GB2264270A - A pneumatic tyre insert. - Google Patents

Abstract

In a pneumatic tyre insert 10 an annular base portion 11 matches the rim 14 of a wheel for which it is intended and in use holds a pneumatic tyre 13 against flanges 16 of the wheel rim 14 and an annular, outer peripheral portion 12 is spaced from the inner surface of a tread portion of the tyre. A resilient hoop 21 is moulded within the base portion 11 and an annular groove 24 in the inner peripheral surface of the base portion 11 communicates via passage means 26 extending through the insert 10 with the air space between the insert 10 and the tread portion of the tyre 13. The insert is inserted into the tyre by deforming the insert to a figure-of-eight shape. The base portion 11 is made of rubber and tyre cord material and the outer peripheral portion 12 is made of rubber. <IMAGE>

Description

A PNEUMATIC TYRE INSERT This invention relates to a pneumatic tyre insert which enables a pneumatic tyre to run flat after a puncture, to a pneumatic tyre fitted with such an insert, and to a method of fitting the insert to a pneumatic tyre.

Tyres are either of the solid or pneumatic type. Solid tyres are subject to a maximum speed rating of about 16 km/h due to the fact that heat build up occurs very rapidly in a solid tyre. Pneumatic tyres are vulnerable to punctures particularly when used on rough terrain. It is also known to "in fill" pneumatic tyres to prevent punctures. "In fill" tyres can operate at higher speed ratings than solid tyres and give similar ride characteristics to pneumatic tyres.

However, filling adds significantly to the weight of the tyre and "in fill" tyres are not therefore satisfactory on large vehicles.

There is a requirement for a pneumatic tyre, lighter than an "in fill" tyre, which will run flat after a puncture and which has a good high speed performance including good balance properties when the tyre is in its inflated form.

Accordingly, the present invention in a first aspect provides a pneumatic tyre insert in the form of a moulding and comprising an annular base portion adapted to substantially match the rim of a wheel for which it is intended and to hold a pneumatic tyre in which in use it is inserted against flanges of the wheel rim, an annular, outer peripheral portion which is in use spaced from the inner surface of a tread portion of the tyre, a resilient hoop which is moulded within the base portion and which will return to its circular shape after the insert has undergone deformation to insert it in the tyre, an annular groove in the inner peripheral surface of the base portion, and passage means extending through the insert and communicating with the annular groove to let air into and out of the space between the insert and the tread portion of the tyre.

Preferably, the resilient hoop comprises a central metal core and a helical winding on the core.

In this case, the winding, preferably, extends helically around the core a plurality of times with successive convolutions lying side by side on the core and, preferably, the winding is formed from a single length of wire joined at opposite ends.

Preferably, the base portion of the tyre is made of rubber and tyre cord material and the outer peripheral portion is made entirely or essentially of rubber.

Preferably, the outer peripheral surface of the insert is provided with a tread pattern.

According to a second aspect of the invention, there is provided a pneumatic tyre fitted with an insert according to the first aspect of the invention, the insert being provided within the tyre between the inner ends of the side walls of the tyre and being spaced from the inner surface of the tread portion of the tyre.

According to a third aspect of the invention, there is provided a method of fitting an insert according to the first aspect of the invention into a pneumatic tyre, the method comprising the steps of: (a) deforming the insert to, or substantially to, a figure-of-eight shape, (b) holding the insert in the aforesaid shape while one end of the insert is forced into the tyre, and then (c) forcing the rest of the insert into the tyre.

Preferably, during step (b) the insert is held in the aforesaid shape by a clamp.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional view through one embodiment of a pneumatic tyre insert according to the first aspect of the invention, and shown fitted in a pneumatic tyre mounted on a wheel rim, Figure 2 is a cross-section through the hoop, on an enlarged scale, and Figure 3 is a side view showing part of the hoop, on the same scale as Figure 2 Referring now to the drawing, there is shown therein an insert 10 which has been formed by compression moulding and which comprises an annular base portion 11 and an annular, outer peripheral portion 12.

The insert 10 is shown fitted in a pneumatic tyre 13 mounted on a wheel rim 14. The wheel rim 14 is of the assembled type, comprising two or more parts assembled together around the tyre 13.

The base portion 11 is made of rubber and tyre cord material and the outer peripheral portion 12 is made entirely or essentially of rubber, and typically from high quality natural rubber based stocks which has a low rolling resistance and a low heat build up. The tyre cord material gives the base portion 11 rigidity to hold it on the wheel and is not affected by temperature rises so that it maintains an interference with the tyre at elevated temperature.

The wheel rim 14 has what is commonly referred to in the art as a drop centre profile with a well 15 in the centre and two side flanges 16. The wheel rim 14 could, however, have other profiles, such as a so-called semi drop centre profile or a so-called wide base profile.

The inner peripheral surface 17 of the base portion 11 is shaped to substantially match the profile of the rim 14. The outer peripheral portion 12 of the insert 10 is more resilient than the base portion 11 and has a tread pattern 20 in its outer peripheral surface to help dissipate heat when the tyre 13 runs on the insert 10 in failure mode. The outer peripheral portion 12 has a waisted portion 12a to create an interference fit with the tyre 13 to hold the tyre firmly against the side flanges 16 and a tapering portion 12b which narrows towards the outer peripheral surface of the insert 10 to keep the weight of the insert low. The tapering portion 12b merges with the outer peripheral surface of the insert via a gradually curved portion 12c which gives the insert 10 a low resistance to steering.

A resilient hoop 21 is moulded into the base portion 11 so that when the insert 10 is mounted on the wheel rim 14, the hoop 21 is midway or substantially midway between the sides of the well 15. The hoop 21 keeps the insert 10 firmly in contact with the wheel rim 14 and does not allow the insert to be displaced radially outwards into the tyre 13 under the influence of centrifugal force.

The hoop 21 must also return to its circular shape after the insert 10 has undergone deformation to insert it in the tyre. 13. It must therefore have a high degree of resiliency and it has been found that this can be achieved by providing the hoop 21 with a steel wire core 22 (typically of 5mm diameter) and a helical winding 23 on the core. The winding 23 extends helically around the core a plurality of times with successive convolutions 23a, 23b etc lying side by side on the core 22, and is formed from a single strand of wire (typically of 2mm diameter) joined together at its two ends.

The insert 10 is fitted in the tyre 13 by deforming it to, or substantially to, a figure-of-eight shape and holding it in this shape with a clamp while one end of the insert is forced into the tyre and into engagement with the inner peripheral surface of the tread portion of the tyre. The clamp is then removed and the rest of the insert 10 is forced into the tyre 13. The insert 10 and tyre 13 can then be mounted on a wheel rim 14 by assembly of the wheel rim, when required.

The insert 10 has an annular groove 24 in its inner peripheral surface so that this will communicate with an air inlet/outlet valve 25 on the wheel rim 14 regardless of the angular position of the insert 10 on the rim 14, and at least one, but preferably two or more, passages 26 which extend through the insert 10 and which communicate at their inner ends with the groove 24 to let air into and out of the space between the insert 10 and inner surface of the tread portion of the tyre 13.

Typically, the insert 10 occupies between 30% and 50% of the internal volume of the tyre 13 and, typically, the tyre is capable of speeds of up to about 126km/h when inflated and of speeds of up to about 60km/h when running flat on the insert 10. The tyre is not only capable of high speeds, but also has good balance properties when in its inflated form.

A tyre as described above has particular application on military vehicles, such as armoured personnel carriers, where there may be a need to get away quickly from a dangerous situation.

When used on wheels with a drop centre profile, it has been found that one hoop 21 is sufficient. However, on wheels with other rim profiles, such as wide base type rims, it may be necessary to use two or more hoops 21 in the base portion of the insert.

Claims (12)

1. A pneumatic tyre insert in the form of a moulding and comprising an annular base portion adapted to substantially match the rim of a wheel for which it is intended and to hold a pneumatic tyre in which in use it is inserted against flanges of the wheel rim, an annular, outer peripheral portion which is in use spaced from the inner surface of a tread portion of the tyre, a resilient hoop which is moulded within the base portion and which will return to its circular shape after the insert has undergone deformation to insert it in the tyre, an annular groove in the inner peripheral surface of the base portion, and passage means extending through the insert and communicating with the annular groove to let air into and out of the space between the insert and the tread portion of the tyre.

2. A pneumatic tyre insert as claimed in Claim 1, wherein the resilient hoop comprises a central metal core and a helical winding on the core.

3. A pneumatic tyre insert as claimed in Claim 2, wherein the winding extends helically around the core a plurality of times with successive convolutions lying side by side on the core.

4. A pneumatic tyre insert as claimed in Claim 2 or 3, wherein the winding is formed from a single length of wire joined at opposite ends.

5. A pneumatic tyre insert as claimed in any preceding claim, wherein the base portion of the tyre insert is made of rubber and tyre cord material and the outer peripheral portion is made entirely or essentially of rubber.

6. A pneumatic tyre insert as claimed in any preceding claim, wherein the outer peripheral surface of the insert is provided with a tread pattern.

7. A pneumatic tyre fitted with an insert as claimed in any preceding claim, the insert being provided within the tyre between the inner ends of the side walls of the tyre and being spaced from the inner surface of the tread portion of the tyre.

8. A method of fitting an insert as claimed in any of Claims 1 to 6 into a pneumatic tyre, the method comprising the steps of: (a) deforming the insert to, or substantially to, a figure-of-eight shape, (b) holding the insert in the aforesaid shape while one end of the insert is forced into the tyre, and then (c) forcing the rest of the insert into the tyre.

9. A method as claimed in Claim 8, wherein during step (b) the insert is held in the aforesaid shape by a clamp.

10. A pneumatic tyre insert substantially as hereinbefore described with reference to the accompanying drawings.

11. A pneumatic tyre fitted with an insert substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of fitting an insert as claimed in any of Claims 1 to 6 into a pneumatic tyre, the method being substantially as hereinbefore described.