AN IMPROVED DYNAMO- ELECTRIC MACHINE
Year: 1881

page_text: LETTERS PATENT to Frederick Ernost Fahrig, of the Town and County of
Southampton, Electrician, for an Invention of "AN IMPROVED DYNAMO-
ELECTRIC MACHINE."
PROVISIONAL SPECIFICATION left by the said Frederick Ernest Fahrig
at the Office of the Commissioners of Patents on the 23rd September 1881.
FREDERICK ERNEST FAHRIG, of the Town and County of Southampton,
Electrician. "AN IMPROVED DYNAMO-ELECTRIC MACHINE."
My Invention is an improved dynamo-electric machine, and the improvement
consists in the form and construction of the armature which is so made that tho
coils may be readily removed and replaced by others when necessary, or any one
or more of them may be omitted entirely according to the quantity or the strength
of the current required.
In the dynamo-electric machine of my Invention the armature revolves between
and in close proximity to the opposite poles of two sets of field electro-magnets,
each set four or more in number placed parallel, those of the one set being
symmetrically opposite to and in line with those of the other set. Their coils may
or may not be connected together in series, and their cores are permanent steel
magnets so that no exciting machine is required. The armature consists of a
number of straight coils with soft iron cores parallel with the axis of rotation of
the armature, and arranged in the form of an annulus or ring; they are received
in holes of corresponding size in the armature frame, and can be readily slipped in
and out when it is required to vary their number or to replace them by others.
The armature is mounted on a horizontal shaft passing between the field magnets,
and mounted in bearings in a suitable frame to which the cores of the field magnets
are also fixed. The armature coils are separately connected to insulated segments
of a commutator on the armature shaft, or they might be joined together in series
if desired, the current being taken from the commutator by brushes in the ordinary
way and partly sent through the coils of the field magnets, and partly utilised for
outside work.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Frederick Ernest Fahrig in the Great Seal Patent Office on the
23rd March 1882,
FREDERICK ERNEST FAHRIO, of the Town and County of Southampton,
Electrician. "AN IMPROVED DYNAMO-ELECTRIC MACHINE,"
My Invention is an improved continuous current dynamo electric machine, and
the improvement consists mainly in the construction of the armature which is such
that the coils may be readily removed and replaced by others according to the
quantity or the strength of the current required.
In order that the construction of the machine may be more readily understood,
I will proceed to describe it with reference to the accompanying Drawings, wherein
Figure 1 represents a side elevation, Figure 2 a plan, Figure 3 an end elevation,
and Figure 4 a longitudinal section of the machine. Figures 5 and 6 respectively
represent an edge and face view of an armature for producing a single are light or
a number of incandescence lights; Figure 7 represents an edge view of an armature
for a machine producing a number of are lights. The other Figures represent
details of parts hereafter referred to. The magnetic field is composed of four or
more pairs of electro magnets A1, A2, A3, A4, A5, A6, A7, A³, arranged as shown, and
mounted on the cast iron end plates B of the machine frame by screw bolts a
screwing into the cores of the magnets. These end frames B are fixed upon a basė
plate B, and are braced at the upper part by tie bolts b. To the poles of each two
upper and two lower magnets are attached by means of countersunk screws
received in holes tapped in the cores heavy semicircular pole pieces N, S, S, N, of
malleable cast iron. The field magnets at opposite sides of the armature have
unlike poles opposite one another, and of those at the same side of the armature
the poles are unlike in the vertical direction, as indicated by the letters N, S, S, N.
The armature is mounted on the shaft D, and revolves between and in close
proximity to the pole pieces. The armature shown in Figures 5 and 6 consists of
a number of transverse coils C (shown separately in end view, side view, and
section in Figure 8) arranged in a circle around and parallel to tho shaft D, these
coils being held between or inserted in holes in pairs of segment shaped plates c of
which the annular frame of the armature is built up, these segments being rebated
at the joints and united by countersunk screws, and are carried by the arms of
spider frames c' fixed upon a boss c³ keyed on shaft D. are iron distance pieces
inserted in the spaces between the coils, and held in place by screws passing
through from side to side of the frame. The coils may either be connected in a
single series, as shown at cx, or alternate coils may be connected as at c** forming
two distinct series for different purposes. The coils are connected by wires e, each
with a metal strip c' of the same or different collectors E, E', according as there
are one or more series in the armature. The armature shown in Figure 7 is
similar in construction, except that the coils are duplicated, thero being two series
C, C³, side by side, the coils of the two series being respectively connected as above
to the two collectors E, E'. When this armature is used the pole pieces are
made narrower or placed wider apart accomodate the increased width of the
armature. The field magnets for these armatures are connected, as shown in
perspective in the diagram Figure 9, that is to say, A1 and A2, A3 and A*, A" and A,
A and A³ are connected by their front ends, whilst A¹ and A³, A² and A, A and A',
A and As are connected by their rear ends so as to have the opposito polarities
indicated by the letters N, S. This however is only one illustration of the way
the magnetic field may be coupled, which may be varied in different ways

page_text: according to the result required; in either case where there is more than one series
of coils in the armaturo they may be wound with wires of different gauge according
to requirements, and the current of one series may be used for exciting the field
magnets, and that of the other for outside work. All of the junctions of the wires
of the coils, both of the armature and magnetic field are made by means of suitable
binding screws adapted to clamp together the looped ends of the wires to be
joined.
By the construction hereinbefore described it is easy to remove and replace any
of the coils of the armature, it being merely necessary to remove one pole piece
and the attached field magnets at one side of the machine only, and an armature
constructed as herein described does not heat as solid cylindrical or circular ring
armatures do.
Figure 10 shows sectional end and side views of a collector; and Figure 11
shows detail views of the copper strips e¹. These strips are easily replaceable in
case of wear or break down, and they are of L shaped section and embedded
around a boss of hard wood or other insulating material e² having a gun metal
bush, and fitted on the shaft D, the strips being secured in place by screws.
The strips have projecting ears with binding screws for the attachment of tho
wires e from the armature coils, as shown, instead of connecting them by soldering
as usual. The current is taken off by a pair of brushes F carried by studs f fixed
to but insulated from a ring f¹ made of two flanged rings screwed together, and
embracing between their flanges segments f' on the frame B, so that the ring can
be shifted round to adjust the brushes circularly as required.
This machine is reversible, that is to say, it may be used as an electro motor by
shifting round the brushes accordingly.
Having described the nature of my Invention, and the manner of performing the
same, I declare that what I claim as my Invention to be protected by the herein-
before in part recited Letters Patent is,―
1st. The improved dynamo-electric machine, constructed and operating sub-
stantially as shown and described.
2nd. In a dynamo electric machine, the construction of the wheel armature,
substantially as herein described, whereby the coils may be readily removed and
replaced as specified.
3rd. In a dynamo-electric machine, the collector constructed of metal strips of
L shaped section secured in insulating material so as to be removable and replace-
able, substantially as shown and described.
In witness whereof, I, the said Frederick Ernest Fahrig, have hereunto set
my hand and seal, this Seventeenth day of March, A.D. 1882.