Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-03-13
2004-02-17
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S098000, C264S036100
Reexamination Certificate
active
06692599
ABSTRACT:
FIELD OF INVENTION
This invention concerns screens for use as filters in vibratory filtration equipment such as shakers that are used in the oil drilling industry for separating solids from the liquid phase of oil and water based muds retrieved from drilling operations and in particular to a method of repairing and refurbishing such screens.
BACKGROUND
Examples of filtering machines in which such screens are used are contained in UK 2237521 and UK 2229771.
One such screen is described in PCT/GB95/00411 (W095/23655).
The earlier design of screen extends the life of a screen by providing a sacrificial support cloth of woven wire below an upper woven wire cloth of harder wearing material than that of at least the surface of the wire from which the lower cloth is woven, so that wear due to rubbing and vibration during use occurs to a greater extent in the lower cloth than in the upper cloth. The specification also describes an improved design of frame across which woven wire cloths can be tensioned and bonded by adhesive, to form a sifting screen, in which the frame is proposed to be formed from glass reinforced gas blown polypropylene with elongate metal reinforcing elements or rods buried in the GRP. The improved frame construction is shown in
FIGS. 3
to
8
of the earlier specification.
It is an object of the present invention to provide an improved method of constructing such a frame and an improved frame for use as the support for layers of woven wire cloth, an improved screen formed from such a frame, and a frame which can be re-used under some circumstances.
SUMMARY OF THE INVENTION
The method of repair or refurbishment provided by the invention is applicable to a filtering screen formed from a support frame which is formed from glass reinforced plastics material, the faces of peripheral edge regions of the support frame over which woven wirecloth is overlaid and to which the cloth is bonded by heating, wherein the peripheral edge regions are formed with a plurality of closely spaced apart parallel ridges so that when the surface is heated, the crests of the ridges soften, and the woven wirecloth laid thereover and tensioned can, under an appropriate downward loading, penetrate and become embedded in the softened crests. Such a filter screen will hereinafter be referred to as a filter screen of the type described.
According to the present invention, there is provided a method of repairing or refurbishing a filter screen of the type described, wherein worn or damaged wirecloth is stripped from the surface of the polymer frame, fresh cloth is placed over the frame and tensioned as appropriate and heat is applied so as to soften the surfaces of the frame over which wirecloth is stretched, so that the latter can penetrate the softened plastics material and become embedded therein, after which the assembly is allowed to cool, the tensioning force is removed, and the wirecloth edges are trimmed back to the surrounding flange of the frame.
In a method of repair or refurbishment as aforesaid plastics material may be applied to the surface of the frame which is to receive the wirecloth before the latter is fitted thereover, to provide additional plastics material for bonding the wirecloth to the frame.
The stripped support frame may be inserted in a mould and fresh polymer material injected into the mould so as to reform on the surfaces of the frame ridges similar to those which existed when the frame was first manufactured, before the wirecloth is applied thereto.
The invention also provides a method of repair or refurbishment, wherein after removing worn or damaged wirecloth from a support frame a plastics sheet similar in size and pattern of openings to the support frame when viewed in plan is placed over the frame which is to be repaired, in alignment therewith, before or after new wirecloth is stretched thereover and before heat and pressure is applied, to provide additional plastics material to bond the new wirecloth to the frame.
The invention thus also provides a repaired or refurbished filter screen wherein worn or damaged wirecloth has been replaced by fresh wirecloth in accordance with the above methods.
A method of constructing a polymer support frame over which woven wire cloth is to be stretched and secured to form a sifting screen of the type described comprises the steps of locating in a mould tool a wire frame assembly comprising two parallel spaced apart arrays of reinforcing wires, closing the tool, injecting liquid polymer so as to wholly encapsulate the wire frame and to form an article having an open central region crisscrossed by intersecting orthogonal ribs bounded on all sides by a rigid flange, in which each of the ribs includes two parallel spaced apart wires of the said wire frame assembly, permitting the polymer to cure, and opening the tool, and removing the moulded article.
By arranging for two parallel spaced apart wires to extend through each of the ribs, one near one edge and the other neaer to the opposite edge of the rigs, each rib has the stiffness of a beam, and the resulting frame has high rigidity and resistance to bending, yet remains relatively lightweight.
Preferably the wire frame is selected so as to impart sufficient structural rigidity to the support frame as to prevent deflection thereof and consequent changes in the tension in the wire cloth when fitted thereto.
Additionally the wire frame is selected so as to impart sufficient strength to the support frame as to allow the latter to withstand shear stresses introduced as the frame is clamped into a vibratory screening machine.
Typically the wire frame is formed from high tensile straightened steel wire, bent as required, and in a preferred arrangement the wire is of 2.5 mm diameter.
A method of making a reinforcing wire frame for use in the above method of making a support frame, comprises the steps of:
equally spacing apart cut lengths of wire in a jig to form a first array,
locating thereover a second equally spaced array of cut lengths of wire at right angles to the first array,
resistance welding the wires of the two arrays at all the points of intersection so as to form a first rectilinear matrix
similarly positioning two similar arrays of similarly cut lengths of wire in a jig and resistance welding the points of intersection of the orthogonal wires so as to form a second, similar rectilinear matrix,
bending in a press break the protruding lengths of wire on at least two of the four sides of one of the rectilinear matrices, so as to bend each protruding section first in a generally upward sense and then at a point nearer to its end in a downward sense so that the end region of each protruding length extends parallel to the plane containing the matrix, but is displaced therefrom, and
and thereafter resistance welding the displaced ends of the protruding wires of the said one matrix to the protruding ends of the wires of the other matrix.
The welding may be in part effected through the intermediary of transversely extending filler wires, so that intersections are provided where welds are to be formed between parallel protruding ends of the reinforcing wires, and the filler wires facilitate the resistance welding of the parallel protruding ends.
Preferably the wire frame fabrication is assembled so that each matrix is bowed in an outward sense, opposite to the other.
During moulding it has been found that the pressure within the mould tool can distort the framework so that the outward bowing of the opposite faces of the framework can be replaced by significant inward bending—so destroying the alignment of the long rods within the upper and lower edges of the interstices of the moulded frame. To avoid this it is proposed that at least one spacer is located within the framework, so that if there is any tendency for the rod arrays to collapse inwards, the spacer will present this collapse occurring.
Preferably a plurality of spacers are located within the wire frame fabrication, each attached to one or other of the matrices so as to extend towards the other, whereby any tendency fo
Bailey Arthur Robert
Cook Gordon James
Hartnup George Charles
Hughes Andrew
Stewart Dugald
Aftergut Jeff H.
Barnes & Thornburg
Corcoran Gladys
United Wire Limited
LandOfFree
Filtering screen and support frame therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Filtering screen and support frame therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Filtering screen and support frame therefor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3280131