Patent Application
20100281919
Solar energy systems are used to collect solar radiation and convert it into useable electrical energy. Concentrated solar energy devices often comprise a primary mirror used to collect and concentrate solar radiation. The mirror may be comprised of any formable material such as glass, metal or plastic and must be made with sufficient precision to direct incoming solar radiation to, for example, a solar cell or a secondary mirror for further concentration. The present invention relates to a method and apparatus for shaping optical components such as a primary mirror of concentrating photovoltaic devices.
A conventional glass shaping apparatus typically includes two rigid molds—a male mold and female mold—which are brought together to conform a heated sheet of glass positioned there between to the shape of the two molds during the press cycle of the bending process. Other methods of manufacturing curved glass components include slump bending in which a heated glass sheet may be held in a single mold and heated to a temperature above the transformation point of the glass. At that point the sheet partially conforms to the shape of the holder. Alternative methods of shaping glass include the vacuum assisted slumping of glass in a single mold which involves the use of negative pressure to facilitate the slumping of glass into the mold. These processes may cause deformations or buckles to form in the final glass component. In addition to the limitations on the quality of the glass produced by conventional glass shaping techniques, there are numerous process controls. For instance, when male and female molds are used, they require accurate alignment which can take up to two hours. Furthermore, the two rigid molds of the conventional glass bending apparatus require substantially perfect alignment of the heated sheet of glass between the two molds which may further slow down the throughput.
Vacuum slumping may reduce the occurrence of manufacturing defects, but imprecise or uneven temperature control in the heating process may lead to defects regardless of the shaping technique. In addition, the process of loading the glass sheet into a mold, heating, vacuum slumping and removal of the curved glass from the mold may be a slow process, leading to uneven cooling of the mold and an overall low throughput in the manufacturing process. There are other slumping methods which utilize a linear oven for slumping of very large parts, i.e. windshield glass. However, while this process produces larger volumes than individual single ovens, it cannot produce parts with sufficient precision to be used as optical components for a solar energy system. A rotary design produces more parts, with more precision, and in a much smaller footprint but are generally used for small optical components and a press molding process. Current single ovens for one at a time production of large parts and current conveyors utilize different processes that may not be suited for all thicknesses of material. Inaccurate temperature control of current methods may cause re-boiling of the glass being shaped, resulting in the warping of the final product. There exists a need in the art for a high throughput method to manufacture precision shaped optical components in an economical fashion.
A method and apparatus are provided for shaping sheets of material in a high throughput manner. Other objects and many of the attendant advantages will be readily appreciated as the subject invention becomes better understood by reference to the following detailed description.
A curved oven and method for using the oven are described for manufacturing a shaped material for optical components by vacuum assisted slumping. The curved oven of the present invention provides a plurality of sequential chambers arranged in a curved path, with entrance and exit apertures and walls separating the chambers. The chambers may have an upper and a lower region, and the walls of the chambers may have openings shaped to match the profile of molds and pedestals being transported through the oven. An optional dual temperature control system may provide for the separate temperature regulation of the upper and lower regions of a chamber. Molds mounted on pedestals may be conveyed through the chambers on a transport system such a rotatable turntable. The design of the oven provides for improved control of the temperature of molds and materials that pass through the oven by reducing the heat loss of molds used to shape materials. The improved control of the molds may improve the consistency, precision, and throughput rate of the manufactured optical components. A vacuum system provides for the application of negative pressure in a portion of the chambers of the oven. The directed application of a vacuum in a portion of the oven chambers may result in an improved consistency and precision of the shaped optical component.
The present invention will now be described more fully herein with reference to the accompanying drawings. While the specification has been described in detail with respect to specific embodiments of the invention, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention. Thus, it is intended that the present subject matter covers such modifications and variations as come within the scope of the appended claims and their equivalents.
By use of the method and device of this invention, precisely shaped optical components may be manufactured in a high throughput manner. The optical components may be made from sheet glass or any other moldable material such as plastic. The optical components may be used in a solar energy device, such as a concentrated photovoltaic energy device. The material may be placed in a mold and conveyed by a transport system through a curved oven. The optical components may be manufactured from material of any thickness. In one embodiment, the thickness of the material used to form the optical components may be less than 3 mm. The temperatures of the material and mold may be precisely and separately controlled resulting in improved consistency of the final optical component.
In the embodiment of
A top view of a curved oven 201 is shown in
A schematic version of a pedestal 305 and mold 306 in a chamber 307 of one embodiment of this invention is shown in
In a further embodiment of this invention, a portion of the chambers 307 may have two or more temperature control systems within a single chamber, beneficially providing for a high level of temperature regulation. The chamber 307 may include a top temperature sensor 317 in a closed loop configuration with the top heat source 315, for separately monitoring and controlling the temperature in the top region of the chamber 307. The chamber 307 may also include a bottom temperature control device 318 in a closed loop with the bottom heat sources 316 to control the temperature of the bottom region of the chamber 307. The temperature sensors 317 and 318 may be located anywhere in the chamber 307. A first temperature control system may be located in the top region of a chamber to advantageously control the temperature of the material to be shaped, while a second temperature control system may be located in the lower region of a chamber to separately control the temperature of the mold 306. In this manner the temperature of the material to be shaped may be controlled separately from the temperature of the mold 306, beneficially offering greater control of the shaping process. Separate control of the material to be shaped and the mold for shaping may reduce defects in the slumped material as sufficient heat is provided to the mold to facilitate slumping while the material to be shaped may be maintained close to the transformation point of the material.
In another embodiment, a temperature sensor may be located outside of the entrance aperture (e.g., aperture 107 of
The present invention provides a method for manufacturing shaped components for optical systems. One aspect of the method of this invention is that the optical components manufactured by the method and device of this invention may be used as primary mirrors in a concentrated solar energy device. In one embodiment the material used to form the optical component may be less than 3 mm thick. In still another embodiment, the material is sheet glass. The shape of the optical component to be manufactured may be defined by the shape of the mold used. In one embodiment the optical component may be a substantially paraboloid. In another embodiment, the shape and diameter may be any size.
A flow chart depicting an exemplary method of this invention whereby optical components may be manufactured by vacuum assisted slumping in a high throughput manner is shown in
The material may be heated to above the transformation temperature for the material. In step 430 the second material may also be similarly heated in the sequential chambers of a curved oven. The heat in the chamber may be regulated by one or more temperature control systems such as a temperature sensor and heat source connected in a closed loop configuration. In one embodiment the temperature control system may include a first temperature sensor and connected heat source located in the upper region of a chamber and a second temperature sensor and connected heat source located in a lower region of a chamber. Independently heating different portions of the chamber advantageously allows for the separate temperature control of the mold and material to be shaped. The material to be shaped may be heated to a temperature above that of the mold temperature regardless of the mold temperature. At the same time, the mold may be separately heated to a uniform temperature that supports the transformation temperature of the material in a way that may reduce warping as the material is slumped into the mold. The first material may then be shaped by vacuum assisted slumping during step 435. A vacuum source may be connected to an aperture in the mold that is mounted to a hollow pedestal. The pedestal may be connected to a vacuum source via a swivel valve in a manner the permits continuous rotation of the pedestal and mold while the vacuum is engaged. The second material may then be similarly shaped by vacuum assisted slumping in step 440. Molds 1 and 2 are then sequentially conveyed through the exit aperture in steps 445 and 450. The shaped materials are removed during steps 455 and 460. As the molds are reloaded with flat materials, the speed of conveying combined with the distance between the exit and entrance apertures prevents the molds from cooling beyond a desired temperature, such as not losing more than 150 degrees or more than 100 degrees in temperature when working with glass (steps 465 and 470). The control of the uniformity and degree of temperature loss advantageously provide for the high throughput manufacture of shaped optical components.
While the specification has been described in detail with respect to specific embodiments of the invention, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention. Thus, it is intended that the present subject matter covers such modifications and variations as come within the scope of the appended claims and their equivalents.
