GB2269887A

GB2269887A - Steering wheels.

Info

Publication number: GB2269887A
Application number: GB9217432A
Authority: GB
Inventors: Dan Persson
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1992-08-17
Filing date: 1992-08-17
Publication date: 1994-02-23
Also published as: GB9217432D0; WO1994004407A1

Abstract

A steering wheel has a rim which comprises a rigid, eg metallic, core 6 surrounded by plastics material comprising an outer skin 9 of thermoplastic material, eg polyurethane, and further thermoplastic material, eg polypropylene, located between the skin 9 and the core 6. In one arrangement, Figures 2 and 3, the further thermoplastic material is in the form of two moulded elements 7, 8 which are mounted on the core 6 and held in place by snap-fit formations 10, 11. Voids 7, 8 may be provided to reduce the amount of material needed and bores 14, 15 extend from the exterior of each element 7, 8 to the core 6 to anchor the outer skin 9 when finally moulded in position. In another arrangement, Figure 4, the metal core 6 is coated with a non-tick material and the thermoplastics layers 16 and 9 are moulded in place. These arrangements facilitate removal of the thermoplastics layers for recycling. <IMAGE>

Description

DESCRIPTION OF THE INVENTION "IMPROVEMENTS IN OR RELATING TO A STEERING WHEEL" THE PRESENT INVENTION relates to a steering wheel for a motor vehicle.

A conventional steering wheel, made at the present time, consists of a metal core to which is applied a sheath or coating. Typically the coating comprises an inner layer which may be formed of thermosetting polyurethane which is moulded in position, and to which is applied a polyvinyl chloride outer coating or "skin". Frequently the polyurethane material is "foamed" and this foaming is presently accomplished utilising a blowing agent, which is typically a chlorofluorocarbon or hydrocarbon. These materials may be those sold under the Trade Mark "FREON".

The existing steering wheel presents various disadvantages. Firstly it is virtually impossible to recycle the material used in forming the steering wheel.

The outer skin of PVC is of a totally different plastic than the inner layer of thermoset polyurethane, since the PVC is a thermoplastic material. Also, the thermoset polyurethane cannot be recycled. A further disadvantage, of course, is that the known procedure involves the use of chlorofluorocarbons and hydrocarbons which are known to be damaging to the environment.

The present invention seeks to provide an improved steering wheel.

According to this invention there is provided a steering wheel having a rim which comprises a rigid core surrounded by plastic material, the plastic material surrounding the core comprising an outer skin of thermoplastic material, and further thermoplastic material located between the skin and the core.

Preferably the plastic material of the outer skin is a different plastic material to that between the skin and the metal.

Conveniently the outer skin is formed from a thermoplastic polyurethane.

Advantageously the outer skin is approximately 3 mm thick and has 60 Shore A hardness.

In one embodiment the thermoplastic between the outer skin and the inner core comprises a plurality of premoulded elements which surround the core.

Preferably the elements are adapted to be snapfastened to each other at spaced positions.

Conveniently the elements are provided, at spaced intervals, with bores extending from the exterior to the inner core, the material forming the outer skin passing through the bores and engaging the inner core to bond the said elements to the inner core.

Advantageously the said elements define at least one void.

In an another embodiment the thermoplastic material between the outer skin and the core comprises thermoplastic material which is moulded in position.

Preferably the moulded thermoplastic is a foamed thermoplastic.

Advantageously the metal core is provided with a coating of low friction material before the thermoplastic between the outer skin and the core is moulded in position.

Conveniently the low friction material comprises polytetrafluoroethylene or a silicone-based material.

Advantageously the further thermoplastic material between the skin and the core is polypropylene.

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 drawings in which FIGURE 1 is a schematic illustration of a steering wheel in accordance with the invention, FIGURE 2 is a sectional view taken on the line A-A of Figure 1, FIGURE 3 is a sectional view taken on the line B-B of Figure 1, and FIGURE 4 is a sectional view of part of the rim of an alternate steering wheel in accordance with the invention.

Referring initially to Figure 1 of the drawings, the steering wheel comprises a central boss 2 from which a plurality of spokes 3 extend substantially radially, the spokes supporting an outer rim 4. At least the outer rim comprises a metal core which is provided with a covering or sheath 5 formed of a plastics material. As thus far described, the steering wheel is conventional.

Referring to Figures 2 and 3 of the drawings it can be seen that the rim of the steering wheel is formed by a metal core 6, to which a coating or sheath 5 is applied.

It can be seen that the coating is formed from two separate inner elements 7,8 which co-operate to initially embrace the metal core 6 of the rim of the steering wheel and an outer covering or skin 9.

The two elements 7,8 are moulded from an appropriate thermoplastic material, such as polypropylene.

The two elements 7 and 8 are, of course, moulded in moulds designed to produce elements which can be mounted on the particular metal core 6. It is to be observed that each element 7,8 is substantially semi-circular in cross-section or of "C" section, so that the two elements can be mounted on the metal rim 6 so as to completely surround the metal rim 6. At points spaced along the elements 7 and 8, cooperating projections 10 and recesses 11 are provided which form a snap-fit. A typical pair of projections and recesses are shown schematically in Figure 2.

Corresponding projections and recesses will be provided at regular spaced intervals.

Also shown in Figure 2 are relatively large voids 12,13 defined by the elements 7 and 8. The elements 7 and 8 may define extensive voids of this type in order to minimise the amount of material actually used in making the elements 7 and 8.

Figure 3 illustrates the cross-section of the elements 7 and 8 at a position spaced from the section of Figure 2. In this region the elements 7 and 8 are each provided with a bore 14,15 which extends from the exterior of each element to the central metallic core 6.

When the two elements 7 and 8 have been mounted in position on the metal core 6, the steering wheel, with the elements 7 and 8 is located in an appropriate mould and the outer skin 9 is moulded in position, again from a thermoplastic material which may comprise thermoplastic polyurethane.

It is to be appreciated that when the outer skin 9 is moulded in position, part of the plastic material will pass down through the bores 14 and 15, thus contacting the rim 6. This will provide a positive anchoring effect ensuring that the outer sheath formed of the elements 7 and 8 cannot slide relative to the inner metal core 6. The outer skin 9 may be approximately 3 mm thick and may have a hardness of 60 Shore A. The thermoplastic polyurethane is used for the outer skin because the material is relatively soft, but is wear and heat-resistant.

Figure 4 illustrates an alternative embodiment of the invention. In this embodiment the metal core 6 of the rim of the steering wheel may initially be coated with a material presenting non-stick properties such as polytetrafluoroethylene or a silicone-based material. A inner layer of a thermoplastic material, such as polypropylene, may then be moulded directly in position on the core 6 of the rim. This layer of material may be foamed using an appropriate blowing agent. Polypropylene is preferred since this material is relatively cheap and provides the required hardness. To the moulded layer 15, an outer skin 9 is again moulded using thermoplastic polyurethane as in the embodiment described with reference to Figures 1 to 3.

It may be necessary, in order to avoid slippage of the outer sheath relative to the metal core 6, to provide the outer surface of the metal core 6 with undulations or other irregular means to engage the inner layer 15.

When a steering wheel in accordance with the invention has finished its useful life, and is to be recycled, a knife or other cutting element may be used to cut the outer skin and, in the embodiment of Figure 4, to cut through the inner layer 15 right down to the metal core 6. The thermoplastic material may then be peeled off from the metal core 6, and may be recycled. The presence of the low friction material, such as polytetrafluoroethylene or the silicone-based material present on the metal core 6 in the embodiment of Figure 4 facilitates the separation of the inner layer 15 from the metal core. The metal core may also be recycled appropriately.

Claims

CLAIMS:

1. A steering wheel having a rim which comprises a rigid core surrounded by plastic material, the plastic material surrounding the core comprising an outer skin of thermoplastic material, and further thermoplastic material located between the skin and the core.

2. A steering wheel according to Claim 1 wherein the plastic material of the outer skin is a different plastic material to that between the skin and the metal.

3. A steering wheel according to Claim 1 or 2 wherein the outer skin is formed from a thermoplastic polyurethane.

4. A steering wheel according to Claim 3 wherein the outer skin is approximately 3 mm thick and has 60 Shore A hardness.

5. A steering wheel according to any one of the preceding Claims wherein the thermoplastic between the outer skin and the inner core comprises a plurality of premoulded elements which surround the core.

6. A steering wheel according to Claim 5 wherein the elements are adapted to be snap-fastened to each other at spaced positions.

7. A steering wheel arrangement according to Claim 5 or 6 wherein the elements are provided, at spaced intervals, with bores extending from the exterior to the inner core, the material forming the outer skin passing through the bores and engaging the inner core to bond the said elements to the inner core.

8. A steering wheel according to any one of Claims to 7 wherein the said elements define at least one void.

9. A steering wheel according to any one of Claims 1 to 4 wherein the thermoplastic material between the outer skin and the core comprises thermoplastic material which is moulded in position.

10. A steering wheel according to Claim 9 wherein the moulded thermoplastic is a foamed thermoplastic.

11. A steering wheel according to Claim 9 or 10 wherein the metal core is provided with a coating of low friction material before the thermoplastic between the outer skin and the core is moulded in position.

12. A steering wheel according to Claim 11 wherein the low friction material comprises polytetrafluoroethylene or a silicone-based material.

13. A steering wheel according to any one of the preceding Claims wherein the further thermoplastic material between the skin and the core is polypropylene.

14. A steering wheel substantially as herein described with reference to and as shown in Figures 1 to 3 of the accompanying drawings.

15. A steering wheel substantially as herein described with reference to and as shown in Figures 1 to 3 of the accompanying drawings as modified by Figure 4.

16. Any novel feature or combination of features disclosed herein.