The present invention is generally directed to a spherical plain bearing having an outer ring at least partially encircling an inner ring and having solid graphite lubricating plugs disposed in pockets formed in the inner ring and/or outer ring and slidingly engaged with mating surfaces of the outer ring and/or the inner ring.
Many types of bearings can be used to support radial, thrust, or combination radial and thrust loads. Such bearings include ball, roller, plain, journal, tapered roller bearings and spherical plain bearings. Spherical plain bearings normally include inner and outer ring members wherein the outer ring member has a spherical concave interior surface that defines a cavity therein, and the inner ring member is disposed in the cavity and has a spherical convex surface that is complementary to, and is dimensioned to match, the interior concave surface of the outer ring member. The concave and convex surfaces are the sliding surfaces or bearing surfaces.
According to a first aspect of the present invention, there is provided a spherical plain bearing including an inner ring defining a convex outer surface and an outer ring defining a concave inner surface. The outer ring at least partially encircles the inner ring. The outer surface and/or the inner surface define a plurality of pockets therein. A solid graphite plug is disposed in one or more of the plurality of pockets and slidingly engages the outer surface and/or the inner surface. The solid graphite plug lubricates an interface defined by the outer surface, the inner surface, and/or the graphite plugs to reduce friction there between. In one embodiment, the solid graphite plugs have less than 10 ppm impurities.
In one embodiment, the solid graphite plug defines a predetermined structure in an as manufactured state and maintains the predetermined structure after exposure to a gamma dose rate of up to 3.63×104Rad/hr; a 60-yr equivalent gamma dose of 1.19×1010 Rads air; and/or a 60-yr neutron fluence dose of 4.64×1018 n/cm2 with neutron energies greater than 1 MeV.
In one embodiment, the inner ring is manufactured from a copper based alloy and the outer ring is manufactured from a stainless steel alloy.
As shown in
As illustrated in
In one embodiment, the circumferentially projected overlap 32 and the axial projected overlap 34 is about 0.01 to about 0.03 inches. In one embodiment, the angular spacing is about 7.7 degrees. While the circumferentially projected overlap 32 and the axial projected overlap 34 is shown and described as being about 0.01 to about 0.03 inches, the present invention is not limited in this regard as any pattern, overlap or no overlap may be employed without departing from the broader aspects defined herein. Although, the angular spacing β is shown and described as being 7.7 degrees, the present invention is not limited in this regard as other angular spacing may be employed including but not limited, to 7.714, 8.0, 8.286, 10, 10.80 and 12 degrees. In one embodiment, the angular spacing β differs from row to row and/or circumferentially around the inner ring 12 or the outer ring 16.
Referring to
In one embodiment, about 35 to about 50 percent of the outer surface 14 is covered with pockets 20 having the graphite plugs 22 disposed therein. In one embodiment, about 45 to 48 percent of the outer surface 14 is covered with pockets 20 having the graphite plugs 22 disposed therein. While about 35 to 50 percent and 45 to 48 percent of the outer surface 14 is shown and described as being covered with the pockets 20 having the graphite plugs disposed therein, the present invention is not limited in this regard as about 35 to about 50 percent, 45 to about 48 percent or other percentages of the inner surface 18 can be covered with pockets 20 with or without having the graphite plugs 22 disposed therein and other percentages of the outer surface 14 can be covered with pockets 20 with or without having the graphite plugs 22 disposed therein.
In one embodiment, the pockets 20 are arranged in a random configuration in the outer surface 14. In another embodiment, the pockets 20 are arranged on the outer surface 14 without the circumferentially projected overlap 32 and/or the axial projected overlap 34.
The solid graphite plugs 22 are manufactured from a nuclear grade solid graphite material having a total porosity of about 23 percent. The less than 10 ppm limit on impurities in the solid graphite plug 22 includes less than 1 ppm of aluminum, boron, calcium, iron, silicon, vanadium and/or titanium. The solid graphite plugs 22 also have predetermined properties including a compressive strength of about 7,500 psi, a tensile strength of 2,500 psi, a flexural strength of about 4,500 psi, a modulus of elasticity of about 1.8×106 psi, a coefficient of thermal expansion of about 1.1×10−6 in/in/° F., a thermal conductivity of about 80 Btu/hr-ft-° F., a density of about 1.74 g/cc, a sclerescope hardness of about 35 and an operational temperature limit of 800° F. While the graphite plugs 22 are described as having a total porosity of 23 percent, the present invention is not limited in this regard as other porosity percentages may be employed include those greater or less than 23 percent, such as but not limited to 5, 10, 15, 20, 25, 30, 35 and 40 percent.
In addition, the solid graphite plugs 22 define a predetermined structure including the 23% porosity and have the above listed properties in an as manufactured state. After exposure to a gamma dose rate of up to 3.63×104 Rad/hr the graphite plugs 22 maintain essentially the same predetermined structure and properties as in the manufactured state. After exposure to a 60-yr equivalent gamma dose of 1.19×1010 Rads air the graphite plugs 22 maintain the essentially the same predetermined structure and properties as in the manufactured state. After exposure to a 60-yr neutron fluence dose of 4.64×1018 n/cm2 with neutron energies greater than 1 MeV the graphite plugs 22 maintain essentially the same predetermined structure and properties as in the manufactured state. After exposure to a temperature of up to 550° F. the graphite plugs 22 maintain essentially the same predetermined structure and properties as in the manufactured state. After exposure to a fluid having a pH of about 4.0 to about 4.5 (e.g., reactor coolant) the graphite plugs 22 maintain the essentially the same predetermined structure and properties as in the manufactured state. After submergence in a fluid (e.g., submergence below about 111 feet of a fluid such as reactor coolant) the graphite plugs 22 maintain the essentially the same predetermined structure and properties as in the manufactured state.
In the embodiment illustrated in
While
In one embodiment, the outer ring 16 is manufactured from a stainless steel, for example, type 316, type 304 and 17-4 PH stainless steel.
In one embodiment, the inner ring 12 is manufactured from a copper alloy, such as but not limited to UNS C86300 Manganese Bronze, UNS C95400 Aluminum Bronze, UNS C95400HT Heat Treated Aluminum Bronze, UNS C95500 Nickel Aluminum Bronze, UNS C95500HT Heat Treated Nickel Aluminum Bronze, UNS C96900 Spinodally Hardened Copper Alloy (ToughMet 3CX), UNS C96900 Toughmet or UNS C72900 Spinodally Hardened Copper Alloy (ToughMet 3AT).
While the inner ring 12 is described as being manufactured from a copper alloy and the outer ring 16 being manufactured from a stainless steel, the present invention is not limited in this regard as other materials may be employed including but not limited to the inner ring 12 being manufactured from a stainless steel and the outer ring 16 being manufactured from a copper alloy. In addition, while the outer surface 14 of the inner ring 12 is shown and described as including a plurality of the pockets 20 formed therein, one of the solid graphite plugs 22 being disposed in each of the pockets and the graphite plugs slidingly engaging the inner surface 18, the present invention is not limited in this regard. For example, as illustrated in
Referring to
In one embodiment, the diameter D1 is 0.502 inches to 0.506 inches and D2 is 0.501 inches to 0.503 inches. In one embodiment, less than 5 percent of the graphite plugs 22 have a diameter D1 less than 0.502 or greater than 0.504 inches. In one embodiment, the diameter D1 is 0.503 to 0.504 inches. The graphite plugs 22 are manufactured within the tolerance range of D1 of 0.502 inches to 0.506 inches. Thus the diameter D1 of each of the graphite plugs 22 is a diameter 0.502 inches to 0.506 inches. For example, some of the graphite plugs 22 have a diameter of 0.502 inches, some have a diameter of 0.503 inches, some have a diameter of 0.504 inches, some have a diameter of 0.505 inches, and some have a diameter of 0.506 inches and others have diameters within the 0.502 inches to 0.506 inches range. The graphite plugs 22 have a length D4 and are generally cylindrical (
The pockets 20 are formed within the tolerance range of D2 of 0.501 inches to 0.503 inches. Thus the diameter D2 of each of the pockets 20 is a diameter 0.501 inches to 0.503 inches. For example, some pockets 20 have a diameter of 0.501 inches, 0.502 inches, and 0.503 inches and other diameters encompassed by the 0.501 inches to 0.503 inches range. Thus depending on the diameter D2 of the pocket 20 and the diameter D1 the graphite plugs 22, some of the graphite plugs have a clearance fit of up to 0.001 inches (i.e., D1 minimum of 0.503 inches minus D2 maximum of 0.501 inches) in the pocket and some of the graphite plugs have an interference fit of up to 0.005 inches (i.e., D1 maximum of 0.506 inches minus D2 minimum of 0.501 inches). The pockets 20 have a depth D3. In one embodiment, the depth D3 is about 0.28 inches. In one embodiment, the graphite plugs 22 having the interference fit are disposed in axially outermost rows A, B, N and P. Thus, during operation or accident conditions when the spherical bearing 10 heats up (e.g., to 550° F.) the pocket 20 expand and some of the graphite plugs 22 could loosen and dislodge from the pockets 20, the graphite plugs 22 disposed in axially outermost rows A, B, N and P remain secured in their respective pockets and retain the remainder of the graphite plugs within a boundary defined by the outermost rows A, B, N and P. While the diameter D1 is described as being 0.502 inches to 0.506 inches, the diameter D2 is described as being 0.501 inches to 0.503 inches, the depth D3 is described as being about 0.28 inches, the length D4 is described as being about 0.28 inches to about 0.375 inches, the present invention is not limited in this regard as the diameters D1, D2 and D3 and the length D4 may be of any suitable magnitude. Although the graphite plugs 22 are described as being generally cylindrical, the present invention is not limited in this regard as graphite plugs of any configuration or shape may be employed including, but not limited to oval, rectangular and hexagonal configurations.
As illustrated in
As illustrated in
Referring to
Each of the upper lateral support 62, the intermediate lateral support 64, and the lateral supports 72 have one or more of the spherical bearings 10 installed therein and moveably link portions of thereof to one another as described herein. For example, with reference to
The inventors performed testing on a flat plate test specimen assembly manufactured from materials from which the spherical bearing 10 employs. In particular, the a portion of the flat plate test specimen assembly representative of the inner ring 12 was manufactured from UNS C96900 Toughmet, another portion of the test specimen assembly representative of the outer ring 16 was manufactured from 17-4 PH stainless steel with H1025 heat treatment and the solid graphite plugs 22 installed in the pockets 20 in the portion of the test specimen assembly representative of the inner ring. The testing demonstrated the surprising result of reduced friction and increased wear life compared to other spherical bearings. For example, the break-away (i.e., static) coefficient of friction ranged between 0.013-0.28 depending on load, temperature, and wear. After running the spherical bearing 10 300 cycles of ±one inch sliding movement at ambient temperature and an 8 ksi pressure load on the spherical bearing, the temperature of the spherical bearing was elevated to 550 degrees Fahrenheit and a bearing pressure load of about 24 ksi was applied. A breakaway coefficient of friction of less than 0.15 was measured at the 550 degrees Fahrenheit temperature and 24 ksi pressure load test condition
While the present disclosure has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.