Martinsburg herald. [volume] (Martinsburg, W. Va.) 1881-1920, 1912-12-28

toauS Oh crushed stone over the
screens into the storage bins. A
third building to the south. not yet
erected. will contain the fine grinding
machinery and sorting screens for by
product manufacture.
The central feature of the whole OPP
Grafton OF this plant is the great
crusher the invention of Thomas A.
Edison, manufactured and installed
under the direction OF the Edison
Crushing Roll Co This crasher con-
sists essentially of two rolls. seven
feet long and six feet in diameter. on
which are bolted heavy iron plates
containing numerous, projections or
knobs, These knobs are OF same size
and shape, about two inches high, ex-
cept on one roll. the slugger, which
has two rows of slugger plates on dia-
metrfcally opposite sides of the roll.
on which the knobs are of little great
er height and sleeper face. Each roll
complete weighs As tons, and they. are
set parallel and revolved in opposite
directions by separate 200.horse pow
er motors at velocity of It's revolu-
tons per minute. The knobs, and es-
pecially the slugger knobs. thus strike
mers, SCATTERING rather than grinding
the stone, with low percentage OF
mes or screenings. Large blocks of
s to 10 tons weight are thus broken
In a few seconds of time. The rolls
are readily adjusted in distance apart
and may be set to crush eight inches
and under or blocks several feet in
diameter
The upper hopper will admit blocks
7xl0 feet in size. A block of 20 tons
weight was crushed at this plant, CON
Stunning about 25 seconds of time, This
would be at rate of 5000 tons an
hour. The theoretical capacity com
puted from the size OF rolls and revo-
lutions per minute is about $4,000 tons
day. The working capacity of the
rolls depends on the capacity of the
elevators for removing the crushed
stone from the crusher, which at the
National plant is 1000 tons an hour,
Or 10000 tons day.
The advantages of the Edison roll
crusher to the National Limestone Co
are large capacity, low blasting cost
at quarry, low cost of repairs, low per-
centage of screenings due to the
sledge-like action of the rolls, low la
Dor cost, as 10 to IL men represent
the total required force to operate the
enure plant, car loading and switch
ing.
In nearly all crushed stone plants
the rock is transferred from the
crusher to the top of the elevated
screens by bucket conveyors or ele-
vators. series of rectangular steel
buckets fastened to an endless chain
running over small pulleys. When
these buckets are large enough to
give capacity of 5000 to 5000 tons
day there is an enormous weight in
the elevator requiring high consump-
ton of power and also high expense
of wear and tear. Rock fragments be-
come lodged between the buckets,
causing breakage and the resultant
interruption in the work.
In the National plant, to. overcome
these troubles double-track skip
hoist was installed similar to those
in the iron blast furnaces. This hoist
incline is lao feet long, set at an angle
of so degrees. and leads from the bot
tom of the pit under the roll crusher
to the top of the screen-house. On
the incline are two tracks, which
merge into one at the bottom under
the crusher. Two steel skip cars
made by the Arthur Kople Company
are drawn UP the incline by steel ca
bles passing over two large sheaye
wheels at the top of the tower build
ing, thence down to the hoist drum
The arrangement is such that as
the loaded car is drawn up the incline
the empty one passes down. The cars
weigh 10 tons each, and hold 20 tons
If crushed stone On the rear axle OF
the cars are two wheels outside the
gauge of the four wheels of the car.
The outside wheels run on a wider
gauge track dt in% iOp VI lhr iiStD''
and this track rises to perpendicu-
lar plane, thus elevating the rear OF
the car until at the end of the opera
ton the car is tilted at an angle OF
As degrees, discharging the entire load
over the screens. On this hoist car
of 20 tons can be dumped every min
ute. or capacity of 1900 tons 'an
hour. The hoist and its control appar-
atus was installed by the Otis Elevar
tor Co.
The hoist is operated by a 375-
Lorse power electric motor, and is
controlled by a magnetic automatic
switchboard containing IA magnet
switches, which in their action by
contact start the cars, reverse the d.
rection Of movement, retard and ac-
CELEBRATE the. car, stop the car at top
of inclines set emergency brake in case
OF overload or loss of current The
control switch is near the hoist and
remote from the main switchboard.
When this switch is thrown the car
etar.ts slowly from under the crusher,