Figure 25.5 shows a selection of flat springs, circlips, and spring pressings. It will be apparent from the selection that it would be difficult, if not impossible, to devise a drawing standard to cover this type of spring, and at present none exists.
Flat springs are usually made from high-carbon steel in the annealed condition, and are subsequently heat-treated; but the simpler types without bends can frequently be made more economically from material pre-hardened and tempered to the finished hardness required. Stainless steels are used for springs where considerable forming has to be done. For improved corrosion-resistance, 18/8 stainless steel is recommended; but, since its spring temper is obtained only by cold-rolling, severe bends are impossible. Similar considerations apply to phosphor bronze, titanium, and brass, which are hardened by cold-rolling. Beryllium copper, being thermally hardenable, is a useful material as it can be readily formed in the solution-annealed state.
(c) Simplified representation (f) Simplified representation Fig. 25.1
Figure 25.6 shows a selection of flat spiral springs, frequently used for brush mechanisms, and also for clocks and motors. The spring consists of a strip of steel spirally wound and capable of storing energy in the form of torque.
The standard for spiral springs is illustrated in Fig. 25.7, (a) and (b) show how the spring is represented in conventional and simplified forms.
If the spring is close wound and fitted in a housing then the illustrations in (c) and (d) are applicable.
(a) Closed ends, ground
(b) Closed ends
(c) Open ends, ground
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