CA2458775A1

CA2458775A1 - Method for the extrusion of a hollow profile or similar body from a bar and corresponding device

Info

Publication number: CA2458775A1
Application number: CA002458775A
Authority: CA
Inventors: Bertram Geigges; Armin Huber; Dieter Woempner; Adolf Ames
Original assignee: Individual
Current assignee: 3A Composites International AG
Priority date: 2001-08-28
Filing date: 2002-08-23
Publication date: 2003-03-13
Also published as: EP1423217A1; WO2003020454A1

Abstract

The invention relates to a method for extruding a hollow profile or similar body, from a bar (24), introduced into a receiver drilling (22) of a housing (18) and fed into a forming cross-section of a forming tool (24) by means of a press stamp, whereby the bar material, along with the surface of the bar (24) is expanded into a chamber (78), preceding the forming tool (32), expanding transversely to the pressing direction (x) with a central inlet and the surface is split apart. A device with a receiver or housing and a moulding tool is used in the above, between which at least one discoid adapter tool (80), with an approximately central inlet (E), is arranged before the tool inlet side of the moulding tool, in the direction of pressing, with a chamber (78), widening in the pressing direction (x), within the cross-section of which, arm inserts (88) or similar elements forming flow reducers, extend across the pressing direction (x).

Description

PCT/EP02/09412 As Published Process for Extrusion Moulding of a Hollow Profile or Similar Body from a Bar, and a Device therefor The invention concerns a process for extrusion moulding of a hollow profile or similar body from a bar or billet which is guided in a receiver bore of a receiver and advanced by means of a press stem or press ram in the pressing direction to a moulding cross-section of a forming tool; the bar or billet material is introduced 1o under pressure into an inlet of the forming tool and the resulting ductile mass advanced in the pressing direction to the moulding cross-section. The invention also concerns a device according to the preamble of claim 4 which is particularly suitable for this process.
DE 198 42 291 A1 by the applicant discloses that on extrusion moulding, the material which is made ductile of a heated casting bar or rolling rod section (preformed in the metal range from non-ferrous, sintered metal or steel, but in particular from an aluminium alloy) is pressed by a die - or for hydrostatic extrusion moulding, by means of a fluid - from a receiver through one or more moulding 2o cross-sections of a forming tool transverse to the pressing direction. In direct or forward extrusion moulding the die moves in the direction of the course of the resulting profile up to the moulding cross-section, in indirect or reverse extrusion moulding the material is pressed against the die direction through a tool held on the hollow die.
To produce hollow profiles, for the extrusion moulding process hollow profile tools with die plates are used such as disclosed for example by DE 24 45 308 A1. The die plate is integrated in a mandrel part to form the profile outer contour.
In the latter part is held a mandrel - for multi-chamber profiles, several mandrels -for so forming the future inner contour so that the mandrel protrudes into the die plate and beyond its forming area. In this process the ductile material is guided by way of inlets into the pressing tool so that the part billets from the individual inlets flow together again below the mandrel supporting arms - in a welding chamber - and weld together. As the pressing process continues, the material or aluminium alloy flows past the mandrel and the die opening and thus assumes the required shape of the hollow profile. The inlets are always arranged on the outside about the profile cavity or cavities; the aluminium alloy is advanced to the forming area of the tool from the outside and above all by way of several inlets. If in the case of multi-chamber hollow profiles the hollow profile inner areas cannot be adequately fed from the outside, material inlets for feeding are also provided in the inner area of the hollow profile. The main inlets are always arranged around the outer contour of the profile cavity.
The size of a hollow profile which can be produced - its maximum possible circumferential diameter - is determined by the receiver diameter and the size of the inlets arranged on the outside about the cavity, and by the load-bearing capacity of the said mandrel supporting arms.
In general the profile size which can be produced with extrusion presses available on the market is limited by the press size, the receiver diameter used and the tool load-bearing capacity. The said DE 24 46 308 A1 and DE 28 12 690 A1 by the applicant concern the dimensioning of the latter property for large hollow profiles 2o with large mandrel surfaces. The quality of the pressing seams is also influenced by the flowing of the slug edge zones into the outer inlets in the extrusion moulding tool, with the possible consequence of having to twist off the slug before use.
Furthermore, the shaping ability and life of the extrusion moulding tool are substantially reduced by the high load on the tool mandrel surface and the creep process caused by this high load and by flexion.
It should also be noted that metal bars, in particular those made of aluminium alloys, are coated with contaminants, for example lubricant residue, and with an oxide layer. Above all the oxide particles on the bar face have proved extremely 3o harmful for the structure of the resulting profile; the resulting zone with contaminated inclusions - also known as the transverse pressing seam - is relatively long as a function of the profile shape and pressing speed and as quality standards rise, requires the removal of ever longer profile sections from the resulting extrusion as waste, with all the resulting consequences of reduced economic efficiency with shrinking profile output; when the new bar is pressed, the transverse pressing seam results between this and the metal remaining in the tool inlets. This appears in the profile extrusion as a tongue. The quality of the transverse pressing seam depends on the tool design and the "clean" working method in the extrusion moulding, but cannot be measured in the profile extrusion without destroying it. Therefore, on profiles which are under mechanical stress, the transverse pressing seam area of greater or lesser length is cut out of the pressed profile billet.
In order to reduce the contaminated area - the said transverse pressing seam -occurring in particular in aluminium alloys during extrusion moulding at the transition of two adjacent blocks or bars, DE 196 05 885 A1 by the applicant proposes, before entry of the front bar end into the moulding cross-section, moving this bar out of the receiver in the pressing direction by a slight protrusion amount, trimming off and removing a resulting disc-like section from the free bar end and bringing the latter up to the moulding cross-section or rear end of the previously pressed slug. By removing this front section its oxide skin or contaminant is also removed so that, assuming a rapid contact with now almost virgin bar face on the 2o tool, contamination of this bar face by oxide particles can be reduced and the occurrence of lengthy waste sections in a profile extrusion kept to a minimum.
In order now to reduce the time gap between the cutting process and the start of further pressing, removal of the bar face should take place at the same time as the other trimming of pressing residue from the tool. The receiver should be moved axially away from this at the end of a pressing process; when its adjacent faces are fixed in relation to each other, the cutting process for the pressing residue and bars can begin. The two cut surfaces are joined together after only slightly more than ten seconds during the pressing process. This means that the cut surfaces so oxidise to a minimum and largely virgin material surfaces are joined in the transverse pressing seam, a condition for the production of good transverse pressing seams.

The device far performance of the process described above offers a cutter with two cutter blades running at a mutual separation which simultaneously are guided in a radial movement path over the opening of the receiver bore and the rear surface of the tool.
It has, however, now been found that the cut surfaces, for example by the increasing adhesion of minute aluminium residue to the cutting blade, have an undefined roughness. When the cut surfaces are joined together, air can be enclosed in the grooves between the ridges, preventing the virgin surfaces from io meeting with good welding over the entire contact surface of the transverse pressing seam.
US 3, 777, 544 discloses a swage for extrusion moulding for production of hollow extrusion profiles. The swage has a prechamber with a cavity cross section which ~5 first expands and then contracts again in order to prevent the inclusion of air in the extruded profile material. The cavity also contains retaining webs which hold in position a centrally arranged swage component serving to form the cavity in the extrusion profile.
2o JP 09047812 describes an extrusion swage for extrusion moulding processes.
This has a frustoconical cavity first expanding conically in the pressing direction, which in the pressing direction is border by a tapered outlet opening on the face from which emerges the extrusion profile.
25 US 3,241,346 discloses a swage for extrusion moulding processes for production of hollow extrusion profiles in which the swage part forming the cavity of the extruded profile is not rigidly connected with the remainder of the swage but lies freely on webs protruding from the inner peripheral area of the swage cavity.
30 In view of these circumstances the inventor has faced the task of making the profile widths which can be produced as independent as possible of the pressing geometry. Also, the contaminant areas which occur on extrusion moulding, in particular of aluminium alloys, are to be eliminated, preventing a fall in the quality of the transverse pressing seam as the pressing ratios become lower and the wall thicknesses rise.
The teaching of the independent claims leads to achieving this object; the sub-claims specify favourable refinements. Also, the invention covers all combinations 5 of at least two of the features disclosed in the description, drawing and/or claims.
According to the invention the bar material is expanded in a chamber with a central inlet which is arranged before the forming tool, and the surface of the bar expands in cross-section in the pressing direction, in the cross-section of which 1o chamber protrude separate elements crossing the pressing direction and forming a flow obstacle, and the surface is torn apart. Thus, before the central inlet opening of the tool, the pressed product enters a prechamber opening up the ductile pressed product; parts of the surface which are oxidised or exposed to air are advantageously torn apart and virgin surface parts passed for diffusion and ~ 5 welding.
The invention concerns an extrusion moulding device with a receiver or holder for a bar - the latter being advanced in the pressing direction by means of a press stem to the moulding cross-section of a forming tool - in which from the tool inlet 2o side, arranged before the forming tool in the pressing direction is at least one preferably disc-like attachment tool with an approximately central inlet and offering a chamber which expands in the pressing direction, into the cross-section of which chamber transverse to the pressing direction, protrude separate elements forming a flow obstacle, preferably formed as arm attachments; according to the invention 25 arranged below the elements or arm attachments are welding chambers for a uniform material flow.
It has also proved favourable to allow the elements or arm attachments to protrude from a chamber wall expanding hopper-like in the pressing direction, i.e.
preferably 3o to produce them integral with the chamber wall.
These elements or arm attachments cause a turbulence in the material flow i.e.
act as an agitator which is moved relative to the material flow. To increase the effect 5a of this agitator, the longitudinal and/or cross-section of the arm attachment, which is angled towards the central axis of the tool, tapers away from the chamber wall and is directed with its free end towards the central axis of the tool.
It has proved particularly favourable to form the element or arm attachment as a flat rib viewed in the press direction, where the distance between the two flank walls diminishes towards the free end of the element or arm attachment. The front face of the element or arm attachment in the press direction is angled towards the central axis of the tool.
~o The free ends of each two elements or arm attachments protruding into the chamber are diametrically opposed to each other, the free ends of several elements or arm attachments of the chamber determine a circular contour about the central axis of the tool. The arm attachments delimit between them two radial gaps.
In a particular embodiment according to the invention the free ends of at least some of the elements or arm attachments are connected with a baffle plate across the pressing direction i.e. the radial gaps between the arm attachments are bordered towards the central axis by the periphery of this baffle plate.
Another form of the arm attachments has side rib-like mouldings which protrude from the arm attachments. These rib-like mouldings - preferably one on each side of the arm attachment - can determine a circular contour about the central axis of the tool and serve as additional flow obstacles. Also, the diameter of the circular contour corresponds to around one-third of the largest diameter of the chamber.
A further shaping which increases the turbulence effect on the elements or arm to attachments is a flat area which is formed facing against the pressing direction and connected with the baffle plate by an end connecting web. This flat area begins on the back of the arm attachment at a distance from the chamber wall.
The arm attachments described, as stated, are moulded on the chamber wall which is expanding hopper-like; in the pressing direction after this wall is a cylindrical section which is preferably formed from the inner surface of a limiting ring let into in the attachment tool, and thus can be designed to be replaceable.
The fact that the tool central axis is the axis of symmetry for the tool cross-section or the tool longitudinal section leads to a chamber shape which is particularly favourable fluidically.
The embodiment of the chamber described above, also known as the agitator prechamber, because of its narrow central inlet allows the production of profiles with large wrap circular diameters - in particular greater than the receiver diameter even from receivers for small slug diameters with high specific moulding pressures.
A further advantage arises in that the pressed product is always advanced to the 3o forming tool from the slug centre. Pressed product from the contaminated slug edge zone area cannot flow into the forming tool; the material of the contaminated edge zone area is collected in the pressing residue and cut away at the end of the pressing process.
Particular advantages of the object of the invention are:
~ production of high quality transverse pressing seams;
~ production of large profiles from small receivers;
~ higher pressing outputs (speeds) by the use of smaller receiver or slug diameters with lower pressing temperatures and high specific moulding pressures;
~ increased pressing output and hence reduced production costs.
Further advantages, features and details of the invention arise from the description below of preferred embodiment examples and with reference to the drawing which shows:
Fig. 1: a perspective view onto part of an extrusion press with a horizontal press stem;
Fig. 2: a cut-away extract enlarged from fig. 1 from another extrusion press;
Fig. 3: a longitudinal section through a sketched receiver of the extrusion press with press stem spaced in front in the pressing direction and the forming tool behind;
Figs 4, 5: the view of the press stem and receiver corresponding approximately to fig. 3 in front of a forming tool in different positions;
Fig. 6: a longitudinal section through another design of the receiver and the forming tool;
Fig. 7: a longitudinal section corresponding to the view in fig. 2 through a variant of the receiver and forming tool with attachment tool in between;

Figs 8, 10, 11: each a front view of an attachment tool;
Fig. 9: a cut-away perspective view of the attachment tool in fig. 8.
An extrusion press 10 for direct extrusion moulding of profiles 12 according to fig.
1 has, on a pressing cylinder 14, a press stem 16 which runs in the longitudinal axis A of a bore 19 passing through a receiver or holder 18. The diameter of a pressing disc 17 at the free face of the press stem 16 is slightly smaller than the 1 o free bore diameter of a receiver bore so that the press stem 16 can be inserted therein.
The said free bore diameter d1 in figs. 3 and 4 is bordered by the inner surface 20 of a receiver bush 21 inserted in the receiver 18 or its bore 19.
Consequently, the ~ 5 interior of this receiver bush 21 is known as the receiver bore 22.
The maximum distance between a receiver front 23 on the die side and the pressing disc 17 in the rest position, not shown, of the press stem 16 is dimensioned such that in front of the receiver bore 22 can be placed by a loading 2o trolley 26 a block or bar of alloy indicated by 24 and in particular of a preheated aluminium alloy, which can be introduced by the press stem 16 in the pressing direction x into the receiver bore 22.
Close to a receiver face 23a remote from the press stem 16, in a swage holder 25 on a crown 30 rests a plate-like swage as a forming tool 32. In fig. 1, in the pressing direction x, this is followed by a discharge channel 34 from the crown 30 through which is removed the profile 12 generated in a mould cross-section of the swage 32. Above the receiver 18 in fig. 1 can be seen a lift device 36 for a cutter 38 with two parallel blades 39 which is provided movable radially to a gap 40 3o which is visible in fig. 3 between the receiver 18 and the forming tool 32.
In the embodiment example of fig. 2, between the receiver 18 and the plate-like swage 32 is provided a mandrel part 33 to produce an inner contour of a resulting profile 12a. The swage plate in the pressing direction 8 is followed by a pressure plate 42 in a pressure plate holder 44. After this pressure plate 42 is a pressure ring 46 and after this a wearing ring 48 in the crown 30. 50 indicates a tool holder for the swage or tool holder 28, the pressure plate holder 44 and the pressure ring 46.
At the end of a pressing process on the end of the receiver bore 22 remote from the die, at the tool surface facing this is a pressing residue 52 from which the pressing disc 17 has been removed. Thanks to an outlet collar 54 formed by the o projection h of the receiver bush 21, this tool surface remains separated from the receiver face 23a. Also, at the rear receiver front 23 the receiver bore 22 surrounds a ring collar 56 as a projection of the receiver bush 21.
On insertion of a new bar 24, the free bar end approaches the pressing residue Of a thickness a for example of 80 mm. The rear bar projection a is maximum 20 mm.
The receiver or holder 18 is retracted - for example as shown in fig. 5 by more than 450 mm - until the pressing residue 52 is clear. The bar 24 of total length t 2o protrudes in a collar length of e.g. around 10 mm to 60 mm beyond the outlet collar 54 of the receiver bush 21; in a subsequent cutting process the bar 24 must not be able to be moved by the cutting blade 38. Before this cutting process the holder 18 is retracted against the pressing direction x until the rear tool surface of the forming tool or swage 32 stands at a distance from the receiver face 23a.
In this position the holder 18 and swage 32 are temporarily fixed.
By lowering a cutter blade indicated in fig. 1 of the cutter 38, the pressing residue 42 or a face disc 58 - determined by the said projection of the collar length t of the bar 24 - is removed from the bar 24 and with this the face 60 pointing in pressing 3o direction x; at the bar face 60, before the process is described here, has formed an oxide layer, the oxide particles of which would cause disruptive contamination on transfer to the resulting profile 12. By removing the face disc 58 with the bar face 60 a face free from oxide layer is achieved.

After the cutting process the receiver 18 is returned to the swage or forming tool 32 and the moulding process begins again.
5 In fig. 6, from the receiver face 23a remote from the press stem 12, at a radial distance from the peripheral edge of the bore 19 - here remaining without the receiver bush 21 - of the holder 18a, there protrudes a form collar 62 of axial length h~ with the radial surface which borders the pockets 64 directed towards the longitudinal axis A. These pockets are intended to receive any pressing particles 1o emerging radially which could contain disruptive contaminants. Although the drawing shows one annular form collar 62 protruding from the receiver face 23a, this moulding or its surface can have a different form in other embodiments.
The same applies to a moulding on the rear receiver front 23; in the drawing the receiver bore 19 surrounds a ring collar 63, directly at its edge.
In the tool inlet side or swage face 31 of the multi-piece forming tool 32 is a flat forming dish 66 of a contour corresponding approximately for example to the receiver bore 19, from which runs a discharge channel 68 running in the pressing direction x; through this channel is expelled a billet 70 produced in the moulding 2o cross-section 67 of the swage 32. The contour of the forming dish 66, holding a disc-like moulding 72 connected with the billet 70, is selected such that it holds all inlets of the tool 32 running in the pressing direction x and not shown in the drawing for reasons of clarity.
During the pressing process, from the slug or bar 24 pressed through the forming tool 32, is generated the billet 70 starting from the disc-like moulding 72;
the moulding 72 is formed in the above-mentioned forming dish 66 of the swage 32 and is integral with the said pressing residue 52 of thickness a protruding from the tool inlet side 31 against the pressing direction x; this residue occurs during the so pressing process in the die-free face end area of the receiver bore 19 when the receiver 18 is retracted against the pressing direction x. The radial surface of the forming collar 62 at the receiver face 23a then stands as a stop face parallel to this at a distance from the tool inlet side or swage face 31. In this position the receiver 18 and the swage 32 are temporarily fixed in order to allow a subsequent cutting process. A new slug or bar 24 is placed before the pressing residue 52 and the allocated surfaces of the bar 24 and pressing residue 52 are cut away in order to improve the quality of the billet 70 in this area. A transverse pressing seam is produced between the metal remaining in the inlets of the forming tool 32 and the new bar 24.
For this, by lowering the two cutting blades 39 indicated in fig. 1 of the cutter 38 simultaneously, the pressing residue 52 and a face disc determined by a 1 o projection of the bar 24 are removed from the bar 24 with its face 60 pointing in the pressing direction x; before the said procedures, on the latter face, there has formed an oxide layer or similar contamination, the oxide particles of which on transfer to the resulting billet 70 would there form the said disruptions in the transverse pressing seam.
As a result of the double cutting process, for high pressing ratios and small wall thicknesses the quality of the transverse pressing seam is such that this can remain in the expelled profile billet 70. As the pressing ratios become smaller and the wall thicknesses increase, the transverse pressing seam quality however 2o diminishes, for which reason before the forming tool 32 is arranged a chamber 78 in an attachment tool 80. Its position within the extrusion press 10 is shown in fig.
7.
The plate-like attachment tool 80 of diameter n of here around 950 mm and height q of 270 mm is shown in front view in fig. 8. A limiting ring 90 is let into the tool face 82 remote from the die as a swage rest; the inner surface 91 of said ring determines a circular outlet contour K of the rear diameter n1 of here around mm and its height q1 corresponds approximately to half the tool height q. At the inner edge 92 of this limiting ring 90 is formed a cone surface 84, sloping at an opening angle w of approximately 30° towards the tool central axis M, of the attachment tool 80 which surrounds a chamber 78 - bordered by an inlet contour determining a front diameter n2 - as a central inlet of frustoconical shape, with the tool central axis M as the axis of symmetry. The front diameter n2 at the front face 86 of the attachment tool 80 measures around 280 mm. Protruding from the sloping cone or chamber wall surface 84, at angular distances w1 of their central axis B of 60°, are arm attachments 88 which are radial in top view, the length b of which in top view according to fig. 8 amounts to around one third of the contour diameter n1. The shape of these arm attachments 88 is shown mainly in fig. 9;
the almost rectangular extended inner cross-section tapers away from the inlet contour E. The inner cross-section forms an inner surface 87 of the arm attachment 88, the flank faces 89 which are formed approximately triangular.
The clear diametric distance z between the free ends 90 of two opposing arm 1o attachments 88 is the diameter of a circle as a geometric location of all these free ends 90.
The chamber 78 thus opens hopper-like in the pressing direction x so that the said transverse pressing seam surface, while passing through the chamber 78 during the pressing process, expands and is torn apart; parts of the transverse pressing seam surface which are oxidised or exposed to air are thus torn apart so that virgin surface parts are supplied for diffusion and welding.
In order to tear apart the transverse pressing seam surface even more, the said 2o arm attachments 88 protrude into the material flow which is expanding hopper-like, under these arm attachments 88 and before the actual extrusion moulding tool are formed sufficiently large welding chambers of different heights and shapes, serving to achieve a uniform material flow. With a design 80a of the attachment tool according to fig. 10, the said circular geometric location of the free ends 90 of the arm attachments 88 determines the contour of a disc-like baffle plate 96 on which are moulded the narrow radial connecting webs 98 of the arm attachments 88. The baffle plate 96 with the arm attachments 88 and chamber wall 84 borders radial openings or gaps 97 for the material flow.
so The connecting webs 98 transform into a blade-like flat area 91 of the arm attachment 88 pointing in the pressing direction, which area at a radial distance f rests on the inner surface 93 of the limiting ring 92 and as described ends at the baffle plate 96. In the example 80b of fig. 11, on both sides of the flat area 91 a side rib 99 is moulded out of the arm attachment 88; these ribs 99 - here twelve -towards the baffle plate 96 adjoin a circular contour k1, the diameter d2 of which corresponds to approximately one-third of the diameter n~ of the outlet contour K.
Thanks to the design described of the chamber 78 - also known as an agitator prechamber - of the tool 80, 80a, 80b with its narrow central inlet, it is possible to produce profiles of large wrap circle diameters even from receiver 18 for small bore diameters with high specific moulding pressure.

Claims

1. Process for extrusion moulding of a hollow profile (12, 12a) or similar body from a bar which is guided in a receiver bore (19) of a receiver (18) and by means of a press stem (16) advanced in the pressing direction (x) to a moulding cross-section (70) of a forming tool (32, 32a, 32b), where the bar material is introduced under pressure into an inlet (72) of the forming tool and the resulting ductile mass is advanced in the pressing direction to the moulding cross-section, characterised in that the bar material expands with the surface of the bar in a chamber with a central inlet which is arranged before the forming tool and which broadens cross-sectional in press direction, whereas in the cross-section of which chamber protrude separate elements crossing the pressing direction and forming a flow obstacle, and the surface of the bar is torn apart.

2. Process according to claim 1, characterised in that parts of the surface which are oxidised or exposed to air are torn apart.

3. Process according to claim 1 or 2, characterised in that virgin surface parts are advanced for diffusion and welding.

4. Device for extrusion moulding of a hollow profile (12, 12a) or similar body from a bar which is guided in a receiver bore (19) of a receiver or holder (18) and advanced by means of a press stem (16) in the pressing direction (x) to a moulding cross-section (70) of a forming tool (32, 32a, 32b), in particular for performance of the process according to any of the previous claims, characterised in that from the tool inlet side (62), arranged before the forming tool (32, 32a, 32b) in the pressing direction (x) is at least one attachment tool (80) with an approximately central inlet (E) which contains a chamber (78) which expands in the pressing direction (x), in the cross-section of which chamber, transverse to the pressing direction (x), protrude 14a separate elements (88) forming a flow obstacle.

5. Device according to claim 4, characterised in that the attachment tool (80) is designed disc-like and the position of its chamber (78) is determined by the tool central axis (M).

6. Device according to claim 4 or 5, characterised in that the elements are formed as arm attachments (88) crossing the pressing direction (x).

7. Device according to any of claims 4 to 6, characterised in that under the elements or arm attachments (88) are arranged welding chambers for a uniform material flow.

8. Device according to any of claims 4 to 7, characterised in that the elements or arm attachments (88) protrude from a chamber wall (84) expanding hopper-like in the pressing direction (x).

9. Device according to any of claims 4 to 8, characterised in that the diameter (n2) of the front inlet contour (E) in the pressing direction (x) of the chamber (78) corresponds approximately to half the diameter (n1) of the outlet contour (K) of the chamber.

10. Device according to claim 8 or 9, characterised in that the elements or arm attachments (88) are integral with the chamber wall (84).

11. Device according to any of claims 8 to 10, characterised in that the cross-section of the arm attachment (88) tapers away from the chamber wall (84).

12. Device according to any of claims 8 to 11, characterised in that the arm attachment (88) with its free end (90) is directed towards the central axis (M) of the tool (80, 80a, 80b).

13. Device according to any of claims 4 to 12, characterised in that the element or arm attachment (88) is formed as a flat rib, where the mutual spacing of the two flank walls (89) diminishes towards the free end (90) of the element or arm attachment (88) (figs. 8, 9).

14. Device according to claim 13, characterised in that the front face (87) of the element or arm attachment (88) in the pressing direction (x) is angled towards the central axis (M) of the tool (80, 80a, 80b).

15. Device according to any of claims 12 to 14, characterised in that the free ends (90) of each two elements or arm attachments (88) are diametrically opposed (z) to each other and the free ends of several elements or arm attachments determine a circular contour about the central axis (M) of the tool (80).

16. Device according to claim 9 and 15, characterised in that the distance (z) corresponds to approximately half the diameter (n2) of the inlet contour (E).

17. Device according to any of claims 12 to 16, characterised in that the free ends (90) of the elements or arm attachments (88) are connected at least partly with a baffle plate (96) crossing the pressing direction (x).

18. Device according to claim 17, characterised in that the elements or arm attachments (88) on the one side and the chamber wall (84) and baffle plate (96) on the other side border radial gaps (97) as flow chambers.

19. Device according to any of claims 4 to 18, characterised in that from the elements or arm attachments (88) protrude lateral rib-like mouldings (94).

20. Device according to claim 19, characterised in that the rib-like mouldings (99) determine a circular contour (k1) laid about the central axis (M) of the tool (80b).

21. Device according to claim 20, characterised by a rib-like moulding (99) on one side of the arm attachment (88).

22. Device according to claim 20 or 21, characterised in that the diameter (d1) of the circular contour (k1) corresponds approximately to one-third of the maximum diameter (n1) of the chamber (78).

23. Device according to any of claims 4 to 22, characterised in that the element or arm attachment (88) has a flat area (91) pointing against the pressing direction (x).

24. Device according to claim 23, characterised in that the flat area (91) is connected with the baffle plate (96) by an end connecting web (98).

25. Device according to claim 23 or 24, characterised in that the shoulder of the flat area (91) is provided at a distance (f) from the chamber wall (84).

26. Device according to any of claims 8 to 25, characterised in that after the chamber wall (84) expanding hopper-like in the pressing direction (x) is a cylindrical section (90).

27. Device according to claim 26, characterised in that the cylindrical section is formed by the inner surface (91) of a limiting ring (90) let into the attachment tool (80).

28. Device according to claim 9 and 27, characterised in that the diameter of the inner surface (91) is the diameter (n1) of the outlet contour (K).

29. Device according to any of claims 4 to 28, characterised in that the tool central axis (M) is the axis of symmetry for the tool longitudinal section.

30. Device according to any of claims 4 to 28, characterised in that the tool central axis (M) is the axis of symmetry for the tool cross-section.