Improvements in or connected with Electric Arc Lamps.
Year: 1898

page_text: Date of Application, 3rd Oct., 1898
Complete Specification Left, 3rd July, 1899-Accepted, 19th Aug.,
1899
Improvements in or connected with Electric Arc Lamps.
I, GEORGE THOMAS-DAVIES, of 53, Primrose Mansions, Battersea Park, in the
County of London, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention for improvements in or canected with electric are lamps has
for its object to increase the life of the carbons by increasing their sectional area
without impairing the light-emitting efficiency, and consists in employing for
each pole or electrode two or more carbons each of a relatively small section.
In use if the separate carbons constituting each pole are not very close together
or in contact throughout their burning length the are actually takes place between
a single carbon of one pole and a corresponding carbon of the other pole and
that when in consequence of the feeding together of the carbons, another or other
pairs come into contact, then the arc will be struck between that pair or one
of those pairs and will continue between that one until in consequence of the
feeding together of the two sets another pair come into contact.
In enclosed arc lamps the separate carbons constituting each electrode or pole
may be in contact or very nearly so throughout their burning length in which case
the arc can travel from one carbon to the other without restriking and without
flickering or necessarily feeding into contact.
This invention is specially applicable to lamps of the type in which the two
carbons or electrodes of the lamp are arranged vertically side by side or at a
small angle to one another.
1000
Improvements in or connected with Electric Arc Lamps.
I, GEORGE THOMAS-DAVIES, of 53, Primrose Mansions, Battersea Park, in the
County of London, Engineer, 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:-
It iswell known that the light radiation efficiency as compared with the power
consumed in an electric arc is diminished by the use of carbons for electrodes the
section of which is very large compared with the current flowing.
On the other hand by the use of carbons of small section as electrodes the luminous
17

page_text: efficiency of the arc is largely increased.
obstruction of light caused by large carbons.
This is so for reasons apart from the
This invention for improvements in or connected with electric are lamps has for its
object to increase the life of the carbons by increasing their sectional area without
impairing the light-emitting efficiency, and consists in employing for each pole or
electrode two or more carbons each of a relatively small section.
In use if the separate carbons constituting each pole are not very close together or
in contact throughout their burning length the are actually takes place between a
single carbon of one pole and a corresponding carbon of the other pole and when in
consequence of the feeding together of the carbons, another or other pairs come into
contact, then the are will be struck between that pair or one of those pairs and will
continue between that one until in consequence of the feeding together of the two
sets another pair comes into contact.
In enclosed are lamps the separate carbons constituting each electrode or pole may
be in contact or very nearly so throughout their burning length in which case the
are can travel from one carbon to the other without restriking and without flickering
or necessarily feeding into contact.
This invention is applicable not only to the usual type of arc lamps in which the
feeding motion of the inoving carbons is parallel to the axis of the carbons but also to
lamps of the type in which the two carbons or electrodes of the lamp are arranged
vertically side by side or at a small angle to one another as described in Patent
No. 10616 of 1898.
In practice the are at any moment springs from one carbon of each electrode and
this one carbon acts thermally for the time being as if it were a separate or single
carbon. If the several elements of an electrode thus composed are in contact with or
very near to each other throughout their length the seat of the arc changes from one
carbon to another without it being necessary for the mechanism of the lamp to
restrike the arc.
The two electrodes of the are may be composed of an unequal number of small
carbons; thus, in a continuous current are lamp the positive electrode may be of two
small carbons held side by side by being clipped so in the positive carbon holder
while the negative electrode may consist of a single carbon arranged so that which-
ever of the two carbons composing the positive electrode is longest will come in
contact first with the single negative carbon preparatory to striking the arc.
In the accompanying sheet of illustrative drawings
Fig. 1, shews the two electrodes constructed according to this invention and
suitable for a continuous current open type are lamp, and
Fig. 2 a plan of the same.
Figs. 3 and 4 are elevations at right angles to one another shewing the carbons
suitable for an alternating current enclosed are lamp.
Fig. 5 is a section plan of the carbons on the line ab Fig. 3.
Referring to Fig. 1 the two round carbons C1 and C2 are clipped side by side with
each other in the positive carbon holder A while a single carbon C3 is held in the
negative holder. C₁ at the moment being the longest element of the positive
electrode the arc is shown between C¹ and C³ and will continue so burning until C¹
has burnt away to such an extent that the end of C² being nearest to C³ the arc will
transfer itself to C² either by the latter actually coming in contact with C³ or by the
are shifting from C¹ to C² before contact takes place. The contact surface between C¹
and C2 is so small that very little conduction of heat takes place from the hot carbon
with the result that it behaves much as an isolated carbon of similar section and
becomes well heated while the idle carbon at its side is for the time comparatively
cool.
Referring to Fig. 3 the two small carbons C¹ and C are clamped side by side in the
carbon holder A and the two carbons C3 and C4 composing the other electrode are
clamped in the other carbon holder B. When the lamp strikes, whichever of the two
pairs of carbons C2 and C³ or C¹ and C+ are in contact will be the seat of the arc and
will continue so until the arc is transferred to the other pair by their greater

page_text: proximity. In reality when the arc is enclosed it will shift in its position between
(say) C2 and C3 and take its place between C¹ and C without contact necessarily
occuring between the latter pair.
It is to be understood that in a continuous current lamp where the section of the
positive carbon has to be greater than that of the negative, the negative carbons (say)
C3 and C may be replaced by a single carbon to act as the negative electrode occupy-
ing their medial position analogous to the arrangement Fig. 1 or again C and C+ in
Fig. 3 might remain and C¹ and C² be replaced by three carbons arranged similarly
side by side in the medial position to act as a positive electrode.
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. An electrode for an are lamp consisting of two or more carbons each of a relatively
small section and clamped in a single holder.
2. The improved electrodes for are lamps substantially as described with reference
to the drawings.
Dated
1000
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.