Apparatus for detecting ferromagnetic material
Patent 4449115 Issued on May 15, 1984. Estimated Expiration Date: 
August 2, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
August 2, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3249915 3319161 3775742 3825889 Inductive loop structure for detecting the presence of vehicles over a roadway Inductive loop vehicle detector Patent #: 3989932 InventorAssigneeApplicationNo. 06/519214 filed on 08/02/1983US Classes:340/941, Inductive340/551Disturbance of magnetic fieldExaminersPrimary: Swann, III, Glen R.Attorney, Agent or FirmInternational ClassesG01V 3/10 (20060101)G08G 1/042 (20060101) AbstractA convertor is used having an impedance responsive to the magnetic field intensity of the earth. The convertor may be coupled to a detector for monitoring the impedance of the convertor and generating a call signal responsive to the change in impedance. Generally, the impedance is primarily inductance and the detector is an oscillator using the convertor in a resonant circuit with a frequency monitor coupled to the detector. The convertor is an open magnetic structure having a non-linear BH curve biased by the earth's magnetic field. The open magnetic structure is a core of a highly permeable material which approaches saturation under the influence of the earth's magnetic field, with the axis of the core at least partially aligned with the magnetic flux lines of the earth's magnetic field, and a coil wound around the axis of the core.Field of SearchDisturbance of magnetic field | |
