JPS6029614B2 - Manufacturing method of extruded tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a hollow cylindrical body made of plastic as the body of an extruded tube, and when a neck and a shoulder are integrally molded thereon by injection molding, the lower end portion of the shoulder is The entire circumference and the end portion of the hollow cylindrical body are welded together, with the end portion of the hollow cylindrical body being an outer layer, and the end portion of the hollow cylindrical body located in the small radius of curvature arc portion described later being curved inside the tube, The present invention relates to a method for manufacturing an extruded plastic tube in which the cross section of the settling point has one or more circular arc portions with a small radius of curvature.

The shape of the cross section of the tube body near the welding point is a circular extruded tube, and the circular arc portion y.
Although the angle 0 between both sides of the tube is small, the radius of curvature of the arc portion y is large; Even if the angle a2 formed by the two sides sandwiching the extruded tube is large, and the end portion of the hollow cylindrical body in each arc portion is bent inside the tube and settled, the following conventional method can be used.
Extruded tubes with smooth and beautiful appearance ports can be manufactured. In the above conventional manufacturing method, for example, in the case of an extruded tube in which the cross-sectional shape of the tube body near the welding point is circular, an inner mold B is placed directly below an outer mold A, as shown in FIG. Insert a plastic hollow cylinder C whose end surfaces are on the same plane, and insert the upper end part 1 of the hollow cylinder C so that it is lower than the lower end green 12 of the shoulder part 11 of the inner mold B. In this state, the inner mold B is raised and positioned in the empty chamber 20 of the outer mold A as shown in FIG.

At this time, the end portion 1 of the hollow cylinder C is curved inward along the entire circumference along the inner surface of the cavity 20 of the outer mold A, and the curved end portion 2
becomes. Next, molten plastic is press-fitted into the central through hole 21 of the outer mold A, filling the gap D between the outer mold A and the inner mold B, and forming the neck 26 and shoulder 22 of the extruded tube. Figure 5). The molten plastic also enters between the curved end 2 of the hollow cylinder and the shoulder 11 of the inner mold B, and as a result, the curved end 2 contracts due to the heat of the plastic, so that the outer mold The extremely shallow, large-pitch undulations that had occurred at the curved end when it was inserted and curved disappeared, and the curved portion 2 of the hollow cylinder C, that is, the shaped portion 1 and the layer portion 22
The lower end portion of the hollow cylinder arrives at the port with the end portion of the hollow cylinder as the outer layer. Finally, after cooling the injection molded body 24 consisting of the neck 26 and shoulder 22, both molds are removed to obtain an extruded tube. The welded portion 23 of this tube has an outer surface that is smooth and free of irregularities over its entire circumference, as shown in FIG. 5, since the undulations in the curved portion of the outer layer have disappeared as described above. However, the cross section of the welding point 23 is shaped like a rhombus shown in FIG. When the small curvature radius arc portion of the end portion of the hollow cylinder is curved along the inner surface of the cavity of the outer mold as described above, the curved portion That is, since the depth S of the wrinkles 30, 31 (see FIG. 7) generated on the curved end is deeper than that of the cross-sectional shape of the settling point when it is circular, elliptical, or square, and the pitch P is small, It has been found that the heat of the plastic poured into the mold also causes the curved end to flatten and wrinkle, thereby degrading the appearance of the weld.

The present invention provides a method for molding the neck and shoulder of an extruded plastic tube, in which the cross-sectional shape of the tube body near the welding point has one or more circular arc portions with a small radius of curvature, by injection molding. and the entire periphery of the end portion of the plastic hollow cylindrical body which becomes the tube chest, and the end portion of the hollow cylindrical body is the outer layer, and the hollow cylindrical body is located at least in the small radius of curvature arc portion. In the conventional method of manufacturing the extruded tube by curving the end portion of the tube to the inside of the tube and using this as the settling point, the purpose is to eliminate the drawback that wrinkles remain at the melted point of the small radius arc portion. The present invention is characterized in that when the cross-sectional shape of the hollow cylinder is set to a predetermined shape, the shape projected onto a horizontal plane is a shape having the small curvature radius circular arc portion. The method involves cutting off an end portion of the body diagonally to provide a notch in the end portion, placing the notch at a location that will become the arcuate portion with a small radius of curvature, and welding the end portion including the notch.

A specific example of manufacturing an extruded plastic tube using the method of the present invention will be explained below.

FIG. 8 is a front view of an extruded tube manufactured by the method of the present invention;
Fig. 9 is a partially sectional side view, and Fig. 10 is a plan view.
FIG. 1 is a perspective view showing the shape of the hollow cylinder used in this specific example. The difference between the method of the present invention and the conventional method is as follows.

In the conventional method, as described above, the plastic hollow cylindrical body C, which has end portions whose end surfaces are on the same plane, is inserted into the inner mold as it is, and then the hollow cylindrical body is inserted into the cavity of the outer mold together with the inner mold. In the present invention, the hollow cylindrical body is curved and welded along the inner surface of the cavity, but in the present invention, the hollow cylindrical body is curved and welded so that the projected shape on the horizontal plane has the small curvature radius circular arc part. Cutting off the end portion diagonally to provide a notch in the end portion (in the above specific example, as shown in FIG. 11, the central axis (imaginary (line) 37, 37' are diagonally cut out to the same size with respect to (Cross section) Shape 4 - curvature radius It should be placed at a location where the radius is circular (in Fig. 11, the notches 34, 34'
The line connecting the lower ends 35 and 35' of is inserted into the inner mold so that it is located on the long axis in the cross section of the inner mold. ), which is different from the subordinate method described above. 8 to 10 show the end portions so that when the cross-sectional shape of the hollow cylindrical body C is made into a shape having a predetermined small curvature radius circular arc portion, the projected shape on a horizontal plane becomes a shape having the small curvature radius circular arc portion. Diagonally cut out the first
This shows a tube manufactured using the inner mold and the outer mold using the hollow cylinder C having the pair of notches 34, 34' shown in FIG. An injection molded body 24 consisting of an end portion of a hollow cylindrical body C having cutout portions 34, 34', and an integrally molded neck portion 42 and shoulder portion 43.
The lower end portion of the shoulder portion 43 in A refers to the small radius of curvature arc portions 44, 44' of the shoulder portion 43 shown in FIG.
The shoulder 43 shown in FIG.
The circular arc portion 4 with a large radius of curvature is the local green portion of the upper horizontal portion 46 of
7, 47' surrounding green parts 45, 45' of a pair of V-shaped parts
(This part is also the periphery of the notch of the hollow cylinder),
The circular arc portions 47, 47' of the large radius of curvature following this (this portion is also the portion 36, 36' between the two notches 34, 34' of the hollow cylinder in the end portion) are welded, In this example, every part of the welded part was manufactured by welding the hollow cylinder so that the end part was curved toward the inside of the tube.

Note that there are usually 2 to 5 skins in the welded area, and in this example, there are 3 skins. The cross-sectional shape of the tube Tsukioka part near the welded part of the extruded tube is cut at the Y-Y point in Fig. 8.
The shape is similar to that shown in the figure. The extruded tube of this example had no wrinkles at the peripheral edges of the small radius of curvature arc portions 44, 44', had a smooth and beautiful appearance, and had a high commercial value.

According to the method of the present invention, wrinkles do not occur even in small curvature radius circular arc parts.The reason why wrinkles do not occur even in small curvature radius circular arc parts is that the end part of the hollow cylinder is cut out diagonally to provide a notch part, and the green around this notch part is welded. Since the circumferential green length of the small curvature radius circular arc portion is longer than in the case of a hollow cylindrical body without a notch, the radius of curvature is large in most of the circumferential green, and the end portion This is presumed to be because the narrowing ratio of the end portion of the small curvature radius arc portion becomes smaller when the tube is bent inward.

The notch at the end of the hollow cylindrical body becomes an arcuate portion with a small radius of curvature when the cross-sectional shape of the hollow cylindrical body is made into a desired shape, for example, the shape shown in FIG. It may also be provided by cutting the part diagonally. The point is to provide a notch whose projected shape on a horizontal plane has the small curvature radius circular arc portion when the cross-sectional shape of the hollow segment is set to a predetermined shape. Although two notches are shown in the above explanation, if the cross-sectional shape of the tube body near the welding point is, for example, in the shape of a cannonball or in the shape of a falling water drop, a cutout with a small radius of curvature may be used. There is only one arcuate portion, so it is sufficient to provide one notch.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams showing an example of the cross-sectional shape of an extruded tube, Figures 3 and 4 are explanatory diagrams of a conventional tube manufacturing method, and Figure 5 is a main part of a tube obtained by the conventional method. 6 is a diagram showing an example of the cross-sectional shape of a tube body having a small radius arc portion, and FIG. 7 is an illustration of wrinkles generated in the small radius arc portion. Figure 8 is a front view of a tube manufactured by the method of the present invention, Figure 9 is a partially broken side view, Figure 10 is a plan view, and Figure 11 is a diagram of the end of a hollow cylindrical body having a notch used in the method of the present invention. It is a perspective view of one example. A: Outer mold, B: Inner mold, C: Plastic hollow cylinder, 1: End portion of hollow cylinder C, 26...
- Tube neck, 22... Tube shoulder, 2... Bent part of end 1, 23... Tube welding location, 24,
24A...Plastic injection molded body, 25...End portion of shoulder portion of molded body 24, 34, 34'...Notch portion, 4
4, 44'...A circular arc portion with a small radius of curvature in the cross-sectional shape. River diagram soup Z diagram ga 3 diagram outside 4 diagram outside 5 diagram outside 6 diagram or diagram ga 8 diagram soup O leg car 0 diagram outside ll diagram

Claims (1)

[Claims] 1. When the neck and shoulder of an extruded plastic tube whose cross-sectional shape near the welding point has one or more arcuate parts with a small radius of curvature are integrally molded by injection molding, the lower end of the shoulder the entire circumference and the entire circumference of the end portion of the plastic hollow cylinder that becomes the tube body, with the end portion of the hollow cylinder as the outer layer, and at least the end of the hollow cylinder that is in the small radius of curvature arc portion. A method of manufacturing the extruded tube by curving and welding a part to the inside of the tube and using it as the welding part, wherein when the cross-sectional shape of the hollow cylindrical body is set to a predetermined shape, An end portion of the hollow cylindrical body is obliquely cut off so that the projected shape has the small curvature radius circular arc portion, and a notch is provided in the end portion, and the notch is connected to the small curvature radius circular arc portion. 1. Manufacturing an extruded tube, characterized in that the end portion including the notch is welded at the location where the cutout is located.