Automatic Brake for Slider

When torque in any direction is applied to green crank, four balls try to move red bush towards. The later via 4 bar linkage stops contact between pink eccentric cam and brown rack-slider, the crank rotating together with the blue gear shaft moves the rack-slider up down. The torque is transmitted to the gear shaft through the balls.
If the torque is removed, red spring moves the bush back and turns the pink cam to brake the rack-slider instantly.
Yellow arrow shows gravity force direction.
Pay attention to design the cam in order that friction between the rack-slider and the cam increases clamping force thanks the gravity force. If not the rack-slider will fall.