Smoking article with improved flow restriction element

Abstract

A smoking article includes a rod of smokable material and a filter including a flow restriction element attached to the rod of smokable material. The flow restriction element includes a first upstream integral tubular portion, a second downstream integral tubular portion of substantially the same external diameter as the first tubular portion, and a third central integral tubular portion located between the first and second tubular portions. The third tubular portion is of reduced external diameter compared to the first and second tubular portions. A transverse barrier having at least one orifice therein is disposed between a first upstream cavity at least partially defined by an inner periphery of the first tubular portion and a second downstream cavity at least partially defined by an inner periphery of the second tubular portion. A ventilation zone in communication with the second cavity is also provided at a location along the filter.

1 . A smoking article comprising:
 a rod of smokable material;   a filter including a flow restriction element attached to the rod of smokable material, the flow restriction element including:
 a first upstream integral tubular portion; 
 a second downstream integral tubular portion of substantially the same external diameter as the first tubular portion; 
 a third central integral tubular portion located between the first and second tubular portions, the third tubular portion being of reduced external diameter compared to the first and second tubular portions; and 
 a transverse barrier having at least one orifice provided therein, the transverse barrier being disposed between a first upstream cavity at least partially defined by an inner periphery of the first tubular portion and a second downstream cavity at least partially defined by an inner periphery of the second tubular portion; and 
   a ventilation zone in communication with the second cavity at a location along the filter.   
     
     
         2 . The smoking article of  claim 1 , wherein the transverse barrier has a single substantially central orifice having a diameter ranging from about 0.4 mm to about 0.8 mm provided therein. 
     
     
         3 . The smoking article of  claim 1 , wherein the filter is attached to the rod of smokable material by a band of tipping paper and the ventilation zone includes at least one circumferential row of perforations provided through a portion of the tipping paper overlying the third tubular portion of the flow restriction element. 
     
     
         4 . The smoking article of  claim 3 , wherein the first cavity of the flow restriction element is at least partially defined by an inner periphery of the first and third tubular portions. 
     
     
         5 . The smoking article of  claim 4 , wherein one or more openings are provided in an upstream transverse end surface of the second tubular portion that form a communication path between the second cavity and the at least one circumferential row of perforations. 
     
     
         6 . The smoking article of  claim 3 , wherein the second cavity of the flow restriction element is at least partially defined by an inner periphery of the second and third tubular portions. 
     
     
         7 . The smoking article of  claim 6 , wherein one or more openings are provided in a circumferential surface of the third tubular portion that form a communication path between the second cavity and the at least one circumferential row of perforations. 
     
     
         8 . The smoking article of  claim 1 , wherein the filter further includes a first filter segment upstream of the flow restriction element and a second filter segment downstream of the flow restriction element. 
     
     
         9 . The smoking article of  claim 1 , wherein the wrapper has a basis weight ranging from about 35 g/m 2  to about 60 g/m 2 , a filler loading ranging from about 20 percent to about 50 percent by weight, a permeability ranging from about 2 Coresta units to about 18 Coresta units, and about 0.3 percent to about 5 percent by weight of a burn modifier. 
     
     
         10 . The smoking article of  claim 1 , wherein the smoking article has a ventilation level of at least about 50 percent, preferably of at least about 60 percent. 
     
     
         11 . The smoking article of  claim 1 , wherein the flow restriction element is at least about 10 mm in length, more preferably at least about 13 mm in length. 
     
     
         12 . The smoking article of  claim 1 , wherein the transverse barrier is concave relative to the direction of mainstream smoke drawn from the rod of smokable material through the filter. 
     
     
         13 . The smoking article of  claim 1 , wherein the smoking article has a carbon monoxide to tar ratio of less than or equal to 1. 
     
     
         14 . A flow restriction element for inclusion in a smoking article of  claim 1 , the flow restriction element including:
 a first integral tubular portion;   a second integral tubular portion of substantially the same external diameter as the first tubular portion;   a third central integral tubular portion located between the first and second tubular portions the third tubular portion being of reduced external diameter compared to the first and second tubular portions;   a transverse barrier having at least one orifice provided therein, the transverse barrier being disposed between a first cavity at least partially defined by an inner periphery of the first tubular portion and a second cavity at least partially defined by an inner periphery of the second tubular portion; and   one or more openings in a surface of the second or third tubular portion in communication with the second cavity.   
     
     
         15 . A filter for a smoking article including the flow restriction element of  claim 14 .