Coil springs
Sep 20, 2007 7:28 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605
I finally got bored enough that I decided to spend some time boning up on coil springs / innerspring mattresses.

Time to learn about Bonnell springs, coil counts, wire gauge, and whatever else is important in the world of innerspring mattresses...
This message was modified Sep 20, 2007 by haysdb
Re: Coil springs
Reply #1 Sep 20, 2007 8:31 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605
What I have found so far as the important "numbers" for a coil unit:
  • Coil count
  • Gauge of wire
  • Type of coil
  • Working turns (actually, I heard this somewhere, but did not run across the term even once tonight.)

Some great info at Hospitality Bedding Co.

95% of all coil units in the United States are made by Leggett & Platt

There is a table there which lists coil counts for different Leggett & Platt coil units. The coil counts are for a full-size mattress.

Bonnell (also called Open Coil)
  • 231 11x21
  • 252 12x21
  • 312 13x24
  • 325 13x25
  • 336 14x24
  • 364 14x26
  • 405 15x27
  • 510 17x30

Offset
  • 308 14x22
  • 330 15x22
  • 368 16x23

Continuous coil (also call Mira-coil)
  • 432 18x24
  • 660 22x30
Some excerpts from their website:
  • COIL COUNT - The first game that you have to watch out for involves the coil count. In the industry, coil counts are quoted by the full size - regardless of what size you're actually buying.
  • ...[a] not so ethical salesman might take advantage of his customer by quoting the actual coil count of a lesser quality bed. For example look at the chart again under Bonnell but this time follow the 252 across to the King column 16x23 which equals 368. So the uninformed customer might think they were getting a bargain when in reality they're getting taken.
  • The 312 unit was the standard coil unit specified by most hotel chains. It did not stand up to the heavy demands placed on it so now the 336 unit is being specified by most chains. Hospitality Bedding Co. always suggests a 364 unit. This unit is the work horse of the bedding industry and simply does not wear out. As a point of fact, the 364 used to be Sealy's Posturepedic coil unit. Sealy wanted a coil unit that was proprietary so they now make their own.
  • GAUGE OF THE WIRE - This refers to the thickness of the wire used. The lower the gauge the thicker the wire and conversely the higher the gauge the thinner the wire
  • TYPE OF COIL - There are basically 3 types of coils: Bonnell, Continuous, and Offset.
  • Bonnell: This is the workhorse of the industry. It is an hourglass shaped coil that nests one into another. The 312, 336 and 364 units all use a Bonnell coil.
  • Continuous Coil: This is where the entire unit is comprised of one continuous wire with a uniform shaped coil that nests one on top of the other. Typically it's a high gauge (usually 17 1/2) making it a thin wire. The 660 unit is an example of this.
  • Offset Coil: Is a blend of the other two. It tapers slightly then back out (Similar to the hourglass shape of the Bonnell) and has an oblong or offset curvature to it. The 368 unit is a good example of this.
  • [Pocketed coils - This article doesn't mention Pocketed / Marshall coils.]
  • Don't confuse "soft" or "firm" with support. Your support comes from the coil unit.
  • The final component to this set is the foundation or box springs. The purpose of the foundation is to help support the mattress by absorbing pressure thus helping to distribute body weight evenly. The proper foundation has a wood frame and properly tempered coils. An all wood foundation is available but since it does not have coils, it cannot help to distribute body weight. The mattresses lifespan is directly connected to the proper support it receives from the foundation. To understand this better think of the boxspring as a shock absorber. If the shock absorber is removed all the weight is transmitted directly to the springs of the mattress rather than being cushioned by the boxspring below. The mattress has to work twice as hard and is prone to wear out faster.
This message was modified Sep 20, 2007 by haysdb
Re: Coil springs
Reply #2 Sep 20, 2007 9:10 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605

www.chooseamattress.com

Innerspring mattresses have wire coils as the support structure. An innerspring mattress has a strong border wire attached to the perimeter of the coils. The border wire supports the coils, helping to retain shape and reduce sagging. The edge is reinforced with specially shaped springs or foam to support the sleep surface right to the edge, to help prevent 'rollout' and edge breakdown. The upholstery is separated from the innerspring system by an insulator, a tough padding, wire or netting layer that prevents the upholstery from sinking into the coils.


Open Coil or Bonnell Coil: These are the oldest and most commonly used. They were adapted from a design used in buggy seats in the 19th Century. This hourglass-shaped wire coil is joined to adjacent coils by small wire spirals called helicals. The open coil design provides good initial support but these coils fatigue more quickly than more technically advanced coil constructions. You'll know this mattress has reached the end of its life when you and your bed partner are experiencing the 'roll together' or you suddenly realize that your mattress feels more like a hammock.


Offset Coil: This coil construction is similar to the open coil but it has a squared head, which in theory enables the mattress to contour better. It is a descendant of the Bonnell or open coil. An offset coil is slightly more cylindrical in shape than an open coil, which may make it more durable. It is also laced to its neighbors by helicals. These are usually the most expensive coils.

Pocket Coil/Independent Coil or Marshal Coils: A pocket or independent coil is a cylindrical spring wrapped in its own fabric pocket. This construction is designed to give the most contour of any support system. Each coil works independently which means that you will feel your partner move much less. Each pocket coil absorbs the weight placed on it without distributing the load to other coils. Because of this, it is possible that the coils will provide less support over time, particularly for heavier people. This type of coil is a good choice for people who toss and turn and for their bed partners because the motion separation may prevent waking from a deep sleep which is very important for well being. Simmons uses this type of coil.


Continuous Coil: The continuous coil is exactly what it says - each row of coils is made of a single wire attached to the next row by helicals. This type of coil is often made into a lattice of coils rather than rows, allowing more coils per mattress than other constructions. This design allows each coil to deflect weight to a great number of springs resulting in less stress on each coil. Mattresses with continuous coils keep their shape longer. Serta and Kingsdown use these types of coils.


This message was modified Sep 20, 2007 by haysdb
Re: Coil springs
Reply #3 Sep 20, 2007 9:27 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605
There seems to be some disagreement about how many different kinds of coils there are. Already I have heard 3, 4, and now 5.

Selecting an Innerspring Mattress (Utah State University)


The five most common coil systems are Continuous, Karr, Knotted Bonnell, Knotted Offset and Marshall

  • The continuous coil system consists of coils formed from a single strand of 18 gauge steel wire strung through the system. This system gives a lot of support because of increased use of wire, even though it is 18 gauge wire.
  • The Karr coil system consists of hour-glass shaped coils with the ends left unknotted. The hour-glassshaped coil offers a soft surface and firmness as pressure is applied. The offset coil configuration of the Karr coil means the coils are not totally round at the top and bottom. This shape is what gives the coils independent movement and reduces leaning by alternating offset from right to left.
[I wonder if this coil type is no longer used?]
  • The Knotted Bonnell coil system consists of the hourglass shaped coils with five turns. It has a knotted end, making the surface firm.
  • The Knotted Offset is similar to the Bonnell except that part of the top and bottom wire sections are squared off to fit together in a parallel fashion on the top surface. This hinge action also prevents leaning and sagging.
  • The Marshall coil system consists of cylindrical coils sewn into a cloth or plastic pocket, so that they move independently of each other. The pockets keep each spring under tension at all times, thus reducing the tendency of the spring to spread when compressed. The Marshall system has a lot of coils. Since there are so many coils, very light wire is used to make the coils, around 18 gauge wire. This coil system is uncommon today, partly because of the high cost.
[Note: this document is dated 1987]
This message was modified Sep 20, 2007 by haysdb
Re: Coil springs
Reply #4 Sep 20, 2007 9:48 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605
Going to the Mattresses - How to cut through the marketing gimmicks of Sealy, Serta, and the rest.

Here's a fun game I play. First, I walk into a mattress store and ask what's on sale. Then, I throw my hands in the air and shout along with the salesman, "EVERYTHING'S ON SALE!!!!" Oh how we laugh, the salesman and I. And while he's still chuckling, I turn around and walk out, because I fricking hate mattress salesmen.

Is there a more maddening industry? They confuse us with silly product names (the Sealy Posturepedic Crown Jewel Fletcher Ultra Plush Pillowtop or the Sealy Posturepedic Crown Jewel Brookmere Plush?). They flummox us with bogus science ("pocketed coils"? "Microtek foundations"? "Fiberlux"?). And they weigh us down with useless features (silk damask ticking?). It's like buying a used car, and almost as expensive—I've seen mattresses going for $7,000. What's a consumer to do?

The secret to mattress shopping is that the product is basically a commodity. The mattress biz is 99-percent marketing. So just buy the cheapest thing you can stand and be done with it, because they're pretty much all the same. And that's all you need to know. But do read on—the world of sleep products is quite fascinating, and I'd like to share it with you.


Here's the lowdown: Mattress makers rename identical products for each different retail store. Different labels, exact same guts. Why? Obfuscation. It's hard to shop for the lowest price when you can't compare apples to apples. Lucky for you, they're all subtle variations on the same apple—not only within each brand, but even among different brands.

The heart of an innerspring mattress is the coils. Otherwise it's just foam, cotton, quilting, and stitches. But the big-name mattress makers (with some exceptions) all get their coils from a single company, Leggett and Platt, for their highest-end mattresses down to their lowest. This is akin to every single car on the market, Lamborghinis to Kias, using an engine made by Ford. Except that mattresses are far less complicated than cars. In fact, they're so simple that there's no real difference among them at all.

Upshot: Ignore brand names. They're meaningless. Just pay attention to comfort.

This is a great read. Some funny and insightful stuff here. Definitely worth a read of the entire article.
  • My favorite mattress name encapsulates the paradox: Simmons Beautyrest World Class Granite Plush. Granite Plush???
  • Larry Thomas of Furniture Today—a man described to me as "the guru of the bedding industry"—told me coil counts are "overrated" and "not a good indicator."
  • Pillowtops: Pillowtops are soft layers of foam (or cotton, or wool) sewn to the top of the mattress. They're hugely popular. They add hundreds of dollars to your purchase. They are, in my opinion, a massive rip-off.
  • Experts I talked to say thickness is just a ploy: It makes beds look comfy in the showroom. If you notice a difference, mazel tov, but thickness isn't vital to a good bed.
  • Mattresses have gotten so thick recently that people are complaining they can't see their headboards. Actual industry response: They made the box-springs thinner. Which of course leads us to ...
  • Box Springs: I find them wholly unnecessary. Think about it: Presumably, you could put a box spring under your box spring for even more "give" and "support." Another box spring under those two. Where do you draw the line?
  • Many Europeans use platform beds without box springs. Do you hear them complaining?
  • "Back pain has a lot to do with how you're built, but not a lot to do with your mattress."
  • Do I Need All Those Extra Features? No. Screw 'em.
  • Ticking and Quilting: People often buy based on how a mattress looks in the store. This is moronic. You're going to spread a sheet over it the second you get home. Belgian damask? Really, now.
  • No-Flip Designs: Manufacturers say to flip your mattress every three months. It's even in some warranties. Yet this year's Simmons Beautyrest 2000 boasts a "no flip" design. And it's selling like hotcakes (for which flipping, incidentally, remains compulsory). Why? People love work-saving innovations—we're too lazy to flip. But what does it really mean? It means there's block foam on one side instead of something you could sleep on. And it means if there's a stain or a rip on the sleeping side, you're SOL. They should have called it the "can't flip" design. It's like a "No Oil Change" car that's simply had the dipstick and cap soldered in place.
  • Select Comfort air mattresses... I didn't like the feeling of air, even though I could adjust the firmness with a remote-controlled pump. When you compress it with your weight, air doesn't seem to have as much give as foam. And it felt like I was camping.
  • Remember: Once you're asleep, every mattress feels the same.
Re: Coil springs
Reply #5 Sep 20, 2007 10:01 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605
Bed Express

There are 4 types of innerspring units used in today's mattresses:
  • Individual Pocket Coil - Considered the most conforming coil. Gives a mattress a very "quiet" feel. This coil produces the least amount of motion when someone else sits or lies on the bed. Coil counts range from 580 to 704.
  • Continuous Coil - Each row of coils is made up of one continuous wire, rather than each coil being a seperate wire. Considered a firm, yet individually conforming coil. The firmest coils Leggett & Platt makes are constructed this way. Coil counts range from 442 to 755.
  • Offset Coil - Each coil is oval in shape lapped over the coil in the next row. Considered a firm, yet individually conforming coil. Coil counts range from 368 to 680.
  • Bonnell Coil - Classic "hour glass" shaped coil found in most basic bedding. Coil counts range from 210 to 364

Innerspring units are named by the number of coils in a full (or double) size bed. To compare coils, you must know the number of coils in a full size, regardless of the size bed you are actually buying.
Leggett & Platt
Reply #6 Sep 20, 2007 10:08 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605
Leggett & Platt (Wikipedia entry)

The 124-year-old firm comprises 28 business units, 33,000 employee-partners, and more than 300 facilities located in over 20 countries.

2004: Revenues exceed $5 billion.

Company History

In 1883 in Carthage, Missouri, far removed from any major metropolitan or urban areas, a historical partnership began. J.P. Leggett, an inventor, initiated the partnership because he had developed an innovative bedspring. Mr. Leggett’s bedspring consisted of single cone spring wire coils, formed and interlaced in a unique manner, then mounted on a wood slat base. The bedspring could then be used as a resilient, durable base for the then-popular cotton, feather or horsehair mattresses. Needing expertise in manufacturing and production, he recruited his brother-in-law, C.B. Platt, whose father owned and operated Platt Plow Works, into the partnership. Together, they perfected the equipment necessary to produce the components of their Leggett & Platt bedspring, which was patented in 1885.


Bedspring vs. Innerspring

At the time of their invention, bedsprings referred to cone-shaped wire coiled springs, attached to a wooden slat foundation, used to support then-popular mattresses. These mattresses were typically made of horse hair, corn husks, cotton, feathers, or another soft material. Early bedsprings functioned similarly to today's box springs in their support of a mattress. However, box springs are rather rigid in structure, while bedsprings provide a more flexible surface.

Innersprings, by contrast, refer to the core system of wire springs that, along with various types of foam and other padding materials, comprise the insides of today's mattress. The mattress is usually coupled with a box spring to create a sleep set. Innersprings can be coiled springs laced together, continuous coil springs, or individually pocketed springs, that support a person sleeping on the mattress.
Re: Coil springs
Reply #7 Sep 20, 2007 10:14 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605

Mattresses (Wikipedia entry)


Types of coils

There are four different 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, also called "pocketed coils," are each wrapped in a fabric encasement and usually are tempered, or in the case of the Simmons Beautyrest carbon magnesium is added. Some manufacturers pre-compress these coils, which makes the mattress firmer and allows for motion separation between the sides of the bed.
  • 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 and up and down fashion forming one row (usually from head to toe) of what appear to be invidiual coils. The advantages of how firm a support the continuous coil provides is somewhat tempered with the 'noise' associated from a typical mira coil unit.

www.sleepdex.org

Offset coils are more expensive than Bonnell or Marshall coil springs but they are designed to hinge for more support and comfort in a mattress. Offset coils conform better to body shape than Bonnell or Marshall coils. Continuous coils are thought to provide the maximum coil strength by working together and gathering strength off of the next coil. Continuous coils work similar to offset coils in that they conform and distribute body weight efficiently and limit the transfer of motion; two qualities that are highly prized in today’s modern mattress.


The Do-Not-Remove Tag

All mattresses and pillows come adorned with the anxiety producing do-not-remove-under-penalty-of-law tag. This innocuous piece of reinforced paper strikes fear into the hearts of millions of consumers who would love to cut the annoying tag off of their product. Well, consumers unite! Go right on ahead and rip off that tag! There are no pillow police or mattress monitors that will show up at your door, cuffs in hand, ready to cart you off to the tag remover reformatory. The tag was intended to provide important consumer information regarding the compliance of the construction materials with federal use and flammability regulations, the content of the product, as well as to give consumers product care instructions and wearability info. If the tag is removed by the seller, it is certainly a violation of federal law. However, the consumer is welcome to remove the tag at will.


The Better Sleep Council - Don't be fooled by their name or their nonprofit status, the Better Sleep Council is the mattress industry and they attempt to get people to buy mattresses. Their website encourages people to throw out old mattresses after 5 to 7 years or even when you find you've had a better night's sleep in another bed. This is probably overkill, although it is a good idea to not continue to sleep on an old dilapidated mattress.


Disposing of old mattresses

The Salvation Army will take donations of mattresses, but they prefer items that are in decent condition. Don't call them if your old mattress is too dilapidated. The good thing about the Salvation Army is that they will come pick up the mattress, and sometimes you can even leave the mattress outside if you aren't going to be home. Call your local Salvation Army (they are in the phone book) to confirm that they will take mattresses and to schedule a pick up.
This message was modified Sep 20, 2007 by haysdb
Leggett & Platt patents
Reply #8 Sep 20, 2007 10:41 PM
Foam Nerd
Location: USA
Joined: Aug 30, 2007
Points: 605
Leggett & Platt patents

A few of their 189 patents

This message was modified Sep 20, 2007 by haysdb
Re: Coil springs
Reply #9 Sep 20, 2007 10:48 PM
Joined: Sep 10, 2007
Points: 690
This website from L&amp;P bedding (Legget &amp; Platt) really explains their products well. You can click on each one of their innerspring systems to see details, including illustrations.&nbsp; I have the LuraFlex open offset coil. Supportive, but conforming.<BR><BR><BR><BR><BR><BR><A href="http://www.beddingcomponents.com/innersprings.asp"><SPAN style="COLOR: #810081">Leggett &amp; Platt - Bedding Group</SPAN></A>
Re: Coil springs
Reply #10 Sep 20, 2007 11:03 PM
Joined: Sep 10, 2007
Points: 690
<BR><BR>Go to Leggett &amp; Platt---Bedding Group<BR><BR><BR>http://www.beddingcomponents.com/innersprings.asp<BR><BR><BR>You will find detailed information on all of their innersprings and boxpsprings. A great site!<BR><BR><BR><BR><BR><BR><BR><BR><BR><BR><BR> haysdb wrote:
I finally got bored enough that I decided to spend some time boning up on coil springs / innerspring mattresses.&lt;BR&gt;&lt;BR&gt;Time to learn about Bonnell springs, coil counts, wire gauge, and whatever else is important in the world of innerspring mattresses...

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