JP4841366B2 - Drying method for plaster mold - Google Patents

Description

  The present invention relates to a method for drying a gypsum mold used for casting a product in a dry atmosphere, the product being, for example, a mold for molding a tire.

As a product cast with a plaster mold, there is a tire molding die used for manufacturing a rubber tire used for a vehicle or the like. This mold is used when vulcanizing a green tire, and is usually formed by combining a plurality of divided molds (hereinafter referred to as “piece molds”). For example, in a so-called sectional mold, the mold is composed of a plurality of piece molds divided in the circumferential direction of the tire.
The gypsum mold is used to cast a piece mold after the gypsum slurry is poured into a rubber mold formed by transferring the master model and then dried.
Here, the reason why the gypsum mold is dried is as follows. The gypsum mold formed by solidifying the gypsum slurry obtained by mixing water with gypsum powder contains a lot of moisture in the form of crystal water and free water, and is used as it is for casting piece molds. If so, a casting defect due to the moisture is generated, so that this casting defect is prevented.
Therefore, in order to remove moisture from the gypsum mold, the gypsum mold is placed in a drying furnace, and drying is performed in an atmosphere in which the gypsum mold is dried (hereinafter referred to as “drying atmosphere”) (for example, Patent Document 1).
Japanese Patent Laid-Open No. 7-256392

By the way, in producing a gypsum mold, an organic additive or an inorganic additive is usually added to the gypsum slurry in order to improve the dispersibility of the gypsum powder, the strength of the mold, and the adjustment of the coagulation time. Further, the gypsum slurry may contain impurities through gypsum powder or additives. The additive or impurities are added to the surface of the gypsum mold when the moisture inside the gypsum mold moves toward the surface due to capillary action accompanying the evaporation of moisture from the surface of the gypsum mold during drying of the gypsum mold. May move and remain or deposit on or near the surface.
Among the additives, organic additives can be eliminated by increasing the temperature of the drying atmosphere, but if the temperature is too high, it will be difficult to ensure the strength of the gypsum mold, and a rapid temperature rise will occur in the gypsum mold. Since it causes mold cracking, the organic additive cannot be easily lost.
If there are additives or impurities on the surface of the gypsum mold that is in contact with the product piece mold, the surface of the piece mold generated when the additive reacts with the molten metal This causes casting defects such as irregularities on the surface of the piece mold caused by additives or impurities.
On the other hand, in order to prevent mold cracking due to the rapid drying of the gypsum mold, if the drying process is performed with a gradual increase in temperature of the drying atmosphere and sufficient time, it takes time to produce the gypsum mold. For this reason, the production efficiency is low, and a large amount of equipment investment is required such as a large number of drying facilities to meet the casting cycle of the mold, resulting in high costs.

  This invention is made | formed in view of such a situation, and the invention of Claims 1-6 is by suppressing the drying on a product surface compared with the drying on a non-product surface in a gypsum mold. An object of the present invention is to provide a method for drying a gypsum mold that can prevent the occurrence of casting defects in a product cast with the gypsum mold. The inventions according to claims 4 to 5 further aim to improve the drying efficiency of the gypsum mold.

According to a first aspect of the present invention, a gypsum mold for casting a product has a product surface that contacts the product and a non-product surface that does not contact the product, and the gypsum mold is dried in a dry atmosphere. In the method for drying a gypsum mold, the drying speed of the product surface is lower than the drying speed of the non-product surface.
According to a second aspect of the present invention, a gypsum mold for casting a product has a product surface that contacts the product and a non-product surface that does not contact the product, and the gypsum mold is dried in a dry atmosphere. The gypsum mold drying method is a gypsum mold drying method in which contact with the dry atmosphere is suppressed on the product side compared to the non-product side.
According to a third aspect of the present invention, in the method for drying a gypsum mold according to the first or second aspect , the product surface is sealed against a dry atmosphere in a state where the product surface is in contact with a peripheral hygroscopic member. is there.
A fourth aspect of the present invention is the gypsum mold drying method according to any one of the first to third aspects, wherein a part of the non-product surface is in contact with the hygroscopic member.
According to a fifth aspect of the present invention, in the method for drying a gypsum mold according to the third aspect, the product surface of the gypsum mold is placed facing a placement surface of a placement table having a hygroscopic property, and the product surface is described above. It is sealed by a pedestal.
A sixth aspect of the present invention is the gypsum mold drying method according to any one of the first to fifth aspects, wherein the non-product surface is exposed to a blown dry atmosphere.

According to the first aspect of the present invention, the drying speed of the non-product surface is larger than that of the product surface, and the drying on the product surface is suppressed as compared with the drying on the non-product surface. It is in a drier state compared to the product surface and its vicinity. For this reason, additives and impurities contained in the gypsum mold move toward the non-product surface and its vicinity together with moisture such as free water that moves toward the non-product surface and its vicinity due to capillary action. Agents and impurities are prevented from remaining or precipitating on and near the product surface. As a result, the surface of the product may be discolored due to a chemical reaction between the additive or impurities and the product forming material in the molten state during casting of the product cast by the gypsum mold, or the surface of the product may be uneven due to the additive or impurities. The occurrence of casting defects is prevented.
According to the second aspect, since the drying on the product surface is suppressed as compared with the drying on the non-product surface, the additives and impurities are present in the product surface and the vicinity thereof as in the first aspect. Residual or precipitation is prevented, and casting defects such as discoloration of the product surface and surface irregularities due to additives or impurities in the product cast by the gypsum mold are prevented.
According to the third aspect, since the product surface is hardly exposed to a dry atmosphere due to the simple structure of sealing the product surface, drying on the product surface is compared with drying on the non-product surface. The occurrence of casting defects in the product is prevented.
Since the water | moisture content of a gypsum mold is removed by the water absorption of a hygroscopic material according to the matter of Claim 4, the drying efficiency of a gypsum mold improves. In addition, since water absorption by the hygroscopic material is performed through the non-product surface, it contributes to preventing additives and impurities from remaining or depositing on the product surface and in the vicinity thereof.
According to the fifth aspect of the present invention, the moisture in the gypsum mold is removed by the water absorption of the mounting table on which the gypsum mold is placed, so that the drying efficiency of the gypsum mold is improved with a simple structure.
According to the sixth aspect, since the non-product surface is in a blown dry atmosphere, the drying efficiency of the gypsum mold is improved. In addition, the movement of moisture toward the non-product surface and the vicinity thereof by capillary action in the gypsum mold is promoted, which contributes to preventing additives and impurities from remaining or precipitated on the product surface and the vicinity thereof.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
The gypsum mold 10 manufactured through the drying process according to the drying method of the present invention is used for casting the tire molding die 1 shown in FIG. The mold 1 is a split mold that is divided into a plurality of piece molds. In this embodiment, as shown in FIG. A plurality of piece molds 2 divided in the circumferential direction of the tire, and an upper mold 3 and a lower mold 4 which are all shown as two-dot chain lines in FIG.

Hereinafter, as an example, a method for producing a gypsum mold 10 for casting a piece mold 2 as a product will be described.
Referring to FIG. 2, a piece mold 2 for forming the tread portion W1 of the tire W is generally cast as follows.
First, the master model 5 of the tread portion W1 is made of synthetic resin or the like (see FIG. 2A)), and then the molten rubber material is poured into the master model 5 to mold the rubber mold 6 (FIG. 2 ( b)). In the molding process of the gypsum mold 10, the gypsum slurry is poured into the rubber mold 6 to mold the gypsum mold 10 (see FIG. 2C). Since the gypsum mold 10 (ie, raw gypsum mold) obtained in this molding step contains a large amount of moisture, a drying process is performed to remove this moisture. Thereafter, a molten metal (for example, an aluminum alloy) as a forming material of the piece mold 2 in a molten state is poured into the gypsum mold 10 in which the moisture is reduced, and the piece mold 2 is cast (see FIG. 2D). A piece mold 2 shown in FIG. 2 (e) is obtained.

  As shown in FIGS. 2 (c) and 2 (d), the gypsum mold 10 is a surface that contacts the piece mold 2 (or a molten metal as a forming material of the piece mold 2 in a molten state) at the time of casting. It has a certain product surface 11 and a non-product surface 12 that is a surface that does not contact the piece mold 2 (or molten metal) during casting. The product surface 11 is composed of a molding surface 11a that comes into contact with the tire W (or green tire) (see FIG. 1) during tire molding and a non-molding surface 11b that does not come into contact with the tire W (or green tire) during tire molding. Is done.

Here, the molding surface 11a is used for molding the most important surface of a product cast by the gypsum mold 10 to which the present invention is applied, or the product is a molded product (in this embodiment, the tire W). In this case, the non-molded surface 11b is a surface other than the molded surface 11a. In FIG. 2 (c) and FIG. 2 (d), the molding surface 11a is indicated by a thick solid line for convenience of explanation.
In addition, the gypsum slurry used in the casting process includes additives (for example, organic additives) for improving the dispersibility of gypsum powder mixed with water, improving the strength of the mold, and adjusting the coagulation time. As a solidification retarder, a surfactant, and a particle size adjusting filler as an inorganic additive.

Next, a drying process in which the gypsum mold 10 obtained in the casting process is dried will be described.
Referring to FIG. 3, in order to dry the gypsum mold 10 in a dry atmosphere, a drying furnace 20 in which a drying chamber 21 is formed is used. The drying furnace 20 includes a fan 22 as a blowing means for applying a dry atmosphere to the gypsum mold 10 placed in the drying chamber 21, and a heater 23 as a heating means for heating the drying atmosphere sent by the fan 22. And an electric motor 24 as an operating means for operating the fan 22 to rotate, and a controller 25 for controlling the heater 23 and the electric motor 24.

  Referring also to FIG. 4, the gypsum mold 10 disposed in the dry atmosphere is placed on and supported by a support shelf 31 that is a support member disposed in the drying chamber 21. A gypsum mold 10 that is defined by the product surface 11 and forms a cavity 13 that is filled with a molten metal when the piece mold 2 is cast has a peripheral edge portion 10a that surrounds the opening 13a of the cavity 13 over the entire circumference.

The gypsum mold 10 is placed in a state in which the peripheral edge portion 10a is in contact with a floor board 32 (for example, a fireproof board) as a hygroscopic member, and a support shelf 31 through the floor board 32 exposed to a dry atmosphere. Placed in. In this state, the product surface 11 faces a mounting surface 32a of a floor plate 32 as a mounting table placed on the support shelf 31, and the cavity 13, and thus the product surface 11, is sealed by the floor plate 32. For this reason, the product surface 11 is sealed against the dry atmosphere and shielded from the dry atmosphere. Further, the molding surface 11a is located at a position separated from the floor plate 32 through the cavity 13.
On the other hand, most of the non-product surface 12 is exposed to a dry atmosphere and is further exposed to the wind of the dry atmosphere sent by the fan 22, and the remaining part is in contact with the floor plate 32 at the peripheral edge 10a. It is the surface 12b.

  For this reason, the product surface 11 covered with the floor plate 32 and sealed against the dry atmosphere is not exposed to the dry atmosphere at all or hardly, so that the contact with the dry atmosphere is suppressed compared to the non-product surface 12 It is in. As a result, the evaporation of moisture from the product surface 11 is slower than that of the non-product surface 12, and the gypsum mold 10 has a drying rate at and near the product surface 11 that is exposed to the dry atmosphere 12 and the vicinity of the drying speed, and the contact surface 12b absorbed by the bed 32 having hygroscopicity and the drying speed in the vicinity thereof.

The control device 25 controls the fan 22 and the heater 23 to control the temperature and the air volume of the drying atmosphere according to the dry state of the gypsum mold 10 in order to promote the drying of the gypsum mold 10.
More specifically, the temperature of the drying atmosphere is gradually increased with the lapse of time after the start of the drying process so that the drying of the gypsum mold 10 is rapidly performed and the mold is not cracked. The temperature is controlled to increase gradually (hereinafter referred to as “stepwise temperature increase”) or continuously increase (hereinafter referred to as “continuous temperature increase”) to reach the maximum temperature. And in this temperature control, a temperature sensor that detects the temperature of the gypsum mold 10 or a timer that detects the time from the start of the drying process is used, depending on the temperature of the gypsum mold 10 or the elapsed time of the drying process, The control device 25 controls the heating amount of the heater 23.
In addition, the air volume in the dry atmosphere is controlled so as to decrease as the temperature of the dry atmosphere increases in order to prevent mold cracking due to a rapid rise in the temperature of the gypsum mold 10, or the gypsum mold as the time of the drying process increases. Since the water content of 10 is reduced, the timer is used and is controlled according to the water content of the gypsum mold 10 or the elapsed time of the drying process, and as the water content decreases or the elapsed time increases. The control device 25 controls the air volume of the fan 22 via the electric motor 24 so that the air volume decreases.

  When the drying furnace 20 is operated, the drying atmosphere heated by the heater 23 and sent to the gypsum mold 10 by the fan 22 circulates in the drying chamber 21. At this time, the non-product surface 12 of the plaster mold 10 is exposed to the dry atmosphere (hot air) blown by the fan 22, while the product surface 11 is not exposed to the dry atmosphere (hot air). For this reason, moisture is efficiently evaporated from the non-product surface 12 to the product surface 11 where moisture evaporation is slow, and the removal of moisture from the non-product surface 12 and its vicinity is The gypsum mold 10 is dried preferentially and efficiently compared to 11 and the vicinity thereof. Further, since moisture is absorbed by the base plate 32 having hygroscopicity from the contact surface 12b which is the non-product surface 12, drying of the gypsum mold 10 is promoted.

In this drying process, the non-product surface 12 and its vicinity are more dry than the product surface 11 and its vicinity, so the additives and impurities contained in the gypsum mold 10 are non-product due to capillary action. Since it moves toward non-product surface 12 and its vicinity together with moisture such as free water that moves toward surface 12 and its vicinity, additives and impurities are prevented from remaining or depositing on product surface 11 and its vicinity. The As a result, the piece mold 2 (see FIG. 1) cast by the plaster mold 10 has a discoloration of the surface of the piece mold 2 due to a chemical reaction between the additive or the impurity and the molten metal, or a piece due to the additive or the impurity. The occurrence of casting defects such as irregularities on the surface of the mold 2 is prevented or suppressed. Further, in the molding surface 11a located at a position separated from the floor plate 32 through the cavity 13, an additive or an impurity that moves together with moisture due to moisture absorption of the floor plate 32 is present compared to the portion 11b1 of the non-molding surface 11b near the contact surface 12b. It becomes difficult to remain or precipitate.
Further, the gypsum mold 10 has a dry atmosphere in which the air volume is controlled after the occurrence of mold cracking is prevented by controlling the temperature of the dry atmosphere so that the temperature rises stepwise or continuously. It is applied to increase the drying efficiency.

  For gypsum molds 10 of the same specification, how to place the gypsum mold 10 on the support shelf 31 (the orientation of the product surface 11), the presence or absence of the floor plate 32, the presence or absence of temperature control of the dry atmosphere (stepwise temperature rise), and the air volume control of the dry atmosphere The result of the quality of the piece mold 2 cast by the gypsum mold 10 after the drying was performed using the presence or absence of a parameter as a parameter, and the results of Examples 1 to 3 of the present invention and Comparative Example 1 It shows in Table 1 about ~ 3.

By comparing Examples 1 to 3 and Comparative Examples 1 to 3, including the comparison between Example 3 and Comparative Example 3, the product surface 11 of the gypsum mold 10 is sealed against the dry atmosphere. The casting mold 2 is cast by the drying speed of 11 being made smaller than the drying speed of the non-product surface 12 or the contact with the drying atmosphere on the product surface 11 being suppressed compared to the non-product surface 12. It can be seen that the occurrence of defects is prevented.
By comparing Example 1 and Example 3, it can be seen that the drying efficiency of the gypsum mold 10 is improved by the floorboard 32 having hygroscopicity. Moreover, by comparing Example 1 and Example 2, it can be seen that the drying efficiency of the gypsum mold 10 is improved by controlling the air volume. By comparing Examples 1 to 3 and Comparative Example 2, the hygroscopicity It can be seen that the drying efficiency is remarkably improved by the combination of the floor plate 32 having the above and the air volume control. The reason for this is that the water absorbed by the plaster plate 32 from the plaster mold 10 is removed from the base plate 32 exposed to the dry atmosphere blown by the fan 22, so that the water absorption efficiency of the base plate 32 is maintained high. This is probably because the removal of moisture from the plaster mold 10 by the floor plate 32 was further promoted.
By comparing Examples 1 to 3 and Comparative Examples 2 and 3 with Comparative Example 1, it can be seen that the stepwise temperature rise is effective in preventing mold cracking.

Next, operations and effects of the embodiment configured as described above will be described.
In the drying method of the gypsum mold 10 in which the gypsum mold 10 is dried in a dry atmosphere, the drying speed of the product surface 11 is made smaller than the drying speed of the non-product surface 12, or the non-product surface 12 in the product surface 11 Compared to, the contact with the dry atmosphere is suppressed, so that the drying speed of the non-product surface 12 is larger than that of the product surface 11, and the drying on the product surface 11 is suppressed compared to the drying on the non-product surface 12. Therefore, the non-product surface 12 and its vicinity are in a more dry state than the product surface 11 and its vicinity. For this reason, the additives and impurities contained in the gypsum mold 10 move toward the non-product surface 12 and its vicinity together with moisture such as free water that moves toward the non-product surface 12 and its vicinity by capillary action. Therefore, additives or impurities are prevented or suppressed from remaining or depositing on the product surface 11 and the vicinity thereof. As a result, when the piece mold 2 cast by the gypsum mold 10 is cast, the surface of the piece mold 2 is discolored due to the chemical reaction between the additive or the impurity and the molten metal, or the surface of the piece mold 2 due to the additive or the impurity. Occurrence of casting defects such as irregularities in the surface is prevented.

  The product surface 11 is sealed against a dry atmosphere, so that the product surface 11 is sealed, so that the product surface 11 is hardly exposed to the dry atmosphere. Drying is suppressed as compared with drying on the non-product surface 12, and the occurrence of casting defects in the piece mold 2 is prevented.

By contacting a portion of the non-product surface 12 with the floor plate 32 that is a hygroscopic member, moisture in the gypsum mold 10 is removed by water absorption of the floor plate 32 in addition to evaporation due to the dry atmosphere. Efficiency is improved. In addition, since the water absorption by the floor plate 32 is performed through the non-product surface 12, it contributes to preventing additives and impurities from remaining or depositing on the product surface 11 and the vicinity thereof.
The plaster mold 10 is placed on a floor board 32 having hygroscopicity, and the product surface 11 is sealed by the floor board 32, whereby the moisture of the plaster mold 10 is removed by water absorption of the floor board 32 on which the plaster mold 10 is placed. Therefore, the drying efficiency of the gypsum mold 10 is improved by a simple structure.

  Further, since the molding surface 11a is located at a position separated from the floor plate 32 through the cavity 13, the molding surface 11a can be added to the contact surface 12b along with moisture absorbed by the floor plate 32 through the contact surface 12b. Since it is away from the impurities, the residue or precipitation of additives or impurities on the molding surface 11a is effectively prevented, and the occurrence of casting defects in the piece mold 2 is prevented.

  By exposing the non-product surface 12 to the blown dry atmosphere, the non-product surface 12 hits the blown dry atmosphere, so that the drying efficiency of the gypsum mold 10 is improved. In addition, the movement of moisture toward the non-product surface 12 and its vicinity due to capillary action in the gypsum mold 10 is promoted, and it contributes to preventing additives and impurities from remaining or depositing on the product surface 11 and its vicinity. .

  Further, by exposing the floorboard 32 having hygroscopicity to the dry atmosphere blown by the fan 22, moisture absorbed from the plaster mold 10 to the floorboard 32 is efficiently removed from the floorboard 32 exposed to the dry atmosphere. Therefore, the water absorption efficiency of the floor plate 32 is maintained at a high level, and the removal of moisture from the plaster mold 10 by the floor plate 32 is further promoted. As a result, the drying efficiency of the plaster mold 10 is significantly improved.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
In the gypsum mold 10 in the dry atmosphere, the product surface 11 is under the condition that the drying speed of the product surface 11 and the vicinity thereof is smaller than the drying speed of the non-product surface 12 and the vicinity exposed to the drying atmosphere. It may be exposed to the dry atmosphere in a state that is suppressed as compared to the non-product surface 12, for example, the flow rate of the dry atmosphere flowing into the cavity 13 is reduced. Compared with the product surface 12, contact with the dry atmosphere is suppressed.
The plaster mold 10 may be placed directly on the support shelf 31 without using the floor plate 32. In this case, the support shelf 31 itself may constitute a hygroscopic member. The product surface 11 may be sealed with a flexible sheet-like cover.
The hygroscopic member may be provided so as to contact the non-product surface 12 other than the contact surface with the floor plate 32 or the support shelf 31 in the gypsum mold, and further provided so as to contact a surface other than the molding surface 11a. May be.
The product cast by the gypsum mold may be a mold other than for molding a tire or an article other than a mold.

1 shows a tire molding die cast by a gypsum mold manufactured through a drying process according to a drying method to which the present invention is applied, (a) is an outline of a main part of a die divided in the circumferential direction of the tire. (B) is the bb sectional view taken on the line of (a). It is sectional drawing explaining the outline of the manufacturing process of the gypsum mold for casting the piece metal mold | die which comprises the metal mold | die of FIG. 1, and the casting process of a piece metal mold | die, (a) shows a master model, (b) Shows the process of molding a rubber mold with a master model, (c) shows the process of molding a gypsum mold with a rubber mold, (d) shows the process of casting a piece mold with a gypsum mold, e) shows the cast piece mold. FIG. 3 is a schematic view of a drying furnace for drying the gypsum mold of FIG. 2. FIG. 4 is an enlarged sectional view of a gypsum mold placed in the drying furnace of FIG. 3.

Explanation of symbols

2 ... Pie mold, 10 ... Gypsum mold, 11 ... Product side, 12 ... Non product side, 20 ... Dry oven, 32 ... Sillboard,
W ... Tire.

Claims (6)

In the gypsum mold drying method, a gypsum mold for casting a product has a product surface that contacts the product and a non-product surface that does not contact the product, and the gypsum mold is dried in a dry atmosphere.
A method for drying a gypsum mold, wherein a drying speed of the product surface is smaller than a drying speed of the non-product surface. In the gypsum mold drying method, a gypsum mold for casting a product has a product surface that contacts the product and a non-product surface that does not contact the product, and the gypsum mold is dried in a dry atmosphere.
The method for drying a gypsum mold, wherein contact with a dry atmosphere is suppressed on the product surface compared to the non-product surface. The method for drying a gypsum mold according to claim 1 or 2 , wherein the product surface is sealed against a dry atmosphere in a state where the peripheral surface hygroscopic member is in contact with the product surface .   The method for drying a gypsum mold according to any one of claims 1 to 3, wherein a part of the non-product surface is in contact with the hygroscopic member. The method for drying a gypsum mold according to claim 3, wherein the product surface of the gypsum mold is placed facing a placement surface of a placement table having hygroscopicity, and the product surface is sealed by the placement table. .   The method for drying a gypsum mold according to any one of claims 1 to 5, wherein the non-product surface is exposed to a blown dry atmosphere.

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