A New or Improved Electric Arc Lamp Carbon, and Apparatus for the Manufacture. of the same.
Year: 1896

page_text: Date of Application, 4th Mar., 1896-4ccepted, 15th Aug., 1896*
COMPLETE SPECIFICATION.
A New or Improved Electric Arc Lamp Carbon, and Apparatus for
the Manufacture. of the same.
A communication from abroad by THEODORE M. FOOTE, of 197 South Canal
Street, in the County of Cook and State of Illinois, United' States of America,
Gentleman.
I, JAMES GRIEVE LORRAIN, M.I.E.E., M.I. Mech: E., of Norfolk House,
Norfolk Street, Strand, London, W.C. in the County of Middlesex, Chartered
Patent Agent, do hereby declare the nature of this invention (as communicated
to me from abroad) and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
This invention relates to a new or improved carbon pencil for are lamps, and to
apparatus for the manufacture of the same.
In the operation of the arc lamp it is well known that the consumption and.
manner of burning off of the carbon particles under the action of the electric
current causes a crater to form at the end of the positive carbon and a pointed'end
on the negative carbon.
Owing to the well known evident fact that the current selects the shortest path
of travel between the carbons in the practical' use of the arc lamp it has been
ascertained that the formed are interval across which the current passes is
constantly shifting, travelling circularly about the edge of the crater of the.
positive carbon and causing shadows, unsteadiness and other objectional results.
The arc interval shifts and travels thus about the crater of the positive carbons by.
reason of. the irregularity of. the edge about the crater. For instance the current
disintegrates a portion of the carbon at one point on the edge of. the crater, thus.
forming a notch in said edge and the current then immediately shifts to the shorter
path across the arc offered by that higher portion of the edge of the crater beyond
the notch until that portion is disintegrated and carried off and. the width. of the
notch increased, this action taking place successively, the current seeking
constantly the shortest arc and shifting about the whole of the circle formed by
the edge of the carbon about the crater. It is evident that as the circular edge
of the crater is comparatively small the current at the arc will consume quite a
considerable portion of its circumference at one time and that in burning out and
carrying away a large portion of the carbon on one side the raised 'portion of the
carbon of the pencil on the opposite side obstructs the rays of light preventing its
diffusion radially in all directions and thus forming shadows which shift and change
position as the are travels about the circle or edge of the crater.
The object of my, invention is to overcome these disadvantages and to provide a
carbon which shall radiate and diffuse the light in all directions,, which shall'
provide a steadier,,clearer. light. of greater luminosity, which carbon may be made
and formed with less difficulty, and which shall present' such a.construction as to
cause more perfect consumption of the carbon particles.
My invention has certain other objects in view and consists in certain features
to be particularly described, reference being now had to the accompanying
drawings in which:
Figure 1 is a side view of one of my improved carbons.
רד
~ of Figure 1

page_text: Showing
having a circularly formed end or bottom.
Figure 4 is a view similar to Figure 2 showing the groove with somewhat more
flaring sides.
Figure 5 is a view similar to Figure 3 with the groove made straight sided and
having a square end or bottom.
Figure 6 is a cross section of an elliptical carbon embodying my improvements.
Figure 7 is a side view of a mould for forming and producing this character of
carbon.
In carrying out my invention I provide a carbon A, of the ordinary character,
either straight or semi-circular and form a groove B therein for the whole length
thereof, as shown. It is obvious however that if desired the groove may terminate
at a point below the upper end of the carbon in order to provide a solid end which
is inserted in the carbon holder.
It will be particularly noted that the longitudinal groove B in the carbon A
extends into the carbon for a certain and determined depth of the curved or
circularly formed carbon and the importance of this feature will be particularly
pointed out.
As previously stated, the arc interval forming across the shortest path between
the carbons causes the formation of a relatively higher and lower portion upon
each side of the crater of the carbon, the arc interval constantly shifting in a
circular path about said edge. As the current at the arc consumes quite a con-
siderable portion of the circumference of the circular edge about the crater it is
evident that if a considerable portion of said edge be notched or cut away prior to
the application of the current and this cut out or notched portion maintained
present constantly at said edge during consumption, the arc interval cannot travel,
in shifting, continuously about the circular edge around the crater. It is ascer-
tained in the practical use of these carbons that the arc interval shifts or moves
within a very materially circumscribed path of travel owing to the ever present
cut out or notched portion maintained by the groove B in the circular edge of the
crater, and instead of moving continuously about the circular path of the edge of
the crater the said arc interval simply shifts or moves alternately back and forth
between the two sides of the groove B about the edge of the crater. With this
limitation of the shifting movement of the arc interval it is demonstrated in
practice that the shadows cannot and do not form since the one side does not, under
these conditions, become of such a relative height as to obscure or cut off the
luminous rays.
It is of importance that the groove B extend for such a depth into the carbon A
as that the groove shall penetrate into the crater formed on the end of said carbon
and thus avoid the formation of projections of the material of the carbon at the
two sides of the groove on the edge of the crater. So also if the said material
be not cut out into said crater the radiation and diffusion of the light is
obstructed.
By this construction I am enabled to produce a light of greater purity and
steadiness and also consume the carbon particles more completely and. also
provide a construction which is capable of being moulded and formed more
readily.
In the use of this form of carbon I have observed the character of light
produced and find it to be purer and much clearer which I attribute to the more
complete circulation of air.
In Figure 7, I have shown a mould or form by which to construct or produce
these carbons consisting of two members H and J pivoted or hinged together and
each having semi-circular indentures K, which when the two members H and J
are brought together form a complete annular channel within which the material
is compressed to form the carbon, the projections or ridges L in each of the
indentures of the member J penetrating said material to form the groove B.
The provision of a like groove extended into that carbon on which the apex or

page_text: cone shaped end is formed also serves a useful purpose in that the formation of a
clinker or slender end at the apex is avoided, which end or clinker breaking off
and becoming separated causes a flashing of the arc, sometimes disestablishes the
arc and often occasions injury to person and property.
It is necessary that the groove shall extend for such a depth as to penetrate-
into or reach to the said apex in order to overcome the formation of this clinker
or slender end.
Having now particularly described and ascertained the nature of my said
invention (as communicated to me from abroad) and in what manner the same is.
to be performed, I declare that what I claim is:
1. As a new article of manufacture a carbon for electric arc lamps having a
longitudinal groove therein extending for such a depth into the carbon as to
penetrate into the crater and apex formed at the end of said carbon, substantially
as set forth.
II. An apparatus for forming the herein described carbon for electric arc lamps
consisting of forming members or parts hinged together each of which members or
parts has semi-circular indentures therein and one of which said parts or members
has projecting ridges adapted to penetrate.the material and form the groove in the
carbon as the material is compressed into the form of a carbon.
Dated this 4th day of March 1896.
J. G. LORRAIN, M.I.E.E., M.I. Mech. E.,
Chartered Patent Agent.