Abstract:
A self-centering arbor adapted to locate a hole in a mechanical object having coaxial openings, such as brackets, bushings or the like, with vastly improved accuracy and repeatability. The self-centering arbor comprises two opposite free floating, spring biased, coaxial, tapered pins mounted in a housing member for engagement with the openings in the axle bracket or the like. The housing includes opposite first and second housings interconnected by a mandrel shaft. Furthermore, two spherical locating members are secured to the housing member and are oppositely aligned on an axis of the tapered pin.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to self-centering arbors, and more particularly to a self-centering arbor for determining positions of axle brackets and other automotive components. 
     2. Description of the Prior Art 
     In the evolution of the modern motor vehicles, the quality of the vehicles has become increasingly more important; particularly, the quality of manufacturing of the vehicles. The quality and performance of the vehicles depend in no small part on the quality of manufacturing of an axle assembly. The vehicular axle assembly includes a plurality of various different brackets and bushings having coaxial holes. In assembling the axle components, it is of utmost importance to accurately locate the axle brackets and bushings. The measuring devices currently used in the vehicular axle manufacturing, such as expending arbors, are unable to determine true location and have poor repeatability. 
     The need therefore exists for a self-centering arbor assembly that accurately and consistently locates axle brackets, bushings and the like in an efficient and inexpensive manner. 
     SUMMARY OF THE INVENTION 
     The present invention alleviates the drawbacks of the prior art. The present invention provides a self-centering arbor adapted to locate a hole in a mechanical object having coaxial openings, such as brackets, bushings or the like, with vastly improved accuracy and repeatability. 
     The self-centering arbor in accordance with the present invention comprises two opposite free floating, spring biased, coaxial, tapered pins mounted in a housing member for engagement with the openings in the axle bracket or the like. The housing includes opposite first and second housings interconnected by a mandrel shaft. Furthermore, two spherical locating members are secured to the housing member and are oppositely aligned on an axis of the tapered pin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in light of the accompanying drawings, wherein: 
     FIG. 1 is a cross-sectional view of a self-centering arbor mounted on an axle bushing in accordance with the first embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of a first housing in accordance with the present invention; 
     FIG. 3 is a cross-sectional view of a second housing in accordance with the first embodiment of the present invention; 
     FIG. 4 is a cross-sectional view of a locating member in accordance with the present invention; 
     FIG. 5 is a cross-sectional view of a free-floating pin in accordance with the present invention; 
     FIG. 6 is a cross-sectional view of a self-centering arbor mounted on an axle bushing in accordance with the second embodiment of the present invention; 
     FIG. 7 is a cross-sectional view of a second housing in accordance with the second embodiment of the present invention; 
     FIG. 8 is a cross-sectional view of a nut adapter in accordance with the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 of the drawings illustrates a novel arrangement a self-centering arbor  10  in accordance with the first embodiment of the present invention, employed for gauging a position of various vehicle axle components having opposite coaxial openings (particularly axial centers of the coaxial openings), such as bushings, brackets, or the like. In this particular embodiment, the self-centering arbor  10  is employed to locate the axial centers of end openings in a central aperture  6  in a hollow core  4  of a bushing  2 . 
     The self-centering arbor  10  comprises a longitudinal axis  11  and a mandrel shaft  12  disposed coaxially with the axis  11 . The shaft  12  has a first end  12   a  and a second threaded end  12   b  opposite to each other. The self-centering arbor  10  further comprises a first housing  14   a  and a second housing  14   b  secured to the opposite ends  12   a  and  12   b  of the mandrel shaft  12  correspondingly. More specifically, the first housing  14   a , illustrated in detail in FIG. 2, has an inner end  15   a , an outer end  16   a , an axial hole  17   a  therethrough and a bore  18   a . The first end  12   a  of the shaft  12  is inserted into the axial hole  17   a  through the inner end  15   a  and is fixedly fastened to the first housing  14   a  (preferably by interference fitting). The second housing  14   b , illustrated in detail in FIG. 3, has an inner end  15   b , an outer end  16   b , a threaded axial hole  17   b  therethrough and a bore  18   b . The second end  12   b  of the shaft  12  is inserted into the axial hole  17   b  through the inner end  15   b  and is threadedly fastened to the second housing  14   b . Thus, the second housing  14   b  is adapted to be adjustably positioned along the second end  12   b  of the shaft  12  and could be completely removed from the shaft  12 . 
     As illustrated in FIG. 1, each of the first and second housings  14   a  and  14   b  respectively, is provided with a locating member  30  that is affixed to the outer ends thereof. The locating members  30  are adapted to indicate axial centers of the end openings in the aperture  6  in the bushing  2 . Each of two generally identical locating members  30 , shown in detail in FIG. 4, has a hole-engaging supporting portion  32 , a gauging portion  34  and an enlarged intermediate portion  36 . The supporting portion  32  and the gauging portion  34  are formed in accurately coaxial relation. The gauging portion preferably has a spherical surface  38  and a precisely held diameter that is the same for all locating members. The spherical gauging surface  38  is formed on a center that lies on the longitudinal axis  11  of the self-centering arbor  10 . 
     The supporting portion  32  of the first locating member  30  is fittingly engaged in the hole  17   a  in the first housing  14   a , whereas the supporting portion  32  of the second locating member  30  is fittingly engaged in a hole  17   b ′ in the second housing  14   b , coaxial to the hole  17   b  and adjacent to the outer end  16   b . A diameter of the hole-engaging supporting portion  32  is determined by that of the holes  17   a  and  17   b ′ to be engaged. This hole-engaging portion  32  may be formed with threads corresponding to threads of the holes  17   a  and  17   b ′, or with a substantially cylindrical portion  39 , preferably having a slight taper for a part of its length for engaging an internal surface of the plain holes  17   a  and  17   b ′. Accurate centering of the locating member  30  in the hole (coaxial with the axis  11 ) is insured by the tapered shape of the part of the portion  39  in combination with the engagement of a shoulder  37  on the locating member  30  with the outer end of the housings  14   a  and  14   b . The shoulder  37  is part of the intermediate portion  36  and is formed precisely perpendicularly to an axis (not shown) of the locating member  30  that is coaxial to the axis  11 . 
     As illustrated in FIG. 1, the self-centering arbor  10  of the present invention is further provided with a pair of generally identical free floating pins  20  disposed opposite to each other in the corresponding bores  18   a  and  18   b  of the first and second housings  14   a  and  14   b  respectively. Each of the floating pins  20 , further illustrated in detail in FIG. 5, includes a cylindrical portion  22 , a tapered end  24  and a collar portion  26 . Furthermore, the pin  20  is provided with an axial opening  28  therethrough. The opening  28  in the pin  20  slidingly engages the mandrel shaft  12  so that the pin  20  is movable along the shaft  12  coaxially with the axis  11 . 
     The tapered end  24  is adapted to engage one of the opposite openings in the hollow core  4  of the bushing  2 . In order to bias the pins  20  toward the openings in the bushing  2 , the arbor  10  is provided with a pair of resilient spring members  42 , such as coil springs or the like. Each of the spring members  42  is disposed within the bore ( 18   a  or  18   b ) of the housing ( 14   a  or  14   b ) between the pin  20  and the outer end ( 16   a  or  16   b ) of the housing. The spring member  42  is resiliently engaging the collar portion  26  urging the pin  20  toward the open end ( 15   a  or  15   b ) of the housing. 
     In order to restrict the axial movement of and retain the pins  20  within the bores  18   a  and  18   b , each of the housings  14   a  and  14   b  is provided with a stop member  44 , preferably in the form of a screw  46  threaded into threaded bore  19   a  or  19   b  formed in the first and second housing  14   a  and  14   b  respectively. Correspondingly, each of the pins  20  is provided with an elongated axial notch  23  formed on the cylindrical portion of the pin  20 . A tip  48  of the screw  46  protrudes into the notch  23 , thus limiting the axial movement of the pin  20  and preventing the pin  20  from falling out of the housing  14   b  when it is removed from the shaft  12 . 
     In operation, the second housing  14   b  is first detached from the mandrel axle  12  along with the pin  20 . Then, the mandrel axle  12  is inserted into the hollow core  4  of the bushing  2  of the axle assembly, and the second housing  14   b  is threaded back to the shaft  12  and tightened until tapered ends  24  of the both pins  20  engage the opposite openings in the hollow core  4  of the bushing  2  and the spring members  42  are slightly compressed. The free floating tapered pins  20  accurately align the arbor  10  with the hollow core  4  of the bushing  2 . Thereafter, a coordinate-measuring machine (CMM) (not shown) locates the center of the spherical surface  38  of the gauging portion  34  of each locating member  30 . Thus, quick and accurate measurement of the location of axle bushings is provided. 
     It is, of course, understood that the foregoing self-centering arbor could equally be employed for measurement of the location not only bushings, but also of various axle brackets. 
     FIG. 6 illustrates a self-centering arbor  110  in accordance with a second embodiment of the present invention, used for gauging a position of a U-shaped axle bracket  102  comprising two protruding arms  103  and  104  provided with coaxial openings  105  and  106  respectively, wherein the arm  104  is provided with a nut affixed thereto coaxially with the opening  106 . 
     The self-centering arbor  110  comprises a longitudinal axis  111  and a mandrel shaft  112  disposed coaxially with the axis  111 . The shaft  112  has a first end  112   a  and a second threaded end  112   b . The self-centering arbor  110  further comprises a first housing  114   a  and a second housing  114   b  secured to the opposite ends  112   a  and  112   b  of the mandrel shaft  112  correspondingly. The first housing  114   a  is similar to the housing described in relation to FIG.  2 . 
     The second housing  114   b , illustrated in detail in FIG. 7, has an inner end  115   b , an outer end  116   b , a threaded axial hole  117   b  therethrough, a first bore  118   b  and a second bore  118   b ′. The first bore  118   b  is adapted to receive the nut  107 , while the second bore  118   b ′ is adapted to receive a nut adapter  150 . The nut adapter is used to position the second housing  114   b  coaxially with the nut  107  and, correspondingly, with the opening  106 . 
     The nut adapter  150 , illustrated in detail in FIG. 8, includes a head portion  152  and a threaded portion  154 , and is provided with a hole  156 . The head portion  152  is secured inside the second bore  118   b ′ preferably by press-fitting. The threaded portion  154  is provided with exterior threads corresponding to interior threads of the nut  107 . 
     The second end  112   b  of the shaft  112  is inserted through the hole  156  in the nut adapter  150  into the axial hole  117   b  in the housing  114   b  through the inner end  115   b  and is threadedly fastened to the second housing  114   b . Thus, the second housing  114   b  is adapted to be adjustably positioned along the second end  112   b  of the shaft  112  and could be completely removed from the shaft  112 . 
     As illustrated in FIG. 6, each of the first and second housings  114   a  and  114   b  respectively, is provided with a locating member  130  that is affixed to the outer ends thereof. The locating members  130  are adapted to indicate axial centers of the openings in the axle bracket  102 . Each of two generally identical to locating members  130  is similar to the locating member described in connection with FIG.  4 . 
     As illustrated in FIG. 6, the self-centering arbor  110  of the present invention is further provided with a free floating pin  120  disposed in the bore  118   a  of the first housing  114   a . The pin  120  is similar to the free floating pin  20  described in connection with FIG. 5. A resilient spring member  142  is provided in order to bias the pin  120  toward the toward an open end of the first housing  114   a.    
     In order to restrict the axial movement of and retain the pin  120  within the first housings  114   a , a stop member  144  is provided which is similar to the stop member  44  described in connection with FIG.  5 . 
     In operation, the second housing  114   b  is first detached from the mandrel axle  112  along with the pin  120 . Then, the mandrel axle  112  is inserted into the openings  105  and  106  of the bracket  102  of the axle assembly so that the tapered end  124  of the pin  120  engages the opening  105  in the bracket  102 , and the second housing  114   b  is threaded back to the shaft  112 . At the same time, the nut adapter  150  is threaded into the nut  107 , which is received inside the second housing  114   b . Next, the second housing  114   b  is tightened until the spring member  142  is slightly compressed. Thus, the free floating tapered pin  120  accurately aligns the locating member  130  affixed to the first housing  114   a  with the opening  105  and the nut adapter  150  accurately aligns the locating member  130  affixed to the second housing  114   b  with the opening  106 . Thereafter, the coordinate-measuring machine (CMM) (not shown) locates the center of the spherical surface  138  of the gauging portion  134  of each locating member  130 . 
     Therefore, the novel arrangement of the self-centering arbor of the present invention as constructed in the above-described embodiments provides quick and accurate measurement of the location of various and different bushings and brackets having coaxial openings. When used in manufacturing vehicular axle assemblies, the present invention allows to reduce the production cost and improve the quality of the axle assembly. 
     The foregoing description of the preferred embodiments of the present invention has been presented for the purpose of illustration in accordance with the provisions of the Patent Statutes. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment disclosed hereinabove was chosen in order to best illustrate the principles of the present invention and its practical application to thereby enable those of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated, as long as the principles described herein are followed. Thus, changes can be made in the above-described invention without departing from the intent and scope thereof. It is also intended that the scope of the present invention be defined by the claims appended thereto.