GB2238510A - Absorbent sheets for cleaning and absorbing ink from ink-jet printheads - Google Patents

Abstract

An absorbent sheet is passed through the paper-feed of an ink-jet printer to clean and absorb ink from the print-head at the printing station. As described, such a sheet is employed during start-up routines (to absorb ink ejected during purge of the nozzles). The thickness of the sheet is such as will ensure contact with the nozzles at the printing station (while not being too thick to be transmitted by the paper feeding mechanism) so that wiping of the nozzles takes place as the sheet is transported past the printhead. As described (Fig 3) a backing (paper) (32) has adhered thereto by an adhesive (40) a plurality of strips of absorbent foam (36) which are overlaid by fabric (clean-room lint free fabric) (38). The sheet may bear distinguishing indicia which may be read by a sensor on the printer. <IMAGE>

Description

HEAD TENDING MEDIA AND SYSTEM FOR AN INK JET PRINT HEAD BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ink jet printers, and particularly to a head tend media and system for performing head tend operations sucii as cleaning or purging the print head on an ink jflt printer.

2. Description of Related Art Typical ink jet printers include a print head which is provided with a plural try of orifices. As the print head moves back and forth over the surface of a print media, ink is expelled through the orifices, or jets, and onto the print media at appropriate intervals to print the desired character or graphics. Proper operation of such a printer depends on a uniform and predictable flow of ink through the orifices.

Otherwise, the character or graphic being printed may have gaps, skips. or other flaws in areas printed by a faulty orifice.

One cause of faulty orifice operation is the prosence of contaminants within the orifice, the ink supply channel leading to the orifice, or on the face of the print head which restrict or obstruct the flow of ink through the orifice. Arcordingly, to ensure reliable operation of ink jet printers, it is necessary to keep the face of the print head, the orifices, and tl1e supply channels free of paper dust, stray ink droplets, or other extraneous and undesirable material.

Bubbles within the ink supply channels can alsn result in restricted or intermittent ink flow through the orifices.

Therefore, occasionally it may be desirable to purge ink from the print head in order to prime the orifices and eliminate any bubbles which may he present in the ink supply cioaniiel . Purging can also be used to expel old or unwanted ink, or o'--tier debris from toe supply channels and oriflces. however, during a purge operation, it is important to collect the expelled ink to prevent it from collecting on the face of the print head or 011 other parts of the printer.

Similarly, in solid ink printers, when the print head is warmed up to operating temperature, ink is frequently discharged from the head as a result of natural expansion. In order to prevent contamination resulting from discharged ink collecting on the print head or other parts of the printer, any discharged ink should be quickly collected and removed from the printer.

Otherwise, if ink is allowed to collect, it may one into contact with the print media producing smudges or other undesirable marks. Further, if the ink is allowed to solidify within the printer, the solidified ink may break off producing particles of solidified ink which can plug an orifice, jam moving parts of the printer, or impede performance of the printer in some other fashion.

To alleviate the problems associated with contamination and ink build up on print heads several head tend device and systems have been developed. For example, a variety of mechanisms for mechanically wiping print heads are available. A number of these wiping systems use a nonabsorbent wiper, such as a re1bber disc or a steel knife edge, which is wiped across the face of the print head to remove accumulated dirt or ink. However, because the wiping element is nonabsorbent, these types of system are not adequate for collecting and removing the quantities 1f ink which are typically released during purge and warm up operotions.

Further, the nonabsorbent wiping element has only limited cleaning capabilities.

Other head tend systems have used absorbent witting elements.

Typically sush systems include a spool of absorbent ribbon or tape whiclo is moved across the surface of tie print head.

However, a printer using such a system must be provided with a drive system for moving the tape and maintaining prcper tape tension and position. As a result of the additional moving parts necessary for the drive system, the cost, reliability, and size of the printer are adversely affected. Further, because the wiping media is typically stored on spools, or within cartridges, the wiping media is typically relatively small and hin. As a result, the amount of ink which can be absorbed by the small, thin wiping media is inherently limited.

Another head cleaning system utilizes a cleaning card and a card guide. The cleaning card has a solvent satura'-ed foam strip attacked near its bottom edge. The card guide is attached to the print head a,0d is adapted to receive the card. Tloe card guide is positioned such that as the card is manually inserted therein, the foam strip is pressed against the surface of t1n print head releasing some of the solvent and wiping the bead. A drainage system is provided to drain the released solvent frr m the print head.

however, because the foam strip is relatively mall and because it is saturated with solvent, its absorbent capacity is limited. Further, the card guide and the solvent drainage system require the presence of additional hardware within the printer.

As with tloe systems described above, this additional hardware adds to the cost, size, and weight of the printer a1d may adversely affect the reliability and operation of tle printer.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved head tend media and system for time print head of an ink jet printer.

A further object of the invention is to providc a head tend media and system which reduces the necessity for hardware dedicated to feeding and manipulating the head tend media.

Another object of the invention is to provide a head tend media which is capable of absorbing and removing unwanted Ink from the printer.

Tn accordance with these niod other objects, thr present invention comprises a head tend media having a backing member dimensioned to be fed through the print media feed mechanism of a printer and a portion of absorbent material positioi ed on the hacking member to contact the face of the print lien' as the media is fed through tulle printer.

Other objects and aspects of the invention wil become apparent t^ those skilled in the art from the detailed description of the illustrated embodiment which is resented by way of example and not as a limitation of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 stows a partially cutaway view of a printer incorporating a preferred embodiment of the head tend media and system of the present invention.

Figure 2 is a front view of a preferred embodiment of the head tend media of the present invention.

Figure 3 is a cross sectional view of the head tend media taken along line 3-3 In Figure 2.

Figure 4 is a cross sectional view showing the relation between the print head, the vacuum belt, and a preferred embodiment of the head tend media of the present invention Figure 5 is a block diagram of a preferred warm up operation utilizing the bead tend media illustrated in Figures 3 and 4.

Figure 6 is a block diagram of a preferred purgn operation using the head tend media illustrated in Figures 3 and 4.

Figure 7 shows a print head purge mechanism in accordance with a preferred embodiment of the present inve .io,o.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT A printer with a head tend media and system in accordance with a preferred embodiment of the present invention is indicated in Figure 1 as reference numeral 10. The printer 1 is provided with a print head 12 mounted on a carriage 14. The carriage 14 is positioned in front of vacuum belt 16 and is later rally movable along guide rails 18.

During normal printing operations, rollers 20 remove one sheet of print media 22 at a time from tray 24 and feed the print media 22 to toe vacuum belt 16. Controller 26 controls movement of the vacuum belt 16 to advance the print media 22 past the print head 12, movement of the carriage 14 to move he print head 12 laterally across the surface of print media 22, rind activation of the print head 12 to release ink onto the print media 22 at the intervals necessary to print desired text or graphics.

A sensor 2R is mounted on the carriage in a fixed position relative to the print head 12. The sensor 28 is 0'. of a variety of sensors kocvn to those skilled in the art and is capable of detecting the presence or absence of print media 22. In this manner, the controller 26 can monitor the sensor 2P to accurately determine the top of form as the vacuum belt 1 r advances the print media 22 and the left and right edges of the form as the carriage 14 traverses the print media 22.

Prior to performing a head tend operation, the head tend media 30 is placed in the tray 24. During the head tend operation, the printers normal print media feed mechanism is used to feed the head tend media. That is, rollers 20 extract the head tend media 30 from the tray 24 and feed the head tend media 30 to the vacuum belt 16. The head tend media 30 is brought into contact with the print head 12 by advancement of the vacuum belt 16.

As seen in Figure 2, the head tend media comprises a hacking member 32 to which absorbent material 34 is attached. The backing member 32 is dimensioned to fit within the print media storage tray 24 and be fed through the normal feed path of the printer 10. Preferably, the backing member 32 has the same general dimensions as the print media 22. The backing member 32 must be flexihle enough to negotiate the bends in the paper feed path and strong enough to support the absorbent material 34.

Although any material meeting these specifications may be used for the backing member, the backing member in the illustrated embodiment is 20 lb. high speed copier paper. If desired, It is possible to print directions iristrncting the operator irow to use the head terra media directly oro the backing member 32.

The absorbent material 34 can be any material which absorbs

ink and Is sturdy enough2withstnnd contact with the print head 12 and movement through tire feed path of the printer lo.

Preferably, the absorbent material 34 is as lint free as possible so that it does not deposit contaminants either on the print head 12 or in tie printer 10.

As best seen In Figure 3, the absorbent material 34 of the illustrated embodiment has a layer of foam material 36 overlaid with a layer of absorbent fabric 38. In this manner, a wick-like effect is created by the more absorbent layer of foam material 36 which pulls ink from the absorbent fabric layer 38 and away from the print head 12. A number of materials suitable for the absorbent material are available and can be readily recognized by those skilled in the art. In the illustrated embodiment, the layer of foam material 36 is formed of polyurethane foam available from T. Burnett & Co. as type 5825 ad the absorbent fabric layer 38 is clean room lint free wipe available from Dupont under the name Sontara.

Tire foam material 36 is attached to the backiri r member 32 with a layer of Adhesive 4C. The adhesive 40 exteri Is beyond the boundaries of the foam material 36 to attach the fabric layer 38 to the backing material 32. In the preferred embodiment, there is no adhesive between the fabric layer 38 and the foam material 36 to iioloibit the free flow of ink from the fabric layer 38 to the foam material 36.Although a variety of adhesives are suitable for attaching the absorbent material 34 to the backing layer 32, in tlie illustrated embodiment a pressure sensitive adhesive available under the name Adchem 728 acrylic is used.

In order for the head tend media 30 to efficiently clean and wipe the print head 12 and absorb excess ink, it is desireable for the absorbent material 34 to be brought into intimate contact with the print head 12. As illustrated in Figure 4, this can be accomplished by choosing the thickness of the head tend media 30 such that, in the area of the absorbent material 34, It is slightly thicker than the gap between the print head 12 and the vacuum belt l, or print media support mechanism.In this manner, the absorbent material 34 is compressed as it is advanced past the print head lp. Thus, the elastic properties of the absorbent material press the surface of the absorbent material into firm, intimate engagement with the print head.

although the actual thickness of the absorbent material 34 may vary soobstantially depending on the type of material used and the 'hysica] configuration of toe print head 12 and printer 10, in the illustrated embodiment, the foam material 36 is approximately 0.64 millimeters thick and the fabric layer 38 is approximately 0.36 millimeters thick. When combined with the backing member 32 ajod the adhesive layer 40, this results in a total tloickness of approximately 0.047 inches.This combination has preen effective when used with the illustrated printer which has a gap of 0.040 incloses between the print head 12 and the vacuum belt 1.

The length and width of the absorbent material, as well as the position of tloe absorbent material on tloe backing member can also vary greatly depending on the physical configuration of the particular printer for which the media is to be used and the method in which the media is to be used. In general. the absorbent material should be large enough to cover tlie orifices on the face of the print head and to absorb excess ink. The absorbent material should be positioned such that it comes into contact with the print head when fed through krinter's normal print media feed path.

In the embodiment illustrated in Figures 2 and 1, the absorbent material 34 is distributed on the backing material in three horizontal strips 34a, 3dub, and 34c of approximately equal size. The strips 34a, 34b, and 34c have a width w slightly wider than the print head 10 and length 1 approximately twice as long as the height of the print head. In the illustrated embodiment w is approximately four inches and 1 is approximately one and one half inches. The strips 34a, 34b, and 34c are locatnd approximately one quarter of an incll apart and are qnnerally centered on the backing material.

This particular configuration is preferred for the head tend system employed in the illustrated printer and described below.

Ilcvever, it should be appreciated that in a different printer with a different head tend system it may be desireatle to distribute the absorbent material on the backing material in a different configuratioio. For example, it may be desireable to use one large piece of absorbent material or to use a number of different sized pieces of absorbent material.

The head tend system of the illustrated printer includes a warm up operation and a purge operation. Based on predetermined information regarding the configuration of the head tend media and information received from toe sensor 28, the controller 26 controls these operations. The warm up operation, which is represented In block diagram form In Figure 5, is initiated each time tloe printer 10 is turned oIl. Prior to turioliog the printer on, a head tend media 30 is placed in tloe tray 24. when the printer 10 is turned on, rollers 20 remove the top media from tray 24 and feed it to the vacuum belt 16. The vacuum belt 16 advances the media until it is detected by the sensor 28.Upon detection the top of form is determined. The carriage 14 then scans across te media to determine the actual left and right edges of the media.

In the illustrated embodiment, the head tend media 30 is provided with identifying marks 42, similar to a bar code, which distinguish the head tend media 30 from print media 22.

Detection of these marks 42 by tloe sensor 28 indicates the presence of tlo bead tend media 30 and the warm up operation continues. I f the macks 42 are not detected, the media is ejected fror the printer 10 and the controller 26 prompts the operator to load the bead tend media 30.

As explained in greater detail below, in addition to the identifying marks 42, the illustrated head tend media 30 is provided with a prior use indicating section 44 which, if blackened, indicates that tloe media 30 has been previously used for a purge operation. If the sensor 28 detects that the head tend media 30 has been previously used, the media 30 is ejected and toe operator is prompted to load a clean head tend media 30.

When the sensor 28 indicates the presence of a lean head tend media 30 within the printer lO, the print head 2 is centered within the top strip of absorbent material idea. Tlois is accomplished by advancing the vacuum belt 16 to move head tend media 30 a predetermined amount beyond the detected top of form and moving the print head 12 a predetermined distance from the detected edge of form. The predetermined distaiices are based on the known configuration of the head tend media 30.

Once the print head 12 is centered within the top strip of absorbent material 34a, the print head 12 is warmed ip. In the illustrated printer lO, this process takes approximately ten minutes. Dirilog tle warm up period the print head remains stationary. Ally iiil: expelled from the print head 12 during the warm up operation is expelled into the top strip of absorbent material 34a where it is quickly absorbed away from the print head 12. After the print head 12 has reached operating temperature the vacuum belt 16 is advanced and the head tend media 30 is ejected from the printer 10.

As the head tend media 30 is advanced, the print head 12 is wiped by the bottom half of the top strip 34a and the second and third strips 34b and 34c of absorbent material. In this manner any ink released durillg the warm up operation s immediately absorbed and removed from the printer and the print head is wiped to remove any accumulaterl debris or contaminants. vlsillg tulle illustrated head tend media, it has been found tloat efficient wiping is accomplished by advancing the media at a rate of approximately one i inch per second. however, the usn of different materials or a different configuration of the media may require a different wiping speed to obtain optimum results.

The purge operation, illustrated in the block diagram of Figure 6, is typically done immediately following the warm up operation to ensure that the ink supply channels and orifices are properly primed and free of any air bubbles or debris.

Additionally, the purge operation may be initiated by the operator at any time. For example, it may be desiieable to purge the print head after a certain number of hours of operation or if visual inspection reveals plugged or faulty orifice operation.

Whirr the purge operation is initiated, the next media in the tray 24 is removed by the rollers 20 and fed to the vacuum belt 16. The media is then advanced to detect top of form and the carriage 14 scans the media to detect the actual edge of form.

As with the warm up operation, during the scan the sensor 28 verifies that the media is had tend media 30 and that it has not been previously used for a purge operation. Once it has been determined that a cleats bend tend media 30 is present in the prltlter 10, the pt illt.er lo blakens the pr leo use iindicating section 44 to prevent use of the same head tend media during subsequent purge operations. The print head 12 is then centered within the second strip of absorbent material 34b and the print head 12 is purged.

During the purge, ink is forced from the ink reservoir 46 (seen in Figure 7), through the supply channels 48, and expelled out the orifices 50 where it is absorbed by the head tend media 30. The purge may be accomplished in a number of ways. In the printer In Illustreted in Figure 1, a purge pump 52 is provided.

As hest seen iI1 Figures 7 and 1, the pump 52 pumps air through a supply lie 54 and into a chamber 56 over the ink rerervoir 46 within tloe print head 12. This increases the air prrssure within the chamber 5r, and forces ink from the reservoir 46 i rota the supply channels 48 and out the orifices 50.

In the illustrated embodiment, the pump 52 Os a standard low flow, low pressure pulsating pump which supplies air qt ahout 1-2 psi . However, the air pressure within the clamber Sn is much lower as a result of air escaping through the overflrw lines 58 and the ink loading windows 60. During the purge opr.ration, the pump 52 supplies air to the chamber 46 for approximately seven seconds. In other embodiments it may be desireable io supply the air for a longer or shorter time depending upon the type of pump used, the pressure of the air supplied, and the physical configuration of the print head.

Following the purge operation, the vacuum belt 6 is advanced to eject the head tend media 30 from tloe printer 10. As the head tend media 30 advances, the print head 12 is wiped by tloe bottom of absorbent strip 34b and the entire absorbent strip 34c to remove any excess ink, debris, or contaminant: which may be present on top face of the print head 12. As in to he warm up operatioll, an advance speed of approximately oton inc'l per second load been found to provide satisfactory results.

In some cases it may be desireable to print a cnnfirmation message following the purge operation. In this mannor, the operator can inspect the printed message and verify that the purge operation was successful and that the print head is functioning properly. In the illustrated embodiment, this can be accomplished by stopping the advancement of the lead tend media following the wiping procedure and printing the control message on the bottom of the backing member 32 prior to ejecting the head tend media 30.

This detailed description is set forth onlv for ouroomes of illustrating

example of the present invention. while it is presently believed that this illustration is the be:t mode of practicing the invention, the detailed description should not be considered to limit the scope of the invention in any way.

Clearly numerous auditions, substitutions, and other modifications can be made to the invention without departing from the scope of the invention which is defined In the appended claims and egulvalents thereof.

Claims (10)

1. Media for tending a print head in an ink jet 1rinter, said media comprisitog: a backing member dimensioned to be fed through the normal feed path of the printer;

an absorbent material attached to the backing member such that the absorbent material is brought into contac with the print head as the media is fed through the printer

2. The media of claim 1 wherein the absorbent material comprises a layer of foam covered hy a layer of cloth.

3. The media of claim 2 wherein the backing material is provided with identification means for wallowing ths printer to identify the media.

4. The media of claim 3 wherein the identification means comprises marks on the backing media which can be detected by a top of form sensor provided in the sprinter.

5. A head tend media for use in an ink jet print during the warm up cycle in which the head is raised to operating temperature and the purge cycle in which ink is purged from the head, said head tend media comprising: a hacking member dimensioned to be fed through the normal print media feed path of the printer; and at least one cleaning strip attached to the backing member, said strip being made of ink absorbing material an,: positioned on the backing member such that the cleaning strip corns into contact with the print head when the head tend medo is advanced through the printer feed path.

6. The head tend media of claim 5 further corprising identification marks detectable by the printers top of form sensor to identify the media as a head tend media.

7. The head tend media of claim 6 further conprising a means for allowing the printer to determine whether the media has been previously used.

8. The head tend media of claim 5 wherein there are three cleaning strips.

9. A method of tending a head in an ink jet rrinter comprising the steps of: providing a head tend media having at least one section of absorbent material attached to a backing member, said head tend media being dimensioned to be fed through the normal feed path of the printer: loading said head tend media into the normal paper feed path of the printer;

feeding the head tend media using the normal paper advance mechanism of the printer to bring the absorbent material into contact with the head and to wipe the head with the absorbent material.

10. In an ink jet printer having a head, a tap of form sensor, and a form feed mechanism for advancing print media through the printer, a method of tending the head ccmprising the steps of: providing a head tend media, said head tend media having at least one portion of absorbent material attached to a backing member and being dimensioned to be advanced through the printer by the form feed mechanism, said absorbent material positioned such that it is brought into contact with the print head as the