Tobacco smoke filter and method and apparatus for making same

摘要

A method and means for making an improved tobacco smoke filter is characterized by the production of longitudinally continuous grooves running from end-to-end in the peripheral surface of a smoke-impervious filter plug wrap with the grooves having a transverse cross-sectional area that varies as a function of longitudinal displacement. Smoke-impervious tipping surrounds the plug wrap to seal the grooves except for small ventilation holes in the tipping which permit communication between the grooves and the ambient air. In the preferred embodiment, the grooves are restricted toward the mouth end of the filter and the degree of restriction determines the direction of air and smoke flow in the grooves. The grooves are each preferably formed as two longitudinal sections of different cross-section.