Field of invention

This invention pertains to a stair climbing wheelchair fitted with a retractable spoke mechanism to enhance the mobility of the physically challenged.

Background of the invention

The number of people who need to move around using artificial means, due to various reasons, is continually increasing. Taking advantage of the technical evolution one can increase the quality of life for the physically challenged and facilitate their integration with the working world. To this end wheelchairs have changed dramatically during the last half of the twentieth century creating greater mobility, independence and social inclusion for the user. One such design is the stair climbing wheelchair with a retractable spoke mechanism and which is affordable for the common man.

Summary of the invention

The main objective is to provide a wheelchair that can operate on a smooth surface. It is like the conventional wheelchair which has two main drive wheels and two maneuverable swivel wheels and a chair with a back and foot rest. It also has handles at the rear for the use of an attendant when required. There is a simple easy structure which the user can readily put into service to override obstruction such as curbs of stairs. The chair remains substantially upright with the provision of a balancing system that has a balancing wheel is attached. This enables the balancing wheel to move up and down maintaining a normal position for the chair even while climbing the steps. This simple construction keeps the cost to a minimum and thus reaches out to a larger number of users.

Brief Description of the Preferred Embodiments INNER RING

The inner ring is made of MS steel and has a thickness of about 20 mm. The inner diameter of the ring is 370 mm and the outer diameter is 450 mm. A projection of thickness 10 mm is made over the ring which will enable it to rotate in the grooves of the outer ring. It has 8 projections of 10 mm all around the circumference equally spaced shown in Figure. 1.

SPOKES

The geometry of the spokes is another special feature of the design shown in Figure.2 at the end side of the spoke is given a curvature. This enables the spokes to adapt to various dimensions of the stairs. Even if the spokes do not grab the stairs normally, the curved edge enables it to roll over the edge like a small wheel. This feature makes the wheel chair to climb stairs of various dimensions even though the design is made based on the geometry of a standard 25 x 25 cm stair.

OUTER RING
The outer ring is also made of MS steel and has the same thickness as that of the outer ring. The inner diameter of the outer ring is 455 mm and the outer diameter is 540 mm. A groove of 10 mm was cut internally. The outer ring too has 8 projections each of 10 mm and equally spaced along the circumference shown in Figure 3.

RETRACTABLE SPOKE MECHANISM

The retractable spoke mechanism as mentioned earlier is used as an aid for climbing stairs. The mechanism consists of some simple linkages. The mechanism essentially consists of an inner ring, an outer ring, and 8 spokes all connected through various linkages. The whole mechanism was attached to each of the rear wheels of the wheel chair.

The outer ring was attached to the rear wheel of the wheel chair quite rigidly by means of welded joints. This causes the outer ring to turn while the wheel rotates. The inner ring was mounted on the shaft of the wheel chair. The inner ring was attached to the outer ring through certain spokes. The spokes were attached to the inner ring by means of pin joints. The spokes have rectangular slots in them in which the projections of the outer ring can slide. The whole mechanism is shown in Fig 4.

THE BALANCING SYSTEM

A balancing system is needed in order to avoid the rolling over of the wheel chair. When the wheel chair is climbing stairs, there are chances for the wheel chair to tilt and causes it to roll over. The balancing system consists of a balancing wheel and a nut and screw arrangement. The balancing mechanism is shown in Fig.5. The balancing wheel is attached to the nut and screw arrangement. Here, the nut is a gear that is internally threaded to a gear which is mounted on the motor is meshed. The nut is prevented from moving up and down by placing constraints. This causes the screw to move up and down whenever the nut is rotated. The balancing wheel attached to the wheel chair will also move up and down. This helps in keeping the wheel chair in a normal position while climbing the stairs as shown in Figure 6.


We claim

This invention provides a wheelchair for users which can climb stairs without any hassles. It is fitted with a specially designed spoke mechanism, chain sprocket assembly and a balancing system. When the wheelchair is climbing the steps the retractable spokes are open and in contact with the stairs. The new design is useful and efficient for any person who needs to use such a mechanism.