Surface Fastener and Molding Device

The present invention relates to a surface fastener and a molding device to be used in manufacturing a surface fastener.

Hitherto known surface fastener products include one provided as a combination of a female surface fastener (hereinafter referred to as a loop member) having a plurality of loops and a male surface fastener (hereinafter, the mail surface fastener is simply referred to as a surface fastener) attachable to and detachable from the loop member. The surface fastener includes, for example, a flat base part and a plurality of engaging elements. The engaging elements project from the base part and are each shaped like a mushroom or the like.

Currently, surface fasteners are in wide uses among various products including items to be detachably put on any part of the body: for example, disposable diapers, infant diaper covers, supporters for protecting joints of limbs and the like, waist corsets (belts for lower-back pain), gloves, and so forth. An exemplary surface fastener intended for disposable diapers and the like is disclosed in International Publication No. 2017/109902 (PTL 1).

The surface fastener disclosed in PTL 1 includes a base part and a plurality of engaging elements projecting from the base part. The engaging elements disclosed in PTL 1 each include a stem portion standing from the base part, and a disc-shaped engaging head formed integrally with the upper end of the stem portion. The engaging head has a plurality of microsized pawl portions projecting from the outer peripheral edge of the engaging head.

The surface fastener disclosed in PTL 1 is manufactured by using a manufacturing apparatus. The manufacturing apparatus includes a molding device configured to perform primary molding, and a hot pressing device configured to perform secondary molding. The molding device includes one die wheel configured to rotate in one direction, a feeding nozzle provided facing the outer peripheral surface of the die wheel, and a pickup roller provided on the downstream side relative to the feeding nozzle in the direction of rotation of the die wheel.

The die wheel includes a circular cylindrical outer sleeve serving as a die, a circular cylindrical inner sleeve provided on the inner side of and in close contact with the outer sleeve, and a driving roller configured to rotate the outer sleeve and the inner sleeve in the one direction. The outer sleeve has a plurality of through-holes each extending through the outer sleeve from the outer peripheral surface to the inner peripheral surface thereof. The inner sleeve has a plurality of recesses in the outer peripheral surface thereof. The hot pressing device includes a pair of upper and lower pressing rollers (calender rollers).

The use of such a manufacturing apparatus enables the manufacture of the surface fastener disclosed in PTL 1 that includes a plurality of engaging elements each having microsized pawl portions provided at the outer peripheral edge of an engaging head thereof.

On the other hand, in a known method of manufacturing a male surface fastener, a twin-roll molding device is used instead of the above molding device including a single die wheel. The twin-roll molding device includes a die wheel having a plurality of cavities in the outer peripheral surface thereof, and a pressing wheel provided facing the die wheel.

In a case where the twin-roll molding device is used, molten synthetic resin is fed from a feeding nozzle toward the gap between the die wheel and the pressing wheel that face each other. Thus, a base part is molded between the die wheel and the pressing wheel, and engaging elements (or primary elements to be molded into engaging elements) are molded on the outer peripheral surface of the die wheel. Therefore, the surface fastener is manufacturable continuously.

In the case of manufacturing a surface fastener by using the above twin-roll molding device, the die wheel and the pressing wheel are capable of molding a base part that is thinner than that obtained in, for example, the manufacturing method disclosed in PTL 1. In the case of using the twin-roll molding device, however, it is more difficult to fill the plurality of cavities in the outer peripheral surface of the die wheel with a molten synthetic resin than in, for example, the manufacturing method disclosed in PTL 1. Accordingly, the above microsized pawl portions cannot stably be formed on each of the engaging elements. Therefore, it has been difficult for the twin-roll molding device to manufacture the surface fastener disclosed in PTL 1 that includes engaging elements having microsized pawl portions.

On the other hand, in the case of manufacturing a surface fastener by feeding synthetic resin from a feeding nozzle toward a single die wheel as disclosed in PTL 1, it is more difficult to obtain in the primary molding process a molded body having a thin base part than in the case of using the twin-roll molding device. Consequently, the flexibility of the surface fastener is reduced. Moreover, such a method may hinder the reduction in the weight and cost of the surface fastener.

Hence, to manufacture a surface fastener including a thin base part by using a molding device including a single die wheel, another technique has been examined in recent years in which after a molded body (primary molded body) including a base part is molded by using a molding device, the base part of the molded body thus obtained is subjected to, for example, a stretching process in which the base part is stretched in a machining direction (MD) so as to be thinned.

In the case where, however, the molded body (primary molded body) obtained by using the molding device disclosed in PTL 1 is subjected to a stretching process to be performed in the machining direction (MD), since the base part is pulled in the machining direction in a stretching device, the base part may break in the machining direction.

In the surface fastener manufactured through the stretching process performed in the machining direction, the tear strength of the surface fastener in a cross direction (CD) may be reduced. For example, if a force is applied to the base part of such a surface fastener, cross-direction tear in which the base part is torn in the cross direction may occur. Therefore, when, for example, such a surface fastener intended for a disposable diaper or the like is pulled to be made to engage with the loop member of the disposable diaper so that the state of fitting of the diaper is retained, the base part obtained through the stretching may be torn or break in the cross direction. Note that the cross direction (CD) refers to a direction orthogonal to the machining direction (MD), which is defined for the manufacturing process.

The above problem has triggered a demand for the development of a surface fastener in which the structure, the strength, or any other relevant factor is made different between the machining direction (MD) and the cross direction (CD).

The present invention has been conceived in view of the above problem in the known art, and an object of the present invention is to provide a surface fastener having a structure and/or characteristic that is different between the machining direction and the cross direction, and a molding device to be used in manufacturing such a surface fastener.

To achieve the above object, the present invention provides 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. The surface fastener is characterized in that 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.

In the surface fastener according to the present invention, it is preferable that an upper half part of the stem portion in the second shape include a part where the outer surface facing the machining direction is formed straightly or substantially straightly, and that 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.

Another embodiment of the present invention provides 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. The surface fastener is characterized in that 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 of the stem portion 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.

Yet another embodiment of the present invention provides 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. The surface fastener is characterized in that 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.

In the surface fastener according to the present invention, it is preferable that the plurality of engaging elements be arranged in a line at a regular pitch in the machining direction to form an element row, that a plurality of element rows be arranged at a regular interval in the cross direction, that the engaging elements in each of the element rows be 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 that in regard to the machining direction, the engaging elements be 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.

Furthermore, in the present invention, it is preferable that 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.

The present invention further provides 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. The molding device is characterized in that the die wheel includes at least one circular cylindrical sleeve and a driving roller configured to rotate the sleeve, that 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, that the plurality of through-holes are arranged in a line at a regular hole pitch in a machining direction to form a hole row, that a plurality of hole rows are arranged at a regular interval in a cross direction that is orthogonal to the machining direction, that 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 that 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.

According to the present invention, a surface fastener having a structure and/or characteristic that is different between the machining direction and the cross direction is provided.

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.

is a copy of a photograph of a part of a surface fastener according to the present embodiment that is taken from above.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.

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.

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.

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.

A surface fasteneraccording to the present embodiment is, as to be described separately below, manufactured by using a manufacturing apparatus, illustrated in, into a shape that is elongate in the machining direction MD of the manufacturing apparatus. The manufacturing apparatusincludes a molding device, a hot pressing device, and a stretching device.

The surface fasteneris 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 fasteneris not particularly limited. The surface fastenermay be made of, for example, a biodegradable resin, a plant-derived resin, or a recycled thermoplastic resin.

As illustrated in, the surface fastenerincludes a thin flat base partand a plurality of engaging elements. The engaging elementsproject from the upper surface of the base partand are each shaped like a mushroom. The base partis elongate in the machining direction MD defined for the process of manufacturing the surface fastener. The base parthas a certain thickness that provides an appropriate strength and an appropriate flexibility. The upper surface (first surface) of the base partand the lower surface (second surface) that is located opposite the upper surface are flat or substantially flat and extend parallel to each other.

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

Here, the shape of the stem portionthat is taken when the engaging elementis seen in the machining direction MD is defined as a first shape,, of the stem portion; and the shape of the stem portionthat is taken when the engaging elementis seen in the cross direction CD is defined as a second shape,, of the stem portion. Under such definitions, since the stem portion(particularly, the lower half part of the stem portion) of each engaging elementis 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, the first shape(see) of the stem portionand the second shape(see) of the stem portionare different from each other.

In the engaging elementaccording to the present embodiment, the first shapeand the second shapeof the stem portionare different from each other mainly in the lower half part of the stem portion. In the lower half part of the stem portionin the first shapeis thinner than the lower half part of the stem portionin the second shape. Therefore, when, for example, the engaging elementreceives a force from above, the engaging elementis 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 portionrefer to, when the stem portionis divided at the center position in the height direction thereof, a part that is farther from the base partthan the center position and a part that is closer to the base partthan the center position, respectively.

The shape of the stem portionwill further be described specifically. In the front view () or rear view of the engaging elementthat is see in the machining direction MD, the stem portionhas the first shape, in which the stem portionhas outer surfacesfacing 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 portionthat adjoins the engaging headto the lower end (a joint part) of the stem portionthat adjoins the base part. Furthermore, in the first shapeof the stem portion, the outer surfacesof the stem portionthat face the cross direction CD each form an angle of about 95° with respect to the upper surface of the base part. In the first shape, the angle between each of the outer surfaces of the stem portionthat face the cross direction CD and the upper surface of the base partis not limited to the above.

Furthermore, in the first shapeaccording to the present embodiment, the outer surfacesof the stem portionthat face the cross direction CD may each include a curved part where the outer surfaceis curved in the up-down direction to be concave in, for example, a lower part of the stem portionthat is near the base part. In such a structure, the straight or substantially straight part of each of the outer surfacesin the first shapemay preferably occupy 50% or greater, more preferably 60% or greater, of the lower half part of the stem portionin the up-down direction.

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, 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 portionincludes 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 surfacesof the stem portionthat 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, the outer surfaceis regarded as having a straight or substantially straight shape as long as the outer surfaceextends straightly or along a nearly straight line.

On the other hand, in a side view () of the engaging elementthat is seen in the cross direction CD, the stem portionhas the second shape, in which the stem portionhas outer surfacesfacing the machining direction MD. Furthermore, the second shapeincludes a part where the outer surfacesextend straightly or substantially straightly, and a curved part where the outer surfaceseach extend while curving in the up-down direction to be concave. In the second shape, the part where the outer surfacesof the stem portionthat face the machining direction MD extend straightly or substantially straightly mainly occupies the upper half part of the stem portionand over an area shorter than the straight or substantially straight part of the first shapeillustrated in. In the second shape, the curved part where the outer surfacesof the stem portionthat face the machining direction MD are curved mainly occupies the lower half part of the stem portion. The curved part of each of the outer surfacesin the second shapemay preferably occupy 30% or greater, more preferably 40% or greater, of the lower half part of the stem portionin the up-down direction. If, for example, the first shapehas a curved part at the lower end thereof, the curved part of each of the outer surfacesin the second shapeoccupies an area longer than the curved part in the first shape.

The outer surfacesin the first shape, illustrated in, that face the cross direction CD define a shape similar to the shape defined by the upper halves of the outer surfacesin the second shape, illustrated in, that face the machining direction MD. For example, in the upper half part of the stem portionin the second shape, the outer surfacesof the stem portionthat 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. On the other hand, in the lower half part of the stem portionin the second shape, a part of each outer surfaceof the stem portionthat is near the base partform an angle of about 160° with respect to the upper surface of the base part. In the second shape, the part where the outer surfacesof the stem portionthat face the machining direction MD extend straightly or substantially straightly is disposed an area of ½ or greater and ¾ or smaller of the total height dimension of the stem portionin the second shape(the dimension in the up-down direction from the upper surface of the base partto the upper end of the stem portion).

Comparing the first shape() and the second shape() of the stem portion, the lower half part of the stem portionin the second shapehas a thickness that is varied significantly in such a manner as to increase toward the base partas illustrated in, more than the thickness of the lower half part of the stem portionin the first shape.

In the first shape, the outer surfacesof the stem portioneach extend straightly or substantially straightly to the lower end of the stem portionthat joints the base part, and a boundary part between the straight or substantially straight outer surfaceand the upper surface (front surface) of the base partbents sharply by an angle near 90° (substantially) 95°.

In contrast, in the second shape, the outer surfacesin the lower half part of the stem portionare each curved gently and widely, and the inclination of each of the outer surfacesof the stem portionbecomes gentler toward the base part. Therefore, the outer surfacesof the stem portionin the second shapeare smoothly continuous with the surface of the base part.

In each of the engaging elements, the upper half part of the stem portionhas a substantially circular columnar shape. Therefore, the outer peripheral surface of the upper half part of the stem portionhas 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 portionis formed so that a section of the upper end part of the stem portionorthogonally to the up-down direction has a circular or nearly circular (substantially circular) shape.

The joint part of the stem portionto the base part(that is, the lower end of the stem portion) 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.

Here, regarding the joint part of the stem portion, the length of the joint part in the cross direction CD with the engaging elementseen in the machining direction MD is defined as first dimension D, and the length of the joint part in the machining direction MD with the engaging elementseen in the cross direction CD is defined as second dimension D. Under such definitions, the stem portionis shaped such that the second dimension Dof the joint part in the second shapeis greater than the first dimension Dof the joint part in the first shape. The second dimension Dof the joint part in the second shapehas a length that is, for example, 1.5 to 2 times the first dimension Dof the joint part in the first shape.

In the present embodiment, the plurality of engaging elementsare regularly arranged in a staggered pattern on the upper surface of the base part. Specifically, the engaging elementsare arranged at a regular pitch in the machining direction MD (the front-rear direction), thereby forming a plurality of engaging-element rows. The plurality of engaging-element rowsare arranged at a regular interval in the cross direction CD (the left-right direction). The engaging elementsin each of the engaging-element rowsare shifted by ½ of the pitch in the machining direction MD relative to the engaging elementsin another one of the engaging-element rowsthat is adjacent in the cross direction CD. Thus, the plurality of engaging elementsin the engaging-element rowsthat are adjacent to each other in the cross direction CD are positioned alternately or in a zigzag manner.

As illustrated in, the plurality of engaging elementsare arranged at positions such that occupied areas, which are occupied by the respective stem portionsof the engaging elementsin regard to the machining direction MD, include portions that overlap each other between the engaging-element rowsthat 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 portionof each engaging elementis 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 portionof another engaging elementin another engaging-element rowthat is adjacent in the cross direction CD.

According to the present embodiment, the strength of the base partin the machining direction MD is effectively increased because the surface fastenerhas at least one of the following features: (1) the second shapeof the stem portionobtained by viewing the engagement elementfrom the cross direction CD includes a part where the outer surfacesof the stem portionis curved, and the second shapeis thicker than the first shapeof the stem portionobtained by viewing the engaging elementfrom the machining direction MD; (2) the joint part of the stem portionjointing to the base partis formed to have an oval or substantially oval shape in which the second dimension Din the machining direction MD is greater than the first dimension Din the cross direction CD; and (3) in the staggered arrangement of the engaging elements, the occupied areasoccupied by the stem portionsof the engaging elementsin the machining direction MD overlap each other between the engaging-element rowsthat are adjacent to each other in the cross direction CD. Therefore, for example, it is less likely for the base partto cause a defect, such as breakage, when the base partis pulled and stretched in the machining direction MD in a stretching process of forming the base partduring the process of manufacturing the surface fastener.