Improvements in Roller-mills.
Year: 1889

page_text: Date of Application, 16th Aor., 1889
Specification Accepted, 1st June, 1889
Improvements in Roller-mills.
I, HERBERT JOHN ALLISON, of the firm of Allison Brothers, of 52 Chancery Lane,
in the County of Middlesex, Patent Agent, do hereby declare the nature of this
Invention (which has been communicated to me from abroad by Heman A. Barnard,
of Moline, in the County of Rock Island, State of Illinois, United States of America,
Engineer, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
Figure 1 is a side elevation of the improved roller-mill. Fig. 2 is a similar view
of the opposite side. Fig. 3 is an end elevation partly in section. Fig. 4 is an
enlarged sectional view showing the roller-adjusting mechanism. Fig. 5 is a similar
view showing a modification of the same.
This invention relates to improvements in roller grinding-mills of the class in
which horizontal pairs of parallel cylinders or rolls are employed to reduce the
material by crushing it between them as they revolve, and it has especial reference
to flour or grain mills of this class having pairs of rolls rotating at different speeds
and in which one roll of each pair is journaled in fixed bearings on the main frame
of the mill and its opposite or exacting roll is journaled in movable arms, so that the
latter roll can be adjusted toward or from the rigid roll to regulate the amount or
quality of reduction of the grain.
The invention has for its objects to provide proper supporting-arms for the journals
of the yielding roll; to pivot or support these arms in such manner that they can be
simultaneously moved to separate the yielding roll from the rigid roll, to stop the
grinding of the material; or moved to restore the roll to its operative position; to
form the journal-blocks of the movable roll in such manner and secure them to the
arms so that each journal of the yielding roll can be adjusted vertically independently
of the other journal or of the movement of the arms; to provide means whereby
the arms can be independently adjusted to shift the roll horizontally and to retain the
roll in such position normally while in operation and yet permit the roll to yield or
separate from the rigid roll should any foreign hard substance fall between them,
so that injury to the faces of the rolls is prevented and whereby the yielding roll is
at once returned to its normal position after the passage of such foreign substance,
and to provide suitable devices for continuously cleaning the surface of the rolls in
the pair during the operation of the mill.

page_text: Further objects of the invention are to provide an improved drive for the four-
roller mill in which the slow rolls of the pairs are driven by separate belts from the
counter-shaft on the same side of the mill while the fast rolls are driven by the main
belt, and to provide tightening devices for the main belt or fast-roll drive and suit-
able devices for simultaneously and equally tightening the separate belts of the slow
rolls.
These objects I attain by the present invention, which consists in the novel con-
struction and arrangements of various parts of the mill and in the arrangement of
the drive-belts, as will be fully understood from the following description when taken
in connection with the accompanying drawings, and particularly specified in the
appended claims.
Before proceeding with the description of the mill I will state that I have shown
a four-roller mill in the drawings, which is the ordinary manner of arranging such
mills, being, in fact, a double mill arranged in one machine.
The rolls of each pair and their relative arrangement and construction of mechanisms
being similar, a description of the mechanisms of one pair of rolls will impart a clear
understanding of both. In the drawings I have also shown an arrangement whereby
the rolls in each pair can be simultaneously separated or caused to approach to
start or stop the grinding operation, and which is fully hereinafter described.
Referring to the drawings by letters, A designates the frame or casing of a four-
roller mill of any proper form and construction, its sido pieces, however, being
provided at opposite ends and in parallel lines with the oppositely-outstanding
arms a a, as will be hereinafter more specifically referred to, the arms a a of each
side piece standing parallel with the arms a a of the opposite side piece at their
respective ends of the mill.
B designates the hopper or feed mechanism casing, secured to casing A above the
grinding-rolls. This hopper is made double, so as to deliver grain to each pair of
rolls, as shown, and each feeding device consists essentially, of a double hinged pair
of valves, each of which can be closed toward the other by means of suitable cams
mounted on proper rods or shafts to be operated from the outside of the casing, and
the outer valve of each pair is adapted to be vibrated by means of a cam-wheel or
vibrator secured on a shaft within the casing and rotated by means of belts and
pulleys on the cam-wheel shafts and on the extended journals of the rolls. These
feed devices are provided with suitable mechanisms for regulating the size of feed-
openings to each pair of rollers and for cutting off the feed at both ends of the mill
simultaneously.
CC designate the rigid rolls of the pairs, which are mounted parallel with each
other in suitable journal-bearings formed in the upper portion of casing A, and
retained in such journal-bearings by half-boxes or caps b, as shown.
Outside of and below the journal-bearings of the rigid rolls the casing A is reduced
in height, as usual, to allow of horizontal adjustment of the yielding roll, as herein
after described.
I will now proceed to describe the means for supporting and adjusting the yielding
rolls.
D D designate the yielding rolls, corresponding in size and form to rolls C and
journaled in pillow-blocks E E, which are mounted upon, and adjustably bolted to,
movable or swinging arms F F, as will be hereinafter more particularly described.
The arms F have their horizontal shanks standing inwardly toward each other
on the same side of the casing A. The ends of these shanks fare provided with the
downwardly-standing enlargements f¹, which are centrally perforated for the passage
of cams g formed on the ends of rods or shafts G, which extend entirely across the
width of the mill and are properly journaled in the sides of casing A thereof.
F¹ designates the upright portion of arms F, which portion rises from shanks f,
outside of their enlargements f, to about the height of the top of the boxes b of the
rigid rolls. The inner faces of shanks fand portions F' are dressed at right angles
to each other and properly finished to form a seat for the journal-blocks E E.
These blocks are held in position on arms F and can be adjusted vertically thereon

page_text: by means of the screw-bolts E¹, which extend vertically through corresponding screw-
threaded openings in shanks f, outside enlargements f, and impinge against the
bottom of blocks E, and by screw-bolts e e, which play through vertical slots f³,
formed in the parts F' of arms F, near the upper and lower ends thereof, and engage
in screw-threaded openings in the block E, so that when the yielding rolls and the
blocks receive their initial vertical adjustment by bolts E', the bolts e riding up or
down through slots f³, the latter screw bolts can be tightened and securely and rigidly
lock the pillow-block E in position on arm F. Each arm F and its pillow-block is
provided with similar adjusting and retaining devices. The blocks È E are made
sufficiently high to give them a firm support against the faces of part F¹ of the
arms and are preferably recessed on their inner surfaces, as shown at e'. The
journal-boxes proper for the shafts of the rolls D are formed in the upper ends of
blocks E and caps , similar to the journal-bearings of rolls C.
H designates an outstanding piece or part of each arm F, standing horizontally
from the portion F¹ and preferably between the slots therein. These parts H are
preferably formed integral with arm F, but may be made separate and secured thereto
in any proper manner.
The part H of each arm F extends outward a sufficient distance to bring its
end directly over the end of the arm a of casing A on its end and side of the
machine.
The end or head h of part H is provided with a central vertical opening, h,
through which passes freely the upper threaded end of a rod, I. The lower threaded
end of each rod I passes through a vertical slot, i formed in the end of arm a, and
through a cylindrical nut, J, which has its ends journaled in proper openings in the
arm a on the sides of slot i, so that while the rod I can be screwed up or down
through the nut J it can also with this nut have a slight lateral rotary or swinging
movement on arm a by reason of the widened upper and lower ends of slot i, as
shown in Fig. 4. The upper end of rod I above head his provided with the hand-
wheel nut K, having a suitable washer, k, interposed between it and head h, the upper
surface of head being suitably rounded to present as little frictional bearing-
surface to the washer k as is found desirable.
K designates a jam-nut on rod I above hand-wheel K.
L designates a suitable spring placed on rod I below head and bearing against
said head through an interposed washer, l, the lower surface of head / being rounded
to reduce friction with the washer, as shown.
L' L' are setting and jam nuts on the lower portion of rod I above arm a and
engaging the lower portion of spring L through interposed washer ', as shown.
The spring L presses the head of part H of arm F upward against the nut K,
the pressure being regulated by the nuts L', so that the arms F are upheld by rods Í
through the springs L thereon, as is evident.
designates a bolt engaging through a suitable threaded opening in the head of arm a
with the nut J, so that the latter can be rigidly locked therein, if desired.
The arms F and their appurtenances and connections with rod I form the setting
and adjusting devices for the yielding roll and are operated as follows: The
arms FF, carrying rolls D D, as described, are mounted on the shaft G or on similar
bearings by their shanks, so that they can swing or rotate on said shaft, there being
two arms for each roll, mounted on opposite sides of the main frame and indepen-
dent of each other, so that either end of the yielding roll can be independently
adjusted to compensate for wear of the surfaces of the rolls C D. The pivots of
arms Fare preferably vertically below the centres of the yielding rolls when the
latter are in grinding position, or may be set outward, so as to naturally incline the
yielding rolls toward the rigid rolls, as is found preferable, but should not be located
to the inside of the shaft of the rolls D, because it is found in practice that when so
located compression is always had upon the governing-springs of the arms, as the
weight of the roll causes it to move outward by gravity, and therefore the springs
ave at all times to support more or less of the weight of the yielding roll.
Consequently the springs are weakened and need frequent regulating.
The

page_text: rolls D being mounted on arms F, as described, if it is found that they are out of
vertical alignment with the rigid rolls, the bolts e are loosened, the bolts E¹ raised or
lowered until the proper alignment is reached, then bolts e e are tightened, and the
rolls are ready for action. The yielding rolls are horizontally adjusted by means of
the rods and their connections. For instance, if it is desired to draw one end
of a roll D outward to parallel the rolls, the rod I of the arm F supporting that end
of the roll is turned down through nut J and engages the upper end of piece H of
the arm F, depressing the latter and causing the arm to turn outward on its pivot and
thereby separate the rolls. If it is desired to set one end of roll D closer toward its
roll B, the rod I is turned upward, carrying with it the nuts K and allowing the
spring L to lift the piece H and turn arm Finward. The springs L at all times keep
the arms H pressed upward against the washers and nuts K, and this spring regulates
the tention of the rolls as usual; but should any hard foreign substance fall
between the rolls when in operation the roll D can by the swinging arms F move
outward, this action causing the compression of spring L through arms H, as is
evident.
It will be observed that while the rolls can be horizontally adjusted by the rods I,
as described, the adjustment of spring L is in no wise affected, the springs being
supported and adjusted solely on the rods, as described, this feature permitting the
rapid setting of the mill to reduce the grain to various grades and obviating the
resisting of the springs at each change of position or "set" of the rolls.
The shanks fof arms F might be, if desired, pivoted to rigid lugs or points on
casing A, and would then permit the required adjustments of the yielding rolls; but.
in order to make the separation of the rolls when it is desired to stop the grinding
without stopping the motion of the rolls, I mount them on the horizontal shafts G, as
shown. These shafts have their ends reduced in diameter forming there by cams g
with the main body of the shaft, the shaft being journaled in the casing A, as
described, so that when it is rotated the axis of cams g will move concentrically
to the axis of the shaft proper. Upon these cams g, at opposite sides of the machine.
are mounted the arms F of each roll D. The cam g of the shaft are extended
beyond the bearings of arms F on one or both sides of the mill, and on one cam g,
outside arm F, is rigidly secured by a set-screw or in other proper maner a lever, M,
which extends downward and outward to a point below arm a, and is adapted to be
engaged by a retaining-catch, m³, of suitable construction, secured to the main
frame A.
m designates an arm rising from the upper end of lever M at or about right
angles thereto, the levers M and m forming a bell-crank journaled or secured at its
angle to the cam g.
O designates a lever arm similar to arm m, secured to the end g of the opposite
shaft G to that bearing lever M and on the same side of the machine. The lever O
inclines inward and downward at right angles to the inclination of arm m when the
parts are in normal position.
N designates a pitman-rod pivotally connected to the levers m and O, so that they
move synchronously when operated.
There may be
similar arrangement of levers and connections on the opposite side
of the mill, if desired.
The normal position of the arm bearing cams g of the shafts G in relation to the
body thereof is to lie at the lowest point of the shaft with their axis in vertical lines
with the axis of the shafts, as shown in Fig. 4.
Now, upon lifting the outer end of lover M, the shaft G, to which it is attached by
cam g, is rotated, and through the connections of arms m and O and pitinan-rod N
the opposite shaft is similarly and simultaneously rotated. The cains g, being accentric
to the main body of the shaft G, will ride upward and outward, thereby lifting the
inner portions of armis F. The pieces H of the arms F, being kept from lifting by
the nuts K on rod I will cause the arms to turn downwardly and outwardly, thereby
separating the rolls D from rolls C, this separation continuing as long as the lever M
is raised. The rods I can swing slightly on their nuts J, and thus prevent any

page_text: friction of pieces H. against the rods, rendering the separating of the rolls both
rapid and easy through the described means. When the lever M is depressed and
again engaged by its catch m¹, the rolls are returned to their grinding position. It
will be observed that, owing to the yielding or swinging of rods as described,
when the rolls are separated by turning shafts G the springs L are not compressed or
put under strain, so that they are ready for instantaneous action immediately upon the
return of the rolls to the grinding position.
It will be observed that, by reason of the cylindrical nuts J, when the arms F are
moved outward the rod I is allowed a corresponding degree of swinging or rotary
movement, so that there is no binding or friction caused by the separating of the
rolls, except at the pivots of arms F and rods I, and the amount of necessary
movement of said parts in this operation is so slight that friction is imperceptible.
In Fig. 5 I have shown a modification of arms F. In this the upright Fis
shortened and the piece H is formed on or secured to the block E, the adjusting
mechanism being the same. On the inner faces of the sides of the casing A, at points
centrally between but below each pair of rolls, are formed the outstanding vertical
pairs of flanges P, united at bottom by a bracket-piece, p. The flanges P on opposite
sides of the mill form guides for and receive the lugs q on the ends of scraper-
frames Q.
These frames are rectangular and consist of side pieces, q¹, and end pieces, q³, on
which are formed the lugs 9, which lie in the longitudinal axial line of the frames and
pivot them centrally in their bearing as shown. The parts of the franies are cast
integral, so that the frames are rigid, and when in position the depression of one
bar q will elevate the other as evident. Upon bars gl are secured by proper screws
the scrapers or brushes R. The journals 9 of the frames are supported in their
bearings upon springs P₁, which are adjusted by set-screws or bolts P2, playing
through proper openings in brackets p and having upon them below these brackets
jam-finger-nuts for locking the bolts P when properly adjusted. By means of
these springs the scrapers are held with sufficient pressure against the rolls to
ordinarily clean their surfaces; but should the roll-surface become broken and catch
the scraper R the springs would permit the frame to descend and disengage the
scraper from the damaged roll without injury; but their principal object is to
compensate for wear of the scrapers, so that they will always effectually cleanse the
rolls without requiring frequent adjustment, as would be the case were no springs
used. If desired, brushes might be substituted for the scrapers, their operation
being the same, but not so effective.
I will now describe the drive of the rolls and the regulating or tightening devices
therefor.
The shafts of roll D in one pair and of roll C in the opposite pair of rolls are
extended on one side of the machine outside their respective bearings, and have
secured upon them the similar pulleys S S'. The shafts of the remaining rolls CD,
are similarly extended on the opposite side of the mill and bear the similar pulleys sst.
The rolls bearing the pulleys S S¹ are the fast rolls and those bearing pulleys & s¹ are
the slow rolls.
T designates a counter-shaft journaled centrally in proper bearings on the main
frame below the rolls and bearing at one end, on the same side of the mill as
pulleys S S', a pulley, t, of suitable diameter, hereinafter referred to.
On the other end of the counter-shaft are fixed two pulleys, T¹, which may be of
equal or unequal diameter, as desired; or one extra-wide pulley may be substituted.
The pulleys S S' are on the front side of the mill and are run by the endless main
driving-belt U, which passes up through the floor upon which the mill rests from a
pulley on a driving-shaft of the mill (not shown in the drawings) to and over
pulley S, thence down to pulley t on the counter-shaft, thence up over pulley S¹,
and then down through the floor to the driving-pulley. The main belt U, it will be
seen, is thus made to drive both fast rolls and also the counter-shaft.
On the rear side of the mill I employ two endless belts V v, for driving the
pulleys of the slow rolls. The belt V-drives pulleys and its roll from inner

page_text: .
pulley T on the counter-shaft, and belt drives pulleys from the outer pulley T³,
the shaft of the roll on which the pulley is splined being extended sufficiently
to bring the pulley s¹ and outer pulley T into proper alignment. It is obvious
that by having the pulley t on the counter-shaft larger than pulleys T¹, I can
obtain the different speeds of the rolls, and can, by varying the sizes of the
pulleys, regulate the amount of differential speed of the rolls. The counter-
shaft T, being situated centrally of the mill, as shown, will be nearer the inner slow
roll than the outer slow roll, as is evident. Now, the belts V v, which drive the slow
rolls, are of unequal lengths, but are simultaneously tightened or tensioned by means
of a single device, which is as follows: W designates an arm pivoted at its lower
end to a suitable support on one side of frame A below the driving-pulleys on the
rolls thereof. The upper end of this arm is bifurcated, as shown, and in the sides of
this bifurcated portion are formed proper bearings for a shaft, W, as shown, and on
this shaft are mounted two pulleys, X, of unequal diameters, one of which may be
keyed on the shaft, if desired, or both left free to turn thereon. The arm W stands
in such position that its pulloys X and rest against the belts V and v. The belt V
runs to the nearest roll, and by pivoting arm W to the main frame on the same side
as the belt before. its pulley X can be brought to hear upon belt V pulley has
engaged and taken up the slack in belt v, as shown. The relative sizes of the
pulleys are such that when arm W is sufficiently moved inward to cause
pulley to take up the slack of belt the pulley X will impinge against belt V, and
any further movement of arm W will similarly affect both belts and tension them
equally and simultaneously, so that the regulation of both belts is affected by one
device. It is obvious that in order to tighten the belt V its loose or slack side must
pass by the line of the tight side of the belt v. Consequently it is imperative that the
pulley for belt must be smaller than that for belt V, or it would prevent the
tensioning of belt V. It is also desired sometimes to employ pulleys of unequal size
on the slow rolls or for their driving-pulleys on the counter-shaft. In this case the
belts are not only of unequal length, but also travel at different speeds, and a single
pulley would be inoperative, so that it is necessary that the pulleys be of unequal
diameters and also independent of each other.
By having the pulleys of unequal diameters a more even and uniform tension of the
helts can be attained.
The means for regulating and adjusting the position of arm W is as follows.
Y designates a rod extending from arm W to and through a bracket on the main
frame, having a hand-wheel nut, Y¹, on its threaded end outside the bracket, by
which the position of the arm can be regulated.
The inner threaded end of rod Y connects with arm W by means of a nut, w¹,
journaled in the sides of a slot formed in the arm, similarly to the nut J and its
connections to rod 1 in the roll-adjusting mechanism. Z designates an arm similar
to arm W in all respects except that it bears but one pulley, z, and is situated on the
opposite side and end of the mill from arm W, being controlled by a rod, Y2, and its
connections, as described. The pulley z of arm Z impinges against belt U and
regulates the tension of the same, as is evident.
Having described my invention I claim―
1. In a roller-mill, the combination of the rigid roll and the yielding roll, with the
swinging arms supporting the yielding roll, the springs controlling said arms mounted
on swinging supports, the transverse shaft G, journaled in the main frame below and
parallel with the yielding roll and having cams formed on its ends upon which the
swinging arms are supported, and the lever to oscillate the shaft and thereby shift
both arms simultaneously to throw the yielding roll away from the rigid roll without
disturbing the alignment of the rolls or the tension of the controling-springs, and
mechanism for holding the yielding roll up to the rigid roll when in operative
position, substantially as specified.
2. In a four-roller mill, the combination of the rigid rolls with the yielding rolls,
the swinging arms supporting the latter, the adjustable springs controlling said arms
:

page_text: mounted on swinging supports, the two shafts G G, journaled in the main frame
below the yielding rolls, having cams g on their ends, upon which said arms are
mounted, the series of connected levers for simultaneously oscillating shafts G G, to
adjust the yielding rolls to or from the rigid rolls without disturbing the tension of
the springs, and mechanism for holding the yielding rolls up to the rigid rolls when in
operation, substantially as specified.
3. In a four-roller mill, the combination of a counter-shaft journaled in the main
frame and receiving motion from the main driving belt at one side of the machine,
pulleys on the other end of said shaft at the opposite side of the machine, pulleys on
the shafts of two of the rolls, and belts of unequal length diverging from the
pulleys on said countershaft to said other pulloys, with a tightening device mounted
on the main frame, having two pulleys of unequal diameters adapted to be brought,
respectively and simultaneously, against the slack sides of said driving-belts, all
substantially as and for the purpose specified.
4. In a roller-mill, the combination of the crushing-rolls and the main frame
provided with vertical guides and horizontal brackets on the inner faces of its sides
with a rectangular frame, Q, carrying suitable roll-cleaning devices and having lugs y
on its ends moving in the guides on the main frame, the springs loosely supporting
the frame, and the bolts P2, carrying the springs whereby the frame can be adjusted,
all constructed and arranged to operate substantially in the manner and for the purpose
described.
5. In a roller mill the combination of the rigid rolls, the yielding rolls, the
upright movable arms F, bearing the yielding rolls, the springs engaging said
arms mounted on swinging supports, the transverse shafts GG, journaled in the
main frame below the yielding rolls, having cams g on their ends, forming the
pivotal supports of said arms, and the connected levers for oscillating said shafts
simultaneously to shift arms F and throw the yielding rolls into or out of grinding
position without disturbing the adjustment of the_controlling-springs; with the
screw-rods and their adjusting-nuts engaging arms F and projections of the main
frame for regulating the grinding adjustment of the rolls, substantially as specified.
6. In a roller-mill the combination of the rigid and yielding rolls and the
independent movable arms F with the vertically-adjustable pillow-blocks mounted on
arms F, forming the journal-bearings of the yielding rolls, the springs L for
regulating the adjustment of the arms F, mounted on swinging supports, the
transverse shafts GG, having on their ends cams g, forming the pivotal supports of
arms F, and the connected levers to oscillate said shaft to simultaneously shift the
arms to throw the yielding rolls into or out of grinding position without
disturbing the tension of the springs; all constructed and arranged substantially in the
manner and for the purpose described.
7. The combination of the swinging arms F, carrying the yielding rolls, the
adjustable swinging screw-rods I, and adjustable nuts and springs L thereon
controling arms F for regulating the grinding operation of the rolls; with the
transverse shafts G, having cams g on their ends, upon which arms F are mounted,
and the levers for oscillating said shafts to shift arms F without disturbing the
tension of springs L, all constructed and arranged substantially as and for the
purpose described.
8. The combination of the adjustable angular arms F and the rod I and its nuts
and springs for regulating and adjusting the arms, substantially as described; with
the angular pillow-blocks E, mounted on said arms, the adjusting bolts E¹ and
retaining-bolts e for said pillow-blocks, and the rolls mounted on the pillow-blocks,
all constructed and arranged to operate substantially in the manner as and for the
purpose described.
9. The combination of the roll-supporting pivoted swinging arms F F, having
out-standing slotted pieces H H, with the journal-nuts mounted on the main frame,
the threaded rods I, I, adjustably engaged at their lower ends in said nuts and playing
freely through openings in pieces H H, the adjusting nuts and jam-nuts on rods I
above pieces H, and the springs L and nuts L' on said rods between nuts J and

page_text: pieces H, whereby the arms F can be adjusted without disturbing the springs, all
constructed and arranged to operate substantially in the manner and for the purpose
described.
10. In a four roller mill, the combination of the rigid roll, the pivoted swinging
arms F, having each an outstanding piece, H, the pillow-blocks E and the yielding
roll mounted in said blocks, and the shafts G, journaled in the main frame below the
yielding roll and having cams 9 g on its ends, forming the pivotal supports of arms F,
with the rods I, springs L, and nuts L₁ thereon, and the journal-nuts J, K, and K',
engaging piece H, whereby the arms F can be adjusted without disturbing the springs,
substantially as and for the purpose specified.
11. In a roller-mill, the combination of the fast rolls having equal-sized pulleys on
their shafts at one side of the mill and the slow rolls having equal-sized pulleys on
their shafts at the opposite side of the mill with the counter-shaft having pulleys on its
opposite ends driven by the main-belt, that also drives the fast rolls, and driving the
slow rolls by different belts of unequal length, and a belt-tightener composed of a
bifurcated bracket pivoted on the main frame and carrying two pulleys on one shaft
adapted to simultaneously tension these belts, and suitable tension devices for the main
belt, substantially as and for the purpose specified.
12. The combination, in a four roller mill having fast and slow rolls and a counter
shaft, T, having single pulleys t at one end and double pulleys T¹ T¹ at the other, of
the main belt U, driving the fast rolls and counter-shaft at one side of the mill, and
the belts Vv, driving the slow rolls from pulleys T' T¹ at the opposite side of the
mill, with the belt tightening devices for belts V v; consisting of an arm, W, pivoted
to the main frame and operated by an adjustable horizontal screw rod, Y, and bearing
in its upper bifurcated end the large pulley X and small pulley mounted upon the
same shaft, engaging respectively the belts V v and the similar arm Z bearing one
pulley, and its operating devices for tightening belt U, all substantially as and for the
purpose described.
1000