IMPROVEMENTS IN CARBON FILAMENTS FOR INCANDESCENT ELECTRIC LAMPS
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
We FREDERICK HENRY VARLEY of Newington Green Road, WILLIAM BEALE
of 370 Holloway Road, and ROBERT HENRY PADBURY of Mildmay Grove all in
the County of Middlesex do hereby declare the nature of our Invention for
IMPROVEMENTS IN CARBON FILAMENTS FOR INCANDESCENT ELECTRIC LAMPS to be
as follows:-
This Invention relates to improvements in incandescent lamps whereby a larger
luminous area of light is obtained.
This we effect by subjecting fine woven fabric preferably made of a vegetable
fibre, or silk to the treatment as described in Letters Patents granted to Frederick
Henry Varley numbered 2776 and 5055 A.D. 1882.
Previous to submitting the fibrous material to the carbonizing process it is
subjected to treatment in borax and alum.

page_text: COMPLETE DE MULTICATION.
We, FREDERICK HENRY VARLEY of 82 Newington Green Road, Islington,
Electrical Engineer WILLIAM BEALE, of 370 Holloway Road, Confectioner and
ROBERT HENRY PADBURY of 24 Mildmay Grove, Engineer all in the County of
Middlesex do hereby declare the nature of our Invention for "IMPROVEMENTS IN
CARBON FILAMENTS FOR INCANDESCENT ELECTRIC LAMPS
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 incandescent lamps whereby a larger
luminous area of light is obtained.
This we effect by subjecting fine woven fabric preferably made of a vegetable
fibre or silk to the treatment as described in Letters Patents granted to Frederick
Henry Varley numbered 2776 and 5055 A.D. 1882.
Previous to submitting the fibrous material to the carbonizing process it is
subjected to treatment in borax and alum.
That is to say we employ preferably silk or cotton muslin or other fibrous or
woven material which we cut into suitable sized pieces generally about one foot
wide by two feet long the size being. determined by the capacity of the converter
as described in Letters Patent granted to Frederick Henry Varley numbered 2776
and 5055 AD 1882.
When cotton muslin is employed we subject it to a warm solution of caustic
soda or other alkali after which it is repeatedly rinsed in distilled water till the
same is perfectly cleaned and free from the alkali.
It is then dried and afterwards iminersed in a heated saturated solution of
borax and allowed to remain for about an hour or for such time as the capillaries
shall be filled with borax solution.
After which it is taken out and immediately immersed in acid to precipitate
boracio acid into and upon the fibres whilst the neutral or acid salt of soda remains
in the solution, after repeated rinsing to remove the acid and salts the fabric is
again dried and is then ready for being immersed either in molten paraffin wax
paraffin oil or other suitable hydro carbons.
We find that strong acetic acid or a solution of alum or sulphuric acid diluted in
the proportion of one part of acid to two of water—gives a rapid and firm deposit
of Boracic acid, but other acids may be employed.
When a sufficient number of the sheets are prepared a book is made up by
laying sheet upon sheet-When India muslin or other very fine fabric is employed
we make the book preferably of alternate sheets of muslin and fine twill to
facilitate their separation after carbonization.

page_text: With silk the process is similar—but only a weak solution of caustic alkali is
used in the first part of the preparation and sometimes omitted, the borax solution
being sufficient to effect the cleansing of the fibre as well as preparing it for
boronizing We also employ platted woven and twisted threads made of silk or
fibrous material and treated in the manner above described-Such threads are
wrapped on carbon moulds made preferably of flexible carbon so as to shape them
in the loop form or other suitable shape, and they are likewise immersed in
paraffine oil or other hydro carbon.
Thus prepared they are packed into the converters and subjected to the heat
requisite as already described in Letters Patent 2776 and 5055, 1882.
When the furnace is sufficiently cooled the carbon is taken out and the sheet is
cut up into strips or bands of widths varying from one to any desired number of
threads either in the direction of the weft or woof of the material or otherwise as
may be desirable.
Fibrous conductors made of Boro-Carbonized Indian muslin have a diaphanous
appearance they likewise present to the current a multiple conductor the filaments
of which radiating upon each other conserve the heat and thereby render the
filament or diaphanous conductor more economical whilst giving a broader luminous
area than solid filaments.
The twisted platted or woven thread made of multifilar conductors also possess
the advantage of conserving the heat whilst the separate conductors comprising
the compound filament act as compensators preventing undue strain through over
incandescence.
In lieu of Boracic acid precipitated into and upon the fibres, we sometimes use
Boro Glyceride-for this purpose or Boron and Alumina-the latter being obtained
by the precipitation of Alumina from Alum in conjunction with Boracic acid in a
manner similar to that already described in the borax and acid treatment in which
the alum solution replaces the acid or other preparation of Boron may be used.
The filaments are connected with platinum wires and the same inserted in glass
bulbs and exhausted in the usual manner-we prefer for attaching the filament to
the platinum conductor to use a carbon socket made from the stems of grass-
treated in the like manner as the filaments and converted into a Boron Carbon
conductor the tube of carbon thus obtained is a conductor in which the fibres run
nearly parallel, and in some cases we use it as a filament in place of woven
materials. We also use the blades of grass for the above purposes.
We cut the carbonized tubes into short lengths for sockets and select the
diameter suitable for the carbon multifilar conductor-for broad bands and
filaments we flatten the grass stem previous to Boro-carbonizing so that it forms an
elongated socket into which the broad filament can be inserted-we complete the
connection by preparing a cement made from fibrous carbon ground very fine and
mixed with water containing chemically precipitated carbon-such as that obtained
by the reaction of sulphuric acid upon syrup glycerine & in some cases after the
filament is attached to the platinum holder by means of the cement and socket
already described-we immerse it in a warm solution of glucose syrup or any
saccharine material or starch & and then by a strong acid precipitated into the
pores of the carbon chemically deposited carbon-The filament is washed free of
acid.
And then dried in a hot air or by immersing into hot molten paraffin wax.
They are next placed in a chamber containing nitrogen gas or other suitable
non-supporter of combustion when they are rendered incandescent by passing an
electric current through the filament the current being increased until the right
degree of temperature is obtained for reducing the boracic acid into conducting
boron and the chemically deposited carbon into conducting graphite. The com-
pound filament is then ready for fixing into the glass bulb previous to exhausting
and completion of the glow Lamp.

page_text: Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that we
claim is
1st the said invention of Improvements in carbon filaments for incandescent
electric Lamps such filaments being composed of multifilar conductors prepared and
carbonized substantially as herein set forth and described.
2nd the employment of conductors or filaments for incandescent lamps wherein
Boron forms part of the conductor substantially as berein set forth and described.