GB1571902A

GB1571902A - Method of manufactureof steering wheel

Info

Publication number: GB1571902A
Application number: GB2123576A
Authority: GB
Original assignee: BALL PLASTICS Ltd
Current assignee: BALL PLASTICS Ltd
Priority date: 1977-04-14
Filing date: 1977-04-14
Publication date: 1980-07-23

Description

(54) METHOD OF MANUFACTURE OF STEERING WHEEL (71) We, BALL PLASTICS LIMITED, a British Company, of Burstead Works, Kennel Lane, Billericay, Essex, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a steering wheel, and more particularly to a steering wheel for use in a motor vehicle, boat or the like.

Certain embodiments of the invention have particular applications in motor cars.

The invention further relates to a method of manufacturing a steering wheel.

One type of prior proposed steering wheel comprises a central circular metal boss and an outer circular metal ring, the boss and the ring being connected to form a steering wheel by means of two or more metal spokes, the metal spokes being angularly displaced about the boss and extending radially from the boss to the outer ring. The outer ring, the spokes and the central boss are coated with a material such as polypropylene or P.V.C. in a moulding process, both to provide a hand grip and to provide a more attractive finish to the steering wheel.

For safety and styling reasons it has now been found desirable, in many instances, for a steering wheel to have relatively large spokes and also a substantial safety hub located adjacent and around the boss. If such a steering wheel is formed by initially producing a metal framework and then providing a coating of polyethylene or polystyrene by utilising a moulding process the resultant steering wheel has been found to be relatively heavy. In a motor vehicle such as a motor car the steering wheel is usually supported on the end of an elongated steering column in turn being supported at some distance from the steering wheel by a support structure. It has been found that if a heavy steering wheel is employed in such an arrangement the steering column may be subject to undesirable vibrations especially when the engine of the vehicle is "ticking over". It has been found that under such conditions, the steering wheel and steering column may vibrate "in resonance" with the engine of the vehicle. Thus the present invention seeks to provide a steering wheel which will have less weight than a corresponding steering wheel made by prior proposed methods and also seeks to provide a method of forming such a steering wheel.

According to the broadest aspect of this invention there is provided a steering wheel comprising a central boss and a framework having first and second framework portions, the first framework portion forming the core of at least one spoke extending outwardly from the boss and also forming the core of a steering ring mounted on said spoke or spokes, said second framework portion of said framework being constituted by a substantially rigid structural foam as hereinafter defined.

It is envisaged that such a steering wheel may be of use in certain applications, e.g.

in connection with a motor boat, but it is envisaged that the present invention will be of prime importance in connection with steering wheels for motor vehicles such as motor cars and it will be appreciated that such a steering wheel must have considerable strength. Thus, desirably the boss and the first framework portion may be formed of a metal.

Conveniently the boss may be formed as a metal die-casting, the or each spoke of the first framework portion being secured to said boss by being inserted into a die mould for forming the boss during the casting process. Furthermore the second framework portion formed of substantially rigid structural foam may cover the steering ring, the or each spoke and also the exterior surface of the boss. In one preferred embodi ment the second framework portion of rigid structural foam defines a central hub for the steering wheel. In addition, the second framework portion of rigid structural foam may also define one or more arms extending from the central hub to other parts of the steering wheel.

Advantageously at least parts of the steering wheel may be externally coated with a non-foamed plastics material and it will be appreciated that such a plastics material may provide an attractive finish and an adequate hand grip.

Preferably the structural foam, which is a substantially rigid foam plastic material is formed of polyprolylene, A.B.S. or P.V.C.

Advantageously the outer coating may be formed of soft P.V.C.

Suitably the second framework portion of structural foam may cover the steering ring core and this covering may be provided with outer corrugations to provide a secure mechanical lock between such structural foam coating and said further outer coating of non-foamed plastics material. In one particular embodiment the or each spoke and/ or also said steering ring mounted thereon and which constitute said first framework portion are also wholly constituted by a substantially rigid structural foam to provide a light-weight wheel of lesser strength for application normally outside the automobile industry.

According to another aspect of this invention there is provided a method of manufacturing a steering wheel, said method comprising the steps of forming a sub-structure comprising a central boss and a first framework portion which forms the core of at least one spoke and which forms also the core of a steering ring mounted on said spoke or spokes; inserting said sub-structure into a mould and moulding on to at least part of said sub-structure a second framework portion of substantially rigid structural foam. Conveniently said method may also comprise the further step of moulding a layer of non-foamed plastics material on to at least portions of said wheel.

It is to be understood that in this specification the words "structural foam" are utilised to mean a substantially rigid foamed plastics material and examples of such a material are foamed polyprolylene, foamed A.B.S. and foamed P.V.C. Also it is to be understood that in this specification the word "ring" is used in a broad context and is to be understood to include a "part of a ring" formed of one or more arcs or segments of a circle.

It will be appreciated that in utilising the present invention it will be possible to manufacture a steering wheel having the desired additional safety and styling hub yet which is of substantially less weight than such a prior proposed steering wheel. Thus, by utilising the present invention, it will be possible to manufacture steering wheels having less weight than would otherwise be the case with the result that in use on the steering column of a motor vehicle there is less likelihood of the steering column vibrating.

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, and with reference to, the accompanying drawings in which: FIGURE 1 is a perspective view of a steering wheel in accordance with the invention; and FIGURE 2 is a cross-sectional view of the steering wheel shown in Figure 1, taken along the line 2-2.

One particular embodiment of the invention comprises a steering wheel 1 adapted for use in a motor vehicle such as a motor car. The steering wheel 1 comprises a central metallic boss 2, and a framework having first and second framework portions. The first framework portion forms spokes 3 (only one of two shown) and a steering ring 4, the spokes 3 protruding substantially radially from the boss 2 to said metallic steering ring 4 which is welded to the free ends of the spokes. This first framework portion is substantially covered by part of said second framework portion comprising structural foam 5. In this embodiment the structural foam 5 is itself covered by a layer 6 of P.V.C.

The central boss 2 is formed of die cast metal and includes a centrally disposed, substantially tubular, portion 7 adapted to embrace and engage the steering column of a motor vehicle. A radially outwardly extending flange 8 protrudes from the portion 7 adjacent one end thereof and this flange terminates in an outer tubular portion 9, which is longitudinally displaced with reference to the central tubular portion. The die cast boss 2 also has substantially radially and axially extending protrusions 10 which embrace and engage the inner ends of the spokes 3.

The spokes 3 are formed of pressed steel, are of substantially rectangular cross-section and are also substantially rectangular in plan. However, each spoke has a widened portion at the end thereof remote from the central boss 2. The spokes may be bent or cranked as necessary.

The steering ring 4 which is welded to the widened ends of the spokes comprises a ring formed of square sectioned tube. However, it is to be understood that the steering ring 4 could comprise a ring formed of round sectioned tube or of round or square steel wire.

In this embodiment of the invention two pressed steel spokes 3 are provided but it is to be understood that the number of steel spokes may be chosen to suit the requirements for the wheel. It is also to be understood that the spokes could be formed of round or square sectioned steel wire.

As stated hereinbefore moulded on to the first framework portion constituted by the metal boss 2, the spokes 3 and the steering ring 4 is structural foam 5 which constitutes the second framework forming portion.

This foam 5 is a substantially rigid foamed plastics material such as polypropylene, A.B.S. or P.V.C. Of course, other foamed plastics materials may be found to be suitable.

In this embodiment of the invention, the second framework forming portion of structural foam 5 not only substantially surrounds the steering ring 4, the spokes 3 and the outer surface of the outer tubular portion 9 of the central boss 2 but in addition it defines a substantially rectangular hub 11 provided at the centre of the steering wheel for safety and design styling purposes. The hub 11 is defined by a substantially planar portion of structural foam which extends radially outwardly from the metallic boss, the structural foam also defining a cavity 12 in said hub, the cavity 12 being above and opening on to said boss 2 to permit access to the boss when the wheel 1 is being secured in position on to a steering column. The central hub 11 is also provided with various rearwardly extending reinforcing ribs of structural foam.

In the present embodiment of the invention the structural foam of the second framework portion also wholly constitutes two arms 13 extending from the central hub 11 to the steering ring 4, these arms 13 generally resembling the arms 14 constituted by the foam coated spokes 3.

The portion of the structural foam 5 provided about the steering ring is provided with corrugations extending around the periphery of this ring shaped portion of the structural foam.

A coating of soft P.V.C. or other such material is provided on the exterior of the structural foam 5, and the surface of this coating of soft P.V.C. may be moulded, for example, to give the appearance of a leather covered steering wheel. In particular the coating of soft P.V.C. entirely covers the ring shaped portion of the structural foam 5 on the steering ring 4, the four arms 13, 14 extending from the central hub 11 to the steering ring 4, the upper and side surfaces of such central hub 11 and the upper surface of the portion of the structural foam defining the cavity 12 in the hub 11. Thus the only exposed structural foam in this embodiment is on the lower side of the hub.

The cavity 12 provided to give access to the boss 2) is provided with a snap fit cover 15 which is formed as a moulding of A.B.S.

The cavity 12 has a substantially rectangularopen mouth and thus the cover 15 is of rectangular configuration and is provided with two lugs 16 adapted to engage snappingly with corresponding lugs provided on the soft P.V.C. coating. The cover 15 is provided with one downwardly extending flange since the rectangular cavity 12 is located adjacent one side of the hub 11 and the cover 15, when in position, covers the cavity 12 and forms one side wall of a part of the hub Il. The cover 15 may if desired include the motif, for example, of a motor company.

It will be appreciated that the spokes and the arms may extend at any desired angle from the central hub, as may be required by design considerations, but in the present embodiment of the invention the two arms 14, provided with spokes 3 subtend an angle of substantially 1600 to each other, whereas the two arms 13 not provided with spokes subtend an angle of approximately 1700 to each other, these arms being located generally to form a chord extending across the lower part of the steering wheel. In- the present embodiment of the invention the steering ring is not coplanar with the upper surface of the hub but is spaced in a plane above the upper surface of the hub. Thus the spokes 3 extend slightly axially from the central hub 11.

In manufacturing a steering wheel as above described, the spokes 2 will have the appropriate ends thereof inserted into a die mould and the central boss 2 will be die cast so that the above described parts thereof embrace and engage the spokes 3.

Subsequently the free ends of the spokes will be welded to the steering ring 4 to complete the first framework portion of the steering wheel, and this first framework portion of the steering wheel will then be located in an appropriate mould and the structural foam 5 constituting a - second framework portion will be moulded on to the first framework portion. The complete framework so formed will then be placed into another mould and the soft P.V.C. coating will be applied. The snap-on cover 15 will be made separately.

Corrugations are provided on the outer surface of the structural foam covering the steering ring to ensure that a good mechanical lock is provided between this portion of the structural foam and the soft P.V.C.

coating.

Whilst the invention has been described with reference to one specific embodiment of wheel it is to be understood that many variations or modifications may be made within the scope of the invention as defined in the appendent claims. For example the number of metal spokes provoded could be increased, or, on the other hand, could be decreased.

It is envisaged that a steering wheel could be produced in which no metal spokes are provided, the sole connection between the metallic boss and the steering ring of the first framework portion being constituted by structural foam constituting the second framework portion. Similarly, it is envisaged that in certain circumstances it may be possible to dispense with the metallic steering ring. It is to be noted that the steering ring need not be in the form of a complete ring, but could, in certain applications, be in the form of one or more arcs or segments of a circle.

Again while certain specific materials have been mentioned in the specification it is to be understood that various other substantially rigid structural foam materials, or other coating materials, could be utilised in the manufacture of alternative embodiments of the invention. For example, whilst foamed materials have been mentioned, e.g. foamed polypropylene, A.B.S. or P.V.C., it will be apparent that other foamed materials having the same general characteristics might alternatively be used.

WHAT WE CLAIM IS: 1. A steering wheel comprising a central boss and a framework having first and second framework portions, the first framework portion forming the core of at least one spoke extending outwardly from the boss and also forming the core of a steering ring mounted on said spoke or spokes, said second framework portion of said framework being constituted by a substantially rigid structural foam.

2. A steering wheel according to claim 1, wherein the boss and the first framework portion are formed of a metal.

3. A steering wheel according to claim 2, wherein the boss is formed as a metal diecasting, the or each spoke of the first framework portion being secured to said boss by being inserted into a die mould for forming the boss during the casting process.

4. A steering wheel according to any one of the preceding claims, wherein the second framework portion formed of substantially rigid structural foam covers the steering ring, the or each spoke and also the exterior surface of the boss.

5. A steering wheel according to any one of the preceding claims, wherein the second framework portion of rigid structural foam defines a central hub for the steering wheel.

6. A steering wheel according to claim 5, wherein the second framework portion of rigid structural foam defines one or more arms extending from the central hub to other parts of the steering wheel.

7. A steering wheel according to any one of the preceding claims, wherein at least parts are externally coated with a nonfoamed plastics material.

8. A steering wheel according to claim 7, wherein the said outer coating is a soft polyvinylchloride material.

9. A steering wheel according to claim 7 or claim 8, wherein the second framework portion of structural foam covers the steering ring core and this covering is provided with outer corrugations to provide a secure mechanical lock between such structural foam coating and said further outer coating of non-foamed plastics material.

10. A steering wheel according to claim 1, wherein the or each spoke and/or also said steering ring mounted thereon and which constitute said first framework portion are also wholly constituted by a substantially rigid structural foam.

11. A steering wheel substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

12. A method of manufacturing a steering wheel, said method comprising the steps of foaming a sub-structure comprising a central boss and a first framework portion which forms the core of at least one spoke and which forms also the core of a steering ring mounted on said spoke or spokes; inserting said sub-structure into a mould and moulding on to at least part of said substructure a second framework portion of substantially rigid structural foam.

13. A method of manufacturing a steering wheel according to claim 12, said method comprising the further step of moulding a layer of non-foamed plastics material on to at least portions of said wheel.

14. A method of manufacturing a steering wheel substantially as herein described and with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. or, on the other hand, could be decreased. It is envisaged that a steering wheel could be produced in which no metal spokes are provided, the sole connection between the metallic boss and the steering ring of the first framework portion being constituted by structural foam constituting the second framework portion. Similarly, it is envisaged that in certain circumstances it may be possible to dispense with the metallic steering ring. It is to be noted that the steering ring need not be in the form of a complete ring, but could, in certain applications, be in the form of one or more arcs or segments of a circle. Again while certain specific materials have been mentioned in the specification it is to be understood that various other substantially rigid structural foam materials, or other coating materials, could be utilised in the manufacture of alternative embodiments of the invention. For example, whilst foamed materials have been mentioned, e.g. foamed polypropylene, A.B.S. or P.V.C., it will be apparent that other foamed materials having the same general characteristics might alternatively be used. WHAT WE CLAIM IS:

1. A steering wheel comprising a central boss and a framework having first and second framework portions, the first framework portion forming the core of at least one spoke extending outwardly from the boss and also forming the core of a steering ring mounted on said spoke or spokes, said second framework portion of said framework being constituted by a substantially rigid structural foam.