Lining tube for restoring defective sewer shafts and method for producing and installing such a tube

A lining tube for restoring a defective sewer shaft, wherein the sewer shaft has a first shaft section with a first diameter and, adjoining the first shaft section, a second shaft section with a widened diameter, the lining tube comprising:

• an inner film tube having a connecting portion, which extends in a longitudinal direction thereof and connects two circumferential portions of said inner film tube running parallel to one another to form a circumferentially closed inner film tube having a defined nominal diameter;
• a radially expandable layer of fiber material arranged around said inner film tube, said layer of fiber material being impregnated with a curable reactive resin;
• and
• a further film tube of an airtight transparent plastics material arranged inside said inner film tube, said further film tube extending in the longitudinal direction of the lining tube over an entire length thereof, and a sealing element closing off one end of said further film tube with an airtight seal to form an air bag that is closed on one side;
• said connecting portion of said inner film tube having a predetermined breaking point, which extends along said inner film tube and is formed to be broken open in the circumferential direction by introducing into said further film tube a pressure medium for radially expanding said inner film tube and said layer of fiber material arranged thereon beyond the nominal diameter.