Year: 1887

page_text: Date of Application, 22nd Mar., 1887
Complete Left, 22nd Dec., 1887
Complete Accepted, 10th Feb., 1888
We JOHN HOPKINSON F.R.S. of 4 Westminster Chambers in the City of
Westminster and EDWARD HOPKINSON of 29 Princess Street Manchester, Engineer
do hereby declare the nature of our invention to be as follows:-
Our Invention more particularly relates to that class of dynamo machines in which
there are more than one magnetic field and its object is to obtain powerful magnetic
fields with a small expenditure of energy, to secure abundant room for the copper
conductor of the armature and to avoid as far as practicable undue variation of the
magnetism of the magnets as the armature revolves. In general we prefer to adopt
that form of machine in which the lines of magnetic force are parallel or approximately
parallel, to the axis of rotation of the armature. The arinature consists of a series of
bobbins having iron cores composed of thin plates placed tangentially or nearly
tangentially to their direction of motion. The cores have by preference polar extension
as such extensions render the field easier to produce and less variable in the magnets
and are in some cases very useful in securing the bobbins laterally. For mounting the
bobbins of the armature we find
which the bobbins rest; the wheel having radiating arms outside of its periphery
convenient to provide a wheel, on the outside of
between which the cores of the armature fit. The bobbins are bound in by rings
which slip over their ends, these rings may conveniently be channel shaped into
which bending wire is wound and are then easily removed, or they may be solid rings
or a simple binding wire may be used.
One way of arranging the magnets is to attach their outer ends to cast iron rings
in which case the wrought iron cores should be let some distance into the iron.
We sometimes fit the magnets with cast iron pole pieces the wrought i. on being in
this case also let into the cast iron. When machines such as we have described are
run at a high speed there is danger of accident from centrifugal force. To obviate
this we place guards at such a small distance from the binding rings that so soon as
these rings begin to stretch on inclination to breaking they come into contact with
the bars which act as a brake. The rings may be secured by screws to snugs on the
wheel of the armature, the plates of the armature cores may be secured together by
bolts or rivets, provided that these are so placed that they shall not close electrical
[Price 11d1

page_text: circuits around lines of magnetic force. The form of the machine may be considerably
varied whilst retaining much that is characteristic of our invention, for example the
magnets may be placed radially, the other parts being varied to correspond. The
armature may be fixed and the magnets revolve or the armature and magnets may
both revolve.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, W.C.,
Agents.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines.
We JOHN HOPKINSON F.R.S. of 4 Westminster Chambers in the City of
Westminster and EDWARD HOPKINSON of 29 Princess Street 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 more particularly relates to that class of dynamo machines in which
there are more than one magnetic field and its object is to obtain powerful magnetic
fields with a small expenditure of energy; to secure abundant room for the copper
conducior of the armature and to avoid as far as practicable undue variation of the
magnetism of the magnets as the armature revolves. In general we prefer to adopt
that form of machine in which the lines of magnetic force are parallel or approximately
parallel to the axis of rotation of the armature. The armature consists of a series of
bobbins having iron cores composed of thin plates placed tangentially or nearly
tangentially to their direction of motion. The cores have by preference polar
extension as such extensions render the field easier to produce and less variable in the
magnets and are in some cases very useful in securing the bobbins laterally.
For mounting the hobbins of the armature we find it convenient to provide a wheel
on the outside of which the bobbins rest; the wheel having radiating arms outside of
its periphery between which the cores of the armature fit. The bobbins are bound in
by rings which slip over their ends these rings may conveniently be channel shaped
into which binding wire is wound and are then easily removed or they may be solid
rings or a simple binding wire may be used.
One way of arranging the magnets is to attach their outer ends to cast iron rings
in which case the wrought iron cores should be let some distance into the cast iron.
We sometimes fit the magnets with cast iron pole pieces the wrought iron being in

page_text: this case also let into the cast iron. When machines such as we have described are
run at a high speed there is danger of accident from centrifugal force. To obviate
this we place guards at such a small distance from the binding rings that so soon as
these rings begin to stretch on inclination to breaking they come into contact with
the bars which act as a brake. The rings may be secured by screws to saugs on the
wheels of the armature the plates of the armature cores may be secured together by
bolts or rivets provided that these are so placed that they shall not close electrical
circuits around lines of magnetic force. The form of the machine may be considerably
varied whilst retaining much that is characteristic of our invention for example the
magnets may be placed radially, the other parts being varied to correspond. The
armature may be fixed and the magnets revolve or the armature and magnets may
both revolve.
And in order that the said Invention may be fully understood we will now proceed
more particularly to describe the same and for that purpose shall refer to the several
figures on the annexed sheet of drawings the same letters of reference indicating
corresponding parts in all the figures.
Figure 1 is an end elevation of one form of a machine constructed or arranged
according to our Invention. Figure 2 is a plan. Figure 3 is a side elevation (a
portion of the magnets being omitted). Figure 4 is an elevation of a portion of the
armature of the inachine. Figure 5 is a plan of one half of an element of the
armature and Figure 6 a section of the armature frame through the axis. Figure 7
is a section of another form of machine made in accordance with a part of our
invention.
A is the bed plate of the machine. B B are side plates which may be made in cast
iron and serve to support the bearings CC of the shaft of the armature shaft and into
which the wrought iron cores of the magnets D D are let as shewn at d in such-wise
that the surface of contact of the wrought iron and cast iron in contact shall be
considerably in excess of the section of the wrought iron. The electro magnets D D
are so arranged that in each set they have alternately opposite magnetic polarity and
that on either side of the armature, poles of opposite polarity are opposed to each
other. We prefer to let the ends of the electromagnets next to the armature into cast
iron pole pieces E and we find it desirable to cut grooves in the faces of these pole
pieces (as shown in Figure S) for the purpose of stopping local currents rising from
the rotation of the armature. In the machine shown in the drawings there are
sixteen electro magnets on each side of the armature but we do not limit ourselves to
that number. The armature body consists of a wheel F of brass or other non-inaguetic
material keyed on a shaft G. This wheel has on its periphery a number of short
arms H which serve to drive the elements of the armature. Each element. I consists
of a core of thin iron plates which should be more or less insulated from each other
(the form of one half of a plate is shewn in Figure 5). Each element is wound with
copper wire or ribbon in the space marked K figure 5. As already stated the
elements are driven by the radial arms H, they are held in against their centrifugal
force by rings L which we prefer to make in channel form of brass and to wind in
the channel phosphor bronze wire or other suitable wire. The position of the rings is
fixed laterally by means of fixings M. attached to the radial arms H of the wheel F.
The cores as shewn have polar extensions at either end which serve to fix the cores
laterally as well as to reduce the tendency to generate injurious electrical current in
the pole pieces and electro-magnets. The conducting wires of the armature are
suitably connected to collecting rings on which fixed collecting brushes make
frictional contact. In order to secure against serious accident from the bursting of
the armature by centrifugal force we fix across from side to side of the machine
bars N placed in close juxta position to the rings L of the armature but not touching
them; if then these rings should stretch preliminary to breaking they will come in
contact with the bars N and stop the machine.
Referring now to Figure 7 P is a ring preferably of cast iron into which are let
the wrought iron cores of the magnets Q in this case arranged radially. The
magnets have pole pieces R into which they are let. It is found advisable in this

page_text: case also to cut grooves as aforesaid in the faces of the pole pieces R to prevent
currents from being induced in them. The armature consists of a wheel S which in
this case may be of cast iron keyed upon a shaft T and by means of bolts holding the
elements of the armature U these elements each consist of a core of wrought iron
plates of the form shown in the drawing having polar extensions V for the same
purpose as before and wound with copper wire or ribbon.
We do not limit ourselves to the precise details described for example we may
arrange the arinature to revolve outside the field in the arrangement Figure 7 and in
that case the bars N may be used and in the arrangement figures 1 to 6 we may
arrange the cores of the field magnets with their outer ends abutting against a
wrought or cast iron ring instead of being let into cast iron as hereinbefore
described.
1st. The dynamo electric machine constructed substantially as herein described
with reference to Figures 1. 2. 3. 4. 5. 6. 7 of the accompanying drawings.
2nd. In a multipolar dynamo electric machine an armature composed of elements,
each element consisting of a core of iron plates around which copper wire or ribbon is
wrapped substantially as herein described with reference to Figures 4, 5, 6 and 7 of
the accompanying drawings.
3rd. In a multipolar dynamo electric machine an armature composed of elements
each element consisting of a core of iron plates having a polar extension or extensions
around which cores copper wire or ribbon is wrapped substantially as herein described
with reference to Figures 4, 5, 6 and 7 of the accompanying drawings.
4th. The means for securing the armature elements upon a wheel with radiating
spokes by rings of metal substantially as herein described with reference to Figures 4
and 6 of the accompanying drawings.
5th. The means for providing against the armature giving way mechanically
consisting of a guard or guards in proximity to the metal rings of the armature so
that if the said rings stretch they come into contact with the said guard or guards
substantially as herein described with reference to Figures 1, 4 and 6 of the
accompanying drawings.
6th. In a multipolar dynamo machine the arrangement of magnets having wrought
iron cores let into a ring of cast iron or abutting against a wrought iron ring and let
into cast iron pole pieces substantially as herein described with reference to Figures 1,
2, 3 and 7 of the accompanying drawings.
7th. In a multipolar dynamo machine the arrangement of magnets having wrought
iron cores let into cast iron pole picces substantially as hereinbefore described and
illustrated in the accompanying drawings.
Sth. In and for dynamo electric machines grooved pole pieces substantially as and
for the purpose hereinbefore described and illustrated in Figure 8 of the accompanying
drawings.
Dated this 17th day of December 1887