Improvements in Dynamo Electric Machines and Electric Motors.
Year: 1893

page_text: Date of Application, 12th May, 1893
Complete Specification Left, 12th Feb., 1894-Accepted, 17th Mar., 1894
PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Machines and Electric Motors.
I HERBERT NAPIER PRENTICE of 17 Bexley Road Erith in the County of
Kent Electrician do hereby declare the nature of this invention to be as
follows:-
The object of my invention is to provide a dynamo electric machine or motor
in which I can employ high magnetic induction without objectionable heating or
other objections (arising in such machines as hitherto constructed when high
magnetic induction is employed) and further in which the air gaps are small so that
the weight of copper necessary is reduced to a minimum, a good mechanical
construction being also secured. Part of the core or body of the armature (which
may be of magnetic material such as solid iron or mild steel) is stationary or
practically stationary, the outside part or periphery, only rotating in close
proximity to the poles of the field magnets. The said outside part is constructed
of copper and magnetic material such as iron, or mild steel, or in some cases it may
be of magnetic material alone, but I prefer to use copper bars as conductors with
laminated iron (consisting preferably of thin insulated plates of charcoal iron)
between the copper bars for the purpose of reducing the magnetic resistance. The
conductors may be connected to the commutator strips in the usual or any
convenient way. The said outer part, or periphery of the armature core may be
rotated by being connected to the shaft by discs or spiders. I do not limit myself
to precise details of construction but I explain what I consider the best construction
to further elucidate the nature of my invention. What I have called the
stationary part of the core of the armature consists of a mass or masses of iron
carried for instance by a bush, or sleeve threaded upon but not fixed to the shaft.
At each end of the core 1 secure discs to the shaft which are of such a diameter
as to extend beyond the periphery of the core and have openings or notches in
their edges to receive the bars of copper constituting the conductors. Between
these bars of copper are insulated plates of iron arranged either lengthwise with,
or transversely to, the copper bars and if necessary secured thereto by a lapping
of wire or in any other convenient way. The said iron strips may extend from
the inside surface of one disc to the inside surface of the other of the portions
thereof situated between the openings or notches in the edges of the discs. As in
this arrangement it is desirable to enable the bush or sleeve upon which the
stationary part of the core is mounted to be removed I prefer to make one or both
of the discs with a central opening large enough to allow of the passage of the
bush or sleeve and to close it by a piece connected thereto and surrounding and
keyed to the shaft the bush or sleeve being connected by means of a flange thereon
through which pass screws into the side of the core so that when the central part
of the disc is removed the bush or sleeve can be detached from the core and
removed either separately or with the spindle. Lubrication may be effected
through an opening in the shaft and the discs may each have a circular trough
upon their inner sides surrounding the shaft and the ends of the bush or sleeve to
receive the surplus lubricant to be returned for re use. Although I have mentioned
bars of copper and plates of iron secured by placing the ends of the
bars
copper
in notches or openings in the edges of the discs I may use the copper and iron in
other form and connect them together and to the discs in any suitable way for
•

page_text: instance, for currents at high pressure it may be desirable to use insulated copper
strip or wire to make up the bars, and for effecting the connection the inner edges
of the discs may be angled inwards towards their outer parts or recessed to engage
with correspondingly angled ends or projections on the iron plates so as to secure
them in place after the manner of dovetails or the copper bars may be passed
through holes in the outward parts of the discs instead of being received in notches
therein.
As before stated I do not limit myself to the precise details which I have
described with regard to the preceding arrangement, for instance 1 may employ
one disc keyed to the rotating shaft and carrying the rotating part of the armature
the stationary part being supported from the opposite side by any suitable bracket
or support and as regards the iron of the rotating part of the armature it may be
composed of laminated rings or segments of rings provided with slots or holes into
or through which the conductors are placed or passed.
The connections between the armature conductors and the commutator may be so
arranged that the current from the armature flows back round the armature before
being taken to the commutator section under the brushes.
Dated this 10th day of Mu.. 1802
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, Agents.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines and Electric Motors.
I, HERBERT NAPIER PRENTICE of Bexley Road, Erith in the County of
Kent, Electrician do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement :-
The object of my invention is to provide a dynamo electric machine or motor in
which I can employ high magnetic induction without objectionable heating or other
objections (arising in such machines as hitherto constructed when high magnetic
induction is employed) and further in which the air gaps are small so that the
weight of copper necessary is reduced to a minimum, a good mechanical construction
being also secured. Part of the core or body of the armature (which is of magnetic
material such as solid iron or mild steel) is stationary or practically stationary the
outside part or periphery only rotating in close proximity to the poles of the field
magnets. The said outside part is constructed of copper and magnetic material
such as iron or mild steel or in some cases it may be of magnetic material, alone
but prefer to use copper bars as conductors with laminated iron (consisting
preferably of thin insulated plates of charcoal iron) between the copper bars for
the purpose of reducing the magnetic resistance. The conductors may be
connected to the commutator strips in the usual or any convenient way.
The said outer part or periphery of the armature core may be rotated by being
connected to the shaft by discs or spiders. I will describe my invention more fully
with reference to the accompanying drawing but I do not limit myself to precise
details of construction illustrated and described.
What I have called the stationary part of the core of the armature consists of a
mass or masses of iron A carried for instance by a bush or sleeve B mounted upon
but not fixed to the shaft C. The part A may consist of a single block of iron or
mild steel but if made up of plates as shewn the said plates may be connected by
bolts c or otherwise.
At each end of this core I secure to the shaft C spiders or discs D D² which are
of such a diameter as to extend beyond the periphery of the part A and have
openings or notches & in their edges as shewn in Figure 6 to receive the bars E of
copper which constitute the conductors. Between these bars of copper are insulated

page_text: plates of iron e which may be arranged either lengthwise of the copper bars as
shewn in Figures 2, 3, 5 and 6 or transversely thereto as shewn in Figure 4 and if
necessary secured thereto by a lapping of wire or in any other convenient way.
For instance the said iron strips may be extended from the inside surface of one
disc to the inside surface of the other of the portions thereof situated between the
openings or notches in the edges of the discs and the ends of the strips may l
.be
notched as shewn at e' to enter under cut recesses in the discs as shown in Figures 2
and 5. These undercut recesses in the discs D D² are at such a depth that when
the iron strips are placed in position they will be nearly in contact with the
stationary part A of the core and the poles of the field magnet there being only
sufficient clearance to admit of this part rotating without having contact therewith
so that the magnetic resistance is reduced to a minimum. As in this arrangement
of the apparatus it is desirable to enable the bush or sleeve B upon which the
stationary part A of the core is mounted to be removed, I prefer to make one or
both of the discs with a central opening as shewn at d in the disc D³ large enough
to allow of the passage therethrough of the bush or sleeve B this opening being
closed by a piece d³ connected to the disc and surrounding and keyed to the shaft C.
The bush or sleeve may be connected to the metal composing the stationary part A
of the core by means of a flange on the said bush through which pass screws c²
into the side of the core, so that when the central part of the disc is removed the
bush or sleeve can be detached from the core and removed either separately or
with the spindle C. When the bush and the spindle are removed the core A may
be supported by rode passed through holes in the core and screwing into holes in
the disc D as shewn by dotted lines in Figure 2. A collar or shoulder C' is
provided on each of the rods c³ which bears on one side of the core A and beyond
this collar the rod extends to outside the flange on the bush B which is provided.
with notches in position corresponding to the position of these rods so that the
sleeve can be removed without interfering with the rods c³.
The lubrication of the rotating parts may be effected through an opening b in
the shaft C and the discs D D' may each have a circular trough upon their inner
sides as shewn at d surrounding the shaft C and the ends of the bush or sleeve B,
to receive the surplus lubricant which may be returned by pipes or passages e³ to
the bearings for re-use. Although I have mentioned bars of copper and plates of
iron secured by placing the ends of the copper bars in notches or openings in the
edges of the discs I may use the copper and iron in other form and connect them
together and to the disc in any suitable way, for instance for currents at high
pressure it may be desirable to use insulated copper strip or wire to make up the
bars and for effecting the connection the inner edges of the discs may be angled
inwards towards their outer parts or recessed to engage with correspondingly
angled ends or projections on the iron plates so as to secure them in place after the
manner of dovetails; or the copper bars may be passed through holes in the
outward parts of the discs instead of being received in notches therein. Instead
of placing the laminated iron plate in contact with each other they may
be kept
apart by distance pieces of mica or other suitable insulating material as shewn at e¹
Figure 6 to provide spaces for the passage of air.
As before stated I do not limit myself to the precise details which I have
described with regard to the preceding arrangement for instance 1 may employ
only one disc D' keyed to the rotating shaft C as shewn in Figures 7 & 8 and
carrying the rotating part of the armature the stationary part A being supported
from the opposite side by any suitable bracket or support such as shewn at D and
as regards the iron of the rotating part of the armature it may be composed of
laminated rings or segments of rings as shown at e Figure 9 provided with slots or
holes into or through which the conductors E are placed or passed.
The connections between the armature conductors E and the commutator H may
be arranged in any suitable manner so that the current from the armature flows
back round the armature before being taken to the commutator section under the
brushes.

page_text: 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
1. In dynamo electric machines or electric motors an armature having a stationary
or practically stationary part of the magnetic core or body and a rotatable
periphery or outside part of the core or body carrying the winding substantially as
hereinbefore described.
.
2. In dynamo electric machines or electric motors an armature having a stationary
or practically stationary part of the core or body constructed of magnetic material
such as iron or mild steel and a rotatable periphery or outside part constructed of
copper bars and laminated iron substantially as hereinbefore described.
3. The constructions combinations and arrangements of parts constituting the
improved dynamo electric machines or electric motors substantially as herein before
described and severally illustrated in the accompanying drawings.
Dated this 12th day of February 1894.