This project ranked FIRST throughOUT ALL design CADIDATES.
The double-pull latch system is one of the most commonly used door latch systems in the automotive industry. During normal operation, a remote actuator cable pulls the Bowden cable, activate “pulling” mechanism.
However, In the event of an actuator failure (particularly in mid-cycle, shown in the figure, Part I and II may stuck), a means needs to be provided to both release the latch and de-couple the actuator.
A novel cable disengagement mechanism has been designed and validated through FEA. The complete design consists of four major linkages — blue, pink, green, and orange
During normal operation, the actuator pulls the Actuator cable, causing the blue, orange, and pink linkages to move horizontally together. It also pulls the Part I cable and drags the Part I, activating the "pulling" mechanism.
If the door latch failure, the technician can pull the Service cable (winded around the green cam), causing the green cam to rotate within its slot. This action will drag the Part II away from the stuck position by the Part II cable that is winded around the cam.
This action knocks against the pink linkage, forcing it to slide along the grooves on the blue linkage, thereby achieving disengagement.
After releasing the service cable, the entire design can be self-reset via two torsional spring—one attached around the green cam, another around the connection between the orange and the pink.
Dimension and allowable external loads (with safety factor of 2)
All critical components' loading properties (static & dynamic) were analyzed via FEA. Regions with maximum stress were identified, and FEA results were validated to be converged, with a minimum safety factor ~2 under the extreme loading scenario.
The team optimized the geometries of each link using a iterative approach, based on FEA results. (The detailed iterative process was not shown here)
