Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-10-16
2002-04-30
Mullen, Thomas (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S572500, C343S719000
Reexamination Certificate
active
06380857
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrical markers that are located underground for the purpose of locating buried structures.
BACKGROUND OF THE INVENTION
Buried structures include pipelines, cables, vaults, etc. Once a structure is buried in the ground, it becomes difficult to locate. Location is useful, for example, to dig up the structure for repair or to avoid the structure when performing nearby excavation or drilling.
Electrical markers are used to located buried structures. The markers are located adjacent to a structure and then are buried with that structure. In the prior art, each marker contains a tuned LC circuit. A number of markers are placed along the structure, which is then buried.
In order to locate a buried marker, an operator moves across the surface of the ground with a transmitter and a receiver. The transmitter sends out an electromagnetic signal tuned to the frequency of the marker. Upon receiving the transmitted signal, the marker resonates and thus produces an electromagnetic response. This response is received by the above ground receiver and converted to a signal that is detectable by the operator (for example, an audio tone). The operator marks the pinpointed location on the ground using paint and then moves on to find the next marker buried along the structure.
Thus, with the prior art, the location of the marker, and the location of the buried structure, can be determined.
The tuned LC circuit inside of the marker includes a coil of wire. The coil, which can have an air core or a ferrite core, has an axis that is generally perpendicular to the coil windings of wire.
In order for the buried marker to be located, the coil should be oriented so as to be horizontal, which in most instances is approximately parallel to the surface of the ground. This is because the coil has a directional response to the transmitter signal. The coil response is strongest along the axis of the coil (i.e. perpendicular to the coil). If a marker is buried with the coil axis being horizontal, then the directional response will be oriented parallel to the ground, making detection difficult. It is desirable that the directional response be perpendicular to the ground so as to extend out of the ground to the receiver.
In the prior art, there is Bolson, Sr., U.S. Pat. No. 4,712,094. Bolson, Sr. orients a coil in a tuned circuit horizontally by floating the coil on the surface of a liquid. Unfortunately, the liquid adds to the weight of the marker and complicates assembly.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electrical marker for use in locating buried structures, which marker has a coil that will orient itself.
It is an object of the present invention to provide an electrical marker for use in locating buried structures, which marker has a coil that will orient itself horizontally.
The present invention provides a passive marker for use in locating a hidden structure. The marker comprises a housing, an inner member and a tuned circuit. The housing has a spherical cavity therein. The inner member is located inside of the housing cavity. The inner member is rotatable within the housing cavity. The tuned circuit comprises an inductance and a capacitance. The tuned circuit provides an electromagnetic response along an axis when subjected to an electromagnetic field at a selected frequency. The tuned circuit is coupled to the inner member so as to rotate with the inner member. A weight is coupled with the inner member and is eccentrically located within the spherical cavity.
The marker of the present invention automatically orients the tuned circuit in the desired orientation independently of the orientation of the outer housing. The eccentrically placed weight is pulled down to the lowest spot by gravity, thereby orienting the tuned circuit.
In one aspect of the present invention, the weight comprises a ball located in a receptacle of the inner member. A portion of the ball contacts the housing.
In another aspect of the present invention, the ball is a glass ball.
In still another aspect of the present invention, the ball is rotatably coupled to the inner member.
In still another aspect of the present invention, a portion of the ball protrudes out from the inner member.
In accordance with still another aspect of the present invention, the weight is located inside of the inner member.
In accordance with still another aspect of the present invention, the weight is located along the axis of the response of the tuned circuit.
In accordance with another aspect of the present invention, the inner member is spherical.
REFERENCES:
patent: 3373498 (1968-03-01), Chabbert
patent: 3683389 (1972-08-01), Hollis
patent: 3689885 (1972-09-01), Kaplan et al.
patent: 3719950 (1973-03-01), Bukhman et al.
patent: 3818487 (1974-06-01), Brody et al.
patent: 3836842 (1974-09-01), Zimmermann et al.
patent: 3938044 (1976-02-01), Lichtblau
patent: 3983552 (1976-09-01), Bakeman, Jr. et al.
patent: 4118693 (1978-10-01), Novikoff
patent: 4119908 (1978-10-01), Cosman et al.
patent: 4240072 (1980-12-01), Fowler
patent: 4260983 (1981-04-01), Falck et al.
patent: 4292590 (1981-09-01), Wilson
patent: 4293816 (1981-10-01), Johnson
patent: 4334227 (1982-06-01), Marks
patent: 4342904 (1982-08-01), Onasager
patent: 4482513 (1984-11-01), Auletti
patent: 4581524 (1986-04-01), Hoekman et al.
patent: 4668912 (1987-05-01), Junker
patent: 4712094 (1987-12-01), Bolson, Sr.
patent: 4761656 (1988-08-01), Cosman et al.
patent: 4859991 (1989-08-01), Watkins et al.
patent: 4873530 (1989-10-01), Takeuchi et al.
patent: 4894663 (1990-01-01), Urbish et al.
patent: 4925605 (1990-05-01), Petronko
patent: 5047715 (1991-09-01), Morgenstern
patent: 5057844 (1991-10-01), Rothstein
patent: 5103234 (1992-04-01), Watkins et al.
patent: 5121103 (1992-06-01), Minasy et al.
patent: 5140334 (1992-08-01), Snyder et al.
patent: 5258766 (1993-11-01), Murdoch
patent: 5276067 (1994-01-01), Doerge
patent: 5280296 (1994-01-01), Tan et al.
patent: 5281941 (1994-01-01), Bernstein
patent: 5319354 (1994-06-01), Myatt
patent: 5397986 (1995-03-01), Conway et al.
patent: 5426443 (1995-06-01), Jenness, Jr.
patent: 5497099 (1996-03-01), Walton
patent: 5499015 (1996-03-01), Winkler et al.
patent: 5539421 (1996-07-01), Hong
patent: 5585811 (1996-12-01), Jetzer
patent: 5592182 (1997-01-01), Yao et al.
patent: 5699048 (1997-12-01), Galloway
patent: 5814986 (1998-09-01), Goskowicz et al.
patent: 6097293 (2000-08-01), Galloway et al.
Galloway George G.
McWilliams Ronald L.
Moss John
Wood William C.
Industrial Technology Inc.
Mantooth Geoffrey A.
Mullen Thomas
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