Windowed airbag cover and method of manufacture thereof

Abstract: A moulded cover (10) for an automotive airbag module is provided with one or more windows (12) therethrough to transmit light from a light source (18) within said module. The light source (18) which may be a light emitting diode is typically used to indicate the location or identify function switches under the moulded cover. The cover (10) and window (12) may be formed by a two part moulding process or an aperture may be left in the cover in which a solid preformed window is fixed. Alternatively the cover may be formed of transparent thermoplastic material and paint applied to define a window region. A thinned cover region (16) may surround the window (12) to increase flexibility and facilitate actuation of a switch located in the module behind the window (12).

Description: This invention relates to the field of automotive airbags. More specifically, it relates to an improved cover for such airbags. The driver's side automotive airbag is widely installed in automotive vehicles. Conventionally, the airbag module stored within the steering wheel takes the form of a reaction canister which houses a folded airbag. An igniter is actuated by a crash sensor to combust a generant and provide the gas for inflating the airbag. The canister and folded airbag are enclosed by a plastic cover which fills the central part of the steering wheel. The plastic cover normally is provided with tearlines which burst under the influence of the expanding airbag, allowing the airbag to expand into the driver's compartment to protect the head and upper torso of the driver. While the airbag module placement is well-suited to protect the driver, it preempts the location favored by many automobile stylists for function and accessory switches for such accessories as radio, ventilation, and air conditioning controls. Although some switches, such as for the horn, may be installed for actuation through the module cover, others require back-lighting. Patent EP-A-0 283 188 (on which the pre-characterising part of claim 1 is based) discloses an airbag module cover in a front surface of which a bulb is incorporated. The bulb merely acts as a warning light and is not depressible to effect actuation of remote equipment. Patent EP-A-0 554 448 discloses an airbag cover in a front surface of which a coloured indicating mark is incorporated. The mark is formed from a material which is different from the remainder of the cover. Accordingly, it is a primary object of the present invention to provide an improved airbag module cover which is formed with windows therein to permit back-lighting of switches or displays and facilitates actuation of such switches. Other objects, features, and advantages will become apparent from the following description and appended claims. The invention comprises a plastic airbag cover which incorporates windows to permit passage of light from sources inside the cover. The invention will now be described by way of example only with reference to the accompanying drawings in which: FIG. 1 is an elevational view of a plastic airbag cover in accordance with the present invention; FIG. 2 is an enlarged cross-section taken substantially along the line 2-2 of FIG. 1 ; FIG. 3 is a view similar to that of FIG. 2 illustrating an alternative cover construction; FIG. 4 is a view similar to that of FIG. 3 illustrating an alternative cover construction; and FIG. 5 is a view similar to that of FIG. 2 illustrating an alternative cover construction. Illustrated in FIG. 1 is a plastic cover 10 for a driver side airbag module. In shape and composition the cover 10 is basically conventional and, accordingly, is not described in detail. It includes the requisite tearlines and the mounting projections required for mounting it to the reaction canister of an airbag module assembly. The distinguishing feature of the airbag module cover 10 is the presence of a plurality of light transmitting windows 12 in the front surface of the cover. One method for achieving the desired windows is illustrated in FIG. 2 . In this embodiment the transparent window 12 is in the form of a cylindrical body surrounded by a circular flange 14 . The pre-formed window 12 would be installed in an injection mold prior to injecting the plastic forming the body of the cover 10 . The plastic material of the cover 10 would surround the flange 14 . After completion of the molding step and removal from the mold, the cover 10 would hold the window 12 firmly in place. Although the window 12 is shown as a circular or cylindrical body in the Figure, it will be appreciated that the window may be of any suitable shape, such as for example, circular, square, rectangular, elliptical, oval or the like. The embodiment illustrated in FIG. 2 shows a thinned cover region 16 surrounding the window area. This feature achieves two functions. First, it reduces the stiffness of the cover material in the region of the window 12 , thereby making it easier to activate an underlying switch. Second, it permits the thickness of the window to be less than that of the cover material. This permits use of a window 12 material which has a relatively low degree of transparency. Also illustrated in FIG. 2 is a light source 18 , such as a light-emitting diode. The diode or other light source such as an electroluminescent material could be, for example, mounted upon the switch. The latter, not being a part of this invention, is not further disclosed. The invention is not limited to the particular method of incorporating a window into an airbag cover. An injection molding method is described above. Another technique would involve a two shot molding process. A translucent or transparent material could be injected into the mold to form the windows. The balance of the cover would then be molded using a desired cover material. Alternatively, the material for the cover could be injection molded first and then the translucent or transparent material could thereafter be injected into the mold to form the windows. This technique would produce a single piece cover with one or more windows to allow the passage of light. Alternative cover forms are described with reference to Figs. 3, 4 and 5. These figures do not show the thinning of the cover immediately adjacent the window. In another technique, holes could be molded into the cover or punched through the cover after forming. The holes could then be filled with the translucent or transparent material, as either liquid or preformed solid. Two versions of the latter are illustrated in FIGS. 3 and 4 . FIG. 3 illustrates a solid window 20 which is pushed through a hole in the cover 10 . The window includes a flange 22 which is secured to the cover by a plurality of heat-staked rivets 24 . FIG. 4 illustrates a similar window 26 whose flange 28 is secured to the cover 10 by ultrasonic welding, adhesives, or other suitable means. In a still further method, the entire module cover could be formed of a transparent or translucent plastic material which is capable of being painted or otherwise colored or dyed as illustrated in FIG. 5 . In this method, after forming the module cover 10 , areas 30 where windows are desired are blocked against painting and the remainder of the cover 32 is painted to make it opaque, leaving transparent windows 12 in the blocked areas. The windows may be made of any suitable transparent or translucent material, especially from transparent or translucent thermoplastic polymers. For example, the windows could be formed from any suitable transparent or translucent thermoplastic polyurethane elastomer, a polypropylene alloy based elastomer such as Santoprene, or the like. In general, the cover will be made of any suitable opaque material, such as for example, a thermoplastic resin such as an opaque styrene based thermoplastic resin sold under the trade name Multibase resins or a copolyester resin available from Du Pont Co. under the brand name DYM resins.

Claims: An automotive vehicle airbag module having a cover (10) and a light emitter (18) for transmitting light to a vehicle occupant characterised in that said light emitter (18) is within said module and said cover (10) has at least one window (12) incorporated in a front surface thereof through which light from the light emitter is transmitted to a vehicle occupant and wherein a portion of said cover immediately adjacent said at least one window (12) is thinned to increase its flexibility. The module according to claim 1 wherein the cover (10) includes a plurality of windows (12). The module according to claim 1 or 2 wherein said cover and the at least one window (12) are thermoplastic polymeric materials and the cover is of a different thermoplastic polymeric material than that of the at least one window. The module according to any preceding claim wherein the light emitter (18) is a light emitting diode. The module according to claim 1 or 2 wherein said cover is made of a transparent thermoplastic and wherein the non-window portions have been painted. A method of making the cover (10) of an automotive vehicle airbag module as claimed in any one of claims 1 to 4, the method comprising: providing an injection mold; placing a light transmitting window (12) within said injection mold; injecting into said mold a thermoplastic cover material and forming a cover (10) to surround and retain said window (12) a portion of said cover immediately adjacent said window being thinned to increase its flexibility; removing said molded cover material and retained window from said mold. A method of making the cover (10) of an automotive vehicle airbag module as claimed in any one of claims 1 to 4, the method comprising: providing an injection mold; injecting into said mold one of (a) a first thermoplastic material capable of being molded into a light-transmitting solid window (12) and forming a window from said first material and (b) a second thermoplastic material capable of being molded into an airbag cover (10) and forming an airbag cover from said second material, and forming one of a window (12) or airbag cover (10); injecting into said mold the other of said first and second thermoplastic materials and forming the other of said window (12) or airbag cover (10); said second material surrounding and retaining said formed window (12) and having a thinned portion immediately adjacent said window to increase its flexibility; and removing from said mold the composite cover so formed. A method of making the cover (10) of an automotive vehicle airbag module as claimed in any one of claims 1 to 4, the method comprising: providing a formed airbag module cover (10) having at least one opening therethrough and a thinned portion immediately adjacent said at least one opening; and filling the at least one opening with a light transmitting material. The method of claim 8 wherein the light transmitting window is a solid preformed window.

Inventors: HARRIS BRADLEY D, LANG GREGORY J, HARRIS, BRADLEY D., LANG, GREGORY J.
Applicants: AUTOLIV ASP INC, AUTOLIV ASP, INC.
Application year: 1995
Main classification: B60R21
IPC codes: B60R21, B60Q1