| 摘要 |
A counterweight system is disclosed, which is advantageously used for counterbalancing the table top of a vertically-adjustable drafting table. Obviously, the counterweight system could be used for other applications. When used in a drafting table of the type including a frame and a table top provided with vertical legs guided for up-and-down movement within the frame, cables are attached to the lower end of the two legs and are trained over a common pulley and attached to said pulley, which is freely rotatably mounted within the frame. A spiral-shape cam member is fixed to one side of the pulley and an additional cable which is attached to the pulley is trained over the cam member and attached at its other end to one end of tension springs, the other end of which is attached to the frame. The varying force exerted by the springs, with the change of their elongation, is compensated by the variable lever arm of the application of said force on the rotational axis of the cam member and pulley, so that the torque exerted by the springs on the pulley is substantially constant over all of the rotated positions of the cam member and pulley. Therefore, the load or table top is substantially counterbalanced by the springs at anyone of its adjusted positions.
|
