Note: Descriptions are shown in the official language in which they were submitted.
10558~3
The present invention relates to screening apparatus,
particularly vibratory screening apparatus employing
screens of flexible non-metallic material tensioned and
supported from beneath to present a cambered screening surface
or deck.
One of the problems encountered in the use of such
screening apparatus is known as the "trampolining effect"
which causes the screen to flap against its supports giving
rise to unnecessary wear and damage and also to the risk of
particles or lumps of the material being screened being pro-
pelled with considerable force off the screening deck.
It is an object of the present invention to
overcome this problem and to this end the screening surface
oE the apparatus is made up Oe one or more apertured screen
plates of flexible non-metallic material having projecting
from the undersurface thereof at intervals along the length
of the or each screen plate, a plurality of attachment bars
extending in the direction o~ the width of the or each screen
plate, and the support structure for the plate or plates com-
2~ prises a plurality of spaced support bars provided at inter-
vals along their length corresponding to the intervals of the
attachment bars running transversely of the attachment bars and
of the or each screen plate with slots of a shape to receive
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the attachment bars of the screen plate or plates. The
¦ cambering of the screen surface is achieved by reason
; ~ of the support bars having diferent haights across the
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width of the screen so that when the screen is attached
- to the support bars it has the desired camber.
Preferably the screening surface is made up o an
. assembly of pre-formed modules the edges oE which are
~ shaped to fit together and/or to provide cavities into
; which a synthetic plastics material can be moulded to
; serve, when set, to lock the individual modules together
to form a unitary screen.
The attachment bars may have a cross-sectional
shape such as to simply rest in the slots in the
support bars of the support structure or such as to
interfit in locking manner in such slots.
Whero the circumstances of use are such as to
require additional strength in the screening surface
reinforcement rods or wires may be moulded into the
material of the screen plates parallel to the support bars.
The screening surface may be tensioned by means of
....
tensioning wires or rods extending through the material
of the screen plates parallel to and above the level of
2Q the attachment bars at least at opposite ends o such bars.
Convenien~ly, where reinorcement rods or wires are also
used the latter may serve to locate the tensioning wires
; between opposite ends during moulding of the screening plate
or plates so that the tensioning wires extend wholly in the
, material of the plate or plates along their entire length.
- Instead of the tensioning rods or wires and/or the'''
reinforcing rods or wires being moulded directly into
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~SS~93
the material of the plate or plates they may pass through bores extending
through the material of the plate. The bores are preferably provided by
moulding thin walled tubes into the material of the plates, the rods or wires
being inserted after formation of the screening surface.
The tensioning and/or reinforcing wires or rods may serve to hold
individual plates or modules in assembled relation with others to form the
screening surface.
~; The various features and advantages of the invention will be appar-
ent from the following description of embodiments thereof taken in conJunc-
tion with the accompanying drawings of which:-
Figure 1 is an isometric view of part of a screen plate and support
bar according to the invention prior to attachment of the one to the other,
Fieure 2 is a section of por-tion of a screen plate illustrating an
alternative way of providing the attachment bars,
Figure 3 is a section of a portion of a screen plate illustrating
'~ t'ne use of crimped reinforcing wires serving to locate tensioning rods, and
Figure 4 is a section similar to that of Figure 3 illustrating the
use of a thin w~lled tube to form bores for the tensioning rods.
Referrine to Figure 1, the screen plate 1 is a generally flat plate
of flexible synthetic plastics material having a pattern of sizing apertures
2 each extending through the thickness of the plate. Formed integrally, for
example by moulding, with the plate 1 to proJect from its undersurface are a
plurality of attachment bars 3 of T-shape in section spaced apart along the
length of the plate and extending across the full width of the plate. The
,:
side edges of the plate 1 have a curved configuration as indicated at 4 to
facilitate clamping of the plates in position in the screening apparatus and,
. if required, the tensioning of the plates. Each of a number of support bars
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1 5, of which only one is shown in Figure 1, has T-shaped slots 6 in its upper
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surface at intervals correspondillg to the spacing of the bars 3 of the screen
1. The slotted parts of these bars may be a capping of resilient non--
metallic material secured to a more rigid base or the whole bar may be formed
either of resilient or rigid material. Three or more bars such as 5 are
spaced apart across the width of the deck, the bars having, or being mounted
; to have, different heights so that the slotted surfaces of all the bars de-
fine the desired camber to be formed by the screen when attached to the bars
` 5-
The screen plate is located in position by threading the T-section
bars 3 through the T-shaped slots in the successive supporting bars 5 across
the width of the deck and clamping edges 4 by any conventional clamping
arrangement which may, i~ desired be arranged to tension the screen plate.
~! The bars 3 and corresponaing slots in bars 5 need not be of T-shape
in section but may be of L-shape or have the bar of the T Or circular form,
all of which sections wowld provide a locking effect. Where a positive lock-
ing effect is not needed the bars and slots may be of simple rectangular
form.
The bars 3 may be formed, as previously mentioned, integrally with
the plate 1 by moulding the plate and bars in the same material. They may
also be formed integrally with plate 1 but in a material having a different
degree of resilience so as to stiffen or otherwise modify the overall phys-
ical charac-teristics of the screen plate.
Instead of the bars 3 being formed integrally with the plate 1
: . .
during the forming of such plate they may be added to a preformed plate
having certain ones of its apertures 2 of stepped form by moulding the bars
into such stepped apertures as indica~ed in Figure 2. In this alternative
form of plate the plate is first formed with the customary pattern of sizing
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apertures except that spaced ones of the apertures lying in each of a plural-
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ity of spaced lines across the width of the screen are formed with a step 7.
The preformed plate is then laid across a ~ould or a plurality of moulds
shaped to provide the T-section of the attachment bars with the mould cav-
ities in register with the lines of stepped form apertures in the sheet. A
suitable moulding liquid is then introduced to fill the mould cavities and
the stepped apertures to form the T-section attachment bars securely attached
to the plate.
This alternative way of providing the attachment bars is partic-
ularly useful when it is desired that the bars should have a different degree
of resilienceto that of the plate itself. It will be appreciated that under
the same circumstances preformed bars could be incorporated as inserts in the
moulding of the screen plate. ,
The screen plate 1 may be reinforced by incorporating metal rods or
wires in the material of the plate above the bars 3 to extend parallel to the ;~
bars 5. The plate 1, or assembly of plates if more than one is used to form
the screening surface, may be tensioned in any conventional manner but pre-
ferred ways of effecting such tensionine are illustrated in Figures 3 and 4.
In Figure 3 there is shown embedded in the material of the plate 1 a rein-
forcing wire 8 of wavy or crimped form which is formed into loops at inter-
vals along its length. Several such wires are incorporated ln the plate
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during moulding of the latter the wires being spaced apart across the width `
o~ the plate with the loops in the various wires in alignment. ~ensioning
rods or wires 9 extend across the width of the plate each through a series
of aligned loops in the wire 8 and are terminated in conventional manner in
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filaments to facilitate the application of tension to the rods or wires 9.
The loops may be omitted and the tensioning rods or wires located simply by
:! the undulations in the crimped form of wire 8.
'~ Instead of incorporating the tensioning rods or wires 9 in the
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1l~5~8~313
material of the plate during moulding the arrangement illustrated in Figure
4 may be employed. In the embodiment of Figure 4 thin walled tubes 10 are
incorporated in the material of the plate during moulding to form bores
through which the tensioning rods or wires can afterwards be threaded. The
same technique can be used for reinforcing rods or wires provided that the
tubes for each form of wire are at different levels. This can conveniently
be achieved by locating the tubes for the tensioning wires in the material
of the attachment bars 3 and the tubes for the reinforcing rods in the mate-
rial of the plate above the bars 3~
The provision of tubes 10 also facilitates the ~oining together of
a series of plate modules ko form a complete screen, such modules being
threaded on to a pair or more of spaced apart tensioning wires in untensioned
state to form a strip of modules extending across the width of the screen and
a series of such strips arranged to form a complete screen. '~he edges of the
modules are preferably of stepped or other interfitting configuration to pre-
vent or limit relative movement between adjacent modules. The shaping of the
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' edges of the modules can conveniently be such as to form apertures between ,
ad~acent modules into which a suitable material such as that of the modules `
themselves can be cast to form the assembled array of modules into a unitary
screen structure.
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