IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by the said John Munro at the Office
of the Commissioners of Patents on the 6th February 1883.
JOHN MUNRO. of West Croydon, in the County of Surrey; Electrician,
"IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
"
My invention relates to the construction of dynamo electric machines, and is
designed, chiefly, by improvements in the construction of the armatures of the said
machines, to effect greater efficiency and cheapness in their construction.
I use the usual electro magnetic poles arranged singly or in groups, and con-
veniently fitted with large pole-plates of soft iron to diffuse the area of the magnetic
field.
In one construction of my improved armature I bring the opposite magnetic
poles close together, and between them, as close as possible without actual contact,
I rotate, as armature, a disc, set on both sides with radial bars or strips of copper,
joined in a grid form, and either running round the borders of the disc, or forming
fanshaped sections on it. These strips are connected together and otherwise
insulated so as to give an induced current by rotation, either in two separate
circuits, one on each side of the disc; or in a single circuit. The current is led
away by suitable collectors or commutators.
In an alternative form of machine I place the magnetic poles wider apart, and
rotate as armature between them a double drum of copper bars or strips, the bars
of each half drum being connected so as to give a separate induced current by
rotation, or if desired, a single current from both halves. One or more drums so
constructed may be employed, and they may rotate on either vertical or horizontal
axes.
I may also alternatively specially construct this drum armature, by overlaying a
stout frame with a grid of sheet copper or other suitable metal, so placed that the
bars run lengthwise along the drum at right angles to the lines of force, from pole

page_text: to pole, of the magnetic field. The end turns or end connecting strips of the grids
are made as short as possible, as they traverse in the magnetic field without practical
inductive effect.
More than one layer or grid can be put on the drum, provided each layer is
suitably insulated from the rest by air, mica, asbestos, or other insulator. The
several grids are properly connected to give the best effect, and collectors or com-
mutators are applied to draw off the current in the usual way.
To increase the strength of the magnetic field, a permanent magnet, or an
electro-magnet, is placed within the armature. This magnet may be fixed
stationary within the armature, or may be pivoted free so that it may be held by
the attraction of the outer electromagnets, or it may be rotated with the armature.
In any of the preceding arrangements the electro-magnets may be wound with
copper strips in place of wires or with iron wire in place of copper, and they may
be enclosed in iron cylinders.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Munro in the Great Seal Patent Office on the 4th August
1883.
JOHN MUNRO, of West Croydon, in the County of Surrey, Electrician,
"IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
و"
My invention relates to the construction of dynamo electric machines, and is
designed, chiefly by improvements in the construction of the armatures of the said
machines, to effect greater efficiency and cheapness in their construction.
I use the usual electro-magnetic poles, arranged singly or in groups, and
conveniently fitted with pole-plates of soft iron to diffuse the area of the magnetic
field.
And in order that the construction of my improved armature may be the better
understood I now proceed to describe the same with reference to the drawing
hereto annexed and to the letters and figures marked thereon.
Like letters refer to similar parts in each of the figures.
Figures 1, 2, and 3, are respectively a side elevation, a transverse section, and an
alternative side elevation of my improved grid disc armature.
Figures 4 and 5 are respectively a side elevation and end view of my improved
grid drum armature.
In one construction of my improved armature, I bring the opposite magnetic
poles close together, and between them, as close as possible without actual contact,
I rotate, as armature, the disc A. Figures 1, 2, and 3, set on both sides with the
radial bars or strips of copper B, joined at the ends in a grid form, and either
running round the borders of the disc, as in Figure 1, or forming fan shaped
sections upon it, as in Figure 3.
These strips are connected together as shown, and otherwise insulated, so as to
give an induced current by rotation, either in two separate circuits, one on each
side of the disc, or in a single circuit.
The current is led away by suitable collectors and commutators, which render it
alternating or continuous as desired.
In an alternative form of machine I place the magnetic poles wider apart, and
rotate as armature between them a drum, Figures 4 and 5, whose circumference is
formed of copper grids C the strips being connected alternately at either end, as
shown, so that the current induced by rotation may be continuous and single
throughout the whole drum, or the grid may be divided in half drum or other
sections so as to develope separate currents.
Single, double, or multiple drums or grids may be employed, and they may
rotate on vertical or horizontal axes.
I construct the circuit of these drum armatures, by overlaying a stout frame D
mounted on a suitable spindle E with a grid of sheet copper C or other suitable
metal, so placed that the strips run lengthwise along the drum at right angles to
the lines of force, from pole to pole of the magnetic field. The end turns, or end
connecting strips, G, of the grids are made as short as possible, as they traverse the
magnetic field without practical inductive effect.
More than one layer or grid can be put on the drum provided each layer is
suitably insulated from the rest by air, mica, asbestos, or other insulator. The
several grids are properly connected to give the best effect, and collectors or
commutators are applied to draw off the current in the usual way.
To increase the strength of the magnetic field, a permanent magnet, or an
electro-magnet, is placed within the armature. This magnet may be fixed

page_text: stationary within the armature, or may be pivotted free, so that it may be held by
the attraction of the outer electro-magnets, or it may be rotated with the
armature.
In any of the preceding arrangements the electro-magnets may be wound with
copper strips in place of wires, or with iron wire in place of copper, and they may
be enclosed in iron cylinders.
And having now described and ascertained the nature of my said invention, be
it known that what I consider novel and desire to protect by Letters Patent is :-
First. In dynamo and magneto electric machines, the construction of the
armature with grids of copper, or other suitable strips or bars, in lien of the
ordinary wires, placed on the sides of a rotating disc, either radially or in fan-like
sections, substantially as described.
Second. In dynamo and magneto electric machines, the construction of the
armature with one or many grids of longitudinal bars of copper or other suitable
material, arranged upon the circumference of a rotating drum frame, substantially
as described.
In witness whereof I, the said John Munro, have hereunto set my hand and
seal this second day of August in the year of our Lord One thousand eight
hundred and eighty-three.
Witness
S. P, WILDING
23 Rood Lane, London. E.C
Patent Agent.
JOHN MUNRO (L.S.)