Transport vehicles that can travel both on roads and over rails are known. These transport vehicles have both rail wheels and (pneumatic) tires. In the known transport vehicles, use is made of the guiding effect of the rails, but the pneumatic tires take over other tasks from the rail wheels on the rails. Thus, French patent specification No. 2741582 discloses a vehicle in which the pneumatic tires are used for the drive and braking. The pneumatic tires are suspended movably from the rail wheels, and the position of the pneumatic tires is adjusted on the basis of the rail wheels, so that the vehicle follows the rail wheels.

U. S. patent specification 3,874,306 discloses a vehicle in which the pneumatic tires engage with the rails to drive and brake the vehicle. Here, too, the rail wheels have a guiding function, although the pneumatic tires also have some guiding effect in that they bend over the rails to some extent.

German patent specification DE 40 41 970 also discloses a mixed rail wheel-pneumatic tire vehicle. It includes a pressure controller to provide that the rail wheels press on the rails with a constant force. Further, French patent specification No. 2467718 discloses a system for turning a rail wheel- pneumatic tire vehicle onto the rails, such that the rail wheels all end up above the rails.

Transport of goods by road has a variety of generally known inherent drawbacks, in particular with regard to energy consumption, environmental impact, noise production and road congestion. Logistically favorable, however, are its speed, flexibility, fine-meshed structure and the individual handling of the transport units (containers). Traveling on tires, it is possible to maneuver freely at transfer locations, allowing various logistic functions

to be realized in a comparatively small space. As far as these logistic aspects are concerned, transport of goods by rail, compared with transport by road, is deficient, certainly when short transport distances are involved. Another drawback of rail transport is the limited grip of steel on steel, which entails very long braking distances. As a consequence, the frequency of travel must necessarily be low, which is logistically unfavorable and moreover disadvantageous to the capacity of the rail. On the other hand, however, an energetically and economically favorable feature of travel on rails is the low rolling resistance.

It is therefore desirable to arrive at a collective transport system of large capacity, which combines the advantages of the two transport modalities and avoids the disadvantages. Such a transport system should offer an alternative to rail and road transport and could function as a complement thereto.

It is then desirable to profit optimally from the low rolling resistance of travel on rails. The known vehicles with both rail wheels and pneumatic tires do not optimally enable this, because the rail wheels in these vehicles have a guiding effect. Mostly, the rail wheels are fairly small, just large enough for a guiding effect, but not aimed towards obtaining a low rolling resistance. Nonetheless, the suspension of the rail wheels must be made of fairly heavy construction to enable transmission of the guiding forces from the rails. Also, the rail wheels must be provided with flanges for the purpose of guidance. The flanges render the rail wheels heavier, produce undue noise and lead to energy loss.

It is one object of the invention to provide a transport vehicle which has both pneumatic tires and rail wheels, but in which the rail wheels do not need to provide a guiding function.

The invention provides a transport vehicle according to claim 1. In the transport vehicle according to the invention, the rail wheel sets have some freedom of movement transverse to the vehicle chassis. Position

determining means measure the position of the transport vehicle transverse to the rails. These means can comprise, for instance, an induction sensor which responds to the metal of the rails, or a dGPS (differential Global Positioning System) receiver, or a receiver of signals from beacons especially arranged for that purpose, etc., or combinations thereof. A control system controls and adjusts the tires on the basis of information obtained from the position determining means, so that the vehicle follows the rails.

The rail wheels are preferably wider than the wheels currently used on rails, so that there is a wider margin for positioning the sets of wheels relative to the rails. The rail wheels are preferably somewhat conically shaped, so that the rail wheel sets of which they are a part are self-centering relative to the rails during travel.

If the transport vehicle moves too far in transverse direction relative to the rails, the rail wheels are preferably automatically retracted, so that the transport vehicle comes to rest completely on the tires.

In one embodiment, the axle pressure of the second wheel sets is controlled, such that each of the first wheel sets always carries a portion of the weight of the transport vehicle and the weight distribution is such that, under normal operating conditions, a stable and slip-free movement is ensured. Upon actuation of the braking mechanism on the first wheel sets, the axle pressure of the second wheel sets, if necessary, is reduced according as the braking force of the first wheel sets increases. In that way, the length of the brake paths corresponds to that of road vehicles, also during travel on rails. The track section in question can therefore facilitate intensive traffic of these hybrid transport vehicles. Traveling in stationary condition, or approximately stationary condition, the greater part of the transport vehicle weight is carried by the rail wheel sets. The energetically favorable effect of the low rolling resistance of travel on rails therefore applies to a large extent to the hybrid transport vehicle as well, provided, naturally, the rails are utilized. During transport over a road or over a transfer location, the rail

wheels are pulled up. Then a control system is utilized with which the first wheel sets can be steered independently of rails and which effectuates specified directions about a route to be followed. Depending on the nature of the logistic environment, this control can be automated, but also man- operated, or can be of hybrid automatic/man-operated design. Traveling in this form, the transport vehicle has the flexibility of a vehicle moving on tires and not bound to rails nor to any other fixed track section. In summary, the invention provides a transport vehicle which combines the advantages of transport on tires with that of rail transportation, while in use the disadvantages thereof can be avoided to a large extent.

To clarify the energetic advantage that can be obtained according to the invention, reference is made to the table below, representing a comparative overview for the transport of sea containers. The top line in this table gives an indication of the required power for a transport vehicle without rail wheels at a speed of 100 km/hour, which is the normal speed of an articulated truck on highways.

Indication of energetic power and energy consumption avera e stationa condition heav loadin speed required power consumption required power relative to 100 100 km/h 244 kW 100% 930 kW 50 km/h 72 ka 60% 400 kW 10 km/h 13 kW 50% 75 kW *50 km/h 38 kW | 33% 350 kW The next two lines of the table give an energetic indication for a transport vehicle without rail wheels at a speed of 50 and 10 km/h, respectively. The bottom line gives an energetic indication for a hybrid transport vehicle which, at a speed of 50 km/h, is supported for 60% on the rail wheels. The column"average stationary condition"reflects the situation without gradient, given normal loading and some wind action. The condition"heavy loading"involves heavy loads, a gradient of 3% and strong head wind. In that circumstance, the speed could be limited to 30 km/h. It is noted that the

kinetic energy and the effect of variations in speed has not been taken into account. For a manned vehicle, the factor of speed is of great importance, in view of the high personnel costs and the regulations regarding driving times. For an unmanned vehicle, speed plays a much lesser role, so that an energetically advantageous manner of driving can be taken into account more. Given a speed of 50 km/h and a support of 60% on the rail wheels, already a very considerable energy saving is obtained, compared with a robotic vehicle without rail wheels, and certainly when compared with a conventional articulated truck. The speed of 10 km/h is relevant for travel at container terminals.

Although the transport vehicle could be manned, important advantages are obtained precisely when the transport vehicle functions as an "automatically guided vehicle"in an open"intelligent logistic system", in which the displacements on the connecting track sections, the maneuvers on the transfer locations, and logistic handling all proceed in coordination. In principle, any vehicle is welcome, provided that standards for driving properties, steering and safety are met. Admission is arranged by communication via a system of"dynamic slotting".

These and other objects and advantages of the transport vehicle according to the invention will be further described with reference to the accompanying drawing.

Fig. 1 shows a hybrid transport vehicle; Fig. 2 shows braking provisions in a hybrid transport vehicle ; Fig. 3 shows a control system in a hybrid transport vehicle.

In the accompanying Figure 1, an example of the hybrid transport vehicle in a design as a robotic vehicle is represented in side elevation. The robotic transport vehicle is provided with two front and two rear first wheel sets, with a second wheel set between them. The wheel sets 2-5 are provided

with wheels with pneumatic tires, while the wheel set 6 is provided with steel rail wheels. The wheels of one of the front wheel sets and of one of the rear wheel sets are motor-driven. The other first wheel sets and the second wheel set are not driven. The transport vehicle is steered by the wheel sets 2-5. The wheel set 6 is suspended so as to be"track-following"in the sense to be described hereinafter. The rail wheels are brought into a highest position when the robotic vehicle, traveling on the pneumatic tires, is moved over the road, and further under the circumstances mentioned hereinafter.

The rail wheels can be lowered when the robotic carrying vehicle is moved over rails; this situation is represented in Fig. 1.

Fig. 2 shows braking provisions in the robotic carrying vehicle.

Schematically shown are rails 35, wheels 36a, b with pneumatic tires, a rail wheel 38, a chassis 39, a brake control 30 with a control signal input 31, a controlled brake 32 on one of the wheels 36a with pneumatic tires, a pressure controller 33 and a pressure control energization 37. Naturally, all parts are connected with the chassis 39, but this is not further shown for the sake of clarity. In operation, the pressure controller 33 regulates the pressure with which pressure control energization 37 presses the rail wheels 38 on the rails 35. When a brake signal comes in at input 32, brake control 30 transmits a signal to the controlled brake 32 to effect braking. In addition, in that case, the brake control transmits a signal to the pressure controller 33 to reduce the pressure on the rail wheels 38.

The pressure at which the rail wheels are pressed against the rails determines the extent of relief of the pneumatic tire wheels. The wheel pressure of the rail wheels can be automatically controlled. On straight rail tracks and in gentle curves, in stationary condition, the wheel pressure of the rail wheels is controlled such that the wheel sets 2-5 at each end jointly carry, for instance, at least 40% of the vehicle weight. In the event of braking, the pressure on the rails is reduced or removed entirely. This last is also the case in sharp bends, so that the effects of the favorable grip of the

tires on the road surface are maintained. When, through whatever cause, the deviation of the transport vehicle relative to the rails becomes too large, the rail wheels are pulled up until the transport vehicle is completely on the track again. The invention is not limited to the exemplary embodiment described here with reference to the drawing; many variants are possible.

Instead of one, for instance two rail wheel sets can be arranged in the middle, optionally suspended in tandem in a common frame. Also, instead of the double first wheel sets at the vehicle ends, single first wheel sets can be arranged. Also possible is a variant as a robotic trailer.

Fig. 3 shows a control system in a hybrid transport vehicle. The figure schematically shows rails 20a, b, rail wheels 22a, b, sensors 24a, b, a controller 26, steering energization 27a, b and wheels 28a, b with tires. These parts are connected with a chassis of the transport vehicle (not shown). In operation, the sensors 24a, b detect the presence of the rails 20a, b, and if rails 20a, b are present, the sensors measure the position of the transport vehicle relative to the rails in transverse direction. Depending on the sensor measurements, the controller 26 controls the steering 27a, b of the wheels 28a, b with tires, so that the transport vehicle follows the rails 20a, b. For this purpose, instead of a sensor for the rails, other means can be used, such as a dGPS receiver, in combination with an electronic card in which the position of the rails in dGPS coordinates is stored, or a receiver of beacon signals from beacons arranged along or between the rails, etc., or combinations of these kinds of position determining means.

A technical aspect is that the hybrid transport vehicle is provided with sensor means to determine the presence of the rails and, if this is the case, to measure the position of the transport vehicle relative to the rails in transverse direction. Induction sensors are eligible for this purpose. When the transport vehicle exhibits a deviation from the centered position on the rails that is greater than a predetermined value, or when the presence of the rails has not been established, the rail wheels are pulled up, or remain

in pulled-up position. When the presence of the rails has been established and the transport vehicle exhibits a deviation relative to the centered position on the rails that is smaller than a predetermined value, and moreover the control instructions give cause therefor, the rail wheels are lowered. The first wheel sets (that is, the wheel sets running on tires) are equipped with a conventional control system, such that when the road surface is provided with rails, these rails can be followed, using the sensor measurements mentioned. In this control, also the positions of the second wheel sets can be taken into account. As already mentioned, the hybrid transport vehicle is provided with at least one rail wheel set. Each rail wheel set is suspended separately, or else in tandem with another rail wheel set, so as to be"track-following"in the sense that both swiveling and some transverse movement are possible. Steering and suspension are such that the occurrence of transverse forces is avoided to a large extent. By analogy with conventional rails, the rail wheels are slightly conically shaped, but are preferably wider, while the conventional wheel flanges are preferably omitted. The rail wheels in a rail wheel set are coupled as regards rotation.

This can be effected by mounting them rigidly on a common shaft. Another possibility is for the two rail wheels suspended opposite each other to be mounted rigidly on their own shaft and to couple these shafts homokinetically in the middle of the transport vehicle. By placing the shafts at that point higher than the wheel center, it can be provided that the rail wheels are supported"horizontally"on the rails. The rails then need to project only little above the road surface. In this set-up, there is no need for rail switch points to cause the transport vehicle to shift to a different route.

The sound of flanges grating along the rails is absent. The transport vehicle is further equipped with a control system with which the first wheel sets can be steered independently of rails and which effectuates specified directions about a route to be followed. In this set-up, no rails are needed on slip roads nor at the logistic stations and the like.

The invention relates to constructional variants for different areas of application, for instance as an alternative to road traffic, as described here, as a transport modality for urban transport of goods, as a transport modality for logistic complexes (such as Schiphol airport, in particular the underground logistic system), but also for urban and regional passenger transportation. The invention encompasses all kinds of modifications, naturally insofar as they fall within the scope of protection of the following claims.