GB2430460A - Railway arrangement - Google Patents

Abstract

A railway arrangement comprises a railway track which includes a pair of parallel rails. Each rail is supported by a resilient material that partially surrounds the rail. The resilient material provides a variable amount resilience along the length of the rail. The upper surface of each rail is laterally inclined, and the amount of lateral inclination varies along the length of each rail. Also, the spacing between the rails varies along their length.

Description

RAILWAY ARRANGEMENT

This invention relates to a railway arrangement. In particular, this invention relates to a railway arrangement comprising a railway track/suspension system for supporting and guiding a railway vehicle. The invention also relates to a method of designing the railway arrangement.

A conventional railway track comprises a pair of parallel rails supported at regular intervals by spaced apart sleepers or at discrete points by a concrete pavement. The rails typically have an I-beam structure, with a head, a narrow web and a base. The rails span the spacing between the sleepers or the discrete points, and the I-beam structure provides the required vertical strength of the rails across the spans.

Where sleepers are used for the support, these are usually mounted on a ballast comprising approximately 40mm to 50mm diameter stone. The ballast * gives some resilience in support but degrades over time and use to cause misalignment of the rails. Where the rails are supported at discrete points by a rigid concrete pavement, the concrete pavement provides a firm foundation for the railway track.

In conventional arrangements, the railway track and a railway vehicle represent two separate elements of the railway system with a controlled interface at the point where the rails are in contact with the vehicle's wheels.

Where a concrete pavement is used, an overriding objective in the design and installation of conventional railway tracks has been that the rails should be supported in such a way that heavy railway vehicles passing over them do not cause any displacement of the rails. Where sleepers supported by ballast are used, heavy railway vehicles passing over them cause some displacement of the rails, but this is not controllable and degrades over time and use.

Consequently, the development of railway vehicles has been dictated to some degree by the constraints provided by conventional railway tracks. One aspect of rail vehicle design in particular, suspension design, has been based on an assumption that a railway track should provide a fixed support for railway vehicles, but with allowances for considerable degradation over time and use.

As such, complex suspension systems have been developed for rail vehicles, typically comprising two levels of springs in a duplex arrangement.

Other aspects of railway vehicle design that are directly or indirectly dependent on characteristics of conventional railway tracks include suspension requirements, wheel durability, steering performance, and the kinematic envelope of the vehicle, i.e. the space needed by the vehicle in which to run.

According to the invention, there is provided a railway arrangement comprising a railway track, the railway track including a pair of parallel rails, wherein each rail is supported by a resilient material that partially surrounds the rail, the resilient material providing a variable amount resilience along the length of the S... rail. *5*. * ...

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The variable amounts of resilience may be employed to achieve a specific designed performance of the railway arrangement at various features along the track, such as curves, bridges and tunnels. The arrangement may be effectively "tuned" to specific performance criteria.

By designing a variable amount of resilience into the supporting structure of the rails, the constraints of conventional railway tracks are avoided, thereby enabling significant improvements in the design of railway vehicles. For example, reduced input forces may enable a railway vehicle's suspension system to be simplified, with advantages in reduced weight, size and complexity. The need for a duplex suspension system may also be avoided.

Additionally, a reduction in the stroke of the vehicle's suspension system may be achieved, thereby minimising the vehicle's sway and its kinematic envelope.

As noted above, the kinematic envelope of the vehicle is the space needed by the vehicle in which to run, i.e. the total volume swept by the vehicle as it travels along a railway track.

The arrangement is preferably compatible with existing railway vehicle designs, as well as railway vehicles that have been designed to benefit from the variable resilience of the rail support.

The resilient support provided by the resilient material is preferably continuous along the length of the rails. In this way, the amount of resilience may be varied in a controlled manner. The resilient material may be an elastomer, and the amount of resilience is preferably varied by design by altering a stiffness of the elastomer by controlling its thickness, shape or density.

The amount of resilience provided by the resilient material may vary by design in the vertical and lateral directions independently. In this way, the dynamic: behaviour of the rails may be accurately controlled.

A wheel supporting surface of each rail preferably has an amount of lateral inclination that also varies by design along the length of each rail. The spacing between the rails preferably also varies along their length. These features enable the design of a vehicle's steering system to be simplified. For example, a reduction in contact forces, wear and fatigue of the vehicle's wheels enable reductions in wheel mass and strength. Increased vehicle durability and reduced maintenance requirements may also result.

A particularly preferred embodiment economically uses a low number of railway track components to achieve the variable resilience and geometry, typically three components. Also, the complexity of adjustable or variable dimension components need not be required to achieve the desired results.

In a particularly preferred embodiment, the railway arrangement further comprises a pair of shells, each shell having a channel shaped crosssection for receiving a respective rail and the resilient material. A portion of the cross- section of each shell has a narrowing that forms a detent or pinch point through which a portion of the rail has to pass during insertion of the rail into the shell to retain the rail. Such an arrangement provides for convenient installation with a snap-action fit of the rails.

The railway arrangement is preferably arranged so that forces exerted by a railway vehicle on the railway track cause resilient displacement of the railway track, thereby providing a variable positional relationship between the wheels of the railway vehicle and the road bed in the vertical and lateral directions. This is in contrast to traditional arrangement, where the positional relationship between the wheels of the railway vehicle and the road bed is generally fixed in the vertical and lateral directions, and where misalignment of the rails may occur due to settlement of ballast. *..

According to the invention, the railway vehicle, the railway rail, and its immediate fastening and support are considered as a single system for the purposes of design, with the defined boundary shifted from the rail/wheel *.

contact point to that between the rail supporting structure and the fixed pavement.

According to another aspect of the invention, there is provided a method of designing a railway arrangement, the method comprising the steps of: calculating forces exerted on the wheels of a railway vehicle (and optionally on the suspension system of the railway vehicle) and on the rails of a railway track for a given scenario; and selecting a rail supporting means to have a variable amount of resilience such that the forces on the wheels are reduced (or optimised) as compared to an arrangement having a fixed rail supporting means.

Preferably, the variable amount of resilience of the rail supporting means is further selected such that the kinematic envelope of the railway vehicle is smaller, as compared to an arrangement having a fixed rail supporting means, such as a ballasted superstructure that can subside under repeated loading.

The reduced kinematic envelope may be achieved by substantially reducing the vehicle sway.

Preferably, the method further comprises selecting an upper surface of each rail to have a variable amount of lateral inclination according to track geometry and location such that the forces on the wheels are reduced (or optimised), as compared to an arrangement having rail upper surfaces with a fixed lateral inclination with respect to a trackbed. This is in addition to conventional super- elevation of the trackbed to compensate for centrifugal forces.

Preferably, the method further comprises selecting a spacing of the rails to vary, such that the forces on the wheels are reduced (or optimised) as compared to an arrangement having a fixed rail spacing.

The invention also provides a method of providing a railway arrangement comprising: the method described above; and materially constructing the railway arrangement so designed.

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Embodiments of the invention will now be described, by way of example only, . with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view showing a first feature of a railway arrangement according to the invention; Figure 2 is a cross-sectional view showing a second feature of the railway arrangement shown in Figure 1; Figure 3 is a cross-sectional view showing a third feature of the railway shown in Figure 1; Figure 4 is a detailed cross-sectional view showing the structure of the railway track of the railway arrangement shown in Figure 1; and Figure 5 is a flow chart illustrating a method of design according to the invention.

It should be noted that all of the Figures are schematic in nature, and are not drawn to scale. The sizes of certain features have been exaggerated for the sake of clarity. Other features have been omitted for clarity.

The invention provides a railway arrangement in which the resilience, lateral inclination and spacing of the railway track rails may continuously vary. The railway track and railway vehicle can then be designed together as an integrated system, thereby optimising the suspension and steering systems, and minimising the forces on, and the kinematic envelope of, the vehicle.

Importantly, unlike completely new arrangements such as magnetic levitation systems, the railway arrangement of the invention is compatible with existing vehicles adapted for conventional railway tracks. As new vehicles are introduced and the existing vehicles are taken out of service, the suspension and steering performance of the arrangement may be progressively optimised.

Figure 1 is a schematic cross-sectional view of the railway arrangement I according to the invention. The railway arrangement I comprises a pair of parallel rails 3, 5. The rails have an I-beam structure, with a head portion 3a, 5a, a narrow web portion 3b, 5b, and a base portion 3c, 5c.

The rails 3, 5 are mounted in channels 7, 9 formed in a concrete road bed. The rails 3, 5 are secured in place in the channels 7, 9 by a resilient material II.

The resilient material 11 is an elastomer selected to provide an appropriate amount of resilience, as will be described below. The resilient material 11 provides continuous support for the rails 3, 5 along their length.

The resilient material II fills the space around the rails 3, 5, so that at least the base portions 3c, Sc of the rails are surrounded by the material 11, with at least the head portions 3a, 5a of the rails being exposed. The web portions 3b, 5b of the rails are surrounded by the material 11 to differing degrees.

For example, it can be seen form Figure 1 that the web portion 5b of the right hand rail is surrounded in the outboard side but not surrounded on the inboard side. It can also be seen from Figure 1 that the thickness of the resilient material 11 surrounding the rails 3, 5 varies in the vertical and lateral direction.

Although it cannot be seen in the Figure, the thickness of the resilient material 11 also varies along the length of the rails, for example the thickness of the base part and/or the side parts.

The varying thickness of the resilient material 11 around and along the rails 3, 5 provides a varying amount of resilient support for the rails 3, 5. Thus, when a railway vehicle travels along the rails 3, 5, the forces exerted on the rails 3, 5 by the wheels of the vehicle cause varying amounts of vertical and lateral displacement. This displacement improves the ride comfort of the vehicle.

Additionally, the above described displacement reduces the input forces to the vehicle's suspension system so that smaller, lighter and less expensive components may be employed. For example, smaller yaw dampers may be: ..

employed because of greater lateral stability. The required stroke of the suspension system is also reduced. In this way the passenger space in the vehicle may be increased without altering the overall dimensions of the * infrastructure required to accommodate the vehicle.

Another beneficial effect is that the controlled displacement of the wheels and rails causes the kinematic envelope of the vehicle to be reduced. Thus, clearance tolerances for tunnels and other structures may be reduced, thereby allowing enlargement of the vehicle without any need to enlarge the tunnels and other structures. The operational integrity of power collection systems such as pantographs and shoe gear may also be improved due to the engineering control available with the designed vehicle/rail/elastomer arrangement.

Figure 2 is another schematic cross-sectional view of the railway arrangement 1 shown in Figure 1. Referring to the Figure, it can be seen that the right hand rail 5 is laterally inclined so that its upper surface is also laterally inclined by angle e. It can also be seen that the left hand rail 3 is not laterally inclined.

Although it cannot be seen in the Figure, the lateral inclination of both rails varies along their length.

Figure 3 is another schematic cross-sectional view of the railway arrangement 1 shown in Figure 1. The Figure is intended to illustrate the feature that the spacing between the rails 3, 5, i.e. the gauge, varies along their length.

Referring to the Figure, In addition to the two rails 3, 5, a second position 13 for the right hand rail 5 is shown. The nominal spacing between the rails 3, 5 in the Figure is D(1), and the spacing between the rails when the right hand rail 5 is in the second position 13 is D(2). Thus, the rail spacing varies along the length of the rails by a distance of D(2)-D(1).

It should be noted that the distance D(2)-D(1) is exaggerated for the sake of clarity. In practice this distance is a small fraction of the rail width. : .. S... *5SS

The varying amounts of rail inclination and spacing, as described with reference to Figures 2 and 3 respectively, provide further improvements to the suspension performance of railway vehicles.

Furthermore, the varying amounts of rail inclination and spacing, together with the variable resilient support for the rails 3, 5, enable improvements to be made to the steering of the railway vehicle. In particular, wear and fatigue of the vehicle's wheels may be reduced by altering the way in which the rails impinge on and contact the wheels at turns in the railway track. Stresses imposed on the wheel sets and bogies of the vehicle may also be reduced (or optimised), thereby allowing reductions in the weight, size and cost of these components.

Figure 4 is a detailed cross-sectional view showing the structure of the railway track described above, and particularly showing the way in which the rails are supported. The Figure only shows one rail 3, but the general structure for each rail 3, 5 is substantially the same.

Referring to the Figure, the rail 3 is held in a shell 22 set in the channel 7 formed in a road bed, or slab 24, of concrete. The shell 22 has an inner profile of an open channel to receive the rail 3 whilst also clamping the rail 3 in place.

The resilient material 11 is provided between the shell 22 and the rail 3.

As noted above, the rail cross section comprises a head portion 3a, a web portion 3b and a base portion 3c. The web portion 3b effectively provides a pinched part 28. To insert the rail 3 into the shell 22, the wider base portion 3c has to pass through the pinched region of the resilient material 11, so that the rail 3 must effectively be sprung into the shell 22 with a snap-action fit.

Despite this pinched part 28 of the rail cross section, the head portion 3a, the web portion 3b and the base portion 3c have substantially the same width. The differences in width are provided primarily to enable the snap-action fitting of: .. *0S*

the rail into the shell as described above, and not necessarily to provide the conventional I-beam cross-section.

The road bed or slab 24 is shown to be lower on one side of the rail than on the other side, to allow the passage of the flange of a wheel of the railway vehicle.

However, the shell 22 provides support for as much as possible of the height of the rail 3 on both sides of the rail. In particular, the shell 22 provides support for at least part of the head portion 3a on both sides of the rail, and over the entire height of the base and web portions 3b, 3c on both sides.

The rail design of Figure 4 is described in greater detail in WO 99/63160.

A design method according to the invention will now be described with reference to Figure 5, which is a flow chart. The design method relates to the design of the railway arrangement described above.

Referring to Figure 5, the first step 101 of the method is to calculate the loads (forces) exerted on the wheels (and optionally the suspension) of a railway vehicle by the rails of a railway track for a given scenario. These loads support and guide the vehicle and are transmitted to the rail supporting means. The given scenario takes into account factors such as vehicle wheel and railway rail dimensions, weight and weight distribution of the vehicle, nominal speed of the vehicle, and the shape of the route taken by the railway track (i.e. curvature, lateral and vertical). These forces may be obtained, for example, by computer modelling. Suitable modelling techniques will be known to those skilled in the art.

The second step (103) of the method is to select a rail supporting means to have a variable amount of resilience such that the applied forces on the vehicle wheels are accommodated by the combined interaction of the resilient rail supporting means and the vehicles suspension system, as compared to a conventional arrangement having a fixed rail supporting means or ballasted track with inconsistent resilience. As the vehicle suspension requirements are: ..

reduced, the kinematic envelope of the railway vehicle is smaller as compared to the conventional arrangement. In this step, the thickness and/or stiffness of the resilient material that supports the rails is selected to provide the varying resilience. In this way, the performance requirements of the vehicle's suspension system may be substantially reduced.

The third step (105) of the method is to select an upper surface of each rail to have a variable amount of lateral inclination such that the forces on the wheels are reduced (or optimised) as compared to a conventional arrangement having rail upper surfaces with a fixed lateral inclination. This is particularly important in steering a railway vehicle.

The fourth step (107) of the method is to select a spacing of the rails to vary such that the forces on the wheels are reduced (or optimised) as compared to a conventional arrangement having a fixed rail spacing.

The above described method provides a design for a railway arrangement, which railway arrangement has the features described above with reference to Figures ito 4.

Specific embodiments of the invention have been described above. It will be apparent that various changes and modifications may be made to these embodiments.

For example, rails having an I-beam structure have been described. However, a large number of different shapes and structures are possible for the rails.

The resilient material in the exemplary embodiments is an elastomer, for example a polymer with elastomeric properties. However, different materials

may be suitable. *.. * S. * S * **.. * S... * S.. * S S *

Claims (14)

1. CLAIMS: 1. A railway arrangement comprising a railway track, the railway

   track including a pair of parallel rails, wherein each rail is supported by a resilient material that partially surrounds the rail, the resilient material providing a predetermined variable amount resilience along the length of the rail.
2. 2. The railway arrangement of claim 1, wherein the support provided by the resilient material along the length of each rail is continuous.
3. 3. The railway arrangement of claim I or 2, wherein a thickness and/or a stiffness of the resilient material varies along the length of each rail.
4. 4. The railway arrangement of any preceding claim, wherein the amount of resilience provided by the resilient material varies along the length of each rail: .. S..

   independently in vertical and lateral directions. S... * S*
5. 5. The railway arrangement of any preceding claim, wherein each rail comprises an upper surface for supporting the wheels of a railway vehicle, wherein the upper surface of each rail is laterally inclined, and wherein the amount of lateral inclination varies along the length of each rail.
6. 6. The railway arrangement of any preceding claim, wherein the spacing between the rails varies along their length.
7. 7. The railway arrangement of any preceding claim, further comprising a pair of shells, each shell having a channel shaped cross-section for receiving a respective rail and the resilient material, wherein a portion of the cross-section of each shell is narrowed to form a detent or pinch point through which a portion of the rail has to pass during insertion of the rail into the shell to retain the rail.
8. 8. The railway arrangement of any preceding claim, arranged so that forces exerted by a railway vehicle on the railway track cause resilient displacement of the railway track, thereby providing a variable positional relationship between the wheels of the railway vehicle and the road bed in the vertical and lateral directions.
9. 9. The railway arrangement of claim 8, further comprising a railway vehicle arranged to be supported and guided by the railway track.
10. 10. A method of designing a railway arrangement, the method comprising: calculating loads (forces) exerted on the wheels and/or suspension system of a railway vehicle and on the rails of a railway track for a given scenario; and selecting a rail supporting means to have a variable amount of resilience such that the forces on the wheels are reduced as compared to an arrangement having a fixed rail supporting means. : .. *..I
11. 11. The method of claim 10, wherein the variable amount of resilience of the rail supporting means is further selected such that the kinematic envelope of the railway vehicle is smaller as compared to an arrangement having a fixed rail supporting means.
12. 12. The method of claim 10 or 11, further comprising selecting an upper surface of each rail to have a variable amount of lateral inclination such that the forces on the wheels are reduced as compared to an arrangement having rail upper surfaces with a fixed lateral inclination.
13. 13. The method of any of claims 10 to 12, further comprising selecting a spacing of the rails to vary such that the forces on the wheels are reduced as compared to an arrangement having a fixed rail spacing.
14. 14. A method of providing a railway arrangement comprising: the method of any of claims 10 to 13; and materially constructing the railway arrangement so designed. * S S * ** * * * ** * * *. * * * S.. *... * * S.. . * *SS * *. S. *