| 摘要 |
A self-centering stock-proof gate comprises an elongate tubular member and an extension piece slideable within the tube, the extension piece carrying an embedded wire for communicating electric shock along the tubular member and along the extension piece. The tubular member is pivotally mounted about a vertical access on a hinge structure and is held in a central closed position by a pair of chain couplings which connect to a single spring lying along the tubular member and coupled thereto. Each of the chain couplings has an end link freely slideable along a pin which extends outwardly to a respective side of the tubular member from the hinge structure. Thus when the gate gets beyond a predetermined open angle, the chain slides along the pin towards the hinge structure thus reducing the mechanical advantage of the spring.
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