Abstract: A device for the electropneumatical testing of the air permeability wherein each cigarette is subjected to at least one test consisting of applying pneumatic pressure to one end of the cigarette and determining the resistance or the pressure drop at the input to the cigarette. The measured pneumatic pressure is transformed into electric measurement signals which are compared with electric reference or threshold signals. According to the invention, the electric measurement signals are compared with the electric reference signals which are shaped as saw-tooth signals and are generated in synchronism with the cigarette tests, that is with the measurement signals. The ascending portions of the saw-tooth reference signals have a rate of increasing magnitude which corresponds approximately to the rate of increase of the electric measurement signals.

Abstract: For the electropneumatic inspection of the longitudinal and/or transversal permeability of the ventilated cigarettes, each cigarette is subjected in any order of succession to at least three of the four inspections consisting in applying a pneumatic pressure alternatively to each of the two cigarette ends, while keeping the opposite end open and subsequently closed. Each of these inspections determines the pneumatic resistance met at the respective cigarette inlet and the values of these resistances are converted into electric signals and used for determining the longitudinal and/or transversal permeability of the cigarette. For this purpose use is made of four-terminal network theory, by considering that the cigarette pneumatic resistance can be regarded as composed of an equivalent transversal resistance, derived from two equivalent longitudinal resistances in series with each other.

Abstract: A method and device for the electropneumatic testing of the air permeability of filter plugs for filter cigarettes. At one end of the filter plug there is applied a pneumatic pressure, the other end of the filter cigarette being connected, through a bore with the atmosphere. The pneumatic pressure applied at the inlet end of the cigarette plug is transformed into an electric test signal, and the signal is compared with an upper alarm threshold and with a higher upper reject threshold respectively, as well as with a lower alarm threshold and an inferior lower reject threshold. The test signal emitted upon reaching of the upper or lower alarm threshold initiates the operation of alarm indicators and/or sends a signal for the control of the filter plug producing machine, so as to modify the air permeability of the filter plugs. Upon reaching the upper or lower reject threshold, it causes rejection of the defective filter plugs.

Abstract: A device for detecting the degree of firmness of cigarette ends comprising a rotating drum moving laterally one after the other to a position to be tested, yieldable feeler means with indicator means positioned according to the firmness of a cigarette end being tested and transducer means for providing a signal depending upon the position of the indicator means. The foregoing can be combined with pneumatic means for testing for integrity of the wrappers of cigarettes.