The ability to release an air pulse very
quickly enables the manufacture of many novel products, the most
important of which could save many lives. Tom Shelley reports
The ability to release compressed air within a
millisecond has allowed the development of compressed air 'guns'
with a multitude of uses.
Objects, including long lengths of cordage, can be launched up to
100m, without having to resort to explosives.
And shocks can be delivered to free up powder
blockages, and single blows or pulses of air delivered to
simulate a variety of physical processes. But best of all, the
valves look to be a better way of powering the multiple air bags
expected to be required on the next generation of cars to be sold
in the US and elsewhere.
Pneumatic air cannons which, deliver sudden pulses of air are
quite well known. It is even possible for readers to make them
themselves, although we at Eureka will take no responsibility for
what readers may do to themselves if they try.
One design available on the Internet requires only a ball valve,
some lengths of pipe and a rubber disk. A family of products
developed in Russia, however, uses a patented valve which
responds unusually quickly, and the company has devised products
which are completely self contained, and which resemble and can
be used and aimed much in the same way as a 'bazooka' rocket
launcher.
Russians seem to like developments which go with a 'bang' and
perhaps for this reason, lead the world in explosive forming and
bonding techniques.
This particular family of products is made by Ista, a company
spun out of a research department at what is now the St
Petersburg State Technical University. The names on the original
patent are Dr Sergey Isakov, now Ista's chief executive officer,
and Dr Sergey Yurkin, now the technical director. The principle
behind most air cannons is to store compressed air or gas, and
let it go suddenly, by releasing pressure holding some kind of
valve or diaphragm in place.
The valve in the Ista design is conical, and release of gas
pressure inside the cone causes it to be pushed backwards away
from its seat, and allows gas to rush past the outside of the
cone in such a way as to minimally restrict passage. Most of the
other designs around, with pistons and diaphragms, which step
backwards require the escaping gas to make some kind of a 'U'
turn. This inevitably reduces final gas velocity, which to be
useful, needs to be as high as possible.
Ista products have the ability to throw a cartridge releasing up
to 100m of line. One of these devices was recently seen on
Russian television when it was used to help rescue a man stuck on
an ice floe. The method used in the West is to use a rocket
attached to a folded line. The rocket can only be used once,
which can be unfortunate for the people being rescued if it
happens to miss and there is no replacement, and the line takes a
very long time to re-fold round all the pins in its holder.
The most common use of the products in Russia is to break down
bridges and funnels formed in powders, particularly bakery flour,
in hoppers and bins. Delivering a sudden pulse of air to the
powder is less damaging to a construction than fixing mechanical
vibrators fixed to the outside, and far less damaging as well as
more effective than hitting the outside with a sledgehammer.
The company has so far supplied a substantial
number of units: 85% to bakeries, 10% for rescue work, and 5% to
laboratories. Shock waves delivered by air cannons are much less
hazardous for student researchers to work with than explosives.
The really exciting possible application, however, according to
Dr Yurkin, is to use the valve in the next generation of
automotive air bags.
Airbags are particularly favoured in the USA where it has been
found difficult to persuade drivers and passengers to always wear
seat belts. Research has shown that because crashes do not always
happen head on, front air bags are not sufficient to protect
occupants. In particular, when the increasingly popular sport
utility vehicles roll over, which they are liable to do because
of their high centre of gravity, it is essential to have side air
bags if occupants are to avoid death or serious injury.
New designs being studied by Mercedes Benz, among others, involve
the use of up to eight air bags in a single vehicle. Present
technology requires the use of pyrotechnic squibs. Use of
compressed gases could be at the same time cheaper, less
hazardous, and more flexible. One gas vessel could power several
adjacent bags, and valves could open according to which bags were
needed instead of firing all of them.
To those who would say that gas valves would be likely to have an
unacceptable amount of leakage over time, one has only to point
to gas filled fire extinguishers. Fire extinguisher valves
generally do not leak, but their gas fill pressure should be
checked from time to time as a part of routine service and
maintenance. Squibs become unreliable after a time, and should be
replaced, but properly maintained fire extinguishers last almost
indefinitely. Pyrotechnic devices are used in some fire
extinguishing systems, but valve based systems are preferred.
Such is likely to be the case with air bags. Dr. Yurkin is
somewhat cagey about prospects for his valves in automotive air
bags, but when we met him at the last Russian Venture Fair in St.
Petersburg, he did say that Daimler-Chrysler was showing
"Great interest" in the idea.
As well as new markets, Ista is also looking for collaborative
arrangements and possible investment, with a view to being able
to expand its production facilities more rapidly.
Russian Venture Capital Association: www.rvca.ru and rvca@rfntr.neva.ru
ISTA: yurkin@ista.spb.ru
Design Pointers
Valve can open fully in about 1ms
Air or gas is released in such a way that it is not required to
change direction, resulting in maximum instantaneous velocity
Main market at present is in clearing blockages in bakery flour
bins and hoppers, but substantial sales are also being found in
line launching for rescue work, and in producing shock waves for
laboratory experiments. The largest potential market, however is
in the next generation of automotive air bags.