Abstract:
An axle bolt has a shaft with a pair of opposed ends. An axle passage extends within the shaft and a transverse passage extends radially outwardly from the axial passage. A head attached to one end of the shaft has an outer face. A recess extends in from the outer face and the bottom of the recess is in communication with the axial passage. A lubrication fitting in the recess has one end in communication with the bottom of the recess and another end designed to be connected to a lubrication device. The recess in the bolt head is sufficiently deep that the second end of the lubrication fitting is within the recess and does not extend beyond the outer face.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 09/506,669, filed Feb. 17, 2000, the entire contents of which is incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to an axle bolt to rotatably mount a wheel or the like to an axle, which includes means for lubricating the bearings which rotatably support the wheel.  
         BACKGROUND  
         [0003]    There are a number of arrangements for lubricating bearings for wheels or other rotating parts, but most are complicated and require structures other than that needed to accomplish the rotatable movement between a shaft and the wheel or the like.  
           [0004]    Previous axle bolts have been provided which include an axle passage for the necessary lubricant and a transverse passage connected to the axle passage to direct the lubricant to a bearing mounted outwardly of the axle bolt. Fittings have been provided to receive the lubricant and to prevent it from flowing out of the axle passage before being delivered to the transverse passage.  
           [0005]    A problem heretofore associated with such prior art axle bolts has been that the fittings had a tendency to be loosened and even broken off during use of the axle bolt. When that happens the fitting must be tightened or replaced before the axle bolt can be used to lubricate the bearing.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a simple means for permitting lubrication of the bearings without requiring additional and complicating structures. Close tolerances are provided between the fitting and the hole formed in the axle bolt to receive the fitting. This as well as the means provided to protect the fitting mounted to the axle bolt prevent it from being loosened or broken.  
           [0007]    This is accomplished by providing an axial passage in the axle bolt which communicates with a lubrication fitting such as a ZERK grease fitting in the cap of the axle bolt and with a transverse passage at the end opposite the ZERK grease fitting. The ZERK grease fitting is mounted in a conical recess formed in the head of the bolt. In this way it is protected and the danger of it being accidentally loosened or broken is substantially diminished.  
           [0008]    Lubrication provided at the ZERK grease fitting is transmitted through the axial passage to the transverse passage to the exterior of the axle bolt to lubricate the bearings or the like carried by the axle bolt. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    A better understanding of the present invention can be had by referring to the included drawings which illustrate a preferred embodiment of the present invention in which:  
         [0010]    [0010]FIG. 1 is an elevational side view of a bolt according to the present invention as initially formed, with the upper portion of the bolt partially cut away to show the recess formed in the head;  
         [0011]    [0011]FIG. 2 is an elevational side view of the bolt of FIG. 1 with axial and transverse lubrication passages added;  
         [0012]    [0012]FIG. 3 is an elevational side view of the bolt of FIGS. 1 and 2 after the final machine step in which the axial passage has been cut to accept a grease fitting; and  
         [0013]    [0013]FIG. 4 is a longitudinal cross section of the axle bolt of the present invention in use. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    As can best be seen in FIG. 1, the axle bolt  10  of the present invention is formed by forming a bolt  10  with a head  12  and a recess  14  formed in the head  12 . As shown, the head  12  has an end face  13  which defines a plane A-A. The recess  14  extends into the head  12  from this end face  13 . The recess  14  is preferably cold formed rather than drilled. The end  16  of the bolt  10  opposite the head  12  is then externally threaded as shown at  18 .  
         [0015]    The recess  14  may be said to be generally a conical recess. The conical recess  14  has a tapered or a conical bottom surface  15  and a sidewall  17  that extends from the tapered or conical bottom surface  15  to where the recess  14  joins the end face  13  of the bolt  10 . Preferably, the bottom surface  15  is tapered or conical across the entire width of the recess  14 . As shown, the tapered or conical bottom surface  15  is symmetrical with respect to the central axis of the bolt  10  and has a central “low point”  19 . The low point  19  is the portion of the bottom surface  15  farthest from the end face  13 . As shown, the edge at which the sidewall  17  joins the end face  13  is preferably a non-square edge  21 . That is, the transition between the sidewall  17  and the end face  13  is not a  90  degree square corner, but is instead relieved, such as by being radiused or tapered.  
         [0016]    [0016]FIG. 2 shows the axle bolt  10  formed with an axial passage  20  which extends from the recess  14  partially along the length of the shaft  11  of the bolt  10 . A transverse passage  22  extends radially from the axial passage  20  to provide communication between the axial passage  20  and the exterior of the axle bolt  10  at a point intermediate the ends of the bolt  10 .  
         [0017]    As mentioned previously, the recess  14  is preferably cold-formed rather than drilled. Traditionally, recesses in bolt heads, such as in the present invention, were formed by drilling the recess. While drilling may provide a recess with a tapered bottom surface, drilling adversely affects the material properties of the head and the surface finish in the recess. Drilling is also a time intensive process. According to the present invention, the recess is cold formed. Cold forming the recess requires tooling that is substantially more expensive than the tooling required for drilling the recess and has therefore not been previously used. Traditional cold forming of a recess would also result in a recess with a flat bottom surface, rather than a tapered bottom surface. The present invention provides the benefit of cold forming and the benefit of having a recess with a tapered bottom surface. The tapered bottom surface creates a central low point to make drilling the axial passage  20  much easier.  
         [0018]    The conical or tapered bottom surface of the recess was a result of extensive development work. The tapered bottom surface leads to better metal flow during the cold forming step, which improves the speed of the process, the repeatability, and the strength of the part, as compared to a part formed with a flat bottom cold formed recess. In addition, the tapered or conical bottom surface creates a part wherein the metal is less brittle, with a more malleable surface, at the central low point where the axial passage  20  is drilled. If traditional cold forming was used to provide a recess in the head of the bolt for the present invention, a lower quality part would result. Also, the low point would be eliminated, thereby requiring the additional step of using a center punch to start the drill for drilling the axial passage  20 . In addition, the central point would be more brittle, increasing tool wear and leading to a lower quality drilled hole, thereby hurting the performance of the part. Also, the repeatability, speed of the process and strength of the part would be compromised, as compared to the novel cold formed tapered bottom surface of the present invention. Another problem with drilling the recess is that drilling creates metal chips which must be cleaned out of the recess, and causes burrs, marks, inconsistency and heating. As one example, drilling will sometimes lead to hard spots in the material, which in turn adversely effects the subsequent drilling of the axial passage.  
         [0019]    The use of cold forming to form the recess for the present invention with a tapered bottom surface has traditionally not been possible because the appropriate tooling was not available. The die used to form this recess is produced using electrical discharge machining (EDM), which has only recently become available. Traditional grinding and other die forming processes would not create a die suitable for producing the present invention.  
         [0020]    As mentioned previously, the transition between the sidewall  17  of the recess  14  and the end face  13  is relieved, such as by being radiused or tapered. This is another benefit of cold forming a recess. The cold forming allows this otherwise sharp edge to be relieved during the cold forming step, without the necessity of an additional cutting step, such as would be required if the recess was drilled. When a recess is drilled, the edges are typically less sharp, which is undesirable to users.  
         [0021]    [0021]FIG. 3 illustrates a finished axle bolt  10 . A fitting such as ZERK grease fitting  24  is mounted in the recess  14  and provides the means for providing lubricant to the passages  20  and  22 .  
         [0022]    As shown in FIG. 4, the ZERK grease fitting  24  is provided with an externally barbed portion  40  on one of its ends, which is driven into and received by an internal portion  42  formed at the entrance of the axial passage  20 . When the fitting  24  is driven into the portion  42 , the fitting  24  is tightly received in the head  12  of the axial bolt  10 . As shown, the fitting  24  engages the conical bottom surface  15 . Also, the fitting  24  is received in a protected position because it is within the conical recess  14 . Close tolerances are maintained between the barbed portion  40  of the fitting  24  and the internal portion  42  to insure that the fitting  24  will be tightly mounted to the axle bolt  10 . This new design provides the fitting a heavy duty power of 3000 psi. The end of the fitting  24  opposite the barbed portion is configured for connection to a lubrication device. The fitting  24  acts as a check valve and lets lubricant flow into the axial passage  20  but prevents it from flowing back out of the passage  20 .  
         [0023]    In addition to the above-discussed benefits of cold forming a recess with a tapered bottom surface, the combination of cold forming the recess with the tapered bottom surface, along with the use of a barbed grease fitting which is driven into a drilled hole at the bottom of the recess, contributes to the reliable and repeatable production of parts that can withstand high pressures. The traditional approach to providing a grease fitting that can withstand high pressures is to provide a threaded grease fitting and to thread the hole into which the grease fitting is received. This is undesirable in the present invention, as the threaded grease fittings will sometimes back out during use. In many cases, the grease fitting is lost and the entire axle bolt is replaced. A grease fitting that falls out is also unacceptable for clean or sterile environments such as hospitals and food service facilities. The fitting would introduce dirty grease and metal into the environment. In any environment, a grease fitting that has fallen out presents a tripping or falling hazard, since the small fitting may act like a small ball under a person&#39;s feet. A threaded grease fitting has the additional disadvantage that they require the additional step of threading the hole into which the grease fitting is received, which leads to increased part cost  
         [0024]    For the above reasons, it is important that a grease fitting, whether threaded or pressed in, does not fall out. It is also important for the fitting to withstand very high pressures, such as 3000 psi, without coming out. High grease injection pressures are used to force grease through the axle bolt and to the bearings. If the fitting comes loose when high pressure is applied, the axle bolt has to be replaced, and the fitting may present sanitary and safety issues. In order to interconnect the grease fitting with the entrance to the axial passage in such a way that it can withstand high pressures, such as 3,000 PSI, it is necessary to very closely control the tolerances on the hole into which the fitting is received. As discussed previously, cold forming the recess with the tapered bottom surface improves the material properties at the low point, where the hole is drilled. This, in turn, allows the axial passage to be drilled much more accurately and consistently, and for tolerances to be controlled. This also increases the useable life of the drill bit used to drill the axial passage, since the material through which it is drilling is more malleable and less brittle. If the recess  14  were instead drilled, the accuracy and repeatability of the drilled axial passage would be lower, making it much more difficult to provide a part that can withstand high pressures.  
         [0025]    [0025]FIG. 4 illustrates the axle bolt  10  of the present invention in use. Bearings  30  rotatably support a hollow shaft  32  in a conventional manner. A cap nut  34  is received by the externally threaded portion  18  of the axle bolt  10  to retain the bolt  10  in position. The bearings  30  are provided with an outer half  36  and an inner half  38  as is conventional with the outer half  36  fixed to the shaft  32  and the inner half  38  fixed to the axle bolt  10 . The shaft  32  can support a wheel (not shown) or the like for rotation about the axle bolt  10 .  
         [0026]    Ball bearings  44  or the like which are disposed between the outer halves  36  and the inner halves  38  of the bearings  30  require lubrication. In the present invention this is provided by introducing grease or other lubricant through the Zerk fitting  24  and into the axial passage  20 . The lubricant will be forced from the axial passage through the transverse passage  22  and into the bearings  30 .  
         [0027]    It should be apparent that the present invention provides an axle bolt which has built into its construction means to provide lubrication to bearings or the like totally supported by the axle bolt. The lubrication is accomplished without the necessity of additional structure and the lubrication is provided directly to the bearings which require the lubrication.  
         [0028]    It should also be apparent that unlike axle bolts of the prior art the fitting  24  does not extend beyond the end face of the head  12  of the bolt  10  so that there is little danger of being damaged or loosened during use. The recess  14  provides protection for the fitting but is large enough to permit the fitting  24  to be connected to a lubricating supply connection (not shown) of conventional construction.  
         [0029]    It should be further apparent that the tight fitting between the fitting  24  and the axle bolt  10  provided by the close tolerances between the barbed projection  40  of the fitting  24  and the internal portion  42 , as well as the heavy duty construction of the fitting  24 , provides a construction which resists separation of the fitting  24  and the axle bolt  10 .  
         [0030]    It should also be apparent that changes and modifications can be made without departing from the spirit or teaching of the invention as set forth in the above description of a preferred embodiment of the invention.