Field of the invention

This invention relates to a press for the shaping of thin sheets to thin products, comprising two cooperating tools and means for pressing one of the tools against the other for the simultaneous shaping of more than one thin product between the tools. The invention relates also to a method for the simultaneous shaping and press-hardening of more than one product in a press.

Background of the invention

Press-hardened beams, for example bumper beams and B-pillars for the automotive industry are usually manufactured in presses of this kind. The tools are cooled and the hot-formed products are hardened with the tools as a fixture after the shaping. Simultaneous shaping in ordinary hot forming and cold forming is also common.

Object of the invention

It is an object of the invention to achieve a uniform quality when several blanks are simultaneously pressed to products.

Brief description of the invention

One of the tools has, for each thin product, an individual forming element which directly or indirectly rests on a pre-stressed spring element for defining the maximum press force for the thin product when the tools are forced together. The invention is defined by the claims.

Brief description of the drawings

Figure 1 shows in cross section a press in its open position.

Figure 2 shows parts of the press in figure 1 in its closed position.

Figure 3 shows a cross section of a modified portion of figure 1 in closed position.

Figure 4 corresponds to figure 3, but showing the press in its closed position.

Figure 5 shows a pre-stressed spring element.

Description of the illustrated example of the invention

Figures 1 and 2 show a press having a frame 11 with a fixed tool and a movable tool 13.The upper tool 13 is the movable one and it is controlled by a slide 14, which is hydraulically driven. The lower tool has a number of cavities 15,16,17,18, for example four as shown, and in the cavities are individual tools, shaping elements 19,20,21 ,22, slidable and they rest on a number of pre-stressed elastic elements 23. Such a pre-stressed element is shown as figure 5 and may, as shown, consist of a stack of spring washers 24 compressed between end plates 25. The end plates are held together by a plurality of screws 26. The pre-stress causes the spring force not to vary so much with the compression, thus equalizing tolerances. Figure 1 shows the press open, i.e. the upper tool 13 is lifted and four flat thin blanks 24 are inserted to rest on the four individual tools 19-22 of the lower tool. Figure 2 shows the press in its closed position, that is, the upper tool 13, the stamp, has punched down and fully formed the blanks 24 between the upper tool 13 and the individual tools 19-22 of the lower tool 12 just before or when the upper tool bottomed on the lower one by means of cooperating bottoming elements 27,28. The pre-stressed elements 23 provide a defined reaction force on the individual tools 19-22 and reduce the normal variations caused by thickness variations of the blanks, manufacturing deviations and accuracy of the press, elastic deformation of the tools and the tool mounting. The movement of the upper tool 13 can be stopped in other ways than by the cooperating bottom elements, for example by limiting of the stroke of the slide 14.

A finished product 30 is shown and only in cross section in figure 2. It is shown as the example hat beams. The tools are provided in the common way with cooling channels through which cooling water flows. The hot blanks of hardenable steel are transported from a furnace to the press and after the pressing, they will be kept in the closed press until they have hardened.

Figure 3 shows a modified embodiment which controls the power distribution between several surfaces or all surfaces of the finished product, in this case between the flanges 41 , (the side flanges) and the top 40 of the hat beam 30. The movable tool 13 has a movable shaping element 42 which is backed by a distance element 43 and a pre-stressed spring element 44. Alternatively, the parts 42,43,44 may be located inside the fixed tool 12. For products of more complicated shape, there may be parts 42,43,44 both in the fixed tool 12 and in the individual tool 19. Besides good tolerances on all surfaces, good contact with both tools is obtained on all surfaces during the hardening, which ensures uniform hardening.

The invention is not limited to the example press hardening, but can be utilized for other pressing, for example hot forming without hardening and cold forming. The invention may be used for pressing of other metals than steel and for other materials.