MXPA99010871A

MXPA99010871A - Rasqu cleaning system

Info

Publication number: MXPA99010871A
Application number: MXPA/A/1999/010871A
Authority: MX
Inventors: F Sawicki Paul; P Premnath Karai; R Woodarek Thomas; J Tannascoli Robert
Original assignee: Tosoh Corporation
Priority date: 1994-03-10
Filing date: 1999-11-24
Publication date: 2000-10-01

Abstract

The invention relates to an improved system for cleaning the nozzle face of an ink jet print head using the cleaning action of a flexible doctor blade. A scraper assembly is located in a cleaning station of a printer. The printhead, in one mode, is mounted on a carriage, which is moved to a cleaning station. The doctor blade projects towards the path of the print head. The blade assembly moves along the face of the nozzle by cleaning the path so that the distal end of the blade is deflected, or bent away from the face of the nozzle. During the cleaning action, the distal end of the blade assumes a position, which is almost parallel to the face of the nozzle. When the wiper cleans the printhead, at the end of a cleaning action, the distal end is quickly unfolded by ejecting or "flying" the ink waste collected on a pickup member positioned to capture the "splashed" ink. The rapid expulsion of the ink results in the removal of approximately 95% of the waste ink in a modality

Description

SCRAPER CLEANING SYSTEM BACKGROUND OF THE INVENTION The present invention relates to a cleaning operation performed on an inkjet print head and, more particularly, to an improved doctor blade cleaning assembly, which includes a blotter paper member and a flexible scraper. An ink jet printer of the so-called "drop-on-demand" type has at least one print head, from which the drops of ink are directed towards a recording medium. Within the print head, the ink may be contained in a plurality of channels, and energy pulses are used to cause the ink droplets to be ejected, as required, from the nozzles at the ends of the channels. In a thermal inkjet printer, the energy pulses are usually produced by resistors, each located in one of the respective channels, which are individually steerable by current pulses to momentarily heat and evaporate ink in the channels that are in contact with the resistances. It has been recognized that there is a need to maintain the ink jet ejection or ejection holes of REF .: 31400 an inkjet printer, for example, cleaning them periodically or cleaning the nozzles when the printer is in use. A print head cleaning system typically includes a single or double doctor blade made of an elastomeric material. The U.S. 5,339,102 shows in FIGURE 1 a double doctor blade arrangement. As described in that patent, a maintenance station 28 is positioned outside the printing zone 10. The print cartridge moves towards the maintenance station in a direction parallel to the scan axis of the print head. The face of the nozzle of the print head is first cleaned by the scrapers; the print head is then moved to a cover assembly, where the nozzle face of the print head is placed in a sealing coupling with a cover 46. The priming operations can then be carried out using the vacuum pump 58 connected to the top. The U.S. 5,489,927 discloses a relatively hard, thin doctor blade with a defined modulus of elasticity range. The operation of the scrapers results in the accumulation of residual ink and paper particles that must be removed periodically. The removal methods include various release and collision systems. For example, U.S. Patent No. 5,555,461 discloses an automatic cleaning scraper system where the cleaned ink from the face of the print head passes through slots on the edge of the blade to be absorbed at the lower edge by means of a cleaning pad. U.S. Patent Nos. 5,559,539 and 5,659,341, both disclose a wiper system where the squeegee moves from a retracted position to one where the distal end of the squeegee traverses the nozzle face of a printhead. U.S. Patent No. 5,610,641 discloses a blade cleaning system for cleaning a multi-color print head. The blade is divided into segments corresponding to two grouping of color nozzles. Each segment is cleaned with a cleaning contact force appropriate for that color. A preferred collection system includes a device similar to a blotting paper, which comes in contact with the edge of the doctor blade and transfers ink and accumulated paper particles to the blotting paper through capillary action. For those systems that use a blotting paper, a continuous problem is the obstruction of the blotting paper due to the accumulation of non-volatile waste, ink. The ink transferred to the blotting paper from the doctor blade resides in the pores of the blotting paper. The evaporation of the volatile compounds in the ink partially renews the blotting paper, but over time, the non-volatile compounds accumulate on the blotting paper, rendering it useless. In addition, the accumulation of non-volatile residues is more prevalent in the contact surface of the blotting paper. A tar build-up on the contact surface of the blotting paper further acts to prevent the underlying volume or body of the blotting material from participating in the ink removal activities.

BRIEF DESCRIPTION OF THE INVENTION According to the invention, a scraper cleaning assembly is located in a maintenance station of an ink printer. The assembly includes at least one scraper made of a material which provides a high degree of elasticity. An ink jet print head is moved from a printing station to the maintenance station, and is placed in a cleaning position. The scraper cleaning assembly moves through the face of the printhead nozzle, so that the blade comes into contact from a position in the initial free state and further begins to clean the face of the nozzle. Due to the elastic nature of the • blade, the blade deflects or bends almost 90 ° from its position in free state. When the scraper cleans the face of the nozzle after a thorough cleaning action, the blade quickly returns to its initial free state by rapidly passing the accumulated cleaned ink to the cleaning end in a direction approximately normal to the print head or scanning direction. The ink is directed, or projected, onto a surface of the ink collecting member, in a preferred embodiment, a blotting paper comprising sintered polypropylene comprises porous sintered polypropylene. Optimal beam parameters are provided, such as the etro dura, Young's modulus of elasticity, free beam length and cleaning speed. More particularly, the present invention relates to the scraper cleaning system for cleaning ink residues from the nozzle face of an ink jet print head placed in a cleaning station, the system comprising: a scraper having a modulus of elasticity of between 500 and 2000 psi (3447.35 and 13789.4 kPa) a movable scraper mounting member for securing the scraper in a vertical cleaning position, means for moving the mounting member along a path of cleaning at a pre-set cleaning speed, starting at a distal end of the doctor blade in contact with the nozzle face, causing the distal end to bend away from the nozzle face, such movement means controlling the movement of the assembly, so that the face of the nozzle of the print head is cleaned by the distal end bending creating an accumulation of ink residue at the end of the istal and an ink collecting member positioned at one end of the cleaning path, to capture ink residues, which are ejected from the distal end of the doctor blade after finishing the cleaning contact between the blade and the face of the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic front elevational view of a partially shown inkjet printer having a doctor blade cleaning system of the present invention. FIGURE 2 is a perspective view of an end of the maintenance station shown in FIGURE 1, showing a prior art wiper assembly of a cleaning cycle. FIGURE 3 is a perspective view of an end, showing the cleaning action of the blade through the face of the nozzle of the print head. FIGURE 4"is a perspective view of one end, showing the doctor blade cleaning the face of the print head and ejecting ink residues towards a collection member • FIGURE 5 is a perspective view of an end, which shows the cleaning blade at the end of a cleaning cycle.

DESCRIPTION OF THE INVENTION FIGURE 1 shows a front elevation view of a thermal ink jet printer, which incorporates the blade cleaning system of the present invention. The printer shown is exemplary only, and the invention can be practiced in other types of ink ejection printing systems, including, but not limited to, piezoelectric ink jet printers. The printer 10 shown in FIGURE 1 has a print head 12, shown in dotted lines, which is fixed to the ink supply cartridge 14, and projects beyond the housing of the cartridge. The cartridge is removably mounted on the cartridge 16, and can be translated back and forth on guide rails 18 as indicated by the arrow 20, so that the print head and the cartridge move concurrently with the cartridge. car. The print head contains a plurality of ink channels (not shown), which end in nozzles 22, on the face of the nozzle 23 (both shown in dotted lines) and convey ink from the cartridge to the ejection or ejection nozzles of the ink jet. respective ink 22. When the printer is in the printing mode, the carriage moves or oscillates back and forth through and parallel to the printing area 24 (shown in dotted lines) and is ejected or ejected selectively ink droplets (not shown) on demand from the nozzles of the print head on a recording me (not shown), such as a paper, in the printing area, to print information about it at one width at a time. During each pass or translation in a direction of the carriage 16, the recording me is stationary, but at the end of each pass, the recording me advances slowly in the direction of the arrow 26 the distance from the height of a printed area as width. For a more detailed explanation of this type of printhead, and therefore printing, refer to the description of U.S. Patent Nos. 4,571,599 and Re. 32,572, both incorporated herein by reference. On one side of the printer, outside the printing zone, there is a maintenance station 28, which includes, at least one blade cleaning assembly 30. The maintenance station may also include additional assemblies, including a mounting assembly. cover 31, where the face of the nozzle of the print head can be "protected" during "intervals without printing. An exemplary maintenance station, which includes a cleaning assembly and priming and protection assemblies, is described, for example, in the U.S. 5,555,461. The blade cleaning assembly 30, shown schematically, consists of a doctor blade 32 mounted on a movable member 34, and an ink collecting member 35. Additional details of the assembly 30 are shown in FIGURE 2. FIGURE 2 is a side view of one end of the maintenance station 28 following the movement of the carriage 16 towards the maintenance station, to place the face of the nozzle 23 in a cleaning position. It should be understood that a cleaning operation of the print head is periodically allowed by the system controller, not shown, but conventional in the art, typically at the end of a printing operation. The movable member of the blade 34 is mounted on a rack and pinion device 36, driven by a motor 38, which is operated in a conventional manner by the signals of the system controller. When the print head is in a cleaning position, the device 36 is actuated, moving the member 34 and the blade 32 in the direction of the arrow 40. The collision member 35, mounted on a fastener 42, is aligned with the blade 32 to capture the cleaned ink from the face of the nozzle 23 and expelled therefrom as will be seen. As stated above, the doctor blade 32 is made of a material with a high degree of elasticity. In a preferred embodiment, the blade 32 is made of a polyurethane ester and has the dimensions of 11.0 mm (height) x 1.0 mm thickness (t) x 10.0 mm (length towards the page). The blade is constructed in a preferred embodiment, with a durómetrb value of 75 +/- 5 Shore A; a Young's modulus of elasticity of 750 psi (5171.025 kPa) and a free length FB of 5.0 mm. Those features provide the blade 32 with a high degree of. flexibility in relation to the prior art scrapers for reasons that will become apparent later. Referring now to FIGURE 3, the doctor blade member 34 has been moved toward the direction of the arrow 40. The distal end 44 of the blade 32 is in contact with the face of the nozzle 23, is bent almost parallel to the face of the the mouthpiece The cleaning action is carried out from right to left in FIGURE 3; for example, in the direction of arrow 40. When the blade continues to move through • the face of the nozzle at a cleaning speed, in a preferred embodiment, 5.0 inches / second (12.7 centimeters / second), the distal end 44 collects an accumulation of ink and other non-volatile contaminants. FIGURE 4 shows the doctor blade cleaning the edge 12B of the print head 12. The blade 32 rapidly bounces back to its upright position in the free state, causing the ink residue 60 to be ejected from the distal end 44 in a direction approximately normal to the initial vertical orientation of the scraper. The debris is sprinkled on, and rapidly absorbed in the collection member 35, which, in a preferred embodiment, is a blotting paper consisting of porous sintered polypropylene. In a real experiment with the preferred blade characteristics and cleaning speed described above, it was found that 96% of the residual ink was removed from the distal end and deposited on the collection surface. The ink that "mocks" the collection surface is deposited by gravity in a collector 50. FIGURE 5 shows the blade at the end of a cleaning mode. As an additional feature, the pickup member 35 is positioned so that the distal end 44 of the blade 32 is in contact with a lower portion of the member 35. This performs a further removal of any ink residue that may still be retained on the distal end. At the end of the cleaning cycle of the cleaner, the carriage 16 can be moved back towards the printing area. The motor 38 is operated to reverse the movement of the rack gear 36 and to return the blade member 34 to its initial location. A spring-loaded mechanism may also be used to retract the cleaner toward its initial location. It will be appreciated from the foregoing description that the projection of the residual ink on the surface of the collection member is a function of the elasticity of the doctor blade and the additional kinetic energy imparted at the end of the cleaning cycle or function of the cleaning speed. In an alternative embodiment, the scraper assembly could be mounted with the print heads moving along. This would not be as effective as the preferred embodiment, since the kinetic energy of the mobile doctor blade would be absent. The characteristics of the blade 32 are chosen to provide the necessary flexibility to provide the necessary and normal splash action to the travel path. Other materials that are useful include Polyurethane Ether, Viton Polyethylene, Ethylene Diene Monomer and Propylene (EPDM). A range of durometer values is 65 Shore A at 85 Shore A; a range of Young's modules of elasticity is 500 to 2000 psi (3447.35 to 13789.4 kPa); the cleaning speed can fluctuate from 3 ips to 8 ips (7.62 cps at 20.32 cps); the interference between the print head and the blade is 2.75 to 1.25 mm. The harvest member 35 comprises an absorbent material which, in addition to the propylene, may include another material such as sintered stainless steel; polyurethane, silicone foams, felts which allow residual ink to penetrate the body of the member. The member would preferably be used until near saturation. Additional variations, consistent with the principles of the invention, include the use of multiple doctor blades to clean multiple nozzle faces in, for example, a color printer, which utilizes two or more print cartridges. Each blade would eject residual ink on any separate collection members or on different portions of an extended common collection member. It will be appreciated from the foregoing teachings that those skilled in the art can make various alternatives, modifications and variations or improvements, which are intended to be encompassed by the following claims. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property.

1. A wiper cleaning system for cleaning ink residues from the face of a nozzle of an ink jet print head, placed in a cleaning station, the system characterized in that it comprises: a scraper having a modulus of elasticity of between 500 and 2000 psi (3447.35 to 13789.4 kPa), a movable scraper mounting member for securing the scraper in a vertical cleaning position, means for moving the mounting member along a cleaning path at a pre-set cleaning speed , starting at a distal end of the doctor blade in contact with the face of the nozzle, causing the distal end to bend away from the face of the nozzle, the moving means controls the movement of the mounting member, so that the face of the nozzle of the print head is cleaned by the folded distal end, creating an accumulation of residual ink at a distal end and a placed ink collection member at one end of the cleaning path to capture the residual ink that is ejected from the distal end of the doctor blade after finishing the cleaning contact between the blade and the face of the nozzle.

2. The system according to claim 1, characterized in that the cleaning speed is between 3 and 8 inches / second (7.62 and 20.32 centimeters / second).

3. A scraper cleaning system for cleaning ink residues from the face of a nozzle of an ink jet print head, placed in a cleaning station, characterized in that it comprises: a scraper mounting member having a surface of assembly; an elastic doctor blade mounted to the mounting member extending in a cleaning direction generally perpendicular to the mounting surface; means for moving the mounting member to cause a distal end of the doctor blade to assume a cleaning position during contact with the face of the nozzle, which is substantially parallel to the face of the nozzle and an absorbent collection member aligned with the doctor blade and positioned at one end of the displacement of the mounting member to capture the residual ink ejected from the distal end after finishing the cleaning contact between the blade and the face of the nozzle of the print head.

4. A scraper cleaning system located in an ink jet print head maintenance station having a print head with nozzles on one side of the nozzle, the scraper cleaning system is adapted to clean waste from the ink jet. Ink from the face of the nozzle of the print head during a cleaning period, the doctor blade cleaning system is characterized in that it comprises: an ink waste collection member, a doctor blade assembly, means for providing relative movement between the printhead and doctor blade assembly, the doctor blade assembly includes at least one flexible doctor blade having a distal end for collecting ink residues during the cleaning contact with the mouthpiece face, the distal end projects into the path of the doctor blade. the printhead during relative movement causing the distal end to bend to a position approximately parallel to the to face the • nozzle, so that, after finishing the cleaning contact between the blade and the face of the print nozzle, the blade is quickly returned to a free state that ejects cleaned ink residue from the face of the nozzle and over the surface of the collecting member. The system according to claim 4, characterized in that the blade is made of a material having a Young's modulus of elasticity of between 500 psi and 2000 (3447.35 kPa and 13789.4). 6. The system according to claim 4, characterized in that the distal end extends towards the path of the print head a distance between 2.75 and 1.25 mm. The system according to claim 4, characterized in that the print head is moved along a fixed doctor blade assembly. The system according to claim 4, characterized in that the scraper assembly moves along a stationary printhead. 9. An ink jet printer, characterized in that it includes: an ink jet cartridge including an ink supply fluidly connected to a print head having a plurality of nozzles for ejecting or ejecting ink from the face of an ink jet. nozzle, a carriage for bidirectionally moving the cartridge during a printing mode and towards a cleaning station during a cleaning mode, an ink collecting member, a scraper cleaning assembly for mounting the nozzle face of the nozzle head, printing, the cleaning assembly comprises at least one flexible doctor blade mounted on a support for projecting a distal end of the doctor blade toward the path of the nozzle face of the print head, means for providing relative movement between the nozzle face of the print head and the doctor blade at a cleaning speed, the doctor blade is deflected towards an orientation which is approximately equal The nozzle faces the face of the nozzle, so that, after finishing the cleaning contact between the blade and the face of the nozzle of the print head, the blade is quickly returned to a free state by ejecting the cleaned ink residues from the print head. the face of the nozzle on the surface of the collecting member. The system according to claim 9, characterized in that the blade is made of a material having a Young's modulus of elasticity of between 500 psi and 2000 psi (3447.35 kPa and 13789.4 kPa). 11. A method for cleaning the face of a nozzle of an ink jet print head, characterized in that it includes the steps of: moving the print head toward a cleaning station; moving an elastic doctor blade across the face of the nozzle at a preset speed and along a preset cleaning path, such that a distal end of the doctor blade bends away from the face of the nozzle, whereby the end distal accumulates ink residues from the nozzle face and places an ink collection member at the end of the cleaning path, so that ink residues expelled from the distal end, when the doctor blade unfolds, are captured and absorbed in the collection member. The method according to claim 11, characterized in that the pre-set speed is between 3 inches / second and 8 inches / second (7.62 centimeters / second 20.32 centimeters / second). The method according to claim 11, characterized in that it includes the additional step of moving the distal end of the doctor blade in contact with the collection member to remove any residual ink remaining from the distal end.