JPS5935690B2 - Method and device for forming bent pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a bent tube from a straight tube and a tube shape retaining device used for the forming.

For piping for nuclear power generation, it is desired to use bent steel pipes due to the reliability of the material.

Conventionally, straight pipes are bent using a press using a bender or jig to obtain bent pipes such as elbows, vents, or elbows with straight pipes. If the bending portion is small, the bending portion will be deformed, wrinkles will form, and the cross-sectional area will decrease. Furthermore, if the wall thickness of the straight pipe is thin, the deterioration of the shape after deformation will be even more significant, and the radius of the bent portion will not be constant. Defects in bent pipes that occur when forming bent pipes from straight pipes cannot be removed by using only bender equipment, press jigs, and molding dies.

In order to eliminate various defects that occur when forming bent pipes from straight pipes as described above, the present invention provides a pipe shape holding device that can change the height of the combination with the outer mold by moving the inner mold up and down. is inserted into the bent part of the straight pipe, and the height of the inner mold is raised so that the outer peripheral surfaces of the inner mold and the outer mold are in contact with the inner peripheral surface of the straight pipe, and then the bending operation is performed. To provide a method for forming a bent tube with a good shape by lowering the height of an inner die after bending is completed and taking out the tube shape retaining device outside the bent tube, and to provide a tube shape retaining device as the device. The purpose is to

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a tube shape retaining device used in forming a bent tube from a straight tube according to the present invention will be described with reference to FIGS. 1 to 5.

The tube shape retaining device consists of an outer mold 1, an inner mold 2, and two wedges 3.
, 3 and fixtures 4, 4 for fixing the wedges 3, 3 to the outer mold 1.

In the bottom surface 1a of the outer mold 1, the center outer side 1a' of the vertical cross section is approximately equal to the inner diameter outer radius R of the bent pipe after molding, and the outer side sides 1, 1' of the cross section are the inner radius R of the straight pipe 10.

almost equal to That is, the bottom surface 1a comes into contact with a portion on the outer radius side of the inner diameter of the bent pipe after forming. In addition, the outer mold 1 is provided with a cavity Ib that accommodates a part of the inner mold 2 and the wedges 3, 3 during use.
The guide surfaces Ic, Ic of the wedges 3, 3 are formed as inclined surfaces from the bottom surface of the mold toward the top surface If of the outer mold. Further, screw holes Ic', Ic' for fixing the wedges 3, 3 to the outer mold 1 are threaded at appropriate locations on the ends of the guide surfaces Ic, Ic. Both side surfaces 1d and Id are substantially vertical surfaces, and one side surface Id is provided with a pressure oil introduction hole Ie communicating with the cavity Ib. The pressure oil introduction hole Ie is connected to an oil feed pipe (not shown) that introduces pressure oil from the outside in order to project the wedges 3 and 3 and bring the inner mold 2 into contact with the inner wall of the straight pipe 10, if necessary. Ru. The upper surface of the head 2a of the inner mold 2 has an inner diameter R of the straight pipe 10. A projection 2e is provided at the center of the lower part of the curved surface to fit into both side walls Ib', Ib' of the cavity Ib of the outer mold and to be guided to the outer mold 1. There is. A wing section 2b having a tapered thickness is formed from both left and right side surfaces of the protrusion 2e (as shown in FIG. 2), and the lower sloped surface of the wing section 2b is connected to the guide surfaces Ic and Ie of the outer mold after assembly. Opposing wedge 3
, 3 are formed. Also, both sides 2d, . 2d forms a vertical surface having approximately the same width as both side surfaces Id, Id of the outer mold. In addition, long holes 3a, 3a are provided at both ends of the wedges 3, 3 as through holes for the bolts 4, 4, respectively.
3a is provided.

Next, a method of using the tube shape retaining device will be explained.

As shown in FIGS. 1 to 3, the inner mold 2 is placed in the center of the outer mold 1, and the protrusion 2e of the inner mold is attached to the side wall Ib' of the cavity of the outer mold.
, Ib', insert both wedges 3, 3 between the guide surfaces of the wedges of the outer mold 1 and inner mold 2, 1c, Ic, 2c, 2c, and lightly tighten the bolts 4, 4. Tighten temporarily to temporarily assemble the tube shape retaining device.

Thereafter, the tube shape retaining device is inserted and installed with its center aligned with the center of the bent portion of the straight tube 10. Next, pressure oil is fed into the empty chamber Ib through the pressure oil introduction hole Ie manually or mechanically, or by using an oil feed pipe (not shown) to connect the wedges 3, 3.
After the upper curved surface of the head 2a of the inner mold is brought into contact with the inner periphery of the straight pipe 10, the bolts 4, 4 are completely screwed, or the wedges 3, 3 and the outer mold 1, or the inner Wedges 3, 3 are fixed by spot welding with mold 2.

Next, as shown in FIGS. 4 and 5, a load is applied to the straight tube 10 to form a bent tube using the molds A and B or by a conventional method using a bender.

Since the inner diameter and outer radius of the bent tube are molded along the bottom surface 1a of the outer mold, a bent tube having the inner diameter and outer radius R1 is formed.
Bolts 4, 4 that fix both wedges 3, 3 after forming the bent pipe
Loosen or cut the spot welds, then attach both wedges 3,
Lightly tap the tips of 3 to loosen both wedges 3 and 3 and open the empty chamber 1b.
The tube shape retaining device is taken out from inside the bent tube by dropping it toward the center of the tube to lower the height of the inner wall 2.

Next, a second embodiment of the tube shape retaining device according to the present invention will be described with reference to FIGS. 6 to 16.

The bottom surface 1'a of the outer mold 1' is formed so as to come into contact with the outer radius side of the inner diameter of the bent tube after molding, similarly to the outer mold 1 of the first embodiment. Cylinders 5, 5 are fixed to both sides of the upper surface 1'f of the outer mold with fixtures 6, 6, respectively. In addition, in the center of the upper surface 1'f, there are wedges 3', which will be described later.
A groove 1'g for slidingly guiding the mold 3' is bored between the central stop wall 1'h, and the inner wall 2' is positioned at the center of the upper surface 1'f of the outer mold to prevent vertical movement. Four guide pieces 1'i to guide
is installed protrudingly. The upper curved surface of the head 2'a of the inner mold 2' has the inner diameter R of the straight tube 10, as in the first embodiment. It forms an arc-shaped curved surface that corresponds to
f and both side inclined surfaces 2'G, 2'g having the same slope as this are formed, and leg portions 2'H, 2'h are further formed on both sides. The upper surface of the wedge 3' (see FIGS. 10, 11, and 12) is formed by the central inclined surface 2'f and both side inclined surfaces 2' of the inner mold.
Central engagement surface 3'f) to be engaged with G, 2'g) Both side engagement surfaces 3'G, 3'g are formed, and the lower surface is slidable by fitting into the groove 1'g of the outer mold. A cap T is formed on the end surface of the leg portion 3'h, which is fixed to one end of the piston rod 5a by screwing or the like.
Both arms 3'I that engage and hold the wings 7a, 7a of
, 3'i are provided, respectively.

The inner mold 2' is guided by the four guide pieces 1'i of the outer mold and placed on the upper surface 1'f of the outer mold.

Therefore, both wings 7 of the cap are fixed to the tips of the piston rods 5a of both cylinders 5 fixed to both sides of the upper surface 1'f of the outer mold.
a and Ta are inserted so as to be held by both arms 3'I and 3'1 of both wedges, and both piston rods 5a and 5a are set to the retracted position, and both wedges 3' and 3' are engaged in the center. Surface 3'f)
and the engaging surfaces 3'G and 3'g on both sides are the central inclined surface 2' of the inner mold.
f and the entrances of both side inclined surfaces 2'G and 2'g, respectively, to bring the inner mold 2' to the lowest position. In this state, the tube shape retaining device is inserted and installed into the straight tube 10 with the center of the tube shape retaining device aligned with the center of the bent portion.

Then, pressure oil is supplied to each cylinder 5 through an oil pipe (not shown).
, 5 and push out both piston rods 5a, 5a,
Insert both wedges 3', 3' fully into the inner mold 2' until the tips of the legs 3'H, 3'h of both wedges come into contact with both sides of the stop wall 1'h of the groove of the outer mold. Then, the bottom surface 1'a) of the outer mold and the head 2'a of the inner mold are brought into contact with the inner peripheral surface of the straight pipe 10, and bending is performed as described in the first embodiment. After forming a predetermined bent pipe, when both cylinders 5, 5 are operated to return and both wedges 3', 3' are moved to the outside of the inner mold 2', the inner mold 2' lowers its height. , the main pipe shape retaining device can be taken out from inside the bent pipe.

In addition to the above example, as a means of moving the inner mold up and down to change the height of the combination with the outer mold, it is possible to install a cylinder vertically in the center of the outer mold and supply and discharge pressure oil from the outside. The inner mold may be moved up and down by moving the piston rod up and down.

As can be understood from the above explanation, when a bent pipe is formed from a straight pipe using the pipe shape retaining device according to the present invention, the inner diameter of the straight pipe changes at the center of the bent part of the formed bent pipe. This prevents cross-sectional deformation at the bend,
In addition, since the inner wall is in contact with the inner radius side of the bent part, no wrinkles will occur on the inner radius side of the bent part, and the bottom surface of the outer mold matches the inner radius and outer radius of the bent pipe, so it can be bent as desired. A bent tube is obtained having an inner diameter and an outer radius of .

[Brief explanation of drawings]

FIG. 1 is a plan view showing a first embodiment of the tube shape retaining device according to the present invention, FIG. 2 is a partially sectional front view, and FIG.
The figure is also a partially sectional side view, Fig. 4 is a partially sectional view showing the pipe shape retaining device attached to the bent part of a straight pipe, and Fig. 5 is a partially sectional side view of the straight pipe when the bending is completed. FIG. 6 is a plan view showing a second embodiment of the tube shape retaining device according to the present invention, and FIG. 7 is a front view thereof. Fig. 8 is a side view of the inner mold used in the second embodiment, Fig. 9 is a sectional view taken along line A-A in Fig. 8, and Fig. 10 is a side view of the inner mold used in the second embodiment. Fig. 11 is a front view of the same, Fig. 12 is a plan view of the same, and Fig. 1 is a side view of the same.
Fig. 3 is a front view of the cap used in the second embodiment, Fig. 14 is a plan view thereof, Fig. 15 is a front view of the outer mold used in the second embodiment, and Fig. 16 is a front view of the cap used in the second embodiment. 16 is a cross-sectional view taken along the line BB in FIG. 15. FIG. 1, 1'...Outside mold, 1a, 1'a...
Bottom, 1b... Empty chamber, 1c... Guide surface, 1d... Side, 1e... Pressure oil introduction hole, If, l'f... ...Top surface, 1'g...
Groove, 1'h... Stopping wall, 1'i... Guide piece, 2, 2'... Inner mold, 2a, 2'a...
...Head, 2b... Wings, 2c...
Guide surface, 2d...Side surface, 2e...Protrusion, 2'f...Central slope, 2'g...
...Slope on both sides, 2'h ... Legs, 3,3
'...Wedge, 3a...Long hole, 3'f
...Central engagement surface, 3'g...Both side engagement surfaces, 3'h...Leg, 3'i...Arm, 4. ...Bolt, 5...Cylinder, 5
a...Piston rod, 6...Fixing tool, 7
... Cap, Ta ... Wings, 10...
...straight pipe, A, B...bending mold.

Claims (1)

[Claims] 1. A pipe shape holding device that can change the height of the combination with the outer mold by moving the inner mold up and down is inserted into the bent part of the straight pipe to increase the height of the inner mold. Bending is performed with the outer peripheral surfaces of the inner mold and outer mold in contact with the inner peripheral surface of the straight pipe, and after the bending work is completed, the height of the inner mold is lowered using a wedge to maintain the pipe shape. A method for forming a bent tube, characterized in that a device is taken out of the bent tube. 2. An outer mold having a bottom surface that comes into contact with the outer radius side of the inner diameter of the bent pipe after forming, a cavity and an inclined surface from the cavity for guiding the wedge, and a shape that matches the inner diameter surface of the straight pipe before forming. an inner mold having an arcuate upper curved surface, a protrusion at the center of the lower part that fits between the side walls of the cavity of the outer mold, and wing parts on both sides of the protrusion that face the inclined surface of the outer mold and guide the wedge. and two wedges inserted between the outer mold and the inner mold. 3. An outer mold having a bottom surface that comes into contact with the outer radius side of the inner diameter of the bent pipe after forming, and a hydraulic cylinder fixed to both sides of the upper surface thereof, and an arcuate upper curved surface that matches the inner diameter surface of the straight pipe before forming. The inner mold has a lower surface that slopes from both end surfaces toward the center, and is located at the center of the upper surface of the outer mold, and the upper surface of the outer mold and the lower surface of the inner mold are engaged with the tip of the piston rod of the hydraulic cylinder. A pipe shape retaining device used for forming a bent pipe from a straight pipe, characterized by comprising a wedge interposed between the pipe and the pipe.