Land vehicles – Step or abutment ascending type vehicle – With spider-type engaging means
Patent
1985-05-06
1987-02-24
Love, John J.
Land vehicles
Step or abutment ascending type vehicle
With spider-type engaging means
180 82, B62B 906
Patent
active
046452222
DESCRIPTION:
BRIEF SUMMARY
From a first aspect the present invention relates to a method of operating a vehicle to climb a flight of steps, the vehicle comprising a load-carrying body provided with front and rear wheel assemblies, wherein one of said wheel assemblies is moved onto a tread of the lowest step of said flight and the positional relation between the wheel assemblies and the body is varied to compensate for the upward movement of the one wheel assembly and to maintain the attitude of the body substantially constant.
According to a second aspect of the invention, there is provided a vehicle comprising a load-carrying body provided with front and rear wheel assemblies, wherein one of the wheel assemblies is movable upwardly and downwardly relative to the body and other wheel assembly whilst the attitude of the body remains substantially unchanged and is such that both wheel assemblies could rest on a horizontal plane, the permitted upward movement of the one wheel assembly relative to the body from the horizontal plane being at least 150 mm.
Upward movement of one wheel assembly relative to the other through a distance of 150 mm is sufficient to maintain the body substantially horizontal when the other wheel assembly moves down a moderate step.
The invention has been devised primarily in relation to a vehicle which is a wheelchair. However, the invention may be applied to other wheeled vehicles where analogous features can be used.
In GB Pat. No. 1,430,714, there is disclosed a load-carrying cart having a pair of rear wheels rotatable about an axis which is fixed with respect to a body of the cart and a pair of front wheels rotatable about an axis which can be moved relative to the body. The cart is intended to be used for carrying loads up and down flights of stairs. The front wheels are mounted on an arm which pivots with respect to the body. However, the cart is so designed that a load-carrying platform which is horizontal, when the cart runs on a horizontal floor surface, is steeply inclined to the horizontal when the cart moves up a flight of stairs. The front wheels are mounted on an arm pivoted to the body for movement along an approximately horizontal path when the load-carrying surface of the body is horizontal.
The present invention provides a vehicle in which a load-carrying surface which is horizontal in normal use on a horizontal floor can remain horizontal during ascent of or descent of at least some flights of stairs.
According to a third aspect of the invention, there is provided a wheelchair comprising a seat and front and rear wheel assemblies wherein one of said assemblies is movable upwardly and downwardly relative to the seat when the seat is in the normal attitude of use and there is provided control means for controlling upward and downward movement of said one assembly in accordance with the relation between rotation of an element of the front wheel assembly and rotation of an element of the rear wheel assembly.
When the wheelchair travels along level ground, said elements of the front and rear wheel assemblies may rotate at the same speed. If one of the wheel assemblies then travels down a step whilst the other wheel assembly moves a relatively short distance along the level ground, one of said elements will rotate at a higher speed than the other during movement of the one wheel assembly down the step and this change in the relative speeds of the elements is used to control relative movement of the seat and other wheel assembly so that the attitude of the seat remains approximately constant. Alternatively, the relative movement may be controlled by the user.
Said one assembly may be movable along a predetermined path relative to the seat, the relation between the path and the seat being such that, when the seat is in the normal attitude of use, movement of said one assembly in one direction along the path can be resolved into an upward component and a horizontal component away from the other wheel assembly and movement in the opposite direction along the path can be resolved into a downward compone
REFERENCES:
patent: 3196970 (1965-07-01), Brenner
patent: 3241848 (1966-03-01), Flory
patent: 3283839 (1966-11-01), Brown
Dukes Mark C.
Love John J.
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