US Patent 7908693 Coil-in coil springs and innersprings

A mattress innerspring having coil-in-coil springs arranged in an array. Each coil-in-coil spring an outside helical coil and an inside helical coil, wherein the outside helical coil has a greater height and diameter than the inside helical coil, each coil having a dual spring rate between that of the outside helical coil and the combined spring rates of the outside and inside helical coils. The coil-in-coil springs may be pocketed or unpocketed in a mattress innerspring.