Patent ID: 6996866

Claim:
In a mattress spring structure having: a plurality of coil springs arrayed in longitudinal and traverse rows of such coil springs between upper and lower margins and opposite side margins of said spring structure, with the coils in each row aligned with the others in each said row, the structure including a border piece which defines said upper, lower and side margins; a fastening device securing each coil spring of each traverse row to a coil spring of an adjacent traverse row, a central area of the spring structure being defined by a selected succession of traverse rows of coil springs, wherein the number of traverse rows of coil springs in an upper spring structure area between the upper margin and the central area and in a lower spring structure area between the lower margin and the central area are greater than or equal to the number of traverse rows of coil springs in the central area; and a strengthening structure receivable exteriorly against a major expanse of the spring structure central area, the strengthening structure characterized by: a continuous frame member encircling a major expanse of the spring structure central area, including a first traverse frame segment extending along a juncture of the coil springs of a traverse row first in selected succession of such with an extra succession traverse row adjacent thereto, there being joining members closely joining together said first traverse segment and each joined pair of coil springs in said first succession traverse row and the extra succession traverse row adjacent thereto, a second traverse frame segment extending along a juncture of the coil springs of a traverse row last in the selected succession of such with an extra succession traverse row adjacent thereto, there being joining members closely joining together said second traverse segment and each joined pair of coil springs in the last traverse row and the extra succession traverse row adjacent thereto, a pair of longitudinal frame segments spaced inwardly from the spring structure side margins and extending longitudinally in between adjacent longitudinal rows of coil springs, opposite ends of the traverse frame members being connected to opposite ends of the longitudinal frame members, there being joining members, closely joining together said longitudinal frame segments and successive ones of pairs of coil springs comprised each of a coil spring in one of the adjacent longitudinal rows and a coil spring in the other of the adjacent longitudinal rows; and a strengthening pattern located within said continuous frame member and received against the spring structure encircled by the continuous frame member, said strengthening pattern is adapted to cause uniform depression of said coil springs limiting undesired upward pressure and comprises elongated metal elements and metal straps joined to the elongated metal elements.