Percussive mole boring device with electronic transmitter

• US 4,907,658 A
• Filed: 09/29/1988
• Issued: 03/13/1990
• Est. Priority Date: 09/29/1988
• Status: Expired due to Term

• Current Assignee: Gas Technology Institute
• Original Assignee: Gas Research Institute (GTI Energy)
• Inventors: Stangl, Gerald A., Lee, Douglas W., Wilson, Dirk A.
• Primary Examiner(s): Kisliuk, Bruce M.
• Application Number:
  US07/250,954
• Time in Patent Office: 530 Days
• Field of Search: 175/40, 175/45, 175/53, 175/19, 175/24, 175/26, 175/61, 175/62, 173/20, 173/21, 405/154, 405/184, 73/151, 181/102, 181/104, 340/870.1, 340/855, 367/25, 367/81, 367/911, 455/128
• US Class Current: 175/19
• CPC Class Codes: E21B 47/013 Devices specially adapted for supporting measuring instruments on drill bits
• CPC Class Codes: E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface
• CPC Class Codes: E21B 47/13 by electromagnetic energy, e.g. radio frequency
• CPC Class Codes: E21B 7/04 Directional drilling
• CPC Class Codes: E21B 7/068 drilled by a down-hole drilling motor down-hole drives per se E21B4/00, E21B7/067 takes precedence
• CPC Class Codes: E21B 7/267 Drilling devices with senders, e.g. radio-transmitters for position of drilling tool

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.

Claims

1. 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.

2. The device recited in claim 1, wherein each of said windows extends approximately 20°

across the exterior surface of said transmitter housing, said 20°

measured in a plane perpendicular to the longitudinal axis of the transmitter housing.

3. The device recited in claim 1, said isolation means comprising first and second isolation elements disposed about opposite ends of said transmitter unit.

4. The device recited in claim 3, wherein said first and second isolation elements each comprise a stack of neoprene washers.

5. A percussive mole boring device for use with percussive means for impacting thereon, said device comprising:

a mole having a forward end and a rearward end;

a boring element attached to the forward end of said mole;

a transmitter housing located behind said boring element 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 at least one window extending at least partially circumferentially around an exterior surface of said housing, said window transparent to the frequency of transmission of said transmitter, said transmitter unit located substantially adjacent said forward end of said mole boring device to accurately transmit the location of the front portion of said mole boring device; and

isolation means disposed in said housing for isolating said transmitter from shocks created by said percussive means impacting on said device, a diametric clearance provided between said transmitter unit and said window allowing for axial movement of said transmitter unit in said housing to effectively cushion said impacts.

6. The device recited in claim 5, said isolation means comprising first and second isolation elements disposed about opposite ends of said transmitter unit.

7. The device recited in claim 6, said first and second isolation elements each comprising a stack of neoprene washers.