Coating apparatus – Projection or spray type – Moving projector
Reexamination Certificate
1999-01-08
2002-05-14
Crispino, Richard (Department: 1734)
Coating apparatus
Projection or spray type
Moving projector
C118S301000, C118S302000, C427S445000, C347S084000, C239S172000, C239S175000, C239S305000, C239S390000
Reexamination Certificate
active
06387184
ABSTRACT:
TECHNICAL FIELD
This invention relates to the precision coating of surfaces and more particularly to extrusion coating of substrates wherein fluid storage, delivery, and dispensing means are contained within a module which can be removably attached to a station containing the remainder of a complete coating apparatus.
BACKGROUND
It is often necessary or desired to provide a coating of a particular substrate. For example, in the video electronics industry it is often desired to coat panels which will serve as flat panel displays (FPD) to be incorporated into television sets, computer monitors and the like. It is important in such applications to ensure the accuracy and consistency of coating thicknesses across the panel.
In the prior art, the fluid delivery means, including fluid supply, pumps, and dispenser or fluid extrusion head assembly, as well as the chuck, substrate and means for distributing a coating of the fluid on the substrate were all part of a single integrated coating apparatus assembly. As such, when it was necessary to change coating fluids, or perform other operations on the fluid delivery means, the entire coating apparatus would be idled. Fluid changeover operations include time consuming tasks such as cleaning all tubing, pumping mechanisms, and essentially all surfaces where residue of the previous coating material could be present. This thoroughness is often necessary because of potentially dangerous chemical reactions between two different coating materials to be used in succession, and because of the danger of cross-contamination between coating materials used in different processes. The idle time for the coating apparatus is expensive and wasteful given that mechanisms unrelated to the fluid delivery system are idled by the operations necessary for fluid changeover. Accordingly, a need exists in the art for a system and method wherein a chuck assembly adapted to position and hold substrates to be coated as well as other components and materials used in the coating process but not part of the fluid delivery system are not left idle during fluid delivery system cleaning operations.
Additionally, in order to avoid dripping or smearing coating material which has gathered around the extrusion head after a coating operation, it is often necessary to clean the extrusion head before a new coating operation begins. In the prior art, cleaning of extrusion mechanisms is usually accomplished manually, potentially leading to inconsistent results and disruption and delay of the coating operations. Therefore, it is a problem in the art that manual cleaning operations are inconsistent and unreliable.
In order to ensure that coating material is applied consistently and evenly right from the start of the coating operation, it is desirable to ensure that a bead is fully and properly formed at the extrusion head prior to starting the coating process. A problem in the prior art exists with respect to properly priming fluid extrusion heads so as to ensure that a proper bead is formed prior to extruding fluid over the substrate, that a consistent rate of coating fluid flow is thereafter achieved, and that the extrusion head can be quickly moved from the priming mechanism to the substrate.
Generally, in prior art coating systems, there is a single pump mechanism located remotely from the extrusion head with appropriate fluid conducting means leading from the pump the head. The use of a single pump, while perhaps economical, makes it difficult to precisely control fluid flow at the extrusion head. Specifically, it may be difficult to start and stop at precisely defined moments and to establish the precise fluid flow rate desired.
In prior art systems, variation in the height of the extrusion head with respect to the substrate can cause breaking of the coating bead and variation in coating thickness. The causes of such height variation include part dimension variation, part placement error, and gradual drift in machine dimensions over time. Accordingly, there is a need in the art for a system and method for ensuring constant extrusion head height over the substrate being coated.
Accordingly, there is a need in the art for a method and system for coating in which the idle time for apparatus not part of the fluid delivery process to be minimized while fluid is being changed or recharged.
A still further need in the art exists for a cleaning station whose functions are automatically accessible to a fluid dispenser in between coating operations.
A still further need in the art exists for a priming station which can be accessed automatically by a fluid dispenser in between coating operations.
A still further need in the art exists for more precisely controllable flow of coating material at the extrusion head.
SUMMARY OF THE INVENTION
These and other objects, features and technical advantages are achieved by a system and method in which the wet components, including the fluid supply, pumping means, fluid dispensing head and utility station operations are located on a carrier, or other device, hereinafter referred to as a mobile device or cart, although it should be appreciated that the present invention may be embodied in any number of devices not completely consistent with the chosen nomenclature, which is removably attachable to the remainder of the coating apparatus. The mobile device is preferably in the form of a cart or fluid station which contains all or substantially all of the components in the coating apparatus which come into contact with coating fluid. The portion of the coating apparatus not part of this mobile fluid module, or fluid cart would preferably contain a chuck and shuttle mechanism, or other transport means. The non-fluid portion of the coating apparatus will be referred to as a base station or work station.
The fluid cart and base station preferably both contain means for being secured together in preparation for a coating operation employing a chosen cart. Means for accomplishing this attachment include but are not limited to clips, clamps, rollers on beams which are forced against a rigid surface, and grippers which may be actuated by electrical, pneumatic, and hydraulic means. Preferably, in the context of a plurality of carts with different coating materials and different types of dispensers on board, and possibly, a plurality of base stations, any cart can be mechanically attached, and appropriately interfaced to any station among the plurality of carts and stations, wherein the interface may serve to transfer information, power, and facility connections such as exhaust or drain connections, by a variety of means including electric, pneumatic, hydraulic, or wireless.
Preferably, both the fluid cart and base station both comprise means for communicating with the other. The need for coordinating fluid flow rates with relative velocity of the dispenser with respect to a substrate among other parameters create a desire for such communication. The communication link between the cart and base station may be made by wire or cable or may be wireless, and is preferably under computer control. If the communication is accomplished via a hard wire connection, this connection will preferably be automatically made when the cart and base station are mechanically joined. Alternatively, the wired connection may be made manually either before or after a rigid mechanical attachment between the cart and base station is accomplished. Upon removing a cart from a base station, all connections made when first joining the cart and base station are disconnected.
In a preferred embodiment, the dispenser, coating head, or extrusion head is associated with a cart as is other equipment with comes into direct contact with the coating fluid. This approach obviates the need to clean the dispenser in between coating operations involving different fluids, and minimizes the amount of mechanical connection and disconnection necessary when changing carts. A preferred embodiment of the cart includes a cowl assembly substantially sealing any exposed wet components, such as the aforementioned
Gibson Gregory M.
Hawes John E.
Kabbani Samer Mahmoud
Newquist Carl W.
Poonawala Altaf A.
Crispino Richard
FAStar, Ltd.
Lorengo J. A.
Winstead Sechrest & Minick P.C.
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