US 4,907,658 A · Percussive mole boring device with electronic transmitter

Abstract

A percussive mole boring device with a location transmitter is disclosed. The transmitter is located in a forward end of a drilling assembly attached to a mole to accurately transmit the location of a boring element or cutting surface to surface detector. The transmitter is surrounded on each end by isolator means which protect the transmitter from damage due to shock created by the percussive device, e.g., a hammer driven by compressed air. In one embodiment the transmitter is located beneath a single window transparent to the transmission frequency, and the cutting surface of the bore is angled. Therefore, the travel direction of the mole can be controlled by rotating the cutting surface to a desired inclination and terminating rotation during forward motion for a short period. The mole travels in a straight path during ordinary travel due to rotation. In a second embodiment, the transmitter is located beneath three equiangularly displacent windows to create a continuous field for detection. This type of mole is not steerable and includes a boring element with a non-angled edge. In a third embodiment which is similar to the second embodiment, the windows are not present, and a transmitter coil is wound in an external groove of the drilling assembly and is covered by epoxy.

Claims7

Dependent claims

In an unguided percussive mole boring device for use with a flexible hose connected to the mole boring device for providing a source of percussive power to drive the mole boring device, percussive means connected to the flexible hose and driven by a percussive power source for impacting the mole boring device, the improvement comprising:

a drilling assembly attached at a forward end of the mole boring device and a boring element attached to the forward end of said drilling assembly, said drilling assembly including a transmitter housing located behind and substantially adjacent said boring element;
an enclosed transmitter unit disposed within said transmitter housing, said transmitter unit enclosing a transmitter therein, said transmitter housing including a plurality of windows extending equiangularly around the circumferential exterior surface of said transmitter housing, said windows transparent to the frequency of transmission of said transmitter, said transmitter unit located substantially adjacent a forward end of said mole boring device to accurately transmit the location of the forward end of said boring element;
and
isolation means disposed in said housing for isolating said transmitter from shocks created by said percussive means impacting on said mole boring device, a diametric clearance provided between said transmitter unit and said windows allowing for axial movement of said transmitter unit in said housing to effectively cushion said impacts.

1 more element

Dependencies are inferred from the claim text.

Percussive mole boring device with electronic transmitter

Life of this patent

Percussive mole boring device with electronic transmitter

Life of this patent

Abstract

Claims7