Abstract: A stack height control apparatus for sheet feeders in sheet processing machines. The apparatus comprises a 2:1 divider connected to stack height sensors, a comparison timing stage connected to the divider, a comparator stage connected to the sensors, to the divider and to the comparison timing stage, a forward-backward shift register connected to the comparator stage and at least two timing stages each connected to the shift register and to the comparator stage. The apparatus allows automatic feeding of sheets to machines such as employed for example as printing presses.

Abstract: The sheet-presenting unit presents received sheets to the printing instrumentality of the machine. The sheet-feeding unit feeds sheets to the sheet-presenting unit. The two units have activators which can be enabled and disenabled. The operator of the machine initiates a start signal. A sheet detector generates missing-sheet, skew-sheet and muliplee-sheet signals, indicating the condition of the sheet at the sheet-presenting unit. Enablement stages determine whether the activators for the feeding and presenting units are to be enabled or not. When the activators are enabled, the start signal is automatically extinguished. A logic circuit receives the start signal and the signals from the sheet detector. The logic circuit has pre-start-up and post-start-up modes of operation, corresponding to generation and termination of the start signal.

Abstract: A printing machine operates at a variable speed, and includes a rotary reference component. Activation and deactivation of positioning units for printing cylinders and other functional units for the printing machine is performed in synchronization with the rotation of the rotary reference component. The positioning units exhibit dead times in their response to applied activating or deactivating signals. The duration of each such dead time expressed in terms of the extent of angular movement of the rotary reference component varies in dependence upon printing machine operating speed, tending to produce improper synchronization between activation and deactivation of positioning units, on the one hand, and machine operation, on the other hand.

Abstract: The printing cylinders or other functional units of a printing machine are engaged and disengaged by positioning units. When a positioning unit receives an activating signal, its response thereto includes a dead time or delay time. Because the activation of the positioning units proceeds in dependence upon the angular position of a rotary reference component of the printing machine, and all operations are synchronized in terms of angular positions and angular spans, the dead time of the positioning units, when expressed in angular units, is a function of the operating speed of the printing machine. If the operating speed is variable, proper angular synchronization tends to be lost. The invention includes a clocked control unit clocked in angular synchronism with machine operation and determining when positioning units are to be activated and time-delay stages which introduce compensatory time delays into the application of activating signals to the positioning units.

Abstract: A sheet-representing signal is registered by successive shift-register stages in simulation of the travel of a sheet through a printing machine. Signal detectors connected to different register stages actuate moving units which in turn change the state of activation of the functional units of the printing machine. Upon a changeover from one-side to two-side printing, there arises a sheet travel path length change composed of a fixed component determined by machine geometry and a variable component determined by sheet length. Each moving unit moves cyclically and can move the associated functional unit only during a certain portion of the cycle. Upon a printing mode changeover, moving units undergo a phase shift of their cycles of motion and signal detectors are disconnected from certain register stages and reconnected to others, thereby compensating for the variable and fixed components of the sheet travel path length change.

Abstract: A printing machine receives single sheets which are removed from a stack by the suction cups of a feeding mechanism which is combined with a monitoring unit serving to detect the absence of sheets at the undersides of suction cups or the lifting of two or more sheets. The monitoring unit employs a transducer having two feelers which determine the thickness of lifted sheet material and an indicating device which is actuated by the feelers and produces signals serving to indicate the absence of sheets, the lifting of two or more sheets and/or to control the operation of the printing machine. The suction cups can form part of the transducer when the latter is designed to detect only the absence of sheets or they form part of a second transducer which is provided in addition to the first mentioned transducer.

Abstract: A printing machine receives single sheets which are removed from a stack by the suction cups of a feeding mechanism which is combined with a monitoring unit serving to detect the absence of sheets at the undersides of suction cups or the lifting of two or more sheets. The monitoring unit employs a transducer having two feelers which determine the thickness of lifted sheet material and an indicating device which is actuated by the feelers and produces signals serving to indicate the absence of sheets, the lifting of two or more sheets and/or to control the operation of the printing machine. The suction cups can form part of the transducer when the latter is designed to detect only the absence of sheets or they form part of a second transducer which is provided in addition to the first mentioned transducer.