Twin track machine and a method for manufacturing composite filters attachable to cigarettes, cigars and the like

A twin track machine for manufacturing composite filters attachable to cigarettes, cigars and the like, typically filters composed of at least two filter plugs made from different materials and/or with different filtration properties, comprising:

• first feed means by which filter sticks of a first type made from a first filter material and/or with first filtration properties are directed in succession along a respective first path;
• at least second feed means by which filter sticks of a respective different type, made from a different filter material and/or with filtration properties different to those of the first type, are directed in succession along a respective second path;
• first cutting means positioned along the first path, by which each filter stick of the first type is cross-cut on at least one transverse cutting line and separated thus into first and second plugs, arranged alternately and end to end;
• the first plugs of the first type destined to form part of a first continuous filter rod and the second plugs of the first type destined to form part of a second continuous filter rod;
• at least second cutting means positioned along the second path, by which each filter stick of the different type is cross-cut on at least one transverse cutting line and separated thus into first and second plugs, arranged alternately and end to end;
• the first plugs of the different type destined to form part of the first continuous filter rod and the second plugs of the different type destined to form part of the second continuous filter rod;
• conveying and assembling means by which the first plugs of the first type and of the different type are taken up, ordered and advanced longitudinally, end-to-end and in alternation, along the track on which the first filter rod is formed, and by which the second plugs of the first type and of the different type are taken up, ordered and advanced longitudinally, end-to-end and in alternation, along the track on which the second filter rod is formed;
• control means monitoring the longitudinal position of at least one first plug of the first rod, and of the corresponding second plug of the second rod, one relative to another;
• correction means by which the position of the at least one transverse cutting line on the filter sticks of the first type, and/or the position of the at least one transverse cutting line on the filter sticks of different type, can be adjusted according to the relative positioning of the first and second plugs.