Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-05-16
2001-06-12
Hofsass, Jeffery (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S572200, C340S572400, C340S572500, C340S572700, C340S572800
Reexamination Certificate
active
06246328
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to passive markers buried with underground utilities such as gas, telephone, water and power lines. Appropriate placement of passive markers facilitates subsequent re-entry for line inspection. More particularly the invention relates to the shapes of coils used in inductance-capacitance tuned circuits to expand the detectable range wherein a locating device will intercept a resonant signal denoting a buried marker's position.
BACKGROUND OF THE INVENTION
Electronic marker devices, of the type having an inductance-capacitance tuned circuit, are known. Such devices comprise an air-core inductance provided by a wire coil connected in parallel with a capacitor. Optimum operation for relocation of such a marker requires vertical orientation of the longitudinal axis of the coil. A core-wound coil, also herein referred to as a solenoid coil, may be replaced in the tuned circuit by a substantially planar coil extending horizontally outward from a central axis. In this case, positioning of the marker beside a utility line preferably sets the coil in a horizontal plane with its central axis in vertical orientation. U.S. Pat. No. 4,712,094 provides a solution to earlier problems in achieving desired coil positioning using a marking device containing a floating tuned circuit that adopts the correct orientation regardless of initial placement of the marker beside a buried line.
Optimum orientation is important for coupling the coil of a passive marker with the coil of a locator device during relocating of a buried marker. Any difficulty associated with relocating a marker will complicate the process of reentry for maintenance or repair of a particular portion of the line. A locator of passive electronic markers normally emits a pulsed electromagnetic field to energize the marker. Between pulses, the marker releases its stored energy, at its resonant frequency, producing its own electromagnetic field. The resonant signal from the marker may be detected by switching the locator from transmitting mode to receiving mode. In the receiving mode, the maximum detectable signal usually identifies the position of a selected marker which lies adjacent to the portion of the utility line or line component requiring inspection. As previously discussed, tuned circuits floating inside a container adopt an orientation for optimum coupling of electromagnetic fields produced by the locator circuit and the marker tuned circuit. U.S. Pat. No. 5,699,048 describes effective coupling of signals using an orthogonal arrangement of plural tuned circuits. This tuned circuit arrangement produces a multidirectional response pattern that is more rapidly detected than that of poorly orientated single circuits.
Rapid, successful detection of the location of a marker reduces the amount of time for line inspection. The distance between a marker locator and a passive electronic marker will affect how quickly the position of the marker may be correctly identified. Successful marker detection depends upon the sensitivity of the marker locator and the range of detectable signal associated with the marker's resonating tuned circuit. Improvement in the range of a detectable signal will add further value to passive, essentially self-orienting marker devices.
SUMMARY OF THE INVENTION
The present invention provides a new coil design, also referred to herein as shape or form factor, for use in electronic markers that will increase the detectable range for a given package size by increasing the resonant circuit's quality (Q) factor. Prior efforts to increase a coil's detectable range involved adding turns of wire to increase the size of a coil, using e.g. ferrites, special wire and sectionalized bobbins and various combinations thereof. A coil using the novel form factor according to the present invention achieves increased Q factor and detectable range without the use of ferrites, special wire or sectionalized bobbins. Further improvement may be realized using ferrites and related materials or components but such use is optional. The form factor or shape for increased Q may be developed using a coil winding method that is also part of the present invention. The winding process occurs at high speed and reduced manufacturing cost.
Passive electronic marker devices according to the present invention provide self-orienting resonators having a greater detectable range to enable rapid identification and positioning of a selected buried marker. Self-orientation uses a floating tuned circuit as described in U.S. Pat. No. 4,712,094. This patent is commonly owned with the present application. The increase in detectable range, of markers according to the present invention, relates to modification of the form factor or shape of a coil element included in the tuned circuit with the capacitor.
A passive electronic marker according to the present invention includes an inductance-capacitance tuned circuit sealed inside a buoyant carrier. The carrier, in the form of a hollow disk, floats in a liquid that partially fills a hollow sphere. Size requirements for the hollow sphere control its internal volume and limit the space for the carrier and the tuned circuit it contains.
Increase in the detectable range of the tuned circuit may occur with an increase in coil size. Such an increase in the size of conventional coils, of either spiral wound or solenoid type, depends on the previously discussed space limitations affecting the size and internal space of the floating carrier. It is difficult, within the confined space of the hollow carrier, to increase the height of a typical solenoid coil or the horizontal dimension of a conventional spiral coil.
Tuned circuits according to the present invention provide improvement in their range of detection without change in the internal vertical or horizontal axes inside the hollow carrier. Improvement of detectable range occurs by forming an orthogonal radial wall at the outer edge of a spiral coil. The resulting coiled structure is dish-shaped with a diameter no larger than the diameter of the carrier and a wall height no higher than the height available inside the carrier. With optimal orientation, a coil of this type includes a spiral coil disposed horizontally, representing the base of the dish. The vertically extending radial wall has a radius substantially equal to the radius of the spiral coil. Formation of a radial wall extension on a spiral coil provides the benefits of an increased number of turns of wire while maintaining the size of the hollow carrier. The novel shaped coil has a better relative range than either a solenoid coil or a planar spiral coil. A passive electronic marker exhibiting a detectable range increase and automatic leveling reduces the time associated with installing and inspecting a utility line. Automatic leveling facilitates installation because the marker adjusts to a desired position even though dropped into a utility trench without thought for its orientation. An extended detectable range provides added value by reducing the time needed to locate a marker and inspect a portion of a utility line.
More specifically the present invention provides an extended range coil for an inductance-capacitance tuned circuit of a passive marker. The extended range coil comprises a wire-wound planar spiral coil, having a circumference, and a wire-wound wall joined to the wire-wound planar spiral coil and extending outward from the circumference thereof. An extended range coil according to the present invention may use a continuous length of wire for winding the wire-wound planar coil and the wire-wound wall.
The invention also includes a passive marker comprising an inductance-capacitance tuned circuit wherein the inductance has an extended range coil including a wire-wound planar spiral portion, having a circumference, and a wire-wound wall portion joined to the wire-wound planar spiral portion and extending outward from the circumference thereof. A hollow sphere partially filled with a liquid provides the container for a bu
Doany Ziyad H.
Parkinson Timothy A.
Hofsass Jeffery
Nguyen Hung
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