In order to adapt the scraper chain to run smoothly from the middle groove to the head sprocket , a transition groove is provided between the middle groove and the head frame . The transition groove is a chute with different heights at both ends, which is connected with the middle groove and the head frame The inner edge of the upper groove at the end is carbon arc overlay welding of 1.5 to 2mmthick wear-resistant alloy blocks. After the wear-resistant blocks are worn, they can be purchased from the manufacturer and replaced.