A Dynamo-electric Machine and Motor.
Year: 1897

page_text: Date of Application, 9th Oct., 1897
Complete Specification Left, 9th July, 1898--Accepted, 10th Sept., 1898
A Dynamo-electric Machine and Motor.
I, ARCHIBALD HENRY FINLAY, of Victoria Square, in the City of Belfast, and
County of Antrim, in Ireland, Electrical Engineer, do hereby declare the nature
of this invention to be as follows:
My invention relates to dynamos of what are known as the unipolar or homo-
polar type, in which the generating conductors move in a uniform magnetic
field.
This dynamo consists of two cylindrical masses of iron, one being inside the
other, the outside one (the field magnet) by preference stationary while the
inner one is fixed to a shaft passing through its axis and free to rotate in suit-
able bearings.
These cylindrical masses are provided with a central chamber between them
in which the exciting coil and inner brushes and collector are enclosed, but are
only separated by a slight space or air gap at each side and together form a singie
ironclad magnetic circuit.
The exciting coil may be fixed to either cylindrical mass but I prefer to attach
it to the stationary one.
The generating conductors are placed preferably in the revolving cylindrical
mass in slots or tunnels near to one of the air gaps and extending from the out-
side to the internal chamber and are insulated in the usual manner. They are
made of copper or other suitable metal and each is connected electrically at each
end to a segment of a collector which may be constructed similarly to the commu-
tator of an ordinary dynamo. Or I may connect several such generating con-
ductors to the same segment or all of them may be connected to a collecting
ring at each end.
Conductors are similarly placed near to the air gap in the other cylindrical mass.
These I term return conductors and each of them is furnished at each end with
a brush or brushes making contact with the collectors. Or several conductors
may be connected to one set of brushes or all the conductors and brushes may
be connected together at each end.
The collectors may be arranged so that the generating conductors can be con-
nected in series or parallel by means of the brushes and return conductors.
They must be arranged so that a generating conductor can never be short
circuited by a return conductor and its brushes, and it is desirable that all the
generating and return conductors should always form part of the circuit.
This machine acts as a continuous current motor but it will act as an alterna-
ting current motor if the iron is laminated and other usual precautions are taken
to prevent eddy currents. In the latter case I may employ a transformer in
connection with the machine to reduce the pressure of the applied current.
Such a motor with some modifications may also be employed as an electricity
meter.
gaps and
There may be generating and return conductors near both of the air
the magnetic circuit may be duplicated by providing two chambers with an

page_text: exciting coil in each, in which case there will be three air gaps and I would
place the generating and return conductors preferably near the middle one
only,
Dated this 8th day of October 1897
A Dynamo-electric Machine and Motor.
I, ARCHIBALD HENRY FINLAY, of Victoria Square, in the City of Belfast, and
County of Antrim, in Ireland, 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 relates to dynamos of what are known as the unipolar or homo-
polar type in which the generating conductors move in an uniform magnetic
field.
This dynamo consists of two cylindrical masses of iron, one being inside the
other, the outer one (the field magnet), by preference, stationary, while the inner
one (the armature) is fixed to a shaft passing through its axis and free to rotate
in suitable bearings. These cylindrical masses of iron are provided with a
central Chamber between them, in which chamber the exciting coil and inner
brushes and collector are inclosed, but they are only separated from each other
by a slight space or air gap at each side and together form a single ironclad
magnetic circuit.
The exciting coil may be fixed to either of the cylindrical masses, but I prefer
to attach it to the stationary one.
The generating conductors are placed in the rotating cylindrical mass in
slots or tunnels near to one of the air gaps and extending from the outside to
the central chamber, and are insulated in the usual manner. They are made
of copper or other metal, and each of these conductors is connected electrically
at each end to a segment of a collector which may be constructed similarly to
the commutator of an ordinary dynamo, or each end of such conductor or of
each set of conductors may be formed in one piece with a segment of such col-
lector when the conductors are placed in slots. But all of the generating con-
ductors may be connected to a collecting ring at each end, or I may employ
several of such rings, insulated from cach other, and connect an equal number
of the conductors to each of them.
Other conductors are similarly placed near to the air gap in the field magnet.
These I term return conductors, and for each of them I provide at each end a
brush or brushes making contact with the collectors. But several return con-
ductors may be connected together at each end in sets of equal numbers, and in
that case I provide a brush or set of brushes at each enl for each such set of
return conductors.
Where the armature or field magnet is arranged with slots or tunnels these
may be covered with a surrounding sheet of iron fixed to the armature or field
magnet respectively when it is necessary to prevent eddy currents.
When segmental collectors are employed the brushes must be arranged so that
the relative positions on the collectors will not alter with wear.
Hence I employ
a fixed box or guide to hold each brush in position, or in which the brush can
only move in the direction of its length, and when slots are used such boxes
may be made in a piece with the return conductor or set of conductors. Or I
may

page_text: employ curved brushes, made of solid metal or carbon, each of which is capable
of turning about its axis of curvature upon a fixed axle which may conveniently
form one of the return conductors. The interval between the toe of one brush
and the heel of the adjacent brush I make greater than the width of a segment.
In some cases I employ flat or disc segmental collectors and a helical spring
surrounding and supported by an extended part of each return conductor so
that each brush, being supported by and sliding upon such conductor, is thereby
pressed against the collector. Or the brushes may be insulated from each other
and built up together upon a ring or frame and pressed against such flat or
disc collector by a spring or springs.
The collectors whether segmental or ring may be arranged so that the generating
conductors can be connected in series or parallel by means of the brushes and
return conductors. With segmental collectors, however, this must be arranged
so that a generating conductor can never be short circuited by a return conductor
and its brushes. When ring collectors are employed the generating and return
conductors always form part of the circuit, but when segmental collectors are
used each segment and its connected generating conductors are out of the circuit
as they pass from brush to brush and consequently, for the moment, no current
will be in these conductors. Now, in order to neutralize the effects of such an
arrangement I provide two or more generating conductors, insulated from each
other, for each slot or tunnel, and I connect each of such conductors with a
different segment of the collector (the number of generating conductors in each
slot or tunnel depending upon the number of segments, per brush, in the collector)
so that the total current passing through each slot or tunnel-that is, the sum of
the currents in the several conductors in the slot or tunnel-remains practically
constant in its relation to the current in the outside circuit and practically no
eddy currents will be induced in the iron surrounding the slot or tunnel owing
to the current ceasing to flow in one of such conductors.
Where I employ segmental collectors I prefer, when connecting up the con-
ductors in series, to divide the circuit into two parts, one part on either side
of the armature in order that opposite sides of the collector will have the greatest
or terminal potential difference between them.
There may be generating and return conductors near both of the air gaps
and the magnetic circuit may be duplicated by providing two chambers, with
an exciting coil in each, in which case there will be three air gaps, and I would
place the generating and return conductors preferably near the middle gap only.
My machine will act as a continuous current motor. But it will also act as an
alternating current motor if the iron is laminated to prevent eddy currents and
other precautions usually applied to such motors are also taken. And I may
employ a transformer in connection with such alternating current motor to reduce
the pressure of the applied current, or combine the transformer and motor, the
transformer coils taking the place' of the exciting coil. I then prefer to con-
nect all the generating conductors to one collecting ring at each end, such ring
being necessarily cut across in one or more places to prevent alternating currents
circulating in it.
The motor I have described may, with some modifications, be employed in
combination with recording clockwork as an electricity meter.
For this purpose I arrange the shaft vertically and connect all the armature
conductors in parallel and likewise the return conductors and I provide mercury
contact for the armature current.
And in order that my said invention may be more fully understood I shall now
proceed to describe the figures on the sheets of drawings annexed hereto the
same letters of reference indicating the same or corresponding parts of my dynamo
electric machine and motor throughout all the figures on such sheets.
Fig. I is an end view partly, diagrammatic of a machine of the single magnetic
circuit type as constructed by me shewing the armature or rotating cylindrical
mass of iron, one of the segmental collectors and its support, twelve slots each

page_text: •
containing two generating conductors connected to different segments of the
collector, and air gaps: also the field magnet or stationary cylindrical mass of
iron, and return conductors in tunnels, six brushes making contact with the
collectors and electrical connections between the return conductors and brushes.
Fig. II is a diagrammatic plan of the generating conductors, segmental col-
lectors and return conductors of the same machine arranged as in Fig. I. The
generating conductors and segments of the collectors are shewn in one piece,
there being two conductors to each segment of a collector. There are the same
number of segments and generating and return conductors as in Fig. I but in
some cases these are shewn twice. This figure shews the connections between
the brushes and the return conductors and the circuit divided into two parts so
that the greatest potential difference will be at opposite sides of the collectors.
It also shows the distance between the brushes to be greater than the width of
a segment of the collector. The arrangement of the various parts is also shewn
in this figure so that a generating conductor cannot be short circuited by a
return conductor and its brushes.
Fig. III is a longitudinal section of the same machine shewing the armature
with a shaft carrying a pulley fixed to it, the bearing pedestals and bed-plate,
the generating conductors in slots, the segmental collectors and support for the
outer one of them, the other one being supported on the armature, each generating
conductor connected to a segment of the collector, the central chamber, air gaps
and exciting coil: also the field magnet, return conductors in tunnels and the
brushes making contact with the collectors, and
Fig. IV is a longitudinal section of a machine of the double magnetic circuit
type shewing the armature, shaft, pulley and bearings, field magnet, two central
chambers and two exciting coils; also bed plate, slots or tunnels for the generating
and return conductors, and three collecting rings in each chamber instead of
segmental collectors.
a is the armature or rotating cylindrical mass of iron; b, b, are the collectors;
,, are segments; and c is the support of the outer collector; d, d, are the
slots or tunnels; e, e are the generating conductors; and, e¹, el, are the connec-
tions between the generating conductors, e, e, and the segments, 61, 61; f, f, are
air gaps; g is the field magnet or stationary cylindrical mass of iron; h, h, are
the return conductors; i, i, are the brushes; and h¹, h³, are the connections
between the return conductors h, h, and brushes, i, i; j, j, and ¹,, are the
terminal conductors being positive or negative in the dynamo according to the
direction of motion of the armature and the direction of the current in the ex-
citing coil is the central chamber; is the exciting coil; m is the bed plate;
n, n, are the bearing pedestals or brackets; and o is the shaft fixed to the armature
and carrying the pulley, p.
When the field magnet, g, is excited by a current passing through the exciting
coil or coils,, there will be a magnetic flux in the field magnet, g, and arma-
ture, a, and it win pass through the air gaps, f, f, radially when there will be
an uniform magnetic field.
Employed as a dynamo, when the armature, a, is rotated the generating con-
ductors, e, e, cutting the uniform magnetic flux, have an electro-motive force set
up in them so that there will be a difference of potential between the col-
lectors, b, b, and if any of the magnetic flux be caused to rotate by reason of
the rotation of the armature, a, then such flux, cutting the return conductors, h, h,
will set up an electro-motive force in such conductors in the opposite direction
to that of the electro-motive force in the generating conductors, e, e. Such electro-
motive force would help that of the generating conductors e, e, when the gene-
rating and return conductors, e, and, h, are connected by means of a collector, b,
and brush, i, and a current would flow from one collector b, to the other, b,
through the return conductor, h, and its brushes, i, i.
Armature reaction is, therefore, neutralized by the current flowing in the

page_text: return conductors, h, h, while in close proximity to the generating conductors, e, e,
and in the opposite direction to that of the current flowing in them.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I would have it to
be understood that I do not claim armatures, exciting coils, field magnets, col-
lectors, conductors, brushes, segments, slots or tunnels, transformers, central
chambers and air gaps except where the same are constructed or employed in
the manner and for the purposes herein before described nor do I claim any of
the separate mechanical parts constituting my improved dynamo electric machine
and motor, but I declare that what I claim is:-
1st. In unipolar or homopolar dynamos the combination of two cylindrical
masses of iron forming a single or double ironclad magnetic circuit in which
the air gaps are parallel to the axis of rotation, with generating and return
conductors in slots or tunnels constructed and employed substantially in the
manner and for the purposes hereinbefore described and shewn in the drawings
hereunto annexed.
2ndly. The combination in such dynamos of an armature consisting of a
cylindrical mass of iron, with generating conductors in slots or tunnels and.
segmental collectors constructed and employed substantially in the manner and
for the purposes herein before described and shewn in Figs. I, II and III of
the drawings hereunto annexed.
3rdly. The combination in such dynamos of an armature consisting of a cylin-
drical mass of iron, with generating conductors in slots or tunnels and ring
collectors constructed and employed substantially in the manner and for the
purposes herein before described and shewn in Fig. IV of the drawings hereunto
annexed.
4thly. The combination in such dynamos of a field magnet consisting of a
cylindrical mass of iron with return conductors in slots or tunnels constructed
and employed substantially in the manner and for the purposes hereinbefore
described and shewn in the drawings hereunto annexed.
5thly. The use in such dynamos having segmental collectors, of two or more
conductors in each armature slot or tunnel connected with different segments
of the collectors, constructed and employed substantially in the manner and for
the purposes hereinbefore described and shewn in the drawings hereunto
annexed.
6thly. The means, in such dynamos having segmental collectors, of connecting
up the generating conductors in series, substantially in the manner and for the
purposes herein before described and shewn in Fig. II of the drawings hereunto
annexed.
7thly. The combination in one machine of a transformer and alternating
current motor constructed and employed substantially in the manner and for
the purposes hereinbefore described, and
8thly. The combination and arrangement of parts constituting my improved
dynamo electric machine and motor constructed and employed substantially
in the manner and for the purposes herein before described and illustrated by.
the drawings hereunto annexed.
HUGH HYNDMAN,
6, Chichester Street, Belfast, Agent for Applicant.