Abstract:
An ink supply device comprising a molding of a settable material, the molding being a two-shot molding having a first part of a first material and a second part of a second material, wherein the first part comprises a plurality of collars of a hydrophobic, elastomeric compound which are configured to be sealingly and releasably engageable with respective ink filling formations of a set of filling formations of an ink reservoir, and the second part defines a number of ink chambers, each ink chamber adapted such that in use, the chamber is in fluid communication with a respective ink channel of one ink reservoir via one collar.

Description:
[0001]     Continuation Application of U.S. Ser. No. 10/636,284 filed on Aug. 8, 2003 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to an ink supply assembly. More particularly, the invention relates to an ink supply assembly for supplying ink to an elongate printhead.  
       SUMMARY OF THE INVENTION  
       [0003]     According to a first aspect of the invention, there is provided an ink supply assembly for supplying ink to an elongate printhead that includes at least one printhead chip, the assembly comprising 
        an ink reservoir that defines a number of channels, each channel being configured to contain an ink of a particular color, the ink reservoir having a number of sets of filling formations, each filling formation of each set being in fluid communication with a respective channel; and     ink supply devices that each comprise 
            a molding of a settable material, the molding being a two-shot molding having a first part of a first material and a second part of a second material, wherein the first part comprises a plurality of collars of a hydrophobic, elastomeric compound which are configured to be sealingly and releasably engageable with respective ink filling formations of each set of the filling formations of the ink reservoir, and the second part defines a number of ink chambers, each ink chamber being configured to contain ink of a particular color and being in fluid communication with a respective ink channel of one ink reservoir via one collar.    
               
 
         [0007]     The ink reservoir may be elongate to span a printing area. The ink supply devices may be configured to be positioned side-by-side along the ink reservoir, in a modular fashion.  
         [0008]     Each ink supply device may include a printhead chip and a tape automated bond (TAB) film connected to the printhead chip to drive the printhead chip. The printhead chip may be positioned so that, when the ink supply devices are positioned on the reservoir, the printhead chips define an array that spans the print area.  
         [0009]     According to a second aspect of the invention, there is provided an ink supply device for supplying ink to an elongate printhead that includes at least one printhead chip, from a reservoir, each reservoir defining a number of channels, each channel being configured to contain an ink of a particular color, and each ink reservoir having a number of sets of filling formations, each filling formation of each set being in fluid communication with a respective channel, the device comprising 
        a molding of a settable material, the molding being a two-shot molding having a first part of a first material and a second part of a second material, wherein the first part comprises a plurality of collars of a hydrophobic, elastomeric compound which are configured to be sealingly and releasably engageable with respective ink filling formations of said ink reservoirs, and the second part defines a number of ink chambers, each ink chamber being configured to contain ink of a particular color and being in fluid communication with a respective ink channel of the ink reservoir via one collar.       
 
     
    
     BRIEF DESCRIPTION OF THE INVENTION  
       [0011]     The invention is now described by way of example with reference to the accompanying drawings in which:  
         [0012]      FIG. 1  shows a three dimensional view, from above, of a printhead assembly that includes an ink supply assembly, in accordance with the invention;  
         [0013]      FIG. 2  shows a three-dimensional view, from below, of the assembly;  
         [0014]      FIG. 3  shows a three dimensional, exploded view of the assembly;  
         [0015]      FIG. 4  shows a bottom view of the assembly;  
         [0016]      FIG. 5  shows a three-dimensional view, from below, of the assembly with parts omitted;  
         [0017]      FIG. 6  shows, on an enlarged scale, an end view of the assembly;  
         [0018]      FIG. 7  shows, on the enlarged scale, a sectional end view of the assembly:  
         [0019]      FIG. 8  shows a three dimensional, exploded view of a printhead module of the assembly;  
         [0020]      FIG. 9  shows a bottom view of the module;  
         [0021]      FIG. 10  shows a plan view of the module;  
         [0022]      FIG. 11  shows a sectional end view of the module taken along line XI-XI in  FIG. 10 ;  
         [0023]      FIG. 12  shows a three dimensional, exploded view of an ink reservoir of the assembly;  
         [0024]      FIG. 13  shows a three dimensional view of a flexible printed circuit board of the assembly;  
         [0025]      FIG. 14  shows a three dimensional, exploded view of a busbar arrangement of the assembly;  
         [0026]      FIG. 15  shows a three dimensional view of a multiple printhead assembly configuration; and  
         [0027]      FIG. 16  shows, on an enlarged scale, a sectional side view of the bonding of the printhead chip to the TAB film. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     A printhead assembly that includes an ink supply assembly, in accordance with the invention, is designated generally by the reference numeral  10 . The assembly  10  uses a plurality of replaceable ink supply devices, also in accordance with the invention, or printhead modules  12 . The advantage of this arrangement is the ability to easily remove and replace any defective modules  12  in the assembly  10 . This eliminates having to scrap an entire printhead assembly  10  if only one module  12  is defective.  
         [0029]     The assembly  10  comprises a chassis  14  on which an ink reservoir  16  is secured. The printhead modules  12  are, in turn, attached to the reservoir  16 .  
         [0030]     Each printhead module  12  is comprised of a micro-electromechanical (Memjet) chip  18  (shown most clearly in  FIG. 8  of the drawings) bonded by adhesive  20  to a Tape Automated Bond (TAB) film  22 , the TAB film  22  being electrically connected to the chip  18 . The chip  18  and the TAB film  22  form a sub-assembly  24  which is attached to a micromolding  26 . The micromolding  26  is, in turn, supported on a cover molding  28 .  
         [0031]     Each module  12  forms a sealed unit with four independent ink chambers  30  defined in the cover molding  28 , the ink chambers  30  supplying ink to the chip  18 . Each printhead module  12  is plugged into a reservoir molding  32  (shown most clearly in  FIGS. 3 and 7  of the drawings) of the ink reservoir  16  that supplies the ink. Ten modules  12  butt together into the reservoir  16  to form a complete 8-inch printhead assembly  10 . The ink reservoirs  16  themselves are modular, so complete 8 inch printhead arrays can be configured to form a printhead assembly  10  of a desired width.  
         [0032]     The 8-inch modular printhead assembly  10 , according to the invention, is designed for a print speed and inkflow rate that allows up to 160 pages per minute printing at 1600 dpi photographic quality. Additionally, a second printhead assembly, of the same construction, can be mounted in a printer on the opposite side for double-sided high-speed printing.  
         [0033]     As described above, and as illustrated most clearly in  FIG. 8  of the drawings, at the heart of the printhead assembly  10  is the Memjet chip  18 . The TAB film  22  is bonded on to the chip  18  and is sealed with the adhesive  20  around all edges of the chip  18  on both sides. This forms the core Memjet printhead chip sub-assembly  24 .  
         [0034]     The sub-assembly  24  is bonded on to the micromolding  26 . This molding  26  mates with the TAB film  22  which, together, form a floor  34  ( FIG. 11 ) of the ink chambers  30  of the cover molding  28 . The chambers  30  open in a flared manner in a top  36  of the cover molding  28  to define filling funnels  38 . A soft elastomeric, hydrophobic collar  40  is arranged above each funnel  38 . The collars  40  sealingly engage with complementary filling formations or nozzles  42  ( FIG. 7 ) of the reservoir molding  32  of the ink reservoir  16  to duct ink to the chip  18 .  
         [0035]     Snap details or clips  44  project from the top  36  of the cover molding  28  to clip the cover molding  28  releasably to the ink reservoir  16 .  
         [0036]     The TAB film  22  extends up an angled side wall  46  of the cover molding  28  where it is also bonded in place. The side wall  46  of the cover molding  28  provides the TAB film  22  with a suitable bearing surface for data and power contact pads  48  ( FIG. 8 ).  
         [0037]     The sub-assembly  24 , the micromolding  26  and the cover molding  28  together form the Memjet printhead module  12 . A plurality of these printhead modules  12  snap fit in angled, end-to-end relationship on to the ink reservoir  16 . The reservoir  16  acts as a carrier for the modules  12  and provides ink ducts  52  ( FIG. 7 ) for four ink colors, Cyan, Magenta, Yellow and black (CMYK). The four ink colors are channelled through the individual funnels  38  of the cover molding  28  into each printhead module  12 .  
         [0038]     The printhead modules  12  butt up to one another in an overlapping angled fashion as illustrated most clearly in  FIGS. 2 and 4  of the drawings. This is to allow the Memjet chips  18  to diagonally overlap in order to produce continuous printhead lengths from 0.8 inches to 72 inches (for wide format printers) and beyond.  
         [0039]     The Memjet chip  18  is 21.0 mm long×0.54 mm wide and 0.3 mm high. A protective silicon nozzle shield that is 0.3 mm high is bonded to the upper surface of the Memjet chip  18 .  
         [0040]     Each Memjet nozzle includes a thermoelastic actuator that is attached to a moving nozzle assembly. The actuator has two structurally independent layers of titanium nitride (TiN) that are attached to an anchor on the silicon substrate at one end and a silicon nitride (nitride) lever arm/nozzle assembly at the other end. The top TiN or “heater” layer forms an electrical circuit which is isolated from the ink by nitride. The moving nozzle is positioned over an ink supply channel that extends through the silicon substrate. The ink supply channel is fluidically sealed around the substrate holes periphery by a TiN sealing rim. Ink ejection is prevented between the TiN rim and the nitride nozzle assembly by the action of surface tension over a 1-micron gap.  
         [0041]     A 1-microsecond 3V, 27 mA pulse (85 nanojoules) is applied to the terminals of the heater layer, increasing the heater temperature by Joule heating. The transient thermal field causes an expansion of the heater layer that is structurally relieved by an “out of plane” deflection caused by the presence of the other TiN layer.  
         [0042]     Deflection at the actuator tip is amplified by the lever arm and forces the nozzle assembly towards the silicon ink supply channel. The nozzle assembly&#39;s movement combines with the inertia and viscous drag of the ink in the supply channel to generate a positive pressure field that causes the ejection of a droplet.  
         [0043]     A transient thermal field causes Memjet actuation. The passive TiN layer only heats up by thermal conduction after droplet ejection. Thermal energy dissipates by thermal conduction into the substrate and the ink, causing the actuator to return to the ‘at rest’ position. Thermal energy is dissipated away from the printhead chip by ejected droplets. The drop ejection process takes around 5 microseconds. The nozzle refills and waste heat diffuses within 20 microseconds allowing a 50 KHz drop ejection rate.  
         [0044]     The Memjet chip  18  has 1600 nozzles per inch for each color. This allows true 1600 dpi color printing, resulting in full photographic image quality. A 21 mm CMYK chip  18  has 5280 nozzles. Each nozzle has a shift register, a transfer register, an enable gate, and a drive transistor. Sixteen data connections drive the chip  18 .  
         [0045]     Some configurations of Memjet chips  18  require a nozzle shield. This nozzle shield is a micromachined silicon part which is wafer bonded to the front surface of the wafer. It protects the Memjet nozzles from foreign particles and contact with solid objects and allows the packaging operation to be high yield.  
         [0046]     The TAB film  22  is a standard single sided TAB film comprised of polyimide and copper layers. A slot accommodates the Memjet chip  18 . The TAB film  22  includes gold plated contact pads  48  that connect with a flexible printed circuit board (PCB)  54  ( FIG. 13 ) of the assembly  10  and busbar contacts  56  ( FIG. 14 ) of busbars  58  and  60  of the assembly  10  to get data and power respectively to the chip  18 . Protruding bond wires are gold bumped, then bonded to bond pads of the Memjet chip  18 .  
         [0047]     The junction between the TAB film  22  and all the chip sidewalls has sealant applied to the front face in the first instance. The sub-assembly  24  is then turned over and sealant is applied to the rear junction. This is done to completely seal the chip  18  and the TAB film  22  together to protect electrical contact because the TAB film  22  forms the floor  34  of the ink chambers  30  in the printhead module  12 .  
         [0048]     The flexible PCB  54  is a single sided component that supplies the TAB films  22  of each printhead module  12  with data connections through contact pads, which interface with corresponding contacts  48  on each TAB film  22 . The flex PCB  54  is mounted in abutting relationship with the TAB film  22  along the angled sidewall  46  of the cover molding  28 . The flex PCB  54  is maintained in electrical contact with the TAB film  22  of each printhead module  12  by means of a pressure pad  62  ( FIG. 7 ). The PCB  54  wraps underneath and along a correspondingly angled sidewall  64  of the ink reservoir molding  32  of the ink reservoir  16 . The part of the PCB  54  against the sidewall  64  carries a 62-pin connector  66 .  
         [0049]     The sidewall  64  of the ink reservoir molding  32  of the ink reservoir  16  is angled to correspond with the sidewall  32  of the cover molding  16  so that, when the printhead module  12  is mated to the ink reservoir  16 , the contacts  48  of the TAB film  22  wipe against those of the PCB  54 . The angle also allows for easy removal of the module  12 . The flex PCB  54  is ‘sprung’ by the action of the deformable pressure pad  62  which allows for positive pressure to be applied and maintained between the contacts of the flex PCB  54  and the TAB film  22 .  
         [0050]     The micromolding  26  is a precision injection molding made of an Acetal type material. It accommodates the Memjet chip  18  (with the TAB film  22  already attached) and mates with the cover molding  28 .  
         [0051]     Rib details  68  ( FIG. 8 ) in the underside of the micromolding  26  provide support for the TAB film  22  when they are bonded together. The TAB film  22  forms the floor  34  of the printhead module  12 , as there is enough structural integrity due to the pitch of the ribs  68  to support a flexible film. The edges of the TAB film  22  seal on the underside walls of the cover molding  28 .  
         [0052]     The chip  18  is bonded on to 100-micron wide ribs  70  that run the length of the micromolding  26 . A channel  72  is defined between the ribs  70  for providing the final ink feed into the nozzles of the Memjet chip  18 .  
         [0053]     The design of the micromolding  26  allows for a physical overlap of the Memjet chips  18  when they are butted in a line. Because the Memjet chips  18  now form a continuous strip with a generous tolerance, they can be adjusted digitally to produce the required print pattern, rather than relying on very close tolerance moldings and exotic materials to perform the same function. The pitch of the modules  12  is 20.33 mm.  
         [0054]     The micromolding  26  fits inside the cover molding  28 , the micromolding  26  bonding on to a set of vertical ribs  74  extending from the top  36  of the cover molding  28 .  
         [0055]     The cover molding  28  is a two shot, precision injection molding that combines an injected hard plastic body (Acetal) with soft elastomeric features (synthetic rubber). This molding interfaces with the sub-assembly  24  bonded to the micromolding  26 . When bonded into place the base sub-assembly, comprising the sub-assembly  24  and the micromolding  26 , mates with the vertical ribs  74  of the cover molding  28  to form the sealed ink chambers  30 .  
         [0056]     As indicated above, an opening of each chamber  30  is surrounded by one of the collars  40 . These soft collars  40  are made of a hydrophobic, elastomeric compound that seals against the ink nozzles  42  of the ink reservoir  16 . The snap fits  44  on the cover molding  28  locate the module  12  with respect to the ink reservoir  16 .  
         [0057]     The ink reservoir  16  comprises the ink reservoir molding  32  and a lid molding  76  ( FIG. 7 ). The molding  32  is a simple four-chamber injection molding with the lid molding  76  that is bonded on top to form a sealed environment for each color ink. Ink supply pipes  78  ( FIG. 12 ) are arranged at one end of the lid molding  76  to communicate with ink channels  80  defined in the reservoir molding  32 . Labyrinthine, hydrophobic air holes  82  are defined at an opposed end of the lid molding  76 . The air holes  82  are included for bleeding the channels  80  during charging. These holes  82  are covered over with a self-adhesive film  84  after charging.  
         [0058]     The lid molding  76  has heat stakes  88 , (pins that are designed to melt and hold the molding onto another part) which position and secure the ink reservoir  16  to the punched, sheet metal chassis  14 . Additional heat stakes  90  are arranged along the reservoir molding  32 . These stakes are shown after deformation in  FIG. 1  of the drawings once the ink reservoir  16  has been secured to the chassis  14 .  
         [0059]     Receiving formations  92  are defined along the sides of the reservoir molding  32  for releasably receiving the clips  44  of the printhead modules  12 .  
         [0060]     As previously described, the sidewall  64  on the side of the reservoir molding  32  provides a mounting area for the flexible PCB  54  and data connector  66 . The reservoir molding  32  also carries details for facilitating the accurate mounting of the V− and V+ busbars  58  and  60 , respectively.  
         [0061]     The metal chassis  14  is a precision punched, folded and plated metal chassis used to mount the printhead assembly  10  into various products. The ink reservoir  16  is heat staked to the chassis  14  via the heat stakes  88  and  90 . The chassis  14  includes a return edge  94  for mechanical strength. The chassis  14  can be easily customized for printhead mounting and any further part additions. It can also be extended in length to provide multiple arrays of printhead assemblies  10  for wider format printers.  
         [0062]     Slots  97  are defined in the chassis  14  for enabling access to be gained to the clips  44  of the modules  12  to release the modules  12  from the ink reservoir  16  for enabling replacement of one or more of the modules  12 .  
         [0063]     Thin finger strip metallic strip busbars  58  and  60  conduct V− and V+, respectively, to the TAB film  22  on each printhead module  12 . The two busbars  58  and  60  are separated by an insulating strip  96  ( FIG. 14 ). The flexible, finger-like contacts  56  are arranged along one side edge of each busbar  58 ,  60 . The contacts  56  electrically engage the relevant contact pads  48  of the TAB film  22  of each module  12  for providing power to the module  12 . The contacts  56  are separated by fine rib details on the underside of the ink reservoir molding  32 .  
         [0064]     A busbar sub-assembly  98 , comprising the busbars  58 ,  60  and the insulating strip  96  is mounted on the underside of the sidewall  64  of the reservoir molding  32  of the ink reservoir  16 . The sub-assembly is held captive between that sidewall  64  and the sidewall  46  of the cover molding  28  by the pressure pad  62 .  
         [0065]     A single spade connector  100  is fixed to a protrusion  102  on the busbar  58  for ground. Two spade connectors  104  are mounted on corresponding protrusions  106  on the busbar  60  for power. The arrangement is such that, when the sub-assembly  98  is assembled, the spade connectors  104  are arranged on opposite sides of the spade connector  100 . In this way, the likelihood of reversing polarity of the power supply to the assembly  10 , when the assembly  10  is installed, is reduced. During printhead module  12  installation or replacement, these are the first components to be disengaged, cutting power to the module  12 .  
         [0066]     To assemble the printhead assembly  10 , a Memjet chip  18  is dry tested in flight by a pick and place robot, which also dices the wafer and transports individual chips  18  to a TAB film bonding area. When a chip  18  has been accepted, a TAB film  22  is picked, bumped and applied to the chip  18 .  
         [0067]     A slot in the TAB film  22  that accepts the chip  18  and has the adhesive  20 , which also functions as a sealant, applied to the upper and lower surfaces around the chip  18  on all sides. This operation forms a complete seal with the side walls of the chip  18 . The connecting wires are potted during this process.  
         [0068]     The Memjet chip  18  and TAB film  22  sub-assembly  24  is transported to another machine containing a stock of micromoldings  26  for placing and bonding. Adhesive is applied to the underside of the fine ribs  70  in the channel  72  of the micromolding  26  and the mating side of the underside ribs  68  that lie directly underneath the TAB film  22 . The sub-assembly  24  is mated with the micromolding  26 .  
         [0069]     The micromolding sub-assembly, comprising the micromolding  26  and the sub-assembly  24 , is transported to a machine containing the cover moldings  28 . When the micromolding sub-assembly and cover molding  28  are bonded together, the TAB film  22  is sealed on to the underside walls of the cover molding  28  to form a sealed unit. The TAB film  22  further wraps around and is glued to the sidewall  46  of the cover molding  28 .  
         [0070]     The chip  18 , TAB film  22 , micromolding  26  and cover molding  28  assembly form a complete Memjet printhead module  12  with four sealed independent ink chambers  30  and ink inlets  38 .  
         [0071]     The ink reservoir molding  32  and the cover molding  76  are bonded together to form a complete sealed unit. The sealing film  84  is placed partially over the air outlet holes  82  so as not to completely seal the holes  82 . Upon completion of the charging of ink into the ink reservoir  16 , the film  84  seals the holes  82 . The ink reservoir  16  is then placed and heat staked on to the metal chassis  14 .  
         [0072]     The full length flexible PCB  54  with a cushioned adhesive backing is bonded to the angled sidewall  64  of the ink reservoir  16 . The flex PCB  54  terminates in the data connector  66 , which is mounted on an external surface of the sidewall  64  of the ink reservoir  16 .  
         [0073]     Actuator V− and V+ connections are transmitted to each module  12  by the two identical metal finger strip busbars  58  and  60 . The busbar sub-assembly  98  is mounted above the flex PCB  54  on the underside of the sidewall  64  of the ink reservoir molding  32 . The busbars  58 ,  60  and the insulating strip  96  are located relative to the ink reservoir molding  32  via pins (not shown) projecting from the sidewall  64  of the ink reservoir molding  32 , the pins being received through locating holes  108  in the busbars  58 ,  60  and the insulating strip  96 .  
         [0074]     The Memjet printhead modules  12  are clipped into the overhead ink reservoir molding  32 . Accurate alignment of the module  12  to the reservoir molding  32  is not necessary, as a complete printhead assembly  10  will undergo digital adjustment of each chip  18  during final QA testing.  
         [0075]     Each printhead module&#39;s TAB film  22  interfaces with the flex PCB  54  and busbars  58 ,  60  as it is clipped into the ink reservoir  16 . To disengage a printhead module  12  from the reservoir  16 , a custom tool is inserted through the appropriate slots  97  in the metal chassis  14  from above. The tool ‘fingers’ slide down the walls of the ink reservoir molding  32 , where they contact the clips  44  of the cover molding  28 . Further pressure acts to ramp the four clips  44  out of engagement with the receiving formations  92  and disengage the printhead module  12  from the ink reservoir  16 .  
         [0076]     To charge the ink reservoir  16  with ink, hoses  110  ( FIG. 3 ) are attached to the pipes  78  and filtered ink from a supply is charged into each channel  80 . The openings  82  at the other end of the ink reservoir cover molding  76  are used to bleed off air during priming. The openings  82  have tortuous ink paths that run across the surface, which connect through to the internal ink channels  80 . These ink paths are partially sealed by the bonded transparent plastic film  84  during charging. The film  84  serves to indicate when inks are in the ink channels  80 , so they can be fully capped off when charging has been completed.  
         [0077]     For electrical connections and testing, power and data connections are made to the flexible PCB  54 . Final testing then commences to calibrate the printhead modules  12 . Upon successful completion of the testing, the Memjet printhead assembly  10  has a plastic sealing film applied over the underside that caps the printhead modules  12  and, more particularly, their chips  18 , until product installation.  
         [0078]     It is to be noted that there is an overlap between adjacent modules  12 . Part of the testing procedure determines which nozzles of the overlapping portions of the adjacent chips  18  are to be used.  
         [0079]     As shown in  FIG. 15  of the drawings, the design of the modular Memjet printhead assemblies  10  allows them to be butted together in an end-to-end configuration. It is therefore possible to build a multiple printhead system  112  in, effectively, unlimited lengths. As long as each printhead assembly  10  is fed with ink, then it is entirely possible to consider printhead widths of several hundred feet. This means that the only width limit for a Memjet printer product is the maximum manufacturable size of the intended print media.  
         [0080]      FIG. 15  shows how a multiple Memjet printhead system  112  could be configured for wide format printers. Replaceable ink cartridges  114 , one for each color, are inserted into an intermediate ink reservoir  116  that always has a supply of filtered ink. Hoses  118  exit from the underside of the reservoir  118  and connect up to the ink inlet pipes  78  of each printhead assembly  10 .  
         [0081]     It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.