Hand truck World

A wheelchair with adjustable swivel castors is described. The wheelchair with adjustable castors includes a mechanism to limit the swivel range of the castors. The swivel range may be limited manually or automatically as a function of the terrain or the speed of the chair.

A wheelchair with adjustable castors which is provided with wheels for driving and steering the wheelchair and with at least oe swivel castor, the swivel castor bearing part of the weight of the wheelchair, the swivel castor having a swivel axle and a swivel range which lies in a first swivel area which includes a straight-on direction of travel of the wheelchair, and the swivel castor being freely pivotable about the swivel axle in the first swivel area; the wheelchair with adjustable castors further being provided with swivel range limiting means which are adapted to be switched on and off and which, when switched on, limit the swivel range of said swivel castor to a second swivel area which is smaller than said first swivel area, with said straight-on direction of travel of the wheelchair being included within the second swivel range;

wherein said swivel range limiting means comprise at least one projection arranged eccentrically on the swivel axle, and at least one movable element which is provided with stop surfaces, said movable element being movable between a first position in which the swivel range of the swivel castor lies in said first swivel area, and a second position in which said element interacts with said projection to limit the swivel range of the swivel castor to said second swivel area.

wherein said arms are capable of being placed by means of pressure-exerting elements, which are movable to and fro over outer surfaces of said arms in a position which limits the swivel area, said pressure-exerting elements being connected to one another by means of a pressure-exerting element holders and being connected to an actuating member by means of a Bowden cable;

wherein said eccentrically positioned projection is situated between said stop surfaces of said arms.
Description

BACKGROUND

The present invention relates to a wheelchair, which is provided with wheels for driving and steering the wheelchair with adjustable castors and with at least one swivel castor, which bears part of the weight of the wheelchair and has a swivel axle, the swivel castor having a swivel range which lies in a first swivel area which includes the straight-on direction of travel of the wheelchair, and the swivel castor being freely pivotable about the swivel axle in the first swivel area.

A wheelchair with adjustable castors of this kind is generally known. The front wheels for driving and steering can be driven by means of manual force or by means of, for example, one or more electric motors. The axes of the axles of the wheels for driving and steering generally coincide. In order to prevent the wheelchair from tipping backwards about the common axis of the front wheels, the wheelchair with adjustable castors at the rear side has substantially freely pivotable swivel castors. The wheels for driving and steering and the swivel castors are positioned such that the mass centre comes to lie between the common axis of the wheels for driving and steering and the swivel castors. The swivel castors have the ability to pivot about the swivel axle such that they are in a position which corresponds to the direction of travel, which is determined by the front wheels, of the wheelchair.

The drawback of a wheelchair with adjustable castors of this kind is that when taking bends the wheelchair tends to break out of the bend. This oversteer effect is caused by the centripetal force acting on the mass centre of the wheelchair. The oversteer effect occurs in particular when taking a bend at high speed.

SUMMARY

The object of the invention is to provide a wheelchair with adjustable castors which does not have this drawback.

To this end, the wheelchair according to the invention is characterized in that the wheelchair comprises means which can be switched on and off and which limit the swivel range of the swivel castor to a second swivel area which is smaller than the first swivel area, with the straight-on direction of travel of the wheelchair with adjustable castors being included within the second swivel range.

The possibility of the wheelchair with adjustable castors breaking out of the bend is counteracted by the frictional forces exerted by the ground on the swivel castors which are in the limited swivel position.

Further preferred embodiments of a wheelchair with adjustable castors according to the invention are described in the claims.

In order to counteract the problem of oversteer of the wheelchair with adjustable castors mentioned in the introduction to the description, a wheelchair which is described below is provided.

In a preferred embodiment of a wheelchair according to the invention, the wheelchair is provided with means for travelling straight on, which means exert on the swivel castor a force which moves the swivel castor into the position which corresponds to the straight-on direction of travel of the wheelchair. The means for traveling straight on can be controlled automatically or manually, possible parameters which can be used for the continuous adjustment of the force being the speed of the wheelchair and/or the condition of the ground.