DEVICE AND METHOD FOR PRESSING A PLASTICALLY DEFORMABLE BLANK

Abstract: The invention concerns a device and a method for continuous pressing of a plastically deformable blank (15) into a three-dimensional section with a predetermined cross-sectional area, comprising a substantially cylindrical, fixed die (10), an opening formed in the die (11), through which the plastic blank (15) is intended to be pressed, and at least one rotary die (12) arranged adjacent to the opening (11), the rotary die having one or more recesses in its peripheral surface for forming the blank, during the rotation of the die, into at three-dimensional section with transverse sectional parts. According to the invention, said rotary die (12) is arranged immediately downstream of said opening (11), whereby the blank is reducible, when passing through said opening, substantially down to said predetermined cross-sectional area, and formable, when passing said rotary die (12), thereby determining the final shape of the three-dimensional section. Furthermore, the device is compatible with conventional extrusion machines in order to allow rapid switching of tools with no need for expensive production stop-pages.

Description: DEVICE AND METHOD FOR PRESSING A PLASTICALLY DEFORMABLE BLANK Technical Field The present invention relates to a device and a method for continuous pressing of a plastically deform- able blank, for example made of a metal, into a three- dimensional section with a predetermined cross-sectional area, comprising a fixed die with an opening formed in the die, through which the plastically deformable blank is intended to be pressed, and at least one rotary die arranged, adjacent to the opening, around an axis ex- tending transversely of the press direction, the die having one or more recesses in its peripheral surface for forming the blank into a three-dimensional section with transverse sectional parts during the rotation of the rotary die. Technical Background In continuous pressing of a plastically deformable blank, for example a heated metal such as aluminium, so- called extrusion, the blank passes an opening with a desired cross-sectional area, thereby forming a section whose longitudinal cross-section is constant. There is a great need for continuous manufacture of sections with transverse sectional parts, such as racks, hollow sections, etc. International Patent Specification W097/12745 dis- closes a method and a device invented by the present inventor, which aim at allowing extrusion of sections with sectional parts protruding transversely of the section. According to this publication, a rotary die is arranged to constitute part of the opening through which the blank is pressed. As the cross-sectional area of the blank is being reduced, the rotating die simultaneously forms it. The rotary die can be designed to produce transverse bars in the section, or to form a raised or embedded company name in the section. The difference compared to various types of di e stamping with rotating elements is to be noted, illus- trated for example in DE 42101746, where only a very limited forming of the blank takes place. When shaping according to the above technique, as referred to by the present invention, the rotating die forms part of the actual extrusion process. The application of this technique in existing, largely standardised, press facilities such as hydraulic pressing plants, screw extruders, conform extrusion machines, etc, was previously impossible. Facilities of said type usually comprise a tool arrangement of the type shown in Fig. 2, with a support 5 for a substantially cylindrical tool 3 comprising a fixed die 1. There is not much space around this tool, and the forces generated during the pressing are very strong. Furthermore, it is very important that the number of production stoppages be reduced, since the cost of un- exploited machine capacity is very high. It is, therefore, desirable that tools can be changed rapidly according to pressing needs. Since Patent Specification W097/12745 was published, the need for sections with a cross-sectional area that varies longitudinally has arisen, i.e. a section having not only transverse sectional parts such as bars, but also a varying cross-section or material thickness along the continuous section. Summary of the Invention The object of the present invention is to provide a device for pressing three-dimensional sections, which is easy to apply to moulds according to prior art, with no need for major adjustments. This object is achieved by means of a device and a method of the type described by way of introduction, wherein said rotary die is arranged immediately down- stream of said opening, whereby the blank is reduced when passing through said opening (11) to substantially the predetermined cross-sectional area, and then formed when passing said rotary die, thereby determining the final shape of the three-dimensional section. Unlike prior art, the area of the blank is thus reduced substantially down to its final cross-sectional area upstream of the rotating die, whereby the forces acting on the rotating die can be minimised. This results in manageable bearing forces, which allows the bearings of the rotary die to be contained in the fixed die . The expression "substantially down to" means primarily down to between 100 % and 130 % of the final pre-determined cross-sectional area. The blank meets with the rotating die radially within its average radius. In this way, some area reduction still takes place at the rotating die, and thus a certain acceleration of the blank occurs during this passage while at the same time the material fills cavities in the rotating die. The expression "immediately downstream of" means that the rotary die is located so close to the opening that the pressure of the pressing is used in the shaping done by the rotating die. If the distance is too long, for example several times the across corner dimension of the section, the blank will self-lock adjacent to the rotating die because of the friction caused upstream against the supporting surfaces when the rotating die is in a pressing phase. The rotary die is preferably mounted in bearings in a transverse cavity formed next to the opening, thereby being rotatable around an axis extending transversely of the pressing direction. This design of the fixed die allows a space-effi- cient location of the rotary die within the machine. 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Φ SH CQ CQ rd -H rd ^ rd • rH Φ φ 0 SH υ Ti β SH ι CQ U £ SH U XI Φ rd Φ β SH SH XI ,-- 4 Φ rd Xl XI rH ft -H υ 0 Φ rd iH -H CD < CD rH rd ft rd H iH ft m rH co 0 Φ CQ CQ 0 -H -H 5 EH XI ft Ti -H XI £ 4J rd £ J rd SH ft β CQ -H XI ft 1 β SH Ti !H rd β 4J 4J 00 -H β 0 -H β CD XI rH , £ CQ rd U Φ 4J J rH -H Φ Φ 4-J CQ n rd -H n > 0 H CJ > 0 xi 4-> rd iH rd 4J Φ υ υ 4J Φ rd Ti Φ Φ 4-J rH -H β 4-) CQ Ti β o rd -H rH CD CD -H 4- ) -H -H XI X -H SH -H φ Φ -H XI rd XI XI rd X! β 4H -H 0 0 β -H CJ 4-1 rd X! Ti 4-> 0 £ H rd Φ £ rd CJ SH O ft 4J 0 SH 4J 4-) £ rd CQ 0 CQ ft rd CQ o O or by passing one or more fixed dies, which offers improved possibilities of varying the pressed sections. The rotary die may suitably have smooth sectors, which in the locked position face the blank, so that, in this position, the blank passes the locked die for forming a smooth sectional segment. By orienting a smooth sector so that it faces the blank when locking the rotary die, the forces acting on the rotary die in the locked position are minimised. Locking the rotary die in a posi- tion where recesses or protrusions are oriented so that they face the blank would in fact require a great locking force and would, in addition, mean a risk of loose pieces forming in the cavities of the die during pressing. Brief Description of the Drawings The present invention will be described in more detail below with reference to the accompanying drawings, which by way of example illustrate preferred embodiments of the invention. Fig. 1 is a schematic representation of an example of an extruding machine. Fig. 2 is an exploded view of a tool arrangement in an extruding machine . Fig. 3 is a rear perspective view of a die according to a first embodiment of the invention. Fig. 4 is a front perspective view of the die in Fig. 3. Fig. 5 is a cross-sectional view of the die in Fig. 3. Fig. 6 is a cross-sectional view of the die in Fig. 3 along the line VI-VI in Fig. 5. Fig. 7 is a partly exploded view of a die according to a second embodiment of the invention. Fig. 8 is a cross-sectional side view of the die in Fig. 7. Figs 9a, b are cross-sectional views of a die according to a further embodiment of the invention, with the rotary die in two different positions. 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The deformation of the blank 15 is shown in more detail in the enlarged view in Fig. 6. With reference primarily to Fig. 5, it is shown how the rotary die 12 is rotatable around an axis C. More particularly, it is fixedly mounted on a shaft 23 mounted in bearings in a cavity 20 in the fixed die 10. The cavity 20 consists essentially of a transverse boring 25a-c formed beside the centre axis B of the die and extending transversely of the pressing direction A. The boring 25a- c has a larger cross section in the areas 25a, 25b, at the respective ends, close to the edge of the die unit. Immediately inside these areas, the cross section of the boring is smaller, getting larger again, finally, m the most central part 25c. In the areas 25a, 25b, two bearings 26 are arranged, for example roller bearings or slide bearings, through which the shaft 23 extends over the whole length of the boring. The die 12 is arranged in the central area 25c and fixed laterally by axial bearings 27 arranged in the area 25c. In the example shown, means for cooling the bearings 26 are arranged in the die unit. The means comprise a ceramic body 22 that is fitted axially outside each bearing, a seal 24 located outside the body 22, and a supply conduit 12 for a cooling agent, such as nitrogen or the like. The die 12 is suitably made of a material with a lower thermal expansion coefficient than at least the central shaft portion 23a on which it is applied. In this way, the die 12 is effectively secured when the temperature of the whole die rises as a result of the extrusion. With reference to Fig. 3, which is a front perspective view of the fixed die 10, i.e. as seen from the point from which the blank 15 is pressed, the opening 11 comprises a recess 29 in the die, the recess causing a first reduction of the area when pressing. This countersink 29 is assymetrically shaped in relation to the centre axis B of the die, and the major part of it is located on the side opposite to the cavity 20. Shaping the recess 29 this way minimises those portions 31 of the die that are weakened, in the pressing direction A, both by the cavity 20 and the recess 29 (see Fig. 6) . It appears from Fig. 4 that the cavity 20 also has an orifice 30 on the front of the fixed die 10, through which the rotary die 12 is visible. The rotary die 12 is mounted by being inserted through the orifice 30, and then by the shaft 23 being inserted through the boring 25 and through the rotary die 12. According to a second embodiment (Figs 7-8) of the invention, a fixed die 110 comprises two rotary dies 12, 12', each arranged on a shaft 23, 23' in a boring 25, 25'. This construction permits pressing of sections that are profiled both on the upper side and on the underside. The two dies may be synchronised with each other in any appropriate way, for example by providing gear wheels to join the shafts 23, 23' . Through the synchronisation the distribution of the load take-up between the dies 12, 12' is improved. The fixed die 110 further comprises a core die 33 fixedly arranged on the die 110 and extending through the opening 11, the opening being divided in two openings 11, 11', thereby permitting pressing of a hollow section. The core die 33, as shown in the perspective view of Fig. 7, comprises, in the embodiment shown, a cruciform portion 34, intended to be fixedly arranged on the die with the aid of fixing means 35 such as bolts, and an elongated portion 36 intended to extend, once the core die is arranged on the die, through the opening 11 as far as or past the centre of the rotary dies. The side 37 of the core die facing the rotary die 12 thereby replaces the above mentioned supporting surface 18 as the element de- fining the opening 17 while at the same time the opposite side 37' defines a second opening 17' . According to another embodiment of the invention, as shown in Figs 9a-b, a fixed die 210 comprises a moveable supporting surface 40 in connection with the rotary die 12. The movable supporting surface 40 is controlled by actuators 42 via link means 41, only schematically illustrated in Figs 9a-b, and is arranged to adjust the opening 11 depending on the size of the opening 17 between the rotary die 12 and the core die 33 (alternatively the supporting surface 18 in the absence of the core die 33) . As shown in Figs 9a and 9b, the supporting surface 40 may be moved between a first starting position (Fig. 9a), in which the opening 11 is essentially the same as in the previously described embodiments, and a second lowered position (Fig. 9b), in which the opening 11 is reduced. This arrangement might be necessary, or at least advantageous, in situations where the peripheral surface of the rotary die has a varying radius, for example when the ro- tating die 12 consists of an oval gear wheel. In the die 210 shown in Figs 9a-b the rotary die 12 is of the same type as in the above examples, but arranged on the shaft 23 slightly offset from the shaft centre. Thus, as illustrated in Fig. 9a, the material of the pressed section gets a larger cross section TI when the centre XI of the rotary die is located above the shaft centre X2 whereas, as illustrated in Fig. 9b, the material of the pressed section gets a smaller cross section T2 when the centre XI of the rotary die is located below the shaft centre X2. The purpose of arranging the supporting surface 40 to reduce the opening 11 in Fig. 9b is to adapt the cross-sectional area of the blank 15 pressed towards the opening 17 to the altered cross sections . Another situation when a moveable supporting surface may be suitable is when using a die 310 as shown in Figs lOa-b. This die is provided with a rotary die 312 having smooth portions 45, which take up an angle sector that is several times bigger than the usual protrusions (gear teeth) . In the example shown, a smooth portion 45 is formed in the rotary die 312 taking up about 30 degrees of the circumference of the die 312. In Fig. 10a pressing is performed in the same way as described above, with the supporting surface 40 in the starting position. In Fig. 10b, however, the smooth portion has reached the opening 17, which is thus given a reduced cross-sectional area. In order to achieve a satisfactory extrusion also in this position, the supporting surface 40 is moved to a lowered position by the actuator 42, whereby the opening 11 is reduced. Furthermore, the die 312 in Figs lOa-b may be ar- ranged to be lockable in the position shown in Fig. 10b. When the die is in this locked position a straight section without transverse sectional parts can be extruded between the smooth portion 45 of the die 312 and the core die 33, alternatively the supporting surface 18. It is to be noted that Figs 9 and 10 are only intended to illustrate the principle behind the described embodiments. A person skilled in the art realises that several of the distances shown in the Figures do not correspond to reality, for example in the case of the inclination of the supporting surface 40, which is exaggerated in order to facilitate understanding. As a consequence of this exaggeration also the distance between the supporting surface and the rotating die 12, 312 is slightly too long. The rotary dies described above may be arranged, as appropriate, to be driven, thereby adding extra power to the extrusion process. A person skilled in the art can provide this drive, for example by connecting the shaft 23, 23' to a driven shaft arranged in the tool support 5. In particular, this drive may be advantageous when pressing sections with varying material thickness, for example as shown in Figs 9a, 9b. It will be appreciated that details of the embodiments shown in the Figures and described above can be combined in an optional way. For example, the core die 33 shown in Figs 8, 9a-b and lOa-b may be excluded when pressing solid sections. The number of rotary dies may vary in all embodiments, and it is mainly for the sake of clarity that most Figures show only one die.

Claims: CLAIMS 1. A device for continuous pressing of a plastically deformable blank (15) into a three-dimensional section with a predetermined cross-sectional area, comprising a fixed die (10; 110; 210; 310) with an opening (11) formed therein, through which the plastically deformable blank (15) is intended to be pressed, and at least one rotary die (12; 312), arranged adjacent to the opening (11) and having one or more recesses m its peripheral surface for forming the blank into a three-dimensional section with transverse sectional parts during the rotation of the die, c h a r a c t e r i s e d m that said rotary die (12, 312) is arranged immediately downstream of said opening (11) , the blank being reducible, when passing through said opening (11), down to substantially said predetermined cross-sectional area, and then being formable, when passing said rotary die (12, 312), thereby determining the final shape of the three-dimensional section. 2. A device according to claim 1, wherein the blank is reducible, when passing through said opening (11), down to between 100 % and 130 % of said predetermined cross-sectional area. 3. A device according to claim 1 or 2 , wherein a cavity (20) located next to one side of the opening (11) is formed in said fixed die (10; 110; 210; 310), and wherein said rotary die (12; 312) is mounted m bearings m the cavity (20) , thereby being rotatable around an axis (C) extending transversely of the pressing direction (A) . 4. A device according to claim 3 , wherein said ro- tary die (12; 312) is axially mounted m bearings with a limited axial play. 5. A device according to claim 4, wherein said rotary die (12; 312) is fixedly arranged on a shaft (23) mounted in bearings in the cavity (20) , said shaft having a limited axial play. 6. A device according to claim 5, wherein a portion (23a) of the shaft (23), said portion extending through the rotary die (12; 312) , is made of a material with a higher thermal expansion coefficient than the rotary die (12; 312) , so that said shaft portion (23a) , when the die and the shaft are heated during pressing, expands more than said die, which is thereby secured to the shaft (23) . 7. A device according to claim 3 , wherein said fixed die (10; 110; 210; 310) further comprises a recess (29) upstream of the opening (11) , intended to cause a first cross-sectional reduction of the blank (15) , the recess being substantially formed on the side of the opening (11) opposite to the cavity. 8. A device according to any one of the preceding claims, further comprising means (40) for varying the cross-sectional area of the opening (11) immediately upstream of the rotary die (12; 312) . 9. A device according to claim 8, wherein the rotary die is mounted on the shaft (23) slightly offset relative to the shaft centre (X2) , which permits pressing of sections of varying cross section. 10. A device according to claim 9, wherein said means (40) for varying the cross-sectional area are synchronised with the rotary die (12) . 11. A device according to claims 8-10, wherein said means for varying the cross-sectional area consist of at least one supporting surface (40) moveable transversely of the pressing direction (A) . 12. A device according to any one of the preceding claims, wherein said rotary die (312) is arranged to be lockable in a predetermined position. 13. A device according to claim 12, wherein said rotary die (312) has smooth portions (45) which, in the locked position, are oriented towards the blank (15) , so that, in this position, the blank passes the locked die (312) to form a smooth sectional segment. 14. A device according to any one of the preceding claims, wherein the rotary die (12; 312) is driven. 15. A method for pressing a plastically deformable blank (15) into a three-dimensional section with a pre- determined cross-sectional area, the blank being pressed past at least one rotary die (12; 312) having one or more recesses in its peripheral surface, so that the blank is formed by the rotation of the die, thereby determining the final shape of the three-dimensional section, c h a r a c t e r i s e d in that the blank is caused to pass an opening (11) immediately upstream of said rotary die (12; 312), whereby the blank (15) , when passing through said opening (11) , is substantially reduced down to said predetermined cross- sectional area. 16. A method according to claim 15, wherein the cross-sectional area of the opening (11) is varied according to the shape of the rotary die (12; 312) and the predetermined cross-sectional area of the three-dimen- sional section. 17. A method according to claim 15 or 16, wherein the rotary die (12; 312) is locked in a predetermined position, so that, while the rotary die is locked, the blank (15) is pressed into a section without transverse sectional parts.

Inventors: JANSSON MARK, JANSSON, MARK
Applicants: JANSSON MARK, MARKRAM DEV AB, JANSSON, MARK, MARKRAM DEVELOPMENT AB
Application year: 2001
Main classification: B29C47
IPC codes: B21C23, B21C25, B21H8, B21J5, B21J13