GB2232129A

GB2232129A - Wheel - trims and a method of moulding articles

Info

Publication number: GB2232129A
Application number: GB8912151A
Authority: GB
Inventors: Daniel Jefferson
Original assignee: STERLING ENGINEERED PRODUCTS L
Current assignee: STERLING ENGINEERED PRODUCTS L
Priority date: 1989-05-26
Filing date: 1989-05-26
Publication date: 1990-12-05
Also published as: GB8912151D0

Abstract

A wheel trim 4 for a wheel 1 which carries a tyre 2 comprises a circular, relatively stiff central region 14 of substantially the same diameter as the wheel 1 to which the trim is to be attached, and an annular, relatively flexible outer region 15 surrounding the central region 14 and adapted to extend in use beyond the outer peripheral edge of the wheel 1 to overlie the side-wall 11 of the tyre 12. The trim 4 may have vents for air flow. A method of injection moulding a wheel-trim, or any other article, having a relatively stiff region and a relatively flexible region is also disclosed. Attachment means 16 may be provided on the central region 14 to secure the trim to the wheel or wheel-mounting bolts or hooks (21) and a lip (19), Fig 3, may be provided to secure the trim to the wheel. <IMAGE>

Description

WHEEL-TRIMS AND A METHOD OF MOULDING ARTICLES This invention relates to a method of moulding articles having a stiff portion and a flexible portion, and to a wheel-trim having a stiff central portion and an outer annular flexible portion.

The invention arose from a desire to improve wheel-trims for vehicle wheels which carry a tyre (wheel trims being circular plates for attachment to vehicle wheels to hide attachment bolts which secure the wheels to an axle). Wheel-trims are known which have substantially the same diameter as, or a slightly smaller diameter than, the wheel to which they are to be applied so that they substantially completely cover the plan area of the wheel up to, but just inside, the radially inner edge of the side-wall of the tyre carried by the wheel.

According to a first aspect of the invention a wheel-trim for a wheel which carries a tyre comprises a circular, relatively stiff central region of substantially the same diameter as the wheel to which the trim is to be attached, attachment means provided on the central region adapted to secure the trim to the wheel, or to wheel-mounting bolts, and an annular, relatively flexible outer region surrounding the central region and adapted to extend in use beyond the outer peripheral edge of the wheel to overlie the side-wall of the tyre carried by the wheel.

Vent means may be provided in the central region.

Preferably the outer region is adapted to bear against the side-wall in use, and flexes with the side-wall when the wheel is used. The outer region may just overlap the side-wall adjacent to the wheel or it may extend for a substantial part of the radial depth of the side-wall. The wheel-trim is preferably moulded in plastics material, and most preferably from two different plastics materials: a first relatively stiff material which forms the central region, and a second relatively flexible material which forms the outer region.

A second aspect of the invention consists in a wheel assembly for a vehicle comprising a wheel, a tyre carried by the wheel, and a wheel-trim according to the first aspect of the invention.

A wheel-trim in accordance with the invention is believed to reduce wind resistance and produce a mor streamlined air flow around the wheel and tyre assembly. This not only reduces drag, but also, because of the less turbulent flow past the wheel due to the vehicles motion, increases the pressure difference between relatively stationary air inside the wheels adjacent the vehicle's brakes and the fast moving air at the outside face of the wheels. This increases the flow of air from adjacent the brakes outwards through the wheel and the wheel-trim, which increases air-cooling of the brakes.

The third aspect of the invention stems from a method of producing the wheel-trims.

According to a third aspect of the invention a method of moulding an article having a relatively stiff region and a relatively flexible region comprises introducing into a mould a first fluid material of first kind to produce one of the regions, and introducing into the same mould a second fluid material of a second kind to produce the other of the regions, regions of the article formed from the first and second materials adhering to each other during the moulding operation.

Preferably the first and second materials are introduced into the mould in two stages, the second material being introduced into the mould after the first material has been introduced. The first material may have substantially set in its desired shape at the time that the second material is introduced into the mould.

The second material may be introduced at least partially to overlie the, at that time non-fluid, first material and to extend beyond the first material to a region in the mould in which there is no first material.

An alternative to sequential introduction of the two materials is to simultaneously introduce them into different parts of the mould at suitable pressures such that the interface between the first and second materials occurs at the desired region of the article.

The first material preferably constitutes material which will set to be relatively stiff and will form the stiff region of the article, and the second material preferably constitutes material which will be relatively flexible when set and which will form the flexible region.

The flexible region may be at the periphery of the stiff region, and may surround the stiff region. The flexible region may be an annular region surrounding a circular central stiff region.

In the preferred embodiment a circular central stiff region of first material is formed in the mould and then a surrounding flexible region of second material is moulded over and around its outer edges.

A wheel-trim and its manufacture will now be described by way of example only, with reference to the accompanying drawings of which: Figure 1 shows schematically a plan view of a wheel assembly fitted with a wheel-trim; Figure 2 is a view of the assembly of Figure 1 taken on line Il-Il; Figure 3 shows schematically another wheel assembly; and Figure 4 shows schematically the moulding of a wheel-trim.

The wheel assembly shown in Figures 1 and 2 comprises a steel wheel 1 which carries a rubber tyre 2, and a plastics material wheel-trim 4 which is releasably secured to the wheel 1.

Figure 2 also illustrates the mounting of the wheel assembly to a wheel mounting flange 5 of a vehicle axle 6 via bolts 7. A disc brake is represented by reference numeral 8.

The wheel 1 has a central portion 9 adapted to be bolted to the wheel-mounting flange 5, a rim 3 on which the tyre 2 is mounted and which has radial flanges 10 against which side-walls 11 of the tyre seal, and an annular intermediate region 12 connecting the central portion 9 to the rim 3. The intermediate region 12 has several vent holes passing through it (not shown) as is conventional. The central portion also has retention holes 13 passing through it which serve to assist in the mounting of the trim 4 to the wheel 1. The retention holes 13 may be selected vent holes, or they may be provided specifically for mounting the trim.

Wheel-trim 4 has a rigid circular central region 14, which extends for substantially the full diameter of the wheel 1 and a flexible annular outer, skirt, region 15 which is contiguous with the central region 14. The central region 14 has integrally formed attachment hooks 16 by means of which the trim is releasably secured to the wheel, the hooks 16 extending through the holes 13 to engage the rear face of the intermediate region 12 of the wheel. A series of vent holes 17 is provided in the central region 14.

The flexible skirt region 15 comprises a lip which effectively continues the central region over the outer side-wall 11 of the tyre 2 and which bears against that side-wall with a relatively small force. The skirt region 15 extends for a substantial part of the radial extent of the side-wall. The flexible lip region 15 flexes with the side-wall 3 during use of the wheel assembly.

A series of locating lugs 18, or a locating ring, is provided on the inner face of the trim to co-operate with the rim 3 to assist in properly locating the trim on the wheel. The lugs 18 may be part of the inner or outer region of the trim since they are provided substantially at the junction between the two regions.

The central region 14 is rigid because it is made of relatively stiff plastics material, such as a mixture of nylon 6, glass material and mineral material, the mixture preferably having between 15 - 3% glass and between 20 - 8% mineral content by weight.

Most preferably the mixture for the rigid plastics material comprises about 5% glass and about 10% mineral content by weight, with the remainder being Nylon 6.

Our most preferred composition has fewer stiffeners than have been previously used and is easier to mould and does not wear the moulding dies so quickly.

The outer region 15 is flexible because it is made from a more flexible plastics material than is the central region, and is preferably a soft or elastomeric plastics such as Nylon 6, or Nylon 66, without the stiffening fillers of the central region's plastics material. Since the central and outer regions are both made from substantially the same base plastics material (with and without stiffeners respectively) there is no great difficulty in fusing the two regions together during moulding of the trim because their respective plastics materials mix readily at their interface during the formation of the trim. The manufacture of the trim will be described later.

Modifications of the trim of Figures 1 and 2 include, of course, using different plastics materials; providing the hooks 16 as separate elements secured to the trim (for example as metal projections moulded into the trim); or providing one or more reinforcing members to increase the rigidity of the central region. Metal hooks or claws may be provided on metal re-inforcing plates embedded in the central region 14.

It is also possible to provide means on the central region 14 which secure the trim to the wheel-mounting bolts 7 instead of directly to the wheel 3 itself. Such alternative mounting elements are known in themselves.

When the wheel assembly is in use on a vehicle the flexible outer skirt region 15 forms a smooth continuation of the central region right up to the edge of the tyre. This gives the wheel assembly a cleaner, smoother, profile than has a wheel assembly in which the trim finishes at the outer peripheral edge of the wheel 3, before the transition from the wheel to the tyre. We believe that this reduces the wind resistance of the wheel, increases the speed of air flow past the wheel assembly, and makes the flow more laminar, will the effect of reducing the air pressure outside of the wheels. This encourages hot, relatively stationary air at a higher pressure adjacent the disc brake 8 to flt, > out through the vents provided in the wheel and in the inner region to cool the brake.

Figure 3 illustrates another wheel assembly in which the rim 3 of the wheel has a radially inwardly depending lip 19, a reinforcing ring 20 is secured to the central region 14, and metal hooks 21 are provided on the ring 20 for engagement with the lip 19 to releasably retain the trim to the wheel.

Figure 4 illustrates the method of manufacture of a wheel trim 4, which method may also be applicable for moulding any article which has a rigid or stiff region and flexible region.

The first stage of moulding is to inject the molten "rigid" plastics material mixture (Nylon 6 + 58 glass + 10% mineral) to form the rigid central region of the trim. This stiffened mixture is injected through an injection nozzle 30 in a stationary moulding die 31 at the centre of the central region. To prevent the stiffened mixture from entering the part of the mould which defines the outer region of the trim an annular die 32 is moved towards a stationary die 51 to close off the outer annular region of the mould.

When the stiffened plastics material has cooled sufficiently to retain its shape the die 32 is withdrawn to the position shown in Figure 4 and molten flexible plastics material (unstiffened Nylon 6 or Nylon 66) is injected into the annular outer region of the mould via injection ports 33 to form the outer region of the trim. The heat of the newly introduced molten plastics temporarily re-melts the outer region of the partially set stiffened plastics centre which is miscible with the molten flexible plastics and the outer region of the trim is fused to the central region.

An alternative to two-stage moulding is to inject the two plastics materials at their different regions of the die substantially together, but arrange their timing and pressures such that the outer region of the trim is made largely of the flexible plastics material and the central region of the more rigid plastics material.

Claims

1. A wheel-trim for a wheel which carries a tyre, the wheel trim comprising a circular, relatively stiff central region of substantially the same diameter as the wheel to which the trim is to be attached, attachment means provided on the central region adapted to secure the trim to the wheel, or to wheel-mounting bolts, and an annular, relatively flexible outer region surrounding the central region and adapted to extend in use beyond the outer peripheral edge of the wheel to overlie the side-wall of the tyre carried by the wheel.

2. A wheel-trim according to claim 1 in which the outer region is adapted to bear against the side-wall in use, and flexes with the side-wall when the wheel is used.

3. A wheel-trim according to claim 1 or claim 2 in which the outer region extends for a substantial part of the radial depth of the side-wall.

4. A wheel-trim according to any preceding claim in which vent means is provided in the central region.

5. A wheel-trim according to any preceding claim which is made of plastics material.

6. A wheel-trim according to claim 5 which is moulded from two different plastics materials, a first relatively stiff material which forms the central region, and a second relatively flexible material which forms the outer region.

7. A wheel-trim substantially as herein described and illustrated with reference to Figures 1 and 2 of the accompanying drawings.

8. A wheel trim substantially as herein described and illustrated with reference to Figure 3 of the accompanying drawings.

9. A wheel assembly for a vehicle comprising a wheel, a tyre carried by the wheel, and a wheel-trim in accordance with any one of claims 1 to 8.

10. A method of moulding an article having a relatively stiff region and a relatively flexible region, comprising introducing into a mould a first fluid material of a first kind to produce one of the regions, and introducing into the same mould a second fluid material of a second kind to produce the other of the regions, regions of the article formed from the first and second materials adhering to each other during the moulding operation.

11. A method according to claim 10, in which first and second materials are introduced into the mould in two stages, the second material being introduced into the mould after the first material has been introduced.

12. A method according to claim 11, which further comprises the step of waiting for the first material to have substantially set in its desired shape before introducing the second material into the mould.

13. A method according to claim 12, in which the second material is introduced at least partially to overlie the, at that time non-fluid, first material and to extend beyond the first material to a region in the mould in which there is no first material.

14. A method according to claim 12 or claim 13 in which a movable part of the mould is moved from a blocking position in which it blocks part of the mould to an open position in which said part of the mould is unblocked, the first material being constrained to remain in the solid part of the mould until it has substantially set.

15. A method according to claim 10 in which the first and second materials are simultaneously introduced into different parts of the mould at suitable pressures such that the interface between the first and second materials occurs at the desired region of the article.

16. A method according to anyone of claims 10 to 15 in which the first material constitutes material which will set to be relatively stiff and will form the stiff region of the article, and the second material constitutes material which will be relatively flexible when set and which will form the flexible region.

17. A method according to anyone of claims 10 to 16 in which the flexible region is at the periphery of the stiff region.

18. A method according to claim 17 in which the flexible region surrounds the stiff region.

19. A method according to claim 18, in which the flexible region is an annular region surrounding a circular central stiff region.

20. A method of moulding a wheel-trim in accordance with any one of claims 10 to 19.

21. A method of moulding a wheel-trim substantially as described herein.