Measuring cigarette pressure drop

A cigarette pressure drop measuring system adapted to measure pressure drop across a rod of tobacco fibers as the rod is formed on a cigarette making machine at a point along the rod where the pressure drop measured correlates with the bound tobacco rod pressure drop of the rod in a finished condition, which comprises a format finger in a cigarette making machine through which a rod of tobacco fibers passes;

• a source of gas disposed to pass gas across the rod of tobacco fibers;
• and
• a gas pressure detecting means located to detect the gas passing across the rod of tobacco fibers;
• there being further provided calculation means for calculating the unbound pressure drop of a finished ventilated plain or filter-tipped cigarette, the calculation means utilizing the bound tobacco rod pressure drop obtained by correlation with the measured pressure drop across the rod in an algorithm held by the calculation means.

A method of determining the unbound cigarette pressure drop of finished ventilated cigarettes before their completion, which comprises measuring the pressure drop across a rod of tobacco fibres as the rod is formed on a cigarette making machine by passing a gas stream across the rod of tobacco fibres and detecting the pressure drop as an electrical signal using pressure sensitive means, the pressure drop being measured as the rod is compacted in a format finger of said cigarette making machine at a point along the rod in the format finger where the pressure drop measured across the rod correlates with a bound tobacco rod pressure drop measurement along the rod when the rod of tobacco fibres is in a finished wrapped condition, the electrical signal being indicative of a particular pressure drop measurement, and calculating using calculation means an unbound cigarette pressure drop for a finished ventilated filter-tipped cigarette made from said rod, the calculation means utilising the bound tobacco rod pressure drop obtained by correlation with the measured pressure drop across the rod in an algorithm held by the calculation means, which algorithm is determined by the specific filter element design of the completed cigarette, and further comparing the calculated unbound cigarette pressure drop value with a preset target range, and either varying a cigarette parameter to maintain the cigarette pressure drop within the target range, or rejecting those cigarettes which do not have an unbound pressure drop within the target range.