Recently, besides a monochrome machine including a scanning optical system employing a single light source, a tandem color machine is also proposed. In the tandem color machine, for the purpose of realizing an increase of speed of scanning on the surfaces of photoconductive drums, plural light sources are provided in one laser unit. A method of increasing the number of laser beams for performing scanning once (a multi-beam method) is used.
In the tandem color machine, a large-capacity cassette feeder (LCF) that can store a large volume of sheets is provided. The large-capacity cassette feeder feeds sheets to a sheet conveying path as required.
If sheets are stacked in left and right independent cassettes in the large-capacity cassette feeder, in order to designate a stacking range of the sheets or in order to prevent the stacked sheets from extending beyond a predetermined stacking range, shutters are provided for each of the cassettes. However, power is required for the opening and closing of the shutters. Therefore, in the past, the number of electronic components such as solenoids used for the opening and closing of the shutters increases. It is possible to reduce the number of shutters in order to hold down the increase in the electronic components. However, if the number of shutters is reduced, the sheets extend beyond the stacking range.