Pinion with a single rectangular tooth

The pinion is a cylindrical part machined with a simple mill (no CNC required). The rectangular tooth engages with the according slot of the linear moving part. The pinion part is placed vertically in regard to the linear moving part. Because of this and the fact that the tooth has adequate length, an axial movement of the pinion during rotation wouldn’t affect functionality of the mechanism. From the below assembly we can see a plunger constantly been loaded by a compression spring against an indexing disc (not shown here). By turning the pinion with a hand lever we force the plunger to retract and disengage the indexing disc. By releasing the hand lever the plunger returns to initial place. The pinion doesn’t require precision placement relative to the moving part.

At the figure below we can see the geometry of the pinion and the corresponding slot at the part moving linearly. The initial position of the pinion regard to other part depends on the angle a and distance P. From distance P also we can calculate the minimum force which moves our part linearly. This force can be a design parameter if the mechanism actuates a clamping lever. The angle b is supplementary and helps only for calculations. Thickness t must be large enough to resist the shearing forces (calculation not shown here). We can see from formula (2) that the clearance s depends on distance P and angle b. The mechanism like the others of similar functionality needs enough grease for smooth operation. When the moving part is at its upper place a positive stop must be provided in order to prevent it from disassembly from pinion (only if slot width B is larger than normal). The formula (5) calculates the linear movement of the part according to the initial data. Iterations and trials are needed in order to select the appropriate basic dimensions of the mating parts.