JPH0247832B2 - RADENNETSUSENNYORUKONKURIITOYOJOKANETSUSOCHIOYOBIKANETSUKAN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a concrete curing heating device and heating tube using bare heating wires.

Steam heating is widely used to shorten the curing period after concrete is poured. Steam is a suitable heat source for curing because it can heat and humidify at the same time. However, there are many troublesome things involved in generating steam, such as obtaining permission to install a boiler at a concrete construction site, obtaining permission to install an oil tank, having a full-time boilerman, installing the boiler, and piping, and moreover, steam curing is not very efficient. Ta. This invention succeeded in using simpler electric heat as a heating source, increasing thermal efficiency, and making it economically comparable to steam curing. For this purpose, we developed an electric heating tube.

A conventional example of electric heating curing of concrete is as shown in U.S. Patent No. 3,938,922, in which heating wires are directly connected to the concrete on the formwork side of a concrete formwork (forming surface is a steel plate) formwork/pretension bench for producing long concrete slabs. embedded. Placing the concrete on the side of the formwork is troublesome because the heating wire is placed as close as possible to the steel plate on the molding surface without touching it, but apart from that, there is a problem of poor thermal efficiency as most of the generated heat is used to heat the concrete, and once the heating wire The problem with this is that if it is embedded, it cannot be repaired even if it burns out.

The inventor of the present invention discovered that even when reinforcing the forming surface steel plate of a formwork by pouring concrete on the back side, the electric heating equipment does not get in the way, that most of the heat generated by the heating wire can be transmitted to the forming surface steel plate, and that the heating wire does not burn out. We searched for curing heating equipment that satisfies the three conditions of easy replacement.

In order to use electric power, which is more expensive than oil for steam generation, the first priority was to increase thermal efficiency, so we first considered bringing the heating wire into direct contact with the forming steel plate through an insulator with good thermal conductivity. This allows most of the heat generated to be used for curing purposes. To do this, a commercially available heating cable coated with an insulator may be brought into close contact with the back surface of the formed steel plate. However, this does not satisfy the third condition. When the internal heating wire burns out, the insulator must be replaced as well, which is impossible if it is embedded in reinforced concrete.

In this way, the heating wire and insulating sheath, which had traditionally been made as a single unit in the concept of heating tools and heating cables, were deliberately separated, and the revolutionary concept of a heating tube in which only the heating wire could be replaced at any time was achieved, and this invention was achieved. It was reached.

First, to explain the difference between conventional heating tools and heating cables and the heating tube of the present invention, the former has a cross-sectional structure shown in Figure 1, with a heating wire (cholestantan, nichrome) 1 in the center, and a strong pressure wire on the outer periphery. There are two integrated insulating powders (magnesium oxide) and metal tubes (copper, cypronickel, stainless steel).
In other words, the heating tube of this invention, as shown in Figure 2,
A heat-resistant glass or ceramic inner tube 11 in which a heating wire (chrome iron, nichrome) 10 is housed in the center so that it can move freely, and a straight steel tube 13 on the outer periphery A mortar injected into the gap between the inner wall and the inner tube 11 to fill it. Or, it is made of insulating powder (such as magnesium oxide) 12. Compared to the former metal pipe 3, the latter steel pipe 13 is easier to weld at different levels.

The conventional heating device shown in FIG. 1 is integrated as a whole by applying pressure from the outer periphery, but the heating tube of the present invention shown in FIG. There is. However, since both ends of the steel pipe 13 are sealed with only the power supply line to the bare heating wire 10 passed through, the heat cannot escape, and all the generated heat reaches the steel pipe 13 through the inner pipe 11, mortar or powder 12.

The inner tube 11 directly receives and supports the bare heating wire 10.
However, since the current temperature of the bare heating wire 10 is gradually raised by controlling the current using a slider, etc., even if the inner tube 11 is a heat-resistant glass tube that is weaker than ceramic, it will not crack up to about 800 degrees Celsius. can withstand. However, even if cracks occur in the inner tube 11, the outer periphery is surrounded by the steel tube 13 and airtightness is maintained, and air (oxygen) is not supplied from the outside. Oxidation is prevented. The curing temperature of concrete is about 60℃, and since it is raised and lowered slowly, heating wire 1
A temperature of about 300°C is sufficient for zero. Therefore, the inner pipe 11
can be made of heat-resistant glass, which is easily available in long lengths and is inexpensive. Cheap chrome iron heating wires are sufficient. However, even with this heating tube, it is possible to heat the temperature up to 1000°C by making the inner tube 11 of ceramic and the heating wire 10 of nichrome.

However, the advantage of this heating tube is that it is not an integrated factory product like conventional products, but can be assembled at any time at the construction site without using special equipment, and it can be installed at the installation location by welding, which was previously impossible. is possible,
It is possible to freely take out and take out bare heating wires and replace them, and it is also inexpensive.

Now, although the heating pipe has been explained first, the concrete curing heating device, which was the original purpose of the invention, will be explained next.

Figures 3 and 4 are long
For the lower formwork mold 20 for manufacturing PC concrete slabs,
FIG. 2 is an explanatory diagram of an embodiment to which the present invention is applied. An upper mold for sliding molding (not shown) developed by the present inventor is run over this lower mold 20, and the concrete spread on the lower mold 20 is converted into a product 14, which is a corrugated PC concrete slab in the illustrated example. After molding and curing,
It is a peel-off type.

The molding surface of the lower mold 20 that molded the product 14 is the steel plate 2
0a, and reinforced with concrete 15 in the formwork. Therefore, the origin of this invention is that if most of the heat generated by the heating wire 10 is transmitted to the forming surface steel plate 20a, the concrete of the product 14 thereon will be most efficiently cured.

Specifically, the steel pipes 13 containing the heating wires 10 were arranged in parallel at appropriate intervals over the entire back surface of the forming surface steel plate 20a of the formwork and fixed by stepping stone welding. Ordinary steel pipe 13 on the outer periphery
The heating tube of the present invention can be easily welded and fixed to a formwork steel plate, and there is no trouble associated with attaching conventional heating tubes that cannot be welded. The welded portion 16 itself serves as a heat conduction path, and also serves to press the steel pipe 13 against the steel plate 20a by cooling and shrinking. A similar effect is produced when the fins of a fin tube used in a heat exchanger are welded with flying stones.

In FIG. 2, the heat generated in the heating wire 10 is transferred to the inner tube 11, mortar or powder 12 by radiation or conduction.
It reaches the steel pipe 13 through. Since this steel pipe 13 is surrounded by concrete and a steel plate 20a via the welded part 16, the heat that reaches the entire circumference of the steel pipe 13 flows freely through the pipe wall and is transferred to the welded part 16 or the steel plate 20a.
Thermal efficiency is good because most of the heat flows into the steel plate 20a.

The temperature of the product concrete due to curing heating is raised and lowered over time so that it forms a gentle hill with a temperature of about 60℃ at the top, so the forming surface steel plate 20
Even if the back surface of the steel plate 20a is heated by the parallel steel pipes 13 spaced apart, the temperature is almost equalized within the steel plate 20a, which has good thermal conductivity. The heating steel pipes 13 may be arranged with this in mind. Depending on the length of the formwork 20, the heating range can be divided as shown in FIGS. 5 and 6. A front and rear partition wall 17 is provided under the forming surface steel plate 20a for each section, and a heating steel pipe 13 is airtightly installed between the partition walls 17, 17, and heating wires 10 are connected to each other outside the partition wall 17.
Alternatively, the heating wire 10 and the power supply line 18 are connected. Reference numeral 19 in FIG. 5 indicates a power supply, and 19a indicates instruments such as a power supply switch, an overcurrent breaker, an earth leakage breaker, an alarm, an automatic temperature recorder, a voltage, an ammeter, an integrated meter, an automatic temperature regulator, and others.

The connection between the heating wire 10 passed through the inner tube 11 and the power supply line 18 is the same as before, and in the case of curing heating, the heating wire 1
There is no problem because the temperature at 0 is about 300℃. FIG. 7 shows an example of a method of sealing both ends of the steel pipe 13, and an example of the connecting portion of the heating wire 10 and the power supply line 18. A butyl rubber stopper 24 is fitted to the end of the tube to support the inner tube 11, and the end of the inner tube 11 and the connecting heat-resistant wire 18a are hermetically connected by a heat-resistant batten 25. The heat-resistant wire 18a is a well-known wire made of a copper tube 21, a glass fiber 22, and a Teflon 23.

As a general rule, a single piece of steel pipe 13 in one section of FIG. 6 and the inner pipe 11 inside it are used. However, if it is necessary to make a connection midway, it may be done as shown in FIG. That is, the steel pipes 13 are airtightly connected with a butyl rubber stopper 24 or heat-resistant putty on the inner surface, and the inner pipes 11 are connected with each other using a heat-resistant tape or a Teflon tube 26. In FIG. 8, a branch pipe 27 is provided in the steel pipe 13 so that mortar or insulating powder 12 can be injected through a rubber hose 28. but,
Generally, as shown in Fig. 7, before closing the end of the steel pipe 13 with a rubber stopper 24, mortar or insulating powder 12 is injected with a conventional injection tool, and the mortar is pushed into the stopper.
It's better to pack 4. The purpose of packing mortar or powder is to prevent the inner tube 11, which is relatively fragile, from moving even if it cracks, and to prevent the heating wire 10 from touching the steel tube 13. Just inject it to make sure.

Note that only one PC steel wire 29 is shown in Figures 3 and 4.
Of course, a large number of such devices are provided. Also, lower mold 2
The reason why the hollow part 30 into which concrete cannot enter is provided in the thick part of the concrete 15 in the lower mold is to reduce the volume of the concrete 15 in the lower mold and reduce the amount of heat absorbed by the concrete.

As explained above with reference to one embodiment, the present invention is characterized in that heating wires are housed in a double heating tube in a replaceable manner, and that the heating tube is placed on the back side of a forming surface steel plate of a concrete formwork. Its main feature is that it is fixed by welding, and it can be varied and applied in a variety of ways depending on the implementation conditions without changing its gist.

In this invention, an ordinary steel pipe is welded with flying stones to the back side of the steel plate on the forming surface of the concrete form, and this steel pipe is heated by an internal heating wire, so that most of the heat generated by expensive electricity is transferred to the steel plate where it is most likely to flow. Because the heat flows in the opposite direction, the heat is efficient, making electric heating economically viable. In addition, concrete formwork is often installed on site, and the curing heating device must also be suitable for on-site assembly, but the heating pipe of this invention is suitable for welding installation at the application location.
Inner tube, heating wire insertion, mortar, powder injection,
It is easy to seal with a stopper and putty, and can be completed by on-site workers alone.

In addition, this invention creates a new heating tool that is inexpensive, can be installed by welding, and can be replaced by welding, by passing a bare heating wire through a glass or ceramic inner tube and wrapping it airtight with a common steel tube through mortar or powder. Created a model. Ordinary steel pipes have a strong protective ability, and the inside is sealed with heat-resistant rubber plugs, heat-resistant putty, etc. to contain hot air, and in the unlikely event that a thermal or mechanical shock sufficient to cause cracks is applied to the inner pipe. However, since the mortar or powder on the outer periphery of the inner tube supports it, there is no risk of the heating wire touching the steel tube. Airtightness is maintained by ordinary steel pipes with sufficient toughness,
There is no risk of air entering through the cracks and oxidizing the heating wire.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional heating tool, Fig. 2 is a cross-sectional view of an embodiment of a heating tube of the present invention, and Fig. 3 is a cross-sectional view of an embodiment in which the present invention is applied to a lower formwork mold for forming a PC concrete slab. FIG. 4 is an enlarged explanatory view of the main parts, FIG. 5 is a plan view showing the electric wiring, FIG. 6 is a longitudinal sectional view, and FIG. 7 is an example of the sealed portion at both ends of the heating tube. FIG. 8 is an explanatory diagram of the connecting portions of the heating wire, the heat-resistant wire for connection, and the power supply line, and FIG. 8 is an explanatory diagram of the mutual connecting portions of steel pipes and inner pipes. 10... Bare heating wire, 11... Inner tube, 12... Mortar or insulating powder, 18... Power supply line.

Claims (1)

[Scope of Claims] 1. Ordinary steel pipes arranged in parallel at appropriate intervals and fixed by welding to the entire back surface of the forming surface steel plate of a concrete form; A heat-resistant glass or ceramic inner pipe passed through the entire internal length of these steel pipes; Insulating powder such as mortar or magnesium oxide injected into the gap between the inner wall of the steel pipe and the inner pipe, bare heating wires passed through each of the inner pipes, and power supply wiring to them, provided at both ends of the steel pipe. is a concrete curing heating device using bare heating wires, characterized in that only the power supply line to the bare heating wires is passed through and sealed. 2. A straight ordinary steel pipe, an inner pipe made of heat-resistant glass or ceramic that runs along the entire length of the steel pipe, an insulating powder such as mortar or magnesium oxide injected into the gap between the inner wall of the steel pipe and the inner pipe, and the above. A heating tube using a bare heating wire, comprising: a bare heating wire passed through the inner tube, and both ends of the steel pipe are sealed so that only a power supply line to the bare heating wire is passed through and sealed.