Improvements in Caps for Enclosed Electric Aro Lamps.
Year: 1898

page_text: Date of Application, 10th June, 1898-Accepted, 10th Sept.,
1898
COMPLETE SPECIFICATION.
Improvements in Caps for Enclosed Electric Aro Lamps.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Charles E
Harthan, residing at Lynn, in the County of Essex, State of Massachusetts,
United States of America, Electrical Engineer), and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement. -
arc
This invention relates to the cap which surrounds the upper carbon of electric
arc lamps, and rests on the top of the small globe or cylinder surrounding the
The object of the invention is to provide a cap for the arc-enclosing cylinder
which will properly regulate the admission of air to the globe and at the same
time withstand the heat to which it is subjected
In the accompanying drawing, which shows an embodiment of the invention,
Figure 1 is a side elevation, partially in section, of an inner globe with the cap
in section, and Figure 2 18 a perspective view of the cap
The lower carbon A is mounted in a suitable holder carried by the lower portion
of frame M The upper carbon B is situated directly above the lower carbon
and in line therewith Surrounding the entire lower carbon and a portion of
the upper carbon 18 a small globe or cylinder D designed to protect the arc from
currents of aur, and also to prolong the life of the carbons The cylinder is held
in place by a suitable holding device C which also prevents the entrance of air
to, or the exit of gases from the cylinder Situated on top of the cylinder is a
cap E having a flange F which is finished on the underside where it rests on the
cylinder, but no attempt is made to make an air-tight joint at this place, the air
being prevented from entering in a manner hereinafter described
The flange
being larger than the cylinder and flat on its under side, the cap 18 free to adjust
itself slightly to compensate for slight irregularities in the carbon
Situated below the flange F and connected thereto by a hub H is a flange G
which is somewhat smaller than the inside of the cylinder, and these flanges,
with the cylinder D, form walls of a circular chamber L containing a mixture
of gas from the arc and pure air, which prevents the sudden rush of air into the
cylinder
The center of the cap is bored out slightly larger than the carbon so as to
permit the latter to pass freely up and down Surrounding the carbon and
formed in the hub are two or more circular chambers I, containing a mixture
of air and gas preventing the sudden admission of pure air to the cylinder In
the present instance two small circumferential chambers I are employed, as this
is sufficient to check the flow of air in the particular type of lamps shown, but
for other types of lamps three or even more chambers may be emploved
It has been customary heretofore to surround the upper carbon by a single
large circular chamber containing a much larger amount of mixed air and gas from

page_text: the chambers I, but it has been found that the arrangement shown is much more
satisfactory, the small chambers tending to interrupt the influx of pure air more
effectually than one large chamber:
So far as known the present invention is the first instance of an enclosed are
lamp having a chamber surroundmg the upper carbon for preventing the un-
limited entrance of air at this point, with a circumferential chamber formed in
the outer edge of the cap near the point where it rests on the cylinder, for pre-
venting the free entrance of air at this point, furthermore, the present invention
is the first instance of a cap for an enclosed arc lamp, which has a plurality of
small chambers surrounding the carbon, with a large circumferential chamber
near the outer edge of the cap for preventing the free entrance of air at this point,
the outer and inner chambers being independent of each other
Situated above the cap and carried by a suitable support J is a cluteh K which
grips the carbon and moves it up and down. The clutch is provided with tripping
Jaws K¹ which under certain conditions strike on the top of the cap and permit
the carbon to feed downward
In the statement of invention is outlined what at present is believed to be the
mode of operation of the improved construction described and claimed It will
be understood however, that the theoretical statements made are not to be,con-
strued as limitations as the invention resides in the construction alone and the
mode of operation may hereafter be found to be different
The action of the invention 18 as follows, as the upper carbon B moves up
and down, it creates local eddy currents in the circular chambers I, which oppose
the free passage of pure air into the cylinder, and air is prevented from entering
the cylinder around the edges of the cap by the eddy currents created in the
chamber L, due to the difference of pressure between the inside and outside of
the cylinder
It has been found that by properly proportioning the internal chambers I and
the external chamber L, the mixture of gases and oxygen in the cylinder 18 such
that the carbons will be consumed slowly and the life of the carbons correspond-
ingly increased This cap is very simple in construction, requires only a very
small amount of machine work, and is capable of successfully regulating the
admission of air to the cylinder
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same
is to be performed, we declare that what we claim is -
1. In a cap for the cylinder of an enclosed electric arc lamp, the combination
of an opening for the carbon to pass through, an air chamber surrounding the
opening and in communication therewith, the chamber acting to prevent the free
entrance of air around the carbon, and a second chamber formed in the cap near
the inner periphery of the cylinder for preventing the free entrance of air around
the top of the cylinder
2. In a cap for the cylinder of an enclosed electric arc lamp, the combination
of an opening for the carbon to pass through, a plurality of small air chambers
surrounding the opening, each in communication therewith, the said chambers
acting to prevent the free entrance of air around the carbon, and an additional
chamber also formed in the cap near its outer periphery for preventing the free
entrance of air around the top edge of the cylinder, the said chamber having no
direct communication with the small air chambers.
3. In a cap for the cylinder of an enclosed electric arc lamp, the combination of a
flange which rests on the top of the cylinder, a second flange situated below the
first, a hub connecting the two flanges and acting with the flanges to form a
chamber, a carbon opening in the hub, and a plurality of small chambers also
formed in the hub, which surround and communicate with the carbon opening
4 In a cap for the cylinder of an enclosed electric arc lamp, the combination
of a flange which is greater in diameter than the top of the cylinder and rests

page_text: thereon, a second flange parallel with the first which is less in diameter than the
inside of the cylinder, a hub connecting the two flanges, but at the same time
separating them so as to form a circular air chamber, a carbon opening formed in
the hub, and a plurality of small circular air chambers surrounding and com-
municating with said opening.
Dotad the 0th 1 of Tu 1900
THE BRITISH THOMSON-HOUSTON CO, LTD
A. R MONKS,
Director,
ALFRED CLEMENTS
Assistant Secretary