Improvements in Semi-incandescent Electric Lamps.
Year: 1892

page_text: Date of Application, 24th Aug., 1892-Accepted, 15th Oct., 1892
COMPLETE SPECIFICATION,
Improvements in Semi-incandescent Electric Lamps.
CARL ANTON JOHANNES HUGO SCHROEDER and HEINRICH EUGEN RICHARD
SCHROEDER, Electrical Engineers, of Whetstone House, Heslop Road, Balham in
the County of Surrey 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 :-
Our new electric lamp gives a much greater efficiency of the electric current than
has been obtained by any other system; its light is steady, and its construction
simple, as it has no clock-work or other complicated mechanism to get out of
order...
The lamp which is represented in the annexed drawing, consists of an iron or
steel tube a, filled with mercury, upon which is placed the float B, pressing under
the lower carbon C. This carbon presses against a body D, made of carbon,
platinum, iridium, or other suitable material, connected with a metal piece E, which
is supported by the metal arm f, at the end of which is a cylinder g pointing down-
wards, and fitting into the metal pillar A.
The pillar A is provided at its upper end with an outer thread, upon which fits
and moves up and down the ring-shaped female screw I. The pillar A is further
provided with a slot K, in which the pin 1, firmly attached to the cylinder g, can
move smoothly up and down.
At the lower end of the pillar A is placed the first terminal screw N, and the
hole S, by means of which one of the cables supplying the current is connected
with the lamp.
The iron or steel tube a is filled with mercury, and is provided at its upper end
with a guiding piece O. The tube a is closed at its lower end by the piece of steel
or iron, which is absolutely sealed by a leather washer p, soaked in paraffin.
The piece P has a hole drilled through its centre, and at its lower end is attached
the indiarubber or leather bag Q, which is also filled with mercury, communicating
by means of the hole s with the mercury in the tube a.
The object of this arrangement is the adjustment of the height of the mercury
column in the tube a. This is effected in either of the following ways:-
1. By the action of the screw in squeezing the indiarubber or leather
bag Q, or
2. By employing a reservoir, filled with mercury communicating with the
mercury in the tube a. In this case it is necessary so to place the reservoir that
the mercury contained in it shall be level with the mouth of the tube a.
This arrangement has the advantage that the level of the mercury remains nearly
the same when the carbon is reduced to a trace, but it has the disadvantage that
the lamp must be kept in a vertical position to avoid spilling the mercury.
The tube a is surrounded by a considerable wider tube R, and the intervening
space is filled with water or other liquid by means of which the mercury is kept
cool. The water is supplied and carried off by the pipes and ".
Both tubes a and R, with their accessories, are suitably connected with the stand
of the lamp. The wooden support H is fixed to the wooden stand F which serves
in this particular case as a support to the tube a and its accessories. To this
support is attached the screw q, which adjusts the height of the column of mercury.
To the lower part of the tube R is fixed the second terminal r.
The general form of the lamp may be varied in accordance with the purpose for
which it is required, whether as stand, hanging lamp, or otherwise.
The simple construction of our lamp, by which a steady light is obtained with the

page_text: greatest economy of current, at a moderate cost for purchase and running expenses,
distinguishes it from all others hitherto made.
These advantages are obtained essentially by the continual contact between the
carbon C and the body D. In order to cool the mercury, water is employed.
The efficiency of the current, which as already said, is very great compared with
other systems, is principally obtained by reducing the electric resistance of the
carbon C to a minimum, so that the lamp requires a voltage of only 10 to 14 volts.
It has further the great advantage of being free from danger.
The time which the lamp can be used without renewal of carbon depends on the
length of the carbon C and the tube a, while the candle-power depends on the
strength of the current and the thickness of the carbon C. The thinnest carbon
that can be used with good results is 2 millimeters in diameter. The lamp can be
constructed in all sizes with equal advantage.
It is evident from the foregoing description that as no wheels, clockwork, or
other complicated mechanism are employed, the lamp is particularly adapted for
street lighting, as it is not liable to get out of order when exposed to the weather
and the dust of traffic.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be carried out, we declare that what we
.claim is:
1. The mechanical arrangement in our electric lamp by which the change of
carbons is quickly and easily effected, without disturbing its adjustment; thus: by
loosening the clamping screw M, the cylinder G is liberated and we can take off
the said cylinder and the arm, with the body D. At the same time the accuracy
of adjustment of the carbon C is fully secured by the position of the screw 1 and
the guiding pin L in the slot K.
2. The above described arrangements for adjusting the height of the column of
mercury, viz.
a. An indiarubber or leather bag Q filled with mercury, which can be com-
pressed by the screw g, or
b. A tank or reservoir filled with mercury communicating with the tube,
the
tank being so placed that the level of the mercury in it is at the same height
as the mouth of the said tube a, both as applied to our electric lamp.
3. The circulation of a suitable liquid, such as water, around the tube a which
contains the mercury, for cooling the latter, thus producing an extremely steady
light.
4. The position of the guide O for the carbon C, as shown in the annexed
drawing.
5. The application of a body E made of thick brass or another suitable metal,
into which is fixed a piece or plate D of platinum, iridium, platinum-iridium, or
wolfram-iridium for making the imperfect contact with the carbon C.
6. The application of a float B made of wood or other material, which floats in
the mercury, and serves for:
I. Producing great buoyancy, even when the carbon C is nearly consumed.
II. Causing an even upward movement of the carbon C which is effected by
a number of fine grooves or holes in the float. The mercury passes slowly
through these grooves or holes thus producing the desired effect.
London, the 23rd day of August 1892.
CARL ANTON JOHANNES HUGO SCHROEDER.
HEINRICH EUGEN RICHARD SCHROEDER.