Abstract:
A support ring for vehicle tires is disclosed. The support ring is to be mounted on a tire wheel for support of the underside of the tire when the tire is operated at underinflated conditions. The support ring has a base, a cap, and a series of supporting arches extending between the base and the cap. The highest point of the arch contacts the support ring cap. During load, the arch flexes and transmits the load force along the arch sides and to the base of the support ring.

Description:
FIELD OF THE INVENTION 
     The present invention relates to support rings for vehicle tires, which are mounted inside the tires on their wheel rims in order to take up the vehicle load in the event of reduced tire pressure. In particular, the support ring has a simplified geometry consisting of a series of repeating arches. 
     BACKGROUND OF THE INVENTION 
     Tires are primarily supported by internal air pressure. A number of tire designs now exist that use a support ring located inside the tire to support the tire when the tire is operated in an underinflated condition. The use of a support ring of annular shape made of a flexible elastomeric material has been known for a long time. 
     One known design for the support ring consists of two circular bands of rubber connected together by a complex web of rubber to reduce weight and maintain strength as the weight of the vehicle descends on the support ring. One example is disclosed in U.S. Pat. No. 5,891,279. However, the complex web structure can create difficulties in mold design and molding of the support ring. 
     The web structure of the support ring of U.S. Pat. No. 5,891,279, and similar designs, has a column-like configuration. However, when the ring supports the vehicle load during underinflation, the incompressibility of the column creates an undesirable strikethrough, or heavy thump, as the tire rotates. 
     The present invention is directed to a tire support ring with a geometry that is easier in respect to mold design and molding, and works to eliminate strikethrough by a unique and flexible web structure. 
     SUMMARY OF THE INVENTION 
     The inventive support ring is intended to be mounted on a wheel rim inside a tire, in order to support the tread strip of the tire in the event of reduced inflation pressure. The support has a contoured base intended to fit snugly around the wheel rim contour, a substantially cylindrical cap. In accordance with the invention, a series of repeating arches extends between and connects the base and the cap. 
     The arches preferably extend continuously along the length of the support ring. The arches may also extend across the full width of the support ring. 
     The support ring may be formed from any suitable material which can support the under-inflated tire during operation and which will remain viable for at least a distance which will enable the vehicle operator to have the tire examined, and fixed or repaired. The material may be elastomeric, thermoplastic, or thermoset. 
     In another aspect of the invention, the arches form at least one cavity that spans the width of the support ring. A second cavity may also be formed radially outward and circumferentially displaced from the first cavity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1  is a cross-section view of a tire, rim, and support ring; 
         FIG. 2  is a side view of the tire support ring; and 
         FIG. 3  is a side view of an another embodiment of the tire support ring. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a support ring  10  according to the invention mounted around a preferential wheel rim  12  and inside the cavity  14  of a corresponding tire  16 . 
     The wheel rim  12  is a one-piece wheel. The wheel rim  12  comprises axially, starting from the same side as the wheel disk  18 , namely from the side intended to be on the outboard side of the vehicle: a first seat  20 , a flat cylindrical region  22  intended to receive the support ring  10 , the diameter of this region  22  is greater than that of the seat  20  to allow the support ring to be mounted easily and directly by slipping it on axially, a stop  24  for the transverse immobilization of the support ring  10 , a mounting well  26 , this well  26  is of minimized size by comparison with conventional mounting wells, a second seat  28  preceded by a retaining hump  30 , the diameter of this second seat is greater than the diameter of the region  22 . One feature of this wheel rim is that the two seats  20 ,  28  are angled in the opposite direction to the seats of conventional wheel rims. 
     The illustrated tire  16  is an asymmetric tire and has two beads  32  of differing diameters. 
     The support ring  10  has three main parts (see FIG.  2 ): an inner base  34 , a substantially cylindrical cap  36 , and a series of arches  38  located between the base  34  and the cap  36 . The arches  38  repeat continuously between the two bands  34 ,  36 , forming at least one cavity  40 , and preferably forming a second cavity  42  radially above and circumferentially offset from the first cavity  40 . The support ring  10  is a continuous unitary article. The height of the support ring  10  is chosen to be such that in all normal use of the tire it will not contact the underside of the tire even with appreciable temporary overload. This height corresponds to approximately half the height of the tire cavity  14  as measured between the wheel rim and the cap of the tire. 
     The support ring  10  may also be defined as having a first side  44  and a second side  46 , each side  44 ,  46  extending circumferentially along the length of the support ring  10 . The arches  38  extend from the inner side  44  to the outer side  46  of the support ring  10 , and thus the cavities  40 ,  42  extend the full transverse width of the support ring  10 . 
     Each arch  38  contacts the cap  36  at the maximum point of the arch  38 . When the support ring  10  is subjected to weight, such as when the tire  16  is operated at an underinflated state and the underside of the tire  16  rests upon the support ring  10 , the arch  38  flexs down, transferring the weight down the sides of the arch  38  and to the base  34  and the wheel rim  12 . 
     The inner side of each arch  38  is defined by a first radius R 1  that defines the majority of the inner side of the arch. A second radius R 2  defines the portion of the arch  38  radially inward where each arch  38  connects with the adjacent arch  38 . Each second radius portion connects with a relatively flat base of the first cavity  40 . Each cavity  40  may also be geometrically described as an arc, with a radius R 1  joined by a chord wherein the connection points between the arc and the chord are rounded out. 
     The outer side of each arch, having a radius R 3 , forms the two lower sides of the three sided second cavity  42 . The second cavity  42  may be geometrically described as an inverted triangle with the junctures between the three legs being rounded out. To minimize the stress on the three junctures, the junctures are all preferably formed with the same radius of curvature R 4 . 
     The radius R 1  of each arch is identical to allow for equal load sharing. The radii of the arches is based upon the thickness of the support material, which in turn can be based upon the material forming the support ring, the height of the support ring depending upon the tire design, the desired support ring characteristics, or other factors affecting the ring and tire performance. 
     By way of examples only, for a support ring in accordance with the invention with an inner radius of 23.25 cm and an outer radius of 28.75 cm, the following are exemplary arch dimensions. Example 1: the arch has a lower radius of 2.54 cm and an upper radius of 3.56 cm, thus having a thickness of approximately 10 mm. Example 2: the arch has a lower radius of 3.0 cm and an upper radius of 3.4 cm, forming a thickness of 4 mm. The thickness of the arch also determines the size of the upper cavity. 
     The number and size of the arches  38  is dependent upon a number of factors, including the material selection, the circumferential length of the support, and the anticipated load characteristics, and desired operating conditions. Because of these factors, some of which may be excluded when designing the rings, and the flexibility of the design, for a single ring size, a variety of rings with different arch dimensions can be designed. 
     The support ring  10  is formed from elastomeric, thermoplastic, or thermoset materials. If the support ring  10  is formed of elastomeric material, such as natural rubber, the elastomer should have a Shore A hardness of 60 to 90. If the support ring  10  is formed of a material such as polyurethane, polyester elastomers, or nylon, than the material should have a Shore D hardness of 30 to 45. 
     As noted above, material selection can affect the arch design. In the examples provided above, the first example support ring, having a greater web thickness, is preferably formed of an elastomeric material, while the second example, with a thinner web thickness, is preferably formed of a resin material. 
     In order to improve the endurance performance of the support, a lubricant is included inside the tire cavity  14  in order to lubricate any contact there may be between the top of the support ring  10  and the inside of the tire  16 . 
     The support ring  10  may be provided with different options, as illustrated in FIG.  3 . The support ring  10  may be provided with either a continuous or non-continuous hump  48  on the underside of the base  34 . The hump  48  would assist in mounting the support ring  10  onto a wheel rim  12  that has a corresponding groove. 
     The support ring  10  may also be provided with continuous or non-continuous grooves  50  on the cap  36  spaced across the width of the cap  36 . The grooves  50  are illustrated as equally spaced across the width of the cap  36 , but may be irregularly spaced. The grooves  50  provide for uniform distribution of the lubricant and heat dispersion during reduced pressure operation. The grooves  50  also help to reduce the weight of the ring  10 , without effecting performance of the ring  10 , when the ring  10  is formed of a heavier material. 
     Additionally, while not illustrated, the base  34  may be reinforced with inextensible reinforcing members. The reinforcing means can be individual wire filaments, individual cables, or wrapped steel cables. The selection of a reinforcing material will be dependent upon the material selection for the support ring  10  and upon the desired strengthening of the support ring  10 . The inextensible reinforcing members assist in preventing growth of the ring  10  during rotation. Such an option is dependent upon the material selection for the ring  10  and is preferably used only when the ring  10  is formed of elastomeric materials. 
     Also, if desired for additional strengthening of support ring  10 , the second upper cavity  42  may be absent, providing additional material underneath the cap  36 . 
     To vary the ride characteristics of the ring  10 , the first or second cavity  40 ,  42  may be filled with a foam rubber. 
     While the arches  38 , and the corresponding formed primary and secondary cavity  40 ,  42  are illustrated as extending straight across the transverse width of the ring  10 , the cavities  40 ,  42  may be in a variety of configurations as the cavities  40 ,  42  extend across the width of the ring  10 . The cavities  40 ,  42  may extend obliquely across the ring width, may be curved across the ring width, or may be v-shaped across the width. By varying the orientation of the cavities  40 ,  42 , and thus the orientation of the arches  38 , under load the cavities  40 ,  42  will progressively collapse and at no time will the load be completely on one single arch  38 , but will be further distributed over adjacent arches  38 . 
     While illustrated and describe as being used with an asymmetric wheel rim  12  and asymmetric tire  16 , the support ring  10  may also, of course, be mounted on a conventional two-part wheel rim with a flat base and mounted within either a conventional tire or a symmetrical runflat tire. The ring  10  may also be modified and formed as a split ring with a securing mechanism for mounting on a one-piece wheel. 
     With the inventive construction, compared to known support rings, the molding of the support ring  10  is simplified and easier to manufacture. 
     As discussed, by providing the reinforcing structure of the ring  10  with arches, as opposed to known columns, the arches flex and compress with load, transferring forces to the wheel rim. The flexing of the arches reduces strikethrough effects of the support ring. Also, the design of the arch provides for great flexibility in the exact design of the support ring. 
     Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.