Bichromate of potassa piles, especially those single liquid ones that
are applied to domestic lighting, all present the grave defect of
consuming almost as much zinc in open as in closed circuit, and of
becoming rapidly exhausted if care be not taken to remove the zinc from
the liquid when the battery is not in use. This operation, which is a
purely mechanical one, has hitherto required the pile to be located near
the place where it was to be used, or to have at one's disposal a system
of mechanical transmission that was complicated and not very ornamental.
In order to do away with this inconvenience, which is inherent to all
bichromate piles, Mr. G. Mareschal has invented and had constructed an
ingenious system that we shall now describe.
[Illustration: FIG. 1.--BICHROMATE OF POTASSIUM PILE, WITH MANEUVERING
APPARATUS.]
Mr. Mareschal's plan consists in suspending the frame that carries all
the battery zincs (Fig. 1) from the extremity of a horizontal beam, and
balancing them by means of weights at the other extremity.
The system, being balanced, the lifting or immersion of the zincs then
only requires a slight mechanical power, such as may be obtained from
an ordinary kitchen jack through a combination that will be readily
understood upon reference to Fig. 2. The axis, M, of the jack,
on revolving, carries along a crank, MD, to which is fixed a
connecting-rod, A, whose other extremity is attached to the horizontal
beam that supports the zincs and counterpoises. If the axle, M, be given
a continuous revolution, it will communicate to the rod, A, an upward
and downward motion that will be transmitted to the beam and produce an
alternate immersion and emersion of the zincs.
Upon stopping the jack at certain properly selected positions of the
rod, MD, the zincs may, at will, be kept immersed in the liquids, or
_vice versa_. This is brought about by Mr. Mareschal in the following
way: The jack carries along in its motion a horizontal fly-wheel, V,
against whose rim there bears an iron shoe, F, placed opposite an
electro-magnet, E. In the ordinary position, this shoe, which is fixed
to a spring, bears against the felly of the wheel and stops the jack
through friction. When a current is sent into the electro-magnet, E, the
brake shoe, F, is attracted, leaves the fly wheel, and sets free the
jack, which continues to revolve until the current ceases to pass into
the electro.
[Illustration: FIG. 2.--PRINCIPLE OF THE APPARATUS.]
The problem, then, is reduced to sending a current into the electro and
in shutting it off at the proper moment. This result is obtained very
simply by means of an auxiliary Leclauche pile. (The piles got up for
house bells will answer.) The current from this pile is cut off from
the electro, F, by means of a button, B, when it is desired to light or
extinguish the lamps. In a position of rest, for example, the crank, MD,
is vertical, as shown in the diagram to the right in Fig. 2. The circuit
is open between M and N through the effect of the small rod, C, which
separates the spring, R, from the spring, R'. As soon as the circuit has
been closed, be it only for an instant, the crank leaves its vertical
position, the rod, C, quits the bend, S, and the spring, R, by virtue of
its elasticity, touches the spring, R', and continues its contact until
the crank, MD, having made a half revolution, the rod, C', repulses the
spring, R, and breaks the circuit anew. The brake then acts, and the
crank stops after making a revolution of 180°, and immersing the
zincs to a maximum depth. In order to extinguish the lamp, it is only
necessary to press the button, B, again. The axle, M, will then make
another half revolution, and, when it stops, the zinks will be entirely
out of the liquid. The depth of immersion is regulated by fixing the
crank-pin. D, in the apertures, T1, or T2, of the connecting rod. This
permits the travel, and consequently the degree of immersion, to be
varied.
The device requires three wires, two for connecting the lamp with the
battery, and one for maneuvering the apparatus through a closing of the
contact, B.
With Mr. Mareschal's system, bichromate of potassa piles may be utilized
in a large number of cases where a light of but short duration is
required until the battery is exhausted, without the tedious maneuvering
of a winch and without inconvenience. The jack permits of a large number
of lightings and extinctions being effected before it becomes necessary
to wind up its clockwork movement. This operation, however, is very
simple, and may be performed every time the battery is visited in order
to see what state it is in.
We regard Mr. Mareschal's apparatus as an indispensable addition to
every case of domestic electric lighting in which bichromate of potassa
piles are used, and, in general, to all cases where the pile becomes
uselessly exhausted in open circuit. It will likewise find an
application in laboratories, where the bichromate pile is in much demand
because of its powerful qualities, and where it is often necessary to
order it from quite a distant point.--_La Nature_.
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