Surface Fastener and Molding Device

Abstract

A surface fastener includes a base part and a plurality of engaging elements formed integrally with the base part. A lower half part of the stem portion has a first shape in which an outer surface is formed straightly or substantially straightly on viewing the engagement element from the machining direction, and the lower half part has a second shape including a part where an outer surface is curved toward the surface of the base part on viewing engagement element from the cross direction. Thus, the surface fastener has a structure and/or characteristic that is different between the machining direction and the cross direction.

Claims

1. A surface fastener made of synthetic resin and including a base part and a plurality of engaging elements-formed integrally with the base part, the engaging elements each including a stem portion and an engaging head, the stem portion projecting from a surface of the base part in a thickness direction of the base part, the engaging head being formed at a distal end part of the stem portion, a section of at least an upper end part of the stem portion orthogonally to the thickness direction having a circular or nearly circular shape, the engaging head having a shape which spreads overall from the distal end part of the stem portion in a direction orthogonal to the thickness direction, wherein: a lower half part of the stem portion includes a part where an outer surface is formed straightly or substantially straightly in a first shape obtained by viewing the engagement element from the machining direction, the outer surface facing a cross direction orthogonal to the machining direction, and the lower half part includes a part where an outer surface facing the machining direction is curved toward the surface of the base part in a second shape obtained by viewing engagement element from the cross direction, the outer surface.

2. The surface fastener according to claim 1, wherein: an upper half part of the stem portion in the second shape includes a part where the outer surface facing the machining direction is formed straightly or substantially straightly, and the part of the second shape where the outer surface is formed straightly or substantially straightly is provided in an area shorter than the part of the first shape where the outer surface is formed straightly or substantially straightly.

3. A surface fastener made of synthetic resin and including a base part and a plurality of engaging elements formed integrally with the base part, the engaging elements each including a stem portion and an engaging head, the stem portion projecting from a surface of the base part in a thickness direction of the base part, the engaging head being formed at a distal end part of the stem portion, a section of at least an upper end part of the stem portion orthogonally to the thickness direction having a circular or nearly circular shape, the engaging head having a shape which spreads overall from the distal end part of the stem portion in a direction orthogonal to the thickness direction, wherein: when, in the engaging element seen from the machining direction, a length of a joint part of the stem portion jointing to the base part in a cross direction orthogonal to the machining direction is defined as a first dimension; and, in the engaging element seen from the cross direction, a length of the joint part in the machining direction is defined as a second dimension, the stem portion has a shape such that the second dimension is greater than the first dimension, and when peel strengths of the surface fastener in the case that the surface fastener and a loop member that are in engagement with each other are peeled from each other in the machining direction and in the cross direction are respectively defined as MD peel strength and CD peel strength, the stem portion has a shape such that the CD peel strength is greater than the MD peel strength.

4. A surface fastener made of synthetic resin and including a base part and a plurality of engaging elements formed integrally with the base part, the engaging elements each including a stem portion and an engaging head, the stem portion projecting from a surface of the base part in a thickness direction of the base part, the engaging head being formed at a distal end part of the stem portion, a section of at least an upper end part of the stem portion orthogonally to the thickness direction having a circular or nearly circular shape, the engaging head having a shape which spreads overall from the distal end part of the stem portion in a direction orthogonal to the thickness direction, wherein: CD flexibility is higher than MD flexibility, the CD flexibility being exerted when a part of the surface fastener that extends in a cross direction orthogonal to a machining direction is bent in the thickness direction, the MD flexibility being exerted when a part of the surface fastener that extends in the machining direction is bent in the thickness direction.

5. The surface fastener according to claim 1, wherein: the plurality of engaging elements are arranged in a line at a regular pitch in the machining direction to form an element row, a plurality of element rows are arranged at a regular interval in the cross direction, the engaging elements in each of the element rows are shifted by half the pitch in the machining direction relative to the engaging elements in another one of the element rows that is adjacent in the cross direction, and in regard to the machining direction, the engaging elements are arranged at positions such that occupied areas occupied by the respective stem portions of the engaging elements include portions that overlap each other between the element rows that are adjacent to each other in the cross direction.

6. The surface fastener according to claim 1, wherein: the engaging elements each include at least one pawl portion projecting in the cross direction from an outer peripheral edge part of the engaging head.

7. A molding device including a die wheel and a feeding nozzle, the die wheel being configured to rotate in one direction, the feeding nozzle being configured to feed molten synthetic resin toward the die wheel, the molding device being used in manufacturing a surface fastener, the surface fastener including a base part provided with a plurality of engaging elements, the engaging elements each including a stem portion and an engaging head, the stem portion projecting from a surface of the base part in a thickness direction of the base part, the engaging head being formed at a distal end part of the stem portion, wherein: the die wheel includes at least one circular cylindrical sleeve and a driving roller configured to rotate the sleeve, the sleeve has a plurality of through-holes penetrating through the sleeve from an outer peripheral surface to the inner peripheral surface of the sleeve, the plurality of through-holes are arranged in a line at a regular hole pitch in a machining direction to form a hole row, a plurality of hole rows are arranged at a regular interval in a cross direction that is orthogonal to the machining direction, the through-holes in each of the hole rows are shifted by half the hole pitch in the machining direction relative to the through-holes in another one of the hole rows that is adjacent in the cross direction, and in regard to the machining direction, the through-holes are arranged at positions such that occupied areas occupied by the respective through-holes-include portions that overlap each other between the hole rows that are adjacent to each other in the cross direction.

8. The surface fastener according to claim 3, wherein: the plurality of engaging elements are arranged in a line at a regular pitch in the machining direction to form an element row, a plurality of element rows are arranged at a regular interval in the cross direction, the engaging elements in each of the element rows are shifted by half the pitch in the machining direction relative to the engaging elements in another one of the element rows that is adjacent in the cross direction, and in regard to the machining direction, the engaging elements are arranged at positions such that occupied areas occupied by the respective stem portions of the engaging elements include portions that overlap each other between the element rows that are adjacent to each other in the cross direction.

9. The surface fastener according to claim 4, wherein: the plurality of engaging elements are arranged in a line at a regular pitch in the machining direction to form an element row, a plurality of element rows are arranged at a regular interval in the cross direction, the engaging elements in each of the element rows are shifted by half the pitch in the machining direction relative to the engaging elements in another one of the element rows that is adjacent in the cross direction, and in regard to the machining direction, the engaging elements are arranged at positions such that occupied areas occupied by the respective stem portions of the engaging elements include portions that overlap each other between the element rows that are adjacent to each other in the cross direction.

10. The surface fastener according to claim 3, wherein: the engaging elements each include at least one pawl portion projecting in the cross direction from an outer peripheral edge part of the engaging head.

11. The surface fastener according to claim 4, wherein: the engaging elements each include at least one pawl portion projecting in the cross direction from an outer peripheral edge part of the engaging head.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a copy of a photograph of a part of a surface fastener according to an embodiment of the present invention that is taken from above.

[0027] FIG. 2 is a copy of a photograph of an engaging element of the surface fastener illustrated in FIG. 1 that is taken from above.

[0028] FIG. 3 is a copy of a photograph of the engaging element of the surface fastener illustrated in FIG. 1 that is taken in a machining direction.

[0029] FIG. 4 is a copy of a photograph of the engaging element of the surface fastener illustrated in FIG. 1 that is taken in a cross direction.

[0030] FIG. 5 is a schematic diagram of a manufacturing apparatus configured to manufacture the surface fastener illustrated in FIG. 1.

[0031] FIG. 6 is a schematic diagram of a part of an outer sleeve included in a molding device included in the manufacturing apparatus illustrated in FIG. 5.

[0032] FIG. 7 is a schematic perspective view of a primary molded body that is molded in a primary molding step.

[0033] FIG. 8 is a diagram for describing a peel-strength test.

[0034] FIG. 9 is another diagram for describing the peel-strength test.

[0035] FIG. 10 is a schematic diagram of a tester configured to measure the flexibility of the surface fastener.

[0036] FIG. 11 is a schematic diagram illustrating a state where the surface fastener is pushed with the tester illustrated in FIG. 10.

DESCRIPTION OF EMBODIMENTS

[0037] A preferred embodiment of the present invention will now be described in detail with reference to the drawings. The present invention is not limited to the following embodiment in any way 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. For example, the length dimension (the dimension in a machining direction MD) and the width dimension (the dimension in a cross direction CD) of the surface fastener according to the present invention are not particularly limited, and the surface fastener may have any shape by, for example, being cut.

[0038] FIG. 1 is a copy of a photograph of a part of a surface fastener according to the present embodiment that is taken from above. FIGS. 2 to 4 are copies of photographs of one of engaging elements formed in the surface fastener according to the present embodiment that are taken from above (plan view), in the machining direction (front view or rear view), and in the cross direction (side view), respectively.

[0039] In the following description, the front-rear direction corresponds to the length direction of the surface fastener and a primary molded body, which each have an elongate shape. The front-rear direction also corresponds to, in the process of manufacturing a surface fastener, a direction (first direction) parallel to a machining direction MD, in which the surface fastener or the primary molded body is to be transported.

[0040] The left-right direction refers to the width direction that is orthogonal to the length direction and parallel to the flat upper surface (first surface) or lower surface (second surface) of a base part of the surface fastener. Herein, the left-right direction and the width direction correspond to a direction (second direction) parallel to a cross direction CD, which is orthogonal to the machining direction MD.

[0041] The up-down direction is the height direction (or the thickness direction of the base part) parallel to the direction orthogonal to the flat upper or lower surface of the base part and is orthogonal to the front-rear direction and to the left-right direction. Herein, with reference to the base part, a side toward which engaging elements project is defined as the upper side in the up-down direction, and a side opposite the upper side is defined as the lower side.

[0042] A surface fastener 10 according to the present embodiment is, as to be described separately below, manufactured by using a manufacturing apparatus 50, illustrated in FIG. 5, into a shape that is elongate in the machining direction MD of the manufacturing apparatus 50. The manufacturing apparatus 50 includes a molding device 60, a hot pressing device 70, and a stretching device 80.

[0043] The surface fastener 10 is made of a thermoplastic resin such as polypropylene, polyester, nylon, polybutylene terephthalate, or a copolymer of any of the foregoing. The material of the surface fastener 10 is not particularly limited. The surface fastener 10 may be made of, for example, a biodegradable resin, a plant-derived resin, or a recycled thermoplastic resin.

[0044] As illustrated in FIGS. 1 to 4, the surface fastener 10 includes a thin flat base part 11 and a plurality of engaging elements 20. The engaging elements 20 project from the upper surface of the base part 11 and are each shaped like a mushroom. The base part 11 is elongate in the machining direction MD defined for the process of manufacturing the surface fastener 10. The base part 11 has a certain thickness that provides an appropriate strength and an appropriate flexibility. The upper surface (first surface) of the base part 11 and the lower surface (second surface) that is located opposite the upper surface are flat or substantially flat and extend parallel to each other.

[0045] The engaging elements 20 each include a stem portion 21, which project upward from the upper surface of the base part 11; a disc-shaped engaging head 22, which is formed integrally with the upper end of the stem portion 21; and two microsized pawl portions 23, which each slightly project outward in the cross direction CD from the outer peripheral edge part of the engaging head 22.

[0046] Here, the shape of the stem portion 21 that is taken when the engaging element 20 is seen in the machining direction MD is defined as a first shape, 31, of the stem portion 21; and the shape of the stem portion 21 that is taken when the engaging element 20 is seen in the cross direction CD is defined as a second shape, 32, of the stem portion 21. Under such definitions, since the stem portion 21 (particularly, the lower half part of the stem portion 21) of each engaging element 20 is obtained through a stretching process that is performed in the machining direction MD as to be described below during the process of manufacturing the surface fastener 10, the first shape 31 (see FIG. 3) of the stem portion 21 and the second shape 32 (see FIG. 4) of the stem portion 21 are different from each other.

[0047] In the engaging element 20 according to the present embodiment, the first shape 31 and the second shape 32 of the stem portion 21 are different from each other mainly in the lower half part of the stem portion 21. In the lower half part of the stem portion 21 in the first shape 31 is thinner than the lower half part of the stem portion 21 in the second shape 32. Therefore, when, for example, the engaging element 20 receives a force from above, the engaging element 20 is more likely to bend in the cross direction CD than in the machining direction MD. Note that the upper half part and the lower half part of the stem portion 21 refer to, when the stem portion 21 is divided at the center position in the height direction thereof, a part that is farther from the base part 11 than the center position and a part that is closer to the base part 11 than the center position, respectively.

[0048] The shape of the stem portion 21 will further be described specifically. In the front view (FIG. 3) or rear view of the engaging element 20 that is see in the machining direction MD, the stem portion 21 has the first shape 31, in which the stem portion 21 has outer surfaces 21a facing the cross direction CD and extending straightly or substantially straightly along a nearly straight line over substantially the entire area from the upper end of the stem portion 21 that adjoins the engaging head 22 to the lower end (a joint part) of the stem portion 21 that adjoins the base part 11. Furthermore, in the first shape 31 of the stem portion 21, the outer surfaces 21a of the stem portion 21 that face the cross direction CD each form an angle of about 95 with respect to the upper surface of the base part 11. In the first shape 31, the angle between each of the outer surfaces of the stem portion 21 that face the cross direction CD and the upper surface of the base part 11 is not limited to the above.

[0049] Furthermore, in the first shape 31 according to the present embodiment, the outer surfaces 21a of the stem portion 21 that face the cross direction CD may each include a curved part where the outer surface 21a is curved in the up-down direction to be concave in, for example, a lower part of the stem portion 21 that is near the base part 11. In such a structure, the straight or substantially straight part of each of the outer surfaces 21a in the first shape 31 may preferably occupy 50% or greater, more preferably 60% or greater, of the lower half part of the stem portion 21 in the up-down direction.

[0050] In the present invention, a shape extending straightly or substantially straightly along a nearly straight line refers to a shape of the outer peripheral surface of the stem portion 21, which has a substantially circular columnar shape as to be described below, that is seen in a direction such as the machining direction MD or the cross direction CD and in which the outer peripheral surface of the stem portion 21 includes no curved part that is significantly or apparently curved in the up-down direction to be concave. For example, even in a case where the outer surfaces 21a of the stem portion 21 that face the cross direction CD each forms an angle greater than 95 (for example, an angle of 100 to 110 with respect to the upper surface of the base part 11, the outer surface 21a is regarded as having a straight or substantially straight shape as long as the outer surface 21a extends straightly or along a nearly straight line.

[0051] On the other hand, in a side view (FIG. 4) of the engaging element 20 that is seen in the cross direction CD, the stem portion 21 has the second shape 32, in which the stem portion 21 has outer surfaces 21a facing the machining direction MD. Furthermore, the second shape 32 includes a part where the outer surfaces 21a extend straightly or substantially straightly, and a curved part where the outer surfaces 21a each extend while curving in the up-down direction to be concave. In the second shape 32, the part where the outer surfaces 21a of the stem portion 21 that face the machining direction MD extend straightly or substantially straightly mainly occupies the upper half part of the stem portion 21 and over an area shorter than the straight or substantially straight part of the first shape 31 illustrated in FIG. 3. In the second shape 32, the curved part where the outer surfaces 21a of the stem portion 21 that face the machining direction MD are curved mainly occupies the lower half part of the stem portion 21. The curved part of each of the outer surfaces 21a in the second shape 32 may preferably occupy 30% or greater, more preferably 40% or greater, of the lower half part of the stem portion 21 in the up-down direction. If, for example, the first shape 31 has a curved part at the lower end thereof, the curved part of each of the outer surfaces 21a in the second shape 32 occupies an area longer than the curved part in the first shape 31.

[0052] The outer surfaces 21a in the first shape 31, illustrated in FIG. 3, that face the cross direction CD define a shape similar to the shape defined by the upper halves of the outer surfaces 21a in the second shape 32, illustrated in FIG. 4, that face the machining direction MD. For example, in the upper half part of the stem portion 21 in the second shape 32, the outer surfaces 21a of the stem portion 21 that face the machining direction MD each form an angle of about 95 with respect to a direction parallel to the upper surface of the base part 11. On the other hand, in the lower half part of the stem portion 21 in the second shape 32, a part of each outer surface 21a of the stem portion 21 that is near the base part 11 form an angle of about 160 with respect to the upper surface of the base part 11. In the second shape 32, the part where the outer surfaces 21a of the stem portion 21 that face the machining direction MD extend straightly or substantially straightly is disposed an area of or greater and or smaller of the total height dimension of the stem portion 21 in the second shape 32 (the dimension in the up-down direction from the upper surface of the base part 11 to the upper end of the stem portion 21).

[0053] Comparing the first shape 31 (FIG. 3) and the second shape 32 (FIG. 4) of the stem portion 21, the lower half part of the stem portion 21 in the second shape 32 has a thickness that is varied significantly in such a manner as to increase toward the base part 11 as illustrated in FIG. 4, more than the thickness of the lower half part of the stem portion 21 in the first shape 31.

[0054] In the first shape 31, the outer surfaces 21a of the stem portion 21 each extend straightly or substantially straightly to the lower end of the stem portion 21 that joints the base part 11, and a boundary part between the straight or substantially straight outer surface 21a and the upper surface (front surface) of the base part 11 bents sharply by an angle near 90 (substantially) 95.

[0055] In contrast, in the second shape 32, the outer surfaces 21a in the lower half part of the stem portion 21 are each curved gently and widely, and the inclination of each of the outer surfaces 21a of the stem portion 21 becomes gentler toward the base part 11. Therefore, the outer surfaces 21a of the stem portion 21 in the second shape 32 are smoothly continuous with the surface of the base part 11.

[0056] In each of the engaging elements 20, the upper half part of the stem portion 21 has a substantially circular columnar shape. Therefore, the outer peripheral surface of the upper half part of the stem portion 21 has a curved surface that is smoothly continuous over the entire perimeter of the outer peripheral surface, with no irregular parts such as ridges or projections. Furthermore, the stem portion 21 is formed so that a section of the upper end part of the stem portion 21 orthogonally to the up-down direction has a circular or nearly circular (substantially circular) shape.

[0057] The joint part of the stem portion 21 to the base part 11 (that is, the lower end of the stem portion 21) has an oval or substantially oval shape that is oblong in the machining direction MD, with the maximum dimension thereof in the machining direction MD being greater than the maximum dimension thereof in the cross direction CD. In the present invention, a substantially oval shape refers to a nearly oval shape and includes, for example, an ellipse or the like.

[0058] Here, regarding the joint part of the stem portion 21, the length of the joint part in the cross direction CD with the engaging element 20 seen in the machining direction MD is defined as first dimension D1, and the length of the joint part in the machining direction MD with the engaging element 20 seen in the cross direction CD is defined as second dimension D2. Under such definitions, the stem portion 21 is shaped such that the second dimension D2 of the joint part in the second shape 32 is greater than the first dimension D1 of the joint part in the first shape 31. The second dimension D2 of the joint part in the second shape 32 has a length that is, for example, 1.5 to 2 times the first dimension D1 of the joint part in the first shape 31.

[0059] In the present embodiment, the plurality of engaging elements 20 are regularly arranged in a staggered pattern on the upper surface of the base part 11. Specifically, the engaging elements 20 are arranged at a regular pitch in the machining direction MD (the front-rear direction), thereby forming a plurality of engaging-element rows 26. The plurality of engaging-element rows 26 are arranged at a regular interval in the cross direction CD (the left-right direction). The engaging elements 20 in each of the engaging-element rows 26 are shifted by of the pitch in the machining direction MD relative to the engaging elements 20 in another one of the engaging-element rows 26 that is adjacent in the cross direction CD. Thus, the plurality of engaging elements 20 in the engaging-element rows 26 that are adjacent to each other in the cross direction CD are positioned alternately or in a zigzag manner.

[0060] As illustrated in FIG. 1, the plurality of engaging elements 20 are arranged at positions such that occupied areas 27, which are occupied by the respective stem portions 21 of the engaging elements 20 in regard to the machining direction MD, include portions that overlap each other between the engaging-element rows 26 that are adjacent to each other in the cross direction CD. In other words, an edge, on one side (the front side, for example) in the machining direction MD, of the stem portion 21 of each engaging element 20 is located between the edges, on the one side (the front side, for example) and the other side (the rear side, for example) in the machining direction MD, of the stem portion 21 of another engaging element 20 in another engaging-element row 26 that is adjacent in the cross direction CD.

[0061] According to the present embodiment, the strength of the base part 11 in the machining direction MD is effectively increased because the surface fastener 10 has at least one of the following features: (1) the second shape 32 of the stem portion 21 obtained by viewing the engagement element 20 from the cross direction CD includes a part where the outer surfaces 21a of the stem portion 21 is curved, and the second shape 32 is thicker than the first shape 31 of the stem portion 21 obtained by viewing the engaging element 20 from the machining direction MD; (2) the joint part of the stem portion 21 jointing to the base part 11 is formed to have an oval or substantially oval shape in which the second dimension D2 in the machining direction MD is greater than the first dimension D1 in the cross direction CD; and (3) in the staggered arrangement of the engaging elements 20, the occupied areas 27 occupied by the stem portions 21 of the engaging elements 20 in the machining direction MD overlap each other between the engaging-element rows 26 that are adjacent to each other in the cross direction CD. Therefore, for example, it is less likely for the base part 11 to cause a defect, such as breakage, when the base part 11 is pulled and stretched in the machining direction MD in a stretching process of forming the base part 11 during the process of manufacturing the surface fastener 10.

[0062] In each engaging element 20 according to the present embodiment, the engaging head 22 is relatively thin in the up-down direction and has a shape which spreads overall from the distal end part of the stem portion 21 in a direction orthogonal to the up-down direction (that is, a direction parallel to the upper surface of the base part 11). Furthermore, when the engaging element 20 is seen from above, the engaging head 22 has an oval or substantially oval shape that is oblong in the cross direction CD as illustrated in FIG. 2. The engaging head 22 having such a disc shape project radially outward relative to the upper end of the stem portion 21 (in other words, the boundary between the stem portion 21 and the engaging head 22). Note that the shape of the engaging head is not limited to an oval or substantially oval disc shape when seen from above. Alternatively, the engaging head may have a shape that is a perfect or nearly perfect circle or a nearly polygonal shape such as a rectangle when seen from above, as long as the engaging head spreads at the distal end part of the stem portion 21 and in a direction parallel to the surface of the base part 11.

[0063] Each engaging element 20 includes the pair of left and right microsized pawl portions 23 that project from the outer peripheral edge part of the engaging head 22 toward opposite sides in the cross direction CD. In such a configuration, the left and right pawl portions 23 are located at the left and right ends of the engaging head 22 that is oblong in the cross direction CD. Furthermore, the outer peripheral edge part of the engaging head 22 includes absent regions where no pawl portions 23 are present. In the present embodiment, the absent regions of the engaging head 22 where no pawl portions 23 are present each faces the machining direction MD.

[0064] As illustrated in FIG. 3, the left and right pawl portions 23 bends obliquely downward toward the base part 11 while extending from the outer peripheral edge part of the engaging head 22 to the distal edge thereof in the direction of projection. Furthermore, in the plan view of the engaging element 20 that is seen from above, each of the pawl portions 23 is of such a microsize that a proximal part thereof connected to the engaging head 22 has a dimension smaller than the maximum dimension of the engaging head 22 in the machining direction MD, preferably a dimension that is or smaller of the maximum dimension.

[0065] Since the engaging elements 20 each include the pawl portions 23 of such a microsize, when a loop member is made to engage with the surface fastener 10, the loops of the loop member engaged with the engaging elements 20 are easily caught by the pawl portions 23. Therefore, the likelihood of the loops being disengaged from the engaging elements 20 is further reduced. In addition, since the pawl portions 23 are of a microsize relative to the engaging heads 22, the influence of the pawl portions 23 upon the feel or tactile sensation at the upper surface of the surface fastener 10 is suppressed to a low level.

[0066] In the present invention, the shape and size of the engaging head are not particularly limited, as long as the engaging head spreads in a direction orthogonal to the up-down direction at the upper end of the stem portion. Furthermore, the shape of the pawl portions, the number of the pawl portions, the direction of projection of the pawl portions from the engaging head, and other relevant factors are not particularly limited. Furthermore, the engaging element may have no pawl portions. Furthermore, a single surface fastener may include engaging elements of a plurality of kinds with respectively different shapes.

[0067] Now, the manufacturing apparatus 50 configured to manufacture the surface fastener 10 according to the present embodiment will be described with reference to FIGS. 5 and 6.

[0068] The manufacturing apparatus 50 according to the present embodiment includes a molding device 60, which is configured to perform primary molding; a hot pressing device 70, which is configured to mold a secondary molded body (pre-fastener body) by performing secondary molding on a primary molded body 40 (see FIG. 7) molded by the molding device 60; and a stretching device 80, which is configured to perform a stretching process on the secondary molded body thus obtained. In the present invention, the pre-fastener body refers to a molded body or member that is obtained in a case where the manufacture of the surface fastener 10 includes a stretching process, and that is yet to undergo the stretching process.

[0069] The molding device 60 includes a die wheel 61, which is driven to rotate in one direction (the counterclockwise direction in the drawing); a feeding nozzle 65, which is provided facing the peripheral surface of the die wheel 61 and is configured to continuously feed a molten synthetic resin material; and a pickup roller 66, which is provided on the downstream side relative to the feeding nozzle 65 in the direction of rotation of the die wheel 61.

[0070] The die wheel 61 includes a circular cylindrical outer sleeve (outer cylinder) 62, which serves as a die; a circular cylindrical inner sleeve (inner cylinder) 63, which is provided on the inner side of and in close contact with the outer sleeve 62; and a driving roller 64, which is configured to rotate the outer sleeve 62 and the inner sleeve 63 in the one direction. The driving roller 64 is provided thereinside with a cooling jacket, which is not illustrated but allows cooling liquid to flow through.

[0071] The outer sleeve 62 has a plurality of through-holes 62a, which penetrate through the outer sleeve 62 from the outer peripheral surface to the inner peripheral surface and each serve as a cavity for molding the below-described primary stem portion 43 of the primary molded body 40. The through-holes 62a each have a substantially circular truncated conical shape with a circle at the outer peripheral surface of the outer sleeve 62 being greater than a circle at the inner peripheral surface of the outer sleeve 62.

[0072] The plurality of through-holes 62a provided in the outer sleeve 62 are positioned in correspondence with the positions of the engaging elements 20 in the secondary molded body to be made. To be more specific about the positions of the through-holes 62a, as illustrated in FIG. 6 for example, the plurality of through-holes 62a are regularly arranged in a staggered pattern in the outer sleeve 62. In such an arrangement, the through-holes 62a are at a regular pitch in the machining direction MD, thereby forming a plurality of hole rows 62b. The plurality of hole rows 62b are arranged at a regular interval in the cross direction CD. The through-holes 62a in each of the hole rows 62b are shifted by of the pitch in the machining direction MD relative to the through-holes 62a in another one of the hole rows 62b that is adjacent in the cross direction CD. Thus, the plurality of through-holes 62a in the hole rows 62b that are adjacent to each other in the left-right direction are positioned alternately or in a zigzag manner.

[0073] Furthermore, the plurality of through-holes 62a are arranged at positions such that occupied areas 62c, which are occupied by the respective through-holes 62a in the machining direction MD, include portions that overlap each other between the hole rows 62b that are adjacent to each other in the cross direction CD. Since the plurality of through-holes 62a are provided in the outer sleeve 62 in the above positional relationship, in the manufacture of the surface fastener 10, the plurality of engaging elements 20 are stably arranged such that the occupied areas 27 occupied by the engaging elements 20 overlap each other between the engaging-element rows 26 that are adjacent to each other in the cross direction CD.

[0074] The inner sleeve 63 has a plurality of recessed grooves in the outer peripheral surface thereof. The recessed grooves each linearly extend in the cross direction CD parallel to the center axis of the inner sleeve 63 and are each recessed in a size that allow molten synthetic resin to flow in. The recessed grooves are arranged at a regular interval in the peripheral direction of the inner sleeve 63 (the machining direction MD). With the die wheel 61 assembled, at least a portion of each of the recessed grooves of the inner sleeve 63 intersects the peripheral edges of corresponding ones of the through-holes 62a at the inner peripheral surface of the outer sleeve 62.

[0075] In the present invention, the form of the recesses provided in the outer peripheral surface of the inner sleeve is not limited to the linear recessed grooves as in the present embodiment. In the present invention, the outer peripheral surface of the inner sleeve may have, for example, recessed grooves that are bent in a zigzag manner, depressions that are depressed three-dimensionally in a cuboidal shape or the like relative to the outer peripheral surface of the inner sleeve, or the like. Moreover, the die wheel is not limited to the one constituted by two sleeves provided on the outer side and the inner side as in the present embodiment. For example, the die wheel may be constituted by a single sleeve having a plurality of through-holes penetrating therethrough from the outer peripheral surface to the inner peripheral surface, and a plurality of recessed grooves provided in the inner peripheral surface thereof.

[0076] The pickup roller 66 includes a pair of an upper nipping roller 67 and a lower nipping roller 68, which are configured to nip the primary molded body 40 molded on the outer peripheral surface of the die wheel 61 from above and below and to pull the primary molded body 40. The upper nipping roller 67 and the lower nipping roller 68 each have at the outer periphery thereof a surface layer, which is not illustrated but is made of elastomer such as polyurethane elastomer.

[0077] The hot pressing device 70 includes a pair of upper and lower pressing rollers (calender rollers) 71 and 72, which are provided on the downstream side relative to the pickup roller 66. The upper pressing roller 71 and the lower pressing roller 72 are positioned facing each other with a predetermined gap therebetween. The gap between the upper pressing roller 71 and the lower pressing roller 72 is adjustable by height-adjusting means, which is not illustrated.

[0078] The upper pressing roller 71 includes thereinside a heat source, which is not illustrated. The surface temperature of the upper pressing roller 71 is set to a temperature that softens the synthetic resin to be formed into the surface fastener 10 (primary molded body 40). In the present invention, the configuration of the hot pressing device is not particularly limited as long as the hot pressing device is capable of forming the engaging elements by pressing at least a portion of the primary molded body 40 as to be described below.

[0079] The stretching device 80 is installed on the downstream side relative to the hot pressing device 70 so as to perform at least a stretching process on the pre-fastener body (secondary molded body) molded by the hot pressing device 70. Although specific illustration is omitted, the stretching device 80 includes a feeding unit configured to introduce the pre-fastener body into the stretching device 80, a discharging unit configured to deliver the surface fastener 10 obtained through the stretching process toward the downstream side, and a plurality of rotatable rollers arranged between the feeding unit and the discharging unit and along a transport path for a processing object (that is, the pre-fastener body or the surface fastener 10).

[0080] The rotatable rollers are each configured to rotate while the processing object is kept in contact therewith, thereby being capable of transporting the processing object toward the downstream side at a speed corresponding to the rotation speed thereof. At least one of the rotatable rollers is capable of heating the processing object with a preset heating temperature while the processing object is kept in contact with the outer peripheral surface of the roller.

[0081] The rotatable rollers of the stretching device 80 include a heating roller configured to perform a heating treatment on the pre-fastener body, a stretching roller configured to perform a stretching process on the pre-fastener body in cooperation with the heating roller, and a relaxing roller provided on the downstream side relative to the stretching roller. In this configuration, the heating roller, the stretching roller, and the relaxing roller are arranged such that the transport path for the processing object meanders up and down.

[0082] The heating roller is configured to transport the pre-fastener body by rotating at a constant speed and to heat the pre-fastener body with the pre-fastener body being kept in contact with the roller surface thereof. The heating roller is provided with a supporting roller (nip roller) positioned facing the heating roller. The heating roller and the supporting roller are configured to rotate at respective constant speeds while nipping and holding the pre-fastener body therebetween from above and below. With the heating roller, the pre-fastener body that is yet to undergo the stretching process is heated to such a temperature as to be stretchable. In the present embodiment, the means and method for performing the heating treatment before the stretching process are not particularly limited.

[0083] The stretching roller is controlled to rotate at a higher rotation speed than the heating roller with the processing object being kept in contact with the roller surface thereof. For example, in the present embodiment, the rotation speed of the stretching roller is set to 110% or higher and 200% or lower of the rotation 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 10. The above combination of the heating roller and the stretching roller enables the performance of the stretching process on the pre-fastener body. Through the stretching process, the below-described tentative base part, 41, of the pre-fastener body is stretched in the machining direction MD, whereby the base part 11 of the surface fastener 10 is obtained.

[0084] The relaxing roller is controlled to rotate at a lower rotation speed than the stretching roller with the processing object being kept in contact with the roller surface thereof. The heating temperature of the relaxing roller is set lower than the melting point of the synthetic resin to be formed into the surface fastener 10. Thus, the tension to be applied to the surface fastener 10 between the stretching roller and the relaxing roller is reduced, whereby the shape and dimensions of the surface fastener 10 are stabilized.

[0085] Note that the above configuration of the stretching device 80 according to the present embodiment is only exemplary. In the present invention, the configuration of the stretching device is not particularly limited as long as the stretching device is located on the downstream side relative to at least the molding device and is capable of stretching in the machining direction MD a molded body, such as the pre-fastener body, delivered from the primary molding device or the hot pressing device.

[0086] Now, a method of manufacturing the surface fastener 10 by using the manufacturing apparatus 50 described above will be described.

[0087] The manufacturing method according to the present embodiment includes a primary molding step of molding a primary molded body 40, such as the one illustrated in FIG. 7, by using the primary molding device 60; a secondary molding step of molding a pre-fastener body (not illustrated) including engaging elements 20 in such a manner as to deform portions of the primary molded body 40 by using the hot pressing device 70; and a stretching step of obtaining a surface fastener 10 through a stretching process performed on the pre-fastener body in the machining direction MD by using the stretching device 80.

[0088] In the primary molding step, molten synthetic resin is continuously fed from the feeding nozzle 65 toward the outer peripheral surface of the die wheel 61. Thus, a tentative base part 41 is continuously molded between the feeding nozzle 65 and the die wheel 61. Furthermore, a plurality of primary elements (tentative elements) 42 are molded integrally with the tentative base part 41 by using the through-holes 62a provided in the outer sleeve 62 of the die wheel 61 and the recessed grooves provided in the inner sleeve 63 of the die wheel 61. Through the primary molding step, a primary molded body 40, illustrated in FIG. 7, is molded.

[0089] The primary molded body 40 thus molded includes the tentative base part 41, which is flat; and the plurality of primary elements 42, which project from the upper surface of the tentative base part 41. The tentative base part 41 is thicker than the base part 11 of a surface fastener 10 to be manufactured.

[0090] The primary elements 42 are subjected to secondary molding (press-molding) in the secondary molding step, thereby being deformed into respective engaging elements 20. The plurality of primary elements 42 are arranged in a staggered pattern on the tentative base part 41. The primary elements 42 each include a primary stem portion 43, which has a circular truncated conical shape projecting from the tentative base part 41; a stick-like rib portion 44, which is a portion of the upper surface of the primary stem portion 43 that is raised upward; and two projecting portions (primary pawl portions) 45, which are formed integrally with the rib portion 44 and project from two respective ends of the rib portion 44. The rib portion 44 and the left and right projecting portions 45 each extend in the cross direction CD. Furthermore, the left and right projecting portions 45 each project outward relative to the upper end face of the primary stem portion 43.

[0091] The plurality of primary elements 42 are positioned in correspondence with the position of the plurality of through-holes 62a provided in the outer sleeve 62. Therefore, occupied areas occupied by the respective primary stem portions 43 of the primary elements 42 in the machining direction MD overlap each other between element rows that are adjacent to each other in the cross direction CD. Note that the primary elements 42 may each include two projecting portions (primary pawl portions) 45 that are each formed as a portion of the upper surface of the primary stem portion 43 that is raised upward. In that case, in the secondary molding step to be described below, four microsized pawl portions 23 are formed in such a manner as to project outward from the outer peripheral edge part of the engaging head 22.

[0092] In the primary molding step according to the present embodiment, the molten synthetic resin is carried by the outer peripheral surface of the die wheel 61 and undergoes half a turn while being cooled, whereby the above-described primary molded body 40 is molded. Subsequently, the primary molded body 40 is continuously peeled from the outer peripheral surface of the die wheel 61 by the pickup roller 66.

[0093] Subsequently, the primary molded body 40 peeled from the die wheel 61 is transported toward the hot pressing device 70 configured to perform the secondary molding step and is introduced between the upper pressing roller 71 and the lower pressing roller 72 of the hot pressing device 70.

[0094] In the secondary molding step that is performed by the hot pressing device 70, the tentative base part 41 of the primary molded body 40 is supported from below by the lower pressing roller 72. Furthermore, at least the upper ends of the primary elements 42 of the primary molded body 40 are heated to be softened and are pressed from above by the upper pressing roller 71. Thus, the primary elements 42 are molded into secondary elements (not illustrated). Accordingly, a pre-fastener body in which a plurality of secondary elements are formed integrally with the tentative base part 41 is obtained.

[0095] The secondary elements that are not illustrated but molded in the secondary molding step each include a secondary stem portion, which has a substantially circular truncated conical shape standing from the tentative base part 41; an engaging head 22, which is formed integrally with the upper end of the secondary stem portion; and two microsized pawl portions 23, which each project outward from the outer peripheral edge part of the engaging head 22.

[0096] In such a configuration, the secondary stem portion of each secondary element has a circular or substantially circular section that is taken orthogonally to the up-down direction, and the diameter of the section gradually decreases in a direction away from the tentative base part 41. The shape of the secondary stem portion of the secondary element seen in the machining direction MD and the shape of the secondary stem portion of the secondary element seen in the cross direction CD are the same or substantially the same as each other. The engaging head 22 and the pawl portions 23 of each secondary element have substantially the same shapes and sizes as the engaging head 22 and the pawl portions 23 of the engaging element 20 illustrated in FIGS. 1 to 4.

[0097] After the secondary molding step is performed, the pre-fastener body delivered from the hot pressing device 70 is transported to the stretching device 80 (see FIG. 5). At the stretching device 80, the pre-fastener body is introduced from the feeding unit, which is not illustrated, into the stretching device 80 and is subjected to a heating treatment (heating step) that is performed by the heating roller, a stretching process (stretching step) that is performed between the heating roller and the stretching roller, and a relaxing treatment (relaxing step) that is performed after the stretching process, in that order.

[0098] In the heating treatment that is performed by the stretching device 80, the pre-fastener body is brought into contact with the roller surface of the heating roller, whereby the pre-fastener body is heated to such a temperature as to be stretchable.

[0099] The pre-fastener body having passed the heating roller is then subjected to the stretching process (uniaxial stretching process) in which the pre-fastener body is stretched in the machining direction MD between the heating roller and the stretching roller that is rotating at a higher rotation speed than the heating roller. In the stretching process, the tentative base part 41 of the pre-fastener body is stretched in the machining direction MD into a base part 11, which is a part of the surface fastener 10. A thickness between the upper surface and the lower surface of the base part 11 obtained as a result of the stretching process become smaller than the thickness between the upper surface and the lower surface of the tentative base part 41 obtained as a result of the secondary molding step.

[0100] In the stretching process according to the present embodiment, the tentative base part 41 is stretched under a processing condition that the lower end portion of the secondary stem portion of each secondary element is stretched together with the tentative base part 41 in the machining direction MD. In this case, the processing condition for the stretching process includes at least one of the following, for example: the temperature of heating the pre-fastener body, the rotation speed of the heating roller, the rotation speed of the stretching roller, and so forth.

[0101] In the stretching process, the secondary stem portion having a substantially circular truncated conical shape is stretched in the machining direction MD by stretching the lower end portion of the secondary stem portion. Therefore, the secondary stem portion is deformed into a stem portion 21, in which the joint part to the base part 11 has an oval or substantially oval shape that is long in the machining direction MD. Furthermore, the stem portion 21 is made to have the first shape 31 and the second shape 32, described above, that are different from each other. Thus, from the secondary element molded in the secondary molding step, the engaging element 20, is molded, which is shaped as illustrated in FIGS. 1 to 4.

[0102] The stretching process makes the base part 11 less likely to break in the machining direction MD. The reason for such a low likelihood of breakage is not clarified, but one possible reason is as follows: in the present embodiment, the secondary elements of the pre-fastener body and the engaging elements 20 of the surface fastener 10 to be manufactured are each configured such that the secondary stem portions or the occupied areas 27 occupied by the stem portions 21 overlap each other between the element rows that are adjacent to each other in the cross direction CD.

[0103] For example, in a case where regions of the tentative base part where the secondary stem portions are absent or regions of the base part 11 where the stem portions 21 are absent are continuous with one another in the cross direction CD, the strength of the tentative base part or the base part 11 may be reduced locally in the regions where the secondary stem portions or the stem portions 21 are absent, and such regions where the strength may be reduced may appear in the tentative base part or the base part 11 in a regular period in the machining direction MD. In contrast, in the present embodiment, since the secondary stem portions or the occupied areas 27 occupied by the stem portions 21 overlap each other between the element rows that are adjacent with each other in the cross direction CD, the probability of local reduction in the strength of the tentative base part or the base part 11 is reduced. Such a mechanism is considered to reduce the probability that the base part 11 may break in the machining direction MD during the stretching process.

[0104] Through the stretching process described above, the pre-fastener body is formed into the surface fastener 10 according to the present embodiment. Note that the method, means, conditions, and other relevant factors of the stretching process are not particularly limited as long as the tentative base part 41 of the pre-fastener body is thinned by being stretched along the machining direction MD and the secondary stem portions each having a substantially circular truncated conical shape are molded into the stem portions 21 that are oblong in the machining direction MD.

[0105] After the above stretching process is performed, the relaxing treatment is performed on the surface fastener 10 including the base part 11 and the engaging elements 20. In the relaxing treatment, the surface fastener 10 is transported between the stretching roller and the relaxing roller, which rotates at a lower speed than the stretching roller, such that the tension to be applied to the surface fastener 10 is reduced. Thus, the shape of the surface fastener 10 is stabilized.

[0106] Subsequently, the surface fastener 10 having passed the relaxing roller is delivered to the outside from the discharging unit of the stretching device 80. The surface fastener 10 discharged from the stretching device 80 is wound into a roll by, for example, a collecting roller or the like and is collected. Alternatively, the surface fastener 10 may be collected after being transported from the stretching device 80 to a cutting unit, not illustrated, and being cut by the cutting unit into pieces each having a predetermined width dimension and/or length dimension.

[0107] Through the manufacturing method including the primary molding step, the secondary molding step, and the stretching step described above, the surface fastener 10 according to the present embodiment illustrated in FIGS. 1 to 4 is obtained.

[0108] In the surface fastener 10 according to the present embodiment thus manufactured, as illustrated in FIGS. 3 and 4, the stem portion 21 of each of the engaging elements 20 has a directional structure in which the first shape 31 that is taken when the engaging element 20 is seen in the machining direction MD and the second shape 32 that is taken when the engaging element 20 is seen in the cross direction CD are different from each other (that is, a difference in the characteristic between the machining direction MD and the cross direction CD).

[0109] In the present embodiment particularly, the surface fastener 10 is configured such that the joint part of the stem portion 21 to the base part 11 has an oval or substantially oval shape that is oblong in the machining direction MD, and such that the occupied areas 27 occupied by the stem portions 21 in the machining direction MD overlap each other between the engaging-element rows 26 that are adjacent to each other in the cross direction CD. Therefore, as described above, although the base part 11 is thinned by undergoing the above stretching process, the base part 11 is less likely to break in the machining direction MD when a force is applied to the base part 11 of the surface fastener 10 (for example, when the stretching process is performed in the process of manufacturing the surface fastener 10).

[0110] Furthermore, in the surface fastener 10 according to the present embodiment, since the structure of each engaging element 20 is different between the machining direction MD and the cross direction CD, the engaging element 20 exhibits a characteristic that is different between the machining direction MD and the cross direction CD as follows.

[0111] For example, regarding the peel strength of the surface fastener 10 with respect to the loop member, a strength that is exerted when the surface fastener 10 is peeled off in the machining direction MD is defined as MD peel strength, and a strength that is exerted when the surface fastener 10 is peeled off in the cross direction CD is defined as CD peel strength. Under such definitions, the surface fastener 10 according to the present embodiment that has the directional structure exhibits a characteristic in which the CD peel strength is greater than the MD peel strength, as to be described below.

[0112] Here, a method of measuring the CD peel strength and the MD peel strength of the surface fastener 10 will be described with reference to FIGS. 8 and 9.

[0113] To measure the CD peel strength of the surface fastener 10, as illustrated in FIG. 8 for example, a long thin cutout piece 91 is first cut out of the surface fastener 10. The cutout piece 91 has a greater dimension in the machining direction MD than in the cross direction CD. Furthermore, the cutout piece 91 is bonded to a supporting member 92, whereby a first test piece 93 is made for the surface fastener 10. Furthermore, a loop member having a predetermined weight per unit area is cut into a piece having a predetermined shape and size, whereby a second test piece 94 is made. The second test piece 94 is to be made to engage with the cutout piece 91 (the surface fastener 10) included in the first test piece 93.

[0114] Subsequently, the surface fastener 10 in the first test piece 93 is made to engage with the second test piece 94, and the second test piece 94 is turned over in such a manner as to form a U shape as illustrated in FIG. 9. Subsequently, the first test piece 93 and the second test piece 94 are clamped with two respective clampers, which are not illustrated, and the clamper clamping the first test piece 93 and the clamper clamping the second test piece 94 are moved away from each other at a constant speed. Thus, loads represented by arrows in FIG. 9 are gradually applied to the first test piece 93 and the second test piece 94 that are in engagement with each other. Furthermore, the average load within a period from the start of application of the loads to a point of 50 mm is calculated through integration (note that the analysis is conducted within a period from a point of 3 mm to a point of 99% of 50 mm in the engaged part). The value thus calculated is divided by the effective width (cm) of the surface fastener 10, whereby the CD peel strength (N/cm) of the surface fastener 10 is measured.

[0115] On the other hand, to measure the MD peel strength of the surface fastener 10, a long thin cutout piece is cut out of the surface fastener 10. The cutout piece has a greater dimension in the cross direction CD than in the machining direction MD. Furthermore, the cutout piece of the surface fastener is bonded to a supporting member, whereby a first test piece is made for the surface fastener 10. Subsequently, a second test piece is made in the same manner as in the case of measuring the CD peel strength. Using the first test piece and the second test piece thus made, the same measurement as for the CD peel strength is conducted, whereby the MD peel strength (N/cm) of the surface fastener 10 is measured.

[0116] In the surface fastener 10 according to the present embodiment, the pawl portions 23 of the engaging elements 20 project in the cross direction CD. Therefore, when the surface fastener 10 is made to engage with the loop member in the cross direction CD, the loops of the loop member are easily caught by the pawl portions 23 of the engaging elements 20. Furthermore, the first shape 31 of the stem portion 21 that is taken when the engaging element 20 is seen in the machining direction MD is thinner than the second shape 32 of the stem portion 21 that is taken when the engaging element 20 is seen in the cross direction CD. Therefore, as described above, the engaging element 20 is more easily bendable in the cross direction CD than in the machining direction MD. Since the stem portion 21 of each of the engaging elements 20 is bendable more easily in the cross direction CD, when the surface fastener 10 is made to engage with the loop member in the cross direction CD, the engaging elements 20 are allowed to advance more deeply into the gaps between the loops of the loop member, utilizing the flexibility of the stem portions 21, than in a case where, for example, the surface fastener 10 is made to engage in the machining direction MD. Hence, the engaging elements 20 are more firmly engageable with the loop member.

[0117] Thus, the surface fastener 10 according to the present embodiment exhibits a characteristic in which, comparing the measurements of the MD peel strength and the CD peel strength, the CD peel strength is greater than the MD peel strength. For example, regarding the surface fastener 10 according to the present embodiment, the CD peel strength and the MD peel strength were each measured a plurality of times, and the respective averages were calculated. Consequently, the CD peel strength was 0.53 N/cm, and the MD peel strength was 0.02 N/cm. This shows that the CD peel strength is greater than or equal to ten times the MD peel strength. Note that, in the present embodiment, in spite of the difference in the structure of each of the engaging elements 20 between the machining direction MD and the cross direction CD, there was no directional difference in the shear strength of the surface fastener 10.

[0118] If the surface fastener 10 according to the present embodiment in which the CD peel strength is greater than the MD peel strength is used for, for example, a disposable diaper, the surface fastener 10 to be attached to the disposable diaper may be preferably oriented in such a manner as to be engaged with or peeled from the loop member in the cross direction CD of the surface fastener 10 (that is, in the orientation illustrated in FIG. 8). Thus, when the surface fastener 10 is made to engage with the loop member of the disposable diaper, the high CD peel strength of the surface fastener 10 stably maintains the state of engagement between the surface fastener 10 and the loop member, preventing the surface fastener 10 from being easily peeled from the loop member. Consequently, the state of attachment of the diaper is stably maintained with the engagement between the surface fastener 10 and the loop member.

[0119] Furthermore, for example, to reattach the disposable diaper, the surface fastener 10 may be strongly pulled to be peeled from the loop member and then be re-engaged with the loop member at an appropriate position. In such a situation, since the engaging elements 20 of the surface fastener 10 according to the present embodiment are bendable more easily in the cross direction CD as described above, when the surface fastener 10 is turned over with a large force to be peeled from the loop member, the loops of the loop member are smoothly releasable from the engaging elements 20, with the stem portions 21 bending in the cross direction CD. Consequently, during the peeling, the loops of the loop member are less likely to break or be damaged. Therefore, engagement and peeling between the surface fastener 10 and the loop member is stably repeatable. Moreover, such repeated engagement and peeling is less likely to reduce the strength of engagement between the surface fastener 10 and the loop member.

[0120] Furthermore, since the engaging elements 20 are bendable more easily in the cross direction CD as described above, when the surface fastener 10 is strongly pulled to be peeled from the loop member, the flexibility of the stem portions 21 makes the loops of the loop member smoothly disengageable from the engaging elements 20, as described above. Therefore, even if the tear strength of the base part 11 in the cross direction CD is reduced by the stretching, application of a large force to the surface fastener 10 that is in engagement with the loop member allows the engaging elements 20 to be disengaged from the loop member. Thus, the base part 11 is prevented from being torn in the cross direction CD.

[0121] In the surface fastener 10 according to the present embodiment, since each of the engaging elements 20 has a structure that is different between the machining direction MD and the cross direction CD, CD flexibility that is exerted when a part of the surface fastener 10 that extends in the cross direction CD is bent in the up-down direction is higher than MD flexibility that is exerted when a part of the surface fastener 10 that extends in the machining direction MD is bent in the up-down direction, as to be described below.

[0122] Here, a method of measuring the MD flexibility and the CD flexibility of the surface fastener 10 will be described with reference to FIGS. 10 and 11.

[0123] FIG. 10 illustrates a state before a flexibility tester is activated. FIG. 11 illustrates a state after the flexibility tester is activated to push the surface fastener 10.

[0124] To measure the MD flexibility, the surface fastener 10 is cut to make a long test piece 101, which has a greater length in the machining direction MD than in the cross direction CD. On the other hand, to measure the CD flexibility, the surface fastener 10 is cut to make another long test piece 101, which has a greater length in the cross direction CD than in the machining direction MD.

[0125] The test pieces 101 thus obtained are each bent in the thickness direction of the base part 11 to form a loop shape near the lengthwise center of the test piece 101, whereby a loop portion 102 is formed in the test piece 101. In this step, the test piece 101 is bent such that the engaging elements 20 of the surface fastener 10 are located on the inner peripheral side of the loop portion 102. Furthermore, two lengthwise ends of the test piece 101 including the loop portion 102 are brought into contact with each other, whereby a doubled portion 103 is formed. In this step, for example, the test piece 101 is bent such that the loop portion 102 has a length of 100 mm, and the doubled portion 103 has a length of 20 mm or greater.

[0126] The flexibility tester includes a movable member 104, which is movable up and down; a pushing element 106, which is attached to the movable member 104 and is configured to push the loop portion 102 of the test piece 101; a clamp 107, which is configured to secure the doubled portion 103 of the test piece 101; and a load cell 105, which is attached to the clamp 107 and is configured to convert the load into an electric signal.

[0127] The clamp 107 supports the test piece 101 by clamping the doubled portion 103 of the test piece 101 such that the loop portion 102 of the test piece 101 is oriented toward the pushing element 106. In this state, the movable member 104 is moved upward. When the movable member 104 moves upward, the pushing element 106 also moves upward. Therefore, as illustrated in FIG. 11, the pushing element 106 pushes the loop portion 102 of the test piece 101. The movable member 104 is further moved upward to a predetermined position, and then the load cell 105 measures the maximum load within the moved range. Such a measurement of the maximum load was conducted a plurality of times for each of the test piece 101 that is elongate in the machining direction MD and the test piece 101 that is elongate in the cross direction CD, and the respective averages were calculated as the MD flexibility and the CD flexibility. Note that the smaller the averages, the higher the flexibility of the surface fastener 10.

[0128] In the surface fastener 10 according to the present embodiment, as illustrated in FIG. 2, the engaging head 22 of each of the engaging elements 20 has an oval or substantially oval shape that is long in the cross direction CD, whereas the joint part of the stem portion 21 to the base part 11 has an oval or substantially oval shape that is long in the machining direction MD. Furthermore, the occupied areas 27 occupied by the stem portions 21 of the engaging elements 20 in the machining direction MD overlap each other between the engaging-element rows 26 that are adjacent to each other in the cross direction CD. Therefore, the surface fastener 10 according to the present embodiment exhibits a characteristic in which, comparing the measurements of the MD flexibility and the CD flexibility, the CD flexibility shows a smaller value than the MD flexibility; that is, the flexibility of the surface fastener 10 is higher in the cross direction CD than in the machining direction MD. For example, as a result of measuring the CD flexibility and the MD flexibility of the surface fastener 10 according to the present embodiment, the MD flexibility was 0.07, whereas the CD flexibility was 0.05; that is, a smaller value than for the MD flexibility.

[0129] If the surface fastener 10 according to the present embodiment in which the CD flexibility is higher than the MD flexibility is used for, for example, a disposable diaper, the surface fastener 10 attached to the disposable diaper may preferably be oriented in such a manner as to be engaged with or peeled from the loop member in the cross direction CD of the surface fastener 10. In such an orientation, when the surface fastener 10 is made to engage with the loop member of the disposable diaper or when the surface fastener 10 is peeled from the loop member, the surface fastener 10 is easily bendable in the thickness direction (the up-down direction) of the base part 11. Thus, the ease of handling of the surface fastener 10 is increased, and the attaching/detaching of the disposable diaper is facilitated.

[0130] Furthermore, even if the tear strength of the base part 11 in the cross direction CD is reduced by the stretching, application of a large force to the base part 11 allows the base part 11 to bend in the thickness direction (up-down direction). Thus, the base part 11 is prevented from being torn in the cross direction CD. Furthermore, since the value of the MD flexibility of the surface fastener 10 is large, the surface fastener 10 is prevented from being turned up in the MD direction when, for example, the baby is held up or is undressed in such a manner that the clothes and the disposable diaper rub each other.

[0131] The secondary molded body according to the above embodiment is made by performing the primary molding step with the use of the molding device 60 and the secondary molding step with the use of the hot pressing device 70. In the present invention, however, the method and means of molding a molded body to be subjected to the stretching process are not particularly limited. In the present invention, for example, the secondary molding step in which thermal deformation is caused as in the above embodiment may be omitted, and a molded body to be subjected to the stretching process may be made directly in a molding step with the use of a molding device having cavities with which the engaging elements each including the stem portion and the engaging head are moldable.

REFERENCE SIGNS LIST

[0132] 10 surface fastener [0133] 11 base part [0134] 20 engaging element [0135] 21 stem portion [0136] 21a outer surface of stem portion [0137] 22 engaging head [0138] 23 pawl portion [0139] 26 engaging-element row [0140] 27 occupied area [0141] 31 first shape [0142] 32 second shape [0143] 40 primary molded body [0144] 41 tentative base part [0145] 42 primary element (tentative element) [0146] 43 primary stem portion [0147] 44 rib portion [0148] 45 projecting portion (primary pawl portion) [0149] 50 manufacturing apparatus [0150] 60 molding device [0151] 61 die wheel [0152] 62 outer sleeve (outer cylinder) [0153] 62a through-hole [0154] 62b hole row [0155] 62c occupied area occupied by through-hole [0156] 63 inner sleeve (inner cylinder) [0157] 64 driving roller [0158] 65 feeding nozzle [0159] 66 pickup roller [0160] 67 upper nipping roller [0161] 68 lower nipping roller [0162] 70 hot pressing device [0163] 71 upper pressing roller (calender roller) [0164] 72 lower pressing roller (calender roller) [0165] 80 stretching device [0166] 91 cutout piece [0167] 92 supporting member [0168] 93 first test piece [0169] 94 second test piece [0170] 101 test piece [0171] 102 loop portion [0172] 103 doubled portion [0173] 104 movable member [0174] 105 load cell [0175] 106 pushing element [0176] 107 clamp [0177] MD machining direction [0178] CD cross direction [0179] D1 first dimension [0180] D2 second dimension