Abstract:
An internally splined component for transmitting torque and the method of producing the same wherein the splines are cold formed to predetermined tolerances.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/362,173, filed Mar. 5, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to couplings and more particularly to splined couplings for transmission of torque.  
           [0004]    2. Description of the Prior Art  
           [0005]    It is common in the field of torque transmission to utilize splined joints to allow extension or compression of the length of a shaft transmitting torque between two components. Such splined joints usually consist of an externally splined male component and an internally splined female component. These components are assembled in the typical fashion.  
           [0006]    Looseness or backlash in such joints can be detrimental to the proper and efficient function of the assembly in efficiently transmitting torque between driving and driven components.  
           [0007]    In order to minimize backlash between the mating splined components, clearance between the spacing between the splines in the female component and thickness of the teeth of the male component is maintained at a minimum. Concentricity between the two splined components of such an assembly is important. Contrary to the backlash consideration and minimization, reasonable manufacturing capability is typically not considered in the associated manufacturing specifications.  
           [0008]    The most cost effective methods in the manufacturing process for volume production of high strength female splined components, include broaching and cold forming. While both of these processes are capable of producing such components with required tolerances on the spacing of the splines and the width of the splines, neither of the processes is effective at maintaining tight tolerances for the major or minor diameter fitting of associated components. This is primarily caused by the elastic properties of the metals used in the formation of these components, and to the internal stresses in the workpiece material. In broaching, the workpiece is oftentimes temporarily deformed due to the pressure exerted on it by the cutting tool. Accordingly, the cutting of the metal of the workpiece is not in its free, undistorted state. When the pressure is released at the end of the cutting operation, the workpiece returns to its free state form and the spline feature of the workpiece varies from its optimum geometry.  
           [0009]    In cold forming the material of the workpiece tends to spring back,from the optimum shape after the forming pressure is released.  
           [0010]    Large changes in the shape of the workpiece, both in the broaching and cold forming processes can result in unstable dimensional integrity of the workpiece. Residual stresses can be left in the workpiece due to previous mechanical or thermal processing. This causes non-uniform strength properties which can result in a workpiece being distorted to an out-of-round condition. Frequently, the distortion in the roundness of these workpieces exceeds the total permitted tolerance variation.  
           [0011]    It is an object of the present invention to produce an internally splined component and a method of making the same wherein the splined components are provided with small cross-section ribs machined to tight tolerances.  
           [0012]    Another object of the invention is to produce a splined component having a rib formed on the spline to achieve close tolerances.  
         SUMMARY OF THE INVENTION  
         [0013]    The above, as well as other objects of the invention are achieved by a splined component for transmitting torque comprising a main body having a longitudinal axis, and a plurality of spaced apart splines extending from the body and generally parallel to the axis of the body, the splines having a small cross-section raised portion extending away from the splines. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The above objects and advantages of the invention will become readily apparent to those skilled in the art from reading the following detailed description of the invention when considered in the light of the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 is a perspective view of a blank of stock from which the splined part of the invention is formed;  
         [0016]    [0016]FIG. 2 is a schematic sectional view of a die and punch arrangement for forming the blank illustrated in FIG. 1;  
         [0017]    [0017]FIG. 3 is a schematic view of the apparatus used to form splines on the internal surfaces of the part formed by the operation illustrated in FIG. 2.  
         [0018]    [0018]FIG. 4 is a top plan view of an internally splined part formed by the operations illustrated in FIGS. 2 and 3 embodying the features of the present invention;  
         [0019]    [0019]FIGS. 5 a ,  5   b , and  5   c  are enlarged fragmentary sectional views of the detail area of the splines on the part illustrated in FIG. 4 showing embodiments of the invention utilizing a single ridge;  
         [0020]    [0020]FIGS. 6 a ,  6   b , and  6   c  are enlarged fragmentary views similar to FIGS. 5 a ,  5   b , and  5   c  showing another embodiment of the invention wherein a plurality of ridges are employed; and  
         [0021]    [0021]FIG. 7 is an enlarged fragmentary view of the detail area illustrated in FIG. 4 showing alternate locations of the ridges. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    Referring to the drawings, wherein like reference numerals refer to similar components throughout, there is illustrated in FIGS. 1, 2, and  3  the various steps of the method for producing an article embodying the features of the invention. More specifically, FIG. 1 illustrates the preferred shape of a blank or slug  10  used to obtain the new and improved article. The blank  10  is typically formed from plate stock of a female meter such as, for example, a 6061 aluminum alloy. The blank  10  is typically provided with a centrally formed aperture  12 . As illustrated in FIG. 2, the blank  10 , to be formed, is then placed on the upper surface of a die  14  provided with a cylindrical cavity  16  extending from the upper surface of the die  14  to the lower surface thereof.  
         [0023]    The blank  10  is disposed such that the central aperture  12  is coaxial with the cavity  16 . A stool  18  is positioned adjacent the lower surface of the die  14  and suitably closes the cavity  16 .  
         [0024]    Once the blank  10  is suitably positioned on the die  14 , a reciprocating punch  20  is driven axially downwardly causing the metal of the blank  10  to flow between the outer surface of the punch  20  and the inner surface of the cylindrical cavity  16  to form a cup shaped part  22 . It will be appreciated that the downward thrust of the punch  20  acts against the stool  18 . At the end of the downward forming movement of the punch  20 , the punch may be withdrawn and the part  22  removed by either causing upward movement of the stool  18  or removing the stool  18  and permitting the part  22  to be released from the die  14 .  
         [0025]    The cup shaped part  22  is then disposed to travel between the outer rotating forming surfaces of an assembly of three forming rollers  24 . Prior to passing through the forming rollers  24 , a cylindrically shaped mandrel  26  having a plurality of longitudinally extending spaced apart splines  28  is inserted within the cylindrically shaped interior of the cup shaped article  22  until the end of the mandrel  26  typically abuts against the bottom of the cup shaped article  22  containing the aperture  12 . Next, force is applied to the mandrel  26  causing it to move in the direction of the arrow in FIG. 3. The force causes the mandrel  26  and the cup shaped article  22  to pass through the cooperating outer peripheral surfaces of the rotating forming rollers  24 . Since the distance between the contacting surfaces of the forming rollers  24 , which are displaced from one another by one hundred twenty (120°) degrees, to the central axis of the mandrel  26  is less than the radius of the outer surface of the cup shaped part  22 , the metal of the side walls of the part  22  is caused to flow such that the metal adjacent the outer formed surface of the mandrel  26  actually flows generally inwardly causing the inner surface of the part  22  to assume the shape of the outer surface of the mandrel  26 .  
         [0026]    [0026]FIG. 4 illustrates configuration of the part  22  after the mandrel  26  has forced the cup shaped part  22 , illustrated in FIGS. 2 and 3, between the outer surface of the cooperating rotating forming rollers  24 . The innermost surface of the part  22  now is formed with an annular array of axially extending spaced apart parallel splines  30 . While the above description describes the method of forming the part  22 , the following description more specifically details the unique configuration of the inner surface of the part  22 .  
         [0027]    In the embodiment of the invention illustrated in FIGS. 5 a ,  5   b , and  5   c  there is illustrated a spline configuration wherein the splines  30  are provided with a rib or ridge  34 , having a small cross-section, formed along the entire length of the highly toleranced surfaces between adjacent ones of the splines  30  of the component  22 . The ribs  34  facilitate the achievement of the required tolerances of the component  22 .  
         [0028]    [0028]FIGS. 6 a ,  6   b , and  6   c  are similar to FIGS. 5 a ,  5   b , and  5   c  showing another embodiment of the invention wherein a plurality of ridges  34 ′ are formed between adjacent splines  20 .  
         [0029]    [0029]FIG. 7 illustrates another embodiment wherein the ridges  34 ″ are formed in locations different from those illustrated in the other figures.  
         [0030]    It will be understood that the ridges or ribs may be created or formed on one or more of the minor diameter surfaces, the major diameter surfaces, the flanks of the splines, or any combination.  
         [0031]    Also, the ribs or ridges may contain individual humps or multiple humps. The surfaces on which the ribs are formed may contain multiple ribs or ridges.  
         [0032]    The ribs or ridges may be formed by many manufacturing methods, including cold forming, broaching, and shaper cutting.  
         [0033]    The ribs or ridges must contain sufficient material to permit the removal or deformation of a portion of the material to cause the component to meet the specified tolerances. By maintaining the ribs or ridges of small cross-sectional dimension, the cutting or deformation forces employed in calibrating the size of the ribs or ridges on the finished component will be small enough to militate against the distortion of the workpiece as a whole.  
         [0034]    In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be understood that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.