| 摘要 |
A tobacco smoke filter having at least one directly ventilated cavity which provides for the formation, over a region of the filter extending inwardly of its peripheral region, of a mixture of at least the major proportion of the smoke and at least a major proportion of the ventilating air entering the said cavity or cavities. The extensive and uniform mixing of smoke and ventilation air gives a satisfying smoke with a low tar count and high nicotine/tar ratio, and can be obtained with the invention due to appropriate shaping of the cavity, or asymmetric positioning of the air ventilating vents, or by means of a flow-disturbing insert mounted in the filter, or a combination of two or more of these factors. Preferably a major part of the smoke is constrained to enter the cavity at an upstream peripheral extremity thereof and air vents are also concentrated at this extremity.
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