JPH07276499A - Method and apparatus for producing heat-shrinkable tube - Google Patents

Abstract

PURPOSE:To relax a high vacuum drawing condition and the pressure difference between mutually adjacent outlet seal parts, to stably ensure a high vacuum degree necessary at the time of tube expansion molding and to prevent the penetration of water into a tube expansion molding pipe to stably perform tube expansion molding in the production of a heat-shrinkable tube. CONSTITUTION:A tube expansion molding pipe 10, the high vacuum drawing chamber 7 formed to the outer periphery of the inlet part of the pipe 10, the cooling chamber 9 formed to the outer periphery of the central part of the pipe 10, the low vacuum drawing pressure reducing chamber 8 formed to the outer periphery of the outlet part of the pipe 10 and the outlet seal means provided to the outlet end of the pipe 10 are provided. The tube expansion molding pipe 10 has a through-hole 10a within the vacuum chamber 7 so as to allow the interior of the pipe to communicate with the interior of the chamber 7 and has a separation part 10b within the pressure reducing chamber 8. Therefore, a heat-shrinkable tube enters a low vacuum degree condition in succession to a high vacuum drawing condition before advancing to the atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat shrinkable tube manufacturing method and apparatus.

[0002]

2. Description of the Related Art A heat-shrinkable tube is extruded into a long tubular shape by a plastic extruder. However, since it is not sufficient as a heat-shrinkable tube by itself, it is separately expanded. There is. This point will be described with reference to FIG. Tube 2 before expansion
After being pulled out of the feeder 1 by the pulling force of the take-up machine 3, it is supplied into the heating tank 5 and heated to a predetermined temperature to be softened so as to easily expand the tube, and then the vacuum drawing head (7, 9, 1) is drawn.
0) to be subjected to tube expansion molding, and the tube 11 after tube expansion thus obtained is drawn into the atmosphere by the take-up machine 3 and taken up by the take-up machine 19.

FIG. 3 shows a conventional example of a portion which will be a vacuum drawing forming head in the above-mentioned manufacturing process, and is formed on the outer circumference of the pipe 10 for pipe expansion and the portion on the inlet side of the pipe 10 for pipe expansion. High vacuum evacuation chamber 7 and cooling chamber 9 formed on the outer periphery of the substantially central portion of the pipe 10 for pipe expansion
And an outlet sealing means (elastic body 12 and water discharge pipe 13) provided at the outlet end of the pipe 10 for pipe expansion.

The expansion pipe 10 has a through hole 10a which communicates with the inside and outside of the high vacuuming vacuum chamber 7.
It is possible to draw a high vacuum inside the pipe.
It is essential that the mating portion between the pipe for expansion molding 10 and the constituent wall of each chamber is hermetically or watertightly sealed. In particular, a packing 18 is provided at the joint between the constituent wall of the cooling chamber 9 and the pipe for expanding molding. A watertight seal is made by interposing it. In addition, 20 is a high vacuum outlet, 21 is a high vacuum drainage port, 22 is a water supply port, and 23 is a drainage port.

Now, the tube-expanding method of the heat-shrinkable tube 2 using the vacuum drawing head as described above will be described. First, the tube 2 before tube expansion is the tube 1 for tube-expanding molding.
At the stage of being supplied to the inside from the inlet side of 0, the pipe is expanded in the high vacuum evacuation chamber 7 while being highly evacuated from the outside through the through hole 10a, and is closely attached to the inner surface of the pipe for expansion molding 10 It is moved in the pipe 10 for pipe expansion by the pulling force, and is cooled from the outside in the cooling chamber 9 to be expanded. The expanded tube 11 thus expanded is drawn into the atmosphere after passing through the elastic body 11 of the outlet sealing means. The outlet sealing means serves as a seal between the high vacuum and the atmosphere for keeping the high vacuum degree of the high vacuum drawing vacuum chamber 7 constant.
Water is applied to the elastic body 12 that fits at the outlet end of the tube and passes through the tube 11 after tube expansion to seal the gap between the tube 10 for tube expansion and the tube 11 after tube expansion to reduce the amount of leakage and It is intended to constantly stabilize the degree of vacuum.

[0006]

According to the above-described manufacturing method and manufacturing apparatus of the prior art, when the apparatus is continuously operated, unstable supply or manufacturing of discharged water can be performed depending on the condition such as the faucet of the water discharge pipe 13. It is undeniable that the seal of the elastic material 12 is unstable due to the adjustment and installation of the worker, and the seal of the elastic material 12 may be damaged even if the elastic material 12 is worn or deteriorated due to continuous operation. Destabilization occurs.

Due to the above reasons, the manufacturing speed cannot be increased. Moreover, it was difficult to obtain the required high degree of vacuum. By the way, referring to FIG. 4 (an explanatory view of the degree of vacuum in the length direction of the pipe for expansion molding), high vacuum drawing (A)
It is difficult to reach the required high vacuum level in the entire length alone, and it is necessary to increase the vacuum pumping volume accordingly.
It was difficult to stably perform high vacuum drawing. Further, the water for sealing the gap between the pipe for pipe expansion and the tube after pipe expansion has tended to enter the pipe for pipe expansion and the tube pipe expansion cannot be stably performed.

[0008] Therefore, as a result of intensive studies conducted by the inventors to break the current state of the art as described above, at the position of the outlet sealing means, a high vacuum state is obtained inside and an atmospheric pressure is obtained outside. The inventors have found a problem to be solved in that the pressure difference becomes extremely large, and as a result, the load on the seal for the outlet sealing means is large and it is difficult to obtain a stable seal.

Therefore, an object of the present invention is to alleviate the high vacuum condition and the pressure difference between the outlet seal portions adjacent to each other, to stably secure a high degree of vacuum necessary for the pipe expansion molding, and the pipe expansion pipe. It is an object of the present invention to provide a manufacturing method and a manufacturing apparatus for a heat-shrinkable tube, which is improved so as to prevent water from entering the inside and stably perform tube expansion molding.

[0010]

According to the method for producing a heat-shrinkable tube provided by the present invention, in a state where the heat-shrinkable tube is passed through the tube for expansion molding, the inside of the tube for expansion molding is elevated from its inlet side. Expand the heat-shrinkable tube while drawing a vacuum, cool the heat-shrinkable tube after expansion, and then mold it, and then separate the heat-shrinkable tube in the tube-expansion-molded state from the tube for tube-expansion molding under low vacuum and reduced pressure. It was exposed to the atmosphere described above and then drawn out into the atmosphere via the outlet sealing means.

Further, the manufacturing apparatus provided for carrying out the above-mentioned manufacturing method includes a pipe for expansion molding, a high vacuum suction vacuum chamber formed on the outer periphery of the inlet side portion of the pipe for expansion molding, and a pipe for expansion molding. A cooling chamber formed on the outer periphery of the central portion of the pipe, a low vacuum evacuation chamber formed on the outer periphery of the outlet side portion of the pipe for expanding pipe, and an outlet sealing means provided at the outlet end of the pipe for expanding pipe. The expansion pipe has a through hole that communicates with the inside and outside of the high vacuum evacuation chamber and has a separation portion in the low vacuum evacuation chamber.

[0012]

According to the manufacturing method and the manufacturing apparatus of the present invention as described above, the heat-shrinkable tube expanded and molded in the tube for expansion molding under the condition of high vacuum degree has the downstream side after the high vacuuming condition. Since it enters into the condition of low vacuum degree and then flows into the atmosphere, a gradient of pressure difference is gently given to the heat-shrinkable tube at the outlet side of the pipe for expansion molding, and by extension, the outer circumference of the heat-shrinkable tube. The outlet sealing means applied on the surface can seal under the condition where the pressure difference is small.
In addition, since the heat-shrinkable tube is exposed to the atmosphere under low vacuum decompression before being separated from the pipe-expansion forming pipe before entering the outlet-sealing means, even if water is dropped on the outlet-sealing means to seal the water, the water-expansion tube expands. It is possible to prevent invasion into a portion under high vacuum conditions in the molding pipe.

[0013]

EXAMPLE FIG. 2 shows a layout of a process for expanding a heat-shrinkable tube according to an embodiment of the present invention. Also, FIG.
FIG. 3 is an enlarged view of a main part of the layout, that is, a vacuum drawing head.

The layout of the manufacturing process will be described according to the flow of the heat-shrinkable tube. The pre-expansion tube 2 fed from the feeder 1 enters the heating tank 5 while being taken by the take-up machine 3, and is heated at a predetermined temperature. Immediately after being heated, it is supplied into the pipe for pipe expanding 10 mounted in the vacuum forming head (7, 9, 8) and subjected to the pipe forming by high vacuum drawing, and then the outlet sealing means provided with the water discharge pipe 13 After being expanded, the tube 11 is drawn out into the atmosphere as the tube 11 by the take-up machine 3 and is taken up by the take-up machine 19.

As shown in FIG. 1, the vacuum drawing head has a high vacuum drawing vacuum chamber 7 formed on the outer periphery of the inlet side portion of the tube expanding pipe 10 and the tube expanding pipe 10. Cooling chamber 9 formed on the outer periphery of the central portion of the pipe, a low vacuum evacuation decompression chamber 8 formed on the outer periphery of the outlet side portion of the pipe for pipe forming, and a water discharge pipe provided at the outlet end of the pipe for pipe forming 10. And an outlet sealing means by 13. And the pipe 10 for expansion molding
Is a through hole 1 for communicating inside and outside in the high vacuum evacuation chamber 7.
0a and a separation portion 10b obtained by separating in the low vacuum evacuation chamber 8.

The high vacuum evacuation chamber 7 has a high vacuum evacuation port 2
0 is provided, and a high vacuum drainage port 21 is provided in consideration of the amount of water leaking from the cooling chamber 9. on the other hand,
The low vacuum evacuation chamber 8 is provided with a low vacuum evacuation port 15 and a vacuum gauge port 16 in parallel, and also considers the amount of water discharged from the water discharge pipe 13 serving as an outlet sealing means inside the pipe outlet side. Then, a low vacuum drainage port 17 is provided. In addition, the packing 1 is provided at the mating portion between the constituent wall of the low vacuum decompression chamber and the outlet end of the pipe 10 for pipe expansion.
8 is interposed so that the sealing water does not flow in. Further, the cooling chamber 9 is provided with a water supply port 22 and a drain port 23 so that the cooling water circulates around the outer periphery of the pipe 10 for pipe expansion. A packing 18 is interposed at a portion where the constituent wall of the cooling chamber 9 and the outer peripheral surface of the pipe 10 for expansion molding are interposed, so that leakage of cooling water is suppressed as much as possible.

Now, a method of manufacturing the heat-shrinkable tube by the manufacturing apparatus of the present embodiment having the above-described structure will be described. The pre-expansion pre-expansion heat-shrinkable tube 2 (in this embodiment, crystalline) 0.15-0.2Gray in absorbed dose by electron beam irradiation with polymer resin tube
A polyethylene tube cross-linked with a) is pulled in from the inlet side into the pipe for pipe forming 10 by the forward tension by a downstream take-up machine (see 3 in FIG. 2), etc. Through the high vacuum in chamber 7 through hole 1
When the inside of the pipe for expansion molding is evacuated through 0a,
Pipe 10 for tube expansion while tube 2 before tube expansion
Is adhered to the inner surface of. The tube expanded in this way is immediately molded by external cooling in the cooling chamber 9 via the pipe 10 for expansion molding to be cured in the expanded state.

The post-expansion tube 11 expanded as described above is separated into the expanded pipe 10 in the low vacuum evacuation chamber 8 on the outlet side of the expansion pipe 10.
It is exposed to the atmosphere 14 under a low vacuum and a reduced pressure from b, and then inscribed again in the pipe 10 for pipe expansion on the outlet side, and the water discharge pipe 13 between the outlet end of the pipe 10 and the tube 11 after pipe expansion. It is drawn out into the atmosphere after passing through the outlet sealing means using water as a medium from the water discharged from.

The heat-shrinkable tube expanded and molded as described above has a high vacuum (A) as shown in FIG. 4 (B).
From the above to a condition of low vacuum evacuation (B) while continuously moving to a range in which the degree of vacuum is reduced stepwise, the pipe is expanded, and then taken out under atmospheric pressure. Therefore, it suffices for the outlet sealing means to seal with a low pressure difference between the low vacuum evacuation condition and the atmospheric pressure, and the pressure can be relaxed to stabilize the sealing. Further, even if the water discharged from the water discharge pipe in the outlet sealing means enters the expansion molding pipe 10 from its outlet end, it flows down from the separated portion 10b of the pipe itself in the decompression chamber 8 and from the low vacuum drain port 17. Low vacuum evacuation drainage is possible without breaking the decompressed state, and pipe for expansion molding 1
It is possible to prevent the intrusion of the seal water into the central portion and the inlet side, which are particularly important for the tube expansion molding of No. 0. Therefore, according to the present embodiment, the outlet side seal can be made stable at all times, and the production line speed can be increased and continuous operation can be performed with such always stable seal.

In the above embodiment, the low vacuum evacuation decompression chamber 8 has been described as only one, but several low vacuum evacuation decompression chambers are connected in series to increase the degree of vacuum from upstream to downstream. It is also possible to further reduce the pressure difference from the atmospheric pressure at the outlet seal portion by giving a so-called low vacuum degree gradient that is made low.

[0021]

According to the method and apparatus for manufacturing a heat-shrinkable tube of the present invention as described above, the conditions under high vacuum evacuation and subsequent conditions under low vacuum evacuation are set, and the downstream side thereof is set. Since the outlet sealing is performed at the outlet, the pressure difference between the vacuum side and the atmosphere side at the outlet sealing can be relaxed, and the outlet sealing can be made stable, and the production speed can be increased to enable continuous operation. . In addition, since the heat-shrinkable tube is exposed to the atmosphere under a reduced vacuum and reduced pressure at the exit side of the pipe for expansion molding, the heat-shrinkable tube is exposed in the atmosphere under reduced pressure, so the gap between the pipe for expansion molding and the tube after expansion is sealed. Even if water is used as described above, it is possible to prevent water from infiltrating into a portion of the tube for expansion molding, which is particularly important for tube expansion molding, and to perform stable expansion of the heat-shrinkable tube.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a main part of a process layout shown in FIG. 2; a vacuum drawing molding head in an embodiment of the present invention.

FIG. 2 is a layout explanatory view of a step of expanding a heat-shrinkable tube according to an embodiment of the present invention.

FIG. 3 is an explanatory sectional view showing an example of a conventional vacuum drawing head.

FIG. 4 is an explanatory diagram of the degree of vacuum in the vacuum drawing head.

[Explanation of symbols]

 2 Tube before tube expansion 7 High vacuum evacuation chamber 8 Low vacuum evacuation chamber 9 Cooling room 10 Tube for pipe expansion 10a Through hole 10b Separation part 11 Tube after tube expansion 13 Water discharge pipe (sealing means) 14 Low vacuum atmosphere under reduced pressure

Claims (2)

[Claims] 1. A heat-shrinkable tube is expanded in a state where the heat-shrinkable tube is passed through the tube for expansion molding while the inside of the tube for expansion molding is evacuated to a high vacuum from the inlet side, and the heat-shrinking after the tube is expanded. The heat-shrinkable tube is cooled and molded, and then the heat-shrinkable tube in the tube-expansion molded state is temporarily separated from the tube for tube-expansion molding, exposed to an atmosphere under reduced vacuum and reduced pressure, and then drawn into the atmosphere through the outlet sealing means. A method for producing a heat-shrinkable tube, which is characterized by the above. 2. A pipe for expansion molding, and a high vacuum evacuation chamber formed on the outer circumference of the inlet side portion of the pipe for expansion molding.
A cooling chamber formed on the outer periphery of the central portion of the pipe for expansion molding, a low vacuum decompression chamber formed on the outer periphery of the outlet side portion of the pipe for expansion pipe, and an outlet sealing means provided at the outlet end of the pipe for expansion pipe And a pipe for expansion molding having a through hole that communicates with the inside and outside in a high vacuum evacuation chamber, and a separation part in a low vacuum evacuation chamber. apparatus.