CZ198595A3 - Extrusion die - Google Patents

Description

Extrusion die • i

Area tachrúkz

BACKGROUND OF THE INVENTION The present invention relates to an extrusion die for extruding hollow extruded products having at least two extrusion cavities each connected to at least two holes, and more particularly to an extrusion die for aluminum and aluminum alloys.

Existing. .state of technology

Such a die with more than one extrusion cavity is already well known in the art.

Various extrusion types can be made for extruding aluminum profiles.

The first type is a so-called flat die, usually comprising a lead connecting an aluminum sculptor to be extruded, a die plate and a support. The die plate comprises a plurality of extrusion cavities through which extrusion occurs, a portion adjacent to the aluminum sculptor to be extruded has a cross-section of the extrudate. The remainder of the extrusion cavity has a gradually increasing cross-section, thereby providing a loose guide for the extruded profile. There are corresponding free-running passages in the support. The first die can be used for profiles with open configuration, ie profiles without tubular parts therein.

AND

Another type of die is the so-called hollow die. In this case, the die consists of a bridge, die plate and support. The support is substantially identical to the supports in the flat die and has free-flow channels for the extruded profiles.

The die plate comprises at least one extrusion cavity, the portion adjacent the extruded billet having a cross section whose outer circumference corresponds to the outer circumference of the cross section of the profile to be obtained. The remainder of the extrusion cavity also has a gradually increasing cross section providing free guidance to the extruded profile.

On the sculptor's side, the extrusion cavity is connected to a recess that is part of the orifice system, which will be described below. The bridge basically has at least two so-called portholes, openings facing the extruded sculptors. The openings are separated from each other by bridge parts. The side of the bridge facing the die is equipped with a mandrel. In the assembled state, the mandrel extends into the extrusion cavity of the die, thereby determining the inner and outer circumference of the extruded profile. The circular openings in the bridge and the recesses in the die form together the flow channels for the aluminum extruded through the extrusion cavities. These flow channels as a whole are usually called portholes. The hollow type punches may also be provided with multiple extrusion hollows.

A special form of punches used in particular to produce thin-walled extruded tubes having a plurality of parallel channels is a punch comprising a punch holder and a punch plate for insertion into a punch holder. The die holder is provided with openings and bridging portions, thereby allowing a support for a mandrel penetrating into the die cavities of the die plate embedded in the holder. Such a die type will be described in more detail below.

In the case of such so-called multi-hole punches, it has been found that the pressure difference between the individual extrusion cavities is due to irregularities in the extrusion channels and to the pressure applied to the billet. These pressure differences result in differences in extrusion velocity between different extrusion cavities, which can be as high as 50 Z.

To reduce the pressure differences, it is proposed to use a rib structure in the openings. These structures equalize the pressure differences between the individual extrusion cavities and thereby reduce the differences in extrusion speed of the individual profiles. Although excellent results are obtained in some applications, it is not possible to use these rib structures when extruding products through multiple holes that require high accuracy and low wall thickness. Due to the flexibility of the die, there is not sufficient securing for the required accuracy.

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It is therefore an object of the present invention to provide an extruder of the above type in which the above-mentioned problem can be avoided.

This object is achieved by at least one opening in each extrusion cavity being connected to one opening of an adjacent extrusion cavity by means of at least one channel.

By providing channels between the individual openings, a pressure equalization between the cavities can be obtained, thereby reducing the difference in the extrusion speed for the individual cavities up to below 10.

Other features and advantages of the invention will be apparent from the following description, with reference to the drawings.

Overview of the drawings

Fig. 1: Front view of a die holder according to the invention

Fig. 2: Cross-section along line II-II in Fig. 1 a

Fig. 3: Cross-section along line III-III in Fig. 1.

No. 1 to "ad. invention

Figure 1 shows a die 2Ώ comprising a die holder 1 for a two-chamber die. The die holder is provided with four holes 2, S and 3, 2 · Holes 2 & Q belong to one extrusion cavity 15 and holes 5 and 2 belong to a second extrusion cavity Between holes 2 »S and 3» 2 are bridging portions 4, 3- The die holder 1 further has two recesses 15 and 1ώ for insertion of the die plate (not shown). Each die plate is provided with an extrusion cavity r

Even in accordance with the cross-sectional area of the extruded profile. The bridge portion may be provided with a mandrel (not shown) extending into the extrusion cavity of the respective extrusion plate, thereby indicating the inner circumference of the extruded profile.

Between the holes 2 there is provided one channel 6 and between the holes S and 2 a second channel Z. These are to the die plate and the holes. It is believed, and the pressure in the extruded metal ducts is in a position as close as possible to allow pressure equalization between that in this region the temperature is such that a near-liquid state is reached, thereby achieving pressure equalization. As a result of this pressure equalization, the extrusion speed between the two cavities becomes almost the same, thus achieving a constant quality in the extruded products independently of the extrusion cavity. This is particularly important for thin-walled products such as heat, especially those used in car systems.

exchanger pipes in air conditioning

It has been found that a good result is obtained when using channels with a cross-section at least equal to the area of one hole.

It is clear that the invention is not limited to the embodiment shown or to the use of special types of extrusion profiles, but that it can generally be used on multi-hole die.

Claims (4)

PATENT CLAIMS An extruder for extruding hollow extruded articles and having at least two extrusion cavities, each of which is connected to at least two holes, in particular an extruder for aluminum or aluminum alloys, characterized in that at least one cavity of each extrusion cavity is connected to one hole adjacent extrusion cavities through at least one channel. 2. Extrusion die according to claim 1, characterized in that each channel has a rectangular cross-section. Extrusion die according to one of the preceding claims, characterized in that the cross-section of the channel connecting the two openings is at least equal to the cross-section of one opening. Extrusion die according to any one of the preceding claims, characterized in that each channel; it is connected to an opening adjacent to the extrusion cavity. The die comprising connected cavities are according to any one of the preceding claims and two die cavities, each of which is at least two holes, characterized by only adjacent holes of the different die holes connected by at least one channel. 6. Extrusion die according to any one of claims 1-4 and comprising at least three cavities arranged in a regular polygon in the extrusion die and wherein each cavity is connected to at least two cavities, characterized in that at least one channel connects each pair of adjacent holes belonging to adjacent cavities.