Classifying – separating – and assorting solids – Sifting – Elements
Reexamination Certificate
2000-06-28
2001-06-05
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
Elements
C209S403000, C209S405000, C209S397000, C209S399000
Reexamination Certificate
active
06241098
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention is directed to filtering and classifying material with vibratory separators; to screens for such separators including, but not limited to, shale shakers; to such apparatuses useful for both dewatering and classification; and methods of screen tensioning, repair and assembly.
2. Description of Related Art
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 or three-dimensional and are mounted generally horizontally on a vibrating mechanism or shaker that imparts either a rapidly reciprocating linear, elliptical and/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 screen and/or wire mesh which are generally described with reference to the diameter of the wires from which they are woven, the number wires per unit length (called a mesh count) and the shape or size of the openings between wires. The type of mesh chosen depends on the application.
Some screens use wire mesh that is tensioned. Tensioning restricts movement of the wires and assists in holding the shape of the wire mesh, keeping the size of the openings consistent. A variety of problems are associated with correct tensioning of screens.
Multiple layers of mesh may be used to alleviate blinding. U.S. Pat. No. 4,033,865, describes layering two meshes in a manner that results in at least one wire of the lower of the two meshes bisecting each opening in the upper mesh. A third “backing” layer of relatively coarse, mill grade mesh is often used to carry most of the load on the screen and to increase the tensile strength of the screen.
Another problem faced in many applications is the tearing of a screen. The problem can be especially acute in heavy duty applications such as drilling and mining. A torn screen must be replaced or repaired. To facilitate repair, the screen layers are bonded to a rigid or semi-rigid support panel that has a pattern of openings, forming on the screen a plurality of cells of wire mesh. When a tear occurs in the screen, the mesh remaining within the cell in which the tear occurred is cut out and the cell is plugged. The capacity of the screen is diminished but its life is extended. Typically, several cells of a screen can be repaired before its capacity drops far enough to require replacement. Unfortunately, bonding the screen all around the edges defining openings through the support panel further restricts relative movement of the layers and the wires in each mesh layer.
Blinding and tearing of a screen reduce the capacity of the screen continually through its useful life. Although capacity can be increased by increasing the total area the screens, the size of the screen is limited in most applications, such as on drilling rigs, especially those on offshore platforms. There has thus been generally a trade-off between capacity, longevity, repairability and resistance to blinding of the screens.
There has long been a need, recognized by the present inventors, for a vibratory separator screen which does not require openings defined by edges or members all of which are in the same plane.
SUMMARY OF THE PRESENT INVENTION
A screen panel has, in certain embodiments, a panel with a plurality of spaced-apart holes therethrough, a plurality of spaced-apart strips on the panel and defined by the plurality of holes, each strips in a plane, a plurality of crossmembers each of which has two ends, one end connected to one of the strips and the other end connected to another strip, the crossmembers in a plane different from that of the plane or planes of the strips. In one aspect the panel has screening material thereon.
A panel for a screen for a vibratory shaker, according to certain aspects of the present invention, has a body with a plurality of spaced-apart holes therethrough, a plurality of strips spaced-apart thereon and defined by the plurality of holes, the strips in a first plane, and a plurality of crossmembers each of which has two ends, one end connected to one of the strips and the other end connected to another strip, the crossmembers in a plane beneath or above the first plane.
A support strip system for a panel of a screen used in a vibratory shaker, according to the present invention, has at least two strips defined by spaced-apart holes through a panel, the strips in a first plane, and at least one crossmember, the crossmember having two ends, one end connected to one of the strips and the other end connected to the other strip.
The present invention, in certain embodiments, discloses a screen for a vibratory shaker for screening material flowing thereto, the screen having a panel with holes therethrough in a first plane, the holes defining a plurality of strips or ribs in the first plane extending generally in one direction, and a plurality of crossmembers linking the strips or ribs, the crossmembers substantially in another plane with ends extending up or down to the first plane of the ribs or strips.
In one aspect screening material (any known screen or mesh in any known number of layers connected to and/or adhered to and/or bonded and/or glued and/or welded together in any known way, or not connected together) is positioned on a panel according to the present invention either above or below (or both) the crossmembers. In certain aspects, the screening material is connected to, adhered to, welded to, glued to, and/or bonded to (all collectively herein henceforth referred to as “connected to”) the ribs or strips only, or only to a portion or each rib and/or each strip. In another aspect, the screening material is connected to the strips or ribs and to the crossmembers. In another aspect the screening material is connected to only select ones of the strips or ribs and/or to only select ones of the crossmembers. In another aspect the screening material is connected to only the crossmembers. In embodiments disclosed herein with “screening material the screening material represents, inter alia, any screening material described above, including but not limited to, a single layer or multiple layers of such material.
In certain embodiments of the present invention screening material is positioned on only one side of a panel, e.g. the top side or the bottom side. In other aspects, there is screening material on the top side and on the bottom side—either side of which or both which may be connected to the panel. In those embodiments in which the screening material is not connected in such a way as to provide connection to both strips/ribs and crossmembers, the connection is sufficient (whether to strips/ribs only or to crossmembers only) to provide desired tensioning inn the screening material.
In certain aspects a screen according to the present invention is a three-dimensional type screen with a panel's first plane and/or screening material having, as viewed from the end, a corrugated or undulating shape defining a plurality of interspersed hills and valleys. It is also within the scope of this invention for the first plane of the panel to be substantially flat and for screening material thereon to be corrugated or undulating.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. There are, of course, additional aspects of the invention described below
McClung, III Guy L.
Schulte David L.
McClung Guy
Miller Jonathan R.
Tubo Scope I/P, Inc.
Walsh Donald P.
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