Print pulse controller for a termal printhead

• US 4,663,734 A
• Filed: 04/02/1984
• Issued: 05/05/1987
• Est. Priority Date: 04/02/1984
• Status: Expired due to Term

• Current Assignee: Atlantek, Inc. (Zebra Technologies Corporation)
• Original Assignee: Gulton Industries, Inc.
• Inventors: Berry, Jeffrey R.
• Primary Examiner(s): Williams, Archie E.
• Application Number:
  US06/595,983
• Time in Patent Office: 1,128 Days
• Field of Search: 364/200 MS File, 364/900 MS File, 364/518, 346/76 PH, 346/1.1, 219/216, 219/216 PH, 400/120
• US Class Current: 400/120.15
• CPC Class Codes: G06K 15/028 by thermal printers

Abstract

A thermal print pulse controller and data shifter accomplishes control of a thermal print pulse by altering the pulse width of the print pulse according to the printing history. Data is obtained from the printhead and recirculated for logical operation with previous records back to the printhead during predetermined phases of the print pulse. As a result of the logical comparison a decision is made to continue or discontinue printing of a dot and thus prevent overheating the printing element.

Claims

1. In a thermal printer, a system for controlling the energization of each one of a plurality of thermal print elements of a thermal printhead, each responsive to a printing pulse, wherein printing is accomplished during given individual print periods or print cycles, and each print period is divided into a plurality of individual and successive time periods or print phases, the system comprising:

print memory means for storing at least a number of lines of data equal to the number of print phases, the newest received line of data being for present printing, the other lines of data being successively "older" lines of data previously printed, during the present time of operation of said printer to print successive lines of data;

recirculative memory means for storing at the beginning of a print period a line of data to be printed, said line of data representing a predetermined combination of said printing pulses for energizing associated individual ones of said printing elements, respectively, at least during the first print phase of the print period;

data path logic means operative at the end of each one of said plurality of print phases other than the last print phase, for (1) receiving from said print memory means the previous line of data printed corresponding "agewise" to the next print phase number to be entered, (2) receiving from said recirculative memory means the contents thereof, (3) comparing via an algorithm the retrieved "previous line of data" with the combination of printing pulses during the last printing phase for the present line of data being printed, and as a result cancelling printing pulses for de-energizing the ones of said print elements required for printing the present line of data that have attacined a temperature sufficient for completing printing in the present print period due to their previous energization in prior print periods, and (4) returning or recirculating the altered line of printing pulses back to said recirculative memory means for reapplication to associated print elements of said printhead; and

control logic means connected to said print memory means, recirculative memory means, and data path logic means, for controlling the operation thereof.

2. The thermal printer of claim 1, wherein said data path logic means includes means (1) for processing a "previous line of data" in accordance with said algorithm into a line of data bits represented by some combination of "ones" and "zeros", said present or current print pulses also being represented by a combination of "ones" and "zeros", and (2) for next comparing the previous data with the current print pulses to eigher terminate or retain each then existing print pulse in the next print phase in accordance with the following logic table:

space="preserve" listing-type="tabular">______________________________________ Next Phase Previous Data Current Print Pulse Print Pulse Result ______________________________________ 0 0 0 0 1 1 1 0 0 1 1 0 ______________________________________

3. In a thermal printer, a method for controlling the energization via print pulses of each one of a plurality of thermal print elements of a thermal printhead, during each successive print period of said printer for printing a line of data, the data being in the form of a combination of "ones" and "zeros", the method comprising the steps of:

(A) dividing each print period into a plurality of equal length print phases;

(B) storing successive lines of data as they are received for printing, the number of lines stored being equal to the number of print phases;

(C) storing print pulses for a present line of data for providing printing pulses for application to associated ones of said printing elements, for initiating printing of the present line of data during a first print phase;

(D) comparing via an algorithm before initiation of each one of the second through next to last ones of said print phases, respectively, successively less recent ones of said lines of data, respectively, with the most recent ones of the print pulses, for terminating only the ones of said print pulses associated with print elements sufficiently heated, due to energization in a previous print period, for completing the printing of an associated dot, respectively, over the remaining printing phases of the present print period; and

(E) recirculating the altered print pules back to associated ones of said print elements, respectively, at the initiation of the next print phase.

4. The method of step 3 further including in step (D) the step of determining said algorithm in accordance with the thermal chracteristics of said thermal printhead.