Tool and Method for the Internal High Pressure Forming of a Hollow Section

Abstract

A tool (1) for the internal high pressure forming of a hollow section (2). The tool (1) is designed both for forming the hollow section (2) and for making an embossment on the outside of the hollow section (2) and for making a hole in the hollow section (2). For this purpose, the tool (1) has an embossing punch (11) displaceable transversely to the longitudinal extent of the hollow section (2) and also a perforating punch (13) arranged coaxially in the embossing punch (11).

Description

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a tool for forming a hollow section by the internal high pressure forming process and to an associated method.

German Patent Document DE 197 33 477 A1 discloses a tool and a method for forming a hollow section of the type mentioned at the beginning. The forming tool has at least one embossing punch which is displaceable transversely to the longitudinal extent of the hollow section and which makes an embossment on the outside of the hollow section after the forming operation. In addition, at least one perforating punch is arranged in the embossing punch coaxially thereto, this perforating punch perforating the hollow section after the embossing operation.

U.S. Pat. No. 6,470,546 B1 discloses a further tool and a further method for forming a hollow section, in which the forming tool has a wall section at which a side facing the hollow section is designed as a shaping die wall and which is displaceable transversely to the longitudinal extent of the hollow section. This wall section contains an embossing punch, by means of which a hole can be embossed in the hollow section after the forming operation.

German Patent Document DE 197 24 037 A1 discloses a tool for the internal high pressure forming of a hollow body and for cutting a flange on this hollow body. To this end, the tool has a cutting device which runs parallel to the longitudinal extent of the hollow section and has a cutting edge which is displaceable in the transverse direction of the hollow section. At the same time, a side of the cutting device facing the hollow section forms a shaping die wall, against which the hollow section bears during the internal high pressure forming.

German Patent Document DE 100 30 882 A1 discloses a further method for cutting a hollow body produced according to the internal high pressure forming process.

The present invention deals with the problem of specifying a method for internal high pressure forming with which in particular a rationalized production process can be achieved. Furthermore, a tool suitable for the abovementioned method is to be provided with which in particular various method steps can be combined.

The invention is based on the general idea of designing a tool for forming the hollow section according to the internal high pressure forming process and also for making an embossment on the outside of the hollow section and additionally for perforating the hollow section and furthermore also for cutting a flange on the hollow section. To this end, the tool has at least one embossing punch displaceable transversely to the longitudinal extent of the hollow section and also at least one perforating punch arranged coaxially in the embossing punch.

In addition, according to the invention, the embossing punch is arranged in such a way that it crosses and passes through a cutting device of the tool in a corresponding opening during the embossing operation, this cutting device extending parallel to the longitudinal extent of the hollow section and being displaceable in the transverse direction of the hollow section. In particular when a side of the cutting device facing the hollow section is designed as a shaping die wall, against which the hollow section bears at least during the internal high pressure forming, this results in simplified kinematics for the tool, and these kinematics can be used for shorter cycle times.

The solution according to the invention therefore offers the advantage that three method steps, namely the internal high pressure forming, the embossing and the perforating, can be carried out with a single tool, so that in particular no tool change is necessary, thereby resulting in a rationalized production sequence. The solution according to the invention therefore helps to streamline the production process and thus achieve time or cost advantages. In addition, the solution according to the invention ensures that the holes produced by the perforating punch have a very high accuracy of position and shape relative to the embossing and thus the quality of the hollow sections produced can be markedly increased. Compared with previous production methods in which the embossments and/or the holes are subsequently made in the already finish-shaped hollow sections, subsequent deformation and thus dimensional inaccuracy of the hollow section can now be avoided. Even for the case where the embossing is effected after the production of the holes, the solution according to the invention offers the great advantage that the embossing punch does not adversely affect the dimensional accuracy, that is to say the position and shape of the holes produced, by the embossing. In principle, with the tool according to the invention, first perforating and then embossing can be carried out after the internal high pressure forming, or vice versa.

According to another development of the solution according to the invention, the tool has a bottom die and a top die which are displaceable relative to one another. The embossing punch may be expediently mounted in a displaceable manner on or in one of these dies. In this way, a defined relative position prevails between the embossing punch and the respective die, a factor which improves the accuracy of the production process. In addition, the cutting device may either be integrated in one of the dies, the cutting edge then forming an integral part of the respective die, or else the cutting device may be designed as a separate component and be fastened to one of the dies in a fixed position, or the cutting device may be arranged on one of the dies in such a way as to be adjustable in stroke. The variants described of the arrangement of the cutting device on the tool already shows the wide range of possibilities that the invention opens up with regard to process-optimized arrangement variants of the cutting devices. For example, a design of the cutting device as a separate component which is fastened to one of the dies in a fixed position offers the advantage that, after a relatively large number of cutting operations, the cutting device or the cutting edge can be exchanged simply and quickly and thus the maintenance cost of the tool can be reduced. If the cutting device is arranged on one of the dies in such a way as to be adjustable in stroke, a markedly smoother mode of operation of the tool is obtained on account of the lower weight, to be moved, of the cutting device compared with the top or bottom die. On the other hand, the integration of the cutting device in one of the dies or the design of the cutting edge as an integral component offers the advantage that an especially precise and powerful cutting operation can be achieved as a result. Due to the many possible ways of arranging the cutting devices on one of the dies, the solution according to the invention therefore makes it possible to react in a flexible manner to the most varied requirements with regard to the material and/or workpiece to be processed.

According to a preferred embodiment of the invention, at least one hold-down, which fixes the flange of the hollow section at least during the cutting operation, is provided in the region of the cutting edge. Such a hold-down, in combination with a positioning device which, before and during the cutting and forming operation, presses the hollow section against that side of the cutting device which faces the hollow section, ensures that the hollow section is held in a fixed position during the cutting operation and thus ensures an exact cut of high quality. In addition, the hold-down provides for always identical positioning of the hollow section inside the tool, as a result of which a high reproducible dimensional accuracy and thus uniformity of the hollow sections to be produced is achieved.

Further important features and advantages of the invention follow from the drawings and from associated descriptions of the figures with respect to the drawings.

The abovementioned features and the features still to be explained below can be used not only in the respectively specified combination but also in other combinations or on their own without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in the drawings and are described in more detail below, identical reference numerals relating to identical or functionally identical or similar components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section through a tool according to the invention with inserted hollow section, before the cutting or forming operation,

FIG. 2 shows an illustration as in FIG. 1, but with actuated positioning device,

FIG. 3 shows a cross section through the tool according to the invention after the cutting and forming operation and before the embossing or perforating operation,

FIG. 4 shows an illustration as in FIG. 3 but with embossing and perforating operation completed,

FIG. 5 shows a cross section through the tool with opened top and bottom dies.

DETAILED DESCRIPTION OF THE DRAWINGS

According to FIG. 1, a tool 1 according to the invention, which is designed for cutting a flange 3 on a hollow section 2, has a bottom die 7 and a top die 8, which are displaceable relative to one another. Here, according to the illustrations in FIGS. 1 to 5, the top die 8 is displaceable toward the bottom die 7. In general, however, it is also conceivable for the bottom die 7 to be displaceable toward the top die 8 or for both to be mounted in an displaceable manner.

To cut the flange 3 on the hollow section 2, the tool 1 has at least one cutting device 4, which runs parallel to the longitudinal extent, has a cutting edge 5 and is displaceable relative to the hollow section in the transverse direction of the hollow section 2. In this case, the cutting device 4 may be integrated in one of the dies 7 or 8, the cutting edge 5 then forming an integral part of the respective die 7 or 8. Alternatively, the cutting device 4 may also be designed as a separate component which is fastened on one of the two dies 7 or 8, here the top die 8, in a fixed position. As a third variant, the cutting device 4 may be arranged on one of the dies 7 or 8 in such a way as to be adjustable in stroke relative to the respective die 7, 8.

In the case of a cutting device 4 integrated in one of the dies 7 or 8, the flange 3 can be cut off or severed in an especially powerful and thus precise manner, as a result of which the quality of a subsequent end product can be markedly increased. On the other hand, the embodiment of the cutting device 4 as a separate component, which is fastened on one of the two dies 7 or 8 in a fixed position, offers the great advantage that the cutting edge 5, which may be designed, for example, as a parting blade, can be exchanged in a simple and cost-effective manner. Hardened metals, for example, which have an especially long service life, are suitable as cutting edge 5. The third embodiment variant, in which the cutting device 4 together with the cutting edge 5 is arranged in a displaceable manner on one of the dies 7 or 8, offers the advantage that the cutting operation can be isolated from a closing operation of the tool 1, i.e. from a movement of the top die 8 and the bottom die 7 toward one another.

According to FIG. 1, a shaping die wall 17 is formed on a side 6 of the cutting device 4 facing the hollow section 2, the hollow section 2 bearing against this die wall 17 after the cutting operation and during the subsequent internal high pressure forming. In this case, according to the illustrations in FIGS. 1 to 5, the tool 1 is designed in cross section, for example, in such a way that the top die 8 and the bottom die 7 each have an L-shaped form, and these L-shaped forms, when they meet, form a cavity 14 in which the hollow section 2 can be shaped by internal high pressure. This cavity 14 is in this case defined at least on one side by the die wall 17 of the cutting device 4.

According to FIG. 1 and FIG. 2, a positioning device 9 is provided on the tool 1, which positioning device 9, before the cutting and forming operation, presses the hollow section 2 against that side 6 of the cutting device 4 which faces the hollow section 2, that is to say against the die wall 17 of the cutting device 4. In this case, the positioning device 9 may be designed, for example, as a punch which is acted upon by spring force or hydraulic pressure and which is arranged so as to be extendable and retractable in one of the dies 7 or 8, here in the bottom die 7. According to FIG. 2, the positioning device 9 is actuated and, in the actuated state, presses the hollow section 2 against the side 6 of the cutting device 4.

Provided in the region of the cutting edge 5 is at least one hold-down 10 which fixes the flange 3 of the hollow section 2 at least during the cutting operation. According to the illustrations in FIGS. 3 and 4, a second hold-down 10′ can also be provided by a stepped design of the cutting edge 5, this second hold-down 10′ fixing the hollow section 2 in position during the forming operation or embossing and perforating operation following the cutting operation.

According to the illustration in FIG. 3, an embossing punch 11 is provided which is displaceable transversely to the longitudinal extent of the hollow section 2 and provides an embossment (cf FIG. 4) on the outside of the hollow section 2 after the forming operation. In this case, the embossing punch 11 can preferably be actuated hydraulically and acts during the embossing against an internal high pressure p_i which prevails inside the hollow section 2. The embossing punch 11 may expediently be mounted in a displaceable manner on or in one of the dies 7, 8 and be arranged in such a way that it crosses and passes through the cutting device 4 in a corresponding opening 12 after the cutting operation and during the embossing operation. During the cutting operation, the embossing punch 11 moves with the cutting device 4 or the top die 8 transversely to its embossing direction. It is conceivable in this case, for example, for an embossing surface 15 formed on the end face of the embossing punch 11 to be part of the shaping die wall 17 of the cutting device 4.

As mentioned above, the embossing of the hollow section 2 is effected against the internal high pressure pi and after the cutting operation, so that, with the embossing, an additional but facultative processing step can be carried out with the tool 1.

According to FIGS. 3 and 4, at least one perforating punch 13, which perforates the hollow section 2 after the completed embossing operation, is provided in the embossing punch 11 and coaxially thereto. An embossing direction of the embossing punch 11 is in this case parallel to a direction of movement of the perforating punch 13. Due to the embossing punch 13, a further likewise facultative processing step, namely the perforating of the hollow section 2, is integrated in the tool 1, as a result of which the production process can be additionally rationalized.

In addition, the embossing or the perforating against the internal high pressure p_i offers the advantage that embossments produced beforehand are not adversely affected by the perforating or perforations produced beforehand are not adversely affected by the embossing on account of the internal high pressure p_i, so that a high quality of the hollow sections 2 produced can be achieved.

One possible method of cutting the hollow section 2 or of forming, embossing and/or perforating the hollow section 2 is to be briefly explained below:

According to FIG. 1, the hollow section 2 is inserted into the tool 1, the two dies 7 and 8 being in the open state, that is to say being positioned at a distance from one another. After the insertion of the hollow section 2, which at this stage is still a hollow section blank (not designated in any more detail), the positioning device 9, according to FIG. 2, pushes the hollow section 2, still before the cutting and forming operation, against that side 6 of the cutting device 4 which faces the hollow section 2, that is to say against the die wall 17. During the positioning, the tool, according to FIG. 2, is still in a partly open state, so that a simple adjustment of the hollow section 2 in the direction of the cutting device 4 is possible.

The cutting operation is effected after the positioning. To this end, according to FIG. 3, the top die 8 moves towards the bottom die 7 and cuts off the flange 3 of the hollow section 2 by means of the cutting edge 5, situated at the front on the cutting device 4 in the direction of movement. At least during the cutting operation, at least one hold-down 10 arranged in the region of the cutting edge 5 fixes the flange 3 of the hollow section 2. After the cutting operation has been completed, a second hold-down 10′ fixes the remaining flange stub of the hollow section 2 and thus fixes the hollow section 2 in its position. After the cutting operation, cutting scrap (not shown) falls through an ejection shaft 16, which according to FIGS. 1 to 5 runs out vertically in the bottom die 7 in the direction of movement of the cutting device 4.

It can be seen from FIGS. 2 and 3 that the cutting of the flange 3 is effected by the closing of the tool 1, that is to say by a movement of the top die 8 toward the bottom die 7. It is also conceivable in this case for the cutting operation to be effected only after the closing of the tool, that is to say when the top die 8 bears against the bottom die 7, by a cutting device 4 which is adjustable in stroke and is designed, for example, as a separate component.

After completion of the cutting operation, the hollow section blank 2′ is formed by internal high pressure forming and in the process changes in size and form in accordance with the illustration in FIG. 3. During the internal high pressure forming, the positioning device 9 is actively shifted back or passively thrust back to a corresponding extent, that is to say the holding or positioning force of the positioning device 9 is (markedly) smaller than the forces which occur during the forming and which widen the hollow section 2.

After the forming of the hollow section 2, an embossing punch 11 displaceable transversely to the longitudinal direction of the hollow section 2 can make an embossment on the outside of the hollow section 2 according to FIG. 4. In this case, such an embossing operation is optionally selectable. Embossing is effected according to FIG. 4 by the embossing punch 11 moving transversely to the longitudinal extent of the hollow section 2 through the opening 12 in the cutting device 4 and embossing a recess in an outer wall of the hollow section 2 by means of the embossing surface 15 provided at the front in the embossing direction.

In addition to or as an alternative to the embossing operation, a perforating punch 13 arranged in the embossing punch 11 coaxially thereto can perforate the hollow section 2 after the embossing operation has been completed (cf. FIG. 4). To this end, the perforating punch 13 travels transversely to the direction of movement of the cutting device 4 and parallel to the embossing direction of the embossing punch 11 and pierces the outer wall of the hollow section 2. According to FIGS. 3 and 4, in each case one perforating punch 13 is provided here. However, it is also possible for a plurality of perforating punches 13 to be arranged. It is also conceivable for perforating to be effected without embossing of the hollow section 2. On account of the embossing punch 11 or perforating punch 13 acting against the internal high pressure p_i, it is possible to carry out both the embossing and the perforating on the hollow section 2 without these processing steps adversely affecting one another as in a conventional method of production in a plurality of steps.

In this case, the embossing surface 15 of the embossing punch 11, this embossing surface 15 being arranged by way of example in the opening 12 of the cutting device 4, may form part of that side 6 of the cutting device 4 which is designed as a shaping die wall 17. However, it is also conceivable for the opening 12 not to open until during an embossing or perforating operation and for it to be closed during the cutting operation or during the forming operation, as a result of which the shaping die wall 17 is formed completely by that side 6 of the cutting device 4 which faces the hollow section 2.

According to FIG. 5, the tool 1 is opened after the cutting and forming operation and/or embossing operation and/or perforating operation by the top die 8 moving away from the bottom die 7. In the process, the embossing punch 11 and also the perforating punch 13 are retracted into the tool 1 or the cutting device 4 at least to such an extent that the two dies 7 and 8 can move apart without any problems and the hollow section 2 can be removed from the tool 1.

In summary, the essential features of the solution according to the invention can be characterized as follows:

In a tool 1 which is designed for forming a hollow section 2 according to the internal high pressure forming process, the invention makes provision for an embossing punch 11 for making an embossment and for a perforating punch 13 therein for making a hole in the hollow section 2. In addition, a cutting device 4 having a shaping die wall 17 may be provided.

The invention thus enables a plurality of processing steps to be combined, for example the trimming, the forming, the embossing and the perforating of the hollow section 2, in one production station, so that, with the tool 1 according to the invention, a plurality of processing steps hitherto separate from one another can be effected promptly and without removal of the hollow section 2 from the tool 1. In addition, the processing steps of embossing and perforating can be carried out optionally, so that, for example, cutting of the flange 3 and subsequent forming and/or subsequent embossing and/or subsequent perforating can be carried out with the tool 1 according to the invention.

That side 6 of the cutting device 4 which is designed as a shaping die wall 17 provides for multifunctional use of the cutting device 4, the cutting device 4 being simple to realize from the design point of view and at the same time constituting an especially successful design solution. In addition, due to the embossing punch 11 or perforating punch 13 acting against the internal high pressure p_i, exact embossing or perforating of the hollow section 2 can be effected, during which the embossing and the perforating do not adversely affect one another, so that an end product of high quality can be achieved overall.

Claims

1-12. (canceled)

13. A tool for forming a hollow section, comprising: at least one embossing punch which is displaceable transversely to a longitudinal extent of the hollow section and which makes an embossment on the outside of the hollow section after a forming operation; at least one perforating punch provided in the embossing punch coaxially thereto, said at least one perforating punch perforating the hollow section before or after the embossing operation; and at least one cutting device which runs parallel to said longitudinal extent of the hollow section, having a cutting edge and displaceable in a transverse direction of the hollow section, wherein the embossing punch is arranged so that it crosses and passes through at least one cutting device in a corresponding opening during the embossing operation; and wherein tool is designed for cutting a flange on the hollow section.

14. The tool as claimed in claim 13, wherein a side of the cutting device facing the hollow section is designed as a shaping die wall, against which the hollow section bears at least during the internal high pressure forming.

15. The tool as claimed in claim 13, further including a bottom die and a top die which are displaceable relative to one another.

16. The tool as claimed in claim 15, wherein the embossing punch is mounted in a displaceable manner in or on one of the top and bottom die.

17. The tool as claimed in claim 15, wherein the cutting device is integrated in one of the top and bottom die and the cutting edge forms an integral part of said one die, or the cutting device is designed as a separate component and is fastened to one of the top and bottom die in a fixed position, or the cutting device is arranged on one of the top and bottom die in such a way as to be adjustable in stroke.

18. The tool as claimed in claim 13, further including a positioning device provided which, before the cutting operation or before the forming operation, presses the hollow section against a side of the cutting device which faces the hollow section.

19. The tool as claimed in claim 13, further including at least one hold-down, which fixes the flange of the hollow section at least during the cutting operation, provided in the region of the cutting edge.

20. A method of forming a hollow section according to an internal high pressure forming process, comprising: making an embossment on the outside of the hollow section by an embossing punch which is displaceable transversely to the longitudinal extent of the hollow section after a forming operation; perforating the hollow section before or after the embossing operation by at least one perforating punch arranged in the embossing punch coaxially thereto; cutting a flange on the hollow section by a cutting device which runs parallel to the longitudinal extent of the hollow section and has a cutting edge which is displaced transversely to the longitudinal extent of the hollow section, wherein the embossing punch crosses and passes through the cutting device during the embossing operation.

21. The method as claimed in claim 20, wherein the hollow section, after the cutting operation, bears during internal high pressure forming, against the side of the cutting device which faces the hollow section and is designed as a shaping die wall.

22. The method as claimed in claim 20, wherein, before the cutting operation or before the forming operation, a positioning device presses the hollow section against a side of the cutting device which faces the hollow section.

23. The method as claimed in claim 20, further comprising arranging at least one hold-down in a region of the cutting edge and fixing the flange of the hollow section at least during the cutting operation.

24. The method as claimed in claim 20, wherein the flange is cut by closing the tool.

25. The method as claimed in claim 24, wherein the embossing punch crosses and passes through the cutting device during the embossing operation.

26. The method as claimed in claim 24, wherein the hollow section, after the cutting operation, bears, during the internal high pressure forming, against a side of the cutting device which faces the hollow section and which is designed as a shaping die wall.

27. The method as claimed in claim 23, wherein before the cutting operation or before the forming operation, a positioning device presses the hollow section against that side of the cutting device which faces the hollow section.

28. The method at least as claimed in claim 24, wherein at least one hold-down arranged in the region of the cutting edge fixes the flange of the hollow section at least during the cutting operation.

29. The method at least as claimed in claim 24, wherein the flange is cut by closing the tool.

30. The tool as claimed in claim 16, wherein the cutting device is integrated in one of the top and bottom die and the cutting edge forms an integral part of said one die, or the cutting device is designed as a separate component and is fastened to one of the top and bottom die in a fixed position, or the cutting device is arranged on one of the top and bottom die in such a way as to be adjustable in stroke.

31. The tool as claimed in claim 14, further including a positioning device provided which, before the cutting operation or before the forming operation, presses the hollow section against a side of the cutting device which faces the hollow section.

32. The method as claimed in claim 21, wherein, before the cutting operation or before the forming operation, a positioning device presses the hollow section against a side of the cutting device which faces the hollow section.