IMPROVEMENTS IN ELECTRIC LAMP APPARATUS.
Year: 1882

page_text: LETTERS PATENT to Herbert John Haddan, of Kensington Middlesex, for an
Invention of IMPROVEMENTS IN ELECTRIC LAMP APPARATUS. A communi-
cation to him from abroad by Charles Francis Brush, of Cleveland Ohio,
United States.
PROVISIONAL SPECIFICATION left by the said Herbert John Haddan at
the Office of the Commissioners of Patents on the 10th August 1882.
"
HERBERT JOHN HADDAN of Kensington Middlesex . " IMPROVEMENTS IN
ELECTRIC LAMP APPARATUS a communication to me from abroad by Charles
Francis Brush of Cleveland, Ohio, United States,
.
The invention relates to incandescent electric lamps and consists in the
combination with a filament of "horse shoe" or equivalent form of a screen
between the limbs; also in making filaments with a surface or surfaces 80
disposed that "radiant matter" projected from one limb of the filament and in
directions normal to the surfaces thereof will not be intercepted by the other limb;
or with a surface or surfaces so disposed that " radiant matter" projected from one
portion of the filament and in directions normal to the surface thereof will not
strike other portious of the filament-The screen may be made of metal, porcelain,
glass, or mica and of sufficient dimensions to screen and protect each limb of the
filament from the action of the flying molecules from the other limb, and may be
flat, curved, or tubular to enclose one limb, or each limb, or a split tube may be
used Two or more of such screens may be used-The lamps can be of any
suitable form or construction and the screen or screens, which may be opaque or
transparent, fixed in any convenient method-The incandescent filament is made
angular in cross section and so disposed that "radiant matter" from each limb
being projected in directions normal to the surface thereof will not strike the
other limb.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Herbert John Haddan in the Great Seal Patent Office on the
10th February 1883.
HERBERT JOHN HADDAN, of Kensington, Middlesex
"IMPROVEMENTS IN
ELECTRIC LAMP APPARATUS," a communication to me from abroad by Charles
Francis Brush of Cleveland, Ohio, United States
The invention relates to electric lamps, and especially to that class known as
incandescent electric lamps, wherein a filament of carbon or other suitable
conductor is raised to a high temperature by the passage of an electric current, and
is protected from oxidation by being enclosed in a transparent receptacle in which
is maintained as perfect a vacuum as possible; and it consists in devices hereinafter
specified, whereby the liability of the incandescent filament to spontaneous rupture
is largely diminished, and whereby it may safely be worked at a higher degree of
incandescence than heretofore; thus securing in the production of light, greater
economy of current energy, as well as greater durability.
It is well known that in incandescent electric lamps wherein carbon filaments
are used as the incandescing material, the best results are attained, and the greatest
durability secured, when the vacuum surrounding the filament is as perfect as it is
practically possible to make it; that is, when the residual gas has a density about,
or less than, one millionth its density at atmospheric pressure. But even under
these circumstances the filament is liable to break at any moment, especially if
worked at a high degree of incandescence; and it is also gradually disintegrated
and worn away, many of its particles being deposited on the glass envelope.
-
The well-known scientist, Mr. Wm. Crookes, F.R.S., has shown that gases under
the low pressures I have indicated possess properties quite distinct from those
displayed under ordinary circumstances, and he has given to the atoms or mole-
"Radiant Matter,"
cules of gases in this highly attenuated condition the name
Mr. Crookes has shown that radiant matter is thrown into violent commotion by
the presence of a highly negatively electrified body, and also by a highly heated
body. He has also shown that the particles of radiant matter are projected in
straight lines from, and in directions normal to, the surface of the exciting body,
and that the projected atoms or molecules are capable of exerting powerful
mechanical action on any object interposed in their path. Mr. Crookes calls this
phenomenon "Molecular Bombardment," and describes its action, under carefully
regulated conditions, as capable of mechanically beating refractory-solids to a white
heat, and fusing or disintegrating them. Under any circumstances in which this
molecular bombardment can obtain, its mechanical action on solid bodies is very
considerable. That this molecular bombardment obtains in the ordinary incan-
descent electric lamps with carbon filaments, there can be no doubt; and when the
horse-shoe form, or coiled form of filament is employed, each limb of the filament
is exposed to the destructive action of the gaseous molecules projected from the
other limb. The higher the temperature of the filament the more energetic does
this action become, while at the same time, the filament being subjected to greater
internal molecular strain, is less capable of resisting external violence. The action
of the flying molecules on the incandescent filament is two-fold: 1st, particles of
carbon are torn or ground off from the filament; the action in this case is analogous
to that of the well-known "sandblast." Owing to the irregular discharging or
projecting surface of each limb of the filament, the bombarding action is more
concentrated on some points than on others, and these points are more rapidly
worn away; 2nd, the filament is thrown into irregular and violent mechanical

page_text: vibration by the blows showered upon it. Finally the filament, which may at
first have been practically uniform in size and strength, breaks at the point where
the attack upon it is most energetic.
I avoid the above described evils by constructing incandescent electric lamps
with a suitable screen between the limbs of the bent filament thereof, whereby the
radiant matter" projected from any part of the latter is prevented from exerting
its destructive action on other portions.
In the drawings, Fig. 1 shows, in vertical and horizontal cross-section, an incan-
descent electric lamp embodying the invention. Figs. 2 and 3, illustrate modified
forms of screen.
In Fig. 1, ab are the usual platinum conductors passing through the glass stem c,
and attached to the ends of, and supporting the bent filament d, of incandescing
material. E is a screen, preferably of glass, and in the form of a small rod or tube,
attached by fusion or otherwise to the glass stem c, and lying in the plane of the
filament loop d d. H is the glass globe enclosing the parts before described, and
in which the customary high vacuum is maintained.
Now since the "radiant matter" within the chamber H is projected in straight
lines from all parts of the incandescent filament d, each limb of the latter is
protected from the action of the flying molecules from the other limb, by the
interposition of the screen E.
Fig. 2 shows a flat screen E, preferably of glass or mica.
Fig. 3 indicates the screen E arranged as a tube enclosing one limb of the
incandescent filament d. The tube E (of glass or other transparent material) may
be split at one side as shown, to facilitate construction. Each limb d of the
filament may be provided with a tubular screen if desirable.
In carrying out this portion of the invention, I do not limit myself to any
particular form of incandescent electric lamp, nor to any particular formn or
construction of the screen E, nor to any particular material of which the screen
shall be made; metal or other opaque substance may be used if desired. Neither
do I limit myself to any particular manner of attaching or supporting the screen E.
The invention also embraces another method of avoiding the evils due to
"molecular bombardment in an incandescent electric lamp, which consists in
giving the incandescing filament such a form of cross-section that "radiant matter"
from each limb of the filament, being projected in directions normal to the surface
thereof, will not strike the other limb."
"
In the drawings, Fig. 4 shows, in vertical and horizontal cross-section, an
incandescent electric lamp embodying this form of the invention.
Fig. 5 is an enlarged view of the filament d d of Fig. 4, in cross-section.
Fig. 6 is an enlarged view of various forms of cross-section of filament.
In Fig. 4 the parts a, b, c, d, and H are similar to those represented by the same
letters and described in connection with Fig. 1; but the filament d is made
angular in cross-section, and is so bent that an angular side of each limb faces the
other limb, as shown in Fig. 5, which is an enlarged cross-section view* of the-
limbs of the filament. The straight lines in Fig. 5, drawn normal to the surface
of the filament d, show the directions in which radiant matter is projected
therefrom, and illustrate how the "radiant matter" from each limb of the filament
is so directed as not to act on the other limb.
"
"
Fig. 6 illustrates a few of the many forms of filament cross-section which may
embody the last described feature of the invention:
Having described the invention in its various forins, I claim :-
1st. An incandescent electric lamp having an incandescing filament or conductor
of "horse-shoe" or equivalent form, and provided with a screen between the limbs
of the said filament, substantially as and for the purpose set forth.
"
2nd. In an incandescent electric lanp, the combination of an incandescing
filament or conductor of "horse-shoe or equivalent form, and a screen located
between the limbs of the said filament, substantially as and for the purpose
described.

page_text: 3rd. An incandescent electric lamp having an incandessing filament or conductor
of "horse-shoe" or equivalent form, the said tilament having surface or surfaces so
disposed that "radiant matter" projected from one limb of the filament, and in
directions normal to the surface thereof, will not be intercepted by the other limb,
substantially as and for the purpose set forth.
"
4th. An incandescent electric lamp having an incandescing filament or conductor
of "horse-shoe or equivalent form, the said filament having surface or surfaces so
disposed that "radiant matter" projected from one portion of the filament, and in
directions normal to the surface thereof, will not strike other portions of the
filament, substantially as and for the purpose described.
In Witness whereof I the said Herbert John Haddan have hereunto set
my hand and seal this 6th day of February A.D. 1883.