ADJUSTABLE HEIGHT LOAD BEARING SUPPORT STRUCTURE

摘要

A height adjustable load support structure (20) has a base frame (22), and a generally planar support surface (32). Preferably, two extendable vertical support assemblies (26) support the surface (32) for vertical movement relative to the base frame (22). Each support assembly (26) is engaged by a spring biased pivotable arm (42) to counterbalance the weight placed on the surface (32). A cam system (44, 46) cooperating between the distal ends of t he pivotable arms (42) and the support assemblies (26) serves to compensate for the changing spring force on the arms by varying the effective moment arms o f the arms (42) thereby equalizing the force on each support assembly through its complete range of vertical travel.