As it happens patent no, 4,832,968 is for a very famous widget, Guinness in a can stout, "The Beer Widget."
The basics:
Inventors: Alan J. Forage & William J. Byrne
Assignee: Arthur Guinness Son & Co., Ltd.
Process:
The gas pod in the can is blow molded with nitrogen (N).
A laser zaps a hole in the pod. (they experimented with holes between
0.2mm and 2.5mm finding that 0.61 mm as ideal)
Pod is inserted in the bottom of can.
Can is filled with CO2/N supersaturated stout. N is present at 1.5% v/v
min up to 3.5% v/v. (FYI, vol/vol is the number of volumes of gas which
are dissolved in a unit volume of beverage at 760mm of Hg & 15.6 oC) CO2
is present at between 0.8 and 1.5% v/v.
During filling, foam rises to top of can. This clears the air.
A charge of liquid N is added to the stout
Can is sealed.
As liquid N boils off in can during pasteurization (60 oC for 15-20
min), top of can pressurizes and forces the stout into the pod, thus
compressing the ambient pressure N in the pod.
Equilibrium is reached at about 25 psi.
As I interpret the patent, this is what happens when the can is opened:
The can quickly depressurizes to ambient pressure. The pod thus expels
the stout contained in it (about 10-15 ml) at high velocity through the
orifice. This causes high local strain of the stout at the plane of the
orifice. This strain exceeds the cohesive forces holding the gases in
solution. As a result, the N/CO2 is liberated from the stout at the
plane of the orifice. The millions of tiny N/CO2 bubbles then become the
foam head. So contrary to my initial belief, while some of the N gas in
the pod escapes directly into the stout, it is actually the "ripping
apart" of the stout as it exits the pod which produces the bubbles,
hence the creamy head.
Most beers are canned or bottled with some carbon dioxide, which
provides the head when you pour the beer from the container into
a glass. Guinness on tap is packaged with CO2 and Nitrogen.
Nitrogen helps make the nice, foamy head you see on glasses of
Guinness in a pub. But CO2 actually gets absorbed into the beer,
while nitrogen does not. When you open a can or bottle of
Guinness, most of the nitrogen escapes into the air before you
can pour it.
The invention is a plastic ball with a small hole in it. Just
before canning, they fill the ball with a little bit of nitrogen
and then some beer under the same amount of pressure than the
beer will be once it's canned (and the CO2 in the beer creates
pressure in the can). The nitrogen stays in the widget as long as
the beer can is sealed. When the can is opened, and the pressure
is released, the nitrogen is released into the beer just as you
pour.
Patents in the U.S. that were filed before 1995 or so last 17
years from the date of issue. (After the rules changed, it became
20 years from the date of filing). So the Guinness widget will
belong to all of us in May!
Only the GWI GigaWidget noted;
PAT. NO. Title
4 6,620,444 Full-Text Two-compartment container
for and method of admixing a flavour to a beverage
5 6,561,388 Full-Text Content lifting and
removing container assembly and method of manufacture thereof
12 5,863,577 Full-Text Pressurized beverage
package with an interior compartment for the production of foam
on opening of the package, and a method of forming such a package
13 5,855,292 Full-Text Fluid storage
15 5,715,874 Full-Text Beverage packaging method
and apparatus
17 5,667,832 Full-Text Method and device for
foam generation by dispersion of bubbles
21 5,571,548 Full-Text Pressurized beverage
package with an interior compartment for the production of foam
28 5,231,816 Full-Text Method of packaging a
beverage
29 5,196,216 Full-Text Beverage package
30 5,009,901 Full-Text Method of packaging a
beverage and a beverage package
Patent
info on the gigawidget