9S4

THEORY AND PRACTICE OF ENGINEERING.

Book II.

consequently it allows a tooth of c to escape; at the same moment another tooth of thewheel c strikes the hollow of the piece d, and restores to the balance-wheel its lost force ;thus at each double vibration of the balance-wheel, the point of the spring nm allows a toothof c to pass, and the balance-wheel receives a new impulse.

Escapement with free Vibrathms, by Berthond. a represents theescapement-wheel, 6c the catch; the pin of the catch suspendsthe action of the wheel, whilst the balance-wheel oscillates freely :the spring d serves to restore the catch as soon as the pallet c hasescaped the arm 6: at this moment a tooth of the wheel a actson the roller carried by the regulator, and transmits its force tomaintain the motion of the balance-wheel; the latter havingfinished its oscillation returns, and in returning the pallet c Fig. 1442.meets the end 6 of the catch ; but it yields in escaping this arm,

and approaching the centre of the circle most distant from 6, the spring e restores it, toengage it again when the balance-wheel has finished its oscillations, in such a manner thatin returning this pallet c presents itself afresh to the arms of the catch to disengage thewheel, and give a new impulse to the balance-wheel.

Breguet's ascending Escapement . a is a metal plate on which the whole of the escape-

ment is fixed; to understand its mechanism thoroughly, we must divide it into three parts,of each of which we shall describe theseparate play, and then their reciprocalaction.

First part; this is composed, first, of thewheel b and of C\ united together; thewheel 6 is submitted to the action of theprimitive mover by a system of wheelswhich tend to turn it in the direction bed.

Secondly, of a pinion g which engages thestopping-wheel 6, and which has a numberof teeth equal to those of the stopping-wheel, which corresponds to the space be-tween two consecutive teeth of the wheelC ; by this means the pinion can, at eachof its revolutions, be opposite one of theteeth of the arming wheels : the axis of thepinion carries a fly igh; the branch pi ofthis fly is shorter than the other gh, at theextremity of which a small piece of steel isfixed. Thirdly, of a stopping spring rrF,at right angles to the direction of the flyfixed at its extremity rr, and in which atabout two-thirds of its length there is a ruby,

V, which may also be made of any preciousstone or of tempered steel. In the state of the machine represented in the figure, the rubyleans against the extremity h of the fly; it there performs the office of a stop, which pre-venting this fly from moving in the direction that the pinion g solicited, by the wheel B Bcauses it to turn, thus suspending the revolutions of the wheel, and consequently theaction of the mover ; but if any cause makes the spring rrF to bend on the side of thepinion g, at the instant when the ruby V is opposite the notch, which is at the extremity h ,the fly' will escape and make a revolution, and if at the end of this revolution the springrr F has assumed its first position h i , it will stop against the ruby' V, and go no further.

Second part is composed, first, of a spring G of impulse curved at its extremity;this spring is the piece which serves to restore the power to the regulator at eachoscillation : it carries a catch or latch m, in which is a small notch with a ruby p on itsexterior surface ; this catch and the ruby serve, with the power we have just described, tostop the pulsion-spring when it has been bent by the arming wheel C, which transmitsto it the action of the primitive mover. Secondly, of a grappling spring a II, fixed at itsextremity a, on which an extremely weak spring n is attached; the spring H carries arubyp, intended to enter the notch m of the catch m , and to fix this spring when it is onthe stretch : another ruby placed on its extremity s retains the spring n in such a manner,that the end of this spring pressed from right to left opposes only a very feeble resistance,and pressed from left to right gives back to the ruby s the whole effort which it experinces,and making the spring II bend, disengages the ruby p from the notch of the catch m.

Third part consists of the pieces h, b, carried by the upper extremities of the axle of thebalance-wheel, and which are placed at a distance of a quarter of the circle from each other ;when the oscillation of the balance-wheel is from right to left, or in the direction 6 k, thepiece h makes the spring bend and passes beyond; and as the piece b is placed above the

Fig. 1443.