Different types of foam and foam parts have been used extensively in seating and bedding as flexible support material. Semi-rigid open and closed cell foams of polyethylene, polyurethane or polystyrene have been used in combination with other components and load-bearing structures, such as wire form innersprings and framing to form flexible supports, such as described in U.S. Pat. Nos. 5,048,167; 5,469,590; 5,467,488 and 5,537,699 and 5,787,532. In most of these springs support products, the foam pieces surround or interfit with spring elements, and rely on mechanical connection with the spring elements to keep the foam pieces in place. Foam pieces have also been adhesively bonded and combined with innersprings. The types of foams used in these applications are typically open-cell polyurethane and latex materials, which can be effectively bonded by compatible adhesives. The open-cell structure of these types of foams results in easier compression or lower ILD which is suitable for many bedding and seating applications, particularly for support surface or topper layers underneath upholstery. They are not generally utilized as structural members in a mattress or support cushion in seating. Also, polyurethane and other non-thermoplastic type foams cannot be bonded or welded by any heat-source process due to their decomposition properties.
Some foam shapes have been used integrally with springs to augment or otherwise support metal spring structure, as shown for example in U.S. Pat. Nos. 5,133,116; 5,239,715; 5,467,488 and 5,687,439. Because this use of foam relies on the surrounding metal structure to hold it in place, the foam itself is not in the form of a unitized three-dimensional support structure with its own load-bearing capacity.
Another use of foam in connection with an innerspring is disclosed in U.S. Pat. No. 5,787,532, wherein an extruded foam piece is used as perimeter wall to an innerspring, with fingers which mechanically engage the coils of the innerspring. While this provides some vertical support at the perimeter of the innerspring, it relies on mechanical attachment to the innerspring for the correct orientation. It also only provides support in the vertical direction and does nothing to stabilize the innerspring in the lateral or horizontal directions.
One type of foam which has been used for these types of applications is closed-cell polyethylene foam which is mold or extruded by known processes into desired shapes. Closed-cell foam has greater support properties due to the fact that each closed cell contains a gas which maintains an inflated state when under compression, as compared to open-cell foams from which a substantial volume of air is displaced when compressed.