JP2004034702A - Method for cleaning nozzle plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method, capable of reducing wear and a tear by a cleaning mechanism for a printing head, and sufficiently satisfying the demand for cleaning. <P>SOLUTION: The method for cleaning a printing head comprises the steps of using a solvent for loosening debris collected on a nozzle plate, brushing the nozzle plate, using a cleaning solvent for cleaning the plate, and eliminating the same by vacuum cleaning. The steps can be combined by use of a brush between the application of the single cleaning solvent and the vacuum cleaning. The motion of the solvent helps the brushing cleaning operation. Various steps can be executed according to a cleaning module having a relatively lateral motion with respect to a head. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an ink jet printing mechanism such as a printer or a plotter.
[0002]
More particularly, the present invention relates to a printhead cleaning mechanism.
[0003]
[Prior art and its problems]
Modern ink jet printing systems are used in a wide variety of equipment and applications, such as fax, color photographic printing, industrial applications, and the like. In these printing systems, ink, and possibly various color inks, is ejected from at least one array of nozzles located on a printhead onto an image receiving material.
[0004]
A known problem with ink jet printers is that the nozzles that eject the passing ink onto the image receiving material are blocked by clogging of the nozzles and the interior of the printhead. This renders the nozzle inoperable, resulting in poor printing or degraded image quality.
[0005]
To improve the clarity and contrast of printed images, recent work has focused on improving the inks used. Pigments used in inks have been developed to provide faster printing of darker blacks and sharper colors and less fade with water. These pigment-based inks have a higher solids content than the earlier dye-based inks. Both types of inks also dry quickly, which allows the ink jet printing mechanism to form high quality images.
[0006]
In certain industrial applications, such as making printing plates using ink jetting methods, inks have certain properties that cause certain problems. For example, there are UV curable inks that allow rapid curing of the ink by UV radiation after printing.
[0007]
The combination of small nozzles and quick-drying inks is sensitive not only to dry ink and small dust or paper fibers, but also to plugging the printhead with solids in the new ink itself.
[0008]
It is known to address or correct the problem of jams by protecting and cleaning the printhead in various ways. That is,
-Capping: when the printhead is not operating, it can be sealed from contaminants by a closing enclosure. This also prevents drying of the ink. The capping unit usually consists of a rubber seal placed around the nozzle array.
[0009]
-Spitting: The nozzles are cleared of clogs by periodically injecting drops of ink through each nozzle into a waste ink receiver, commonly called spitoon. This can focus on nozzles that are not used for some time, but usually all nozzles are activated during spitting.
[0010]
-Vacuum-assisted purging: During certain operations, especially in order to clean clogged or completely clogged nozzles, a printing cycle is started while a vacuum is applied outside the nozzles. This aids in nozzle cleaning and cleaning. Purging is typically done when the printhead is in the capping unit. This is because this unit provides a good seal around the nozzle array for creating a vacuum.
[0011]
-Application of solvent: The application of the solvent dissolves the ink residues and cleans the print head. For example, Patent Document 1.
[0012]
Wiping: Before and during printing, the ink jet print head is wiped and cleaned by using an elastomeric wiper to remove ink residues, paper dust and other impurities.
[0013]
-Various combinations for cleaning ink jet print heads are known.
[0014]
In Patent Document 2, wiping is performed in combination with vibration and application and removal of a solvent. This method particularly wears the nozzle plate due to contact and vibration due to the wiping action.
[0015]
In Patent Document 6, ink is released from a nozzle plate, and then the plate is brushed and wiped. Due to the wiping action, abrasion and peeling of the nozzle plate are severe.
[0016]
The system described in U.S. Pat. No. 6,037,086 uses only a longitudinal cleaning with an elastic columnar member and resiliently cleans the zigzag groove in combination with the nozzle portion. This gives unsatisfactory results and can further damage the printhead.
[0017]
These devices, designed to clean and protect the printhead, are typically concentrated at a service station mounted within the plotter's chassis, which moves the printhead over the station for maintenance. Can be. An example of such a service station can be found in US Pat.
[0018]
As explained above, cleaning actions that come into contact with the head, such as wiping, can cause considerable wear and tear of the nozzle plate. The special coating on the plate that renders the nozzle plate ink-repellent is susceptible to breakage, which often requires that the printhead be replaced. This is a significant expense.
[0019]
Another problem is that certain prior art cleaning methods do not fit well with any type of ink.
[0020]
There is a need to provide a cleaning method that reduces abrasion and stripping while at the same time being sufficient for cleaning requirements.
[0021]
So far, no satisfactory cleaning method has been provided.
[0022]
[Prior art]
[0023]
[Patent Document 1]
EP-A-1080909
[Patent Document 2]
US Pat. No. 6,241,337
[Patent Document 3]
US Pat. No. 6,193,353
[Patent Document 4]
US Pat. No. 6,164,754
[Patent Document 5]
US Pat. No. 5,864,348
[Patent Document 6]
US Pat. No. 5,557,306
[Patent Document 7]
US Pat. No. 4,340,897
[Means for Solving the Problems]
The advantageous effects described above are embodied by a method having the particular features described in claim 1. A method for adjusting a printhead is provided in an embodiment.
[0031]
An ink jet printing apparatus for using this method is provided in embodiment 9. Particular features of the preferred embodiment of the invention are set forth in the dependent embodiments.
[0032]
Further advantages and embodiments of the present invention will become apparent from the following description and drawings.
[0033]
[Detailed Description of the Invention]
Providing a combination of wet brushing and solvent cleaning in which solvent movement on the nozzle plate is provided provides a satisfactory and non-abrasive cleaning method.
[0034]
First, a solvent is applied on the nozzle plate.
[0035]
Brushing the nozzle plate with a brush in the presence of a solvent provides another step for loosening the debris collected on the nozzle plate.
[0036]
Solvent cleaning of the nozzle plate is provided in two stages.
[0037]
-In another stage, or in a stage combined with the first stage above,
A cleaning solvent is applied.
[0038]
-Finally, the nozzle plate is vacuum cleaned.
[0039]
The brushing step in the presence of a liquid or solvent has the advantage that wet brushing has less wear than dry brushing and that this brushing step is very effective in loosening debris collected on the nozzle plate have.
[0040]
The application of the cleaning solvent and the subsequent steps of vacuum cleaning result in the movement of the solvent on the nozzle plate, which is very effective in removing debris and ink residues from the nozzle plate and cleaning the nozzle.
[0041]
Some methods using the method of the present invention will be given below.
[0042]
[First Embodiment]
In the following examples, wet brushing and solvent cleaning are provided in four different stages.
[0043]
Please refer to FIG. 1 in which a nozzle plate 1 including a nozzle 2 is drawn.
[0044]
The various steps of the method are performed by separate means 3, 4, 5 moving on the nozzle plate 1 in the direction indicated by arrow D. Thus, the different steps performed by the separate means are performed consistently and continuously at different locations.
[0045]
In a first step, a solvent is applied to the nozzle plate 1. In this embodiment, the ink itself is used as the solvent. Inks are water-based inks that can be easily used as solvents due to low drying rates. The application is effected by ejecting the ink from the nozzles 2 in such a way that the ink is ejected with very little force, so that the ink remains on the nozzle plate 1. Special application means, such as special solvents applied by non-imaging jet systems, can also be used.
[0046]
The second stage is performed by moving the brush 3 on the nozzle plate 1. The brush 3 in contact with the nozzle plate 1 is usually made of a polytetrafluoroethylene (PTFE) fabric known as Teflon (trade name). Other types of brushes 3 can be used.
[0047]
The wet brushing step ensures that the ink residues and other debris collected on the nozzle plate 1 are loosened without wear.
[0048]
After the wet brushing, a cleaning solvent is applied, for example, by means of the jetting means 4. The solvent may be applied using a contact system, but the use of a non-contact system is preferred.
[0049]
Immediately after the application of the cleaning solvent on the nozzle plate 1, the solvent is removed by vacuum cleaning by the vacuum cleaning means 5. For constant application of the cleaning solvent and vacuum cleaning, a movement of the solvent in the direction opposite to that of the direction D is created on the nozzle plate 1 on the nozzle 2.
[0050]
The lateral movement of the solvent also provides the mechanical effect of the cleaning solvent to pull loose particles.
[0051]
Another fact is that the movement improves the dissolution of the ink residue. This can contribute to the same effect by dissolving the solid more quickly when the solvent and the solid are stirred.
[0052]
[Second embodiment]
It is possible to combine the steps of applying a solvent to allow wet brushing and applying a cleaning solvent. This produces the configuration of FIG.
[0053]
In a first stage, the solvent is applied to the nozzle plate 1 by the injection means 4 or any other suitable system. The solvent will serve two purposes. That is, the solvent will allow wet brushing and will serve as a cleaning solvent.
[0054]
This method does not waste ink to enable wet brushing and does not require two different solvent applications.
[0055]
Immediately after application, the nozzle plate 1 is brushed using the brush 3. A non-woven felt was used in contact with the print head.
[0056]
As in the above example, the last stage is a vacuum cleaning stage, in which a solvent movement is likewise created between the jetting means 4 and the vacuum cleaning means 5. If a system using a brush 3 having a certain water permeability is provided, the brush 3 will not obstruct the flow of the solvent.
[0057]
This system has the additional advantage that the brush 3 itself is also cleaned or rinsed by the flow of solvent through it.
[0058]
This system provides good cleaning of the nozzle plate 1 with little apparent wear.
[0059]
Further possible embodiments and modifications are described below with relevant considerations.
[0060]
[brush]
The structure of the brush 3 can be changed, and a suitable woven fabric, for example, velvet or a non-woven fabric, for example, a felt brush 3 can be used. The chemical composition of the brush 3 can be adapted to the composition of the ink and / or the nozzle plate 1. Possible materials which can be used and have a proven effect are, for example, polytetrafluoroethylene (PTFE) and polypropylene.
[0061]
Other materials are possible. The following list should not be considered limiting. PTFE, PP, PET, PUR, nylon ...
Making the brush 3 from PTFE has the advantage that the brush fibers are chemically inert and that the brush 3 has some self-cleaning properties. The low hardness of the material avoids scratching the nozzle plate.
[0062]
The brush 3 can also assist the cleaning process by creating a more uniform solvent flow over the print head.
[0063]
The configuration of the brush 3 is a compromise between several desired parameters. For example, in order to provide good brushing and to exert some force on the printhead 1, the brush fibers need to have some rigidity and more fibers or brush bristles to be able to clean well. It is. However, if the steps of solvent application and cleaning solvent application are combined, there must be some porosity of the brush 3 to allow movement of the solvent on the nozzle plate 1.
[0064]
As shown in FIG. 4, the bristles of the brush 3 can be attached to a perforated base 7. This allows for easy removal of debris and solvent in additional directions. This can be enhanced by applying a light vacuum at the perforations.
[0065]
The brush 3 can be a fixed bat type, but it can be made more efficient by providing an automatic mechanism for renewing the brush 3, especially when using very viscous ink.
[0066]
FIG. 5 shows that such a possible mechanism is a system with a brush 3 in the form of a textile ribbon 3. At this time, the device includes:
[0067]
A feeding roll 8 for supplying fresh brush fabric 3 to the cleaning module 6;
A brush surface 9 for supporting the part of the ribbon used as the active brush 3,
An intake roll 10 for winding up the used brush fabric.
[0068]
This facilitates updating of the brush 3 when necessary.
[0069]
[Cleaning direction and speed]
The most preferred cleaning system cleans the print head longitudinally, but is capable of cleaning in the transverse direction or any direction across the nozzle array, depending on the dimensions of the head or internal printer array.
[0070]
The cleaning speed can vary between 0.001 and 0.05 m / s, but is preferably between 0.005 and 0.02 m / s.
[0071]
Cleaning can be performed by moving the printhead over the cleaning station with the cleaning module or station 6 stationary, but a mobile cleaning station 6 that moves over the printhead is also possible.
[0072]
To enhance the cleaning ability, it is possible to provide the brush 3 with additional movement. The brush 3 can be vibrated during movement to enhance the melting ability. The introduction of acoustic or ultrasonic vibration also enhances the loosening of debris and dry ink. These movements can be driven, for example, by piezoelectric transducers.
[0073]
The brush 3 can be a rotary brush that can be cleaned by using a stationary scraper that wipes collected debris from the bristles of the brush.
[0074]
[Brush adjustment]
For example, it has been found that when the brush 3 dries due to long periods of non-use, it takes some time to completely wet again, and it is initially found that cleaning is inadequate. This can be avoided by storing the non-operational cleaning module or brush 3 in the anti-drying capping of the brush 3 inside the printer to maintain a solvent saturated atmosphere.
[0075]
Within the capping, the cleaning module can be operated to rinse the brush 3 free of debris and dry particles.
[0076]
If a cleaning solvent is used, the cleaning and dissolving ability is predominantly determined by the properties of the solvent.
[0077]
One of the most important properties is surface tension. If the surface tension is too low, the film will remain on the nozzle plate forming droplets, which after drying will result in small dry particles. High surface tension allows easy removal of the solvent but makes contact between the solvent and contaminants (dry ink, debris) difficult.
[0078]
Another aspect is the chemical compatibility of the solvent with the contaminant.
[0079]
Pure inks are usually completely compatible with the dried inks and have a low surface tension and therefore cannot be easily removed by vacuum.
[0080]
Pure water has a low dissolving capacity that can be easily removed. A small trade-off between wetting and dissolving capacity was found. This can occur, for example, by mixing ink and water.
[0081]
Further aspects affecting the cleaning ability of the cleaning solvent are, for example, the composition of the anti-wetting coating of the nozzle plate 1, possible additives in the solvent, the temperature of the solvent ...
[0082]
Another aspect is the volume of cleaning solvent that must be balanced with the strength of the vacuum. When the degree of vacuum is low, the cleaning solvent will remain on the print head, while when the degree of vacuum is too low, there is not enough time to loosen and dissolve the dried ink and debris.
[0083]
When the solvent is removed by vacuum, the cleaning solvent can be collected as waste for later removal. However, in a more preferred embodiment, the solvent is recycled and reused, for example, after filtration or other purification methods. This reduces the amount of waste generated by the printer.
[0084]
[Injection of cleaning solvent]
In order to create a flow of the solvent on the nozzle plate 1, the cleaning solvent is preferably sprayed onto the nozzle plate 1 by the solvent application means 4 at an angle between 0 and 80 ° with the normal to the nozzle plate 1. .
[0085]
This provides a good thorough cleaning of the nozzle 2 and allows for the generation of a solvent flow over the nozzle plate 1.
[0086]
The direction of the jet can be adapted to the cleaning rate or jet volume of the function. The flow rate of the solvent is preferably between 5 and 200 ml / min and is fed through the inlet 7.
[0087]
Instead of using a standard laminar flow of the applied solvent, more efficient forms are possible. That is,
-Air bubbles are introduced into the stream of cleaning solvent, which gives a more aggressive and efficient cleaning.
[0088]
The pulsating flow of solvent also gives more efficient cleaning.
[0089]
[Vacuum cleaning]
Vacuum cleaning performs the following two functions. That is,
-Removal of cleaning solvents and debris;
The vacuum directs the flow of the cleaning liquid;
[0090]
Usually, the solvent jetting module 4 applying the solvent will first move over the print head, after which the means for vacuum cleaning 5 will remove the solvent. At this time, the direction of the flow is opposite to the direction of movement of the cleaning module 6.
[0091]
However, the application of a higher degree of vacuum allows the vacuum cleaning means 5 to first pass over the print head before the cleaning fluid ejection module 4. Then, the cleaning solvent is sucked into the vacuum means 5 in the same direction as the movement of the cleaning module 6. This obviously requires a stronger vacuum.
[0092]
The pressure P inside the print head below the vacuum slit 5 is usually between -5 and -50 kPa (-0.05 to -0.5 bar).
[0093]
The first value is the minimum value for removing the solvent, while the second value provides good cleaning without drawing a lot of ink from the nozzles 2 of the print head.
[0094]
When determining the distance from the cleaning module 6 to the surface of the nozzle plate 1, the same considerations must be taken.
[0095]
If the distance is too short, the print head may be accidentally damaged, more ink may be withdrawn from the nozzles 2, solvent flow may be difficult, and so on. If the distance between the head and the cleaning module 6 is too large, poor cleaning or the like due to loss of vacuum is expected.
[0096]
The distance used can vary between 0.1 and 1 mm depending on the vacuum applied and the flow rate of the solvent.
[0097]
The distance between the cleaning module 6 and the nozzle plate 1 can be maintained by providing the projections 11 on the cleaning module 6. These projections 11 are preferably located outside the cleaning area and contact the outside of the print head of the nozzle plate 1. When cleaning takes place, the projections 11 slide on the print head and keep a constant distance to the nozzle plate 1 placed in sliding contact.
[0098]
The ideal combination of parameters for all cleaning components must be found on a case-by-case basis.
[0099]
Changes in ink composition, cleaning speed, brush properties, etc. all affect cleaning results.
[0100]
For example, the cleaning module 6 may try a plurality of settings to determine an operating point at which no future cleaning fluid leaks. The correct combination of the flow rate of the cleaning solvent and the extraction of air by the vacuum unit 5 is important.
[0101]
The operating point has to be determined and can vary greatly depending on various parameters, such as: That is,
The type and size of the brush,
The distance from the cleaning module to the nozzle plate,
The configuration of the cleaning module: width, length, distance between the fluid applicator and the vacuum slit, and distance to these brushes and the edge of the cleaning module;
The length and width of the slit.
[0102]
Changing these parameters allows, for example, having less vacuum requirements for certain operating points, which can be easily obtained.
[0103]
[Example]
In order to carry out the method according to the invention, the ink jet printing system was equipped with a cleaning module 6 shown in FIG.
[0104]
The printing press uses an aqueous dye ink.
[0105]
The module 6 moves in both directions on the print head in a final sweep in the direction D indicated by the arrow, in which case the vacuum slit 5 always passes through the print head. Normally, only one back and forth sweep is used. This provides sufficient cleaning of the print head.
[0106]
Module 6 comprises a slit or nozzle array 4 for applying a solvent to the print head.
[0107]
The following settings were tested to obtain good cleaning results.
[0108]
The application volume of the cleaning solvent is 45 ml / min and is supplied via the inlet 12;
[0109]
A vacuum is applied and the pressure in the vacuum chamber behind the slit 5 is raised to a relative pressure of -10;
An air flow rate of about 58 l / min was obtained by setting kPa (-0.1 bar).
[0110]
In the center, a brush 3 for brushing the print head is provided. The other side of the slit 5 is connected to a vacuum source via a vacuum connection 13. The openings of the slits 4 and 5 are 0.5 mm wide.
[0111]
The module 6 moves on the print head at a distance of 0.3 mm from the nozzle plate 1 at a speed of 0.005 to 0.05 m / sec.
[0112]
An effective method of printhead adjustment for further printing can be provided by the following steps. That is,
-Vacuum assisted purging: During this stage, a vacuum is applied outside the nozzle plate 1. This can be done by contacting the print head with a capping unit connected to a vacuum source. If necessary, the nozzles 2 of the print head are activated to help clean the clogged nozzles 2.
[0113]
The print head is driven during the firing phase to further clean the nozzle 2;
[0114]
A cleaning step according to the invention is provided.
[0115]
-To protect the print head in the standby state, the print head is brought into contact with the capping unit so as to prevent further contamination of the nozzles 2 and drying of the ink.
[0116]
Of particular importance is the combination of a vacuum assisted purging step and improved cleaning to provide good alignment of the printhead. If the firing can be performed and printing does not start immediately, only capping is required.
[0117]
The cleaning module 6 can be specially designed to work in both directions. A central liquid ejection portion is provided between the two brushes. Two vacuum modules 5 are provided on the outside. This allows the use of jetting, brushing and vacuuming in both directions of movement.
[0118]
Although the preferred embodiment of the invention has been described in detail, it will become apparent to those skilled in the art that many changes may be made thereto without departing from the scope of the invention as defined in the claims. There will be.
[0119]
The embodiments of the present invention are as follows.
[0120]
1. A method for cleaning a nozzle plate (1) of an ink jet print head, comprising:-providing a solvent to said nozzle plate (1);
-Loosening debris collected on said nozzle plate (1) by brushing said nozzle plate (1) with a brush (3) in the presence of said solvent;
Applying a cleaning solvent to the nozzle plate (1),
-Followed by steps of removing said cleaning solvent and debris from said nozzle plate (1) by vacuum cleaning,
The method according to claim 1, wherein the application of the cleaning solvent and the subsequent removal of the cleaning solvent provide a movement of the solvent on the nozzle plate (1).
[0121]
2. 2. The method according to embodiment 1, wherein the step of providing the solvent and the step of applying the cleaning solvent are the same.
[0122]
3. A cleaning module for cleaning a nozzle plate (1) from an ink jet printer,
Means (4) for providing a cleaning solvent to said nozzle plate (1);
A brush (3) for brushing the nozzle plate (1) in the presence of the solvent to loosen debris collected on the nozzle plate (1);
A vacuum cleaning means (5) for removing the cleaning solvent and debris from the nozzle plate (1) and for providing a movement of the solvent on the nozzle plate (1).
Cleaning module with a.
[Brief description of the drawings]
FIG. 1 shows a layout of components of a first embodiment according to the present invention.
FIG. 2 shows the layout of the components of a second embodiment according to the invention, in which the application of the solvent and the application of the cleaning solvent are at the same stage.
FIG. 3 shows a cleaning module for performing the steps according to the invention.
FIG. 4 shows a cleaning module with additional vacuum cleaning passing through a brush.
FIG. 5 shows a cleaning module with a system for renewing a brush fabric.

Claims (2)

A method for cleaning a nozzle plate (1) of an ink jet print head, comprising:
Providing a solvent to said nozzle plate (1);
Loosening debris collected on the nozzle plate (1) by brushing the nozzle plate (1) with a brush (3) in the presence of the solvent;
Applying a cleaning solvent to the nozzle plate (1),
-Followed by steps of removing said cleaning solvent and debris from said nozzle plate (1) by vacuum cleaning,
The method according to claim 1, wherein the application of the cleaning solvent and the subsequent removal of the cleaning solvent provide a movement of the solvent on the nozzle plate (1). A cleaning module for cleaning a nozzle plate (1) from an ink jet printer,
Means (4) for providing a cleaning solvent to said nozzle plate (1);
A brush (3) for brushing the nozzle plate (1) in the presence of the solvent to loosen debris collected on the nozzle plate (1);
A vacuum cleaning means (5) for removing the cleaning solvent and debris from the nozzle plate (1) and for providing a movement of the solvent on the nozzle plate (1).
Cleaning module with a.

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