Method and apparatus for installing pipes

Abstract From the Canadian patent

Sensor apparatus (18) for use in installing a plastic service pipe (16) inside a steel service pipe (10) connected to a main consists of a flexible element (42) which is fed through the steel pipe (10) and through the plastic pipe (16). The element (42) has at its remote end two light-emitting diodes (80) and two photoconductive cells (82). The flexible element (42) and the pipe (16) are fed together into the steel pipe (10). The sensor apparatus (18) indicates when the cells (82) have entered the main (14) because the intensity of the light reflected to the cells (82) falls to a low value and gives an audible or visual signal. This also indicates that the end of the plastic pipe …