Abstract:
A traction system for a vehicle has a support frame that defines a circular track belt support that is revolvable about an axis at its center, a flexible track belt; and a track belt stretching assembly comprising one or more track belt stretching rollers. The system has one traction configuration in which the flexible traction belt is held on said support track forming a substantially circular, wheel-like traction surface, and can change to a stretching state in which said rollers engage said belt and stretch it from its state in said one traction configuration to a stretched state to define one or more other traction configurations of the system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation application of U.S. patent application Ser. No. 10/498,235, filed Jun. 10, 2004, which is a national stage entry of PCT/IL02/00807, filed Oct. 3, 2002, which claims the benefit of U.S. Provisional Patent Application No. 60/326,430 filed Oct. 3, 2001. These three applications are incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to traction systems. More specifically the invention is in the field of personal carriage of disabled persons. 
       BACKGROUND OF THE INVENTION 
       [0003]    Versatile traction systems that permit movement on various different terrains are required for a number of different purposes. A particular example is a wheelchair. In most wheelchairs the traction system consists of wheels (typically one main, large wheel and one auxiliary, small wheel on each side) and it permits to move the wheelchair over smooth horizontal surfaces of such floors or pavements. These traction systems are not suitable for passing obstacles such as steps and others, moving through staircases or moving over rough terrains. A versatile traction system has been described in PCT Publication WO 99/21740. In the system described in this publication, means are provided that can change at will the traction configuration for the purpose of increasing the trafficability and safety. A preferred use of the system described in this PCT publication is wheelchairs. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with the invention a new traction system for a vehicle is provided. The term “vehicle” usually refers to a platform that moves over a terrain through wheels or track. This includes self-powered vehicles, for example a sport utility vehicle (SUV) or a carriage without self-powering means. A wheelchair is one specific embodiment of the vehicle in accordance with the invention. As will be appreciated from the disclosure below, the traction system provided by the invention is suitable for a wide variety of vehicles such intended for travelling over different terrains. 
         [0005]    The traction system provided by the invention is versatile in that it has a variety of different configurations. It has one configuration particularly suitable for travelling over a relatively smooth terrain, for example, in the case of a wheelchair over floors, pavements or roads. Other configurations are suitable for travelling over difficult terrains, for example, rough surfaces, e.g. a non-paved road, and obstacles. In the case of a wheelchair, for example, the traction system permits the wheelchair to ascend or descend through staircases. 
         [0006]    In accordance with the invention, a traction system is provided which utilizes auxiliary rollers that can stretch a flexible traction belt from a substantially circular configuration, into which the traction belt is naturally biased, into other traction configurations, as will be described below. 
         [0007]    By a first aspect of the invention there is provided a traction system for a vehicle that comprises: 
         [0008]    a support frame defining a circular track belt support that is revolvable about an axis at its center, said axis being in a fixed position with respect to a chassis of the vehicle; 
         [0009]    a flexible track belt; and 
         [0010]    a track belt stretching assembly comprising one or more track belt stretching rollers; 
         [0011]    said system having one traction configuration in which the flexible traction belt is held on said support track forming a substantially circular, wheel-like traction surface, said belt stretching assembly can change to a stretching state in which said rollers engage said belt and stretch it from its state in said one traction configuration to a stretched state to define one or more other traction configurations of the system. 
         [0012]    Also provided by the invention, according to another of its aspects, is a vehicle comprising one or more, typically two, traction systems of the first aspect. One example of a vehicle in accordance with this aspect, is a wheelchair. 
         [0013]    In accordance with one embodiment, the rollers of the traction system, typically small wheels, are held on distal ends of belt extension arms respectively, that are in turn attached at their proximal ends, typically in a pivotal manner, to the vehicle&#39;s chassis. 
         [0014]    In accordance with another embodiment of the invention, the revolvable support frame comprises two coaxial support members with a gap between them, that together define said circular track belt support. The void space that extends radially from the axis to the lateral part of the gap defines a belt-stretching assembly-holding space and in said one traction configuration, the belt-stretching assembly is housed within said space. 
         [0015]    In the latter embodiment, the belt has preferably a central projection or series of projections that extend into the gap securing the track belt from sliding off its support. The belt-extension rollers similarly consist of two cooperating coaxial wheels that have a gap between them and said projections or series of projections fit into the gap when said rollers engage the track belt in said one or more other traction configurations of the system. 
         [0016]    Also provided by another aspect of the invention is a flexible track belt for use in the above traction system. 
         [0017]    By one embodiment of this latter aspect, a flexible track belt is provided that forms a closed loop, said belt consisting of a plurality of connected belt elements each of which includes at least two stretchable components. Each of the belt elements is biased into a contracted state by said components in which all members together bias the belt to assume a circular shape. Said belt can be stretched, forming a succession of stretched states by first causing the stretching of one of the at least two of said stretchable components, while the others are still relatively relaxed and gradually, with further extension, causing other of said stretchable components to stretch. 
         [0018]    In accordance with a preferred embodiment, all of said belt members are integrally formed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0019]    In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0020]      FIG. 1A  is a schematic illustration of a side view of an embodiment of a traction system of the invention with retracted chain-stretching arms; 
           [0021]      FIG. 1B  shows the traction system of  FIG. 1A , in one traction configuration with the two belt-extension arms extending beyond the wheel&#39;s parameters; 
           [0022]      FIG. 1C  shows the traction system of  FIG. 1A  in another traction configuration with only one of the belt-extension arms extended; 
           [0023]      FIG. 1D  shows the traction system of  FIG. 1A  with one of the belt-extension arms in the configuration of  FIG. 1C , passing over an obstacle. 
           [0024]      FIG. 2  is a schematic illustration of a cross-section through line II-II in  FIG. 1A . 
           [0025]      FIG. 3A  is a schematic illustration of a side view of an embodiment of the invention including an angle limiter fitted on the chassis. 
           [0026]      FIG. 3B  shows the embodiment of  FIG. 5A  with a belt-extension abutting the angle limiter. 
           [0027]      FIG. 4A  shows one contracted configuration of a traction system in accordance with an embodiment of the invention. 
           [0028]      FIGS. 4B and 4C  are, respectively, side elevation and isometric views of the traction system of  FIG. 4A  with the front wheel and the flexible track belt removed for better viewing of the track belt tensioning system. 
           [0029]      FIGS. 4D-4G  show a succession of different traction configurations of a traction system in accordance with another embodiment of the invention. 
           [0030]      FIG. 5A  is a schematic illustration of a portion of a flexible track belt according to an embodiment of the invention showing ring-like elements of which the belt is made. 
           [0031]      FIG. 5B  is a schematic illustration of a portion of the track belt of  FIG. 5A  in a stretched state. 
           [0032]      FIG. 5C  is a schematic illustration of a portion of a flexible track belt according to an embodiment of the invention showing elements of the kind shown in  FIG. 5A  with tracking soles filled thereto. 
           [0033]      FIG. 5D  is a schematic illustration of a portion of the track belt of  FIG. 5D  in a stretched state. 
           [0034]      FIG. 6  is a schematic illustration of a side view of a portion of stretchable belt according to another embodiment of the invention. 
           [0035]      FIG. 7  shows a traction belt in accordance with another embodiment of the invention seen here in isolation in its circular form. 
           [0036]      FIGS. 8A-8D  show a longitudinal cross-section through a portion of the track belt of  FIG. 7  in an initial and a succession of stretched states. 
           [0037]      FIGS. 9A and 9B  show the traction system of the invention fitted onto a wheelchair, in two different traction configurations. 
           [0038]      FIGS. 10A and 10B  show the traction system of the invention fitted onto an SUV, in two different traction configurations. 
           [0039]      FIGS. 11A and 11B  show the traction system of the invention fitted onto a motor cycle, in two different traction configurations. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]    A side view of a traction system according to an embodiment of the present invention is shown in a schematic manner in  FIGS. 1A ,  1 B,  1 C and  1 D to which reference is now made. The traction system generally indicated by arrow  10  includes a large circular frame (to be referred to hereinbelow as “wheel”)  12  revolvable around an axle  13 . Fitted on the rim of wheel  12  is a flexible traction belt  14 . Two extendible belt-stretching arms  16  and  18  are disposed behind wheel  12 . The extension of arms  16  and  18  in the embodiment is through a telescopic hydraulic pressure-activated elongation arrangement. Each of the stretching arms  16  and  18  is pivotally connected at its upper end by means of pivots  17  and  18 , respectively to a portion  24  of a chassis of a vehicle (not shown). Each of the stretching arms  16  and  18  has a respective tension wheel  20  and  22  connected at its lower end. In the traction configuration seen in  FIG. 1A , the traction belt  14  is tightly fitted around wheel  12  and has the wheels in a circular shape. This traction configuration is particularly suitable for moving over a smooth terrain. 
         [0041]    In  FIG. 1B  the same system is shown with both stretching arms extended in length and angularly displaced one from the other, defining a traction configuration in which traction belt  14  stretches around the upper part of wheel  12  and arrow tension wheels  20  and  22 . This traction configuration, as will also be explained below, has improved maneuverability over rough terrains, such as for example, a non-paved surface, as compared to the traction configuration of  FIG. 1A . 
         [0042]    In  FIG. 1C  a different traction configuration is shown in which only one stretching arm  18  and the associated tension wheel  22  is extended, essentially horizontally with the wheel  22  being somewhat more elevated than in the configuration shown in  FIG. 1B . In  FIG. 1D  the system with the same tracking configuration as in  FIG. 1C  is shown passing over an obstacle, such as a rock  24 , with the belt being deformed by the change in distribution of strains on traction belt  14 . 
         [0043]    Reference is now being made to  FIG. 2  giving a schematic cross-section made through lines II-II in  FIG. 1 . It should be noted that the relative dimensions of the various components do not actually reflect those dimensions in real life and the changes that were made were for the purpose of ease of illustration. As can be seen, the circular frame consists of wheel  12  and a corresponding coaxial wheel  12 A. A gap  30  is formed between them with the space confined between the two wheels constituting a track belt extension assembly confined to space  32 . 
         [0044]    As can also be seen, wheel  20  has a cooperating coaxial wheel  28  with a gap formed between them as well. 
         [0045]    Traction belt  14  is formed with a longitudinal projection or a succession of projections  34  projecting into gap  30 . Projection  34  ensures that the belt does not slip off the wheels. As can be seen both in  FIG. 1A  and  FIG. 2 , in this retracted configuration, the belt extension assembly is confined to space  32 . 
         [0046]    Reference is now being made to  FIG. 3A and 3B  showing another embodiment of the invention, similar to that shown in  FIGS. 1A-1D , with the addition of an angular limiters  80  and  82  intended to limit the angular displacement of the belt stretching arms. The traction configuration in  FIGS. 3A and 3B  correspond to those of  FIG. 1A  and  FIG. 1B  and the same reference numerals as those used in  FIGS. 1A and 1B  used herein as well to indicate the same components. 
         [0047]    Reference is now being made to  FIGS. 4A-4G  showing a traction system in accordance with another embodiment of the invention in a variety of views and in different successive traction configuration. 
         [0048]    Reference is first being made to  FIG. 4A  showing a traction system generally designated  100  with a traction belt support  101  that includes two cooperating and coaxial support wheels  102  with a gap between them. These two wheels  102  define between them a track belt stretching assembly confining space that houses a track belt extension assembly generally designated  104 , some components of which can be seen through the cut-out in wheel  102  and which will be explained further below. Fitted over track belt support  101  is a flexible and extendible track belt  106  that is tightly held over track belt support  101 . The entire traction system in the configuration shown in  FIG. 4A  revolves about a fixed axle  107  through the intermediary of bearings  108 . 
         [0049]    Reference is now being made to  FIGS. 4B and 4C  which are respectively side elevation and isometric view of the traction system in the configuration shown in  FIG. 4A  with one of wheels  102  and with the track belt removed to permit better view of the components of the track belt stretching system  104 . 
         [0050]    Stretching system  104  includes two pairs of track belt extension wheels, including wheels  110 , and wheels  112 , revolvably attached at respective ends of arms  114  and  116 . Arms  114  and  116  are each pivotally fixed at  118  and  120 , respectively, two respect pivot members  122  and  124  that are rigidly linked to axle  107  (the link not shown for ease of illustration). 
         [0051]    System  104  also includes two hydraulic piston members  130  and  132  pivotally anchored at  134  and  136  to a member (not shown) which is rigidly linked to axle  107 . In this manner arms  114  and  116  as well as piston members  130  and  132  are indirectly anchored to the chassis of the vehicle (through axle  107  which is in fact a chassis extension). 
         [0052]    Provided on each of arms  114  and  116  are a pair of auxiliary wheels  138  and  140 . 
         [0053]    Piston members  130  and  132  are linked, in a pivotal manner, to levers  146  and  148  which are in turn pivotally linked at  150  and  152  to respective arms  114  and  116 . Thus, by extension of the piston, arms  114  and  116  are angularly displaced in the direction of arrows  160  and  162 , respectively, thereby stretching the track belt as will be shown below. 
         [0054]    System  104  also includes a spring system generally designated  170  that includes a spring member  172  that provides a biasing force for retracting the arms  114  and  116  on the one hand and provides some resilience to the arms in their stretched position on the other hand. 
         [0055]    A series of successive stretched configurations of the traction system  100  can be seen in  FIGS. 4D-4G . In  FIGS. 4F and 4G , the stretchable track belt has been included for clear illustration of the function. With reference made now to  FIG. 4F , it can be seen that in this configuration the track belt is stretched defining a straight ground engaging section  180 . In this configuration, the vehicle is in fact supported by the main wheel  102  and by the track belt tensioning wheels  110  and  112 . In this configuration, auxiliary wheels  138  and  140 , serve to further stabilize the track belt in its position. 
         [0056]    In the configuration of the traction system  100  which can be seen in  FIG. 4G , the track belt is fully stretched and the surface support is now only through wheels  110  and  112 , with the vehicle being elevated above the ground as compared to the configuration in  FIG. 4F . 
         [0057]    As can be appreciated, support  101  may be engaged rotatably to a motor in order to propel the vehicle. 
         [0058]    Reference is now being made to  FIG. 5A , which is a schematic representation of a portion of a track belt  200  which includes a plurality of linked ring-like elements  202 . Each of these ring-like elements which is made from a flexible thermoplastic material  204  and includes an internal reinforcement element  208 . Thus when stretched, into the position shown in  FIG. 5B , through the reinforcing element  208 , the integrity of the track belt is maintained. 
         [0059]    Another embodiment of a track belt  210  can be seen in  FIG. 5C . Similarly as in the embodiment of  FIG. 5A , the track belt includes a plurality of integral belt elements  212  linked by members  214 , which serve both for ground engagement and for structure reinforcement. When extended, members  214  maintain the track belt integrity. 
         [0060]    Another embodiment of a track belt is shown schematically in  FIG. 6 . Here again, a portion of the belt only is seen and similarly as in the embodiment of  FIGS. 5A and 5C , it includes a plurality of belt elements  222  including each an elongation limiter  224 . 
         [0061]    A portion of the track belt  240  in accordance with another embodiment of the invention can be seen in  FIG. 7 . In accordance with this embodiment, the track belt is formed integrally from a flexible elastic material. The track belt is formed with a plurality of repeating integrally formed units  242 . Each unit  242  includes a relatively rigid surface engaging member  244 , an opposite radial projection  246  which fits into the gap formed between two pairs of wheels  242  and two pairs of stretching wheels  110  and  112  (see  FIGS. 4A-4G ). Each element includes also two linking elements including an outwardly undulated sheet  250  and oppositely a thinner and shorter sheet  252 . A third connecting element is sheet  254  that extends between adjacent projections  246 . 
         [0062]    A side elevation of a portion of the track belt of  FIG. 7  in various states including a contracted state shown in  FIG. 8A  and a succession of stretched states shown in  FIGS. 8B-8D . As can be seen in  FIG. 7 , to which reference is again made, in the contracted state, the track belt is biased into a circular shape. Upon stretching, the first element to be stretched is connecting element  252 , with the other connecting element  250  being relatively relaxed. Upon further stretching, element  250  is recruited into the stretching process. 
         [0063]    In its contracted state, the track belt travels relatively smoothly over a smooth surface. In case of a rough surface, in which case the traction system is changed to the configuration of the kind shown in  FIG. 4F  or  4 G, the flanks of members  244  can firmly engage with ground elements, obstacles, stairs, etc. 
         [0064]    A wheelchair, an SUV and a motor cycle, fitted with a traction system of the invention, each, in two traction configurations, can be seen in  FIGS. 9A to 11B .