This invention relates to tyre in tyre systems in which a wheel is provided with an outer ground engaging tyre mounted on a rim of the wheel and an inner inflatable member is mounted on the rim inside the outer tyre, the wheel rim having a first inflation valve mounted on the rim to introduce air into and release air from the inner inflatable member, and a second inflation valve mounted on the rim for introducing air into and releasing air from the interior of the ground engaging tyre external to the inner inflatable member.

Such tyre in tyre systems are well known (see, for example, US Patent Publication No. US/2005/0279160) as a convenient arrangement to allow the tyre pressures of large tyres, such as those used on agricultural tractors, to be relatively easily changed between the relatively low pressures of say 0.8 bar used when undertaking field work to the higher pressures of say 2 bar used on road work. These systems speed up the changing of the effective tyre pressure as often only the pressure of the volume external to the inner inflatable member needs to be changed to achieve the required effective tyre pressure. This significantly reduces the volume of air which must be pumped in or vented.

The ability to relatively easily and speedily change between field and road pressures is becoming increasingly important as it is necessary to operate the tractor as economically and safely as possible which requires the use of the appropriate tyre pressure at all times. Existing tyre in tyre systems can be relatively expensive to implement as they may require the use of non standard wheel rims.

It is an object of the present invention to provide a wheel with a tyre in tyre system which is relatively cheap to implement and which can be used on a standard wheel rim. Thus according to the present invention there is provided a wheel provided with a tyre in tyre installation in which an outer ground engaging tyre is mounted on a rim of the wheel and an inner inflatable member is mounted on the rim inside the outer tyre, the wheel rim having a first inflation means mounted on the rim to introduce air into and release air from the inner inflatable member, and a second inflation means mounted on the rim for introducing air into and releasing air from the interior of the ground engaging tyre external to the inner inflatable member, the second inflation means being provided with guard means to ensure that air can at all times enter and leave the interior of the ground engaging tyre via an inner end of the second inflation means, the guard means including one or more radially extending bores or formations formed in the inner end of the second inflation means or a component mounted thereon through which air can enter or leave the ground engaging tyre.

The second inflation means may comprise an inflation valve having a support body for sealing engagement in a valve hole provided in a rim of the wheel, the support body having an axially extending internal bore to receive the valve and a head portion designed to be located within the ground engaging tyre, the head portion including the radially extending bores or formations which communicate with the axially extending internal bore.

The second inflation means valve may comprise an inflation valve the inner end of which is provided with a separate head portion which includes the radially extending bores or formations and which is secured to the inner end of the inflation valve so that the radially extending bores or formations communicate with an axially extending bore in the valve.

The head portion or separate head portion of the inflation valve may be dome shaped.

The valve support body may include a sealing groove for snap-in sealing engagement with the valve hole.

The valve support body may alternatively be held within the valve hole by a nut which engages a thread on the exterior of the support body and is sealed to the rim by a sealing member clamped to the rim by the nut. Where a separate head portion is provided and a nut attachment of the valve is used, the separate head portion may also provide the sealing member for clamping against the rim by the nut.

The guard means may comprise a cover which extends over the inner end of the second inflation means and which holds the inner inflatable member away from the inner end of the second inflation means and has openings in the sides of the cover which allow air to enter or leave the ground engaging tyre from the second inflation means.

The invention also provides a tyre inflation valve support body for supporting an associated tyre inflation valve in a sealed relationship in a wheel rim mounting hole, the support body having an axially extending internal bore to receive the valve, an external sealing formation for sealing with the rim mounting hole, and an inner end portion designed to be located within the associated tyre when the valve is located in the rim mounting hole, the inner end portion having one or more generally radially extending bores or formations so that air can pass through the valve along the axially extending bore and through said radially extending bores or formations.

There is also provided an attachment for a tyre inflation valve, the attachment having a domed head portion including radially extending bores or formations which communicate with an internal bore in the head portion which receives an inner end tyre inflation valve to allow air to pass to and from an associated valve retained in the internal bore via the radially expanding bores or formations.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:_

Figure 1 shows a section through a wheel having a tyre in tyre installation in accordance with the present invention;

Figure 2 shows a standardized valve with snap-in fastening to an associated rim; Figure 3 shows a standardized valve with a sealing washer and nut fastening to an associated rim;

Figure 4 shows a section of the wheel of Figure 1 with the standardised snap-in valve of Figure 2 with the guard means of the present invention;

Figure 5 shows a new valve design including the guard means of the present invention;

Figure 5A shows the design of Figure 5 with the air passages emerging through the underneath of a domed shaped body;

Figure 6 shows the valve of figure 5 mounted on an associated wheel;

Figure 7 shows the standardised snap-in valve of Figure 2 fitted with a separate inner head portion which includes the guard means of the present invention;

Figure 8 shows the standardised nut fastened valve of Figure 3 in which a sealing ring is replaced by a an inner head portion which includes the guard means of the present invention;

Figure 9 shows the standardised snap-in valve of Figure 2 provided with a guard means in the form of a cover which extends over the inner end of the valve, and

Figure 10 shows the standardised nut fastened valve of Figure 3 provided with a guard means in the form of a cover which extends over the inner end of the valve.

Referring to the drawings, a tractor wheel 10 has a rim 1 1 and a disc 12. A ground engaging tyre 13 is mounted on the rim and an inner inflatable member 14 is mounted inside tyre 13 in the well of the rim. A first inflation valve 15 is provided to introduce air into and release air from within the inner inflatable member 14 and a second inflation valve 16 is provided to introduce air into and release air from within the interior of the ground engaging tyre external to the inner inflation member. This is a so-called tyre in tyre installation which is a convenient arrangement to allow the tyre pressures of large tyres, such as those used on agricultural tractors, to be relatively easily changed between the relatively low pressures of say 0.8 bar used when undertaking field work to the higher pressures of say 2 bar used on road work. These tyre in tyre arrangements speed up the changing of the effective tyre pressure as it is often only necessary to change the pressure of the volume external to the inner inflatable member in order to achieve the desired operating pressure which significantly reduces the volume of air which must be pumped in or vented from within the ground engaging tyre.

Figure 2 shows a standardized valve 20 with a snap-in function designed with a valve cap 21, a valve core 22, a valve body 23 and an outer rubber sealing part rubber 24 with a sna -in groove 25 for mounting the valve on the rim 1 1. This valve is mounted on the rim from the inside of the rim in the conventional manner.

Fig. 3 shows a standardized valve 30 with screw on nut attachment function. The valve has a valve cap 31, a valve core 32, a valve core housing 33, a valve body 34, a nut 35, a washer 36 and a sealing ring 37. The valve is mounting on the rim by inserting the sealing ring 37 from inside the rim and the valve body 34 is then inserted through the sealing ring 37 from within the rim. The valve is secured on the rim using the washer 36 and nut 35 which are applied from outside the rim.

Because air must flow in both directions through the valves 20 and 30 the normal check valve built into such valves is not necessary.

The standard valve shown in figure 2 is preferred for use as the second inflation valve 16 of the present invention because the rubber part 24 with the snap in groove 25 allows the valve to move in the event of a collision.

The first inflation valve 15 is directly vulcanised into the inner inflatable member 14 as shown, for example, in Figure 6.

Figure 4 shows a standardized valve 20 according to Figure 2 with guard means in accordance with the present invention in the form of radially extending bores 40 through which air can enter of leave the volume controlled by valve 20 as indicated by arrows X in Figure 4. Radial bores 40 communicate with the remainder of valve 20 via axial bore 41 which may also extend at 42 through the inner end of the valve part 24. As can be seen from Figure 4, the flow of air through bores 40 is ensured even if the inner inflatable member contacts the end of valve portion 24.

Figure 5 shows a new valve 50 according the present invention which consists of a standard valve 20 according Figure 2 in which the rubber part 24 with snap-in groove 25 is replaced by a valve part 51 which is dome shaped at 53 and which includes radial bores 52 which communicate with the associated valve 20... Figure 6 shows the new valve 50 in its operational position in the wheel rim.

Figure 5A shows the valve 50 of Figure 5 with the bores 52 emerging through the underneath surface 51 a of part 51. This provides a construction in which the blocking of bores 52 is even less likely.

Figure 7 shows a standardized valve 20 according Figure 2 having a separate head portion 60 with radial bores 61 which is mounted on the inner end of valve portion 24 by any suitable means such as screws, glue, pressing, curing etc. Arrows X again show the air flow paths.

Figure 8 shows a standardized valve 30 according Figure 3 in which the sealing ring 37 is replaced through a part 71 of a dome shaped head portion 70 which includes radial bores 72 to provide the air flow shown again by arrows X. This arrangement is mounted on the rim by inserting the part 71 of head portion 70 through the hole in the rim from within the rim and then inserting the valve through the part 71 via the opening 73 in the inner end of the head portion 70.

Figure 9 shows a standardized valve 20 according to Figure 2 provided with a guard means in the form of a cover which extends over the inner end 26 of the second valve 20 and which holds the inner inflatable member 14 away from the inner end of the second valve and has openings 81 in the sides of the cover which allow air to enter or leave the ground engaging tyre from the valve 20. The cover is fastened to the rim by screws, glue, welding etc. The valve 20 can be mounted on the rim via the hole 81a in the cover 80.

Figure 10 shows a standardized valve 30 according to Figure 3 with the same cover 80 as described in Figure 9.

Although the invention has been described above in relation to arrangements in which first and second inflation valves 15 and 16 mounted on or adjacent the rim 1 1 are used to control the admission and release of air from within the inner inflatable member 14 and tyre 13 respectively, one or both of these valves may be mounted remotely from the rim 11 (e.g. on the associated wheel disc 12) with an air pipe extending from the remote inflation valve into the interior of the member 14 and/or tyre 13.

In such an arrangement, the various guard means described above involving radial bores or other formations or covers may be used to protect the entry of air from the end of the associated air pipe into the member 14 and/or the tyre 13.