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.
FIG. 2--RANQUE'S NEW FORM OF LIGHTER
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.