Improvements in the Construction of Multipolar Dynamo-electric Machines.
Year: 1892

page_text: Date of Application, 26th Mar., 1892
Complete Specification Left, 24th Dec., 1892-Accepted, 25th Mar., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Multipolar Dynamo-electric
Machines.
I, WILFRID L. SPENCE of The Elms, Seymour Grove, Manchester, Engineer,
do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in the construction of multipolar dynamos,
which improvements are applicable more particularly to machines of the disc or
short ring type.
The field magnets I construct in the manner shown in the drawings, Sheet 1
Figures 1 to 3.
The magnetising coils are wound so as to be of approximately equal diameter to
the mean diameter of the armature, a casting in two or more parts with the
requisite number of poles as shown, Figures 1 to 3 is then placed so as to surround
the coil, more or less, on all sides, by this means an "ironclad " field is produced of
very high efficiency and of comparatively light weight. It has the advantage,
moreover, when used in a machine of the type shown, of requiring an armature of
only one-half the size of those used in most existing dynamos with ironclad fields;
or, which amounts to the same thing, such an armature when used with my improved
field magnets is capable of giving double its former output.
The two methods of construction which I prefer are shown, one in elevation and
section, Figures 1 & 2, and the other in section only, Figure 3, both sections
being as on a single diameter for the sake of simplicity.
It will be seen that the north poles, projecting inwardly from the outside,
alternate with the south poles projecting outwardly from the inside.
The simplest form of casting would be one such as that shown but in one piece
only, the exciting coil would then have to be wound by bending the wire or cable
over and under the successive pole pieces. I prefer, however, to have the casting
in at least three pieces as shown on the left hand of Figure 1; all the south poles
are cast in one with the inner ring S, S, S, the exciting coil is then wound in the
groove as shown in Figure 2 and the north poles, N, N, N, in two parts are then
bolted round the casting, S, S, S, by the lugs L, L.
Another form, Figure 3, is preferable in some respects, here the exciting
coil, C, C, is separately wound on a former and the whole field on one side of the
armature is in two pieces only, an inner ring N, carrying all the north poles and an
outer shell S, carrying all the south poles.
My improved construction is applicable either to machines with rotating
armatures or with rotating fields and in each case I prefer a method of sup
porting the fields which permits of their being drawn back so as to make the
armature coils accessible.
My improvements relate, secondly, to a method of securing in place armature
coils of the type shown on Sheet 2 of the drawings. The method will be obvious
on inspection, on the left hand is shown a stationary armature which consists of an
outer shell of cast iron, or other suitable metal, to which the coils are attached by
means of the tension wedges shown. On the right hand the same method is
applied to a rotating armature, the coils in this case being secured to an inner
shell. The wedges I construct of almost any flexible material having sufficient
tensile strength, such as copper strip, vulcanized fibre, paper, textile fabric &c.,
and of the form shown or its equivalent. They are tightened up by means of bolts
or by being rolled upon a spindle or in any other suitable manner.

page_text: These wedges may also be constructed of a single strip attached in any appro-
priate way to a head, at one end, shaped to fit the coils, and at the other to the
tightening device.
Dated this 26th day of March 1002
WILFRID L. SPENCE.
COMPLETE SPECIFICATION.
Improvements in the Construction of Multipolar Dynamo-electric
Machines.
I, WILFRID L. SPENCE of The Elms, Seymour Grove, Manchester, Civil
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 :-
My improvements relate to the construction of multipolar dynamo electric
machinery, and they are more particularly applicable to machines of the disc or
short ring types.
1. The field magnets I construct in the manner shown in the drawings, Sheet I
Figures 1 to 3, left with the. Provisional Specification, and Sheet III herewith.
The magnetizing coils are wound so as to be of approximately equal diameter to
the mean diameter of the armature. A. casting in two or more parts with the
requisite number of poles is placed so as to surround the coil more or less com-
pletely on all sides. By this means an "iron-clad" field is obtained of very high
efficiency and of comparatively light weight. It has the advantage moreover,
when used in a machine of the type shown, of requiring an armature of only one
half the size of those used in most existing dynamos with iron-clad fields; or,
which amounts to the same thing, such an armature when used with my improved
field magnets is capable of giving nearly double its former output.
The methods of construction which I prefer are shown by the Figures 1 to 6.
It will be seen that the north poles, say, projecting inwardly from the outside
alternate with the other poles projecting outwardly from the inside.
The simplest form of casting would be one such as that shown but in a single
piece only. The exciting coil would then have to be wound by bending the
conductor over and under the successive pole pieces. I prefer, however, to have
the casting in at least three pieces as shown on the left hand of Figure 1, all the
south poles, say, are cast integral with the inside ring, S SS; the exciting coil is
then wound in the groove as shown in Figure 2 and the remaining poles, N N N,
to complete the magnetic circuit into the armature are then bolted round the
casting, SSS, by the lugs, LL.
Another modification, Figure 3, is preferable in some respects. Here the
exciting coil, CC, is wound on a former inside the groove between the north poles,
say, projecting from the inside and the yoke portion at the back; thus the whole
field on one side of the armature is in two pieces only, an inner ring, N, carrying all
the north poles and an outer shell, S, bearing all the south poles.
Figures 4, 5 and 6, Sheet III, show the construction which I consider the most
convenient. It is merely a repetition of Figure 3 with the inner ring of poles
separated from the yoke portion. This method permits of the exciting coil being
removed from the frame without unwinding.
My improved construction is applicable either to machines with rotating fields
or with rotating armatures, and in each case I adopt a plan which admits of the
fields being drawn back so as to render the armature coils accessible.
My improvements relate secondly to a means of securing in place armature coils
of the type shown on Sheet II left with the Provisional Specification.
The
arrangement will be obvious on inspection. At the left hand is shown a stationary
armature, A, consisting of an outer shell, S, of cast iron or other more suitable metal
to which the coils, C, are attached by the tension wedges, W, seen between adjacent

page_text: coils. On the right hand the same device is applied to a rotating armature, A', the
coils, C, in this case being secured to an inner shell, S¹.
The wedges, W, may be constructed of any more or less flexible substance such
as copper or steel strip (non-magnetic), vulcanized fibre, hard wood, textile
fabric, etc., and of the form shown or its equivalent. They may consist of a single
strip secured at one end to a head shaped to fit the coils and at the other to the
tightening device, or they may pass more or less completely round the coil. These
tension wedges are tightened up by means of bolts, B, by being rolled upon a spindle
or in any other appropriate manner. If made of metal suitable precautions, by
laminating and avoiding closed circuits, are taken to avoid eddy currents.
I would have it clearly understood with reference to the first part of my invention
that I make no claim to the use of an "iron-clad" field of the general type illustrated
and described.
My invention relates only to the particular arrangement of castings which avoids
the necessity for independent pole pieces.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. In disc or short ring armature dynamo electric machines field magnets
constructed substantially as herein described and illustrated, that is to say, of an
inner ring-shaped casting bearing all the poles of the same name, say north, and
having the yoke portion cast with it combined with an outer ring-shaped casting
bearing the alternate poles of opposite name, say south; the outer ring being in
one, two, three or four pieces secured round the inner ring.
2. In dynamo electric machines of the types referred to in the previous claim
field magnets constructed substantially as described and illustrated, that is to say,
of an inner ring shaped casting bearing all the poles of the same name, say
north, combined with an outer ring-shaped casting bearing the alternate poles of
opposite name, say south, and of a yoke portion cast, (a) wholly with the outer
ring, (b) part with the outer and part with the inner rings, or (c) separately as a
detachable ring, the whole secured together by bolts or otherwise.
3. In dynamo electric machines with disc armatures securing the coils in place by
means of tension wedges or bands substantially as described and illustrated.
Dated this 25th day of December 1892.
WILFRID L. SPENCE.