Year: 1886

page_text: Date of Application, 13th Nov., 1886.
Complete Left, 10th Aug., 1887.
Complete Accepted, 16th Sept., 1887.
[ WILHELM LAHMEYER of Aachen in the Empire of Germany Engineer, do hereby
declare the nature of this invention to be as follows :—
This Invention relates to dynamo machines, and particularly to the arrangement
and construction of the iron portions thereof.
In the construction of dynamo machines it is a fundamental condition to so arrange
the electro-magnets as to reduce to a minimum the magnetic resistance opposing the
lines of force passing from one pole to the other through the cores and their con-
necting pieces, as the number of the lines of force-i.c.—the intensity of the magnetic
field obtained by means of a certain number of Ampère turns is inversely proportional
to the magnetic resistance which opposes the lines of force on their way between the
armature and electro-magnet. For this reason it appears necessary to use electro-
magnet cores of the shortest and thickest dimensions possible; it is also important
that the iron frame be constructed of one piece if possible corresponding to the course
of the lines of force. It has been found that interruptions in the molecular structure
of an electro-magnetic construction put together by means of screws or rivets, cause a
considerable increase of the magnetic resistance, even in the most carefully fitted con-
nections. It is, furthermore, a well-known fact that these dynamno connections gradually
become loose owing to vibration and continual heating and cooling, while the metallic
purity of the connecting surfaces (the principal requirement for good conductivity) is
destroyed by damp which forms rust, and hence a diminution of the magnetic intensity
and of the current-tension must ultimately result.
To obviate these evils is the object of the apparatus shewn in the accompanying
drawing in which the electro-magnet frame is constructed in one piece. Figure 1 is
a transverse section, and figure 2 a longitudinal section of the dynamo.
The electro-magnet cores E E' of the form and proportions shewn (i.e. short and of

page_text: great sectional area) are situated at opposite sides of the armature A and their
faces e e¹ are curved to correspond to the circumference thereof whilst the opposite
portions are in good conductive magnetic connection by means of the massive
connecting portions B.B'. The dimensions are such that the length of the electro
magnet cores is less than the distance between the edges a b figure so that the coils
of the electro magnets (previously wound on a corresponding frame) can be readily
slipped on to their cores from the direction of the armature. As it is unnecessary to
dismount anything in order to coil the electro-magnet, it is possible to make the
whole frame, including the base-plate if desired, in one casting.
The peculiar form shewn in the drawing has been selected principally for the
following reasons-In arranging the magnetic field of a dynamo it is important
that a so-called dispersion of the lines of force be obviated, that is to say, that all
lines of force be compelled to thread through the armature on their way from one
pole to the other. In order to effect this as completely as possible it is necessary to
make the section of the air column through which the lines of force pass from pole to
pole as small as possible. It should here be remarked that the section of this con-
ducting air is very great for the lines of force at some distance from the surfaces
where the dispersing lines of force have their origin in the iron, and consequently tho
magnetic resistance is very slight notwithstanding the specifically bad magnetic con-
ducting capacity of the air at this part. The form of the conducting air approximately
follows the form of a double cone supposing the equi-potential surfaces of the magnetic
field to be at right angles to the axis of the cone.
The magnetic resistance of the double cone of course depends mainly on the smaller
sections thereof-vizt.-the apexes. The latter however correspond to the portions of
the electro-magnets which are adjacent to the poles, and from which lines of force can
escape into the air without being immediately absorbed by the iron of the armature.
Based on this principle the pole shoes as generally used with their rear surfaces turned
away from the armature are obviated in this Invention because these favor to a high
degree a dispersion of the lines of force.
This improved construction of electro-magnet which obviates the injurious magneti-
cally polarizing surfaces which are not directly turned towards the armature has the
effect of concentrating the magnetic lines of force on to the armature almost without any
loss, for the purpose of generating current.
In order to cast the whole electro magnet frame in one piece and enable it to be
easily mounted it was necessary to make the electro-magnet cores particularly short.
If therefore the limited dimensions of the coil space of the cores be rendered practicable
by the above advantages of small magnetic resistance and avoiding the dispersion of
the lines of force the form selected has the result that the upper and lower convolutions
of the coils are utilized for magnetic induction both inwards and outwards while the
fewest ampère turns possible generate a powerful magnetic field.
In order that the poles N'S should not be actually formed by the exterior induction
but increase the magnetism of the poles N and S by their action, the dimensions of the
machine are such that the portions B B' shall be especially massive so that they shall
not offer any appreciable magnetic resistance. In this manner the poles N¹ S' are
brought magnetically together and are not formed so that the entire external iron mass
of the magnet remains unpolarized.
When employing the frame constructed in one piece as above described it is
necessarily of cast iron, the conductive capacity of which is less than that of wrought
iron in the proportion of 2 to 3. Were wrought iron employed and the same dimen-
sions retained an increased magnetization would be obtained in the proportion of
3 to 2. Therefore, to compensate for this difference it is sufficient when employing
cast iron to increase the average section of the iron in the same proportion of 3 to 2.
As the electro-magnet cores in the present construction are very short, but the sections
of the other parts of the iron frame conducting the lines of force may be made of any
desired size, it is clear that by means of this construction it is possible, by choosing
suitable dimensions, to more than equalize the lesser specific magnetic conductive
capacity of the cast iron.

page_text: The armature is provided with centrifugal ventilating openings, and the plates B.
and B are provided with air slits in order to directly ventilate the upper and lower
portions of the coils. Further, there are perforated iron plates both sides. of the
machine which both increase the magnetism thereof and serve as a protection for the
delicate parts against injury from the side. It will be seen from the description of
this construction of the dynamo-electrical machine that it combines the advantage of
extraordinarily great electrical performance with considerable stability which renders
it entirely insensible to vibrations etc. in respect of constant generation of current and
has the advantage of being light and readily transported.
Dated this 13th day of November 1886.

page_text: .
1, WILHELM LAHMEYER of Aachen in the Empire of Germany, 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:
This Invention relates to dynamo machines, and particularly to the arrangement and
construction of the iron portions thereof.
In the construction of dynamo machines it is a fundamental condition to so arrange
the electro-magnets as to reduce to a minimum the magnetic resistance opposing the
lines of force passing from one pole to the other through the cores and their connect-
ing pieces, as the number of the lines of force-i.e. the intensity of the magnetic
field attained by means of a certain number of Ampère turns is inversely proportional
to the magnetic resistance presented to the lines of force on their closed path through
the armature and electro-magnet. For this reason it appears necessary to use electro-
magnet cores of the shortest and thickest dimensions possible; it is also important
that the iron frame be constructed of one piece if possible corresponding to the path
of the lines of force. It has been found that the interruptions in the molecular
structure when the parts are assembled together by means of screws or rivets, cause a
considerable increase of the magnetic resistance, even in the most carefully fitted con.
nections. It is furthermoro, a well-known fact that these dynamo connections gradually
become loose owing to vibration and continual heating and cooling, while the metallic
purity of the connecting surfaces (the principal requirement for good conductivity) is
destroyed by damp which forms rust, and hence a diminution of the magnetic intensity
and of the current-tension must ultimately result.
To obviate these evils is the object of the apparatus shown in the accompanying
drawing in which the electro-magnet frame is constructed in one piece, being either a
single casting with the electro-magnet cores, or cast around wrought iron cores so
that all screws and the consequent increase of the magnetic resistance are avoided.
Figure 1 is a transverse section; Figure 2 is a horizontal section, figure 3 is an end
view, and figure 4 a plan of the dynamo.
The electro-magnet cores E E¹ of the form and proportions shewn (i.e. short and of
great sectional area) are situated at opposite sides of the armature A and their faces e e¹
are curved to correspond to the circumference thereof whilst the opposite portions fƒ'
are in good conductive magnetic connection by means of the massive connecting
portions B B. The dimensions are such that the length of the electro-magnet cores
is less than the distance between the edges ab figure 1, so that the previously wound
coils s s¹ can be readily introduced between, and slipped on to, the cores E E¹ before
the armature A is mounted in place. As it is unnecessary to dismount anything in
order to wind the electro-magnets, it is possible to make the whole frame, including
the base-plate if desired, in one casting.

page_text: The peculiar form shewn in the drawing has been selected principally for the follow-
ing reasons-In arranging the magnetic field of a dynamo, it is important that a so
called dispersion of the lines of force be obviated, that is to say, that all lines of force
be compelled to thread through the armature on their way from one pole to the other.
In order to effect this as completely as possible it is necessary to make the section of
the air column through which the lines of force pass from pole to pole, as small as
possible. It should here be remarked that the section of this conducting air is very
great for the lines of force at some distance from the surfaces where the dispersing
lines of force have their origin in the iron, and consequently the magnetic resistance
is very slight, notwithstanding the specifically bad conductive capacity of the air at
this part. The form of the conducting air is approximately that of a double cone
supposing the equi-potential surfaces of the magnetic field to be perpendicular to the
axis of the cone. The magnetic resistance of the double cone of course depends
mainly on the smaller sections thereof-vizt., the apexes. The latter however, corre-
spond to the portions of the electro-magnets which are adjacent to the poles, and from
which lines of force can escape into the air without being immediately absorbed by the
iron of the arinature. The use of pole shoes with their rear surfaces directed away
from the arinature as usual, is therefore avoided, because these favor to a high degree
a dispersion of the lines of force.
This improved construction of electro-magnot having the cores placed radially and
in which all injurious magnetic polarizing surfaces not directed immediately towards
the armature are avoided, has the effect of concentrating the magnetic lines of
force on to the armature almost without any loss, for the purpose of generating
current.
In order to cast the whole electro-magnet frame in one piece and enable it to be
easily mounted, it was necessary to make the electro-magnet cores particularly short.
If therefore, the limited dimensions of the coil space on the cores be rendered practic-
able by reason of the small magnetic resistance and the avoidance of dispersion of the
lines of the force, the form chosen is such that with the fewest possible ampère turns a
powerful magnetic field is produced, the upper and under convolutions of the coils
being utilized for magnetic induction not only towards the interior but towards the
exterior also. In order that poles N' S' should not be actually formed by the exterior
induction but should increase the magnetism of poles N and S. by their action, the
dimensions of the machine are such that the portions B B' shall be especially massive,
so that they shall not offer any appreciable magnetic resistance. The polos N' S' are
thus brought magnetically together and do not come into existence, so that the entire
external iron mass of the magnet remains unpolarized.
When employing the frame constructed in one pioce, as above described, it is
necessarily of cast iron, the conductive capacity of which is less than that of wrought
iron in the proportion of 2 to 3. Were wrought iron employed and the same dimen-
sions retained an increased magnetization would be obtained in the proportion of
3 to 2. Therefore, to compensate for this difference, it is sufficient when employing
cast iron, to increase the average section of the iron in the same proportion of 3 to 2.
As the electro-magnet cores in the present construction are very short but the sections
of the other parts of the iron frame conducting the lines of force may be made of any
desired size, it is clear that by means of this construction it is possible, by choosing
suitable dimensions, to more than equalize the lesser specific magnetic conductive
capacity of the cast iron.
The armature is provided with centrifugal ventilating openings, and the parts B B¹
are provided with air slits g in order to directly ventilate the upper and lower portions
of the coils. Further, there are perforated iron plates M at both sides of the machine,
which both increase the magnetism thereof and serve as a protection for the delicate
parts against external injury. It will be seen from the description of this construction
of the dynamo electrical machine that it combines the advantage of extraordinarily
great electrical performance with considerable stability which renders it entirely
insensible to vibrations etc., in respect of constant generation of current, and has the.
advantage of being light and readily transported.

page_text: Having now particularly described and ascertained the nature of the said invention'
and in what manner the same is to be performed, I declare that what I claim is ;-
1. In a dynamo electrical machine, the construction of the frame K K' of the
electro-magnet and the base plate B' in a single iron casting with or around the
electro-magnet cores E E' whose geometrical axes are diametrical to the armature
and whose faces e e¹ are curved to correspond to the circumference thereof, whilst the
outer ends ff¹ are brought into perfect magnetic connection with each other by means
of the surrounding frame BB' which embraces the coils 38' on two sides, substantially
as described and shewn in the drawings.
2. In a dynamo-electric machine, the employment of ventilating air slits g in the
upper plate B and centrifugal ventilating openings in the armature A for the direct
ventilation of the upper and lower portions of the coils; also perforated iron plates M
screwed to the frame at both ends of the armature to protect the coils from injury and
permit the free entrance of air to the interior of the dynamo.
Dated this 10th day of Anet 1887