JPS6312775B2 - - Google Patents

Description

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

BACKGROUND ART Conventionally, heat-shrinkable tubes have been manufactured by processing plastic tubes, rubber tubes, etc. to impart heat-shrinkable properties using the following method. That is,
A material tube made of thermoplastic resin is placed in a specified cylindrical mold, and while it is heated, internal pressure is applied by pushing liquid or gas into the material tube to cause it to expand, and it is brought into close contact with the inner wall of the mold and cooled. This is a method of manufacturing. 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.

The above method is relatively effective when expanding at a low magnification, but when expanding at a high magnification, that is, 3 to 10 times the inner diameter of the material tube, it expands significantly in the length direction, making it difficult to manufacture. When a completed product is heated and shrunk, it also shrinks in the length direction, and in extreme cases, it becomes about 2/3 to 1/4 of the length before heating.

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, and the shrinkage in the length direction should be small. It is a problem that the length direction shrinks to 1/4. Furthermore, frictional resistance increases due to close contact between the inner wall of the mold and the material tube, making it difficult to move the material tube within the mold. Therefore, continuous production is practically impossible, and a batch method has to be used, which requires a large number of man-hours.

An object of the present invention is to provide a method for manufacturing a heat-shrinkable tube that can continuously produce a heat-shrinkable tube that has a small heat shrinkage rate in the length direction and a high shrinkage rate in the radial direction.

The method for manufacturing a heat-shrinkable tube of the present invention includes a heating tube formed into a substantially straight tube shape and heated to near the softening point of the material tube; A tube group is provided in which a heating expansion tube to be heated above and a straight cooling tube formed to have approximately the same diameter as the large diameter side of the heating expansion tube are arranged in this order, and within this tube group, the inner shape of the tube group is A plurality of slits are formed in the tube group in the axial direction to serve as passages through which the excess portion of the tape-like member that is wound around the outer periphery of the material tube is passed through by applying internal pressure so as to be expanded. Then, a plurality of the tape-like members formed in an endless shape and driven are brought into contact with the outer periphery of the material tube within the tube group, and the material tube is heated within the tube group, expands by applying internal pressure, and is then cooled. In this method, the outer periphery of the raw material tube is driven by the tape-like member through frictional force, and is caused to travel from the heating tube side to the cooling tube side, thereby continuously manufacturing a heat-shrinkable tube.

An embodiment of the method for manufacturing a heat-shrinkable tube of the present invention will be described below with reference to FIGS. 1 to 3.

16 is a preheating tube, which is a straight tube with a slightly larger diameter than the material tube 1a inserted inside, and is formed to be heated to a temperature approximately 10° C. lower than the softened material tube 1a; 17 is a heating tube; Material tube 1
It is designed to be heated above the softening point of a.
Reference numeral 18 denotes a heating expansion tube, which is formed into a conical cylindrical shape so that the heating tube 17 side has the same diameter as the heating tube 17 and the cross-sectional area is gradually expanded, and is heated to a temperature above the softening point of the raw material tube 1a. Reference numeral 19 denotes a cooling pipe, which is formed to have the same diameter as the large portion of the heating and expansion tube 18, and is designed to be cooled.

The preheating tube 16, the heating tube 17, the heating expansion tube 18, and the cooling tube 19 are arranged in this order, forming a tube group 20.

FIG. 2 shows a sectional view of the preheating tube 16, in which a heat medium passage 13 for preheating the jacket is formed between the preheating tube inner plate 3 and the preheating tube outer plate 12. Reference numeral 4 designates a slit, 9 a guide rail, and 10 a tape-like tension member.The heating tube 17 and heating expansion tube 18 are also formed to have the same cross-sectional structure as in FIG. 2. FIG. 3 shows a cross-sectional view of the cooling pipe 19, where 14 is an outer cooling pipe plate, 6 is an inner cooling pipe plate, and 15 is a cooling pipe outer plate.
is the refrigerant passage. Further, in FIG. 1, 2 is a tape-like member which is driven in the direction of the arrow by a drive device (not shown), 7 is a roll on the tape-like member delivery side, and 8 is a tape-like member take-up roll. It's a side roll. In addition, the tape-like member delivery side roll 7
The temperature at the front side is not higher than the softening point temperature of the material tube 1.

The tape-like member 2 is formed in an endless shape and has a first
As shown in FIGS. 3 and 3, the material is driven in the direction of the arrow between the outer periphery of the material tube 1a, the preheating inner plate 3, the cooling tube inner plate 6, etc. at the position where it is wrapped around the outer periphery of the material tube 1a inserted into the tube group 20. The material tube 1a is driven by the frictional force between the material tube 1a and the outer periphery of the material tube 1a. Internal pressure is applied to the inside of the material tube 1a by an internal pressure pressurizing device (not shown), and therefore, the material tube 1a has a preheating tube 16, a heating tube 17, and a heating expansion tube. Inside each tube 18, each tube is heated to a temperature close to or above the softening point, so the diameter is expanded to a shape corresponding to the inner shape of the tube, and a frictional force is generated between the outer periphery and the tape-shaped member 2. do. Note that the structure is such that no friction occurs between the tape-like member 2 and the inner periphery of the tube group 20. The material tube 1a is thus applied with internal pressure and expanded into a conical shape while passing through the heating expansion tube 18 and its diameter is enlarged, and then cooled in the cooling tube 19 with internal pressure applied from the largest diameter member. It becomes a heat-shrinkable tube 1b and is continuously sent out in the direction of the arrow.

As shown in FIG. 3, the width of the tape-like member 2 is such that it can come into contact with the outer diameter of the material tube 1a when the material tube 1a is at its maximum diameter. tube 1a
Since the outer diameter of the material tube 1a is the smallest, the outer diameter of the material tube 1a is set to 2.
The widthwise portion of the excess portion covered by the tape-like member 2 is pulled out from the slit 4 by the tape-like member tension member 10 in the guide rail 9, as shown in FIG. Therefore, the heating expansion tube 1
As the outer diameter of the material tube 1a gradually increases at the 8th section, the widthwise portion pulled out from the slit 4 decreases until it finally reaches the minimum state shown in FIG.

In the process of being heated by the heating expansion tube 18 and expanding its outer diameter, the material tube 1a is between a state where it is cooled by the cooling pipe 19 and a state where the tube diameter remains small and cannot be expanded even when heated. Since it is expanded in the diametrical direction, it does not expand in the axial direction, and therefore, when the completed heat-shrinkable tube is heat-shrinked, there is no shrinkage in the axial direction. The material for the tube is not particularly limited, and may include synthetic resins such as polyvinyl chloride, polyethylene, and fluoropolymer, or mixtures thereof, or processed materials such as polychloroprene, chlorinated polyethylene rubber, and ethylene propylene rubber. Sulfur rubber etc. can be used. Further, the tape-like member 2 may be of any wide shape, tape-like or sheet-like, and flexible. For example, cloth such as cotton cloth, glass cloth, synthetic fiber, or a plastic coating thereof, steel, stainless steel sheet, steel, plastic or rubber sheet, etc. can be used. Further, although the case where there are two tape-like members has been described, if three or more tape-like members are used and the number of slits in the tube group is the same, the effect will be the same as in the above embodiment.

As described above, according to the method for manufacturing a heat-shrinkable tube of the present invention, a material tube that is heated and subjected to internal pressure is inserted into a conical tube whose cross section is successively enlarged, and then the outer diameter is enlarged. Since it is manufactured by cooling and driving it through an endless tape-like member, it continuously produces heat-shrinkable tubes that have a small heat shrinkage rate in the length direction and a high shrinkage rate in the radial direction. It has the effect that it can.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an apparatus used in the method of manufacturing a heat-shrinkable tube of the present invention, and FIG. 2 is a plan view of the apparatus shown in FIG.
FIG. 3 is an enlarged cross-sectional view taken along the - arrow in FIG. 1. 1a: Material tube, 1b: Heat-shrinkable tube, 2: Tape-like member, 4: Slit, 16: Preheating tube, 17: Heating tube, 18: Heating expansion tube, 1
9: Cooling pipe, 20: Tube group.

Claims (1)

[Claims] 1 A heating tube formed into a substantially straight tube shape and heated to near the softening point of the material tube, a heating expansion tube whose cross section is gradually enlarged from approximately the same diameter as the heating tube and heated to above the softening point, and a straight tube shape. A tube group is provided in which cooling tubes formed to have approximately the same diameter as the large diameter side of the heating expansion tube are arranged in this order, and internal pressure is applied to the tube group so as to expand the inner shape of the tube group. A plurality of slits are formed in the tube group in the axial direction to serve as passages through which the excess portion of the tape-like member wound around the outer periphery of the material tube is taken out of the tube. The above tape-shaped member is brought into contact with the outer periphery of the material tube within the tube group, and the material tube is heated within the tube group, and internal pressure is applied to expand the material tube, which is then cooled. 1. A method for manufacturing a heat-shrinkable tube, characterized in that the heat-shrinkable tube is continuously manufactured by being driven by a member and traveling from a heating tube side to a cooling tube side.