GB2558408A

GB2558408A - Tramway system

Info

Publication number: GB2558408A
Application number: GB1718967.1A
Authority: GB
Inventors: Pierce Martin Parry John
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-11-17
Filing date: 2017-11-16
Publication date: 2018-07-11
Also published as: GB201718967D0

Abstract

The tramway system has one or more steel rail tracks (fig.1,11) with at least one gas supply port 72 adjacent the tracks. One or more trams (fig.1,10) travel on the tracks, each having a flywheel 20 to store energy; a gas driven motor 18; a gas inlet duct 61 with a valve (fig.5,84) and one or more pressurised containers 60. The gas may be natural gas or compressed air. Preferably, a number of stationary trackside compressors 66 pressurise mains supplied natural gas, or air, to be stored in stationary storage tanks 68. The tram may have a compressor 62, the trams containers storing the gas at up to 20MPa. The power to drive the tram may be provided indirectly from the flywheel, the tram comprising either a hydrostatic pump and motor; or an alternator and traction battery driving one or more electric motors. The gas supply port may have an electrically activated valves 70, which only permit gas flow when connected and sealed to the inlet duct of a tram. Claims for trams having a source of fuel derived energy, or a compressed air motor are also included.

Description

(56) Documents Cited:

GB 2377680 A US 20120085459 A1 US 20030209374 A1 GB 190227370

US 20140033738 A1 US 20080121136 A1 (71) Applicant(s):

John Pierce Martin Parry

Mucklow Hill, Halesowen, West Midlands, B62 8BS, United Kingdom (72) Inventor(s):

John Pierce Martin Parry (74) Agent and/or Address for Service:

Coller IP Management Limited

Fugro House, Hithercroft Road, Wallingford,

Oxfordshire, 0X10 9RB, United Kingdom (58) Field of Search:

INT CL B61C, B61D

Other: WPI; EPODOC; Patent Fulltext (54) Title ofthe Invention: Tramway system

Abstract Title: A tramway system with a tram having a flywheel and a gas-driven motor (57) The tramway system has one or more steel rail tracks (fig. 1,11) with at least one gas supply port 72 adjacent the tracks. One or more trams (fig. 1,10) travel on the tracks, each having a flywheel 20 to store energy; a gas driven motor 18; a gas inlet duct 61 with a valve (fig.5,84) and one or more pressurised containers 60. The gas may be natural gas or compressed air. Preferably, a number of stationary trackside compressors 66 pressurise mains supplied natural gas, or air, to be stored in stationary storage tanks 68. The tram may have a compressor 62, the trams containers storing the gas at up to 20MPa. The power to drive the tram may be provided indirectly from the flywheel, the tram comprising either a hydrostatic pump and motor; or an alternator and traction battery driving one or more electric motors. The gas supply port may have an electrically activated valves 70, which only permit gas flow when connected and sealed to the inlet duct of a tram. Claims for trams having a source of fuel derived energy, or a compressed air motor are also included.

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Tramway System

The present invention relates to a tramway system, that is to say a system with steel rails along which trams can travel to provide a passenger service.

The low frictional losses encountered where a metal wheel rolls along a steel rail would suggest that there are energy savings available by using trams rather than conventional buses. Where trams run primarily along dedicated rights-of-way they can provide a frequent and reliable service; and where the tramlines run along a conventional road the trams may be given right of way. Buses are perceived as being more flexible, as their routes can be easily changed, whereas tramlines are fixed in position. Nevertheless, particularly in urban environments, there are perceived to be significant environmental and energy benefits in operating trams in place of buses. However, the construction of a tramway system involves considerable capital outlay, and a significant part of the cost is the provision of overhead electrical power cables, and ensuring a current return path through the rails. For small-scale tramway systems it may therefore not be economically justified to construct an electrically-powered system. On the other hand, the use of diesel engines leads to emission of small particulates and gaseous pollutants, which may not be acceptable. The use of bottled gas such as propane to power an engine gives less pollution, but may necessitate the manhandling of heavy gas bottles, which may be inconvenient.

The use of a flywheel to store energy in a tram vehicle, as described in GB 2 377 680 B (JPM Parry & Associates Ltd), in combination with a source of fuel-derived energy such as a fuel cell stack or an internal combustion engine, can be beneficial in such a context, as it makes possible use of a smaller and less powerful energy source, because whenever extra power is required it can be provided from the flywheel, and when the vehicle decelerates energy can be transferred back to the flywheel. However there is still the problem of how best to provide the conventional source of energy.

According to the present invention there is provided a tramway system comprising at least one tram and at least one track with steel rails along which trams can travel, wherein the tram comprises a flywheel to store energy and also comprises a gas-driven motor, wherein the tram also comprises a gas inlet duct with an inlet valve, at least one container for storing pressurised gas; and wherein the system also comprises at least one gas supply port adjacent to the track.

The power required to drive the tram may be provided from the flywheel, typically indirectly, for example using a hydrostatic pump and a hydrostatic motor; or alternatively the flywheel may drive an alternator, the alternator providing power to a traction battery, and the power required to drive the tram being provided by one or more electric motors driven by the traction battery and/or by the alternator.

The power to drive the flywheel is provided by the gas-driven motor.

The provision of the gas supply port adjacent to the track, for example at a terminus or at an intermediate tram stop, means that the tram can refill with pressurised gas at intervals during its operation. Hence it does not need to have sufficient fuel or sufficient battery power to operate all day: it can refuel as often as is required in the course of the day.

In one aspect of the invention the gas is natural gas. In this case gas supply port would typically be provided with natural gas at normal mains gas pressure (which is only slightly above atmospheric pressure); and the tram would additionally include a compressor to compress natural gas supplied through the inlet duct and to supply compressed natural gas to the or each container.

In this aspect, the invention hence provides a tramway system comprising at least one tram and at least one track with steel rails along which trams can travel, wherein the tram comprises a flywheel to store energy and also comprises a source of fuel-derived energy, wherein the tram also comprises a natural gas inlet duct with an inlet valve, at least one container for storing pressurised gas, and a compressor to compress natural gas supplied through the inlet duct and to supply the compressed natural gas to the or each container; and wherein the system also comprises at least one gas supply port adjacent to the track.

In a preferred embodiment the system comprises a plurality of gas supply ports at positions along the track. The or each gas supply port can be connected to a conventional natural gas mains supply duct, so the natural gas is supplied into the inlet port at substantially the pressure of natural gas in the mains, which is somewhat above atmospheric pressure; this pressure must be no less than the gas supply pressure within a domestic supply, which should be equivalent to at least 7 inches of water i.e. at least 1740 Pa above atmospheric pressure. Each gas supply port must incorporate an outlet valve, which may be arranged such that gas can leave the gas supply port only when the gas supply port is connected and sealed to the inlet duct of a tram.

The source of fuel-derived energy may be an internal combustion engine, and it derives energy by combustion of the compressed natural gas in each container. Since the fuel is natural gas, the combustion process is comparatively clean; and the provision of the flywheel means that a comparatively small source of fuel-derived energy can suffice. An advantage of using natural gas as the fuel in this way is that in urban environments a gas main is available in almost every street, so that multiple gas supply ports can be provided at locations throughout the tramway system. Consequently a tram that is running low on fuel need never travel far to reach the next gas supply port, where it can take on additional fuel. By way of example a gas supply port may be provided every kilometre along the track, or at every tram stop.

In a preferred system, stationary gas storage tanks and stationary compressors are provided at a plurality of locations in the tramway system, each such location also having a gas supply port adjacent to the track in communication with the stationary gas storage tank, and the stationary compressors are used to compress natural gas from the mains into the stationary gas storage tanks, so it is stored at a pressure suitable for use on the trams. For example it may be stored at a pressure of 10 or 20 MPa (about 100 or 200 bar); in some cases operation at a pressure of up to 25 or 30 MPa (about 300 bar) may be used. This enables trams to refuel quickly when they reach such a location, by connecting to the stationary gas storage tank.

In another aspect of the invention the gas is compressed air. In this case the gas supply port would typically be provided with compressed air, so the tram would not require an on-board compressor. In this aspect stationary compressed air storage tanks and stationary compressors are provided at a plurality of locations in the tramway system, each such location also having a gas supply port adjacent to the track in communication with the stationary compressed air storage tank, and the stationary compressors are used to compress air into the stationary compressed air storage tanks, so it is stored at a pressure suitable for use on the trams. For example it may be stored at a pressure of 10 or 20 MPa (about 100 or 200 bar). This enables trams to refill with compressed air quickly when they reach such a location, by connecting to the gas supply port which communicates with the stationary compressed air storage tank.

The stationary compressors can therefore operate at comparatively low power continuously, storing energy in the form of the compressed air. Hence a tram can replenish its energy supply quickly, by refilling the on-board container for storing pressurised gas with compressed air. (By contrast, if a tram were only to utilise batteries for power, and were to use fast charging to replenish the tram's energy supply, that would cause a spike in the electricity consumption from the mains.)

The present invention also provide trams suitable for use in such tramway systems.

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 side view of a tram of the invention, on a track, with a portion of the tram side partly broken away;

Figure 2 shows a driven bogie of the tram, which includes a flywheel;

Figure 3 shows the gas supply system, part of which is mounted on the tram;

Figure 4 shows a gas delivery valve at a refilling point;

Figures 5a to 5d show perspective views of a connection being made between a gas supply port and a tram; and

Figure 6 shows a perspective view, partly in section, of a sensor mechanism for use in the tram system of figure 1.

Referring now to figure 1 there is shown a tram 10 on a tram track 11 which includes steel rails. The tram 10 has a central driven bogie 12 and non-driven bogies 13 at each end. There are access doors 14 at each end of the tram 10, leading to an entry section with a low floor from which steps lead up to a main floor 15, shown in the broken-away section, the main floor 15 extending substantially the whole length of the tram 10 and being raised above the bogies 12 and 13. This is by way of example, and as an alternative there might instead be driven bogies 12 at both ends of the tram 10, and a non-driven bogie 13 at the centre; another alternative tram might have only two bogies, either both being driven bogies 12, or one being a driven bogie 12 and the other a nondriven bogie 13.

Referring now to figure 2, this shows a perspective view of the driven bogie 12, which in most respects is the same as that described in GB 2 425 290. The driven bogie 12 has a chassis 16 within which is a drive system comprising a flywheel, a drive means, and a natural-gas powered internal combustion engine 18 (shown schematically).

The flywheel (not shown) is mounted and enclosed within a flywheel housing 20 which is located generally low down and centrally in the bogie 12, the flywheel being mounted within the housing 20 for rotation about a vertical axis, and having two axial stub shafts. The housing 20 may be evacuated to minimise the drag forces acting on the flywheel.

A bevel gearbox 22 is positioned adjacent the flywheel housing 20, and is coupled to one of the stub shafts of the flywheel. An output shaft of the engine 18 is coupled to a reduction gearbox 30, with an output shaft 32 of the reduction gearbox being coupled via a fluid coupling 34 to an input shaft 36 of the bevel gearbox 22. Thus, when the engine 18 is operated, the flywheel is caused to rotate, with the rotating flywheel being used to store energy, in some cases the reduction gearbox 30 may be omitted, and the output shaft of the engine 18 coupled directly to the fluid coupling 34,

The drive means of the drive system comprises the bevel gearbox 22, a first hydrostatic converter 40, a second hydrostatic converter 46, a third hydrostatic converter 48 and bevel gearboxes 54 and 56. An output shaft 38 of the bevel gearbox 22 is coupled to the first hydrostatic converter 40, which is connected by fluid lines 42,44 to the second and third hydrostatic converters 46, 48. The hydrostatic converters 46, 48 have output shafts 50, 52 which are coupled to the bevel gearboxes 54, 56, whose output shafts are coupled to axles 24, 26 of the bogie 12,

The drive means operates in two modes. In the first mode, rotational motion of the flywheel is applied to the first converter 40 via the bevel gearbox 22. The first converter 40 converts this motion to increased fluid pressure, and the second converter 46 converts this to rotational motion, and applies this motion to the axle 24 via the gearbox 54. Similarly, the third converter 48 receives energy from the first converter 40, and converts this energy to rotational motion, and applies the motion to the axle 26 via the gearbox 56. Thus the wheels 28 of both axles 24 and 26 of the bogie 12 are caused to rotate. In the second mode, rotational motion of the axles 24, 26 is applied to the second and third converters 46, 48 via the gearboxes 54, 56 respectively. The second and third converters 46, 48 each convert the motion into increased fluid pressure, and the first converter 40 converts this into rotational motion which is applied to the flywheel via the bevel gearbox 22.

The drive system of the bogie 12 also comprises a control system (not shown). The control system comprises sensors to measure the rotational speed of the flywheel and to measure the speed of the bogie 12. The control system further comprises an actuator to control operation of the flywheel. The control means is operative to sense the speed of rotation of the flywheel, and to determine whether or not it is necessary for energy to be drawn from the engine 18 and applied to the flywheel.

In use, the tram 10 travels along the track 11, Typically, the track 11 starts at a depot where the tram 10 is housed when not in use. Before starting the route, the flywheel of the driven bogie 12 may be charged up to its normal rotational speed. This may be accomplished using energy from the engine 18, or from a power source located at the depot so as not to drain the on-board supply of gas.

If the flywheel is already at its normal rotation speed, the driver can use the vehicle and bogie control systems to increase the speed of the bogie 12, by controlling the operation of the first, second and third converters 40, 46, 48 of the drive means to increase the mechanical motion applied to the axles 24, 26. When it is desired to decrease the speed of the bogie, the speed control means controls the operation of the converters 40, 46, 48 to break off application of the mechanical motion to the axles 24, 26.

As mentioned above, the engine 18 is powered by natural gas, and natural gas is stored in one or more pressurised gas cylinders 60 mounted on the underside of the tram 10; three such gas cylinders 60 are shown in the cutaway portion of figure 1. Referring now to figure 3, the natural gas supply system is shown schematically, with the tram 10 being indicated in broken lines. As regards the items mounted on the underside of the tram 10, natural gas from a coupling 61 is provided to a compressor 62 and stored in the gas cylinders 60. Gas from the gas cylinders 60 is supplied through a safety valve 63 and a pressure reduction valve 64 to the engine 18. By way of example the gas in the storage tanks 60 may be compressed to as much as 10, 20 or 25 MPa (about 100 bar, 200 bar, or 250 bar), while the gas pressure at the inlet to the engine 18 may be reduced to for example less than 1 MPa, for example 700 kPa (about 7 bar (gauge)). By way of example each gas cylinder 60 may have a capacity of more than 100 L, for example 300 L. The compressor 62 may be driven by the engine 18.

At certain places within the network, for example at a depot or at tram stops along the route where there is a supply of natural gas at the normal gas-main supply pressure, and access to mains electricity, the gas from a gas main 65 is compressed by an electrically-powered compressor 66 and is stored in a high-pressure storage tank 68. When a tram 10 that requires additional fuel is at such a place, the high-pressure storage tank 68 may be connected via a delivery valve 70 to the coupling 61; the temporary connection to the coupling 61 is indicated by a broken line in figure 3 and is described in more detail in relation to figure 5. The natural gas stored in the high-pressure storage tank 68 is usually at the required pressure for the storage tanks 60, so that when the tram 10 is at such a place in the network the storage tanks 60 can be refilled to the desired pressure without using the on-board compressor 62.

If the natural gas pressure within the storage tank 68 is not at the required pressure for the storage tanks 60, the gas from the gas main 65 or from the storage tank 68 can nevertheless be supplied through the coupling 61, and compressed by the compressor 64 to the desired storage pressure for the tanks 60. This may be more convenient for refilling the storage tanks 60 at the depot, overnight; and may also be applicable if for any reason there is insufficient natural gas in a storage tank 68 on the tram route.

Referring now to figure 4 there is shown a longitudinal sectional view through the delivery valve 70 that is installed at a tram stop where there is access to a natural gas mains pipe. Gas from the gas main 65 (as shown in Figure 3) is supplied through an inlet pipe 71 to the delivery valve 70, and the delivery valve 70 controls whether or not gas can emerge through an outlet pipe 72. The delivery valve 70 defines a generally cylindrical chamber 73 whose longitudinal axis is vertical, and which has tapered shoulders 74 linking to portions of slightly smaller diameter at its top and bottom ends, and O-rings 75 locate in the walls of the chamber 73 adjacent to the tapered shoulders 74. The inlet pipe 71 communicates with the bottom of the cylindrical chamber 73, while the outlet pipe 72 communicates with one side of the cylindrical chamber 73, about halfway along its length.

Within the cylindrical chamber 73 is a steel ball 76; and an electromagnet 77 is mounted above the top of the chamber 73, and is covered by a cap 78. The steel ball 76 is of such a size that it can move up or down within the chamber 73 between limits set by engagement between the steel ball 76 and the O-rings 75. When gas is to be supplied, the electromagnet 77 is energised, and the steel ball 76 is therefore held in its top position (as shown) by the electromagnet 77, the ball 76 resting against the upper O-ring 75. In this situation, as indicated by the bold arrows, gas can flow from the inlet pipe 71 to the outlet pipe 72. When the supply of gas is to be terminated, the electric current to the electromagnet 77 is turned off, so the ball 76 falls under gravity, into the position in which it rests on the lower O-ring 75, and in this position the engagement between the ball 76 and the O-ring 75 prevents gas flow through the delivery valve 70.

Referring now to figures 5a to 5d, these show perspective views of successive stages in the linkup between a tram 10 and a stationary natural gas storage tank 68 at a refuelling point 80, for example at a tram stop. The coupling 61 is mounted on a part of the chassis 81 of the tram 10, extending through a slot in the chassis 81 so it can move vertically through a limited range, and with a pneumatically-actuated mechanism 82 to move the coupling 61 sideways to alter the extent to which it projects from the side of the chassis 81. At the outer end of the coupling 61 is a roller 83, and a plunger-actuated valve 84. The outlet pipe 72 from the delivery valve 70 is connected to a stationary end fitting 85 which is fixed in position adjacent to the track 11, the end fitting 85 being mounted on a base plate that defines two inclined ramps 86, between which is a flat section with a shallow central recess 87 aligned with the end fitting 85. The end fitting 85 also has a valve (not shown) at the end.

Figure 5a shows an initial stage in which the tram 10, travelling at a slow speed of about 5 km/hr in the direction indicated by the arrow A is approaching the refuelling point 80; the tram 10 then slows down to a crawl.

Figure 5b shows the next stage, in which the coupling 61 is pushed out by the mechanism 82, so that the roller 83 can engage with the inclined ramp 86. The roller 83 rolls up the ramp 86, and the tram 10 moves even more slowly.

Figure 5c shows the next stage, in which the roller 83 has reached the top of the ramp 86; and the tram 10 stops as the roller 83 reaches the central recess 87. This ensures alignment between the coupling 61 and the stationary end fitting 85.

Figure 5d shows the next stage, in which the pneumatic mechanism 81 is further actuated to bring about connection between the outer end of the coupling 61 and the end fitting 85, thereby opening the plunger-actuated valve 84 at the end of the coupling 61 and also the valve at the open end of the end fitting 85. The plunger-actuated valve 84 may be provided with a pneumaticallyexpanded elastomeric seal around its periphery, to ensure it is sealed to the end fitting 85. At this stage the tram 10 provides a signal, for example by Wi-Fi, to enable energisation of the electromagnet 77 in the delivery valve 70, so that pressurised gas from the stationary storage tank 68 is provided to the coupling 61 and hence to the storage cylinders 60.

The control mechanism for the tram 10 ensures that the tram brakes are always applied all the time that the coupling 61 is connected to the end fitting 85. Consequently, when refuelling is complete, the tram 10 provides a signal to cease energisation of the electromagnet 77; and the pneumatic mechanism 81 is actuated to pull the coupling 61 back into the chassis 81. Disconnecting the coupling 61 from the end fitting 85 causes the plunger-actuated valve 84 and the corresponding valve at the end of the end fitting 85 to close again. When this has been completed, the brakes can be released.

To ensure that the brakes of the tram 10 are applied in such a way as to ensure that the tram 10 stops when the roller 83 reaches the central recess 87, the brakes may be actuated automatically in response to monitoring of the position of the tram 10 as it approaches the end fitting 85. By way of example this may be achieved by providing two successive breaks between rails in the track 11, so that a track circuit sensor on the tram 10 can detect when it reaches each of these predetermined positions.

Referring now to figure 6 there is shown a sensor mechanism 90 for use within the track 11 to identify the position of the tram 10. Such a sensor mechanism 90 may be utilised in the section of track 11 leading up to a refuelling point 80. The track 11 includes a running rail 91 along which the wheels 28 roll, and a section of spacer rail 92 mounted parallel to the running rail 91. It will be appreciated that the track 11 may be embedded in a road surface, so that only the top surfaces of the running rail 91 and the spacer rail 92 are exposed; but if the track 11 is along a dedicated route, both these rails 91 and 92 may be mounted above ground level. The rails 91 and 92 each have a base flange, a vertical web, and a rail head 93, and the rail heads 93 define the top surfaces. The gap between the rail heads 93 of the rails 91 and 92 is sufficiently wide to accommodate the flange of the wheel 28. These features are all conventional.

Between the running rail 91 and the spacer rail 92 is a generally cylindrical flexible tube 94 which is of such a shape as to fit between the running rail 91 and the spacer rail 92 below the rail heads 93, the flexible tube 94 having a thicker portion 95 which is of generally rectangular crosssection, and which projects from the flexible tube 94 and fits between the rail heads 93. The upper surface of the thicker portion 95 defines a tread 96, and in its normal position the top of the tread 96 is at substantially the same height as the top surfaces of the rails 91 and 92. The flexible tube 94 may for example be of length 1 m, or 0.5 m, or 0.2 m, and is closed at each end. The structure and material forming the flexible tube 94 with its thicker portion 95 may be the same as that used to form a vehicle pneumatic tyre, for example with wires or cords embedded in vulcanised rubber. In this example a short tube 97 is bonded to the flexible tube 94 and projects through a corresponding hole in the spacer rail 92, the tube 97 including a valve, so that air can be pumped into the flexible tube 94 in the same way as a vehicle tyre can be pumped up. Within the flexible tube 94 is a pressure sensor 98, from which electrical leads extend through the wall of the flexible tube 94 to a sensing circuit (not shown).

Whenever a tram 10 travels long the section of track 11 that includes the sensor mechanism 90, the flange of the tram wheel 28 rolling along the running rail 91 will depress the thicker portion 95 down into the gap between the rail heads 93. When the tram wheel 28 is no longer in contact with the thicker portion 95, the thicker portion 95 will spring back into its original position due to both the resilience of the material and the air pressure within the flexible tube 94. While the tram wheel 28 is depressing the thicker portion 95 there is an increase in air pressure within the flexible tube 94, and this is sensed by the pressure sensor 98. Consequently the sensing circuit can detect when the wheel 28 is at the location of the sensor mechanism 90.

In the preferred arrangement there are two such sensor mechanisms 90 in the section of track 11 where there is a refuelling point 80, the sensor mechanisms 90 being spaced apart by the distance between the wheels 28 of a bogie 12 or 13. The pressure sensor 98a associated with the second such sensor mechanism 90 is shown in figure 6, but the other components of the second sensor mechanism 90 are not shown. By way of example, energisation of the electromagnet 77 in the delivery valve 70 may be allowed only if both the pressure sensors 98 and 98a indicate the presence of a bogie 12 or 13.

It will be appreciated that the flexible tube 94 can only be installed between the rails 91 and 92 when it is deflated. Once it is inflated, it cannot be removed.

It will be appreciated that a tram system can be modified in various ways while remaining within the scope of the invention, as defined by the claims. For example the position sensing to enable the tram 10 to accurately determine its position as it approaches a refuelling point 80 might instead utilise RFID tags adjacent to the track 11. There might be fewer gas storage tanks 60 or more gas storage tanks 60; they might store gas at a different pressure; and they might be located at different places within the tram 10, for example with a low-floor tram the gas storage tank 60 may be above the ceiling rather than below the floor.

Furthermore, as mentioned above, the tram 10 may include a traction battery, and an alternator driven by the flywheel, and electric motors driven by the traction battery and/or the alternator. These components may be used instead of the bevel gearbox 22, the hydrostatic converters 40, 46, and 48 and the bevel gearboxes 54 and 56, in order to provide rotational torque to the axles 24, 26 of the bogie 12.

Furthermore the natural-gas powered internal combustion engine 18 may be replaced by a compressed air-driven motor, in this case the on-board gas storage tanks 60 would store compressed air; and at a depot or at tram stops along the route where there is access to mains electricity, an electrically-powered compressor 66 would be used to store compressed air in a highpressure storage tank 68. When a tram 10 that requires additional fuel is at such a place, the highpressure storage tank 68 may be connected via a delivery valve 70 to the coupling 61, in the same way as described above.

This alternative arrangement using compressed air, and electric motors with a traction battery, provides no harmful exhaust gas emissions during operation, as the only exhaust gas is air. On-board the tram the compressed air motor may operate at fairly low power and torque, for example at a power between 5 kW and 10 kW, avoiding the risk of freezing up of the compressed air motor, and can provide a constant torque to the flywheel within the housing 20. The overall result is to provide a rapid way of recharging power to a battery powered tram, so significantly increasing its potential range. This also enables the tram to use a less expensive traction battery than would otherwise be required.

The tram 10 described above includes bogies 12, 13, but it will be appreciated that the present invention is equally applicable to a tram 10 with fixed axles.

Other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features that are already known and which may be used instead of, or in addition to, features described herein. Features that are described in the context of separate embodiments may be provided in combination in a single embodiment. Conversely, features that are described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

It should be noted that the term comprising does not exclude other elements or steps, the term a or an does not exclude a plurality, a single feature may fulfil the functions of several features recited in the claims and reference signs in the claims shall not be construed as limiting the scope of the claims. It should also be noted that the Figures are not necessarily to scale; emphasis instead generally being placed upon illustrating the principles of the present invention.

Claims

1. A tramway system comprising at least one tram and at least one track with steel rails along which trams can travel, wherein the tram comprises a flywheel to store energy and also comprises a gas-driven motor, wherein the tram also comprises a gas inlet duct with an inlet valve, at least one container for storing pressurised gas; and wherein the system also comprises at least one gas supply port adjacent to the track.

2. A tramway system as claimed in claim 1 wherein power to drive the tram is provided indirectly from the flywheel, the tram comprising a hydrostatic pump and a hydrostatic motor; or the tram comprising an alternator, a traction battery, and one or more electric motors driven by the traction battery and/or by the alternator.

3. A tramway system as claimed in claim 1 or claim 2 wherein the gas is natural gas and the tram also comprises a compressor to compress natural gas supplied through the inlet duct and to supply compressed natural gas to the or each container.

4. A tramway system as claimed in claim 1 or claim 2 wherein the gas is compressed air.

5. A tramway system as claimed in any one of the preceding claims wherein there are a plurality of gas supply ports at positions along the track.

6. A tramway system as claimed in any one of the preceding claims wherein each gas supply port incorporates an outlet valve arranged such that gas can leave the gas supply port only when the gas supply port is connected and sealed to the inlet duct of a tram, and also an electrically-activated delivery valve.

7. A tramway system as claimed in claim 4 wherein stationary compressed air storage tanks and stationary compressors are provided at a plurality of locations in the tramway system, at locations where there is access to mains electricity, the compressors being connected to the mains electricity supply.

8. A tramway system as claimed in claim 3 wherein stationary gas storage tanks and stationery compressors are provided at a plurality of locations in the tramway system, locations where there is access to mains electricity and to the natural gas mains supply, the stationary compressors being connected to the natural gas mains supply.

9. A tramway system as claimed in claim 8 wherein the stationary gas storage tanks are arranged to store natural gas at a pressure suitable for use on the trams.

10. A tramway system as claimed in any one of the preceding claims wherein the container for storing pressurised gas on the tram is arranged to store gas at a pressure of up to 10 or 20 MPa (about 100 or 200 bar).

11. A tramway system as claimed in any one of the preceding claims including a sensor device to detect a flange of a wheel of a tram.

12. A tramway system as claimed in claim 11 wherein the sensor device comprises a pneumatic chamber with a depressible wall portion alongside a rail of the track, such that the wall portion is depressed when a wheel rolls along that portion of the rail.

13. A tram suitable for use on a tramway system as claimed in claim 3 or any one of claims 8 to 12 when dependent on claim 3, comprising a flywheel to store energy and also a source of fuelderived energy, the tram also comprising a natural gas inlet duct with an inlet valve, at least one container for storing pressurised gas, and a compressor to compress natural gas supplied through the inlet duct and to supply the compressed natural gas to the or each container.

14. A tram suitable for use on a tramway system as claimed in claim 4, claim 7 or any one of claims 10 to 12 when dependent on claim 4 or claim 7, comprising a flywheel to store energy and also a compressed air motor, the tram also comprising a compressed air inlet duct with an inlet valve, at least one container for storing compressed air.

15. A tram as claimed in claim 14 also comprising an alternator driven by the flywheel, a traction battery, and one or more electric motors driven by the traction battery and/or by the alternator to drive the tram.

Intellectual

Property

Office

Application No: GB1718967.1 Examiner: MrKeirHowe