ES341154A1 - Method of and apparatus for making filtering material for cigarettes - Google Patents

Abstract

A web of fibrous material is treated to render it particularly adapted to be gathered laterally and enclosed in a wrapper to make a filter cord subdividable into effective filters for cigarettes, by advancing a moistened essentially inelastic web 1 of the material through the nip between a pair of meshing heated corrugating and stretching rollers 8, 9 having narrow circumferential grooves 20 alternating with narrow circumferential ribs 21 whereby the web is longitudinally corrugated and laterally stretched to loosen and expose fibres without substantial impairment of the transverse continuity of the web 1, and advancing the corrugated and stretched web 1 emerging from the nip in contact with the roller 9 through an appreciable wrap angle to partially dry and reharden the web to preserve the structure imparted thereto by passage through the nip. As shown in Fig. 1, the smooth web 1 passes from a roll 2 through perforating apparatus, preferably comprising a pronged or toothed roller 3 and a counter roller 4 one of which is driven, to produce irregularly-shaped frayed portions extending out of the plane of the web. The perforating device 3, 4 may be followed by a similar device, e.g. rollers 3, 4 with their positions reversed to form frayed projecting portions on the other side of the web. The web 1 is then rendered yielding by passage through a moistening device comprising a rotating metal roll 5 dipping into a water bath 6 and a rubber pressure roller 7. Alternatively, the web may be rendered yielding by spraying it with a liquid or by submitting it to a steam treatment. The web 1 then passes around meshing grooved corrugating and stretching rollers 8, 9, 10, see also Fig. 2, all of which are preferably adjustably heated, e.g. by interior electrical heaters, to a temperature between 100 C and 500 C. Preferably, the rollers 9, 10 mesh to a greater extent than the rollers 8, 9 to deepen the corrugations and further laterally stretch the web 1. After each corrugating step, the web 1 remains in contact with the roller 9 or 10 for a wrap angle of 180 to effect partial drying. The web 1 is directed by idler rollers 11, 12 to drying apparatus 13 and then passes between rollers 14, 15 at least one of which is driven and at least one of which has a coarse knurled surface to deform the corrugations in an irregular manner. Alternatively, the web 1 may be flattened somewhat by fine knurled or smooth surfaced rollers. The web 1 passes around a rotating drying drum 16 heated by electrical heating elements or hot air to completely reharden and set the web 1. Finally, the web may pass between perforating rollers 17, 18 similar to rollers 3, 4. Alternative arrangements of two to four corrugating and stretching rollers are described, Figs. 5-12 (not shown).