GB2291019A - Hand propelled wheelchair - Google Patents

Abstract

The wheelchair has hand drive wheels 30 coaxially mounted with main ground wheels 20 but rotating separately therefrom. The two wheels are connected by means of a reduction gear provided between the hubs of the said wheels. The reduction gear may comprise an epicyclic gear arrangement, figure 3. Pairs of planet pinions 50, 52 on a fixed spider mesh with each other one being meshed with ring gear 45 on the inside of the road wheel hub, and the other with gear 44 on the outside of the hand wheel hub, so providing a reduction drive between the hand wheel and the road wheel, while also reversing the rotation 50 that both wheels rotate in the same direction. The road wheel may also have a conventional push rim 24 for direct drive. <IMAGE>

Description

HAND PROPELLED WHEELCHAIRS This invention relates to wheelchairs of the type commonly used by invalids, disabled and infirm people, and which are equipped with an annular push rim attached near the periphery of each road wheel in order that the occupant can manually propel the chair along. There are several shortcomings associated with conventional manual wheelchairs. An occupant of a conventional chair must typically expend considerable energy to travel on rough terrain or up inclines or ramps. On steep ramps the force required for propelling the wheelchair up the slope and indeed to try to stop it rolling back down again may well exceed the strength and stamina of the occupant, and on longer journeys may result in considerable fatigue.

Whilst motorised wheelchairs of many different designs address the problems, motorised wheelchairs are expensive, difficult to transport from location to location and virtually impossible to unload from another vehicle without the aid of another person or expensive mechanical equipment. Also the use of mechanically powered chairs could result in the muscle atrophy of the occupant and thus further disability. As a result of the above problems related to mechanical wheelchairs hand propelled wheelchairs are the main method for a disabled person to use in making a journey over any distance.

However in those instances when the occupant is faced with rough terrain, slight slopes, inclines or even small variations in kerb height, if an able bodied person is not available to assist the occupant using the handles provided on the back of the frame the user can experience difficulty in moving the wheelchair at all.

The object of the invention is to provide manually powered propulsion mechanism for wheelchairs, and wheelchairs having such mechanism, which are economical to manufacture and maintain, durable and effective in use, simple to operate, and which enable substantial gains in mobility and reduction in effort for the wheelchair user.

According to a first aspect of the invention there is provided manually powered propulsion mechanism for a wheelchair as defined by Claim 1 of the appended claims.

According to a further aspect of the invention there is provided a wheelchair as defined by Claim 6 of said claims.

An example of the invention is now more particularly described with reference to the accompanying drawings wherein: Figure 1 is a side elevation of a wheelchair, Figure 2 is a part sectional rear elevation of said wheelchair.

Figure 3 is a sectional view on an axial plane through a hub of a drive wheel of said wheelchair, and Figure 4 is a sectional view of said hub on line 4-4 of Figure 3.

Referring firstly to Figures 1 and 2, a wheelchair 10 comprises a pair of side frames 12 linked by collapsible struts 14 providing a chassis for the wheels, the arms and other rigid members of the chair or seat 16 and rearwardly directed handles 18 for when an able bodied person pushes the wheelchair from behind. The frame can be folded in the usual way by collapsing struts 14 to bring the sides together.

There is a pair of large diameter drive road wheels 20 towards the rear of the chair and small diameter front castor wheel 22 to the front. Each road wheel 20 has a primary hand wheel in the form of an annular push rim 24 mounted directly on its spokes adjacent its periphery by means of which an occupant of the wheelchair can apply direct manual force to turn the road wheels for propelling the chair, and can also steer it. As thus far described wheelchair 10 is conventional in construction and operation.

In embodying the invention each drive road wheel 20 forms part of propulsion mechanism further including a secondary hand wheel having a push rim 30 of somewhat lesser diameter than rim 24, this secondary wheel being mounted concentrically with the respective road wheel 20 but not being directly coupled thereto. Each secondary hand wheel has its own radial arms or spokes 32 carrying its push rim 30 on a central hub 34 journalled on a common fixed axial shaft 36 (Figures 3 and 4) which also journals the respective road wheel 20. Each said propulsion mechanism further includes gearing drive connecting the hub 34 of the secondary hand wheel with the hub 37 of the road wheel as now described in further detail with reference to Figures 3 and 4.

The fixed axle shafts 36 are secured to frames 12 co-axially as seen in Figure 2. The hub 37 of each road wheel 20 is a hollow cup-shaped casing whose axially outer end portion 38 is of greater diameter than the inner end portion 40, each said portion being provided with flanges 42 to which the wheel spokes are anchored.

Said casing is journalled on shaft 36 by ball bearings enclosed within the casing for protection.

The hub 34 of each secondary hand wheel is also journalled on the outer end of the respective shaft 36 by ball bearings and extends axially into end portion 38 of the casing. This projecting part of said hub is formed as an externally toothed gear 44.

The interior of portion 38 has an internally toothed ring gear 45 formed or secured therein spaced concentrically from gear 44.

A spider 46 fixed on each respective shaft 36 includes stub shafts 48 carrying three pairs of planet pinions 50, 52 best seen in Figure 3. Each pair of pinions is meshed with each other but their respective stub shafts 48 are offset radially of shaft 36 and the diameter of the pinions is such that the inner one 50 of each pair meshes with hub gear 44 and the outer one 52 meshes with ring gear 45.

As the pitch diameter of hub gear 44 is substantially less than that of the ring gear 45, in the example shown in the drawings the ratio is about 1 to 2, a substantial mechanical advantage is provided so that rotational force applied to secondary hand wheel rim 30 produces greatly increased torque and driving effort at the related road wheel 20 though with proportionate reduction in speed of rotation.

As the drive is transmitted through the meshing pairs of pinions 50, 52 the direction of rotation through the gear train is reversed, thus forward rotation of hub gear 44 produces forward rotation of ring gear 45 and corresponding forward movement of the respective road wheels.

Three sets of pinions 50, 52 are provided at equiangular positions around the main axis to spread the load and avoid off-centre forces on the main bearings.

However, it will be appreciated that other step-down gearing arrangements of a planetary, epicyclic or other nature are possible within the scope of the invention.

The propulsion mechanism enables an occupant of the chair, even one suffering some disability or weakness of upper body or arms, to propel the wheelchair unaided on difficult terrain or surfaces such as rough or soft ground, through long grass or vegetation, or up quite steep slopes or ramps in safety and with full control.

Where conditions are good the primary push rims 24 acting directly on road wheels 20 can be used to propel wheelchair 10 in conventional manner. Where adverse conditions are met, or if the occupant is weak or tired, he or she will use the push rims 30 of the secondary hand wheels to take advantage of the step-down ratio of the gear train. Both push rims 24 and 30 are turned in the same direction which corresponds to the desired forward (or backward) rotation of road wheels 5 so that operation is simple and particularly user-friendly. A further advantage of the invention is that the propulsion mechanism provides enhanced braking force for retarding rotation of the road wheels when necessary such as when travelling down slopes or ramps giving much improved safety and manoeuvrability.

The preferred mechanism above described is compact and has few moving parts. It adds little to the weight and overall dimensions of a conventional wheelchair and does not restrict or impair the folding thereof for transport or storage. The gearing is durable and totally enclosed and protected, yet is simple to repair and maintain.

Claims (9)

1. Manually powered propulsion mechanism for a wheelchair including a road wheel, a hand wheel mounted co-axially with the road wheel and having a hub formation extending axially into a hub formation of the road wheel, and at least one gear train connecting said hub formations to transmit rotation of the hand wheel causing the road wheel to rotate in the same direction while giving a substantial mechanical advantage by stepping down the drive ratio.

2. Mechanism as in Claim 1 wherein the hub formation of the hand wheel includes or mounts an externally toothed gear, the hub formation of the road wheel includes or mounts a concentric internally toothed ring gear of substantially greater pitch diameter than said externally toothed gear, and the gear train includes at least one pair of intermeshing pinions one of which meshes with the latter gear and the other of which meshes with the ring gear.

3. Mechanism as in Claim 2 including a plurality of said pairs of pinions spaced at equiangular positions about the road wheel axis.

4. Mechanism as in Claim 1, 2 or 3 wherein the road wheel mounts a primary push rim or hand wheel for direct driving rotation independently of said gear train.

5. Manually powered propulsion mechanism for a wheelchair substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

6. A wheelchair including manually powered propulsion mechanism as in any one of Claims 1 to 6.

7. A wheelchair as in Claim 6 having a pair of operatively laterally spaced side frames carrying a seat, and a said road wheel journalled on each side frame; each said road wheel being comprised in a respective said propulsion mechanism.

8. A wheelchair as in Claim 7 adapted for selective folding when not occupied by bringing the side frames and road wheels towards each other.

9. A wheelchair substantially as hereinbefore described with reference to and as shown in the accompanying drawings.