SOLID TIRE PROVIDED WITH MEANS FOR SIGNALLING THE STATE OF EXCESSIVE WEAR

Abstract

A solid tire (4; 8) is described comprising two or more circular layers overlapped in a radial direction. At least the outermost layer is made of elastic material and consists of an external portion or tread (16). The solid tire (4; 8) furthermore comprises at least one layer for indicating excessive wear (10), arranged in a predefined position inside the outermost portion or tread (16). The layer for indicating excessive wear (10) is made in a colour different from the one of the external portion or tread (16). The layer for indicating excessive wear (10) is made with a specific compound of materials. This specific compound of materials makes the layer for indicating excessive wear (10) easy to see. This specific compound of materials also makes the solid tire (4; 8) less hysteretic, and therefore less subject to the development of heat, when compared to similar solid tires.

Claims

1. A solid tire (4; 8) comprising two or more circular layers overlapped in a radial direction, wherein at least the outermost layer is made of an elastic material and consists of an external portion or tread (16), wherein said solid tire (4; 8) further comprises at least one layer for indicating excessive wear (10), arranged in a predefined position inside said external portion or tread (16), and wherein said at least one layer for indicating excessive wear (10) is made with a colour different from that of said external portion or tread (16), said solid tire (4; 8) being characterized in that said at least one layer for indicating excessive wear (10) is manufactured with the following compound of materials in the following percentages by weight: rubber: 50%/60%; silica: 20%/30%; one or more plasticising additives: 2%/8%; one or more compatibilizing agents between rubber and silica: 2%/3%; pigments: 3%/8%; one or more protective agents: 1%; one or more crosslinking agents: 3%/8%, wherein mineral binders are added to the pigments, in such a way that the binding of said pigments and said mineral binders gives rise to a mineral colour.

2. The solid tire (4; 8) according to claim 1, characterized in that the rubber is of the synthetic type.

3. The solid tire (4; 8) according to claim 1, characterized in that the rubber is of the natural type.

4. The solid tire (4; 8) according to claim 1, characterized in that the protective agents of the so-called “no-staining” type and contribute to keeping said mineral colour brighter, thus avoiding the migration of colouring components onto the surface of the compound.

5. The solid tire (4; 8) according to claim 4, characterized in that the protective agents are selected in the category of the hindered phenols.

6. The solid tire (4; 8) according to claim 1, characterized in that the compatibilizing agents between rubber and silica are selected in the category of silanes.

7. The solid tire (4; 8) according to claim 1, characterised in that it consists of a super-elastic tire (4) comprising a plurality of circular layers of elastic material overlapped in a radial direction, said layers forming, proceeding from the centre of the super-elastic tire (4) towards the periphery, an internal portion or bead (12), an intermediate portion or middle portion (14) and said external portion or tread (16).

8. The solid tire (4; 8) according to claim 7, characterized in that it further comprises a raised circular portion (22), arranged on the shoulder of the super-elastic tire (4) at the sides of the contact area between said external portion or tread (16) and said intermediate portion or middle portion (14).

9. The solid tire (4; 8) according to claim 8, characterized in that said at least one layer for indicating excessive wear (10) is positioned in said external portion or tread (16) at said raised circular portion (22).

10. The solid tire (4; 8) according to claim 1, characterized in that it consists of a POS/POB tire (8) comprising, proceeding from the centre of the POS/POB tire (8) towards the periphery, an internal portion consisting of a metal ring (24) and said external portion or tread (16), which is fitted around said metal ring (24).

11. The solid tire (4; 8) according to claim 10, characterized in that it further comprises, in a predefined position inside said external portion or tread (16), a wear limit (26) which is designed to indicate the point of excessive wear of said external portion or tread (16).

12. The solid tire (4; 8) according to claim 11, characterized in that said at least one layer for indicating excessive wear (10) is positioned in said external portion or tread (16) at said wear limit (26).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The characteristics and advantages of a solid tire according to the present invention will be clearer from the following description, which is explanatory and nonlimiting, with reference to the attached schematic drawings, in which:

[0021] FIG. 1 is a cross-sectional view of the thickness of a super-elastic tire according to the prior art;

[0022] FIG. 2 is a cross-sectional view of the thickness of a first example of an embodiment (super-elastic tire) of a solid tire provided with means for visually signalling the state of excessive wear according to the present invention;

[0023] FIG. 3 is a cross-sectional view of the thickness of a POS/POB tire according to the prior art; and

[0024] FIG. 4 is a cross-sectional view of the thickness of a second embodiment (POS/POB tire) of a solid tire provided with means for visually signalling the state of excessive wear according to the present invention.

DETAILED DESCRIPTION

[0025] With particular reference to FIGS. 2 and 4, two preferred embodiments of a solid tire according to the present invention are shown. In detail, in FIG. 2 the solid tire consists of a super-elastic tire, indicated as a whole by the reference numeral 4, whereas in FIG. 4 the solid tire consists of a POS/POB tire, indicated as a whole by the reference numeral 8.

[0026] Both the super-elastic tire 4 and the POS/POB tire 8 are substantially formed by the same parts that respectively form the super-elastic tires and the POS/POB tires according to the prior art. The same reference numerals previously stated have therefore been used for these parts. Therefore, in general, the solid tire 4 or 8 comprises two or more circular layers overlapped in a radial direction, wherein at least the outermost layer is made of an elastic material and consists of an external portion or tread 16.

[0027] The solid tire 4 or 8 comprises, in addition, at least one layer for indicating excessive wear 10, arranged in a predefined position inside the external portion or tread 16. For example, in the super-elastic tire 4 the layer for indicating excessive wear 10 can be positioned in the external portion or tread 16 at the raised circular portion 22 (“60J line”), whereas in the POS/POB tire 8 said layer for indicating excessive wear 10 can be positioned in the external portion or tread 16 at the wear limit 26.

[0028] The layer for indicating excessive wear 10 is in any case made with a colour that can be clearly distinguished from the colour of the tread 16. In particular, the layer for indicating excessive wear 10 is made with a colour different from that of the tread 16. In this manner, when the wear of the tread 16 is such that the layer for indicating excessive wear 10 becomes exposed, it is immediately and easily visible.

[0029] According to the invention, the layer for indicating excessive wear is manufactured with the following compound of materials in the following percentages by weight: [0030] rubber: 50%/60%; [0031] silica: 20%/30%; [0032] one or more plasticising additives: 2%/8%; [0033] one or more compatibilizing agents between rubber and silica: 2%/3%; [0034] pigments: 3%/8%; [0035] one or more protective agents: 1%; [0036] one or more crosslinking agents: 3%/8%.

[0037] The rubber can be both of a synthetic type and a natural type. Mineral binders are also added to the pigments, so that the binding of pigments with mineral binders gives rise to a mineral colour.

[0038] In particular, the protective agents are of the so-called “no-staining” type and contribute to keeping the mineral colour brighter, thus avoiding at the same time the migration of colouring components onto the surface of the compound. The protective agents furthermore contribute to reducing the ageing effect of the rubber. A special category of non-staining protective agents, typically used in the compound, consisting of the category of the hindered phenols known, for example, with the commercial names “Wingstay L” and “Lowinox GP 45”.

[0039] One of the main performance requirements of a solid tire is its resistance to accumulation of heat. During its use, the solid tire is continuously subject to cycles of fatigue due to its rotational speed and the combinations of loads that bear thereon. These cycles of fatigue generate heat, which accumulates inside the solid tire. If the work cycles are long and if each lasts more than eight hours a day, the solid tire does not have time to rest and cool down. If the internal temperature of the solid tire exceeds 130° C., its ageing is accelerated and the solid tire can degrade more easily.

[0040] The silica and the compatibilizers between rubber and silica (that can be selected from the category of silanes such as, for example, vinyltrimethoxysilane) create a special compound that makes the solid tire 4 or 8 less hysteretic, and therefore less subject to the development of heat, when compared to similar solid tires according to the prior art. In fact, since the layer for indicating excessive wear 10 comprises the aforementioned compound, said layer for indicating excessive wear 10 generates a discontinuity in the solid tire 4 or 8, reducing the accumulated heat and making the solid tire 4 or 8 suitable for heavy duty (2-3 consecutive shifts or work cycles of 18-24 hours).

[0041] It has thus been seen that the solid tire according to the present invention has achieved the aforementioned objects.

[0042] The solid tire of the present invention thus conceived is however susceptible to numerous modifications and variations, all falling within the same inventive concept; furthermore, all the details are replaceable with technically equivalent elements. In practice the materials used, as well as the shapes and sizes, can be of any type according to the technical needs.

[0043] The scope of protection of the invention is therefore defined by the attached claims.