Improvements in Dynamo Electric Machines.
Year: 1898

page_text: Improvements in Dynamo Electric Machines.
We. WILLIAM BROOKS SAYERS, of Glenwood, Bearsden, near Glasgow, in the
County of Dumbarton, Electrical Engineer, and MAVOR & COULSON LIMITED, of
47, King Street, Mile End, Glasgow, aforesaid, Engineers and Electricians, do
hereby declare the nature of this invention to be as follows:-
In the Specification of Letters Patent No. 27209 of 1896 there is described a
construction of continuous current dynamo electric machine in which, in order
to obtain a fixed position of the brushes, there is provided at each of two opposite
sides of each pole of the field magnet or magnets a polar projection, the two such
polar projections of each pole constituting a pair being arranged longitudinally
in relation to the cylindrical surface of the armature but separate therefrom and
connected together magnetically, as by an iron frame, so as to form with the
armature core a magnetic circuit in which there will be produced, when a current
is flowing in the armature, a magnetic flux that will be proportional to the arma-
ture current throughout a considerable range and will be in the proper direction
in the adjacent polar projections of successive pairs of polar projections to bring
about, by means of the commutator coils, the reversal of the currents in the
armature sections at the required times in whichever direction the armature may
be running and whether as a generator or as a motor.
Now the present invention has for object to simplify the construction and
improve the working of dynamo electric machines of the kind referred to.
According thereto the reversing poles are mounted in close proximity to the
field magnet poles, but are separated therefrom by an air gap or by solid non-
magnetic material, and are so arranged as to be readily adjustable both as regards
the distance between each pair and the distance of the pole faces from the arma-
ture. The arrangement is such that the reversing pole pieces are magnetized
initially by the field magnet poles but to a lower degree than these poles, and that
the effect of the armature current is to differentiate between the magnetisation
of the two reversing pole pieces which co-operate to produce commutation on one
side of the armature. Thus in the case of a generator, the trailing pole piece
is strengthened and the leading pole piece weakened or even reversed in sign by
the armature current, and in the aggregate the effect is the same as if the two
reversing pole pieces had had initially no magnetism.
In one arrangement suitable for multipolar machines, the two pole pieces
arranged between and in proximity to adjacent field magnet poles are adjustably
mounted on a carrier of non-magnetic material that comprises end plates con-
nected by longitudinal inner members to which the reversing pole pieces are
secured, and a thin outer strip or member that is secured at its centre by a bolt
to the yoke piece between the field magnet poles and is acted upon by adjustable

page_text: screws by operating which the distance of the faces of the reversing pole pieces
from the armature can be adjusted.
In another arrangement suitable for two-pole machines, each reversing pole
piece is provided with distance pieces and secured to but at a short distance from,
one side or end of the corresponding field magnet pole by a screw and is provided
with an adjusting screw by which its position relatively to the field magnet pole
and the armature can be varied. Such pole pieces may in some cases be secured
upon extensions of the field magnet poles and be each made of approximately
L-shape in end view.
In some cases, as for instance in large machines, and when it is desired to obtain
the minimum of heating and the minimum of objectionable noise, we may make
the air-gap between armature surface and field magnet face gradually increase
in radial width towards the pole edge which is strengthened by the armature
re-action, and then, in order to get a sufficiently rapid gradient in the reversing
field to act satisfactorily on the commutator coils, we may fix the reversing pole
comparatively close to the armature, and we may also, when necessary and in order
to reduce eddy currents and avoid noise, make the reversing pole pieces of
laminated iron, the plane of lamination coinciding with that in the armature core.
We are aware that it has heretofore been proposed to obtain a fixed position of
the brushes with armatures wound in accordance with the Specifications of Letters
Patent No. 16572 of 1891 and No. 10298 of 1893 by adjusting the gap between
the trailing and leading pole tips with reference to the commutator coils to the
same relationship as that described for our reversing poles in the Specification of
Letters Patent No. 27209 of 1896 hereinbefore referred to, but the arrangement
of the pole pieces according to the present invention has the advantage that the
magnetisation of the armature teeth under the trailing pole edge will be changed
less rapidly than is the case when the edge of the field magnet pole itself is used,
the result being that the heating, due to eddy currents and hysteresis, is much less
with our present arrangement than with former arrangements.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines.
We, WILLIAM BROOKS SAYERS, of Glenwood, Bearsden, near Glasgow, in the
County of Dumbarton, Electrical Engineer, and MAVOR & COULSON, LIMITED, of
47, King Street, Mile End, Glasgow, in the County of Lanark, Engineers and
Electricians, 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 ;-
-
In the Specification of Letters Patent No. 27209 of 1896 there is described a
construction of continuous current dynamo electric machine in which, in order
to obtain a fixed position of the brushes, there is provided at each of two opposite
sides of each pole of the field magnet or magnets, a polar projection, the two such
polar projections of each pole constituting a pair being arranged longitudinally
in relation to the cylindrical surface of the armature but separate therefrom and

page_text: connected together magnetically, as by an iron frame, so as to form with the
armature core' a magnetic circuit in which there will be produced, when a current
is flowing in the armature, a magnetic flux that will be proportional to the arma-
ture current throughout a considerable range and will be in the proper direction
in the adjacent polar projections of successive pairs of polar projections to bring
about, by means of the commutator coils, the reversal of the currents in the
armature sections at the required times in whichever direction the armature may
be running and whether as a generator or as a motor.
Now the present invention has for object to simplify the construction and
improve the working of dynamo electric machines of the kind referred to.
According thereto the reversing poles are mounted in close proximity to the
field magnet poles, but are separated therefrom by an air gap or by solid non-
magnetic material, and are so arranged as to be readily adjustable both as regards
the distance between each pair and the distance of the pole faces from the arma-
ture. The arrangement is such that the reversing pole pieces are magnetized
initially by the field magnet poles but to a lower degree than those poles, and that
the effect of the armature current is to differentiate between the magnetisation
of the two reversing pole pieces which co-operate to produce commutation on one
side of the armature. Thus in the case of a generator, the trailing pole piece
is strengthened and the leading pole piece weakened or even reversed in sign by
the armature current, and in the aggregate the effect is the same as if the two
reversing pole pieces had had initially no magnetism.
Fig. 1 of the accompanying drawings shows in end elevation, part of a four
pole dynamo provided with one arrangement of reversing pole pieces according
to this invention. Fig. 2 shows in end elevation, part of a two-pole dynamo with
a modified arrangement of reversing pole pieces. Fig. 3 shows in end elevation
and to a larger scale, a further modified arrangement of reversing pole. Fig. 4
is a similar view to Fig. 1 but showing a modified form of the field magnet pole.
Figs. 5 and 6 are elevations at right angles to each other, showing a further
modified construction of reversing pole.
In the arrangement shown in Fig. 1, which is suitable for multipolar machines,
the two reversing pole pieces 1 and 1ª arranged between and in proximity to
adjacent field magnet poles 2 are adjustably mounted on a carrier of non-magnetic
material that comprises end plates 3 connected by inclined longitudinal inner
members 3 to which the reversing pole pieces 1, 1ª are secured, and a thin outer
strip or member 3b. Each pole piece 1, 1ª may be adjustably connected to the
correspondingly inclined member 3ª of the carrier by pin and slot connection for
example by providing it with pins 1 with nuts arranged to work in slots 3* in the
inclined members, and the carrier may be secured at its centre by bolts 4 to the
yoke piece 5 and be acted upon by adjustable set screws 6, the arrangement being
such that by adjusting the position of the pair of pole pieces 1, 1ª on the inclined
members 3 of the carrier, the position of the nuts 4 on the bolts 4 and the
position of the set screws 6, the distance of the reversing pole pieces 1, 1ª from each
other and the armature and from the field magnet poles 2, can be adjusted to
suit requirement and so as to give the necessary gradient in the reversing field
with the minimum of heating of the armature, which is an important feature of
the invention.
In the modified arrangement shown in Fig. 2, which is suitable for two pole
machines, each reversing pole piece 1 is provided with distance pieces 1b, of which
only one can be seen in the end view, and is secured to, but at a short distance
from, one side or end of the corresponding field magnet pole 2 by a screw 8, the
said reversing pole piece being provided with an adjusting screw 9 by means of
which its position relatively to the said field magnet pole and armature can be
adjusted.
Such pole pieces may in some cases be each secured upon an extension 2ª of
the field magnet pole 2, as shown in Fig. 3, and be each made approximately of
L shape in end view as represented.

page_text: In some cases, as for instance in large machines, and when it is desired to
obtain the minimum of heating and the minimum of objectionable noise, the
air-gap between the armature surface and the field magnet face may, as shown in
Fig. 4, be made to gradually increase in radial width towards the pole edge which
is strengthened by the armature reaction, and then, in order to obtain a sufficiently
rapid gradient in the reversing field to act satisfactorily on the commutator coils,
the reversing pole may be fixed comparatively close to the armature as shown.
When necessary, and in order to reduce eddy currents and avoid noise,
the reversing pole pieces may be made of laminated iron, the plane
of lamination coinciding with that in the armature core. Figs. 5 and 6
show a reversing pole piece 1 built up of laminated iron plate clamped between end
and side plates 10, with interposed insulating material 11, the whole being
secured to the end of the field magnet pole 2 by set screws 8 passing through
slots 1 in the pole piece and plates, and adjusted in position by set screws 9 as
in the arrangements shown in Figs. 2 and 3, the said slots 1* allowing of adjust-
ment of the pole piece towards the slotted armature 7 and of the distance between
two opposing pole pieces. The clamping plates 10 may be of iron and the
inner one may rest at its outer end against the field magnet pole 2, as shown, so
as to be in direct magnetic contact therewith, as also may the pole pieces shown in
Figs. 2 and 3 if the distance pieces 1b be of iron.
In each case the distance apart of each pair of reversing pole pieces 1,1°
measured around the armature, is made approximately equal to the distance apart
of the sides of each of the commutator coils 11, (Fig. 2) with which the armature
is provided according to the said prior Specification No. 27209 of 1896, the object
of each of the arrangements, as with the arrangement described in the said prior
specification, being to enable the brushes to be fixed in a sparkless position for
varving load.
We are aware that it has heretofore been proposed to obtain a fixed position of
the brushes with armatures wound in accordance with the prior Specifications
No. 16572 of 1891 and No. 10298 of 1893 by adjusting the gap between the trailing
and leading pole tips with reference to the commutator coils to the same relation-
ship as that described for our reversing poles in the said prior Specification
No. 27209 of 1896, but the arrangement of the pole pieces according to the present
invention has the advantage that the magnetisation of the armature teeth under
the trailing pole edge will be changed less rapidly than is the case when the edge
of the field magnet pole itself is used, the result being that the heating, due to
eddy currents and hysteresis, is much less with the arrangements herein described
than with former arrangements.
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:-
1. A dynamo-electric machine of the kind herein referred to wherein the
reversing pole pieces are adjustably supported in close proximity to the polar
edges of the field magnet poles by a non-magnetic carrier or by the field magnet
poles themselves or extensions thereof and are separated from the said field
magnet poles at their inner ends by non-magnetic material, the arrange-
ment being such that the reversing pole pieces can be adjusted relatively
to the armature and to the field magnet poles and are magnetized
initially by the latter but to a lower degree and that the pole pieces
can be adjusted so as to give the necessary gradient in the reversing field, with
the minimum of heating of the armature.
2. A dynamo-electric machine of the kind referred to in the preceding claim
wherein the air gap between the armature surface and each field magnet pole is
made to gradually increase in radial width towards the pole edge which is
strengthened by the armature re-action and the reversing pole in proximity to
such pole edge is arranged comparatively close to the armature, substantially

page_text: as herein before described with reference to Fig. 4 of the drawings annexed for
the purpose specified.
3. Dynamo electric machines of the kind herein referred to constructed with
reversing pole-pieces arranged and operating substantially as hereinbefore
described with reference to and shown in Fig. 1; in Fig. 2; in Fig. 3 and in
Figs. 5 and 6 of the drawings annexed.
Dated this 2nd day of December 1898.
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.