IMPROVED CONSTRUCTION OF GRAMME ARMATURES FOR ELECTRIC GENERATORS AND MOTORS
Year: 1885

page_text: Generators and Motors.
I, GEORGE EDENSOR DORMAN of Brook House, Stafford in the county of
Stafford, Engineer, do hereby declare the nature of my invention for IMPROVED
CONSTRUCTION OF GRAMME ARMATURES FOR ELECTRIC GENERATORS AND MOTORS,
to be as follows:-
My invention relates to the construction of that type of armature with its
modifications known as the Gramme and consists in mounting the armature, or
the core of the armature, on a number of narrow pulleys, partly or wholly made of
nonmagnetic metal, insulated from one another except at the spindle hole, strung
and keyed on a shaft, and screwed together by nuts on the shaft or bolted with
insulated bolts.
In applying this invention to an armature in which the induction coils are
formed of wire, I make the pulleys with spokes of nonmagnetic metal, the hubs of
nonmagnetic metal or not, and the rims preferably of wrought iron, but they may
be made of nonmagnetic metal, each pulley being provided with flanges of wrought
iron, or a flange may be fixed to each end pulley of the set of pulleys, between the
flanges of each pulley, or the two flanges of the end pulleys of the set of pulleys,
the pulleys having first been screwed together and keyed to the shaft, and with the
flanges, having been sheathed with suitable insulating material, I wind or place
the insulated iron wire or discs, to form the core of the armature, on the ring thus
formed and mounted I wind or place the copper wire or in a bar armature made in
this manner, the copper bars to form the induction coils, the wire or bars being
threaded between the spokes of the pulleys.
To adapt this invention in a better manner to a bar armature I make the
pulleys entirely of nonmagnetic metal without flanges, and I place the interior
induction bars on the rims of the pulleys, the bars being furnished with end or
radial bars or connections, which I prefer to make much wider than the interior
and circumferential bars in order to afford a broad contact at the joints with those
bars, in order to give the bars on the armature the helical arrangement I place the
circumferential bars somewhat obliquely on the armature core, and I place the wire
or discs to form the core of the armature, in the bobbin formed by the interior
induction bars and their end connections or bars, in order to furnish sufficient

page_text: driving friction between the pulleys and the interior induction bars, I bind those
bars on to the pulleys with insulated steel wire or rings, or some of the bars may
be made deeper than the rest and be let into slots in the rims of the pulleys, being
suitably insulated so as to act as keys, or the two end pulleys may be made with
flanges to tighten up against the radial bars, or the pulleys may be divided into
two sets, each set being slightly tapered or coned and bolted together separately,
the interior induction bars being slightly bent or tapered, to conform to the shape
of the pulleys, the bars and core having been built up on these pulley cones, the
pulley cones on being screwed up, will tighten the bars against the pulleys and the
core.
Wire induction coil armatures may also be mounted on the pulleys coned in this
manner.
The commutator bars may be mounted on pulleya coned in the above manner,
which may force the bars against circumferential insulated rings.
In some cases the pulleys may have holes bored in their rims, and be spaced
by suitable means a slight distance apart, in order to afford ventilation to the
armature.
The pulleys may be slotted at intervals to retain bars of insulating material,
which may be used to space the circumference of the pulleys into sections, or the
bars of insulating material may be used as keys or drivers.
.
T
100
COMPLETE SPECIFICATION.
Improved Construction of Gramme Armatures for Electric
Generators and Motors.
I, GEORGE EDENSOR DORMAN of Brook House, Stafford, in the county of Stafford,
Engineer, do hereby declare the nature of my invention for IMPROVED CON-
STRUCTION OF GRAMME ARMATURES FOR ELECTRIC GENERATORS AND MOTORS, 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 the construction of that type of armature, known as the
"Gramme" and to such of its modifications as those, in which, as in the original
Gramme ring and in the modification by Maxim (Specification No 1392, of A.D.
1880) the form, of the armature or the core of the armature is known as that of
a ring cylinder" or clongated ring," not relating to such modifications as are
known, as the "flat ring" type, and consists in mounting the armature or the coro
"

page_text: of the armature on the rims of a number of narrow pulleys partly or wholly made
of nonmagnetic metal, insulated from one another except (for the sake of ease in
construction) at the spindle hole, strung and keyed on a shaft, and screwed up
together by nuts on the shaft, or bolted with insulated bolts. In applying my
invention to an armature in which the induction or armature coils are formed of
wire, I make the pulleys with spokes of nonmagnetic metal, the hubs of non-
magnetic metal or not, and the rims preferably of wrought iron, but they may be
made of nonmagnetic metal, each pulley being provided with flanges of wrought
iron, or a flange may be fixed to each end pulley of the set of pulleys, between the
flanges of each pulley, (or between the flanges of the end pulleys of the set of
pulleys, the pulleys having first been screwed together and keyed to the shaft) the
pulleys with the flanges having been sheathed with suitable insulating material,
I wind or place the insulated iron wire, to form the core of the armature, on the
core or ring or skeleton of a Gramme armature thus formed and mounted, I wind
or place the copper wire, or in a bar armature which may also be made in this
manner, the copper bars to form the induction or armature coils, the wire or bars
being threaded between the spokes of the pulleys.
To adapt my invention in a better manner to a bar armature, I make the pulleys
entirely of nonmagnetic metal, without flanges, and I place the interior induction
bars of the armature on the rims of the pulleys, the bars being furnished with end
or radial bars or connections, which I prefer to make much wider than the interior
and circumferential bars in order to afford a broad contact at the joints with those
bars, (in order to give the bars on the armature the helical arrangement, I place
the circumferential bars somewhat obliquely on the armature core) and I place the
wire or discs to form the core of the armature, in the bobbin formed by the interior
induction bars and their end connections, in order to furnish sufficient driving
friction between the pulleys and the interior induction or armature bars, I bind
those bars on to the pulleys with insulated steel wire or rings, or some of the bars
may be made deeper than the rest and be let into slots in the rims of the pulleys,
being suitably insulated so as to act as keys, or the pulleys may be divided into
two sets, each set being slightly tapered or coned and screwed or bolted together
separately, the interior induction bars being slightly bent or tapered, to correspond
with the taper of the pulleys, the bars and core having been built up on these
pulley cones, the pulley cones on being screwed up will tighten the bars against the
pulleys and the core, it is evident that the core or ring may be constructed and
wound first and then be mounted on the tapered pulleys. In some cases the pulleys
may be slotted at intervals to retain bars of insulating material, which may be used
to space the circumference of the pulleys into sections, or to act as keys or drivers.
In order that my invention may be better understood, I have illustrated it by
the accompanying drawings. Figure 1, shows an end view and longitudinal section
of the core of a Gramme armature mounted according to my invention, in which
cach of the narrow pulleys is flanged, the wire forming the core being for clearness
shown wound between the flanges of some only of the pulleys, the pulleys being
insulated from one another and kept apart by means of nonconducting washers on
the shaft. Figure 2, shows an end view and longitudinal section of a core,
mounted on pulleys in which the end pulleys only of the set of pulleys are flanged.
Figure 3, shows an end view and longitudinal section of a Grainme bar armature
mounted on pulleys, some of the bars of the induction coils being let into slots in
the circumference of the pulleys, so as to act as keys or drivers. Figure 4, shows
an end view and longitudinal section of a bar armature mounted on two sets of
tapered pulleys.
In the arrangements shown in Figure 1 and Figure 2, where the rims of the
pulleys are preferably made of wrought iron, it is evident that the rims form part
of the core, carrying some of the lines of force.
In armatures of a large diameter in which the centre of the ring is traversed by
few or no lines of force, it is evident that a central hub or drum of iron of a largo
diameter may be used to carry the pulleys.

page_text: When necessary the pulleys may be insulated from one another at the spindle
hole by using a nonconducting sleeve on the shaft, the key or spline being also
insulated.
Variations may be made in the arrangements I have described, in some cases the
cores or armatures I have described as suitable for being wound with wire, may be
wound with bars and vice versa, and discs or wire may be used for the cores as
found preferable.
In cases where the rims of the pulleys form part of the core of the armature as
in Figure 1, and Figure 2, it is evident that the rims of the pulleys, when the
pulleys are made entirely of nonmagnetic metal, should be as thin as possible, so
as to allow the wire of the induction coils to come within a slight distance of the
core, the spokes of the pulleys, of which there may be any convenient number,
should also be thin. The rims of the pulleys when of wrought iron may be rivetted
or fixed on to the spokes in any suitable manner.
The nonmagnetic parts of the pulleys, may be cast in brass or gunmetal or other
suitable metal.
My design in this invention has been to produce an armature easy and
mechanical in construction, and at the same time by breaking in the manner above
described, the electrical continuity of the mounting or support of the armature, to
arrest in a degree the circulation of "Foucault" currents, which, in armatures in
which the support or mounting is continuous for the length of the armature (as in
armatures mounted on metallic keys, or wings, or vanes, or cylinders) are liable to
circulate, causing heat, and lessening the efficiency of the machine.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is,
First. The construction or mounting of Gramme armatures of the "ring
cylinder" or "elongated ring" typo, on the rims of a number of narrow metallic
pulleys, either partly or wholly made of nonmagnetic metal, and partly or entirely
insulated from one another, as described.
Second. The construction or mounting of Gramme armatures on a number of
narrow insulated pulleys, in the manner described and shown in Figure 1, Figure 2,
Figure 3, and Figure 4.