Ink level sensing for disposable ink jet print head cartridges

• US 5,966,144 A
• Filed: 05/14/1997
• Issued: 10/12/1999
• Est. Priority Date: 11/24/1992
• Status: Expired due to Term

• Current Assignee: Funai Electric Co., Ltd.
• Original Assignee: Lexmark International Incorporated (Ninestar Corporation)
• Inventors: Edwards, Mark Joseph
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Nguyen, Judy
• Application Number:
  US08/856,160
• Time in Patent Office: 881 Days
• Field of Search: 347/7, 347/19, 347/171, 347/237
• US Class Current: 347/7
• CPC Class Codes: B41J 2/17566 Ink level or ink residue control
• CPC Class Codes: B41J 2002/17569 based on the amount printed or to be printed
• CPC Class Codes: B41J 2002/17579 Measuring electrical impedance for ink level indication

Abstract

A printer having a disposable print head which contains a consumable ink supply includes the capability of determining the level of ink in the print head without directly measuring the ink supply. The print head includes a number of resistors which can be driven to an open circuit condition by the printer. The printer includes a counter and memory for tracking the usage of the print head and a driver for selectively driving the print head resistors to an open circuit condition based upon such usage. The printer is also capable of detecting the condition of the resistors on the print head and producing a resultant visual display.

Claims

1. A disposable print head cartridge for an ink jet printer providing a first voltage and second voltage different from said first voltage, the cartridge containing, a print head containing an ink droplet activation device, an ink supply in flow communication with said ink droplet activation device and an ink supply indication circuit comprising:

a plurality of burn-out resistors, each of said burn-out resistors having a closed circuit condition and a permanent open circuit condition upon activation, having first ends for being connected by means of a first conductor to the first voltage, and having second ends;

a plurality of resistor dividers, each of said resistor dividers being connected in series with one of said burn-out resistors, each of said resistor dividers having first and second resistors having predetermined resistances, each of said first resistors having a first end connected to one of the second ends of said burn-out resistors and having a second end, and each of said second resistors having a first end connected to the second end of one of said first resistors and a second end connected by means of a second conductor to the second voltage;

a plurality of third conductors, each of said third conductors connected to a unique one of the second ends of said burn-out resistors and the first ends of said first resistors for supplying a third voltage to the second ends of said burn-out resistors, the difference between the first and third voltages being sufficient to burn the burn-out resistor and create an open circuit condition at the position of the burned burn-out resistor to update the data stored by said burn-out resistors in order to indicate the approximate amount of ink remaining in the ink supply;

a plurality of fourth conductors, each of said fourth conductors being connected to a unique one of said resistor dividers between the first and second resistors of the resistor dividers for communication with said printer to indicate said open or closed circuit condition of said bum-out resistors, said fourth conductors supplying a fourth voltage having a magnitude proportional to the ratio of the predetermined resistance of said second resistor divided by the sum of the predetermined resistances of said first and second resistors and the resistance of said burn-out resistor to indicate a closed circuit condition.

2. The print head cartridge of claim 1 wherein said open circuit condition is inversely proportional to said ink supply level.

3. The print head cartridge of claim 1 comprising at least eight burn-out resistors.

4. The print head cartridge of claim 1 comprising at least eight resistor dividers.

5. The print head cartridge of claim 1 comprising at least eight first resistors and at least eight second resistors.

6. The print head cartridge of claim 1 wherein the burn-out resistors and resistor dividers are disposed on the print head.