Classifying – separating – and assorting solids – Sifting – Elements
Reexamination Certificate
2000-08-05
2002-09-24
Nguyen, Tuan N. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
Elements
C209S401000, C209S403000, C210S489000, C210S493100, C210S498000
Reexamination Certificate
active
06454099
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to screens for vibratory separators, shale shakers, screens for classifying and/or filtering material, and such screens, in certain aspects, with one or more ridge end openings covered with or made integrally from non-flat and/or seamless material.
2. Description of Related Art
The need for solids control in drilling mud used in hydrocarbon well drilling is well known in the prior art. Drilling mud, typically a mixture of clay and water and various additives, is pumped down through a hollow drill string (pipe, drill collar, bit, etc.) into a well being drilled and exits through holes in a drillbit. The mud picks up cuttings (rock) and other solids from the well and carries them upwardly away from the bit and out of the well in a space between the well walls and the drill string. At the top of the well, the solids-laden mud is discharged over a shale shaker, a device which typically has a series of screens arranged in tiered or flat disposition with respect to each other. The prior art discloses a wide variety of vibrating screens, devices which use them, shale shakers, and screens for shale shakers. The screens catch and remove solids from the mud as the mud passes through them. If drilled solids are not removed from the mud used during the drilling operation, recirculation of the drilled solids can create weight, viscosity, and gel problems in the mud, as well as increasing wear on mud pumps and other mechanical equipment used for drilling.
In some shale shakers a fine screen cloth is used with the vibrating screen. The screen may have two or more overlying layers of screen cloth. The prior art discloses that the layers may be bonded together; and that a support, supports, or a perforated or apertured plate may be used beneath the screen or screens. The frame of the vibrating screen is resiliently suspended or mounted upon a support and is caused to vibrate by a vibrating mechanism, e.g. an unbalanced weight on a rotating shaft connected to the frame. Each screen may be vibrated by vibratory equipment to create a flow of trapped solids on top surfaces of the screen for removal and disposal of solids. The fineness or coarseness of the mesh of a screen may vary depending upon mud flow rate and the size of the solids to be removed.
Many screens used with shale shakers are flat or nearly flat (i.e. substantially two-dimensional). Other screens, due to corrugated, depressed, or raised surfaces are three-dimensional. U.S. Pat. Nos. 5,417,793; 5,417,858; and 5,417,859 disclose non-flat screens for use with shale shakers. These screens have a lower planar apertured plate with a multiplicity of spaced-apart apertures or openings therethrough. Undersides of troughs of undulating screening material are bonded to the apertured plate. Such screens present a variety of problems, deficiencies, and disadvantages, including: decreased flow area due to area occluded by solid parts of the apertured plate; necessity to either purchase relatively expensive apertured plate or provide for in-house perforating of a solid plate; plate weight increases wear on parts such as rubber screen supports or cushions and can inhibit required vibration; large plate surface area requires relatively large amount of bonding means for bonding screens to the plate; and a finished screen which is relatively heavy increases handling problems, hazards, and cost of shipping.
Vibrating screens have been employed for many years to separate particles in a wide array of industrial applications. One common application of vibrating screens is in drilling operations to separate particles suspended in drilling fluids. The screens are generally flat and are mounted generally horizontally on a vibrating mechanism or shaker that imparts either a rapidly reciprocating linear, elliptical or circular motion to the screen. Material from which particles are to be separated is poured onto a back end of the vibrating screen, usually from a pan mounted above the screen. The material generally flows toward the front end of the screen. Large particles are unable to move through the screen remaining on top of the screen and moving toward the front of the screen where they are collected. The smaller particles and fluid flows through the screen and collects in a pan beneath the screen.
A vibrating screen may be formed from one or more layers of wire mesh. Wire mesh is generally described with reference to the diameter of the wires from which it is woven, the number wires per unit length (called a mesh count) and the shape or size of the openings between wires. Wire mesh comes in various grades. “Market” grade mesh generally has wires of relative large diameter. “Mill” grade has comparatively smaller diameter wires and “bolting cloth” may have the smallest diameter wire. The type of mesh chosen depends on the application.
U.S. Pat. No. 5,417,858 discloses screen assemblies for vibrating screening machines which have screen ridge openings blocked by bent over portions of screens. The screens are on top of a plate. The screen portions are joined along a seam, e.g. by adhesive, welding, brazing or in any suitable manner. A lower most side of the screen covering portion is sealed to the plate along a joint. The thus-formed ridge opening cover is flat, does not project outwardly beyond the ridge end or beyond the plate, and requires a seam that somehow connects two bent-over screen portions. There is no teaching or suggestion in this patent of: an integral curved rounded or bulbous ridge end; a seamless cover for a ridge opening or a seamless ridge end; a non-flat or bulbous ridge end or cover for a ridge opening; of a ridge end that tapers from a ridge top down to a bottom level of screening material or of a ridge end that is not plugged but is integrally formed of screen and/or mesh material.
The related art section of each of the above-identified applications and patents is incorporated here fully by reference.
SUMMARY OF THE PRESENT INVENTION
The present invention discloses, in certain aspects, a screen assembly for a vibratory separator or shale shaker, the screen assembly having a ridge-valley series of screening material with a plurality of alternating ridges and valleys, each of the ridges with two spaced-apart ridge ends, a ridge top and a ridge bottom, and each ridge end having a portion of screening material that tapers down from its corresponding ridge's ridge top to a level of screening material at its corresponding ridge's ridge bottom. Such ridge ends may have a generally bulbous shape, a rounded shape, or any desired curved shape. In certain aspects the screening material with the ridge-valley series of screening material has an outer perimeter and an outermost edge or end of each ridge end at the level of the screening material at the ridge bottom is within the perimeter of the screening material; i.e., the ridge end is not flush with or perpendicular to a plate edge or frame side. In certain aspects the present invention discloses a screen assembly for a vibratory separator or shale shaker, the screen assembly including a ridge-valley series of screening material with of a plurality of alternating ridges and valleys of screening material, each of said ridges having two spaced-apart ridge ends, and each ridge end comprising a seamless portion of screening material. In certain aspects the present invention discloses a screen assembly for a vibratory separator, the screen assembly with a ridge-valley series of screening material with of a plurality of alternating ridges and valleys of screening material, each ridge having two spaced-apart ridge ends, each ridge having two spaced-apart bottom edges in a bottom plane, and each ridge end with a portion of screening material at a non-perpendicular angle to the bottom plane. Any ridge disclosed herein may have only one non-flat ridge end (or only one of any other ridge end disclosed herein) and may have one ridge end like any known ridge end.
The present invention discloses, in certain embodi
Adams Thomas C.
Grichar Charles N.
Largent David W.
McClung, III Guy L.
Schulte David L.
McClung Guy
Nguyen Tuan N.
Varco I/P, Inc
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