IMPROVEMENTS IN THE MANUFACTURE OF CARBON CONDUCTORS FOR INOAN- DESCENT ELECTRIC LAMPS
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by the said Edward Griffith Brewer
at the Office of the Commissioners of Patents on the 3rd May 1881.
EDWARD GRIFFITH BREWER of 33 Chancery Lane in the County of Middlesex
"IMPROVEMENTS IN THE MANUFACTURE OF CARBON CONDUCTORS FOR INOAN-
DESCENT ELECTRIC LAMPS" A communication from abroad by Thomas Alva
Edison of Menlo Park in the State of New Jersey, United States of America
Electrician.
In the so called and well known "Edison" lamps incandescing carbon conductors
have been used. Such carbons though differing in methods and materials used in
manufacture had in common certain unitary essential qualities viz. flexibility and
high resistance.
Graphite or plumbago graphotoidal silicon, boron and zerconium under some
circumstances are desirable and excellent materials to use for such conductors, but
their use has been impeded by the fact that no method or means had been devised
of treating them which would produce a flexible filamentary conductor having in
its small compass the necessary high resistance.
The object of this Invention is to furnish a method by which such incandescent
conductors may be made of the materials named and of allied substances all as
hereafter described.
First; The material used is reduced to an impalpable powder and where necessary,
thoroughly purified.

page_text: Second; By suitable pressure this material is pressed into sheets of the thickness
desired for the carbon loops or horse-shoes.
Third The material is then subjected while at a high heat to the action of
hydro-carbon vapour. (This step however may be deferred until after the next
herein noted.)
Fourth; From the sheets the conductors in the proper shape such as loops or
horse shoes are stamped or cut with enlarged ends for clamping homogeneous with
the body of the conductor.
If a greater resistance is desired than can normally be obtained with the
materials noted it may be attained by mixing therewith a proportion of powdered
carbon or charcoal the greater being this proportion the higher being the resistance
in the resultant carbons of any given density.
By this means carbon conductors or loops may be made of the materials noted,
possessing considerable flexibility and high resistance and which under certain
conditions and for certain purposes form a desirable, addition to the styles of carbon
now known.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Edward Griffith Brewer in the Great Seal Patent Office on the
3rd November 1881.
EDWARD GRIFFITH BREWER of 33 Chancery Lane in the County of Middlesex.
"IMPROVEMENTS IN THE MANUFACTURE OF CARBON CONDUCTORS FOR INCAN-
DESCENT ELECTRIC LAMPS." A communication from abroad by Thomas Alva
Edison of Menlo Park in the State of New Jersey, United States of America
Electrician.
In British Letters Patent No. 4576 and 5127 of 1879, 578 and 3765 of 1880
and 562 of 1881 various methods are described of manufacturing from various
materials, the incandescing carbon conductors for electric lamps. Such carbons
though differing in methods and materials. used in manufacture, had in common
certain unitary essential qualities; viz., flexibility and high resistance.
Graphite or plumbago, graphotoidal silicon, boron and zirconium under some
circumstances are desirable and excellent materials to use for such conductors, but
their use has been negatived by the fact that no method or means had been devised
of treating them which would produce a flexible filamentary conductor, having in
its small compass the necessary high resistance.
The object of this Invention is to furnish a method by which such incandescent
conductors may be made of the materials named and of allied substances.
The material used is reduced to an impalpable powder and where necessary
thoroughly purified. A quantity thereof is placed in a metal box sufficiently
strong to withstand a high pressure.
The box should have a perfectly smooth polished bottom, and edges or sides
extending upwardly so as to form a chamber about one sixteenth of an inch deep
or even more if relatively quite thick sheets are desired.
A die with smooth polished face is used, fitting into this box which is substan-
tially a mould and may be so designated.
The mold is filled with the pulverized material, the top thereof evened off and
the die brought down thereon with great pressure, for which purpose it is preferable
to use a hydraulic press.
The result is a sheet of homogeneous material whose density depends upon
the pressure used which may be varied to suit the requirements of special
purposes.
If it is desired to increase the resistance of the resultant material, the preferable
way is to incorporate with the material noted, before pressure into sheets, a
proportion of powdered carbon or charcoal, the larger the proportion of carbon or
charcoal used, the greater the resistance of the sheets of any given density.
As the density inay be varied by varying the pressure used and the resistance
regulated by proportioning the amount of pulverized carbon or charcoal mingled
with the basic material, it follows that both density and resistance may be regulated
to suit the varying requirements of different systems of lamps.
While all kinds of carbons may be used, as a rule the substances mentioned are
the easiest of manipulation.
If however it be desired to use carbons having little or no cohesion, such as
charcoal, it may be done by mixing therewith a fluid having in solution a hydro-
carbon, the menstruum being one that is readily evaporable; the resultant paste
being dried, powdered, pressed and treated with hydro-carbon vapor as hereinafter
noted.
From the sheets before noted the conductors or horse shoes are to be stamped or
cut and so that enlarged ends for clamping are made homogeneous with the body
of the conductor,

page_text: In such operation there is a certain percentage of loss or breakage. This
percentage materially reduced by treating the sheets with hydro carbon while
heated to incandescence or at least to a very high heat. To this end the sheets
may be placed in a closed flask or retort provided with means whereby hydro
carbon vapor may be passed therethrough, over and around the sheets, the flask or
retort placed in a furnace and the sheets brought up to a very high heat, or the
material may be heated by electrical incandescence while in a hydro carbon vapor
the result being that the material becomes tough and flexible.
Instead of the dry powdered material being placed in the mold, it may be made
into a paste or dough with any readily evaporable agent and the mold filled with
the paste or dough and allowed to dry.
After the sheets are formed the loops or "horse shoes" of any desired shape may
be cut or stamped out, and then treated with the hydro-carbon as described, instead
of the sheets being so treated before punching, cutting or stamping, but the latter
is preferable.
WHAT IS CLAIMED IS :-
First. The method of manufacturing incandescent conductors of the materials
set forth, consisting in pressing the material into sheets and then cutting or
stamping the conductors therefrom, substantially as set forth.
Second. The method of manufacturing incandescing conductors consisting in
pressing the materials named into sheets, then treating with hydro-carbon and heat
as described, and then cutting or stamping the conductors therefrom, substantially
as set forth.
Third. An incandescing flexible and high resistance conductor for electric
lamps formed of the materials noted and by the method described, substantially as
set forth.
Fourth. An incandescing conductor for electric lamps formed of graphite,
plumbago or graphotoidal silicon, boron or zirconium subjected to pressure and
the action of hydro carbon and heat, substantially as set forth.
Fifth. The method of varying the resistance of carbons formed of graphite,
plumbago or graphotoidal silicon, boron or zirconium by incorporating therewith
a proper percentage of powdered carbon or charcoal, substantially as set
forth.
Sixth. An incandescing conductor formed of the materials and in the manner
described and having enlarged ends for clamping, integral therewith, substantially
as set forth.
In witness whereof I the said Edward Griffith Brewer have hereunto
set may hand and seal this First day of November in the year of our
Lord One thousand eight hundred and eighty-one.
E. G. BREWER. (L.S.)