GB2024737A - An inflatable interior support structure for a pneumatic tire - Google Patents

Abstract

An inflatable interior support structure for a pneumatic tire comprises an inflatable extensible elastomeric primary inner tube 3 disposed against the wheel rim. A plurality of internally threaded bushings 12 are spaced circumferentially around the radially outer surface of the inner tube. A relatively inextensible flexible inner tire 4 having beads 20 surrounds the primary inner tube and is inflatable thereby so that the beads bear against the beads of the pneumatic tire. The inner tire has holes radially aligned with the bushings in the inner tube. A secondary inner tube 5 divided into radial compartments fills the space between the inner tire and the pneumatic tire and each compartment has an air inlet duct 15a,b radially aligned with the bushing. A check valve assembly passes through each aligned combination of bushing, inner tube hole and secondary inner tube inlet duct to interconnect the primary inner tube and respective compartment of the secondary inner tube, the check valve being such as to permit inflation of both inner tubes to equilibrium pressure but to prevent deflation of the primary inner tube in the event of deflation of any compartment of the secondary inner tube. <IMAGE>

Description

SPECIFICATION An inflatable interior support structure for a pneumatic tire and an inner tire for such structure This invention relates to an inflatable interior support structure for a pneumatic tire having so called "puncture-proof" qualities and an inner tire for such structure.

As long as there have been pneumatic tires on vehicles, such tires have been subject to puncture by nails and other sharp objects on the roadway and consequent deflation and inoperability. Various solutions have been proposed over the years for so called "puncture-proof" tires, that is, pneumatic tire assemblies which would remain operable to some degree nothwithstanding a puncture. Many of the proposed solutions have involved pneumatic tires or inner tubes compartmentalized in one way or another.

For example, it is already known in the art to provide a "puncture-proof" compound inflatable interior support structure for a pneumatic tire which comprises an annular primary inner tube made of substantially inextensible material disposed adjacent to the rim of the vehicle wheel and provided with an ordinary inflation valve designed to pass through the rim, and a secondary inner tube unit made of elastically extensible material and circumferentially surrounding the primary inner tube, said secondary inner tube being connected with the primary inner tube by at least one check valve which will permit equilibrium pressures in both tubes upon inflation of the system but which will automatically close the moment the pressure in the secondary inner tube unit drops below that prevailing in the primary inner tube.In this prior art structure the secondary inner tube is, as a rule, comprised of a plurality of separate elementary enclosures, bags or balloons arranged circumferentially side by side around the periphery of the primary inner tube and each connected separately therewith by a check valve. Such a compound inflatable interior support system is described in U.S. Patent No. 4,054,169 issued October 18, 1977 to us as co-inventors.

Such an inflatable interior support structure makes it possible to continue travelling in the event of puncture of one or a plurality of the separate elementary enclosures of the secondary inner tube, for the primary inner tube remains inflated by virtue of the automatic closing of the check valves connecting the separate elementary enclosures of the secondary inner tube to the primary inner tube.

Such prior art structures have various drawbacks: -Forming the secondary inner tube from a plurality of separate small balloons or bags circumferentially adjacent to each other results in friction between the adjacent balloons during travel, thereby causing premature impairment of the secondary inner tube through wear and fatigue; thus, the benefit that had been hoped for by using separate small balloons, to wit: the circumferential expansion of the unpunctured balloons adjacent to the punctured balloons so as to occupy substantially the space that available and that has been created by the deflation of the punctured balloons, is offset by a serious drawback, premature deterioration of the inner tube due to wear; -The inflatable compound interior support structures of the aforementioned art are, because of the structure ofthe primary inner tube, not such that a particular structure of that type is adaptable for use on the rims of the same diameter but having a variety of widths; and -The assembly of said prior art structure is relatively difficult with reference to the assembly of the check valves through the walls of the primary and secondary inner tubes.

The novel structural features of the present invention eliminate these drawbacks.

According to the present invention an inflatable interior support structure for a pneumatic tire on a wheel rim comprises an inflatable extensible elastomeric primary inner tube disposed against the axially central, radially exterior surface of the rim, said primary inner tube being provided with a plurality of internally threaded bushings spaced circumferentially along its radially outward surface in the region of its equatorial plane; a relatively inextensible flexible inner tire having beads, said inner tire being disposed radially externally of said primary inner tube and inflatable thereby so that the beads thereof bear against the axially internal surfaces of the beads of the pneumatic tire; said inner tire being provided with a plurality of circumferentially spaced holes corresponding in number and radial alignment to said bushings in said primary inner tube; an extensible elastomeric annular secondary inner tube divided into radial compartments and disposed to fill the space between said inner tire and the pneumatic tire, each said radial compartment being provided with an air inlet duct through its radially inner surface said ducts being circumferentially located to correspond with the radial alignments of the said threaded bushings in the primary inner tube and the said holes in the inner tire; and a plurality of check valve assemblies equal in number to the radial compartments and each connected to and passing through a bushing in said primary inner tube and passing through a radially aligned hole in said inner tube and an inlet duct in said secondary inner tube to provide pneumatic interconnections between said primary inner tube and each such radial compartment of said secondary inner tube, said check valves being such as to permit inflation of both primary and secondary inner tubes to equilibrium pressure but prevent deflation of said primary innertube in the event of deflation of any radial compartment said secondary inner tube.

This structure differs from earlier arrangements in that the primary innertubes has an extensible wall and that, sandwiched between the primary inner tube and the secondary inner tube is an inner tire having a fabric carcass and being flexible but relatively inextensible. The sidewalls of the inner tire encase the primary inner tube and extend to the wheel rim. The radially inward edges of the sidewalls of the inner tire terminate in beads reinforced by bead wires around which the carcass plies of the inner tube are wrapped. The beads are adapted to be fitted onto the wheel rim in such a way that, upon inflation of the structure, the beads of the inner tire are forced into braced contact with the internal surface of the beads of the exterior pneumatic tire supported by the structure.

Preferably the compartments of the secondary inner tube are defined by radial partitions integral with the annular walls of the secondary inner tube so that the entire secondary inner tube is a unitary structure in the form of a hollow, extensible, radiallypartitioned annulus.

Desirably the cords of the carcass plies embedded in the rubber or elastomeric body of the inner tire are disposed along two intersecting directions and at an angle of from 250 to 65" with respect of the equatorial plane of the tire, the angle preferably being 45" in each case.

A single band of tire cord may be used to build the carcass of the inner tire, the central portion of the band being extended between the bead wires of carcass and the two outer portions of band being folded about the bead wires into an overlapping and superimposed position to form a two-ply carcass having a preferred annular relationship of the plies.

Among the advantages of the invention defined above over the prior art is that, because the primary inner tube is extensible and without reinforcing plies of tire cord, it is relatively easy to manufacture.

Another advantage is that the structure of the fabric reinforced and beaded inner tire makes a single compound inflatable interior support structure adaptable to wheel rims of different widths. This is because the structure of the inner tire, while limiting any appreciable radial expansion thereof, permits its side walls and beads to spread laterally under the effect of the pressure of the primary inner tube so its sidewalls and beads are forced into contact with the axially interior faces of the pneumatic tire. In this way the two beads are locked against each other.

The inflated shape of the inner tire depends, of course, upon the width of the rim on which the structure is mounted. But it depends also upon the structure of the tire itself and particularly on the structure and relative angular orientation of the cords in the carcass plies.

The chambered construction of the unitary annular secondary inner tube eliminates the friction and wear previously associated with the use of individual small bags or balloons such structures.

Moreover the structure of this invention leads itself to a greater ease of assembly than structures of the prior art. All that is necessary is to fit the inner tire over the primary inner tube, insert the check valves through the holes in the former and screw them into the integral bushings of the latter. Then the extensible secondary inner tube is stretched over the inner tire and the tip of each check valve is forced into the duct of each corresponding chamber of the secondary inner tube.

The invention also extends to an inner tire for use in the aforesaid support structure, the inner tire comprising a carcass vulcanised within an elastomeric material said carcass two circumferential bead wires and a single band of tire core wrapped around said two wires to form a two-ply carcass, the central portion of the band forming the inner ply and the two outer portions being overlapped to form the outer ply, the cord angle of the band being between 25 and 65 with respect to the equatorial plane of the tire.

In the accompanying drawings which illustrate a preferred form ofthe invention: Figure 1 is a radial sectional view of a vehicle wheel rim on which is mounted a pneumatic tire interially supported by a preferred form of the compound inflatable interior support structure of this invention; Figure 2 is a fragmentary sectional view of the secondary inner tube of the invention; Figure 3 is a sectional view of one of the elements of the secondary inner tube designed to assemble to the check valves of the compound structure, taken prior to its valcaninsation to the rest of the secondary inner tube; Figure 4 is a partially exploded view of one of the check valves of the structure;; Figure 5 is a fragmentary schematic view of the inner tire of the structure showing the preferred angular orientations of the cords comprising the carcass thereof as well as the holes provided therein for assembly of the structure; Figure 6 is a radial schematic cross-section of the carcass plies and bead wires of a preferred form of the inner tire of the invention; and Figure 7 is a fragmentary schematic plan view of the carcass plies of the inner tire as viewed from line 7-7 of Figure 6.

Depicted in Figure lisa pneumatic tire 1 mounted on a wheel rim 2. The other elements depicted in Figure 1 comprise a preferred form of the compound inflatable interior support structure of the invention depicted in an inflated state.

As may be seen particulary in Figure 1 as supplemented by the other views in the drawings, the inflatable interior support structure comprises several majorsubcomponents, namely: an extensible primary inner tube 3 disposed circumferentially against the axially central, radially exterior surface of the wheel rim 2; a relatively inextensible inner tire 4 disposed radially externally of the primary inner tube 2 and inflated thereby so that the beads 19a and 19bthereof bearagainstthe beads la and lh respectively of the pneumatic tire 1; an extensible, radially compartmentalized annular secondary inner tube 5 disposed to fill the space between the inner tire 4 and the pneumatic tire 1; and a plurality of check valve assemblies 9 interconnecting the primary inner tube 3 with each compartment (e.g. 6a) of the secondary inner tube 5, the entire inflatable interior support structure being inflatable through a conventional valve stem 8 extending from the primary inner tube 3 through a hole in the rim 2. The respective structures of each of these subcomponents will be described in order.

The primary inner tube 3 comprises an annular tube of extensible elastomeric material inflatable through the valve stem 8. The radially outermost area 14 of the tube 3 is thickened circumferentially.

Internally threaded bushings 13 are vulcanized into the thickened portion 14 of the tube 3 at regular circumferential intervals, the number of the bushings 13 corresponding to the number of chambers or compartments 6a, 6b, 6c, etc of the secondary inner tu be 5.

The inner tire 4 comprises a carcass 21 of flexible but relatively inextensible tire cord plies vulcanized within a covering of natural or synthetic elastomer 22, the innertire having bead regions or "beads" 19a and 19b and sidewall regions or "sidewalls" 4a and 4b extending from the beads 19a and 19b to the equatorial plane of the inner tire. The carcass 21 is formed by wrapping a plurality of carcass plies of tire cord about a pair of relatively inextensible bead wires 20a and 20b.

As is illustrated in Figure 5, in the usual case the carcass 21 will comprise effectively two plies of tire cord. Ideally the cords in the respective plies will be disposed at angles of 45D and +45 respectively to the equatorial plane 25 of the inner tire so that the cord angles Al and A2 intersect at an angle of approximately 90". Such a condition is optimium because it permits easier shaping of inner tire. Also as may be noted from Figure 5, the inner tire is provided with a series of circumferentially spaced holes 18 corresponding in number and spacing to the number and spacing of the threaded bushings 13 in the primary inner tube 3.For this reason as well it is desirable to maintain approximately a 90" cord intersection angle between the respective carcass plies. It has been found that if the cord angles of the respective plies are excessively small, the hole 18 region of the carcass 21 is weakened because more cords are severed by the holes 18, whereas, if the cord angles are excessively large, the casing is weakened in a circumferential direction. While some latitude of cord angle is permissible, it is recommended that the respective cord angles of the carcass plies fall within the limited of 25 and 65".

Figure 6 and 7 illustrate schematically a preferred form of the carcass of the inner tire in which a single band of tire cord having a bias angle of 45" is used to form both plies of the carcass 21. In this embodiment the central portion 21a of the tire cord band forms the inner carcass ply with the outer portions 21b and 21c are respectively wrapped around the beads 20a and 20b and are overlapped in the crown region d of the inner tire 4 to form the outer carcass ply. Because of the overlap and the 45" bias angle of the tire cord band the hole 18 region of the carcass is reinforced by having additional parallel cords adjacent to the holes 18.

The individual cords of the plies of the carcass 21 may be of any suitable relatively inextensible reinforcement material including, for instance, metal, fiberglass, aliphatic polyamide (e.g. Nylon), aromatic polyamide or aramide (e.g. "Kevlar"), polyester or rayon.

An important feature of the structure of the inner tube 4 is that when inflated by pressure of the primary inner tube 3, its beads 19a and 19b will spread apart until they are forced into locking contact with the beads of the pneumatic tire 1. Thus, a given compound inflatable interior support structure of the invention is inter-changable for use on rims of different widths provided that the rims have the same diameter.

As may be seen in Figure 1 and 2, the secondary inner tube 5 is an extensible elastomeric compart mentalized annulus wherein the annular tube is divided by radial walls (e.g. 7a and 7b) into a number of circumferential compartments (e.g. 6a, 6b, and 6c) corresponding in number and spacing to the holes 18 in the inner tire 4 and the threaded bushings 13 in the primary inner tube 3.In order to provide for pneumatic interconnection of the secondary inner tube5 with the primary inner tube 3 via the plurality of check valves 9, the secondary inner tube 5 is provided internally on the radially interior side of each compartment and centered on the equatorial plane 25 of the tube with a valve connection in the form of a frustroconical elastomeric mass 15 provided with axial duct 15a and an axial valve chamber 1 sub. Such a valve connection in its vulcanized state 15' is depicted in Figure 3, the duct 15'a and the valve chamber 15'b being also shown. In the finished secondary inner tube, the valve connections 15 are vulcanized with the compartmentalised secondary inner tube 5 so that the entirety forms a unitary elastomeric structure.

The plurality of check valve assemblies 9 which interconnect the primary inner tube 3 with the respective chambers 6a,6b, 6c, etc. of the secondary inner tube5 are fractionally conventional spring loaded pneumatic check valves which permit inflation of the chambers of the secondary inner tube to an equilibrium pressure relative to the pressure in the primary inner tube 3, but prevent deflation of the primary inner tube 3 through said check valve when the pressure in any chamber of the secondary inner tube 5 falls below equilibrium pressure due, for example, to a puncture of the secondary inner tube 5.

As may be seen from Figures 1 and 4, each check valve assembly 9 comprises a body 9a containing the functional elements of the valve and having a knurled annular surface 10. Extending from the body 9a is a tubular bayonet tip 9b provided with a plurality of anchoring ribs 11. The tip 9b and the duct 15a of the secondary inner tube are of such relative diameters as to be capable of being force fitted together. The body 9a of the valve and the valve chamber 1 sub of the secondary inner tube are of such relative dimensions that the former may be clearance fitted totally within the latter. In the valve embodiment illustrated, a tubular connected piece 9c constitutes a separate component of the valve assembly 9. The connecting piece 9c is provided with a hexagonal nut portion 17 and two exteriorly threaded portions 24 and 12, the former being desgined to be screwed into the valve body 9a and the latter being designed to be screwed into a threaded bushing 13 of the primary inner tube 3. A sealing gasket 9d compietes the valve assembly 9. It should be appreciated that other functionally equivalent check valve assemblies could be employed, e.g.

the threaded portion 19 of the connecting piece 9c can be an integral part of the valve body 9a.

Further with respect to the fully assembled and inflated structure shown in Figure 1, the relative lengths of the bayonet tip 11 of the valve assembly9 and the duct 15a of the secondary inner tube 5 are such that when the former is fully inserted in the latter the free end of the valve tip is well within the elastomeric mass 15. For this reason, should a compartment, e.g. 6a, of the secondary inner tube 5 become deflated the valve tip 11 will not bear directly against the outer radial wall of the secondary inner tube S.

Claims (12)

1. An inflatable interior support structure for a pneumatic tire mounted on a wheel rim comprising: an inflatable extensible elastomeric primary inner tube disposed against the axially central, radially exterior surface of the rim, said primary inner tube being provided with a plurality of internally threaded bushings spaced circumferentially along its radially outward surface in the region of its equatorial plane; a relatively inextensible flexible inner tire having beads, said inner tire being disposed radially externally of said primary inner tube and inflatable thereby so that the beads thereof bead against the axially internal surfaces of the beads of the pneumatic tire; said innertire being provided with a plurality of circumferentially spaced holes corresponding in number and radial alignmentto said bushings in said primary inner tube; an extensible elastomeric annular secondary inner tube divided into radial compartments and disposed to fill the space between said inner tire and the pneumatic tire, each said radial compartment being provided with an air inlet duct through its radially inner surface said ducts being circumferentially located to correspond with the radial alignments of the said threaded bushings in the primary inner tube and the said holes in the inner tire; and a plurality of check valve assemblies equal in number to the radial compartments and each connected to and passing through a bushing in said primary inner tube and passing through a radially aligned hole in said innertube and an inlet duct in said secondary inner tube to provide pneumatic interconnection between said primary inner tube and each such radial compartment of said secondary innertube, said check valve being such as to permit inflation of both primary and secondary inner tubes to equilibrium pressure but prevent deflation of said primary inner tube in the event of deflation of any radial compartment of said secondary inner tube.

2. A structure according to claim 1 wherein the radially outermost area of the primary inner tube is thickened circumferentially and the threaded bushings are vulcanized into this thickened area at circumferential intervals.

3. A structure according to claim 1 or claim 2 wherein the air inlet duct in each radial compartment of the secondary inner tube passes through an estomeric mass contained therein and vulcanzied to the radially internal wall of said compartment, said mass being of sufficient depth to accomodate internally the check valve assembly without any portion thereof protruding radially outwardly beyond said mass.

4. A structure acording to any one of the preceding claims, wherein the inner tire is comprised of a carcass vulcanized within an elastomeric material, said carcass comprising two circumferential bead wires and an even numbered plurality of plies of tire cord wrapped around both bead wires, the cord angles of adjacent carcass plies intersecting and being from 25 to 65" with respect to the equatorial plane of the inner tire.

5. A structure according to claim 4 in which the carcass of the inner tire comprises two plies of tire cord constituted by a single band of tire cord wrapped around said two bead wires to form a two-ply carcass, the central portion of the band forming the inner ply and the two outer portions being overlapped in the crown region of the inner tire to form the outer ply.

6. A structure according to claim 4 or claim 5 in which the cord angle in each carcass ply is approximately 45 .

7. A structure according to any one of the preceding claims in which the compartments of the secondary inner tube are defined by radial partitions integral with the annular walls of the secondary inner tube.

8. An inflatable interior support structure for a pneumatic tire mounted on a wheel rim, substantially as herein described with reference to the accom panying drawings.

9. The combination of a wheel rim having a pneumatic tire mounted thereon, the tire being supported by an inflatable interior support structure according to any one of the preceding claims.

10. An innertirefora compound inflatable support structure for a pneumatic tire, the inner tire comprising a carcass vulcanized within an elastomeric material said carcass comprising two cir cumferential bead wires and a single band of tire cord wrapped around said two bead wires to form a two-ply carcass, the central portion of the band forming the inner ply and the two outer portions being overlapped to form the outer ply, the angle of the band being between 25 and 65" with respect to the equatorial plane of the inner tire.

11. An inner tire according to claim 10 wherein the cord angle of the band is approximately 459

12. An inner tire fora compound inflatable support structure for a pneumatic tire, the inner tire being substantially as herein described with refer ence to Figues 1,5,6 and 7 of the accompanying drawings.