Backlash-free speed reducing device

Abstract

A backlash-free speed reducing device includes a drive unit, a rotary unit, and a power output unit. The drive unit consists of a drive motor having a drive shaft. A first power transmission cable is wound around the drive shaft. The rotary unit has two first cylinders, with the first transmission cable fixed to the external surface of the first cylinders at opposite ends thereof and wound around or unwound from the first cylinders in response to a rotation of the drive shaft. Each of the first cylinders is concentrically fitted over a rotating shaft such that the first cylinders are linearly movable along the rotating shafts in opposite directions. A second power transmission cable is fixed to the external surfaces of the rotating shafts of the two first cylinders at opposite ends thereof. The power output unit has a second cylinder, with the second transmission cable wound around the second cylinder. This second cylinder is concentrically fitted over a power output shaft such that the cylinder is linearly movable along the power output shaft. The two power transmission cables thus maintain desired tension during an operation of the speed reducing device for achieving a high speed reduction ration, and so it is possible to prevent a backlash of the cables during such operation.