An Improved Method of Mechanically Strengthening Dynamo- electric Machine Inductors.
Year: 1891

page_text: Date of Application, 9th Dec., 1891-Accepted, 20th Feb., 1892
COMPLETE SPECIFICATION.
An Improved Method of Mechanically Strengthening Dynamo-
electric Machine Inductors.
We, LAZARUS PYKE and EDWARD STEPHEN HARRIS, Electrical Engineers,
of 34, New Tothill Street, in the City of Westminster, 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 :-
Many modern dynamo electric machines are constructed in such a manner, that
the magnetic field, inducing and induced wire coils are all fixed and produce electric
currents by commutation of the magnetism, by means of moving masses of magnetic
material usually termed inductors.
In many cases these inductors are subject to great magnetic or centrifugal strains,
to resist either of which requires extreme rigidity.
The magnetic material, of which the inductors are composed, is usually built
up of the softest iron laminæ (often in sufficient number to form a great width
in proportion to the thickness of the inductors), and the lamina are fixed
by bolts of considerable thickness to strong metal (usually bronze) supports
or braces.
These connecting or strengthening parts, placed as they are, in a
powerful magnetic field of varying intensity, are favourably situated for the
generation in themselves of a considerable amount of eddy currents producing local
heat and waste of power.
Our invention consists in interleaving the strengthening metal (preferably formed
of thin sheets) between the laminæ of soft iron which constitutes the inductor.
The accompanying drawing shows an example of an inductor embodying our
invention,
Fig. 1 being a side elevation, Fig. 2 a plan, and Fig. 3 an end elevation.
In these drawings / designates the soft iron laminæ, s the strengthening plates,
the bolts for holding together the lamina and plates, B the bolts for fixing the
inductor to the inductor carrier, C shows in dotted lines the contiguous part of the
inductor carrier.
In the present example the inductors are placed parallel to the axis of rotation of
the carrier, but they may be radial or in any other suitable position. The number
of strengthening plates in each inductor and the number of soft iron plates between
a pair of strengthening plates will, of course, vary according to requirements;
the outer strengthening plates (those right and left of the inductor) may be omitted,
and the method of fixing the inductors to the carrier will depend on various
conditions.
The lamina or plates are separated from each other by thin sheets of paper, as is
usual in the case of laminated iron cores. These insulating sheets are not shown in
the drawings.
Steel and German silver may be used for the strengthening lamina and bolts. We
prefer the two metals for the purposes in the order mentioned, that is to say, the
latter metal for the bolts, a magnetic metal not being desirable for this purpose,
because the heads and nuts project beyond the desired zone of inductor influence.
The advantages attained by our method of construction are as follows:
1. Diminution of waste by eddy currents.
2. Cooler working.
3. Greater or more uniform rigidity.

page_text: Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, we declare that what
we claim is :
In dynamo electric machines of the type, in which the field magnet, inducing and
induced wire coils are all fixed, a magnetic inductor composed of soft iron lamina 5
interspersed with thin sheets of hard metal, for the purpose of strengthening the
same.
Dated this 8th day of December 1891.
L. PYKE.
E. S. HARRIS.
By Fairfax & Wetter,
433, Strand, London, Agents.