Abstract: An electric actuator which comprises an electric motor operable to a varying degree correspondingly to cause a spring to generate on an output member an output force which varies in accordance with the varying degree of operation of the electric motor.

Abstract: An electric actuator having an output member movable into and out of a force-exerting position, electric motor means operable both to move the output member to and from its force-exerting position and, when the output member is in that position, to control a spring system to generate a required output force on the output member, and means for withholding the spring system from generating a force on the output member until the output member is determined as being in its force-exerting position.

Abstract: A piston sealing arrangement particularly for pistons used in railway brake cylinders, comprising a flexible piston seal and a multi-function ring in the form of a separate wear band. The wear band is allocated on the pressure side of the piston seal to minimize radial motion of the sealing ring if the piston rocks.In FIG. 1 is shown a pneumatic brake cylinder 10 in which is located a piston 11. Piston 11 has an external flange 14 which backs a piston seal 15. Located on the pressure side of the piston seal 15 is a wear band 16 which is located very close to the piston seal 15 on the pressure side. The rubber piston seal 15, has a sealing lip 18 in contact with the inner wall of the cylinder 10.The wear band is chamfered at 19 so that the portion 20 of the wear band closest to the sealing ring 15 is the part of the wear band that actually contacts the inner wall of the cylinder.

Abstract: An electric actuator having an electric motor operable to control the output force generated by a spring system of the actuator on an output member of the actuator; measuring means responsive to a characteristic of the spring system which is indicative of the value of the output force; and an electrical circuit by which operation of the electric motor can be initiated and can be terminated when the measuring means detects the characteristic as being indicative of the output force of a required value.

Abstract: An interlocking system comprising a plurality, e.g., three, of parallel sub-systems operating asynchronously to produce identical replicated outputs which are mutually compared to determine the correct output and disqualifying a minority output thereby ensuring high system integrity. Each sub-system includes a similar arrangement for computing the difference between all possible pairs of sub-systems. Comparison of these results with a reference table of all possible difference results and then comparison of the difference equations yields a common factor which is the sub-system producing the error. Action can then be taken to disqualify its output, e.g., by switching-off its power supply. A final output is taken, preferably from one sub-system, with a second as standby.

Abstract: A railway signalling receiver in which a signal carried by the railway lines is sensed and the sensed signal is sampled, digitized and subjected to a discrete Fourier transform operation which transform the time domain samples into the frequency domain. The frequency content of the signal may then be examined in order to identify the original signal or to decode the information carried. The signal may be a frequency shift keyed carrier signal. A technique of maintaining the safety of the system by discriminating against potentially confusingly similar ASK signals, which can arise spontaneously in electric traction territories, is described. A technique of digitally heterodyning down a carrier signal so that the transform operates on the lower sidebands frequencies in order to maximize efficiency of the transform calculations is also described. The receiver is useful as a jointless track circuit receiver and also in a part of the train borne equipment of an automatic train protection system.

Abstract: A railway vehicle braking system is provided with a "snow brake" control arrangement which is used in freezing temperatures to apply a small brake force for prolonged periods to engage blocks or shoes on the vehicle wheels to reduce icing. The "snow brake" control arrangement itself includes an pneumatic valve system that includes a relay valve unit which, in a first mode, provides "snow brake" operation and, in a second mode, provides for application of brake pressure from the straight air pipe to the brake cylinders. A solenoid valve, actuated responsive to energization of a control solenoid by a snow brake control switch, controls connection of "snow brake" pressure from a supply reservoir to a control chamber of the relay valve. When the straight air pipe is pressurized responsive to call for service or emergency braking, the solenoid is de-energized and the control chamber vents to atmosphere through the solenoid valve.

Abstract: Vital transmission checking apparatus is disclosed for a communication channel which transmits quasi-static signals representing several alternative states of a function, e.g., the control function for a signal in a railway control system, one of which states is potentially unsafe. Each function channel transmits a digital signature code of predetermined length which is continuously repeated in a selected form, e.g., non-inverted, inverted, or alternately inverted and non-inverted, to represent the different states of the function. To provide a check of proper transmission, the repeated signature code is periodically corrupted in accordance with a predetermined error pattern which is repeated at a lower repition frequency than the code. The channel receiver is so designed that its output can only be held in the selected state when both the signature code and the error pattern in the received signal are correct. If a fault is detected, the receiver output is shifted to the most safe state of the function.

Abstract: This invention relates to a valve assembly for a railway braking system, including a brake cylinder pressure-maintaining valve which, during brake application, takes air from the brake pipe and feeds it into the brake cylinder until it reaches minimum brake pressure. To avoid the need for an extra valve, the brake cylinder pressure-maintaining valve is used as a quick service bulb exhaust valve during brake release and member are provided to ensure that the brake cylinder pressure maintaining valve opens immediately on brake release. Once the brakes have been applied, pressure in the brake cylinder is maintained from the quick service bulb 59. Brake cylinder exhaust pressure taken from a point 124 after the brake cylinder exhaust valve 50, but before the brake cylinder exhaust choke 70, is directed to chamber G above the inshot and brake cylinder-maintaining valve diaphragm 131. Since the pressure in port 124 upstream of the brake cylinder exhaust choke 70 attains a pressure well within 10 p.s.i.

Abstract: This invention relates to braking systems for railway vehicles in which a fall in brake pipe pressure is employed to initiate braking via a brake cylinder inlet valve.In accordance with the present invention, the brake cylinder inlet valve is rendered in-operative by the absence of auxiliary reservoir pressure, thus dispensing with the need for a complicated mechanical sequence requiring fine machining tolerances etc. and avoiding the necessity of employing an additional valve.The brake cylinder (BC) inlet valve 60 is operable by a diaphragm 54. When the system is fully charged, the brake cylinder inlet valve 60 is closed as shown in the accompanying drawing. The diaphragm 54 is subject to brake pipe pressure in chamber C and to auxiliary reservoir pressure in chamber D. In the absence of auxiliary reservoir pressure in chamber D, the pressure in chamber C holds the diaphragm in the position shown and prevents the ball valve 60 from being opened, thus preventing brake application until braking is demanded.

Abstract: This invention relates to a railway braking system in which a drop in brake pipe pressure calling for brake application initiates a pilot pressure and this pilot pressure is used to operate other valves pneumatically to effect braking. In this system, during the initial part of a brake application, air flows to atmosphere through a pilot exhaust choke. To avoid problems during release of the braking, it is proposed to isolate or restrict this pilot exhaust choke during at least the initial part of the brake application stage. To achieve this, an interlock valve is introduced into a passage between a release ball valve and a pilot exhaust choke. The interlock valve is operated by a diaphragm biassed by a spring and separating two chambers. Brake pipe pressure is applied to the first chamber and auxiliary reservoir pressure to the second chamber. A very small drop in brake pipe pressure closes the valve and cuts off connection between the release ball valve and the pilot exhaust choke.

Abstract: A contact shim for insertion between an electrode internal contact member and a contact surface of a semiconductor element in a semiconductor device assembly. The shim has a generally continuous body (2) provided with a number of apertures (4, 5, 6, 7) having a land (1) or finger extending at least partially thereacross, preferably a land comprises a bar which bisects an aperture (4, 5, 6, 7). The apertures and bisecting lands may be used as visual guides in aligning the shim with reference marks on the contact surface of the semiconductor element and, the means of attaching the shim to the element may be applied to the lands in order that any distortion consequent upon attachment is confined to the lands leaving the body of the shim undistorted.

Abstract: Scraper rings are known which are mounted in the back plate of a hydraulic cylinder to scrape a hydraulic piston rod. Known scrapers are not very suitable for applications where the piston rod is liable to movement and vibration e.g. in pneumatic pistons and cylinders. The present invention provides a shaft scraper ring arrangement in which the scraper ring is so supported so as to be movable, to a limited extent, in a plane transverse to the shaft or rod which is to be scraped. Cylinder 1 contains a piston 2 and a back plate 3. Supported centrally in the back plate 3 is a housing 4 which supports a plate 5 carrying a rod scraper 5a. Piston 2 is supported by a piston rod 2a which is scraped by the rod scraper. A seal 10 located on the rod scraper plate 5 bears against the rod 2a. Rod scraper plate 5 has limited freedom for movement in a plane transverse to the rod 2a. The plate 5 is loosely carried by the housing 4 being located between two felt oil retaining annular rings 8.

Abstract: A road brake automatic slack adjuster mechanism having input and output members each pivotable about a common axis to apply and release a brake-applying force. These two members are interconnected by a force-transmitting member which, on the one hand, is threadedly engaged with the output member and, on the other hand, is releasably clutched to the input member. To effect slack adjustment, the mechanism includes brake-clearance determining device settable to predetermine the required brake clearance. This brake-clearance determining device includes a stepless clutch which interconnects the brake-clearance determining device and the output member. The clutch is released upon pivotal movement of the output member in a brake-force applying direction, equating with the required brake-clearance to allow the clutch to slip during movement of the output member corresponding to excessive clearance.

Abstract: A plug-in "universal" information display module for use in an information display system, e.g. a train describer system, of the kind in which all information to be displayed is multiplexed onto a data highway routed to all display locations. The heart of the module is a microprocessor which "listens" to the multiplexed messages on the data highway, selects for decoding only those containing the address of its location and produces a decoded message in the form of a two-dimensional matrix display format suitable for scanning to drive an L.E.D. matrix display panel. An address programming means is connected to an address input to the microprocessor so that a module is normally programmed with a location address at the time of connection to the data highway either by a manual operation or automatically upon mating of the plug connector.

Abstract: A plug door for a vehicle, such as a railway carriage, is carried and driven by a swinging lever which has a sliding fulcrum mechanism the effect of which is to flatten the arc through which the door is carried. The edge of the door which trails in an opening movement is guided either by means of a relatively long pivot arm or by a curved or straight track. The alternative guide means give different trajectories to the leading edge of the door, the long pivot arm guide keeps the door closest to the side of the vehicle during opening. A duplicate swinging lever with sliding fulcrum mechanism as a guide for the trailing edge will move the door parallel to the side of the vehicle and the sliding fulcrums will substantially reduce the outward excursion. By mounting the driving swinging lever over-center, i.e. closer to the trailing edge of the door the plug action is provided for so that a closed door may be flush with the vehicle skin.

Abstract: A railway vehicle braking system is provided with snow-brake control means operable in freezing temperatures for overriding the normal full brake release condition in a vehicle coasting or traction situation to apply a small brake force for prolonged periods to engage blocks or shoes on the vehicle wheels to reduce icing. The snow brake control means itself includes an override arrangement for, from time-to-time, effecting complete but temporary release of such a snow brake application so as to enable whatever slack adjustment is necessary to thereby insure continued validity of the brakes for a service application despite brake wear resulting from prolonged snow brake application.

Abstract: Empty/load control valve apparatus is proposed for use with direct release triple valves which operate by switching in an extra volume with the brake cylinder for empty loaded conditions. This improvement provides a valve operated in response to leakage away of brake cylinder pressure to enable dissipation also of the extra volume pressure to prevent brake cylinder isolation resulting from the extra volume pressure.

Abstract: When the forward load current through a thyristor is commutated it does not immediately recover its availability to block forward current flow due to re-applied forward voltage, the time taken for this blocking ability to return is known as the thyristor turn-off time. Hitherto a low valued current has been passed through the thyristor immediately after commutation in the reverse direction to achieve reduction of the turn-off time. The present invention operates to achieve a greater reduction of the turn-off time by passing a low-valued current through the thyristor in a forward direction immediately after commutation. Several alternative circuit arrangements and operating configurations for supplying the forward recovery current are described.

Abstract: A rail vehicle braking apparatus which operates with brake control valves on successive vehicles of a train controlled by pressure in a brake pipe extending along the train has warning means responsive to rising brake pipe fluid flow to warn of possible non-released brakes in the train and the warning means being inhibited by a rising fluid pressure-sensing means to prevent an undesired warning due to brake pipe fluid flow during release of the brakes.