Patent Grant
7520598
Reference is made to commonly-assigned, U.S. patent application Ser. No. 11/746,117, filed currently herewith, entitled “A FLUID FLOW DEVICE AND PRINTING SYSTEM,” and U.S. patent application Ser. No. 11/746,104, filed currently herewith, entitled “A FLUID FLOW DEVICE FOR A PRINTING SYSTEM.”
This invention relates generally to the management of gas flow and, in particular to the management of gas flow in printing systems.
Printing systems incorporating a gas flow are known, see, for example, U.S. Pat. No. 4,068,241, issued to Yamada, on Jan. 10, 1978.
The device that provides gas flow to the gas flow drop interaction area can introduce turbulence in the gas flow that may augment and ultimately interfere with accurate drop deflection or divergence. Turbulent flow introduced from the gas supply typically increases or grows as the gas flow moves through the structure or plenum used to carry the gas flow to the gas flow drop interaction area of the printing system.
Drop deflection or divergence can be affected when turbulence, the randomly fluctuating motion of a fluid, is present in, for example, the interaction area of the drops that are traveling along a path and the gas flow force. The effect of turbulence on the drops can vary depending on the size of the drops. For example, when relatively small volume drops are caused to deflect or diverge from the path by the gas flow force, turbulence can randomly disorient small volume drops resulting in reduced drop deflection or divergence accuracy which, in turn, can lead to reduced drop placement accuracy.
Accordingly, a need exists to reduce turbulent gas flow in the gas flow drop interaction area of a printing system.
According to one aspect of the present invention, a gas flow device includes a passage for a gas including a wall. A gas flow source is operable to cause the gas to flow in a direction through the passage. A liquid flow source operable to cause a liquid to flow in a direction along the wall of the passage, and the flow direction of the liquid is in the same direction as that of the gas flow.
According to another aspect of the present invention, a printing system includes a liquid drop ejector operable to eject liquid drops having a plurality of volumes along a first path and a passage for a gas including a wall. A gas flow source is operable to cause the gas to flow in a direction through the passage. A liquid flow source operable to cause a liquid to flow in a direction along the wall of the passage, and the flow direction of the liquid is in the same direction as that of the gas flow. Interaction of the gas flow and the liquid drops causes liquids drops having one of the plurality of volumes to begin moving along a second path.
According to another aspect of the present invention, a method of moving gas includes providing a passage including a wall; providing a gas flow from a gas flow source, the gas moving in a direction through the passage; and moving the wall along a travel path in the same direction as that of the gas flow. A liquid flow source operable to cause a liquid to flow in a direction along the moving wall of the passage, and the flow direction of the liquid is in the same direction as that of the gas flow.
In the detailed description of the preferred 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. The example embodiments of the present invention are illustrated schematically and not to scale for the sake of clarity. One of ordinary skill 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. In the following description, identical reference numerals have been used, where possible, to designate identical elements.
Although the term printing system is used herein, it is recognized that printing systems are being used today to eject other types of liquids and not just ink. For example, the ejection of various fluids such as medicines, inks, pigments, dyes, and other materials is possible today using printing systems. As such, the term printing system is not intended to be limited to just systems that eject ink.
When present in printing systems, for example, like those commonly referred to as continuous printing systems, turbulence, particularly wall-turbulence in the drop deflector system, is induced mainly by boundary friction (drag on the gas flow, for example, air, exerted by the walls of the deflector system). Drag and therefore turbulence can be reduced or even eliminated by actively controlling the boundary regions of the system. Boundary regions include, for example, areas of the system where the gas flow is adjacent to a solid portion, for example, a wall, of the system.
Drag reduction is accompanied by reductions in the magnitude of shear stress, commonly referred to as Reynolds shear stress, throughout the gas flow. This also helps to reduce or even eliminate turbulence. For example, when a liquid, moving along a boundary region, is moving in the same direction and at substantially the same velocity as velocity of the gas flow, drag can be reduced and the gas flow, for example, a laminar gas flow, can be maintained in the drop deflector system. The moving liquid surface decreases or even eliminates the fluid velocity gradient induced by boundary friction. The moving liquid moving on the wall of gas flow passages can also keep the wall free of contaminations such as particles or dry ink. Additionally, the moving liquid traveling along or over the wall of gas flow passage can also keep the temperature of the wall from increasing if heat is generated during wall movement. For example, friction associated with the moving wall may generate heat. In this situation, the addition of the moving liquid may help to keep the moving wall from overheating.
A liquid flow source 170 is operatively associated with the flow system 100 and is operable to cause a liquid 180 to flow in a direction along a wall 110 of the passage 120, and the flow direction (represented by a hollow arrow 190) of the liquid flow 181 being in the same direction as the direction of the gas flow 140. Liquid flow source 170 can be any type of mechanism suitably used to create the liquid flow 181. For example, liquid flow source 170 can be of the type that creates a positive pressure type liquid flow source such as liquid ejectors or a pump. The liquid flow source 170 can be located at the front side 150 of the passage 120. It is preferred that the velocity of liquid flow 181 be substantially equal to the velocity of the gas flow 140. However, the velocity of liquid flow 181 can be different than the velocity of the gas flow 140 depending on the specific application being contemplated.
The shape of the walls 110 of the passage 120 can be straight or be curved as needed. The walls 110 of the passage 120 can be any suitable materials such as aluminum, stainless steel, plastics, glass etc.; the surfaces of the wall 110 may be coated as necessary with hydrophobic or hydrophilic materials, depending on the type of liquid 180 being used, to facilitate liquid 180 to move along the wall 110. The liquid 180 can be, but not limited to, water or ink, or specifically engineered liquid with specific properties, such as a relative low surface tension coefficient, low viscosity, high thermal conductivity and/or high specific heat capacity. The gas of the gas flow source 130 can be air, vapor, nitrogen, helium, carbon dioxide, etc.
One wall of the walls of the passage can be static or have a travel path, in the same direction as that of the gas flow.
Referring to
The printhead 303 includes a drop forming mechanism operable to form drops 370 having a plurality of volumes traveling along a first path. A drop deflector system including gas flow device 301 applies a gas flow force to the drops traveling along the first path. The gas flow force is applied in a direction such that drops having one of the plurality of volumes diverge (or deflect) from the first path and begin traveling along a second path while drops having another of the plurality of volumes remain traveling substantially along the first path or diverge (deflect) slightly and begin traveling along a third path. Receiver 340 is positioned along one of the first, second and third paths while a catcher 350 is positioned along another of the first, second or third paths depending on the specific application contemplated. Printheads like printhead 303 are known and have been described in, for example, U.S. Pat. No. 6,457,807 B1, issued to Hawkins et al., on Oct. 1, 2002; U.S. Pat. No. 6,491,362 B1, issued to Jeanmaire, on Dec. 10, 2002; U.S. Pat. No. 6,505,921 B2, issued to Chwalek et al., on Jan. 14, 2003; U.S. Pat. No. 6,554,410 B2, issued to Jeanmaire et al., on Apr. 29, 2003; U.S. Pat. No. 6,575,566 B1, issued to Jeanmaire et al., on Jun. 10, 2003; and U.S. Pat. No. 6,588,888 B2, issued to Jeanmaire et al., on Jul. 8, 2003.
At least some of the ejected drops contact a receiver 340, such as paper or other media, while other drops are collected by a mechanism such as a catcher 350. Ink received by the catcher 350 is circulated through an ink recirculation mechanism 360 for reusing. Typically, the width 304 of the gas flow device 301 is wider than the length 305 of the nozzle array of the printhead 303 which helps to reduce or eliminate the boundary effects described above. However, passage width 304 that is equal to, or less than the length 305 of the nozzle array of the printhead 303 is permitted.
Referring to
Any one of or all of walls 411 of gas flow device 410 can have a travel path, and can be moveable in the example embodiment shown in
Referring to
The moving wall 511 in the inlet potion 521 of the gas flow passage moves in the direction the same as that of the gas flow. A liquid flow source 530 is operatively associated with the inlet portion 521 of gas flow passage. Liquid such as pumped water or ink from an ejector, for example, can be introduced from the inlet portion 521of the gas passage. The liquid 513 ejected from the liquid source 530 moves on and along the moving wall 511 of the passage with the same direction as that of the gas flow. It is preferred that the combined velocity of liquid 513 and the moving wall 511 be substantially equal to the velocity of the gas flow 514. However, the combined velocity of liquid 513 and the moving wall 511 can be different than the velocity of the gas flow depending on the specific application being contemplated. A liquid recirculation mechanism 531 is devised to circulate the liquid back to the liquid flow source 530 for reuse. Typically, the width of passage is wider than the length of the nozzle array of printhead which helps to reduce or eliminate the boundary effects. However, passage widths that are equal to of less than the length of the nozzle array of printhead are permitted. The liquid 513 can be, but not limited to, water or ink, or specifically engineered liquid with specific properties, such as a relative low surface tension coefficient, low viscosity, high thermal conductivity and/or high specific heat capacity. The surface of the moving wall 511 can be coated with hydrophobic or hydrophilic materials, depending on the type of liquid 513 being used, to facilitate liquid 513 to move along the moving wall 511.
Referring back to the figures, the present invention can be used to accomplish other printing system functions. For example, the liquid flow can be used to clean one or more portions of the printing system. The liquid flow can be used to clean the wall of the passage. Optionally, the liquid can be recirculated and filtered after it has traveled along the passage wall. Additionally, the catcher mechanism of the printing system can be cleaned using the liquid or a second liquid provided from a second liquid source, for example, one or more of the printhead nozzles, that is caused to flow along a wall of the catcher mechanism in a direction substantially toward an inlet of the catcher mechanism.
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.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4068241 | Yamada | Jan 1978 | A |
| 6457807 | Hawkins et al. | Oct 2002 | B1 |
| 6491362 | Jeanmairc | Dec 2002 | B1 |
| 6505921 | Chwalek et al. | Jan 2003 | B2 |
| 6554410 | Jeanmaire et al. | Apr 2003 | B2 |
| 6575566 | Jeanmaire et al. | Jun 2003 | B1 |
| 6588888 | Jeanmaire et al. | Jul 2003 | B2 |
| 6588889 | Jeanmaire | Jul 2003 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20080278549 A1 | Nov 2008 | US |
