Patent Grant
7173641
1. Field of the Invention
The present invention relates to printers and more particularly to improved printers that use micro electro-mechanical switches to decrease cost and improve performance.
2. Description of the Background Art
Two common types of printers in wide use are the laser printer and the ink jet printer that are designed for both home and office. The laser printer is a well-known and commercially successful type of indelible printer. It utilizes static electricity to build up an electrical charge on a photoreceptor made out of highly photoconductive material. This material looses a charge when activated by light photons from the laser. Since the laser draws the image of the page onto the photoreceptor, a scanning assembly is needed to scan the laser across the photoreceptor and this assembly must be incredibly precise.
The typical laser scanning assembly includes a laser, a movable mirror and lens, all of which are expensive. The laser is modulated to print tiny dots that make up the image to be printed one horizontal line at a time. As the laser beam moves across the photoreceptor, the laser emits a pulse of light for every dot to be printed, and no pulse where a dot is not to be printed. Because the laser doesn't actually move the beam itself, the laser beam is bounced off of the moveable mirror. As the mirror moves, it shines the laser beam through a series of lenses that compensate for image distortion caused by the varying distance between the mirror and dots along the photoreceptor. In a laser printer, the mirror spins incredibly quickly and is synchronized with the laser switching on and off. A typical laser printer will switch millions of times every second.
The charged photoreceptor attracts electrically charged toner in the shape of the image that is then transferred onto a sheet of paper. The sheet of paper is then heated to fuse the toner to the paper. The laser printer is typically preferred for business applications because the printed image is indelible which means that it will not smear, smudge and is generally of archival quality.
A major disadvantage of the laser printer is the cost of the components and specifically the cost of the laser, the laser scanning system and the photoreceptor. Not only are these components expensive, they are also subject to wearing out and the photosensitive drum requires regular replacement. Further, the process of getting the image from the computer to the paper requires sophisticated control software and electronics, optics, mechanics and chemistry. Because of high cost components and system complexity, laser printers are relatively expensive so what is needed is a simple, indelible printer that does not require expensive components such as the laser, scanning optic or a photoreceptor.
Another type of commonly used printer is the ink jet printer. Ink jet printers are relatively inexpensive compared to laser printers because they use charged particles or ink rather than toner. Ink jet printers work on the principle that a printing head by means of several physical principles, e.g., heat, ultrasonic pulse, etc., is made to eject a small ink droplet onto an absorbent paper. The droplets form the desired graphical image. Ink jet printers produce different colors by mixing at least cyan, magenta, and yellow inks and can accurately create an extremely large range of colors. Ink jet printers are often used to print digital photographs. The major disadvantage of the ink jet printer is that the printed image tends to fade rather quickly, often in as little as three to six months. The image is not moisture-fast, and images with significant quantities of deposited ink are often wrinkled by the moisture. It is clearly desirable to provide a low cost indelible color printer.
With respect to ink jet printers, conservation of ink is clearly desirable. For this reason many ink jet printers utilize drop on demand technology where a ink drop is generated only when needed. Many other ink jet printers generate a continuous stream of ink that relies on the deflection of drops that are to be applied to the paper. The non-deflected drops are collected and recycled. However, recycling ink drops can introduce air to the ink reservoir and is generally undesirable. The drop on demand technology utilizes piezo-electrical crystals that change their dimensions when an electrical current is applied to generate a drop. Such crystals are expensive so a lower cost alternative to generate a drop of ink is necessary.
Another disadvantage of current printers is that lack of a low cost printer that can print on paper that is wider than about twelve inches. It would be advantageous if a printer could print on paper having a width that exceeds twelve inches.
Embodiments of the present invention provide a matrix of micro electro-mechanical switches that can be used in various printer applications. More specifically, the switches can be used in an indelible printer to attract charged toner material in a useful pattern and release said toner as required. This technology and process can provide a significant improvement in printer systems.
In one embodiment, the micro electro-mechanical switches replace the laser, laser scanning system, and the photoreceptor in an indelible printer with low cost plastic switches. Since the cost of construction of the matrix of micro electro-mechanical switches is a small fraction of the cost of construction of a laser scanner system, it will be appreciated that this results in a significant cost reduction. Further, the matrix of micro electro-mechanical switches provide a significant improvement in lifetime over that of the photosensistve printing drum and the reduction in operating costs is substantial.
In another embodiment, one or more switches replace the piezo-electric crystal in a drop on demand ink jet printer. When the switch is in the ON state, ink is drawn into the chamber. When a drop is to be expelled from the chamber, the switch is changed to the OFF state. The change in volume generates a shock wave that expels the ink droplet.
The interior volume of each switch may be packed with an incompressible material to increase the force that causes the switch contacts to break. Because of the well-known phenomenon of the stiction of switch contacts in use, it is necessary to insure that the retraction force is greater than the make contact force.
The foregoing and additional features and advantages of this invention will become apparent from the detailed description and review of the associated drawing figures that follow.
In the description herein for embodiments of the present invention, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention.
Referring now to the drawings more particularly by reference numbers, a simplified block diagram of a printer 100 in accordance with one embodiment of the present invention is shown in
Receptor assembly 106 contains a plurality micro electro-mechanical switches each of which define a charged electrostatic region. As receptor assembly 106 rotates past hopper 102, charged toner is attracted to the oppositely charged regions of receptor assembly 106. The toner material is then deposited onto the paper, which has a stronger electrostatic charge than receptor assembly 106. Advantageously, printer 100 does not require a scanning laser unit with expensive optical components such as a scanning mirror or lenses or a photoreceptor assembly.
Printer controller 108 may include a RISC processor or other suitable computer and memory and is responsible for controlling operation of printer 100. In other embodiments, controller 108 consists merely of a printer memory with the image to be printed determined by a host computer. Controller 108 receives a page description from another source, such as from a computer file system, from a display screen or from a network connection, and generates the necessary image pattern on receptor assembly 106. The page description typically consists of vector information of the entire image to be printed on a page of paper. This allows controller 108 to use basic geometric principles to determine how to best create the image on paper. Where the image to be printed is communicated to it via a page description language, controller 108 converts the description into a bitmap. This result is an image (in memory) of every dot that will be placed on the paper.
Resolution of printer 100 is determined by electrostatic receptor assembly 106, which has a plurality of micro electro-mechanical switches with each switch controlling the charge assigned to a picture element or dot on the sheet of paper. Since a sheet of A4 size paper is 8.5 in across and 11 in deep, receptor assembly 106 can have more than eight million dots at 300 dots per inch (dpi) while at 600 dpi a page can have 33 million dots compared with the eight hundred thousand pixels on a 1024 by 768 display device such as a computer monitor. The micro electro-mechanical switches are preferably formed in a geometric array pattern and wrapped around a drum to form a rotating assembly. The array may be linear, interdigitated, or some other geometric pattern.
During operation of printer 100, receptor assembly 106 rotates in counter-clockwise direction as indicted by arrow 208. Preferably, receptor assembly 106 rotates in a direction that is opposite from the direction that the page of paper travels, the direction of which is indicated by arrow 210. Prior to picking up toner, it may be desired to ensure that receptor assembly 106 is clean and substantially free of toner material. A corona wire 212 has a large negative charge so that attracts the positively charged toner from regions of receptor assembly 106. The regions proximate to wire 212 do not have any electrostatic charge. Charge is removed from receptor assembly 106 by setting switches in area 202 to an OFF position.
Once a switch is clean of residual toner, it may be selectively switched to an ON state prior to pass by toner hoper 102. Switches in area 204 will have received toner if they were in the ON state when they passed by hopper 102 and will not receive toner if they were in the OFF state. Since the toner has a positive charge, it clings to the areas of the receptor assembly that have a negative charge (that is areas that have a corresponding switch in the ON state), but not to the positively charged “background” areas.
As receptor assembly 106 continues to rotate, switches, as indicated at 206, will come into proximity of the electrically charged piece of paper or other substrate. With the powder pattern affixed, the drum rolls over a sheet of paper, which is moving along a belt below. Before the paper rolls under the drum, it is given a negative charge by a charge wire or charged roller 216. This charge is stronger than the negative charge of the electrostatic image, so the paper can pull the toner away from receptor assembly 106. Since the paper is moving at the same speed as the receptor assembly, the paper picks up the image pattern exactly.
When the paper is positioned under receptor assembly 106, the charge is removed from the switch at the area indicated at 218 to ensure maximum toner transfer to the paper. This feature is not possible with a photoreceptor based printing system. As the sheet of paper is moved by the paper transport mechanism 104 (
Another embodiment of printer 100 is shown in
In one illustrative embodiment, plate 302 comprises at least 33 million switches so that a sheet of A4 size paper can be imaged with 600 dpi resolution. In another embodiment, a lower resolution printer is provided by using a plate 302 that has eight million switches to provide 300 dpi resolution. In yet another embodiment, the switches are controlled so that various colors of toner are deposited on adjacent switches to provide a printed color image. For example, one color of toner may be cyan, another color of toner may be yellow and the third color may be magenta.
In operation, a sheet of lightly charged paper is positioned over plate 302 and each of the plurality of micro electro-mechanical switches in the array is electronically driven to either an OFF state or an ON state. Then, as hopper 102 translates across the sheet of paper and the underlying switches, toner is attracted from hopper 102 toward the sheet of paper wherever the underlying switch is ON. If the switch is OFF, no toner will be applied to the paper. Once hopper 102 has passed over the paper, the paper is moved through fusing rollers 220 to fuse the toner to the paper. In this embodiment, hopper 102 may have the same width as plate 302, in which case it translates only in the “x” direction as indicted by arrow 304 when depositing toner. As the printed sheet of paper is moved past the fusing rollers, hopper 102 is repositioned to an initial position as a new unprinted sheet of paper is moved into position over plate 302.
In another embodiment hopper 102 has a fixed width but it may translate in both an “x” direction and a “y” direction to distribute toner over the paper. Such X-Y plotter mechanisms are well known. In yet another embodiment, multiple hoppers (not shown) are provided with each hopper having a different color of toner. In this embodiment, a sheet of paper is positioned and then only switches that are associated with one of the hoppers are selected and set to either an ON or OFF position as that hopper translates across the paper. All non-selected switches remain in the OFF position so that no toner will be deposited. In yet another embodiment, multiple hoppers are provided, one each for cyan, magenta, yellow and black toners by way of example, and all switches are selected and set to either an ON or OFF position as each hopper sequentially translates across the sheet of paper.
Refer now to
After the ink drop is ejected, switch 408 flexes in the opposite direction, as illustrated in
Use of micro electro-mechanical switches in a printer application is one of the novel features of the present invention contribute to reducing the cost of the various embodiments of the present invention. Micro electro-mechanical switches that can be printed on flexible substrate are described in U.S. patent application Ser. No. 10/959,604, filed on Oct. 5, 2004, the disclosure of which is incorporated herein by reference.
The 60/532,234 application describes a multi-membrane plastic structure on which is patterned row and column drivers to form the matrix of electromechanical micro switches that can be manufactured using low cost printing techniques. The matrix of switches may be flexed or twisted into novel shapes such as the shape of a drum. Each switch 500 in the matrix of switches comprise a plastic membrane 502 on which is printed a plurality of column electrodes 504.
The mechanism of the switch activation involves the electrostatic deflection of flexible membrane 508 such as is illustrated in
For each embodiment of this invention, it is desired to have the switch quickly change from an ON (or closed) state to an OFF (or open) state. Since switch 500 comprises a substantially sealed cell, the force that causes the switch to open is a combination of both an elastic force caused by the deformation of membrane 508 and a pneumatic force caused by the volumetric compression of the atmosphere with the cell. The selection of appropriate materials for the flexible membrane allows one, linear, degree of freedom in determining how quickly the switch will open. Treating the cell as a pneumatic device, another completely different degree of freedom is added to the switch design. Pneumatic devices exhibit different behavior in response to deflection of the flexible membrane, and this behavior can be very non-linear in nature. Boyle's Law defines the relationship of pressure, P, and volume, V, for these devices as:
PV=nRT
With “n” being the number of moles of gas, R the Universal Gas Constant, and T the temperature in degrees Kelvin.
The cell can be defined by its volume at rest and the amount of volume change allowed by the flexibility of the membrane and the interior cell configuration. For simplicity, the behavior of the flexible membrane can be characterized at three points in the deflection of the membrane film, specifically switch open, initial switch contact and latched switch contact.
As most clearly seen in
In the absence of any intentional perforations in the membranes, an increase in gas pressure occurs as the volume of switch 500 changes from V0 to VA to VL. However, by altering volume V0 by “packing” the gas volume defined by VL. Packing involves replacing the gas volume VL with a material that is substantially incompressible such as is illustrated in
The effect of packing on the pressure within the cell as the flexible film is deflected is illustrated in
As seen by comparing the non-linear response of the pressure with volume change for an unpacked cell 1002 to a packed cell 1004 shows that it is possible to tailor the pressure build up. Thus, when going from V0 to VA and from VA to VL it is possible to customize the cell such that low electrostatic power is needed to create the initial switch contact and a high pressure is generated when the latch contact is made. This boost in pressure from VA to VL means that the elasticity of the film is not the only restoring force when it comes time for the contact to break.
Accordingly, the micro electro-mechanical switch may be used to generate an electrostatic region on a drum, plate or used as the actuator that generates a drop on demand in an ink jet printer. Rapid switching is achieved by packing the cell of each switch to ensure rapid return from a closed position to an open position. Switches 500 act as a charged receptor when in the ON or closed state to attract electrically charged toner in the shape of the image that is then transferred onto a sheet of paper. Advantageously, the switches may be printed on flexible substrates and formed in the shape of a drum, or similar geometric shape. Each switch corresponds to a dot and may be determined electrically. Further, the switch can be used in place of the piezo-electric crystal to generate the shock wave that expels a drop of ink on demand.
Although the invention has been described with respect to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of the invention. In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention.
Reference throughout this specification to “one embodiment,” “an embodiment,” or “a specific embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention and not necessarily in all embodiments. Thus, respective appearances of the phrases “in one embodiment,” “in an embodiment,” or “in a specific embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present invention may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the present invention.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. It is also within the spirit and scope of the present invention to implement a program or code that can be stored in a machine-readable medium to permit a computer to perform any of the methods described above.
Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Furthermore, the term “or” as used herein is generally intended to mean “and/or” unless otherwise indicated. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear.
As used in the description herein and throughout the claims that follow, “a,” “an,” and “the” includes plural references unless the context clearly dictates otherwise.
Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention.
Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims.
This application claims priority from provisional U.S. patent applications entitled “On the use of electro-mechanical switching elements to create a electrostatic printer technology” U.S. application No. 60/532,234, filed Dec. 22, 2003 and “On the use of pneumatic and elastic restoration of membrane switches used for display backplanes and other applications” U.S. application No. 60/532,026, filed Dec. 22, 2003, the entire disclosures of which are herein incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20020180857 | Silverbrook | Dec 2002 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20050134644 A1 | Jun 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60532234 | Dec 2003 | US |
