Powered Mid-Wheel Drive Wheelchair with Standing Function

Abstract

The powered mid-wheel drive (MWD) wheelchair (1-1) comprises a chassis (3) and a seat system (15) mounted on the chassis (3). The seat system (15) is operated between a sitting position and a standing position. The wheelchair comprises a pair of drive wheels (13), a pair of front swing arms (5) rotatably connected to the chassis (3), and front support wheels (9) mounted on one side of each of the front swing arms (5). Each front swing arm (5) pivots relative to the chassis (3) between a first position where the front support wheel (9) is in the uppermost position relative to the chassis (3) and a second position where the front support wheel (9) is in the lowermost position relative to the chassis (3). The front swing arm (5) pivots to the first position when the seat system (15) is in the standing position. As a result, the chassis (3) tilts forward relative to the ground or floor surface (18).

Description

Technical Field

[0001] The present disclosure generally relates to mid-wheel drive wheelchairs.

Background Art

[0002] A mid-wheel drive wheelchair (mid-wheel drive MWD wheelchair) has a front wheel, a rear wheel, and a drive wheel disposed between the front wheel and the rear wheel.

[0003] Among mid-wheel (intermediate wheel) drive MWD wheelchairs, some have a standing function (standing capability). That is, a seating system having a seat and a backrest can be operated between a default low position or seated position and an upright position. In the upright position, the seat surface tilts forward while the backrest is maintained in a generally vertical state, thus supporting the user's standing position.

[0004] The mid-wheel drive MWD wheelchair must be stable so as not to tip forward when the seating system is set to the upright position.

[0005] Patent Document 1 discloses a stand-up wheelchair having a central wheel drive unit and a front wheel that are operatively connected (operatively connected, operatively coupled) by an endless chain. The frame has a front part and a rear part that are indirectly connected to each other. In the sitting position, the front wheel is not in direct contact with the ground. In the standing position, the front wheel is in contact with the ground, but the central wheel is not in contact with the ground. The drawback of this wheelchair is that the turning radius is large, so it is not practical for indoor use. Furthermore, not only is the configuration (arrangement, arrangement) of the drive device complex and costly, but the fact that the front wheel is separated from the ground in the seated position has an adverse effect on the driving comfort for the user.

[0006] Patent Document 2 discloses a standing assist device (stander) for a powered (electric) wheelchair having a drive wheel (drive wheel, drive wheel) and front and rear support wheels (support wheels, support wheels). This wheelchair is configured to be movable between a seated position and a standing position. As a result of the center of gravity moving forward and / or upward in the standing position, a suspension assembly is provided to prevent the wheelchair from tipping over. This suspension assembly allows the suspension system to articulate when the user positioning system is in the seated position, while restricting or completely locking such articulation when the user positioning system is in the standing position. However, this is achieved by a system of links and lock / limit elements that necessarily increases complexity and raises costs.

[0007] Patent Document 3 discloses a wheelchair having a pair of base frames. The front (front part) caster arms are fixedly secured to the base frames. This wheelchair further has movable frames connected to one of each of the base frames to change the position of the user.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] A general object of the present disclosure is to provide a mid - wheel drive (MWD) wheelchair that solves or at least alleviates the problems of the prior art.

Means for Solving the Problems

[0010] Accordingly, a powered mid-wheel drive (MWD) wheelchair having the following configuration is provided. The powered (electric) mid-wheel drive MWD wheelchair includes a chassis and a seat (seating) system attached to the chassis. The seat system is configured to be maneuvered between a seated position and a standing position. The powered mid-wheel drive MWD wheelchair includes a pair of drive wheels, a pair of front swing arms pivotally coupled to the chassis, and front support wheels attached to one of each of the front swing arms. Each front swing arm is configured to rotate between a first position and a second position relative to the chassis. In the first position, the front support wheel is at the uppermost position of the front support wheel relative to the chassis. In the second position, the front support wheel is at the lowermost position of the front support wheel relative to the chassis. The front swing arm is configured to rotate to the first position when the seat system is in the standing position. Thus, the chassis is tilted forward relative to the ground or floor surface.

[0011] Accordingly, the seat system can be set to the standing position while maintaining a sufficient level of stability because the front swing arm bottoms out in the first position and the chassis is tilted forward. The drive wheels maintain contact with the ground or floor surface and support the weight of the mid-wheel drive MWD wheelchair and the occupant.

[0012] It is possible to achieve sufficient stability without using a complex locking mechanism to prevent further tipping behavior (tipping behavior). Since the locking mechanism is prone to quality problems, it restricts the movement of the suspension in extreme seating positions. Since there is no need to add sensors, actuators (actuation devices), or warning systems, compared with the solutions found in the prior art, this solution is more robust and cost-effective. Therefore, this solution can be made completely passive.

[0013] According to one embodiment, the tilt angle of the chassis with respect to the horizontal ground or floor surface when the seat system is in the upright position can be up to 6°, for example, within the range of 2° to 4°.

[0014] When the front swing arm is rotated to the first position, the chassis may tilt forward as a result of the center of gravity shift caused by the seat system reaching the upright position. The rotation (pivot) of the front swing arm to the first position, which bottoms out, and the tilt of the chassis thus respond to the movement of the seat system from the seated position to the upright position and are therefore passive.

[0015] According to one embodiment, in the upright position of the seat system, the common center of gravity of the powered mid-wheel drive MWD wheelchair and its occupant is located between the first vertical plane and the wheel axle plane. The first vertical plane extends through the pivot connection of the front swing arm to the chassis. The wheel axle plane is the second vertical plane that includes the wheel axle of the front support wheel when the powered mid-wheel drive MWD wheelchair is stationary on a flat horizontal surface.

[0016] The term "occupant" means the user for whom the mid-wheel drive MWD wheelchair is adapted to the user's weight and body type. Each front swing arm may be rigid.

[0017] According to one embodiment, for each front swing arm, there is a horizontal distance L between the pivot connection of the front swing arm to the chassis and the wheel axle plane. The common center of gravity is included in a third vertical plane that is between 20% and 75%, for example between 30% and 60%, of the horizontal distance L measured from the pivot connection when the seat system is in the upright position.

[0018] One embodiment includes a pair of rear swing arms pivotally connected to the chassis. Each front swing arm is connected to a respective rear swing arm to enable the transmission of force between the front swing arm and the rear swing arm.

[0019] Each rear swing arm may be rigid. One embodiment includes link members. Each front swing arm and the connected rear swing arm are connected via respective link members.

[0020] According to one embodiment, each link member is rigid or substantially rigid. The link member may alternatively be provided with a certain degree of resilience, that is, have limited or slight flexibility, or be semi-rigid.

[0021] One embodiment includes a first resilient member connected to the chassis and each respective rear swing arm. The first elastic member may be a spring such as a coil spring, an air spring, a leaf spring, etc., or may be made of a material having elasticity such as rubber.

[0022] In one embodiment, the wheelchair includes a shock absorbing device (shock absorbing device) including a first elastic member and a damper unit. One embodiment includes a pair of suspension arms. Each suspension arm connects each front swing arm and rear swing arm. Each first elastic member is directly connected to each suspension arm and the chassis.

[0023] One embodiment includes a second elastic member. Each second elastic member is directly connected between each pair of rear swing arms and suspension arms. The second elastic member may be a spring such as a coil spring.

[0024] According to one embodiment, each second elastic member is configured to forcefully pull apart (force apart) the pair of rear swing arms and suspension arms to which it is directly connected.

[0025] As a result, when the chassis is tilted forward at the upright position of the seat system, the rear swing arm makes ground contact. This may not contribute to further stability, but can visually convey higher stability to the user.

[0026] According to one embodiment, each suspension arm and the connected rear swing arm share a pivot connection (connection) to the chassis.

[0027] One embodiment includes a seat support to which a seat system is attached (mounted). In a standing position, the seat support is at an angle α of at least 50°, for example at least 60°, or at least 70°, with respect to the horizontal plane when a powered mid-wheel drive (MWD) wheelchair is stationary (resting) on the horizontal plane, or brings the seat of the seat system to that angle α.

[0028] One embodiment includes a battery, and the chassis houses the battery. The chassis may be a chassis box. According to one embodiment, the front swing arm bottoms out in the first position.

[0029] According to one embodiment, in the standing position of the seat system, the front swing arm is pivoted to the first position, as a result of which the chassis tilts forward.

[0030] According to one embodiment, the pivoting of the front swing arm to the first position and the forward tilting of the chassis are achieved completely passively, i.e., without a motor or actuator.

[0031] In general, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. Also, references to "a / an / the, element, apparatus, component, means", etc. are all to be construed openly as referring to at least one instance of the element, apparatus, component, means, etc., unless explicitly stated otherwise.

[0032] Next, specific embodiments of the concepts of the present invention will be described by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0034] Hereinafter, the concept of the present invention will be described in more detail with reference to the accompanying drawings showing exemplary embodiments. However, the concept of the present invention can be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete and will fully convey the scope of the concept of the present invention to those skilled in the art. Like numbers refer to like elements throughout this specification.

[0035] FIG. 1 schematically shows an example of a mid-wheel drive MWD wheelchair 1. The mid-wheel drive MWD wheelchair 1 includes a chassis 3. The chassis 3 may be an openable and closable chassis box.

[0036] The mid-wheel drive MWD wheelchair 1 is configured to include a pair of front swing arms (front oscillating arms) 5. Only one of the front swing arms 5 is shown in the side view of FIG. 1.

[0037] The front swing arm 5 is pivotally (pivotally, pivot) connected to the chassis 3. The mid-wheel drive MWD wheelchair 1 includes front support wheels (front support wheels) 9. Each front support wheel 9 is connected to each front swing arm 5.

[0038] As shown in FIG. 1, the front support wheel 9 may be a caster wheel (caster wheel, caster). Alternatively, the front support wheel 9 may be, for example, a multi-directional wheel or an omni-wheel.

[0039] The mid-wheel drive MWD wheelchair 1 is configured to include a pair of rear (rear, rear) swing arms 7. Only one of the rear swing arms is shown in the side view of FIG. 1.

[0040] The mid-wheel drive MWD wheelchair 1 is configured to include rear support wheels (rear support wheels) 11. Each rear support wheel 11 is connected to each rear swing arm 7. As shown in FIG. 1, the rear support wheel 11 may be a caster wheel. Alternatively, the rear support wheel 11 may be, for example, a multi-directional wheel or an omni-wheel.

[0041] The mid-wheel drive MWD wheelchair 1 is configured to include a pair of drive wheels (drive wheels) 13. The drive wheels 13 are disposed between the front support wheels 9 and the rear support wheels 11.

[0042] The drive wheels 13 are pivotally connected to the chassis 3. The mid-wheel drive MWD wheelchair 1 is configured to include a battery (not shown) disposed inside the chassis 3.

[0043] The mid-wheel drive MWD wheelchair 1 is provided with a drive motor (not shown) configured to drive each one of the drive wheels 13. The drive motor is configured to be powered from a battery.

[0044] The mid-wheel drive MWD wheelchair 1 is configured with a seat system (seating device, seating system) 15. The seat system 15 is attached to the chassis 3. The seat system 15 is configured with a seat 15a and a backrest 15b.

[0045] The seat system 15 is configured to be maneuverable between the seated position (seated position) shown in FIG. 1 and the standing position (standing position). The mid-wheel drive MWD wheelchair 1 may include a maneuvering (maneuver, operation) system configured to vertically lift (lift) the seat 15a and / or tilt (tilt forward) the seat 15a forward. Examples of suitable maneuvering systems include the lift / tilt configuration (arrangement, arrangement) disclosed in Patent Document 4. Such a system is operable by a motor and, in certain embodiments, is capable of providing one of forward tilt (anteria tilt), rear tilt (posteria tilt), full standing tilt (full standing tilt), and lift (lift), or a combination of forward tilt / rear tilt, full standing tilt, and lift.

[0046] The maneuvering system is also capable of being configured to control the movement of the backrest 15b. By providing tilt (tilting) and lift (lifting), the maneuvering (maneuver) system is configured to maneuver the seat system 15 between the seated position (seated position) and the standing position (standing position).

[0047] The mid-wheel drive MWD wheelchair 1 is provided with a seating system support 17 to which a seating system 15 is attached. The seating system support 17 is configured to include a seat support 17a and a backrest support 17b rotatably connected to the seat support 17a. The seat support 17a may be a seat frame (seat frame, seat portion frame). The backrest support 17b may be a backrest frame. The seat 15a may be attached to the seat support 17a. The backrest 15b may be attached to the backrest support (backrest support, backrest support body) 17b.

[0048] The seat support 17a is configured to move together with the seat 15a when the seat 15a tilts or is lifted (tilt or lift). Each front swing arm 5 is configured to pivot between a first position and a second position with respect to the chassis 3. In the first position, the front support wheel 9 is at the uppermost position of the front support wheel 9 with respect to the chassis 3. In FIG. 1, this means that the front swing arm 5 pivots counterclockwise. The front swing arm 5 bottoms out in the first position. The first position is thus one of two extreme positions that the front swing arm 5 can reach with respect to the chassis 3. The pivot to the first position can occur, for example, when the front support wheel encounters a raised obstacle or when the seating system 15 is set to the upright position, as will be described in more detail.

[0049] In the second position, the front support wheel 9 is at its lowest position (the bottommost position) with respect to the chassis 3. In FIG. 1, this means that the front swing arm 5 is rotating clockwise (pivoting). The rotation to the second position can occur, for example, when crossing a curb or overcoming a pothole, when the ground level under the front support wheel 9 (ground level under the front support wheel 9) is lower than under the drive wheel 13 (under the drive wheel 13).

[0050] In the remaining figures, the front swing arm and the rear swing arm are each schematically illustrated to show the operative connection between the attachment point (attachment point) within the chassis and the front support wheel and the rear support wheel. Although the caster wheels are not drawn as such, the illustrated embodiments in FIGS. 2 - 9 each assume the use of caster wheels as the front support wheel and the rear support wheel.

[0051] FIG. 2 schematically shows one example of the realization of the mid - wheel drive MWD wheelchair 1 in FIG. 1. In the illustrated mid - wheel drive MWD wheelchair 1 - 1 in FIG. 2, the seat system 15 is in the seating position. In FIG. 2, the ground or floor surface 18 on which the mid - wheel drive MWD wheelchair 1 - 1 is placed is a flat and horizontal surface (flat horizontal plane). All the wheels, namely, the rear support wheel 11, the drive wheel 13, and the front support wheel (front wheel) 9, are in contact with the ground or floor surface 18.

[0052] According to the embodiment, the drive wheels 13 are each attached to each front swing arm 5. Each front swing arm 5 has a pivot connection portion 5a to the chassis 3 on each lateral side of the chassis 3.

[0053] Each rear swing arm 7 has a pivot connection portion 7a to the chassis 3 on each side of the chassis 3. The mid-wheel drive MWD wheelchair 1-1 is configured with two link members 19. Each link member 19 connects one of the plurality of front swing arms 5 to the corresponding rear swing arm 7. As a result, each front swing arm 5 is connected to each rear swing arm 7 and enables the transmission of force between the front swing arm 5 and the rear swing arm 7. Therefore, the pivotal movement of the front swing arm 5 may cause a pivotal movement response of the rear swing arm 7 to which the front swing arm 5 is connected.

[0054] According to the embodiment, the link member 19 is rigid. Specifically, each link member 19 is rigid along the longitudinal axis of the link member 19 between the connection points of the link member 19 to the front swing arm 5 and the rear swing arm 7.

[0055] The mid-wheel drive MWD wheelchair 1-1 includes a first elastic member (resilient member) 21 connected to the chassis 3 and the rear swing arm 7. The first elastic member 21 is enabled to form part of the shock absorption device of the mid-wheel drive MWD wheelchair 1-1.

[0056] FIG. 3 shows the mid-wheel drive MWD wheelchair 1-1 when the seat system 15 is in the upright position. The drive wheels 13 are in contact with the ground or floor surface 18 when the seat system 15 is in the upright position (standing position).

[0057] In the upright position of the seat system 15, the seat support portion 17a is at an angle α of at least 50°, for example at least 60°, or at least 70°, with respect to the horizontal ground or floor surface 18, or the seat 15a has the angle α.

[0058] In the standing position of the seat system (seating device) 15, the front swing arm 5 is rotated to the first position. As a result, the chassis 3 is tilted forward (tilt forward). For this reason, while the lower front edge 3a of the chassis 3 approaches the horizontal ground or floor surface 18, the lower rear edge 3b of the chassis 3 moves away from the horizontal ground or floor surface 18. It should be understood that the rotation of the front swing arm 5 to the first position (i.e., bottoming out) and the inclination of the chassis 3 are passive. Similarly, the forward inclination of the chassis 3 is also passive. This passive movement responds to the movement of the seat system 15 from the seating position (Figure 2) to the standing position (Figure 3).

[0059] The angle α = β + θ. β is the angle between the seat support portion 17a and the upper part (top) of the chassis 3. θ is the inclination angle of the chassis 3 with respect to the horizontal ground or floor surface 18. The inclination angle θ of the chassis 3 is typically at most 6°, for example, 2° - 4°.

[0060] The common center of gravity G of the mid-wheel drive MWD wheelchair 1-1 and its occupant is located between the first vertical plane P1 and the wheel axis plane P2. The first vertical plane P1 extends through the pivot connection portion 5a of the front swing arm 5. The wheel axis plane P2 is the second vertical plane that includes the wheel axis (wheel axle) of the front support wheel 9 when the mid-wheel drive MWD wheelchair 1-1 is stationary on the horizontal ground or floor surface 18.

[0061] Here, when the front support wheel 9 is a caster wheel, it should be noted that the wheel axis (wheel axle) moves between the forward driving direction and the rearward driving direction. Therefore, in the case of a caster wheel, the wheel axis plane P2 is defined when the caster wheel is in the most rearward position. This is the position that the caster wheel assumes when the mid-wheel drive MWD wheelchair 1-1 is driven in the straight-ahead direction.

[0062] For each front swing arm 5, there is a horizontal distance L between the pivot connection portion 5a of the front swing arm to the chassis 3 and the wheel axle plane P2. According to an example, the common center of gravity G is included in the third vertical plane P3. The third vertical plane P3 is located between 20% and 75%, for example, between 30% and 60%, of the horizontal distance L measured (major) from the pivot connection portion 5a when the seat system 15 is in the upright position and the mid-wheel drive MWD wheelchair 1-1 is placed on a horizontal ground or floor surface 18.

[0063] Figure 4 schematically shows another embodiment of the mid-wheel drive MWD wheelchair 1 of Figure 1. The illustrated mid-wheel drive MWD wheelchair 1-2 in Figure 4 has a seat system 15 in the seated position. The mid-wheel drive MWD wheelchair 1-2 is generally similar to the mid-wheel drive MWD wheelchair 1-1. The differences are explained below.

[0064] In relation to the mid-wheel drive MWD wheelchair 1-1, the mid-wheel drive MWD wheelchair 1-2 further includes a pair of suspension arms 23. The suspension arms 23 are pivotally connected to the chassis 3.

[0065] Each suspension arm 23 connects each front swing arm 5 and the rear swing arm 7-2. Each rear swing arm 7-2 shares the pivot connection portion to the chassis 3 with each suspension arm 23.

[0066] According to the embodiment, each link member 19 is directly connected between the front swing arm 5 and the suspension arm 23. Each first elastic member 21 is directly connected to each suspension arm 23 and the chassis 3.

[0067] The mid-wheel drive MWD wheelchair 1-2 is configured to include a second elastic member 25. Each second elastic member 25 is directly connected between each pair of rear swing arms 7 and the suspension arm 23.

[0068] Each second elastic member 25 is configured to forcibly separate a pair of rear swing arms 7-2 and a suspension arm 23 to which the second elastic member 25 is directly connected. The pair of rear swing arms 7-2 and the suspension arm 23 have the same pivot connection portion with respect to the chassis 3. Therefore, the second elastic member 25 attempts to separate the rear swing arm 7-2 and the suspension arm 23 from each other.

[0069] FIG. 5 shows the mid-wheel drive MWD wheelchair 1-2 when the seat system 15 is in the upright position. The front swing arm 5 is rotated to the first position. As a result, the chassis 3 tilts forward like the mid-wheel drive MWD wheelchair 1-1 shown in FIG. 3.

[0070] Due to the second elastic member 25, the rear swing arm 7 rotates toward the ground or the floor surface 18 so that the rear support wheel 11 contacts the ground or the floor surface 18. Therefore, when the seat system 15 is in the upright position, the rear support wheel 11 rests on the ground or the floor surface 18.

[0071] FIGS. 6 to 9 show various other embodiments of the mid-wheel drive MWD wheelchair 1. All of these show the chassis, the front swing arm, and the rear swing arm when the seat system is in the upright position and the chassis is tilted forward.

[0072] In the example of FIG. 6, the mid-wheel drive MWD wheelchair 1-3 has rear swing arms 7-3 that are not connected to each front swing arm 5 via a link member. Further, according to this embodiment, each first elastic member 21 is directly connected between the chassis 3 and each front swing arm 5. The same applies to the mid-wheel drive MWD wheelchair 1-4 in FIG. 7.

[0073] In the example of the mid-wheel drive MWD wheelchair 1-5 of FIG. 8, the first elastic member 21 is directly connected between the chassis 3 and the front swing arm 5. Further, there is an additional elastic member 21-5 that is already directly connected between each rear swing arm 7-5 and the chassis 3.

[0074] FIG. 9 shows an example of a mid-wheel drive MWD wheelchair 1-6 in which the front swing arm 5 is connected to the chassis but not to the drive wheels. The mid-wheel drive MWD wheelchair 1-6 is configured to include an additional front swing arm 5-6. The additional front swing arm 5-6 is rotatably connected to the chassis 3 at a connection point different from that of the front swing arm 5 and is parallel to each front swing arm 5. Each additional front swing arm 5-6 is rotatably connected to a mounting arrangement (mounting arrangement) within a housing to which the front support wheel 9 is connected. Further, an additional elastic member 21-6 is connected to each rear swing arm 7-6 and the chassis 3.

[0075] As described above, the concept of the present invention has been mainly described with reference to several embodiments. However, as will be immediately understood by those skilled in the art, other embodiments other than those disclosed above are equally possible within the scope of the concept of the present invention defined by the appended claims.

Claims

1. A powered mid-wheel drive (MWD) wheelchair (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6), and a powered mid-wheel drive MWD wheelchair (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6) is, Chassis (3) and A seating system (15) attached to the chassis (3), wherein the seating system (15) is configured to be operated between a seated position and a standing position, A pair of drive wheels (13) and A pair of front swing arms (5; 5-6) are rotatably connected to the chassis (3), and A front support wheel (9) is attached to one of each of the front swing arms (5; 5-6), It is equipped with, Each of the front swing arms (5; 5-6) is configured to rotate between a first position and a second position relative to the chassis (3), in the first position the front support wheel (9) is at its uppermost position relative to the chassis (3), and in the second position the front support wheel (9) is at its lowest position relative to the chassis (3). The front swing arms (5; 5-6) are configured such that when the seat system (15) is in the standing position, the front swing arms (5; 5-6) rotate to the first position, causing the chassis (3) to tilt forward with respect to the ground or floor surface (18). Powered mid-wheel drive MWD wheelchair (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

2. In the standing position of the seating system (15), the common center of gravity (G) of the powered mid-wheel drive MWD wheelchair (1;1-1;1-2;1-3;1-4;1-5;1-6) and its occupant is located between the first vertical plane (P1) and the wheel axle plane (P). The first vertical plane (P1) extends through the pivot connection portion (5a) of the front swing arm (5; 5-6) to the chassis (3), The wheel axle plane (P) is a second vertical plane that includes the wheel axle of the front support wheel (9) when the powered mid-wheel drive MWD wheelchair (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6) is stationary on a horizontal plane. A powered mid-wheel drive MWD wheelchair according to claim 1 (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

3. For each of the aforementioned front swing arms (5; 5-6), there exists a horizontal distance L between the pivot connection portion (5a) of each of the aforementioned front swing arms (5; 5-6) with respect to the chassis (3) and the wheel axle plane (P). The common center of gravity (G) is contained within the third vertical plane (P3), which is located between 20% and 75% of the horizontal distance L measured from the pivot connection (5) when the seat system (15) is in the upright position, for example between 30% and 60%. A powered mid-wheel drive MWD wheelchair according to claim 2 (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

4. The aforementioned powered mid-wheel drive MWD wheelchair (1;1-1;1-2) further comprises a pair of rear swing arms (7) rotatably connected to the chassis (3), Each of the front swing arms (5) is connected to each of the rear swing arms (7) in order to enable the transmission of force between the front swing arms (5) and the rear swing arms (7). A powered mid-wheel drive MWD wheelchair according to any one of claims 1 to 3 (1; 1-1; 1-2).

5. The aforementioned powered mid-wheel drive MWD wheelchair (1;1-1;1-2) is further equipped with a link member (19), and each of the front swing arms (5) and the connected rear swing arm (7) are connected via the respective link members (19). A powered mid-wheel drive MWD wheelchair according to claim 4 (1; 1-1; 1-2).

6. Each of the aforementioned link members (19) is rigid. A powered mid-wheel drive MWD wheelchair according to claim 5 (1; 1-1; 1-2).

7. The aforementioned powered mid-wheel drive MWD wheelchair (1; 1-1; 1-2) is further equipped with a first elastic member (21), The first elastic member (21) is connected to the chassis (3) and each of the rear swing arms (7). A powered mid-wheel drive MWD wheelchair according to claim 4 (1; 1-1; 1-2).

8. The aforementioned powered mid-wheel drive MWD wheelchair (1; 1-2) is further equipped with a pair of suspension arms (23), Each of the suspension arms (23) connects each of the front swing arms (5) and the rear swing arm (7). Each of the first elastic members (21) is directly connected to each of the suspension arms (23) and the chassis (3). A powered mid-wheel drive MWD wheelchair according to claim 7 (1; 1-2).

9. The aforementioned powered mid-wheel drive MWD wheelchair (1; 1-2) is further equipped with a second elastic member (25), Each of the second elastic members (25) is directly connected between each pair of the rear swing arms (7) and the suspension arms (23). A powered mid-wheel drive MWD wheelchair according to claim 8 (1; 1-2).

10. Each of the second elastic members (25) is configured to forcibly separate the pair of rear swing arms (7) and the suspension arm (23) to which the second elastic member (25) is directly connected. A powered mid-wheel drive MWD wheelchair according to claim 9 (1; 1-2).

11. Each of the aforementioned suspension arms (23) and the connected rear swing arm (7) share a pivot connection portion with respect to the chassis (3). A powered mid-wheel drive MWD wheelchair according to claim 10 (1; 1-2).

12. The aforementioned powered mid-wheel drive MWD wheelchairs (1-1; 1-2; 1-3; 1-4; 1-5; 1-6) are equipped with a seat support section (17a) to which the seat system (15) is attached. In the standing position, the seat support portion (17a) makes an angle α of at least 50°, for example, at least 60°, or at least 70° with respect to the horizontal plane when the powered mid-wheel drive MWD wheelchair is stationary on the horizontal plane, or In the standing position, the seat support (17a) positions the seat (15a) of the seat system (15) at an angle α of at least 50°, for example, at least 60°, or at least 70° with respect to the horizontal plane when the powered mid-wheel drive MWD wheelchair is stationary on the horizontal plane. A powered mid-wheel drive MWD wheelchair according to any one of claims 1 to 3 (1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

13. The aforementioned powered mid-wheel drive MWD wheelchairs (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6) are further equipped with a battery, The chassis (3) houses the battery. A powered mid-wheel drive MWD wheelchair according to any one of claims 1 to 3 (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

14. The front swing arm (5) is bottomed out in the first position. A powered mid-wheel drive MWD wheelchair according to any one of claims 1 to 3 (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

15. In the upright position of the seat system (15), the front swing arm (5) is rotated to the first position, and as a result, the chassis (3) tilts forward. A powered mid-wheel drive MWD wheelchair according to any one of claims 1 to 3 (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

16. The rotation of the front swing arm (5) to the first position and the tilting of the chassis (3) forward are achieved passively. A powered mid-wheel drive MWD wheelchair according to any one of claims 1 to 3 (1; 1-1; 1-2; 1-3; 1-4; 1-5; 1-6).

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