Improvements in Electric Motors and Dynamo Electric Machines.
Year: 1898

page_text: [Communicated from abroad by EUGENIO CANTONO, of Pavie in the Kingdom of
Italy, Captain of Engineers.]
Improvements in Electric Motors and Dynamo Electric Machines.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
45, Southampton Buildings, in the County of Middlesex, do hereby declare the
nature of this invention to be as follows:-
The present application has for its object an arrangement permitting of varying
the speed of an electric motor by means of a slight variation of the excitation.
This variation has the result of modifying the attraction of the armature or arma-
tures by the inducing system in such a manner that if I arrange armatures capable
of slight displacement along their axis of rotation under the action of an opposing
mechanism, such, for example, as springs, the attraction exercised by the inducting
system will be equalised by the degree of separation which the springs above
referred to tend to impart to the armatures.
Equilibrium will be established for all values of the attraction comprised within
suitable limits, this attraction itself being produced by the action of the inducing
current. The result is that for each value of the exciting current there will be a
fixed distance of air space which modifies the intensity of the field. This arrange-
ment is applicable to the control of motors at a distance and it enables also
automatic variation of potential to be obtained for charging accumulators by means
of dynamos.
When it is a question of controlling motors at a distance and when it is not
advantageous to use mechanical means for causing the air space to vary the most
practical solution of the problem is that given by the type of motor forming the
subject of the present application for a patent.
When it is desired to apply motors for electric traction, for working cranes, for
working apparatus generally such as is used on ships, cases in which the motor is
not within reach of the persons directing them, this system is capable of rendering
appreciable services.
Two armatures opposite one another close the magnetic circuit formed by an
even number of straight electro magnets.
When the electro magnets come into action they attract the two armatures which
would come against the polar extensions of the said electro magnets, unless pre-
vented by the two stops of the axis which limit the movement of their support.
Between the supports two springs or indiarubber buffers are arranged. By
means of screws the sleeves of the armature, which are passed upon the shaft may
be adjusted in such manner that the two armatures which are simply keyed have
a longitudinal play, enabling them to produce two extreme limits of air-space, one
of which represent the maximum and the other the minimum speed to be adopted.
Between this maximum and minimum limited by the bearings of the shaft the

page_text: armatures may assume varying positions, corresponding always with a position of
equilibrium between the attraction of the electro magnets and the repelling action
of the spring or elastic material.
The manner in which the air-space and consequently the speed can be altered
will now be readily understood.
Suppose the motor excited in series as is most generally done with traction
motors. A rheostat is arranged in shunt at the extremities of the exciting circuit.
The object of this rheostat is to enable the inducing field to be weakened at will.
A very slight diminution in the excitation, by weakening the attraction and con-
sequently increasing the air-space, will produce a very considerable increase of
speed.
Thus the principle which consists in acting on the field to produce variations
of speed becomes practical, in the sense that the variations to be given remain
within very small and consequently permissible limits.
The result is that the tension of the inducing field varies but little, the resultant
of the two fields (the inducing and the armature) preserves the mean position, and
consequently it is unnecessary to alter the adjustment of the brushes.
This system allows also the modification by means of a spring or elastic sub-
stance of any existing type in such a manner as to cause the polar extensions to
approach or recede from the armature which remains fixed.
The type of double armature has the advantage, in the cases of the special appli-
cations which have been mentioned, of not giving rise to passive resistances which
need to be overcome, which resistances are always caused in the known types
by the magnetic adhesion obtaining between the movable and fixed parts of the
machine.
The position adopted for the double flat ring armature became practicable only
after lengthy experiments. The objection was always raised that the ring armature
formed by a rolled band were not mechanically practicable.
This objection was raised chiefly when both faces of the armature were sub-
jected to the inducing flux in such a manner that the lateral attraction acting upon
the two sides, in the opposite sense was always nearly neutralized.
In the arrange-
ment in question, the attraction being exercised on only one face, these armatures.
could not be used. It was thus necessary to find a practical means of overcoming
this inconvenience. These experiments resulted in the adoption of the following
arrangement:
The ring is constructed in three parts:
1. A continuous internal ring some millimetres in thickness.
2. A winding upon the said ring formed of a thin band of iron insulated by
varnish or other insulating material. This winding comprises nearly the whole
radial thickness of the ring.
3. A second continuous ring arranged on the winding
The internal part of the ring is made in the form of a truncated cone.
The bronze winged supports should have the same conicity.
These supports are intended to carry the ring. The dimensions of the too
truncated cones should be such that the shoulder of the supports may be forced
into the wide part of the cone.
-
The mounting of the ring upon the winged supports is done by hydraulic pres-
sure, which gives to the armature the same solidity as if it were made in one piece.
With this form of construction the use of ring armatures combined with the
arrangement above described becomes quite practicable.
The field magnet cores are cast in one piece with their supporting crown which
forms a ring perpendicular to the cores and connects them all. This crown should
be sufficiently thin, in order that the area of its radial section should be small in
relation to the section of the field magnet core. In this manner the difference of
the induction flux which issues from the too opposite polar extensions of the same
core, remains nearly constant. This is an indispensable condition in order that
the pressure along the axis of the shaft supporting the armature, which results from

page_text: the two pressures exerted by the two armatures should be trifling and not detri-
mental in practice.
This form of field magnet, one of the most simple to construct, gives excellent
results from the point of view of facility of centering the field magnet as a whole
as well as the cores.
The field magnet as a whole is kept in place by the frame of the motor which is
formed of two cast metal boxes nearly hemispherical in shape which are fastened
together on the crown of the field-magnet and thus protect all the parts of the
motor.
In the bottom of these boxes or casings, is provided an opening, in which a
bearing is fixed supporting the shafts of the armature.
A practical arrangement for this kind of motor consists in dividing each part
of the casing into two parts along a section horizontal with respect to the axis
of the armature, and to form the field magnet in two parts, dividing the crown
above described in the direction of its radius, in such a manner that the upper
sector thus obtained contains one of the cores of the field magnet system of four
or more pairs of cores.
In this manner it is very easy to remove the armature when necessary; it is
only necessary to remove the two upper parts of the cast metal boxes
forming the casing, then the upper field magnet core forming part of the uncovered
sector, the armature can then be easily taken out.
In some cases the upper parts of the boxes can be joined to the lower by means
of hinges thereby facilitating the inspection of the parts of the motor.
In order to regulate the position of the armature when mounting it and to
prevent the inconvenience of heating, which is of frequent occurrence in other
types of motors with flat rings, in consequence of the axial movement due to the
differing attractions of each side of the polar extensions, recourse has been had to a
ball bearing.
The bearing comprises two concave rings supporting the balls an intermediate
double cone screwed on to the shaft of the armature and secured in the desired
position by a key. To facilitate the keying the double cone has on its lower part
several notches which pass successively before the key way or groove of the
threaded part of the shaft, by tightening or loosening this double cone the position
of the shaft can be altered by a fraction of a revolution, when the key may be
replaced in its groove and that particular notch which registers with it.
ADVANTAGES OF THE LIGHT MOTOR WITH VARIABLE SPEED.
The first advantage of this motor is its great lightness, inasmuch as its output
is equal to that of motors hitherto used but with a saving in weight of 30 to 40%.
The use of two armatures and the alteration of the air space enable motors to be
obtained giving any degree of speed desired without using passive resistances as is
done in the types hitherto known. By the use of this new type of motor very
appreciable advantages which may be summed up as follows:
1. Diminution of weight.
2. Economy and simplicity in construction and installation.
3. Increased output, in consequence of dispensing with the loss through passive
resistances.
4. Dispensing with jerks and the great expenditure of current upon starting
with motors working tramways or carriages on the level. This doing away with
jerks results in reality from the coupling in serres of the two collectors when start-
ing and from the automatic reduction of the air space when series excitation is
emploved.
5. Absolute protection of all the parts which are thus protected from dust and
damp.
6. Great facility in varying the speed which it provides either by the use of the
rheostat or by means of the automatic alteration of the air space of the motor
resulting from an increasing strain to be overcome.

page_text: USE OF ACCUMULATORS.
When it is a question of using a motor changing speed by alteration of air space
with accumulators, a considerable saving is effected, as much from the point of view
of uniform supply as of the life of the accumulators.
The arrangement of motor above considered can he applied also to generating
dynamos an application which may be of great service, particularly in charging
accumulators. Indeed, assuming that the speed of the machine should be constant,
and if we suppose that the dynamo is to be excited in shunt, if the output of the
machine diminishes in consequence of the increase of the counter electro motive
force of the battery, the difference of potential at the terminals of the machine
will increase. An increase of excitation will result herefrom and in consequence
of the attraction of the air space will diminish consequently the electro-motive
force developed will increase and will re-establish the output of the machine.
The machine, in this case, should be designed in such a way as to arrest the
greater part of the losses due to its working in the armature internal resistance
in order to make the automatic regulating action more sensitive.
This method of charging accumulators enables the use of rheostats and other
apparatus to be dispensed with at the same time effecting great economy in labour
and permitting the maintenance of a uniform current for battery charging.
In case of compound working or the working in groups of the dynamos con-
trolled at a distance the arrangement above considered may also be of great service.
Dated this 8th day of February 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
Improvements in Electric Motors and Dynamo Electric Machines.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
45, Southampton Buildings, in the County of Middlesex, 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:-
This invention relates to electric motors and dynamo electric machines and has
for its object an arrangement permitting of varying the speed of an electric motor
by means of a slight variation of the excitation. This variation has the result of
modifying the attraction of the armature or armatures by the inducing system in
such a manner that if I arrange armatures capable of slight displacement along
their axis of rotation under the action of an opposing mechanism, such, for
example, as springs, the attraction exercised by the inducing system will be
equalized by the degree of separation which the springs above referred to tend to
impart to the armature.
Equilibrium will be established for all values of the attraction comprised within
suitable limits, this attraction being produced by the action of the inducing
current. The result is that for each value of the exciting current there will be a
fixed distance of air space which modifies the intensity of the field. This arrange-
ment is applicable to the control of motors at a distance and it enables also
automatic variation of potential to be obtained for charging accumulators by means
of dynamos.
When it is a question of controlling motors at a distance and when it is not
advantageous to use mechanical means for causing the air space to vary the most

page_text: practical solution of the problem is that given by the type of motor forming the
subject of the present application for a patent.
When it is desired to apply motors for electric traction, for working cranes, for
working apparatus generally such as is used on ships, cases in which the motor is
not within reach of the persons directing them, this system is capable of rendering
appreciable services.
This invention is illustrated in the accompanying drawings in which:
Figure 1 is a longitudinal section of a motor constructed according to the
present invention;
Figure 2 a view partly in elevation and partly in section;
Figure 3 a front view of the field-magnet;
Figure 4 a transverse section of this latter;
Figure 5 shows the arrangement of the armature partly in front elevation and
partly in section.
Two armatures F F opposite one another close the magnetic circuit formed by
an even number of straight electro magnets N.
When the electro-magnets N come into action they attract the two armatures
which would come against the polar extensions of the said electro magnets, unless
prevented by the two stops a à of the axis X, which limit the movement of the
armature supports.
Between the supports two springs or indiarubber buffers g g are arranged. By
means of screws the sleeves y of the armature, which are passed upon the shaft
may be adjusted in such manner that the two armatures which are simply keyed
have a longitudinal play, enabling them to produce two extreme limits of air-
space one of which represents the maximum and the other the minimum speed to
be adopted.
Between this maximum and minimum limited by the bearings of the shaft the
armatures may assume varying positions, corresponding always with a position of
equilibrium between the attraction of the electromagnets and the repelling action
of the spring or elastic material.
The manner in which the air-space and consequently the speed can be altered
will now be readily understood.
Suppose the motor excited in series as is most generally done with traction
motors. A rheostat is arranged in shunt at the extremities of the exciting circuit.
The object of this rheostat is to enable the inducing field to be weakened at will.
A very slight diminution in the excitation by weakening the attraction and con-
sequently increasing the air-space, will produce a very considerable increase of
speed.
Thus the principle which consists in acting on the field to produce variations
of speed becomes practical, in the sense that the variations to be given remain
within very small and consequently permissible limits.
The result is that the tension of the inducing field varies but little, the resultant
of the two fields (the inducing and the armature) preserves the mean position, and
consequently it is unnecessary to alter the adjustment of the brushes.
This system allows also the modification by means of a spring or elastic sub-
stance of any existing type in such a manner as to cause the polar extensions to
approach or recede from the armature which remains fixed.
The type of double armature has the advantage, in cases of the special appli-
cations which have been mentioned, of not giving rise to passive resistances which
need to be overcome, which resistances are always caused in the known types
by the magnetic adhesion obtaining between the movable and fixed parts of the
niachine.
The position adopted for the double flat ring armature became practicable only
after lengthy experiments. The objection was always raised that the ring armature
formed by a rolled band were not mechanically practicable.
This objection was raised chiefly when both faces of the armatures were sub-
jected to the inducing flux in such a manner that the lateral attraction acting upon

page_text: .
the two sides, in the opposite sense was always nearly neutralized.. In the arrange-
ment in question, the attraction being exercised on only one face, these armatures
could not be used. It was thus necessary to find a practical means of overcoming
this inconvenience. These experiments resulted in the adoption of the following
arrangement:
The ring is constructed in three parts:
1. A continuous internal ring e some millimetres in thickness.
2. A winding upon the said ring formed of a thin band of soft iron H, insulated
by varnish or other insulating material. This winding comprises nearly the whole
radial thickness of the ring.
3. A second continuous ring f arranged on the winding.
The internal part of the ring is made in the form of a truncated cone.
The bronze winged supports S S should have the same capacity.
These supports are intended to carry the ring. The dimensions of the two
truncated cones should be such that the shoulders of the supports may be forced
into the wide part of the cone.
The mounting of the ring upon the winged supports is done by hydraulic pres-
sure, which gives to the armatures the same solidity as if it were made in one piece.
With this form of construction the use of ring armatures combined with the
arrangement above described with reference to Figure 1 becomes quite practicable.
The field magnet cores N are cast in one piece with their supporting crown K
which forms a ring perpendicular to the cores and connects them all. This crown
should be sufficiently thin, in order that the area of its radial section should be
small in relation to the section of the field-magnet core. In this manner the
difference of the induction flux which issues from the two opposite polar exten-
sions of the same core, remains nearly constant. This is an indispensable condition
in order that the pressure along the axis of the shaft supporting the armature,
which results from the two pressures exerted by the two armatures should be
trifling and not detrimental in practice
This form of field magnet, one of the most simple to construct, gives excellent
results from the point of view of facility of centering the field magnet as a whole
as well as the cores.
The field magnet as a whole is kept in place by the frame of the motor which
is formed of two cast metal boxes L (Figure 2) nearly hemispherical in shape
which are fastened together on the crown K of the field magnet and thus protect
all the parts of the motor.
In the bottom of these boxes or casings is provided an opening, in which
a bearing M is fixed supporting the shaft of the armature.
A practical arrangement for this kind of motor consists in dividing each part
of the casing L into two parts along a section horizontally with respect to the
axis of the armature and to form the field magnet in two parts, dividing the crown
above described in the direction of its radius, in such a manner that the upper
sector thus obtained contains one of the cores of the field magnet system of four
or more pairs of cores.
In this manner it is very easy to remove the armature when necessary; it is
only necessary to remove the two parts of the cast metal boxes forming the casing,
then the upper field magnet core forming part of the uncovered sector, the
armature can then be easily taken out.
In some cases the upper parts of the boxes can be joined to the lower by means
of hinges thereby facilitating the inspection of the parts of the motor.
In order to regulate the position of the armature when mounting it and to
prevent the inconvenience of heating, which is of frequent occurrence in other
types of motors with flat rings, in consequence of the axial movement due to the
differing attractions of each side of the polar extensions, recourse has been had to a
ball bearing.
In Figure 1, 0 represents the bearing which comprises two concave rings m
and n supporting the balls, T represents an intermediate double cone screwed on

page_text: to the shaft of the armature and secured in the desired position by a
key. To facilitate the keying, the double cone T has on its inner part several
notches c Figures 8, 9, 10 which pass successively before the key way or groove b
of the threaded part of the shaft X (Figures 6 and 7); by tightening or loosen-
ing this double cone T, the position of the shaft can be altered by a fraction of a
revolution when the key may be replaced in its groove band that particular
notch c which registers with it.
ADVANTAGES OF THE LIGHT MOTOR WITH VARIABLE SPEED.
The first advantage of this motor is its great lightness, inasmuch as its output
is equal to that of motors hitherto used but with a saving in weight of 30%
to 40%.
The use of two armatures and the alteration of the air space enable motors to be
obtained giving any degree of speed desired without using passive resistances as is
done in the types hitherto known. By the use of this new type of motor very
appreciable advantages are obtained which may be summed up as follows:
1. Diminution of weight.
2. Economy and simplicity in construction and installation.
3. Increased output, in consequence of dispensing with the loss through passive
resistances.
4. Dispensing with jerks and the great expenditure of current upon starting
with motors working tramways or carriages on the level. This doing away with
jerks results in reality from the coupling in series of the two collectors when start-
ing and from the automatic reduction of the air space when series excitation is
employed.
5. Absolute protection of all the parts which are thus protected from dust and
damp.
6. Great facility in varying the speed which it provides either by the use of the
rheostat or by means of the automatic alteration of the air space of the motor
resulting from an increasing strain to be overcome.
USE OF ACCUMULATORS.
When it is a question of using a motor changing speed by alteration of air space
with accumulators a considerable saving is effected, as much from the point of view
of uniform supply as of the life of the accumulators.
The arrangement of motor above considered can be applied also to generating
dynamos an application which may be of great service, particularly in charging
accumulators. Indeed, assuming that the speed of the machine should be constant,
and if we suppose that the dynamo is to be excited in shunt, if the output of the
machine diminishes in consequence of the increase of the counter electro-motive
force of the battery, the difference of potential at the terminals of the machine
will increase. An increase of excitation will result therefrom, and in consequence
of the attraction the extent of the air space will diminish, consequently the
electro-motive force developed will increase and will re-establish the output of the
machine.
The machine, in this case should be designed in such a way as to cause the
greater part of the losses due to its working to be almost exclusively dependent
upon the armature internal resistance in order to make the automatic regulating
action more sensitive.
This method of charging accumulators enables the use of rheostats and other
apparatus to be dispensed with, at the same time effecting great economy in labor,
and permitting the maintenance of a uniform current for battery charging.
In case of compound working or the working in groups of the dynamos con-
trolled at a distance the arrangement above considered may also be of great service.
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 me by
my foreign correspondent, I declare that what I claim is:-
-
1. The arrangement above described enabling the speed of an electric motor to

page_text: "
be modified, by altering the air space automatically by means of an electro-
mechanical action obtained by means of a slight alteration of the exciting current.
2. The arrangement enabling a variation of speed in electric motors to be obtained
by acting either with a rheostat in series in the exciting circuit in the case of a
shunt" motor, or with a rheostat arranged in shunt in the exciting circuit in
the case of a series" motor, or in any manner whatever arising from the simul-
taneous or partial use of the afore-mentioned regulation in the case of "compound'
motors, and this without the action of the rheostat being detrimental to the speed
of the motor, inasmuch as the alteration of the speed proceeds from the alteration
of the air space caused by the rheostat.
23
3. The arrangement enabling the automatic regulation of the speed of motors
with two armatures to be obtained, by the use of the variation of the air space the
attraction due to the field magnets being opposed by the action of springs or any
elastic material interposed between the two armatures which have a tendency to
approach one another, which is equivalent to saying that the speeds vary in the
inverse ratio of the driving couple to be provided; the consequence being that the
output is maintained nearly constant in spite of the variation of the resistances to
be overcome.
4. The arrangement rendering practicable, from the point of view of mechanical
ability, the construction of armatures suitable for use in the double armature
machine shewn in Figure 1.
5. The arrangement enabling an assemblage of simple and inexpensive. straight
electro-magnets with their supports to be obtained, when using the said arrange-
ment of straight electro-magnets with double armatures shewn in Figure 1.
6. The arrangement described enabling an almost constant current to be auto-
matically obtained from a dynamo working at a constant speed, for charging
accumulators requiring a potential always increasing preferably by employing the
type of machine above described and shewn in Figure 1.
Dated this 7th day of November 1808
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.