JPS5818892B2 - Bent pipe forming method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a curved pipe forming method.

When a bent pipe is formed from a semi-hardened straight pipe, as shown in FIG. 1, shrinkage A occurs on the inside and elongation B occurs on the outside.

In this case, the elongation B does not have much effect, but when the shrinkage A occurs, a dumpling-like raised portion C is formed as shown in FIG. 2, which is undesirable in terms of the product because it creates an uneven surface.

This is particularly noticeable in the case of composite resin pipes using sand mortar.

The present invention provides a curved pipe forming method capable of solving the above-mentioned problems, and one embodiment thereof will be described below with reference to FIGS. 3 to 10.

In the present invention, first, a bending jig 1 as shown in FIG. 3 is prepared.

This bending jig 1 includes a pair of rings 3A located concentrically,
3B and these rings 3A.

3B, and an elastically deformable beam member 2 that connects opposing surfaces at appropriate positions in the circumferential direction.

The bending jig 1 includes a beam member 2 made of rubber (chemical resistance, heat resistance, and dimensional stability) or an elastic metal, and a ring 3A.
3B made of inelastic metal or made entirely of rubber are used.

This bending jig 1 is inserted into a splittable cylindrical mold 4 as shown in FIGS.

This cylindrical shape 4 can be divided into upper and lower parts along the axial line, and its molded surface 4a has a slit groove 5 into which the beam member 2 can be fitted, and an annular shape into which the rings 3A and 3B can be fitted. Groove 6A
, 6B are formed.

Therefore, when the bending jig 1 is inserted into the cylindrical mold 4, the inner surfaces of the beam member 2 and the rings 3A, 3B are aligned with the molding surface '4.
be flush with a.

Next, as shown in FIG. 5A9, a resin pipe or composite resin pipe 7 is centrifugally molded on the molding surface 4a while rotating the cylindrical mold 4.

This centrifugal molding is similar to the conventional method.
A composite resin pipe as shown in the figure is centrifugally molded.

Here, FIG. 9 shows the reinforcing layer 8, which is an FRP layer or CFR layer incorporating raw pink, roving cloth, roving cloth tape, chopped strand, etc.
is an outer layer, a mortar layer 9 which is a sand or concrete layer is an intermediate layer, and a reinforcing layer 10 which is an F'RP layer or a CFR layer as described above is an inner layer.

Further, in FIG. 10, the reinforcing layer 11, which is an FRP layer, is the outer layer, and the corrosion-resistant layer 12, which is a chopped strand layer, is the inner layer.

Next, the rotation of the cylindrical mold 4 is stopped while the tube 7 formed as described above is semi-hardened.

Then, the inner surface of the tube 4 is pressurized.

That is, as shown in FIG.
4 or the like to inflate this elastic body 13 by filling it with air or liquid.

As a result, a uniform internal pressure P is applied to the entire inner surface of the tube 7, thereby making the internal pressure uniform in the thickness direction.

Next, as shown in FIGS. 7A and 7B, the cylindrical mold 4 is divided into upper and lower parts, and the tube 7 and the bending jig 1 are taken out as one piece.

Thereafter, as shown in FIG. 8, the tube 7 is bent so that the beam member 2 is located inside.

During this bending action, the outside of the tube 7 stretches, but the inside of the tube 7 does not shrink because it is restricted by the bending jig 1, that is, the beam member 2.

Thereafter, a desired bent pipe can be obtained by removing the bending jig 1 from the pipe 1, but the bent pipe is hardened before or after removal.

FIG. 11 shows another embodiment in which a plurality of auxiliary beam members 16 are provided between the rings 3A and 3B and are removable by operating bolts 15, and these auxiliary beam members 16 are removed immediately before bending the tube.

According to the present invention described above in the embodiments, when bending a semi-hardened pipe, the beam member of the bending jig restricts the shrinkage of the inside of the semi-hardened pipe, thereby ensuring a high quality product without uneven surfaces etc. You can get a bent pipe.

In addition, since the bending jig is prepared at a suitable position from the time of centrifugal forming, its installation does not cause deformation of the pipe due to work, and simplifies the entire manufacturing process, compared to, for example, a method in which it is attached after straight pipe forming. It can be done quickly.

[Brief explanation of drawings]

Fig. 1 is a front view showing a conventional example, Fig. 2 is an enlarged cross-sectional view of the inner side thereof, and Figs. 3 to 10 show an embodiment of the present invention.
Figure 3 is a perspective view of the bending jig, Figure 4 A 2, Figure 5 I 9
Figure 6, Figure 6, Figure 7, Figure 8 shows the manufacturing process, Figures 4 to 7, Figure 8, vertical front views, 9 and 10 are longitudinal side views of the main parts of the tube, and FIG. 11 is a perspective view showing another embodiment. 1...Bending jig, 2...Beam member, 3A
, 3B...Ring, 4...Cylindrical, 4a
...Molding surface, 5...Slit groove, 6A
, 6B... Annular groove, 1... Resin pipe or composite resin pipe, 18... Elastic body, 16...
...Auxiliary beam member, P...Internal pressure.

Claims (1)

[Claims] 1. A bending jig consisting of a pair of rings located at the core and connecting opposing surfaces at appropriate positions in the circumferential direction with an elastically deformable beam member is placed in a splittable cylindrical shape. The tube is inserted so that it is flush with the molding surface, and the resin tube or composite resin tube is centrifugally molded on the molding surface while rotating the tube.Then, while the tube is in a semi-hardened state, the tube is divided. 1. A method for forming a bent pipe, which comprises taking out a pipe and a bending jig, bending the pipe so that the beam member of the bending jig is located inside, and then removing the pipe bending jig.