Patent ID: 7448991

Claim:
A system for monitoring a continuous thread being incorporated within a cigarette filter rod, comprising: a source of continuous thread; an array of light emitting parts operable to emit light; an array of light responsive parts operable to receive light from the array of light emitting parts; the arrays being mounted in a bracket such that they are facing each other on opposite sides of a measuring gap; a passageway defined within said bracket adapted to guide the thread into the measuring gap and providing a predetermined clearance around the thread; a positioning device comprising a mandrel that forms an opening in a moving filter tow positioned downstream from the measuring gap to entrain the thread within the cigarette filter rod, wherein the entrainment pulls the thread through the measuring gap; an air manifold, wherein the air manifold is capable of removing lint or debris accumulated in the passageway and/or the measuring gap; a photoelectric sensor connected to the light emitting parts and the light responsive parts and operable to generate signal values due to intensity of light received by the light responsive parts; and a programmable logic controller (PLC) which compares signal values from the photoelectric sensor and determine whether a thread present in the measuring gap is moving or stationary due to differences in the signal values output by the photoelectric sensor.