Ink jet print station with improved start up and a method for starting up inkjet printers

An ink jet print station with improved start-up reliability includes an ink reservoir and a printhead. The printhead has at least two drop generators, a return line connected to the generator's fluid ports, an orifice plate connected to the drop generator for forming jets, at least two filters, a controller for operating the valves to control flow, and an ink pump. The ink pump is adapted to move ink from the reservoir to the printhead. Upon startup, fluid is applied independently to the first filter and then the second filter. A method for at least partially filling filters in an ink jet uses the ink jet print station with improved start up reliability.

FIELD OF THE INVENTION

The present embodiments relate to filling the ink jet printing system filters, such as for those of dual-feed ink jet printheads during the initial introduction of ink into the printhead during startup.

BACKGROUND OF THE INVENTION

Under currently known ink jet printing system, when printheads first introduce ink to the system, the filters are typically only filled approximately ½ to ¾ full. With an only partially filled filter, problems can occur in operating the system. Problems particularly arise when trying to fill the remaining filter once pressure and flow are established. By closing one valve and opening another, a first filter at least partially filled requires a large pressure increase to fully wet out and at least partially fill the second filter. This large pressure increase is expensive, requiring additional energy, and with the increase in pressure, the potential to strain the system increases, causing leaks from other lines or seas.

A need exists for a method that will introduce ink into a printhead with a series of steps that will fill two printhead ink filters to a full position thereby controlling the amount of fluid that may weep from the printhead and minimize the pressure peaks that may occur that accidentally opening a shutdown valve in the system.

The embodied methods herein are designed to meet this need.

SUMMARY OF THE INVENTION

An improved ink jet printer start up and an ink jet print station with improved start up reliability includes a reservoir containing ink, a printhead fluid supply line, drop generator supply lines, associated valving, and a printhead. The printhead includes one or more drop generators with associated fluid ports, a return line connected to fluid ports, and an orifice plate connected to the drop generator for forming jets. Filters are connected between the valves and the fluid ports. A controller operates the valves, the ink pump, and the pressure transducer. The ink pump is connected to the drop generator fluid supply lines and operated by the controller and is adapted to move ink from the reservoir to the printhead. Upon startup, fluid is applied independently to the first filter and then the second filter.

The method for at least partially filling filters in an ink jet print station entails activating the pump at a drive level while opening a first valve to displace air from the first filter and at least partially filling the first filter with liquid and, then, shutting off the pump. The pump is activated at the drive level a second time while opening the second valve and closing the first valve to displace air from the second filter and at least partially filling the second filter with liquid. The first valve is opened to allow the liquid to circulate at a fixed pressure.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining the present embodiments in detail, it is to be understood that the embodiments are not limited to the particular descriptions and that it can be practiced or carried out in various ways.

The inventive method and ink jet printing station uses at least two filters. The method involves a series of steps that entail at least partially filling both ink filters independently and controlling the amount of fluid flow from the printhead.

The ink jet printing station involves the use of a printhead with a drop generator and two filters, an orifice structure, a charge device, a catcher, and an eyelid that can be actuated open or closed.

The method prevents the build up of ink in the gap created between the orifice structure and the eyelid, and minimizes the pressure peaks that may occur during filling of filters prior to entering a drop generator

This method handles ink jet printhead filter filling pressures of 50 psi or less, in a manner that is safer than currently available techniques.

The methods have the added feature of keeping the filling pressure below 50 psi to create a more reliable performance of the printing system and a higher quality of printing.

The methods have advantageously shown an improved reliability because, by at least partially filling the filters first, the presence of air bubbles in this printing system is minimized. Air bubbles often cause failures in printing. The methods additionally provide a better balance of fluid flow between the two ports of a dual feed drop generator.

With reference to the figures,FIG. 1depicts an ink jet print station with improved start up reliability, wherein the print station includes a printhead12and a reservoir10containing ink11. An example of an ink jet print station is a Kodak Versamark DT92 print station available from Kodak Versamark of Dayton, Ohio.

The printhead12includes a drop generator14, having at least a first fluid port16and a second fluid port18, and an orifice plate20connected to the drop generator forming a plurality of jets22,24,26, and28. A first filter40and a second filter42are connected to the drop generator as well as a return line54connected to the drop generator.

A printhead fluid supply line30connects the reservoir10with a first drop generator supply line32and a second drop generator supply line34.

The first drop generator supply line32connects to the first fluid port16and the second drop generator supply line34connects to the second fluid port18.

Additionally, a first valve36is disposed in the first drop generator supply line32between the printhead fluid supply line30and the first fluid port16. A second valve38is disposed in the second drop generator supply line34between the printhead fluid supply line30and the second fluid port18.

The reservoir10in a preferred embodiment can contain between one liter and six liters of ink. The ink can be a water-based ink, such as inks available from Kodak Versamark of Dayton, Ohio. The ink can also be a solvent-based ink, polymer-based inks, oil-based inks, dye-based inks, pigment-based inks and combinations thereof.

A first filter40is connected between the first valve36and the first fluid port16. A second filter42is connected between the second valve38and the second fluid port18.

A controller44communicates with the first valve and the second valve. The controller44communicates with an ink pump46connected to printhead fluid supply line30. The controller44is adapted to move fluid from the reservoir10to the drop generator14upon startup. This system can be used to provide the fluid from the reservoir10independently to the first filter and then the second filter.

The controller can be an electronic controller with a central processing unit (CPU). The controller can control a plurality of valves, ink pumps and vacuum pumps in this system.

The system can optionally use a catcher48disposed opposite the drop generator14. The catcher has a catcher return line50connecting the catcher to the reservoir10.

A charge device52, such as a charge plate, can be secured to the catcher for providing a charge to the drops from the jets22,24,26and28that are not to be used for printing.

A return line54connects the drop generator to the reservoir10. A controllable valve56connected to the controller44disposed in the return line54can be used to open and close the return line. One or more pressure transducers58can be located in the return line between the drop generator and the controllable valve to sense the pressure in the system and communicate that information to the controller.

This system can be used to sequentially, at least partially fill a first filter to a full condition and then at least partially fill a second filter to a full condition. Alternatively, this system can be used to at least partially fill a first filter such as to three-quarters full, then a second filter to at least partially three-quarters full and then should the first filter have become less then full because ink has flowed into the drop generator, then at least partially filling the a filter once again.

The system can also utilize an eyelid60for sealing the fluid flowing to the catcher during start up. A vacuum pump62can optionally be connected to the reservoir10and the controller enabling fluid to be passed through the return line from the drop generator.

FIG. 2depicts a method for filling filters for a system shown inFIG. 1. The steps involve first activating the pump46shown inFIG. 1that can be an ink pump or a solvent fluid pump for pumping cleaning fluid through the printing station, at a drive level. A drive level is either a voltage level supplied to a pump or a duty cycle provided with a pulse width modulation (Step100). Simultaneously, the first valve is opened to displace air from the first filter and at least partially filling the first filter with fluid. The second valve is kept closed. This orientation enables the first filter to be at least partially filled with liquid from the reservoir, which can be ink or cleaning fluid.

The next step involves shutting off the pump when the first filter is at least partially filled or more preferably, totally filled (Step102).

The pump46is, then, again activated at the drive level a second time while opening the second valve and closing the first valve to displace air from the second filter and at least partially fill the second filter with liquid (Step104).

After at least partially filling the second filter with ink, the first valve is opened, permitting the pump to circulate the liquid at a fixed pressure (Step106).

The methods can be used to at least partially fill the first or the second filter to any capacity with liquid, but full is preferred.

The liquid usable in this method can be an ink or a solvent. If an ink is chosen, the ink can be a polymer-based ink, a solvent-based ink, or a water-based ink.

The fixed voltage or drive level of the pump at the first activation can be between 10 volts to 15 volts.

Prior to the first step the method could involve engaging a vacuum pump (Step108) to pull fluid into the filters, such as ink, or ink out of the filters. Similarly, the vacuum pump can be used to pull cleaning fluid through the filters and other printhead components.

The method could additionally include concurrently with the first step, a step of employing a return line between either the first or second port of the drop generator and the reservoir to permit liquid to flush through at least one of the filters prior to being returned to the reservoir (Step110aand Step110b).

The methods additionally has a step of keeping a controllable valve in the return line open each time the pump turns on at a drive level and closed when the pump is turned off (Step112aand Step112b).

The methods can additionally have a step where the pump is shut off for between three seconds and six seconds.

The embodiments have been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the embodiments, especially to those skilled in the art.

PARTS LIST