TOOL FOR FORMING COATED SHEET-METAL BLANKS

Abstract

The disclosure relates to a tool with a material layer on one or both sides, said tool having a cutting bell rigidly coupled to an upper forming punch and a drawing cushion coupled to a hold-down device, the upper forming punch and a lower forming punch being movable relative to one another to close the tool, and a first gap present between the cutting bell and the hold-down device when the tool is closed, and an end stop formed by the lower forming punch for a lower pressure piece that can be moved relative to it, that the sheet metal blank can be clamped between the upper and the lower pressure piece, and that during a relative movement between the lower forming punch and the lower pressure piece, the upper and the lower pressure piece remain in their position relative to one another clamping a sheet metal blank.

Claims

1. A tool for forming sheet metal blanks provided with a material layer on one or both sides, said tool: comprising a cutting bell which is rigidly coupled to an upper forming punch and a drawing cushion which is coupled to a hold-down device, the upper forming punch and a lower forming punch being movable relative to one another to close the tool; a first gap being present between the cutting bell and the hold-down device when the tool is closed; and an end stop formed by the lower forming punch for a lower pressure piece that can be moved relative to it, that the sheet metal blank can be clamped between the upper forming punch and the lower pressure piece, and that during a relative movement between the lower forming punch and the lower pressure piece, the upper forming punch and the lower pressure piece remain in their position relative to one another clamping the sheet metal blank.

2. The tool according to claim 1, wherein the lower forming punch comprises a pocket-shaped recess in which the lower pressure piece is accommodated.

3. The tool according to claim 1, wherein the sheet metal blank can be clamped between the upper forming punch and the lower pressure piece in such a way that a second gap S.sub.2 is formed between the sheet metal blank and the cutting bell.

4. The tool according to claim 2, wherein the width of the first gap S is the sum of the thickness D of the sheet metal blank and the width of the second gap S.sub.2.

5. The tool according to claim 4, wherein the width is up to 200% greater than the thickness.

6. The tool according to claim 4, wherein the width is 0.1 mm greater than the thickness.

7. The tool according to claim 1, wherein the drawing cushion is rigidly coupled to the hold-down device and the lower pressure piece.

8. The tool according to claim 1, wherein the hold-down device is connected to a drawing cushion via at least one drawing pin.

9. The tool according to claim 1, wherein the lower pressure piece is connected to the drawing cushion via at least one drawing pin.

10. The tool according to claim 1, further comprising an ejector is provided for ejecting the formed sheet.

11. The tool according to claim 10, wherein the ejector and the drawing cushion are subjected to a permanent force.

12. The tool according to claim 4, wherein the width (W) is 10-50% greater than the thickness.

Description

DETAILED DESCRIPTION OF DRAWINGS

[0021] In the following, an embodiment example of the invention will be explained with the aid of accompanying figures. They show:

[0022] FIG. 1a shows a simplified illustration of a longitudinal cut of a first deep-drawing tool,

[0023] FIG. 1b shows a simplified illustration of a longitudinal cut of a second deep-drawing tool,

[0024] FIG. 2a shows a simplified illustration of a longitudinal cut of a deep-drawing tool,

[0025] FIG. 2b shows an enlarged view of the detail A from FIG. 2a,

[0026] FIG. 3a shows a simplified illustration of a longitudinal cut of a deep-drawing tool,

[0027] FIG. 3b shows an enlarged view of the detail B from FIG. 3a,

[0028] FIG. 4a shows a simplified illustration of a longitudinal cut of a deep-drawing tool,

[0029] FIG. 4b shows an enlarged view of the detail C from FIG. 4a,

[0030] FIG. 5a shows a simplified illustration of a longitudinal cut of a deep-drawing tool,

[0031] FIG. 5b shows an enlarged view of the detail D from FIG. 5a.

DETAILED DESCRIPTION

[0032] As shown in FIG. 1a, the deep-drawing tool is essentially composed of the cutting bell 1, the ejector 2, the upper forming punch 3 with the inserted upper pressure piece 4, the cutting ring 5, the hold-down device 6, the lower forming punch 9 with the inserted lower pressure piece 10 and the drawing cushion 12. The hold-down device 6 and the lower pressure piece 10 are connected to the drawing cushion 12 via drawing pins 7, 11. A force P2 acts on the drawing cushion 12, which can be applied pneumatically or hydraulically, e.g. by compression springs. The upper pressure piece 4 is provided on an optional basis, as demonstrated in FIG. 1b.

[0033] The sheet 20 to be deep-drawn is between the upper forming punch 3 and the lower forming punch 9. The sheet 20 is painted or coated with a material layer (e.g. laminated). The coating material can be chosen at will. FIGS. 2a and 2b depict the initial position of the tool before forming. FIGS. 3a and 3b show the start of the deep drawing. The ejector 2 is in contact with the sheet 20. The upper pressure piece 4 rests on the upper side and the lower pressure piece 10, which is inserted into a pocket-shaped recess 9.1 in the lower forming punch 9, rests on the lower side of the sheet 20. The dimensions of the pressure pieces 4, 10 are selected so that a first gap S forms in this position between the cutting bell 1 and the hold-down device 6. The width W of the gap S, which is obtained from the sum of the thickness D of the sheet metal blank 20 and the set gap D1, can be adjusted for the respective application by altering the gap S1.

[0034] FIGS. 4a and 4b show the start of the deep drawing process. The upper forming punch 3 and the lower forming punch 9 continue to move towards each other without the distance between the cutting bell 1 and the hold-down device 6 changing, as the upper pressure piece 4 and the lower pressure piece 10 remain in their position relative to each other. The force that occurs when the tool is closed and that is generated by the upper forming punch 3 and the lower forming punch 9 is transferred from the lower pressure piece 10 via the drawing pins 11 to the drawing cushion 12, which is loaded with the force P2. The lower pressure piece 10 moves in the pocket-shaped recess 9.1 relative to the lower forming punch 3 until it comes to rest in the base of the recess 9.1. The distance between the cutting bell 1 and the hold-down device 6 corresponds to the sum of the thickness D of the sheet metal blank 20 and the set second gap S.sub.2. As a result, the sheet 20 can move radially inwards in the annular space between the cutting bell 1 and the hold-down device 6 during deep drawing and is not clamped, thereby stopping any threads from forming at the outer edge of the sheet metal blank 20 during deep drawing.

[0035] FIGS. 5a and b show the final position of the tool. The sheet 20 is completely formed, the annular space between the cutting bell 1 and the hold-down device 6 is still the sum of the sheet thickness D and the set second gap S.sub.2. If the inner edge 1.1 of the cutting bell 1 is rounded, it makes it easier to slide the sheet 20 along and minimizes frictional forces acting on the sheet 20.

[0036] The forces acting on the drawing cushion 12 and the ejector 2 can be constant. These forces move the drawing cushion 12 and the ejector 2 in the direction of the sheet 20. When mechanical contact is made between the upper pressure piece 4 and the lower pressure piece 10, the sheet 20 is clamped and the force is transferred through the sheet. This results in a certain degree of automatic thickness compensation when using different types of sheet metal. The distance between the cutting bell 1 and the hold-down device 6 required to reduce fuzz adjusts accordingly to the thickness D of the sheet metal blank 20. No additional drive other than the tool or pressing movement itself is needed to create the gap S. As a result, the mechanism for creating the gap S is completely integrated into the tool and no separate attachments are required underneath, next to or outside of the tool.

[0037] The mechanism for generating the first gap S ensures a reliable force cut-off below a definable minimum distance between the cutting bell 1 and the hold-down device 6. This force cut-off restricts the clamping force for the sheet 20. The adjustable minimum gap S to the sheet can be maintained very precisely and almost instantaneously thanks to the mechanical end stop with thickness compensation. The tolerances of the resulting gap S are in the range of <0.1 mm.