JP6254855B2 - Cleaning method and cleaning apparatus for tire mold - Google Patents

Description

  The present invention relates to a method and apparatus for cleaning a tire mold.

  In the tire vulcanization process, a mold is used. In the vulcanization process, a preformed raw cover is put into a mold. The raw cover is heated while being pressurized in a cavity surrounded by the mold and the bladder. The rubber composition of the raw cover flows in the cavity by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained.

  When air is left between the cavity surface of the mold and the raw cover during pressurization, a bear is formed on the surface of the tire. Bears reduce tire quality. A typical mold has vent holes or grooves. Air is discharged through the vent hole or groove.

  The cross-linking reaction in the vulcanization process described above involves the generation of by-products. Since many tires are manufactured with one mold, by-products are deposited on the cavity surface. This deposit can be a factor that degrades the quality of the tire. For this reason, the mold is periodically cleaned.

  As a mold cleaning method, “shot blast” which is inexpensive and easy to handle is widely used. In this method, abrasive is sprayed onto the cavity surface by an injector. By spraying this abrasive, the deposit on the cavity surface is scraped off. In this method, “clogging” in which the abrasive is clogged in the vent hole or groove may occur. Clogging of vent holes and grooves causes tire bears. For this reason, after cleaning, an operation for removing the clogging is necessary. A study on a cleaning apparatus and a cleaning method using shot blasting is reported in Japanese Patent Application Laid-Open No. 2009-119819.

JP 2009-119819 A

  As an abrasive used in shot blasting, glass or synthetic resin (typically melamine resin) is mainly used. A typical material for the mold is an aluminum alloy. Glass is harder than aluminum alloys. If cleaning with a glass abrasive is repeated over a long period of time, the cavity surface may be worn away. Furthermore, “pinholes” may occur on the cavity surface. These impair the tire quality. In order to maintain the tire quality, it is necessary to rework the mold. This leads to an increase in tire production costs.

  Synthetic resin is softer than glass. When a synthetic resin is used as an abrasive, wear on the cavity surface can be suppressed. However, abrasives made of synthetic resin are inferior in cleaning power compared to abrasives made of glass. This leads to an increase in cleaning time. In addition, synthetic resin is more likely to clog vent holes and grooves than glass. When an abrasive made of a synthetic resin is used, a longer time is required for the work of removing this clogging than when an abrasive made of glass is used.

  An object of the present invention is to provide a method and an apparatus for cleaning a mold at a low cost in a short time while suppressing the wear of a cavity surface and maintaining high quality of a tire.

  In the method for cleaning a tire mold according to the present invention, the cavity surface is cleaned by spraying an abrasive having an egg shell onto the cavity surface of the tire mold.

  Preferably, the average particle diameter of the egg shell is not less than 50 μm and not more than 600 μm.

Preferably, the pressure of the air sprayed with the abrasive is 2.5 kg / cm ² or more and 6.0 kg / cm ² or less.

  In the tire mold cleaning apparatus according to the present invention, the cavity surface is cleaned by spraying an abrasive having an egg shell onto the cavity surface of the tire mold.

  In the tire mold cleaning method according to the present invention, the abrasive used in shot blasting has an egg shell. The Mohs hardness of egg shells is lower than that of glass. In this method, wear of the cavity surface is suppressed as compared with a method using an abrasive made of glass. In this method, the generation of pinholes on the cavity surface is suppressed. This contributes to the improvement of tire quality. This reduces the frequency of mold rework and contributes to a reduction in production costs.

  The crushed egg shell has a moderate particle size distribution. In addition, there are sharp horns in the crushed egg shell. These contribute to the improvement of the cleaning power of the abrasive. An abrasive having an egg shell has an excellent detergency compared to an abrasive made of synthetic resin. When this abrasive is used, cleaning can be performed in a shorter time than when an abrasive made of synthetic resin is used.

  Egg shells can be moved more easily in vent holes and grooves than synthetic resins and glass. Egg shells are less prone to clogging than synthetic resins and glass. Moreover, even if an egg shell gets stuck in a vent hole or a groove, these can be easily removed. When an abrasive having an egg shell is used, the work time for removing clogging can be shortened compared to the case where an abrasive made of synthetic resin or glass is used.

FIG. 1 is a plan view showing a part of a tire mold used in a cleaning method according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a perspective view illustrating a mold cleaning method according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  1 and 2 show a part of a tire mold 2 used in the cleaning method of the present invention. This is a split type mold 2. The mold 2 includes a large number of tread segments 4, a pair of upper and lower side plates 6, and a pair of upper and lower bead rings 8. The planar shape of the segment 4 is substantially arcuate. A large number of segments 4 are arranged in a ring shape. The side plate 6 and the bead ring 8 are substantially ring-shaped. In FIG. 1, the direction perpendicular to the paper surface is the axial direction. The direction indicated by the double arrow A is the circumferential direction. In FIG. 2, what is indicated by R is a raw cover.

  FIG. 3 is a perspective view showing the segment 4 of the mold 2 of FIG. In FIG. 3, the X direction is the radial direction, and the Y direction is the axial direction. The circumferential direction is orthogonal to the X direction and the Y direction. The segment 4 has a cavity surface 10. The cavity surface 10 is formed on the inner surface in the radial direction of the segment 4. The cavity surface 10 includes a convex portion 12 and a concave portion 14. This convex part 12 respond | corresponds to the groove | channel of the tread of a tire. A tread pattern is formed on the tire by the convex portion 12 and the concave portion 14. The shape of the convex part 12 and the recessed part 14 is suitably determined according to a tread pattern. 2, illustration of the convex part 12 and the recessed part 14 is abbreviate | omitted.

  In the tire manufacturing method using this mold 2, raw cover R (unvulcanized tire) is obtained by preforming. Although not shown, the tread of the raw cover R is formed by spirally winding a strip made of uncrosslinked rubber in the circumferential direction. The raw cover R is put into the mold 2 in a state where the mold 2 is open and the bladder is contracted. The mold 2 is tightened and the bladder expands. The raw cover R is pressed against the cavity surface 10 of the mold 2 by a bladder and pressurized. The raw cover R in this state is shown in FIG. At the same time, the raw cover R is heated. The rubber composition flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained. The process in which the raw cover R is pressurized and heated is referred to as a vulcanization process. A core may be used instead of the bladder.

  As shown in FIGS. 2 and 3, in the mold 2, the segment 4 has a vent hole 16. During the pressurization, the air remaining between the cavity surface 10 of the mold 2 and the raw cover R is discharged from the vent hole 16.

  As described above, by-products can be deposited on the cavity surface 10 in the vulcanization process. This deposit can be a factor that degrades the quality of the tire. For this reason, the mold 2 is periodically cleaned. Below, the washing | cleaning method of the mold 2 is demonstrated.

The method for cleaning the mold 2 according to the present invention includes:
(1) Step of taking out segment 4;
And (2) a step of spraying an abrasive.

  In the step of taking out the segments 4, the mold 2 is disassembled and each segment 4 is taken out. This segment 4 is placed in a washing tank. By disassembling into segments 4 units, cleaning can be performed easily.

  In the step of spraying the abrasive, as shown in FIG. 3, the abrasive 20 is sprayed onto the cavity surface 10 of the segment 4 by the injector 18. The abrasive 20 is sprayed onto the cavity surface 10 together with air. In this cleaning method, the abrasive 20 has an egg shell. The abrasive 20 scrapes off the deposit on the cavity surface 10. Thereby, the cavity surface 10 is cleaned.

  This cleaning method may further include a step of arranging a plurality of segments 4 between the steps (1) and (2). In this case, the plurality of segments 4 are washed at a time. Cleaning time can be shortened.

  The step (1) of taking out the segment 4 may be omitted. In this case, the abrasive 20 is sprayed onto the cavity surface 10 of the mold 2 that has not been disassembled.

  The injector 18 in FIG. 3 is a cleaning device for the tire mold 2 that cleans the cavity surface 10 by spraying an abrasive 20 having an egg shell onto the cavity surface 10 of the tire mold 2.

  Hereinafter, the function and effect of the present invention will be described.

  As abrasives used in shot blasting, glass or synthetic resin (typically melamine resin) has been mainly used so far. However, if cleaning with a glass abrasive is repeated over a long period of time, the cavity surface may wear out. Furthermore, “pinholes” may occur on the cavity surface. These impair the tire quality. Abrasives made of synthetic resin are inferior in detergency compared to abrasives made of glass. This leads to an increase in cleaning time. Furthermore, the synthetic resin is likely to be clogged in the vent hole and the groove as compared with the glass. When an abrasive made of a synthetic resin is used, a longer time is required for the work of removing this clogging than when an abrasive made of glass is used.

  In the method for cleaning the tire mold 2 according to the present invention, the abrasive 20 used in shot blasting has an egg shell. The Mohs hardness of egg shell is equivalent to melamine resin. The Mohs hardness of egg shells is lower than that of glass. In this method, wear of the cavity surface 10 is suppressed as compared with a method using an abrasive made of glass. In this method, the generation of pinholes in the cavity surface 10 is suppressed. This contributes to the improvement of tire quality. This reduces the frequency of reworking the mold 2 and contributes to a reduction in production cost.

  The crushed egg shell has a moderate particle size distribution. In addition, there are sharp horns in the crushed egg shell. These contribute to the improvement of the cleaning power of the abrasive 20. The abrasive 20 having an egg shell has an excellent detergency compared to an abrasive made of synthetic resin. When this abrasive | polishing agent 20 is used, compared with the case where the abrasive | polishing agent which consists of synthetic resins is used, it can wash | clean in a short time.

  Eggshells are “smooth” compared to synthetic resins and glass. For example, when an egg shell, melamine resin, and glass are each passed through a glass funnel, the egg shell is the fastest through the funnel. The egg shell can be easily moved in the vent hole 16 or the groove as compared with melamine resin and glass. Egg shells are less prone to clogging than synthetic resins and glass. Further, even if the egg shell is clogged in the vent hole 16 or the groove, these can be easily removed. When the abrasive 20 having an egg shell is used, the working time for removing clogging can be shortened compared to the case where an abrasive made of synthetic resin or glass is used.

  The main component of the egg shell is calcium carbonate. For this reason, the egg shell is almost white. When removing the clogging, the operator can easily see the egg shell. This contributes to shortening the work time for removing work clogging.

  Egg shells are inexpensive. The abrasive 20 made of egg shell is inexpensive. This contributes to a reduction in the cleaning cost of the mold 2.

  The average particle diameter D of the eggshell used for the abrasive 20 is preferably 50 μm or more. The abrasive 20 having an egg shell with an average particle diameter D of 50 μm or more is excellent in cleaning power. When this abrasive 20 is used, the mold 2 can be cleaned in a shorter time.

  The average particle diameter D is preferably 600 μm or less. The abrasive 20 having an egg shell with an average particle diameter D of 600 μm or less is less likely to clog the vent hole 16 or the groove. When this abrasive 20 is used, clogging after washing can be removed in a shorter time. In the abrasive 20 having an egg shell with an average particle diameter D of 600 μm or less, wear of the cavity surface 10 is suppressed. This contributes to the improvement of tire quality. This reduces the frequency of reworking the mold 2 and contributes to a reduction in production cost. From these viewpoints, the average particle diameter D is more preferably 500 μm or less.

  In the present specification, the average particle diameter means a median value (median diameter) of particle size distribution. This is calculated from the volume distribution of the particles measured by a laser diffraction particle size distribution meter.

The pressure P of air that blows the abrasive 20 is preferably 2.5 kg / cm ² or more. In the cleaning method in which the pressure P is 2.5 kg / cm ² or more, an excellent cleaning power is realized. In this method, the mold 2 can be cleaned in a shorter time. From this viewpoint, the air pressure P is more preferably 3.0 kg / cm ² or more.

The pressure P of air is preferably 6.0 kg / cm ² or less. In the cleaning method in which the pressure P is 6.0 kg / cm ² or less, wear of the cavity surface 10 is suppressed. This contributes to the improvement of tire quality. This method reduces the frequency of reworking the mold 2 and contributes to a reduction in production costs. From this viewpoint, the air pressure P is more preferably 5.0 kg / cm ² or less.

  In this embodiment, the cleaning method according to the present invention has been described for the split mold 2. This cleaning method is not limited to the split mold 2. It can also be applied to two-piece molds.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A mold for a tire having a size of 195 / 65R15 was prepared. This mold has a vent hole. A segment was taken out from the mold, and an abrasive consisting of an egg shell was sprayed onto the cavity surface. The eggshell used has a Mohs hardness of 3. As shown in Table 1, the average particle diameter D was 130 μm, and the air pressure P for spraying was 4.5 kg / cm ² .

[Comparative Example 1]
A mold having the same specifications as in Example 1 was prepared. A segment was taken out from the mold, and an abrasive made of glass was sprayed onto the cavity surface. The glass used has a Mohs hardness of 4.5-6. As shown in Table 1, the average particle diameter D was 250 μm, and the air pressure P for spraying was 4.5 kg / cm ² . This is a conventional mold cleaning method using glass as an abrasive.

[Comparative Example 2]
A mold having the same specifications as in Example 1 was prepared. A segment was taken out from the mold, and an abrasive made of melamine resin was sprayed onto the cavity surface. The melamine resin used has a Mohs hardness of 3. As shown in Table 1, the average particle diameter D was 300 μm, and the air pressure P for spraying was 4.5 kg / cm ² . This is a conventional mold cleaning method using melamine resin as an abrasive.

[Example 2-5]
Example 2-5 was the same as Example 1 except that the average particle diameter D was changed to the value shown in Table 2.

[Example 6-9]
Example 6-9 is the same as Example 1 except that the average particle diameter D is 300 μm and the air pressure P is set to the value shown in Table 3.

[Washing time]
Using the same mold, the tire was vulcanized 1000 times. All the segments of this mold were taken out and arranged in a washing tank. Abrasive was sprayed on these at once to perform cleaning. The time from the start of spraying to the removal of all segment deposits was measured. This time measurement was performed on five sets of molds and the average value was calculated. The results are shown in Tables 1 to 3 below as cleaning times. A smaller numerical value is preferable.

[Clogging removal time]
In all the segments after the abrasive was sprayed in the above evaluation of the cleaning time, the vent hole was clogged and removed. The time from the start of work until all clogging was removed was measured. The measurement was carried out on five sets of molds in the same manner as the evaluation of the cleaning time described above, and the average value was calculated. This result is shown in the following Tables 1 to 3 as clogging removal time. A smaller numerical value is preferable.

[Mold wear degree]
After the abrasive mold was sprayed on the unused mold segments for 20 hours, the mass of the segments was measured. This mass is shown in Tables 1 to 3 below as an index with the mass of the unused segment as 100. The higher the value, the lower the attrition. Larger numbers are preferable.

  As shown in Table 1-3, in the mold cleaning method according to the present invention, the cleaning time and the clogging removal time are shortened while suppressing wear of the mold. According to this cleaning method, it is possible to clean the mold at a low cost in a short time while suppressing the wear of the cavity surface and maintaining the high quality of the tire. From this evaluation result, the superiority of the present invention is clear.

  The cleaning method described above can be applied to cleaning various molds.

2 ... Mold 4 ... Segment 6 ... Side plate 8 ... Bead ring 10 ... Cavity surface 12 ... Convex part 14 ... Concave part 16 ... Vent hole 18 ... Injection 20 ... Abrasive

Claims (3)

A method for cleaning a tire mold, wherein the cavity surface is cleaned by spraying an abrasive having an egg shell having an average particle diameter of 50 μm or more and 600 μm or less onto the cavity surface of the tire mold. 2. The method for cleaning a tire mold according to claim 1, wherein a pressure of air for spraying the abrasive is 2.5 kg / cm ² or more and 6.0 kg / cm ² or less. A tire mold cleaning apparatus for cleaning a cavity surface of a tire mold by spraying an abrasive having an egg shell having an average particle diameter of 50 μm or more and 600 μm or less onto the cavity surface of the tire mold.

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