Abstract:
The specification discloses a pulley assembly including a spun-formed pulley and a bearing secured within the pulley. The bearing is secured using any combination of press-fitting, adhering, coining, or peening. A manufacturing method also is disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to rotatable objects, such as pulleys, and more particularly to rotatable objects fabricated by spin-forming.  
           [0002]    Rotatable objects, such as pulleys, and their methods of manufacture are well known. This patent application discusses the invention in the specific context of a pulley, but is equally applicable to other rotatable objects, such as wheels.  
           [0003]    A pulley includes a hub, a grooved rim, and a web interconnecting the hub and the rim. Relatively low-cost pulleys are fabricated using two techniques.  
           [0004]    In a first technique, the pulley is formed by intersecuring two generally identical halves into a sandwich. A bearing can be trapped between the two halves within the hub. Pulleys made in accordance with this technique suffer several shortcomings. First, the two halves can separate during use, resulting in the failure of the machinery on which the pulley is installed. Second, precise alignment of the two halves during manufacture is difficult at best. Often the hub is slightly eccentric with the rim, rather than precisely concentric as desired. Eccentricity, also known as run-out, can result in premature wear of the bearing within the pulley.  
           [0005]    In a second technique, the pulley is fabricated using spin-forming technology. The resulting pulley is typically referred to as a “split steel” pulley. In this technique, a metal blank is spun at a relatively high speed; and mandrels and rollers are used to shape the blank into a one-piece pulley. Spin-forming results in at least one advantage and at least one disadvantage. The advantage is that the hub is precisely concentric with the rim. The disadvantage is that, because the pulley a single piece, bearings cannot be trapped between two pulley halves. Consequently, spun-formed pulleys are used in applications in which the pulley is mounted directly on a shaft for rotation with the shaft. Spun-formed pulleys have not been suitable for pulley applications requiring bearings.  
         SUMMARY OF THE INVENTION  
         [0006]    The aforementioned problems are overcome in the present invention wherein a spun-formed rotatable object, such as a pulley, includes a bearing secured within the object&#39;s hub. In the disclosed embodiment, the bearing is press-fit within the object. The bearing may be pressed, coined, and/or glued to the hub to enhance the intersecurement of the two pieces.  
           [0007]    In pulley applications, the present invention results in a relatively low-cost, high-precision pulley with a bearing. Because spin-forming is used to create the pulley, the bearing is precisely concentric with the rim. Therefore, the pulley reduces run-out.  
           [0008]    These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the Detailed Description of the Preferred Embodiment and the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective exploded view of a pulley assembly made in accordance with the present invention;  
         [0010]    [0010]FIG. 2 is a side elevational view of the pulley;  
         [0011]    [0011]FIG. 3 is a bottom plan view of the pulley assembly;  
         [0012]    [0012]FIG. 4 is a top plan view of the pulley assembly;  
         [0013]    [0013]FIG. 5 is a cross-sectional view of the pulley;  
         [0014]    [0014]FIG. 6 is a top plan view of the pulley blank prior to spin-forming;  
         [0015]    [0015]FIG. 7 is a side elevational view of the pulley blank shown in FIG. 6;  
         [0016]    [0016]FIG. 8 is a top plan view of the pulley blank after spin-forming;  
         [0017]    [0017]FIG. 9 is a side elevational view of the pulley shown in FIG. 8;  
         [0018]    [0018]FIG. 10 is a top plan view of a first alternative embodiment of the invention;  
         [0019]    [0019]FIG. 11 is a side elevation view of the embodiment shown in FIG. 10;  
         [0020]    [0020]FIG. 12 is a top plan view of a second alternative embodiment of the invention;  
         [0021]    [0021]FIG. 13 is a side elevation view of the embodiment shown in FIG. 12;  
         [0022]    [0022]FIG. 14 is a top plan view of a third alternative embodiment of the invention;  
         [0023]    [0023]FIG. 15 is a side elevation view of the embodiment shown in FIG. 14;  
         [0024]    [0024]FIG. 16 is a top plan view of a fourth alternative embodiment of the invention; and  
         [0025]    [0025]FIG. 17 is a side elevation view of the embodiment shown in FIG. 16. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    A pulley assembly constructed in accordance with a preferred embodiment of the invention is illustrated in the drawings and generally designated  10 . With reference to FIG. 1, the pulley assembly  10  includes a pulley  12  and a bearing  14 . The pulley  12  is a single piece including a hub  19 , a web  20 , and a rim  21 . The bearing  14  is secured, preferably by press-fitting, within the hub  19 . The pulley  10  can be fabricated of any one of a wide variety of metals.  
         [0027]    With reference to FIGS. 1-5, the rim  21  includes a floor  22  and two flanges  24 . The floor  22  is connected to the web  20 , and each flange  24  is connected to the pulley  12  along one of the upper or lower peripheries  54 ,  56  of the floor  22 .  
         [0028]    The hub  19  defines a center hole  26 . As can be seen from FIGS. 2-4, the center hole  26  is substantially circular, the diameter of the center hole  26  corresponding to the diameter of the bearing  14 . The dimensions of the center hole  26  should be such that a close fit exists between the bearing  14  and the center hole  26  when the bearing  14  is incorporated into the pulley. Accordingly, the size and shape of the center hole  26  will vary with the dimensions of the bearing  14 . As illustrated, the height of the hub  19  is greater than the height of the bearing  14 , but a bearing of any relative size may be used.  
         [0029]    The hub  19  includes a lip  40  projecting a short distance inwardly from the top edge  42  of the hub  19 . The lip  40  is a substantially flat projection upon which the base of the bearing  14  rests after connection of the bearing  14  to the pulley  12 .  
         [0030]    As seen in FIG. 5, the web  20  is substantially S-shaped and includes a first leg  50  and a second leg  52 . The first leg  50  projects outwardly from the edge  42  of the hub  19 . The second leg  52  extends in the opposite direction from the first leg  50  and is connected to the floor  22 , as will be explained in more detail below. The size and shape of the web is relatively unimportant.  
         [0031]    The floor  22  of the hub  19  is a continuous flat wall encircling the hub  19 . The outer wall has an upper periphery  54 , a lower periphery  56  and an inner surface  58 . The second leg  52  of the web  20  is preferably connected to the inner surface  58  of the floor  22  at approximately the center of the floor  22 .  
         [0032]    The flanges  24  are connected to each of the upper periphery  54  and lower periphery  56  of the floor  22 . Each flange  24  extends radially outwardly from the floor  22 . As disclosed, the flanges  24  protrude from the floor  22  at approximately a 30-degree angle.  
         [0033]    The bearing  14  can be any one of a wide variety of suitable bearings known to those skilled in the art. As disclosed, the bearing is press-fit within the hub  19 .  
       Method of Manufacture  
       [0034]    The first step in manufacturing the pulley assembly  10  is to form a blank  100  (FIGS. 6-7) by stamping. The blank  100  is preferably formed of metal and includes the hub  19  and a border  102 .  
         [0035]    The blank  100  is further shaped by spin-forming. Because spin-forming techniques and equipment are well know to those skilled in the art, the spin-forming equipment is not illustrated. To form the floor  22  and flanges  24  of the pulley  12 , the blank  100  is connected to a mandrel of a spin forming machine. As the blank  100  is rotated, rollers are brought into contact with the border  102  of the blank  100 . As an initial step, a roller may be used to round the outer edge  104  of the border  102  and to true the border  102 , if necessary. Next, a first shaping roller is brought into contact with the outer edge  104  of the border  102  of the blank  100 . As the first shaping roller is pressed against the outer edge  104  of the blank  100 , the metal of the blank is displaced causing the border  102  to split into two sections. A second shaping roller may then be used to enlarge and shape the gap between the two sections. A third shaping roller is optionally used to further enlarge and shape the gap between the two sections. After the two sections have been expanded the desired distance, a finishing roller is used to complete the shaping of the pulley  12 .  
         [0036]    The bearing  14  is then press-fit into the spun-formed pulley  12 . When press-fit into the hub  19 , the base of the bearing  14  lies flat against the lip  40  hub  19  of the hub  19 . Because the center hole  26  of the hub  19  is designed to closely receive the bearing  14 , frictional forces should permanently retain the bearing  14  in the hub  19  after the bearing  14  is press-fit into the center hole  26 . To enhance the press-fit intersecurement and/or as an alternative to the press-fit intersecurement, 1) the hub  19  can be coined, peened, or otherwise shaped, 2) the bearing  14  can be glued to the hub  19  using a metal-to-metal adhesive, and/or 3) other suitable techniques now know or subsequently discovered can be incorporated.  
       Alternative Embodiments  
       [0037]    Four alternative embodiments of the rotatable object are illustrated in FIGS. 10-17. The first alternative embodiment  110  (FIGS. 10-11) is a pulley for a V-belt. The second alternative embodiment  210  (FIGS. 12-13) is another pulley for a V-belt. The third alternative embodiment  310  (FIGS. 14-15) is a wheel. And the fourth alternative embodiment  410  (FIGS. 16-17) is another wheel. These four alternative embodiments are included as representative samples of other rotatable assemblies included within the scope of the invention. The configurations of additional possibilities are virtually limitless. All of the alternative embodiments are fabricated using methods similar to the method described above.  
         [0038]    The above descriptions are those of preferred embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.