This disclosure relates generally to micro-fluidic devices that eject fluid from a liquid supply in the device and, more particularly, to ink ejectors in print heads that eject ink onto imaging substrates.
Drop on demand inkjet technology has been employed in commercial products such as printers, plotters, and facsimile machines. Generally, an inkjet image is formed by the selective activation of inkjets within a print head to eject ink onto an ink receiving member. For example, an ink receiving member rotates opposite a print head assembly as the inkjets in the print head are selectively activated. The ink receiving member may be an intermediate image member, such as an image drum or belt, or a print medium, such as paper. An image formed on an intermediate image member is subsequently transferred to a print medium, such as a sheet of paper.
Ink flows from manifold 12 through a port 16, an inlet 18, a pressure chamber opening 20 into the body 22, which is sometimes called an ink pressure chamber. Ink pressure chamber 22 is bounded on one side by a flexible diaphragm 30. A piezoelectric transducer 32 is secured to diaphragm 30 by any suitable technique and overlays ink pressure chamber 22. Metal film layers 34, to which an electronic transducer driver 36 can be electrically connected, can be positioned on either side of piezoelectric transducer 32.
A firing signal is applied across metal film layers 34 to excite the piezoelectric transducer 32, which causes the transducer to bend. Because the transducer is rigidly secured to the diaphragm 30, the diaphragm 30 deforms to urge ink from the ink pressure chamber 22 through the outlet port 24, outlet channel 28, and nozzle 14. The expelled ink forms a drop of ink that lands onto an image receiving member. Refill of ink pressure chamber 22 following the ejection of an ink drop is augmented by reverse bending of piezoelectric transducer 32 and the concomitant movement of diaphragm 30 that draws ink from manifold 12 into pressure chamber 22.
Typically, the layers of inkjet 10 are laminated metal plates or sheets. These sheets may be stainless steel, for example, that are chemically etched to form the structures and cavities in the plates that are then stacked to form the inkjet stack. Referring once again to
Ink that flows through a print head may contain solid debris. This debris may be small enough to enter a manifold within a print head, but large enough to clog an inlet, an outlet, or an aperture. To address this issue, filter layers may be included in an inkjet ejector stack. These filters may be included in a channel layer to filter ink flowing into an inkjet ejector through an inlet. Typically, these filters are fabricated from stainless steel, nickel electroformed screens, woven mesh screens, or polyimide layers. The pores are required to be smaller in diameter than the final aperture through which the fluid passes so they block the passage of contaminants large enough to block the final aperture. Ancillary structure may also be provided to redirect fluid flow to another portion of the filter in the event that a portion of the filter becomes clogged.
A known goal of print head design is to increase the number of inkjet ejectors per unit of distance in a print head. As the number of inkjet ejectors per unit of distance increases, the size of the inkjet ejectors is reduced. Consequently, the fluid passageways in the inkjet ejectors become smaller and clean ink flowing in those passageways becomes increasingly important. Therefore, effective filtering of the ink continues to be an important factor in print head design.
A manifold assembly has been constructed that filters ink before the ink enters an inkjet ejector in an inkjet print head. The manifold assembly includes an adhesive layer having openings, an ink manifold layer having a plurality of openings, the openings in the adhesive layer being aligned with the openings in the ink manifold layer, and a polymer layer having a plurality of filter areas, the filter areas being aligned with the openings in the ink manifold layer and the openings in the adhesive layer, the adhesive layer being interposed between the polymer layer and the ink manifold layer.
A method for assembling an inkjet print head with a filter that filters ink before the ink flows into an inkjet ejector has been developed. The method includes aligning openings in an adhesive layer to openings in an ink manifold layer, tacking the adhesive layer to the ink manifold layer, aligning filter areas in a polymer layer with the openings in the ink manifold layer and the openings in the adhesive layer, the adhesive layer being interposed between the polymer layer and the ink manifold layer, and bonding the polymer layer to the ink manifold layer.
The manifold assembly may be used to construct an inkjet print head having a filter positioned external to the inkjet ejectors in the print head. The inkjet print head includes an inkjet body layer having a plurality of pressure chambers, a flexible diaphragm plate bonded to the inkjet body layer to form a wall of each pressure chamber, the flexible diaphragm plate including a plurality of openings, each opening in the flexible diaphragm plate fluidly communicating with one pressure chamber in the inkjet body layer, a plurality of piezoelectric transducers, the piezoelectric transducers being attached to the diaphragm plate, an adhesive layer having a plurality of openings, an ink manifold layer having a plurality of openings, the openings in the adhesive layer being aligned with the openings in the ink manifold layer, and a polymer layer having a plurality of filter areas, the filter areas in the polymer layer being aligned with the openings in the ink manifold layer and the openings in the adhesive layer and each opening in the flexible diaphragm layer fluidly communicating with only one opening in the ink manifold layer to enable a filtered ink to flow from the ink manifold layer to a pressure chamber in the inkjet body layer.
The foregoing aspects and other features of an improved filter layer and how the improved filter layer facilitates micro-fluidic device assembly are explained in the following description, taken in connection with the accompanying drawings.
For a general understanding of the environment for the system and method disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the word “printer” encompasses any apparatus that performs a print outputting function for any purpose, such as a digital copier, bookmaking machine, facsimile machine, a multi-function machine, etc. In the description below, reference is made in the text and the drawings to an ink jet stack; however, the discussion is applicable to other micro-fluidic devices that dispense liquid or pump fluid. Therefore, the description should not be read to limit the application of the method to ink jet stacks alone.
Referring specifically to
Referring to
A process 300 for bonding a polymer layer such as the polymer layer 116 of
The adhesive layer and polymer layer are tacked together in order to maintain the alignment of the adhesive during the bonding process (block 304). A flow diagram that describes an example of a process 400 for tacking the polymer layer and adhesive material is depicted in
The tacking process continues by placing the target layers above the first bonding plate (block 416). In this instance, the target layers are the polymer layer and the adhesive material. The polymer layer is placed above the first bonding plate with a release agent coating on the polymer layer facing the first bonding plate. The release agent coating may be a fluoropolymer material and the release agent prevents the polymer layer from adhering to the first bonding plate during the tacking process. The polymer layer has tooling holes that accept the fixture pins and align the polymer layer with the first bonding plate. The adhesive is then placed above the polymer. The adhesive layer has a series of openings that are aligned to expose the regions of the polymer layer that serve as a filter, while covering regions of the polymer layer that will be bonded to other components. The adhesive material is temporarily held in position using thermal tape capable of withstanding the temperatures of the tacking process. The thermal tape is applied to the edge of the adhesive, leaving the surface of the adhesive above the polymer layer exposed.
Because the adhesive should not adhere to the bonding plates used in the tacking and bonding processes, a release agent covers the exposed surface of the adhesive material (block 420). The release agent is applied above the adhesive, typically as a thin sheet of a fluoropolymer, such as polytetrafluoroethylene (block 424). The release agent prevents the adhesive from tacking to a second bonding plate, which is placed above the adhesive and polymer layer in alignment with the fixture pins (block 428). The second bonding plate may be identical in form to the first bonding plate and provides a uniform upper surface for the tacking process. Another layer of release agent, preferably a thin polyimide film, such as Upilex (formed from biphenyl tetracarboxylic dianhydride monomers), is applied above the second bonding plate (block 432). A pad is placed over the release agent coating of the second bonding plate (block 436). The pad allows for an even transfer of pressure to the target layers during the tacking process. In the embodiment of
The assembly formed in blocks 412-440 is placed in a heated pressure chamber in order to tack the polymer layer to the adhesive (block 444). Pressure is applied vertically through the pad, second bonding plate, polymer layer, adhesive, first bonding plate, and the fixture. The combination of heat and pressure causes the adhesive to tack to the polymer layer. In the example embodiment of
Returning to
The bonding process of
The assembly formed in blocks 412-440 is placed in a heated pressure chamber in order to bond the polymer layer to the adhesive (block 444). Pressure is applied vertically through the pad, second bonding plate, polymer layer, manifold layer, first bonding plate, and the fixture. The combination of heat and pressure causes the adhesive to bond the polymer layer and manifold layer together. In the example embodiment of
The process 300 of
The polymer layer is prepared for a second tacking process in block 324 by removing the layer of release agent coating the polymer's exposed surface. This release agent allows the polymer layer to be exposed to pressure and heat from the bonding plates, but could interfere with tacking the second adhesive layer. The prepared polymer layer is tacked to a second adhesive layer (block 324). The process used for tacking the second polymer layer also uses the steps of
The manifold layer and polymer layer with tacked adhesive may now be bonded to the rest of the inkjet stack (block 328). This bonding process is similar to the bonding process used for bonding the polymer layer to the manifold layer, and the second adhesive layer is typically aligned in the same manner as the first adhesive layer, to align openings in the adhesive layer with areas of the polymer layer that are exposed to filter ink (block 312). In binding the polymer layer to the inkjet stack, the polymer layer is aligned with ink inlets in the jet stack so that the areas with filtered openings allow ink to flow from the manifold, through the filtered area of the polymer layer, and into the body chamber in the inkjet stack. In the example embodiment of
The processes disclosed in
Once a filter has been positioned within an inkjet stack as described above, the filter is positioned in a flow of ink that eventually supplies ink to an inlet channel of an inkjet ejector in an inkjet stack. Construction of the filter from polymer material reduces the cost of filter fabrication when the filter is included within the inkjet stack. Specifically, previously known filters positioned within the inkjet stack are formed with metal plates that are brazed with gold. As the filter openings constitute a significant surface area that is brazed with gold, such filters are relatively expensive. Additionally, positioning the filter outside the inkjet stack enables the filter to remove debris from the ink flow at a location that reduces the number of filters required for a print head. That is, when a filter is placed within the inkjet stack, a filter is required for each inkjet ejector in a print head. When the filter is positioned at the inlet to or within a manifold, the filtered ink may be supplied to two or more inkjet stacks coupled to the manifold for ink. Not only does such positioning of the filter help render the construction of a print head more economical, it also aids in the design of an inkjet stack ejector that can be operated at a higher frequency than previously known.
It will be appreciated that various of the above-disclosed and other features, and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.
This application claims priority from U.S. application Ser. No. 12/638,553, which was filed on Dec. 15, 2009, and is entitled “An Ink Ejector Having an Improved Filter.”
Number | Date | Country | |
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Parent | 12638553 | Dec 2009 | US |
Child | 13439494 | US |