发明授权
US4160536A Counterbalanced arm 失效
平衡臂

Counterbalanced arm
摘要:
An equapoised arm assembly is counterbalanced by springs enclosed within tubes that are components of the arm assembly. The arm assembly has a lower pair of parallel arms which are pivoted at their lower ends to a swivel bracket that turns about a vertical axis in a fixed bracket. Each of these arms is pivoted at its upper end to a floating bracket that is pivoted to a similar upper pair of parallel arms. An article support bracket is mounted upon the other end of the upper pair of arms and may include a universal joint assembly. The arms are tubular and each pair forms a parallelogram by virtue of the pivotal connections with the respective brackets. A coil spring is enclosed within one arm of each pair of arms to exert a counterbalancing effect upon its pair of arms. A nylon shoe is connected to at least one end of each spring and is slidable within the tube. The shoe is connected through a rod to an adjacent bracket of the assembly to transmit the counterbalacing force from the spring to the adjacent bracket. By connecting a shoe and rod to both ends of the spring, it is stretched from both these ends whereby its counterbalancing force is doubled. This force is a function of the tangent of the angle between the direction of the spring force (i.e. the longitudinal axis of the tube it is in) and the connection(s) between the slide and bracket, whereby the actual spring force may be smaller than that used to produce the same counterbalancing force in prior equapoised arm assemblies.
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