Patent Application
20090016658
This invention relates to bearings and in particular to bearings for butterfly valves in ground-based power generation systems.
A ball-roller bearing comprises an inner ring and an outer ring that define raceways for a combination of roller elements comprising balls and rollers. The travel of the rollers in a ball-roller bearing may be guided by a channel in the outer ring or in the inner ring.
The present invention resides in one aspect in an improvement in a ground-based power generator that comprises a hot gas valving system that includes a butterfly valve in a gas flow conduit. The improvement comprising that the butterfly valve is mounted in the conduit by a ball-roller bearing.
Many ground-based power generation systems, including turbine generator systems, produce hot gases that need to be vented in a controlled manner, and for this purpose, the generation systems include gas flow conduits (such as flues) that are equipped with butterfly valves. A butterfly valve has a valve baffle mounted on axles that extend from opposites sides of the valve baffle and that are mounted on the gas flow conduit. A butterfly valve may be subject to extreme conditions of temperature, pressure, and/or exposure to corrosive chemical species in the gas.
An improved butterfly valve for a hot gas venting system in a ground-based power generation system comprises ball-roller bearings. The ball-roller bearings may enable the axles to pivot with the valve baffle, or they may permit the valve baffle to pivot relative to the axles. Optionally, the ball-roller bearing may be used for a butterfly hot air bleed valve.
There are several possible configurations for a ball-roller bearing as described herein, relating to variations on the location of a guide channel for the roller (whether the inner ring or the outer ring comprises a guide channel, if not both) and whether the rollers are closer to the load zone than the balls, or farther away. In addition, when two ball-roller bearings are used on coaxial axles, the ball-roller bearings may be in face-to-face or back-to-back arrangement.
In a particular embodiment, a ball-roller bearing for use as described herein may comprise rings and rollers made from a stainless steel alloy such as BG-42, per Aerospace Material Specification AMS 5749. The rings and rollers may bear a thin, dense chrome plate. The balls may be made from silicon nitride ceramic, for example, Si3N4. In various specific embodiments, such bearings may have one or more of the characteristics set forth in the following Table 1A (in which dimensions are stated in inches, unless otherwise indicated).
A bearing as in Table 1A may have a diametral clearance (after plating) of about 10 micrometers (um) to about 40 um (about 0.0004-0.0016 in.) for the rollers and about (about 0.0021-about 0.0037 in.) for the balls.
A particular example of a bearing as described by Table 1A is depicted in
Bearing 510 is expected to have the following bearing loads carrying capacities (static) as shown in Table 1B, where it is assumed that radial capacities are additive and two bearings will share a total radial load and the axial load may be borne by either bearing:
In other specific embodiments, such bearings may have one or more of the characteristics set forth in the following Table 2A (in which dimensions are stated in inches, unless otherwise indicated).
A bearing as in Table 1A may have a diametral clearance (after plating) of up to about 40 um (about 0.0016 in.) for the rollers and about 53 to about 78.7 um (about 0.0021-about 0.0031 in.) for the balls.
In a particular embodiment of a bearing characterized in Table 2A, bearing 610 has an axial width W of about 1.2 cm (about 0.47 in.), an outside diameter Do of about 4.13 cm (about 1.625 in.), and an inside diameter Di of about 1.9 cm (about 0.75 in.). The centers of the balls 616 are disposed in an annual configuration having a diameter DBC of about 1.14 inch, whereas the rollers 620 are disposed in an annular configuration in which their axes of rotation have a radius DAR of about 3 cm (about 1.2 in.).
Bearing 610 is expected to have the following bearing loads carrying capacities (static) as shown in Table 2B, where it is assumed that radial capacities are additive and two bearings will share a total radial load and the axial load may be borne by either bearing:
In other embodiments, the balls, rollers and rings may be made from other materials.
A ground-based power generation system in which a ball-roller bearing-mounted butterfly valve may be used is disclosed in U.S. Pat. No. 5,953,898 to Dryden, dated Sep. 21, 1999, which is hereby incorporated herein by reference.
The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. In addition, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Although the invention has been described with reference to particular embodiments thereof, it will be understood by one of ordinary skill in the art, upon a reading and understanding of the foregoing disclosure, that numerous variations and alterations to the disclosed embodiments will fall within the spirit and scope of this invention and of the appended claims.
This application claims the benefit of U.S. provisional application Ser. No. 60/959,326 filed Jul. 12, 2007, which is hereby incorporated herein by reference, in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60959326 | Jul 2007 | US |
