In order to further transform the steam engine, Watt absorbed the principle of using an exhaust valve to make the cylinder continuously reciprocate, which was proposed by the German Leubold in 1772, and began the development of a double-acting steam engine. After many experiments, Watt finally used a flywheel and a curved crank to turn the reciprocating motion of the piston into circular motion, and the experiment was successful. But before Watt applied for a patent, the news was leaked. The crank connecting rod mechanism invented by Watt to convert the reciprocating motion of the piston into rotational motion had been patented by Pickard first.