Acoustic fluid flow device for printing system

A printing system includes a liquid drop ejector, a fluid passage, and a fluid flow source. The liquid drop ejector is operable to form liquid drops having a plurality of volumes moving along a first path. The fluid passage includes a wall. A source of acoustic energy is associated with the wall. A fluid flow source is associated with the passage and is configured to provide a fluid flow through the passage. Interaction of the fluid flow and the liquid drops causes liquids drops having one of the plurality of volumes to begin moving along a second path.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly-assigned, U.S. patent application Ser. No. 11/770,774, filed currently herewith, entitled “ENERGY DAMPING FLOW DEVICE FOR PRINTING SYSTEM,” and U.S. patent application Ser. No. 11/770,804, filed currently herewith, entitled “PERFORATED FLUID FLOW DEVICE FOR PRINTING SYSTEM.”

FIELD OF THE INVENTION

This invention relates generally to the management of fluid flow and, in particular to the management of fluid flow in printing systems.

BACKGROUND OF THE INVENTION

Printing systems that deflect drops using 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 (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.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a printing system includes a liquid drop ejector, a fluid passage, and a fluid flow source. The liquid drop ejector is operable to form liquid drops having a plurality of volumes moving along a first path. The fluid passage includes a wall. A source of acoustic energy is associated with the wall. A fluid flow source is associated with the passage and is configured to provide a fluid flow through the passage. Interaction of the fluid 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 printing includes forming liquid drops having a plurality of volumes moving along a first path using a liquid drop ejector; causing a fluid to flow through the fluid passage using a fluid flow source associated with the passage; and providing acoustic energy to the fluid flow using a source of acoustic energy associated with a wall of the fluid passage, wherein interaction of the fluid flow and the liquid drops causes liquids drops having one of the plurality of volumes to begin moving along a second path.

DETAILED DESCRIPTION OF THE INVENTION

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.

Referring toFIG. 1, a schematic view of a printing system10incorporating an example embodiment of an acoustic energy source20is shown. Printing system10includes a liquid drop ejector or printhead30positioned to eject drops32through passage35. At least some the drops32contact a receiver36while other drops are collected by a catcher38.

A fluid flow16is provided through fluid passage40with wall42. Acoustic energy sources20are attached on wall42. With power supply50, an acoustic sound generator55produces a broad spectrum of frequencies of sound that are feed into band filter60to filter out unwanted frequencies. The signal is then passed through amplifier65, a sound level gauge70, and sent to plurality of acoustic energy sources20.

Printhead30includes a drop forming mechanism31operable to form drops32having a plurality of volumes traveling along a first path. The fluid flow16is applied in a direction such that drops having one of the plurality of volumes diverge (or deflect) from the first path (not shown inFIG. 1) and begin traveling along a second path33while 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 path34. Receiver36is positioned along one of the first, second, and third paths while catcher38is positioned along another of the first, second and third paths depending on the specific application contemplated. Printheads like printhead30are 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.

After being ejected by the drop forming mechanism of printhead30, drops32travel along the first path which is substantially perpendicular to printhead30. Acoustic energy source20is attached to wall42of the first passage40of fluid flow. A fluid flow source16is operatively associated with one or both of the inlet portion80and the outlet portion85. For example, pressurized gas (e.g. air) from a pump can be introduced in the inlet portion80and/or a vacuum (negative air pressure relative to ambient operating conditions) from a vacuum pump can be introduced in the outlet portion85. When fluid flow sources like these are introduced on the inlet portion80and the outlet portion85a sink for the fluid or gas flow is provided. The fluid or gas flow (represented by arrows16) of the drop deflector interacts with ejected drops32and causes drops32to diverge or deflect as described above. The amount of deflection is volume dependent with smaller volume drops being deflected by the fluid or gas flow more than larger volume drops. The acoustic energy source20attached to wall42incorporates mechanisms to supply acoustic wave into the boundary layer that provides damping effect to the turbulence. In other words, the acoustic energy interferes with the boundary layer and leads to laminar-turbulent transition delay. The specific range of desired frequencies is dependent upon a number of variable factors including the rate of fluid flow, passage size, etc. In general, however, it is sufficient that the frequencies produced by acoustic energy source20be at least twice as high as the as Tollmien-Schlichting waves, the airflow disturbances within a range of predictable oscillatory frequencies.

An example embodiment of wall42of first passage40and acoustic energy source20shown inFIG. 2. In this embodiment, wall42contains opening90where acoustic energy source20is mounted. Such an arrangement facilitates the propagation of the acoustic energy into first passage40. A typical shape of opening90is circular, elliptical. Other shapes include square and rectangle. Plurality of openings90may exist for one acoustic energy source20.

Another example embodiment of wall42of first passage40and acoustic energy source20is shown inFIG. 3. In this embodiment, wall42contains porous section95where acoustic energy source20is mounted. Such an arrangement facilitates the propagation of the acoustic energy into first passage40. A typical shape of porous section95is circular, elliptical. Other shapes include square and rectangle. Plurality of porous sections95may exist for one acoustic energy source20.

Yet another example embodiment of wall42of first passage40and acoustic energy source20is shown inFIG. 4, where acoustic energy source20is not in direct contact with wall42. Instead, secondary wall45exists on which plurality acoustic energy sources20are mounted. Wall40consists plurality of openings90. Space46between wall42and secondary wall45can be at ambient air pressure. It can also be kept to have an air pressure lower or higher than that of passage40. When the pressure in space46is higher than that in passage40, air will enter into passage40from space46. When the pressure in space46is lower than that in passage40, air will leak into space46from passage40.

Yet another example embodiment of wall42of first passage40and acoustic energy source20is shown inFIG. 5, where acoustic energy source20is not in direct contact with wall42. Instead, secondary wall45exists on which plurality acoustic energy sources20are mounted. Wall40consists plurality of porous sections95. Space46between wall42and secondary wall45can be at ambient air pressure. It can also be kept to have an air pressure lower or higher than that of passage40. When the pressure in space46is higher than that in passage40, air will enter into passage40from space46. When the pressure in space46is lower than that in passage40, air will leak into space46from passage40.

The example embodiment shown inFIG. 5can also be extended to include a wall with travel path. The concept of printing system with a wall or web traveling along a path has been described in, for example, commonly assigned U.S. patent application Ser. Nos. 11/746,117; 11/746,104; 11/746,094, the disclosures of which are incorporated by reference herein. According to one aspect of that 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 fluid including a wall. A fluid flow source is operable to cause the fluid to flow in a direction through the passage. The wall of the passage has a travel path with the travel path of the wall being in the same direction as that of the fluid flow. Interaction of the fluid flow and the liquid drops causes liquids drops having one of the plurality of volumes to begin moving along a second path. InFIG. 5, wall42is considered to be a wall with a travel path. It moves along the same direction as the fluid flow16. In this case, porous section95can be replaced by openings or solid wall.

According to embodiments of the present invention, the porous section95may be formed from various types of material including, but not limited to, woven fabrics, nonwoven fabrics, combinations of woven and nonwoven fabrics, and polymer foams. The porous section95may include a metallic mesh. Moreover, the porous section95may include a combination of metallic mesh and fabric (e.g., woven fabric, nonwoven fabric, combinations of woven and nonwoven fabric, etc.). The fabric can be chosen to optimize desired properties, such as airflow rate and acoustic wave transmission, etc. Porous section95may consist polymer foam made from alkenyl aromatic resins, such as polystyrenic resin(s), and polyesters such as polyethylene terephthalates. The term “alkenyl aromatic polymer” includes polymers of aromatic hydrocarbon molecules that contain an aryl group joined to an olefinic group with only double bonds in the linear structure. The polymeric foam may also be made from polyolefinic resins such as LDPEs, HDPEs, LLDPEs, and the like. The polymeric foam is preferably made from a polystyrenic resin(s), such as a general purpose polystyrene, because of economical considerations at the present time. The polymeric foam, however, may be made from other polystyrenic resins such as impact polystyrenes. The impact polystyrenes that are generally used include medium impact polystyrenes and high impact polystyrenes. The polymeric foam may also be made from a combination of virgin and/or reprocessed material.

The invention has been described in detail with particular reference to certain example embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention.

PARTS LIST