Abstract:
Embodiments of the present invention provide a method of forming a component comprising; providing a sleeve member formed from a metal matrix, composite material; and casting a cast portion of the component whereby at feast a portion of the cast portion Is provided within the sleeve member. Embodiments of the invention have the advantage that a component of increased stiffness may be fabricated compared with a cast component not comprising the sleeve member. The component may be formed to he of greater stiffness and reduced weight compared with a component of comparable strength and stiffness formed from a material such as steel.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a sleeve member and method of casting. Aspects of the invention relate to castings and to a method of casting a component. 
       BACKGROUND 
       [0002]    It is known to provide a cast aluminium component by casting molten aluminium into a mould. Aluminium and other relatively light metals such as aluminium alloy, magnesium or magnesium alloy may be used instead of heavier materials such as steel in order to reduce a weight of a component. This assists a manufacturer of a multi-component product such as a motor vehicle to control a weight of the product. However, aluminium has a relatively low Young&#39;s modulus (around 70 GPa). If a light but stiff component is required to be formed from aluminium, it is typically necessary to use more material than would otherwise be required of a part made from a stiffer material such as steel (having a Young&#39;s modulus of around 207 GPa). The extra material is normally distributed so as to increase the second moment of area of the component. Thus the geometry of the component is adjusted to increase stiffness of the component, for example bending and/or torsional stiffness or rigidity. In some applications, the available space into which a component must fit may be limited, requiring a stiffer material such as steel to be used in order to meet the required stiffness specification of the component. The use of steel however results in an increase in the weight of the component and is highly undesirable in some applications. 
       SUMMARY OF THE INVENTION 
       [0003]    Embodiments of the invention may be understood with reference to the appended claims. 
         [0004]    Aspects of the present invention provide a method, a component, a system, a vehicle, an aircraft and a vessel. 
         [0005]    In one aspect of the invention for which protection Is sought there is provided a method of forming a component comprising:
       providing a sleeve member formed from a metal matrix composite material; and   casting a cast portion of the component whereby at least a portion of the cast portion is cast within the sleeve member.       
 
         [0008]    It is to be understood that by reference to the cast portion being provided within the sleeve member is meant that the cast portion is provided within a bore of the sleeve member. 
         [0009]    Embodiments of the invention have the advantage that a component of Increased stiffness may be fabricated compared with a cast component not comprising the sleeve member. The component may be formed to be of greater stiffness and reduced weight compared with a component of comparable strength and stiffness formed from a material such as steel. 
         [0010]    In some embodiments a sleeve member may be placed in a mould for casting without requiring support whilst in the mould. 
         [0011]    Some embodiments of the invention have the advantage bending and/or torsional stiffness or rigidity may be increased relatively to a component not having the sleeve member. Some embodiments allow a component of comparable stiffness to know components to be made more compact and/or lighter. 
         [0012]    The component may be substantially elongate in shape. The component may be subject to one or more bending stresses in use. 
         [0013]    The method may comprise casting the cast portion of the component such that the sleeve member defines at least a portion of an outer surface of the component. 
         [0014]    The method may comprise forming the component whereby the sleeve member defines a conduit through which molten metal may flow to fill the sleeve member, the method comprising at least partially filling the sleeve member with molten metal. 
         [0015]    Advantageously the method may comprise substantially filling the sleeve member with molten metal. 
         [0016]    The method may comprise providing a substantially blind sleeve member having a single opening for molten metal to flow therein. 
         [0017]    The method may comprise providing a sleeve member having a plurality of openings formed therein for molten metal to flow therethrough. 
         [0018]    Advantageously the method may comprise causing molten metal to flow through the sleeve member to fill the sleeve member and allowing the molten metal to coot whereby respective portions of the cast portion of the component project from the sleeve member through respective openings defined by the sleeve member. 
         [0019]    The step of providing a sleeve member formed from a metal matrix composite material may comprise providing a sleeve member formed from an aluminium matrix composite (AMC) material. 
         [0020]    Advantageously the cast portion may be formed from a molten material comprising aluminium. 
         [0021]    The molten material may be one selected from amongst aluminium and an aluminium alloy. 
         [0022]    The method may comprise forming the component to be an automotive or aerospace component. 
         [0023]    The method may comprise forming the component whereby the component is a component of a suspension system. 
         [0024]    The component may be any suitable component of a suspension system such as a suspension arm, a linkage or any other suitable component. 
         [0025]    Advantageously the metal matrix composite material may comprise alumina and at least one metal providing a matrix in which the alumina is embedded. 
         [0026]    Advantageously the method may comprise placing the sleeve member in a mould; and introducing molten metal Into the mould. 
         [0027]    In a further aspect of the invention for which protection is sought there is provided a component comprising a sleeve member, the sleeve member comprising a metal matrix composite material, the component comprising a cast portion wherein at least a portion of the cast portion is provided within the sleeve member. 
         [0028]    The cast portion is advantageously formed to contact the sleeve member, optionally substantially the whole of an internal surface of the sleeve member is in contact with the sleeve member. 
         [0029]    Advantageously the metal matrix composite material of the sleeve member may comprise an aluminium matrix composite material. 
         [0030]    The metal matrix composite material may comprise alumina and at least one metal providing a matrix in which the alumina is embedded, optionally the at least one metal comprises aluminium, optionally the at least one metal consists essentially of aluminium. 
         [0031]    The cast portion of the component may comprise one selected from amongst aluminium and an aluminium alloy. 
         [0032]    The component may be a vehicle suspension component. 
         [0033]    In a further aspect of the invention for which protection is sought there is provided a vehicle suspension system comprising a component according to the preceding aspect. 
         [0034]    In a still further aspect of the invention for which protection is sought there is provided a motor vehicle, aircraft or vessel comprising a component according to a preceding aspect. 
         [0035]    In a further aspect of the invention for which protection is sought there is provided a component comprising a sleeve member, the sleeve member comprising a metal matrix composite material, the component comprising a cast portion wherein at least a portion of the cast portion is provided within the sleeve member. 
         [0036]    Within the scope of this application if is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described with reference to one embodiment are applicable to all embodiments, unless such features are incompatible. 
         [0037]    For the avoidance of doubt, it is to be understood that features described with respect to one aspect of the invention may be included within any other aspect of the invention, alone or in appropriate combination with one or more other features. 
         [0038]    Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described with reference to one embodiment are applicable to all embodiments, unless such features are incompatible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures in which: 
           [0040]      FIG. 1  shows a known component of a motor vehicle suspension system formed from a cast aluminium alloy; 
           [0041]      FIG. 2  shows a component of a motor vehicle suspension system according to an embodiment of the present invention; and 
           [0042]      FIG. 3  shows a cross section through the A-A plane of the component of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    Embodiments of the present invention are directed to providing an improved component formed in a casting operation. 
         [0044]      FIG. 1  shows a known component  100  of a motor vehicle suspension system formed by casting an aluminium alloy In a mould. The component forms a suspension arm of the suspension system and is of a substantially hooked shape. The component  100  has a first mounting portion  110  formed at a first end thereof and a second mounting portion  130  formed at a second end thereof opposite the first end. It is to be understood that if it is required to increase a strength and/or stiffness of the component  100 , the conventional approach would be to increase a thickness of the component at one or more locations thereof, or to form the component from a different material such as steel. Each of these options may be undesirable. For example, there may be insufficient available packaging space to allow the component to be made from the same material but of thicker proportions. Similarly, it may be undesirable to employ a different material such as steel due to increased weight of the resulting component, and problems associated with corrosion in service. 
         [0045]      FIG. 2  shows a component  200  according to an embodiment of the present invention having a similar size to the known component of  FIG. 1  but having a substantially increased stiffness. Like features of the component of  FIG. 2  to the component of  FIG. 1  are shown with like reference signs incremented by  100 . 
         [0046]    The component  200  comprises a sleeve member  220  formed from an aluminium matrix composite material (AMC). In the present embodiment the AMC composes alumina fibres that have been bent to form the sleeve shape. The fibres have been impregnated with aluminium metal to form a composite material composed of alumina fibres and aluminium. In some embodiments the sleeve member  220  may be formed by wrapping the fibres around a former in order to define the shape of the sleeve, subsequently removing the former and impregnating the fibres with aluminium metal. 
         [0047]    The sleeve member  220  may also be referred to as an overcast or overcast member in some arrangements, since it may form an outer surface of a component when the component has been cast. 
         [0048]    The component  200  is formed by placing the sleeve member  220  in a mould and injecting molten aluminium into the mould to fill the mould. The molten aluminium may be arranged to cause at least partial melting of the metal comprised by the sleeve member  220  in order to enable a strong bond to be formed between a cast portion  205  of the component and the sleeve member  220 . Other arrangements are also useful. 
         [0049]      FIG. 3  shows a cross-section through the A-A plane of the component  200  illustrated in  FIG. 2 . The component  200  comprises the sleeve member  220  and the cast portion  205  as discussed above. In some embodiments an interface  225  between the sleeve member  220  and the cast portion  205  becomes less defined than that shown in FIG  3 . This occurs where the sleeve member  220  is placed in the mould prior to casting and the introduction of molten metal to the mould fills the sleeve member  220  causing at least partial melting of the inner surface  220   i  of the sleeve member  220 . This is advantageous because the at least partially melted portion fuses with the cast portion  205  to form the component  200  which efficiently reacts bending stresses between the first mounting portion  210  and the second mounting portion  230 . 
         [0050]    In some embodiments, the sleeve member  220  may not comprise metal prior to casting. Thus, the alumina fibres that comprise the sleeve member  220  may be impregnated with aluminium when the mould in which the component is formed is filled with molten aluminium. 
         [0051]    Embodiments of the present invention have the advantage that a component of comparable size and weight to known cast aluminium components may be formed having a substantially increased stiffness due to the employment of a sleeve member. 
         [0052]    The sleeve member may be a blind sleeve member, for example in the form of a mitten or glove member having a single opening from which a portion of the cast portion of the component projects. 
         [0053]    Alternatively the sleeve member may have a plurality of openings, as in the sleeve member  220  of the embodiment of  FIG. 2 , which has two openings formed therein. The sleeve member may be open at opposite ends thereof such as in the embodiment of  FIG. 2 . Other arrangements are also useful. 
         [0054]    Embodiments of the present invention have the advantage that a given component may be formed to he of substantially increased strength and/or stiffness in a convenient manner by providing a sleeve member formed from a metal matrix composite. The sleeve member may in some embodiments be Inserted into a mould from which the component is to be formed, and a cast portion of the component cast in the mould in the conventional manner. Some embodiments of the invention allow a component to be formed of increased stiffness with relatively little disruption to a fabrication facility. In some embodiments, a mould of the type that has been used to form a component without a sleeve member may be used to form a component of the type having a sleeve member with little or no modification. In some embodiments the sleeve member may be formed such that it may simply be inserted into the mould and molten metal poured or injected into the mould in the conventional manner. 
         [0055]    Embodiments of the present invention enable a component with improved strength and/or stiffness characteristics to be provided in a relatively convenient manner using similar materials to those previously used to form similar components, and he of comparable or substantially Identical dimensions. In some embodiments a component may be formed to have smaller dimensions from those of a comparable component not having a sleeve member, and enjoy enhanced or similar strength and/or stiffness characteristics. Other arrangements are also useful. 
         [0056]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. 
         [0057]    Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to he understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
         [0058]    Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.