| 摘要 |
Apparatus for detecting bumps in a web, such as are caused by double threads or knots in a web of fabric, as the web is advanced past the detecting apparatus, comprises a blade, preferably a plurality of partially overlapping blades, arranged across the web and riding on the web. Each blade comprises one element of a switch the other element of which is constituted of a contact member arranged above the blade a distance from the blade greater than the height of the bumps to be detected. The blade is sufficiently light and so mounted that when it is struck by a bump on the web, it bounces out of engagement with the web and contacts the contact member thus closing the switch which is in an electrical circuit. A deactuatable means for moving the web is operatively associated with the switch whereby closing of the switch deactuates said web moving means. A marking means for marking the web when the switch is closed may also be operatively associated with the switch. Similarly, an audible signal may be operatively associated with the switch.
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