Abstract: A starter motor for an internal combustion engine includes a shaft rotated by an electric motor, a pinion gear wheel carried by the shaft the gear wheel being rotated with the shaft and axially movable relative thereto between an operative position and a rest position, and an electro-magnet for moving the pinion from its rest position to its operative position. The electro-magnet includes an armature which is coupled to the pinion gear wheel, and which is guided for movement parallel to the shaft. First and second electro-magnet poles are spaced apart around the shaft and are spaced from the armature in the rest position of the armature in the direction of movement of the armature.

Abstract: A data transmission system for a road vehicle has an aerial on the road vehicle for picking up signals from an external transmitter. This aerial passes a signal to a receiver on the vehicle which in turn passes the information to a memory unit which stores the information at a fast rate and then supplies the information at a slow rate to an electrical voice synthesizer.

Abstract: A hydraulic actuator arrangement has a pair of double acting actuator devices coupled together for movement in unison. Each device has two control valves respectively operable to cause the device to move in opposite directions. The four control valves are resiliently coupled so that both actuator devices are normally energised simultaneously. Each control valve has an associated pressure relief valve so that failure of any one of the control valves permits the pressures on either side of the associated actuator device to be equalized.

Abstract: In a method of forming a refractory product wherein a mixture consisting of effective amounts of silica, alumina, aluminium nitride, and with or without silicon nitride, is provided, the mixture is surrounded with a protective medium and sintered at a temperature between 1200.degree.-2000.degree. C to form a single phase silicon aluminium oxynitride corresponding to the formula: Si.sub.6.sub.-z Al.sub.z N.sub.8.sub.-z O.sub.z, where z is greater than zero and less than or equal to 5, and when there is no silicon nitride in the mixture z is greater than or equal to 4 and less than or equal to 5, the improvement being the step of introducing into said mixture magnesium oxide in an amount of not more than 5% by weight to form a magnesium silicate glass and aid in densification of the ceramic material.

Abstract: A ceramic material includes at least 90% of a single phase silicon aluminum oxynitrite having the general formula:--Si.sub.6.sub.-z Al.sub.z N.sub.8.sub.-z O.sub.z --where z is greater than 0 and less than or equal to 5.One method of producing the ceramic material involves sintering a mixture including not more than 75% by weight of high active surface area alumina powder of particle size less than 10 microns and silicon nitride powder of particle size less than 20 microns.In another method of producing the ceramic material, a mixture of silicon and alumina powders of particle size less than 20 microns is nitrided at a temperature between 1250.degree. C and 1600.degree. C. The proportions of silicon and alumina in the mixture being nitrided are such that the atomic ratio of silicon to aluminium is not less than 1:3.

Abstract: A method of producing hot pressed products, especially products of complex shapes, wherein the material from which the component is formed is hot pressed between a plurality of die parts of which at least one is of substantially uniform density and substantially compressible. This enables the shape of the die part to conform exactly or nearly so to the shape of the body being sintered throughout hot pressing, thereby resulting in obtainment of products of complex shapes.

Abstract: A switching circuit has an operational amplifier connected between positive and negative supply lines and has its non-inverting input terminal connected through a resistor to an intermediate supply line. The inverting input terminal of the amplifier is fed with a signal the polarity of which varies with respect to the intermediate input terminal, and a capacitor and a resistor are connected in series between the output and non-inverting input terminal of the amplifier. The arrangement can be used in a control circuit for an electrically driven vehicle.

Abstract: A fuel control system for a gas turbine engine includes a metering device and a servo-operated control valve through which fuel flows from the metering device to the engine. A pilot valve for the servo-operated control valve is responsive to engine speed and is also operable, when a metering device control member moves past a predetermined position, to cause the servo-operated control valve to reduce fuel flow.

Abstract: A control circuit for an electrically driven vehicle has contactors for determining the direction of operation of the motor, but these contactors cannot be operated until the current flowing through the motor is below a predetermined level.

Abstract: A fluid control valve has a port means across which a control element, mounted on a lever, is slidable. An input control arm rotates a cam which imparts linearly-related angular movement to a further lever. A roller is engaged between the two levers and is movable to vary the distances from the pivotal axes of the levers to their points of engagement with the roller. These distances are different on each lever. Movement of the roller thus varies the linear relationship between movement of the input arm and the control element.

Abstract: In an electrically driven vehicle which is controlled by a thyristor chopper circuit having a main thyristor in series with the traction motor and a commutating thyristor for turning the main thyristor off, demand means is provided for setting a required current through the motor and firing the commutating thyristor when the required current is attained. An overriding control permits firing of the commutating thyristor when the main thyristor has been on for a predetermined period, and timing means operates when the overriding control is operative for setting the minimum off period of the main thyristor.

Abstract: A radial piston type pump or motor having a rotor with two rows of radial pistons and a pair of eccentrically disposed rings against which the pistons bear so that they reciprocate as the rotor rotates, the eccentricity of the rings being of equal magnitude and at opposite sides of the axis of rotation of the rotor, the eccentricity of the rings being controlled by a pair of side by side control pistons acting against the rings respectively and a spool contained in the bore communicating with the outlet of the pump to control the supply of fluid to the control pistons.

Abstract: A centrifugal pump has a rotor with two aligned frusto-conical passages, between the larger ends of which is a centrifugal impeller. The lower, smaller end of one of the passages forms a pump inlet. Frusto-conical funnels within the passages act to separate a vapor core from a liquid which is ejected by the impeller. The vapor is ejected from the smaller end of the other passage. A deflector and vanes within the rotor assist ejection of the vapor.

Abstract: A control valve for a gas turbine engine fuel control system has a control member responsive to a servo signal. The servo signal is derived from a pilot valve which is movable against a biasing spring in response to a pressure signal dependent on engine speed, the arrangement being such that an increase in engine speed causes the pilot valve to vary the servo signal so as to reduce fuel flow to the engine. The bias applied by the spring is variable by means of an electrical actuator responsive to other engine operating parameters.

Abstract: A fuel control system for a gas turbine engine includes a fuel metering arrangement and a spill valve responsive to an increase in pressure drop across the metering arrangement to spill fuel from the upstream side thereof. During engine starting the spill valve may be urged shut to increase fuel flow through the metering arrangement.

Abstract: A flame tube for a gas turbine engine comprises an annular casing within which is disposed a plurality of rings of silicon nitride tiles. The tiles are arranged in axially extending rows and are located by means of a tongue and groove arrangement. The tiles in each row are urged into mutual engagement by a clamp arrangement at one end of the row and an abutment surface fixed relative to the casing at the other end of the row.

Abstract: A hydraulic actuating arrangement for an aircraft control surface has a control circuit, responsive to a position selection input signal, for providing six nominally identical output control signals. Six pilot valves respectively responsive to the control signals provide six servo pressure signals to respective ones of six intermediate actuators. The intermediate actuators are resiliently coupled to each of two main hydraulic control valves. Three of the intermediate actuators and one of the main control valves are supplied from a first hydraulic pressure source, the remaining three intermediate actuators and the remaining main control valve being supplied from a second hydraulic pressure source. An output actuator is responsive to output pressures from either of the main control valves.

Abstract: The flyweights of a governor of the general kind having magnetised flyweights and a field coil for modifying the bias of the flyweights, are magnetised by applying a voltage pulse to the coil when the governor is stationary.

Abstract: A flame tube for a gas turbine engine which is arranged within an annular casing and comprising two rows of silicon nitride rings, with one row being disposed adjacent an inner annular wall of the casing and the other row being disposed adjacent an outer annular wall of the casing. Each row is urged into engagement with shoulders at one end of the casing by a clamping arrangement at the opposite end of the casing.

Abstract: A control circuit for an electrically driven vehicle has a switch with a central off position, and operative positions in which the motor of the vehicle drives the vehicle forwardly and rearwardly. Delay means is provided operable when the switch is in its central off position for maintaining energisation of the control circuit for a predetermined period of time, so that loads are not deenergised as the switch is moved through its off position to change the direction of operation of the truck. In the preferred form, movement of the switch to its off position reduces the demanded armature current to zero.