Gauge for measuring the thickness of an unsupported web

A gauge for measuring the thickness of a web, the gauge comprising:

• a first sensor located above one side of the web and a second sensor located below the opposite side of the web;
• each sensor having a laser which is aimed to direct a laser beam onto the respective side of the web adjacent to which the sensor is disposed, each sensor also having a detector which is positioned in relation to the web and to the respective laser so that the beam from the laser will be reflected from the web to the detector, and each detector including means for determining triangulation measurements of the distance between the respective sensor and the web;
• means for defining a respective path of travel for each sensor spaced from the respective surface of the web and across the web;
• a further laser for emitting a further laser beam and a further detector disposed in the path of the further laser beam, the further laser and the further detector being so located in the gauge that deviation in the vertical motion of at least one of the sensors in a direction toward or away from the web while the sensor is traveling along the path of travel across the web, shifts the further laser beam over the further detector responsive to the deviation of the motion of the sensor;
• mirror means disposed beyond one lateral edge of the web for deflecting the further laser beam, the further laser being aimed to direct the further laser beam toward the mirror means, and the further detector being aimed at the mirror means, whereby the further laser beam is deflected by the mirror means from the further laser to the further detector;
• and
• means for combining the information from each of the detectors for adjusting the web thickness triangulation measurements dependent upon the deviating motion of the sensors along the path of travel.

A gauge for measuring the thickness of a web, the gauge comprising:

• a first triangulation sensor located above one side of the web and a second triangulation sensor located below the opposite side of the web;
• each sensor having a laser which is aimed to direct a laser beam onto the respective side of the web adjacent to which the sensor is disposed, each sensor also having a detector which is positioned in relation to the web and to the respective laser so that the beam from the laser will be reflected from the web to the detector, and each detector including means for determining triangulation measurements of the distance between the respective sensor and the web;
• means for defining a respective path of travel for each sensor spaced from the respective surface of the web and across the web;
• a frame for supporting the means defining the path of travel for the sensors;
• a further laser for directing a further laser beam, and a respective further detector disposed in the path of the further laser beam, the further laser and the further detector being so located in the gauge that deviation in the vertical motion of at least one of the sensors in a direction toward and away from the web while the sensor is travelling along the path of travel across the web, shifts the further laser beam over the further detector responsive to the deviation in the vertical motion of the sensor.
• mirror means disposed in the frame beyond a lateral edge of the web for deflecting the further laser beam from the further laser to the further detector;
• and
• means for combining the information from each of the detectors for adjusting the web thickness triangulation measurements dependent upon the deviating motion of the sensors along the path of travel.