Method and device for stretching and forming a foil blank and product produced herewith

Abstract

The invention relates to a method and a device for stretching and forming a foil blank as well as to a product, which is produced by means of this method.

Description

The invention relates to a method and a device for stretching and forming a foil blank as well as to a product produced herewith.

According to the state of the art, foil blanks are stretched biaxially prior to the deforming, for vacuum forming of bathtubs or inner containers of refrigerators, e.g.. Through this, the foil thickness can already be designed to be thinner or thicker in certain areas prior to the deformation.

In the case of the production of inner parts for vehicles, such as instrument panels or door side panels, the stretching degree of the surface structure can additionally be influenced.

Such devices and methods are known from EP 1 140 470 B1, U.S. Pat. No. 3,635,640, U.S. Pat. No. 3,579,718, JP 60049921 and JP 63197626, for example.

All of these inventions have in common to pre-stretch the foil blank prior to the deformation. The fact that a defined sliding along of the foil is not made possible during the forming process is a disadvantage of these described methods and devices.

Such a sliding along is realized in U.S. Pat No. 5,271,352 by means of a second clamping frame 59, which is controlled via spring elements 54. Contrary to this state of the art, it is the object of the instant invention to improve the known devices and methods.

According to a first aspect of the invention, this object is solved by means of a method for stretching and forming a foil blank, whereby a foil blank is elongated in one direction and the foil slides along in one direction during the deformation. A stretching of the foil blank in more than one direction is also possible. Likewise, the foil can slide along in more than one direction. In particular, the stretching can be carried out by means of a method or a device, respectively, as it is described in DE 69909835 T2. Stretching is to be understood thereby as the elongating or expanding, respectively, of the foil blank. Preferably, this takes place such that the form of the foil blank is not distorted. In the case of a particularly suitable embodiment, the stretching takes place consistently in a plurality of directions. Sliding along is to be understood such that the foil can follow the tension, which is created by means of the forming process. A further elongation of the foil caused by the forming process can be avoided completely or partly through this.

The sliding along can be controlled in the case of a particularly suitable embodiment. In certain applications, however, it is already sufficient when the sliding along of the foil is not controlled, but is created independently via the tension of the foil in response to the deformation.

Advantageously, the tension force can also be regulated. The tension force is to be understood as the force, by means of which the foil blank is stretched. This force can be adapted to the used foil blank or to the desired process parameters, respectively, by means of a regulation.

The tension speed can also be regulated. The tension speed is to be understood as the speed, by means of which the foil blank is elongated. Here, a regulation also provides for an adaptation to the used foil blank as well as for a regulation of the process parameters and thus for an impact on the end product.

It is further advantageous when a forming aid is used during the deformation and/or in a downstream step. While the deformation is carried out from the inside by means of a forming tool, onto which the foil is drawn, forming aids can act from the outside, so as to support the forming process. The foil can thus be pressed against the forming tool in areas, in which the foil does not come to rest on the forming tool when the foil is drawn onto the forming tool.

A second aspect of the invention comprises a device for stretching and forming a foil blank, in particular for carrying out a method according to the invention comprising a clamping frame and a holding element, wherein the holding element is slidingly supported in the foil plane, so that it slides along in response to the forming.

In a preferred embodiment, the clamping frame is embodied with at least one longitudinal and at least one cross beam. In particular, the clamping frame can be embodied as described in DE 69909835 T2. The foil plane is to be understood as the plane, in which the foil is held by means of the clamping frame. On the one hand, the heat expansion of the foil is compensated by means of such a device. On the other hand, the foil can be stretched in at least one axis and the foil can slide along during the forming process.

It is advantageous when the clamping frame can be displaced in x and/or y and/or z direction. The clamping frame can thus be moved completely freely in all spatial directions, for example relative to the forming tool.

It is further advantageous when the clamping frame is arranged so as to be pivotable out of the foil transport plane about a center of gravity. The foil transport plane is to be understood as the plane, in which the foil is transported into the clamping frame. The angle between forming tool and clamping frame can be changed through this. This provides for an improved contour-dependent sliding along of the foil at the surface, which is to be formed. This is advantageous in particular in the case of complex formed parts.

Advantageously, the clamping frame is supported so as to be rotatable about a fixed point. A clockwise rotation as well as a counter-clockwise rotation about any angles is thereby possible. The foil blank can thereby be optimally oriented towards the contour, which is to be formed. This rotation can take place in a controlled manner during the forming process.

According to a further embodiment of the invention, the clamping frame encompasses a clamping device, which can be moved in x and/or y and/or z direction. It can be arranged, in particular, on the clamping frame.

The clamping device can preferably be supported so as to be rotatable about a fixed point. It can be brought into contact with the foil blank by means of displacement as well as by means of rotation.

Finally, it is further advantageous when the device encompasses a forming aid. A forming aid is to be understood thereby as every device, which aids in better placing the foil blank onto the contours of the forming tool.

A last aspect of the invention comprises a product, which is produced by means of a method according to the invention and/or a device according to the invention.

The invention will be defined below in more detail by means of exemplary embodiments with reference to the drawings.

FIG. 1 shows a device according to the invention prior to the forming,

FIG. 2 shows a device according to the invention during or after the forming, respectively,

FIG. 3 shows a device according to the invention comprising an adjustable clamping frame,

FIG. 4 shows a device according to the invention comprising a clamping frame having clamping elements,

FIG. 5 shows a device according to the invention comprising a clamping frame, which can be adjusted in foil plane,

FIG. 6 shows a device according to the invention comprising an additional forming aid,

FIG. 7 shows a clamping frame and

FIG. 8 shows a clamping frame comprising attached clamping elements.

FIG. 1 shows a device 1 according to the invention for stretching and forming a foil blank 2 before the second step of the method according to the invention, that is, the forming, is carried out. The foil 2 is clamped in the clamping frame 3. Said clamping frame consists of an upper clamping frame 4 and a lower clamping frame 5. The forming tool 6 is not yet in contact with the foil 2.

As is illustrated in FIG. 2, in a next step, the forming tool 6 is moved into the foil 2, which is held by the clamping frame 3. Through this, the foil adapts to the contours of the forming tool. According to the invention, it is hereby possible for the foil to slide along in at least one direction. When a sliding along is not possible, the foil is further expanded by the forming. This effect is reduced or completely avoided by means of a partial or complete sliding along of the foil.

As is illustrated in FIG. 3, the clamping frame 3 can be adjusted in x, y and z direction. On the one side, the clamping frame was moved closer to the forming tool, while the distance on the other side of the forming tool has increased through this.

In addition, the clamping frame 3 can encompass clamping elements 7, 8, as is illustrated in FIG. 4. These are fastened on the upper clamping frame 4 and additionally hold the foil 2.

Finally, as is illustrated in FIG. 5, the clamping frame can be displaced in the foil plane. The clamping frame 3 is located considerably lower on the one side of the forming tool than on the other side.

To provide for a better adaptation of the foil blank 2 to the contour of the forming tool 6, a forming aid 9 can additionally be used, as is illustrated in FIG. 8.

FIG. 7 shows a clamping frame 11 in top view. It consists of two L-shaped frame parts 12, 13, which are in each case assembled on a longitudinal and a cross beam. They can be displaced with respect to one another, whereby the surface between the clamping frame parts 12, 14 increases. In addition, the clamping frame is rotatable.

A clamping frame 21 is illustrated in FIG. 8 in top view. The clamping frame parts 22 and 23 are extended completely, whereby the foil is stretched to a maximum. Clamping elements 24, 25, 26, 27 and 28 are attached onto this clamping frame. They are arranged so as to be adjustable as well as rotatable and can thus be brought into contact with a foil, which is clamped into the clamping frame, during the forming.

Claims

1. A method for stretching and forming a foil blank, wherein a foil blank is elongated in at least one direction and slides along in at least one direction during the deformation.

2. The method according to claim 1, wherein the sliding along is controlled.

3. The method according to claim 1, wherein the clamping force is regulated.

4. The method according to claim 1, wherein the clamping speed is regulated.

5. The method according to claim 1, wherein a forming aid is used during the deformation and/or in a downstream step.

6. A device for stretching and forming a foil blank, for carrying out a method according to claim 1, comprising a clamping frame and a holding element, wherein the holding element is slidingly supported in the foil plane, so that it slides along in response to the forming.

7. The device according to claim 6, wherein the clamping frame can be displaced in x and/or y and/or z direction.

8. The device according to claim 6, wherein the clamping frame is arranged so as to be pivotable out of the foil transport plane about a center of gravity.

9. The device according to claim 6, wherein the clamping frame is supported so as to be rotatable about a fixed point.

10. The device according to claim 6, wherein the clamping frame encompasses a clamping device.

11. The device according to claim 6, wherein the clamping device can be moved in x and/or y and/or z direction.

12. The device according to claim 6, wherein the clamping device is supported so as to be rotatable about a fixed point.

13. The device according to claim 6, wherein the device encompasses a forming aid.

14. A product, which is produced by means of a method according to claim 1 and/or by means of a device for stretching and forming a foil blank.