Spur Gear Mechanism for Accurate Angular Indexing and Locking of Angular Position by Using Additive Manufacturing

Abstract

Ratchet and pawl mechanism is used neither in many applications to provide precise locking of components either in linear nor in rotational directions. The number of locking positions depends on the total number of teeth on the ratchet. The objective is to increase the number of locking positions and thus minimizing the interval angle. For this objective to be fulfilled, spur gear is treated as ratchet, and meshing spur gear teeth is treated as pawl (named as lock). Due to the geometry of the spur gear teeth, the apparatus facilitates bidirectional locking. Spur gear permits 18 teeth in angular positions (P) achieved by a traditional ratchet mechanism with interval angles (A) of 20°. The locking of desired angle is impossible except for 18 positions of 20°, 40°, and 60°up to 360°. This study gives a better solution for increasing the number of locking position as well as decreasing the interval angles by introducing an innovative mechanism. Here, rearranging the position of the lock results in increasing the number of angular positions without increasing the number of teeth. Outcome of the paper is developed design which provides four times increase and reduction of angular positions. The locking position is derived by a mathematical formula, and simulation of the assembly was performed by using CAD software. Finally, the concept was proven by physical prototype fabricated through additive manufacturing technology and compared with traditional ratchet mechanism.