Patent Application
20190152832
Provided herein are methods of tempering glass using microwave energy and related systems for use in tempering glass.
Glass products can be strengthened by any of a number of processes, such as annealing, heat strengthening, and tempering. Typical methods of strengthening glass products involve heating and cooling the glass. Tempering can be achieved by rapidly cooling glass from a high temperature, e.g., greater than 600° C. and typically around 620° C., for example in the range of 627° C. to 704° C. or 1160° F. to 1300° F., to a lower temperature. This is typically achieved by blasting the surface of the glass with high pressure air in a process called “quenching.” The rapid cooling results in a sharp temperature gradient in the glass between the outer surface of the glass and the inside of the glass, with the center of the glass creating tension by pulling away from the cooler exterior surfaces, and the outer surface going into compression. In an alternate method, tempering can be achieved by “chemical tempering,” where ions within the glass surface are exchanged by other, typically larger ions by ion exchange methods, thereby causing the compression in the glass surface. Chemical tempering is less commonly used than quenching, but is more pertinent to thin glass sheets, such as those used in displays.
Flat and bent glass products, such as architectural transparencies or land, air, and water vehicular transparencies, are typically tempered by quenching. During the conventional heat tempering process, glass is heated in a conventional oven (furnace), equipped with conventional infrared (IR) heaters (e.g., coils) and/or convection systems using heated gas. Often, in order to achieve uniform heating of a large sheet in a conventional oven, a reciprocating/oscillating “shake-and-bake” technique is utilized. Despite the ability to control motion of the glass product, oven temperature, and convection, typical three-dimensional (3D) IR heating ovens cannot accurately and rapidly heat all surfaces of a glass product.
Further, IR-based or heated gas-based heating processes heat a glass sheet from the outside-inward, generating a parabolic heat profile in a cross-section of the glass. In order to adequately heat the inside of a glass product by conventional methods, the outside of the glass is often heated at a greater temperature than desired and/or for longer times, increasing the chance for deformities, especially at contact points on the surface of the glass product, for instance at contact points of a bending iron, rollers, or other carrier used to transport glass when it is heated for the purpose of tempering. For example, fully tempered glass that has been made in a horizontal furnace may contain surface distortions. Specifically, while the glass surface is heated to (or near) the softening point, the glass is moved by hard conveyer rollers that create marks on the surface of the glass. In addition, the high temperatures cause the glass to become less flat, i.e., the glass becomes bowed.
In addition, a traditional IR heating furnace cannot accurately control the glass temperature due to the limited heating coils' density and radiation heat distribution in the furnace. The non-uniform glass sheet temperature in combination with the internal temperature gradient of the glass are two reasons for glass tempering distortion exhibited in traditional thermal tempering processes.
Further, many substrates have IR-reflective layers, which further compound the difficulties inherent in heating a glass product by conduction in a conventional oven. Due to the outside-in heating effect of conventional ovens, heating the glass product takes time, which increases with thickness and/or reflectivity of the glass product. Multi-layered substrates and thicker substrates are particularly susceptible to these difficulties.
A method of strengthening a glass sheet is provided. The method comprises: heating the glass sheet to a tempering temperature using a microwave beam produced by a microwave generator; and quenching the glass sheet heated to the tempering temperature using the microwave beam to produce a tempered glass sheet.
A method of strengthening a glass sheet is provided. The method comprises contacting the glass sheet with ions with a larger ionic radius than ions in the glass sheet; and heating the glass sheet using a microwave beam produced by an ultra high frequency microwave generator.
A system for production of a tempered glass product is provided. The system comprises: a glass tempering quenching chamber comprising a forced-air manifold and at least one opening; a conveyor system for conveying a glass sheet extending into the quenching chamber; and a microwave generator that produces a microwave beam that intersects a position of a glass sheet carried on the conveyor system adjacent to the quenching chamber such that a glass sheet carried by the conveyor is transferred directly from the position on the conveyor system that intersects the microwave beam into the quenching chamber.
As used herein, all numbers expressing dimensions, physical characteristics, processing parameters, quantities of ingredients, reaction conditions, and the like, used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical values set forth in the following specification and claims can vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical value should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass the beginning and ending range values and any and all subranges subsumed therein. For ranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less, e.g., 1 to 3.3, 4.7 to 7.5, 5.5 to 10, and the like. Further, as used herein, the term, “over” means on but not necessarily in contact with the surface. For example, a first substrate “over” a second substrate does not preclude the presence of one or more other substrates of the same or different composition located between the first and the second substrates. Plural encompasses singular and vice versa. For example, while the invention has been described in terms of “an” oven, “a” thermocouple, or “a” gyrotron, or “a” gyrotron beam, multiple ovens, thermocouples, gyrotrons, or gyrotron beams can be used. When ranges are given, any endpoints of those ranges and/or numbers within those ranges can be combined within the scope of the present invention. “Including” and like terms means “including but not limited to”. As used herein, spatial or directional terms, such as “left”, “right”, “inner”, “outer”, “above”, “below”, and the like, relate to the invention as it is shown in the Figures. However, it is to be understood that the invention can assume various alternative orientations and, accordingly, such terms are not to be considered as limiting.
The word ‘comprising’ and forms of the word ‘comprising’ as used in this description and in the claims does not limit the invention claimed to exclude any variants or additions.
The methods and systems described herein are useful for tempering glass sheets, including flat glass sheets, e.g. useful as architectural transparencies, or bent glass sheets, e.g. for use as an aircraft transparency. A “glass sheet” refers to a glass structure having a mid-plane and a pair of opposing extended surfaces. By reference to the “skin”, “outside”, or “major surface” of the glass sheet, it is meant to include an outermost surface of the glass as well as a portion directly adjacent thereto. By reference to the “edge” of the glass sheet, it is meant the leading or trailing ends of the sheet or the extended opposing side “minor surfaces” thereof.
The glass sheet can include a single glass layer, multiple glass layers, or coated glass having one or more layers for controlling electromagnetic energy transmission, absorbance, refraction, or reflection, as are broadly-known in the glazing arts. For example, the glass sheet can be opaque, transparent or translucent to visible light. By “opaque” it is meant having visible light transmission of 0%. By “transparent” it is meant having visible light transmission in the range of greater than 0% to 100%. By “translucent” is meant allowing electromagnetic energy (e.g., visible light) to pass through but diffusing this energy such that objects on the side opposite the viewer are not clearly visible. The glass sheet may be a transparent glass sheet. Non-limiting examples of glass materials from which the glass sheet is formed include conventional soda-lime-silica glass, borosilicate glass, and lithia-alumina-silica glass. The glass can be clear glass. By “clear glass” it is meant non-tinted or non-colored glass. Alternatively, the glass can be tinted or otherwise colored glass. The glass may be conventional float glass and can be of any composition having any optical properties, e.g., any value of visible transmission, ultraviolet transmission, infrared transmission, and/or total solar energy transmission. By “float glass” it is meant glass formed by a conventional float process. Examples of float glass processes are disclosed in U.S. Pat. Nos. 4,744,809 and 6,094,942, which patents are hereby incorporated by reference. The glass may be a clear lithia-alumina-silica glass of the type disclosed in U.S. Pat. No. 8,062,749, or the glass may be a clear soda-lime-silica glass of the type disclosed in U.S. Pat. Nos. 4,192,689; 5,565,388, and 7,585,801.
The glass sheet can be used in the manufacture of shaped monolithic or shaped laminated transparencies for an aircraft. However, as can be appreciated, the tempered glass sheets can be used in the manufacture of any type of transparency, such as but not limited to windshields, windows, rear lights, sunroofs and moon roofs; laminated or non-laminated residential and/or commercial windows; insulating glass units, and/or transparencies for land, air, space, above water and under water vehicles.
The microwave energy used in the present invention may be produced by a microwave generator operating at a frequency of at least 100 kHz or at least 1 MHz, or at least 1 GHz (gigahertz), or at least 20 GHz. The term “ultra high frequency microwave generator” is used herein to describe a system for production of microwave electromagnetic radiation of at least 20 GHz. A “gyrotron” is a non-limiting example of an ultra high frequency microwave generator. Other examples of ultra high frequency microwave generators include klystrons or traveling wave tubes as are broadly-known. The ultra high frequency microwave generator has an output wavelength and energy suitable for rapid and precise heating of glass, for example in the range of from 20 GHz to 300 GHz (e.g., corresponding to wavelengths ranging approximately from 1 5 mm to 1 mm), and having electrical power ranging from 1 kW (kilowatt) to 100 kW. Thus, an ultra-high frequency microwave generator having an output ranging from 20 GHz to 300 GHz and a power output of at least 1 kW, at least 5 kW, for example, from 1 kW to 100 kW may be used in the methods and systems described herein. In use, the beam may be pulsed. Pulsed beams may have temporary power outputs, when the beam is active, or greater than 100 kW, but the overall average power output, including active and inactive time periods, typically is 100 kW or lower.
A “beam” of electromagnetic radiation can be coherent, collimated, split, guided (that is, with an electromagnetic waveguide), and/or focused. For ultra high frequency microwave generators, a waveguide, for example a magnetic waveguide, as is known in the art, may be used to produce a beam. A microwave beam may have a diameter ranging from 10 mm to 150 mm. The beam may be continuous or pulsed, for example, having a pulse width of from 1 to 25 seconds, and a cycle time of from 1 minute to 10 minutes. Combinations of continuous and/or or pulsed microwave beams may be used.
A “beamsplitter” is an optical device, such as a cube beamsplitter (two cemented right angle prisms, plate beamsplitters, or a half-silvered mirror that splits a single beam of electromagnetic radiation into a plurality of, and typically two, beams. For example, a beam generated by the ultra high frequency microwave generator, for example a gyrotron, can be split by a beam splitter into two or more beams.
A “conveyor” is any suitable device, system, or mechanism for transferring an object from a first physical location to a second. For example, the conveyor transfers glass sheets, for example flat glass sheets or bent glass sheets, from one location to another. The conveyor may include any necessary elements, such as, without limitation: rollers, stub rolls, motors, actuators, gearing, drive elements, platforms, robotic elements, electronic elements, optical elements, control elements, computers, positional sensors, weight sensors, shakers, frames, and/or guides, that cause, facilitate, and control movement of a glass sheet through the glass tempering and production systems described herein. Conveyors and conveyor systems are broadly-known in the art and further description of the variations thereof are not necessary.
For any element of the method or systems described herein, an element, subsystem, system or device “able to” perform a specific activity, function, task, etc. is configured to, is adapted to, and/or is capable of performing the specific activity, function, task, etc. In such a case, where an element, subsystem, system or device is said to be able to perform a specific activity, function, task, etc., one of ordinary skill will readily understand how to specifically configure, arrange, adapt, install, or connect the element, subsystem, system, or device into the described system.
Due to the ability of the ultra high frequency microwave generator to heat glass, optics, including lenses, mirrors, and beam splitters, may be manufactured from materials that are not heated by the microwave radiation produced by the ultra high frequency microwave generator. First-surface or metal mirrors that reflect the microwave radiation are useful. Transparent substrates can be used within the beam path, e.g., in a beamsplitter, if they are not heated by the gyrotron beam, that is at millimeter wavelengths, and include dielectrics, ceramics, polymers, crystals and composite materials, such as diamond, silica, low-loss solid state dielectrics, low-loss ferrites, or low-loss composites. One of ordinary skill in the optics field can design and/or choose suitable optical components for the beam path.
An “oven” or “furnace” is a chamber in which, in the context of the disclosure herein, a glass product is heated, whether for the purpose of pre-warming, warming, bending, heating for tempering, heating for annealing, or any other purpose. An oven comprises walls that are suitably insulated or shielded, and can be any useful shape, such as a cube or rectangular prism. An oven comprises at least one opening, and may comprise a conveyor passing through the opening and into the oven and configured to carry a glass product into the oven. The oven may comprise a second opening, with the conveyor extending from outside the oven, through the first opening, through the oven and through the second opening. The conveyor can be any useful configuration comprising, for example, rollers that either roll freely or which are driven by a motor, such as a motor controlled by a computer process, to move the glass product along the conveyor. Sensors, such as positional sensors, may be used to monitor a position of a glass product along the conveyor and within the oven, and the movement of the glass product along the conveyor can be controlled manually or by computer control. The position of the glass product on the conveyor may be obtained in the form of positional data produced by a positional sensor, the positional data may be analyzed by a computer process and motors controlling the conveyor may be controlled by a computer process so that the glass product is moved along the conveyor according to a predetermined protocol. An oven typically comprises a door at one or more openings, which can be manually opened or closed, but may be opened and closed by a motor. The opening and closing of the door may be coordinated by an automated method, such as by a computer process, that synchronizes ingress and egress of a glass product by the conveyor into and out of the oven.
An oven may comprise one or more heating elements, such as an infrared, e.g. resistive coil, heating element and/or heated gas heaters. The IR heater may be a high-intensity heating coil, e.g. having a power output of 3.6 W/cm2. A heating element may be placed on one or more walls of the oven. In the case of a rectangular prism- or cube-shaped oven, for example, the heating may be three dimensional (3D)—meaning the oven comprises at least two different heating elements on different walls. In order to achieve more even heating of a glass product in an oven, a fan may be employed within the oven to create convection.
It is understood that the invention is not limited in its application to the specific illustrated examples as these are merely illustrative of the general inventive concept. Further, the terminology used herein to discuss the invention is for the purpose of description and is not of limitation. Still further, unless indicated otherwise in the following discussion, like numbers refer to like elements.
The approach to tempering described herein combines traditional glass quenching technology with microwave-based heating to achieve desired glass tempering properties. The unique capability of microwave heating of glass enhances traditional thermal tempering capability for glass panels, improves tempering quality, reduces or eliminates glass distortion, allows for shorter cycle times, and/or allows for an overall cost reduction in the process. A single tempering process may be used to produce high quality tempering on both coated and uncoated glass systems with minimal or no change in process. The same tempering process could be utilized for both coated and uncoated glass.
Unlike conventional electric heating, microwaves can penetrate through glass, thereby heating glass volumetrically and efficiently. Combined with electric (e.g., IR) heat, microwave heating of the present invention generates a desired profile across glass thickness suitable for thermal tempering.
The challenges of glass tempering processes include: to achieve good temper glass quality without losing the shape of the glass, to maintain good optical quality, and/or to minimize the breakage during the glass tempering process. Traditional thermal glass tempering conducted in an IR heating furnace relies on the IR heating furnace to pre-heat the glass to the tempering temperature. However, due to the nature of IR heating, it is difficult to effectively and sufficiently heat the glass sheet mid-plane. In turn, a “negative” parabolic temperature gradient with lower mid-plane temperature (see, e.g.,
A glass sheet will cool off once it leaves the heating oven(s), and in a conveyor system, the leading edge of the glass sheet leaves the oven(s) before the trailing edge, therefore having longer time to cool than the trailing edge before commencement of quenching in the quenching chamber.
Therefore, a glass sheet having a leading edge and a trailing edge may be heated using a microwave beam to a temperature profile where the temperature of the glass sheet rises from the trailing edge to the leading edge (see, e.g.,
Provided herein are methods and systems for use in tempering glass sheets, such as flat sheets or bent sheets. The methods and systems provide, e.g., a more uniform heating profile to achieve rapid, uniform tempering of glass products, including shaped and multi-layer products. A method is provided for tempering a glass product that may comprise pre-heating a glass sheet in an oven, heating the glass sheet to a tempering temperature profile using ultra-high frequency microwave radiation, e.g., using a gyrotron, and quenching the glass sheet to produce a tempered glass sheet.
The temperature profile produced by the microwave beam may be substantially flat (e.g., varying by at most ±10° C.) through the thickness of the glass sheet (
Systems are provided herein for tempering using microwave heating of a glass sheet to a tempering temperature. Based on the unique feature of the microwave (e.g., gyrotron) heating process, systems and methods may comprise two stages. In the first stage, the glass sheet is heated by the microwave (e.g., gyrotron) system, which, for example, can comprise two chambers (e.g., IR pre-heat and microwave heating chambers) or one chamber, in which the glass sheet is heated by the high power microwave (e.g., gyrotron) system with optional accompaniment of conductive heating, for example using IR heating. In the second stage, a quenching system rapidly reduces the glass temperature to achieve good glass temper quality.
These systems and related methods are applicable to flat or bent glass sheets. For aerospace transparencies, or for other uses where bent glass sheets are produced, the tempering systems described herein optionally directly follow a bending process, which may include microwave bending, to produce a semi-continuous glass bending-glass tempering process. When present, a connected conveyor between the microwave bending process and the tempering system may ensure that the transition of the glass from the microwave bending chamber to the quenching system is proper in terms of the tempering temperature and heat loss. It also can ensure that the transition is reliable and robust. With this approach the cost and total process throughput may be optimized, thereby increasing total output and/or reducing the cost of the manufacturing cost to make the aerospace transparency. The glass sheet may be pre-heated in a first oven, moved to a second oven, heated to a tempering temperature profile with a microwave beam in the second oven, moved to a quenching chamber, and quenched in the quenching chamber. Alternatively, the glass sheet may be pre-heated and then heated to a tempering temperature profile with a microwave beam in a first oven, moved to a quenching chamber, and quenched in the quenching chamber. In either instance, the heating of the glass sheet to the tempering temperature is accomplished using the microwave beam, and optionally with additional infrared heating.
The microwave beam may be applied from above the glass sheet, for example in the case of non-coated glass sheets. Where the top major surface of the glass sheet is coated, for example with a reflective and/or low-emissivity coating, the glass sheet may be heated from below by the microwave beam. More than one microwave beam may be employed to heat the glass sheet, for example when the glass sheet is heated from below, or in any instance where obstructions could block a single microwave beam from effectively heating a complete glass sheet. Providing more than one microwave beam can be accomplished by using more than one ultra high frequency microwave generators, e.g., gyrotron devices, but more economically, and flexibly, a beam splitter may be used to split one microwave beam into two or more beams. For example, when a glass sheet is heated from below, for instance where an upper surface of the glass sheet has a reflective coating, elements of the conveyor or frame carrying the glass sheet might interfere with the coverage and heating of the entire surface of the glass sheet with a single microwave beam. In another case, for example with larger glass sheets, a single microwave beam may be less effective to heat the glass sheet adequately or evenly for tempering purposes. In these cases, a beam splitter, e.g., as described herein, may be employed to provide multiple microwave beams.
The following further describes various non-limiting examples of the devices, methods, and systems described herein.
Control systems for transferring sheets from station to station in the treatment of glass, e.g. in the tempering of glass, including but not limited to motion of the glass sheet, opening and closing doors of ovens, quenching chambers, microwave chambers, chemical tempering chambers, bending chambers, and/or other chambers may be controlled manually or by a computer. A computer comprises a microprocessor system that includes a microprocessor that processes instructions for performing a task. Instructions may be programmed in any suitable programming language, and may be used to monitor, control, and/or report on, e.g., various mechanical, electrical, or optical aspects of the systems described herein, including, for example and without limitation: monitoring and/or controlling temperature of a sheet or oven, monitoring and/or controlling of position of a sheet, monitoring and/or controlling shape of a sheet, monitoring and/or controlling heating of a sheet for tempering, and/or monitoring and/or controlling quenching of a sheet. For example in reference to
With continued reference to
Additional fixed or moveable and computer-controlled optics may be selected and employed by one of ordinary skill in the art to direct and/or modify beams a, b, c, and/or c′, as is needed to be able to adequately heat a glass sheet.
As would be recognized by one of ordinary skill, in reference to
The microprocessor or computer system 193 (
The obtaining and processing of thermal data, and the use of those data to produce temperature profiles may be repeated one or more times during the heating process, e.g., at intervals ranging from every 0.0001 to 60 seconds, including every 0.0001, 0.001, 0.01, 0.1, 0.5, 1, 2, 5, 10, 15, 20, 30 and 60 seconds including any increment therebetween. Even shorter time intervals are contemplated, and are only limited by the throughput (e.g., processing power) of the computer system. The gyrotron system may not be able to respond to the computer system as quickly as the computer system can analyze data, so scanning intervals may be set based on the responsiveness of the gyrotron system. That said, the scanning and analyzing of thermal and optionally spatial profiles may be performed at faster rates than the controlling of the gyrotron, within limits of the pertinent hardware.
In operation of the systems and methods described herein, a glass sheet is first prepared and is optionally bent to a desired shape. When the sheet is otherwise ready for tempering, the sheet is tempered using the systems described herein, and/or the methods described herein. The glass sheet is moved into a furnace in which it may be preheated and then, either within the same furnace chamber or in another chamber or station, is heated to a tempering temperature profile using the microwave heating method and systems as described herein. The glass sheet heated to the tempering temperature profile using the microwave beam is then quenched to produce a tempered glass sheet. That is, the glass sheet is heated to a tempering temperature profile using a microwave beam, and although the temperature profile of the glass sheet may change before quenching is initiated, the glass sheet remains at a suitable tempering temperature between the microwave heating to a tempering temperature and the initiation of rapid cooling during quenching. As would be understood by those of ordinary skill in the art, the respective configuration and relative locations of the preheating oven, the microwave beam, and quenching chamber can be varied, so long as adequate and acceptable heating and quenching can be accomplished. The quenching may directly follow the heating, meaning there is little or no further treatment of the glass sheet between microwave heating to a tempering temperature and quenching, but any intervening treatment may be utilized that does not negatively interfere with the described microwave heating to a tempering temperature and quenching of the glass sheet heated to the tempering temperature using the microwave beam to produce a tempered product. In the system described herein, the microwave generator may be adjacent to the quenching chamber, meaning there is little or no further treatments of the glass sheet between a position on a conveyor system where the microwave heating to a tempering temperature takes place, and the quenching, but any intervening treatment may be utilized that does not negatively interfere with the described microwave heating to a tempering temperature and quenching of the glass sheet heated to the tempering temperature using the microwave beam to produce a tempered product.
Glass is tempered by rapidly-cooling the surface of the glass sheet with a stream of gas or air, e.g., compressed air, in a process known as quenching.
In an alternative to heat tempering, glass sheets, and particularly thinner glass sheets, may be chemically tempered. Chemical tempering is achieved by ion exchange between smaller ions in the glass, such as sodium or lithium ions, with larger ions, which cause the characteristic compression effect found in tempered glass. Traditional chemical tempering methods are broadly-known, and involve exposing a glass sheet comprising smaller ions to a solution comprising the larger ions. For example sodium ions in sodium-containing glass are exchanged for potassium ions in a bath of potassium nitrate, or lithium ions in lithium-containing glass are exchanged for sodium ions in a bath of sodium nitrate. A chemical strengthening process is provided herein. In the method, a glass sheet is contacted with, or otherwise exposed to ions with a larger ionic radius than ions in the glass sheet, for example the glass sheet is contacted with a vapor comprising ions with a larger ionic radius than ions in the glass sheet, while concurrently heating the glass sheet with a beam from an ultra high frequency microwave generator, such as a beam from a gyrotron. A chemical deposition chamber 400 is depicted schematically in
The methods and systems described herein may rely on a computer, for example like, but not limited to, a microprocessor 193, at least for monitoring and controlling progress of the heating and tempering the glass sheets as described herein. A computer or computer system may take any physical form, such as a personal computer (PC), credit card-sized computers, personal digital assistant (PDA), smartphone, tablet, workstation, server, mainframe/enterprise server, and/or clusters. The terms “computer”, “computer system”, “microprocessor system”, or “computer microprocessor system” are herein used interchangeably. A computer includes one or more processors, e.g. a central processing unit (CPU), which carries out instructions for the computer. A computer also includes memory, e.g., RAM and ROM (storing, e.g., the UEFI or BIOS), connected to the processor by any suitable structure such as a system bus. Computers also may comprise non-transient storage for storing programming and data, in the form of computer readable medium/media, such as, for example, a hard drive, a solid state drive (SSD), an optical drive, a tape drive, flash memory (e.g., a non-volatile computer storage chip), a cartridge drive, and control elements for loading new software. Computer systems as described herein are not limited by any topology or by the relative location of the various hardware elements, recognizing the varied physical and virtual structures those of ordinary skill employ in implementing a computer system.
Data, protocols, controllers, software, programs, etc., may be stored locally in the computer, e.g., in a hard drive or solid state drive (SSD); within a local or wide-area network, or cloud, e.g., in the form of a server, a network associated drive (NAS); or remotely, such that connection is made over an internet connection, e.g., via remote access. Data, such as images, temperature profiles or shape profiles produced or used by the methods and systems described herein may be organized on computer readable media in a database, which is an organized collection of data for one or more purposes. Other exemplary hardware that form elements of a typical computer, include input/output devices/ports, such as, without limitation: Universal Serial Bus (USB), SATA, eSATA, SCSI, Thunderbolt, display (e.g., DVI or HDMI) and Ethernet ports, as are broadly known, and graphics adaptors, which may be an integral part of the CPU, a subsystem of the motherboard, or as separate hardware device, such as a graphics card. Wireless communications hardware and software, such as Wi-Fi (IEEE 802.11), Bluetooth, ZigBee, etc. may also be included in the computer. Elements of a computer need not be housed within the same housing, but may be connected to a main computer housing via any suitable port/bus. In a typical computer, at least the CPU, memory (ROM and RAM), input/output functionality, and often a hard drive or SSD and a display adaptor may be housed together and are connected by a high-performance bus of any useful topology.
The computer, having storage and memory capabilities, includes controller aspects that allow for the design, storage, and execution of instructions, executable by a processor for independently or collectively instructing the computer system to interact and operate as programmed, referred to herein as “programming instructions”. In the context of computing, a computer-implemented process (e.g., program), broadly speaking, refers to any computer-implemented activity that generates an outcome, such as implementation of a mathematical or logical formula, operation, and/or algorithm.
One example of a controller is a software application (for example, basic input/output system (BIOS), unified extensible firmware interface (UEFI), operating system, browser application, client application, server application, proxy application, on-line service provider application, and/or private network application) installed on the computer system for directing execution of instructions. The controller is a WINDOWS™-based operating system. The controller may be implemented by utilizing any suitable computer language (e.g., C\C++, UNIX SHELL SCRIPT, PERL, JAVA™′ JAVASCRIPT, HTML/DHTML/XML, FLASH, WINDOWS NT, UNIX/LINUX, APACHE, RDBMS including ORACLE, INFORMIX, and MySQL) and/or object-oriented techniques.
The controller may be embodied permanently or temporarily in any type of machine, component, physical or virtual equipment, storage medium, or propagated signal capable of delivering instructions to the computer system. In particular, the controller (e.g., software application, and/or computer program) may be stored on any suitable computer readable media (e.g., disk, device, or propagated signal), readable by the computer system, such that if the computer system reads the storage medium, the functions described herein are performed.
The computer may contain and implement a “protocol”, for example instructions and data that control e.g., the tempering process for a glass sheet. Various modeling techniques may be used to develop protocols and may be implemented as part of a computer-implemented protocol. Modeling techniques include scientific and mathematical models, specific for glass tempering and optionally bending processes, which are able to determine the required temperatures at different stages of the process necessary to achieve a final glass sheet of high-quality. Protocols include, for example, the preheat temperature at the exit of the first furnace, glass forming/bending temperature profile in the glass forming furnace, exit glass temperature once the forming process is complete, glass tempering preheating profile, and the glass tempering temperature profile. The protocol may control the gyrotron beam system to establish a heating profile to achieve a specific heat profile to temper a glass sheet. A gyrotron beam may be manipulated in various ways, such as by altering the path, speed, width, shape, frequency, dwell time at a location (position on the glass sheet), or intensity/energy (e.g., kilowatts, kW) of the gyrotron beam. In one example, beam width, beam shape, intensity/energy and/or frequency may be held constant, but the location, path, speed, and/or dwell time at a location of gyrotron beam may be altered to provide a desired heating profile on the glass sheet. In another example, the gyrotron beam's electrical power may be manipulated, while the beam may be moved at a constant speed across the surface of the glass sheet to produce a desired heat profile. In another example, both the electrical power and beam speed may be changed to achieve the desired effect. The protocol may comprise instructions at least for controlling any or all possible parameters of the gyrotron beam, such as: location, path, intensity/energy, speed, beam shape, beam diameter, and output frequency, which may be controlled by the gyrotron unit or the post-gyrotron optics. For example, the mirrors described herein in connection with the gyrotron (
As part of the protocol, the computer may receive and process real-time data from the thermal and positional sensors, particularly the thermal sensor and, optionally the positional sensors. The computer then may produce a temperature profile, and optionally a shape profile, from the real-time data. The temperature profile and shape profile are merely representations in the computer that can be compared to reference temperature and, when applicable, shape profiles stored in association with the bending protocol. The computer system may compare produced profiles to the reference profiles to determine differences between the produced profiles and the reference profiles at one or more locations on the glass sheet, and, if differences are present and one or more positions on the glass sheet require heating to match the temperature and shape of the glass sheet to the reference profiles, the computer may control one or more parameters of the gyrotron beam to selectively heat a portion of the glass sheet to correct those differences. In addition to the above, optionally, the computer may receive additional temperature data from one or more temperature sensors, such as thermocouples and/or IR scanners of one or more chambers and/or furnaces of the system according to any examples described herein, and may act as a thermostat, monitoring and adjusting the ambient temperature of the chamber, e.g., by adjusting the output of IR heaters, blowers, etc. utilized in the system. In one example, thermocouples detect the temperature of the microwave heating chamber 78, as shown in
The thermal sensor 324 (
Positional sensors may be used to track motion and/or shape of the glass sheet within any system described herein. Where pertinent and needed to permit positional monitoring of the glass sheet, a suitable light source to provide illumination of the glass sheet to the extent necessary to permit imaging also may be employed, though heated glass typically emits enough light, e.g. at an IR or visible wavelength, for imaging purposes. The positional sensor(s) may comprise a single unit or multiple units that allow for either image capture or capture of data in real time, indicating the spatial position of one or more positions on the glass sheet. A non-limiting example is a positional sensor obtained from Rockwell Automation (Allen Bradly), for example, the 42 CM 18 mm LaserSight or the 42EF LaserSight RightSight are suitable positional sensors. The positional sensor may be an imaging sensor, such as one or more CCD and/or laser-light sensor devices housed either together or at separate locations within the heating or quenching chamber. CCD and/or laser-light sensor devices sensor devices output 2D images that may be processed within the computer or within the device. The images may be used in their 2D form, or can be processed to form a 3D image by the computer to produce a profile of the glass sheet that indicates the real-time spatial position and temperature of any portion or point on the glass sheet, and then compares that profile to a reference profile associated with the protocol, and adjusts heating with the gyrotron beam to match the profile of the glass sheet with a reference profile. A large variety of position, distance, measurement, displacement, profile, 2D, and 3D sensors, e.g., laser sensors, are commercially available, for example and without limitation from Rockwell Automation (Allen Bradly), Emerson Electric of St. Louis Mo., Schmitt Industries, Inc. of Portland Oreg., and Omron Automation & Safety of Hoffman Estates, Ill. In any case, the positional sensor may be connected to the computer, and data obtained from the positional sensor, optionally in coordination with the IR data described above, may compared to reference data associated with a protocol for tempering a particular glass sheet, and the temperature of any portion of the glass sheet may be adjusted using the gyrotron beam.
A composite 3D image or set of images of the glass sheet at any given time point may be generated by a computer implemented process so as to evaluate the shape or temperature of the glass sheet at any time point. The computer system generated 3D image, composite image, or set of images of the glass sheet and/or a portion thereof can be compared to values of the reference profile of the protocol, and if a deviation from the desired temperature profile stored in the protocol is present, the computer system controls the gyrotron 177 and/or ambient temperature of the second furnace 78, optionally in combination with infrared image data from an infrared imaging sensor to heat the glass sheet, or portions thereof, to shape the glass sheet to meet the requirements of a tempering protocol.
A “temperature profile” or “temperature distribution profile” refers to the temperature of any portion or portions of a specific glass sheet at any time point or points during the process of heating, bending, tempering, and cooling that sheet of glass. As used herein, a “reference temperature profile” refers to a temperature distribution profile for any specific glass sheet stored locally in or remotely from the computer system in association with a protocol for tempering that specific glass sheet. The reference temperature profile is created or developed by any method, such as by formula and/or trial-and-error, to produce a specific tempering of the specific glass sheet. The reference temperature distribution profile for producing a desired tempering of a glass sheet will depend on a variety of factors, including, among other factors: the composition of the glass sheet, the physical (conveyor) path between the heating station and the quenching chamber, and the desired tempering effect. By using a predetermined temperature profile as a reference, and ultimately manipulating the gyrotron system to selectively heat the sheet of glass, a desired tempering temperature distribution may be produced not only inside of the glass, but throughout the glass. The terms “tempering profile” refers to the temperature distribution of a glass sheet at any time point or points during the process of heating, tempering, and cooling a sheet of glass during the tempering process.
The use of safety equipment to limit or prevent damage to the persons operating the equipment, and/or to prevent or limit damage to the equipment is contemplated. For example and not limiting to the discussion, the equipment might include an arc detector. The arc detector may be mounted in the furnace and includes a photocell connected to the microprocessor 193 by way of a cable. The arcing, as is known in the art, is ionized matter, e.g. but not limited to an air born pocket of dust appearing as a burst of light. The arcing phenomenon is well known in the art and no further discussion is deemed necessary. The photocell of the detector senses the arcing and forwards a signal along the cable. The microprocessor 193 forwards a signal along the cable to shut the gyrotron down to prevent damage to the personnel around the furnace and to the gyrotron equipment.
The systems of the invention described herein are provided as illustrative of various aspects of the invention.
One system 500 is provided as depicted schematically in
A system 600 is provided as depicted schematically in
A system 700 is provided as depicted schematically in
A glass tempering method and system useful in minimizing glass defects due to excessive glass surface temperature and reflectance of a low emissivity coating is also provided. The method and system combines the traditional IR heating technology with microwave energy in a glass tempering process that can significantly reduce the glass tempering process cycle time, particularly for the low emissivity coated glass, and/or produce various glass tempers which is impossible to produce in the traditional glass tempering process. The method and system may significantly reduce the glass tempering cost by reducing the cycle time and/or minimizing product defects. The method and system provide flexible glass tempering capabilities for different glass temper products. As would be appreciated by those of ordinary skill, the glass product may have sides with different optical properties, one side typically being more reflective than the other. As a consequence, the microwave beam may be best applied from a side of the glass sheet with lower reflectivity. In a typical process, an upward-facing surface of the glass sheet is treated in a manner to have superior reflectivity as compared to a downward-facing surface. As such, the microwave beam may be applied to the least-reflective side of the glass sheet, which often is the bottom side of the sheet.
A system 800 is provided as depicted schematically in
Of note, with
In any of the preceding examples, traditional IR heating energy may be used to pre-heat the glass to within the range of 900° F. to 1150° F., and microwave electromagnetic energy may be used to provide additional heating, to bring the glass to a tempering temperature, e.g., of 1182° F., or higher, depending on the composition, shape, and structure of the glass sheet and desired tempering profile. For example and without limitation, in the IR heating chamber, the glass sheet is preheated with high intensity IR (3.6 W/cm2), e.g., in an IR furnace set to 690° C. (1274° F.), until the glass average temperature reaches 605° C. (1121° F.) (surface about 625° C. (1127° F.), mid-plane about 595° C. (1103° F.).
In the systems and methods provided herein, the microwave energy can be a continuous, focused microwave beam with a diameter of between 10 mm to 150 mm, which continuously heats the glass sheet, or a pulsed, focused microwave beam with similar diameters but with a pulse width of 1 seconds to 25 seconds and a cycle time of between 1 minutes to 10 minutes.
Referring to
A semi-continuous glass manufacturing process also is provided, combining microwave glass bending with glass thermal tempering and chemical tempering processes to create to significantly improved glass quality and processing efficiency. The system and method combines microwave-based shaping, microwave based thermal tempering and microwave-based chemical tempering into a highly efficient and automatic glass making process from bending to tempering. This is expected to transform the current process flow from a manual and slow process into an automatic, and fast glass tempering process, thereby reducing labor and material costs. The components of a continuous glass bending-tempering system are shown in
Glass loading station 903: A mechanical system is used to load the raw glass;
Preheating chamber 904: An oven with top, bottom, front/back, and left/right wall IR heating elements. A conveyer drive system and a position measurement system may be used to ensure accurate carriage/tooling/glass positioning for high process repeatability. An optical measurement system also may be installed to provide the operator full-surface glass temperature information.
Microwave glass bending chamber 906: In this chamber, the main equipment is the microwave energy source as described herein (e.g., between 10 GHz to 100 GHz, and 1 KW to 60 KW). A gyrotron device may be used for the glass bending. The installed microwave energy source may be supplemented with a mirror system including an optical box and a mirror box, for example as described above. The optical box shapes the electrical magnetic wave generated from the microwave generator into a desired shape either a circle (10 mm to 200 mm in diameter), a stripe, or other shapes. The mirror box with 2·axis controlled motion projects the energy and scan on the surface of the glass sheet. Additionally, a supplemental IR heating system (e.g., top, bottom, left, right, back, and/or front wall) may be also included in this chamber to maintain proper ambient temperature for minimum glass heat lost during processing. Alternately, the microwave beam is split as described herein using a beam splitter.
Holding (temperature control) chamber 908: This chamber may be used to separate the glass stack into singlets (where required) and/or to heat the glass to a pre-tempering temperature. A robotic system can be used to achieve the mechanical separation of a glass stack. A three dimensional IR heating system may be installed to provide enough power to obtain desired glass pre-tempering temperature. As described herein, high power heating, e.g., microwave heating as described herein is used to heat glass to 1,200° F. before quenching. However, if the glass is to be chemically tempered, then the glass may proceed to a cooling (annealing) chamber. A glass temperature measurement system, such as non-contact IR temperature sensors, may be installed in this chamber to monitor glass temperature. Chamber 908 may comprise a gyrotron beam source as shown for example in
Thermal tempering (quenching) chamber 910: In this chamber, the glass is cooled with a designed rate to achieve proper temper level, for example as shown in
Glass annealing (cooling) chamber 912: if the glass product is a chemical tempering product, then the glass is transported from the holding chamber 908 into this chamber for annealing. In order to achieve controllable annealing schedule, the controllable cooling equipment, such as the IR heating coils and controllable cooling fan system, is installed in this chamber.
Microwave chemical tempering chamber 914: A new approach to chemically tempering glass is used in this chamber (See, e.g.
The following clauses describe various aspects of the invention:
Having described this invention, it will be understood to those of ordinary skill in the art that the same can be performed within a wide and equivalent range of conditions, formulations and other parameters without affecting the scope of the invention or any embodiment thereof.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/025746 | 4/3/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62317712 | Apr 2016 | US |
