JPH11290940A - Manufacture of square pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a square pipe that fulfills required precision at low cost by press forming. SOLUTION: The square pipe is manufactured through the following processes: the primary bending process which makes the primary intermediate product by using a rectangular metallic plate as the base stock and bending both of its breadthwise ends in the longitudinal direction at right angles to form flanges Wa; the secondary bending process which makes the secondary intermediate product W2 having a nearly U-shaped cross section by forming a concave surface Wb in a prescribed width in the center breadthwise along the longitudinal direction of the primary intermediate product and by bending both ends of the concave surface Wb nearly at right angles inward; and the restriking process which makes the flanges Wa abut on each other that are formed at both breadthwise ends by pressurizing inward both side walls Wc of the concave surface Wb of the secondary intermediate product W2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a square pipe which can be obtained by press-forming a square pipe.

[0002]

2. Description of the Related Art For example, a square pipe is used for a frame of an electronic device such as a copying machine, and this square pipe has been manufactured by welding two members as shown in FIG. 12 or FIG.

FIG. 12 and FIG. 13 are partial perspective views of a square pipe. A square pipe 110 shown in FIG. The square pipe 210 obtained by welding and shown in FIG.
This is obtained by butting two angled members 201 and 202 in a letter shape and welding the butted portion partially or continuously.

However, in manufacturing the square pipe 110 shown in FIG. 12 and the square pipe 210 shown in FIG. 13, a welding process is required, and the weld beads X and Y formed at the respective joints are finished. Since it is necessary to grind, there is a problem that the number of processing steps is increased and the manufacturing cost is increased, and the square pipes 110 and 210 are thermally deformed by the influence of welding heat.

Therefore, a method of manufacturing a square pipe by press molding has been proposed (for example, Japanese Patent Publication No. 56-1).
No. 5977), this method is described in FIG. 14 and FIG.
It will be described based on.

FIGS. 14 and 15 are sectional views showing a method of manufacturing a square pipe by press molding. In this method, as shown in FIG. 14, an inverted U-shaped convex portion 301a is formed at the center in the width direction. Is formed on the metal plate 301 on which the die 3 is formed.
02 of the metal plate 301.
01a is crushed by the punch 303. The die 302 includes a fixed portion 302a and a movable portion 302b that can move up and down with respect to the fixed portion 302a. The movable portion 302b is supported by a spring 304.

[0007] Thus, the convex portion 301 of the metal plate 301
When the punch 303 further moves down after the flat portion a is crushed by the punch 303 and becomes flat, the movable portion 302b of the die 302 is pushed down against the urging force of the spring 304 as shown in FIG. 301 is squeezed between the fixed portion 302a of the die 302 and the punch 303, and the left and right halves are bent together. As a result, an intermediate product having a substantially U-shaped cross section with an open top is obtained.

[0008]

However, in the manufacturing method by press molding, since the two flange portions 301b, which are the mating surfaces of the metal plates 301, are opened by springback, the two flange portions 301b are butted after press molding. In addition to the above, the above-mentioned problems associated with welding occur, and the accuracy (for example, tolerance ± 0.1) required for the square pipe cannot be satisfied.

Accordingly, it is an object of the present invention to provide a method of manufacturing a square pipe which can manufacture a square pipe satisfying required accuracy at low cost by press molding.

By the way, conventionally, necessary drilling is performed later on a ready-made square pipe by drilling, so that problems such as deformation of the square pipe, generation of cutting chips, burrs, and the like due to the processing have occurred.

Therefore, an object of the present invention is to simultaneously perform drilling, notching, drawing, and the like at the time of forming a square pipe, thereby omitting post-processing, deforming the square pipe due to the post-processing, and cutting chips. It is an object of the present invention to provide a method for manufacturing a square pipe that can solve problems such as generation of burrs and the like.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, a rectangular metal plate is used as a material, and both ends in the width direction are bent at right angles in the same direction along the length direction. A first bending step of obtaining a primary intermediate product by forming a flange portion, forming a concave curved surface having a predetermined width along a length direction at a central portion in a width direction of the primary intermediate product, and forming both ends of the concave curved surface. A second bending step of bending a second intermediate product inward at a substantially right angle to obtain a secondary intermediate product having a substantially U-shaped cross section, and pressing inward the side walls on both sides of the concave curved surface of the secondary intermediate product to each end. A square pipe is obtained through a restriking process of abutting the formed flange portions.

According to a second aspect of the present invention, in the first aspect of the present invention, a pre-processing step of subjecting the material to at least one of punching, notching, and drawing by pressing is performed in the first bending step. It is characterized in that it is performed before.

Therefore, according to the first aspect of the present invention, the concave curved surface formed at the center in the width direction of the secondary intermediate product when the side walls of the secondary intermediate product are pressed inward in the restrike process. In order to suppress the outward opening of both side walls due to spring back, if both sides are pressed inward in the restriking process and the flanges abut each other, the flanges will not stick together without opening A square pipe with a rectangular cross section can be obtained only by press forming, which eliminates the need for a welding process and can prevent the increase in processing man-hours and processing costs associated with welding, and prevent deterioration in accuracy due to thermal deformation. Can be manufactured at low cost.

According to the second aspect of the present invention, since the material is preliminarily subjected to punching, notching, drawing, and the like before the first bending step, it is possible to perform drilling and notching by post-processing. Processing, drawing, and the like are not required, and problems such as deformation of the square pipe and generation of chips and burrs due to post-processing can be solved.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing a pre-processing step (piercing step), FIG. 2 is a cross-sectional view of a primary intermediate product obtained by a first bending step, and FIGS. FIG. 6 is a cross-sectional view showing the order of operation, FIG. 6 is a cross-sectional view of a secondary intermediate product obtained by the second bending step, FIG. 7 is an enlarged detailed view of a portion A in FIG.
FIG. 10 to FIG. 10 are cross-sectional views showing the restriking process in the order of operation, and FIG. 11 is a partial perspective view of a square pipe manufactured by the method of the present invention.

In the manufacturing method according to the present embodiment, a pre-processing step (piercing step) for forming a hole in a material by pressing.
And a first bending step of bending both ends in the width direction of the material along the length direction at right angles in the same direction to form a flange portion, thereby obtaining a primary intermediate product; While forming a concave curved surface of a predetermined width along the length direction,
Both ends of the concave surface are bent inward at a substantially right angle to form a substantially U-shaped cross section.
A second bending step of obtaining a letter-shaped secondary intermediate product, and a restriking process in which the side wall portions on both sides of the concave curved surface of the secondary intermediate product are pressed inward to abut the flange portions formed at each end. It is characterized in that a square pipe is obtained through a process.

First, in a pre-processing step (piercing step), as shown in FIG. 1, a raw material W composed of a rectangular metal plate is placed and set on a piercing die 1.
A plurality of piercing holes 1a are provided at predetermined positions of the piercing die 1.

On the other hand, a plurality of piercing punches 2 are provided above the piercing holes 1a of the piercing die 1 in a punch holder 3.
When the punch holder 3 is moved downward and the piercing punch 2 supported by the punch holder 3 punches out the raw material W, a desired hole is formed in a predetermined position of the raw material W. In this pre-processing step, the material W may be subjected to notch processing, drawing processing, or the like by press working in addition to drilling.

As described above, the material W having been subjected to the hole processing at a predetermined position in the pre-processing step is subjected to a known press working in the next first bending step, as shown in FIG. 2 are bent at right angles in the same direction (upward in the illustrated example) along the length direction (perpendicular to the plane of FIG. 2). By this bending, a primary intermediate product W1 having a flange Wa standing upright at right angles at both ends in the width direction is obtained. In addition, in FIG.
Is a circular hole for positioning.

Then, the primary intermediate product W1 obtained in the above-described first bending step is subjected to a second bending step by a press device shown in FIGS.

The configuration and operation of the press shown in FIGS. 3 to 5 will now be described.

The illustrated press device includes an upper die 11 and a lower die 21. The upper die 11 has a punch 12 having a predetermined width (= inner width of a square pipe) which is long in a direction perpendicular to the plane of the drawing. doing. The punch 12 is vertically supported by a punch holder 13, and the lower surface thereof forms an arc-shaped concave surface 12 a having a predetermined curvature, and a relief hole 12 b is formed at the center in the width direction. .

In the drawing, reference numeral 14 denotes a stripper. The punch 12 is fitted in a groove 14a formed in the center of the stripper in the width direction. A spring 15 is interposed between them. A killer pin 16 projects vertically downward from a part of the lower surface of the stripper 14.

On the other hand, the lower die 21 includes a die 22 which is long in the direction perpendicular to the paper of the drawing and a die holder 23 for holding the die.
A knockout block 24 having a predetermined width (= outer width dimension of a square pipe) long in the direction perpendicular to the paper of the drawing is inserted through a through hole 23a formed in the die holder 23 so as to be vertically movable. It is connected to the upper end of the sub cushion pin 26 via a joint 25.
The sub cushion pin 26 is connected to a die cushion (not shown) of the press body via a cushion pin (not shown).

The knockout block 24
Has an arc-shaped convex surface 24a having a curvature equal to that of the concave surface 12a of the punch 12, and a positioning pin 27 is protrudingly provided at the center in the width direction.

In the set state before molding shown in FIG. 3, the upper mold 11 is located at the upper limit, and in this state, the primary intermediate product W1 is provided with flange portions formed at both ends in the width direction. Wa is placed and set on the die 22 of the lower mold 21 so as to rise vertically upward. At this time,
The primary intermediate product W1 is accurately positioned by fitting the circular hole We (see FIG. 2) formed at the center in the width direction into the positioning pin 27 protruding from the knockout block 24.

Thereafter, the upper mold 1 is moved from the set state shown in FIG.
1 is moved downward, as shown in FIG.
The stripper 14 is fixed to the position shown in the drawing because the lower end of the lower die 21 contacts the upper surface of the die holder 23 of the lower die 21. Accordingly, when the upper die 11 moves further downward, the punch 12 goes down through the stripper 14 and the
Spring 1 interposed between the punch holder 13
5 is compressed.

Then, the punch 12 eventually becomes the primary intermediate product W.
As shown in FIG.
The next intermediate product W1 is pressed at its center in the width direction by being sandwiched between the arcuate concave surface 12a of the punch 12 and the arcuate convex surface 24a of the knockout block 24.
At the center in the width direction of the next intermediate product W1, a concave curved surface Wb having a predetermined width along the length direction is formed.

Further, since the knockout block 24 is pushed down by the pressing force of the punch 12 as shown in FIG.
The intermediate portion of the primary intermediate product W1 in the width direction is formed between the knockout block 24 and the punch 12, and both ends of the concave curved surface Wb are bent inward at substantially right angles. As a result, side walls Wc are formed on both left and right sides of the concave curved surface Wb of the primary intermediate product W1, and both side walls Wc are bent until the flange Wa formed at the end thereof comes into contact with the side of the punch 12. As a result, as shown in FIG. 6, the upper part is opened (the left and right flange parts Wa are opened) and the cross section 2 is substantially U-shaped.
The next intermediate product W2 is obtained. At this time, since the positioning pins 27 projecting from the upper surface of the knockout block 24 are buried in the clearance holes 12b formed on the lower surface of the punch 12, the processing in the second bending step is smoothly performed without any trouble.

By the way, as shown in detail in FIG. 7, at the corners inside both ends of the concave curved surface Wb of the secondary intermediate product W2,
A groove-shaped bottom protrusion bead Wd is formed along the length direction to suppress the side walls Wc from opening outward due to springback.

Thus, through the pre-processing step (piercing step) to the second bending step described above, the secondary intermediate product W2 shown in FIG.
Is obtained, the secondary intermediate product W2 is subjected to a restrike process by the press device shown in FIGS.

Here, the configuration and operation of the press device shown in FIGS. 8 to 10 will be described.

As shown in the figure, a pair of left and right slide cams 32 are slidably mounted on a lower die set 31 in the left and right directions by a cam holder (not shown). A tapered surface 32a is formed.

On the other hand, a pair of left and right driver cams 33 is disposed above the slide cam 32 while being supported by an upper die set 34. A tapered surface 33a formed on each driver cam 33 is provided below the slide cam 32. It is engaged with the tapered surface 32a of each slide cam 32 located.

At the center of the upper die set 34 in the left-right direction, a pressing block 35 is inserted and supported so as to be able to move up and down.
4 is urged downward by a spring 36 which is compressed between them.

In the setting state shown in FIG. 8, the secondary intermediate product W2 has a concave curved surface Wb in the space between the left and right slide cams 32 on the lower die set 31. Set so that it is below. At this time, the secondary intermediate product W2 is positioned by fitting a positioning pin 37 projecting from the lower die set 31 into a circular hole We (see FIG. 2) formed in the concave curved surface Wb. ing. When the upper die set 34 is moved downward from this state, the driver cam 33 and the pressing block 35 supported by the upper die set 34 are integrally moved downward.

Then, the right and left slide cams 32 engaged with the driver cam 33 are tapered surfaces 32 of the two cams 32, 33.
a and 33a move inward (in the direction of the arrow in the drawing) by the same amount and approach each other, and as shown in FIG.
The left and right side walls Wc of the next intermediate product W2 are simultaneously pressed inward and bent inward, and the flanges Wa formed at the respective ends thereof are abutted against each other. As a result, the concave curved surface Wb constituting the bottom surface of the secondary intermediate product W2 is formed into a flat shape by receiving the pressing force from the lower die set 31. At the same time, the pressing block 35 abuts on the flange Wa of the secondary intermediate product W2 and is fixed.
Since the spring 36 is compressed by the further downward movement of 4, the pressing block 35 presses the flange Wa of the secondary intermediate product W2 by the strong elastic force of the spring 36.

By the way, in the above-mentioned restrike process, the concave curved surface Wb formed at the center in the width direction of the secondary intermediate product W2 has a function of suppressing the outward opening of the side wall portions Wc due to spring back. In this restriking process, the side wall portions Wc are pressed inward, and the flange portions W
a, the upper die set 34, the driver cam 33, and the pressing block 35 are moved upward as shown in FIG. 10, and the left and right slide cams 32 are moved outward (in the direction of the arrow shown in the drawing) by return springs (not shown). ), The flange portion Wa is tightly closed without being opened, and the rectangular pipe 10 having a rectangular cross section can be obtained only by press molding.

As described above, according to the manufacturing method of the present invention, since the square pipe 10 can be obtained only by press forming, a welding process is not required. It is possible to prevent a decrease in accuracy or the like due to deformation, and it is possible to manufacture the square pipe 10 satisfying the required accuracy at low cost.

Here, a specific example of the square pipe 10 actually manufactured by the method of the present invention is shown in FIG. 11. According to the method of the present invention, the material W is punched by pressing before the first bending step. Since the notch processing or the like is performed in advance, the bracket 10 a and the plurality of circular holes 10 are already formed in the square pipe 10.
b, and notches 10c and 10d of an arbitrary shape are formed, and these need not be formed by post-processing.

Therefore, according to the method of the present invention, it is possible to omit post-processing, and it is also possible to solve the problems such as the deformation of the square pipe and the generation of chips and burrs caused by the post-processing. .

[0044]

As is apparent from the above description, claim 1
According to the invention described above, when the side walls of the secondary intermediate product are pressed inward in the restriking process, the concave curved surface formed at the center in the width direction of the secondary intermediate product is formed by the spring back of the both side walls. In order to fulfill the function of suppressing the opening to the outside, in the restriking process, if both side walls are pressed inward and the flanges abut each other, the flanges are tightly attached without opening and the rectangular pipe with a rectangular cross section is pressed. Obtained only by molding, the welding process is not required, and the number of processing steps and costs associated with welding can be increased, and precision deterioration due to thermal deformation can be prevented. The effect that it can be obtained is obtained.

According to the second aspect of the present invention, since the material is preliminarily subjected to punching, notching, drawing, and the like before the first bending step, the material is subjected to post-processing drilling, notching. Processing, drawing, and the like become unnecessary, and an effect is obtained in that problems such as deformation of the square pipe and generation of chips and burrs due to post-processing can be solved.

[Brief description of the drawings]

FIG. 1 is a pre-processing step (piercing step) in the method of the present invention.
FIG.

FIG. 2 is a cross-sectional view of a primary intermediate product obtained by a first bending step in the method of the present invention.

FIG. 3 is a sectional view showing a second bending step in the method of the present invention.

FIG. 4 is a sectional view showing a second bending step in the method of the present invention.

FIG. 5 is a sectional view showing a second bending step in the method of the present invention.

FIG. 6 is a cross-sectional view of a secondary intermediate product obtained by a second bending step in the method of the present invention.

FIG. 7 is an enlarged detail view of a portion A in FIG. 6;

FIG. 8 is a cross-sectional view showing a restrike step in the method of the present invention.

FIG. 9 is a cross-sectional view showing a restriking step in the method of the present invention.

FIG. 10 is a cross-sectional view showing a restrike step in the method of the present invention.

FIG. 11 is a partial perspective view of a square pipe manufactured by the method of the present invention.

FIG. 12 is a partial perspective view of a square pipe obtained by a conventional manufacturing method.

FIG. 13 is a partial perspective view of a square pipe obtained by a conventional manufacturing method.

FIG. 14 is a cross-sectional view showing a conventional method of manufacturing a square pipe by press molding.

FIG. 15 is a cross-sectional view showing a conventional method for manufacturing a square pipe by press molding.

[Explanation of symbols]

 10 Square pipe W Material W1 Primary intermediate product W2 Secondary intermediate product Wa Flange part Wb Concave curved surface Wc Side wall part

Claims (2)

[Claims] 1. A first bending step of obtaining a primary intermediate product by using a rectangular metal plate as a raw material and bending both ends in the width direction thereof at right angles in the same direction along a length direction to form a flange portion; At the center of the primary intermediate product in the width direction, a concave curved surface having a predetermined width along the length direction is formed, and both ends of the concave curved surface are bent inward at substantially right angles to form a U-shaped cross section.
A second bending process for obtaining a next intermediate product, and a restriking process in which the side wall portions on both sides of the concave curved surface of the secondary intermediate product are pressed inward to abut the flange portions formed at each end portion, and then the corner is formed. A method for producing a square pipe, characterized by obtaining a pipe. 2. The method according to claim 1, wherein a pre-processing step of performing at least one of punching, notching, and drawing by press working on the material is performed before the first bending step. Manufacturing method of square pipe.