JPH0367451B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention applies pressure while applying high hydraulic pressure to a straight pipe for processing, thereby forming a tapered part at the end and forming a tapered part in the center. The present invention relates to a method and apparatus for high-hydraulic expansion molding of a tapered pipe material used to form a polygonal vertical cross-section or flange-like bulge in a pipe.

(Prior art) As shown in FIG. 7, this type of general high-pressure expansion molding is a two-part upper part with expansion molding parts 2a and 2b recessed on the inner surface of the central part. This is carried out using the mold 1a, the lower mold 1b, and left and right pressure rods 4a, 4b for pressing both end surfaces of the raw material tube 3, which is a straight pipe for processing. In the expansion molding step, the material tube 3 is set on the lower mold 1b with the upper mold 1a raised and open. Then, the upper mold 1a is combined with the lower mold 1b as shown above the center line in the figure, and is fastened by applying a compressive force Wa. Thereafter, both pressure rods 4a and 4b are inserted from both sides and brought into contact with the end surface of the material tube 3 with low force, thereby closing the tube end opening of the material tube 3 except for the liquid injection port. In this state, while applying high hydraulic pressure P to the material tube 3, pressurizing rods 4a and 4b are powerfully advanced inward to apply pressure to the material tube 3. Due to the compressive force F by the rods 4a and 4b, the material tube 3 is compressed as shown in the lower part with respect to the center line in the figure.
It is bulged toward the bulging molded parts 2a and 2b to form a bulging part 3a in the material tube 3. In addition, FIG. 7 shows the state before the start of molding in the upper part with respect to the center line, and the state in which molding is completed is shown in the lower part with respect to the center line.

(Problems to be Solved by the Invention) However, when attempting to mold a thick-walled material tube 3 by the above-mentioned molding means, the bulging portion 3a
When there is a request to reduce the installation radius R1 and the corner radius R2, the pressure rods 4a and 4b simply apply compressive force F from both sides, which requires an extremely high hydraulic pressure P. There is a problem in that it interferes with the molding machine. Further, although a tapered end portion is often molded together with the bulging portion 3a, a separate molding step for the tapered portion is required before or after the bulging portion 3a is formed, and therefore, the number of molding steps is large. As a result, the number of molds required for molding increases, resulting in a very high molding cost.

(Object of the Invention) The present invention has been made in view of the above problems, and it is possible to form a bulge with a small bulge base radius and a small corner radius with a relatively low high hydraulic pressure.
It is an object of the present invention to provide a high-hydraulic expansion molding method for a tapered tube material and an apparatus therefor, which can form a tapered portion in addition to a bulging portion in a series of expansion molding steps.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a guide mold divided into a plurality of parts, an expansion mold in the center,
In addition, left and right end molds having tapered molding portions are fitted on both sides of the expansion mold at a predetermined distance from each other, and the straight pipe for processing is fitted with either end of the pipe on either side. By setting the guide mold across the left and right end molds, and joining and fastening another guide mold to this guide mold, the pipe end of the straight pipe can be radiused with the tapered part of each end mold. A tapered constricted pipe portion is formed by compressing the diameter in the direction, and then,
While applying high hydraulic pressure inside the straight pipe, the pressure rods on the left and right sides are press-fitted from both sides into the combined guide mold, and are pressed against the end forming mold combined with the pipe end of the straight pipe, thereby causing the expansion. The tapered pipe material is expanded under high hydraulic pressure so that the end portion of the straight pipe is held by the end mold that moves in a direction close to the extrusion mold, and the center portion of the straight pipe is bulged into the expansion mold. An extrusion molding method, a guide mold divided into a plurality of parts, a bulge mold divided into a plurality of parts fitted to the inner surface of a central part of the guide mold, and a bulge mold formed at both ends of the guide mold. left and right end molds each having a tapered part that is movably fitted at a predetermined distance from the guide mold and reduces the diameter of the end of the straight pipe for processing when the guide molds are combined and fastened; Pressure that is press-fitted into the guide mold from both sides and simultaneously presses the pipe end of the straight pipe and the end mold, and moves the end mold to bulge the center part of the straight pipe into the expansion mold. The gist of the present invention is a high-hydraulic expansion molding apparatus for tapered pipe material comprising a rod.

(Function) With the above-described molding method and molding apparatus, when the straight pipe is set and the guide molds are combined and fastened, the tapered molded portions of the end molds fitted to both ends of the guide molds are compressed by this compressive force. Accordingly, a tapered constricted pipe portion can be formed at the end of the straight pipe.
That is, the aperture tube portion and the bulging portion can be molded at once in a series of molding steps using the same mold.

In addition, there is a space between the expansion mold and the end mold, and the end mold can be moved in this space. As the pipe deforms, the end mold moves while holding the end of the straight pipe. In other words, since there is no relative sliding between the throttle tube portion formed in the straight tube and the end molding die, the ground radius and corner radius of the bulging portion can be made much smaller than in the past.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a longitudinal cross-sectional view of one embodiment, and the upper part with respect to the center line shows the state before molding starts, and the lower part shows the molding completed state. Further, FIGS. 2 to 4 are sectional views taken along line AA in FIG. 1, respectively, showing the order of the molding steps, and similarly, FIG. 5 is a sectional view taken along line BB in FIG. 1. In these figures, the mold structure is mainly divided into upper and lower halves with bulging parts 6a and 7a for bulging the central part of the straight pipe 5 for processing. Type 6,
7, upper and lower left end molds 8 and 9, and upper and lower right end molds, which are divided into two to press both ends of the straight pipe 5 in the radial direction to form a tapered shape. 10, 11, contact the pipe end surfaces on both sides of the straight pipe 5 to close the opening, and at the same time direct the left and right end molds 8, 9, 10, 11 toward the bulge mold in the bulge molding process. The left and right pressure rods 12 and 13 for pressing, and the upper and lower half-divided molds 6 to 13 are arranged with their axes coaxial, and the left and right end molds 8 to 11 upper and lower guide molds 14 and 15 for guiding the molds so that they can move coaxially toward the expansion molds 6 and 7 disposed between them;
It is composed of. In addition, each end mold 8~
11 have tapered molded parts 8a to 11a, respectively.
is formed.

Next, to explain another configuration based on the expansion molding process, first, by raising the upper guide mold 14, the semi-cylindrical part 14a of the upper guide mold 14 is formed as shown in FIGS. 2 to 5. The upper molds 6, 8, and 10 that have been fitted are also lifted up together and separated and opened. A means for attaching each of the upper molds 6, 8, 10 to the semi-cylindrical portion 14a of the upper guide mold 14, and a lower guide mold 15 of each of the lower molds 7, 9, 11.
As shown in FIGS. 2 to 5, the mounting means for attaching to the semi-cylindrical portions 15a employs a structure in which the housing plates 16 are fitted into the semi-cylindrical portions 14a and 15a so as to be held therein. The expansion molds 6 and 7 are fixed at the center positions of the corresponding guide molds 14 and 15, and the end molds 8 to 11 are held in place by coil springs 17 fitted into these recesses 8b to 11b. Each of the guide molds 14 and 15 is urged outward and rests against a stopper 18 protruding from the guide molds 14 and 15, maintaining a predetermined distance from the expansion molds 6 and 7, respectively.

In the split open state due to the above-described elevation of the upper guide mold 14, the straight pipe 5 is set so as to span over each of the tapered molded parts 9a and 11a of the end molding molds 9 and 11 on the left and right sides of the lower part. After that, the upper guide mold 14 is lowered and combined with the lower guide mold 15 and fastened together. Both guide types 14,1
The process of fastening 5 is shown in FIGS. 2 to 4 in order. First, FIG. 2 shows a state in which both guide molds 14 and 15 are opposed to each other, and when both guide molds 14 and 15 are fastened from this state, a pair of opposing two-part end molding molds 8, 9, 10, 11, as shown in FIG.
When the pipes are completely fastened, both ends of the straight pipe 5 are pressed in the radial direction by the tapered forming parts 8a to 11a and drawn into a tapered shape, as shown above the center line in FIGS. 4 and 1. It is processed and reduced in diameter to form the throttle tube portion 5a.

Then, the left and right pressure rods 12 and 13 are respectively moved inward from the positions shown in the upper part with respect to the center line in FIG. Then, the opening of the straight pipe 5 is closed except for the liquid inlet. At this time, the stepped portions 12a, 13a of the pressure rods 12, 13 are joined to the end surfaces of the respective end molds 8-11. Next, when the pressure rods 12 and 13 are forcefully advanced inward while applying high hydraulic pressure Pm inside the straight pipe 5, the stepped portions 12a and 13a of the pressure rods 12 and 13 Each end mold 8-1
1 also moves inward together with the pressure rods 12 and 13, and the straight pipe 5 is subjected to compressive force while the constricted pipe portion 5a of the straight pipe 5 is joined and held by the end forming molds 8 and 11. It deforms while moving toward the center at Fm, and the expansion molding process progresses. As this progresses, the space for movable expansion molding formed in the gap between the expansion molds 6 and 7 and each end mold 8 to 11 decreases, and at the end of the expansion molding process, the space for movable expansion molding is reduced. As shown below the center line in Figure 1, each end mold 8
11 are in close contact with the expansion molds 6 and 7. In this bulge forming step, there is no relative sliding between the tapered surface of the constricted pipe portion 5a of the straight pipe 5 and the respective tapered formed portions 8a to 11a of the end formed tubes 8 to 11, so that the above-mentioned If the space for movable expansion molding, which is the gap between the expansion molds 6 and 7 and each of the end molding molds 8 to 11, is appropriately set, the straight pipe 5 will be formed into an octagonal shape as shown in FIG. The base radius R3 and the corner radius R4 shown in FIG. 1 of the bulging portion 5b can be molded to be much smaller than in the conventional molding method.
When the formation of the bulging portion 5b is completed in this way, the high-pressure liquid in the straight pipe 5 is discharged to the atmosphere, and at the same time, the pressure rods 12 and 13 are retreated, and the upper guide mold 14 is further raised. to open each mold and take out the molded product.

In addition, when applying screws, relief grooves are sometimes provided for the purpose of making it easier to cut the end of the screw, but since such relief grooves depend on the structure of the mold, both guide molds in the above-mentioned molding process are 14,
It becomes possible to form the tapered surface at the same time as the drawing of the tapered surface of the tube end in step 15, that is, when processing the drawn tube portion 5a.

FIG. 6 shows another embodiment of the present invention, in which the same or substantially equivalent parts as in FIGS. 1 to 5 are given the same reference numerals. and,
Flange bulging molding parts 20a and 25a each consisting of a stepped part are provided in the bulging molds 20 and 25, and tapered molding parts 21a to 24 of each end molding mold 21 to 24 are provided.
This embodiment differs from the previous embodiment in that the slope of a is larger than that of the previous embodiment.

The molding process is exactly the same as the above-mentioned embodiment, and by providing the flange bulge molding part in the bulge mold 20, the high liquid pressure Pn and the pressure rods 12, 13 are reduced during the bulge molding process. Although the compressive force Fn is slightly higher than that in the above embodiment, it is possible to bulge the flange portion 5c on the straight pipe 5 as shown below the center line in the figure showing the completed molding state. The molded product having this flange portion 5c can have increased rigidity of the bulged portion compared to the molded product of the same thickness in the above embodiment.

Also, to explain the drawing tube portions 5d at both ends, drawing with an excessively large diameter reduction rate (diameter reduction/diameter before processing x 100) will cause figure-eight buckling, making drawing impossible. becomes. The buckling limit is influenced by the material of the straight pipe 5 and the ratio of wall thickness to outer diameter (t/D), but the buckling limit of general low carbon steel pipe is an extremely thin walled pipe with t/D = 0.005. Approximately 2%, t/
Approximately 4% for a thin-walled pipe with D=0.02, and t/D=
At 0.1, it is approximately 8%, and a diameter reduction rate exceeding this will induce buckling. Figure 6 shows an example where a tapered shape with a diameter reduction rate exceeding this buckling limit is required. Both guide molds 14 and 15 are joined and fastened with the guide molds 21 to 24 located further outward than in the case shown in FIG. After pressing in the radial direction to perform drawing, additional drawing of the taper is performed in the process of moving the end forming molds 21 to 24 inward, thereby creating a taper with a diameter reduction rate that exceeds the buckling limit described above. A throttle tube portion 5d having a shape is obtained. According to this method, it is possible to perform a drawing process that is approximately twice or more than the above-mentioned limit value of the diameter reduction rate.

It should be noted that the present invention is not limited only to the above-mentioned embodiments, and it goes without saying that various embodiments are possible without departing from the scope of the claims. for example,
In the embodiment described above, the bulging portion 5b was formed into an octagonal shape.
Since it is bulge molding using the structure of the mold as described above, it can be formed into any polygonal shape. Also,
If expansion molding is performed by placing a separate desired object in place of the expansion mold, the desired object can also be fixed to the flanged expansion molded product.

(Effect of the invention) The present invention uses the above-described expansion molding method,
Alternatively, by having the structure and operating as described above, the bulge part and the tapered part, that is, the iris tube part can be obtained at the same time in a series of bulge molding processes that are almost the same as the bulge molding process required in the conventional method. At the same time, it is possible to minimize the field radius and corner radius. Moreover, there is an advantage that a necessary escape groove and flange portion can be formed at the end of the screw.

[Brief explanation of drawings]

1 to 5 show an embodiment according to the present invention, and FIG. 1 shows the state before processing above the center line.
In addition, the lower part is a vertical cross-sectional view showing the state after processing, Figures 2 to 4 are cross-sectional views taken along the line A-A in Figure 1 showing the process order, and Figure 5 is a cross-sectional view taken along line A in Figure 1. - A cross-sectional view taken along line A; FIG. 6 is a vertical cross-sectional view of another embodiment of the present invention, showing the pre-processing state above the center line and the post-processing state below the center line;
The figure is a longitudinal sectional view of a conventional apparatus, showing the pre-processing state above the center line and the post-processing state below the center line. 5... Straight pipe, 6, 7, 20, 21... Expansion mold, 8-11, 21-24... End mold, 8a
~11a, 21a~24a... Taper molded part,
12, 13... Pressure rod, 14, 15... Guide type.

Claims (1)

[Claims] 1. A guide mold divided into a plurality of pieces, with a swelling mold in the center and left and right end molds having tapered molding parts on both sides of the swelling mold. The straight pipes for processing are arranged at predetermined intervals and fitted, and the straight pipes for processing are set with both ends of the pipes straddled over the left and right end forming molds of any of the guide molds, and the other guide molds are placed in this guide mold. By joining and fastening, the end of the straight pipe is compressed in the radial direction using the tapered part of each of the end forming molds to form a tapered constricted pipe part. Pressure rods on the left and right sides are press-fitted into the combined guide mold from both sides while applying hydraulic pressure to press the pipe end of the straight pipe and the combined end mold, and the expansion mold is formed. The height of the tapered pipe material is characterized in that the end part of the straight pipe is held by the end part mold that moves in a direction approaching the straight pipe, and the center part of the straight pipe is bulged into the expansion mold. Hydraulic expansion molding method. 2. A guide mold divided into a plurality of parts, a bulge mold divided into a plurality of parts fitted on the inner surface of the central part of the guide mold, and a predetermined interval at both ends of the guide mold with respect to the bulge mold. left and right end molds each having a tapered part that is movably fitted and reduces the diameter of the end of the straight pipe for processing when the respective guide molds are combined and fastened; a pressure rod that is press-fitted from both sides and presses the pipe end of the straight pipe and the end mold at the same time, and moves the end mold to bulge the center part of the straight pipe into the expansion mold; A high-liquid expansion molding device for tapered pipe material, comprising: