Abstract: In a co-ordinate measuring machine a probe is connected to the head of the machine by a pivotal arm, and the orientation of the probe is changed by moving the head so that the arm engages a fixed structure and a moment is applied to the arm which is thereby caused to turn and present the probe in the required orientation.

Abstract: The invention relates to a mould assembly including a plurality of individual moulds. The mould assembly of the present invention is made by separately transfer moulding a starter base 16, a plurality of moulds 12, a downpole 14 and pouring cup 19, providing each with mechanical locking features, such as screw threads, and joining them together into the assembly. Much greater flexibility is thereby achieved in materials and wall thicknesses, which can be different in different parts of the assembly to suit strength and heat transfer requirements, individual bits can be replaced, and the transfer moulding produces a compact homogeneous ceramic structure.

Abstract: A method of removing refractory material from a component comprises contacting the refractory material with a chemically active agent whereby to convert the refractory material to a more easily removable substance, and removing the more easily removable substance. The method enables alumina cores defining cooling passages in cast blades for use in gas turbine engines to be removed at practically useful rates.

Abstract: In electrochemical machining, arcing across workpiece and forming electrode can result in both being scrapped. Efforts have been made to detect the electrical signals which develop on occurrence of the spark which normally terminates in an arc. Ordinary electrical noise however, tends to have similar amplitude to that of the spark and so make it difficult for the detection device to differentiate between that noise and spark noise. Consequently the machine tool was disabled though no spark had occurred. The invention enables differentiation between the two noise sources by virtue of detecting the term over which noise occurs. This is achieved by dividing the noise pulses into two trains and passing one train via a pulse delay device 32 to a gate 34 and passing the other train directly to the gate 34. If pulses from both trains arrive at the gate 34 this is indicative of the generation of a spark and the gate 34 emits a signal which is utilized to disable the machine.

Abstract: A hollow turbine blade 10 of aerofoil shaped cross section is provided with walls 18 of varying thicknesses to provide thermal slugging at those regions around the aerofoil profile where the blade experiences high thermal fluxes. The thicker regions of the blade 10 are provided with cooling channels 22 which are elongated in a direction extending from the external surface of the wall towards the internal surface of the wall. The thermal slugging slows down the rate of change of blade wall temperature to a value similar to the rates elsewhere in the blade section. The cooling channels 22 ensure that the temperature gradient across the wall 18 is low around the profile of the aerofoil.

Abstract: A probe for use in measuring apparatus has a base member including a two-dimensional seat for an intermediate member which, in turn, includes a two-dimensional seat for a stylus holder. The two seats face in opposite directions so that the stylus holder can be displaced from the seated position in either of two opposite directions.

Abstract: A gas turbine engine comprises an annular combustion chamber (13) intended for low nitrogen oxide emission. The chamber has a pre-mixing section (20) in which an air-fuel mixture is brought to a significant degree of vaporization before issuing through a grill (22) at the end of the pre-mixing section into a main section (21) of the chamber. Pilot sections (18,19) at opposite sides of the pre-mixing section have outlets (28,29) through which burning mixture from the pilot sections is discharged into main section (21). The grill (22) defines openings (35) through which the fresh mixture from the pre-mixing section (20) is discharged across the outlets (28,29) of the pilot sections (18,19) to mix with and become ignited by the burning mixture.The pre-mixing section (20) is an annular duct (33) having walls (15,16) which extend in the direction of the axis of the chamber and are straight in that direction though slightly convergent. The arrangement favors vaporization in the duct without auto-ignition.

Abstract: In a work piece measuring probe the movement of a stylus in three dimensions is sensed by respective inductive transducers having sensing coils fixed to a support in positions adjacent three mutually perpendicular surfaces defined on the stylus.