Patent ID: 7390379

Claim:
A paper machine apparatus comprising: a paper web or fabric run defining a plane, the paper web or fabric run extending in a machine direction over a guide, the guide having a roll which is mounted at one end to a bearing pedestal, the bearing pedestal mounted for movement in the machine direction; a motor mounted for driving the bearing pedestal in the machine direction so that the paper web or fabric run can be guided in a cross machine direction, transverse to the machine direction; an ultrasonic sensor contained in a housing and fixedly mounted with respect to the paper machine, the housing connected to a supply of compressed air, and arranged to pass cooling air over the ultrasonic sensor, and having portions forming an air knife arranged to blow air to prevent obstruction of the ultrasonic sensor; wherein the ultrasonic sensor is arranged to transmit a beam of ultrasonic sound waves towards portions of the paper web or fabric run which define an edge spaced from the roll, so that the beam will reflect from the edge; wherein the ultrasonic sensor is arranged to transmit a beam of ultrasonic sound waves which strikes the edge within a plane inclined 0-10 degrees from the plane defined by the paper web or fabric run; and wherein the ultrasonic sensor is in controlling communication with the motor so that a measured cross machine position of the edge is used to guide the paper web or fabric run in the cross machine direction.