Year: 1886

page_text: Date of Application, 21st July, 1886.
Complete Left, 21st Apr., 1887.
Complete Accepted, 21st June, 1887.
I JOHN AMBROSE FLEMING of 13 Albert Mansions Victoria Street Westminster
Electrical Engineer do hereby declare the nature of this Invention to be as follows:-
This Invention has for its object the improvement of Dynamo Electric Machines
applied for the generation of Electric current under circumstances where the speed of
rotation is necessarily variable over certain ranges. In applying dynamo electric
machines for the purpose of generating electric current to be applied in Electric
lighting and other purposes as for instance charging accumulators secondary batteries
or other electric operations it is well known that in order to secure uniformity of
electromotive force or pressure a uniform speed of rotation of the generator must be
maintained. Any variation in speed of the rotation of the armature or generating-
bobbins makes itself immediately felt in irregularity in electromotive force which may
greatly interfere with the success of the operations whether electric lighting or other-
wise which it is desired to perform. Generally speaking in order to secure this
uniformity of speed separate motive power is applied by gas steam or water engines
and it has not hitherto been found practicable to drive dynamo electric-machines off
shafting or by Engines of which the speed is very variable. My Invention has for its
object the improvement of the mode of winding the exciting magnets of dynamo
electric machines with the special object of enabling a constant or approximately
constant electromotive force to be maintained between the terminals of such machine
whilst its speed of rotation varies between certain limits. The special object sought
to be obtained being to so modify the machine that it can be successfully used in
generating electric current for the purposes of Electric lighting or other purposes
where uniformity of electromotive force is essential when driven off. A shaft such
as the axle of a railway carriage or any shaft in a ship factory or other place of which
the angular velocity is not uniform, but varies within certain limits. In carrying out
my Invention I propose to use an ordinary shunt wound dynamo electric machine but
I wind the field magnet coils in sections cutting up the whole wire into any number
of sections required. These sections are joined up in series and one end of the series
terminates on one brush or main terminal of the machine. The other end of the series
of section is insulated. From the junction of each field magnet sectional coil a con-

page_text: ducting wire is led to a commutator or divided contact are consisting of a number of
metal pieces each insulated from its neighbour. From each metal piece a conducting
wire proceeds which terminates at the junction of one of the field magnet sections.
Over this commutator or sectional arc moves a radial contact piece termining in a
spring or roller contact and to this radial contact arm is attached a wire leading to the
other brush or main-terminal of the machine. It is evident that according to the position
of this contact piece the number of sections of the field magnet coils interpolated
between the main terminals of the machine will be varied. These sections of the
field magnet coils may be wound as follows:-
The first section consists of sufficient wire of appropriate size and length to form
an exciting shunt coil when the machine is running at the lowest speed at which
it is desired to begin to obtain uniformity of electromotive force. All the succeeding
section of the field magnet coils are wound on in an opposite direction so that the
successive addition in series of every coil after the first adds negative ampere
turns as regards the excitation of the field magnets. Conjoined to the dynamo
machine is a speed indicator or tachometer it may be a centrifugal governor of any
approved form. This speed indicator may be driven by the dynamo machine and made
to operate a connecting lever or levers to cause the radial contact arm above referred
to to take a definite position corresponding to each particular speed of the machine and
hence to insert or cut out the successive section of the field magnet winding which
oppose in magnetising power the first section. Hence as the speed of the machine
increases the speed indicator or governor introduces negative magnetising coils and
reduces the total magnetising power acting on the iron of the field magnets. It is
found possible within certain limits to cause the intensity of the interpolar magnetic
field of the machine to vary inversely as the speed of rotation and hence to bring
about a uniformity of Electro motive force over a certain range of varying speed. In
applying the improvement in the case of railway train Electric lighting the dynamo
may be driven off the axle of the Carriage and the controlling mechanism may be also
operated by the same axle. In such cases as it is preferable to employ the current of
the machine to change secondary batters it becomes necessary to provide an arrange-
ment to prevent the back current from the secondary battery flowing through the
armature of the dynamo when the speed diminishes below a certain value. This is
achieved by making the speed indicator or centrifugal or other governor open or close
a relay circuit at a certain speed. This electro magnetic relay takes current from one
or more of the secondary cells and operates a switch which closes or opens the charging
circuit. The switch is in its normal position open as soon as the dynamo reaches a
certain speed the tachometer closes a circuit and the main circuit switch is then closed
by taking current from some of the secondary cells as a source of energy.
It is possible so to arrange this mechanism that the main circuit is opened just at
the instant when the back current from the cells has reduced the dynamo current to
zero hence there is little or no resultant current and no sparking. Or a non-sparking
switch may be employed in which the switch gradually introduces resistance. I
provide also means for permitting the direction of rotation of the dynamo to be reversed
without reversing the direction of the outward current. On the shaft of the dynamo
is a pulley and this by friction gearing or a slipping belt is made to effect a change or
reversal of the terminals of the wire of the armature and those of the field magnets.
The terminations of the field magnet circuits always remain fixed relatively to the
external conductors but the two terminations of the armature wire are put on to the
main circuit wire one way or the other according to the direction of rotation and this
reversal may be effected by a friction or shipping gear attached to the shaft of the
dynamo.

page_text: I, JOHN AMBROSE FLEMING of 13 Albert Mansions Victoria Street, Westminster,
Electrical Engineer 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 :-
My Invention has for its object the improvement of dynamo Electric machines,
applied for the generation of Electric current, under circumstances where the speed
of rotation is necessarily variable over certain ranges. In applying dynamo Electric
machines for the purpose of generating Electric current to be applied in Electric
lighting and for other electrical operations or purposes, such for instance as for
charging accumulators or secondary batteries, it is well known that in order to secure
uniformity of electro motive force or pressure a uniform speed of rotation of the
armature of the generator must be maintained as any variation in such speed makes
itself immediately evident in irregularity in Electro motive force which greatly
interferes with the success of the electric lighting or other operation for which the
Generator is used. My Invention has for its object to secure the uniformity of
electro motive force which I effect by a mode of winding the exciting magnets of the
machines with the special object of enabling a constant or approximately constant
electro motive force to be maintained between the terminals of such machines, whilst
the speed of rotation varies within certain limits, the special object sought to be
obtained by my Invention being to so modify the machines that they can be
successively used in generating electric current for electric lighting or other purposes
where uniformity of Electro motive force is essential, even when such machines are
driven from a source of motion subject to great variation, such as for instance, the
axle of a Railway-Carriage or a Shaft in a Ship or factory or other place the speed of
which shaft is not uniform. I will explain my Invention with reference to the
accompanying Diagrams, and as applied to an ordinary Shunt-wound Dynamo,
Electric machine from which its general application will be understood. Referring
first to Figures 1 and 2. Figure 1, shews the general arrangement and Figure.2 in
Diagram the coils of the field magnets.-I-wind the field-magnet coils of the
dynamo F in sections dividing the whole wire into any number of Sections required.
These Sections are joined up in series, and one end of the series terminates on one
brush 6, or main terminal of the machine-The other end at n, of the series of
Section is insulated. From the junction of each field magnet Sectional coil, a
conducting wire is led to a commutator or divided contact are C, consisting of a
number of conducting pieces c, each insulated from its neighbour. From each such
conducting piece, a conducting wire c' proceeds which terminates at the junction of
one of the field magnet Sections, (see c* Figure 2). Over this commutator or
Sectional arc C, moves a radial contact piece R, terminating in a spring or roller
contact T, and to this radial contact arm is attached a wire leading to the other
brush or main terminal (b) of the machine. It is evident that, according to the

page_text: position of this contact-piece, R, the number of Sections of the field-magnet_coils
interpolated between the main terminals b 6 of the machine will be varied. These
Sections of the field magnet coils may be wound as follows:-The first Section
consists of sufficient wire of appropriate size and length to form an exciting Shunt
coil (the part marked S, in figure 2 supposed to be wound underneath in figure 1,)
when the machine is running at the lowest speed at which it is desired to begin to.
obtain uniformity of electro motive force. All the succeeding Sections (those
marked n n etcetra in figure 2,) of the field-magnet coils are wound on in an
opposite direction so that the successive addition in series of every coil, after the first,
adds negative ampére turns as regards the excitation of the field magnets-
Conjoined to the dynamo machine is a governor speed indicator or the like, which
may be a centrifugal governor (as shewn at G) of any suitable construction and is
driven by the dynamo machine and is connected by the collar g to the radial contact
arm R (which is centered, at to the bracket B) to take a definite position
corresponding to each particular speed of the machine and hence to insert or cut out
the successive sections (n¹ n³ &c.) of the field magnet winding which oppose in
magnetising power the first section (S). Hence as the speed of the machine increases
the speed indicator or governor introduces negative magnetising coils and reduces
the total magnetising power acting on the iron of the field magnets. It is found
possible within certain limits to cause the intensity of the interpolar magnetic field of
the machine to vary inversely as the speed of rotation and hence to bring about a
uniformity of electro motive force over a certain range of varying speed. In
applying the improvement in the case of railway train electric lighting the dynamo
may be driven off the axle of the carriage and the controlling mechanism may be
operated directly from the same axle. In cases where the current of the machine is
used to change secondary batteries it becomes necessary to provide an arrangement to
prevent the back current from the secondary battery flowing through the armature of
the dynamo when the speed diminishes below a certain value-This is achieved by
making the speed indicator or centrifugal or other governor G open or close a relay
circuit at certain predetermined speeds-This electro magnetic relay circuit is shewn
at R. C in Figure 3. It takes current from one or more of the secondary cells B, and
operates a switch T which closes or opens the charging circuit. This switch is shewn
as consisting of two cups of mercury M¹ M' in the charging circuit between the
dynamo D and the secondary batteries B into which cups a fork or bridge piece T
dips to complete the charging circuit. This piece T is connected to the core I of a
solenoid coil S in the relay circuit RC-Sp is a spring tending to draw the bridge
piece T out of the cups-The switch is in its normal position open but as soon as the
dynamo reaches a certain speed the governor closes the circuit R C at K by any
suitable arrangement such for example as by connecting the circuit wires respectively
to the mercury cup m³ (Figure 1) and to the lever R which is formed at its rear
with a contact piece which dips into the cup m³ when the governor rises to any
predetermined degree and maintains contact whilst the machine works at or above
that speed. The current through RC then draws the core I down and the main
circuit switch T is then closed. It is possible so to arrange this mechanism that the
main circuit is opened just at the instant when the back current from the cells has
reduced the dynamo current to zero hence there is little or no resultant current and
no sparking Or a non sparking switch may be employed in which the switch
gradually introduces resistance. I provide also means for permitting the direction of
rotation of the dynamo to be reversed without reversing the direction of the outward
current. This is illustrated by Figures 4 and 5 and the arrangement is also shewn in
position in Figure 1. On the shaft S D of the dynamo is a pulley P¹ and this by
friction gearing or a slipping belt is made to effect a change or reversal of the
terminals of the wire of the armature and those of the field magnets. In the diagrams
the arrangement consists of a frictional belt F B passing over a pulley P' on the axis
of which the contacts are arranged they consisting of the dipping pieces a 6 which dip
either those on one side of the axis into the mercury cups 1, 2, or those on the other
side into the other, mercury cups 3, 4. The field magnet wires always remain fixed

page_text: relatively to the external conductors but the two terminations of the armature
wire c d are connected to the pieces a and b respectively so that they are put on to
the main circuit wires 1 m one way or the other according to the direction of rotation
and the reversal may be effected by a friction or slipping gear attached to the shaft of
the dynamo for if the machine rotates one way the belt FB will partially turn the
pulley P2 so that the contacts a benter the cups 1, 2 and the current will then flow
from d through 2 to m and from 1 through 1 to c and when the motion of the machine
is reversed the belt F B will partially rotate the pulloy P' in the reverse direction
removing the contacts a from the cups 1, 2 and putting them into the cups 3, 4
when the current will flow from c through 3 to m and from 7 through 4 to d.
Figure 5 is a diagram illustrating the placement at x of the switch Figure 4. In
this Figure F are the fields magnets and A the armature of the dynamo machine cd
and Im are the wires as in Figure 4. B are the batteries and L is the external
circuit.
Having now particularly described and ascertained the nature of my said Invention
and in what manner the same is to be performed I declare that what I claim is,-
First In dynamo electric machines field magnets having coils wound in sections
reversely to the principal magnetising coil or coils and connected to a commutator
or divided contact are over which moves a contact piece actuated by a governor or
speed indicator, or the like, substantially as and for the purpose herein before
described.
Second In connection with dynamo electric machines charging a secondary
battery an electro magnetic relay in combination with a governor or speed indicator
or the like so operated by current from the secondary battery as that when the speed
of the dynamo electric machine diminishes to a predetermined degree back current
from the secondary battery is prevented from flowing through the armature coils of
the dynamo electric machine.
Third-In connection with a rotating portion of a dynamo electric machine an
arrangement of contact makers and friction gearing or slipping belt or the like for
permitting the direction of rotation of the machines to be reversed without reversing
the direction of the outward current substantially as hereinbefore described and
illustrated by the accompanying diagrams.
Dated the 16th day of April 1887.