Railway coupler is used for connecting locomotives and vehicles or vehicles and vehicles,transferring traction and impact,and maintaining a certain distance between the vehicles.According to the opening ways it can classify top operating and bottom operating.Opening the coupler by the lifting mechanism above the coupler head is called top operating (General wagons adopt ), Opening the coupler by the ejector lever action down the coupler head is called bottom operating(Passenger trains adopt).

Coupler consists of three parts head , shank and tail. The thick section is called coupler head in front of the coupler.The coupler head is equipped with knuckles,knuckle pivot pins,knucklelocks,knuckle throwers and lock-lift pins.Coupler rear is called coupler tail. The couplers tail have keyhole,in order to connect with the yokes