Leonardo da Vinci’s proposed device for lifting heavy loads with a continuously turning threaded mechanism was a screw jack.
Leonardo studied screw-based lifting mechanisms in his notebooks, applying the principle of mechanical advantage to heavy construction and engineering work. Turning a handle rotated a threaded screw, converting circular motion into a slower but powerful upward movement. The device could therefore lift a load with less force than a direct manual lift, although it required more turns.
Screw mechanisms were not invented by Leonardo; ancient Greek engineers had already used screws and screw presses. Leonardo’s contribution was his detailed investigation of mechanical arrangements and his adaptation of familiar principles to practical machines.
A screw jack differs from a crane or pulley system because the lifting force comes primarily from the screw’s threads. Leonardo’s sketches often present mechanisms as studies rather than evidence of completed commercial products. For that reason, the safest description is a screw-jack design or study, not a claim that he invented the entire class of devices.