THEORY AND PRACTICE OF ENGINEERING.

Boor II-

$82

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Fig. 1431.

An invention of Breguet as applied to an equation clock,is composed of two parts, one fixed, the other movable. Thefixed part is the plate o, held by four screws; it is cut out inthe form of an equation curve. 'The movable part is composedof a plate gg, having its centre of motion at c. It carries abalancing rod, whose centre is at b; its two extremities c andd lean, the one, c, against the edges of the curve, the other, d, onthe prolongation of an indicator or needle e, which has the samecentre of rotation as the plate gg. The prolongation of the needleis maintained against the extremity d of the balance, by meansof a spring o screwed to the plate gg; the needle n is fixed, and is concentric to thesame plate; the movable system is carried by the plate gg , which makes a completerevolution in a year. It may be conceived that the needle n, which is fixed to the plate,may indicate the days of the year, provided it is placed on a dial divided into 365 parts.The needle e, it appears, ought to go over the same space in the same time, which never-theless is not the case : when the lever c leans on the part of the curve most distant fromthe centre, the needle e should be behind n a certain number of divisions ; when on thecontrary the arm leans on the pait m, which is nearest the centre, the needle e will pre-cede n by a certain number of divisions. This difference of motion of the needle n fromthe needle e is produced by the lever cbd y which leans on the curve of the plate o, andthis curve is such that it causes the needle e to gain or lose on the needle n by a certainnumber of divisions, equal to that of the minutes by which the true time differs from themean time at the date of the days which the needle n indicates.

Ratchet Lever, invented by Garousse. Thecircular alternate motion is changed intocircular continuous without the reciprocaltaking place: the stirrups a,b,c y d y movableon the points a,c, are so disposed that thelever, by an alternate continuous motion, forcesone to draw the ratchet-wheel continuallytowards it, whilst the other escapes the toothit had taken, and engages another. Theauthor applies his lever to a machine fordriving four corn-mills at once.

Lever with a toothed Wheel , invented byGarousse; a modification of the preceding.

The great lever a has its fulcrum at c; above and below are two claws or feet d, e ymovable round their pivots; each of these claws leans on one of the staves of the lanternb. The circular alternate motion of the great lever will produce the circular continuousmotion of the wheel b ; if the axle of the wheel b be enveloped with a cord, a con-tinuous rectilinear motion will be produced.

b is a species of pendulum attached toa horizontal cylinder, which serves to im-press on it a circular alternate motion ; thetwo catches n,o are adapted to its surfaceat its two extremities by hinges, and en-gage the opposite teeth of the wheel st,cut in a ratchet shape, by communicatinga continuous circular motion to it, wTienthe power acts without interruption : thishas been employed in the construction of amachine for drawing loads : a modificationof Garousse’s lever, but inferior to it becausethe power does not act continually, is shownin this diagram.

Fig. 1432.

Fig. 1433.

Fig. 1434.

Fig. 1435.

a is a wheel toothed upon its edge, partly horizontal; b andc are two toothed wheels fixed to the axle de; their distanceshould be equal to the diameter of the wheel a. It is evidentthat the toothed part of the wheel a, which is always less than halfthe circumference, will engage alternately the wheels b and c, andwill communicate a circular alternate motion to the axle de.

In calculating the numbers for the movement of machinery, wemust remember that a wheel divided by its pinion shows howmany turns the pinion has to one turn of the wheel; and in thatof a watch, from the fusee to the balance, the wheels drive thepinions, consequently these latter run faster, or make more revolutions than the wheel;but the contrary is the case from the great wheel to the dial wheel.

imm n

Fig. 1436.