Floating, serviceable horn switch, air bag modules

Abstract: An assembly comprising an inflatable restraint module (24) mounted on armature portion 14 of a steering wheel by attachment studs eg 56. A horn switch assembly associated with at least one of the studs which comprises a shoulder bolt includes inner 68 and outer 66 non-conductive housings, which snap together and are held extended by a pre-stressed compression spring 64. Opposed electrical contacts 94 and 96 are supported on flanges 70 and 88 of the first 66 and second 68 housings respectively. The gap between the contacts 94 and 96 is governed by the vehicle vibration requirements and the stiffness of the compression spring. The switch assembly is serviceable without dismantling the restraint module.

Description: This invention relates to an improvement in horn blowing switch arrangements for automotive vehicle steering wheels that are provided with an inflatable air bag occupant restraint module, and more particularly to a floating, serviceable center blow horn switch assembly for use with such air bag module. Horn switches, typically, are easier to operate when mounted in the center of a steering wheel. That location has not been utilized for horn switch assemblies, however, in order to avoid the risk of injury to the driver and passengers when the air bag is deployed. Consequently, horn switch assemblies have been mounted to one side of the air bag module. Upon deployment of the air bag, the horn switch assembly is maintained in place, thus avoiding risk of injury to occupants of the vehicle. A disadvantage of such horn switch assemblies is that they are more difficult to access for blowing the horn compared to a conventional horn pad positioned above the hub in the center of the steering wheel. U.S. Patent Nos. 3.819,205 to Dunford et al. and 4,325,568 to Clark et al. each disclose an inflatable air bag occupant restraint module on the steering wheel of an automotive vehicle together with a horn blowing switch arrangement. In each case the horn blowing switch arrangement is mounted on the module in a position adjacent the rim of the steering wheel and is manually depressible for blowing the horn. U.S. Patent No. 4,785,144 to Fosnaugh et al (on which the pre-charcterising part of claim 1 is based) discloses an inflatable air bag occupant restraint module on a vehicle steering wheel together with a floating horn blowing switch module that is spring mounted between the air bag module and the hub of the steering wheel. The switch module for blowing the horn is actuated when the module is manually depressed. If, after assembly on the steering wheel, access to the switch module is desired, the air bag module must be disassembled from the switch module. There is a need in the automotive industry for a serviceable center blow horn switch assembly for use with an air bag module. Current commercial availability includes a floating horn switch arrangement, similar to that disclosed in the Fosnaugh et al. patent, which floats on four stud or mounting locations. These switches are integral with the air bag module assembly. Thus, the module must be disassembled and replaced to service the switch. Disassembly of the air bag module is not a viable option because of the liability related to an air bag occupant restraint system. Replacement is a costly proposition. Thus, there is a need and a demand for a floating center blow horn switch assembly for use with air bag modules that are provided on vehicle steering wheels, which switch assembly is serviceable without disassembling or replacing the air bag module. The present invention was devised to satisfy such need and demand. An object of the invention is to provide an improved center blow horn switch assembly for use with an air bag module mounted on the steering wheel of an automotive vehicle that is characterised in allowing the switch assembly to be serviced without disassembling or replacing the module. Thus according to the invention there is provided a combination comprising an inflatable restraint module assembly, a steering wheel having a rim portion and an armature portion, attachment studs extending through corresponding apertures in the armature portion for holding the module assembly to the steering wheel, a separate horn blowing switch assembly individually associated with at least one of said attachment studs, each such horn blowing switch assembly being operative normally to hold a portion at least of the module assembly in predetermined spaced relation to the armature portion said horn blowing switch assembly comprising a pre-stressed compression spring and a first cylindrical housing having a flange disposed on one end thereof and housing said compression spring, a first electric contact and a second electric contact wherein said compression spring holds said first cylindrical housing in a predetermined position with said electric contacts separated from each other by a predetermined gap, whereby pressing on said module assembly against the force of said compression spring causes said electric contacts to be brought into engagement with each other to close an electric circuit from a power source to a horn mechanism, characterized in that said attachment studs are fixedly attached to said module assembly so as to extend outwardly therefrom in spaced apart relation, said switch further comprises a second cylindrical housing having a flange disposed on one end which flange is positioned in a predetermined spaced relation with the flange of the first housing, said first and second electric contacts are respectively positioned on the flanges of said first and second housings and are disposed in opposing relation, said housings are made of electrically non-conductive material and snap together with said stud and compression spring in concentric relation therewith such that said compression spring holds the housings in a predetermined positional relationship and relative movement between said housings against the force of said spring causes said electric contacts to be brought into engagement, and wherein servicing of said switch assembly is possible without disassembly or replacement of said module assembly. In a preferred embodiment of the invention, the top of the air bag module is fixed with existing, that is, conventional, attachment means to two upper studs of the armature of the steering wheel whereby the gap on the upper show surface of the module is held to tight tolerances with the electrical contact gap at two bottom studs on the armature of the steering wheel being held to a minimum in order to reduce the bottom module show surface gap. In accomplishing these and other objectives of the invention, a horn switch assembly is provided including a shoulder bolt and stud which in conjunction with an assembly retainer and lock nut hold the air bag module assembly to the steering wheel. The horn switch assembly consists of a pre-stressed compression spring and two concentric housings that snap together. The housings act as an electrical insulator and house the spring and electrical contacts. Suitably insulated lead wires are provided for connection of the electrical contacts to a power source and the horn mechanism. The distance between the contacts, that is, the electrical contact gap, is determined by the vibration requirements of the automotive vehicle and stiffness of the compression spring. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the specification. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. With this description of the invention, a detailed description follows with reference being made to the accompanying figures of drawings which form part of the specification, in which like parts are designated by the same reference numbers, and of which: Fig. 1 is a top view of an embodiment of the invention mounted to the steering wheel of an automotive vehicle; Fig. 2 is a bottom view of the air bag module of Fig. 1; Fig. 3 is a cross sectional view taken along the lines 3-3 of Fig. 1 and illustrates the horn blowing switch arrangement according to the invention; Fig. 4 is an enlarged view of the portion of Fig. 3 that is circumscribed by a circular dotted line; and Fig. 5 is an exploded view illustrating how the horn blowing switch according to the invention is put together. Fig. 1 illustrates an automotive vehicle steering wheel assembly 10 having a rim 12 and including an armature 14 (which is referred to hereinafter as a second support means) with four spokes, designated, respectively, 16, 18, 20 and 22, projecting therefrom to the rim 12. An air bag module 24 and a horn blowing switch assembly 26 for use therewith (not shown in Fig. 1) are mounted on the steering wheel assembly in a manner illustrated in Figs. 2-5. In Fig. 3, a view taken along the lines 3-3 of Fig. 1, there is illustrated a cross-sectional view of the air bag module 24 and the horn blowing switch assembly 26. A steering wheel shroud 25 is provided in association with the armature 14. The air bag module 24 is housed in a container 27 including a cover 28 having a generally rectangular box-like shape and a supporting housing member 29 having a plate portion 30 which is disposed in press fit relation with cover 28 and on which are mounted an inflator and a folded air bag (both of which are not shown). The plate portion 30 of the supporting housing member 29 is referred to hereinafter as a first support means. The inflator and air bag per se form no part of the present invention and have not been shown to avoid undue complication of the drawing. The plate portion 30 is generally rectangular and deep dish-like in shape. An extreme upper edge 32 of the upstanding side wall 34 of the plate 30 is curled outwardly, as shown, for engaging and being captured or locked in a groove 36 that is provided on the inner surface 38 of depending wall 40 of cover 28, when pressed in place. The module 24 is attached at the upper portion thereof to the armature 14 of the steering wheel 10 by two bolts or studs 42 and 44 each of which have a head at one end and is threaded at the other, and that extend outwardly in spaced apart relation from the housing plate 30. Stud 42, as shown in Figs. 2 and 3, extends outwardly from aperture 46 in plate 30 and into and through aperture 48 in the armature 14 of steering wheel 10, and is held securely in place by a nut 50. Stud 44 similarly extends outwardly from aperture 52 in plate 30, extends into an aperture (not shown) in armature 14, and is held securely in place by a nut (not shown) that is similar to the nut 50. For enabling the module 24 to be deflected slightly, when depressed, in order to blow the horn, the plate 30, as best seen in Figs. 2 and 3, is provided with an embossment or offset portion 54 that extends for the full width of the module 24. If desired, however, the embossment 54 may comprise a circular or truncated embossment that surrounds each of the apertures 46 and 52 in the plate 30 through which the respectively associated studs 42 and 44 extend. The plate portion 30 of housing member 29 includes a first pair of apertures 46 and 52 (which are sometimes referred to herein as upper apertures) and a second pair of apertures 55 and 57 (referred to herein as lower apertures). Similarly, at the lower portion of plate portion 30, a first shoulder bolt and stud 56 extends outwardly from lower aperture 55 in the plate 30 and a second shoulder bolt and stud 62 extends outwardly from lower aperture 57. As shown in Fig. 3, shoulder bolt and stud 56 extends through aligned aperture in armature 14 and is retained by a lock nut 60 in a manner described hereinafter. The horn switch assembly 26, as seen in Figs. 3 and 4, consists of shoulder bolt and stud 56 which in conjunction with a perforated cup shaped assembly retainer 58 and the lock nut 60 holds the assembly including the air bag module 24 to the steering wheel 10. The second shoulder bolt and stud 62 is provided in association with a second horn switch assembly (not shown) that is identical to the horn switch assembly 26. The two horn switch assemblies serve to hold the module 24 in a floating, that is, deflectable relationship to the steering wheel 10 for enabling horn blowing to be effected by pressing on the module 24. As shown in Figs. 3 and 4, the horn switch assembly 26 consists of a pre-stressed coil compression spring 64 and two concentric flanged cylindrical housings, specifically an outer housing 66 and an inner housing 68 that are arranged to snap together as described hereinafter. Outer housing 66 includes a relatively thick radially outwardly extending flange portion 70 with a flange portion 72 that extends radially inwardly for a relatively short distance, forming an aperture 72a in outer housing 66 through which a cylindrical portion 74 of inner housing 68 extends in a snug fit. Flange portion 70 includes a tapered edge portion 70a that is configured to match a tapered edge portion 76a of a cavity or depression 76 in the armature 14 of the steering wheel 10 such that the surface 70b of the flange 70, which surface 70b is flat, lies in the same plane as the flat surface in the armature 14 when the outer housing 66 is positioned in operative relationship with the latter. At the center of the cavity 76 in the armature 14 is an aperture 78 through which the cylindrical portion 80 of the outer housing 66 extends in a snug fit. The inner wall of the cylindrical portion 80 of the outer housing 66 is stepped upwardly whereby there is effected a substantial reduction in the thickness of the wall of cyldndrical portion 80 for a region immediately below the flange 70, as best seen in Fig. 4. At the base 82 of the outer housing 66 there is provided an aperture 84 through which the stud 56 extends in a snug fit. Inner housing 68 includes a circumferential ridge 86 that slopes upwardly and inwardly on the outer surface of a cylindrical wall 87 thereof, and in addition, a flange portion 88 that extends radially outwardly and a flange portion 90 that extends radially inwardly forming an aperture 92 in the inner housing 68 through which the stud 56 extends in a snug fit. When the inner housing 68 is inserted through aperture 72a in the outer housing 55, into concentric relation with the outer housing 66, flange portions 88 and 90 of the inner housing 68 are held spaced from the flange portions 70 and 72 of the outer housing 66 by compression spring 64 which is seated between the inner housing flange portion 90 and the base 82 of the outer housing 66. At a predetermined spacing between flange portions 70, 72 and 88, 90, the circumferential ridge 86 on the cylindrical surface of the inner housing 58 slides over the lower edge of the aperture 72a in the outer housing 66. This causes the two housings to snap together, capturing the inner housing 68 in concentric relation with the outer housing 66. The housings 66 and 68, which are made of electrical insulating material such as a suitable plastic, houses electrical contacts 94 and 96 which are configured in the form of flat rings and are made of good electrically conductive material, with contact 94 being suitably adhered to the flange portion 70 of the outer housing 66 and the contact 94 being suitably adhered to the flange portion 88 of the inner housing 66. Suitably insulated electrical lead wires 98 and 100 provide a connection from contacts 94 and 96, respectively, to a suitable electrical power source and the horn mechanism within the vehicle. The gap between the electrical contacts 94 and 96 is governed by the vibration requirements of the automotive vehicle in which the air bag module 24 and horn assembly 26 is installed and the stiffness of the compression spring 64. Fig. 5 is an exploded view that shows how the assembly of the air bag module 24 and the two horn blowing switch assemblies 26 are put together. With the air bag module 24 held fixed at the upper two studs 42 and 44, as illustrated, the gap 102 on the upper show surfaces of the module 24 can be held to tight tolerances. The gaps between the electrical contacts 94 and 96 at the lower two studs 56 and 62, that is, at the horn switch assemblies 26, can be held to a minimum to help in reducing the lower or bottom show surface gap 104. It is contemplated that, if desired, a horn blowing switch assembly 26 may be provided at each of the four steering wheel attachment points or stud locations instead of only at the two attachment points at the lower portion of the module 24, as illustrated herein. For blowing the horn on the vehicle, the driver is required only to press the air bag module 24 inwardly against the steering wheel 10 from a generally central portion thereof. This results in closure of the electrical contacts 94 and 96 of each of the horn switches 26 to complete an electrical circuit through the lead wires 98 and 100 to a source of power and the horn. With the module 24 fixedly attached at the upper attachment studs 42 and 44, there is no possibility of lateral movement thereof as it is pressed against the steering wheel 10. When a horn switch assembly 26 is provided at each of the four attachment points of the module 24, blowing of the horn may be effected by pressing inwardly on the module from any upper surface portion thereof, with no lateral movement of the module occurring. In the event of a need to service the horn switches 26, the nuts 50 for retaining studs 42 and 44 and the lock nuts 60 for retaining shoulder bolt studs 56 and 62 can be removed by the use of a suitable wrench inserted through respectively associated openings 106 and 108 that are provided in the steering wheel shroud 25. By reference to Fig. 5, it will be seen that such removal of the nuts 50 and 60 permits the air bag module 24 to be removed intact, that is with no invasion thereof, from the steering wheel armature 14, with the studs 42, 44, 56 and 62 fixedly attached thereto, as shown. Such removal provides easy access to each of the horn switch assemblies 26 for servicing thereof. Upon the completion of such servicing and the reinsertion of the serviced horn switches 26 in the apertures 78 in the armature 14, the air bag module 24 is readily reassembled to the armature 14 by the insertion of the shoulder bolt studs 56 and 62 through the apertures 84 and 92 of the horn switches, and the insertion of the studs 42 and 44 through the respectively associated apertures in the armature 14. Thus, in accordance with the invention, there has been provided a center blow horn switch assembly for use with an air bag module mounted on the steering wheel of an automotive vehicle that allows the horn switch assembly to be readily serviced without disassembling or replacing the module. The center blow horn switch assembly further is characterized in that it can be used at each of the steering wheel attachment studs, or the top portion of the module can be fixed with the existing attachment means that have been provided. An advantage obtained with the module held fixed at the upper two studs is that the gap on the upper show surface can be held to a tight tolerance. The electrical contact gap at the lower two studs can be held to a minimum to help in reducing the lower show surface gap.

Claims: A combination comprising an inflatable restraint module assembly (24), a steering wheel (10) having a rim portion (12) and an armature portion (14), attachment studs (42, 44, 56, 62) extending through corresponding apertures (78) in the armature portion (14) for holding the module assembly (24) to the steering wheel (10), a separate horn blowing switch assembly (26) individually associated with at least one of said attachment studs (56, 62), each such horn blowing switch assembly (26) being operative normally to hold a portion at least of the module assembly in predetermined spaced relation to the armature portion said horn blowing switch assembly (26) comprising: a pre-stressed compression spring (64) and a first cylindrical housing (66) having a flange (70) disposed on one end thereof and housing said compression spring (64), a first electric contact (94) and a second electric contact (96) wherein said compression spring holds said first cylindrical housing (66) in a predetermined position with said electric contacts (94, 96) separated from each other by a predetermined gap, whereby pressing on said module assembly (24) against the force of said compression spring (64) causes said electric contacts (94, 96) to be brought into engagement with each other to close an electric circuit from a power source to a horn mechanism, characterized in that: said attachment studs (42, 44, 56, 62) are fixedly attached to said module assembly (24) so as to extend outwardly therefrom in spaced apart relation, said switch further comprises a second cylindrical housing (68) having a flange (88) disposed on one end which flange is positioned in a predetermined spaced relation with the flange (70) of the first housing (66), said first and second electric contacts (94, 96) are respectively positioned on the flanges (70, 88) of said first and second housings (66, 68) and are disposed in opposing relation, said housings (66, 68) are made of electrically non-conductive material and snap together with said stud (56, 62) and compression spring (64) in concentric relation therewith such that said compression spring (64) holds the housings in a predetermined positional relationship and relative movement between said housings against the force of said spring (64) causes said electric contacts (94, 96) to be brought into engagement, and wherein servicing of said switch assembly (26) is possible without disassembly or replacement of said module assembly (24). A combination as claimed in claim 1 wherein the module assembly (24) includes a housing member (29) with first (46, 52) and second (55, 57) pairs of spaced apertures through which the attachment studs (42, 44, 56, 62) extend. A combination as claimed in claim 1 or 2 wherein a separate horn blowing switch assembly (26) is individually associated with each of two at least of said attachment studs (56, 62). A combination as claimed in any preceding claim wherein each said attachment stud (56, 62) associated with a switch assembly is a shoulder bolt and stud and wherein said cylindrical housings (66, 68) and spring (64) associated with such an attachment stud are positioned radially outwardly thereof. A combination as claimed in claim 4 further comprising a perforated cup shaped assembly retainer (58) and a lock nut (60) for each horn blowing switch assembly (26), wherein each said assembly retainer (58) is positioned in covering relationship with a lower portion of the associated said first cylindrical housing (66), and wherein each said lock nut (60) is screwed on the adjacent end of the associated shoulder bolt and stud which extends through the associated said first cylindrical housing (66). A combination as claimed in claims 4 or 5 wherein for each switch assembly (26); said first cylindrical housing (66) has a base member (82) having an aperture (84) through which said shoulder bolt and stud extends in a snug fit, said flange (88) of said second cylindrical housing (68) includes a portion (90) that extends radially inwardly towards the associated said shoulder bolt and stud (56, 62), and said compression spring (64) is positioned between said base member (82) of said first cylindrical housing (66) and said radially inwardly extending flange portion (90) of said second cylindrical housing (68). A combination as claimed in any preceding claim wherein for each switch assembly (26): said flange (70) on said first cylindrical housing (66) includes a radially inwardly extending portion (72) forming an aperture (72a) therein through which the cylindrical portion of said second housing (68) is movable in sliding relation, and a cylindrical portion of said second housing includes a circumferential sloping rib (86) thereon positioned intermediate the length thereof, which rib (86) is arranged upon being moved completely through said aperture (72a) in said radially inwardly extending portion (72) of the flange of said first housing (66) against the force of said compression spring moves radially outwardly under an edge of said radially inwardly extending portion (72) of the flange of said first housing (66) thereby to capture said second housing (68) within said first housing (66) by snap engagement. A combination as claimed in any preceding claim wherein a threaded end of one of said studs extends through each of said apertures (78) in said armature (14) and a nut (50, 60) screwed on each of the threaded ends of said studs fixedly attaches said inflatable restraint module (24) to the steering wheel (10), and said compression spring (64), said second cylindrical housing (68), and said first cylindrical housing (66) are disposed in concentric relation with said one of said attachment studs radially outwardly thereof in the order recited in the individually associated aperture in said armature (14). A combination as claimed in claim 1 wherein for each switch assembly: said attachment stud (56, 62) has a head portion at one end and a threaded portion at the other end, and is fixedly attached to said module assembly (24) through an aperture (55) therein by said head portion, said first housing (66) has a cylindrical portion (80) with a base portion (82) at one end and the associated flange (70) at the other end which flange (70) has a radially outwardly extending portion and a radially inwardly extending portion (72) with respect to the cylindrical portion (80) thereof, said first housing (66) being inserted in one said aperture (78) of said armature portion (14), said second housing (68) has a cylindrical portion (87) with the associated flange (88) at one end, which flange (88) has a radially outwardly extending portion and a radially inwardly extending portion (90) with respect to said cylindrical portion (87) thereof, the diameter of the cylindrical portion (87) of said second housing (68) being less than that of the cylindrical portion (80) of said first housing (66), said first electric contact (94) is positioned on the outwardly extending portion of the flange (70) of said first housing, said second electric contact (96) is positioned on the outwardly extending portion of the flange (88) of said second housing (68), said compression spring is positioned between said first housing (66) and said radially inwardly positioned flange portion (90) of said second housing (68), an assembly retainer (58) is provided positioned in covering relation with said first housing (66) on the threaded portion of said stud (56), and a lock nut (60) is provided screwed on the threaded portion of said stud. A combination as claimed in any preceding claim wherein said studs include stud means (42, 44) not associated with a switch assembly (26) attached to and extending through and from apertures in said module assembly through associated aligned apertures (48) in said armature (14), said further included stud means (42, 44) each having a head at one end and a threaded portion at the other end thereof, and nut means (50) screwed on the threaded ends of each of said further included stud means to attach said inflatable restraint module (24) to said armature (14).

Inventors: ALLARD JOHN E, SADERHOLM DAVID G, SMITH BRADLEY W, ALLARD, JOHN E., SADERHOLM, DAVID G., SMITH, BRADLEY W.
Applicants: MORTON INT INC, MORTON INTERNATIONAL, INC.
Application year: 1993
Main classification: B60R21
IPC codes: B60Q5, B62D1, B60R21