GB1577899A

GB1577899A - Inner tube assembly for run-flat tyres

Info

Publication number: GB1577899A
Application number: GB919877A
Authority: GB
Original assignee: UNIROYAL
Current assignee: UNIROYAL
Priority date: 1976-03-04
Filing date: 1977-03-04
Publication date: 1980-10-29
Also published as: DE2708868A1; AU2287377A; JPS52118707A; FR2342858B2; CA1045964A; BE852066R; FR2342858A2; BR7701334A

Description

(54) INNER TUBE ASSEMBLY FOR RUN-FLAT TIRES (71) We UNIROYAL, of Clairoix, Oise, France, a corporation organised and existing under the laws of France, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to an inner tube assembly for a pneumatic tire, and has for its objective the provision of an assembly that, when mounted in a tire will give that tire a "run-flat" capability and will hold the tire beads against the wheel rim flanges.

Our co-pending application No. 29506/76 (Serial No. 1 561 701) describes and claims an inner tube assembly for a pneumatic tire comprising an annular flexible primary tube designed to lie axially between and in contact with the beads of the tire when the assembly is mounted in the tire, a primary valve connected to and communicating with the interior of said primary tube, secondary inflatable means having a radially inner wall which radially surrounds the radially outer wall of said primary tube, secondary valve means interconnecting the interiors of said primary tube and said secondary inflatable means, and a substantially inextensible flexible annular band extending circumferentially around the radially outer wall of said primary tube for limiting the radial expansion of said primary tube upon inflation thereof over at least a portion of the axial extent of said primary tube whereby said primary tube expands axially to bear against the beads of the tire, said secondary valve means remaining open and intercommunicating the interiors of said primary tube and said secondary inflatable means for as long as there remains an equilibrium of pressure therebetween, and said secondary valve means including closure means for pneumatically isolating the interiors of said primary tube and said secondary inflatable means from one another when there occurs a pressure drop in said secondary inflatable means relative to said primary tube.

In order to inflate such a pneumatic tire all that is required is to feed compressed air through the primary valve (which may be conventional) of the primary tube, thereby bringing about the simultaneous inflation of the primary tube and inflatable means. Conversely, for the purpose of deflating the pneumatic tire, all that is needed is to push down manually the inside pin of the conventional primary valve, thereby permitting the air to escape from the primary tube. The air in the secondary inflatable means will simultaneously escape into and thence out of the first inner tube via the secondary valve means.

In the modification to which the present application relates the annular band is apertured and extends axially from sidewall to sidewall across at least the full internal width of the inflated tire at the radial location of the band when fitted in the tire. This use of a full axial width band allows the use, for the primary tube, of a simple non-reinforced ordinary inner tube material that is preferably elastically extensible, such as, for instance, a pneumatic tire inner tube for a motorcycle wheel or the like. The annular band, which is preferably removable has an inside diameter that is substantially equal to the maximum specified outside diameter that the primary tube is to define in its standard inflated mounted and operating configuration. The band acts as a hoop or collar that retains the inner primary tube in a specifified maximum diametral condition annularly spaced from the inner crown region of the tire it is to be disposed into. The latter said annular space is filled by a secondary inflatable means that is separated from the primary tube via the annular band.

The annular band forms in this way a partitioning wall providing a respective radially external bearing surface for the primary inner tube and a radially internal bearing surface for the secondary inflatable means, the axial extent or width of the said band being at least equal to the span of the internal space of the pneumatic tire in its inflated operating configuration at the site that the band is to be employed. The aforemenlioned secondary valve means that interconnect the primary tube to the secondary inflatable means project through the aperture or apertures in the band.

The aforesaid band may suitably be made of a synthetic plastics material such as, preferably, polyurethane, whose hardness may be selected within wide limits, for instance between a Shore A hardness of 30 and 90". Alternatively the band may be made of synthetic rubber or of a thermoplastic synthetic elastomer known under the trademark designation "UNIROYAL TPR", a material which has certain of the properties of a vulcanized rubber and, in particular, high heat resistance. The band may be made by injection molding, in particular under pressure.

Preferably, said secondary valve means includes a body extending through an aperture in said band, said body being attached at one end thereof to said primary tube and at the other end thereof to said secondary inflatable means.

Although ordinary inner tube material has been described as being suitable for the extensible primary tube restrained by the flexible annular band, the primary inner tube may alternatively be made by, for example, injection molding, from a thermoplastic material selected from among the group of substances comprising in particular plasticized polyvinyl chloride, a polyamide, polypropylene, polyurethane, a plastisol constituted by a vinyl component in an aqueous emulsion, or by a colloidal dispersion of a vinyl resin in a plasticizing solvent. It is in particular advantageous to use a vinyl plastisol of the type ordinarily used for the manufacture of beach play-balls or the like. This arrangement also offers the im portant advantage of substantially reducing the manufacturing cost of the primary inner tube.

The present invention will be better under stood from the following detailed description of a particular example thereof, taken in conjunction with the accompanying drawings, in wliich : Figure l is an enlarged, fragmentary, verti cal, cross-sectional view of the tube system of the present invention; and Figure 2 is a perspective view of a retainer element used in the system; and Figure 3 is a cross-sectional view of a valve in the open position, which valve may inter connect the primary tube and secondary inflatable means of the system.

Referring now to the drawings, there is illus trated in Figure 1 a pneumatic tire 1 that is mounted on a wheel rim 2. The pneumatic tire 1 is comprised of a crown region 3 surrounded by a tread 4. The sidewalls are rein forced by a pair of annular beads 5, by means of which the tire 1 is mounted on the wheel rim 2. Confined in the tire 1 is a radially internal primary hinder tube 6 and a radially external secondary inflatable means 7.

The wheel rim 2 is preferably, but not necessarily, of the hollow base type comprising a rim bottom 8 in the internal peripheral median or central portion, two external or extreme peripheral lateral edges, for instance upturned edges 9, and two intermediate portions 10 constituting a bead rest and connecting respectively the hollow base 8 of the rim with its edges 9.

The primary inner tube 6 is made from an extensible or dilatable flexible material, in particular a material that is elastically dilatable or extensible when inflated. The tube 6 is surrounded substantially coaxially by an annular retainer element in the form of a band 43 extending axially from one internal tire sidewall to the opposite internal sidewall across the full internal width of the inflated tire at the radial location of the fitted band. The band 43 is interpositioned between the radially internal periphery of the secondary inflatable means 7 and the radially external periphery of the primary inner tube 6.

The retainer band 43 (Figure 2) is provided with circumferentially spaced apart orifices 44, the centers of which are situated in the median equatorial plane of the retainer band 43. The number of such orifices 44 corresponds to the number of valves 13 connecting and intercommunicating the secondary inflatable means 7 with the primary inner tube 6. The valves 13 are of the type which remain open as long as there is a pressure equilibrium in the means 6 and 7, and which close when such equilibrium is lost, for example, when the inflatable means 7 is punctured. Clearly, the valves 13 project through the apertures 44 to intercommunicate the means 6 and 7. The secondary inflatable means 7 may comprise a plurality of discrete, separately inflatable chambers, each of which is associated with a respective one of the valves 13.

The retainer band 43 is substantially cylindrical or hoop-shaped. The opposite ends of the band 43 are each provided with an annular or raised flange 45 that is at least substantially truncated or cone-shaped and divergent. The two flanges 45 are preferably substantially symmetrical with respect to the median equatorial plane of the band 43. The band 43 is made of an inextensible material that is, however, flexible. The provision of the flanges 45 is advantageous in the sense that they embrace and anchor the axially endmost portions of the secondary inflatable means 7.

As illustrated in Figure 1, there remains open two spaces 34 on each side between the pneumatic tire 1, the band 43, and the primary inner tube 6. It is contemplated that such spaces 34 be filled with respective annular elements (not shown). Such elements may be made of rubber or the like appended to, for example, the wall structure of the tube 6. The appended annular elements would, preferably, be contoured to correspond to the contour of the spaces 34, and may be vulcanized or otherwise affixed to the tube 6.

Each valve 13 has a body portion 14 constrained in a respective rubber tube stub 15 that is formed as part of the inner tube 6, the opposite end portion of each valve 13 being affixed to the secondary inflatable means 7.

Pursuant to a preferred form of such an arrangement, each tube stub 15 is associated with its corresponding valve 13 in snap-fit, detachable relation. For example, each tube stub may be provided with an internal annular, collar-like, flange 46, and each corresponding valve 13 may have an associated annular groove 47.

As shown in Figure 3, inside the hollow body 14 (which has substantially the shape of a tubular sleeve traversed on either side by a longitudinal or axial duct or borehole), there is mounted the mechanism of the valve 13, which comprises a hollow element having the shape of a casing 17 made for instance of steel that has been inserted into the hollow body 14 and screwed by a radially external threaded end portion into a threaded portion 18 of the axial borehole of the hollow body 14. Leakproof tightness between the smooth or unthreaded external lateral portion of the sleeve 17 and the corresponding smooth internal wall of the borehole of the hollow element 14 is provided by an annular gasket 19 mounted inside a circumferential groove or throat provided in the surface of the external wall of the sleeve 17. As a variant, the ring 19 could be mounted inside an internal throat of the borehole 20 of the body 14 and be in elastic or compressed contact with the external lateral surface of the sleeve 17.

The terminal surface of the radially internal end of the casing 17 constitutes with the edges of its borehole an annular valve seat 21 against which a plug-like element 22 is capable of axially engaging. The element 22 is shaped somewhat like a dome and is forced back along the radially internal side toward the primary inner tube 6 in its open position by at least one return spring, for instance a helicoidal compression spring 23 coaxially surrounding the stem rod 24 of the valve 22. The spring 23 is braced by its radially external end against the valve head 22, and, with its opposite or radially external end, against an internal annular shoulder 39 of the borehole 25 of the sleeve 17.

The valve stem 24 extends from the valve head 22 in a radially external direction and is movable axially along the bore 25 in the sleeve 17.

The bore 25 is of sufficient diameter such that there remains an annular clearance around the stem 24 up to an opening 40 at the external end of the bore 25. The bore 25 inside the sleeve 17 therefore constitutes the path for the passage of air through the valve 13 in two opposite directions. The valve rod or stem 24 ends at its radially external extremity in an enlarged or head portion 41 that is for instance truncated or cone-shaped. The head portion 41 constitutes an abutment that is engageable with the edge of the opening 40. The portion 41 is preferably provided with one or a plurality of longitudinal grooves 24 allowing for the passage of air when the head portion 41 abuts against the sleeve 1 7.

The spring 23 must be calibrated so that its force is relatively weak so that the valve 22 can close under the effect of an excess of pressure of, for instance, 0.3 atmospheres within the primary inner tube 6 with respect to the pressure prevailing in the secondary inner tube 7 as a result of a puncture of the latter. The valve 13 is in this manner relatively sensitive to variations of the pressure in the secondary inflatable means 7.

As an alternative to the snap-fit connecting means between the secondary inflatable means 7 and the primary inner tube 6, the connecting means can constitute two connectable linkage elements such as an instantaneous pawl type automatic unit with a quick-action locking capacity, or a screw-type assembly with the said elements comprising for instance a male and a female element that can be joined or fitted into one another. The male part can be provided on the secondary inflatable means and the female element can be provided on the primary inner tube.

According to the latter embodiment illustrated in Figure 3, the aforesaid female connecting element is formed by the radially external portion of the body 14 of the valve 13 that is integral with the wall of the primary inner tube 6. That portion is provided with an internally threaded hole or bore 26 that is substantially coaxial with the valve 13 and communicates with its mechanism. The opening 26 is access ible and open on its radially external side while the aforesaid male connecting element is constituted of a metallic hollow metal or similar tubular sleeve 27 made for instance of brass that is externally threaded substantially along its entire length. The sleeve 27 is integral and leakproof with one radially external end of the radially internal wall of the secondary inflatable means.

The sleeve 27 can be screwed completely into the threaded hole 26 extending substan tially coaxially with the inside bore 20 of the valve body 14 as an aligned prolongation of the latter. In the completely screwed-in position, the sleeve 27 abuts with the crosswise terminal face of its radially internal end against an annular packing or gasket 28 placed against an internal shoulder of the opening 26.

The axial borehole 29 of the sleeve 27 communicates with the inside cavity of the secondary inflatable means 7 via an orifice 30 traversing the wall of that means and having a diameter corresponding substantially to that of the borehole 29 of the sleeve 27. The sleeve 27 is preferably embedded, in particular by means of molding, with one extremity in retainer element 43. The retainer element 43 is vulcaniz ed onto the sleeve 27. By the same token, the rubber tip 15 is vulcanized on the body of 14 of the valve 13.

Because of this arrangement, the secondary inflatable means 7 can be readily mounted onto and dismantled from the primary inner tube 6 simply by screwing or unscrewing the sleeve 27.

It will be understood that the components of the valve 13 and the sleeve 27 could be made of plastic instead of metal. The moment the sleeve 27 is screwed completely into the body 14 of the valve 13, the retainer element 43 presses at least against the end cross-face of the radially external end of the valve housing 14 as illustrated in Figure 3. It ought to be noted that the axial bore 20 of the valve housing 14 has a concave truncated intermediate inner wall 32 converging toward the radially internal side and situated substantially at the level of the gasket 19. Thus, by introducing and by screwing the sleeve 17 into the valve housing 14 from the outside through the opening 26, the gasket 19 is gradually tightened against the conical bearing 32. Moreover, the rubber tip 15 covers or overlaps the solid annular portion of the terminal cross-surface of the radially internal end of the valve housing 14 thereby functioning as a protector pad or bead to prevent a possible contact by the hard or metallic internal end of the valve 13 with the radially internal opposite wall of the primary inner tube 6 in the event of a collapse or a flattening of the primary inner tube 6.

WHAT WE CLAIM IS: 1. An inner tube assembly for a pneumatic tire, said assembly comprising an annular flexible primary tube designed to lie axially between and in contact with the beads of the tire when the assembly is mounted in the tire, a primary valve connected to and communicating with the interior of said primary tube, secondary inflatable means having a radially inner wall which radially surrounds the radially outer wall of said primary tube, an apertured inextensible flexible annular band radially interposed between said primary tube and said secondary inflatable means, said band having a width such that it will extend axially from sidewall to sidewall across at least the full internal width of the inflated tire at the radial location of the band when fitted in the tire and being capable of limiting the circumferential expansion of said primary tube upon inflation of the latter via said primary valve, secondary valve means interconnecting the interiors of said primary tube and said secondary inflatable means through the aperture or apertures in the band, said secondary valve means remaining open and intercommunicating the interiors of said primary tube and secondary inflatable means for as long as there remains an equilibrium of pressure therebetween, and said secondary valve means including closure means for pneumatically isolating the interiors of said primary tube and secondary inflatable means from one another when there occurs a pressure drop in said secondary inflatable means relative to said primary tube.

2. An inner tube assembly as claimed in claim 1, in which said secondary valve means includes a body extending through an aperture in said band, said body being attached at one end thereof to said primary tube and at the other end thereof to said secondary inflatable gleans.

3. An inner tube assembly as claimed in claim 1 of claim 2, in which the band includes at each of the axially opposite ends thereof a respective frusto-conical flange.

4. An inner tube assembly as claimed in any one of claims 1 to 3, in which the primary tube means is flexible and extensible.

5. An imier tube assembly as claimed in any one of claims 1 to 3, in which the primary tube means is flexible and substantially inextensible.

6. An inner tube assembly as claimed in any one of the preceding claims, in which the band is provided with a central, circumferential array of apertures corresponding in number to the number of said secondary valve means.

7. An inner tube assembly for a pneumatic tire, substantially as herein described with reference to Figures 1 and 2 or to Figures 1 to 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of the valve 13. Because of this arrangement, the secondary inflatable means 7 can be readily mounted onto and dismantled from the primary inner tube 6 simply by screwing or unscrewing the sleeve 27. It will be understood that the components of the valve 13 and the sleeve 27 could be made of plastic instead of metal. The moment the sleeve 27 is screwed completely into the body 14 of the valve 13, the retainer element 43 presses at least against the end cross-face of the radially external end of the valve housing 14 as illustrated in Figure 3. It ought to be noted that the axial bore 20 of the valve housing 14 has a concave truncated intermediate inner wall 32 converging toward the radially internal side and situated substantially at the level of the gasket 19. Thus, by introducing and by screwing the sleeve 17 into the valve housing 14 from the outside through the opening 26, the gasket 19 is gradually tightened against the conical bearing 32. Moreover, the rubber tip 15 covers or overlaps the solid annular portion of the terminal cross-surface of the radially internal end of the valve housing 14 thereby functioning as a protector pad or bead to prevent a possible contact by the hard or metallic internal end of the valve 13 with the radially internal opposite wall of the primary inner tube 6 in the event of a collapse or a flattening of the primary inner tube 6. WHAT WE CLAIM IS:

1. An inner tube assembly for a pneumatic tire, said assembly comprising an annular flexible primary tube designed to lie axially between and in contact with the beads of the tire when the assembly is mounted in the tire, a primary valve connected to and communicating with the interior of said primary tube, secondary inflatable means having a radially inner wall which radially surrounds the radially outer wall of said primary tube, an apertured inextensible flexible annular band radially interposed between said primary tube and said secondary inflatable means, said band having a width such that it will extend axially from sidewall to sidewall across at least the full internal width of the inflated tire at the radial location of the band when fitted in the tire and being capable of limiting the circumferential expansion of said primary tube upon inflation of the latter via said primary valve, secondary valve means interconnecting the interiors of said primary tube and said secondary inflatable means through the aperture or apertures in the band, said secondary valve means remaining open and intercommunicating the interiors of said primary tube and secondary inflatable means for as long as there remains an equilibrium of pressure therebetween, and said secondary valve means including closure means for pneumatically isolating the interiors of said primary tube and secondary inflatable means from one another when there occurs a pressure drop in said secondary inflatable means relative to said primary tube.