller than the thickness between the top and bottom surfaces of the precursor base part 51 obtained by the secondary forming step.

[0100] Furthermore, in the present embodiment, the concave portions in the transferred asperity portions 56 formed in the upper surface of the precursor base member 51 tend to be stretched more in the above stretching process than regions of the precursor base member 51 where no transferred asperity portions 56 have been formed. However, according to the present embodiment, the transferred asperity portions 56 each extend in a direction inclined at an inclination angle θ of 4° or more with respect to the transverse direction CD.Therefore, in each of the transferred asperity portions 56 formed in the precursor base part 51, as compared with a case where, for example, the transferred asperity portions formed in the precursor base part each extend in the transverse direction, the concentration of stress (tensile force) to be applied to the transferred asperity portions 56 in the stretching process is reduced, which can suppress the local stretching and the local thickness reduction in areas including the transferred asperity portions 56.

[0101] Furthermore, in the above stretching process, although the concave portions formed in the upper surface of the precursor base part 51 before the stretching process tend to be stretched more than the areas of the precursor base part 51 where no portions with transferred asperities 56 have been formed, since such a concave portion is actively stretched, an area around the concave portion is less likely to be stretched. In addition, the areas of the precursor base part 51 where no portions with transferred asperities 56 have been formed are also stretched to have a reduced thickness. Therefore, after the stretching process, convex portions are formed near and on the front and back surfaces of the concave portion, and such a convex portion on each of the front and back surfaces is less conspicuous.In such a case, since the transferred asperity portions 56 according to the present embodiment each extend in a direction inclined at an inclination angle θ of 4° or more with respect to the transverse direction CD, the local thickness reduction at the concave portion and the extent of formation of the convex portion around the concave portion are reduced. Consequently, the difference in dimensions between the concave portion and the convex portion is reduced.

[0102] In the present invention, there are no particular limitations on the method, means, conditions and other relevant factors of the stretching process as long as the precursor base part of the pre-touch fastener body is thinned by stretching in the machine direction MD.

[0103] After performing the above stretching process, the surface fastener 70 having the base part 71 and the engaging elements 72 undergoes stress-relieving treatment. During the stress-relieving treatment, the surface fastener 70 is conveyed between the stretching roller and the stress-relieving roller, which rotates at a lower speed than the stretching roller, so that the stress to be exerted on the surface fastener 70 is reduced. This stabilizes the shape of the surface fastener 70.

[0104] Subsequently, the surface fastener 70, which has passed through the relaxation roller, is discharged to the outside by the discharge unit of the stretching device 30. The surface fastener 70 discharged from the stretching device 30 is wound into a roll and collected, for example, by a collecting roller or the like. Alternatively, the surface fastener 70 may be collected after being transported from the stretching device 30 to a cutting unit (not shown) and cut by the cutting unit into pieces each having a predetermined width and / or length.

[0105] By the manufacturing method according to the present embodiment, which includes the primary forming step, the secondary forming step and the stretching step as described above, the Fig. 7 shown surface fastener 70 is obtained.

[0106] The surface fastener 70 obtained by the manufacturing method according to the present embodiment includes the plurality of engaging elements 72 on top of the base part 71, which has the shape of a thin plate. Since the surface fastener 70 has been subjected to the stretching process performed in the MD machine direction, its base part 71 has a smaller thickness than a typical prior art surface fastener obtained without subjecting it to a stretching process. For example, the base part 71 of the surface fastener 70 according to the present embodiment has a thickness of 30 μm or more and less than 90 μm, preferably 40 μm or more and 80 μm or less. Therefore, the surface fastener 70 according to the present embodiment manufactured as above offers advantageous effects caused by thinning the base part 71, such as:increased flexibility, reduced weight, increased productivity and reduced manufacturing costs.

[0107] The surface fastener 70 according to the present embodiment is manufactured by the stretching process performed on the primary molded body 50 having the plurality of rectilinear portions and having the transferred asperities 56. Instead, the transferred asperities 56 portions each extend in a direction inclined at an inclination angle θ of 4° or more with respect to the transverse direction CD. Such a configuration effectively suppresses local stretching and local thickness reduction in the areas having the transferred asperities 56, which may occur when the stretching process is performed as described above.

[0108] Therefore, even if the base part 71 subjected to the stretching process as described above is thinned to a thickness of less than 90 μm, the unevenness height difference between the concave portion and the convex portion included in each of the transferred unevenness portions 56 of the base part 71 is reduced to a small value of 20 μm or less. Consequently, the transferred unevenness portions 56 on the upper surface of the base part 71 become less conspicuous to the extent that they are difficult to recognize upon direct visual observation. This reduces the influence of the transferred unevenness portions 56 on the appearance quality of the surface fastener 70. In addition, the fluctuations in the thickness of the base part 71 and the pitch of the engaging elements 72 that tend to occur in the longitudinal direction of the surface fastener 70 (machining direction MD) are reduced.Consequently, the variation in the peel strength of the surface fastener 70 (particularly the variation in the longitudinal direction) is reduced to a small value.

[0109] In the present invention, the unevenness height difference in the transferred unevenness portions and the unevenness height difference between the concave portion and the convex portion included in the transferred unevenness portions both refer to the difference in the up-down direction between the position in the up-down direction of the bottom of the concave portion and the position in the up-down direction of the upper end portion of the convex portion adjacent to the concave portion included in a single transferred unevenness portion. The unevenness height difference in the transferred unevenness portions can be determined, for example, by measuring the surface profile of the base part with a laser microscope.

[0110] In the above embodiment, the pre-fastener body 60 is manufactured by performing the primary molding step using the primary molding device 10 and the secondary molding step using the hot-pressing device 20. However, in the present invention, there are no particular limitations on the method and means for molding a pre-fastener body. In the present invention, for example, the pre-fastener body 60 can be manufactured without performing the secondary molding step in which thermal deformation is effected as in the above example, but by performing a molding step using a molding device having cavities with which the engaging elements 72 each including the stem portion 73 and the engaging head portion 74 can be formed. EXAMPLES

[0111] The present invention will be specifically described below by means of working examples and comparative examples. (Working examples 1 to 8)

[0112] Surface fasteners 70 were manufactured as working examples 1 to 8 using the manufacturing apparatus 1 described in the above embodiment.

[0113] For each of Working Examples 1 to 8, the outer sleeve 12 included in the die wheel 11 was made of a thin plate member 18 made of stainless steel with a thickness of 0.30 mm. To manufacture such an outer sleeve 12 for each Working Example, the thin plate member 18 was first rolled into a circular cylindrical shape and was welded to have a welded portion 12b extending at an inclination angle θ summarized in Table 1 below with respect to the transverse direction CD, thereby forming a circular cylinder. Subsequently, a piercing process was performed on the circular cylinder with an electron beam, thereby forming a plurality of through holes 12a. Further, a surface polishing process and a coating process were performed on the circular cylinder, thereby obtaining an outer sleeve 12.

[0114] The inner sleeve 13 was obtained from a thin plate member with a thickness of 0.20 mm made of a stainless steel that is softer than that for the outer sleeve 12. To manufacture such an inner sleeve 13 for each working example, first, an etching process was performed on the thin plate member, thereby creating a plurality of depressed groove portions 13a. Then, the thin plate member with the depressed groove portions 13a was rolled and welded to have a welded portion 13b extending at an inclination angle θ summarized in Table 1 below with respect to the transverse direction CD, thereby forming a circular cylinder. Then, a plating process was performed on the circular cylinder, thereby obtaining an inner sleeve 13.

[0115] In order to fix the thus obtained outer sleeve 12 and inner sleeve 13 to the rotatable drive roller 14 of the die wheel 11, the inner sleeve 13 was inserted into the outer sleeve 12, and the outer sleeve 12 and the inner sleeve 13 were joined together such that the welded part 12b of the outer sleeve 12 and the welded part 13b of the inner sleeve 13 were separated by 180°.

[0116] Subsequently, while blowing air from the outer peripheral surface of the rotary drive roller 14, the outer sleeve 12 and the inner sleeve 13 were moved in such a manner as to cover the rotary drive roller 14. Then, the air blown from the rotary drive roller 14 was stopped, whereby the outer sleeve 12 and the inner sleeve 13 were joined and fixed to the rotary drive roller 14 at a predetermined fixing position. In this way, a forging wheel 11 comprising the outer sleeve 12 and the inner sleeve 13 with the welded parts 12b and 13b extending at the inclination angles θ summarized in Table 1 was prepared.

[0117] Subsequently, the primary forming step was performed using the primary forming device 10 having the die wheel 11 prepared as above, and the secondary forming step was performed using the hot-pressing device 20, thereby obtaining a pre-fastener body 60 comprising a precursor base part 51 having a thickness of 90 μm. Furthermore, the stretching step was performed on the pre-fastener body 60 using the stretching device 30. Thus, a surface fastener 70 was manufactured for each of Working Examples 1 to 8.In the stretching step, the stretching process was performed in the stretching device 30 under the condition that the pre-touch fastener body 60 heated to 140 °C was stretched to 150% in the machine direction MD between the heating roller and the stretching roller, thereby reducing the thickness (90 µm) of the precursor base part 51 and obtaining a base part 71 with a thickness of 60 µm.

[0118] Subsequently, to evaluate the surface fasteners 70 manufactured for Working Examples 1 to 8, each of the surface fasteners 70 was cut into a 1-meter-long surface fastener 70 sample in the MD machining direction. Furthermore, the top surface of the base part 71 of the sample was visually observed, and the number of visually recognizable portions with transferred asperities 56 was counted. Furthermore, the asperity height difference in the portions with transferred asperities 56 formed in the base part 71 of the sample was measured using a laser microscope.

[0119] The unevenness height difference in the transferred unevenness portions 56 was measured for the transferred unevenness portions 56 due to the welded portion 12b of the outer sleeve 12 and the transferred unevenness portions 56 due to the welded portion 13b of the inner sleeve 13. The laser microscope used to measure the unevenness height difference was a VK-X250 / VK-X260 profile analyzing laser microscope manufactured by Keyence Corporation. This laser microscope was equipped with a 10x magnification objective lens. The profile of the upper surface of the base part 71 in a range of 10 mm or more in the machining direction MD was measured by combining different fields of view. Thus, the unevenness height difference in the transferred unevenness portions 56 was measured.

[0120] Furthermore, for comparison with the unevenness height difference in the transferred unevenness portions 56 of the surface fastener 70, the unevenness height difference in the transferred unevenness portions 56 formed in the precursor base part 51 of the pre-fastener body 60, which had not yet undergone the stretching step, was also measured with the above-mentioned laser microscope. The unevenness height difference in a case where convex portions were clearly formed was determined as the difference in the up-down direction between the lowest position in the concave portion and the highest position in the convex portions formed on the front and back sides of the concave portion.The unevenness height difference in a case where convex portions were formed indistinctly was determined as the difference in the up-down direction between the lowest position in the concave portion and areas of the top surface of the base part 71 or the precursor base part 51 located on the front and back sides of the concave portion.

[0121] The bump height difference in the transferred bump sections 56 was measured for each pre-fastener body 60 and each surface fastener 70, as summarized in Table 1 below. (Comparison examples 1 and 2)

[0122] Surface fasteners as Comparative Examples 1 and 2 were manufactured, in which the inclination angles θ of the welded parts 12b and 13b in the outer shell 12 and the inner shell 13 with respect to the transverse direction CD were respectively set as summarized in Table 1 below. Note that factors except for the inclination angles θ of the surface fasteners manufactured as Comparative Examples 1 and 2 were the same as those of Working Examples 1 to 8. As in the case of Working Examples 1 to 8, the unevenness height difference in the transferred unevenness portions was measured for each pre-fastener body and each surface fastener in each of Comparative Examples 1 and 2.

[0123] The unevenness height differences measured for Comparative Examples 1 and 2 in the sections with transferred unevenness are summarized in Table 1 below. [Table 1] Inclination angle θ of the welded part Unevenness height difference in sections with transferred unevenness of the pre-adhesive fastener body (before stretching process) Unevenness height difference in sections with transferred unevenness of the surface fastener (after stretching process) Visual observation Outer sleeve inner sleeve Outer sleeve inner sleeve Outer sleeve inner sleeve degree degree µm µm µm µm Working example 1 4 4 13,7 17 14,5 17,8 0 Working example 2 6 6 13,6 16,7 14,1 17,3 0 Working example 3 8 8 12,9 16,1 13,7 16,8 0 Working example 4 10 10 11,8 14,9 12,2 15,2 0 Working example 5 4 0 13,8 23,2 14,6 26,4 1 Working example 6 0 4 20,9 17,1 23,1 17,8 1 Working example 7 8 0 13 23,3 13,8 26,6 1 Working example 8 0 10 21,1 15,1 23 15,4 1 Comparison example 1 0 0 21 22,9 23,3 26,3 2 Comparison example 2 2 2 20,8 23 23,2 26,5 2

[0124] Table 1 shows that the surface fastener 70 obtained after the stretching process tends to have a larger unevenness height difference in the portions with transferred unevennesses 56 than the pre-fastener body 60 obtained before the stretching process. Furthermore, it can be noted that in the surface fasteners 70 of Working Examples 1 to 8, in which the inclination angle θ of at least one of the welded parts 12b of the outer sleeve 12 and the welded part 13b of the inner sleeve 13 was 4° or larger, the unevenness height difference in at least one of the portions with transferred unevennesses 56 formed in the base part 71 was smaller than in the surface fasteners of Comparative Examples 1 and 2, in which the inclination angle θ was smaller than 4°.

[0125] Specifically, in the surface fasteners 70 of Working Examples 1 to 4 in which the inclination angle θ for both welded parts 12b and 13b of the outer sleeve 12 and the inner sleeve 13 was set to 4° or larger, the unevenness height difference for each of the two transferred unevenness portions 56 formed by the welded parts 12b and 13b of the outer sleeve 12 and the inner sleeve 13 was smaller.

[0126] Specifically, in the surface fasteners 70 of Working Examples 1 to 8, the unevenness height difference in the transferred unevenness portions 56 formed by the welded parts 12b and 13b, which were located at an inclination angle θ of 4° or more, was as small as 20 μm or less, particularly 18 μm or less, indicating that the transferred unevenness portions 56 formed had such sizes and shapes that they were difficult to recognize by direct visual observation. In contrast, in Comparative Examples 1 and 2, the transferred unevenness portions formed in the surface fastener each had a large unevenness height difference of more than 23 μm and were easily recognized by visual observation.Thus, it was found that Working Examples 1 to 8 (particularly Working Examples 1 to 4) can each produce less conspicuous portions of transferred unevenness 56 on the base part 71, resulting in a surface fastener 70 having excellent quality of appearance.

[0127] Furthermore, when comparing Working Examples 1 to 8, it was found that increasing the inclination angle θ of the welded parts 12b and 13b further reduces the unevenness height difference in the transferred unevenness portions 56 formed in the base part 71 of the surface fastener 70 and also further reduces the variation between the unevenness height differences before and after the stretching process.

[0128] In addition, the portion with transmitted asperities 56 formed by the welded part 13b of the inner sleeve 13 tended to have a larger asperity height difference than the portion with transmitted asperities 56 formed by the welded part 12b of the outer sleeve 12. The reason for this is considered to be as follows: the thickness (0.20 mm) of the inner sleeve 13 was smaller than the thickness (0.30 mm) of the outer sleeve 12; and the inner sleeve 13 was made of a softer metal than the outer sleeve 12. Consequently, the difference in hardness of the inner sleeve 13 between the welded part 13b and the area excluding the welded part 13b was larger than that of the outer sleeve 12. Therefore, it is considered that the amount of deformation of the welded part 13b that occurred when the inner sleeve 13 was fixed to the die wheel 11 (that is, when the inner sleeve 13 was inflated) became larger than that of the welded part 12b of the outer sleeve 12. List of reference symbols 1 manufacturing device 10 primary forming device 11 Die wheel 12 Outer sleeve (outer cylinder) 12a Through hole 12b welded part 13 Inner sleeve (inner cylinder) 13a recessed groove section 13b welded part 14 rotating drive roller 15 Feed nozzle 16 Pick-up roller 16a upper squeeze roller 16b lower squeeze roller 18 thin plate part 19 pages 19a First pair page 19b Second pair page 20 Hot pressing device (secondary forming device) 21 upper press roll (calender roll) 22 lower press roll (calender roll) 30 stretching device 50 primary molded body 51 Precursor base part 52 Primary element (precursor element) 53 primary stem section 54 rib section 55 protruding section (primary latch section) 56 Section with transferred bumps (transfer mark) 57 element series 60 Pre-adhesive closure body (secondary molded body) 70 surface fastener 71 Base part 72 engagement element 73 stem section 74 Intervention head 75 latch section (engagement latch section) CD transverse direction MD machining direction

Claims

[1] A method for producing surface fasteners for producing a surface fastener (70) made of synthetic resin and comprising a base part (71) having a plurality of engaging elements (72), the method comprising at least a molding step of performing molding by supplying molten synthetic resin to a die wheel (11) rotating in one direction, and a stretching step of performing a stretching process in a machining direction after the molding step, the manufacturing method characterized by is that it includes: Using the die wheel (11) in the forming step, wherein the die wheel (11) comprises at least one sleeve (12, 13) with cavities with which the engaging elements (72) or precursor elements (52) to be deformed into the engaging elements (72) are to be formed, wherein the sleeve (12, 13) has a circular cylindrical shape and is obtained from a thin metal plate part (18) by bringing one end portion and another end portion of the thin plate part (18) into contact with each other in a first direction and joining the one end portion and the other end portion that have been brought into contact with each other by welding, wherein the one end portion and the other end portion that have been joined with each other form a welded part (12b, 13b), wherein the welded part (12b, 13b) is at an angle (θ) of 4° or more with respect to a second direction is inclined,wherein the second direction is perpendicular to the first direction and is arranged along an axial direction of the sleeve (12, 13). [2] A method for producing surface fasteners according to claim 1, characterized by , that the sleeve (12, 13) comprises an outer sleeve (12) and an inner sleeve (13) which is in close contact with an inner peripheral surface of the outer sleeve (12), the outer sleeve (12) has a plurality of through holes (12a) penetrating the outer sleeve (12) from an outer peripheral surface to the inner peripheral surface of the outer sleeve (12), the inner sleeve (13) has a plurality of recessed portions (13a) provided in an outer peripheral surface of the inner sleeve (13), and an outer peripheral edge of at least one of the through holes (12a) on the inner peripheral surface of the outer sleeve (12) includes a portion overlapping a recessed portion (13a) provided in the inner sleeve (13). [3] A method for producing surface fasteners according to claim 1 or 2, characterized by that the inner sleeve (13) is made of a softer metal than the outer sleeve (12). [4] A surface fastener (70) made of synthetic resin and comprising a base part (71) and a plurality of engaging elements (72), wherein the base part (71) has a first surface and a second surface facing away from each other, wherein the engaging elements (72) protrude from the first surface of the base part (71), wherein the base part (71) is designed as a thin plate which is elongated in a first direction, wherein the surface fastener (70) characterized by is that the base part (71) has a thickness between the first surface and the second surface of less than 90 µm, the first surface of the base part (71) has a portion with transferred asperities (56) comprising a concave portion and a convex portion formed in the first surface, the transferred unevenness portion (56) is formed rectilinearly along a direction inclined at an angle (θ) of 4° or more with respect to a second direction perpendicular to the first direction, and an unevenness height difference in the section with transferred unevennesses (56) is 20 µm or less. [5] A molding device (10) for use in producing a surface fastener (70), the surface fastener (70) being made of synthetic resin and comprising a base part (71) having a plurality of engaging elements (72), the molding device (10) comprising a die wheel (11) adapted to rotate in one direction and a feed nozzle (15) adapted to feed molten synthetic resin in the direction of the die wheel (11), the molding device (10) characterized by is that the die wheel (11) comprises at least one sleeve (12, 13) with cavities with which the engagement elements (72) or precursor elements to be deformed into the engagement elements (72) are to be formed, the sleeve (12, 13) has a circular cylindrical shape and is obtained from a thin metal plate part (18) by bringing one end portion and another end portion of the thin plate part (18) into contact with each other in a first direction and joining the one end portion and the other end portion which have been brought into contact with each other by welding, and the one end portion and the other end portion, which have been joined together, form a welded part (12b, 13b), the welded part (12b, 13b) being inclined at an angle (θ) of 4° or more with respect to a second direction, the second direction being perpendicular to the first direction and being arranged along an axial direction of the sleeve (12, 13). [6] Forming device according to claim 5, characterized by , that the sleeve (12, 13) comprises an outer sleeve (12) and an inner sleeve (13) which is in close contact with an inner peripheral surface of the outer sleeve (12), the outer sleeve (12) has a plurality of through holes (12a) penetrating the outer sleeve (12) from an outer peripheral surface to the inner peripheral surface of the outer sleeve (12), the inner sleeve (13) has a plurality of recessed portions (13a) provided in an outer peripheral surface of the inner sleeve (13), and an outer peripheral edge of at least one of the through holes (12a) on the inner peripheral surface of the outer sleeve (12) includes a portion overlapping a recessed portion (13a) provided in the inner sleeve (13). [7] Forming device according to claim 5 or 6, characterized by that the inner sleeve (13) is made of a softer metal than the outer sleeve (12).

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