BACKGROUND ART This invention relates to machines in general and more particularly to internal combustion engines, compressors and pumps having reciprocating pistons which move in closely fitting bores and which are connected to rotating parts such as crankshafts. Most such machines have fixed parts of which the most significant are generally known as the head, the cylinder block and the crankcase (or sump). Apart from containing the working gases and supporting the moving parts of the engine, it is desirable for these parts to provide or facilitate other requirements of the engine such as holding the respective parts together, conveying fluids to appropriate parts, resisting wear and allowing convenient mounting of accessories on the engine and of the engine itself. Many inventions, including the present one, have been concerned with improving the design and methods of manufacture of machines for the primary purpose of reducing the costs of manufacture.

Improved methods of manufacture of machines including the use of extrusions have been disclosed particularly in connection with internal combustion engines. For example US Pat. No. 4,523,549 (Lacey, March 1, 1984) discloses an engine wobbler mechanism wherein parts of the said engine have extruded aluminium alloy modules. US Pat. No. 5,460,140 (Porter, July 22,1994) discloses a two cycle engine block machined from a solid extruded block of aluminium alloy. Other principles of manufacture are disclosed in European Patent Office No. 0 602 472 A1 (Ausserhofer et al, 093.12.92), Australian Patent Office No. AU-A-54693/90 (Lyon, 14.11.91), Japanese Patent No. 62-83453, British Patent Office No. 29,780

(Bartlett, 21 December 1911), British Patent Office No. 563,790 (Paxman, 10 March 1943), German Patent Office DE 4408137 A1 (Bognar et al, 10.3.94), German Patent Office DE 2642640 A1 (Kubota, 22.9.76).

Present methods of manufacturing engines on a large scale require certain parts of the engine, for example the block and the head, to be cast from iron or aluminium alloys.

The process of unit casting (ie casting a major part of the engine as a single unit) is complicated, labour intensive and places limitations on the design of the engine. One of the significant complications is that cooling channels and ducts have to be incorporated within the casting, particularly for liquid cooled engines. Furthermore as the assembly of cast engines requires the use of bolts or studs, load bearing threaded holes have to be made in the castings. In order to withstand the forces on these threads the casting has to be larger and bulkier than would otherwise be the case.

Casting of such complicated shapes requires a mould to be produced, at least part of which has to be destroyed to recover the casting.

Modern casting methods require the manufacture of production moulds from suitable mixtures of sand, binders, cements, fillers and the like from a master mould. A master mould is required because the production mould is destroyed each time it is used. The master mould, which closely resembles the final part required, has to be tapered to allow the production moulds to be separated from it. For a casting with interior apertures or channels, the production mould has to be made in the form of several components which are assembled for the casting process. Thus several different master moulds are required.

Even in the earlier sand casting process that was previously used, tapered master moulds or patterns had to be produced which are placed in a box and packed with moulding sand. The pattern was then carefully removed,

and the sand mould reassembled without the pattern. Molten metal was then poured into the mould to make the casting.

Some engines, particularly aluminium engines, are made in a process known as die casting. In this process, a robust re-useable steel mould is made so that the spaces within it are the shape of the desired casting.

Molten aluminium alloy is poured into the steel mould and allowed to solidify. The steel mould is partly disassembled to allow the removal of the solid alloy casting. Such moulds are expensive to manufacture and still impose severe constraints on the design of the engine, such as the general requirement of tapered shapes for removal from the mould, pouring channels and the like.

No casting method in current use provides adequate accuracy for the requirements of the engine. Consequently all cast engine components have to be machined considerably to provide smooth, accurate surfaces.

The main cast engine components are heavy because they are generally cast in a full form with all the cylinders in one block, or at least half the cylinders in one block if the engine is a V6 or V8 and because, again to minimise costs, the cylinder block typically includes the crankcase.

Additional heaviness arises because the casting process requires thicker walls due to the lack of precision, due to inefficient shapes as a result of the requirement for mould tapering and from the difficulty of forming engine cooling channels within the casting itself for the flow of coolant though the engine.

Limitations of the design of an engine block for manufacture by a casting process mean that dead ends are included in the coolant jackets inside the engine block and engine head. This restricts the flow of cooling fluid through the engine and compromises the performance of the engine. It is generally not practical to cast lubricant holes or small diameter apertures and so these are drilled into the castings later on.

A further problem with cast engines is that the complicated nature of engine design required for these methods means that manufacturers are reluctant or slow to change to more advantageous or efficient engine designs because of the high capital costs of altering the master casts and re-making the machines for machining different engine blocks and heads, and for the associated perceived difficulties and costs.

It would be advantageous if there could be provided a method of engine manufacture that overcomes these problems. Such a method may also allow different, more satisfactory, design of other associated engine functions and components.

It is the object of the present invention to address the forgoing problem or at least provide the public with a useful choice.

Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION Principles of the present invention will be described in relation to internal combustion engines such as those commonly used in motor vehicles. It should be appreciated however that the principles of the present invention can apply to other engines, pumps, compressors and to machines wherein linear motion is carried out in association with sealing of fluids in chambers for at least some part of the operation of the machine.

Modular form of multi cylinder engines According to one aspect of the invention there is provided a method of manufacture of an engine or parts of an engine in which a multiplicity of similar components ("modules") are made and are joined or interlocked together to form an engine of arbitrary size. In a preferred embodiment the multiplicity of components includes cylinder blocks and crankcase blocks which may be separate modules or combined so that each unit

module includes at least one cylinder segment and at least one crankcase segment.

According to at least one aspect of the invention, arbitrary length pieces of essentially uniform cross section corresponding to that required for the modules are manufactured such that at least some engine components can be made from sections obtained by cutting off appropriate lengths from the said manufactured piece. Additional machining and finishing processes may however be required before the module is ready for use in the engine assembly.

Such pieces as envisaged in the invention may be made with either casting or extrusion as part of the manufacturing process for the modules.

Alternatively, in another aspect of the invention modules may be manufactured by casting or extruding material to an appropriate cross section for the module and finishing it to the correct length in the same process such as the extrusion or casting process. For example, the mould for casting may be the correct length for a single module, or it may be of a length suitable for a particular number of modules, or it may be of arbitrary length. Where certain material such as aluminium alloy, ceramic paste, plastic or sinterable material are extruded, parts may be automatically cut to size as material exits the extruder. This may be prior to other finishing processes such as firing, heat treatment, chemical treatment or machining.

Modules can be made interlocking Since the cylinders, crankcase components and other parts of the engine may be manufactured singly, but be required to be assembled to form a multicylinder engine, the engine system may include means of joining the components to form a single engine. One method of assembling the engine is to hold the components in place with a combination of bolts, brackets, welding and so forth.

However in preferred embodiments the assembly of the engine can be optimised by making associated modules with complementary re-entrant forms and lugs, and with complementary semi holes and matching extruded holes so that part of the engine may be self locking and other parts may be united with tie bolts and the like. Longitudinal holes, semi- holes, grooves, channels, lugs and re-entrant slots can be readily incorporated into both extrusions and cast modules and so are particularly applicable to this application.

For example it is envisaged that an interlocking connection such as a dove tail or tongue and groove arrangement would be employed to assist the relative location of similar parts or matching parts, such as a row of cylinder or crankcase modules, or a cylinder module and a side cover or an end cover. Such methods have the advantage that they can readily be incorporated in an extrusion and result in the component being secured over its whole length rather than just at a small number of points.

General principles of use of extrusions According to another aspect of the invention there is provided a method of manufacturing an engine or parts of an engine characterised by the steps of: a) extruding a length of material though a suitably shaped die to form a shape appropriate for at least part of an engine; and b) cutting the extruded material into lengths or sections such that these become at least part of a component for said engine.

The process of extrusion is not currently used for any major component of any engine. This may be because the current design of engines is such that it would be difficult to apply the extrusion process to make parts for current engine designs. For example, present designs do not have the substantially constant cross section required for extrusion, and generally have different functional components grouped together to reduce the

number of separate castings because of the cost and difficulties of the casting process. The extrusion process typically requires different functions to be associated with different extruded sections.

The applicant has recognised that a new engine design could enable at least part of the engine to be produced by the extrusion process with all of its advantages, in place of at least some of the cast or machined components. It is envisaged that standard extrusion processes can be used with the present invention. Thus cylinders, apertures, passages, channels, Tee slots and interlocking forms which can all readily be included in extrusions allow improvements in the design and manufacture of engines.

Such closed or open passages or apertures can provide for the operation of reciprocating pistons, the passage of tie bolts, bolts, pipes, rods, cables, signal lines, strengthening members and the like, and form channels for cooling fluids and lubrication.

A significant feature of extrusions is that the process of extrusion improves the grain structure and density of the material. Flaws are eliminated in the process and the integrity of extrusions is extremely high.

Extremely accurate tolerances can be obtained, and generally no additional finishing of the extruded surfaces is required.

A wide range of materials can be used The engine may be made with components extruded or cast from a variety of materials; for example some components may be extruded from aluminium alloy, others from plastics, and some may be from composites or reinforced composites such as Kevlar reinforced aluminium. Other engine components may be made of iron or other materials as appropriate.

Plastics, ceramic and composites may also be used for some static or moving parts of the engine. For example an engine made in accordance with the present invention would have at least some parts functioning at a

sufficiently low temperature such that extruded or cast plastic material could withstand the temperatures developed.

Thus in some embodiments of the invention, hardened or toughened plastic, composite or ceramic may be extruded or cast as uniform cross section lengths for all or part of the engine. This may include cooling fins surrounding the cylinder, components of pistons, pistons valves, manifold connections and the like. Extruded components can be heat treated or fired subsequent to extrusion to improve properties. For example, certain components can be extruded from ceramic paste or sinterable material paste which on firing forms a strong, tough material suitable for some engine components.

Forms of extrusions which can be used for engine A single main cylinder and side cylinder"unit block"module may be manufactured by the extrusion process, or in alternative embodiments a whole engine block with multiple cylinders may be extruded at one time.

In the case of extruding modular sections consisting of a single main cylinder with or without side cylinders the unit blocks can be extruded so that they lock together to form a multiplicity of cylinders by means of dovetails or other re-entrant locking methods. Similarly, other components such as the crankcase parts can be extruded as a whole, or as separate modular components that can be agglomerated to form a larger engine with a multiplicity of cylinders, valves, cranks and bearings.

One advantage of extruding components in the form of single cylinder and single crank units as opposed to those for a whole multicylinder engine is that the extrusion processes is considerably easier for single units. For example the extrusion for single units has less material and less mass and is thus easier to handle in terms of size and weight. The dimensions and power of the extruder needed for such single unit extrusions is much less than required for whole multicylinder engine assemblies.

Many engines can be manufactured from same extrusion profiles A further advantage resulting from the modularity of using single unit (eg single cylinder or single crankcase section) extrusions is that engines of arbitrary capacity, number of cylinders and length can be manufactured from the same extrusions without changing any moulds or fixed dimension components associated with the block, head, crankcase or sump. This results in a flexible and cost-effective manufacturing system.

For example a 3 litre engine may have the same extrusion section profiles as a two litre engine but be 50% longer by having more cylinders or may have the same number of cylinders but with a stroke 50% longer. This is an important property of the invention which provides a degree of uniformity and standardisation not previously found in engine manufacture. It should be appreciated that traditional manufacturing methods based on unit casting require different capacity and different sized engines to have quite different moulds and machining arrangements.

In comparison, the present invention ensures uniformity of design and thus efficiency in the manufacturing and management process.

Superior tolerance and reduced mass from extrusion process The extrusion process results in a considerably tighter tolerance on the dimensions of the extruded components. It is possible to produce extrusions containing main cylinder bores and piston bores where no additional machining or finishing of the bores is required. Further, the less mass there is, the less restriction there has to be made on the design of the extrusion die to ensure that there is minimal distortion of the extrusion during the cooling process.

Incorporation of cooling lubrication and tie bolt channels in extrusion A further advantage of the present invention is that since apertures can be extruded, lubrication and cooling channels and jackets, cooling fins, bolt or tie bolt holes and fixing channels and cavities can all be incorporated in

the extrusion and thus do not have to be machined or added separately.

This is in contrast to previous manufacturing processes which involve complicated time-consuming machining to create the fluid passages.

Modular components made from castings can, in some designs such as those applying to this invention, also be made to function as described herein for extrusions.

Nature of cast modules An important feature of using modular castings for the engine is that modular castings as embodied in the invention allow castings to be made without blind cores, unlike conventional cast engine blocks. Therefore re- useable moulds which do not have to be partly broken to remove the castings can be used. The same mould shape can be used for a multiplicity of modular components for an engine. The mould design and manufacture is simpler for this case.

The modules manufactured by casting are generally intended to have a shape similar to that which could be obtained by an extrusion process, since this effects a simpler engine design which can be manufactured at less cost and with greater flexibility than conventional engines based on whole block castings.

In a preferred embodiment in which the modules are of uniform cross section, semi-continuous or continuous casting can be used, or the pieces from which the module is manufactured can be cast in arbitrary lengths and subsequently cut to the required length for the particular modules being made.

Form of cast modules which can be used for engine A single main cylinder and side cylinder"unit block"module may alternatively be manufactured by extrusion or by casting. In the case of a single main cylinder with or without side cylinders the modules can be made so that they lock together to form a multiplicity of cylinders by

means of dovetails or other re-entrant locking methods. Similarly, other components such as the crankcase parts can be cast as separate components that can be agglomerated with the aid of re-entrant locking methods and tensile members to form a larger engine with a multiplicity of cylinders, cranks and bearings. Modules can be manufactured from cast sections of uniform cross section and arbitrary length in the same manner as can be done from extrusions.

Usine cast modules for a range of ensine sizes One advantage of modules in the form of single cylinder and single crank units as opposed to those for a whole multicylinder engine is that the processes are considerably easier to apply and are more flexible for single units. For example single modules require less material and less mass and are thus easier to handle in terms of size and weight.

A range of engine sizes can be developed using the same cast modules, but with different numbers of such modules to allow, for example, different numbers of cylinders to be provided for different engines to provide different capacity and output power. Alternatively the same mould can be used with the modules being cut to different lengths for engines of different capacity. The present invention allows such length changes to be easily done as there are no blind cores and the cross section of the cast module appropriate for the present application is essentially constant along its length. This results in a flexible and cost-effective manufacturing system.

Heat & chemical treatments Heat treatment, chemical treatment and other methods used to improve the properties of the extrusion or module can be simply carried out on the relevant modules without the need to treat other parts which do not require treatment. This is much better than a unit casting where the

entire casting has to be managed and treated when it is merely desired to improve the properties of a small part of it.

Following extrusion and sectioning or modular casting, and if appropriate other treatments such as heat treatment, some or all parts of the engine may be chemically treated with liquids, gases or plasma to improve properties such as wear resistance. The nature and shape of the modular components described in this invention simplifies the application of such treatments because of the more suitable shape of these components, their light weight and small size compared to a whole engine and the fact that only the relevant components need to be treated instead of a whole engine block as would be the case with cast engine blocks.

For example, some or all of the modular components can be anodised, nickel plated, chromed, implanted with iron or any other treatment for wear resistance such as the propriety Nikasil treatment, or for the purposes of corrosion resistance, colouring, allowing wear depths to be visually assessed or for other purposes.

All such treatments can be carried out either before or after the extruded or cast sections are cut to size for the modules. This allows selection of the most efficient method for each particular treatment to made.

Method is appropriate for piston valves, including side piston valves In preferred embodiments of the present invention the modular development is applied to engine designs having piston valves. In particular the applicant has designed a new side valve engine as detailed in New Zealand Patent Application Nos. 314113 and 299841. Piston valves operate by arranging for a piston typically sealed with one or more sprung piston rings to move in a bore, usually circular, such the controlled movement of the piston uncovers and exposes ports in its own cylinder bore to the combustion chamber and permits gas flow in or out of the combustion chamber. Normally separate valves are used for inlet gases

and exhaust gases, but a single piston valve could be used for both with the assistance of at least one other valve.

It should be appreciated that the present invention can apply to engines having alternative designs. For example an engine may be constructed using the above method which employs poppet valves or rotary valves as opposed to piston valves; and that such valves may be placed beside the cylinder as side valves or above the cylinder as overhead valves. In preferred embodiments of the present engine some of (but not limited to) the parts of the engine which are modular castings or extrusions include the main piston cylinder; cylinders for side piston valves; cooling channels or jackets surrounding the cylinders and if appropriate cooling fins; the engine head (particularly for a side valve engine); the engine crankcase with bearing pedestals; and the engine sump cover.

Scotch yoke mechanism for operating piston valves The piston valves that are used in certain preferred embodiments of the invention can have their position determined by scotch yokes connected to one or more auxiliary crankshafts. The aperture profile of such a yoke which is operated by the offset journal of a crankshaft may be curved in order to optimise the position versus rotation profile of the yoke operated piston valves. This method of control of the piston valve allows the valve motion to be optimised for transfer of gases in and out of the combustion chamber.

Bearins housings included in crankcase extrusion It is envisaged that the sump or crankcase extrusion may also include the housing for the crankshaft and for the main (crankshaft) bearings of the engine. The bearings used in this assembly can be roller or ball races or conventional shell bearings, or if the module is of a suitable material, the material of the crankcase and/or sump can also be the bearing surface for the crankshaft main bearings. This dispenses with the need for main

bearing caps, as the opposing halves of the crankcase modules surround the main bearings (whether additional bearing surfaces or arrangements are included or not) and are typically held in place enclosing the crankshaft by means of tie bolts or members that hold the engine modules in place. Such arrangements can significantly reduce the manufacturing costs of the engine.

Bore sleeving not required With the use of suitable piston ring material or with the application of suitable wear resistance coating to the bores, there is no need for a sleeve to be inserted in the cylinder. The pistons with their sealing rings can be operated either directly in the extruded bores, or in extruded bores that have been treated to improve wear resistance. These considerations apply both to power cylinders and to piston valve cylinders. Cast bores do, however, require machining but can subsequently be treated as described for extrusions.

Use of separation plate between cylinders and crankcase In certain preferred embodiments of the engine a separation plate between the cylinder modules and crankcase modules allows these modules to be assembled together without having to make the modules matched to each other. This simplifies manufacture especially when extrusions are used, and it allows tie bolts to pass through both the modules and the separation plate to hold the engine together, with the modules in compression. In other preferred embodiments it is also necessary to have a sealing plate between the crankcase module assembly and the cylinder block module assembly in order to terminate and separate the cooling and lubricating channels and to provide pathways to the respective reservoirs.

The separation plate can be machined from a suitable material such as aluminium. However it may preferably be extruded or cast from a suitable plastic material and thereby serve both as a separation plate and self sealing plate without needing additional gaskets between it and its

associated modules. Feed channels or ducts to the lubricant or cooling reservoirs can be incorporated in this separation plate. The separation plate may incorporate full or half housings for bearings or journals of camshafts or auxiliary crankshafts, such as may be used for operating valves.

Use of tie bolts Tie bolts are high strength steel rods which have a thread on at least one end and a head or thread on the other end. The tie bolt is applied by placing a nut on each threaded end, rather than being screwed into any threaded component of the engine. For the purposes of this invention, tie bolts are used in tension as through tensile members to keep the components between the two ends of the tie bolts in compression.

The use of extrusions or cast modules as embodied in the present invention allows a strong, rigid engine structure to be obtained by assembling the engine components such as the extruded sections or modules with a single locking system such as tie bolts. The advantages of this method include the elimination of many load bearing threads in the engine components, thus saving labour, weight and cost. It allows weaker or thinner material to be used because of the elimination of such threads.

The engine components held together by the tie bolts are held in compression and this allows the components to be designed for greater stresses than in the case of conventional assembly methods. Thus thinner cross sections can be used, reducing preparation time, weight and cost.

These tie bolts can pass though holes, semi holes or apertures incorporated in the extrusions or modules.

The entire engine may be configured with separate sump, block and head portions for each cylinder or there may be a common sump, head or block for some or all of the cylinders. In the latter case, using a single head and/or a single sump cover for a multiplicity of modules with the engine held together with tie bolts or the like introduces additional strength and

rigidity to the cylinder or crankcase module assemblies. For example, the manufacturing axes of the cylinder and crankcase modules are at right angles to the manufacturing axes of the head and sump cover. The mutual assembly of these parts of different axis orientations with the head and sump cover passing over a number of modules provides strength and rigidity to the assembly in all planes.

Use of dowel pins for alignment While some embodiments of the invention use re-entrant fixing and alignment profiles and tie rods to align and hold the major components together, additional connections and alignment devices may be employed to assist with or perform some or all of these requirements. In one embodiment, additional connection and alignment means may be provided by dowel pins or alternatively by sleeves which can fit into holes or apertures within or between the components and serve to align and secure the components to each other. Tie bolts may pass through some of the alignment sleeves.

Cooling, heat transfer and lubrication Heat transfer and cooling of the modular engine components is more satisfactory than in unit cast engine designs. Extrusion or modular casting of the cylinders and head allows walls of controlled uniform thickness to be produced. The flow-through nature of the modular cylinder unit block allows simpler and superior cooling arrangements to be designed into the engine. For example, in some embodiments no dead ends need be incorporated into the cooling channels as with a traditional cast block.

Instead the cooling fluid can flow from the cylinder head though channels in the cylinder block modules and return though other channels so that a continuous flow is achieved in all parts of the block and head. Cooling fluid may be channelled through apertures in the crankcase modules or in the sump cover and thereby assist in cooling the engine oil directly.

Optimising the cooling to avoid high temperature gradients can reduce distortion during operation and improve engine efficiency and reduce wear and tear. The flexibility and precision of the extrusion process or modular casting allows cooling design to be carried out precisely and the wall and fin thickness and shapes to be accurately determined and made to achieve superior engine performance.

Lubrication also needs to be associated with cooling, both for the transfer of heat from critical components to the lubricant and for the transfer of heat from the lubricant to the coolant. The distribution of lubricant within the engine according to the present invention is simplified by the incorporation of lubricant channels in the cylinder and/or crankcase modules and by having these channels intersect with corresponding passages in the engine head, separation plate and/or sump cover.

Furthermore the provisions of such passages assists in the cooling of the lubricant compared with conventional engines where there is less contact with cooled areas of an engine.

Attachment of auxiliaries to engine block with Tee slots By incorporating Tee slots or other re-entrant shapes into the extrusion walls, accessories and auxiliaries can be attached to the engine and the engine can be mounted without the need to drill or tap holes in the engine components. This method again reduces costs and adds flexibility. Such re- entrant slots can also be used to interlock parts of the engine together, such as separate cylinder extrusions and covers, end plates and the like.

Suitable bolts or fittings in these slots can assist in holding the engine components together and in creating a light but rigid engine assembly.

Manifolds and other essential components such as starters, alternators, oil filters etc. can be simply attached to the engine with the aid of these re- entrant slots.

Engine mounting using Tee slots An efficient and effective method of mounting the engine or of attaching engine mounts to it is to use Tee bolts or similar fasteners which lock in the Tee slots or re-entrant cavities on the outside of appropriate modular components. Such attachments can easily be moved or adjusted and form a universal method of fixing the engine to a chassis or structure. This is a further advantage of the system embodied by the present invention.

Shock absorbers in pistons or their connections In a preferred embodiment of the engine, a shock absorber is used in the linkage mechanism between the piston or piston valve and its associated crankshaft in order to reduce the noise, damage and wear resulting from shock loadings on the associated components and bearing surfaces in this linkage. Such shock absorbers may be elastomer bushes or blocks in, or at the ends of, the conrods or between the piston and its connection with the conrod or scotch yoke aperture block.

Description of a working engine based on the invention A working engine manufactured substantially as shown in Figure 6 has been operated successfully. This four cylinder engine used an extruded module for each cylinder, with the module of the form illustrated in Figure 2, containing a large cylindrical bore for the main piston and two smaller bores for the inlet and outlet piston valves. The valves are operated by two auxiliary crankshafts partly mounted in the separation plate between the cylinder modules and the crankcase modules. The crankcase modules are constructed from two identical extrusions similar to that illustrated in Figure 4, with machined semi holes housing the main crankshaft shell bearings. Each group of extruded modules are interlocked by means of dove tail profiles extruded into each end of the extruded sections as illustrated in the Figures. The complete engine assembly is held together in compression with 26 tie bolts. Accessories including a starter motor, oil

pump, alternator, water pump and crankshaft position sensor are attached to the engine by means of Tee head bolts in Tee slots extruded in the exterior sides of each module. Inlet and outlet manifolds are fixed to the appropriate sides of the assembly of cylinder modules by means of Tee head bolts sliding in the extruded Tee slots. The gas connections from these manifolds to the respective piston valves were made by machining ports in the side of the piston valve cylinders, with the ports being uncovered by the piston valves when the valves are moved downwards by the scotch yoke operated by the respective auxiliary crankshafts. The engine was mounted by fixing the engine mounts to the engine with Tee bolts in Tee slots.

Avantages over prior art It should be apparent that the present invention has a number of advantages over the prior art. These advantages include: a) Profiles of engine components which have a similar cross section throughout their length, making them simple to manufacture by extrusion or by casting without the use of blind cores. b) An efficient method of producing at least some of the engine components which requires less material and less energy. c) A process which reduces the machining of the metal to form the required shape and size of at least some engine parts. d) Cheaper tools for producing the required engine components in large quantities. e) Reduced labour costs since separate moulds and mould inserts are not required to be made and destroyed each time an engine block or head is cast.

The design of the engine components can be simplifie and optimised by eliminating requirements of tapered shape, internal cast cavities, large single units and the like. g) Less parts, or at least less different parts, are required in the manufacture of the engine, particularly when it incorporates side piston valves. h) The engine is more compact and weighs less than a comparable cast engine; this improvement is greater when side piston valves are used.

Because of uniformity of parts, simpler design and the elimination of load bearing threads in the engine components the engine is simpler and quicker to assemble. j) A range of engines of different capacities, stroke lengths and/or number of cylinders can be assembled from modules made from the same extruded or cast profiles, which minimises costs and improves flexibility of manufacture. k) The cooling for the engine can be optimised and can minimise temperature gradients which reduces stresses, improves efficiency and use of materials, and reduces wear.

The ability to use alternative materials to cast iron means that the engine can be lighter in weight which amongst other advantages gives easier handling and greater power to weight ratios. m) By constructing the engine from assembles of similar modules which have the same profile and which interlock allows for flexibility of design and the manufacture of a range of engine sizes each with the same principal fixed components.

n) The method of manufacture allows a combination of optimum materials to be used for components which were previously single castings such as an engine block or engine head. o) Engine mountings and fixings added to the engine including accessories such as manifolds, alternators, starter motors etc can be attached with a simple method using the extruded Tee slots or similar arrangements. p) The engine components are more readily amenable to, and economic for, treatments to improve wear resistance than is the case with cast engines. q) The design allows optimum use of piston valves resulting in a reduction of the component count and a more compact engine for the same capacity.

BRIEF DESCRIPTION OF DRAWINGS Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 is a perspective view of single cylinder block module made in accordance with one embodiment of the present invention; Figure 2 is an alternative design of a cylinder block module with external interlocking profiles which allow these modules to be assembled into a multicylinder engine block.

Figure 3 is an extruded engine head which can be used with the cylinder block modules shown in Figure 2; Figure 4 is an extruded crankcase (sump) module which can be used with the cylinder block modules shown in Figure 2;

Figure 5 is an extruded sump cover plate which can be used with the cylinder block modules shown in Figure 2; Figure 6 is an exploded view of an assembled four cylinder engine using the componentry illustrated in Figures 2 to 5; and Figure 7 is a perspective view of an alternative cylinder block module design for the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION Figure 1 is a diagrammatic perspective view of a single cylinder block generally indicated by arrow 1.

The cylinder block (1) has been designed to have a substantially constant cross section to allow the block (1) to be readily extruded.

It can be seen that the cylinder block (1) has minimal additional machining, namely the bolt holes (2) and exhaust and inlet ports (3) and (4). Alternatively to the bolt holes (2), Tee slots (not shown in Figure 1, but shown in Figures 2,4,6,7) can be incorporated in the extrusion and used for attaching the manifolds to the exhaust and inlets ports (3) and (4).

The cylinder block (1) has a main cylinder (5) and two side cylinders (6) and (7). In preferred embodiments of the this invention the cylinders (5), (6), (7) are anodised or chemically treated to improve wear resistance.

Surrounding the cylinders are fluid channels or"jackets" (8) which allow cooling fluid to pass from the head of the engine (when assembled) down to the crankcase at the opposite end of the block, and vice versa.

Protruding into the fluid channel (8) are cooling fins (9) which improve the transfer of heat from the exhaust valve cylinder (7).

The design of the cylinder block (1) has been constructed to provide a number of slots and plugs which enable the individual cylinder blocks to

be fitted together with a dovetail arrangement. These slots and lugs are indicated by arrows (10).

In addition, bolt or tie bolt holes (11) have been provided which enable the engine cylinder block (1) to be readily bolted to the crankcase or sump (not shown), and head (not shown) of the assembled engine.

It can be seen from Figures 3 to 5 that other components in addition to the engine block or unit blocks can be extruded as well.

Figure 3 shows an engine head which has its underside (not shown) machined to provide the upper part of the engine combustion chamber.

Figure 4 is an illustration of an extruded crankcase or sump module of an engine.

Figure 5 is an illustration of an extruded sump cover plate.

The workings of an exploded four cylinder engine shown in Figure 6 should be readily apparent to one skilled in the art and therefore a table of the various componentry is given below: Component: Figure 6 reference number: Spark plug 20 Extruded engine head 21 Tie rods 22 Exhaust manifold 23 Inlet manifold 24 Main piston head 25 Side piston valves 26

Main piston conrod 27 Crankshaft 28 Extruded engine unit block 29 Extruded crankcase (sump) 30 Extruded sump cover 31 Dowel sleeve 32 Oil way 33 Figure 7 is an alternative design of an engine block module extrusion which includes cooling fins (34).

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.