JPS5917934B2 - 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 of 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 is expanded by applying internal pressure by pushing liquid or gas into the tube while heating it. When it came into close contact with the inner wall of the mold, it was cooled and solidified. This method is good when expanding at a low magnification, but when expanding at a high magnification, that is, 3 to 10 times the inner diameter of the tube, it expands significantly in the length direction as well, making it difficult to complete the manufacturing process. When heated and shrunk, the length direction becomes 2/3 of the length before heating.
Shrinkage occurred to about 1/4. The heat-shrinkable tube stores the item inside and shrinks the tube tightly by heating.
Since it is used for moisture-proofing, dust-proofing, insulation, packaging, etc., it is desired that the shrinkage in the length direction is small, and the shrinkage in the length direction of 2/3 to 1/4 is problem (5). Another method is to insert two rods into a material tube and forcibly expand the material tube by widening the gap between the two rods while heating the material tube.

Although this method can produce products with low heat shrinkage in the length direction, it is not suitable for producing products with high magnification in the diameter direction or long products. That is, the diameter of the two rods must be smaller than the diameter of the material tube, which poses a problem in terms of strength. It comes differently.
This tendency is particularly noticeable in the case of high magnification expansion or long products. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a method for manufacturing a heat-shrinkable tube that exhibits small heat shrinkage in the longitudinal direction and a large shrinkage rate in the diametrical direction. The present invention heats a material tube of a heat-shrinkable tube that contracts when heated to a temperature higher than its softening point, and applies fluid pressure inside the material tube to expand and expand the material tube in the diametrical direction, so that the material tube reaches a predetermined position. When manufacturing a heat-shrinkable tube that is cooled and solidified when expanded to a diameter of
The process in which the above material tube expands in the diametrical direction is
One end of the tubular slit-forming member, in which slits are formed parallel to the axial direction of the material tube, is fixed to the edge of the slit via a wide tape holder, and the other end is wound around the outer periphery of the material tube located inside the slit-forming member. After being rotated, a wide tape-like member is pulled out and held outside the slit forming member, and the material tube is expanded while being controlled via a control means that contacts the outer periphery of the material tube. An example of the method for manufacturing a heat-shrinkable tube of the present invention will be described below.
This will be explained using figures.

Reference numeral 2 denotes a pipe-shaped slit forming member, in which a slit 5 into which the middle portion of the wide tape-like member 1 can be inserted doubly is formed in the axial direction of the material tube 3.

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 attached to the material tube placed inside the slit-forming member 2 as described above. After winding it around the outer periphery of the slit forming member 2 so as to lightly tighten it, it is taken out from the slit 5 and held on the outer periphery of the slit forming member 2. Then, change the material tube 3 to material tube 3.
The heated material tube 3 is heated through a heating means (not shown) that heats the material to a temperature higher than the softening point temperature of the material.
The diameter of the material tube 3 is expanded through a diameter expanding means (not shown) which expands the material tube 3 in the diameter direction by applying gas or liquid fluid pressure therein. 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 slit-like member 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 its outer diameter is controlled, so that it does not expand in the axial direction during expansion. The material for the tube 2 is not particularly limited, and may include polyvinyl chloride, polyethylene, synthetic resins such as fluorine-based polymers, mixtures or crosslinked materials thereof, polychloroprene, chlorinated polyethylene rubber, ethylene, etc. Use vulcanized rubber such as propylene rubber.

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, fabrics such as cotton cloth, glass cloth, synthetic fibers, or those processed with plastic coating, steel, etc.
Use stainless steel mesh, plastic sheet, rubber sheet, etc. FIG. 2 shows another embodiment in which the heating means and the cooling means are formed by providing a jacket around the outer periphery of the slit forming member, that is, by providing a gap between the slit forming member 7 and the outer periphery of the slit forming member 7. A jacket 8 is formed between the outer wall 6 and the outer wall 6.

A slit 9, a steam outlet pipe 10, a cooling water outlet pipe 11, a steam inlet pipe 12, and a cooling water inlet pipe 13 are attached to the jacket 8, each having a valve attached thereto.
Heating and cooling can be done smoothly. The heating means may be such that the material tube 3 is previously heated to a temperature higher than its softening point and wrapped in a wide tape, or for example, a heating device such as a heating wire may be incorporated into the wide tape-like member 1. In the embodiment shown in FIG. 1, the tubular slit forming member 2 expands the material tube 3 until it touches the inner diameter, and makes the outer diameter uniform over the whole after expansion.
Although it is used to form the slit 5, it may be configured to have separate functions. For example, in order to obtain the slits 5, grooves may be provided in a flat plate-like material, and in order to make the outer diameter uniform throughout, the wide tape-like member 1 may be formed using a material with good dimensional stability such as a steel plate. The wide tape-like member 1 may be accurately fed out using a tool. Furthermore, in FIG. 1, a wide tape-like member 1,
By moving the material tube 3 in the length direction of the slit forming member 2, continuous production can be achieved. In this case, two types of slit forming members 2 are required: one for heating and one for cooling. As described above, the method for manufacturing the heat-shrinkable tube of this embodiment involves heating the 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 is controlled through the special control means as described above, it is possible to manufacture a heat-shrinkable tube with less heat shrinkage in the longitudinal direction and a large shrinkage in the diametrical direction. As described above, according to the method for manufacturing a heat-shrinkable tube of the present invention, it is possible to manufacture a heat-shrinkable tube that has a small heat shrinkage in the longitudinal direction and a high shrinkage rate in the diametrical direction.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a sectional view of a main part of an apparatus for carrying out the method for producing a heat-shrinkable tube according to the present invention, and Fig. 2 is a sectional view of another apparatus for carrying out the method for producing a heat-shrinkable tube according to the present invention. It is a sectional view of the constituent parts of the heating means and the cooling means of an Example. 1... Wide tape-like member, 2, 7...
Slit forming member, 3...Material tube, 4.
...Wide tape presser, 5,9...Slit.

Claims (1)

[Claims] 1 The material tube of a heat-shrinkable tube that contracts when heated is heated to a temperature higher than its softening point, and fluid pressure is applied inside the material tube to expand and expand the material tube, and the material tube is expanded to a predetermined diameter. In the method for manufacturing a heat-shrinkable tube in which the material tube is expanded and expanded in the diametrical direction by cooling and solidifying, the process of expanding and expanding the material tube in the diametrical direction is performed at the edge of the slit of a tubular slit forming member in which a slit is formed parallel to the axial direction of the material tube. One end is fixed via a wide tape holder, and the other end is wound around the outer circumference of the material tube, which is placed inside the slit forming member, and then pulled out and held outside the slit forming member. A method for manufacturing a heat-shrinkable tube, characterized in that the tube is expanded in a controlled manner through a control means in contact with the tube.