My guess would be a 120v electric motor using a screw gearing.
Screw gearing can transfer torque very well in one direction, and you can use very small motors because they’re usually a very high gear ratio (so they don’t move quickly).
The uni-directional torque transfer is why screw gearing keeps the bed from collapsing, and why screw gear is extensively used in steering systems (especially for heavier vehicles, like trucks).