Improvements in and connected with Electro-magnetic Friction Clutches.
Year: 1890

page_text: ate of Application, 22nd July, 1890-Accepted, 27th Sept., 18
Improvements in and connected with Electro-magnetic Friction
Clutches.
I, THEODORE MARSHALL FOOTE, of Boston, in the County of Suffolk, and State of
Massachusetts, United States of America, Electrician do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to friction clutches which are designed to be operated by means
of electricity.
In the operation of an electric motor it will be found advantageous to provide such
a connection between the motor and its work that this work can be connected or
disconnected at will without stopping the motor, so that the latter will be maintained
in rotation whether doing work or not.
Magnetic attraction affords a convenient means for accomplishing this result, and
my invention therefore, relates to devices whereby I utilize magnetic attraction for this
purpose.
The essential principle of my invention consists in establishing an adhesive union
between a moving part which is permanently connected to and moves with the motor
shaft, and a part which is connected with the work and moves the same, but is loose
upon the motor shaft. This union being established by electro magnetisın.
A convenient method of accomplishing this result consists in the combination as
hereinafter more fully set forth in a clutch of a collar of magnetic metal fixed upon
the rotating shaft of the motor and moving with it, another collar of magnetic metal
loose upon the shaft, a connection between this collar and the work and means for
magnetizing either of these collars so that the two may be caused to attract each other
by their faces and will move upon one another with a sliding contact until they adhere
firmly and move together.
Another feature of my invention consists in the provision as hereinafter more fully
set forth of radial grooves in the opposing faces of the collars whereby after a sliding
movement upon one another to a certain extent they are caused to adhere firmly
together by magnetic attraction.
In the accompanying drawing,
Fig. 1 is a view of a form of coupling embodying the principle of my invention.
Fig. 2 is a sectional view of the same.
Fig. 3 is a view of the face of one of the members of the coupling.
Fig. 4 is a view showing the coupling applied to an electric car truck.
Fig. 5 is a view partly in plan and partly in section showing the coupling used in
connection with gearing for reversing the direction of the rotation of the car axle
without reversing the direction of the rotation of the motor.
Fig. 6 is a view, partly in plan and partly in section, showing the coupling used in
connection with gearing for varying the speed without reversing the direction of the
rotation of the motor.
Fig. 7 is a sectional view of the device shown in Fig. 5, and
Fig. 8 is a sectional view of the device shown in Fig. 6. In these several figures
the same letters refer to the same parts.
I have represented my invention as applied a form of electric motor invented by
me, in which the rotating armature is mounted upon a sleeve upon a non-rotating
shaft, but the device can be used with any other form of motor.
Referring to the drawing, A is the non-rotating shaft of the motor, Bis the rotating
sleeve to which the rotating armature of the motor is fixed, C is a collar of magnetic
metal, preferably iron, loose upon the sleeve and made in the form of a pulley for the
reception of a belt, connecting it to the work, but it may be in the form of gear wheel
if this is preferable.

page_text: D, D, are two collars of magnetic metal, preferably iron, fixed on the sleeve B or
each side of the collar C, and rotating with the sleeve; upon each of these collars is
wound a wire, forming part of an electric circuit, so that the collar becomes an electro
magnet. Each of these collars will have a longitudinal movement upon the sleeve, and
when the electro magnets become operative, each will move against the opposite face
of the collar and adhere to the same, and will slide upon the same with a frictiona
contact until the face adheres together and the collars move together, as in other
forms of frictional clutches, thereby preventing injury by sudden connection or
disconnection.
Upon each of the opposing faces are cut a series of radial grooves a, a, the effect of
which is to form angles which increase the magnetic attraction. These grooves need
not be opposite to one another, as a sliding contact to a certain extent is desirable, but
when the angles come opposite to one another, the magnetic attraction will be increased
at these points to such an extent as to tend to cause the firm adhesion of the collars.
Instead of the two fixed collars, one on each side of the loose collar, there may be
only one fixed collar, in which case either the loose collar or the fixed collar may have
a sliding movement upon its shaft. The loose collar may be extended on one or both
sides of the pulley or gear wheel on the same, and on this extension or these extensions
may be wound a coil of wire forming part of an electric circuit. In this case the
loose coilar is the electro magnet, and the fixed collar or collars the armature or
armatures for the same.
Instead of a collar wound with a wire, the collar may be in the form of a disc, and
electromagnets parallel to the sleeve and concentric with it may be attached to this
disc, or any other suitable arrangement to obtain connection between the members of
a clutch by electro magnetism, as may be adopted.
The current may be carried to coils on the clutch by means of brushes E, which
bear upon collars of non-magnetic metal F, fixed on the sleeve or each side of the
clutch.
The coils on the clutch may be in an independent circuit, or the circuit through
them may form part of the circuit through the motor.
1 do not limit the use of my electro-magnetic coupling to the connection of the
motor of an electric car to the car axle, but it can be used for connecting any motor
to its driven mechanism.
For example, there may be a series of these clutches upon a single shaft, and the
Joose collars may each be connected to a different machine. Any one of the driven.
machines can thus be connected or disconnected from the driving shaft.
When the clutch magnets are placed in the same circuit with the motor magnets,
and breaking the circuit in the clutch magnets breaks the circuit in the motor, the
armature of the motor, owing to the inertia of the moving mass, will not immediately
stop rotating when the circuit is broken.
As the stops of streets cars are generally of short duration, the speed of the moving
part of the motor will generally be but slightly diminished before the current is
re-established.
When it is desired to stop a car provided with this improved electric motor, the
circuit of the electro magnet or magnets of the clutch is broken, whereby the running
gear of the car is disconnected from the motor, and the ordinary brake mechanisma
is then applied to stop the running gear. The car is started by closing the circuit
through the electro-magnet or magnets, whereby the running gear is gradually
re-connected with the motor by the action of the friction discs. The motor armature.
continues to rotate while the running gear is disconnected, and its momentum is
utilized in starting the car, so that there is no necessity of increasing the power to
overcome inertia.
In the application of the electric motor to the propulsion of street cars, it has been
found desirable for electrical reasons to rotate the armature of the motor at a high.
speed and to connect the motor shaft to the car axle by gearing whereby the speed.
at which this car axle rotates is reduced below the speed of the motor shaft to the
extent required for the speed which is adopted for the car. When, therefore, the
.

page_text: car moves slowly, the speed of the motor shaft is correspondingly reduced with a
consequent reduction, in accordance with well known electrical laws, in the economic
efficiency of the motor, or, in other words, in the ratio of the useful work done by it
to the work done by the generator and prime mover, and inasmuch as it is desirable
in an electrical railroad system to maintain the generator and prime mover at or
near a constant speed as possible, there is often work done by the generator which
is not utilized by the motor, for the reason that its speed is not the best to utilize
this energy.
When the car is running at a constant speed upon a level track, so that the load
upon the motor is constant, the motor operates at its best efficiency, but when the
load is increased by the additional work required to ascend inclines or pass around
curves, the motor moves slowly and consequently operates less economically, or if the
speed is to be maintained an increased current is required and this current may be of
such strength as to develop sufficient heat to burn out the armature.
In order to avoid this danger and to provide the necessary reserve power for
ascending inclines or passing around curves, the motors now used upon cars are
much larger and of much greater power than is required for propelling the cars upon
a level and straight track. This is a disadvantage, inasmuch as it not only increases
the cost of a car, but also increases the weight of the same and requires a greater
current.
It would therefore much reduce the cost of operating an electric railroad system if
the motor upon the car could be constantly maintained at what is known as its
critical" speed or that at which it does its work most efficiently, and with the least
waste of energy; and if means could be provided for coupling the car at will to the
constantly rotating motor shaft
This result it accomplished by the electro magnetic coupling herein described and
this coupling can be utilized for connecting the motor shaft at will with different tiers
of gearing whereby with a constant speed of the motor the car axle may be made to
rotate at different speeds as may be desired.
In the accompanying drawing, Figs. 6 and 8, I have shown a device which embodies
the principle of my invention as applied to a car truck.
Referring to the drawing. K is the car truck, G is the axle of the car wheels,
which axle is connected by suitable gearing to the motor shaft.
I have shown toothed gearing, but any other suitable gearing may be used. Lis
the motor, and B is a rotating sleeve forming the motor shaft. The form of motor
which I have shown as used with this device is that in which the armature is
mounted upon a sleeve B, which rotates upon the fixed shaft A, but any other
form of motor may be used. In the invention which is herein described there are
two sets of magnetic coupling, and two loose collars C, C of different diameters, and
ach respectively gearing with a toothed wheel N N of different diameters upon a
counter shaft gearing by means of a pinion H with a toothed wheel upon the car
axle. The number of teeth on the collar C and wheel N bears such a relation to the
number of teeth on the collar C and wheel N that with the same speed of rotation of
the armature the wheel N' will rotate slower than the wheel N and consequently with
the same speed of rotation of the armature the car axle will have a different speed
of rotation, according as one or the other of the magnetic couplings is excited by
the current so as to establish a connection between the motor and the car axle.
These magnetic couplings are arranged side by side upon the same sleeve and are
separate from one another by a collar M of non magnetic metal.
The current is conveyed from one of the terminals of the generator to a strip of
metal which bears upon the face of this collar and thence passes to the coils on either
side according to the position of a switch P in the circuit, and strips of metal c, which
bear upon the faces of the rotating collars, convey the current from the coils to the
conducting wire. I have shown the motor as included in the circuit, but it may be
placed on a branch circuit or in a separate circuit.
By magnetizing either of these sets of couplings the motor can be connected with
the wheel N or with the wheel N¹ so as to cominunicate a faster or slower speed of

page_text: rotation to the axle of the wheels, but inasmuch as the motor is always maintained at
the same speed, the effect of reducing the speed of the car axle is to cause more
power to be applied to this axle and therefore to enable an increased load to be
overcome.
When the car is required to ascend inclines or pass around curves, the increased
load upon the motor is overcome by shifting over from one gearing to the other
without reducing the speed of the motor, so that with a reduction on the speed of the
car axle the motor acts upon the same with an increased leverage, thus obviating the
necessity of increasing the current through the motor.
The wheels N, N¹, instead of being upon the same shaft may be upon different
shafts, in which case they may be of the same size.
The principle of my invention consists in providing two or more sets of gearing
which with the same speed of rotation of the armature shaft communicate a different
speed of rotation to the car axle, and this principle may be carried into effect by any
suitable form or arrangement of gearing. I may have more than two sets of coupling
with corresponding gearing, and I do not limit myself to two sets.
By means of this magnetic coupling the motor is quickly and easily connected
without shock to any of the sets of gearing as may be required.
This magnetic coupling can also be utilized to obtain a device whereby it is
rendered possible to reverse the direction of the rotation of the car axle at will
without reversing the direction of the rotation of the motor as shown in Figs. 5
and 7.
Referring to the drawing, K. is the car truck; L is the motor; B is the rotating
sleeve A is the fixed shaft; and G is the axle of the car wheels. Upon the sleeve
are two loose collars of magnetic metal CC and on each side of each of these loose
collars is a collar D of magnetic metal, rotating with the sleeve, but capable of
longitudinal movement upon the same. These collars are magnetized by means of
coils upon the same which are traversed by an electric circuit. Between the pairs
of collars is a collar M, of non-magnetic metal, fixed upon the sleeve. 1 is a
counter shaft which carries a pinion H which gears with a gear wheel I upon the
car axle.
Upon the counter shaft are also two gear wheels N N¹ one of which N gears
directly with the collar C and the other gears with the collar (through a pinion O
so that when the collar CI rotates, the car axle is caused to rotate in a reverse
direction to that which it has when the collar Crotates. One of the terminals of
the generator is connected to a strip of metal which bears upon the collar D and
the current passes through the coils upon the collars to springs which bear upon the
collars and are connected in the circuit. A switch P with suitable connections,
is provided, by means of which the current can be caused to pass at will through
either of the sets of couplings; when the coils adjacent to the loose collar are
magnetized, the fixed collars adhere to the loose collar, and the rotating sleeve is
connected to the work, through the gear wheel but when the current is caused to
pass through the coils adjacent to the collar the fixed collars on each side adhere
to the loose collar and the rotating sleeve is connected to the work through the
pinion and gear wheel N thus reversing the direction of the rotation of the
counter shaft I and shaft G connected therewith.
It will thus be seen that the direction of the rotation of the car axle can be reversed
at will without changing the direction of the rotation of the motor.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :
First. The combination of a dynamo-electric motor, mechanism driven thereby, and
an electro-magnetic friction clutch disposed in the motor circuit, one member of said
clutch being connected with the armature shaft of said motor and the other member
thereof with said mechanism.
Second. The combination of a motor, mechanism driven thereby, and an electro-

page_text: magnetic friction cluch interposed between said motor and the driving mechanism,
the meeting faces of the clutch members being provided with radial grooves entirely
below the plane of contact and forming angles on said faces which increase the
magnetic attraction.
Third. The combination of a car-body, a dynamo-electric moior thereon, running
gear supporting said car-body, an electro-magnetic clutch interposed between said
motor and said running gear for connecting the latter with the former and a brake for
stopping the car when the motor and running gear are disconnected.
Fourth. The combination of a dynamo electric motor, mechanism driven thereby,
two collars fixed to rotate on the motor shaft, two collars loose on said shaft, each of
said loose collars being geared with said mechanism, magnetizing coils on two of said
collars, electric circuits connected with said coils and a circuit changer for shifting the
current from one circuit to the other.
Fifth. The combination substantially as and for the purpose set forth with the
rotating shaft of an electric motor of two or more collars of magnetic metal loose upon
this shaft and each geared to the work to operate the same with different power, two
or more sets of collars capable of being magnetized upon the motor shaft and rotating
with it and having a longitudinal movement on the same and each acting when
magnetized to establish a frictional contact with one of the loose collars, coils for
magnetizing these fixed collars, a source of electrical energy, electrical circuits from this
source of energy, each passing respectively through coils upon the fixed collars, and a
device for establishing at will an electrical connection between the source of electrical
energy and the coils of either of the fixed collars.
Sixth. The combination substantially as and for the purpose set forth, of the
motor L, the rotating sleeve B, the collars of magnetic metal G, C, loose upon the
sleeve, each geared to the work to operate the same with different power, the collars D
of magnetic metal rotating with the sleeve, but capable of longitudinal movement on
the same, magnetizing coils on these collars, the collar M. the spring bearing on the
same, the springs C bearing upon the fixed collars, a source of electrical energy,
electric circuits passing from the generator and through the coils upon each set of
fixed collars and means for establishing at will an electric circuit through the coils of
either set of collars.
Seventh. The combination substantially as and for the purpose set forth, of the
motor L, the rotating sleeve B, the counter shaft 1 gearing with the car-axle, the
loose collar C, upon the rotating sleeve gearing with the wheel N', to communicate a
slower speed to the counter shaft than the gearing N; the collars D, D, one on each
side of a loose collar and capable of longitudinal movement on the sleeve, magnetizing
coils upon the fixed collars and means for magnetizing at will either pair of fixed
collars whereby by magnetic attraction a frictional contact is established between each
of the loose collars and the fixed collars.
Eighth. The combination of a dynamo electric motor, two sets of magnetizable
collars on the motor shaft, one collar of each set being loose on the shaft and the other
being fixed to rotate therewith and adapted to slide longitudinally thereon, and one
collar of each set being provided with a magnetizing coil, electric circuits passing
through said coils, a switch for changing the current from one set of collars to the
other set, a counter shaft, provided with two gear wheels one of which gears directly
with one of said loose collars, and an intermediate gear which gears with the other of
said gear wheels and with the other of said loose collars, substantially as described.
Ninth. The combination substantially as and for the purpose set forth of the
motor L, the rotating sleeve B, the collars C, C of magnetic metal loose upon the
same, each geared to the work to operate the same in a different direction,
the collars D, D, of magnetic metal rotating with the sleeve, but capable of longi-
tudinal movement on the same; magnetizing coils on these collars, the collar M the
spring, bearing upon the same; the springs C bearing upon the fixed collars, a source
of electrical energy, electric circuits passing from the generator and through the
coils upon each set of fixed collars and means for establishing at will an electric
circuit through the coils of either set of collars.

page_text: Tenth. The combination substantially as and for the purpose set forth of the
motor L, the rotating sleeve B. the loose collars C, C₁, loose upon the sleeve; the
collars D D of magnetic metal, one on each side of one of the loose collars, rotating
with the shaft, but capable of a longitudinal movement on the same, magnetizing coils
upon the fixed collars, means for magnetizing at will either pair of the fixed collars
whereby by magnetic attraction a frictional contact is established between each of the
loose collars and the fixed collars; the counter shaft I gearing with the car-axle,
the wheel N, and the wheel N and pinion O.
Dated this Seventeenth day of July 1890.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.