Improvements in Electric Arc Lamps.
Year: 1899

page_text: Date of Application, 16th Aug., 1899-Accepted, 16th Sept., 1899
Improvements in Electric Arc Lamps.
I, JOSEPH LESTHEVENON, of 38, Rue Picot, Toulon, France, 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, reference being had to the accompanying drawings and to the letters
and figures marked thereon, that is to say:-
This invention relates to a new electric arc lamp, characterized, on the one
hand, by the very high resistance (exceeding 500 ohms) which I give to the
solenoid, arranged in shunt, and, on the other hand, by the extreme sensitiveness
of its mechanism, and lastly, by the fact that I can vary the capacity of the lamp
and consequently its illuminating power, by acting in a suitable manner on the
mechanism.
I have carefully avoided introducing into my lamp, springs and friction brakes,
as I am aware that such devices nearly always interfere with the regular and
certain working of lamps.
And in order that my invention may be readily understood, I will describe
the same fully with reference to the annexed drawings, in which:
Fig. 1 is a partial sectional elevation of my lamp, through the carbon holder,
Fig. 2 is a side view, and
Fig. 3 is a plan thereof.
a is a solenoid which is arranged in shunt, and in which in moves a soft iron
core b. This core is pivoted at its upper end to a beam cd, whose axis of
oscillation e is on the upper end of the solenoid. On the longer arm d of
the beam, is an adjustable counterweight f, the purpose of which is to increase
or diminish the force necessary to attract the soft iron core in the solenoid. The
position of this counterweight on the arm d of the beam, is regulated by means
of a screw-thread, or otherwise, and said beam may be marked off into gradua-
tions indicating the position to be given to the counterweight for the resistance
which it is desired to obtain. On the rod g connecting the two plates of the
lamp, are arranged two stops h and i for limiting the oscillations of the beam c d.
The feeding of the lamp is effected by means of escapement mechanism similar
to those employed in horology, and actuated by the weight of the upper carbon
holder. This mechanism consists of two T-shaped cheeks or plates ; connected
together by cross rods or pieces and mounted on an axis in a frame or
support fixed to the base plate of the lamp. The free end m of the horizontal
arm of the T is connected by a bent or cranked lever n¹ and a small connecting
rod o to the shorter arm c of the beam c d. The ends of the vertical arms of
the cheeks are connected by an axis p serving as the axis of oscillation of a
pendulum g, and carrying between the cheeks an anchor r furnished with teeth
or pins s, oscillating above a toothed wheelt keyed on the axis u which extends
between the middle of the checks j. This axis u also carries a ratchet

page_text: wheel formed in one with a drum (on which is wound the suspension cord
of the upper carbon holder) and with a second drum y, on which is wound a
cord z. These three, v, x, y, turn freely on the axis u. On the toothed wheel t,
is pivoted a click 1 adopted to engage with the teeth of the ratchet wheel, and
held against them by a spring 2.
The lower carbon holder (not shewn in the drawings) is stationary, and the
upper carbon holder 3 slides, with slight friction, in a tube or sheath 4 connecting
the lamp with the plate 5 to which the globe is fixed. This arrangement allows
the creation of a partial vacuum in the globe, thus diminishing to a certain extent
the resistance of the air to the formation of the arc.
As will be seen, the whole of the mechanism of my lamp is suspended from
two axes e, ; it is constituted by a kind of balance c, e, d, the arm c of
which is controlled by the solenoid and by the weight of the upper carbon holder
(transmitted by the connecting rod o), and the other arm of which is controlled
by the adjustable counterweight f. This counterweight being arranged for any
desired capacity or power of the lamp, this latter works in the following
manner:-
The carbons, when at rest, are separated from each other by reason of the
preponderance of the counterweight f, the arm & of the beam being at ¹ (Fig. 1).
When the circuit of the lamp is closed, the soft iron core is attracted downwards,
the connecting rod o descends while allowing the checks to oscillate about the
axis, and the carbons approach each other.
The shock to the arm against the stop h, may be deadened by a spring; the
descent of the core being also deadened by reason of the resistance of the air
confined underneath it.
Directly the carbons come into contact, the solenoid is short circuited, and its
action ceases the counterweight f raises the cheeks j and with them the upper
carbon, so striking the arc.
From this moment the equilibrium tends to maintain itself between the various
parts of the mechanism, whose dimensions must be such that the core of the
solenoid is at about the middle of its stroke when the arc is normal. As the
resistance of the arc increases by reason of the consumption of the carbons, the
difference of potential increases at the terminals 6, 7, of the lamp, thus causing
the attracting force of the solenoid on the core b also to increase. This core
therefore descends slowly and allows the upper carbon to descend with it. When
this descent shall have attained a certain limit, determined and regulatable at
will, the teeth or pins s of the anchor will allow one tooth of the wheel t to
escape; the upper carbon will therefore be fed for an amount determined by the
number of teeth on the wheel t, and by the diameter of the drum a. Directly
the resistance of the arc diminishes, the attractive force of the solenoid also
diminishes, and the counterweight f again becomes preponderant; the upper
carbon is raised to restore the arc to its normal length, and the working con-
tinues.
When the positive carbon is consumed, the upper carbon-holder is then fully
drawn up by pulling the cord z. The click 1 allows the drum to move in this
direction, whereas in the contrary direction it locks the drum fast with the
wheel t.
This very sensitive mechanism, combined with the power of creating the
vacuum around the arc, effects a very appreciable economy of current.
I will now give some figures which will, at the same time, allow me to still
better explain the function of the counterweight f.
In one of my lamps, which I have working normally at 1 ampere and 50 volts
at the terminals, when I wish to increase its illuminating power I increase the
current to 2 amperes, and from this fact alone the voltage at the terminals rises
to about 65 volts, but as these data do not correspond to the best efficiency of
the lamp, I attain this by increasing the lever arm of the counterweight until the
voltage exceeds 70 volts.

page_text: Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is―
1. An electric arc lamp, the solenoid of which is arranged in shunt and which
is operated by the weight of the upper carbon holder, characterized by the very
high resistance of the solenoid, and by the arrangement of its mechanism con-
stituting a kind of balance, the beam (c d) of which is controlled on the one
hand by the core (b) of the solenoid and the weight of the upper carbon holder,
and on the other hand by an adjustable counter-weight (f) for the purpose of
producing a lamp capable of working economically at different powers, sub-
stantially as described.
2. In a lamp, as above claimed, the employment of an escapement mechanism
mounted between two cheeks j articulated about a fixed axis in a frame k,
and controlled by a pendulum q, such mechanism being connected at its other
end, through the connecting rod o, with the arm c of the balance beam cd, and
carrying a drum a, on which is wound the suspension cord of the upper carbon
holder, said drum being connected with the escapement wheel t by a click 1 and
ratchet wheel e, substantially as described.
3. In electric arc lamps, the arrangement of the upper carbon holder 3 in an
enclosing sheath 4 wherein it slides with slight friction, thus enabling a partial
vacuum to be created in the globe in which the arc is struck, substantially as
described.
4. My improved electric arc lamp. substantially as hereinbefore described and
as shewn in the annexed drawings.
n in the annexed drawings.
ted this 16th day of August 1899.
ERNEST DE PASS,
Chartered Patent Agent,
78, Fleet Street, London, and 5A, Market Street, Nottingham,
Agent for the Applicant.