Pocket coils, also known as pocketed coils, encased coils, wrapped coils or Marshall coils, are light gauge open-end coils in fabric pockets. They were invented in 1900 by James Marshall, an Englishman who migrated to Canada. In Toronto, Ontario, Canada he founded the Marshall Mattress Company to make mattresses using his technology. The company is still in business, focusing solely on pocket coil mattresses. It was featured in a 2011 BedTimes Magazine story.
The pockets are attached to each other, but the coils are not. This allows each coil to respond independently to weight place directly on it. According to Brad Warner, owner of Marshall Mattress, the pocket coils were invented to meet a need: “Legend has it that Mrs. M. was bedridden and Marshall created the support system for her, with coils wrapped in unbleached muslin, quilted with horsehair and outer tufted.”
At first, since they had to be made and encased by hand, pocket coils cost so much to manufacture that they could be used in only the most expensive mattresses. Then in 1925, Simmons engineer J. F. Gail invented a machine to make the coils and insert them into cotton pockets. This reduced the cost of a pocket coil mattress enough to place it in the general market.
Pocket coils are now very common around the globe. According to Marshall Mattress, “Marshall’s pocket spring-filled mattress system has become the original worldwide standard for spring-filled mattress construction and remains to this day.”
The main advantage of Marshall coils is the individualized support they offer. The independent response of each coil conforms the entire unit to the shape of the user’s body, resulting in even support for the entire body. This means two things:
(1) Larger parts of the body do not bear a disproportionate load. This reduces or eliminates pressure points.
(2) In-between sections of the body are supported. This keeps the spine in proper posture, relieving or preventing back and neck pain.
Refinement of pocket coils is ongoing. Relatively recent developments are microcoils and dual coils. Microcoils are short, small diameter pocket coils. Though no industry-wide standard definition of microcoil has been set, the term is used for coils as much as 4″ tall.
Dual coils are a coil-in-coil design, first patented in 2010 by Sealy engineer L. K. DeMoss. The two coils are made of one wire. They turn in opposite directions. The outer coil is taller with fewer turns, making it more responsive. The inner coil is short and has more turns, making it more supportive. This configuration makes it more durable than the hourglass figure of Bonnell coils, which also have a dual response.
Another development in pocket coils is tall coils, some as much as 10″ high. The objective of this development is to make the mattress less dependent on less durable comfort materials such as memory foam, latex, and foam in general, as well as reducing the overall height of ultra plush innerspring mattresses.
Though pocket coil technology is over 115 years old, the basic value of individually wrapped pocket coils along with continuing development of this form of innerspring support indicates that Marshall coils are here to stay.
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