Note: Descriptions are shown in the official language in which they were submitted.
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DEHUSKING GRAIN
FIELD OF TH~ INVENTION
This invention relates to the production of grain
flour, primarily wheat Elour, and more particularly to an
apparatus fcr the dehusking of such grain preparatory to the
grinding thereof to produce the flour.
B~CKGROUND ART
.
After removal of the grain from the heads of the
stalks of cereal plants, it is usual, at least in modern
western technology, to mill it by passing a stream of it
successively through a "train" of paired rollers. These
rollers, when at the upstream end of a flour mill, have
figured or otherwise roughened surfaces and are journalled
so as to provide a nip therebetween commensurate with grain
size whereas, at the downstream end of such a mill, the
rollers are journalled so as to have a much narrower nip and
are provided with substantially smooth surfaces.
During its passage through such a train of pairs
of prior known rollers, the grain is only partially dehusked
and also, inevitably, partially crushed and/or ground at
each stage. Between the stages and especially in the region
of the upstream stages the grain is winnowed, or subjected
to a shaking process which may be accompanied by a fanning
or blowing step, either of which steps is intended to blow
the bran, that is to say, comminuted grain husk, free from
the heavier material which is composed partly of grain
kernel and partly of those parts of the husk and other
unwanted material not yet removed~
It is a disadvantage of the above-described
process - which is known as the "break system" that a
considerable number of rollers (usually between eight and
thirty-six, but often more than thirty-two) must be employed
to produce flour. However, even the use of perhaps
thirty-two rollers does not give a very high grade of flour
because it is not practicable to remove all the bran from
the kernels.
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This bran has little or no dietary value as it is
too finely comminuted to be readily hydrated in the gut, and
so contributes virtually nothing to the desirable fibre
co~ponent of a diet. More seriously the remaining detritus
S in the flour will include not only the powdered husk but
also unspecified dirt and tiny particles of insects such as
curculionidea or weevils.
Attempts have been made to improve the quality of
milled flour by increasing the effectiveness of the
winnowing step between the rolling stages of the "break
system" of milling, but this has proved to be disastrously
uneconomic because a high proportion of the flour itself is
also lost. This overall contretemps has produced a
situation in which the chefs of many high quality
restaurants insist on hand-ground flour, needless to say at
high cost.
DISCLOSURE OF THE INVENTION
It is thus an object of the present invention to
provide, in a flour milling system, means whereby the
dehusking ef grain is substantially complete before rolling
(for the purpose of br~aking the kernels) comme~ces, and
wh~reby the number of pairs of rollers may be thereby
reduced whilst at the same time producing flour of improved
quality as compared with that presently commercialIy
available.
Accordin~ to the invention there is provided an
improvement in an apparatus for dehusking grain in which a
helical screw having a central bore therethrough is
rotatably and concentrîcally mounted on a generally
horizontal axis within an at least partly cylindrical
housin~. Means is provided to rotate the screw within the
housing and the unhusked grain is introduced into a first
end of the housing, is dehusked and moved through the
housing by the screw and is discharged from a second end of
the housing as dehusked grain. The improvement involves
the helical screw being made up of a plurality of discoid
element~, each side of each discoid element being formed to
provide a number of shallow compartments, each compartment
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being partially defined by a pair of substantially radially
disposed ribs extending away from the surface of the discoid
chamber. Each compartment has an open end ad~acent the outer
periphery of the discoid element and a closed end adjacen~ the
central bore of the helical screw. The compartments are
disposed so that those on one side of a discoid element are
sta~gered and offset with respect to the compartment on the
other side. Each of the discoid elements is provided with an
array of dehusking elements upon its helical ~urfaces. Grain
impelled through the cylindrical housing is sub~ected to
agitated, turbulent flow by contact with the discoid elements
of the helical screw, thereby removing husk material from the
grain.
Ideally, each discoid element may consist of a pair
of identical half-elements; preferably each element or half-
element is a steel casting and is case hardened.
An apparatus for the dehusking of grain, may
comprise an elongated frame; a horizontally-disposed driven
shaft supported in bearings within an upper part of said
frame; at least one helical screw or worm arrangement mounted
about said shaft; a cylindrical mesh housing enclosing said
at least one helical screw or worm arrangement; a plurality
of hoppers within a lower part of said frame and beneath said
housing; an outlet at the downstream end of said apparatus for
removal of bran, a grain inlet at the upstream end of said
apparatus; and means for rotatably driving the said shaft;
the or each helical screw worm arrangement being
composed of a plurality of discoid elements as herein
described.
Preferably, the bran removal outlet and an outlet
for dehusked grain discharge are both disposed in a casing
which is rubber lined to avoid fracture of the dehusked grain.
In order that the reader may gain a bet$er
understanding of the present invention, hereinafter will be
described a preferred embodiment thereof, by way of example
only and with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a part-sectional, diagrammatic side
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elevation of an apparatus incorporating the present
inventlon;
Figure 2 is a corresponding front end elevation;
Figure 3 is a corresponding rear end elevation;
Figure 4 is a composite drawing illustrating
various configurations of shallow depresssions and ribs; and
Figure 5 is a scrap, schematic drawing aimed at
showing staggering or offsetting of the depressions and
ribs.
Throughout the drawings, like integers are
referenced by the same numeral.
DESCRIPTION OF THE PREFERRED EMBODIME~TS
.
In the drawings, there is to be seen an elongated
frame 1 in which is supported a horizontally-disposed driven
shaft 2, running in bearings. Shaft 2 is rotatably driven
from an electric motor 3 via a transmission train of such as
V-belts-and-pulleys. The motor 3 is mounted on a side-panel
of frame l, for a degree of vertical adjustment to correctly
tension the V-belts.
As will be noted, shaft 2 runs in the upper part
4 of frame 1, while in the lower part 5 is a plurality of
hoppers, as 6 in Figure 2.
Mounted upon shaft 2, for rotation therewith, is
at least one, and ideally two in tandem, helical screw or
worm arrangements, as those re~erenced 7 and 8 ln Figure l,
and enclosing it, or them, i5 a cylindrical steel mesh
housing 9. The or each screw or worm arrangement may well
be composed of a plurality of angularly-mounted steel
discoid elements disposed along shaft 2 so as to form a
helical flight of vanes. Each discoid element has an array
of dehusking elements, these being ribs 12 mounted
substantially radially upon the sides of the discoid
elements. These screws or worms will be described in
greater detail hereinafter with reference to Figures 4 and
5.
At the upstream end of the apparatus there is a
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graln inlet 10 and, at the downstream end an outlet 11 for
the removal of bran under suction.
Also at the downstream end of the apparatus there
is a dehusked ~rain discharge outlet 13, both it and bran
removal outlet 11 being disposed in a casing 1~ which is
rubber lined to avoid fracture of the dehusked grain.
In the embodiment shown, there are four in-line
hoppers 6, 6A, 6B and 6C, each being as wide as the frame,
at the top, tapering to outlets 15, 15~, 15B and 15C at the
bottom, respectively for husk, husk/bran, fine bran etc.
Grain inlet 10 is provided with an auxiliary air inlet 16
which is adapted to entrain the gravity-fed grain in an
air~flow. However, in some applications, two in-line
hoppers may be preferable; all hoppers may have a vertical
discharge form, as in Fi~ure 2, or they may have an angled
discharge form, similar to the dehusked grain discharge
outlet 13, shown in Figure 3.
The hoppers ideally have access panels 17, 17A to
17C and the upper part of frame 1 may also have somewhat
similar access panels 18.
Figure 4 is a composite drawing for the purpose
of illustraing yarious shapes and configurations of the
shallow depressions and the ribs.
Preferably a discoid element 7, 8 consists of a
pair of identical half-elements, as 19. Each side of each
half-element 19 has cast therein a number of identical
shallow depressions, as 20; each depression 20 has an open
end, as 21, adjacent the periphery of the half-element and a
closed end 22 adjacent a central bore 23; the periphery may
be toothed as shown, these teeth may be of varied profile
and size.
The geometry of central bore 23 is such that,
when a plurality of the half-elements are mounted on shaft
2, a helical screw or worm arrangement results. The
half-elements are so mounted that, at their closest points
of approach, the peripheries of adjacent full discoid
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elements are about 10 mm. apart, and the diametrically-
opposed points on their peripheries about 40-50 ~nm. apart.
Each half-element l9 is provided with an array of
what may be termed dehusking elements, ideally in the form
of substantially radially-disposed ribs cast upon the faces
or sides of the half-element. These ribs may be
geometrically radial, as 24; angled, as 25; curved, as 26;
or sinuous, as 27, the sinuosity of the latter, adjacent the
open end of a depression, aiding in the formation of inward
grain-flow. In all cases, these ribs constitute sidewalls
of the shallow depressions. The depressions may well-have a
bight, as 28, or an aperture, as 29.
It is important that the depressions in one side
of the half-element 19 be staggered, or offset, with respect
to those in the other side; the schematic scrap drawing,
Figure 5, is merely intended to illustrate what is meant,
and does not represent an actual cross-section.
While depressions on the "one sides" are offset
with respect to those of the "other sides", in a completed
worm arrangement all the depressions on "one sides" are not
in register. As grain is impelled through the apparatus in
turbulent flow, a side-to-side motion is imparted to it as a
result of the particular juxtaposition of adjacent discoid
elements and this aids in the dehusking of the grain.
Each half-element 19 is ideally a case-hardened
steel casting having a roughened surface which also aids in
dehusk ing .
While the discoid elements which form the screw
arrangement have been described as radial rib-bearing, the
dehusking elements may well take any other form, for
example, foraminations, serrations, grooves, either smooth,
or rubber, or plastic coated, textured in any suitable
manner, or given an intaglio pattern.
Moreover, each discoid element may be composed of
quarter-elements, or even be only a three-quarter-discoid
element.
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Whatever may be envisaged, the criterion is only
that they will be capable of dehusking grain.
Thus, by the use of various dehusking elements
and/or by varying their angles, shapes, numbers, sizes
and/or spacings and the surface pattern or texture, a wide
variety of grains may be dehusked as for example wheat,
barley, oats, buckwheat, sorghum, millet, rice, and other
cereal grains including such Eastern grains as mung beans,
borghul, chick peas, as well as such other products as
certain nuts.
Use of the inventive apparatus makes it feasible
to free grain of its outer covering irrespective of whether
the grain is wet or dry. The apparatus thoroughly 'cleans'
each individual grain so that it leaves the apparatus
completely dehusked and dust-free; thus, if the miller is
provided with such completely dehusked kernels as above
described, he will have no need to use so-called "cleaning"
rollers at all - at a considerable saving in power usage.
Throughput capacity is envisaged to be perhaps 18
tonnes per hour, power requirements being readily provided
by a 15 kilowatt electric motor providing from 600 to 1000
r.p.m. and ideally 800 r.p.m.
While prior art apparatus rarely yields 76% of
usable flour - the remainder being contaminated with husk
material - the device of the present invention yields 90% of
usable flour, a huge increase of great economical
importance.
For a particularly extensive milling operation,
it will be advantageous to install two inventive dehusking
apparatus - the first one down stream from the usual
vibrating grain sifter and the second downstream from the
usual transit rest container, and hence onto the grinding
mill.
From the abovegoing, it will be readily
appreciated by those skilled in the art that numerous
variations and modifications may be made to the invention
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without departing from the scope and spirit thereof as set
out in the following claims.
