The present invention relates to a horn switch. Motor vehicles are equipped a horn that is typically activated by a switch. The switch comprises two electrical contacts, one of which is disposed on the airbag module, and the other on an armature of a steering wheel.

The present invention provides a horn switch that is coupled between a stationary member such as a steering wheel and a movable member such as an airbag module. The horn switch includes a plurality of electrically conductive elements such as wires or stampings that are moved into contact with each other to generate a signal. Further applications of the present invention will become apparent from the following detailed description.

Figure 1 is a perspective view of a steering wheel having a horn switch according to the present invention.

Figure 1a shows a number of ancillary elements of a steering wheel.

Figure 1b shows a mounting plate that could be part of an airbag module.

Figure 2 is a perspective view of a steering armature for use with the horn switch of Figure 1.

Figure 2a is an enlarged view of the armature showing spring clips secured to the armature.

Figure 2b is another enlarged view of a portion of the armature showing a portion of one of the spring clips.

Figure 2c is a plan view showing the mounting plate secured to the steering wheel armature.

Figure 3 shows a plurality of conductive elements that form electrical contacts of a horn switch.

Figure 3a is an isometric view of a horn switch.

Figure 3b is an exploded view of a horn switch.

Figure 3c is a partial view of the horn switch and illustrates the crisscrossing of the conductive elements of the horn switch.

Figure 4 is a cross-sectional view of a portion of the horn switch through section 4 - 4 of Figure 6.

Figure 4a is a cross-sectional view of a portion of the horn switch through section 4a - 4a of Figure 6.

Figure 4b is a cross-sectional view of a portion of the horn switch through section 4b - 4b of Figure 6.

Figure 5 is an isometric view showing the horn switch mounted to the armature.

Figure 6 shows the horn switch with portions of insulating material removed.

Figure 7 is a perspective view of the horn switch according to an alternative embodiment.

Figure 7a illustrates only the conductive elements such as wires used in Figure 7 and also shows an alternate embodiment.

Figure 8 is a perspective view of the horn switch of Figure 7 prior to assembly.

Figure 9 is a perspective view of the horn switch according to a second alternative embodiment.

Figure 10 shows another alternate embodiment.

Although the following description is related to a horn switch for use in a motor vehicle, it will be understood that this switch could be utilized with any appropriate application.

In Figures 1 through 6, a steering wheel assembly 12 is shown for use with a motor vehicle. The steering wheel assembly 12 includes an airbag module 14, a horn switch 16 and steering wheel 18. The steering wheel comprises a metal armature 300 and a number of other parts 301 , which are not pertinent to the present invention and are diagrammatically illustrated in Figure 1a. These other parts may include foam and/or resin molded about the metal armature; a back cover connected to the armature; leather covering; and switches. The horn switch 16 is disposed between a movable member such as the airbag module 14 and a stationary member such as the steering wheel 18. The airbag module is secured to the steering wheel armature 18a by a spring clip assembly 19. The horn switch 16 can be located between any two cooperating members configured to squeeze the elements of the horn switch 16 together. It is within the invention to construct a horn switch 16 by

separating the upper and lower horn switch housings 50, 52 and connecting the upper horn switch housing 50 to the plate 24, or a pushing member, and connecting the lower horn switch housing 52 to the armature 300, or fixed member as shown in Figure 10. Upon introduction of the spring 54 and assembly of the airbag module 14 to the steering wheel 18, the horn switch 16 will be assembled and have the above configuration.

Figures 2, 2a and 2b show features of the steering wheel armature 300 and spring clip mechanism 19. The steering wheel armature 300 comprises a metallic material, often cast magnesium, aluminum or steel. The armature 300 includes a hub 302, and a plurality of spokes 303 that connect the hub 302 to a rim 304. The hub includes a number of hooks 306 and pins 308, each preferably integrally formed as part of the hub. The hub includes a connection 305 connectable to the steering shaft of the vehicle. The connection features, such as the hooks and pins, secure each spring clip 19a, 19b of the spring clip assembly 19 to the armature 300.

In Figures 1 and 2a each spring clip 19a or 19b comprises a resilient material including a polymer or metal that may be preformed into a desire shape. Each spring clip has a shaft 320 having a medial bend 322 therein and an optional looped section 324 at one end. The medial bend 322 includes a ramped surface 322a, which facilitates removal of the spring clip from the armature. Each spring clip includes ends 326, 328, which as illustrated are straight and secure the end of each pin 34 of the airbag module 14 to the armature shown in Figure 1b. Each spring clip is secured to the armature 300 by bending the spring clip about a hook 306 and two pins 308 to achieve the configuration shown in Figure 2a. The spring clips 19a, 19b can be removed by reversing the above process or by pulling the looped section 324 toward the top of the armature 300. As the spring clip is moved, the medial bend 322 slides around the adjacent pin 308, which causes the end 326 to disengage a lower pin 34. The spring clip is pulled out of the armature to disengage from each pin 34. In this configuration the spring clip is stressed and presses against a corresponding wall of the

hook 306 and pins 308. The vertically extending portion 306a, see Figure 2b, of hook 306 operates as a pin, the horizontal portion of which limits the upward displacement of the looped end 324 from the hub 302.

In Figure 1b each of the pins 34 may be surrounded by a plastic body 34a, which increases the diameter of the body of the pin. The wider part 34a is received within passageways in upper and lower horn switch housings 50, 52. The plastic body is only shown about some of the pins 34 in Figure 1b.

The armature 300 includes a number of support members 330, which support the horn switch 16 and guide the airbag module 14 into its mounted location upon the armature. Four support members 330 are used in the illustrated embodiment. The location of the support members 330 is determined in part by the dimensions and construction of the airbag module. Each support member includes a passageway 332 to receive a pin 34, shown in phantom line in Figure 2a, of the airbag module 14. Each pin 34 engages an end 326, 328 of the spring clip 19a, 19b. Each support member 330 includes a top or anvil surface 334, which supports and reacts against a lower horn switch housing 52, and a lower surface 338, as shown in Figure 2b. The lower surface 338 is elevated above the hub 302 and defines a space or groove 340 into which the end of the spring clip is received. A tool 339 may be inserted into the looped end 324 of each clip 19a, 19b to apply pressure to the looped end 324 to remove the clip from the armature.

The airbag module 14 includes a cover 20 to protect an airbag 22. The cover 20 is illustrated as rectangular; however, any desired shape could be employed. The cover 20 may comprise a polymeric material, but any other suitable material could be used. The cover 20 may be coupled, in a known manner, to a mounting plate 24 to define a cavity for the containing the airbag 22 and an inflator 26. The inflator 26 deploys the airbag 22 in a crash.

The armature 300 can be replaced by another stationary member. The airbag module 14 or plate 24 can be replaced by another movable member. If the plate did not use pins 34 to locate the module upon the airbag, the armature 300 need not include the through holes 332.

The plate 24 may have a central aperture 28 to receive and support a portion of the infiator 26, a first or top side 30, and a second or lower side 32. The first side 30 is provides an interface for the airbag 22 and infiator 26. The second or lower side 32 of the plate 24 includes a plurality of prongs or pins 34 and a plurality of flanges 36 to couple the plate 24 to a similar element 36a on the cover 20. In this embodiment, the second side 32 of the plate 24 includes four pins 34, which include at least one attachment mechanism 37, such as conically shaped tip, clip, hook or flange, which are each operable to couple the airbag module 14 and the horn switch 16 to the armature 300.

The horn switch 16, as shown in Figures 3, 3a and 3b, comprises two relatively movable electrical conductors formed, for example, an upper electrical wire 40 and a lower electrical wire 42. The wires 40, 42 are configured so that when in engagement and closing the electric circuit for the horn 27, they are capable of crossing or contacting in a plurality of locations. Each such location 44, shown within dotted circles in Figure 3, forms electrical contacts or contact points. When the two wires are used in a horn switch, three or four crossing or contact points appears to be adequate to accommodate normal usage of the horn. The vehicle operator may push upon the airbag cover at many different locations which causes at least one contact to be closed. The vehicle operator may press upon the center of the cover 20 or at its top, bottom, sides, etc. Respective ends 48 of each wire are adapted to be connected to one or more electrical connector(s) 49 to provide communication with an electrical control unit 25, which communicates the horn activation signal produced upon contact of the wires to a horn 27 (see Figure 2c). In Figure 3, the ends 48 are configured to be closely spaced, so that one electrical connector can be used. Two connectors are shown in Figure 3a. The electrical conductors 40, 42 need not be extruded wires. The electrical conductors can be formed by stamping, casting or molding.

The horn switch 16 includes a first or upper housing 50 and a second or lower housing 52. The housings 50, 52 are movable and are biased apart by one or more springs, such as a plurality of helical springs 54. Each housing 50, 52 encloses, protects and insulates a respective

conductor 40, 42. Each housing 50, 52 supports exposed portions 4Od, 42d of each wire, which function as an electrical contact. The spring support permits the two housings to move together so that all of the electrical contacts close simultaneously. The springs permit a relative rotation of the horn switch housings 50, 52, which occurs when the airbag cover is pushed at an off- center location, in which case one or more of the contacts will close. The relative rotation of the horn switch housings will cause the exposed wires 4Od, 42d to contact at slightly different locations and also create a wiping action to keep the wires 48 free of particles that may enter the horn switch 16.

Each wire (conductor, conductive element) 40, 42 has a plurality of legs 40a, 40b, 40c and 42a, 42b, 42c. One wire 42 is C-shaped, while the other wire 40 is U-shaped. This configuration provides for the four contact points 44. Wires of differing shape are within the scope of the present invention and each such shape will vary with the desired number of contacts, the relative placement of the contacts and the available space for the switch. Each of the upper and lower switch housings 50, 52 is insert molded about the conductive elements or wires 40, 42 and includes a respective insulating sheathing 56. Corresponding insulating sections or legs 56a - c are molded about the legs 40a - c and sections 58a - c are molded about legs 42a - c of the wires 40, 42. Each of the upper and lower switch housings 50, 52 includes a plurality of support members 60, 160, which support both the insulated and uninsulated portions of each wire. The support members and insulating sheaths are formed during the molding operation. In the illustrated embodiments, the support members 60, 160 have a central passageway to permit passage of the pins 34 of the airbag module. If the airbag module does not include such pins a passageway is not needed. The pins 34, which pass through the horn switch and portions of the armature, effectively locate the horn housings 50, 52 as well as the airbag module 14 relative to the steering wheel armature 300. Each of the conductive elements 40, 42 includes curved portions 45 that are molded into the respective support members 60, 160. The curved construction accommodates the need for a passageway in the support members 60, 160 and can be eliminated.

Each of the upper support members 60 in Figures 3a, 3b, and 4a, has a body 64, which as illustrated has an oval shape or egg shape, having a wide portion 66 and tapered 68 portion, which support both the insulated and the uninsulated portions 40d of wire 40 (see Figure 3). Each body 64 has an exterior or outer wall 70, a top surface 72 and lower surface 74. A passageway 76 extends through the wide portion 66 of the body 64. A narrow passageway 76a extends through the tapered portion of the body. The passageway 76 is an integrally formed first cylinder or cylindrical member 78, which is hollow and preferably extends below the lower surface 74; however, this is not a requirement of the invention. The extending portion of cylinder 78 is shown as 78a. The interior wall of the body forming the passageway includes two opposing grooves 80, 82, each of which terminates in a horizontal end or ledge 84. These grooves are an assembly feature and are optional to the invention and are useful in limiting the outward movement of the spring housing 50, 52. This motion limit function can be provided on other parts of the systems adjacent to the horn switch.

Each lower support member 160 comprises a body 164, which as illustrated has an oval shape or egg shape, that is a wide portion 166 and a tapered 168 portion, which supports both the insulated and the uninsulated portions of wire 42 (see Figure 3). Each body 164 has an exterior or outer wall 170, a top surface 172 and lower surface 174. A passageway 176 extends through the wide portion 166 of the body 164. A narrow passageway 176a extends through the tapered portion of the body. The passageway 176 is an integrally formed second cylinder or cylindrical member 178, which is hollow and preferably extends below the lower surface 174; however, this is not a requirement of the invention. The lower extending cylindrical part 178a shown in Figure 3a is received in a corresponding passageway 322 in armature 300.

The uninsulated, exposed conductive portion 4Od, 42d the conductive member that traverses the passageway 76a of each support member 60, 176a can span the sides of this passageway without being supported. This may be the case where the conductive members 40, 42 are relatively rigid and do not deform much when in contact. Some of the

passageways 76a of the support member 60 are shown as simple cylindrical passageways. The support member 160 and in particular passageway 176a can be constructed the same way. In some situations it is desirable to support the conductive portions 4Od, 42d, for example if the conductive members 40 and/or 42 are made of a soft material such as copper. Figures 3a, 3b, 4a and 4b illustrate ways of supporting the uninsulated, conductive portions 40d and/or 42d. Some of the passageways 76a, 176a include a bridge structure with two facing posts 94 of insulating material that extend down sides of passageway 76 to support the conductive portion 40d, 42d. These exposed conductive portions can be supported by another bridge structure, which is fabricated as a wall 96 of insulating material spanning the passageway 76a, 176a. The upper edge or the lower edge of the wall 96 supports the conductive portion, for example wire segment 42d, 40d as shown in Figure 4b.

The cylinder forming the passageway 176 includes two opposing, radially extending flanges 180, 182, which slide into one of the grooves 80, 82 and when moved apart by the springs 54 engage one of the ledges 84 to limit or stop the separation of each upper and lower support member of the upper and lower switch housings. If the grooves 80, 82 are not utilized, then the flanges 180, 182 can be eliminated as well. The lower cylindrical part 178a can optionally be formed with one or more extensions 179, as shown in Figures 3a and 3b, terminate in a hook-like formation 181. When the lower switch housing 52 is seated upon the armature 300, each of the hook-like formations 181 extends to the lower surface 338 of the armature 300 to secure the switch 16 in place, which is shown in Figure 4b. These extensions 179 and formations 181 are optional, but they provide a benefit in shipping and installation. If the horn switch and armature are assembled at a facility remote from the final module assembly location, the horn switch 16 can be installed and shipped as part of a partially assembled armature sub- assembly. The extensions 179 and hook-like formations 181 provide faster assembly of the horn switch to a cooperating part such as the armature 300. The member that presses upon the horn switch 16, which in this case is the mounting plate 24 of the module 20, can be installed later. The horn switch

can be used with any two relatively movable parts, and the use of the switch is not limited to steering wheel armatures and airbag modules.

Upon assembly of the horn switch, a cylinder 178 is received in cylinder 78 and the flanges 180, 182 are seated in grooves 80, 82. Each of the cylinders 78, 178 forms a respective, opposing annular space 86, 186 in the upper and lower support members for reception of a spring 54.

Figure 5 shows the horn switch 16 mounted to the armature 300. A plastic sheathing 56a - c of the upper switch housing 58a - c and of the lower switch housing respectively cover the wire legs 40a - c and 42a - c. As illustrated each of the legs 40a - 40c and 42a - 42c is bent or curved with an apex at the center of each leg. Each of the legs or segments 40a - 40c comprises two linear sections that intersect at an angle or apex. The legs or segments 40a -40c and 42a -42c are bowed outwardly and extend horizontally while segments 40b, 42b are bowed, vertically downward. The bowing or curvature of the legs can be in any direction as space may permit. A similar configuration can be achieved if the wire segments are arcuately shaped. The linear distance from the end point of each wire segment 40a - 40c and 42a - 42c (from the points 90, 90a through the apex 92) is longer than the distance between each end point 90, 90a, (see Figure 3a) to the other end point. This construction permits the legs 40a - c and 42a - c to be extended or straightened to more easily fit or position each of the support members 60, 160 into or about a passageway in the armature and compensates for tolerance differences between the various parts.

The thickness of the protective coatings 56, 58 may be about 1 - 2 mm. As the thickness increases, the stiffness of the legs 56 - 58 of the horn switch increases, which may make it more difficult to seat the horn switch 16 to the armature 300 if the tolerances are not controlled.

Figure 6 shows an alternate embodiment of the invention wherein the plastic coating or sheathing 56, 58 in the vicinity of some or all of the inflection points is formed with a void or space exposing the conductive wire 40, 42. With some of the sheathing removed, the legs of the horn switch become easier to extend, bend or straighten, facilitating placement of the lower horn switch support members 160 in a respective passageway 322 in the armature

and making it easier to align the upper support members 60 to the lower support members 160. The sheathing can be removed from other locations of the legs to facilitate extension of the legs.

In Figure 3c the plastic portions forming the upper housing 50 have been eliminated to show how the exposed portions of wires 40, 42 cross over each other. The contact portion 40d of wire 40 of the first or upper switch housing 50 will contact the contact portion 42d of wire 42 of the second or lower housing 40 at an angle, due to the shape of the first housing 50 and second housing 52. The exposed wire segment 4Od, which extends through the housing 50 and spans the first formed passageway 76a, is offset at an angle of 45 to 135 degrees with respect to the wire 42d, which passes through housing 52 and which spans the passageway 176a of the second housing 52.

Alternatively a horn switch 100, shown in Figures 7 and 8, can be formed with an octagonal shaped first or upper housing 102 and a rectangular second lower housing 104, as shown in Figures 7 and 8. In this alternative embodiment the first housing 102 and second housing 104 may be molded in a family mold with a pair of conductive elements, or wires 106, positioned near the center of a mold (not shown). The first housing 102 and the second housing 104 may comprise any suitable electrically insulating material. To eject the first housing 102 and second housing 104 from the mold, the wires 106 are each severed to provide four areas in which the wires 106 are exposed. The plurality of support members 60, 62, each to be aligned with a respective passageways 76, 176, may be molded into the first and second housing 102, 104 to couple the horn switch 100 to the airbag module 14 and wheel 18, as will be discussed in greater detail below. The shape of the wire(s) 106 in each of the upper and lower spring housings 102, 104 yields eight contact points 44, as illustrated in Figure 7a, compared with four contact points shown in the earlier embodiment. An elliptically shaped housing 102' (shown only in phantom line) is also shown in Figure 7a, which crosses housing 104 eight times to illustrate that various wire shapes and variously shaped housing parts can provide more electrical contacts.

The upper housing 102 is octagonal, and may be an irregular octagon having alternate sides 110, which are parallel along both an x axis and y axis.

A second set of sides 112 is skewed forty five degrees with respect to the x axis and y axis. The exposed wire segments 106a extend the length of the second set of sides 112. Each of the second set of sides 112 supports one of the support members 60. The passageways 76 are displaced from the sides 112 by a projection 114. The projection 114 enables the passageways 76, 176 of the first and second housings 102, 104 to be aligned.

The lower or second housing 104 is rectangular with sides 116 and chamfered corners 118. The exposed wire segments 106 extend along the corners 118 and may extend a distance D10 along the sides 116. The corners 118 are coupled to the support members 62 located on the corners 118 to enable the passageways 176 of the second housing 104 to align with the passageways 76 of the first housing 102. The horn switch 100 may have first and second housings that define three contact points disposed radially about the center of the airbag module as shown in Figure 9.

To activate the horn switch 16, 100, 200 a vehicle operator applies force to an upper part, such as cover 20 of the airbag module 14, positioned adjacent the upper switch housing 50, 102. The force may be applied to any location on the cover 20 to activate the horn switch 16, 100, 200. The cover 20 distributes the force, which ensures that the application of force to any location will activate the horn switch 16, 100, 200. The force, wherever applied to the cover 20, causes the springs 54 in the support members 60, 160 to compress. As the springs 54 compress, the exposed wire segments 40d, 106a of the first upper switch housing 52, 102 will contact the wires 42d, 106a of the second or lower housing 50, 104.

The horn switch 100 is activated by a surface 314 of the wire 106a of the first housing 102 contacting a surface 314' of the wire 106 of the second housing 104. The relative movement of the surface 314 against the surface 314' will cause the transmission of an electrical charge through an electrical connector 315 coupled to each of the wires 106 to the electrical circuit, and hence enable electrical energy to flow to the horn 27. The relative motion of the surface 314 of the wire 106 against the surface 314' will work as a wiping action to keep the wires 106 free of debris or other particles that may enter the horn switch 100. Due to the shape of the first housing 102 and

second housing 104, the surface 314 of the wire 106 of the first housing contact the surface 314' of the wire 106 of the second housing 104 at an angle or parallel to the surface 314' of the wire 106 of the second housing 104.

Since the horn switch 16, 100 contains a plurality of areas in which the wires 40, 42, 106 are exposed, the multiple areas of exposed wire ensure that the horn switch 16, 100 may be activated by to the application of the force at various locations on the cover 20 of the airbag module 14. The horn switch assembly 16, 100, 200 of the present invention reduces manufacturing complexity by enabling the horn switch assembly 16, 100, 200 to be formed in any suitable molding process, and also reduces the cost of the horn switch assembly 16, 100, 200.

In Figure 10 the horn switch 16 is separated with the upper horn switch housing 50 secured to the plate 24, or to a movable element used to actuate the horn switch. The lower horn switch housing 52 is secured to the armature 300. The springs 54 are mounted to the lower horn switch housing 52. Upon assembly of the airbag module to the armature, the horn switch 16 is realized. The upper section of Figure 10 shows that the plate 24 may include pins 34 to couple the movable element 24 to the stationary element. Two such pins are shown extending through the upper support members 60.