The present invention relates generally to mechanical seals, and more particularly, to rotary end face seals designed for use in severe environments in which the primary seal is formed between mating faces of two metal seal rings of special alloy compositions lying in opposed relation to each other and making contact along a seal band portion formed on parts of the respective radially extending end faces of the seal rings. Seals made according to the present invention are an improvement over known heavy duty grit seals of a similar nature, such as seals of the types shown in U.S. Pat. No. 3,241,843, and other patents.
Seals of this type are commonly used to exclude grit, water and the like from stationary and rotatable members in severe service environments, such as those encountered by earthmoving vehicles where the track rollers, idlers and final drive system may be exposed to mud, dust, sand, or rock at temperatures which may reach the extremes found in either the deserts or the artic regions. Such seals perform their primary sealing function under these conditions, both because the end faces are precisely finished and because the seal rings themselves are accurately positioned and loaded by elastomeric rings of various configurations, with such rings also applying the desired loading forces, forming a secondary seal, and providing sufficient driving torque so that relative rotation occurs only at the primary seal faces of the seal rings and not between the seal rings and the elastomer or between the elastomer and another part of the sealed mechanism.
In order to function successfully under these relatively severe conditions, the seal rings must not only possess strength, corrosion resistance, and abrasion resistance, but also must be able to withstand the shock normally associated with earthmoving operations, even when carried out at subzero temperatures. Accordingly, the metal ring portions of heavy duty seals are normally made of metal alloy compositions containing elements such as cobalt, molybdenum, and vanadium which are relied upon to impart the desired properties to the seals. However, the main disadvantage encountered in the use of these alloys is their relatively high cost. Inasmuch as the service life of the seal rings made from such high cost alloys often exceeds the actual service life of the components associated therewith, many seals using these alloys are prohibitively expensive for many applications.
In view of the need for an improved moderately priced seal and for an alloy composition from which such seals can be made, it is an object of the present invention to provide an improved, inexpensive alloy composition having high strength, high corrosion and abrasion resistance, and high impact strength over a wide range of temperatures.
It is a further object of the present invention to provide a seal ring made from such improved, inexpensive alloy composition.
A still further object of the invention is to provide a track roller having seals made from an improved alloy composition.
Another object is to provide an alloy composition and a track roller having a seal ring made from such composition, with the composition being characterized by a service life which is exceptionally long in relation to the cost of the material from which the metal rings are made.
Yet another object is to provide a metal composition which has outstanding wear resistance but which is sufficiently economical so that seal rings of substantial cross section can be made therefrom without incurring undue expense.
A still further object is to provide a seal ring having a service life which is nearly as long as the service life of the best seal rings heretofore known but which can be made at a fraction of the cost of such seals.
Another object is to provide primary seal rings made from high performance, low cost alloys, which seal rings can be used interchangeably with prior art seal rings, that is, to provide a primary seal ring which may be used with secondary seal rings of existing designs, thereby providing flexibility in the manufacture and inventory control of complete seal assemblies.
It is a further object of the present invention to provide a seal ring comprising, in weight percent, from about 3.0 percent to about 4.0 percent carbon, not more than 1.5 percent manganese, from about 0.5 percent to about 2.0 percent silicon, from about 15.0 percent to about 20.0 percent chromium, from about 0.5 percent to about 2.5 percent vanadium, from about 2.0 percent to about 5.0 percent molybdenum, from about 0.25 percent to about 1.75 percent cobalt, from about 1.5 percent to about 3.5 percent tungsten, the remainder of the composition being iron, with the alloy containing a minimum amount of impurities.
It is a further object of the present invention to provide a seal assembly having seal rings comprised of the improved metal alloy.
It is a further object of the present invention to provide a track roller assembly having seals which include seal rings made from the improved alloy.
The exact manner in which these and other objects of the invention are achieved will become more readily apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings in which like reference numbers indicate corresponding parts throughout the several figures.