Patent Application
20110025787
The present invention relates to printers and in particular inkjet printers.
The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference.
The Applicant has developed a wide range of printers that employ pagewidth printheads instead of traditional reciprocating printhead designs. Pagewidth designs increase print speeds as the printhead does not traverse back and forth across the page to deposit a line of an image. The pagewidth printhead simply deposits the ink on the media as it moves past at high speeds. Such printheads have made it possible to perform full colour 1600 dpi printing at speeds in the vicinity of 60 pages per minute, speeds previously unattainable with conventional inkjet printers.
Printing at these speeds consumes ink quickly and this gives rise to problems with supplying the printhead with enough ink. Not only are the flow rates higher but distributing the ink along the entire length of a pagewidth printhead is more complex than feeding ink to a relatively small reciprocating printhead.
The high print speeds require a relatively large ink supply flow rate. This mass of ink is moving relatively quickly through the supply line. Abruptly ending a print job, or simply at the end of a printed page, means that this relatively high volume of ink that is flowing relatively quickly must also come to an immediate stop. However, suddenly arresting the ink momentum gives rise to a shock wave in the ink line. The components making up the printhead are typically stiff and provide almost no flex as the column of ink in the line is brought to rest. Without any compliance in the ink line, the shock wave can exceed the Laplace pressure (the pressure provided by the surface tension of the ink at the nozzles openings to retain ink in the nozzle chambers) and flood the front surface of the printhead nozzles. If the nozzles flood, ink may not eject and artifacts appear in the printing.
Resonant pulses in the ink occur when the nozzle firing rate matches a resonant frequency of the ink line. Again, because of the stiff structure that define the ink line, a large proportion of nozzles for one color, firing simultaneously, can create a standing wave or resonant pulse in the ink line. This can result in nozzle flooding, or conversely nozzle deprime because of the sudden pressure drop after the spike, if the Laplace pressure is exceeded.
According to an aspect of the present invention there is provided a printhead for an inkjet printer, the printhead comprising:
a printhead integrated circuit (IC) with an array of nozzles for ejecting ink;
a support structure for supporting the printhead IC, the support structure having ink conduits for supplying the array of nozzles with ink, each ink conduit includes a plurality of cavities distributed along a roof of the ink conduit, wherein an opening to each respective cavity has an upstream edge and a downstream edge, the upstream edge contacting the ink before the downstream edge during initial priming of the ink conduits from an ink supply, the upstream edge having a transition face between the ink conduit and the cavity interior, the transition face being configured to inhibit ink from filling the cavity by capillary action during initial priming of the ink conduit.
Other aspects are also disclosed.
Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:
In
The total connector force between the cartridge contacts 104 and the printer contacts 22 is relatively high because of the number of contacts used. In the embodiment shown the total contact force is 45 Newtons. This load is enough to flex and deform the cartridge. Turning briefly to
The print engine pipeline is a reference to the printer's processing of print data received from an external source and outputted to the printhead for printing. The print engine pipeline is described in detail in U.S. Ser. No. 11/014,769 (RRC001US) filed Dec. 20, 2004, the disclosure of which is incorporated herein by reference.
The print engine 1 is shown in detail in
The cartridge unit 10 is shaped and sized to be received within the cradle unit 12 and secured in position by a cover assembly 11 mounted to the cradle unit. The cradle unit 12 is in turn configured to be fixed within the printer unit 2 to facilitate printing as discussed above.
The printhead cartridge 96 is shown in
The various elevations of the printhead cartridge 96 are shown in
Particular features and advantages of the inlet and filter manifold 116 will now be described with reference to
In a cartridge coupling, it is highly convenient for the inter-engaging valves to open each other. This is most easily and cheaply provided by a coupling in which one valve has an annular elastomeric member which is engaged by a rigid member on the other valve, and the other valve has a central elastomeric member that is compressed by the central rigid member of the first valve. If the elastomeric member is in a diaphragm form, it usually holds itself against the central rigid member under tension. This provides an effective seal and requires relatively low tolerances. However, it also requires the elastomer element to have a wide peripheral mounting. The width of the elastomer will be a trade-off between the desired coupling force, the integrity of the seal and the material properties of the elastomer used.
As best shown in
The coupling is configured for ‘no-drip’ disengagement of the cartridge from the printer. As the cartridge is pulled upwards from the printer the elastomeric sleeve 126 pushes the collar 146 to seal against the fixed valve member 128. Once the sleeve 126 has sealed against the valve member 128 (thereby sealing the cartridge side of the coupling), the sealing collar 146 lifts together with the cartridge. This unseals the collar 146 from the end of the conduit 148. As the seal breaks an ink meniscus forms across the gap between the collar and the end of the conduit 148. The shape of the end of the fixed valve member 128 directs the meniscus to travel towards the compressible member 144 instead of pinning to a point. Once the meniscus reaches the compressible member 144 it pins and retains the ink on the printer valve 142 instead of leaving drops on the cartridge valve 114 that can drip and stain prior to disposal of the cartridge.
When a fresh cartridge is installed in the printer, the air trapped between the seal of the cartridge valve 114 and that of the printer valve 142, will be entrained in to ink flow 152 and ingested by the cartridge. In light of this, the inlet manifold and filter assembly have a high bubble tolerance. Referring back to
Bubbles on the upstream side of the filter member 130 can affect the flow rate—they effectively reduce the wetted surface area on the dirty side of the filter membrane 130. The filter membranes have a long rectangular shape so even if an appreciable number of bubbles are drawn into the dirty side of the filter, the wetted surface area remains large enough to filter ink at the required flow rate. This is crucial for the high speed operation offered by the present invention.
While the bubbles in the upstream filter chamber 132 can not cross the filter membrane 130, bubbles from outgassing may generate bubbles in the downstream filter chamber 134. The filter outlet 156 is positioned at the bottom of the downstream filter chamber 134 and diagonally opposite the inlet 158 in the upstream chamber 132 to minimize the effects of bubbles in either chamber on the flow rate.
The filters 130 for each color are vertically stacked closely side-by-side. The partition wall 162 partially defines the upstream filter chamber 132 on one side, and partially defines the downstream chamber 134 of the adjacent color on the other side. As the filter chambers are so thin (for compact design), the filter membrane 130 can be pushed against the opposing wall of the downstream filter chamber 134. This effectively reduces the surface area of the filter membrane 130. Hence it is detrimental to maximum flowrate. To prevent this, the opposing wall of the downstream chamber 134 has a series of spacer ribs 160 to keep the membrane 130 separated from the wall.
Positioning the filter inlet and outlet at diagonally opposed corners also helps to purge the system of air during the initial prime of the system.
To reduce the risk of particulate contamination of the printhead, the filter membrane 130 is welded to the downstream side of a first partition wall before the next partition wall 162 is welded to the first partition wall. In this way, any small pieces of filter membrane 130 that break off during the welding process, will be on the ‘dirty’ side of the filter 130.
The LCP molding 64, flex PCB 108 and printhead ICs 68 assembly are shown in
The LCP molding 64 has recesses 178 to accommodate electronic components 180 in the drive circuitry on the flex PCB 108. For optimal electrical efficiency and operation, the cartridge contacts 104 on the PCB 108 should be close to the printhead ICs 68. However, to keep the paper path adjacent the printhead straight instead of curved or angled, the cartridge contacts 104 need to be on the side of the cartridge 96. The conductive paths in the flex PCB are known as traces. As the flex PCB must bend around a corner, the traces can crack and break the connection. To combat this, the trace can be bifurcated prior to the bend and then reunited after the bend. If one branch of the bifurcated section cracks, the other branch maintains the connection. Unfortunately, splitting the trace into two and then joining it together again can give rise to electro-magnetic interference problems that create noise in the circuitry.
Making the traces wider is not an effective solution as wider traces are not significantly more crack resistant. Once the crack has initiated in the trace, it will propagate across the entire width relatively quickly and easily. Careful control of the bend radius is more effective at minimizing trace cracking, as is minimizing the number of traces that cross the bend in the flex PCB.
Pagewidth printheads present additional complications because of the large array of nozzles that must fire in a relatively short time. Firing many nozzles at once places a large current load on the system. This can generate high levels of inductance through the circuits which can cause voltage dips that are detrimental to operation. To avoid this, the flex PCB has a series of capacitors that discharge during a nozzle firing sequence to relieve the current load on the rest of the circuitry. Because of the need to keep a straight paper path past the printhead ICs, the capacitors are traditionally attached to the flex PCB near the contacts on the side of the cartridge. Unfortunately, they create additional traces that risk cracking in the bent section of the flex PCB.
The invention addresses this by mounting the capacitors 180 (see
Isolating the contacts from the rest of the components of the flex PCB minimizes the number of traces that extend through the bent section. This affords greater reliability as the chances of cracking reduce. Placing the circuit components next to the printhead IC means that the cartridge needs to be marginally wider and this is detrimental to compact design. However, the advantages provided by this configuration outweigh any drawbacks of a slightly wider cartridge. Firstly, the contacts can be larger as there are no traces from the components running in between and around the contacts. With larger contacts, the connection is more reliable and better able to cope with fabrication inaccuracies between the cartridge contacts and the printer-side contacts. This is particularly important in this case, as the mating contacts rely on users to accurately insert the cartridge.
Secondly, the edge of the flex PCB that wire bonds to the side of the printhead IC is not under residual stress and trying to peel away from the bend radius. The flex can be fixed to the support structure at the capacitors and other components so that the wire bonding to the printhead IC is easier to form during fabrication and less prone to cracking as it is not also being used to anchor the flex.
Thirdly, the capacitors are much closer to the nozzles of the printhead IC and so the electro-magnetic interference generated by the discharging capacitors is minimized.
Turning briefly to
Unfortunately, some of the nozzles at the ends of a printhead IC 68 can be starved of ink relative to the bulk of the nozzles in the rest of the array 220. For example, the nozzles 222 can be supplied with ink from two ink supply holes. Ink supply hole 224 is the closest. However, if there is an obstruction of particularly heavy demand from nozzles to the left of the hole 224, the supply hole 226 is also proximate to the nozzles at 222, so there is little chance of the nozzles depriming from ink starvation.
In contrast, the nozzles 214 at the end of the printhead IC 68 would only be in fluid communication with the ink supply hole 216 were it not for the ‘additional’ ink supply hole 214 placed at the junction between the adjacent ICs 68. Having the additional ink supply hole 214 means that none of the nozzles are so remote from an ink supply hole that they risk ink starvation.
Ink supply holes 208 and 210 are both fed from a common ink supply passage 212. The ink supply passage 212 has the capacity to supply both holes as supply hole 208 only has nozzles to its left, and supply hole 210 only has nozzles to its right. Therefore, the total flowrate through supply passage 212 is roughly equivalent to a supply passage that feeds one hole only.
The reason for this is that the printhead IC 68 is fabricated for use in a wide range of printers and printhead configurations. These may have five color channels—CMYK and IR (infrared)—but other printers, such this design, may only be four channel printers, and others still may only be three channel. In light of this, a single color channel may be fed to two of the printhead IC channels. The print engine controller (PEC) microprocessor can easily accommodate this into the print data sent to the printhead IC.
Traditionally printers have relied on the structure and components within the printhead, cartridge and ink lines to avoid fluidic problems. Some common fluidic problems are deprimed or dried nozzles, outgassing bubble artifacts and color mixing from cross contamination.
Optimizing the design of the printer components to avoid these problems is a passive approach to fluidic control. Typically, the only active component used to correct these were the nozzle actuators themselves. However, this is often insufficient and or wastes a lot of ink in the attempt to correct the problem. The problem is exacerbated in pagewidth printheads because of the length and complexity of the ink conduits supplying the printhead IC.
The Applicant has addressed this by developing an active fluidic system for the printer. Several such systems are described in detail in U.S. Ser. No. 11/677,049 (Our Docket SBF006US) the contents of which are incorporated herein by reference.
The fluidic architecture shown in
The ink tank 60 has a venting bubble point pressure regulator 72 for maintaining a relatively constant negative hydrostatic pressure in the ink at the nozzles. Bubble point pressure regulators within ink reservoirs are comprehensively described in co-pending U.S. Ser. No. 11/640,355 (Our Docket RMC007US) incorporated herein by reference. However, for the purposes of this description the regulator 72 is shown as a bubble outlet 74 submerged in the ink of the tank 60 and vented to atmosphere via sealed conduit 76 extending to an air inlet 78. As the printhead IC's 68 consume ink, the pressure in the tank 60 drops until the pressure difference at the bubble outlet 74 sucks air into the tank. This air forms a bubble in the ink which rises to the tank's headspace. This pressure difference is the bubble point pressure and will depend on the diameter (or smallest dimension) of the bubble outlet 74 and the Laplace pressure of the ink meniscus at the outlet which is resisting the ingress of the air.
The bubble point regulator uses the bubble point pressure needed to generate a bubble at the submerged bubble outlet 74 to keep the hydrostatic pressure at the outlet substantially constant (there are slight fluctuations when the bulging meniscus of air forms a bubble and rises to the headspace in the ink tank). If the hydrostatic pressure at the outlet is at the bubble point, then the hydrostatic pressure profile in the ink tank is also known regardless of how much ink has been consumed from the tank. The pressure at the surface of the ink in the tank will decrease towards the bubble point pressure as the ink level drops to the outlet. Of course, once the outlet 74 is exposed, the head space vents to atmosphere and negative pressure is lost. The ink tank should be refilled, or replaced (if it is a cartridge) before the ink level reaches the bubble outlet 74.
The ink tank 60 can be a fixed reservoir that can be refilled, a replaceable cartridge or (as disclosed in 11/014,769 incorporated by reference) a refillable cartridge. To guard against particulate fouling, the outlet 80 of the ink tank 60 has a coarse filter 82. The system also uses a fine filter at the coupling to the printhead cartridge. As filters have a finite life, replacing old filters by simply replacing the ink cartridge or the printhead cartridge is particularly convenient for the user. If the filters are separate consumable items, regular replacement relies on the user's diligence.
When the bubble outlet 74 is at the bubble point pressure, and the shut off valve 66 is open, the hydrostatic pressure at the nozzles is also constant and less than atmospheric. However, if the shut off valve 66 has been closed for a period of time, outgassing bubbles may form in the LCP molding 64 or the printhead IC's 68 that change the pressure at the nozzles. Likewise, expansion and contraction of the bubbles from diurnal temperature variations can change the pressure in the ink line 84 downstream of the shut off valve 66. Similarly, the pressure in the ink tank can vary during periods of inactivity because of dissolved gases coming out of solution.
The downstream ink line 86 leading from the LCP 64 to the pump 62 can include an ink sensor 88 linked to an electronic controller 90 for the pump. The sensor 88 senses the presence or absence of ink in the downstream ink line 86. Alternatively, the system can dispense with the sensor 88, and the pump 62 can be configured so that it runs for an appropriate period of time for each of the various operations. This may adversely affect the operating costs because of increased ink wastage.
The pump 62 feeds into a sump 92 (when pumping in the forward direction). The sump 92 is physically positioned in the printer so that it is less elevated than the printhead ICs 68. This allows the column of ink in the downstream ink line 86 to ‘hang’ from the LCP 64 during standby periods, thereby creating a negative hydrostatic pressure at the printhead ICs 68. A negative pressure at the nozzles draws the ink meniscus inwards and inhibits color mixing. Of course, the peristaltic pump 62 needs to be stopped in an open condition so that there is fluid communication between the LCP 64 and the ink outlet in the sump 92.
Pressure differences between the ink lines of different colors can occur during periods of inactivity. Furthermore, paper dust or other particulates on the nozzle plate can wick ink from one nozzle to another. Driven by the slight pressure differences between each ink line, color mixing can occur while the printer is inactive. The shut off valve 66 isolates the ink tank 60 from the nozzle of the printhead IC's 68 to prevent color mixing extending up to the ink tank 60. Once the ink in the tank has been contaminated with a different color, it is irretrievable and has to be replaced. This is discussed further below in relation to the shut off valve's ability to maintain the integrity of its seal when the pressure difference between the upstream and downstream sides of the valve is very small.
The capper 94 is a printhead maintenance station that seals the nozzles during standby periods to avoid dehydration of the printhead ICs 68 as well as shield the nozzle plate from paper dust and other particulates. The capper 94 is also configured to wipe the nozzle plate to remove dried ink and other contaminants Dehydration of the printhead ICs 68 occurs when the ink solvent, typically water, evaporates and increases the viscosity of the ink. If the ink viscosity is too high, the ink ejection actuators fail to eject ink drops. Should the capper seal be compromised, dehydrated nozzles can be a problem when reactivating the printer after a power down or standby period.
The problems outlined above are not uncommon during the operative life of a printer and can be effectively corrected with the relatively simple fluidic architecture shown in
Sharp spikes in the ink pressure occur when the ink flowing to the printhead is stopped suddenly, such as at the end of a print job or a page. The Assignee's high speed, pagewidth printheads need a high flow rate of supply ink during operation. Therefore, the mass of ink in the ink line to the nozzles is relatively large and moving at an appreciable rate.
Abruptly ending a print job, or simply at the end of a printed page, means that this relatively high volume of ink that is flowing relatively quickly must also come to an immediate stop. However, suddenly arresting the ink momentum gives rise to a shock wave in the ink line. The LCP moulding 64 (see
Resonant pulses in the ink occur when the nozzle firing rate matches a resonant frequency of the ink line. Again, because of the stiff structure that define the ink line, a large proportion of nozzles for one color, firing simultaneously, can create a standing wave or resonant pulse in the ink line. This can result in nozzle flooding, or conversely nozzle deprime because of the sudden pressure drop after the spike, if the Laplace pressure is exceeded.
To address this, the LCP molding 64 incorporates a pulse damper to remove pressure spikes from the ink line. The damper may be an enclosed volume that can be compressed by the ink. Alternatively, the damper may be a compliant section of the ink line that can elastically flex and absorb pressure pulses.
To minimize design complexity and retain a compact form, the invention uses compressible volumes of gas to damp pressure pulses. Damping pressure pulses using gas compression can be achieved with small volumes of gas. This preserves a compact design while avoiding any nozzle flooding from transient spikes in the ink pressure.
As shown in
It can be seen in
Priming the cartridge will now be described with particular reference to the LCP channel molding 176 shown in
The main channels 184 are relatively long and thin. Furthermore the air cavities 200 must remain unprimed if they are to damp pressure pulses in the ink. This can be problematic for the priming process which can easily fill cavities 200 by capillary action or the main channel 184 can fail to fully prime because of trapped air. To ensure that the LCP channel molding 176 fully primes, the main channels 184 have a weir 228 at the downstream end prior to the outlet 232. To ensure that the air cavities 200 in the LCP molding 64 do not prime, they have openings with upstream edges shaped to direct the ink meniscus from traveling up the wall of the cavity.
These aspects of the cartridge are best described with reference
In
As shown in
Another mechanism that the LCP uses to keep the cavities 200 unprimed is the shape of the upstream and downstream edges of the cavity openings. As shown in
Similarly, the Applicant's work has found that a sharp downstream edge 236 will promote depriming if the cavity 200 has inadvertently filled with some ink. If the printer is bumped, jarred or tilted, or if the fluidic system has had to reverse flow for any reason, the cavities 200 may fully of partially prime. When the ink flows in its normal direction again, a sharp downstream edge 236 helps to draw the meniscus back to the natural anchor point (i.e. the sharp corner). In this way, management of the ink meniscus movement through the LCP channel molding 176 is a mechanism for correctly priming the cartridge.
The invention has been described here by way of example only. Skilled workers in this field will recognize many variations and modification which do not depart from the spirit and scope of the broad inventive concept. Accordingly, the embodiments described and shown in the accompanying figures are to be considered strictly illustrative and in no way restrictive on the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006901084 | Mar 2006 | AU | national |
| 2006901287 | Mar 2006 | AU | national |
| 2006201083 | Mar 2006 | AU | national |
The present application is a Continuation application of U.S. application Ser. No. 11/688,864 filed on Mar. 21, 2007, which is a Continuation-in-part of 11/677,049 filed Feb. 21, 2007, now issued U.S. Pat. No. 7,771,029, all of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11688864 | Mar 2007 | US |
| Child | 12905073 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11677049 | Feb 2007 | US |
| Child | 11688864 | US |
