JPS59291B2 - Method for forming thin-walled flat bottomed tubes using impact extrusion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a thin-walled flat bottomed tube by impact extrusion.

As is well known, in order to form a thin-walled bottomed tube using the impact extrusion method, a billet with approximately the same cross-sectional shape is placed in a female recess with an open top surface that matches the outer shape of the tube, and the inside of the tube is A punch with a cross-sectional shape that matches the shape is used to press the billet from above, and the billet is extruded into the tubular gap created between the female cavity and the punch.

In this case, if the bottomed tube to be formed is relatively thick, such as circular or polygonal, the centers of the punch and female mold recess will align, so
A bottomed tube of a predetermined shape can be obtained with almost no problems, and the yield is good.

However, if the bottomed tube to be formed has a narrow cross-sectional shape where the length b of the short side is smaller than the length a of the long side, as shown in Fig. 1, the long side More than 65 units of defective products were produced in which one side wall along the line was torn or could not be extruded to the specified height, resulting in extremely poor yields.

The present inventor investigated the causes of poor walking and developed the present invention. According to the present invention, a narrow thin-walled flat bottomed tube is replaced with a thick thin-walled tube such as a circular or regular polygonal shape. It has the revolutionary effect of being able to be molded with the same yield as the bottom tube.

The poor molding yield of thin-walled flat-bottomed tubes, which the inventors have investigated, is due to
When the billet is placed in the female mold recess, a small gap of about 0.05 xi will inevitably be created between the female mold recess and the billet, and when applying strong pressure with a punch, the billet will be placed inside the female mold recess based on that gap. This is due to the fact that the tube wobbles and tilts in the width direction of the tube, and is extruded in an inclined state.

The small gap between the billet and the female mold recess that allows this wobbling is essential for fitting the billet into the female mold recess. It is not possible to fit it into the female mold recess, which is undesirable because production efficiency decreases and the female mold recess wears out more quickly.

Therefore, the present inventor recognized the existence of this slight gap in order to quickly fit the billet into the female mold recess, and when pressing the billet with a punch, the billet mainly plays in the width direction due to this slight gap. They came to the conclusion that all they had to do was prevent it, and they applied a method to the tip of the punch (bottom surface) and the top surface of the billet, and it was successful.

Furthermore, when parts are assembled inside a bottomed tube, it has conventionally been difficult to stabilize the parts in a predetermined position using an extremely simple structure.

Therefore, the inventor of the present invention made use of the above-mentioned means applied to the tip of the punch and the top surface of the billet to stabilize the component at a predetermined position within the bottomed tube with an extremely simple structure.

That is, as illustrated in FIGS. 2 and after, a fitting part 5 consisting of a protruding line 3 and a concave line 4 that fit tightly together at least along the long side direction is provided on the tip of the punch 1 and the upper surface of the billet 2. It is established.

In this embodiment, the protruding stripes 3 are provided at the tip of the punch 1, and the four stripes 4 are provided on the top surface of the billet 2.
A protruding strip may be provided on the upper surface of the billet 2.

The relationship between the protruding line 3 and the concave line 4 is such that when the punch 1 descends while aligning the center with respect to the female recess 6 and presses the billet 2 housed in the female recess 6, they fit into each other. The billet 2, which had been tilted in either direction in the width direction due to a small gap in the female mold recess, is now erected and no longer tilted.In other words, the center 2' of the billet 2 is also connected to the punch and the female mold recess. (Figure 4).

Therefore, in the female mold recess 6, the billet 2 is formed between the convex line 3 and the concave line 4.
When they are not fitted, they tilt in either direction in the width direction in the recess, and the center 2' intersects the center C of the female recess at a slight angle α, but the punch is lowered. and uneven stripes 4,
3 are fitted, the center 2' is aligned with the female recess and the center C of the punch and stands erect, and is strongly pressed in this state.

As a result, the billet is extruded upward through the intended tubular gap between the punch 1 and the female cavity 6, leaving no room for tearing due to the knitting orientation or for producing defective products due to insufficient extrusion height. .

The lowermost position of the punch is at the bottom 7 of the formed bottomed tube 7.
The grooves 4 or 3 formed on the top surface of the billet are set so that they remain on the top surface of the billet (FIG. 5).

By doing this, the bottom 7' of the bottomed tube 7 will not come off, and the bottom 7' will not come off.
'The grooves 4 or the protrusions 3 formed on the top surface can be used for positioning parts to be installed later.

For example, when a container-shaped part is installed in a predetermined position inside the bottomed tube 7, the positioning portion of the convex or concave line that can fit into the concave line 4 or the convex line remaining on the bottom γ of the bottomed tube 7 is attached to the container. By forming a positioning part on the lower surface of the bottom of the container-shaped part and fitting this positioning part into the groove or convex part of the bottomed pipe 7, the container-shaped part can be stabilized at a predetermined position in the bottomed pipe 7. .

In particular, when a synthetic resin container-shaped part made by injection molding is assembled into a bottomed tube, the above-mentioned positioning effect is effective because the part is tapered in the length direction of the part.

The effects of the present invention are also evident from the fact that excellent products can now be obtained with a yield of 100 units, whereas previously the yield was 30 to 35 units.

In addition, since billets are generally made by punching out material, the grooves or convex lines formed on the top surface of the billet are formed using a punching die that has the above-mentioned relationship to match the convex lines or concave lines at the tip of the punch. If a strip is provided, it can be formed accurately at the same time as punching.

In addition, an aluminum alloy billet was used in the experiment, and the fitting part 5 had a width of 2.5 mm and a depth or height of about 1.5 mm, making it possible to produce flat bottomed tubes with a 100% yield. However, the same results can be obtained with billets made of other materials.

In addition, the flat bottomed tubes to be produced are not limited to having side walls parallel to each other along the long sides as shown on the left side of Figure 1, but with both side walls facing outward as shown on the right side of Figure 1. It may be slightly curved and protruding, or concave.

Further, the fitting portion 5 may be provided in a cross shape or an inverted letter shape, instead of being provided over substantially the entire length of the long side as shown.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention. Figure 1 is a perspective view of two types of flat bottomed tubes formed according to the present invention, and Figure 2 is a diagram showing a punch and a billet, and the protrusions and recesses provided on both. A plan view illustrating the relationship between the fitting parts consisting of strips, Figure 3 is a partially sectional front view of the punch immediately after it starts descending, and Figure 4 shows the fitting part in the fitted state. Similar front view, 5th
The figure is a similar front view with the punch lowered to its lowest position, and in the figure, 1 is the punch, 2 is the billet, 3 is the convex strip, 4 is the concave strip, and 6 is the female recess.

Claims (1)

[Scope of Claims] 1. A billet having a slightly smaller outer diameter is placed in a female recess whose cross-sectional shape matches the outer shape of the bottomed tube to be formed, and a billet whose outer diameter is slightly smaller than the female recess has a cross-sectional shape that matches the outer shape of the bottomed tube to be formed. A method for forming a thin-walled flat bottomed tube using an impact extrusion method, in which a cross-sectional punch is aligned with the center of a female-shaped recess and lowered into the recess, and the punch is used to forcefully press the billet to form a thin-walled flat-bottomed tube. In order to compensate for the inclination of the billet in the female mold recess due to the slight dimensional difference between the outer shape of the billet and the inner shape of the female mold recess, a protrusion and a recess are provided that fit together between the tip of the punch and the top surface of the billet. An impact extrusion method characterized in that a fitting part consisting of a strip is provided, and when the punch strongly presses the billet, the fitting part is fitted prior to this, and the billet is erected in the female mold recess. A method for forming thin-walled flat bottomed tubes. 2. In the molding method of claim 1, the lowest lowering position of the punch is determined such that one of the fitting parts formed on the top surface of the billet remains on the top surface of the bottom of the formed tube. A method for forming thin-walled flat bottomed tubes.