Among the most valuable, and, up to the present time, the least
generally appreciated services that electricity can render for domestic
purposes is that of its application in lighters. At the present epoch
of indifferent matches, to have, instantaneously, a light by pulling
a cord, pressing on a button, or turning a cock, is a thing worthy of
being taken into serious consideration; and our own personal experience
permits us to assert that, regarded from this point of view, electricity
is capable of daily rendering inappreciable services.
According to the nature of the application that is to be made of them,
the places in which they are to be put, and the combustible that they
are to inflame, etc., electric lighters vary greatly in form and
arrangement.
We shall limit ourselves here to pointing out the simplest and most
practical of the numerous models of such apparatus that have been
constructed up to the present time. All those that we shall describe
are based on the incandescence of a platinum wire. A few have been
constructed based on the induction spark, but they are more complicated
and expensive, and have not entered into practical use. Before
commencing to describe these apparatus, we shall make a remark in regard
to the piles for working them, and that is that we prefer for this
purpose Leclanché elements with agglomerated plates and a large surface
of zinc. In order to bring about combustion in any given substance, it
is necessary to bring near it an incandescent body raised to a certain
temperature, which varies with the nature of the said substance, and
which is quite low for illuminating gas, higher for petroleum, and a
white heat for a wax taper or a candle. We have said that we make use
exclusively of a platinum wire raised momentarily to incandescence by
the passage of an electric current. The temperature of such wire will
depend especially upon the intensity of the current traversing it;
and, if this is too great, the platinum (chosen because of its
inoxidizability and its elevated melting point) will rapidly melt;
while, if the intensity is too little, the temperature reached by the
wire will itself be too low, and no inflammation will be brought about.
Practice soon indicates a means of obviating these two inconveniences,
and teaches how each apparatus may be placed under such conditions that
the wire will hardly ever melt, and that the lighting will always be
effected. For the same intensity of current that traverses the wire,
the temperature of the latter might be made to vary by diminishing or
increasing its diameter. A very fine wire will attain a red heat through
a very weak current, but it would be very brittle, and subject to break
at the least accident. For this reason it becomes necessary to employ
wires a little stronger, and varying generally from one to two-tenths
of a millimeter in diameter. The current then requires to be a little
intenser. The requisite intensity is easily obtained with elements
of large surface, which have a much feebler internal resistance than
porous-cup elements; and since, for a given number of elements, the
intensity of the current decreases in measure as the internal resistance
of the elements increases, it becomes of interest to diminish such
internal resistance as much as possible. The platinum wires are usually
rolled spirally, with the object in view of concentrating the heat into
a small space, in order to raise the temperature of the wire as much as
possible. There is thus need of a less intense current to produce the
inflammation than with a wire simply stretched out. In fact, the same
wire traversed by a current of constant intensity scarcely reaches a
_red_ heat when it is straight, while it attains a _white_ heat when it
is wound spirally, because, in the latter case, the cooling surface is
less.
[Illustration: FIG. 2--RANQUE'S NEW FORM OF LIGHTER WITH EXTINGUISHER.]
We shall now proceed to the examination of a few practical forms of
electric lighters.
In Fig. 1 will be seen quite a convenient spirit or naphtha lighter,
which has been devised more especially for the use of smokers. By
pushing the lamp toward the wall, the wick is brought into proximity
with the spiral, and the lamp, acting on a button behind it, closes
the current. Pressure on the lamp being removed, the latter moves back
slightly, through the pressure of a small spring which thrusts on the
button. Owing to this latter simple arrangement, the spiral never comes
in contact with the flame, and may thus last for a long time. Mr.
Loiseau, the proprietor of this apparatus, employs a very fine platinum
wire, flattened into the form of a ribbon, and it takes only the current
from a _single element_ to effect the inflammation of the wick. The
system is so arranged that any one can easily replace in a moment the
spiral that has accidentally got out of order; and, in order that this
may be done, the maker has placed the spiral on a small, distinct piece
that he styles the "conflagrator." The latter consists of two small,
thin tubes of brass, held parallel and firmly by means of a brass
cross-piece. A small bit of paper wound round each tube in front of the
cross-brace insures insulation. The outer extremity of the two tubes
supports the platinum spiral, which is fixed to them very simply by the
aid of two small brass needles of conical form, which pinch the wire
in the tube and hold it in place. There is nothing easier to do than
replace the wire. All that is necessary is to remove the two little rods
with a pair of pincers; to make a spiral of suitable length by rolling
the wire round a pin; and to fix it into the tubes, as we have just
explained. With two or three extra "conflagrators" on hand, there need
never any trouble occur.
In Fig. 2 we show a new and simple form of Mr. Ranque's lighter, in
which an electro-magnet concealed in the base brings the spiral and
the wick into juxtaposition. The extinguisher, which is balanced by
a counterpoise, oscillates about a horizontal axis, and its support
carries two small pins, against which act successively two notches in a
piece of oval form, fixed on the side of the movable rods.
In the position shown in the cut, on the first emission of a current the
upper notch acts so as to depress the extinguisher, but the travel of
the rods that carry the spiral is so limited that the latter does not
strike against the extinguisher. On the next emission, the lower notch
acts so as to raise the extinguisher, while the spiral approaches the
wick and lights it. It is well to actuate these extinguishing-lighters,
which may be located at a distance, not by a contact button, but by some
pulling arrangement, which is always much more easy to find in the dark
without much groping about. There might be used for such a purpose the
very motion of the front door, when opened, for lighting the hall; but
that would offer the inconvenience of operating likewise in the daytime,
and of thus needlessly using up the pile and the naphtha. In all these
spirit or naphtha lighters it is important that the spiral _shall not
touch_ the wick, but that it shall be placed a little above and on the
side, in the mixture of air and combustible vapor.
Several apparatus have likewise been devised for lighting gas by
electricity, and a few of these we shall describe.
The simplest form of these is Mr. Barbier's lighter for the use of
smokers, for lighting candles, sealing letters, etc. It consists of a
small gas-burner affixed to a round box, seven to eight centimeters in
diameter, and connected to the gas-pipe by a rubber tube. By maneuvering
the handle, the cock is opened and an electric contact set up of
sufficient duration to raise to a red heat the spiral, and to light the
gas. It is well in this case, for the sake of economizing in wire, to
utilize the lead gas-pipe as a return wire, especially if the pile is
located at some little distance from the lighter. In the arrangement
generally in use the key is provided with a special spring, which tends
to cause it to turn in such a way as to assume a vertical position, and
with a tooth, which, on engaging with a piece moving on a joint, holds
it in a horizontal position as soon as it has been brought thereto. In
order to extinguish the burner, it is only necessary to depress the
lever, and thus allow the key to assume again the vertical position,
that is to say, the position that closes the aperture through which the
gas flows out. In a new arrangement, the notch, spring, and the lever
are done away with, the cock alone taking the two positions open or
closed.
Another very ingenious system is that of Mr. Loiseau, consisting of an
ordinary gas-burner (fish-tail, bat's-wing, etc.), carrying at its side
a "conflagrator," analogous to that of the spirit-lighter (Fig. 1), but
arranged vertically. One of the rods of the "conflagrator" is connected
with the positive of the pile, and the other with the little horizontal
brass rod which is placed at the bottom of the burner. On turning the
cock so as to open it, a small flow of gas occurs opposite the platinum
spiral, while at the same time a rigid projecting piece affixed to the
cock bears against a small, vertical metallic piece, and brings it in
contact with the brass rod. The circuit is thus closed for an instant,
the spiral is raised to a red heat, and lights the gas, and the flame
rises and finally lights the burner. It goes without saying that on
continuing the motion the contact is broken, so as not uselessly to
waste the pile and so as to stop the escape of gas.
For gas furnaces, Mr. Loiseau is constructing a _handle-lighter_ which
is connected with the side of the furnace by flexible cords. The contact
button is on the sleeve itself, and the spiral is protected against
shocks by a metallic covering which is cleft at the extremity and the
points bent over at a right angle. All the lighters here described work
well, and are rendering valuable services. They may be considered as the
natural and indispensable auxiliaries of electric call bells, and their
use has most certainly been rendered practical through the Leclanche
pile.
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