Note: Descriptions are shown in the official language in which they were submitted.
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Title: Screens, a method of making screens and
apparatus for making screens
DESCRIPTION
This invention relates to screens, a method of
making screens and apparatus for making screens.
Screens comprised of elongate straight wires or
rods, usually of wedge section, held in parallel
relation at predetermined spacings are well known in
the form of gratings having parallel opposite sides
bounded by edge-most said wires or rods and opposite
ends at which ends of all constituent wires or rods may
be free or joined by suitable wire-end-locating
boundary parts. Such gratings can readily form flat
rectangular screens beds, and can make up
non-rectangular beds, by cutting from a rectangular
grating or fabricated using appropriate different
lengths of constituent wire or rod. Arcuate, even
cylindrical screens are also known made up from
; rectangular grating that is bent, usually rolled, to
impose a curvature about an axis at right angles to the
lengths of the parallel constituent rods or wires. If
spaced locaters for the grating can also be bent
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without damage to their attachment to the rods or bars,
curved gratings could be made with those rods or bars
parallel with the axis of curvature.
It is an object of this invention to provide a
novel and advantageous screen structure that is capable
of other applications.
According to this invention, a screen structure
such as eg. disclosed in DE-A-2633372, and having a
bas~c shape curved about an axis comprises a plurality
of coaxial curved elements for which screening spacings
are at progressively increasing radial distances from
said axis up to a boundary element also curved about
said axis, and locating means for holding said elements
relative to one another at said spacings said screen
1~ structure being 'formed flat for up to one turn about
that axis and a three-di :lensional
screen structure is formed from said structure by
reshaping into a part conical or conical or part
helical or helical screen.
In applying this invention we find that
particular advantages arise from a basic screen
structure that is flat and comprises either concentric
rings of rod or wire at prescribed spacings determined
by the cross-section of constituent rod or wire and
diameters of the rings. Such a basic structure will
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normally have radially extending locaters or locating
means ~ssoci~ted therewith. For conce c ~ ne
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of such radial locaters could serve to join ends of
lengths of rod or wire forming the rings, or such
joints may be staggered to distribute them amongst more
than one radial locater.
From such basic circular screen structures, it is
further proposed herein that other actual screens or
gratings be made, for example conical by cutting along
one radius, or cutting out a sector, and rolling up
into the desired conical shape, which it is to be noted
can readily have its constituent turns or rod or wire
partially superposed. Self-evidently, basic elements
hereof need not be of full circular form when flat.
Another possibility that arises is for making
helical screens or gratings, which for one full part
turn of effective internal diameter reduction dependent
on pitch (or a part turn of less diameter reduction),
could be flat annular said basic screen structure cut
as aforesaid and opened up into a radical helical
ribber, with spacing of its constituent rod or wire
maintained, by spacing its end along the said axis and
further turns or part turns can be added by end-to-end
connecting such opened-up basic elements or parts
thereof, conveniently at radial locaters. It is,
however, possible to form all required successive turns
i 25 of such helical, radial-ribbon, screen or grating on a
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continuous basis, with a concentric ring construction.
Hitherto, of course, for prior screens using
wedge-section rods or wires, it has been customary for
their relatively broad and narrow edges to lie in
opposite faces of the resulting screens or grating i.e.
with the centre lines of a symmetrical wedge section
oriented always perpendicular to the plane of the
screen. The same considerations apply to basic screen
structures hereof, i.e. flat circular/annular elements,
when used directly as screens or gratings, say in a
circular section passage or as a circular framed bed.
Moreover, for either or both of the conical and
helical screens gratings mentioned above, it is further
pointed out that canting of such screen-section
relative to prior practice might be useful in order to
achieve whatever final sectional orientation is
desired, specifically including at right angles to
the surface of the resulting structure.
The above is concerned with screens comprised of
curved rod or wire, or other elongate (filamentary)
material which are at progressively increasing radial
distances from an axis up to a boundary rod or wire
also curved about said axis. A flat circular screen
element is described, having spaced concentric rings.
It is also specifically envisaged that sectoral parts
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thereof, whether cut from complete flat circular or
annular elements or formed ab initio only as sectors,
can be formed up to conical shape by rolling
operations. Further, a helical formation is envisaged
with each constituent wire or rod, etc., forming an
individual helical spiral, i.e. generally in
ribbon-like array.
Such screening elements, being novel in
themselves, some convenient way is required for their
manufacture, and it is an aim of another aspect of this
invention so to provide.
According tc another aspect of the invention, a
means for forming a screen structure having
a basic shape curved about an axis comprisinq a
plurality of coaxially curved elements for which
screening spacings are at progressively increasing
radial distances from that axis up to a boundary
element also curved about said axis, said mea~s
comprising a locating table or template grooved to
match the intended consecutively radially spaced
location of constituent elements, means to feed such
elements into such grooving of the table or template
means for securing supports or locaters to screen
elements on the table or template, and means serving to
impart requisite relative movement between such table
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or template and such elements and where said basic
shape is formed flat for upto one turn about that axis
and a 3-dimensional structure is formed by reshaping.
The use of a grooved table or template is
particularly effective in forming a master to which
produced radial screen elements must perforce comply
within the tolerance of its grooves to the engaged rod
or wire, etc., which can be very close. Moreover,
such table need not itself be expensively fabricated
from tool steel for maximum life, indeed is preferably
not, say being of brass or even plastics material cast
or moulded to shape from a negative formation. It is
even possible for the latter to be itself an
intermediate, if desired a "one-trip" intermediate~
made from a true master used only for casting/moulding
operations. Such a true master is readily made these
days, whether by machining, etching or eroding, or
combinations thereof, some original or softer readily
worked material from which the durable master is made
and then serves in making replicas for itself as well
as intermediate masters. We do not, however, rule out
any method of making a grooved table that is
satisfactory in view of actual tolerances on stock rod
or wire, etc., and desired tolerances for spacings
thereof in the ultimate screen.
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When using wedge-section rod or wire, etc., the
grooving of the table or template may match that wedge
section from its narrow end, i.e. be of V-shape, or may
accommodate the section from its wide end, i.e. be of
right-angled channel-shape.
Such tables or templates, whether of full
circular or part-circular, i.e. sectoral or segmental,
shape are readily associated with means for securing
radial supports or locaters to screen elements made
thereon, for example using a radial beam extending from
the axis of the table or template, which beam is
readily adapted to perform sequential welding or other
attachment/forming of such radial supports/locaters,
whether by electrical resistance welding or other
processes suitable for metal, or by heating, solvent,
adhesive or other welding or joining of other materials
sucb as plastics. Such beam may be rotatable about
said axis, or the table or template may be so rotatable
relative to the beam.
We find that wire or rod, etc., can be readily
fed onto the grooving of the table, as a plurality
thereof, one per concentric groove. Plural feeding
can be done using conical roller means to get the
required differentials of feed rates, preferably using
grooved roller means for accurate spacing purposes, and
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whether as a single such roller or as a nip between two
such rollers. It is preferred for wire or rod etc., to
have its end or ends suitably formed, typically simply
bent into curvature of the grooving at first entry
thereto.
An alternative is, of course, for the wire or
rod, etc., to be gripped in the grooving of the table
or template, say by clamping at or near entry ends, and
for the table or template to draw off such wire or
rod, etc., by its own driven rotation.
According to another aspect of the invention a
method of forming a screen structure having a basic
shape curved about an axis and comprised of a plurality
of coaxially curved elements for which screening
spacing are at progressively increasing radial
distances from that axis up to a boundary element also
curved about said axis, co~rising introducing
said plural elements into a substantially flat table or
template grooved to match the intended consecutively
radially spaced location of constituent elements,
securing supports or locators to the screen elements to
maintain said spacings, and imparting requisite
relative movement between such table or template and
such elements to form said basic shape flat for up to
~5 one turn about that axis and then forming a
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3-dimensional structure by reshaping into a part
conical or conical or part helical or helical screen.
The above method and means are intended as
examples of how the afore-described screens could be
made and not to be taken as limiting the manufacturing
method/apparatus. There is described below by way of
example a further alternative apparatus which can be
used for making the aforesaid screens.
According to another aspect of the invention
there is provided apparatus defining a grooved locating
template for use in forming a screen structure having a
basic shape curved about an axis and comprised of a
plurality of coaxial curved elements, for which
screening spaces are at progressively increasing radial
distances from an axis up to a boundary element also
curved about said axis, the apparatus comprising a
plurality of spaced radial grooved guide members for
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receiving the aforesaid elements and carried in a frame
and the grooves define channels at progessively
increasing radial distance for said ele~ents, and
wherein a plurality of spaced radial location members
S are provided for retaining said elements in the grooves
until locaters are fixed to the elements, the radial
guide members bein~ grooved to match the intended
consecutively radially spaced location of the
constituent elements and the screen structurebeing formed
flat for up to one turn about that axis priorto
for~ing a 3-di~ensional structure by res~a?ing,
These guide members and the location members are
preferably positioned in pairs one above the other with
the open side of the grooves facing the (preferably
ungrooved) location member, with the pairs of members
secured together by fixing means. Conveniently, the
location members are carried on arcuate members forming
an integral frame which are secured to the arcuate
members of the guide members.
By the above described apparatus, wires can be
positioned in concentric relationshiP for full or
part circular arrangements. Any welding required to
fix the wires together can be carried out between the
radiating segments. The use of this apparatus removes
any limitation of the size in which radial curved
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panels can be produced compared with say a grooved
locating table.
~ he above described apparatus may be utilised in
several ways in the cbnstruction of a screen structure.
Wires may be placed in the grooves by hand and the
locating members secured in position to hold the wires.
This may be done by threading the wires into the
grooves from one end with the locating members already
in position. Alternatively, the wires may be laid
over the open grooves, and the locating members secured
in position as a whole, or sequentially when location
members are discrete components, starting either from
one end, the centre or any other convenient point with
the wires being bent as necessary.
Alternatively, an automatic/mechanical loading
arrangement may be employed with say ends of wires
being located in a radial beam pivotable about the axis
of the arcuate template, and pulled around the arc of
the template with the locating members being secured in
place to constrain the passage of the wires to the
desired arcuate configuration.
Specific implementation of particular
embodiments and aspect of this invention will now be
described hereinafter by way of example only, with
2~ reference to the accompanying diagrammatiC drawings, in
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which:-
Figure 1 shows a flat circular annular basic
screen structure 10 comprised of concentric rings Rl -
Rn;
Figure 2 is a fragmental sectional view;
Figure 3 shows a conical screen or grating;
Figure 4 shows a helical screen or grating;
Figure 5 is a plan view including a circular
table or template 70;
Figures 6 and 7 are alternative partial sections
of table or template grooving;
Figure 8 shows feed rollers 80A, 80B;
Figure 9 is a plan view of another embodiment of
apparatus for forming curved screens;
Figure 10 is a front view of Figure 9;
Figure 11 is a section on XX of Figure 10; and
Figure 12 is an enlarged end view of a radial
member.
In Figure 1, the basic flat circular annular
screen structure 10 has its rings Rl - Rn successively
spaced at substantially equal radial spacings X.
Radially extending locaters are indicated at 12.
- The rings Rl - Rn are indicated as being of
customary wedge-section, see Figure 2,and will normally
be of steel, and the locaters 12 may be of any suitable
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material and attachment, for example of metal readily
welded, soldered or brazed into place, ideally entering
the spaces X past broader base parts B of the
wedge-section constituent rod or wire, or simply of
welding/soldering metal, or of plastics material either
moulded for snap-fitting onto the base 8 or partially
flowed into their final location by heat, solvent,
ultrasonic or other attaching process.
The basic screen elements of Figure 1 can
obviously be used directly in circular cavities or
holders, and their constituent wire or rod bases B for
wedge-section can, as indicated in Figure 2, be
effectively flush with one side of the screen element
10, 20.
However, if such basic elements are cut radially,
they can be rolled up into a conical shape, see Figure
4, which omits the locaters 12 for clarity, but same
will normally run up and down on inside or outside of
the illustrated frusto-conical shape 40. It will be
appreciated that joining up the wire or rod ends formed
by the radial cutting operation is readily achievable
at the position of a said locater 12, 12', preferably
one omitted from the original flat circular element 10,
20.
It will further be appreciated that sectors only
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of a basic circular element 10, 20 can be bent up to
form cones, or parts of cones, of different diameter
and side gradient. Indeed, basic elements hereof need
only be of part-circular form, at least when formed
from pluralities of rods or wires as is inevitably the
case for the consecutive ring structure 10 of Figure 3.
Moreover, displacement of ends of such a radially
cut basic screen element 10, 20 can result in up to a
full turn of a helical arrangement such as shown in
multi-turn form at 50 in Figure 4 bounded at dashed
lines 52, 54 say within a tube about another tube or
shaft. However, the further possibility presents
itself of making a multi-turn helical screen
structure as shown in Figure 4 in a single operation
wherein constituent wires are fed in, as a ribbon-like
array, and with a desired offset of its ends through
its production,
The elements hereof are readily made in various
ways~ one of which involves the use of a table grooved
to correspond to the intended final curvature(s) and
into which plural wires are fed or drawn.
Self-evidently there will be suitable means for
imparting relative movement between a circular or
sectoral table as aforesaid and the rod/wire or
rods/wires to constitute the desired screen element.
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Referring now to the drawings of Figures 5 to 8
there is described with reference thereto a method of
forming curved screens. A circular table or template
is shown with concentric grooves Gl - Gn about its
axis 72 and on one side thereof. For wedge-section
rod or wire, etc., those grooves may be of ~-section to
match to and accurately locate the narrow ends of the
wedge-section, see Figure 7, or they may be of
right-angled channel-section to match to and accurately
locate the wide ends of the wedge-section, see Figure
~. It is, in fact, envisaged that tables or templates
be separable into constituent segments or sectors, say
at quadrants 70A-70D as indicated.
For a full circular concentrically grooved table
or template, or for segmental or sectoral tables or
templates with concentric grooving, there is a
requirement to feed in plural wire or rod, etc., stoc~
as indicated purely diagrammatically at Sl - Sn of
Figure 1. A suitable plural feed arrangement uses
conical roller means to get the required differential
feed rates, see Figure 9 showing a pair of conical
rollers 80A, 80B with a nip along common generator
lines, also preferably with shallow locating grooving
at least at the roller (80B) taking the wider end of
the envisaged wedge-section stock material. It will
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be evident that other such locating grooving of the
roller means could be used if preferred.
As shown in Figure 5, the plural stock S is shown
straight at entry to the grooving Gl which suits an
arrangement where that stock is gripped into the
grooving at its entry thereto and the table or template
70 is rotated about its axis 72 to draw in and form
that stock to the desired configuration of successive
radial spacings of a basic element of flat
circular/annular or part circular/annular form. It
will be evident that, for a sector or segment only of
the table or template 70, such in-feed can be at a
level aligning reasonably accurately with the
grooving. However, for a full circular table such
stock entry is best done at a suitable angle onto the
table or template 70 and its grooving (not shown),
typically via a radial placement roller and using a
stock end radial clamp that rotates with the table or
template 70. For an alternative stock feed and
forming arrangement where only the stock feed roller
means 80A, 80B is driven, no such radial clamp would
not be required, though further rollers similar to the
. placement roller might usefully be provided at radial
spacings round the table or template 70.
At least for feeding stock into grooving of a
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stationary table, that is facilitated if the stock has
some curve-preformation, at least for first end-entry
into the grooving. Such preforming does not, of
course, have to be accurate relative to the curvature
of the grooving, just somewhere near enough to ease
handling. With pressure from above and below at the
stock feed rollers 80A, 80B, preformation curving at
right-angles to the joint contact nip can be prior to
each rollers without the latter acting to change it.
Suitable guides could thus be used at or before entry
to the feed rollers. Alternatively, if the stock is
in reel form, it may be enough simply to rely on its
reel-imposed curvature, especially where same is
achievable by partially relieving such curvature.
Radial supports as permanent locaters for the
flat arcuate/annular or circular configuration formed
on the grooved table or template 70 are shown emplaced,
see 16 in Figure 5, by a forming station in a beam 18
past which the stock wire or rod, etc., passes in or
with the table or template 70. The beam 18 may also be associated
with we~din~ apparatus.
Where screen elements or sectors or segments or
radially-cut circles or annuli are roller to form
cones, the wires or rods, etc., will be joined or
rejoined at then-abutting ends. If necessary or
desirable to get wedge-sections oriented with their
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broad ends coplanar with a cone operator, i.e lying
flat in the surface of an imaginary internal cone
surface, the stock material may be canted relative to
what is shown in Figures 6 and 7, say by corresponding
inclination of the bases of the grooves of Figure 7.
A related relative twist of the stock as fed may be
achieved in the feed rollers or in guides, usually then
prior thereto, perhaps combined with any curve inducing
guide means.
Finally, we advert to continuous production of
multi-turn helical screen structures, which can readily
be achieved using a sectoral or segmental table 70 by
taking exiting product down past a guide inclined
according to required pitch. As for conical screen
structures, canting of constituent stock material
section may be employed.
Referring now to Figures 9 to 12 there is shown
an alternative embodiment of apparatus for forming
curved wire screens, such as the afore described
screens. It comprises a plurality of spaced radial
grooved guide members 101, seventeen in the
illustration, for receiving the wires or rods making
up the screen. In the enlargement of Figure 12 the
grooves are shown as ~-shaped - being particularly
suited to receiving wedge wire. Alternatively, the
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grooves may have right-angled corners to receive the
bases of said wedge wire.
The radial members 101 are located at opposite
ends on respective arcuate members 103, 105. As
illustrated these members are part circular and the
apparatus is such as to be particularly suited to
making part circular or annular curved screens. The
angle of arc is chosen for the particular application,
that illustrated being but an example. A complete
annulus is an alternative. As shown the member 103 and
105 are concentric with one another.
The apparatus further comprises a plurality of
spaced radial location members 107, preferably
ungrooved as illustrated, and used to hold wires in
place. The guide members 101 and the location members
are located in pairs one above the other as illustrated
with the open side of the grooves facing the clamping
(flat) edge of the location member. The location
members are similarly secured at opposite ends to
arcuate members 109, 111. Aligned bores in the
arcuate members 103, 105, 109, 111 serve to secure the
guide members and location members together to locate
therebetween the wires forming the screen.
Alternatively, each location member may be
provided with means for fixing them individually to the
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arcuate members of the guide members.
With each of the guide members having the same
groove configuration, the desired curved wire screen
can be made. For example, individual wires can be
positioned in the grooves to form concentric wires.
Radial locaters are then secured to the concentric
wires, say by welding to form the desired length of
part circular screen, or even an annular screen, by
making up in sections and securing individual sections
together endwise, or using the jig to form sequential
arcuate sections from continuous lengths of wires. A
spiral wire pattern could be provided on the jig if so
desired.
The advantage of the described jig is that larger
sizes of screen can be produced compared with that
which is practical with the aforesdescribed circular
table. The jig is particularly suitable for screens
having an outer minimum radius of at least 0.5m and
preferably of the order of 1 metre or greater.
The wires may be fed into the grooves from one
end i.e. with the guide members and locaters in
position, or the wires may be laid into the grooves,
slightly curved, and the location member placed in
position to hold the wires whilst the locaters are
secured to the wires.
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