JPS6147695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-shrinkable tube made of a cross-linked plastic tube, particularly a thick heat-shrinkable tube.

Up to now, various methods have been planned and put into practical use for producing heat-shrinkable tubes using cross-linked plastic tubes, and they can be broadly classified into gas pressure expansion methods and mechanical stretching methods.

The production of heat-shrinkable tubes using the gas pressure expansion method is as follows:
The material tube was heated uniformly and inserted into the guide pipe, one end of the material tube was closed, a gas valve was attached to the other end, and gas pressure was applied inside the tube to inflate it and bring the tube into close contact with the guide pipe. This is a method of cooling and solidifying in a state suitable for manufacturing thin tubes. However, especially in the case of a thick tube as contemplated by the present invention, it is extremely difficult to achieve uniform expansion of the tube in the circumferential direction and length direction during the expansion process due to gas pressure, and This impairs the practicality of using shrinkage.

On the other hand, in manufacturing using the mechanical stretching method, multiple rods are inserted into the material tube and heated uniformly, and the rods are moved outward to expand the tube diameter to form a polygonal columnar tube. Then, the tube is further inserted onto a predetermined guide pipe and subjected to reheating and shrinkage treatment to tightly solidify the tube onto the pipe. This manufacturing method can produce excellent heat-shrinkable tubes when carried out under precisely selected processing conditions, but the processing steps such as heating, stretching, and modification are complicated and cannot be mass-produced.
Furthermore, there is variation in the lengthwise expansion and contraction of the tube during reheating and shrinkage, which is inconvenient for practical use.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a manufacturing method capable of eliminating the above-mentioned drawbacks of the conventional techniques, simplifying the process, improving productivity, and improving the quality of the product.

The gist of the present invention is to provide an introduction pipe portion that has a large number of small through holes on its outer peripheral surface and into which a material tube is inserted, and a taper whose diameter is gradually expanded to a predetermined expanded diameter dimension. Using an expansion molding pipe in which a pipe section and an expansion pipe section formed with a predetermined expanded diameter are arranged in series in the axial direction, the material tube inserted onto the introduction pipe section is uniformly heated and tapered. It passes through the pipe section and is moved to be located on the expansion pipe section, where it is cooled and solidified.
In particular, the purpose is to apply gas pressure to the tube through the through hole of the formed pipe so that the tube can smoothly expand and move on the formed pipe.Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A method of manufacturing a heat shrinkable tube according to an embodiment of the present invention is as shown schematically in FIG. From the opposite free end of the expansion molded pipe 3, whose one axial end is fixed by the support stand 2, the material tube 4 is inserted onto the introduction pipe section 5 of the pipe 3 located at the free end side. The material tube 4 on the introduction pipe section 5 has its inner insertion side end fixed to a ring (not shown) located concentrically with the pipe 3 and having a diameter larger than the maximum diameter of the pipe 3. As shown in FIG. 2, the index is held by each clip 7 provided at the other end of a plurality of heat-resistant cords 6 disposed at intervals, and is movable in the axial direction of the pipe 3. It is connected to the stand 8. Next, the heater 9, which is movable in the axial direction of the pipe 3, is moved to the position of the material tube 4 on the introduction pipe section 5 to uniformly heat the material tube to the required temperature for expansion. The vessel 9 is removed from the pipe 3. As shown in FIG. 3, the heated material tube is heated by gas supplied into the hollow part 12 in the expansion molding pipe 3 through the valve 11 which is connected to the hose 10 and is provided so as to pass through the support base 2. The diameter of the pipe 3 is expanded by ejecting it through a large number of small through holes 13 bored in the peripheral wall of the pipe 3. At this time, it is preferable that the temperature of the gas for diameter expansion be appropriately raised so as not to rapidly cool the heated tube, and the amount of gas injected per hour is determined by the amount of gas ejected from the through hole 13. should be selected to be a value appropriate for the expansion of the heating tube. While the gas is ejected from the through hole, the index stand 8 is gradually moved toward the support stand 2, and thereby,
The heating tube is moved to a tapered pipe section 14 continuous with the introduction pipe section 5, gradually expanded in diameter to a predetermined diameter, and then moved onto an expansion pipe section 15 having a predetermined expanded diameter. Here, the expansion of the diameter of the heating tube can be performed more uniformly as the injection gas pressure is higher, the slope of the tapered pipe portion is smaller, the frictional force between the heating tube and the pipe is smaller, and the indexing speed is slower.

When the tube is moved onto the expansion pipe section 15, the index table 8 is stopped and the gas supply is stopped, and the tube whose diameter has been expanded by preheating is shrunk and shaped, and the tube is moved onto the expansion pipe section 1 by natural or forced cooling.
5. Adhere and solidify on top. The solidified tube is made to float slightly above the expansion pipe by ejecting gas from the through hole 13 again, and is manually moved to the free end side of the expansion molding pipe 3 and taken out.

Although the above process is a standard heat shrink tube according to the present invention, if the heat shrink tube is required to not shrink in the length direction during heat shrink or use, the index table 8 and heater 9 is fixed at a predetermined position, the material tube 4 is connected to the introduction pipe section 5 and the index table 8 is connected to its end, heating and gas are supplied, as described above, and the support table 2 is fixed. is gradually moved in the direction of the heater 9, and when the material tube 4 moves on the expansion molding pipe and is expanded in diameter and reaches a position on the expansion pipe section 15,
The movement is stopped, and the gas pressure is reduced to the extent necessary to reduce friction, and the gas is continuously ejected, while the heater 9 performs appropriate reheating contraction to release the longitudinal strain of the tube. so that it is regulated to a constant temperature. When the diameter-expanded tube is reheated and shrunk, heating and gas supply are stopped, the support base 2 is returned to the opposite direction, and the tube is cooled, solidified, and taken out from the pipe in the same manner as described above.

Here, there is a possibility that the pressure of the gas ejected from the many through holes of the expansion molded pipe 3 may be too high or too low for the tube during the expansion process of the pipe. Therefore, as shown in FIG. 4, the inside of the expansion molded pipe 3 is divided into a plurality of spaces such as spaces 5a, 14a, and 15a corresponding to the introduction pipe section 5, the tapered pipe section 14, and the expansion pipe section 15. It is preferable to divide the space and supply gas to each space at an appropriate pressure so as to generate an appropriate gas injection pressure at each part from the through hole.

Further, although the large number of gas ejection through holes 13 provided on the outer surface of the expansion molded pipe so as to substantially levitate the tube are arranged at high density, they are essentially discontinuously arranged. Microscopically, it is considered to locally lift the tube. Therefore, in order to achieve more uniform expansion, as shown in Figures 5a to 5c, the outlet side of the through hole is widened to diffuse and eject the gas flow toward the tube.
A through-hole structure in which the tube is bored so as to be inclined in the direction of movement so as to facilitate the movement of the tube, or the hole is formed in such a manner as to be inclined in mutually opposing directions so as to disperse and change the direction of the injection. Furthermore, as an example, the perforation shape of each through hole in the introduction pipe section, the tapered pipe section, and the expansion pipe section may be adjusted to suit the action for expanding the diameter of each of the above-mentioned sections. Preferably, those in Figures 5a, b and c are applied.

Furthermore, by injecting a liquid having a lubricating oil such as temperature-controlled silicone oil into the inside of the expansion molded pipe 3 instead of gas, the liquid is pumped between the tube and the pipe, thereby substantially closing the tube. This is effective for uniformly floating the tube, reducing the frictional force between them, and facilitating smooth movement for expansion and diameter expansion of the tube.

As described above, according to the present invention, the diameter of the tube inserted onto the introduction pipe section is expanded to a predetermined size at the tapered pipe section, and the tube is formed into a heat-shrinkable tube of the required size at the expansion pipe section. The tube can be manufactured in one flow, and the tube being expanded and expanded in diameter is moved by the fluid in a substantially floating state from the expansion molding pipe, so uniform expansion can be ensured at all times, and the tube is expanded in the length direction. This means that high-quality heat-shrinkable tubes can be manufactured with high productivity through a simplified process, such as being able to adjust the elongation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the general configuration of an apparatus used in the manufacturing method of the present invention. FIG. 2 is a diagram showing the connection between the material tube and the index stand. FIG. 3 is a sectional view of the expansion molded pipe of FIG. 1. FIG. 4 is a sectional view showing a modification of the expansion molded pipe. FIGS. 5a to 5c are partial cross-sectional views showing modifications of the through holes drilled in the expansion molded pipe shown in FIGS. 1 and 4. FIGS. 2... Support stand, 3... Expansion molded pipe, 4...
Material tube, 5...Introduction pipe section, 8... Index table, 9... Heater, 13... Through hole, 14... Taper pipe section, 15... Expansion pipe section.

Claims (1)

[Claims] 1. A material tube is inserted from the free end side of the expansion molded pipe onto the introduction pipe section, and the opposite end of the tube is connected to an index stand, and the temperature is brought to the required expansion temperature using a heater. At the same time, the tube is substantially levitated above the pipe by fluid ejected from a large number of small through holes arranged on the outer surface of the pipe, and after heating the tube to the required temperature, the tube is relatively A heat-shrinkable tube characterized in that the tube is moved to a tapered pipe section of a pipe to expand its diameter to a predetermined expansion diameter dimension, and then the tube is moved onto an expansion pipe section having the required dimensions and cooled and solidified. Production method. 2 The hollow part of the expansion molding pipe, which serves as a passage for ejecting the fluid from each through-hole, is divided into a plurality of spaces, and the ejection force of the fluid from the through-hole corresponding to each space corresponds to each space. Claim 1 characterized in that the supply of fluid to each space can be adjusted so as to appropriately adjust the injection pressure to the tube whose diameter is expanded and which moves on each outer surface portion of the expansion molded pipe. Manufacturing method described.