Abstract: A method of foreseeing and controlling wearing in the tread of a tire based on the use of cuts of a limited depth (in the order of tenth parts of one millimeter) formed on the external surface of the tread, in the thickness of the elastomeric material. The cut is preferably made by a laser beam. Rotation of the tire on a road or on any other friction surface enables both the uneven wearing of the tread, highlighted by localized spots devoid of cuts, to be quickly verified by inspecting the maintenance state of the cuts. Also, and the wear rate of the tread can be drawn from calculation of the time, during the rotation, elapsing between the disappearance of two groups of cuts of different depth.

Abstract: A sheet discriminating apparatus comprising means for detecting both light reflected by and light transmitted through a sheet, upon irradiation of light onto the sheet; hole-detecting means for detecting whether or not there is a hole in the sheet on the basis of an output of the light-detecting means, the hole detecting means generating a signal when a hole is detected in the sheet; means for gating the output of the light-detecting means in accordance with the hole signal; and means for detecting the degree of soiling of the sheet in accordance with an output of the gating means. During operation of the sheet discriminating apparatus, when excess light is detected by the light-detecting means, the hole-detecting means outputs a hole signal, and in response to the hole signal the gating means selectively gates the output of the light-detecting means to the means for detecting the degree of soiling. If there is no hole in the sheet, it is then judged whether or not the sheet is fit or unfit for continued use.