Improvements in Filaments and Carbons for Electric Lamps.
Year: 1895

page_text: Date of Application, 25th Jan., 1895
Complete Specification Left, 23rd May, 1895-Accepted, 29th June, 1895
PROVISIONAL SPECIFICATION.
Improvements in Filaments and Carbons for Electric Lamps.
I, PETER STIENS, of 15 Carroun Road, Clapham Road, in the County of
Surrey, Electrical Engineer and Constructor, do hereby declare the nature of this
invention to be as follows:-
With a view to improve the carbon filaments of incandescent lamps and to increase
the light which they emit, it has been before proposed to treat such filaments with
boric acid.
Up to the present time the advantages sought to be derived by this treatment have
not been satisfactorily attained.
The cause for this I find to be that the boric acid has not been properly and suitably
prepared. It is necessary that the boric acid should in the first place be burnt or
exposed to high heat. It may afterwards be dissolved in water or other solvent
or it can be applied in a finely powdered state.
If the filament or the material for forming the filament be already in the solid
state it is to be boiled in a solution of the burnt or prepared boric acid or it is to be
dusted over with the powder or both.
If the material for making the filament be originally in a liquid state the burnt
or prepared boric acid is to be mixed with the liquid material from which the
filament is to be formed.
Also after carbonisation the filament
In either case the filament is carbonised.
may be treated with the burnt or prepared boric acid.
The result is that the burnt or prepared boric acid thoroughly impregnates
the filament and renders it highly resisting and of high luminosity when in use.
The filament is to be flashed by the electric current in a vacuum to which a small
quantity of carburetted hydrogen is admitted.
A filament of vulcanised fibre may thus be prepared with great advantage.
I also use burnt boric acid in preparing the carbons for electric arc lamps
and thereby I render the carbons more durable and increase the luminosity when
in use.
Dated this 18th day of January 1895.
COMPLETE SPECIFICATION.
Improvements in Filaments and Carbons for Electric Lamps.
I, PETER STIENS, of 15 Carroun Road, Clapham Road, in the County of
Surrey, Electrical Engineer and Constructor, 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 :-
With a view to improve the filaments and carbons for electric lamps and to increase.
LD

page_text: the light which they emit, a treatment with 'horic acid has before been proposed. Up
to the present time the advantages sought to be derived from this treatment have not
been satisfactorily attained.
The cause for this I find to be that the boric acid has not been suitably prepared.
It is necessary that the boric acid should in the first place be burnt or exposed to a
high heat. This may conveniently be done in an open crucible of graphite; the
crucible is placed in a furnace and it, with its contents, is raised to a white heat.
The boric acid melts and whilst it is in this state the crucible is left in the furnace
for two or three hours; the crucible is then lifted out and the charge poured upon
a slab, preferably of graphite. When cold the glass like mass is pounded and
sifted so as to obtain as fine a powder as is practicable.
I proceed to incorporate this burnt boric acid with the filament or carbon.
If a filament suitable for an incandescent lamp is to be prepared say from
vulcanised fibre (or it might be from any other of the solid materials commonly
employed for the purpose) I prepare strips of suitable length and thickness, I
place them in a vessel preferably of glass and I boil them, using sufficient water
to enable the strips to move about freely in the water and in the water I have an
excess of the finely powdered burnt boric acid that is to say considerably more
than the water is able to dissolve. I continue the boiling for some hours by
which time the strips will appear white from the burnt boric acid adhering to them.
After having been thoroughly dried the strips are laid around a mandril or other-
wise brought to the form required and then they are carbonised and at a high heat
in any of the ordinary ways. After carbonization the filament is carefully dusted
over with the finely powdered burnt boric acid and preferably to enable the powder
the better to adhere I previously dip the filament into benzine. The filament being
thus coated I place it in a glass enclosure holding its ends by metal clips so that an
electric circuit may be closed through it.
I remove the air from the enclosure and when a good vacuum is obtained I open
a connection with a flask containing benzol; or in any other of the well known
ways admit to the glass enclosure a carbonaceous vapour or gas. I again exhaust
the enclosure down to a pressure of a few millimetres and then I pass an electric
current through the filament commencing with a small current and gradually
increasing it until the difference of potential between the two leads is much greater
than it will be in the after use of the filament, the filament consequently emits a very
brilliant light. On cooling the filament will be found to have a metallic lustre. The
after treatment in the manufacture of the lamp and the "standardising" or adjusting
the resistance is as heretofore.
If filaments are to be made from a liquid or semi-liquid material such for example
as dissolved cellulose then I mix the finely powdered burnt boric acid with the
liquid or semi-liquid material and in this way I introduce as much of the powder
as I can without interfering with the usual mechanical operations for producing
filaments therefrom. The carbonization is conducted as heretofore. Also after
carbonization I expose the filaments to the further treatment with boric acid and
carbonaceous vapour or gas as hereinbefore described. Also in the manufacture
of carbons for the arc lamp I use burnt boric acid. I mix it with the other materials
from which the carbons are moulded. The quantity of burnt boric acid so employed
may be varied but ten per cent. will produce a good .result. I can also with good
effect boil the carbons with burnt boric acid.
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.:-
1. Filaments and carbons for electric lamps prepared with burnt boric acid.
2. The treatment of filaments and carbons in course of manufacture by boiling
them with burnt boric acid.
3. The treatment of filamente in mouton at

page_text: them with burnt boric acid and then heating them by the electric current in the
presence of carbonaceous vapour or gaɛ.
4. The manufacture of filaments and carbons for electric lamps substantially as
herein described.
P. STIENS.