The present invention relates to an electric stair-climbing wheelchair. The wheelchair according to the invention also moves downstairs and on level ground.

The invention is designed for people with walking problems due to illness or disability and is meant to aid them move on stairs and on level ground.

An example of a stair-climbing electric wheelchair was disclosed in the USA patent No. 5123495 of 23 June 1992. The title of this invention is "Wheelchair stair climbing control system", whilst its authors include Douglas J. Littlejohn, John H. Henssler and Baxter R. Watkins. The wheelchair is equipped with a chassis and a solid frame, to which two parallel battery-powered caterpillar tracks are mounted. The chassis frame is jointed to a post, maintained in the vertical position by actuators. The said wheelchair is equipped with an automatic system, detecting the tilt of the seat and controlling the actuators. A pair of tracks is used to move the wheelchair on level ground and while ascending or descending an incline. When the wheelchair is in the position for ascending or descending stairs, caterpillar tracks drive onto the stairs and the wheelchair together with the seat tilts forward. The automatic system controls the seat tilt and turns on actuators, which lift the seat post to a vertical position so that the seat cushion is consequently set horizontally. The same system works when the wheelchair turns from the ascending or descending mode to movement on level ground.

Another multifunctional electric stair-climbing wheelchair is known by the name of Independence Mobility System, also referred to as iBOT. Its construction has been designed in the USA by Deka Products Limited Partnership, set up by Dean L. Kamen, an inventor of a number of medical appliances. IBOT was approved for use by the US Food and Drug Administration on 13 August 2003. Since then, it was manufactured in the USA by Johnson & Johnson. Production of this wheelchair was put to an end in January 2009. The iBOT wheelchair is equipped with a seat, whose frame is connected to two pairs of parallel levers. The levers are connected with a shaft bearing supported in the chassis drive box. The shaft is battery-powered and makes it possible to tilt the levers by 45 degrees relatively to the chassis. The drive box also supports a horizontal shaft, at the ends of which identical flat mechanism casings are fixed. The mechanisms have two output shafts each, coupled with two ground wheels of 300 mm outside diameter. The shaft connecting mechanism casings propels the rotation movement of the casings as well as the driving wheels. IBOT is also equipped with an automatic balance system, which uses the gyroscope effect to maintain wheelchair equilibrium, even though the wheelchair is supported by two wheels only. IBOT assumes two configurations. In the first configuration, the levers and mechanism casings are positioned horizontally and the wheelchair is supported by four wheels. In this configuration, the wheelchair moves on level ground and the seat is positioned at the height of approx. 50 cm. In the other configuration, the levers are tilted relatively to the horizontal plane by approx. 45 degrees; the casings are positioned vertically and the wheelchair is supported by two wheels; the seat is lifted to the height of approx. 80 cm. In this configuration, the wheelchair begins and ends the stair mode or sometimes moves on level ground. In the stair-climbing or descending mode, the mechanism casings rotate in the same direction with identical velocity; simultaneously, driving wheels rotate in the same direction. Pairs of wheels subsequently support the wheelchair on successive stairs, whilst the wheelchair balance is maintained by the automatic system. The movement is supported by an assisting person, holding the wheelchair by the handles. In the case of narrow stairs with handrails, the climbing movement may be manually aided by the wheelchair user.

Another stair-climbing wheelchair that is known was disclosed in the USA patent No. 6484829 of 26 November 2002. It was created by Kenneth Ray Cox. The title of this invention is "Battery powered stair-climbing wheelchair". The said wheelchair is equipped with a seat whose frame supports a cross-sectional horizontal drive shaft. At both ends of the shaft, identical three-spider wheel spokes and three-wheel assemblies are mounted. The said wheelchair is equipped with two extension arms at the front and one at the back. The movements of extension arms are realized through electric actuators, controlled by an onboard computer, which cooperates with the sensor monitoring the wheelchair tilt relatively to the ground. The ends of extension arms are coupled to skids, supporting the front and rear part of the wheelchair during the stair-climbing movement. The wheelchair is also equipped with a vertical shaft securely attached to a horizontal axis of two non- drive rear wheels. This shaft is rotated by an electric linear actuator, and together with the axle constitutes the wheelchair steering system. During movement on level ground, the wheelchair is supported by two drive wheels of the three-wheel assemblies and two non- drive rear caster wheels. In such a case, extension arms are lifted above the ground level. The wheelchair turns into the climbing mode, ascends or descends stairs, or returns to level ground movement controlled by the onboard computer cooperating with the tilt sensor. The computer controls actuators which ensure that the wheelchair is supported by the skids in the front and at the back so that the seat remains in the horizontal position. In the stair mode, the movement is realized by three-spider wheel spokes and three-wheel assemblies.

Another known stair-climbing wheelchair solution was disclosed in the USA patent No. 6857490 B2 of 22 February 2005 under the title "Stair-climbing wheelchair". This one was created by Robert T. Quigg. The wheelchair is equipped with a seat, whose frame is jointed to the chassis frame. The frame is jointed to two X-braces, which move in a scissor- like manner. They can be manually opened or closed by the user with the help of a lever. The wheelchair is equipped with wheels for movement on level ground and tracks for the stair-climbing mode. The set of wheels comprises two front caster wheels controlled by the user with the help of a lever and two battery-powered rear wheels. The track assembly consists of two parallel front track sections and two parallel rear track sections. The track assembly is also battery-powered. The wheelchair can operate in two configurations, which are manually changed by the user with the help of a lever. In the first configuration, when the X-braces are closed and track assemblies lifted, the wheelchair is supported by the set of wheels and moves on level ground. In the other configuration, the stair-climbing mode, the X-braces are opened, the wheels are lifted, and the track assembly is lowered down. Configuration changes are performed by the user with the help of a lever when the wheelchair transfers from the ground level mode to the stair-climbing mode and vice versa.

Another known invention is the electric stair-climbing wheelchair created by Herve Le Masne De Chermont, a French engineer and scientist. The invention was disclosed in the US patent No. 7384046 on 13 May 2004 under the name "Powered wheeled vehicle capable of traveling on level ground, over uneven surfaces and on stairs". In this wheelchair, the backrest is supported with a joint, whilst the seat cushion is supported with an actuator tilting the seat by approximately 30 degrees. The wheelchair is equipped with two non-drive front wheels, outside diameter of 200 mm, and two drive rear wheels, outside diameter of approximately 350 mm. The front wheels are caster wheels, lifted and lowered with the help of an actuator. The rear wheels are mounted to motoreducer shafts, lifted and lowered by another actuator. The wheels are lifted or lowered during the configuration change. Beneath the chassis, two parallel battery-powered caterpillar tracks are mounted. The front and rear part of the wheelchair is equipped with electric sensors, which cooperate with the onboard computer and detect the position of the wheelchair relatively to the stairs. Once the computer has recognized the position, it halts the wheelchair and changes the configuration. During movement on level ground, the wheelchair is supported by four wheels and the seat cushion is positioned horizontally. Whilst during the stair mode, the wheels are raised and the wheelchair is supported by the caterpillar tracks; the seat cushion is positioned in a horizontal plane under the action of the actuator controlled by the onboard computer.

The wheelchair according to this invention answers the need for a safe and simple construction constructed from durable elements, which can move on level ground and on stairs. The wheelchair does not require the use of an automatic tilt monitoring system, extension arms, an automatic balance system, or a local computer with sensors monitoring the position of the wheelchair relatively to the stairs.

The said wheelchair is constructed in such a way that (fig. 1, 2, 3, 4 and 5) its seat

(I) is equipped with the solid frame (2), symmetrical relatively to the vertical symmetry plane (P - P) running along the wheelchair. The wheelchair frame consists of two identical side frames (3), connected by at least three upper beams (4, 5 and 6) and at least two bottom beams (7 and 8). The side frames (3) or the upper beam (6) are securely connected with two bent posts (9), cross braced by at least one crossbar (10) and ended with handles

(II) . The wheelchair frame is connected with the seat cushion (12), backrest (13), armrests (14), footrest (15) and headrest (16). The wheelchair is equipped with two front drive wheels (17), outside diameter (dj) of approximately 400 mm, each with a fixed rotation axle (18) supported by a bracket (19) coupled to the side frame (3). The invention is equipped with the drive (21), used so far in certain conventional electric wheelchairs. Such a drive is also used in electric three-wheel scooters designed for disabled persons. The said drive consists of the motor (22) with the electromagnetic brake (23), reduction gear (24) and differential gear (25) with axle shafts (26). Two rear driving wheels (27), with the diameter (d ₂ ) of approx. 160 mm, are mounted in two wheel forks (28) with vertical fork shafts (29). The shafts are supported by identical bushings (30) with fork shaft (29) ends (31) protruding at the top. The bushings are coupled to vertical bushing plates (32). The invention is equipped with the steering system (33), used so far in certain conventional electric wheelchairs. The system consists of two identical levers (34), the steering rod (35) and the electric actuator (37). The levers are securely attached to shaft (29) ends (31) and jointed to the rod (35) equipped with the bracket (36). The bracket is jointed to the linear actuator (37) lug (38); whilst the actuator is also equipped with another lug (39). The wheelchair is equipped with a favorably gel battery (41) suitable for multiple loading, favorably placed in a box mounted to the wheelchair frame. The battery is connected with two manual control panels (43 and 44), used so far in these conventional electric wheelchairs, which are equipped with such a drive (21) and steering system (33) as in the present invention. Both panels are connected with the electric installation (42), motor (22), brake (23) and electric linear actuator (37). One panel is mounted to the seat armrest, the other to the back handle (11).

In the said invention, the front wheels (17) are propelled by the drive (21) via identical strand transmissions (20), connecting the axle shafts (26) of this drive with rotation axles (18) of the wheels. The drive is mounted to upper beams (4 and 5) with screws.

Another significant feature of the invention is that the lug (39) of the steering system actuator is jointed to the beam (40), which is securely attached at the top to bushings (30) of the length (h ₂ ) favorably approx. 300 mm.

The wheelchair according to the invention is equipped with the drive (45) that lifts and lowers the rear wheels (27) together with the steering system to the height (hi) of approx 250 mm. The drive consists of two identical slideways (46), used so far particularly in car pullers. The slideways are securely attached to frames (3) so that they are mutually parallel and symmetrical relatively to the symmetry plane (P - P). Both slideways bear identical sliders (47), vertically hollow, which are securely attached to vertical bushing plates (32 and 30). Inside the sliders, identical non-rotational nuts (48) were fit with screws

(49) ; these are bearing supported by the sliders. The screws are rotated by identical motors

(50) or motoreducers through permanent couplings (51). The motors are favorably screwed to slideways (46) at the top. The motors are connected with the electric battery by the three-position switch (52) controlled manually. The switch is equipped with the middle neutral position and has been used so far particularly in direct current motors rotating in two directions clockwise and counterclockwise. The connection has been created in such a way that after turning on, both motors rotate in the same direction, and in another mode the motors rotate in the opposite direction. The switch is favorably mounted the motor (50).

Another significant feature of the disclosed invention is the apparatus enabling stair-climbing movement (53), consisting of the drive (54), front mechanism (58) and rear mechanism (75). The drive (54) includes the motoreducer (55) with the motor (56) and the output shaft (57). The motoreducer is mounted to the upper beams (7 and 8) with screws. The front mechanism consists of the countershaft (60), tilting frame (62), electric linear actuator (69) and input shaft (66) with two three-wheel assemblies (68) applied so far particularly in manual carts used for transporting objects on stairs. The countershaft is supported by the bearing brackets (59) firmly mounted to the bottom part of the side frames (3) in such a way the rotation axis (Xi) runs perpendicularly to the symmetry plane (P - P). The shaft is rotated by the output shaft via the chain transmission (61). The tilting frame is equipped with two identical front bearing lugs (63) and two identical rear bearing lugs (64). Rear lugs support the frame on the countershaft. The front lugs support the input shaft (66), whose rotation axis (X ₂ ) is perpendicular to the symmetry plane (P - P). The input shaft is rotated by the countershaft via the chain transmission (67). At the ends of the shaft, the two three-wheel assemblies (68) have been securely attached, symmetrically to the symmetry plane (P - P). The frame is tilted by at least one electric linear actuator (69), whose extension axis (Z) lies within the symmetry plane (P - P). One of the lugs (70) of the actuator is jointed to the bracket (71) securely attached to the upper beam (5), whilst the other actuator lug is jointed to the bracket (73) securely attached to the crossbeam (65) of the frame. The actuator has been adjusted in such a way that it tilts the frame from the upper position (fig. 4) to the lower position (fig. 1) and vice versa. In the upper position, the frame is tilted relatively to the ground by the angle (a), approximately 10 degrees; so that the three-wheel assemblies are lifted above the ground level. Whilst in the lower position, the angle (β) of the frame tilt relatively to the horizontal plane is favorably lower than 35 degrees. The actuator is connected with the electric battery and the three-position switch (74) controlled manually, with the middle neutral position. The connection has been created in such a way that after turning on, the actuator tilts the frame towards the upper position and in another mode the frame is moved towards the lower position. The switch is favorably mounted the element (9). The rear mechanism consists of two identical brackets (76) securely attached to the rear part of side frames (3). The brackets are equipped with bearing assemblies (77) with identical rear shafts (78) of common rotation axis (X ₃ ), perpendicular to plane (P - P). The shafts are propelled by the countershaft (60) via identical chain transmissions (79). The ratio of these transmissions equals the ratio of the front transmission (67), which is why the front shaft and rear shafts rotate with identical velocity. At both rear shafts, the known three-wheel assemblies (80) are securely attached, favorably identical to the front assemblies (68). The rear assemblies (80) are symmetrically positioned relatively to the plane (P - P). The motor (56) is connected with the electric battery and the three-position switch (81), constructed in such a way that the lever is set manually into the on position, whilst manually or electrically into the neutral position. The connection has been created in such a way that after turning on, the motor rotates in one direction, and in another mode the motor rotates in the opposite direction. This propels the two-directional rotary movement of three-wheel assemblies and enables the wheelchair to move up or down the stairs. The switch is favorably mounted to the wheelchair handle (50).

Another significant feature of the invention is that during the stair-climbing movement, the three- wheel assemblies are stopped automatically every 120 degrees; the rear assemblies (80) are positioned (fig. 5) so that the rear wheels (27) become reversible during movement on level ground thanks to the steering system. This eliminates the need to control the rear assemblies with the drive after finishing the stair mode. Such a solution has been obtained by means of the electric system with the limit switch (124) and cooperating three elements (125) favorably identical. The system is connected with the motor (56) of the drive and the switch (81). The elements are mounted to the arms of the rear assembly (80) every 120 degrees (φ) of the circle whose radius (r) equals approx. 40 mm. Apart from the assembly, also the limit switch (124) is mounted to the rear bracket (76). The switch is mounted so that when the assemblies turn by 120 degrees the switch is engaged. It turns off the motor (56) and moves the lever of the switch (81) into the neutral position. At the same time the rear three-wheel assemblies stop in such a position that they do not obstruct the reversible movement of rear wheels during the level ground mode (fig. 4 and 5).

The wheelchair according to the invention assumes two movement configurations. In the first configuration (fig. 4), when the wheelchair moves on level ground, the rear wheels are lowered and the front frame is in the upper position so that the front three- wheel assemblies are above ground. In this mode, the wheelchair is supported by two driving front wheels and two rear wheels. In the other configuration, which is the stair mode, (fig. 1, 2 and 3) the rear wheels of the wheelchair are raised to the height (1M) of approximately 250 mm, whilst the front frame is in the lower position tilted by the angle (β) lower than 35 degrees to the ground. The wheelchair is supported by the four wheel assemblies and the seat is positioned favorably horizontally. This configuration is applied on level surface; the seat is then tilted relatively to the ground at the angle of approx. 35 degrees. The tilt makes it necessary to counterbalance the wheelchair by an assisting person, holding the wheelchair by the handles. Configuration changes are handled by the switches (52 and 74) by an assisting person.

The wheelchair movement on stairs is commenced by the switch lever (81). Setting the lever in an appropriate position turns the three- wheel assemblies by the angle of 120 degrees and the upward or downward movement of the wheelchair on the subsequent stair. Then, the drive of the motor is turned off automatically by the limit switch and the lever returns to the neutral position. The continuation of wheelchair movement requires turning on the switch (80) on subsequent stairs. The lever (81) can be manually set in the middle position at any time, which stops the stair-climbing movement. The movement of this wheelchair on the stairs is manually supported by an assisting person. During the ascending movement, the wheelchair is pulled up by the handles using little force, which makes the wheelchair move by several centimeters. During the descending movement, the wheelchair is pushed down using little force, which also makes the wheelchair move by several centimeters. The manually controlled movement of the wheelchair on subsequent stairs is performed with disengaged drive.

Before the wheelchair switches from the level ground movement to the descending mode, it is necessary to change the configuration when both front three-wheel assemblies reach the same distance from the stairs, favorably not larger than 20cm. After turning on the stair mode, the assisting person pushes he wheelchair towards the stairs; then the descending movement begins. The descending movement is finished when front and rear wheel assemblies reach level ground. Afterwards, the wheelchair should be restored to level ground configuration. During that mode, the wheelchair is controlled by the user with the panel mounted to the armrest or by the assisting person with the panel mounted to the handle.

The wheelchair switches from the level ground movement to ascending mode when both rear three-wheel assemblies reach the same distance from the stairs, favorably not lower than 20cm. The wheelchair moves one step up the stairs each time the drive is turned on. The ascending movement is finished when front and rear wheel assemblies reach level ground. Afterwards, the wheelchair needs to be pulled away so that the distance between the front wheel assemblies, which support the wheelchair at the moment, and the stairs favorably exceeds 20 cm. The wheelchair configuration should be then restored to the level ground mode.

The embodiment of the solutions disclosed in the invention is presented at the drawings, where fig. 1, 2, and 3 refer to the wheelchair in the stair mode. Fig. 1 is a side view; fig. 2 is a top view, and fig. 3 is a front view. Fig. 4 is a side view of the wheelchair in the level ground mode, whilst fig. 5 presents a magnified view of the rear part of the wheelchair with fig. 4, taking into consideration rear wheel assemblies 80 stopped by the limit switch 124 in such a position that the rear wheels 27 are reversible; a necessary feature for movement on level ground.

The wheelchair according to the invention consists of the seat 1 equipped with a solid frame 2 which has a vertical symmetry plane P - P running along the wheelchair. The construction consists of two identical side frames 3, connected by three upper beams 4, 5, 6, and at least two bottom beams 7 and 8. The upper beam 6 is attached to two bent posts 9. These elements are connected with at least one crossbar 10 and ended with handles 11. The seat is equipped with the seat cushion 12, backrest 13, armrests 14, footrests 15 and headrest 16. The front driving wheels 17 of diameter di of approx. 400 mm have fixed rotation axles 18, borne by the brackets 19 securely coupled to the side frames 3. The axles are driven by identical strand transmissions 20, propelled by axle shafts 26 of the drive 21 , applied in some other conventional electric wheelchairs. The drive consists of the motor 22 with the electromagnetic brake 23, reduction gear 24 and differential gear 25 with axle shafts 26. The drive is mounted to upper beams 4 and 5 with screws. Rear driving wheels 27, with the diameter d ₂ of approx. 160 mm, are mounted in two wheel forks 28 with vertical fork shafts 29. The shafts are borne by identical bushings 30 of the length h ₂ approx. 300 mm. The bushings are connected at the top with a solid beam 40. The shafts have such a length that their ends 31 protrude at bushing ends 30. The bushings are coupled to vertical bushing plates 32. The wheelchair according to the invention is equipped with the steering system 33, used so far in certain conventional electric wheelchairs. The system consists of two identical levers 34, the steering rod 35 and the actuator 37. The levers are securely attached to shaft 29 ends 31 and jointed with the rod. The actuator lug 38 is jointed to the rod bracket 36, whilst the other lug 39 is jointed to the beam 40. The wheelchair is equipped with a favorably gel battery 41 suitable for multiple loading, the electric installation 42 and two manual control panels 43 and 44, used so far in some other conventional wheelchairs. The panels are connected with the motor 22, brake 23 and electric linear actuator 37. One panel is mounted to the seat armrest, the other to the rear handle.

The wheelchair is also equipped with the drive 45 that lifts and lowers the rear wheels 27 together with the steering system to the height i of approx 250 mm. The lift drive consists of two identical vertical slideways 46, securely mounted to the side frames 3. The slideways are parallel and positioned symmetrically to the symmetry plane P - P. The slideways bear identical sliders 47, vertically hollow, which are securely attached to vertical bushing plates 32 and 30. Inside the sliders, identical non-rotational threaded cubes 48 were fit with identical screws 49; these were borne by the sliders. The screws are rotated by identical motors 50 through permanent couplings 51. The motors are mounted to the slideways at the top with screws and connected with the electric battery and the three- position switch 52 controlled manually, with the middle neutral position. The connection has been created in such a way that after turning on, both motors rotate in the same direction, and in another mode the motors rotate in the opposite direction. The switch is favorably mounted to the motor 50.

The invention is also equipped with the stair-climbing apparatus 53, consisting of the drive 54, front mechanism 58 and rear mechanism 75. The drive includes the motoreducer 55 with the output shaft 57, and the electric motor 56. The motoreducer is mounted to bottom beams 7 and 8 with screws. The front mechanism 58 consists of the countershaft 60, solid tilting frame 62, input shaft 66 with the three-wheel assemblies 68 and the electric linear actuator 69. The countershaft 60 is supported by two identical bearing brackets 59, securely attached to side frame bottoms 3 so that the rotation axis X] of the shaft is perpendicular to the plane P - P. The shaft is propelled by the output shaft 57 of the reducer via the transmission chain 61. The frame 62 is equipped with two identical front bearing lugs 63, two identical rear bearing lugs 64 and the crossbeam 65. Rear lugs make it possible to suspend the frame on the countershaft. The front lugs support the input shaft 66, whose rotation axis X ₂ is perpendicular to the symmetry plane P - P. The input shaft is propelled by the countershaft via the chain transmission 67. At the ends of the input shaft, two identical three-wheel assemblies 68 are mounted, symmetrically to the plane P - P. The frame 62 is tilted by an electric actuator 69, whose extension axis Z lies within the symmetry plane P - P. One actuator lug 70 is jointed to the bracket 71 securely attached to the beam 5, whilst the other lug 72 of this actuator is jointed to the bracket 73, securely attached to the frame 62 crossbeam 65. The actuator has been adjusted in such a way that it tilts the frame from the upper position to the lower position and vice versa. In the upper position, fig. 4, the frame is tilted relatively to the ground at the angle a, approximately 10 degrees; so that the three-wheel assemblies are lifted above the ground level. Whilst in the lower position, fig. 1, the angle β of the frame tilt relatively to the horizontal plane is favorably lower than 35 degrees. The motors are connected with the electric battery by the three-position switch 74 controlled manually. The connection has been created in such a way that after turning on, the actuator tilts the frame towards the upper position and in another mode the frame is moved towards the lower position. The switch is favorably mounted the element 9.

The rear mechanism 75 consists of two identical brackets 76 securely attached to the rear part of side frames 3. The brackets are equipped with identical bearing assemblies 77 with identical rear shafts 78 of common rotation axis X ₃ , perpendicular to plane P - P. The shafts are propelled by the countershaft 60 via identical chain transmissions 79. The ratio of these transmissions equals the ratio of the front transmission 67 so that the input shaft and the rear shafts rotate with the same velocity. At rear shafts, the three-wheel assemblies 80 are securely attached, symmetrically to the plane P - P. The rear assemblies 80 are favorably identical to the front assemblies 68. The motor 56 of the drive is connected with the battery and the three-position switch 81 constructed in such a way that the lever is set manually into the on position, whilst manually or electrically into the neutral position. The switch has been mounted in such a way that after turning on, the motor rotates in one direction, and in another mode the motor rotates in the opposite direction. The switch is favorably mounted to the wheelchair handle 11.

Moreover, the wheelchair according to the invention is equipped with the electric system with the limit switch 124 and three identical elements 125 cooperating with the switch. The system is connected with the motor 56 and the switch 81. The elements are mounted to the arms of the rear assembly 80 every 120 degrees (angle φ) of the circle whose radius r equals approx. 40 mm. Besides, the limit switch is mounted to the rear bracket 76 in such a way that each time the assemblies rotate by 120 degrees one of the elements engages the switch. It turns off the motor 56 and moves the lever of the switch 81 into the neutral position. At the same time the rear three-wheel assemblies stop in such a position that they do not obstruct the reversible movement of rear wheels during the level ground mode, fig. 4 and 5.