The present invention relates to a product optical control method.
Here and hereinafter, the term "control" is intended to mean control for determining whether products--consisting for example of cardboard blanks--are of the right type and/or are oriented correctly and/or face the right way and/or are positioned correctly.
The present invention is particularly advantageous for controlling blanks supplied successively to a user machine in the tobacco industry, such as a cigarette packing machine, to which the following description refers purely by way of example.
The blanks fed along the conveyor of a cigarette packing machine are known to be controlled using a fixed digital sensor for detecting the passage, at a given instant, of a given graphic mark on the surface of each blank.
In the event the blank is not the right type, or is upside down, faces the wrong way, or is simply positioned wrongly, the digital sensor, on failing to detect the passage of the graphic mark at the predetermined instant, emits an error signal to arrest the packing machine.
The above method involves a particularly painstaking process for correctly positioning the digital sensor in relation to the blanks. Indeed, since the digital sensor provides solely for emitting a YES-NO signal in response to detection, or not, of a graphic mark in a predetermined location at a predetermined instant, the sensor must be positioned extremely accurately in relation to the path of the blanks, to prevent even small and substantially acceptable inaccuracies in the positioning of the blanks from resulting in stoppage of the machine.