IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by the said John Hopkinson at the
Office of the Commissioners of Patents on the 22nd February 1883.
JOHN HOPKINSON of Westminster Chambers in the County of Middlesex F.R.S.
"IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES".
The object of the first portion of this Invention is to obtain a greater effect
from existing Dynamo machines without increase of size and weight of machine
or to obtain as great an effect from a machine of smaller size as now obtained
from machines of larger size. This object is obtained by increasing the sectional
area of the exciting magnets and diminishing their length. In some cases I make
the magnets of ring form excepting that part where the armature revolves. By
these means I am able to produce a very intense magnetic field but I find that by
the employment of this improvement with the armature now in use the iron
becomes very hot and ny Invention therefore further consists in obviating this evil
by increasing the mass and magnetic cross section of the iron of the armature.
My improvements thus consist in increasing the iron of the armature and in
combining this altered armature with the magnets improved in the manner firstly
above mentioned. These improvements are specially applicable to Dynamo-
machines having armatures of the form known as the Siemens Armature and more
particularly to that improved form known as the Edison machine and may be used
whether the machines are for producing electric currents or for motors. According
to a further portion of my Invention when the conductors of the armature in the
above mentioned machines are copper bars I make the end connections of opposite
bars by a conductor consisting of two radial parts in one plane and a semicircular
or approximately semicircular part in a parallel plane this brings the end connections
into a very compact and convenient form.

page_text: .
SPECIFICATION in pursuance of the conditions of the Lotters Patent filed by
the said John Hopkinson in the Great Seal Patent Office on the 4th August
1883.
JOHN HOPKINSON of Westminster Chambers in the County of Middlesex F.R.S.
"IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES "
The object of my Invention is to obtain greater effect from existing Dynamo
machines without increase of size and weight of the machine or to obtain as great
an effect from a machine of a small size as has hitherto been obtained from
machines of a larger size.
My Improvements are applicable to Dynamo machines--having armatures of the
form known as the Siemen's Armature and specially to the improved form known
as the Edison machine and may be used whether the machines are for producing
Electric currents or for motors.
My said Improvements consist first in increasing the sectional area of the
exciting magnets and diminishing their length. Figures 1 and 2 of the accom-
panying drawings, will. explain this more clearly;--Figure-1 representing the
proportions of an ordinary machine known as an "Edison Dynamo and Figure 2
representing a machine constructed in accordance with my Invention from which
it will be seen that the sectional area of the cores of the magnet does not differ
greatly from the whole area of a cross section of the armature through the axis
and that the length of the said cores is about two and a half times the diameter
of the armature but I do not limit myself to the exact proportions shewn. In
some cases I make the exciting magnets of a ring form with a gap or space therein
for the armature to revolve in. Figure 3 represents a machine with the magnet
thus formed. The general proportions of this form will be seen to be substantially.
the same as those of the form of machine shewn in Figure 2. By this Improve-
ment I am able to produce a very intense magnetic field; and to further enhance
the advantage thus obtained, I increase the mass and magnetic cross section of the
iron core of the armature and I combine this improved armature with the improved
exciting magnets herein before described. The improvement in the armature will
be readily understood by reference to figures 4 and 5 of the accompanying drawings
of which figure 4 represents a longitudinal section of the ordinary armature of what
is known as an "Edison Dynamo," A being the shaft, B the Lignum Vitae sleeve,
C the iron and paper discs, D the fastening bolts and nuts and E the insulating
and binding washers.
It will be observed that the sectional area of the core of the armature shown in
Figure 4 is diminished both by the bolt holes for the bolts D.and the hole through
the centre for the lignum vitæ bush and the shaft. In my improved armature as
shewn in Figure 5 these losses are avoided and the sectional area. of the armature
is increased. The hole through the centre is diminished in diameter and the bolts D
shewn in figure 4 are omitted and consequently the bolt holes are unnecessary
The discs C³ are clamped together by means of the washers H and the nuts I
running upon screws K. cut upon the shaft A of the machine. The discs are in all
cases properly insulated from each other and the iron parts of the body by fibre
.ebonite or other insulating material,
Owing to the increased intensity of the magnetic field, I am able to increase the
sectional area of the copper upon the armature and the current circulating around
the armature as well as the electro motive force without the alteration of the
position of the collecting brushes on the commutator rendered necessary by the
induction of these currents upon. each other,

page_text: From a machine of the construction shewn in figures 2 or 3 and 5 I am able to
obtain an out put of more than three times as much electrical energy as from a
machine of the old construction shewn in figures 1 and 4 at the same time I attain
improved efficiency that is a greater ratio of mechanical power applied to electrical
power delivered by the machine.
I do not confine myself to exciting magnets of a circular section nor to armatures
of the length shewn. For example, where the armatures are long in proportion to
their diameter, I may make the cross section of the core of an oval form.
Having now described and particularly ascertained the nature of my said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is :-
The improved Dynamo electric machine, consisting of exciting magnets and
armature, constructed substantially as and for the purpose hereinbefore described
with reference to figures 2, 3 and 5 of the accompanying Drawings.
In witness whereof I the said John Hopkinson have to this my Specification
set my hand and seal this twenty-fourth day of July One thousand eight hundred
and eighty three.
•