Abstract: The lateral position of a web or fabric edge 11 in a paper machine is determined using an ultrasonic sensor. The ultrasonic sensor has a detector head 42, with an air channel system which opens to the vicinity of the head for forming an air knife which prevents accumulation of dirt on the head. The protective cover 35 has an air guide 43 extending further than the detector head 42, with air flowing thereabove from inside the protective cover 35 through an opening 36. The end component is on top of the protective cover allowing air to flow from the opening between the air guide and the end component to a detent, which turns the direction of the air flow. This provides efficient cleaning without disturbing, however, the operation of the ultrasonic sensor.

Abstract: The lateral position of a web or fabric edge 11 in a paper machine is determined using an ultrasonic sensor. The ultrasonic sensor has a detector head 42, with an air channel system which opens to the vicinity of the head for forming an air knife which prevents accumulation of dirt on the head. The protective cover 35 has an air guide 43 extending further than the detector head 42, with air flowing thereabove from inside the protective cover 35 through an opening 36. The end component is on top of the protective cover allowing air to flow from the opening between the air guide and the end component to a detent, which turns the direction of the air flow. This provides efficient cleaning without disturbing, however, the operation of the ultrasonic sensor.