Improvements in or connected with Frictional Devices for Transmitting Power.
Year: 1890

page_text: Date of Application, 16th Sept., 1890
Complete Specification Left, 25th May, 1891-Accepted, 27th June, 1851
PROVISIONAL SPECIFICATION.
Improvements in or connected with Frictional Devices for
Transmitting Power.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23 Southampton Buildings in the
County of Middlesex, Patent Agent, do hereby declare the nature of this
invention, a communication to me by Edward Hibberd Johnson, Electrician,
of the City of New York, in the United States of North America, to be as
follows:-
The invention relates to frictional connecting devices for transmitting power or
motion from a moving part or body to one moved thereby. More particularly the
invention relates to apparatus of the general character set forth in Patent
No. 8528 dated June 2, 1890, in which a friction surface connected with the driving
shaft or body is moved by the revolution thereof into frictional engagement with a
friction surface connected with the driven shaft or body and a spring or other
elastic device is used to retard or oppose the movement which brings the friction.
surfaces into engagement and so to determine the degree of frictional engagement
and the value of the power transmitting connection in accordance with the power
required, and also to apply the power gradually and permit the driving part to
develop speed and power in starting, this heing especially useful in the employment
of electric motors for the propulsion of driven machinery or apparatus, although it
is adapted generally for use in transmitting power from a driving motor to a driven
machine or apparatus.
With an apparatus such as just generally described, difficulty may arise because
the load which the driving part has to start when connected with the driven part
may sometimes be too great for the capacity of the apparatus, or of some portion of
it, so that although the driving part continues to increase its frictional engagement
with the driven part, the latter does not start and the excessive strain thus placed
upon the apparatus may result in injury thereto-which may be the breaking of some
mechanical part or other injury to the driving or driven apparatus or the gearing
itself. In order to overcome these difficulties, a power transmitting apparatus of
the character already generally described is provided with a stop or limiting device
which positively limits the movement of the engaging frictional surfaces toward
each other, to such a point as while it permits the driven part to be started with
any load not in excess of the safe capacity of the apparatus, will not exceed this
capacity of the apparatus, or of such portion thereof as it is especially desired to
protect; and if when this point is reached the driven part does not start, the power
is then expended in turning the friction surfaces in contact with each other, until
relief is obtained from the excessive load.
There have also been made other additions to and improvements upon the device
set forth in the Patent already referred to, which also constitute part of the present
invention and will be hereinafter referred to.
The device in question, will be seen, is adapted generally for transmitting power
or motion from one shaft or body to another in any situations. I will describe its
arrangement and operation for the purpose of transmitting power from a shaft or
axle to a wheel loose thereon, the said shaft or axle being connected with a suitable
driving motor or source of power.
Keyed to the shaft or axle near the wheel is a sleeve having an external or male
screw thread. Engaging with this is another sleeve having an internal or female
crew thread and which is keyed externally into the hollow hub of a friction ring
or disc which is adapted to engage a friction surface on the inner side of the wheel.
On the shaft or axle at the inner end of the hub is a sliding disc behind' which is a
pring coiled on the shaft or axle between said disc and a collar which is fixed on

page_text: the shaft or axle adjustably so that the tension of the spring may be altered and
adjusted to compensate for wear, loss of tension etc.
The female member of the screw has a deeper thread than the male member, and
near each end of the former is a projecting stop. At corresponding but opposite
portions of the thread are like stops.
In operation, when the shaft is turned, the friction surfaces being always in
contact and the spring under an initial tension, the rotation of the shaft will screw
one or the other of the two sleeves out along the shaft against the sliding disc. If
the axle turns in one direction the inner sleeve will be moved out, if in the other
direction, the outer sleeve, and in either case the other sleeve will tend to
move toward the wheel, and both sleeves being in contact at their outer ends
with the friction disc, which embraces the shaft between said sleeves and the
wheel, the result of movement in either direction is to compress the spring and
to increase the frictional engagement of the friction disc with the wheel, until
the same is enough to turn the wheel, if the load is not too great; the arrival at
this point being determined by the spring so that the power is applied gradually
and the driving motor allowed to develop speed.
If however the load is too great for the safe capacity of the apparatus, the
limiting stops in the screw thread prevent such movement as will cause such
capacity to be exceeded. At the beginning of the movement of the screw, the stops,
being on opposite sides of the channels of the screw threads, move past each other.
But near the end of the movement, the stop at one end of one sleeve will engage
that at the opposite end of the other sleeve and the relative movement of the
sleeves will be stopped. The stops are usually so arranged that this point will be
reached somewhat before the apparatus reaches its safe capacity, and at this time,
there being no further increase in frictional contact between the friction disc and
the wheel, these surfaces will slip on each other and the axle will thereupon continue
to turn, continuing to exert the same power as before and therefore not losing the
speed and inertia which it has already acquired, although there is no increase in
the load upon it, and this will continue until relief is afforded.
It will be seen that the motor is allowed to apply its power gradually and to
develop its speed before the load is placed upon it, and is prevented from exceeding
its safe capacity.
1
1000
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings.
COMPLETE SPECIFICATION.
Improvements in or connected with Frictional Devices for
Transmitting Power.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23 Southampton Buildings, in the
County of Middlesex, Patent Agent, do hereby declare the nature of this invention,
a communication to me by Edward Hibberd Johnson of the City of New York in
the United States of North America, Electrician, and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:―
The invention relates to frictional connecting devices for transmitting power or
motion from a moving part or body to one moved thereby.
More particularly the invention relates to apparatus of the general character set
forth in Patent No. 8528 dated June 2, 1890, in which a friction surface connected
with the driving shaft or body is moved by the revolution thereof into frictional
engagement with a friction surface connected with the driven shaft or body, and a
spring or other elastic device is used to retard or oppose the movement which
brings the friction surfaces into engagement, and so to determine the degree of

page_text: frictional engagement and the value of the power transmitting connection in
accordance with the power required, and also to apply the power gradually and
permit the driving part to develope speed and power in starting, this being especially
useful in the employment of electric motors for the propulsion of vehicles and of
driven machinery or apparatus, which is the use for which this invention was mainly
designed, although it is adapted generally for use in transmitting power from a
driving motor to a driven machine or apparatus.
With an apparatus such as just generally described, difficulty may arise because
the load which the driving part has to start when connected with the driven part
may sometimes be too great for the capacity of the apparatus or of some portion of
it, so that, although the driving part continues to increase its frictional engagement
with the driven part, the latter does not start, and the excessive strain thus placed
upon the apparatus may result in injury thereto, which injury may be the breaking
of some mechanical part, but in the case of an electric motor is apt to be the
burning out and destruction of the armature thereof, or the excessive demand for
electric current may injure the generator or source of electric supply, especially
where this consists of secondary batteries, a serious obstacle to the introduction of
which has been the "buckling" and consequent rapid deterioration of the plates
due to their being called upon in this way to exceed the current capacity for which
they were designed. It is the object of the present invention to overcome these
difficulties.
To this end the invention consists, mainly, in providing a power transmitting
apparatus of the character already generally described with a stop or limiting
device which positively limits the movement of the engaging frictional surfaces
toward each other to such a point as, while it permits the driven part to be started
with any load not in excess of the safe capacity of the apparatus, will not exceed
this capacity of the apparatus or of such portion thereof as it is especially desired
to protect and if, when this point is reached, the driven part does not start, the
power then expended in turning the friction surfaces in contact with each other
until relief is obtained from the excessive load.
In addition to this general feature, the invention consists in the various novel
devices and combinations of devices employed in effectively accomplishing the
objects above enumerated, as hereinafter set forth and claimed.
The invention is illustrated in the accompanying drawings.
Figure 1 is a top view of a portion of the truck of an ordinary electrically
propelled street car provided with the present invention.
Figure 2, a longitudinal section of the power transmitting device, and
Figure 3, a view of the screw mechanism with the outer sleeve in section and the
inner one in elevation.
In Figure 2, A is the driving shaft, body, or part, which in this case is a car axle
connected with a suitable motor and having the wheel B, which is the driven part,
placed loosely upon it between nut a and internal flange a' of hub E. Secured to
the shaft A by a feather thereon is a sleeve F having an external screw thread at b.
Engaging with this is a sleeve G internally screw threaded at and feathered to
the sleeve E, which sleeve forms the hub of a friction ring D, which is adapted to
engage a friction surface on the inner side of the wheel B. This friction ring forms
an intermediate frictional connecting device between the axle and the wheel, said
ring constituting a movable friction member adapted to be moved by the operation
of the screw mechanism formed by the sleeves F, G, into frictional engagement
with the friction surface on the inner side of the wheel B. Upon the shaft at the
end of the hub is a sliding disc H, behind which is a spring I coiled on the shaft
between the disc H and collar K, whose position on the shaft is adjustable by
loosening the set screw whereby the tension of the spring may be altered and
adjusted. Each screw thread is made up, as shown in Figure 3, of several distinct
threads, each extending from one end to the other of the threaded sleeve, whereby
a thread of long pitch is obtained. The screw thread is deeper than the screw
thread b, and near each end of the former is formed or placed on the thread, a

page_text: projection or pin d or d. At corresponding but opposite portions of the screw
thread 6 are like projections e and e¹. These are the limiting stops to avoid the
exertion of the motor above the desired capacity.
In the screw mechanism formed by sleeves F. G, both members of the screw
mechanism being in mechanical contact or connection with the friction ring D,
movement in either direction causes an increased pressure upon such friction
member, and the movement in either direction is opposed by the spring, which is
arranged to have normally a certain degree of tension, this initial tension being
increased by the screw movement which it opposes.
In operation, the shaft A. being turned and the friction surfaces of wheel B and
ring D being always in contact, the effect of the rotation of the shaft is to screw
either the sleeve For the sleeve G out along the shaft against the disc H. If the
shaft turns in one direction, sleeve F will be moved longitudinally, and if in the
other direction, sleeve G, and in each case the other sleeve will have a tendency to
move toward the wheel. In either case the effect is to compress the spring and to
increase the frictional engagement of friction ring D with wheel B until the same is
sufficient to turn the wheel, provided the load is not greater than the safe capacity
of the apparatus, the arrival at this point being retarded by the spring I, so that
the power is applied gradually and the driving motor is allowed to develope speed.
If, however, the load is too great for the capacity of the apparatus, the limiting
stops provided for the purpose will prevent such movement as will cause such
capacity to be exceeded. If, for instance, the sleeve G moves toward the spring
at the beginning of the movement, the projections e, and e, d, move past each
other, they being on opposite sides of the channel of screw thread ', but near the
end of the movement the projection will engage projection e¹ and the travel of
the sleeve will be stopped. A similar operation occurs when the shaft runs in the
opposite direction and sleeve F moves toward the spring. The stops are preferably
so arranged that this point will be reached somewhat before the apparatus reaches
the limit of its safe capacity, and at this time, there being no further increase in
frictional contact between B and D, their surfaces will slip on each other and the
shaft will thereupon continue to turn, continuing to exert the same power as before,
and therefore not losing the speed and inertia which it has already acquired,
although there is no increase in the load upon it, and this will continue until relief
is afforded in any suitable way.
Figure 1 illustrates the equipment of an ordinary electric street car, it being
understood that each axle of the car is provided with the devices shown.
M is the armature and N the field magnet, of a suitable electric motor.
The
armature shaft has a pinion O engaging a toothed wheel P on a counter shaft,
which has a pinion Q engaging toothed wheel R on axle A. The motor is supported
partly upon the axle by the centreing supports m, m, sleeved on the axle, the other
end of the motor being supported at n, n, by spring supports in any usual or
convenient manner.
Each wheel B is loose on the axle and provided with the power transmitting
devices already described, and their operation is as explained. By the use of such
devices the motor is allowed to apply its power gradually and to develope its speed
and counter electro motive force before the load is placed upon it and is prevented
from exceeding its safe capacity.
In electric railways one of the most serious difficulties has been the excessive
draft on the motors in starting the load being placed upon the motor before it
reaches such a condition that it can safely exert its full effective power, and the
consequent abnormal flow of current in its armature often resulting in the destruction
thereof. In the application of the present invention to such uses the spring and
the limiting-stops of the screw mechanism are so proportioned that the increase of
frictional engagement will be stopped at a point which is the limit, or preferably
somewhat less than the limit, of the safe capacity of the motor so that it can never
get beyond such capacity. In other cases the apparatus may be so proportioned or
adjusted as to provide for the safety of storage-batteries or other sources of

page_text: electrical supply, or the present invention may be employed in the same manner to
prevent injury by excessive strain to the mechanical portions of a driving or
propelling apparatus of any kind.
The purpose of the adjustable collar K is to enable the tension of the spring to
be adjusted at any time to compensate for wear on the friction-surfaces, loss of
tension &c.
Having now particularly described and ascertained the nature of the said inven-
ion and in what manner the same is to be performed I declare that what I
claim is-
1. In power transmitting apparatus, the use of the movable friction member
connected with the driving part so as to be moved by the motion of the driving part
into frictional engagement with the driven part, in connection with a spring or
elastic cushion opposing such movement, and a stop positively limiting the frictional
engagement with relation to the safe capacity of the apparatus substantially as
hereinbefore described.
2. The screw mechanism for operating the friction device, the same being
composed of concentric sleeves, the inner one being feathered on the shaft and the
outer one screw-threaded on the inner one and connected with the source of power,
and springs opposing the travel of the sleeves substantially as herein before
described.
UILLEU UHS
ALL
L
1001
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.
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