US20240100586A1

US20240100586A1 - Metal fiber, and method and apparatus for producing metal fiber

Info

Publication number: US20240100586A1
Application number: US18/461,460
Authority: US
Inventors: Kunio Ito
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-09-22
Filing date: 2023-09-05
Publication date: 2024-03-28
Also published as: TW202421307A; JP7217380B1; JP2024046247A; WO2024062959A1

Abstract

A metal fiber for fiber reinforced concrete includes a linear main body that extends in an X-Y plane, having width in a Y direction, a length in an X direction, and a thickness in a Z direction within a three dimensional space defined by X, Y, and Z axes which are perpendicular to each other. Ends of the linear main body are bent portions which are bent at an obtuse angle in the Z direction. An elongate metal plate is intermittently conveyed in the Y direction on a die of a pressing machine at a pitch corresponding to the width of the metal fiber in the Y direction. The leading end of the metal plate is sheared to cut out and produce the metal fiber.

Description

This application claims priority to Japanese Patent Application Number 2022-151523, filed 22 Sep. 2022, the specification of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

At least one embodiment of the invention is related to a metal fiber to be placed within a material such as concrete, to improve the tensile strength, bending strength, durability, etc. of the material. At least one embodiment of the invention is also related to a method and an apparatus for producing such a metal fiber.

Description of the Related Art

Conventionally, cutting machines having a fixed blade and a movable blade that cuts a thin metal plate to produce short metal fibers is known as apparatuses for producing metal fibers to be employed in fiber reinforced concrete, as disclosed in Japanese Unexamined Patent Publication No. H2-106218 and Japanese Patent Application Publication No. S53-1369. These apparatuses produce the short metal fibers by deforming the metal plates in the form of a wave in a direction perpendicular to the plane of the metal plates. When shearing the metal plates, the metal plates are pulled in the length direction of the fibers to be produced, that is, the width direction of the metal plates, and shearing is performed while the metal plates are being stretched. Therefore, the metal plates are limited to those which are soft and easily stretched. In the case that an iron plate is employed for this reason, it is not suitable to reinforce concrete because iron is susceptible to rust, and therefore is not realistic. In addition, employing the above method to deform a metal plate of a hard material in the form of a wave in a direction perpendicular to the plane of the metal plate while stretching the metal plate requires time to stretch the material, and is not suited for mass production.
As disclosed in Japanese Patent No. 6405066, metal fibers to be utilized to reinforce concrete must be rustproof steel to be practical. FIG. 10 of Japanese Unexamined Patent Publication No. H2-106218 discloses an example of a rotating cutting machine. However, a rotating cutting machine is not capable of shearing a steel plate. Shearing a stainless steel plate with a thickness of 0.6 mm, for example, requires 8 to 10 tons of force, and shearing a stainless steel plate with a rotating cutting machine is not possible. In addition, stretching a stainless steel plate to form fibers in the shape of waves by the methods employed by the apparatuses of Japanese Unexamined Patent Publication No. H2-106218 and Japanese Patent Application Publication No. S53-1369 is realistically impossible from the viewpoints of time and cost, and is considered impractical.
In view of these circumstances, techniques for providing metal fibers for reinforcing concrete employing highly weather resistant steel wire rods are being developed, as disclosed in Japanese Patent No. 6405066. In the method that employs the highly weather resistant steel wire rods, in addition to the steel wire rods being formed into annular shapes or polygonal shapes, examples in which the two ends of straight or partially bent steel wire rods are bent at acute angles are disclosed. However, this method requires that steel wire rods be bent, and a great number of production steps are necessary. Therefore, this method is also considered to be not suited for mass production.

BRIEF SUMMARY OF THE INVENTION

A great amount of metal fibers are necessary at sites that employ metal fibers to reinforce concrete, and a great amount of metal fibers, 30 tons or more, for example, are produced. It is desired for the metal fibers to be of a bent shape, from the viewpoint of resistance from being drawn out from concrete (refer to page 9, line 43 (paragraph 0033, line 13) of Japanese Unexamined Patent Publication No. 2020-100523). For these reasons, (1) a technique for mass producing metal fibers having bent shapes at low cost is desired, and further, (2) metal fibers produced by such a technique will exhibit superior draw out resistance if they are bent in three dimensions, which is desirable. In view of this background, at least one embodiment of the invention provides a metal fiber capable of being mass produced in one shot at low cost and exhibits superior draw out resistance. At least one embodiment of the invention also provides a method and an apparatus for producing such a metal fiber.
A metal fiber for fiber reinforcement according to one or more embodiments of the invention has a width in a Y direction, a length in an X direction, and a thickness in a Z direction within a three dimensional space defined by X, Y, and Z axes which are perpendicular to each other. The metal fiber is constituted by a linear main body in the form of a wave that extends within the X-Y plane (as used herein, the “form of a wave” is not limited to shapes that progress regularly in a serpentine manner as curved lines or bent lines, but broadly encompasses various shapes that deviate from a straight line a plurality of times within a plane), and a bent portion at least one end of the main body which is bent at an obtuse angle in the Z direction. That is, the metal fiber of at least one embodiment of the invention is characterized by the bent portion which is bent at an obtuse angle in the Z direction being present at one end of the metal fiber, at two ends of the metal fiber, or at an intermediate portion of the metal fiber other than the two ends of the metal fiber in the length direction thereof, in addition to the two ends of the metal fiber.
In addition, at least one embodiment of the invention provides a method for producing the above metal fiber. The method is characterized by a metal plate in the form of a band having a thickness in the Z direction equal to that of the metal fiber, a width in the X direction greater than or equal to the length of the metal fiber and extends extensively in the Y direction being intermittently conveyed in the Y direction on a die of a pressing machine at a pitch corresponding to the width of the metal fiber in the Y direction, and a cutting blade of a punch of the pressing machine cutting (shearing) the front edge of the metal plate in the Y direction, while a pressing portion that protrudes at an inclination of an obtuse angle from the lower surface of the punch in the Z direction simultaneously presses the leading end of the metal fiber in the X direction, in the Z direction.
Further, at least one embodiment of the invention provides a pressing machine for cutting the above metal fiber. The pressing machine is characterized by being equipped with a die having a lower blade in the form of a wave which is the contour of the linear main body that extends in the X-Y plane of the metal fiber and a punch that moves vertically in the Z direction, having an upper blade that corresponds to the lower blade of the die, the punch having a pressing portion that protrudes at an inclination of an obtuse angle downward from the lower surface thereof, for pressing the metal fiber downward in the Z direction simultaneously with the punch cutting the ends of the metal fiber in the X direction.
Still further, at least one embodiment of the invention provides a pressing mold for use in the pressing machine above. The pressing mold is characterized by being constituted by a die having a lower blade in the form of a wave which is the contour of the linear main body that extends in the X-Y plane of the metal fiber and a punch that moves vertically in the Z direction, having an upper blade that corresponds to the lower blade of the die, the punch having a pressing portion that protrudes at an inclination of an obtuse angle downward from the lower surface thereof, for pressing the metal fiber downward in the Z direction simultaneously with the punch cutting the ends in the X direction of the metal fiber.
Note that at least one embodiment of the invention also encompasses metal fibers which do not have a portion bent in the Z direction and are only bent within two dimensions, in addition to the metal fiber described above which is bent in three dimensions and has the portion bent in the Z direction. This is because a great number of metal fibers can be produced at high speed and mass production can be realized at low cost, only by the steps of conveying a metal plate having an X-Y plane and cutting the metal plate with a punch of a pressing machine that moves in a direction perpendicular to the X-Y plane to punch out metal fibers which are bent only within the X-Y plane.
That is, a method according to a second aspect of at least one embodiment of the invention is a method for producing a metal fiber for reinforcing concrete having a width in a Y direction, a length in an X direction, and a thickness in a Z direction within a three dimensional space defined by an X, a Y, and a Z axis which are perpendicular to each other and is constituted by a linear main body in the form of a wave that extends in an X-Y plane. The method is characterized by a metal plate in the form of a band that extends in the Y direction having the above thickness in the Z direction and a width greater than or equal to the above length in the X direction being intermittently conveyed in the Y direction at a pitch corresponding to the width in the Y direction onto a die equipped with a lower blade in the shape of a wave having the contour of the linear main body in the form of a wave, and the leading edge of the metal plate in a conveyance direction being cut by a punch that moves vertically in the Z direction and has an upper blade in the shape of a wave that corresponds to the lower blade of the die of the pressing machine.
In addition, a pressing machine according to the second aspect of at least one embodiment of the invention is a pressing machine for cutting metal fibers. The pressing machine according to the second aspect of at least one embodiment of the invention is characterized by being equipped with a die having lower blade in the shape of a wave which is the contour of a linear main body in the form of a wave that extends in an X-Y plane of a metal fiber, and a punch that moves vertically in the Z direction and has an upper blade in the shape of a wave that corresponds to the lower blade of the die.
Further, a pressing mold according to the second aspect of at least one embodiment of the invention is a pressing mold to be utilized in a pressing machine for cutting metal fibers. The pressing mold according to the second aspect of at least one embodiment of the invention is characterized by being constituted by a die having lower blade in the shape of a wave which is the contour of a linear main body in the form of a wave extends in an X-Y plane of a metal fiber, and a punch that moves vertically in the Z direction and has an upper blade in the shape of a wave that corresponds to the lower blade of the die.
The metal fiber of at least one embodiment of the invention is that in which a linear main body having a width in the Y direction, a length in the X direction, and a thickness in the Z direction within a three dimensional space defined by X, Y, and Z axes is in the form of a wave that extends within the X-Y plane, the linear main body having a bent portion which is bent at an obtuse angle in the Z direction at at least one end thereof. Therefore, not only is the metal fiber formed (cut) in a shape which is bent within the X-Y plane, but is also bent in the Z direction perpendicular to the X-Y plane. As a result, the metal fiber exhibits superior draw out resistance. Note that being “bent in the Z direction” does not mean that the bent end extends in a direction 90 degrees with respect to the X-Y plane, but that the bent end extends in a direction having a Z direction component (a direction at an obtuse angle with respect to the X-Y plane). A reason why the bent portion is limited to being bent at an obtuse angle is because an obtuse angle within a range that does not require a strong bending force when simultaneously punching out the metal plate instantaneously in one shot and pressing a portion (the end) of the metal plate is preferred. Another reason is that if a metal fiber is of a shape in which an end thereof is bent at 90 degrees or an acute angle, there is a possibility that fibers will become entangled with one another and form a clump of fibers called a “steel ball” (refer to paragraph 0031 of Japanese Patent No. 6405066). In addition, it is possible to form this shape by cutting the leading end in a direction of advancement of the metal plate with the punch of the pressing machine while the metal plate is intermittently conveyed in the width direction (Y direction) of a metal fiber to be formed as will be described later. As a result, an advantageous effect, that large scale mass production at a rate of SPM 300 (5 per second) or SPM 600 (10 per second) with minimal wasted material is enabled, is exhibited.
In addition, the metal fiber according to the second aspect of at least one embodiment of the invention which is constituted by a linear main body in the form of a wave that extends in the X-Y plane but does not have a portion bent in the Z direction also exhibits the same advantageous effect of being able to be mass produced at low cost. That is, a great number of metal fibers can be produced at high speed and mass production can be realized at low cost, only by the steps of conveying a metal plate having an X-Y plane and cutting the metal plate with a punch of a pressing machine that moves in a direction perpendicular to the X-Y plane to punch out metal fibers which are bent only within the X-Y plane. Note that as used in the specification, the expressions “X direction”, “Y direction”, and “Z direction” denote the directions of three axes that form right angles with each other, and are not limited to the directions indicated by arrows within the drawings (up and down, for example).
Further, the purpose of the metal fiber of at least one embodiment of the invention is to be mixed into cement to improve the strength of concrete, and therefore high dimensional precision is not required. In contrast, slight deformations that occur when shearing by the pressing process is welcomed, and it is not necessary for cut surfaces to be accurately sheared. Accordingly, there is also a practical advantage that requirements for precision that impact cost are not present. Performance is not affected by low precision, and rather deformations and fluctuations are welcome.
Therefore, there is still another advantageous effect that realistically, it is not necessary to conduct inspection of produced metal fibers, and production can be realized at extremely low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a collection of diagrams that illustrate at least one embodiment of a metal fiber according to the invention, wherein A is a perspective view of an example, B is an end view thereof as viewed from a length direction thereof (X direction), C is a front view as viewed from a thickness direction thereof (Z direction), and D is a plan view as viewed from a bending direction of a form of a wave thereof (Y direction).

FIG. 2 is a plan view that illustrates the basic configuration of an apparatus for producing the metal fiber of at least one embodiment, and the directions of the axes X, Y, Z are illustrated in the drawing.

FIG. 3 is a collection of plan views for explaining an operating state in which a metal plate is conveyed to an apparatus for producing the metal fiber of at least one embodiment and a punch is driven for the first time to cut off a leading end of the metal plate, wherein A illustrates the state of the machine and B is a diagram of a first piece which is sheared from the leading end of the metal plate, as viewed from the Z direction.

FIG. 4 is a collection of plan views for explaining an operating state in which a metal plate is conveyed to an apparatus for producing the metal fiber of at least one embodiment and a punch is driven to cut off a leading end of the metal plate, wherein A illustrates the state of the machine, B is a diagram of a piece which is sheared from the leading end of the metal plate, as viewed from the Z direction, and C is a diagram of a metal fiber obtained from the metal plate by being sheared by the punch, as viewed from the Y direction.

FIG. 5 is a cross sectional diagram taken along line V-V in FIG. 2 for explaining a state when a punch of an apparatus for producing the metal fiber according to at least one embodiment of the invention cuts a leading end of a conveyed metal plate by a punch shearing the metal plate.

FIG. 6 is a collection of diagrams that illustrate a die having a lower blade of a pressing mold of the machine for producing the metal fiber according to at least one embodiment of the invention, wherein A is a plan view, B is a front view taken from the right direction in A, C is an end view taken from the lower portion of A, and D is a perspective view.

FIG. 7 is a collection of diagrams that illustrate a punch having an upper blade of the pressing mold of the machine for producing the metal fiber according to at least one embodiment of the invention, wherein A is a bottom view taken from the lower Z direction and B is a front view taken from the Y direction.

FIG. 8 is a collection of perspective views of the punch of FIG. 7 , wherein A is a perspective view taken from the upper front, and B is a perspective view taken from the upper back.

FIG. 9 is a perspective view that illustrates a heel back of the machine for producing the metal fiber according to at least one embodiment of the invention that supports and guides the punch from behind that slides during vertical motion of the punch.

FIG. 10 is an end view that illustrates the heel back of FIG. 9 from the side.

FIG. 11 is a collection of diagrams that illustrate a metal fiber according to at least one embodiment of the invention, wherein A is a perspective view of an example, B is an end view thereof as viewed from a length direction thereof (X direction), C is a front view as viewed from a thickness direction thereof (Z direction), and D is a plan view as viewed from a bending direction of a form of a wave thereof (Y direction).

FIG. 12 is a collection of diagrams that illustrate a punch having an upper blade of a pressing mold of the machine for producing the metal fiber according to at least one embodiment of the invention, wherein A is a bottom view taken from beneath the punch in the Z direction, and B is a front view as viewed from the Y direction.

DETAILED DESCRIPTION OF THE INVENTION

One or more embodiments of the invention will be described below, with reference to the attached drawings. First, the configuration of one or more embodiments of a metal fiber of the invention will be described with reference to FIG. 1 . A through D of FIG. 1 illustrate one or more embodiments of the metal fiber of the invention. As is clear from these drawings, the metal fiber 10 of at least one embodiment of the invention is formed as a linear main body that extends from a first end 11 to a second end 15, and has an intermediate portion in which a peak portion 12, a valley portion 13, and a peak portion 14 connected in this order in the shape of a wave. The intermediate portion having the peak portion 12, the valley portion 13, and the peak portion 14 extend within an X-Y plane. The two ends 11 and 15 are bent at obtuse angles from the X-Y plane in a Z direction, resulting in the metal fiber 10 having a three dimensional shape as a whole. As a modification, a portion of the valley portion 13 at the center of A of FIG. 1 may be deformed in the Z direction as well as the two ends 11 and 15. Portions which are displaced in the Z direction may be present other than at the two ends in this manner. Alternatively, a portion which is displaced in the Z direction may be present only at one end instead of two ends. Note that the number of peak portions and valley portions is not limited to that of the example above, and may be increased or decreased according to intended uses. In addition, the size and the shapes of the bends of the metal fiber may also be freely designed according to intended uses. For an example of a metal fiber for reinforcing concrete, that having a length of 30 mm, a width of 0.7 mm, a thickness of 0.6 mm, a difference (height) between the peak portions and the valley portions of 2 mm, and a bend of 0.78 mm for the bent ends may be considered. These dimensions are freely variable as a matter of course.
Next, FIG. 2 illustrates a die 21, a punch 22, and a heel back 23 that supports and guides the punch 22 from behind that slides during vertical motion of the punch 22, which are set in a pressing machine that cuts and produces the metal fiber of the invention by shearing the metal fiber from a metal plate (steel plate). The die 21 has blade tips of a lower blade 21 a of a shape that corresponds to the contour in the X-Y plane of the metal fiber 10 to be cut out. The punch 22 has blade tips of an upper blade 22 a of a shape that corresponds to the lower blade 21 a. The gap between the blade tips of the lower blade 21 a and the blade tips of the upper blade 22 a illustrated in FIGS. 2, 3, and 4 correspond to the width of the metal fiber 10 to be cut out from the metal plate 25 by shearing. Note that the gap is emphasized and exaggerated in the drawings.
Next, the operation of an apparatus for producing the metal fiber of at least one embodiment of the invention will be described with reference to FIGS. 3, 4, 5, and 6 . First, the metal plate 25 having a width W equal to the length of a metal fiber to be cut out in an X direction and that extends in a Y direction is conveyed from the left side of the drawings (FIG. 3 ). Note that in at least one embodiment, the width W of the metal plate 25 is equal to the length of the metal fiber 10 in the X direction, and therefore the metal plate 25 can be utilized without waste. However, the invention is not limited to such a configuration, and the width W of the metal plate 25 needs only to be at least the length of the metal fiber 10 in the X direction. That is, the width W of the metal plate 25 may be greater than or equal to the length of the metal fiber 10 in the X direction. In the case that the width of the metal plate is greater than the length of the metal fiber, the shapes of the lower blade 21 a of the die and the upper blade 22 a of the punch 22 may be those that cut off excess portions from the ends of the metal fiber 10 in the X direction. A leading end 25 a of the metal plate 2 prior to shearing is of a linear shape perpendicular to the length direction. Therefore, the leading end 25 a is advanced toward the blade tips of the lower blade 21 a of the die and the blade tips of the upper blade 22 a of the punch for a width in the Y direction of the metal fiber to be cut out, and the punch is driven downward to shear the leading end 25 a of the metal plate 25. Then, a cut piece 25 b of the metal plate having the shape illustrated in B of FIG. 3 is cut off. Thereafter, if the metal plate 25 is advanced for a length in the Y direction corresponding to the width of the metal fiber and shearing is conducted by the punch 22, the metal fiber illustrated in B of FIG. 4 is cut out. The operations of intermittently advancing the metal plate 25 in the form of a band that extends in the Y direction at a pitch corresponding to the width in the Y direction of the metal fiber 10 and cutting the leading end of the metal plate 25 in the direction of advancement are repeated.
At this time, simultaneously with cutting the leading end of the metal plate 25 in the direction of advancement in the form of a wave with the punch 22 and cutting the ends 11 and 15 of the metal fiber 10 in the X direction with the cutting blade 22 a of the punch 22, a pressing portion 22 c inclined at an obtuse angle (FIG. 7 and FIG. 8 ) that protrudes in the Z direction from the lower surface 22 b of the punch 22 presses the two ends of the metal fiber 10 in the Z direction, to plastically deform the two ends 11 and 15 at an obtuse angle. By this configuration, the metal fiber 10, of which the two ends 11 and 15 are bent in the Z direction, may be produced.
The lower surface 22 b of the punch 22 is illustrated in detail in FIGS. 7 and 8 . A of FIG. 7 illustrates the lower surface and B of FIG. 7 illustrates a front surface. Recesses 22 e are formed in the side surfaces of the punch 22 as retaining recesses to be engaged by engaging portions provided in a punch plate for holding the punch 22. FIG. 8 is a perspective view of the punch 22, and illustrates the pressing portion 22 c which is formed to protrude inclined at an obtuse angle from the lower surface 22 b.
As is clear from the above description, the method and apparatus for producing a metal fiber of the invention intermittently advances the metal plate 25 in the form of a band in the Y direction at a pitch of the width in the Y direction of the metal fiber 10, cuts the leading end in the direction of advancement of the metal plate 25 with the punch 22 of the pressing machine into the shape of a wave, cuts the ends 11 and 15 in the X direction of the metal fiber 10, and simultaneously presses the metal fiber 10 in the Z direction with the pressing portion 22 c that protrudes inclined at an obtuse angle in the Z direction from the lower surface of the punch 22. Thereby, the metal fiber 10 having the linear main body in the shape of a wave within the X-Y plane and is bent at an obtuse angle in the Z direction is produced simultaneously by a single descending operation of the punch 22.
Note that as a method for intermittently advancing the metal plate 25 in the Y direction at a pitch corresponding to the width in the Y direction of the metal fiber 10, as an alternative to controlling a conveying machine that advances the metal plate 25 such that the metal plate 25 is intermittently conveyed at the above pitch, the metal plate 25 may be conveyed with a weak force, the leading end 25 a of the metal plate may be stopped at a cutting position by causing the leading end 25 a to abut a stopper (not shown) embedded in the heel back 23, the metal plate 25 may be cut by the punch 22 at the cutting position, and then advancing the metal plate 25 for a length corresponding to the cut width at the weak force. In the case that the stopper is utilized, it is necessary for a clearance to be provided in the lower surface 22 b of the punch 22 such that the punch 22 does not interfere with the stopper.
As illustrated in FIGS. 9 and 10 , the apparatus for producing the metal fiber of the invention is provided with the heel back 23 that supports a rear surface 22 d of the punch 22 from behind (23 b) and guides the sliding vertical movement of the punch 22. A protrusion 23 a is integrally formed on the upper portion of the heel back 23. The heel back 23 receives pressure of a reaction force from the lower blade 21 a and the upper blade 22 a when the punch 22 shears the metal plate 25, to enable smooth vertical movement of the punch 22.
Further, the operations of an apparatus for producing a metal fiber constituted by a linear main body in the form of a wave and extends only within an X-Y plane, that is, a metal fiber according to at least one embodiment of the invention which does not have a three dimensional shape, will be described with reference to FIG. 11 and FIG. 12 . First, the configuration of the metal fiber according to at least one embodiment of the invention will be described with reference to FIG. 11 . A through D in FIG. 11 illustrate the metal fiber according to at least one embodiment of the invention. As is clear from these drawings, the metal fiber 10 according to at least one embodiment of the invention extends from a first end 11 to a second end 15 and forms a linear main body in the form of a wave having an intermediate portion with a peak portion 12, a valley portion 13, and a peak portion 14 which are connected in this order between the first end 11 and the second end 15. The metal fiber 10 differs from the metal fiber according to at least one embodiment in the point that it does not have ends 11 and 15 which are bent in the Z direction at obtuse angles. Note that it goes without saying that the number of peak portions and valley portions is not limited to that of the example above, and may be increased or decreased according to intended uses. In addition, it also goes without saying that the size and the shapes of the bends of the metal fiber may be freely designed according to intended uses of one or more embodiments.
FIG. 12 illustrates a punch 22″ of at least one embodiment of the invention. The punch 22″ differs from the punch of previously discussed in the point that it does not have a pressing portion (element 22 c in FIG. 7 ) that protrudes downward inclined at an obtuse angle in the Z direction on the bottom surface of the punch at the leading end in the X direction. Metal fibers constituted by linear main bodies in the form of a wave that extend within an X-Y plane can be produced, by applying this punch 22″ in the production method of at least one embodiment.

REFERENCE NUMERALS

- 10 metal fiber
- 11 end (bent portion)
- 12 peak portion
- 13 valley portion
- 14 peak portion
- 15 end (bent portion)
- 21 die
- 21 a lower blade of die
- 22, 22″ punch
- 22 a upper blade of punch
- 22 c pressing portion
- 23 heel back
- 25 metal plate

Claims

1. A metal fiber for fiber reinforced concrete comprising:

a width in a Y direction, a length in an X direction, and a thickness in a Z direction within a three dimensional space defined by X, Y, and Z axes which are perpendicular to each other;

the metal fiber being constituted by a linear main body in the form of a wave that extends within the X-Y plane, and a bent portion at at least one end of the main body which is bent at an obtuse angle in the Z direction.

2. A method for producing the metal fiber according to claim 1, comprising

intermittently advancing a metal plate in the form of a band having a thickness in the Z direction of the metal fiber, a width in the X direction greater than or equal to the length of the metal fiber, and extends in the Y direction on a die of a pressing machine at a pitch corresponding to the width of the metal fiber in the Y direction, and

cutting the ends in the X direction of the metal fiber with a cutting blade of a punch of the pressing machine, while a pressing portion that protrudes in the Z direction from the lower surface of the punch simultaneously presses the metal fiber in the Z direction.

3. A pressing machine for cutting the metal fiber by the method according to claim 2, comprising:

a die having a lower blade in the form of a wave which is the contour of the linear main body that extends in the X-Y plane of the metal fiber; and

a punch that moves vertically in the Z direction, having an upper blade that corresponds to the lower blade of the die, the punch having a pressing portion that protrudes downward from the lower surface thereof, for pressing the metal fiber downward in the Z direction simultaneously with the punch cutting the ends in the X direction of the metal fiber.

4. A pressing mold utilized by the pressing machine for cutting the metal fiber according to claim 3, comprising:

5. A method for producing a metal fiber for reinforcing concrete having a width in a Y direction, a length in an X direction, and a thickness in a Z direction within a three dimensional space defined by an X, a Y, and a Z axis which are perpendicular to each other and is constituted by a linear main body in the form of a wave that extends in an X-Y plane with a pressing machine, comprising:

intermittently advancing a metal plate in the form of a band that extends in the Y direction having the above thickness in the Z direction and a width greater than or equal to the above length in the X direction at a pitch corresponding to the width in the Y direction in the Y direction onto a die equipped with a lower blade in the shape of a wave having the contour of the linear main body in the form of a wave; and

cutting the leading edge of the metal plate in a conveyance direction with a punch that moves vertically in the Z direction and has an upper blade in the shape of a wave that corresponds to the lower blade of the die of the pressing machine.

6. A pressing machine to be utilized for the method defined in claim 5, comprising:

a die having lower blade in the shape of a wave which is the contour of a linear main body in the form of a wave that extends in an X-Y plane of the metal fiber; and

a punch that moves vertically in the Z direction and has an upper blade in the shape of a wave that corresponds to the lower blade of the die.

7. A pressing mold to be utilized for the method defined in claim 5, comprising:

a die having lower blade in the shape of a wave which is the contour of a linear main body in the form of a wave extends in an X-Y plane of the metal fiber; and