An Improvement in Brush-holders for Electric Machines.
Year: 1899

page_text: Date of Application, 28th June, 1899-Accepted, 5th Aug., 1899
COMPLETE SPECIFICATION.
An Improvement in Brush-holders for Electric Machines.
I, JAMES BURKE, of the Bergmann Elektromotoren und Dynamo Werke, of
Outenarder Strasse 23, Berlin, N., in the Empire of Germany, 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:-
This invention relates to a construction of brush-holders for dynamo electric
machines or motors differing in essential points from others as it possesses a
high degree of flexibility, while it effects good and constant contact with the
commutator surface with moderate pressure and a minimum of wear of the rub-
bing surfaces.
It is of the greatest importance that the electric current shall pass from the
brush to the commutator or conversely without creating sparks at the point of
contact, this depending to a great extent, on perfect contact between the brushes
and the commutator. Brush-holders as they are usually made, consist either
of rigid levers carrying copper or carbon brushes pressed by springs against
the commutator, or of flat springs pressing against the end of a copper or carbon
brush held in a metal tube or box in which the brush slides towards the com-
mutator as it is worn.
Both of these constructions have the fault of making insufficient contact
whenever there is the slightest roughness on the surface of the commutator and
after the contact pieces have been reduced to a certain extent by wear.
I have invented a brush-holder which at all times gives the contact brush an
even pressure and in such a manner, that the whole contact surface of the brush
is always in complete contact with the commutator as I shall describe referring
to the accompanying drawings.
Fig. 1 is a side view and Fig. 2, is a plan of a brush-holder according to my
invention.
t is a pin or stud which is insulated from other parts of the machine, and
carries the brush-holder; is a clamp ring open on one side and fixed on t by
the screw n; ?? are two pairs of metal links each having its one end pivotted
tor by pins d, and the other end by pins to the dovetailed brush carrier h,
in which a wedge-shaped carbon or metal brush is secured by the screw s;
f is a helical spring connecting the clamp ring r to the brush carrier h. Its
pressure can be adjusted by means of a screw 6 passing through the lug 7 and
the nut m which latter has a V-shaped groove engaging on a corresponding rib
c is a flexible
on the lug to prevent loosening of the screw by vibration.
copper conductor connecting the ring r to the brush carrier h.
Obviously, instead of the ring clamped to a stud t, a sleeve block or piece
of any other suitable form may be fixed on an insulated part, the sleeve block.
or piece being such that the pairs of parallel links can be pivotted to it.
י
The two pairs of metal links p p form a parallelogram between the ring r
and the brush carrier h, permitting the brush to act upon the commutator at all
its points with equal pressure, as the parallel motion due to this arrangement
037

page_text: of the links prevents any tilting motion such as occurs when the brush
holder is a rigid lever pivotted on the holder stud.
A great advantage that this brush-holder possesses over other constructions
is due to the very small friction of its moving parts as the friction on the
pins d and d may be almost entirely neglected; this permits the brush-holder
to move freely and to remain in good contact even in cases when the commu-
tator is slightly roughened, whereas brush-holders of other kinds produce sparks
on account of. their slow movements in re-establishing contact due to the great
friction on the brush-holder stud.
As a consequence of the perfect. contact obtained by the brush-holder
described, and the small pressure required, there is a great reduction of wear
of the commutator and brushes.
Instead of two pairs of parallel links p, there may obviously be a greater
number of pairs.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is:-
A brush-holder for an electro-dynamic machine or motor having a ring or
other suitable piece fixed on an insulated part connected to the holder proper
by two
or more pairs of parallel links and an adjustable helical spring
substantially as and for the purpose set forth.
Dated this 28th day of June 1800
ABEL & IMRAY,.
Agents for the Applicant.