GB2403999A

GB2403999A - Vehicle horn

Info

Publication number: GB2403999A
Application number: GB0316441A
Authority: GB
Inventors: Romain Chebret
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2003-07-14
Filing date: 2003-07-14
Publication date: 2005-01-19
Also published as: WO2005005229A1; GB0316441D0

Abstract

An electrically conductive steering wheel frame 1 with an electrical contact for actuating a vehicle horn, the electrical contact formed by a protrusion 2,3 on the frame 1 coated with an electrically conductive paint 5, the paint 5 preventing corrosion of the contact 4. The protrusion 2,3 may be frustroconical with a cylindrical section defining the contact 4, the cylindrical section may have a diameter of 8 mm. The painted area may be 35-50 microns thick The paint 5 may contain metal particles which may be nickel or copper and the paint 5 may be a solvent paint drying as a result of the evaporation of a solvent, alternatively it may be an oxygen curing paint or multi-component paint. The frame 1 may be a metal comprising magnesium or aluminium.

Description

DESCRIPTION OF INVENTION

"IMPROVEMENTS IN OR RELATING TO A VEHICLE STEERING WHEEL" THE PRESENT INVENTION relates to a vehicle steering wheel, and more particularly relates to a steering wheel provided with an electrical contact, such as a contact for actuating the vehicle horn function.

It has been proposed to provide a steering wheel comprising a steering wheel frame having an electrical contact for actuating the vehicle horn function. The electrical contact is configured to allow an electrical connection between the steering wheel frame and another electrical contact.

Vehicle steering wheel frames are normally constructed from metals such as aluminium or magnesium. These metals are relatively reactive, and will react with the oxygen in the air to form a metal oxide. This process, also known as corrosion, results in a thin metal oxide layer forming on the surface of the steering wheel frame. The metal oxide layer does not have good electrically conductive properties, and electrically insulates the main body of the steering wheel frame from any external contacts.

A vehicle's horn function is normally actuated by using the steering wheel frame as a ground connection for the horn function circuit. In order to provide an electrical connection between the main body of the steering wheel frame and an external electrical contact, it has been proposed to use contacts formed from rivets made of metal or a mixture of metals which are not prone to corrosion by the air. Rivets are typically made from mixtures of copper and aluminium or silver and aluminium. The surface of the rivet engages directly with the main body of the steering wheel frame, preventing an oxide layer forming between the rivet and the steering wheel frame. As no insulating oxide layer forms on the surface of the rivet, an electrical current can easily flow from a contact touching the rivet, through the rivet and into the main body of the steering wheel frame.

Although using rivets to form an electrical contact on a steering wheel frame initially works effectively, it is possible that vibrations produced by the motion of the vehicle will cause the rivets to become loose. Once a rivet has become loose the electrical contact which it provides on the steering wheel frame becomes unreliable, and the section of the steering wheel frame underneath the rivet becomes open to corrosion by the air. Using rivets to form an electrical contact also increases the complexity of the steering wheel construction process, and any repairs which are needed to fix a loose rivet prove to be very costly.

The present invention seeks to provide an improved steering wheel.

According to one aspect of this invention there is provided a vehicle steering wheel comprising an electrically conductive frame with an electrical contact formed by a protrusion on the frame, at least an operative area of the profusion being painted with electrically conductive paint.

Preferably the protrusion comprises a frustoconical base section.

Conveniently the protrusion comprises a cylindrical section, the end of the cylindrical section defining the operative area.

Advantageously the cylindrical section has a diameter of 8 mm.

According to another aspect of this invention there is provided a method of making a steering wheel, the method comprising the steps of applying, to an operative area of a protrusion formed on an electrically conductive frame of the steering wheel, an electrically conductive paint.

Advantageously the electrically conductive paint is applied to bare metal on the operative area.

In one embodiment the electrically conductive paint is applied to the operative area soon after it has been cast and before an oxide layer has developed.

Alternatively the electrically conductive paint is applied to the operative area after an oxide layer has been removed from the area.

Preferably the painted area has a thickness of between 35-50pm.

Conveniently the painted area is formed from a paint containing metal particles. l

In one embodiment the metal particles comprise particles of nickel.

Alternatively the metal particles comprise particles of copper.

Conveniently the metal particles are metal dust.

In one embodiment the electrically conductive paint is a solvent paint which dries as a result of evaporation of a solvent.

Alternatively the electrically conductive paint is an oxygen curing paint which sets, or dries, when exposed to oxygen.

Alternatively again the electrically conductive paint is a multi component paint which cures after the components are mixed.

Advantageously the electrically conductive frame is made of metal and comprises aluminium.

Alternatively the electrically conductive frame is made of metal and comprises magnesium.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawing in which: FIGURE 1 is a sectional view of part of a steering wheel frame. s

Figure 1 shows a sectional view of part of a steering wheel frame 1 cast from aluminium or magnesium. A protrusion on the frame has a frustoconical base section 2 which extends outwardly from the steering wheel frame 1, and a cylindrical section 3, of smaller diameter than the narrow end of frustoconical S base section 2, is situated on top of frustoconical base section 2. The diameter of cylindrical section 3 is typically 8 mm. The top of cylindrical section 3 forms an operative area 4 which is to be the operative area of an electrical contact.

The operative area 4 is to be painted with an electrically conductive paint. Unless the frame has been cast recently it is probable that there is an oxide layer on the operative area 4. This oxide layer, if initially present, is removed from operative area 4 by a mechanical or chemical process, to ensure that there is a bare metal area on operative surface 4.

Electrically conductive paint is then applied to operative surface 4 to form a coating 5 of thickness between 35-50,um. The electrically conductive paint may contain nickel or copper in the form of metal particles or metal dust.

The electrically conductive paint could be a solvent paint which dries as a result of the solvent evaporating, or it may be an oxygen curing paint which sets, or dries, when exposed to oxygen. Alternatively the electrically conductive paint may be a multi-component paint which, when mixed, cures as the components react.

The paint may be applied using any convenient technique. The paint seals the bare metal beneath it from the surrounding air, thus preventing corrosion.

The painted operative area forms a robust electrical contact which is cheap to produce.

In the present specification "comprises" means "includes or consists of' and "comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS: 1. A vehicle steering wheel comprising an electrically conductive

frame with an electrical contact formed by a protrusion on the frame, at least an operative area of the protrusion being painted with electrically conductive paint.
2. A vehicle steering wheel according to Claim 1, wherein the protrusion comprises a frustoconical base section.
3. A vehicle steering wheel according to any one of the preceding Claims, wherein the protrusion comprises a cylindrical section, the end of the cylindrical section defining the operative area.
4. A vehicle steering wheel according to Claim 3, wherein the cylindrical section has a diameter of 8 mm.
5. A vehicle steering wheel according to any one of the preceding Claims, wherein the painted area has a thickness of between 35-501lm.
6. A vehicle steering wheel according to any one of the preceding Claims, wherein the painted area is formed from a paint containing metal particles.
7. A vehicle steering wheel according to Claim 6, wherein the metal particles comprise particles of nickel.
8. A vehicle steering wheel according to Claim 6 or 7, wherein the metal particles comprise particles of copper.
9. A vehicle steering wheel according to Claim 6, 7 or 8, wherein the metal particles are metal dust.
10. A vehicle steering wheel according to any one of the preceding Claims, wherein the electrically conductive paint is a solvent paint which dries as a result of evaporation of a solvent.
11. A vehicle steering wheel according to any one of Claims 1 to 9, wherein the electrically conductive paint is an oxygen curing paint which sets, or dries, when exposed to oxygen.
12. A vehicle steering wheel according to any one of Claims 1 to 9, wherein the electrically conductive paint is a multi-component paint which cures after the components are mixed.
13. A vehicle steering wheel according to any one of the preceding Claims, wherein the electrically conductive frame is made of metal and comprises aluminium.
14. A vehicle steering wheel according to any one of Claims 1 to 12, wherein the electrically conductive frame is made of metal and comprises magnesium.
15. A method of making a steering wheel, the method comprising the steps of applying, to an operative area of a protrusion formed on an electrically conductive frame of the steering wheel, an electrically conductive paint.
16. A method according to Claim 15, wherein the thickness of the electrically conductive paint is between 35-50pm.
17. A method according to Claims 15 or 16, wherein the electrically conductive paint contains metal particles.
18. A method according to Claim 17, wherein the metal particles comprise particles of nickel.
19. A method according to Claims 17 or 18, wherein the metal particles comprise particles ofcopper.
20. A method according to Claims 17, 18 or 19, wherein the metal particles are metal dust.
21. A method according to Claims 15 to 20, wherein the electrically conductive paint is a solvent paint which dries as a result of evaporation of a solvent.
22. A method according to Claims 15 to 20, wherein the electrically conductive paint is an oxygen curing paint which sets, or dries, when exposed to oxygen.
23. A method according to Claims l S to 20, wherein the electrically conductive paint is a multi-component paint which cures after the components are mixed.
24. A method according to Claims 15 to 23, wherein the electrically conductive paint is applied to bare metal on the operative area.
25. A method according to Claims 15 to 23, wherein the electrically conductive paint is applied to the operative area soon after it has been cast and before an oxide layer has developed.
26. A method according to Claims 15 to 23, wherein the electrically conductive paint is applied to the operative area after an oxide layer has been removed from the area.
27. A vehicle steering wheel hereinbefore described with reference to and as shown in the accompanying drawing.
28. A method of making a steering wheel substantially as herein described with reference to the accompanying drawings.
29. Any novel feature or combination of features disclosed herein.