SPRING COIL AND SPRING ASSEMBLY

摘要

A spring coil has an open-ended terminal convolution which is connected to the body of the coil through a gradient arm. The gradient arm can be readily varied in length in manufacture to alter the compression and thereby the firmness of the spring coil. One or more offset portions can further be provided on the terminal convolution. Such offset portions are advantageously formed with a major straight part which is outwardly spaced from minor straight parts. This provides a three point engagement for the offset portion when connected to a border wire with a border wire helical spring. The springs making up an innerspring assembly are arranged in rows and columns. The offset portions of adjacent springs are overlapped in rows and are joined together with cross-helical springs that extend along columns and encircle the overlapped portions. The offset portions of the spring coils have inside and outside shoulders adjacent their ends, and the pitch of the cross-helicals is advantageously chosen so that a crosshelical simultaneously engages the outside shoulders of one of a pair of overlapped offset portions to hold the spring coil against rotation. The cross-helical preferably also catches the inside shoulders of the other overlapped portion to additionally hold that spring coil against rotation. A mattress innerspring is further disclosed with the rows arranged across the width of the mattress and the columns extending along its length. Cross- helicals can also be used across the width of the mattress in addition to those extending along the longitudinal columns. The width cross-helicals can be used for extra firmness for the entire mattress, or for selected areas, such as the middle third. One embodiment further shows the use of such orthogonal cross-helicals with overlapping spring coil rows.