Development of the Auto-Fit Dial and its application to protective vests

This study proposes the Auto-Fit Dial, which is suitable for high-speed fitting; it includes a function that can wind wire at high speed using an energy storage–release mechanism. The Auto-Fit Dial can store energy in advance in the spiral spring via the rotation of the knob cover, and it releases the stored energy to wind the wire when required by pushing the knob cover. Firstly, the concept design and working principle of the Auto-Fit Dial are explained. Next, a detailed design and structural stability analysis of the mechanical components are described based on the design formula and finite-element analysis. An Auto-Fit Dial prototype is manufactured according to the detailed design with the weight, diameter, and height of 9.7 g, 30.5 mm, and 16.7 mm, respectively. The maximum number of rotations is 5.2 turns, which can wind a wire up to a length of 320 mm. The pulling force applied when the Auto-Fit Dial pulls the wire is initially measured as 5.10 N. The time required to wind a 320 mm wire is 0.015 s, which results in an average speed of 21.33 m/s. Moreover, the Auto-Fit Sleeve is fabricated and applied to the arm sleeve to verify the utility of the Auto-Fit Dial, which combines wire and fabric. Finally, the Auto-Fit Vest is developed by applying a protective vest to the Auto-Fit Dial.