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    Pole vault crossbar
    1.
    发明授权
    Pole vault crossbar 失效
    POLE VAULT CROSSBAR

    公开(公告)号：US3572697A

    公开(公告)日：1971-03-30

    申请号：US3572697D

    申请日：1969-02-07

    申请人： RAPPAS JAMES A

    发明人： RAPPAS JAMES A

    IPC分类号： A63B5/04 ,  A63B5/06

    CPC分类号： A63B5/04

    摘要： A crossbar for pole vaulting, high jumping and the like of triangular cross section is formed of two strips of synthetic resin, a generally flat base strip and an inverted V-shaped strip, the lower portions of the legs of the inverted V-shaped strip being cemented to the base strip. The crossbar is given a predetermined upward arch or camber to counteract the tendency to sag under its own weight. This may be done by cementing the two parts to each other and clamping them in an arched position while the cement is setting, or by applying a tensile stress lengthwise of the base strip and maintaining such tensile stress with the parts clamped in a straight line relationship while the cement is setting. In the latter case release of the clamping pressure causes the composite crossbar to assume an upwardly cambered form, due to internal tensile-compressive stress equilibrium.