Electricity: measuring and testing – Conductor identification or location – Inaccessible
Reexamination Certificate
1998-08-12
2001-04-10
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Conductor identification or location
Inaccessible
C324S326000
Reexamination Certificate
active
06215293
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a stud detectors.
2. Description of Prior Art
The invention relates more particularly to a stud detector that is capable of detecting wooden studs, metal objects or wires, and live wires carrying an AC current.
Stud detectors are well-known and rely on detecting changes in dielectric constants. The stud detectors are typically used by tradesmen to detect wooden studs or beams that are hidden from view, behind plaster or other wall coverings, by moving the detector across and closely adjacent a wall surface. It is necessary to determine the relative position of the studs so that other construction items or fittings can be securely attached the wall. For example when fitting a ceiling fan, support anchor bolts must, where appropriate, be screwed into ceiling joist that is above and behind the ceiling plaster. It is therefore desirable to locate the ceiling joist without damaging the ceiling coating. A portable stud locating device is fully described in U.S. Pat. No. 4,099,118.
The tradesman may also wish to locate any live electric wires that are likewise hidden from view behind a plastered or covered surface. A device that combines wooden stud detection and live wire location is described in U.S. Pat. No. 4,464,622. The combined device has improved calibration, but a disadvantage that the AC detection is dependent the wood detector circuit operation.
Further, the described combined device of U.S. Pat. No. 4,464,622 is incapable of detecting electric power cables that are disconnected from a mains supply or detecting metallic conduits, strips or other objects that may be important for the tradesman's activities. Such metallic elements may be required in some cases to provide a sound anchorage for a construction addition or wall fitting, for example. In other cases, the metallic elements may represent an impediment to anchorage of any fixings and so must avoided.
SUMMARY OF THE INVENTION
It is an object of the invention to overcome or at least reduce this problem.
According to the invention there is provided a portable device for selectively locating a wooden object, a metal object or a live AC wire positioned behind a wall surface covering when the device is moved along the wall surface, the device comprising means for indicating the presence of wooden objects including, a first capacitor plate, a pair of second capacitor plates on opposite sides of the first capacitor plate and in substantially the same plane as the first capacitor plate, means for producing an output signal representative of a change in the effective dielectric constant between the first capacitor plate and the pair of second capacitor plates as the device is moved along the wall, and means for monitoring the output signal and arranged to indicate a change; means for indicating the presence of metal objects, including means for generating a magnetic field that in use extends into the wall, means for detecting changes in the effective reluctance due to metal objects in the vicinity of the device, and indicating means arranged to provide signals whenever the effective reluctance changes; and means for indicating the presence of a live wire in the vicinity of the device, including a passive antenna for responding to electromagnetic radiation and generating output signals, a bandpass filter for rejecting components of the generated output signals outside a predetermined range of frequencies, means for monitoring an output of the bandpass filter caused by any live wire for providing the indication of the proximity of a live wire.
The indicating means comprise LED's, and/or a loudspeaker controlled to produce discriminating different signals according to what is being detected.
The device is preferably controlled by a single microprocessor.
The microcontroller may be programmed to detect and to indicate the proximity of metal objects only, even when wooden objects are also adjacently present.
The microcontroller may also be programmed to detect and to indicate the proximity of objects according to a priority in the order of live wires, metal objects and wooden objects.
REFERENCES:
patent: 4464622 (1984-08-01), Franklin
patent: 4859931 (1989-08-01), Yamashita et al.
patent: 5457394 (1995-10-01), McEwan
patent: 5512834 (1996-04-01), McEwan
patent: 5917314 (1999-06-01), Heger et al.
Jackson Walker L.L.P.
Patidar Jay
Solar Wide Industrial Limited
Zaveri Subhash
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