Abstract:
The present invention provides an apparatus that fastens elements of a frame assembly. The frame assembly implements fasteners as independent elements from both a housing and a corresponding housing cover. Exemplary embodiments of such fasteners may include the hook nut fasteners disclosed herein. Generally, such fasteners include a central portion providing a contact area disposed in the plane of a housing fastening aperture, an extension tab providing a contact area on a housing interior wall, and an extension block providing a contact area on a housing exterior wall. The extension block may include a hollow portion configured to receive a securing bolt. One advantageous application of the invention relates to automobile motor assembly housings. Specifically, in that embodiment the hook nut fastening assembly reinforces the motor housing and provides additional support to the assembly by reinforcing the joints between an end-cover and a motor assembly main body.

Description:
RELATED APPLICATION  
       [0001]     The instant application hereby claims priority to the U.S. provisional patent application Ser. No. 60/520,107 for a “Hook Nut Connector Apparatus” filed on Nov. 13, 2003, which is also incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to a type of fastener, more particularly, to an apparatus that may be used to assist in assembling a motor frame.  
       BACKGROUND OF THE INVENTION  
       [0003]     An exemplary application of the present invention relates generally to facilitating assembly of an electric motor that typically has an external motor housing and two end shields or housing covers mounted on opposing lateral ends of the housing for holding the motor components therein.  
         [0004]     Electric motors are manufactured in a variety of types and configurations. Typically an electric motor assembly is formed from a collection of parts, including elements such as a stator, a rotor, a shaft, a pair of end shields (or end bells), bearings, and a motor housing supporting and enclosing the various components. In addition to these primary motor components, some motors may include electronic components that are used to modify operating characteristics for particular applications. A hollow substantially cylindrical shaped housing includes axial opposite end surfaces, and a rotor and shaft rotatably disposed within the hollow interior bore of the housing. The stator has windings wound axially through the stator, and end-turns from the stator windings are positioned adjacent to the stator end surfaces. The end shields protect the stator windings and end turns from inadvertent contact and grounding while providing a mounting surface for rotor bearings and shaft bushings. The end shields also prevent debris from entering the hollow interior of the stator and interfering with operation of the motor.  
         [0005]     Conventionally, there are a number of ways to assemble motor frames. One such method is to use nuts, in coordination with long bolts (or in the alternative key bars), which extend through a distal side of one end shield, through the housing and through the opposite end shield, to secure the assembly together, as shown in U.S. Pat. No. 5,412,270. The high compressive forces produced by bolts act to maintain the end shields in a static position with respect to the housing. This assembly method is especially suitable for a motor with a lower length-to-diameter ratio. For motors with larger length-to-diameter ratios, however, this assembly method is prohibitive due to the structural instability inherent as the length of the bolts increases to match the greater length of the motor.  
         [0006]     Another frame assembly method incorporates tapping directly at the housing end surfaces, creating attachment sites (i.e., threaded spaces) integrally as part of the housing itself. Specifically, short bolts are threaded into the housing through the end shield. However, this necessitates either a significant increase in the housing wall thickness, or a housing design with complex structures formed with additional material that integrally provide a portion of the housing configured to receive a bolt or a screw.  
         [0007]     Electric motors to which the present invention pertains are common in the art. These motors, for example, might be used in electric vehicles. However, there is in a need for viable frame assembly methods that are formed so as to reduce both manufacturing costs and assembly cycle time. Moreover, it would be especially advantageous if the assembly elements did not need to be accounted for at the initial stage of forming the housing or housing cover. Such assembly methods should provide reliable and cost effective ways for facilitating normal motor operation.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides frame assemblies with fasteners implementing hook nut reinforcement, which addresses the concerns discussed above. Specifically, in an advantageous embodiment, a hook nut fastener reinforces the motor housing so as to provide additional support to the assembly by reinforcing the joints between an end-cover and a motor assembly main body.  
         [0009]     Typically, a motor housing is formed into a cylindrically shaped tube and end covers are attached to the tube after the motor is inserted. According to an advantageous embodiment, a fastener is configured to engage the motor housing, a securing bolt, as well as a housing cover. Fastening apertures are formed in the lateral ends of the housing. The fastener includes elements that engage the housing through a plurality of contact areas. Specifically, the fastener includes a central portion that establishes a contact area in the plane of the aperture, as well as a base extension tab that establishes at least one contact area with the interior wall of the housing. The fastener also includes an extension block that establishes a contact area with the exterior of the housing and engages a securing bolt. The securing bolt threads through an aperture in the housing cover and engages the fastener, thereby securing the housing cover to the housing, situated between the securing bolt head and the fastener&#39;s extension block.  
         [0010]     Advantageously, this type of fastener, a hook nut fastener, reinforces the motor housing so as to provide additional support to the assembly by reinforcing the joints between an end-cover and a motor assembly main body. Furthermore, the invention secures the housing cover to the housing by simply engaging the housing and the securing bolt. Accordingly, the fastener acts to simplify housing/housing cover manufacturing and the assembly process. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]      FIG. 1  is a perspective view of an exemplary motor housing with fastening apertures formed at the axial ends of the housing.  
         [0012]      FIGS. 2A-2B  is a perspective view of an exemplary embodiment of the present invention illustrating a triangle-base hook nut.  
         [0013]      FIGS. 3A-3D  illustrate a method of assembly for a motor housing assembly utilizing the exemplary embodiment shown in  FIGS. 2A-2B .  
         [0014]      FIGS. 3E and 3F  illustrate top views of a central portion and a base extension tab before and after a fastener is rotated, as shown in  FIGS. 3A-3D .  
         [0015]      FIG. 4A  is a perspective view of an exemplary square-base hook nut embodiment of the invention.  
         [0016]      FIG. 4B  is a cross-sectional view of a central portion and a base extension tab for the square-base hook nut embodiment of  FIG. 4A .  
         [0017]      FIG. 4C  illustrates the insertion and rotation of a fastener according to the embodiment illustrated in  FIGS. 4A and 4B .  
         [0018]      FIG. 5A  is a perspective view of an exemplary Z-type hook nut.  
         [0019]      FIG. 5B  is an illustration showing of a Z-type hook nut engaged with a housing and an end shield.  
         [0020]      FIG. 6A-6B  illustrate a fastener according to an alternate exemplary embodiment of the invention, wherein the fastener is engaged with the housing from the interior.  
         [0021]      FIG. 7  illustrates a fastener according to a further exemplary embodiment of the invention, wherein a central portion and a base extension tab are cylindrical.  
         [0022]      FIG. 8  illustrates the invention according to an additional exemplary embodiment implementing a detachable base extension tab. 
     
    
     DETAILED DESCRIPTION  
       [0023]     In the following description of the various embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention.  
         [0024]      FIG. 1  illustrates an exemplary housing prior to inserting a motor and securing housing covers to the housing. Generally, a motor is inserted into a protective casing to protect the various motor components. As shown in  FIG. 1 , a motor housing  100  may be formed as a hollow cylindrical tube. The tube is manufactured with axial ends  120  remaining open to facilitate motor insertion. Once the stator core and the rotor are inserted, the axial ends are covered with end shields (not illustrated) which correspond to the circumference of the cylindrical tube and block off the axial ends  120 . In the embodiment illustrated in  FIG. 1 , the cylindrical tube is formed from a single piece of sheet metal that includes rectangular fastener apertures  110  formed adjacent to the lateral ends  120 . A motor housing may be formed in steel, aluminum, or another type of suitable metal.  
         [0025]     The fastening apertures  110  may be formed in the sheet metal, by any known method of metal working, such as machining, punching or stamping. Moreover, it is to be understood that the fastener apertures  110  are not limited to rectangular shapes. Depending on the specific application and the manufacturing process, the fastening apertures  110  may be circular, elliptical, pear-shaped, triangular, irregular, or any other shape tailored for a matching fastener. To ease the installation process, the dimension of the fastening aperture  110  on the housing is slightly larger than that of a fastener&#39;s base extension tab (discussed below).  
         [0026]      FIGS. 2A and 2B  illustrate a perspective view of an exemplary embodiment of the present invention. Specifically,  FIG. 2A  illustrates a triangle-base hook-nut fastener  200  with a triangular-shaped base extension tab  225 . The triangle-base hook nut fastener  200  includes a substantially rectangular box, which when engaged with the housing  100 , forms an extension block or extension body  205  of the fastener  200 . Extension block  205  includes a hollow portion  210  extending the length of external block  205 .  
         [0027]     Based on the specific application of the fastener, the interior of the hollow portion  210  may be formed with threads to complement corresponding threads on a securing bolt, such as a screw. As another example, the hollow portion  210  may be smooth, and configured to accept a pin with a spring-loaded locking mechanism at the distal end. It is to be understood that numerous other securing mechanisms would be apparent to one of skill in the art.  
         [0028]     In the various embodiments of the invention, the fastener utilizes both horizontal and vertical forces in relation to the housing when the fastener engages the housing&#39;s fastening aperture. The extension block and base extension tab may impart forces on the exterior and interior housing walls in a vertical direction. These vertical forces work in coordination with horizontal forces imparted by the central portion of the fastener and the force created by engaging a securing bolt with the extension block.  
         [0029]     With regard to engaging the securing bolt with the extension block, the securing bolt used during the fastening process applies a load to the fastener. The load works, in coordination with the fastener contact areas, to maintain the vertical and horizontal fastener position with respect to the housing, the housing cover, and the securing bolt. The contact areas apply a retaining force or pressure to the interior and exterior walls of the housing, as well as apply a force in the plane of a fastening aperture portion of the housing. Moreover, it is to be understood that hollow portion  210  does not necessarily have to extend the entire length of extension block  205 . If the securing bolt is a screw, the hollow portion  210  may extend only a certain length of the extension block  205 . Also, hollow portion  210  may decrease in circumferential diameter as the hollow portion  210  extends into the extension block  205 . Such an embodiment advantageously provides additional anchoring material for engaging a screw.  
         [0030]     The underside of extension block  205  joins central portion  215  to create a second section of fastener  200 . The central portion  215  lies in the plane of the fastening aperture  110 , when the fastener  200  engages the housing  100 . Central portion  215  also separates the base extension tab  225  and extension block  205  in fastener  200 . The central portion  215  is formed so that after the fastener  200  is rotated (to be described with regard to  FIGS. 3A-3D  in greater detail below) the central portion  215  provides additional structural support, as well as an additional contact area between the fastener  200  and housing  100 . Generally, both the extension block  205  and the base extension tab  225  extend beyond the central portion  215  to engage the surface of the housing. This advantageously allows for the fastener to firmly engage both the interior and exterior sides of the housing wall, as well as a securing bolt.  
         [0031]      FIG. 2B  illustrates a cross-sectional view of triangular base extension tab taken along lines A-A in  FIG. 2A . It is to be understood for a given embodiment both fastening aperture  110  and the base extension tab  225  are designed to match and work together. Generally, the base extension tab  225  is formed with a similar contour as the fastening aperture  110 , but it is to be understood that in some embodiments the contours may be shaped differently. The shape of the fastening aperture  110  on housing  100  also contributes to determining the shape of central portion  215  (shown shaded). The wedge shape of central portion  215  allows it to engage the triangular fastening aperture  110 . As shown in  FIG. 2B , the geometry of forming the fastening aperture  110  substantially in the shape of a triangle leads to a complementary contoured triangular base extension tab  225 . Varying the shape of the fastening aperture  110  leads to subtle implementation variances in the placement of the retention forces securing the elements and will be illustrated in alternate embodiments detailed below.  
         [0032]      FIGS. 3A-3D  illustrate the steps of engaging the fastener with the housing  100  for an exemplary hook nut fastener with a triangular base extension tab. Initially, as shown in  FIG. 3A , the fastener  200  is positioned above a fastening aperture  110 , thereby aligning the complementary contours of the triangular base extension tab  225  and the fastening aperture  110 . After the elements are aligned, the fastener  200  is inserted into the fastening aperture  110  in the direction of arrows  250 . In  FIGS. 3B-3D , the central portion  215  and the triangular base extension tab  225  are represented by dashed lines because they are in the plane of or beneath the fastening aperture  110  and on the interior side of the housing  100 . In an embodiment of the invention to ensure a secure connection between the fastener  200  and the housing  100 , the thickness of the central portion  215  is equal to the housing thickness.  FIG. 3B  shows the triangular hook nut fastener  200  with central portion  215  and base extension tab  225  inserted into fastening aperture  110 . The extension block  205  prevents the fastener  200  from fully passing through fastening aperture  110  and advantageously provides another area of contact between the fastener  200  and the housing  100 . As shown in  FIG. 3C , once the fastener  200  has been inserted, the fastener  200  is rotated by 180° with respect to the axial edge  120  of the housing  100 .  FIG. 3D  illustrates fastener  200  in the final rotated position with the base extension tab  225  extending away from an axial edge  120 . The degree of rotation is one of the subtle implementation-specific aspects of the fastening processes referenced above.  
         [0033]     In the embodiment illustrated in  FIG. 3C , the geometry associated with a triangular base extension necessitates a 180° rotation for the fastener  200 . The 180° rotation illustrated in  FIG. 3E  from a top perspective creates staggered contact areas for the apex  300  and the base corners  305  of the base extension tab  225  and the triangular aperture  110 . In  FIG. 3E , the base extension tab  225 , and the complementary aperture  110  are aligned to facilitate insertion of fastener  200  into the aperture  110 . As shown, central portion  215  is set back from the leading edge of the base extension tab  225 .  
         [0034]      FIGS. 3E and 3F  illustrate the fastener from a top view before and after the rotation of fastener  200 , respectively. The apex  300  of the base extension tab  225 , and the base corners  305  of the base extension tab  225  are rotated into the position illustrated in  FIG. 3F . Rotating the fastener provides for three contact areas on the interior surface of the assembly housing, which in turn, provides additional structural support for the fastening assembly. Specifically, as the hook nut is inserted into the slot and turned around 180 degrees, the three corners of the base extension tab  225  engage the housing&#39;s internal wall, thereby providing radial support for balancing the bending moment acting on the fastener as the securing bolt is engaged.  
         [0035]     Once the fastener is engaged with the housing, the other elements of the assembly may be secured to the housing. The fastener  200  also includes an extension block  205  that establishes a contact area with the exterior of the housing and engages a securing bolt (not illustrated). The securing bolt threads through an aperture in the housing cover and engages the hollow portion of the extension block. The engaged securing bolt and fastener rigidly secure the housing cover between the securing bolt head and the fastener&#39;s extension block. This securing process is illustrated in greater detail in  FIG. 5B  for a Z-type hook nut fastener. It is to be understood that the fastener may work alone or in coordination within other fasteners situated at areas along the circumference of the axial end  120  to secure the housing cover  315  to the housing  100 .  
         [0036]      FIG. 4A  illustrates a perspective view of an alternate exemplary embodiment of the invention, specifically a square hook nut fastener. As shown in  FIG. 4A , the embodiment is similar to the embodiment shown in  FIGS. 3A-3G , except that the central portion  415  and the base extension tab  425  of the square hook nut fastener  400  are substantially square shaped. This aspect of the embodiment can be seen in greater detail in  FIG. 4B . In  FIG. 4B , the central portion  415  of the square hook nut fastener  400  is set back from the edge of the base extension tab  425 . As discussed above, this allows for an additional contact area when the fastener  400  engages the housing  100 .  
         [0037]      FIG. 4C  illustrates the process of inserting the fastener  400  with a square shaped base extension tab  425  into the fastening aperture  410 . As discussed above, varying the geometry of the fastening aperture  410 , the base extension tab  425 , and central portion  415  leads to subtle differences in the placement of the retention forces. Specifically, as the fastener  400  engages the securing bolt  320  and the housing  100 , there are different retaining forces exerted on the interior wall of housing  100  by the square base extension tab  425 . As shown in  FIG. 4C , the square-shaped base extension tab  425  has four independent areas of contact  420  with the interior wall of the housing  100 . Further, due to the geometry associated with this embodiment, the fastener  400  is rotated 45° to engage the fastener  400  with the housing  100 . The other aspects of engaging the fastener  400 , the housing  100 , the housing-cover, and the securing bolt  320  are similar to those discussed above with regard to triangle-base fastener discussed above.  
         [0038]      FIG. 5A  illustrates a fastener according to an alternate exemplary embodiment of the invention. The fastener  500  in  FIG. 5A  has a Z-shaped side profile. Unlike the embodiments discussed above, the Z-type hook nut fastener  500  includes a base extension tab  525  that extends in a lateral direction opposite that of the extension block  205 . Accordingly, the Z-type hook nut fastener  500  is tilted for inserting into a housing fastening aperture, but does not need to be rotated to engage the housing  100  and the securing bolt.  
         [0039]      FIG. 5B  illustrates in greater detail the Z-type hook nut fastener  500  engaged with the securing bolt  520 , the housing  100 , and a circumferential edge  515  of the housing-cover. As shown, the securing bolt  520  is a screw threaded into a Z-shaped fastener. Also, the securing bolt head  530 , retains the outer circumferential edge of the housing cover  515 , as the securing bolt  520  engages fastener  500 . Moreover,  FIG. 5B  shows three areas of contact for fastener  500  with the housing  100 —the base extension tab  525  is in contact with the interior wall of the housing  100  at contact area  540 ; the central portion of the fastener  515  in contact with the housing  100  in the plane of the fastening aperture  510  at contact area  545 ; and the extension block  205  in contact with the exterior of the housing  100  at contact area  550  for this embodiment of the invention. It is to be understood that the actual number of contact areas between the fastener  500  and the housing  100  may vary depending on application and the type of fastener utilized.  
         [0040]     Furthermore, it is to be understood that depending on the geometry implemented for the hook nut fastener, the contact area of the base extension tab and the housing interior wall may vary. One exemplary contact area implementation may contact the housing&#39;s interior wall on the side of the fastening aperture closest to the axial end of the housing, as illustrated in  FIG. 7  with the cylindrical hook nut. Specifically, the cylindrical base extension tab  725  contacts the interior wall of the housing on the side of fastening aperture  710  closest to the housing&#39;s axial end  120 . Alternately, in the Z-type hook nut shown in  FIG. 5B , the base extension tab  525  contacts the housing interior wall at contact area  540  on the side of the fastening aperture  510  opposite the housing&#39;s axial end  560 . As shown in  FIG. 6B , a circumferential base hook nut  600  contacts the housing&#39;s interior wall on both sides of the fastening aperture  610 .  
         [0041]      FIGS. 6A and 6B  illustrate a circumferential base hook nut fastener according to an alternate exemplary embodiment of the invention, wherein the circumferential base hook nut fastener  600  is inserted into the fastening aperture  610  from the interior side of the housing  100 . As shown, in  FIG. 6A , the extension block  205  of fastener  600  is inserted along arrow  620  into the fastening aperture  610 . This embodiment of the invention involves a fastener with a base extension tab  625  that extends around the entire circumference of the fastener. The continuous base hook nut  600  contacts the entire circumference of the interior wall of housing  100  along the fastening aperture  610 . In  FIG. 6B  once the fastener  600  is inserted into the fastening aperture  610 , a securing bolt (not illustrated) acts to apply a load along arrow  605 . The securing bolt acts in coordination with the continuous base extension tab  625  to secure both the fastener  600  and the housing cover to the housing  100 .  
         [0042]      FIG. 7  illustrates a fastener according to an additional alternate exemplary embodiment of the invention for a cylindrical hook nut  700 . The cylindrical hook nut  700 , as the name implies, incorporates both a cylindrical central portion  715  and a cylindrical base extension tab  725 . As shown, the base extension tab  725  and the central portion  715  are formed as cylindrical elements of fastener  700 . In order to complement the cylindrical shape of these elements, fastening aperture  710 , is generally pear-shaped with the smaller end of the aperture disposed toward the axial end  120  of the housing  100 . This geometry facilitates the fastener&#39;s insertion along arrow  730  after which, the fastener  700  is moved along arrow  705  to engage both the housing  100  and a securing bolt (not illustrated), which acts to apply a load. With regard to  FIG. 7  and  FIG. 8 , arranging the housing cover between the securing bolt head and the fastener is similar to the process describe and shown in  FIG. 5B .  
         [0043]      FIG. 8  illustrates an alternate exemplary embodiment of the invention illustrating a multi-component hook nut  800 . Specifically, the multi-component hook nut incorporates a base extension tab  825  as a detachable element. Because this embodiment implements a detachable base extension tab  825 , the fastening aperture  810  contour may correspond to the central portion&#39;s  815  contour. Moreover, after inserting the central portion  815  into the fastening aperture  110 , the detachable base extension tab  825  lockably engages with the central portion  815 . It is to be understood that such the detachable base extension tab is not limited to the circular locking mechanism illustrated in  FIG. 8 . The locking mechanism may be implemented as a securing pin engaged with a hole in the central portion  815  or any other acceptable locking mechanism that one skilled in the art would recognize. The manufacture of separate fastener and detachable base extension tabs may lead to less expensive production costs associated with simpler elements, as well as a less complex manufacturing and assembly process.  
         [0044]     It should be understood that the above description is only representative of illustrative embodiments. For the convenience of the reader, the above descriptions have focused on a representative sample of possible embodiments, a sample that teaches the principles of the invention. The description has not attempted to exhaustively enumerate all possible variations. That alternate embodiments may not have been presented for a specific portion of the invention or that further undescribed alternate embodiments may be available for a portion is not to be considered a disclaimer of those alternate embodiments. It will be appreciated that many of those undescribed embodiments incorporate the same principles of the invention and others are equivalent. Thus, it is to be understood that the embodiments and variations shown and described herein are merely illustrative of the principles of this invention and that various modifications may be implemented without departing from the scope and spirit of the invention.