David Ladd Swigert
Engineers at Cinnamon Ct, Fort Collins, CO
License number
Colorado 16667
Issued Date
Sep 28, 1979
Renew Date
Feb 1, 2008
Expiration Date
Jan 31, 2010
Type
Professional Engineer
Address
Address
3227 Cinnamon Ct, Fort Collins, CO 80524
Professional information
Tunnel Roof Monitor Employing An Induction Coil Extensometer
US Patent:
4271407, Jun 2, 1981
Filed:
Nov 13, 1979
Appl. No.:
6/093324
Inventors:
Robert F. Kehrman - Louisville CO
Arnold J. Farstad - Boulder CO
Michael G. Gibbons - Boulder CO
David L. Swigert - Fort Collins CO
Arnold J. Farstad - Boulder CO
Michael G. Gibbons - Boulder CO
David L. Swigert - Fort Collins CO
Assignee:
Westinghouse Electric Corp. - Pittsburgh PA
International Classification:
G08B 2100
US Classification:
340690
Abstract:
A ferrite core is suspended from the base of a borehole in a tunnel roof structure and is positioned within coil turns located at the roof surface such that movement of the roof structure causes displacement of the core with respect to the coil turns thus producing a change in inductance. The coil and core are incorporated as a frequency-determining element in an LR oscillator. Therefore, movement of the tunnel roof structure is reflected as a change in the frequency of the oscillator. This frequency is monitored and, if the change exceeds a predetermined threshold, an alarm is given. Several methods of suspending the core in the coil are disclosed, one of which allows for a non-verticle borehole.