Abstract: A support assembly for a computer input device includes a generally C-shaped slide member mountable to the underside of a desk surface for slidingly receiving a vertical column member. Notches formed in the column member are engaged by teeth of a collar portion of a support arm. The arm is thereby adjustable to various vertical positions on the column. A computer keyboard or mouse pad may thereby by supported on the arm with both height adjustability and the ability to be retractable beneath the desk surface. Where the assembly is used to support a keyboard, a slide arm supporting the keyboard may be provided with ribs engaging slots of the support arm. By configuring the support arm with an S-shaped side elevation, movement of the slide arm on the support will allow the keyboard to tilt through a negative angle permitting the keyboard operator to adjust the angle of tilt to a comfortable neutral tilt position.

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