Method of interlocking overlapping sheet material

Abstract

To fasten together two or more overlying sheets of metal or other material having plasticity or deformable properties by partially piercing and deforming minor areas of the sheets, a pierce-and-forming punch is used in cooperation with a double-acting press having two separately actuatable rams. For displacing the minor areas of the overlying sheets, one of the rams carries a hollow cylindrical pierce-and-forming die, the die cavity of which is vertically aligned with, and cooperates with, a pierce-and-forming punch supported in the base. The other of the rams carries a flattening punch which is slidably movable within the central bore of the hollow cylindrical die. Fine adjustment means are included so that the position of the die may be adjusted for different thickness of sheets to be fastened, and also for wear on the die and/or punch. Phase adjustment means are included which permits the angular relationship between the flattening punch and the die to be adjusted such that the downwardly-moving flattening punch engages the upper displaced minor area or areas just after the lower displaced minor area is uncovered by the upwardly-moving cylindrical die, thereby to spread the lower displaced minor area while the upper minor area or areas are still constrained. To reduce the extent to which the displaced minor areas project above the major areas of the sheets, the edge portions of the major areas adjacent the piercings or cuts are displaced downwardly.

Dependencies are inferred from the claim text.