A Swinging and Self-Actuating Friction Drive Device Used in Large-Scale Rotary Devices

Abstract

Background: Large-scale rotary devices often employ friction drives in order to be manufactured easily and usually select a large driving radius to reduce the friction forces needed. In traditional devices, the driver and driven friction wheels are required to be of higher roundness to avoid slipping between them. This makes the driven friction wheel difficult to be machined. In addition, generating adequate contact load between contacting surfaces is essential for friction drives, and the best way to achieve it is self-actuating loading. Objective: The purpose of this paper is to propose and analyze a patent about a new friction drive device, in which the driver friction wheel can roll along with the driven friction wheel throughout, and the contact load between the driver and driven friction wheels can be generated on the torque demand. Methods: By using two swinging gearboxes, the two driver friction wheels are both swinging, and thus both can roll along with the driven friction wheel floatingly. Therefore, the driven wheel can have some deviation in roundness. Besides, this design offers a condition to construct a torque-actuated loading mechanism. Driven by the input torque, each driver wheel turns and exerts a friction force on the driven wheel, and then the driven wheel applies a reactive force to each driver wheel. This reactive force tends to pull the driver wheel to the driven wheel, producing a wedging action. Thus, an appreciable amount of contact load between the driver and driven wheels will be generated. Results: The results show the contact load between the driver and driven friction wheels is directly proportional to the resistant torque acting on the friction drive device. The results also show that a “frictional locking” condition for the device to avoid slipping between the driver and driven friction wheels is needed and it depends on the geometric parameters of the device. Conclusion: A swinging and self-actuating friction drive device is developed by using two swinging gearboxes. Design principles were described and a design example for this friction drive device was demonstrated. This kind of friction drive device not only offers an alternative way to drive large-scale rotary devices, but also develops a new method to realize self-actuating loading for friction drives.