Patent Application
20130098294
The present invention relates generally to a conveyor assembly, and more particularly to a conveyor assembly that is well-suited for moving substrates through a vapor deposition system.
Production of thin film photovoltaic (PV) modules (also referred to as “solar panels”) typically involves conveyance of a substrate, such as a glass panel, into and out of a vapor deposition chamber wherein a thin film layer (generally recognized in the industry as less than 10 μm) of a semiconductor material, such as cadmium telluride (CdTe) is deposited onto the surface of the substrate. The deposition process may be any known process, for example a close space sublimation (CSS) system, a chemical vapor deposition (CVD) system, or physical vapor deposition (PVD) system.
Solar energy systems using CdTe PV modules are generally recognized as the most cost efficient of the commercially available systems in terms of cost per watt of power generated. However, the advantages of CdTe not withstanding, sustainable commercial exploitation and acceptance of solar power as a supplemental or primary source of industrial or residential power depends on the ability to produce efficient PV modules on a large scale and in a cost effective manner. In this regard, it is highly desirable to reduce down-time of the vapor deposition system used in production of the PV modules.
Typically, various types of conveyors are utilized to move the PV module substrates through the vapor deposition system. Components of the conveyors may be exposed to the source material vapors, which can condense into a detrimental buildup of the source material on the conveyor components. In this situation, the conveyor components need to be removed and cleaned or replaced with clean components. The conveyor components may also need to be removed for periodic maintenance, replacement, or other procedures requiring shutdown of the system. Reduction of system downtime associated with conveyor maintenance, replacement, or other reasons is an ongoing concern.
The conveyor assemblies must also be capable of precisely controlled movement of the substrates to ensure a uniform deposition of the source material and vapor deposition parameters. Unfortunately, the goals of easy removal/replacement of the conveyor components and precisely controlled conveyance rates are often at odds from a technological standpoint, and it is difficult to achieve both.
Accordingly, there exists a need for an improved conveyor assembly particularly suited for conveyance of substrates conveyed through a vapor deposition that reduces downtime associated with component replacement and maintenance yet ensures precise and consistent conveyance capabilities. The present invention relates to a conveyor assembly that serves these purposes.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
An embodiment of a conveyor assembly in accordance with aspects of the invention for conveying substrates includes a first carriage rail disposed at a drive side of the conveyor assembly with at least one roller position defined therealong. A drive wheel is disposed at the roller position and is configured for driving engagement against a roller. The drive wheel includes an axial cylindrical extension and an elastomeric sleeve disposed on the cylindrical extension. The elastomeric sleeve has a defined outer diameter. With this configuration, a roller placed in the roller position rests by gravity on the elastomeric sleeve and is rotationally driven by rotation of the drive wheel such that a substrate conveyed by the roller is displaced a defined distance for each rotation of the drive wheel as a function of the outer diameter of the elastomeric sleeve.
In a particular embodiment, a second carriage rail is disposed at an opposite side of the conveyor assembly. The opposite side may be a non-driven idler side, or may also be a drive side. Each of the first and second carriage rails include a plurality of roller positions spaced longitudinally along the length of the rails. These roller positions may be open-ended recesses defined in the rails. The first and second carriage rails also include a pair of wheels at each of the roller positions. These wheels are spaced apart so as to define a cradle at each respective roller position. A plurality of the roller positions along at least the first carriage rail are drive positions wherein one of the wheels is a respective drive wheel. The other wheel may be an idler wheel, or may also be a drive wheel. The roller positions are configured such that a plurality of rollers may be placed between the first and second carriage rails, with the rollers having ends that drop into the cradles defined by the wheels, which rotationally support and drive the rollers. The rollers are removable from the carriage rails by being lifted out of the cradles at the roller positions.
The outer diameter of the elastomeric sleeve is defined to be concentric relative to a precise reference diameter and axis of the drive wheel. For example, in a particular embodiment, the axial extension is a cylindrical member having an inner diameter, with the outer diameter of the elastomeric sleeve defined to be concentric with the inner diameter of the cylindrical member. In another embodiment, the reference diameter may be the outer diameter of the axial extension.
In a certain embodiment, the axial extension may include a circumferential groove defined therein, with the elastomeric sleeve seated within the groove. The groove may serve to maintain the relative axial position of the sleeve, and may include sidewalls that engage axial ends of the elastomeric sleeve and prevent axial expansion of the elastomeric sleeve from, for example, compression of the sleeve by the roller.
The elastomeric sleeve may be a separately formed cylindrical sleeve member that is stretched and fitted onto the axial extension. In an alternate embodiment, the elastomeric sleeve may be molded directly onto the axial extension. The outer diameter of the elastomeric sleeve may be ground or otherwise machined after the sleeve is fitted or molded onto the axial extension.
In one embodiment, the drive wheels along the first carriage rail are rotationally driven by a common drive belt.
A plurality of the roller positions along the second carriage rail may also be drive positions and include at least one of the drive wheels having an axial cylindrical extension and elastomeric sleeve, as discussed above.
Variations and modifications to the embodiment of the conveyor assembly discussed above are within the scope and spirit of the invention and may be further described herein. Although particularly well-suited for conveying substrates through a vapor deposition module or system, it should be appreciated that the conveyor assemblies in accordance with aspects of the invention are not limited to this particular use.
The invention also encompasses various embodiments of a vapor deposition module that may be used for conveying a substrate through a vapor deposition system wherein a source material is sublimated (i.e., converted to vapor) and deposited onto a surface of the substrate. An embodiment of such a module includes a housing and a conveyor assembly operably configured within the housing to convey substrates through the housing. The conveyor assembly may be configured as discussed above.
Variations and modifications to the embodiment of the vapor deposition module discussed above are within the scope and spirit of the invention and may be further described herein.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.
A full and enabling disclosure of the present invention, including the best mode thereof, is set forth in the specification, which makes reference to the appended drawings, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention encompass such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring to
The exemplary system 10 includes a vacuum chamber 12 defined by a plurality of interconnected modules. Any combination of vacuum pumps 40 may be configured with the interconnected modules to draw and maintain a vacuum effective for the deposition process within the chamber 12. A plurality of interconnected heater modules 16 define a pre-heat section of the vacuum chamber 12 through which the substrates 14 are conveyed and heated to a desired temperature before being conveyed into a vapor deposition apparatus 60. Each of the heater modules 16 may include a plurality of independently controlled heaters 18, with the heaters defining a plurality of different heat zones. A particular heat zone may include more than one heater 18. The heaters 18 may be disposed above or below the module bodies.
The vapor deposition apparatus 60 may take on various configurations and operating principles within the scope and spirit of the invention, and is generally configured for vapor deposition of a source material, such as CdTe, as a thin film on the PV module substrates 14. In the embodiment of the system 10 illustrated in
The vacuum chamber 12 also includes a plurality of interconnected cool-down modules 20 within the vacuum chamber 12 downstream of the vapor deposition apparatus 60. The cool-down modules 20 define a cool-down section within the vacuum chamber 12 in which the substrates 14 having the thin film of source material deposited thereon are allowed to cool at a controlled cool-down rate prior to the substrates 14 being removed from the system 10. Each of the modules 20 may include a forced cooling system wherein a cooling medium, such as chilled water, refrigerant, or other medium is pumped through cooling coils configured with the modules 20.
In the illustrated embodiment of system 10, at least one post-heat module 22 is located immediately downstream of the vapor deposition apparatus 60 and before the cool-down modules 20. As the leading section of a substrate 14 is conveyed out of the vapor deposition apparatus 60, it moves into the post-heat module 22, which maintains the temperature of the substrate 14 at essentially the same temperature as the remaining portion of the substrate 14 within the vapor deposition apparatus 60. In this way, the leading section of the substrate 14 is not allowed to cool while the trailing section of the substrate 14 is still within the vapor deposition apparatus 60. If the leading section of a substrate 14 were allowed to cool as it exited the apparatus 60, a non-uniform temperature would be generated longitudinally along the substrate 14. This condition could result in the substrate breaking from thermal stress.
As diagrammatically illustrated in
Still referring to
An exit vacuum lock station is configured downstream of the last cool-down module 20, and operates essentially in reverse of the entry vacuum lock station described above. For example, the exit vacuum lock station may include an exit buffer module 42 and a downstream exit lock module 44. Sequentially operated valves 34 are disposed between the buffer module 42 and the last one of the cool-down modules 20, between the buffer module 42 and the exit lock module 44, and between the exit lock module 44 and an exit conveyor module 46. A fine vacuum pump 38 is configured with the exit buffer module 42, and a rough vacuum pump 32 is configured with the exit lock module 44. The pumps 32, 38 and valves 34 are sequentially operated to move the substrates 14 out of the vacuum chamber 12 in a step-wise fashion without loss of vacuum condition within the vacuum chamber 12.
System 10 also includes a coordinated conveyor system configured to move the substrates 14 into, through, and out of the vacuum chamber 12. In the illustrated embodiment, this conveyor system includes a plurality of individually controlled conveyor assemblies 100, with each of the various modules in the system 10 including one of the conveyor assemblies 100. All or any combination of these conveyor assemblies 100 may be configured in accordance with aspects of the invention, as described in greater detail below. The respective conveyor assemblies 100 include conveyor drive units 102 that control the conveyance rate of substrates 14 through the respective module.
As described, each of the various modules and respective conveyors in the system 10 are independently controlled to perform a particular function. For such control, each of the individual modules may have an associated independent controller 50 configured therewith to control the individual functions of the respective module, including the conveyance rate of the conveyor assemblies 100. The plurality of controllers 50 may, in turn, be in communication with a central system controller 52, as illustrated in
Referring to
The respective conveyor assemblies 100 include at least one drive unit 102 configured with the modules 138. In the embodiment illustrated in
The conveyor assemblies 100 are not limited to any particular type or configuration of drive unit 102. In this regard, the drive unit 102 is generically depicted in the figures. In a particular embodiment described herein, the drive unit 102 may be a motor that serves to drive a drive belt 126 (
Referring to
The first and second carriage rails 104, 106 may be formed of any suitable material configured for the particular type of environment in which the conveyor assembly 100 is intended. In an embodiment wherein the conveyor assemblies 100 are used in a relatively high temperature vacuum deposition system 10, as described above with respect to
Referring particularly to
The wheels 114, 116 are disposed relative to the bottom of the respective recesses 110 so as to define a cradle for the rollers 120. In other words, the rollers 120 rest on the wheels 114, 116 without contacting the walls of the recesses 110. The wheels 114, 116 serve to rotationally support and drive the respective rollers 120.
Referring to
As seen in
The drive units 102 may be configured to drive the belt 126 in its endless-loop path by any suitable mechanical configuration. For example, the drive unit 102 may include a motor that is rotationally engaged with one or more of the drive pulleys 115 through any suitable gearing arrangement. In an alternate embodiment, a separate drive pulley may be provided anywhere along the path of the belt 126 to drive the belt in its endless-loop path. It should be readily appreciated that various suitable drive arrangements are within the scope and spirit of the invention for this purpose.
As mentioned above with respect to the discussion of
Referring to
An elastomeric sleeve 158 is disposed on the cylindrical axial extension 150, as particularly illustrated in
The elastomeric sleeve 158 transfers rotational drive to the roller 120 via a frictional elastomer-metal interface. Accordingly, the elastomeric material used to form the sleeve 158 is particularly selected to have a high frictional characteristic so as to prevent slippage between the roller 120 and sleeve 158.
An important consideration for accurate and precise conveyance of a substrate with a conveyor assembly 100 in accordance with the invention is that the outer diameter of the elastomeric sleeve 158 is precisely defined and maintained over the course of operation of the conveyor assembly 100. In addition, the diameter must be consistent between the different drive wheels 114 within any given conveyor assembly 100. In addition, the diameter must be concentric with the axis of rotation of the drive wheels 114. For this purpose, it is desired to reference the outer diameter 170 of the elastomeric sleeve 158 to a precisely defined reference diameter of the drive wheel 114, which establishes the drive wheel's axis of rotation. In the illustrated embodiment, the axial cylindrical extension 150 is formed as a cylinder with a precisely defined inner diameter 156. This inner diameter 156 may serve as the reference diameter for the outer diameter 170 of the sleeve 158. For example, after the sleeve 158 is formed or placed on the axial extension 150, the outer cylindrical surface 160 of the sleeve may be ground or otherwise finished in a post-application process to an outer diameter 170 that is a function (e.g. defined percentage increase) of the inner diameter 156. In an alternative embodiment, the reference diameter may be the outer diameter of the cylindrical extension 150.
Referring particularly to
The elastomeric sleeve 158 may, in one embodiment, be a separately formed cylindrical sleeve member that is fitted onto the cylindrical extension 150 in a post-fabrication process wherein the cylindrical sleeve 158 is stretched onto the cylindrical extension 150 and, for example, seated within the groove 166. With this embodiment, the sleeve 158 may be formed with an excessive outer diameter 170 so that the sleeve can be ground to a precisely determined outer diameter, as discussed above.
In a separate embodiment, it may be desired to mold the elastomeric sleeve 158 directly onto the cylindrical extension 150 and to grind or finish the outer diameter 170 of the sleeve in a post-mold process. A molding process may be desired in that the outer diameter of the sleeve 158 may be molded within an acceptable concentricity tolerance without subsequent post-processing.
Although not depicted in the figures, it should be appreciated that any manner of other structure may be disposed along the top surface of the respective rails 104, 106 to prevent inadvertent ejection of the rollers from the respective roller positions 108. The structure may be, for example, shielding, a lock bar, or any other type of readily removable structure. If such structure is provided, then the structure would need to be removed from the rails 104, 106 for subsequent removal of the rollers 120.
As mentioned, the present invention also encompasses any manner of vapor deposition modules for use in conveying a substrate 14 through a vapor deposition system, such as the system 10 in
Similarly, the present invention also encompasses a vapor deposition system, such as the system 10 described above with respect to
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
