148 



HOROLOGY. 



Repeating 



Clocks 



H/.ATE 



CCCV. 

 Figs. 1, 2, 

 3.4,5. 



the returning or minute wheel S, of the same number 

 of teeth, and of the same diameter as the wheel m. The 

 pinion of the wheel S makes twelve revolutions in the 

 time that the hour wheel C makes one. The wheel (', 

 which is one of the dial wheels, takes then twelve 

 hours to make one revolution, and is that which car- 

 ries the hour hand. 



It must be observed, with regard to these three wheels, 

 C, m, S, which are called dial wheels, that they are al- 

 ways the same, whether the clock is a striking one or 

 a repeating 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, M, N, Fig. 1. and 

 the fly V, form the wheel work of the repeating part. 

 The object of this wheel work, as has already been 

 mentioned, is to regulate the interval between each 

 blow of the hammer. The ratchet R, and the pin 

 wheel G, are fixed on the same arbor in common with 

 the wheel L, within whose centre it freely turns. 

 The spring r, 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. 3. fixed on the 

 same arbor as the pulley, retrogrades, or goes back- 

 ward, and the inclined planes of the teeth raise the 

 end of the click at O. 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 car- 

 ry the hammers /, m, Fig. 2. Each piece m, n, is 

 pressed by a spring, to bring forward the hammers, af- 

 ter the pins had made them rise up or go backward. 

 The spring r is only seen, which acts on the piece m ; 

 that which acts on the piece n, 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 mx, 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 quar- 

 ter hammer fixed on the arbor which carries the piece 

 m. 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 back part of the 

 arm m, 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 G, a small spring, which acts on these 

 pieces m, obliges them to get engaged between the 

 spaces of the pins, and to present the right planes on 

 which these pins act to raise the hammers. 



The pulley P, Fig. 2. carries the pinion a, 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 

 hour 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 pieceTR, moveable itself in T. Thispiece 

 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 

 bears 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 the Repeating 



centre of the star, until the tooth of the star arrives at 



the angle of the jumper, which happens when it has jTT""" 



made half of the way which it ought to do. Having c v'.' 



escaped this angle, the inclined plane of the jumper j.'j g . g| 



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 jumper 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 S, 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 p makes the arm Q fall on the quarter 

 snail, and the finger U presents itself to one or 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 enga- 

 ged in the pins of the pulley, this arm bends and 

 yields to the pins of the pulley, which at this in- 

 stant cause it to retrograde or go backward ; it is ne- 

 cessary that the pin for the present in hold can make 

 the finger move separately from the piece Q. The 

 spring B brings back the finger 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 arm falls on the step 1, &c. 



Having seen the most essential parts of the repeti- 

 tion, there remains only one of which an idea must be 

 given, and which we shall endeavour to make the read- 

 er understand. This is the all or nothing, which has this 

 property, that if the cord is not fully drawn, so as to 

 make the arm b of the rack C press on the snail L, the 

 hammer will not strike, so that by this ingenious me- 

 chanism, the piece will repeat the exact hour, if other- 

 wise it will not repeat at all. 



We have seen, that when the cord X is pulled, the pin 

 wheel G, (Fig. 1.), oversets the piece m, and makes it 

 come to x; and that before the hammer can strike,a small 

 spring must bring back this piece m, to put it in holding 

 with the pins ; after that, it is easy to see that if, in 

 place of allowing the piece m to take its situation, it 

 were made to be still more overset, the repeating spring 

 bringing back the pin wheel, the hammer would not 

 strike while this piece remained overset; this is precise- 

 ly the effect that the piece TR (Fig. 2.) produces, 

 which is on that account called the all or nothing 

 piece. This is effected in the following manner: The 

 piece TO (Fig 1.) carries a pin, which goes through 

 the plate by the opening o, (Fig. 2.) ; if we pull the 

 cord, the pin wheel causes the piece m to move, as we 

 have just now seen. The pin which it carries comes 

 to press against the end o of the all or nothing piece, and 

 sets it aside, so that the pin shall arrive at the extremi- 



