US Patent 7506581 Press machine

A press machine is configured with an adjustable slide stroke length. The press machine comprises a frame, a crankshaft borne rotatably on the frame, a slide disposed under the crankshaft, a first lever swingably supported on the frame, a second lever swingably connected to the first lever through a first pin, a displacing mechanism for displacing the first pin, and a linear approximation mechanism that exerts a horizontal force to the first pin so as to convert a rotation of each eccentric portion of the crankshaft into an elevating motion of the slide.