METHOD FOR THE MULTI-AXIS SHAPING OF A HOLLOW WORKPIECE AND SUPPORTING CORE FOR USE IN THE METHOD

Abstract

A method is provided for the multi-axis shaping of a hollow workpiece, such as a polygonal hollow workpiece. The hollow space of the workpiece has introduced into it a supporting core, which has a central body with at least two differently oriented, inter-communicating cylinder bores and also has pistons, which are accommodated in the cylinder bores and can be subjected to the action of pressure fluid through a fluid connection of the central body. Prior to the radial shaping of the workpiece in a radial press, in a process in which at least two radial dimensions are to be decreased, the supporting core is expanded radially, with the pistons being extended out of the cylinder bores by the pistons being subjected to the action of pressure fluid.

Claims

1. A method for multiaxial forming of a hollow workpiece (W), in particular a square tube (8), a hexagonal tube or another polygonal hollow workpiece (W), comprising: a) providing the hollow workpiece (W) to be formed; b) inserting a support core (10) into the cavity (H) of the workpiece (W), wherein the support core (10) comprises a central body (11) with differently oriented cylinder bores (13) communicating with one another and with pistons (17) which are accommodated therein and can be pressurized by a pressurized fluid through a fluid connection (21) of the central body (11), the differently oriented cylinder bores (13) being offset from one another in the axial direction and cylinder bores of different orientation not being arranged in a common plane; c) radial expanding of the support core (10) while extending the pistons (17) out of the cylinder bores (13) by pressurizing the pistons (17) with pressurized fluid; d) inserting the workpiece (W) to be formed into a radial press; e) radial forming of the workpiece (W) in the radial press with reduction of at least two radial dimensions; f) opening the radial press; g) removing the formed workpiece (W) from the radial press; and h) removing the support core (10) from the cavity (H) of the workpiece (W).

2. The method of claim 1, wherein in step e) the pistons (17) move into the cylinder bores (13) in a controlled manner.

3. The method of claim 2, wherein in step e) the pressurized liquid is discharged in a controlled manner through the fluid connection (21) of the central body (11) while maintaining a counterpressure.

4. The support core for use in the method of claim 1 comprising a central body (11) with differently oriented, mutually communicating cylinder bores (13) and pistons (17) which are accommodated therein and can be pressurized by pressurized fluid through a fluid connection (21) of the central body (11), wherein the differently oriented cylinder bores (13) are offset from one another in the axial direction and cylinder bores of different orientation are not arranged in a common plane.

5. The support core of claim 4, wherein the cylinder bores (13) are realized as through bores (14), in each of which two pistons (17) travelling in opposite directions are accommodated.

6. The support core of claim 4, wherein the cylinder bores (13) communicate with each other via an axial channel (15).

7. The support core of claim 4, wherein at least two pairs of cylinder bores (13) oriented parallel to one another are provided, offset axially relative to one another, i.e. in the axial direction of the support core (10).

8. The support core of claim 7, wherein the pistons (17) traveling in the same direction are coupled to one another via pressure plates (18).

9. The support core of claim 8, wherein the pressure plates (18) each have a flat workpiece support surface(S).

10. The support core of claim 8, wherein the pressure plates (18) each have an uneven, in particular a one- or two-dimensionally domed or curved workpiece support surface(S).

Description

BRIEF DESCRIPTION OF THE DRAWING

[0021] With regard to further preferred design features of the support core, reference is madein order to avoid repetitionto the above explanations and to the following explanation of a preferred embodiment of the present invention, which is illustrated in the drawing.

[0022] FIG. 1 shows a partially schematic vertical section, perpendicular to the press axis, through the relevant area of a radial press designed as a yoke press with inserted workpiece-support core assembly, in a fully open configuration before the start of radial pressing,

[0023] FIG. 2 shows the radial press with inserted workpiece-support core assembly as shown in FIG. 1 in fully closed configuration after completion of radial pressing,

[0024] FIG. 3 shows a perspective view in greater detail of the support core used in the embodiment shown in FIGS. 1 and 2 with the piston and pressure plates fully retracted, and

[0025] FIG. 4 shows a combined representation comprising a partial longitudinal section (top) and a partial side view (bottom) of the support core according to FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The radial press illustrated partially schematically in the drawing is based on the sufficiently known state of the art in terms of its design, its construction and mode of operation as well as its structural features (see, for example, DE 10 2011 015 706 A1,2 and the product range of Uniflex-Hydraulik GmbH, DE-61184 Karben). It comprises a base (not shown), a stationary lower yoke 1 and an upper yoke 2, which can be moved vertically up and down relative to the lower yoke 1 by means of a drive unit-only indicated as the tie rods 3 (see double arrow B). In a known manner, the radial press has eight base jaws 4 arranged evenly and concentrically around a pressing axis X, which, as a result of the relative movement of the upper yoke 2 and the lower yoke 1 with respect to each other, can be moved synchronouslywhen the upper yoke 2 is loweredradially in the direction of the pressing axis X andwhen the upper yoke 2 is raisedradially away from the pressing axis X. Return springs 5 act between adjacent base jaws 4. The base jaws 4 each have a cylindrically curved contact surface 6 on the inside for replaceable pressing jaws 7.

[0027] Since the radial press is configured for radial pressing of a polygonal workpiece W, for example a square tube 8 with a square cross-section, the pressing surfaces 9 provided radially on the inside of the pressing jaws 7 are configured specifically; four of the pressing jaws 7 have flat pressing surfaces 9.1, while the pressing surfaces 9.2 of the other four pressing jaws 7 are grooved at an angle. The design of the pressing surfaces 9.1 and 9.2 is coordinated in such a way that they define a square cross-section when the radial press is completely closed (see FIG. 2).

[0028] Before the square tube 8 is subjected to radial pressing in the appropriately prepared radial press (see FIGS. 1 and 2), a support core 10 (see also FIGS. 3 and 4) is inserted into the square tube 8, i.e. into its cavity (hollow space) H. The support core comprises an essentially prismatic central body 11 with a central bore 12 extending along the axis A and a total of sixteen cylinder bores 13. These are distributed over two mutually perpendicular planes, which intersect in the axis A. In each case, two cylinder bores 13 are diametrically opposite each other and are aligned with each other in that they are each part of a through bore 14 extending transversely through the central body 11. The total of eight through bores 14 are thus oriented alternately offset to one another in the axial direction, i.e. in the direction of axis A. The central bore 12 forms a channel 15 via which the eight through bores 14 (and thus the sixteen cylinder bores 13) communicate with each other fluidically.

[0029] In each cylinder bore 13, sealed by means of an inserted seal 16, a piston 17guided for displacement along the respective cylinder axis Y, which is perpendicular to the axis Ais accommodated. In each case, four pistons 17, which functionally act in the same direction, are mechanically coupled to each other in parallel via a (common) pressure plate 18, which is connected to the four associated pistons 17 by means of screws 19.

[0030] While the central bore 12 at one end of the central body 11 of the support core 10 is sealed tightly by means of a plug 20 screwed into it, a fluid connection 21 is provided at the opposite end of the central body 11. The channel 15 can be pressurized with pressurized fluid via this connection, and the sixteen cylinder bores 13 can in turn be pressurized simultaneously and with identical pressure via this channel 15. This pressurized fluid application causes the pistons 17 to extend out of the central body 11 (arrow C), causing the pressure plates 18 to move away from the axis A. During this extension of the pistons 17, the two O-rings 24, which serve as anti-loss devices 22 and are placed around pins 23 arranged on the end faces of the pressure plates 18 and extending parallel to axis A, are stretched accordingly. If the O-rings 24 are replaced by veritable, correspondingly strong annular springs, the pistons 17 are extended against an effective restoring force; in this case, the annular springs would each be part of a restoring device provided at the end of the support core 10.

[0031] Before radial pressing of the workpiece W inserted into the radial press begins, the four pressure plates 18 are brought into contact with the inside of the hollow polygonal workpiece W to be formed by extending the pistons 17 and applying pressure to them as described; the workpiece support surfaces S are then in contact with the associated inner surfaces of the square tube 8. The supply of pressurized fluid into the support core 10 via its fluid connection 21 is then switched to holding the pressurized fluid via a counterpressure valve. As a result, during the radial pressing of the workpiece W, during which the pressure plates 18 are displaced in the direction of the axis A, the pistons 17 move into the cylinder bores 13 in a controlled manner so that the pressurized fluid is drained in a controlled manner through the fluid connection 21 of the central body 11, i.e. flows back into the tank, while maintaining a counterpressure. The back pressure is adjustable so that it can be adapted to the respective workpiece W.

[0032] After radial pressing is complete, the counterpressure valve (or a bypass for this purpose) is opened so that the pressure in the pressurized fluid is released and the pistons 17under the action of the two restoring devices 22can retract to their maximum retracted position. By retracting the pressure plates 18 accordingly, provided they have not already been displaced into their respective end position during radial pressing of the workpiece W, the support core 10 assumes its configuration with minimum cross-section and can be removed from the formed workpiece W before or after the radial press is opened and, if necessary, the formed workpiece W is removed from it.

[0033] In view of the above description of a support core 10 configured for the internal support of a square tube, a person skilled in the art can easily design a support core for the internal support of a hexagonal tube or another hollow polygonal workpiece, for example, by means of a corresponding transfer.