Abstract:
An integrated lip seal provides a containment system for isolating debris generated in welding an enclosure and preventing contamination of interiors of devices. The closure system is especially useful in preventing aggregate from welding contaminating the interiors of torque converters during the final stages of assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional application No. 60/876,217, filed Dec. 21, 2006. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to welding debris isolation systems, and more particularly, to improved methods for welding enclosures that avoid introducing welding aggregate into interior spaces. The invention is especially advantageous for use in connection with sealing torque converters, wherein potentially damaging debris from welding is isolated from entry into the interior of such devices. The systems and methods provide a more economic alternative to time consuming manual flushing of converter interiors, and so called “Select-Fit” methods, for example. 
       BACKGROUND OF THE INVENTION 
       [0003]    Torque converters are positioned between the engine and transmission case of motorized vehicles. They play an important role by controlling on/off power from the engine to the rest of the drive train. In addition, they provide torque multiplication, dampen engine vibration and assure smooth start-ups and speed changes. 
         [0004]    A typical torque converter assembly comprises as principal components, an impeller or pump, a turbine and a stator positioned between the turbine and pump. As a step in the final assembly of torque converters a sealed chamber is formed when the front and back covers are welded together. However, in the process of sealing the front and back covers debris from the welding step has a tendency to enter the interior of the converter as contaminants. Welding aggregate, if allowed to remain in the interior of torque converters for motor vehicles can cause excessive wear on internal components and to transmissions. Consequently, current practices in the final assembly require additional steps for removal of debris, which is time consuming and costly, not only requiring more labor, but also requiring substantial capital investment for adding further floor space for the final assembly steps. 
         [0005]    Weld contamination inside torque converters has been difficult to eliminate with current machining tolerances and processes. One method practiced has been to isolate weld contamination while joining two components during the welding process. This requires bottoming two component edges together. The process is commonly referred to as “Select-Fit” (See U.S. Pat. No. 4,867,641) and requires the use of costly shims and added method steps to reduce axial movement. Hence, while Select-Fit may reduce contamination from enclosure welding, the method is not entirely satisfactory. 
         [0006]    Accordingly, there is a need for improved, more economic systems and methods for eliminating internal contamination from welding in manufacturing processes, and more particularly, to torque converters having improved features which avoid internal contamination from welding debris, including methods of manufacturing, wherein torque converter assembly and manufacture are performed without additional costly hardware components or without requiring internal flushing of the final assembly after welding. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    It is therefore one principal object of the invention to provide improved methods for joining a plurality of hardware components during welding by the steps of:
       (i) providing at least an outer hardware component and an inner hardware component. The hardware components comprise axial overlapping mating surfaces with terminal edges, wherein the terminal edge of the inner component comprises a flange extension curved and/or bent sufficiently so as to engage with a surface of the outer component when the inner component engages with the outer component;   (ii) forming an internal weld cavity with the curved and/or bent flange extension for isolation and containment of welding debris or contaminants by aligning the terminal end of the inner component with the terminal end of the outer component so the outer component overlaps with the mating surface of the inner component, and   (iii) forming a seal for the internal weld cavity for collecting and isolating welding debris by welding the outer and inner components together in an overlapping format.       
 
         [0011]    The method is preferably practiced, wherein the outer hardware component comprises an exterior surface and an interior surface and the curved and/or bent flange extension of the inner hardware component is sufficiently curved to engage with and form an interference fit with the interior surface of the outer component when the inner and outer components are in overlapping engagement. As a further preferred feature, the curved and/or bent flange extension, which may be in the form of a hook-shaped extension, comprises an enlarged terminal lip seal for maximizing weld contamination control. Similarly, the mating surfaces of the inner and outer hardware components are notched to form an indentation on the overlapping surfaces. 
         [0012]    It is yet a further principal object of the invention to provide torque converters for motorized vehicles featuring a novel welding debris isolation and containment system, especially for preventing welding debris from contaminating their interiors. The systems include torque converter front and back covers with annular terminal edges for inner and outer overlapping engagement with one another, wherein the inner overlapping edge comprises a curved and/or bent flange extension wherein at least a portion of the extension is in contact with the inner surface of the torque converter front cover making an interference fit with the inner surface to form a pocket or weld cavity for collecting debris from welding of front and back covers of torque converters. While the flange extension may be generally hook-shaped it may be virtually any configuration sufficiently curved and/or bent so as to engage with the outer overlapping edge to form an internal reservoir for containment of welding debris. As with the foregoing embodiment of the invention, the hooked-shaped extension is rounded/curved outwardly sufficiently to provide an interference fit with the interior surface of the outer overlapping edge. 
         [0013]    Other optional, but preferred features of the torque converter of the invention may include a bow or hook-shaped extension with an enlarged lip seal at the terminus of the hook for optimal sealing of the weld cavity for maximizing welding debris isolation and interior contamination control. 
         [0014]    It is still a further object of the invention to provide a device comprising a welding debris isolation and containment system with at least an outer structural element and an inner structural element. The structural elements comprise parallel overlapping mating surfaces with terminal edges. The terminal edge of the inner structural element comprises a generally hook or bow-shaped extension curved sufficiently outwardly to form a loop and to engage with a surface of the outer structural element when the inner structural element engages with the outer structural element forming a sealed cavity for isolating and containment of debris generated during the step of welding the inner and outer structural elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0016]      FIG. 1  is a side sectional elevational view of a torque converter featuring a front cover and back impeller cover having a continuous sealed weld cavity according to the present invention referencing  FIG. 2 ; 
           [0017]      FIG. 2  is enlarged fragmented view of the welded joint of  FIG. 1  illustrating a sealed weld cavity with isolated welding aggregate contained therein; 
           [0018]      FIG. 3  is an enlarged fragmented view of the initial step in forming a joint according to the present invention by engaging overlapping edges of outer and inner components of a device prior to welding; 
           [0019]      FIG. 4  is an enlarged fragmented view of the next stage of assembly wherein the outer overlapping structure engages the hook-shaped extension of the inner edge to form an interference fit; 
           [0020]      FIG. 5  illustrates the final stage of assembly of components prior to welding; 
           [0021]      FIG. 6  is a modified variation of the flange extension of  FIG. 5 ; 
           [0022]      FIG. 7  represents still a further embodiment of the flange extension with a generally bow-shaped extension forming a welding debris reservoir, and 
           [0023]      FIG. 8  is yet a further alternative embodiment of a flange extension engaging the edge of a torque converter front cover to provide an interference fit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    Turning first to  FIG. 1 , a torque converter  10  is illustrated with four principal components, namely back cover  12  as the pump shell, front cover  14 , turbine  16  and stator  18 . In torque converter  10 , a fluid circuit is created by the pump, sometimes called an impeller, the turbine and the stator, sometimes called a reactor. The fluid circuit allows the engine to continue rotating when a vehicle is stopped, and accelerate the vehicle when desired by the driver. 
         [0025]    As illustrated, torque converter  10  becomes a sealed chamber when front cover  14  is welded to back cover  12  by means of welded lap joint  20 .  FIG. 2  is an enlarged partial view of welded lap joint  20  according to the present invention consisting of front cover rim  22  arranged parallel with back cover rim  24 . The terminus of rim  24  includes a narrowed extension or flange  26  having a generally U-shape or hook-like configuration when viewed sectionally, as to provide a central sealed weld cavity  28  as a reservoir for collecting and isolating welding aggregate  30  or other debris generated at weld  32 . Cavity  28  protects the torque converter by preventing welding aggregate from entering the converter interior during the welding step. 
         [0026]    The interior surface  34  of front cover rim  22  preferably comprises a notched or indented surface  36 , wherein a somewhat enlarged machined seal  38  at the terminal end of the U-shaped hook  26  engages making an interference fit and seal with the indented interior surface  36 . The interference fit generated by the machined seal  38  engaging with indented surface  36  provides a narrow slit  40  as conduit means for transmission of welding debris from weld  32  to weld cavity  28 . 
         [0027]      FIG. 3  illustrates the initial assembly step of the front and back covers of the torque converter, wherein the indented surface  36  of front cover rim  22  slidably engages with the narrowed U-shaped extension or flange  26  of rim  24  in front of machined seal  38  of back cover  12 . 
         [0028]      FIGS. 4 and 5  illustrate the engagement of the front cover rim  22  wherein the indented inner surface  36  engages the top-edge of the U-shaped extension  26  with an interference fit with machined seal  38  to form slit  40  as conduit means for transmitting weld aggregate to the weld cavity  28 . 
         [0029]    The weld cavity  28  incorporating the machined seal  38  does not require additional structural components. Seal  38  contacts the mating axial surface  36  of the front cover rim  22 , and is preferably a machined feature of hook  26 . A minimum interference of about 0.2 mm radially is designed into this feature. A thin cross-section of material forms the upper edge of the hook  26  is preferred for deflection and to ensure the seal maintains contact with the mating surface  36 . A minimum radial load for seal  38  is desired so that at final assembly axial movement of the impeller and cover  12  will not cause damage to either one of these components, nor cause the need for a special press operation. 
         [0030]    The invention is not limited to the specific embodiments of  FIGS. 2-5 , but contemplates alternative embodiments, such as those illustrated in  FIGS. 6-8 . In this regard, back cover rim  44  may include a larger capacity welding debris cavity or reservoir  47  formed from flange extension  46  which comprises a generally rectangular shaped reservoir for collecting welding debris. Cavity  47  is formed from a horizontal arm followed by a vertical extension with a machined seal  48  at the terminus end engaging with indented surface  51 . The embodiment of  FIG. 6  includes a slit  50  as means for channeling welding debris from weld  52  into welding debris cavity  47 . 
         [0031]      FIG. 7  represents a further embodiment of the invention wherein the back cover rim  54  includes a generally curved bow shaped flange extension  56  forming a concave shaped welding debris interior  58  with the terminal end portion  60  in pressing engagement with indented surface  62  of the front cover rim  64 . Welding debris from weld  66  enters welding cavity/reservoir  58  via slit  68 . 
         [0032]    A still further embodiment of the lip seal invention for controlling weld contamination is illustrated by  FIG. 8 , wherein the front cover rim includes an indented inner surface  72 . The back cover rim  74  includes flange extension  76  having a modified concave-like depression forming welding debris cavity/reservoir  78  for receiving welding debris via slit  80  from weld  82 . A flattened upper edge of terminal portion  84  of flange extension  76  engages with the indented inner surface  72  of the front cover rim to form a closed dependable reservoir for retention of the debris. 
         [0033]    Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention.