Patent Grant
8529038
This disclosure relates generally to printing devices having one or more print heads that eject liquid ink onto an image receiving member, and more particularly, to printing devices that use pressure to supply ink to the one or more printheads.
Phase-change ink printing systems include various imaging devices that 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, and sharper images.
A typical solid ink or phase-change ink imaging device includes an ink loader, which receives and stages solid ink for delivery to a melting device. The ink supply can be replenished by a user inserting more solid ink into the loader. The loader has separate loader channels, each of which supplies a different color of ink to a melting device. For example, four loader channels are provided in an imaging device that uses cyan, magenta, yellow, and black (CMYK) ink to form ink image images. Solid ink is supplied in a variety of forms that include blocks, sticks, pellets, and pastilles, for example.
Solid ink imaging devices melt the solid ink to a liquid phase for imaging operations. In a typical embodiment, a melting device heats the solid ink to a temperature at which the solid ink enters a liquid phase. The one or more printheads in an imaging device receive the liquid ink and eject liquid drops of the ink through a plurality of inkjets onto an image receiving member, such as paper, or an indirect receiver, such as a rotating drum or endless belt. Many printer embodiments maintain a supply of liquefied ink in an ink reservoir that is fluidly coupled to one or more printheads for printing onto the image receiving member.
In some printers, gravity urges ink in the reservoir to flow to the printheads. In other printers, a pumping system applies pressure to liquid ink in the reservoir to urge the ink to the printheads. Continuous feed printers form images on an elongated media web that moves through the printer at a high speed for high-volume production. These continuous feed printers often consume ink at a high rate and require a pressurized ink reservoir to maintain a uniform supply of ink to the printheads. In one type of continuous printer, two separate delivery reservoirs supply ink to a common set of printheads using an alternating operating technique. In the alternating operating technique, one of the two delivery reservoirs is connected to a low pressure reservoir to enable ink to flow from the low pressure reservoir to the connected delivery high pressure reservoir side while the other delivery reservoir is disconnected from the low-pressure reservoir and the high pressure reservoir side is pressurized to deliver ink to the printheads. When the level of ink in the pressurized delivery reservoir drops below a predetermined fluid level, the pressurized delivery reservoir is disconnected from the pressure source, a double-ended seal piston is toggled to enable ink to flow from the low pressure reservoir. The other ink delivery reservoir is disconnected from the low-pressure reservoir and pressurized to deliver ink to the printheads. In one implementation of the alternating process, each of the ink delivery reservoirs includes a piston. The two pistons are mechanically linked so that one piston seals one ink delivery reservoir from the low-pressure reservoir, while the other piston simultaneously opens the other ink delivery reservoir to receive ink from the low-pressure reservoir. The alternating arrangement of the two delivery ink reservoirs enables a substantially continuous supply of ink to the printheads during printing operations.
One challenge facing a pressurized reservoir system involves the depressurization of the ink delivery reservoirs. The challenge arises from the pressurization of an air pocket positioned over the ink held in the ink delivery reservoir. When the level of ink in the pressurized reservoir drops below the predetermined threshold and the ink delivery reservoir is placed in fluid communication with the low-pressure reservoir, the pressurized air exits the delivery reservoir and enters the low-pressure reservoir through the valve seat opening. This pressurized air exits through the valve seat opening to cause ink held in the low-pressure reservoir to splatter and aerosol some of the ink in the low-pressure reservoir. Ink droplets resulting from the splatter may escape the low-pressure reservoir through openings in the low-pressure ink reservoir. Some of the escaped ink may contaminate the air supply vents and cause premature failure by blocking the air flow in the vent line. Consequently, improvements to the operation of the pressurized ink delivery system to prevent ink contamination would be beneficial.
In one embodiment, an ink delivery system in a phase change ink printer has been developed. The system includes a housing forming a first ink reservoir and a second ink reservoir, a first ink inlet formed in the housing to enable liquid ink to enter the first ink reservoir, a first ink outlet formed between the first ink reservoir and the second ink reservoir in the housing to enable liquid ink to move from the first ink reservoir to the second ink reservoir, a second ink outlet formed in the housing to fluidly couple the second ink reservoir to at least one printhead, a member positioned within the housing and configured to move between a first position and a second position, the member forming a seal with the second outlet opening to enable liquid ink to enter the second reservoir through the first ink outlet in the first position, and the member forming another seal with the first ink outlet to enable ink to exit the second ink reservoir through the second ink outlet in the second position, a conduit formed through the housing, the conduit having an inlet configured to receive pressurized air and an outlet in fluid communication with the second ink reservoir to enable pressurization of air in the second ink reservoir when the member is in the second position, and an orifice formed in the conduit, the orifice being configured to enable the pressurized air in the second ink reservoir to exit the second ink reservoir through the conduit when the member is in the second position.
In another embodiment, a method of operating an ink delivery system in a phase change ink printer has been developed. The method includes receiving liquid ink in a first ink reservoir, moving a member to a first position that enables the liquid ink in the first ink reservoir to exit the first ink reservoir through a first ink outlet and enter a second ink reservoir, moving the member to a second position that seals the first ink outlet and enables the ink in the second ink reservoir to exit the second ink reservoir through a second ink outlet that is fluidly coupled to at least one printhead, activating a source of pressurized air to supply pressurized air to the second ink reservoir through a conduit fluidly coupled to the second ink reservoir, deactivating the source of pressurized air to enable pressurized air in the second ink reservoir to exit the second ink reservoir through an orifice formed in the conduit, and moving the member from the second position to the first position to enable ink in the first ink reservoir to enter the second ink reservoir through the first ink outlet after deactivation of the source of pressurized air.
In another embodiment, an ink delivery system in a phase change ink printer has been developed. The system includes a housing forming a first ink reservoir, a second ink reservoir, and a third ink reservoir, a first ink inlet formed in the housing to enable liquid ink to enter the first ink reservoir, a first ink outlet formed between the first ink reservoir and the second ink reservoir to enable the liquid ink to move from the first ink reservoir to the second ink reservoir, a second ink outlet formed between the first ink reservoir and the third ink reservoir to enable the liquid ink to move from the first ink reservoir to the third ink reservoir, a third ink outlet formed in the housing to fluidly couple the second ink reservoir to at least one printhead, a fourth ink outlet formed in the housing to fluidly couple the third ink reservoir to the at least one printhead, a first member positioned within the housing and configured to move between a first position and a second position, the first member forming a seal with the third outlet opening to enable liquid ink to enter the second ink reservoir through the first ink outlet in the first position, and the first member forming another seal with the first ink outlet to enable ink to exit the second ink reservoir through the third ink outlet in the second position, a second member positioned within the housing and configured to move between a third position and a fourth position, the second member forming a seal with the fourth outlet opening to enable liquid ink to enter the third ink reservoir through the second ink outlet in the third position, and the second member forming another seal with the second ink outlet to enable ink to exit the second ink reservoir through the fourth ink outlet in the fourth position, a first conduit formed through the housing having a first inlet configured to receive pressurized air and a first outlet in fluid communication with the second ink reservoir to enable pressurization of air in the second ink reservoir when the first member is in the second position, a second conduit formed through the housing having a second inlet configured to receive pressurized air and a second outlet in fluid communication with the third ink reservoir to enable pressurization of air in the third ink reservoir when the second member is in the fourth position, a first orifice formed in the first conduit, the first orifice being configured to enable pressurized air in the second ink reservoir to exit the second ink reservoir through the first conduit when the first member is in the second position, and a second orifice formed in the second conduit, the second orifice being configured to enable pressurized air in the third ink reservoir to exit the third ink reservoir through the second conduit when the second member is in the fourth position.
The foregoing aspects and other features of an ink delivery system that controls a pressure applied to a pressurized ink reservoir are explained in the following description, taken in connection with the accompanying drawings.
For a general understanding of the environment for the system and method disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the word “printer” encompasses any apparatus that performs a print outputting function for any purpose, such as a digital copier, bookmaking machine, facsimile machine, a multi-function machine, or the like.
Referring to
The melting apparatus 11 further includes a high efficiency heater 15. The heater 15 generally includes a plurality of heated fins onto which the solid ink pellets are dispensed. The pellets are continuously melted by the fins and the melted ink drips between the fins into a low pressure reservoir 18. In the illustrated embodiment, the low pressure reservoir is formed within a housing 16 that includes a slanted floor positioned directly beneath the heater 15. The slanted floor of the low pressure reservoir is configured to direct the melted ink received through heater 15 toward a collection region 19 where the melted ink can be conveyed to the high pressure reservoirs described below. 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 high 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 one or more printheads. In one embodiment, two such reservoirs are provided, namely reservoirs 20A and 20B, which are formed within a housing 17. In one embodiment, the housing 17 is integral with the housing 16, while in other embodiments the housing 17 is separate from the housing 16, which forms the low pressure reservoir 18. For purposes of the present disclosure, the high pressure reservoirs 20A, 20B may be referred to as the first and second reservoirs or as reservoir A and reservoir B, respectively. Like components of the reservoirs may also be designated with a subscript A or B to refer to the associated high pressure reservoir.
The reservoirs 20A, 20B are connected by pressure 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 20A, 20B is sufficient to feed high pressure inkjets of the one or more printheads, as is known in the art. As explained in more detail herein, the high pressure reservoirs 20A, 20B 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 20A, 20B is provided with a corresponding ink level sensor 27, 28, which determine 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. Each high pressure reservoir 20A, 20B includes 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 channels 37A, 37B, through the filter element 39 and outlet 40 to an array of tubing (not shown), which is coupled to the printhead(s). The pressure in the outlet channel 37A, 37B is produced by pressure within the high pressure reservoir 20A, 20B that is currently pressurized. The ink delivery apparatus 10 disclosed herein provides a mechanism for alternately fluidly coupling one of the high pressure reservoirs to the ink outlet 40 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 valve assemblies 52A, 52B, rocker assemblies 54A, 54B, and an actuator assembly 56.
For the purposes of illustration, the valve assembly 52B is described with the understanding that the valve assembly 52A is substantially identically configured. The valve assembly 52B includes a valve seat body 60 disposed at or over the inlet opening 32B. The valve seat body 60 defines one or more flow openings 62 that communicate between the low pressure reservoir 18 and the inlet opening 32B. The valve seat body 60 is provided with a mounting flange 63 in one embodiment that mates the body with the housing 17 defining the reservoir. The valve seat body 60 further includes a sealing hub 65 projecting from the mounting flange and configured to fit snugly within the inlet opening 32B. The sealing hub 65 includes a sealing element 66, such as an O-ring or flat rubber face seal washer, between the hub 65 and the housing 17. The sealing hub 65 defines a sealing face 68B facing a seal member 70B, as illustrated in
The seal member 70B is disposed for translation within a chamber 61 aligned between the inlet opening 32B and the outlet opening 36B. The chamber 61 is partially defined by the housing 17 in the high pressure reservoir 20B in one embodiment and is defined by a number of walls that help align and guide the seal body 70B in other embodiments. In the latter case, the walls are configured to ensure a constant supply of molten ink to the outlet opening 36B and sized to achieve an optimal flow rate. Seal members 70A, 70B forming part of the respective valve assembly 52A, 52B are substantially identical in construction, both bodies being configured to translate between an uppermost position sealing the inlet opening 32A, 32B, and a lowermost position sealing the corresponding outlet opening 36A, 36B. As shown in
The seal member 70B includes an upper seal 71B and a lower seal 73B. The upper seal is configured for sealed engagement with the sealing face 68B of the valve seat body 60 described above. The seal member 70B in
The length of the seal members 70A, 70B are less than the distance between the opposed inlet 32A, 32B and outlet openings 36A, 36B in each high pressure reservoir 20A, 20B. The length of the seal members 70A, 70B are calibrated such that when the seal member is sealing one opening (such as inlet opening 32B) the member does not impede ink flow through opposite opening (such as outlet opening 36B). At the same time, the travel distance of the seal members 70A, 70B between the first position, sealing the outlet opening, and the second position, sealing the inlet opening, is preferably limited so that the time delay between unsealing one opening and sealing the opposite opening is minimized. In one specific embodiment, the length of the seal members 70A, 70B are about 80-90% of the distance between the inlet and outlet openings in a given high pressure reservoir.
In order to translate the seal members 70A, 70B, each valve assembly 52A, 52B is driven by a corresponding rocker assembly MA, MB. Rocker assembly MB includes a control rod 75B that extends downward through the housings 16, 17, and the seal body 70B. The control rod 75B is affixed to the seal member 70B by an attachment pin 76 extending transversely through the rod 75B and seal member 70B, as depicted in
As shown in
As the piston 95 is driven upward by air pressure through inlet 99, the actuator rod 94 travels upward to pivot the link arm 91 clockwise about the axle 89. The clockwise rotation of the link arm 91 drives the control rod 75A and seal member 70A downward to the position shown in
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 upwardly) 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 assembly and stepper motor configured to drive the rocker arm into the two positions shown in
The embodiment of
In the position shown in
While the high pressure reservoir 20A is being filled, the other high pressure reservoir 20B is discharging the ink contents of the reservoir 20B under pressure. The internal level of the ink inside the reservoir is monitored by the low level sensor 28 to prevent emptying the contents and driving air into the system. The high pressure reservoir 20B thus has the seal member 70B in the position shown in
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 20A, 20B 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.
When the system switches ink supply to the printheads from high pressure reservoir 20A to high pressure reservoir 20B, the pressure source of pressure input 24 ceases providing pressurized air. The pressure in high pressure reservoir 20A decreases according to a known pressure decay curve as the air escapes from the high pressure reservoir 20A through the orifice 100 and into the low pressure reservoir 18. In one embodiment, the seal member 70A remains in a sealing position with inlet opening 32A for approximately six seconds after the pressure input ceases, to allow the pressure in the high pressure reservoir 20A to substantially equalize with the low pressure reservoir 18. In other embodiments, the time required to substantially equalize the pressure between high pressure reservoir and low pressure reservoir may be less than or greater than six seconds, depending on the size of the precision inlet of the orifice and the pressure difference between the high pressure reservoir and low pressure reservoir. In some embodiments, the high pressure reservoir 20A includes a pressure sensor to monitor the pressure in the high pressure reservoir 20A, and the delay time after the pressure input ceases is determined from the pressure sensor. The printheads in the system are configured to continue to operate with ink stored in the printhead units, lines, and manifold for the time required to reduce the pressure in the high pressure reservoir and switch the pressure source to the other high pressure reservoir.
Once the pressure between the high pressure reservoir 20A and the low pressure reservoir 18 is substantially equal, the seal member 70A is translated downwardly into a seal with outlet opening 36A as the seal member 70B is translated upwardly into a seal with inlet opening 32B. The pressure source of pressure input 25 is then activated to pressurize high pressure reservoir 20B. High pressure reservoir 20B begins supplying ink to the printheads through outlet opening 36B and outlet channel 37B. High pressure reservoir 20A is fluidly connected to low pressure reservoir 18 through inlet opening 32A and begins filling with molten ink.
Because the pressure in the low pressure reservoir 18 and the high pressure reservoir 20A are substantially equal when the sealing member 70A switches from sealing the inlet opening 32A to the outlet opening 36A, no pressurized air bubble transfers from the high pressure reservoir 20A to the low pressure reservoir 18. Therefore, ink inside the low pressure reservoir 18 is less likely to be perturbed and escape through holes and vents in the low pressure reservoir 18. By dropping the high pressure reservoir to atmosphere and then switching the seal actuators, the spray of ink is avoided.
When active, the pressure source(s) of pressure inlets 24, 25 are configured to operate at input pressures sufficient to compensate for the air escaping through the orifice 100, while maintaining the desired ink pressure to the corresponding high pressure reservoir 20A, 20B and the printheads. In one embodiment, the pressure through the pressure inlet is nine psi (62 kPa) above atmospheric pressure, resulting in ink pressure to the high pressure reservoir of eight psi (55 kPa). The pressure input may vary in other embodiments depending on the size of the orifice and the desired pressure in the high pressure reservoirs.
The coordinated action of the actuator assembly 56 of the ink delivery control mechanism 50, the pressure inputs 24, 25 to the high pressure reservoirs, the heater 15, and the heating element 30 are controlled by a suitable master control system in one embodiment (not shown). For instance, the master control system controls valves that supply pressurized air to the pressure inputs 24, 25. Likewise, the master control system controls valves that alternately vent and pressurize the air inlets 98, 99 for the pressure cylinder 97 in the actuator assembly 56 associated with the high pressure reservoirs 20A, 20B. In some of the embodiments, the master control system is an electronic controller that is integrated into the printing machine and is operable to control other functions of the machine. The electronic controller is programmable to enable changes to 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.
It will be appreciated that various of the above-disclosed and 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.
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| Number | Date | Country | |
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| 20130044165 A1 | Feb 2013 | US |
