JPH0148137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a tube, and more particularly to a method of manufacturing a plastic tube in which the end of the plastic tube is curled outward approximately once.

Plastic tubes can be manufactured continuously by extrusion molding, etc., so they have the advantage of producing uniform products with little loss.Generally, the tube is the main body, and a resin mouth is fused to the end of the main body. A tube container is used in which the opening is closed with a cap and the other end is sealed. However, such tube containers are expensive, require fast molding, have complicated processes, involve a lot of loss, and require highly accurate tube bodies, among other problems.

Therefore, instead of having a fused opening, tube containers have been developed that have a sealed surface that is easy to open. However, in order to easily open the sealed surface, fusion of the main body, resin molding, and the tube main body is strong and difficult to open, so a method is to seal with a film that has a resin layer that is easy to fuse but weak in strength. There is.

Therefore, if such a film is tried to be fused to the tube body, it will not be stiff and the fused area will be small, making it impossible to achieve a perfect seal, so it is better to curl the end of the tube.

By the way, for the above purpose, for example, the end of the tube may be bent 90 degrees to make it horizontal.
When handling such a film, a user may touch the end portion or the film with a finger and damage it. Therefore, the above-mentioned problem can be solved by curling (rounding) approximately the end portion once.

However, even if one simply attempts to curl the end of the tube one turn as described above, the tube cannot be easily curled.

Moreover, even if it is curled, it will easily return to its original shape, or the edges will become less rounded. Therefore, the present inventor invented a tube manufacturing method as described below.

FIG. 1 is a cross-sectional view of a tube formed by the manufacturing method of the present invention. In curling such a tube A, the present invention involves preliminarily starting from the end of the plastic tube with a diameter that is at least twice the winding diameter to be curled. In this method of manufacturing a tube, the tube is deformed outward so that the diameter of the tube is 1.5 to 2.5 times thicker than the original diameter of the roll to be curled in terms of width, and then the end portion is curled outward once.

Here, the material of the tube used in the present invention may be any thermoplastic resin, and it is particularly preferable to use a material such as polyethylene because it is easily deformed by heat. In this case, it is preferable to use a material that does not undergo a sudden drop in viscosity or large deformation due to temperature, and for polyethylene, a resin with a melt index (hereinafter referred to as MI) of 3 or less is preferable. This is because if the degree of deformation is different due to temperature variations, uniform curling will not be possible, and if the viscosity suddenly decreases when sealing the film to the curled part, the stress in the curled part will cause a change in wall thickness during sealing. In severe cases, problems such as holes may occur, and there may be problems with deformation due to temperature unevenness during annealing to remove stress.
These are likely to occur when MI is 3 or higher.

Explaining in detail below using the drawings, a method of enlarging the diameter below the end before curling is, for example, as shown in Figure 2, inserting the tube 1 into the rotating jig 2, The end portion 3 is exposed from the rotating jig 2, the exposed portion is locally heated with a hot air generator 4, and then the deforming roll 5 is heated.
A possible method is to deform the support roll 6 so as to curve it outward. In addition, as shown in Fig. 3, the tube 1 is attached to the rotating mandrel 7, and while the other end is stopped by the support ring 8 and rotated, the portion of the tube 1 that protrudes above the rotating mandrel 7 is locally heated by the hot air generator 4. After heating the tube 1, insert the heated tube 1 into the rotating mandrel 7' as shown in Fig. 4 and press it from above and below using the holding ring 9 to reduce the length. There is also a way to make it thicker. Alternatively, after heating the end 3 of the tube, the tube 1 can be placed in a blow mold 10 as shown in FIG. 5, and the warp can be made thicker using air pressure from the blow pin 11.

Next, the process of curling the end portion 3 of the tube, which has been deformed so that the center is convex in a semicircular shape, U-shape, dogleg shape, etc. as shown in FIG. Rotate tube 1 with mandrel 7' as shown.
, and rotate it while holding the end and bottom to be curled with the support jig 12 , hold it with the curling tool 13 in the direction perpendicular to that, bend the tip outward, and immediately after that, roll it with one roll 14 . Press down and curl 180°. Next, the end of the tube is pushed inward using the veneer 15 shown in FIG. 7, and the end of the tube is pressed down with the roll 14 to prevent it from returning and curl. At this time, it is necessary that the rotating mandrel 7' be inside the tube, and the elasticity of the tube causes the above-mentioned curl.

The tube that has been curled once as described above is heated with hot air or the like from the outside while being inserted into the rotating mandrel 7', and annealing is performed to stretch the curled outer surface of the tube and remove stress. This creates a tube in which the end of the tube body has been rotated once.

In the tube manufacturing method of curling the end of the tube as described above, the diameter of the tube is adjusted in advance to a width that is more than twice the diameter of the winding (a in Figure 1) to be curled at the end 3 of the tube 1. Deform it so that it is 15 to 2.5 times thicker than the diameter to be curled, that is, b in Figure 8 1, 2, and 3 is 0.75.
If it is deformed outward by ~1.25a, it will not only curl easily and improve the defective rate significantly, but also have less stress during curling and be easily stabilized by annealing. Therefore, the tube end 3 is deformed by expanding outward by at least twice the winding diameter (a in Fig. 1), preferably 2.5 to 4 times. Not only is the effect small, but the force working to make the diameter smaller is unreasonable. Moreover, if it exceeds 4 times, it will be difficult to form a rounded curl, and it will tend to become vertically long, making it difficult to apply a film seal. Therefore, the winding diameter after curling should be at least twice the diameter, preferably 2.5~
The deformation width is four times better, and the maximum deformation diameter during the primary processing is close to the final curled diameter. It is desirable that the diameter be 1.5 to 2.5 times larger than the original diameter. However, if you make this thicker by more than 2.5 times, the second stage curling process, that is, the stage of curling from 180 degrees to 360 degrees, will not go well.
If you make it less than 1.5 times thicker, it will be difficult to curl and will not be effective, so make it 1.5 times the diameter of the roll than the original diameter of the tube.
A good method is to make it 2.5 times thicker.

The present invention is a method for manufacturing a tube as described above, and the tube end portion formed according to the present invention not only has good film sealing properties, good handling properties, and has a good appearance, but also has a good film sealing property and good handling properties. Of course, it can also be used for seaming and tightening processing, and conventionally, it is not perfect,
This is a method that can firmly and completely seal plastic tubes that inevitably leak their contents.

As described above, the manufacturing method of the present invention is a good manufacturing method for producing containers and the like by curling the end of the tube at low cost and with little loss.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is a sectional view of a tube whose end is curled once, and FIGS. 2, 3, 4, and 5 are cross-sectional views. FIG. 6 is an explanatory diagram showing a state in which the end of the tube is heated and deformed; FIGS. 6 and 7 are explanatory diagrams showing a state in which the deformed tube is curled once, and FIG. 8 is an explanatory diagram showing a state in which the tube is curled once. FIG. 3 is a partial cross-sectional view showing the shape of the end portion that is previously deformed. 1...Tube, 2...Rotating jig, 3...Tube end, 4...Hot air generator, 5...Deformation roll, 6...Support roll, 7, 7'...Rotating mandrel, 8... Support ring, 9...Retaining ring, 1
0...Blow type, 11...Blow pin, 12...
Support jig, 13... Curling roll, 14... Roll, 15... Veneer.

Claims (1)

[Scope of Claims] 1. In a tube manufacturing method in which the end of a plastic tube is curled, the end of the plastic tube is heated in advance to a width that is at least twice the winding diameter after curling. A method for manufacturing a tube, which comprises deforming the tube outwardly so that it becomes thicker by 1.5 to 2.5 times the winding diameter than the diameter of the tube, and then rotating the end portion outward once. 2. The method for manufacturing a tube according to claim 1, wherein the shape of the tube end portion to be heated and deformed is a semicircular shape, a U-shape, a dogleg shape, etc., with a convex center.