System for ink short protection

• US 6,578,940 B2
• Filed: 07/25/2001
• Issued: 06/17/2003
• Est. Priority Date: 07/25/2001
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Rehmann, David A, Elgee, Steven B
• Primary Examiner(s): Nguyen, Judy
• Assistant Examiner(s): Huffman, Julian D.
• Application Number:
  US09/912,981
• Publication Number:
  US 20030025740A1
• Time in Patent Office: 692 Days
• Field of Search: 347/5, 347/9, 347/10, 333/12, 333/4, 370/278, 370/284, 375/257
• US Class Current: 347/5
• CPC Class Codes: B41J 2/04541 Specific driving circuit
• CPC Class Codes: B41J 2/0458 controlling heads based on heating elements forming bubbles
• CPC Class Codes: B41J 2/04581 controlling heads based on piezoelectric elements
• CPC Class Codes: B41J 2/17566 Ink level or ink residue control
• CPC Class Codes: B41J 29/393 Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns

Abstract

A system for ink short protection for signaling to inkjet printheads includes a differential signaling driver having a first and a second terminal, a differential signaling receiver having a first and a second terminal, a first capacitor in series between the first terminals, a second capacitor in series between the second terminals, and circuitry for reducing charge accumulation on the capacitors. A method for ink short protection and a printing mechanism having such an ink short protection system are also provided.

Claims

1. A printing mechanism, comprising:

an inkjet printhead which selectively ejects ink;

an ink short protection system for signaling to the inkjet printhead comprising;

a differential signaling driver having a first and a second terminal;

a differential signaling receiver having a first and a second terminal;

a first capacitor in series between the first terminals;

a second capacitor in series between the second terminals;

passive circuitry for dissipating charge accumulated on the capacitors; and

active circuitry for manipulating a data stream transmitted from the driver by steering current to the driver first terminal for a logic 1 data element and alternatively steering current to the driver second terminal for a logic 0 data element, whereby signals present on the first and second driver terminals tend to cancel the charge applied to the capacitors by previous signals.

2. A printing mechanism according to claim 1, wherein the passive circuitry for dissipating charge accumulated on the capacitors comprises:

a first bleeder resistor connected in parallel across the first capacitor; and

a second bleeder resistor connected in parallel across the second capacitor.

3. A printing mechanism according to claim 2, wherein the active circuitry for manipulating the data stream including a configuration to:

segment the data stream into data packets;

track whether a majority of logic 1 data elements or a majority of logic 0 data elements have been transmitted by the driver;

examine each data packet prior to transmission by the driver to determine whether a majority of logic 1 data elements or a majority of logic 0 data elements are in the data packet;

invert the data elements of the data packet prior to transmission by the driver if necessary to keep the number of transmitted logic 1 data elements approximately equal to the number of logic 0 data elements; and

combine a data header with the data packets, including an invert data element to indicate whether the data elements of the data packet being transmitted by the driver are inverted.

4. A printing mechanism according to claim 1, wherein the passive circuitry for dissipating charge accumulated on the capacitors comprises:

a first bleeder resistor connected from the first receiver terminal to a positive voltage; and

a second bleeder resistor connected from the second receiver terminal to a local ground.

5. A printing mechanism according to claim 4, wherein the active circuitry for manipulating the data stream includes a configuration to:

segment the data stream into data packets;

track whether a majority of logic 1 data elements or a majority of logic 0 data elements have been transmitted by the driver;

examine each data packet prior to transmission by the driver to determine whether a majority of logic 1 data elements or a majority of logic 0 data elements are in the data packet;

invert the data elements of the data packet prior to transmission by the driver if necessary to keep the number of transmitted logic 1 data elements approximately equal to the number of logic 0 data elements; and

combine a data header with the data packets, including an invert data element to indicate whether the data elements of the data packet being transmitted by the driver are inverted.

6. A printing mechanism according to claim 1, wherein the passive circuitry for dissipating charge accumulated on the capacitors comprises:

a first pull-up resistor connected to the first receiver terminal and configured to receive a DC pull-up voltage; and

a second pull-up resistor connected to the second receiver terminal and configured to receive the DC pull-up voltage.

7. A printing mechanism according to claim 6, wherein the active circuitry for manipulating the data stream includes a configuration to:

segment the data stream into data packets;

track whether a majority of logic 1 data elements or a majority of logic 0 data elements have been transmitted by the driver;

examine each data packet prior to transmission by the driver to determine whether a majority of logic 1 data elements or a majority of logic 0 data elements are in the data packet;

invert the data elements of the data packet prior to transmission by the driver if necessary to keep the number of transmitted logic 1 data elements approximately equal to the number of logic 0 data elements; and

combine a data header with the data packets, including an invert data element to indicate whether the data elements of the data packet being transmitted by the driver are inverted.

8. A printing mechanism according to claim 1, further comprising:

a first termination resistor; and

a second termination resistor connected in series with the first termination resistor between the first receiver terminal and the second receiver terminal.

9. A printing mechanism according to claim 8, wherein the passive circuitry for dissipating charge accumulated on the capacitors comprises a pull-up resistor, connected between the first termination resistor and the second termination resistor, configured to receive a DC pull-up voltage.

10. A printing mechanism according to claim 9, wherein the active circuitry for manipulating the data stream includes a configuration to:

segment the data stream into data packets;

track whether a majority of logic 1 data elements or a majority of logic 0 data elements have been transmitted by the driver;

examine each data packet prior to transmission by the driver to determine whether a majority of logic 1 data elements or a majority of logic 0 data elements are in the data packet;

invert the data elements of the data packet prior to transmission by the driver if necessary to keep the number of transmitted logic 1 data elements approximately equal to the number of logic 0 data elements; and

combine a data header with the data packets, including an invert data element to indicate whether the data elements of the data packet being transmitted by the driver are inverted.