SEGMENTED-BAND BANDED TIRE

Abstract: A banded radial run-flat pneumatic tire with a trans­ versely segmented band (28) that varies the bending stiff­ ness of the band circumferentially relative to the bending stiffness across the band. The band can be segmented into annular side-by-side hoop-like coaxial band elements (30) either of the same or of different diameters. An elastomer (32) bonded between adjoining circumferential edges of the band elements connects them for co-operative association to give the band its desired operating characteristics. The elasticity of the elastomer and the spacing between the band elements can be selected to tailor the performance of the band. Preferably the bending stiffness of the band is 1000 times as great circumferentially as it is transversely across the band.

Description: SEGMENTED-BAND BANKED TIRE Field Of The Invention This invention relates to banded radial run-flat pneumatic tires and, more particularly, to banded tires having a tranversely segmented band. Background Of The Invention The run-flat pneumatic tire is an area of tire technology that has engaged investigators over the years. A run-fl8f tire is one designed to be able to support a vehicle for operating at reasonable speeds for somepredetermined distance even if the tire has partially or totally lost its inflation pressure. A recent successful development in the art of run-flat tires is the band-reinforced radial''tire invented by one of the inventors in the present invention, Edward G. Markow, which banded tire is the subject of U.S. patent No. 4,111,249, assigned to the assignee the present invention. The tire of the present invention is in the class of banded tires set forth in the aforementioned patent to Edward G. Markow, which is incorporated herein by reference. A factor in the design of banded run-flat tires that affects the handling of the vehicle on which the tires are mounted is the bending stiffness of the band across the tire with respect to the bending stiffness circumferentially. performance of a banded run-flat tire can be improved in a significant manner if the band is constructed such that its bending stiffness in a lateral direction across the band is substantially less than the bending stiffness circumferentially. Description Of The Prior Art The present invention relates to a banded radial runflat pneumatic tire having a transversely segmented band. In the prior art, banded radial run-flat tires are disclosed in the Markow patent, U.S. No. 4,111,249, referenced previously herein. Unlike the transversely segmented bands of the present invention, that Markow patent teaches a solid unsegmented band having a width substantially spanning the width of the crown of the tire. In the prior art, also, Arthur H. Marks, in U.S. patent No. 840,503, teaches a run-flat tire having one or more flat, comparatively heavy metal rings, preferably of steel, embedded in the tire crown. In Marks, however, the object is to produce a tire that has a practically rigid tread such that there is little or no flattening of the tire at the point of contact witch the ground. A rigid tire thus is not a run-flat tire-of a class in which a comparatively thin band is employed in the crown of the tire, the resilient thin band being supported and stabilizssd by a multiplicity of radial spoke-like elements in the sidewalls of the tire. Further, there is nothing disclosed in Marks that teaches a segmented band having a bending stiffness circumferentially that is considerably greater than the bending stiffness laterally across the tire. Because of the mentioned consideration the tire of Marks would be totally unacceptable for present day use because of ride, handling, and service life deficiences inherent in a tire provided with a heavy, rigid metal band in its crown. Summary Of The Invention This invention is a banded radial run-flat pneumatic tire having a transversely segmented band. The operating performance of a banded run-flat tire is improved if the band is designed so that its bending stiffness in the circumferential direction is in the order of approximately 1000 times as great as its bending stiffness transversely across the width of the band. The band can be segmented into annular side-by-side hooplike coaxiai band elements either of the same or of different diameters. An elastomer bonded between adjoining circumferential edges of the band elements connects them for cooperative association in operation. The elasticity of the elastomer and the spacing between the band elements are selected to give the band its desired operating characteristics. It is thus a principal object of the invention to provide a banded run-flat radial pneumatic tire having a segmented band such that the control, handling, and service life characteristics of the tire are significantly improved. It is a further object of the invention to provide a banded run-flat radial tire in which lateral bending stresses induced by road surface anomalies such as bumps, holes, rocks, and the like, are reduced and band fatigue life is significantli enhanced. Yet another object of the invention is to provide a banded run-flat radial tire having a segmented band such that a multi-step failure sequence is provided for safety. A still further object of the invention is to provide a banded run-flat radial tire having a segmented band in which it is possible by using segments of different diameters to accommodate for tread curvature without the requirement for the crowning of individual band segments or elements. A yet further object of the invention is to provide a banded run-flat radial tire having a segmented band whose design is compatible with conventional tire making processes and equipment and with conventional servicing and maintenance equipment and procedures. Other objects and advantages will become apparent from a reading of the Specification and a study of the accompanying drawings. Description Of The Drawings For the purpose of illustrating the invention, there is shown in the drawings the forms which are presently preferred; however, it should be understood that the invention is not necessarily limited to the precise arrangements and instrumentalities here shown. Fig. 1 is a cross-sectional view of an embodiment of the tire of the invention; and Fig. 2 is a cross-sectional view of a further embodiment of the tire of the invention. Description Of The Preferred Embodiments Having more particular reference to the drawings, Fig. 1 illustrates an embodiment of the tire 10 of the invention. Tire 10 comprises a carcass or casing 12 having an outer peripheral tread portion 14 in the crown 16 of the casing and sidewalls 18 extending from either side of the crown to beads 20 in the radially inside peripheral regions of the sidewalls. Treads 22 in any desired pattern can be incised in the tread portion 14 of the tire casing. Beads 20, which can be reinforced with the usual annular cords or wires 24, are adapted to seat in the usual manner in an airtight relationship in the rim of a wheel (not shown) upon which the tire will be mounted for operation. The sidewalls 18 of the casing are reinforced by the usual known weftiess radial plies or elements 26 of radial tires. Radial elements 26 can be fabricated out of steel wires or suitable textile fibers as is well known in the art. Located in the crown of the radial tire just described underlying the tread thereof is an annular com pression element or band 28. Band 28 is reinforced and stabilized by the radial elements 26 in the sidewalls 18 to give tire 10 its run-flat capabilities. As stated previously herein, the performance of a banded run-flat radial tire is improved if the band is designed such that its bending stiffness in the hoopwise circumferential direction is' significantly, up to a 1000 times, as great as its bending stiffness in the lateral direction across the width of the band. Bending stiffness herein is defined as the product of the bending modulus of elasticity E and section moment of inertia Z. h latter quantity is arbitrarily derived as will be described in further detail herein. In this invention, the desired bending,stiffness ratio of the band transverse its width with respect to the hcopwise direction is obtained by transversely segmenting the band 28. Thus, the band has a number, preferably three, side-by-side band elements 30 connected by an elastomer 32. To achieve the desired 1000: 1 #I ratio, the spacing between the band elements 30 is tailored in direct proportion to the stiffness of the elastomer 32. In a typical design of a tire provided with a segmented band in accordance with the teachings of the invention, using a FR 70-14 radial tire with a three-segment fiberglas/epoxy band and a tire rubber elastomer 32, the hoopwise EI was 20,837 lb-inj and the equivalent lateral EI was approximately 20 lb-in2. In the design of the band, hoopwise bending stiffness is expressed by multiplying the bending modulus of elasticity E of the composite from which the band is made by the total section of inertia I of all the band elements or segments, ignoring the bending stiffness of the elastomer. For an existing band, the E of its composite material can be determined by a three-point bending test on a laboratory specimen cut from the band. It will be appreciated that this specimen will be standard except for its curvature. Lateral bending stiffness, for the purposes of this design, is an arbitrarily derived EI product for a uniform beam whose maximum bending deflection is equivalent to that of an actual non-uniform composite/elastomer beam consisting of a unit-width slice across the band. For an existing band, such a slice can be tested by simply supporting it at its ends and measuring its maximum deflection under load. To avoid concentrate loads on the elastomer, the test specimen should be loaded uniformly. Prom the known loading, deflection, and beam length, a uniform beam EI can be calculated by the standard formula: EMI6.1 where w 5 load per inch L P length between support 8 = deflection at center For a proposed design where no sample exists, a unit idth lateral slice can be described as a beam of non-uniform section, assigning handbook values of E to the primary material and the elastomer of the band respectively. Using the more com; plex handbook formula for a non-uniform beam with a uniformly distributed load, the maximum deflection can be calculated. This will then allow the equivalent uniform beam EI to be calculated as set forth above. In the Fig. 1 embodiment 10 of the tire of the invention a segmented band 28 having side-by-side band elements of equal diameter is used. In the further embodiment illustrated in Fight 12 the tire 10 has a band 32 that is segmented into band elements 34 , 36, and 38, with the intermediate band element 36 having a greater diameter than the band elements 34 and 38 on either side of it. A segmenting of the band into three band elements is preferred but, of course, the band can be segmented into a different number of segments to meet specific requirements. To substantially eliminate the possibility that a puncturing object will penetrate the band 32 through the elastomer 40 connecting the band elements, the adjoining edges of those elements can be overlapped. Thus, circumferential edges 42 and 44 of band element 36 can overlap circumferential edges 46 and 48 of band elements 34 and 38 respectively. As shown, the radially inside surface¯df band element 36 at edges 42 and 44 is bevelled to match bevels ,#n the radially outside surfaces of band elements 34 and 38 at the radiallyoutside their edges 46 and 48. With the exception that the elements of the bind are not of equal diameters, tire 10' is substantially identical to the tire 10 embodiment of the invention illustrated in Fig. i. The two embodiments have the same casing, sidewalls, tread portion radial elements, and the like. In the interests of brevity, a detailed description thereof thus will not be given. Although shown and described in what are believed to be the most practical and preferred embodiments, it is apparent that departures from the specific methods and designs described and shown will suggest themselves to those skilled in the art and may be made without departing from the spirit and scope of the invention. We, therefore, do not wish to restrict ourselves tq the particular constructions described and illustrated, but desire to avail ourselves of all modifications that may fall within the scope of the appended claims.

Claims: CLAIMS 1. A banded radial run-flat tire comprising a resilient annular band in the crown region of said tire, said band being reinforced and stabilized by a multiplicity of radial elements in the tire sidewalls, said band being transversely segmented into a number of operatively associated coaxial band elements such that the bending stiffness of said band circumferentially with respect to the lateral bending stiffness transversely across said band are varied to enhance the fatigue life thereof by reducing the lateral stresses thereon. 2. The run-flat tire according to claim 1 wherein the bending stiffness of said band is defined as the product of the bending modulus of elasticity and section moment of inertia and wherein said bending stiffness circumferentially of said band approximately 1000 times as great as its bending stiffness transversely. 3. The run-flat tire according to claim 1 wherein the band comprises at least two resilient coaxial annular hoop-like band elements having identical diameters spaced side-by-side with an elastomer therebetween such that said band elements are operatively associated one with the other. 4. The run-flat tire according to claim 1 wherein the band comprises at least two resilient coaxial annular hoop-like band elements having different diameters spaced side-by-side with an elastomer therebetween such that said band elements are operatively associated one with the other. 5. The run-flat tire according to claim 4 wherein the circumferential edges of the band elements of greater diameter extend transversely beyond the circumferential edges of the band elements of lesser diameter. 6. The run-flat tire according to claim 5 wherein the circumferential edges of the radially outer surfaces of the band elements of smaller diameter and the circumferential edges of the radially inner surfaces of the band elements of larger diameter are matchingly bevelled. 7. The run-flat tire according to claim 3 wherein the lateral stiffness of the band is established by the hardness of the elastomer and the spacing between the band elements.

Inventors: KOPSCO, M. ALAN, MARKOW, EDWARD G.
Applicants: GRUMMAN AEROSPACE CORPORATION
Application year: 1983
Main classification: B60C9
IPC codes: B60C17, B60C9