Improvements in Dynamo Electric Machines.
Year: 1896

page_text: Date of Application, 11th Aug., 1896-Accepted, 3rd Oct., 1896
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 38 Parliament
Street, Westminster, in the County of London, Electrical Engineers, do hereby
declare the nature of this invention (which has been communicated to us from
abroad by David P. Thompson, and Albert H. Armstrong, Electrical Engineers,
both of Schenectady, in the State of New York, United States of America,) and
in what manner the same is to be performed to be particularly described aud
ascertained in and by the following statement:-
The present invention relates to dynamo electric machines; and has for its
object to provide a convenient way of mounting the coils upon the cores in such
structures, and in particular upon their armatures. It may well be applied to
field-magnets where such a construction as the one indicated would be suitable, and
has particular utility in modern types of alternating current apparatus.
In general, the invention consists in a core provided with slots in which coils are
to be inserted, and having teeth of a peculiar shape. The teeth overlap a part of
the slot with an L-shaped projection. The under side of the L-shaped projection
is under-cut, and the rear portion of the L has as small notch also under-cut so
that a wedge may be driven over the coils to retain them in place. The opening
in the slot is approximately one-half of the entire slot width, and the coils are
dropped into it in such a way that the insulation of the coil is not disturbed. The
slot may also be lined with insulation, which is not abraded in the process of
inserting the coils, and after these latter are put in place, a wedge is driven in so
that they are firmly retained, preserving their position against centrifugal strains,
if the construction be used in a revolving armature, and against magnetic stress.
The accompanying drawing shows the invention
Fig. 1 being a plan of a stationary armature,
Fig. 2 a side elevation of the part shown in Fig. 1, and
Figs. 3 4 and 5 detail views of modifications.
In Fig. 1 A is the core, B, B' are the coils, C, C are the teeth, and D are the
slots or openings between them. The shape of the teeth is best seen in Fig. 2.
Each tooth C has a projecting portion e shown on the left in the figure, having an
undercut side c', and upon the back of the L-shaped tooth is a similar surface c². The
operation of inserting the coils is also best seen in this figure.
The coil B is first inserted and is then moved to the right occupying the lower
right-hand portion of the slots. The next coil B' is then inserted, and occupies
the left-hand portion of each slot, each coil of course spanning as many teeth as
may be desired, either the polar pitch of the machine or such portion thereof as the
designer may arrange.
In Fig. 3 a section is shown with all four of the coils which would ordinarily be
used in place. On the left in Fig. 2 and in Fig. 3 at d is shown a sheet of insulation
applied to the interior of the slot, and at E is shown the wedge, preferably wood,
which is driven in over this insulation. It will be seen that the wedge does not
come in contact with the coil, so that its insulation is never impaired. The upper
wo coils B and B in Fig. 3 are inserted in the same way as those shown in Fig. 2.
It will be observed that they occupy a trifle less than balf the width of the slots.
In practice the slight inequalities of coils and the thickness of the surrounding
heet of insulation will be sufficient to make them fit closely, but without any
endency to abrade the insulation in insertion.

page_text: In Fig. 4 we show a modified form of the tooth C, the other parts being as
shown in the preceding figures. In this case the under-cut portion c¹ of the tooth
forms the entire overhang on the left side, and similarly the under-cut portion c*
forms the entire overhang upon the right.
In Fig. 5 a further modification is shown, although this is not the preferred
form, in which one side of the tooth is straight, and the base of the L forms the
overhang upon the other side.
By forming each of the coils in such a way as to occupy substantially an aliquot
part of the slot, we are enabled to contract the opening and yet insert the coil
without abrasion, the coils being simply dropped into the slot and then adjusted in
position, the wedges E, E afterwards compressing them sufficiently to make a firm
engagement. In other forms of construction with which we are familiar, this
result has been obtained by separating the wires of the coil and inserting them one
at a time through the slot and afterward arranging them in place. This however
has the great disadvantage of rendering uncertain the insulation of the coil as a
whole. In still another form with which we are familiar, the coil is compressed as
it passes through the slot, thus rendering abrasion of the insulation liable to occur;
while in still another form the coil is divided but is made smaller than the portion
of the slot through which it enters, and the coils are then separated by wedges
previously placed in the slot; the construction being troublesome to put in place,
and insecure after it is arranged.
An added feature of usefulness in the present invention lies in the fact that the
slots have sides parallel with the radius passing through their centers, so that the
sides of the coils may be substantially straight, and yet they will occupy, as above
pointed out, an aliquot portion of the cross section of the slot.
It is manifest that the present invention is not limited to the use of four coils in
each slot, as other numbers, more or less, could be used by simply altering the size
of the coils.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to us from
abroad we declare that what we claim is:
1. An armature for a dynamo electric machine, comprising a core having slots
the sides of which are parallel with the radii passing through their centers,
L-shaped teeth having under-cut portions, coils each occupying an aliquot portion
of the slot, and wedges engaging with the under-cut portion of the teeth for
retaining the coils in place.
2. An armature for a dynamo electro machine, comprising a slotted core, the
sides of the slots being parallel to the radii passing through their centers, separately
wound and insulated coils the working portions of which occupy aliquot parts of
different slots, L-shaped teeth between the slots, the teeth having under-cu
portions upon the base and back of the L, and wedges engaging with the under-cu
portions for holding the coils in place.
Dated this 11th day of August 1896.