WO2019092756A1

WO2019092756A1 - Solid tyre provided with visual indication means of excessive tread wear and related production method

Info

Publication number: WO2019092756A1
Application number: PCT/IT2017/000247
Authority: WO
Inventors: Gianluca Abbati; Gianluca MELODORO; Gianni AGAMETTI; Steve PETRESCU; Charles Davis; Dinesh Gunasekara; Martin HIGNETT
Original assignee: Trelleborg Wheel Systems Italia S.P.A.
Priority date: 2017-11-09
Filing date: 2017-11-09
Publication date: 2019-05-16
Also published as: TW201922531A

Abstract

A solid tyre (1) is described, comprising a metal rim (2) and a circular layer (3) made of a compound (30) of materials radially overlapping on the metal rim (2), said circular layer (3) comprising an inner portion (5) in contact with said metal rim (2), an outer portion, referred to as tread (6), suitable to make contact with the ground and two lateral surfaces or shoulder (4). Said solid tyre (1 ) comprises at least one lateral seat (9) formed in said tread (6) by means of an opening on one of the shoulders (4), said at least one lateral seat (9) being configured to house an insert (10) having a different colouring with respect to the compound (30) of the circular layer (3) and being suitable to form a visual indication means of nearly reaching a wear bar (7) of the tread (6).

Description

SOLID TYRE PROVIDED WITH VISUAL INDICATION MEANS OF EXCESSIVE TREAD WEAR AND RELATED PRODUCTION METHOD

The present invention relates to a solid tyre provided with visual indication means of excessive tread wear and related production method.

As it is well-known, numerous industrial and commercial applications require the use of airless tyres, having a solid structure, since they are more resistant to puncture and have a high load capacity. Said tyres are also known as "solid tyre".

A first type of solid tyre is the resilient tyre. Structurally, resilient tyres are obtained by radially overlapping circular layers of elastic material, said layers forming, proceeding from the centre towards the periphery of the tyre, an inner portion or heel, an intermediate portion known as middle and an outer portion known as tread.

The useful life of this type of tyre depends on the tread wear and for this reason resilient tyres are provided with visual indication means of excessive tread wear, said means being adapted to indicate when the wear limit (i.e. the so-called wear bar) of the tread is nearly reached, thus allowing the driver of the vehicle, provided with the tyre, to be able to plan a future replacement of the same.

In particular, the patent document ITRM20120408 (titled Trelleborg Wheel Systems Italia Spa) describes visual indication means of excessive tread wear represented by a layer, comprised between the various radially overlapping circular layers, made of the same material, or of a material compatible with that with which the tread and middle are made, but with the peculiarity of having a colour that can be easily distinguished from the colour of the tread. Said indication layer is interposed between the layers that form the tread and those that form the middle, so that when the tread wear reveals said indication layer of excessive wear, it is immediately and easily visible to the user.

A second type of solid tyre known as POS (Press On Steel) or POB (Press On Band) is also known. The POS also has a solid structure, yet it comprises a metal rim, which is part of the same tyre, and is made by various industrial processes including the one referred to as injection moulding. To perform the injection moulding, it is common to use presses which substantially comprise an injection assembly suitable for injecting a compound, at high temperature and pressure, inside a cavity of a closed mould which, at the end of the process, is opened to extract the tyre thus obtained.

However, as can be easily understood, during such a process it is not possible to put into practice the teachings known from the resilient tyres manufacturing technique to obtain said visual indication means of the state of excessive wear of the tyre. It is therefore not possible to obtain a POS solid tyre provided with known visual indication means.

In view of the issues above, the object of the present invention is to provide a solid tyre wherein it is possible to visually detect the reaching of the tread wear bar, thus allowing the driver of the vehicle, provided with the tyre, to plan a future replacement of the same.

A further object of the present invention is to provide a production method for a solid tyre with the aforementioned properties.

According to the present invention, said object is achieved by means of a solid tyre and the related production method according to claims 1 and 9, respectively.

The features and advantages of the present invention will be apparent to those skilled in the art from the following detailed description of a practical embodiment thereof illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 shows a perspective view of a solid tyre according to the present invention;

Figure 2 shows a front view of the solid tyre of Figure 1 ;

Figure 3 shows a sectional view of a part of the solid tyre of Figure 1 ;

Figure 4 shows a sectional view of a detail of the solid tyre of Figure 1 ;

Figure 5 shows the visual indication means of excessive tread wear of the solid tyre of Figure 1 ;

Figure 6 shows a mould for manufacturing the solid tyre of Figure 1.

With reference to Figure 1 , a solid tyre 1 according to the present invention is generally denoted with number 1.

The solid tyre 1 , known as POS (Press On Steel) or POB (Press On Band), is an airless tyre that, particularly, has a solid structure. By way of example, solid tyres are used on many types of industrial vehicles. In particular, one of the most common applications for solid tyres is that of material handling equipment (forklifts).

Structurally, the solid tyre 1 comprises a metal rim 2 (typically made of steel) and a circular layer 3 made with a compound 30 of materials radially overlapping the metal rim 2, said compound 30 having a certain colouring; for example, the circular layer 3 can be totally black, but also white or grey.

As shown in Figure 3, the circular layer 3 comprises two lateral surfaces, or shoulders 4 of the tyre 1 , an inner portion 5 in contact with the metal rim 2, and an outer portion, referred to as tread 6, suitable to make contact with the ground. Advantageously, the circular layer 3 can be fixed to the metal rim 2 by means of special binding agents.

The tread 6 is represented, in particular, by the portion of the circular layer 3 comprised between a wear bar 7 and a contact surface 8 with the ground (Figure 3). The wear bar 7 is formed by a circumference (sometimes embossed on a shoulder 4 of the tyre) and is suitable for indicating the excessive wear of the tread 6 reached for which the tyre must be replaced (Figures 2, 3).

The tread 6 can be smooth or have grooves which number, shape and depth of which varies depending on the use for which the tyre is intended.

The solid tyre 1 further comprises at least one lateral seat 9 (Figures 3, 4) made in said circular layer 3, at the tread 6, by means of a through opening on one of the shoulders 4 of the tyre. Said at least one lateral seat 9 is configured to house an insert 10 of a colouring different than that of the compound 30 of the circular layer 3. The tyre 1 can comprise a plurality of lateral seats 9. For example, in the figures an embodiment of tyre comprising three lateral seats 9 is shown.

The insert 10 can be made with the same material as the circular layer 3 or also with a different material. Thus, the insert 10 can be made of, for example, a plastic material or a rubber compound or a metallic material or another solid material and have a colouring that is clearly distinguishable from that of the compound 30 of the circular layer 3 (such as orange, red, yellow, etc.).

In particular, said at least one lateral seat 9 is formed between said wear bar 7 and said contact surface 8 of the tread 6, so that the corresponding insert 10 is also placed between the wear bar 7 and the contact surface 8.

The insert 10 represents a visual signalling means of nearly reaching said wear bar 7 of the tread 6, thus allowing the driver of the vehicle, provided with the tyre, to plan a future replacement of the same. The appearance of the insert 10 (with its own colour that can be easily distinguished from that of compound 30) due to wear of the tread 6, is in fact a visually relevant event for the user, so that it is easy to determine the near reaching of the wear bar 7.

In a preferred embodiment, the insert 10, as well as the corresponding lateral seat 9 housing the same, has substantially the shape of a rectangular parallelepiped which, when the insert 10 is inserted in the seat 9, has the bases oriented according to a plane substantially orthogonal to the surface represented by the corresponding shoulder 4 of the tyre 1.

Advantageously, the insert 10 comprises a plurality of protrusions 1 1 suitable to engage in respective recesses 12 made in said lateral seat 9, the coupling between said protrusions 1 1 and said recesses 12 being such as to firmly block the insert 10 inside the lateral seat 9.

In particular, the protrusions 1 1 are present in at least one of the two bases of the parallelepiped which forms the insert 10 and extend along a predominant direction which, when the insert 10 is inserted into the corresponding lateral seat 9, is parallel to surface represented by the corresponding shoulder 4, so that they form constraints suited to block the exiting of the insert 10 through said opening in the shoulder 4 due to the load pressure to which the tyre is subjected. For example, as shown in Figure 5, the insert 10 comprises two protrusions 1 1 on a top base of the parallelepiped which form the insert 10, said two protrusions 11 being suited to couple with two corresponding recesses 12 made in said lateral seat 9.

In addition, the insert 10 can internally comprise at least one sensor (not shown in the figures) suitable for, among others, monitoring the wear level of the tyre 1 , or the inner temperature of the tyre during use.

The solid tyre 1 according to the present invention is made by using an industrial manufacturing process known as injection moulding, but can also be produced with other processes such as compression. In order to perform the injection moulding it is common to use presses which essentially comprise an injection assembly, a mould 15 (Figure 6), and a closing assembly for the mould.

The injection assembly comprises: S

- a hopper, placed on top of the machinery, suitable for containing said sheet moulding compound,

- a feeding screw arranged inside a cylindrical duct heated by means of electric resistances, said cylindrical duct being suited to receive the sheet moulding compound 30 from the hopper and leading it towards said mould 15; a front outlet hole of the cylindrical duct is suited to convey the compound into an inlet channel 20 of the mould 15.

The mould 15 delimits a substantially annular cavity 21 with the shape of said solid tyre and comprises a pair of semi-moulds 22, 22', i.e. two halves, of which at least one (e.g., half mould 22) is movable with respect to the other. A special housing 23 is also provided, suited to house the metal rim 2 around which the compound 30 is injected.

The mould 15 is configured to take a closed position in which the compound 30 is injected by means of the injection assembly (particularly by the injection nozzle through said inlet channel 20), and an open position in which the extraction of the moulded tyre is allowed.

In addition, the semi-moulds 22, 22' forming the mould 15 comprise at least one projection 24 suited to form said lateral seat 9 in the tread 6 of the tyre during the moulding process for housing the insert 10. As explained, also said at least one projection 24, such as the insert 10, substantially has the shape of a rectangular parallelepiped and, advantageously, comprises a plurality of protrusions.

The closing assembly is suited to hold the mould 15 (hydraulically or mechanically) in a closed position during the injection step which otherwise would tend to open the two halves of the mould 15 due to the pressure.

The method for producing the solid tyre 1 according to the present invention, by means of an injection moulding machine, comprises the following steps:

- the injection, at high pressure and temperature, of said compound 30 inside the mould 15 which delimits the cavity 21 with the shape of said solid tyre 1 ,

- the vulcanization of the compound 30,

- the extraction of the solid tyre 1 from said cavity 21 of the mould 15,

- the insertion of said at least one insert 10 through said at least one opening in the shoulder 4 inside said lateral seat 9 by means of suitable further mechanical means.

It is evident that due to the solid tyre and its relative manufacturing process according to the present invention, it is possible to obtain an injection moulded tyre which is provided with an effective signalling means, providing the user with an apparent warning of nearly reaching the limit of excessive tread wear, allowing the user to plan a future replacement of the same.

The present invention has been described by way of illustrative, but non- limiting example, according to its preferred embodiment, but it is to be understood that alternatives and/or modifications can be made by those skilled in the art without departing from the respective protection scope, such as defined by the attached claims.

Claims

1. A solid tyre (1 ) comprising a metal rim (2) and a circular layer (3) made with a compound (30) of materials radially overlapping on the metal rim (2), said circular layer (3) comprising an inner portion (5) in contact with said metal rim (2), an outer portion, referred to as tread (6), suitable to make contact with the ground and two lateral surfaces or shoulders (4), said solid tyre (1 ) being characterized in that it comprises at least one lateral seat (9), formed in said tread (6) by means of an opening provided on one of the shoulders (4), said at least one lateral seat (9) being configured to house an insert (10) having a different colouring with respect to the compound (30) of the circular layer (3) and suited to form a visual indication means of nearly reaching a wear bar (7) of the tread (6).

2. The solid tyre (1 ) according to claim 1 , characterized in that said tread (6) is represented by the portion of the circular layer (3) ranging between said wear bar (7) and a contact surface (8) with the ground, said lateral seat (9) being made between said wear bar (7) and said contact surface (8) so that said insert (10) is also arranged between the wear bar (7) and the contact surface (8).

3. The solid tyre (1 ) according to claims 1 or 2, characterized in that said insert (10) is made of a plastic material or of a rubber compound or of a metal material or any other solid material and has a notable colouring that can be clearly distinguished from that of the compound (30) of the circular layer (3).

4. The solid tyre (1 ) according to claims 1 or 2, characterized in that said insert (10), as well as the corresponding lateral seat (9) housing the same, substantially has the shape of a rectangular parallelepiped that, when the insert (10) is inserted inside the lateral seat (9), the respective bases are oriented in a plane substantially orthogonal to the surface of the corresponding shoulder (4) of the tyre (1 ).

5. The solid tyre (1 ) according to claims 1 or 2, characterized in that said insert (10) comprises a plurality of protrusions (11 ) suitable for engaging in respective recesses (12) made in said lateral seat (9), the coupling between said protrusions (11) and said recesses (12) being such as to firmly block the insert (10) inside the lateral seat (9).

6. The solid tyre (1 ) according to claims 4 and 5, characterized in that said protrusions (1 1 ) are present in at least one of the two bases of the parallelepiped which forms the insert (10) and develop along a predominant direction which, when the insert (10) is inserted inside the lateral seat (9), it is parallel to the surface represented by the corresponding shoulder (4).

7. The solid tyre (1 ) according to claim 6, characterized in that said insert (10) comprises two protrusions (1 1 ) on an upper base of the parallelepiped which forms the insert (10).

8. The solid tyre (1 ) according to claim 1 , characterized in that the insert (10) internally comprises at least one sensor suitable for, among others, monitoring the wear level of the tyre (1 ), or the inner temperature of the tyre during use.

9. A production method of a solid tyre (1 ) comprising a metal rim (2), a circular layer (3) made of a compound (30) of materials radially overlapping on said metal rim (2) and comprising a tread (6) suitable to make contact with the ground, and at least one lateral seat (9) made in said circular layer (3) in the area of the tread (6) and inside which an insert (10) is housed, suitable to form a visual indication means of nearly reaching a wear bar (7) of the tread (6), said process being characterized in that it comprises:

- the injection, at high pressure and temperature, of said compound (30) inside a mould (15) which delimits a substantially annular cavity (21 ) with the shape of said solid tyre (1 ), said mould (15) comprising at least one projection (24) suitable to form said at least one lateral seat (9) in the area of the tread (6),

- the vulcanization of said compound (30),

- the extraction of the solid tyre (1 ) from said cavity (21 ) of the mould (15),

- the insertion of said at least one insert (10) inside said at least one lateral seat (9).

10. The method according to claim 9, characterized in that said at least one projection (24) substantially has the shape of a rectangular parallelepiped.

1 1. The method according to claim 9, characterized in that said at least one projection (24) comprises a plurality of protrusions.