JPS5923973B2 - Method for manufacturing heat-shrinkable tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heat-shrinkable tube that shrinks when heated.

In the conventional method for manufacturing heat-shrinkable tubes, a tube made of thermoplastic resin is placed in a cylindrical mold with a predetermined diameter larger than the tube, and liquid or liquid is injected into the tube while heating. Internal pressure was applied through operations such as pushing in gas to form one eye, and when it came into close contact with the inner wall of the mold, it was cooled and solidified. This method is good when performing one eye at low magnification, but when one eye is made at high magnification, that is, 3 to 10 times the inner diameter of the tube, there will be one eye in the length direction as well, and the production will be completed. When heated and shrunk, the lengthwise shrinkage occurred to about 2/3 to 1/4 of the length before heating. Heat-shrinkable tubes are used for storing items inside and shrinking the tubes tightly by heating, and are used for moisture-proofing, dust-proofing, insulation, packaging, etc., so it is desirable that the shrinkage in the length direction is small, 2/3 ~ It is a problem that the length direction shrinks to 1/4. Another method is to insert two rods into a material tube and widen the gap between the two rods while heating the material tube, thereby forcing the cedar to become one eye.

Although this method can produce products with low heat shrinkability in the length direction, it is not suitable for producing products with high magnification in the diameter direction or long products. In other words, the diameter of the two rods must be smaller than the diameter of the material tube, which poses a problem in terms of strength; in this case, the two rods bend and their diameters vary depending on their position in the length direction. . This tendency is particularly noticeable in the case of single lenses with high magnification or long products. On the other hand, in view of the above points, the present applicant has previously proposed a method for manufacturing a heat-shrinkable tube that has a small heat shrinkage in the longitudinal direction and a large shrinkage rate in the diametrical direction, in order to eliminate the above-mentioned drawbacks. (Special request 1976
(Refer to No. 4-172263) This method heats the material tube of the heat-shrinkable tube, which shrinks when heated, to a temperature higher than its own softening point, and applies fluid pressure inside the material tube to shrink the material tube. When a material tube is expanded to a predetermined diameter by expanding in the diametrical direction, it is cooled and solidified to produce a heat-shrinkable tube.
The process of expanding and expanding the material tube in the diametrical direction is controlled through means that contacts the outer periphery. This will be explained below with reference to FIG. 2
is a pipe-shaped slit forming member, and wide tape-shaped member 1
A slit 5 is formed in the axial direction of the material tube 3 into which the intermediate portion of the material tube 3 can be inserted in a double manner.

One end of the wide tape-like member 1 is fixed to the edge of the slit 5 on the outer periphery of the slit forming member 2 via a wide tape presser 4, and the other end is fixed to the material tube 3 disposed inside the slit forming member 2. After being wound, it is pulled out from the slit 5 to the outside of the slit forming member 2. In the case of manufacturing a heat-shrinkable tube, the wide tape-like member 1, one end of which is fixed to the edge of the slit 5 of the slit-forming member 2, is placed inside the slit-forming member 2 as described above. The material is wound around the outer periphery of the slit forming member 2 through the slit 5 and held there.

Then, the material tube 3 is heated through a heating means (not shown) that heats it to a temperature higher than the softening point of the material of the material tube 3, and fluid pressure of gas or liquid is applied inside the heated material tube 3, thereby increasing the temperature of the material tube. The diameter of the material tube 3 is expanded through a diameter expanding means (not shown) that expands the material tube 3 in the diametrical direction. In this process of expanding the diameter of the material tube 3, the expansion of the diameter of the material tube 3 is controlled by the wide tape-like member 1, that is, the outer diameter is tightened by the wide tape-like member 1, and the shape is regulated. , by gradually loosening the wide tape-like member 1 inside the slit-forming member 2.

Then, when the material tube 3 is expanded to a predetermined diameter dimension, which is the inner diameter of the slit forming member 2, the material tube 3 is cooled and solidified to complete manufacturing. However, it may be cooled and solidified at a predetermined diameter that does not reach the inner periphery of the slit forming member 2. The material tube 3 is processed so that its diameter is expanded and expanded while controlling its outer diameter so that it does not expand in the axial direction during expansion. In addition, the material for the material tube 3 is not particularly limited, and may include synthetic resins such as polyvinyl chloride, polyethylene, fluorine-based polymers, mixtures or crosslinked materials thereof, polychloroprene, chlorinated polyethylene, etc. Use rubber, vulcanized rubber such as ethylene propylene rubber, etc.

The wide tape-like member 1 used to wrap the material tube 3 and adjust the expansion rate may be made of any material as long as it is flexible and has a wide shape. For example, cloth such as cotton cloth, glass cloth, or synthetic fiber, or a cloth treated with plastic coating or the like, a mesh such as steel or stainless steel, a plastic sheet, a rubber sheet, etc. are used. The method for manufacturing a heat-shrinkable tube disclosed in Japanese Patent Application No. 54-172263 involves heating a material tube to a temperature higher than its softening point and filling the inside with pressurized fluid to expand and expand the material tube only in the radial direction. Since the outer periphery of the process is controlled through the control means, it is possible to manufacture a heat-shrinkable tube with less heat shrinkage in the length direction and a large shrinkage in the diametrical direction.

However, it has been found that the manufacturing method disclosed in Japanese Patent Application No. 172,263/1980 has a problem in that the material tube 3 tends to have uneven thickness in the portion 3'' of the slit 5 (the thickness is thick and the thickness tends to be uneven). This occurs because the material tube 3 expands to a smaller extent in the portion 3' of the slit 5 than in other portions because it is exposed to the outside air. It is an object of the present invention to provide a method for manufacturing a heat-shrinkable tube which eliminates the drawbacks of Japanese Patent Application No. 172263/1982 and which can produce a heat-shrinkable tube having a uniform thickness without uneven thickness throughout.

That is, the gist of the present invention is to heat the material tube of a heat-shrinkable tube that contracts when heated to a temperature higher than the softening point of the material tube itself, and apply fluid pressure within the material tube to expand and expand the material tube. When the material tube is expanded to a predetermined diameter, the process of expanding the material tube to the diameter is controlled by a control means in contact with the outer periphery. The purpose is to expand this while rotating it in the circumferential direction.

Next, embodiments of the present invention will be described with reference to FIGS. 2 and 3 of the accompanying drawings, but it goes without saying that the present invention is not limited to these embodiments.

In the figures, parts that are the same as those in Figure 1 are designated by the same numbers.
Explanation will be omitted.

In FIG. 2, one end of the wide tape-like member 1 is connected to a wide tape-like member delivery drum 6 provided outside the slit-forming member 2, and the other end is connected to a material disposed inside the slit-forming member 2. After being wound around the tube 3, it is pulled out from the slit forming member 2 through the slit 5 and connected to a wide tape-like member winding drum 7.

In the case of manufacturing a heat-shrinkable tube, the wide tape-like member 1 is wound around the outer periphery of the material tube 3 placed inside the slit-forming member 2 so as to be lightly tightened, and then the slit-forming member is formed from the slit 5. 2. Take out the time and place it on the outer periphery of No. 2.

Then, the material tube 3 is heated via a heating means (not shown) that heats the material of the material tube 3 to a temperature higher than the softening point temperature, and at the same time, fluid pressure of gas or liquid is applied inside the heated material tube 3 to form the material. The diameter of the material tube 3 is expanded through a diameter expanding means (not shown) that expands the tube 3 in the diametrical direction, and at the same time, the drums 6 and 7 to which the wide tape-like member 1 is fixed are Forcibly rotate the material tube 3 in the direction of the arrow to
Rotate about 5 to 4/5 turns. In the process of expanding the diameter of the material tube 3, the expansion of the diameter of the material tube 3 is controlled by the wide tape-like member 1, that is, the outer diameter is tightened by the wide tape-like member 1, and the shape is regulated. ,
By gradually loosening the wide slit-like member inside the slit-forming member 2 and expanding it, at the same time, by forcibly moving the wide tape-like member 1 along the circumferential direction of the material tube 3, The material tube 3 is rotated in the circumferential direction.

When the material tube 3 is expanded to a predetermined diameter, which is the inner diameter of the slit forming member 2, the material tube 3 is cooled and solidified to complete the manufacturing process. Further, FIG. 3 shows another embodiment in which the wide tape-like member 1 is endless.

8 is a feed roll provided in the middle of the wide tape-like member 1.

In this case as well, the process of expanding and expanding the material tube 3 in the diametrical direction can be performed while rotating it in the circumferential direction by means of a control means in contact with the outer periphery, in substantially the same way as in the case of FIG. 2 described above. I can understand that.

In this way, the method for manufacturing the heat-shrinkable tube of this example is as follows:
The material tube is heated to a temperature above its softening point, and the inside of the material tube is filled with pressurized fluid to expand and expand only in the radial direction. Since this is controlled, it is possible to manufacture a heat-shrinkable tube that has less heat shrinkage in the length direction, a large shrinkage in the diametrical direction, and has no uneven thickness around the entire circumference.

As described above, according to the method for producing a heat-shrinkable tube of the present invention, a heat-shrinkable tube is produced that has a small heat shrinkage in the length direction and a large shrinkage rate in the diametrical direction, and has no uneven thickness around the entire circumference. It has the effect that it can.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of an apparatus for carrying out a conventional method for manufacturing a heat-shrinkable tube, and FIGS. be. 1: Wide tape-like member, 2: Slit forming member, 3:
Material tube, 4: wide tape presser, 5: slit, 6
: wide tape-like member delivery drum, 7: wide tape-like member winding drum, 8: feed roll.

Claims (1)

[Claims] 1 Heat the material tube of a heat-shrinkable tube that shrinks when heated to a temperature higher than its own hardening point and apply fluid pressure inside the material tube to expand and expand the material tube so that the material tube has a predetermined diameter. In a method for manufacturing a heat-shrinkable tube, in which the material tube is expanded and expanded in the diametrical direction, the material tube is expanded and expanded by cooling and solidified. After being wound around the outer periphery of the material tube placed inside the material tube, the remaining portion is pulled out to the outside of the forming member through the slit, and furthermore, the material tube is sequentially moved around the outer periphery of the material tube in the direction of rotating the material tube. A method for manufacturing a heat-shrinkable tube, which comprises expanding the material tube while rotating it in the circumferential direction by means of controlling the outer periphery of the material tube using a wide tape-like member obtained.