Abstract: The weft yarn leaving a drum of a weft yarn store of a loom is monitored by a monitor device disposed between the drum and a yarn eye in the zone of the yarn balloon. The monitor device includes a ring with an internal surface across which the yarn balloon slides during take-off. At least one light transmitter is mounted in the ring to emit a light beam across the path of the yarn and at least one transmitter is also mounted in the ring to receive the light beam for sensing when the yarn passes through the beam.

Abstract: The weft yarn store includes a stationary drum for a supply of weft yarn as well as an electromagnetic yarn clamp for retaining the weft yarn on the drum periphery. The clamp includes a locking pin which is connected to an armature of the electromagnet for pressing a yarn against an abutment surface of the drum. The electromagnetic yarn clamp is also provided with apertures through which cooling air may flow into and through the clamp in order to cool the winding and armature. In addition, the cooling air may be directed onto the abutment surface of the drum to keep this area free from deposits of fluff.