Encoder-based control of printhead firing in a label printer

• US 6,788,324 B2
• Filed: 02/06/2002
• Issued: 09/07/2004
• Est. Priority Date: 02/06/2002
• Status: Active Grant

• Current Assignee: Brady Worldwide Incorporated (Brady Corporation)
• Original Assignee: Brady Worldwide Incorporated (Brady Corporation)
• Inventors: Gale, David T., Kremers, Douglas R., Workman, Daniel K., Fisher, Richard P.
• Primary Examiner(s): Feggins, K.
• Application Number:
  US10/068,235
• Publication Number:
  US 20030146966A1
• Time in Patent Office: 944 Days
• Field of Search: 347/188, 347/54, 347/57, 347/14, 347/218, 400/279, 400/280, 400/582, 400/583
• US Class Current: 347/188
• CPC Class Codes: B41J 11/42 Controlling printing material conveyance for accurate alignment of the printing material with the printhead; Print registering
• CPC Class Codes: B41J 3/4075 Tape printers; Label printers

Abstract

A method of determining the position of a label media and printing to the label media based on the label media position is disclosed. The method includes using an encoder to track the position of the label media. As the label media advances during printing, an encoder shaft rotates with an encoder traction roller upon which the label media rides. As the encoder shaft rotates, optical reflections that occur within the encoder are interrupted, each interruption corresponding to a desired media travel distance. When the optical reflection is interrupted, the encoder sends a signal to the controller, which then sends a control signal to fire the printhead, and consequently the label media is thermally printed. The system is useful in thermal printer systems to provide more accurate position information of the label media, and consequently, more accurate printing. In this manner, with the encoder tracking the motion of the media, the timing of the printing of the label media is determined upon the actual position of the label media itself.

Claims

1. A media positioning and printing system comprising:

a printhead assembly having a printhead;

a controller for controlling firing of the printhead;

a label media to be printed to by the firing of the printhead; and

an encoder system in operational association with the printhead assembly, the encoder system including an encoder shaft having an encoder traction roller securably attached to the encoder shaft, the label media riding along the encoder traction roller, and an encoder attached to the encoder shaft for monitoring the rotation of the encoder shaft and transmitting a signal to the controller, the encoder including an optical source, an optical detector and a reflective optical disk that rotates with the encoder shaft, the reflective optical disk having a reflective pattern, the optical source generating an optical signal, and the reflective optical disk reflecting the optical signal back to the optical detector, the reflective pattern having non-reflective spaces, the optical detector not receiving a reflected optical signal when the optical signal hits the non-reflective spaces of the optical disk, thereby interrupting the optical signal;

wherein, when the encoder shaft rotates, the encoder optical signal is alternately reflected and interrupted so as create a signal interruption, and when the optical signal is interrupted, each resulting signal interruption corresponding to a label media travel distance, the encoder sends a signal to the controller and the controller, based on the signal from the encoder, sends a firing signal to the printhead to fire the printhead in order to effect printing of the label media based on the label media travel distance.

2. The system of claim 1 wherein the label media travel distance is approximately {fraction (1/300)}th of an inch.

3. The system of claim 1 wherein the encoder is a rotary-to-digital encoder.

4. The system of claim 1 wherein the rotation of the encoder shaft corresponds to an angular displacement that is read by the encoder and translated into a digital signal that is sent to the controller.