GB2346430A

GB2346430A - Mould for a steering wheel skeleton

Info

Publication number: GB2346430A
Application number: GB9902208A
Authority: GB
Inventors: Jason Carl Lisseman
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1999-02-02
Filing date: 1999-02-02
Publication date: 2000-08-09
Also published as: GB9902208D0

Abstract

A mould for a motor vehicle steering wheel skeleton is disclosed comprising of first and second mould parts 4,6 each being made up of separate mould elements 10,12,14;20,22,24, respectively, corresponding to hub spoke and rim elements of the skeleton. It is therefore possible to redesign elements of the steering wheel skeleton and thereby replace corresponding mould elements without requiring new tooling for the entire skeleton.

Description

Mycle Assembly The present invention relates to a mdtor vehicle assembly, and in particular to the manufacture of a skeleton forming part of a steering wheel assembly for a motor vehicle.

A steering wheel assembly includes a skeleton. The skeleton comprises hub, spoke and rim elements. An air bag module may conveniently be mounted to the skeleton between the hub and the spoke elements. A coating is then provided on the skeleton and air bag module to present a uniform appearance to users of the rotor vehicle. The skeleton is typically die cast from a metal such as magnesium. A split moyld comprising an upper mould part and a lower mould part, the upper and lower mould parts defining a cavity when brought together, is used to cast the skeleton.

Once a design of steering wheel has beep finalise, the design of the associated skeleton can be produced. A suitable cavity may thej be formed in the mould parts, for example by electro-erosion of the mould surface. In any case, if the design of the steering wheel is altered, and of necessity the design of the skeleton is altered, it will then be necessary to create new tooling for the entire skeleton to entable the new design of skeleton to be produced.

Conversely also, unless required by regulatio, for example driver impact criteria, redesign of the steering wheel or the skeleton, for examjple to provide a more stable airbag platform, is unlikely due to the cost of providing new moulu parts.

An alternative method of manufacture of a skeleton is to cast the hub, spoke and rim elements separately, and subsequently to welcl the elements together as required. It will be understood that such a method while providing suitable flexibility in the design of the skeleton is both time and labour intensive leading to a h} oh unit cost for such skeletons.

It is an advantage of the present inventio that it eliminates or substantially reduces the problems noted above.

According to a first aspect of the present invention, a mould for a motor vehicle steering wheel skeleton comprises first and second mould parts, each of the first and second mould parts being made up of separate mould elements corresponding to hub, spoke and rim elements of the skeleton.

This enables the benefits of a die cast skeleton to be combined with a large degree of design flexibility as will be explained.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a partial side section illustrating a mould in accordance with the present invention ; Figure 2 is a plan view of a part of a lower mould in accordance with the present invention showing a four spoke configuration ; and Figure 3 is a plan view of a part of a lower mould in accordance with the present invention showing a three spoke configuration.

Referring first to Figure 1, there may be seen a mould tool 2 in accordance with the present invention. A mould for die casting a motor vehicle steering wheel skeleton comprises a first mould part 4 and a second mould part 6 defining a cavity therebetween. Each of the first and second mould parts comprises a number of separate mould elements 10,12,14 ; 20,22,24. The mould elements correspond to hub, spoke and rim elements of a cast skeleton 8.

In the embodiment illustrated in Figure 1, the first lower mould part 4 comprises a lower hub centre element 10, a lower spoke ring element 12 and a lower ring element 14. The upper mould part 6 comprises an upper hub centre element 20, an upper spoke ring element 22 and an upper ring element 24. These elements are retained within an outer fixture ring 30 forming a part of a casting apparatus. Keying means are provided to key the elements to one another and to the outer fixture ring. This is for the purposes of illustration only. It will be understood that any other suitable means of maintaining the elements within the fixture ring in the correct spatial relationship to one another tnay also be suitable.

An upper surface 16 of the lower ring element 14 defines a recess which will produce a lower surface of a rim of a cast skeleton. A lower surface 26 of the upper ring element 24 defines a recess which will produce an upper surface of the rim of the cast skeleton.

The upper and lower spoke ring elements 12,22 include a number of recesses corresponding to the number of spokes it is desired to cast. The spoke elements of the first or second mould part may formed as a unitary component. Alternatively, the spoke elements may be built up from a library of parts such that spokes of the cast skeleton are disposed at a desired angular orientation to one another.

In addition, it can be seen that the spoke ring elements, in conjunction with the upper and lower hub elements, can be used to define the amount by which a hub of the cast skeleton will be recessed from the rim. The recess or recesses in the spoke ring elements can also be used to define location points for an airbag assembly in the cast skeleton. The spoke ring elements are used to define the inside of the rirtg of the cast skeleton.

An upper surface 18 of the lower hub element 10 defines a lower surface of the hub of the cast skeleton. A lower surface 28 of the upper hub element defines an upper surface of the hub of the cast skeleton 8. The lower hub element will typically also include a feed point or gate (not shown) through which the molten mtal will enter the mould cavity when cast. It will be understood that the gate, or further gatejs, may be provided elsewhere in the mould.

In use, the upper and the lower mould parts are brought together to define a mould cavity into which molten metal is introduced. The metal is allowed to cool and solidify before the mould parts are separated and the cast skeleton removed. Any undesirable flashings that may result from the casting process may be renfoved in any suitable manner.

Figure 2 is a view from above of a section of a lower mould part showing a cast skeleton 108 prior to removal. The skeleton includes four spokes, of which two 138,140 are shown, A spoke ring element 112 and a rim element 114 are shown located within an outer fixture ring 130. The spoke ring element 112 is provided with four spoke channels corresponding to the desired locations of the spokes.

Figure 3 is a view from above of a section of a lower mould part showing a cast skeleton 208 prior to removal. The skeleton includes three spokes, of which two 238,240 are shown.

A spoke ring element 212 and the rim element 114 are shown located within the outer fixture ring 130. The spoke ring element 212 is provided with four spoke channels corresponding to the desired locations of the spokes.

It will be immediately understood that instead of requiring two separate sets of moulding tools, upper and lower mould parts for the four spoke skeleton 108 and upper and lower mould parts for the three spoke skeleton 208, the invention enables those parts 114,130 of the first set of tooling that have not been changed to remain in use. Only those parts 112,212 of the mould required for moulding of the spokes need be created anew. Similarly if a part of the mould tooling becomes damaged, for example the hub mould parts, then only these parts need be replace or repaired, while the remaining mould parts may complete their useful working life.

It is also anticipated that the relatively easy manner in which the tooling may be changed will lead to increased development in the design of motor vehicle steering wheels. In particular, the construction of the mould tool enables a particular element of the mould to be modified separately from other elements of the mould. Also the construction of the mould parts allows for rapid changing of the elements to create new mould configurations.

Claims

1. A mould for a motor vehicle steering wheel skeleton comprising first and second mould parts, each of the first and second mpuld parts being made up of separate mould elements corresponding to hub, spoke and rim elements of the skeleton.

2. A mould according to claim 1, characterised in that the elements of the first mould part include means to enable the elements of jhe first mould part to be joined to one another.

3. A mould according to claim 1 or clair 2, characterised in that the elements of the second mould part include means to entable the elements of the second mould part to be joined to one another.

4. A mould according to any preceding claim, characterised in that the spoke element of the first or second mould part is formed as a unitary component.

5. A mould according to any preceding claim, characterised in that gate means are provided in one of the hub elements.

6. A mould for a motor vehicle steering Wheel skeleton substantially as described herein with reference to and as illustrated in Figures 1 to 3 of the accompanying drawings.