JPH02307739A - Reclamation of tire tread - Google Patents

Abstract

PURPOSE:To prevent the generation of strain in a tread groove bottom or the periphery thereof, to obtain a reclaimed tire having a uniform shape and to facilitate pressure control by supplying a pressure fluid of a separate system having pressure lower than that of the pressure fluid supplied to a pressure container to the space between a skin/tread and a tire casing. CONSTITUTION:A pressure fluid is supplied into the tire casing 1 received in a pressure container through an expansible bag 31 to expand the tire casing. When the internal pressure of the pressure container reaches a predetermined value, the air remaining in the grooves of a tread 4 and a rubber base bond layer 3 is forcibly discharged and, when the pressure in the pressure container reaches set pressure, the fluid of a separate system set to pressure lower than the pressure in the pressure container is supplied to the spaces 25 inside a skin 5 to bring the difference between the internal and external pressures of the skin 5 to a very low level and the whole of the tread 4 is brought in contact with the outer peripheral surface 2 of the tire casing 1 under almost uniform pressure and the bond layer 3 is vulcunized and cured by heating to bond the tread 4 to the tire casing 1. The pressure fluid supplied to the space 25 inside the skin 5 can be set to compressed air and the pressure thereof is pref. set to 95 - 50% the pressure of the pressure fluid supplied to the pressure container.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tire tread retreading method in which a precured tread is bonded to the outer peripheral surface of a tire casing from which the tread worn out due to use has been removed.

(Prior art) Conventionally, a replacement tire from which worn tread rubber has been removed, i.e., a tire casing, is coated on the outer circumferential surface of the tire.
A tire tread retreading method has been adopted in which a new tread that has been previously vulcanized and molded is vulcanized and bonded via unvulcanized cushion rubber. During this tread rehabilitation, as shown in FIG. 5, a pre-cured tread 4 is adhered to the outer peripheral surface 2 of the ear casing 1 with unvulcanized cushion rubber 3 to form a tire assembly. ,
It is covered with a flexible liquid-tight outer skin (also called envelope) 5. The tire assembly covered with the outer skin 5 is placed in a pressure vessel, that is, a vulcanizing can 6, as shown in FIG. A pipe 8 is connected so that air and other gases within the skin 5 are removed by a vacuum pump 9, and a pressure fluid supply conduit 10 is connected inside the vulcanizing can 6.
Pressurized air and heating steam are supplied through a conduit 11 and 11, respectively. The conduits 7.10 are each connected to a pneumatic pressure source 14 via pressure regulating valves 12.13, and on-off valves 15, 16, 17 are provided in the middle of the conduits 7.10.
is provided. In addition, a pressure regulating valve 13 is provided in the conduit 10.
A bypass pipe 18 is provided before and after the on-off valve 19. The exhaust pipe 8 is provided with a vacuum pressure regulating valve 20°21.
．． 22 and on-off valves 23 and 24 are provided.

Therefore, when vulcanizing and adhering the tire assembly, the vulcanizing can 6
Air is supplied inside the tire casing 1 at a pressure slightly lower than that inside the tire casing 1, and pressurizes the trend 4 through the outer skin 5.
The air inside the tire assembly is evacuated by natural exhaust or by a vacuum pump 9, and heating steam is introduced from a conduit 11 to vulcanize and bond the tire assembly.

(Problem to be solved by the invention) By the way, in the above tire tread retreading method, I
- The pressure of the red 4 on the tire casing 1 is performed through the outer skin 5, and as shown in FIG. 6, the outer skin 5 does not reach the tread groove bottom 4A, so a space 25 is created at the groove bottom;
Pressure is not evenly applied to the tread groove bottom 4Δ and its surroundings, and therefore, the external pressure P from the outside of the outer skin 5. A large pressure difference occurs between the internal pressure p of the space 25 (vacuum or atmospheric pressure). At this time, the tread groove bottom 4A is kept under the external pressure P of the outer skin 5 in order to eliminate air remaining in the tread 4 and the adhesive layer of the cushion rubber 3 or other gases generated during vulcanization. Natural evacuation is performed by pressing the air, or forced evacuation is performed using the vacuum pump 9. Therefore, the tread groove bottom 4A gradually deforms during the process in which the rubber 3 becomes fluid due to heating and is vulcanized and hardened, and the exhaust gas increases this deformation. In addition, the position where the cushion rubber 3 is attached is such that the outer skin 5 is in close contact with the side surface of the tread 4, and the residual air in the cushion rubber 3 layer cannot be exhausted.
As shown in FIG. 7, an air venting cloth 26 is inserted into the inner peripheral surface of the outer skin 5 between both bead portions.

However, distortion occurs in the tread groove bottom 4A and its surroundings,
It is not possible to form a tire with a uniform shape, and the cushion rubber 3 below the tread groove bottom 4 flows left and right and becomes thinner (see Figure 8). Furthermore, when the tread groove width is wide, the cushion rubber 3 There were problems such as the floating point (see Figure 9). Therefore, the outer skin 5 and the tire casing 1
Techniques have been disclosed that attempt to solve the above problems by supplying pressurized fluid to the space between the tread 4 and the tire assembly to maintain a pressure difference between the inside and outside of the outer skin 5. (Refer to Publication No. 63-66658)
.

However, this disclosed technique has a problem in that the pressure fluid il+li control system configuration is complicated and control is extremely troublesome.

The present invention was made in view of the above-mentioned circumstances, and
To provide a method for retreading a tire tread, which prevents distortion from occurring at the tread groove bottom and its surroundings, provides a retreaded tire with a uniform shape, and allows easy pressure control of pressurized fluid.

(Means for Solving the Problems) In the present invention, the following technical measures were taken in order to achieve the above object.

That is, in the present invention, a pre-cured tread 4 is bonded to the outer circumferential surface 2 of the tire casing 1 from which the worn tread has been removed via an unvulcanized rubber heath bond layer 3, and at least the tread of the trend 4 and the tire casing 1 is Adjacent side wall portions are covered with a flexible airtight outer skin 5, the tire casing 1 and tread 4 covered with the outer skin 5 are housed in a pressure vessel 6, pressure fluid is supplied into the pressure vessel 6, and the outer skin 5 is In a tire tread retreading method in which the tread 4 is pressed onto the tire casing 1 through a vulcanization bond, the tread 4 is supplied into the pressure vessel 6 into the space 25 formed by the outer skin 5 and at least the grooves of the tread 4. It is characterized by supplying a separate system of pressure fluid with a pressure lower than that of the pressure fluid.

The pressure fluid supplied to the inner space 25 of the outer skin 5 may be compressed air, and its pressure is preferably 95 to 50% of the pressure of the pressure fluid supplied into the pressure vessel 6.

(Function) According to the present invention, pressurized fluid is supplied into the tire casing 1 housed in the pressure vessel 6 through the expansion bag 31 to inflate the tire casing 1 , and at the same time the tire casing 1 is inflated in the pressure vessel 6 .
supplying a pressure fluid slightly lower than that of the inflation pressure fluid in the
When the pressure inside the pressure vessel 6 reaches a predetermined value, the air remaining in the grooves of the tread 4 and the rubber base bond layer 3 is forcibly discharged, and when the pressure inside the pressure vessel 6 reaches the set pressure, the pressure inside the pressure vessel 6 is lowered. A separate system of fluid set at a low pressure is supplied to the space 25 inside the outer skin 5 to minimize the pressure difference between the inside and outside of the outer skin 5, so that the entire tread 4 is maintained at a substantially uniform pressure in the tire casing 1.
The tread 4 is bonded to the tire casing 1 by pressing the bond layer 3 onto the outer peripheral surface 2 of the tire casing 1 and heating it to vulcanize and harden the bond layer 3. The pressure fluid supplied to the space 25 inside the outer skin 5 is supplied from a pressure fluid source 39 that is separate from the pressure fluid source 14 that is supplied into the pressure vessel 6 and the tire casing 1, and therefore can be easily controlled. It will definitely be done.

(Example) Embodiments of the present invention will be described below based on the drawings.

1 to 3 show embodiments of the present invention, and FIG.
Components common to those of the conventional example shown in FIGS.

As shown in FIG. 2, the flexible and airtight outer skin 5 employed in the method of the present invention has a conduit 30 for supplying pressure fluid, such as compressed air, to the outer peripheral surface 5A and for discharging internal air, etc.
is provided so that compressed air can be supplied between the tread 4 and the outer skin 5 and can be exhausted. Furthermore, inside the tire casing, there is a doughnut-shaped expansion air bag 31.
is fitted, the bead part IB of the tire casing 1 is fitted to the rim 33 via the flange 32, and the left and right inner circumferential ends 5B of the outer skin 5 are located inside the flange 32 to maintain airtightness. It is now possible to do so.

An on-off valve 34, a relief valve 35, and a three-way switching valve 36 are interposed in the conduit 30, and a compressed air supply pipe 37 and the exhaust pipe 8 are connected to the three-way switching valve 36, respectively. Further, an air pressure source 39 of another system is connected to the compressed air supply pipe 37 via a pressure regulating valve 38 .

In the above embodiment, the vulcanizing can 6 is opened, the tire assembly with the outer skin 5 is set in the vulcanizing can 6, the conduit 7 is connected to the expansion bag 31, and the conduit 30 is connected to the outer skin 5. After the connections are made, the vulcanization can 6 is closed and the vulcanization bonding process is started. First, the on-off valves 15, 16, and 17 are opened, and pressurized fluid, ie, compressed air, is supplied into the inflation bladder 31 in the tire casing 1 and into the vulcanization can 6 via the pressure regulating valve 12.13. At this time, the air pressure P supplied into the vulcanizing can 6. is set slightly lower than the air pressure P'r supplied into the inflation air bag 31, and when the on-off valve 34 is opened, the three-way switching valve 36 opens the conduit 30.
The exhaust pipe 8 is placed in communication with the exhaust pipe 8.

As shown in FIG. 3, the pressure P inside the vulcanizer 6.

When the amount reaches 3 kg/c+fl, the vacuum pump 9 starts, and the air remaining in the space 25 of the groove bottom 4A of the tread 4 and the cushion rubber N (unvulcanized rubber base bond layer) 3 is forcibly discharged. Then, the pressure inside the vulcanizing can 6 is P. When the pressure reaches the set pressure (4.5 kg/cIII), the vacuum pump 9 is stopped. Next, the three-way switching valve 36 is operated to connect the conduit 30 and the compressed air supply pipe 37, and compressed air is supplied from the air pressure source 39 into the space 25, and the pressure inside the space 25 is increased. The pressure inside the sulfur canister 6 is maintained at 3.5 kg/cJ, which is slightly lower than the pressure P0. By these operations, the pressure difference between the outer circumferential surface of the tread 4, the groove bottom 4A, and the surrounding area is small, and a uniform pressure is applied to the groove bottom 4A, thereby preventing the groove bottom 4A from deforming. Parallel to this,
Heating steam is supplied into the vulcanizing can 6 through the conduit 11, the temperature inside the vulcanizing can 6 is raised to a predetermined temperature, and vulcanization hardening progresses.
The tread 4 is vulcanized and bonded to the outer peripheral surface 2 of the tire casing 1 via three layers of cushion rubber.

Note that the pressure P in the inner space 25 of the outer skin 5 is equal to the set pressure (3
, 5kg/C), the relief valve 35 operates to maintain the appropriate set pressure. In addition, if the outer skin 5 is damaged during vulcanization and the highly compressed air inside the vulcanizing can 6 enters the inner space 25 of the outer skin 5, the relief valve 35
However, if the impact on other tires exceeds this, it is sufficient to close the on-off valve 34 of the conduit 30.

The internal pressure P of the inner space 25 of the outer skin 5 (that is, the internal pressure of the tread groove bottom 4A or the groove bottom shape retention pressure for tire performance) is determined to be the internal pressure P of the vulcanization can 6 from various test results.

95-50% is optimal. That is, the pressure P+ inside the outer skin 5 is the pressure P inside the vulcanizing can 6. If it exceeds 95%, it is sufficient to maintain the shape of the tread groove bottom 4, but the gas generated during vulcanization passes through the air vent cloth 26 due to the pressure inside the trend groove bottom 4A space 25. It becomes difficult for gas and air to flow out to the tread groove bottom 4^, and gas and air remain in the tread 4 and the adhesive layer of the Kunjeon rubber 3. Moreover, the pressure P1 inside the outer skin 5 is the pressure P inside the vulcanizing can 6.

If the pressure is less than 50%, the air or gas in the tread 4 and cushion rubber 3 adhesion layer may be sufficiently exhausted, but the pressing force at the tread groove bottom 4A will be insufficient, causing deformation of the tread groove. .

The table below shows test results regarding the influence of pressure PI/PoX100 on groove deformation.

In this way, when the vulcanization adhesion of the tread 4 to the tire casing 1 is completed, the pressure fluid inside and outside the outer skin 5 and inside the expansion bag 31 inside the tire casing 1 is discharged, and the pressure is returned to atmospheric pressure. The tire is taken out from the vulcanizing can 6 together with the outer skin 5.

Of course, the present invention is not limited to the above embodiments.

(Effects of the Invention) As described above, the tire tread retreading method according to the present invention provides a pressure lower than the pressure fluid supplied to the pressure vessel 6 in the space 25 between the outer skin 5, the tread 4, and the tire casing 1. Since the pressure fluid is supplied from a separate system, it is possible to prevent distortion from occurring in the tread groove bottom 4A and its surroundings, and to obtain a retreaded tire with a uniform shape. The remaining gas between the tread 4 and the tire casing 1 can be discharged to improve quality. In addition, since the pressure fluid supplied around the tread groove bottom 4A in the outer skin 5 is provided with a pressure source in a separate system from the pressure fluid supplied in the tire casing 1 and the pressure vessel G, the pressure can be controlled. is easy, and the control device can be simplified.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention. FIG. 1 is a schematic diagram of a tread retreading system, and FIG. 2 shows a tire assembly covered with an outer skin on a rim for carrying out the method of the present invention. 3 is a graph showing an example of the relationship between each pressure in the tire casing, the outer skin, and the pressure vessel and time; FIGS. 4 to 9 show conventional examples; The figure is a schematic diagram of the tread retreading system, Figure 5 is a sectional view of the tire assembly covered with the outer skin attached to the rim, Figure 6 is an enlarged sectional view of section A in Figure 5, and Figure 7 is the inner surface of the outer skin. Cross-section corresponding to Figure 6 showing the state with the air vent cloth inserted'
8 and 9 are explanatory diagrams of modified examples of the tread groove bottom. 1... Tire casing, 2... Outer circumferential surface, 3...
Rubber base bond layer (cushion rubber)...4...
- Tread, 5... Outer skin, 6... Pressure vessel (vulcanizing can), 25... Space. Patent applicant Otsu Tire Co., Ltd. July 6, 1999 1. Display of the case 1999 Patent Application No. 129796 2 Name of the invention Tire tread retreading method 3 Person making the amendment Relationship to the case Patent applicant name Otsu Tire Co., Ltd. 4 Agent No. 577 Address Higashiosaka, Osaka Prefecture 1013 Ichimikuriya Showa year
Date (Voluntary) 6. Subject of amendment/detailed explanation of the invention in the specification column 7. Contents of the amendment (1) "Liquidtight shell" is stated in lines 4 and 8 of page 3 of the specification. is corrected as "hermetic envelope".

Claims (3)

[Claims] (1) Tire casing with worn tread removed (
An unvulcanized rubber base bond layer (
3), a pre-cured tread (4) is adhered to the tire casing (1), and at least the tread-adjacent side walls of the tread (4) and the tire casing (1) are covered with a flexible airtight outer skin (5), and the outer skin ( The tire casing (1) and tread (4) covered with
In a tire tread retreading method, the tread (4) is pressed onto the tire casing (1) via the outer skin (5) by supplying pressure fluid to the tire casing (1), and the tread (4) is vulcanized and bonded to the tire casing (1). 4) A tire tread retreading method characterized in that a pressure fluid of a different system having a lower pressure than the pressure fluid supplied into the pressure vessel (6) is supplied to the space (25) formed by the groove of the above-mentioned pressure vessel (6). . (2) The tire tread retreading method according to claim 1, wherein the pressure fluid supplied to the inner space (25) of the outer skin (5) is compressed air. (3) The pressure of the pressure fluid supplied into the inner space (25) of the outer skin (5) is 95 to 50% of the pressure of the pressure fluid supplied into the pressure vessel (6). Tire tread retreading method described.