Torsion Springs
A torsion spring is a mechanical device that stores and releases rotational energy. The ends of a torsion spring are connected to a mechanical component. As the spring is rotated around its axis on one end, the winding of the spring is tightened and stores potential energy.
During the winding process, one end is deflected about the body centerline axis, while the other end is held fixed. As the winding gets tighter and resists more rotational force, the spring stores more potential energy.
Once a torsion spring is released, it will unwind as it makes an elastic rebound, and the stored energy is released. An equal rotational force is exerted on the opposite end of the spring, which can apply torque on the attached mechanical component. Torsion springs statically hold mechanical components in place.
The mechanics of torsion springs is based on their resistance to rotation or twisting. The mechanical energy produced by the resistance is stored and exerts torque in opposition to the twisting force that is proportional to the angle that it is twisted. Common types of torsion springs are helical, torsion bars, and spiral wound. Each of the various types are made from wire, sprung steel, or rubber.
Torsion springs are subjected to more bending stress than rotational stress as the spring is twisted to make a tighter winding. They are unlike other springs because only rotational force is involved. Linear force is not part of torsion springs, unlike compression and tension springs.
The mechanical forces of torsion springs depend on the elasticity of its material, which enables torsion springs to revert to their original winding after being twisted. Torsion springs can be rotated and apply force in a clockwise or counterclockwise direction and must be rotated in the direction of the winding to generate maximum force.
Torsion springs are found in a wide range of applications, almost in every industry. These springs come in many configurations.
I. Basic Parameters of Torsion Springs
1. The Inner Diameter of a torsion spring is the width inside the helix of the coil, measured perpendicularly to the centerline axis. This dimension determines the outside diameter of a shaft or mandrel that can smoothly fit into the spring. It is recommended that the inside diameter has a 10% clearance for the inserted component to operate freely.
2. The Outer Diameter of a torsion spring is the width outside the helix of the coil, measured perpendicularly to the centerline axis. This dimension determines the diameter of the hole through which the spring is inserted, taking all clearances for the spring to operate freely into consideration.
3. The Wire Diameter refers to the diameter of the wire coiled to construct the torsion spring.
4. The Mean Diameter is equal to the outer diameter minus the wire diameter used in stress and spring rate calculations.
5. The Body Length is the length of the torsion spring at an unloaded condition. This dimension is obtained by measuring the outer surfaces of the end coils. As torque is applied in the spring, the body length will increase as the spring diameter is decreased.
6. The Leg Length is the distance from the end of a torsion spring’s leg to the centerline axis of the coil. It determines the load or torque required to store energy in the spring. Shorter legs need higher torque input to bend the coils. The legs of a torsion spring may have different leg lengths.
7. The Total Coil of a torsion spring is the number of active coils present in the winding. Active coils are the turns in the torsion spring winding that twist or deflect when a load is applied to the leg and release energy when the spring is released. In torsion springs, the total coil is a fraction less than the total number of coils present in the winding because the legs are accounted for by the number of inactive coils in the value of the total coil. For torsion springs having a 00 leg angle at the free position, the value of the total coil is a whole number.
II. Winding Direction
The coils of a torsion spring are wound in a specific direction. Torsion springs may have a right or left hand winding, where the coils rotate in a clockwise or counterclockwise direction, respectively. The direction of the winding can be easily determined by looking at the top of the torsion spring.
III. Leg Angle
The leg angle of a torsion spring refers to the angle that the legs make when it is in the free position before any load is applied to the leg. It varies from 0°-360°. Standard torsion springs are available in stores whose leg angles are 90°, 180°, 270°, and 360°. The leg angle can also be customized by the manufacturer based on the client’s needs.
IV. Leg Orientation
The leg orientation is how the legs are bent with respect to the spring diameter. The sharp bends on the leg can limit the capacity of the spring since stress concentrates on the bent area. The types of leg orientations are axial, tangential, radial, and radial-tangential. The tangential leg configuration encounters the lowest stress.
V. Leg Style
The legs of a torsion spring can be twisted, bent, hooked, and looped to make installation and operation convenient. The common leg styles of torsion springs are enumerated below; however, leg styles can be customized upon customer request.
The majority of the information above is excerpted from IQSDirectory.com.
