Minnesota Mining and Manufacturing Company

3M Innovative Properties Company

Armond D Cosman

Joe T Minarovic

Larry R Cox

Gary H Knippelmier

Kwang H Chu

Richard L Miklos

David C Worboys

A composite material for electromagnetic fusion bonding materials together includes interconnected first and second portions forming a patterned array. The first portions include layer absorptive magnetic particles in a polymer matrix. The second portions include a polymer positioned to separate each first portion from each other first portion.

Susceptor composite material patterned in neat polymer

A passive electronic marker uses a plurality of ferrite cores to increase locating range, and the cores are attached in such a manner that a slight bend of the marker at a junction between the cores does not significantly affect the markers performance. Stable locating range and tuned frequency are achieved by controlling the air gap between the cores, using specially shaped ends or a sphere which is positioned between the cores. By selecting the appropriate geometry for the core ends and winding interconnections, the first order permeability across the air gap is held constant during bending of the marker.

Ferrite core marker

A sonde for tracing an underground conduit has a separable casing which receives a removable inner shell, the transmitter electronics being located in the shell. The electronics may be permanently potted in the inner shell or removable therefrom. The interchangeability of the transmitter facilitates the use of different types of transmission signals without requiring the more expensive casing for each such transmitter. The shell also advantageously supports the battery, and further is free to rotate within the housing such that, as the cap is screwed onto the housing, the shell and battery are free to rotate, precluding damage to the battery leads which may be caused by twisting of the leads.

Sonde with replaceable electronics and a rotatable, tubular inner shell

A marker tape for location of a buried conduit, having a plurality of electronic markers spaced thereon at predetermined intervals. The distance between the markers encodes information about the buried conduit. The tape may be a nonconductive ribbon or cord, and the markers are preferably passive circuits tuned to a specific frequency. The tape ribbon embodiment may include slots therein for receiving the markers. The markers may be oriented in a predetermined pattern to encode additional information.

Self-dispensing spaced electronic markers

A marked conduit allowing electronic location of the conduit after burial, having a plurality of electronic markers spaced thereon at predetermined intervals. The distance between the markers encodes information about the buried conduit. The markers are preferably passive circuits tuned to a specific frequency. The markers may be oriented in a predetermined pattern to encode additional information, and may be attached to the outer or inner surface of the conduit, or imbedded in the wall of the conduit.

A method and system for determining the location of a first insulated conductor and a plurality of similar branch conductors that are branches of the first conductor, but without ohmic contact being made with the first conductors. A passive marker having a resonant circuit that includes an inductor and capacitor is provided for each of the branch conductors and is positioned to be inductively coupled to the first conductor and the associated branch conductor. The first conductor is a part of a closed loop circuit and each branch conductor is a part of separate closed loop circuits. An alternating signal applied to any one of the closed loop circuits is inductively transmitted to each of the other closed loops that is inductively coupled to a passive marker having a resonant frequency equal to the frequency of the alternating signal. Flow of alternating signals in the closed loops and passive markers cause a detectable electromagnetic signal to be produced to identify the location of the first conductor, branch conductors and passive markers when conducting the alternating signals.

System and method with passive resonant circuit markers for locating

A marking tape that is positioned underground above utility lines wherein the marking tape carries a pair of closely spaced, parallel, insulated conductors that extend the length of the tape and at least one other insulated conductor extending the length of the tape which is separated from the pair of conductors at a distance that is greater than the distance between the conductors of the pair of conductors. Passive markers having a resonant circuit can be selectively placed along the tape wherein the resonant circuit is electromagnetically coupled to the pair of conductors and the other conductor. The other insulated conductor can be one of a pair of conductors similar to the other pair of conductors. A method is disclosed whereby the making tape can be electromagnetically traced with the position of the passive markers established. A method is also disclosed for determining the distance to a break in the tape which causes the pair of conductors to be severed.

Marking tape with wire conductors and methods for use

A passive marker device including a tuned circuit enclosed in a housing which includes a base member with an upstanding rim with a cover member bonded to the rim and to a central portion of the base member. An opening is provided that extends through the housing at the central portion of the housing. A boss extends from the central portion of the base member to the cover member. The boss is recessed on the side of the base member that is away from the cover.

Growing community of inventors

Austin, TX, United States of America

Armond D Cosman