Gear reducer for slow rotating downhole tool

摘要

A speed reducer for use in a slow rotating downhole tool, has an input shaft (94) attached to a rotor. The input shaft has an eccentric portion (161) and has an input gear (204) disposed about the eccentric portion. The input gear is a solid gear having a first outer geared surface (208) and a second outer geared surface (210). The pitch diameter of the first outer geared surface is less than the pitch diameter of the second outer geared surface. A speed reducer body (68) has a geared inner surface (200) defined thereon in geared engagement with the first outer geared surface. A follower gear (216) is disposed in the body and is in geared engagement with the second outer geared surface. Rotation of the input shaft (94) causes the eccentric portion thereof to rotate in the input gear (204) causing eccentric rotation of the input gear. Eccentric rotation of the input gear is translated into pure rotation by the follower gear (216) which rotates the output shaft (116). <IMAGE> <IMAGE> <IMAGE>