Mills (company name) air compressor

This is a bit off-topic, but does anyone collect documents / records of air compressor companies?

I'm curious to learn the corporate history, and eventual fate of a company named "Mills" that made air compressors, and possibly other industrial equipment.

I don't know much more than the name, and they at least made a very nice two cylinder unit with the name cast into she side of the crankcase.

I've had one up in the rafters of my shop for decades where it has done yeoman service until recently when the paper gasket between the valve plate and cylinders blew ( the cylinders are 180 degrees out of phase ) and I finally had to take it apart.

It has a stroke of about 3 inches and bore of maybe a bit less than 2, on each cylinder.

I've been curious about this beast since I got it, and when the web finally came along in the early 90's I occasionally did some half hearted research, but never found anything. The search engines all fixate on "Mills" as a noun, not a proper noun.

Now that I have it apart, I am even more impressed, the intake side is vented to the crankcase down a hole in the block, so that it self lubricates (a bit) and it has new-looking valves. The intake valves are flappers inside the cylinders, (reed type) and the outputs are disks held down by springs on the top side of the valve plate.

Except for the blown gasket, everything looks fine. The blown gasket is clearly a hand-cut (not original) part, probably blew because the part between the cylinders was too thin, and the material was too thick, still, it lasted more than the 30 years I've used it.

I'm thinking that I could make a new gasket with only holes in it where the valves are, instead of cutting big holes the same size as the cylinder diameter. The bottom of the valve plate is flat, I will check the clearance to the top of the pistons at TDC before doing this. There doesn't seem to be any reason to make the gasket narrow between the cylinders.

Anyway, I would like to find out who made this beast, and where they were, and when, where they came from and who bought the company if it didn't just fold. I am no expert on compressors, but I'm guessing this thing could be from any time in the early to mid 20th century.

Thanks;
John Colt

"I'm thinking that I could make a new gasket with only holes in it where the valves are, instead of......"

Think twice about changing the design of something that worked well for 30 years !!!

How about just trying to make the best gasket you can to the original design?

Oh, sure, it's not easy to make a head gasket, but the WW2 USN Seabees made head gaskets for big construction equipment many times. It can be done.

I might try starting with some sort of suitable gasket material sandwiched between thin copper sheeting.

Then again, I know people who would cut it out of an old breakfast cereal box, coat it with "Indian Head" compound, and probably get years of service out of it !

John Ruth

Shirt cardboard (akin to the cereal box cardboard) painted with oil based aluminum paint works pretty well. Put together wet and run until dry.

Permatex makes a spray "gasket tack" that works pretty well too. Let dry to tacky and then put together.

Joe

Hi John - I agree, but it's clear that this gasket was not original. My suspicion is that this failed gasket was made by simply laying it on the block and pushing down to get an impression. The gasket between the "top" head and the valve plate looks original - and has to take the same pressure, at least on the output side - is a simple paper gasket, but it's captured between bigger areas than the gasket between the valve plate and the top of the block.

The bottom of the valve plate is totaly flat, except where there are two flappers on the intake holes. So it's not like the gasket will be flapping in the breeze. If I do this right, the gasket material will be in tension if it decides to move sideways between the bores, rather than just looking like some loose fiber packing and blowing out.

I'm thinking that the blown gasket I found installed was:

1) made from too thick material - so in a small cross section it was able to releive itself sideways and loose compression (sorry about the pun) between the block and the valve plate,

2) cut too narrow between the bores.

In this design, there can be a large pressure differential between the bores, so this needs to be solid.

Since it lasted 30 years in my service, and who know how long before that, I am willing to put in a simple gasket from ordinary material, no copper sheet, etc. But, I do think that adding some width in that critical area is a good idea. If I could neatly roll the edge of a piece of copper, so that it actually captured the gasket laterally, I might be willing to fabricate an automotive style head gasket, but simply putting in a couple of sheets of thin metal would simply change the surface that the fiber material had to stick to. I'd end up with the fiber blown out from between the thin metal surfaces perhaps.

In 30 years it will not be so easy for me to climb up into the rafters to service this beast!

- JC

I have to question the copper part of a head gasket for compressor. Not that I know from a life time of compressor work, but from my 4 compressors I have at home. My 20 Hp, 3 cyl LeRoi/Dressor 880 pump had paper head gaskets, my little 3 hp Ingersol, 2 cyl had solid metal gasket if I remember correctly {thin shim stock thickness}, my ancient Curtis two cyl had paper head gasket. My reworked Champion (1940 vintage) didn't have seperate head/cly, but the valve/port gaskets was copper, kind of like an O ring. For compensation for expansion/contraction from extreme heat as well as seating? I do not work for a compressor company.

Guess it would depend on how it was engineered at time of conception, but to thick a gasket might not be what you want either. Hence my questioning the copper automotive type head gasket. How about some pictures of this mysterious beast? Cheers, John.

I agree, no need for copper automotive type gasket, after looking at the other gasket on this beast - simple paper. Also agree, don't want too thick a gasket, just from general principles, adds to the (side) surface area, gives worse aspect ratio to the weakened area, all sorts of bad things.

I'm a bit suprised that no-one from the antique machinery group has ever herd of "Mills". I'm pretty sure I can fabricate a decent gasket and get the compressor back on-line, but I've been curious for years about the ancestry of this thing!

I have the valve plate inside in a well lit area, but might also be able to get some photos of the beast itself up in the rafters. If I get time tonight will post whatever I get. It's pretty hidden up there, just enough room to get in there and take the head and valve plate off, but I think I can get a decent camera angle on it.

Do you have head bolt torque specs for your various compressors? This one has twelve 1/4 inch dia. bolts, each about 4 inches long, with maybe the end 1-1/2 inches threaded, arranged around the outside of the casting - oval, with nothing between the bores. The combined thickness of the head and valve plate can't be more than 2 inches, so plenty of thread engaged, and also plenty of "stretch" length.

- JC

I am sure some mechanics out there could give a better guesstimate then I can. I am fascinated by compressors and like the old cast iron recips. I had wanted a bigger than needed one for my shop for a long time. Ended up with an old Champion for my end choice. I had no detailed shop manual and just guessed about torque. With those small bolt I would imagine "inch pounds", with more emphasis on correct bolt tightening rotation than actual torque, just don't over tighten like I usually do and keep the torque even. I watched Ebay for a long time kind of learning as I went about older recips and who was who back in the 1930s-1950 give or take a decade. I do not recall Mills. Could it possibly be that "Mills" was a brand name produced by another larger company? Like Miller Elect makes a ton of welders for other people with different color paint and decals? Years ago that might not of been so common a practice though. Many of my machines came from a closed plant in Philly, with a machine dealers tag on them. While the makers were actually P&W, Excelsior and Cinn/Bickford etc. I do not recall the name Mills coming up, maybe a smaller regional company that sold mostly in a smaller region rather than the bigger companies. Seems like the LeRoi Dresser pumps like I need for parts are all over the east coast and eastern, midwest, but rather hidden in my area. Maybe just can't find them too. These compressors {most of them} ran so good for so long they might of put themselves out of business. Between these quality products that took forever to quit running and the deindustrialization of America, the market must of been tight. Most people with the antique machine interests seem to go towards machine tools, engine driven or steam driven machines. After all what does one do with a really cool recip other than run air tools, the really big industrial pumps are to big for most of us. Though I want one. Just recently there was a post about early IR that had two opposing cyl, wonder if it looked anything like them? Cheers, John.

Thanks for your take on older compressors. I think you may have a point about compressors being pretty well figured out, and perhaps a big shakeout in the industry as the market shrinked.

I suppose it's possible that "Mills" is just a name, stuck on someone else's product, I have no way of knowing. Years ago, when I installed the beast, I looked all over it for some numbers or identifying mark, but found nothing, except for the name in the crankcase casting.

Now that I've cleaned the gunge off the surface of the valve plate casting, I see that someone once cleaned it with a sharp implement - probably a chisel. I also see a small piece of flat spring that broke off, but apparently that happened long ago also, based on the way the gunge was distributed, and the way the end of the spring must have been trimmed to get it to look so square.

Anyway, I didn't go back out to the barn and climb into the rafters, so don't have pictures of the whole deal, will take some when I assemble it again. Instead I have some photos of the valve plate casting, with the reed valves and so forth installed, plus the old gasket, and new gasket I've just made.

I can't do this from the quick reply function, so will attach them as .jpg files.

The first image shows the side of the valve plate that faces the pistons, you can see the reed valves on the intakes, and the old gasket with the missing section in the middle.

The second one shows the other side of the valve plate, with the brackets that cover the outlet valves.

Finally, there is an image of the new gasket I've made, with a wider section between the cylinders.

I should get some time in the next week to put it together, then will be able to test.

- JC

I've GOT a Mills. It's an ammonia compressor, best I can tell. Been debating on getting it running or using my Brunner single cyl. Figure they are about the same capacity.

Mike;

Hmm, I tried looking for refrigeration companies as well as straight up air compressor builders, didn't have any luck either way.

Can you explain why you think it's an ammonia compressor?

How much do you have that might have been sourced or branded "Mills"? All I have is the compressor itself, with the flywheel/fan/pulley casting. No mounting hardware, plumbing, or motor, etc.

Any identifying marks besides the name cast into the unit?

Will definately try to get some pictures of the whole assembly posted soon.

- JC

The hole to the crankcase maybe a telltail sign that it is a refrigeration compressor. The passage might be there to take the gasses that bypass the rings and return them. Is there a vent on the crankcase? If not it problely a refrigeration compressor.

Mine has the original flywheel, the aftercooler, and what I believe is the original single phase 3hp 110/220v motor (32 amps at 110v... yeah right, lol). It is also sitting on a skid mount with two small longitudinal tanks underneath. I'll have to go out and check tomorrow, but I think it says something about refrigeration compressor on the skid.

I never could find anything on it online.

No vent on the crankcase, just what I took to be an oil fill hole that could have been used as a vent I suppose, but certainly no cast-in hole with a filter, or cap arrangement.

Got my new gasket installed, working in the confined space, I managed to tear it from one of the bolt holes to one of the bores, so that bolt hole is now pressurized - but it's a blind hole and it's not leaking under the bolt cap, so not going to do anything about it yet. Basically, I need to pick up more gasket material, or buy a new shirt or box of cereal for the cardboard!

Used 8-10 ft-lbs, based on my best guess of the bolt hardness, and what I could do with a short wrench in the previously mentioned confined space.

The whole thing seems to be working fine, has run a few cycles over the past few days, no funny noises, no hissing sounds, except from a bad gasket on the polycarbonate filter bowl under the regulator - have to fix that pronto too!

So I've see more of the guts of this thing, but still have no idea where it came from, or when, or who designed it, or for what, although it's starting to appear that's it's a refrigeration compressor of some sort - thanks to all for the various insights.

See the attached photo for a general view, after the head was re-installed. View is from the outlet side. I believe the flywheel is original, but no aftercooler or anything else. I found a number cast into the other side of the crankcase - need to go out with a different prescription in my eyeglasses and copy it down.

Does this look anything like the one you have Mike?

- JC

I know squat about your compressor, but my guess it is indeed a refrigerator compressor in it's earlier incarnation. Obviously it works for you so it doesn't matter what it was originally. I can see where you wouldn't want to work on it up there for long. Just the way the head is plumbed and the dead/plugged ports. Interesting thread thanks for shaing your adventure. Cheers, John.

Looks identical. Busy weekend, I'll try to get pics this week.

Thanks again guys - looking forward to seeing your pictures Mike.
If you find a patent number anywhere on the assembly, that might help us get some history on the company.

When I got mine, all those ports were plugged, it looks like the output was orignially a flanged tube held on with a plate that screwed into two threaded holes, but it has a regular tubing adapter in it now, not sure when that got there either...

It was free, I was low on funds, and and I needed more air capacity, so I put it up there, sometime around 1985 or so, never thought it would go so long, with luck it will go another 30 years, although it's probably time to hydro test the old tank again.

Did some more research, found a Mills Novelty Company in Chicago, with a patent on compressor inlet valves, probably more digging in the patent records will be fruitful looking for company info.

Eh, thing is so buried out in the shop right now I couldn't get a pic. Did manage to crawl under my little cement mixer and read the tag, though, lol.

Mills Industries Incorporated
Chicago, USA
Model #150839
Ser# 8238
Refrig F-12

And here is what I just found using the new info...

http://www.millsnovelty.com/index.php?option=com_content&view=article&id=13&Itemid=86

Among other things, their main product line was slot machines! LOL!

Looks like these were probably commercial ice cream maker compressors.

Oh, that Mills. I have seen dozens of the Mills Violano Virtuoso coin operated player violins in the homes of very rich collectors. These nice people allow people like me in their homes to see their collections worth millions of dollars. They like antique machinery as well as most of us here on PM. And one of them also has lathes, steam engines and tower clocks along with his over-sized music boxes and world's biggest theater pipe organ. I was there in June, for my fifth visit. Every time I see it, his collection has grown, along with the buildings to house it.

Larry

Yup, that Mills. And they still support the Violano... but not the compressors, heheh.

Not to hijack, but Larry, I have a recording given to me by an elderly lady friend many years ago. It's on cassette tape, but it is of a certain unique type of player piano. This paino was unique in that it not only recorded the order of the notes, but also the velocity of the key strikes, and the pedal positions of the person playing it. It recorded the notes such that it didn't get that rinky-tinky rhythmic pattern usually heard on a player, it was very smooth and reponsive. The recording she gave me is Gershwin playing Rhapsody in Blue. Absolutely mindblowing. It's like a tape recording, but it's the piano playing itself back.

Nice work Mike;

After finding the patent assigned to Mills Novelty, had not followed up, but your cross referencing from the tag on your unit pretty much confirms who the maker was.

It's possible that Mills was making a lot of compressors, since they made vending machines for more than one refrigerated product:
http://www.vintagevending.com/coca-cola-delivery-instructions-for-a-mills-vending-machine

Looks like the end was messy:
http://books.google.com/books?id=tx...=onepage&q="Mills Industries" chicago&f=false

Any idea of what sort of player-piano made that smooth recording? The modern electro-mechanical versions that can do that, (from Yamaha for example) have been around for 20 years or so, but would be interested to learn about some purely pneumatic or mechanical unit.