This invention relates generally to the field of fluid dispensers and, in particular, to flow through liquid drop dispensers that eject on demand a quantity of liquid from a continuous flow of liquid.
Traditionally, inkjet printing is accomplished by one of two technologies referred to as “drop-on-demand” and “continuous” inkjet printing. In both, liquid, such as ink, is fed through channels formed in a print head. Each channel includes a nozzle from which droplets are selectively extruded and deposited upon a recording surface.
Drop on demand printing only provides drops (often referred to a “print drops”) for impact upon a print media. Selective activation of an actuator causes the formation and ejection of a drop that strikes the print media. The formation of printed images is achieved by controlling the individual formation of drops. Typically, one of two types of actuators is used in drop on demand printing—heat actuators and piezoelectric actuators. With heat actuators, a heater, placed at a convenient location adjacent to the nozzle, heats the ink. This causes a quantity of ink to phase change into a gaseous steam bubble that raises the internal ink pressure sufficiently for an ink droplet to be expelled. With piezoelectric actuators, an electric field is applied to a piezoelectric material possessing properties causing a wall of a liquid chamber adjacent to a nozzle to be displaced, thereby producing a pumping action that causes an ink droplet to be expelled.
Continuous inkjet printing uses a pressurized liquid source that produces a stream of drops some of which are selected to contact a print media (often referred to a “print drops”) while other are selected to be collected and either recycled or discarded (often referred to as “non-print drops”). For example, when no print is desired, the drops are deflected into a capturing mechanism (commonly referred to as a catcher, interceptor, or gutter) and either recycled or discarded. When printing is desired, the drops are not deflected and allowed to strike a print media. Alternatively, deflected drops can be allowed to strike the print media, while non-deflected drops are collected in the capturing mechanism.
Printing systems that combine aspects of drop on demand printing and continuous printing are also known. These systems, often referred to a flow through liquid drop dispensers, provide increased drop ejection frequency when compared to drop on demand printing systems without the complexity of continuous printing systems. As such, there is an ongoing effort to increase the reliability and performance of flow through liquid drop dispensers.
According to one feature of the present invention, a liquid dispenser includes a liquid supply channel, a liquid dispensing channel including an outlet opening, and a liquid return channel. A liquid supply provides liquid under pressure from the liquid supply channel through the liquid dispensing channel to the liquid return channel. A selectively actuatable diverter member imparts heat energy directly to a first portion of the liquid to divert a second portion of the liquid toward outlet opening of the liquid dispensing channel.
According to another feature of the present invention, a method of printing includes providing a liquid dispenser including a liquid supply channel, a liquid dispensing channel including an outlet opening, a liquid return channel; providing liquid under pressure from the liquid supply channel through the liquid dispensing channel to the liquid return channel; and selectively actuating a diverter member that imparts heat energy directly to a first portion of the liquid to divert a second portion of the liquid toward outlet opening of the liquid dispensing channel.
In the detailed description of the example embodiments of the invention presented below, reference is made to the accompanying drawings, in which:
The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. In the following description and drawings, identical reference numerals have been used, where possible, to designate identical elements.
The example embodiments of the present invention are illustrated schematically and not to scale for the sake of clarity. One of the ordinary skills in the art will be able to readily determine the specific size and interconnections of the elements of the example embodiments of the present invention.
As described herein, the example embodiments of the present invention provide a liquid dispenser, often referred to as a printhead, that is particularly useful in digitally controlled inkjet printing devices wherein drops of ink are ejected from a printhead toward a print medium. However, many other applications are emerging which use inkjet printheads to emit liquids (other than inks) that need to be finely metered and deposited with high spatial precision. As such, as described herein, the terms “liquid” and “ink” refer to any material that can be ejected by the liquid dispenser described below.
Referring to
Liquid dispenser 10 of the present invention does not include a nozzle like conventional flow through liquid dispensing devices. Instead, liquid dispensing channel 12 includes an outlet opening 26, defined by a beginning 18 and an ending 19, that opens directly to atmosphere. As such, liquid ejected by liquid dispenser of the present invention does not need to travel through the nozzle of conventional devices which helps to reduce the likelihood of the nozzle area of the device being contaminated or clogged. The beginning 18 of outlet opening 26 also at least partially defines the exit 21 of liquid supply channel 11.
Liquid dispenser 10 also includes a liquid supply 24 that provides liquid 25 to liquid dispenser 10. During operation, liquid 25, pressurized by a regulated pressure source 16, for example, a pump, flows (represented by arrows 27) from liquid supply 24 through liquid supply channel 11, liquid dispensing channel 12, liquid return channel 13, and back to liquid supply 24 in a continuous manner. When a drop 15 (also referenced as drop 42 in some of the example embodiments described below) of liquid 25 is desired, diverter member 20 is actuated causing a portion of the liquid 25 in liquid dispensing channel 11 to be ejected through outlet opening 26 along drop ejection guide structure 14. Typically, regulated pressure source 16 is positioned in fluid communication between liquid supply 24 and liquid supply channel 11 and provides a positive pressure that is above atmospheric pressure.
Optionally, a regulated vacuum supply 17, for example, a pump, can be included in the liquid delivery system of liquid dispenser 10 in order to better control liquid flow through liquid dispenser 10. Typically, regulated vacuum supply 17 is positioned in fluid communication between liquid return channel 13 and liquid supply 24 and provides a vacuum (negative) pressure that is below atmospheric pressure.
Liquid dispenser 10 is typically formed from a semiconductor material (for example, silicon) using known semiconductor fabrication techniques (for example, CMOS circuit fabrication techniques, micro-electro mechanical structure (MEMS) fabrication techniques, or combination of both). Alternatively, liquid dispenser 10 can be formed from any materials using any fabrication techniques known in the art.
Referring to
Liquid return channel 13 includes a porous member 22, for example, a filter, which helps to minimize pressure changes associated with actuation of diverter member 20 and a portion of liquid 25 being deflected toward outlet opening 26. This reduces the likelihood of air being drawn into liquid return channel 13 or liquid spilling over outlet opening 26 of liquid dispensing channel 12 during actuation of diverter member 20. Porous member 22 is typically integrally formed in liquid return channel 13 during the manufacturing process that is used to fabricate liquid dispenser 10. Alternatively, porous member 22 can be made from a metal or polymeric material and inserted and affixed to one or more of the walls that define liquid return channel 13.
Regardless of whether porous member 22 in integrally formed or fabricated separately, the pores of porous member 22 can have a substantially uniform pore size. Alternatively, the pore size of the pores of porous member 22 can include a gradient so as to be able to more efficiently accommodate liquid flow through the liquid dispenser 10 (for example, larger pore sizes (alternatively, smaller pore sizes) on an upstream portion of the porous member 22 that decrease (alternatively, increase) in size at a downstream portion of porous member 22 when viewed in a direction of liquid travel). The specific configuration of the pores of porous member 22 typically depends on the specific application contemplated.
Porous member 22 is positioned in liquid return channel 13 parallel to the flow direction 27 of liquid 25 in liquid dispensing channel 12 such that the openings (pores) of porous member 22 are substantially perpendicular to the liquid flow 27. As shown in
In
In the example embodiment shown in
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As described above with reference to
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Generally described, liquid dispensing channel 12 includes a first wall 50 and a second wall 52 positioned opposite each other. First wall 50 and second wall 52 extend from the exit 21 of liquid supply channel 11 to the end 19 of outlet opening 26 of liquid dispensing channel 12. First wall 50 and second wall 52 are spaced farther apart from each other at the end 19 of outlet opening 26 of liquid dispensing channel 12 when compared to the spacing of first wall 50 and second wall 52 at the exit 21 of liquid supply channel 11. Typically, first wall 50 and second wall 52 are positioned opposite each other. First wall 50 and second wall 52 can be positioned perpendicular to an area defined by outlet opening 26 of liquid dispensing channel 12. Alternatively, first wall 50 and second wall 52 can be positioned parallel or substantially parallel to the area defined by outlet opening 26 of liquid dispensing channel 12. Typically, first wall 50 and second wall 52 are symmetrically positioned relative to each other in order to minimize changes in the flow characteristics of the liquid.
In some example embodiments described below, liquid supply channel 11 narrows (or “necks down”) in the vicinity of exit 21 of liquid supply channel 11 as viewed in the direction 27 of liquid flow through liquid dispenser 10. That is, the wall to wall spacing of a first wall 54 and a second wall 56 of liquid supply channel 11 is closer together near the exit 21 than at a location upstream from exit 21. As such, the cross sectional area of the exit 21 of liquid supply channel 11 is less than the cross section area of liquid supply channel 11 at a location 58 of the liquid supply channel that is upstream of the exit of the liquid supply channel. This is done to maintain or even increase the velocity of the liquid flowing through liquid dispensing channel 12. Additionally, in a liquid dispenser 10 array, there is limited space between neighboring liquid dispensers 10. A narrow exit 21 allows a portion the liquid dispensing channel 12 to be wider than exit 21 in order to control the meniscus height of the liquid in the liquid dispensing channel opening 26 so as to reduce or even prevent liquid spills when the diverter member 20 is not activated.
In
In
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In
The example embodiments described with reference to
When an active device is implemented liquid dispenser 10 is typically configured as follows. Liquid dispensing channel 12 includes a first wall 50 and a second wall 52 positioned parallel to each other and opposite each other. First wall 50 and second wall 52 extend from the exit 21 of liquid supply channel 11 to the end 19 of outlet opening 26 of liquid dispensing channel 12. First wall 50 and second wall 52 include a selectively actuatable device that, when actuated, causes the spacing of first wall 50 and second wall 52 to be farther apart from each other at the end 19 of outlet opening 26 of liquid dispensing channel 12 when compared to the exit 21 of liquid supply channel 11. Alternatively, the active device can be included in a wall 60 of liquid dispensing channel 12 that is positioned opposite outlet opening 26. Wall 60 extends from the exit 21 of liquid supply channel 11 to the end 19 of outlet opening 26 of liquid dispensing channel 12. The active device is a selectively actuatable device that, when actuated, causes the spacing of wall 60 to be farther apart from outlet opening 26 at the end 19 of outlet opening 26 of liquid dispensing channel 12 when compared to the exit 19 of liquid supply channel 11.
Referring to
Generally described, liquid dispenser 10 includes a liquid supply channel 11 that includes an exit 21. Liquid dispensing channel 12 includes an outlet opening 26 that includes an end 19. Liquid dispenser 10 also includes a liquid return channel 13 and a liquid supply 24 that provides liquid 25 under pressure from liquid supply channel 11 through liquid dispensing channel 12 to the liquid return channel 13. Diverter member 20 is selectively actuatable to divert a portion 15 of liquid 25 toward outlet opening 26 of liquid dispensing channel 12. Also, as described above with reference to
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Additionally, liquid dispenser 10a and liquid dispenser 10b can be integrally formed on a common substrate using the fabrication techniques described above thereby creating a two dimensional monolithic liquid dispenser array structure. When compared to other types of liquid dispensers, monolithic dispenser configurations help to improve the alignment of each outlet opening relative to other outlet openings which improves image quality. Monolithic dispenser configurations also help to reduce spacing in between adjacent outlet openings which increases dots per inch (dpi).
In
The plurality of first liquid dispensers 10a and the plurality of second liquid dispensers 10b can be configured differently in first direction 74. For example, in
In
Referring to
Liquid dispensing channel 12 includes an outlet opening 26, defined by a beginning 18 and an ending 19, that opens directly to atmosphere. The beginning 18 of outlet opening 26 also at least partially defines the exit 21 of liquid supply channel 11. Liquid dispensing channel 12 includes a diverter member 20.
Liquid dispenser 10 also includes a liquid supply 24 that provides liquid 25 to liquid dispenser 10. During operation, liquid 25, pressurized by a regulated pressure source 16, for example, a pump, flows (represented by arrows 27) from liquid supply 24 through liquid supply channel 11, liquid dispensing channel 12, liquid return channel 13, and back to liquid supply 24 in a continuous manner. When a drop 15 of liquid 25 is desired, diverter member 20 is actuated causing a portion of the liquid 25 in liquid dispensing channel 11 to be ejected through outlet opening 26 along drop ejection guide structure 14. Drop ejection guide structure 14 which guides the portion of liquid 25 that has been diverted by actuation of diverter member 20 from outlet opening 26 of liquid dispensing channel 12 toward atmosphere is located downstream relative to outlet opening 26 of liquid dispensing channel 12 and upstream relative to the location of vent 23 of liquid return channel 13. Typically, regulated pressure source 16 is positioned in fluid communication between liquid supply 24 and liquid supply channel 11 and provides a positive pressure that is above atmospheric pressure.
Optionally, a regulated vacuum supply 17, for example, a pump, can be included in the liquid delivery system of liquid dispenser 10 in order to better control liquid flow through liquid dispenser 10. Typically, regulated vacuum supply 17 is positioned in fluid communication between liquid return channel 13 and liquid supply 24 and provides a vacuum (negative) pressure that is below atmospheric pressure.
Liquid dispenser 10 also includes a liquid cooling channel 32 positioned relative to liquid dispensing channel 12. Diverter member 20 includes a first side 20a that faces liquid dispensing channel 12 and a second side 20b that faces liquid cooling channel 31. Diverter member 20 is selectively actuatable using heat energy to divert a portion 15 of liquid 25 toward outlet opening 26 of liquid dispensing channel 12. Diverter member 20 either includes a heater or incorporates using heat in its actuation. The liquid flowing through liquid cooling channel 32 helps to cool diverter member 20 after diverter member 20 has been actuated. This helps to increase the frequency at which diverter member 20 can be actuated thereby improving the overall print speed of liquid dispenser 10.
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In the example embodiment shown in
First liquid supply 24, using regulated pressure source 16 and, optionally, regulated vacuum source 17, regulates the velocity of the first liquid 25 moving through liquid dispensing channel 12 while second liquid supply 86, using second regulated pressure source 35 and, optionally, second regulated vacuum source 36, regulates the velocity of second liquid 84 moving through liquid cooling channel 32 so that liquid pressure on both sides of diverter member 20 is balanced. This helps to minimize differences in liquid flow characteristics that may adversely affect liquid diversion and drop formation during operation. Alternatively, liquid dispensing channel 12 and liquid cooling channel 32 can be sized such that liquid pressure on both sides of diverter member 20 is balanced.
Referring to
Liquid dispensing channel 12 includes an outlet opening 26, defined by a beginning 18 and an ending 19, that opens directly to atmosphere. The beginning 18 of outlet opening 26 also at least partially defines the exit 21 of liquid supply channel 11. Liquid dispensing channel 12 includes a diverter member 20. In
Liquid dispenser 10 also includes a liquid supply 24 that provides liquid 25 to liquid dispenser 10. During operation, liquid 25, pressurized by a regulated pressure source 16, for example, a pump, flows (represented by arrows 27) from liquid supply 24 through liquid supply channel 11, liquid dispensing channel 12, liquid return channel 13, and back to liquid supply 24 in a continuous manner. When a drop 15 of liquid 25 is desired, diverter member 20 is actuated causing a portion of the liquid 25 in liquid dispensing channel 11 to be ejected through outlet opening 26 along drop ejection guide structure 14. Drop ejection guide structure 14 which guides the portion of liquid 25 that has been diverted by actuation of diverter member 20 from outlet opening 26 of liquid dispensing channel 12 toward atmosphere is located downstream relative to outlet opening 26 of liquid dispensing channel 12 and upstream relative to the location of vent 23 of liquid return channel 13. Typically, regulated pressure source 16 is positioned in fluid communication between liquid supply 24 and liquid supply channel 11 and provides a positive pressure that is above atmospheric pressure.
Optionally, a regulated vacuum supply 17, for example, a pump, can be included in the liquid delivery system of liquid dispenser 10 in order to better control liquid flow through liquid dispenser 10. Typically, regulated vacuum supply 17 is positioned in fluid communication between liquid return channel 13 and liquid supply 24 and provides a vacuum (negative) pressure that is below atmospheric pressure.
Liquid dispenser 10 also includes a drop ejection guide structure 14 that reduces viscous drag on the portion of the liquid 25 that has been diverted by diverter member 20. Drop ejection guide structure 14 includes a liquid structure 44 in
Surface portion 90 that includes guide structure 14 can be contrasted with another portion 94 of surface 92 that does not include structure that reduces viscous drag on the portion of liquid 25 that has been diverted by diverter member 20. This other portion 94 can be located anywhere down stream from outlet opening 26.
In
Referring to
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Liquid dispensing channel 12 includes an outlet opening 26, defined by a beginning 18 and an ending 19, that opens directly to atmosphere. The beginning 18 of outlet opening 26 also at least partially defines the exit 21 of liquid supply channel 11. Liquid dispensing channel 12 includes a diverter member 20.
Liquid dispenser 10 also includes a liquid supply 24 that provides liquid 25 to liquid dispenser 10. During operation, liquid 25, pressurized by a regulated pressure source 16, for example, a pump, flows (represented by arrows 27) from liquid supply 24 through liquid supply channel 11, liquid dispensing channel 12, liquid return channel 13, and back to liquid supply 24 in a continuous manner. When a drop 15 of liquid 25 is desired, diverter member 20 is actuated causing a portion of the liquid 25 in liquid dispensing channel 11 to be ejected through outlet opening 26 along drop ejection guide structure 14. Drop ejection guide structure 14 which guides the portion of liquid 25 that has been diverted by actuation of diverter member 20 from outlet opening 26 of liquid dispensing channel 12 toward atmosphere is located downstream relative to outlet opening 26 of liquid dispensing channel 12 and upstream relative to the location of vent 23 of liquid return channel 13. Typically, regulated pressure source 16 is positioned in fluid communication between liquid supply 24 and liquid supply channel 11 and provides a positive pressure that is above atmospheric pressure.
Optionally, a regulated vacuum supply 17, for example, a pump, can be included in the liquid delivery system of liquid dispenser 10 in order to better control liquid flow through liquid dispenser 10. Typically, regulated vacuum supply 17 is positioned in fluid communication between liquid return channel 13 and liquid supply 24 and provides a vacuum (negative) pressure that is below atmospheric pressure.
In
In the example embodiment shown in
Typically, diverter member 20 is positioned in liquid dispensing channel 12 opposite outlet opening 26. However, diverter member 20 can be positioned in liquid supply channel 11. For example, diverter member 20 can be located on a wall 100 of liquid supply channel 11 that is an extension of a wall 102 of liquid dispensing channel 12 that is opposite outlet opening 26 of liquid dispensing channel 12. When positioned in liquid supply channel 11, diverter member 20 is located upstream relative to outlet opening 26. When located upstream relative to outlet opening 26, diverter member 20 can be located on a wall 104 of liquid supply channel that is adjacent to outlet opening 26 of liquid dispensing channel 12. Diverter member 20 can also be positioned in liquid return channel 13. For example, diverter member 20 can be located on a wall 106 of liquid return channel 13 that is an extension of a wall 102 of liquid dispensing channel 12 that is opposite outlet opening 26 of liquid dispensing channel 12. When positioned in liquid return 13, diverter member 20 is located downstream relative to outlet opening 26. When located downstream relative to outlet opening 26, diverter member 20 can be located on a wall 108 of liquid return channel 13 that is adjacent to outlet opening 26 of liquid dispensing channel 12.
Combinations of diverter member 20 locations are also permitted. For example, in
In
When the velocity of the liquid in the liquid dispensing channel 12 is below a threshold velocity (the specific velocity varies depending on the application that the liquid dispenser 10 is being used for), the liquid in the liquid dispensing channel 12 stays in contact with surface 110 in the liquid dispensing channel 12 due to Coanda effect. When the velocity of the liquid in the liquid dispensing channel 12 is above the threshold velocity, the momentum of the liquid overcomes the Coanda effect and the liquid in the liquid dispensing channel 12 detaches from surface 110 in the liquid dispensing channel 12 and the liquid is diverted out of the opening 26 of the liquid dispensing channel 12 to form liquid drops 42.
The Coanda effect on the liquid in the liquid dispensing channel 12 can be enhanced or reduced through asymmetric heating of the liquid in the liquid supply channel 11 through activation of different heaters located on the walls of the liquid supply channel 11. Asymmetric heating causes a portion of the liquid to be heated, the portion of heated fluid has lower viscosity and higher velocity than the adjacent unheated fluid portion. When the asymmetric heating enhances the Coanda effect, the liquid in the liquid dispensing channel 12 stays in contact with surface 110 in the liquid dispensing channel 12 and flow towards to the liquid return channel 13. When the asymmetric heating reduces the Coanda effect, the liquid in the liquid dispensing channel 12 detaches from surface 110 in the liquid dispensing channel 12 and the liquid is diverted out of the opening 26 of the liquid dispensing channel 12 to form liquid drops 42.
The example embodiments described above can be implemented individually (by themselves) or in combination with each other to obtain the desired liquid dispenser performance. Accordingly, a liquid dispenser of the present invention can include more than one feature described above. As such, the diverter member features described with reference to
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention.
10 liquid dispenser
10
a first liquid dispenser array
10
b second liquid dispenser array
11 liquid supply channel
12 liquid dispensing channel
13 liquid return channel
14 drop ejection guide structure
15 drop
16 regulated pressure source
17 regulated vacuum supply
18 beginning
19 ending
20 diverter member
20
a first side
20
b second side
21 exit
22 porous member
23 vent
24 liquid supply
25 liquid
26 outlet opening
27 arrows
28 wall
31 second liquid supply channel
32 liquid cooling channel
33 vapor bubble
34 second liquid return channel
35 second regulated pressure source
36 second regulated vacuum supply
42 drops
43 solid structure
44 liquid structure
50 first wall
50
a non-parallel portions
50
b parallel non-recessed portions
52 second wall
52
a non-parallel portions
52
b parallel non-recessed portions
54 first wall
56 second wall
58 location
60 wall
62 outer wall
64 outer wall
68 arrows
70 arrows
72 curvature
74 first direction
76 second direction
80 wall
82 end
84 second liquid
86 second liquid supply
88 arrows
90 surface portion
92 surface
94 another portion
100 wall
102 wall
104 wall
106 wall
108 wall
110 Coanda surface
Reference is made to commonly-assigned, U.S. patent applications Ser. No. ______ (Docket 95396), entitled “FLOW THROUGH DROP DISPENSER INCLUDING POROUS MEMBER”, Ser. No. ______ (95704), entitled “FLOW THROUGH DISPENSER”, Ser. No. ______ (Docket 95705), entitled “FLOW THROUGH DISPENSER INCLUDING TWO DIMENSIONAL ARRAY”, Ser. No. ______ (Docket 95706), entitled “FLOW THROUGH DISPENSER INCLUDING DIVERTER COOLING CHANNEL”, and Ser. No. ______ (Docket 95707), entitled “FLOW THROUGH DISPENSER INCLUDING IMPROVED GUIDE STRUCTURE”, all filed concurrently herewith.