Method of monitoring the function of a stop motion arrangement in an air

Abstract

In an air jet loom including a stop motion arrangement with first and second light beam sensor devices for detecting the presence of an inserted weft thread, the functionality of the sensor devices is continuously monitored. An inserted weft thread is expected to reach the first sensor device during an angular range (.alpha.1) of one rotation of the main shaft of the loom, whereupon the first sensor device emits a weft arrival signal (S1). In the event of a weft break, the weft thread reaches the second sensor device during the angular range (.alpha.1), whereupon the second sensor device emits a weft fault signal (S2). To monitor the functionality of the first sensor device, an interference signal (S3) emitted thereby during a second angular range (.alpha.2) not corresponding to the first angular range (.alpha.1) is evaluated. To monitor the functionality of the second sensor device, its light beam is positively interrupted by a projection (12') of a machine component (12) during each weft insertion cycle as the reed beats-up the inserted weft thread. Thus, the second sensor device positively emits a test signal during each reed beat-up at a time outside of the first angular range (.alpha.1). The presence, absence or irregularities of the signals (S3) and (S4) are statistically evaluated to determine whether a loom stop is necessary.