Dual Field Pi Coils

[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

[Carl-NC]

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

- Carl

[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

[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

[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

[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

[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

[Carl-NC]

I'm at home today and don't have the application number, and for some reason it's not a published application.

I'm sure White's would not bother with home-hobbyist infringements, and may even be interested in allowing 3rd-party developments.

[Aziz]

Who is more fool?

...( half the time the patent description is wrong and does not describe the manufactured item anyway )
MooDz

Are the patent examiners dumb?
Are the patent appliers dumb?
Are the patent appliers fooling us?
Or are we the patent readers stupid only?



Aziz

[Rov]

I havent back engineered anybody elses commercial manufactured coil to produce my own,it was quite a bit of work to perfect on my own a twin loop to work successfully ,getting suitable wires,testing ,winding,inductances right an achieve a low ohms,that a lot of PI machines will see an drive Ok.Maybe I just call it something else a Duo Loop or whatever?
Yes Aziz I can make a tri loop coil.I have the recipe for the electrical characteristics required.Will give this a go.Then I suppose that somebody may suggest Ive harvested the idea from Garretts on some 3 loop imaging coil or something.
Ive still got a couple hundred meters of lovely silverplated multistrand teflon (yes very expensive wire)to use for something.Best use it up an see what I can come up with.
regards Rov

[moodz]

Are the patent examiners dumb?
Are the patent appliers dumb?
Are the patent appliers fooling us?
Or are we the patent readers stupid only?



Aziz

Most patent examiners are not experts in specific technical fields like metal detecting though they may have knowledge of engineering principles ... they are experts in determining whether the claims are sufficiently different in a legal perspective from prior art or existing patents. Since they dont build the device you are claiming they have absolutely no clue if the device actually works ( or can even be built ). So legally they are smart but technically dumb. ( for example in science you cannot make a claim unless someone CAN duplicate your results )

The patent appliers think that they are protecting their IP however it is very expensive to lodge a patent, secondly to determine if someone might be infringing your patent and then to try and sue them. Best left to large corporations. For a small person .. patents are a waste of your valuable development time.

The patent appliers are trying to fool us partly because the patent is not written like a set of instructions on how to build the device and partly because the appliers make wild claims using terms like 'a plurality of coils' but then describe the 'preferred embodiment' which only uses one coil .... go figure. Not to mention all the hand drawn diagrams like in patent 7649356 with no time base / amplitude or indication how they were generated.

The patent readers are stupid because under the research exemption clause for patents hobbyists should read more patents ... most of the time they mistakenly believe they have to come up with their own solutions ... and most of the time reinventing the wheel or even going backwards. If you knew everything that had been patented in a certain field you would be more sure of not going over old ground and coming up with new ideas.

MooDz

[WM6]

T

the small quantity produced to date have not been commercially sold.only distributed to hobbiests/enthusiasts for personal testing an appraisal,

Hi Rov

I am interesting to test one and of course to give you noncommercial compensation for the costs and your work in it.

Regards

[Aziz]

Well,

White's have to give the proof of pending patent for a dual field coil. I did not find the patent in the data base yet. I found a two-box solution from Garret (rectangular and a smaller circular coil) only.

As long as the proof is not given, we can assume that it is not protected.

BTW, I have been using dual PI coils in my school time (1980..1990) already.

Aziz

[Qiaozhi]

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

- Carl

Just to make things clear here:
When the term "Dual Field Coils" is used, I assume this refers to the case where the outer and inner coils are in series, and are used in the same way as a mono coil ... and does not refer to the usual IB coil arrangement. I think this needs to be clarified, as there appears to be some confusion here.

[Aziz]

Hi Moodz,

I am getting tired, to read the entire patent paper. Last times, I look at the pictures and read the claims only.

"A plurality of coils":
Well, a spiral coil is one. It has as many coils as it has windings.

Aziz