Improvements in Magnet Frames for Dynamo Electric Machines and Motors.
Year: 1899

page_text: Date of Application, 11th Dec., 1899-Accepted, 27th Jan.,
1900
COMPLETE SPECIFICATION.
Improvements in Magnet Frames for Dynamo Electric Machines and
Motors.
I, JAMES BURKE, of Oudenarderstrasse 23/30, Berlin, in the Empire of Germany,
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:-
It is a well known practice to provide the polepieces of dynamo electric machines
with extensions in order to cover a greater portion of the armature surface;
various arrangements of such polar extensions are employed, the most common
method being to bolt the extensions on the inner face of the pole pieces after
the magnet windings have been inserted. It is of great importance, that such
polar extensions are readily removable for the purpose of taking out the magnet
windings in case of necessary repairs.
The present invention has for its object to provide the pole pieces with exten-
sions of such construction, that they can be readily removed to permit the insertion
or removal of the magnet windings and to serve as a means for securely holding
the magnet windings in their place on the pole pieces, while the pole extensions,
forming an integral part of the pole pieces, can be brought to a higher degree
of magnetic saturation than can be achieved by a superficial fastening of the
pole extensions to the pole pieces.
I will describe the said invention with reference to the accompanying drawings
in which Fig. 1 shows part of a cross section of a magnet frame.
Fig. 2 shews one of the separate pole pieces having an extension employed in
Fig. 1.
Fig. 3 represents an expansion piece consisting of two claws with grooves on
their outer edges, a screw bolt with shoulder and a locknut.
Figs. 4, 5 and 6 shew different applications of the invention.
In Fig. 1 G is part of a magnet frame of an electromagnetic machine, P P are
pole pieces, being integral parts of G; V V are separate parts of the pole pieces
provided with polar extensions, made of solid or laminated iron or steel; S S
are magnet windings placed on the pole pieces.
As is clearly shown by the drawing, the pole pieces P have angular offsets at
both sides which serve as seats for the correspondingly angular ends of the detached
parts V of the pole pieces, which are inserted after the windings S have been
fitted on the pole pieces. The detached parts V of the pole pieces thus complete
the necessary cross section and at the same time form polar extensions thus
increasing the surface of the pole pieces toward the armature. As these detach-
able parts of the pole pieces are embraced by the magnet windings, it is evident,
that the magnetic effect on the polar extensions will be more intense than can be
obtained by attaching the extensions on the pole surface as heretofore.
In order to firmly secure the inserted parts of the pole pieces in their respective
positions, an expansion piece E preferably of non magnetic material, as shewn
in Fig. 3, is inserted between the polar extensions of two adjacent separate pole
pieces V as is clearly shown in Fig. 1. By turning the expansion screw of E the

page_text: separate pole pieces V on two adjacent poles will be firmly forced into their
seats, the expansion device E then being secured against loosening by a locknut
or other suitable device.
The pressure produced by the expansion device will produce a good magnetic
contact between the fixed and the inserted parts of the pole pieces, holding them
firmly in their seats.
A similar result may be attained in nearly the same or a less degree, by slight
modifications in the shape of the separate parts of the pole pieces or by a different
form of expansion device, but it is an essential feature of this invention, that the
polar extension piece forms part of the magnet pole and is partly embraced
by the magnet winding, being held in position by pressure exercised by an expan-
sion piece or a wedge or a similar device placed between two poles or between one
pole and some fixed part of the magnet frame.
The expansion piece shown in Fig. consists of two metal claws a a provided
at their ends with grooves, interlocking with similar grooves on the ends of the
polar extensions; a screw 6 screwing into the one claw and the stud end of the
screw abutting in the other claw, will permit a strong pressure being exercised on
the two claws in opposite directions by turning the screw b, thereby forcing the
inserted parts V of the pole pieces firmly into their seats; a locknut on the screw
bolt will prevent the loosening of the screw by vibration.
; Fig. 4 shews a modification of the arrangement shewn in Fig. 1. In this case
only one part V on each pole piece P is formed as a separate inserted piece, the
polar extension to the one side being made an integral part of the magnet frame
while the other extension forms a part of the inserted section of the pole piece V
of which a separate view is shewn at Fig. 5.
Such an arrangement will permit the slipping of the magnet winding on the
pole piece before the insertion of the separate part V, this being inserted after-
wards, thus securing the magnet winding in its position. In this case the pole
piece may be divided throughout its entire length, the inserted part V of the
same being seated in the yoke G of the frame, and it may be firmly held in
position by expansion piece in the same manner as shown in Fig. 1; with this
construction only half the number of expansion pieces E are necessary, if the
inserted parts of the pole pieces are alternately placed to the right and left side
of the fixed pole pieces P as shewn.
The arrangement shewn in Fig. 4 is available in cases, where the magnet frame
of a dynamo or motor consists of two or more parts, the polar extensions being
interlocked with each other by the expansion pieces E independently in each part
of the magnet frame. Fig. 6 shews another modification applied to a two-pole
magnet frame; instead of interlocking two inserted parts V of the pole pieces P
each detachable pole piece is braced by an expansion piece E against a supporting
point on the inner side of the yoke G the expansion device E may be arranged in
any suitable manner for firmly securing the inserted parts V of the pole pieces in
their position.
It will be seen that with all the above described arrangements while the
expansion pieces E hold the separate pole pieces firmly in position, they are at
once released so as to allow the magnet winding to be removed on releasing the
expansion pieces.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I declare that what I claim is :-
1. In a magnet frame for dynamo electric machines and motors constructing the
pole pieces with separate parts so arranged in connection with the parts that are
integral with the magnet frame, that they are surrounded by the magnet wind-
ings, such separate parts being formed with polar extensions so that on being
inserted after the winding has been fitted on the fixed pole piece, and secured
by expansion devices, they securely hold the winding in position, substantially
as described.

page_text: 2. In a magnet frame for dynamo electric machines and motors the combina-
tion of pole pieces with polar extensions P forming an integral part of the magnet
frame, separate pole pieces with polar extensions V fitted to the fixed pole pieces
so as to be surrounded by the magnet windings, and expansion pieces such as E
abutting against the polar extensions of contiguous separate pole pieces or against
one such extension and a fixed abutment, so as to lock the said separate polar pieces
firmly in position, substantially as described.
Dated this 11th day of December 1800
ABEL & IMRAY,
Agents for the Applicant.