Patent Grant
8591016
The present disclosure generally relates to high speed printing machines which have one or more print heads that receive molten ink heated from solid ink elements. More specifically, the disclosure relates to improvements in pressurized ink transport.
So called “solid ink” printing machines encompass various imaging devices, including printers and multi-function platforms, which offer many advantages over other types of document reproduction technologies, such as laser and aqueous inkjet approaches. These advantages often include higher document throughput (i.e., the number of documents reproduced over a unit of time), fewer mechanical components needed in the actual image transfer process, fewer consumables to replace, sharper images, and an eco-friendlier process.
A typical solid ink or phase-change ink imaging device includes an ink loader which receives and stages solid ink elements that remain in solid form at room temperatures. The ink stock can be refilled by a user by simply adding more ink as needed to the ink loader. Separate loader channels are used for the different colors. For example, only black solid ink is needed for monochrome printing, while solid ink colors of black, cyan, yellow and magenta are typically needed for color printing. Solid ink or phase change inks are provided in various solid forms, and more particularly as pellets or as ink sticks.
An ink melt unit melts the ink by raising the temperature of the ink sufficiently above its melting point. During a melting phase of operation, the solid ink element contacts a melt plate or heated surface of a melt unit and the ink is melted in that region. The melted ink is often retained in a melt reservoir, which is itself heated to keep the ink above its solidification temperature until a print operation is demanded. The liquefied ink is supplied to a single or group of print heads by gravity, pump action, or both. In accordance with the image to be reproduced, and under the control of a printer controller, a rotating print drum receives ink droplets representing the image pixels to be transferred to paper or other media. To facilitate the image transfer process, a pressure roller presses the media against the print drum, whereby the ink is transferred from the print drum to the media. The temperature of the ink can be carefully regulated so that the ink fully solidifies just after the image transfer.
In higher throughput systems, the melted ink is pressurized for high speed delivery to the printheads. The throughput of such machines is ultimately controlled by the ability to maintain a constant supply of liquefied ink at the ready for delivery to the printheads. This ability is determined in part by the melt rate, i.e., the amount of solid ink that can be melted per unit time. In a typical ink stick system, the melt rates can vary between 6 and 16 gm/min. Higher melt rates can be often be achieved using solid ink pellets stored in a drum and fed to a high efficiency, high wattage melter. One such high volume melter is disclosed in commonly-owned U.S. patent application Ser. No. 12/638,863 (the '863 Application), which issued on Aug. 14, 2012 as U.S. Pat. No. 8,240,829, and is entitled “SOLID INK MELTER ASSEMBLY”, the disclosure of which is incorporated herein by reference in its entirety. Melters of this type can achieve melt rates of up to 250 gm/min with sufficient power to exceed the ink's heat of fusion and the latent energy required to raise the ink to the final setpoint temperature for moving to the printheads.
There remains a need for a system capable of delivering ink to the print heads at a rate that can take full advantage of these high melt rates.
According to aspects disclosed herein there is provided an ink delivery system for delivering molten ink to a printing mechanism comprising a receiving reservoir for receiving molten ink and a reservoir system in fluid communication between the receiving reservoir and a molten ink outlet in communication with the printing mechanism. The reservoir system includes: a first reservoir having a first inlet in communication with the receiving reservoir and a first outlet in communication with the molten ink outlet; a separate second reservoir having a second inlet in communication with the receiving reservoir and a second outlet in communication with the molten ink outlet; a first valve assembly disposed between the first inlet and the first outlet and including a first seal member movable between a discharge position closing the first inlet and an intake position closing the first outlet; a separate second valve assembly disposed between the second inlet and the second outlet and including a second seal member movable between a discharge position closing the second inlet and an intake position closing the second outlet; and an actuator assembly operably coupled to the first and second valve assemblies and configured for coordinated movement of the first and second seal members so that one of the seal members is in the discharge position and the other of the seal members is in the intake position. In another aspect, the reservoir system is incorporated into a printing machine comprising a heating element for melting solid ink, a receiving reservoir for receiving ink melted by the heating element, and a printing mechanism coupled to the molten ink outlet to receive molten ink under pressure from the reservoir system.
In a further aspect, a method for delivering molten ink to a printing mechanism is disclosed comprising: receiving molten ink in a receiving reservoir; preventing fluid communication between a first reservoir and the receiving reservoir while permitting fluid communication between the first reservoir and the printing mechanism; and substantially simultaneously permitting fluid communication between a second reservoir and the receiving reservoir while preventing fluid communication between the second reservoir and the printing mechanism.
A further method for delivering molten ink to a printing mechanism, comprises: receiving molten ink in a receiving reservoir; and alternating which of a plurality of reservoirs is opened to the receiving reservoir to receive molten ink while at least one other of the plurality of reservoirs is opened to dispense molten ink to the printing mechanism,
Referring to
The melting apparatus 11 further includes a high efficiency melter 15. The melter 15 may be constructed as disclosed in the '863 Application, the disclosure of which has been incorporated herein by reference in its entirety. Details of the structure and operation of the melter can be learned from the '863 Application, the melter generally includes a plurality of heated fins onto which the solid ink pellets are dispensed. The pellets are continuously melted by the fins and drip between the fins into a low pressure reservoir 18, as shown in
The reservoir 18 is identified as “low pressure” because the reservoir is generally maintained at ambient pressure within the printing machine, or at a pressure less than the pressurized reservoirs described herein. Alternatively, the melting apparatus 11 may be slightly pressurized or maintained at atmospheric pressure.
In accordance with one feature, the ink delivery apparatus is provided with multiple high pressure reservoirs that are used to provide a continuous uninterrupted supply of melted ink to the one or more printheads. In one embodiment, two such reservoirs are provided, namely reservoirs 20 and 22, which are formed by a housing 17. The housing 17 may be integral with or separate from the housing 16 forming the low pressure reservoir. For purposes of the present disclosure, the reservoirs may be referred to as the first and second reservoirs or as reservoir 1 and reservoir 2. Like components of the reservoirs may also be designated with a subscript 1 or 2 to refer to the associated high pressure reservoir.
The reservoirs 20, 22 are connected at inputs 24, 25 to a pressure source, which may be an air pressure supply that is controlled and regulated by a controller (not shown) of the printing machine. The pressure in the reservoirs 20, 22 is sufficient to feed high pressure jets of the one or more printheads, as is known in the art. As explained in more detail herein, the reservoirs 20, 22 are periodically pressurized as the ink supply is discharged to the printhead(s) and de-pressurized as a new supply of molten ink is introduced into the reservoir.
Each high pressure reservoir 20, 22 may be provided with a corresponding ink level sensor 27, 28 that determines the volume or level of ink remaining in the reservoir. The sensors 27, 28 may be of any construction suitable for providing a signal indicative of the ink level and/or indicative of the ink level dropping to a threshold value. The sensor may be a mechanical float-type sensor or may be an electrical probe assembly such as the sensor assembly disclosed in and commonly-owned U.S. application Ser. No. 12/241,626, which issued on Nov. 29, 2011 as U.S. Pat. No. 8,065,913, and is entitled “INK LEVEL SENSOR”, the disclosure of which is incorporated herein in its entirety.
Each high pressure reservoir 20, 22 may preferably include a heating element 30 that is operable to maintain the molten ink at a temperature above the solidification temperature of the ink. As shown in
As shown in
In operation, pressurized liquid ink is forced from the outlet channel 37, through the filter element 39 and outlet 40 to an array of tubing coupled to the printhead(s). The pressure in the outlet channel 37 is produced by pressure within an active one of the high pressure reservoirs 20, 22. The ink delivery apparatus 10 disclosed herein provides a mechanism for alternately fluidly coupling one high pressure reservoirs to the outlet channel to discharge molten ink to the printhead(s) while the other high pressure reservoir is fluidly coupled to the low pressure reservoir 18 to be re-filled with liquid ink. The apparatus 10 thus comprises an ink delivery control mechanism 50 that includes a valve assembly 52, a rocker assembly 54 and an actuator assembly 56.
Turning to
The valve assembly 522 further includes a seal body 70 disposed for translation within a chamber 61 aligned between the inlet opening 322 and the outlet opening 372. The chamber 61 may be a portion defined by the housing 17 in the high pressure reservoir 22, or may be defined by a number of walls that help align and guide the seal body 70. In the latter case, the walls are preferably configured to ensure a constant supply of molten ink to the outlet opening 372 and sized to achieve max flow rate.
The seal body 70 includes an upper seal 71 and a lower seal 73. The upper seal is configured for sealed engagement with the sealing face 68 of the valve seat body 60 described above. The seal body 702 in
The seal body 70 is movable to a position for sealing contact or engagement with the sealing face 38 at the outlet opening 362. Thus, the seal body includes a lower seal 73 that is configured to achieve a fluid-tight seal with the sealing face. The seal body 701 on the left side of
It can be appreciated that the length of the seal body 70 is less than the distance between the opposed inlet and outlet openings in each high pressure reservoir. The length of the seal body is calibrated so that when the seal body is sealing one opening (such as inlet opening 321) the body does not impede ink flow through opposite opening (such as outlet opening 322). At the same time, it is desirable that the travel distance of the seal body 70 between its two positions be limited so that the time delay between “unsealing” one opening and sealing the opposite opening is minimized—i.e., so that the valve assembly is quick and responsive to a command to changer high pressure reservoirs. In one specific embodiment, the length of the seal body 70 is about 80-90% of the distance between the inlet and outlet openings in a given high pressure reservoir.
In order to accomplish this movement, each valve assembly 52 is driven by a corresponding rocker assembly 54. The rocker assembly includes a control rod 75 that extends downward through the housings 16, 17, and more particularly through the seal body 70. The control rod 75 may be fastened or affixed to the seal body in various manners, including with an attachment pin extending transversely through the rod and seal body, as depicted in
As shown in
It can be appreciated from
In lieu of providing pressurized air alternately to the two inlets 98, 99, the piston 95 may be spring-biased to one position or the other (for instance biased upward) and a single inlet, such as inlet 98, can be alternately pressurized to act against the spring bias or released to allow the piston to return under spring-bias. As a further alternative, the air cylinder can be replaced by other actuators such as a cam assy and stepper motor configured to drive the rocker arm into the two positions shown in
In the position shown in
While the high pressure reservoir 20 is being filled, the other high pressure reservoir 22 may be emptied by discharging its ink contents under pressure. The internal level of the ink inside the reservoir may be monitored via a low level sensor, such as the level sensor 28, to prevent emptying the contents and driving air into the system. (Air must be prevented from entering the reservoir which can causes the ink heads to burp and spray onto the substrate during a refill operation.) The high pressure reservoir 22 will thus have the seal body 70 in the position shown in
It can be appreciated that the ink delivery control mechanism 50 disclosed herein provides a constant source of pressurized molten ink to be delivered to the printhead(s) by periodically switching between high pressure reservoirs 20, 22 feeding the molten ink. When one reservoir is “active” or “on-line”—i.e., supplying ink to the printhead(s)—the other reservoir can be re-filled from the low pressure reservoir. Once the ink in the active high pressure reservoir is at or near depletion, the control mechanism 50 can automatically open the other reservoir which has been filled with molten ink during its “inactive” or “off-line” state. The volumes in the chambers are sized so that the amount of ink buffered in both sides is sufficient to provide ink flow to meet the overall demand at maximum coverage on the substrate.
The coordinated action of the actuator assemblies 56 of the ink delivery control mechanism 50, the pressure inputs 24, 25 to the high pressure reservoirs, the melter 15 and the heating element 30 may be controlled by a suitable master control system (not shown). For instance, the master control system may control valves that either vent or supply pressurized air to the pressure inputs 24, 25. Likewise, the master control system may control valves that alternately vent and pressurize the air inlets 98, 99 for the pressure cylinder 97 in the actuator assembly 56 associated with each high pressure reservoir 20, 22. The master control system may be an electronic controller that is integrated into the printing machine and that may be operable to control other functions of the machine. The master control system may be programmable such as to change the ink level maximum and minimum thresholds, the air pressure provided to the actuator cylinders, any dwell in cylinder pressurization or de-pressurization, or other operating parameters of the ink delivery system.
In one approach, this coordinated action is keyed to the ink level within the two high pressure reservoirs, based on signals generated by the ink level sensors 27, 28 as interpreted by the master control system. At start-up, solid ink is initially dispensed to the inlet distributor 11 and the high efficiency melter 15 activated. The first high pressure reservoir 20 is then charged by closing the outlet 36 and opening the inlet 32. This step entails providing pressurized air to the air inlet 99 of cylinder 97 to drive the piston upward and the control rod 75 and seal body 70 downward to the position shown in
Once the first high pressure reservoir 20 is charged the control system may then implement a coordinated action as depicted in the flowchart of
As the ink is being utilized by the printheads, the “offline” reservoir is being refilled. Consequently, in the next step, the melter 15 in the low pressure reservoir is activated and the intake tube 12 opened to begin melting the solid ink. Since the Reservoir “Y” is open to the low pressure reservoir, the melted ink is continuously fed to the inactive Reservoir “Y”. In one branch of the flowchart of
Concurrently, the control system also monitors the ink level in the “active” Reservoir “X”. When the ink level drops below a predetermined threshold indicative of a depleted or nearly depleted reservoir, the control system switches the two reservoirs and re-starts the sequence of steps to activate the previously inactive Reservoir “Y” and replenish or recharge the previously activated Reservoir “X”. It can be appreciated that the sequence of steps in the flowchart of
The ink levels in a two reservoir system are illustrated in the graphs of
As depicted in
In the illustrated embodiment, the seal body 70 is an elongated generally cylindrical body. The length of the seal body 70 is dictated in part by the distance between the inlet opening 32 and the outlet opening 36 in each high pressure reservoir 20, 22. It is important that the seal body remain substantially clear of one opening when sealing the other opening so that the seal body does not adversely impact the flow of ink through the respective opening. The need for this sufficient gap is particularly important at the outlet opening 36 to avoid any turbulence as the ink is discharged under pressure.
The seal body 70 is depicted in the present disclosure as a generally solid body. Alternatively, the seal body may constitute separate seals at the upper and lower positions on the control rod 75, provided that the separate seals can exert sufficient sealing pressure against the respective sealing face 38, 68,
In the illustrated embodiment the seal bodies are moved upward and downward by the rocker assembly 54 and actuator assembly 56. Other mechanisms are contemplated to achieve the coordinated movement of the seal bodies within the high pressure reservoirs 20, 22. For instance, each control rod 75 may be an element of a linear actuator, without the rocker assembly 54. In another alternative, the pressure cylinder 97 may be replaced by a mechanical actuator suitable to alternately translate the seal body 70 upward and downward. For instance, a cam and stepper motor may be configured to pivot the clevis 85 and link arm 91 or, alternatively, to directly reciprocate the control rods 75. In this case, the control system would be operable to send electrical control signals to a motor driver to control the operation of the stepper motor.
In certain applications individual control of the valve assemblies for the different high pressure reservoirs is needed. Alternatively, the movement of the seal bodies 70 within the reservoirs can be coordinated through a common actuator assembly. In this alternative, for instance, the control rods of two high pressure reservoir seal bodies can be attached at opposite ends of a single rocker arm. Pivoting the rocker arm alternately and simultaneously raises one control rod and seal body and lowers the other. In another alternative, the two rocker arms may be coupled to a single hydraulic cylinder so that upward movement of the piston pivots one rocker arm to a discharge position, for instance, while downward movement of the piston pivots the other rocker arm to the discharge position. As a further alternative, the relative movement of the seal bodies may be administered through a cam arrangement to, for instance, introduce a dwell period before raising or lowering a respective seal body.
In the present disclosure, two high pressure reservoirs 20 and 22 are provided. The ink delivery control mechanism 50 may be modified to accommodate more than two reservoirs. Appropriate changes may be implemented in the master control system to account for the timing of movement of the seal bodies and pressurization/depressurization of each of the additional high pressure reservoirs, all with the goal of ensuring a constant supply of pressurized melted ink to the printhead(s). In the case of three or more high pressure reservoirs, it can be contemplated that the inactive reservoirs may be simultaneously re-filled with molten ink from the low pressure reservoir while their respective outlets are closed by the seal body. This configuration may require a larger low pressure reservoir to melt enough ink to fill more than one high pressure reservoir.
It will be appreciated that various of the above-described features and functions, as well as other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
This application claims priority from U.S. application Ser. No. 12/775,844, which was filed on May 7, 2010, is entitled “High Flow Ink Delivery System,” and which issued as U.S. Pat. No. 8,303,098 on Nov. 6, 2012.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4814786 | Hoisington et al. | Mar 1989 | A |
| 5489925 | Brooks et al. | Feb 1996 | A |
| 5757390 | Gragg et al. | May 1998 | A |
| 5992990 | Childers et al. | Nov 1999 | A |
| 6022102 | Ikkatai et al. | Feb 2000 | A |
| 6276784 | Ikkatai et al. | Aug 2001 | B1 |
| 6494553 | Donahue et al. | Dec 2002 | B1 |
| 6799844 | Leighton et al. | Oct 2004 | B2 |
| 6860591 | Slotto et al. | Mar 2005 | B2 |
| 6866375 | Leighton et al. | Mar 2005 | B2 |
| 7401907 | Perez | Jul 2008 | B2 |
| 7416292 | Leighton | Aug 2008 | B2 |
| 7475971 | Herbert et al. | Jan 2009 | B2 |
| 7604333 | Horsnell et al. | Oct 2009 | B2 |
| 7703898 | Klein Meuleman et al. | Apr 2010 | B2 |
| 7780278 | Brown et al. | Aug 2010 | B2 |
| 7878637 | Leighton | Feb 2011 | B2 |
| 7931359 | Esdaile-Watts et al. | Apr 2011 | B2 |
| 20010019347 | Hauck | Sep 2001 | A1 |
| 20040174417 | Kobayashi et al. | Sep 2004 | A1 |
| 20060164472 | Perez | Jul 2006 | A1 |
| 20070002107 | Leighton | Jan 2007 | A1 |
| 20070076023 | Knierim et al. | Apr 2007 | A1 |
| 20090009574 | Leighton | Jan 2009 | A1 |
| 20100077855 | McCracken et al. | Apr 2010 | A1 |
| 20110141212 | Smith et al. | Jun 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 0933217 | Aug 1999 | EP |
| 1452322 | Sep 2004 | EP |
| 2006078931 | Jul 2006 | WO |
| Entry |
|---|
| United Kingdom Search Report corresponding to UK Application No. 1107364.0, United Kingdom Intellectual Property Office, Newport, South Wales, UK, Sep. 1, 2011 (3 pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20120320134 A1 | Dec 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12775844 | May 2010 | US |
| Child | 13595705 | US |
