friction-gearing

Century Dictionary and Cyclopedia

1. n. A method or system of imparting the motion of one wheel or pulley to another by simple contact. The advantages of this kind of gearing are threefold: it enables the parts of a machine to be thrown quickly into or out of play; it gives a variable speed or power; and it prevents the injury caused by a breakage or stoppage from extending from one part of the mechanism to another or from the machine to the motor. The most simple form of friction-gearing is a pair of wheels with thin faces, which may be covered with leather, a fabric, or other elastic material, in more or less close contact. In some such wheels the faces are grooved, or the wheels are cone-shaped and placed at a right angle and with grooves cut on the faces. In others a collar on a shaft may carry pivoted arms which if turned one way press against the inner face of a wheel, and if turned the other way fall back out of contact and cease to impart their motion. In other forms one wheel revolves within another, contact being assured by means of springs. If the resistance overcomes the springs the contact is destroyed and motion is no longer imparted. Variable speed and reversal of direction are also secured by causing a friction-wheel placed at right angles with a disk and against it to move from the rim toward the center or past the center of the disk, as in the feed-motion of some forms of gang-saws.