spiral spring

A coil whose rounds have the same diameter, and which is generally utilized by compre ion or extension in the line of its axis. Spiral -spring coupling : A coupling for a pair of shafts meeting at an angle. The ends of the spiral connect to the respective shafts and make a bent coupling. spiral-ve els, s. pl. Bot.: Membranous tubes with conical extremities, their interior occupied by a fiber twisted spirally, and capable of unrolling with elasticity. Called also Trachem. They are designed for the transmi ion of air. When formed by the convolutions of a single spire they are called Simple, when by those of many turning in the same direction they are called Compound. spiral-wheels, s. pl. Mach.: A species of gearing which serves the same purpose as bevel-wheels, and is better adapted for light machinery. The teeth are formed upon the circumferences of cylinders of the required diameter, at an angle with their respective axes, when the direction of the motion is to be changed. By this construction the teeth become in fact small portions of screws or spirals winding round the cylinders. Wheels of this kind are used when the two shafts require to pa each other; when the shafts are in the same plane bevel-wheels are em ployed. The In a