JPS5937207B2 - How to demold molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for demolding a molded product, and more particularly to a method for demolding a hollow cylindrical concrete molded product such as a humid pipe from a mold.

BACKGROUND ART Conventionally, as a mold for forming a humid tube or a similar hollow cylindrical body, a split type mold that is divided into one or two parts in the longitudinal direction has been used.

However, when molding a hollow cylindrical body using such a split formwork, it takes a long time from preparing the formwork to demolding the molded product, and it takes a long time to assemble and demold the split formwork. There have been various problems such as noise caused by tightening or releasing bolts during disassembly and vibrations that are undesirable for workers.

Therefore, a method has been proposed for demolding the molded product without dividing or disassembling the mold.

In this demolding method, a thermally expandable mold is heated to cause thermal expansion, and at this time an extrusion force is applied to the molded product within the mold.

By the way, in the process of manufacturing a hollow concrete IJ-note molded product, the hollow concrete IJ-note molded product inside the form is compacted by rotating the rear limb formwork in which reinforcement is placed inside the formwork and concrete is injected. The process includes steam curing after the concrete inside the form is compacted, and the concrete begins to harden during the compaction process.

In the steam curing process, the compacted molded product is heated together with the formwork in a steam room for a certain period of time while it is placed in the formwork, and then it is generally allowed to cool naturally until it reaches the same temperature as in the atmosphere. temperature is lowered.

The above-mentioned conventional method of heating and demolding the mold is carried out after this steam curing.

That is, the molded product is heated together with the mold in a steam chamber, and then cooled down to atmospheric temperature, and then the mold is heated again in order to carry out the method described above.

In this way, the conventional method of heating the formwork and demolding requires heating the formwork again after the formwork has returned to atmospheric temperature during the steam curing process, so it is difficult to remove the mold from formwork preparation. As a result, the rotation rate of the mold (the number of times one mold is used for molding the molded product) is poor.

Therefore, an object of the present invention is to improve the rotation rate of the mold by demolding the molded product by utilizing the temperature applied to the mold during the curing process.

The demolding method of the present invention includes heating a hollow cylindrical concrete molded product formed in a formwork with open ends made of a thermally expandable material together with the formwork during a curing process. Cooling the molded product by supplying a cooling medium to the hollow part, and opening one of the molds while loosening occurs between the molded product and the mold due to cooling contraction of the molded product. The method is characterized in that an extrusion force is applied to the molded product from one end toward the other open end, thereby taking out the molded product from the mold.

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

Heat curing performed when forming a hollow cylindrical body such as a concrete pipe is performed after the concrete in the formwork has been compacted into a predetermined shape, and this heat curing is usually performed using steam.

That is, the formwork and the compacted concrete pipe are placed in a steam curing chamber, and atmospheric pressure steam is introduced into the chamber.

Therefore, the temperature of both the formwork and the molded product inside, which were at atmospheric temperature at point a in Figure 1, is raised to approximately 60°C at point b, and then that temperature is maintained for a certain period of time, that is, to point C. .

The time from point a to point C is approximately 4 hours.

At the point C, the steam inside the steam curing chamber is removed, and then both the formwork placed in the chamber and the molded product therein are naturally cooled.

Then, when the temperature of the mold falls to about 40° C. during this cooling (point d), only the molded product inside the mold is cooled uniformly throughout the molded product through the hollow portion of the molded product.

This cooling can be done by supplying a cooling medium, such as air or cold air, to the hollow part of the molded article.

In this way, only the molded product within the mold is cooled for a predetermined period of time from point d.

The solid line from point a to point d in Figure 1 shows the change in temperature of the mold and the molded product inside it over time. The dotted line shows the temperature change.

Comparing the temperature drop in the formwork from point d and the temperature drop in the molded product inside, the temperature drop in the molded product is larger as is clear from the graph in Figure 1. contraction increases.

As a result, the degree of adhesion between the mold and the molded product inside the mold is relaxed, resulting in relaxation between the outer surface of the molded product and the inner surface of the mold.

At this time, the molded product can be demolded by applying an extrusion force to the molded product from one open end of the mold to the other open end.

This extrusion force may be applied during or after the molded product is cooled, as long as the cooled molded product is shrinking and the adhesive force with the mold is decreasing.

Since the linear expansion coefficients of the steel that makes up the formwork and the concrete that is the molded product are almost the same, if you try to cause the relaxation by heating alone, as in the past, a lot of heating time and thermal energy are required. shall be.

In addition, if we try to cause the above-mentioned relaxation only by cooling, concrete has a significantly larger heat capacity than steel, so it requires a lot of cooling time and cooling energy. When the temperature difference between the temperature and the temperature of the cooling medium is large, a crank occurs on the inner peripheral surface of the concrete.

However, according to the present invention, by cooling the concrete molded product during heat curing, heating of the formwork and cooling of the concrete molded product are performed in parallel, so that relaxation is caused only by heating or cooling. Compared to the above, the relaxation time and thermal energy allow the relaxation to occur quickly and without cracking.

Therefore, according to the method of the present invention, the time from point a to demolding point 1 is about 5 hours, which shortens the time until demolding by about 3 hours compared to the conventional method which required about 8 hours. be done.

As a result, the temperature of the mold that has been demolded can be rapidly returned to atmospheric temperature by appropriate means, and the mold can be used for preparing the next molded product.

This makes it possible to use one mold twice a day in the case of molding hume tubes.

In other words, since the concrete molded product is demolded from the formwork during the heat curing process, the time required from the start of molding to the demolding of the concrete molded product is significantly shortened, and the usage turnover rate of the formwork is significantly improved. do.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the temperature change of the mold and the molded product inside the mold during steam curing, the temperature change of the molded product during demolding, and the temperature change of the mold over time.

Claims (1)

[Claims] 1. During a curing process that includes heating a hollow cylindrical concrete molded product formed in a steel formwork with both ends open together with the formwork, a cooling medium is supplied to the hollow part of the molded product to improve the forming process. While the product is being cooled and relaxation is occurring between the molded product and the mold due to thermal expansion of the mold and cooling contraction of the molded product, the opening of the mold is extended from one open end of the mold to the other. A method for demolding a concrete molded product, comprising applying an extrusion force to the molded product toward an open end.