Spring mattresses have a history of over decades. People have been using different kinds of spring mattresses ever since mattress companies started manufacturing them.
Here, we provide some information about some common types of spring system used in mattresses.
Continuous coils
An innerspring configuration in which the rows of coils are formed from a single piece of wire. They work in a hinging effect like that of offset coils.
Bonnell coils
The oldest and cheapest. Bonnell springs are a knotted, round-top, hourglass-shaped steel wire coil. When laced together with cross wire helicals, these coils form the simplest innerspring unit, also referred to as a Bonnell unit. Steel coils make innerspring mattress are bouncy and do not offer motion isolation.
Offset coils
An hourglass type coil on which portions of the top and bottom convolutions have been flattened. In assembling the innerspring unit, these flat segments of wire are hinged together with helical wires. The hinging effect of the unit is designed to conform to body shape. LFK (Left Facing Knot) coils are an offset coil with a cylindrical or columnar shape.
Pocketed coils
Also known as wrapped or encased coils or Marshall coils, are thin-gauge, barrel-shaped, knotless coils individually encased in fabric pockets—normally a fabric from man-made, non-woven fiber. Some manufacturers pre-compress these coils, which makes the mattress firmer and allows for motion separation between the sides of the bed. As the springs are not wired together, they work independently: the weight on one spring does not affect its neighbours. This allows them to react to pressure independently instead of all together, which minimizes movement and allows for a more buoyant feel. These are used by the most premium mattresses.
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