| 摘要 |
A vertically adjustable backboard support includes a fixed position structure to which a shiftable backboard structure is sliding attached for vertical adjustment between several selectable elevations. A torsion spring counterbalance apparatus on the fixed position structure facilitates manual shifting of the adjustable backboard structure to any of its vertically adjusted positions. A vertically disposed outer tube of the fixed position structure includes vertically spaced openings in one of its side walls for receiving a cam secured to a vertical operating rod rotatably mounted to the shiftable backboard structure for selecting and maintaining desired vertical positions of backboard adjustment.
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