The concept of a revolving cylinder goes way back. James Puckle obtained a patent for a tripod-mounted firearm with a single 1.25 inch bore barrel and rotating cylinders in 1718.
Elisha Collier made an effective flintlock revolver in 1818. [Patent Pending Blog, 22NOV04]
Some sources say Colt saw the Collier revolver in London, and improved on it by inventing the percussion cap his Patterson revolver used. Colt's patent was obtained in early 1836.