Design of Constant-Force Mechanisms Based on Straight-Line Linkages

Abstract

This paper presents two novel constant-force mechanisms (CFMs) based on Scott-Russell and Hart’s straight-line linkages with mechanical springs. By articulating either two compression springs (type C-C) or one compression spring with another one extension spring (type C-E) onto each of these two CFMs, the point(s) which trace straight-line trajectories can illustrate a constant force within the mechanism workspace. We also show that the preload of the extension spring for type C-E CFMs will not affect its constant-force property but can define the amount of the output force. The proposed concepts of CFMs are relatively simple and concise, which could be useful for the complex mechanical systems that request a constant output force. A constant-force robotic gripper is illustrated by using the proposed Scott-Russell-type CFM.