GB2329160A

GB2329160A - Accommodating pressure loss in tyre and wheel assemblies

Info

Publication number: GB2329160A
Application number: GB9719439A
Authority: GB
Inventors: Peter Robert Marriott
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 1997-09-13
Filing date: 1997-09-13
Publication date: 1999-03-17
Anticipated expiration: 2017-09-13
Also published as: GB9719439D0; GB2329160B

Abstract

In an assembly comprising a pneumatic tyre on a wheelrim, sensing means (26) are provided to detect pressure loss from the tyre and cause expansion initiation means (27) to actuate expansion means (25) to initiate expansion of an expandable member (24) to cause it to contact at least one of the tyre beads in order to retain it in position on the wheelrim bead seat. The sensing means may comprise a pressure detector to detect rapid inflation pressure loss and the expandable member may be an airbag. A method of retaining the tyre assembled on a wheelrim is also claimed.

Description

IMPROVEMENTS TO TYRE AND WHEEL ASSEMBLIES The present invention relates to improvements to an assembly of a pneumatic tyre on a wheelrim and in particular to improving the safety of such an assembly in the event of sudden loss of internal inflation pressure from the tyre.

In a conventional assembly of a tyre 1 on a wheelrim 2, as shown in Figure 1, the scheduled internal pressure within the tyre serves to tension the tyre carcass to provide load support and to keep the tyre beads 3 spaced apart and firmly seated on the inwardly tapered bead seats 4 and against the flange 5 of the wheelrim. Axially between the bead seats of the wheelrim there is a wheel well 6 which is provided to assist in fitting the tyre to the wheelrim.

In the event of a partial or complete loss of internal inflation pressure from the tyre during use, sideways forces acting on the tyre such as occur in cornering may move the tyre beads from their respective bead seats on the wheelrim affecting the control and safety of the vehicle.

Furthermore there is grave danger of one or both beads falling into the wheelrim well 6 giving rise to complete separation of tyre and wheelrim and thereby the most dangerous situation wherein the wheelrim flange comes into contact with the road surface.

It is therefore an object of the present invention to improve the safety of a pneumatic tyre and wheel assembly by preventing movement of the tyre beads in the event of a sudden loss of inflation pressure from the tyre.

According to one aspect of the present invention there is provided an assembly of a pneumatic tyre on a wheelrim, the tyre having spaced apart beads located on bead seats on the wheelrim, characterised by sensing means to detect a deflated tyre, an expandable member disposed axially between the tyre beads, expansion means to expand the expansion member, expansion initiation means to initiate expansion of the expandable member when a deflated tyre is detected, the expandable member being expandable in at least the axial direction to contact at least one of the tyre beads only in order to retain it in position on the wheelrim bead seat.

Further aspects of the invention will become apparent from the following description, by way of example only, of one embodiment and in conjunction with the following diagrammatic drawings in which: Figure 1 shows an axial cross-section of a conventional pneumatic tyre and wheelrim; Figure 2 shows an axial cross-section of an assembly according to the present invention including an expandable member in an unexpanded state; Figure 3 shows a part-circumferential section of the assembly of Figure 2 taken along plane X-X'; and Figure 4 shows a cross-section of the embodiment of Figures 2 and 3 in the condition where the tyre is deflated and the expandable member is fully expanded.

The assembly according to the present invention shows in Figure 2 comprises a tyre 21 mounted on a wheelrim 22 having a wheelrim well 23. Within the wheelrim well 23 is disposed an expandable member 24 including expansion means 25 contained within the expandable member, and sensing means 26 for detecting a loss of internal inflation pressure from the tyre.

In the unexpanded condition the expandable member, expansion means and sensing means lie radially entirely within the wheelrim well so that they do not interfere with assembly of the tyre onto the wheelrim.

Whilst the expandable member 24 may extend circumferentially part-way around the wheelrim well preferably it extends around the whole periphery of the wheelrim. Shown in Figure 3 is a sectional view taken in the direction X-X' in Figure 2 showing the expandable member 24 disposed within the wheelrim well 23.

The expandable member 24 in the embodiment comprises a torroidally-shaped closed airbag. The expansion means 25 may comprise rapid gas generation by explosion as is common in the automotive usage of airbag technology. Such an explosive expansion is preferable as the expansion of the airbag is achieved in a very short time period.

The sensing means may comprise for example means for detecting rapid inflation pressure loss from the tyre. In this embodiment one such means being an electronic pressure detector 26 is shown which is operatively connected to expansion initiation means 27 mounted on the expansion means 25.

Where the sensing means is a pressure loss sensor however it should not cause expansion when the tyre is deliberately deflated such as would occur when the tyre is being demounted from the wheelrim.

As will be apparent the sensing means and expansion initiation means may be combined into one unit which may also be combined with the expansion means.

In implementing the method of the invention in response to the detection of a deflated tyre by any suitable means, the expansion means 25 within the expandable member 23 is activated to expand the expandable member 24 in at least the axial direction and to contact and retain in place at least one tyre bead. In a preferred embodiment shown in Figure 4 the expandable member expands axially to contact and hold both beads in place.

According to the above-described method and assembly the proper seating of the pneumatic tyre on the wheelrim can be assured even when the inflation medium is partially or wholly lost thus retaining maximum control of the vehicle for the driver. The various components of the assembly can be made very small to fit within the well of the conventional wheelrim so that they do not interfere with fitting or normal operation of the tyre on the wheelrim.

Claims

1. An assembly of a pneumatic tyre on a wheelrim, the tyre having spaced apart beads located on bead seats on the wheelrim, characterised by sensing means to detect a deflated tyre, an expandable member (24) disposed axially between the tyre beads, expansion means (25) to expand the expansion member (24), expansion initiation means (26) to initiate expansion of the expandable member (24) when a deflated tyre is detected, the expandable member (24) being expandable in at least the axial direction to contact at least one of the tyre beads only in order to retain it in position on the wheelrim bead seat.

2. A tyre and wheelrim assembly according to claim 1, wherein the expandable member contacts both tyre beads.

3. A tyre and wheelrim assembly according to either claim 1 or 2, wherein the expandable member 11 is provided between the tyre beads around the whole circumferential periphery of the tyre beads.

4. A tyre and wheelrim assembly according to any of claims 1 to 3, wherein the sensing means comprises a pressure detector to detect rapid inflation pressure loss.

5. A tyre and wheelrim assembly according to either claim 1 or 2, wherein the expandable member is an explosive airbag inflated by release of a gas.

6. A tyre and wheelrim assembly according to any of claims 1 to 4, wherein the expandable member is fixed and retained in the well of the wheelrim.

7. A method of retaining a tyre assembled on a wheelrim during use of the assembly on a moving vehicle comprising detecting the loss of internal inflation pressure from the tyre and when detected initiating expansion of an expandable member (11) to contact at least one bead of the tyre so that the bead is retained on its normal bead seat on the wheelrim.

8. A method according to either claim 7 or 8, comprising operating an explosive airbag as an expandable member.

8. A method of retaining a tyre assembled onto a wheelrim according to claim 1, comprising the step of expanding the expandable member to contact and hold both beads on their normal bead seats.