Stiiltrer' s Electric essential change was introduced (1847) by Starer of Leipsic (fig. 4), who was the first to use a permanently magnetized armature, by which he attained advantages not possessed by any previous device. One end of the soft-iron armature as is rigid, and carries the arbor of the anchor resting in its bearing at z, while the other end plays between the poles of the electro-magnet E, E; one of the poles of a permanent magnet if is placed opposite and in close proximity to the end of the armature, which is fastened to the shaft at a; the permanent magnet thereby induces magnetism in the armature, whose extremities are transformed into two opposite magnetic poles. If now an electric current passes through the coil of the electro-magnet and that end of the arma ture which is moving between it poles has a south polarity, the armature will be repelled by the south pole and attracted by the north pole. To effect a movement of the armature in the opposite direction, the current passing through the electromagnet is reversed to change its polarity; this repeated successively will of course produce an oscillatory movement of the armature. The manner of transferring the movement of the armature to the clock-train is also a more appropriate one than those above described. For this purpose the well-known recoiling anchor-escapement is employed, which, without providing for any extra check for the escape-wheel, moves one tooth after another by the oscillations of the pallets of the anchor in the usual manner. This clock possesses many advantages; no retracting spring is needed to remove the armature from the poles of the electro magnet, to overcome whose tension necessarily requires considerable loss of magnetic energy, and no extra provision is needed to keep the armature in position when inactive, since this is done by the magnetism induced in the armature. The Starer system has been brought to a high state of perfection by Dr. M. Hipp, whose modification has become a favorite one in Europe.
All the above-described time telegraphs, which are characterized by a certain similarity, depend upon the action of one armature, and as they are similarly constructed, so are they similarly defective. The movement of the armature is not one of a gradual progress, but is instantaneous, and is suddenly checked when in very close proximity to the poles, where the magnetic attraction is nearly the greatest. This action has proved to be a serious defect in all time telegraphs, owing to the resulting violent blows, which inevitably impair the mechanism.
Spallier Time Telegraph.—The electro-inagnetic escapement invented in iS76 by L. H. Spellier has removed the above-noted defects of electric clocks. Figure 5 (p1. 126) shows the arrangement of this escapement. A is an iron wheel divided into six equal segments, each segment repre senting an armature, and B is the escapement-wheel, with inclined teeth, corresponding in number to the armatures of the wheel A, both wheels being rigid on one shaft. L is a weighted lever which presses by means of a little roller (P) into the teeth of the escapement-wheel B. The elec tromagnet A/ attracts the armature as soon as the electric current passing through the coil is closed. This armature takes its position right over the pole of the magnet, as represented in Figure 5. When in this position the lever L is raised, and presses the roller P against the upper part of a tooth of the escapement-wheel B. As soon as the circuit is broken the weight of the lever moves both wheels in the direction indicated by the arrow and places them in the position shown in Figure 6. The armature / is now removed from the pole of the magnet, while the armature has closely approached it. When the circuit is again closed, armature f.? will
be attracted and the roller P will raise the lever and pass over the apex of the next tooth of the escapement-wheel, where it will remain until the cir cuit is again broken, when the same action as described will be repeated. It will be seen that by this arrangement not the slightest blow is imparted either to the armature or to the escapement-wheel, for there is no impact, nor is the armature submitted to the objectionable instantaneous check when it arrives at its halting place, but it will describe over the poles, before coining to a standstill, a few short, rather decided vibrations.
The making and breaking of the electric circuit, which are apparently the easiest of all operations in time telegraphy, proved for a long time to be the weakest and most troublesome point. Two difficulties arc to be met. When the electric circuit is broken, there appears at the point of separation a spark, which gradually oxidizes or entirely burns away the metal and prevents the passage of the current. For a long time this was the most serious evil presented in the proper action of electric clocks, but it was filially completely removed by devising a means of suppressing the formation of the spark (Hipp and Spellier). For the passage of the electric current contacts should be sufficiently energetic to make than positive; the contact-maker is operated either by the pendulum or the escapement-wheel, according to the requirements of the electric dial, but neither possesses sufficient energy to secure a firm enough contact, espe cially if a large number of clocks arc dependent upon them. Gamier resorted to the expedient of a separate clock-work, which was very inge niously set going by the master clock and had sufficient power to make a firm contact. Spellier (i884) succeeded in devising a means by which the escape-wheel of the master clock develops sufficient energy for a firm contact (pi. 126, fig. 6). The escape-wheel IV of the master clock moves in the direction of the arrow, its arbor bearing rigidly a long arm (//) having on one end a pin (P). While the arm revolves with the escape-wheel, this pin comes in contact with the inclined projection of the spring /1'; when this takes place the electric current passes from the galvanic battery, with which the arm is connected by wires, through the contact-spring L to the escape wheel arbor, thence through the contact-arm If into the spring R, which is connected by wires with any number of electric clocks, and returns front the last of them to the battery. Ordinarily, the escape-wheel would not have sufficijnt power to force the pin over the inclined contact-surface of the spring R, and to accomplish this is the purpose of the "power-accu mulator" AB; the arbor carries, besides the contact-arm II, a cam (A), against whose curve the weighted lever B is pressed by a little roller R. It will be seen that just now time roller of the lever presses against the incline I of the cam, thereby imparting additional power to the shaft of the escapement-wheel, and assisting in overcoming the obstruction offered by thc tension of the contact-springs. The moment the pin has passed the projection of the spring, the roller R of the weighted lever reaches the lower part of the cam, and the roller is gradually raised as the escapement-wheel revolves; and this operation is repeated at the next contact of the contact pin. It is obvious that there is a gradual storing tip of a portion of the power expended by the escape-wheel during the course of its revolutions, which power is returned to the escape-wheel at the proper moment for the purpose above indicated.