Track transportation systems

The invention relates to transportation systems and concerns systems which comprise a track and one or more vehicles adapted to travel along the track, and in which the track comprises means to support the weight of the vehicles, to guide them laterally to prevent yawing, and to provide transverse righting couples as necessary to prevent rolling of the vehicles about their longitudinal axis.

The track may comprise structures which are at ground level or are elevated, and which provide such guide surfaces as are required for the functions mentioned above. The vehicles may be of two main types:

"Bottom supported" vehicles are known, in which the vehicle is supported on a number of wheels, for example four wheels, at the bottom of the vehicle. Thus, a conventional motor car or a conventional railway train is a "bottom supported" vehicle. If a bottom supported vehicle travels along a track it may be guided by engagement of its support wheels with a guideway, as is the case with a conventional railway train, or it may be guided by special guide wheels which engage vertical surfaces at the sides of the track. Righting couples to prevent rolling may be provided by differences in loading between laterally separated support wheels.

"Cantilever supported" vehicles are also known, in which upper and lower vertically spaced guide surfaces on the track are engaged by cantilever support means on one side of the vehicle, so that the vehicle is supported on the track from one side only. Since the centre of gravity of the vehicle is near the middle of the vehicle, the weight of the vehicle produces a rolling couple and this is opposed by a righting couple produced by engagement of the cantilever support means with the guide surfaces on the track. For this purpose the upper and lower guide surfaces on the track are engaged respectively by upper and lower cantilever support means, usually guide wheels, on one side of the vehicle.

Cantilever supported vehicles allow the use of tracks which are narrower than the tracks required for bottom supported vehicles. In the case of elevated tracks, this permits economy in the use of materials and, in addition, tracks for travel in two opposite directions may be provided on opposite sides of the same track structure. The upper and lower guide surfaces may be connected and mounted on a support structure by means of vertically extending structural members. However, this arrangement creates problems if it is required to include in the track a junction where the vehicle may follow one of a number of alternative routes.

For example, in the case of a divergent junction where a vehicle on one ingoing guideway can follow either of two alternative outgoing guideways, the two divergent outgoing guideways are initially necessarily close together. Consequently, it is difficult to locate the vertical structural members supporting each guideway without blocking the path of vehicles travelling along the other guideway. Several partial solutions are known, but each has its own serious disadvantages.

"Overpass" and "underpass" systems are known. In such systems the outgoing guideways are diverged vertically before being diverged horizontally. However, this necessitates a large, expensive and unsightly support structure.

"Throughpass" systems are also known in which the vertically extending structural members are omitted in the vicinity of the junction to allow one vehicle to pass between the upper and lower guide surfaces supporting the other vehicle. However, the omission of the structural members weakens the structure so that it is only suitable for very light vehicles.

"Alternative cantilevering" systems are known in which each vehicle is provided with cantilever support means on both sides of the vehicle, so that the vehicle can optionally be cantilever supported from either side. In such an arrangement, cantilever support guide surfaces on the track are simultaneously offered to both sides of the vehicle and a switching device is preset to select one or other of the guide surfaces so that the vehicle is cantilever supported from the appropriate side, depending on the route which it is to follow out of the junction. The two guideways then diverge. In such an arrangement a complex sequence of load changes takes place in the vicinity of the junction, between various support and guide surfaces and the associated wheels on the vehicle.

The present invention, in one aspect, provides a transportation system for cantilever supported vehicles which is free from all or some of the above defects.

According to this aspect of the invention there is provided a transportation system comprising a track providing upper and lower guide surfaces and at least one vehicle having upper and lower cantilever support means on one side of the vehicle for engagement respectively with said guide surfaces, whereby the vehicle is cantilever supported from one side only on the guide surfaces as it travels around the track, the track including at least one junction where the vehicle can follow one of a number of alternative routes, and the track including, at the junction, a substantially flat horizontal surface and the vehicle having a plurality of bottom support wheels which may run on said flat surface and support the weight of the vehicle, the aforesaid cantilever support means being capable of temporary disengagement from said guide surfaces when the weight of the vehicle is supported on said flat horizontal surface at the junction, selectively operable guide means being provided to direct the vehicle to follow a required route at the junction, while it is temporarily supported on said flat horizontal surface.

The selectively operable guide means may comprise means for steering the bottom support wheels of the vehicle, which steering may be automatic but which could be under manual control, in similar manner to a motor car. Precise transverse location may be provided by supplementary vertical guide surfaces, automatic steering being provided to urge the vehicle against a selected guide surface according to the route required out of the junction.

The invention also provides a transportation system having a novel guide means for guiding the vehicle through a junction. This aspect of the invention is, again, particularly applicable to systems having cantilever supported vehicles, but is not limited to such systems.

According to this aspect of the invention there is provided a transportation system comprising a track and at least one vehicle adapted to travel along the track, the track including at least one junction where the vehicle can follow one of a number of alternative routes, and the track including, at the junction, a substantially flat horizontal surface and the vehicle having a plurality of bottom support wheels which may run on said flat surface and support the weight of the vehicle, there being provided guide means for guiding the vehicle as it travels across said flat surface, which guide means comprise at least one guideway recessed in said flat horizontal surface and defining a route across the junction, and follower means on the vehicle selectively engageable with said guideway according to the route which the vehicle is required to follow across the junction.

The following is detailed description of embodiments of the invention, reference being made to the accompanying diagrammatic drawings in which:

• Figure 1 is a rear elevation of a cantilever supported vehicle on its track, the track being shown in vertical section,
• Figure 2 is a diagrammatic plan view of the vehicle showing the relative disposition of its support and guidance wheels,
• Figure 3 is a diagrammatic plan view of a portion of the track, at a divergent junction,
• Figure 4 is a rear elevation of the lower part of the vehicle, on an enlarged scale, showing the lower part of the track in section, and
• Figure 5 is a plan view of an alternative form of track, at a divergent junction.

Referring to Figure 1, the vehicle 10 is cantilever supported on a track 11. The track 11 is an elevated track extending between spaced vertical support posts 12.

The track 11 comprises a vertical wall portion 13 connecting a lower horizontal flange 14 and an upper horizontal flange 15. The lower flange 14 is formed at its extremity with an upstanding side wall 16 and the upper flange 15 is formed at its extremity with a depending wall 17. The lower portion of the main wall 13 of the track defines a further vertical side wall 18.

The vehicle 10 is provided at the bottom with bottom support wheels 19, 20, 21 and 22 rotatable about horizontal axes, only the rear wheels 19 and 20 being seen in Figure 1. The wheels 19, 20, 21 and 22 are provided with resiliently flexible tyres, for example pneumatic rubber tyres.

As best seen in Figure 1, the left hand bottom support wheels 19 and 21 run on the upper surface of the lower flange 14 of the track. The centre of gravity of the vehicle, indicated at 23, is located at approximately the middle of the vehicle and the weight of the vehicle therefore applies a clockwise couple thereto, as indicated at 24 in Figure 1. To oppose this couple, the vehicle is provided with upper guide wheels 25 and 26 which rotate about vertical axes and bear against the inner face of the upper side wall 17. The distance of the side wall 17 from the main wall 13 of the track is greater than the diameter of the wheels 25, 26 so that the wheels will normally be spaced away from the inner surface of the main wall 13.

Adjacent the bottom support wheels 19, 20, 21 and 22 respectively there are mounted four lower guide wheels rotatable about vertical axes. Only the two rear guide wheels 27 and 28 can be seen in Figure 1. The lower guide wheels, such as 27, on the left hand side of the vehicle bear on the lower vertical wall part 18 of the main wall 13 of the track.

To minimise risk of derailment, rollers, such as indicated at 29, are coaxial with the bottom support wheels respectively and can cooperate with the upstanding side wall 16 to limit displacement of the vehicle to the right in Figure 1. Similarly, rollers such as 30 are coaxial with the lower guide wheels 27 and 28 and can cooperate with an inward flange 31 on the inner surface of the main wall 13 of the track to limit vertical displacement of the vehicle.

In normal operation the vehicle 10 travels around the elevated track 11 cantilevered from its left hand side. One or more of the bottom support wheels may be power driven to drive the vehicle around the track, or any other suitable form of drive may be employed.

Although the invention is applicable to arrangements in which the vehicle is capable of being cantilever supported from only one side, arrangements are possible where the vehicle may optionally be cantilever supported from either side. In this case, further upper guide wheels, such as are indicated in dotted lines at 32 and 33, may also be provided on the upper part of the right hand side of the vehicle.

As previously mentioned, problems can arise in arranging for such cantilever supported vehicles to be guided through the required route at a divergent junction, and there will now be described methods of guiding the cantilevered vehicle of Figure 1 through such a junction, where the vehicle can follow either of two alternative routes out of the junction.

The junction is shown diagrammatically in plan view in Figure 3, which shows the bottom vertical side wall portion 18 of the track, the lower horizontal flange 14 and the short vertical side wall 16. The upper flange 15 and upper side wall 17 are not shown. The corresponding parts of the track on the two alternative routes out of the junction are indicated at 14a, 16a, 18a and 14b, 16b and 18b respectively.

Across the junction, the lower horizontal flanges 14, 14a and 14b of the different portions of the track are all co-planar with, and lead onto, a substantially flat continuous horizontal surface 34. The left hand side of the surface 34 (looking in the direction of travel from left to right in Figure 3) is bounded by the side wall portions 18 and 18a, whereas the right hand side is bounded by a vertical guide wall 35 which is curved to correspond to the curved path leading from the flange portion 14 to the flange portion 14b. A portion of the upstanding side wall 16 on the track is removed to provide an elongate gap 36 extending across the central portion of the horizontal surface 34.

The horizontal surface 34 is formed with two guideways 37, 38 recessed into the surface thereof, which guideways extend across the junction. One of the guideways, 37, is straight and is parallel to the portion of the track provided by the flanges 14, 14a. The other guideway, 38, is curved and follows the curvature, across the junction, between the flanges 14, 14b.

Mounted in the lower part of the vehicle are two sets of rocker arms 39, 40 which are pivotally mounted on the vehicle to swing about a central longitudinal horizontal axis, indicated at 41. The rocker arms carry at their ends respectively steel flanged wheels 42, 43 which act as followers for cooperation with the recessed guideways 38 and 37 respectively. The follower system 39-43 is duplicated at the forward end of the vehicle.

The passage of the vehicle through the junction shown in Figure 3 will now be described, reference being made to the various positions indicated on Figure 3 with the references A to G.

As the vehicle approaches the junction, for example in the position indicated at A, the vehicle is cantilevered from the left, as shown in Figure 1. On reaching position B the outer bottom support wheels 20 and 22 of the vehicle run onto the horizontal track surface 34 of the junction, which may be slightly ramped upwards at position B to facilitate this. The vehicle then is entirely bottom supported and the load on the upper cantilever support wheels 25, 26 is removed. The lower part of the vehicle when in this position is shown, enlarged, in Figure 4. It will be seen that, in this position, the left hand lower guide wheels 27 engage the left hand wall portion 18 of the main wall of the track whereas the right hand guide wheels 28 engage the boundary wall 35 on the horizontal surface 34.

Assuming that it is wished to divert the cantilevered vehicle to the right hand route out of the junction, the rocker arms 39 are swung downwardly to bring the left hand follower wheels 42 into engagement with the recessed guideways 38. The right hand follower wheels 43 are raised out of engagement with the guideway 37, as shown in Figure 4. The vehicle then continues to the position indicated at C. At this position the left hand bottom support wheels 19 and 21 reach the gap 36 in the upstanding flange 16 and the upper guide wheels 25, 26 meet a corresponding gap in the depending side wall 17 at the upper part of the track. The bottom supported vehicle is thus free to follow the curved path of the recessed guideway 38, being guided along that guideway by engagement of the guideway by the follower wheels 42. The lower guide wheels 28 remain in engagement with the wall 35, but as the vehicle moves across the surface 34 the left hand lower guide wheels 27 are brought out of engagement with the wall portion 18.

When position F is reached, the left hand bottom support wheels 19, 21 engage the lower flange 14b, between the outer wall portion 18b and the upstanding wall 16b. Similarly, at the same time, the upper guide wheels 25 and 26 enter between the upper side wall 17 and the upper part of the main wall 13 of the track.

As the vehicle continues to position G its right hand bottom support wheels 20 and 22 leave the edge 39 of the surface 34, which may be sloped downwardly to provide a smooth transition, so that the vehicle is no longer bottom supported but is again cantilevered from the left hand side in the position corresponding to that shown in Figure 1.

If it is required, when the vehicle is in position B, that the vehicle should leave the junction along the straight ahead route, that is to say along the route of the flange 14a of the track, the other rocker arms 40 are swung downwardly to bring the right hand guide wheels 43 into engagement with the straight recessed guideway 37. The cooperation of the wheels 43 with the guideway 37 then cause the vehicle to be guided straight ahead so that the left hand lower guide wheels 27 remain in engagement with the wall portion 18 and the right hand lower guide wheels 28 are brought out of engagement with the wall 35. The vehicle continues along the straight ahead path until the position D is reached where the upper guide wheels 25, 26 again enter between the side wall 17 and the main wall of the track whereafter, at position E, the horizontal surface 34 slopes downwardly to remove the support from the right hand bottom support wheels 20, 22 so that the vehicle is again cantilever supported from the left hand side.

Although the arrangement is shown as applied to a divergent junction having two alternative exit routes, it will be appreciated that a similar arrangement may be applied to a convergent junction.

The arrangement of rocker mounted guide wheels cooperating with recessed guideways may also be used to guide the vehicle if it is required that it should temporarily leave the cantilever track altogether and travel over a greater length of flat surface on bottom support. For example, the vehicle may even travel over ordinary roads provided the roads are formed with suitable recessed guideways. In this case, it may be advantageous to arrange the rocker arms so that all four guide wheels can be lowered simultaneously for engagement with two parallel recessed guideways to provide more stable guidance to the vehicle.

Referring to Figure 4, it will be seen that the disposition of the guide wheels 42 and 43 is such that they are prevented from disengagement with the guideways under outwardly acting transverse loads on the vehicle, due to the fact that the central pivot axis 41 is above the point of contact between the wheels and the guideway. As a result of this, a transverse load on the vehicle results in a reaction force which is inclined downwardly, thereby having a vertical component tending to urge the guide wheel downwardly into engagement with its guideway. If desired, this downward force may be reinforced, for example by a compression spring acting to urge the rocker downwardly.

In the arrangement shown, the recessed guideways 37 and 38 are illustrated as being simple grooves in the surface 34, but it will be appreciated that they might instead be in the form of recessed spaced rails, similar to tramlines. It will be appreciated that certain fundamental problems of using tramlines for guidance are overcome in the present construction. In the arrangement described the downward loading upon the steel wheels 42 and 43 is light, because they do not have to support the weight of the vehicle, the weight being supported on the pneumatic tyred wheels 19, 20, 21 and 22. On the other hand, the arrangement of the wheels 42, 43 on the rocker arms is such that they can sustain heavy horizontal transverse loads, if necessary, as previously described.

In an alternative arrangement for guiding the vehicle across the junction, the recessed guideways 37 and 38, and the guide wheels 42 and 43, are dispensed with. Since, at the junction, the normally cantilever supported vehicle is bottom supported, it becomes possible to steer the vehicle through the junction, either automatically or manually, by providing for certain of the bottom support wheels, usually the front wheels 21 and 22, to be steerable. Thus, when position B is reached in Figure 3, the front wheels of the vehicle may be steered to the right so as to bias the vehicle to the right and thus to maintain the right hand guide wheels 28 in engagement with the wall 35. The vehicle will thus automatically follow the curved path to the right until the cantilever support wheels again engage the track at position F. Similarly, in order for the vehicle to continue straight ahead, the steerable wheels will be turned to the left so as to bias the vehicle to the left and maintain the left hand guide wheels 27 in engagement with the wall part 18.

The bottom support wheels of the vehicle, and particularly the steerable front wheels, are preferably provided with a castor action for stability.

It will be appreciated that the arrangement described above, whereby the vehicle is guided by means of follower wheels engaging recessed guideways, is not restricted to systems where the vehicle is normally cantilever supported. Figure 5 shows a divergent junction on a track where the vehicle is constantly bottom supported throughout the track. In this case the vehicle is provided only with the bottom support wheels 19, 20, 21 and 22 and the lower guide wheels 27 and 28. The bottom support wheels run on the flat lower surface 40 of the track and the guide wheels 27 engage upstanding side walls 41 and 42 respectively.

At the junction, the flat substantially continuous horizontal surface of the track is formed with recessed guideways 43, 44 which correspond to the guideways 37 and 38 respectively of Figure 3. The vehicle is provided with rocker and guide wheel systems corresponding to the system 39-43 of Figures 2 and 4 and the vehicle is guided to a selected route out of the junction by lowering the appropriate guide wheel as previously described.

It is to be understood that in the arrangements described the rocker arms 39 and 40 of Figures 2 and 4 may be replaced by any other suitable arrangement for raising and lowering the guide wheels 42 and 43. Although it is preferable that the followers should be in the form of guide wheels, to reduce friction, the invention includes within its scope arrangements in which non-rotating, sliding followers engage the recessed guideways. Any form of recessed guideway may be used, provided that the guideway is substantially co-planar with the surface on which the vehicle is supported, so that the bottom support wheels of the vehicle may pass, without significant displacement, over the recessed guideways.