EP0592427B1

EP0592427B1 - A wheel chair with a driving unit, and a driving unit for wheel chairs

Info

Publication number: EP0592427B1
Application number: EP91915590A
Authority: EP
Inventors: Knud Raun
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-08-27
Filing date: 1991-08-27
Publication date: 1996-02-28
Anticipated expiration: 2011-08-27
Also published as: WO1992003114A1; DE9116932U1; DK0592427T3; DE69117540T2; DE69117540D1; ES2087302T3; AU8435091A; DK204590D0; ATE134501T1; EP0592427A1

Abstract

There is a clear distinction between hand driven, simple wheel chairs and much higher developed motor driven wheel chairs. The invention provides for a compromise, where a wheel chair of a simple design is or can be provided with a special driving unit (30), which as a self-contained unit, may serve to drive the wheel chair by having one or more driving wheels (32) located between the main wheels (26) of the chair in direct driving engagement with the ground. The driving unit can be secured in such a manner that the driving wheel or wheels (32) may move up and down relative to the main wheels (26), such that a driving engagement can be maintained during driving along a non-planar ground surface. The unit is well suited for mounting on both new and existing wheel chairs. When the driving wheel or wheels (32) are placed accurately midways between the ground engaging portions of the main wheels there will be no problems with respect to lateral dragging of the driving wheels in response to changes of the driving direction.

Description

The present invention relates to a wheel chair having an auxiliary driving unit, as specified in the introductory clause of claim 1.
It becomes more and more usual that wheel chairs are built as selfpropelled units, in which the whole structure is designed for that purpose, e.g. by a direct motor drive on the wheel shafts. However, there exist - and is still made - many wheel chairs which are only adapted for manual propulsion, either by the wheels being driven by the user, who grips a peripheral portion of the wheels, or by an attendant pushing the wheel chair. It would be desirable add some motor power to the wheel driving even in these chairs, but prior attempts of adding a preferably releasable motor drive have not been successful.
A relevant prior proposal is disclosed in GB-C-1,517,311. At the lower longitudinal chassis rods of a wheel chair chassis there is mounted an auxiliary driving unit comprising a battery carrier tray which is rigidly fixed to the rear part of the chassis rods or tubes. To the rear portion of this tray there is vertically pivotably secured the front end of a motor and driving wheel carrying subchassis having at its rear end a motor driven wheel arranged so as to engage the ground approximately midways between the ground engaging areas of the main wheels of the wheel chair. Hereby the wheel chair may be driven with the aid of the motor even through horizontal curves, due to the positioning of the driving wheel right between the main wheels of the chair, and the driving wheel will maintain its driving engagement with the ground, despite irregularities therein, due to the driving wheel being arranged on a vertically pivotable subchassis.
However, this arrangement, despite its advantages at the principal level, suffers from marked drawbacks when seen in the light of the present invention. It is a major contribution of the invention that an auxiliary drive of the type referred to can be arranged in such a manner that it will provide for a lifting action on the front end of the wheel chair and thus on the small front swivel wheels which, by a manual pushing of the chair from an elevated rear position, present the problem that they are caused to be forced downwardly by the pushing momentum about the axis of the main wheels. Due to their small size these front wheels should not be forced too firmly against the ground, as they will exhibit a relatively high rolling resistance on a non-smooth ground, even though they are still operable to act as swivel wheels.
In the said known arrangement the said driving system, here also called the wheel leg, is pivotally connected with the chair chassis at a middle or rearmost area thereof, i.e. the line of connection between the pivot axis and the ground engagement area of the driving wheel or wheels will be rather steep. The counter momentum of the driving force on the wheel will act on the chair chassis in a direction perpendicular to the said connection line, thus resulting in the steep wheel leg seeking to pivot forwardly and downwardly to a still steeper position, forcing the driving wheel into the ground and thus excerting a lifting action on the rear main wheels. If the ground is not completely smooth this system is bound to produce a shaky driving in response to variations in the rolling resistance of both the steering wheels and the driving wheel or wheels, and the total rolling resistance will be increased because the small driving wheel will take over some of the load on the main wheels.
A similar system is known from US-A-4,759,418, where the very steep wheel leg is clearly shown in Fig. 5. Here, the driving wheel contacts the ground spaced behind the ground contact line between the main wheels, so the wheel chair will be difficult to steer, as the driving wheel will have to be dragged laterally over the ground by each change of direction.
According to the present invention it has been found that it is possible to provide a driving system of the type referred to, by which the described drawbacks of the steep wheel leg are completely eliminated, and by which further advantages are achieved, all by a rather simple modification.
According to the invention the driving system is arranged as specified in the characterizing clause of claim 1, i.e. instead of the wheel leg being held in a steep position of the rear of the chair chassis it is arranged almost horizontally, pivotally connected with the chassis at a low level and adjacent the front end thereof. This changed geometry of the system results in a number of advantages:

1) The said counter momentum of the wheel leg will show one well defined effect, viz. a lifting effect on the front end of the chassis and thus also on the front swivel wheels, whereby the chair will be easier to steer;
2) The wheel leg with its associated motor will carry nothing but its own weight; the driving wheel can follow irregularities in the ground surface without in any way influencing the pressure on the main wheels, i.e. these will roll and be loaded entirely independently of the chair being driven or not driven by the auxiliary drive system; the total rolling resistance will not be increased by the driving wheel taking over some of the load on the main wheels;
3) The wheel leg will act on the chair chassis as a pulling means more than as a pushing means; in the said known systems the resulting action of the wheel legs is to push against a rear part of the chassis, thus effecting compression of the chassis, while in the system of the invention the traction is effected at an area at least closer to the front end of the chassis, thus predominantly creating pulling forces in the chassis; according to relevant chair manufacturers the latter system is much to be preferred as regards the constructional stability of the chassis.

The invention also comprises the auxiliary driving unit specified in claims 2-5, adapted for mounting on a wheel chair so as to constitute, together therewith, a system as claimed in claim 1.
In the following the invention is described in more detail with reference to the drawing, which is a partially cut, perspective view of a chassis of a driving chair according to the invention.
The chassis shown is in a conventional manner designed with a pair of opposed, longitudinal side members 2, each belonging to an upright side frame structure having a foremost vertical pipe 4 for receiving a lower castor 6, upper longitudinal side members 8 and 10, which hold, inter alia, a forwardly and downwardly projecting pipe 12 for holding a foot support member 14, and rear upright pipes 16 and 18, of which the pipe 18 carries a post 20 for a rearwardly projecting driving handle 22. These two side structures are mutually connected by a lower cross connection comprising a seat carrying structure 24 between the side members 2. In the embodiment shown the carrying wheels 26 of the wheel chair are mounted on bracket plates 28, which project rearwardly from the upright rear pipe 16.
The wheel chair can be driven manually by an attendant holding the driving handles 22.
According to the invention such a chair may be completed by mounting underneath the cross structure 24 a driving unit consisting of a chassis having underlying driving wheels 32 and an upper electric motor 34 driven from a battery in a box 36. This chassis has a forwardly projecting rod 38, the front end of which is rigidly connected with a transverse pipe 40 continuing at both ends in respective telescopic members 42 that are securable to the pipe by means of clamp handles 44. At their outer ends the telescopic members 42 rotatably secured to mounting members 48 that are fixed to the side members 2 by means of clamps 48.
The entire unit 30 may thus pivot freely up and down about the traverse constituted by the parts 40 and 42, i.e. the wheels 32 may rest against the ground also where the latter is out of level with the areas of engagement between the ground and the wheels 26. The related level difference will not go very high, and since e.g. by lifting the chair up into a car it will be unsuitable if the unit 30 pivots down vertically, the pivotability thereof is caused to be limited with the use of suitable stop means or - as shown - with the use of carrier chains 50 interposed between the rear end of the unit and holding fittings 52 at the rearmost portion of the horizontal pipes 8.
From the unit 30 a cable 56 extends up to a handle lever 56 on one of the driving handles 22. This connection, mechanical or electrical, serves to enable a control of the motor 34 by means of the handle lever 56 by on/off operation or by a more graduated actuation of the motor for driving the wheels 32. A battery charger 58 will belong to the equipment.
It will be desirable that the unit 30 can be raised from its driving engagement with the ground for making it freely manually drivable, and this can be achieved in a simple manner by the rear end of the unit being connected with a pivot lever cooperating with one of the lower side members 2 and having at its rear end a pedal 60, which is thus operable to cause the rear end of the unit to pivot upwardly into an upper position in which it is releasably locked, in a manner not shown. The pivot point of the said lever may be identical with the suspension point for the lower end of the chain 50, whereby the mounting of the pivot lever will be particularly simple. The reestablishing of ground contact for the driving wheels 32 can be obtainable merely by a lifting of the pedal member 60.
The driving wheel or wheels 32 should be located midway between the chair wheels 26, while in the longitudinal direction they should be located in a position such that they engage the ground on the same transverse line as defined by the points of ground engagement of the chair wheels 26, this line being designated 62 in the drawing. Admittedly the drawing is wrong on this point, as the wheels 32 are shown located noticeably in front of this line. If that was the case the result would be that by every turning of the driving wheel chair the wheel or wheels 32 would have to be dragged laterally over the ground, this being avoided when this or these wheels engage the ground on the line 62.
The discussed driving unit 30 may be produced as a standard product, which will be well suited for mounting on the major part of the already existing wheel chairs, as the required adaptation will mostly be a question of adapting the length of the telescopic member 40,42.
The disclosed driving unit will also be highly well suitable for installation in new wheel chairs that are beforehand desired to be motor driven, as hereby a cheap series produced driving unit 30 can be used in connection with even a conventional chair design.

Claims

A wheel chair having rear, relatively large main wheels (26) and foremost, smaller swivel wheels (6) and fitted with a driving unit (30), which is placed in a low position between the main wheels (26) and comprises a subchassis (38) carrying a driving motor (34) and one or more driving wheels (32) arranged so as to be operable to engage the ground at or near the line of connection between the ground contact points of the main wheels (26), said subchassis (38) being vertically pivotally connected to a chassis (2) of the chair about a transverse axis (40) above and in front of said connection line, characterized in that the subchassis (38) has a substantial length, such that the transverse pivot axis (40) is located at the foremost lower part of the chassis (2) of the chair, preferably at a low level closely behind the foremost swivel wheels.
A driving unit for a wheel chair according to claim 1, comprising a chassis (38) carrying at its rear end a driving motor (34) and one or more driving wheels (32) and having at its front end connector means (46) for vertically pivotal connection with a main chassis (2) of a wheel chair in front of the connection line between the ground engaging points of the opposed main wheels of the chair, characterized in that the pivotal chassis (32) of the driving unit (30) has a length amounting to a considerable part of the length of an ordinary wheel chair, such that the front end of the chassis (38) is pivotally connectable with the chair chassis closely behind the front swivel wheels (6) thereof, when the driving wheel or wheels (32) are located so as to engage the ground at or near the line of connection (62) between the ground contact areas of the main wheels (26) of the wheel chair.
A driving unit according to claim 2 and including carrier means for a motor energizing battery system, (36) characterized in that the carrier means are arranged at the rear part of the pivotal chassis (38).
A driving unit according to claim 2, characterized in that the front end of the pivotal chassis (38) is provided with opposed, laterally projecting arm portions (40) having outer mounting fittings (46,48) for connection with foremost portions of lower side rods (2) of the wheel chair chassis, the pivotal chassis (38) being arranged to be pivotal about the axis of this cross connection.
A driving unit according to claim 4, characterized in that the said arm portions are made as telescopically length adjustable elements (40,42).