Image Number 2 for United States Patent #4647256.
A method of producing underground pipes, with pipe sections being pressed ahead into the ground. For each pipe section, at least two partial pipe shells are used which are separated from one another in the longitudinal direction, and are joined about supply lines which are guided through the pipe. The joining process is effected before the pipe section is pressed into the ground. With this method, the supply lines do not have to be interrupted when a new pipe section is introduced. The apparatus for carrying out the method is provided with at least one joining station for joining the partial pipe shells in a precisely fitting manner, and a combining station for interconnecting the partial pipe shells.