WO2004047709A1

WO2004047709A1 - Self-propelled steering wheelchair for disabled persons

Info

Publication number: WO2004047709A1
Application number: PCT/EP2003/011806
Authority: WO
Inventors: Emilio Toselli
Original assignee: T.G.R. S.R.L.
Priority date: 2002-11-25
Filing date: 2003-10-24
Publication date: 2004-06-10
Also published as: ITBO20020121U1; EP1496828A1

Abstract

The self-propelled steering wheelchair for the disabled, with lifting and lowering movements, particularly for use in the domestic environment, is of the type that comprises a base frame (1) that stands on the ground via wheels, some of which are idle casters and others are driving and steering wheels, and which is equipped at the back with an upwardly extending integral straight guide (2) on which a runner (3) carrying the chair (P) on which the disabled person is sitting can be caused to travel. The base (1) is provided with rubber-tyred wheels that are all of large diameter, two of which (12) are idle casters arranged symmetrically on the sides of the said frame, while at least one third driving and steering wheel (13) is supported by the centre line of the rear part of the said frame (1) and at least one fourth driving wheel (14) that steers in phase with the said rear wheel is positioned at the front centre of the same frame (1) and is mounted on means that allow it to move vertically elastically with a predetermined travel. The whole is arranged in such a way that the rear driving and steering wheel (13) is always loaded by the weight of the user, while the front driving and steering wheel (14) ensures, by means of its elastic loading, that the chair advances correctly even on a floor that presents small upward or downward obstacles.

Description

TITLE:

"Self-propelled steering wheelchair for disabled persons", DESCRIPTION

The invention relates to self-propelled steering wheelchairs designed for use in the domestic environment by disabled persons, characterised by being very compact in plan view, by a small steering radius and by the fact that it can be adjusted up and down to allow the disabled person to move with sufficient freedom and convenience in an environment of normal composition. The wheelchairs referred to are of the type which comprises a base structure of basically rectangular plan view, with bevelled corner regions and oriented so that the major dimension is longitudinal, and which at present stands on the ground via four small-diameter caster wheels arranged in the corner regions of this structure and with two rubber-tyred wheels of larger diameter mounted at the ends of a leaf spring. This spring is positioned along the longitudinal centre axis of the base structure and pivoted to it at an intermediate point of the spring on a transverse central axis, so that these wheels are both in permanent contact with the ground, even if there are small upward or downward irregularities in the ground. These larger-diameter wheels are both powered for forward or reverse travel and both have servo-controlled steering, in the sense that they are designed to steer simultaneously and in opposite directions to allow the wheelchair to pivot on itself if required. In chairs of the above mentioned type, it has been found that the use of small-diameter caster wheels causes serious problems in overcoming even small obstacles and the casters rapidly damage delicate floors such as those with a covering of wood or synthetic materials. It is an object of the invention to overcome these drawbacks by using caster wheels of the same diameter as the driving and steering wheels. The number of caster wheels is reduced to two and these wheels are located in the centre line or preferably slightly forward of the centre line of the side members of the base frame which thus has only four wheels of large diameter: two casters at the sides, as stated earlier, and two central driving and steering wheels which have themselves however also been modified in the following manner. Previously, driving wheels of known type mounted on the ends of the leaf spring which is pivoted at an intermediate point to the carriage frame, bore on the ground only by the pressure provided by the elasticity of the leaf spring and not by the weight of the user sitting on the chair. This meant that, if the user was very heavy, or if there were even small obstacles in the way, the driving wheels could slip or be unable to move the wheelchair. These drawbacks have been avoided by mounting one of the driving wheels, preferably the rear driving wheel, on the base frame of the wheelchair, and locating the side caster wheels slightly forward of the centre line of the same frame, as already stated, in such a way that the rear driving wheel is always loaded by the weight of the user, and mounting on the front end of a longitudinal leaf spring whose other end is fixed to the carriage frame, the single front driving and steering wheel, which ensures that the wheelchair advances correctly even where there are small ups or downs in the floor. Other features of the present wheelchair, and the advantages procured thereby, will become clearer in the course of the following description, which refers to the figures of the attached sheets of drawings, in which:

Fig. 1 is a diagrammatic side view of the wheelchair in the low position for travelling over the floor;

Fig. 2 is a perspective view from one side of the carriage base of the wheelchair; - Figs. 3 and 4 illustrate other details of the carriage base depicted in

Figure 2, seen in plan view from above, and from the side, respectively, with parts in section;

Fig. 5 illustrates in part by a block diagram the electrical circuit controlling the wheelchair; - Fig. 6 is a perspective rear view of the wheelchair highlighting the wheelchair lifting and lowering means; and

Fig. 7 is a diagrammatic end elevation of the other details of the lifting and lowering means of Figure 6.

In Figures 1 , 2, 3, 4 and 6, the reference number 1 denotes the carriage frame, the plan view of which is basically rectangular, with the corner regions suitably bevelled. Fixed to the rear cross member 101 is a straight guide 2 that extends upwards and slightly backwards and on which a runner 3 carrying the chair P, with its arms, on which the disabled person sits can be caused to travel by means of a servocontrol that will be described later. In wheelchairs of known type, the frame 1 is usually designed to hold a single rechargeable electric battery, its size being calculated to keep the wheelchair running for a specified number of hours, which are those of normal usage of the wheelchair in the course of one day. If, in the course of a day, the user has to use the wheelchair for longer than the discharge time of the battery, its use is prevented, giving the user the problem that the chair may stop at a very inconvenient moment. In order to mitigate these problems, the battery could be designed with a capacity such as to ensure a small reserve of operation beyond the officially stated time, and yet sometimes this reserve might not be sufficient. To this problem would be added the fact that, if the user were to use the wheelchair daily for a length of time that was normal or less than the rated time, at the end of the day the battery would be connected up to the recharger while still partially charged and could therefore experience incomplete recharging because of the known effects of polarization of its electrodes.

It is an object of the invention to overcome these problems with the following solution. A longitudinal housing 4 is formed on the centre line of the frame 1 : it consists for example of longitudinal sections 104 of flat type and L-section crosspieces 204 and is able to hold two rechargeable electric batteries A, A' having identical characteristics, preferably chosen to have a single capacity such that one battery discharges completely at or even before the end of the normal daily use of the wheelchair. From the diagram shown in Figure 5, it can be seen that the batteries A, A' are connected by their positive poles to a switch 5 whose common 105 is connected to two electronic boards 6 and 106. Board 6 controls the operation of the various electric traction and steering motors M of the chair (see later) through the joystick 7 on one of the arms of the chair. Board 106 controls, via controls 122 also on an arm of the chair, the operation of the electric seat-moving motors M'. The common 105 of the switch 5 is also connected to the outlet of a battery charger 8 which, via an on-off switch 9 and a plug 10 can be connected to the household mains supply when recharging the batteries. Means (not illustrated) are provided so that, by selecting the recharging function via the on-off switch 9, all the functions of the chair are automatically disabled. The negative poles of the batteries are connected to the negative pole of the boards 6, 106. Through the switch 5, the chair is supplied by only one of the two batteries A or A', and towards the end of the day, if the chair is used normally, it is expected that this battery will have discharged and this condition, besides being indicated by a slowing down of the movements of the wheelchair, is notified by a warning device 11 , which may be optical, for example. In these cases, if the user still needs to use the wheelchair, he or she operates the switch 5 to isolate the discharged battery and connect the charged battery to the boards 6, 106. At the end of the day, when the wheelchair is put away and the plug 10 connected to the mains, the user moves the switch 5 to the position it was not in, to connect the drained battery to the battery charger 8 and activates this component through the on- off switch 9. The next day, the user turns off the on-off switch 9, removes the plug 10 from the mains and operates the switch 5 to isolate the battery which was charged overnight and activate the battery that was used only temporarily on the previous day.

It will be obvious that both the objects are in this way accomplished, namely of giving the wheelchair great autonomy of operation and recharging the batteries thoroughly and efficiently, minimising the effects of polarisation of the electrodes of these components. It should be understood that the manual switch 5 can be replaced with a corresponding automatic switch controlled by means for detecting the condition of the batteries and of the battery charger, these points being perfectly obvious to, and easily carried out by, those skilled in the art.

The same Figures 1 to 4 and 6 show that the base frame 1 stands on the ground via four wheels only, preferably with rubber treads, all of large diameter and all the same as each other. In particular, two caster wheels 12 are mounted so as to rotate freely on vertical pins 112, slightly forwards of the centre line of the frame 1 , one on each side of the said frame. A third wheel 13 rotates about its own vertical pin 113 mounted on a bracket 201 located in the centre line of the rear face of the frame 1. A fourth wheel 14 is located centrally at the front of the frame 1 and rotates about a vertical pin 114 connected to the end of a leaf spring 15 which runs longitudinally along the centre line of the frame 1 and is welded to the intermediate crosspieces of the frame 4 and at the other end to the cross member 101 and/or to the neighbouring crosspiece 204 of the same frame 1 on which the batteries are carried. The free end of the leaf spring 15 is characterized by an upwardly concave profile, such that the spring does not normally touch the front crosspiece 204' of the frame 4 and, when the wheelchair is at rest, the wheel 14 is in the position indicated in Figure 4 at 14' in chain line, so that the chair contacts the ground through the wheels 14, 13 and through only one of the side wheels 12. However, when the user sits on the chair, his or her weight causes the chair to contact the ground through all four wheels because the wheel 14 moves to the position indicated in Figure 4 in solid line. In this position the spring 15 is able to pivot further upwards, as shown at 14" in broken line or downwards as indicated at 14', in order to overcome small up and down obstacles in the floor (see later).

Both wheels 13 and 14 are powered by respective motor/gearbox assemblies 16, 16' having identical characteristics and with d.c. electric motors M able to turn in both directions of rotation, connected to the board 6 of Figure 5 and flanged to the frames of these wheels, which at the top have lever arms 213, 214 of identical length, oriented one on the left-hand side and the other on the right-hand side of the frame 1. The ends of these levers are connected, by means of ball joints, to the ends of respective tie rods 17, 17' whose other ends are pivoted, again by ball joints, to the ends of the head of a T-shaped lever 18, the base end of this lever is fixed to the vertical spindle 119 (which rotates slowly) of a motor/gearbox assembly 19 with an electric motor M which is also direct-current, is able to rotate in both directions of rotation and is connected to the board 6 to allow it to be operated through the joystick 7 of Figures 1 and 5. The motor/gearbox assembly 19 is flanged to a bridge 20 fixed beneath and in the intermediate part of the frame 4, as can be seen in Figures 2, 3 and 6, roughly where the leaf spring 15 is fixed at an intermediate point, so that the steering position of the wheel 14 does not vary when the spring 15 oscillates. The synchronous steering in opposite directions of the wheels 13 and 14 brought about by the motor/gearbox assembly 19 will allow the wheelchair to steer, if required, about itself and to move even in narrow spaces. It will be understood that suitable electronic and/or mechanical means are provided to limit the steering angle, so that the system of tie rods 17, 17' and levers 213, 214 do not pass dead centre.

In Figure 3 it is clear that the weight of the user now rests essentially on the three wheels 12 and 13 and that the rear wheel 13 therefore always has good grip on the ground. If the wheelchair is required to overcome a small obstacle on the ground, such as a joining strip between two different parts of the floor or a track for a sliding door, this obstacle will be overcome without difficulty by the spring-loaded front wheel 14 because the chair is being efficiently pushed by the rear wheel 13. The side wheels 12 can also easily overcome the obstacle as they are being pushed efficiently by the rear driving wheel 13 and also by the traction of the front wheel 14. As the rear wheel 13 approaches the obstacle, the leaf spring 15 is still not touching the crosspiece 204' at the front of the frame 4, so the user can lean his or her body forwards so that the wheelchair rocks on the side wheels 12, which act as fulcra, and lifts the rear wheel 13, which can thus easily surmount the obstacle, assisted by its own rotation and by the traction of the front driving wheel 14.

It will be understood that either or both of the driving and steering wheels 13 and/or 14 may be double wheels or may be replaced by pairs of wheels whose steering movements are synchronized. To enable the user to position himself or herself such that the plane of the seat of the chair is level with or slightly lower than a toilet seat, in order to be able to move easily from the latter to the chair, servocontrols have been used for the movement of the runner 3, so that these conditions can also be reached. Figures 6 and 7 show that the guide 2 is a portal frame and that the channel-section sides of the runner 3 slide, with intermediate inserts of a suitable plastic material, up and down its uprights. At the bottom of the guide 2, fixed to its uprights, is a plate 21 to which is flanged a motor/gearbox assembly 22 with a d.c. electric motor M' able to turn in both directions of rotation, the slow shaft of which passes through a hole in the said plate 21 and is secured to a small-diameter sprocket 23. The motor M' of the motor/gearbox assembly 22 is operated via the control 122 located on one of the arms of the wheelchair and connected to the board 106, Figure 5. Fixed to the top member of the guide 2 is a downward bracket 124 to which is rotatably attached a sprocket 24 larger than the drive sprocket 23, and at least one robust chain 25 passes around these sprockets and is connected by its ends to a bracket 26 integral with the runner 3 so that as the motor/gearbox assembly 22 rotates in one direction or the other, the chair rises or falls. The gearbox of the assembly 22, like those of assemblies 16, 16' and 19, is of irreversible type, e.g. is a worm and helical wheel. Due to the weight of the chair and the user sitting on it, the length of chain running between the bracket 26 and the upper sprocket 24 and between this sprocket and the bottom sprocket 23, is always under tension, while the length of chain running between the bottom sprocket 23 and the bracket 26 is never under tension and it is here that the little lengthenings suffered by the chain in the course of use can accumulate. To ensure that this run of the chain which is not under tension meshes correctly with the drive sprocket 23, it may if desired be connected to the bracket 26 by spring-loaded compensation means (not shown), and it is in any case intended that the plate 21 carry a small casing 27 equipped with a collar 127 circumscribing that part of the sprocket 23 which carries the chain 25. It has divergent ends 127 and supports a small integral shoe 227 that acts on the inside of the said chain run, so as to orient it correctly, even if slack, as it meshes with the drive sprocket 23. The chain run extending between the sprockets 23, 24, which is continuous, is enclosed in a tubular guide of polygonal section 28 mounted on the adjacent upright of the guide 2, e.g. by means of brackets 128, and the pin of a shoe 29 of e.g. plastic is inserted into one of the links of this chain run. This shoe 29 has bevelled front and rear edges and is guided as it travels inside the said guide 28. Openings are provided in the wall of the guide 28 on which the shoe 29 runs, to house the terminals of microcontacts 30, 30' which stop the movement of the chair at the top of its lifting travel and at the end of the maximum descent travel respectively, while an intermediate microcontact 30" operated for example by the runner 3 or by parts attached to this runner, enables horizontal movement of the vehicle only if the chair P is close enough to the frame 1 to ensure the stability and safety of the said horizontal movement.

The electric cables 31 connecting the lower actuators on the frame 1 to the controls on the arms of the chair, only one of which is visible in Figure 6, are of spiral type: a cylindrical helical spring 32 passes through the middle of each, the top end 132 being fixed to the runner 3, together with a length of the cable 31 , while the bottom end is fixed at 232 to the fixed plate 21 , together with a corresponding point of the said cable 31 , all of this being done in such a way that the cable can lengthen and shorten while being guided by the spring and without interfering with the relatively moving parts of the wheelchair which will be equipped with appropriate protective casings having both safety functions and aesthetic functions, though these have not been illustrated as they are not necessary to an understanding of the invention.

The present wheelchair is also equipped at the front and underneath the seat with a known parallel-motion structure 33 supporting at the front a footrest 133 which can be adjustably extended and which, when the chair is fully down, rests via its own component 233 on the frame 1 to keep the said footrest a suitable distance from the ground. In known wheelchairs, the structure 33 is hooked to the wheelchair by a chain which ensures the correct downward extension of the jointed structure 33 when the chair is raised. The invention dispenses with this chain, which can restrict the user's movements, and replaces it with an adjustable screw 34 attached for example to the upper link of the parallelogram 33 and extending towards the opposite link so as to touch the nearest of the vertical sides of the parallelogram when the chair is up and the links are inclined downwards. This will be obvious to, and is easily carried out by, those skilled in the art.

Claims

1. Self-propelled steering wheelchair for the disabled, with lifting and lowering movements, particularly for use in the domestic environment, of the type that comprises a base frame (1 ) that stands on the ground via wheels, some of which are idle casters and others are driving and steering wheels, and which is equipped at the back with an upwardly extending integral straight guide (2) on which a runner (3) carrying the chair (P) on which the disabled person is sitting can be caused to travel, which wheelchair is characterised in that the said base (1 ) is provided with preferably rubber-tyred wheels that are all of large diameter, two of which (12) are idle casters arranged symmetrically on the sides of the said frame, while at least one third driving and steering wheel (13) is supported by the centre line of the rear part of the said frame (1 ) and at least one fourth driving wheel (14) that steers in phase with the said rear wheel is positioned at the front centre of the same frame (1 ) and is mounted on means that allow it to move vertically elastically with a predetermined travel, all in such a way that the rear driving and steering wheel (13) is always loaded by the weight of the user, while the front driving and steering wheel (14) ensures, by means of its elastic loading, that the chair advances correctly even on a floor that presents small upward or downward obstacles.

2. Wheelchair according to Claim 1 , in which the side caster wheels (12) are set slightly forward of the centre line of the carriage frame (1 ), in such a way that the weight of the chair and of the user always bears on these side wheels and on the rear driving and steering wheel (13), unless the user angles his or her trunk forwards, as a result of which the chair pivots on the said side wheels (12) and bears on the ground via the front driving and steering wheel (14), which can move elastically with a travel of predetermined maximum amplitude, while the rear driving and steering wheel (13) rises proportionately, so as easily to be able to surmount small upward obstacles on the floor.

3. Wheelchair according to Claim 1, in which the front driving and steering wheel (14) is mounted rotatably by its pin (114) to the front end of a leaf spring (15) positioned longitudinally and in the centre line of the carriage frame (1 ), to which it is fixed at at least the other end.

4. Wheelchair according to Claim 3, in which the leaf spring (15) is welded at the rear end and preferably also at an intermediate point to the carriage frame (1 ) and the front end of the same leaf spring has an upwardly concave profile such that the said spring normally does not touch a front crosspiece (204') of the frame above it, and when the frame is at rest and not loaded by the weight of the user the said chair stands on the ground via the front and rear wheels (14, 13) and via only one of the side wheels (12), whereas when the user is sitting in the chair the said chair stands on the ground via all four wheels (14, 13, 12), the front wheel (14) still being able to move further upwards before its leaf spring (15) touches the said crosspiece (204'), in such a way that this wheel can pivot freely downwards or upwards in the presence of small upward or downward obstacles on the floor.

5. Wheelchair according to claim 1 , in which the driving and steering wheels (13, 14) are powered by respective motor/gearbox assemblies (16, 16') having identical characteristics, with d.c. electric motors (M) capable of turning in both directions of rotation, flanged to the frames of these wheels, which at the top carry lever arms (213, 214) of equal length, oriented one on the left-hand side and the other on the right-hand side of the carriage frame (1), the ends of the said levers being connected by means of ball joints to the ends of respective tie rods (17, 17'), the other ends of which are jointed, again by means of ball joints, to the ends of the head of a T- shaped lever (18) whose base end is fixed to the vertical spindle (119), which rotates slowly, of a motor/gearbox assembly (19) with an electric motor (M) which is likewise direct-current and able to turn in both directions of rotation and which, together with the motors turning the said wheels, is designed to be operated via a joystick (7) mounted on one of the arms of the chair, the said motor/gearbox assembly (19) being mounted on a bridge (20) fixed beneath and in an intermediate part of the frame (1), roughly at the intermediate fixing point of the leaf spring (15) on which the front wheel (14) is mounted, in such a way that the steering position of this wheel does not vary when the said spring moves up and down.

6. Wheelchair according to Claim 1 , in which the carriage frame (1 ) supports longitudinally and in the centre line a frame with side walls (4), capable of containing two rechargeable electric batteries (A, A') having a total capacity such as to enable the said wheelchair to operate normally even for a longer period of time than that of normal daily use.

7. Wheelchair according to Claim 1, in which the rechargeable electric batteries (A, A') are connected one at a time to the chair's user circuit and each of them preferably has a capacity such as to be discharged towards the end of normal daily use of the chair, indicator and switching means being provided to isolate the discharged battery and connect the charged battery, and means are provided so that at the end of the day, when the wheelchair is put away and left charging, only the discharged battery is recharged and to ensure that the next time the chair is operated, the battery used is the one that has not been most recently recharged, all in such a way as to limit the effects of polarization which occur when the batteries are charged without having been fully discharged.

8. Wheelchair according to Claim 7, in which the means of switching between the batteries (A, A') are of manual type (5).

9. Wheelchair according to Claim 7, in which the means of switching between the batteries (A, A') are automatic and controlled by means for detecting the condition of said batteries and of the recharging unit (8).

10. Wheelchair according to Claim 1 , in which the guide (2) on which the runner (3) travels, carrying the chair (P), is a portal frame, and a plate (21 ) is fixed to the bottom of its uprights on which the channel-section sides of the said runner (3) slide, flanged to which plate (21) is a motor/gearbox assembly (22) with a direct-current electric motor (M') capable of turning in both directions of rotation and operated via a control (122) mounted on one of the arms of the chair and the slow shaft of this motor/gearbox assembly passes through a hole in the said plate (21) and is fixed to a small-diameter sprocket (23), parallel to which is a larger-diameter sprocket (24) supported idly by a bracket fixed on the centre line of the top member of the said guide (2), these sprockets carrying at least one robust chain (25) connected by its consecutive ends to a bracket (26) integral with the said runner (3), in such a way that when the said motor/gearbox assembly (22) rotates in one direction or the other, the chair (P) rises or falls.

11. Wheelchair according to Claim 10, in which the run of chain (25) that extends between the lower drive sprocket (23) and the bracket (26) fixed to the runner (3) with the chair (P) can be connected to this bracket by a spring which keeps this run of chain taut at all times and correctly oriented relative to the said sprocket (23).

12. Wheelchair according to Claim 10, in which there is mounted on the plate (21 ) carrying the motor/gearbox assembly (22) with the lower chair lifting and lowering sprocket (23), a casing (27) having a curved edge (127) that circumscribes the length of chain (25) in mesh with this sprocket, and that ends in divergent upper sections and supports a shoe (227) capable of keeping correctly oriented relative to this sprocket the run of chain extending between this sprocket and the upper bracket (26) fixed to the runner (3) with the chair (P).

13. Wheelchair according to Claim 10, in which the run of chain (25) that extends between the said sprockets (23, 24) and which is continuous, runs through a tubular polygonal-section guide (28) fixed to the adjacent upright of the guide (2) by means of brackets (128), and one of the links of this run of chain receives the pin of a shoe (29) made of e.g. plastic, which is guided as it travels inside the said guide (28), one wall of which contains openings housing the terminals of microcontacts (30, 30') capable of engaging with the said shoe to stop the lifting or lowering movement of the chair at the top of the lifting travel and at the end of the maximum descent travel, a safety microcontact (30") also being provided to allow horizontal movement of the vehicle only if the seat (P) is sufficiently close to the carriage frame (1) to ensure stability during the said horizontal movement.

14. Wheelchair according to the previous claims, in which all the motor/gearbox assemblies (16, 16', 19, 22) comprise irreversible-type speed reducers, such as worms and helical wheels.

15. Wheelchair according to Claim 1 , in which the electrical cables (31 ) connecting the lower actuators mounted on the carriage frame (1 ) to the controls on the arms of the chair (P) are of spiral type and are each wrapped around a cylindrical helical spring (32), of which the top end (132) is attached to the runner (3) with the chair (P), together with a length of the said cable (31), and the bottom end (232) of which is attached to the fixed plate (21) with the motor/gearbox assembly (22), together with a corresponding point of the said cable (31 ), all in such a way that the latter can length and shorten while still being guided on the spring without interfering with the relatively moving parts of the wheelchair.

16. Wheelchair according to Claim 1 , in which the parallel-motion structure (33) which carries in front an adjustable footrest (133), which when the chair is fully down rests via one (233) of its components on the carriage frame (1), to keep the said footrest at a suitable distance from the ground, when it is extended by the lifting of the chair, is limited in this extension travel by an adjustable screw (34) mounted on one of the links of the said parallel-motion structure (33) and directed towards the opposite link so as to touch the nearest of the vertical sides of the said parallel- motion structure or some other fixed part.