IMPROVEMENTS IN ELECTRICAL GENERATORS AND MOTORS
Year: 1883

page_text: LETTERS PATENT to Thomas John Handford of 42 Southampton Buildings
in the County of Middlesex Patent Agent for an Invention of "IMPROVEMENTS
IN ELECTRICAL GENERATORS AND MOTORS" communicated to him from abroad
by Thomas Alva Edison of Menlo Park in the County of Middlesex and State
of New Jersey, United States of America
PROVISIONAL SPECIFICATION left by the said Thomas John Handford at
the Office of the Commissioners of Patents on the 29th October 1883.
THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex Patent Agent "IMPROVEMENTS IN ELECTRICAL GENERATORS AND
MOTORS" & communication to me from abroad by Thomas Alva Edison of Menlo
Park in the County of Middlesex and State of New Jersey, United States of
America,
This Invention relates to the construction of dynamo-electric machines and
electro-dynamic motors having continuously wound bobbins connected at intervals
to commutator bars whereby the sparking at the commutator will be greatly
reduced or wholly obviated, overcoming the necessity for changing the current
collectors upon the commutator in accordance with variations in the load upon the
inachines when used either as generators or motors, increasing the capacity of the
machines, and decreasing the heat generated in the armature coils, and also
diminishing the wear of the commutators and the collectors.
This is accomplished by opposing the electro-motive force of the coils, as they are
short circuited at the commutator (by the bridging of commutator bars by the
current collectors) by a counter electro-motive force. This counter electro-motive
force is preferably equal or nearly equal to the electro-motive force of the short-
circuited coils in which case no current will flow in the short-circuited coils and the
sparking will be completely obviated, or the counter force may be somewhat less
or even greater than the direct force but not sufficiently one way or the other to
make the spark due to the current produced by the predominating electro-motive
force of practical importance.

page_text: The counter force is produced by making the connections between the bobbin
and the commutator bars through conductors which pass through the field of force
and in which there is a counter electro-motive force opposed to the direct force of
the short-circuited coils. These connections are preferably in the form of loops
upon the armature.
In machines with continuous windings, the commutator bars have been
heretofore connected with the armature bobbin by conductors running directly from
the commutator bars to the bobbin. By this Invention, however, each connection
is made by a conductor which is connected to the bobbin and is carried back on the
armature loop from the point of connection therewith and follows it one or more
times around the armature and is then connected to a commutator bar.
The extra loops may be conductors of the same size as the bobbin but much
smaller conductors are preferably used and since each extra loop is in circuit a
portion of the time only the heat due to the main current is dissipated.
A counter force equal to the direct force is obtained by giving each extra loop
the same length as one loop or section of loops of the main bobbin, or in
constructions where this is not desirable the extra loops may be placed in advance
of the loops of the main bobbin so that as each main loop or section of loops is
short-circuited the opposing extra loop or section of loops is in a stronger magnetic
field and in this way the counter force of the extra loop can be made equal or
nearly equal to the direct force of the short-circuited loop. The larger resistance of
the extended connections between the armature coils and the commutator bars also
has a beneficial effect in diminishing the spark.
This Invention is applicable to all continuous wound machines whether of the
Gramme, Siemens or other type.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas John Handford in the Patent Office on the 29th April
1884.
"
THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex Patent Agent "IMPROVEMENTS IN ELECTRICAL, GENERATORS AND
MOTORS a communication to me from abroad by Thomas Alva Edison of Menlo
Park in the County of Middlesex and State of New Jersey United States of
America
The said invention relates to the construction of dynamo-electric machines and
electro-dynamic motors, having continuously wound bobbins connected at intervals
to commutator bars, whereby the sparking at the commutator will be greatly
reduced or wholly obviated, thus overcoming the necessity for changing the current
collectors upon the commutator in accordance with variations in the load upon the
machines, when used either as generators or motors, increasing the capacity of the
machines and decreasing the heat generated in the armature coils, and also
diminishing the wear of the commutators and the collectors:
This is accomplished by opposing the electro-motive force of the coils as they
are short circuited at the commutator (by the bridging of commutator bars by the
current collectors) by a counter electro-motive force. This counter electro-motive
force is preferably equal or nearly equal to the electro-motive force of the short
circuited coils, in which case no current will flow in the short circuited coils and
the sparking will be completely obvinted; or the counter force may be somewhat
less or even greater than the direct force but not sufficiently one way or the other
to make the spark due to the current produced by the predominating electro-
motive force of practical importance.
The counter force is produced by making the connections between the bobbin
and the commutator bars through conductors which pass through the field of force,
and in which there is a counter electro-motive force opposed to the direct force of
the short circuited coils. These connections are preferably in the form of loops
upon the armature.
In machines with continuous windings, the commutator bars have been
heretofore connected with the armature bobbin by conductors running directly
from the commutator bars to the bobbin.
By this invention however each connection is made by a conductor which is.
connected to the bobbin, and is carried back on the armature loop from the point
of connection therewith and follows it one or more times around the armature
and is then connected to a commutator bar.
The extra loops may be conductors of the same size as the bobbin, but much
smaller conductors are preferably used, and since each extra loop is in circuit a
portion of the time only, the heat due to the main current is dissipated.
A counter force equal to the direct force is obtained by giving each extra loop
the same length as one loop or section of loops of the main bobbin, or in
constructions where this is not desirable, the extra loops may be placed in advance
of the loops of the main bobbin, so that as each main loop, or section of loops, is
short circuited the opposing extra loop or section of loops is in a stronger magnetic
field, and in this way the counter forco of the extra loop can be made equal or
nearly equal to the direct force of the short circuitod loop.
The larger resistance of the extended connections between the armature coils
and the commutator bars also has a beneficial effect in diminishing the spark.
This invention is applicable to all continuous wound machines, whether of the
Gramme, Siemens or other type.

page_text: And in order that the said Invention may be perfectly understood I shall
now proceed more particularly to describe the the same and for that purpose shall
refer to the several figures on the accompanying sheet of drawings the same letters
of reference indicating corresponding parts in all the figures.
Figure 1 of the accompanying drawings represents a perspective view of a
number of armature loops removed from the armature and of a number of
commutator bars, the connections between the loops and bars being shewn by
dotted lines.
Figure 2 a perspective view of a wound armature of the Siemens type and a
commutator with two commutator connections illustrated; and
Figure 3 a side elevation of a wound armature of the Gramme typo with the
commutator in vertical section, all the commutator connections being illustrated.
A represents commutator bars, and B the coils or loops of a continuously wound
armature. The field magnet, the location of which will be well understood is not
shown in any of the figures. C reprosents the conductors connecting the loops with
the commutator bars. These conductors are wound as loops upon the armature
and hence pass through the field of force, and in them is developed a counter
electro-motive force which neutralizes wholly or partially the electro-motive force
of the coils as they are short circuited.
•
It will be seen that each conductor C instead of extending from the point of
connection with B directly to a commutator is run back upon the coil B to which
it is.connected and follows that coil around the armature and is then connected to
a commutator bar.
If the winding B is a plural winding each conductor C may also be wound two
ar more times around the armature.
In figure 2, two connections only are shown for clearness, but it will be
understood that the other commutator bars will be connected in, the same. way, with
the armature coils..
In figure 3, the connections C pass once around the ring armature before being.
connected with the coinmutator bars, but these connections may be, run, two, or
more times around the armature to give the required electro-motive force.
The larger resistance of the extra coils, forming high resistance connections
between the armature coils and commutator bars, also acts, to reduce the spark at
the commutator.
Having now described and particularly ascertained the nature, of, the said
Invention and the manner in which the same is or may be used or carried
into effect I would observe in conclusion that what I consider to be. novel and.
original and therefore claim as the invention secured to me by. the hereinbefore
in part recited Letters Patent is
In electrical generators and motors, the method of overcoming, wholly or
partially, the spark at the commutators, substantially as herein before described and
illustrated in the accompanying drawings.
In witness whereof I the said Thomas John Handford have to this my
Specification set my hand and seal this twenty eighth day of April in the year
of our Lord One thousand eight hundred and eighty four..