Lube-Free, Powerful Vane Air Motors
Sliding-vane air motors, powered by compressed air, are found everywhere in industry: in grinders, drivers, and in assembly tools. Commonly, the compressed air from the motor is exhausted into the shop environment. This can pose a problem, in that tool exhaust most usually contains minute quantities of lubricating oil and other contaminants. Beyond causing shop mess, exhausted oil can possibly spoil a work piece.
Oil enters the compressed air stream as an inexpensive way to lubricate the vane air motor. The sliding vanes of such motors contact the cylinder of the motor as they rotate around an eccentrically positioned shaft. They also move in and out of a slot on the shaft, enabling the volume between the vanes to increase or decrease as driven by the compressed air (and controlling the direction of rotation). Sliding-vane air motors generally operate at 20,000 rpm using 90 psi air. Cylinder bores vary widely, but range from 5/8 inch to 3 inch in diameter. Vane tips commonly move at speeds of 5000 to 6000 fpm.
All this movement obviously causes friction and wear. Worse, some shops may not lubricate their tools enough, or may periodically not lubricate at all. Tools wear and fail.
This organization is looking for a technology that can produce a lube-free and contamination-free solution.
Solutions and tradeoffs
There are lube-free sliding-vane air motors on the market. However, such solutions tend to be de-rated motors that can accept the resulting wear for their service life. Even these "lube-free" solutions can place molecular contaminants from fast-wearing parts into the air stream and eject them from the exhaust of the tool into the shop environment.
Rather than de-rating a motor that would otherwise require lubrication, this organization seeks a solution without major compromise; that is, a motor design/materials solution that is lube-free, that does not lower power or durability, and that does not exhaust any contaminants into the work place. In short, they seek a design that is comparable in every way to vane air motors that require lubrication.
Engineering means tradeoffs. Speed, power, durability, torque, and heat generation are all factors that must be balanced by the right solution (or by the right mix of solutions, if there is more than one). The R&D department has already experimented with vane materials including ceramics, carbon, plastics, composites, and coatings. They have changed the vane and bore design by using cylinder finishes, coatings, linings, and by changing the tip chamfer. However, they don´t claim to have exhausted the possibilities of design changes. Radical design solutions may be a possibility, but all suggested technologies from any industry should be mature, implementable, and cost-effective.
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