Note: Descriptions are shown in the official language in which they were submitted.
CA 02353298 2001-07-19
PRESSURE VESSEL
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an over-wrap for pressure vessels, and in
particular to an over-wrap for a fibre wound pressure vessels.
BACKGROUND
Pressure vessels are well known in the art. They are commonly used to store
a variety of gasses at high pressure, and applications for these vessels
include air
canisters for breathing apparatus, fuel canisters for storing combustible
gasses such
as propane, or for storing gasses in industrial or laboratory settings.
One problem with pressure vessels is the weight of material required to store
the gasses. To allow the vessel to store higher volumes of gasses, these
gasses
must be stored at higher pressures. In order to prevent failure of these
pressure
vessels they must be made of sufficient material to contain this pressure
without
rupturing and endangering those using the gasses. This material requirement
causes
the vessels to have a weight that becomes problematic when the vessels are
used
in portable applications such as SCUBA tanks, firefighting equipment, or
oxygen
tanks for those with respiratory difficulties.
One solution to this has been to create tanks with a thin metal liner
surrounded
by a filament-epoxy winding. This gives a better strength to weight ratio than
all-
metal tanks: An example of this type of vessel is taught by U.S. patent no.
5,287,987
to Gaiser.
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However, filament-epoxy wound containers have several deficiencies. These
vessels do have a good impact resistence capability, and are susceptible to
rupturing
if damaged. Further, rupturing of these vessels generally causes fragments to
be
propelled at high speeds, endangering those near the vessel.
Another problem with fibre-epoxy windings is that they do not withstand
adverse environmental conditions very well. Exposure to caustic environments
is
possible, for example, in firefighting applications or in breathing devices
designed for
evacuation from chemical or industrial plants. These devices therefore need
protection from the adverse environment.
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings of the prior art by providing
a high strength flexible over-wrap for use on pressure vessels. Specifically,
the
present invention provides for the use of a carbon composite filament
saturated with
a liquid rubber compound which is wound around an existing pressure vessel and
cured. In a preferred embodiment the carbon composite is KevlarT"".
The over-wrap of the present invention is used to add strength, impact
resistance, explosion containment, and exposure protection to any existing
pressure
vessel.
Therefore, according to one aspect of the present invention there is provided
a protective over-wrap for a pressure vessel comprising a carbon composite
thread
and a liquid rubber; wherein said carbon composite thread is immersed in said
liquid
rubber and subsequently wound about said pressure vessel, and wherein said
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pressure vessel with said carbon composite thread and liquid rubber winding
are then
cured.
According to a further aspect of the present invention there is provided a
method of creating a protective over-wrap for pressure vessels comprising the
steps
of: saturating a carbon-composite thread in a liquid rubber compound; winding
said
saturated thread about said pressure vessel; and curing said pressure vessel
and
saturated thread; whereby said rubber and carbon composite thread comprise
said
protective over-wrap
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross-sectional plan view of a preferred embodiment of the
present invention.
DETAILED DESCRIPTION
Reference is now made to Figure 1. This figure shows a pressure vessel 1
that is comprised of a liner 10 and a structural layer 20. These layers are
well known
in the art, and in general liner 10 is a metal layer to better contain a gas
within
pressure vessel 1. Structural layer 20 can be a carbon fibre / epoxy mixture,
as
disclosed in the background section above. This structural layer 20 ensures
that the
vessel can be inflated its preset pressure without rupturing.
In an alternative embodiment, liner 10 may not be necessary if structural
layer
20 is comprised of stainless steel or aluminium. These materials provide
enough
containment and corrosion resistance to be used without a liner.
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The present invention consists of an over-wrap layer 30 over structural layer
20. Over-wrap layer 30 is comprised of a carbon composite thread that is
immersed
in a liquid rubber. In a preferred embodiment the carbon composite thread
consists
of KevIarT""
The thread and rubber are then filament wound around the vessel to a
predetermined thickness. In a preferred embodiment the winding is done using a
computerized lathe in order to achieve a uniform thickness about pressure
vessel 1.
Once the winding is complete, pressure vessel 1 with its over-wrap layer 30
are then cured to solidify over-wrap layer 30. Pressure vessel 1 is then ready
to use.
Over-wrap 30 overcomes many of the disadvantages that pressure vessels
currently have. In particular, due to the high strength of KevIarT"", the
present over-
wrap layer 30 will provide complete containment in the case of a failure of
the
pressure vessel. This will therefore protect those around the pressure vessel
who
could previously have been harmed or killed by high velocity fragments created
by
the failure of the pressure vessel.
Also, the rubber within the windings will create a better impact resistence
for
the pressure vessel, further protecting it. As is well known in the art,
rubber will
cushion any impact to the pressure vessel.
Still further, due to the rubber in the winding, the pressure vessel will
better be
able to withstand caustic environments without being damaged, ensuring greater
safety for those dependent on the pressure vessel.
Also, due to the presence of the over-wrap, pressure vessel 1 can be
pressurized closer to its maximum capacity. This will allow more gas to be
stored
within the pressure vessel.
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Although the present invention has been described in detail with regard to the
preferred embodiment thereof, one skilled in the art will easily realize that
other
versions are possible, and that the invention is only intended to be limited
in scope
by the following claims.
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