Screw With Truncated Thread End For Reverse Rotation Resistance

Instead of the conventional approach where the thread tapers continuously to zero at the head end, the patent inverts this by providing a threadless shank section between the thread and screw head. This inversion creates a mechanical lock where the thread end abuts against the sheet stack, preventing reverse rotation while maintaining manufacturing feasibility through standard thread rolling processes followed by a simple cutoff.

The shank is segmented into two distinct sections: a threaded section for engagement with the sheet stack and a threadless shank section adjacent to the screw head. This segmentation allows the thread to terminate abruptly rather than tapering to zero, creating a positive stop that resists reverse rotation while keeping the manufacturing process relatively simple.

The patent applies local quality by creating a specific geometric configuration at the thread end where the flank forms an angle with the screw axis. This localized angular feature ensures that the thread end contacts the sheet stack at an optimal angle, providing both reverse rotation resistance and minimizing play through precise geometric engagement rather than relying on friction alone.

The thread flank angle creates an asymmetric engagement where the thread end contacts the sheet stack in a way that provides mechanical advantage against reverse rotation. The asymmetric geometry ensures that tightening forces are efficiently transmitted while preventing loosening, reducing play through directional engagement.