IMPROVEMENTS IN FRICTION CLUTCHES
Year: 1883

page_text: LETTERS PATENT to Alexander Melville Clark of the firm of A. M and
W Clark of 53 Chancery Lane in the County of Middlesex Fellow of
the Institute of Patent Agents for an Invention of IMPROVEMENTS IN
FRICTION CLUTCHES Communicated to him from abroad by Gabriel Nicolas
Schoenberg of Paris, France
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 24th January 1883.
ALEXANDER MELVILLE CLARK of the firm of A. M. and W. Clark of 53 Chancery
Lane in the County of Middlesex, Fellow of the Institute of Patent Agents
"IMPROVEMENTS IN FRICTION CLUTCHES [Communicated to him from abroad
by Gabriel Nicolas Schoenberg of Paris, France]
"
This Invention relates to improvements in friction clutches in which the adhesion
or friction is produced between plane surfaces, and which embodies in a practical
and simple way the principle of the total envelopment of a pulley by its belt which
yields as regards the ratio of the weight raised to the pressure of contact, a result
greater than unity.
In order that the Invention may be more readily understood, I will proceed to
describe it with reference to the accompanying drawings which represent examples
thereof, it being understood that the form and dimensions of the various parts are
capable of variation according to the nature of the application without departing
from the Invention.
The Invention consists essentially in fixing between two metal rings of suitable
form such as shown in cross section at a b c, d fg, hik, and l m n (figure 1) a flat
band of any kind of material used for such purposes, and in applying the friction
to the edges of said band by means of a third ring a¹ b¹ c¹ d'.
To avoid the frequent repetition of the letters of reference, the rings will be
herein-after referred to as follows:-
(1.) The metal ring a b c, d e f encircled by band as the inner ring.
(2.) The metal ring hik, l m n enveloping the band as the outer ring.
(3.) The metal ring a b₁ c² dl as the friction ring.

page_text: (1.) The inner ring has a cylindrical part bc, fd equal to the width of the
band and a flange a b, fg at right angles to the cylindrical part and equal to the
thickness of the band when coiled on the said ring as hereafter described.
(2.) The outer ring is made of slightly less internal diameter than that of
the band when coiled on the inner ring and turned down as hereafter described
and it is also slightly coned internally so as to increase its pressure upon the band
when applied thereon; the flange of this ring may be made of any desired form as
will be hereinafter described.
(3.) The friction ring is intended to transmit or receive the necessary pressure
for the transmission of motion and should be provided with one or more projecting
flanges op Figure 1 of plane or angular form but capable of entering easily the
space between the two rings in which the band is coiled. The cylindrical part
of the inner ring should be in one of the forms illustrated in Figures 2. 3. 4.
The mode of attaching the band is as shown in Figure 2. A slot is made in the
cylindrical part of the ring for the passage of the band and the cylindrical part at
one side of this slot is reduced in thickness to an extent equal to the thickness of
the band as shown at a the sunk surface a bd gradually running out at the
circumference of the ring a quarter or a half way round the same
The mode of attaching the band may vary
(1st) If the ring is large enough the end of the band may be clamped between
two angle iron plates m n, roughened on their inner faces and rivetted together.
This done the band is then inserted in the slot as shown the plates m n formning
stops.
(2nd) If the band is to be coiled upon the hub of a pulley, or a solid core where
no internal space is available as in Figure 3 a single clamp only is used of the form
shown which is tapered and curved so as to extend a quarter to half way round
the hub in which it is countersunk as shown, the end of the band being attached
thereto by rivets or screws, the clamp being further secured to the hub by a
number of studs screwed into the bottom of the recess in which it is countersunk
and projecting up through the band and rivetted down thereon or secured by nuts.
(3rd) When the power to be transmitted is small it is sufficient to screw a
number of pins into the hub as in Figure 4 the said pins passing through the band,
and being rivetted down thereon over thin washers or secured by screw nuts which
sink by their own pressure into the thickness of the band. The mode of winding
the band upon the ring is as follows. Suppose the mode of attachment Figure 2 to
be employed, I mount in a lathe, a face plate or chuck A B (Figure 5) keyed upon
a shaft CD turning between centres or otherwise. The face plate has a turned
flange M N on it upon which is fitted the inner ring G H, said ring being fixed to
the plate by means of three screws K, L, O, the end of the band P with the double
clamp applied being introduced into the slot in the ring, as shown.
Supposing the band selected to be of leather (although indiarubber, gutta percha,
canvas, or other fabric in flat form may be used) of equal width to the cylindrical
part of the ring the band is first of all inserted in the slot and then stretched
tightly over a pulley either by means of a weight P¹ or by direct traction. In
the first case the pulley Qwould be mounted loose upon the fixed shaft R placed
in proximity to the lathe.
The chuck A B being then rotated the band will be coiled upon the periphery of
the ring. The band may or may not be cemented upon itself as it is coiled up,
according to the nature of the leather and the number of the coils.
In order to
regularise the tension in winding after the preliminary stretching of the band and
if necessary to ensure the adhesion of the coils together, a friction roller S may be
pressed against any suitable point of the ring by another weight P2 attached to the
end of a cord which passes over a grooved tension pulley T the other end of the
cord being attached to the rod U which carries the spindle of the pressing roller.
This rod is of square section and slides in a corresponding socket D which may be
fixed on the tool holder of the lathe without impeding the working of the guide or
rod U. The grooved tension pulley may be mounted on the same shaft as the

page_text: pulley so as to enable the tensions to be applied simultaneously or separately,
whether at the commencement to apply the band closely upon the cylindrical part
of the ring or at the end to stretch anew the end of the band whilst the pressure of
the roller is relaxed so as without loss of tension to be able to introduce between
the leather band and the roller a binding strap of sheet iron of such length as to
tightly embrace the coil of leather and provided at each end with ears or lugs of
which one V is tapped to receive a coupling screw turning freely in the other. As
soon as this binding strap is introduced as shown in Figure 5 the pressure of the
roller S is reapplied the tension of the leather band is relaxed and the band is cut
at about the point X so that it shall overlap a little beyond the depression P GY
at the commencement of the coil, as shown at X' beneath the roller which it will
be seen is a little higher than the original depression represented by cross hatching.
If the band has not been cemented throughout its whole length, the two last coils
must be glued carefully especially towards the end. The severed end X is then
brought round as shown at X' until the end is as nearly under the roller as possible
without passing beyond the point of contact. In this way the form of the band
coiled up will be closely assimilated to that of the ring. The two ends of the
metal strap are then brought together (the pressure of the roller being meanwhile
maintained) and connected and tightened up by the screw. The ring may then be
detached from the chuck A B by being forced off by means of the screws y y' y¹¹ or
may remain on the chuck until the glue is set. The binding strap being then
removed the coiled band now become a solid ring is turned truly round and of
uniform diameter at all points
The operation of coiling as herein described produces such an alteration of form
as enables any desired dimensions whether in width or thickness of the coiled
ring to be adopted the homogeneity of the ring depending only on the pressure
and cementing and being rendered as perfect as may be desired by means of the
apparatus described.
The outer ring envelops the coiled mass of the band and serves 1st to retain the
form obtained in the lathe and 2ndly to impart additional pressure by the slight
conicity of the ring which tightly compresses the circumference of the coiled band
and 3rd prevents subsequent distortion under the pressure of the friction ring.
It consists of a cylindrical part 1 k-m l Figure 1 (which shows it in face view
and section) equal to or greater than the width of the coiled band as in Figure 6.
In the latter the internal diameter of the ring is rather less than the external
diameter of the coil and slightly coned at the entering side. This outer ring is
forced on until it is near enough to the plate to screw on the threaded part a b
Figure 6 or to be screwed to the back plate O, N Figure 7 by means of the bolts
a a¹ a" which are shown applied to each of the rings in Figure 7. In the first
case Figure 6 the ring is forced on until the threads engage and then turned round
in the direction of winding until screwed home.
In the other arrangement shown in Figure 7 the covering ring it will be seen
encloses the entire coil with a pressure which may be as great as the winding
tension and transform without possibility of alteration the flattened coil into two
surfaces of unlimited area as in winding on a coil of any width desired (and which
in all cases represents the width of the band) it will also be possible to obtain any
desired amount of friction surface for all kinds of material. If desired the outer
ring may also be heated and conted with glue on the inside and then forced upon
the coil wound and turned true as above described. As regards the external forn
of the covering ring, it may be varied. Thus in Figure 7 for example it is the
last of a series of concentric rings mounted upon the boss and plate fixed on the
spindle CD. Each of these rings is prepared to receive a coil in the manner
before described and in this particular case they act both as inner and outer
rings.
The first coil is attached to the boss M in the manner shown in Figure 3 and
the other coils to the successive rings as shown in Figure 4 each ring being forced
on the band (previously coiled and turned true as described) until nearly close up

page_text: to the plate M, N, O and then drawn home by means of the three screws a a¹ a"
upon each ring. This plate which forms a pulley in this case, also has three other
holes b, b, bopposite each ring, which are tapped to receive screws like that
shown at D¹ whereby any one of the rings, may be removed without difficulty or
injury to this or to any other of the rings.
The outermost ring F G H K may either serve as a pulley as in this example,
or as a gear wheel or otherwise; its flange K and F together with the flange of
ring N' O' herein before referred to as the friction ring serves to box in the friction
surfaces and prevent the introduction of foreign matters between them. The
ring N'O' is cast in one with a pulley and as many concentric circular ribs as
there are coils and nearly equal in height to the width of the coiled band.
The advantage of this system consists essentially in the possibility of utilising
by successively increasing depth of penetration at least four-fifths of the coiled
mass for the purposes of friction. This advantage is derived both from the mode
of coiling and the means of fixing the end of the band. As the coiling cominences
in a depression or countersink in the inner ring or hub equal in depth to the
thickness of the band, the latter remains intact in the neighbourhood of the
attachment during the whole duration of the band and will continually help to
maintain the remainder in position.
Another advantage is that the engagement and disengagement may be effected
without sensible change of position of the contact surfaces (provided the two plates
have been truly faced up and mounted on their spindles) and as the distance to
be moved is almost nil, great power may be transmitted without much pressure
being necessary if a proper material has been selected for the coiled band.
The outer ring may also be cast in one with its disc as shown at a a b b Figure 6
which involves no change either in the mode of winding or encircling the coil with
the outer ring but simplifies the construction and enables this mode of attaching
the band to be applied to the exterior of a pulley C D E F of this shape as shown
in Figures 6 and 8. In the latter Figure the box I J K cast on the inside of the
pulley renders invariable the mode of attachment and enables the band to bend
to right or left at will and not in contact with the metal but with two tapered
pieces of leather rivetted between the band and the clamps at either side, which
pieces form an elastic cushion preventing all injury to the band at this point when
the latter is used for any purpose of traction.
.
In Figure 6 the two friction discs whether driving or driven are provided with
their pulleys K and L as before and their flanges M and N are of sufficient depth
to use up by wear the of the thickness of the coiled band. By means of the
pulleys at their backs and an open and crossed band alternate circular motion may
be imparted to the central pulley and the band attached thereto. Lastly the two
discs C D E F will be rotated by friction if the arrangement represented be
adopted that is to say the two discs forming the central pulley being fixed on
the shaft and caused to act alternately on the friction rings M and N as above
described.
Instead of plane surfaces, angular or half round surfaces may be employed
by turning the face of the coiled mass to the shape best suited to the purpose.
Hitherto there has been a considerable loss in the transmission of motion by
direct friction as witness for example the very variable value of the work done
by a belt on its pulley. This depends, the pressure being equal, upon the successive
length of the arcs embraced by the band and it is established by experiment that
the latter will transmit the whole of the pressure exerted if the envelopment takes
place under this same pressure over the whole circumference of the pulley. To
attain this result the inventor
1 Envelops continuously the whole of circumference of the material selected
and retains its circular form. 2nd Establishes contact by pressure with another
circular form of which no portion escapes contact The inner and outer rings with
the friction ring acting between them answer the purpose perfectly as the adhesion
of the friction ring on the total surface of the edge of the flat coiled band is exactly

page_text: equal to that of a belt of equal width completely encircling a pulley of a diameter
equal to the mean diameter of the coil. The diameter of the coil may be varied
at will and by fixing the rings to the arms of a gear wheel or fly wheel, I utilise
advantageously space and material heretofore but partially made use of. By
varying the configuration of the rings as in Figure 9, it is possible to utilise
certain materials which have a favorable coefficient of friction but cannot be
prepared except in the form of segments or by casting moulding or otherwise
formed in the shape of a complete ring and fixed in the space a b c d provided for
their reception between the two rings, the edges of which are turned inwards to
retain the friction composition in position. The friction ring ef may as above
stated have a plane, half round, or angular surface or be constructed of segments
so as to put into frictional contact so much as it is desired to utilise.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Melville Clark in the Great Seal Patent Office on the
20th July 1883.
ALEXANDER MELVILLE CLARK of the Firm of A, M, and W, Clark of 53 Chancery
Lane in the County of Middlesex Fellow of the Institute of Patent Agents
"IMPROVEMENTS IN FRICTION CLUTCHES" A communication to me from abroad
by Gabriel Nicolas Schoenberg of Paris, France.
This Invention relates to improvements in friction couplings or clutches in
which the adhesion or friction is produced between plane surfaces and which
embodies in a practical and simple way the principle of the total envelopment of
a pulley by its belt.
In order that the Invention may be more readily understood, I will proceed
to describe it with reference to the accompanying drawings which represent an
example thereof, it being understood that the form and dimensions of the various
parts are capable of variation according to the nature of the application without
departing from the Invention.
The Invention consists essentially in fixing between two metal rings of suitable
form such as shown in cross section at ab c, d fg, hik, and l, m, n (figure 1)
a flat band of any kind of material used for such purposes, and in applying the
friction to the edges of said band by means of a third ring a' b' c' d'. To avoid
the frequent repetition of the letters of reference, the rings will be hereinafter
referred to as follows:-
(1.) The metal ring a b c, d f g encircled by the band as the inner ring.
(2.) The metal ring h i k, mn enveloping the band as the outer ring.
(3.) The metal ring a¹ b' c' d' as the friction ring.
(1.) The inner ring has a cylindrical part bc, fd-equal to the width of the
band and a flange a b, fg at right angles to the cylindrical part and equal to the
aggregate thickness of the several layers of the band when coiled on the said ring
as hereafter described.
(2.) The outer ring is made of slightly less internal diameter than that of the
band when coiled on the inner ring and turned true as hereafter described, and it
is also slightly coned internally so as to increase its pressure upon the band when
applied thereon; the flange of this ring may be made of any desired form as will
be hereinafter described.
(3.) The friction ring is intended to transmit or receive the necessary pressure for
the transmission of motion and should be provided with one or more projecting
flanges op Figure 1 of plane or angular form but capable of entering easily the
space between the two rings in which the band is coiled. The cylindrical part of
the inner ring should be in one of the forms illustrated in Figures 2. 3. 4. The
mode of attaching the band shown in Figure 2 is as follows. A slot is made in
the cylindrical part of the ring for the passage of the band, and the cylindrical part
at one side of this slot is reduced in thickness to an extent equal to the thickness
of the band shown at a, the sunk surface abd gradually running out at the
circumference of the ring at a quarter to half way round the same.
The mode of attaching the band may vary, (1) If the ring is large enough the
end of the band may be clamped between two angle iron plates m n roughened on
their inner faces and rivetted together. This done, the band is then inserted in
the slot as shown, the plates m n forming stops.
(2.) If the band is to be coiled upon the bub of a pulley or a solid core where
no internal space is available as in Figure 3 a single clamp only is used of the

page_text: form shown which is tapered and curved so as to extend a quarter to half way
round the hub in which it is countersunk as shown, the end of the band being
attached thereto by rivets or screws, the clamp being further secured to the hub
by a number of studs screwed into the bottom of the recess in which it is counter-
sunk and projecting up through the band and rivetted down thereon or secured
by nuts.
(3.) When the power to be transmitted is small it is sufficient to screw a number
of pins into the hub as in Figure 4, the said pins passing through the band and
being rivetted down thereon over thin washers or secured by screw nuts which
sink by their own pressure into the thickness of the band. The mode of winding
the band upon the ring is as follows. Suppose the mode of attachment, figure 2,
to be employed, I mount in a lathe a face plate or chuck A B (Figure 5) keyed
upon a shaft C D turning between centres or otherwise. The face plate has a
turned flange M N upon it on which is fitted the inner ring G H, said ring being
fixed to the plate by means of three screws K L O, the end of the band P with
the double clamp applied being introduced into the slot in the ring as shown.
Supposing the band selected to be of leather (although indiarubber, guttapercha,
canvas, or other fabric in flat form may be used) of equal width to the cylindrical
part of the ring, the band is first of all inserted in the slot and then stretched
tightly over a pulley Q either by means of a weight P' or by direct traction. In
the first case the pulley Qwould be mounted loose upon the fixed shaft R placed
in proximity to the lathe. The chuck A B being then rotated the band will be
coiled upon the periphery of the ring. The band may or may not be cemented
upon itself as it is coiled up, according to the nature of the leather and the number
of the coils. In order to regularise the tension in winding after the preliminary
stretching of the band, and if necessary to ensure the adhesion of the coils
together, a friction roller may be pressed against any suitable point of the ring
by another weight P2 attached to the end of a cord which passes over a grooved
tension pulley T, the other end of the cord being attached to the rod U which
carries the spindle of the pressing roller. This rod is of square section and slides
in a corresponding socket D which may be fixed on the tool holder of the lathe
without impeding the working of the guide or rod U. The grooved tension pulley
may be mounted on the same shaft as the pulley Q so as to enable the tensions to
be applied simultaneously or separately, whether at the commencement to apply
the band closely upon the cylindrical part of the ring or at the end, to stretch
anew the end of the band whilst the pressure of the roller is relaxed so as without
loss of tension to be able to introduce between the leather band and the roller, a
binding strap of sheet iron of such length as to tightly embrace the coil of leather,
and provided at each end with ears or lugs, of which one V is tapped to receive a
coupling screw turning freely in the other. As soon as this binding strap is
introduced, as shown in Figure 5, the pressure of the roller S is reapplied, the tension
of the leather band is relaxed, and the band is cut at about the point ✗ so that it
shall overlap a little beyond the depression PGY at the commencement of the
coil, as shown at X' beneath the roller which it will be seen is a little higher than
the original depression represented by cross hatching. If the band has not been
cemented throughout its whole length the two last coils must be glued carefully
especially towards the end. The severed end X is then brought round as shown
at X' until the end is as nearly under the roller as possible without passing beyond
the point of contact. In this way the form of the band coiled up will be closely
assimilated to that of the ring. The two ends of the metal strap are then brought
together, (the pressure of the roller being meanwhile maintained) and connected.
and tightened up by the screw. The inner ring with the coil upon it may then be
detached from the chuck A B by being forced off by means of the screws y Y¹ y²
or may remain on the chuck until the glue is set. The binding strap being then
removed, the coiled band now become a solid ring, is turned truly cylindrical.
The operation of coiling as herein described produces such an alteration of form
as enables any desired dimensions, whether in width or thickness of the coiled ring

page_text: to be adopted, the homogeneity of the ring depending only on the pressure and
cementing and being rendered as perfect as may be desired by means of the
apparatus described.
The outer ring envelops the coiled mass of the band and serves, 1st to retain the
form obtained in the lathe, and 2nd to. impart additional pressure by the slight
conicity of the ring which tightly compresses the circumference of the coiled band,
and 3rd prevents subsequent distortion under the pressure of the friction ring. It
consists of a cylindrical part i k ml figure 1 (which shows it in face view and
section) equal to or greater than the width of the coiled band, as in Figure 6. In
the latter the internal diameter of the ring is rather less than the external diameter
of the coil and slightly coned at the entering side. This outer ring is forced on
until it is near enough to the plate to screw on the threaded part ab figure 6, or
to be screwed to the back plate ON figure 7, by means of the bolts a a¹ a² which
are shown applied to each of the rings in Figure 7. In the first case (figure 6) the
ring is forced on until the threads engage and then turned round in the direction of
winding until screwed home. In the other arrangement shown in Figure 7, the
covering ring it will be seen encloses the entire coil with a pressure which may be
as great as the winding tension. If desired the outer ring may also be heated and
coated with glue on the inside and then forced upon the coil, wound and turned
true as above described. As regards the external form of the covering ring, it may
be varied. Thus, in Figure 7 for example it is the last of a series of concentric
rings mounted upon the boss and plate fixed on the spindle CD. Each of these
rings is prepared to receive a coil in the manner before described, and in this
particular case they act both as inner and outer rings.
The first coil is attached to the boss M in the manner shown in Figure 3, and
the other coils to the successive rings as shown in Figure 4, each ring being forced
on the band (previously coiled and turned true as described) until nearly close up
to the plate M N O and then drawn home by means of the three screws a a¹ a² upon
each ring. This plate which forms a pulley in this case, also has three other
holes b b 62 opposite each ring which are tapped to receive screws like that shown
at D¹ whereby any one of the rings may be removed without difficulty or injury
to this or to any other of the rings. The outermost ring F G H K may either
serve as a pulley as in this example, or as a gear wheel or otherwise; its flange K
aud F together with the flange of ring N¹O' hereinbefore referred to as the friction
ring, serves to box in the friction surfaces and prevent the introduction of foreign
matters between them. The ring N¹ O' is cast in one with a pulley and as many
concentric circular ribs as there are coils and nearly equal in height to the width
of the coiled band.
The advantage of this system consists essentially in the possibility of utilising
by successively increasing depth of penetration at least four-fifths of the coiled
mass for the purposes of friction. This advantage is derived both from the mode
of coiling and the means of fixing the end of the band. As the coiling commences
in a depression or counter-sink in the inner ring or hub equal in depth to the
thickness of the band, the latter remains intact in the neighbourhood of the
attachment during the whole duration of the band and will continually help to
maintain the remainder in position. Another advantage is that the engagement
and disengagement may be effected without sensible change of position of the
contact surfaces (provided the two plates have been truly faced up and mounted
on their spindles) and as the distance to be moved is almost nil, great power may
be transmitted without much pressure being necessary if a proper material has been
selected for the coiled band.
The outer ring may also be cast in one with its disc as shown at a a b b Figure 6
which involves no change either in the mode of winding or encircling the coil with
the outer ring, but simplifies the construction and enables this mode of attaching
the band to be applied to the exterior of a pulley CDEF of this shape as shown
in Figures 6 and 8. In the latter figure the box I J K cast on the inside of the
pulley renders invariable the mode of attachment and enables the band to bend to

page_text: right or left at will and not in contact with the metal but with two tapered pieces
of leather rivetted between the band and the clamps at either side, which pieces
form an elastic cushion preventing all injury to the band at this point when the
latter is used for any purpose of traction.
5
In Figure 6 the two friction discs whether acting as drivers or followers are
provided with their pulleys K and L as before, and their flanges M and N are of
sufficient depth to use up by wear the of the thickness of the coiled band. By
means of the pulleys at their backs and an open and crossed band, alternate
circular motion may be imparted to the central pulley and the band attached
thereto. Lastly, the two discs CD E F will be rotated by friction if the arrange-
ment represented be adopted, that is to say, the two discs forming the central
pulley being fixed on the shaft and caused to act alternately on the friction rings M
and N as above described. Instead of plane surfaces, angular or half round
surfaces may be employed by turning the face of the coiled mass to the shape best
suited to the purpose.
Hitherto there has been a considerable loss in the transmission of motion by
direct friction, as witness for example the very variable value of the work done by
a belt on its pulley. This depends, the pressure being equal, upon the successive
length of the arcs embraced by the band, and it is established by experiment that
the latter will transmit the whole of the pressure exerted if the envelopment takes
place under this same pressure over the whole circumference of the pulley. To
attain this result the Inventor (1) Envelops continuously the whole circumference
of the material selected and retains its circular form. (2) Establishes contact by
pressure with another circular form of which no portion escapes contact. The
inner and outer rings with the friction ring acting between them answer the
purpose perfectly as the adhesion of the friction ring on the total surface of the
edge of the flat coiled band is exactly equal to that of a belt of equal width
completely encircling a pulley of a diameter equal to the mean diameter of the
coil. The diameter of the coil may be varied at will and by fixing the rings to the
arms of a gear wheel or flywheel, space and material heretofore but partially made
use of, is utilised advantageously. By varying the configuration of the rings as in
Figure 9, it is possible to utilise certain materials which have a favorable
coefficient of friction but cannot be prepared except in the form of segments or by
casting, moulding or otherwise formed in the shape of a complete ring and fixed in
the space a b c d provided for their reception between the two rings, the edges of
which are turned inwards to retain the friction composition in position. The
friction ring ef may, as above stated, have a plane, half round, or angular surface,
or be constructed of segments, so as to put into frictional contact so much as it is
desired to utilise.
The material of the ring or washers may be rigid or elastic, of wood, metal, stone,
leather, caoutchouc, or any composition or mixture, and this ring or washers may
be obtained by moulding or by any other suitable mode of manufacture.
In Figure 10, a is the disc fixed to the shaft on which is mounted by screws b
the rings c which serve as inner rings for the ring d d' placed around them, and as
outer rings for those placed within them. These rings have an internal flange e
which holds the rings à d¹ in place, and it will be seen that the rings may easily
be successively fixed in position by beginning with the innermost one, the outer-
most one having if desired the periphery i of a pulley. The disc f has as many
concentric friction rings g as there are rings d d and is loose and movable longi-
tudinally upon the shaft and provided with a pulley h. The rings marked d are
formed of one piece of material or of a composition of matter, and those d¹ of
superposed flat washers or rings.
To prevent the ends of shafts upon which couplings are placed, as in Figure 11,
from getting out of alignment by wear, the end of the one A is received within the
other B as shown at C, and this entering end may penetrate beyond the hub of
plate D and within the journal bearing E. One of the greatest objections to this
arrangement is the difficulty of oiling the part, but even if this difficulty be overcome,

page_text: the oil would soon flow out by centrifugal action and get between the friction.
surfaces F and so diminishing the co-efficient of friction, this diminution in the case
of iron and leather being, according to Morin, as much as from 0.56 to 0.15. Thus
if, on the one hand, the oil fails to reach the friction surfaces of the shafts there is
danger of the shafts seizing, and on the other hand it will soon interfere with the
operation of the friction coupling.
Figure 12 represents a section, and Figure 13 an elevation of an arrangement
which overcomes these difficulties. It consists of the disc A keyed on the end of
shaft B mounted in bearing C. This disc has cast on it the friction ring D and
also the peripheral flange E F forming a pulley. L is a disc fitting loosely on the
other shaft M and secured to disc A by screws K entering bosses G cast upon the
inside of its flange. The hub of disc L has an oil hole O for lubricating said disc
as if it were a loose pulley. When disc L is rigidly secured to A, a box pulley
(a b c d figure 13) is formed, one half of whose hub is keyed on the one shaft and
the other half is loose on the other shaft, whereby the ends of the two shafts are
securely retained in true alignment. The end of shaft M projects at N on the
inside of disc L and has keyed upon it the disc P to which is fixed the friction
coil and its outer ring R. The two friction discs are thus contained within the
width of an ordinary pulley, thus dispensing with the use of fast and loose pulleys
when it is required to arrest the notion imparted to this single pulley. By this
construction any excess of oil entering at the hole O will spread between discs L
and P to the circumference E F of the pulley and should any greasy matters become
detached from the periphery and fall on the rings R or D, the friction surfaces will
be preserved from contact with such matters as the said rings may fit the one over
the other to any desired extent. The friction surfaces being thus doubly protected
by said rings and by the outer periphery, will continue to always yield their
maximum effect with but little wear which may be at any time easily taken up by
the arrangement represented at S, now to be described.
One of the advantages of this friction coupling resulting from the very small
separation of the surfaces for throwing the coupling in and out of gear, necessitates
the shaft of the follower disc P being so held as to prevent the discs approaching
one another after being thrown out of gear, and it is also necessary to be able
easily either to compensate for wear or increase the effect of the pressure if the
portion of the friction coupling carried by the shaft B has a given dimention. To
this end the shaft M is prolonged as in Figure 2 and a nut I is applied and bears
against the bushing U against which it is maintained by the thrust bearing con-
sisting of the arm V in which is fixed a screw rod X by nuts y y', so that in order
to compensate for wear or increase the pressure, it is only necessary to unscrew
the nuts T and y' and to tighten up the nut y. Moreover after having brought the
friction discs A and P into contact it is easy to adjust exactly the play to be left
between the plates according to that between the end of the shaft and the thrust
pivot so that it is unnecessary to uncover the dises to adjust them. The arm V
may be of any form, for instance that shown in dotted lines in Figure 3, and the
space I may receive a crank pulley, gear wheels, or cams for transmitting the
motion. It will be seen that only three bearings are required and two pulleys as in
Figure 3. The end B of the shaft carrying the plate A is left free and any desired
mode of applying pressure thereto may be adopted such as a screw as in drilling
machines, or a fork with friction rollers, levers or racks, according to the purpose
for which the coupling is to be applied.
Having described the nature of the said Invention and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein before in part recited Letters Patent is.
1st In a friction coupling the combination of the inner ring, the flat band wound
thereon, the outer ring embracing the same, and the friction ring or disc adjusted
to press upon the band coiled between the rings, substantially as described and
shown in Figure 1.
2nd The mode of attaching the band to the inner ring and the method of coiling

page_text: and securing it under tension and pressure, substantially as described in reference
to Figures 2 to 5.
3rd The formation of a homogeneous friction ring by coiling (and wholly or
partially cementing) a flat band by means of the apparatus represented in
Figure 5.
4th The construction of a friction disc with a number of concentric friction rings
substantially as described and shown in Figure 7, and the combination thereof with
a friction disc provided with friction surfaces corresponding to the different rings or
coiled bands, substantially as specified.
5th The combination of the friction coupling herein described with the arms of a
pulley, drum, or flywheel to which it is applied in such way as to utilise the space
between the said arms as specified.
6th In a friction coupling, the application between inner and outer rings of flat
bands, segments, or materials capable of transmitting motion by friction, substan-
tially as and for the purpose specified.
7th In a friction coupling the arrangement between two rings or a series of
concentric rings fixed to a disc, of a friction surface in the form of a ring formed by
the superposition of a number of flat rings of elastic or non-elastic material, substan-
tially as described and shown in Figure 10:
8th The mode of connecting the ends of two shafts by means of a friction coupling
enclosed between two discs, substantially as described and shown in Figures 12
and 13 for the purpose specified.
9th The combination with the friction coupling connecting the ends of two shafts,
of the adjustable thrust bearing for regulating the friction substantially as shown
and described in Figures 12 and 13.
In Witness whereof I the said Alexander Melville Clark have hereunto set my
hand and seal this eighteenth day of July, A.D. 1883.