| 摘要 |
A counterbalanced adjustable height load bearing support structure with a pretensioning mechanism comprises a pair of pivotable arms each having a free end in engagement with a support assembly and being biased by a torsion spring. A lever arm is connected to each torsion spring and exerts a biasing force on the pivotable arm when the lever is rotated, thereby preloading the springs. A cable connects the lever arms and passes over a central bushing. The bushing receives a threaded shaft which may be turned to move the bushing and thereby adjust the tension in the cable. Because the cable is capable of sliding engagement with the bushing, tension in the cable is substantially uniform throughout its length and thus the resultant forces on the lever arms is approximately equal. Correspondingly, the forces on the two pivotable arms and associated support assemblies is approximately equal, whereby binding or racking of the support assemblies is minimized as the support surface is raised or lowered.
|
