An Innovative Low-Backlash Wolfrom Gearbox with Beveloid Gears for Robotic Applications

Industrial robot requirements in terms of positioning accuracy, repeatability, and dynamic performances require gearboxes to have minimal torsional backlash, high tilting stiffness, and low weight; also, a compact design and a long operating life are needed for practical use. In this work, we describe a novel gearbox for serial-robot joints, which combines two known design concepts, namely, a Wolfrom planetary architecture and beveloid gears. It is found that this design can achieve a high reduction ratio (up to 1:125) in a compact shape. The main advantage of beveloid gears is the ability to adjust the contact position through axial movements, achieving a torsional backlash close to zero (<1 arcmin). The novel gearbox is available in two versions, with or without a hollow central axis for cable routing. In this article, we describe the gearbox architecture, its main features, and its kinetostatic model.