Sofa bed

A sofa bed is a multifunctional piece of furniture designed to serve two purposes. Most often, it functions as a standard sofa or couch for sitting. However, it also hides a sleeping area underneath the seating cushions. This hidden area usually consists of a metal frame and a thin mattress. When the frame is unfolded or opened, the furniture becomes a bed.

Because they combine seating and sleeping, these items are excellent for saving space. In the United States, people use many names for them, such as a pullout sofa, a hide-a-bed, or a sleeper-sofa.

The mechanism of a sofa bed depends on how the frame and mattress interact. In many models, the user moves the cushions to access the metal structure below. Some designs use a telescoping frame to manage this transition. A telescoping frame is a support system that allows parts to slide into one another. This allows the bed platform to recess below the level of the seating cushions. Another common design is the slide-away bed. In this version, the sofa slides toward a wall to form the seating area. The mattress in a slide-away bed is hinged. This means it can fold to create both the seat and the back support.

There are several distinct types of convertible furniture. A western-style futon is one type, though it differs from a traditional sofa bed. While they are different, many sofa beds do use futon mattresses. Another type is the sleeping chair, which is also called a chair bed or an armchair bed. These are much narrower than a standard sofa because they are made for only one person. Some sleeping chairs are even more multifunctional. They can act as a recliner or a chaise longue when they are in the upright position.

The history of these inventions involves many different creators and patents. Leonard C. Bailey filed a patent for a folding bed on July 18, 1899. His design featured a metal bed frame that could be folded. Later, Rudolf Coopersmith became a major figure in this field. He filed over 30 patents for mechanical parts and mattress machinery between 1905 and 1947. In 1925, he patented a sofa bed that served as a precursor to the modern pullout sofa. Another famous inventor, William Lawrence Murphy, created the "In-A-Dor bed." This is known today as the Murphy bed because it folds into a wall closet to save space.

In 1931, Bernard Castro used $400 of his own savings to sell the "Castro convertible." His specific design is the evolution of most sofa beds sold in the modern era. Other inventors, such as Manning Lane, Warren J. Hauck, and Roy O. Sweeney, developed the primitive version of the slide-away bed in Cincinnati, Ohio. The industry also saw advancements in hinged mattresses. A patent for a knock-down sofa bed with a hinged mattress was filed in 1978 and issued in 1980.

Mattress construction is a highly technical part of the sofa bed. Most models use a queen short mattress, but they also come in twin, full, and king sizes. The average thickness for these mattresses is only 4 inches. Many are made using springs or foam. Spring mattresses involve complex measurements like free length and solid height. Free length is the total length of a spring without a load. Solid height is the length when the coils touch each other. The difference between these two is called the working length.

Quality is often measured by active coils, which are the coils free to move under a load.

Foam is another common material used for these thin mattresses. Engineers look at density, which is the weight of the foam per cubic meter. High-density foams can be made very soft, while low-density foams can be very firm. Professionals also measure Indentation Force Deflection, or IFD. This measures how many Newtons or pounds of force are needed to indent the foam. Another advanced design uses pocket-coil mattresses. In this setup, each individual coil rests inside its own pocket. This allows the mattress to keep its shape over a long period of time.