| 摘要 |
A plurality of main springs and a plurality of intermediate support springs are arranged on a rectangular base plate. Each main spring is made of a single steel wire and consists of two coil portions and a straight rod portion connecting these two coil portions. The rod portions of the main springs are arranged at right angles, thus forming a lattice. One end of each coil portion is fastened to a frame. The other end of each coil portion is fastened to the base plate. Each coil portion is shaped like a cone, an inverted cone, a hourglass or a barrel.
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