Improvements in Electrical Conductors, particularly applicable to Commutator Brushes and Arc Light Pencils.
Year: 1892

page_text: Date of Application, 6th Sept., 1892-Accepted, 14th Jan., 1893
COMPLETE SPECIFICATION.
Improvements in Electrical Conductors, particularly applicable to
Commutator Brushes and Arc Light Pencils.
I, PHILIP HENRY HOLMES of Gardiner in the County of Kennebec State of
Maine, United States of America, Mechanical 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:-
The object of my invention is to construct an improved electrical conductor,
more particularly commutator brushes and are light pencils.
In the accompanying drawings,—
Figure 1 is a perspective view of an arc light pencil or stick, made in accordance
with my invention.
Figure 2 is a similar view of a commutator brush also made in accordance with
my invention.
Figure 3 is a diagrammatic sectional plan view, illustrating the manner of
producing the conductor; and
Figure 4 is a section on the line 1-2, Figure 3.
In making my improved conductor I-prefer to make it of a composition in which
plumbago in a finely divided state is combined with fibre and compressed and
united by a suitable binder.
The main feature of my present invention consists in so making the conductor
that it will be stratified or laminated and the strata will be disposed in planes
parallel with what may be termed the direction of flow of the electrical current
through the conductor when it is used as or in an electric circuit.
This I do by making a plastic mass, preferably of plumbago, fibre and water,
or other liquid and add thereto a suitable granular mineral substance, such as
gypsum. Suitable proportions by weight are plumbago 15 parts; fibre 1 part,
water enough to make a paste that can be readily pumped and granular mineral
substance I part but I do not limit myself to these proportions. After thoroughly
mixing the ingredients I place the mixture in a mould A (Figure 3) having in the
bottom, top or side (as the case may be) a series of small passages. Then upon
forcing a plunger into the mould, under heavy pressure, the water or other liquid
in the mixture will be forced to pass out through the small openings a the fibre and
the granular material acting as a filter and preventing the escape of the plumbago,
while the fibres and the particles of plumbago will be turned in the direction of
flow of the water or other liquid and will thereby be caused to lie parallel, or
substantially parallel, with the face of the plunger. When the material is removed
from the mould it is dried so as to completely rid the mass of any moisture, and is
then submerged in a drying oil, or equivalent binder which, when it has become
hardened (preferably under artificial heat) binds the mass together.
The oil treatment may be omitted in cases where the strengthening and
toughening of the composition resulting from such treatment are not essential, or
on the other hand, when the oil treatment is used, the fibre may, in some cases, be
omitted from the compound.
In making commutator brushes or are light pencils, the pressure is exerted in a
direction transverse to the length of the desired article, so that the strata, lying in
planes parallel with the face of the plunger, will, when the commutator brush is
shaped as shewn in Figure 2, or the arc light pencil is shaped as shewn in Figure 1,
lie in planes parallel with the direction of flow of an electric current through the
conductor, when in use.
I have found that a conductor with the strata so arranged offers less resistance

page_text: to the electric current than does one in which the strata are in planes transverse to
the flow of the current.
Another advantage gained by the disposal of the strata in the manner herein-
before described, is that, in commutator brushes, the strata are presented on end to
the commutator, so that the commutator brush does not wear away so fast as it
would do if the strata were arranged in a different manner.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed declare that what 1
-claim is :-
1. An electric conductor composed of particles of plumbago disposed in strata,
which lie in planes parallel with the direction of the electric current.
2. An electric conductor composed of particles of electric conducting carbon and
divided fibre disposed in strata, which lie in planes parallel with the direction of
:the electric current.
3. An electric conductor composed of particles of electric conducting carbon,
united by an oil or equivalent binder, and disposed in strata, which lie in planes
parallel with the direction of the electric current.
Dated this 6th day of September 1892.
J. H. JOHNSON & Co.,
Agents.