Print sheet brake

A method for operating a device for braking and positioning a print sheet in a processing machine, wherein along the feeding direction for the print sheet at least one mechanism exerts a braking force onto the print sheet causing a positioning of the print sheet in connection with the operation of a downstream-arranged processing station, the method comprising:

• generating, with at least one first mechanism, pneumatic, braking-force triggering pulses to act upon the print sheet;
• generating, with at least a second mechanism, a braking-force triggering frictional force to act upon the print sheet;
• acting upon the print sheet with intermittent, uniform or oscillating braking forces generated with the first and second mechanisms;
• and
• controlling the braking forces generated by the first and second mechanisms by a control unit which is operated with changeable control profiles based on at least one of queried operating parameters and on stored control profiles.

A method for braking and positioning a print sheet in a feeding direction and for delaying the print sheet during an intake for a folding operation and/or to counter flattering movements that occur during print sheet intake, the method comprising:

• computing an air pressure needed for braking based on a specified production data including at least one of a folding pattern, paper weight, paper width and cut-off length, and sending an information regarding the computed pressure to an automatic pressure controller, taking into consideration the print sheet has different values on the left and right side based on a folding pattern;
• computing the air pressure required for slowing down the print sheet during intake into the folding station and/or to counter the flattering movements based on specified production data including at least one of the folding pattern, paper weight, paper width and cut-off length, and sending the information regarding the computed air pressure to an automatic pressure controller, taking into consideration that the left and right side of the print sheet have different values, depending on the folding pattern for the print sheet;
• filling a pressure reservoir located in front of a pneumatic switching valve in the flow direction with the computed pressure;
• detecting the print sheet entering or fed into a folding region by a light barrier along the back edge of the print sheet, wherein the light barrier simultaneously serves to ensure a synchronizing of a folding sword with a precise clock speed, and the light barrier detects irregularities within the belt transport of the print sheet and compensates for the irregularities with the control unit;
• triggering a signal for activating a pneumatic switching valve based on an activated trigger signal, taking into consideration a dead time and speed compensation;
• following the triggering, releasing abruptly the air stored in the pressure reservoir to cause an air nozzle to release a pulse-type air blast;
• transmitting the released air blast directly onto the print sheet or indirectly to a lever, which transmits a force of the air blast and the corresponding normal force onto the print sheet;
• pressing the print sheet during the feeding operation and/or during the folding process onto a table-type support and generating a braking force for the print sheet as a result of friction;
• exerting simultaneously or with a phase delay an additional braking force onto the back edge of the print sheet, wherein a material stretching results from the braking operation to cause stiffening of the print sheet;
• selecting the stopping instant such that the print sheet is braked securely to 0, or fits uniformly against the sheet end stop, or the folding sword takes over the print sheet or it is delayed during the folding process;
• and
• following release of the air pulses, closing the pneumatic switching valve immediately and filling the air reservoir again by the pressure controller with air to a predetermined pressure level to make air available for the following cycle.