A self-sealing filter module for inkjet printing.

(54) Title: SELF-SEALING FILTER MODULE FOR INJECTION PRINTING.

(54) Title: A SELF-SEALING FILTER MODULE FOR INKJET PRINTING.

(57) Summary

A filter module (38) for a continuous ink jet printer (10) comprising a filter housing (40) and a filter medium (42) fixed within the housing (40). The filter housing (40) further includes an inlet port (44) through which ink flows into the housing under pressure and a first self-sealing valve assembly (54) disposed within the inlet port. In addition, the housing includes an outlet port (46) through which ink flows out of the housing (40) under pressure and a second self-sealing valve assembly (56) disposed within the outlet port (46). The first and second valve assemblies (54, 56) open when mechanically connected to an ink flow path (34) from an ink reservoir (18) to a print head (14), and the first and second Valve assemblies (54, 56) seal when mechanically disconnected from the ink flow path (34).

(57) Abstract

A filter module (38) for a continuous inkjet printer (10) comprising a filter housing (40) and a filter medium (42) fixed within the housing (40). The filter housing (40) further ineludes an inlet portal (44) through which ink 1 lows into the housing under pressure and a first self-sealing valve assembly (54) disposed within the inlet portal. In addition, housing ineludes an outlet portal (46) through which ink flows out of the housing (40) under pressure and a second self-sealing valve assembly (56) disposed within the outlet portal (46). The first and second valve assemblies (54,56) open when mechanically connected to an inkflow path (34) from an ink tank (18) to a print head (14), and the first and second valve assemblies (54, 56) seal closed when mechanically disconnected from the ink flow path (34).

SELF-SEALING FILTER MODULE FOR INJECTION PRINTING

Field of the invention

The present description relates to ink jet printing and very particularly to the filtration of ink supplied to a print head of a continuous ink jet printer.

Background of the invention

In inkjet printing systems, the print is made up of individual droplets of ink, generated at a nozzle and propelled onto a substrate. There are two main systems: drop on demand, where ink droplets are generated for printing when required; and continuous ink jet printing in which droplets are continuously produced and only those selected are directed towards the substrate, the others being recirculated to an ink supply.

Continuous ink jet printers supply pressurized ink to a print head drop generator in which a continuous stream of ink emanating from a nozzle is broken up into individual regular drops, for example by an oscillating piezoelectric element. The droplets are directed past a charging electrode, where they are selectively and separately given a predetermined charge before passing through a transverse electric field provided through a pair of deflection plates. Each charged drop is deflected by the field by an amount that depends on its magnitude of charge before striking the substrate while the uncharged droplets continue without deflection and are collected in a channel from where they are recirculated to the ink supply for reuse. The charged drops deviate from the channel and strike the substrate at a position determined by the charge on the drop and the position of the substrate relative to the print head. Generally, the substrate is moved relative to the print head in one direction and the drops are deflected in a direction generally perpendicular to it. although the baffle plates may be oriented at an incline to the perpendicular to compensate for the speed of the substrate (movement of the substrate relative to the print head between incoming drops means that a line of drops would not otherwise extend very perpendicularly to the direction of movement of the substrate).

In continuous inkjet printing, a character is printed from a matrix that includes a regular array of potential drop positions. Each array comprises a plurality of columns (runs), each of which is defined by a line that includes a plurality of potential drop positions (eg, seven) determined by the load applied to the drops. Therefore, each drop used is charged according to its intended position in the race. If a particular droplet is not to be used, then the droplet is not loaded and is captured in the channel for recirculation. This cycle repeats for all races in an array and then starts over for the next array of characters.

Ink is supplied under pressure to the print head by an ink supply system that is generally housed within a compartment of a cabinet that includes a separate compartment for control circuitry and a user interface panel. The system includes a main pump that draws ink from a reservoir or tank and supplies it under pressure to the print head. As the ink is consumed, the reservoir is refilled as needed from a replaceable ink cartridge that is freely connected to the reservoir via a supply conduit. The ink is fed from the reservoir through a flexible supply conduit to the print head. Unused ink droplets captured by the channel are recirculated to the reservoir through a return conduit by a pump or venturi. The flow of ink in each of the conduits is generally controlled by solenoid valves and / or other similar components.

Ink filtration is provided to capture or limit the amount of particles in the ink that is supplied to the print head for printing. More specifically, a filter module provides filter media in the ink flow path from an ink source to the print head. Filters used in these printing systems have a known effective life, so filter replacement is done at timed service intervals. Replacing the filters can be time consuming, which means that the continuous inkjet printer is not working, which is undesirable for production line printing and marking. In addition, when a filter module is replaced, it often contains such an amount of ink that it is considered HAZMAT residue and special precautions must be taken to dispose of the filter module.

Summary of the invention

The present disclosure provides a filter module with self-sealing valve assemblies, which is configured to leave a minimal amount of printing fluid in the module after use.

In one aspect, a filter module for a continuous ink jet printer includes a filter housing, a filter medium attached within the housing, and an inlet port through which ink flows into the housing under pressure. A first self-sealing valve assembly is disposed within the inlet port. Ink exits the housing under pressure through an outlet port. A second self-sealing valve assembly is disposed within the outlet port. The first and second valve assemblies open when they are mechanically connected to an ink flow path from an ink reservoir to a print head and the first and second valve assemblies are sealed when they are mechanically disconnected from the flow path. from ink.

In another aspect, a continuous ink jet printer includes an ink tank for holding ink, a print head in fluid communication with the ink tank, and the print head having an ink nozzle for expelling ink droplets onto a substrate to print an image, an ink flow path providing fluid communication from the ink reservoir to the print head and a pump arranged in the ink flow path and in fluid communication with the ink reservoir and the print head to supply ink from the ink tank to the print head under pressure. A filter module is arranged in the ink flow path between the pump and the print head.

The preceding paragraphs have been provided by way of a general introduction, and are not intended to limit the scope of the following claims. The presently preferred embodiments, along with other advantages, will be better understood with reference to the following detailed description taken in conjunction with the accompanying drawings.

Brief description of the drawings

The invention is explained in the following description in view of the drawings showing:

Figure 1 is a schematic illustration of the ink flow circuit for a continuous ink jet printer.

Figure 2 is a bottom perspective view of a filter module in accordance with embodiments of the invention.

Figure 3 is a sectional view of the filter module of Figure 2.

Figure 4 is a sectional view of a self-sealing valve assembly in accordance with embodiments of the invention.

Figure 5 is a sectional view of the self-sealing valve of Figure 4 actuated to an open position.

Detailed description of the invention

The inventors have recognized that during the service of a continuous inkjet printer, the filter modules to be replaced often contain a sufficient volume of ink such that the component is regarded as HAZMAT, thus requiring certain precautions in As for disposing of the filter module. Filter modules sometimes have a tendency to leak when replaced, thus fouling the work area and parts of the printer. Furthermore, the removal of filter modules is often a relatively complicated task that can be time consuming and messy. Accordingly, the inventors have developed a self-sealing filter module that minimizes or eliminates ink runoff after removal from a continuous jet ink flow path. To this end, the filter is adapted to maximize the drain of ink from the filter module when the pressure in the ink lines and the filter module is removed. Accordingly, the filter module is provided in accordance with embodiments of the invention that empties ink from the filter module such that there is less than a certain amount (eg, 30 ml) which avoids the need for HAZMAT precautions. for disposal.

Now, referring to FIG. 1, an ink flow circuit for a continuous inkjet printer 10 is illustrated. Printer 10 includes a fluid system 12, a print head 14, and a condenser 16. The printing system Fluid 12 includes an ink tank or mixer 18 for containing ink, a make-up tank 20 for containing solvent, and an ink source 22. The ink source 22 and make-up tank 20 provide fluids to the mixing tank 18. Solvent is added to the ink tank or mixer 18 during printer operation to replace the loss of solvent due to evaporation and to properly control the viscosity of the ink. Inks for continuous inkjet printers are generally complex mixtures of many substances, with a large proportion of volatile organic solvents. Typical organic solvents include methyl ethyl ketone (MEK), acetone, and ethanol. The printhead 14 includes a nozzle 26 in fluid communication with the ink reservoir 18 to eject ink droplets and a channel 30 to receive, through an ink receiving inlet thereof, ink droplets that are not they use to print. A channel flow path 32 begins at the ink receiving port or inlet of channel 30 and provides fluid communication to the ink reservoir, for ink and air that has entered channel 30 through the ink receiving port. A return line (not shown) may be placed in fluid communication with channel 30 to transport air from condenser 16 to channel 30 and to enter channel flow path 32, which returns ink to mixing tank 18.

Ink is supplied to the print module or print head 14 through an ink flow path 34. A pump 36 is provided in the ink flow path 34 to supply ink to the print head 14 under pressure for printing. . In addition, a filter module 38 is provided in the ink flow path 34 between the pump 36 and the print head 14 to filter particles from the ink before it reaches the print head 14. The filter module 38 is shown in more detail in Figures 2 and 3, and includes a housing 40 with a top 40A and a bottom 40B. Filter media 42 is mounted within housing 40 to filter ink supplied to module 38 under pressure. The filter can be a 5 µ polypropylene filter capable of filtering the ink supplied to the module at a pressure of from about 2.5 bar to about 3.5 bar.

Module 38 includes an inlet port 44 and an outlet port 46, at the bottom 40B of the module 38, and through which ink enters and exits the module 38. A second outlet port 48 may also be provided for the ink return in module 38 to mixing tank 18 through return line 52. In order to maintain the pressure in the module 38 at a desired level or within a desired range, some ink in the module 38 is periodically vented through the second outlet port 48 by operation of the Venturi pump 51 and returned. to mixing tank 18, while ink continues to flow to printhead 14. Additionally, or alternatively, the second outlet port 48 and / or additional ports may be incorporated into the module 38 to circulate pigmented ink through the module (and not necessarily through the filter medium 42) so that the pigment in the ink do not collect or settle in ink tank 18.

The module may be provided with an electronic data storage device such as a memory chip 45 with surface mounted electrical contacts for connection to corresponding contacts provided on the printer. The memory chip 45 can be any suitable electronic storage device, can be supported on any suitable substrate, and can be connected to suitable electrical contacts (or contacts) in any convenient way, provided that said contacts are accessible for connection to the printer when the filter module 38 is inserted into the printer. The memory chip 45 includes at least Read Only Memory (ROM). The data on the memory chip can be any suitable data and would normally include information such as the filter module serial number, production date, model number, expiration date, and the like. The memory chip can include security data so that only suitable or recognized filter modules can be used with the printer. Other data on the memory chip 45 may include fluid type (such as solvent, ink type, dye-based or pigmented ink), shelf life, and the like. The memory chip can also include a writable data portion. The printer can write to the memory chip to indicate that the filter module has reached the end of its useful life, so that the filter module can no longer be used in the printer or any other printer.

Self-sealing valve assemblies 54, 56 are mounted within inlet port 44 and outlet port 46, respectively. A similar valve assembly may also be mounted in the second outlet port 48. Since valve assemblies 54, 56 are identical in structure and function, the following description of valve assembly 54 applies to valve assemblies 54, 56 from both outlet ports 46, 48. These automatic shutoff valve assemblies 54, 56 allow for mechanical connection of the module 38 to the ink flow path and, by disconnecting the module 38 from the ink flow path, minimize or eliminate ink runoff.

With respect to Figures 4 and 5, valve assembly 54 is illustrated in more detail and includes a valve housing 60 having an upper end 62 and a first opening 64 in the lower portion of assembly 54 distal to upper end 62. In particular, the valve assembly is illustrated engaging an ink flow pin 70 that is mounted on a top of an ink reservoir. The ink reservoir may include at least two of the ink flow pins 70 for engaging, or opening, the valve assemblies 54, 56. As shown in Figure 4, a biasing mechanism 76, such as a spring , deflects a ball 66 toward the second opening 64 and against a seal 71, when in a closed position. When filter module 38 is attached to an ink reservoir, ink flow pin 70 extends through first opening 64 and seal 71 to move ball 66 toward upper end 62 of valve housing 60. More specifically, Figure 5, when valve assemblies 54, 56 or filter module 38 are mechanically connected to the ink flow path and ink container, pin (s) 70 forces ball 66 toward the upper end 62 to open the valve assemblies 54, 56. Ink flow pin 70 includes conduit 72 and openings 74 through which ink flows into module 38 through side openings 82 in valve assembly 54. When module 38 is connected to the ink flow 33, valve assemblies 54,56 open automatically for ink to flow through module 38, filter medium 42 and to print head 14. The terms mechanically connected and mechanically disconnected refer to the mechanical interaction between the components of the filter module 38 and parts and / or components connected to the ink path or ink reservoir of the printer, wherein the mechanical interaction serves to open and closing valves to control the flow of ink through the filter module.

As further shown in Figures 4 and 5, in one embodiment of the invention, the ink flow pin 70 comprises a contoured outer surface that includes an upper shoulder 84 that tapers inward relative to an axis 88 of the pin 70. In addition, an inner surface 84 of seal 71 is contoured, and also generally corresponds to the shape of pin 7 0 in shoulder 84. Consequently, when valve assembly 54 and filter module 38 are attached to the ink reservoir, an inclined surface 84 of seal 71 abuts shoulder 81 of pin 70. This sealed interface between pin 70 and seal 71 prevents any backflush of ink that runs off valve assembly 54 during operation of printing system 10.

To that end, since valve assembly 56 is configured identical to valve assembly 54, the similar sealed interface in valve assembly 56 prevents ink flowing from filter module 38 from dripping out of filter module 38 and the valve assembly 56. Seal 71 is further configured and dimensioned at first opening 64 and within a base 86 of housing 60 to provide a seal against shaft 88 to further prevent ink from leaking from valve assembly 54 and also supports filter module 38 in the ink tank. Also referring to Figure 2, flanges 90 with bolt holes 92 may be provided toward the bottom of housing 60 to secure module 38 to an ink tank with bolts or other fasteners.

When the printer 10 is serviced, the ink pump 36 is deactivated by removing pressure from inside the internal volume of the module 38 and the ink passes through the second outlet port 48 through the return line 52 and the pump venturi 51 and is returned to ink tank 22. However, as the valve assemblies 54, 56 and the similar valve assembly of the second outlet port 48 remain open, the ink flow pin 70 abuts the seal 71, as described above, preventing or reducing minimizes ink runoff. When module 38 is disconnected from ink flow path 33, deflection mechanism 76 forces ball 66 against seal 71, automatically closing valve assemblies 54, 56 so that no ink remains in module 38 .

Although embodiments of the invention described herein show valve assemblies 54, 56 depending on a lower portion 40B of housing 40, the invention is not limited to such configuration. For example, valve assemblies 54, 56 could be disposed entirely within housing 40 such that second opening 64 is generally flush with a bottom of housing 40 or is disposed entirely within housing 40.

In the embodiment illustrated in Figure 3, the module 38 may also comprise an ink flow pressure damper 58 which is used to control or minimize pressure fluctuations in the ink flow path 33. As will be further described In more detail later, the damper 58 may also aid in the evacuation of ink from the module 38. The damper comprises a diaphragm 78 operatively connected to the top 40A of housing 40 and which is suspended within module 38 and an inner circumference of filter medium 42. A biasing mechanism 80, such as a helical coil spring, is also operatively connected to the top 40A of the housing 40 and is located within the diaphragm 78 to bias the diaphragm 78 toward the bottom 40B of the housing 40 and valve assemblies 54. , 56.

When ink is supplied to module 38 under pressure, the ink flow forces deflection mechanism 80 and diaphragm 78 toward the top 40A of housing 40. Deflection member 80 and diaphragm 78 apply a counter-force against the pressurized ink flow to absorb pressure fluctuations in the ink flow. When the pressure is removed from the module 38 by deactivating the pump 36, the bypass mechanism 80 forces the diaphragm towards the valve assemblies 54, 56 and the second outlet port valve assembly 48 thereby forcing the evacuation of ink from the chamber of the module 38. In this way, when module 38 is disconnected from ink flow path 33, only a nominal amount of ink remains and module 38 can be disposed of in the normal waste stream without having to take precautions to dispose of toxic waste. . Preferably, after being used and then removed from the printer, the used module includes less than 30 ml, less than 20 ml or less than 10 ml of printing liquid.

Although various embodiments of the present invention have been shown and described herein, it will be obvious that those embodiments were provided by way of example only. Numerous variations, changes, and substitutions can be made without departing from the present invention. Accordingly, the invention is intended to be limited solely to the spirit and scope of the appended claims.