Patent Publication Number: US-7896353-B2

Title: Large diameter seals

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of co-pending U.S. patent application Ser. No. 11/427,381, entitled METHOD OF MAKING IMPROVED LARGE DIAMETER SEALS, filed on Jun. 29, 2006, which is hereby incorporated herein in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to large diameter seals and, more particularly, to large diameter seals having thin, pliable coatings on their outside diameters, and methods of making such seals. In general, this process can be performed on any so-called assembled seal. 
     Ordinary oil seals of from, perhaps, one inch to six inches in diameter, are made from a rigid casing and have bonded rubber lips of various kinds. Such seals are usually produced by compression molding, transfer molding or injection molding the rubber portion onto a steel, aluminum or like casing. Large diameter seals, for example, those of eight inches to sixty inches or more in diameter, are far too big to be economically manufactured by such a molding process. In other words, trying to inject rubber in a mold having an inside diameter of at least eight inches, but usually 12 inches up to 60 inches or more in diameter, would be very awkward, expensive, and impractical. To make such a mold would be extremely costly, especially considering that the mold would ordinarily be very seldom used. 
     In a regular or small diameter oil seal, the casing is made from a stamping or drawing. Such seals have either a metal or rubber OD (“outside diameter”). However, a large diameter seal is customarily made by a different method, with such method involving forming the casing in one step by a spinning operation, wherein the two radial flanges surround a major or axial portion of the casing. Thus, the casing is formed by placing a ring of metal in a spinning apparatus and spinning or bending the flanges thereon to form a generally U-shaped casing, as is well known in the art. 
     Thereafter, a portion of the elastomeric seal body is formed separately, cut into whatever overall length is desired, the end portions are bonded to each other to create a closed loop, and thereafter, the elastomeric portion is placed within the casing, and secured thereto by clinching. The resulting seal, which may be made with or without a garter spring, or in some cases with an embedded garter spring, is then ready to be used. 
     However, the present invention uses a different method. The seal is desired to have a rubber outside diameter (OD), for several important reasons. Installing a large diameter seal in a seal-receiving area, customarily a counterbore on a large machine such as a the rollers in a paper mill, steel mill or some other such application, because of the size of the seal, is customarily difficult. When the seal is even slightly too small for the application, it allows leakage between the counterbore and the OD of the casing. This is also the case with irregularities in the surface. If the seal is too large, the seal is unable to be installed, because the line-to-line contact necessary is extremely difficult to obtain. It is customary for such a large diameter seal-receiving area to be required to be free from nicks, scratches or the like, and as a result, installing such seals correctly becomes a major operation, particularly if the machine on which it is to be installed is old or has suffered from lack of maintenance. 
     Consequently, there has been a desire to manufacture a large diameter seal which would enable the secondary seal or the outside diameter of the seal to the counterbore to be completely and effectively sealed. Such a seal would also require a chamfer on at least one surface of its outside diameter, in addition preferably to being made from an elastomeric material which would be able to accommodate a slight out-of-round condition or other irregularities in the seal-receiving counterbore. 
     Accordingly, it is an object of the present invention to provide an improved large diameter seal. 
     Another object is to produce a large diameter seal, which includes a band of elastomeric material on its outside diameter. 
     Another object is to provide a method of creating an outside diameter rubber seal without creating a large-diameter mold, and which would not require equipment other than that required to make the remainder of the seal itself. 
     A still further object would be to provide a seal which would accommodate small imperfections in the installed or outside diameter, including an out-of-round condition or having nicks or other irregularities in the OD. 
     A still further object is to provide a method which involves creating an elastomeric seal band by bonding the end portions of a continuous strip of thin, elastomeric material into a closed loop, placing a bonding adhesive on the casing, and thereafter stretching the rubber band thus made into a larger diameter, allowing it to spring back and cling to the outside diameter of the casing, and then trimming one or both edges to provide a chamfer to accommodate and simplify the installation of such a seal. 
     A further object of the invention is to provide a rubber OD on a seal which would thereafter allow for improved ease of installation and removal, and would not damage the customer&#39;s hardware. 
     An object of the invention is to develop a rubber material for the OD of a seal which allows a certain amount of compression set during installation but thereafter remains resilient indefinitely. 
     Another object would be to provide an improved, rubber outside diameter seal which is especially useful in steel production, mining, pulp and paper and other industries generally requiring large diameter seals. 
     A still further object would be to provide a large diameter seal having a greatly reduced press-in or installing force, and a reduced extraction force. 
     A related object is to provide a seal which can be reinstalled without leaking in the application after removal from the counterbore. 
     Another object is to provide a seal which could compensate for an out-of-round or worn condition of the counterbore in which it is received. 
     A further object is to provide a seal which will not cause any damage to its associated counterbore, even during extraction. 
     A still further object is to provide a seal which has an outside diameter lead-in chamfer or radius. 
     SUMMARY OF THE INVENTION 
     The invention achieves its objects and others by providing an improved seal and method for making it, including unrolling a portion of rubber shim stock, cutting the shim stock to a smaller length than that required to encircle the outside diameter of the seal, bonding the ends together, stretching the seal over the casing, bonding shim stock to the casing and thereafter trimming the rubber to impart chamfers to one or both sides, thereby compensating for worn or out-of-round conditions or imperfections in the counterbore in which it is to be installed, and which therefore eliminates any damage to the bore during subsequent extraction. 
     The exact manner in which these advantages and objects and others which are inherent in the invention are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the invention set forth by way of example and shown in the accompanying drawings in which like reference numbers indicate corresponding parts throughout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of the so-called rubber shim stock, which is received in large diameter coils and of which a portion is shown just beginning to be unrolled from the coil; 
         FIG. 2  schematically illustrates plural, equal lengths of the rubber shim stock being cut after being taken from the coil; 
         FIG. 3  is a schematic vertical sectional view of the rubber shim stock, showing liquid adhesive being affixed to the two end portions thereof, and showing the shim stock about to be formed into a circular loop; 
         FIG. 4  is a schematic vertical sectional view showing the end portions of the rubber shim stock when the ends are fully bonded to each other to form a circular loop; 
         FIG. 5  schematically shows a circular piece of rubber shim stock being stretched to a larger radius so as to fit over a casing, showing the manner in which the liquid adhesive is added to the OD of the metal casing, and showing the rubber shim stock in the process of being allowed to return to just more than its totally relaxed diameter; 
         FIG. 6  is a vertical sectional view of a seal casing with the rubber comprising the seal body already inserted into the steel casing and bonded in place; 
         FIG. 7  shows the casing with the rubber shim stock bonded thereto by the use of the adhesive shown in  FIG. 5 , and; 
         FIG. 8  shows the rubber OD being trimmed to impart a chamfer to the shim stock on both axial sides of the seal. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     While the invention may be practiced by the illustrated methods or by somewhat different methods, and the seal made thereby has several features of novelty, an illustration will be given of one preferred method of making a seal, and the resulting seal having a rubber OD with a selected amount of shim stock bonded thereto. 
     Referring now to the drawings in greater detail, there shown in  FIG. 1  a coil generally designated  20  of rubber so-called shim stock  22 . This shim stock  22  is shown as being unrolled at  24  wherein an individual piece is taken from a much longer roll. It will be understood that this drawing is schematic and that the shim stock in question, usually 0.094 inches in thickness, comes in several hundred foot lengths. In this case, for illustration, the shim stock is cut into two individual pieces  26 ,  28 , ( FIG. 2 ) each having end portions  30 ,  32  spaced apart in selected, predetermined lengths. The lengths  26 ,  28  of each section of shim stock are treated successively. In  FIG. 3 , there is shown one such piece  26  having two end portions  30 ,  30  in the presence of a liquid adhesive  34 . The first liquid adhesive  34  is a powerful, contact adhesive which enables the two ends  30 ,  30  to be bonded together into a continuous loop  36  as shown in  FIG. 4 . 
       FIG. 4  shows the completed loop  36  made by bonding two ends of the loop  30 ,  30  together.  FIGS. 5 ,  6  and  7  show the next steps in the process.  FIG. 6  is a drawing showing a cross section of a large diameter seal. Here, there are shown the main components of a large diameter seal, namely, the body generally designated  38 , and including frusto-conical air and oil side surfaces  40 ,  42  meeting along a line of intended contact  44  with the shaft  45 . These surfaces are sometimes referred to as the inside face, or oil side  42  of the seal, and as the outside face, or air side  40  of the seal. The seal body of  38  is shown to include a curvilinear, generally somewhat circular, contoured opening  46  and an upper or radially outward portion  48  of the seal body  38 . This seal body or elastomeric portion  38  is received within a casing generally designated  50  and shown to include a principal, axial portion  52  and a pair of radial flanges  54 ,  56 . Also shown is garter spring  71  which can optionally be installed or embedded to seal body  38 . 
     These flanges  54 ,  56  are produced by spinning the an originally flat portion  52  until the correct curvature and the desired flanges  54 ,  56  are obtained. Thereafter, the seal body  38  is formed and placed within the casing generally designated  50 . Needless to say, the seal could be reversed and the flanges directed outwardly. 
     Referring now to  FIG. 5 , there is shown a stretched portion of rubber shim stock surrounding the portion  52  of the casing. The rubber portion  26  is shown as being somewhat spaced apart from the axial portion  52  of the casing. Liquid adhesive  58  is shown schematically as being deposited on the axial portion  52  of the casing, and the piece of shim stock  26  as having had its end portions secured together. A loop  26  is then formed and the loop  26  having been stretched to a larger diameter than that of the flange  52 . The forces holding the shim stock spaced apart from the flange  52  are then released, allowing the shim stock  26  to contact the casing  50  through the adhesive. In  FIG. 7 , it is shown that the shim stock is now bonded to the casing, and has become a permanent fixture. 
     Referring now to  FIG. 8 , there are shown two knives  60 ,  62 , which are positioned spaced apart but adjacent the edge portions  66 ,  68  of the shim stock, and they are thereafter moved into position so as to trim these edges  64 ,  66 . This cuts out small strips  68 ,  70 , from the shim stock  26  overlying the axial portion  52  of the casing  50 . Thereupon, the new large diameter seal is ready for installation. 
     Referring now to certain aspects of the invention and the method of performing it, preferably the rubber used is initrile (Buna N) rubber, but other synthetic rubbers and other rubbers such as natural rubber, silicone rubbers and other kinds of rubber could be used. The adhesive  34  used is a fast setting, clear cyanoacrylate adhesive, which bonds the rubber ends together and which is further identified as a room-temperature curing adhesive, for example, Locktite 420. This rubber is ready for the next step almost immediately. This loop of rubber is then sanded lightly to render the surface suitable for bonding with the next adhesive. The rubber is stripped of any residual oil. 
     The second process starts by cleaning the metal of any oil, etc. used in forming the metal casing. Next, applying the rubber to the casing  50 —is done by applying a similar adhesive—Locktite brand 4212 or 4211, to the metal casing. Both adhesives are described as thermally resistant (250° F.) high viscosity toughened adhesives. The next step involves stretching the one-piece band  26  of rubber to about 105% to 125% of its relaxed length, and covering the casing with such rubber band. The rubber should have no less length than 102%, and up to 110%, of the length in its relaxed condition. The bond will form in about 5 minutes, and the joint is then allowed to cure for 24 hours. 
     After a suitable curing period of 24 hours or more, the knives or razor blades may be used to trim the chamfer on one or both sides of the rubber OD coating. Normally, this is done by placing the inclined blade on the edge of the casing and rotating the casing until the margin of the rubber have been trimmed off. A 30 degrees from the horizontal is preferred. 
     It will thus be seen that the invention provides a novel seal and method having a number of advantages and characteristics, including those herein pointed out and other which are inherent in the invention.