| 摘要 |
A helmet comprises a helmet shell, an outer liner layer 14 fixed inside the helmet shell; and an inner liner layer 12 positioned against the outer liner layer 14; the outer liner layer 14 having a dome-like concave curved internal surface; the inner liner layer 12 having a dome-like convex curved external surface; the said surfaces of the inner and outer liner layers 12, 14 being substantially spherical where they overlap for allowing rotational sliding movement of the inner liner layer against the outer liner layer; means being provided for limiting rotation between the inner and outer liner layers. Preferably, at least one of the said surfaces of the inner and outer liner layers 12, 14 have recesses (18, fig.2) for weakening the layer and for facilitating crushing of the layer when a sufficiently large radial force is applied, loosening the inner liner layer 12 within the outer liner layer 14. The inner and outer layers may be formed of expanded polystyrene. The amount of rotation may be limited by an elastic headband. |
