JP3174132B2 - Core material for bending plastic pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending core material useful for manufacturing a curved plastic pipe.

[0002]

2. Description of the Related Art A plastic bent pipe is used in a bent portion of a pipe (gas, water, sewage, etc.) formed by a plastic pipe. In the manufacture of this plastic bent tube,
In order not to impair the roundness of the tube, fill the inside of the tube with a granular filler such as sand, insert a rubber core, and then heat the tube under a softened condition. After bending, cooling and demolding, a method of discharging a filler or extracting a core material is employed.

Recently, as a method of manufacturing such a bent plastic tube, the present applicant has inserted a core material having a substantially circular cross section by laminating thin plates or consolidating wires into a plastic tube. Then, a method was proposed in which the plastic tube was bent while sliding between the thin plates or wires under a heat-softened state, and the core material was drawn out after cooling the bent and bent plastic bent tube (Japanese Patent Application No. 2002-214,197). Hei 3-230306 ).

[0004] The core material in the above invention has a thickness of, for example, 2 mm.
A thin plate such as a polyethylene plate of about mm is cut into a width approximately equal to the inner diameter of the tube to be bent and laminated, and then the corners of the four corners of the laminated material are cut with a lathe or the like to make a rod with an octagonal cross section. Further, those obtained by cutting and finishing this into a cylindrical shape are used. The reason why the thickness of the thin plate is set to about 2 mm is 1
If it is less than mm, it is easy to be damaged, and the waist becomes weak, making it difficult to handle as a single item.

[0005]

When the core material for bending obtained by laminating the above-mentioned thin plates is used repeatedly, when the core material is pulled out from the plastic tube, the core material is placed between the outer surface of the core material and the inner surface of the plastic tube. The resulting friction causes wear on the outer surface of the core. In particular, among the plurality of thin plates constituting the core material, the two outermost thin plates have a large area in contact with the inner surface of the plastic pipe as compared with the other thin plates, and therefore are significantly worn. Moreover, wear proceeds in the direction of reducing the thickness.

However, the outermost thin plate of the above-mentioned core material for bending work has a thickness of only about 2 mm like the other thin plates, so that the outer thin plate immediately becomes difficult to handle due to wear. The plate thickness (1 mm or less) has been left, and the problem that frequent replacement is required remains. In addition, since the outermost thin plate has to be cut and finished on one surface, the thinner the thickness, the more difficult the work becomes, and the lower the accuracy. Therefore, since it is difficult to manufacture only the outer thin plate, if the wear of the outer thin plate progresses, the entire core material must be replaced. Therefore, if the durability of the core material can be improved, the manufacturing cost of the bent plastic pipe can be greatly reduced, and it has been eagerly desired to improve the durability of the outermost thin plate.

[0007] Further, the core material in which the wires are bundled has a problem that the maintenance ratio of roundness during bending is slightly inferior to the core material in which the thin plates are laminated.

An object of the present invention is to provide a core material for bending a plastic pipe which has a high degree of maintaining roundness and has high durability, focusing on the above-mentioned problems.

[0009]

In order to achieve the above object, a plastic pipe bending core material according to the present invention comprises a plurality of thin plates laminated so as to have a substantially circular cross section. Of these, the outermost thin plate was formed to be thicker than the other thin plates.

[0010]

When manufacturing the core material of the present invention, first, a plurality of thin plates are cut into a width substantially equal to the inner diameter of the pipe to be bent and laminated. At this time, a thin plate thicker than the other thin plates is laminated on both outer sides. Next, four corners of the laminated material are cut with a lathe or the like, and the cut material is further cut into a substantially cylindrical shape. At this time, the thin sheet laminated on both sides has a larger cutting area than the other thin sheets, but since it is formed thicker than the other thin sheets, it becomes stiff and easy to handle as a single item. At the same time, the rigidity is increased, and it is difficult to break. In addition, the cutting operation can be easily performed, and the dimensional accuracy can be accurately obtained.

When the plastic tube is bent using the core material of the present invention, the core material of the present invention is inserted into the plastic tube, and then the plastic tube is heated under a heated condition. Bending while sliding between thin plates,
After cooling this bent plastic bent tube,
Pull out the core material. That is, since the cross-sectional shape hardly changes during the bending of the plastic tube, the cross-section of the plastic tube can be maintained in the original shape even after the forming. Also, by repeating this bending process, when the core material is pulled out, abrasion occurs on the outer surface of the core material due to friction generated between the outer surface of the core material and the inner surface of the plastic pipe. Since it is formed to be thicker than the other thin plates, it does not immediately become difficult to handle due to abrasion, and the durability is not extremely deteriorated as compared with other thin plates.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. FIG. 1 is a side view showing a plastic pipe bending core material of the present embodiment, and FIG. 2 is a plan view showing the core material. The core material 1 is made of a plurality of plastics so that the cross section becomes a perfect circle. The thin plates 11a, 11b, 11c, 11d, and 11e are formed by laminating the thin plates 11a to 11e.
Among them, the outermost thin plate 11a is formed to be thicker than the other thin plates 11b to 11e. The thickness of each of the thin plates 11a to 11e varies depending on the material thereof, the diameter of the core material 1, and the like.
Is preferably about 4 to 6 mm (2 to 3 times of other thin plates), and the other thin plates 11 b to 11 e are preferably about 2 to 3 mm. Further, it is preferable to use the thin plates 11a to 11e which do not thermally deform at the temperature (usually 45 ° C.) in the plastic pipe at the time of bending. For example, olefin-based plastics, particularly ultra-high-molecular-weight polyethylene, high- / medium-density polyethylene, and the like are preferable. However, when a resin or metal with low slip is used, lubricating oil or a lubricant may be applied.

A binding ring 12 is provided at both ends of the core material 1. The binding ring 12 includes a bolt 13 passing through a bolt hole 111 passing through all the thin plates 11a to 11e, and a bolt 13 Are fastened by a nut 14 screwed into the nut. Also, the bolt hole 11 of the core 1
Numeral 1 is formed in the shape of a long hole elongated in the axial direction of the core material 1, and the bolt 13 plays in the axial direction of the core material 1.

Next, the operation of the embodiment will be described.

(I) Manufacture of core material Referring to FIG. 3, the procedure of manufacturing the core material of the present embodiment will be described. First, as shown in FIG.
1a to 11e are cut to a width substantially equal to the inner diameter of the pipe to be bent and laminated. At this time, a thin plate 11a thicker than the other thin plates 11b to 11e is laminated on the outermost side. Next, as shown in (b), the four corners of the laminated material are cut with a lathe or the like to form a rod having an octagonal cross section, and this is further cut into a substantially cylindrical shape as shown in (c). I do.

At this time, the outermost laminated thin plate 11
a has a larger cutting area than the other thin plates 11b to 11e, but since the thin plate 11a is formed thicker than the other thin plates 11b to 11e, the stiffness is increased and the single sheet is handled. Is easy, and the rigidity is increased, so that it is hard to break. In addition, the cutting operation can be easily performed, and the dimensional accuracy can be accurately obtained. Further, depending on the thickness, the outermost thin plate 11a can be manufactured alone.

(Ii) At the time of bending the plastic pipe Referring to FIG. 4, the procedure for bending the plastic pipe 2 using the core material 1 of the present embodiment will be described. First, the plastic pipe 2 is heated to near the softening temperature. ,next,
As shown in (a), the core material 1 is inserted into the heated plastic tube 2. At this time, the core material 1 has an outer diameter substantially equal to the inner diameter of the plastic tube 2 and a length longer than the length of the plastic tube 2.

Thereafter, as shown in (b), the plastic tube 2 into which the core material 1 has been inserted is slid between the thin plates 11a to 11e by using a mold 6 to obtain a desired bending radius and bending. Bend to an angle. The bending of the plastic tube 2 is performed, for example, by hooking a wire 7 on a bolt 13 and pulling the wire 7 with a winch 8 in a desired direction.

Next, the plastic pipe 2 is cooled and solidified by passing cooling water through the mold 6, and when the plastic pipe 2 is solidified, it is released from the mold. Thereafter, as shown in FIG. Pull out the core material 1 from 2. Plastic tube 2
When the core material 1 is pulled out from the core material, one of the bolts 13 and the nut 14 and the binding ring 12 are removed from the core material 1, the end of the plastic tube 2 is hooked on the extraction stand 9, and the other bolt 13 and the nut 14 are The core material 1 is collectively pulled out from the plastic tube 2 by pulling with a winch or the like. Then, the thin plates 11a to 11e can be pulled out from the plastic tube 2 without being separated.

That is, even when the plastic tube 2 is bent and formed, the cross-sectional shape of the core material 1 hardly changes, so that the cross-section of the plastic tube 2 can be maintained as it is after the forming.

Further, by repeating this bending process, the outer surface of the core 1 is worn due to the friction generated between the outer surface of the core 1 and the inner surface of the plastic tube 2 when the core 1 is pulled out. Outer thin plate 11a
Is formed thicker than the thickness of the other thin plates 11b to 11e, so that it does not immediately become difficult to handle due to abrasion. For example, the outer thin plate 11a
Is three times the thickness of the other thin plates 11b to 11e, the durability of the outer thin plate 11a is three times or more as compared with the case where the thickness of the other thin plates 11b to 11e is the same. .

As described above, according to the core material 1 of the present embodiment, since the cross-sectional shape hardly changes during the bending of the plastic tube, the bending process is performed while maintaining the cross-sectional shape of the plastic tube as it is. Can be made and multiple thin plates 1
1a to 11e, the outermost thin plate 11
Since a is formed thicker than the thickness of the other thin plates 11b to 11e, the durability of the outer thin plate 11a is improved, and therefore, the manufacturing cost of the plastic bent tube can be reduced.
Further, since only the outermost thin plate 11a can be manufactured, the durability of the outer thin plate 11a is reduced.
If the durability of e is inferior, only the outer thin plate 11a can be replaced, thereby greatly reducing the manufacturing cost of the bent plastic pipe.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. Are also included in the present invention. For example, in the embodiment, a core material for bending with a true circular cross section is shown. However, since the cross-sectional shape of the core material needs to correspond to the cross-sectional shape of the plastic pipe to be bent, a polygon, an ellipse, or the like is used. It may be a modification such as an oval shape.

[0024]

As described above, in the core material for bending a plastic pipe of the present invention, the cross-sectional shape hardly changes even when the plastic pipe is bent. The bending process can be performed while maintaining the state as it is, and the durability of the outermost thin plate is improved, so that the effect of reducing the manufacturing cost of the plastic bent tube can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing a core material for bending a plastic pipe of the present embodiment.

FIG. 2 is a plan view showing a core material for bending a plastic pipe of the present embodiment.

FIG. 3 is a view showing a manufacturing procedure of a bending core material of the present embodiment, wherein (a) shows a state in which thin plates are cut and laminated,
(B) shows a state in which four corners of the laminated material are cut into a rod shape with an octagonal cross section, and (C) shows a state in which the laminated material is cut and finished in a column shape.

4A and 4B are diagrams showing a method of bending a plastic pipe using the core material for bending according to the present embodiment, wherein FIG. 4A shows a state in which the core material is inserted into the plastic pipe, and FIG. (C) shows a state where the plastic core material is pulled out.

[Explanation of symbols]

 1 Core material 11a-11e Plastic thin plate

Claims (1)

(57) [Claims] 1. A plurality of thin plates laminated so as to have a substantially circular cross section, and the outermost one of the plurality of thin plates is formed to be thicker than the other thin plates. A core material for bending plastic pipes.