MENTS IN DYNAMO ELECTRIC MACHINES
Year: 1883

page_text: LETTERS PATENT to Charles Horace Benton of Norland Works, Wharf Road,
Latimer Road in the County of Middlesex for an Invention of “IMPROVE
MENTS IN DYNAMO ELECTRIC MACHINES"
PROVISIONAL SPECIFICATION left by the said Charles Horace Benton
at the Office of the Commissioners of Patents on the 13th October 1883.
CHARLES HORACE BENTON of Norland Works, Wharf Road Latimer Road in
the County of Middlesex, "IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
"
This invention consists of improvements in dynamo electric machines by which
the ratio of the actual magnetization of the exciting magnets to the magnetic
force of the magnetizing helices is economically increased, and by which the field
of force thus economically obtained is more completely utilized for the production
of an electric current.
The coefficient of induced magnetism is greatest in soft iron free from carbon
and in soft steel or in those qualities of iron in which the molecules are more
easily turned on their axes into polar directions; this latter quality is better
attained in thin strips of iron than in solid masses. I therefore take thin bars
of iron of the nature above referred to and bolt them together so as to form a solid
thick bar. I then forge on to the middle of this set of bars a pole piece hollowed
out on one side to conform to the form of the armature. The use of soft iron for
magnet cores and pole pieces is not in itself new but as hitherto applied its use
has been attended with great expense in making the connections and joints with
the cast iron frame or in making a wrought iron frame. Now the active parts.
which form the pole pieces and cores are all that need be of iron of good magnetic
conductivity. I therefore heat two sets of bars with pole pieces and place them
in a mould and I then cast upon them the neutral parts which parts also form the
armature bearings. The winding of the helices so as to form consequent points
at the poles is effected in the ordinary manner. By my method of building up
the active parts of the magnets and casting upon them the neutral parts I secure a
substantial base for the machine and a machine as a whole free from the expense
of mechanically shaping and fitting joints and from the danger of poor magnetic
connections between the parts,

page_text: At the collector end of the armature shaft I mount the journals in plummer
blocks which are capable of being removed to allow the armature shaft to be
drawn out until the armature itself is free from the pole pieces when it can be
lifted perpendicularly from the machine.
I construct the armature upon a principle described in the Specification of a
French patent of M. Worms de Romilly N° 70679 dated 3rd March 1866. After
describing a drum armature wound externally and internally, the Specification of
this patent says:-"The passage of the plate covered with wire will give rise on
the one side to a current produced by the wire travelling before a north pole for
example and a south pole is produced in the plate itself by the influence of the
fixed pole while on the opposite side of the plate there is set up in the coil of wire
a contrary current produced by the passage in the same direction before a south
pole resulting from the influence on the soft iron plate." The said specification
further describes that an interior exciting magnet is employed to intensify the
magnetism in the soft iron drum or core. This however presents certain mechanical
difficulties Now I attain the same end and obviate these difficulties by making
the distance between the rotating iron core and the pole pieces of the exterior
fixed magnets very small. If the armature is wound with wire the cylindrical
form together with the insulation causes much waste in the space between the
drum and the pole pieces in planes parallel to the plane of the axis and
perpendicular to the axis of the armature. This throws the armature core so far
distant from the pole pieces that its magnetism in a contrary sense to that of the
fixed magnet is so slight that its induction upon the interior part of the conductor
is almost null and in this method of winding the interior part of the conductor is
generally spoken of as the "inactive part of the bobbin." When however the
core as in this improvement is brought so near the fixed magnet that the core
itself becomes a strong magnet in a contrary sense to that of the fixed magnet the
induction on the interior. part of the conductor is as great as if not greater than in
the exterior part of the turn. The space between the armature core and the pole
pieces in planes parallel to the plane of the axis and perpendicular to the axis of
the armature is therefore of great value while laterally the space necessary for
insulation is not of so much use. I save this space by making the conductor
angular in form instead of cylindrical. In carrying out this part of my invention
I take a plate or strip of copper the section of which is a sector of a circle. I form
a hole in the centre and have a projection at one corner of the plate. I then
slit the plate across the corner and through the projection. I place a number
of these plates on the core by bending aside the upper part of the plate sufficiently
to allow it to be slipped on to the core. I then connect the plates one to another
by soldering the top of the projection of one plate to the lower portion of the
projection of the adjacent plate the cut which is formed through the corner
projection serving to make the soldering more efficient and in this manner a
continuous circuit is produced. This method of constructing an armature helix is
not altogether new as in the Specification of E. A. King's English patent N° 11,188
dated 30th April 1846 there is described:-"An improved method of constructing
the coils for the armature of magneto electric machines by a coil formed of plates
or rings of copper soldered together so as to form a spiral (helix). This is adapted
to a cylindrical armature each ring is cut open on one side and a second ring
soldered to it by the edges thus produced." By constructing an armature as above
described the space between its core and the pole pieces of the exciting magnets
is reduced to a minimum and the interior of the conductor is also strongly induced
by the polarity in the core, and as the space between the shaft and the core is not
of the same value as that between the core and the fixed magnets the interior
part of the plate can be made as wide as the mechanical construction will allow,
and it should be at least as large in section as the section of the exterior part of
the conductor.
To prevent the "Foucault" currents in the soft iron core, instead of constructing
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page_text: forming in section a rectangular trough and I fasten them together with screws
passing through insulating bushes and I have insulation between the rings. I fill
the trough with iron wire gauze ribbon wound edgwise and I fill the meshes
with iron filings and apply insulating material between the successive turns of the
ribbon. The armature core as thus built up allows no currents in the core
perpendicular to the direction of rotation and the iron being finely subdivided
gives great facility to the molecules to rotate quickly upon their axes so as to
change the polar directions which is necessary in each revolution of the armature:
If insulated iron wire is used for this purpose each separate layer produces a
prejudicial magnetic induction upon the layer beneath. With wire gauze however
used as above described the strands running from the periphery toward the axis
prevent this and make the magnetic conduction continuous between the outer and
inner edges of the core

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Horace Benton in the Patent Office on the 8th April
1884.
CHARLES HORACE BENTON of Norland Works Wharf Road, Latimer Road in
the County of Middlesex "IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
"
This invention consists of improvements in dynamo electric machines by which
the ratio of the actual magnetization of the exciting magnets to the magnetic force
of the magnetizing helices is economically increased, and by which the field of
force thus economically obtained is more completely utilized for the production of
an electric current.
The co efficient of induced magnetism is greatest in soft iron free from carbon
and in soft steel or in those qualities of iron in which the molecules are more
easily turned on their axes into polar directions, this latter quality is better
attained in thin strips of iron than in solid masses.
I therefore take thin bars of
iron of the nature above referred to and bolt them together so as to form a solid
thick bar. I then forge on to the middle of this set of bars a pole piece hollowed
out on one side to conform to the form of the armature. In the annexed drawings
Figure 3 is a plan and Figure 4 a section on line A B of Figure 3 of an exciting
magnet with its pole piece made as just described. a is the solid thick bar formed
of a number of thin bars and b is the pole piece. The use of soft iron for magnet
cores and pole pieces is not in itself new but as hitherto applied its use has been
attended with great expense in making the connections and joints with the cast
iron frame or in making a wrought iron frame. But the active parts which form
the pole pieces and cores are all that need be of iron of good magnetic conductivity.
I therefore place 2 sets of bars a a heated at their ends when thought necessary
with pole pieces 6 6 in a mould and I then cast upon them the neutral parts cc,
see Figures 1 and 2 which are respectively a plan and an end view of a dynamo
electric machine constructed according to my invention; the neutral parts c c also
form the armature bearings as seen in the figures; d is the armature; e the
collector and fƒf the brushes. By my method of building up the active parts of
the magnets and casting upon them the neutral parts I secure a substantial base
for the machine and a machine as a whole free from the expense of mechanically
shaping and fitting joints and from the danger of poor magnetic connections
between the parts.
In order that the armature may when required be taken out of the machine I
mount the armature journal at the collector end in a plummer block g which can
be removed by taking out its securing bolts, first removing the cap gl; the
armature shaft can then be drawn out longitudinally until the armature itself is
clear of the pole pieces when it can be lifted perpendicularly from the machine.
g is a cast iron piece to continue the magnetic connection from one core a to the
other, this being rendered desirable owing to the liability of a break of continuity
by the plummer block not being screwed down sufficiently tight. This piece g³
must of course be first removed when it is wished to remove the plummer block.
I construct the armature so that the distance between the rotating iron core and
the pole pieces of the exterior fixed magnets is very small. If the armature is
wound with wire the cylindrical form together with the insulation causes much
waste in the space between the drum and the pole pieces in planes parallel to the
plane of the axis and perpendicular to the axis of the armature. This throws the
armature core so far distant from the pole pieces that its magnetism in a contrary
sense to that of the fixed magnet is so slight that its induction upon the interior
part of the conductor is almost null, and in this method of winding, the interior
part of the conductor is generally spoken of as the "inactive part of the bobbin."
When however the core as in this improvement is brought so near the fixed

page_text: This
magnet that the core itself becomes a strong magnet in a contrary sense to that of
the fixed magnet the induction by the sudden magnetisation of the core, on the
interior part of the conductor is as great as, if not greater than, in the exterior
part of the turn. The space between the armature core and the pole pieces in
planes parallel to the plane of the axis and perpendicular to the axis of the armature
is therefore of great value while laterally the space necessary for insulation is not
of so much use. I save this space by making the conductor angular in form
instead of cylindrical. In carrying out this part of my invention I take a plate or
strip of copper the section of which is a sector of a circle, that is to say conical or
tapered as seen in Figure 5 which is a face view and in Figure 6 which is an end
view of one of these copper plates. In the middle of each plate h I form a hole i
and at one corner of the plate I have a projection k which is slit or divided as seen
at from the hole i to the end. I place a number of these plates on the armature
core m-see Figures 8 and 9 which are respectively a transverse section and a
longitudinal section of the armature-by bending aside that part of the plate
which is above the slit sufficiently to allow it to be slipped on to the core.
I then connect the plates one to another by soldering the upper portion of the
projection of every plate on the one side to the lower portion of the projection of
the adjacent plate and in this manner a continuous zigzag or helical like circuit is
produced extending the whole circumference of the core m. Figure 7 shows 5 of
these plates thus connected but of course there will be a large number (say 400
for example) similarly connected to complete the circuit on the core m
method of constructing an armature helix is not altogether new as in the
Specification of E. A. King's English patent N° 11,188 dated 30th April 1846
there is described: "An improved method of constructing the coils for the armature
of magneto electric machines by a coil formed of plates or rings of copper soldered
together so as to form a spiral (helix). This is adapted to a cylindrical armature,
each ring is cut open on one side and a second ring soldered to it by the edges
thus produced." By constructing an armature as above described the space
between its core m and the pole pieces 6 of the exciting magnets is reduced to a
minimum and the interior of the conductor is also strongly induced by the polarity
in the core, while the armature is not liable to have its magnetism decreased by
the induction of its own coil as is the case when the armature is at a greater
distance from the pole pieces and a strong current is flowing through the induced
conductor; and as the space between the shaft n of the armature and the core is
not of the same value as that between the core and the fixed magnets the interior
part of the plates h h that is to say the part of the plates inside the core m can be
made as wide as the mechanical construction will allow, and it should be at least
as large in section as the section of the exterior part of the conductor, that is to
say the part of the plates h h which is outside the core m. The plates h h should
be insulated from each other by suitable material interposed between them.
Some or all of the plates hh say every fourth plate are connected with the
collectors as will be well understood for which purpose the plates to be so
connected have projecting pieces o as seen in Figure 7 and in dotted lines in
Figure 5.
In dynamo machines for large currents where the section of the plates h h must
be considerable I connect several plates together "in quantity" and I couple each
group to the adjacent group by means of a copper piece instead of by bending part
of the plate as before described. The object of connecting several plates together
in lieu of using a single bar or plate of the requisite thickness is to obviate the
formation of local currents which are set up when thick bars are used. The
division or opening at the end of the plates is in this case as seen in Figure 10 as
wide as the hole i.
Figure 11 represent copper pieces which connect the
plates together "in quantity" in groups of 3 (for example), these pieces rr likewise
serving to connect the upper portion of each group, that is, the portion above the
opening to the lower portion of the adjacent group.
To prevent the "Foucault" currents in the soft iron core, instead of constructing

page_text: it of a solid drum I build it up as follows:-I take rings of soft steel or other
suitable magnetic material of trough section as clearly seen in Figure 9 these rings
being separated from each other by insulating material p p and fastened together
with screws 99 passing through insulating bushes. I fill the trough with iron
wire gauze ribbon r wound edgwise and I fill the meshes of the gauze with iron
filings and apply insulating material between the successive turns of the ribbon.
The armature core as thus built up allows no currents in the core perpendicular to
the direction of rotation and the iron being finely sub-divided gives great facility
to the molecules to rotate quickly upon their axes so as to change the polar
directions which is necessary in each revolution of the armature. If insulated iron
wire is used for this purpose each separate layer produces a prejudicial magnetic
induction upon the layer beneath. With wire gauze however used as above
described the strands running from the periphery toward the axis prevent this and
make the magnetic conduction continuous between the outer and inner edges of
the core.
Having now described the nature of my said invention and in what manner the
same is to be performed I declare that I claim as my improvements in dynamo-
electric machines:-
1. A dynamo electric machine in which the cores of the exciting magnets are
composed of a number of thin bars possessing good magnetic conductivity secured
together and are fixed to pole pieces and have cast upon them end pieces which
form the neutral parts of the magnetic system the whole forming a single piece
substantially as herein before described.
2. In a dynamo electric machine, cast iron end pieces forming the bearings for the
armature shaft and cast upon the cores of the exciting magnets substantially as
hereinbefore described.
3. An armature for dynamo electric machines baving its coil composed of copper
plates the form of which in section is conical or tapered, the said plates having a
hole in the middle to fit over the soft iron core and having a division or opening
extending from the said hole to one end of the plate, and the said plates being
connected together so as to form a continuous zigzag or helical like circuit
on the circumference of the core substantially as and for the purpose hereinbefore
described.
4. An armature for dynamo electric machines having its soft iron core in the form
of a drum made of rings of trough section insulated from each other and fastened
together and with iron wire gauze ribbon wound edgwise in the troughs the
meshes of the gauze being filled with iron filings, substantially as and for the
purpose herein before described.
5. The combination in an armature for dynamo electric machines of a coil composed
of copper plates having the form hereinbefore described and fitted upon the core
and connected together as shown, and of a core in the form of a drum composed
of rings of trough section insulated from each other and fastened together and
having iron wire gauze ribbon with its meshes filled up with iron filings wound
edgwise in the troughs substantially as herein before described and represented in
the annexed drawings.
6. Constructing dynamo electric machines as herein before described and represented
in the annexed drawings.
In witness whereof I the said Charles Horace Benton have hereunto set my
hand and Seal this seventh day of April One thousand eight hundred and eighty
four