Improvements in Coal Screening Apparatus.
Year: 1894

page_text: Date of Application, 10th Aug., 1894
Complete Specification Left, 7th June, 1895-Accepted, 13th July,
1895
PROVISIONAL SPECIFICATION.
Improvements in Coal Screening Apparatus.
We, DAVID DAVY, of Broom Croft, Parkhead, Sheffield, in the County of York,
Engineer, and DAVY BROTHERS LIMITED, of Park Ironworks, Sheffield
aforesaid, Engineers, do hereby declare the nature of this invention to be as
follows:-
This invention relates to coal screening apparatus, and has for its object to
impart such a motion to the coal when travelling down the screen as to ensure the
separation from the mass of the small coal of which a large proportion is liable to
be carried along by, and remain mixed with, the large coal instead of passing through
the screen.
It is usual to impart a shaking motion to the screen in the direction of its
length but this alone has been found insufficient to ensure the complete disentangle-
ment of the small from the large coal and the invention consists in imparting to
independent sets of screen bars up and down movements in opposite directions so
that the screen surface instead of being a constant plane is continually undulating
in the transverse direction in such manner that as the coal slides down it is gently
tumbled about from side to side so as to vary the relative position of the large
lumps in the mass and thereby disengage the small coal from amongst them and
allow it to pass down through the mass and thence between the bars of the screen.
The preferred mode of carrying the invention into effect is to support alternate
pairs of screen bars on one set of bearers and the remainder on another set of
bearers, both sets of bearers being fitted to slide up and down in the shaker frames
and actuated by arms or wipers carried by rock shafts journalled in the shaker
frames, the bearers being arranged in pairs and supported by the oppositely
directed arms or wipers of the same rock shaft so as counterbalance one another
and move in opposite directions, the several rock shafts being provided with lever
arms all coupled to a fixed point in such manner that the shaking motion of the
screen will produce a rocking motion of the shafts and an up and down motion of
the two sets of screen bar bearers, the one set and the bars carried thereby moving
up when the other is moving down, and vice versa.
Dated this 10th day of August 1894
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
Improvements in Coal Screening Apparatus.
We, DAVID DAVY, of Broom Croft, Parkhead, Sheffield, in the County of York,
Engineer, and DAVY BROTHERS, LIMITED, of Park Iron Works, Sheffield,
aforesaid, Engineers, 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 coal screening apparatus, and has for its object to impart

page_text: such a motion to the coal when travelling down the screen as to ensure the
separation of the small coal which is otherwise liable to remain mixed with the
large coal instead of passing through the screen.
It is usual to impart a shaking motion to the screen in the direction of its length
but this alone has been found insufficient to ensure the complete separation of the
small from the large coal, and the invention consists in supplementing the usual
longitudinal shaking motion by other motions obtained by imparting to alternating
sets of screen bars, up and down movements in opposite directions so that the screen
surface instead of being a constant plane is continually undulating in the transverse
direction in such manner that as the coal slides down it is gently tumbled about
from side to side so as to vary the relative position of the large lumps in the mass
and thereby disengage the small coal from amongst them and allow it to readily
pass down through the mass and thence between the bars of the screen.
The preferred mode of carrying the invention into effect is illustrated in the
accompanying drawings, forming part of this Specification, wherein Figure 1 is a
longitudinal sectional elevation, on line 1-1 Figure 2, and Figure 2 a plan of the
screen, parts being removed in each figure to shew the parts behind and beneath
them.
The screen is suspended at an inclination in the usual manner by means of
suspension rods and receives to and fro oscillating or shaking motion by any
suitable means. The screen bars comprise at least two distinct sets arranged in
alternate order or in alternating groups of two, three, or more bars in each group.
In the example illustrated there are two sets in alternating groups of three,
the groups marked A being the bars of one set and those A¹ the bars of the
other set.
The groups of bars A are supported on one set of bearers B and the groups A¹
on another set of bearers B', the bearers of both sets being fitted to slide up and
down in guide grooves c in the sides C of the shaker frames. Both sets of
bearers B and B are supported by the same rock shafts D journalled in the
shaker frames C, the bearers being arranged in pairs one B and B¹ of each set
resting on the oppositely directed arms or wipers E, E', of the same rock shaft D
so as to counterbalance one another and be moved in opposite directions by the
oscillation of the rock shafts. The bars A rest in the notches 6 of the bearers B
and the bars A¹ in the notches of the bearers B¹, and each bearer is cut away as
at 3, where it comes opposite the screen bars supported by the bearers of the
other set so as to permit of the simultaneous opposite motions of the screen
bars. The several rock shafts D are provided with lever arms F all coupled by
links F¹ to a fixed point G so that when the usual shaking motion is imparted to
the screen in the direction of its length by means of a pair of eccentrics H, this
longitudinal motion of the screen will produce an angular motion of the rock
shafts D in their bearings and the wipers E, E¹, will consequently impart a
simultaneous up and down motion to the two sets B, B', of screen bar bearers
which rest upon them, the one set B and the bars A carried thereby moving up
and rising above the common level when the other set of bearers B', and bars A₁,
is moving down and sinking below the common level, and vice versa.
It will be obvious that instead of giving up and down motion to the bars of two
sets in opposite directions simultaneously, the one set might be stationary and the
other set move up and down to, say, twice the extent here indicated, but this would
be less advantageous since the rise of the load would not be balanced by the fall
and more power would, therefore, be consumed.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. In coal screening apparatus, dividing the screen bars into two or more
independent sets, the bars or grouns of bare of the and eat haine alternated with on

page_text: adjacent to the bars or groups of bars of the other set or sets, and imparting to the
bars of the several sets up and down motion simultaneously in opposite directions
the one with regard to the other, in addition to the ordinary shaking motion of the
whole screen, substantially as and for the purpose specified."
2. In coal screening apparatus, dividing the screen bars into two or more
independent sets, the bars or groups of bars of the one set being alternated with or
adjacent to the bars or groups of bars of the other sets or sets, and imparting to
the bars of the one set up and down motion with regard to the bars of the other
set in addition to the ordinary shaking motion of the whole screen, substantially as
and for the purpose specified.
3. Coal screening apparatus wherein the screen bars are divided into two sets
alternating singly or in groups with each other, the two sets being supported by
different sets of bearers supported in pairs, one of each set, on the opposite sides of
the axes of the same rocking shafts so as to receive up and down motion
therefrom simultaneously in opposite directions, substantially as and for the
purpose specified.
4. Coal screening apparatus wherein the screen bars are divided into two sets
alternating singly or in groups with each other, the two sets being supported by
different sets of bearers, supported in pairs, one of each set, on the opposite sides
of the axes of the same rocking shafts, said bearers and shafts being so mounted as
to partake in the shaking motion of the screen and the rock shafts being coupled to
a fixed point so as to derive their rocking motion from the shaking motion of the
screen, substantially as specified.
5. The herein described improved coal screening apparatus constructed and
arranged to operate substantially as specified and illustrated in the drawings.
Dated this 7th day of June 1895.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.