| 摘要 |
PURPOSE: A multi-coil spring structure is provided prevent the sagging of a bed mattress, and to improve the elasticity and the lifetime of springs for offering the comfort to users. CONSTITUTION: A multi-coil spring structure comprises a cylindrical double coil spring(100) obtained by twisting an elastic steel wire into a helical coil shape. The double coil spring is formed with a rigid coil unit(110) and a soft coil unit(120) on the upper and lower sides, respectively. The soft coil unit is obtained by twisting the elastic steel wire to have a predetermined interval in the center when producing the double coil spring. The rigid coil unit is obtained by closely adhering the elastic steel wire when twisting the elastic steel wire to produce the double coil spring.
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