GB2625793A

GB2625793A - Single piece wheel rim and manufacturing method

Info

Publication number: GB2625793A
Application number: GB2219697.6A
Authority: GB
Inventors: Carl Willmott Alexander
Original assignee: Titan Steel Wheels Ltd
Current assignee: Titan Steel Wheels Ltd
Priority date: 2022-12-23
Filing date: 2022-12-23
Publication date: 2024-07-03
Also published as: WO2024134136A1; GB202219697D0

Abstract

A single piece wheel rim and associated methods of manufacturing the single piece wheel rim are described. The single piece wheel rim is preferably suitable for use on a very large vehicle. The wheel rim comprises: an axially inner rim portion and an axially outer rim portion. The axially inner rim portion and an axially outer rim portion together defining a drop centre. The drop centre comprises: a first region with a first radius of curvature (R1) and a second region with a second radius of curvature (R2). A ratio between the first radius of curvature and second radius of curvature is greater than or equal to 3 to 2; and/or the first radius of curvature (R1) equal to 15 or greater than 35 mm and the second radius of curvature (R2) equal to or greater than 15 mm.

Description

SINGLE PIECE WHEEL RIM AND MANUFACTURING METHOD

TECHNICAL FIELD

The present disclosure relates to a single piece wheel rim. Particularly, but not exclusively, the disclosure relates to a single piece wheel rim suitable for use with a very large vehicle. Aspects of the invention relate to a single piece wheel rim, a wheel, a very large vehicle with a wheel, a method of manufacturing a single piece wheel rim and methods of manufacturing a wheel.

BACKGROUND

Very large vehicles ('VLVs"), such as vehicles used as mobile cranes, heavy hauling vehicles, quarry excavation or transport of mined material have large diameter wheels.

These are bigger than the wheel's of road going heavy goods vehicles ("HGVs''). Commonly, given their working environment, these types of vehicles are required to operate on unpaved routes or rough terrain, often termed "off-road". Such vehicles require a robust wheel rim and tyre combination.

As these wheels must work in challenging-often remote-environments it is important that the wheels are able to withstand the loading requirements on them and not buckle. Such a requirement is especially acute as VLVs may be loaded to carry cargo of several tonnes or greater. With uneven ground the load applied through each wheel may vary with some wheels experiencing higher loads than others. Through normal use the wheels will experience fatigue during loaded or unloaded movement of the vehicle, and also when a load is added then removed from the vehicle. Fatigue on wheels can cause stress-cracks to grow, which can be exacerbated by stress-crack corrosion, potentially causing the ultimate failure of the wheel. As VLVs operate in challenging and often remote environments any buckling or cracking of the wheel may require repair or replacement. Repairing or replacing a VLV wheel can be time consuming and downtime resulting from this can be costly.

Some prior art wheel rims have a drop centre. This is a recessed portion of the wheel disposed between an inner and outer facing parts of the wheel. The walls of inner and outer wheel rim define at least a part of the drop centre. The drop centre can be described as a substantially U-shaped region. In these prior art wheel rims, the radius of curvature at each bend may be equal.

Wheel rim profiles for VLVs are heavily standardised, therefore there is little incentive within the field to adapt previous wheel assemblies to provide improvements. Such improvements if they do not fall within a standard are unlikely to be adopted. Therefore, there may be little-tono change in the profile of a VLV wheel over many years as there is a prejudice against change.

The present invention aims to improve usable life of wheels for VLVs, improve ease of manufacturability and to improve on wheels in the art.

SUMMARY OF THE INVENTION

Aspects of the invention will now be described.

According to a first aspect of the invention a single piece wheel rim is provided. The single piece wheel rim comprising: an axially inner rim portion and an axially outer rim portion; the axially inner rim portion and an axially outer rim portion together defining a drop centre; the drop centre comprising: - a first region with a first radius of curvature; - a second region with a second radius of curvature; and wherein a ratio between the first radius of curvature and the second radius of curvature is greater than or equal to 3 to 2.

The applicant has found that altering R1 and the relationship with R2 has had surprising technical effects on the final product.

Advantageously, having a larger first radius of curvature than the second radius has the effect of increasing the fatigue life of the component dramatically. This is compared to a single piece wheel rim with a drop centre which has a shaped portions with identical radii of curvature across the drop centre. The increase in the ratio of R1 to R2 has been found by the applicant to have at least approximately a twofold increase in the fatigue life in relation to wheels of a similar type. This increase in fatigue life is both in relation to radial fatigue and separately cornering fatigue which are experienced by the final wheel in use.

Increasing the radius maintains the prime functionality of the wheel but increases the fatigue life at the same time. A smaller radius in the drop centre increases the ease of getting a tyre onto the wheel. The applicant has found that increasing R1 (in comparison to R2) has maintained the ability to easily mount the tyre onto the wheel but at the same time has increased the fatigue life of the final product.

The increased radius of curvature R1, in an area of high stress in use, means that in practice there is a lower likelihood of stress-cracking occurring. The radius of curvature of the plate is increased in a location, which, the applicant has found to be more susceptible to fatigue crack growth. Further, the greater radius of curvature of enables easier inspection and cleaning of the wheel in use on the outer facing side, for example at the connection between the rim and the disc.

Further, the applicant through extensive research and modelling of the present device has found that the change in ratio may lead to an approximately 20% reduction in stress at a region in the drop centre area when compared to prior art wheels. This approximately 20% reduction in the region in the drop centre area is an area which can be the region experiencing the highest loading and stress in use. Advantageously, this change can also lead to an approximately 6% reduction in stress in the area at the connection between the drop centre and the tyre seat, this area may be the region which experiences the second highest stress in use. Such modelling and testing has been undertaken using means and methods known to the skilled person, for example finite element analysis. For such an analysis the simulation may be carried out utilising parameters within the range of: 10 to 11 bar tyre pressure and 7,000 to 8,000 kg of vertical load.

Moreover, rather counter-intuitively, by altering the ratio of R1 to R2 there is a decreased disc to wheel rim interface in the final wheel assembly which results in increased mechanical properties of the finalised product substantially near this region. As the swept area of R1 is greater in the present wheel rim as compared to prior art devices there is a comparatively smaller area for the interface of the rim on the wheel disc. This smaller interface has however not resulted in a decrease in performance as will be noted from the increased mechanical strength and fatigue resistance.

The radii are controlled to enable correct tyre fitting on the rim.

According to a second aspect sharing features in common with the first aspect, a single piece wheel rim is provided. The rim comprising: an axially inner rim portion and an axially outer rim portion; the axially inner rim portion and an axially outer rim portion together defining a drop centre; the drop centre comprising: - a first region with a first radius of curvature equal to or greater than 35 mm; - a second region with a second radius of curvature equal to or greater than 15 mm; and wherein the first radius of curvature is greater than the second radius of curvature.

Providing an increased first radius of curvature of 35 mm as compared to 15 mm with the second radius of curvature enables the production of wheels which have greater resistance to fatigue in the same or similar fashion as has been set out with respect to the first aspect.

The other advantages of the second aspect are similar to those of the first aspect as will be clear to the skilled reader; for reasons of brevity these advantages have not been repeated here.

Preferably a ratio between the first radius of curvature and second radius of curvature is greater than or equal to 3 to 2.

Advantageously the first and second aspect can be combined as will be apparent to the skilled person. For example, as follows: A single piece wheel rim comprising: an axially inner rim portion and an axially outer rim portion; the axially inner rim portion and an axially outer rim portion together defining a drop centre; the drop centre comprising: and wherein: - a ratio between the first radius of curvature and second radius of curvature is greater than or equal to 3 to 2; and/or - the first radius of curvature equal to or greater than 35 mm and the second radius of curvature equal to or greater than 15 mm.

The following preferable features may be employed on either of the first or second aspect or both the first and second aspect or the combined first and second aspect.

Preferably the ratio is between 3 to 2 and 4 to 1. A ratio between the two radii of curvature within this range provides the advantageous effect. Between in this instance is taken to mean any ratio in the range set by 3 to 2 and 4 to 1 and may also include both 3 to 2 and 4 to 1.

Preferably the ratio is 7 to 3. The inventors have found that this ratio has been particularly effective at providing the increased fatigue resistance as described above.

Preferably, the drop centre comprises a third region with a third radius of curvature.

Preferably, the second radius of curvature and third radius of curvature are equal. Providing the same radius of curvature for these two regions simplifies the manufacturing of the wheel rim.

Preferably, the rim further comprises at least one elbow region connected to the drop centre with a fourth radius of curvature wherein the fourth radius of curvature differs from the first radius of curvature and the second radius of curvature.

Preferably, the ratio of first radius of curvature to second radius of curvature to fourth radius of curvature is 7 to 3 to 4.

Preferably, the first radius of curvature is 15 mm to 55 mm; and more preferably the first radius of curvature is 35 mm.

Preferably, a distance between a centre of curvature of the first radius of curvature and a centre of curvature of the second radius of curvature is a minimum of 15 mm to 55 mm; and preferably the distance is a minimum 35 mm.

Preferably a distance between a centre of curvature of the first radius of curvature and a centre of curvature of the second radius of curvature is a minimum of 15 mm to 55 mm; and more preferably the distance is a minimum of 35 mm.

Preferably, the first region is part of the axially outer rim portion.

Preferably, the second region is part of the axially inner rim portion.

Alternatively, the first region may be on the axially inner portion and/or the second region may be on the axially outer portion.

Preferably, the rim comprises: a steel alloy; or an aluminium alloy. Steel alloy is advantageously relatively cheap which reduces costs in manufacture. Aluminium alloy, whilst generally more expensive is less dense than steel, therefore aluminium alloy can be employed in situations where weight savings are important, for example for use in cranes which travel between job sites on main roads often over long distances.

Preferably, the rim is unitary and manufactured as a single component. Manufacturing from a single piece of stock material helps to ensure that homogenous material properties are obtained throughout the final rim product.

Preferably the rim is manufactured in at least two parts which are welded together to form the rim. Manufacturing from at least two parts enables different manufacturing processes to be undertaken on the first and second parts. As a result, different mechanical or physical or thermal processes can be undertaken, for example one of the two parts could undergo a slightly different heat treatment or forging step which results in tailored microstructural properties in regions which on the first or second part undergo high mechanical loading in use as compared to the other of the second or first part.

Preferably, the rim further comprises a wall and wherein the first radius of curvature is a distance from the wall; and wherein the distance is less than or equal to 105 mm.

Preferably the single piece wheel rim is suitable for a heavy vehicle and/or a very large vehicle. Heavy vehicles include commercial vehicles and agricultural vehicles and VLVs. VLVs are a subset of heavy vehicles and have relatively larger diameter wheel rims compared to the other types of heavy vehicles, such that relatively thick material may be used in the manufacturing of VLV wheels. More relatively thin vehicle wheel rims are generally not suitable for use with VLVs. Preferably the width of the rim is 280 mm.

According to a third aspect a wheel comprising a single piece wheel rim according to the first aspect and a disc is provided. The disc is connected to the single piece wheel rim.

Preferably the wheel also comprises a tyre.

Preferably, the wheel is able to withstand 1,000,000 to 3,000,000 cycles when benchmarked using a radial fatigue test carried out under EUWA ES-3.12 standard. Preferably the number of cycles is approximately 2,000,000 cycles. The EUWA ES-3.12 standard describes benchmarking tests for agricultural wheels. The type of wheels described here are manufactured in lower quantities and without specific testing standards associated with them. The applicant has followed the test in accordance with the standard with an additional load more applicable to the end application in question, for example 160 kN, which may be experienced by VLVs in service. The applicant has found that advantageously the wheel of the present aspect performs twice as well compared to wheels utilising prior art rims benchmarked in the same fashion.

Preferably, the wheel is able to withstand 200,000 to 400,000 cycles when benchmarked using a cornering fatigue test carried out under EUWA ES-3.12 standard. Preferably the number of cycles is approximately 300,000 cycles. The wheel will pass the EUWA ES-3.12 standard when tested to between 200,000 to 400,000 cycles when tested using a cornering fatigue test carried out under said standard. The EUWA ES-3.12 standard describes benchmarking tests for agricultural wheels. The type of wheels described here are manufactured in lower quantities without specific testing standards associated with them. The applicant has followed the cornering fatigue test set out under the EUWA ES-3.12 standard. The benchmarking of a wheel according to this aspect and in accordance with the standard has been made with parameters more applicable to the end application in question. For example, when calculating the test bending moment, M (kNm), set out in the EUWA ES-3.12 standard then one or more of the following parameters may be used: a tyre max load Fv (Kg) of 7,600 Kg; wheel offset, d (m) of 0.05 m; a traction coefficient, p, of 0.65; a tyre radius under load, R (m) of 0.775 m; a test acceleration factor, S, of 2. This can be used to used to calculate a test bending force T = M/b where b is the length of the load application arm of the testing machine in m.

Cornering fatigue tests are particularly severe tests which simulate constant cornering of a wheel and simulate the stresses on the interface between the rim and disc. The applicant has found that the reduced interface between disc and rim, that is as a direct result of altering the first radius of curvature, has had the effect of increased cornering fatigue resistance. This has led to a 50 % increase in number of cycles to crack propagation as compared to prior art wheels using wheels using prior art rims benchmarked in a similar fashion.

According to a fourth aspect a heavy vehicle comprising at least one wheel of the third aspect is provided. Preferably, the heavy vehicle is a very large vehicle; more preferably wherein the very large vehicle is a mobile crane.

According to a fifth aspect a method of manufacturing a single piece wheel rim is provided.

The method of manufacturing the single piece wheel rim may comprise one or more of the features of the previous aspects. The method comprising the steps of: providing a first cylindrical blank component, a second cylindrical blank component and an annular disc blank; - press forming the first blank component to form a one piece, axially outer rim portion; - press forming the second blank component to form a one piece, axially inner rim portion; circumferentially joining the outer and inner rim portions to form a single piece wheel rim having a base; wherein either: - the axially inner rim portion has a first region with a first radius of curvature and the axially outer rim portion has a second region with a second radius of curvature; or - the axially outer rim portion has a first region with a first radius of curvature and the axially inner rim portion has a second region with a second radius of curvature; and wherein: - a ratio between the first radius of curvature and second radius of curvature is greater than or equal to 3 to 2; and/or - the first radius of curvature (R1) equal to or greater than 35 mm and the second radius of curvature (R2) equal to or greater than 15 mm.

Advantageously the method enables the single piece wheel rim to be manufactured in two parts which can be then joined together. For example, by welding. Manufacturing the inner and outer rim portions separately enables greater control of the materials properties and enables them to be tailored. For example, press-forming can be controlled to ensure greater toughening of the inner or outer wheel rim portion if such a part requires greater toughening in use.

According to a fifth aspect a method of manufacturing a wheel comprising the method of manufacturing a single piece wheel rim of the fourth aspect is provided. The method comprising the further steps of: - machining the inside diameter of the wheel rim base; press forming the disc blank to form a press-formed disc; machining the outside edge of the press-formed disc; press fitting the press-formed disc to the wheel rim base at the machined inside diameter; and welding the press-formed disc to the wheel rim base at the machined inside diameter.

According to a sixth aspect an alternative method of manufacturing a wheel is provided. The method of manufacturing the single piece wheel rim may comprise one or more of the features of the previous aspects. The method comprising the steps of: machining a billet to form a single piece wheel rim comprising: - an axially inner rim portion and an axially outer rim portion; the axially inner rim portion and an axially outer rim portion together defining a drop centre; the drop centre comprising: a first region with a first radius of curvature; a second region with a second radius of curvature; and wherein: - a ratio between the first radius of curvature and second radius of curvature is greater than or equal to 3 to 2; and/or - the first radius of curvature equal to or greater than 35 mm and the second radius of curvature equal to or greater than 15 mm.

The ability to manufacture the wheel from a single machined billet enables good control of the material properties. The billet may be a forged billet (of a type known in the art). Preferably, the billet used in this process is an aluminium billet.

Preferably, the method further comprises the step of machining a disc from the same billet or a different billet. Machining the wheel disc using the same billet increases the likelihood of consistent material properties between the wheel disc and the wheel rim. Alternatively, using a different billet, which may have undergone a different heat treatment or forging process may enable greater control of properties towards the centre of the wheel where there may be differing requirements. E.g., hardening in locations surrounding the bolt holes for fixing the wheel to a VLV may be required.

Preferably the wheel is machined from the billet as a unitary component. Manufacturing the wheel as a single unitary component enables greater microstructural control of the final product. A wheel manufactured from a single piece of metal such as a billet is more likely to have homogenous microstructure throughout the material.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of the wheel sub-assembly of the present invention; Figure 2 is a partial cross-sectional view of the wheel sub-assembly of figure 1 taken at line X-X showing the wheel disc; Figure 3 is a partial cross-sectional view of the wheel sub-assembly of figure 1 taken at line X-X not showing the wheel disc; Figure 4a is an enlarged view of Figure 3 showing the drop centre; Figure 4b is an enlarged view of Figure 3 showing part of the drop centre; Figure 5 is a table containing normalised dimensions of an embodiment; and Figure 6 is a table containing dimensions.

Figure 7 is a series of section views showing the press forming sequence of an outer rim portion; Figure 8 is a series of section views showing the press forming sequence of an inner rim portion; and Figure 9 is cross-sectional view through a wheel with a tyre mounted on the single-piece wheel rim, for clarity the disc is not shown here.

DETAILED DESCRIPTION

A circular wheel rim assembly 100 (also referred to as wheel 100) having an external diameter of 721mm is shown in figure 1. A cross-section taken at line X-X (see figure 2) shows that the wheel sub-assembly 100 comprises two principal components, a single piece wheel rim 1 and a disc 14. The single piece wheel rim 1 and/or the disc 14 are substantially rotationally symmetrical. For brevity, the single piece wheel rim 1 is also shortened to the "rim" 1 in this document. The wheel assembly 100 also has a valve hole 68 ten equally circumferentially-spaced wheel hub holes 83 for attachment to the axle of a vehicle (not shown). In alternative configurations alternative number of hub hole 83 may be provided to provide an attachment arrangement known in the art.

In use a tyre 102 (which may have treads 104) is mounted on the wheel rim 1 as is shown in cross-section in Figure 9. For clarity, the disc 14 is not shown here. The axially outer part of tyre 102 is mounted to an axially outer seat mount 106a and the axially inner part of tyre 102 is mounted to an axially inner seat mount 106b. The tyre seat 106a, 106b shown in the figures is at 5 degrees from the horizontal. In an alternative arrangement a 15 degree tyre seat 106a, 106b may be employed. The tyre 102 also abuts flanges 22, 26 as will be apparent from Figure 9. The flanges 22, 26 of the rim 1 help to retain the tyre 102 on the wheel 100 in use.

The single piece wheel rim 1 is shown in figure 3 in more detail along line A-A, for clarity the disc 14 is not shown in this view. The rim 1 is made up of an axially inner rim portion 10 and an axially outer rim portion 12. The axially outer rim portion 12 is located in use on the tyre mounting side 2 and the axially inner rim portion 10 is located on the inner side 4. However, it is envisioned that the current disclosure may work in a similar fashion with the components reversed, in other words the inner side 4 features located on the tyre mounting side 2 and vice versa.

The axially inner rim portion 10 and axially outer rim portion 12 together defining a drop centre 16 as shown in figure 3 and in close up in figure 4a and partially in figure 4b.

The drop centre 16 comprises a first region 30 and a second region 32. The first region 30 is curved (when viewed in cross-section in figure 3) the curve of the first region 30 is defined by a radius of curvature Fli. The second region 32 is curved (when viewed in cross-section in figure 3) the curve of the second region 32 is defined by a radius of curvature Rz. Dashed arrows are used to indicate the radii of curvature in the figures, for clarity the radii of curvature are not provided to scale but rather indicate where they are measure to/from. In Figure 3 the first region 30 is shown located on the axially outer rim portion 12 and the second region 32 is located on the axially inner rim portion 10.

The first radius of curvature Ri is greater than the second radius of curvature Rz. The ratio between the first and second radii of curvature R1/R2 is greater than or equal to 3 to 2. Alternatively, the ratio may be greater than or equal to any one of: 3 to 2, or 3 to 1, or 2 to 1, or 4 to 1, or 5 to 1, or 4 to 3, or 5 to 3, or 7 to 3, or 8 to 3, or 5 to 4; the ratio alternatively may be any subset or range of the ratios. For example, the ratio may be between 5 to 4 and 5 to 1. Most preferably, the ratio is greater than or equal to 7 to 3.

The centre of curvature C1 of the first radius of curvature Ri is a distance L from the centre of curvature C2 of the second radius of curvature R2 as shown in figure 4a and 4b. Preferably the distance is a minimum of 15 mm to 55 mm; preferably the distance L is 35 mm or a minimum of 35 mm.

The rim 1 also comprises a third region 34, shown in Figure 3 located on the axially inner rim portion 10. The third region 34 has a third radius of curvature R3 which may be equal or different to Rz. Preferably, P2 and R3 are the same. As such the ratio between Ph and R3 may be the same as that between Ri and Rz.

As shown in figure 4a, the drop centre 16 has two elbow regions 40, 42, an outer elbow region 40 and an inner elbow region 42. The outer elbow region 40 connects the drop centre 16 to the rest of the axially outer rim portion 12. Likewise, the outer elbow region 42 connects the drop centre 16 to the axially inner rim portion 10.

The outer elbow region 40 has a curve when viewed in cross-section in figure 3 and 4. The curve has a radius of curvature R4. The bend in the curve is in an opposite sense to the bend at region 30 as can be seen in figure 4a.

The inner elbow region 42 has a curve when viewed in cross-section in figure 3 and 4a. The curve has a radius of curvature R4. The bend in the curve is in an opposite sense to the bend at region 30 as can be seen in figure 4a. Alternatively, the outer elbow region 42 may have a different radius of curvature R4.

The rim 1 will now be described in its entirety from the tyre mounting side 2 (left hand side in figure 3) to the inner side 4 (right hand side in figure 3).

On the left-hand side of figure 3 is the tyre mounting side 2 flange 22 that is part of the axially outer rim portion 12. The is defined by two radii of curvature a fifth radius of curvature R5 and a seventh radius of curvature R7 as can be seen in figure 3. The fifth radius of curvature R5 defines a curve of the edge of the flange 22. The seventh radius of curvature R7 defines the curvature of the flange 22 itself.

Adjacent to the flange 22 is an axially outer wall 21 which connects the flange to an axially outer ridge 20. The wall 21 and ridge 20 are connected by a curved region 36. The curved region is defined by a sixth radius of curvature R6. The ridge 20 makes up part of the tyre seat 106a as shown in Figure 9 which shows the tyre 102 sitting on the rim 1.

The centre of curvature Ci of the first radius of curvature Ri is a distance Q from the inside face of the wall 21 (facing the drop centre 16) as shown in figure 4b. The distance 0 is less than or equal to 105 mm, Preferably the distance is between of 50 mm to 105 mm. The distance Q may be 105 mm or a maximum of 105 mm.

The ridge 20 is then connected to the outer elbow region 40 at the other side.

The outer elbow region 40 is connected to the drop centre 16 as discussed above. Subsequently moving further to the right and towards the inner side 4 in figure 3 the drop centre 16 is connected to the inner elbow region 42.

The inner elbow region 42 is connected to an axially inner ridge 24 in a similar fashion as between the outer elbow region 40 and the outer ridge 20. The ridge 24 makes up part of the tyre seat 106b as shown in Figure 9 which shows the tyre 102 sitting on the rim 1.

The ridge 24 is subsequently connected to an axially inner wall 23 by a curved region 36.

The curved region is defined by the sixth radius of curvature 1:16.

On the right-hand side of figure 3 there is a substantially similar flange 26 to flange 22 on the axially inner rim portion 10. The flange 26 may similarly be defined by the fifth and seventh radii of curvature R5 and R7 as the other flange 22. In use, the tyre sits between the two flanges 22, 26.

As shown in Figure 3, the rim 1 may comprise a valve hole 68, also shown in figure 1 and 2. The valve hole 68 is for a valve for inflating a tyre disposed on the rim 1.

Preferably, the ratio of R1:R2:R3:Ftzt:R2:R6:R7 is 7:3:3:4:1:2:4.5 as shown in Figure 5.

The ratio of Ri to R2 may be 7:3. The ratio of R1 to R3 may be 7:3. The ratio of R1 to R4 may be 7:4.

The ratio of R1 to 1:15 may be 7:1.

The ratio of Ri to 116 may be 7:2. The ratio of Ri to 117 may be 7:4.5.

Preferably, the radii of curvature are dimensioned as shown in Figure 6. Whereby "min" indicates a minimum value and "max" indicates a maximum value.

The single piece wheel rim 1 may be manufactured from steel or an aluminium alloy. The steel may be a hot rolled steel, such as a hot rolled coil steel; or a cold rolled steel, such as a cold rolled coil steel.

The manufacturing of the single piece wheel rim 1 by press-forming will be described with the aid of figures 7 and 8. The radii of curvature Ri to R7 are formed during the manufacturing process as will be apparent.

The outer rim portion 12 is a press-formed annulus made in a press tool using a series of six press operations 121, 122, 123, 124, 125, 126 (see figure 7) on the outer rim blank 120.

Similarly, the inner rim portion 10 is a press-formed annulus made in a press tool using a series of five press operations 111, 112, 113, 114, 115 (see figure 8) on the inner rim blank 110.

The outer rim portion 12 additionally includes valve hole 68.

The disc blank 81 is an annulus, which undergoes a single press operation 82 to create a disc 14 with a diameter of preferably 440mm at its outside edge 88. The disc 14 includes 10 equally circumferentially-spaced wheel hub holes 83 for attachment to the axle of a vehicle (see figure 1). In alternative configurations alternative number of hub holes 83 may be provided.

The press formed parts are assembled to form the wheel sub-assembly 100 as follows: The inner rim portion 10 and outer rim portion 12 both include a machined detail, which interlock when the inner rim portion 10 and outer rim portion 12 are circumferentially joined, forming a wheel rim base. A circumferential weld is applied at this interface. The wheel rim base defines a wheel well with preferably a width of 280mm and a depth of 200mm for locating the pneumatic tyre (not shown).

The inside diameter of the wheel rim base is machined on the outer rim portion side of the wheel rim base. The outside edge 88 of the press formed disc is machined. The disc 14 and wheel rim base are fitted together at these machined surfaces and a circumferential weld 89 is applied at this interface.

The disc blank 81 is an annulus, which undergoes a single press operation 82 to create a disc 14 with a diameter of 440mm at its outside edge 88. The disc 14 includes 10 equally circumferentially-spaced wheel hub holes 83 for attachment to the axle of a vehicle (not shown).

The press formed parts are assembled to form the wheel sub-assembly 100 as follows: The inner rim portion 10 and outer rim portion 12 both include a machined detail 49, 69 respectively, which interlock when the inner rim portion 10 and outer rim portion 12 are circumferentially joined, forming a wheel rim base. The machined details 49, 69 are shown in figure 2. A circumferential weld 69a is applied at this interface. The wheel rim base defines a wheel well with a width of 280mm and a depth of 200mm for locating the pneumatic tyre (not shown).

Subsequent finishing operations can thereafter be undertaken.

The manufacturing of the single piece wheel rim 1 by machining will now be described.

A single piece wheel rim 1 may be manufactured by machining the rim 1 from a billet to form at least part of the finalised wheel structure. The inner and outer rim portions 10, 12 may be manufactured from a billet as a single unitary component or they may be machined separately in separate operations and the two parts 10, 12 may be joined together, for example, by welding.

The disc 14 may at the same time be machined from the billet to produce a unitary wheel. Alternatively, the disc 14 may be manufactured separately and welded to the machined rim 1.

Subsequent finishing operations can thereafter be undertaken.

FEATURE REFERENCES Centre of Curvature C2 Centre of Curvature C3 Centre of Curvature Ca Centre of Curvature C5 Centre of Curvature Distance Distance Radius of Curvature R2 Radius of Curvature R3 Radius of Curvature R4 Radius of Curvature R5 Radius of Curvature 1 Wheel Rim 2 Tyre Mounting Side 4 Inner Side Axially inner rim portion 12 Axially outer rim portion 14 Disc 16 Drop centre 20 Axially Outer Ridge 21 Axially Outer Wall 22 Flange 23 Axially Inner Wall 24 Axially Inner Ridge 26 Flange Region 32 Region 34 Region 36 Region 40 Outer Elbow Region 42 Inner Elbow Region 49 Machined Detail 68 Valve Hole 69 Machined Detail 69a Weld 81 Disc Blank 83 Hub Hole 88 Outside Edge 89 Weld 100 Wheel / Wheel Rim Assembly 102 Tyre 104 Tyre Tread 106a Tyre Seat 106b Tyre Seat 110 Inner Rim Blank 112 Press Forming Step 113 Press Forming Step 114 Press Forming Step Press Forming Step Outer Rim Blank 121 Press Forming Step 123 Press Forming Step 124 Press Forming Step Press Forming Step 126 Press Forming Step 126 Press Forming Step

Claims

Claims 1. A single piece wheel rim (1) comprising: an axially inner rim portion (10) and an axially outer rim portion (12); the axially inner rim portion (10) and an axially outer rim portion (12) together defining a drop centre (16); the drop centre (16) comprising: - a first region (30) with a first radius of curvature (Ri); - a second region (32, 34) with a second radius of curvature (R2); and wherein a ratio between the first radius of curvature (R1) and the second radius of curvature (R2) is greater than or equal to 3 to 2.
2. A single piece wheel rim (1) comprising: an axially inner rim portion (10) and an axially outer rim portion (12); the axially inner rim portion (10) and an axially outer rim portion (12) together defining a drop centre (16); the drop centre (16) comprising: - a first region (30) with a first radius of curvature (Ri) equal to or greater than 35 mm; -a second region (32, 34) with a second radius of curvature (R2) equal to or greater than 15 mm; and wherein the first radius of curvature (R1) is greater than the second radius of curvature (R2).
3. The single piece wheel rim of claim 2, wherein a ratio between the first radius of curvature (R1) and second radius of curvature (R2) is greater than or equal to 3 to 2.
4. The single piece wheel rim (1) of any preceding claim, wherein the ratio is between 3 to 2 and 4 to 1, preferably wherein the ratio is 7 to 3.
5. The single piece wheel rim (1) of any preceding claim, wherein the drop centre (16) comprises a third region (34) with a third radius of curvature (R3).
6. The single piece wheel rim (1) of claim 5, wherein the second radius of curvature (R2) and third radius of curvature (R3) are equal.
7. The single piece wheel rim (1) of any preceding claim, wherein the rim (1) further comprises at least one elbow region (40, 42) connected to the drop centre (16) with a fourth radius of curvature (R4) wherein the fourth radius of curvature (R4) differs from the first radius of curvature (R1) and the second radius of curvature (R2).
8. The single piece wheel rim (1) of claim 7 wherein the ratio of first radius of curvature (R1) to second radius of curvature (R2) to fourth radius of curvature (R4) is 7 to 3 to 4.
9. The single piece wheel rim (1) of any preceding claim, wherein the first radius of curvature (R1) is a minimum of 15 mm to 55 mm; and preferably the first radius of curvature is 35 mm.
10. The single piece wheel rim (1) of any preceding claim, wherein a distance (L) between a centre of curvature (Ci) of the first radius of curvature (Ri) and a centre of curvature (C2) of the second radius of curvature (R2) is a minimum of 15 mm to 55 mm; and preferably the distance (L) is a minimum of 35 mm.
11. The single piece wheel rim (1) of any preceding claim, wherein the first region (30) is part of the axially outer rim portion (12).
12. The single piece wheel rim (1) of any preceding claim, wherein the second region (32, 34) is part of the axially inner rim portion (10).
13. The single piece wheel rim (1) of any preceding claim wherein the rim (1) comprises: a steel alloy; or an aluminium alloy.
14. The single piece wheel rim (1) of any preceding claim, wherein the rim (1) is unitary and manufactured as a single component; or wherein the rim (1) is manufactured in at least two parts which are welded together to form the rim (1).
15. The single piece wheel rim (1) according to any preceding claim, wherein the rim (1) further comprises a wall (21) and wherein the first radius of curvature RI is a distance (0) from the wall (21); and wherein the distance (0) is less than or equal to 105 mm.
16. The single piece wheel rim (1) according to any preceding claim, wherein the single piece wheel rim (1) is suitable for a heavy vehicle and/or a very large vehicle; and/or wherein the rim (1) has a width of 280 mm.
17. A wheel (100) comprising a single piece wheel rim (1) according to any preceding claim and a disc (14) connected to the single piece wheel rim (1).
18. The wheel (100) according to claim 17, wherein the wheel is able to withstand 1,000,000 to 3,000,000 cycles when benchmarked using a radial fatigue test carried out under EUWA ES-3.12 standard.
19. The wheel (100) according to claim 17 and/or 18, wherein the wheel is able to withstand 200,000 to 300,000 cycles when benchmarked using a cornering fatigue test carried out under EUWA ES-3.12 standard.
20. A heavy vehicle according comprising at least one wheel (100) according to any of claims 17 to 19; preferably wherein the heavy vehicle is a very large vehicle; and more preferably wherein the very large vehicle is a mobile crane.
21. A method of manufacturing a single piece wheel rim (1) comprising the steps of: providing a first cylindrical blank component, a second cylindrical blank component and an annular disc blank; press forming the first blank component to form a one piece, axially outer rim portion (12); press forming the second blank component to form a one piece, axially inner rim portion (10); circumferentially joining the outer and inner rim portions (12, 10) to form an single piece wheel rim (1) having a base; wherein either: the axially inner rim portion (10) has a first region (30) with a first radius of curvature (Ri) and the axially outer rim portion (12) has a second region (32, 34) with a second radius of curvature (R2); or - the axially outer rim portion (12) has a first region (30) with a first radius of curvature (R1) and the axially inner rim portion (10) has a second region (32, 34) with a second radius of curvature (R2); and wherein: - a ratio between the first radius of curvature (R1) and second radius of curvature (R2) is greater than or equal to 3 to 2; and/or -the first radius of curvature (R1) equal to or greater than 35 mm and the second radius of curvature (R2) equal to or greater than 15 mm.
22. A method of manufacturing a wheel (100) comprising the method of manufacturing a single piece wheel rim (1) of claim 21 and comprising the further steps of: machining the inside diameter of the wheel rim base; - press forming the disc blank (81) to form a press-formed disc (14); - machining the outside edge (88) of the press-formed disc (14); press fitting the press-formed disc (14) to the wheel rim base at the machined inside diameter; and welding the press-formed disc (14) to the wheel rim base at the machined inside diameter.
23. A method of manufacturing a wheel (100) comprising the steps of: machining a billet to form a single piece wheel rim (1) comprising: - an axially inner rim portion (10) and an axially outer rim portion (12); the axially inner rim portion (10) and an axially outer rim portion (12) together defining a drop centre (16); the drop centre (16) comprising: o a first region (30) with a first radius of curvature (Hi); o a second region (32, 34) with a second radius of curvature (R2); and and wherein: -a ratio between the first radius of curvature (R1) and second radius of curvature (R2) is greater than or equal to 3 to 2; and/or - the first radius of curvature (R1) equal to or greater than 35 mm and the second radius of curvature (R2) equal to or greater than 15 mm.
24. The method of claim 23, wherein the method further comprises the step of machining a disc (14) from the same billet or a different billet.
25. The method of claim 23 or 24 wherein the wheel (100) is machined from the billet as a unitary component.