Patent ID: 8424540

Claim:
A smoking article comprising: a tobacco rod adapted to produce mainstream smoke; a filter attached to the tobacco rod by tipping paper, the filter having an upstream end adjacent the tobacco rod, a mouthpiece filter plug of low filtration efficiency cellulose acetate at a downstream end thereof, a restrictor defining at least one flow passage therethrough, an empty cavity located between the mouthpiece filter plug and the restrictor, a ventilation zone extending through the tipping paper and communicating with the cavity, and a valve which moves from a first position at which mainstream smoke freely passes through the at least on orifice in the restrictor to a second position at which the valve partially or fully closes the at least one orifice in the restrictor, the valve being effective to slow or stop flow of mainstream smoke through the restrictor at elevated draw pressures and allow free flow of mainstream smoke through the restrictor at lower draw pressures, wherein the valve comprises a first flap located upstream of an inlet of the at least one orifice in the restrictor, the first flap being movable at high draw pressure so as to partially or fully close the inlet of the at least one orifice in the restrictor, the valve including a second flap downstream of an outlet of the at least one orifice in the restrictor, the second flap being movable from a position closing the outlet to a position opening the outlet during a puff on the smoking article.