JPH0157658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a branch line guard.

Branch wires are attached to utility poles to prevent them from tipping sideways. The branch line consists of a mooring device that rises diagonally from the ground on the side of the utility pole, and a connecting line that connects the top end of the mooring device diagonally to the top of the utility pole. Although the mooring equipment is usually fixed at a location that does not obstruct traffic, it is still necessary to avoid collisions with passersby.
A guard is attached to this. This is the branch line guard.

Branch lines often had the structure shown in Figure 1. In FIG. 1, a is a telephone pole, b is a mooring tool, and c is a connecting line.
The mooring tool b rises obliquely from the ground toward the top of the utility pole a, and has a ring d at its tip. A connecting wire c is passed through the ring d, and the connecting wire c strongly pulls the upper part of the utility pole and the mooring tool b to support the utility pole a. As shown in FIG. 2, a guard for protecting such a branch line has been used, in which a large diameter pipe e and a small diameter pipe f are connected together.

Branch wire guards like the one shown in Figure 2 were often made of synthetic resin. The branch line guard shown in Figure 2 includes parts with different pipe diameters, so
It cannot be readily produced by extrusion. Therefore, conventionally, it has been manufactured using a blow molding method. However, using the blow molding method not only takes time to manufacture, but also requires a split mold for blowing, which is not advantageous. in addition,
When using the blow molding method, the small diameter pipe has a thicker wall than the large diameter pipe, which is inconvenient to use and has the disadvantage of increasing costs. Therefore, it was desired to develop a more advantageous manufacturing method.

This invention was developed in response to the above-mentioned main points. This invention uses a resin pipe with a diameter corresponding to the large diameter part as a material, inserts an inner mold extending from the large diameter part to the shoulder part into the resin pipe and fixes it to both ends of the resin pipe, and fixes the central part of the resin pipe to The main idea is to reduce the tube diameter by pulling it and form a small diameter section.

This invention uses an inner mold consisting of a large-diameter portion, a small-diameter portion, and a shoulder portion that connects these, and the small-diameter portion is attached to both ends of a thermoplastic resin tube having an inner diameter that fits into the large-diameter portion. Insert the inner mold toward the outside, press both ends of the resin tube from the outside to fix the large diameter part, stretch the resin tube together with the inner mold, make the longitudinal center of the resin tube a small diameter, and The present invention relates to a method for manufacturing a branch line guard, characterized in that a small diameter portion is cut at the center in the longitudinal direction, and a split is provided in each cut portion passing through the pipe in the longitudinal direction.

The method of this invention will be explained as follows based on the drawings. 3 and 4 are partially cutaway sectional views showing the implementation process of the method of this invention. FIG. 5 is a perspective view of the branch line guard;
It also shows how it is used.

In FIGS. 3 and 4, 1 is an inner mold, 2 is a thermoplastic resin pipe, and 3 is a fixture. The inner mold 1 is made up of a large diameter part 11, a small diameter part 12, and a shoulder part 13 connecting these parts, and these parts are integrated. The resin pipe 2 has an inner mold that fits into the large diameter portion 11. Regarding the inner mold 1, the outer diameter of the large diameter portion 11 is slightly smaller than the inner mold of the resin pipe 2, and is just large enough to fit into the resin pipe 2 with almost no gap. There is.

Two of these are used for the inner mold 1, both of which have a small diameter portion 1.
2 facing inward, insert it from both ends of the resin tube 2,
Fix it at both ends of the resin tube 2. A fixture 3 is brought into contact with the outside of the resin pipe 2, and the fixture 3 is tightened so that the fixture 3 clamps the resin pipe 2 on the large diameter portion 11. Each fixture 3 is fixed on a support stand 4, respectively, and the two support stands 4 are attached on a foundation 5 so that they can move toward or away from each other.

Thereafter, the supports 4 to which the resin tubes 2 are fixed are moved away from each other. Then, the shape of the resin tube 2 cannot be changed at the portion where it contacts the large diameter portion 11 because it is held by the fixture 3. However,
Around the small diameter portion 12, the plastic tube 2 is not supported either from the inside or the outside, so the plastic tube is stretched, reducing the outer diameter and the wall thickness. Therefore, when the support base 4 is pulled further away, the resin tube 2 forms a tapered part along the shoulder part 13 of the inner mold, and finally comes into close contact with the small diameter part 12, so that the resin tube 2 has an outer diameter like the inner mold 1. It constitutes a drum-shaped molded body with a cylindrical shape.

Although the above-mentioned tension can be performed at room temperature, it is easier to do so when the material is slightly heated. When heating, it is necessary to keep the plastic tube at a uniform temperature, especially in the circumferential direction. For this reason, it is desirable to heat the resin tube while rotating it.

After tension is applied and the tension is removed, the resin tube tends to return to its original shape to some extent, thus shrinking in the longitudinal direction. Therefore, in order to reduce this shrinkage, annealing is performed. Annealing is performed at a temperature close to the glass transition point of the resin.

After annealing, the small diameter portion of the resin tube is cut approximately perpendicularly to the longitudinal direction at the longitudinal center to obtain a tube having a large diameter portion at one end and a small diameter portion at the other end. Next, a crack is made in the tube wall to extend through the tube in the longitudinal direction. The result is a branch line guard.

As shown in FIG. 5, the branch guard has a large diameter section e at one end, a small diameter section f at the other end, and a split g passing through in the longitudinal direction. This branch line guard forcibly opens the split g, passes the branch line through the split, and stores the mooring tool b of the branch line within the large diameter portion e.
The connecting wire c is housed within the small diameter portion f. When the opening is stopped, the guy wire guard closes the split and is positioned as shown by the dotted line in FIG. 5 to protect the guy wire. In this respect, the branch line guard obtained by the present invention is no different from the conventional branch line guard.

The branch line guard obtained by the method of this invention is
It has the great advantage of being easy to attach to branch lines. That is, since the small diameter portion f is made by stretching and has a thin wall, it is easy to open the small diameter portion along the split g and cover the connecting line c. When conventional branch wire guards are made by blow molding, the small diameter part f is thicker than the large diameter part e, so not only is it difficult to open because of the small diameter, but the wall thickness is large and it is even more difficult to open. Because of this, it was not easy to open the split g and cover the small diameter portion f over the connecting wire c. The product obtained by the method of the invention offers significant advantages in terms of ease of installation.

In addition to the advantages described above for the products obtained by the method, the method of the present invention provides a significant advantage in that the branch guard can be manufactured easily and reliably. In other words, manufacturing is easy because the inner mold is inserted into the thermoplastic resin pipe, the outer part is pressed down to fix the resin pipe to the inner mold, and then the small diameter part and the large diameter part can be created by simply pulling. It is. On top of that, use an inner mold consisting of a large diameter part, a small diameter part, and a shoulder part connecting these parts, insert the inner mold into the resin pipe with the small diameter part facing the inside, and press it with the outside facing away. Since the large diameter portion is fixed by tightening, it is possible to reliably shift the diameter to the small diameter along the shoulder portion by tension, and therefore, it is possible to reliably create a branch line guard having a desired shape. Furthermore, since two branch line guards can be created with one pull,
It is an efficient manufacturing method. The method of this invention provides these various benefits.

Various thermoplastic resins can be used. For example, resins with good stretchability such as polyethylene and vinyl chloride resins can be used. Among these, suitable resins are those having an elongation rate that exceeds the stretching ratio of the portion to be stretched. Furthermore, by blending 5 to 20% by weight of a low-crystalline copolymer or olefin-based crosslinked polymer with these resins, it is possible to improve the decrease in the elongation rate in the longitudinal and perpendicular directions of the resin tube during stretching. preferable.

Next, the details of the method of this invention will be explained with reference to Examples.

Example A thermoplastic resin pipe was made of polyethylene containing 6% by weight of ethylene-vinyl acetate copolymer and 2% by weight of pigment, etc., with an outer diameter of 71.4 mm and a wall thickness of 3.2 mm.
A resin pipe with a circular cross section and a length of 2.77 m was prepared.
In addition, the inner mold has an outer diameter of 64.5 mm at the large diameter part, and a length of 1.1 m.
A circular cross-section was used, with the small diameter part having an outer diameter of 41.4 mm and a length of 28.5 cm, and the shoulder part between the large diameter part and the small diameter part having a length of 10 cm.

First, the resin tube was preheated for 5 minutes with hot air at 80°C. Next, inner molds were inserted into both ends of the resin tube with the small diameter portions facing inward, so that the inner molds abutted approximately at the center of the resin tube. Next, from both ends of the resin tube
A length of 1 m each is held between the large diameter part of the inner mold and the large diameter part of the inner mold using a fixture from the outside, and the length of the extended part of the resin pipe is 77 cm.
cm. Next, in hot air at 120° C., the supports to which the fixtures were fixed were moved away from each other at a speed of 2 m/min, and the stretched portion of the resin pipe was stretched approximately 3.1 times. The maximum tensile force at this time was 600 kg.
Next, the tensile force was released and the resin tube was annealed by leaving it in hot air at 120° C. for 2 minutes, returning the stretched portion to about 2.7 times its original length. Then, heat the resin tube to 18℃.
After cooling with water for 30 seconds, release from the inner mold and fixture,
The center portion of the resin tube was cut, and a split was formed along the longitudinal direction of the resin tube with a cutting edge.

In this way, the outer diameter of the large diameter part is finally 71.4
mm, wall thickness 3.2mm, length 1m, outer diameter of small diameter part 45.0mm,
Two products were obtained, each having a wall thickness of 1.8 mm, a length of 90 cm, and a length of 10 cm between the large diameter part and the small diameter part.

[Brief explanation of drawings]

FIG. 1 is a side view of a utility pole with a branch line. Second
The figure is a partially cutaway vertical sectional view of a conventional branch line guard. FIGS. 3 and 4 are partially cutaway sectional views showing the process of carrying out the method of this invention. FIG. 5 is a perspective view showing a branch line guard obtained by the method of the present invention and how it is used.

Claims (1)

[Claims] 1 Using an inner mold consisting of a large-diameter part, a small-diameter part, and a shoulder part that connects them, place the inner mold on both ends of a thermoplastic resin pipe with an inner diameter that fits into the large-diameter part, with the small-diameter part facing inward. Insert the mold, press both ends of the resin tube from the outside to fix the large diameter part, stretch the resin pipe together with the inner mold to make the longitudinal center of the resin pipe a small diameter, and make the small diameter part of the resin pipe longitudinally A method for producing a branch line guard, the method comprising: cutting at the center of the pipe, and providing each cut section with a split that passes through the pipe in the longitudinal direction.