Tension Springs are obtained by helically winding a round wire made of metal or metal alloy. The heads of the tension springs are usually curved in the form of hooks or rings. One end of these springs is kept fixed and the other end is pulled and the spring stores energy. Thanks to this energy, when the force applied to the spring is removed, the spring begins to pull towards itself. Tension springs are generally produced as pre-tensioned and adjacent wound. Critical shear stress levels should be carefully examined in order to avoid bending and torsion fractures in the hooks and attention should be paid to the absence of any notches, small radii and cross-sectional narrowing in the hooks.
Tension springs, in other words, closed springs differ greatly according to hook types. Tension spring hooks can be designed from the spring's own material, or they can be manufactured from different materials in different types and forms. According to these, spring shapes, which are expressed as choke tension springs or pin tension springs, are born. In this type of tension springs, the hook material diameter must be above the spring material diameter. Under normal conditions, tension springs should be able to be pulled without deformation by at least one times their closed length. The retaining hook points of closed springs should be centered on the spring and should not disturb the axial perpendicularity. Otherwise, the axis straightness of the springs is disturbed.