Abstract: Disclosed is a mechanism, associated with a thermoplastic bag making machine, for preparing a strip of thermoplastic to produce bags having the upper edges of the bag mouth formed in a sinusodial shape such that the peak of such shape is substantially equi-distant relative to the side edges of the bag. While the disclosed bag machine is of the type that advances the web strip incrementally, shaping of the web strip in the sinusodial shape occurs while a portion of the web strip is advanced at substantially constant velocity. A mechanism is provided for maintaining constant tension in the web despite the constant and intermittent feeding of the web.

Abstract: The disclosed cutting method and apparatus produces a pattern cut in web material by providing a generally conically-shaped rotatable anvil and oppositely disposed knife edge shaped to produce the pattern cut. The axes of symmetry containing the apex of the cone is positioned at an acute angle to the axes about which the cone is rotated. With the web positioned over the knife, the knife is brought into pressure engagement with the anvil thereby piercing the web substantially at a point. Rotation of the anvil effects progressive cutting as the anvil surface traces the cutting edge of the knife.