| 摘要 |
Method and apparatus for web break detection employing a sonic signal generator to generate regularly repetitive sonic signals (7) of selected frequency, duration and time spacing between signals and disposed to direct the sonic signals toward a moving web (1) of selected material so the signals are reflected from the web, a receiver device to receive the reflected signals (8), a time signal generating device (71), to generate signal pulses during the time period between the generation of a sonic signal and receipt of the reflected signal, a counter device to count the time generated between the transmission of the sonic signal and the reflected signal so that the number of time signals generated is indicative of the presence of the web as well as the distance of the web from the signal generator and receiver, and a logic system (29) to actuate a cutter mechanism (3) to cut the web if it should fall outside a preselected ''window'' in which the web is positioned. |
