Tension springs are tightly wound coils that are designed to operate with tension. The spring stretches to a specific length as the load/force is applied to it.
In an unloaded position, the loops of the spring are touching, with either a loop or hook attached at one end, and it is when this attachment is directed with force that the spring stretches. When these components are pulled apart, usually from either side, the spring tries to hold itself together, causing the springing action, until the force is stopped and it can return to its original form.
The initial tension applied to the tension springs can be controlled using the cold coiled process, in which the wire is formed into a spring shape using a coiling machine.
Examples for uses of tension springs include lever mechanisms and doors. A good example of tension springs in action is the counterbalancing of garage doors.