Abstract: A contact arrangement for a semiconductor device (typically a GTO thyristor), in which a disc-shaped first connector electrically connects one region of the semiconductor element with its associated contact. The first connector having therein apertures through which pass resiliently-loaded electrical connections to a second region of the element, the surface of that second region lying below the surface(s) of the first region. The various parts of the device may be so shaped as to ensure correct relative positioning of the parts during assembly and the maintenance of that positioning during subsequent handling.

Abstract: A brake control system for a multiple unit train of mixed motor cars and trailer cars--of the type usually to be found operating as metro or mass transit trains--and in which the motor cars have dynamic brakes operation of which is blended with, but given preference over, the friction brakes of all units. A brake demand signal calling for a given level of train retardation is weighted on each vehicle, according to the load of the vehicle, and the level of dynamic braking effort invoked on each motor car is limited in accordance with a maximum adhesion level calculated n proportion to the measured load of that car. In a modified arrangement the adhesion level is calculated in accordance with the load of the lightest loaded motor car. Signals representing the amount of dynamic brake effort achieved by each motor car is supplied to a trailer car and subtracted from the load weighted braking effort for the trailer car and the result used to actuate the friction brakes of the trailer.

Abstract: To ensure the safe operation of an electronic circuit, for example an amplitude modulated carrier signal generator, an output of the circuit is analyzed to prove the presence of predetermined signal characteristics, for example the carrier signal, or a modulation frequency. The predetermined signal alternatively may be superimposed on an input to the electronic signal and proved subsequently to be present in the output. The output of the circuit is passed inhibited, according to whether or not the signal characteristics are proved present, by means of an output enable gate which is self-latching providing the output continues to be proved correct. A start-up circuit delays a possible inhibit for a limited period following initial power connection to the circuit in order that the output can become established.

Abstract: An AND function gating circuit for A.C. signals comprising several magnetic circuits around a common limb, each circuit having a separate input winding and a single output winding on the common limb. The magnetic flux level in the common limb is greatly increased when all input windings are simultaneously energized by A.C. signals of the same frequency and in phase relative to the output achieved under other input signal conditions.

Abstract: An electrically-controlled force-exerting actuator comprising a force-applying power spring arranged to exert a force on an output member, a force-applying control spring arranged with respect to the power spring such that the force exerted by the control spring is detracted from the force exerted by the power spring to determine the residual force exerted on the output member by the power spring, and an electric motor operable to vary the detractive force exerted by the control spring.

Abstract: An electric actuator having an electric motor operable to determine the output force generated on an output member by a spring; a drive shaft arranged to be driven by the electric motor and having first and second drive means, a non-rotational but axially movable intermediate member which is threadedly engaged with first driven means arranged to be driven by the first drive means; the spring being located between the intermediate member and the output member and arranged so that axial movement of the intermediate member is transmitted to the output member so long as the latter is free to move and, when the output member is restrained from movement, generates the output force on the output member upon continued operation of the electric motor; a stop carried by the intermediate member and positionally adjustable with respect thereto in the direction in which the intermediate member is axially movable, and second driven means with the second drive means, the first driven means being engageable with the stop to

Abstract: Electrical circuit configurations are described for the operation of an electrically powered actuator in an emergency to drive the actuator to a predetermined position. In particular the actuator is connected to apply friction brakes of a railway vehicle. The configurations have in common are emergency power circuit connected between an emergency power source and the actuator, means for breaking the power circuit when the actuator reaches the emergency position and latching means to prevent run-back. Preferably and in order to minimize size and weight the emergency power source is of limited capacity, sufficient for, say, two such emergency applications and is recharged from a normal power supply; the recharging circuit being interlocked with the latching means such that the actuator may not be released from the emergency position unless the power source has sufficient charge for at least one further emergency operation.

Abstract: A railway track circuit arrangement particularly suitable for the short track circuit, down to approximately 40 metres, required in metro transit systems. Based on conventional A.C. track signalling principles for continuous track rails, the boundaries between adjacent track sections are defined by electric separation zones. An electrical short is connected between the running rails and an A.C. signal tuning unit is connected approximately 6 metres away to tune the end loop thus formed to resonance at the selected track signal frequency. The tuning units comprise a capacitor, the value of which is selected for resonance tuning, and a transformer a winding of which is connected in series with the capacitor, and a track circuit signal transmitter or receiver is connected through a second winding of the transformer. In order to reduce mutual coupling between track circuits by longitudinal leakage, in each joint, two electrical short may be connected between the rails spaced apart approximately 0.75 metre.

Abstract: A bridge network 1 of current switching devices 2, 3, 4, 5 is operated in full wave manner by controlling signals A, B, C, D respectively produced by two similar, parallel and pulse width modulated power control circuits 12, 13 connected to receive a common input signal, one pair of opposing switch devices (2, 5) being controlled by one circuit 12 and the other pair 3, 4 being controlled by the other circuit 13. The pulse width control inputs 14 of the circuits 12, 13 are connected to voltage sensing means in the bridge supply circuit so that the pulse width of the control signals A, B, C, D is determined in accordance with the bridge supply level. The arrangement is such that the control circuits 12, 13 although not be designed to fail-to-safety standards operate in a fail-safe manner to provide a constant level output of the input signal.

Abstract: A semiconductor housing particularly useful for very high current devices, e.g. transistors and G.T.O. thyristors, in which a control lead to the base or gate of the device, which also has to carry a relatively high current, passes through an insulating wall of the housing. This control lead is enclosed within a tube which passes through an insulating wall of the housing and which is hermetically sealed to it, the tube is also hermetically sealed to the conductor at either end. The coefficient of expansion of the tube is chosen so as to be substantially the same as the coefficient of expansion of the material of the insulating wall, which may be made of ceramic material or the like. The arrangement avoids corrosion effects as a result of the entrapment of plating salts etc. which are known to adversely affect the assembly and especially the electrical performance of the control lead connection.

Abstract: A governing factor of the switching characteristics of a thyristor device is base layer resistivity, for example in a gate turn-off device, to maximize load current it is preferably low but, the reverse breakdown voltage of the emitter-base junction is improved if the resistivity is high. The invention proposes a modified base layer dopant diffusion process in which the dopant diffusion process in which the dopant source is removed before completion in order that the peak of concentration is diffused-in below the surface so as to produce a graduated resistivity profile which increases nearer the surface. In shorted-emitter thyristors the surface region is masked during subsequent emitter diffusion so that the remaining short columns contain higher resistivity material.

Abstract: A sliding door arrangement which provides lateral support for the free edge or bottom nose corner of a door comprises a retractable member which is raised through an aperture in the floor or doorway threshold to interlockingly engage said edge of the door in the closed position. When the door is opened the engaging member is automatically retracted to lie flush with the floor surface. The member is carried by a rocking lever under the floor which is linked to another counter-balanced lever nearer the door frame which also has a raised protrusion which is abutted by a cam on the door as it reaches the closed position.

Abstract: A force-applying system is provided which combines a first direct electric actuator and a second, electrically controlled spring-applied actuator. The output force-applying member of the second actuator is operable through a force-transfer device one member of which is operatively loaded by the force-applying spring of the second actuator and another member of which is controlled by a solenoid. The operation is such that when the solenoid is energized, the members are out of engagement and when the solenoid is de-energized, the two members are engaged so as to operatively connect the spring to the output member. The solenoid and the electric motor of the direct actuator are controlled through an electrical circuit which ensures that the electric motor of the direct actuator is de-energized when the solenoid is de-energized.

Abstract: An electro-pneumatic brake system in which an electric brake demand signal controls the energization of a stepping motor. The shaft of the motor is threadedly engaged with a captive nut which bears against an abutment carried by a brake controlling valve, the opening of which determines brake actuating pressure downstream of the valve. Rotation of the motor therefore directly controls the brake pressure by movement of the valve.

Abstract: A control valve arrangement adapted to produce and maintain a pilot signal comprises a number of standard modules. The basic element has two standard modules, each of which includes a diaphragm-controlled on-off valve. An input signal is applied to a first valve against a reference pressure such that when the valve is on, a signal is generated and held as a pilot pressure. A second valve responds to a fall in input signal pressure to cancel out pilot pressure. The two valves together constitute a bistable operator. A particular use of this operator is in a railway braking system in which the first valve is used as an application valve and the second valve is used as a release valve. A third module may be used as a pilot pressure-maintaining valve. The pneumatically-operated diaphragm assembly shown in FIG. 1, comprises three modules, 1, 2 and 3. Module 1 is the brake application module, module 2 is the release module and module 3 is an optional pilot pressure-maintaining module.

Abstract: An F.M. demodulator of the phase quadrature type is adapted for fail-safe operation and in particular for use in a railway signalling system. A Bessel band-pass filter is chosen for the design basis of the phase delay arm, its characteristics, failure modes and resulting effects are considered and the design adaptations required to avoid the potentially unsafe effects of failures are determined. Due to loss of failure in the unmodified filter design the slope of the phase characteristic can increase effectively broadening the filter bandwidth and reducing attenuation of out-of-band signals which could, as a result, provide a false output. The demodulator may be combined with a fiber-optic link to form part of a complete signaling transmission system.

Abstract: An arrangement for checking the integrity and operability of a semiconductive device including a control circuit for injecting test signals into a normal control signal to induce a momentary change of the operating condition of the semiconductive device, a sensing circuit connected in parallel with the semiconductive device sensitive to an induced change to produce an output indicating the induced change, and a correlation circuit operative to correlate the test pulses with the sensed response which is arranged to carry out predetermined action in the event that the correlation circuit determines a state of inoperability of the semiconductive device.

Abstract: An empty-load railway vehicle braking system wherein the piston-and-cylinder of the empty-load valve operates against the rack of a rack-and-pinion arrangement of which the pinion is drivingly connected to an arresting member the position of which is determined by the loading of the vehicle.

Abstract: An electric actuator having an electric motor operable to determine the output force generated on an output member by a spring system, and an adjustable stop by which can be limited the maximum value of the output force, the position of the adjustable stop being variable in accordance with variation of the required maximum value of the output force to be exerted by the output member.

Abstract: The present invention provides an electric actuator having an output member movable from a first variable position to a second variable position; an electric motor operable to control a spring system to exert an output force on the output member when in its second position; a device for generating an electrical signal when the output member is about to leave the second position as it returns to the first position; and a motor-control electrical circuit which recognizes the generation of the electrical signal and thereafter operates the electric motor to a pre-determined degree to move the output member a corresponding pre-determined distance back to the first position so that there is preserved a substantially constant distance between the first and second positions.