Leg positions and torsion springs
Torsion springs - leg positions and maximum angular deflection
A standard torsion spring is available with 4 different leg positions. You state the leg positions for an unloaded torsion spring. You define the leg position as 0°, 90°, 180° or 270°.
You then choose which leg position is most suitable for your assembly so the torsion spring can be mounted with the least possible but correct initial tension.
Leg position shown in unloaded state:
A torsion spring is normally mounted in a pre-tensioned position, and then operates at x degrees. To ensure that the spring is not damaged by excessive angular deflection, you have to make sure you always use a spring with as many coils as possible. The more coils, the greater the angular deflection. If you use a torsion spring that can theoretically cope with a 90° angular deflection where it is pretensioned 20° and thereafter turned through 70°, this spring will be maximally loaded and will have a short service life as a consequence.
On the other hand, if you use a torsion spring that can cope with 270° and the desired effect can be achieved at just 100°, this spring will have a considerably longer service life. The combination of wire thickness, spring body diameter and number of coils is what should be considered in the assembly. It is often the case that not enough space is allowed in the assembly for the correct number of coils on a torsion spring.
This leads to a torsion spring with too little angular deflection being used, with a shorter service life as a consequence. Also make sure you have proper control of the body of the torsion spring, so that it does not flex or twist when loaded.
A torsion spring must always be loaded in the direction of the spring wire so the spring body closes.
Large diameter and many coils give a large angle of deflection.
Small diameter and few coils give a small angle of deflection.