CONFIGURATION APPLIED TO ENVELOPE FOR TiRE RETREADING

Abstract

The invention proposes a configuration applied to envelope for tire retreading in a cold retreading process. In the state of the art, envelopes consisting of two parts are known. However, the known methods of sealing among the pieces are not satisfactory either due to sealing problems, or by reducing the useful life of the envelope. In order to overcome these limitations, the invention proposes an envelope (20) comprising three parts (22, 24, 26), in which a flap (224) of the first part (22) presents a free end with a differentiated cross-section (224b), in which a flap (244) of the second part (24) has a free end with a differentiated cross-section (244b) and in which the third part (26) presents a shape of an elastic ring with enough width to cover the differentiated cross-section (224b) of the flap (224) of the first part (22) and the differentiated cross-section (244b) of the flap (244) of the second part (24).

Claims

1. CONFIGURATION APPLIED TO ENVELOPE FOR TIRE RETREADING, in which a tire casing (12) is covered by a pre-shaped tread (14) having a top (145) with a particular pattern of grooves (141), wherein the envelope (20) is comprised of three parts (22, 24, 26); wherein the first part (22) comprises a side wall (222), from which extends a flap (224), the said sidewall (222) containing a shape able to cover at least a part of the outer portion of a first flank (121) of the casing (12) and a first shoulder (142) of the tread (14), and the said flap (224) having a shape capable of covering a first portion of the top (145) of the tread pattern (14) wherein the free end of the said flap (224) has at least a differentiated cross-section (224b) with a thickness greater than the thickness of the said flap (224); wherein the second part (24) comprises a side wall (242), from which extends a flap (244), the said side wall (242) having a shape able to cover at least part of the outer portion of a second flank (122) of the casing (12) and a second shoulder (144) of the tread (14), and the said flap (244) having a shape able to cover a second portion of top (145) of the tread (14), other than the first portion covered by the flap (224) of the first part (22), and the free end of the flap (244) of the second part (24) has at least a differentiated cross-section (244b) with a thickness greater than the thickness of the flap (244); wherein the third part (26) comprises an elastic ring shape wide enough to cover the differentiated cross-section (224b) of the flap (224) of the first part (22) and the differentiated cross-section (244b) of the flap (244) of the second part (24); and wherein at least the first part (22) or the second part (24) is equipped with an air valve (28).

2. CONFIGURATION APPLIED TO ENVELOPE FOR TIRE RETREADING of claim 1, wherein the first part (22) comprises a uniform thickness, with the exception of its differentiated cross-section (224b), and the second part (24) comprises a uniform thickness, with the exception of its differentiated cross-section (244b), and the thickness of the first part (22) identical to the thickness of the second part (24).

3. CONFIGURATION APPLIED TO ENVELOPE FOR TIRE RETREADING according to claim 1, wherein the thickness of the first part (22) and second part (24) is greater from a transition point (T) to a point immediately preceding the differentiated cross-section (224b, 244b) present in the respective flap (224, 244), where each transition point (T) is located on the sidewall (222, 242) of the respective part (22, 24) into a position next to the said shoulder (142, 144) of the tread pattern (14).

Description

[0020] The invention will be better understood with the detailed description below, which is best interpreted with the aid of figures, namely:

[0021] FIG. 1 depicts a cross section perspective view, of a set of tire casing (12) and tread (14) covered by an envelope (20), according to the invention, closed with the aid of an inner envelope (30).

[0022] FIG. 2 depicts a plan view of a cross section of a set of tire casing (12) and tread (14) covered by an envelope (20) with uniform thickness, the said envelope (20) being closed with the aid of an inner envelope (30).

[0023] FIG. 3 depicts a plan view of a cross section of a set of tire casing (12) and tread (14) covered by an envelope (20) with variable thickness, the said envelope (20) being closed with the aid of an inner envelope (30).

[0024] FIG. 4 depicts a cross section perspective view, of a set of tire casing (12) and tread (14) covered by an envelope (20), in accordance with the invention, closed with the aid of a ring (40).

[0025] FIG. 5 depicts a plan view of a cross section of a set of tire casing (12) and tread (14) covered by an envelope (20) with uniform thickness, the said envelope (20) being closed with the aid of a ring (40).

[0026] FIG. 6 depicts a plan view of a cross section of a set of tire casing (12) and tread (14) covered by an envelope (20) with variable thickness, the said envelope (20) being closed with the aid of a ring (40).

[0027] FIG. 7 depicts a plan view of a cross section of a set of tire casing (12) and tread (14) covered by an envelope (20) with uniform thickness, the said envelope (20) being closed by a continuity of the side wall (222) of the first part (22).

[0028] In the cold retreading process of a tire, a tire casing (12) ready to be retreaded is covered by a new pre-shaped tread (14) having a top (145) with a particular pattern of grooves (141). The casing (12) consists of a pair of flanks (121, 122), each flank (121, 122) from a region called bead (124) until they are joined together by a central portion (123). The tread (14) is delimited by a pair of shoulders (142, 144) and is positioned on the outer surface of the central portion (123) of the casing (12), where the shoulders (142, 144) define the lateral ends of the tread (14) positioned according to its related flank (121, 122) of the casing (12). For the primary connection of the tread (14) on the casing (12) a suitable means is used, such as a connection rubber or a orbicushion rubber, both known to be state of the art.

[0029] The set of casing (12) and tread (14) should be taken to a pressurized and heated environment, such as an autoclave, for a given time. At the end of the process of cold retreading, the new tread (14) is integrated in the tire casing (12), re-establishing the conditions of use for the tire.

[0030] However, before taking the formed set of the casing (12) and tread (14) to the pressurized and heated environment, it is necessary to cover the said set with an envelope and perform the vacuum forming internally to the envelope, to obtain a tight environment.

[0031] The invention proposes a configuration of an envelope (20) for tire retreading, the said envelope (20) being comprised of three parts (22, 24, 26); wherein the first part (22) comprises a side wall (222), from which extends a flap (224), the said sidewall (222) containing a shape able to cover at least a part of the outer portion of a first flank (121) of the casing (12) and a first shoulder (142) of the tread (14), and the said flap (224) having a shape capable of covering a first portion of the top (145) of the tread (14), wherein the free end of the said flap (224) has at least a differentiated cross-section (224b) with a thickness greater than the thickness of the said flap (224); wherein the second part (24) comprises a side wall (242), from which extends a flap (244), the said side wall (242) having a shape able to cover at least part of the outer portion of a second flank (122) of the casing (12) and a second shoulder (144) of the tread (14), and the said flap (244) having a shape able to cover a second portion of the top (145) of the tread (14), other than the first portion covered by the flap (224) of the first part (22), and the free end of the flap (244) of the second part (24) has at least a differentiated cross-section (244b) with a thickness greater than the thickness of the flap (244); wherein the third part (26) comprises an elastic ring shape wide enough to cover the differentiated cross-section (224b) of the flap (224) of the first part (22) and the differentiated cross-section (244b) of the flap (244) of the second part (24); and wherein at least the first part (22) or the second part (24) is equipped with an air valve (28). The first part (22) and the second part (24), as well as the third part (26) in the shape of an elastic ring, are produced in flexible waterproof material, such as rubber.

[0032] According to the proposed solution, the third part (26) in the shape of an elastic ring remains pressed against the flap (224) of the first part (22) and against the flap (244) of the second part (24), creating a seal between the parts (22, 24, 26).

[0033] At the same time, the presence of the differentiated cross-section (224b) on the free end of the flap (224) of the first part (22) increases the sealing effect between said first part (22) and the third part (26), and the presence of the differentiated cross-section (244b) on the free end of the flap (244) of the second part (24) increases the sealing effect between said second part (24) and the third part (26), created by the suction of air through the air valve (28).

[0034] Thus, advantageously, an envelope (20) which provides an excellent seal in relation to the set of casing (12) and tread (14) is obtained, in order to prevent any air from entering internally to the envelope (20) after enveloping and vacuum forming.

[0035] Preferably, the flap (224) of the first part (22) extends until a previous position to the median plane (M) of the tread (14) and, preferably, the flap (244) of the second part (24) extends until a previous position to the median plan (M) of the tread (14). It can be noted that, preferably, the first part (22) and the second part (24) are manufactured in a single die, so they are identical to each other. Thus, advantageously, in case of damage in one of those parts (22, 24), only the damaged part is replaced.

[0036] The envelope (20) must also be closed next to the casing (12) for the formation of the vacuum internally to the envelope (20). For this purpose, for example, as can be seen in FIGS. 1 to 3, an inner envelope (30) installed inside the casing (12) can be used, so that the inner envelope (30) covers all internal surfaces of the casing (12), outlining the regions of the bead (124) of the casing (12) and advancing over part of the external surface of each flank (121, 122) of the casing (12). In this outside region of each flank (121, 122), a region of the end of the sidewall (222, 242) of the respective part (22, 24) is positioned over a respective region of the end of the inner envelope (30), in order to form a seal joint when forming the vacuum.

[0037] Alternatively to using the inner envelope (30), a ring (40) for closing the envelope (20) next to the casing (12) can be used, as it can be seen in FIGS. 4 to 6. In this case, both the side wall (222) of the first part (22) and the side wall (242) of the second part (24) move close to the bead (124) from their flank (121, 122) of the casing (12) and remain pressed against the outer surface of the rim (40), forming sealed joints.

[0038] Alternatively to the use of an inner envelope (30) or ring (40), for closing the envelope (20) next to the casing (12), as can be seen in FIG. 7, the side wall (222) of the first part (22) advances and gets around the bead region (124) of the first flank (121) of the casing (12), covers the entire inner surface of the casing (12), gets around the bead region (124) of the second flank (122) and advances over part of the outer surface of the second flank (122) of the casing (12). In this outside area of the second flank (122), a region of the end of the sidewall (242) of the second part (24) is positioned over a region of the end of the first part (22), in order to form a sealing joint when the vacuum is formed.

[0039] Once the envelope (20) is closed and the vacuum is formed internally to the envelope (20), by suction of air through the air valve (28), the set of casing (12) and tread (14) is ready to be taken to the pressurized and heated environment, such as an autoclave.

[0040] Moreover, as can be seen in FIGS. 2, 5 and 7, the first part (22) has a uniform thickness, with the exception of its differentiated cross-section (224b), and the second part (24) having a uniform thickness, with the exception of its differentiated cross-section (244b), and the thickness of the first part (22) identical to the thickness of the second part (24). Preferably, the thickness of the first part (22) and of the second part (24) assumes a value of 2 to 3.5 mm.

[0041] Alternatively, as you can see in FIGS. 3 and 6, the thickness of the first part (22) and the second part (24) is greater from a transition point (T) until a point immediately preceding the differentiated cross-section (224b, 244b) present in the flap (224, 244), where each transition point (T) is located on the sidewall (222, 242) of the respective part (22, 24) in a position next to the respective shoulder (142, 144) of the tread (14). Preferably, each transition point (T) is located in a position above half of the height of its flank (121, 122) of the casing (12) and prior to the top (145) of the tread (14).

[0042] The configuration in which the first part (22) and the second part (24) of the envelope (20) present variable thickness is preferred in relation to the configuration where the first part (22) and the second part (24) of the envelope (20) have uniform thickness, since the fact that a portion of the respective sidewall (222, 242) after the transition point (T) and the corresponding flap (224, 244) of the first part (22) and of the second part (24) have a greater thickness allows the said parts (22, 24) of the envelope (20) to assume a more structured shape and closest to the shape of the set of casing (12) and (14) tread. Thus, advantageously, the handling and installation of the first part (22) and of the second part (24) on the set of casing (12) and tread (14) become easier.

[0043] In addition, the fact that the respective flap (224, 244) of the first part (22) and of the second part (24) have a greater thickness prevents the said flap (224, 244) from being stretched into the grooves (141) of the tread (14), whether due to vacuum formed internally to the envelope (20), or due to external pressure applied to the envelope (20) during the autoclave process. Thus, advantageously, deformations in the flaps (224, 244) of the said parts (22, 24) of the envelope (20) are avoided, and, consequently, fatigue stresses that would be caused by this repeated deformation over several cycles of using the same envelope (20) are avoided, contributing to an increase of its useful life.

[0044] On the other hand, the fact that a portion of the sidewall (222, 242) prior to the transition point (T) is of a lesser thickness, advantageously, represents a savings of material in the production of the first part (22) and of the second part (24) of the envelope (20).

[0045] Preferably, the thickness of the portion of the side wall (222, 242) prior to the transition point (T) assumes a value of 2 to 3.5 mm. Preferably, the thickness of the side wall portion (222, 242) after the transition point (T) and the thickness of the flap (224, 244) until a point immediately preceding the differentiated cross-section (224b, 244b), assume a value greater than the value of the thickness of the side wall portion (224, 244) prior to the transition point (T). Preferably, this higher value is no more than 6 mm.

[0046] For example, if the first part (22) and the second part (24) of the envelope (20) were made having a side wall portion (224, 244) prior to the transition point (T) with a 3 mm thickness, the thickness of the sidewall (224, 244), from the transition point (T), and the thickness of the flap (224, 244) will have a value greater than 3 mm. This increase in thickness can be achieved gradually, as depicted in FIGS. 3 and 6, for example, starting with 3.1 mm at a point immediately after the transition point (T) and ending with 5 mm at one point immediately preceding the differentiated cross-section (224b, 244b). Or this increase in thickness can be achieved abruptly, according to a non-represented configuration, for example, from 3 mm to 5 mm at a point immediately after the transition point (T) and remaining uniform at 5 mm up to the point immediately preceding the differentiated cross-section (224b, 244b).

[0047] In all represented variations of the envelope (20), as can be seen in the Figures, the differentiated cross-section (224b, 244b) present in the free end of the flap (224, 244) of the first part (22) and of second part (24) has a rectangular shape. However, each differentiated cross-section (224b, 244b) can have another shape, such as, for example, a circular shape. The thickness of each differentiated cross-section (224b, 244b) assumes a value greater than the thickness of the flap (224, 244), at one point immediately preceding the said differentiated cross-section (224b, 244b), preferably between 8 and 12 mm.

[0048] Preferably, the thickness of the third part (26) in the shape of an elastic ring assumes a value between 3 and 5 mm.