US Patent 10131047 Driving tool

A driving tool, such as a nailer, includes a compression piston slidably disposed within a compression cylinder. An electric motor and a crank mechanism reciprocally drive the compression piston within the compression cylinder, and a sensor directly or indirectly detects the position of the compression piston. Prior to the start of a driving operation, a return operation is performed to move the compression piston to its bottom dead center when the sensor detects that the compression piston is located at a position other its bottom dead center.