US 6,318,849 B1Grant
Fluid supply mechanism for multiple fluids to multiple spaced orifices
Issue Date:2001-11-20
•8 Claims
•8 Drawing Sheets
Abstract
This patent describes an improved form of ink supply to an ink supply head for printing images. The supply is required for a number of different fluids to be supplied to a plurality of different supply slots, the supply slots being spaced apart at periodic intervals in an interleaved manner. The supply includes a fluid inlet portion for each of the plurality of different fluids and a main channel flow portion for each of the different fluids, connected to the fluid inlet portion and running past each of the supply slots; and a sub-channel flow portion connecting each of the supply slots to a corresponding main channel flow portion; two of the main channel flow portion run along the first surface of a moulded flow supply unit and another of the main channel flow portion runs along the top surface of the moulded piece with the subchannel flow portion being interconnected with the slots by way of through-holes through the surface of the the moulded piece. The supply member can be plastic injection moulded and the pitch rate of the slots can be 1,000 slots per inch.
Metadata
Assignee
- Silverbrook Research Pty Ltd
Inventor
- Kia Silverbrook
Application Information
Application Number:US 09/113,103
Filing Date:1998-07-10
Priority Date:1997-07-15
Art Unit:7
Classifications
IPC:
B41J 2175B41J 2155B41J 221
Field of Search:
347 42347 40347 65347 43347 20347 50347104
Patent Drawings (8 sheets)
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0002] The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application serial numbers (USSN) are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] The present invention relates to the supply of fluid, such as inks or the like to a mechanism such as a printhead which consumes the ink supplied.
BACKGROUND OF THE INVENTION
[0005] Recently, small compact printheads have been proposed for page width printheads with the printheads operating at high speeds and, in a page width manner, for the printing out of ink. A printhead able to print full color pictures relies upon the supply of at least three inks (cyan, magenta and yellow) and, when operated in a pagewidth manner, is likely to consume a substantial amount of ink.
[0006] Recently, a page width printhead has been proposed having full color output capabilities. A problem in providing a full color slim pagewidth inkjet head is the supply of ink to the ink jet head. Obviously, a number of different colored inks have to be supplied to ink ejection chambers within an ink jet head in a continuous manner so as to support high speed operation.
[0007] Further, any system of ink supply must be compact and suitable for incorporation into any printing system utilizing the supply.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide an improved form of ink supply to an ink supply head for printing images.
[0009] In accordance with a first aspect of the present invention, there is provided a fluid supply means for supplying a plurality of different fluids to a plurality of different supply slots, wherein the supply slots are being spaced apart at periodic intervals in an interleaved manner, the fluid supply means comprising a fluid inlet means for each of the plurality of different fluids, a main channel flow means for each of the different fluids, connected to said fluid inlet means and running past each of the supply slots, and sub-channel flow means connecting each of the supply slots to a corresponding main channel flow means. The number of fluids is greater than 2 and at least two of the main channel flow means run along the first surface of a moulded flow supply unit and another of the main channel flow means runs along the top surface of the moulded piece with the subchannel flow means being interconnected with the slots by means of through-holes through the surface of the moulded piece.
[0010] Preferably, the supply means is plastic injection moulded and the pitch rate of the slots is substantially less than, or equal to 1,000 slots per inch. Further the collection of slots runs substantially the width of a photograph. Preferably, the fluid supply means further comprises a plurality of roller slot means for the reception of one or more pinch rollers and the fluid comprises ink and the rollers are utilised to control the passage of a print media across a printhead interconnected to the slots. The slots are divided into corresponding colour slots with each series of colour slots being arranged in columns.
[0011] Preferably, at least one of the channels of the fluid supply means is exposed when fabricated and is sealed by means of utilising sealing tape to seal the exposed surface of the channel. Advantageously, the fluid supply means is further provided with a TAB slot for the reception of tape automated bonded (TAB) wires.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings which:
[0013] FIG. 1. illustrates an exploded perspective in section of a printing system;
[0014] FIG. 2. illustrates a perspective view, partly in section of the ink-head supply unit of FIG. 1;
[0015] FIG. 3. illustrates a bottom perspective view, partly in section, of the ink-head supply unit of FIG. 1;
[0016] FIG. 4. illustrates an enlarged top view of the ink-head supply unit of FIG. 1;
[0017] FIG. 5. illustrates an enlarged bottom view, partly in section, of the ink-head supply unit of FIG. 1;
[0018] FIGS. 6 and 7 illustrate perspective views of the ink-head supply unit illustrate placement of rollers therein;
[0019] FIG. 8 illustrates a plan view of the ink-head supply unit providing further details on the flow of ink within the ink-head supply unit.
DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS
[0020] In the preferred embodiment, there is provided an inkjet in supply means for the supply of ink to a pagewidth printhead, the width of the page being variable in accordance to requirements.
[0021] Turning initially to FIG. 1, there is illustrated 1 an exploded perspective view, in section, of a full printing system 1 is based around a printhead 2 which ejects ink drops on demand on to print media 3 so as to form an image. The print media 3 is pinched between two set of rollers comprising a first set 5, 6 and second set 7, 8.
[0022] The printhead 2 operates under the control of power, ground and signal lines 10 which provide power and control for the printhead 2 and are bonded by means of Tape Automated Bonding (TAB) to the surface of the printhead 2.
[0023] Importantly, the printhead 2, which can be constructed from a silicon wafer device suitably separated, relies upon a series of anisotropic etches 12 through the wafer having near vertical side walls. The through wafer etches 12 allow for the direct supply of ink to the printhead surface from the back of the wafer for subsequent ejection.
[0024] The ink is supplied to the back of the ink jet head 2 by means of ink-head supply unit 14. The ink jet head 2 has three separate rows along its surface for the supply of separate colors of ink. The ink head supply unit 14 also includes a lid 15 for the sealing of ink channels.
[0025] In FIGS. 2-7, there is illustrated various perspective views of the ink-head supply unit 14. Each of FIGS. 2-7 illustrate only a portion of the supply unit which can be constructed of indefinite length, portions only as shown so as to provide exemplary details. In FIG. 2, there is illustrated a bottom perspective view, FIG. 3 illustrates a top perspective view, FIG. 4 illustrates a close up bottom perspective view, partly in sections, FIG. 5 illustrates a top side perspective view showing details of the ink channels, and FIG. 6 illustrates a top side perspective view as does FIG. 7.
[0026] There is considerable cost advantage in forming ink-head supply unit 14 from injection moulded plastic instead of, say, micromachined silicon. The manufacturing cost of a plastic ink channel will be considerably less in volume and manufacturing is substantially easier. The design illustrated in the accompanying drawings assumes a 1600 dpi three color monolithic print head, of a predetermined length. The provided flow rate calculations are for a 100 mm photo printer.
[0027] The ink-head supply unit 14 contains all of the required fine details. The lid 15 (FIG. 1) is permanently glued or ultrasonically welded to the ink-head supply unit 14 and provides a seal for the ink channels.
[0028] Turning to FIG. 2, the cyan, magenta and yellow ink flows in through ink inlets 20-22, the magenta ink flows through the through-holes 24,25 and along the magenta main channels 26,27 (FIG. 3). The cyan ink flows along cyan main channel 30 and the yellow ink flows along the yellow main channel 31. As best seen if FIG. 4, the cyan ink in the cyan main channels then flows into a cyan subchannel 33. The yellow subchannel 34 similarly receiving yellow ink from the yellow main channel 31.
[0029] As best seen in FIG. 5, the magenta ink also flows from magenta main channels 26,27 through magenta through-holes 36, 37. Returning again to FIG. 4, the magenta ink flows out of the through-holes 36, 37. The magenta ink flows along first magenta subchannel e.g. 38 and then along second magenta subchannel e.g. 39 before flowing into a magenta pit area 40. The magenta ink then flows through magenta vias e.g. 42 which are aligned with corresponding inkjet head through-holes (e.g. 12 of FIG. 1) wherein they subsequently supply ink to inkjet nozzles for printing out.
[0030] Similarly, the cyan ink within the cyan subchannel 33 flows into a cyan pit area 49 which supplies ink two cyan vias 43, 44. Similarly, the yellow subchannel 34 supplies yellow pit area 46 which in turn supplies yellow vias 47, 48.
[0031] As seen in FIG. 5, the printhead is designed to be received within printhead slot 50 wilt the various vias e.g. 51 aligned with corresponding through holes, e.g. 12 in the printhead wafer (FIG. 1).
[0032] Returning to FIG. 1, care must be taken to provide adequate ink flow to the entire printhead chip 2, while satisfying the constrains of an injection moulding process. The size of the ink through wafer holes 12 at the back of the print head chip is approximately 100 μm×50 μm, and the spacing between through holes carrying different colors of ink is approximately 170 μm. While features of this size can readily be moulded in plastic (compact discs have micron sized features), ideally the wall height must not exceed a few times the wall thickness so as to maintain adequate stiffness. The preferred embodiment overcomes these problems by using a hierarchy of progressively smaller ink channels.
[0033] In FIG. 8, there is illustrated schematically, a section of an arrangement 70 of the printhead 2 of FIG. 1. The section is divided into 3 series of nozzles comprising the cyan series 71, the magenta series 72 and the yellow series 73. Each series of nozzles is further divided into two rows, e.g. 75, 76 with the printhead 70 having a series of bond pads 78 for bonding of power in control signals.
[0034] The printhead includes the ink supply channels, e.g. 81, equivalent to anisotropic edge hole 12 of FIG. 1. The ink flows from the back of the wafer through supply channel 81 and in turn through the filter grills, e.g. 82, to ink nozzle chambers, e.g. 83. The operation of the nozzle chamber 83 and printhead 2 (FIG. 1) is, as mentioned previously, per described in the abovementioned patent specification.
Ink Channel Fluid Flow Analysis
[0035] Turning now to an analysis of the ink flow, the main ink channels 26, 27, 30, 31 (FIG. 2, FIG. 3) are around 1 mm×1 mm, and supply all of the nozzles of one color. The subchannels 33, 34, 38, 39 (FIG. 4) are around 200 μm x 100 μm and supply about 25 inkjet nozzles each. The printhead through holes 43, 44, 47, 48 and water through holes, e.g. 81 (FIG. 10) are 100 μm×50 μm and supply 3 nozzles at each side of the print head through holes. Each nozzle filter 82 has 8 slits, each with an area of 20 μm×2 μm and supplies a single nozzle.
[0036] An analysis has been conducted of the pressure requirements of an ink jet printer constructed as described. The analysis is for a 1,600 dpi three color process printhead for photograph printing. The print width was 100 mm which gives 6,250 nozzles for each color, giving a total of 18,750 nozzles.
[0037] The maximum ink flow rate required in various channels for full black printing is important. It determines the pressure drop along the ink channels, and therefore whether the printhead will stay filled by the surface tension forces alone, or, if not, the ink pressure that is required to keep the printhead full.
[0038] To calculate the pressure drop, a drop volume of 2.5 pl for 1,600 dpi operation was utilized.
[0039] While the nozzles may be capable of operating at a higher rate, the chosen drop repetition rate is 5 KHz which is suitable to print a 150 mm long photograph in an little under 2 seconds. Thus, the printhead, in the extreme case, has a 18,750 nozzles, all printing a maximum of 5,000 drops per second. This ink flow is distributed over the hierarchy of ink channels. Each ink channel effectively supplies a fixed number of nozzles when all nozzles are printing.
[0040] The pressure drop Ap was calculated according to the Darcy-Weisbach formula:
[0041] Where ρ is the density of the ink, U is the average flow velocity, L is the length, D is the hydraulic diameter, and first a dimensionless friction factor calculated as follows:
[0042] Where Re is the Reynolds number and k is a dimensionless friction coefficient dependant upon the cross section of the channel, both calculated as follows:
[0043] Where υ is the kinematic viscosity of the ink, and for a rectangular cross section, k can be approximated by:
[0044] Where a is the longest side of the rectangular cross section, and b is the shortest side. The hydraulic diameter D for a rectangular cross section is given by:
[0045] Ink is drawn off the main ink channels at 250 points along the length of the channels. The ink velocity falls linearly from the start of the channel to zero at the end of the channel, so the average flow velocity U is half of the maximum flow velocity. Therefore, the pressure drop along the main ink channels is half of that calculated using the maximum flow velocity.
[0046] Utilizing these formulas, the pressure drops can be calculated in accordance with the following tables:
[0047] The total pressure drop from the ink inlet to the nozzle is therefore approximately 701 Pa for cyan and yellow, and 845 Pa for magenta. This is less than 1% of atmospheric pressure. Of course, when the image printed is less than full black, the ink flow (and therefore the pressure drop) is reduced from these values.
Making the Mould for the Ink-head Supply Unit
[0048] The ink head supply unit 14 (FIG. 1) has features as small as 50μ and a length of 106 mm. It is impractical to machine the injection moulding tools in the conventional manner. However, even though the overall shape may be complex, there are no complex curves required. The injection moulding tools can be made using conventional milling for the main ink channels and other millimetre scale features, with a lithographically fabricated inset for the fine features. A LIGA process can be used for the inset.
[0049] A single injection moulding tool could readily have 50 or more cavities, so could make many millions of ink channels per year, at a minimal cost. Most of the tool complexity is in the inset. As the insets are replicated lithographically, the total toolmaking cost should not be excessive.
[0050] Returning to FIG. 1, the printing system 1 is constructed via moulding ink supply unit 14 and lid 15 together and sealing them together as previously described. Subsequently printhead 2 is placed in its corresponding slot 50. Adhesive sealing strips 52, 53 are placed over the magenta main channels so to ensure that they are properly sealed. The Tape Automated Bonding (TAB) strip 10 is then connected to the inkjet head 2 with tab bonding wires running in TAB slot 55. As can best be seen from FIGS. 6 and 7, aperture slots 56 to 63 are provided for the snap in insertion of rollers 5, 7 (FIG. 1). The slots provide for the “clipping in” of rollers with a small degree of play subsequently being provided for simple rotation of the rollers.
[0051] It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. The present embodiment is, therefore, to be considered in all respects to be illustrative and not restrictive.
Ink Jet Technologies
[0052] The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.
[0053] The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.
[0054] The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.
[0055] Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:
[0056] low power (less than 10 Watts)
[0057] high resolution capability (1,600 dpi or more)
[0058] photographic quality output
[0059] low manufacturing cost
[0060] small size (pagewidth times minimum cross section)
[0061] high speed (<2 seconds per page).
[0062] All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table under the heading Cross References to Related Applications.
[0063] The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.
[0064] For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.
[0065] Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.
Tables of Drop-on-Demand Ink Jets
[0066] Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.
[0067] The following tables form the axes of an eleven dimensional table of ink jet types.
[0068] Actuator mechanism (18 types)
[0069] Basic operation mode (7 types)
[0070] Auxiliary mechanism (8 types)
[0071] Actuator amplification or modification method (17 types)
[0072] Actuator motion (19 types)
[0073] Nozzle refill method (4 types)
[0074] Method of restricting back-flow through inlet (10 types)
[0075] Nozzle clearing method (9 types)
[0076] Nozzle plate construction (9 types)
[0077] Drop ejection direction (5 types)
[0078] Ink type (7 types)
[0079] The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 which matches the docket numbers in the table under the heading Cross References to Related Applications.
[0080] Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.
[0081] Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The U01 to U45 series are also listed in the examples column. In some cases, print technology may be listed more than once in a table, where it shares characteristics with more than one entry.
[0082] Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.
[0083] The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.
Claims
What is claimed is:
1. A fluid supply unit for supplying a plurality of different fluids to a plurality of supply slots, said supply slots being spaced apart at substantially regular intervals in an interleaved manner, said fluid supply unit comprising:
an elongate element with a recess defined in one surface of the elongate element, the supply slots opening into said recess;
fluid inlet means for each of said plurality of different fluids arranged at one end of the elongate element;
a main channel flow means, defined at least partially by the elongate element, for each of said different fluids, a main channel flow means being in communication with each of said fluid inlet means; and
a sub-channel flow means extending from each of the main channel flow means for placing each of said supply slots in communication with a corresponding main channel flow means;
wherein the element is a one-piece moulded element, the number of fluids to be supplied is greater than 2 and at least one of said main channel flow means runs along said one surface of the elongate element and others of said main channel flow means run along an opposed surface of said elongate element, the sub-channel flow means being in fluid communication with said supply slots by means of through-holes through the surfaces of said elongate element.
2. A fluid supply unit as claimed in claim 1 which is plastic injection moulded.
3. A fluid supply unit as claimed in claim 1 wherein a pitch rate of said slots is substantially less than or equal to 1,000 slots per inch.
4. A fluid supply unit as claimed in claimed 1 wherein the supply slots are arranged in a collection of slots and the collection extends substantially the width of a photograph.
5. A fluid supply unit as claimed in claim 1 further comprising:
a plurality of roller slot means for the reception of one or more pinch rollers and wherein the plurality of different fluids comprise inks and said rollers are utilised to control the passage of a print media across a print-head in communication with said supply slots.
6. A fluid supply unit as claimed in claim 5 wherein said supply slots are divided into corresponding colour slots with each series of colour slots being arranged in columns.
7. A fluid supply unit as claimed in claim 1 wherein at least one of said main channel flow means is exposed when fabricated and is sealed by means of utilising sealing tape to seal the exposed surface of said channel.
8. A fluid supply unit as claimed in claim 1 which is further provided with a TAB slot for the reception of Tape Automated Bonded (TAB) wires.