Improvements in Dynamo Electric Generators and Motors.
Year: 1886

page_text: Date of Application, 16th June, 1886.
Complete Left, 16th Mar., 1887
Complete Accepted, 3rd May, 1887.
PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Generators and Motors.
We, LLEWELYN BIRCHALL ATKINSON, of Erwood House, Beckenham, in the
County of Kent, Civil Engineer, and WALTER THOMAS GOOLDEN, of 2 Victoria
Mansions, Westminster, London, and ALEXANDER PELHAM TROTTER, of Bull Green
Works, Halifax, in the County of York, Electrical Engineers, do hereby declare the
nature of the said invention, for "IMPROVEMENTS IN DYNAMO ELECTRIC GENERATORS
AND MOTORS to be as follows :-
"
This invention relates to improvements in the methods of making connection
between the external circuit and the coils on the revolving armatures, of dynamo
electric generators and motors, by means of brushes and commutators or collectors,
whereby sparking, scoring, and burning of commutators and wearing of brushes is
avoided or much diminished.
According to this invention, this is effected by providing at each point where con-
nection is made to the external circuit, two or more brushes, or brushes with two or
more plates, or series of plates, between which are inserted resistances of suitable
magnitude, whose coefficients of self induction or electro magnetic inertia are zero,
or as small as can conveniently be made, such brushes or plates being slightly in
advance of one another round the circumference of the commutator..
In the usual arrangement of brushes, each coil of the armature as it passes under
the brush is short circuited, by the brush bridging over the insulating strip which
separates adjacent commutator bars, the coil then carrying no current passes into
circuit with the other coils, and at this point sparking occurs, since owing to the self
induction or electro magnetic inertia of the coil, a sensible time elapses before the full
current can be started in the coil, and during this time the circuit is more or less
broken except for the air circuit which the spark evidences.

page_text: In this improved method of making connection by means of multiple brushes con-
nected as above described, the first or main brush bridging over the insulating strip
short-circuits two adjacent strips, when one of these passes off the first brush, the
circuit is not broken, for since it remains under the next brush, the circuit is complete
through the resistance between the first and second brush, which at first carries the
whole current, but in a short interval of time part of the current is passing in the coil
which has just passed into circuit. When the commutator strip leaves the second brush,
it is still under the third, which may be connected to the first by a higher resistance,
thus diverting more current through the coil, and thus gradually or by more or less
rapid increments the resistance between the commutator strip and the first or main
brush is increased to infinity, thus allowing time for the current to be started in the
armature coil before the connection between the commutator strip and the brush is
finally broken. By this means the maintenance of the current by sparking through
air circuits, with its detrimental, effects, is avoided.
Dated this 9th day of June 1886.
LLEWELYN BIRCHALL ATKINSON.
WALTER THOMAS GOOLDEN.
ALEXANDER PELHAM TROTTER.

page_text: COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Generators and Motors.
We, LLEWELYN BIRCHALL ATKINSON, of Erwood House, Beckenham, in the
County of Kent, Civil Engineer, and WALTER THOMAS GOOLDEN of 2 Victoria
Mansions, Westminster, London, and ALEXANDER PELHAM TROTTER of Bull Green
Works, Halifax, in the County of York, Electrical Engineers, 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 improvements in the methods of making connection
between the external circuit and the coils on the revolving armatures of dynamo
electric generators and motors by means of brushes and commutators or collectors
whereby sparking scoring and burning of commutators and wearing of brushes is
avoided or much diminished.
According to this invention, this is effected by providing at each point where con-
nection is made to the external circuit, two or more brushes, or brushes with two or
more plates, or a series of plates, between which are inserted resistances of a suitable
magnitude, whose coefficients of self-induction or electro magnetic inertia are zero,
or as small as can conveniently be made, such brushes or plates being slightly in
advance of one another round the circumference of the commutator.
In the usual arrangement of brushes each coil of the armature as it passes under
the brush is short circuited, by the brush bridging over the insulating strip which
separates adjacent commutator bars, the coil which may then be carrying no current
passes into circuit with the other coils, and at this point sparking occurs, since owing
to the self induction or electro magnet inertia of the coil, a sensible time elapses
before the full current can be started in the coil, and during this time the circuit is
more or less broken except for the air circuit which the spark evidences..
In this improved method of making connection by means of multiple brushes con-
nected as above described, the first or main brush bridging over the insulating strip
short-circuits two adjacent strips, when one of these passes off the first brush, the
circuit is not broken, for since it remains under the next brush the circuit is complete
through the resistance between the first and second brush, which at first carries the
whole current, but in a short interval of time part of the current is passing in the
coil which has just passed into circuit. When the commutator strip leaves the second
brush, it is under the third which may be connected to the first by a higher resistance,
thus diverting more current through the coil, and thus gradually or by more or less
rapid increments the resistance between the commutator strip and the first or main
brush is increased to infinity, thus allowing time for the current to be started in the
armature coil before the connection between the commutator strip and the brush is
finally broken. By this means, the maintenance of the current by sparking through
air circuits, with its detrimental effects, is avoided.
Referring to the accompanying sheet of drawings,
Fig. 1 shews a diagrammatic view of the improved method of connection with the
collector. A is an arinature coil, B and C are the main and subsidiary brushes, con-
nected by the resistance D of small electro magnetic inertia. If the brush C were

page_text: removed the coil would have just entered the circuit of the other coils on the armature,
and a spark would pass from the strip under C to the brush B. In the improved
arrangement as shewn, the current at the first instance passes through the
resistance D, which being preferably of higher resistance than the coil A, quickly
diverts nearly all the current through A, so that when the segment leaves the brush C,
there is little or no spark.
•
Fig. 2. shews in side elevation an arrangement of two separate brushes in one
holder, the main brush B is in metallic connection with the holder and with the
external circuit. The brush is held between two insulating slips above and below
and is only connected to B, and the holder, through the resistance D which may be of
the forms to be described. The brush C touches the collector one section in front of
the point where B touches.
Fig. 3 shews the front elevation of the same. The two brushes, B and C may be
arranged in holders separate from one another and admitting of independent angular
adjustment.
Fig. 4 shews one form which the resistance of low coefficient of self induction may
take, that is a plate of thin metal or other conductor, or semiconductor having strips
sawn out so that it presents a circuit of considerable resistance to the passage of the
current, the plate being fixed to slate or other insulator. For a resistance of this
kind may be substituted other forms, such for instance as coils of wire doubly wound
as for standard resistance coils, or an incandescent lamp of suitable resistance, or a
liquid or electrolytic resistance, as for example a secondary battery.
Fig. 5 shews an arrangement sometimes suitable, of one brush built up of a main
body B, with a front plate or plates C insulated from B except at the upper end, such
plate being of thin brass, German silver or flexible or solid carbon, of high resistance,
there may be a series of such separate plates each connected to the adjacent plate in
such a manner that the ends of adjacent plates where they are on the commutator are
separated by a suitable resistance.
By means of brushes arranged in these or analogous manners conformably to the
arrangement described and illustrated in Fig. 1, it is possible to collect the current
from the commutator even when the brushes are not on the neutral line, of the
commutator, and in varying positions as to angular lead, without sparking or flaring.
Having now particularly described and ascertained the nature of this invention, and
in what manner the same is to be performed, we declare that what we claim is :-
1. The combination with a collector or commutator of two or more independent
brushes, connected to one another through a circuit or circuits of small electro magnetic
inertia, substantially as described.
2. The combination with a collector or commutator of brushes consisting of two or
more separate plates or series of plates, so arranged that between their ends adjacent
to the commutator there is considerable resistance of small self induction or electro
magnetic inertia, substantially as set forth.
3. The combination with brushes as described of resistances constructed of thin
plates sawn so as to form circuits of considerable resistance and mounted on plates or
cylinders of insulating material, substantially as described.
4. The combination with brushes as described of electric glow lamps of suitable
resistance.