JPS6025249B2 - Concrete pipe manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing concrete pipes such as centrifugally formed Hume pipes using seamless formwork (seamless pipes), and more specifically relates to a method for manufacturing concrete pipes such as centrifugal forming Hume pipes using seamless formwork (seamless pipes). The concrete pipe formed in the joint formwork was placed in a curing chamber together with the pipe and cured and cured with steam for 2 to 4 hours at 55 to 7 degrees. The present invention relates to a method for manufacturing a concrete pipe, characterized in that the concrete pipe is demolded from a seamless pipe using an extruder or a drawing machine while the temperature is maintained at a temperature of 760°C.

Recently, for example, Mochiko No. 52-37481,
As exemplified in No. 57-39208 and No. 57-3920, the centrifugal molding method using a seamless pipe formwork with a taper is superior to the conventional split mold type formwork. However, it came to be used because it saves labor in work such as demolding and improves product quality.
Apply paraffin or wax to the inner surface of the first formwork and melt it by heating the formwork to form a gap between the formwork and the concrete pipe and remove the concrete pipe from the formwork. The molding method has the disadvantage that it is difficult to uniformly apply paraffin etc. to the entire surface of the mold, and if uneven coating occurs, the smoothness of the surface of the concrete pipe will be impaired, and it is also costly. There was a drawback.

Next, just before the second demolding process, only the formwork is heated from the outside, and a gap is formed between the formwork and the concrete pipe using the difference in expansion coefficient between metal and concrete, and the mold is demolded. teeth,
Because the formwork is heated rapidly from the outside, the concrete pipe with low internal thermal conductivity cannot follow the expansion of the formwork in the axial direction, creating tensile or bending stress inside the concrete, causing cracks and breakage. There was a serious flaw. Furthermore, the method of rapidly cooling only the concrete pipe and creating a temperature difference between the formwork and the pipe just before the third demolding process is practical because it rapidly cools the thick concrete inside the formwork. This method has the same drawback as the second method that defects such as cracks occur inside the concrete pipe. In particular, the method of demolding by creating a temperature difference between the second and third formwork and the concrete pipe may have a serious adverse effect on the internal concrete pipe. The present invention relates to a completely new technology developed in view of the drawbacks of conventional methods.

As a result of various experiments over many years, the inventor of the present invention found that the concrete pipe formed within the seamless pipe was
If the pipe and concrete pipe are cured at a certain temperature range for a certain period of time, the pipe and concrete pipe will separate from each other, and even once curing is completed, if the pipe and concrete pipe are in a certain temperature range, there will be no separation between the two. It was discovered that there was a small gap between the two.

The present invention makes use of this principle, and removes the concrete pipe that has been cured at a certain temperature for a certain period of time from the curing room together with the seamless pipe, and then extrudes the concrete pipe from the pipe while the pipes are kept at a certain temperature. Or it relates to a method of pulling out. If a concrete pipe with a thickness of 26 or more walls is formed within a seamless pipe made of relatively thin steel plates with a thickness of 4 to 6 sides, and these are integrally steam-cured, the thermal conductivity between them will decrease. Because there is a difference in thermal conductivity (the thermal conductivity of steel plates is about 2 pm of that of concrete), the expansion of the pipe occurs before the expansion of the concrete pipe, and furthermore, the difference in the coefficient of expansion between steel plates and concrete is small at room temperature. However, as the temperature rises, the expansion coefficient of concrete tends to decrease, resulting in a difference in the amount of expansion between the two, and based on this principle, when the temperature in the curing chamber rises to a certain temperature, the seamless pipe and the molding inside A small gap is created between the pipe and the concrete pipe. In order to reliably create the gap necessary for demolding between the seamless pipe and the concrete pipe, it varies depending on the diameter of the concrete pipe, but for example, the diameter of the concrete pipe is 35W.
For pipes below the gunwales, the temperature of pipes and concrete pipes is 56
As shown in the experimental data shown in FIG. 1, it has been found that demolding is difficult at temperatures below 55°C.

Therefore, the pipes and concrete pipes taken out from the curing room can be placed in a demolding machine such as an extruder or a puller while maintaining a high temperature of 590°C or more without taking a long time. The mold can be removed smoothly by sliding the concrete pipe.

In the above embodiment, a mineral column is placed in advance in the seamless pipe.
When an oil-based or water-soluble release agent containing paraffin or the like as a main component is applied, the adhesion between the two is cut off, and a mutually separated state is maintained, making demolding work smoother.

As a result of various experiments, the inventor of the present invention found that after curing the pipe and concrete pipe for 2 to 4 hours in a curing chamber maintained at a temperature of 55 to 790°C, the pipe and concrete pipe were heated to approximately 55 to 75°C. At the same time, take them out of the curing room and add about 2
When demolding was performed using a demolding machine within 2006, demolding could be easily and reliably performed.

After the concrete pipe cured under the conditions described above is taken out from the curing room, it cools down over time, and if it cannot be kept at 55°C or higher, which is the optimum temperature for demolding, it will be used in Experiment 2 and Figure 2 below. As shown in the figure, the pipe and the concrete pipe are immersed in a hot water bath of about 70 to 8 pi
It is possible to demold the mold only when it is flooded to 5°C or higher, and by this method it was possible to obtain the same effect as when demolding the mold immediately after taking it out from the curing chamber described above.

Experiment 1 This experiment was conducted using a seamless pipe and a concrete pipe (diameter: 20W) heated to 75℃ in a curing room.
When the mold is taken out from the curing room, to what temperature can it be demolded? If the temperature in the demolding area is set to 170C, how many minutes after taking it out from the rolling room can demolding be done smoothly? This was an experiment to measure whether this could be achieved, and the results are shown in Figure 1.

The results revealed that demolding is possible until the temperature of the concrete pipe drops to about 5°C, and that it takes about 1 unit for the temperature to drop to 55°C.

Experiment 2 In this experiment, the pipes and concrete etc. taken out from the curing room were soaked in a moat tank of 8 pm again after the temperature had dropped to 4 pm, but the results are as follows. It was as shown in Figure 2.

When both the pipe and the concrete pipe are flooded under the above conditions, both reach a temperature of 75°C after about 5 minutes, and after that, there is no change in temperature over time. When I took it out separately and demolded it, in both cases I was able to demold it smoothly.

As mentioned above, the method according to the present invention involves demolding the seamless pipe and concrete pipe that have been flooded in a curing chamber at a constant temperature for a certain period of time while they maintain a constant temperature. There is no need to heat or cool the pipe or concrete pipe in a completely separate process, therefore, a troublesome process can be omitted, and the pipe or concrete pipe does not need to be heated or cooled rapidly. Therefore, there is no risk of tensile or bending stress being generated in the concrete pipe, resulting in cracks, etc., and the work is easy and reliable.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing experimental examples for carrying out the method of the present invention. Figure 1 Figure 2

Claims (1)

[Claims] 1. A concrete pipe formed in a seamless pipe (seamless formwork) having a predetermined taper was put into a curing chamber together with the pipe and cured by steam at 55 to 75°C for 2 to 4 hours. After that, these are taken out, and the concrete pipe is demolded from the seamless pipe using an extruder or a drawing machine while maintaining the pipe and the cocrete pipe at a temperature of 55 to 75°C, respectively. Production method. 2. If the temperature of the seamless pipe and concrete pipe taken out of the curing room drops below 55°C over time, immerse them in a hot water tank and heat them both evenly to 55-75°C again. A method for manufacturing a concrete pipe, further comprising demolding the concrete pipe using a demolding machine immediately after taking it out from the hot water bath.