Abstract: A piston (10) containing a cavity (16) is manufactured by forming a box (20; 50; 70; 80). The interior of the box defines the cavity (16). The box ms mounted in a die cavity (26) and the piston is cast around the box. The box is provided with projections (22c; 24c; 52; 58; 73) which enter recesses in the wall of the die cavity and support the box. After removing the piston from the die cavity, the projections are machined off.

Abstract: A camshaft (10) is formed from a plurality of individual chill cast cams (12) and an elongated shaft (24). Each cam (12) has a hole (20) therethrough which has a groove (22) in its surface at a predetermined angular position. The shaft (24) has a plurality of cam receiving portions (24a) thereon which are spaced along the shaft and each have an outer peripheral surface (26) which is a close fit in the hole (20) in one of the cams (12). The outer peripheral surface (26) has a groove (28) therein at a predetermined angular position. The grooves (22,28) cooperate in forming a passage (30) which receives a wedge member (32) to hold the cam (12) in a fixed orientation relative to the shaft (24).

Abstract: Cylinder head gasket which includes between adjacent cylinder bore apertures a heat-conductive element which is in thermal contact with the metal eyelets of those apertures and extends into a coolant aperture of the gasket.Such a gasket is less liable to failure through non-uniform heating during engine operation.

Abstract: A piston holding device in which a conical register is provided inside the skirt of a piston and is engaged by a conical locating surface on a tailstock. The tailstock may also include a ram which is adapted to push on the inside of a piston crown and force the piston against a headstock. The holding device is used during piston machining.

Abstract: The invention relates to a piston for a cylinder of a two-stroke internal combustion engine, the engine having an auxiliary air inlet port which communicates with a cavity within the crown structure of the piston as the piston passes through bottom dead center. The air within the cavity is caused to resonate at high frequency, thereby enhancing the combustion process, enhancing low speed power, torque and eveness of engine running, and reducing or eliminating engine pre-combustion "knock".

Abstract: A rotary valve is described together with engines embodying such valves. A rotary valve for an internal combustion engine or compressor comprises a generally cylindrical valve body member of a ceramic material, the valve body having at least one gas duct passing through the valve body wall to communicate with an axially extending passage which is closed at one end and open at the opposite end and at least one channel formed in the valve body wall surface for the passage of gas. Examples of engines embodying the rotary valve in a V-8 cylinder block and in the cylinder head of an in-line four cylinder engine are given.

Abstract: Ceramic cylinder assemblies for internal combustion engines, particularly diesels, are described. The assemblies comprise at least two portions including at least one main cylinder portion and at least one combustion region portion, the at least two portions being contained within a metal sleeve and wherein the at least one combustion region portion has a generally axially directed slit therein, the slit passing through the whole thickness of the ceramic material.

Abstract: In a machine tool, the tool is moved using a signal representing a required profile of the surface being machined. This signal is fed to a transducer, such as a piezoelectric crystal or a D.C. linear motor, which converts the signal into a corresponding linear movement which is transmitted to the tool. The tool can also be vibrated ultrasonically during machining. Such machines can be used for producing workpieces which are non-circular in cross-section and/or which are barrelled or tapered along their length.

Abstract: Pistons and cylinders are manufactured to an oval shape, which is defined as being an oval where the ratio of the major axis to the major axis is between 1.1:1 and 3:1. Pistons and cylinders are generally finish machined by relative rotation between the tool and the workpiece and movement of the tool in a defined path to produce a finished profile. In general, however, conventional machine tools cannot machine such oval profiles at commercial production rates because of the excessively high tool accelerations which this would involve and of which the conventional machine tools are not capable. Disclosed are a machine tool for matching such oval pistons in which an oval piston blank is rotated in a path such that, when each part of the piston surface reaches the tool, it is at a constant datum position. Thus the tool considers that it is machining a surface of constant radius and normal tool movements can be performed.

Abstract: A camshaft is prepared from separately formed cams and a shaft. The cams may for example be formed by sintering. The cams are provided with holes which are under-sized and are provided with serrations. They are located on a correspondingly shaped dummy shaft in their required relative orientations and angular positions. Next, the cams are clamped in these positions and the dummy shaft removed. The cams are then heated to red heat and the serrated holes in them broached to bring them to their final size and to concentricity. Finally, a shaft having an exterior profile corresponding to the shape and size of the broached profile of the holes, at ambient temperature, is introduced into the holes and the cams are then cooled so that they shrink fit on to the shaft so ensuring that they are accurately positioned on the shaft. The cams are then released from the jig to give a finished camshaft.

Abstract: A cat-head type machine tool is controlled by an electronic control system (28, 31) so as to allow relative movement between the rotating tools (11, 12) and the stationary workpiece (22) within a revolution of the tools, such that non-uniform and/or barrelled or oval profiles may be machined on a cyclindrical workpiece. This is particularly useful for the high speed production of pistons for internal combustion engines where such profiles can give a piston improved performance.

Abstract: A water-cooled internal combustion engine has at least one cylinder and a valve controlled exhaust port (11). A valve seat insert (17) is provided around the entrance to the port and is formed with a sealed passage (24) therearound which is in direct communication with the water-cooling system. Water is thus circulated around the passage to cool the valve seat insert and the associated valve.

Abstract: A piston (10) for a diesel engine is formed with a combustion bowl (21) which has a lesser volume until the cylinder pressure reaches that at which fuel ignition takes place. The volume of the combustion bowl is then increased to reduce the maximum pressure in the cylinder. The volume is again decreased during the expansion stroke. This has a number of beneficial effects on the engine including reducing the stress on the engine parts and allowing increased level of pressure-charging.

Abstract: A valve seat insert surrounds an inlet valve of a reciprocating internal combustion engine and provides a seat for a movable valve. The flow characteristics of a charge of air or an air/fuel mixture leaving the inlet valve are determined at least in part by the form of the valve seat insert and these characteristics can affect the performance of the internal combustion engine. The improved valve seat insert defines an aperture through which the charge passes. The aperture has an area to one side of a plane including the axis of an annular valve engaging surface of the insert which is greater than the area of the aperture to the other side of the plane. The smaller of the areas is bounded by one or more curved sections. This insert can be used in an internal combustion engine or deflect a charge passing through the aperture and to give the charge a velocity profile which, for example, improves starting and reduces fuel consumption.