In designing a hand-actuated microspine gripper, a ratcheting locking mechanism was required that had discrete points of locking engagement. The mechanism had to actuate smoothly in the positive vertical direction while resisting the force of springs trying to pull the mechanism back down in the negative vertical direction. This locking mechanism needed to resist upwards of 50 pounds of load or more trying to disengage the mechanism in one direction, while being easily actuated by a person in the other direction.
The chosen design utilizes long-nose spring plungers in the actuating donut, and a center rail with discrete locking positions moving vertically along the rail. The rail is specially designed to allow actuation in one direction and prevent actuation in the opposite direction. To unlock the mechanism, the rail is rotated about its central axis to move the spring plungers out of alignment with the locking positions.
The locking positions are a novel slot designed with a drilled hole at one end and a gradual slope (chamfer) as one moves along the rail. This allows a gentle slope to compress the spring plungers as one moves towards the next drilled hole. A small amount of squeeze is required in order to rotate the rail to unlock the dowel, which prevents the lock from accidentally disengaging.
The novelty of this mechanism comes from the ability to lock the mechanism, but still allows for smooth hand actuation in a squeeze without the possibility of disengaging the lock back in the other direction. The rotation of the rail to engage and disengage the lock is also novel. Creating a hand tool for crew members that is easy to use is crucial. This technology will also give rise to flight applications where microspine grippers can be used as EVA hand tools for astronauts working in micro-g or zero-g environments.
This work was done by Andrew R. Willig for NASA’s Jet Propulsion Laboratory. For more information, contact