GB2442811A

GB2442811A - Segmental tyre

Info

Publication number: GB2442811A
Application number: GB0620417A
Authority: GB
Inventors: Donald Sinclair Gillanders
Original assignee: Airboss Ltd
Current assignee: Airboss Ltd
Priority date: 2006-10-14
Filing date: 2006-10-14
Publication date: 2008-04-16
Also published as: WO2008044035A1; GB0620417D0

Abstract

The tyre comprises a plurality of segments 12 secured to a hub 10, at least one of the segments 12 comprising a mounting plate 30 moulded into a polymer material component 12a, the mounting plate 30 having at least one securing component 14 mounted thereon, e.g. welded, wherein at least part of the mounting plate 30 engages the hub 10. The component is a round-headed stud 14 held by a nut16. The component 12a incorporates silica to reduce migration of cuts of slits and can have white material to avoid resulting tyre marks in food or pharmaceutical environments..

Description

Segmental Tyre This invention relates to a segmental tyre.

Segmental tyres are well known and typically comprise a plurality of tyre segments bolted, clamped or otherwise secured to a central hub. Each tyre segment typically includes an inner wall adapted, in use, to engage the hub, an outer wall shaped to define a tread pattern, and interconnecting walls connecting the inner and outer walls to one another. The inner, outer and interconnecting walls are typically formed integrally with one another, and typically together defme a cavity allowing the outer wall to deflect, in use, for example to conform with the surface upon or over which the tyre is driven.

In use, minor damage to a tyre segment, for example a small split or cut, tends to migrate across the segment when the associated wheel is rotated whilst under load.

Such migration may result in sections of the segment becoming significantly weakened or even in sections becoming detached. Under such circumstances the segment may need to be replaced and this causes the vehicle upon which the segmental tyre is used to be taken out of use. Obviously this is undesirable.

A further disadvantage with known segmental tyres is that they tend to leave marks on the surface over which they are driven, and this is undesirable particularly if used in clean environments, for example in which foods or pharmaceuticals are processed or handled.

Another disadvantage with known segmental tyres is that correctly fitting the segments in position is difficult. Typical segments include a threaded stud, a head of which is secured to a plate encapsulated in the rubber or rubber-like material of the segment. When fitting the segment, it is important to ensure that precisely the desired load is applied when tightening a nut onto the stud. The presence of rubber or rubber-like material between the plate and the hub to which the segment is mounted makes this difficult to achieve.

It is an object of the invention to provide a segmental tyre, and a segment for use therein, wherein the disadvantages set out above are overcome.

According to one aspect of the invention there is provided a segmental tyre comprising a plurality of segments secured to a hub, at least one of the segments including a moulded polymer material component moulded from a material including silica.

It has been found that the use of silica in the material reduces the migration of splits and cuts across the segment.

Preferably, the silica makes up approximately 10-20 pphr of the material, conveniently about l6pphr.

The invention also relates to a segment for use in such a tyre.

According to another aspect of the invention there is provided a segmental tyre comprising a plurality of segments secured to a hub, at least one of the segments including a moulded polymer component moulded from a material which is white.

Such an arrangement avoids leaving black marks on surfaces over which the tyre is driven and thus is suitable for use in clean areas including food or pharmaceutical * preparation or handling areas.

The invention also relates to a segment suitable for use in such a tyre.

According to a further aspect of the invention there is provided a segmental tyre comprising a plurality of segments secured to a hub, at least one of the segments comprising a mounting plate moulded into a polymer material component, the mounting plate having at least one securing component mounted thereon, wherein at least part of the mounting plate engages the hub.

Such an arrangement is advantageous in that the tightening load applied thereto can be precisely controlled. Additionally, where the securing components comprise screw-threaded studs, they can be of reduced length.

This invention also relates to a segment suitable for use in such a tyre.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view illustrating part of a segmental tyre; and Figure 2 is a view illustrating one of the segments of the lyre of Figure 1.

The segmented tyre arrangement illustrated diagrammatically in Figures 1 and 2 comprises a hub 10 of generally cylindrical form upon which a plurality of tyre segments 12 are mounted. Each tyre segment 12 comprises a polymer material moulded component 12a from which a stud 14 extends, the studs 14 extending through openings formed in the hub 10 and having screw-threaded nuts 16 mounted thereon to secure the segments 12 to the hub 10. In common with many designs of segmental tyre, the polymer moulded component I 2 of each segment 12 includes an inner wall 18 arranged to engage the outer surface of the hub 10, an outer wall 20 upon or in which treads 22 are formed, the treads 22 engaging, in use, the surface over which the lyre is driven, and interconnecting walls 24 connecting the inner and outer walls 18, 20 to one another. The inner and outer walls 18, 20 and interconnecting walls 24 together define hollows 26 allowing resilient deformation of the component 12, in use.

In accordance with one aspect of the invention, in order to reduce the risk of small slits or cuts propagating along the polymer component l2 of each segment 12, the polymer component 12 is formed from a composition incorporating silica. It has been found that the incorporation of silica into the material tends to resist such migration of splits or cuts, therefore reducing the risk of parts of the component 12 becoming weakened or breaking off. Table I (below) provides details of a preferred composition for the material. However, it will be appreciated that the quantity of silica provided may depart from that set out in Table 1. For example it may fall in the range lO-2Opphr.

TABLE 1

Ingredient ppbr (parts per hundred resin) SMR2O 80 SBR15O2 20 PVI.4 N330 Black 58 Silica 16 Stearic acid 7 Zinc Oxide 5 TMQ 2 6PPD 2 Paraffinwax 3 MBS 80% 1.2 DPG8O% .8 Sulphur 3 Naphthenic oil 8 Total 206. 4 Although the composition set out in Table I is of black form, if desired the composition may be modified to omit the black pigments and instead the moulded component I 2 of the segment 12 will be coloured white. The provision of white treads may be advantageous where the segmental tyre is to be used in a clean environment, for example in an area in which food of pharmaceuticals are prepared or handled, as the use of a tyre of white colour avoids leaving black tyre marks on the surface over which the tyre is driven.

As illustrated in Figure 2, each segment 12 incorporates a plate 30 moulded into the polymer moulded component 12g. Welded to the plate 30 is the screw-threaded stud 14. The shape of the plate 30 is such that although for the most part it is embedded within the polymer material of the component I 2, a part 32 thereof is exposed at the inner wall 18 of the component and, in use, bears against the outer surface of the hub 10. This is advantageous in that during fitting of the segment 1 2 to the hub 10, as the nut 16 is tightened onto the screw-threaded stud 14, plastics material is not compressed between the part 32 of the plate 30 and the hub 10 but rather the part 32 bears directly against the hub 10. Consequently, the nut 16 can be tightened to a precisely defined degree. Typically, the nut 16 is tightened to a torque in the range of 7 to 20 fl-lb. The tightening torque will depend upon, for example, the tyre size.

As well as enabling the tightening load to be precisely obtained, the use of a plate 30 shaped such that a part 32 thereof is exposed at the wall 18 is advantageous in that, compared to arrangements in which the plate is not exposed, the stud 14 can be or reduced length. By way of example, it is thought that a stud of length 25mm can be used, typical arrangements requiring a stud of 30mm length. Further, the shaping of the plate 30 allows a round headed stud to be used, typical arrangements requiring a hexagonal headed stud, and the shape of the metal plate 30 further allows an automated welding process, for example, induction welding to be used in the assembly of the plate and associated studs 14.

It will be appreciated that a range of modifications and alterations to the arrangement described hereinbefore may be made without departing from the scope of the invention.

Claims

1. A segmental tyre comprising a plurality of segments secured to a hub, at least one of the segments comprising a mounting plate moulded into a polymer material component, the mounting plate having at least one securing component mounted thereon, wherein at least part of the mounting plate engages the hub.

2. A tyre according to Claim 1, wherein the securing component comprises a screw-threaded stud.

3. A tyre according to Claim 2, further comprising a nut mounted upon the stud.

4. A tyre according to Claim 3, wherein the nut is tightened to a torque in the range of 7 to 20 ft-lb.

5. A tyre according to any of Claims 2 to 4, wherein the stud is of length 25mm.

6. A tyre according to any of Claims 2 to 5, wherein the stud is a round headed stud.

7. A tyre according to any of Claims 2 to 6, wherein the stud is welded to the mounting plate.

8. A segmental tyre comprising a plurality of segments secured to a hub, at least one of the segments including a moulded polymer material component moulded from a material including silica.

9. A tyre according to Claim 8, wherein the silica makes up approximately 10-20 pphr of the material.

10. A tyre according to Claim 9, wherein the silica makes up about 16 pphr of the material.

11. A segmental tyre comprising a plurality of segments secured to a hub, at least one of the segments including a moulded polymer component moulded from a material which is white.

12. A tyre segment adapted for use in a tyre according to any of the preceding claims.