Welding head of inner-cooling seam welder

The utility model discloses a welding head of an inner-cooling seam welder, which comprises a welding head seat, a front oil seal mounted on the welding head seat, a first bearing connected with the front oil seal, a first insulating sheet connected with the first bearing, a head taper shaft connected with the first bearing, and a cooling water path, an output water path and a backflow water path arranged on the head taper shaft. A cooling groove is formed in one side of the machine head taper shaft, a waterway gland is installed in the cooling groove, a backflow channel is formed between the waterway gland and the cooling groove, a first switching waterway is arranged in the waterway gland, the machine head taper shaft is connected with a welding wheel, the welding wheel is provided with a second switching waterway, and the machine head taper shaft is connected with a rear gland water inlet and outlet seat. The rear gland water inlet and outlet seat is provided with a water inlet and a water outlet, the wate