Improvements in Brush Holders for Dynamo-electric Motors and Generators.
Year: 1890

page_text: Date of Application, 18th Aug., 1890
Complete Specification Left, 19th May, 1891-Accepted, 27th June, 1891
PROVISIONAL SPECIFICATION.
Improvements in Brush Holders for Dynamo-electric Motors and
Generators.
I, ALFRED JAMES JARMAN of 158 High Street Clapham, in the County of
Surrey, Electrical Engineer, do hereby declare the nature of this invention to be
as follows:-
My invention relates to improvements in brush holders for dynamo-electric
motors and generators, and has for its objects a perfectly elastic contact with the
commutator, tending to preserve the true surface thereof, and is not influenced by
vibration or irregular motion, and said contact is also, according to my invention,
quite independent of the direction of rotation, so that a sudden reversal, stoppage,
or a variation of the speed of the dynamo-electric machine to which it is applied,
does not cause sparking, to the deterioration of the commutator.
Therefore the improved brush holders according to my invention are particularly
applicable to electric traction, since the disadvantages they are intended to obviate
are more common than in other cases of the application of an electric current.
In carrying my invention into effect, I provide two pendulous arms, depending
from a common pivot or pin, and so arranged that one of said arms is upon each
side of the commutator, while the point of suspension is in a line with the axis
thereof, and may be fitted upon a radial lever, to allow of angular adjustment. A
guide frame is cast upon each of the pendulous arms before referred to, which is
adapted to the shape of the brush that is intended to be used. Said brush is bent at
right angles, or approximately so, and fitted at the upper extremity with a solid
metallic frame, by soldering, brazing or equivalent means, said frame being also
provided with a pivot, or recesses into which pivot pins or screws may engage.
An extension is formed upon each of the pendulous arms, which carries the pivots,
pivot pins, or screws of the brushes, and said brushes are arranged so as to move
freely within the guide frames above referred to, working upon the centre of the
pivots in the extension of the arms. Said pivots are placed at or near to the
centres of the metallic frames which are attached to the ends of the bent brushes,
in such a manner that an adjusting screw may be passed through a hole in the part
which projects above the pivot, said screw regulating the tension of a spiral or
elastic spring, bedded upon a lug cast upon the extension of the arms before men-
tioned. This spring controls the free movement of the bent brush through the
opening in the guide frame, and to a certain extent, the pressure of the working.
edge upon the commutator. I may, if necessary provide friction rollers or similar
devices within the uide frames for facilitating the free movement of the brushes.
The lower parts of the pendulous arms are furnished with adjusting screws and
muts, between whic. a spiral, volute, or elastic spring is retained in tension, and
may be regulated hereby, this being arranged to pass under the commutator.
The connection bet een the pendulous arms and the pivot upon which they are
suspended is electr Ily insulated, and each arm is insulated from the other, the
necessary connecti. being made as near as possible to the point of suspension so
that no flexion of
connecting wires or cables may influence the contact of the
brushes upon the r umutator. A second connecting wire, preferably flexible may
be carried to the ..e of the brush from each pendulous arm, in order to prevent
an imperfect cont: between the pivots or pivot screws, and also to ensure that no
sparking or fusion takes place at this point.
In the application of my invention to the brushes of dynamo electric generators
and motors, the chief advantages are in that the bearing edges that project beyond
the guide frames are not extended beyond the necessary length to prevent the

page_text: actual contact of the guide frames or other part of the pendulous arms with the
commutator, therefore the wearing portion of the brush is not subjected to strains
during a reversal of the direction of rotation, nor when starting the dynamo electric
machine, and the elasticity of the contact which is in fact the preventative of
sparking depends not only upon the two springs, one of which is normally in tension
and the other in compression, but also upon the natural clasticity of the brush itself,
which owing to the angular shape, causes the working edge to freely follow any
irregularity of the surface of the commutator, Said brushes also being radially
and oppositely placed relatively to said commutator, a reversal of rotation, or a
sudden stoppage may iake place without distorting or injuring the points of
contact.
Instead of making use of ordinary metallic brushes, I may employ carbon con-
tacts, which fit freely within the guide frames herein before mentioned, and are kept
in contact with the commutator by means of the tension of spring plates, pivotted
to the upper parts of the pendulous arms, and controlled by spiral springs and
stops. The carbon is preserved from fracture, due either to vibration or angular
strain, by the guide frame.
The improved brush holder is adapted to any kind of brush or contact.
Dated in 7th dow of Anawat
FREDK. WALKER,
11, Furnival Street, London, E.C., Agent for the Applicant
COMPLETE SPECIFICATION.
Improvements in Brush Holders for Dynamo-electric Motors and
Generators.
I, ALFRED JAMES JARMAN of 158 High Street Clapham in the County of
Surrey, Electrical 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:-
My invention relates to improvements in brush holders for dynamo electric
motors and generators, and has for its objects a perfectly elastic contact with the
commutator tending to preserve the true surface thereof and is not influenced by
vibration or irregular motion, and said contact is also, according to my invention
quite independent of the direction of rotation, so that a sudden reversal, stoppage,
or, a variation of the speed of the dynamo-electric machine to which it is applied,
does not cause sparking to the deterioration of the commutator.
Therefore the improved brush holders according to my invention are particularly
applicable to electric traction since the disadvantages they are intended to obviate
are more common than in other cases of the application of an electric current.
In order that my invention may be clearly understood I have appended the
accompanying sheet of drawings, in which Figure 1 is a front elevational view of
an approved form of brush holder, shewn partly in section, and Figure 2 is an end
view of the same, similar letters being employed to denote corresponding parts in
both views.
In carrying my invention into effect, I employ two pendulous arms A A',
depending from a pin or spindle B, and so arranged that one of said arms is upon
each side of the commutator C, while the centre of suspension is in a line with the
axis thereof, and the pin or spindle B may be fitted upon a radial lever to allow
of angular adjustment. A guide frame D D' is cast upon each of the pendulous
arms before referred to, and is adapted to the shape of the brushes E E' that are
intended to be used. I may use metallic brushes bent at right angles and pivotted
at F F or use a modification as shewn, and hereinafter to be fully described. The
pendulous arms A A' are extended below the guide frames D D' as shown by G G
and a spiral, volute or other elastic spring H is retained in tension by adjustable
screws II', for the purpose of maintaining a perfectly regular contact between the

page_text: brushes and the commutator under any condition of vibration or angular movement.
The pendulous arms A A' are insulated from each other, and also from the pin or
spindle B, the necessary connections between them and the field magnet coils or
main leads being made at J, J¹, as near as possible to the point of suspension, so
that no flexion of the connecting wires or cables may influence the contact of the
brushes upon the commutator.
Instead of employing metallic brushes, I prefer to use carbon contacts E E',
which may or may not be coated with metal. Said contacts fit freely within the
guide frames D D', and any required number may be placed therein, according to
the width of the face of the commutator, and each contact is capable of independent
movement and conduction. The requisite tension is maintained by spring plates K K¹
held within the holders L L' by screws bb'. Said holders L L'are pivotted at FF
to suitable extensions cast upon or attached to the arms A A', and tension is applied
to the ends of the contacts E E' through the plates K K' by means of screws a a¹.
The carbon contacts E El are preserved from fracture, due either to vibration or
to angular strain, by the guide frames D D¹ from which they project but slightly
when properly arranged. Each contact is provided with a separate flexible lead c
the upper part of which is attached to the holders L or L, and the lower part to
the contacts, sufficient length being allowed for freedom of motion.
c. c²
I may, however, substitute for these contacts, the ordinary metallic brushes, the
angular or bent contacts hereinbefore described, or any suitable contact or brush
in combination with the improved holder as described and shewn.
In the application of my invention to the brushes of dynamo electric generators
and motors, the chief advantages are in that the bearing edges that project beyond
the guide frames are not extended beyond the necessary length to prevent the
actual contact of the guide frames or other part of the pendulous arms with the
commutator, therefore the wearing surface of the brushes or contacts are not sub-
jected to strains during a reversal of the direction of rotation, nor when starting the
dynamo electric machine, and the elasticity of the contact, which is in fact, the
true preventative of sparking, depends, not only upon the spring plates K K',
which are in compression, but upon the spring H which is in tension, and maintains
the arms A A¹ in position, the whole arrangement causing the working edges of
the contacts to freely follow any irregularity of the face of the commutator. Said
brushes also being radially and oppositely placed relatively to said commutator, a
reversal of the direction of rotation, or a sudden stoppage may take place without
distorting or injuring the points of contact, or causing sparking.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is;-
First. The improved brush-holder substantially as described and shewn.
Second. The construction and use of a brush holder consisting in two pendulous
arms A A', spring H, guide frames D D', pivotted holders L L and radial brushes
or contacts, substantially as herein described and shewn by the appended
drawings.
Third. The construction and use of carbon contacts E E', separate flexible
leads cc, and spring plates K K¹ in combination with the improved brush holder,
substantially as described and shewn by the drawings.
Fourth. The construction and use of bent metallic brushes in combination with
the improved brush holder substantially as herein described.
FREDK. WALKER,
11, Furnival Street, Holborn, London, E.C., Agent for the Applicant.