JPS6261405B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for demolding a hollow molded product molded in a cylindrical mold, and in particular to a method for demolding a hollow molded product formed in a cylindrical mold, and in particular, by supplying a heating medium only to the mold, the gap between the mold and the mold is removed. The present invention relates to a method for thermally demolding a molded product, which breaks the adhesion and causes relaxation, and during this period applies an extrusion force or a pulling force to the molded product.

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. It was hot. Therefore, conventional methods have been used to demold the molded product without disassembling the mold, in other words, heating and expanding a thermally expandable mold, which breaks the adhesion between the mold and the molded product inside the mold. A method has been proposed in which an extrusion force is applied to the molded product while the molded product is loosened, thereby removing the molded product from the mold.

However, in this conventional heat demolding method,
The heating medium used to heat the formwork enters the hollow part of the molded product inside the formwork and heats not only the formwork but also the molded product inside the formwork, causing expansion of the formwork and the molded product. The difference becomes so small that it is impossible to reliably break the adhesion between the formwork and the molded product, and as a result,
A drawback is that the molded product is damaged when it is extruded or pulled out of the mold.

Therefore, an object of the present invention is to reliably break the adhesion between the mold and the molded product by heating only the mold to increase the difference in expansion between the mold and the molded product, thereby preventing the molded product from forming when extruding or pulling out from the mold. The purpose is to prevent damage to the

In the heating demolding method for a molded article of the present invention, the supply of the heating medium to the outer peripheral surface of the mold is sealed or shielded at both open ends of the mold, and the heating medium flows into the hollow part of the molded article. By supplying the heating medium in this way, it is possible to prevent the molded product from being heated and expanded together with the mold, and as a result, the mold and the molded product are By ensuring a large expansion difference between the two, it is possible to reliably and quickly break off the adhesion between the two.

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

The heat demolding method for a molded product according to the present invention preferably involves rotating a cylindrical mold frame 12 with both ends open using a mold demolding device 10 as shown in FIG. It involves heating the mold 12 from the outside during rotation and then extruding or pulling out the hollow molded product 14 inside the mold 12.

When demolding the molded product 14 from the formwork 12, first, the cylindrical formwork 12 in which the hollow concrete molded product 14 is centrifugally formed is placed on rollers 20 provided on the base 16. Thereafter, the roller 20 is rotated by a drive device 22 provided under the base 16, thereby rotating the formwork 12.

As shown in FIG. 1, the formwork 12 includes tires 26 provided on the outer periphery of both ends of a cylindrical main body 24 for rotating the formwork. The illustrated formwork 12 has a lower specific heat than the concrete molded product 14 and is more expandable, and is made of steel. Therefore, formwork 1
2 expands before the molded product 14 when heated at a constant temperature.

The formwork 12 is heated by supplying a heating medium to the outer peripheral surface of the formwork 12 while the formwork is rotating.
Prior to heating the mold, both open ends 28, 30 of the mold 12 are sealed. In this case, as shown in FIG. 1, a plug 36 is supported via a rod 34 on means 32 for moving it toward and away from the open ends 28, 30 of the formwork 12 (indicated by arrows in the figure). The open ends 28, 30 are sealed.
This prevents the heating medium from flowing into the hollow part of the molded product 14, thereby preventing the heating medium from flowing into the molded product 14 together with the mold frame 12.
4 can be prevented from expanding due to heating. The plug 36 is connected to the rod 34 via a bearing 37 and rotates together with the formwork 12. Thereafter, as shown in FIG.
8 to the vicinity of the outer peripheral surface of the formwork 12, and the conduit 3
The heating medium is sprayed evenly in the circumferential direction and the longitudinal direction over the entire circumferential surface of the form 12 by a large number of jet holes provided at regular intervals along the longitudinal direction of the form 12.

In this way, the heating medium is
The formwork 12 is prevented from flowing into the hollow part.
As a result, the mold 12 expands over its entire area, while the molded product 14 hardly expands, resulting in a large expansion difference between the two.
As a result, the adhesion between the mold 12 and the molded article is broken, and continuous relaxation occurs between the two. In addition, the first
As shown in the figure, a cover 4 is placed near the outer periphery of the formwork 12 to form an airtight chamber covering the formwork 12.
0, thereby preventing outside air from entering the chamber and reducing the thermal efficiency when heating the formwork 12.

While continuous relaxation occurs between the formwork 12 and the molded article 14, as shown in FIG.
The molded product 14 is extruded from one open end of the mold 12 toward the other open end via extrusion rings 42 attached to both ends of the mold. 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 14 from the mold frame 12 by extruding it, the molded product 14 may be pulled out from either of the open ends of the mold frame 12 and released from the mold.

When the formwork 12 is heated and expanded, the formwork 12 is heated evenly in the circumferential direction and the longitudinal direction. The heating medium may be supplied to the formwork 12 so that the expansion occurs first at both ends and gradually reaches the middle portion. As a result, formwork 1
The cylindrical body 24 of 2 is made of steel, and the formwork 12
There is a difference in material between the two, such as the tire 26 is made of cast iron, and the tire 26 is made of cast iron.
Even if the expansivity is smaller, it is possible to break the adhesion between the mold 12 and the molded product 14 from both ends of the mold 12 toward the middle, thereby creating continuous relaxation between them. In addition, the cylindrical body 2 of the formwork
4 and the tire 26 are made of the same material, the tire 2
6 prevents the main body 24 of the mold 12 from expanding, but by gradually expanding from both ends of the mold 12 to the middle as described above, both can be expanded equally.

In order to supply the heating medium to the formwork 12 so that the expansion of the formwork gradually occurs from both ends to the middle part, a larger amount of the heating medium is supplied to both ends of the formwork 12 than to the middle part. Therefore, as shown in FIG. 2, a large number of ejection holes 43 of equal diameter are provided in the longitudinal direction of the conduit 38, and the intervals between the ejection holes are made to gradually increase from both ends 38a of the conduit 38 toward the center 38b. Set to . Further, as shown in FIG. 3, a large number of ejection holes 43 are provided at equal intervals in the longitudinal direction of the conduit 38, and the diameter of the ejection holes is made gradually smaller from both ends 38a of the conduit 38 to the center 38b. Set to .

In addition, the formwork 12 can be heated by supplying a heating medium having a higher temperature than the middle part to both ends of the formwork 12 or by supplying the heating medium to both ends before the middle part.
2 can be expanded first at both ends.

Furthermore, as shown in FIG. 4, by supplying the heating medium from both ends of the formwork 12 toward the middle part so that the heating medium flows toward the middle part, both ends of the formwork 12 can be caused to expand first.

In addition, in the example described above, the plug 36 is used to close the formwork 1.
Although both open ends 28 and 30 of the formwork 12 are sealed, both open ends 28 and 30 of the formwork 12 may be shielded as shown in FIG. In this case, a shielding plate 44 made of a heat insulating material such as rubber or resin is placed in contact with the end face of the formwork 12, and together with the cover 40, an airtight chamber 46 is formed near the outer periphery of the formwork 12. This can prevent the heating medium from flowing into the hollow part of the molded product 14 and heating the molded product 14 together with the mold frame 12.

Further, the conduit 38 extending in the longitudinal direction of the formwork 12 shown in FIG. 1 may be further extended in an arc shape along the circumferential direction of the formwork 12, and a large number of ejection holes may also be provided in the extended portion.

According to the heating demolding method for a molded article according to the present invention,
The heating medium is supplied to the outer peripheral surface of the mold while the heating medium is prevented from flowing into the hollow part of the molded product by sealing or shielding both open ends of the mold. Only the mold frame can be heated without heating the molded product inside the frame. Therefore, a large expansion difference occurs between the mold and the molded product, which ensures that the adhesion between the two is broken quickly and that the molded product is not easily extruded or withdrawn from the mold. Damage is prevented.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an apparatus for carrying out the method according to the present invention, FIG. 2 is a view showing an example of a jet hole provided in a conduit in the apparatus shown in FIG. 1, and FIG. FIG. 4 is a longitudinal sectional view showing another example of the device shown in FIG. 1. FIG. 10: demolding device, 12: formwork, 14: molded product,
24: Cylindrical body, 26: Tire, 28, 30:
Both open ends of formwork, 36: plug, 38: conduit, 43:
Nozzle hole, 44: Shielding plate.

Claims (1)

[Scope of Claims] 1. A heat demolding method for a hollow molded product centrifugally molded in a heat-expandable cylindrical mold with both ends open, and having a different expansion property from the mold, the method comprising: supplying a heating medium to a frame, and extruding or pulling out the molded article from the mold while the mold and the molded article are relaxed due to an expansion difference between the molded article and the molded article; Heating of a molded product, characterized in that the heating medium is supplied to the outer peripheral surface of the mold while sealing or shielding both open ends of the mold to prevent the heating medium from flowing into the hollow part of the molded product. Demolding method. 2. The heating demolding method for a molded article according to claim 1, wherein the heating medium is supplied while the mold is being rotated.