Page:The Kinematics of Machinery.djvu/586

 56 4 KIN EM A TICS OF MA CHINEE Y.

without further examination. There is one other click-train, how- ever, the one represented by Figs. 414 and 415, which deserves a little notice here. In both these forms the train can .also be used as a ratchet-train. The train of Fig. 414 was called by Eedtenbacher the "one-toothed-wheel;" it is somewhat widely known by the names of Maltese cross or Geneva ratchet, the one being taken from the form of the wheel I, the other from the employment of this click-train in Geneva musical-boxes. Fig. 415 shows that the essential condition of the train is not that the wheel a should have one tooth only ; in the majority of cases, however, the wheel b is more or less star-shaped, on which ground it has been proposed *

���FK;. 414.

to call the wheels Star- wheels. It is evident that we have here a special form of the train (C 2 C, 7 ) or if it be preferred, of (C 2 H }t ), and it is desirable to indicate by a special formula its relation to the other wheel-chains. The special characteristic of the wheels is their segmental arrangement. We may therefore use here the symbol A, and will indicate chains of the kind before us by the formula (C 2 A Z :), or more generally (0 2 A Z :).

If the radius of the wheel b in the click-train (C'^AJ) be made infinite, b becomes a rod or bar, carrying upon it the curved recesses and the hollows for receiving the teeth. Its formula then becomes (C^P L A" r f). The bolt-train in the Bramah lock, Fig. 416 furnishes us with an interesting example of this. The piece ABCD belongs to the bolt b ; the opening 2 in it is the hollow for the tooth 2 of a, A B and C D are adjacent curved recesses in the piece


 * Polytech. Zcntralblatt, 1864, Aster, Sternrdder.

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