WO2002090014A1 - Method and device for the production of varying elements - Google Patents

Abstract

The invention relates to a method and a device for the production of varying elements in a hollow profile, enclosed around the circumference thereof. The device comprises an internal high pressure moulding tool, into the die recess of which a hollow profile blank may be inserted. A branch leads radially off from the die recess, in which the hollow profile blank may be expanded by means of a fluid internal high pressure to form the varying element. According to the invention, varying elements of almost any shape may be formed in the hollow element in a simple and process-secure manner with regard to the moulding process, whereby the device further comprises a membrane and a pressure generator, by means of which the membrane may be pressurised by a pressure medium in such a way that the membrane lies supported against the expanding direction during the expansion of the varying element as said element is formed. The membrane yields elastically on progressive formation of the varying element until the end form is achieved. The membrane is mounted on the tool outside the longitudinal edge of the die recess and stretching across the branching.

Description

 Method and device for producing secondary shaped elements

The invention relates to a method for producing secondary shaped elements according to the preamble of patent claim 1 and a device for carrying out the same according to the preamble of patent claim 3.

A generic method or a generic device is known from US 4,840,053. In this case, a hollow profile is inserted into a divided internal high-pressure shaping tool, the upper part of which has a pot-shaped branch originating from the engraving. After an internal high pressure has been exerted within the hollow profile, it widens into the branch and lies against the contour of the branch, as a result of which the secondary shaped element corresponding to the branch is formed. In order to achieve a controlled and process-reliable design of the secondary molding element, a solid body is slidably arranged in the branch, which supports the end face of the secondary molding element that is formed. This form of support is implemented in the usual way by means of steel stamps that are actively operated from the outside. However, this is only possible in the case of branches or for secondary shaped elements, whose surface lines on the inside or outside run in a straight line and parallel to one another, so that the stamp can be guided freely in the branch.

The invention has for its object to develop a generic method or a generic device such that in a simple manner and reliable from the Shape course almost any shaped secondary elements can be formed on the hollow profile.

The object is achieved by the features of claim 1 with regard to the method and by the features of claim 3 with regard to the device.

Due to the elastic membrane covering the branch, which in the position of use is under a support pressure that is always slightly below the expanding internal high pressure during the expansion of the hollow profile, the flexible and large-area adaptation of the membrane to the structural conditions of the branch shape makes it easy quickly and at all times the supporting element that is being formed is provided with sufficient supporting force, through which the hollow profile material can nestle optimally against the wall contour of the branch without running the risk of exceeding the yield point, which would result in the hollow profile bursting, and on the other hand due to the elasticity of the membrane a - with respect to the wall contour of the branch - retreating true to shape is achieved and jamming between the end face of the secondary mold element being formed and the branch wall is avoided. By means of the solution according to the invention, secondary shaped elements can be reliably produced on hollow profiles and can have almost any cross-sectional changes. Thus, the formation of undercuts is easily possible and support of the secondary form element can be realized even with large transition radii from the longitudinal extent of the tool engraving to the branch from the beginning of the forming. The latter is of particular advantage when using materials with low ductility, such as light metal alloys, to ensure process reliability. The arrangement of a membrane is very simple in terms of equipment and can also be easily retrofitted to existing forming tools. Expedient embodiments of the invention can be found in the subclaims; otherwise the invention is explained in more detail below with reference to an embodiment shown in the drawings; shows:

1 in a lateral longitudinal section, a section of a device according to the invention in the undeformed state of the hollow profile with a pressure-relieved membrane,

2 in a lateral longitudinal section a section of the device from FIG. 1 in the undeformed state of the hollow profile with a supporting membrane,

3 in a lateral longitudinal section, a section of the device from FIG. 1 during the expansion of the hollow profile into a branch of the forming tool of the device with a supporting membrane,

Fig. 4 in a lateral longitudinal section a section of

1 in the final state of the hollow profile with secondary form element and membrane in the starting position.

1 shows a device for producing secondary shaped elements on a circumferentially closed hollow profile, which includes an internal high-pressure forming tool 1. In its engraving 2, a hollow profile blank 3 is inserted along its longitudinal extent. A branch 4 radially extends from the engraving 2 and penetrates the tool 1. The branch 4 is rounded in the region 5 of the transition to the longitudinal extent of the engraving 2 with large radii. The branch wall 6 has a bead 7 locally approximately in the middle, so that the wall 6 has an undercut with the flank 8 of the bead 7 facing away from the hollow profile blank 3. The branch 4 is covered on its end 9 remote from the hollow profile by a resilient membrane 10 belonging to the device in a high-pressure-tight manner spans. For this purpose, the membrane 10 is attached with its edge 11 circumferentially between the rear side 12 of the forming tool 1 and a clamping plate 14 of the device provided with a recess 13 in the covering area. As a result, the membrane 10 can be easily replaced in the event of a wear state that is no longer tolerable. To ensure pressure tightness, the membrane 10 is sealed at its edge 11 opposite the rear side 12 of the forming tool 1 with an annular seal 15 and the clamping plate 14 located on the rear side 12 of the forming tool 1 is sealed on the underside thereof with an annular seal 16. On the clamping plate 14 there is a support plate 17 on which the membrane 10 according to FIG. 1 rests in a relaxed, pressure-relieved state. A pressure channel 18 runs in the support plate 17 of the device, which is connected on the one hand to a pressure generator and on the other hand opens out on the side 19 of the support plate 17 facing the membrane 10. The support plate 17 is also sealed for reasons of pressure tightness with an annular seal 20 against the clamping plate 14.

By means of the pressure generator, a pressure medium, which can be liquid or gaseous due to the ease of handling, is now fed into the pressure channel 18, after which the membrane 10 is pressurized on the back when it exits. As a result and due to the elasticity in the absence of back pressure, the membrane 10 is stretched in such a way that it conforms to the branch wall 6 on the one hand and on the hollow profile blank 3 on the other hand (FIG. 2). Here, an internal high pressure can already be present in the hollow profile blank 3. In this phase, this is either not yet so high that it has a widening effect, or indeed corresponds to an expansion pressure, but then the support pressure stretching the membrane 10 is the same, so that no deformation of the hollow profile blank 3 can take place into the branch 4 , As an alternative to the printing media mentioned, mechanical expansion devices are also conceivable in which, for example, an elastically deformable body made of solid rubber is deformed by a stamp, whereby the rubber mass displaced thereby presses the membrane 10 against the contour of the branch wall 6.

After the membrane 10 has applied to the blank 3, the support pressure and the expansion pressure are increased, the ratio of the expansion pressure to the support pressure during the expansion phase being such that on the one hand the expansion pressure is considerably greater than the support pressure so that the blank 3 expands. On the other hand, the support pressure relative to the expansion pressure must not be so low that the blank 3 ruptures. Above all, the pressure conditions must be designed in such a way that a certain state of stress is formed within the blank material, which permits process-reliable expansion. As the expansion continues, the expansion pressure is increased. 3, the blank 3 is arched into the branch 4 at the location thereof, the membrane 10, which counteracts the expansion direction being pressurized, being pushed back by the arch 21.

The membrane 10 advantageously consists of a low-friction material or is provided with a low-friction coating, so that the friction of the curvature 21 of the blank 3 on the membrane 10 is as small as possible and therefore no stretching of the blank 3 in the area of the supporting system the membrane 10 takes place. This contributes to the process security of the expansion.

As the formation of the secondary mold element 23 progresses until the final shape is reached, the membrane 10 elastically recedes. At the end of the expansion, the finished hollow profile 22 now has a secondary shaped element 23 which bears almost completely on the entire contour of the branch 4 (FIG. 4). The membrane 10 now assumes its starting position and is supported on the back by the support plate 17 covering the branch 4 at the location of the end position of the end face 24 of the secondary form element 23. It can be a useful co <! α ιQ ιQ tr r + "3 (- ¹ rr CΛ DJ ω co d σ co DJ Hi rt s: CL Φ S φ N ω tr Φ Ω <j φ O P- Φ Φ tr Φ Φ DJ o Φ rt P- d Ω φ a P- flj: tr O: Φ Φ Φ hj P- ad Φ Φ ^ - ^• tr o

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Weitgangses and pressure relief the membrane 10 springs back from a tensioned state in the starting position. This ensures that there is no adhesion of the membrane 10 to the end face 24 of the secondary form element 23 and no jamming between the latter and the branch wall 6. However, this variant is only useful in the case of secondary form elements 23, which do not involve special contouring of the end face 24. Furthermore, the support plate 17 can be omitted in a component-saving manner. For this purpose, the pressure medium can also be supplied to the membrane 10 in some other way. After the expansion has ended, the internal high pressure is first released and then the supporting pressure is released, so that the desired end position of the end face 24 can be maintained and no further forming takes place. The pressure ratio of the support pressure and the internal high pressure can also be such that the support pressure increases in the final phase of the expansion until it is almost equal to the internal high pressure in the end position of the end face 24. This causes the expansion to stop. Then both pressures have to be reduced to the same extent at the same time, so that further forming does not take place.

This fact can be brought about in that the device includes a bypass line which connects the pressure line of the internal high pressure to the pressure line of the support pressure. For this purpose, a controllable valve is arranged in the bypass line, which keeps the bypass line closed during the expansion and opens the bypass line after the end position 24 of the end face element 23 has been reached. In this case, pressure equalization is created in a relatively simple manner, which enables the secondary form element 23 to be kept in shape. The pressure control described can be used in all device variants within the scope of the invention in the last phase of the expansion and then takes the place of the other pressure controls described.

Claims

claims 1. A method for producing secondary shaped elements on a circumferentially closed hollow profile, wherein a hollow profile blank is expanded by means of a fluidic internal high pressure into a branch originating from an engraving of the internal high pressure forming tool to form the secondary molded element, characterized in that the secondary molded element (23) which is formed by means of a diaphragm (10) acted upon by an external pressure is supported against the widening direction during the expansion, such that the diaphragm (10) resiliently withdraws as the secondary mold element (23) progresses until the final shape is reached. 2. The method according to claim 1, so that the supporting of the secondary form element (23) takes place with the progressive expansion of the increasing support pressure. 3.Device for producing secondary form elements on a circumferentially closed hollow profile, with an internal high-pressure forming tool, in the engraving of which a hollow profile blank can be inserted, a branch branching off radially from the engraving, into which the hollow profile blank can be expanded by means of a fluidic internal high pressure to form the secondary shaped element . that the device includes a membrane (10) and a pressure generator, by means of which the membrane (10) can be pressurized via a pressure medium, such that the membrane (10) is supported against the expansion direction during processing on the secondary mold element (23) that is being formed abuts, the membrane (10) elastically receding as the secondary mold element (23) progresses until the final shape is reached, and that the membrane (10) spans the branch (4) outside the longitudinal extent of the engraving (2) on the tool (1 ) is attached. 4. The device according to claim 3, so that the membrane (10) is fastened in an annular recess within the branch (4). 5. The device according to claim 3, so that the membrane (10) is attached to the rear (12) of the engraving-forming tool (1) at the end (9) of the branch (4). 6. Device according to one of claims 3 to 5, characterized in that the device contains a support plate (17) which the branch (4) at the location of the end position of the end face (24) of the secondary form element (23) on the rear side of the membrane (10) covers. 7. The device as claimed in claim 6, so that the support plate (17) is spaced from the membrane (10) which is unloaded with respect to a support and / or high internal pressure. 8. Device according to one of claims 6 or 7, characterized in that a pressure channel (18) runs in the support plate (17), which is connected on the one hand to the pressure generator and on the other hand opens out on the side of the membrane (10). 9. Device according to one of claims 3 to 8, so that the end position of the end face (24) of the secondary form element (23) is spaced from the pressure-relieved position of the membrane (10). 10. Device according to one of claims 3 to 9, that the pressure medium transmitting the support pressure is liquid or gaseous. 11. The device according to any one of claims 3 to 10, that the membrane (10) consists of a low-friction material or is provided with a low-friction coating. 12. Device according to one of claims 3 to 11, characterized in that the device includes a bypass line which connects the pressure line of the internal high pressure with the pressure line of the support pressure and contains a controllable valve which keeps the bypass line closed during expansion and after reaching the end position the end face (24) of the secondary form element (23) opens the bypass line.