JPS6128506B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for molding a rectangular tube made of a plastic sheet.

The bodies of rectangular containers, which are widely used as simple packaging containers, require plastic sheets that have been cut in advance to match the individual body lengths to be bent into a rectangular tube shape, and then the overlapped edges are glued together. However, in the past, each of these steps was performed manually, which not only required a great deal of effort to manufacture, but also had the drawback of not being able to achieve high precision, especially in terms of dimensions. It was hot.

In view of these circumstances, the present invention first creates fold lines corresponding to the number of corners of a desired rectangular tube on the surface of a long plastic sheet fed at a constant speed, using a heater,
After forming a series of strips using an appropriate heating means such as a laser beam, electromagnetic waves, or ultrasonic waves, the sheet is then fed to a square tube forming device and sequentially bent into a square tube shape, while the overlapping edges are By adhering to each other,
This enables continuous molding of square tubes, greatly increasing productivity and precision.

Hereinafter, the molding method of the present invention will be explained in more detail based on an embodiment in which a heater is used to engrave the fold lines. A heating zone 1b formed by paralleling a number of heaters H corresponding to the number of heaters H, a V groove 2 cut on an extension line of the heating zone, and a tip 3' of each V groove 2, 2... It consists of a push roll 3 that rotates so as to be invaginable.

Reference numeral 4 denotes a square tube forming device, which includes a series of plates or rollers, etc., which gradually bends the plastic sheet S having the fold line (a) carved thereon and forms it into a square tube shape. A forming part 4a consisting of a forming part 4a, and a prismatic mandrel 4b corresponding to the desired prismatic cylinder shape are installed near the end of the forming part 4a, and a bonding machine 4c is installed on the mandrel to heat the overlapping edges of the prismatic cylinders passing through the forming part 4a. , or other adhesives.

Incidentally, in the figure, R and R' indicate feed rollers that are appropriately arranged at required locations, and 1c indicates a heat insulating material for the heater H.

In the method of the present invention, a long thermoplastic sheet S having a certain width is placed on the base plate 1a.
Sequentially feed at a constant speed to the top of the heater
While passing through the heating zone 1b kept at a predetermined temperature by
Then, a series of fold lines (a) are carved on the sheet S by the push roll 3.

Next, the sheet S provided with the fold line (a) is further fed into the rectangular cylinder forming device 4, so that the sheet S is gradually bent from the fold line (a) while passing through the forming section 4a. It is erected and then formed into a prismatic tube shape on a prismatic mandrel 4b,
The overlapping edges are bonded by the adhesive machine 4c, and are further cooled in the latter half of the prismatic mandrel 4b, allowing for continuous molding of highly accurate prismatic tubes with no dimensional errors. .

Therefore, the body of the desired rectangular container is immediately cut by cutting the series of rectangular cylinders that have passed through the rectangular mandrel 4b through the above-mentioned steps to an appropriate length using a cutter or the like (not shown). is obtained.

In addition to the heating means using the heater H shown in the above embodiment, the folding line attaching means in the present invention may optionally utilize laser beams, electromagnetic waves, ultrasonic waves, etc. In that case, the above folding line attaching device It goes without saying that the mechanism may be changed to one with a structure suitable for each.

As described above, the molding method of the present invention involves bending a long plastic sheet S into a rectangular tube shape along several fold lines provided on the sheet. Square tubes, which used to require a lot of effort, can now be continuously molded extremely efficiently.
The product is expected to have high accuracy and other excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of the device of the present invention, and FIG.
The figure is a sectional view taken along the line X-X in Figure 1, and Figure 3 is a Y-X cross-sectional view in Figure 1.
- Y-line sectional view; FIG. 4 is a Z-Z line enlarged sectional view. In the figure, 1... Folding line attachment device, 2... V groove, 3... Push roll, 4... Square tube forming device.

Claims (1)

[Scope of Claims] 1. A method for forming a rectangular tube in which a long thermoplastic sheet fed at a constant speed is bent into a rectangular tube shape, and both sides of the tube are joined to each other. A method for forming a square tube, which comprises heating and softening the surface of a plastic sheet corresponding to each corner of the tube, and then forming fold lines on the corners. 2. In a rectangular tube forming device that bends a plastic sheet into a rectangular tube shape along a mandrel and joins both edges of the sheet with an adhesive machine,
A heating zone formed by paralleling heating sections corresponding to the number of fold lines of the corners of the rectangular tube on the base plate through which the plastic sheet passes, and a fold line consisting of a groove section on an extension of the heating section and a push roll that can be fitted into the groove. A rectangular tube forming device characterized in that an attached device is connected in front of the rectangular column mandrel.