JPS5820766B2 - Heat demolding method for molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for demolding a hollow molded product that has been centrifugally formed in a cylindrical mold, and in particular to a method for demolding a hollow molded product that has been centrifugally molded in a cylindrical mold, and in particular to a method for removing the mold between the mold and the mold by supplying a heating medium to the mold. The present invention relates to a method for heating and demolding a molded product, in which the molded product is loosened and an extrusion force is applied to the molded product during this time.

Generally, a split-type mold that is divided into two in the longitudinal direction has been used for molding a hollow cylindrical body.

However, when molding a hollow cylindrical body using such a split-type mold, there is a problem in that many work steps and time are required from preparing the mold to demolding the molded product. there were.

Therefore, conventional methods have been used to remove molded products without disassembling the formwork, that is, heating and expanding a thermally expandable formwork.
As a result, a method has been proposed in which the molded product is released from the mold by applying an extrusion force to the molded product while the adhesion between the molded product and the molded product in the mold is broken and relaxation occurs.

By the way, when heating a mold for demolding a molded product, it is necessary to heat the mold so that continuous relaxation occurs between the mold and the molded product.

However, the formwork used for centrifugal force forming is generally equipped with so-called tires on the outer periphery of both ends in order to rotate the formwork, and the cylindrical body of the formwork is made of steel, and the tires are made of cast iron. There is a problem in that there is a difference in the materials between the two, and the main body of the formwork has a higher expansion capacity than the tire, and the tires surrounding the main body of the formwork restrict the expansion of the main body of the formwork.

Therefore, if the entire circumference of the mold is heated evenly using the conventional heating demolding method, a difference in expansion will occur between the middle part of the mold and both ends, and the molded product and the mold will not stick together in the middle of the mold. Even if the mold is cut off, the molded product and the mold are still attached to each other at both ends of the mold, and if the molded product is extruded under this condition, the molded product will be damaged.

Furthermore, under the above conditions, there is a problem in that the expansion force generated on the surface of the molded product is not transmitted to both ends of the molded product and remains within the molded product, causing cracks in the molded product.

Therefore, an object of the present invention is to create continuous relaxation between a mold having parts having different expansibility and a molded product inside the mold, so that the molded product can be extruded from the mold. The objective is to prevent damage to the molded product and also to prevent cracks from occurring in the molded product due to heating of the mold.

The heating demolding method for a molded product according to the present invention is different from a cylindrical mold that is thermally expandable and that is centrifugally molded in a cylindrical mold that has portions with different expandability at both open ends. A method of heating and demolding hollow molded products of different properties, in which a larger amount of foam is added to both ends of the mold than in the middle so that expansion occurs at both ends of the mold and the expansion gradually reaches the middle. By supplying a heating medium, the difference in expansion between the mold and the molded product causes relaxation between the mold and the molded product from both ends of the mold to the middle part, and while the relaxation is occurring, The method is characterized in that the molded product is extruded from one open end of the mold toward the other open end, and the molded product is demolded.

In addition, the thermal demolding method according to the present invention can be carried out by supplying a heating medium having a higher temperature than the intermediate part to both ends of the mold, or by supplying a heating medium to both ends before the intermediate part. Expansion of the frame is caused first at both ends of the mold, and the expansion gradually reaches the middle part, so that separation of the grinding frame and the molded product gradually progresses from both ends to the middle part. It is characterized by what it did.

The features of the invention will become clearer from the following description of the illustrated embodiments.

The heating demolding method for a molded product according to the present invention uses a molded product demolding device 10 as shown in FIG. The process consists of extruding a hollow molded product 14.

When demolding the molded product 14 from the formwork 12, first, a heating medium is supplied to the formwork 12 to heat the formwork 12. Prior to heating the formwork, the formwork 12 is rotated and the molded product 14 is heated. Preferably, the mold 12 is heated during rotation of the mold.

In this case, a cylindrical formwork 12 formed by centrifugally forming a hollow concrete molded product 14 is placed on rollers 18 provided on a base 16.

Thereafter, a drive device 20 provided under the base 16 rotates the rollers 18, thereby rotating the formwork 12.

As shown in FIG. 1, the formwork 12 includes tires 24 provided on the outer periphery of both ends of a cylindrical main body 22 for rotating the formwork.

The illustrated formwork 12 has a smaller specific heat than the concrete molded product 14 and is more expandable, and is made of steel.

Therefore, the mold 12 expands before the molded product 14 when heated to a constant temperature.

Furthermore, it is preferred that both open ends 26, 28 of the mold 12 be sealed prior to heating the mold 12.

In this case, as shown in FIG. 1, the mold is supported via a rod 32 on a means 30 for moving it toward and away from both open ends 26 and 28 of the formwork 12 (indicated by arrows in the figure). A plug 34 seals said open end 26,28.

This can prevent the heating medium from flowing into the hollow portion of the molded product 14, heating the molded product 14, and expanding the molded product together with the mold frame 12.

The plug 34 is connected to the rod 32 via a bearing 36 and rotates together with the mold.

Thereafter, a heating medium is supplied to the formwork 12 while the formwork is rotating.

As shown in FIG.
8 to the vicinity of the outer peripheral surface of the formwork 12, and a large number of ejection holes 40 of equal diameter are provided in the conduit 38 in the longitudinal direction of the formwork 12,
The heating medium is sprayed onto the entire circumferential surface of the formwork 12 through the jetting holes 40 .

As shown in FIGS. 1 and 2, the spacing between the jet holes 40 is adjusted to
It is set so that the size gradually increases from both ends 38a toward the center 38b, and the expansion is made uniformly in the circumferential direction of the formwork 12 and unevenly in the longitudinal direction, that is, both ends of the formwork 12 are expanded first. A larger amount of heating medium is supplied to both ends of the formwork 12 than to the middle part so that the expansion gradually reaches the middle part.

As a result, the form body 2 gradually moves from both ends to the middle part.
The adhesion between 2 and the molded article 14 is broken, allowing the surface portion of the molded article to expand in the longitudinal direction of the molded article, while causing relaxation which leads to separation of the two.

The molded product is allowed to expand in the longitudinal direction at its surface portion, that is, the portion where it attaches to the mold body 22.
No cracks will occur on the surface during expansion.

As shown in FIG. 1, a cover 42 is provided near the outer periphery of the formwork 12 to form an airtight chamber covering the formwork 12.
It is preferable to arrange this to prevent outside air from entering the chamber and reducing the thermal efficiency when heating the formwork.

While continuous relaxation occurs between the mold 12 and the molded article 14, the mold 12 is removed via extrusion rings 44 attached to both ends of the molded article 14, as shown in FIG. The molded product 14 is extruded from one open end to the other open end.

At this time, since the adhesion between the mold frame 12 and the molded product 14 is completely broken, the molded product 14 can be easily released from the mold without causing damage such as cracks.

Instead of releasing the molded product from the mold frame 12 by extruding it, the molded product 1 is released from one of the open ends of the mold frame 12.
4 may be pulled out and released from the mold.

When supplying the heating medium to the formwork 12, a larger amount of the heating medium was supplied to both ends of the formwork 12 than to the middle part.
By supplying a heating medium having a higher temperature than the middle part to both ends of the mold 12 or by supplying a heating medium to both ends before the middle part, expansion can be caused at both ends of the formwork 12 first.

In order to supply a larger amount of heating medium to both ends of the formwork 12 than to the middle part, as shown in FIG. may be set so that it gradually becomes smaller from both ends 38a of the conduit 38 toward the center 38b.

Note that the conduit 3 extending in the longitudinal direction of the formwork 12 shown in FIG.
8 may be further extended in an arc shape along the circumferential direction of the formwork 12, and a large number of ejection holes may be provided in the extended portion.

According to the present invention, since the mold is heated so that expansion occurs at both ends of the mold and the expansion gradually reaches the middle part, separation between the mold and the molded product occurs at both ends of the mold. It gradually progresses from the point where the expandability of the frame differs to the middle part.

Therefore, until the separation between the formwork and the molded product is completed over the entire area of the formwork, the expansion of the surface of the molded product in the unseparated areas caused by heat transfer from the heated formwork is transmitted in the longitudinal direction. This makes it possible to prevent cracks from occurring.

Furthermore, since the formwork and the molded product are not attached to each other from both ends where separation progresses more slowly than at the middle part, there is no risk of leaving unseparated areas between the formwork and the molded product.

Therefore, when extruding the molded product from the mold, it is possible to prevent the molded product from being damaged.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an apparatus for carrying out the method according to the present invention;
FIG. 2 is a view showing an embodiment of the ejection hole provided in the conduit in the apparatus shown in FIG. 1, and FIG. 3 is a view showing another example of the ejection hole shown in FIG. 2.

Claims (1)

[Scope of Claims] 1. Hollow molding that is centrifugally formed in a cylindrical mold that is thermally expandable and has parts with different expandability at both open ends, and that has a different expandability from the mold. A method for heating and demolding an article, the method comprising: supplying a larger amount of heating medium to both ends of the formwork than in the middle part so that expansion occurs at both ends of the formwork and the expansion gradually reaches the middle part; Heating the molded article, comprising extruding the molded article from one open end of the mold toward the other open end while the mold and the molded article have a relaxation between them due to differential expansion. Demolding method. 2. Heating and demolding a hollow molded product that is centrifugally formed in a cylindrical mold that is thermally expandable and has parts with different expandability at both open ends, and that has a different expandability from the mold. The method comprises: supplying a heating medium having a higher temperature than the middle part to both ends of the formwork so that expansion occurs at both ends of the formwork and the expansion gradually reaches the middle part; A method for heating and demolding a molded article, the method comprising extruding the molded article from one open end of the mold toward the other open end while relaxation is occurring between the two due to an expansion difference between the two. 3. Heat-demolding a hollow molded product that is centrifugally molded in a cylindrical mold that is thermally expandable and has parts with different expandability at both open ends, and that has a different expandability from the mold. The method comprises: supplying a heating medium to both ends of the formwork before the middle part so that expansion occurs at both ends of the formwork and the expansion gradually reaches the middle part; A method for heating and demolding a molded article, the method comprising extruding the molded article from one open end of the mold toward the other open end while relaxation occurs between the two due to an expansion difference.