Self-packing filtration module for jet printing

<b>FIELD OF THE INVENTION</b>

[01] The present invention relates to inkjet printing, and more particularly, to filtering ink supplied to a print head of a continuous ink jet printing apparatus.

<b>BACKGROUND OF THE INVENTION</b>

[02] In inkjet printing systems, a print is made up of individual ink droplets formed at a nozzle and applied to a substrate. There are two principal systems: an on-demand supply system in which droplets of ink for printing are formed on demand; and an ink supply system with continuous ink supply, in which droplets are formed continuously, and only selected droplets are directed to the substrate, while others are returned to the ink source.

[03] Continuous inkjet printers supply ink under pressure to the droplet generator of the print head, where the continuous ink stream supplied from the nozzle is split into separate, uniform droplets, for example, by means of an oscillating piezoelectric element. Drops are directed past the charging electrode, in which they are selectively and separately given a predetermined charge before passing through a transverse electric field provided between a pair of deflecting plates. Each charged drop is deflected by the field by an amount that depends on the size of its charge, before it hits the substrate, while uncharged drops move without deviation and collect in the gutter, from which they return to the ink source for reuse. Charged droplets bypass the chute and fall into the substrate at a position determined by the droplet charge and the position of the substrate relative to the print head. Typically, the substrate moves relative to the print head in one direction, and the droplets deviate in a direction generally perpendicular to this direction, despite the fact that the deflecting plates can be oriented obliquely to the perpendicular to compensate for the speed of the substrate (moving the substrate relative to the print head between the arrival of drops means that otherwise, the line of drops does not pass sufficiently perpendicular to the direction of movement of the substrate).

[04] In continuous inkjet printing, a mark is printed from a matrix including an equidistant array of possible drop positions. Each matrix contains many columns (strokes), each of which is formed by a line that includes many possible positions of the droplet (for example, seven) formed by the charge communicated to the droplets. Thus, each drop used is charged according to its predetermined position in the stroke. If a drop is not used, then this drop is not charged and is captured in the trench for recycling. This cycle is repeated for all strokes in the matrix and then starts again for the matrix of the next character.

[05] Ink is supplied under pressure to the print head through an ink source system, which is generally located inside a cabinet compartment, which includes a separate compartment for a control circuit and a user interface panel. The system includes a main pump that draws ink from the tank or tank and delivers them under pressure to the print head. As ink is consumed, the reservoir is replenished as necessary from a replaceable ink cartridge, which is removably connected to the reservoir by means of a supply pipe. Ink is supplied from the tank through a flexible supply line to the print head. Unused droplets of ink trapped in the gutter are returned to the tank through the return line via a pump or a venturi pump. The ink flow in each of the pipelines as a whole is controlled by solenoid valves and / or other similar components.

[06] Ink filtering is provided to capture or limit the amount of particulate matter in the ink that is supplied to the print head for printing. More specifically, the filter module provides the filter material in the ink channel from the ink source to the print head. The filters used in these systems have a known effective life, so that filters are replaced at service intervals. Replacing the filters can be time consuming, which means that the continuous inkjet printing apparatus does not work, which is undesirable for printing and marking in the production line. Moreover, when the filter module is replaced, it often contains a certain amount of ink, in which they are considered hazardous waste, and special precautions must be taken when disposing of the filter module.

<b>Summary of the invention</b>

[07] The present invention provides a filter module with self-sealing valves assembly that is configured to leave a minimum amount of printing fluid in the module after use.

[08] According to one aspect, a filter module for a continuous ink jet printing apparatus includes a filter housing, filter material fixed inside the housing, and an inlet through which ink flows into the housing under pressure. The first self-sealing valve assembly is located inside the inlet. Ink flows out of the housing under pressure through the outlet. A second self-sealing valve assembly is located inside the outlet. The first and second valves assembly are open when mechanically connected to the ink channel from the ink tank to the print head, and the first and second valves assembly are tightly closed when mechanically disconnected from the ink channel.

[09] According to another aspect, the continuous ink jet printing apparatus includes an ink holding tank for ink, a print head in fluid communication with the ink tank, the print head having an ink nozzle for ejecting ink droplets onto an image printing substrate a channel for ink, providing a message on the fluid from the ink tank to the print head, and a pump, located in the ink channel and in fluid communication with the ink tank and the print head for delivering ink from the ink tank to the print head under pressure. The filter module is located in the ink channel between the pump and the print head.

[010] The preceding paragraphs are given as an introduction and are not intended to limit the scope of the following claims. Embodiments that are currently preferred, along with other advantages, will be better understood from the following detailed description when considered in conjunction with the accompanying drawings.

<b>Brief Description of the Drawings</b>

[O11] The invention is described below with reference to the accompanying drawings, in which:

[012] FIG. 1 is a schematic illustration of an ink supply circuit for a continuous ink jet printing apparatus.

[013] FIG. 2 is a bottom perspective view of a filter module according to embodiments of the invention.

[014] FIG. 3 is a sectional view of the filter module of FIG. 2.

[015] FIG. 4 is a sectional view of a self-sealing valve assembly according to embodiments of the invention.

[016] FIG. 5 is a sectional view of the self-sealing valve of FIG. 4 brought into the open position.

<b>Detailed Description of Embodiments of the Present Invention</b>

[017] The inventors realized that when servicing a continuous inkjet printing apparatus, the filter modules to be replaced often contain sufficient ink to make this component a hazardous material, and precautions regarding the disposal of the filter module must be followed. . Sometimes filter modules tend to leak during replacement, resulting in contamination of the work area and parts of the inkjet printer. In addition, extracting filter modules is often a complex task that can be time consuming and can be dirty. Accordingly, the inventors have developed a “self-sealing” filter module that minimizes or eliminates ink leakage when the continuous ink system is removed from the ink channel. To this end, the filter is configured to minimize ink removal from the filter module when depressurizing the ink lines and the filter module. Accordingly, there is provided a filter module according to embodiments of the invention in which ink is discharged from the filter module so that their amount is less than a certain amount (for example, 30 ml), thereby eliminating the need for precautions when disposing of hazardous materials.

[018] Next, with reference to FIG. 1, an ink supply pattern for an ink jet printing apparatus 10 with a continuous ink supply is illustrated. The inkjet printing apparatus 10 includes a fluid system 12, a printhead 14, and a condenser 16. The fluid system 12 includes an ink tank or a mixing tank 18 for containing ink, a tank 20 of an auxiliary substance 20 for containing solvent, and a source 22 ink. The ink source 22 and the auxiliary tank 20 supply fluids to the mixing tank 18. The solvent is added to the ink tank or mixing tank 18 during operation of the inkjet printing apparatus to compensate for the loss of solvent due to evaporation and to properly control the ink viscosity. Inks for continuous inkjet printers are typically complex mixtures of many materials with most volatile organic solvents. Common organic solvents include methyl ethyl ketone (MEK), acetone, and ethanol. The print head 14 includes a nozzle 26 in fluid communication with the ink tank 18 for ejecting ink droplets, and a chute 30 for receiving, through its ink trap, ink droplets that are not used for printing. Channel 32 of the gutter begins at the ink trap or the mouth of the gutter 30 and provides fluid communication with the ink reservoir for ink and air that enter the chute 30 through the ink trap. A return line (not shown) can be located in fluid communication with the chute 30 to transfer air from the condenser 16 to the chute 30 and to enter the channel 32 of the chute, which returns ink to the mixing tank 18.

[019] Ink is supplied to the print module or print head 14 through the ink channel 34. A pump 36 is provided in the ink passage 34 for supplying pressurized ink to the print head 14 for printing. In addition, a filter module 38 is provided in the ink channel 34 between the pump 36 and the print head 14 to filter particulate matter from the ink before ink enters the print head 14. The filter module 38 is shown in more detail in FIGS. 2 and 3 and includes a housing 40 with an upper portion 40A and a lower portion 40B. A filter medium 42 is installed inside the housing 40 to filter the ink supplied to the module 38 under pressure. The filter may be a polypropylene filter with a throughput of 5 μm, configured to filter the ink supplied to the module under a pressure of about 2.5-3.5 bar.

[020] Module 38 includes an inlet 44 and an outlet 46, on the lower portion 40B of the module 38, through which ink enters and leaves the module 38. A second outlet 48 may also be provided for returning ink in the module 38 to the mixer tank 18 via a return line 52. To maintain the pressure in the module 38 at the required level or in the required range, some ink in the module 38 is periodically discharged through the second outlet 48 through the operation of the Venturi pump 51 and returned to the mixer tank 18, while the ink continues to flow to the print head 14 . In addition, or alternatively, a second outlet 48 and / or additional openings can be integrated into the module 38 to circulate pigmented ink through the module (and optionally through the filter material 42) so that the pigment from the ink does not accumulate or precipitate in the tank 18 for ink.

[021] The module may be provided with an electronic information storage device, such as a memory chip 45 with surface-mounted electrical contacts for connection to respective contacts provided on an inkjet printing device. The memory chip 45 may be any suitable electronic information storage device, may be supported on any suitable substrate, and may be connected to suitable electronic contacts (or a contact) in any convenient manner, provided that these contacts are accessible for connection to a printing device when the filter module 38 is inserted into the inkjet printing apparatus. The memory chip 45 includes at least read-only memory (ROM). The information on the memory chip can be any suitable information and can usually include information such as the serial number of the filter module, manufacturing date, model number, expiration date, and the like. The memory chip may include security information so that only suitable and recognized filtering modules can be used with the printer. Other information on the memory chip 45 may include a type of fluid (such as a type of solvent, ink, or whether dye-based ink is pigmented or pigmented), service life, and so on. The memory microcircuit may also include a portion of rewritable information. An inkjet printing device can record on a memory chip to indicate that the filter module has reached the end of its life, so that the filter module can no longer be used in this inkjet printing device or in any other inkjet printing device.

[022] The self-sealing valves 54, 56 assembly are mounted inside the inlet 44 and the outlet 46, respectively. A similar valve assembly may also be installed in the second outlet 48. Since the valve assemblies 54, 56 are identical in design and function, the following description of the valve assembly 54 is applicable to the valves 54, 56 of the assembly of both outlets 46, 48. These self-sealing valves 54, 56 assembly provide a mechanical connection between the module 38 and the ink channel, and when the module 38 is disconnected from the ink channel, they minimize or eliminate ink leakage.

[023] Figures 4 and 5 show in more detail the valve assembly 54 including a valve body 60 having an upper end 62 and a first opening 64 at a lower portion of the valve assembly 54 remote from the upper end 62. In particular, the valve the assembly is shown to engage with the ink flow support pin 70, which is mounted on top of the ink tank. The ink tank may include at least two pins 70 to allow ink flow to engage or open the assembled valves 54, 56. As can be seen in FIG. 4, a pressing mechanism 76, such as a spring, presses the ball 66 against the second hole 64 and toward the seal 71 while in the closed position. When the filter module 38 is attached to the ink tank, the ink flow support pin 70 passes through the first hole 64 and the seal 71 to move the ball 66 to the upper end 62 of the valve body 60. More specifically, as can be seen in FIG. 5, when the valves 54, 56 are assembled, or the filter module 38 is mechanically connected to the ink channel and the ink container, a pin (s) 70 pushes the ball 66 toward the upper end 62 to open the valves 54, 56 assembly. The ink flow support pin 70 includes a channel 72 and windows 74 through which ink flows into the module 38 through the side openings 82 in the valve assembly 54. When the module 38 is connected to the ink channel 33, the assembled valves 54, 56 are automatically opened to allow ink to flow through the module 38, the filter material 42, and to the print head 14. The terms "mechanically coupled" and "mechanically detached" refer to the mechanical interaction between the components of the filter module 38 and the parts and / or components connected to the ink flow or ink reservoir of the inkjet printing device, the mechanical interaction being used to open and close the valves for controlling the flow ink through the filter module.

[024] As can be further seen in FIGS. 4 and 5, in an embodiment of the invention, the ink flow support pin 70 comprises a contoured outer surface including an upper arm 83 that converges inwardly with respect to the shaft 88 of the pin 70. In addition, , the inner surface 84 of the seal 71 is contoured so as to generally correspond to the shape of the pin 70 at the shoulder 83. Accordingly, when the valve assembly 54 and the filter module 38 are attached to the ink tank, the inclined surface 84 of the seal 71 abuts against the shoulder 83 of the pin 70. This sealed contact boundary between the pin 70 and the seal 71 prevents any back flow of ink flowing from the valve 54 assembly during operation of the printing system 10. For this, given that the valve assembly 56 is identical to the valve assembly 54, the same sealed contact boundary of the valve assembly 56 prevents leakage from the filter module 38 and the valve assembly 26 of the ink coming out of the filter module 38. In addition, the seal 71 is made and has such dimensions at the first hole 64 and inside the base 86 of the housing 60 to provide a seal with the shaft 88 to further prevent ink leakage from the valve 54 assembly, as well as to maintain the filter module 38 on the tank ink. As again seen in FIG. 2, flanges 90 with bolt holes 92 may be provided at the bottom of the housing 60 for attaching the module 38 to the ink tank by means of bolts or other fasteners.

[025] When the inkjet printing apparatus 10 is being serviced, the ink pump 36 is turned off, as a result of which the pressure in the internal volume of the module 38 is released and the ink is discharged through the second outlet 48 through the return line 52 and the Venturi pump 51 and returned to the ink tank 22. However, since the valves 54, 56 assembly and the same valve assembly of the second outlet 48 remain open, the pin 70 to ensure ink flow abuts the seal 71 as described above, preventing or minimizing ink leakage. When the module 38 is disconnected from the ink channel 33, the prepress mechanism 76 presses the ball 66 against the seal 71, automatically closing the valves 54, 56 assembly, preventing any ink remaining in the module 38 from escaping.

[026] Although, in the embodiments described herein, the valves 54, 56 assembly depend on the lower portion 40B of the housing 40, the invention is not limited to such a configuration. For example, the assembled valves 54, 56 may be located completely inside the body 40, so that the second hole 64 is generally flush with the bottom of the body 40 or completely located inside the body 40.

[027] In the embodiment shown in FIG. 3, module 38 may also include an ink flow pressure compensator 58 that is used to control pressure fluctuations in the ink passage 33 or to minimize them. As described in more detail below, the compensator 58 may also contribute to the removal of ink from the module 38. The compensator comprises a diaphragm 78 operatively connected to the upper part 40A of the housing 40 and suspended inside the module 38 and the inner circumference of the filter material 42. A pressing mechanism 80, such as a coil spring, is also functionally connected to the upper part 40A of the housing 40 and is located inside the diaphragm 78 for pressing the diaphragm 78 to the lower part 40B of the housing 40 and the valves 54, 56 assembly.

[028] When ink is supplied to the module 38 under pressure, the ink stream presses the pressing mechanism 80 and the diaphragm 78 to the upper part 40A of the housing 40. The pressing mechanism 80 and the diaphragm 78 exert a counteracting force on the pressure ink stream to absorb pressure fluctuations in the ink stream . When pressure is released from the module 38 by turning off the pump 36, the pressing mechanism 80 presses the diaphragm against the valves 54, 56 assembly and the valve assembly of the second outlet 48, thereby causing ink to exit the chamber of the module 38. Thus, when the module 38 is disconnected from the ink channel 33, only the nominal amount of ink remains in it, and the module 38 can be thrown into the normal waste stream without having to take precautions when disposing of toxic waste. Preferably, after use and subsequent removal from the inkjet printing apparatus, the expended module contains less than 30 ml, less than 20 ml, or less than 10 ml of printing fluid.

[029] Although various embodiments of the present invention are shown and described in this document, it should be understood that these embodiments are provided by way of example only. Many modifications, changes and replacements can be made without departing from the invention described in this document. Accordingly, the invention is limited only by the nature and scope of the attached claims.