Refrigeration – Using electrical or magnetic effect – Thermoelectric; e.g. – peltier effect
Reexamination Certificate
1999-10-12
2001-03-06
Doerrler, William (Department: 3744)
Refrigeration
Using electrical or magnetic effect
Thermoelectric; e.g., peltier effect
C062S003300, C062S371000, C062S264000, C062S246000, C062S078000, C062S003700
Reexamination Certificate
active
06196001
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention relates to movable work-in-process (WIP) transports and more particularly to a WIP transport apparatus for moving materials requiring a temperature and humidity controlled environment.
2. Description of Related Art
Assemblies for carrying items currently exist for transporting materials from one area to another. Examples of such transport units are wheeled platforms with or without motor drives and wheeled shelves. Such units are used to transport a variety of materials including items extremely sensitive to the environment. Items such as disk drives, semiconductor wafers, and flat panel displays require clean environments and controlled temperature and humidity conditions at all times during their manufacture. Environmental control can become a problem in the manufacture of these materials, especially as they are transported between processing tools. During this transport, these materials may be exposed to contaminants such as particles or electrostatic charges as well as temperature and humidity variations. Exposure to uncontrolled environmental conditions can produce, for example, uneven deposition layers in semiconductors, induced thermal stresses, reduced yield, and an overall decrease in the quality of the final product.
To store materials, e.g., semiconductor wafers, in controlled environments between processing stages, specially designed storage containers are used as an intermediate storage. However, these containers are static and not easily transportable, thus requiring additional transport and exposure to the environment to and from these containers. Environment controlled transportation units currently exist to transport sensitive materials, e.g., motion picture films. See U.S. Pat. No. 4,922,721 (Robertson et al.), which is incorporated herein by reference. However, there is a need for a transport unit which controls a variety of environmental factors for transporting sensitive materials such as semiconductor wafers, disk drives, flat panel displays, and other electronic devices.
SUMMARY
In accordance with the invention, a transportable cart assembly is described which controls various environmental conditions within an enclosure while transporting items such as semiconductor wafers or flat panel displays. A fan and filter unit is used to control the spread of small particles within the cart, and the unit also circulates nitrogen pumped in from an external source or air within the enclosure to help control the temperature and humidity levels. The cart assembly also has a heating and cooling unit, which can be a thermoelectric heater such as a Peltier junction, to control the temperature within the enclosure. The use of Peltier junctions as the heating and cooling units offer the advantages of reduced power consumption, compact size, and flexibility of use.
The fan and filter unit works in conjunction with the heating and cooling unit in a single-pass flow or recirculating cycle; this aids in maintaining temperature levels within the enclosure at desired accuracy. The cart also has lighting and an ionization unit to control the electrostatic discharge on transported items and on the cart enclosure itself. The cart assembly is able to power its individual on-board units from an external power supply through a retractable power cord; or because of the transportable nature of the cart, power can be supplied through its on-board power supply while items are being transported.
Additionally, the cart assembly can be specially configured to transport flat panel displays during the fabrication process. This involves the attachment of a platform tilted at an angle while mounted within the cart enclosure. Having a tilted platform ensures that the flat panel display cassette remains securely seated within the platform during transport, offers ergonomic loading onto shelves, and ensures proper airflow between panels. Also, to ensure the structural integrity of the cart assembly, a singular bracket is used to hold the frame assembly of the cart together at the joints as well as to ease the assembly of the cart.
REFERENCES:
patent: 3982584 (1976-09-01), Spanoudis
patent: 4922721 (1990-05-01), Robertson et al.
patent: 5331840 (1994-07-01), Williams
patent: 5415012 (1995-05-01), Maier-laxhuber et al.
patent: 5466915 (1995-11-01), Meier et al.
patent: 5910210 (1999-06-01), Violi et al.
Lewis Paul E.
Tannous Adel G.
Allied-Signal Inc.
Doerrler William
Shulman Mark
Skjerven Morrill & MacPherson LLP
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