Pneumatic tongs for feeding and discharging of crankshafts

The invention discloses pneumatic tongs for feeding and discharging of crankshafts. The pneumatic tongs comprise a machine frame, mechanical tongs, a cylinder, a left guide rail, a left rack, a gear, a right rack and a right guide rail, wherein the mechanical tongs, the cylinder, the left guide rail, the left rack, the gear, the right rack and the right guide rail are mounted on the machine frame. The mechanical tongs comprise a front grab finger set and a rear grab finger set which are symmetrically arranged front and back. The front grab finger set and the rear grab finger set each comprise multiple grab fingers arranged in the left-right direction. The rear grab finger set is fixedly connected to an output shaft of the cylinder through a rear arm, the rear arm is fixedly connected with the left rack, and the left rack is connected to the left guide rail through multiple first sliding blocks. The left rack and the right rack are both horizontally arranged, and the left rack is connected with the right rack through the gear. The front grab finger set is fixedly connected to the right rack through a front arm, and the right rack is connected to the right guide rail through multiple second sliding blocks. Compared with the prior art, the pneumatic tongs are more complete in structure function, more accurate in control and capable of being well adaptive to feeding and discharging of shaft type parts, such as the automobile crankshafts, with phase requirements.