Method and control device for preventing register errors
AssigneeNexPress Solutions LLC
InventorsPatrick Metzler, Stefan Schrader
Life of this patent
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Abstract
Printers wherein a snub pulley gripping the conveyor belt from below changes contact force, a first register error occurs; and due to change of the spacing between the image lines on the sheet change, a second register error occurs. To prevent the first register error, time-lags of the first start signals (START OF FRAME) for the application of image lines are changed; and to prevent a second register error, time-lags of the second start signals (START OF LINE) for the application of image frames are changed.
Claims6
Method to prevent register errors in printers, such register errors being caused by a variable contact force of a snub pulley (27) gripping a conveyor belt (1) forming a print stack (3) transport nip with a printing drum (25), the method comprising:
- changing time-lags for a first START OF FRAME signal for application of image frames to prevent a first register error;
- and, changing time-lags of second START OF LINE signals, in corresponding relation to the variable contact force of a snub pulley in the transport nip, for the application of image lines to prevent a second register error.
In a printer having a plurality of printing modules including an illustration device (22) for transferring image lines to a printing drum (25) and thereafter to a print stock (3) transported by said conveyor belt and, a snub pulley (27) exerting variable force on a print stock conveyor belt (1), a control device (10) for preventing register errors comprising:
- a first sensor (12) for detecting a print stock (3) in front of said plurality of printing modules, a second sensor (13) for detecting register marks behind said printing modules, a rotary encoder (26) for capturing a rotation angle of said printing drum (25) and a device (30) for storing time-lags of first START OF FRAME signals for the application of image frames and of second START OF LINE signals for the application of image lines, which are determined by the variable contact force of said snub pulley (27) griping the conveyor belt (1).
Dependencies are inferred from the claim text.