Abstract:
A wheel assembly for a surface vehicle is presented. The wheel assembly comprises a tire comprising an envelope structure which by its inner surface encloses a cavity. The envelope structure comprises an outer, surface-engaging side having a circumferential surface, and opposite side walls which are integral with and extend from the surface-engaging side. The sides walls by their free ends define an inner, rim-engagement side of the tire by which the tire is connectable to a wheel hub. Each of the opposite side walls comprises a surface pattern defining a suspension assembly within the side wall to thereby prevent stretching of the tire envelope towards its maximal volume when the envelope is compressed with gas, while allowing deformation of the tire envelope when loaded or depressurized such that the surface engaging side of the tire maintains a substantially constant contact with the surface.

Description:
TECHNOLOGICAL FIELD AND BACKGROUND 
       [0001]    This invention relates to a tire and/or wheel assembly for a vehicle, aimed at improving the propelling of a surface vehicle. 
         [0002]    It is generally known that in order to provide effective maneuverability of a surface vehicle, its rim-mounted tires should be inflated to their inflation pressure, while puncture of a tire envelope especially in the sidewall of such tire may cause a very rapid loss of internal inflation pressure. Known techniques aimed at solving a problem of driving the vehicle upon deflation of its tire are associated with the provision of sensors or deflation warning devices capable of earlier detection of a change in the gas pressure within the tire in order to warn the user of a loss of pressure, as well as provision of various facilities for delaying effects of puncture on tires for as long as possible. For example, a tire of the conventional type may be provided thereinside with various elements, some including elastomers such as rubber polyurethanes and others, such that, in the event of puncture of the main outer tire or loss of pressure by the latter, the inner structure might serve as a support for the outer tire. Devices are also known which are placed inside the tire and which, though not inflated in normal use, may reduce pressure loss in the tire in the event of puncture of the latter. Moreover in a standard tire there is a strong dependency between the pressure and the tire ability to withstand torque and lateral forces, i.e. the less internal pressure in a standard tire the less stable it will be and its accurate steering ability will be reduced. 
       General Description 
       [0003]    The present invention provides a novel locomotion assembly which can be used for carrying and propelling a surface vehicle. More specifically, the present invention provides a novel approach for the configuration of a surface vehicle&#39;s tire. The tire of the invention may be configured as gas envelope, while in some embodiments the gas can be air. The configuration of the tire of the present invention is such that the technological procedure associated with the tire inflation may be eliminated or at least significantly reduced. 
         [0004]    In this connection, the following should be understood. As indicated above, in order to provide effective maneuverability of a surface vehicle, its wheel assembly should be substantially flexible in order to deform, and while deforming the wheel assembly would better follow the contact surface allowing for better traction and at the same time the flexibility will allow for shock absorption that contributes both to ride comfort and general stability and safety of the vehicle. In many cases the flexibility is gained by using gas (mostly air) inflating the tire. A standard tire consists of a closed inflated flexible envelope, where the gas/air stretches the envelope substantially to its full radial dimension therefore defining substantially the largest potential volume for the given envelope, any flexibility or deformation in such tire envelope involves deflection and stretching in the surface of the envelope. The deformation generates heat and causes fatigue resulting in wear-out and energy loss. Moreover, the way that said deformation accrued, will not allow sufficient contact between the deflected area of the tire (the contact patch of the tire tread) and the surface, as will be described further below. 
         [0005]    The present invention provides a semi-flexible envelope that by mathematical definition defines a volume that is substantially smaller than the theoretical volume which such envelope can potentially define, i.e. when compressed with gas the envelope is limited by its unique structure thus preventing stretching towards its maximum volume. Moreover, the profile of the envelope allows deformation of the tire when loaded or when depressurized in a way that the tread part of the tire maintains a good constant contact with the surface, as well as maintains its ability to deliver torque and bear side forces from the vehicle to the ground, and generates substantially less heat while doing so. 
         [0006]    The sidewall of the tire of the present invention presents a combination of curved surfaces. To this end, a combination of curved surfaces can be described as a combined surface formed by an infinite number of points that maintain a relation between them, i.e. relative distance to one another along the surface, such that curving or folding of the surface will not change the relation between the points along the surface, and therefore will not involve stretching or deflection in the surface. In contrary, the sidewall of a standard tire can be defined as a spherical surface which can be described as an infinite number of points that maintain singular relation, i.e. any change in the sphere will result in a change in relation between some of the points, and will thus involve stretching and deflection, that in many cases generate heat and may cause fatigue in the surface material. 
         [0007]    Thus, by one broad aspect of the invention there is provided a wheel assembly for a surface vehicle, comprising a tire envelope configured to be mountable on a wheel hub, the tire envelope by its inner surface defining a gas cavity having a certain maximal volume defined by a geometry of the envelope (namely the maximal volume achievable in the absence of structural constraints), wherein the tire envelope comprises or defines a suspension assembly within its side walls (e.g. a suspension assembly embedded in side walls of the tire envelope). Consequently under gas pressure in said cavity the volume achievable through gas-pressure imposed expansion is substantially smaller than said maximal volume defined by the geometry of the envelope. 
         [0008]    The tire of the present invention can be filled by gas/air to better suspend a vehicle, but has no such requirement for delivering torque or to withstand side forces. The tire can be designed to operate as pneumatic tire while using the gas/air as a suspension shock absorbent, however it may function safely with no gas/air, being designed as a non-pneumatic wheel and exploiting its structure to deliver torque and bear side forces. The non-pneumatic configuration is useful also in cases when gas/air cannot be used or its use is undesirable, such as in a Luna vehicle for example. 
         [0009]    The tire has an outer, surface-engaging side (termed “tread”, having a circumferential surface), and opposite side surfaces/walls which are integral with and extend from the surface-engaging side and by their free ends define an inner, rim-engagement side, of the tire by which the tire is connectable to the locomotion assembly. According to the invention, each of the opposite side walls of the tire has a pattern in the form of a surface relief, which in some embodiments defines at least one groove which has a substantially V-shaped cross-section and is located between the surface-engaging side (tread) and the rim-engagement side. Such a groove with substantially V-shaped cross section is referred to below as a V-shaped groove. It can also be described as if each V shape groove divides the sidewall into 2 two-dimensional curved surfaces. 
         [0010]    Thus, by such embodiments the side wall has a surface pattern defining one or more V-shaped grooves extending between the surface engaging side and the ring-engagement side (i.e. along the radial axis of the tire). The provision of such grooves which are made in a generally flexible/elastic tire material and which have substantially round apexes provides the tire with a desired suspension assembly. This allows the tire (locomotion assembly) containing very low air pressure (even zero pressure inside) to be still able to withstand forces and rotate and drive the vehicle with sufficient maneuverability. 
         [0011]    Generally, the required V-shape geometry of the groove may be achieved by any suitable apex angle. In some embodiments, the intersecting sides of the V-shape groove are formed by a pair of opposite segments of substantially frustum-conical structures (or generally conoid structures). The general concept of using frustum-conical in locomotion assembly of a surface vehicle is described in the International (PCT) application No. PCT/IL2011/000115, which is assigned to the assignee of the present application, and which is incorporated herein by reference. 
         [0012]    According to the present invention, the tire constitutes a wheel-tire unit which may be constituted just by the above described envelope structure of elastomeric material composition (or semi elastomeric materials) enclosing a cavity/lumen which may or may not be filled by gas medium. The tire is preferably configured to have desired rigidity and flexibility distribution along and across its sides. To this end, rigidity and flexibility may be different at different regions of the side wall, i.e. the side walls might have a certain rigidity/flexibility pattern at least along the radial axis (radial pattern) of the tire and in some embodiments a further rigidity/flexibility pattern along the circumference of the side wall (circumferential pattern). These different levels of rigidity and flexibility can be achieved by several ways, which may include implantable/embedded rigid material such as plastics, steel, spring etc., the rigidity may be gained by forming a ‘beam’ structure using combination of non streaking elements such as cables, or cords such as textile cords nylon, Kevlar, etc. and/or relatively hard/stiff elastomers such as hard rubber, as will be described more specifically further below. 
         [0013]    In case the envelope is filled with compressed gas/air, the structure has to eliminate the gas from bulging the envelope to define the biggest possible volume it can. Therefore a certain restrain has to be set in order to keep the desired shape of the envelope. The inner part of the groove (closer to the rim/hub engagement side of the tire) tends to increase its diameter. Therefore, constructing the inner side of the groove with un-stretchable elements will support the envelope structure, preventing the inner side from ‘bulging’ out. 
         [0014]    Moreover, in order for the inner and outer sides of the groove to withstand the gas/air pressure, both the inner and outer sides of the groove are sufficiently rigid along the radial axis of the tire. In some embodiments of the invention, it is desirable to maintain the radial rigidity of the groove sides but at the same time to gain circumferential flexibility, therefore the groove structure might be strengthened in an uneven way so it may contain relatively rigid elements only along the radial axis, or it may be designed in a way that an array of pattern elements (slots, projections, thinner regions) is provided which are arranged in a spaced-apart relationship circumferentially around the groove side(s) thereby weakening the circumferential structure while keeping the radial rigidity. A similar principle may be applied where an array of bulges extend circumferentially around the groove side(s) providing similar results. 
         [0015]    Thus, the tire may have a certain rigidity pattern across its side walls, i.e. between the surface-engaging and rim-engagement sides. This pattern is defined by that the apex of the groove and its corners at opposite sides of the groove are sufficiently elastic (e.g. achieved by making the tire with smaller thickness within these regions) as compared to the tire regions between them. As a result, the two parts of the groove function as two beams that can be bended but not deformed. The general shape of such grooved tire is maintained and any change is reversible. On the other hand, the tire should have sufficient flexibility to absorb the forces falling on it while not breaking down. Additionally, the inner side of the groove might have a relatively higher rigidity, with respect to both “radial” and “circumferential” rigidities, in order to maintain the generally wheel-like shape of the tire, and the outer part of the groove (closer to the surface-engaging side of the tire) might be of relatively lower rigidities. 
         [0016]    Thus, the desired combination of rigidity and flexibility can be achieved by the provision of appropriate rigidity pattern in the generally flexible material of the tire, i.e. higher radial and circumferential rigidity at the inner part of the groove than that of the outer part, while securing three flexing points along the radial direction, i.e. at the apex and corners at opposite sides of the V-shaped groove. As indicated above, a second rigidity pattern can be provided as a circumferential pattern along the circumferential direction of the inner and outer parts of the groove. This may be achieved by an array of spaced-apart slots (e.g. regions with implanted material of different rigidity than in spaces between the slots and/or uneven wall thickness) arranged along the groove with the slots&#39; orientation being substantially perpendicular to the tire plane (across the groove). Thus, the tire with such groove extending along its circumference has a first rigidity pattern in a radial direction of the tire (across the groove) and possibly also a second rigidity pattern in a circumferential direction. 
         [0017]    Thus, according to another broad aspect of the invention, there is provided a tire envelope for a surface vehicle, comprising a surface pattern in its side walls extending between a surface-engaging side and a rim-engagement side of the tire, said surface pattern configured as a suspension assembly embedded in the side walls to thereby prevent stretching of the tire envelope towards its maximal volume when the envelope is compressed with gas, while allowing deformation of the tire envelope when loaded or depressurized such that the surface engaging side of the tire maintains a substantially constant contact with the surface. 
         [0018]    According to yet another broad aspect of the invention, there is provided a tire for a surface vehicle, the tire comprising an envelope structure which by its inner surface encloses a cavity, said envelope structure comprising an outer, surface-engaging side having a circumferential surface, opposite side walls which are integral with and extend from said surface engaging side, the sides walls by their free ends defining an inner, rim-engagement side of the tire by which the tire is connectable to a locomotion assembly, wherein each of the opposite side walls comprises a surface pattern extending between the surface-engaging side and the rim-engagement side and defining a surface relief in the form of at least one groove having substantially V-shaped cross section, and wherein each of the side walls is configured with a predetermined rigidity pattern across the side wall. 
         [0019]    The rigidity pattern may comprise relatively small rigidity and thus relatively high flexibility of regions of the tire at apex of the V-shaped groove and corners defined by connection between the groove with respectively the surface engaging side and the rim engagement side of the tire. 
         [0020]    The rigidity pattern may comprises different rigidities of the tire within respectively an outer side of the groove closer to the surface engaging side and an inner side of the groove closer to the rim engagement side of the tire. For example, the inner side of the groove comprises an array of support elements embedded therein and extending along at least one of radial and circumferential axes of the tire. 
         [0021]    The surface engaging side is configured to have predetermined rigidity along a circumferential axis of the tire. To this end, the surface engaging side may comprise an array of support elements embedded therein. 
         [0022]    Alternatively or additionally, the rigidity pattern may be formed by varying thickness of at least one of the outer and inner sides of the groove. 
         [0023]    Generally speaking the grooved side walls of the tire and appropriate rigidity/flexibility distribution of the tire material within the tire creates an optimal suspension assembly allowing the effective operation of a locomotion assembly using such tire with practically no limitations to the lack/reduction of pressure in the tire cavity. 
         [0024]    As indicated above, the tire regions at the apexes of the grooves (and outer corners) are relatively flexible. It has been realized in accordance with an embodiment of this invention that in a deformable wheel the flexible portions of the side walls (particularly at said apexes), considerable strains may develop. The present invention offers a solution to reduce such strains by providing a specifically designed load-bearing arrangement. 
         [0025]    The present invention thus in its yet further aspect provides a deformable wheel assembly with an inflatable enclosure defined by the above described tire, and a load-bearing arrangement formed by a plurality of support elements, comprising a first array of spaced-apart elements and a second array of spaced-apart elements, the elements in each of the arrays defining together a substantially frustum-conical structure (i.e. the lines that link defined points at distal ends of the elements together define a frustum-cone), the two frustum-conical structures intersecting one another with the elements of one dove-tailing those of the other structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0027]      FIG. 1A  illustrates the typical behavior of a traditional tire when being loaded, as compared to that utilizing the tire of the invention having grooved side walls; 
           [0028]      FIGS. 1B and 1C  illustrate the footprint of the locomotion assembly utilizing the tire of the present invention in respectively loaded and unloaded state of the tire; 
           [0029]      FIG. 2A  illustrates an example of the tire of the present invention; 
           [0030]      FIGS. 2B and 2C  show more specifically an example of the pattern provided in the side walls of tire of the present invention; 
           [0031]      FIG. 3  illustrates an example of the geometrical and rigidity patterns provided in the tire of the present invention; 
           [0032]      FIGS. 4A and 4B  illustrate specific but not limiting example of the configuration of a support assembly embedded in the tire to provide the desired rigidity pattern; 
           [0033]      FIG. 4C  exemplifies an additional rigidity pattern that can be used in the tire of the invention; 
           [0034]      FIGS. 5A and 5B  show another possible support assembly embedded in the tire to provide a desired rigidity and flexibility pattern, and 
           [0035]      FIGS. 6A and 6B  illustrate advantageous operational features of the tire of the present invention. 
           [0036]      FIG. 7  is a perspective view of a deformable wheel, according to an embodiment of the invention; 
           [0037]      FIG. 8  is a perspective cross-sectional view of the wheel of  FIG. 7 ; 
           [0038]      FIG. 9  shows a large cross-sectional view of a portion of the wheel with the internal load-bearing structure contained within the tire; and 
           [0039]      FIG. 10  is a cross-sectional perspective view of a portion of the tire illustrating the manner of association of a reinforcing element with side walls of the tire. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0040]    In order to better understand the features of the tire configured according to the present invention, utilizing the V-shape groove structure described above, reference is made to  FIGS. 1A to 1C  describing the physical reason that is behind the typical behavior of a traditional tire (regardless of its size or cross section) as compared to the tire of the present invention.  FIG. 1A  shows a tire in its loaded and unloaded states. In the figure, a circle C 1  in the middle with diameter  620  constitutes a rim, a circle C 2  is the unloaded tire, and lines L 1  and L 2  between the rim C 1  and the outer circumference of the unloaded tire C 2  indicate the line of the tire sidewall in a normal tire. The sidewall in the fully inflated tire defines the maximal distance between the outer circumference and the rim, i.e. the outer circumference under any condition cannot breach the outer diameter of the tire. Curve R 1  corresponds to a condition of a conventional tire when deflated, while curve R 2  corresponds to that of a tire in accordance of the present invention when deflated. 
         [0041]    When air is discharged from the tire, the tire will collapse (under the vehicle weight) and the rubber will have to be displaced somewhere. Since the circumferential dimension cannot increase the original diameter (lines L 1  and L 2 ), the rubber will shrink and compress a little bit and will increase the footprint a bit. If the tire is further deflated, it will have to collapse, and since it cannot collapse outside, it will collapse inside as shown by curve R 1 . When the same occurs with the tire of the present invention, the outer circumference will be pushed away (under the load), and, since it has no limitation (the sidewall here is actually the “wall of the cup” and is almost horizontal, and it can ‘get away’ from the rim), it will deform to absorb and receive the shape of the ground, as by curve R 2 . 
         [0042]      FIGS. 1B and 1C  show the footprint of the tire of the present invention in respectively, inflated and deflated states thereof. As can be seen, a 200% increase in footprint is achieved. 
         [0043]    Reference is now made to  FIGS. 2A to 2C , illustrating tires configured according to the invention.  FIG. 2A  shows the tire  100  which is configured as an envelope structure whose inner surface  111  encloses a cavity  112 . The latter may be filled by gas, e.g. air. Generally, the tire may or may not be inflatable. The tire envelope  100  has an outer, surface engaging side  110  (tread, having a circumferential surface), and opposite side walls  120 A and  120 B which are integral with the surface engaging side  110  and extend therefrom. The side walls by their free ends  160  are connectable to a rim of a locomotion assembly (not shown) and thus actually define a rim engagement side. According to the invention, each of the opposite side walls  120 A and  120 B has a surface pattern defining at least one substantially V-shaped groove  140  between the surface engaging side  110  and the rim engagement side  160 . In the present not limiting example, a single-groove pattern is provided in each side wall. 
         [0044]    The groove  140  has inner and outer sides  150  and  130  intersecting at the groove apex  180 . As better seen in  FIG. 2B , the outer side  130  of the groove is connected to the surface engaging side  110  via a corner region  170  of the tire envelope  100 , and the inner side  150  of the groove is connected to the rim engagement side  160  via another corner region  190  of the envelope  100 . The configuration is such that these corner and apex regions  170 ,  180  and  190  have lower rigidity and higher flexibility/elasticity than the inner and outer sides of the groove. Thus, each of the side walls  120 A,  120 B, has a surface pattern forming at least one V-shaped groove, and also has a rigidity pattern extending across the side wall (i.e. along radial axis) of the tire. As also shown in the figure, the tire at its rim engagement side  160  is typically formed with non-stretchable circumferential member (bead) that secure the tire to the rim and in most cases is constructed from steel cords. 
         [0045]    Preferably, the side walls  120 A and  120 B have additional rigidity pattern defined by different rigidities of the inner and outer sides  150  and  130  of the groove  140 . More specifically, the inner side  150  of the groove  140 , by which it is connected to rim engagement side  160  of the tire  100  has higher rigidity than the outer side  130  of the groove connected to the surface engaging side  110  of the tire. The inner side  150  has higher rigidity than the outer side  130  along both radial and circumferential axes. 
         [0046]      FIG. 3  shows more specifically the surface and rigidity patterns. As shown, these patterns extend along a path  310 , i.e. across the side wall  120 A, which can generally be defined as “radial axis” of the tire  100 . One of the patterns is in the form of a surface relief defined by the provision of at least one groove  140 , and the other pattern is the rigidity pattern along the path  310  (e.g. material composition). The rigidity pattern is formed at least by providing lower rigidity at the corners  170 ,  190  and apex  180 , and possibly also by different rigidities of the outer and inner sides  130  and  150  of the groove. 
         [0047]    Generally, the rigidity pattern across the side wall may be achieved by using different materials or the same material, such as rubber, that has undergone different degrees of hardening processes and/or has different thicknesses. The rigidity pattern may be produced by embedding a support structure within the tire. The support structure is typically in the form predetermined arrangement of support elements, such as cables, fabrics, cords, textile, micro fibers. The support elements are oriented with respect to circumferential and radial axes in order to provide the desired rigidity and flexibility distribution in the tire, which provide for securing the circumferential length all along the cross section of the tire defined by path  310  from the rim engagement side (bead)  160  to the surface engaging side (tread)  110 , as well as maintain circumferential flexibility along the same cross section. Also, the rigidity and flexibility distribution should be selected to maintain radial rigidity over the inner and outer sides (cones)  150  and  130  while keeping the sufficiently flexing points at the corner regions, i.e. region  190  between the groove and bead, region  180  between the inner and outer sides (i.e. the groove apex region), and region  170  (so-called “shoulder”) between the groove and tread. 
         [0048]    Reference is made to  FIGS. 4A and 4B  showing a specific but not limiting example of the tire  100  of the present invention. As shown in the figures, the sides if the groove as well as the surface engaging side are provided with the support elements. The support elements include a so-called shoulder belts extending along the surface engaging side close to the shoulder ( 170  in  FIG. 3 ), inner cone plies and outer cone plies oriented with certain angular relation between them and with respect to the radial and circumferential axes. 
         [0049]    As shown in the specific example of  FIG. 4A , the rigidity pattern can be achieved by providing cables  410  and  420  embedded in the tire envelope, in the surface engaging side  110  and the outer and inner sides of the groove in the side wall  120 A.  FIG. 4B  shows the same configuration of  FIG. 4A  from a different angle. It should be noted that the cables  410  are used to secure the circumferential length of the tire at the surface engaging side  110 , close to the corner  170 . 
         [0050]    Reference is now made to  FIG. 4C  that illustrates another feature of the invention, which can additionally be used in any of the above-described examples. In some embodiments of the invention, the tire has additional rigidity pattern extending along the circumferential axes of at least one of the outer and inner sides of the groove  140  made in the side wall  120 A. As can be seen in this specific not limiting example, the outer and inner sides  130  and  150  of the groove  140  have a varying thickness defining the rigidity patter. The varying thickness is formed by an array of spaced apart of relatively thick regions  450  spaced by thinner flexing regions  460 , where the array extends along the circumferential axis of the respective side of the groove, and the regions area aligned substantially perpendicular to the tire plane (i.e. across the groove side). This configuration allows for achieving a desired circumferential rigidity pattern by, inter alia, appropriately selecting the pattern features, i.e. the thickness of different regions  450  and  460 , and a distance between the locally adjacent thick regions  450  (i.e. the length of the thin flexing zones  460 ). 
         [0051]    It should be noted, although not specifically illustrated, that the desired rigidity may be obtained by replacing the projecting (thicker) regions  450  by slots thus forming thinner regions spaced by thicker regions of the tire. In a different embodiment, such varying rigidity (rigidity/flexibility pattern) along the groove side may be achieved by forming the groove side with spaced-apart recesses/grooves and attaching/embedding there desirably rigid elements. 
         [0052]    As already described above, the tire of the present invention should be rigid along its radial direction. In some embodiments of the invention, it is desirable to maintain the radial rigidity of the tire while at the same time keep circumferential flexibility. Therefore, the V-shaped groove might be strengthened in an uneven way. This can be achieved by providing/embedding in the tire a support structure which adds rigidity to the tire along the radial axis but at the same time enabling the tire to be sufficiently flexible in its circumferential direction. 
         [0053]    An example of obtaining this is by using a spring-like support structure as exemplified in  FIGS. 5A and 5B .  FIG. 5A  illustrates one possible not limiting example of such spring-like support, in the form of a continuous spring  510  embedded in the outer and inner sides  150  and  130  of the groove  140 . The continuous spring  510  extends across the entire groove  140 , from the outer side  150  of the groove to its inner side  130  while passing through the apex  180 . This configuration gives the groove and the whole tire the desired rigidity in the radial and circumferential directions while the rigidity in the circumferential direction is significantly lower than that in the radial direction, by this achieving the desired flexibility along the circumferential axis. 
         [0054]      FIG. 5B  exemplifies a somewhat different configuration of the support structure which is formed by separate spring-like support members, the first one  520 A is embedded in the outer side  150  of the groove, and the second one is embedded within the inner side  130 . In addition, a belt  530  is embedded in each of the inner and outer sides of the groove, closer to the groove apex  180 . It should be noted that the configuration in  FIG. 5A  is probably more rigid in the radial axis than the configuration shown in  FIG. 5B , enabling the design of different tires with different rigidities as may be required in specific situations. 
         [0055]    It should be noted that the above exemplified springs may be substituted by any other suitable support elements made of substantially stiff material such as polymers, composite materials, and other alloys. 
         [0056]    Reference is now made to  FIGS. 6A and 6B  illustrating some advantageous operational features of the tire  100  of the present invention. The tire is shown while being subject to pressure caused by inflation (filling gas in the cavity  112 ). In order for the tire  100  to hold the air pressure that exerts forces on the side walls  120 A and  120 B and pushes the outer side  130  and inner side  150  of the groove outside as exemplified by their positions  130 ′ and  150 ′ respectively, it is necessary to provide the side walls  120 A and  120 B with sufficient radial stiffness, otherwise the side walls may fold, collapse and bulge out. 
         [0057]    As described above, the side walls have rigidity patterns that give the outer and inner sides of the groove the required rigidity to withstand the gas (air) pressure and prevent the side walls from collapsing, i.e. bulging out. One possible occurrence is exemplified in  FIG. 6B  in which the relatively flexible apex  180 ′ bulges outside due to high pressure, whereas the rigidity applied to the outer and inner sides of the groove keep the tire from bursting and or collapsing. 
         [0058]    As indicated above, the above described tire (i.e. with V-shaped grooves across its side walls and with a specific rigidity pattern/profile along the groove) may by itself present a vehicle&#39;s wheel assembly, or such tire may be mounted on a load-bearing arrangement to form together a wheel assembly. The wheel assembly may have two configurations: a rounded, non-deformed configuration in which a surface-engaging side of the tire is substantially circular and a deformed configuration in which the surface-engaging side of the tire is non-circular and has an extended portion that engages the surface. As also indicated above. the wheel assembly of the present invention in some embodiments thereof presents an improvement of the locomotion assembly of the kind disclosed in a co-owned international application No. PCT/IL2011/000115, which is incorporated herein by reference. 
         [0059]    As also indicated above, the tire regions at the apexes  180  of the grooves  140 , as well as corner regions  170  and  190  at opposite sides of the groove are relatively flexible. In a deformable wheel assembly utilizing such tire the flexible portions of the side walls (particularly at said apexes), considerable strains may develop. Such strains can be reduced by providing a specifically designed load-bearing arrangement. The load-bearing arrangement may be formed of discrete, dove-tailing elements, which are arranged in a manner to define two oppositely oriented substantially frustum-conical structures. The side walls of the tire-enclosure trace the frustum-conical surfaces and have thus an overall V-like cross-sectional shape with the apexes of the V-shapes of the two side walls facing one another. Such a locomotion/wheel assembly is at times referred to herein as “deformable wheel”. 
         [0060]      FIG. 7  illustrates a deformable wheel generally designated  200  with a tire  100  formed around a wheel hub  104  (sometimes known as “rim”) arranged about an axis A, which in use coincides with the wheel&#39;s axle. The tire  100  has a surface engaging side/member  110  (tread, having a circumferential surface) with an appropriate surface relief for firm gripping of the surface and has side walls  120 A and  120 B. 
         [0061]    As can be seen in  FIGS. 8 and 9 , the side walls  120 A,  120 B have respective peripheral portions  114 A,  114 B defining a groove  140  with a generally V-shaped cross-section, ending with more central, respective, skirt portions  190 , which are configured to form a gas-tight seal with the hub  104  (manner of forming gas-tight seal best seen in  FIG. 2 ). The tire may be reinforced by metal, e.g. steel, fibers or cables, two of which:  113 A and  113 B,  115 A and  115 B, which are circumferential fibers embedded within the rubberized matrix of the tire, are illustrated in  FIG. 9 . 
         [0062]    The surface engaging side  110 , side walls  120 A,  120 B, and hub  104  generally define an enclosure  100  for holding pressurized gas, e.g. air. As described above, by change in gas pressure within the enclosure  100 , the wheel can change its configuration from a generally circular one to a deformed configuration, in which an extended portion of the surface engaging member engages a surface. 
         [0063]    As exemplified in the embodiment of  FIG. 9 , included within the tire is a load-bearing arrangement generally designated  540 , which is formed by a plurality of support elements comprising elements  132  arranged in a first array in a spaced-apart manner; and a second array of elements  134  arranged in a second spaced-apart manner. The support elements provide desired rigidity pattern/profile along the V-shaped groove. 
         [0064]    In this embodiment, elements  132  and  134  are identical and the arrays are substantially, slightly axially-shifted (shifted by about half of the angular displacement between adjacent elements in an array) mirror images of one another. Each array of elements define substantially frustum-conical structures that intersect one another at an intersection zone  550 , whereby the elements  132  and  134  are arranged in a dovetailing manner with each of elements  132  and  134 , being flanked by two elements  134  and  132 , respectively. 
         [0065]    As can be seen in  FIG. 9  and also in  FIG. 10  (the latter representing in isolation element  132  to illustrate its structure and manner of association with the rubberized portion of the tire), each of elements  132 ,  134  has a generally curved side elevation. To facilitate easier reading, the description of the structure of each element will focus on element  132 , which is substantially identical to that of element  134 . 
         [0066]    As can be seen in  FIGS. 9 and 10 , element  132  has a generally curved side profile and includes a metal rib  142  embedded in a rubberized matrix  144 . The overall curved structure defines a first segment  132 A and a second segment  132 B, defined on two opposing sides of the point of intersection  550 , and an intermediate section  132 C. The metal rib thus has corresponding segments  142 A,  142 B and  142 C. Segments  142 A and  142 B are located in parallel and spaced apart planes. 
         [0067]    Upon deformation of a portion of the wheel, the first array of elements  132  and the second array of elements  134  pivot one against the other, in the direction of arrows X 1  and X 2 . As a result, segment  134 A of element  134  comes into closer elevation proximity to segment  132 A of element  132 ; and the same applies with respect to segments  132 A and  134 B. Side wall portions  114 A,  114 B have respective first regions defining outer sides  130  of the groove, which trace the frustum-conical surface defined by segments  134 A,  132 A (and thus by themselves define a substantially frustum-conical surface); and similarly have regions  150  that also trace a frustum-conical surface defined by segments  132 B,  134 B, with intermediate regions  180  at the apex of the V-shaped cross-section. 
         [0068]    Pivotal movement, as illustrated by arrows X 1  and X 2 , also puts a strain on the rubberized portions of the tires, particularly at regions  180 . However, in the arrangement shown herein, where the segments on each side of a point of intersection  550  are situated in different spaced apart parallel (slanted) planes, the strain is considerably reduced as compared to what would occur in the case of a substantially straight element of the load-bearing structure. Each of elements  132 ,  134 , defined between substantially parallel opposite side faces, has surface contours permitting tight association with corresponding portions of regions  130 ,  150 ,  180 , as is clearly illustrated in  FIGS. 9 and 10 . 
         [0069]    In the embodiment illustrated in these figures, the elements are fixed to the side faces  120 A,  120 B through gluing or welding. By other embodiments of the invention, the association may be less tight, permitting some movement tolerance between opposite faces of the elements and the side walls. 
         [0070]    Thus, the present invention provides a novel configuration of a surface vehicle tire/wheel, which incorporates a different approach for providing a desired suspension assembly within the tire formed by the tire geometry and material characteristics. The suspension assembly is achieved by provision of substantially V-shaped grooves (in cross section) in the side walls of the tire envelope and desired rigidity and flexibility parameters of different regions/sides of the groove, and possible also of the surface engaging side of the tire.