MXPA99011672A - Clean-in-place system for an ink jet printhead - Google Patents

Abstract

A clean-in-place system is disclosed for use in an ink jet printhead (10). The clean-in-place system features a compartment (17) in which the printhead components (18a, 20, 22, 24) are disposed. An end plate (28) has a slot (26) therein to permit ink drops to be projected from the compartment (17) onto a substrate to be marked. For cleaning purposes, a pneumatic shutter (42) is disposed adjacent the slot (26) to seal it. Thereafter, the compartment (17) is flooded with ink solvent (107) by means of a pump (103) from a solvent reservoir. The solvent may be agitated by air or mechanical means. Thereafter, a drain line (116, 117) is used to remove the solvent from the compartment (17) and air is blown therethrough to dry the components. The pneumatic shutter (42) is reopened after the solvent is withdrawn to enhance the drying of the components. The shutter (42) may consist of an inflatable tubular member and a pump for supplying compressed air to the tubular member (42) to inflate and deflate it.

Description

CLEANING SYSTEM IN PLACE FOR AN INK JET PRINT HEAD FIELD OF THE INVENTION The invention relates in general to ink jet printing and, in particular, to continuous jet printers. These devices are well known in the art and are used in industrial and commercial applications to print marks on various product surfaces, which normally move on a conveyor system. The signs may contain useful information, such as date codes, plant identification information and the like. These printers are subject to long periods of continuous use and must be very reliable. However, at regular intervals, it is necessary to clean the print head, which is usually located at a distance from the printer's electronic system and the ink supply. The print head is connected to the printer system by an umbilical cord, which contains the electronic components, the ink supply and the ink return lines.

BACKGROUND OF THE INVENTION In high-voltage inkjet devices high voltage is used to bypass P1757 / 99MX electrostatically charged droplets of ink on the substrate that will be marked. The unloaded drops are directed towards a discharge channel, which returns them to the ink tank for reuse. Typical ink jet systems of this type are disclosed in U.S. Patent No. 3,683,396 assigned to the present assignee. Over time, the ink droplets generate small particles or ink mist, which, when combined with dust, etc., can be electrostatically attracted to the charge electrode of the high-voltage deflection plates and related components. inside the print head. This results in an undesirable accumulation on the components of the print head and, over time, degrades the quality of the print by distorting the electric field, preventing the projection of the drops or causing the drops to be misdirected. For this reason, the print head should be cleaned periodically. Currently, when an inkjet printer is turned off at the end of a shift or shows a degraded printing operation, the print head is manually disassembled and cleaned. This requires an experienced operator who removes the cover of the printhead and normally places the mechanism of the printhead, which consists of a nozzle, a charging electrode, P1757 / 99MX deflection electrodes and the discharge channel unit in a special cleaning tray. Then he sprinkles the print head with a compatible solvent for cleaning, removes the solvent and dissolves the ink, and then dries the components, either by drying them manually or blowing them with compressed air. Obviously, this manual operation consumes a lot of labor, requires experienced personnel to perform the task in a very specialized miniaturized electronic component and to dispose of the contaminated cleaning solvent. Incorrect cleaning techniques can lead to damage to the print head or an improper printing operation.

SUMMARY OF THE INVENTION In accordance with the invention, a cleaning system is provided in place for the components of an ink jet print head: (a) a defined compartment within the print head, which contains components, a end of the compartment ends in an end plate having a groove therethrough to allow ink droplets to exit the compartment during normal printing conditions; (b) a seal is provided adjacent the slot; (c) a means arranged to seal the compartment, so that it can be flooded P1757 / 99MX at least partially with an ink solvent, the means provided for sealing includes means for operating the obturator to close and seal the groove; (d) a means provided for introducing the ink solvent to at least partially flood the sealed compartment to dissolve the ink that may have been deposited on the components; Y (e) a means arranged to remove the solvent from the compartment and the dissolved ink. Further, in accordance with the invention, there is provided a method for cleaning in place the components of an ink jet print head contained within a compartment in the print head terminating in an end plate having an aperture. Through it to allow ink droplets to exit the compartment during normal printing operations, the method comprises the steps of: (a) providing a shutter adjacent to the opening; (b) sealing the compartment, so that it can be flooded, at least partially, with an ink solvent, the sealing step includes operating the shutter to close and seal the opening during cleaning; (c) introducing the ink solvent to flood, at least partially, the sealed compartment to dissolve the ink that may have deposited on the components; (d) Remove or remove from the solvent compartment and the ink P1757 / 99MX dissolved; and (e) operating the obturator to reopen the opening after the solvent has been removed. The cleaning system in place that gives body to the invention has the advantage that the need for manual cleaning of the ink jet print head is eliminated. The cleaning of the print head components is achieved automatically, instead, without disassembling the print head. This avoids exposing the technician to dangerous fluids and the printhead remains sealed and protected against damage by handling and the environment that may exist at the point of use. In addition, the automatic cleaning system of the present invention is relatively inexpensive and requires little modification to existing print head designs. The components include a nozzle, a charging ring that applies a charge to selected drops of ink coming out of the nozzle, deflection electrodes and the unloaded droplet collector. In operative relation to the slot through which the drops of the print head exit, there is a pneumatically inflatable tube or membrane. During normal operation of the print head, the tube is inflated. For automatic cleaning, the tube is inflated, sealing the groove tightly. The cleaning fluid, such as the replenishing ink solvent, is directed towards the P1757 / 99MX print head compartment, where it floods the components contained in it. After this, mechanical vibration or air pressure can be used to agitate the cleaning fluid and ensure the effective removal of dry ink which, over time, accumulates on the components of the print head. After this, the cleaning fluid is removed from the print head by means of drain lines, after which the tubular member is deflated and air is introduced to dry the components. The normal printing operation can then be resumed.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described further below, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view, partly in section of a jet print head. of ink of the type for which the present invention is suitable and in which the inflatable tube is installed; Figure 2 is an enlarged perspective view, similar to Figure 1 but with the printhead removed; Figure 3 is a side elevational view of the print head, illustrating the placement of the inflatable tube with respect to the slot P1757 / 99MX output from the end plate; Figures 4a and 4b show the open and closed outlet slot, respectively, depending on the pressurization state of the inflatable tube; and Figure 5 is a schematic diagram of the various valves and supply lines used to perform the automatic cleaning procedure, in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES As indicated in the background section of this specification, it is important to periodically clean the components of a print head to eliminate the dry ink that eventually forms on the various components contained therein. This requirement is in addition to the requirement to periodically purge the nozzle, the ink collector and the ink return line to eliminate the dry ink that accumulated in them. With respect to the nozzle, the ink return line and the ink collector, there are several cleaning procedures, such as that used by the present assignee, referred to as "Auto Flush". It is intended that the present invention be used after an Auto Flush operation and that it be in addition to said operation.

P1757 / 99MX The Auto Flush, which is available for Videojet EXCEL® printers, manufactured by this transferee, allows the printer to automatically wash the nozzle manifold and the ink return line in the printhead, each time the printer turns off. This reduces the maintenance of the printer. In the Auto Flush procedure, a printer pumps approximately four milliliters of pressurized solvent or replenishing fluid through the nozzle of the printhead into the manifold for approximately sixty seconds. This perfectly cleans the nozzle and ink return line of the print head, reducing the problems that may arise when the printer is restarted, because the ink dried inside the nozzle or the return line from ink. The details of the Auto Flush procedure and the system associated with it can be found in the Videojet Manual titled "Addendum for EXCEL 170i Printer with Auto Flush, Part Number 365293-01-A, dated 8/94. invention is attached to the process of Auto Flush, in order to clean the components of the print head, in addition to the nozzle, the collector and the return line.For components of the print head, we will refer in particular to The surfaces P1757 / 99MX from the nozzle, to the charging ring used to charge the ink droplets, as they break or separate from the ink stream, the deflection eledes used to deflect the charged droplets, projected through the groove or opening provided in the end plate and the external surfaces of the discharge channel or return, through which the unused drops are recycled to the ink supply. It is in these components that, over time, dry ink builds up on the surfaces, which can interfere with the proper formation and deflection of the ink droplets on the surfaces that will be marked. These components are not cleaned by the Auto Flush procedure. Therefore, it has been necessary for a technician to manually disassemble the print head by removing the printer from the service, removing the print head cover and manually applying the solvent to the components, usually on a laboratory tray or a similar container. After this, the components must be dried and the print head must be assembled again before the printer can be put back into service. The present invention eliminates the need for manual intervention and provides high quality printing over a prolonged period of time. The component or compartment of the P1757 / 99MX print head seals and stops being sealed, automatically. The compartment is then flooded with a solvent. After which, the solvent is removed or removed and the components are dried. After which, the printhead can be put back into service. When you want to clean the print head, the Auto Flush process is used first to clean the nozzle and return lines. After that, the description of the present invention is used to clean the components of the print head. Preferably, the Auto Flush solvent system is used to deliver the solvent through the orifice of the nozzle into the print head compartment for the purposes of the present invention. Alternatively, the solvent is simply directed through the nozzle into the print head compartment. More specifically, when shutting down the ink jet printer, the slot or outlet of the drops is closed using a membrane or pneumatic tube. The solvent is then supplied through the orifice of the nozzle from the Auto Flush system to fill the compartment completely or partially. Preferably, compressed air is then introduced into this compartment for stirring by bubbling or otherwise stirring the solvent over the P1757 / 99MX surfaces of the components that will be cleaned. After a predetermined cleaning time, the solvent is drained from the print head by the drain / vent lines. Preferably, the drained solvent is recycled to the ink system to be used as a replenishing solvent during the printing process. This reduces waste and eliminates the need to dispose of this material. The print slot then opens when deflating the pneumatic tube. To dry the components of the print head, compressed air is introduced through an air line. The print head is then ready to return to print. Referring to Figure 1, a printhead 10, modified in accordance with the present invention, is shown. The print head includes a cover 12 that is removably secured to the manifold 14, which is coupled to an umbilical cord 16 (shown in dashed line) containing the electrical lines, the supply and return lines of ink for the operation Normal print head. By means of a portion in section the components of interest of the print head contained in a compartment 17 are shown. These components include a nozzle face 18a, a loading tunnel 20, deflecting electrodes 22 and 24 and an outlet slot.

P1757 / 99MX 26 through the end plate 28. In Figure 1 the ink collector 30 shown in Figure 3 is not clearly shown. The compartment 17 is defined by the backing members 19 and 23 of the electrodes deflectors 22 and 24; a dividing screen 40; and the side walls were omitted from the drawing for clarity. As those skilled in the art know, the ink is supplied to the nozzle 18 under pressure. It comes out of the nozzle through a small hole like an ink stream. A piezoelectric transducer 21 or similar mechanical device applies a stimulation voltage to the nozzle, causing the ink stream to decompose or fragment into a series of discrete droplets as the current passes through the charging tunnel 20. The selected droplets are charged and, thus, when the deflection electrodes 22 and 24 pass, they deviate from their normal flight path upwards to pass through the groove 26 and onto the surface to be marked. As shown in Figure 3, uncharged droplets that are not deflected pass directly into the manifold 30 which returns these droplets to the ink supply for later use. For the purposes of the present invention, it is desired that these major components used in inkjet printing be contained P1757 / 99MX inside compartment 17 for the print head, which can be sealed for solvent flooding. This can be better appreciated in Figure 2, which is an enlarged view of a portion of Figure 1. It will be appreciated that with the cover 12, on the printhead, the components 20, 22 and 24 are fully sealed, at one end , by the end plate 28, and by the other end, by the dividing screen 40 and in the upper and lower portions thereof, by the supporting structure to which they are mounted. Thus, with the exception of the collector 30 and the slot 26, there is no access to these components. In accordance with the present invention, when it is desired to clean the components in the compartment 17, the groove 26 is sealed and the solvent is introduced to at least partially flood the components. After which, mechanical agitation or air is used to agitate the solvent and cause complete contact with the surfaces of the components to dissolve and, thus, eliminate the dry ink, dust and anything else that may have dried about the components. After this, the solvent and the dissolved material are removed or removed and the slot 26 is reopened, so that printing can be resumed. Referring to Figures 4a and b, P1757 / 99MX illustrates the manner in which the slot 26 can be sealed and unsealed. Figure 4a illustrates the slot 26 in the normal, open condition, where the ink droplets can pass out of the slot. Placed adjacent the slot next to the end plate 28, there is a pneumatic obturator, in the form of an inflatable tube 42, whose lower end is connected to a conduit 44 for supplying thereto an air pressure source. The inflatable tube 42 is also shown in Figure 3, in relative position against the end plate 28. In Figure 4b, the tube 42 is shown in the inflated condition, in which the air pressure has caused it to expand. sufficient to completely seal the groove 26. In this position, the compartment 17 for the print head, which contains the loading tunnel, the deflection plates, the face of the nozzle and the collector, are completely sealed (with exception of the collector ink return line and the drain / vent lines described in connection with Figure 5). As indicated by the broken lines in Figures 4a and 4b, the walls 50 and 52, perpendicular to the end plate, are preferably provided so that, as shown in Figure 4b, when the tube is inflated, its configuration is confined by the walls to ensure the hermetic sealing of the groove 26.

P1757 / 99MX Although a pneumatic obturator is preferred, other forms of obturators could be used. For example, a spring-loaded or electronic shutter would be satisfactory if cost and space permit. It is simply necessary that the shutter has the ability to hermetically seal the chamber during the cleaning process. From the above, the mode of operation of the invention will be evident. However, to complete, Figure 5 presents a schematic circuit diagram of the ink jet valves and typical supply lines used in conjunction with the present invention, including those that have been added to carry out the invention. A consideration of Figure 5, with respect to the following description, will fully indicate the mode of operation. After the printer has gone offline, you want to perform the Auto Flush operation and then clean the print head. The following steps are used. An electric valve 101 is energized to supply compressed air that comes from a source of compressed air, to inflate and, in this way, stop to close the shutter or pneumatic tube 42, by line 102. A pump 103, designated as an Auto pump. Flush is then activated to pump the fluid or replenishing solvent through line 104 and wash by P1757 / 99MX entrains valve 105 to nozzle 18. Stream or solvent jet 107 passes through the printhead and enters manifold 30, from which it is drawn back into ink tank 109, through the line 110 and the valve 111, which is connected to the vacuum source by the valve 121. After a predetermined time, the pump 103 is turned off and the duct 110 is allowed to evacuate. After a further predetermined period of time, the valve 121 is de-energized to eliminate the vacuum of the valve 111. This closes the valve 111 and removes the vacuum from the duct 110 and the manifold 30. This completes the Auto Flush sequence. To initiate the cleaning sequence of the print head, the pump 103 is again activated to inject the additional replacement fluid through the conduit 104, the valve 105 and the nozzle 18. However, this time the valve 111 is closed, so that the fluid can not pass to the ink collector 30 and the return line 110. Instead, the compartment 17 in which the components of the print head are located, is flooded with the solvent, either partially or totally. When the compartment 17 for the print head is filled with the desired amount of solvent, the pump is stopped and the P1757 / 99MX agitation. According to a preferred embodiment, the agitation is achieved using the valve 113 to direct compressed air through the conduit 114, via a flow restrictor 115, into the compartment 17 for the print head. This causes the stirring of the replacement fluid in the chamber. The air entering the chamber is vented to the atmosphere through any of the conduits 116 or 117 (depending on the orientation of the print head), the two lead to a solvent trap 118 and into the atmosphere, through the conduit 119 and valve 120. Trap 118 for solvent retains liquid that can be trapped as the air is vented. After a predetermined time, the valve 113 closes and the valve 120 is operated to apply a vacuum to the trap 118 for solvent, through the conduit 119. This removes the replenishment fluid from the chamber 17 through the conduit 116. or 117 (again depending on the orientation of the print head) towards the solvent trap 118, which recycles the solvent thus captured, back to the ink tank. The recovered solvent is then used to replace the solvent lost during printing, due to evaporation. The solvent of the trap 118 is displaced by the operation of the valve 123 which controls the valve 125 to allow the P1757 / 99 X solvent flows from the trap 118 for solvent, through the float valve 126, the filter 127, the valve 125 and the duct 128 to the ink tank 109. After the solvent has been removed from the compartment 17 for the print head, it is necessary to dry the components. To this end, the valve 120 is de-energized, again ventilating the compartment 17 to the atmosphere. The valve 101 is also de-energized, opening the pneumatic obturator by deflating the tube 42. The valve 129 is then energized, allowing compressed air to flow through the conduit 130 into the chamber 17 for the print head. This air flow quickly dries the components within the chamber 17. After a predetermined time, the valve 129 is de-energized to close or cut the compressed air. This completes the cleaning cycle of the print head. After this, the print head can be returned to the operation. At this point, both the nozzle and the return line have been cleaned by the Auto Flush procedure and the print head compartment and the components contained therein have been cleaned by the cleaning procedure just described. The valve 105 described in connection with Figure 5 is of the type disclosed in the P1757 / 99 X United States No. 4,555,719 assigned to this assignee. Thus, as described, the invention consists of a cleaning system for an ink jet printhead itself that can be modernized or, which can be incorporated in new printheads of the developed type, to eliminate the need to manually disassemble the printhead. printhead to clean the ink deflector components contained in the printhead chamber.

P1757 / 99MX

Claims (14)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A cleaning system in place for the components of a printing head. ink jet, comprising: (a) a compartment defined within the print head, which contains the components, one end of the compartment ends in an end plate having a slot, through which it is allowed to drops of ink come out of the compartment during normal printing operations; (b) a shutter provided adjacent the slot; (c) a means arranged to seal the compartment, so that it can be flooded, at least partially, with an ink solvent, the means provided for sealing includes means for operating the shutter to close and seal the slot; (d) a means arranged to introduce the ink solvent to at least partially flood the sealed compartment and dissolve the ink that may have deposited on the components; and, (e) a means arranged to remove or remove from the compartment the solvent and the dissolved ink.
2. 2. A system according to claim 1, wherein the components comprise: a face of P1757 / 99MX nozzle, a charging electrode, deflection electrodes and a collector for no-load ink droplets.
3. A system according to claim 1 or 2, further including: (f) a means for agitating the ink solvent in the compartment to improve the contact of the solvent with the components.
4. 4. A system according to claim 3, wherein the means for agitation is a source of compressed air, introduced into the compartment and a vent line for communicating the compartment with the atmosphere.
5. A system according to any of the preceding claims, wherein the obturator is a tubular member that can be inflated to seal the groove and deflated to stop sealing the groove.
6. A system according to any of the preceding claims, wherein the means disposed to remove or remove the solvent comprises: a drain line communicating with the compartment and a vacuum source for extracting the solvent through the drain line .
7. A system according to claim 6, wherein the means arranged to remove the solvent further comprises a solvent trap in circuit with the drain line to receive the solvent.
8. 8. A system according to any of the P1757 / 99MX preceding claims, wherein the obturator is a pneumatic seal.
9. 9. A system according to any of the preceding claims, further comprising a means for drying the components in the compartment, after removal of the solvent.
10. A system according to claim 9, wherein the means for drying comprises a means for introducing air into the compartment.
11. 11. An ink jet print head including a cleaning system in place, as claimed in any of the preceding claims.
12. 12. A method for cleaning in place the components of an ink jet print head contained within a compartment in the print head terminating in an end plate having an opening therethrough to allow the ink droplets exit the compartment during normal printing operations, the method comprising the steps of: (a) providing a shutter adjacent to the opening; (b) sealing the compartment, so that it can be flooded, at least partially, with an ink solvent, the sealing step includes operating the shutter to close and seal the opening during cleaning; (c) introduce the solvent of ink to flood, at least partially, to the compartment P1757 / 99 X sealed to dissolve the ink that may have been deposited on the components; (d) removing the solvent and dissolved ink from the compartment; and (e) operating the obturator to reopen the opening after it has been removed to the solvent.
13. 13. A method according to claim 12, further comprising the step of drying the components, after removal of the solvent. A method according to claim 13, wherein the drying step comprises introducing compressed air into the compartment. P1757 / 99MX