Patent Application
20050087536
1. Field of the Invention
This invention relates to high pressure gas cylinders and, more specifically, to aluminum cylinders having a plastic interior coating.
2. Background Information
Cylinders used for high pressure gas storage commonly are typically one of three varieties: all metal (commonly steel), a metal shell over-wrapped with composite materials, or a plastic shell over-wrapped with composite materials. Each type cylinder will have “fill-use” cycle lives of 8,000-10,000 cycles—before ending their useful life. Each type of cylinder has advantages and disadvantages. For example, a steel cylinder is strong but heavy; a composite/aluminum cylinder is light, but typically has a limited fill-use cycle; and a composite/plastic cylinder is light but is weak and prone to damage.
There have been two general combinations of these technologies. Steel cylinders have been wrapped with composite materials to allow thinner, lighter shells while maintaining their strength. Additionally, steel cylinders have included independent plastic linings to prevent reaction with stored fluids. However, because composite/aluminum cylinders and composite/plastic cylinders shared the advantage of being light, while generally being more inert than steel, there has not been a need to combine these two technologies.
It has been determined that when an composite/aluminum cylinder is combined with a plastic coating, the total weight of the cylinder is reduced, compared with the all metal cylinders, and the cycle life is significantly extended over that achievable by the base designs. More specifically, it has been found that use of the plastic coating on a composite/aluminum cylinder increases the cycle life of a cylinder between about 50% to 150%.
The aluminum/composite/plastic cylinder is a light weight, thin walled cylinder containing an interior plastic coating that is heat-bonded to the aluminum. The aluminum liner is surrounded by a composite outer wrap, typically carbon or aramid and fiberglass filaments held within an epoxy resin matrix. The cylinder is designed to contain gas ranging in pressure from 500 to 10,000 psi. The cylinders typically range in volume from 0.5 to 500 liters. Such cylinders are especially adapted to be used as a self-contained breathing apparatus, a home oxygen therapy cylinder, a commercial aviation cylinder, a fuel storage cylinder in natural gas and hydrogen vehicles, and with military and aerospace applications.
A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
As shown in
The composite wrap 20 is disposed on the cylinder outer side 26. The composite wrap 20 includes a filament material and an epoxy resin. Preferably the composite wrap 20 includes carbon or aramid and fiberglass material. The composite wrap 20, preferably, covers the entire cylinder outer side 26. The composite wrap 20 may include multiple layers 20A, 20B, 20C applied over the cylinder outer side 26.
The plastic coating 24 is applied to the cylinder inner side 28 and is, preferably, adhered by heat bonding. The plastic coating 24 is, preferably, a polyethylene copolymer such as polyolefin resin and olefinic polymer blends.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
