Abstract:
A universal bell housing which may be adapted to a variety of automotive engine and transmission combinations and method of making the same is disclosed. The bell housing is made by spin forming a sheet of steel and welding a transmission plate onto the cone. The cone and transmission plate are indexed to mount to a specified engine-transmission combination.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 of a provisional application Ser. No. 60/983,347 filed Oct. 29, 2007, which application is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Transferring power from a rotating engine or motor to a transmission or other implement requires an attachment mechanism to absorb the rotational torque differential between the engine and the desired transmission or implement. The attachment maintains a specific relationship of the components to prevent unwanted loss of energy from friction associated with misalignment of the rotating shaft from the motor with a transmission or other component. Additional consideration is given for the forces generated from the environment the assembly is to be employed. In an internal combustion engine the area between the engine and the transmission is commonly called a bellhousing. Historically Automobile, Truck, and Implement Manufacturers have provided their bellhousings from several processes; namely metal casting; metal pressing using dies and presses and occasional a hydro form pressing method requiring a less costly form of die. 
     A bellhousing also provides an area for controlling power transfer from the motor to the attachment to it. 
     Inside the bellhousing a clutching mechanism and often a starting system for the motor is placed. The bellhousing encapsulates these mechanisms protecting the components from the outside environment and hopefully contains any failure of the components within the bellhousing. 
     Bellhousings are attached to the motor with taps and commonly to the transmission or implement with taps. The pattern of the tapped holes varies from manufacturer to manufacture and from motor type to motor type as well as transmission type to transmission type. Additional variations occur within subgroups from above to accommodate the clutching and starting systems required for each application. Manufacturers most often design and build a casting from aluminum or iron for each application. The process requires a large commitment of capital and time designing the molds. They can only justify the large initial startup costs through the economics of mass production. 
     The manufacturer is faced with a tradeoff of weight versus strength when selecting either aluminum or steel. In the marketplace there has developed a need for a lighter weight steel bell housing to accommodate the manufacturer&#39;s production needs. New high torque engines create stresses that cause failure of the traditional cast bell housing. 
     In areas of motor sports all the circumstances above; flexibility of application; strength versus weight; production cost; and safety are equally important. Most motor-sport sanctioning bodies are now requiring bellhousings capable of containing all the components within the bellhousing in the event of a failure. Most require a steel bellhousing. Modern engines are producing torque in excess of the design parameters of traditional bell housing. The consumer desires an affordable and safe bellhousing that can be tailored to multiple combinations common in their competition. This market is not economically viable for traditional mass production methods since the price per piece is not sufficiently off set by production numbers. 
     Automotive restoration and modification has demands similar to the motor sport consumer. The flexibility and strength of the spun bellhousing enables combinations of almost any imaginable at a reasonable cost Likewise, all high torque, limited production applications of rotating energy from a motor to an attachment will benefit from the lower per unit cost of spun bellhousing. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention generally relates to an improved attachment, hereafter, “bellhousing” for use in rotating power transmission systems. The bellhousing is formed from a sheet of metal into generally coned shaped housing having an integrally formed flange extending from the cone. A plate is attached onto the opposing end of the cone that attaches to a transmission or other implement. This assembly are then machined and cut to accommodate any number of motor to transmission or implement combinations. 
     The process reflects the latest in technological advances in metallurgy and metal spinning. When first introduce modern high strength alloys exceeded the existing capabilities of traditional metal spinning. Recent improvements in metal spinning now allow high strength alloys to be formed in a spin forming machine. 
     A spun bell housing from a high strength alloy maintains its shape since the spin forming eliminates residual stress associated with tradition pressing methods. The combination of modern alloys and high power spinning machines eliminates the costly development of molds for casting or forms for pressing or hydro forming. The finished product is stronger, lighter, and stable than traditional pressed or cast attachments. The process allows short production runs decreasing per unit costs and the benefits of infinite flexibility. Modern spin forming and alloys provide a safer, stronger more stable product with fewer costs than the other processes. 
     The present invention generally relates to an improved bell housing for use in an automobile, the bell housing being formed by spin forming a sheet of metal into a generally cone shaped housing having an integrally formed flange extending from the cone. A transmission plate is then welded onto the cone. Finally, the transmission plate and integrally formed flange are shaped and cut to accommodate any of a number of engine and transmission combinations. 
     The process of making such a bell housing does not require the development of forms, such as those required for hydroforming or pressing, and may be formed from steel plate, thereby increasing the safety factor of the bell housing. Additionally, a variety of engine and transmission combinations may be used without expensive or weighty adapter plates between the bell housing and engine or transmission. The spin forming step also eliminates residual stress in the bell housing, further increasing its safety qualities. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the bell housing according to a preferred embodiment. 
         FIG. 2  is a perspective view of the bell housing from an opposite end. 
         FIG. 3  is an end view of the preferred embodiment. 
         FIG. 4  is a side view of the preferred embodiment. 
         FIG. 5A  shows a method of forming the bell housing by use of an internal spin forming machine. 
         FIG. 5B  shows a method of forming the bell housing by use of an external spin forming machine. 
         FIG. 6  shows the various steps in producing the bell housing according to the preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of this invention is a universal bell housing design and manufacturing process that allows a small number of housing sizes to be configured to mate with a large number of engine and transmission models. This is an important aspect of this invention as each engine and transmission has a unique mounting pattern and size and thus would require separate tooling. 
     As shown in  FIGS. 1-4 , the bell housing  10  generally comprises a cone  12 , a flange  20 , and a transmission plate  30 . The flange  20  has a hole pattern  24  corresponding to a mating surface on an engine. The transmission plate  30  also has a hole pattern  34  and a profile  32  corresponding to a transmission. The cone  12  also features a number of openings  14  which allow the bell housing  12  to fit about the engine transmission interface while allowing access for the shifter cable and starter. The arrangement of the openings  14 , and the hole pattern  24  on the flange  20  and hole pattern  34  on the transmission plate  30  are shown merely by example, as each engine-transmission combination may require different shapes or arrangement of these features. 
     As previously discussed, there are different methods available for the construction of bell housings. These methods include hydroforming, casting, or pressing. Each of these methods is not preferable for custom made bell housings because of an increased startup cost as well as limitations in the type of material which may be used. 
     The present invention contemplates the use of spin forming to form the basic bell housing shape. The process is generally shown in  FIGS. 5A and 5B , with the specific assembly process for the bell housing shown in  FIG. 6 . 
       FIGS. 5A and 5B  show alternative methods of spin forming a sheet of steel into a cone for use in the bell housing.  FIG. 5A  shows the use of an internal type spin forming and  FIG. 5B  shows the use of an external type spin forming. 
       FIG. 5A  shows internal-type spin forming. A sheet of steel  40  is placed onto the spinning machine  50  with the central axis  58  passing through the indexing hole  42 . The sheet  40  is then secured by a support  60  and spun at a high speed. As the sheet  40  spins, a roller  56  exerts force downward onto the sheet  40  forcing it into the cavity  52 . The sheet  40  is shaped to the cavity  52  while leaving a flange  20  integrally formed about the edge of the cavity  52 . 
     External spin forming is generally shown in  FIG. 5B . In this method, a sheet of steel  40  is placed onto a spinning machine  50  atop a mandrel  54 . The central axis  58  passes through the indexing hole  42  and the sheet  40  is secured with a support  60 . The sheet  40  is then spun at high speed and a roller  56  forces the sheet about the mandrel  54 . In this manner, a cone shape is formed about the mandrel with a flange  20  integrally formed with the cone  12 . As shown in  FIG. 5B , once the cone  12  is formed, the flange  20  is not level to the cone  12 . Therefore, a separate step is required to level the flange  20  prior to final machining. This step could be performed by a press or other similar process known in the art. 
     As shown in  FIG. 6 , the process starts with a single sheet  40  of steel, preferably ⅜″ for safety reasons. 
     Next, an indexing hole  42  is drilled through the center of the sheet  40 ; this hole  42  is preferably approximately 1″ in diameter and is used to align the sheet  40  onto the spinning machine  50 . 
     The sheet  40  is then formed by spin forming into a cone  12  with a narrow end  16 , a wide end  18 , and a flange  20  extending from the wide end  18 . The cone is defined by its height, diameter and angle of taper. 
     The cone  12  is next cut to a preferred height relative to the flange  20 . This distance is determined by the precise specifications between the engine and transmission. Along with cutting the cone height, noncritical operations are also performed. The openings  14  are also cut and the profile  22  of the flange is cut. These features are not held to the tight tolerances of the transmission and engine interfaces, and so may be performed at this stage. The cuts are preferably performed by an automated 5-axis laser cutter. Being automated, such as by CNC, individual bell housing profiles may be stored and retrieved according to production demands. The 5-axis laser cutter eliminates error due to moving the part and allows cuts to be made at a variety of positions and angles. 
     The transmission plate  30 , already having a profile  32  and center hole  36  for aligning with the transmission, is then welded onto the narrow end  16  of the cone  12 . As with the flange profile  22 , the transmission profile  32  is not required to be held to a tight tolerance. Therefore, a number of transmission plates  30  corresponding to a variety of different transmissions may be cut before welding the transmission plate  30  to the bell housing  10 . The central hole  36  of the transmission plate  30  is within a tolerance (e.g., 0.1″) of the final dimension. This central hole  36  is centered onto the cone  12 , thereby ensuring concentricity between the flange  20  and transmission plate  30 . 
     As a final step, the bell housing  10  is moved to a table for precision machining. First, the transmission plate  30  and flange  20  are leveled relative to one another to a precision tolerance (e.g., 0.001″). The hole pattern  24  in the flange  20  is then cut, including precision fit dowels. The central hole  36  and hole pattern  34  of the transmission plate  30  are also cut at this time, corresponding to the selected transmission. All of the operations in the final step are performed on a single machine, thereby ensuring a precise tolerance (e.g., 0.001″). 
     As has been previously described, the method of forming the bell housing allows for a variety of transmission and engine combinations to be assembled together through the use of a single bell housing. It should be appreciated to those skilled in the art that alternative embodiments of the method of forming the bell housing may also be used. For example, the cone may be formed by hydroforming, pressing, or casting. The remaining steps would then be followed as described above in order to produce a universal bell housing. 
     Hydroforming is a process by which a form is pressed out of a sheet of metal by the use of hydraulic pressure. The sheet of metal is placed onto a flexible diaphragm and a male mold is pressed into the sheet. Hydraulic pressure provides the energy for deforming the sheet. The flexible diaphragm provides resistance, thereby eliminating the need for a complimentary female mold. This type of metal forming is inexpensive as it does not require complimentary molds and can be used for a variety of shapes. 
     Pressing is a process by which a form is pressed out of a sheet of metal by a ram. The sheet of metal is placed onto a female die and a ram forces a male die onto the sheet. The sheet is then formed into the shape formed by the dies. This process is faster than hydraulic pressing, but requires more startup cost to form the dies. 
     Casting is a process of depositing molten metal into a form and then cooling the metal to set the form. The form must be designed for each individual bell housing. This process requires a high startup cost, and is generally not suitable for use with high-strength steel. However, the process is preferred for large quantities of products. 
     Other alternative processes obvious to those in the field of art are considered to be included in this invention. The above description is merely a single embodiment and limitations to the invention are described in the patent.