IMPROVEMENTS IN AND CONNECTED WITH GRINDING MILLS
Year: 1882

page_text: LETTERS PATENT to Philip Middleton Justice of 14 Southampton Buildings
{
in the County of Middlesex Patent Agent for an invention of IMPROVEMENTS
IN AND CONNECTED WITH GRINDING MILLS Communicated to him from abroad
by Melvin Batchlor Church of Grand Rapids County of Kent State of
Michigan United States of America
PROVISIONAL SPECIFICATION left by the said Philip Middleton Justice
at the Office of the Commissioners of Patents on the 13th June 1882.
PHILIP MIDDLETON JUSTICE of 14 Southampton Buildings in the County of
Middlesex Patent Agent "IMPROVEMENTS IN AND CONNECTED WITH GRINDING
MILLS a communication to me from abroad by Melvin Batchlor Church of
Grand Rapids County of Kent State of Michigan United States of America
"
This invention relates to grinding mills and consists of two principal parts. The
first part relates to the construction of the stones and to their mode of operation
and the second to apparatus for feeding the material to the stones in quantity
uniformly and exactly regulated automatically to the speed of the stones whereby
the material is fed in any given amount that may be desired for a given speed of
the stones and automatically varies with any variation of the speed so that the
proper feed being once determined it is automatically maintained whatever
variation there may be in the movement of the stones The improvement relating
to the stones and the mode of grinding is first described
This part of my invention relates to grinding mills of that class in which the
material is ground between upper and lower stones
The improvements relate to a certain extent to the form of the stones and more
particularly to their mode of operation I contemplate principally the grinding and
regrinding of substances which may be reduced wholly to a very fine dust or
powder, such as gypsum, chalk, earth paints ores and the like though under some
[Price Gd21
3

page_text: circumstances it is applicable to other substances The object of my invention is to
avoid the great amount of friction incidental to the old form of stones and great
waste of power the heating of the substances and irregular grinding by reason of
which another expensive process is necessary-namely that of bolting in order to
secure the necessary uniformity of fineness which is required of materials which
are used for coating walls and for many other purposes. The essential principle
of my invention lies in grinding between substantially smooth surfaces of stones
with the under stone level and the upper dished and slightly separated leaving the
space kept uniformly and constantly crowded full whereby the goods are caused
mainly to grind by attrition and crushing of particle with particle of their own
substances The lower stone which must always be the moving one is made with
a perfectly plane level surface from eye to skirt which surface is either perfectly
smooth or formed with a very fine shallow crocking for the purpose of helping
the stones to stick to the goods and whirl them about and prevent them from
packing down on the stones The upper stone is formed very slightly and
uniformly dishing from eye to skirt and the surface of it may be crocked in a
manner similar to the lower
It is better in practice to form a slight pocket immediately about the eye
sufficient in size to admit the granules of the material to be ground fill between
the upper and lower stones when they are in position for work Ordinarily as
required for regrinding plaster I dish the upper stone about one eighth of an inch
at the eye gradually lessening in not more than two inches towards the skirt to
1/16 of an inch and from that line the dish gradually decreases to the skirt These
dimensions are for a stone of 36 inches in diameter These stones are provided
with suitable mechanism for feeding the material uniformly thereto; for giving
rotary motion to the lower stone and for bringing the stones together It is also
essential as will hereinafter appear that the feed should be perfectly adjustable to
the stones and should be automatically varied to suit the variations of the speed
of the stones when running
This feed is accomplished by an apparatus hereinafter fully described and by
means of it the feed can be regulated to the stones and afterwards all the
variations are automatic The dish of the stone must be such that every part of
the space will be kept full This is accomplished by exactly proportioning the
dish on the principle that as the goods move outward they will have the same
space (decrease in depth in proportion to the increase in length with allowance for
increased bulk by reduction) in zones of a given width at every point from centre
to skirt
The second part of this invention relates to the feed regulator specially fitted to
operate in connection with the above described mill and method of regrinding
plaster and like materials Such materials when placed in the hopper or large
garner for regrinding tend to pack in proportion to the weight of the mass and
this packing interferes materially with the regularity of this feed It cannot be
made to flow regularly and uniformly by the use of any ordinary devices and will
not feed at all or with any certainty by its own weight Various devices have
been heretofore used for this and like purposes but I have found after much
experiment that an absolutely positive feed is essential for this and like materials
when it is to be fed to stones for regrinding This positive feed in order to work
uniformly must also work as I have found by experiment, in a mass of the
material so that the feeding screw shall always be packed
This portion of my invention consists first of a second or intermediate chamber
between the garner and the stone, and second of a feeding screw about one half of
which is covered by a closely fitting case at the delivery end and the other half
exposed in the chamber upon all sides to the material which is to be fed As the
case fits closely to the screw and contains none of the feed except that carried
along by the screw, it therefore compels the screw to act uniformly and evenly and
prevents it from crowding the mass into the delivery end of the chamber But as

page_text: the stone is constantly varying in speed it is necessary to vary the rate of move-
ment of the screw This is accomplished by extending the shaft or shank of the
screw outside the chamber and providing it with an ordinary cone pulley con-
nected by a band to a like reverse pulley, the shaft of which is suitably connected
to any convenient part of the mechanism which drives the stone The feed may
be regulated in relation to any given speed of the stone by adjustment of the band
upon the cone pulleys After such adjustment it will be plain that variation of the
speed of the stone will directly vary the speed of the screw and thereby the
amount of feed The lower chamber may be omitted and the feeding screw be
located in the bottom of the garner, but it is better to use the lower chamber in
order that access may be had to the screw in case of accident The screw must
still be arranged with the last half covered in the same manner as heretofore
described This feed mechanism is also applicable to other kinds of mills and to
feed grains or other granules or pulverulent materials

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Philip Middleton Justice in the Great Seal Patent Office on the
8th December 1882.
PHILIP MIDDLETON JUSTICE of 14 Southampton Buildings in the County of
Middlesex Patent Agent "IMPROVEMENTS IN AND CONNECTED WITH GRINDING
MILLS a communication to me from abroad by Melvin Batchlor Church of
Grand Rapids, County of Kent, State of Michigan, United States of America
"
This Invention relates to grinding mills and consists of two principal parts. The
first part relates to the construction of the stones and to their mode of operation,
and the second to apparatus for feeding the material to the stones in quantity
uniformly and exactly regulated automatically to the speed of the stones, whereby
the material is fed, in any given amount that may be desired for a given speed of
the stones and automatically varies with any variation of the speed, so that the
proper feed being once determined, it is automatically maintained whatever
variation there may be in the movement of the stones The improvement relating
to the stones and the mode of grinding is first described. This part of the
invention relates to grinding mills of that class in which the material is ground
between upper and lower stones. The improvements relate to a certain extent, to
the form of the stones, and more particularly to their mode of operation I con-
template principally the grinding and re-grinding of substances which may be
reduced wholly to a very fine dust or powder, such as gypsum, chalk, earth paints,
ores and the like, though under some circumstances it is applicable to other
substances. The object of the invention is to avoid the great amount of friction
incidental to the old form of stones, and great waste of power, the heating of the
substances and the irregular grinding, by reason of which another expensive
process is necessary-namely that of bolting, in order to secure the necessary
uniformity of fineness, which is required of materials which are used for coating
walls and for many other purposes. The mill stones heretofore commonly used
have as is well known, furrows, approximately radial in the grinding faces of the
upper and lower stones, the effect of which is to act upon the material ground
(technically called the "food" or
goods") by a shearing action, to crowd such
goods upon the lands where they are abraded by surfaces held apart by the goods
themselves, and also to regulate the outward flow of the goods from the eye to the
skirt. It is the crowding action of these furrows and the friction of the closely
Bet stones in the land portions, which causes the great friction The uneven
distribution of air creates a tendency to heat and the grooves often cause a
discharge of a part of the material coarser than the rest which interferes with the
uniformity of the grinding and makes subsequent bolting necessary The essential
principle of the invention, lies in grinding between substantially smooth surfaces
of stones with the under stone level and the upper dished and slightly separated,
leaving the space kept uniformly and constantly crowded full, whereby the goods
are caused mainly to grind by attrition and crushing of particle with particle of
their own substances. I have found that certain forms and conditions of the
stones are essential and effective. The approximate form of stone is shewn in the
accompanying drawing, forming part of this specification and in which Figure 1
represents a section taken vertically through the stones
"
Figure 2 shows the face of the stones and
Figure 3 shows in the upper part, the improved adjusting and regulating devices
for the feed, being partly in section, and in the lower ordinary devices for driving
the lower stone and for adjustment of the stones
In these figures the lower stone A which must always be the moving one is
inade with a perfectly plane level surface from eye to skirt, which surface is either
perfectly smooth or formed with a very fine shallow crocking, for the purpose of

page_text: helping the stones to stick to the goods and whirl them about and prevent them
packing down on the stones. The upper stone B is formed very slightly and
uniformly dishing from eye to skirt, and the surface of it may be crocked in a
manner similar to the lower. It is better in practice to form a slight pocket
immediately about the eye sufficient in size to admit the granules of the material
to be ground, fill between the upper and lower stones when they are in position
for work. Ordinarily, as for re-grinding plaster the upper stone is dished about
one eighth of an inch at the eye gradually lessening in not more than two inches
towards the skirt to one sixteenth of an inch and from that line, the dish gradually
decreases to the skirt These dimensions are for a stone of 36 inches in diameter.
These stones are provided with suitable mechanisms for feeding the materials
uniformly thereto, for giving rotary motion to the lower stone and for bringing the
stones together, It is also essential as will hereafter appear that the feed should
be perfectly adjustable to the stones and should be automatically varied to suit the
variations of the speed of the stones when running This feed is accomplished by an
apparatus hereinafter fully described and by means of it, the feed can be regulated
to the stones and afterwards all the variations are automatic It will be understood
from the statement heretofore given as to the conditions required, namely, that
the material shall be caused to crush or grind itself mainly against its own
substance, and crush and grind its whole substance to a condition of uniform
fineness, that all the parts of the space between the stones must be filled
and crowded with the goods If there be any place in any part of that space
between the stones not thus filled, there will be no action or only imperfect action
about that place Whenever the goods lie upon the lower stone and not in close
contact with the upper, no crushing or grinding will take place, since the stones
run no where in contact. It follows therefor that the dish of the stone must be such
that every part of the space will be kept full This is accomplished by exactly
proportioning the dish (which proportions have been given above) but the principle
is that as the goods move outward they will have the same space (decrease in
depth in proportion to the increase in length with allowance for increased bulk by
reduction) in zones of a given width at every point from centre to skirt; for if the
goods occupying a zone, say one inch in width at the distance of six inches from
the eye, quite fill that space, and as they are whirled around and reach a space one
foot from the eye, where the zone of an inch width would be much longer they
would find if there were no dishing, or too little dishing much larger space and they
would not be crowded On the other hand, if the dishing were too great, they
would be overcrowded and clog Again it is essential that the surface of the lower
stone should be a perfectly plane surface since the goods rest upon that surface and
are carried outward by the centrifugal action alone which would be insufficient if
this stone were dishing. With the stones as formed a speed of 350 to 400
revolutions per minute is required to give the proper motion to the goods It has
been found that with this construction there is no heating of the goods as the air
is furnished uniformly over the whole surface The mode of operation of these
stones has been partially indicated in the description of their form and movement
It may be further stated that the goods must be fed in quantity or amount exactly
sufficient to occupy the space between the stones constantly crowded full and no
more, and this must be done at all times and under all variations of the speed of
the stones When the feed is once established and adjusted to suit these conditions,
the material is ground to any desired degree of fineness and of such perfect
uniformity that no bolting is afterwards required; and further I have found by
actual experiment that the mill can be run with about one fourth the amount of
power to grind the same amount and class of goods and there is the further saving
in the cost of dressing the stones In running these stones according to the
improved method the operator will be able to adjust the feed to the stones by
carefully observing their action and the condition of the material escaping from
the discharge spout. Supposing the mill to be provided with the automatic feed
regulator such as heretofore referred to, and the stones with the ordinary adjusting

page_text: C
and driving mechanisms, the operator will start the feed turning the spout aside
and observing the discharge If the stones have been set properly and the feed
properly adjusted the discharge after a slight delay while the space is filling will
appear of a proper degree of fineness and uniformity. But if; as may happen,
especially if the operator be inexperienced, the stones are not properly set at the
start, he should gradually bring the stones up until the proper degree of fineness
and uniformity is attained If before reaching that point, he finds that the stones
begin to clog in the eye and check the motion, he will then understand that the
feed is too great for that degree of fineness He will then lessen the feed by means
of the cone pulleys or by any other equivalent mechanism which may be used
Having reduced the feed, the operator will again proceed on, raise the stone until
he arrives at proper results, or will continue this method of adjustment until he
finds the feed properly regulated to the stone This being once reached can be
maintained for the same class of goods, but might have to be varied for another
class If the operator finds that the stone clogs at the eye without the motion
being checked he will understand that the feed is too great or the granules of the
goods are too large for the pocket or dish immediately about the eye To remedy
this and to fit the stone for such granules, the eye and the pocket immediately about
the eye must be increased for it will be understood that in this respect the stones
must be varied for different sizes of granules In regrinding plaster 36 inch stones
with five horse power will grind one ton an hour finer than can be obtained with the
finest flour bolt If the stones should not appear to be performing their full amount
of work, the operator should increase the feed and if necessary re-adjust the stones
until the desired results are obtained. The second part of this invention relates to
the feed regulator specially fitted to operate in connection with the above described
mill and method of regrinding plaster and like materials Such materials when placed
in the hopper or large garner for regrinding, tend to pack in proportion to the weight
of the mass and this packing interferes materially with the regularity of this feed It
cannot be made to flow regularly and uniformly by the use of any ordinary devices,
and will not feed at all or with any certainty by its own weight Various devices
have been heretofore used for this and like purposes, but I have found after much
experiment that an absolutely positive feed is essential for this and like material
when it is to be fed to stones for regrinding This positive feed in order to work
uniformly, must also work as it has been found by experiment in a mass of the
material so that the feeding screw shall always be packed This portion of the
invention consists first of a second or intermediate chamber between the garner and
the stone and second of a feeding screw, about one half of which is covered by a
closely fitting case at the delivery end and the other half exposed in the chamber
upon all sides to the material which is to be fed In the drawing A' represents the
garner, capable of holding a sufficient quantity of the plaster or other material.
Åt its bottom where the sloping sides unite is placed a throat or passage a provided
with a valve 6 This passage a opens into another chamber B' which it is preferred
to make about two feet long, fourteen inches wide and twelve inches high The
diameter of the throat a is about eight or ten inches These proportions are not
essential and may be varied but I deem them well adapted for the purpose It
will be understood that the material passes by its own weight through the throat a
and fills the chamber B' In the bottom of this chamber I place a screw or augur d
supported in suitable bearings and extending the entire length of the chamber
Over a part of the screw or augur I place a covering f which encloses the augur
from the chamber closely about the sides but is open at both ends The open end
within the box receives the material which is carried along by the screw into the
covering or case fand is delivered by the same motion at the outer end into an
open pipe g leading to the stones That part of the screw not thus closely covered
is constantly in contact with the plaster or other material and as the screw works
in this mass, it works constantly full and an uniform movement of the screw
fitting closely in case f carries an uniform amount through such case and delivers
it to the stone As the case f fits closely to the screw and contains none of the

page_text: feed except that carried along by the screw It therefor compels the screw to act
uniformly and evenly and prevents it from crowding the mass into the delivery end
of the chamber But as the stone is constantly varying in speed it is necessary to
vary the rate of movement of the screw This is accomplished by extending the
shaft or shank of the screw outside the chamber and providing it with an ordinary
cone pulley E connected by a band to a like reverse pulley F the shaft of which is
suitably connected to any convenient part of the mechanism which drives the stone
The feed may be regulated in relation to any given speed of the stone by adjust-
ment of the band upon the cone pullies After such adjustment it will be plain
that variation of the speed of the stone will directly vary the speed of the screw
and thereby the amount of feed. The lower chamber may be omitted and the
feeding screw be located in the bottom of the garner but it is better to use the
lower chamber in order that access may be had to the screw in case of accident
The screw must still be arranged with the last half covered in the same manner as
heretofore described This feed mechanism is also applicable to other kinds of mills
and to feed grains or other granules or pulverulent materials
Having thus described the nature of the invention as communicated to me by
my foreign correspondent What I claim and desire to secure by Letters Patent is
1 In a grinding mill a lower stone adapted to be driven and formed with its
face perfectly plane from centre to skirt, in combination with an upper stone, said
stone having a substantially smooth dress, and the upper stone dished substantially
from eye to skirt in the manner described, whereby the spaces between the stones
in zones of a given width on any part from centre to skirt are made of equal
capacity all as set forth
2nd The improvement in the art of grinding which consists in feeding the
material to be ground between the stones, the lower one revolving and having
a plain face and the upper one having a dished face, the dishing, giving equal
capacity to zones of equal width at different distances from the centre; in
adjusting and regulating the feed to the speed of the stone keeping them crowded
full, in adjusting the speed of the stone to accord with the pressure necessary to
the degree of fineness required and in discharging the finely and uniformly ground
material by centrifugal force all substantially as described
3rd In a grinding mill, a garner a chamber B¹, below the garner, a throat leading
from the garner to said chamber, a feed screw located in said chamber properly
driven, and having a close case covering it at the discharge end, said case leaving
about one half of the screw uncovered, and exposed to contact with the material
within the chamber, all the parts being combined, substantially as described
4th The combination of the screw d the box or chamber containing the material
to be fed, the casing f open at both ends and covering only part of the screw as
described and suitable driving mechanism connected to that driving the stone as
set forth
In Witness whereof I the said Philip Middleton Justice have hereunto set my
hond and cool this eighth dev of December in the year of Our Lord one
Signed Sealed and delivered
in presence of
ALLEN P JONES
53 Chancery Lane
London W.C
PHILIP M. JUSTICE (L.S.)