Preparing cigarette filters

Abstract

Cigarette filters are made by passing a continuous rod of filter material continuously through a moving die to form a continuous filter element having a repeated pattern of staggered grooves so arranged that the continuous filter element can be cut at regular intervals to form individual filter elements each having in its peripheral surface a number of grooves extending substantially axially alternately from opposite ends of the element.

We claim: 
     
       1. A method for making cigarette filters comprising (a) forming filter material into a continuous rod,   (b) feeding said continuous rod of filter material along a predetermined path,   (c) shaping the continuous rod by at least one moving die which provides said rod with a plurality of circumferentially-spaced longitudinally-extending rows of grooves separated by a plurality of longitudinally extending ribs adapted for flow of cigarette smoke therethrough in a direction transverse to the axis of the rod, each row comprising a plurality of individual elongated grooves arranged successively in spaced end-to-end relationship in a longitudinal direction with filter material occupying the space between the ends of adjacent grooves in each row and each groove of each row overlapping longitudinally with at least two successive grooves of each adjacent row of grooves, each rib extending continuously between adjacent rows of grooves, and   (d) cutting the formed continuous rod at the space between the ends of successive grooves in at least one row into filter lengths such that none of the grooves in said filter lengths fully extend between opposite ends thereof.   
     
     
       2. A method according to claim 1 comprising forming a plurality of circumferentially spaced V-sectioned grooves with a longitudinally extending rib between each groove of each row at least two successive grooves of each adjacent row of grooves, said V-sectioned grooves being so shaped in cross-section that substantially parallel sides are formed on said ribs to maintain uniform flow of smoke through said ribs between adjacent grooves in different rows. 
     
     
       3. A method according to claim 1 comprising forming grooves of substantially the same length, the grooves of alternate rows being axially aligned, and cutting the filter material at the space between the ends of successive grooves of said alternate rows. 
     
     
       4. A method according to claim 3 comprising cutting the filter material at the space between the ends of successive grooves of the rows intermediate said alternate rows. 
     
     
       5. A method according to claim 1 comprising (a) rotating a plurality of wheels, each having at least one rib projecting from the peripheral surface thereof, arranged with their peripheries forming a moving die about said path, and   (b) feeding said continuous rod through said moving die to form said grooves in said continuous rod.   
     
     
       6. A method according to claim 1 .[.in which the continuous rod is enclosed.]. .Iadd.comprising enclosing the continuous rod .Iaddend.in a continuous wrapper and .[.is.]. then .[.cut.]. .Iadd.cutting the wrapped continous rod .Iaddend.into .[.the.]. double filter lengths for joining between two cigarette lengths. 
     
     
       7. A method for making cigarette filters comprising (a) forming filter material into a continuous rod,   (b) feeding said continuous rod of flter material along a predetermined path,   (c) rotating a plurality of wheels arranged with their peripheries forming a moving die about said path, each of said wheels having at least one rib projecting from the peripheral surface thereof on each side of a central plane through the wheel, the ribs on one side of the central plane being staggered with respect to the ribs on the opposite side of the central plane to form said continuous rod with a plurality of circumferentially-spaced longitudinally-extending rows of grooves, each row comprising a plurality of grooves arranged successively in a longitudinal direction and each groove of each row overlapping longitudinally with at least two successive grooves of each adjacent row of grooves, and   (d) cutting the formed continuous rod between the successive grooves in at least one row into lengths. .Iadd.   
     
     
       8.  In a method for making ciagarette filters (a) forming filter material into a continuous rod,   (b) feeding said continuous rod of filter material along a predetermined path,   (c) shaping the continuous rod by at least one moving die which provides said rod with a plurality of rows of grooves separated by a plurality of continuous elongated ribs adapted for flow of cigarette smoke therethrough in a direction tranverse to the axis of the rod, each row comprising a plurality of individual elongated grooves arranged successively in spaced end-to-end relationship with filter material occupying the space between the ends of adjacent grooves in each row, and each groove of each row overlapping with at least a portion of each of at least two successive grooves of each adjacent row of grooves, and   (d) cutting the formed continuous rod into individual filter lengths such that none of said grooves in said filter lengths fully extend between opposite ends thereof..Iaddend. .Iadd.9. In a method for making cigarette filters   (a) forming filter material into a continuous rod,   (b) feeding said continuous rod of filter material along a predetermined path,   (c) shaping the continuous rod by at least one moving die which provides said rod with a plurality of rows of grooves separated by a plurality of continuous elongated ribs adapted for flow of cigarette smoke therethrough in a direction transverse to the axis of the rod, each row comprising a plurality of individual elongated grooves arranged successively in spaced end-to-end relationship with filter material occupying the space between the ends of adjacent grooves in each row, and each space between the ends of adjacent grooves in each row being located between the ends of a groove in each adjacent row of grooves, and   (d) cutting the formed continuous rod into individual filter lengths such that none of said grooves in said filter lengths fully extend between opposite ends thereof..Iaddend. .Iadd.10. In a method for making cigarette filters   (a) forming filter material into a continuous rod,   (b) feeding said continuous rod of filter material along a predetermined path,   (c) shaping the continuous rod by at least one moving die which provides said rod with a plurality of rows of grooves separated by a plurality of continuous elongated ribs adapted for flow of cigarette smoke therethrough in a direction transverse to the axis of the rod, each row comprising a plurality of individual elongated grooves of predetermined length arranged successively in spaced end-to-end relationship with filter material occupying the space between the ends of adjacent grooves in each row, and each space between the ends of adjacent grooves in each row being located between the ends of a groove in each adjacent row of grooves, and   (d) cutting the formed continuous rod into individual filter lengths such that none of said grooves in said filter lengths fully extend between opposite ends thereof.