Abstract:
A transport mechanism ( 104 ) for transporting a load-assembly ( 102 ), the transport mechanism comprising a closed flexible track ( 106 ) supported at an internal side thereof by at least two support rollers ( 108, 110 ), which at a first position one of the support rollers ( 108 ) exerts a force having a downward component onto the flexible track ( 106 ) at a point of contact thereof with a ground surface and biasing arrangement for biasing said flexible track ( 106 ) so as to assume a substantially circular shape. A displacing mechanism ( 112 ) is coupled to at least one of the support rollers for mutually displacing the support rollers into a second position, against the biasing arrangement in which the support rollers force the track to assume a state in which an extended portion ( 122 ) thereof is in contact with the ground surface and at least two of the support rollers are positioned at two ends of the portion.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a transport mechanism. More specifically, the present invention relates to a transferred mechanism adaptable for different terrains and to pass over various obstacles. Such a transport mechanism is useful in a large variety of vehicles. In the following, the term “vehicle” will be used to denote any mobile device making use of wheels or close tracks for transport including cars, trucks, hand trucks, wheelchairs, vehicles dedicated for specific applications, etc. 
     BACKGROUND OF THE INVENTION 
     A very wide variety of transport mechanisms are known. On the one extreme are wheels, which are characterized by a minimal contact with the ground, and hence minimal friction or drag develops with the surface over which the vehicle tracks, and on the other extreme are chains and belts which contact the ground over a relatively large surface, and hence have a large drag. Wheels are adapted for transport over essentially solid surfaces, whereas chains are intended far use on rough or loose ground terrains, such as soil or snow, or for overcoming different obstacles. 
     The transport mechanism of a vehicle is designed according to the terrain or the type of surface for which the vehicle is intended. However, at times, the vehicle is confronted with terrains different than that to which it is designed, or has to overcome various obstacles. For example, field vehicles which are at times provided with regular, air field rubber wheels, have an installation allowing deflating of the wheels in order to increase surface grip, e.g. when passing in an area with loose or muddy ground. 
     Wheelchairs are typically provided with a wheel, which is either hand or motor-powered, which allows safe transport of handicapped individuals over flat and hard surfaces. However, there is a serious problem in transporting a wheelchair over various obstacles, e.g. such as the edge of a sideboard, stairs, etc., as well as to transport a wheelchair over unpaved ground or snow. 
     It is the object of the invention to provide a novel transport mechanism which is versatile in that it can be configured to transfer a vehicle, such as a wheelchair, over different terrains, to allow it to safely pass over various obstacles, etc. 
     GENERAL DESCRIPTION OF INVENTION 
     The present invention provides a transport mechanism for transporting a load-bearing assembly, said transport mechanism comprising: 
     a closed flexible track supported at an internal side thereof by at least two support rollers, which at a first position one of the support rollers exerts a force having a downward component on to the flexible track at a point of contact thereof with a ground surface; 
     biasing arrangement for biasing said flexible track so as to assume a substantially circular shape; and 
     a displacing mechanism couple to at lest one of said support rollers for manually displacing the support roller into a second position, against said basing arrangement, in which the support rollers force the track to assume a state in which an extended portion thereof is in contact with the ground surface and at least two of said support rollers are positioned at two ends of said portion. 
     In accordance with one embodiment of the invention, the transport mechanism is motor operated, in accordance with this embodiment at least one of the support rollers are coupled to a motor and the flexible track is engaged with said at least one support rolling for imparting rotary motion to said track. 
     In accordance with one preferred embodiment of the invention, the transport mechanism is a transport mechanism of a wheelchair. 
     The load-bearing assembly may be, for example, a setting unit of a wheelchair, a platform in a hand truck, a body of a vehicle, etc. 
     It should however be noted that the invention is not limited to this embodiment, as will also be illustrated further below. 
     In accordance with a embodiment of the invention, said flexible track is made of a resilient material with stiff and springy reinforcement wire embedded therein for biasing the flexible track to assume its essentially circular shape. 
     In accordance with another embodiment, the flexible track is made of a resilient material with stiff radial projections from the internal side of the flexible track, each of the projections being connected to adjacent projections by resilient linking elements for biasing the flexible track to assume its substantially circular shape. A track in accordance with this embodiment may be made of a continuous flexible body, or alternatively, may consist of a plurality of segments pivotally connected to one another. 
     In accordance with still another embodiment, a first of the at least two support rollers is mounted at an end of a first arm, and a second of the at least two support rollers is mounted at an end of a second arm displaceable with respect to the first arm. At a first state of the mechanism the first and the second support rollers are positioned at opposite ends of a line defining the diameter of the circular shape; at a second state the first and second support rollers are positioned such that they are in contact with the track at portions thereof which contact the ground. 
     The load-bearing assembly may be connected directly to one or more of the support rollers. Alternatively, the load-bearing assembly is connected to the displacing mechanism of the transport assembly. In the latter case, the load-bearing assembly may be associated with a mechanism for angular displacement of the load-bearing assembly with respect to the displacing mechanism responsive to position and inclination of the flexible track so as to retain a stable center of gravity. 
     In accordance with one embodiment of the invention, the load-bearing assembly is associated with a mechanism for maintaining it at an essentially horizontal position, regardless of the position and inclination of the flexible track. 
     In accordance with still a further embodiment of the invention, the flexible track consists of two sets of identical links, each link having a first and a second face, a first and second radial edge, a peripheral edge forming part of the track&#39;s periphery and an internal edge; the links of each set being arranged in a closed path with the first radial edge of each link facing and being adjacent the second radial edge of an adjacent link, and with the first faces of links of one set facing the first faces of links of the other set; each link of one set being pivotally linked at a first corner thereof defined by the first radial edge and by the peripheral edge with the first corner of one link of the second set, and pivotally linked at a second corner thereof, defined by the second radial edge and by the internal edge with the second corner of a link of the other set adjacent said one link; there being a biasing member biasing each link to converge with respect to the adjacent links. 
     In accordance with another embodiment, the flexible track consists of a plurality of identical segments connected to one another by links; each segment having a peripheral edge forming part of the track&#39;s periphery, an internal edge and two side edges, the side edges being inclined such that when the track assumes its circular shape, side edges of adjacent segments are in contact with one another; the segment being connected to the links at corners formed between the peripheral and side edges in a slidable and pivotal manner; the track further comprising one or more biasing members biasing segments towards one another. Such biasing members may be a resilient strap or a non-resilient strap which is manually tensioned to apply the biasing force on the segments for assuming the circular shape of the track. 
     According to still another embodiment of the present invention one of the support rollers is mounted on a first arced rail and another of the support rollers is mounted on a second arced rail co-axial with the first arced rail, said arced rails being mutually slidably displaceable with respect to one another so as to displace the respective support rollers between the first and second positions. 
     By a further aspect the present invention also provides a track for use in the above transport mechanisms with specifications as defined. 
     The invention will now be illustrated in a non-limiting manner in the following specific embodiments with reference to the annexed drawings: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a transport mechanism, in accordance with one embodiment of the invention, fitted on a hand truck. 
     FIG. 2 shows the sport mechanism of the embodiment of FIG. 1 upon encountering an obstacle such as a stair. 
     FIGS. 3 and 4 show the embodiment of FIG. 1 in two different states of the track in which it has an extended portion in contact with the ground surface 
     FIG. 5 shows another embodiment of a transport mechanism, with the track in its circular shape, when the mechanism has three support rollers. 
     FIG. 6 shows the transport mechanism of FIG. 5 in a different state. 
     FIG. 7 is a side elevation of a specific embodiment of a track in accordance with the invention, shown in its circular state. 
     FIG. 8 shows the track of the embodiment of FIG. 7 in a state in which it has an extended portion in contact with the ground surface. 
     FIG. 9 is an isometric view of a portion of the track of the embodiment of FIGS. 7 and 8 in the state shown in FIG.  7 . 
     FIG. 10 is an exploded view of the section of FIG.  9 . 
     FIG. 11 is an isometric view of a segment of a track in accordance with another embodiment. 
     FIG. 12 is an exploded view of the segment of FIG.  11 . 
     FIG. 13 is a side elevational view of a track in accordance with another embodiment of the invention, shown in a circular state. 
     FIG. 14 shows the track of FIG. 13 in a different state. 
     FIG. 15 shows a segment of the track of the embodiment of FIGS. 13 and 14, in the state of FIG.  14 . 
     FIG. 16 is an exploded view of a segment of FIG.  15 . 
     FIG. 17 is an isometric view of a wheelchair fitted with a transport mechanism in accordance with the invention, with the transport mechanism in a first state. 
     FIG. 18 shows the wheelchair of FIG. 17 in a second position while ascending a flight of stairs. 
     FIG. 19 shows a motorcycle fitted at its back with a transport mechanism in accordance with the invention. 
     FIG. 20 shows the motorcycle of FIG. 19 with the track in a different state for transport over uneven terrains. 
     FIGS. 21 and 22 showing a four-wheel vehicle fitted with a transport mechanism in accordance with the invention in states corresponding to those of FIGS. 19 and 20, respectively. 
     FIG. 23 is a side elevational view of a wheelchair incorporating another embodiment of a transport mechanism, with the track in its circular shape. 
     FIG. 24 shows the transport mechanism of FIG. 23 in which the track is at its extended portion. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference is first being made to FIG. 1 showing a vehicle  100 , which in this specific embodiment is a hand truck, which comprises a load-bearing assembly  102  fitted with a control handle  103  and a transport mechanism  104  in accordance with the embodiment of the invention. As will be appreciated from the description below, a hand truck, is only but one example, of a vehicle which can be fashioned with a transfer mechanism of the invention, other examples being a car, truck, wheelchair, motorcycle, lift trucks, snow vehicles, etc. 
     The transport mechanism  104  comprises a closed track  106  supported by support rollers  108  and  110  rotatably mounted at opposite ends of a telescopic arm  112 , which provides a biasing force pushing the support rollers away from one another. Arm  112  is pivotally connected to a displacing mechanism  114  which consists of a displacing arm  116  pivotally connected to the load-bearing assembly  102  and can be selectively rotated by the user about pivot  118 . Track  106  is flexible, but has intrinsic biasing arrangement for biasing it into its circular shape, such as steel bands or wires (not seen), similarly as in conventional tires, embedded within the flexible material of the track. In addition, the biasing arrangement may be any one of the embodiments of such arrangements to be described further below, as well as many others. 
     In the position of the displacing mechanism shown in FIG. 1, arm  112  has a vertical position whereby support roller  108  bears on the track at its lowermost portion which is in touch with the ground, and support roller  110  bears on the track at its uppermost portion. In this position drag on the transport mechanism is minimal, whereby the vehicle rolls smoothly over the ground surface. 
     As can be seen in FIG. 2, the flexible nature of track  106  allows it to easily overcome obstacles such as a step  120 . When approaching the step, the track flexes to a shape dictated by the shape of the obstacle. Preferably, the displacing mechanism  114  is activated, either manually or automatically, either by rotation of arm  116  about pivot  118  or by rotation of arm  112  around pivot  115  into positions  108 ′ and  110 ′, respectively, represented in FIG. 2 by dashed lines. In this position, support roller  110  is already on top of step  120  and support roller  108 ′ is in a position whereby it does not hinder the overcoming of this obstacle. 
     It will be appreciated by the artisan that the displacing mechanism may be provided with motors for assisting in displacing the transport mechanism between positions, such motors may be, for example, electric, hydraulic or pneumatic and may be associated with suitable activating and control means as known per se. 
     FIG. 3 illustrates vehicle  100  in a different state of transport mechanism  104 . In this state, arm  116  is rotated by 90° about pivot  118 , whereby arm  112  is horizontal, such that support rollers  108  and  110  are horizontal, each bearing on track  106  at two ends of an extended portion  122  which is in contact with the ground surface. By extension of rod  113  of arm  112 , the two support rollers  108  and  110  bias track  106  into a position shown in FIG. 4 to assume a fill track state. In this state, the contact with the ground surface is maximal. While the state shown in FIG. 1 is useful for transport over solid and even surfaces, the states shown in FIGS. 3 and 4 are suitable for transport over an uneven or loose terrains, as well as to overcome various obstacles such as climbing or descending over a flight of stairs, as will be illustrated below, etc. 
     A transport vehicle  130  which for the sake of illustration is a hand-truck, is shown in FIG.  5 . This vehicle has essentially the same load-bearing assembly  102  as in the embodiment of FIG. 1, but different therefrom by having a different transport mechanism  132 . In this case, transport mechanism  132  comprises three support rollers  134 ,  136  and  138 . Support roller  134  is at an end of a first telescopic arm  140  and support roller  136  is at an end of a second telescopic arm  142 , with the two telescopic arms being pivotally connected at  144  to a pivot extending at an end  146  of displacing arm  148  (best seen in FIG.  6 ), similar to arm  116  of the embodiment of FIG. 1, which is pivotally connected at  150  to load-bearing assembly  102 . Support roller  138  is rotatable about an axis  152 , coaxial with axle  144 . 
     In the state shown in FIG. 5, the track  154 , which may be similar to track  106  of the embodiment shown in FIGS. 1-4, has a circular shape, and each of the support rollers  134 ,  136  and  138  bears on track  154 , at different points thereof, with support roller  138  bearing at a point of contact of track  154  with the ground. The vehicle  130  has a displacing mechanism allowing to pivotally diverge the arms  140  and  142  away from one another, into a position shown in FIG. 6 wherein there are essentially aligned on one straight line, and consequently track  154  assumes, as can be seen, a full track position, in which a large portion engages the ground surface. This position is useful in riding over loose terrain or for tracking over flights of stairs, in which case the transport vehicle  130  will further comprise a mechanism for retaining the load-bearing assembly  102  at an essentially horizontal position, or at any other angle or keep the center of gravity fixed, regardless of the angular position of the transport mechanism. It is appreciated that a skilled person is familiar with such mechanism as well as their construction and operation. 
     FIG. 7 shows a flexible track  180  according to an embodiment of the invention. The track according to this embodiment is made of a plurality of links  182  and the flexibility, and the bias to assume a circular shape is imparted by the manner in which the links are connected to one another, as will hereinafter be explained with reference to FIGS. 9 and 10. The state of the track as seen in FIG. 7, corresponds to that of track  106  as seen in FIG. 5, with the support rollers  184 , supporting the track in its circular position. The support rollers may however be displaced into the position shown in FIG. 8, which corresponds to that of track  106  as seen in FIG. 6, with a maximal portion of the track being in tact with the ground. 
     For better understanding of the manner of construction of track  180 , reference is made to FIGS. 9 and 10 which show a portion  188  of the track in an assembled and in an exploded view, respectively. 
     The links are arranged in two sets, a first set  190  and a second set  192 . The links in both sets are identical. Each link has a first face  194  and a second face  196 , with the first faces of links of the two sets facing one another. Each link has further a first radial edge  198 , a second radial edge  200 , a first radial edge of one link facing and being adjacent a second radial edge of another link and further comprising a peripheral edge  202  and an internal edge  204 . 
     Each link of one set is pivotally linked at a first corner thereof which is defined by edges  198  and  202  to the corresponding corner of a link of the second set, by means of pivot pins  210 , which is retained at the other end by washers  212 . Each link is further pivotally linked at a second corner thereof defined by edges  200  and  204 , with the corresponding corner of a link in the other set, adjacent the link to which it is pivotally linked at its other corner, which linking is by means of pins  214 , and washes  216 , which may be the same or different than pins  210  and washers  212 , respectively. 
     Formed within the first faces at the aforementioned corners of each link are circular recesses  220  and  222 , connected by a groove  224 . Provided is also a helical spring  226  with two end arms  228  and  230 , with the spring being fitted into recesses  220  and  222 , coaxial with pins  210  and  214 , with their arms  228  and  230  fitting into grooves  224  of the two facing links. The springs are preferably pre-tensioned such that they provide a biasing converging force on the two links with which they are associated. Consequently, the track is biased to a close proximity of the links to one another, as can be seen in FIG. 9, whereby it assumes a circular shape seen in FIG.  7 . 
     As can be seen, each of the aforementioned corners has a trimmed and curved corner edge which facilitates smooth pivotal movement. 
     An alternative embodiment similar to that of FIGS. 7-10 can be seen in FIGS. 11 and 12. The main difference in these embodiments reside in that each of links  140 , rather than having a planar shape, has an L-like cross-sectional shape, allowing cooperation with a grooved support roller or with two support rollers coupled to one another, and further the outer face  142  can be better fitted with a rubber friction or ground retaining band. 
     Another difference from the embodiments of FIGS. 7-11 can be seen in FIG.  12 . Some elements are identical and have the same function to those which can be seen in FIG. 10, and were accordingly given like numbers with a prime indication. The linking arrangement between links of the different sets  190 ′ and  192 ′ makes use of a torsion strip  240 , which is inserted into bores  242  and is received at each of its ends by a connector  244  snugly received within bores in a manner not enabling its rotation. The torsion of this strap provides the biasing force biasing the two opposite links towards conversion one with respect to the other. One advantage of this arrangement over that of the spring is that it can replaced without need to disassemble the track. 
     A track in accordance with another embodiment can be seen in FIGS. 13-16. The track  150  of this embodiment has a plurality of trapezoidal segments  152  linked to one another at their peripheral corners by links  154 , each defining an elongated opening  156  which receives pins  158  of opposite corners of adjacent links. In this manner, each two adjacent links can change the distance and the angle one with respect to the other. 
     Also provided is a flexible tension band  160  which is retained by and biased against a set of pins  162  at inner corners of segments  152 . Also provided is a tensioning mechanism for tensioning band  160  which can either be an intrinsic flexibility of the band, or an extrinsic tensioning arrangement, such as key  166  which turns tensioning wheel  168  over which an end of band  160  is wound. The other end of band  160  is firmly fitted, e.g. to one of pins  162 . 
     As can be seen again in FIG. 13, by releasing band  160 , the track can be formed from its circular state shown in FIG. 13, to its extended state shown in FIG.  14 . 
     A wheelchair  180  fitted with a transport mechanism  182  can be seen in FIG.  17 . The state shown in FIG. 17 is similar to that of the embodiment shown in FIG.  5 . Similarly as in the case of the embodiment of FIG. 5, the transport mechanism can assume an extended state, which can be seen in FIG. 18 allowing the wheelchair to better ascend or descend a flight of stairs  184 , as well as to pass over a variety of uneven terrains. 
     Two other types of vehicles, a motor cycle  190  and a field vehicle  192  fitted with a transport mechanism  194  and  196 , respectively, in accordance with the invention, can be seen in FIGS. 19-21, each in two different states, a circular state of the track (FIG.  18  and FIG. 20) and an extended state of the track (FIGS.  19  and  21 ). 
     Further attention is now directed to FIGS. 23 and 24 illustrating a wheelchair  250  generally consisting of a transport mechanism  252  and a load-bearing assembly  254  which in the present application is the seating unit of the wheelchair. The transport mechanism  252  comprises a closed track  256  supported by support rollers  258 ,  260  and  262 , which rollers are mounted on a displacing mechanism  264 . 
     The displacing mechanism  264  comprises a frame member  265  generally having the shape of a sector of a circle formed at its periphery element  266  with an arced rail portion  268 . Roller  258  is rotatably fixed at an end of the peripheral element  266  and roller  260  is rotatably fixed at the apex of the sector-like shape frame  265 . An arced rail member  270  is co-axially mounted and slidably received within the rail portion  268 , with roller  262  rotatably fixed at a free end thereof. The seating unit  254  is displaceably supported by the segment-like shaped member  266  as will become apparent hereinafter. 
     In the position seen in FIG. 23, the arced rail member  270  is entirely received within rail portion  268 , whereby the track  256  assumes its circular shape, as explained with respect to previous embodiments, whereby roller  260  bears on the track at its lowermost portion which is in touch with the ground. 
     In the position seen in FIG. 24, the arced rail member  270  is retracted from the arced rail portion  268  with simultaneous displacement of the frame member  265 , in a clockwise direction about the axis roller  260 , whereby rollers  258  and  262  become aligned with roller  260 , biasing track  256  to assume a full track state, in which its contact with the ground surface is maximal and suitable for transport of the wheelchair over uneven terrains and for overcoming obstacles, typically climbing or descending a flight of stairs. 
     As can further be noted, the frame member  265  is fitted at its rear end with a free wheel  272  which in the position of FIG. 23 is in contact with the ground, whereas in the position of FIG. 24 it is elevated from the ground. It will further be appreciated that mutual displacement of the arced rail  270  with respect to the arced portion  268  is facilitated by an electric motor as known per se. Typically, a wheelchair in accordance with the embodiment of the present invention will be provided with a mechanism for retaining an essentially horizontal position or retaining a stable center of gravity of the seating unit, regardless of the position and inclination of the displacement mechanism as will no doubt be appreciated by the artisan.