Measuring total thickness of hollow-cavity plastic double glazing panels on-line employs ultrasonic sensors with drop of water to control adjustment of extrusion die and calibrator

摘要

The sensors (9) lie close to the panel surfaces. Only two drops (11) of fluid, wetting each sensor and panel surface, are required for acoustic coupling. The total panel thickness (D) is determined from the ultrasonically-measured distances between surfaces and sensors, coupled with a prior knowledge of the sensor separation. Preferred features: Individual wall thicknesses (do, du) are measured from echoes, based on propagation time differences of reflections from respective surfaces. Sensors follow the calibrator (4) outlet. Mounted on a traverse, they can be moved over the full width of the outer walls (6, 7). Water forms the coupling fluid; it is heated. It is wiped or sucked away, to remove it afterwards. The panels are plastic. The measurement method is used in manufacture; a typical control system compares measured with desired dimensions, and calls for judicious variation in tool and/or calibrator settings.