JPS6248570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for manufacturing a heat-shrinkable tube.

In the conventional method for manufacturing heat-shrinkable tubes, a tube made of thermoplastic resin is placed in a predetermined cylindrical mold with a larger diameter than the tube, and liquid or gas is forced into the tube while heating. The material was expanded by applying internal pressure, and when it came into close contact with the inner wall of the mold, it was cooled and solidified. In this case, there is also a method in which the material tube is heated in advance to a temperature above its softening point and then placed in a cylindrical mold and expanded. Although this method is good for low-magnification expansion,
When the tube is expanded to a high magnification, that is, 3 to 10 times the inner diameter of the tube, it expands significantly in the length direction.
Shrinks to ~1/4. Heat-shrinkable tubes store items inside and are used for moisture-proofing, dust-proofing, insulation, packaging, etc. by shrinking and sealing the tubes by heating, so it is desirable that the shrinkage in the length direction be small.
It is a problem that the length direction shrinks to ~1/4.

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 shrinkability in the length direction, it is not suitable for producing products with high magnification in the radial 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.
In this case, the two rods bend and have different diameters depending on their longitudinal positions. 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 provide a method for manufacturing a heat-shrinkable tube that eliminates the above-mentioned drawbacks and can easily produce a heat-shrinkable tube that has small heat shrinkage in the longitudinal direction and large shrinkage in the radial direction. be.

The method for manufacturing a heat-shrinkable tube of the present invention involves heating a material tube placed in the center of a tubular body made of a spiral spring to a temperature above its softening point, and applying internal pressure through a fluid to reduce the inner diameter of the material tube. This method involves gradually enlarging the material against the tension of the spiral spring, and cooling and solidifying the material after reaching a predetermined diameter.

An embodiment of the method for manufacturing a heat-shrinkable tube of the present invention will be described below with reference to the drawings. A material tube 2 is heated to a temperature above its softening point and is placed in the center of the tubular body 1 formed from a spiral spring. In the case of manufacturing, pressurized air is supplied into the material tube 2 to apply internal pressure to expand it to a predetermined size, and then cool and solidify to complete a heat-shrinkable tube. Material The material of tube 2 is polyvinyl chloride,
Synthetic resins such as polyethylene and polyester, mixtures or crosslinked products thereof, or materials mainly made of vulcanized rubber such as chloroprene, chlorinated polyethylene rubber, and ethylene propylene rubber are used.

In addition, the material of the spiral spring of the tubular body 1 used when manufacturing the heat-shrinkable tube, such as steel or nickel chrome steel, does not change its elastic modulus much even at the heating temperature of the material tube 2 compared to room temperature. Things are good. Further, for example, it may be made of synthetic rubber such as silicone rubber, a synthetic resin in which wires of steel or the like are embedded, or steel wires etc. woven into a fabric such as gas cloth. Note that a separator material may be interposed between the material tube and the tubular body.

In the above embodiment, the case where the material tube is heated above the softening point in advance and inserted into the spiral spring has been described, but the material tube may be heated after being inserted into the spiral spring. In this case, heating can be done by heating the material of the spiral spring using a heating element such as nickel chrome steel, or by immersing it in a heated gas or liquid. be.

In this way, the method for manufacturing the heat-shrinkable tube of this embodiment heats the material tube placed in the center of the tubular body made of a spiral spring to a temperature above its softening point, and at the same time heats the material tube through a fluid to create an internal pressure. The inner diameter is gradually expanded by adding the inner diameter, and after reaching a predetermined inner diameter while the outer periphery is in contact with the tubular body, it is cooled and solidified, so that it does not expand in the longitudinal direction but expands only in the diametrical direction. Therefore, during heat shrinkage, it does not shrink in the longitudinal direction but largely shrinks only in the radial direction. Moreover, the work is simple and easy, and even small-diameter products can be manufactured.

As described above, the method for manufacturing a heat-shrinkable tube of the present invention has the effect of easily manufacturing a heat-shrinkable tube that has a large shrinkage in the radial direction and a small heat shrinkage in the longitudinal direction.

[Brief explanation of the drawing]

The figure is a schematic diagram of an apparatus for carrying out the method of manufacturing a heat-shrinkable tube of the present invention. 1...Tubular body, 2...Material tube.

Claims (1)

[Claims] 1. In a method for manufacturing a heat-shrinkable tube that contracts when heated, a material tube placed in the center of a tubular body made of a spiral spring is heated to a temperature higher than its softening point and a fluid is introduced into the material tube. A method for producing a heat-shrinkable tube, which comprises applying internal pressure through the tube to gradually expand the inner diameter against the tension of the spiral spring, and cooling and solidifying the tube after reaching a predetermined diameter.