Mattress Coils:
From Wikipedia, the free encyclopedia

Spring mattress core

The core of the mattress supports the sleeper’s body. Modern spring mattress cores, often called “innersprings,” are made up of steel coil springs, or “coils.”

The gauge of the coils is another factor which determines firmness and support. Coils are measured in quarter increments. The lower the number, the thicker the spring. In general, higher-quality mattress coils have a 14-gauge (1.63 mm) diameter. Coils of 14 to 15.5-gauge (1.63 to 1.37 mm) give more easily under pressure, while a 12.5-gauge (1.94 mm) coil, the thickest typically available, feels quite firm.

Connections between the coils help the mattress retain its shape. Most coils are connected by interconnecting wires; encased coils are not connected, but the fabric encasement helps preserve the mattress shape.

Here are five types of mattress coils:

• Bonnell coils are the oldest and most common. First adapted from buggy seat springs of the 19th century, they are still prevalent in less expensive mattresses. Bonnell coils are hourglass-shaped, and the ends of the wire are knotted or wrapped around the top and bottom circular portion of the coil and self-tied.
• Marshall coils are each wrapped in a fabric encasement and usually are tempered. In the case of Beautyrest, high carbon magnesium is added, while the steel itself remains untempered. Some manufacturers pre-compress these coils, which makes the mattress firmer and allows for motion separation between the sides of the bed.
  

  

  Bonell springs

• Encased Coils or encased springs, are a component part of a mattress in which each coil is separately wrapped in a textile material. Encased coils may also be generically referred to as Marshall coils or wrapped coils.
• Offset coils are designed to hinge, thus conforming to body shape. They are very sturdy, stable innersprings that provide great support.
• Continuous coils Or Mira-coils, work by a hinging effect, similar to that of offset coils. In a basic sense a continuous coil is simply that, one continuous coil in an up and down fashion forming one row (usually from head to toe) of what appear to be individual coils. The advantages of how firm a support the continuous coil provides it is somewhat tempered with the “noise” associated from a typical Mira-coil unit. The largest company using a Mira-coil design, is Serta Mattress Company, though their coil units are supplied by Leggett & Platt.

Bonell springs are hour-glass shaped, which means their resistance increases with load. They are therefore best suited for firm mattresses.

Pocket springs provide support along the entire length of the body. This design works to maintain natural spinal alignment throughout the night.^{[clarification needed]}

A Coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. They are made of an elastic material formed into the shape of a helix which returns to its natural length when unloaded.

Coil springs are a special type of torsion spring: the material of the spring acts in torsion when the spring is compressed or extended.

Metal coil springs are made by winding a wire around a shaped former – a cylinder is used to form cylindrical coil springs.

Variants

The two usual types of coil spring are:

• Tension coil springs, designed to resist stretching. They usually have a hook or eye form at each end for attachment.
• Compression coil springs, designed to resist being compressed. A typical use for compression coil springs is in car suspension systems.

Degradation

Many types of coil spring are wound in an annealed (soft) condition and then tempered to achieve their strength as a spring. Over time, this tempering can be lost^{[citation needed]} and the spring will sag because it can no longer withstand the loads applied. Such springs can be re-set by annealing, returning to their original length (or deliberately setting them to a different length) and then re-tempering. Damage to springs, such as using oxy-acetylene to cut the end off a car suspension spring to lower a vehicle’s ride height, can destroy the tempering in localised areas of the spring.