JPS6110435A - Manufacture of heat-shrinkable tube - Google Patents

Abstract

PURPOSE:To obtain a heat-shrinkable tube whose thickness in a diametral direction is nonuniform, by a method wherein density variations are given to conductance in the diametral direction of a molding cylinder by making the number of holes and the sizes of the holes of the surface of the molding cylinder provided into a vacuum cylinder in an insertion state vary. CONSTITUTION:An original pipe of a tube made of a crosslinked polyethylene having a uniform thickness is led into a molding cylinder 3 provided within a vacuum cylinder in an insertion state and heated at the temperature of more than the softening temperature of the pipe within the molding cylinder 3 which is provided within the vacuum cylinder in the insertion state and the surface of which is being provided with holes 4 by making the holes and/or the sizes of the holes vary in a diametral direction. Then a tube 5 whose thickness is nonuniform and having a thin and thick parts 5a, 5b is obtained by expanding the pipe through vacuum drawing. As for the molded cylinder 3, for example, holes 4a, 4b, 4c having different diameters d1, d2, d3 (d1>d2>d3) from each other are provided in the diametral direction of the cylinder 3 at equal intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention relates to a method for manufacturing a heat-shrinkable tube, particularly a heat-shrinkable tube with uneven thickness in the radial direction.

Conventionally, heat shrink tubes (hereinafter referred to as
When manufacturing a tube (abbreviated simply as a tube), an apparatus having a cross-sectional structure as shown in FIG. 1 is used. That is, a forming tube (3) is inserted into the vacuum tube (]), and holes (4) of the same size are bored at equal intervals in the radial direction on the surface of the forming tube (3). As a result, the conductance t in the radial direction of the forming cylinder (3) can be kept constant, so that the cross section of the expanded tube (5) has a uniform wall thickness as shown in FIG.

By the way, when the shape of the adherend to which the tube (5) is attached is hollow or solid cylindrical, the tube (5) shown in F is used.
), the desired purpose can be achieved because the thickness becomes uniform after heat shrinkage. However, when heating and shrinking a tube that is added to a bent part of a cable or piping, or a large tube with a diameter of about 200+ m$1=, it is generally done by In the gas heating method, uneven thickness tends to occur in the Fi radial direction, and uneven thickness that occurs during such work not only deteriorates the tube properties but also makes it impossible to meet the customer's specifications.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tube manufacturing method capable of overcoming the deficiencies of the prior art as described above, and minimizing the degree of thickness deviation in the radial direction of the tube after heat shrinkage.

[Summary of the invention]

The gist of this invention is to manufacture a tube by heating a tube material such as cross-linked polyethylene (XLPE) having a uniform wall thickness to a temperature above its softening temperature and then expanding it by vacuuming. In the method, the forming tube (3) is formed by changing the number and/or size 4 of the holes (4) bored in the surface of the forming tube (3) inserted into the vacuum tube (1) in the radial direction. ) is due to the fact that the conductance in the radial direction is made coarser and denser.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 3 to 5. FIG. 3 is a perspective view showing an example of a molded cylinder used in the present invention, and the surface of the molded cylinder has different diameters d in the radial direction.
Holes (4a, 4b, 4C) having holes 1, dz, ds (d+>dz>ds) are drilled at equal intervals. In such a formed tube, the conductance of the lower half is larger than that of the upper half, and therefore, after expansion, a tube with uneven thickness as shown in FIG. 4 is obtained. Note that a small hole (4a) is formed in the upper surface of the molding cylinder (3).

The number of 4b) may be reduced or zero, but
In that case, it is necessary to increase the number of large holes (4c) to expand the range occupied by the large holes (4c) in the radial direction, as shown in FIG. In Figure 5, A is the large hole 4a
, B indicates the range occupied in the radial direction of the medium diameter 4b, C indicates the range occupied by the small hole 4c, D also indicates the range of the large hole 4a, and E indicates the range without a hole.

In the above embodiments, the case where the size of the hole in the radial direction of the forming tube (3) is changed has been explained.
A similar effect can be obtained by changing the number of holes in the radial direction of the molding tube (3), for example, by increasing the number of holes on one side and decreasing the number on the other side in the longitudinal direction of the molding tube (3).

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to manufacture a tube that has a uniform wall thickness after heat shrinkage and is suitable for use as a large-diameter tube or a tube to be attached to a curved part where workability is poor. .

[Brief explanation of the drawing]

Fig. 1 shows a vacuum tube expansion section in a conventional tube manufacturing device, (a) is a cross-sectional view, (b) is a longitudinal sectional view, and Fig. 2 shows the uniform wall thickness obtained by the manufacturing device in Fig. 1. FIG. 3 is a perspective view showing an example of a molded tube used in the present invention, FIG. 4 is a cross-sectional view of an uneven thickness tube manufactured according to the present invention, and FIG. 5 is a cross-sectional view of a tube manufactured according to the present invention. FIG. 3 is a diagram showing the ranges occupied in the radial direction of large holes, medium holes, and small holes in a molded cylinder that can be used for. In each figure, the same or equivalent parts are given the same reference numerals, 1 is a vacuum tube, 2 is a vacuum layer, 3 is a forming tube, 4 holes, 4a is a large hole, 4b is a medium size hole, 4C is a small hole, 5 is a small hole. In the tube, 5a is a thin part and 5b is a thick part. ni'lr, sv 4Tomobi 4 Figure

Claims (1)

[Claims] In a heat shrink tube manufacturing method that involves heating a heat shrink tube original pipe with a uniform wall thickness to a temperature higher than its softening temperature and then expanding it by vacuuming, holes on the surface of a molded tube inserted into a vacuum tube are 1. A method for manufacturing a heat-shrinkable tube, characterized in that the radial conductance of a molded tube is varied in density by varying the number and/or size in the radial direction.