Improvements in Middlings Purifiers.
Year: 1893

page_text: Date of Application, 10th Jan., 1893-Accepted, 4th Mar., 1893
COMPLETE SPECIFICATION.
Improvements in Middlings Purifiers.
A communication by WILLIAM DICKSON GRAY, of Milwaukee, in the County of
Milwaukee and State of Wisconsin, United States of America, Gentleman.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street,
Manchester, both in the County of Lancaster, and 323, High Holborn, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to that class of machines in which the material is treated
on a flat shaking sieve or screen, subject to the influence of a current of air
rising constantly therethrough and serving to carry away the dust and light
impurities.
It is the aim of the present invention to produce a compact simple machine, in
which the dust laden air rising from the sieve may be purified or deprived of the
solid matters held in suspension, and the purified air returned through the sieve
from below, and this in such manner as to secure a substantially uniform flow of the
air through all portions of the sieve, and to prevent the formation of vertical or
eddying currents thereunder.
With these ends in view, the current of air which has passed through the sieve
is divided, and after it is deprived of the dust, it is returned downward past the two
sides of the sieve into the chamber thereunder, so that it may again ascend there-
through. By thus dividing the air and causing it to flow inward and upward
beneath the sieve from the two sides, a practically uniform distribution and
equalisation of the separation or screening action not otherwise attainable are
secured.
The invention comprehends broadly the idea of dividing the purified air and
delivering the same under opposite sides of the sieve in directions transverse to the
length of the sieve that it may ascend therethrough, so that the counteracting or
opposing currents flowing beneath the sieve will in a measure neutralise each
other, and thus prevent the formation of vertical or eddying currents as before
mentioned.
While a machine is represented herein in the preferred form and a dust catcher
of the preferred construction, it is to be understood that the details of construction
may be modified and that a dust-catcher of any form the equivalent of that herein
shown may be employed.
In the accompanying drawings-
Figure 1 represents a longitudinal vertical section through the machine on the
line 1-1 of Figure 2; and
Figure 2 is a vertical cross-section of the machine on the line 2-2 in Figure 1.
Referring to these drawings-
A, represents an external body or casing, which may be of any suitable form and
construction adapted to contain the operative parts hereinafter described. B is an
ordinary flat shaking sieve, provided with bolting-cloth or other suitable material,
and suitably graded from head to tail, as usual. C is a longitudinal suction
chamber lying above the sieve so that all air ascending through the sieve must
enter this chamber. The walls of the chamber converge toward the top in
cross-section, as shown, and communicate at one end with an exhaust fan D.
E represents a dust catcher hereinafter described in detail, into which the fau
discharges and from which the purified air is delivered at the tail end of the
machine in a downward direction into two longitudinal flues or chambers F, lying

page_text: outside of the suction chamber and communicating at their lower sides with open
spaces extending downward past the sides of the sieve frame into the chamber
thereunder.
It will be observed that under the sieve arrangement there is a continuous
circulation of the same or practically the same body of air upward through the
sieve into the suction chamber, thence to the fan and through the dust-catcher, and,
finally, through the longitudinal chambers F, and downward again to the chamber
beneath the sieve. It will be observed that the chambers F distribute the purified
air throughout the length of the machine and that it flows downward in two currents
past the sides of the sieve so as to enter thereunder in opposite directions and
*transversely to the direction in which the material is flowing over the sieve. Since
the air currents entering below the sieve have little or no tendency in the direction
of its length, therefore the air acts simply with a vertical lifting action on the
material, allowing it to fall through the graded portions of the surface directly into
the conveyors at the base. When the air currents have a whirling or eddying
motion beneath the cloth or when they have a strong tendency toward the tail of
the machine, it is found that they will take up and mix the different grades of
material so as to prevent the clean and sharp grading which should be effected by
the conveyors.
In order to regulate the force and velocity of the air ascending through the
sieve, a stationary grated horizontal partition G is located in the upper part of the
suction chamber, and a corresponding grated valve H is placed thereunder provided
at one end with a protruding handle h, by which it may be adjusted. In order to
prevent the air delivered by the fan from diving directly downward beneath the
sieve thereby producing a stronger blast at the tail than at the head of the machine,
below the fan and over the tail of the side chambers F are located a stationary
horizontal board or deflector I, and a longitudinally movable overlying board 1.
By moving the last named board toward the head of the sieve, the descending blast
will be deflected to a greater or less extent along the side chambers F, so as to
equalise the descending current throughout the length of the sieve. This
equilisation is desirable not only because of the reasons above stated, but also
because the coarse cloth at the tail of the sieve, offering less resistance than the
fine cloth at the head, permits the air to ascend more readily so that an artificial
regulation is advisable. The material to be treated may be delivered to the head
of the machine by means of an ordinary closed hopper I, with a shaking shoe
thereunder, as shown.
The dust-catcher which, as above mentioned, may be of any appropriate
character, is so constructed, as shown in the drawing, as follows-
e,
Attached to and revolving with the horizontal shaft and the fan, there is a
cylindrical perforated screen e of sheet metal or other suitable material. Within
this cylindrical screen there is a stationary cylindrical drum or chamber
closed
at its ends, so that the air entering from the fan is compelled to flow through the
annular space existing between the outside of the drum and the inside of the screen.
This cylindrical screen is encircled by a series of stationary pockets or chambers e,
terminating at a distance from the screen, and each having at the inner edge an
annular flange or lip e, arranged as shown in Figure 1, so that the entrance into
each chamber consists simply of a narrow passage between the edges of the adjacent
flanges.
The cylindrical screen is provided at intervals along its length with out-reaching
arms L, projecting into the annular chambers and provided at their outer ends
with cross-arms or blades out of contact with the walls of the chamber. On one
side of the machine, all the annular chambers e communicate along the bottom with
a closed side chamber M, intended to receive the dust and other solid matters, and.
provided at its base with a conveyor screw N, to effect its discharge. As the air
is driven forward by the fan, it passes through the meshes or perforations on the
cylindrical screen, and is projected outward in part through the annular passage
into the chamber e, in which it receives a whirling or eddying motion, leaving

page_text: behind it the dust and solid matters, after which the air returns again toward the
screen, and so on repeatedly through the successive chambers until it leaves the
tail end of the machine. The blades or flyers L, cause a movement of the air
sufficient to discharge the precipitated matters from the chambers
into the
receiving chamber M.
e,
Owing to the rotary motion of the fan, it will have a tendency to direct the air
downward more violently and in larger volume on one side of the machine than on
the other. To counteract this tendency and equalise the flow, a hinged laterally
movable valve or deflector O is provided at the tail end of the machine in the path
of the descending air.
It is not desired to claim herein the construction of the dust-catcher shown in the
drawings separately considered, as it will form the subject matter of a separate
application for a Patent.
It will be observed that the machine is self-contained; in other words, that it
comprises within itself and in compact form, all the instruments necessary for the
gradation and purification of the middlings or other grain products, and for the
purification of the dust-laden air.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is-
1. In a middlings purifier, the combination of an enclosing chamber, a sieve
therein, a dust-catcher, a fan inducing an air current upward through the sieve and
thence through the dust-catcher, and means for dividing the air current above the
sieve and compelling it to return downward past the two edges of the sieve and the
space thereunder.
2. In a middlings purifier, the combination of a sieve, a suction fan drawing air
upward therethrough, a dust-catcher to which the fan delivers the dust laden air,
and two longitudinal chambers at opposite sides of the machine through which the
purified air is distributed lengthwise of the machine and from which it descends to
the chamber beneath the sieve.
3. In a middlings purifier, a screen, the overlying exhaust chamber, the fan, the
two longitudinal chambers at opposite sides through which the purified air is
distributed lengthwise of the machine and returned beneath the sieve, and means,
as deflectors, to ensure the uniform distribution of the air throughout the length of
the machine.
4. In combination with the sieve, the suction chamber, the fan and the side
chambers for returning the air from the fan, a laterally-adjustable valve or
deflector O, to equalise the current at the two sides of the machine.
5. In a middlings purifier, the combination of the body or casing, the screen
thereunder, the suction chamber thereunder, the fan, the dust-catcher consisting of
the cylindrical screen and the annular chambers surrounding the same, and
chambers or flues arranged to conduct the purified air from the dust-catcher
beneath the two sides of the sieve.
6. The combination in a middlings purifier of a sieve, a fan acting to induce a
current upward through the sieve, a dust-catcher communicating with the fan
chamber, longitudinal air passages at opposite sides of the machine communicating
with the dust-catcher, and opening into the chamber below the sieve past the sides
of the latter.
WM. P. THOMPSON & Co.,
Agents for the Applicant.