Screen element
Methods of manufacturing screen elements for use with vibratory separators are disclosed. The screen elements include a curved structural frame with perforations therein, the perforations designed to maximize both open area and process liquid throughput. At least one layer of screen cloth is attached to the curved structural frame by means of fluidized powdered epoxy resin.
This Non-Provisional patent application, filed under 35 U.S.C. § 111(a), claims the benefit under 35 U.S.C. § 119(e)(1) of U.S. Provisional Patent Application No. 60/839,141, filed under 35 U.S.C. § 111(b) on Aug. 16, 2006, and which is hereby incorporated by reference in its entirety. This Non-Provisional patent application is related to U.S. application Ser. No. 10/922,342, entitled “Screen assemblies utilizing screen elements retained in perforated troughs,” and filed on Aug. 20, 2004, and to U.S. Provisional Patent Application No. 60/838,565, entitled “Screen assemblies utilizing screen elements retained in perforated supports,” and filed on Aug. 18, 2006.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable.
THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENTNot applicable.
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON COMPACT DISCNot applicable.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates generally to methods of manufacturing an apparatus with which material is separated or assorted according to size or dimensions of components by presentation to a series of openings or passages through which the components having dimensions below those of the openings or passages pass while those having dimensions greater than those of the passages or openings do not pass through. More specifically, the present invention relates to methods of manufacturing screen assemblies used in vibratory separators.
2. Description of Related Art
Vibratory screen separators with replaceable screen assemblies have long been known, and include a base, a resiliently mounted housing, a vibratory drive connected to the housing, and screen assemblies positioned on the housing. The screen assemblies are periodically replaced when process conditions dictate or when the performance of the screening media degrades due to abrasion, failure, or blinding. The screening media can be flat or pleated, single or multi-layered, laminated or un-laminated. Screen assemblies include screening media bonded to components structural in nature that are used to fasten or tension the screening media to a vibratory separator so that the motion of the separator is imparted to the screening media.
Flexible rectangular screen assemblies constructed by using structural components that form a “J” or similar shape on two sides of screen are known as hookstrip style screens. Hookstrip style screens are fastened to vibratory separators by pulling the screen assembly taut over a crowned deck. The “crown” or “radius” in the deck is necessary because the geometry of the crown keeps the flexible screen in contact with the vibrating deck without approaching tension levels that would damage the screening media.
Screen assemblies constructed by bonding screening media to rectangular structural frames that minimize the flexibility of the screen assembly are known as panel style screens. The structural frame may or may not have internal supporting cross members. Panel style screens are fastened to vibratory separators by clamping one or more surfaces of the structural frame to a mating surface (or deck) of the vibratory separator. The decks of vibratory separators that accept panel screens are noticeably less crowned than the decks of vibratory separators that accept hookstrip style screens, but the decks are usually slightly crowned to prevent panel style screens from flexing or chattering when the vibratory separator is in motion.
BRIEF SUMMARY OF THE INVENTIONThe present invention is directed to novel methods of manufacturing screen elements for vibratory separators, especially in mass production environment. Such screen assemblies include a structural frame that is mounted in a vibratory separator into which a plurality of lightweight and flexible screen elements are inserted into multiple rows of perforated screen supports. The perforated screen supports are bonded to each other and to the structural frame. The perforated screen supports are aligned parallel to the direction in which solids are conveyed by the vibratory motion. The perforated screen supports are assembled to the structural frame so that unscreened material cannot substantially bypass the screening media. The cross sectional geometry of the perforated screen support and of the formed screen elements can be rectangular, triangular, half-circular, half-ellipsoid, catenary, hyperbola, or other similar geometric shape. The screen elements include one or more layers of screening media that may be bonded to each other and may be preformed to conform to the geometry of the perforated screen support.
The present invention provides methods of manufacturing screen elements that substantially increase the available area for screening compared to the available area of the prior art when a screen assembly creates a flat or crowned screening surface on a vibratory separator. Furthermore, the ease of replacing small, (typically three inches wide and 24 inches long) and lightweight (typically less than one pound) individual screen elements in the present invention saves time and material by eliminating the periodic replacement of large, heavy, and cumbersome screen assemblies in conventional vibratory separators. Typically, these conventional screen assemblies weigh anywhere from 20 to 50 pounds and are approximately two to three feet long and up to four feet wide. In addition, when the present invention is used to replace hookstrip style screens with crowned screening surfaces, the effective screening area is increased by channeling the flow of unscreened material and preventing the pooling of liquid on either side of a crown deck. The crowned screen deck causes the processed material to flow away from the center of the screen (the crown) towards the sides, causing a large area of the screen surface to be under-utilized.
BRIEF DESCRIPTION OF THE DRAWINGSFor a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements.
Before the subject invention is further described, it is to be understood that the invention is not limited to the particular embodiments of the invention described below, as variations of the particular embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments, and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.
In this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs.
EXAMPLE 1 Screen Element Frame Manufacturing Steps The invention features, in one aspect, a screen element frame (80) created by perforating a sheet of thin metal plate, preferably flat, to achieve a preferred pattern (
Using a special molding press (31), the screen element frame (80) is then curved to a predetermined diameter, thus forming a curved screen element frame (85) (
The exact forming method is described in Example 5, “Description of the frame forming press,” below.
EXAMPLE 2 Curved Element Frame Coating The curved screen element frame (85), shown in
The curved screen element frame (85) is then heated in an oven (not shown) of any type for metal heating of the prior art. Normal temperature range for epoxy coating of metal components is 400 to 500° F., however, higher temperatures (up to 600+° F.) may be required due to the small volume of metal in the curved screen element frame (85), to compensate for rapid heat loss depending of the time it takes to move the curved screen element frame (85) from the oven to the fluidized bed (14), shown in
The hot curved screen element frame (85) is then dipped into a fluidized bed (14) containing special epoxy (25), specially designed to have low heat cure temperature and a suitable thixotropic index to prevent molten epoxy (25) from spreading, during the laminating process, into areas of screen cloth (92) covering the perforations in the curved screen element frame (85). The curved screen element frame (85) is kept in the fluidized epoxy (25) for three to five seconds. Depending on the desired epoxy coat thickness, a longer or shorter time—such as one to seven seconds—may be needed. The coated frame (88) is then placed on a cooling rack (16) to cool (
The heat lamination press cradle (42) of
The coated frame (88) is placed into the special heat lamination press cradle (42), as shown at
The round heating element (73) is then kept down in the heat lamination press cradle (42) at sufficient temperature and for a predetermined amount of time, preferably about four to five minutes, for the epoxy (25) coating to first melt and be forced through all the precut screen cloth layers (92) and then to cure it. It will be appreciated by those skilled in the art that the temperature and time required to cure any epoxy that could be used with the present invention may depend on particular characteristics of the epoxy used, but that such temperature and time are readily ascertainable by one skilled in the art without undue experimentation.
The round heating element (73) is then lifted up, and the laminated screen element (89) is removed from the heat lamination press cradle (42) and allowed to cool (
Once the laminated screen element (89) has been cooled, all excess screen cloth will be trimmed away along the outer edges of the laminated screen element (89) curved screen element frame (85), yielding a finished screen element (86) as shown at
Preferably, curved screen element frame (85) should be constructed of material that would allow adequate support for the precut screen cloth layers (92), such as carbon or stainless steel.
Also preferably, the curved screen element frame (85) should have the maximum open area possible to maximize process liquid throughput.
Also preferably, the curved screen element frame (85) should be made of material that allows precut screen cloth layers (92) to attach to it by fluidized epoxy (25), such as carbon or stainless steel.
Also preferably, the curved screen element frame (85) should be light weight, inexpensive and suitable for mass production.
Also preferably, the finished screen element (89) should retain its designed shape to facilitate installation into a support frame (98).
Also preferably, the element (89) should withstand the process environment long enough to yield lower overall operating cost.
EXAMPLE 5 Description of the Frame Forming Press
Fluidized powdered epoxy resins are applied by dipping heated metal parts into an aerated powder bed. The powdered resin coats the hot metal part, and melts. The result is a smooth, continuous plastic film encapsulating the metal part. It should be noted, however, that although a metal part may be coated with epoxy, the epoxy may or may not be cured. If the epoxy is not yet cured, certain advantages may be gained by re-melting the epoxy coat and then curing it, as described herein.
The fluidized bed (14) of
All references cited in this specification are herein incorporated by reference as though each reference was specifically and individually indicated to be incorporated by reference. The citation of any reference is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such reference by virtue of prior invention.
It will be understood that each of the elements described above, or two or more together may also useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.
Claims
1. A method for producing a laminated screen element comprising the following steps: providing a sheet of thin metal plate; providing at least one layer of screen cloth; providing epoxy; providing a frame forming press; providing a laminating press; perforating the sheet of thin metal plate to produce a screen element frame having inner edges that circumscribe the perforations, and outer edges that circumscribe the screen element frame; curving the screen element frame with the frame forming press to produce a curved screen element frame having inner edges that circumscribe the perforations, and outer edges that circumscribe the curved screen element frame; coating the curved screen element frame with epoxy, thereby producing a coated frame having inner edges that circumscribe the perforations, and outer edges that circumscribe the coated frame; placing the coated frame into the laminating press, and placing the at least one layer of screen cloth over the coated frame in said laminating press; heating the coated frame and the at least one layer of screen cloth placed over the coated frame in the laminating press, thereby producing a laminated screen element.
2. The method of claim 1, wherein the sheet of thin metal plate is flat carbon steel or flat stainless steel.
3. The method of claim 1, wherein the perforating is designed to maximize open area, provide adequate heat capacity for epoxy coating, and provide proper support for the at least one layer of screen cloth.
4. The method of claim 1, wherein the curved screen element frame is cleaned before said coating the curved screen element frame with epoxy.
5. The method of claim 4, wherein said cleaning is by dipping the curved screen element frame into a caustic bath, thereby producing a cleaned frame.
6. The method of claim 5, wherein said cleaned frame is heated to a temperature between 400° F. and 600° F., thereby producing a heated frame, before said coating the curved screen element frame with epoxy.
7. The method of claim 6, wherein said epoxy is a fluidizable powdered epoxy resin.
8. The method of claim 7, wherein said fluidizable powdered epoxy resin is fluidized, and the heated frame is passed through the fluidized powdered epoxy resin, thereby coating the curved screen element frame with epoxy and producing a coated frame.
9. The method of claim 8, wherein said at least one layer of screen cloth is pre-cut to a surface area approximating that of the curved screen element frame.
10. The method of claim 9, wherein said heating the coated frame and the at least one layer of screen cloth placed over the coated frame in the laminating press is at a temperature and for a time sufficient to allow the epoxy to be pushed through the at least one layer of screen cloth, and to cure.
11. The method of claim 10, wherein any of the at least one layer of screen cloth that extends beyond the outer edges of the coated frame is trimmed from said laminated screen element.
12. A laminated screen element comprising an epoxy-coated screen element frame and at least one layer of screen cloth, wherein the epoxy-coated screen element frame comprises an epoxy coating, a curve, and perforations such that the epoxy-coated screen element frame has inner edges that circumscribe the perforations, and outer edges that circumscribe the screen element frame, and wherein the epoxy-coated screen element frame and the at least one layer of screen cloth are bonded to one another via the epoxy coating.
13. The laminated screen element of claim 12, wherein the epoxy-coated screen element frame is of carbon steel or stainless steel.
14. The laminated screen element of claim 13, wherein the perforations maximize open area, provide adequate heat capacity for the epoxy coating, and provide proper support for the at least one layer of screen cloth.
15. The laminated screen element of claim 14, wherein the epoxy coating is a fluidizable powdered epoxy resin.
Type: Application
Filed: Aug 16, 2007
Publication Date: Apr 24, 2008
Inventors: Ari Hukki (Boynton Beach, FL), Glenn Lilie (Pearland, TX)
Application Number: 11/893,480
International Classification: B32B 3/10 (20060101); B23P 15/16 (20060101);