Abstract:
An externally splined clutch hub and method for making the same is disclosed wherein a flat circular metal preform with a central opening is provided and contacted with a single forging die to simultaneously cold forge a centrally disposed tubular neck extending outwardly from one side of the preform and simultaneously a splined annular ring at the periphery of the preform and extending outwardly from the other side of the preform wherein the tubular neck and the annular ring are coaxial.

Description:
This application is a continuation of U.S. provisional patent application Ser. No. 60/390,338, filed Jun. 21, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a low cost, externally splined clutch hub and a process for making the same. 
     2. Description of the Prior Art 
     Currently externally splined clutch hubs are produced by a roll forming process from tubular preforms. The process requires the use of tubes formed of very high quality low carbon steel. These tubes are expensive and currently are available from one overseas source. The roll forming process typically exerts severe loads on the tools and the associated machinery. Process downtime is a frequent occurrence. 
     An alternate process for producing externally splined clutch hubs is a progressive stamping process. In the progressive stamping process, a strip of sheet metal, or individual disks of steel, are transferred along a multiple station-stamping tool. These multiple stations progressively change the shape of the workpiece by stretching and drawing the material to achieve the final shape. The process requires very expensive tools and associated machines. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the invention to produce a process for producing a cold forged externally splined clutch hub. 
     Another object of the invention is to produce a cold forged externally splined clutch hub which is economical and may be readily reproduced. 
     Still another object of the invention is to produce an entire externally splined clutch hub in a single cold forging step. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The 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 illustrations, in which: 
         FIG. 1  is a top plan view of a metal blank from which the externally splined clutch hub of the invention is formed; 
         FIG. 2  is a sectional view of the blank illustrated in  FIG. 1  taken along line  2 — 2  thereof; 
         FIG. 3  is a fragmentary view partly in section illustrating the position of the blank illustrated in  FIGS. 1 and 2  in associated tooling wherein the cooperating punch and die members are separated preparatory to the operative forming stages; 
         FIG. 4  is a fragmentary view similar to  FIG. 3  showing the tooling after the punch has been driven into the die to cold forge the externally splined clutch hub of the invention; 
         FIG. 5  is a top plan view of the externally splined clutch hub produced in accordance with the tooling illustrated in  FIGS. 3 and 4 ; and 
         FIG. 6  is a cross sectional view of the hub Illustrated in  FIG. 5  taken along line  6 — 6  thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, the preferred process requires a flat circular metal workpiece or preform  10  as clearly illustrated in  FIGS. 1 and 2 . Typically, the preform  10  is formed by a stamping operation and is robust enough to accept standard variations within steel grades. The preform  10  is in the form of a flat circular metal workpiece with a centrally disposed opening  12 . As illustrated in  FIGS. 3 and 4 , a single forging die set is comprised of an upper die or punch  20  and a lower die  22 . The dies  20  and  22  cooperate to cause the metal adjacent the central opening  12  of the preform to flow in one direction to form a tubular neck  14  extending from one surface of the preform  10 , as more clearly shown in  FIGS. 5 and 6 . Simultaneously, the forging die set causes the metal of the preform  10  adjacent the peripheral circumference to flow outwardly to form a depending ring  16  having radially outwardly extending splines  18  extending from the opposite surface of the preform  10 . The tubular neck  14  and the splined ring  16  of the finished splined clutch hub are coaxial with one another as illustrated in  FIGS. 3 ,  4 ,  5  and  6 . Tooling is reduced to a single forging die set, with the possible addition of one set of calibrating tools. The simplified tooling can be run on less expensive equipment than the progressive stamping process, resulting in cost improvements in machine maintenance as well as in tooling maintenance. 
     In the production of the splined clutch hub of the invention, the preform  10  is typically initially lubricated in preparation for the cold forging operation. The lubrication may be a phosphorous compound in combination with a soap as well known in the art. The lubricated preform  10  is then placed in the lower die  22  of the die set. The lower die  22  is generally cylindrical in shape and is provided with a centrally formed coaxial interior wall  24  which terminates in an inwardly extending beveled annular shoulder  26  and thence a cylindrical section  28  having an inwardly extending array of spaced apart parallel splines  30 . 
     The lower die  22  is finally provided with a lowermost cylindrical wall  32  for receiving a lower die insert  34 . The lower die insert  34  is provided with a coaxially formed cylindrical wall  36  for receiving the upper portion of a cylindrically shaped stool  38 . The lower portion of the stool  38  is typically received within a cylindrical opening within a backup member  40  which rests upon the upper surface of a cooperating backup member  42 . The backup members  40  and  42  cooperate to determine the vertical positioning of the lower die  22  within the lower die shoe  44 . 
     The operating portion of the lower die  22  which is comprised of the lower die  22  and the lower die insert  34 . These die members are typically tightly secured within an outer shrink ring  46 . In assembling the lower die  22  and the lower die insert  34  into an integral unit, the shrink ring  46  is formed of a metal which when heated will expand a degree sufficient to receive the assembled lower die  22  and the lower die insert  34 . Once the lower die  22  and lower die insert  34  are satisfactorily received within the heated and expanded shrink ring  46 , the shrink ring  46  is allowed to cool and thereby shrink to tightly and securely hold the lower die  22  and the lower die insert  34  therewithin. The assemblage is then inserted into the lower die shoe  44  preparatory to the placement of the preform  10  within the assemblage as illustrated in  FIG. 3 . 
     The punch or upper die member  20  is attached to a press  50  in a manner well known in the art. The punch or upper die member  20  is comprised of a cylindrical body portion having an outer wall configuration  52  which is often referred to as a pilot diameter. The wall  52  initially contracts the inner wall  24  of the lower die  22  and functions to guide the punch  20  as the press  50  causes the punch  20  to be moved downwardly at the commencement of the forging operation. 
     The wall  52  terminates in an inwardly inclined shoulder  54  formed with a radius. A cylindrical wall  56  depends from the shoulder  54  and is of a diameter less than the diameter of the cylindrical wall  52 . 
     The lowermost end of the punch  20  is formed with a depending cylindrical wall  58  which is receivable within the cylindrical wall  36  of the lower die insert  34 . 
     Continuing with the description of the operation, it will be appreciated that as the press  50  forces the punch  20  downwardly, the punch  20  is guided to maintain concentricity by the formation of the lower die member  22  until the lowermost surface  60  and the wall  58  of the punch  20  contact the preform  10  causing the metal of the preform adjacent the central opening  12  to flow downwardly to form a tubular neck  14 , as illustrated in  FIGS. 4 and 6 . Simultaneously, the forging die set causes the metal adjacent the peripheral circumference to flow outwardly and upwardly to form a depending ring  16  wherein the outer portion of flow thereof enters the splines  30  of the lower die  22  to form outwardly extending splines  18 . 
     The benefits and advantages of the invention reside in the improved strength due to greater degree of cold working and higher carbon steel; the improved machinability to higher carbon steel; and the improved tolerances due to eliminating springback in the forming process. 
     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.