Manufacture Of Articles

Abstract

The specification discloses a method of making a road wheel for a vehicle in which the material of the wheel has anisotropic properties. The wheel comprises a central portion, a peripheral or rim portion and a plurality of separate radial portions between the central portion and the rim portion. The specification describes how anisotropic properties can be obtained in the radial portions and the peripheral portion by causing the material to flow radially along the radial portions and peripherally around the peripheral portion during the formation of the wheel. This formation is effected by placing a billet of flowable material in a cavity and then moving selected elements of the cavity to produce the desired flow of the material. The wheel can be made of a thermoplastic, synthetic polymeric material with or without fibre reinforcement, a thermosetting, synthetic polymeric material with fibre reinforcement or a metal with or without fibre reinforcement.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the manufacture of articles, particularly wheels, having a central portion, a peripheral portion and a plurality of separate radial portions radiating from the central portion to the peripheral portion and interconnecting the central and peripheral portions.

The invention finds particular utility in the manufacture of road wheels for motor vehicles although it is also applicable to the manufacture of articles other than road wheels which have continuous or discontinuous peripheral portions and radial portions radiating from a central portion to the peripheral portion.

2. Description of the Prior Art

Heretofore, road wheels have been made from metal and conventional wheels have been made from steel having a ring-like rim which is fixedly or detachably mounted on a disc. The lighter type road wheels usually comprise a one piece rim welded to a disc. Heavier wheels comprise multipart rims secured to discs. Cast road wheels of light alloy are also known. In metal wheels it has been unnecessary to develop any anisotropic mechanical properties in the metal since the normal isotropic properties are sufficiently good to withstand the stresses in use.

It has also been proposed to manufacture road wheels from fibre-reinforced, synthetic polymeric material by forming wheel halves by laying up on a mould pieces of glass fibre mat, impregnating these by hand with the polymeric material, allowing the latter to cure and then fixing the two halves together with, if required, a circumferential layer of resin-impregnated reinforcement.

There is a continual search for ways of making, from synthetic polymeric material, articles which have previously been made of metal. The method described above of forming wheel halves with hand laid and impregnated layers of glass fibre cloth is not susceptible to the mass production of wheels. Moreover. since the yield point and ultimate tensile strength of normal synthetic polymeric material are less than those of steel it is necessary to develop the best possible mechanical properties in the material to withstand the stresses that occur in use.

In a road wheel embodying the invention the radial portions act as spokes between the central portion which will be the hub and the peripheral portion which will be the rim. The spokes are subjected mainly to stress in radial directions and therefore it is desirable that the best mechanical properties of the material in the spokes are exhibited in radial directions. On the other hand, the rim will be subjected mainly to hoop stress and therefore it is desirable that the best mechanical properties of the material forming the rim are exhibited in peripheral directions. The invention has as its object to provide a method of and apparatus for forming an article having the above characteristics in which the mechanical properties of the material in the radial portions are improved in radial directions with respect to such properties in other directions and in which the mechanical properties of the material in the peripheral portion is improved in circumferential directions with respect to such properties in other directions.

SUMMARY OF THE INVENTION

According to one aspect of the invention we provide a method of making an article, e.g. a wheel, having a central portion, a peripheral portion and a plurality of separate radial portions radiating from the central portion to the peripheral portion by causing flow of flowable material within a cavity having central, radial and peripheral parts in which said central radial and peripheral portions are respectively formed, the method comprising displacing the material from the central parts of the cavity into the radial parts thereof and then reducing the volume of said radial parts to cause material therein to flow radially outwardly and into the peripheral part around which said material flows peripherally.

The result of this method is to produce an article formed of material having anisotropic properties in both radial portions and the peripheral portion such that the mechanical properties e.g. the yield point, are better in radial than other directions in the radial portions and are better in peripheral than other directions in the peripheral portion.

During the first phase of forming in which the material is displaced from the central part into the radial parts some material may flow into the peripheral part but this will be insufficient to fill the peripheral part which will only be filled when the reduction in size of the radial part takes place with consequent displacement of material from the radial parts into the peripheral part.

In a preferred way of carrying out the method, during the displacement of the material from the central part of the cavity into the radial parts the peripheral part is held at a larger volume than its final volume at which the peripheral portion is formed and the peripheral part is subsequently reduced in size to its final volume simultaneously with, or after, said reduction in size of the radial parts.

This reduction in size of the peripheral part will assist in the peripheral flow of the material in the peripheral part and thus the obtaining of the desired anisotropic properties in the peripheral portion. Preferably the reduction in size of the peripheral part takes place after the reduction in size of the radial parts has taken place or at least after the reduction in size of the radial parts has commenced thus establishing a flow of material into the peripheral part from the radial parts.

The material from which the article is made is preferably either thermoplastic synthetic polymeric material with or without fibre reinforcement or a thermosetting synthetic polymeric material with fibre reinforcement. The reinforcing fibres will be of any convenient material e.g. carbon or glass. The invention is also applicable to the manufacture of an article by causing metal to flow in the manner described above and the metal can be fibre reinforced, e.g. with tungsten or boron fibres.

When the material is a thermoplastic synthetic polymeric material, the polymer chains will be orientated by the flow of the material during manufacture of the article so that the chains extend radially in the radial portions and peripherally in the peripheral portions thus giving the desired anisotropic properties. Where the material, whatever it is, is reinforced with fibres then the fibres will be orientated generally radially in the radial portions and generally peripherally in the peripheral portions which further assists in obtaining the desired anisotropic properties. With the cross-linked thermosetting polymeric materials the anisotropic properties will be obtained by the orientation of the fibre reinforcement.

The material during its flow as the size of the radial parts is reduced will follow L-shaped paths. Thus during the second forming phase the material will be caused to flow radially outwardly along a radial part and then peripherally in the peripheral part. Where the article has a continuous peripheral portion, e.g. a wheel rim, the material may be caused to flow in generally T-shaped paths. Thus the material may be caused to flow radially outwardly along each radial part and then, when it reaches the peripheral part, caused to flow peripherally in opposite directions until the material initially fed along one radial part meets in the peripheral part, material initially fed radially outwardly along an adjacent radial part into the peripheral portion.

The areas of the article between the radial portions mentioned above may be formed by webs in which the material forming them has flowed biaxially. That is to say that as the material flows outwardly from the central part of the cavity it will expand both radially and peripherally and therefore the polymer chains, metal grains and/or reinforcing fibres as the case may be will be oriented substantially half in radial directions and substantially half in peripheral directions. Where such webs are provided the cavity will include intermediate parts each defined between two adjacent radial parts, the central part and the peripheral part. These intermediate parts will be brought to their final volume simultaneously with, or before, the first phase of the forming when the material is displaced from the central part into the radial parts, the material being simultaneously disposed into said intermediate parts.

In one way of carrying out the method the material is initially in the form of a slug which is deformed and caused to flow between moving parts which define the cavity and are moved to obtain the desired directions of flow of the material.

The slug may be formed in situ in the central part of the cavity by injection.

When the material being formed is a thermoplastic polymeric material or a metal, reduction in size of the mould cavity is arranged to occur at an appropriate time and speed to effect cold work on the material and thus improves the physical properties thereof.

According to another aspect of the invention we produce apparatus for forming from flowable material an article having a central portion, a peripheral portion and a plurality of separate radial portions radiating from the central portion, the apparatus comprising a plurality of relatively movable elements which define a cavity having a central part, radial parts and a peripheral part for forming the central, radial and peripheral portions respectively, the elements defining the radial parts being movable relative to other/of said elements whereby the radial parts of said cavity may be varied in size independently of other parts of the cavity.

The elements defining the peripheral part of the cavity are movable relative to other of said elements whereby the movable relative to other of said elements whereby the peripheral part of the cavity may be varied in size independently of other parts of the cavity.

The cavity includes intermediate parts, each such part being defined by two adjacnet radial parts and the central and peripheral parts and the elements defining the intermediate parts are movable relative to other of said elements whereby the intermediate parts of the cavity may be varied in size independently of other parts of the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail by way of example with reference to the accompanying diagrammatic drawings in which:

FIG. 1 is a section through a cavity showing a billet of material about to be deformed by the method of the invention to produce a road wheel;

FIG. 2a is a section through the cavity showing the billet partly deformed and in a section containing one of said radial parts of the cavity;

FIG. 2b is a section through the cavity corresponding to FIG. 2a but in a section through one of said intermediate parts of said cavity;

FIG. 3 is a section similar to FIG. 2a showing the fianl position of the mould elements in a section containing a radial part;

FIG. 4 is a section through the apparatus with the elements in their open positions showing the finished wheel ready for ejection;

FIG. 5 is a section through the finished wheel on the line 5--5 of FIG. 6;

FIG. 6 is a plan of the wheel of FIG. 5;

FIG. 7 is a section through one of the radial portions of the wheel spokes on the line 7--7 of FIG. 6; and

FIGS. 8 and 9 are a diagrammatic section and plan respectively of another form of apparatus for forming a road wheel embodying the invention.

Referring first to FIGS. 5, 6 and 7, the wheel comprises a rim or peripheral portion 10 and eight spoke-like or radial portions 11. FIG. 7 shows that each spoke-like portion 11 is thicker in the axial direction of the wheel than the immediately surrounding or intermediate portions 12. These intermediate portions 12 form generally triangular webs between the adjacent radial portions 11 and are further defined by the rim portion 10 and a central or hub portion 13 from which the spoke portions 11 radiate to the rim portion 10.

Referring now to FIG. 1, this is a section through the apparatus used to produce the wheel of FIGS. 5 to 7. There are two annular outer elements 14 which form the outer surfaces 15 of the rim, see FIG. 5 and there is a split core element 16 which forms the inner surface 17 of the rim. The core element 16 is made in three or more parts to enable it to be withdrawn from the finished wheel. There is a telescopic shut off betwee the elements 14 and 16 constituted by mating surfaces 14a and 16a.

Within each element 14 is an assembly 18 of 16 elements, thus there are either elements corresponding to the spokes or radial portions 11 and eight elements corresponding to the swebs or intermediate portions 12. The elements corresponding to the spokes can be moved independently of the elements corresponding to the webs.

A slug 19 of deformable material is shown between the elements in FIG. 1. All the elements in the central assemblies 18 are moved together to cause the material of the slug 19 to flow outwardly from the central part 20 of the cavity into the radial parts 21, the intermediate parts 22 and the peripheral part 23. The amount of material in the peripheral part is insufficient to fill it and tis situation is shown in FIGS. 2a and 2b. In FIG. 2a the elements indicated at 24 correspond to the spoke portions 11. In FIG. 2b the elements 25 correspond to the web portions 12. In this first stage of forming the elements 24 are moved to their final positions as shown in FIG. 2b but the elements 24 and 14 are moved only part way to their final positions as shown in FIGS. 2a and 2b. The material of the slug 19 which is to form the webs 12 is therefore caused to flow outwardly into the cavity parts 22 and can expand peripherally due to the triangular shape of the cavity parts 22 so that the orientation of the polymer chains (if a thermoplastic polymer is used) or metal texture (ie the larger grain boundaries and inclusions) and the fibre reinforcement if used is biaxial in the webs 12. That is to say that if the material is a thermoplastic plymer approximately half of the chains are oriented radially and approximately half peripherally. Similarly, if the material is metal it will be substantially equally textured in radial and peripheral directions. Any fibre reinforcement will be oriented half radially and half peripherally. The small amount of material is indicated at 26 which has entered the peripheral cavity part 23 within which the rim is to be formed.

In FIGS. 2a and 2b it will be noted that the mould elements 14 and 24 are spaced apart by a greater distance than the thickness of the finished spoke portions 11 and rim portion 10 respectively but that the faces 14a and 16a are in engagement thus closing the cavity. The elements 24 are now closed together as shown in FIG. 3 and this causes the material in the spoke parts 21 of the cavity to move radially as indicated by the arrow 27 in FIG. 3 and the material enters the cavity part 23. The material in the cavity part 23 is caused to move peripherally around the part 23 both by being caused to enter the part 23 from the parts 21 and also by the movement of the elements 14 together to the positions shown in FIG. 3. The material which flows radially outwardly from a cavity part 21 flows peripherally around the cavity part 23 until it meets the material flowing from the adjacent cavity part 21. Suitable arrangements are made for venting the cavity parts. It will be seen, therefore, that the flow of material in the spoke cavity parts 21 is generally radial and the flow around the rim cavity part 23 is generally peripheral. This has the effect of producing anisotropic properties as described above with the corresponding advantages.

FIG. 4 shows the mould open with the core 16 withdrawn and the finished wheel about to be ejected by ejectors 28.

It will be seen from a consideration of FIG. 6 that the material flow is along a generally T-shaped path as indicated by the arrows 29 in that figure. Alternatively, it could be considered that the material follows a generally L-shaped path i.e. radially along the spoke cavity part and then peripherally around the rim cavity part.

FIGS. 8 and 9 show a second embodiment of apparatus for producing a wheel similar to that shown in FIGS. 5,6 and 7 except that there are triangular openings between the spoke portions 11 in place of the webs 12.

Referring to these figures, the apparatus comprises a lower die element 29 which is of generally circular shape in plan and which is formed, around its outer periphery, with an upstanding ring 30 which provides a die shut off face 31. Immediately within the ring 30 there is an annular die face 32 shaped to form the outer surface of the rim i.e. the surface corresponding to the surface 15 in FIG. 5.

The central part of the element 29 has upstanding therefrom eight generally sector shaped abutments 33 which correspond to the spaces between adjacent poke or radial portions of the wheel. Between the inner ends of the abutments 33 there is defined a central part 34 of the die cavity and fitting closely into this central part is a central element 35.

Formed between adjacent abutments 33 are radially cavity parts 36 in which the radial portions of the wheel are formed. Moveable in each of these radial parts 36 is a radial element 37.

There is a peripheral element 38 having a die face 39 which shapes the other outer surface of the rim and is similar to the die surface 32 and there are three core members 40 which form the inner surface of the rim in a manner similar to the core members 16 of the first embodiment. The peripheral element 38 provides a shut off face 41 and the shut off faces 31 and 41 co-operate with shut off faces 42 and 43 respectively on the core elements 40.

In operation, the core elements 40 are moved together to form a ring and the lower die element 29 is moved upwardly into the position shown in FIG. 8 so that the shut off faces 30 and 31 are in engagement. The elements 35, 37 and 38 are in their withdrawn positions and a billet of material is then placed in the central part 34 of the cavity. The elements 35, 37 and 38 are then moved downwardly, the elements 37, closing the radial parts 36 of the cavity and the element 38 closing the peripheral part 44 of the cavity but the elements 37 and 38 are not moved to their final positions. The element 35 is moved to its final position thus displacing material into the radial part 36 and some material into the peripheral part 44. The elements 37 are then moved to their final positions thus causing radial flow of the material along the radial parts 36 of the mould cavity and simultaneously with or subsequently with the movement of the die elements 37, the die element 38 is moved to its final position thus causing peripheral flow of the material around the die cavity 44.

The completed wheel is removed from the cavity by returning the parts to their open position and ejectors not shown, are used for disengaging the wheel from the elements.

The material which may be used for carrying out the method in either embodiment may be a synthetic polymeric material or a metal. In the former case, if the polymeric material is thermoplastic then the anisotropic properties desired are obtained both by orientation of the polymer chains and, if fibre reinforcement is present, orientation of the fibres of the reinforcement. Thus the chains and the reinforcement if provided will be oriented generally radially in the spoke or radial parts 11 of the finished wheel and the polymer chains and or fibre reinforcement if provided will be oriented peripherally in the rim part of the finished wheel. If the synthetic polymeric material is a thermosetting material then there will be no orientation of the polymer chains since of course cross linking occurs but with a termosetting polymeric material it will be reinforced with a fibre reinforcement and the orientation of the reinforcement will be radial in the spoke portions of the wheel and peripherally in the peripheral portions of the wheel.

If the material used for making the wheel is metal then the grain boundaries will be oriented as described and if fibre reinforcement is used then the reinforcing fibres will also be oriented in the required manner.

It is not necessary that the peripheral part of the cavity be variable in size except for the purpose of course of opening the cavity. Thus in a modification of the method, the peripheral part of the cavity may be brought to its final size with the first phase of the forming i.e. in the phase illustrated in FIGS. 2a and 2b. The overall flow of the material around the peripheral part of the cavity would, in such an arrangement, be obtained by the radial displacement of the material from the radial parts of the cavity into the peripheral part thereof.

Where the peripheral part of the cavity can be changed in size then this change in size can either be caused to occur simultaneously with the movement of the mould elements 24 to their final positions or subsequently to such movement. Preferably, the peripheral part of the cavity is brought to its final size at least after the commencement of the movement of the parts 24 to their final size so that such movement of the parts 24 establishes a flow of material into the peripheral part of the cavity before the latter is brought to its final size.

The invention has been described in relation to a road wheel having a continuous rim but obviously a similar method can be followed for a wheel or similarly shaped article having a discontinuous rim.

Claims

We claim:

1. A method of making an article having a central portion a peripheral portion and a plurality of separate radial portions radiating from the central portion to the peripheral portion by causing flow of flowable material within a cavity having central, radial and peripheral parts in which said central, radial and peripheral portions are respectively formed, the method comprising displacing material from the central part of the cavity into the radial parts thereof and then reducing the size of said radial parts to cause material therein to flow radially outwardly into the peripheral part around which the material flows peripherally.

2. A method according to claim 1 wherein, during the displacement of the material from the central part of the cavity into the radial parts thereof, the peripheral part of the cavity is held at a larger volume than its final volume at which the peripheral portion is formed and the peripheral part is subsequently reduced in size to its final volume, said reduction commencing no earlier than said reduction in size of the radial parts.

3. A method according to claim 2 wherein said reduction in size of the peripheral part of the cavity takes place after the reduction in size of the radial parts.

4. A method according to claim 1 wherein the material flows in T-shaped paths from the radial parts of the cavity into the peripheral part thereof.

5. A method according to claim 1 including the step of forming, between adjacent radial portions, webs by causing the material to flow biaxially into intermediate cavity parts between the radial cavity parts.

6. A method according to claim 5, wherein the cavity includes intermediate parts each defined between two adjacent radial parts, the central part and the peripheral part and wherein the method is carried out by bringing the intermediate parts to their final volumes no later than the displacement of the material from the central part into the radial parts, the material being simultaneously displaced into said intermediate parts.

7. Apparatus for forming from flowable material an article having a central portion, a peripheral portion, a plurality of separate radial portions radiating from the central portion, and a plurality of intermediate portions each defined between two adjacent radial portions and the central and peripheral portions the apparatus comprising a plurality of relatively movable elements which define a cavity having a central part, radial parts, a peripheral part and intermediate parts, each intermediate part being defined by two adjacent radial parts and the central and peripheral parts, for forming the central, radial, peripheral and intermediate portions respectively, the elements defining the radial parts being movable relative to other of said elements whereby the radial parts of said cavity may be varied in size independently of the other parts of the cavity, the elements defining the peripheral part of the cavity being movable relative to other of said elements whereby the peripheral part of the cavity may be varied in size independently of the other parts of the cavity, and the elements defining the intermediate parts being movable relative to other of said elements whereby the intermediate parts of the cavity may be varied in size independently of the other parts of the cavity.