Patent Abstract:
A fastener is disclosed for sealed engagement with a workpiece. The fastener has a head having a lower face, and a shank extends from the lower surface of the head. A groove is formed in the lower surface, the groove having an inner wall and an outer wall. The inner wall has a proximal end which is adjacent the lower surface of the head and which is disposed radially remotely from the shank. A sealing element, such as an O-ring, is disposed at least partially within the groove. The groove may be configured so that a distal end of the inner wall is near to the axis of the shank than is the proximal end of the inner wall.

Full Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a Continued Prosecution Application under 37 C.F.R. § 1.53(d) based upon parent application Ser. No. 08/683,818, now abandoned. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     REFERENCE TO A “MICROFICHE APPENDIX” 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     This invention is directed generally to the fastener arts, but specifically to sealing fasteners having an undercut groove or channel in the underside of a fastener head for accommodating a sealing element, (specifically an o&#39;ring type elastomer) to accomplish sealing engagement with a workpiece having a threaded or unthreaded aperture. In general sealing fasteners are well known in the art, spurred on by the space age when finding new ways to seal fasteners became a primary focus. Outdated methods such as copper washers, rtv sealant, etc. are still used to seal fasteners in some applications; however, as the sophistication our world increases, the need for reliable methods of sealing fasteners also becomes increasingly more crucial. That is why many of these inferior methods of sealing are gradually being phased out and replaced with more reliable sealing methods. One of the best ways to accomplish this task is to provide a formed groove or channel in a normally flat undersurface of the fastener head to accommodate a sealing element that is held captive in the fastener head, also achieving metal to metal contact with the workpiece and the outer rim of the fastener head. However, all previous designs have not properly calculated the groove in the fastener head. This causes sealing element failure. In static sealing threaded fastener designs, it is crucial that the groove be precisely calculated in depth, volume, angle, and configuration if one hopes to maintain a positive “seal line” between the sealed surfaces. Without a precisely calculated groove design, the sealing element will either compress too much or not compress enough. For example, by using too large a sealing element it will not have enough volumetric space to accommodate it and will, therefore, force the excess volume of the sealing element beyond the groove area, causing the sealing element to extrude and pinch between the screw and the workpiece in a process known as extruding “on the take down face”. Another problem associated with previous designs is a process known as compression set. A sealing element must maintain a continuous “seal line” between the sealed surfaces. The establishment of this “seal line” is a function of groove design and sealing element cross section which determines the proper amount of squeeze (compression) on the sealing element. When a sealing element volume is larger than the area sealed, it causes excessive squeeze on the sealing element. This excessive squeeze causes sealing element deformation and loss of seal integrity, therefore rendering the sealing element ineffective. A third problem with previous designs is a process known as installation damage. As the fastener is being assembled to the workpiece, the excessive compression of the sealing element causes it to stick between the end wall surface of the groove in the fastener head and the workpiece, thereby twisting and deforming the sealing element and/or causing sealing element extrusion as previously mentioned. When too small a sealing element is used, there is not enough compression on the sealing element to maintain a continuous “seal line” between the sealed surfaces rendering its sealing capabilities useless. As an additional matter, it is vital that fasteners of this type be cold formed without removal of material from the shank or head portion of the fastener since an alteration of this type weakens the grain flow structure of the fastener in a high stress area and greatly increases the chances of head separation either before or after the fastener is tightened to its proper torque specification. It is extremely important that these fasteners maintain the ability to withstand the stress involved when tightened to normal torque values. The main reason for a modification of this type is that during cold forming or roll forming threading operations there is generally an external screw thread of up to one and one half thread pitches of incomplete thread between the undersurface of the fastener head to where the thread begins on the fastener shank. This unthreaded portion would normally keep the mating surfaces from achieving adequate metal to metal contact thus preventing a positive seal. However, using a smaller diameter cold forming wire than is normally used when manufacturing similar products of the same diameter affords the flexibility necessary to maintain high quality while forming the fastener to the minimum pitch diameter. This in conjunction with limiting the unthreaded length from the head to a maximum of 1 incomplete thread assures a complete metal to metal engagement with a workpiece having a standard size threaded or unthreaded aperture. This eliminates the need for any alterations to the fastener as mentioned above and thereby maintains fastener integrity. 
     BRIEF SUMMARY OF THE INVENTION 
     It is the general object of this invention to provide a novel fastener having a formed groove or channel precisely calculated in depth, volume, angle and configuration to greatly improve reliability and substantially eliminate the problems associated with prior art design. 
     A more specific object is to provide a fastener with a formed annular groove or channel having a sealing element completely captive in said groove and maintaining a continuous positive “seal line” between the fastener and the workpiece while maintaining a stable metal to metal contact between fastener head and the workpiece. 
     Another object is to provide a fastener with a formed groove or channel in the shape of a trapezoid precisely calculated in depth, volume, and angle to achieve a predetermined percentage of compression on the sealing element preventing sealing element deformation and assuring sealing element reliability and reusability. 
     It is another object to provide a fastener with a formed groove or channel in the shape of a parallelogram precisely calculated in depth, angle, and volume like the trapezoidal shaped groove to assures a continuous positive “seal line” in larger clearance hole applications. 
     It is another object to manufacture a fastener with a formed groove or channel in such a way that assures complete mating of the fastener with the workpiece in metal to metal contact without materially altering the physical dimensions of the fastener, thereby retaining the shear and tension characteristics of the said fastener. This prevents head separation by maintaining the necessary strength to withstand the stress involved with using standard torque values. 
     It is a related object to provide a fastener with a formed groove or channel of the highest quality, reliability of material, and performance. Our design has eliminated the guess work by precisely designing the fastener to assure confidence in aerospace applications, but at the same time, keeping the manufacturing costs down to make it affordable for all industries. 
     It is another object to have a design method that is versatile enough to use in similar applications such as nuts &amp; rivets and special product configurations. This allows the flexibility necessary to design new products quickly and easily without excessive cost to the customer and at the same time assuring fastener sealing reliability. 
     A. An annular groove or channel formed in the undersurface of a threaded or unthreaded fastener head and combined there with a sealing element (o&#39;ring). The fastener is comprised of a vertically disposed externally threaded elongate shank extending from an enlarged fastener head that contains an annular groove or channel substantially similar to the shape of a trapezoid formed in the essentially flat undersurface of the fastener head and combined there with a sealing element (specifically an o&#39;ring type elastomer). The said fastener shank is designed to enter into complete engagement with a mating workpiece having an internally threaded or unthreaded aperture. When threaded the shank of the fastener has a screw thread profile that defines a minimum major or thread crest diameter, a minor diameter or thread root diameter, a pitch diameter, and flanks. The unthreaded portion of the fastener shank directly adjacent to the fastener head would have a maximum length of 1 incomplete thread. The said unthreaded diameter of the fastener shank is in accordance with the minimum pitch diameter as specified by IFI standards. The inner wall surface of the groove or channel begins from the periphery of the pitch diameter and is inclined up and outward concentric with the axis of the fastener shank to a predetermined depth, and there connects with a relatively flat annular end wall surface that extends radially outward concentric with the axis of the fastener shank and parallel to the undersurface of the fastener head. The outer wall of the groove having a decline down and outward concentric with the axis of the fastener shank that ends at the undersurface of the fastener head completing the trapezoidal shaped groove configuration. 
     B. When used to seal a workpiece having an oversized threaded aperture the enlarged fastener head would be 1 to 5 times larger than the fastener head described above. This fastener head contains an annular groove or channel substantially similar to the shape of a parallelogram formed in the essentially flat undersurface of the fastener head and combined there with a sealing element (specifically an o&#39;ring type elastomer).The shank of the fastener having a screw thread profile that defines a minimum major or thread crest diameter, a minor diameter or thread root diameter, a pitch diameter, and flanks. The said fastener shank is designed to enter into complete engagement with a workpiece having an oversized internally threaded aperture. The said groove has an inner wall surface that begins from the periphery of the theoretical pitch diameter (calculated as the pitch diameter of a fastener having a screw thread 1-2 sizes larger than the threaded aperture to be sealed) and is inclined up and inward frusta-conically concentric with the axis of the fastener shank and there connects with a relatively flat annular end wall surface that extends radially outward concentric with the axis of the fastener shank and parallel to the undersurface of the fastener head. The outer wall of said groove having a decline down and outward frusta-conically concentric with the axis of said fastener shank that ends at the point where the said outer wall meets the undersurface of the fastener head completing the parallelogram shaped groove configuration. 
     C. The nut is comprised of a nut body that has an external wrenching portion normally of a conventional hexagonal configuration. The nut body has a nut face surface that is generally planar and normal to the axis of the said nut body. Incorporated through the nucleus of the nut body is a threaded bore. The said threaded bore having a screw thread profile that defines a minor diameter or thread crest diameter, a minimum major diameter or thread root diameter, and flanks. The nut body is designed to enter into complete engagement with a workpiece having an externally threaded stud or screw extruding from a threaded or unthreaded aperture. An annular groove substantially similar to the shape of a trapezoid is formed in the essentially flat nut face and is combined there with a sealing element (specifically an o&#39;ring type elastomer). The said groove has an outer wall surface that begins at a precalculated outer groove dimension and is inclined up and inward frusta-conically concentric with the axis of the threaded bore, there it intersects with the relatively flat axially facing base surface or end wall surface that extends radially inward into the nucleus of the threaded bore concentric with the axis of the threaded bore and parallel to the nut face. As the sealing element is compressed between the end wall surface of the groove and the facing surface of the workpiece the sealing element has a controlled inward radial flow into the threaded bore to connect with the threads of the mating fastener shank. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIGS. 1A and 1B are an illustration of the basic concept of the threaded self-sealing fastener and self-sealing nut as employed in a through hole application. 
     FIG. 2 is a threaded self-sealing fastener showing an enlarged view of the section that illustrates the sealing element in the trapezoid shaped groove prior to engagement with its mating surface. 
     FIG. 3 is an enlarged view of a threaded self-sealing fastener that illustrates the sealing element in the trapezoid shaped groove and the sealing relationship with its mating surface at complete engagement. 
     FIG. 4 is an enlarged view of a threaded self-sealing nut that illustrates the sealing element in the trapezoid shaped groove prior to engagement with its mating surface. 
     FIG. 5 is an enlarged view of an oversized head threaded self-sealing fastener that illustrates the sealing element in the parallelogram shaped groove and the sealing relationship with its mating surface at complete engagement. 
     FIG. 6 is an enlarged view of a threaded self-sealing nut that illustrates the sealing element and groove configuration similar to the trapezoidal shaped groove configuration as shown in FIGS. 2&amp;3. Also illustrated is the sealing relationship with its mating part at complete engagement. 
     FIG. 7 is an enlarged view of a prior art threaded sealing fastener that illustrates its inability to effectively seal and how its violation of fastener integrity effects the sealing relationship with its mating surface at complete engagement. 
     FIG. 8 is an enlarged view of a non-threaded self-sealing solid rivet that illustrates the sealing element in the trapezoid shaped groove and the sealing relationship with its mating part at complete engagement. 
     FIG. 9 is an enlarged view of a non-threaded structural self-sealing blind rivet that illustrates two separate sealing elements with trapezoidal shaped groove configurations similar to those as illustrated in FIGS.  2 , 3 &amp; 6 . Also illustrated is the sealing relationship with their respective mating parts at complete engagement. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and initially to FIG.  7 . This undercut sealing threaded fastener in accordance with prior art construction will be described first. The fastener illustrated in FIG. 7 is substantially similar to the fastener construction shown in U.S. Pat. No. 4,701,088 by Crull, to which reference is also invited. It should be noted that the drawings of the Crull patent illustrates an ineffectual sealing fastener assembly. As shown in FIG. 7 removal of material from the fastener shank weakens the grain flow structure in a high stress area, thus when the fastener is tightened to standard torque specifications, head/shank separation is to be expected. The material removal also creates a significant gap between the fastener and workpiece. This in combination with groove angle and o&#39;ring volume larger than the groove volume makes o&#39;ring extrusion and/or o&#39;ring compression set inevitable. However, Crull is considered to be the best prior art. 
     As shown in FIG. 7 the prior art fastener  30  is in full engagement with the workpiece  42 . Metal has been removed at the area  56  of the fastener shank  32 . This was intended to allow the fastener shank  32  to freely advance in relation to the workpiece opening  60 . However, it should be noted that this removal of material from the area  56  of the fastener shank  32  disrupts the grain flow structure and weakens the fastener  30  in a high stress area  56 . This increases the likelihood of separation between the fastener head  34  and the fastener shank  32  at the unthreaded area  56  when the fastener  30  is tightened to normal torque standards. It should be further noted that in their method of sealing, Crull utilizes a sealing ring  48  preferably a torus in form and defines a volume greater than the volume defined by the undercut groove  44 . The material removal from the area  56  of the fastener shank  32  creates a significant gap at the workpiece opening  60  between the area  56  of the fastener shank  32  and the workpiece  42 . This material removal at the area  56  in conjunction with the oversized sealing ring  48  and the inner wall  64  angle of the groove  44  shown as 90 degrees from the unthreaded portion  56  into the fastener head  34  at the groove  44  causes the sealing ring  48  to extrude into the gap at the workpiece opening  60  as the fastener  30  is tightened to full engagement with the workpiece  42 . When this extrusion occurs it takes away from the volume of the sealing ring  48  in the groove  44 . This causes an inadequate “seal line” between the sealing ring  48 , the facing surface  42 A, and the end wall surface  66 . When external pressure is applied to the fastener head  34  the volume reduction increases allowing the fluid or pressure to pass around the sealing ring  48  causing the edges of the o&#39;ring on the low pressure or downstream side of the groove to exhibit a chewed or chipped appearance as the “seal line” is corrupted. This fluid or pressure would follow a path traveling between the workpiece  42  and the fastener  30  more specifically at the point where the annular flat surface portion  70  of the workpiece  42  mates with the undersurface  46  of the fastener head  34  from there traveling up between the sealing ring  48  and the outer wall  68  of the groove  44  then between the sealing ring  48  and the end wall surface  66  and from there traveling down between the sealing ring  48  and the inner wall  64  of the groove  44  and through the workpiece opening  60  between the sealing ring  48  and the relieved area  56  of the fastener shank  32  into the component product that was to be sealed. This sealing ring is incorporated in a groove  44  with the inner wall  64  angle at substantially 90 degrees from the unthreaded portion  56  into the groove  44  and the outer wall  68  angle substantially 45 degrees relative to the axial direction of the fastener shank  32 . First it should be recognized that to have an inner wall  64  angle of 90 degrees from the unthreaded portion  56  into groove  44  is impractical and costly to manufacture. It should be further recognized that to have an inner wall  64  angle of 90 degrees from the unthreaded portion  56  into groove  44  and outer wall  68  angle substantially at 45 degrees will cause unequal distribution of the sealing ring volume  48 . This in conjunction with the oversized sealing ring  48  causes a problem known as installation damage that occurs when the fastener  30  is fastened to the workpiece  42 . The excess volume of the sealing ring  48  is forced out of the groove  44 . This in combination with the turning pressure applied to the sealing ring as it is compressed causes the sealing ring  48  to twist at  20  the same time it is pinched between the under surface  46  of the fastener head  34  and the annular flat surface portion  70  of the workpiece  42 . Not only does this cause the deformation of the sealing ring  48  compromising seal integrity, it also gives a spongy or false torque reading. This usually results in the fastener head  34  backing away from the workpiece  42  during the product operation. Again it should be noted that by incorporating a sealing ring  48  with a volume larger than the volume of the groove  44  that is to be filled will cause compression set and/or extrusion of the sealing ring  48  as previously described. Discussing now the effects of compression set which is a different variation of the same problem. As previously stated Crull utilizes a sealing ring  48  preferably a torus in form and defines a volume greater than the volume defined by the undercut groove  44 . This excess sealing ring  48  volume causes extreme compression (squeeze) on the sealing ring  48  as the sealing ring  48  is compressed between the end wall surface  66  of the groove  44  and the facing surface  42 A of the workpiece  42 . This extreme compression on the sealing ring  48  stresses the sealing ring  48  beyond its deflection endurance point causing the sealing ring  48  to lose seal integrity. The sealing ring  48  becomes permanently deformed into a flat sided oval shape, the flat sides of which were the original seal interface under compression before failure. This prevents the sealing ring  48  from exerting the necessary compression force to maintain a positive “seal line” between the end wall surface  66  of the groove  44  and the facing surface  42 A of the workpiece  42 . 
     Turning now to FIGS. 1A-6. The obvious advantages of our novel threaded and unthreaded self-sealing fastener invention will be fully understood by the following detailed descriptions that demonstrate how the deficiencies of the prior art sealing fastener as illustrated in FIG. 7 have been avoided. FIGS. 1A and 1B are a full view of the basic concept of the threaded self-sealing fastener and self-sealing nut as employed in a through hole application. FIGS. 2-9 view only a partial section of the self-sealing fastener referenced as number  30 . It is to be understood that this fastener  30  may generally be considered as a bolt, screw, or rivet type fastener that is characterized by an elongated shank  32  that extends axially from an enlarged fastener head  34  of a generally cylindrical arrangement that contains an annular groove or channel  44  substantially similar to the shape of a trapezoid formed in the essentially flat undersurface  46  of the fastener head  34  and combined there with a sealing element  48  (specifically an o&#39;ring type elastomer).or as in FIGS. 4&amp;6 a self-sealing nut type fastener  12  that is characterized by a nut body  12  having a threaded center bore  13  through which the threads  28  of a mating fastener shank  75  contact axially, and having an annular groove  44  substantially similar to the shape of a trapezoid formed in the essentially flat nut face  22  that is combined there with a sealing element  48  (specifically an o&#39;ring type elastomer). The head  34  or the nut body  12  may vary considerably in dimension, style, or configuration although the basic concept of the groove  44  design would remain the same. Referring first to the threaded self-sealing fastener  30  with a trapezoidal shaped groove  44  as illustrated in FIGS. 2&amp;3, the fastener shank  32  of the fastener  30  has screw threads defined by reference number  33 . These threads  33 , define a minimum major or thread crest diameter  36 , a minor diameter or thread root diameter  31 , flanks  35 , a pitch diameter shown generally by reference number  43 , and the unthreaded diameter defined by reference number  40 . This unthreaded diameter  40  is substantially similar to the minimum pitch diameter as specified by IFI standards. This unthreaded diameter  40  has an unthreaded grip length  37  that begins at the periphery of the pitch diameter  41  directly adjacent to the fastener head  34  and extends axially outward from the fastener head  34  on the fastener shank  32  and ends at point  38  on the fastener shank  32  being a maximum of 1 incomplete thread from the fastener head  34 . The self-sealing fastener  30  as shown in FIGS. 2&amp;3 has a fastener shank  32  that is formed with a cold forming wire that is substantially equal with the minimum pitch diameter of the screw. This diameter wire is smaller than the cold forming wire that is normally used when manufacturing similar products of the same diameter. This assures that the fastener  30  will maintain high quality while forming the fastener shank  32  to the minimum pitch diameter. This in conjunction with limiting the unthreaded grip length  37  of the unthreaded diameter  40  on the fastener shank  32  directly adjacent to the fastener head  34  to a maximum of 1 incomplete thread assures that the fastener  30  will achieve a complete metal to metal engagement between the outer rim  70  of the fastener head  34  and the facing surface  42   a  of the workpiece  42  having an internally threaded aperture with the standard thread run out. This eliminates the need for material removal from the unthreaded diameter  40  of the fastener shank  32  as in the case of prior art design as illustrated in FIG.  7 . In addition to being practical and inexpensive to manufacture, our design significantly decreases the gap at the workpiece opening  60  allowing the fastener  30  to achieve a closer tolerance between the fastener shank  32  at the unthreaded diameter  40  of the fastener  30 . This in conjunction with precisely calculating the sealing element  48  maximum or uncompressed volume to be substantially similar to the minimum volume of the trapezoid shaped groove  44  allows the sealing element  48  to be held completely captive within the groove  44  and eliminates the possibility of o&#39;ring extrusion between the unthreaded diameter  40  of the fastener shank  32  and the workpiece opening  60  of the workpiece  42 . As the fastener shank  32  is brought into engagement with the threads  27  of mating workpiece  42  the sealing element  48  is equally distributed within the groove  44  and the fastener head  34  of the fastener  30  is brought into complete metal to metal engagement between the outer rim  70  of the fastener head  34  and the facing surface  42   a  of the workpiece  42 . Without the removal of material from the unthreaded diameter  40  of the fastener shank  32  the fastener  30  maintains an uninterrupted material grain flow structure. Thus the fastener  30  retains the tensile and tension characteristics necessary to maintain fastener integrity in this high stress area (unthreaded diameter  40 ) eliminating the danger of head separation when the fastener head  34  of the fastener  30  is tightened into full engagement with the workpiece  42  using standard torque values. 
     From the periphery of the pitch diameter  41  the inner wall  92  of the groove  44  is inclined up and outward into the fastener head  34  frusta-conically concentric with the axis of the fastener shank  32  substantially in the order of 10 degrees forming the inner wall  92  of the groove  44 , at this juncture the inner wall  92  intersects with the relatively flat end wall surface  66 . This end wall surface  66  extends radially outward concentric with the axis of the fastener shank  32  and intersects with the outer wall  93  which declines down and outward fiusta-conically concentric with the axis of the fastener shank  32  substantially in the order of 10 degrees ending at the undersurface of the fastener head  34 , and creating a groove configuration that is substantially similar to the shape of a trapezoid. This trapezoidal shaped groove  44  configuration is incorporated with a sealing element  48  the material of which is generally composed of but not limited to a rubber or rubber based composition and is ideally a torus in cross sectional configuration. The inner wall  92  and the outer wall  93  of the groove  44  enter into the fastener head  34  to connect with the end wall surface  66  substantially equal in wall depth and degree of angle, the wall angles being substantially in the order of 10 degrees. This is vital to assure a proper seating of the sealing element  48  within the groove  44 . The maximum sealing element  48  volume is substantially similar to the minimum volume of the trapezoidal shaped groove  44 . This in conjunction with the inner wall  92  and the outer wall  93  of the groove  44  being substantially equal in wall depth and degree of angle forces the sealing element  48  to be equally distributed within the groove  44 . As the sealing element  48  is compressed to its precalculated rate the sealing element  48  extends radially outward concentric with the axis of the fastener shank  32  being guided and held captive by the inner wall  92  of the groove  44  and the outer wall  93  of the groove  44  forcing the sealing element  48  into a perfect seat within the groove  44  and eliminating the possibility of installation damage as the fastener  30  is brought into complete engagement with the mating workpiece  42 . A positive metal to metal engagement is achieved between the outer rim  70  of the fastener head  34  and the facing surface  42   a  of the workpiece  42 . This eliminates sealing element  48  extrusion in this area and prevents the fastener  30  from backing away from the workpiece  42  as the fastener  30  is tightened into full engagement with the relative workpiece  42 . Metal to metal contact is also necessary to achieve an accurate torque reading as the fastener  30  is tightened to normal torque specifications. The inside diameter of the sealing element  48  is slightly smaller than the inner wall  92  diameter of the groove  44  where the inner wall  92  intersects with the periphery of the pitch diameter  41  at the base of the groove  44  on the fastener shank  32 . This causes the retention of the sealing element  48  in the groove  44  prior to engagement with mating workpiece  42 . As previously stated the sealing element  48  is designed not to exceed the volume of the groove  44  by having a maximum or uncompressed sealing element  48  volume that would be substantially similar to the minimum volume of the trapezoidal shaped groove  44 , keeping in mind the outward radial flow of the sealing element  48  so that the groove  44  would receive and accommodate the full volume of the sealing element  48 . The sealing element  48  is compressed (squeezed) between the end wall surface  66  of the groove  44  and the facing surface  42   a  of the workpiece  42  to a percentage that is precisely calculated to apply pressure on the sealing element  48  making the sealing element  48  compression a minimum of 25%; this is the minimum compression force necessary to assure a continuous positive “seal line” between all sealed surfaces. A maximum sealing element  48  compression of 40% is necessary to maintain seal integrity. Keeping the sealing element  48  compression below the deflection endurance point of approximately 42% prevents sealing element  48  deformation and also retains the proper seal interface under compression assuring a continuous positive “seal line” between all sealed surfaces, and eliminating the possibility of compression set, as is common with excessive sealing element  48  compression (squeeze) such as is illustrated with the prior art fastener design of FIG.  7 . Our design is created to maximize the optimum sealing performance of the sealing element  48 , and to maintain seal integrity providing a completely reliable and reusable product. 
     Referring now to the threaded self-sealing fastener with a parallelogram shaped groove as illustrated in FIG.  5 . This fastener  30  is similar the fastener  30  with the trapezoidal shaped groove  44  as illustrated in FIGS. 2&amp;3. However, the differences and purpose of this fastener will be fully understood by the following description of FIG.  5 . This fastener  30  contains a fastener head  34  that may vary considerably in dimension, style, or configuration. This fastener  30  may generally be considered as a bolt, screw, or rivet type fastener that is characterized by an elongated shank  32  that extends axially from an enlarged fastener head  34  of a generally cylindrical arrangement that contains an annular groove or channel  44  substantially similar to the shape of a parallelogram formed in the essentially flat undersurface  46  of the fastener head  34  and combined there with a sealing element  48  (specifically an o&#39;ring type elastomer). The fastener shank  32  of the fastener  30  has screw threads defined by reference number  33 . These threads  33 , define a minimum major or thread crest diameter  36 , a minor diameter or thread root diameter  31 , and flanks  35 . No reference is made to a pitch diameter since the pitch diameter is not crucial to this design. However, instead of the standard pitch diameter a theoretical pitch diameter is shown and is generally referenced by number  47 . This fastener  30  is used primarily in applications where the threaded aperture  60  of the workpiece  42  is oversized to the extent that it would not allow the sealing element  48  in the trapezoidal groove configuration  44 , as illustrated in FIGS. 2&amp;3, to achieve a proper seal engagement with the workpiece  42  and therefore a positive “seal line” could not be achieved between the groove  44  in the fastener head  34  and the workpiece  42 . To accommodate the parallelogram shaped groove  44  the head  34  size is one to five times larger than the head  34  size of the fastener  30  with the trapezoidal shaped groove  44  as illustrated in FIGS. 2&amp;3 that would normally be used to seal a threaded aperture of this diameter. The inner wall  92  of the groove  44  has an outside diameter that is larger than the outside diameter of the threaded aperture  60 . This section is referred to as the theoretical pitch diameter  47 . From the periphery of this theoretical pitch diameter  47 , the inner wall  92  of the groove  44  inclines up and inward into the fastener head  34  frusta-conically concentric with the axis of the fastener shank  32  substantially in the order of 20 degrees into the groove  44 , and there intersects with the relatively flat end wall surface  66 . This end wall surface  66  extends radially outward concentric with the axis of the fastener shank  32  and parallel with the relatively flat undersurface  46  of fastener head  34  and at this juncture intersects with the outer wall  93  of the groove  44  which declines down and outward frusta-conically concentric with the axis of the fastener shank  32  at an angle substantially in the order of 20 degrees ending at the undersurface  46  of the fastener head  34  creating a groove  44  configuration substantially similar to the shape of a parallelogram. The inner wall  92  and the outer wall  93  enter into the fastener head  34  to intersect with the end wall surface  66  substantially equal in wall depth and degree of angle. The inside diameter of the sealing element  48  is smaller than the theoretical pitch diameter  47 . The sealing element  48  is designed to stretch up to 5% upon assembly into the fastener head  34  and snaps securely in place being held captive within the groove  44 . This causes the retention of the sealing element  48  in the groove  44  even prior to assembly with the mating workpiece  42 . This parallelogram shaped groove  44  configuration is incorporated with a sealing element  48 , the material of which is generally composed of but not limited to a rubber or rubber based composition, which is ideally a torus in cross sectional configuration. The inner wall  92  and the outer wall  93  of the groove  44  enter into the fastener head  34  to connect with the end wall surface  66  substantially equal in wall depth and degree of angle, the wall angles being substantially in the order of 20 degrees. This is vital to assure a proper seating of the sealing element  48  within the groove  44 . The maximum sealing element  48  volume is substantially similar to the minimum volume of the parallelogram shaped groove  44 . This in conjunction with the inner wall  92  and the outer wall  93  of the groove  44  being substantially equal in wall depth and degree of angle forces the sealing element  48  to be equally distributed within the groove  44 . As the sealing element  48  is compressed to its precalculated rate the sealing element  48  extends radially outward concentric with the axis of the fastener shank  32  being guided and held captive by the inner wall  92  of the groove  44  and the outer wall  93  of the groove  44  forcing the sealing element  48  into a perfect seat within the groove  44  and eliminating the possibility of installation damage as the fastener  30  is brought into complete engagement with the mating workpiece  42 . 
     A positive metal to metal engagement is achieved between the outer rim  70  of the fastener head  34  and the facing surface  42   a  of the workpiece  42 . This eliminates sealing element  48  extrusion in this area and prevents the fastener  30  from backing away from the workpiece  42  as the fastener  30  is tightened into fill engagement with the relative workpiece  42 . Metal to metal contact is also necessary to achieve an accurate torque reading as the fastener  30  is tightened to normal torque specifications. As previously stated the sealing element  48  is designed not to exceed the volume of the groove  44  by having a maximum sealing element  48  volume that would be substantially similar to the minimum volume of the parallelogram shaped groove  44 , keeping in mind the outward radial flow of the sealing element  48  so that the groove  44  would receive and accommodate the f u ill volume of the sealing element  48 . The sealing element  48  is compressed (squeezed) between the end wall surface  66  of the groove  44  and the facing surface  42   a  of the workpiece  42  to a percentage that is precisely calculated to apply pressure on the sealing element  48  making the sealing element  48  compression a minimum of 25%; this is the minimum compression force necessary to assure a continuous positive “seal line” between all sealed surfaces. A maximum sealing element  48  compression of 40% is necessary to maintain seal integrity. Keeping the sealing element  48  compression below the deflection endurance point of approximately 42% prevents sealing element  48  deformation and also retains the proper seal interface under compression assuring a continuous positive “seal line” between all sealed surfaces, and eliminating the possibility of compression set, as is common with excessive sealing element  48  compression. Our design is created to maximize the optimum sealing performance of the sealing element  48 , and to maintain seal integrity providing a completely reliable and reusable product. 
     Referring now to the threaded self-sealing nut as illustrated in FIGS. 4&amp;6 of our drawings. This nut  12  has a groove  44  design similar to that of the trapezoidal shaped groove  44  as illustrated in FIGS. 2&amp;3 previously described. The nut body  12  generally has an external wrenching portion  15  and is normally of a conventional hexagonal configuration. The nut body  12  has a nut face surface  22  that is generally planar and normal to the axis of the nut body  12  and having a threaded bore  13  through the nucleus of the nut body  12 . This threaded bore  13  having a screw thread profile that defines a minor diameter or thread crest diameter  17 , a minimum major diameter or thread root diameter  19 , and flanks  20 . The said nut body  12  is designed to enter into complete engagement with a workpiece having an externally threaded shank  75  extruding from the aperture  60  of the workpiece  42 . An annular groove  44  is formed in the nut face  22  defined by a frusta-conical radial inward annular wall surface  16  and an axially facing base surface or end wall surface  66 . Beginning at the point where the nut face  22  intersects with the outer wall  16  of the groove  44 , this outer wall  16  is inclined up and inward substantially in the order of 10 degrees frusta-conically concentric with the axis of the threaded bore  13  penetrating into the nut body  12  forming the outer wall  16  of the groove  44 . There it intersects with a relatively flat end wall surface  66 . This end wall surface  66  extends radially inward into the nucleus of the threaded bore  13  concentric with the axis of the threaded bore  13  and parallel with the nut face  22 . This assures that the entrance of the outward radial flow of the sealing element  48  will completely engage with the threads  28  of the mating fastener shank  75 . The inner wall being the threads  28  of the mating fastener shank  75  in conjunction with the outer wall  16  of the groove  44  creates a groove  44  configuration that is substantially similar to the shape of a trapezoid. This trapezoidal shaped groove  44  configuration is incorporated with a sealing element  48  that is bonded to the end wall surface  66  of the groove  44 . The sealing element  48  material is composed of but not limited to a rubber or rubber based composition and is ideally a torus in cross sectional configuration. The sealing element  48  volume in this design differs from that of the groove  44  design in FIGS.  2 , 3  &amp;  5  previously illustrated in that the threads  28  of the mating fastener shank  75  act as the inner wall of the groove  44  as illustrated in FIGS. 4&amp;6 of our drawings. Therefore, this design not only accounts for the volume of the actual groove  44  but also for the volume of the outward radial flow of the sealing element  48  into the threads  28  of the mating fastener shank  75 . As the nut body  12  is tightened into full engagement with the mating workpiece  42 , the sealing element  48  is guided by the outer wall  16  of the groove  44 . As the sealing element  48  is compressed between the end wall surface  66  of the groove  44  and the face surface  42   a  of the workpiece  42 . 
     The sealing element  48  being held captive by the outer wall  16  of the groove  44  forces the sealing element  48  to extend radially inward concentric with the axis of the threaded bore  13 , this forces the sealing element  48  into a perfect seal within the groove  44 . At the same time the sealing element  48  having a controlled inward radial flow into the threaded bore  13  achieves a positive seal engagement with the threads  28  of the mating fastener shank  75  and the nut  12  is brought into complete engagement with the mating workpiece  42 . A positive metal to metal engagement is achieved between the outer rim  24  of the nut  12  and the facing surface  42   a  of the workpiece  42 . This eliminates sealing element  48  extrusion in this area and prevents the nut  12  from backing away from the workpiece  42  as the nut  12  is tightened to full engagement with the relative workpiece  42 . Metal to metal contact is also necessary to achieve an accurate torque reading as the nut  12  is tightened to normal torque specifications. As previously stated this groove design as illustrated in FIGS. 4&amp;6 differs from the groove  44  design in FIGS.  2 , 3  &amp;  5  previously illustrated in that the threads  28  of the mating fastener shank  75  act as the inner wall of the groove  44  by accounting for the inward radial flow of the sealing element  48  the groove  44  would receive and accommodate the full volume of the sealing element  48 . This assures a positive engagement between the sealing element  48  and the threads  28  of the mating fastener shank  75 . As this occurs the sealing element  48  is compressed (squeezed) between the end wall surface  66  of the groove  44  and the facing surface  42   a  of the workpiece  42  to a percentage that is precisely calculated to apply pressure on the sealing element  48  making the sealing element  48  compression a minimum of 25%. This is the minimum compression force necessary to assure a continuous positive “seal line” between all sealed surfaces. A maximum sealing element  48  compression of 40% is necessary to maintain seal integrity. Keeping the sealing element  48  compression below the deflection endurance point of approximately 42% prevents sealing element  48  deformation and also retains the proper seal interface under compression assuring a continuous positive “seal line” between all sealed surfaces, and eliminating the possibility of compression set, as is common with excessive sealing element  48  compression. Our design is created to maximize the optimum sealing performance of the sealing element  48 , and to maintain seal integrity providing a completely reliable and reusable product. 
     Referring now to the unthreaded self-sealing fastener  20  as illustrated in FIG. 8 of our drawings. This unthreaded fastener  20  contains a fastener head  34  that may vary considerably in dimension, style, or configuration. This fastener  20  may generally be considered as a solid rivet type self-sealing fastener  20  that is characterized by a vertically disposed unthreaded elongated shank  32  that extends axially from an enlarged fastener head  34  that contains an annular groove or channel  44  substantially similar to the shape of a trapezoid formed in the essentially flat undersurface  46  of the fastener head  34  and is combined there with a sealing element  48  (specifically an o&#39;ring type elastomer). With the exception of the unthreaded fastener shank  32 , this fastener  20  is substantially similar to the fastener  30  with the trapezoidal shaped groove  44  configuration as shown in FIGS. 2&amp;3 of our drawings. Since the only difference between this fastener  20  and the fastener  30 , as shown in FIGS. 2&amp;3, is the way in which the fastener  20  is secured to the workpiece  42  instead of reiterating that which has already been described in detail, namely the groove  44  information as shown in FIGS. 2&amp;3, we will instead focus on how this fastener  20  differs from the fastener  30  of FIGS. 2&amp;3. This fastener  20  is designed to be inserted into a standard size unthreaded aperture  60  of a workpiece  42  in order to join the workpiece  42  with the workpiece  40  to make one component by forcing the workpiece  42  into full metal to metal engagement with the workpiece  40 . The unheaded portion  62  of the fastener shank  32  extends beyond the unthreaded aperture  60  of the workpiece  42 . This extended portion  62  of the fastener shank  32  would by the use of a solid rivet tool have pressure applied to both the extended portion  62  of the fastener shank  32  and the rivet head  34  simultaneously. This pressure causes the rivet shank  32  at the extended portion  62  to collapse up and outward against the workpiece  42  in the direction of the rivet head  34  securing the workpiece  40  with the workpiece  42 , as the compressed material  49  forms the head  81  from the previously extended portion  62  of the rivet shank  32 . At the same time the rivet head  34  is moved into complete metal to metal engagement with the workpiece  40 , the head  81  is formed from the previously extended material  62  and moved into complete metal to metal engagement with the workpiece  42 , thus securing the two workpieces and the rivet in place, while assuring a positive “seal line” with all sealed surfaces. 
     Now referring to the blind rivet of FIG.  9 . This unthreaded blind rivet  20  contains a fastener head  34  that may vary considerably in dimension, style, or configuration. This blind rivet  20  is generally considered as a structural flush break mechanically locked pull mandrel type self-sealing blind rivet  20  that is characterized by an unthreaded elongate shank  32  that extends axially from an enlarged fastener head  34  of a generally cylindrical arrangement. This blind rivet  20  assembly has an unthreaded aperture  65  through the nucleus of the blind rivet body  20 . This unthreaded aperture extends vertically from the top of the rivet head  34  to the end of the rivet shank  32 . This rivet  20  incorporates a mandrel  67  through the center of the aperture  65  in the blind rivet body  20 . This mandrel  67  mates with a self-sealing locking collar  45  at the trapezoidal shaped indention  49  in the enlarged fastener head  34 . A more detailed description is as follows; the mandrel  67  has a pre-formed head  25  having a semi-rounded cylindrical top surface  12  and a relatively flat under-surface  86 . This mandrel  67  also has mating collar locking teeth  85  on the mandrel shank  69 . These mating collar locking teeth  85  are angled down and out in the direction of the mandrel head  25  substantially in the order of 72 degrees. This mandrel shank  69  also has a threaded portion  78  at the end of the mandrel shank  69  opposite the mandrel head  25 . This threaded portion  78  mates with a mandrel pull tool to apply pulling pressure to the rivet body  20 . This pulling pressure draws the mandrel  67  away from the rivet head  34  causing the rivet shank  32  to be pulled through the aperture  65  forcing the rivet head  34  into complete engagement with the workpiece  42 . The collar  45  is a generally cylindrical arrangement. The outer wall  82  of the collar  45  is inclined up and outward from the collar face  72  frusta-conically concentric with the axis of the unthreaded aperture  65  substantially in the order of 25 degrees. The inner wall  50  angle is substantially in the order of 90 degrees through the nucleus of the collar  45  and the locking teeth  84  are angled up and inward substantially in the order of 72 degrees in the direction of the nucleus of the unthreaded aperture  65  opposite the direction of the collar face  72 . This collar face  72  has a groove or channel  54 . This groove  54  is substantially similar to the nut groove  44  design as illustrated in FIG.  6 . As the blind rivet  20  is mated with the workpiece  42 , the mandrel  67  has a pulling pressure applied at the threaded portion  78  of the mandrel  67 . This pressure pulls the mandrel  67  through the aperture  65  at the nucleus of the rivet body  20 . At the same time the pressure is applied to the threaded portion  78 , it is also applied to the collar  45  at the pull tool face  38  and at the mandrel undersurface  86  of the mandrel head  25 . As this pressure is applied to the collar  45 , it causes the collar  45  to engage with the mating locking teeth  85  of the mandrel  67  and pressure is also applied to the mandrel head  25 . This causes the rivet shank  32  to collapse at a pre-calculated rate moving the material next to the workpiece  42  to form a head  92  at the workpiece  42  opposite the rivet head  34  and securing the rivet  20  to the workpiece  42 . When this pressure is applied to the collar  45 , it forces the collar  45  into complete engagement with the trapezoidal shaped indention  49  in the fastener head  34  and metal to metal contact between the mating wall surface  47  and the angled wall surface  82  of the collar  45  is achieved. As the collar  45  engages with the trapezoidal shaped indention  49  in the fastener head  34 , the sealing element  46  (which is generally composed of but not limited to a rubber based composition and is ideally a torus in cross sectional configuration) is guided by the outer wall  17  of the groove  54  causing the sealing element to be compressed between the end wall surface  16  of the groove  54  and the collar face surface  72  in the rivet head  34 . This groove  54  design in FIG. 9 is substantially similar to the groove  44  design as illustrated in FIGS. 4&amp;6. The sealing element  46  volume in this design differs from that of the groove  44  design in FIGS.  2 , 3  &amp;  5  as illustrated in that the mating collar locking teeth  85  of the mandrel  67  act as the inner wall of the groove  54  as illustrated in FIG. 9 of our drawings. Therefore, this design not only accounts for the volume of the actual groove  54  but also for the volume of the outward radial flow of the sealing element  46  into the mating collar locking teeth  85  of the mandrel  67 . This assures that the sealing element  46  while being held captive in the groove  54  has a controlled inward radial flow into the nucleus of the rivet body  20  to connect into complete engagement with the mating collar locking teeth  85  of the mandrel  67  creating a positive seal. The distance between the end wall surface  16  of the groove  54  and the facing collar mating surface  72  is precisely calculated to apply pressure on the sealing element  46  and accounting for the inward radial flow of the sealing element  46  and the engagement of the sealing element  46 , with the mating collar locking teeth  85  of the mandrel  67 , the sealing element  46  squeeze would be a minimum of 25% assuring a continuous “seal line” between the sealed surfaces and a maximum squeeze of 40% to prevent sealing element  46  compression set thus maintaining a reliable seal. 
     As pressure is applied to the mandrel  67 , the tensile stress required for separation of the mandrel  67  is achieved at the precalculated mandrel breaking area  36  and the mandrel  67  breaks off flush with the top of the rivet head  34 . As the mandrel  67  breaks off flush with the rivet head  34 , the locking teeth  84  of the collar  45  snap back and lock tight with the mating collar locking teeth  85  on the mandrel  67  into full metal to metal engagement. This in turn brings the rivet head  34  into fill engagement with the workpiece  42 . As previously stated this enlarged fastener head  34  contains a formed groove or channel  44  in the undersurface  41  of the said head  34  that incorporates a sealing element  48  that is held captive in the groove  44 . Now describing the groove  44  as shown in FIG.  9 . This groove  44  is substantially similar to that of the trapezoidal shaped groove  44  configuration as illustrated in FIGS. 2&amp;3 of our drawings. From the periphery of the pitch diameter  41  the inner wall  92  of the groove  44  is inclined up and outward into the rivet head  34  frusta-conically concentric with the axis of the fastener shank  32  substantially in the order of 10 degrees forming the inner wall  92  of the groove  44 , at this juncture the inner wall  92  intersects with the relatively flat end wall surface  66 . This end wall surface  66  extends radially outward concentric with the axis of the fastener shank  32  and intersects with the outer wall  93  which declines down and outward frusta-conically concentric with the axis of the fastener shank  32  substantially in the order of 10 degrees ending at the undersurface of the rivet head  34 , creating a groove  44  configuration that is substantially similar to the shape of a trapezoid. This trapezoidal shaped groove  44  configuration is incorporated with a sealing element  48  the material of which is generally composed of but not limited to a rubber or rubber based composition and is ideally a torus in cross sectional configuration. The inner wall  92  and the outer wall  93  of the groove  44  enter into the rivet head  34  to connect with the end wall surface  66  substantially equal in wall depth and degree of angle, the wall angles being substantially in the order of 10 degrees. This is vital to assure a proper seating of the sealing element  48  within the groove  44 . The maximum sealing element  48  volume is substantially similar to the minimum volume of the trapezoidal shaped groove  44 . This in conjunction with the inner wall  92  and the outer wall  93  of the groove  44  being substantially equal in wall depth and degree of angle forces the sealing element  48  to be equally distributed within the groove  44 . As the sealing element  48  is compressed to its precalculated rate the sealing element  48  extends radially outward concentric with the axis of the fastener shank  32  being guided and held captive by the inner wall  92  of the groove  44  and the outer wall  93  of the groove  44  forcing the sealing element  48  into a perfect seat within the groove  44  and eliminating the possibility of installation damage as the rivet  20  is brought into complete engagement with the mating workpiece  42 . A positive metal to metal engagement is achieved between the outer rim  70  of the rivet head  34  and the facing surface  42   a  of the workpiece  42 . This eliminates sealing element  48  extrusion in this area and prevents the rivet  20  from backing away from the workpiece  42  as the rivet  20  is tightened into full engagement with the relative workpiece  42 . The inside diameter of the sealing element  48  is slightly smaller than the inner wall  92  diameter of the groove  44  where the inner wall  92  intersects with the periphery of the pitch diameter  41  at the base of the groove  44  on the rivet shank  32 . This causes the retention of the sealing element  48  in the groove  44  prior to engagement with mating workpiece  42 . As previously stated the sealing element  48  is designed not to exceed the volume of the groove  44  by having a maximum sealing element  48  volume that would be substantially similar to the minimum volume of the trapezoidal shaped groove  44 , keeping in mind the outward radial flow of the sealing element  48  so that the groove  44  would receive and accommodate the full volume of the sealing element  48 . The sealing element  48  is compressed (squeezed) between the end wall surface  66  of the groove  44  and the facing surface  42   a  of the workpiece  42  to a percentage that is precisely calculated to apply pressure on the sealing element  48  making the sealing element  48  compression a minimum of 25%, this is the minimum compression force necessary to assure a continuous positive “seal line” between all sealed surfaces. A maximum sealing element  48  compression of 40% is necessary to maintain seal integrity. Keeping the sealing element  48  compression below the deflection endurance point of approximately 42% prevents sealing element  48  deformation and also retains the proper seal interface under compression assuring a continuous positive “seal line” between all sealed surfaces, and eliminating the possibility of compression set, as is common with excessive sealing element  48  compression (squeeze). Our design is created to maximize the optimum sealing performance of the sealing element  48 , and to maintain seal integrity providing a completely reliable product. 
     We have described only the preferred form and application of our invention. It is intended that this present invention not be limited or restricted to the specific details as described herein, but that we reserve the right to any variations or modifications that may appear to those skilled in the art without departing from the spirit or scope of our invention as defined in the appended claims.

Technology Classification (CPC): 8