Note: Descriptions are shown in the official language in which they were submitted.
1141305
This invention relates to rotary sieve apparatus
for the separation of solids from a liquid in which the
solids are susPended. The invention is applicable to
separation of solids from liquids in the treatment of sanitary
sewage, abattoirs wastes, meat packaging residues and many
others.
: It is already well known to separate solids from
liquids in rotary sieves comprising an open-ended, screening
sleeve disposed and rotatable about a horizontal axis.
The fluent matter to be treated is introduced at one end
of the sleeve, the liquid falls through the screen inter-
stices, and the solids are expelled from the sleeve at its
opposite end.
It is also known to use, as the screening
cylindrical wall of the sleeve, a multiplicity of closely-
spaced, parallel "wedge-wires" which extend longitudinally
of the sleeve, and a plurality of circular binder hoops
; which encircle the array of wedge-wires, and to which all
of the wires are joined. The screening sleeve may take
many different forms; for example, the binder "hoops" may be
. formed as a single spring-like helix. Again, in some
reverse flow sieve apparatus of the kind under discussion
(see United States patent 3,876,548 - Donald P. Welles -
for example) the medium to be separated is applied to the
outside of the sleeve so that the solid matter departs
externally of the sleeve and the liquid penetrates the
screen by passing from the outside to the interior of the
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sleeve. In this example the "wedge-wires" may run
longitudinally or circumferentially of the sleeve, if
desired they may be in the form of a closely wound helix.
In each of these known forms however, the wedge-wire
principle is employed.
The term "wedge-wire" is something of a misnomer
since the wires are better described as being of trapezoidal
cross-sectional shape. Be that as it may, the principle
is a known one having been customarily used for the bars
of man-hole and drainage gratings and in other ways where
it is required for a liquid to run through an apertured
plate or screen, and solids suspended in the arriving liquid
(being over an acceptable minimum size) are to be prevented
from going through the screen. This is done so that if
a particle of acceptable small size can negotiate the
entrance end of a screen-hole then it is assured of
ample mechanical clearance during the remainder of its
passage through that increasingly widening hole; thus to
ensure, as far as possible, against blinding of the screen-
hole by the particle.
The present invention is concerned only withwedge-wire screen-sleeves of the kind in which the fluent
matter to be separated is fed to the interior of the
screen-sleeve, the solids leave the screen axially of the
sleeve and the liquids depart radially outwardly. Because
of this, the remainder of this discussion will be confined
to the use of screen-sleeves of that type.
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It will be appreciated that in any screen-
sleeve it is desirable for the total screen-hole area to
be as great as possible, compared with the un-holed area,
so as to provide maximum get-away passage for the liquid.
The wedge-wire principle of screen-sleeve construction is
particularly effective in this respect, since the holes
are virtually continuous throughout the length of the
sleeve; that continuity being curtailed to only a slight
extent due to the presence of the support hoops.
Experience has shown that internally-fed wedge-
wire screens of the kind discussed above are about the
most efficient kind of rotary sleeve sieve now in use in
the art, however, my work has shown that this efficiency
is not generally being fully realised, and this, ~ have
found, is due to insufficiently widespread deposit of
matters to be treated on the screening surface.
The object of this invention is to ameliorate
the mentioned shortcoming.
The invention provides a sieve of the kind
comprising:
an open-ended wedge-wire sleeve having a receiving
end and a solids departure end, and having its longitudinal
axis disposed substantially horizontally, means to rotate
said sleeve about that axis, and means for infeed of
material to be sieved into the sleeve by way of said
receiving end; characterised in that said infeed means
comprise:
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a trunk disposed co-axially with the sleeve,
having one end outside the sleeve through which material
to be sieved is delivered into said trunk and an opposite
end portion which projects into and through the receiving
end of the sleeve to extend within the sleeve over a
distance equal to from one quarter to one half the axial
length of the sleeve, and a material departure aperture in
the top of said end portion bordered by a horizontal weir
extending axially of said end portion for a distance at
least half the axial length of that portion measured from
the innermost end o~ said portion.
An example of the invention is illustrated in the
drawings herewith.
Fig. 1 is a perspective view of a wedge-wire
sieve with some parts broken away.
Fig. 2 is a partly sectioned side elevation of
an in~eed trunk.
Fig. 3 is a sectional end elevation taken on
line 3-3 in Fig. 2.
Fig. 4 is a partial plan taken on line 4-4 in
Fig. 2.
The illustrated sieve comprises an open-ended
wedge-wire sleeve 5 having a receiving end 6 and a solids
departure end 7. The sleeve may be cylindrical, or it may
be acutely frustro-conical as indicated by dotted lines in
Fig. 2. Its longitudinal axis may be absolutely horizontal,
or it may be virtually horizontal by reason of its axis
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tilting slightly downwardly towards the departure end of
the sleeve.
In this case, the sleeve consists of closely-
spaced longitudinally extending wedge-wires 8 circumferen-
tially bound by hoop-wires 9 secured about the wedge-wires
by welding.
Means to rotate the sleeve comprise grooved
runner-rings 10 which rest on rollers 11 and a motor (not
shown) drive connected to the sleeve, or to one or more of
the rollers 11, in conventional manner.
Liquids and sieve permitted fine solids leave
the sleeve radially to fall into catchment sump 12 furnished
with drain 13 and having splash-guards 14. Sieve-discriminated
solids leave the sleeve by way of end-ring 15 which discharges
onto stationarily mounted spout 16.
The infeed means whereby matters to be sieved
are deposited in the sleeve consist of a trunk 17 mounted
on supports 18 so that it is substantially in axial
coincidence with the sleeve. This trunk has one end 19,
outside the sleeve, equipped for delivery, to the trunk,
of matter to be sieved, in conventional manner.
Trunk 17, at its opposite end, has an end portion
20 whereof the length is about equal to that of the trunk
fragment illustrated in Fig. 4. End portion 20 extends
inwardly of the sleeve by an amount equal to from one
quarter to one half the axial length of the sleeve. The
top of portion 20 has a mater~al departure aperture 21
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bordered and defined by a horizontal weir constituted by
the upper edges 22 of end portion side walls 23 and the
upper edge 24 of end portion inner end wall 25 Aperture
21 preferably extends axially of end portion 20 for as
much of the rull length of that portion as is compatible
with matters welling out of the aperture not escaping
through the receiving end 6 of sleeve 5 At its minimum
length, aperture 21 is at least equal in length to one half
the axial length of end portion 20 measured from end wall 25.
End portion 20 preferably includes at least one
"upstream" anti-surge baffle plate 26 which extends
laterally of portion 20 and from the top of that portion
towards the centre thereof, and at least one "downstream"
anti-surge baffle plate 27 which extends laterally of
portion 20 and from the bottom of that portion towards the
centre thereof. Portion 20 also preferably includes a
plurality of part-helical flow guide ribs 28 which are
near vertical but incline slightly so that their upper ends
are closer to the weir end edge 24. With regard to ribs
28 I have found that their presence tends to stabilise
evenness of flow over the weir edges 22 and 24 Ribs 28
are secured to the end portion side walls, by welding or
otherwise, so that their upper ends are substantially flush
with weir edges 22.
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