JPS6317534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a thin-walled irregularly curved pipe from a circular pipe.

An example of a thin-walled irregularly curved pipe is shown in FIGS. 1 to 4.
In Fig. 1, 1 is a thin-walled irregularly curved pipe, and Figs. 2 to 4 are respectively - and - in Fig. 1.
, - shows a cross section. The conventional method for forming such a thin-walled irregularly curved pipe was to press-form a thin plate into upper and lower halves and then weld them at position 2 in FIG. 1. However, the current process requires a large number of man-hours to correct deformation due to welding and has poor dimensional accuracy, making mass production difficult and creating problems in cost reduction. In addition, since the irregularly curved tube is formed from a thin circular tube by bending, the cost can be reduced, but due to the thin wall, buckling and "wrinkles" occur, making it difficult to obtain good dimensional accuracy.

An object of the present invention is to eliminate the above-described drawbacks of the prior art, improve the dimensional accuracy of a thin-walled irregularly curved pipe, and at the same time reduce the number of working steps.

In order to achieve the above object, the present invention provides a mold consisting of a split mold for bending, a lower mold, and a pressure sealing part, seals both ends of a thin-walled circular tube, applies a required internal pressure inside the tube, and adjusts the tube diameter. At the same time as increasing the size, bending is performed sequentially using split molds for bending.
Finally, by forming the tube into a predetermined shape by fitting it with a lower mold, a thin, irregularly shaped curved tube with good dimensional accuracy is formed by hydraulic bending.

The present invention will be explained below with reference to one embodiment shown in FIGS. 5 to 7. Reference numerals 16, 17, 18, and 19 are split molds for bending, and the split molds are divided into smaller parts as the portions 18 and 19 are bent more. Reference numeral 20 is a lower mold provided opposite to the split mold, and the cavity formed by the lower mold 20 and the split molds 16, 17, 18, and 19 provides a predetermined irregular curved pipe outer shape. . 12, 13, 14, 15 are split molds 1
The rams 6, 17, 18, and 19 are respectively fixed, and the rams 12, 13, 14, and 15 can be moved in the vertical direction by a drive source (not shown).

Reference numeral 3 denotes a raw material pipe, and 4 and 5 denote upper and lower pipe holders for fixing the ends of the raw material pipe 3. The pipe holder 5 can be moved in the vertical direction by a ram 11 fixed thereto. Reference numeral 6 denotes a seal cylinder for sealing the material pipe 3. An O-ring 7 is attached to the tip of the seal cylinder 6, and the seal cylinder 6 can be moved back and forth by a ram 8.

In the hydraulic bending mold configured in this way,
Ni-based heat-resistant alloy material pipe 3 (outer diameter φ50, plate thickness
0.6) is fixed between the upper pipe holder 5 and the lower pipe holder 4 by driving the ram 11. Further, the seal cylinder 6 is driven by the ram 8, and by inserting the seal cylinder 6 into the material pipe 3, the O-ring 6 is pressed against the inner surface of the material pipe 3 to seal it. After opening the valve 10 to remove the air in the material pipe 3, the valve 9 is opened to fill the material pipe 3 with liquid, and the valve 10 is closed. When this air removal is completed, reduce the fluid pressure to 130.
by increasing the circumferential strain to Kg/ ^cm2 .
Perform 10% tube expansion. Further, while maintaining the hydraulic pressure, the rams 12 to 15 are driven to form the split molds 16 to 15 for bending.
In step 19, bending is performed as shown in FIG. For bending, the final stroke of each split mold was divided into 5 parts, each of which was defined as one bending amount, and bending was performed in 5 stages. FIG. 6 shows the state after the third stage of molding has been completed.

FIG. 7 shows the state in which all bending has been completed.
While maintaining this state, the liquid pressure is increased to 320 kg/cm ² to conform to the shape inside the mold, and then the liquid pressure is released and the molded product is taken out.

As explained in detail above, the present invention uses a bending split mold to hydraulically bend a thin-walled irregularly bent pipe, thereby significantly reducing the number of man-hours compared to the conventional welding method, and at the same time preventing buckling. This has the effect of reducing wrinkles and improving dimensional accuracy.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a thin-walled irregularly curved pipe, Fig. 2 is a cross-section of Fig. 1, Fig. 3 is a cross-section of Fig. 1, Fig. 4 is a cross-section of Fig. 1, and Figs. 7th
The drawings are front views showing one embodiment of the present invention, in which Fig. 5 shows a state in which the material pipe is set and hydraulic pressure is applied, Fig. 6 shows the state of hydraulic bending, and Fig. 7 shows the condition of hydraulic bending. It is a figure which shows the completion state of molding. 3...Processed pipe (material pipe), 16, 17, 1
8, 19... split die for bending (upper die), 20... lower die.

Claims (1)

[Claims] 1. A cavity consisting of an upper mold made of a plurality of split molds and a lower mold that faces the upper mold and gives a predetermined irregularly curved pipe outer shape, and which applies internal pressure to the inside of the pipe to be processed. A hydraulic bending mold for thin-walled, irregularly shaped curved pipes, characterized by having a sealing part for adding parts. 2. Applying a predetermined internal pressure to the pipe to be processed and expanding it, at the same time, move each of the split molds for bending divided into a plurality of pieces in order to press the pipe to be processed against the lower mold, and change the outer shape of the pipe to the split mold. A method for hydraulic bending of a thin-walled irregularly curved pipe, characterized by forming the pipe into a cavity shape formed by a lower mold and a lower die.