Controlling lengths cut from continuously advancing string material - by detecting beginning and end of each string section and providing signal indicating moment at which string is cut

摘要

Controlling lengths cut from continuously advancing string material by using sensor detecting begining and end of each string section and providing signal indicating moment which string is cut. The method is for monitoring continuously advancing string material (1) for example a cigarette filter string, with regard to cutting the string (1) into identical plugs (7) for checking anc correcting the position of each cut. Prior to being cut the string (1) is scanned by an optical sensor unit (4) which detects the beginning and end of each string section. A device associate with the cutting device (5) generate an output signal to indicate the moment when the string (1) is cut. Between this output signal and the moment at which the sensor unit (4) issues a signal corresponding to the end of the string section to be cut, a measured value is obtained which is independent of the feed into of the string (1) and which is proportioned to the length of the string section between the two signals. This measured value is then compared with reference value and the operative stroke of the cutting device (5) is adjusted by a servo motor (35) driven helical drive (29) when a certain number of successive measured value is the number of pulses produced by a generator driven indirectly by the feed mechanism.