I am looking for information about how commercial soft serve ice cream
machines function, in technical terms.  I've done some research and
there appear to be two classes of machine, "commercial grade" units
made by Taylor and Coldelite which generally cost between $2,000 and
$15,000, and small home units which cost between $50 and $100.  These
home units appear to be little more than mixing devices or "mushing"
devices.

I'm curious about the mechanisms involved in the commercial units and
the physical processes that occur therein.  I have observed the
operation of a commercial soft serve machine in which soft serve mix
was poured in the top of an empty machine, and within several seconds,
real, frozen soft serve was dispensed from the machine.  Clearly, it
is more than your typical freezer/compressor, but I've been unable to
find any decent explanation of the workings of these machines online -
the websites of the manufacturers I mentioned above (Taylor,
Coldelite) are remarkably light on technical details.

What I do know is that these machines are usually described as either
"gravity" or "pump" based, and though I can guess, I'm not positive
what those terms mean specifically (presumably "pump" machines use
some kind of pressurized dispensing technique?).  There also appear to
be "air cooled" and "water cooled" variants, but I think this only
refers to the system for heat removal rather than the actual freezing
process.  I am glad to have this question answered with either useful,
detailed online resources, or with a more complete explanation of what
goes on in the guts of these machines.

Hi rcgabriel,

You’re certainly right about there being a number of different methods
(with correspondingly different machines) for making soft-serve ice
cream.  Fortunately, however, detailed information about the inner
workings of such machines is readily available from the U.S. Patent
and Trademark Office.  Their main search page is here:
http://www.uspto.gov/patft/index.html

Doing a search for “soft serve machine”  yielded a return of 20
patents.
 
1)6,395,314 Process for forming an oat-based frozen confection 
2)6,145,701 Machine for dispensing a soft-serve product such as
ice-cream, frozen yoghurt, or the like
3)6,039,988 Laminated baked product and method of making the same 
4)5,989,598 Process for forming an oat-based frozen confection 
5)5,789,008 Ice cream sandwich and method of making the same 
6)5,723,162 Oat-based frozen confection 
7)5,516,537 Frozen comestibles 
8)5,400,614 Frozen dessert apparatus 
9)5,208,050 Mixing orifice extruder 
10)4,956,980 Apparatus for producing soft serve dairy products, in
particular yogurt
11)4,878,760 Mixing and dispensing apparatus for a frozen confection
machine
12)4,836,420 Cleaning in place valve actuator 
13)4,826,699 Method for the production of a powdered additive for use
in preparing food products having a foamed structure
14)4,702,611 Cup protecting mixer 
15)4,497,841 Low calorie dessert mixes and products prepared therefrom
16)4,364,666 Machine for mixing and cooling batches of dry powder
ingredients and water
17)4,364,491 Horizontal ice cream cone dispenser 
18)4,275,567 Method and apparatus for controlling operation of a
soft-serve machine
19)D256,124  Soft serve machine 
20)4,031,261 Preparation of fat-containing beverages 

Here's the url for the search return: 
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2Fsearch-bool.html&r=0&f=S&l=50&TERM1=soft+serve+machine&FIELD1=&co1=AND&TERM2=+&FIELD2=&d=ptxt
 If for any reason you can't access these search results, either run a
new "quick search" using the term "soft serve machine," or enter each
patent number individually using the number search.

Also, each patent listed will have, at the very beginning, a list of
“references” to other patents that are directly related, and also in
its narrative, will refer to “prior art” or patents of previous and
similar machines.  To see those individual patents, if they are not on
the list, just enter the patent numbers in the search box.

Each of these patents will have detailed drawings of the apparatus as
well as detailed narrative descriptions.  However, in order to be able
to see the drawings you will need to download a special viewer.  But
it’s free, not too large, and works well.  Here’s a link to the page
where you can get further information on that and links for
downloading: http://www.uspto.gov/patft/help/images.htm

I hope this satisfies your request for detailed online resources for
learning about the manufacture and operation of soft serve ice cream
machines.  If not, please do ask for clarification so I might have the
opportunity to ensure you’re satisfied with the information provided.

Best regards,
Byrd-ga
Google Answers Researcher

Search strategy:

--Bookmarked link for the USPTO Office, thence a search using the
term:
“soft serve machine” 
--Bookmarked link for the USPTO office image viewer information