Improved Feed Device for Grinding Mills and other Machines requiring a Uniform Feed of Granular or Pulverulent Material.
Year: 1899

page_text: Date of Application, 31st Oct., 1899-Accepted, 13th Jan.,
1900
Improved Feed Device for Grinding Mills and other Machines requiring
a Uniform Feed of Granular or Pulverulent Material.
I, FRIEDRICHI WEGMANN, of Zürich, in the Republic of Switzerland, Manufac-
turer, 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:-
Roller mills used in flour mills fitted either with my porcelain rolls or with
ordinary cast iron rolls are usually fed from a hopper by means of a feed-roll
arranged at the bottom of the feed-hopper or -box and carrying forward in
its rotation the material. The supply is regulated by means of a slide or feed-
gate provided above the roll in such a way that the space between slide and roll
can be increased or decreased at will, to allow of more or less feed passing
through, as may be required.
This arrangement, however, has not proved satisfactory when the feed contains
light, flaky or stringy material. Such material does not sufficiently adhere to
the feed roll, like heavy granular particles of wheat, but being retained by the
slide, accumulates here and blocks the passage. The consequence is that the
feed is irregular and if the mill be not carefully looked after, it may run for
hours causing waste and doing bad work all round, and this is especially the
case, when moth balls or lumps are present. The feed will be equally defective
if large foreign particles of a size too large to pass through the adjusted feed
opening are present in the material to be ground.
Hitherto the only way to get over this difficulty has been to clear the passage
by hand, with a spatula, wire or other instrument, or the slide has had to be
further raised for a short time, in order to allow the accumulated material to
pass through. Unless this is done very carefully, however, the accumulation falls
down in masses, and entering between the grinding rolls, presses these suddenly
apart, and then equally rapidly permits them to close together again, whereby
the rolls frequently receive injury. Even if this be not the case, the dressing
machinery is always exposed to damage.
66
The arrangement invented by me and now frequently adopted by the trade,
viz. that of having two horizontal rolls, one in advance of the other, both rotating
in the same direction, the front one running faster and lifting the feed up and
distributing it over the entire length of the grinding-rolls has not proved uni-
dunst" more
formly satisfactory. In the case of grinding fine material called
particularly. the feed often gets between the two feed rolls and is thus rolled
together, falling in lumpy masses upon the grinding rolls. The result is imper-
feet running of the mill and irregular, not uniform, grinding, the arrangement
therefore, proving no better than the device, above described of raising the
slide.
The problem to be solved has been therefore to automatically remove all
obstructions of the character referred to, by mechanical means; or to prevent
such obstructions forming at all. I have solved it by my present invention of

page_text: the devices herein described. The new feed mechanism for grinding mills and
other flour milling machines has the following advantages:
1. It prevents accumulations of stock, moth balls, lumps and other foreign
matter, so that when grinding finest flaky "dunst," the material is uniformly
distributed and fed to the grinding rolls.
2. Should large lumps or hard foreign bodies of unusual size be present in the
material to be ground the feed is automatically stopped, so that the obstruction
may be removed; all danger of injury to the grinding rolls and dressing
machinery is thus removed.
The mode of carrying out this invention is shown in Figures 1, 2 and 3 of
the accompanying drawings.
+
Figure 1 is a vertical section of the new feed device.
Figure 2 is a side elevation of the same showing the driving arrangement.
Figure 3 is a similar view, showing one of the end levers in which the upper
roll is rotatably fixed and the mechanism for working the same.
The general arrangement of the mill is similar to that ordinarily employed..
but instead of the feed roll a having a flat slide arranged above it, a second
roll is provided. The two rolls a and b rotate in opposite directions and a
much slower speed is given to the latter roll. The upper roll b receives its
motion by means of worm gear cdef, as shown in Figure 2.
The ratio between the circumferential velocities of both the rolls is roughly
150, when using the said gear, but the applicant does not in any way limit
himself to such particular ratio, for the device will also answer the purpose in
view when the ratio is still greater than that stated.
t (Figure 1) is a flap, which may be hinged to the feed hopper or box by
means of a strip of leather. The object of this flap is to shut off the upper
surface of the roll b from the feed box, or in other words to prevent the feed
reaching the top surface of roll b. The flap also fulfils another purpose, as will
be hereinafter described.
The roll b is rotatably mounted at each end in a lever 9 (see Figure 3).
The two levers g are similar and each has its fulcrum on a shaft h. They are
connected together by means of this shaft which moves in bearings in the frame-
work. The roll 6 thus being able to pivot upon the shaft h can be raised or
lowered parallel to the lower roll a. By means of this arrangement two points
are secured:
a The roll can be easily adjusted relatively to the roll a, for the regula-
tion of the thickness of feed thus doing the work of the ordinary slide or feed-
gate.
b/ The roll b possesses a certain degree of resiliency and can automatically
move in an upward direction beyond the regulated distance between it and roll a,
in order to make room for moth balls, hard lumps, strings and other foreign
bodies, which cannot pass through i.e. to increase the opening between both the
rolls according to the size of these bodies.
The mechanism by which this is effected is clearly shown in Figure 3, but it
is only given as an example, as other constructions may be used.
One of the levers is extended above the bearing of the roll b, and is
pivoted at to a double armed lever k. One arm of the latter extends upwards,
its end m bearing upon a bracket or projection n on the feed box. The lower
arm of the lever k projects outwardly and is provided at its end with a set
screw o. If then the latter be turned so as to increase the distance between
the lower end of the lever k and the fulcrum h, the lever k as a whole will rise
since it is supported at the bracket n and screw o. The result is that the roll b
is also raised, as it is suspended from the lever k at the joint . In this man-
ner the extent of opening between the rolls a and can be fixed at will for
the smallest distance, so that the roll 6 performs what is otherwise done by the
slide, as it is stated above under the heading a/.
+
Should, on the entrance of obstructing material, the roll b rise from the

page_text: roll a more than the distance for which the screw o is adjusted, the latter will
not be affected, since the lever k will then merely slide up and down on the
bracket n.
In order, however, to prevent the roll 6 from lifting too much and letting
large masses and foreign bodies which might damage the grinding rolls pass
through, mechanism must be provided to stop the rotation, when such obstruc-
tions occur, so that these latter may remain sticking between the rolls. For
this purpose the lever g is provided with a projection 9, carrying a set screw
at its end. When the roll 6 lifts unduly, the head of the screw r strikes the
levers, pivoted to the framing. (The said screw may be inserted in the
levers instead of being screwed into the projection 9). This lever s carries a
catch, the engaging or releasing of which causes the feed roll a to be auto-
matically set in motion, or stopped, respectively.
The mill is provided with the usual alarm device which when a stoppage
takes place calls the attention of the attendant. The latter can then remove the
obstruction from the front; or he can press back the flap t, already referred to,
with the hand and reach the obstruction from behind the rolls.
The devices described, however, will only operate in the desired manner, if
the circumferential velocity of the upper roll 6 is very considerably slower than
that of the lower feed roll a. This slower speed is necessary not only that the
upper roll may perform the service of a slide or feed gate, but also to prevent
obstructions and to stop large foreign bodies in their passage.
To act effectively in place of a slide, the upper roll must exert a retarding
action on the material being fed, and if necessary cut-off the supply. This roll,
therefore, must not rotate rapidly, as this would increase the flow of material
on to the grinding rolls. For that purpose the roll is sufficient; the roll b,
on the contrary, by means of its pressure and motion has to produce a slight
pressing and pushing forward motion in order to increase the adhesion of the
obstructive matter to the lower roll a. Such action must necessarily be a slow
one, otherwise the lifting of the roll b, owing to the resiliency of the arrange-
ment, would be very irregular. Furthermore, the slow speed of the upper roll,
in conjunction with the faster speed of the lower roll, causes the obstructive
matter to be drawn asunder and divided before it has time to accumulate and
form balls or lumps. This action will be the more effective the slower the speed
of the upper roll. In the case of large, hard foreign bodies, which it is desired
shall remain sticking, instead of passing through, the slow motion of the upper
roll is again effective, inasmuch as it is precisely such retarded motion which
holds back the foreign matter until the feed is automatically stopped.
The limits of motion and revolution of the two rolls (which in view of their
action may be termed respectively "feed" and "brake roll") have been thor-
oughly tested by experiments extending over a number of years.
This new feed device introduces entirely novel features, and it is an essential
advance in the milling industry. By its use, various causes of interruptions
and consequent bad work are overcome, the commercial advantages obtained
from the invention being therefore of the highest importance.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. A feed device for grinding mills and other machines requiring a uniform
feed of granular or pulverulent material, consisting of a feed-box and of two
rolls arranged one above the other at the bottom of the said feed-box, the top
roll having a less circumferential velocity than the bottom roll, substantially
as described.
2. In a feed device for grinding mills and the like, the combination of a
feed-box and two rolls arranged one above the other at the bottom of the said
feed-box, the top roll having a less circumferential velocity than the bottom roll,

page_text: with means allowing the rising and falling of the top-roll and a device flexibly
connected to the feed-box and lying against the top roll at the back, substanti-
ally as described.
3. In a feed device for grinding mills and the like, the combination of a feed-
box and two rolls arranged one above the other at the bottom of the said feed-
box, the top roll having a less circumferential velocity than the bottom roll,
with means allowing the rising and falling of the top roll and means for stopping
the rotation of the said rolls, when the top roll rises too high, substantially as
described.
Dated this 30th day of October 1899
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.