Improvements in Pulp-screening Machines.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in Pulp-screening Machines.
I, CHARLES JOSEPH FOSTER, of Westbrook, in the County of Cumberland,
State of Maine, United States of America, Carpenter, 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 :-
My invention relates to improvements in pulp-screening machines, the object
being to so improve the construction and arrangement of the parts that the whole
shall become a cheap and easily working machine.
This object I attain by the mechanism shown in the accompanying drawings, in
which
Fig. 1 is a view showing in longitudinal, vertical section the main machine and
its frame, some of the smaller parts being shown in elevation.
Fig. 2 is a cross vertical section showing some of the parts more in detail.
The characteristics of this device are, that it is a continuously working machine,
the parts being duplicate, each duplicate acting as a counterbalance for the other,
so that the action of the force of gravity on the descending part assists in lifting
the ascending part, thus greatly reducing the power required to drive the machine.
In the drawing Fig. 1, B B represents the frame and supports of the machine
and A A the receiving tank or tanks. The screen plates S S are made in the usual
manner and serve to receive and hold the unscreened pulp.
D, D', are diaphragms adapted to be moved up and down by the pitmen T and T'
which are operated by a walking beam F or by any other suitable mechanism. The
motion of the two diaphragms being alternate, one going up while the other is
going down.
It being necessary for the well working of the machine that the diaphragms D, D¹,
shall be practically air and water tight, I use closely fitting plates K, K, prefer-
ably of brass, which are connected adjustably to the upturned edges of the
diaphragms D, D' as shown, these outer edges fitting accurately against the brass
packing plates H; this arrangement admits of the diaphragms moving up and
down, and yet making a practically air tight joint.
The outlet pipes N, N, Figs. 1 and 2 which are located between the screen plates
and the diaphragms serve to allow the screened pulp to flow into the receiver R
(see Fig. 2) one of the ends of these pipes N, N, being shown at N¹. Each of the
outlet pipes N, N, is provided with a suitable self-acting check valve which will
allow the pulp to flow out but not to re-enter.
These check valves in the pipes N, N, are very important as they serve, when
the diaphragms are going down to increase the vacuum in the space between the
screen plates and the diaphragms, and thus to increase to a very great extent the
production of the machine.
Another important feature of my invention consists in the air pipe arrangement,
which I will now explain.
Immediately under each screen plate I place an air pipe P, provided with an air
check valve (see P¹ Fig. 2). The object of the air pipes P is to regulate the
suction through the screen plates; also to admit air under the screen plates to clear
the latter during each upward stroke of the diaphragms; the air being prevented
from going out through said pipes P by the check valves on said pipes.
Each of the pipes P also has a valve P₁ (Fig. 2) by which the amount of air
flowing into the pipe P and through there into the space between the diaphragms
and screens may be regulated.
L, L, Fig. 1 represents a trough which is located under the edges of the
diaphragms and serves to catch any leakage that may pass between the packing
joints of the diaphragms,

page_text: The operation of my machine is as follows: The pulp to be screened is placed in
the tank or tanks and the machine is started, as the diaphragms D D' move, they
form, in connection with the screen plate, bellows which alternately compress and
exhaust; the action of compression being to force air up through the screen plates,
thus clearing them at each upward motion, and the downward or exhausting motion
of the diaphragms, serves to draw the pulp down through the screen plates, thus
filling the space between the screens and the diaphragms up to the level of the
outlet pipes N; while the diaphragm is going down, a sufficiency of air is drawn
in through the air pipes P to act (while the diaphragm goes up) to clear the screen
plates by forcing air through them. These actions are repeated at each motion of
the diaphragms.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a pulp-screening machine the combination of the balancing diaphragms D, D'
having metallic packings H, K, as described, the troughs L; with screen plates
and tank all adapted to form a bellows or suction screen without the use of leather
or other flexible packing, substantially as and for the purpose set forth.
2. In a pulp-screening machine the combination of the balancing diaphragms D, D',
having metallic packings as described; with the air pipes P having check valve Pi
and regulating valve P operating substantially as and for the purpose set forth.
3. In a pulp-screening machine the combination of the balancing diaphragms D, D¹
having metallic packings as described; with outlet pipe N having valves as described,
and adapted to operate substantially as and for the purpose set forth.
Dated this 02-1 dow of A-11001
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents for the Applicant.