PURPOSE: To make it possible to moderate the lowering of a paper tray by its weight, by providing, in a paper tray lowering mechanism in a high speed copying machine, a brake device which may brake a transmission device only upon lowering of the paper tray.

CONSTITUTION: A paper tray lowering mechanism in the paper feed section of a copying machine, comprises a clutch 7 provided on a transmission device for transmitting a power from a d.c. motor 10 to a paper tray in order to raise the latter, a centrifugal brake 13 provided to a rotary shaft 12 rotated in association with the vertical movement of the paper tray. Accordingly, the rotational speed of the rotary shaft 12 is lower when the paper tray is raised, and therefore, no brake is effected by the centrifugal brake 13 while the clutch 11 cuts off the transmission of a power. The rotational speed of the rotary shaft 12 becomes higher when the paper tray is lowered by it weight, and therefore, brake is effected by the centrifugal brake 13. With this arrangement, the lowering speed of the paper tray is restrained to moderate the lowering of the paper tray. Therefore, it incurrs no breakage and failure of the paper feed device, and further, it is possible to prevent stacked papers on the tray from collapsing.