Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD OF MAKING A SCREEN, A SCREEN, AND A SYSTEM FOR
MAKING A SCREEN
This invention relates to a to a method of making a
screen, a screen made by the method and A system for
making a screen. The screens are more particularly, but
not exclusively, for use in separating solids from
circulating oil (mud) used in the drilling of oil and gas
wells.
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, 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 the drill bit. 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 screens
catch and remove solids from the mud as the mud passes
through them. The mud is then reused. 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 layers may be
bonded together. A support, such as 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
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caused to vibrate by a vibrating mechanism, for example,
the vibrating mechanism may comprise 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 the 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. Patents 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. The 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.
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 the
mesh count) and the shape or size of the openings between
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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" has the smallest
diameter wire. The type of mesh chosen depends on the
application. Smaller diameter wires have less surface
and thus less drag, resulting in greater flow rates.
Smaller diameter wires also result, for a given opening
size, in a larger percentage of open area over the total
area of the screen, thus allowing greater flow rates and
increased capacity. However, screens of bolting cloth
tear more easily than market or mill grade screens,
especially when used in harsh conditions such as drilling
and mining operations. The smaller diameter wires tend
to have less tensile strength and break more easily, and
the finer mesh also tends not to retain its shape well.
Most meshes suffer from what is termed "near sized
particle blinding". During vibration, wires separate
enough to allow particles of substantially the same size
or slightly larger than the openings to fall between the
wires and become lodged, thus "blinding" the openings of
the screen and reducing capacity of the screen. If a
particle becomes lodged when the wires are at their
maximum distance apart, it is almost impossible to
dislodge the particle. Sometimes, however, wires will
subsequently separate further to release the lodged
particle. Unfortunately, some wire mesh, especially
bolting cloth, is tensioned. Tensioning restricts
movement of the wires. Restricting movement assists in
holding the shape of the wire mesh, keeping the size of
the openings consistent to create a more consistent or
finer "cutting point" and reducing abrasion from wires
rubbing against each other. However, restricted movement
of the wires reduces the probability that, once a near
sized particle becomes stuck, the wires will subsequently
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separate to allow the particle to pass. Use of smaller
diameter wires, with smaller profiles, helps to reduce
blinding. With a smaller diameter wire, a particle is
less likely to become lodged midway through the opening.
Multiple layers of mesh may be used to alleviate
blinding. U.S. Patent 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. The openings in each mesh are at least
twice as wide as the diameters of the wires and the lower
mesh has openings the same size as or slightly larger
than the openings in the upper mesh. The lower mesh,
when held tightly against the upper mesh, prevents
particles from migrating far enough into an opening in
the upper mesh to be trapped. Some relative movement of
the layers also helps to dislodge particles caught in the
upper layer. The two-layer arrangement has the further
benefit of a finer "cutting point," allowing smaller
particles to be separated out. 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 most applications is the
tearing of the 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
large openings, forming on the screen a plurality of
small 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
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replacement. Unfortunately, bonding the screen to the
support panel further restricts relative movement of the
layers and the wires in each mesh layer, thus coatpounding
the problem of blinding.
Blinding and tearing of the screens 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 txade-off between capacity, longevity,
repairability and resistance to blinding of the screens.
There is a need for a supported (either non-flat or flat)
screen which is consumable, efficient and cost-effective,
yet readily and inexpensively made, easy to handle, and
relatively inexpensive to transport.
Accordingly, the present invention provides a method
for making a screen assembly for a vibratory separator,
the method comprising the steps of placing at least two
layers of screening matexial one on top of the other,
introducing glue to one of the at least two layers of
screening material for adhering at least portions of them
together, said glue introduced to one of the at least two
layers of screening material from a xoller with a
patterned surface thereon such that the amount of glue is
introduced to the at least two layers of screen~.ng
material in a pattern substantially corresponding to said
patterned surface of the roller.
Other features and steps in the method of the
30~ present invention are.set out in claims 2 to 35.
The invention also relates to a screen made by the
method and to a system for snaking a screen in accordance
with the method a.s set out in the claims.
The invention also provides a method for making a
screen, sand method comprising the step of injecting glue
5'l
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on to a first screening material in a predetermined
pattern, and in, a subsequent Qperation pressing at least
a second screening material thereon to forau a multi-
layered screen.
Other features and steps in the method of the
present invention are set out in claims 37 to 42.
The invention also relates to a screen made by the
above method and to a system fox making a screen in
accordance with the method, as set out in the claims.
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For a better understanding of the present invention,
reference will now be made, by way of example, to the
accompanying drawings, in which:
Figure 1 is a side schematic view of a first
embodiment of an apparatus for making screens in
accordance with the present invention, indicating steps
in a method of making screens in accordance the present
invention;
Figure 2 is a side schematic view of a second
embodiment of an apparatus for making screens in
accordance with the present invention, indicating steps
in a method of making screens in accordance the present
invention;
Figure 3 is an enlarged side view of an alternative
roller apparatus for use in the apparatus as shown in
Figures 1 or 2;
Figure 4A is an enlarged front view of part of a
pattern roller for apparatus as in Figure 1;
Figure 4B shows a glue bead in cross-section;
Figure 5A is an end view of a first embodiment of a
pattern roller;
Figure 5B is a side view of the roller of Figure 5A;
Figure 6A is an end view of a second embodiment of
pattern roller ;
Figure 6B is a side view of the roller of Figure 6A;
Figures 7 and 8 are side views of alternative
pattern rollers ;
Figure 9 is a top view of a screen in accordance
with the present invention;
Figure 10 is a top view of a screen in accordance
with the present invention with parts cut-away; and
Figure 11 is a side view of a pattern roller.
Figure 1 shows a system 100 according to the present
invention for making a screen 2 according to the present
invention by a method according to the present invention.
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As shown the system 100 produces a screen 2 which
includes a lower coarse mesh or screen 4, an intermediate
mesh or screen 6, and a top mesh or screen 8. Any one of
these meshes (or screens) 4, 6, 8 may be omitted.
Alternatively one or more additional mesh layers may be
added.
The coarse mesh 4 is initially wound on a roller 11
from which it is unwound and passes over a rotating
roller 13. From the roller 13 the coarse mesh moves to a
position beneath a gluing station 20 where glue in a
pattern is applied on the coarse mesh 4. In one aspect
the coarse mesh is 19 mesh made of wire with a diameter
of about 0.32cm (0.126 inches). Of course any suitable
mesh may be used.
A pattern roller 30 applies a layer of glue in a
desired pattern onto the coarse mesh 4. Glue 40 from a
reservoir/manifold 50 flows to a space forming a "pond"
of glue between a first roller 15 and a transfer roller
17. Either or both of these rollers may be a heated
roller. Alternatively, or in addition to heat from a
heated roller or rollers, hot air from an optional heater
H may be blown at the rollers) and/or at the "pond",
and/or it may heat the glue in the reservoir/manifold 50.
The transfer roller 17 rotates counter-clockwise as
viewed in Figure 1 and the first roller 15 rotates
clockwise; thus a film of glue is deposited on the outer
surface of the transfer roller 17 which film, in turn,
contacts parts of a pattern in or on an outer surface of
the pattern roller 30 which rotates clockwise as viewed
in Figure 1. The film on the pattern parts of the
pattern roller 30 is applied in the pattern onto the
coarse mesh 4 moving beneath the pattern roller 30. In
another aspect, glue is applied on top of a combination
of two, three, or more meshes prior to entering between
the rollers 61 (rather than on top of the coarse mesh
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when it comes off the roll 11). In another aspect, the
glue is applied only to the mesh from either the roll 9
or the roll 7.
An adjustable roller 21, whose tension against the
mesh is adjustable by moving the roller up/down, supports
the coarse mesh 4 with glue thereon. The coarse mesh 4
with glue thereon in a desired pattern determined by the
pattern on the pattern roller 30 advances to a pressing
station 60. The intermediate mesh 6 is fed between
rollers 61 and 62 of the pressing station 60 from a roll
7 as is the top mesh 8 from a roll 9.
Between the rollers 61, 62, the three meshes are
pressed together and the glue is pressed between all
three meshes to bond them together. Optionally, coolant
fluid from a coolant reservoir 70 is pumped with a pump
71 through one or both of the rollers 61, 62 to cool the
mesh combination passing between the rollers 61, 62. The
finished screen 2 (including all three meshes and glue)
exit from between the rollers 61, 62 . Optionally, a fan
or fans and/or air movers or other cooling devices) 74
may be used to cool the screen 2.
The various meshes for the screen 2 may be fed
through the system 100 by hand and the finished screen 2
may be pulled by hand from between the rollers 61, 62
and/or one or more of the rollers in the system may be a
driven roller, rotated by a motor appropriately connected
to the roller for rotating it with desired speed and
torque (for example, but not limited to, motors M driving
rollers 61, 62). A suitable gearing system may be used
interconnecting the motor and roller. In certain aspects
one or more of the rolls and/or rollers) are drive rolls
and/or rollers which are rotated so that the mesh is
moved through the system at a speed of between 6.1 and
18.3 metres per minute (twenty and sixty feet per
minute). In other particular aspects, the speed is about
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3.05 metres per second (ten feet per minute). Any or all
of the rolls and/or rollers may be coated with
polytetrafluorethylene and/or plastic ceramic, or cermet
material. By adjusting roll and/or roller rotation
speed, e.g. with suitable brake and/or drag apparatus,
tension can be maintained on the mesh or meshes to keep
it or them sufficiently taut while moving through the
system. Motor Systems M represent (schematically)
rotating systems for the rolls and/or rollers. Any,
some, or all of the systems M may be omitted.
Optionally, the finished screen 2 may be wound onto
a drum or roller 79.
Figure 2 shows a system 200 like the system 100 of
Figure 1 with like parts indicated by like reference
numerals in the one hundred series. The system 200 does
not have the gluing station 20; but has a gluing
apparatus 120 for applying a desired pattern of glue to
the coarse mesh 104 that includes a glue
reservoir/manifold 125 from which glue is supplied to a
plurality of glue nozzles 126 (three shown). According
to the present invention, a sufficient number of nozzles
are used sufficiently spaced-apart and positioned to
create a desired glue pattern on the coarse mesh 104.
The resulting screen 102 is like the screen 2 and
optional parts of the system 100 may be used in the
system 200. Other features of the system of Figure 2 may
be included in the system 200.
In other embodiments, a fine mesh is unwound from
the roll 111 and fine, finer, or coarse mesh or meshes
are unwound from the rolls 107 and 109.
Figure 3 shows one embodiment for a pressing station
67, like the pressing station 60, with rollers 68 and 69.
A spring 66 biased between a support member 55 and a
roller shaft mount 64 yieldingly urges the roller 68
against a multi-mesh combination 5.
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The meshes 4, 6, and 8 or 104, 106 and 108 may be
any mesh or screen disclosed herein. The glue 40, 140
may be any suitable glue, including, but not limited to,
polyethylene glues and hot melt glues at a suitable
temperature for flowing to and from a reservoir/manifold
and onto a mesh, for example, but not limited to at about
121°C (250°F), between 121°C (250°F) and
204°C (400°F),
or at other suitable temperatures for the particular glue
being used.
Figures 5A and 5B show a pattern roller 80 useful as
the pattern roller 30 of the system 100 in Figure 1.
Raised portions 81 on an exterior surface 82 of the
pattern roller 80 form the desired pattern for applying
glue to a mesh. The roller 80 is solid with end shafts
83 for mounting to suitable supports for rotation. Any
pattern roller disclosed herein may be solid with end
shafts like the end shafts 83. Alternatively, recesses,
holes, or indentations in one or both ends of the roller
may be used to mount the roller to an appropriate shaft,
mount, or support. Any of the pattern rollers disclosed
herein, and any other roller used in systems according to
the present invention, including, but not limited to
systems as in Figures 1 to 3, may be coated with
polytetrafluoroethylene.
Figures 6A and 6B show a roller 80a like the roller
80, but with a bore 84 through the roller from one end to
the other. Such a bored roller or "sleeve" may be
installed on a common shaft or roller positioned as is
the pattern roller 30 in Figure 81. With a plurality of
such sleeves with different patterns thereon, changing
the system to produce a different glue pattern is greatly
facilitated. Also, a worn or degraded sleeve is easily
removed and replaced. Such sleeves also facilitate
clean-up of the system.
It is within the scope of this invention for the
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roller 80 (and any roller according to the present
invention) to include only the raised portions 81 with no
body or structure therebeneath nor between pattern
components so that the portions 81 and ends of the roller
not only define a pattern but also form a perforated tube
or sleeve. Such a tube or sleeve may be made from a
piece of solid stock by machining and/or laser cutting.
Any pattern for a roller described herein may be formed
by grooves or recesses in a roller surface rather than by
raised portions on a roller surface.
Figures 7 and 8 present pattern rollers with
patterns or raised portions different from that of the
patterns of the rollers of Figures 5B and 6B. The
rollers of Figures 7 and 8 may have any of the options of
the rollers of Figures 5B and 6B (including, but not
limited to end shafts 83 and bore 84, or a perforated
tube structure). A roller 85 in Figure 7 has raised
lines 86 that define a pattern across the roller. A
roller 87 in Figure 8 has raised portions 88 and 89 that
define a pattern across the roller.
Figure 9 shows a screen 90 produced with a system
like the system 100 of Figure 1, using a roller like the
roller 85 of Figure 7. Figure 10 shows a screen 92 with
a glue layer 93 according to the present invention
produced with a system like the system 100 of Figure 1
using a roller like the roller 87 of Figure 8. The
screen 92 is like the screens disclosed in U.S. Patent
4,575,421 (incorporated fully herein for all purposes),
but made with a system according to the present invention
and by a method according to the present invention. The
screen 92 has three layers of mesh or screening material
56, 57 and 58 and a lower perforated plate 54. Any of
the layers of mesh may be omitted and the glue 93 may be
applied on top of any of the layers. In one aspect the
plate 54 is omitted. In one aspect the plate 54 is
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deleted and any other support is used. The screen 90 is
like a screen disclosed in U.S. Patents Des. 366,040
(incorporated fully herein for all purposes) and U.S.
5,971,159 (incorporated fully herein for all purposes).
An optional frame 90a is used around the screen 90.
Figure 4A shows an enlargement of part of a pattern
roller 96 which is similar to the roller 80 of Figure 5B,
but which has valleys, recesses or grooves 97 in raised
portions 98 of the roller. Glue is received within the
grooves 97 so that a relatively higher or thicker level
or bead of glue is applied to a mesh by the roller as
compared to the layer or film of glue applied by a roller
like the roller 80. Any raised portion of any roller
disclosed herein may include such a valley recess, or
groove to increase the amount of glue applied on a mesh .
In one aspect the grooves 97 are between about 0.8mm
(one-thirtysecond inch) to about l.6mm (one-sixteenth
inch) deep and in one particular aspect are about l.6mm
(one-sixteenth of an inch) deep. Viewed on end in cross-
section the grooves may be V or U shaped, square-shaped,
trapezoidal, or semicircular. Optionally the roller 96
has a bore through it (like the bore 84 of Figure 6B) and
holes are provided through the roller so that the
roller's interior is in fluid communication with the
grooves via the holes and glue can be flowed or pumped
from the roller interior to the grooves to provide the
glue for the pattern to be applied to the mesh.
Alternatively, in embodiments in which the grooves are
not used, holes are provided through the roller through
the raised portions of a patterned surface. Figure 4B
shows a cross-section of one glue bead's B profile
applied to a screen S with a pattern roller having
grooves in raised portions of the pattern. The distance
"a" is, in this embodiment, about 0.16cm (one-sixteenth
of an inch). Preferably the distance "b" is as thin as
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possible. It is within the scope of this invention to
provide partial grooves or recesses in only a portion of
the raised portions of a pattern rollers surface, e.g.,
but not limited to, only to the outer edges or only to
the center, only to the edges and center, or only to
certain spaced-apart portions on the roller to create a
series of strips on the screen.
Fig. 11 shows a pattern roller 100 which has raised
pattern areas 101 for forming a series of strips of glue
on a screen or mesh or combination of layers thereof,
including, but not limited to, a series of strips like
the strips shown above. It is within the scope of this
invention to use an appropriately configured pattern
roller to form any series of strips (like any series of
strips disclosed herein for a screen or panel) on a
screen or mesh with glue as described above. It is also
within the scope of this invention for the areas or parts
of them to have grooves around their entire surface
(grooves or recesses as described above) or in part of
the surfaces. Such a roller with or without grooves may
also have holes as described above for introducing glue
from the interior of the roller to the grooves and/or to
the raised areas. By using a roller like the roller 100
with only the two outer raised portions 101, two spaced-
apart sides can be created on screen or mesh. By turning
a piece of such screen or mesh ninety degrees and feeding
it again through a gluing system two additional spaced-
apart sides are created so that all four sides of the
screen or mesh are glued.
