FI57707C - FOERFARANDE OCH ANORDNING FOER KALLFLYTPRESSNING AV MJUKA METALLER TILL OEPPNA KONFORMIGA TUBAEMNEN - Google Patents

Description

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Patent- och raglftaratyralaan '' AiwMcm utitgd och uti. $ Krtfun pubiicand 30.06.80 (32) (33) (31) Pyr * «« y tuolken-lat »rd priority 25.11.71

France-France (FR) 71/1 * 2251 (71) SCAL Societe de Conditionnement en Aluminum, U7 rue de Monceau,

Paris 8e, France-France (FR) (72) Michel Phlippoteau, Saint-Maur, France-France (FR) (7U) Berggren Oy Ab (5U) Method and apparatus for cold extrusion of soft metals into open conical tube blanks - Förfarande och anordning för kall- flytpressning av mjuka metaller account öppna konformiga tubämnen

The invention relates to a method and an apparatus for manufacturing flexible, truncated cone-shaped metal tube blanks.

Flexible, frustoconical metal tubes, used primarily as packaging for pasty substances, have been known for a long time. They are generally made by cold extrusion (also called impact extrusion) of a metal, most preferably aluminum or its alloys.

However, these tubes, which are very convenient to use, have one major drawback before they are filled: because they are made by cold extrusion, they have a cylindrical shape, so transporting them from the factory where they are made to the factory where they are filled requires spacious packaging, which is usually are cardboard, as each tube must be placed in a separate compartment as they are sensitive to even the slightest thrust. Thus, transportation and storage costs significantly increase the price of the pipes.

57707 It was therefore invented to make these flexible metal tubes in the shape of a slightly truncated cone so that they could be packed together. This resulted in two results: a reduction in the volume of the package and a reduction in the risk of damage to the pipes.

In one method used to make the tubes conical, the blanks are placed in a conical matrix and expanded by means of an expandable membrane or by blowing air directly into them, the mouth of the tube being closed by a truncated conical portion which progresses as the filling opening expands.

However, shaping a hardened cylindrical tube into a conical shape causes a certain cold treatment in the metal, which makes it difficult to form a sealing fold. In addition, in order to carry out this work step, an additional machine is needed for an already long chain, in which a ready-to-pack tube is created from the metal plate.

The whole idea of shaping the tube directly into a conical shape already at the manufacturing stage runs into the fact that it is not possible to use a conical press. In cold extrusion, the metal must be pressed through an annular opening between the press and the die, which extends parallel to the axis of the press at a tenth of a millimeter from the wall of the press.

This distance is necessary so that the metal, as it cools as it moves away from the annular opening, does not shrink on the pusher itself. The resulting friction would impede the free flow of metal and pur-sutus would occur uncontrollably. It is clear that a conical presser would prevent metal from flowing parallel to the wall of the presser.

Attempts have also been made to lubricate the product extruded by the press during high-pressure at high pressure by means of an air flow from inside the press, from openings at the height of the extrusion edge.

Due to the numerous deformed tubes obtained by this method and, above all, the tubes which have longitudinally dissipated, this method has not been able to be used rationally.

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Attempts have also been made to provide pipe blanks whose cross-section gradually increases with extrusion (DE-OS 1 452 509, DE-OS 1 627 672 and US-PS 2 483 376). For this purpose, part of the press has had annular ridges, the circumference of which extends from the outer end of the press, cutting to form a body whose axis coincides with the axis of the press.

However, only a limited number of ridges can be used in this method, as each of them causes a sudden increase in the diameter of the blank and therefore the greater the resistance the more ridge protrudes. The number of all of these resistors eventually exceeds the fracture resistance of the flexible tube during its extrusion and folds into an “accordion”.

To make bottle capsules from soft metal, it is known (US-PS 2,096,018) to perform an extrusion in a suitable tool having a matrix having a frustoconical cavity and a presser rotatably arranged in the cavity. Along the circumference of the presser, parallel to its base line, are mounted several narrow rollers which perform the rolling of the metal against the conical inner wall of the matrix which rises up along the presser. Extrusion at such a high flow rate as is used in conventional impact extrusion is hardly possible in this complicated and stressed tool.

Thus, in practice, it has not been possible to obtain a cone angle of the tubes sufficient to allow them to be nested so that their distance, i.e. the distance between two consecutive edges, is 20 millimeters.

More particularly, the present invention relates to a method for coextruding soft metals into open conical tube preforms, the cross-section of which thus increases towards the open end of the preform so that the preforms can be stacked together, according to which the press extrudes the metal in the matrix. The characteristics of the method are set out in the following requirement 1. The features of the device according to the invention appear from the following claim 3.

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The pitch of the helix with respect to a plane perpendicular to the longitudinal axis of the pusher is most preferably of the order of 20 °, and in the axial longitudinal section of the pusher, the angle of inclination of the guide side for the extruded metal of the ridge is most preferably about 25 °.

The invention will be explained in more detail below with reference to the accompanying drawings, which show examples of an apparatus by means of which the method can be implemented.

Figure 1 schematically shows an apparatus for carrying out the method according to the invention.

Figure 2 shows on a very large scale a sectional view of the ridge on the upper surface of the presser.

Figure 3 shows means for grinding a blank at the end of the work step.

Figure 4 shows an embodiment of a pusher by means of which the tube can be flattened during extrusion.

The device schematically shown in Figure 1 comprises a matrix 1, which is generally of the type used in the manufacture of flexible metal tubes as an impact extrusion technique. The presser 2 has the shape of a slightly truncated cone and corresponds to the desired conicity of the tube. The opening angle of these tubes is generally 1-2 °, i.e. the angle between the base line of the cone and the longitudinal axis is 30 'to 1 °. When making a very large diameter and very long pipe, this angle may be more than 2 °.

The lower end of the pusher 2 has a circular extrusion rim 3, the operation of which is known per se. After extrusion, the metal must be cooled, as a result of which the metal shrinks. This shrinkage must therefore be taken into account when increasing the diameter of the pusher at temperatures determined according to the coefficient of expansion of the metal. The increase in this diameter varies between 0.05 and 0.1 mm.

The distance between the extruded metal and the presser must be maintained along the entire length of the conical presser. According to the invention, it is provided by means of one or more helical ridges 4. The angle α formed by this helix with a plane perpendicular to the longitudinal axis of the pusher is most preferably 20 °.

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On the other hand, it is important that the extruded metal does not touch the pusher wall at all between the two helical ridges. The vertical projection of the ridge base is always immediately inside the ridge • below it with a defined base line of the plunger. Several helical ridges can be arranged evenly along the circumference of the pusher so that the distance between the two helices is 12-20 mm.

This distance is calculated perpendicular to the horizontal coils at an angle of 20 °.

Another measure for determining the number of parallel edges is the height of these ridges, which is generally constant over the entire length of the pusher. Figure 2 shows a section of an example ridge. Its shape approaches that of the trapezoid, but it should be noted that the bottom side of this half-trapezoid forms a certain angle with the axis of the pusher, while its short side is substantially parallel to the axis of the pusher. The height x of this pseudo-trapezoid, i.e. the height of the ridge, may vary from 0.2 mm to 0.5 mm; in this example it is 0.3 mm.

Pursutettaessa alloy proceeds in the direction of the arrow 5 (lower part of Figure 2) and the face of the ridge. The choice of the angle b, which determines the inclination of the inclined side 6 guiding the metal flow, is very important: the inclination of this side must be such as to facilitate the sliding of the metal without forcing it into longer contact. In practice, good results are obtained at an angle of about 25 °. The width of the small side must be somewhat small, while the slope of the other oblique side has no real bearing on the operation of the device. The latter dimensions are determined essentially by the material of the press and its method of manufacture.

On this basis, it is easy to understand how the method according to the invention works in practice: a piece of metal is placed in a matrix 1, a presser 2 crushes it with a pre-calculated stroke and metal (e.g. aluminum) bursts along this presser 2 to form a tube 7. Metal bursts from a gap between the extrusion edge 3 and the matrix 1 and flows in the direction of the axis of the pusher 2 until it meets the ridge 4. This encounter occurs gradually due to the helicality of the ridge, according to the pitch of the helix.

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The sloping side 6 of the ridge 4 directs the flow of metal to the end of this side, from where it continues in its original direction parallel to the axis of the pusher 2 until it meets the next ridge. Because these encounters and deviations from the original flow direction occur point by point, the metal is not subjected to significant edge compression for a moment and the diameter of the tube gradually increases.

At the end of the work step, the tube blank 7 is removed from the press 2. It then has one or more helical depressions caused by the ridges.

If the blanks need to be leveled to improve stackability or for aesthetic reasons, no special new machine is required to perform this step, as this work can be performed simultaneously with the finishing steps normally used in the process, such as sheath milling, shank leveling or oral threading.

For the leveling step, the blank 7 is fitted to a mandrel 8 which is in the same shape as the inner wall of the finished tube. This mandrel 8 is made to rotate by means of a drive wheel 9. One or more rollers 10, freely arranged on the axis 11 parallel to the baseline of the mandrel 8, perform an axial movement by any mechanism (not shown in the figure). As a result of the rollers 10, the helical depressions disappear and at the end of the work step (see Fig. 3) the tube blank is smooth and in the shape of a truncated cone.

By means of a variation of the above embodiment, the smoothing can already be performed when the blank is conical (see Fig. 4). For this purpose, the plunger 12 has a cylindrical core 13 which must be sufficiently solid to be able to perform the impact extrusion. It is expanded at its free end to form a complete impact surface 14 with the extrusion rim 3. This extension forms a rim 15 which supports the shell 16.

The outside of the shell 16 is shaped to correspond to the pusher 2, i.e. its outer surface is in the shape of a slightly truncated cone and has one or more helical ridges 4. The inner surface of the shell 16 is cylindrical and the whole shell can rotate around the core 13.

Claims (6)

1. A method for cold-flowing soft metals into open conical tubes, whose cross-sections increase to such an extent towards the open end of the blank, that the blanks can be stacked together, whereby a press-stamp floats the metal contained in a matrix, known as - characterized in that each cross-section of the blank is subjected to radial expansion forces over only a portion of the circumference of the blank during the entire pressing operation, and that this portion is displaced circumferentially from cross-section to cross-section along the longitudinal axis of the blank. Method according to claim 1, characterized in that the blank is subjected to radial expansion forces in several cross-sections at the same time in several places with uniform circumferential spaces. Apparatus for carrying out the method according to claim 1 or 2, wherein soft metals are cold-flow pressed into open conical tube blanks (7), whose cross-section increments to the open end of the blank so that the blanks can be stacked together, which comprises a matrix (1) for the metal and a compression stamp (2) with conically expanded circumferential surface in the direction of the open tube end, characterized in that the conical extension is formed with at least one protruding helical As (4) pA stamp (2). Device according to claim 3, characterized in that said helical axis (4) has a pitch angle (a) pA c. 20 °. Apparatus according to claim 3 or 4, characterized in that said axis (4) in axial longitudinal section through the pressing piston (2) has an inclined guide flange (6) with an inclination angle (b) pA about 25 ° for the axial direction. the floating metal.