Patent Document

This application claims benefit of provisional application No. 60/108,990 filed Nov. 18, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to a notching construction and method that facilitates fracture of an otherwise solid cross section. More particularly, the present invention pertains to a notching construction and method that facilitates fracture of an outer ring of a spherical plain bearing. 
     BACKGROUND OF THE INVENTION 
     In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. 
     It is often desirable to separate a bearing ring into different pieces by intentionally fracturing the ring at a desired location. 
     One such bearing ring that is advantageously fractured at one or more locations along its circumference is an outer ring of a spherical plain bearing. Spherical plain bearings are used in numerous applications, such as in construction and other equipment. 
     FIG. 1A is a plan view of a spherical plain bearing  200 . The bearing  200  generally comprises a continuous inner ring member  202  and an outer ring member  204 . The outer ring  204  as illustrated in FIG. 1A is “double fractured” or segmented into two pieces that can be moved apart and mounted over the inner bearing ring  202 . When mounting of the outer ring  204  is complete, the free ends  205  of the double fractured ring are brought together and the gaps between the two ring parts are closed. 
     FIG. 1B is a cross-sectional view taken along the section line  1 B— 1 B of FIG. 1A, and illustrates certain features of the inner bearing ring  202 . The inner bearing ring  202  generally includes a substantially cylindrical inner surface  206 , and optionally having an inner peripheral groove  208  which distributes lubricant along the inner surface  206 , the edge surface  210  and the outer arcuate surface  212  of the inner bearing ring  202 . The outer arcuate surface  212  of the inner bearing ring  202  may optionally be provided with an outer peripheral groove  213  disposed therein. A through hole (not shown) radially interconnecting the inner and outer peripheral grooves  208  and  213  may also be provided for allowing lubricant to flow between the grooves  208  and  213 . 
     FIG. 1C is a sectional partial perspective view of the outer bearing ring  204 , prior to fracture. The outer bearing ring  204  generally comprises an inner arcuate surface  214  that receives the outer arcuate surface  212  of the inner bearing ring  202  in a nested relationship. The edge surfaces  216  of the outer bearing ring  204  each extend radially, and are interconnected by a substantially cylindrical outer peripheral surface  218 . An outer peripheral groove  220  may be provided in the outer peripheral surface  218  of the outer bearing ring  204  to distribute lubricant along the outer peripheral surface  218 . 
     A notched area  222  is provided in the outer bearing ring  204  by any suitable material removal technique, such as sawing or milling. The notched area  222  does not extend completely through the bearing ring  204 . A centrally-located blind hole  224  or a multiple number of blind holes across the surface  218  may also be provided in the outer bearing ring  204 . The blind hole  224  may be formed by any suitable material removal technique, such as drilling. Although only one notched region  222  and accompanying blind hole  224  are shown in FIG. 1C, typically a substantially identical construction is provided on the diametrically opposite side of the outer bearing ring  204 . 
     FIG. 1D is a cross-sectional view taken along the section line  1 D— 1 D of FIG.  1 C and illustrates certain features of the notched area  222 . A gap or space  226  on either side of the cross-section of the outer ring  204  represents the area where the material of the outer ring  204  has been removed to form the notched area  222 . As illustrated by gap  226  in FIG. 1D, only a portion on either side of the cross-section of outer ring  204  is removed. That portion of the cross-section that remains defines an interconnecting region or fracture region  228  which is represented by the cross-hatched area shown in FIG.  1 D. The interconnecting region  228  is bounded by the inner arcuate surface  214 , a portion of the edge surfaces  216 , the arcuate surfaces  230  on either side of the cross section, and a portion of outer substantially cylindrical surface  218 . The blind hole  224  may be provided in the region  228 . 
     The outer ring  204  with the above-described construction is case or surface hardened and then fractured. The outer ring  204  is fractured along the interconnecting region  228  to form two ring parts having separated ends  205  (FIG.  1 A). The outer ring  204  is fractured by the application of mechanical force to the outer periphery of the ring in the notched area(s)  222 . 
     By providing the interconnecting region  228  with a relatively small cross-sectional area the case hardening or surface hardening treatment can more easily penetrate through the entire interconnecting region  228  and cause this region to become sufficiently “brittle”, thus facilitating fracturing. In addition, the blind hole  224  is provided to further facilitate the penetration of the case or surface hardening treatment through the cross section. 
     The fracture mechanics of this construction can be better understood by reference to FIGS. 1E-1H. Typically, a pair of notches N 1 , N 2  is formed at both axial sides of the ring  204 . As a mechanical force MF is applied to the outer periphery of the ring  204 , cracks A, B originate within the interconnecting region  228  at points IE A o , B o  in the vicinity of the notches N 1 , N 2 , respectively. These cracks A, B propagate toward each other. 
     Under ideal circumstances, cracks A, B propagate toward each other until the leading end or tip of one crack A, B runs into the leading end or tip of the other crack B to thereby define a fracture plane F corresponding to a line interconnecting B o , B and A o , A, as illustrated in FIG.  1 F. However, it has been discovered that in practice this rarely occurs. Instead, a fracture pattern similar to that illustrated in FIG.  1 G and/or FIG. 1H often occurs. 
     As shown in FIG. 1G, the cracks A, B propagate toward one another, but the leading ends or tips of the cracks pass one another and do not intersect. Instead, the leading end of one crack B may eventually run into or intersect a portion of the other crack A at a point spaced from the leading end of the other crack A. The distance between this point of intersection and the leading end of the crack being intersected A defines a secondary fracture SF which represents a residual fracture or crack that is not needed to form the fracture plane across the cross section of the outer ring  204 . 
     Alternatively, as shown in FIG. 1H, the leading end of one crack may never entirely intersect the body of the other crack. Instead, an offset crack OC can form between the leading end of one crack B, with this offset crack C then intersecting the body of the other crack A. This forms a secondary fracture SF between the point where offset crack OC intersects the body of the crack A and the leading end of the crack being intersected A. 
     These secondary or residual fractures define a weakness in the cross-section of the outer ring  204  and can further propagate, possibly causing a chip of material to be dislodged from the outer ring  204 . This can result in a reduction in service life of the bearing and the equipment in which the bearing is installed. 
     After the outer ring  204  has been fractured at the region  228 , the resulting free ends  205  have a surface area defined by the area of the region  228 . The free ends  205  are brought into contact with each other after the outer ring has been placed over the inner ring  202 . Because the area of the region  228  is relatively small, by virtue of the amount a significant amount of material removed from the cross section in the regions  226 , the contact pressure between the free ends  205  of the split ring is relatively large. This increased contact pressure can cause damage to the ends  205  of the outer ring  204 . 
     Therefore, it would be desirable to provide a notched area that promotes cleaner separation by reducing or eliminating secondary fractures. 
     It would also be advantageous to reduce the amount of material removed from the cross-section when forming the notched area in order to maintain a relatively large area of contact between the free ends formed by the fracture, thereby reducing the contact pressure between the free ends of the outer ring. In addition, it would be advantageous to reduce the amount of machining or milling required to remove material from the cross section when forming the notch area. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above-mentioned problems, and others, by providing a unique notching configuration that promotes a clean fracture, while reducing the amount of material that must be removed to form the notch configuration. 
     A fracture area formed consistent with the principles of the present invention includes a plurality of distinct interconnecting regions defining a plurality of separated fracture regions, and at least one interruption entering from one side of the cross section and exiting through another side, the at least one interruption provided to separate and create a plurality of fracture planes. 
     A method of separating or fracturing a cross section consistent with the principles of the present invention includes forming an interruption in the cross section thereby separating the interconnecting region into a plurality of distinct interconnecting regions or fracture planes, providing a crack initiating formation at either side of the cross section, and applying mechanical force to the outer periphery of the ring in the area of the gap or space causing at least one crack to form at each initiating formation and propagate toward and into the at least one interruption, thereby fracturing the cross section at the fracture planes to form separated opposed ends from the interconnecting regions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1A is a plan view of a spherical plain bearing; 
     FIG. 1B is a cross-sectional view taken along line  1 B— 1 B of FIG. 1A; 
     FIG. 1C is a sectional partial perspective view of an outer bearing ring; 
     FIG. 1D is a cross-sectional view taken along line  1 D— 1 D of FIG. 1C; 
     FIG. 1E is a cross-sectional view of like FIG. 1D illustrating an ideal fracture pattern; 
     FIG. 1F is a partial bottom view from the perspective of line  1 F— 1 F of FIG. 1E illustrating the ideal fracture pattern; 
     FIG. 1G is bottom a view like FIG. 1F, illustrating a typical fracture pattern; 
     FIG. 1H is a bottom view like FIG. 1F, illustrating another typical fracture pattern; 
     FIG. 2A is a sectional partial perspective view of an outer bearing ring constructed accord the present invention; 
     FIG. 2B is a cross-sectional view taken along line  2 B— 2 B of FIG. 2A; 
     FIG. 2C is a cross-sectional view of like FIG. 2B illustrating a fracture pattern of the present invention; and 
     FIG. 2D is a partial bottom view from the perspective of line  2 D— 2 D of FIG. 2C illustrating the fracture pattern of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2A is a sectional partial perspective view of an outer bearing ring  4  constructed according to the principles of the present invention. The outer bearing ring  4  can be made from any suitable bearing material. For example, the outer bearing ring  4  can be made from a steel, such as AISI 8620 steel. The outer bearing ring  4  is preferably subjected to a suitable hardening treatment. In one preferred embodiment the ring is case or surface hardened such that the surface region of the ring has a hardness that exceeds the core region of the ring. For instance, the outer ring  4  may be treated in a manner that provides the surface of the outer ring  4  with a high Rockwell C hardness, and a core with a lower Rockwell C hardness. 
     The outer bearing ring  4  generally comprises an inner arcuate or circular surface  14  that receives an outer arcuate or circular surface of an inner bearing ring in a nested relationship. The outer bearing ring  4  includes radially extending edge surfaces  16  that are interconnected by a substantially cylindrical outer surface  18 . A first generally centrally-located outer peripheral groove  20  may be provided in the outer surface  18  to direct lubricant along the outer surface  18  of the outer bearing ring  4 . A second outer peripheral groove  26  may optionally be provided in the outer surface  18  to form a seat for a snap ring (not shown) or similar member that helps hold the separated segments of the ring together. 
     A notched area  22  for promoting fracture is provided in the cross section of the outer bearing ring  4  by any suitable material removal technique, such as sawing or milling. As clearly shown, for example, in FIG. 2A, notched area  22  may include two parallel side walls  22 ′,  22 ″. A centrally located and radially directed through hole  24  extends completely through the outer bearing ring  4  from the outer surface  18  to the inner surface  14 . The through hole  24  can be formed by any suitable material removal technique, such as drilling. 
     Although only one notched area  22  and accompanying through hole  24  are illustrated in FIG. 2A, any suitable number may be provided. For example, an essentially identical construction can be provided on the diametrically opposite side of outer bearing ring  4 . 
     FIG. 2B is a cross-sectional view of the notched area  22 . A gap or space  27  on either side of the cross section of the outer ring  4  represents the area where the material of the outer ring  4  has been removed. As shown, only a portion of the cross section of the outer bearing ring  4  is removed. That portion of the cross section that remains defines an interconnecting region or fracture region  31  which is represented by the cross hatched area in FIG.  2 B. This interconnecting region  31  is actually defined by a plurality of separate and distinct adjacent interconnecting regions  28  and  30 , which are separated by the through hole  24 . This through hole  24  thus forms an interruption in the interconnecting region  31 . While the illustrated embodiment utilizes the through hole  24  to form the interruption, other structures that define such an interruption may be utilized, such as another form of void. The through hole  24  may optionally include a grooved or countersunk area  25  along the outer surface  18  of the outer ring  4  to promote a cleaner fracture. 
     In the illustrated embodiment, each of the interconnecting regions  28  and  30  are bounded and defined by a portion of the inner arcuate surface  14 , a first surface  32 , second surface  34  and a third surface  36 . 
     In the embodiment illustrated in FIG. 2B, the first surface  32  extends in a spaced parallel relationship to the edge surface  16 . However, it is within the scope of the present invention that the first surface  32  form an angle with respect to the edge surface  16 . The first surface  32  is connected to the second angled surface  34 . The second angled surface  34  is connected to the third surface  36 . In the illustrated embodiment surface  36  extends in a spaced parallel relationship to the outer surface  18 . It can be seen that in the illustrated embodiment the third surface  36  is spaced radially inwardly of the outer surface  18  of the outer bearing ring  4 . Of course other configurations are possible. For example, third surface  36  can be at least partially coextensive with the outer surface  18 , in a manner similar to that described in connection with FIG.  2 D. 
     By virtue of the present invention, including the provision of the through hole  24 , it is possible to obtain a clean fracture of the outer bearing ring  4 , yet not remove as much material from the cross section of the outer bearing ring as is necessary in other constructions. In the illustrated embodiment, the combined cross-sectional area of the interconnecting regions  28  and  30  is significantly greater than the cross-sectional area of the interconnecting regions of other constructions, such as the interconnecting region  228  of FIG.  1 D. By way of example, the cross-sectional area of the interconnecting regions  28  and  30  could be on the order of 1.6 times greater than the cross-sectional area of other interconnections, regions, such as region  228  of FIG.  2 D. 
     This increased cross-sectional area in the interconnection region  31  advantageously allows for a reduction in costly machining processes. In addition, the contact pressure (when the bearing is mounted) between the ends of the ring  4  formed after fracture is reduced relative to conventional constructions. 
     As mentioned above, separating the interconnecting region  31  into a plurality of distinct and completely separated regions or fracture regions  28 ,  30  advantageously provides a cleaner fracture and reduces or eliminates secondary fractures when the outer bearing ring is fractured through the application of a mechanical force. This is due at least in part to the provision of the interruption or through hole  24  which completely separates the interconnecting region  31  into two separate regions or fracture regions  28 ,  30 . The interruption or through hole  24  avoids the problems described above in that the leading ends of the cracks propagating from both axial sides of the outer bearing ring need not intersect one another to obtain a clean fracture. Rather, the interruption or though hole  24  defines a point at which the leading ends of the cracks stop and cannot propagate further. 
     To fracture the outer bearing ring  4 , a pair of notches N 1 , N 2  is formed at both axial sides of the cross section of the ring  4  as illustrated in FIGS. 2C and 2D. A mechanical force MF is then applied to the outer periphery of the ring  4 . This mechanical force MF causes cracks A, B to originate within the interconnecting region  31  at the points A o , B o  in the vicinity of the notches N 1 , N 2 , respectively. These cracks A, B then propagate toward each other. The centrally-located through hole  24  substantially interrupts the cracks A, B before they can cross each other. By this construction, detrimental residual and secondary cracks are avoided. 
     The method of separating or fracturing a cross section such as an outer bearing ring according to the principles of the present invention may include creating a gap or space  27  by removing material from the cross section by any suitable technique, such as sawing or milling, thereby leaving an interconnecting region  31 . 
     An interruption in the cross section that separates the interconnecting region into a plurality of distinct interconnecting regions  28 ,  30  or fracture regions is formed. In one embodiment, this interruption is formed by the through hole  24 . The through hole  24  can be formed by any suitable technique, such as drilling. 
     A crack initiating formation is provided at either side of the cross section. In one embodiment, the crack initiating formation is in the form of a plurality of notches N 1 , N 2 . 
     A radially inwardly directed mechanical force MF is then applied to the outer periphery  18  of the ring  4  in the area of the gap or space  27 . This force MF causes at least one crack A, B to form at each initiating formation A o , B o . The crack propagates toward and into the at least one interruption  24 , thereby fracturing the cross section at the fracture regions  28 ,  30  to form separated opposed ends from these regions  28 ,  30 . 
     It should be noted that under certain circumstances, it is possible to omit the above-mentioned material removal step. For example, the size of the cross-section and/or properties of the ring material can make it possible to fracture the ring without creating a space or gap  27  therein. 
     The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments described. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes, and equivalents which fall within the spirit and scope of the invention be embraced thereby.

Technology Category: 2