Improvements in and relating to Grinding Mills and the Construction of Grinding Surfaces therefor.
Year: 1893

page_text: Date of Application, 2nd Jan., 1893
Complete Specification Left, 1st Nov., 1893-Accepted, 23rd Dec., 1893
PROVISIONAL SPECIFICATION.
Improvements in and relating to Grinding Mills and the Construction
of Grinding Surfaces therefor.
I, PERCY JOHN NEATE, of 16, The Banks, High Street, Rochester, in the
County of Kent, Engineer, do hereby declare the nature of this invention to be as
follows:
:-
My invention relates to certain improvements in and relating to grinding mills
and to the construction of grinding surfaces used therein, and has for its objects:-
1st. To so construct an edge runner mill as to better utilize the centrifugal force
of the runners and thus increase the efficiency of the mill ;
2nd. To provide for the easy adjustment of the runners and the better protection
of same from grit, dust, and the like; and
3rd. To so construct and arrange the grinding surfaces of mills that equally
efficient and level surfaces will always be presented notwithstanding the wear and
tear, and such surfaces shall be capable of adjustment as and when required, either
together or independently of one another. My invention is applicable as a whole
for dry grinding and in part for wet grinding.
Referring to the above heads :-
1stly. In edge runner dry grinding mills as hitherto constructed so far as I know
the axes of the runners or crushers have been arranged nearly horizontal, and the
grinding path in consequence has been flat or but moderately sloped, so that the
material to be ground has been able to rest upon it.
According to my invention I increase the inclination of the face of the grinding
path beyond the natural slope of the material to be ground, i.e. the material cannot
rest upon it, but would fall by gravity to the base of the grinding path where a
receptacle is provided to receive it when the mill stops.
The runners and the axles are set at an angle corresponding to this steep
inclination and the material to be ground is fed to the grinding path in the usual
manner; then, in order to bring it effectually into the path of the runners I provide
a series of lifting scrapers which may be similar to those described in my Patent
No. 8532 of 1890, and mounted upon radial arms intermediate between each pair of
runners. These serve the novel purpose of intercepting and throwing the material
up the grinding path with such force that before the particles have time to fall
back again a runner will pass over them and arrest their downward course.
Almost at or but little below this point the next following scraper will catch and
throw them up still higher than before, and so on until at last the ground particles
are thrown over the grinding path and beyond the action of these scrapers and
runners, and fall upon the collecting path. This is or may be inclined to a less
degree than the grinding path in order to avoid the violent throwing of the said
particles against the exterior apparatus hereinafter described, and it is or may be
perforated either wholly or in part, or may have isolated openings in it for the
passage of the particles to their next destination which is or may be effected by
ordinary adjustable collecting scrapers sweeping same, and conveniently carried
by the same radial arms as the lifting scrapers above mentioned or otherwise.
2ndly. The runners may be of any suitable construction, and in order to adjust
their positions and provide for wear I slightly bend or crank the lower end of the
axle which is squared and pivotted at a suitable point in a slot in the central or
bearing casting so that its angularity can be adjusted and fixed by the screw pivot.
To protect the axles from dust, grit, etc., when a runner wears and runs untrue,
I arrange a stuffing box in the axle box into which is fitted a plain gland with a
flanged base; the gland fits well on the axle but loosely in the stuffing box, and its

page_text: flange fits well and tightly against the axle box, to which it is screwed by studs
passing through slotted holes in the flange. Over the gland base I fit a flat smooth
annular washer of leather protected by an ordinary metal washer. The gland
compresses the packing and whilst both the gland and leather are allowed lateral
play, they are prevented from rotating by the said fixed studs. This economises
space and also gives a longer bearing surface on the axle.
3rdly. Instead of using an ordinary collecting path as described outside-the runner
path I may dispense with it entirely or employ only a narrow smooth upward incline
outside of the roller path, or in combination with such last mentioned incline: I may
arrange one or more supplementary annular grinding surfaces, the lower one or set
being fixed and the upper one or set adapted to rotate upon the lower, thereby
grinding between same the particles ejected from the runners. It is the construction
of these grinding surfaces exterior to the roller path, which forms the third head
of my improvements. Each grinding surface is in the form of an annulus and is
built up of segments of hard material such as cast iron, having helicoidal flanks or
surfaces (somewhat after the form of ploughshares). Near the acting surfaces the
outer parts or surfaces of these adjacent segments are in contact and together serve
to form a practically solid and continuous zone or annular grinding plane, but inside
the zone (of the surfaces of segments in contact) the acting surfaces of the segments
are notched or contracted transversely by reducing their thickness (after the
manner of the "dress" of an ordinary millstone, the before-mentioned solid zone
of the annulus representing the "blind skirt" of such a stone). On the upper and
lower surfaces of the respective segments a change of contour is effected (at the
point where the "skirt" ends and the "dress "begins,) this being for the purpose of
preventing the formation of a groove across the "skirt" in continuation of the
furrow in the "dress" by which insufficiently ground particles might escape.
I have found that narrow surfaces are more effective than if made broad, and
therefore I prefer to use two or more narrow annuli each separately loaded in use
and capable of independent vertical adjustment in any convenient manner as and
when required. Over one or more of such fixed annuli (which are equivalent to
"nether" millstones,) I mount corresponding and similarly constructed but inverted
annuli arranged to be rotated upon the nether annuli by the vertical shaft of the
edge runners or otherwise, and these are separately loaded to the required pressure
by suitable weights, springs, or other contrivances.
Where material of a fine nature such as sand has to be ground, the runners are
unnecessary as the work may then be done, either wet or dry, but preferably
wet, by the exterior annuli only. On the other hand when rough crushing only is
required the use of the annuli may be dispensed with altogether, and for intermediate
work the annuli may be loaded as above described but the loading weights or a
portion of them may be prevented by adjustable stops from exerting their pressure
upon the annuli when the distance between the faces is less than a given amount.
Dated this 2nd day of January 1892.
J. C. CHAPMAN,
Agent.
COMPLETE SPECIFICATION.
Improvements in and relating to Grinding Mills and the Construction
of Grinding Surfaces therefor.
I, PERCY JOHN NEATE, of 16, The Banks, High Street, Rochester, in the
County of Kent, Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement :-
My invention relates to certain improvements in and relating to grinding mills
and to the construction of grinding surfaces used therein, and has for its objects :-
1st. To so construct an edge runner mill as to better utilize the centrifugal force
of the runners and thus increase the efficiency of the mill ;

page_text: 2nd. To provide for the easy adjustment of the runners; and
3rd. To so construct and arrange the grinding surfaces of mills that equally
efficient and level surfaces will always be presented notwithstanding the wear and
tear, and that such surfaces shall be capable of adjustment as and when required,
either together or independently of one another.
My invention is applicable as a whole for dry grinding, and in part for wet
grinding.
In fully describing my invention I will refer to the accompanying drawings
illustrating my improvements, and in which Fig. 1 is a plan, Fig. 2 a vertical
section, and Fig. 3 a part vertical section of a mill showing my improvements
chiefly referred to under 1st. and 2nd. above headings. R are the edge runners
revolving on axles A carried by a rotary central casting C driven by driving
shaft D. P is the grinding path, B the base of the mill below same.
Firstly, in edge runner dry grinding mills as hitherto constructed, so far as I
know the axes of the runners or crushers have been arranged nearly horizontal, and
the grinding path in consequence has been flat or but moderately sloped, so that
the material to be ground has been able to rest upon it.
According to my invention I increase the inclination of the face of the grinding
path P from the horizontal as illustrated, so as to lie beyond the natural slope of
the material to be ground, i.e. the material cannot rest upon it, but would fall by
gravity to the base B of the grinding path P. This base B is in the form of an
annular receptacle of sufficient capacity to receive all the material on the runner
path at the moment of stopping of the mill, and in such manner as to be clear
of the runners and thereby facilitate starting. From this receptacle I provide an
outlet shoot b with or without a regulating valve for clearing out in case of its
becoming overcharged, or when required. Thus the received material may either
be thrown back on to the runner path by suitable scrapers on starting the mill, or
removed through the outlet shoot b as preferred.
The runners R and the axles A are set at an angle corresponding to the aforesaid
steep inclination of the path P, and the material to be ground is fed to the grinding
path P by the central feed shoot H and the centrifugal action of the central
casting C as shown, or in any suitable manner; then in order to bring it effectually
into the path of the runners R I provide a series of lifting scrapers S (which may
be similar to those described in my Patent No. 8532%), each blade of which is
separately adjustable in regard to the grinding path; these scrapers S are mounted
upon nearly radial arms s intermediate between each pair of runners.
These scrapers serve the novel purpose of intercepting and throwing the material
up the grinding path P with such force that before the particles have time to fall
back again a runner will pass over them and arrest their downward course.
Almost at or but little below this point of arrest the next following scraper will
catch and throw the particles up still higher than before, and so on until at last the
ground particles are thrown over the grinding path P and beyond the action of
these scrapers S and runners R and fall upon the collecting path E. This is or
may be inclined to a less degree than the grinding path, as shown in Fig. 3 in
order to avoid the violent throwing of the said particles against the exterior casing
of the mill or the apparatus hereinafter described, and it is or may be perforated
wholly or in part, or may have isolated openings such as e, Fig. 3, in it for the
passage of the particles to their next destination, as indicated by the arrow in
Fig. 3, which is or may be effected by ordinary adjustable collecting scrapers
sweeping same as illustrated at S', Fig. 3, and conveniently carried by the same
radial arms s as the lifting scrapers S, Fig. 2, above mentioned.
Secondly. The runners R may be of any suitable construction; and they are
carried by the axles A ; in order to adjust their positions and provide for wear I
slightly bend or crank the lower end a of the axle A, Figs. 2 and 3, and the part is
squared and pivotted at a suitable point a' in a slot a² in the central or bearing
casting so that its angularity can be adjusted and fixed by the pivot bolt a¹.
Instead of using an ordinary collecting path E outside the runner path Pas

page_text: more
described in reference to Fig. 3, I may dispense with it entirely or employ only a
narrow smooth incline such as p, Figs. 1 and 2, outside of the runner path P; or
in combination with such last mentioned incline I may arrange one or
supplementary grinding rings with annular grinding surfaces, one, preferably the
lower one or set being fixed, and the other preferably the upper one or set
adapted to rotate upon the lower, thereby grinding between same the particles
ejected from the runners. In Figs. 1 and 2 I have shown one pair of such
superposed annular grinding rings G G' the construction of which is hereafter
described. The lower annulus G (which is equivalent to a nether millstone)
"
is stationary as regards rotation upon a ring F supported upon the bedplate F¹ and
is capable of vertical adjustment thereon by the set screws f in order to compensate
for wear and tear as and when required. Over it I mount a corresponding and
similarly constructed but inverted annulus G¹ arranged to be rotated' upon the
aforesaid "nether" annulus by the main driving shaft D in suitable manner; for
example, I have illustrated it as carried by the radial arms s fixed to the central
casting C and also carrying the scrapers S. The annulus G' is fixed to a
continuous annular bedplate F2 into which are screwed or secured the stanchions gg
passing freely through and driven by the arms s, thereby being capable of self
adjustment for wear.
In Figs. 4 and 5 I have shown a double set of annuli G G' arranged precisely
in similar manner to the single set above described. These annuli are separately
loaded to the required pressure by suitable weights, springs, or other contrivances.
I have shown in Fig. 6 a spring loading. The stanchion carrying the upper
annulus G¹ passes freely through the arms and terminates in a taper engaging a
hollow cone KK represent standards forming a frame rigidly erected upon
the arms and having a cross bar k through which an adjusting screw k¹ is threaded
and engages an inverted hollow cone g². These two cones g¹ g² are confined between
three compression bolts k2, and retain between them a spring 3 of suitable resistance.
The spring is partially and permanently compressed by the bolts and
cones 99, and thus in use only a small compression of the adjusting screw k
will serve to put considerable pressure upon the annulus G'; or on the other
hand if the screw k¹ be left just clear of the cone g², a minute rise of the
annulus G¹ will not be attended with material resistance, but any further rise
will be met and counteracted by the full resistance of the already compressed
spring R³.
The object of the arrangement is to avoid excessive wear and tear between the
acting surfaces of the rings G G¹ in the event of the mill being negligently worked
with insufficient feed or when running empty, and also in special cases to provide
facilities for "cracking" the small particles instead of "
"flouring them.
"
The construction of the grinding surfaces of the annuli G G forms the third
head of my improvements.
I have endeavoured to illustrate this as far as possible in the drawings. Fig. 7
is a part plan; Figs. 8 and 9 respectively inside and outside elevations of a lower
or "nether" annulus; Fig. 10 is a plan of one segment; and Fig. 11 an inside
elevation of same. Referring to these figures, each grinding surface is in the form
of an annulus as stated and is built up of a number of solid segments Q of hard
material such as cast iron, each being bounded by two identical and parallel plane
surfaces N N' at the top and bottom. These surfaces are connected by helicoidal
flanks or surfaces q (somewhat after the form of ploughshare or the blade of a
screw propeller) near the outer parts of their horizontal acting surfaces marked N
the outer parts or surfaces of these adjacent segments Q are in contact, see Fig. 7,
and together serve to form a practically solid and continuous zone Z or annular
grinding plane, but inside the zone Z of the surfaces of segments in contact the
acting surfaces N of the segments are notched or contracted transversely by
reducing the thickness at the "eye" side marked 92 (after the manner of the dress
of an ordinary millstone, the before mentioned solid zone Z of the annulus
representing the "blind skirt" of such a stone). On the upper and lower surfaces

page_text: of the respective segments one or more changes of contour is or are effected by
reflex or inclined surfaces (at or exterior to the point where the "skirt" ends and
the "dress" begins) q³, each such reflex fitting with and coming in close contact
with the next, when the segments Q are assembled, the lines of junction of same
being tangential to an inner concentric circle, as indicated by the dotted lines in
Fig. 7, this being for the purpose of preventing a groove across the "skirt" in
continuation of the furrow q in the "dress" by which insufficiently ground particles
might escape. I have shown but one such reflex q³, but two or a series of serrations
may be employed. The furrows q' may be advantageously filled in with a relatively
softer material such as Portland cement to cousolidate the whole annulus.
I have found that narrow surfaces at N2 are more effective than if made broad,
and therefore I prefer to use two or more narrow annuli concentrically arranged as
in Figs. 4 and 5, and each separately loaded in use and capable of independent
vertical adjustment as specified, as and when required, or I may use two narrow
annuli working in connection with one broad nether annulus.
The superposed rotating annuli G' are constructed exactly as above set forth, but
are inverted in use so that the respective grinding surfaces are in contact. Each
segment is firmly secured to its bed F F2 by bolts z. z. with countersunk heads, the
holes of which are marked z¹ in Figs. 10 and 11.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In grinding mills of the edge runner kind, arranging the grinding path (P)
with an inclination beyond or steeper than the natural slope (angle of rest) of the
material to be ground, in combination with runners (R), corresponding with same
inclination, and lifting or retaining scrapers (S) intermediate between each runner
substantially as and for the purpose set forth.
2. In edge runner grinding mills such as are above referred to, the means of
adjusting the runners as and when required, consisting in slightly cranking the
axles and mounting same substantially in the manner above described.
3. In mills such as above referred to, the provision in combination with the
steeply inclined grinding path of an annular receptacle such as B for receiving all
the material in the mill clear of the runners at the moment of stoppage and dealing
with same substantially as set forth.
4. The combination with edge runner grinding mills such as above referred to
and claimed of the outer collecting path (E) with discharge orifices and collecting
scrapers substantially as set forth.
5. The hereinabove described construction of nether and upper grinding
annuli (GG) consisting in building same up of a number of separate solid
segments (Q) each bounded by two identical and parallel plane surfaces N N¹ at
top and bottom connected by hélicoidal surfaces and formed as specified with one
or more changes of contour (at or exterior to the point where the "skirt" ends and
the "dress" begins) effected by means of one or more reflex or inclined surfaces (9³)
in close contact one with another, whereby a practically solid continuous "blind
skirt" or grinding zone (Z) is formed, and whereby a groove across the skirt in
continuation of any furrow is prevented substantially as and for the purpose set
forth.
6. The use in combination with edge runner grinding mills of one or more pairs
of exterior supplementary grinding annuli constructed of separate helicoidal
segments as above specified, and arranged and adapted to operate substantially in
the manner and for the purposes set forth.
7. The arrangement and mounting of the nether and upper grinding annuli G G¹
substantially as set forth.
8. The means of loading the rotating annulus G¹ with already compressed
springs as required, substantially as set forth in reference to Fig. 6, whereby

page_text: severe friction between the grinding faces when the mill is running empty is
prevented.
9. The use of two or more concentric annuli each built up of a number of
separate segments of hard grinding material and rubbing upon similar concentric
stationary annuli or upon one broad similar stationary annulus, one or both sets of
such annuli being capable of independent vertical adjustment for wear, substantially
as set forth.
Dated this 1st day of November 1893,
For the Applicant,
J. C. CHAPMAN,
70, Chancery Lane, London, W.C., Chartered Patent Agent.