Designer throws a curve into furniture market

Ten years ago Frank Petersilie, a former art professor at Appalachian State University in Boone, N.C., decided he could introduce a new kind of dual-sleep furniture that didn't have a frame, a springing system, a folding mechanism, or even the usual rectangular shape.

Mr. Petersilie's version of a convertible sofa or chaise is made of 11 -inch-thick, high-density polyurethane foam. It is softly curving, and the bed it makes is usually round. His trick of conversion from seating surface to sleeping bed is a quick flip-over action of the foam components, which are covered in fabric and hinged with fabric.

It was a different kind of casual convertible sofa, and many people liked it and bought it. That initial sofa, which was the designer's first effort and which converts into a round bed, is still his best seller.

But the project behind his round sleeper was his idea (hatched when he first left teaching for the business world) for a round, igloo type of modular housing. He formed a company called Investments and Innovative Concepts Inc. to make the igloo houses for the second-home market. But after the recession of 1973, he discovered that people were really more interested in his round furniture than in his round houses.

So the igloos were dropped and the division called Spherical Furniture Company came into being to manufacture and distribute the former art professor's round sleepers. Sales have been climbing ever since, with ottomans and other square, oblong, diagonal, and elliptical-shaped components added from time to time to allow more interesting seating configurations.

Today, some thousands of foam sitting-sleeping units later, Petersilie is designer and chairman of the board and Bruce Shelton is president of Spherical. The company has factories in Boone, N.C., and Gardena, Calif., and specialty-store accounts across the country and in Hawaii.

Petersilie says his sleeper furniture has been unusual in several ways. Each of his units weighs between 100 and 150 pounds - far less than the 350-pound conventional convertible sofas. For a mobile society that moves frequently and enjoys changing interior landscapes, the lesser heft is a distinct advantage. No mechanisms mean nothing to jam, nothing to tear bed sheets, and nothing to bump shins against. He claims his high-density foam construction will last from 10 to 15 years under normal wear.

Standard sheets can be used on all Spherical units, which are neatly tucked into ''pocketing bands.'' Fabric covers of all units zip off for easy cleaning, and new or additional slipcovers are available through dealers.

''When we first came out, people called us gimmicky,'' Mr. Shelton said in a recent interview. ''But they weren't reckoning on shrinking living spaces and changing life styles, and on the fact that a lot of people were ready for something new.''

Retail prices range from $399 to $1,299. Shelton says most of Spherical's styles are purchased for condominiums, second homes, and apartments. They usually find their niche in family rooms, dens, and children's bedrooms. Contrary to what most people might think, most of the customers are aged 35 and over.