GB2364124A

GB2364124A - Load measuring device

Info

Publication number: GB2364124A
Application number: GB0011141A
Authority: GB
Inventors: Andrew Douglas John Buckingham
Original assignee: SERCO RAILTEST Ltd
Current assignee: SERCO RAILTEST Ltd
Priority date: 2000-05-10
Filing date: 2000-05-10
Publication date: 2002-01-16
Anticipated expiration: 2020-05-10
Also published as: GB0011141D0; GB2364124B

Abstract

A load force measuring device (10) locatable in a rail baseplate (12) of generally known design and operable to measure vertical and horizontal load forces (Fv, Fl) imparted by a rail vehicle (V) on a rail (R) mounted on the baseplate (12). The baseplate is that which mounts the rail on the sleeper. The device (10) comprises electrical strain gauges arranged in Wheatstone Bridge configuration.

Description

2364124 Load Measuring The present invention relates to load measuring and

in particular but not exclusively to measuring load forces imparted upon a rail by a rail vehicle.

Not least for reasons of railway safety and maintenance, it is necessary to be able to reliably and accurately measure the load forces imparted by rail vehicles on the rails on which they run.

A railway line usually comprises a series of two parallel rails each of which is made of rail sections located end-on-end to provide co-linear tracks.

The rails are usually mounted on support members often termed sleepers which extend generally laterally beneath the rails Baseplates are usually used to mount the rails on the sleepers The design of baseplates has developed over the years to provide effective and secure mounting of rails on sleepers.

According to the present invention there is provided a load measuring device locatable in a rail baseplate of generally known design and operable to measure load forces imparted by a rail vehicle on a rail on the baseplate.

Preferably the device supports a rail, in use, desirably to align the rail at its normal height relative to the baseplate Preferably the device is locatable for use so as not to interfere with the usual arrangement for attaching the rail to the baseplate.

Preferably the device is located, in use, generally centrally within a baseplate, and may be accommodated in a recess formed in the baseplate.

Preferably the device sits, in use, on the baseplate on flexible feet formations whereby providing the device with flexible mounting, in particular rotational flexibility, to allow the device selective movement in use The flexible formations are preferably provided generally along opposite edges of an underside of the device, and may be produced by working the material thereof, which is preferably steel, in conditions of relatively high stress.

Preferably the device is operable to measure both substantially vertical and substantially horizontal load forces imparted onto a rail in use The device preferably measures the load forces electrically, desirably using electrical strain gauges.

Preferably the device supports a rail on two surfaces, which surfaces are desirably elongate and preferably extend across the whole or the majority of the width of the device along which a mounted rail extends The support surfaces may be resilient and/or deformable to accommodate variations in the surface of a rail bearing thereon, whereby to ensure accurate line loads are applied across the device.

Preferably a plurality of strain gauges is used to measure load forces at predetermined locations on the support surfaces Preferably a strain gauge is located at or near the ends of each of the elongate support surfaces to measure substantially vertical load forces acting on a supported rail A further plurality of strain gauges may be provided to measure substantially horizontal load forces imparted on a supported rail The said plurality and further plurality of strain gauges may be located generally adjacent each other A further set of strain gauges may be located away from the support surfaces to provide for compensatory measurements, such as for ambient temperature changes.

Preferably the strain gauges are operable to measure compression and extension of sensor means therein caused by load forces imparted to a supported rail Preferably said sensor means are operable to vary in electrical resistance as a consequence of exerted load forces Preferably the strain gauges are electrically configured into a Wheatstone Bridge for measurement purposes.

Preferably the plurality of strain gauges operable to measure substantially vertical load forces are configured in a first Wheatstone Bridge and the further plurality of gauges operable to measure substantially horizontal load forces are configured into a second Wheatstone Bridge.

Conditioning and/or amplifier circuitry may be provided, desirably for each load direction circuitry Such circuitry is preferably located within the baseplate.

Preferably the electrical components of the device are potted in a resin or similar material to provide protection thereof, for example against environmental factors.

The device may be electrically insulated from the baseplate The support feet may be comprised of electrically insulating material and/or mounted on electrically insulating material.

The device may be resiliently mounted on the baseplate The resilient mounting may be electrically insulating.

Further according to the present invention there is provided a rail baseplate of generally known design adapted to accommodate a load measuring device as hereinbefore described in any of the above eleven paragraphs.

The invention also provides a rail baseplate comprising a load measuring device substantially as described in any of the preceding twelve paragraphs.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which:- Fig 1 is an exploded view of a rail assembly comprising a load measuring device and baseplate according to the present invention; Fig 2 is a perspective view of a load measuring device according to the present invention; Fig 3 is an underside perspective view of the device of Fig 2, with electrical circuitry and covering resin removed to show the configuration of strain gauges; Fig 4 is an underside view of the device of Fig 2; Fig 5 is a diagrammatic view of the load measuring device in use to measure substantially vertical load force Fv; Fig 6 is a diagrammatic representation of a Wheatstone Bridge of the circuitry of Fig 5; Fig 7 is a diagrammatic representation of the device of the invention when measuring lateral load force Fl; Fig 8 is a diagrammatic Wheatstone Bridge illustration associated with measurement of a lateral force Fl; Fig 9 is a perspective view of a rail assembly of a further embodiment of the rail assembly; Fig 10 is a diagrammatic cross-sectional view of a load measuring device and baseplate arrangement according to a further embodiment of the present invention; Fig 11 is a similar view to Fig 10 of a still further embodiment of the invention; and Fig 12 is a diagrammatic representation of a flexible mounting foot of the device according to the invention.

Referring to the drawings, there is provided a load force measuring device 10 locatable in a rail baseplate 12 of generally known design and operable to measure load forces Fv/Fl imparted by a rail vehicle V (Figs 5 and 7) on a rail R mounted on the baseplate 12.

The invention also provides the rail baseplate 12 comprising a load measuring device 10 as will be described, and also a rail baseplate of generally known design adapted to accommodate a load measuring device 10 again as described herein.

In more detail, the baseplate 12 is generally of known design comprising a body 14 through which passages 16 extend The passages 16 receive fixing bolts 18 which threadedly engage in a sleeper S on which the baseplate 12 is mounted to secure the baseplate 12 in conventional manner.

In accordance with the invention the baseplate 12 comprises a generally central recess 18 to accommodate the load measuring device 10 The provision of the recess 18 may to some degree affect the strength of a conventional baseplate 12, and it may be necessary to compensate for this by using stronger material and/or provide strengthening features to the baseplate 12.

The recess 18 is dimensioned to snugly receive the device 10 and comprises two parallel support ledges 20 on which the device 10 sits as will be described The recess 18 may be open at its lower end to allow electrical wiring 22 to extend through the bottom of the baseplate 12 to channelling 24 in the sleeper S The wiring 22 connects the device 10 to control apparatus (not shown) at the side of the rail track as will be described.

The recess 18 and support ledges 20 are configured to support a rail R, in use, desirably in alignment at its normal height relative to the baseplate 12 and (CM) also so as not to interfere with the usual Pandro{clip arrangement 26 used to mount the rail R on the baseplate 12.

The baseplate 12 may be comprised of cast iron, steel or other suitable material Drainage channels 28 are provided in the underside of the baseplate 12 to cooperate with drainage channels 30 formed in the sleepers to facilitate drainage of rain water and other liquid from the arrangement.

The device 10 comprises a generally rectangular body 32 along the in use upper surface of which extend two load surfaces 34 These extend generally parallel in spaced configuration, each having stress relieving grooves 36 running along both sides Four strain gauges VI, V 2, V 3 and V 4 (Fig 3) are connected generally at respective ends of the elongate load surfaces 34, such that V 1 and V 2 are at opposite ends of one elongate load surface 34 a and V 3 and V 4 substantially at opposite ends of the other 34 b.

The strain gauges VI, V 2, V 3, V 4 are of generally known design, and essentially comprise a resistance which varies according to the load forces experienced by a sensor in each gauge The gauges VI, V 2, V 3, V 4 are electrically configured together in a Wheatstone Bridge as shown in Fig 6 such that any variations in their resistance is detected and used to determine the load force as will be explained The strain gauges VI, V 2, V 3 and V 4 are used to detect substantially vertical load force Fv (Fig 5) as will be explained A second set of strain gauges LI, L 2, L 3 and L 4 (Fig 3) are located in similar configuration and adjacent to VI, V 2, V 3 and V 4 and are configured in a second Wheatstone Bridge (Fig 8) to detect substantially lateral load Fl (Fig 7), again as will be described.

Further strain gauges Dl, D 2, D 3 and D 4 are located around the centre line between the parallel load surfaces 34 to provide for compensation on variations in resistance of the gauges VI, V 2, V 3, V 4 as a result of environmental factors, such as ambient temperature changes.

The various gauges V 1-V 4, L 1-L 4 and D 1-D 4 are configured as mentioned above in Wheatstone Bridges and once tested and calibrated are potted in a resin 38 (Fig 4) for protection against environmental damage The electrical wiring 22 extends from the resin 38 to pass through the bottom of the baseplate 12 for connection to processing apparatus (not shown) outside of the rail track.

Referring to Figs 5 and 6, the gauges VI, V 2, V 3 and V 4 measure the load force components P 1, P 2 on the respective load surfaces 34 The sum of the forces P 1, P 2 equates to the vertical load force Fv imparted by vehicle V on the rail R.

Fig 6 diagrammatically shows how the strain gauges V 1-V 4 and D 1-D 4 are configured in a Wheatstone Bridge from which the vertical load Fv can be determined (following calibration) as being a function of the sum of the resistances of V 1, V 2, V 3 and V 4 less the resistances of D 1, D 2, D 3 and D 4.

That is, Fv=const (V 1 +V 2 D 1-D 2 + V 3 +V 4 D 3-D 4).

Referring to Fig 7, measurement of the lateral load force Fl equates to the force Pl minus P 2 The Wheatstone Bridge illustrated in Fig 8 shows how the resistances of the sensors LI, L 2, L 3, L 4 are configured and used to measure the lateral force Fl due to the lateral force being a function of L 1 +L 2 L 3-L 4.

That is Fl=const (L 1 +L 2 L 3-L 4).

It is an important aspect of the present invention that the device 10 can measure both lateral and vertical load forces.

The device 10 comprises two generally elongate parallel support feet 40 which rest on the support ledges 20 on the recess 18 The feet 40 are flexible to provide essential rotational flexibility needed to allow the device 10 to flex as if pivoted at each end whilst avoiding the need for pivot pins, bearings and their associated rubbing friction, wear, corrosion etc The flexibility in the feet 40 is obtaining by working the metal of the baseplate 12 in that region at relatively high stress Working the steel in this way has to be carefully controlled to ensure adequate fatigue life Fig 12 shows the flexibility of a support foot 40, the movement shown being exaggerated for the purposes of illustration The neck formation 42 of each foot 40 helps to ensure the feet 40 flex at the appropriate location The drainage channel 50 may divide each foot 40 part way along its length.

The device 10 is tested and then securely housed in the baseplate 12 and the strain gauges and associated circuitry tested preferably off site in a test laboratory or similar This enables very careful and accurate testing and calibration of the device 10 prior to installation.

Installation of the device 10 on a railway system simply involves removing a standard baseplate and replacing it with a baseplate 12 comprising a device 10 in accordance with the present invention The fact that the baseplate 12 has been adapted from a conventional baseplate means that simple substitution of an existing baseplate 12 can be made which with minimum disruption and no appreciable change in appearance of the assembly.

The baseplate 12 is mounted on a sleeper S using conventional fixing means 18 and the rail R is placed to reft on the load surfaces 34 and secured in place by the conventional Pandrotarraigement 26 The fact that the device 10 is housed within the baseplate 12 and beneath the rail R provides the further advantage that it is substantially protected from damage or unauthorised interference.

The device 10 is then connected to data processing apparatus, which may be housed in a housing at the side of the rail track It is envisaged that a plurality of devices 10 may be employed over an area of rail track to be tested, and these devices and their output collated and processed and analysed by the processing apparatus (not shown).

The baseplate 12 described above is primarily intended for mounting on a wood, and in particular hardwood sleeper S It will be appreciated that in accordance with the present invention, the baseplate and device can be mounted to non-wooden sleepers, such as metal and concrete In the case of metal, the baseplate 12 may be welded in place.

In cases where the sleeper may provide electrical conduction between the rails R, it is desirable to provide electrical insulating material between the device 10 and the baseplate as can be seen in Fig 10 Strips of material 44, 46 are shown running along the side and across the support surface 20 of the baseplate 12.

In high speed rail vehicle applications, it may be preferably to provide further resilient mounting of the device 10 in a baseplate, and Fig 11 illustrates the use of additional resilient material 48 between the feet 40 and the support surface 20.

Various modifications may be made without departing from the spirit or scope of the present invention.

For example, with reference to Fig 9, the load surfaces 34 may be deformable such that upon initial placement of a rail R thereon, the load surfaces 34 are deformed, preferably plastically, to accommodate any undulations or other misshapes in the lower surface of the foot of the rail, whereby to facilitate load sensing.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1 A load measuring device locatable in a rail baseplate of generally known design and operable to measure load forces imparted by a rail vehicle on a rail on the baseplate.

2 A device as claimed in claim 1, in which the device supports a rail, in use.

3 A device as claimed in claim 2, in which the device supports a rail to align the rail at its normal height relative to the baseplate.

4 A device as claimed in any preceding claim, in -which the device is locatable for use so as not to interfere with the usual arrangement for attaching the rail to the baseplate.

A device as claimed in any preceding claim, in which the device is located, in use, generally centrally within a baseplate.

6 A device as claimed in any preceding claim, in which the device is accommodated in a recess formed in the baseplate.

7 A device as claimed in any preceding claim, in which the device sits, in use, on the baseplate on flexible feet formations whereby providing the device with flexible mounting, in particular rotational flexibility, to allow the device selective movement in use.

8 A device as claimed in claim 7, in which the flexible formations are provided generally along opposite edges of an underside of the device.

9 A device as claimed in claim 7 or claim 8, in which the formations are produced by working the material thereof in conditions of relatively high stress.

A device as claimed in any of claims 7 to 9, in which the flexible formations comprise steel.

11 A device as claimed in any preceding claim, in which the device is operable to measure both substantially vertical and substantially horizontal load forces imparted onto a rail in use.

12 A device as claimed in any preceding claim, in which the device measures the load forces electrically.

13 A device as claimed in claim 12, in which the device measures forces using electrical strain gauges.

14 A device as claimed in any preceding claim, in which the device supports a rail on two surfaces.

A device as claimed in claim 14, in which the surfaces are elongate.

16 A device as claimed in claim 15, in which the surfaces extend across the whole or the majority of the width of the device along which a mounted rail extends.

17 A device as claimed in any of claims 14 to 16, in which the support surfaces are resilient and/or deformable to accommodate variations in the surface of a rail bearing thereon, whereby to ensure accurate line loads are applied across the device.

18 A device as claimed in any preceding claim, in which a plurality of strain gauges is used to measure load forces at predetermined locations on the support surfaces.

19 A device as claimed in claim 18, in which a strain gauge is located at or near the ends of each of the elongate support surfaces to measure substantially vertical load forces acting on a supported rail.

A device as claimed in claim 18 or claim 19, in which a further plurality of strain gauges is provided to measure substantially horizontal load forces imparted on a supported rail.

21 A device as claimed in any of claims 18 to 20, in which the said plurality and further plurality of strain gauges are located generally adjacent each other.

22 A device as claimed in any preceding claim, in which a further set of strain gauges is located away from the support surfaces to provide for compensatory measurements, such as for ambient temperature changes.

23 A device as claimed in any of claims 18 to 22, in which the strain gauges are operable to measure compression and extension of sensor means therein caused by load forces imparted to a supported rail.

24 A device as claimed in any of claims 18 to 23, in which said sensor means are operable to vary in electrical resistance as a consequence of exerted load forces.

A device as claimed in any of claims 18 to 24, in which the strain gauges are electrically configured into a Wheatstone Bridge for measurement purposes.

26 A device as claimed in claim 25, in which the plurality of strain gauges operable to measure substantially vertical load forces are configured in a first Wheatstone Bridge and the further plurality of gauges operable to measure substantially horizontal load forces are configured into a second Wheatstone Bridge.

27 A device as claimed in any preceding claim, in which conditioning and/or amplifier circuitry is provided.

28 A device as claimed in claim 27, in which circuitry is provided for each load direction.

29 A device as claimed in claim 27 or claim 28, in which the circuitry is located within the baseplate.

A device as claimed in any preceding claim, in which electrical components of the device are potted in a resin or similar material to provide protection thereof, for example against environmental factors.

31 A device as claimed in any preceding claim, in which the device is electrically insulated from the baseplate.

32 A device as claimed in any of claims 14 to 31, in which the support surfaces comprise electrically insulating material and/or mounted on electrically insulating material.

33 A device as claimed in any preceding claim, in which the device is resiliently mounted on the baseplate.

34 A device as claimed in claim 33, in which the resilient mounting is electrically insulating.

A rail baseplate of generally known design adapted to accommodate a load measuring device as hereinbefore described in any of the preceding claims.

36 A rail baseplate comprising a load measuring device substantially as described in any of the preceding claims.

37 A device substantially as hereinbefore described with reference to the accompanying drawings.

38 A rail baseplate substantially as hereinbefore described with reference to the accompanying drawings.

39 Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.