Three-dimensional netted structure having four molded surfaces

1. A three-dimensional netted structure having an upper surface, a lower surface, two side surfaces, a left end surface, and a right end surface, said structure comprising a plurality of filaments helically and randomly entangled and thermally bonded together, wherein:

said filaments are formed out of a thermoplastic resin by extrusion molding followed by cooling in a liquid;

said structure is four-surface molded, the upper surface, the lower surface and the two side surfaces being molded;

said structure has a first pattern of sparse and dense portions arranged alternately in a direction in which the resin is extruded wherein said structure has a single or multiple high-density regions arranged in a direction of width of said structure;

said structure has a second pattern of sparse and dense portions wherein all surfaces of an outer peripheral region of said structure that are in parallel to the direction in which the thermoplastic resin is extruded have a higher density than a density of remaining portions of said structure; and

said first pattern of sparse and dense portions and said second pattern of sparse and dense portions are formed by cooling in a liquid.

2. A three-dimensional netted structure having an upper surface, a lower surface, two side surfaces, a left end surface, and a right end surface, said structure comprising a plurality of filaments helically and randomly entangled and thermally bonded together, wherein:

said filaments are formed out of a thermoplastic resin by extrusion molding followed by cooling in a liquid;

said structure is four-surface molded, the upper surface, the lower surface and the two side surfaces being molded;

said structure has a first pattern of sparse and dense portions arranged alternately in a direction that is perpendicular to a direction in which the thermoplastic resin is extruded wherein said structure has a single or multiple beam-like high-density regions arranged in a direction of thickness of said structure;

said structure has a second pattern of sparse and dense portions wherein all surfaces of an outer peripheral region of said structure that are in parallel to the direction in which the thermoplastic resin is extruded have a higher density than a density of remaining portions of said structure; and

said first pattern of sparse and dense portions and said second pattern of sparse and dense portions are formed by cooling in a liquid.

3. A three-dimensional netted structure having an upper surface, a lower surface, two side surfaces, a left end surface, and a right end surface, the three-dimensional netted structure comprising a plurality of filaments helically and randomly entangled and thermally bonded together, wherein:

said plurality of filaments are formed out of a thermoplastic resin by extrusion molding followed by cooling in a liquid;

said upper surface, said lower surface, and said two side surfaces are molded; said upper surface, said lower surface, and said two side surfaces are flat; regions of the three-dimensional netted structure, which extend a predetermined distance from said upper surface, said lower surface, and said two side surfaces into an inner portion of the three-dimensional netted structure are compressed; and a density of said regions is higher than a density of said inner portion of the three-dimensional netted structure; and

the three-dimensional netted structure has sparse portions and dense portions arranged alternately in a direction in which the thermoplastic resin is extruded.

4. The structure of claim 3 further comprising a plurality of second regions arranged in a direction of thickness of the three-dimensional netted structure; wherein

each of said plurality of second regions is in a shape of a beam; and

a density of said plurality of second regions is higher than a density of remaining portions of the three-dimensional netted structure.

5. The structure of claim 4 , wherein said beam has a vertical sectional area that is rectangular.