Yarn Sensor for Textile Machinery

A yarn sensor is the machine's watcher: a sensing device on the yarn path that confirms yarn is present and running, and signals a stop the moment an end breaks, runs out or stops moving. On a knitting machine the cost of a missed break is high — needles continue to knit without yarn, producing press-offs, holes and ladders that scrap fabric and can damage the machine — so sensors are fitted per feed and trusted like safety devices. This page covers what yarn sensors detect, the supervisor types in use, and the Italian maker whose range is built around yarn supervision.

Detecting Presence, Drop and Tearing

Yarn supervision works by several principles, reflected in the supervisor families RMB Massardi lists. A supervisor by drop watches the yarn's tensioned position: while yarn runs, it holds its sensing element up, and when the end breaks the element drops and triggers the stop. A supervisor by tearing responds to the yarn being pulled or torn — detecting faults where yarn is dragged or snatched rather than simply absent. Combined supervisors by tearing and drop cover both behaviours in one device. Electronic yarn sensors extend the same idea with contactless sensing of yarn presence and movement, feeding the machine's stop motion and, on modern machines, its fault recording, so the operator is called to the exact feed that failed.

Fitted alongside slide electronic yarn control devices, sensors turn yarn behaviour — presence, motion, tension events — into machine signals at every feed. The stop the sensor calls is as important as the detection: the machine must halt quickly enough that the broken end does not travel, yet without a shock stop that breaks other ends or disturbs the fabric, and the signal must identify where the fault sits so the operator goes straight to the failed feed on a machine that may carry dozens of them. Sensor ranges are therefore matched to the machine's own stop-motion and control system, not bought as isolated devices. A sensor that stops the machine reliably but cannot be threaded quickly after a repair will be bypassed by a pressed operator, so ease of rethreading is a genuine selection point alongside sensitivity.

Fitting and Looking After Yarn Sensors

Sensors only protect the machine when they are clean, correctly threaded and actually in circuit: lint across a sensing point, a yarn path threaded around rather than through a sensor, or a defeated stop motion all silently remove the protection. Mills check sensor function at every machine start and after every break repair, keep sensing points blown clean with the machine's routine, and replace damaged units rather than bridging them. RMB Massardi of Italy, listed below, manufactures yarn sensors within its parts range for circular and flat knitting machines, alongside its yarn supervisors by drop, by tearing and by tearing and drop, slide electronic yarn control devices, yarn retainers, safe needles, bulb sockets and electric shears — the feed-area protection parts sourced from one maker.

Companies Supplying Yarn Sensor