Abstract: A media stack height sensor in an image forming apparatus with a flag arm that is in contact with a top surface a media stack. The arm is coupled to a flag characterized by varying transmissivity. The flag is moveable by the flag arm so that as the position of the arm changes in relation to the stack height, a different portion of the flag is positioned between a transmitter and receiver of an optical sensor disposed within the body of the image forming apparatus. The flag accordingly reduces the amount of optical energy received by the receiver. The receiver output signal indicates the height of the media stack. The flag also includes features that further limit light transmission to the receiver to provide discrete stack height indications such as low, empty, full, or intermediate states.

Abstract: A method and apparatus for limiting the height of media inserted into a media tray of an image forming apparatus 10 while also allowing for the inserted media to expand due to changing environmental conditions is described herein. An exemplary stack height limiting system comprises an elongated arm with a striking end spaced from a control end, where the arm is movable between first and second positions. A limiter positioned relative to the arm defines the first position, where the striking end is spaced from the bottom surface of the tray by a first gap. As media disposed in the tray expands beyond the first gap, the expanding media moves the arm to form a second, greater distance between the striking end and the bottom surface of the tray. As a result, pinch points between the first end and the media are avoided.