Abstract:
An apparatus for climbing and descending stairs or other obstacles has three flexibly connected sections and a pair of crawler belt systems on opposite sides of the unit. Each of the crawler belt systems comprised of three crawler belts are driven by one of a pair of motors that directly drives a pinion that engages two of the crawler belts, one of which then drives the last crawler belt through another pinion. The stair-climbing apparatus also includes a mounting platform for coupling a carrier device such as a wheelchair or a box. In order to provide cushioning and stability for movements from a horizontal surface to an inclined surface and vice versa, shock absorbers are provided between the three sections. A linear actuator is also provided to provide stabilization as well as the ability to raise and lower both the stair-climbing crawler unit as well as the wheelchair, providing three modes of operation including manually wheel driven mode, motor wheel driven mode, and motor crawler driven mode.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates generally to a stair-climbing apparatus to be attached to a conventional load carrier vehicle or wheelchair to enable movement ascending and descending stairs and other obstacles such as curbs without assistance from another individual.  
         [0003]     2. Description of the Prior Art  
         [0004]     Stair-climbing apparatuses mounted on wheelchairs or load carrier vehicles are known.  
         [0005]     Representative examples of stair-climbing apparatuses disclosed in reference patent documents are discussed below.  
         [0006]     For the most part, these apparatuses are battery powered, motor driven, with a chair or platform permanently connected. These vehicles, and particularly wheelchairs, are heavy, bulky, and equipped with complicated shock absorber systems.  
         [0007]     U.S. Pat. No. 6,619,414 discloses a personal mobility vehicle comprising a frame with a pair of parallel tracks for moving the vehicle, a lifter arm to assist the vehicle in traversing the upper end of a flight of stairs in either the ascending or descending directions, and a retractable rod with freewheeling roller to prevent the vehicle from tipping rearward as the vehicle ascends a slope.  
         [0008]     U.S. Pat. No. 4,564,080 and U.S. Pat. No. 4,671,369 describe wheelchairs wherein a pair of cushioning arms and fluid piston and cylinder assemblies operate to avoid rapid downward movements of the front and the rear of the wheelchair as the wheelchair moves from a horizontal surface to an inclined surface or from an inclined surface to a horizontal surface. This system performs latching and unlatching the cushioning arms, respectively, when the wheelchair moves over a horizontal surface or senses proximity to an inclined surface.  
         [0009]     The complicated systems disclosed in the above references require a suitable sensing and control mechanism.  
         [0010]     The retractable rod (of U.S. Pat. No. 6,619,414) and cushioning arms (of U.S. Pat. No. 4,671,369) have a roller (or wheel) at the end of an arm, which engages a horizontal surface, such as a landing surface when moving down a step or curb, or rolls over a step or curb when climbing up a step or curb. The location of these cushioning arms in the interior of the wheelchair between two driving crawlers can cause accidents when the roller engages a horizontal surface and suddenly meets with a resistive element (such as a lug or a hollow) that it cannot override. In this case, since the wheelchair is being driven with tracks that continue moving ahead, the wheelchair will turn over. To prevent such a dangerous accident, a complicated sensing and control mechanism was desired.  
         [0011]     The systems described in U.S. Pat. No. 4,564,080 and U.S. Pat. No. 4,671,369 comprise ground-engaging wheels and a pair of endless flexible tracks. Since each wheel and track is driven by individual motor, four individual motors and a suitable control is provided to allow for forward, reverse, and turning movements of the wheelchair. This system is only power-driven and is not suitable to be operated manually as a conventional wheelchair.  
         [0012]     In the above mentioned patents, the user&#39;s chair is able to be switched between two fixed positions: 1) horizontal when the wheelchair moves on its wheels on a horizontal surface or 2) tilted backward at a fixed angle related to the frame when the wheelchair moves on the tracks up or down an inclined surface. In the latter case, the orientation of the chair relative to the horizontal surface depends on the slope of the inclined surface. So, at a certain slope, a wheelchair user may experience discomfort.  
         [0013]     U.S. Pat. No. 4,898,256 describes a crawler unit for coupling to a wheelchair. The unit is designed to climb stairs and travel up access ramps. The crawler unit comprises power-driven tracks, fits between the main wheels of the wheelchair, and includes an adapter for securing the wheelchair in a rearward tilted traveling position in which the wheels of the wheelchair are lifted off the ground.  
         [0014]     Due to the structure, the wheelchair user is enabled selectively to lift the crawler unit and control and manipulate the wheelchair as usual while the elevated crawler unit remains on the wheelchair.  
         [0015]     The crawler unit comprises a shock absorber system similar to that described above. In this structure, supporting rails curved upwards like the blade tip of a cross-country or running ski are used instead of cushioning arms with a roller. This construction increases the danger of an accident if the supporting rail suddenly meets with an obstacle while landing on a horizontal surface.  
         [0016]     In U.S. Pat. No. 4,564,080, the wheelchair is tilted backward at a fixed angle relative to the frame of the crawler unit and can cause discomfort to a wheelchair user at a certain rate of inclined slope as described above.  
         [0017]     U.S. Pat. No. 5,158,309 describes an apparatus attached to a conventional, collapsible wheelchair so as to enable a wheelchair user to independently ascend and descend stairs and other obstacles without assistance from another individual. The stair-climbing apparatus comprises a pair of laterally spaced and aligned tread units. The tread units are split into two sections: forward and rear. Treads when lifted allow the wheelchair to be propelled on its wheels. Treads in position to engage the surface are manually driven by main wheels, which are disengaged from the ground and stairs. This structure of the apparatus does not prevent the rapid downward movement of the front and the rear of the wheelchair as the wheelchair moves from a horizontal surface to an inclined surface or from an inclined surface to a horizontal surface that can cause discomfort to a wheelchair user.  
         [0018]     In summary, it should be emphasized that the above-mentioned power driven, stair-climbing vehicles comprise complicated mechanical and kinematic structures and also incorporate a suitable servo control system that influence a system cost, reliability, and safety.  
         [0019]     Only some of the apparatuses described above provide manual driving and maneuvering on the wheels as a conventional wheelchair that is very important for indoor usage.  
       SUMMARY OF THE INVENTION  
       [0020]     A general object of the present invention is to provide a stair-climbing crawler unit which can be coupled with a load carrier vehicle or particularly a conventional wheelchair, to provide a structure which has substantially improved maneuverability as compared with known structures.  
         [0021]     Due to the structure of the invention, when the stair climbing unit is coupled with a wheelchair, a user can selectively switch the operation to one of three modes: manually driven wheels, motor driven wheels, or motor driven crawlers.  
         [0022]     Another object of the present invention is to provide flexibility to the crawlers by splitting the crawlers into three sections resulting in tread guides of the separate sections that are flexibly joined by pivots while each section guide bears its own tread.  
         [0023]     The next object of the invention is to provide a structurally simple, effective, and safe cushioning mechanism based on the flexibility of the crawlers.  
         [0024]     One more object of the present invention is to provide vertical axis stabilization of the wheelchair or load carrier vehicle in every possible position of the vehicle related to the horizontal surface as the vehicle moves up or down a slope.  
         [0025]     Other objects of this invention will become apparent as the following specification progresses, reference being had to the accompanying drawings for an illustration of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  presents a perspective view of an assembly of a stair-climbing crawler unit coupled to a wheelchair.  
         [0027]      FIGS. 2 and 2 A present right and left perspective views, respectively, of the stair-climbing crawler unit.  
         [0028]      FIG. 3  presents the assembly in manually wheel driven mode of operation.  
         [0029]      FIG. 4  presents the assembly in motor wheel driven mode of operation.  
         [0030]      FIG. 5  presents the assembly in motor crawler driven mode of operation.  
         [0031]      FIG. 6  presents the assembly beginning the process of climbing stairs.  
         [0032]      FIG. 7  presents the assembly climbing stairs.  
         [0033]      FIG. 8  presents the assembly climbing stairs and beginning the transition from an inclined surface to a horizontal surface.  
         [0034]      FIG. 9  presents the assembly climbing stairs at a point where the center of gravity of the assembly has not yet passed the critical point.  
         [0035]      FIG. 10  presents the assembly climbing stairs at a point where the center of gravity of the assembly has already passed the critical point.  
         [0036]      FIG. 11  presents the assembly climbing stairs (or descending stairs) at the point where the center of gravity of the assembly is crossing the critical point. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]     In the illustrative embodiment shown in  FIG. 1 , the assembly  100  is composed of a stair-climbing crawler unit  1  and a conventional wheelchair  2 .  
         [0038]     The wheelchair  2  includes a seat portion  10  with a back rest  13 , a foot rest  12 , main wheels  11 , and a supporting wheel  14 .  
         [0039]     Referring to  FIG. 2  and  FIG. 2A  the stair-climbing crawler unit  1  comprises a main section  40 , a front section  50 , and a rear section  60 . The main section  40  includes a guide frame  8  with two supports  17  which support an axle  18  ( FIG. 2A ). A platform  43  pivotally rests on the axle  18 . Four holes  21  of the platform  43  are used to fasten the wheelchair  2  as it appears in the preferred embodiment ( FIG. 1 ). The body  9   a  of a linear actuator  9  is flexibly connected with the shaft  25  at the front of the platform  43 . The ram  26  of the linear actuator  9  is connected by a pivot  28  to the cross bar  41  of the guide frame  8 . So, linear movement of the ram  26  rotates the platform  43  on the axle  18 . A left motor  7   a  and right motor  7   b  are mounted on side support plates  42  at front of the guide frame  8 . Two double drive pinions are located at the left side of the guide frame  8  at the front  5   a  and rear  5   c . Two double drive pinions are located at right side of the guide frame  8  at the front  5   b  and rear  5   d . At the front of guide frame  8 , left double drive pinion  5   a  is keyed with the stub drive shaft of left motor  7   a . Similarly, right double drive pinion  5   b  is keyed with the stub drive shaft of right motor  7   b . At the rear of guide frame  8 , the left and right double drive pinions  5   c  and  5   d  are free rotating on their axles (not shown). Motor  7   a , by front left double drive pinion  5   a , drives left flexible crawler belt  46   a  of the front section and left main flexible crawler belt  44   a . The left main flexible crawler belt  44   a , through rear left double drive pinion  5   a , drives the left flexible crawler belt  46   c  of the rear section. Similarly, motor  7   b , by front right double drive pinion  5   b , drives right flexible crawler belt  46   b  of the front section and right main flexible crawler belt  44   b . The right main flexible crawler belt  44   b , through rear right double drive pinion  5   d , drives the right flexible crawler belt  46   d  of the rear section. The flexible crawler belts have internal gear teeth and external tread cleats. The main flexible crawler belts  44   a  and  44   b  are supported by a set of conventional idler pulleys  6  that are free rotating on their axles mounted on the side plates of the guide frame  8 .  
         [0040]     The axles (not shown) of the double drive pinions  5   a  and  5   b  at the front bear the frame  32  of the front crawler section  50 . The axles (not shown) of the double drive pinions  5   c  and  5   d  at the rear bear the frame  33  ( FIG. 2A ) of the rear section  60 .  
         [0041]     So, the front section  50  with flexible crawler belts  46   a  and  46   b  and the rear section  60  with flexible crawler belts  46   c  and  46   d  are able to swing on the support bearings.  
         [0042]     The front crawler section  50  is equipped with special pulleys of enlarged diameter on the left  4   a  and right  4   b  sides of the frame  32  in order to form an upwardly-sloping flight of crawler shape. The rear crawler section  60  is also equipped with enlarged diameter pulleys on the left  4   c  and right  4   d  sides of the frame  33 .  
         [0043]     The motors  7   a  and  7   b  are powered by a battery carried on the wheelchair. Conventional controls (not shown) are provided so that the motors may be operated together in forward or reverse, individually, and/or oppositely for steering purposes.  
         [0044]     The angle of displacement of the front section  50  is limited by stopper  23  on the guide frame  8  and a lug  24  on the frame  32  of the front section  50 . The angle of displacement of the rear section  60  is limited by support  17  on the guide frame  8  and lug  36  on the frame  33  ( FIG. 2A ) of the rear section  60 . The lock  13  and pin  30   a  placed on the lug  24  are used for latching the front section  50 . The lock  20  and pin  30   b  placed on the lug  36  are used for latching the rear section  60 . The lock  20  has two grooves to enable latching the rear section  60  in one of two possible positions. The front section  50  and rear section  60  can be released by opening locks  13  and  20 .  
         [0045]     A front shock absorber  15   a  is connected between the guide frame  8  and the front section frame  32 , which is pivotally connected with the piston rod  16   a  of the front shock absorber  15   a , which comprises a one way dampening system and a spring return mechanism to the unengaged position. Similarly, a rear shock absorber  15   b  is connected between the guide frame  8  and the rear section frame  33 , which is pivotally connected with the piston rod  16   b  of the rear shock absorber  15   b.    
         [0046]     Referring to  FIG. 3 , the assembly  100  of the preferred embodiment is presented in the manually wheel driven mode of operation as a conventional wheelchair  2 . The assembly  100  is rested on the horizontal surface (floor or ground) on its wheels  11  and  14 . The stair-climbing crawler unit  1  are lifted above the surface. The front section  50  and the rear section  60  are latched. The rear section  60  is latched in the first position, so that the main wheels  11  and rear flexible crawler belts  46   c  and  46   d  (not shown) do not touch each other. Accordingly, a user of the wheelchair is able to control it manually.  
         [0047]     Referring to  FIG. 4 , the assembly  100  of the preferred embodiment is presented in the motor wheel driven mode of operation as a wheelchair  2  with motor driven wheels. This mode of operation is similar to the previous mode shown in  FIG. 3  but the rear section  60  is latched in a second position wherein the rear flexible crawler belts  46   c  and  46   d  (not shown) contact the main wheel  11  and form a friction gear.  
         [0048]     Switching the rear section  60  between the first and second positions can be performed ether by a manual arm or by an electronic controller like a joystick or touch button keyboard with a display (not shown) placed on the armrest of the chair. The mode of motor wheel driven operation is useful, for example, in assisting the user to travel a long distance on a flat or sloped surface.  
         [0049]     Referring to  FIG. 5 , the assembly  100  of the preferred embodiment is presented in the motor crawler driven operation mode in which the crawlers engage the surface (floor or ground). The crawlers are shifted to this position by activating the linear actuator  9 . The ram  26  of the actuator  9  lowers the crawlers down until they engage the surface after which the ram  26  of the actuator  9  lifts the wheelchair  2  with the platform  43 . The lock  13  ( FIG. 2 ) of the front section  50  is opened and the front crawler section  50  is released. The rear section  60  is latched by lock  20  ( FIG. 2A ) in the first position. The assembly  100  is ready to climb stairs.  
         [0050]     Referring to  FIG. 6 , the assembly  100  is presented at the beginning of its ascent up stairs.  
         [0051]     When the assembly  100  moving backwards meets the first stair, the rear section  60 , which has been released at this stage, turns counterclockwise until the lug  36  ( FIG. 2A ) meets the supports  17 . At this point, the flexible crawlers  46   c  and  46   d  (not shown) begin ascending the stairs.  
         [0052]     Referring to  FIG. 7 , the assembly  100  is presented climbing stairs. The wheelchair  2 , while moving along an inclined surface, is stabilized in a horizontal position by actuator  9 , which is activated by an automatic follow up control system equipped with an appropriate sensor and servo motor.  
         [0053]     Referring to  FIG. 8  the assembly  100  is presented at a point where the rear crawler section  60  has reached the horizontal surface. The spring mechanism of shock absorber  15   b  ( FIG. 2 ) turns the rear section  60  clockwise so the flexible crawlers  46   c  and  46   d  (not shown) of the rear section  60  engage the horizontal surface.  
         [0054]     Referring to  FIG. 9 , the assembly  100  is presented climbing stairs at a point where the center of gravity of the assembly  100  has not yet passed the critical break point (CBP). In this position, the rear section  60  is turned clockwise by the spring mechanism of the shock absorber  15   b  ( FIG. 2 ). The point where the stair-climbing crawler unit  1  touches the horizontal surface supports the main section  40 .  
         [0055]     Referring to  FIG. 11 , the assembly  100  is presented climbing stairs at the point where the center of gravity of the assembly  100  is crossing the critical break point (CBP). The rear section  60  under the weight of the user and the wheelchair  2  will turn counterclockwise against the shock absorber  15   b  ( FIG. 2 ) and continue supporting the main section  40  and providing a gentle landing on the horizontal surface. The shock absorber  15   a  ( FIG. 2 ) of the front section  50  performs the same cushioning function and supports the main section  40  at the front.  
         [0056]     Referring to  FIG. 10 , the assembly  100  is presented at the point where it begins descending stairs. At this point, the front section  50  has not yet passed the critical break point (CBP). The spring of shock absorber  15   a  ( FIG. 2 ) turns the front section  50  counterclockwise so that the flexible crawlers  46   a  and  46   b  (not shown) are moving along the stairs supporting the front of the main section  40 . When the center of gravity of the assembly  100  passes the critical break point (CBP), the front section  50 , under the weight of the wheelchair turns clockwise against the shock absorber  15   a  ( FIG. 2 ). The main crawler section  40  will gently land on the descending surface. This situation is similar to the situation presented by  FIG. 9  and described above. When the assembly  100  has landed on the horizontal surface, the rear section  60  begins turning counterclockwise against shock absorber  15   b  ( FIG. 2 ), which performs its cushioning function. This process is similar to that presented by  FIG. 6  and described above.  
         [0057]     In comparison to the prior art, where a cushioning arm with a passive roller is used, the flexibility of the crawlers, which are driven by motors, improve safety and reliability of the assembly  100  while moving either on the stairs or on the ground even if it suddenly meets with a resistive element (such as a lug or a hollow).  
         [0058]     Referring to above description, the assembly  100  is described as being directed rearward to go up stairs. In this case, a user&#39;s back faces the stairs. But the structure of the preferred embodiment provides climbing stairs face forward as well because the crawler unit structure comprises similar front  50  and rear  60  sections ( FIGS. 2 and 2 A).  
         [0059]     The stair-climbing crawler unit disclosed in the present invention can be coupled with any other conventional vehicle, or some case or basket that can be mounted on its platform  43  ( FIGS. 2 and 2 A), to create the assembly  100  for lifting and lowering a heavy load along a stair well.  
         [0060]     While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.