GB2339612A

GB2339612A - Vehicle hand lever formed by a dual-moulding process

Info

Publication number: GB2339612A
Application number: GB9815352A
Authority: GB
Inventors: David Leeder
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-07-16
Filing date: 1998-07-16
Publication date: 2000-02-02
Also published as: GB9815352D0

Description

2339612 A LEVER MEMBER In accordance with the present invention there is

provided a lever member for a motor vehicle, and more particularly for the handbrake and gear stick of such a vehicle.

Traditionally, long metal components have been used for levers within a motor vehicle, ie. as the handbrake and gear stick. Unfortunately, metal components can be both expensive and difficult to accommodate within the safety requirements necessitated or acceptable in modern motor vehicle design. Furthermore, it will be appreciated that such metal components will require painting or covering in order to achieve the desired level of aesthetic appearance within a motor vehicle cabin. Alternatively. rods of plastics material could be used. However, to achieve the necessary rlgiditx for a motor vehicle lever, it is necessary to use highly filled structural plastics which do not have the necessary surface appearance from visual and tactile acceptability within a motor vehicle. Thus, a simple solid plastic rod of material may be expensive and would also require a covering to meet aesthetic requirements.

It is an object of the present invention to provide a lever member for a motor vehicle which substantially relieves the above-mentioned problems.

In accordance with the present invention there is provided a lever member for a motor vehicle comprising a structural inner component and aesthetic outer component, said inner component being rigid and including a plurality of structural ribs about a central cavity whilst said outer component envelopes said inner component to obscure fabrication imperfections of said inner component including any shrinkage sinks due to said structural ribs within the cavity, said fabrication imperfections facilitating key locking between said inner and said outer component in order to inhibit split separation therebetween.

Typically, the inner component will be made from a high modulus plastics polymer. Thus, a glass-filled polymer with an excess of 20% by weight glass fibres may be used or a mineral filled plastics polymer with an excess of 40% by weight of a talc filler may be used.

The outer component may be made from a low modulus plastics 15 polymer, eg. TPE with good tactile feel and appearance.

To further facilitate keying between the inner and outer component. the inner component may include radiating dog structures which can be enveloped by the outer component.

Typically, the outer component will have a thickness of at least 2 mm in order to ensure adequate coverage of any fabrication imperfections of the inner component.

Normally, the lever member will be formed by a two-part or dual injection moulding process such that, whilst still molten, there can be a degree of fusion bonding between the inner and outer components to additionally inhibit splitting therebetween due to the stresses of lever operation within a motor vehicle.

Embodiments of the present invention will now be described by way of 10 example only with reference to the accompanying drawings, in which:

Figure 1 is a schematic side elevation of a handbrake lever arrangement; Figure 2 is a cross-section of the handbrake lever member depicted in Figure 1 as viewed in the direction X-X; and Figure 3 is a schematic cross-section of a gear lever including a lever member in accordance with the present invention.

As an illustration of a use of a lever member within a motor vehicle, Figure 1 depicts in schematic side elevation, a handbrake lever arrangement. Thus, a handbrake lever member 1 is secured to a handbrake mechanism actuation arrangement 2 with a release button 3 configured at one end of the member 1. Operation of handbrake lever mechanism arrangements is well known in the art and generally comprises a cable activation of rear brakes upon the vehicle with cable pull against a toothed pawl or cam, the tooth engaging in a ratchet-type manner the toothed pa-'N'l and release being effected through the button 3. The essential function of the lever member 1 is to provide lever advantage about a pivot 4 in order, with limited effort, to pull the cables and therefore activate the handbrake.

In such circumstances it will be appreciated that the member I must have sufficient stiffness and strength to allow such lever advantage.

As indicated above, previously a metallic tube or a solid plastics material rod has been used in order to achieve the necessary strength as described for lever advantage. In accordance with the present invention and as depicted in Figure 2, a hollow two-part lever member is described. ThLIS. a structural inner component 21 is associated with an aesthetic outer component 22. The structural inner component 21 includes structural ribs 23 which provide the necessary strength for function as a lever member within a motor vehicle. The aesthetic outer component 22 provides an aesthetic surface consistent with the interior of a motor vehicle along with an acceptable tactile feel.

An inherent problem with high-strength, high-modulus plastic polymers is generally that they have a rough surface. Furthermore, when structural ribs such as 23 are included, there is a shrinkage imperfection or sink 24 created therebelow due to variations in the materials coefficient of expansion as the polymer sets. Such surface roughness and sink imperfections render a single high-strength hollow plastics component unacceptable for aesthetic reasons within a motor vehicle. A hollow lever member is preferred to reduce weight and cost along with providing a conduit for control mechanisms.

In accordance with the present invention, a second, aesthetic outer component 22 is moulded with the inner structural component 21 in ordeito obscure any imperfections within the inner component 21. Thus, the aesthetic outer component 22 will generally have a thickness at least sufficient to cover any shrinkage sinks 24 created by fabrication of the structural inner component 21. Manufacture of the lever member will be generally in accordance with a dual injection technique.

During a dual injection moulding technique, the inner component 21 will be moulded about a forming tool. This forming tool will include the necessary grooves in order to precipitate in the structural inner component 21 the desired structural ribs 23. Once the structural inner component 21 is formed, a second outer component 22 will be moulded thereabouts. As a -6, dual two-stage process is employed to manufacture the lever member, it will be appreciated that the inner component 21 generally/at least partially, sets with the precipitation of the sinks 24 and surface roughing prior to injection moulding of outer component 22. Thus, the outer component 22 is readily keyed through the sinks 24 to the inner component 21 with a consequent stronger bond therebetween. Although not depicted in Figure 2, it will be appreciated that specific dog teeth could be provided within the mould for the inner component 21 to further augment such keying between the inner component 21 and the outer component 22.

Keying between the inner component 21 and the outer component 22 is important to ensure split separation between the two components 21, 22 does not occur in use. It will be appreciated that the necessary stre'; ses or strains inherent through a lever action can propagate any weaknesses in bonding between the inner component 21 and the outer component 22. The sinks 24, along with any specific dog tooth keying between these components 21, 22, act to interrupt propagation of such weaknesses into separation or splitting. It will be appreciated that implicitly at least the mechanical properties of the materials from which the inner component 21 and the outer component 22 are made will be different. Thus, the boundary bond 25 between these components 21, 22 can be fertile ground for stress or strain induced splitting. However, it will also be understood that by appropriate choice of materials for the components 21, 22 a degree of fusion bonding can be provided during the dual moulding process.

It will be appreciated that the inner component 21 includes a cavity 26 in order to reduce the material content and therefore weight along with cost of the member 1. However, as indicated above, it is necessary to include structural ribs 23 in order to achieve an appropriate strength for lever operation by the member 1. It will be understood that essentially the mechanical effect of the member I is provided by the structural inner component 21 and thus this component 21 should not appreciably bend under load. Again, such bending under a load may precipitate splitting between the components 21, 22 which will produce unsightly bulging with an inherent reduction in aesthetic appeal. Finally, the cavity 26 also allows a conduit through which control cabling and actuation elements can pass for operation of, for example, a handbrake mechanism.

Although the present invention has been described with regard to a handbrake lever in Figures 1 and 2, it will be appreciated that lever members are used for a wide range of uses within a motor vehicle. For example, a lever member may be used in the gear stick or interior door handle, etc. With regard to a gear stick, a schematic side elevation is illustrated in Figure 3. Thus, a lever member 31 comprises a respective structural inner component (hidden and so not shown) and an aesthetic outer component 32. This lever member 31 is secured at one end 33 to a gearbox mechanism (not shown) and at the other end 34 includes a gear stick knob 36. The gearstick knob 36 may include a graphic depicting gearbox operation or other detail. Furthermore, this gearstick knob 36 could be secured into a cavity created as described with regard to Figure 2 through a screw thread or penetrative member from the knob 36 secured with adhesive.

A cross-section of the lever member 31 would be similar to that described with regard to figure 2. Thus, similar consideration will be made to provision of adequate stiffness and strength for the inner component and aesthetic appeal for the outer component 32.

It will be understood that the strength requirements of a door handle lever member will be significantly less than that of a handbrake lever member. Thus, fewer or less robust ribs may be required which in turn should precipitate less shankage sinking and so a thinner outer component will be acceptable.

Claims

-9CLAIMS

1. A lever member for a motor vehicle comprising a structural inner component and an aesthetic outer component, said inner component being rigid and including a plurality of structural ribs whilst said outer component envelopes said inner component to obscure fabrication imperfections of said inner component including shrinkage -Mk-; (iLic io sd structural r'bs, said fabrication imperfections facilitating key' al 1 1 1 1 1, - ing between said inner and said outer component in order to inhibit splitting or separation therebetween.

2. A member as claimed in Claim 1, wherein the inner component is formed from a high modulus plastics polymer.

3. A member as claimed in Claim 2, wherein the high modulus plastics polymer includes in excess of 20% by weight glass fibres.

4. A lever member as claimed in Claim 2, wherein the high modulus plastics polymer includes at least 40% by weight of a mineral filler such as talc.

5. A lever member as claimed in any preceding claim, wherein the aesthetic outer component comprises a low modulus plastics polymer such as TPE with good tactile feel and appearance.

10- 6. A lever member as claimed in any preceding claim, wherein the structural inner component includes dog members to augment keyina, between the inner structural component and the outer component to further inhibit splitting therebetween.

7. A lever member as claimed in any preceding claim, wherein the aesthetic outer component has a thickness of at least 2 mm in order to adequately obscure fabrication imperfections within the inner component.

8. A lever member as claimed in any preceding claim, wherein the inner component and the outer component are fusion bonded at the interface therebetween.

9. A lever member substantially as hereinbefore described with reference to the accompanying drawings.

10. A motor vehicle including a lever member as claimed in any preceding claim.