Apparatus and method for detecting the position of application of a sealing strip onto a web of packaging material for food products

摘要

There is described an apparatus (10, 10') for detecting the position of application of a sealing strip (7) of heat-seal plastic material onto a multilayer web (3) of packaging material for food products advanced along a predetermined path (P) and including at least one base layer for stiffness and strength and one or more heat-seal plastic layers; the sealing strip (7) has a first longitudinal portion (42), applied onto a longitudinal edge (8) of the web (3), and a second longitudinal portion (43) projecting laterally from the longitudinal edge (8). The apparatus (10, 10') comprises a light source (45, 45'), configured for irradiating a transversal portion of the web (3) during movement thereof along its path (P), and a sensor (46, 46') in use detecting a quantity (I, I') related to the different behavior of the materials forming the web (3) and the sealing strip (7) to light exposure and generating an output signal (W) related to the width of the second portion (43) of the sealing strip (7) in a direction (X) orthogonal to the travelling direction of the web (3) and parallel to said web (3).