Patent Application
20140022310
This invention relates generally to the field of digitally controlled liquid dispensing devices and, in particular, to liquid dispensing devices that include a flexible membrane.
Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because of its non-impact, low-noise characteristics, its use of plain paper, and its avoidance of toner transfer and fixing. Ink jet printing mechanisms can be categorized by technology as either drop on demand ink jet (DOD) or continuous ink jet (CIJ).
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.
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 devices—heat actuators and piezoelectric actuators. When a piezoelectric actuator is used, 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. When a heat actuator is used, a heater, placed at a convenient location adjacent to the nozzle, heats the ink. Typically, this causes a quantity of ink to phase change into a gaseous steam bubble that displaces the ink in the ink chamber sufficiently for an ink droplet to be expelled through a nozzle of the ink chamber.
In some applications it may be desirable to use an ink that is not aqueous and, as such, does not easily form a vapor bubble under the action of the heater. Heating some inks may cause deterioration of the ink properties, which can cause reliability and quality issues. As described in U.S. Pat. No. 4,480,259 and U.S. Pat. No. 6,705,716, one solution is to have two fluids in the print head with one fluid dedicated to respond to an actuator, for example, to create a vapor bubble upon heating, while the other fluid is the ink. The performance capabilities of these types of print heads is often limited due to the resistance of the membrane or diaphragm that separates the actuator fluid from the ink which reduces the amount of volumetric displacement that occurs in ink chamber as a result of the pressure caused by the vaporization of the actuator fluid.
Although U.S. Pat. No. 4,480,259 and U.S. Pat. No. 6,705,716 both describe flexible diaphragms, it is well understood by one skilled in the art that it is difficult to manufacture a micro-fluidics device such as an ink jet print head using conventional MEMS technology while incorporating a sufficiently elastic material for use as a diaphragm. Additionally, repeated cycles of stretch and relax cause material fatigue in the diaphragm resulting in reduced device reliability and poor device performance.
As such, there is an ongoing effort to increase the reliability and performance of print heads that include two fluids and a flexible membrane.
According to one aspect of the present invention, a liquid dispenser includes a first liquid chamber and a second liquid chamber. The first liquid chamber includes a nozzle. A heater is associated with the second liquid chamber. A flexible corrugated membrane is positioned to separate and fluidically seal the first liquid chamber and the second liquid chamber from each other.
According to another aspect of the present invention, a method of printing includes providing a liquid dispenser made in accordance with the invention described herein and using it to dispense liquid drops.
According to another aspect of the present invention, a liquid dispenser includes an ink chamber that contains a liquid that is located next to and shares a common side wall with a working fluid chamber. The ink chamber includes a nozzle outlet through which ink is ejected when an actuator located in the working fluid chamber is actuated. The nozzle outlet is opposite the shared side wall. The shared side wall between the working fluid chamber and the ink chamber includes a corrugated flexible diaphragm that is displaced by operation of the actuator. For example, the corrugated flexible diaphragm can be displaced by a vapor bubble created in the working fluid chamber by actuating a heater actuator. The displacement of the flexible membrane then displaces the ink in the ink chamber resulting in an ejection of ink though the ink nozzle.
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 print head, which is particularly useful in digitally controlled inkjet printing devices in which drops of ink are ejected from a print head toward a print medium. However, many other applications are emerging which use liquid dispensers, similar to inkjet print heads, 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” are used interchangeably and refer to any material, not just inkjet inks, which can be ejected by the example embodiments of the liquid dispenser described below.
In addition to inkjet printing applications in which the fluid typically includes a colorant for printing an image, the liquid dispenser of the present invention is also advantageously used in ejecting other types of fluidic materials. Such materials include functional materials for fabricating devices (including conductors, resistors, insulators, magnetic materials, and the like), structural materials for forming three-dimensional structures, biological materials, and various chemicals. The liquid dispenser of the present invention provides sufficient force to eject fluids having a higher viscosity than typical inkjet inks, and does not impart excessive heat into the fluids that could damage the fluids or change their properties undesirably.
Referring to
Liquid dispenser 100 includes a selectively actuatable thermal actuator that uses heat energy to divert a portion of a liquid (often referred to as a first liquid) located in first liquid chamber 111 through nozzle 120. The thermal actuator includes a heater in one example embodiment of the invention that is commonly referred to as a “bubble jet” heater. When selectively actuated, the heat generated by this type of thermal actuator vaporizes a portion of a liquid (often referred to as a second liquid) in the vicinity of the actuator creating a vapor bubble 160 (shown in
Referring back to
First chamber 111 is adapted to receive a liquid that is supplied to first chamber 111 in a conventional manner. Second chamber 112 is adapted to receive a liquid that is supplied to second chamber 112 in a conventional manner or in a manner according to one aspect of the present invention (described in more detail below). As flexible membrane 140 fluidically seals first chamber 111 and second chamber 112 from each other, first chamber 111 and second chamber 112 are physically distinct from each other which allows the first liquid and the second liquid present in each respective chamber to be different types of liquid when compared to each other in example embodiments of the invention.
Referring to
Referring to
Referring to
As described above and shown in
A liquid supply channel 251 is in fluid communication with second chamber 212 and a liquid return channel 252 is in fluid communication with second chamber 212. Liquid supply channel 251 and liquid return channel 252 are also in fluid communication with a liquid supply 255. During a drop ejection or dispensing operation, liquid supply 255 provides a liquid (commonly referred to as a working fluid or a working liquid) that flows continuously from liquid supply 255 through liquid supply channel 251 through second liquid chamber 212 through liquid return channel 252 and back to liquid supply 255. The circulating working fluid helps to increase the drop ejection frequency by removing at least some of the heat generated by heater 230 when it is actuated during drop ejection. The circulating working fluid can help increase the drop ejection frequency by pushing at least some of vapor bubble 160 off of and away from the heater 230 area as vapor bubble 160 collapses or increasing the speed of liquid replenishment relative to heater 230. As shown in
Typically, liquid is supplied to first chamber 211 in a manner similar to liquid chamber refill in a conventional drop on demand device. For example, during a drop dispensing operation using liquid dispenser 200, the liquid is not continuously flowing to first chamber 211 during a drop ejection or dispensing operation. Instead, first chamber 211 is refilled with liquid on an as needed basis that is made necessary by the ejection of a drop of the liquid from first chamber 211 through nozzle 220.
Typically, a regulated pressure source 257 is positioned in fluid communication between liquid supply 255 and liquid supply channel 251. Regulated pressure source 257, for example, a pump, provides a positive pressure that is usually above atmospheric pressure. Optionally, a regulated vacuum supply 259, for example, a pump, can be included in order to better control liquid flow through second chamber 212. Typically, regulated vacuum supply 259 is positioned in fluid communication between liquid return channel 252 and liquid supply 255 and provides a vacuum (negative) pressure that is below atmospheric pressure. Liquid supply 255, regulated pressure source 257, and optional regulated vacuum supply 259 can be referred to as the liquid delivery system of liquid dispenser 200.
In one example embodiment, liquid supply 255 applies a positive pressure provided by a positive pressure source 257 at the entrance of liquid supply channel 251 and a negative pressure (or vacuum) provided by a negative pressure source 259 at the exit of liquid return channel 252. This helps to maintain the pressure inside second liquid chamber 212 at substantially the same pressure (for example, ambient pressure conditions) at the exit of nozzle 220 when the heater 230 is not energized. As a result, flexible membrane 241 is not deflected during a time period of drop dispensing when the heater 230 is not energized.
A high degree of flexibility in flexible membrane 241 is preferred to effectively transmit the pressure generated by vapor bubble 160 in the working fluid (a second liquid) to the fluid or liquid of interest (a first liquid), for example, ink, located in first chamber 211. In one example embodiment of the invention, this aspect of the invention is achieved by incorporating a corrugated shape in a high modulus material membrane. The corrugated membrane can be made out of high modulus materials such as alloys, metals, or dielectric materials, to meet fabrication requirements of mechanic strength, durability, or thinness of the flexible membrane. These types of relatively strong materials may not have a high degree of elasticity, but the effect of the corrugation helps to greatly increase the membrane flexibility without requiring the use of an elastic material when compared to non-corrugated membranes.
As flexible membrane 241 fluidically seals first chamber 211 and second chamber 212 from each other, first chamber 211 and second chamber 212 are physically distinct from each other which allows the first liquid and the second liquid present in each respective chamber to be different types of liquid when compared to each other in example embodiments of the invention. For example, the second liquid can include properties that increase its ability to remove heat while the second liquid can be an ink. The second liquid can include properties that lower its boiling point when compared to the first liquid. The second liquid can include properties that make it a non-corrosive liquid, for example, nonionic liquid, in order to improve and maintain the functionality of heater 230 or increase its lifetime.
Referring to
A liquid supply channel 251 is in fluid communication with second chamber 212 and a liquid return channel 252 is in fluid communication with second chamber 212. Liquid supply channel 251 and liquid return channel 252 are also in fluid communication with a liquid supply 255. During a drop ejection or dispensing operation, liquid supply 255 provides a liquid (commonly referred to as a working fluid or a working liquid) that flows continuously from liquid supply 255 through liquid supply channel 251 through second liquid chamber 212 through liquid return channel 252 and back to liquid supply 255. The circulating working fluid helps to increase the drop ejection frequency by removing at least some of the heat generated by heater 230 when it is actuated during drop ejection. The circulating working fluid can help increase the drop ejection frequency by pushing at least some of vapor bubble 160 off of and away from the heater 230 area as vapor bubble 160 collapses or increasing the speed of liquid replenishment relative to heater 230. As shown in
Typically, a regulated pressure source 257 is positioned in fluid communication between liquid supply 255 and liquid supply channel 251. Regulated pressure source 257, for example, a pump, provides a positive pressure that is usually above atmospheric pressure. Optionally, a regulated vacuum supply 259, for example, a pump, can be included in order to better control liquid flow through second chamber 212. Typically, regulated vacuum supply 259 is positioned in fluid communication between liquid return channel 252 and liquid supply 255 and provides a vacuum (negative) pressure that is below atmospheric pressure. Liquid supply 255, regulated pressure source 257, and optional regulated vacuum supply 259 can be referred to as the liquid delivery system of liquid dispenser 200.
In one example embodiment, liquid supply 255 applies a positive pressure provided by a positive pressure source 257 at the entrance of liquid supply channel 251 and a negative pressure (or vacuum) provided by a negative pressure source 259 at the exit of liquid return channel 252. This helps to maintain the pressure inside second liquid chamber 212 at substantially the same pressure (for example, ambient pressure conditions) at the exit of nozzle 220 when the heater 230 is not energized. As a result, flexible membrane 240 is not deflected during a time period of drop dispensing when the heater 230 is not energized.
A high degree of flexibility in flexible membrane 240 is preferred to effectively transmit the pressure generated by vapor bubble 160 in the working fluid (a second liquid) to the fluid or liquid of interest (a first liquid), for example, ink, located in first chamber 211. Since flexible membrane 240 is not corrugated, an elastic material can be included with or substituted for a high modulus material during flexible membrane fabrication.
As flexible membrane 240 fluidically seals first chamber 211 and second chamber 212 from each other, first chamber 211 and second chamber 212 are physically distinct from each other which allows the first liquid and the second liquid present in each respective chamber to be different types of liquid when compared to each other in example embodiments of the invention. For example, the second liquid can include properties that increase its ability to remove heat while the second liquid can be an ink. The second liquid can include properties that lower its boiling point when compared to the first liquid. The second liquid can include properties that make it a non-corrosive liquid, for example, nonionic liquid, in order to improve and maintain the functionality of heater 230 or increase its lifetime.
Referring to
A corrugated flexible membrane including corrugations including a variable height, a variable pitch, or a combination of both is advantaged in some applications when compared to other types of membranes. One advantage includes the ability to provide a flexible membrane having a reduced overall stiffness which helps increase displacement capabilities of the flexible membrane. Another advantage includes the ability to provide a flexible membrane having a reduced variation of stress which helps increase the life of the flexible membrane. Another advantage includes the ability to direct the pressure wave in the fluid on the other side of the flexible membrane which helps increase or enhance the efficiency of the actuator. For example, this type of flexible membrane can focus the pressure wave toward or at a nozzle located on the other side of the flexible membrane in a manner that is similar to the function of a Fresnel lens. Referring to
In the perpendicular view of flexible membrane 241 shown in
Liquid dispenser 100, 200 is typically formed from a semiconductor material (for example, silicon) using semiconductor fabrication techniques (for example, CMOS circuit fabrication techniques, micro-electro mechanical structure (MEMS) fabrication techniques, or a combination of both). Alternatively, liquid dispenser 100, 200 can be formed using conventional materials and fabrication techniques known in the art.
A liquid dispenser array structure made according to the present invention includes a plurality of liquid dispensers 100, 200 described above 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.
Reference is made to commonly-assigned, U.S. patent application Ser. No. ______(Docket K000904), entitled “CORRUGATED MEMBRANE MEMS ACTUATOR FABRICATION METHOD”, Ser. No. ______(Docket K000950), entitled “MEMBRANE MEMS ACTUATOR WITH MOVING WORKING FLUID”, all filed concurrently herewith.
