FASTENING PART, METHOD OF PRODUCING THE SAME, AND MOLD DEVICE

Fastening part includes: a two-dimensional arrangement of engagement elements including a plurality of engagement elements arranged corresponding to a plurality of lattice points of a planar lattice; a plurality of first ribs; a plurality of second ribs, and a plurality of apertures formed in a fastening region in which the two-dimensional arrangement is provided. The first rib connects the engagement elements adjacently arranged in a first direction. The second rib connects the engagement elements adjacently arranged in a second direction that is different from the first direction. The plurality of first ribs and/or the plurality of second ribs is arranged to allow the plurality of apertures to include two or more apertures each having an aperture area corresponding to two or more unit cells of the planar lattice.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims a benefit of Japanese Patent Application No. 2022-091836 filed in Japan on Jun. 6, 2022, the entire content of which is hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present invention relates to a fastening part, a method of producing the same and a mold device.

BACKGROUND

U.S. Pat. No. 7,246,416 discloses a fastening part in which multiple engagement elements are arranged on a base where multiple windows are formed (SeeFIG.1of the same literature).

International Publication No. 2019/107444 discloses a surface fastener entirely formed of thermoplastic elastomer. Plural first strands and plural second strands cross to form multiple holes. The surface fastener is produced through stretching as illustrated inFIG.4of the same literature.

Other types of surface fasteners are also known (e.g. see Japanese Registered Utility Model No. 2586918, and Japanese Patent Application Laid-open No. 3-205001).

In a case where a mold is provided with protrusions to form apertures in a fastening part, the protrusions of the mold would suffer a higher risk of damage proportional to the number of the protrusions in the mold. The lifespan of the mold directly affects the production cost of fastening part, and thus it is desirable to avoid or inhibit the shortened lifespan of the mold.

SUMMARY

Prolonged lifespan of a mold used for production of fastening part may be facilitated by modifying a structure of fastening part, as newly identified by the present inventors.

Fastening part according to embodiment 1 of the present disclosure includes: a two-dimensional arrangement of engagement elements including a plurality of engagement elements arranged corresponding to a plurality of lattice points of a planar lattice; a plurality of first ribs each connecting the engagement elements adjacently arranged in a first direction in the two-dimensional arrangement; a plurality of second ribs each connecting the engagement elements adjacently arranged in a second direction in the two-dimensional arrangement, the second direction different from the first direction; and a plurality of apertures formed in a fastening region in which the two-dimensional arrangement is provided. The plurality of first ribs and/or the plurality of second ribs is arranged to allow the plurality of apertures to include two or more apertures each having an aperture area corresponding to two or more unit cells of the planar lattice.

In some embodiments, (i) the plurality of apertures are formed as net openings in accordance with at least the plurality of first ribs and the plurality of second ribs in the fastening region; and/or (ii) each of said two or more apertures is wider in one direction of the first and second directions and narrower in the other direction of the first and second directions; and/or (iii) each of said two or more apertures has the aperture area corresponding to two or three unit cells in the planar lattice.

In one of or any combination of the above-described embodiments, the unit cell of the planar lattice and/or an aperture shape of the aperture may be square, rectangle, parallelogram or rhombus.

In one of or any combination of the above-described embodiments, the fastening part may further include: a base frame that surrounds the fastening region; and a plurality of third ribs each connecting, to the base frame, the engagement element at outermost position in the two-dimensional arrangement. Embodiment is envisaged where the first rib and/or the second rib is thicker than the base frame, and the third rib is thinner than the first rib and/or the second rib.

In one of or any combination of the above-described embodiments, each engagement element of the plurality of engagement elements may include at least an engagement head and a stem, and the stem may have a T-shaped cross section in a plane parallel to the planar lattice. Embodiment is envisaged where the stem includes a first stem wall connected to the engagement head, the first stem wall having a first width ranging from one end to the other end of the engagement head in one direction of the first and second directions; and a second stem wall connected to the engagement head, the second stem wall having a second width ranging from one end of the engagement head to the first stem wall in the other direction of the first and second directions. The engagement head may include a curved top surface and a flat locking surface located at the opposite side of the top surface.

In one of or any combination of the above-described embodiments, a number of the first ribs may be equal to or less than ⅔ or ½ of a total number of the first ribs allocatable for connection between the engagement elements in the fastening region (or in the planar lattice). Embodiments is envisioned where a number of the second ribs is equal to a total number of the second ribs allocatable for connection between the engagement elements in the fastening region (or in the planar lattice). Density of the engagement elements in the two-dimensional arrangement may be in a range of 2 to 28 elements per cm2. Total number of the apertures in the fastening region may be equal to or greater than total number of the unit cells in the planar lattice.

Mold device according to another aspect of the present disclosure is a mold device configured to produce a fastening part of any one of the above-described fastening parts, the mold device including: a first mold; and a second mold, the first mold including a plurality of recesses that respectively mold at least the engagement heads of the engagement elements in the two-dimensional arrangement, the second mold including a plurality of block portions arranged corresponding to the plurality of apertures, the plurality of block portions including two or more block portions each having an area corresponding to two or more unit cells of the planar lattice. In some embodiments, the plurality of block portions includes plural types of block portions that are different in width and length when a main surface of the second mold is viewed in front, the length orthogonal to the width. The present disclosure also relates to a method of producing fastening parts using the above-discussed mold device.

According to an aspect of the present disclosure, a fastening part may be supplied which may facilitate the prolonged lifespan of mold.

DETAILED DESCRIPTION

Hereinafter, non-limiting embodiments and features of the present invention will be described with reference to drawings. A skilled person would be able to combine respective embodiments and/or respective features without requiring excess description, and would appreciate synergistic effects of such combinations. Overlapping description among the embodiments are basically omitted. Referenced drawings aim mainly for describing inventions and are simplified for the sake of convenience of illustration. The respective features should be appreciated as universal features not only effective to fastening parts presently disclosed but also effective to other various fastening parts not disclosed in the present specification.

Descriptions will be made to a fastening part1with reference toFIGS.1-8.FIG.1is a perspective upside schematic of the fastening part1according to an aspect of the present disclosure.FIG.2is a perspective downside schematic of the fastening part1.FIG.3is a schematic top view of the fastening part1.FIG.4is a schematic bottom view of the fastening part1.FIG.5is an expanded perspective view of a two-dimensional arrangement20of engagement elements2.FIG.6is a schematic end view of the fastening part1, illustrating an end view taken along imaginary line R1, R3, R5extending in row direction inFIG.3.FIG.7is a schematic end view of the fastening part1, illustrating an end view taken along imaginary line R2, R4extending in row direction inFIG.3.FIG.8is a schematic end view of the fastening part1, illustrating an end view taken along imaginary line C1, C2, C3, C4extending in column direction inFIG.3.

The fastening part1is designed to be engageable and disengageable with another fastening part structured identically, i.e. it may be a type of hook-to-hook fastening part. The fastening part1is made of soft and elastic material (e.g. thermoplastic elastomer (TPE)), and has both softness and a capability of retaining its shape (shape stability). In particular, the fastening part1can bend and deflect in accordance with applied external force, but can recover to the initial shape after the applied force is removed. Thus, it would be possible to repeatedly perform engaging and disengaging of the fastening parts1for a long period of time. Typically, the fastening part1is provided with engagement elements which are larger in size relative to male elements of common surface fastener, and its density may be in a range of 2 to 28 elements per cm2for example but should not necessarily be limited to this. Of course, various features in the present disclosure do not premise such a type of the fastening part (i.e. this is not a requisite). Thermoplastic Polyurethane (TPU) and Thermoplastic Styrene (TPS) can be named as example of thermoplastic elastomer usable for the fastening part1, but should not be limited to this.

The fastening part1has a two-dimensional arrangement20of hook-type engagement elements2, a plurality of first ribs31, a plurality of second ribs32, a plurality of third ribs33and a group4A of apertures and a base frame5. In the two-dimensional arrangement20of the engagement elements2, the plurality of engagement elements2is arranged corresponding to a plurality of lattice points of a planar lattice set in a plane PL1. Typically, the planar lattice may be one of square lattice, rectangular lattice, parallelogram lattice and rhombus lattice. Note that a unit cell (a minimum unit) of the square lattice is square. A unit cell (a minimum unit) of the rectangular lattice is rectangle (oblong). A unit cell (a minimum unit) of the parallelogram lattice is parallelogram. A unit cell (a minimum unit) of the rhombus lattice is rhombus. In any type of the unit cells, the respective lattice points are aligned in a first direction and aligned in a second direction that is different from the first direction, resulting in the formation of the two-dimensional arrangement20. The first direction and the second direction may cross at arbitrary angle. In the square and rectangular lattices, the first direction and the second direction are orthogonal. In the parallelogram and rhombus lattices, the first direction and the second direction are not orthogonal and cross at a given angle. Note that it is possible not to arrange the engagement elements2to all of the lattice points of the planar lattice but possible to omit several engagement elements2to be arranged to several lattice points.

FIGS.3and4will be referred for a purpose of clearer and detail descriptions. Square lattice shown inFIGS.3and4is defined by imaginary lines R1to R5parallel to a first direction (a row direction here) and imaginary lines C1to C4parallel to a second direction (a column direction here). Number of the imaginary lines parallel to the first direction may be in a range between 3 to 15. The same applies to the number of imaginary lines parallel to the second direction. The imaginary lines R1to R5are arranged at a constant pitch. The same applies to the imaginary lines C1to C4. In a case of square lattice, the pitch P1of the imaginary lines C1to C4is equal to the pitch P2of the imaginary lines R1to R5, but those pitches could be different if other types of planar lattices were employed. The pitch P1is equal to an interspace between lattice points in the first direction. The pitch P2is equal to an interspace between lattice points in the second direction. Typically, the interspace between the lattice points in the first and second directions is in a range between 1.9 mm to 6.5 mm.

Descriptions will be made with a particular attention to the imaginary lines R1to R5. Nodes between the imaginary line R1and the respective imaginary lines C1to C4are lattice points, and the engagement elements2are arranged on the imaginary line R1at a constant pitch to form a linear arrangement of the engagement elements2along the first direction. The same applies to other imaginary lines R2to R5. As such, a group of linear arrangements of the engagement elements2on the imaginary lines R1to R5form the above-described two-dimensional arrangement20. Descriptions will be made with a particular attention to the imaginary lines C1to C4. Nodes between the imaginary line C1and the respective imaginary lines R1to R5are lattice points, and the engagement elements2are arranged on the imaginary line C1at a constant pitch to form a linear arrangement of the engagement elements2along the second direction. The same applies to other imaginary lines C2to C4. As such, a group of linear arrangements of the engagement elements2on the imaginary lines C1to C4form the above-described two-dimensional arrangement20. Note that every lattice points are in the plane PL1.

Each engagement element2is of a type of hook not a type of loop, and typically includes at least an engagement head6and a stem7. The engagement head6has a curved top surface61and a flat locking surface62located at the opposite side of the top surface61. The top surface61faces upside (in a direction away from the first rib31, the second rib32and the base frame5), and the locking surface62faces downside (in a direction toward the first rib31, the second rib32and the base frame5). For a purpose of simplified molding or for other objects, the engagement head6may be shaped to have a spherical crown or hemisphere which is a shape imaginarily obtainable by cutting a sphere by a plane. The engagement head6has a circular profile when viewed from above as shown inFIG.3, but could have other shapes such as oval, cross and star. Maximum width (or maximum diameter) of the engagement head6in the first and second directions may be in a range of 70% to 95% of the interspace between lattice points in the first and second directions, e.g. in a range between 1 mm to 5 mm. The locking surface62may be a surface parallel to a plane PL1in which the base frame5is arranged or the planar lattice exists.

The stem7may be connected to plural ribs. Moreover, the stem7may have a T-shaped cross section in a plane parallel to the planar lattice or the plane PL1in which the planar lattice exists (SeeFIG.5). This may be a result of that total three ribs are connected to one engagement element2(here, the first to third ribs31,32,33are totally referred to as “rib” as a generic term without distinguishing them). In other words, each engagement element2may be connected to neighboring engagement elements and/or the base frame5via the total 3 ribs. This allows suitable balancing between softness and mechanical strength of the fastening part1. In the illustrated example, this feature is applicable to all of the engagement elements2, but it would be possible to allocate two or four ribs per an engagement element2with respect to several ones of the engagement elements2.

Advantageously, the stem7includes a first stem wall71connected to the engagement head6and having a first width W1ranging from one end to the other end of the engagement head6in one direction of the first and second directions (the second direction inFIG.5); and a second stem wall72connected to the engagement head6and having a second width W2ranging from one end of the engagement head6to the first stem wall71in the other direction of the first and second directions (the first direction inFIG.5). The engagement head6and the stem7are directly connected without a gap as noted above, allowing simplified structure of mold for production of the fastening part1(e.g. use of vertically separable dies only, for example) and/or facilitating the prolonged lifespan of the mold. Note that, the engagement elements2are connected via linear ribs such as the first rib31and the second rib32, ensuring adequate softness of the entirety of the fastening part1.

In a case where the fastening parts1are to be engaged in the up-down direction, the respective top surfaces61of the engagement heads6in the upper and lower fastening parts1are brought into contact, and the fastening parts1would be properly aligned owing to the curved top surfaces61of those engagement heads6(i.e. the top surface61serves as a guide surface for alignment of the fastening parts1). As the upper and lower fastening parts1are engaged, the locking surfaces62of the engagement elements2of the upper and lower fastening parts1are brought into contact (e.g. partial contact). Increase or decrease of the contact area between the locking surfaces62allows modification of locking strength between the fastening parts1per a unit area and modification of force required to engage the fastening parts1per a unit area.

The first rib31connects the engagement elements2(e.g. its stems7) adjacent in the first direction in the two-dimensional arrangement20. The second rib32connects the engagement elements2(e.g. its stems7) adjacent in the second direction, which is different from the first direction, in the two-dimensional arrangement20. The third rib33connects, with the base frame5, an engagement element2(e.g. its stem7) positioned at the outermost position (the outermost circumference) in the two-dimensional arrangement20. Note that, in an embodiment where the base frame5is omitted, the third rib33may also be omitted or may be provided for other purposes than connection to the base frame5.

The first rib31, the second rib32and the third rib33are all linear ribs and arranged in a same plane (e.g. in the plane PL1), and there is no interrelation that one rib is stacked onto another rib. Each first rib31has a predetermined width in the second direction. This predetermined width may be constant over a distance (interspace) between the engagement elements2adjacent in the first direction and connected by the present first rib31. Similarly, each second rib32has a predetermined width in the first direction. This predetermined width may be constant over a distance (interspace) between the engagement elements2adjacent in the second direction and connected by the present second rib32. The third rib33may extend along one of the first and second directions and may have a constant predetermined width similar to the first rib31and the second rib32. Such embodiment allows a portion for molding the locking surfaces62of the engagement heads6to be shaped like a block, thus facilitating simplified structure of the mold.

The group4A of apertures includes a plurality of apertures4formed in a fastening region15(seeFIG.3) where the two-dimensional arrangement20is provided. The plurality of apertures4is formed in the fastening region15, and the engagement elements2are connected by the ribs (particularly by the first and second ribs31and32) in the fastening region15. Each aperture4is a through hole penetrating through a portion of the fastening part1which is positioned in a same layer or in a same plane as the ribs (particularly the first ribs31and the second ribs32), and allows spatial communication between upper and lower spaces relative to the plane where the ribs (particularly the first and second ribs31and32) exist. Note that, in a case where the base frame5is provided, each aperture4penetrates through a portion of the fastening part1positioned in a same layer or in a same plane as the base frame5. Typically, every aperture4is arranged in the plane PL1.

Typically, the plurality of apertures4are formed as net openings (in other words, two-dimensionally and regularly) in accordance with at least the plurality of first ribs31and the plurality of second ribs32in the fastening region15. For example, the plurality of apertures4is formed corresponding to a plurality of unit cells in the planar lattice in which the engagement elements2are arranged at the respective lattice points. Total number of the apertures4in the fastening region15may be equal to or greater than 70% or 80% or 90% of the total number of the unit cells in the planar lattice. This would facilitate reduction of weight of the fastening part1and ensures higher softness of the fastening part1. Each aperture4in the group4A may be formed to have an aperture shape such as square, rectangle, parallelogram or rhombus in accordance with a type of the planar lattice. Each aperture4may be seized to have a same or different aperture area (a size of a net opening). Note that the aperture area of the aperture4indicates an aperture area of the aperture4in a same layer (same plane) as the ribs (particularly the first and second ribs31and32) and/or the base frame5, and it is irrelevant if it is partially covered by the engagement head6of the engagement element2or not. Minimum number of the aperture4which is sufficient to be formed as net openings may be 50% or 60% or 70% of the total number of unit cells in the planar lattice.

The aperture4may be defined by different portions dependent to its location in the fastening region15. For example, an aperture4surrounded by the imaginary lines C1, C2, R2and R4is defined based on that the engagement elements2on each imaginary line R2,R4are connected via the first rib31and the engagement elements2on each imaginary line C1,C2are connected via the second ribs32. Unlike this, an aperture4surrounded by the imaginary lines C1,C2,R2and the base frame5is defined based on that the engagement elements2on the imaginary line R2are connected via the first rib31, the engagement elements2on each imaginary line C1,C2are connected via the second rib32, and furthermore the engagement element2on each imaginary line C1,C2is connected to the base frame5via the third rib33. An aperture4located at a corner of the rectangular fastening region15is defined based on that the engagement element2is connected to the base frame5via a third rib33extending in the first direction and via a third rib33extending in the second direction. As noted above, there are apertures4which do not require the first and second ribs31,32for a purpose of defining of the aperture4but these are few. It would be possible to further modify the shape of these apertures4by changing the shape of the base frame5and changing the length of the third rib33.

Formation of the apertures4as net openings does not require that the apertures4are formed corresponding to all of the unit cells of the planar lattice. For example, it would be possible to seal one or more apertures4by thin portions. The thin portion prevents the mold protrusions from colliding with one another during a process of matching the molds, facilitating the prolonged lifespan of mold protrusions. The thin portion may have a thickness equivalent to that of the base frame5.

Reticulated or mesh structure is built from the two-dimensional arrangement20, the first rib31, and the second rib32(and optionally the third ribs33) in the fastening region15. The base frame5is arranged to surround the fastening region15(also the mesh structure), reinforcing the mechanical strength of the fastening part1while ensuring its adequately high softness. In a case where the base frame5is arranged, the base frame5may be sewn or glued or adhered to an article, allowing easier and simple attachment of the fastening part1to that article. The base frame5includes a pair of frame portions51extending in the first direction and a pair of frame portions52extending in the second direction. The frame portions51are spaced by a constant interspace in the second direction. The frame portions52are spaced by a constant interspace in the first direction. Note that an embodiment is envisaged where the frame portions extend in a direction different from the first and second directions. The base frame5exists in the plane PL1.

Descriptions will be made with reference toFIGS.6to8. The first rib31and/or the second rib32may be formed thicker than the base frame5. This allows suitable balancing of the mechanical strength, softness and sewing-easiness of the fastening part1. Note that the third rib33may be thinner than the first rib31and/or the second rib32, e.g. it may be formed to have a same thickness as the base frame5.

Groove8is formed between two engagement element2adjacently arranged in the first direction, and the groove8extends from an open end interposed between the engagement heads6of those engagement elements2to a bottom end defined by the first rib31. Similarly, a groove8is formed between two engagement element2adjacently arranged in the second direction, and the groove8extends from an open end interposed between the engagement heads6of those engagement elements2to a bottom end defined by the second rib32. The first and second rib31,32are thinned by such grooves8, allowing easier deformation of the engagement elements2and facilitating smoother engagement of fastening parts1.

In the present embodiment as seen in the referenced figures, the plurality of first ribs31and/or the plurality of second ribs32is arranged to allow the group4A of apertures (i.e. a plurality of apertures) to include two or more apertures4each having an aperture area corresponding to two or more unit cells of the planar lattice. This enables higher softness of the fastening part1and reduction of total number of block portions in a mold used for production of fastening part1. Increase in aperture area of the two or more apertures also allows reduction of material cost. In a case where the engagement elements2are used in each of which no gap is formed between the engagement head6and the stem7, the above-described configuration facilitates displacement and deformation of the engagement elements2.

No that, in an illustrated example ofFIGS.3and4, the plurality of first ribs31is arranged to allow the group4A of apertures to include the above-noted two or more apertures4, but the plurality of second ribs32is not arranged as such. A fundamental point lies in omitting (i.e. subtracting) two or more first ribs from the total number of first ribs allocatable for connection between the engagement elements2(or lattice points) adjacent in the first direction with respect to the planar lattice and, additionally or alternatively in omitting (i.e. subtracting) two or more second ribs from the total number of second ribs allocatable for connection between the engagement elements2(or lattice points) adjacent in the second direction with respect to the planar lattice. Note that typically, a single molded portion is used as a rib for connection between the engagement elements2(or the lattice points).

An aperture (referred to as a first aperture) surrounded by the imaginary lines C1,C2,R2,R4has an aperture area corresponding to two unit cells of the planar lattice. Additionally to this aperture, the same holds true to an aperture (referred to as a second aperture) surrounded by the imaginary lines C2,C3,R1,R3, aperture (referred to as third aperture) surrounded by the imaginary lines C2,C3,R3,R5, and aperture (referred to as fourth aperture) surrounded by the imaginary lines C3,C4,R2,R4. Each of the first to fourth apertures is wider in the second direction and narrower in the first direction. It is of course possible to form the first to fourth apertures to be wider in the first direction and narrower in the second direction. Practical benefit lies in a case where the first to fourth apertures each has an aperture area corresponding to two or three unit cells of the planar lattice. That is, in a case where the first to fourth apertures each has an aperture area corresponding to four or more unit cell, there may be a possibility of reduced mechanical strength of the fastening part1outside its permissible extent.

Now referring toFIG.4, the total number of first ribs31allocatable in the fastening region15is 15. In connection to this, the number of first ribs31actually arranged in the fastening region15is 7. That is, a number of first rib31may be equal to or less than ⅔ or ½ of the total number of first ribs31allocatable for connection between the engagement elements2in the fastening region15(or in the planar lattice). Such reduction (i.e. subtraction) in number of first ribs31allows easier formation of aperture having an aperture area corresponding to two or more unit cells. Note that just one first rib31is used for connecting adjacent two engagement elements2.

We now refer toFIG.4for further descriptions, the total number of the second ribs32allocatable in the fastening region15is 16. In connection to this, the number of second ribs32actually arranged in the fastening region15is 16. That is, the number of second ribs32is equal to the total number of second ribs32allocatable for connection between the engagement elements2in the fastening region15(or in the planar lattice). This ensures a desired mechanical strength of the fastening part1despite of the above-described subtraction of the first ribs31. Note that just one second rib32is used for connecting adjacent two engagement elements2.

FIG.9is a schematic perspective view of a fastening device constructed from a pair of fastening parts1,1′ which are made of same material and structured identically.FIG.10is an elevational view of the fastening device illustrating a manner of engagement between the fastening parts1,1′.FIG.11is a cross-sectional view of the fastening device illustrating a manner of engagement between the fastening parts1,1′. With respect to the illustrated fastening parts1,1′ illustrated inFIGS.9-11, the fastening part1would be referred to as a lower part and the fastening part1′ would be referred to as an upper part.

Referring toFIG.11, the upper part1′ is gently pushed down for a purpose of engaging the upper and lower parts1′,1together, the engagement elements2of the upper and lower parts are brought into contact in their respective top surfaces61and the both parts would be brought into proper alignment. As the upper part1′ is pushed down to the lower part1, the engagement element2of the lower part1passes by the engagement head6of the engagement element2of the upper part1′ and enters into the aperture4of the upper part1′, and the engagement elements2of the upper and lower parts1,1′ would be brought into contact each other at their respective locking surfaces62. In that manner, the upper and lower parts1,1′ are engaged. A peripheral end of the upper part1′ may be grasped and pulled away from the lower part1so that the upper and lower parts1,1′ would be disengaged. Note that, in a state shown inFIG.10, the engagement heads of the engagement elements2of the lower part1can be seen by eyes through the apertures4of the upper part1′. As the upper part1′ and the lower part1have been fully engaged, there is an interspace between the plane PL1′ in which the planar lattice of the upper part1′ exists and the plane PL1in which the planar lattice of the lower part1exists. This interspace may be substantially equal to the height of the engagement element2, but not necessarily limited to this. Furthermore as the upper part1′ and the lower part1are equally sized, there are offsets between positions of peripheral rims of the upper and lower parts1′ and1as indicated by the arrows inFIG.11, and they are not stacked in a way to perfectly match one another.

The fastening part1can be produced by injection molding using a mold device built from a first mold100shown inFIG.12and a second mold200shown inFIG.13. For example, the second mold200is a stationary mold, and the first mold100is a movable mold and is moved up and down relative to the second mold200. The first mold100shown inFIG.12has a main surface101formed corresponding to the fastening region15, protrusions103for thinning the third ribs33, a plurality of recesses106each for forming the engagement head6of the engagement element2of the two-dimensional arrangement20, and protrusions108for forming the above-described grooves8in the first and second ribs31and32. The recess106is recessed from the main surface101. The protrusions103and the protrusions108are raised from the main surface101. Step may be formed along the periphery of the main surface101to ensure the thickness of the first and second ribs31and32.

The second mold200shown inFIG.13has a plurality of block portions204arranged corresponding to the plurality of apertures4. Grooves201,202,203are formed between the block portions204to mold the ribs (the first to third ribs31,32,33) and/or the stem walls (the first and second stem walls71and72). Among the block portions204, there are two or more block portions (see204B) included each of which has an area corresponding to the two or more unit cells of the planar lattice discussed above for the fastening part1when the main surface of the second mold200is viewed in front as illustrated inFIG.13. This enables increased strength of the block portions and facilitates the prolonged lifespan of the second mold200.

When the first mold100and the second mold200are matched together, the block portion204is in contact with the main surface101of the first mold100, thereby defining a molding cavity for the fastening part1. Preferably, the plurality of block portions204includes plural types of block portions204which are different in width or length orthogonal to the width when the main surface of the second mold200is viewed in front. This may contribute to satisfy a restriction of the shape of fastening part1additionally to the softness and mechanical strength of fastening part1. Note that each block portion204may have a main block surface (which is rectangular when viewed in front, for example) that will be in contact with the main surface101of the first mold100, and a plurality of sidewall surfaces (e.g.4sidewall surfaces) each extending in a depth direction of the groove from a rim of the main block surface. Here again, the two or more block portions may have respective main block surfaces each having an area corresponding to the two or more unit cells of the planar lattice, enabling the increased strength of the block portions and facilitating the prolonged lifespan of the second mold200. The main block surface may typically be a flat surface. If the aperture shape of the aperture4is modified, then the shape of the block portion204would be modified accordingly. Note that, the sidewall surface of the block portion204may have a draft, i.e. it may be a non-vertical surface with draft but should not be limited to this, and it may be a vertical surface without draft.

Another embodiment will be discussed with reference toFIGS.14-17, but the above-discussed various features and any combination of them would be similarly applicable here.FIG.14is a perspective upside schematic of a fastening part according to another aspect of the present disclosure.FIG.15is a perspective downside schematic of the fastening part ofFIG.14.FIG.16is a schematic top view of the fastening part ofFIG.14.FIG.17is a schematic bottom view of the fastening part ofFIG.14. As shown inFIGS.14-17, the square lattice is set obliquely to the base frame5and as a result of this, the first to third ribs31-33extend obliquely (compared withFIGS.3and4). Even in this embodiment, the subtraction of the first rib31and/or the second rib32enables similar effects as those discussed above.

The fastening part1can be produced in a way other than the injection molding as schematically shown inFIG.18. InFIG.18, the first mold100is provided as a first die-wheel and the second mold is provided as a second die-wheel. Mold structure shown inFIG.12is continuously formed in the circumferential surface of the first die-wheel. Mold structure shown inFIG.13is continuously formed in the circumferential surface of the second die-wheel. The first die-wheel and the second die-wheel are arranged adjacently with a predetermined minimum gap therebetween and controlled to rotate continuously. Molten material is supplied from an extruder300to the interspace between the first and second die-wheels so that the fastening parts1are continuously formed.

Based on the above teachings, a skilled person in the art would be able to add various modifications to the respective features and embodiments. Reference codes in Claims are just for reference and should not be referred for the purpose of narrowly construing the scope of claims.