WO2009004660A1

WO2009004660A1 - Method for producing wooden steering wheels for vehicles

Info

Publication number: WO2009004660A1
Application number: PCT/IT2007/000485
Authority: WO
Inventors: Luigi Cavalli
Original assignee: Cavalli S.R.L.
Priority date: 2007-07-05
Filing date: 2007-07-05
Publication date: 2009-01-08
Also published as: EP2183147A1

Abstract

A wooden steering wheel for vehicles is produced by means of: a step of manufacturing at least one wood fiber agglomerate shell portion (10), the shell portion (10) being shaped and dimensioned so as to be fitted on a segment (11) of a supporting structure (2) of the steering wheel (1) to be produced; a step of decorating an essentially convex external surface (15) of the shell portion (10), wherein a decoration (31) printed on a water-soluble supporting film (30) is transferred onto said surface (15) of the shell portion (10) by direct contact in a water bath (33); and a step of assembling, wherein the shell portion (10) is fixed onto the structure (2).

Description

_ _

METHOD FOR PRODUCING WOODEN STEERING WHEELS FOR VEHICLES

TECHNICAL FIELD

The present invention relates to a method for producing wooden steering wheels for vehicles. STATE OF THE PRIOR ART

There are known various methods for the production of wooden steering wheels, i.e. steering wheels having a supporting structure (normally consisting of a metallic core covered by a polymeric material) on which wood covering portions are applied.

Some known methods make use of laminated wood, of which compact blocks are made; the blocks are then cut and mechanically machined to obtain curved shapes which are glued onto the structure of the steering wheel.

These methods are relatively long, complex and costly.

In order to reduce the costs and the complexity of the methods making use of laminated wood, it has been suggested to employ recycled wood in aggregate form with polymeric binders, as shown for example in European patent application EP1162125. This type of method is neither fully satisfactory, especially in terms of costs and appearance .

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a method for producing wooden steering wheels which is free from the drawbacks of the prior art hereto described; specifically, it is an object of the invention to provide a method which allows to make high quality steering wheels at relatively low costs.

The present invention thus relates to a . method for producing wooden steering wheels for vehicles as defined in general terms in accompanying claim 1 and, for further preferred aspects, in the dependent claims.

The method according to the invention allows to produce high quality steering wheels »at relatively low costs.

Indeed, the wooden components of the steering wheel are produced using a cheap material (wood fiber agglomerate) , which is however improved by means of a surface decoration which confers an excellent appearance to the part.

Although the decoration technique employed for finishing the appearance of the wooden components is relatively expensive per se, because it requires the use of printed, water-soluble films which are usually expensive, the method of the invention allows such films to be fully and efficiently exploited, the films being used in sufficient measure to cover only the actual useable surfaces, without wastes.

.BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the present invention will be apparent in the following description of a non-limitative embodiment thereof, with reference to the figures in the accompanying drawings, in which:

- figure 1 is an exploded, diagrammatic, -section view of a portion of a wooden steering wheel for vehicles produced according to the invention;

- the figures from 2 to 6 diagrammatically show the main steps of the production method of the steering wheel in figure 1. *

BEST MODE FOR CARRYING OUT THE INVENTION Figure 1 shows, only partially and diagrammatically, an exploded and cross section view of a wooden steering wheel 1 for vehicles produced according to the method of the invention.

Shape and general structure of steering wheel 1 are essentially ^"known and thus neither described nor illustrated in detail for the sake of simplicity. In general terms, steering wheel 1 comprises a supporting structure 2 formed by a central core 3, e.g. metallic, surrounded by a radially external polymeric coating layer 4; a wooden covering 5 is applied on coating layer 4.

With reference also to figures 2 and 3, the method -for producing steering wheel I₁ firstly comprises a step of manufacturing at least one wood fiber agglomerate shell portion 10, the shell portion 10 being shaped and dimensioned so as to be fitted on a segment

11 of structure 2, as diagrammaticalIy and only partially shown in figure 1, to form a corresponding portion of wooden covering 5.

Obviously, according to the part of steering wheel 1 to be covered in wood, a plurality of shell portions 10 shaped and dimensioned so at to be fitted on respective segments of structure 2 and to be reciprocally joined on structure 2 may be manufactured.

Preferably, as shown in figures 1-3, one or more pairs of opposite shell portions 10a, 10b, are manufactured, shaped and dimensioned so as to be fitted from opposite sides about segment 11 of structure 2 and form a curved tubular body 12 in use.

Each shell portion 10 extends along a curved longitudinal axis A and has an arched transversal section curved about axis A, for example shaped as an arc of a circle or oval or ellipsis; each shell portion 10 presents a pair of longitudinal edges 13 essentially parallel to axis A and a convex internal surface 14, intended to couple with structure 2, and a concave external surface 15, intended to remain in sight on steering wheel 1 and define a gripping surface for the user.

Opposite shell portions 10a, 10b present respective mating connection parts 16 for the mechanical coupling, e.g. by fitting, between shell portions 10a, 10b. In the non-limitative example shown, parts 16 are formed by respective longitudinal protrusions, essentially parallel to axis A and protruding from edges 13 of shell portions 10 and which overlap in the radial direction (transversalIy to axis A) . Shell portions 10 are produced using a wood fiber agglomerate, meaning with this term a material formed by cellulose/wood fibers blended and made coherent to one another by means of hot pressing/molding operations with the use of binding polymeric resins; typically, the wood fibers are formed by wood shavings or powder of various caliber, for example resulting from woodworking industry machining waste or recycled wood.

Each shell portion 10 is directly formed in the required shape during a hot_* molding step, diagrammaticalIy shown in figures 2 and 3, in which a molding compound comprising cellulose/wood fibers and binding polymeric resins in essentially non-agglomerated pasty form is inserted in a curved shape mould 20 having a cavity 21 which is defined between two half-moulds 22, 23 and which copies the shape of shelϊ portion 10 to be produced.

During the molding step, the binding polymeric resins in the molding compound polymerize/reticulate, binding the cellulose/wood fibers forming the wood fiber agglomerate which forms shell portion 10. Molding temperature, pressure and time are chosen so as to allow the transformation of the molding compound from the pasty form to the compact solid agglomerated state. .Preferably, the molding compound further comprises polymeric components so as to make shell portion 10 water-repellent, e.g. a water-repellent melaminic powder .

Shell portions 10, extracted from moulds 20, are sent to a decorating step of respective external surfaces 15.

The decorating step, diagrammaticalIy shown in figures 4 and 5, is specifically a step of three- dimensional decorative printing, of the "dip print" or "cubic print" type.

As known, this printing technique essentially consists in transferring a three-dimensional decoration from a water-soluble film which carries the required drawing, produced with appropriate water-resistant pigments/inks, onto a surface of an artifact. Transfer is obtained by direct contact of the surface to be decorated with the film immersed in a water bath; the pressure of the water makes the decoration adhere onto the surface of the artifact, while the water-soluble film dissolves.

During the decorating step, therefore, a water- soluble supporting film 30, on which a decoration 31 to be applied onto surfaces 15 is printed with appropriate water-resistant pigments/inks, for example a decoration which reproduces the appearance of wood, is prepared; it is apparent that decoration 31 may reproduce specific wood varieties, or different high-quality materials, such as carbon fiber and other, or geometric motifs, fancy patterns, etc.

Film 30 is suspended over a tank 32 containing a water bath 33 at controlled temperature; shell portions 10, supported and moved by a conveyor system 34, are carried over film 30 and lowered onto film 30 and thus into tank 32 in a direction essentially orthogonal to film 30 and the surface of bath 33; shell portions 10 are thus immersed in bath 33 along with film 30; which is in contact with surfaces 15 of shell portions 10; while film 30 dissolves in bath 33, decoration 31 is transferred onto surfaces 15, in virtue of the pressure exerted by the water which acts as a wrapping press .

The inks/pigments forming decoVation 31 may be activated before the decorating step, by means of treatment with specific activator.

Decorated shell portions 10 are then extracted from bath 33 and optionally sent to a washing step (if required for removing the residues of film 30 possibly remaining on surfaces 15) , and/or a drying step (if required to completely remove the water) .

A finishing step follows, specifically by applying a transparent paint on decorated surfaces 15, in order to provide a better appearance effect and to ensure an adequate protection to decoration 31. As the decorating step occurs by immersion in water bath, at least surfaces 15 of shell portions 10, or even entire shell portions 10, must be- water- repellent or waterproofed.

As previously described, in the preferred embodiment to which reference is made herein, shell portions 10 are water-repellent in virtue of the molding compound used to produce them.

It is however understood that the method .of the invention may comprise a different treating step, performed before the decorating step, to make at least external surfaces 15 of shell portions 10 water- repellent.

Shell portions 10 are finally mounted on structure 2 of steering wheel 1 during an assembling step diagrammatically shown in figure 6; specifically, the pair of opposite shell portions 10a, 10b are fitted on opposite sides about segment 11, facing each other and with respective mating connection parts 16 joined to each other.

Each shell portion 10 is fixed onto segment 11 of structure 2, for example, by gluing.

Advantageously, the fixing of shell portions 10 is performed according to the method illustrated in European patent EP0985590 and thus, specifically, by use of a layer 36 of a polymeric gluing resin impregnated fabric (partially and diagrammatically shown in figures 1 and 6) which is interposed between coating layer 4 of structure 2 and internal surfaces 14 of shell portions 10 to ensure an adequate adhesion of shell portions 10 to coating layer 4 and thus to structure 2.

Finally, steering wheel 1, provided with wooden covering 5 formed by decorated shell portions 10, may be possibly finished with known finishing operations.

It is understood that further changes and variations can be made to the method described and illustrated herein without departing from the scope of the accompanying claims .

Claims

1. A method for producing steering wheels for vehicles, characterized by comprising: - a step of manufacturing at least one wood fiber agglomerate shell portion (10) , the shell portion (10) being shaped and dimensioned so as to be fitted on a segment (11) of a supporting structure (2) .of the steering wheel (1) to be produced; - a step of decorating an essentially concave external surface (15) of the shell portion (10) , wherein a decoration (31) printed on a water-soluble supporting film (30) is transferred onto said surface (15) of the shell portion (10) by direct contact in water bath; - a step of assembling, wherein the shell portion (10) is fixed onto said segment (11) of the structure (2) .

2. A method according to claim (1), characterized in that the shell portion (10) is formed in a molding step, wherein a molding compound comprising cellulose/wood fibers and binding polymeric resins is inserted in a mould (20) having a cavity (21) which copies the shape of the shell portion (10) to be formed.

3. A method according to claim 2, characterized in that the molding step is a hot molding step, wherein the binding polymeric resins in the molding compound polymerize/reticulate thus binding the cellulose/wood fibers and forming the wood fiber ^v aggregate which constitutes the shell portion (10) .

4. A method according to claim 2 or 3 , characterized in that the molding compound comprises polymeric components so as to make the shell portion (10) water-repellent.

5. A method ■^" according to one of the preceding claims, characterized in that the decorating step is a three-dimensional decorative printing step of the "dip print" or "cubic print" type.

6. A method according to one of the preceding claims, characterized in that in the decorating step, the transfer of the decoration (31) onto the surface (15) of the shell portion (10) occurs by direct contact of said surface (15) with the film (30) by immersdon in a water bath.

7. A method according to one of the preceding claims, characterized by comprising a treating step, performed before the decorating step, to make at least the external surface (15) of the shell portion (10) water-repellent .

8. A method according to one of the preceding claims, characterized in that opposite shell portions

(10) are manufactured, having shapes and dimensions so as to be fitted on opposite sides about a segment (11) of the structure (2) of the steering wheel.

9. A method according to claim 8, characterized in that the opposite shell portions (10) present respective mating connection parts (16) for the mechanical coupling between the opposite shell portions

(10).

10. A method according to one of the preceding claims, characterized in that during the assembling step, the shell portion (10) is glued onto the segment

(11) of the structure (2) with interposition of a polymeric resin impregnated fabric layer (36) .

11. A steering wheel (1) for vehicles, characterized in that it is produced with the method according to any of the preceding claims .