DIMENSION MEASURING METHOD

PURPOSE:To accurately measure a shape without allowing freight to fall in the gap between rollers by placing the freight on a transparent plate sufficiently larger than the freight in the advance direction of the freight to transfer the same on conveyor rollers. CONSTITUTION:Freight A is placed on a transparent plate 5, for example, an acrylic resin plate to be transported on drive rollers 1. At the time of the measurement of dimensions, beam 4c transmits through the plate 5 from a floodlight projector 4a to be detected by a light receiving device 4b provided under the rollers 1. When the freight A advances in the direction shown by an arrow right-angled to the rollers 1, the beam 3c between a light projecting element 3a and a photodetector 3b is temporarily blocked with the advance of the freight A. Therefore, when the rotational speeds of the rollers 1 are constant, the length of the freight A is instantaneously calculated from the moving speed of a conveyor and the light blocking time. Since the freight A is placed on the sufficiently large transparent plate to be transported, the freight A does not fall in the gap between the rollers 1 even when the interval between the rollers of the conveyor is wide and the dimensions of the freight can be accurately measured.