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Author Topic: Cooling fan (Patent 4757547)  (Read 11059 times)

Wayne Parham

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Re: Cooling fan (Patent 4757547)
« Reply #30 on: October 17, 2006, 01:11:51 pm »


Will we see this cooling system on any Danley Sound Lab products?  Since you are the patent holder, it seem natural to me that you would use it on your own products.

Tom Danley wrote on Sun, 15 October 2006 11:17

You say “They also both use conduction or radiation to carry heat to the fins.”
Actually radiation is not a significant part of transferring heat from either a transistor or engine block to the radiator, it is conduction.  Even amplifier heatsink convection is a conduction driven mechanism, when the air in contact is heated, it rises.


My point is that all three types of heat transfer are happening.  In a car engine, the combustion chamber produces heat which is radiated into the heads and cylinder block.  This plus the heat of friction is conducted into the water (if water cooled) or out to the fins (if air cooled).  If water cooled, the heat is carried out to the radiator and heat is exchanged there, convection carries it away from the fins.  If air cooled, the fins are on the block itself.  All three types of heat transfer are in play.

Same thing with a transistor.  Heat is generated as current flows through the junction.  Heat is conducted and radiated to the metal case or tab where it is conducted to a heat sink.  The fins of the heat sink provide convection cooling.

There is no reason to discount any method of heat transfer.  In the case of the loudspeaker, the voice coil is surrounded by a large pieces of metal and ceramic.  Those work as a radiant cooler until they become hot.  That's why removing the heat from the pole piece and magnet structure is important, in addition to air cooling through the vents.  It is counterproductive to allow the magnet and pole piece to reach a high temperature.

Tom Danley wrote on Sun, 15 October 2006 11:17


Your still missing a major concept here.
Consider your surface area argument and then consider that the motor that I linked has less exposed area than one could have with a modest sized VC.  Even so, a vary large increase of heat capacity is demonstrated in its measurements via passing air directly across the hot conductors.
Like the loudspeaker, the problem is not cooling off the case but cooling off the part producing heat which is much much hotter.


No, Tom, I am not missing anything.  I am not saying that air cooling should not be used.  I am stating its limitations, but I am not advocating removing the cooling vents.  What I am saying is that radiant cooling is in play also, if the pole piece and magnet are kept cool.  I am also saying that the amount of heat transferred by radiation is significant.  So what I am advocating is the use of pole piece cooling plugs and heat sinks in addition to cooling vents.
   
Tom Danley wrote on Sun, 15 October 2006 11:17


You keep dwelling on cone offset, perhaps your also missing part of the concept here.
Off set force is equal to area times pressure.
Lets say you had a peak pressure of  2 inches H2O, (this is also a pressure of .074 PSIG).
This pressure if applied as I had shown in the Patent, is applied at the VC pocket.


I get the concept, it's neat.  But if you put a vacuum on the voice coil gap, you'll pull the cone down.  You can increase suspension stiffness to reduce it, but it is still a cone offset and it creates a one-way force that tends to make driver movement asymmetrical.  You could probably use it to balance the asymmetry caused by flux modulation or something, that would be cool.  But the point is that no matter how you slice it, the (positive or negative) pressure required to create cooling air flow also causes a cone offset and an asymmetrical force.
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Wayne Parham
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John Roberts {JR}

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Re: Cooling fan (Patent 4757547)
« Reply #31 on: October 17, 2006, 02:04:32 pm »

Tom is the inventor but the patent shows as assigned to Intersonics. Tom has posted previously that Intersonics charged a high license fee that discouraged use by others.

Just because you get your name in the inventor box, you don't automatically control that technology. Perhaps ironic when an inventor can't use his own inventions but I know a little about that. Confused

I don't know for a fact that Tom can't, and he can answer for himself. Just thought I'd share the obvious assignment information.

JR  
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Wayne Parham

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Re: Cooling fan (Patent 4757547)
« Reply #32 on: October 17, 2006, 02:32:05 pm »


Very good point, John.  Is Intersonics still around?  Might be worth a call to his old boss at Intersonics, just to see how he felt about using this technology.  Seems underutilized, nobody is using it as far as I can tell.

Tom said Intersonics had no interest in the voice coil version of the patent.  I'm sure they would license it for a song to Tom if licensing were needed.  Might be a mute point because I think the patent expires next year, but I imagine Tom would contact his old boss anyway, out of courtesy.

I think if Tom is really sold on this technology he could probably use it if he wanted.
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John Roberts {JR}

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Re: Cooling fan (Patent 4757547)
« Reply #33 on: October 17, 2006, 02:46:05 pm »

Wayne Parham wrote on Tue, 17 October 2006 13:32


Very good point, John.  Is Intersonics still around?  Might be worth a call to his old boss at Intersonics, just to see how he felt about using this technology.  Seems underutilized, nobody is using it as far as I can tell.

Tom said Intersonics had no interest in the voice coil version of the patent.  I'm sure they would license it for a song to Tom if licensing were needed.  Might be a mute point because I think the patent expires next year, but I imagine Tom would contact his old boss anyway, out of courtesy.

I think if Tom is really sold on this technology he could probably use it if he wanted.



They weren't interested before when they also charged too much.

If the patent becomes moot due to expiration in a year, one could start pedalling now because it takes time to tool etc, were one so inclined. It also takes capital and/or a driver mfr with deep pockets willing to pursue an idea that BTW is no longer protected. I suspect Tom has a full plate already but we can always stack on a few more projects.  Laughing

He is probably swiftly moving from the fun part of a new company startup when everything is new and engineering is a blank sheet of paper, to the more work like support of a stable of products in production that need lovin too, but he's got some good crew working with him.

JR
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Wayne Parham

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Re: Cooling fan (Patent 4757547)
« Reply #34 on: October 17, 2006, 03:03:32 pm »



John Roberts  {JR} wrote on Tue, 17 October 2006 13:46


If the patent becomes moot due to expiration in a year, one could start pedalling now because it takes time to tool etc, were one so inclined.


The best part for Tom is that, as shown in the photo he posted, all he really has to do is hook up a fan and minimal ducting.  The use of his cooling system doesn't require a lot of tooling to be done;  The biggest thing is pressing or threading fittings into the radial vents on the back plate.  The rest is duct work, and can be done with off-the-shelf parts.

Since his tapped horns have both sides of the driver exposed to the mouth, the ducting doesn't have to even be run to the outside.  The rear plate already is outside, so all that is required is a pump to scavenge air from the radial vents.
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Tom Danley

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Re: Cooling fan (Patent 4757547)
« Reply #35 on: October 17, 2006, 06:00:54 pm »

Hi Wayne, All

Because of the NASA work Intersonics did, the first 13 of my Patents were assigned to that company and then its patent holding company.  
While I am the inventor, I do not own any of them and don’t use any of them currently.

Sounds like John has worn these shoes too, spot on, sorry to hear it.
Well the up side is it was a “learning experience”.

A couple things, radiation is how the heat from a light bulb filament heats the glass or how the heat from combustion is transferred in the “flash” to the metal around it.
Heat does not radiate through metal, think like light, photons that is radiation and it isn’t comparatively significant until something is real pretty hot.  Look up Doug Button’s paper, I think he had the breakdown.
You say” Those work as a radiant cooler until they become hot.” Yet, like light, one can’t radiate cool or darkness, they are simply lower energy states.

My point is that in order for the magnet to become heated, the air in the gap must conduct most of that energy, since the air is already hot, just remove it.
Of the possible things one could do, it offers the largest increase in phc.
If done as in the Servodrive speakers, the cooling ejects the heat from the cabinet altogether so the increase is long term.

Yes there is a tiny asymmetrical force proportional to cooling flow for a VC, but it is acoustically insignificant in practice and in the example above.

Tom
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Michael 'Bink' Knowles

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Re: Cooling fan (Patent 4757547)
« Reply #36 on: October 17, 2006, 11:48:24 pm »

Quote:

...when I presented my AES paper on “eliminating power compression”,  Doug B from JBL presented right after one of the first papers to acknowledge its existence...


Wow, there's a story there. Doug Button? Is this the mid- to late-'80s? Did Doug ever speak to you again after this embarassment?  Twisted Evil

-Bink
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Wayne Parham

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Re: Cooling fan (Patent 4757547)
« Reply #37 on: October 18, 2006, 11:31:55 am »


Tom Danley wrote on Tue, 17 October 2006 17:00

A couple things, radiation is how the heat from a light bulb filament heats the glass or how the heat from combustion is transferred in the “flash” to the metal around it.
Heat does not radiate through metal, think like light, photons that is radiation and it isn’t comparatively significant until something is real pretty hot.  Look up Doug Button’s paper, I think he had the breakdown.


Actually, radiated heat is significant.  Incandescence is not required for radiant heat.  Incandescence (light from a hot body) or luminescence (light from a cold body) just means that radiation is in the visible spectrum.  Radiation happens anytime an object is above absolute zero, which is to say all objects are radiant.  When you feel heat from something, it is almost always radiant heat that you feel.  Stand by a fire, a warm car, a hot pavement, even next to a person.  Radiant heat is what you feel, not convected heat from the air.

Tom Danley wrote on Tue, 17 October 2006 17:00

You say” Those work as a radiant cooler until they become hot.” Yet, like light, one can’t radiate cool or darkness, they are simply lower energy states.


Look up radiant coolers.  It's a simple concept.  Any time an object that is cool is placed near an object that is warm, there is radiant heat transfer.  The amount of heat transferred is determined by the temperature difference between the objects, their size and their distance.

Tom Danley wrote on Tue, 17 October 2006 17:00

My point is that in order for the magnet to become heated, the air in the gap must conduct most of that energy, since the air is already hot, just remove it.


That's not true.  I think you misunderstand radiant heat transfer and that's why you are misunderstanding this concept.  The heat that passes into the magnet and pole piece is almost entirely radiated, not convected or conducted.

Tom Danley wrote on Tue, 17 October 2006 17:00

Yes there is a tiny asymmetrical force proportional to cooling flow for a VC, but it is acoustically insignificant in practice and in the example above.


The asymmetrical force is obviously directly related to the air pressure, and therefore cooling air flow.  The more flow, the more force.  That's the main thing that concerns me about this cooling system.

Fortunately for you, it appears that the patent will expire in a year, so you can use it in Danley Sound Labs products very soon if you want.
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Phil Pope

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Re: Cooling fan (Patent 4757547)
« Reply #38 on: October 18, 2006, 02:51:58 pm »

Wayne Parham wrote on Wed, 18 October 2006 16:31


The asymmetrical force is obviously directly related to the air pressure, and therefore cooling air flow.  The more flow, the more force.  That's the main thing that concerns me about this cooling system.



if you draw air through the small holes round the voice coil then the pressure differential is only acting on the area of the end of the voice coil, right? assume 10 cm diameter coil, assume 3mm thick, gives an area of the order of 10cm^2. assume a pressure of 10cm water gives a force of about 1 Newton, right? as the suspension compliance is usually of the order of 0.1mm/N this should be practically insignificant as long as my reasoning is right.

If I understand correctly there will be far greater problems with offset if you suck air out the big pole vent rather than blow into the small holes.

I haven't done any further tests for lack of suitable blower. my shop vac isn't suitable as it isn't variable and can't be switched to blow easily. can't find much choice of stuff that runs off 110 or 120 Vdc. 12V fans would be OK run off a step down transformer but those I have seen don't have nearly high enough static pressure ratings. can anyone point me in the right direction?

Phil
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Phil Pope

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Re: Cooling fan (Patent 4757547)
« Reply #39 on: October 18, 2006, 03:12:06 pm »

sorry, the last point I made has already been answered.

Tom Danley wrote on Sun, 15 October 2006 19:55


There is no resultant air pressure on the dust cap or cone, the only net force on the system is caused by the cooling pressure and end area of the VC (OD area – ID area).
Some drivers now are made with a vent to this location, like some B&C drivers but the ones I have seen also have a matching set of holes on the front plate.
These defeat the idea when a fan is used as the front holes give a much easier air flow path which doesn’t involve scrubbing up against the hot VC in the gap.



taping over the holes on the front plate by the spider will make the air cooling work. I thought spiders were fairly porous so there is no reason this will cause any harm is there?

Phil
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