"Killer" Screen Driven Push-Pull Amp Initial Queries

[JLH]

If you know the Patent number, then the best site to use to view patents is --> www.pat2pdf.org

Here is the patent you were trying to link to --> http://www.pat2pdf.org/patents/pat4127238.pdf

Rgs, JLH

[smoking-amp]

Thanks JLH!

Clever design too. Probably the best thing to come out of Livermore Lab. Billions of your taxpayer dollers at work, finally paying off.

Don

[ErikdeBest]

Nice find Don!

I printed the patent and tried to understand the working, but it is not completely clear for me, yet. Besides I have enough projects to finish for which I already have the needed iron

Still very interesting, my first application thought was to wind an autoformer type transformer volume control. The single winding should be the easiest to get right?!

Erik

[kenpeter]

The simple version is a bicycle rim. Cut all the way through in one
place, so you can get it onto and off of the toroid. Then wind your
wire onto the rim as-if a huge bobbin. Then from the bobbin onto
the toroid.

Or you could build something complicated...

[ErikdeBest]

Kenpeter

Now I got it. Must be because there are so many bicycles here in the Netherlands, while there are not many complicated things

Erik

[smoking-amp]

"The simple version is a bicycle rim."

You are going to have trouble getting the spokes thru the toroid. The shuttle type winders are the most complicated designs when you consider all the roller supports and gearing, and the least flexible or capable (they cannot handle a small winding window).

The Potthoff design doesn't use any shuttle. Only wire travels thru the toroid. Its easy to build too. Just three sheets of teflon, machined into a C shape and a timing belt running around it. Parts are on the way already.

Don

[kenpeter]

Originally posted by smoking-amp
You are going to have trouble getting the spokes thru the toroid.

Exactly why they invented the "Spoke Shaver"...
I mean geez man, do I have to think of EVERYTHING?

[jkeny]

Great ideas pop up in the most unusual threads. Thanks Don for uncovering this patent.

I've read it a number of times but fail to understand:

- How the wire is wound around the C-shaped belt loop & through the toroid at the same time? - I can see how a belt can rotate around in a c-shaped sausage driven by an inner cog but if the wire is threaded through the toroid & attached to the belt which is then turned how does a second & subsequent loop go through the toroid?

- Presuming all the loops needed are threaded through the toroid & around the C belt how are they then slipped off the belt individually in a controlled fashion?

I am keen to build one of these winders, maybe a separate thread could be started which would give this more exposure to the concept for the benefit of the community?

[smoking-amp]

Moderator assistance request:

Looks like we should break out the toroid winder stuff as a separate thread if interest continues.


Jkeny:

"How the wire is wound around the C-shaped belt loop & through the toroid at the same time? ....."

As Kenpeter was attempting to explain, the easiest way is to look at it is as a shuttle type winder first. Imagine a hoop like shuttle or bobbin thru the core (bicycle rim). The wire is first spun onto the rim by spinning the rim and winding on wire (on the rim). Normally the wire start would be taped down to the rim.

Then the finishing end of the wire is attached to
the core holddown and the rim is slowly spun again. The wire winds around the core and pulls itself off one edge of the rim as needed. Ie, it spills over the edge of the rim by wire tension. Some friction effect is required to tension the wire and keep it held on the rim till needed too, this is often done by a C shaped spring leaf over the wire bundle on the rim.

Next, we conceptually replace the rim with the C shaped Teflon grooved, or slotted C, with a timing belt running around in its groove. (The initail wire windup procedure is modified so that one loop of wire is hand tightened around the C and thru the core and then twisted together in the core notchout of the C) The wire stays on the outside of the C, just like on the old rim, resting on the belt surface (but not the inner section of belt around the cog pulley). (the belt does its c-shaped sausage around the inner cog pulley simply for drive motion.)

The C stays stationary and remains outside the toroid. A notch (core notchout) in the C allows the toroid to rest around the pre-wound wire flow. The drive belt can be driven and the wire rotates around the C's loop thru the core. So the "shuttle or rim" is filled up initially with wire just like before. Then the wire end is tied down to the core holdown as before.

Now the winding procedure starts by running the belt drive again. The pre-wound wire bundle rotates around thru the core like before (just like with the rim, but now the effective rim is missing where the core notchout is) and the wire spills off the edge of the C for wire feed. The spill edge is rounded and of Teflon for easy feed. Instead of a spring tensioner, the patent design uses a teflon disk pressed up against the side of the C, forming a narrow gap (call it the slack accumulator) for the wire to pass thru.

During winding, the wire rotates around the C (on the belt surface) and thru the core, feeding wire off the C edge as needed. Obviously, when the current feed point recedes to the back of the C and then starts moving forward toward the core again, some excess wire occurs. This ends up forming a temporary loop in the slack accumulator until used up again by subsequent winding. The slack accumulator is a flat gap in the patent design, but a better approach might be a rounded spherical double surface so as to encourage the wire to form a round loop without sharp bends in the accumulator.

Looking at it from the side and following the spill off point: The wire wraps around the toroid until the spill point reaches the back of the C, then curves to form a loop in the accumulator as the spill off point moves forward again toward the core. Friction in the accumulator gap maintaining tension on the wire around the toroid even though there is excess wire spilled. Once the spill point passes thru the core again, the excess wire accumulator loop pulls smaller until it pulls down on the core thru the gap. Tension then pulls more wire off the spill point in the subsequent cycle until the spill point reaches the back side of the C again.

So from the core viewpoint, the wire mostly is pulling out of the accumulator gap for most of the cycle even when the spill off point passes thru the core. After the spill off point has passed thru and begins to recede from the core, the wire is pulled thru the core as the accumulator wire loop shrinks. The wire loop eventually pulls out of the inner edge of the gap and tightens around the core. Winding tension is determined by the friction in the accumulator gap, which is spring tensioned against the spill off side of the C.

So the accumulator gap provides close control of the wire winding position (on the toroid) during winding. Ideally it would have its notchout shaped to the contour of the core outer winding surface.

Whats nice here is the simplicity of construction with few moving parts and the lack of a shuttle or wheel rim passing thru the core. This gives the maximum room for wire to wind on the core. (you could even wind the core up to 100% fill if the wire length was adjusted just right, but this would not be a good idea for audio OTs. )

The shuttle type designs need elaborate rollers to keep the rim positioned during rotation (and not block spill off on the side) and to drive it. The rim itself must have provision for splitting to fit thru the toroid initially too. This makes a rough spot on the rim that spilloff wire has to pass over repeatedly. Different size rims may also be required for small and large toroids.

For both designs, the control of friction for side feed and wire tensioning is crucial. Significantly different wire sizes for primary and secondary require adjustability of this tensioning too. So this friction control is the achilles heel or greatest risk to limited DIY design efforts.

Don

[jkeny]

Thanks Don, for the comprehensive explanation - I think I have the idea now even though my spatial imagination is not as good as I'd like. I'll have to build a quick mock-up to picture how the wire will spool off the rim without tangling up - I'm sure your explanation of a spherical guide will stop the sharp bends.

Anyway, once built this would be a boon to this dIY hobby as I presume it could also be used in reverse to unwind cheap PS toroids & reuse cores. A great saving and a wonderful experimenters tool also - bifilar, progressive windings, etc.

Please keep us informed of your progress with this and your approach to progressive winding that seems to hold much promise for wide bandwith trafos.

Yes, please moderators a separate thread please if interest warrants

Edit: Just after posting, a thought occurred: Kenpeter's idea could work without cutting out a section of the rim - just pull the toroid core away from the rim with springs, i.e no need for the C-shaped belt at all? Am I right/wrong?