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Patented Dec. 3, 1946
Joseph W. Droll, Wilmette, Ill.
Application December 21, i944, serien Ne. 569,150
1 Claim (Cl. 176-119)
around the core, and a conductive coating l2 of
The invention relates to carbon electrodes for
copper around the shell. Each carbon stickvis
picture projectors.
provided at one of its ends with a longitudinal
In a carbon electrode as set forth in Letters
socket I4 and its other end with a stem I5 which
Patent No. 2,120,243 the telescopic ends of the
constitute, respectively, female and male mem
carbon sticks with a metallic conductive coating
bers of a telescopic joint for end-to-end connec
therearound are connected in end-to-end relation
tion of similar sticks. The inner periphery of the
by a conductive sleeve for continuous light pro
socket Il and the outer periphery of the male
jection. In practice it has been found that the
member I5 are preferably formed in the hard
coating of the telescopic ends on the carbon sticks
leaves, in many instances, irregularities in the 10 carbon of the shell Il. The end faces I6 of the
male and female members are located so that they
contacting surfaces between the contiguous ends
will substantially abut against each other when
of the sticks and that the ypores in the contact
the sticks are telescopically joined. At the joint
ing surfaces of the carbon sometimes cause flick
between the two carbon sticks a sleeve I8 of metal"_
ering or irregularities in the projected light and
that as the joined ends are consumed the short 1.5 of high conductivity, such as copper, is provided
to receive and resiliently grip the _end portions of
end of a nearly consumed stick becomes sepa
rated from the following stick during the projec
a pair of sticks, for providing a continuous path
of conduction of current between the coating
tion >of a picture.
of the joined sticks. The sleeve is provided with
The primary object of the invention is to pro
vide in connection with a carbon electrode of the 20 indentations 2| for better gripping the sticks.
For efllcient projection of light it is necessary to
aforementioned character an improved joint
provide a continuous uniform path for electric
which during continuous projection or use of the
current through the copper coating and through
the carbon portions of the sticks. In cutting the
light and separation of the short end of a stick
from a full length stick during projection, and 25 telescopic ends on the sticks, fragments of the
carbon in the cut surfaces sometimes break away
which makes it possible to reduce the length of
and leave them porous which results in an im
the telescopic ends of the sticks.
perfect path for current. Very short ends of a
This object is' achieved by bonding together by
nearly completely consumed stick will, some-.
a suitable adhesive the telescopic ends -of the
carbon sticks in order to, effect uniform continu 30 times during continuous projection, become loose
and fall apart from the following stick. This will .
ous electrical conduction through the carbon in
also cause undesirable irregularities in the- pro
the sticks and a more efficient joint between the
jected light. It is also desirable to shorten the
telescopic ends, to reduce waste. To prevent
Other objects will appear from the detailed de
35 these irregularities and provide amore secure
joint the invention provides for bonding together
The invention consists in the various novel fea
the telescopically connected >ends by a` suitable
tures which are hereinafter set forth and are
bonding agent such as a thin solution of phenol
more particularly defined by the claim at the
formaldehyde resin. The male member of theA
conclusion hereof.
40 telescopic joint on the end of each stick, when it
In the drawing:
is joined to a partially consumed stick, is dipped
Figure l is a perspective of a pair of electrode
in the resin, so as to leave, as indicated at 20, a
sticks with the bonding resin applied to one of
suillcient quantity of resin on the stick to form
them preparatory to joining the telescopic ends
a thin coat between the male and female mem
of a partially consumed stick and a stick of nor
electrode will prevent flickering of the projected
mal length;
45 bers of the telescopic joint, when the thinly
coated» member is inserted into the female mem
ber. The resin is spread as the members are
the joint between a partially used stick and a
joined, and forms a thin but secure bond between
stick of normal length; and
the carbon surfaces of the joint. This resin is
Figure 3 is a perspective of the sleeve.
The invention is exemplified in electrodes 50 preferably thermosetting so it will quickly set and
form an efficient bond between the sticks which
which are designed for use in the lamp house of
supplements the telescopic joint and the sleeve in
a picture projector. Each carbon electrode for
securing the sticks together. This thin coating
efficient illumination for picture projection com
also results in uniform flow of lcurrent between
prises a stick consisting of a partially soft core I0
of neutral carbon, a shell Il of hard carbon 55 the carbon in the joined sticks so that flickering
Figure 2 is a section on an enlarged scale of
in the projected light is prevented and small ends
of consumed sticks will not be separated from
‘ the stick o! normal length. Additionally, it be
comes possible to shorten the' telescopic members,
to reduce the waste caused by cutting away the
carbon in forming the telescopic endsi
The linvention provides carbon electrodes for
projectors which are adapted to be successively
connected together for continuous light projec
Having thus described the invention what I
claim as new and desire to secure by Letters Pat
ent is:
That improvement in connecting together for
continuous light projection. a pair oi stick elec
trodes, each including a core of soit carbon, a
shell of hard carbon around the core, and a con
ductive coating around the shell, the hard car
bon of the sticks beingprovided with telescopic
tion without resultant ilickering in the >light or 10l male and female ends, which comprises >applying `
a thin solution of phenol formaldehyde resin to
irregularities in the light projected, as the result
one of the telescopic ends. joining the telescopic
mating ends of the pair of sticks together and
spreading the resin to form a thin coating which
and which makes it possible to use a relatively
short telescopic joint to reduce waste.
15 bonds ktogether the hard carbon in the sticks. and
of small pieces of the electrode being separated
as the electrode is consumed across the Joint
The invention is not to be understood as re
stricted to the details set forth since these may be '
modiiied within the scope of the appended claim
» without departing from the spirit and scope of the
additionally connecting the sticks with a sleeve of
electric conducting material in order to eiîect
electrical conduction between the conductive
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