The Ring Screw

Modelling, Development and Evaluation of a Novel Screw Transmission

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Rotational electric actuators are the most popular choice for actuation in modern day automation. These actuators are commonly used in combination with a transmission system. In this paper, the development of a new rotational to linear transmission technology, called the ring screw, is described, and its real-world performance is evaluated experimentally. The ring screw consists of freely rotating rings that constrain a rod to a screwing motion. The line contact between those rings and the rod allows for perfect rolling, resulting in a highly efficient screw transmission. The theoretical performance of the ring screw for the metrics maximal velocity, maximal thrust force and mechanical efficiency
are explored analytically. Based on these performance metrics, this paper presents a method to find the optimal design parameters when the desired properties are provided. A prototype was evaluated in a custom developed test rig. In these experiments the ring screw is proven to be able to operate at 15,000RPM and deliver 750N with an efficiency of 90%. The ring screw operates at more than double the speed possible with other screw transmissions such as a ball screw, with the same high efficiency.