Metal detector for an asphalt milling machine

1. A milling machine for milling a paved surface, comprising:

milling tools connected to an underside of a body of the machine;

at least one ferrous metal detector attached to a front end of the machine;

the at least one metal detector comprises a characteristic of creating a magnetic field and detecting an induced magnetic field from metal objects; and

electronic equipment in communication with the metal detector, the equipment being adapted to interpret feedback from the detector;

wherein the metal detector is adapted to determine a depth of a metal object by having at least two metal detectors at different distances from the paved surface;

wherein when the electronic equipment interprets a metal object that interferes with milling, the electronic equipment causes the milling machine to automatically shut off.

2. The machine of claim 1 , wherein the machine comprises at least two metal detectors positioned such that a detection range of a first detector extends farther into the surface than a detection range of a second detector.

3. The machine of claim 1 , wherein the machine comprises a magnetic shielding intermediate the metal detector and the body, such that the detector is magnetically shielded from the body.

4. The machine of claim 3 , wherein the magnetic shielding is made of a material selected from the group consisting of ferrite, aluminum oxide, chromium, nickel, copper, iron, molybdenum, alloys thereof and any combination thereof.

5. The machine of claim 3 , wherein the magnetic shielding is attached to the underside of the body.

6. The machine of claim 3 , wherein the magnetic shielding comprises a relative magnetic permeability of at least 100.

7. The machine of claim 3 , wherein the magnetic shielding focuses a magnetic field from the detector in a predetermined direction.

8. The machine of claim 3 , wherein the metal detector is also magnetically shielded from the milling tools.

9. The machine of claim 3 , wherein the magnetic shielding comprises a u-shaped geometry.

10. The machine of claim 1 , wherein a detection range of the metal detector is controlled by a variable voltage source.

11. The machine of claim 1 , wherein the metal detector is adapted to detect metal objects up to 1 foot deep.

12. The machine of claim 1 , where the metal detector is adapted to determine the size of a metal object.

13. The machine of claim 1 , wherein the metal detector is adapted to locate an edge of the metal object.

14. The machine of claim 1 , wherein the machine comprises a plurality of ferrous metal detectors arranged in a plurality of arrays, each array positioned at a different distance above the paved surface.

15. The machine of claim 1 , wherein the milling tools are adapted to be automatically laterally adjusted in a closed-loop system by the electronic equipment in response to feedback from the detector.

16. The machine of claim 1 , wherein the machine comprises a plurality of ferrous metal detectors positioned at different angles.

17. The machine of claim 1 , wherein the metal detector is vertically adjustable.

18. The machine of claim 1 , wherein the metal detector is attached to the front end such that during operation the detector is positioned from 1 to 8 inches above the paved surface.

19. A method for metal detection during milling of a paved surface, comprising the steps of:

providing a milling machine having milling tools connected to an underside of a body of the machine and at least one ferrous metal detector attached to a front end of the machine;

providing electronic equipment disposed within the machine and in communication with the metal detector, the equipment being adapted to interpret feedback from the detector; and

inducing a magnetic field in a metal object by applying a variable voltage to the detector, allowing the detector to detect metal objects over various ranges of depths;

wherein at least two metal detectors are positioned at different distances from the paved surface;

wherein when the electronic equipment interprets a metal object that interferes with milling, the electronic equipment causes the milling machine to automatically shut off.