GB2043496A - Improvements in or relating to vehicle wheels, wheel discs and method of manufacturing them - Google Patents

Abstract

Wheel discs and method of manufacturing them are disclosed in which disc blanks are punched from a continuous length of strip material in an echelon nested pattern so as to reduce stock scrap and wastage. The disc blanks are substantially flat and have a peripheral edge defined by a series of concentric convex crowns separated from each other by concave or straight edge recesses. The disc blanks are each formed to a final cross sectional configuration which optimizes the relationships of disc strength to weight. The disc is welded into a drop well wheel rim to provide a vehicle wheel for pneumatic tubeless tyres. <IMAGE>

Description

SPECIFICATION Improvements in or relating to vehicle wheels, wheel discs and method of manufacturing them The present invention relates to vehicle wheels, and more particularly to wheel discs and method of manufacturing them.

According to one feature of the present invention there is provided a method of forming wheel discs which comprises the steps of simultaneously punching an echelon pattern of a plurality of disc blanks from a continuous length of strip stock with the echelon pattern pointing lengthwise of the strip stock and with each of the disc blanks having an outline defined by an alternating series of convex and concave or straight edge portions having opposed nested side edges in the echelon pattern.

Preferably each of the disc outlines comprises three convex edge portions interconnected by three concave edge portions in a uniform perimetric array, and the convex edge portions of one disc outline are nested within concave portions of adjacent disc outlines, with the outer edges of the three convex edge portions lying on a circle, and the disc blanks are arranged in groups of three and three blanks are punched out simultaneously.

According to another feature of the present invention a disc blank for use in forming a disc for a vehicle wheel comprises a substantially flat section of sheet metal structure having a peripheral outline defined by alternating equally spaced convex and concave or straight edge portions in a continuous edge pattern, each of said convex portions being adapted to engage a wheel rim.

According to a further feature of the present invention a wheel disc comprises a central portion including an array of bolt holes for clamping the wheel disc snugly against an internal wheel supporting structure, a first conical portion extending angularly outwardly of said central portion to an outwardly convex hat portion having a radius of curvature in the range of 11.938 to 1 3.462 units, and a second conical portion extending angularly inwardly from said hat portion and coupled thereto by a first blend portion having a radius of curvature in the range of 8.895 to 10.416 units.

Preferably a wheel disc is combined with a wheel rim having a drop well, with the disc being welded to the base of the drop well around the outer portion of the disc to form a vehicle wheel for pneumatic tubeless tyres.

A wheel disc embodying the present invention can be more economical to manufacture than, and yet retain the strength and durability of wheel discs of the prior art. Consequently a vehicle wheel disc embodying the present invention can possess an enhanced strength/weight ratio, and thus utilize less stock material than do prior art wheel discs of comparable strength.

Moreover a wheel disc embodying the present invention can achieve a more uniform stress distribution throughout the disc material.

A method of manufacturing wheel discs embodying the present invention can reduce scrap or wastage of stock material, and therefore be more economical than comparable methods of the prior art.

The invention will be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a block diagram of a method for manufacturing wheels and wheel discs in accordance with one embodiment of the invention, Figure 2 is a fragmentary perspective view drawn to scale of a continuous sheet of strip stock illustrating the disc blanking patterns thereon, Figure 3 is a fragmentary perspective view of the stock material illustrating the step of punching disc blanks from strip stock material in accordance with one embodiment of the invention, Figures 4 to 7 are elevational views bisecting a wheel disc blank and illustrating successive stages of formation of the disc contour in accordance with one embodiment of the invention, Fig. 4 being taken along the line 4-4 in Fig. 3 and Fig. 7 being taken along the line 7-7 in Fig. 8, Figure 8 is a front elevational view of a completed disc in accordance with one preferred embodiment of the invention, Figures 9 and 10 are respective fragmentary bisectional and front elevational views of a completed vehicle wheel in accordance with one preferred embodiment of the invention, Figure 11 is a graph drawn to scale and illustrating the optimized disc contour in accordance with one preferred embodiment of the present invention, Figures 12 and 13 are respective fragmentary bisectional and front elevational views of a completed wheel disc in accordance with another embodiment of the invention, and Figures 14A to 14H illustrate various disc contours which have been analyzed in developing the invention, the contour of Fig. 1 4A being preferred.

Referring to Figs. 1 to 4, in accordance with a preferred embodiment of the present invention a plurality of disc blanks 21 are punched from a continuous length of strip stock material 20 in a fully automated punching operation and in a blanking pattern which minimizes stock scrap and wastage. Individual disc blanks 21 in accordance with one preferred embodiment of the invention are best illustrated in Figs. 2 and 4 as each comprising a nominally flat section of sheet steel having an outline or perimeter 24 (Fig. 2) defined by a circular array of equally spaced crown or convex edge portions 26 separated from each other by recessed or concave edge portions 28. The outer edges of convex edge portions 26 for each blank 21 lie substantially on a circle 30 (Fig. 2) having a diameter D centered on the disc blank.Concave edge portions 28 are essentially curvilinear secants to the circle 30 having a radius of curvature R1 centered in the next-adjacent blank 21. Concave portions 28 are blended into crowns 26 by transitional edge portions 31 having a radius of curvature R2. Thus, the edge 24 of each blank 21 is essentially a symmetrical six-sided series of equally spaced alternating crowns 26 and recesses 28. In one embodiment of the invention for a fourteen inch wheel, diameter D is equal to 14.56 inches, radius R1 is equal to nineteen inches and radius R2 is equal to three inches.

Radius R1 is centered 24.97 inches from the center of the associated blank 21 on a line which passes through the centers of the blank and of the next-adjacent blank. Fig. 2 is scaled substantially to these exemplary dimensions.

Disc blanks 21 are punched from strip stock 20 in successive symmetrical echelon or Vshaped patterns 32 of three blanks 21 each, as best illustrated in Figs. 2 and 3, stock 20 being advanced step-wise between blanking of successive patterns and held stationary while blanks 21 are punched therefrom. Referring to Fig. 2, disc blanks 21 are laid out in each echelon 32 with a crown 26 of the center disc blank C directed forwardly with reference to the direction of stock travel indicated at 33. The other crown portions of the central disc blank C are nested within opposing side concave portions 28 of the left and right disc blanks L and R immediately to either side of the central blank C within the same echelon 32.The forwardly directed crown 26 of center blank C in the succeeding echelon 32a is nested within a rearwardly opening concave portion 28 of the center blank C in the preceding echelon 32, and the forward side concave edge portions 28 of the center blank C in echelon 32a receive the opposed rearward convex edge portions 26 in the side blanks L and R of the preceding echelon 32. The opposing edges of the respective disc blanks 21 (C, L and R) are separated from each other in the same and adjacent echelons by a relatively narrow margin of stock material to accommodate fracture or break-out resulting from the punching operation. Stock width is selected to be slightly greater than the width of the echelonned disc blank patterns 33 so as to provide a slight margin at the strip edges.It will be appreciated that the nested disc blank patterns illustrated in Figs. 2 and 3, which is to say both the edge pattern 24 of the individual discs 21 per se and the echelonned nested arrangement thereof on the strip stock material 20, provides efficient utilization of stock material with little scrap or wastage.

The individual disc blanks are next formed in a drawing operation to the centrally crowned or cupped configuration illustrated at 40 in Fig. 5, and a central hole 42 is pierced in the disc blank simultaneously with the drawing operation. The crowned disc center and the disc margin or edge are then formed in a series of bending and stretching operations to the final desired disc cross sectional configuration (Fig. 6), such as by using conventional stamping press techniques.

More specifically, an axially extending flange 44 is formed downwardly in Fig. 6 or outwardly (with reference to the orientation of the wheel assembly to a wheel hub 70 in Fig. 11) around the perimeter of center disc hole 42 to pilot the disc onto the wheel hub. A circular array of depressions or pockets 46 is simultaneously formed around center hole 42 concentrically therewith for later formation of the wheel mounting bolt holes. Coaxial segmented circular shoulders 71 and 72 separate pockets 46 from each other. The disc perimeter or edge is turned upwardly or inwardly so as to form a perimetrically continuous flange 50 around the disc edge, flange 50 undulating along the outer edges of both disc edge crowns 26 and recesses 28 (as best seen in Fig. 8).The flange segments 51 extending axially of each disc edge crown 26 are cocylindrical and coaxial with the disc axis at the center of hub hole 42. An outwardly or downwardly crowned hat portion 48 is formed intermediate the disc flange 50 and depressions 46. The contour of the intermediate disc portion, including crowned portion 48, will be discussed in greater detail hereinafter in connection with Fig. 11.

The partially formed disc shown in Fig. 6 is then further worked to the final configuration in Figs. 7 and 8. In the next method step, disc formation is completed by piercing the bolt mounting holes 52 in the bases of respective depressions 46 concentrically with center hole 42, and then beveling the perimeter 54 of each bolt hole 53 in a coining operation both to remove break-out resulting from the piercing operation and to facilitate eventual centering of the disc and rim on a vehicle. The completed disc 59 (Figs. 7 and 8) may then be assembled to drop well wheel rim 60 (Figs. 9 and 10) for pneumatic tubeless tires by welding cocylindrical flange portions 51 to the inside surface 65 of rim drop well 64. The flanged edges of disc peripheral recesses 28 form inwardly bowed or concave secants or chords to the cylinder of revolution defined by the opposing inner surface 65, thereby defining three equally spaced chain slots or vent openings intermediate the convex disc portions so as to lend a three-spoked appearance to the wheel assembly.

Fig. 11 is a graphic illustration of an important aspect of the present invention by means of which the intermediate portion of the disc between the circle of mounting holes 52 and the rimengaging flange portions 51 (shown in Fig. 7 but omitted from Fig. 11) is tailored or contoured so as to optimize the strength-to-weight characteristic of the disc. When a disc is mounted to a vehicle hub 70 or the like by means extending through bolt holes 52, the central portion of the disc is clamped snugly against the opposing hub surface such that the disc portion around the bolt holes absorbs or "sees" only clamping stresses. In the particular presently preferred disc configuration, the bolt holes 52 are offset from the opposing hub surface, and the disc is in essentially circular line contact with the hub surface along shoulders 71, 72.The outer or flanged portion of the disc is welded or otherwise rigidly attached to the wheel rim 60. Thus, it is the intermediate portion of the disc between rim flange 50 and the point or line of contact between shoulder 72 and hub 70 which absorbs or "sees" dynamic loading stresses, and is the portion to which Fig. 11 is directed.

Specifically, Fig. 11 is drawn to scale and illustrates the contour of the cross sectional or thickness centerline of the disc intermediate portion between shoulder 72, which is taken as the origin in Fig. 11, and rim flange 50. In Fig. 11, the line 80 represents the preferred nominal centerline of the disc intermediate portion in the upright orientation of Fig. 9, while the lines 82, 84 respectively illustrate the outer and inner tolerance limits of the disc contour centerline of the disc intermediate portion in accordance with a preferred embodiment of the invention.The lines 80, 82 and 84 have been plotted to scale in inch units from the points listed in the following table: Table I (all measurements in mm) Y x-min (84) x-nominal (80) x-max (82) 0.0000 -3.175 0.0000 3.1750 3.1852 -2.2667 0.9093 4.0843 6.3551 0.2845 3.4595 6.6345 9.5250 -0.2489 6.1011 12.4511 12.7000 2.4689 8.8189 15.1688 15.8750 5.1054 11.4554 17.8054 19.0500 7.8029 14.1529 20.5029 22.2250 10.4191 16.7691 23.1191 25.4000 13.1420 19.4920 25.8420 28.5750 15.7683 22.1183 28.4683 31.7500 18.4455 24.7955 31.1455 34.9250 20.5283 26.8783 33.2283 38.1000* 21.7424 28.0924* 34.4424 41.2750 21.5900 27.9400 34.2900 43.1800 20.6908 27.0408 33.3908 47.6250 18.4455 24.7955 31.1455 50.8000 12.5019 18.8519 25.2019 53.9750 8.1432 14.4932 20.8432 57.1500 5.8115 12.1615 18.5115 60.3250 4.5466 10.8966 17.2466 63.5000 3.3020 9.6520 16.0020 66.6750 2.0269 8.3769 14.7269 69.8500 0.9601 7.3101 13.6601 73.0250 -0.3454 6.0046 12.3546 76.2000 -1.5392 4.8108 11.1608 79.3750 - 3.5154 2.8346 9.1846 80.6399* -7.5946 7 5946 1.2446* 5.1054 The peak of hat portion 48, and the junction with disc flange 50 are shown at 110, 112 respectively in Fig. 11 and are denoted with an asterisk (*) in Table I.

The known prior art closest to the presently preferred disc contour illustrated graphically in Fig. 11 and to scale in Figs. 7 and 9 is that disclosed in United States Patent Specification No.

3,135,559 and is illustrated at 100 in Fig. 11.

The disc intermediate portion, which has been hereinabove defined as that portion between hub-contacting shoulder 72 and rim flange 50, may best be verbally described in greater detail with reference to Figs. 7 and 9. Starting from shoulder 72, the contour of the disc intermediate portion includes a first conical portion 92 extending axially and radially outwardly (of hub 70) having an angle with respect to the disc axis in the range of 45 to 55t. Conical portion 92 terminates in previously-described hat portion 48 which, in the preferred embodiment shown to scale in the drawings, has a radius of curvature in the range of 11.938 to 1 3.462 mm. This radius is centered at x = 19.050 mm and y = 39.624 mm.A second conical portion 94 extends inwardly (again with reference to mounting hub 70) at an angle in the range of 65 to 75 , and is coupled to hat portion 48 by the arcuate blending portion 96. Portion 96 has a radius of curvature in the range of 8.895 to 10.416 mm and is centered at x= 24.638 mm, y= 61.267 mm. Conical portion 94 is coupled to flange 50 by the disc flange radius 98 in the preferred range of 7.112 to 8.636 mm. The flange radius is centered at x = 0.4 mm, y = 74.079 mm. It will be noted with particular reference to Fig. 11 and Table I that the upper edge of the intermediate disc portion adjoining flange 50 is preferably substantially coplanar with the circular line of contact between shoulder 72 and hub 70-i.e. at x = 0.

Various disc thickness centerline contours were analyzed by finite stress analysis techniques on an appropriately programmed digital computer during development of the preferred embodiment hereinabove described. A number of such contours are illustrated in Figs. 1 4A to 1 4H, that at 14A being the same as that shown at 80 in Fig. 11 and herein preferred. Among the various parameters which distinguish the embodiments of Figs. 1 4A to 14H, the order of importance in yielding superior results as to Fig. 1 4A is believed to be as follows: the radius of curvature of hat portion 48, the center point of such radius, the angles of intermediate conical portions 92 and 94, and the location and curvature of flange radius 26.

Figs. 12 and 13 illustrate a four-spoke disc 101 comprising a series of four flanged outer disc crowns '1 02 separated from each other by the substantially flat flanged secants 104. Upon applying finite stress analysis to the four-spoke disc, it was found somewhat surprisingly that the optimum contour for the four-spoke design is substantially identical to that for the three-spoke disc illustrated graphically in Fig. 11 and discussed previously. Accordingly, disc portions Figs.

12 and 13 are identical by reference numerals identical to those previously discussed.

It will be appreciated that the invention has been described using directional adjectives such as "outer" and "inner" with reference to the contemplated axial orientation of the wheel as assembled to a vehicle. These and other directional adjectives will be understood to constitute words of description and not limitation when utilized in the appended claims. Similarly, a preferred embodiment of the invention for use on a fourteen inch wheel has been described in detail. However, the dimensions and coordinates, etc., may be readily scaled for other wheel sizes without departing from the scope of the invention in its broadest aspects.

Claims (38)

1. A method of forming wheel discs which comprises the steps of simultaneously punching an echelon pattern of a plurality of disc blanks from a continuous length of strip with the echelon pattern pointing lengthwise of the strip stock and with each of the disc blanks having an outline defined by an alternating series of convex and concave or straight edge portions having opposed nested side edges in the echelon pattern.

2. A method as claimed in claim 1, in which each of said disc outlines comprises three convex edge portions interconnected by three concave edge portions in a uniform perimetric array, and in which convex edge portions of one disc outline are nested within concave portions of adjacent disc outlines.

3. A method as claimed in claim 2, in which the outer edges of said three convex edge portions lie substantially on a circle.

4. A method as claimed in claim 1, 2 or 3, in which the disc blanks are in groups of three and three blanks are punched out simultaneously.

5. A method as claimed in claim 1, in which each disc outline comprises four convex edge portions interconnected by four straight or concave edge portions in a uniform perimetric array.

6. A method as claimed in claim 5, in which four disc blanks are punched out simultaneously.

7. A method as claimed in claim 2, 3 or 4, in which the convex edge portions of each disc edge outline are nested within concave edge portions of each adjacent disc edge outline both in the same echelon and in the immediately preceding and subsequent echelons, whereby to reduce wastage of stock material defined by interstices between disc blanks.

8. A method as claimed in claim 2, 3, 4 or 7, including the step of advancing said strip stock stepwise in the direction of its length and successively punching at each incrementali step of the stock an echelon pattern of three disc blanks, the strip stock having a predetermined width, and the echelon pattern pointing lengthwise of the strip stock and extending across said width.

9. A method as claimed in claim 1, 2, 3, 4, or 7, in which said echelon patterns and said disc blanks are substantially as illustrated to scale in Fig. 2 of the accompanying drawings.

10. A method as claimed in any of claims 1 to 9, including the additional step of bending each of said convex edge portions of a disc blank to form a plurality of co-cylindrical flanges for attaching a disc to a wheel rim.

11. A disc blank for use in forming a vehicle wheel disc manufactured by the method as claimed in any of claims 1 to 9.

12. A disc blank for use in forming a disc for a vehicle wheel, comprising a substantially flat section of sheet metal structure having a peripheral outline defined by alternating equal spaced convex and concave or straight edge portions in a continuous edge pattern, each of said convex portions being adapted to engage a wheel rim.

13. A disc blank as claimed in claim 12, in which said convex edge portions lie substantially on a circle.

14. A disc blank as claimed in claim 12 or 13, in which said peripheral outline is substantially as shown in scale in Fig. 2 of the accompanying drawings.

15. A wheel disc manufactured from a wheel disc blank as claimed in claim 11, 12, 13 or 14, by the additional step of bending each of the convex edge portions of a blank to form a plurality of cocylindrical flanges for attaching the disc to a wheel rim.

16. A wheel disc as claimed in claim 15, comprising a central portion including an array of bolt holes for clamping the wheel disc snugly against an internal wheel supporting structure, a first conical portion extending angularly outwardly of said central portion to an outwardly convex hat portion having a radius of curvature in the range of 11.938 to 1 3.462 units, and a second conical portion extending angularly inwardly from said hat portion and coupled thereto by a first blend portion having a radius of curvature in the range of 8.895 to 10.416 units.

17. A wheel disc comprising a central portion including an array of bolt holes for clamping the wheel disc snugly against an internal wheel supporting structure, a first conical portion extending angularly outwardly of said central portion to an outwardly convex hat portion having a radius of curvature in the range of 11.938 to 1 3.462 units, and a second conical portion extending angularly inwardly from said hat portion and coupled thereto by a first blend portion having a radius of curvature in the range of 8.895 to 10.416 units.

18. A wheel disc as claimed in claim 16 or 17, further comprising an outer portion coupled to said second conical portion by a second blend portion having a radius of curvature in the range of 7.112 to 8.636 units.

19. A wheel disc as claimed in claim 18 adapted to be snugly clamped in contact with wheel supporting structure on a plane perpendicular to the disc axis, and in which the center of said radius of curvature of said blend portion lies substantially in said plane.

20. A wheel disc as claimed in claim 16, 17, 18 or 19 in which said first conical portion is at an angle with respect to the disc axis in the range of 45 to 55 and in which said second conical portion is at an angle with respect to the disc axis in the range of 65t to 75 .

21. A wheel disc as claimed in claim 17, 18 or 19, or in claims 18 and 20, in wich said radius of curvature of said second blend portion is centered on a point substantially defined by the scaled relation 0.4/74.079, wherein x is measured in said units axially outwardly of said disc from the nominal point of contact between said disc and the wheel supporting structure and y is measured in said units radially of said disc from said nominal point of contact.

22. A wheel disc as claimed in any of claims 16 to 21, in which said radius of curvature of said hat portion is centered on a point defined substantially by the scaled x-y relation 19.050/30.624 and said radius of curvature of said first blend portion is centered on a point substantially defined by the scaled x-y relation 24.638/61.267, wherein x is measured in said units axially outwardly of said disc from the nominal point of contact between said disc and the wheel supporting structure and y is measured in said units radially of said disc from said nominal point of contact.

23. A wheel disc as claimed in claim 22, in which said units are millimeters.

24. A wheel disc as claimed in any of claims 18 to 23, in which the intermediate portion coupling said central portion to said outer portion has a cross-sectional centerline falling within the range illustrated by the lines 82 and 84 drawn to scale in Fig. 11 of the accompanying drawings.

25. A wheel disc as claimed in claim 24, in which said cross-sectional centerline is defined substantially by the line 80 drawn to scale in Fig. 11 of the accompanying drawings.

26. A wheel disc as claimed in any of claims 18 to 23, in which the intermediate portion coupling said central portion to said outer portion has a cross-sectional centerline defined to scale by points within the range of x-min. to x-max. in Table I of the description, wherein x is measured axially outwardly of said disc from the nominal point of contact between said central portion and said wheel supporting structure and y is measured radially of said point of contact.

27. A wheel disc as claimed in claim 26, in which said centerline is defined by the points xnominal in said Table I.

28. A wheel disc as claimed in any of claims 18 to 23, in which the intermediate portion extending between said central and outer portions has a cross-sectional centerline which includes a point at the peak of said hat portion defined by a first scaled x-y relation in the range of 0.856/1.5 to 1.356/1.5, and also includes a point at said outer portion defined by a second scaled x-yrelation in the range of 0.299/3.1748 to 0.201/3.1748, wherein xis measured axially outwardly of said disc from the nominal point of contact between said central portion and said wheel supporting structure and y is measured radially of said disc from said nominal point of contact.

29. A wheel disc as claimed in claim 28, in which said first scaled relation is substantially 1.106/1.5 and said second scaled relation is substantially - 0.049/3.1748.

30. A wheel disc as claimed in any of claims 15 to 29, in combination with a wheel rim having a drop well around the outer portion of the disc to form a vehicle wheel for pneumatic tubeless tyres.

31. A wheel disc as claimed in claim 30, in which said outer portion includes three circumferentially discontinuous co-cylindrical flange portions welded to said drop well and separated from each other by integral flanged secant portions spaced radially inwardly from said rim.

32. A wheel disc as claimed in claim 30, in which said outer portion includes four circumferentially discontinuous co-cylindrical flange portions welded to said drop well and separated from each other by integrally flanged secant portions spaced from said rim.

33. Methods of forming wheel discs, substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 1 to 9 and 11 of the accompanying drawings.

34. Methods of forming wheel discs, substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 11, 12 and 13 of the accompanying drawings.

35. A wheel disc blank substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 2, 3 and 4 of the accompanying drawings.

36. A wheel disc, constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 7, 8 and 11 of the accompanying drawings.

37. A wheel disc, constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 11, 12 and 13 of the accompanying drawings.

38. A wheel disc, as claimed in claim 36 or 37, in combination with a drop well wheel rim to form a vehicle wheel, constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 9 and 10 of the accompanying drawings.