A tension spring (also called a resistance spring, or simply a tension spring) is a helical spring that bears axial tension. Tension springs are generally made of round cross-section material. When not under load, the coils of a tension spring are usually tightly wound with no gaps.
The coils are tightly wound to allow it to stretch under load, with each end wrapped in a loop.
The following are essential data for a tension spring:
(1) Free length: (a) Total length, (b) Total coil length, (c) Length within the hook loop.
(2) Control diameter: (a) Outer diameter, (b) Inner diameter, (c) Inner diameter of the sleeve.
(3) Wire size (diameter).
(4) Material (type, grade).
(5) Number of coils: (a) Total number of coils and (b) Right-hand or left-hand helix.
(6) End type.
(7) Load capacity within the hook. (8) Load factor, deflection, pounds per inch.
(9) Maximum tensile length.
