Gravity Scalper, Grader, and Bolter.
Year: 1890

page_text: Date of Application, 4th Nov., 1890-Accepted, 24th Jan., 1891
COMPLETE MULTI
Gravity Scalper, Grader, and Bolter.
We, FRANK NOBLE and HIRAM SNYDER, Mechanics, both of the City of
Minneapolis, County of Hennepin, State of Minnesota, United States of America,
lo 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:-
Our invention relates to that class of grinding mill appliances known as gravity
scalpers, graders and bolters.
As is well known to those familiar with the art, in modern milling this class of
device are usually so constructed that the sieves stand at different levels with the
head of one adjacent to and adapted to receive the tailings from the foot of the other.
In other words, the finer meshed sieves or bolts are placed at the uppermost level
and the coarsest at the bottom, and the different grades are drawn off in the same
order.
To obtain a machine which will do this work well and rapidly, bas so far been
found extremely difficult. Hitherto, straight, sieves have been used for the purpose.
In order to make this effective, the sieves must stand at a very sharp angle, not less
than forty-five degrees, in order to give the stock the requisite start at the head of the
sieve. The result is to make imperfect contact with the sieve surface at all other
parts of the sieve, on account of the accelerated motion of the stock. This point of
difficulty we overcome in our preferred construction by making the sieve concave on
its face. We can therefore start the stock at the proper angle and the concavity of
the sieve will retard its progress enough to off-set the acceleration due to gravity.
Perfect contact is thus afforded over the entire surface of the sieve, giving a very
remarkable difference in result and greatly increasing the capacity of the sieve.
Another point of difficulty with all kinds of sieves has hitherto been to impart
exactly the right kind of shaking motion thereto. Hitherto, so far as we are aware
these motions have either been to-and-fro motions lengthwise of the sieve, or unevenly
distributed vertical motions, both of which are more or less imperfect in their effects.
We overcome these limitations and obtain a uniformly distributed vibratory motion
by centrally mounting the sieves on spring bars, the flexible ends of which are secured
to some relatively fixed support. These spring bars are constructed with a rigid
central portion and flexible ends and the sieve is entirely supported by the rigid
portion of the bar. Knockers are arranged to strike the bar to impart vibration to
the sieve and inasmuch as the flexible arms are both secured in fixed supports and
the sieve is rigidly secured to the rigid part of the arms, a series of short vibrations
are thus imparted to the sieve which is uniformly distributed over its entire surface,
which has been found to be most efficient in its action.
This form of support is of course applicable either to a straight or curved sieve,
but we prefer to use therewith the curved sieve as it gives the most serviceable
combination. The flexible arms of the spring bars are perfectly secured to the fixed
supports by adjustable devices, so that the angle of the sieve may be varied
at will.
In the accompanying drawings wherein like letters refer to like parts throughout,
Figure 1 is a vertical section of a gravity scalper built in accordance with our
preferred construction.
Figure 2 is a front elevation of the same, some parts being broken away.
1 is the frame case of the gravity scalper, and 2 and 3 are sieves mounted therein,
which have curved or concave faces. 44 are bars provided with thickened central
portions 4 and flexible or spring-like arms 42, one of said bars being attached to

page_text: Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be preferred, we declare that what we
claim is:
(1.) The combination with a spring having a rigid central portion and flexible
ends secured to relatively fixed supports of a sieve mounted on the rigid portion of
said bar and solely supported thereby and a knocker adapted to strike said bar and
impart vibration to said sieve.
(2.) The combination with a suitable frame of a pair of spring-bars having rigid
central portions and flexible ends, adjustable devices for adjustably securing the ends
of said bars to said frame, a sieve mounted on the rigid portions of said bars and
supported solely thereby, and knockers for striking the rigid portion of said bars and
imparting vibration thereto, substantially as described.
(3.) A gravity scalper, comprising a series of curved sieves vibrating at a right
angle to their top surface each set at an angle to the horizontal plane, and at different
levels, the head of one to the tail of the other, for treating the stock in succession,
substantially as and for the purpose set forth.
(4.) The combination with a spring-bar having a rigid central portion and flexible
ends secured to relatively fixed supports, of a curved sieve centrally mounted on the
rigid portion of said bar and a knocker for striking said bar and imparting vibration
to said sieve, substantially as and for the purpose set forth.
(5.) A gravity scalper comprising a suitable frame, a series of sets of spring-bars,
one pair for each sieve, having rigid central portions and flexible ends secured to
relatively fixed supports, a series of curved sieves centrally mounted one on each set
of said spring-bars and solely supported thereby, and knockers for striking the
rigid portions of said bars and imparting vibration to the sieve, substantially as
described.
Dated this 14th day of October 1890.
FRANK
NOBLE.
HIRAM SNYDER.
Abel & Imray,
Agents for the Applicants.