Abstract:
A power seal bolt assembly includes a bolt having a head and a shaft having an unthreaded shaft portion and a threaded portion. A washer is fixed to the bolt proximate to the head. A compressible washer retainer frictionally engages the unthreaded shaft portion and contacts the head. The compressible washer retainer includes a retainer portion having flexible legs extending inwardly into a washer retainer through aperture. The flexible legs flex to frictionally engage the retainer portion to the unthreaded shaft portion. A compressible washer portion homogenously connected to the retainer portion is oriented to contact the washer when a bolt torque is applied. The compressible washer portion includes at least one raised ring contacting the washer to create a fluid seal at the washer; and at least one partial cavity permitting the compression washer portion to axially compress upon application of the torque.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/987,910, filed on Nov. 14, 2007. The entire disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to devices and methods for use of pre-assembled fastener assemblies used to fasten a first workpiece to a second workpiece where the workpieces include different materials. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Fastening members are widely used to join materials of different properties to one another including applications such as fastening plastic or polymeric parts such as covers and trim pieces to metal components or parts of an automobile vehicle assembly. One such device is disclosed in U.S. Pat. No. 5,807,052 to Van Boven et al. The &#39;052 patent defines an assembly for bearing the load from a metallic fastener coupled through a plastic part to a vehicle metallic part. Several disadvantages exist for the design of the device of the &#39;052 patent. These include the incorporation of a springing flange into the design of a sleeve which requires additional machining to achieve the springing function with the required clearance to permit the flange to deflect during assembly of the fastener. A further disadvantage is the fastener itself must be specially machined or formed having a protruding shank rib member to prevent the fastener from releasing from the sleeve assembly prior to installation. 
         [0005]    Further disadvantages of the design of the &#39;052 patent include a machining or forming process required on the internal bore of the sleeve to create a stop which engages the shank rib member. This machining or forming process removes material from the sleeve and is accomplished inside the sleeve bore and therefore generally increases the cost of the sleeve. A lower or second flange created on the sleeve further increases the cost of the sleeve by requiring an additional operation to create the flange or a machining operation to remove material to create the flange. 
         [0006]    Plastic or polymeric components such as valve covers used in conjunction with an automobile vehicle engine block reduce the cost and weight of the cover, however the thermal cycling over time and/or the stress/strain over time of the cover can generate creep in the plastic material used for the cover and a subsequently loose connection between the cover and the engine block. A reduced complexity fastener assembly is therefore warranted for this application as well as additional applications where dissimilar materials are fastened. 
       SUMMARY 
       [0007]    According to an embodiment of the present disclosure, a power seal bolt assembly includes a bolt having a head and a shaft having an unthreaded shaft portion and a threaded portion. A washer is fixed to the bolt proximate to the head. A compressible washer retainer frictionally engages the unthreaded shaft portion and contacts the head. The compressible washer retainer includes a retainer portion having flexible legs extending inwardly into a washer retainer through aperture. The flexible legs flex to frictionally engage the retainer portion to the unthreaded shaft portion. A compressible washer portion homogenously connected to the retainer portion is oriented to contact the washer when a bolt torque is applied. The compressible washer portion includes at least one raised ring contacting the washer to create a fluid seal at the washer; and at least one partial cavity permitting the compression washer portion to axially compress upon application of the torque. 
         [0008]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0009]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0010]      FIG. 1  is a front elevational view of a power seal bolt assembly of the present disclosure; 
           [0011]      FIG. 2  is a front elevational view of a bolt-washer assembly for the power seal bolt assembly of  FIG. 1 ; 
           [0012]      FIG. 3  is a top plan view of the bolt-washer assembly of  FIG. 2 ; 
           [0013]      FIG. 4  is a front elevational view of a partially assembled power seal bolt assembly of  FIG. 1 ; 
           [0014]      FIG. 5  is a front elevational view of a compressible washer retainer of the present disclosure; 
           [0015]      FIG. 6  is a top plan view of the compressible washer retainer of  FIG. 5 ; 
           [0016]      FIG. 7  is a cross sectional plan view taken at section  7  of  FIG. 5  of the retainer portion of the compressible washer retainer; 
           [0017]      FIG. 8  is a partial cross sectional elevational view of a completed installation of a power seal bolt assembly of the present disclosure; and 
           [0018]      FIG. 9  is a partial cross sectional elevational view of a completed installation of an additional embodiment of a power seal bolt assembly of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0020]    Referring to  FIG. 1 , a power seal bolt assembly  10  of the present disclosure can include a bolt  12  having a head  14  homogeneously connected to a head engagement flange  16 . Head engagement flange  16  can abut against a first outer face  18  of a washer  20 . Bolt  12  further includes a shaft  21  having an unthreaded shaft portion  22 , a threaded portion  24 , and an anti-cross-thread end  26 . Unthreaded shaft portion  22  extends homogenously from head engagement flange  16 , with threaded portion  24  and anti-cross-thread end  26  extending away from unthreaded shaft portion  22 . Unthreaded shaft portion  22  has a shaft diameter “A”. Threaded portion  24  has a thread pitch “B” which defines a diameter smaller than shaft diameter “A”. 
         [0021]    A polymeric material compressible washer retainer  28  which can by made by a molding operation is slidably fit over the unthreaded shaft portion  22 . Compressible washer retainer  28  includes a retainer portion  30  which is adapted to slidably and frictionally engage the unthreaded shaft portion  22 . Compressible washer retainer  28  further includes a compressible washer portion  32  homogenously connected to retainer portion  30 . Compressible washer retainer  28  is slidably disposed over unthreaded shaft portion  22  until compressible washer portion  32  contacts a second inner face  34  of washer  20 . Compressible washer retainer  28  is thereafter frictionally retained in the position shown in  FIG. 1  by frictional engagement between retainer portion  30  and unthreaded shaft portion  22  which will be described in greater detail in reference to  FIGS. 5-7 . 
         [0022]    Referring to  FIG. 2  and back to  FIG. 1 , prior to installation of compressible washer retainer  28  a bolt-washer assembly  36  is created by sliding washer  20  over the unthreaded shaft portion  22  of bolt  12 . A positive engagement feature  38  such as a knurl is created after washer  20  engages head engagement flange  16  so that washer  20  is fixedly retained in contact with head engagement flange  16 . In the assembled condition shown, bolt-washer assembly  36  has a working stem length “C” measured from the second inner face  34  to a free end  39  of anti-cross-thread end  26 . Working stem length “C” includes a shaft length “D” of unthreaded shaft portion  22  plus a threaded portion length “E” of threaded portion  24  and anti-cross-thread end  26 . Each of working stem length “C”, shaft length “D”, and threaded portion length “E” can be varied at the discretion of the manufacturer to suit different engagement lengths for bolt  12 . A total stem length “F” is measured from head engagement flange  16  to the free end  39 . Working stem length “C” differs from total stem length “F” by a thickness of washer  20 . According to several embodiments head  14  is provided with a plurality of engagement faces  40  defining a geometric shape such as a hexagon for head  14 . The quantity of engagement faces  40  is predetermined to suit a standard tool size used for installation of bolt  12 . 
         [0023]    Referring to  FIG. 3 , head engagement flange  16  has an engagement flange diameter “G”, and washer  20  has a washer diameter “H” which is larger than engagement flange diameter “G”. A flat-to-flat spacing dimension “J” is common between opposing ones of the engagement faces  40 , for example between engagement faces  40 ′ and  40 ″. 
         [0024]    Referring to  FIG. 4 , after assembly of bolt-washer assembly  36 , compressible washer retainer  28  is slidably disposed over unthreaded shaft portion  22  in an installation direction “K” until a contact end  44  of compressible washer portion  32  contacts second inner face  34  of washer  20 . Compressible washer retainer  28  and unthreaded shaft portion  22  are each co-axially aligned with a longitudinal axis  46  of bolt  12 . 
         [0025]    Referring to  FIGS. 5 and 6 , compressible washer retainer  28  is created by co-molding compressible washer portion  32  with the retainer portion  30  during a molding process such as an injection molding process. Retainer portion  30  is modified from the retainer disclosed in U.S. Pat. No. 7,073,997, issued Jul. 11, 2006, and commonly owned by the assignee of the present disclosure, the subject matter of which is incorporated herein by reference. 
         [0026]    Retainer portion  30  has a retainer length “L”, a retainer outer diameter “M”, and a retainer end diameter “N” measured at a retainer free end  48  of retainer portion  30 . A circular-shaped slot  50  is created on opposed sides or faces of compressible washer portion  32  and positioned between each of a first outer raised ring  52  and a second inner raised ring  54 . First and second outer and inner raised rings  52 ,  54  are duplicated as substantially mirror images of each other formed on an opposite side of compressible washer portion  32  and are therefore identified as first and second outer and inner raised rings  52 ′,  54 ′ on an upwardly directed face of compressible washer portion  32  as viewed in  FIG. 5 . A plurality of partial cavities  56  are created in the faces defined by circular slots  50 ,  50 ′. In the example shown, eight partial cavities  56  are formed in each of the faces defined by circular slots  50 ,  50 ′ however this quantity can vary above or below the quantity of eight at the discretion of the manufacturer. Partial cavities  56 ,  56 ′ are provided in part to allow for compression of compressible washer portion  32  when an axial load from bolt  12  (not shown in this view) is induced on compressible washer portion  32  by applying a torque to bolt  12 . 
         [0027]    Compressible washer portion  32  has a washer portion length “P”. Each of the partial cavities  56 ,  56 ′ have a partial cavity depth “Q”. A depth of circular slots  50 ,  50 ′ can also be controlled by the manufacturer to provide additional capability for compression or to resist compression of compressible washer portion  32 . First and second outer and inner raised rings  52 ,  54  also provide fluid seal function as a seal for fluids or gasses when compressible washer portion  32  is compressed during use. 
         [0028]    Referring more specifically to  FIGS. 1 and 6 , a plurality of flexible legs  58  extend into a through aperture  60  of compressible washer retainer  28 . Free ends of each of the flexible legs  58  define a flexible leg contact circle “R” which is smaller than shaft diameter “A” of unthreaded shaft portion  22 . This difference in diameter dimension induces the flexible legs  58  to deflect outwardly when compressible washer retainer  28  is disposed onto unthreaded shaft portion  22  of bolt  12 . Clearance for deflection of each of the flexible legs  58  as unthreaded shaft portion  22  is received is provided by a clearance provided between flexible leg contact circle “R” and an inner wall diameter “S” of retainer portion  30 . 
         [0029]    Referring now to  FIG. 7 , a quantity of eight (8) flexible legs  58  are shown, however the quantity of flexible legs  58  can vary either above or below the quantity of eight at the discretion of the manufacturer and to suit the required frictional contact if shaft diameter “A” of unthreaded shaft portion  22  changes for different embodiments. Each of the flexible legs  58  such as exemplary flexible leg  50 ′ defines a leg orientation angle α with respect to a reference line  61  oriented normal to an inner wall  68  of retainer portion  30 . Each of the flexible legs  58  has a first leg face  62  and an opposite second leg face  64  each commonly oriented with respect to the other flexible legs  58 . A leg free end  66  of each of the flexible legs  58  is oriented to face the unthreaded shaft portion  22  (not shown) of bolt  12  in the as-molded condition of retainer portion  30 . Each of the flexible legs  58  are homogenously created and extend into through aperture  60  from inner wall  68  with retainer portion  30  in an as-molded condition. 
         [0030]    Referring to  FIG. 8  and again to  FIG. 5 , a completed installation  70  of power seal bolt assembly  10  utilizes power seal bolt assembly  10  to releasably fasten a polymeric member  72  such as a valve head cover for an automobile engine to a metal member  74  such as an engine block. Completed installation  70  is provided by inserting power seal bolt assembly  10  in an insertion direction “T” such that compressible washer portion  32  is received in a counter-bore  76  created in polymeric member  72 . At the same time, retainer portion  30  is frictionally received within a through aperture  78  of polymeric member  72 . A through aperture diameter “V” of through aperture  78  is smaller than retainer outer diameter “M” of retainer portion  30  such that an interference or frictional fit is obtained between retainer portion  30  and an inner wall  79  defined by through aperture  78 . 
         [0031]    Threaded portion  24  of bolt  12  is threadably engaged with a threaded bore  80  created in metal member  74 . Threaded bore  80  can be a closed bore such as the bore shown in  FIG. 8 , or can also be a through threaded bore at the discretion of the manufacturer. Bolt  12  is rotated to complete the installation  70  such that threaded portion  24  in engagement with threaded bore  80  further pulls bolt  12  in the insertion direction “T” until shaft end face  42  of unthreaded shaft portion  22  contacts a contact surface  82  of metal member  74 . A counter-bore depth “U” of counter-bore  76  is less than the washer portion length “P” of compressible washer portion  32 . The greater thickness or length of compressible washer portion  32  compared to counter-bore depth “U” promotes compression of compressible washer portion  32  as bolt  12  is torqued into position. Axial compression of compressible washer portion  32  continues until second inner face  34  of washer  20  contacts a member outer surface  84  of polymeric member  72 . During compression of compressible washer portion  32 , the first and second outer and inner raised rings  52 ,  52 ′ and  54 ,  54 ′ respectively create fluid seals with each of the second inner face  34  of washer  20  and a counter-bore end face  86  of counter-bore  76 . Contact between shaft end face  42  of unthreaded shaft portion  22  and the contact surface  82  of metal member  74  also creates a compression limiting capability for power seal bolt assembly  10  to limit the compressive force applied to polymeric member  72  by bolt  12 . 
         [0032]    Referring again to each of  FIGS. 4 and 8 , with compressible washer retainer  28  positioned on unthreaded shaft portion  22  as shown in  FIG. 4 , the bolt-washer assembly  36  can be received within polymeric member  72  such that frictional contact between retainer portion  30  and inner wall  79  of polymeric member  72  will retain power seal bolt assembly  10  in frictional engagement with polymeric member  72  prior to engagement between threaded portion  24  and threaded bore  80  of metal member  74 . This provides a capability of preloading power seal bolt assemblies  10  in one or more locations of polymeric member  72  for shipment of polymeric member  72  to an installation facility and subsequent installation of polymeric member  72  with metal member  74 . With further reference also to  FIG. 7 , bolt  12  is frictionally held by contact with each of the flexible legs  58  during this interim period and before the completed installation  70  of  FIG. 8  is created. 
         [0033]    Referring to  FIG. 9 , and again to  FIGS. 5 and 8 , a completed installation  70 ′ of power seal bolt assembly  10 ′ utilizes power seal bolt assembly  10 ′ to releasably fasten a polymeric member  72 ′ such as a valve head cover for an automobile engine to metal member  74  such as an engine block. Polymeric member  72 ′ is modified from polymeric member  72  to include a reduced total height “W” and to eliminate counter-bore  76 . A compressible washer portion  32 ′ is modified from compressible washer portion  32  such that compressible washer portion  32 ′ is adapted to separately receive a retainer portion  30 ′ such that compressible washer portion  32 ′ and retainer portion  30 ′ are not required to be homogenously connected. Retainer portion  30 ′ can include an insertion portion  88  partially received in and frictionally engaged by compressible washer portion  32 ′. Completed installation  70 ′ is created by inserting power seal bolt assembly  10  in insertion direction “T” such that compressible washer portion  32 ′ directly contacts an outer facing surface  90  of polymeric member  72 ′. At the same time, retainer portion  30 ′ is frictionally received within a through aperture  78 ′ of polymeric member  72 ′. A through aperture diameter “V” of through aperture  78 ′ is smaller than retainer outer diameter “M” of retainer portion  30 ′ such that an interference or frictional fit is obtained between retainer portion  30 ′ and an inner wall  79 ′ defined by through aperture  78 ′. 
         [0034]    Threaded portion  24  of bolt  12  is threadably engaged with threaded bore  80  created in metal member  74 . Bolt  12  is rotated to complete the installation  70 ′ such that threaded portion  24  in engagement with threaded bore  80  further pulls bolt  12  in the insertion direction “T” until shaft end face  42  of unthreaded shaft portion  22  contacts the contact surface  82  of metal member  74 . During threaded engagement of threaded portion  24  washer portion length “P” of compressible washer portion  32 ′ is reduced by compression of compressible washer portion  32 ′, and a gasket  92  installed between polymeric member  72 ′ and metal member  74  is also partially compressed. 
         [0035]    Combined axial compression of compressible washer portion  32 ′ and gasket  92  continues until shaft end face  42  of unthreaded shaft portion  22  contacts contact surface  82  of metal member  74 . During compression of compressible washer portion  32 ′. With further reference to  FIG. 8 , the first and second outer and inner raised rings  52 ,  52 ′ and  54 ,  54 ′ can be entirely eliminated from compressible washer portion  32 ′, or only one each of first and second outer and inner raised rings  52  or  52 ′ and  54  or  54 ′ can be used. In several embodiments, a diameter of a modified washer  20 ′ can be substantially equal to a diameter of compressible washer portion  32 ′. 
         [0036]    Power seal bolt assemblies  10 ,  10 ′ of the present disclosure provide several advantages. By co-molding and combining or frictionally engaging the compressible washer portion  32  with the retainer portion  30  to create compressible washer retainer  28 , a one-piece molded part or a frictionally engaged assembly can be used which provides both a retention capability for bolt  12  and frictional engagement of compressible washer retainer  28  with polymeric member  72  so the power seal bolt assembly  10  can be pre-inserted and shipped with polymeric member  72 . By providing a compressible feature of compressible washer portion  32  a fluid-tight seal can also be created when power seal bolt assemblies  10  of the present disclosure are torqued into position. In addition, by incorporating the shaft end face  42  onto unthreaded shaft portion  22  of bolt  12  a compression limiting capability is also provided for power seal bolt assembly  10 . The compressible feature of compressible washer portion  32  also includes compensation for misalignment and construction tolerances between the first and second workpieces. Also, by controlling a total length of unthreaded shaft portion  22  and threaded portion  24  of bolt  12 , different thicknesses for the polymeric member  72  can be accommodated using a commonly sized compressible washer retainer  28  of the present disclosure.