EP0561986B1 - Auxiliary drive unit for a manual wheelchair - Google Patents

Abstract

A self-contained drive unit (1) which can be detachably mounted to the back (4) of a usually manual wheelchair (2) comprises a set of one or two motors (9) mounted head-to-tail at the ends of a linear rigid chassis, or a rigid frame (15), to drive pinions (5) or similar at the sides. Said pinions may be brought into positive engagement with the rear wheels (6) of the wheelchair (2) to drive them. The said linear chassis or rigid frame (15) has at least one carrying handle (16) and comprises adequate attachment fittings (18) for rapid mounting of the wheelchair back (4) on the frame. The attachment fittings (18) for the chassis or frame (15) can co-operate if necessary with a device for engaging and disengaging drive pinions (5) with respect to the main wheels (6). The motors (9) driving pinions (5) co-operate with control means (12) and operate so as to provide essentially assistance in moving the said wheelchair (2).

Description

The present invention relates to an autonomous and removable powertrain particularly suitable for assisting the advancement of a wheelchair for the disabled.

A number of removable propulsion units are known for wheelchairs for the disabled. In particular, in patent DE-A-3 131 504, an electric propulsion unit is proposed which can be fixed in a removable manner to the back of a wheelchair by means of a lifting and tilting mechanism incorporated in a trolley transport ; the powertrain has a flat configuration to adapt to the back of the seat and comprises, on each side, drive rollers for the large wheels of the chair, powered by one or two motors powered by a battery. In addition, these drive rollers can be disengaged by means of a control lever easily accessible to the disabled person. Such a device is however heavy and bulky; in particular, it is not transportable and its installation on the wheelchair requires the assistance of a person other than the disabled.

US Pat. No. 3,688,857 discloses an improvement in electric power units for wheelchairs partially overcoming the drawbacks mentioned above. To this end, the propulsion unit, which is here again supported by a carrier trolley separate from the wheelchair, can be coupled to the latter in a semi-automatic manner, the disabled person having the means of controlling and carrying out himself coupling or uncoupling of said propulsion unit. The fact remains, however, that this device turns out to be very bulky and very heavy; it is therefore difficult to handle and, in any case, very discreet.

Another device of the same kind, described in patent US-A-3 351 148, has a lighter structure than the previous device but still requires a very bulky support frame due to the relatively large weight and size of the supply battery. Indeed, like the two armchairs proposed in the earlier patents mentioned above, the wheelchair described in this latter patent becomes, after coupling of the removable powertrain, an electric chair in its own right; in this sense, the chair is driven and guided only by electrical means. In this regard, the starting torque which is normally supplied by the drive motor or motors of the friction members acting on the wheels of the chair must be sufficiently high; it is therefore understood that the power of the motors used, generally series wound motors, are relatively powerful, which effectively requires having a substantial power supply on the chair.

Finally, in patent CH-A-649,464, a disengageable propulsion unit can be mounted on the back of a wheelchair without using a trolley or the like; this device, which once again transforms the chair into an exclusively electric chair, has the disadvantage of being difficult to handle and in any case cannot be installed by a disabled person alone. In addition, the battery carried by the chair remains very bulky for the same reasons developed above.

However, observing the needs of all people with disabilities who use wheelchairs to get around shows that the division between the use of a manual wheelchair and the use of an electric wheelchair is not as obvious that one would a priori think it. In this regard, a person with an evolutionary handicap, who must thus switch from the manual wheelchair to the electric wheelchair, is suddenly led to no longer use the muscles of his arms, which undoubtedly constitutes a serious additional psychological constraint. We also understand that a person with a lower degree of disability, but who is obliged to use an electric wheelchair for his outdoor travel, wishes to use a manual wheelchair for reduced travel, especially since boarding a car is necessary. Indeed, in the latter case, the size and weight of the chair, especially if it is powered, becomes a very delicate problem if the disabled person is not helped.

This is why it appeared necessary to develop an electric, autonomous and removable powertrain which is particularly light, easy to handle by the disabled person himself, easily transportable and whose coupling to the wheelchair is extremely simple. It was thus realized that a momentary and disengageable assistance with the advancement procured all the preceding advantages with, as additional and essential advantage, the fact to leave to the handicapped person a great autonomy, the choice to use or not his wheelchair using his arms and, in all cases, complete control of the wheelchair, namely its braking, its direction and its speed, which is not the case with previous electric wheelchairs, whether or not fitted with groups removable thrusters.

To this end, the present invention relates to an autonomous propulsion unit which can be removably mounted on the back of a generally manual wheelchair, and comprising a set of one or two motors mounted head to tail at the ends. respective of a linear rigid frame or a rigid frame for laterally driving rollers or the like which can be brought into positive support on the rear wheels of said chair, in order to cause their rotation, characterized, on the one hand, in that said chassis or said frame is provided with at least one carrying handle and includes adequate means for rapid attachment to the armatures of the back of said chair, on the other hand, in that said means for fixing the chassis or the frame cooperate, as the case may be where appropriate, with a device for coupling and uncoupling the rollers from their support on said rear wheels, and, in addition, in that said one or more roller drive motors cooperate with control means operating in such a way as to essentially provide assistance with the advancement of said wheelchair.

Since there is no attempt to permanently drive the wheelchair positively, it is clear that the motors intended for driving the rollers or the like, acting by friction on the rear wheels, can be considerably less powerful and require a lower power supply, and therefore lighter. It then becomes possible, in accordance with a complementary characteristic of the present invention, to ensure that the means of electrical supply of the motors are arranged, on the linear chassis or the rigid carrying frame, between said motors, so as to produce a particularly light, compact and handy aligned assembly. Likewise, it is preferable that the motor control means are arranged, preferably between said motors, on the same linear chassis, or on the same rigid frame.

The device closest to the present invention is described in patent US-A-4,050,533. This latter patent reveals, in fact, an electric wheelchair whose drive motors are controlled by the value of the torque applied by the disabled person on the handrails normally fitted to the two wheels of the wheelchair; a motor torque proportional to the torque transmitted manually to the wheels is thus produced by the control electronics, with the advantage of effectively giving full freedom of control to the disabled person. This prior device, which is neither removable and which cannot be temporarily uncoupled from the wheels, does not however offer the flexibility of use of the propulsion system according to the invention. In particular, the transformations to be carried out on a manual wheelchair, in particular on the handrails, prove to be large and expensive; conversely, the present invention makes it possible to provide an advancement aid adaptable to all armchairs, which is removable, autonomous, light, disengageable and inexpensive.

• dans le brevet antérieur, le couple moteur appliqué sur chaque roue du fauteuil dérive directement du couple positivement appliqué sur les mains courantes par la personne handicapée, ce qui provoque d'ailleurs un avancement par à-coups pouvant s'avérer désagréable pour l'utilisateur ;
• selon la présente invention, le couple moteur qui est fourni aux roues ne dépend pas du couple couple manuel trasmis aux mains courantes, mais est normalement obtenue par un ensemble de contacteurs appropriés, procurant préférentiellement un fonctionnement en tout ou rien au groupe propulseur. En fait, ce couple moteur dépend même exactement, à l'inverse, du couple résistant agissant sur les moteurs, tenant par exemple à la nature du terrain ou encore à l'intensité du freinage provoqué sur l'une ou les deux roues par l'utilisateur.

On the other hand, it will be observed that the principle of assistance with advancement described in the same patent US-A-4,050,533 differs completely from the principle recommended by the present invention. Indeed :

• in the prior patent, the motor torque applied to each wheel of the chair derives directly from the torque positively applied to the handrails by the disabled person, which moreover causes jerky advancement which may prove to be unpleasant for the user ;
• according to the present invention, the engine torque which is supplied to the wheels does not depend on the manual torque couple transmitted to the handrails, but is normally obtained by a set of appropriate contactors, preferably providing all-or-nothing operation of the powertrain. In fact, this engine torque even depends exactly, conversely, the resistive torque acting on the engines, for example due to the nature of the terrain or the intensity of the braking caused on one or both wheels by l 'user.

For this purpose, the electric power supply of the drive motor of a roller or the like is supplied to this motor only when the latter receives beforehand a driving torque provided by the first movement, either of the disabled on the handrail or on the wheel on which said roller acts, either by accompanying it pushing or pulling the chair; conversely, the supply is automatically cut off as soon as said motor is subjected to a preset maximum torque.

Among other advantages, a manual wheelchair equipped according to the invention with simple advancement assistance can, without learning or apprehension, be used by any occasionally accompanying person who would then have no difficulty in handle such an armchair provided with its device, perfectly light and removable, which is not the case with the previously known advancement aid device which is of no help to the accompanying person.

On the other hand, it is advantageous that certain handicapped people, who temporarily or even definitively need more assistance for training their wheelchair, can keep their original manual wheelchair as long as possible. Given that it is then functionally and psychologically harmful for the disabled person that this assistance may appear to an observer as a new prosthesis, the propulsion unit according to the invention can advantageously be enclosed in an envelope of the type of a bag, or a suitcase, leaving no outside impression on the user's handicap to the outside observer.

According to a last important characteristic of the invention, the protective casing of the propulsion unit according to the invention, in addition to its contribution as regards the trivialization of the engine by hiding it from observers, can be advantageously used to fix the propellant assembly for example in the back of the chair so that the drive and control elements, emerging from the same bag, can perform their function while retaining overall ease of handling and above all its very temporary nature. In this particular variant, it should be noted that the connection of the propulsion unit via the bag is relatively precarious; this is why it will be preferred to add a rigid fixing system between the chassis of the manual wheelchair and the linear rigid chassis, or the rigid frame, supporting the motorization with its transmission and control members; it is obvious that these fixing means, which are also universal, will be such that they allow very easy mounting and dismounting of the propulsion unit on any manual chair.

It is therefore understandable that the powertrain according to the invention constitutes a decisive advance in the field of mobility aid for the disabled in wheelchairs, insofar as the very temporary addition of a motorization which is a priori not very visible contributes to the comfort of the disabled person and his entourage, while keeping the latter in his original chair, thus avoiding the physical and psychological trauma of switching from a manual chair to an electric chair, heavy and often unsightly.

• - la figure 1 est une représentation en perspective d'un fauteuil manuel équipé d'un groupe propulseur disposé dans une enveloppe souple de protection,
• la figure 2 est une vue schématique du groupe propulseur de la figure 1, montrant la distribution particulière des divers éléments composant ledit groupe propulseur,
• - la figure 3a est une vue partielle d'un fauteuil manuel montrant un élément de fixation rapide du groupe propulseur mis en place sur une armature verticale du dossier,
• - la figure 3b est une vue de dessus agrandie d'un élément de fixation rapide permettant d'adapter le groupe propulseur sur n'importe quelle armature du dossier d'un fauteuil roulant manuel,
• - la figure 4 est une vue plus détaillée d'un groupe propulseur, pouvant ou non être enfermé dans un sac, et qui est pourvu d'un dispositif d'accouplement et de désaccouplement des galets d'entraînement des grandes roues du fauteuil,
• - les figures 5 à 7 sont des schémas montrant le principe de fonctionnement et de réglage du dispositif d'accouplement et de désaccouplement précédent.

Several embodiments of a propulsion unit according to the invention will be described below, and this by way of nonlimiting examples with reference to the appended drawings in which:

• FIG. 1 is a perspective representation of a manual wheelchair equipped with a propulsion unit arranged in a flexible protective envelope,
• FIG. 2 is a schematic view of the powertrain of FIG. 1, showing the particular distribution of the various elements making up said powertrain,
• FIG. 3 a is a partial view of a manual wheelchair showing a quick fastening element for the propulsion unit installed on a vertical frame of the backrest,
• FIG. 3 b is an enlarged top view of a quick fastening element making it possible to adapt the propulsion unit to any frame of the back of a manual wheelchair,
• FIG. 4 is a more detailed view of a propulsion unit, which may or may not be enclosed in a bag, and which is provided with a device for coupling and uncoupling the drive rollers of the large wheels of the chair,
• - Figures 5 to 7 are diagrams showing the principle of operation and adjustment of the previous coupling and uncoupling device.

In accordance with FIGS. 1 and 2, and according to a first variant of the invention, the propulsion unit 1 according to the invention, which is intended to assist in the advancement of a perfectly arbitrary manual wheelchair 2, is fixed to the two substantially vertical uprights 3 of its back 4, so as to rest, by its drive rollers 5, on the rear wheels 6 of said chair 2. In this first variant, the propulsion unit 1 is placed inside of a flexible envelope 7 from which the drive rollers 5 emerge laterally as well as, according to FIG. 2, fastening elements 8 cooperating with the vertical uprights 3 of the backrest 4. The flexible envelope 7 has the function of protecting the group propellant 1 against external aggressions, such as dust or bad weather, while constituting a discreet covering revealing only the banal shape of a bag.

In accordance with FIG. 2, the powertrain 1 more particularly consists of two engines 9 mounted head to tail at the respective ends of a linear rigid chassis, or of a rigid frame 15, so that each end of the axis 10 , which supports a roller 5, is turned outwards and can be found directly above the rear wheels 6 of the chair 2, if necessary in an adjustable manner. The two motors 9 are advantageously identical, and for example, they will be direct current electric motors developing an effective power of 100 watts under a direct voltage of 12 volts.

The space between the two motors 9 is advantageously used to place one or two batteries 11 mounted in parallel to supply the said motors 9 with electronic control means 12. It should be noted that the batteries 11 can be of any type, but that they are advantageously rechargeable. It is quite important to note that the batteries 11 are in fact very compact, since the energy required by the motors 9 is relatively low due to the fact that they contribute, in principle, only to assistance with advancement, and not to a permanent drive as known on conventional electric wheelchairs. On the other hand, it is clear that the maximum resisting torque can be obtained naturally due to too much effort to produce, or by voluntary feedback from the user on the handrails of the manual wheelchair 2.

The two motors 9 of the powertrain 1 are managed by two contactors 13 and 14 independent of each other, each contactor 13, 14 being fixed at the end of a flexible interfaced connection wire to the electronic control means 12. These contactors 13, 14, advantageously of the type of capacitive proximity detectors, can be fixed to the armature of the chair in the places most accessible to the disabled person, for example on each side of the chair 2, at the level of the seat and in front of the rear wheels 6, so that, during the movements made by the arms to propel the chair 2, the hands naturally pass near said contactors 13, 14.

• le premier contacteur 13 est destiné à gérer la fonction marche-arrêt des deux moteurs 9, ainsi que le passage de l'arrêt à la première vitesse, et réciproquement,
• le deuxième contacteur 14 gère le passage de la première vitesse à la seconde vitesse, et réciproquement.

For the sake of simplicity, and as explained above, the motors 9 are controlled all or nothing with a preferentially reduced choice of accessible speeds, which makes it possible to ensure assistance with continuous advancement to the user, just limited by a predetermined resistive torque, the excess of which will immediately stop supplying said motors 9. For this purpose, an example of a control logic is as follows:

• the first contactor 13 is intended to manage the on-off function of the two motors 9, as well as the transition from stopping to first speed, and vice versa,
• the second contactor 14 manages the transition from first speed to second speed, and vice versa.

In a complementary manner, the electronic control means 12 are designed so that simultaneous pulses on the contactors 13, 14 cause the rotors of the two motors 9 to short-circuit, with the advantage of causing braking of the wheelchair 2.

It should be noted that the control means 12 are also provided so that only the pulses on the contactors 13, 14 whose duration exceeds 0.4 seconds are taken into account, which makes it possible to avoid the drawbacks linked to the unwanted change. engine speed 9, due to involuntary contact of the disabled person's hands with said contactors 13, 14; it was in fact possible to determine that the duration of an involuntary contact was generally greater than the abovementioned limit duration.

In this first variant of the invention, the rigid frame 15 is advantageously provided with two carrying handles 16 facilitating the positioning of the propulsion unit 1 on the manual chair 2, and its removal. In this regard, and according to a first embodiment of the invention shown in FIGS. 3 a and 3 b , it will be noted that the propulsion unit 1, protected or not by its flexible envelope 7, is rapidly joined to the file 4 of the chair 2 by means of the fastening elements 8, for example of the type of slideways coming to slide on lugs 17 integral with two quick fastening systems 18, which are locked by a thumb screw 19 to the vertical uprights 3 of said folder 4 .

According to FIG. 3 b , each of the two quick fastening systems 18 is produced from a molded cylindrical part, preferably made of a composite material having a certain elasticity, the cylindrical part 20 having a vertical opening sufficient to be clipped onto the 'one of the vertical frames 3 of the backrest 4. It is obvious that the spacing of the two slides 8 integral with the rigid frame 15 of the propulsion unit 1 is adjustable so as to be able to adapt to the backrest of practically all the armchairs textbooks 2; it will be observed that the mounting of the slides 8 sliding on the rigid frame 15 has not been shown in detail in the figures since the person skilled in the art is able to carry out this type of mounting.

It will be observed that, in this first variant of the invention shown in FIGS. 1 to 3, the rollers 5 rest permanently on the rear wheels 6, which means that assistance with the advancement of the wheelchair 2 is not disengageable only insofar as the motors 9 are stopped. In this case, it is obvious that the rollers 5, which continue to rub on the wheels 6, contribute to slowing the manual advancement of said chair 2. This is why, in a second variant of the present invention which will be described with reference in Figures 4 to 7, it is proposed that the fastening means 18 of the linear frame or of the rigid frame 15 on the backrest 4 of the wheelchair 2 cooperate with a device for coupling and uncoupling the rollers 5 from their support on the wheels rear 6. For this purpose, the quick fastening devices 18 are in the form shown in FIGS. 5 to 7, where the lugs 17 have been replaced by support plates 21 orthogonally supporting plates 22 serving to maintain the group propellant 1; in the embodiment proposed by way of example in FIG. 4, the support plates 22 have at their upper part a cutout in the shape of a "V" to favor the engagement of pins 23 extending the linear frame or the rigid frame 15 outwards, these pins 23 being normally parallel to the rollers 5.

FIG. 4 details the coupling and uncoupling device according to the invention: this first comprises a control lever 24, mounted for rotation about an axis parallel to that of the rollers 5; at the end of said lever 24 is arranged a gripping member 25 easily manipulated by the disabled person; the control lever 24 acts, by means of a known transmission system of a person skilled in the art, on a piston 26 sliding substantially horizontally in a sheath 27 secured to the linear frame or the rigid frame 15; this piston 26 extends towards the backrest 4 of the chair 2 by a rod 28, the length of which can be adjusted, and which normally comes to bear, in the so-called engaged position, on the upper part of one of the two plates support 21 of the quick fixing device 18, preferably perpendicular to said plate 21; on the side of the rigid frame 15, opposite the backrest 4 relative to the spindle 23 provided to support the propulsion unit 1 on the support plate 22, there is a connecting rod 29 mounted for rotation around an axis offset at the rear of that of said spindle 23, this rod 29 having the role of transmitting the movement of the rod 28, extending the piston 26, to a second rod 30 normally fixed to the right of said rod 29 to come to bear, in the so-called disengaged position, against the lower part of the support plate 21 of the quick fixing device 18; the rod 30 is of adjustable length; in addition, the position of the end of the link 29 along the rod 28 is also adjustable by means of two stops 31 located on either side of said link 29, which is pierced with an oblong hole 32 (detail in FIG. 4) leaving a vertical play in the displacement of the rod 28 relative to said link 29. The preceding construction details are of course only an exemplary embodiment and are therefore not limiting.

• suivant la figure 5, l'angle entre la plaque d'appui 21 et l'axe passant par le galet 5 et la broche 23 varie selon les fauteuils ; grâce au réglage de la longueur de la tige 28, prolongeant le piston 26, il est possible de ramener cet angle à une valeur donnée prédéterminée pour que, lorsque le levier de commande 24 est repoussé vers l'arrière du fauteuil 2, en position dite embrayée, l'appui de la tige 28 sur la plaque 21 contribue à repousser positivement les galets 5 au contact des roues arrières 6.
• suivant la figure 6, une fois la valeur de l'angle de la tige 28 réglé, il convient de faire en sorte que les positions extrêmes de la biellette 29 - qui correspondent aux positions extrêmes du levier de commande 24 vers l'avant ou vers l'arrière du fauteuil roulant 2 - soient sensiblement à égale distance d'une position neutre - levier de commande 24 à la verticale, en position intermédiaire, - choisie comme étant celle pour laquelle ladite biellette 29 se trouve perpendiculaire à la tige 28 prolongeant le piston 26 ; ce réglage est obtenu au moyen des deux butées 31 situées de part et d'autre de la biellette 29 le long de ladite tige 28. La position intermédiaire du levier 24 permet de retirer le groupe propulseur 1 de l'arrière du dossier 4 du fauteuil roulant 2.
• suivant la figure 7, la longueur de la tige 30, qui est actionnée par l'intermédiaire de la biellette 29, permet le contrôle de la position dite débrayée du groupe propulseur 1 ; en effet, lorsque le levier de commande 24 est ramené vers l'avant du fauteuil 2, la tige 30 est poussée contre la partie basse de la plaque d'appui 21 du dispositif de fixation rapide 18, ce qui doit libérer les galets 5 de leur contact sur les roues arrières 6, simplement du fait que les broches 23 étant bloquées dans le fond de la découpe en "V" des plaques supports 22, le groupe propulseur 1 ne peut que pivoter autour de ces broches 23, entraînant ainsi lesdits galets 5 vers le haut. Le réglage de la longueur de la tige 30 permet de désaccoupler les galets 5 avec une position haute telle que l'effort à fournir sur le levier de commande 24 reste raisonnable.

The possibilities for adjusting the coupling and uncoupling device which have just been described take account of its possible adaptation to the many types of existing manual wheelchairs; in particular, the inclination of the backrest 4 is not standardized, and the location of the quick fastening devices 18 can vary depending, in particular, on the diameter of the rear wheels 6 of the wheelchair 2. As it is desirable that, according to this variant of the invention, the rollers 5 of the power unit 1 can or not come to bear on the rear wheels 6, the adjustments proposed on the coupling and uncoupling device described above fulfill the following three objectives:

• according to Figure 5, the angle between the support plate 21 and the axis passing through the roller 5 and the spindle 23 varies depending on the chairs; by adjusting the length of the rod 28, extending the piston 26, it is possible to reduce this angle to a given predetermined value so that, when the control lever 24 is pushed back towards the rear of the chair 2, in the so-called position engaged, the support of the rod 28 on the plate 21 contributes to positively pushing the rollers 5 in contact with the rear wheels 6.
• according to FIG. 6, once the value of the angle of the rod 28 has been adjusted, it is necessary to ensure that the extreme positions of the link 29 - which correspond to the extreme positions of the control lever 24 towards the front or towards the rear of the wheelchair 2 - are substantially equidistant from a neutral position - control lever 24 vertically, in the intermediate position, - chosen as being that for which said link 29 is perpendicular to the rod 28 extending the piston 26; this adjustment is obtained by means of the two stops 31 located on either side of the link 29 along said rod 28. The intermediate position of the lever 24 makes it possible to remove the propulsion unit 1 from the rear of the backrest 4 of the chair rolling 2.
• according to Figure 7, the length of the rod 30, which is actuated by means of the rod 29, allows the control of the so-called disengaged position of the propulsion unit 1; in fact, when the control lever 24 is brought back towards the front of the chair 2, the rod 30 is pushed against the lower part of the support plate 21 of the quick fixing device 18, which must release the rollers 5 from their contact on the rear wheels 6, simply because the pins 23 being locked in the bottom of the "V" cutout of the support plates 22, the propulsion unit 1 can only pivot around these pins 23, thus driving said rollers 5 upwards. The adjustment of the length of the rod 30 makes it possible to decouple the rollers 5 with a high position such that the effort to be provided on the control lever 24 remains reasonable.

The exemplary embodiment of the coupling and uncoupling device described above is not limitative of the invention which includes, of course, any similar device having the function of allowing the disabled person to couple and uncouple the rollers 5 of their support on the rear wheels 6, this using a control lever 24 with three positions: a so-called engaged contact position, a raised position called disengaged and an intermediate position for the removal of the powertrain 1 from the back of the back of the wheelchair 2 2.

The invention is not only intended for the equipment of wheelchairs for the disabled, and can equally prove to be useful for the transport of any valid person, or even constitute an aid for the advancement of trolleys, shopping carts. and the like.

Claims (12)

1. Autonomous drive unit (1) able to be removably mounted on the backrest (4) of a generally manual wheelchair (2), and comprising an assembly of one or of two motors (9) mounted head-to-tail at the respective ends of a rigid linear chassis, or of a rigid frame (15), in order laterally to drive rollers (5) or the like which may be brought into positive abutment on the rear wheels (6) of said wheelchair (2) in order to provoke drive thereof, comprising adequate means (18) for rapid fixation to the reinforcements of the backrest (4) of said wheelchair (2) which cooperate, if necessary, with a device for coupling and disconnecting the rollers (5) to and from said rear wheels (6), said linear chassis or said rigid frame (15) being provided with at least one handle (16) for transport and said motor or motors (9) for driving the rollers (5) cooperating with control means (12) functioning so as essentially to procure an assistance in the advance of said wheelchair (2), i.e. a momentary assistance automatically or voluntarily disengageable during its displacement, characterized in that the electrical supply of the motor (9) for driving a roller (5) - which is supplied to this motor (9) only when the latter previously receives a drive torque procured by the first movement, either of the handicapped person on the hand rail or on the wheel (6) on which said roller 5 acts, or of the accompanying person pushing or pulling the wheelchair (2) - is, inversely, automatically cut off as soon as said motor (9) is subjected to a pre-regulated maximum torque.
2. Drive unit according to Claim 1, characterized in that the means for electrically supplying the motors (9) are disposed, on the linear chassis or the rigid frame (15), between said motors (9), so as to produce an aligned assembly which is particularly light, compact and easy to handle.
3. Drive unit according to either one of the preceding Claims, characterized in that the means (12) for controlling the motors (9) are disposed, on the linear chassis or on the rigid frame (15), between said motors (9).
4. Drive unit according to any one of the preceding Claims, characterized in that the motors (9) are controlled in all or nothing mode with a reduced choice of accessible speeds.
5. Drive unit according to any one of the preceding Claims, characterized in that management of the motors (9) is effected via two contactors (13, 14) independent of each other, each contactor (13, 14) being fixed to the end of a supple connecting wire interfaced with the electronic control means (12).
6. Drive unit according to the preceding Claim, characterized in that the contactors (13, 14) are of the capacitive proximity detector type.
7. Drive unit according to either one of Claims 5 or 6, characterized in that the electronic control means (12) are provided so that only those pulses on the contactors (13, 14) whose duration exceeds 0.4 second are taken into account.
8. Drive unit according to any one of the preceding Claims, characterized in that the means for connection to the wheelchair (2) are obtained by the cooperation of elements, for example male ones (17), fitted by clamps (18) with screws (19) to each lateral reinforcement (3) of the backrest (4), with elements, for example female ones (8) of the slideway type, fast with the rigid frame (15) of which the spaced apart relationship may be easily adjusted to correspond to the male elements (17) of the backrest (4).
9. Drive unit according to the preceding Claim, characterized in that the means for connection to the wheelchair (2) comprise bearing plates (21) supporting at right angles plates (22) serving to maintain the drive unit (1) via spindles (23) extending the linear chassis or the rigid frame (15) towards the outside, these spindles (23) normally being parallel to the rollers (5) for driving the rear wheels (6) of the wheelchair (2).
10. Drive unit according to the preceding Claim, characterized in that the device for coupling and disconnecting the rollers (5) to and from their abutment on the rear wheels (6) comprises a control lever (24) with three positions, namely a so-called engaged contact position, a so-called disengaged raised position and an intermediate position for the withdrawal of the drive unit (1) from the rear of the backrest (4) of the wheelchair (2).
11. Drive unit according to the preceding Claim, characterized in that the device for coupling and disconnecting the rollers (5) to and from their abutment on the rear wheels (6) comprises:

    - a control lever (24), mounted to rotate about an axis parallel to that of the rollers (5),

    - a transmission system connecting said lever (24) to a piston (26) mounted to slide in a sleeve (27) fast with the linear chassis or rigid frame (15),

    - a rod (28), of adjustable length, and extending the piston (26) in order normally to come into abutment, in so-called engaged position, on the upper part of one of the two bearing plates (21), preferably perpendicularly to said plate (21),

    - a small rod (29) mounted to rotate about an axis offset to the rear of that of the spindle (23) mounted on the bearing plate (22), and connecting the rod (28) to a second rod (30) which normally abuts, in so-called disengaged position, against the lower part of said bearing plate (21), said rod (30) being of adjustable length,

    - two stops (31) located on either side of the small rod (29), along said rod (28), said small rod (29) being pierced with an oblong hole (32) leaving a vertical clearance limited to the displacement of said rod (28) with respect to said small rod (29).
12. Drive unit according to any one of the preceding Claims, characterized in that the unit is entirely enclosed within a protective envelope (7), preferably of the rucksack or suitcase type, from which only the rollers (5), the fixation means (8) and, if necessary, the spindles (23), emerge.

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