The invention relates to a movable vehicle provided with a frame that supports wheels , wherein at least one of the wheels is a caster wheel , which caster wheel is provided with a plane of rotation .

US 9 , 381 , 124 provides an example of such a vehicle . This document teaches a wheeled vehicle , wherein at least one ground-engaging wheel is connected to a pivotable hub, the pivotable hub being attached to the body of the vehicle by a fixed pivot member and a laterally-adj ustable pivot member, the position of the laterally-adj ustable pivot member being adj ustable to cause the hub to pivot and thereby adj ust the camber of the said wheel , and wherein the pivotable hub is provided with one or more lugs arranged to engage the later- ally-adj ustable pivot member when the wheels are in a minimum or maximum camber position . In this way it is possible for the user to lower the center of gravity of the vehicle in use , thereby rendering the vehicle more stable on uneven or inclined terrain and to reduce the tendency for the vehicle to topple .

US2020/ 0079153 discloses a movable vehicle provided with a frame that supports wheels , wherein at least one of the wheels is a caster wheel , which caster wheel is provided with a plane of rotation, which plane of rotation of the at least one caster wheel is positioned or positionable at a selectable angle with reference to the frame such that during use of the vehicle on a supporting surface , said caster wheel is or can be obliquely oriented with reference to the supporting surface , wherein the at least one caster wheel is suspended from the frame by a connector, wherein the at least one caster wheel exhibits an axle connecting the caster wheel with the connector, and wherein the connector can hinge with reference to the frame so as to provide the axle of the caster wheel with an oblique position in comparison with a neutral hori zontal orientation of the axle when the vehicle is placed on a hori zontal supporting surface .

It is an obj ect of the invention to provide a movable vehicle according to the preamble of the main claim with a predefined or selectable steering characteristic, which enables the user to propel the vehicle with an of f-center force without necessarily causing the vehicle to turn .

The vehicle of the invention is provided with one or more features according to the appended claims .

In a first aspect of the invention the vehicle is equipped with a user operable mechanical transmission and a user input organ for setting the user operable mechanical transmission during use of the vehicle enabling during said use of the vehicle an instantaneous control of the orientation of the caster wheel with reference to the frame . The inventors have found that this is an ef fective way of controlling the steering characteristic of the vehicle . It is thus for instance possible to provide an of f-center driving force to the vehicle whilst maintaining that the vehicle propels in a straight line rather than make a turn or to provide a centric driving force and make the vehicle turn . This is particularly helpful with a wheelchair or hospital bed must be moved, wherein it is not always possible or desirable to provide a central driving force to the wheelchair or hospital bed . This can occur when it is desirable that the person that drives the wheelchair or hospital bed tries to maintain eye contact with the person in the wheelchair or hospital bed . In the prior art this is a strenuous and di f ficult challenge which may inflict physical inconveniences for the person that provides the driving force to the vehicle , and which are avoided in the invention .

Preferably the at least one caster wheel is suspended from the frame by a connector, wherein the at least one caster wheel exhibits an axle connecting the caster wheel with the connector, and wherein the axle of the caster wheel can assume an oblique position in comparison with a neutral hori zontal orientation of the axle when the vehicle is placed on a horizontal supporting surface . This can for instance be reali zed by arranging that the connector can hinge or rotate over a limited angle with reference to the frame . It is found that the sideways extending oblique position of the caster wheel is particularly helpful in compensating a torque that is applied to the vehicle by the of f-center driving force , whereas the also possible backwards trailing position of the caster wheel improves stability in the sense of maintaining a given driving direction . It is of course also possible to combine both positions of the caster wheel .

In another embodiment it may be desirable that the connector is spring-loaded with a spring so as to provide the caster wheel with a preferential angularly displaced position in comparison with a motional direction of the vehicle . This can be applied both in the situation that the axle of the caster wheel is in a neutral hori zontal orientation or in the situation that the axle of the caster wheel is in an oblique orientation with reference to the neutral hori zontal orientation when the vehicle is placed on a hori zontal supporting surface .

The vehicle of the invention can be embodied in many ways , and preferably the vehicle is selected from the group comprising a wheelchair, a trolley, a hospital bed, an unmanned ground vehicle , an automobile , lorry or caravan, a forkli ft truck, a space rover .

The invention is also embodied in a mounting block with a caster wheel , wherein the mounting block is arranged for later placement on a frame of a vehicle , wherein the caster wheel has a plane of rotation, which plane of rotation of the at least one caster wheel is positioned or positionable at a selectable angle with reference to the mounting block . The mounting block with the caster wheel can then be later provided to upgrade an existing vehicle to take advantage of the benefits of the invention . The at least one caster wheel is suspended from the mounting block by a connector which can hinge with reference to the mounting block, so as to execute for example a translation to modi fy caster trail , or a rotation about a forward-pointing axis , to create an oblique orientation of the caster wheel . According to the invention the connector is spring-loaded with a spring . Accordingly this provides an ef fective way of controlling the steering characteristics of an already existing vehicle on which the mounting block is applied in the aftermarket .

The invention will hereinafter be further elucidated with reference to the drawing of an exemplary embodiment of a movable vehicle according to the invention that is not limiting as to the appended claims .

In the drawing :

- figure 1A/B shows a vehicle according to the invention in a top view and side view, respectively;

- figure 2A/B shows a vehicle of the invention in an isometric view and side view, respectively;

- figure 3A/B/C shows another example of a vehicle of the invention in an isometric view, a frontal view and a side view, respectively;

- figure 4A/B shows still another example of a vehicle of the invention in an isometric view and side view, respectively; and

- figure 5A/B shows an embodiment of the vehicle of the invention in a side view and bottom view, respectively;

- figure 6A/B shows a vehicle of the invention embodied as a wheelchair in an isometric view and frontal view, respectively; and

- figure 7 shows a schematic of a mechanical transmission to be applied in a vehicle according to the invention to control its steering behaviour .

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts .

Making first reference to figures 1A/B, it shows a movable vehicle 1 provided with a frame 2 that supports wheels 3 , 4 wherein at least one of the wheels 3 , 4 is a caster wheel 4 .

Figure 1A shows the vehicle 1 when it is arranged to be consistent with a conventional vehicle according to the prior art , wherein the caster wheel 4 is oriented at right angles with reference to a supporting surface 5 . In this situation the plane of rotation of the caster wheel 4 is indeed at right angles with the supporting surface 5 . When the vehicle assumes this orientation a force F that is applied to the vehicle 1 of f-center, will cause the vehicle 1 to make it turn according to the arrow A.

The turn of the vehicle 1 according to the arrow A as shown in figure 1A can be prevented by providing that the plane of rotation of the at least one caster wheel 4 is positioned or positionable at an angle with reference to the frame 2 such that during use of the vehicle 1 on a supporting surface 5 , said caster wheel 4 is or can be obliquely oriented with reference to the supporting surface 5 . This is shown in figure IB . When in this situation a force F is applied of f- center to the vehicle 1 , the vehicle 1 will follow a straight line B, depending of course on the magnitude of the force F and the amount of obliqueness provided to the caster wheel 4 .

In the figures 2 - 4 it is shown that the at least one caster wheel 4 is suspended from the frame 2 by a connector 6 . The angle at which the connector 6 is suspended from the frame 2 as shown in the respective figures 2 - 4 is representative for the feature that , wherein the at least one caster wheel 4 exhibits an axle 9 connecting the caster wheel 4 with the connector 6 , the axle 9 of the caster wheel 4 can assume an oblique position in comparison with a neutral horizontal orientation of the axle 9 when the vehicle 1 is placed on a hori zontal supporting surface 5 . This provides the caster wheel 4 and its axle 9 with at least one of a sideways extending oblique position ( see figure 2A/B ) and a backwards trailing position ( see fig . 3A/B/C and in particular figure 4A/B ) in comparison with a neutral hori zontal orientation of the axle 9 when the vehicle 1 is placed on a hori zontal supporting surface 5 .

The figures 2 - 4 also depict that the invention can be embodied in a separate mounting block 7 provided with a caster wheel 4 , wherein the mounting block 7 is arranged for placement on a frame 2 of a vehicle 1 , and wherein the plane of rotation of the at least one caster wheel 4 is positioned or positionable at a selectable angle with reference to the mounting block 7 .

Also here the at least one caster wheel 4 is suspended from the mounting block 7 by a connector 6 which is movable with reference to the mounting block 7 . Preferably the connector 6 is spring-loaded with a spring as elucidated hereinafter .

Figure 5A/B is provided to show that the connector 6 can be spring-loaded with a spring 12 so as to provide the caster wheel 4 with a preferential angularly displaced position in comparison with a motional direction of the vehicle 1 , which corresponds to a limited rotation of the caster wheel 4 in comparison with the orientation of the other wheels 3 .

Figure 7 depicts a scheme that reflects that the vehicle 1 is equipped with a user operable mechanical transmission for controlling the orientation of the caster wheel 4 with reference to the frame 2 of the vehicle 1 . In figure 2B this is implemented with a user organ 10 for setting a mechanical transmission 11 that instantaneously controls the orientation of the caster wheel 4 with reference to the frame 2 of the vehicle 1 .

Without intent to exclude any other possible application of the invention, figure 6A/B depicts that the movable vehicle according to the invention is embodied as a wheelchair 8 . There are however many other possible applications , to be selected from the group comprising a wheelchair, a trolley, a hospital bed, an unmanned ground vehicle , an automobile , lorry or caravan, a forkli ft truck, a space rover . The word ' comprising' entails that the group is not exhaustive , and that other -not-mentioned- applications may be included in this group .

Although the invention has been discussed in the foregoing with reference to an exemplary embodiment of the movable vehicle of the invention, the invention is not restricted to this particular embodiment which can be varied in many ways without departing from the invention . The discussed exemplary embodiment shall therefore not be used to construe the appended claims strictly in accordance therewith . On the contrary the embodiment is merely intended to explain the wording of the appended claims without intent to limit the claims to this exemplary embodiment . The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using this exemplary embodiment .