Technique for steering and monitoring the orientation of a powered underground boring device

In an apparatus for providing an underground tunnel by means of an elongated boring device which is caused to move through the soil underground, the improvement comprising means for monitoring the pitch angle defined by the elongation axis of said boring device relative to a horizontal ground plane, independent of the roll position of the device, said monitoring means including a sensor carried by said device for producing signals corresponding to the pitch of the device independent of its roll position and means for detecting and processing said signals, said sensor including

• (a) a closed, hollow tubular container having its axis positioned parallel with the elongation axis of said boring device and defining a co-axially extending internal chamber having opposite ends,
• (b) electrical circuit means including first and second contact means located within and at the opposite ends of said chamber and a third contact means located within and extending around said chamber at a point intermediate its opposite ends,
• (c) an electrolytic solution partially filling said chamber so as to make contact with all three of said contact means, the extent of contact being made by the solution with said first and second contact means depending on the pitch angle of said boring device but independent of its roll position and said signals depending upon the extent of contact being made by the solution with said first and second contact means.

A method for providing a continuous underground tunnel, comprising the steps of:

• (a) providing an elongated boring device having a central elongation axis and including an axially extending main body, a forward boring head coaxially positioned with and rotatably mounted to said main body, and a nozzle on said boring head in a forward facing position off axis with respect to said device;
• (b) supplying fluid under pressure to said nozzle whereby to produce a pressurized fluid jet at the output of said nozzle in a direction forward of and off axis with respect to said device, said jet being sufficiently strong to bore through soil;
• (c) urging the boring device forward as said jet is being produced whereby to cause the device to move forward into the area being bored out by said jet;
• and
• (d) moving said boring head and nozzle about the axis of the device in a first way for causing the device to move forward along a straight path and in a second way for causing the device to move forward along a particular curved path that depends upon the way in which the boring head is rotated, said boring head being moved in said one way so as to rotate at a constant speed around the axis of said boring device whereby to move forward along a straight path and being moved in said second way so as to rotate about the axis of said boring device such that said fluid jet spends more time along a particular segment of its rotating path than on the rest of its path of movement so that the particular segment of said rotating path determines the particular curved path taken by the boring device.

In an apparatus for providing an underground tunnel by means of an elongated boring device which is caused to move through the soil underground, said boring device having a central elongation axis and including an axially extending main body, a forward boring head coaxially positioned with and rotatably mounted to said main body, and a nozzle on said boring head for providing a fluid jet in a forward facing position off-axis with respect to said device, the improvement comprising means for monitoring the roll angle of said boring device relative to a reference roll position and means for monitoring the rotational position of said fluid jet relative to a given reference whereby to be able to determine the rotational position of said jet relative to said reference roll position, said roll angle monitoring means including a potentiometer having an annular resistance element mounted on said boring device in coaxial relationship with its elongation axis, a wiper arm connected with said resistance element such that the latter is rotatable about its own axis relative to the wiper arm, and means for gravitationally biasing the wiper arm, said means for monitoring the rotational position of said jet including a magnetic circuit including a first circuit component made up of a series of circumferentially spaced-apart Hall effect sensors defining a circle and fixedly mounted to and coaxially with said main body and a second circuit component including a single magnet mounted to said boring head.