Patent Application
20090219325
The present invention relates to printers and in particular inkjet printers. It has been developed primarily to provide a fluidics system which controls a hydrostatic ink pressure during normal printing, whilst enabling priming and depriming for printhead replacement.
The following applications have been filed by the Applicant simultaneously with the present application:
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 of around 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 ink to the printhead. 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. In particular, the hydrostatic ink pressure requires careful control to avoid printhead flooding. The Applicant has previously described means for controlling hydrostatic ink pressure in an ink supply system for a pagewidth printhead (see U.S. application Ser. No. 11/677,049 filed Feb. 21, 2007 and U.S. application Ser. No. 11/872,714 filed Oct. 16, 2007, the contents of which are herein incorporated by reference).
Additionally, the Applicant's design of high speed A4 pagewidth printers requires periodic replacement of a printhead cartridge, which comprises the printhead. In order to replace a printhead cartridge, it is necessary to deprime a printhead, remove the printhead from the printer, replace the printhead with a new replacement printhead, and prime the replacement printhead once it is installed in the printer. Hence, the ink supply system must be able to perform prime and deprime operations efficiently and, preferably, with minimal ink wastage.
wherein, in a printing configuration, a second level of ink in said snorkel is equal to said first level of ink in said chamber.
an inlet port for connection to an ink reservoir via an ink supply line;
an outlet port for connection to an ink inlet of the printhead via an upstream ink line;
a return port for connection to an ink outlet of the printhead via a downstream ink line;
a snorkel extending from said return port and terminating at a snorkel outlet positioned above said first level of ink;
an air vent open to atmosphere, said air vent communicating with a headspace above said ink; and
a float valve for maintaining said predetermined first level of ink by controlling a flow of ink into said inlet port.
(i) providing a printhead having a plurality of nozzles for ejection of ink, an ink inlet and an ink outlet;
(ii) providing an ink chamber having an outlet port connected to said ink inlet via an upstream ink line, said ink chamber having an inlet port controlled by a valve;
(iii) priming said printhead by pumping ink from said ink chamber, through said printhead and into a downstream ink line connected to said ink outlet; and
(iv) opening said valve if a level of ink in said chamber falls below a predetermined first level and replenishing with ink from an ink reservoir when said valve is open.
(i) providing a printhead having a plurality of nozzles for ejection of ink, an ink inlet and an ink outlet;
(ii) providing an ink chamber having an outlet port connected to said ink inlet via an upstream ink line, said ink chamber having an inlet port controlled by a valve;
(iii) depriming said printhead by pumping ink from a downstream ink line connected to said ink outlet, through said printhead and into said ink chamber; and
(iv) closing said valve when a level of ink in said chamber reaches a predetermined first level, thereby isolating said ink chamber from an ink reservoir in fluid communication with said inlet port.
an inlet port for connection to an ink reservoir via an ink supply line;
an outlet port for connection to an ink inlet of a printhead via an upstream ink line;
an air vent open to atmosphere, said air vent communicating with a headspace above said ink; and
a float valve for maintaining said predetermined first level of ink by controlling a flow of ink into said inlet port, wherein said float valve is biased towards a closed position by a positive ink pressure at said inlet port.
When inserting the printhead cartridge 2 into the print engine 3, electrical and fluidic connections are made between the cartridge and the print engine. Contacts 33 on the printhead cartridge 2 (see
Referring again to
Ink is supplied to a rear of an inlet socket 20B from pressure-regulating chambers 106, which are usually mounted towards a base of the print engine 3 (see
Ink exits from a rear of an outlet socket 20A, which is connected via conduits to a bubble-bursting box (not shown in
Referring now to
A die attach film 66 has one surface bonded to an underside of the LCP channel molding 68 and an opposite surface bonded to a plurality of printhead ICs 30. A plurality of laser-ablated holes 67 in the film 66 provide fluidic communication between the printhead ICs 30 and the main channels 24. Further details of the arrangement of the printhead ICs 30, the film 66 and the LCP channel molding 68 can be found in the US Publication No. 2007/0206056, the contents of which is incorporated herein by reference. Further details of the inlet manifold 48 and outlet manifold 50 can be found in, for example, U.S. application Ser. No. 12/014,769 filed Jan. 16, 2008, the contents of which is incorporated herein by reference.
Electrical connections to the printhead ICs 30 are provided by a flex PCB 70 which wraps around the LCP moldings 72 and 68, and connects with wirebonds 64 extending from bond pads (not shown) on each printhead IC 30. The wirebonds 64 are protected with wirebond protector 62. As described above, the flex PCB 70 includes the contacts 33, which connect with complementary contacts in the print engine 3 when the printhead cartridge 2 is installed for use.
From the foregoing, it will be appreciated that the printhead cartridge 2 has a plurality of ink inlets 60 and ink outlets 61, which can feed ink through main channels 24 in the LCP channel molding 68 to which printhead ICs 30 are attached. The fluidics system, which supplies ink to and from the printhead, will now be described in detail. For the avoidance of doubt, a “printhead” may comprise, for example, the LCP channel molding 68 together with the printhead ICs 30 attached thereto. Thus, any printhead assembly with at least one ink inlet and, optionally, at least one ink outlet may be termed “printhead” herein.
Referring to
For simplicity, the fluidics system 100 is shown for one color channel. Single color channel printheads are, of course, within the ambit of the present invention. However, the fluidics system 100 is more usually used in connection with a full color inkjet printhead having a plurality of color channels (e.g. five color channels as shown in
Typically, during normal printing, it is necessary to maintain a constant hydrostatic ink pressure in the fluidics system, which is negative relative to atmospheric pressure. A negative hydrostatic ink pressure is necessary to prevent printhead face flooding when printing ceases. Indeed, most commercially available inkjet printheads operate at negative hydrostatic ink pressures, which is usually achieved through the use of a capillary foam in an ink tank.
In the fluidic system 100, a pressure-regulating chamber 106 supplies ink 104 to an ink inlet 108 of the printhead via an upstream ink line 134. The pressure-regulating chamber 106 is positioned below the printhead 102 and maintains a predetermined set level 110 of ink therein. The height h of the printhead 102 above this set level 110 controls the hydrostatic pressure of ink 104 supplied to the printhead. The actual hydrostatic pressure is governed by the well-known equation: p=ρgh, where p is the hydrostatic ink pressure, ρ is the ink density, g is acceleration due to gravity and h is the height of the set level 110 of ink relative to the printhead 102. The printhead 102 is typically positioned at a height of about 10 to 300 mm above the set level 110 of ink, optionally about 50 to 200 mm, optionally about 80 to 150 mm, or optionally about 90 to 120 mm above the set level.
Gravity provides a very reliable and stable means for controlling the hydrostatic ink pressure. Provided that the set level 110 remains constant, then the hydrostatic ink pressure will also remain constant.
The pressure-regulating chamber 106 comprises a float valve for maintaining the set level 110 during normal printing. The float valve comprises a lever arm 112, which is pivotally mounted about a pivot 114 positioned at one of the arm, and a float 116 mounted at the other end of the arm 112. A valve stem 118 is connected to the arm 112, between the pivot 114 and the float 116, to provide a second-class lever. The valve stem 118 has valve head, in the form of an umbrella cap 119, fixed to a distal end of the valve stem relative to the arm 112. The valve stem 118 is slidably received in a valve guide so that the umbrella cap 119 can sealingly engage with a valve seat 122. This valve arrangement controls flow of ink through an inlet port 124 of the pressure-regulating chamber 106. The inlet port 124 is positioned towards a base of the chamber 106.
The set level 110 is determined by the buoyancy of the float 116 in the ink 104 (as well as the position of the chamber 106 relative to the printhead 102). The umbrella cap 119 should seal against the seat 122 at the set level 110, but should unseal upon any downward movement of the float 116 (and thereby the valve stem 118). Preferably, there should be minimum hysteresis in the float valve so as to minimize variations in hydrostatic pressure.
When the float valve is closed, the umbrella cap 119 is urged against the seat 122 (defined by an outer surface of a base of the chamber) by positive ink pressure from the ink reservoir 128. This positive sealing pressure minimizes any ink leakages from the chamber 106 via the inlet port 124 when the valve is closed.
As ink 104 is drawn from an outlet port 126 of the chamber 106 during normal printing, the float 116 incrementally moves downwards, which unseats the umbrella cap 119 and opens the inlet port 124, thereby allowing ink to refill the chamber from the ink reservoir 128 positioned above the chamber. In this way, the set level 110 is maintained and the hydrostatic ink pressure in the printhead 102 remains constant.
The float 116 preferably occupies a relatively large volume of the chamber 106 so as to provide maximum valve closure force. This closure force is amplified by the lever arm 112. However, the float 116 should be configured so that it does not touch sidewalls of the chamber 106 so as to avoid sticking.
Ink 104 is supplied to the pressure-regulating chamber 106 by the ink reservoir 128 positioned at any height above the set level 110. The ink reservoir 128 is typically a user-replaceable ink tank or ink cartridge, which connects with an ink supply line 130 when installed in the printer. The ink supply line 130 provides fluidic communication between the ink reservoir 128 and the inlet port 124 of the pressure-regulating chamber 106.
The ink reservoir 128 vents to atmosphere via a first air vent 132, which opens into a headspace of the ink reservoir. Accordingly, the ink 104 can simply drain into the pressure-regulating chamber 106 when the float valve opens the inlet port 124. The vent 132 comprises a hydrophobic serpentine channel 135, which minimizes ink losses through the vent when the ink cartridge is tipped. The vent 132 may also be covered by a one-time use sealing strip (not shown), which is removed prior to installation of an ink cartridge in the printer.
The printhead 102 has an ink inlet 108, which connects to the outlet port 126 via an upstream ink line 134. The printhead 102 is removable by means of the inlet and outlet couplings 48 and 50.
It will be understood that pressure-regulation as described above may be achieved with ‘closed’ printheads having an ink inlet, but no ink outlet. However, for the purposes of priming (described below), the printhead 102 shown in
The return port 152 is positioned at the base of the chamber and is connected to a snorkel 160 which extends towards the roof of the chamber above the level of ink 104. The pump outlet line 150 has an inline filter 154 between the pump 140 and the return port 152. The chamber 106 and snorkel 160 are configured so that a snorkel outlet 161 is always above the level of ink 104, even if the level of ink reaches the roof the chamber. For example, the snorkel outlet 161 may be positioned in a roof cavity of the chamber 106. It will be appreciated that the snorkel 160 may be defined by a channel or cavity in a sidewall of the chamber so as to maximize space inside the chamber 106.
During normal printing, the pump 140 is left open and the hydrostatic pressure of ink in the fluidics system 100 is controlled solely by the set level 110 of ink in the pressure-regulating chamber 106. A second air vent 162 is provided in a roof of the chamber 106, and communicates with a headspace via an air-permeable membrane 163 (e.g. Goretex®). Since ink 104 in the upstream ink line 134 and the downstream ink line 138 is open to atmosphere via the second air vent 164, this ink is held at the same hydrostatic pressure. Hence, ink in the snorkel 160 equilibrates at the set level 110 during normal printing when the pump 140 is left open. To this end, it is important that the downstream ink line 138 has a “loop section” 137 which passes below the level of the set level 110, allowing equilibration of the upstream and downstream sides of the printhead 102 to the set level. The return port 152, positioned in the base of the pressure-regulating chamber 106, and the snorkel 160 effectively ensure that this is the case.
As mentioned above, the printhead 102 is provided with a plurality of air cavities 26, which are configured to dampen fluidic pressure pulses as ink is supplied to printhead nozzles. Ink pressure surges are problematic in high-speed pagewidth printing and high quality printing is preferably achieved when ink is supplied at a substantially constant hydrostatic pressure. The air cavities 26 are configured and dimensioned to dampen high-frequency pressure pulses in the fluidics system by compressing air trapped in the cavities.
In order to dampen low-frequency ink pressure pulses, the pump inlet line 149 (which is a section of the downstream ink line 138) communicates with an air accumulator 139 having a larger volume than each of the air cavities 26. Low-frequency ink pressure pulses are dampened by compressing air trapped in the air accumulator 139.
The air accumulator 139 may alternatively form part of the printhead 102, although positioning in the downstream ink line 138 is preferred, since over-dampening in the printhead can adversely affect the ability of the printhead to prime.
The combination of the air cavities 26 and the air accumulator 139 provides excellent dampening of both high-frequency and low-frequency ink pressure pulses during normal printing. Moreover, the gravity-controlled supply of ink from the pressure-regulating chamber 106 provides a stable and accurate hydrostatic pressure in the fluidics system 100 during printing.
Printhead priming may be required after replacement of a printhead 102, when a printer is first set up, or when a printer has been left idle for long periods. Printhead priming requires ink 104 to be fed into the ink inlet 108 of the printhead 102 via the upstream ink line 134, through the printhead 102 and out again via the ink outlet 136 connected to the downstream ink line 138. Once the ink 104 is fed through the main channels 24 in the LCP channel molding 68 of the printhead 102, the printhead ICs 30 are primed by capillary action.
Referring to
Pumping is timed and may be continued for a period necessary to fully prime the printhead 102 and/or pump out all air bubbles from the fluidics system 100. Hence, even if the printhead 102 has already been primed, a priming operation may still be required to eradicate air bubbles, which may have accumulated since the last priming operation (for example, by atmospheric pressure changes, atmospheric temperature fluctuations, printhead cooling etc). It should be noted that recycling of ink via the return port 152 during priming ensures that no ink is wasted, even if ink is pumped through the system for a relatively long period e.g. 5-30 seconds.
An inline filter 154 is positioned between the return port 152 and the pump outlet 144 to protect the printhead 102 from any potential pump debris during priming. The filter 154 may be a component of the pressure-regulating chamber 106, as shown schematically in
When ink 104 is pumped from the chamber 106 to a deprimed printhead, the level of ink 104 in the chamber initially drops as the ink fills up the LCP channels 24 and downstream ink line 138. When the level of ink in the chamber 106 drops, the float valve opens the inlet port 124, allowing ink in the chamber to be replenished from the ink reservoir 128 (by analogy with the operation of the float valve during normal printing). Hence, the float valve can maintain the set level 110 during initial priming. After a short period of pumping, equilibrium is reached whereby ink drools from the snorkel outlet 161 at the same rate as ink is being pumped from the outlet port 126. Since the level of ink in the chamber is at the set level 110, the inlet port is closed by the float valve once ink begins to flow from the snorkel outlet 161. Ink may be circulated around the system in this equilibrium state for any period sufficient to ensure removal of air bubbles, and without wasting any ink.
During priming (or depriming), the ink reservoir 128 is protected from any backflow of ink from the chamber 106 by an inline check-valve 170. The check valve 170 is positioned in the ink supply line 130 interconnecting the ink reservoir 128 and the inlet port 124, typically as part of a coupling 172 to the ink reservoir. The check valve 170 allows ink to drain from the ink reservoir 128 into the chamber 106, but does not allow ink to flow in the opposite direction.
In order to replace a printhead 102, the old printhead must first be deprimed. Without such depriming, replacement of printheads would be an intolerably messy operation. During depriming, the peristaltic pump 140 is reversed and ink is drawn from the downstream ink line 138, through the printhead 102, and back into the pressure-regulating chamber 106 via the outlet port 126.
Since the level of ink 104 in the pressure-regulating chamber 106 now rises, the float valve closes the inlet port 124, thereby isolating the chamber 106 from the ink reservoir 128. Hence, the float valve not only regulates the hydrostatic ink pressure during normal printing, but also serves to isolate the pressure-regulating chamber 106 from the ink reservoir 128 during depriming. Of course, the pressure-regulating chamber should have sufficient capacity to accommodate the ink received therein during depriming.
Significantly, there is minimal or no ink wastage during depriming, because ink in the printhead 102 and downstream conduit 138 is all recycled back into the pressure-regulating chamber 106 for re-use.
A filter system 180 protects the printhead 102 from potential pump debris during depriming. The filter system 180 comprises an inline filter 182 in the pump inlet line 149 and an optional check-valve loop 184, which ensures ink is forced through the filter 182 during de-priming but not during priming. Hence, any pump debris is confined in the section of the downstream ink line 138 between the two filters 154 and 182, and cannot therefore contaminate the printhead 102.
Once all the ink in the downstream ink line 138, the printhead 102 and the upstream ink line 134 has been drawn into the pressure-regulating chamber 106, the pump 140 is switched off. The pump 140 is typically switched off after predetermined period of time (e.g. 2-30 seconds). When the pump is switched off, some ink 104 from the pressure-regulating chamber 106 flows into the upstream line 134 until it equalizes with the level of ink in the chamber 106. Since, at this stage of depriming, the volume of ink 104 in the pressure-regulating chamber is relatively high, the ink equalizes at a level higher than the set level 110, and the float valve keeps the inlet port 124 closed. Hence, ink 104 is prevented from draining from the ink reservoir 128 into the upstream ink line 134, because the float valve isolates the ink reservoir from the chamber 106.
After the depriming operation and with the pump is switched off, the printhead 102 may be removed and replaced with a replacement printhead. Since the printhead 102 is drained of ink by the depriming operation, the replacement operation may be performed relatively cleanly.
Once installed, the replacement (unprimed) printhead may be primed by the priming operation described above.
It will, of course, be appreciated that the present invention has been described purely by way of example and that modifications of detail may be made within the scope of the invention, which is defined by the accompanying claims.
| Number | Date | Country | |
|---|---|---|---|
| 61033357 | Mar 2008 | US |
