Method and apparatus for manufacturing thick-walled bent pipe

TECHNICAL FIELD

The present invention relates to a method and an apparatus for manufacturing a thick-walled bent pipe.

BACKGROUND ART

As for a metal elbow for piping, one with an elbow body

111

being attached to a piping block

113

or the like with a fastening nut

112

as shown in

FIG. 8

, is used conventionally. Both ends of the elbow body

111

are threaded, and one thread is screwed into the piping block

113

or the like and fastened with the nut

112

, while a pipe not shown is attached to the other thread. The elbow body

111

can be freely oriented to the piping and fixed by being fastened with the nut

112

. The elbow body

111

is provided with parallel plane portions

111

s

and

111

s

so that the elbow body

111

can be fixed with a spanner or the like when it is attached. Further, the elbow body

111

is bent at almost the right angle, which reduces the protruding amount from the piping block

113

or the like, thus requiring less piping space.

In a section of the elbow body

111

, two fluid paths

111

d

and

111

d

cross each other at almost the right angle as shown in FIG.

9

. Further, since the elbow needs to be threaded, a margin to cut needs to be secured, which makes a material for the elbow thick-walled. In addition, it is necessary to secure pressure resistance of an elbow in order to respond to high-pressurization of the fluid devices in recent years, and the wall thickness of the elbow body

111

after being worked becomes larger.

Accordingly, it is difficult to manufacture the elbow body

111

as shown in

FIG. 9

by bending a thick-walled metal pipe at a small radius, since the pipe is crushed or the wall thickness of the pipe is reduced. Thus, a material of the elbow is made by cutting out a thick metal plate and forming it into a right-angle elbow, then the material is drilled from both end sides thereof to make the fluid passages

111

d

and

111

d

crossing each other at almost the right angle, and thereafter screw thread cutting is performed for both ends to thereby manufacture the elbow body

111

.

However, in the above manufacturing method, the process of cutting the material includes two drilling operations and two screw thread cutting operations, which results in too many working steps, and thus the number of steps of preparing the material is large. Further, burrs caused by drilling occur at a crossing portion of the fluid passages

111

d

and

111

d

crossing each other at almost the right angle, which are made by drilling. Thus, an operation for removing the burrs that have occurred has to be performed, and the deburring operation is not easy and takes time, since burrs in the small holes have to be removed. Further, many cutting operations increase cutting amount of the material, thus reducing yields. Consequently, manufacturing cost is increased.

In order to eliminate the above disadvantages, a method for manufacturing a curved pipe material described in Japanese Patent Laid-open No. 59-163024 as shown in

FIG. 10

to

FIG. 12B

is proposed. An apparatus thereof has a presser die A and press bearer dies B and C for supporting guide shafts b and c symmetrically positioned and respectively attached below the presser die A so as to be rotatable and horizontally slidable by inserting though and supporting them by horizontally long holes p and q provided in corresponding support frames P and Q. Bearing portions

2

b

and

3

c

for securely supporting both end portions of a straight pipe-shaped semiprocessed product N, which is formed by performing predetermined forging or grinding for a round metal bar, are respectively formed on the press bearing dies B and C. With the apparatus as described above, a thick-walled curved pipe can be manufactured by placing the straight pipe-shaped semiprocessed product N on the press bearing dies B and C, and lowering the press presser die A to thereby press and bend the straight pipe-shaped semiprocessed product N.

However, the method of manufacturing the curved pipe material described in Japanese Patent Laid-open No. 59-163024 has the following disadvantages.

The straight pipe-shaped semiprocessed product N is provided with a pipe hole

1

and bulging parts for connection at both ends as shown in

FIG. 12A. A

pipe part

4

is provided with uneven wall thickness on an upper side and an lower side with wall thickness being made smaller on the upper side and larger on the lower side as shown in FIG.

12

B. Accordingly, forging or grinding, and boring are performed to form the round bar-shaped material into the straight pipe-shaped semiprocessed product N as described above, thus requiring plenty of time to perform the working.

Further, when the straight pipe-shaped semiprocessed product N is pressed and bent, the press bearing dies B and C are moved transversely within the ranges of the horizontally long holes p and q to widen a space between them following the deformation of the straight pipe-shaped semiprocessed product N, while rotating as shown in FIG.

11

. The moving amount is determined by an outer shape dimension and wall thickness dimension of the straight pipe-shaped semiprocessed product N, and the aforesaid moving amount varies according to the variations in the outer shape dimension and the wall thickness dimension of the straight pipe-shaped semiprocessed product N. Accordingly, the dimension of the straight pipe-shaped semiprocessed product N in a longitudinal direction thereof, that is, a dimension in the left and right direction in

FIG. 11

varies within the range of the horizontally long holes p and q in which the dies B and C move transversely to widen the space between them. Specifically, the longitudinal dimension of the straight pipe-shaped semiprocessed product N changes and varies. If the dimension of the straight pipe-shaped semiprocessed product N varies, positioning becomes difficult when machining is performed in the next process, which is not preferable.

SUMMARY OF THE INVENTION

The present invention is made in view of the above disadvantages, and its object is to provide a method and an apparatus for manufacturing a thick-walled bent pipe capable of manufacturing an elbow material for piping with higher size accuracy with use of a thick-walled pipe material.

In order to attain the above object, a method for manufacturing a thick-walled bent pipe according to the present invention has a configuration including the steps of:

placing a thick-walled metal pipe material of a predetermined length on a lower die including a pair of bottom dies having sliding surfaces each in a circular arc form and placed on slide surfaces of a lower guide;

pressing a middle portion in a longitudinal direction of the thick-walled metal pipe material by means of an upper die including an upper guide having a guide surface in a circular arc form for guiding the lower die, and a presser die;

rotating the bottom dies respectively while they are facing to each other, by lower end portions of the bottom dies respectively abutting to and sliding along the slide surfaces at the same time when the sliding surfaces abut to and slide along the guide surface in the circular arc form to thereby bend the thick-walled metal pipe material.

According to the above configuration (a first configuration of the method), a pair of bottom dies of the lower die rotate along the guide surface in the circular arc form of the upper die having a center of rotation while they are facing to each other. Thereby, changes in the distances between both the end surfaces of the thick-walled pipe material and the center of rotation at the start of bending and at the completion of bending are reduced, thus making it possible to form a thick-walled elbow material with less variations in size.

As a result, an elbow material can be provided by cutting the thick-walled pipe, thus making it unnecessary to prepare a forged material. Further, since a thick-walled pipe can be used, drilling for making small holes to form fluid passages is unnecessary, and deburring at the crossing portion of the drilled holes, which is conventionally performed, is made unnecessary. Further, since the thick-walled pipe has a round outer shape, the margin to cut for screw thread cutting is reduced. Accordingly, a special drill is not needed, and the time required for working, and tool cost can be substantially reduced, and the yield of the material can be improved.

Further, the hole in the thick-walled elbow material thus formed is not a crossing drilled hole as in the conventional art, but is a smoothly curved hole, thus making it possible to reduce pressure loss of a fluid passing through the elbow. Further, the bending angle can be set at will by adjusting the descending stroke of the upper die, thus making it easy to manufacture many kinds of thick-walled elbow materials with different bending angles.

Further, the method for manufacturing the thick-walled bent pipe may have a configuration in which

both end surfaces of the thick-walled metal pipe material are restrained by a stopper provided in the bottom dies.

According to the above configuration (a second configuration of the method), bending work is performed with the thick-walled pipe material being restrained so that it has a size set by the upper die, the lower die and the stopper, thus making it possible to form the thick-walled elbow material of accurate size.

Further, the method for manufacturing the thick-walled bent pipe may have a configuration in which,

the stopper includes a first stopper and a second stopper which are allowed to slide in the bottom dies in the longitudinal direction of the thick-walled metal pipe material, the first stopper and the second stopper are guided to be closer to the guide surface in the circular arc form as the first stopper and the second stopper are at an upper portion of the upper guide by stopper guide surfaces provided on the upper guide, and the first stopper and the second stopper push both the end surfaces of the thick-walled pipe material toward a center portion in the longitudinal direction when the bottom dies rotate.

According to the above configuration (a third configuration of the method), the first stopper and the second stopper are respectively slidable in the longitudinal direction. Further, one end surfaces of the first stopper and the second stopper abut to and slide along the stopper guide surfaces so that they are closer to the guide surface in the circular arc form of the upper guide as they are at the upper portion of the upper guide. Thus, the other side surfaces of the first stopper and the second stopper can push against both the end surfaces of the pipe material during bending while they are serving as the stoppers for both the end surfaces of the pipe material.

As a result, the pipe material is accurately formed into the thick-walled elbow material of a size set by the one end surface of the first stopper and the one end surface of the second stopper respectively abutting along the stopper guide surfaces. Further, by replacing the fist stopper and the second stopper with those of different lengths, various kinds of thick-walled elbow materials of different sizes can be manufactured with one kind of dies.

An apparatus for manufacturing a thick-walled bent pipe according to the present invention has a configuration including:

a lower die including a pair of bottom dies having sliding surfaces each in a circular arc form;

an upper die including an upper guide having a guide surface in a circular arc form for guiding the lower die, and a presser die; and

a lower guide having slide surfaces for placing the bottom dies thereon, and a configuration in which

the bottom dies are allowed to rotate respectively while they are facing to each other, by lower end portions of the bottom dies respectively abutting to and sliding along the slide surfaces at the same time when the sliding surfaces respectively abut to and slide along the guide surface in the circular arc form in connection with descent of the upper die.

According to the above configuration, the same operational effects as in the first configuration of the above method can be obtained.

Further, the apparatus for manufacturing the thick-walled bent pipe may have a configuration in which,

the bottom dies are provided with a stopper abutting to both end surfaces in a longitudinal direction of a material to be worked. According to the above configuration, the same operational effects as in the second configuration of the above method can be obtained.

Further the apparatus for manufacturing the thick-walled bent pipe may have a configuration in which,

the stopper includes a first stopper and a second stopper which are allowed to slide in the bottom dies in the longitudinal direction of the material to be worked;

the upper guide is provided with stopper guide surfaces; and

the stopper guide surfaces respectively guide the first stopper and the second stopper so that the first stopper and the second stopper are closer to the guide surface in the circular arc form as the first stopper and the second stopper are at an upper portion of the upper guide.

According to the above configuration, the same operational effects as in the third configuration of the above method can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a view according to a first embodiment of the present invention, and is an explanatory view of an apparatus for manufacturing a thick-walled bent pipe in a state in which a thick-walled pipe material is placed thereon;

FIG. 2A

is a sectional view taken along the

2

A—

2

A line in

FIG. 1

;

FIG. 2B

is a sectional view taken along the

2

B—

2

B line in

FIG. 1

;

FIG. 2C

is a sectional view taken along the

2

C—

2

C line in

FIG. 1

;

FIG.

3

A and

FIG. 3B

are views showing a form of a material of a thick-walled elbow according to the first embodiment,

FIG. 3A

is an explanatory view of the thick-walled pipe material provided to be worked, and

FIG. 3B

is an explanatory view of the thick-walled elbow material after being worked;

FIG. 4A

,

FIG. 4B

, FIG.

4

C and

FIG. 4D

are explanatory views showing working steps according to the first embodiment,

FIG. 4A

shows a state in which a pipe material is placed on a lower die.

FIG. 4B

shows a state in which a protruded portion of a presser die abuts to the pipe material,

FIG. 4C

shows a state in a middle step of bending the pipe material, and

FIG. 4D

shows a state in a final step of bending the pipe material;

FIG. 5

is an explanatory view of an apparatus for manufacturing a thick-walled bent pipe according to a second embodiment of the present invention;

FIG. 6

is an explanatory view of an apparatus for manufacturing a thick-walled bent pipe according to a third embodiment of the present invention;

FIG. 7

is a sectional view of another example of groove forms of a presser die and a lower center die according to the present invention;

FIG. 8

is an explanatory view showing a conventional elbow for piping;

FIG. 9

is a sectional view of an elbow body in

FIG. 8

;

FIG.

10

and

FIG. 11

are explanatory views of a conventional method for manufacturing a curved pipe material,

FIG. 10

shows a state at the start of bending a straight pipe-shaped semiprocessed product, and

FIG. 11

shows a state in which the straight pipe-shaped semiprocessed product is further pressed and bent;

FIG. 12A

is a sectional view of the straight pipe-shaped semiprocessed product obtained by the conventional method for manufacturing the curved pipe material; and

FIG. 12B

is a section taken along the

12

B—

12

B line in FIG.

12

A.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments according to the present invention will be explained below with reference to the drawings.

A first embodiment will be explained based on

FIG. 1

to FIG.

4

D.

FIG. 1

depicts a state in which a thick-walled pipe material

111

a

shown by a two-dot chain line is placed on an apparatus for manufacturing a thick-walled bent pipe. In this embodiment, the thick-walled pipe material

111

a

is used as a material

111

a

to be worked. An upper die

10

is attached at a lower end of a ram

80

of a press or the like to be ascendable and descendable. A lower die

20

is mounted on a support

40

attached to a fixed frame

90

to be movable up and down. A lower guide

30

for receiving the lower die

20

is attached to the fixed frame

90

. The lower die

20

and the lower guide

30

are disposed with centers thereof being aligned with a vertical center line X of the upper die

10

.

The upper die

10

has an upper guide

11

part of that is shown in a section in

FIG. 1 and a

presser die

12

. As shown in

FIG. 2C

, the presser die

12

is provided in a center portion of the upper guide

11

, and a protruded portion

12

b

is placed between guide surfaces

11

a

and

11

a

in a circular arc form of the upper guide

11

. In the protruded portion

12

b

provided at an lower end portion of the presser die

12

, grooves

12

a

and

12

a

in a circular arc form in section, which conform to an outer shape of a thick-walled elbow material

111

b

, are symmetrically provided on both sides of the vertical center line X. The grooves

12

a

and

12

a

in the circular arc form in section are connectingly formed at an angle α corresponding to a bending angle of the thick-walled elbow material

111

b

, for example, 90 degrees, with a tip end portion of the protruded portion

12

b

as the vertex. An R surface with the radius of R

01

, for example, 2 mm, which is so small that it gives no flaw on the thick-walled elbow material

111

b

during forming, is formed at top portions of the grooves

12

a

and

12

a

in the circular arc form in section.

The lower die

20

is guided by the upper guide

11

, which is provided with the guide surface

11

a

in a circular arc form with a radius R

1

having a center O

1

on the vertical axis X. An inner side surface

11

b

in a circular arc form with a radius R

2

also having the center O

1

is provided in an inner side of the guide surface

11

a

. Further, the upper guide

11

is provided with stopper guide surfaces

11

c

and

11

c

in a circular arc form with a radius R

3

having two different centers O

1

a

and O

1

a

, which guide a first stopper

51

and a second stopper

52

. The centers O

1

a

and O

1

a

are located to be separated from the center O

1

by a predetermined length L

1

leftward and rightward in a horizontal direction and by a predetermined length L

2

downward in a vertical direction from the center O

1

. Vertical positions of the stopper guide surfaces

11

c

and

11

c

near the vertical center line X are conformed to that of the guide surface

11

a

. Specifically, the stopper guide surfaces

11

c

and

11

c

are made closer to the guide surface

11

a

as they are at the upper portion of the upper guide

11

. The stopper guide surfaces

11

c

and

11

c

are closer to the center O

1

as they are at the upper portion of the upper guide

11

. Chamfers H

as

and H

as

are provided at both end portions of the guide surface

11

a

in the circular arc form, chamfers

11

bs

and

11

bs

are provided at both end portions of the inner guide surface

11

b

in the circular arc form, and chamfers

11

cs

and

11

cs

are provided at the respective lower end portions of the stopper guide surfaces

11

c

and

11

c

in the circular arc form so that the lower die

20

smoothly abut to the upper die

10

when the upper die

10

descends to abut to the lower die

20

.

As shown in

FIG. 2A

being a sectional view taken along the

2

A—

2

A line in

FIG. 1

, the stopper guide surfaces

11

c

and

11

c

in the circular arc form with the radius R

3

are provided in a center portion in a width direction of the upper guide

11

. The guide surface

11

a

in the circular arc form with the radius R

1

and the inner guide surface

11

b

in the circular arc form with the radius R

2

are provided outside the stopper guide surfaces

11

c

and

11

c

of the upper guide

11

in a width direction of the stopper guide surfaces

11

c

and

11

c

of the upper guide

11

.

In this embodiment, the upper guide

11

is made to be a two-split on a split surface Z shown in

FIG. 2A

, and is fixed integrally with the presser die

12

by means of a bolt and the like (not shown) to define the upper die

10

, but the upper die

10

may be defined by the upper guide

11

and the presser die

12

, which are made of one component.

The stopper guide surfaces

11

c

and

11

c

may not be aligned with the guide surface

11

a

at the vertical position near the vertical center line X. In this case, the stopper guide surfaces

11

c

and

11

c

may only be closer to the guide surface

11

a

as they are at the upper portion of the upper guide

11

. As for the circular arc form of the stopper guide surfaces

11

c

and

11

c

, they may be guide surfaces in a circular arc form having the same center and the same radius on the vertical center line X at a position separated by a predetermined distance downward from the center O

1

, and in addition the stopper guide surfaces

11

c

and

11

c

may be closer to the guide surface

11

a

as they are at the upper portion of the upper guide

11

.

The lower die

20

is defined by a pair of bottom dies

21

and

22

. In the bottom dies

21

and

22

, the respective end surfaces

21

g

and

22

g

abut to each other on the vertical center line X. The pair of bottom dies

21

and

22

are respectively provided with sliding surfaces

20

c

and

20

c

each in a circular arc form having a center O

2

on the vertical center line X with radiuses R

1

a

and R

1

a

. At an inner side of the sliding surfaces

20

c

and

20

c

, inner sliding surfaces

20

d

and

20

d

in a circular arc form having the center O

2

with radiuses R

2

a

and R

2

a

are provided.

As shown in

FIG. 2B

being a sectional view taken along the line

2

B—

2

B in

FIG. 1

, sections of the pair of bottom dies

21

and

22

form a T-shape. The sliding surface

20

c

is designed to be a surface with a large width, and the inner sliding surface

20

d

is provided as two surfaces with smaller widths at the inner side of the sliding surface

20

c.

The radiuses R

1

a

and R

1

a

of the sliding surfaces

20

c

and

20

c

in the circular arc form are made slightly smaller relative to the radius R

1

of the guide surface

11

a

in the circular arc form of the upper guide

11

. Specifically, a very small clearance of, for example, 0.1 mm is provided between the guide surface

11

a

and the sliding surfaces

20

c

and

20

c

. The radiuses R

2

a

and R

2

a

of the inner sliding surfaces

20

d

and

20

d

in the circular arc form are made slightly larger than the radius R

2

of the inner guide surface

11

b

in the circular arc form of the upper guide

11

. Specifically, a very small clearance of, for example, 0.1 mm is provided between the inner sliding surfaces

20

d

and

20

d

and the inner guide surface

11

b.

The inner guide surface

11

b

of the upper guide surface

11

and the inner slide surfaces

20

d

and

20

d

of the lower die

20

are for stabilizing the rotation of the pair of bottom dies

21

and

22

, but they may not be provided.

Support grooves

20

b

and

20

b

with U-shaped sections and open bottoms for placing the bottom dies

21

and

22

on a pair of support rods

41

and

41

are provided in lower portions of the pair of bottom dies

21

and

22

. Grooves

20

a

and

20

a

with circular arc sections conforming to the outer shape of the thick-walled elbow material

111

b

after forming are respectively provided in upper portions of the bottom dies

21

and

22

.

Holes

20

e

and

20

e

for inserting the first stopper

51

and the second stopper

52

for abutting to the end surfaces of the thick-walled pipe material

111

a

placed are respectively provided in upper portions of the bottom dies

21

and

22

and at end portions on extension lines of the grooves

20

a

and

20

a

. Step portions

20

ed

and

20

ed

are respectively provided at center portions of the holes

20

e

and

20

e.

A stopper

50

has the first stopper

51

and the second stopper

52

. The first stopper

51

and the second stopper

52

have end surfaces

51

a

and

52

a

in a plane form at one end surfaces and end surfaces

51

b

and

52

b

in a spherical form at the other end surfaces respectively. The first stopper

51

and the second stopper

52

are respectively split in two. Specifically, the first and the second stoppers

51

and

52

respectively have portions forming planar end surfaces

51

a

and

52

a

which are inserted into the vertical center line X side of the holes

20

e

and

20

e

, and portions forming spherical end surfaces

51

b

and

52

b

with the step portions

20

ed

and

20

ed

between them. These two portions are integrally connected respectively with screws or the like not shown.

Clearances are respectively given in a longitudinal direction between connecting portions of the portions forming the end surfaces

51

a

and

52

a

and the portions forming the end surfaces

51

b

and

52

b

of the first stopper

51

and the second stopper

52

, and the step portions

20

ed

and

20

ed.

Consequently, the first stopper

51

and the second stopper

52

are slidable in the longitudinal direction corresponding to the clearances. Further, lengths Ls

1

and Ls

2

of the first and the second stoppers

51

and

52

are determined so that the horizontal positions of the planar end surfaces

51

a

and

52

a

from the vertical center line X are at predetermined positions corresponding to dimensions LE

1

and LE

2

(See

FIG. 3B

) of the thick-walled elbow material

111

b

after forming.

The lower guide

30

for bearing the lower die

20

has slide guides

31

and

32

provided with slide surfaces

30

a

and

30

a

which lower end portions

20

f

and

20

f

of the pair of bottom dies

21

and

22

of the lower die

20

abut to and slide on. The lower guide

30

has a lower center die

33

provided with a protruded portion

33

a

on the vertical center line X and with a groove

30

c

in a circular arc form conforming to the outer shape of the thick-walled elbow material

111

b

after forming. The slide guides

31

and

32

and the lower center die

33

are attached to the fixed frame

90

with bolts or the like not shown.

The slide guides

31

and

32

and lower center die

33

of the lower guide

30

are provided with two grooves

30

b

and

30

b

with U-shaped sections opened upward in order to avoid interference occurring when the pair of support rods

41

and

41

descend. The slide guides

31

and

32

and the lower center die

33

may be separate or integral. The slide surfaces

30

a

and

30

a

of the slide guides

31

and

32

are formed to be oblique surfaces slanting downward toward the vertical center line X, but it can go without saying that they may be horizontal surfaces or may be oblique surfaces with the slant in the reverse direction.

As shown in

FIG. 2C

being a sectional view taken along the line

2

C—

2

C in

FIG. 1

, the support grooves

20

b

and

20

b

of the bottom dies

21

and

22

are respectively provided at both sides of the lower portions of the bottom dies

21

and

22

. The lower guide

30

is provided with the grooves

30

b

and

30

b

at both sides. As a result that the support grooves

20

b

and

20

b

are respectively provided at both sides of the lower portions of the bottom dies

21

and

22

, the bottom dies

21

and

22

can be placed on the pair of support rods

41

and

41

with stability.

The support

40

has the pair of support rods

41

and

41

, support guides

42

and springs

43

. Guide holes

40

a

and

40

a

are provided at both end portions in a longitudinal direction of the support rod

41

. The support guide

42

is inserted into the guide hole

40

a

and the spring

43

. The support guide

42

is fixed to the fixing frame

90

. Further, a stopper portion

42

a

for preventing the support rod

41

from slipping off is provided at an upper end portion of the support guide

42

. Consequently, the support rod

41

slides along the support guide

42

and is movable up and down. Further, the support rod

41

is given momentum upward by the spring

43

, and holds the bottom dies

21

and

22

placed thereon. Stoppers

41

a

and

41

a

for positioning the bottom dies

21

and

22

in the horizontal direction are provided at symmetrical positions with the vertical center line X therebetween near a center of the support rod

41

. Instead of being given upward momentum by the support guide

42

and the spring

43

, the support rod

41

may be hung with a spring via a bracket, which may be provided with a stopper for stopping ascent, thereby giving upward momentum to the support rod

41

.

Next, the operation of the first embodiment will be explained according to a forming method of the thick-walled pipe material

111

a.

Initially, a predetermined length LEO of the thick-walled pipe material

111

a

(hereinafter, called the pipe material

111

a

) as shown in

FIG. 3A

is cut at a right angle to a longitudinal direction. Then, as shown in

FIG. 4A

, with the ram

80

such as a press being fixed at a rising end position, and with the upper die

10

and the lower die

20

being separated from each other, the pipe material

111

a

is placed on the lower die

20

.

Subsequently, as shown in

FIG. 4B

, when the ram

80

is lowered to thereby lower the upper die

10

, the protruded portion

12

b

of the presser die

12

of the upper die

10

abuts to the pipe material

111

a

. Simultaneously, the sliding surfaces

20

c

and

20

c

of the pair of bottom dies

21

and

22

of the lower die

20

begin to abut to the guide surface

11

a

in the circular arc form of the upper die

10

. The lower end portions

20

f

and

20

f

of the bottom dies

21

and

22

then abut to the slide surfaces

30

a

and

30

a

of the lower guide

30

to start press-bending.

In this situation, the center O

1

of the radius R

1

of the guide surface

11

a

in the circular arc form of the upper die

10

corresponds to the center O

2

of the radius R

1

a

of the sliding surfaces

20

c

and

20

c

of the pair of bottom dies

21

and

22

of the lower die

20

. Consequently, the sliding surfaces

20

c

and

20

c

abut to and slide along the guide surface

11

a

, and thus the bottom dies

21

and

22

can smoothly rotate around the center O

1

.

As shown in

FIG. 4C

, when the ram

80

such as a press is further lowered to thereby lower the upper die

10

, in connection with this, the respective sliding surfaces

20

c

and

20

c

of the bottom dies

21

and

22

abut to and slide along the guide surface

11

a

of the upper die

10

toward the upper portion of the guide surface

11

a

. Simultaneously, the lower end portions

20

f

and

20

f

of the bottom dies

21

and

22

abut to and slide along the slide surfaces

30

a

and

30

a

in a direction away from the vertical center line X. Then the bottom dies

21

and

22

face to each other so as to have the center O

1

of rotation on the vertical center line X respectively, and they rotate so that a relative angle made by the upper surfaces is made smaller. At the same time, the downward press-bending force of the upper die

10

lowers the support

40

.

A center line Y of the pipe material

111

a

passes through the center O

1

of rotation at the time of start of the bending as shown in FIG.

4

B. As shown in

FIG. 4D

, when the bending proceeds, the center line Y curves to be a curved line S having a very small radius R

0

of, for example, 12 mm, in the vicinity of the center O

1

with the center O

1

of rotation being as a boundary, connects to a center line Y

1

, and the bending angle approaches a right angle. In this situation, the center line Y and the center line Y

1

rotate with a point of intersection thereof being the center O

1

so that an angle formed by the center line Y and the center line Y

1

becomes small.

The pipe material

111

a

is pressed and crushed by the presser die

12

by bending, whereby thickness at a center portion in a longitudinal direction of the pipe material

111

a

on the upper side from the center line Y and the center line Y

1

is compressed. As a result, thickness at the center portion in the longitudinal direction of the pipe material

111

a

on the lower side from the center line Y and the center line Y

1

is elongated. Thus, the thickness at the compressed side tries to move to the elongated side on the lower side from the center line Y and the center line Y

1

, but the grooves

20

a

and

20

a

with the circular arc sections of the lower die

20

restrain it so that the thickness cannot move to any other places and thus move in the longitudinal direction of the pipe material

111

a.

The pipe material

111

a

then extends in the longitudinal direction, and both end surfaces of the pipe material

111

a

try to push the planar end surfaces

51

a

and

52

a

of the first stopper

51

and the second stopper

52

. However, since the spherical end surfaces

51

b

and

52

b

of the first stopper

51

and the second stopper

52

abut along the stopper guide surfaces

11

c

and

11

c

in the circular arc form of the upper guide

11

, the planar end surfaces

51

a

and

52

a

serve as the stoppers for both the end surfaces of the pipe material

111

a

to restrain the movement of the thickness of the pipe material

111

a.

The spherical end surfaces

51

b

and

52

b

respectively abut to and slide along the stopper guide surfaces

11

c

and

11

c

in the circular arc form, and the stopper guide surfaces

11

c

and

11

c

are made closer to the guide surface

11

a

as they are at the upper portion of the upper guide

11

. In other words, the stopper guide surfaces

11

c

and

11

c

are designed to be closer to the center O

1

being the center of rotation of the pair of bottom dies

21

and

22

as they are at the upper portion of the upper guide

11

. Consequently, the first stopper

51

and the second stopper

52

are slidable in the longitudinal direction by the longitudinal length of the clearance between the step portions

20

ed

and

20

ed

at the center portion and the first and the second stoppers

51

and

52

, and thus they push against both the end surfaces of the pipe material

111

a

. In other words, following the rotation of each of the pair of bottom dies

21

and

22

, the planar end surfaces

51

a

and

52

a

press both the end surfaces of the pipe material

111

a

toward the center O

1

, thereby limiting the movement of the thickness of the pipe material

111

a.

Further, when the upper die

10

is lowered, the lower surfaces

20

g

and

20

g

of the bottom dies

21

and

22

abut to the slide surfaces

30

a

and

30

a

of the lower guide

30

as shown in FIG.

4

D. Thereupon, the upper die

10

stops descending as the slide surfaces

30

a

and

30

a

serves as stoppers.

Further, as the pair of lower dies

21

and

22

rotate, their end surfaces

21

g

and

22

g

abutting to each other on the vertical center line X are separated, and thereby a space occurs. However, when the bending proceeds and the lower central portion of the pipe material

111

a

abuts to the lower center die

33

having the groove

30

c

in the circular arc form of the lower guide

30

, the groove

30

c

limits the movement of the thickness at the lower central portion of the pipe material

111

a

. As a result, the thickness at the upper central portion of the pipe material

111

a

, which is compressed and crushed by the presser die

12

, cannot move to any other places and move in the longitudinal direction of the pipe material

111

a.

Then the spherical end surfaces

51

b

and

52

b

abut to and slide along the stopper guide surfaces

11

c

and

11

c

in the circular arc form as described above, and thus the planar end surfaces

51

a

and

52

a

serve as the stoppers for both the end surfaces of the pipe material

111

a

to limit the movement of the thickness of the pipe material

111

a.

Further, since the stopper guide surfaces

11

c

and

11

c

are made to be closer to the guide surface

11

a

as they are at the upper portion of the upper guide

11

, the planar end surfaces

51

a

and

52

a

are pushed toward the center O

1

of rotation as described above. Consequently, since the first and the second stoppers

51

and

52

are respectively slidable in the longitudinal direction by the longitudinal length of the clearance between the step portions

20

e d

and

20

e d

and the first and the second stoppers

51

and

52

, they push against both the end surfaces of the pipe material

111

a.

Accordingly, as shown in

FIG. 4D

, the pipe material

111

a

is bent so that its center line joins the center line Y and the center line Y

1

via the curved line S. As the result, the center line of the pipe material

111

a

joins the center line Y, the curved line S with the radius R

0

near the intersection point OE

1

of the center line Y and the center line Y

1

, and the center line Y

1

as shown in FIG.

3

B. Thus, the thick-walled elbow material

111

b

having the predetermined bending angle α with the predetermined lengths LE

1

and LE

2

from both the end surfaces to the intersection point OE

1

is formed. On the bending work, the intersection point OE

1

of the center line Y and the center line Y

1

corresponds to the center O

1

of rotation described above.

Specifically, the pipe material

111

a

is accurately formed to be in a size set by the spherical end surface

51

b

of the first stopper

51

and the spherical end surface

52

b

of the second stopper

52

abutting along the stopper guide surfaces

11

c

and

11

c

in the circular arc form. Subsequently, the upper die

10

is raised to return to the state shown in

FIG. 4A

, whereby the thick-walled material

111

b

after the forming is taken out. The pipe material

111

a

may be heat-treated and thereafter placed on the lower die

20

to be bent.

As described above, since the thick-walled pipe material

111

a

is restrained by the upper die

10

, the pair of bottom dies

21

and

22

, the first stopper

51

, the second stopper

52

and the lower center die

33

to be formed, it can be accurately formed to be the thick-walled elbow material

111

b

in a predetermined size and shape.

On the bending work, the point of intersection of the center line Y and the center line Y

1

of the pipe material

111

a

is on the center O

1

being the center of rotation of the bottom dies

21

and

22

. Accordingly, regarding the bottom dies

21

and

22

and the pipe material

111

a,

the relative positions in the longitudinal direction on the center lines Y and Y

1

do not change even if the bottom dies

21

and

22

rotate. In other words, when the bottom dies

21

and

22

rotate, frictional force works between the pipe material

111

a

and the bottom dies

22

and

22

by the compression force of the upper die

10

, but the frictional force works so that the distance between the positions of both the end surfaces of the pipe material

111

a

and the center O

1

are not changed.

Accordingly, both the end surfaces of the pipe material

111

a

are restrained in the range of the aforesaid frictional force relative to the center O

1

, thus reducing the change in the size of the pipe material occurring at the start and the completion of the bending, which is caused by the bending work, as described in the above Japanese Patent Laid-open No. 59-163024. As a result, even if the first stopper

51

and the second stopper

52

are not provided, the thick-walled elbow material

111

b

with less variations in the predetermined lengths LE

1

and LE

2

from the point of intersection OE

1

to both the end surfaces can be formed.

Next, a second embodiment will be explained with FIG.

5

. It should be noted that the same components as in the first embodiment are given the identical reference numerals and symbols and the detailed explanation thereof will be omitted.

Unlike the first embodiment, an upper guide

11

A of the upper die

10

are not provided with the stopper guide surfaces

11

c

and

11

c

in the circular arc form with the radius R

3

. The upper guide

11

A is provided with the guide surface

11

a

in the circular arc form having the center O

1

on the vertical center line X with the radius R

1

for guiding the lower die

20

, and the inner guide surface

11

b

in the circular arc form with the radius R

2

.

The lower die

20

is defined by a pair of bottom dies

21

A and

22

A. Unlike the first embodiment, the pair of bottom dies

21

A and

22

A are not provided with the holes

20

e

and

20

e

for inserting the first stopper

51

and the second stopper

52

therein, but are provided with stopper portions

21

f

and

21

f

respectively. Horizontal distances Lsa

1

and Lsa

2

of the stopper portions

21

f

and

22

f

from the vertical center line X are determined according to a size of the thick-walled elbow material

111

b

after the forming.

Next, the operation of the second embodiment will be explained.

When the bending work is performed by placing the pipe material

111

a

on the lower die

20

, the pipe material

111

a

is compressed and crushed by the presser die

12

of the upper die

10

by bending. As a result, thickness at a center portion in a longitudinal direction at the upper side from the center line Y of the pipe material

111

a

tries to move to a lower side from the center line Y, but it is restrained by the grooves

20

a

and

20

a

with the circular arc sections of the lower die

20

and thus it cannot move to any other places, therefore moving in the longitudinal direction of the pipe material

111

a.

Thereupon, the pipe material

111

a

tries to extend in the longitudinal direction, but the stopper portions

21

f

and

22

f

of the bottom dies

21

A and

22

A serve as the stoppers for both the end surfaces of the pipe material

111

a

, and limit the movement of the thickness of the pipe material

111

a.

In this case, since the pair of bottom dies

21

A and

22

A respectively rotate around the O

1

being the center of rotation as in the first embodiment, as for the stopper portions

21

f

and

22

f

, the distances from the center O

1

being the center of rotation do not change during rotation. Consequently, the distances between both the end surfaces in the longitudinal direction of the pipe material

111

a

and the center O

1

do not change even while the bottom dies

21

A and

22

A are rotating in the bending work. Thus, the size of the pipe material

111

a

is accurately formed in the size of the thick-walled elbow material

111

b

after the forming, which is determined by the distances Lsa

1

and Lsa

2

of the stopper portions

21

f

and

22

f

from the vertical center line X.

Accordingly, the thick-walled pipe material

111

a

is formed while being restrained by the upper die

10

, the lower die

20

, and the lower center die

33

, thus making it possible to form the thick-walled pipe material

111

a

to be in a predetermine size and shape. Further, since the bottom dies

21

A and

22

A are provided with the stopper portions

21

f

and

22

f

, the number of components of the lower die

20

is reduced. The other operations and effects are the same as those in the first embodiment, and the explanation thereof will be omitted.

Next, a third embodiment will be explained based on FIG.

6

. It should be noted that the same components as in the first embodiment are given the identical reference numerals and symbols and the detailed explanation thereof will be omitted.

The lower die

20

is defined by a pair of the bottom dies

21

B and

22

B. The support grooves

20

b

and

20

b

as are provided in the bottom dies

21

and

22

in the first embodiment are not provided in lower portions of the bottom dies

21

B and

22

B. The support

40

has a pair of support mounts

41

A and

41

A having V-shaped grooves

41

A

a

for supporting the lower portions of the pair of bottom dies

21

B and

22

B, and a pair of springs

43

A and

43

A.

The support mounts

41

A and

41

A and the springs

43

A and

43

A are inserted into guide holes

31

A

d

and

32

A

d

respectively provided in slide guides

31

A and

32

A of the lower guide

30

. The support mount

41

A and

41

A are given upward momentum by the spring

43

A and

43

A to hold the bottom dies

21

B and

22

B placed thereon.

In the above configuration, when the pipe material

111

a

is placed on the lower die

20

to be bent as in the first embodiment, the support mounts

41

A and

41

A are pushed into the guide holes

31

A

d

and

32

A

d

of the slide guides

31

A and

32

A by the bottom dies

21

B and

22

B which are descending. Consequently, the pair of bottom dies

21

B and

22

B of the lower die

20

can be supported by the support mounts

41

A and

41

A with stability.

According to the third embodiment, it is not necessary to perform working to provide grooves in the lower portions of the pair of bottom dies

21

B and

22

B of the lower die

20

, thus making it possible to reduce working cost. Further, the support

40

has the pair of support mounts

41

A and

41

A and the pair of springs

43

A and

43

A, which makes the number of components four, thus reducing the number of components compared with the first embodiment in which the number of components of the support

40

is

10

. Accordingly the production cost of the components can be reduced. Since the other operations and effects are the same as those in the first embodiment, and the explanation thereof will be omitted.

In each of the embodiments of the present invention explained above, the bending angle α of the thick-walled pipe material

111

a

can be optionally set by adjusting the descending stroke of the upper die

10

. Accordingly, not only the right-angled thick-walled elbow material

111

b

but also the thick-walled elbow material

111

b

with the bending angle α of, for example, 45 degrees or 60 degrees can be manufactured, thus making it possible to manufacture various kinds of thick-walled elbow materials

111

b

with use of one kind of dies.

In the first and the third embodiment, a plurality of first stoppers

51

and second stoppers

52

with the length Ls

1

and Ls

2

being varied respectively may be prepared, and by properly selecting and using them, the sizes of the predetermined lengths LE

1

and LE

2

of the thick-walled elbow material

111

b

can be set optionally. Accordingly, by only replacing the first stopper

51

or the second stopper

52

, various kinds of thick-walled elbow materials

111

b

can be manufactured with use of one kind of dies.

Further, as shown in

FIG. 7

, the grooves in the protruded portion

12

b

of the presser die

12

and the lower center die

33

may be formed into a U-shape with a large width, and thereby plane portions

111

s

and

111

s

for a spanner can be formed at both sides of the center portion of the elbow. Accordingly, assembly can be done with a spanner being securely abutted to the plane portions

111

s

and

111

s

as necessary, thus making it possible to manufacture the thick-walled elbow material

111

b

with further improved assembling ease.

The support

40

is for supporting the bottom dies

21

,

22

,

21

A,

22

A,

21

B and

22

B of the lower die

20

with stability. However, each pair of the bottom dies

21

and

22

,

21

A and

22

A,

21

B and

22

B may be faced to each other with the respective end surfaces

21

g

and

22

g

being abutted to each other, and may be directly placed on the slide surfaces

30

a

and

30

a

of the lower guide

30

to be set, without using the support

40

.

In order to evaluate the method and the apparatus for manufacturing the thick-walled bent pipe of the present invention, 60 mm of a thick-walled pipe material of high-carbon steel, with a diameter of 20 mm and thickness of 7 mm was cut out and provided as the pipe material

111

a

. After the portion to be bent of the pipe material

111

a

was heat-treated at about 1000° C., bending work was performed at the bending angle of 90 degrees. As the result, crushing of the inner diameter portion almost did not occur, the thick-walled elbow member

111

b

excellently formed in a set accurate size with the length LE

1

of 35 mm and LE

2

of 25 mm was obtained.

As explained thus far, according to the method and the apparatus for manufacturing the thick-walled bent pipe of the present invention, the pair of bottom dies

21

and

22

of the lower die

20

rotate along the guide surface

11

a

of the upper die with the center O

1

on the vertical center line X. As a result, the change in the distances between both the end surfaces of the thick-walled pipe material

111

a

and the center O

1

of rotation at the start of the bending and at the end of the bending is reduced, thus making it possible to form the thick-walled elbow material

111

b

with less variations in size.

Bending work is performed with the thick-walled pipe material

111

a

being restrained so that it has the length set by the upper die

10

, the lower die

20

and the stopper

50

of the lower die, thus making it possible to form the thick-walled elbow material

111

b

of accurate size.

The hole in the thick-walled elbow material

111

b

thus formed is not a drill-hole which is crossed as in the prior art, but is a smoothly curved hole, thus making it possible to reduce the pressure loss of a fluid passing through the elbow. Further, the bending angle α can be set at will by adjusting the descending stroke of the upper die

10

, thus making it possible to manufacture various kinds of thick-walled elbow materials

111

b

with different bending angles α.

The first stopper

51

and the second stopper

52

are respectively slidable in the longitudinal direction. The spherical end surfaces

51

b

and

52

b

of the first stopper

51

and the second stopper

52

abut to and slide along the guide surface

11

a

in the circular arc form of the upper guide

11

of the upper die

10

, which is closer to the center O

1

being the center of rotation of the pair of bottom dies

21

and

22

at the upper portion of the upper guide. Thus, the planar end surfaces

52

a

and

51

a

of the first stopper

51

and the second stopper

52

can push against both the end surfaces of the pipe material

111

a

during bending work while they serve as stoppers for both the end surfaces of the pipe material

111

a.

As a result, the pipe material

111

a

can be accurately formed to be the thick-walled elbow material

111

b

of a size set by the end surface

51

b

of the first stopper

51

and the end surface

52

b

of the second stopper

52

respectively abutting to the guide surface

11

a

of the upper guide

11

.

Number	Date	Country
3150426	Jul 1983	DE
283084	Oct 1990	DE
2122521	Jan 1984	GB
39-10727	Jun 1964	JP
59-163024	Sep 1984	JP
62-3831	Jan 1987	JP
1278064	Dec 1996	SU

Method and apparatus for manufacturing thick-walled bent pipe

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Foreign Referenced Citations (7)