MECHANISM FOR THE TRANSMISSION OF POWER
Year: 1884

page_text: We JAMES ALFRED EWING of University College Dundee, Professor of
Engineering and FLEEMING JENKIN of 3 Great Stuart Street Edinburgh Civil
Engineer, do hereby declare the nature of our Invention for "MECHANISM FOR
THE TRANSMISSION OF POWER" to be as follows:-
The mechanism is of the class in which power is communicated between pieces
in rotation by means of frictional adhesion. It is specially suited for the
transmission of power from a shaft revolving slowly to a shaft revolving fast,
or vice versa.
The shafts between which power is to' be transmitted, and which may be termed
the driver and follower, are arranged in line with each other and a disc or drum of
suitable diameter is rigidly fastened to each. Two or more intermediate shafts are
provided, each of which has keyed or otherwise fastened to it two discs or drums,
and each of these intermediate shafts is set parallel to the line of the driving and
following shafts, in such a manner that the two discs or drums on each intermediate
shaft press against and roll on the discs or drums in the driver and follower
respectively. The group of intermediate shafts is symmetrically disposed with
respect to the axis of the driver and follower, and if only two intermediate shafts
are used, they are preferably placed at opposite ends of one diameter.
The necessary pressure of the intermediate shafts against the discs or drums on
the driving and following shafts is provided by encircling the group of inter-
mediate shafts by a tight band which runs on pulleys on each intermediate shaft
and revolves with them. This has the effect of holding the drums on each
intermediate shaft closely pressed against the drum on the driver and follower-
The necessary tension of the band is maintained, either by its own elasticity, or
where that would be insufficient or uncertain, by taking it under or over a separate
tightening pulley, which is forced by means of a spring or weight in the direction
required to keep the band tight. The band is preferably multiple, that is to say,
it encircles the group of intermediate shafts several times, but in one continuous
length and passes over or under the tightening pulley only once.
By this means the pressure on the axle of the tightening pulley which causes
disadvantageous friction, bears a small ratio to the whole force with which the
intermediate shafts are pressed towards the central axis,

page_text: Each intermediate shaft is carried in slot guides which permit of motion through
a small distance towards or from the central axis.
The mechanism is specially applicable to the driving of dynamo electric machines,
where the armature is required to revolve at a high speed. The armature shaft
would in that case be the follower, and usually the crank shaft of a steam engine
the driver. The mechanism is equally applicable to the driving of a relatively slow
running piece by means of an electric motor.
The ratio of velocity between the driver and the follower is compounded of the
ratio between the diameters of. the drum on the driver and the follower, and the
ratio of the diameters of the rolling drums on each intermediate shaft. The latter
ratio must be the same for all the intermediate shafts, and preferably the drums and
pulleys are made of the same size on both or all the intermediate shafts.
Dated this 16th dow of Santember 188&

page_text: COMPLETE SPECIFICATION.
We JAMES ALFRED EWING of University College Dundee Professor of
Engineering and FLEEMING JENKIN of 3 Great Stuart Street Edinburgh Civil
Engineer do hereby declare the nature of our invention for "MECHANISM FOR
THE TRANSMISSION OF POWER" and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement :-
The mechanism is of the class in which power is communicated between pieces
in rotation by means of frictional adhesion. It is specially suited for the trans-
mission of power from a shaft revolving slowly to a shaft revolving fast or vice
versa
The shafts between which power is to be transmitted and which may be terme·l
the driver and follower are arranged in line with each other and a disc or drum of
suitable diameter is rigidly fastened to each. Two or more intermediate shafts are
provided each of which has keyed or otherwise fastened to it two discs or drums
and each of these intermediate shafts is set parallel to the line of, the driving and
following shafts in such a manner that the two discs or drums on each intermediate
shaft press against and roll on the discs or drums on the driver and follower
respectively. The group of intermediate shafts is symmetrically disposed with
respect to the axis of the driver and follower and if only two intermediate shafts
are used they are preferably placed at opposite ends of one diameter.
The necessary pressure of the intermediate shafts against the discs or drums on
the driving and following shafts is provided by encircling the group of inter-
mediate shafts by a tight band which runs on pulleys on each intermediate shaft
and revolves with them. This has the effect of holding the drums on each
intermediate shaft closely pressed against the drum on the driver and follower.
The necessary tension of the band is maintained either by its own elasticity or
where that would be insufficient or uncertain by taking it under or over a separate
tightening pulley which is forced by means of a spring or weight in the direction
required to keep the band tight. The band is preferably multiple that is to say it
encircles the group of intermediate shafts several times but in one continuous
length and passes over or under the tightening pulley only once. By this means
the pressure on the axle of the tightening pulley which causes disadvantageous
friction bears a small ratio to the whole force with which the intermediate shafts
are pressed towards the central axis.
Each intermediate shaft is carried in slot guides which permit of motion through
a small distance towards or from the central axis.
The mechanism is specially applicable to the driving of dynamo electric machines
where the armature is required to revolve at a high speed. The armature shaft
would in that case be the follower and usually the crank shaft of a steam engine
the driver. The mechanism is equally applicable to the driving of a relatively
low running piece by means of an electric motor.
The ratio of velocity between the driver and the follower is compounded of
he ratio between the diameters of the drums on the driver and the follower and
he ratio of the diameters of the rolling drums on each intermediate shaft. The

page_text: latter ratio must be the same for all the intermediate shafts and preferably
the drums and pulleys are made of the same size on both or all the intermediate
shafts.
Figures 1 to 4 are diagrams illustrating the arrangement of working parts.
A and B (Figure 1) are the shafts to be connected of which B is to revolve much
more rapidly than A. These shafts are set in the same, or very nearly the same,
straight line. Two or more intermediate shafts C. C. are pressed towards the
centre line of AB by means of a rope or other band which passes round pulleys e. e.
fixed to the shafts C. C. Preferably this band passes many times round the
pulleys e. e. which are grooved to receive it, in the manner shown in Figure 1, and 1
is kept tight by means of a tightening pulley f which also serves to guide the bight
of the band diagonally across from one to the other of the pulleys e. e.
In this way
enough pressure is applied at the surfaces of contact between à and c. c. and
between b and d. d. to give frictional adhesion so that when either A or B is caused
to revolve the intermediate shafts receive motion from it and communicate motion 1
to B or A respectively.
The pulleys e. e. are preferably placed at such a position between c and d as to
distribute the pressure of the shafts C. C. on the rollers a and b in the ratio
required to make the occurrence of slip equally unlikely at the surfaces of a and of b.
If the co-efficient of friction between a and c is the same as between 6 and d the
proper position of the pulleys e. e. is that which makes the resultant tension of the
band lie between c and d at or near to a position whose distance from c is to its
distance from d as the diameter of d is to the diameter of c.
•
To avoid unnecessary length in the mechanism the pulleys e. e. are preferably
placed close to c. c. The mechanism may be further shortened by making the
pulleys e. e. consist each of two parts one on each side of the rollers c. c. in which
case two separate tightening bands would be found convenient.
The shafts C. C. are supported in slot guides (not shown in Figures 1 to 4)
which permit them to move through a short distance towards the centre line A. B.
Instead of two intermediate shafts three or a larger number may be used.
Whatever their number they are most advantageously grouped symmetrically
about the centre line. Figure 4' illustrates an arrangement with three intermediate
shafts.
The pulley which is used to keep the band on e. e. tight may conveniently be
alung above or at the side of the rest of the mechanism from the roof or from a
bracket or standard as in Figure 2, or it may hang in a well or recess below as in
Figures 3 and 4. It is to be pulled by means of weight or spring in the direction
required to keep the band tight. The plane of the pulley ƒ may be controlled
by suitable guides but this is in general unnecessary.
A form of the gear with two intermediate shafts is shown more completely in
Figures 5. 6. and 7 of which Figure 5 is a sectional end elevation, Figure 6 a side
elevation and Figure 7 a plan of which one half is in section corresponding parts
are similarly lettered in these and the other figures. In this example the gear is
made entirely self contained. The frame D which furnishes slot guides for the
intermediate shafts C. C also furnishes two plummer block supports for each of the
shafts A and B. If A is to be the driver of B, A may conveniently be provided.
with fast and loose pulleys to receive motion by a belt and to permit of disengage-
ment, and B may conveniently be coupled by means of a flexible coupling to the
fan or other machine or tool which is to be driven at a high speed. The
shafts C. C. are supported in bushes capable of sliding towards or from the axial
line of the shafts A and B In the example shown the grooved pulleys e, e. and the
rollers a and d. d. are of cast iron while the rollers c. c. and 6 are of compressed
paper. When paper rollers are used they may conveniently be constructed in the
manner which is practised in the case of callender rollers and as shewn in the
section Figure 7. The paper is pressed between a flange at one end which flange is
in one piece with the nave and a collar at the other end which slips over the nave
and is held in place by a split ring fitting into a recess in the end of the nave

page_text: which projects beyond the collar. The split ring is held in place by a second ring
shrunk on over it. In this example of the gear the tightening pulley is represented
as hanging in a well.
Instead of a continuous frame as in Figures 5 to 7 separate provision may be
made for the slot guides at the two ends of the intermediate shafts and also for the
support of the driving and following shafts A and B either or both of which may
be supported quite independently of the frame which furnishes guides for the
shafts C. C.
Figures 8 and 9 show fully in end and side elevation a form of the gear having
three intermediate shafts. Here the frame D furnishes the slot guides and also
affords support to the fast running shaft B but not to the slow shaft A which is
supposed to have independent support as for example where A is the overhung
end of the crank shaft of a steam engine. Here the tightening pulley is supposed
to be slung from the roof and to be pulled upwards by means of a rope passing
over a fixed pulley on the roof and carrying a weight. The rods g. g. are intro-
duced to stiffen the frame.
The slot guides for the one or both ends of intermediate shafts may be placed
between the rollers c and d instead of outside these rollers and hinged supports or
any other mechanical equivalent may be substituted for slot guides for the purpose
of permitting the intermediate shafts to press towards the centre line.
Amongst other advantages possessed by this form of friction gearing are these
that it secures a large velocity ratio between the driving and following shafts
without taking up much space and especially that the pressure necessary to
produce frictional adhesion is provided in a manner which introduces exceedingly
little disadvantageous friction. The mechanism is well suited for communicating
motion to the armatures of dynamo-electric machines, to blowing fans, circular
saws grinding wheels and the revolving cutters of wood working machinery and
also for taking motion from high speed electric motors.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is
(1). Mechanism transmitting power from one to another of two shafts arranged
in line and consisting of two or more parallel intermediate shafts provided with
rollers in contact with other rollers on the first mentioned shafts and caused to
press against them by a band or its equivalent embracing pulleys on the inter-
mediate shafts substantially as described.
(2). The use in the mechanism described above for the purpose of pressing the
said intermediate shafts towards the driving and following shafts, of a continuous
rope or other band (or of more than one such rope or band) arranged to embrace
the intermediate shafts by passing several times round grooved pulleys fixed
thereon and kept tight by passing over a tightening pulley or pulleys.furnished
with a weight or spring or other device for maintaining a suitable tension in the
band.