BE AM Airs LOCK. 565
5 corresponding to the circular recesses which are made in b in Fig. 415. There is no longer any segment of a made to fit these curved recesses (as in Figs. 414 and 415), the pin 2 sufficiently answers the purpose of such a segment. Similar arrangements are to be found in other locks, although not often in such a
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�distinct form. In the Bramah lock the piece a is further con-
nected with a fast click-train, the ingenious nature of which is
well known.
In cam and slider-cam trains, and also in their special forms click-trains pressure-organs are sometimes used. This always occurs, however, in compound chains.
158 -
Pulley Chains.
The mono-kinetic properties of the tension-organs greatly increase the difficulty of arranging them in simple chains along with rigid elements (cf. 41 d seq.). Such simple chains do exist, however, in belt-chains or rope -chains, as Fig. 417, and also in chain -gear ing, where T takes the form T z . The form taken by these chains, apart from the special form of the tension-organ, is (C 2 E, i2 ). Of such higher forms as (C z ff,^ or (CJS^ but few applications exist. One special and limiting form of the chain, however, demands special mention. If we imagine a belt-train with crossed belts (Fig. 418) to have its two pulleys a and c brought into contact, and then the pulley c made infinite in radius, the pair
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