Classifying – separating – and assorting solids – Sifting – Elements
Reexamination Certificate
1999-09-22
2001-03-20
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
Elements
C209S403000, C209S397000, C209S399000, C209S315000, C209S311000, C209S409000
Reexamination Certificate
active
06202856
ABSTRACT:
The field of the present invention is screening systems employing vibrational energy, the screens thereof and their manufacture.
BACKGROUND OF THE INVENTION
Vibratory screen systems have long been employed in both circular and rectangular form. The devices typically include a resiliently mounted housing having a screen extending across the housing. A vibration generating drive is coupled with the housing to vibrate the screen in an advantageous manner to increase screening efficiency. The screens are either self-contained by including screen cloth tensioned and bonded to a frame or rely on mechanisms on the resiliently mounted housing for placement and tensioning. In the latter circumstance, the screen typically includes screen cloth to which may be mounted hooks or eyes for attachment of tensioning mechanisms associated with the housing.
Alternatively, screens can include a perforated plate with screen cloth bonded thereto. When a plate is used, the screen may be tensioned before bonding to the plate. The screen cloth may be bonded to the plate by a layer of epoxy or thermoplastic material. The bonding material is positioned on the plate and the screen tensioned thereover. The material is then treated, commonly by heating to either initiate curing of the epoxy or fusing of the thermoplastic material. Nonstick layers of Teflon sheet may be employed where the assembly is compressed during the curing or fusing step. Multiple layers of screen cloth are known to be used in such assemblies.
Screens which employ hooks or eyes for tensioning by a separate mechanism have also been known which include laminated layers. A bonding by spot welding, epoxy or fusible material are known. Further, fusing multiple layers of screen cloth into the top of a frame structure made of fusible material having a peripheral frame and a pattern of open cells defined by cell walls has been done. The multiple screen cloths are bonded to the frame and to the cell walls by fusing the frame structure and resolidifying it after impregnation through the screen cloth or cloths. Such a structure is disclosed in U.S. Pat. No. 5,851,393, the disclosure of which is incorporated herein by reference.
Where bonding and laminating occurs in such a manner that the bonding or laminating material passes through the screen cloth or screen cloths to form a surface at the screening surface of the screen, a smooth surface results. The screen cloth often transports the material to be screened in a desired pattern. These smooth surfaces allow the material being screened to slip rather than transport the material and the overall transport of the material is inhibited.
SUMMARY OF THE INVENTION
The present invention is directed to a screen having two or more porous layers with at least one of those layers being a screen cloth and a solidified layer having perforations therethrough with the solidified layer impregnating the screen cloth to provide a first surface on one side of the screen.
In a first separate aspect of the present invention, the screen includes a frame, a first screen cloth, a second screen cloth and the solidified layer having perforations therethrough with the solidified layer impregnating the screen cloths to provide a first surface on one side of the screen and a second surface on the other side of the screen. The screen cloths are fixed in tension about the periphery thereof to the frame.
In a second separate aspect of the present invention, the screen of the first aspect further includes a third screen cloth being of intermediate interstices and positioned between the first and second screen cloths. The solidified layer impregnates all three screen cloths.
In a third separate aspect of the present invention, the screen includes a first porous layer including a screen cloth, a second porous layer and a solidified layer having perforations therethrough. The solidified layer impregnates at least a first screen cloth and is textured at the surface of the first screen cloth.
In a fourth separate aspect of the present invention, a process for manufacturing a screen includes layering at least two porous layers and a fusible layer having perforations together. Nonstick sheets are then layered on the foregoing lamination. The resulting lamination is heated and compressed to fuse the fusible layer to impregnate at least one of the two porous layers with the fusible material. The layer is resolidified and the resulting laminated screen structure is tensioned and bonded to a frame.
In a fifth separate aspect of the present invention, the fourth separate aspect may further include the use of two or more screen cloths impregnated by the fusible layer.
In a sixth separate aspect of the present invention, a process for manufacturing a screen includes the layering of at least two porous layers with a fusible layer having perforations therethrough. Nonstick layers are applied to the layered assembly and heating and compressing fuses the fusible layer to impregnate at least one of the porous layers including screen cloth. The fusible material thus defines a surface at the surface of the screen cloth. This surface has a texture molded therein.
In a seventh separate aspect of the present invention, the foregoing aspects are contemplated to be employed in combination to added advantage.
Thus, an object of the present invention is to provide improved screens and a process for the manufacture of improved screens. Other and further objects and advantages will appear hereinafter.
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Emerson Electric Co.
Jones David
Lyon & Lyon LLP
Walsh Donald P.
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