Method and apparatus for ultrasonically cutting sheet material

Claim 1

In an apparatus for automatically cutting limp sheet material including support means defining a penetrable support surface for holding the limp sheet material spread in a multi-ply layup, a cutting head mounted for movement relative to the penetrable support surface and the sheet material thereon with an elongated cutting blade, and reciprocation drive means for reciprocating the cutting blade along an axis extending generally perpendicular to the penetrable support surface, the cutting blade having a sharp leading cutting edge that is advanced through the limp sheet material along a cutting path in cutting engagement with the material during a cutting operation, and controlled motor means connected with the support means and the cutting head for moving the cutting blade and sheet material relative to one another along a predefined cutting path, the improvement comprising: a drive linkage in the reciprocation drive means including ultrasonic transducer means for superimposing on the reciprocating motions of the cutting blade ultrasonic vibration, the ultrasonic transducer means being cooperative with the cutting blade to establish ultrasonic vibrations in the form of a standing wave with multiple nodes, the wave extending longitudinally along the blade in the direction of the axis of reciprocation, and the reciprocating drive means includes means for reciprocating the cutting blade with a stroke substantially greater than the ultrasonic vibrations to move the nodes of the ultrasonic vibrations at the cutting edge of the blade between different plies of the layup of sheet material.