WO1999065685A2

WO1999065685A2 - Method and apparatus for an ink jet printer system

Info

Publication number: WO1999065685A2
Application number: PCT/US1999/013576
Authority: WO
Inventors: Miles Busby; Michael Bailey
Original assignee: Source Technologies, Inc.
Priority date: 1998-06-16
Filing date: 1999-06-16
Publication date: 1999-12-23
Also published as: WO1999065685A3; AU4687299A

Abstract

A method and apparatus for an ink jet printer system (10) for efficiently and economically printing magnetic image character recognition images is disclosed. The ink jet printer system includes a movable carriage (14) and an ink jet print head (12) disposed on the carriage and having a piezoelectric element adapted to jet magnetic ink onto a recording medium. The magnetic ink preferably has a viscosity of more than 4 centipoise, and more preferably at least 8 centipoise. Additionally, a computer (30) may be in communication with the carriage for performing a printer monitor function. The method for performing such function includes monitoring the movement of the carriage and initiating a predetermined carriage movement after sensing a predetermined idle time from the carriage.

Description

Method and Apparatus for an Ink Jet Printer System

Cross-Reference to Related Applications

This application claims the benefit of U.S. Provisional Application No.

60/089,497, filed June 16, 1998.

Field of the Invention

The present invention relates to a process and apparatus for printing images which may be read by magnetic ink character recognition (MICR) devices, and more particularly, to a system that allows for MICR printing utilizing a piezo electric ink jet printer.

Background One way to automatically read printed characters is to form the characters with inks that can be magnetized and read by magnetic ink character recognition (MICR) devices. For example, characters passing through a MICR reader are first energized with a magnetic field and then the magnetic signal from each character is sensed to determine the character. The ability of a MICR reader to recognize a magnetic ink character is a function of the quality of the form of the character and the ability of the magnetic ink to sustain a magnetic field once it has been magnetized, measured by the ink's remnance and coercivity. Maximizing the amount of magnetic pigment added to the ink enhances the magnetic ink's ability to sustain a magnetic field, and thus, increases the readability of the character. Current methods of MICR printing produce characters that can be reliably read, however, these methods are relatively sophisticated and expensive. A lot of MICR printing is currently performed using offset presses, laser printers, and impact printers. The offset press process generally involves large, expensive, complicated machinery and magnetic inks/pastes that may be difficult to handle. This type of machinery is used mainly by businesses whose main concern is printing large volumes of materials, as opposed to businesses where MICR printing is a secondary or internal concern. Similarly, MICR printing with laser printers is relatively expensive as the laser printer itself is very costly. Additionally, using magnetic toners is expensive as printing with laser toner cartridges is already one of the more costly methods of printing, while the specialized magnetic toners add even more cost. Impact printers with magnetic printer ribbons are also costly and are not as efficient and reliable as other methods because they rely on mechanical parts to perform the printing. Thus, a low cost, unsophisticated, yet practical and reliable way to perform MICR printing is desired.

Another method of MICR printing, disclosed in a patent but not commercially implemented as far as can be determined, involves thermal ink jet technology. A thermal ink jet printer uses thermal energy pulses to produce a bubble in an ink filled channel. When the bubble collapses, ink in the channel forms a droplet and is expelled from the channel toward a recording medium.

Inkjet technology in general is attractive because it is relatively inexpensive compared with offset printing and laser printing. Inkjet technology, however, has never been commercially successful for MICR printing as far as can be determined. One of the basic problems is that in order to form a character that can hold the required magnetic field, a large mass of magnetic particles is required in the ink solution. Additionally, the increased mass of magnetic particles results in a higher viscosity ink solution. The larger mass of particles and resulting higher viscosity solution combine to make it difficult for ink jet printers to form and expel droplets. Also, different types of ink jet heads, such as the thermal printer head, are not able to be used successfully with the higher viscosity inks that are required to form reliable MICR characters.

Further, once an appropriate combination of magnetic particles, ink viscosity, and ink jet printer head are found, it is difficult to keep the magnetic particles from falling out of suspension. And when the magnetic particles do happen to fall out of suspension, it is difficult to redistribute the particles because they tend to clump together. Thus, printing MICR characters with ink jet technology printers has not yet proven to be commercially feasible. The above-mentioned thermal ink jet MICR printer attempts to overcome these problems by making magnetic ink characters more efficient. By properly orienting the magnetic particles in the formed character on the recording medium, the magnetic properties can be theoretically maximized. As a result, less mass of magnetic particles may be required per character to produce a desired magnetic signal. Yet, no commercially successful magnetic particle orientation ink jet printers are available. Apparently even with optimizing the magnetic particle orientation, it is difficult for an ink jet printer to produce a magnetic ink character with the proper magnetic qualities.

Another problem with magnetic ink printing, especially for ink jet printers, is that it is difficult to maintain the proper mixture of the liquid magnetic ink solution, as the heavy magnetic particles tend to settle. A similar problem with ink having large and heavy pigment particles has led to the development of devices to agitate the ink wells storing the ink to be printed. These separate agitators, however, require additional parts that increase the expense, and reduce the reliability, of the device. Further, a thicker or more viscous magnetic ink solution may be utilized to reduce the amount of settling. This produces printing problems, however, especially with ink jet printers. For example, the viscosity of magnetic ink that one patent purportedly claims can be jetted through a thermal magnetic ink jet printer is on the order of 0.04 poise (P) or less, which equals 4 centipoise (cP) or less. Poise is a unit of dynamic viscosity of a fluid in which there is a tangential force of 1 dyne per square centimeter resisting the flow of two parallel fluid layers past each other when their differential velocity is 1 centimeter per second per centimeter of separation. No such thermal ink jet printer, however, has ever been seen commercially.

Thus, a solution to the above problems is desired to produce an economical, reliable ink jet printer capable of producing MICR images.

Summary of the Invention

To solve the problems of the prior art, an embodiment of the present invention introduces an ink jet printing device that includes a movable carriage and an ink jet print head disposed on the carriage, wherein the print head comprises a piezo electric element capable of jetting magnetic ink having a viscosity of more than 4 centipoise (cP), preferably at least 6 cP, onto a recording medium to facilitate scanning by MICR equipment. According to another embodiment, an ink jet printer system of the present invention includes the above ink jet printing device and further includes a computer in communication with the carriage to perform a print monitor function to insure the magnetic materials remain suspended by monitoring the movement of the carriage and initiating a predetermined carriage movement after sensing a predetermined idle time.

The present invention also provides a method for agitating an ink reservoir in an ink jet printer system to insure the magnetic materials in the ink contained within the reservoir remain suspended, wherein the method includes at least providing a movable carriage, disposing the ink reservoir on the carriage, sensing a predetermined idle time of the carriage, and moving the carriage upon sensing the predetermined idle time. Accordingly, MICR printing can be performed effectively and economically without any drawbacks often associated with the aforementioned prior art.

Brief Description of the Drawings Fig. 1 is a perspective view, with portions removed for clarity, of a typical ink jet printer of the present invention;

Fig. 2 is a cut-away side view of the ink jet printer of Fig. 1 ; and Fig. 3 is a perspective view of an ink jet printer system that includes an ink jet printing device connected to a computer for performing a print monitor function.

Detailed Description of the Invention

According to the present invention, an ink jet printing system for magnetic ink character recognition (MICR) printing comprises a print head advantageously utilizing a piezo electric element for generating ink droplets. The piezo electric ink jet head successfully jets solvent-based ink comprising magnetic materials (magnetic ink) onto a recording medium to facilitate scanning by MICR equipment. The ink is delivered to the print head from an ink supply reservoir. The ink jet printing system of the present invention facilitates efficient delivery of the magnetic ink to the piezo electric print head by agitating the ink supply, which advantageously keeps the magnetic materials in solution. Additionally, the ink jet printing system comprises an ink supply reservoir formed to enhance the ability of the system to keep the magnetic materials in suspension. Finally, the ink supply reservoir is advantageously keyed to the carriage to ensure secure mounting.

Referring to Figs. 1 and 2, one example of an ink jet printer system 10 utilized in the present invention comprises an ink jet print head 12 and ink supply reservoir 14 removably mounted to a carriage 16. Carriage 16 translates on guide rails 18 from one end of housing 20 to the other. Carriage 16 is adjacent to and moves parallel to rotatable wheels 22 that feed recording medium 24, such as paper, into printer system 10. During the printing operation, droplets of ink are jetted from the translating ink jet print head 12 onto recording medium 24. Wheels 22 rotate to move recording medium 24 to enable print head 12 to jet ink onto the recording medium.

According to an advantageous feature of the present invention, a piezo electric ink jet print head is provided. The piezo electric head beneficially allows solvent- based inks with suspended magnetic materials or pigments to be efficiently jetted onto the recording medium to form images that may be read by MICR equipment. Conventional ink jet heads, such as thermal heads, purportedly are only able to jet ink having a viscosity of less than about 4 centipoise (cP). The piezo electric ink jet head, however, unexpectedly allows the successful jetting of ink having a viscosity of up to about 19 cP. By providing for the use of high viscosity ink of up to about 19 cP, the piezo electric head advantageously allows the magnetic ink to comprise a larger mass of magnetic particles. In turn, the images formed with this higher viscosity ink are able to better sustain a stronger magnetic field that increases the recognition of the images by MICR equipment.

The piezo electric print head generates ink droplets by positioning a piezo crystal in the print head. Magnetic ink in a channel within the print head is broken up into droplets by a controllable vibration of the piezo crystal. The droplets are expelled from the channel and onto the recording medium to form an image. The image is typically in the pattern of industry recognizable E13B and CMC7 fonts to facilitate recognition by MICR equipment. A suitable example of a piezo electric print head includes the PIEZO JET^® 64 ink jet print head manufactured by Xaar Limited. A suitable printer that may be modified for use in the ink jet printer system of the present invention includes commercially-available printers such as the ADDMASTER™ K60 printer The magnetic materials in the solvent-based ink generally comprise ferrous materials, such as iron oxide particles. One skilled in the art, however, will recognize that other materials capable of being magnetized may be utilized.

It has been found that an ink viscosity of about 6 cP or more is required to obtain the level of magnetic material necessary for MICR reading. As such, prior art ink jet heads, such as the thermal head, are ineffective at jetting such high viscosity inks. The present ink jet printer system enables reliable ink jet MICR printing by utilizing a piezo electric print head. Preferably, the present invention is able to utilize ink having a viscosity in the range of up to about 19 cP, more preferably about 4 - 19 cP, even more preferably about 6 - 10 cP, and most preferably 8 - 10 cP. Thus, MICR printing can now be performed effectively and economically with the present invention.

Additionally, the present invention synergistically combines the motion of the carriage with a print monitor function to insure the magnetic materials in the ink remain suspended. One problem with inks having high viscosity is that the heavier materials in the ink tend to settle to the bottom of their reservoir and clump together or attach to each other. This problem is particularly true in pigmented inks with large pigment particles. The ink reservoirs for pigmented inks are typically located away from or off-board the print head, as opposed to being directly adjacent to the print head as in some ink jet applications, because pigmented inks are typically used in large format print heads that require a large amount of ink. The off-board reservoirs for pigmented inks thus are typically agitated mechanically, such as through a shaking mechanism, or through an ultrasonic device to keep the heavy particles from settling. The settling and clumping together of the particles causes the printer to clog up. Additionally, the settling of the heavy particles may cause the printer to print with ink that contains less than the desired amount of particles. Thus, the synergistic combination of the carriage motion and the print monitor function of the present invention maintains the heavy magnetic particles in suspension.

This synergistic combination works as follows. The ink reservoir of the present invention is preferably mounted adjacent to the print head, and preferably contains from about 10 cc to 50 cc of magnetic ink. The normal motion of the print head during printing helps to keep the magnetic materials suspended in the ink solution. The print monitor function, however, monitors the motion of the print head and determines when extra movement is required to keep the magnetic materials in suspension. When the print monitor determines that extra movement is required, then it is able to control the carriage movement to agitate the magnetic materials in the magnetic ink. Referring to Fig. 3, according to one embodiment of the present invention, the print monitor function is performed by a computer 30 that is electronically connected to the ink jet printer system 10. Computer 30 has memory 32 and processor 34 for respectively storing and performing operations on electrical signals representing data and software programs. Suitable examples of computer 30 include personal computers, processors, microprocessors, hard- wired processors or controllers such as a programmable logic unit, servers, mainframe computers, and computer workstations. Further, computer 30 may be a separate component or integral with ink jet printer system 10, such as a processor or controller mounted within the printer. In particular, computer 30 includes monitoring software and/or hardware 36 for monitoring the movement of the printer carriage and initiating a predetermined carriage movement to shake up the ink after a predetermined idle time. For example, the print monitor function tracks when the printer has been idle. After a predetermined idle time, the print monitor function automatically instructs the carriage carrying the print head and ink reservoir to move a predetermined length in a predetermined agitation time for a predetermined number of strokes to shake up the ink and insure the magnetic particles are in suspension. For example, the predetermined idle time may be as long as about 10 - 15 minutes, after which the carriage may be moved over about a 2 - 3 inch length in about 1 - 5 seconds for up to about 10 - 12 strokes. As may be appreciated, however, that the predetermined idle time, the length and timing of the carriage movement, and the number of strokes may vary depending on the characteristics of the ink being utilized. Further, as may be appreciated, the print monitor function and agitation of the ink may not be required for some inks. Thus, the present invention advantageously monitors the movement of the print head and ink reservoir and imparts energy to the magnetic ink to insure the magnetic materials are kept in full suspension.

Further, magnetic ink reservoir 14 preferably comprises a cartridge that keys into carriage 16 and fluidly connects to print head 12. The cartridge is formed with a special keyed portion that matches with a keyed portion on carriage 16. The keying of the cartridge to carriage 16 insures proper positioning of the cartridge for the proper functioning of the system. The keying also insures that the outlet from ink reservoir 14 is properly connected to the inlet to the ink channel in print head 12. As is well known in the art, the cartridge may be injected molded plastic with a interior cavity holding a plastic bag that contains the ink. The interior cavity of the cartridge is advantageously formed to enhance the suspension of magnetic materials in the ink. For example, the interior cavity may have a substantially a long, shallow, concave bottom portion that facilitates the dispersion of magnetic materials in the ink. Compared to typical cartridges which are tall, deep, square-bottomed containers, the shallow depth of the cartridge of the present invention does not allow the magnetic materials to separate as far from the rest of the ink solution. Because of the reduced separation between the ink solution and the magnetic materials, the present invention allows for higher viscosity magnetic inks to be used in ink jet printing of MICR readable images.

Although the invention has been described with reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be apparent to one skilled in the art and the following claims are intended to cover all such modifications and equivalents.

Claims

ClaimsWhat is claimed is:

1. An ink jet printing device, comprising: a movable carriage; and an ink jet print head disposed on said carriage, said print head comprising a piezo electric element adapted to jet an ink having a viscosity of more than about 4 centipoise (cP).

2. An ink jet printing device as recited in claim 1 , wherein said ink is a magnetic ink.

3. An ink jet printing device as recited in claim 1 , wherein said ink has a viscosity of at least 6 cP.

4. An ink jet printing device as recited in claim 1 , further comprising an ink reservoir in communication with said print head, said ink reservoir disposed on said carriage and containing said ink; and said ink reservoir having a shallow, concave bottom portion that facilitates the dispersion of said ink.

5. An ink jet printer system, comprising: a movable carriage; an ink jet print head disposed on said carriage, said print head comprising a piezo electric element adapted to jet an ink having a viscosity of more than 4 centipoise (cP); and a computer in communication with said carriage for monitoring the movement of said carriage and initiating a predetermined carriage movement after sensing a predetermined idle time.

6. An ink jet printer system as recited in claim 5, wherein said predetermined carriage movement comprises a predetermined length of movement for a predetermined time for a predetermined number of strokes.

7. An ink jet printer system as recited in claim 5, further comprising an ink reservoir disposed on said carriage and containing said ink.

8. An ink jet printer system as recited in claim 5, wherein said ink comprises magnetic particles.

9. An ink jet printer system as recited in claim 7, wherein said ink comprises magnetic particles.

10. An ink jet printer system as recited in claim 5, wherein said ink has a viscosity of at least 6 cP.

11. A method for agitating an ink reservoir in an ink jet printing device, comprising: providing a movable carriage; disposing the ink reservoir on the carriage; sensing a predetermined idle time of the carriage; and moving the carriage upon sensing the predetermined idle time.

12. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 11 , wherein moving the carriage comprises moving the carriage a predetermined length.

13. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 12, wherein the moving the carriage the predetermined length is accomplished in a predetermined amount of time.

14. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 11, wherein the ink reservoir is for containing ink for ink jet printing.

15. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 14, wherein the ink comprises magnetic particles.

16. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 14, wherein the ink has a viscosity of more than about 4 cP.

17. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 14, wherein the ink has a viscosity of about at least 6 cP.

18. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 14, wherein the ink comprises a magnetic ink with a viscosity of more than 4 centipoise.

19. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 11, further comprising disposing a print head on the carriage and adjacent to the ink reservoir.

20. A method for agitating an ink reservoir in an ink jet printing device as recited in claim 19, wherein the print head comprises a piezo-electric element.