SUMMER 2012

46 THE DISTRIBUTOR’S

46 THE DISTRIBUTOR’S LINK Spirol International Corporation 30 Rock Avenue, Danielson, CT 06239 Tel: 1-860-774-8571 Fax:. 1-860-774-2048 Email: info@spirol.com www.spirol.com HOW TO DESIGN THE OPTIMUM HINGE by Christie L. Jones, Market Development Manager There are two primary types of hinges: 1) A Free Fit Hinge has little to no friction or drag when the latch or handle is rotated. Hinge components are “free” to rotate independent of one another. 2) A Friction Fit Hinge requires interference to prevent free rotation of components relative to one another. Depending on design intent, resistance can vary from a slight drag to a value sufficient to maintain the fixed position of components anywhere in their full range of rotation. Although many pin styles are available, Coiled Spring Pins are particularly well suited for use in both friction and free fit hinges. To achieve optimum long-term hinge performance designers should observe some simple design guidelines. Regardless which pin type is used, the gap between hinged components should be minimized to reduce clearance and avoid bending of the pin (Figure 1). Free Fit Hinge If a free fit hinge is desired, the Coiled Pin’s preinstalled diameter is of negligible importance as pin diameter is determined by the retaining, or smallest hole(s). Coiled Pins are functional springs and recovery & retention in free fit locations must be considered. The amount of recovery/retention is dependant upon the diameter of the tight (retaining) hole(s) and the ‘free span’ of the pin. Free span would be defined as the distance a pin passes through a free fit component. As free span increases, the pin diameter will also increase as it “recovers” a portion of its pre-installed diameter (Figures 2a & 2b). It is recommended for better load distribution and closer tolerance hinges that the tight fit of the Coiled Pin be in the outer members of the hinge (Figure 2a). please turn to page 161

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