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CHAIN CLOSURE OF SPRINGS. 185
endless band, is now coming into more extended use as a double- acting water-rod.
Springs also, like tension- and pressure-organs, can be completely constrained and used in mechanisms by means of chain-closure. The common clock-spring, Fig. 144, illustrates this. The spring a is con- nected at one end with the cylinder c, and at the other with the barrel b, which is paired with c, and connected to the clock-work. It thus forms a link in a closed kinematic chain, and this is one of its special uses in machinery, where in some cases a constrained motion of special exactness becomes of great importance.
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