Tabakrauchfilterelement

1336465 Tobacco smoke filters EASTMAN KODAK CO 5 Oct 1971 [5 Oct 1970 5 April 1971 9 Aug 1971] 46312/71 Heading A2C A tobacco smoke filter element comprises a porous body having an outer side wall and end walls and first and second indentations extending from the side wall into the body, the arrangement being such that in use a pressure differential is created between the indentations so that a portion of the smoke flows at a reduced velocity in a generally diagonal direction from the area of one indentation towards the other indentation. The element, which is enclosed in an outer wrap, may be made of any suitable filter material such as creped paper or a tow of crimped themoplastic fibres, e.g. fibres of polyolefin, polyester, cellulose ester, or mixtures and the indentations may be made by heat and/or pressure or by a cutting operation. The two indentations 11, 13, Fig. 1, are in the form of elongate grooves differentially spaced from the ends so that if, e.g. smoke is flowing from left to right the pressure in the groove 13 will have a higher value than that in the groove towards 11. The two grooves may alternatively be directly opposed to each other and the two ends of the filter cut obliquely. In modifications, each groove is replaced by a series of parallel indentations or by a cut-away portion in the form of a segment of a cylinder. Fig. 11 shows a further embodiment in which the indentations are in the form of grooves 31, 33 deepening progressively from points on the outer surface of the filter towards the ends. In modifications of this embodiment, the grooves have rounded bottoms, one of the grooves terminates short of the end, and two additional grooves extend from one end a short way along the filter. In a further embodiment, a continuous rod is passed through a tube 136, Fig. 27, and pierced by heated pins 144 guided by holes 142 in the tube, the rod subsequently being severed at the dotted lines 146. The piercing may alternatively be effected by hollow pins through which hot air is passed or by hollow or porous inserts through which a solvent is injected. Also, inserts that will disappear after the filter has been firmed, e.g. of ice, may be used.