Improvements in Grinding Mills.
Year: 1894

page_text: Date of Application, 15th June, 1894
Complete Specification Left, 15th Mar., 1895-Accepted, 20th Apr., 1895
Improvements in Grinding Mills.
I, GEORGE BUTCHARD, of Milton Iron Works, Gravesend, and Tower Portland
Cement Works, Northfleet, both in the County of Kent, Engineer and Cement
Manufacturer, do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in grinding mills chiefly designed for
grinding cement clinker and cement core but also applicable for grinding other
materials, the chief object of my invention being to ensure that a ground product
of uniform grade can be obtained at one operation in the grinding machine no
subsequent sifting or separating being required.
According to my invention the grinding is effected upon a circular path by means
of edge-running wheels, the said wheels being arranged at an angle of, say 45 degrees
to a vertical shaft in such a manner that when the mill is running the grinding
action will be due to the weight of the said wheels acting partly in a vertical
direction under the action of gravity and partly in a horizontal direction under the
action of centrifugal force. The material as it is ground to the required degree of
fineness is carried off by a current of air and deposits in a suitable settling chamber
within the casing of the mill from which settling chamber the material is discharged
through inclined shoots under the action of gravity.
The material to be ground is introduced into the mill by means of a hopper or
otherwise and falls onto a disc or plate which directs the material into the grinding
path, a shield being placed around the outer periphery of the said path to prevent
the unground material from falling into the passage between the path and the
casing of the mill through which the air laden with the ground material passes.
The grinding wheels are carried on axes supported and driven at the lower end
by a boss on the central shaft and at the upper end by radial slides on the under-
side of the disc which directs the material into the path; these radial slides being
arranged in such a manner that the axes may yield to allow of the grinding wheels
accommodating themselves to the inequalities of the material upon the path and also
to the wear of the grinding wheels and path. In order to utilise to the fullest
extent possible the centrifugal force of the grinding wheels, and reduce friction of
bearings, the said wheels are formed with elongated hubs having enlargements on-
the undersides of the wheels and, as the central shaft has a tendency to rise under
the centrifugal action of the angularly placed grinding wheels, I prefer to make
one of the bearings in the form of a thrust block.
The air for carrying off the ground material is introduced by means of a fan or
blower into a hollow inverted cone arranged inside and underneath the grinding
path whence it passes upwards over the grinding path carrying the properly ground
material with it and thence passes down around the outside shield of the grinding
path to the settling chamber beneath where the ground material is deposited the air
returning from the upper part of the mill casing to the exhaust or inlet side of the
fan or blower.
In order to prevent any pieces of material which are not sufficiently ground from
falling into the chamber into which the ground material is delivered, I advan-
tageously arrange inside the path in connection with the inverted hollow cone a
shoot leading to the outside of the casing.
In the arrangement above described the fan or blower is placed outside the mill

page_text: casing but it will be obvious that the fan or blower may be placed inside the mill
casing by suitably modifying the arrangement.
Dated the 15th day of June 1894.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Grinding Mills.
I, GEORGE BUTCHARD, of Milton Iron Works, Gravesend, and Tower Portland
Cement Works, Northfleet, both in the County of Kent, Engineer and Cement
Manufacturer, 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 grinding mills chiefly designed for
grinding cement clinker and cement core but also applicable for grinding other
materials, the chief object of my invention being to ensure that a ground product of
uniform grade shall be obtained at one operation in the grinding machine no
subsequent sifting or separating being required.
According to my invention the grinding effected upon a circular path by means
of edge-running wheels, the said wlieels being arranged at an angle of, say, 45 degrees
to a vertical shaft in such a manner that when the mill is running the grinding
action will be due to the weight of the said wheels acting partly in a vertical
direction under the action of gravity and partly in a horizontal direction under the
action of centrifugal force. The material as it is ground to the required degree of
fineness is carried off by a current of air and deposits in a suitable settling chamber
within the casing of the mill from which settling chamber the material is discharged
under the action of gravity.
The air for carrying off the ground material is introduced by means of a fan or
blower into a hollow inverted cone arranged inside and underneath the grinding
path whence it passes upwards over the grinding path carrying the properly ground
material with it and thence passes down around the outside shield of the grinding
path to the settling chamber beneath, where the ground material is deposited.
In order to prevent any pieces of material which are not sufficiently ground from
falling into the chamber into which the ground material is delivered, I advan-
tageously arrange in connection with the inverted hollow cone a shoot leading to
the outside of the casing.
In the arrangement above described the fan or blower is placed outside the mill
casing but it will be obvious that the fan or blower may be placed inside the mill
casing by suitably modifying the arrangement.
To enable my invention to be fully understood I will describe the same by
reference to the accompanying drawings, in which :-
Figure 1 is an elevation of my improved grinding mill; and,
Figure 2 is a plan:
Figure 3 is a section on the line 3-—–3, Figure 1 :
Figure 4 is a section on the line 4-4, Figure 3:
Figure 5 is a section on the line 5-5, Figures 2 and 4:
Figures 6 and 7 are sectional views illustrating modifications of my
invention.
Similar letters of reference indicate corresponding parts in the several figures.
a is the casing of the apparatus which, as shewn, is square in horizontal section
and the interior of which is divided into two compartments or chambers by the
inclined partition b, which forms the bottom of the settling chamber and is arranged
at an angle of, say, 45°; the lower of which chambers is open at one side c so as
to afford access to the interior thereof. The part of the casing below the partition b
may be dispensed with, the upper part being carried upon suitable supports. If

page_text: desired the said casing may be round or of any other suitable shape in horizontal
section. The said casing is closed at the top by a domed cover d, and openings,
are formed in the casing a level with the lower edge of the inclined partition >> for
the purpose hereinafter described, the said openings being provided with flap
doors d', d.
e is the circular grinding path which, as shewn in the drawings, is supported by
plates upon the inner surface of an inverted hollow cone frustum secured to
the casing a at its four points of contact therewith, a ring plate h extending from
the larger periphery of the cone frustum to the top of the casing, as shewn most
clearly in Figure 5, in order to cut off direct communication between the interior
of the cone frustum and the spaces i at the angles or corners of the casing. The
diameter of the pathe is less than the diameter of the ring plate h so that a
passage j is left between the said path and the ring plate.
k, kare the edge-running grinding wheels, and is the vertical shaft for driving
the same, the said shaft running in bearings m, n, the former of which is formel
upon the corer d of the apparatus and the latter attached to a bracket o fixed to
the underside of the inclined partition b. The bearing a is preferably in the forin
of a thrust bearing so that it serves not only for supporting the weight of the shaft
but also for preventing the said shaft from lifting under the centrifugal action of
the grinding wheels. The opening through which the shaft passes through the
partition is provided with a stuffing-box p or other device for preventing air and
dust from passing through the said opening. The lower end of the shaft 7 is
represented as being provided with a driving pulley q.
The grinding wheels k, kare carried on axes », supported at the lower ends by
a boss s on the central shaft 7 and at the upper ends being capable of moving in
radial guidest, in a mushroom plate u also mounted on the vertical shaft and
rotating therewith. By employing these radial guides t, t, the axes are allowed to
yield vertically to permit of the grinding wheels accommodating themselves to the
inequalities of the material upon the path and also to their own wear and that of
the path e. In order to utilize to the fullest extent possible the centrifugal force
of the grinding wheels and reduce friction upon the bearings thereof, -the said "
wheels are formed with elongated hubs having enlargements A, k, the said
enlargements whilst increasing the weight which bears against the grinding path
under the centrifugal action also tending to overcome the tendency which the
upper parts of the said wheels have to fly outwards.
The material to be ground is introduced into the mill by means of a hopper or
the like through an aperture in the cover d and falls on to the plate u which
directs the material on to the grinding path e, a shield being placed around the
outer periphery of the said path to prevent the material falling into the passage j
around the said path.
w is the hollow inverted cone arranged within the grinding path, the said cone
at its lower end being connected to a passage (the opening for which in the
wall of the casing a is provided with a flap door w¹) and having at its upper en a
shield which serves to prevent as far as possible the material upon the path e
falling into the said inverted cone w. Should, however, any material fall or be
knocked over the said shield, such material will enter the passage from which,
when a sufficient weight of material has accumulated, it will be discharged the
door opening automatically. A passage & serves for conducting air from the
fan into the interior of the said cone. y, y are openings which are formed in
the casing a adjacent to two of the angle spaces i, i, the said openings, as shewn,
establishing communication between the said angle spaces and an external casing y
which communicates with the atmosphere through apertures y², y².
The operation of the apparatus herein before described is as follows:-The
central shaft being set in motion the edge-running grinding wheels k, k are caused
to run around the circular path e. Material to be ground is then introduced
through the aperture d' in the cover and deposited around the path e whereby it is
acted upon by the grinding wheels k, at the same time a current of air is introduced

page_text: through the passage into the interior of the hollow inverted cone to, the air
thence passing above the shields w³ and into the passage carrying with it the
particles of ground material which are in suspension in the air. From the passagej
the air passes into the cone frustum g and thence into the chamber above the
partition b, in which chamber the dust which the air contains is deposited upon
the said inclined partition, whilst the air freed from dust passes up through.
two of the angle spaces i, i to the apertures y and thence into the casing y', from
which it can escape into the atmosphere through the apertures y³, y². In practice,
however, I find it advantageous to arrange that the fan which produces the current
of air shall draw its supply of air from the said apertures y³, y' so that the same
air is used over and over again. The dust which deposits upon the inclined
partition gradually slides to the lower end of the same until sufficient is
accumulated to force open the doors d, d when the material escapes to the outside
of the apparatus, the doors again closing during the grinding operation.
U
In the apparatus shewn in Figure 3 only a very fine grade of material can be
produced as ouly the particles of material which rise above an imaginary line
connecting the edges of the two shields to and u will be carried off by the air
current. In order to produce a lower grade of material I may vary the height
of the shield v; in this case, however, it is necessary to employ an auxiliary
shield v', as shewn in Figure 6, to prevent the material falling off the plate u from
passing over the edge of the shield into the passage h. As shewn in the
drawings, a series of holes are formed in the shield through which the air passes,
the auxiliary shield covering the said holes.
The arrangement where I employ an internal fan or blower is shewn in Figure 7,
in which figure indicates a fan or blower which is mounted upon the tubular
shaft rotating on the vertical shaft and carrying at its lower end beneath the
inclined partition a pulley whereby the fan may be driven at a higher rate of
speed than the shaft driving the grinding wheels k. In this modification the air
drawn from beneath the fan is passed over the shields w2 and of the grinding
path, whence it passes into the passagej around the path into the chamber above
the partition where, after depositing its dust, it is again drawn through the fan.
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. A grinding mill wherein a series of grinding wheels or rollers runs upon a
circular path over which a current of air is caused to pass whereby the particles of
material which rise from the path during the grinding operation are carried
off and delivered into a chamber in which they are deposited, substantially as
described.
2. In a grinding mill in which edge-running wheels are used in conjunction with
a circular path, mounting and driving the said wheels substantially in the manner
herein before described and illustrated in the accompanying drawings.
3. In a grinding mill having a circular grinding path with edge-running grinding
wheels thereon, an inverted hollow cone arranged under the said grinding path and
connected at its lower end with the outside of the apparatus and having introduced
into it a current of air for carrying the ground product into a depositing chamber,
substantially as, and for the purpose, described.
4. The manufacture and use of the improved grinding mill hereinbefore
described and illustrated in Figures 1 to 4 of the accompanying drawings.
5. The arrangement of my invention wherein an internal fan is employed
substantially as described with reference to Figure 7 of the accompanying
drawings.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.