JP2004268566A - Device and method to uniformly and equally supply ink to both ends of liquid droplet generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a turbulent flow in a liquid droplet generator even if a print head becomes long or the amount of liquid droplet generated is increased. <P>SOLUTION: A liquid droplet generator is related to an inkjet printer, and the liquid droplet generator is composed of many fluid ports for the liquid droplet generator. At least one of the many fluid ports functions as a one-way entrance port when liquid is supplied to the liquid droplet generator. At least one of the many fluid ports is of a bi-directional type, and functions as an exit at the time of start and stop of the print head. It also functions as an additional ink exit port during an ordinary operation of the print head. Thereby, the flow rate at the entrance is reduced below the flow rate when a turbulent flow occurs. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to continuous ink jet printers, and more particularly, to an apparatus and method for reducing turbulence in a fluid cavity of a droplet generator.

  For example, a printhead receives one or more rows of orifices that receive a conductive recording fluid, such as water-soluble ink, from a pressurized fluid supply manifold and eject the fluid as a parallel stream of rows. Defining inkjet printing devices are known. Printers using such printheads selectively charge and deflect droplets in each of the streams, and print at least a portion of the droplets while other droplets strike the droplet capture device. By attaching to a receiving medium, reproduction of a figure or the like is realized.

  Droplet generators are a key component in continuous ink jet printheads. Droplet generators often use a nozzle plate attached to a resonator to stimulate the jet. Several different methods are currently being implemented to supply fluid to the nozzle plate. One known method includes a fluid passage starting at the nodal line of the resonant body, with an internal cavity reaching the nozzle plate. Another known method can achieve fluid entry by pumping ink through a fluid port formed in the end wall of the drop generator, wherein the fluid port is located on the face of the nozzle plate of the drop generator. To be located close to the bottom. This obviates the long internal cavities required of a nodal feed drop generator. This latter method is referred to as a bottom front feed drop generator. As a variant of this idea, it is known that the droplets are supplied from the side rather than from the front side.

  Standard operation of an ink jet printer known in the art is disclosed in U.S. Pat. No. 4,999,647 and co-assigned U.S. Pat. No. 09 / 211,059. , Based on the ink being supplied into one end of the droplet generator. During start-up of the printer, as ink flows transversely through the drop generator, it provides a return path for the ink and removes internal particles, and ink residue from previous printer shutdowns. An outlet port is used to redissolve the This "single feed" configuration is satisfactory for products with an orifice number of up to 2700 and droplet generation of 110,000 kHz / jet; many such printers use Operable without throwing flow into the turbulent region.

  As printheads become longer or more droplets are generated, one challenge is to reduce turbulence in the droplet generator. At some point, the high flow of ink into the droplet generator results in turbulence in the fluid cavity of the droplet generator. Turbulence in the fluid cavities of such droplet generators can affect the appropriate direction and velocity of the ink liquid formed by droplet generation. As an example, at the current 300 dpi, 2 drops per pixel printer (2 drops per 300 dpi pixels are required to fully cover the pixels), when run at an ink temperature of 43-C, 750 mL / Min ink flow rate is required. The ink flows through the 4.318 mm (0.170 inch) diameter fluid cavity bore without initiating turbulence. For this particular drop generator configuration, turbulence begins to occur as the flow rate approaches 800 mL / min. It is known to reduce the onset of this turbulence if the manufacturing of the part is altered, such as the uniformity of tube bending or the machining of grooves. For a 300 dpi 1 drop per pixel printer, the flow rate of ink required to meet the conditions to generate drops at a rate of 165,000 drops per second is 1300 mL / min or more. Attempts to supply this stream of ink to the drop generator with a single feed line of the same bore diameter result in a significant drop in drop format due to fluid turbulence at the inlet end. Will be. As a result, print quality and printhead operating attitude can be adversely affected. For this reason, it is desirable to operate the printhead such that there is no turbulence in the fluid cavity.

  Increasing the diameter of the through bore will, for the same flow rate, reduce the fluid inlet velocity and effectively increase the critical flow rate for turbulence. However, this is not an acceptable choice because of the problems associated with reduced operating cycles and reduced uniformity of jet break length. One possible means of reducing turbulence in the printhead is disclosed in U.S. Pat. No. 4,638,327. The droplet generator in U.S. Pat. No. 4,638,327 is divided into an upper portion and a lower portion by a turbulent damping multilayer screen structure. Such a structure is satisfactorily operable with a bolted drop generator, as shown and described in the above patents. However, such a bolted design is only useful for low resolution drop generators where the drop generation cycle is small. High resolution, high drop volume drop generators tend to require an integrated design that does not easily incorporate such turbulence damping means.

  Therefore, it is desirable to be able to operate a high-period, long-row droplet generator that does not create the problem of turbulence in the fluid cavity.

This object is met by an apparatus and method according to the present invention in which ink is evenly and equally supplied to both ends of a droplet generator to suppress turbulence in a high frequency, long array of droplet generators. .
According to one aspect of the invention, an ink jet printer is associated with a droplet generator having a plurality of fluid ports for the droplet generator. At least one of the multiple fluid ports functions as a unidirectional inlet port through which fluid is supplied to the drop generator, and at least one of the multiple fluid ports is bi-directional, for printhead startup and It functions as an outlet during shutdown and as an additional ink inlet port during normal operation of the printhead, thereby reducing the inlet flow below that at which turbulence begins.

  Advantageous effects of the present invention for other objects will be apparent from the following description, the accompanying drawings, and the claims.

Detailed description of the embodiment

  The present invention provides an apparatus and method for suppressing turbulence in a fluid cavity of a high-period, long-array droplet generator. The apparatus and method for suppressing turbulence allows for a uniform and equal supply of ink to both the inlet and outlet ports of the droplet generator.

  Referring now to the drawings, FIG. 1 shows a schematic diagram 10 of a fluid that provides an existing single-feed ink supply to a drop generator for a typical single printhead inkjet printer. . Ink is supplied from the fluid device 12 to the printhead rest station 14 via a heated umbilical cord 16. Single feed ink supply is provided along ink path 18.

  With continued reference to FIG. 1 and also to FIG. 2, ink is supplied to printhead 20 via ink path 18 and reaches cooling plate 22. This cooling plate uses ink supplied to the printhead to provide high voltage, as described and claimed in commonly assigned U.S. patent application Ser. No. 09 / 211,251. Cools the charged plate driver electronics components. Ink continues to flow along the ink path 18 through the cooling plate and printhead frame and re-enters the printhead rest station 14. It then passes through an ink temperature sensor, such as a thermistor 24, before re-entering the printhead to be filtered, for example, through a 1.2μ Pall filter element 26, and then drops. It is introduced at the inlet 28 of the generator 30.

A second filter 32 in the printhead filters the air used during the printhead shutdown period and is usually identical to the ink filter element 26. During normal operation, the valve V _F, V _I, V _A is closed all. At startup, valve V _O is opened to allow ink to flow through drop generator 30 and exit through outlet port 34 of the drop generator. Next, the ink passes through the pressure transducer 35 through the cross-flash solenoid valve V _O and back to the fluid device 12. This will flush air, dry ink and other dust from the drop generator. The valve _VO may then be closed to pressurize the drop generator such that an ink jet is formed in each of the orifices of an orifice plate (not shown) coupled to the drop generator. This ink can be returned to the fluidic device by a catcher 36 and a capture pan 38. Next, the inkjet can be selectively charged and deflected. Some droplets are selected to be printed droplets, and some droplets are deflected into a trap 36, which drops from the trap via fluid line 40 in FIG. Can be returned to the ink tank 42 shown in FIG.

During operation stop, the operation of the ink pump is stopped, also, in a predetermined order, allowing the cleaning fluid to open the valve V _F, V _I is washed ink from the droplet generator 30 and the last filter 26 . Then, deactivation order and closes the valves V _F, to open the valve V _A, an air pump 44 disposed in the printing station is to blow out the cleaning fluid is actuated from the droplet generator 30. Start and stop sequences are well known and are used in prior art devices.

  When the droplet generator 30 is a high frequency, long array of droplet generators, it must address and mitigate turbulence in the fluid cavities of the droplet generator. The present invention provides a fluid flow splitting and feeding both the inlet port 28 and the outlet port 34 of the droplet generator 30 which increases as the ink flow rate and the array length of the droplet generator increase. To eliminate the turbulence.

FIG. 3 illustrates a fluidic device according to the present invention, which provides an apparatus and method for uniformly and equally supplying ink to both the inlet and outlet ports of a droplet generator. The ink travels through the frame of the printhead 20 and the cooling plate 22 before splitting the ink flow. As compared to prior art fluidic devices, all modifications are located in printhead rest station 14 and printhead 20. During normal operation, the valve V _F, V _A is closed. Ink supplied to the printhead rest station cools the printhead electronics through cooling plate 22. The supplied ink then encounters the valves V _I , V _IB . At start-up, valve V _IB is closed, valves V _I and V _O are open, allowing ink to flow across the thermistor for temperature measurement through drop generator 30 ′ and drop generator outlet port. Allow to exit from 34 '. After an appropriate amount of cleaning, valve V _IB is also opened. This will flush air and dust from the JA-to-JB fluid supply line LB with valve V _IB and last filter 32. Since the outlet valve V _O is open, the ink flowing out of the fluid supply pipe bypasses the droplet generator 30 ′ and returns to the ink tank 42 shown in FIG. Then, it is possible to make the ink jet is formed a drop generators 30 'closes the valve V _O pressurized, each of the orifices of the orifice plate (not shown). Since both valves V _I and the valve V _IB is open, the ink fluid supply tube LI, are supplied to the through both the LO drop generator 30 '. By using the same type of valves and filters in both the fluid supply lines LA, LB, the flow rates of the fluid flowing through the two ports 28 ', 34' to the droplet generator 30 'are approximately balanced. Similarly, the valves and filters on both fluid supply lines LA, LB are balanced, and since there is no heater source associated with either fluid supply line, the ink supplied through fluid supply line LA will The temperature becomes substantially equal to the ink supplied through the tube LB. Temperature differences can cause differences in irritation, droplet deflection and ink / paper interaction across the width of the droplet generator. In this way, the fluid velocity into the drop generator 30 'is approximately equal to that encountered in the prior art, reducing the Reynolds number of the fluid flow and reducing turbulence during the printing mode of operation. Eliminate flow problems.

  In accordance with the present invention, the drop generator 30 'has at least a unidirectional inlet port 28' through which fluid is supplied to the drop generator, and an outlet during printhead startup and shutdown. It has a number of fluid ports, including a bi-directional fluid port 34 'that functions and functions as an additional ink inlet port during normal operation of the printhead. This arrangement reduces the inlet flow below the flow at which turbulence begins for the droplet generator 30 '.

When the operation is stopped, the valves V _I and V _IB are continuously operated in cooperation with the valves V _O , V _F and V _A. The drop generator and the fluid supply to the printhead can be cleaned and dried. Typically, the deactivation sequence is such that one of the two planes V _I , V _IB is closed while the other is open to effect high flow through the fluid supply tube, filter and drop generator to various components. Conditions may be included that facilitate achieving the required flow rate for efficient flushing and drying.

  The dual feed technique described herein employs an ink flow to the drop generator with a balanced flow within 3% of the 50% split flow at the inlet and outlet ports of the drop generator. An apparatus and a method for supplying are provided. The arrangement according to the invention also provides a mechanism for independently controlling the two supply lines by respective valves in the supply lines. This allows each of the filters to be drained separately, thereby increasing the filter's ability to remove any remaining ink. Thus, the present invention directs flow through a single port to the droplet generator during start-up and shutdown, to more effectively flush the droplet generator and other components. It has the advantageous effect of allowing.

  Although the present invention has been described in detail with reference to its preferred embodiments, it will be apparent that other modifications and variations are possible without departing from the scope of the invention as set forth in the appended claims. Would.

1 is a schematic diagram illustrating the prior art of one exemplary ink jet printer fluid. FIG. 2 is an enlarged view of the printhead pause station of the fluid schematic of FIG. 1 showing a single feed ink supply to the drop generator. 1 shows an apparatus and method for suppressing turbulence in a printhead. FIG. 3 is an enlarged view of a printhead rest station modified in accordance with the present invention.

Explanation of reference numerals

10 Schematic representation of a fluid with a single feed ink supply 12 Fluid device 14 Printhead rest station 16 Heated umbilical cord 18 Ink path 20 Printhead 22 Cooling plate 24 Thermistor 26 Ink filter elements 28, 28 'Liquid Droplet inlet 30, 30 ′ Droplet generator 32 Second filter 34, 34 ′ in printhead Droplet outlet port 35 Pressure transducer 36 Capturer 38 Capture pan 40 Fluid tube 42 Ink tank 44 Air pump

Claims (10)

In an ink jet printing apparatus including a print head having a droplet generator,
The droplet generator,
A unidirectional inlet port through which fluid can flow when supplied to the droplet generator;
It is connected to the droplet generator and functions as an outlet port during start-up and operation stop of the print head, while it functions as a fluid inlet port during the print operation of the print head, and the flow rate at which the turbulent flow of the fluid flows is generated. An ink jet printing apparatus comprising: The ink jet printing apparatus according to claim 1, wherein during a print operation of the printhead, the flow of fluid through the bidirectional fluid port to the droplet generator passes through the unidirectional inlet port. An ink jet printing device that is approximately equal to the flow of fluid into the printer. The ink jet printing apparatus according to claim 1, wherein during a print operation of the printhead, the temperature of the fluid flow through the bidirectional fluid port to the droplet generator is such that the droplets pass through the unidirectional inlet port. Ink jet printing device where the temperature of the fluid stream to the generator is approximately equal. In a method for supplying a flow of ink to a droplet generator provided in a print head of an inkjet printer,
Introducing ink into the printhead along the ink flow path;
Dividing the ink flow path into an inlet port flow path and an outlet port flow path so that ink flows into the droplet generator at substantially equal flow rates at both ends of the droplet generator. A method for supplying a flow of ink to be provided. 5. The method of claim 4, wherein clean air is supplied to the droplet generator through the inlet port flow path to remove liquid from the droplet generator. 5. The method of claim 4, wherein air and contaminants can be exhausted from the outlet port channel while the outlet port channel functions as an outlet port of the droplet generator. A printhead having a droplet generator having first and second fluid ports;
And a fluid device for supplying a fluid to the droplet generator.
The fluid device is
Means for supplying a fluid to the first fluid port of the droplet generator;
The second fluid port functions as a bi-directional port that acts as an exit port during start-up and shutdown of the printhead, while reducing the fluid inflow during the print operation of the printhead below the turbulent flow rate. Means for controlling the flow of fluid to the second fluid port of the droplet generator to function as a fluid inlet port for reduction. 8. The ink jet printing apparatus according to claim 7, wherein during a printing operation of a printhead, a flow of fluid through the second fluid port to the droplet generator causes the droplet generation through the first fluid port. An ink jet printing device that is approximately equal to the fluid flow to the container. 8. The ink jet printing apparatus according to claim 7, wherein air and contaminants can be discharged from the second fluid port while the second fluid port acts as an outlet port of the droplet generator. . 8. The ink jet printing apparatus according to claim 7, wherein the fluid supply tube supplying ink to the second fluid port includes air and contamination when the second fluid port acts as an outlet port for the droplet generator. An inkjet printing device that can be cleaned to remove material.

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