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

Claim 0:
1. An intermediate transfer drum (ITD) printing apparatus for registering and printing 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, and wherein the print roll has a radius, from an axis of rotation to a surface of the print roll, that is variable which introduces a device offset of the print roll, said apparatus comprising:
a print head positioned over the print roll;
a processor operatively connected to the print head, said print head transferring the image, when commanded by said processor, to the print roll at an imaging point;
a substrate transport operatively connected to the processor and driven in a process direction towards the transfer nip;
a first sensor for detecting 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;
a second sensor, operatively connected to said processor, for detecting a plurality of discrete angular positions that correspond to rotation of said print roll, said processor using said plurality of discrete angular positions and predetermined data of the print roll to continuously update the device offset of the print roll;
a third sensor, operatively, connected to said processor, which measures a distance traveled by the substrate between said first sensor and the print roll; and
wherein when said first sensor alerts said processor of the detection of said registration mark, said processor begins counting down the most current device offset 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.