GB2093778A - Road wheels for vehicles - Google Patents

Abstract

A vehicle wheel is made as an integral moulding of fibre reinforced plastics material and comprises a hub 21 and rim 25 interconnected by circumferentially spaced and alternating pairs of spokes 26 and 27. The two spokes of each pair 26 or 27 cross each other in a circumferential direction, being integrally moulded at their crossing point 28 or 29 and extending at opposite inclinations to a radius of the wheel through a crossing point, and the pairs of spokes 26 are oppositely axially inclined to the pairs 27, with the pairs 26 extending from one side of, and the pairs 27 from the opposite side of, the hub 21. The illustrated wheel is for an invalid chair, but an embodiment for a motor car is also disclosed. The plastics may be polyamide containing about 30% by weight of glass or carbon fibre, and in making the wheel the mould is cooled so that the rim sets before the hub and spokes. <IMAGE>

Description

SPECIFICATION Road wheels for vehicles Road wheels for motor cars are most commonly made as steel pressings, or as die castings of light alloy. Road wheels for bicycles and motor cycles generally have pressed steel rims and hubs connected to each other by wire spokes which are held under tension. Wheels which are generally similar to bicycle wheels are also used on other light vehicles such as invalid wheel-chairs.

The manufacture of vehicle wheels out of plastics material is a very desirable objective since it will enable the wheels to be made both much lighter and much more cheaply than conventional pressed steel wheels and conventional wheels having pressed steel rims and hubs connected to each other by wire spokes. However, as far as we are aware, the only vehicle wheels moulded out of plastics material which are yet commercially available are for lightweight motor cycles and the construction of these wheels has been based on the same concept as die-cast wheels and they consist of a hub and a rim with integrally moulded spokes which extend radially between the hub and the-rim and have sufficient bending strength and are sufficiently rigidly connected to both the hub and the rim to transmit between the hub and the rim the driving and braking torques applied to the wheel.Difficulties are involved in making wheels such as this sufficiently strong as the crosssectional thickness of the spokes in particular is so great as to give rise to difficulties in the moulding operation.

The present invention provides a vehicle wheel, which is made as a single integral moulding integral moulding of plastics material and which avoids the difficulties which occur with spokes of heavy cross-section. The vehicle wheel in accordance with the invention can also be made lighter than conventional plastics wheels with heavy spokes and with an improved resistance to axial forces between the hub and the rim.

According to this invention, such a wheel comprises a hub, a rim and a series of spokes, which interconnect and are moulded integrally with the hub and the rim, the spokes being arranged in pairs around the wheel, the two spokes of each pair crossing each other in a circumferential direction, being integrally moulded at their crossing point and extending at opposite inclinations to a radius of the wheel through the crossing point to provide circumferential rigidity between the hub and the rim, and alternate pairs of spokes being axially inclined in opposite directions with one pair of spokes extending from one side of the hub towards the opposite side of the rim and the adjacent pair of spokes extending from the opposite side of the hub towards the one side of the rim, but the adjacent pairs of spokes, which are axially oppositely inclined, being circumferentially offset from each other so that the spokes of the one pair do not cross or overlap either of the spokes of the adjacent pair as viewed in the axial direction of the wheel.

We have found that by forming the wheel with integrally moulded spokes arranged in this way, which in appearance is somewhat similar to the arrangement of the spokes of a wire spoked wheel, the wheel can be provided with sufficient circumferential and axial strength between the hub and the rim to withstand the forces applied to the wheel in use on a vehicle whilst making the spokes with a diameter or other cross-sectional dimensions comparable with the thickness of the hub and rim.

As there are no great differences between the thicknesses of the various parts of the wheel, the tendency for difficulties in the moulding operation is largely overcome.

It is also of the greatest importance that the arrangement in which the two spokes of each pair are made integral with each other where they cross, but adjacent pairs of spokes, which are axially separated from each other, do not overlap in a circumferential direction, makes it possible to mould the wheel in a mould which is so formed that the parts of the mould which form the spokes can be separated on planes transverse to the axis of the wheel to enable the moulded wheel to be ejected from the mould when moulding is complete.

The plastics material is preferably reinforced with glass fibre or carbon fibre filler. The plastics material is preferably a polyamide (nylon) resin, but it may alternatively be a polycarbonate, an acetal resin or a modified polyphenelene oxide resin. The fibre filler is preferably present in an amount of about 30% by weight and glass fibre is preferably used for wheels for light vehicles such as invalid wheel-chairs, bicycles and light motor cycles and carbon fibre filler is preferably used for heavier wheels for motor cars.

To enable the moulded wheel to be ejected satisfactorily from the mould, the mould is preferably provided with floating splits or side cores which form the outwardly concave section of the rim in which the beads of the tyre, which is fitted to the wheel, are seated.

The invention also consists in a method of manufacturing a wheel in accordance with the invention by injection moulding, wherein plastics material is injected into a mould and the mould is cooled in such a way that the plastics material which forms the rim sets before the plastics material which forms the hub and the spokes, and, as the plastics material forming the hub and the spokes subsequently sets, this material contracts within the rim so that shrinkage effects cause the spokes to be under tension when the whole of the wheel is subsequently at ambient temperature.

To cause the plastics material which forms the rim to set before the remainder of the plastics material which forms the hub and the spokes, the mould may be cooled to a lower temperature around the rim than it is adjacent the spokes and the hub. For this purpose the mould is preferably provided with at least two separate cooling water duct systems, one system extending in the part of the mould adjacent the rim and the other system or other systems extending in the part of the mould adjacent the spokes and the hub. Cooling liquid is circulated through the duct system in the part of the mould adjacent the rim at a lower temperature than that circulated through the duct system or systems in the part of the mould adjacent the spokes and the hub.

The rim is preferably moulded to much the same cross-section as that of the rim of a conventional pressed steel wheel or a conventional wire spoked wheel so that the wheel can receive conventional tyres without any modification of the beads of the tyres being necessary. Since the rim is a single continuous moulding, it is particularly suitable for receiving tubeless tyres with no risk of air leakage from the tyres occurring.

In a wheel which is especially suitable for use on a motor car, the hub is preferably tubular with a web extending across the tube in a plane perpendicular to the axis of the wheel and substantially at the middle of the axial length of the wheel. This web is formed with holes for receiving wheel fixing bolts and, in order to distribute the load from the fixing bolts and nuts to the wheel, the hub is preferably reinforced with a pan-shaped metal insert which is bonded into position within the tubular part of the hub in contact with one face of the web of plastics material. The bolt holes then extend both through the plastics web and through the metal insert. The metal insert has a peripheral wall which is bonded to part of the inside of the peripheral wall of the hub.The axial extent of the peripheral wall of the metal insert is dependent, amongst other factors, upon the load which the wheel has to carry.

The cost of a moulded plastics wheel in accordance with the invention may, when the wheels are produced in large quantities, be substantially less than the cost of a pressed steel wheel, or of a wire spoked wheel with a pressed steel rim, of similar size and load carrying capacity.

Further, a moulded plastics wheel may be used as moulded with no after treatment or finishing being required as is necessary with pressed steel wheels after pressing has taken place. Further, in the case of wheels for motor vehicles, the spoke structure allows for a very large air flow for the cooling of brakes of the vehicle of either the drum or the disc type.

Two examples of wheels in accordance with the invention are illustrated in the accompanying drawings in which: Figure 1 is a front elevation of a first example; Figure 2 is a section through the first example as seen in the direction of the arrows on the line Il-Il in Figure 1; Figure 3 is a front elevation of a second example; and, Figure 4 is a diametric section through the second example as seen in the direction of the arrows on the line IV--IV in Figure 3.

The first example shown in Figures 1 and 2 is intended for use on a motor car and this example of the wheel comprises a hub 1 which has a cylindrical part 2 and a web 3 extending across the cylindrical part 2 in a plane perpendicular to the axis of the wheel. The web 3 is reinforced by a pan-shaped steel insert which may either be insert moulded into the wheel or is a tight press fit within the cylindrical part 2.

The wheel further comprises a rim 5 and a series of pairs of spokes 6 and 7 which connect the rim 5 to the cylindrical part 2 of the hub.

As shown most clearly in Figure 1, the two spokes of each of the pairs 6 are oppositely circumferentially inclined to each other so that they cross each other at point 8 and the spokes 7 are also circumferentially inclined in a similar manner so that they cross each other at a point 9.

The spokes 6 of each pair are integrally moulded where they cross at 8 and so are the spokes 7 where they cross at 9. The spokes 6 of each pair are both axially inclined and extend from the front side 10 of the rim 5 to the rear side 11 of the cylindrical part of the hub and the spokes 7 are oppositely axially inclined and extend from the front side of the cylindrical part 2 of the hub to the rear side 13 of the rim 5.

As is shown in Figure 1, the pairs of spokes 7 are circumferentially offset from the pairs of spokes 6 so that there is no overlap between the spokes 6 and 7 as seen in Figure 1, that is as viewed in an axial direction, and accordingly the two mould parts which respectively form the front faces of the spokes 6 and 7 and the rear faces of the spokes 6 and 7 can be separated from each other in an axial direction. This would not of course be possible if there were any overlap in a circumferential direction between the spokes 6 and 7 with axial offsetting of the spokes 6 and 7 as well. The mould parts can be separated in spite of the crossing of the spokes 6 at 8 and the crossing of the spokes 7 at 9 because, as already mentioned, the spokes 6 of each pair and the spokes 7 of each pair are integrally moulded where they cross each other.

The web 3 of the hub and the steel reinforcing pan 4 are formed with holes 14 and 15 respectively for receiving wheel fixing studs and the steel pan 4 is provided with conical surfaces 1 6 surrounding the hole 1 5 to form bearing surfaces for wheel fixing nuts.

The wheel, apart from the steel reinforcing pan 4, is formed as a single injection moulding out of carbon fibre filled polyamide resin, there being a 30% by weight content of carbon fibre. The mould within which the wheel is moulded is provided in a conventional manner with floating splits or side cores which form the outwardly concave section of the rim 5 in which the beads ofa pneumatic tyre, which, in use, is fitted to the wheel, are seated. However, in distinction to conventional moulds which generally have a single interconnected system of cooling water ducts formed in the mould sections, the mould has two separate systems of cooling water ducts. One system extends through the walls of the part of the mould which defines the rim 5 and the other system extends through the walls of the parts of the mould which define the hub 2 and the spokes 6 and 7.

Cooling water at a lower temperature is circulated through the first duct system and causes the rim 5 to set. Cooling water at a higher temperature is circulated through the second duct system so that the spokes 6 and 7 and the hub 2 set later and, owing to their shrinkage after setting of the rim 5, the spokes 6 and 7 remain under tension when the whole wheel is cooled to ambient temperature.

The injection moulding operation can be carried out in a conventional injection moulding machine having a mould locking force of 500 tonnes and a shot capacity of from 2500 to 3400 grams.

The weight of the first example of the wheel, which has an external rim diameter of 330 mm is approximately 2 kg and this compares with a weight of 5 kg for a pressed steel wheel of the same size. The wheel therefore effects a saving in total weight of 1 5 kg in a motor car having four wheels and one spare wheel and it also appreciably reduces the unsprung weight of the vehicle.

The second example shown in Figures 3 and 4 is intended for fitting to a manually driven invalid wheel-chair. It is generally similar in its principles of construction to the first example, but its proportions are different and owing to the difference in proportions that is the ratio of axial width to overall diameter, the arrangement of the spokes is somewhat different.

The wheel comprises a hub 21 which has an outer cylindrical part 22 and an inner cylindrical part 24 connected by a web 23. The inner cylindrical part 24 is arranged to be fitted directly upon a wheel spindle and because the wheel is intended to carry only much smaller loads than the first example, no metal reinforcing pan is necessary. This example of the wheel is, however, intended to be fitted with an internally expanding hub brake which is located in the annular space between the outer and inner hub parts 22 and 24 and flanges 24a and pins 24b are provided for holding the brake in position and transmitting torque from the brake to the hub 21.

The wheel further comprises a rim 25 and a series of pairs of spokes 26 and 27.

As shown in Figure 3, the two spokes of each of the pairs 26 and of the two spokes of each of the pairs 27 are oppositely circumferentially inclined to each other in the same way as the spokes of the first example so that they cross each other at points 28 and 29 respectively. The spokes 26 and 27 are integrally moulded at their crossing points in the same way as the spokes of the first example.

As will be seen from Figure 4, however, the axial inclination of the spokes of each of the pairs 26 and 27 is different from that of the spokes 6 and 7 in the first example. Each of the pairs of spokes 26 is axially inclined in an opposite direction to each of the pairs of spokes 27, and each of the pairs of spokes extends from the righthand side of the hub 21, as seen in Figure 4, with an axial inclination towards the left-hand side of the rim 25, but as shown, one of the spokes 26 has only a small axial inclination and extends to the right-hand side of the rim 25 while the other of the pair of spokes 26 is more steeply axially inclined and extends to the left-hand side of the rim 25.The pair of spokes 27 are similarly arranged and both spokes extend with an axial inclination from the left-hand side of the hub 21 towards the right-hand side of the rim 25, but one of the spokes extends up to the right-hand side of the rim 25, the other of the pair of spokes 27 extends to the left-hand side of the rim 25.

The opposite axial and circumferential inclinations of the spokes 26 and 27 do however between them provide adequate circumferential and axial strength between the hub 21 and the rim 25 to withstand both axial and tangential forces.

The rim 25 is provided with integrally moulded lugs 30, of which there are six at equal angular spacings around the wheel, as shown in Figures 3 and 4. These lugs are intended for bolting a propelling rim to the wheel to enable the wheel to be turned manually by the occupant of a wheelchair to which the wheel is fitted.

The second example of the wheel is also injection moulded out of a polyamide resin, but since it does not need to be so strong as the first example, the resin is reinforced with 30% by weight of glass fibre filler. The wheel is moulded in an injection moulding machine of the same type as that used for the first example and the mould is constructed in the same general manner with two cooling water duct systems to enable the rim to be cooled and set before the spokes and hub. The rim 25, which is intended to receive a standard bicycle tyre and inner tube, has an external diameter of 509 mm to receive the tyre having a nominal external diameter of 560 mm (22 inches). The wheel has a weight of just under 1 kg and is both lighter and much cheaper to manufacture than a conventional wire spoked bicycle wheel having a pressed steel rim of the same nominal diameter.

Wheels which are of generally similar construction to the second example can also be used on bicycles, very light motorcycles and other light vehicles, such as barrows or light trailers.

Claims (11)

1. A vehicle wheel which is made as a single integral moulding of plastics material, the wheel comprising a hub, a rim and a series of spokes, which interconnect and are moulded integrally with the hub and the rim, the spokes being arranged in pairs around the wheel, the two spokes of each pair crossing each other in a circumferential direction, being integrally moulded at their crossing point and extending at opposite inclinations to a radius of the wheel through the cross point to provide circumferential rigidity between the hub and the rim, and alternate pairs of spokes being axially inclined in opposite directions with one pair of spokes extending from one side of the hub towards the opposite side of the rim and the adjacent pair of spokes extending from the opposite side of the hub towards the one side of the rim, but the adjacent pairs of spokes, which are axially oppositely inclined, being circumferentially offset from each other so that the spokes of the one pair do not cross or overlap either of the spokes of the adjacent pair as viewed in the axial direction of the wheel.

2. A wheel according to Claim 1, in which the plastics material is reinforced with glass fibre or carbon fibre filler.

3. A wheel according to Claim 2, in which the fibre filler is present in an amount of substantially 30% by weight.

4. A wheel according to any one of the preceding Claims, in which the plastics material is a polyamide resin.

5. A wheel according to any one of the preceding Claims, in which the rim is shaped to receive a conventional pneumatic tyre.

6. A wheel according to any one of the preceding Claims, in which the hub is tubular with a web extending across the tube in a plane perpendicular to the axis of the wheel, the web being formed with holes for receiving wheel fixing bolts.

7. A wheel according to Claim 6, in which the hub is reinforced with a pan-shaped metal insert which is bonded into position within the tubular hub in contact with one face of the web and the bolt holes extend through the web and through the metal insert.

8. A wheel according to Claim 7, in which the metal insert has a peripheral wall which is bonded to the inside of the peripheral wall of the tubular hub.

9. A method of making a wheel in accordance with any one of the preceding Claims by injection moulding, wherein plastics material is injected into a mould and the mould is cooled in such a way that the plastics material which forms the rim sets before the plastics material which forms the hub and the spokes, and, as the plastics material forming the hub and the spokes subsequently sets, this material contracts within the rim so that shrinkage effects cause the spokes to be under tension when the whole of the wheel is subsequently at ambient temperature.

10. A method according to Claim 9, in which, to cause the plastics material which forms the rim to set before the plastics material which forms the hub and spokes, the mould is provided with at least separate cooling liquid duct systems, one system extending in the part of the mould adjacent the rim and the other system extending in the part of the mould adjacent the spokes and the hub, and cooling liquid at a lower temperature is circulated through the duct system in the part of the mould adjacent the rim and cooling liquid at a higher temperature is circulated through the duct system or systems in the part of the mould adjacent the spokes and the hub.

11. A wheel according to Claim 1, substantially as described with reference to Figures 1 and 2, or Figures 3 and 4, of the accompanying drawings.