Patent ID: 11868058
Assignee: XEROX CORPORATION
Field: Optics (Instruments)
Classification: CPC G  B | IPC B  G

Claim 7:
8. A method for controlling an intermediate transfer drum (ITD) printing apparatus to register and print an image on top of another image already printed on a substrate and wherein the ITD includes a print roll and a transfer roll interfaced to form a transfer nip for applying the image to the substrate, the print roll having a variable radius which introduces a device offset of the print roll, said method comprising:
positioning a print head over the print roll;
operatively connecting a processor to the print head such that, when commanded by said processor, said print head transferring the image to the print roll at an imaging point;
operatively connecting a substrate transport to the processor and wherein the substrate transport is driven in a process direction towards the transfer nip;
detecting, using a first sensor, a registration mark present on the image already printed on the substrate to alert said processor of the approach of the substrate towards the ITD;
operatively connecting a second sensor to said processor for detecting a plurality of discrete angular positions that correspond to rotation of said print roll and wherein said processor uses said plurality of discrete angular positions and predetermined data of the print roll to continuously update the device offset of the print roll; and
alerting said processor, by said first sensor, of the detection of said registration mark; and
counting down the most current device offset, by said processor, until the device offset is completed at which time said processor commands said print head to transfer the image to said print roll at said imaging point such that the image is subsequently transferred, at the transfer nip, to the substrate upon the another image in a registered position.