Improvements in the Construction of Cores for Electro-magnets, Armatures for Dynamo-electric Machines or Electric Motors, and for similar Appliances.
Year: 1889

page_text: Date of Application, 9th Apr., 1889
Specification Accepted, 8th June, 1889
[Communicated from abroad by Professor ELIHU THOMSON, of Lynn, Massachusetts,
United States of America, Electrical Engineer.]
Improvements in the Construction of Cores for Electro-magnets,
Armatures for Dynamo-electric Machines or Electric Motors,
and for similar Appliances.
HENRY HARRIS LAKE of the firm of Haseltine Lake & Co. Patent Agents,
Southampton Buildings in the County of Middlesex 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 :-
This invention relates to the construction of that form of electro magnet in which the
coil or coils are applied to a closed magnetic circuit of iron which in general may be
defined as of endless form and as having its circumferential axis passing through or
threading the coils.
The said invention relates inore particularly to the form of magnet in which the
endless core is a laminated one, that is, consists of a number of plates of iron piled one
upon another to form a laminated structure to which the electric coil or coils are applied,
and the object of the invention is to secure case of construction, simplicity efficiency
and facility of repair, and at the same time to obtain a perfect closure of the magnetic
circuit which passes through the centre of the coils.
I am aware that it has been heretofore proposed to make circular or ring electro
magnets in one or more sections for the purpose of facilitating the application of the
coils, the magnetic circuit being completed after application of the coils by a bridge
or arinature of iron completing the gap or gaps through which the coils are applied.
The present invention relates to the particular manner of completing the magnetic
circuit as will be hereinafter described, and generally speaking may be said to consist
in closing a gap or notch left in the laminated core for application of the coils, by
means of a magnetic laminated plug or stopper having a width of diameter in the
direction of the magnetic axis that is substantially the width of the gap or notch and
fitted, forced or driven tightly into the notch or gap so as to completely close the

page_text: magnetic circuit; such plug or stopper having its laminations parallel to the laminations
of the main body of the core.
The invention applies obviously to electro magnets or electro magnetic structures
having either one or more coils connected to the same or different circuits and used
for any electro magnetic or magneto electric apparatus, and applies therefore to self-
inductive or reactive coils as used on alternating current circuits, induction coils, com-
pensating coils in which either coil becomes primary or secondary according to circum-
stances, as well as many other kinds of apparatus.
The invention is especially applicable to the construction of ring armatures for
dynamo electric machines or motors, that is to say, to the form of armature in which
a ring core like that of a Gramme machine is employed having coils disposed upon the
ring in such way that the circumferential axis of the ring passes through the centre of
the coils.
It has heretofore been proposed to construct ring armatures in sections to facilitate
the application of the coils, but the plans heretofore proposed require the use of
cumbrous fastening devices interfering with the disposition of the coils upon the core
and in many cases rendering it necessary to employ a less number of coils than would
be permitted in the case of a plain ring or hollow cylinder. In other cases the con-
struction detracts from the amount of iron in the core when such core is a laminated
one or interferes with the continuity of the magnetic circuit in the core thus giving
rise to irregularity of action in the machine.
The object of the invention as applied to a ring armature is to obtain an armature in
which the core may be a laminated structure in which the magnetic circuit shall be
almost perfectly closed, to facilitate the work of construction by permitting the coils to
be formed and afterwards placed on the core, to perinit easy repair in case of damage
to any part of the winding or its insulation and to produce at the same time an
armature structure which shall bo symmetrical, free from unwieldly projections from
its core, and in general easy and cheap of construction. In constructing a ring
armature in accordance with this invention, I proceed as follows:-
A laminated ring core is constructed in any suitable way with a notch or gap in
one side of sufficient width to permit the inserting of the coils. The core may be
made by piling pieces or washers of sheet iron upon one another and clamping or
bolding them together. Each ring piece or washer may be stamped out of shoet
metal as a discontinuous ring, that is to say, a ring a portion of which is lacking at
one side to form the notch or gap and a number of such pieces piled together, or
the complete cylinder may be formed of completo rings and the notch or gap
afterwards cut out. The cylinder or ring is generally formed with internal slots to
receive the arms of a spider frame carried by the shaft of the machine. The ring
core may be covered, before placing the coils thereon, with a heavy layer or
coating of insulating material to prevent the coils from making contact with the
core, and the plates of which the core is built up may be insulated from one another
by paper or a thin layer of other insulating material. The coils, preferably wound
previously upon a suitable form, are now applied through the notch or gap and,
after a sufficient number have been applied, the narrow section or notch, is filled
up with a plug or bundle of sheet iron pieces either the same or in every practical
respect equivalent to those which have been removed to form the notch, or of a size
to exactly fill the space left in the rings or washers from which the core is built
up. Such bundle or plug is forced tightly or snugly into place and is so constructed
and applied that when in place its laminae shall lie in planes parallel to those of
the remainder of the core, so that in effect there shall be in the completed structure
a complete magnetic ring circuit formed by each plate.
The coils are now disposed with reference to the spider in the position which
they shall finally occupy one or more of them preferably occupying a position
over or lapping upon the plug, and the core is then applied to the spider frame.
Before or after this operation binding rings or wire wound over the coils may
be applied to keep the plug or bundle in place, or other devices are applied to secure
the same in place.

page_text: In applying the invention to ordinary electro magnets such for instance as
transformers, it is of course immaterial so far as concerns the general purposes of
the invention, what geometrical form the completed closed magnetic circuit forming
the core of the coils may take; whether curved or angular or a combination of curved
and angular portions.
In setting forth this application of the invention I have however, confined the
description principally to the form of core which may be described generally as a
horse shoe or U shaped core the gap or opening between whose legs is filled by "
an inserted plug or stopper fitting tightly therein as will presently appear.
The said invention in addition to the general feature of construction hereinbefore
set forth consists in certain improved details to be more particularly specified in the
claims at the end of this specification.
Having described the general nature of the invention, I will proceed to describe
the same more particularly by referring at the same time to the accompanying
drawings in which :-
Figure 1 shows in isometrical projection an armature core, without any winding
upon it and without any shaft shown or spider support therefor.
Figure 2 illustrates the manner of placing the winding on the core.
Figure 3 shows the manner of filling the gap in the core which has been left for
the insertion of the winding.
Figure 4 is a view of the armature complete, as it appears when constructed and
finished with the coils placed thereon, and with the outside binding which holds the
coils and plug or bundle down.
Figures 5 and 6 illustrate modified forms of plug adapted to be forced into place
from within outward and having one or more lateral projections by which they are
prevented from being displaced by centrifugal force when the armature is revolving.
Figures 7 and are elevations of a self inductive or induction coil constructed
in accordance with my present invention.
Figures 9 and 10 show the iron or core part separately.
Figures 11 and 12 are side and edge views of one of the separate plates of the core.
Figure 13 illustrates a manner of applying the coils to the core.
Figure 1 shows a preferred winding when the device is to be used as an induction
coil.
Figures 15 and 16 illustrate modifications in the distribution of the coils.
Figures 17 and 18, are diagrams illustrating modifications in the connections of
the coils.
Figure 19, is a perspective view of a device embodying my invention, the coils:
being shown in dotted lines.
Figures 20, 21 and 22, illustrate modifications in the geometrical form of the iron
erre or magnetic circuit threaded through the coil.
Figure 23 shows a modification in the location of the coils upon the magnetic circuit.
Figure 24 is a side elevation and
Figure 25 a plan, of a form of transformer, converter, or self inductive coil in
which the magnetic circuit of the core for the coil is closed around the outside of the
coil to both sides thereof.
I will first describe the invention as applied to the armature of a dynamo electric
machine or motor.
In Figure 1, A, A, is the body of the armature complete built up of rings with a
notch or gap cut into it for the insertion of the plug W. The rings or washers A, A,
have as usual notches inside for stringing them upon the core spider or support, and
are bolted together or held in place with respect to each other in any suitable way
common to the art. Each ring, however, is notched at one side with a narrow notch
or intersection cut therefrom. This enables the coils C, which are to be slipped over
the ring, Figure 2, to be put through the slot and then carried around the ring to
the desired position, coil after coil being thus added until the desired number has been
strung upon the ring core.
After this has been done the plug or bundle of pieces W Figure 3, which are
j
i

page_text: preferably bolted together by being strung upon an insulated bolt, is inserted, and
forced into place by the exertion of considerable pressure, the fit being tight enough
to require a considerable amount of mechanical force to bring the piece or plug W,
down into position. As will be seen the laminae of the plug abut with their ends
against the ends of the laminae of the body of the core the latter having their
magnetic circuits separately closed by the laminae of the plug.
.
The sides of the notch or slit can be either slightly tapered or preferably, quite
parallel, so that if the plug W, has been once inserted with great pressure it is not
easily removed even by the revolution of the whole structure at a high rate of speed.
In Figure 3 the internal notches n, n, n, n are shown by which the whole structure
is: afterwards supported, and the notch or gap in the rings A, A, is indicated at y.
After the placing of the coils and the insertion of the plug the distribution of the coils
may be made, the carrying support or spider H, Figure 4, inserted into the notches
for carrying the structure upon the shaft, and the outside binding B, B, of wire applied
over the coils which have been placed on the armature. This binding is put on suffi-
ciently tight, and bears down upon the coils, to give an additional security in holding
the plug W, in place. If not firmly secured the tendency during revolution being.
outwards it might gradually work out, but the binding being tightly applied will
act as an effective check upon such movement. Other means however might be
employed for holding the plug in place.
Figure 5 illustrates a form of plug which is absolutely incapable of being thrown out
of place by centrifugal action even though no external fastening device be employed.
The sides of the plug are parallel or approximately parallel, or if they taper at all,
taper from within outward. The plug is inserted from the interior of the ring or core
and properly forced into place. The lateral projection m effectually holds against
flying out of its socket by centrifugal force.
The form of plug shown in Figure 6, has similar projections to each side.
The construction explains itself.
In constructing an ordinary electro magnet such as a transformer, I proceed as
follows:-.
In Figures 7 and 8, u, u, u, is a pile of sheets or plates of iron, with or without
insulating paper or other insulating material between. In most cases it is preferred
to insulate them from each other, as with paper, mica, hard varnish or the like. The
pieces Figure 9, which form the main body of the core may be stamped out in the
form of a notched plate; having two limbs, and piled together as in Figure 10, and
also bolted, or firmly held, by bolts, b, b, passing through openings or holes in the
sheets.
The parts U, U, of the core, it will be seen, consist virtuaily of a laminated body
of metal, whose two limbs are substantially parallel, and which limbs may be joined by
the insertion of a magnetic plug or stopper consisting of a bundle or collection of small
flat pieces, Figures 9 and 10, insulated from each other flatwise by suitable means,
such as paper between the sheets, and held together by binding bolts, b, b, passing
through openings in the pieces, or by other means.
It will be evident that upon the insertion of the bundle of pieces W, between the limbs
of the core U, U, in the manner shown, there is formed a hollow square or rectangle
composed of iron, with parallel laminae or plates insulated more or less perfectly from
each other. Each piece with its accompanying piece W, acts separately as a closed
magnetic circuit, and the magnetic circuit so formed is illustrated so far as a single
sheet is concerned in Figure 11, the sheet itself being shown on edge in Figure 12.
The joints so formed between the laminae of the plug and the ends of those making up
the core form what may be termed butt joints. An advantage occuring from this
feature of construction is that the whole magnet core or circuit may be practically
solid iron less the space taken up by the thin layers of insulating paper or such like
material.
$
In order to produce the structure Figures and 8, it is necessary that the coils of
insulated wire C, C, be placed so as to surround the limbs of the main part of..the
core U, U,,U,.as shown in the figures. This.is.best done by. separately winding the

page_text: coils and slipping them either singly or together over the mos, as in Figure 15,
after which the short circuiting plug or bundle W. Figures 7, 9, and 10, is forced >
into place. It is very desirable that the fit of the piece W, be made very tight or
close, so that it will require some considerable pressure to force it into place, after:
which it will not move unless pulled out by mechanical force applied for that purpose.
By making the fit sufficiently tight or close I secure the absence of the humming or
noise which might otherwise be produced by the alternations of magnetism, and also
produce a well closed magnetic circuit. The particular structure shown in Figure 7,
which embodies the invention and secures these ends, might be described as consisting;
of a laminated horse-shoe magnet with one laminated keeper W, inserted between the
opposing edges and the polar ends, and tightly forced into position.
1
The manner of winding the coils is not very important, the chief end being to so
construct them that they are capable of being slipped over the core, and also that thoy."
may be kept thoroughly insulated from one another and from the core. This is done.
in the usual way by the interposition of varying thicknesses of materials of an
insulating nature, according to the requirements of the case. The coils themselves;
may be wound upon a frame or mould, taking the form as shown in Figures 14
and 15, and of as many turns of wire as are needed, or of different sizes of wire, or.
of the same size, wound together or superposed, so as to form primary and secondary
coils, or coils which are interchangeably primary and secondary.
When a single coil is used on each limb such coil may be placed thereon for the:
purpose of obtaining its self inductive effect or reaction in a circuit, or a primary
nay be wound upon one limb and a secondary placed on the other limb in which case
the primary and secondary coils would become separate and the structure acquire new:
and different properties from what it would possess if the coils were adjacent or
superposed on one portion of the core.
In Figure 14, a coil is shown as composed of an interior secondary S, outside of
which is a primary P.
In Figure 15, the primary P, is above the secondary S, so that the two coils are
adjacent but not superposed.
In Figure 16, the secondary S, is shown placed. between the two faces of the
primary P, P. Numerous changes of this character can be made and do not affect.
the working of the apparatus outside of the conveniences of construction.
I
}
.In any case in which there are coils placed on both legs the connections of the
two corresponding coils may be made in series or in multiple are as desired. Thus,
if but two coils are used C, C, Figure 17, they may be connected in series as they
are shown, for their combined self-inductive action, or they may be connected as
shown in Figure 18, in multiple are, thus loosening the self inductive action and:
increasing the current carrying capacity.
If the core has several windings which are to be connected into different circuits,
any two corresponding coils on the two limbs may be likewise connected in series or
in multiple. Modifications in the winding would naturally suggest themselves to the
engineer in accordance with the work to be accomplished, and are therefore made no
part of the present case.
Figure 19, shows in a very complete way the relations of the various parts of the
core itself and the coils C, C, the latter being shown by dotted lines.
It will be evident that should it be necessary to change, replace, or reinsert one or
the other of the coils on the limbs of the core, U, U, it is only necessary to pull out
the bundle of small laminae W, thus allowing all the coils to be readily removed, or
replaced, and that the reinsertion of the plug or laminated piece W, restores the
closure of the magnetic circuit through the axis of the coils.
While in the preceeding figures 1 have shown the main core pieces as square or
rectangular in form it is obvious that the form might be varied as indicated in
Figure 20. Here the core is made up of plates in the form of washers or rings, and
the notched bundle upon which the coils are threaded has its magnetic circuit closed
as before by. the closely fitting. plug or stopper. W, inserted after application of the
coils and having its laminations arranged as before described. .
1

page_text: . Figure 21, shows another configuration of the main body or core piece. The plug
or bundle W, is here shown as having sharply tapering sides so as to be of pronounced
wedge shape. It can be inserted as already described between the properly shaped
opposing faces of the main core pieces at the notch or gap..
It is well to have the taper of the plug small so that it may remain firmly seated..
In the case of a large taper it is well to provide a bracing or some other device for
holding it in position.
Figure 22, shows that the position of the coils on the core may be modified so that
one coil is upon the main core piece, U, U, and the other is around the portion of core
piece consisting of the bundle of laminated pieces W. This, however, is a more
difficult construction and is without any special advantage.
Figure 23, shows that the pieces U, U, may be a true U shape or horse-shoe piece
between whose limbs the block piece or bundle W, of laminations is inserted after the
manner of a plug or stopper.
In Figures 24 and 25, the core or carrier is shown as of the double U form, or as
of E shape. The three arms or prongs are preferably parallel and of substantially
equal length and the openings between the arms or prongs are preferably closed by
plugs applied as before described.
When the coil is applied to the central arm as a core, the magnetic circuit for said
core is closed around the outside of the coil in two directions and an effect is obtained
approximating that obtained by completely enveloping the coil in iron.
It is obvious that a coil might be applied to each outside arm or prong of the
E piece the centre prong then serving in conjunction with the plug to close the
magnetic circuit for each coil. Or the coils might be applied to parts of the iron
carrier made up of the E piece or pieces and the magnetic plugs or stoppers inserted
in each gap, or notch at the ends of the prongs.
The plug in the various forms of the invention herein before described can be forced
or driven into place by means of a drop, or by hydraulic pressure.
'
Induction coils having main core pieces notched and very similar in outline to some
of these hereinbefore described, have been used heretofore, but in the present inven-
tion it will be seen that but one. such assemblage of pieces is used and that the
magnetic circuit closing piece W, has its laminations, or the pieces of which it is
made, parallel in plane with the pieces in the main core U, U. This permits making
the sheet iron pieces by punching and allows utilization of the portions cut out of the
notch in making the magnetic circuit closing piece W, thus giving a considerable
saving of material.
The construction also secures the placing of the magnetic limbs in as perfect a
relation as possible magnetically and produces a perfect closure of the magnetic
circuit.
Having now particularly described and ascertained the nature of my said
invention and the manner in which it is to be performed as communicated to me
by my foreign correspondent I wish it understood that what I claim is-
First. In an electro magnet having a closed magnetic circuit, threading its coils, a
laminated core piece having a notch or gap for application of the coils, closed by a
driven laminated plug or stopper whose laminations are parallel to and in magnetic
connection with those of the body of the core and form a butt joint with the same, as
and for the purpose described.
Second. Á horse-shoe electro magnet having coils placed upon the legs of the
horse-shoe, and a core piece for said magnet made up of a bundle or pile of plates of
general form, in combination with a laminated plug or stopper driven or forced
into the gap between the legs of the horse-shoe with its laminations parallel to and
in direct magnetic contact with those of the core to form a closure of the magnetic
circuit threading the coils as and for the purpose described.
Third. The combination with the laminated magnet core having a gap or notch, of
a closing piece for the magnetic circuit consisting of a tapered laminated plug or
stopper forced or driven tightly into the gap or notch.
;

page_text: Fourth. In a ring armature for dynamo electric machines or motors, a laminated
core having a notch or gap at one side for the insertion of the coils, closed magnetically
by a laminated plug or bundle fitted tightly into the notch or gap to complete or
restore the magnetic circuit after application of the coils, in combination with suitable
fastening devices for holding said plug against displacement by revolution of the
armature.
Fifth. In a ring armature, a laminated ring core having a gap or notch at one side
closed by a tightly fitting plug or, bundle of plates abutting against the ends of the
plates of the body of the core so as to close the magnetic circuits of the latter and
form electrically a uniform continuous laminated ring armature, as and for the purpose
described.
Sixth. In a ring armature, a core having a notch or gap at one side closed by a
plug inserted from the interior of the ring and provided with a lateral projection m,
one or more, as and for the purpose described.
Tate this at Ammil 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London,
Agents for the Applicant.