Improvements in Screens for Screening or Sizing Coal or the like.
Year: 1893

page_text: Date of Application, 13th Oct., 1893
Complete Specification Left, 12th July, 1894-Accepted, 18th Aug., 1894
PROVISIONAL SPECIFICATION.
Improvements in Screens for Screening or Sizing Coal or the like.
1, MARTIN LUTHER MULHOLLAND, of Ferryhill Engine Works, West
Cornforth, in the County of Durham, Engineer, do hereby declare the nature of
this invention to be as follows:-
My invention relates more especially to screens for screening and sizing coal,
but from the following description it will be seen that it is equally adapted to screens
when used for screening minerals generally such as slag, ores, breeze, whinstone,
granite, or gravel whether constructed as jigging, vibrating, revolving or stationary
screens.
In screening and sizing coals to the several grades in which they are supplied
to the market the operation of changing the screen from one grade of mesh to
another has hitherto been attended with much difficulty and delay such as stopping
the pit whilst one screen is entirely removed and another put in its place.
The object of my invention is to provide a screen which can be expeditiously
adjusted to any required size of mesh within the series of gradations for which the
screen is designed and which gradations may range from the largest size in use in
the trade, such as a four inch mesh for "cobbles to a dead plate.
In carrying out my invention I dispense with the existing bars or wire gauze and
substitute therefor two or more plates suitably perforated and arranged to slide
one over another in surface contact so that the requisite change of mesh is attained
by the perforations of each plate more or less overlapping those of the other plates.
These perforations may be of any suitable size or shape but I prefer to make
them square in form and of equal size in all the plates for the reason that by setting
these squares diagonally or cornerwise to the travel of the plates the perforations
retain the same form for every change of mesh thus avoiding the disadvantage of
forming elongated openings which are detrimental to uniform screening. When
the plates are placed with their pattern or arrangement of perforations to coincide
it is obvious that I now get the full sized mesh, that is to say that the perforations
of each plate are unobstructed by any other plate and taking this as one extreme
position of the screen and moving any one plate therefrom whether sideways or
end wise I reduce the mesh of the screen to a degree corresponding to the extent of
such movement and by providing a sufficient number of plates in the screen to
cover the perforations in the first plate their relative movements can be so arranged
and operated as to extend the gradation of meshes from the largest size required in
the trade to a dead plate.
The relative movements to be imparted to the several plates may be understood
from the following suggested construction.
Taking their movements to be end wise and by making the bottom plate a fixture,
let this plate be overlapped end wise by the next plate of the series, the overlapping
ends of which are furnished with downturned ledges which limit its sliding move-
ment either way over the fixed plate. This plate is similarly overlapped endwise
by the next plate of the series which slides upon it and so on by which it will be
een that a lateral movement of the top plate in either direction brings it into an
end wise contact with the plate upon which it slides when both move together to
end wise contact with the third plate and so on until all further movement is stopped
by the bottom or fixed plate, any suitable device being attached to the screen for
D077

page_text: effecting these movements in the manner required for the
invention.
Dated this 19th down of October 1802
purposes of my
G. J. CLARKSON,
Chartered Patent Agent, Stockton-on-Tees,
Agent for the Applicant.
Improvements in Screens for Screening or Sizing Coal or the like.
I, MARTIN LUTHER MULHOLLAND, of Ferryhill Engine Works, West
Cornforth, in the County of Durham, 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 :-
My invention relates more especially to screens for screening and sizing coal, but
from the following description it will be seen that it is equally adapted to screens
when used for screening minerals generally, such as slag, ore, breeze, whinstone,
granite or gravel, whether constructed as jigging vibrating, revolving or stationary
screens. But as my invention has been devised principally with a view of sizing
and grading coal, I shall so describe it.
In screening and sizing coals to the several grades in which they are supplied to
the market the operation of changing the screen from one grade of mesh to another
has hitherto been attended with much difficulty and delay, such as stopping the pit,
whilst one screen is entirely removed and another put in its place.
The object of my invention is to provide a screen which by
means of its
construction and the combination of its several parts can be expeditiously adjusted to
any required grade of mesh within the series of gradations for which the screen is
designed, and which gradations may range from the largest size in use in the trade
such as a four or five inch mesh for "cobbles to a dead plate.
"
But in order that my invention may be clearly understood and readily carried
into effect, I will proceed to describe the essential features thereof, which for that
purpose are embodied in certain machines as illustrated in the accompanying
drawings and hereinafter described from which its general application will be
understood.
In carrying out my invention I dispense with the existing bars or wire gauze and
substitute therefor two or more plates suitably perforated and arranged to slide
one over another in surface contact so that the requisite change of mesh is
attainable by the perforations of each plate more or less overlapping those of the
other plates. These perforations may be of any suitable size or shape, but I prefer
to make them square in form and of equal size in all the plates for the reason, that
by setting these squares diagonally or cornerwise to the travel of the plates, the
perforations retain the same form for every change of mesh, thus avoiding the
disadvantage of forming elongated openings which are detrimental to uniform
screening.
In the drawing
Figures 1 to 6 inclusive illustrate a combination of four such plates set to
different positions in each figure, to show how the mesh is graded thereby,
Figures 2, 4 and 6 being sectional views taken longitudinally along Figures 1, 3
and 5 respectively, and Figures 7 to 9 inclusive illustrate a four plate screen
combined with suitable operating mechanism, Figures 8 and 9 being longitudinal
sectional views taken on lines x x and y y respectively of Figure 7. Figure 10 is
a transverse sectional view which is common to several of the previous figures, as
for instance when taken on line Z Z of each of the Figures 1, 7, 8 and 9.
Figures 11, 12 and 13 illustrate a two plate screen in combination with operating
mechanism modified to suit; Figure 12 being a longitudinal sectional view on

page_text: line YY of Figure 11 and Figure 13 a transverse sectional view on line Z Z of
Figure 11.
Taking the letter d to indicate the mesh, and the combined letters Ad, Bd, Cd,
Dd to indicate the openings or perforations in the several plates A, B, C and D
respectively from which the said mesh is derived, when the plates are placed with
their pattern or arrangement of perforations to coincide as in Figures 1 and 2 it
is obvious that I now get the full sized mesh the screen is designed for. By sliding
the plate A to the position shown in Figures 3 and 4, the lap of the perforations A d
over the coinciding perforations Bd, Cd, Dd, obstructs the mesh in the manner
shown, and substitutes four small holes for every large one existing before. In
Figures 5 and 6 a movement has been imparted to all the plates except D which
may of course remain stationary and a corresponding change of inesh is the
consequence.
But in order to impart the requisite movement to the several plates of which the
screen is made up, it is found in practice that each plate under the control of the
operating mechanism must be in, apable of any but the intended movement provided
for by operating the said mechanism and so far as the arrangement for effecting this
purpose has been described in my Provisional Specification, I have since found that
such an arrangement does not make effective provision in this respect, and I
substitute therefor as an example of suitable mechanism for effecting this purpose
the combination of parts as illustrated in Figures 7 to 9 or in Figures 11 to 13.
In Figures 7 to 9, e and fare screw shafts fixed in the under frame of the
screens of which the shaft e engages with the top plate A only. The shaft ƒ is
screwed with a differentially pitched thread, one pitch engaging with the plate B
only and the other with plate C only. By turning the screw shaft e either way a
corresponding sliding motion is imparted to the plate A and by turning the
differential screw shaft fa corresponding differential sliding motion is imparted to
the plates B and C, and in this way the mesh of the screen is varied at will. In
the two plate machine illustrated in Figures 11, 12 and 13, a single screw shaft e
is actuated by a worm wheel g and worm h and imparts a sliding motion to the
plate A to the extent and in the direction required.
It is to be understood that the invention is not limited to a combination of its
essential features with any precise arrangement of details for operating the slides
which may be modified and adapted to the general construction of the machine, it
being only essential that the particular movement intended and no other shall be
imparted at will, and in the manner required to the several slides comprised in the
machine and the arrangements of operating mechanism shown in the drawings are
to be taken as examples of a practical way of operating the slides, for the purposes
of my invention.
Neither do I limit myself to the precise details of my invention as hereinbefore
specified and illustrated in the annexed sheets of drawings, in which flat rectangular
plates are furnished with square perforations, because equivalent modifications and
variations can be made embodying the essential or characteristic features of my
invention, but what I claim is :-
In screens for screening coal or the like minerals as a means for adjusting the
mesh of the screen, the use of a series of perforated plates, combined arranged and
operating together, substantially as and for the purpose as hereinbefore described
and illustrated by way of example in the accompanying drawings.
Dated this
day of July 1894.
G. J. CLARKSON,
Stockton-on-Tees, Chartered Patent Agent,
Agent for the Applicant.