Dual Field Pi Coils

[moodz]

there is no problem with patents for hobbyists :-) part 2

...oh .. if you make an exact copy of an existing design like the circuit board, software or particular feature like a brand logo ( in other words counterfeit ) you would not be in breach of patent but other laws like copyright etc ...and they could sue you for that.

So if you are going to build something dont copy / reverse engineer the item ... build it from the patent description. ( half the time the patent description is wrong and does not describe the manufactured item anyway )

MooDz

[moodz]

there is no problem with patents for hobbyists :-)

The common law research exemption is an affirmative defense to infringement where the alleged infringer is using a patented invention for research purposes. The doctrine originated in the 1813 decision by Justice Joseph Story appellate decision Whittemore v. Cutter, 29 Fed. Cas. 1120 (C.C.D. Mass. 1813). Story famously wrote that the intent of the legislature could not have been to punish someone who infringes "merely for [scientific] experiments, or for the purpose of ascertaining the sufficiency of the machine to produce its described effects." Subsequent decisions later distinguished between commercial and non-commercial research.
In 2002, the Court of Appeals for the Federal Circuit dramatically limited the scope of the research exemption in Madey v. Duke University, 307 F.3d 1351, 1362 (Fed. Cir. 2002). The court did not reject the defense, but left only a "very narrow and strictly limited experimental use defense" for "amusement, to satisfy idle curiosity, or for strictly philosophical inquiry." The court also precludes the defense where, regardless of profit motive, the research was done "in furtherance of the alleged infringer’s legitimate business." In the case of a research university like Duke University, the court held that the alleged use was in furtherance of its legitimate business, and thus the defense was inapplicable.


What all this means is that if you are an experimenter / hobbyist who builds / uses a patented device for idle amusement, curiosity, interest, education, proving the device works as stated in patent etc but not commercial use, sale or furtherance of business THEN YOU CAN USE ANY PATENTED DESIGN YOU LIKE.in addition if you make improvements to the device and someone sues you ... immediately lodge a petty patent quoting the suer's patent as prior ...they will have to defeat your patent in court first ...this will take a long time and hopefully lots of money ( from them ). Hobbyist use of a metal detector even for valuable items is not deemed commercial use as the device is not patented as a 'gold or valuable detector detector' ( this would not apply to LR detectors IMHO).


In Australia if not elsewhere a researcher may construct and use a patented device in order to learn how the device works for the purposes of developing subsequent improved ( and patentable ) features. Of course some of that research ( if not all of it ) would be done in the field.



Of course if you are a metal detector dealer or associated in any way with a manufacturer or related industry or commercial interest you are precluded from using the 'research exemption clause'.



MooDz

[Aziz]

Hi Rov,

no problem. Just make a triple coil. It is an approximation of a spiral coil. The dual field coil only reduces the shield and interwire coil capacitance. If you can make a low capacitance shield, make a spiral coil. It works best.

The triple coil suggestion:

Constant diameter division:
Coil 1: 1/3 Diameter
Coil 2: 2/3 Diameter
Coil 3: 3/3 Diameter

Well, you could also divide the radius section Ri (inner) to Ro (outer) in equal distances (coil radius - not diameter):
Coil 1: Ri + 0*(Ro-Ri)/(3-1) = Ri
Coil 2: Ri + 1*(Ro-Ri)/(3-1) = Ri + 0.5*(Ro-Ri)
Coil 3: Ri + 2*(Ro-Ri)/(3-1) = Ro

All sub coils (1,2,3) should have same number of windings. All the sub coils are connected in series.

Aziz

[Aziz]

Hi Carl,

Rick, be aware that White's has a patent pending on dual field coils.

- Carl

I would be interested in the patent. It is granted yet? What's the filing date and patent number?

Aziz

[Rov]

Thanks for the heads up Carl.any reference of branding will be removed,an any commercial manufacture reference concluded.
the small quantity produced to date have not been commercially sold.only distributed to hobbiests/enthusiasts for personal testing an appraisal,an a bit of club use.this will be as is.an no further.
I dont wish to ruffle anybodies commercial interests.I understand commercial intelectual property is important.
Looks like twin coil development by me will be concluded.pity?
regards Rov

[Carl-NC]

Rick, be aware that White's has a patent pending on dual field coils.

- Carl

[Rov]

Hi a bit of success for home built dual field coils.built by an for the hobbiest an enthusiast.
Suit the Pulsemate PI detector an others,Minelabs Pi,in the sd/gp/gpx series etc.
wired to 5pin specs to suit minelabs Pi.
12inch outer coil,an a 6 inch inner for sensitivity on small targets.combined.
with screening for brush an knock resistance in the field from falsing.an EMI.
overall low ohms in the range of 0.9ohms total.
Silver plated multi strand/teflon wire used for these.
ElectroDag screening on internals etc.
Works very well!on many PI.
regards Rov