Abstract: Apparatus for slitting or cutting material comprises a driving roller 10 and a driven roller 12. Each roller 10 or 12 has on its periphery a plurality of ribs at a predetermined pitch and helix angle. The pitch of the ribs 18 on the driving roller 10 is smaller than the pitch of the ribs 30 on the driven roller 12, and the helix angle of the ribs 18 on the driving roller 10 is of opposite direction to, and of smaller magnitude than, the helix angle of the ribs 30 on the driven roller 12. The ribs 18, 30 cooperate to cut with a shearing action a web 16 of sheet material fed into the nip between the rollers 10, 12.

Abstract: This invention is directed to a method of making an expandable metal product for use in extinguishing fires and controlling explosions by means of revolving cylinders equipped with slitting knives. The method steps produce the product from a continuous sheet of metal foil by making slits of a configuration extending to the margins. The method also produces a floatable, ellipsoid for nestling in fuel containers.