FASTENER ASSEMBLY WITH SEALING GROMMET

Abstract: A threaded fastener assembly (10) which includes a threaded fastener (12) over which is securely held an axially movable washer (14) with a resilient grommet fitted thereover (16). The threaded fastener assembly (10) is adapted to be preassembled in a first apertured work piece (50) such as a rocker arm cover which is to be mounted on a second apertured work piece (52) such as an engine block. The threaded fastener assembly (10) is retainable within the first apertured work piece (50) while holding the fastener in a freely axially movable configuration which permits the fastener to be moved into an elevated position to prevent the fastener from projecting through the bottom surface of the work piece, thus preventing interference with other surfaces and the structure provides seals for preventing fluid from leaking through the apertures.

Description: This invention relates to a fastener assembly according to the preamble portion of patent claim 1. In prior art fastener assemblies such as those shown in U.S. patent No. 4,732,519 solutions to various fastener assembly problems have been advanced. In the mentioned patent, a fastener is held in axially movable engagement within a washer and a rubber grommet stretched over the outside thereof to seal the aperture through which the assembly is inserted. While this patent provides a solution for a specific problem, it provides no solutions to both the problems of completely sealing an aperture against fluid flow from the inside of the assembled work pieces and securely pre-assembling an axially movable fastener in a work piece in an elevated position. In many instances, such as in the assembly of a rocker arm cover onto an engine block, fastener assemblies are required to seal the apertures in which they are inserted against fluid flow and to securely retain the assembly in an elevated position to avoid interference with surfaces on which the preassembled work piece may be placed during assembly or while in storage. A general object of the invention is to provide an axially movable threaded fastener assembly which completely seals the aperture through which it is installed against fluid flow from the inside of the work pieces which it fastens, and which retains a fastener in a freely axially movable configuration which permits the fastener to be moved into an elevated position with respect to a work piece with which it is preassembled to prevent the fastener from projecting through the bottom surface of the work piece, thus preventing interference with other surfaces. This object is attained by the features of patent claim 1. In accordance with the foregoing, the present invention comprises an axially movable threaded fastener assembly with a fastener, washer, and a grommet of rubber or other resilient sealing material which completely seals the apertures through which it is inserted, and prior to final installation, the assembly retains the fastener in an elevated position to prevent the fastener from projecting through the bottom surface of a work piece to prevent interference with outer surfaces. Further, in the present invention the amount of compression created by the fastener on the resilient grommet and the resilient gasket is limited. Further advantageous features are covered by subclaims. The features of the present invention may best be understood by reference to the following description, taken in connection with the accompanying drawing in which like reference numerals identify like elements, and in which: Fig. 1 is an exploded perspective view of the fastener assembly of the present invention showing the telescopic relationship between the fastener, washer means, and grommet; Fig. 2 is a partial sectional view of the preassembled fastener assembly in a partially assembled condition; Fig. 3 is a fragmentary partial sectional view of the fastener assembly as installed to fasten a first apertured work piece to a second apertured work piece; Fig. 4 shows a fragmentary partial sectional view of the fastener assembly incorporating a modified form of the present invention partially assembled with a first work piece; Fig. 5 shows a fragmentary partial sectional view of the fastener assembly of Fig. 4 fully assembled with first and second work pieces; and Fig. 6 shows a fragmentary partial sectional view of the fastener assembly incorporating another modified form of the present invention fully assembled with first and second work pieces. Detailed Description of the Illustrated Embodiment Fig. 1 shows an exploded view of a fastener assembly 10 illustrating the relationship between a fastener 12, a washer 14 and a resilient grommet 16. The fastener 12, which is formed of steel or other suitable rigid material, is comprised of a head portion 18, including a tool engaging section 20 and a clamping surface 22, attached to an axially projecting shank portion 24. The shank portion 24 is formed with an upper shank section 26, two protuberant wings 28, a lower threaded shank section 30, and a reduced diameter entering end 32. Preferably the wings or protuberances 28 are integrally formed on the shank 24 between the upper shank portion 26 and the threaded lower shank portion 30 at approximately 180° to each other. The washer 14 is comprised of a flange portion 34 and a sleeve portion 36 extending axially therefrom and having an annular crimp or internal bead 38 formed therebetween. The washer 14 includes a central bore 25 which slidably receives the shank portion 24 which projects through the washer bore 25 and is held in place by the crimp or bead material 38 which provides inwardly projecting abutment means of reduced internal diameter which is smaller than the dimension from wing tip 28 to wing tip 28. Thus the fastener is retained within the washer while permitting axial movement between the pieces by engagement of the bead or abutment means 38 with the protuberances 28. A flare 40 is formed at the distal end of the washer sleeve 36 for the purpose described below. The washer 14 telescopically extends through a central bore 41 in the grommet 16. The grommet 16 has a body portion 42 around which is formed an annular radially projecting gripping and sealing flange or bead 44. An annular sealing ring 46 projects axially from an end face of the body 42 and a sleeve 48 of substantial length also extends axially from an inner annular margin of the body 42. The fastener assembly 10 is adapted to be preassembled with a first work piece 50 for subsequently securing the first work piece 50 to a second work piece 52. The work piece 50 is formed with a bore or aperture 54 having an enlarged outer end or counterbore 58 for receiving the fastener assembly. The work piece 52 is formed with an internally threaded aperture 56 positioned for alignment with the aperture 54. The annular bore gripping flange 44 helps to compressibly hold the grommet 16 and fastener 12 retained therein when inserted into the aperture 54 in a first work piece. Preferably the grommet 16 is integrally formed of a resilient rubber or other suitable synthetic material which is resistant to the fluids which may be encountered in sealing an aperture, such as oils and other petroleum products in an automotive application. Axial movement between the fastener 12 and the washer 14 is possible since the diameter of the washer bore 25 is greater than the diameter of the shank portion 24. On the other hand, freedom of movement is not desirable between the washer 14 and the resilient grommet 16 since it is the grommet 16 that holds the fastener assembly 10 in preassembly in an aperture. Therefore, the grommet 16 and washer 14 are dimensioned and formed to provide a snug fit which resists minor forces which might otherwise free the washer 14 from the grommet 16. Fig. 2 shows the components of the preassembled fastener assembly 10 in a partially assembled condition. As shown, the crimp or bead 38 has a smaller diameter than the wings 28 on the shank 24, thereby allowing relative axial movement between the fastener 12 and washer 14, which movement is limited by the spacing of the wings 28 from the clamping surface 22. Also shown is the manner in which the flare 40 distorts the sleeve 48 of the rubber grommet 16. Since the outside diameter of the flare 40 is greater than the inside diameter of the rubber grommet sleeve 48, the sleeve 48 must be stretched over the flare portion 40 which aids in retaining the grommet 16 on the washer 14. As shown in Fig. 2, when the fastener assembly 10 is preassembled with the work piece 50, the fastener 12 can be displaced upwardly so that its lower end does not project below the bottom surface of the work piece. This facilitates subsequent positioning and alignment of the work piece 50 with the second work piece 52. Fig. 3 provides the best illustration of the use of the preferred embodiment of the fastener assembly 10. In Fig. 3, the first work piece 50 is positioned over the second work piece 52 such that the apertures 54, 56 of the two work pieces are substantially aligned. Once in such a position, the fastener 12 of the assembly 10 which has been preassembled with the work piece 50 is pushed through the aperture 54 of the first work piece 50 to bring the threaded portion of the shank 30 in aligned interengagement with the complementarily threaded aperture 56 in the second work piece 52. As shown, when the fastener 12 is driven into the second work piece aperture 56, the rubber grommet 16 becomes seated in the counterbore 58. Since the washer 14 is dimensioned and formed to provide space between the washer 14, shank 24 and bore 25 thus allowing free telescoping movement between the pieces, two potential fluid flow paths are formed through the aperture 54 of the first work piece 50. The first path is formed by the gap 59 between the inside surface of the aperture 54 and the outside surface of the washer sleeve 36. This path is at least partially sealed by the rubber grommet sleeve 48 which compressibly fills the gap between the two surfaces. The rubber grommet 14 also seals this gap against fluid flow from inside of the assembled work pieces 50, 52, by the sealing engagement of the annular sealing ring 46 with the bottom of the counterbore 58 and sealing engagement of the flange 44 with the sidewall of the counterbore 58. The second fluid flow path is formed by a gap 60 between the outside surface of the fastener shank 24 and the inside surface of the washer sleeve 36. This gap 60 is sealed by compressing the underside of the clamping surface 22 sealingly against an axially extending annular rim 47 of the grommet body 42 which projects around the flange 34 of the washer. In this compressed configuration, the washer flange 34 seats in a rim counterbore 61, thereby sealing the washer flange 34 against the base of the rim counterbore 61 and countersinking the flange 34 to prevent interference with the seal between the clamping surface 22 and the annular sealing rim 47. The above described sealing structure has the advantage of effectively sealing the aperture 54 while retaining the telescopically movable characteristics of the fastener 12 by positioning the sealing material on the outside of the washer 14. Additionally, the grommet 16 configuration of the present invention and the annular bore gripping flange 44 help to center the fastener assembly 10 when inserted in the aperture 54. The annular bore gripping flange 44 also assists in retaining the fastener assembly 10 within the aperture of the first work piece 50 prior to final assembly with the second work piece 52 by compressibly gripping the inside wall of the counterbore 58. Further, when the clamping surface 22 is tightened against the sealing rim 47, the compressive forces tend to compressibly deform the body portion 42 and also compress the annular gripping flange 44 against the inside surface of the counterbore 58, thus providing additional sealing against fluid flow as mentioned above. Yet another advantage of the sealing structure shown in Fig. 3 is that when properly tightened a bottom rim 57 of the washer 14 contacts a top surface 63 of the second workpiece 52. The contact of the rim 57 against the surface 63 prevents over compressing the grommet 16 or an additional sealing gasket 65. Turning now to an alternative embodiment, shown in Figs. 4 and 5 wherein elements corresponding to those described above are designated by the same reference numerals with the suffix a added, a simplified version of rubber grommet 16a is illustrated which has a fastener elevating annular ring 62 formed around the inside wall of the rubber grommet sleeve 48a. The annular ring 62 is dimensioned to provide a minor obstruction to the passage of the assembled washer 14a and fastener 12a through the grommet sleeve 48a. The obstruction created by the ring 62 elevates the fastener 12a and suspends the washer 14a in the aperture 54a. The washer flange 34a engages the clamping surface 22a, thus limiting the axial travel of the fastener 12a in the washer 14a and grommet 16a. The obstruction is easily overcome by the pressure and/or the weight of a tool applied to the tool engaging member 20a to drive the threaded portion of the shank 30a into the complementary threaded aperture 56a of the second work piece 52a. Retention of the washer 14a and the fastener 12a in this elevated configuration allows the fastener assembly 10a to be preassembled in the first work piece 50a so that when the work piece 50a is placed on another surface or on top of the second work piece 52a, prior to aligning the aperture 54a in the first work piece 50a with the aperture 56a in the second work piece 52a, the fastener 12a does not project through the bottom of the first workpiece and therefore does not interfere with the other surface. Further, the retaining characteristics of the fastener assembly 10a tolerate a degree of tip without unseating the fastener assembly 10a from the aperture 54a in the first work piece 50a. Fig. 5 illustrates the fastener assembly 10a as shown in Fig. 4 installed in the first and second work pieces 50a, 52a. When the fastener 12a is driven into the threaded aperture, the fastener elevating annular ring 62 is compressed between the inside surface of the aperture 54a and the outside surface of the washer sleeve 36a to form a sealing couple with the flare 40a of the washer sleeve 48a. Another alternative embodiment of the present invention is illustrated in Fig. 6 wherein elements corresponding to those described above are designated by the same reference numerals with the suffix b added. The embodiment shown in Fig. 6 provides a simplified grommet which is formed without the above-mentioned counterbore 61. As noted above, the exposed rim 47 seals the path between the inside surface of the washer 14 and the outside surface of the fastener 12 (see Figs. 2-5). In the absence of sealing engagement between the rim 47 and clamping face of the screw, a resilient coating material 68 is applied to the threaded portion 30b of the shank 24b. This coating material seals both the inside surface of the washer and the threads in the secondary work piece aperture 56b. In use, the fastener assembly 10 is inserted into an aperture 54 on the first work piece 50. Once inserted, the fastener assembly 10 is retained in the aperture 54 by the frictional interaction between the outside surface of the grommet 16 and the inside surface of the aperture 54. The fastener 12 may be held and retained in an elevated position within the grommet 16 while positioning the work piece 50 over the work piece 52. The fastener 12 is extended to interengage the threaded aperture 56 of the second work piece 52. Once the first and second work pieces 50, 52 are fastened together, the fastener assembly 10 prevents fluid flow from the inside of the assembled work pieces. The fluid flow path formed by the gap 59 between the inside surface of the aperture 54 and the outside surface of the washer 14 is sealed by the sleeve 36 lining the aperture 54 in the first work piece 50 and the body portion 42 being radially compressed into the counterbore 58 of the first work piece 50. In an embodiment of Figs. 4 and 5 employing a ring 62 on the inside of the grommet sleeve 36, compression of the ring 62 further enhances this sealing action. The fluid flow path formed by a gap between the outside surface of the fastener shank 24 and the inside surface of the washer 14 is sealed by the underside of the clamping surface 22 vertically compressing directly against the rim 47 at the top side of the body portion 42. In this configuration the counterbore 61 is provided as an inset for the washer flange 34 such that when the washer flange 34 is compressed into the counterbore 61, the washer flange 34 does not interfere with the seal formed between the clamping surface 22 and the rim 47. In the alternative embodiment of Fig. 6, the clamping surface 22b contacts the top side of the washer flange 34b and not the body portion 42b. The second path is sealed by the resilient coating material 68 on the threaded lower shank portion 30b. When the fastener 12b is driven into the second work piece aperture 56b the resilient coating material 68 seals both the threads of the aperture 56b and the area between the shank 24b and the lower portion of the washer sleeve 36b and the flare 40b.

Claims: A fastener assembly comprising first and second work pieces (50, 52; 50a, 52a; 50b, 52b) having bores (54; 54a, 54b),said fastener assembly (10; 10a; 10b) comprising a fastener (12; 12a; 12b), a washer (14; 14a; 14b) and a resilient grommet (16; 16a; 16b), said fastener (12; 12a; 12b) having a head (20; 20a) with a clamping surface (22; 22a; 22b) thereunder and a shank (24; 24a), said shank having an upper shank portion (26), a threaded lower shank portion (30) and protuberance means (28) spaced a predetermined axial distance from said head (20; 20a; 20b) between said upper shank portion (26) and said threaded lower shank portion (30), said washer (14; 14a; 14b) including a flange (34; 34a; 34b) and an axially extending sleeve (36; 36a; 36b) and abutment means (38) projecting inwardly of said sleeve (36; 36a; 36b), said washer (14; 14a; 14b) being slidably telescopically associated with said fastener (12; 12a; 12b), with an inner dimension of said abutment means (38) being less than an outer dimension of said protuberance means (28) thereby securing said fastener (12; 12a; 12b) within said washer (14; 14a; 14b), said resilient grommet (16; 16a; 16b) surrounding and sealingly engaging said washer (14; 14a; 14b) and including means (46) sealingly engageable with one substantially horizontal sealing surface of one work piece (50; 50a; 50b), so as to seal a first fluid flow path (59) between said washer (14; 14a; 14b) and said bore (54; 54a) of said one work piece (50; 50a; 50b) as a result of an axial compression of said grommet (16; 16a; 16b) with respect to said at least one substantially horizontal sealing surface, said shank (24; 24a) and said washer (14; 14a; 14b) defining a second fluid flow path (60) therebetween, characterized in that said one work piece (50; 50a; 50b) has counterbored recess means (58) defined therein so as to define said at least one substantially horizontal sealing surface and at least one substantially vertical sealing surface, said grommet (16; 16a; 16b) including means (46, 44) disposed within and sealingly engageable with said at least one substantially horizontal sealing surface and said at least one substantially vertical sealing surface of said counterbored recess means (58), and means (47; 68) are provided for sealing said second flow path (60) when said fastener assembly (10; 10a; 10b) is fully assembled with said one work piece (50; 50a; 50b). The fastener assembly according to claim 1, wherein said grommet (16; 16a; 16b) includes a sleeve (48) surrounding said washer sleeve (36; 36a; 36b), said grommet sleeve (48) including an annular ring (41) integral with an inside surface thereof for retaining said washer (14; 14a; 14b) in said resilient grommet (16; 16a; 16b). The fastener assembly according to claim 1 or 2, wherein a body portion (42; 42b) of said resilient grommet (16; 16a; 16b) comprises said bore (54; 54a; 54b), an annular bore gripping element (44) being integrally formed on the outside thereof having and outside dimension slightly larger than or equal to said recessed means (58) for securing and centering said fastener assembly (10; 10a; 10b) in said recessed means (58) of said first work piece (50; 50a; 50b). The fastener assembly according to claim 1 which includes a band (68) of resilient sealing material around said lower threaded shank portion (30b) of said fastener shank for sealing threads of the bore (56b) into which said lower threaded shank portion (30b) interengages. The fastener assembly according to one of the claim 1 to 4, wherein said sleeve (58) of said resilient grommet (16; 16a; 16b) has an annular ring (62) integrally formed about the inside surface of said sleeve (58) for maintaining said fastener (12; 12a) in an elevated position in relation to said work piece (50a) when said fastener assembly (10a) is preassembled in said first work piece (50a). The fastener assembly as defined in one of the claims 1 to 5, wherein said seal for said second flow path (60) comprises an annular rim (47) of said body portion (42) sealingly engageable with said head of said fastener (12). The fastener assembly as defined in one of the claims 1 to 6, wherein said body portion comprises an annular sealing ring (46) engageable with a bottom surface of said counterbore (58). The fastener assembly as defined in one of the claims 1 to 7, wherein a tubular sleeve (36; 36a; 36b) of said washer (14; 14a; 14b) extending axially from said flange (34; 34a; 34b) a distance substantially less than a distance between said protuberance means (28) and said head (20; 20a) and means (38) projecting inwardly from said sleeve (36; 36a; 36b) for engagement with said protuberance means (28) for retaining said washer (14; 14a; 14b) and fastener (12; 12a; 12b) in assembled relationship. The fastener assembly as defined in one of the claims 1 to 8, wherein said grommet (16; 16a; 16b) includes a tubular sleeve (48) extending axially beyond a free end of said washer sleeve portion (36; 36a; 36b), said grommet sleeve (48) being engageable with said washer sleeve (36; 36a; 36b) for initially retaining said grommet (16; 16a; 16b) and washer (14; 14a; 14b) in a partially assembled relationship, said washer (14; 14a; 14b) when in said partially assembled relationship supporting said fastener (12; 12a; 12b) for preventing an entering end (32; 32a; 32b) of said fastener (12; 12a; 12b) from projecting beyond said first work piece (50; 50a; 50b).

Inventors: WAGNER, DAVID PRUGH
Applicants: ILLINOIS TOOL WORKS INC.
Application year: 1990
Main classification: F16B43
IPC codes: F16B41, F16B43, F02B77, F16B33