HK1056669B - Metal wire rod for forming slide fastener coupling elements - Google Patents

Description

Metal wire for making zipper teeth

Technical Field

The present invention relates to a metal wire for a slide fastener, generally called Y wire, from which a fastener element is made.

Background

In recent years, the market of slide fasteners has been globalized, and customers have attempted to purchase products manufactured in areas where the production cost is low. In this trend, the price competition of the product is accelerated. Therefore, further improvement in quality is required so that the product value thereof is in the interest of customers. In order to manufacture a slide fastener which is lower in price and higher in quality than conventional products, attention must be paid to the correctness of individual elements constituting the slide fastener, and particularly, a metal element having a slide fastener opening/closing function has a strong demand for reduction of labor cost and material cost, as well as mounting strength.

Conventionally, there are three main methods for manufacturing such a metal element, which are a pressing method in which a flat wire is produced by pressing, a molding method in which a mold is used for production, and a Y-wire method in which a metal wire having a substantially Y-shaped cross section is cut to a predetermined thickness. According to the Y-wire method, a cut fastener element includes a head and a pair of legs extending from the head through an intersection point and having coupling projections formed by a punching head.

In order to form a metal wire material having a Y-shaped cross section for forming a fastener element, a common metal wire material is rolled into a circular cross section, and the metal wire material is deformed into a Y-shaped cross section by a Y-wire method. This method ensures higher strength and no waste material, as compared with the production of a metal fastener element by pressing from a flat plate. In addition, since it is suitable for mass production, the production of the metal element by the Y-wire method is the most reasonable production method.

In manufacturing the metal fastener element by the Y-wire method described above, the metal wire material of circular cross section for manufacturing the fastener element is intermittently fed with the wire material of circular cross section at predetermined intervals, and is subjected to multi-stage rolling to produce a substantially Y-shaped cross section. The particular profile of the left and right legs is formed to be splayed. The cut elements have claws projecting inwardly from the front end of each leg.

The thus obtained wire rod having an irregular shape is fed at a pitch corresponding to the thickness of each element, and when feeding of one pitch is completed, feeding is stopped so that the wire rod protrudes by the thickness of the element at the front end stop position on the cutting die. At this time, the projecting portion of the wire rod is cut off by the cutting punch, and at the same time, the cut-off fastener element material is fed from the cutting die to the forming die. The forming punch acts on the head of the element material mounted on the forming die to form a coupling projection on the head, which is called ramp forming.

On the other hand, on the leg side of the element material subjected to the slope forming as described above, the fastener tape is fed at each element mounting pitch at a predetermined interval in relation to the element material such that the edge portion of the fastener tape where the elements are mounted faces the intersection between the two legs. After the ramp formation is completed, the fastener elements are directed toward the element mounting edge portion of the fastener tape so that the element mounting edge portion is gripped by the pair of legs which are opened outward. At this time, the caulking punch is started to inwardly converge the pair of legs, thereby completing the setting work of the fastener chain to the fastener tape.

Such an element material obtained by cutting the above-mentioned metal wire material having a Y-shaped section used as an element has been disclosed, by way of example, in japanese utility model laid-open publication No.51-13903, japanese patent application laid-open publications nos. 6-217810 and 8-56714, and korean patent laid-open publication No. 20-229751. According to these publications, the inner surface of the crossing of the element is formed into a circular or flat plane, and the inner surface of each of the left and right legs, which are symmetrically spread and connected to the crossing, is formed into a curved surface or plane, because it is desirable that the entire leg is uniformly curved when the legs converge.

As pointed out in the above-mentioned japanese patent application laid-open No.8-56714 and korean patent publication No.20-229751, the open angle of the left and right legs must be very large because the attachment strength of the fastener element to the fastener tape depends on the engagement strength of the claws projecting inward from the front ends of the left and right legs, which is based mainly on the projection length of the claws and the intersection angle of the claws with respect to the extending direction of the legs. Therefore, the opening angle between the left and right legs is required to be considerably large.

Generally, the multi-stage rolling method applied to the metal wire rod is performed by using a plurality of rolling rolls which are arranged to surround the wire rod. After the rolling process is completed, the respective rolls are removed from the middle of the wire. If the claws protrude beyond the end face of the roll, the claws will interfere with the end face of the roll as it moves away from the claws, thereby preventing the roll from moving apart. To avoid this interference, the inner surfaces of the jaws are designed to be parallel to the end surfaces of the rolls, with the result that the left and right legs must be spread apart to a greater extent. The conventional leg opening angle is therefore about 92 °.

In addition, in terms of the strength of the conventional fastener element material, the strength of all portions including the head and the leg is substantially equal because the metal wire rod is formed by changing its outer shape and sectional shape through a multi-stage rolling process.

When the intersections of the metal fastener elements and the inner surfaces of the legs are only flat or curved as described above, uniform positioning accuracy cannot be obtained when the same metal wire rod is deformed by rolling. Therefore, it is difficult to machine the entire shape of the element symmetrical with respect to the center line connecting the center of the head and the midpoint of the straight line connecting the front ends of the pair of legs. In addition, when the coupling element having such a configuration is attached to the fastener tape by converging the legs from the outside by the caulking punch, the legs cannot be bent equally from the intersection. In addition, the element may rotate relative to the head, so that the element is often not accurately mounted at a symmetrical position of the element-mounting portion of the clip fastener tape.

In particular, if the opening angle of the right and left legs extending from the intersection is as large as that of a conventional metal fastener element, the mounting position of the fastener element on the fastener tape is unstable, so that the fastener element may rotate about its head, which causes a decrease in productivity. Therefore, the opening angle should be as small as possible.

On the other hand, from the viewpoint of the mounting strength of the fastener tape to the element, the head of the element is not directly related to the mounting strength, but the left and right legs are directly related to the mounting strength, which depends on the shape and strength of the legs, and therefore, it is only the head of the element that can reduce the amount of material. However, if the element head is reduced, the strength of the intersection between the head and the leg is greatly reduced when it is attached to the fastener tape by the converging leg portion because the width dimension of the intersection is reduced due to the deformation of the leg.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a metal wire material which can reduce material, ensure mounting strength to a fastener tape and strength of an entire element, and make an element having such a configuration and strength that can stabilize a mounting position of the element to the fastener tape.

Disclosure of Invention

The present inventors have considered that reducing the amount of material per element directly results in a reduction in material costs, but results in a reduction in element installation strength. In addition, the mounting strength depends on the stability of the mounting position of the fastener tape to the fastener element and the magnitude of the inner surface pressure of the leg against the core wire portion extending along the fastener tape element mounting portion. In order to reduce the material of the fastener element and to secure the mounting strength, it is not necessary to pay much attention to the material of the metal wire and the sectional shape of the fastener element.

The present invention is made by aiming at the shape of the leg portion of a metal wire material forming a fastener element. According to a first aspect of the present invention, there is provided a metal wire material forming a fastener element, having a head portion and a pair of leg portions extending from the head portion through an intersection portion, and having a Y-shaped cross section; the method is characterized in that: three or more bent portions bent inward are formed one by one on the inner surfaces of the claw portions from the intersection portion to the front end of each leg portion in the extending direction of the leg portion, each claw portion protrudes inward from the front end of the leg portion, and the gap between the inner surfaces of the claw portions becomes narrower gradually from the base end portion to the front end thereof.

According to this aspect of the present invention, the multistage bent portions are formed one by rolling on the inner surface extending from the intersection of the metal wire rods to the claw portion on the front end of the leg portion in the leg portion extending direction. The multi-stage bent portion thus has a function of positioning the wire when rolling. The sectional shape of the wire can be always symmetrical with respect to a plane obtained by connecting the center point of the straight line connecting the front ends of the left and right leg portions of the wire and the center of the head.

In addition, another aspect of the present invention is obtained by paying attention to the fact that the claw portions protrude inward from the front ends of the wire leg portions. More specifically, according to a second aspect of the present invention, there is provided a metal wire material for forming a fastener element, having a head portion, a pair of leg portions extending from the head portion through an intersecting portion, and claw portions projecting inwardly from front ends of the leg portions; the wire has a substantially Y-shaped cross-section characterized by: the gap between the inner surfaces of the claw portions is gradually narrowed from the base portion to the tip portion of the claw.

The inner surfaces of the left and right claw portions projecting from the front end portions of the conventional metal wire leg portions are designed to be parallel to each other for the convenience of rolling processing. Therefore, when the element obtained by cutting the element forming metal wire material having such a pawl portion configuration is mounted on the fastener tape by converging the legs, its mounting strength is insufficient unless its converging angle is set large. However, if the convergence angle is set to be large, the amount of convergence of the left and right legs is inevitably increased, which causes unnecessary load to be applied to the fastener tape, thereby causing a risk of damaging the tape. In contrast, according to the present invention, the gap between the inner surfaces of the left and right claw portions becomes gradually narrower toward the front ends thereof, and therefore, the claws can bite into the fastener tape as much as or more as the conventional fastener elements at the converging leg portions at a smaller curl angle than the conventional one, or at a converging angle equal thereto. Therefore, higher mounting strength than that required for the fastener element can be obtained without damaging the fastener tape.

The claw portions preferably protrude inward from the front ends of the left and right leg portions, and a bent portion between an inner surface of the leg portion and an inner surface at a base end portion of the claw portion is located outside a straight line passing through the front ends of the claw portions, the straight line being parallel to a straight line (center line) connecting a midpoint of a straight line connecting the front ends of the left and right claw portions and a center of the head portion.

Specifically, the claw portion protrudes from each leg portion such that a bent portion between an inner surface of the leg portion and an inner surface of a base end portion of the claw portion is located outside a plane passing through front ends of the claw portions, the plane being parallel to a plane connecting a center point of a straight line connecting front end points of the left and right claw portions and a center of the head portion. As a result, when the element obtained by cutting such a metal wire material is attached to the fastener tape by the convergence method, the claw of the element bites into the fastener tape at a sharp corner provided on the element. Therefore, even when a lateral force is applied to the slide fastener, the fastener elements do not slip out of the fastener tape, which can maintain a stable mounted state of the fastener elements.

Further, the opening angle between the pair of leg portions on the left and right sides is preferably 75 ° to 85 °. As described above, the opening angle between the conventional leg portions is about 92 °. The reason why the opening angle is required is that the inner surfaces of the left and right claws need to be set parallel to each other and a predetermined biting angle for the fastener tape at the time of convergence needs to be secured. The opening angle of the leg portion must be large.

On the other hand, according to the present invention, since the inner surfaces of the left and right pawl portions are moved closer to the front ends, the above-mentioned biting angle required for the fastener element can be easily obtained even when the leg opening angle is increased by the amount of the movement. If the spread amount of the leg portion is reduced, the fastener elements are unlikely to rotate on the fastener tape even when converging. Therefore, its mounting position can be stabilized to be mounted to the fastener tape in a well-balanced state.

In addition, the outer side surface of the connecting portion of the head and the leg portion has a projecting portion projecting outward therefrom. In the case where the outer surface of the connecting portion between the head portion and the leg portion is made flat as in the conventional wire material, since the outer surface of the leg portion is pulled when the leg portion is converged, the outer surface of the connecting portion is recessed inward to thin the connecting portion, so that the strength of the connecting portion is reduced, the attaching strength of the connecting portion to the fastener tape is reduced, and the predetermined strength is not achieved.

In contrast, according to the present invention, since the bulge or the thick portion is formed on the connecting portion between the wire head and the leg portion, even if the thick portion on the connecting portion is pulled upon subsequent convergence or volume reduction, the reduced portion can be supplemented by the thick portion, and thus the connecting portion can be prevented from being narrowed. Therefore, the strength of the connecting portion is prevented from being reduced, so that the mounting strength of the fastener tape is not reduced.

Further preferably, at least the connecting projection forming portion of the head portion has a rigidity lower than that of the leg portion. If the head portion is less rigid than the leg portion or is made softer, the coupling projection of the fastener element head to be obtained later can be easily formed to a desired height. Therefore, since the nose has a desired height, the engagement strength between the coupling elements can be improved. In addition, the load applied to the forming punch and forming die used for forming the coupling boss can be reduced, and therefore the life of the boss forming punch and die can be extended.

Drawings

Fig. 1 is a perspective view partially showing the configuration of an exemplary metal wire embodiment forming a fastener element of the present invention.

Fig. 2 is a plan view showing a section of a metal wire and an outer shape of a fastener element obtained from the wire.

Fig. 3 is a partial sectional view showing a state in which the coupling element of the present invention is mounted on the fastener tape, the coupling element being obtained from a metal wire material.

Fig. 4 is a plan view of fig. 3.

Fig. 5 is a partial sectional view showing a mounted state of elements according to a modified example of the elements of the present invention on a fastener tape.

Fig. 6 is a partial sectional view showing a mounted state of a fastener element of another modified example of the present invention on a fastener tape.

Fig. 7 is a longitudinal sectional view partially showing a coupling state of elements along a fastener tape.

Fig. 8 is an explanatory view for explaining the action of the coupling projection along the element row in the coupled state when a rotational force with respect to the coupling center is applied to the fastener tape.

Detailed Description

Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a perspective view of a part of a metal wire material forming a fastener element taken out from a leg side, which shows a first embodiment of the present invention. Fig. 2 is a plan view showing a cross section of the same wire rod, showing an outer shape of the fastener element obtained by cutting the same wire rod.

Fig. 1 and 2 show a metal wire 10, which is a material forming a metal fastener element. Generally, the wire 10 is not formed by extrusion or drawing, but is formed by multi-stage rolling of a circumferential surface having a circular cross section, deforming it to have a cross-sectional shape as in fig. 1. The wire 10 forming this embodiment includes, as with a conventional metal wire, a head portion 11 cut out to become a connecting head 21, a pair of left and right leg portions 13 extending from the head portion 11 through an intersecting portion 12 so as to flare outwardly, and a claw portion 14 projecting inwardly from each leg portion and intersecting the leg portions 13.

After the wire 11 having such a configuration is cut to a predetermined thickness, a coupling boss 21a is formed at the center of the coupling head 21, and the boss 21a serves as the coupling element 20. The coupling elements 20 are mounted along the element mounting portions on each of the opposite side edge portions of the fastener tape (not shown), with the result that a fastener chain can be produced.

The member of the above-described metal wire rod 10 of the present embodiment has five features as follows:

(1) the inner surface of each of the left and right leg portions 13 that open from the intersection portion 12 has a plurality of bent portions 13a, 13b that are bent inward, and a bent portion 14a of a claw portion 14 that protrudes from the front end portion of each leg 23 so as to be bent inward. The plurality of bent portions 13a, 13b and the bent portion 14a form a plurality of steps in the extending direction of the leg portion 13.

(2) The inner surfaces of the claw portions 14 projecting inward from the front end portions of the pair of leg portions 13 are not parallel to each other but inclined so as to approach each other toward the end portions thereof. I.e., when passing the front end O of each of the left and right claw portions 14₂Drawing a line parallel to the center O of the cross-section taken through the head 11₁And front ends O of the left and right claw parts 14₂Straight line L of₁Midpoint O of₃Line L of connection₂At this time, the claw portion 14 is projected inward so that a wide bending point between the leg portion 13 and the base end portion of the tab of the claw portion 14 is located on the straight line L₃Outside of (a).

(3) The opening angle of the left and right leg parts is set to 75-85 degrees, which is smaller than the traditional angle.

(4) A slightly outwardly projecting protrusion 12a in the shape of a hill is formed on the outer surface of the intersection 12 of the connecting head 11 and the left and right leg portions 13. I.e. the thickness of the intersection 12 increases locally outwards.

(5) Although not shown in the drawings, the rigidity of the middle portion of the head portion 11 is set lower than that of the leg portion 13.

In the present invention, any of these structures may be used alone or in combination as appropriate.

The bent portions 13a, 13b, 14b described in the above structures (1) and (2) may be formed with rolling rolls of various circumferential surface shapes at the time of rolling the metal wire rod 10. The structure of the claw portion 14 as described above protruding from the leg portion to be bent inward can be obtained by rolling the inner surfaces of two claw portions 14 parallel to each other as in a conventional method and then bending the claw portions 14 with respect to the leg portion 13. The structure described in (5) can be achieved by local quenching as an example. Of course, other methods of manufacture, such as rolling, can provide different stiffness.

In the metal wire material 10 forming the fastener element of the present embodiment having the above-described characteristic structure, the plurality of curved surfaces 13a, 13b curved inward are formed one by one from the intersection 12 to the front end of the leg portion 13 by rolling processing on the basis of the above-described structure (1), and these curved portions are positioned on the wire material 11 while rolling the wire material 11. Thus, a precisely symmetrical configuration of the wire 10 with respect to a plane in which the wire 10 extends longitudinally can be obtained, the opposite plane being a plane connecting the front ends O of the left and right claw portions₂、O₂Straight line L of₁Midpoint O of₃From the center of the head 11. Therefore, the fastener element 10 obtained by cutting the wire 10 is positioned with respect to the straight line L as shown in fig. 2₂And is precisely symmetrical so that the mounting position of each element can be stabilized when the elements are mounted to the fastener tape.

According to the structure in (2), the inner surfaces of the left and right claws 14 projecting inward to intersect with the front ends of the leg portions are not designed to be parallel to each other so as to avoid interference with one end surface of the roll as in the conventional metal wire rod, but according to the present invention, the inner surfaces of the left and right claws 14 are formed to project toward each other by a small gap, and the extending portions in the direction of the front ends intersect with each other. That is, each claw portion 14 is bent such that a bent portion 14a wider between the inner surface of the leg portion 13 and the inner surface of the base end portion of the claw portion 14 is located outside a plane passing through the front end of the claw portion 14 and parallel to the front end O connecting the left and right claw portions 14₂，O₂Middle point O of the straight line of (1)₃And the center O of the head 11₁The resulting plane has a bend angle α of 10 ° or less, preferably about 3 to 7 °. Therefore, the gaps between the inner surfaces of the claw portions 14 opposed to each other are different, but the gaps between the inner surfaces of the claw portions 14 gradually narrow from the base ends to the leading ends of the claw portions 14.

With such a structure, when the fastener elements obtained by cutting the metal wire material 10 are attached to the fastener tape by the convergence method, the claws bite into the fastener tape at sharp corners with respect to each of the fastener elements. As a result, even when a force pulling the element in the direction of pulling away the fastener tape, that is, a lateral force is added, the element never comes off from the fastener tape, and therefore stable attachment strength can be secured.

On the other hand, according to the present embodiment, if the angle θ between the left and right leg portions 13 is set not to be larger than 92 ° as conventionally but to be smaller such as 75 ° to 85 ° as explained in the configuration (3), the coupling element made by cutting becomes less rotated on the fastener tape at the time of convergence. Thus, the mounting position of the fastener elements is stabilized, so that not only can the fastener elements be easily mounted to the fastener tape in a well-balanced state, but also a desired engagement angle of the claws can be easily obtained, thereby further enhancing the mounting strength.

According to this embodiment, as in the structure (4), the head portion 11 and each of the left and right leg portions 13 are connected in an outward hill shape by the projection 12a formed by projecting from the outer surface of the intersection 12. In the case where the outer surface of the connecting portion between the head portion and the leg portion is a flat surface as in the conventional fastener element, the leg portion of the fastener element obtained from the wire material is deformed and bent inward when the leg portion is converged by the convergence punch, and as a result, the outer surface is stretched in the connecting portion, and therefore the outer surface of the connecting portion is recessed inward, thereby thinning the connecting portion. Therefore, the strength of the connecting portion is reduced, and the coupling elements are warped on the connecting portion, thereby greatly reducing the mounting strength of the fastener tape.

In contrast, according to the present embodiment, on the connecting portion between the head portion 11 and the leg portion 13 of the metal wire 10, a convex portion 12a, i.e., a thicker portion, is formed on the outer surface of the intersection portion 12. Therefore, when the fastener element 20 is mounted to the fastener tape, the projecting portion formed on the outer surface of the intersection 22 is pulled, and therefore, even if the thickness is reduced, the thickness reduction is complemented by the thick portion, and therefore, the connection portion never suffers from a strength drop, and therefore, the mounting strength of the fastener tape is secured.

If the rigidity of at least the coupling projection forming the head region is set to be smaller than that of the leg portion as in the structure (5), the rigidity of the head 21 of the fastener element 20 obtained later is smaller than that of the leg 23. When the legs 23 have a normal stiffness, the head 21 is soft and easily deformed. Therefore, when the rigidity of the leg portion is ensured, the coupling boss 21a having a desired height can be easily formed on the head 21. When the predetermined height of the nose 21a has been obtained, the necessary engagement strength between the coupling elements 20 can be improved. In addition, since the head 21 is soft, the force applied to the boss forming punch and the die at the time of forming the boss 21a can be reduced, and therefore, the service life thereof can be greatly improved even if the original punch is used.

Fig. 3 and 4 show a state in which the fastener elements made of the metal wire material 10 forming the fastener elements of the above-described embodiment are attached to the fastener tape.

The fastener element 20 of this embodiment is manufactured by cutting a metal wire 10 having a cross section as shown in fig. 2, which is cut stepwise to a predetermined thickness, and then forming a coupling boss 21a, which boss 21a is formed in the middle of the engaging head 21 to project from one side of the fastener element by a head forming punch and die (not shown).

Each element 20 obtained from the metal wire 10 of this embodiment has a pair of legs 23, 23 protruding from the head 21 through the intersection 22. The inwardly bent portions 23a, 23b are formed stepwise on the inner surface of the leg 23 in the extending direction of the leg 23, extending from the intersection 22 toward the front end portion of the leg 23, so as to be bent in two stages. In addition, one claw 24 is projected to be bent inward from the front end portion of the leg 23. The curved portion 24a is a boundary surface connecting the inner surface of the base end portion of the claw 24 protruding from the leg 23 and the inner surface of the leg, the boundary surface being located on the straight line L₃Outside of the straight line L₃By the front end O of the claw 24₂、O₂And is parallel to the straight line L₂(hereinafter referred to as center line), L₂Is connected with the front end O of the left claw 24 and the right claw 24₂、O₂Straight line L therebetween₁Midpoint O of₃And center O of head₁The connecting line of (2).

When the left and right legs 23, 23 of the element 20 having such a structure are attached along the core wire portion T1 extending along the element attaching portion of the fastener tape side edge portion by convergence of the converging weight (not shown), the legs 23 of the element 20 are bent uniformly along each of the bent portions 23a, 23 b. As a result, as shown in fig. 3, the claw 24 bites firmly into the fastener tape T, and the inner surface of the element 20 extending from the intersection 22 toward the front end of the leg 23 including the claw 24 forms a polygon. The entire periphery of the core portion T1 is thus subjected to uniform and strong pressing forces of the curved portions 23a, 23b and 24a and the respective holding flat surfaces 25a, 25b between the inner holding flat surfaces 25c of the claws 24, with the result that not only the attachment strength of the claws 24 of the above-described structure to the fastener tape T is increased, but also the attachment strength of the above-described flat surfaces is increased. In addition, the frictional resistance between the inner surface of the polygonal leg 23 and the core portion T1 is also increased, so that the element 20 is prevented from sliding with respect to the core portion T1, thereby maintaining the element in a stable mounting position.

On the other hand, as described above, in producing the metal wire rod 10, the rigidity of the head 11 is set lower than the rigidity of the leg portion 13, but since the rigidity on and around the boss 21a is increased when the head 21 and the boss 21a are formed by the boss forming punch and the die (not shown) after cutting, the head 11 can maintain the rigidity necessary at the time of connection.

According to the present embodiment, as shown in fig. 3 and 4, the above-mentioned coupling projection 21a is formed in the form of a polygonal pyramid, which forms a multistage inclined surface 21c having a plurality of projected ridges 21b on the circumferential surface of the coupling projection 21 a. Therefore, even if an external force for rotating the right and left fastener tapes T with respect to the coupling center of the fastener elements 21 as shown in fig. 8 is applied at the time of mutual engagement as shown in fig. 7, the coupling boss 21a is less likely to rotate in its received recess portion due to the rib 21b having the polygonal cross section. Therefore, even when a pushing force is applied between the elements 20 of the slide fastener in this state, or an external force is applied to bend the left and right fastener elements of the slide fastener along the line connecting the element rows of the left and right fastener elements, or when the coupling state elements are pulled laterally outward, the coupling of the elements is never released.

In addition, in the fastener element 20 of the present embodiment as shown in fig. 3, there is a difference between the width D of the head 21 and the width D between the outer side surfaces of the left and right legs 23. This is to reduce the cost of manufacturing the element 20 and to make the legs 23 have a greater strength than the head 21, which is one member of the element 20, thus reducing the amount of material used for the head 21. Therefore, the width of the head 21 is set smaller than the width D between the outer surfaces of the pair of legs 23. Even when the width D of the head 21 is set smaller than the width D of the pair of legs 23, as described above, the mounting strength of the fastener tape T to the fastener element 20 and the connecting strength between the fastener elements 20 can be secured, thereby resulting in a reduction in material cost. Thus reducing the manufacturing cost of the slide fastener.

When the width of the head 21 is set smaller than the width D of the legs 23, the appearance is poor and the incongruity occurs. The surface of the head 21 here, however, appears to be comparatively large because the coupling projection 21a of the coupling element 20 is configured in the form of a polygonal pyramid as described above. It therefore looks good without appearing to reduce the amount of material used for the head 21, on the contrary it appears that the decapping is still relatively large.

Fig. 5 and 6 show modified examples of the present invention. According to the modified example shown in fig. 5, a curved portion 23a is formed as a first step on the inner surface of each of the left and right legs 23; the bent portion 23b is located on the nose at the base end of the claw 24, near the claw 24; the bent portions 24a, 24b as two stages are each formed on the claw 24. In the modified example shown in fig. 6, three-stage bent portions 23a to 23c are formed on the inner surface of each leg, while two-stage bent portions 24a, 24b are formed on the inner surface of the claw 24, whereby mutually adjacent pinching planes 25a to 25e are formed by the bent portions 23a to 23c, 24a, 24 b. Therefore, in the modified example of fig. 5, the polygon formed by the intersections 22, the legs 23, and the claws 24 when the coupling elements are mounted on the fastener tape is different in shape from the embodiment shown in fig. 3, but can be similarly represented by a heptagon, and the modified example shown in fig. 6 is an 11-sided polygon.

The above description is only an exemplary embodiment of the present invention, and it is needless to say that the present invention can be modified in various ways within the scope of the technical features described in the patent claims.

Claims (5)

1. A metal wire material (10) forming a fastener element has a head portion (11) and a pair of leg portions (13) extending from the head portion (11) through an intersection portion (12), and has a Y-shaped cross section; the method is characterized in that: three or more bent portions (13a, 13b, 14a) bent inward are formed one by one on the inner surface of the claw portion (14) from the intersection portion (12) to the front end of each leg portion (13) in the extending direction of the leg portion (13),

each claw part (14) protrudes inwards from the front end of the leg part (13),

the gap between the inner surfaces of the claw portions (14) gradually narrows from the base end portions to the tip ends of the claw portions (14).

2. The metal wire material for forming a fastener element according to claim 1, wherein: the bent portion (14a) between the inner surface of the leg portion (13) and the inner surface of the base end portion of the claw portion (14) is located on a straight line L₂And a straight line L₃Outside the region in between, the straight line L₂The front ends (O) of the left and right claw parts (14)₂) Straight line L₁Middle point of (O)₃) And the center (O) of the cross section of the head (11)₁) The line of (a), the straight line L₃Is parallel to the straight line L₂And passes through the front end (O) of the claw part (14)₂) Is measured.

3. The metal wire material for forming a fastener element according to claim 1, wherein: the opening angle between the pair of leg portions (13) is 75 DEG to 85 deg.

4. The metal wire material for forming a fastener element according to claim 1, wherein: the outer side surface of the connecting portion of the head portion (11) and the leg portion (13) has a projecting portion (12a) projecting outward therefrom.

5. The metal wire material for forming a fastener element according to claim 1, wherein: at least the connecting projection forming region of the head portion (11) has a rigidity lower than that of the leg portion.