JPS639531A - Production of heat-shrinkable tube - Google Patents

Abstract

PURPOSE:To stably produce a heat-shrinkable tube having a uniform enlarged outside diameter with favorable workability, by enlarging the diameter of a tube by a means for sealing between the tube not enlarged in diameter and a sealing cylindrical body through a liquid and then separating the sealing liquid from the tube, and a means for supplying a liquid to the vicinity of an inlet to a cooled sizing die. CONSTITUTION:A sealing die 12 having an introducing hole 12a having an outside diameter approximately equal to that of a tube 13a not enlarged in diameter is fitted to a casing 11, which has a horizontally cylindrical shape and the interior of which constitutes a reduced- pressure chamber 11a, on the tube-introducing side. A cylindrical body 8 having an aperture approximately equal to or slightly greater than the die 12 is provided on the tube-introducing side in the manner of extending from the die 12. A heating medium supplying pipe 8a is connected to a desired intermediate position of the cylindrical body 8, and is opened 8b. The sealing die 12 is provided with a small hole 22 for separating a sealing liquid from the tube 13a, and the tube 13 is uniformly enlarged in diameter by operating a pressure- reducing means 18. The tube diameter enlarging chamber 11a is provided with a pouring pipe 23 having a nozzle 23a for supplying a lubricating liquid for preventing the sizing die 14 and the tube 13 enlarged in diameter from making direct contact with each other, thereby reducing frictional resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a heat-shrinkable tube.

(Prior Art) Examples of means for continuously manufacturing heat-shrinkable tubes include US Pat. No. 3,370,112 and Japanese Patent Publication No. 38-26581.
No. and Special Publication No. 55-604.5 are known.

The method first disclosed in US Pat. No. 3,370,112.

The internally pressurized crystalline polymer resin tube is heated to above the crystal melting point in a heating bath, passed through a sealing die in the heated state and drawn into a decompression chamber, and cooled while expanding the diameter of the tube due to the differential pressure between them. In this method, a heat-shrinkable tube is obtained by introducing the tube into a forming tube having a device and cooling and fixing it.

(Problem to be Solved by the Invention) The biggest problem when expanding the diameter of a tube using such a differential pressure is the method of maintaining the above-mentioned reduced pressure. The contact area between the two changes, and the friction between the two is greatly affected, and the elongation in the length direction due to the pulling force of the enlarged diameter tube changes, and as a result, it is often impossible to obtain a product that is uniform and has a small amount of elongation.

Japanese Patent Publication No. 38-26581 proposes a method of suppressing the longitudinal elongation of the tube as much as possible by using, for example, an endless belt engaged with a slide fastener as a conveyance means. However, other drawbacks have been pointed out in this method, such as the use of the endless belt reduces cooling efficiency and complicates the apparatus.

This is a method of expanding the diameter of a tube using an expansion control cooling tube that has through holes in the tube wall, based on the idea of solving the problem. However, in this case, the heating medium attached as a lubricant to the surface of the heat-shrinkable tube whose diameter has been expanded to the inner diameter of the aforementioned diameter expansion control cooling tube is pushed out through the tube wall through-hole,
As a result, the frictional resistance between the diameter expansion control cooling pipe wall and the diameter expansion tube increases. Moreover, there is a problem that the tube may sink into the through hole, which may encourage an increase in frictional resistance. Such problems are especially true when thin-walled tubes are used or when the expansion magnification is high.

The inventors have previously developed a method for depressurizing the outside of the tube to provide a differential pressure when expanding the diameter of the tube, by dividing it into two decompression chambers in the direction of movement of the tube, and performing each separately, and a method for sealing the introduction side. By devising this method, the elongation in the longitudinal direction of the tube was suitably suppressed, and the diameter was expanded stably, achieving great results.

However, even in these methods, the amount of sealing liquid flowing into the enlarged diameter chamber at the introduction portion is affected by fluctuations in the outer diameter of the tube before diameter expansion, and the outer diameter of the enlarged tube is difficult to stabilize.

That is, if the outer diameter of the pre-expansion tube is small and the amount of sealing liquid flowing in is too large, the inflowing sealing liquid will move between the diameter expansion tube and the sizing die, and that portion will not be expanded to the desired diameter. In addition, if the outside diameter of the tube before diameter expansion is large and the amount of sealing liquid flowing in is small, there will be a lack of lubricant between the inner surface of the sizing die and the outer surface of the diameter expansion tube, and the two will come into direct contact, resulting in increased resistance and less elongation in the length direction. growing.

For this reason, it is not only necessary to prepare a large number of sealing dies that match the outer diameter of the tube before diameter expansion, but it is also essential to minimize fluctuations in the outer diameter of the tube before diameter expansion. This is especially important when manufacturing heat shrinkable tubes with small inner diameters, such as those with a diameter of less than 3 mm.

As a result of various studies on these points, the inventors found that the amount of liquid existing between the inner surface of the cooling sizing die and the outer surface of the enlarged diameter tube flows into the enlarged diameter chamber through the gap between the outer surface of the unexpanded tube at the introduction section and the inner surface of the sealing die. It is determined by the amount and force of suction depending on the degree of pressure reduction, and if this amount is too large, it will accumulate between the inner surface of the cooling sizing die and the outer surface of the diameter expanding tube, preventing the tube from being expanded to a predetermined diameter.

It has also been found that when this amount is small, there is insufficient lubrication between the outer surface of the expanded diameter tube and the inner surface of the cooling sizing die, resulting in increased contact resistance and elongation of the expanded diameter tube in the length direction.

Therefore, the sealing liquid in the introduction part, which changes due to the change in the outer diameter of the tube before diameter expansion, is separated so that it does not directly enter between the cooling sizing die and the diameter expansion tube, and the lubrication between the diameter expansion tube and the cooling sizing die is prevented. By supplying the necessary amount of lubricating fluid by another means, the outer diameter of the expanded tube can be stabilized even in unexpanded tubes with slight outside diameter fluctuations, and the lengthwise direction can be stabilized. The present invention has been completed by making it possible to continuously obtain heat-shrinkable tubes while suppressing elongation.

That is, in the method of the present invention, a thermoplastic tube that has been softened by heating is sealed from one side with an unexpanded tube on the tube introduction side and an expanded diameter tube on the take-off side, and the casing is equipped with an appropriate pressure reducing means. A cooling sizing part, in which the outer periphery of the enlarged tube is inscribed and cooled, is introduced into the enlarged diameter part of the tube at the bottom of the groove, and the enlarged diameter part of the tube reduces the pressure on the outside of the tube, creating a differential pressure between the inside and outside. In a method of manufacturing a heat-shrinkable tube in which the diameter of the tube is continuously expanded by cooling and fixing the diameter in the cooling sizing section, and the tube is taken off to the other side, the tube is introduced into the casing equipped with the pressure reducing means. A cylindrical body with a diameter slightly larger than the outside diameter of the unexpanded tube is installed at the side end, and the heated liquid is supplied to the tube introduction part through this cylindrical body, and the unexpanded diameter is supplied to the tube introduction part at the seal part on the introduction side. After sealing between the tube and the sealing cylindrical body via a liquid having fluidity, the tube is provided with a means for separating the sealing liquid from the tube and a means for supplying the liquid near the inlet of the cooling sizing die to expand the tube diameter. It is characterized by the fact that it is designed to be performed.

(Function) In the method of the present invention, an excessive amount of sealing liquid in the inlet is moved to the cooling sizing die to prevent diameter expansion from being obstructed, and the cooling sizing die is also used to suppress elongation in the length direction. By separately supplying a lubricating liquid between the enlarged tubes, it is possible to obtain a heat-shrinkable tube that has a stable outer diameter even if there is some variation in the outer diameter of the tube, and that has suppressed elongation in the length direction. It became.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall explanatory view of the method for continuously expanding the diameter of a heat-shrinkable tube according to the present invention, and (1) is a feeding reel around which the unexpanded tube (13a) is wound.

The tube (13a) is pressurized inside and moves around the guide roll (
It is fed into the heating tank 4 via ζ(3). Heating tank (4
) is filled with liquid heat medium and the guide roll (5J (
While passing between 6D, the tube (13a) is heated and softened, and at the same time, the diameter is slightly expanded in response to the internal pressurization.

The heating liquid heat medium mentioned above is most commonly silicone oil or glycerin, but other liquids can be used as long as they are fluid at room temperature. It is desirable for this to have as low a viscosity as possible upon cooling.

The preheated unexpanded tube (13a) is guided by guide rolls (7) and introduced into the expanded diameter section On through a slightly larger diameter cylindrical body (8). This enlarged diameter portion OG is shown enlarged in FIG. For example, 0D has a horizontal cylindrical interior with a decompression chamber (1
A sealing die 02 having an introduction hole (12a) approximately equal to the outer diameter of the unexpanded tube (13a) is attached to the introduction side of the unexpanded tube (13a) in the case 1a),
Then, the cylindrical body (8) having approximately the same diameter or a slightly larger diameter is installed so as to extend toward the introduction side, and the heating medium supply pipe (8a) is connected to a desired intermediate position of the cylindrical body (8) to open the cylindrical body (8). (8b) Let it happen.

Inside the casing αυ, a cooling sizing portion α4 corresponding to the diameter of the enlarged diameter tube [13] is provided in the axial direction as in the conventional method.

The decompression chamber (lla) has a vacuum trap (
1!9. Connect a pressure reducing means formed by piping a vacuum degree needle αe and a vacuum pump αη in this order. The above-mentioned unexpanded diameter tube (13
a) is introduced into the introduction hole (12a) through the cylindrical body (8).

Through this, it is guided so that it is taken up one by one to a take-up section to be described later, and the pressure reducing means 08 is operated here.

The unexpanded diameter tube (13a) is expanded in diameter as shown in the figure, cooled while being inscribed in the cooling sizing section I, and then taken as an expanded diameter tube α.

At this time, the heating medium attached to the unexpanded diameter tube in the heating tank (4) and the same heating medium supplied through the supply pipe (8a) are mixed with the unexpanded diameter tube (13a) and the cylindrical body (
8) satisfies the clearance between the tubes (13a) and eliminates the intake of air into the decompression chamber side due to fluctuations in the outer diameter of the tube (13a);
The degree of vacuum can be kept stable. In addition, seal dice (1
2) is provided with a small hole (22 holes) for separating the sealing liquid from the tube (13a).
Almost no liquid is attached to the surface of the tube moved to step 11a), and the diameter is expanded uniformly. Depending on the tube size, several or more small holes (22) may be arranged at equal intervals in the circumferential direction. Also, in the diameter expansion chamber (11a), there is an injection pipe J3 having a nozzle (23a) for supplying lubricant to avoid contact between the cooling sizing die (14) and the diameter expansion tube (J3) and reduce resistance. ) is provided. A fixed amount of the lubricating liquid sent by a metering pump (not shown) is always supplied to the surface of the enlarged diameter tube (13) through this nozzle (23~), and an appropriate amount of the lubricating liquid is attached to the surface. It moves and is interposed between the sizing die (14) and the diameter-expanding tube (13), reducing contact resistance and suppressing elongation of the tube in the length direction.

The diameter-expanded tube eel, which has been expanded in diameter and cooled and fixed as described above, is guided to the cooling tank (19) in FIG. (2o) and the take-up reel (21)
It is wound up. In this case, it is preferable to provide an air blower (not shown) either before or after the take-up roll (20) to remove the cooling water adhering to the cooling tank.

Next, FIG. 3 shows another embodiment of the present invention.

Figure 3 (24) is a plate-shaped body with a hole of the same or slightly smaller inner diameter than (12a), and is a sealing die α2.
It is fixed at an appropriate distance with screws, etc. The sealing liquid is separated from the tube (13a) through the gap between the sealing die (12) and the plate-shaped body (2).

A nozzle (23a) for supplying lubricant is provided near the entrance of the cooling sizing die (14) and has a ring-shaped recess on the inner surface so that the lubricant is supplied uniformly to the entire outer circumference of the enlarged diameter tube (13). ing. In the case shown in FIG. 1, even if an excessive amount of lubricant is supplied, the lubricant will simply adhere to the entire surface of the tube. Further, in the case as shown in FIG. 3, it is necessary to change the supply amount depending on the tube size.

(Effects of the Invention) As explained above, according to the present invention, when manufacturing a heat-shrinkable tube, sealing is performed using a heated liquid on the tube introduction side of the tube enlarged diameter section, and the sealing liquid is applied to the end of the sealing section. By separating it from the tube at , the degree of pressure reduction at the enlarged diameter part is stabilized even if the outer diameter of the tube changes slightly, and by constantly supplying a constant amount of lubricant to the inner surface of the cooling sizing die, fluctuations in the outer diameter of the tube can be prevented. It is possible to stably manufacture a heat-shrinkable tube having a uniformly expanded outer diameter without being affected by changes in the sealing liquid due to changes in the sealing liquid.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of the main parts of an example device for carrying out the method of the present invention;
FIG. 2 is an overall schematic diagram of the same, and FIG. 3 is an enlarged view of main parts of another embodiment. DESCRIPTION OF SYMBOLS 1... Feeding reel, 4... Heating tank, 8... Cylindrical body, 8a... Heating medium supply pipe, 10... Expanded diameter part, 14
...Cooling sizing section, 13.13a...tube,
19... Cooling tank, 21... Winding section 1, 22... Small hole, 23... Nozzle, 24 - Plate-shaped body.

Claims (1)

[Claims] From one side, a thermoplastic tube that has been softened by heating is sealed with an unexpanded tube on the tube introduction side and an expanded diameter tube on the take-off side, and is an expanded tube made of a casing equipped with appropriate pressure reduction means. The outer periphery of the tube is inscribed and cooled, and the tube is introduced into the enlarged diameter part of the tube that constitutes the cooling sizing part, where the outer circumference of the tube is inscribed and the cooling sizing part is cooled. In the method for manufacturing a heat-shrinkable tube in which the diameter of the heat-shrinkable tube is increased, the diameter is cooled and fixed in the cooling sizing section, and the tube is taken out to the other side, an unexpanded tube is placed at the end of the tube introduction side of the casing provided with the pressure reduction means. A cylindrical body with a diameter slightly larger than the outer diameter is installed, and the heated liquid is supplied to the tube introduction part through this cylindrical body, and the unexpanded diameter tube and the sealing cylindrical body are sealed at the sealing part on the introduction side. The tube is characterized by being equipped with a means for separating the sealing liquid from the tube and a means for supplying the liquid near the inlet of the cooling sizing die after sealing the gap with a liquid having fluidity, thereby expanding the diameter of the tube. A method for manufacturing heat-shrinkable tubes.