Mattress: Encyclopedia II - Mattress - Spring mattress core

Mattress - Spring mattress core

The core of the mattress is the most important part in the support of the body. In most modern mattresses (except for the foam-only ones), it is made up of steel coils springs, also known simply as coils. The spring mattress core is also called innerspring. It provides support to the set. Proper support is where the wire coils push back in response to weight deflection to hold the body in alignment. The steel coil spring was invented during the industrial revolution and was first patented for use in a chair seat in 1857. Then, in 1871, Heinrich Westphal invented the innerspring mattress. He lived in Germany and died in poverty, having never profited from his invention.

Mattress - Number of coils

Basically, the more coils a mattress has, the more support it will give the user. As a general rule, very firm mattresses have a high coil count. Generally, but depending on the mattress size, they come with 300 to 800 coils. Depending on the size, 500 to 800 coils is considered firm. However, some expensive and comfortable mattress only have around 400 coils. and it takes as few as 312 coils in a full mattress to provide decent support. Assuming that the overall coil count is decent, a heavy duty innerspring mattress may also increase the longevity of the mattress for large users.

Mattress - Gauge of the coils

Obviously, heavy gauge (thick) coils will offer a great deal of support while light gauge coils will give less support. A low coil count and heavy gauge wire can pass as a firm mattress in the store, but it is likely that this mattress will become lumpy quickly because it does not have enough coils. Many premium mattresses feature 14-gauge (1.63 mm) coils. Coils are measured in quarter increments. The lower the number, the thicker the spring. With coils of 14 to 15.5 gauge (1.63 to 1.37 mm), it is important that the total coil count be high to compensate for the fact that they give so easily under pressure. A 12.5 gauge (1.94 mm) innerspring, the thickest typically available, may feel rock hard in a double mattress even with a coil count of 400 or less.

Mattress - Connections between the coils

Generally, the number and quality of these interconnecting wires is not published by the manufacturers. If there are too few of these interconnecting wires a mattress can lose its shape more quickly than one that has an adequate amount. Mattresses that sag quickly usually have few interconnecting wires. There are some manufacturers that make individually pocketed coils, which avoid movement on different sides of the bed because they are not interconnected. However, the special pockets provide the support required by the coil instead of the interconnection with other coils.

Mattress - Types of coils

Construction-wise, most manufacturers claim to have the best coil-to-gauge ratio. However, there are only a few innerspring manufacturers and 4 general types:

These are the oldest ones and most commonly used. They were adapted from buggy seat springs of the 19th century. They are still prevalent in low priced mattresses. They have an hour-glass shape, and the ends of the wire are knotted or wrapped around the top and bottom circular portion of the coil(round-topped and self tied).

Also called pocketed coils, they are individually pocketed and less frequently used. Might not be properly tempered. The brand Simmons uses pocketed coils in their mattresses. Simmons also does some things that other brands that use pocketed coils don't. They "pre-compress" their pocketed coil, which means that they pack the coil into a "pocket" that is shorter (usually by a couple inches) than the coil. By "pre-compressing" the coil, it becomes a firmer coil, thus making up for the steel not being tempered. Additionally, when two people sleep on the same mattress, the individually wrapped (or individually pocketed) coil provides motion separation (when one person tosses and turns, the other doesn't feel it.) This is important because when one person tosses and turns, it may not completely wake the other person, but, it can take them out of a deep sleep which is when the body does all of its regeneration. When a sleeper is undisturbed at night they can fall into that deep sleep faster, stay in a deeper sleep longer and wake up feeling more refreshed because it allows the sleeper to get more use out of their sleep.

Bonnell coils evolved into Offset coils, which are currently popular, but happen to be the most expensive ones. They are almost identical to the Bonnell coils, except that the top and bottom circular part of the coils have flat or straight sides, which allow for better hinging action when they are placed together in a spring unit, and which can be easily aligned. An evolution of the offset coils brought the elimination of the knot that tied the end of the wire to the coil. In other words, offset coils might be tied off or feature a loose end (sensory arm). These are called "open end offset coils". These improvement gave offset coils an extra turn of working wire for greater spring action on each end of the coil. However, loose ends increase the odds that a spring will begin to punch through the padding. Brands like Sealy and Spring Air use open end offset coils in their mattresses. Additionally, some brands change over the years for many reasons including, but not limited to, the change of ownership of a manufacturer. For example Stearns and Foster was made with a Bonnell coil system for many years, however, when they were purchased by Bain Capitol (the same company that now owns Sealy) the coil system was changed to a Double Offset system exactly like the Sealy Posturepedic.

They look like double wire spirals or loose ringlets, creating a network of wire that runs nonstop through the entire bed. The brand Serta uses continuous coils in their mattresses.

Adapted from the Wikipedia article "Spring mattress core", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki