GB2464472A

GB2464472A - Guided vehicle and overhead track system

Info

Publication number: GB2464472A
Application number: GB0818848A
Authority: GB
Inventors: Anthony Ralph Kennard
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-10-15
Filing date: 2008-10-15
Publication date: 2010-04-21
Anticipated expiration: 2028-10-15
Also published as: GB2464472B; GB0818848D0

Abstract

A system comprising an overhead guide track 22 and a vehicle which is self steering until engaging the track 22. Electrical power can be drawn from the track or the vehicle can be self powered. The vehicle has a rotatable overhead guide runner assembly which can align the steering axle by engaging one of a pair of guides. The guide runners 21 on the assembly are set forward of the central vertical axis 10 of the steering axle. At a bend in the track 22 contact by a runner 21 with the concave edge of a guide aligns the steering. When the steering axle or axles align on a radius of the curve the vehicle follows the track 22. Vertical and horizontal tolerances between the runners and the guides are set to allow some lateral and vertical movement of the vehicle in relation to the track 22.

Description

DESCRI PTION Title

A GUIDED VEHICLE SYSTEM

Background

This invention concerns guided wheeled vehicles which are used in in urban public transport.

There are many working systems for guided diesel or petrol buses, usually with some form of ground level guidance. Other schemes have sought to transform the trolley bus into an automatically guided vehicle, often using the overhead installation to provide electronic guidance. There is a possible industrial use in materials handling where guided rubber wheeled vehicles might have an advantage on a production line or in a warehouse.

In its most likely usage, this proposal is closest to trolley buses. It offers an overhead guidance track which works mechanically, but is simply adapted to provide electric current to power the vehicle. However, the track and guidance system will work with a self powered vehicle, if the opportunity is not taken to use the overhead infrastructure to double up as a safe electric power supply.

Trolley buses have in the past been steered independently of the conductor wires by a human driver. This allows such vehicles to be steered along a path which does not have exactly to follow that of the conductors. To collect power the vehicles are connected to the conductor wires by rods and flexible joints. If the vehicle deviates too far from the conductor wires contact can be lost and has to be re established manually while the vehicle is stationary.

As stated above, many attempts have been made to develop automatic guidance systems for vehicles of this type. A vehicle steered automatically makes the task of a driver much simpler and prevents loss of contact with the conductors. The vehicle deviates much less from the set path so that less road space has to be allocated to it and use in constricted locations becomes easier. Automatic steering enables the vehicle to stop to collect and deposit passengers with more precision so that platforms or closed passenger access bays with safety doors can give easier and safer boarding for passengers and an opportunity to control and collect fares off the vehicle. As an electric vehicle it would be non polluting at point of use. It can also substitute for a tram in some uses where it will have the advantage of being less expensive and disruptive to build because a ground level rail infrastructure does not have to be built into the road surface.

Statement of Invention

A guided vehicle system comprising a guidance track consisting of a rigid guide or guides supported overhead by multiple pylons, with appropriate crossings and junctions and which can be used to supply electrical power, and a vehicle which can be self powered or draw electrical power from the guidance system, moving by traction on a surface which carries its weight and which steers itself either mechanically, electrically, hydraulically or through servomechanisms until overridden by interaction with the guidance system. The self steering of the vehicle being overridden whenever one of a pair of overhead guide runners engages the edge of a guide either mechanically or through a proximity sensor, the runners being mounted on an assembly which is rotatable about an appropriately positioned vertical axis, so the rotation of the assembly through its linkage either mechanically, electrically, hydraulically or through a servomechanism adjusts the steering axle or axles.

The position of the guide runners being set forward of the vertical axis so that when the moving vehicle enters a curve in a guide track the leverage of a guide runner acting on the concave edge of a guide or the signal from a proximity sensor to a servo mechanism turns the assembly about its vertical axis and through its linkage overrides the self steering to adjust the steering axle or axles until the leverage is abated or the signal from the proximity sensor is sufficiently reduced by the steering axle or axles tending to align on radii of the curve, along with the rear axle of the vehicle tending to align on a similar radius, thereby allowing the vehicle to follow the path of least resistance which is the curve of the guides.

Advantages The principal advantage of this invention is that the guidance system can be implemented as a simple mechanical arrangement which does not depend on electronic or electrical components, which might otherwise add to complexity and cost, and which also can be simply adapted to supply electrical motive power.

Introduction to Drawings

The drawings illustrate a basic vehicle which is driven by a rear axle mounted electric motor, has a king pin steering system and is operated with a system of guides which has the runners engaging the outsides of a pair of guides. The guides are used to supply electrical current.

The first two drawings are general illustrations of the vehicle. This has an extension of the bodywork as a ladder frame which rotates about a vertical axis which also passes through the centre of the steering axle. The next two drawings shows the configuration of the steering assembly and the guide runner assembly which is rigidly mounted on the upper part of the extension of the bodywork. This is followed by a drawing showing the basic interaction of the vehicle with the guides on a bend. The last four drawings show how junctions in the pair of guides work.

Figure 1 is a side view of the vehicle.

Figure 2 is a front view of the vehicle.

Figure 3 is an overhead view of the front steering axle of the vehicle which shows the configuration of the king pin steering mechanism.

Figure 4 is an overhead view of the guide runner assembly of a vehicle in operation in a straight section of the guides.

Figure 5 is an overhead view of the guide runner assembly in operation at a curved section of the guides.

Figure 6 is an overhead view of the guide runner assembly in operation at a junction of two pairs of guides which cross at right angles.

Figure 7 is an overhead view of the guide runner assembly operating at a junction which merges curved and straight sections of guides.

Figure 8 is an overhead view of a junction which is an adaptation of the one in Figure 7 and which is used to divide one pair of guides into two using moveable sections of guides.

Figure 9 is a side view of a moveable section of guide which can be used to bridge a gap at a junction as in Figure 8.

Detailed Description

Figure 1 shows a side view of the vehicle which is driven by the rear wheels. The central section is a rigid box chassis 1 which supports front and rear assemblies of what has to be a tall vehicle so that the guide track does not obstruct other vehicles and any electrical supply can be drawn from conductors which are high enough to meet electrical safety requirements. Rigidity of the bodywork helps to ensure that the guiding forces generated well above the wheelbase of the vehicle are transferred accurately to the wheels. The electric motor 2 and driving axle incorporating a differential gearbox 3 (neither visible) are mounted on a sub frame 4 which is fixed to the rear of the central box section. A front sub frame 5 supports the steering assembly 9 (see Figure 2), the ladder frame 8 and the guide runner assembly 16. A mounting 6 projects from the lower part of the front sub frame 5 to support the steering assembly 9 (see Figure 2).

Frame mountings 7 extend forward from the front sub frame 5 to support the ladder frame 8 and allow it to rotate about the vertical axis 10 (see Figure 2).

Figure 2 shows a front view of the above vehicle. The front wheels turn independently of each other on stub axles as part of the front steering assembly 9. At its lower end the frame 8 rotates about a spindle shaft through the front steering assembly 9 and in the vertical axis 10. The stub axles of the front steering wheels rotate in G shaped bearers 11 supported at their upper and lower ends in the king pin axes 12 about which they can turn in a horizontal plane.

The guides 22 are attached to and kept electrically separate by bearers 23 which are supported by a series of spaced pylons 24. As stated with respect to Figure 1, the height of this track is determined by safety requirements for the use of exposed high tension electrical supply.

Figure 3 shows the steering axle assembly 9 from above. The stub axle bearers 11 are linked by rigid track rod arms 13 to a track rod 14. The centre of this track rod is linked to the ladder frame 8 by the steering lever 15 which moves the track rod with the rotation of the ladder frame 8 about the vertical axis 10 (see Figure 2) to align the stub axle of the wheels. The axle is made self steering by some stiffening of the linkages so that minor forces do not turn the wheels but the friction can still be overridden by the guidance mechanism.

Figure 4 shows the guide runner assembly 16 from above. This is mounted on the upper end of the ladder frame 8 (see Figure 2). From each side of the transverse beam 17 short guide arms 18 project forward. At the forward ends of each guide arm a bearer 19 carries electrical pick-ups 20 and guide runners 21 (simply referred to as runners) raised to run against the outer sides of the guides 22. The bearer 19 acts as electrical bus bar for all the pick-ups on that side of the guide runner assembly, while electrically isolated from the bearer on the other side.

The electrical pick-ups, which are curvilinear trailing springs, are each arranged so that maximum possible contact is maintained with the outside of the guides. The force exerted is not enough to cause a counter reaction through the flexible springs which could turn the guide runner assembly. This is assisted by the electrical pick-ups engaging the guides closer to the vertical axis 10 than the guide runners 2land thus exert a lower turning moment. One electrical pick-up on each side must be in contact with a guide to ensure continuity of electrical supply. The pick-ups are deep enough to allow for some vertical movement as they slide against the guides.

At its forward end each bearer has a guide runner 21 which, because it is rigid and is a sufficient distance from the vertical axis 10, can provide a moment strong enough to turn the entire guide runner assembly through the guide arms and about the vertical axis 10.

Figure 5 is an overhead view of the guide runner assembly which shows how the steering geometry of the vehicle works on a curved section of guides. When a vehicle, which is steered by turning the front axle (or axles), travels around a corner the line (or lines) along the axle(s) of the steering wheels should meet on a line 25 through the rear axle of the vehicle. For the vehicle also to follow the guides, this same point should be the centre 26 of the concentric circles of which the arcs of the guides are part. Stated differently, all the axles should lie along radii of the concentric circles of the guides, whether there is one front axle as with a bogie/wagon axle or a separate steering axle for each front wheel as with a king pin steering system. The unmodified king pin steering as described below is able to operate though it does not meet this requirement exactly.

As stated above, the vehicle as illustrated in Figure 5 has simple king pin steering with no Ackerman adaptation. On entering a curve the guide runner 21 acts against the concave inner guide of the pair to lever the guide runner assembly into turning about the vertical axis 10, which turns the track rod arms 13 through the track rod 14 and the steering lever 15. This turning of the track rod arms continues until the concave side stub axle aligns itself on the radius 29 at which point the leverage is abated because the vehicle can move forward with little more than sliding friction of the runner against the guide. Thus the vehicle follows the path of least resistance which is the curve of the guides.

With this version of the vehicle, it is important for smooth running at this point that the self steering characteristics of the steering axle have been re-asserted to hold the stub axle aligned on the radius 29, because if it tends to twist behind the radius there are no other immediate forces to resist it. The convex side runner would come into operation too late for the vehicle to run evenly.

Note that in addition, all four wheels follow arcs which have radii of different lengths from those of the guides but tend towards being concentric with them. The convex side front wheel only approximately aligns on the point 26 but does not stop the configuration working. Ackerman steering can bring the convex side axle to align more closely on the point 26, depending on how it is configured.

As indicated above, the runner on the convex side of the guide pair does not engage the guide nearest it and is therefore not part of the guiding process at this point, but the electrical pick-ups continue to supply power because their pressure against the guide is sustained. As the bend in the curve straightens out, the convex side guide runner may come into operation to help the vehicle follow the line of the guide track.

From the basic geometry of a circle, the guide runner contact point 27 lies at one end of a chord of the innermost circle which is bisected at right angles by the radius line 29. (With unmodified king pin steering the guide arms will lie parallel to this chord) One of the implications of this geometry is that as the guide arms are lengthened the vehicle position of Figure 5 is forced closer to centre of the circles 26.

In Figure 5, the guide arms 18 are set to a length which ensures sufficient leverage to turn the guide runner assembly and prevent under steer when entering or leaving a curve in the guides.

Consequently the line through the guide contact point 28 is well forward of the radius 29 and therefore lies skewed across the guides. The distance between the guide runners has to be at least equal to this skewed distance across the guides. This distance however is greater than the width of the guides and thus there will tend to be a gap between the guides and the runners, which can otherwise appear on either one or on both sides.

It is possible to minimise these gaps and configure the guide runner assembly with much tighter tolerances against the guides. Examination of figure 5 shows that with king pin steering the interior side stub axle on a curve is forced forward of the vertical axislO. The length of the guide arms can be reduced so the contact point 27 lies more or less on the line 29 and still produces leverage about the vertical axis 10. The line 28 through the runner contact points would therefore be more or less coincident with the radius line 29 and the runners could be set to a width close to the width (or gauge) of the guides. Such an arrangement is more workable if an Ackerman steering configuration is adopted with the line of the exterior stub axle 30 also lying on a radius through the point 26. However, such a configuration with tight physical tolerances is much less forgiving of variations in the gauge of the guides, discontinuities at junctions and movements in the bodywork of the vehicle generated by uneven surfaces and other disruptions to smooth travel. Therefore the configuration as in figure 5, with longer, higher leverage guide arms and wider physical tolerances between guides and runners is the chosen option. The design of the electrical pick-ups is adjusted to cope with the larger gaps which result.

In addition, having wider tolerances between the runners and the guides gives a reason for making the runners operate against the outside of the pair of guides. If the guide runner assembly lies entirely between the guides with wide tolerances it is possible for the assembly to twist round within the guides with possibly dangerous consequences. This is much more difficult with the outer running configuration which has the guides between the runners.

Therefore this is another chosen design feature of the vehicle described.

It is not necessary for the vertical axis of rotation of the overhead guide runner assembly to pass through the centre of the steering axle as a single pivot axis. The guide runners will still work if the axis of rotation of the assembly is still on the centre line of the vehicle but a little displaced from the vertical axis of the steering axle and connected to it by horizontal linkages. It is also possible to substitute these mechanical links and to transfer the rotation of the overhead guide runner electrically to a powered steering axle. Alternatively, an hydraulic system could be used to turn the steering axle from the rotation of the guide runner assembly There may be an opportunity to replace some parts of the design with suitable electronic or other means of guidance and control. Proximity sensors replacing or incorporated into the guide runners might be used to locate the guides and generate a signal which would cause a guide runner assembly powered by a servomechanism to follow the guides in the same way as in Figure 5. The default mode of the servomechanism might be to hold the vehicle in a straight line by returning an error signal if the transverse beam 17 (see Figure 4) turned away from being at right angles to the centre line of the vehicle. At a curve in the guides a signal could come from one of the proximity sensors which would override the default signal to turn the guide runner assembly.until the signal from the sensor was reduced to a minimum. With appropriate adjustment of the servomechanism to prevent instability and hunting', the default signal might then hold the guide runner assembly against the guide as in Figure 5. The resulting angle between a line at right angles to the transverse beam 17 and the centre line of the vehicle might be sent as a reference signal to a separate steering axle servomechanism.

The steering servomechanism might then operate to return the angle of declination between the steering lever 15 and the centre line of the bodywork (or its equivalent for other configurations of the steering geometry) to the reference value of the angle sent from the guide runner assembly as above. Thus the steering axle need not be rigidly slaved to the guide runner assembly so that any minor variations in load from traction which disrupt the steering might be corrected at the steering axle.

The system might be adjusted so that there would be no significant change in the steering when the sensors passed over a gap in the guides at a junction. Given that the guides could be used to supply power, any proximity sensors would need to be resistant to electromechanical (and other) interference. A pulsed infra red sensor might well be preferred in the conditions. This may require the profile of the guides which faces the sensors to be altered to provide a good infra red target, whilst allowing for the retention of the guide runners as a mechanical fall back system. However, the vehicle described shows the basic principles of the guidance system using the simple mechanical version.

Figure 6 shows an overhead view of how the guide runner assembly can pass through a crossing with another pair of guides at right angles. The crossing has intermediate sections of guide 31 set between the opposite guides at right angles to maintain the electrical continuity of each crossing pair of guides. Two electrical pick-ups 20 for each side of a guide runner assembly allow it to pass over gaps 32 in the guides by keeping at least one electrical pick-up pressing against a section of the guide. To achieve this the distance between the pick-up points should be larger than the gap 32 but less the length of the intermediate sections of the guides 31. This prevents two pick-ups 20 being over a gap 32 at the same time.

Figure 7 shows an overhead view of a junction at which a curved pair of guides meets a straight pair at a shallow angle and which can be used to merge the two pairs into one. The geometry of this arrangement means that a much wider gap 33 than gaps 32 (see Figure 6) is created in the concave section of the guides which the electrical pick-ups 20 are designed to pass over without interruption in supply. The advantage of this arrangement in Figure 7 is that vehicles can merge from either pair of guides without mechanical changes in the configuration of the junction.

With the guide runner assembly operating against the outsides of the guides, there is a possibility of reducing the guide pair to a composite monorail, with appropriate separation of any electrical supply circuits. However with a guiding monorail a junction such as the one illustrated in Figure 7, which merges tracks without any kind of mechanical rearrangement, would be much more difficult to design. With relatively wide separation of the guides as in Figure 7 the pairs of guides can be effectively enmeshed at the junction and the runner engaging the concave guide entering the junction cannot avoid picking up the guide which leaves the junction. Therefore the design as in Figure 7 with separated guides is the chosen option.

However if the guides at a junction are to diverge into different paths, the junction has to be configured differently for each path. Figure 8 is an overhead view of an adaptation of the junction in Figure 7 which enables it to be used in the opposite direction to divert the vehicle onto one or other of the two sets of guides emerging from the junction. Moveable intermediate sections of guide are used to bridge one or other of the gaps. These bridging sections can be operated from horizontal members linking pylons 24 (see Figure 1) and can be raised above the operating height of the main guides when not in use so the guide runner assemblies of vehicles can pass underneath them. In Figure 8 the straight moveable intermediate section 34 is lowered into place so the vehicle must continue in a straight line.

Figure 9 is a side view which shows how the gap 33 (see Figure 8) is left clear by raising the intermediate moveable section of guide 35 above the alignment of the main guides 22. The intermediate section 35 is mounted on a bearer section 36 which is suspended by linking bars 37 to the horizontal pylon member 38. These linking bars are pivoted at each end which enables the bearer section 36 to be swung upwards in parallel with the guides and out of use.

It is also possible to reset the junctions by turning or sliding any moveable intermediate sections of guide in the horizontal plane of the track, to open or close the gaps the runners must pass either through or over. This is can be particularly effective if the runners are set between the guides to operate against their inner edges. Pivoting the intermediate section of guide about a point in the centre of the guide pair allows it to be turned to open or close gaps at its ends, which either allows the runners through or diverts them onto a different track.

Claims

A GUIDED VEHICLE SYSTEMCLAIMS1. A guided vehicle system comprising: a guidance track consisting of a rigid guide or guides supported overhead by multiple pylons, with appropriate crossings and junctions and which can be used to supply electrical power; and a vehicle, which can be self powered or draw electrical power from the guidance system, moving by traction on a surface which carries its weight and which steers itself either mechanically, electrically, hydraulically or through servomechanisms until overridden by interaction with the guidance system; the self steering of the vehicle being overridden whenever one of a pair of overhead guide runners engages the edge of a guide either mechanically or through a proximity sensor, the runners being mounted on an assembly which is rotatable about an appropriately positioned vertical axis, so the rotation of the assembly through its linkage either mechanically, electrically, hydraulically or through a servomechanism adjusts the steering axle or axles; the position of the guide runners being set forward of the vertical axis so that when the moving vehicle enters a curve in a guide track the leverage of a guide runner acting on the concave edge of a guide or the signal from a proximity sensor to a servo mechanism turns the assembly about its vertical axis and through its linkage overrides the self steering to adjust the steering axle or axles until the leverage is abated or the signal from the proximity sensor is sufficiently reduced by the steering axle or axles tending to align on radii of the curve, along with the rear axle of the vehicle tending to align on a similar radius, thereby allowing the vehicle to follow the path of least resistance which is the curve of the guides.
2. A guidance system as in Claim 1 comprising either a single guide or pairs of guides supported overhead by multiple pylons at an appropriately safe distance above the surface of travel, modified if required to act as targets for proximity sensors, and which may be used to supply electrical power; pairs of guides being appropriately supported by the pylons so the guide runners as in Claim 1 can run between the guides and act against their inner edges or run outside of the guides and act against their outer edges, a single guide being a version of the outer running option with the guides combined as two outer edges but provision to keep any electrical circuits separate; insulation and support of the guide or guides so they can if required supply electrical power or support separate electrical circuits to supply electrical power; gaps in the guide or guides with continuity of any electrical circuits to allow junctions and crossings of separate guidance tracks to operate; fixed intermediate sections of guide with continuity of any electrical circuits for use with crossings or junctions of pairs of separated guides where wider gaps may need intermediate guide bridges; moveable intermediate sections of guide with continuity of any electrical circuits which can be used to configure crossings or junctions to divide or merge guide tracks either as separate single guide tracks or as separate tracks with pairs of guides, by selectively lifting the intermediate section out of use or by rotating or sliding the intermediate section in the same horizontal plane of the track so appropriate gaps can opened or closed.
3. A vehicle as in claim 1 which is steered by its front axle and which can be driven by its front or rear axle; the front steering axle being a bogie or wagon axle pivoted about its centre or a king pin steering axle, with or without Akerman modification, adapted mechanically, electrically, hydraulically or by using a servomechanism in conjunction with the guide runner assembly to steer the vehicle until overridden by interaction with the guidance system; the front axle being linked mechanically, electrically, hydraulically or through a servomechanism to the guide runner assembly able to make contact with the overhead guides as in claim 1, such that rotation of the guide runner assembly adjusts the steering axle or axles; the assembly being turned by leverage arising from sliding contact of a guide runner mounted forward of the centre of the steering axle with an edge of an overhead guide or by a servomechanism linked to a proximity sensor replacing or as part of the guide runner; the sliding face of the guide runners being deep enough to allow for some undulation of the guides and vertical movement of the bodywork of the vehicle or the proximity sensors being adapted to allow for the same undulation in the guides; the distance between the guide runners or proximity sensors being set to allow any necessary tolerance between them and the guide or guides which may be required by a skewed position of the runners across the guides forward of a radius of a curve in the guides or to allow for some lateral movements of the bodywork; electrical pick-ups being supported by the vehicle which draw current from the guides when they are supplying power or from other electrical supply circuits, the pick-ups being deep enough to allow for vertical movement of the vehicle bodywork or variations in the guide track and which are sufficiently flexible laterally and under sufficient pressure to retain electrical contact with any electrical circuits.Amendments to the claims have been made as followsA GUIDED VEHICLE SYSTEMCLAIMS1. A guided vehicle system comprising: a guidance track consisting of a rigid guide or guides supported overhead by multiple pylons, with crossings and junctions and which can supply electrical power; and a vehicle, which can draw electrical power from the guidance system, moving by traction on a surface which carries its weight and which steers itself either mechanically, electrically, hydraulically or through a servomechanism or servomechanisms until overridden by interaction with the guidance track; the self steering of the vehicle being overridden whenever one of a pair of overhead guide runners engages the edge of a guide either physically or through a proximity sensor which signals a trigger distance from the edge of a guide, the runners being mounted on an assembly which is rotatable about a vertical axis, so the rotation of the assembly through its linkage either mechanically, electrically, hydraulically or through a servomechanism or servomechanisms linked to the proximity sensor adjusts the steering axle or axles; the position of the guide runners being set forward of the vertical axis so that when the moving vehicle enters a curve in a guide track the leverage of a guide runner acting on the concave edge of a guide or the signal from a proximity sensor to a servo mechanism or servomechanisms turns the assembly about its vertical axis and through a linkage overrides the self steering to adjust the steering axle or axles until the leverage is abated or the signal from the proximity sensor is sufficiently reduced by the steering axle or axles tending to align on radii of the curve, along with a rear axle of the vehicle tending to align on a similar radius, thereby allowing the vehicle to follow the path of least resistance which is the curve of the guides.**, 2. A guided vehicle system as in Claim 1, having a guidance track which is either a single guide or pairs of guides supported overhead by multiple pylons at a safe distance above the surface of travel, modified if required to act as targets for proximity sensors, and which can supply electrical * , power; pairs of guides being supported by the pylons so the guide runners as in Claim 1 can run between the guides and act against their inner edges or run outside of the guides and act against their outer : :* edges, a single guide being a version of the outer running option with the guides combined as two outer edges but provision to keep any electrical circuits separate; * insulation and support of the guide or guides so they can supply electrical power or support separate electrical circuits to supply electrical power; gaps in the guide or guides with continuity of any electrical circuits to allow junctions and crossings of separate guidance tracks to operate; fixed intermediate sections of guide with continuity of any electrical circuits for use with crossings or junctions of pairs of separated guides where wider gaps may need intermediate guide bridges; moveable intermediate sections of guide with continuity of any electrical circuits which can be used to configure crossings or junctions to divide or merge guide tracks either as separate single guide tracks or as separate tracks with pairs of guides, by selectively lifting the intermediate section out of use or by rotating or sliding the intermediate section in the same horizontal plane of the track so gaps can be opened or closed.3. A guided vehicle system as in claim 1, having a vehicle which is steered by its front axle and which can be driven by its front or rear axle; the front steering axle being a bogie or wagon axle pivoted about its centre or a king pin steering axle, with or without Akerman modification, adapted mechanically, electrically, hydraulically or by using a servomechanism or servomechanisms in conjunction with the guide runner assembly to steer the vehicle until overridden by interaction with the guidance track; the front axle being linked mechanically, electrically, hydraulically or through a servomechanism or servomechanisms to the guide runner assembly able to interact with the overhead guides as in claim 1, such that rotation of the guide runner assembly adjusts the steering axle or axles; the assembly being turned by leverage arising from physical interaction of a guide runner mounted forward of the centre of the steering axle with an edge of an overhead guide or by a servomechanism or servomechanisms linked to a proximity sensor replacing or as part of the guide runner; the acting face of the guide runners being deep enough to allow for some undulation of the guides and vertical movement of the bodywork of the vehicle or the proximity sensors being adapted to allow for the same undulation in the guides or vertical movements of the bodywork; the distance between the guide runners or proximity sensors being set to allow any necessary tolerance between them and the guide or guides which may be required by a skewed position of the runners across the guides forward of a radius of a curve in the guides or to allow for some lateral movements of the bodywork; electrical pick-ups being supported by the vehicle which can draw current from the guides when * they are supplying power or from other electrical supply circuits, the pick-ups being deep enough to *. allow for undulations in the guides or other electrical circuits or vertical movements of the vehicle bodywork and which are sufficiently flexible laterally and under sufficient pressure to retain electrical contact with the guides or other electrical circuits.*:.
4. A guided vehicle system as claimi, which uses of a self powered vehicle with the guidance * track: ::. the guidance track being otherwise the same but does not supply electrical power to the vehicle; :: and the vehicle being otherwise the same but having a source of power independent of the guidance track; and self steering of the vehicle being overridden by interaction with the guidance track in the same manner.