Patent Publication Number: US-11382808-B2

Title: Wheelchair

Description:
TECHNICAL FIELD 
     The invention relates to a wheelchair having a chassis on which there are arranged opposite each other at least one drive unit which has a drive wheel and an electric drive, a front wheel which is arranged on a front pivot arm and a rear wheel and the drive unit and the front pivot arm are pivotably arranged in a vertical plane relative to the chassis and are connected to each other by a first coupling means. 
     BACKGROUND 
     Such a six-wheel wheelchair is, for example, known from U.S. Pat. No. 9,308,143 B2. The coupling of the drive unit and front pivot arm can be carried out by means of a spring/damper unit. This unit is supported in an articulated manner at both of the ends thereof, wherein the bearing locations are arranged with respect to each other in such a manner that, when the wheelchair travels on a straight horizontal plane, the main portion of the force applied by the spring/damper unit acts on the drive wheel in order obtain good traction. 
     A wheelchair having a central wheel drive is distinguished by a very small turning circle. As a result of the fact that the center of gravity, that is to say, the body rotation point, of the user is located above the drive axis, this wheelchair can also be driven in the tightest of spaces. Furthermore, such a wheelchair also provides optimum traction as a result of the weight distribution. As a result of the coupling of the front pivot arm to the drive, when travelling over obstacles, such as, for example, pavement edges, only small movements are introduced into the seat and consequently into the driver. 
     SUMMARY 
     An object of the invention is to improve the known wheelchair in terms of its travel properties and in terms of its ability to mount curbs. 
     The object is achieved in that the drive unit and the front pivot arm are additionally connected to each other by a second coupling means. 
     As a result of the second coupling means, it is possible to decouple the front wheel and drive unit at two locations so that, as a result of the additional possibility of decoupling, fewer hard impacts when driving over an uneven substrate (paving stone) reach the drive carrier and consequently the seat of the wheelchair. The driving behavior consequently becomes substantially more pleasant for the user, which in particular for the most severely disabled users is a significant gain in terms of comfort. 
     The front and/or the rear wheel may be a steering wheel. 
     DE 20 2010 005 233 U1 discloses a generic electric wheelchair which has a drive frame which receives the drive unit, a front wheel frame and a chassis. Between the front wheel frame and the drive frame a front bumper is provided as a single coupling means. An auxiliary bumper is arranged between the drive frame and the chassis. When travelling over an obstacle, the front wheel pivots upward, wherein the front bumper is pressed together and forces the drive frame onto the substrate, whereby the tension spring in the auxiliary bumper is tensioned. 
     US 2005/0127631 A1 and US 2008/0264702 A1 disclosed electric wheelchairs in which the front pivot arm with the drive unit are connected to each other by means of a bumper as a coupling means. 
     The first and/or second coupling means may be a spring and/or damper unit. When the second coupling means is a spring and/or damper unit, it may be completely sufficient for the first coupling means to be formed by a rigid connection rod or the like. 
     Preferably, the second coupling means is a swing arm which is secured to the chassis so as to be able to be pivoted about a first pivot axis A and a second pivot axis B and in which the front pivot arm is pivotably supported about a third pivot axis C and the drive unit is pivotably supported about a fourth pivot axis D. 
     When the first pivot axis A and the second pivot axis B are located on a notional line which extends with respect to the vertical at an angle α of from 0° to 45°, there is produced a parallelogram of the pivot locations which leads to the pivot locations of the pivot arm and the drive unit being variable both in their horizontal position and in their vertical position, therefore the position thereof changing during a movement. 
     The swing arm is preferably formed by two opposing yokes which are connected to each other by means of at least one upper plate which receives the first pivot axis A and at least one lower plate which receives the second pivot axis B. 
     Each yoke can be formed by two plates which are arranged in a parallel manner and which can be constructed in a substantially triangular manner and which are connected to each other by means of a bolt. 
     In this instance, it is advantageous for each plate which forms the yoke to be connected to an upper plate and a lower plate and for the upper plates to be connected by means of a first bolt and the lower plates to be connected by means of a second bolt. The first and the second bolts may be constructed identically. 
     The upper plate and lower plate may be resiliently supported in a housing which is secured to the chassis. The upper plate and the lower plate may also be resiliently connected to each other. Such a connection can be produced, for example, by means of at least one resilient element, which in particular may be a torsion spring. 
     The connection of the upper plate to the lower plate may, however, also be carried out by means of at least one element which comprises an elastomer material (for example, a rubber buffer). 
     Preferably, the rear wheel is also arranged on a rear pivot arm which is pivotably connected to the chassis. If a third spring/damper unit is arranged between the rear pivot arm and the chassis, excessive oscillations when travelling over uneven ground are effectively prevented from being introduced into the chassis. 
     The rear pivot arm and the drive unit are preferably not coupled to each other in terms of their movements. 
     Preferably, the third pivot axis is arranged at one side of the notional line and the fourth pivot axis is arranged at the opposite side of the notional line. 
     If the third pivot axis is arranged lower with respect to a substrate on which the wheels are standing, that is to say, the carriageway, than the fourth pivot axis, the introduction of the movement into the front pivot arm or the drive unit is carried out gently. 
     Preferably, the resilient means are provided in the swing arm at the articulation location of the front pivot arm. The resilient means may also be arranged in the swing arm at the articulation location of the drive unit, wherein the resilient means may be arranged both at the articulation location of the pivot arm and at the articulation location of the drive unit. 
     In a preferred embodiment, the resilient means surround the first and the second pivot axes. 
     If the first and second bolts have at least two diametrically arranged projections and the resilient means surround the first and second pivot axes, the upper and lower plates which connect the two yokes can pivot. 
     Preferably, the projections are embedded in the element which comprises an elastomer material. 
     The upper plate may be connected to the lower plate in a preferred embodiment by means of two resilient elements. The first resilient element can then be arranged in the region of the third pivot axis and the second resilient element can then be arranged in the region of the fourth pivot axis. 
     The wheelchair preferably has a seat and in a preferred embodiment a pivot arm may be formed on the drive unit. Preferably, the seat is arranged on the chassis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are intended to be described in greater detail below with reference to a wheelchair and drawings. In the drawings: 
         FIG. 1  is a simplified side view of a wheelchair; 
         FIG. 2  is a cut-out of  FIG. 1 ; 
         FIG. 3  shows the illustration according to  FIG. 2  with a lowered steering wheel; 
         FIG. 4  shows the illustration according to  FIG. 2  with a raised steering wheel; 
         FIG. 5  is an enlarged illustration from  FIG. 4  without a drive wheel; 
         FIG. 6  is a first perspective part-illustration of the wheelchair; 
         FIG. 7  is a second perspective part-illustration of a wheelchair; 
         FIG. 8  is a partial illustration of the wheelchair; 
         FIG. 9  is an enlarged illustration from  FIG. 8 ; 
         FIG. 10  is an enlarged part-illustration from  FIG. 9 ; 
         FIG. 11  shows the illustration according to  FIG. 10  with explanations; 
         FIG. 11 a    is an enlarged illustration of the spring and/or damper unit; 
         FIG. 11 b    is an enlarged cut-out of  FIG. 11   a;    
         FIG. 12  shows the illustration according to  FIG. 10  in a partially cut-away state; 
         FIG. 13  is a schematic drawing; 
         FIG. 14  is another schematic drawing; 
         FIG. 15  is a perspective illustration of the swing arm in a first embodiment; 
         FIG. 16  is a perspective illustration of the swing arm in a second embodiment; 
         FIG. 17  is the perspective illustration of the swing arm in a third embodiment; 
         FIG. 18  is the illustration of the swing arm according to  FIG. 13  with additional schematic depictions; 
         FIG. 19  is a perspective, partial illustration of the third embodiment of a swing arm; 
         FIG. 20  is an illustration which corresponds to  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
     The wheelchair  100  substantially comprises the seat  50  which is arranged on the chassis  1 , the drive wheels  21  which are arranged at both sides on the chassis  1 , the front steering wheels  3  and the rear support wheels  7 . Since the arrangement and suspension of the wheels  3 ,  21 ,  7  is symmetrical to the left and right of the chassis  1 , the subsequent description is carried out only with reference to a single-sided construction. For the opposing portion, this then applies accordingly. The front steering wheel  3  is rotatably supported in a fork  30  about a horizontal axis. The fork  30  is rotatably arranged about a vertical axis in the front pivot arm  4 . The support wheel  7  is arranged on a rear pivot arm  6 , which is pivotably fitted to the chassis  1  and which is supported via a spring/damper unit  9  on the chassis  1 . The drive unit  20  which drives the drive wheel  21  is connected via a spring/damper unit  8  to the front pivot arm  4 . Another connection between the drive unit  20  and front pivot arm  4  is carried out via a second spring/damper unit  10  which is pivotably secured to the chassis  1  about a first pivot axis A and a second pivot axis B. The front pivot arm  4  is pivotably supported about a third pivot axis C in the spring/damper unit  10  and the drive unit  20  is pivotably supported about a fourth pivot axis D in the spring/damper unit  10 . 
     The steering wheel  3  can, when driving over uneven surfaces, as formed, for example, by a pavement edge, be raised or lowered with respect to the carriageway F so that the drive wheel can then be raised from the wheel contact surface F (carriageway) (cf.  FIGS. 2 and 4 ). In this instance, the swing arm  10  which is secured to the chassis  1  is rotated. 
     If the swing arm  10  is rotated about the pivot axes A and B, there is formed a parallelogram by means of which the pivot axis C of the front pivot arm  4  and the pivot axis D of the drive unit  20  change their vertical and horizontal position relative to the chassis. 
     The swing arm  10  is, as illustrated in  FIGS. 6 to 9 , securely screwed by means of two bolts  16 ′,  17 ′ to the chassis  1 , wherein a first pivot axis A is formed by the first bolt  16 ′ and a second pivot axis B is formed by the second bolt  17 ′. By means of a front bolt  18 ′ which is arranged on the swing arm  10 , the front pivot arm  4  is pivotably arranged about a third pivot axis C and, by means of a bolt  19 ′ on the rear end of the swing arm  10 , the drive unit  20  on which a pivot arm  23  is formed is pivotably supported about the pivot axis B. 
       FIG. 11  shows the movements of the pivot axes A, B, C, D which are connected to each other by means of the parallelogram depicted. As a result of the construction, the pivot axes C and D move on a circular path. The radius of the circular path is approximately 26 mm. The movements are indicated by the arrows P 1 , P 2 , P 3 , P 4 . The fixed bearings  1 ′ indicated illustrate the fixed connection of the swing arm  10  to the chassis  1 . 
       FIG. 11 a    shows the situation of the swing arm  10  in different pivot positions. A central position  25  is illustrated by means of the central linear construct, by means of which the pivot axes A, B, C and D are connected to each other. The connection lines  26  and  27  connect the different axes when the swing arm  10  is pivoted through ±10°. This leads to a displacement of the pivot axes C and D which are not indicated separately. 
       FIG. 11 b    illustrates an enlarged cut-out from which it can be seen that the pivot axis C when pivoted through ±10° is pivoted to the positions C′ and C″. This takes place along a circular path with a radius R which is identical for all pivot axes. 
       FIGS. 15 and 16  show a first embodiment of the swing arm  10 . This swing arm  10  comprises the two yokes  18  and  19  which are arranged opposite each other and which each comprise two substantially triangular plates which are each connected to each other by means of a bolt  18 ′,  19 ′. The pivot axes C and D are formed in the bolts  18 ′,  19 ′. The triangular plates  18 ,  19  which are located opposite each other in a parallel manner are each screwed to an upper plate  16  and a lower plate  17 . The two upper plates  16  are screwed to each other by means of a bolt  16 ′ and the two lower plates  17  are screwed to each other by means of a bolt  17 ′. The bolts  16 ′,  17 ′ are securely arranged on the chassis  1  and form the pivot axes A and B. The upper plate  16  and the lower plate  17  are connected by means of two springs  12  which comprise an elastomer material and which are formed on a base member  12 ′. These springs  12  act in the manner of a torsion spring when pivot movements are introduced via the front steering wheel  3  into the front pivot arm  4  or via the drive wheel  21  into the drive unit  20 . 
     The system operates with a redirection/rotation of the upper and lower plates  16 ,  17  from +10° to −10°. 
     An alternative embodiment of an element  13  which comprises an elastomer material is shown in  FIGS. 17 and 18 . In order to produce the torsion spring, the block-like base member is provided with slots  13 ′ or with recesses  13 ″. The cross-sectional shape of the recesses  13 ″,  13 ′″ is possible in different variations. As a result of an appropriate selection of the slots  13 ′ and/or recesses  13 ″,  13 ′″ and the cross-sectional shape thereof, the spring rate of the elastomer element  13  can be adjusted. 
     A third alternative for the construction of a torsion spring is shown in  FIGS. 19 and 20 . In this instance, the upper plate  16  and the lower plate  17  are pivotably supported in an elastomer element  11  which is surrounded by a housing  40 . The upper plates  16  and lower plates  17  can rotate about the pivot axes A, B through a predetermined angle. In order to prevent over-rotation, the bolts  16 ′,  17 ′ are provided with projections  16 ″,  17 ″ which are arranged diametrically relative to each other on the bolts  16 ′,  17 ′ and whose outer spacing with respect to each other is greater than the width of the housing  40  so that, when excessively high forces are introduced, they strike the inner wall of the housing  40  and are blocked in terms of a further pivot movement.