A fastener stud for a snap-on mounting attachment

Abstract: A fastener stud (20) for a snap-on mounting attachment for connecting a base plate of an airbag module to a mounting, has a sleeve (32) of generally cylindrical profile with a reduced diameter portion (135). When the stud is assembled there is a ring (133) at one end of the sleeve. The ring (133) has a plurality of yieldable, outwardly-biased barbs (36,36a,36b,36c) which yieldably retreat towards the reduced diameter portion (135) as the stud is thrust into an opening in the mounting, the barbs springing outwardly once they have passed through the opening so as to secure the plate to the mounting. The sleeve (32) has a throughbore (136) which receives a threaded mounting post (34) extending from an enlarged head (30). The underside of the head is arranged to abut against the ring (133), and the distal end portion of the post (34) is arranged to extend beyond the sleeve for the purpose of securing the stud to the base plate.

Description: The present invention relates to the mounting of an airbag inflator module to a steering wheel or other support in a motor vehicle utilizing a snap-on mounting attachment which requires no tools, minimizes the potential for rattles, and accommodates tolerances in the assembly. It has long been desirable to mount an airbag inflator module to a vehicle support, such as a vehicle steering wheel, without requiring the use of tools. Snap type attachments have been used for this purpose, for example in U.S. Patent No. 5,333,897 entitled SNAP LOCK PIN INFLATABLE RESTRAINT MODULE MOUNTING MECHANISM. That mounting mechanism generally comprises a pair of barbed mounting studs extending from the rear of an airbag inflator module, and a plate secured to the steering wheel of a vehicle wherein the plate has spaced-apart apertures for receiving the mounting studs. Other mounting systems have similarly used a pair of studs extending rearwardly from an airbag inflator module such that the inflator module may be pressed into apertured mounting plates on the vehicle for quick and easy mounting of an airbag inflator. However, in these prior art mounting mechanisms, the alignment between the mounting studs and the apertures of the mounting plate is inflexible other than that achieved by providing a tapered end on the studs, and this also adds some degree of difficulty to the mounting, in that it is not usually possible to view the mounting plate as the studs are placed therein. Further, careful attention to tolerances is required to achieve good alignment of the assembled parts, and also to prevent rattling, and even then some rattling may occur under certain operative circumstances. The alignment of the airbag inflator module cover and the steering wheel cover present a special problem, in that these parts are molded from soft thermoplastic wherein precise shapes are difficult to maintain. EP0672558 discloses a snap-on mounting attachment for securing an airbag inflator module to a steering wheel of a motor vehicle. The snap-on attachment has a connecting pin fixed to a base of the inflator module by a head part and the steering wheel has a flange with an opening for the connecting pin. The pin has a plurality of spring tongue type arresting members which are radially moved towards one another as the pin is thrust into the opening, the tongue type arresting members snapping back radially outwardly once they have passed through the opening so as to lock and hold the airbag inflator module to the steering wheel. Accordingly, there is a need for an improved mounting system for use in securing an airbag inflator module to a vehicle support, which operates easily and which accommodates tolerances and prevents rattles. An object of the present invention is to provide a new and improved fastener stud for a mounting attachment for securing an airbag inflator module to a vehicle support, such as a steering wheel, without the use of tools. According to the present invention there is provided a fastener stud having a longitudinal axis, comprising securing means at one end for securing the stud to a baseplate of an airbag module or vehicle support, a main body portion mounted thereon and a ring portion having a plurality of yieldable, outwardly-biased means thereon terminating in distal tips and extending angularly outwardly therefrom normally extending away from said main body portion and adapted to yieldably retreat when the outwardly-biased means are moved inwardly towards the longitudinal axis of the fastener stud, characterised in that said main body portion comprises a sleeve of generally cylindrical profile terminating in a reduced diameter and said plurality of yieldable, outwardly biased means are adapted to yieldably retreat into the reduced diameter of the sleeve when the outwardly-biased means are moved inwardly towards the longitudinal axis of the fastener stud. The fastener stud may be used in a new and improved snap-on mounting attachment for securing an airbag inflator module having a base plate to a support provided on a motor vehicle, the mounting attachment including the fastener stud with at least one yieldable holding barb angled outwardly therefrom, the fastener stud secured to and extending from one of an airbag inflator module base plate and vehicle support, and a snap receptor mounted in floating encapturement on the other of the airbag inflator base plate and vehicle support. The snap receptor has an opening extending therethrough for receiving the fastener stud and defines a lip engaged by the holding barb. The snap receptor is held in floating encapturement permitting a limited range of movement of the snap receptor while maintaining it securely mounted, facilitating aligning the opening of the snap receptor with the fastener stud. This further permits the assembled snap receptor and fastener stud to shift in order to fit the airbag inflator module at the desired position in the vehicle support The mounting attachment enables dimensional tolerances to be accommodated in an airbag inflator module and vehicle support. The mounting attachment is able to operate easily and quickly, even when the attachment area is not readily viewable by the installer. Furthermore, the mounting attachment minimizes rattling between and among the assembled parts. The mounting attachment is strong and able to withstand the forces generated during operation of the vehicle and operation of the airbag inflator module in deploying an airbag. A resilient bias stop may be provided to bias the assembled parts into constant, rattle free engagement. A particular bias stop is elastomeric and bears against the base plate of the airbag inflation module. The snap receptor is desirably mounted to one of the airbag inflator module or vehicle support by a capture bracket having upper and lower retainer plates holding the snap receptor in floating encapturement. The retainer plates may have openings larger than the stud-receiving opening of the snap receptor, wherein the opening of the snap receptor is exposed to the fastener stud throughout the motion permitted by the floating encapturement. Additionally, the capture bracket may also provide a vertical component of movement between the upper and lower retainer plates, facilitating the limited movement characterizing the floating encapturement of the snap receptor. At least one of the upper and lower retainer plates of the capture bracket may have registered attachment holes for mounting the capture bracket to the vehicle support or airbag inflator module. Particular upper and lower retainer plates may both have attachment holes for both securing the upper and lower plates together and mounting them. The snap receptor may have a collar surrounding the stud receiving opening, and the collar extending through the opening in the upper retainer plate to position the snap receptor within the capture bracket. Additionally, the stud-receiving opening of the snap receptor may be counter sunk for readily receiving and centering the fastening stud. The snap receptor may comprise a metal ring embedded in a polymer shell, the ring being exposed in the receptor opening and defining the lip engaged by the holding barb of the fastening stud. Additionally, the shell is preferably generally annular, and the shell may be fabricated of nylon. The invention, together with features, advantages and aspects thereof, will be more clearly understood from the following description of the preferred embodiments taken in connection with the accompanying drawings. FIG. 1 is a rear elevation view of an airbag inflator module having two fastener studs forming a part of a snap-on mounting attachment according to the invention herein; FIG. 2 is a front elevation view of a vehicle steering wheel including two capture brackets and snap receptors forming a part of the snap-on mounting attachment of the invention herein; FIG. 3 is a side elevation view of the airbag inflation module and fastener studs of FIG. 1 and a partial side elevation view of the vehicle steering wheel with capture brackets and snap receptors of FIG. 2 , forming the snap-on mounting attachment according to the invention herein; FIG. 4 is an enlarged side elevation view, partially cut away and partially in section generally along lines 4-4 of FIG. 2 , of the snap-on mounting attachment of FIG. 3 , prior to the airbag inflator module and vehicle steering wheel being secured together; FIG. 5 is a side elevation view, partially cut away and partially in section generally along the lines 4-4 of FIG. 2 , of the snap-on mounting attachment according to the invention herein, shown securing the airbag inflator module to the vehicle steering wheel together; FIG. 6 is an exploded perspective view of the snap-on mounting attachment of FIG. 3 ; FIG. 7 is an exploded perspective view of the snap receptor and capture bracket of another snap-on mounting attachment according to the invention herein; FIG. 8 is a sectional view of the capture bracket and snap receptor of FIG. 7 , in assembled condition; FIG. 9 is a bottom view of the capture bracket and snap receptor of FIG. 7 , in assembled condition; FIG. 10 is an exploded view of the stud alone of FIGS. 1 to 9 ; FIG. 11 is an exploded view of a modified stud in accordance with the teachings of the invention; FIG. 12 is an exploded view of another modification stud in accordance with the teachings of the invention; and FIG. 13 is an assembled view of the stud alone of FIG. 12. The same reference numerals refer to the same elements throughout the various figures. FIGS. 1-6 generally illustrate an airbag inflator module 10 and securing it to a vehicle support in the form of a steering wheel 12 by snap-on mounting attachments 14 and 16 , according to the invention herein. The principal elements of snap-on mounting attachment 14 are shown in FIG. 6 , attachment 16 being identical, and FIGS. 1-5 show the relationship and operation of the snap-on mounting attachments in securing the airbag inflator module 10 to the steering wheel 12 . With reference to FIG. 6, the snap-on mounting attachment 14 generally comprises a fastener stud 20, a snap receptor 24 and a capture bracket 26 having a lower retainer plate 28 and an upper retainer plate 30 . The fastener stud 20 has a generally cylindrical sleeve 32 having a threaded mounting post 34 extending therefrom. The fastener stud 20 has a plurality of yieldable outwardly biased holding barbs including barbs 36, 36a, 36b, each of the holding barbs having a distal tip 38, 38a, 38b, 38c, respectively, spaced incrementally outwardly from the sleeve 32. The holding barbs extend angularly outwardly and are bendable inwardly to fit within the profile of the sleeve 32 as the sleeve passes into the snap receptor 24 , and the barbs spring outwardly to present the tips for holding purposes, as more fully discussed below. The fastener stud 20 and its holding barbs are preferably fabricated of steel. The snap receptor 24 is generally annular and defines a stud-receiving opening 40 for receiving the sleeve and holding barbs of the fastening stud 20 . With reference to FIG. 4 , the snap receptor 24 has a ring 42 embedded in a shell 44 , wherein the ring and shell together define the opening 40. The ring 42 has a lip 46 at its lower, inside edge which receives the tips 38, 38a, 38b ... of the fastener stud holding barbs 36, 36a, 36b ..., as best seen in FIG. 5. The ring 42 is fabricated of steel, but can be made of other metals or suitably strong material to provide the engagement interface of the snap-on mounting attachment. The shell 44 includes an upstanding collar 48 , and the shell including the collar 48 is counterbored at 50 to provide a flared entry portion of the opening 40 in the snap receptor 24. The shell is fabricated of nylon or other strong polymer, nylon being particularly suitable because of its strength and its tendency to reduce rattle noises upon contact with metal parts. The capture bracket 26 has a lower plate 28 and an upper plate 30 . The lower plate 28 has a base 52 defining an opening 54 , and has mounting ears 56 and 58 defining attachment holes 57 and 59 , respectively. The upper plate 30 has a top panel 60 elevated from flanking mounting ears 62 and 64 by legs 66 and 68 . The mounting ears define attachment holes 63 and 65 , respectively, which align with the attachment holes 57 and 59 of the mounting ears of the lower plate, and the top panel 60 defines an opening 70 which aligns with the opening 54 in the lower plate 28 . Screw fasteners 92 and 93 are used to secure the upper and lower plates of the capture bracket together and mount the capture bracket 26 to the steering wheel 12, as illustrated in FIGS. 2, 4 and 5. The collar 48 extends into the opening 70, but is of smaller diameter than the opening 70 , so that the snap receptor 24 has a limited amount of lateral movement within the capture bracket 26 . Also, the top panel 60 and base 52 are spaced apart by a greater dimension than the thickness of the outer portion of the shell, such that the snap receptor also has a limited degree of vertical movement within the capture bracket. Thus, the snap receptor 24 is in floating encapturement within the capture bracket 26 , and may move through a range of lateral and vertical motion to facilitate insertion of the fastening stud 20 , and to accommodate tolerances in the manufacture of the attached parts, such as the airbag inflator module and steering wheel. With reference to FIGS. 1-3, the airbag inflator module 10 has a base plate 72 mounting an inflator 74. A cover 76 encloses an airbag, not illustrated, which is deployed upon operation of the inflator module 10. With particular reference to FIG. 1, the rear of the airbag inflator module 10 has four corner lands 78 which are formed as a part of the base plate or underlying inflation module structure. Airbag inflator modules are well-known in the art and the internal structure and operation are not relevant to the present invention. The fastener stud 20 of the snap-on mounting attachment 14 and fastener stud 80 of the snap-on mounting attachment 16 are secured to the base plate 72 of the airbag inflator module 10 by means of the threaded mounting post 34 and extend rearwardly therefrom. It should be noted that the snap-on mounting attachments 14 and 16 are the same in all respects, and the two attachments 14 and 16 are provided for properly mounting the airbag inflation module. The steering wheel 12 has a rim 82 , a hub 84 , and four spokes 85-88 connecting the rim and hub. The rim and portions of the spokes are provided with a cover 89 which is shaped in the vicinity of the spokes to receive the cover 76 of the airbag inflator module 10 . The shapes are complementary to provide a complete cover of the steering wheel and airbag inflator module. As best seen in FIGS. 4 and 5, the spokes 85 and 86 define mounting pads 90 and 91, respectively, which receive the aligned mounting ears 56, 58, 62, 64 of the capture bracket 26 , the ears 56, 58, 62, 64 being secured to the mounting pads by fasteners 92 and 93 . The stud keeper of the snap-on mounting attachment 16 is similarly mounted to spokes 87 and 88 . The spokes 85 and 86 also define posts 94 and 95 , post 94 being seen in FIGS. 4 and 5 , the posts having resilient bias stops 96 positioned on the ends thereof. Spokes 87 and 88 also form posts 94, 95 with bias stops 96 on the respective ends thereof. The airbag inflation module 10 is mounted to the steering wheel 12 by orienting it above the steering wheel, as shown in FIGS. 3 and 4 , with the mounting studs 20 and 80 generally aligned with the openings in the snap receptors. As the airbag inflation module is pressed into the steering wheel, the fastener studs are inserted into the snap receptors. The holding barbs 36, 36a, 36b... yield to pass through the ring 42 of the snap receptor, and the holding barbs snap open so that their tips 38, 38a, 38b ... engage the lip 46 and secure the fastener stud 20 from being withdrawn. When the airbag inflator module is so mounted, its cover 76 aligns with the cover 89 of the steering wheel to present a smooth and attractive assembly. The floating encapturement of the snap receptor 24 within the capture bracket 26 facilitates aligning the fastener stud and snap receptor for insertion of the fastening stud, and also permits some lateral movement in lining up the airbag inflation module cover and the steering wheel cover. This accommodates dimensional tolerances in these parts, which often occur when thermoplastic parts, such as the covers, are cooled. With reference to FIG. 5 where the assembly process has been completed, the bias stops 96 are compressed and bias the snap receptor against the upper plate 30 of the capture bracket 26 . This bias action, together with the selection of materials maintains the assembly in rattle free condition. The engagement between the mounting stud and snap receptor is strong, being provided by steel barbs at a low angular orientation, and the structure of the snap receptor itself and the capture bracket holding it are also strong, whereby the snap-on mounting attachment is well adapted to bear the shocks and loads associated with mounting the airbag inflator module and holding it during its operation. The mounting studs may alternatively extend from the steering wheel and the capture bracket be mounted on the airbag inflator module. However, the arrangement shown is preferable because the airbag inflator module may be released for service or replacement by unscrewing the fastener studs from the base plate. The end of mounting stud 20 is provided with a star-shaped depression 99 (FIG. 1 ), configured to receive a tool for that purpose. It will also be appreciated that one or more snap-on mounting attachments can be used to mount an airbag inflator module to vehicle supports other than a steering wheel, e.g., to a dashboard bracket for passenger side airbags. With reference to FIGS. 7-9 , snap receptor 102 and capture bracket 104 which, together with fastener stud 20, provides another snap-on mounting attachment according to the invention herein. The capture bracket 104 has a lower plate 106 and upper plate 108 . The snap receptor is similar to the snap receptor 24 described above, having a ring 110 , preferably of metal, embedded in a shell 112 , preferably of nylon. The shell and ring define a stud-receiving opening 114 which is preferably counterbored at the top thereof, but does not have a collar. The ring 110 defines a lip 116 for engaging the holding barbs of the fastener stud. The bottom plate 106 includes a generally rectangular center portion defining opening 105 and further incorporates mounting ears 122 and 124 having attachment holes 123 and 125, respectively. The upper plate 108 is formed as a rectangular box and includes a top panel 120 defining a central opening 121 and a rectangular peripheral sidewall 134. At the corners of the sidewall extend four tabs 140-143 , which are bent over the bottom plate 106 , to mount the upper plate to the bottom plate, as best seen in FIG. 9 . The snap receptor 102 is retained in floating encapturement within the capture bracket, i.e., the snap receptor is permitted limited lateral and vertical movement within the sidewall, bottom plate and upper plate, capture bracket, to facilitate aligning the snap receptor and fastener studs and to accommodate tolerances between assembled parts. The capture bracket 104 , with the snap receptor 102 therein, may be mounted to the spokes of the steering wheel 12 in the same manner as the capture bracket 24 described above, and achieve snap on mounting of the airbag inflator module to the steering wheel in the same manner and with the same advantages as well. As seen in FIG. 6 , fastener stud 20 is shown in assembled condition. Stud 20 is shown in exploded view in FIG. 10 . Stud 20 includes an enlarged head 30 at one end having an irregularly shaped socket, such as hex socket 130, for receiving a like configured tool therein. A knurled portion 131 extends from head 30 , integral therewith, to threaded mounting post 34. Post 34 terminates in a distal end 132. Aforementioned barbs 36, 36a, 36b and 36c, (the remaining barbs opposite barbs 36, 36a, 36b and 36c are not visible in FIG. 10) and all the remaining barbs extend from and around ring portion 133 integral therewith. Ring portion 133 has an opening 234 therethrough adapted to receive shaft 34 therethrough. Ring portion 133 abuts against the underside of head 30 as seen in assembled view in FIG. 6, the barbs extending away from head 30. Sleeve 32 has an outer cylindrical main body portion 334 terminating in a reduced diameter end 135. Sleeve 32 has a throughbore 136 receivable about knurled portion 131 and retained thereon, the end 135 being disposed inside of ring portion 133 when assembled to shaft 34 as seen in FIG. 6 . The final installed position is shown in FIG. 6 where sleeve 32 retains ring portion 133 in position. Although a knurled portion 131 is shown in FIG. 10 , as seen in FIG. 11 wherein like numerals refer to like parts of the stud 20 of FIG. 10, stud 200 shows shaft 340 threaded in the area adjacent head 30 . Ring portion 133 is assembled to stud 200 similarly to the embodiment of FIG. 10 . However, sleeve 320 , otherwise identical to sleeve 32 of FIG. 10 , has a threaded throughbore 137 threadably receivable on threaded shaft 340 . In both embodiments in FIGS. 10 and 11 the final assembled view is as shown in FIG. 6 wherein the terminal end, the threaded shaft 34 extends away from sleeve 32 . However, as seen in FIG. 12 wherein again like numerals refer to like parts of the embodiment of FIG. 11 , sleeve 138 is substantially longer than sleeve 320 of FIG. 11 having a threaded throughbore 139 threadably receivable on threaded shaft 340 . The final installed position is shown in FIG. 13 . Thus, for some applications, a threaded shaft 202 (FIG. 13 ) extending from the application 201 may be threaded into the threaded throughbore 139 of sleeve 138.

Claims: A fastener stud (20) having a longitudinal axis, comprising securing means (34) at one end for securing the stud to a baseplate (72) of an airbag module (10) or vehicle support, a main body portion (334) mounted thereon and a ring portion (133) having a plurality of yieldable, outwardly-biased means (36, 36a, 36b, 36c) thereon terminating in distal tips (38, 38a, 38b) and extending angularly outwardly therefrom normally extending away from said main body portion and adapted to yieldably retreat when the outwardly-biased means are moved inwardly towards the longitudinal axis of the fastener stud, characterised in that said main body portion (334) comprises a sleeve (32) of generally cylindrical profile terminating in a reduced diameter (135) and said plurality of yieldable, outwardly biased means are adapted to yieldably retreat into the reduced diameter of the sleeve when the outwardly-biased means are moved inwardly towards the longitudinal axis of the fastener stud. A fastener stud (20) according to claim 1, wherein said outwardly-biased means (36, 36a, 36, 36c) are resilient. A fastener stud (200) according to claim 1 or 2, wherein said securing means includes a threaded end (139) of said sleeve (138). A fastener stud (20, 200) according to claim 1 or 2, wherein said securing means includes a threaded shaft portion (34, 340) integral with said main body portion. A fastener stud according to any preceding claim, including an integral and enlarged end (30) configured (130) for engagement by a tool for removing the fastener from the airbag module baseplate (72) or vehicle support by rotation of the tool. A fastener stud according to any preceding claim, wherein said main body portion has an enlarged head (30) at one end and a threaded shaft portion (34, 340) at the other end, said outwardly-biased means includes a ring portion (133) mounted on said main body portion encircling the same abutting against said head, and a plurality of barbs (36, 36a, 36b, 36c) extending toward said shaft portion, said sleeve (32, 320) mounted on said main body portion abutting against said ring portion (135), and retaining means associated with said main body portion and said sleeve (32, 320) for retaining said sleeve in a fixed position on said main body portion. A fastener stud (20) according to claim 6, wherein said sleeve (32) has an interior wall (136) and said retaining means includes a knurled portion (131) on said main body portion gripping the interior wall of said sleeve. A fastener stud (200) according to claim 6, wherein said sleeve (138, 320) has an inner threaded wall (137, 139) and said retaining means includes mating threads on said inner threaded wall of said sleeve and said main body portion. A fastener stud according to claim 8, wherein said inner threaded wall (139) is longer than the distance between said ring portion (133) and a terminal end of said threaded shaft portion (340) whereby, when said sleeve (138) and said ring portion are mounted on said main body portion, said sleeve has a threaded open end adapted to receive a like threaded shaft (202) therein.

Inventors: DURAN JOHN A, RICKS MERLE K, SCHARRET JEFFREY L, SORENSON JANIEL, DURAN, JOHN A., RICKS, MERLE K., SCHARRET, JEFFREY L., SORENSON, JANIEL
Applicants: AUTOLIV ASP INC, AVIBANK MFG INC, AUTOLIV ASP, INC., AVIBANK MFG., INC.
Application year: 1997
Main classification: B60R21
IPC codes: F16B21, B60R21