GB2432565A

GB2432565A - Pantograph with sensors

Info

Publication number: GB2432565A
Application number: GB0524119A
Authority: GB
Inventors: Peter Keen
Original assignee: AEA Technology PLC; DeltaRail Group Ltd
Current assignee: DeltaRail Group Ltd
Priority date: 2005-11-28
Filing date: 2005-11-28
Publication date: 2007-05-30
Anticipated expiration: 2025-11-28
Also published as: GB2432565B; GB0524119D0

Abstract

A pantograph, used by an electric train to pick up electric power from an overhead electrical line incorporates a pickup head which includes at least one contact strip (33) connected by left and right side beams (32) which are pivotally connected to a support frame (24, 22). Each side beam (32) is shaped so as to define a load cell structure to transmit forces, the load cell structure incorporating strain gauges so that the vertical forces on each side of the pickup head can be measured. The side beam (32) is slotted to provide parallel bars (50), forming a hollow rectangle, between lower and upper narrow support bars (48,52).

Description

Pantograph with Sensors The present invention provides a pantograph

incorporating sensors so that the forces exerted between the pantograph pickup and an overhead electrical line can be monitored.

Pantographs are used on electric trains to pick up electric power from an overhead electrical line. It would be desirable to be able to monitor the forces exerted between the pantograph pickup and the overhead line, and such measurements can enable faults in the installation of the overhead line to be detected, and also variations in the performance of the pantograph itself, for example due to mechanical resonances. However electronic components mounted on the pantograph may effect its aerodynamic properties, and force sensors in the pickup of a pantograph may be affected by internal stresses within the pickup itself, which vary with its temperature. It will also be appreciated that any electronic components on the pickup are in an electrically-noisy high-voltage environment, which makes measurement difficult.

According to the present invention there is provided a pantograph incorporating a pickup head, the pickup head comprising at least one contact strip connected by left and right side beams, the side beams being pivotally connected to a support frame, wherein each side beam is shaped so as to define a load cell structure to transmit forces.

The load cell structure on each side incorporates strain gauges, so that the vertical forces on each side of the pickup head, due to contact of the pickup head with an overhead line, can be measured. The strain gauges are preferably connected in the form of a balanced bridge whose output is connected to an amplifier. The amplifier signals are preferably digitised, and supplied to a microcontroller through an optical isolator.

Preferably the microcontroller incorporates a multiplexer and an encoder, and provides output signals via a light-emitting diode to an optical fibre.

Preferably the pantograph is also provided with accelerometers arranged to detect vertical and longitudinal accelerations, and the signals from such accelerometers are also supplied via a digitiser to the microcontroller.

This arrangement ensures that there need be only two cables connected to the pantograph pickup head for the sensors: one cable to provide electrical power, which may for example be at 12 V supplied from a rechargeable battery, and an optical fibre to carry the signals representing the measurements of forces and accelerations. Preferably the pantograph incorporates hollow arm members pivotally connected together, and these cables are within the hollow arm members, so that the aerodynamic properties of the pantograph are not altered.

It will also be appreciated that such a pantograph may also be provided with sensors of other parameters, such as the height of the pickup head above the base of the pantograph; the displacements of the arms of the pantograph; and measurements of airflow, for example using pitot tubes.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of a pantograph; Figure 2 shows a plan view in the direction of arrow 2 of figure 1, showing the pickup head; Figure 3 shows a perspective view in the direction of arrow 3 in figure 1 (and figure 2), showing one side of the pickup head; and Figure 4 shows a block diagram of the electronic circuitry of the sensors of the pantograph of figure 1.

Referring to figure 1, a pantograph 10 is mounted on a roof of a railway vehicle 12. The pantograph 10 consists of a base frame 14 mounted on electrical insulators 16; a lower arm 18 is of rectangular cross-section, and at one end is pivoted to the frame 14; at its other end it is pivoted at an elbow linkage 20 to an upper arm 22 which is of circular cross-section, tapering along its length. To the upper end of the upper arm 22 is pivoted an apex frame 24, and this carries a pickup head 30. The lower arm 18 can be raised by a pneumatic cylinder (not shown), and the elbow linkage 20 ensures that when the lower arm 18 is raised, the upper arm 22 is raised too (relative to the horizontal) Referring to figure 2, the apex frame 24 is of generally U-shape, with two diverging arms to whose ends the pickup head 30 is pivotally connected (as described below) . The apex frame 24 also includes two short arms carrying small aerofoils 26; adjusting the angle of the aerofoils 26 enables the aerodynamic lift forces on the pantograph 10 to be adjusted.

Referring also to figure 3, the pickup head 30 consists of a generally rectangular frame made up of two side beams 32 and two contact strips 33 each of which consists of a graphite layer 34 fixed onto an aluminium bar 35 of rectangular hollow cross-section, the bars 35 being fixed by bolts 36 to flanges 37 on the side beams 32. Left and right horns 40, formed of tubular steel, are also bolted on to the flanges 37, and project outwardly and downwardly from either side of the rectangular frame. The features of the pantograph 10 described up to this point are known in some existing pantographs, and it will be appreciated that the power supply to the vehicle 12 will be provided by an electric current flowing from the pickup head 30 through the upper arm 22 and the lower arm 18 to the base frame 14, from where a heavy-duty cable (not shown) would take the current to an input transformer within the vehicle 12.

As shown in figure 3, each side beam 32 rests on a pivot pin 42 projecting from the apex frame 24 and which locates in a slot 43 in the underside of the side beam 32, and each is further secured by a pin 44 locating in either an open-ended slot 45 (as shown) or a short closed-ended slot 46, the slots 45 and 46 being of such dimensions as to prevent the pickup head 30 turning over, by preventing it turning by more than about 10 around the pivot pins 42.

Each side beam 32 is slotted so as to define a narrow support bar 48 about 20 mm wide directly above the pivot pin 42; directly above this the slots define a pair of 6 mm-wide parallel bars 50 forming a hollow rectangle, the bars 50 being about 150 mm long and being joined together at their ends; above this is another narrow support bar 52 about 20 mm wide. The support bars 48 and 52 are directly opposite each other, and aligned with the midpoints of the parallel bars 50, which in normal operation extend approximately horizontally. It will be appreciated that the support bar 48, the parallel bars 50 and the support bar 52 are integral with each other, being defined by slots in the side beam 32. The support bar 52 is integral with the remainder of the side beam 32, which as described above links the contact strips 33 of the pickup head 30.

The forces acting on the pickup head 30 in the vertical direction are consequently applied by the support bars 48 and 52 to the parallel bars 50. This arrangement consequently acts as a load cell.

Referring now to figure 4 the electronic circuitry associated with the pantograph 10 is shown diagrammatically. Within each load cell constituted by one of the side beams 32, strain gauges 60 are attached to the parallel bars 50, arranged symmetrically on either side of the midpoints (where the support bars 48 and 52 are), and these strain gauges are electrically connected into a bridge circuit (as shown in figure 4), connected to a regulated low voltage power supply 62, and the output of the bridge is supplied through an amplifier 64 and an analogue-to-- digital converter 66 to an optical isolator 68. The optical isolator 68 provides digital signals to a microcontroller 70; there is a single microcontroller 70 which receives the digital signals from the strain gauges 60 on each of the side beams 32.

The microcontroller 70 also receives digital signals through similar optical isolators 72 and ADCs 73 corresponding to other measured parameters, for example an accelerometer 74 measuring the horizontal acceleration of the pickup head 30 along the direction of the railway line, and another accelerometer 75 measuring the vertical acceleration of the pickup head 30.

The microcontroller 70 temporarily stores the data from the various sensors, encodes it, and multiplexes it, providing electric output signals to a light-emitting diode 78 coupled to an optical fibre 80. Preferably the data signals from each sensor are transmitted down the optical fibre 80 at least 200 times a second.

An electrical cable providing the low voltage power supply to the electronic circuitry, and the optical fibre 80 carrying the data signals in digital form from all the sensors, extend in ducts within the apex frame 24, the upper arm 22, and the lower arm 18. The power supply may be a battery 62 mounted within the base frame 14, while the optical fibre 80 may extend through the roof of the vehicle 12 to a data store or analysis unit within the vehicle 12. The microcontroller 70 is preferably no more than about 60 mm by 30 mm by 20 mm, and the electronic components of the microcontroller 70 are preferably enclosed within a metal container to suppress interference, so that their operation is not affected by the high voltage noise signals which may arise in their vicinity. Indeed, other components of the circuitry such as the amplifier 64, the analogue-to-digital converter 66 and/or the optical isolator 68 may also be within this container. This container may be mounted within the upper arm 22.

It will be appreciated that the pantograph 10 may incorporate sensors for other parameters. For example it may incorporate a sensor to measure the pantograph voltage, and hence to detect any loss of contact with the overhead line; this may be a high voltage potential divider. It may also incorporate sensors to measure the height of the pickup head 30 above the base frame 14, and air speed sensors such as pitot tubes.

Claims

Claims 1. A pantograph incorporating a pickup head, the pickup head

comprising at least one contact strip connected by left and right side beams, the side beams being pivotally connected to a support frame, wherein each side beam is shaped so as to define a load cell structure to transmit forces.

2. A pantograph as claimed in claim 1 wherein the load cell structure on each side incorporate strain gauges, and the strain gauges are connected in the form of a balanced bridge whose output is connected to an amplifier.

3. A pantograph as claimed in claim 2 wherein the signals from the amplifier are digitised, and transmitted through an optical fibre.

4. A pantograph as claimed in any one of the preceding claims wherein signals representing a plurality of measured parameters are supplied to a microcontroller through optical isolators, and the microcontroller provides output signals via a light-emitting diode to an optical fibre.

5. A pantograph as claimed in any one of the preceding claims wherein a cable providing electrical power to sensors in the pickup head and a cable transmitting signals representing measurements by those sensors extend within hollow arm members of the pantograph.

6. A pantograph as claimed in any one of the preceding claims wherein at least one electronic component selected from an amplifier, digitiser, an optical isolator and a microcontroller is installed within a hollow arm member of the pantograph.

7. A pantograph incorporating sensors in the pickup head, the pantograph being substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.