Year: 1885

page_text: We, JOHN HOPKINSON F.R.S. of 4 Westminster Chambers in the City of West-
minster and EDWARD HOPKINSON of Salford Iron Works, Manchester, Engineer do
hereby declare the nature of this Invention to be as follows:-
Our Invention relates to that class of dynamo-electric machines in which there
more than one magnetic field. In such machines it is usual to provide separate
electro magnet coils for the several fields. According to our Invention we make
use of a less number of electro magnets than of magnetic fields; arranging the
fields as branches from the electro magnets. By this means we obtain the needful
magnetic fields by a smaller expenditure of copper and of energy than is the case
when the machines are constructed in the usual way.
This Invention is generally applicable to multipolar machines, but in one way of
carrying it out we use the following arrangements. The armature is of disc form
with a series of coils of ribbon or wire near its periphery which cut through polar
fields of alternately oppositely directed polarity. We prefer to introduce a certain
quantity of iron into the cores of the armature coil. The frame of the disc is made
of non-conducting material in the part cutting the magnetic fields.
Dated this 10th day of Ontaho- 100k
J. HENRY JOHNSON,
Agent for the said John Hopkinson
and Edward Hopkinson.

page_text: Improvements in Dynamo-Electric Machines.
We, JOHN HOPKINSON, F.R.S. of 4 Westminster Chambers in the City of West-
minster and EDWARD HOPKINSON of Salford Iron Works, Manchester, Engineer, 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:
Our Invention relates to that class of Dynamo Electric Machines in which there
is more than one magnetic field.
In such machines it is usual to provide separate electro-magnet coils for the
several fields.
According to our Invention we make use of a less number of electro-magnets
than of magnetic fields and arrange the fields as branches from the electro-magnets
By this means we obtain the needful magnetic field by a smaller expenditure of
copper and of energy than is the case when the machines are constructed in the
usual way.
This Invention is generally applicable to multipolar machines and the accom-
panying drawings show one way of carrying our Invention into effect as applied to
a multipolar machine with a disc armature, but we do not restrict our claim to
such as it is applicable to multipolar machines of other form.
Figure 1 is a longitudinal section of a machine constructed according to one
method of applying our Invention and Figure 2 is an end elevation of the same.
Figure 3 is a section and Figure 4 an end view of the armature.
a a are the frame
sides of the machine having projections thereon forming the pole pieces a². These
sides a are connected by the electro magnets b to frames c also having short pro-
jections c³ thereon forming poles arranged in position alternately with those (a³)
on the frame sides a the alternate poles thus being of similar polarity.
In the machine shown there are 16 poles on each side of the armature e and
these are excited by the two electro magnets b on each side of the armature thus
securing the necessary magnetic field with great economy in copper and electric
energy:
The course of the lines of magnetic force will be through the soft iron cores 6 on
the left of Figure 1 from the vicinity of the armature to the cast iron frame side a
thence, dividing, through the elongated pole pieces a³ and across the space in which
the armature moves to the short pole pieces of the frame c to the right of the
armature thence through the soft iron cores b on that side to the frame side a on
the extreme right of Figure 1 thence, dividing, through the elongated pole pieces a³
from right to left across the space in which the armature moves to the short pole
pieces c² of the frame c on the left of the armature and to the right hand end of the
soft iron cores 6 thus completing the magnetic circuit.
The armature shown in Figures 3 and 4 is of the disc type consisting of bobbins d
of wood or any other suitable material upon which the conductor in any suitable
form is wound. These bobbins are carried in a disc or framework h of wood or
other material which may be made in segments as shown for convenience and as a
precaution against warping and the segments then securely fastened by bolts or
" :

page_text: other means to a hub of brass or other material e secured to the revolving shaft or
spindle f. The collector g on the machine shown is placed inside the machine
between the bearing and the armature but of course it may be placed in the most
convenient position for the type of machine to which our invention is applied and
may be of any convenient form.
Having now particularly described and ascertained the nature of our Invention
and in what manner the same may be carried into effect we declare that what we
claim is,
A multipolar dynamo machine in which the number of electro-magnets is less
than the number of magnetic fields.