Improvements in Dynamo-electric Machines.
Year: 1889

page_text: Date of Application, 16th Nov., 1889
Complete Specification Left, 29th Aug., 1890-Accepted, 18th Oct, 1890
PROVISIONAL SPECIFICATION.
Improvements in Dynamo-electric Machines.
I, JOHN HUBERT DAVIES of Johannesburg, South African Republic, Electrical
Engineer, do hereby declare the nature of this invention to be as follows:-
The present invention relates to improvements in dynamo electric machines, whether
used as generators or motors, and is particularly applicable to those machines pro-
ducing or using high electro-motive forces.
"
22
It has hitherto been difficult to satifactorily construct dynamo electric machines of
the continuous circuit type (such as the Gramme ring and Siemens drum) to give, or
use, very high electro-motive forces principally owing to the liability to arcing
across the top of the thin insulation between the segments of a many part commutator.
It has not been found possible in the ordinary method of construction to thicken this
insulation and so increase the distance between the segments without either increasing
the diameter of the commutator or reducing the number of the segments, both
of which methods are disadvantageous and practically can only be carried out to a
small extent.
The present invention is intended to obviate this difficulty and consists in placing
two separate circles of commutator segments on the spindle of the machine arranged
and connected as if from an ordinary commutator every alternate segment was removed
and displaced longitudinally on the spindle until it was beyond the original commu-
tator, the gaps between the segments in both circles being preferably filled with
insulating material such as mica or glass. The width of the insulation between any
two segments on one of the circles is, by this method, increased from about and. inch
to that amount plus the width of a segment which would, in ordinary cases, make
about th. inch. Each circle has it's own brush, or set of brushes, at the collecting
points, the brushes at the same collecting point of both circles being connected
together so that as the armature revolves the current is collected from, or delivered to,
the commutator by the brushes of the two circles alternatively. Instead of constructing
the commutator in two circles of segments I may divide it into three or more circles.
In the case of three circles a convenient arrangement is to connect one coil on the
armature between a segment in the first circle and a segment in the second; the
next coil between this segment in the second circle and a segment in the third; and
the next coil between this segment in the third circle and the next segment in
the first; and so on.
Dated this 16th day of November 1889.
COMPLETE SPECIFICATION.
Improvements in Dynamo-electric Machines.
I JOHN HUBERT DAVIES of Johannesburg, South African Republic, Electrical
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 :-
The present invention relates to improvements in dynamo electric machines, whether
used as generators or motors, and is particularly applicable to those machines pro-
ducing or using high electro-motive forces.
It has hitherto been difficult to satisfactorily construct dynamo electric machines of
the continuous circuit type (such as the Gramme ring and Siemens drum) to give, or
use, very high electro-motive forces principally owing to the liability to "arcing".
across the top of the thin insulation between the segments of a many part comutator.
DQ37

page_text: It has not been found possible in the ordinary method of construction to thicken this
insulation and so increase the distance between the segments without either increasing
the diameter of the commutator or reducing the number of the segments, both of
which methods are disadvantageous and practically can only be carried out to a small
extent.
The present invention is intended to obviate this difficulty and consists in placing
two separate circles of commutator segments on the spindle of the machine arranged
and connected as if from an ordinary commutator every alternate segment was
removed and displaced longitudinally on the spindle until it was beyond the original
commutator, the gaps between the segments in both circles being preferably filled
with insulating material such as mica or glass. The width of the insulation between
any two segments on one of the circles is, by this method, increased from about
2nd. inch to that amount plus the width of a segment which would, in ordinary cases,
make about th. inch. Each circle has its own brush, or set of brushes, at the
collecting points, the brushes at the same collecting point of both circles being elec-
trically connected together so that as the armature revolves the current is collected
from, or delivered to, the commutator by the brushes of the two circles alternately.
Instead of constructing the commutator in two circles of segments I may divide it
into three or more circles the limit being reached when there are as many circles as
commutator segments, so that there is only one segment in each circle. In each case
with a two pole field magnet there will be a brush or set of brushes at the two opposite
ends of a diameter on the commutating line of cach circle, all the brushes on either
side of the commutator being electrically connected together as will be understood.
In the case of three circles a convenient arrangement is to connect one coil on the
armature between a segment in the first circle and the nearest segment in the second;
the next coil in order between this segment in the second circle and the nearest
segment in the third; and the next coil in order between this segment in the third
circle and the next segment in the first; and so on.
My invention will be more clearly indicated by the accompanying sheet of drawings
which illustrates a two circle commutator.
Figure 1 is a longitudinal section and Figure 2 a cross section on the line Y Z in
Figure 1.
Similar letters indicate corresponding parts in both figures.
The commutator is built up on the bush B which is carried by the dynamo shaft or
spindle A and held in place by the screw E. This bush is cast with a flange on one
end of the section shown. On to the bush is passed an insulating ring G of vulcanised
fibre or other suitable material and having longitudinal slots equal in number to the
number of segments in one circle cut or formed in it as shown; over this another
insulating ring H is passed. Then the insulating collar P 1, formed to the section
shown, is slipped on and the first circle of metallic segments with their insulating
pieces or segments K 1 is put in place. The metallic segments in the first circle are
shown in Figure 2 dotted behind K 2 and the insulating pieces dotted behind J 2. The
metallic segments in this first circle have lugs L1 formed on, or attached to them,
which lugs are attached to the connections from the armature winding M 1. The
insulating collar P 2, the metallic binding ring F and the insulating collar P 3 are next
slipped on. Then the solid insulating ring N is partly put on and the second circle of
metallic segments J 2 with their insulating pieces K 2 are slipped into place and
arranged so that the metallic segments in this second circle are in line with the
insulating pieces in the first circle. These segments J 2 have lugs L2 formed on
them into which the connections to armature winding M 2 are soldered before they
are put into place. The insulated connections M 2 pass through the longitudinal slots
in G. Where the connections M 2 pass through the flange on B they are protected
by insulating eyelets O. When the second circle is complete the ring N is pushed
into its proper position and the insulating collar P4 and the movable flange put on,
the whole being clamped up tightly together by the nut D. The circumference is
then turned or ground up true.
In Figure 2 only a few of the metallic segments and insulating pieces are shown.

page_text: Those at the top of the figure all have their sides in a radial plane, while the insulating
pieces at the bottom of the figure have their sides parallel and the metallic segments
of such a section as to fill the intervening space. The arrangement shown at the top
is suitable when the insulating material is of such a nature that it can be formed or
ground into the shape shown; but in the case of mica, which I preferably use, the
arrangement at the bottom of the figure is most suitable. The brushes are not shown
in the drawings but the arrangement of these will be well understood from the fore-
going description. The arrangement of a commutator with three or more circles will
be readily understood from the drawings and the above description.
It is to be understood that my invention is not confined to the exact mechanical
construction described and illustrated in the drawings.
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 1
claim is
1st. The construction and use of dynamo electric machines with commutators
baving two or more circles of metallic segments as and for the purpose described.
2nd. The construction and use of dynamo electric machines with commutators sub-
stantially as described and illustrated in the accompanying drawings.
CHARLES EDWARD DAVIES,
Acting for and on behalf of the said John Hubert Davies.
Tiny 10 Cun uaez su