IMPROVEMENTS IN THE CONSTRUCTION OF DYNAMO-ELECTRIC MACHINES, PARTLY APPLICABLE ALSO TO OTHER PURPOSES
Year: 1883

page_text: LETTERS PATENT to Harry Theodore Barnett, of Saint John's Wood, in
the county of Middlesex for an Invention of IMPROVEMENTS IN THE
CONSTRUCTION OF DYNAMO-ELECTRIC MACHINES, PARTLY APPLICABLE ALSO TO
OTHER PURPOSES
PROVISIONAL SPECIFICATION left by the said Harry Theodore Barnett at
the Office of the Commissioners of Patents on the 14th February 1883.
HARRY THEODORE BARNETT of Saint John's Wood in the County of Middlesex
"IMPROVEMENTS IN THE CONSTRUCTION OF DYNAMO-ELECTRIC MACHINES PARTLY
APPLICABLE ALSO TO OTHER PURPOSES
دو
The objects of these Improvements are the construction of a powerful and
compact Dynamo Electric Machine and the suppression of the Foucault or induced
currents in the cores of the armatures and field magnets of such machines and
in the cores of electro magnets, induction coils, and similar machines and apparatus.
These improvements relate especially to those machines in which the armature
rotates in a plane perpendicular to the fields of force, that is to say wherein the
field magnets are arranged in two parallel circles or planes with the armature
between them, but they are also applicable in part to other dynamo electric
machines, to electro magnets of all kinds to secondary or induction coils and to
similar apparatus.
In constructing the armature Turnel the coils of wire or other conductor upon
a false bobbin or reel having one or both discs or cheeks removable. One or both
of the cheeks of the false bobbins have holes or slots formed through or in them
at a convenient distance from the centre so that a rod may be passed through
parallel with the core. I first wind on the false core one or more layers of wire,
then insert the rod and continue the winding to completion. The coil may then
or subsequently be saturated with cement or bound with wire or thread to
strengthen it and hold the helix together. The coil being wound is removed from
the false bobbin and the rod is withdrawn when two holes will be found through
it, one produced by the false core in the centre and another formed by the rod.
The hole for the core may then be filled by the special core to be hereinafter
described or in some cases the core may be omitted. A sufficient number of coils
having been prepared as described the further construction of the armature may
be proceeded with.
Upon the shaft or axis of the armature I secure a metal disc or framing and
parallel thereto I place loosely on the shaft a second disc or framing. At equal

page_text: distances from each other the second disc carries metal or other pins rods or
projections formed to fit the holes in the coils produced by the rod. The first or
fixed disc may have holes or recesses formed in it to receive the ends of the pins
rods or projections. Instead of the pins rods or projections being fitted on the
loose disc they may be carried by the other but I prefer the method first described.
To cause the two discs to occupy their relative positions to each other I form a
screw thread on the shaft beyond the loose disc or framing and by turning a out
on this screw I cause the loose disc to approach the fixed disc when the nut may be
secured in position by a lock nut or equivalent device. Instead of having a screw
and nut as last described I may employ equivalent means, such for example as
screw bolts passing through both discs. To secure adhesion between the coils and
discs I sometimes serrate the faces of the discs at the points of contact between
them and the coils and secure the special cores to the discs by cement screws or
pins. The discs may be slotted or perforated if desired so as to prevent or reduce
the generation within them of induced currents.
In putting the armature together the coils are placed upon the rods pins or
projections curved by one of the discs as already indicated and the field coils are
so arranged that there shall be as little unoccupied space as possible between them
and the armature.
The armature coils may be connected in parallel circuit or in series the poles of
one sign being connected either to the metal of the machine or to a commutator
-or-ring of metal-upon the shaft, the poles of the other sign being connected to an
insulated ring on the shaft whence the current may be led off by collectors or a
collector and terminal in the usual manner. If it is desired to obtain a continuous
current from the machine I take each pole to a segment of the commutators. One
of the commutators is constructed somewhat like a spur toothed wheel but with
the spaces wider than the teeth and each of the teeth representing a segment of
the commutator. The other commutator is provided with projecting segments and
it is so placed and formed that these projecting segments may occupy a portion of
the width of the spaces between the segments of the first commutator or both the
commutators may be constructed in the manner last described so that by shifting
the position of the collectors the machine may be made to yield either a continuous
or an alternating current.
The field magnets may be constructed in the ordinary manner but I prefer to
cap the iron cores with pole pieces of the same magnetic material used for the
armature cores.
I will now proceed to describe the special cores bereinbefore referred to and
which I propose to use also in the construction of the coils of other dynamo electric
and similar machines, electro motors, electric magnets of all kinds and secondary
or induction coils for the purpose of suppressing or diminishing Foucault or induced
currents therein and to prevent heating.
I form my special cores of finely divided magnetic metal such as iron each
granule of which is as far as possible insulated from every other by being oxidised
or by being covered with a film of varnish or other suitable material. The finely
divided magnetic metal thus insulated may be compressed in suitable moulds or in
the space left in the coil for the core or be otherwise formed to the requisite shape
when plastic or be cut out of the solid mass when set. A convenient method of
insulating the particles of method from each other and forming the required solid
mass is to mix the finely divided metal with powdered resin, shellac or similar
material and then to compress the mixture at the same time employing sufficient
heat to melt the resin or its equivalent and allowing it to cool. A method of
oxidising and cementing is that of mixing iron filings with salammoniac as is usual
in making what is known as "rust joint cement." If desired in some cases to
obtain a more coherent mass I mix with the mass hair or fibres and when
ventilation is thought requisite the core may be pierced with holes.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, and of
an Order of the Lord Chancellor, filed by the said Harry Theodore Barnett
in the Great Seal Patent Office on the 20th August 1883.
HARRY THEODORE BARNETT of Saint Johns Wood in the County of Middlesex,
"IMPROVEMENTS IN THE CONSTRUCTION OF DYNAMO-ELECTRIC MACHINES PARTLY
APPLICABLE ALSO TO OTHER PURPOSES
"
The object of these improvements are the construction of a powerful and compact
dynamo electric machine and the suppression of the "Foucault" or induced
currents in the cores of the armatures and field magnets of such machines and in
the cores of electro magnets, induction coils and similar apparatus.
These improvements relate especially to those machines in which the armature
rotates in a plane perpendicular to the fields of force, that is to say wherein tho
poles of the field magnets are arranged in two parallel circles or planes with the
armature between them, but they are also applicable in part to other dynamo
electric machines, to electro-magnets of all kinds, to secondary or induction coils
and to similar apparatus.
In constructing the armature I wind the coils of wire or other conductor upon a
false bobbin or reel having one or both discs or cheeks removable. One or both of
the cheeks of the false bobbins have holes or slots formed through or in them at a
convenient distance from the centre so that a rod may be passed through parallel
with the core. I first wind on the false core one or more layers of wire, then
insert the rod and continue the winding to completion. The coil may then or
subsequently be saturated with cement or bound with wire or thread to strengthen
it and hold the helix together. The coil being wound is removed from the false
bobbin and the rod is withdrawn when two holes will be found through it, one
produced by the false core in the centre and another formed by the rod. The hole
for the core may then be filled by the special core to be hereinafter described, or in
some cases the core may be omitted.
In the accompanying drawings Figs. 1 and 2 serve to illustrate the shape of the
coils and the method of forming the same, Fig. 1 being a cross section and Fig. 2
an axial section of a false bobbin wound with wire. A is the false core, B a fixed
and B' a removable flange and O the removable rod.
A sufficient number of coils having been prepared as described the further
construction of the armature may be proceeded with.
Upon the shaft or axis of the armature I secure a metal disc or framing, and
parallel thereto I place loosely on the shaft a second disc or framing. At equal
distances from each other the second disc carries metal or other pins, rods or
projections formed to fit the holes in the coils produced by the rod. The first or
fixed disc may have holes or recesses formed in it to receive the ends of the pins,
rods, or projections. Instead of the pins, rods, or projections being fitted on the
loose disc, they may be carried by the other but I prefer the method first described.
To cause the two discs to occupy their relative positions to each other I form a
screw thread on the shaft beyond the loose disc or framing and by turning a nut
on this screw I cause the loose disc to approach the fixed disc when the nut may be
secured in position by a lock nut or equivalent device. Instead of having a screw
and nut as last described I may employ equivalent means, such for example as
screw bolts passing through both discs. To secure adhesion between the coils and
discs I sometimes serrate the faces of the discs at the points of contact between
them and the coils and secure the special cores to the discs by cement, screws or

page_text: pins. The discs may be slotted or perforated if desired so as to prevent or reduce
the generation within them of induced currents.
In putting the armature together the coils are placed upon the rods pins or
projections carried by one of the discs as already indicated and the field coils are so
arranged that there shall be as little unoccupied space as possible between them
and the armature. Instead of two discs one disc or frame or more than two may
be employed for supporting the wire coils.
In the accompanying drawings Fig. 3 is a cross section and Fig. 4 an axial
section of an armature constructed according two my invention. D is the main shaft
of the dynamo machine, E and E¹ are the two discs or frames which carry the
bobbins; a, a.
are the coils, b. b. . . . their cores, cc... the pins or
rods which pass through the coils and serve to secure them to the discs.
The armature coils may be connected in parallel circuit or in series, the poles of
one sign being connected either to the metal of the machine or to a commutator or
ring of metal upon the shaft, the poles of the other sign being connected to an
insulated ring on the shaft whence the current may be led off by collectors or a
collector and terminal in the usual manner. If it is desired to obtain a continuous
current from the machine I take each pole to a segment of the commutators. One
of the commutators may be constructed somewhat like a spur toothed wheel but
with the spaces wider than the teeth and each of the teeth representing a segment
of the commutator. The other commutator is in this case provided with projecting
segments and it is so placed and formed that these projecting segments may
occupy a portion of the width of the spaces between the segments of the first
commutator, or both the commutators may be constructed in the manner last
described so that by shifting the position of the collectors the machine may be made
to yield either a continuous or an alternating current.
The field magnets may be constructed in the ordinary manner, but I prefer
to cap the iron cores with pole pieces of the same magnetic material used for the
armature cores.
I will now proceed to describe the special cores herein before referred to and
which I propose to use also in the construction of the coils of other dynamo electric
and similar machines, electro motors, electro magnets of all kinds and secondary or
induction coils for the purpose of suppressing or diminishing Foucault or induced
currents therein and to prevent heating.
I form my special cores of finely divided magnetic metal such as iron ench
granule of which is as far as possible insulated from every other by being covered
with a film of varnish or other suitable material. The finely divided magnetic
metal thus insulated may be compressed in suitable moulds or in the space left in
the coil for the core or be otherwise formed to the requisite shape when plastic or
be cut out of the solid mass when set. A convenient method of insulating the
particles of metal from each other and forming the required solid mass is to mix
the finely divided metal with powdered resin, shellac or similar material and then
to compress the mixture at the same time employing sufficient heat to melt the
resin or its equivalent, and allowing it to cool. If desired in some cases to obtain
a more coherent mass I mix with the mass hair or fibres and when ventilation is
thought requisite the core may be pierced with holes.
Having now described my invention, and the manner in which the same is to be
performed, I wish it to be understood that I do not claim the construction or
arrangement of the commutator or its connection with the armature coils, and that
I do not limit myself to the exact details shown by the drawings;
What I claim is;
1. In armatures of dynamo-electric and similar machines, the use of wire coils
secured to the frame or frames of the armature by means of pins, bolts or
studs fitting into holes formed in winding the coil and situated between the
core opening and the shaft of the armature or at that extremity of the coil
which is nearest to the shaft, substantially as described.

page_text: 2. The use of a magnetic compound containing some finely divided magnetic metal
mixed with insulating material, for the cores of armature coils, electro-magnets
and induction coils, substantially as described.
In Witness whereof I, the said Harry Theodore Barnett, have hereunto set my
hand and seal this 18th day of August AD 1883.