It must be observed, with regard to these three wheels, C, 71t, S, which are called dial wheels, that they are always the same, whether the clock is a striking one or a repeat ing one ; their effect being, to cause the hour or dial wheel C to make a revolution in the space of twelve hours. The wheels G, L, Dl, N, Fig. 1. and the fly V, form the wheel work of the repeating part. The object of this wheel woe k, as has already been mentioned, is to regulate the in terval between each blow of the hammer. The ratchet R, and the pin wheel G, are fixed on the same arbor in com mon with the wheel L, within whose centre it freely turns. The spring 7', and the click c, are all placed on the wheel L.
When the cord X, which is wound round the pulley P, Fig. 2. is pulled, the ratchet R, Fig. 2. fixed on the same arbor as the pulley, retrogrades, or goes backwards, and the inclined planes of the teeth raise the end of the click at 0. Then the repeating spring brings back the ratchet, whose teeth butt or stop against the end of the click, which carries about the wheel L, and the wheel work M, N, V : but while the ratchet R thus carries the wheel L, and while the pin wheel G, and the pulley P of Fig. 2. which are fixed on the same arbor, turn also, the pins of the wheel G act on the pieces m, n, Fig. 1. whose arbors prolonged carry the hammers 1, in, Fig. 2. Each piece nz, n, is pressed by a spring, to bring forward the hammers, after the pins had made them rise up or go backward. The spring r is only seen, which acts on the piece in; that which acts on the piece 72 is placed under the plate which carries the motion work, Fig. 2. The piece o serves to communicate the motion of that of m to the arbor or piece n, which carries the hour hammer.
The piece, (bascule,) or see-saw m x, Fig. 1. is move able on the arbor which carries the quarter hammer. On this arbor below m x, an arm like that of m moves, on which act the three pins placed on the under side of the wheel G. These_ three pins serve to raise the quarter hammer fixed on the arbor which carries the piece in. It is this hammer which the spring r presses. When the cord is pulled, the wheel G is made to go backward, the' pins of which come to act on the hack part of the arm in, which yields, and comes from m to x. The small arm which is below for the quarters makes the same motion ; and when the repeating spring brings back the wheel 0, a small spring, which acts on these pieces m, obliges them to get engaged between the spaces of the pins, and to pre sent the light planes on which these pins act to raise the hammers.
The pulley P, Fig. 2. carries the piniona, which pitches into the rack b C, the effect of which is, as has been said, to make the point b go upon the steps of the snail L, and determine the number of blows which the bout' hammer must give.
The star wheel E, and the snail L, are fixed together by two screws. This star moves on a screw stud V, Fig. 2. attached to the piece TR, moveable itself in T. This piece forms, with the plate, a small frame, in which the star E and snail L turn. One of the radii or teeth of the star hears on the jumper Y, which is pressed by the spring g. When the pin c of the quarter snail turns the star wheel, the jumper Y moves out, receding from V to the centre of the star, until the tooth of the star arrives at the angle of the jumper, which happens when it has made half of the way which it ought to do. Having escaped this angle, the inclined plane of the jumper pushes it as it were behind, and makes it precipitately finish the other half; so that from the changing of one hour to another, that of the star and of the snail is done in an instant, which is when the minute hand points to the 60th minute on the dial.
The juniper finishing thus in turning the star, each tooth placed in c comes on the back of the pin c, and makes the surprise s, to which it is fixed, advance. The surprise is a thin plate, adjusted on the quarter snail ; it turns with it by means of the pin_ which comes through an opening made in the surprise ; the advance Which the star wheel teeth causes the surprise to make, serves to prevent the arm Q of the finger from falling into the step 3, which would make the three quarters be repeated when at the 60th minute. As soon as the star changes the hour, it then obliges the surprise to advance to receive the arm Q; so that if the cord is pulled at this instant, the hammer will strike the precise hour.
The arm Q and the finger are moveable on the same centre. When we have drawn the cord, and when the pins of the pulley have freed or left the finger at liberty, then the spring h makes the arm Q fall on the quarter snail, and the finger D presents itself to one or the other of the pins in the pulley. These two pieces can turn one on the other, and be moved separately : This serves in the case where the arm Q going to fall on the step h of the quarter snail, and the finger D being engaged in the pins of the pulley, this arm bends and yields to the pins of the pulley, which at this instant cause it to retrograde or go backward ; it is necessary that the pin for the present in hold can make the finger move separately from the piece Q. The spring B brings back the linger D, as soon as the pin has retrograded, so that it may present itself to the pin which stops for the hour alone, or for the quarter, if the at in falls on the step 1, Etc.