Improvements in Electric Arc Lamps.
Year: 1890

page_text: Date of Application, 28th July, 1890-Accepted, 30th Aug., 1890
COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
I SAMUEL PLEASANTS PARMLY of 1007 Opera House Block, Chicago, Illinois,
United States of America, Engineer, do hereby declare the nature of this invention,
d in what manner the same is to be performed, to be particularly described and
scertained in and by the following statement :-
My invention relates to electric arc lamps and is shewn in the accompanying
drawing.
Figure 1 is a side view of a single lamp.
Figure 2 of a double lamp.
Figure 3 a single lamp at right angles to the view shown in Figure 1.
Figure 4 a modification.
Figure 5 a horizontal section through the same.
Figure 6 is a section through the upper carbons of figure 1.
Figure 7 is a modification."
a is the case. a is the carbon rod; a² a³ are the two upper carbons secured to
said carbon rod by the set screws a' a' and opposed to the lower sheet carbon a*,
supported on the holder a³. as a are the portions of the frame. Bis the case which
contains the regulating mechanism of the double lamp, B¹, c', carbon rods, B² B³, the
two upper carbons secured to the rod B' and two upper carbons secured to the
rod c. Be are the respective lower sheet carbons, Be their holders and B B
the supporting frame. Dis the carbon rod of the modified form, which has secured
to it the multiple upper carbons D1 D2 D3 D4, opposed to which is the enlarged lower
carbon D. The lower carbon is made in sheet form having one diameter substantially
the same as that of the single upper carbon, and its other diameter substantially the
same as the distance between the outer edges of the opposed upper carbons. Of
course these proportions may vary considerably, but what I have shown is the preferred
form. I may also round the corners of the lower carbons, as indicated in figure 3,
but substantially this would result from the process of burning.
I have also
contemplated placing the upper carbons in actual contact with each other, or even
rolling them out so that they will be connected by a short rib, or so that the sides of
the upper carbons would be corrugated, as it were, as shown in figure 7, but the
result would be practically the same and hence I consider such a carbon substantially
the same as what I have shown. This would be true at least in respect to certain
features of the lamp. Any sort of regulating mechanism can of course be used,
and I do not dwell upon these matters as they are immaterial to my invention.
:
Referring to the lamps shown in figures 1 and 3 when the lamp is out of operation,
the two upper carbons would normally rest upon the lower carbon or in contact
therewith. When the current is applied the regulating or lifting mechanism in the
case a raises the carbon rod a' and both carbons a² and a³, thereupon an are will be
established between one of said carbons a² and a³ and the lower carbon a*. I have
found by experimenting that this lamp will form its are in a lower voltage than in the
case of a lamp similar in all other respects, except that the carbon a' is divided into
two carbons similar to the upper pair. I also find that in the process of burning, the
carbon a², if it should happen to be the first to establish the arc, will induce the
formation of a sort of cone upon the opposed surface of the carbon a', and the adjacent
portions of such carbon will scale away. After a time, in the process of feeding and
burning, the carbon a³ will come in contact with the opposed portion of the carbon a*
whereupon the arc will be extinguished in the carbon a' and established in the
carbon a³. A similar cone will now form in the carbon a and in this manner the
arc will shift at intervals of a few minutes from cone to cone of the lower carbon a*.
The lower carbon a', being of the size and shape indicated in figures 1, 2, 3 and 6,

page_text: will be kept warm or hot, and hence when the arc shifts from one cone to the other,
or from one of the upper carbons to the other, the shifting takes place with very little
noise and it is not necessary for the lower carbon to be reheated, as would be the case
were two distinct carbons substituted for the carbon at. It is thus part of the object
of my invention, while having distinct carbons above or at the pair upon which the
current of electricity is received or at one electrode to have a single large carbon
below or at the other electrode which will thus freely receive the current so as to form
an are at a low voltage and will also remain constantly heated throughout its upper
portion so as to avoid the noise and unsteadiness of the light incident to the shifting of
the arc.
It is also part of the purpose of my invention to have the lower carbon or one
electrode so constructed and of such size and shape as will cause the formation of the
cones above referred to in opposition to the points of the upper carbons. I find that
these cones are best formed when the parts have the proportions indicated. I have
also discovered by experiments, that if both the upper and lower carbons should be
made of sheets of carbon presenting parallel edges, that the arc shifts from one point
to another with great rapidity and regularity, and I also find that by use of two
carbons above, the arc is localized, as it were, for a definite and considerable period as
to the carbon a'. In this manner I am able to provide a lamp which will burn twice
as long as if but one of the two upper carbons were employed and will do so with a lower
voltage and with comparative fixedness of light and without most of the disadvantages
incident to an alternation of the arc. I can of course apply more than two carbons
above, as illustrated in figures 4 and 5, where quadruple carbons are shown, but here
the advantges which I have above enumerated as appertaining to my invention are to
a, certain degree abandoned though the length of burning of the lamp is increased. For
many purposes it is immaterial which electrode is provided with the single carbon,
whether the upper or lower.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is:
A multiple carbon lamp whose electrodes approach end to end, one of them composed
of a single strip or sheet of carbon and the other of two or more carbon pencils, as
shown and described.
FREDERIC PRINCE,
1, Quality Court, Chancery Lane, W.C., Agent for Applicant.