Helical Springs

Figure 11-8.-Bevel gear differential. slightly curved bars, plates, or leaves. They also include special flat springs (fig. 11-7, A [3]), made from a flat strip or bar formed into whatever shape or design best suited for a specific position and purpose. Spiral Springs Spiral springs are sometimes called clock, power (1 1-7, B), or coil springs. A well-known example is a watch or clock spring; after you wind (tighten) it, it gradually unwinds and releases power. Although other names for these springs arc based on good authority, we call them “spiral” in this text to avoid confusion. Helical Springs Helical springs, also often called spiral (fig. 11-7, D), are probably the most common type of spring. They may be used in compression (fig. 11-7, D [1]), extension or tension (fig. 11-7, D [2]), or torsion (fig. 11-7, D [3]). A spring used in compression tends to shorten in action, while a tension spring lengthens in action. Torsion springs, which transmit a twist instead of a direct pull, operate by a coiling or an uncoiling action. In addition to straight helical springs, cone, double-cone, keg, and volute springs are classified as helical. These types of springs are usually used in compression. A cone spring (11-7, D [4]), often called a valve spring because it is frequently used in valves, is formed by wire being wound on a tapered mandrel instead of a straight one. A double cone spring (not illustrated) consists of two cones joined at the small ends, and a keg spring (not illustrated) consists of two cone springs joined at their large ends. Volute springs (fig. 11-7, D [5]) are conical springs made from a flat bar that is wound so that each coil partially overlaps the adjacent one. The width (and thickness) of the material gives it great strength or resistance. You can press a conical spring flat so that it requires little space, and it is not likely to buckle sidewise. 11-6