JPH031438B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to prestressed concrete (hereinafter referred to as
Twisted wire (strand) used for tensioning (noted as PC)
This invention relates to a rust-proof coating method for PC strands.

(Prior art) Conventionally, a PC strand is inserted into a synthetic resin sheath, and a rust-preventive material such as grease is filled between the sheath and the strand to form a so-called unbonded cable, which is then buried in concrete. There is the unbond method, which involves tensioning, and the post-tension bond method, which involves inserting a steel sheath buried in concrete and tensioning it, then filling the sheath with a grafting material such as cement milk and integrating it with the concrete. It is used in pretension bond construction methods, etc., in which the PC strand is tensed in advance without being used, it is buried in concrete, and the ends are cut off after the concrete hardens.

Among these construction methods, anti-rust materials are used in the unbonded construction method, but when used in other construction methods, the PC strands are in direct contact with the concrete, and water flows through the concrete.
It is now ready to reach the strand.

On the other hand, even in the unbonded construction method, if the outermost sheath is damaged, water will penetrate into the sheath.
Since it reaches the PC strand, it cannot be said to be sufficient rust prevention.

Therefore, in recent years, the outer surface of the PC strand is coated with a synthetic resin layer with adhesive properties, and the outer surface of the PC strand is inserted into the synthetic resin sheath via a lubricant layer to be used in the post-tension unbond method.
A product has been developed that can be used in the pretension bond method, in which a synthetic resin-coated material is placed directly into concrete after tensioning.

(Problem to be Solved by the Invention) Even though such conventional PC strands are coated with synthetic resin, there are gaps between each of the single wires that make up the strand, and water and water can enter into these gaps from the ends. There was a problem with air entering and corroding the PC strands.

In view of these conventional problems, the present invention provides a protection method for PC strands that can completely fill the gaps between each single wire of the PC strand with a synthetic resin material and at the same time cover the outer surface of the PC strand using a simpler process. The purpose is to provide a rust coating method.

(Means for Solving the Problems) The gist of the present invention for achieving the above-mentioned objects is to provide a PC made by twisting a plurality of single wires.
After heating the strands, the PC strands are continuously fed into a twisting and spreading machine to spread the twists so that the individual wires of the PC strands are separated from each other, and the PC strands in the twisted and spread state are passed through a synthetic resin extrusion molding machine. After heating and melting a thermoplastic synthetic resin material with adhesive properties, it is injected between each single wire, returned to the original twisted state, and sequentially extruded from the center of the molding nozzle of the molding machine to form inside and outside of the PC strand. PC characterized by forming a synthetic resin coating layer
It consists in a method of coating the strands with anti-rust coating.

(Operation) In this method, the PC strands are passed through a twisting and spreading machine to spread them in the radial direction so that the individual wires are separated from each other. By passing it through a synthetic resin extrusion molding machine in this state, the entire untwisted PC strand is inserted into the heated and melted synthetic resin material.
A synthetic resin material is inserted between each single wire. after that,
The PC strand returned to its original twisted state within the molding machine due to its own elasticity, and passed through the molding die with the synthetic resin material filled in the gaps between each single wire, so that the outer surface was molded into the shape of the die. A synthetic resin coating is applied.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an outline of each step of this embodiment. First, the PC strand coil 1 is placed on the unwinding table, and the PC strand 2 is continuously unwound.
It is passed through a heating furnace 3, an untwisting machine 4, a synthetic resin extrusion molding machine 5, and a cooling tank 6 in this order, and then wound onto a reel 8 on a winding table 7.

In the heating furnace 3, the PC is heated to approximately the same temperature as the synthetic resin material heated and melted in the extrusion molding machine 5, which will be described later.
Strand 2 is heated.

The untwisting machine 4 has a feed roller 10 that forcefully pushes out the PC strand 2, and a plurality of single wire insertion holes 11, 11, . It has a circular twisting and spreading die 12 with an open opening, which die 12 is rotatably housed in a support ring 13. Each single wire insertion hole 1 of this die 12
1, 11... from the tip of the PC strand 2, the twist is slightly untwisted, each single wire 2a, 2a... is inserted and sent out by the feed roller 10, and the twist is expanded at the die 12 position. After passing this position, the twist gradually returns to its original state due to the elasticity of the PC strand.

When the PC strands 2 are separated from each other by the untwisting machine 4, each single wire 2a is separated from the other by the untwisting machine 5, and the synthetic resin extrusion molding machine 5 melts the entire molten thermoplastic synthetic resin having polyolefin adhesive properties. The synthetic resin material 13 is inserted into the material 13, and the molten synthetic resin material 13 is infiltrated between each of the single wires 2a, and after the twist returns to its original state, the outer surface is molded by the base 14. In Figure 3, 15 is a crosshead, 16 is a material extrusion screw, and 17 is a core bar. Molded base 14 coaxially arranged with core bar 17
is located. The rear end of the core bar 17 is communicated with the intake chamber 18, and by reducing the pressure inside the core bar 17, the molten synthetic resin material is made to enter tightly between the twisted and spread single wires 2a.

In the cooling tank 6, the synthetic resin heated and melted in contact with the PC strand 2 is cooled and hardened by air blowing.

By adjusting the amount of coating in the coating tank 5 to a small amount, the PC strand 2 coated with the synthetic resin in this manner is solid and has an outer surface that matches the inner shape of the cap 14, as shown in FIG. A covering layer a having the same shape is formed.

(Effects of the Invention) As described above, the method for anti-corrosion coating of PC strands of the present invention involves continuously feeding the PC strands into a twisting and spreading machine, spreading the twists, separating the individual wires from each other, and extruding them into synthetic resin extrusion molding. By passing it through a machine to form a coating layer, the gaps between each single wire are filled with synthetic resin, and the solid synthetic resin coating is continuously and automatically performed, making it possible to completely coat the single wire with a simple process. This made it possible to obtain a rust-proof coating.

[Brief explanation of the drawing]

Fig. 1 is a side view showing a schematic configuration of an embodiment of the present invention, Fig. 2 is a front view of the twisting and spreading die, Fig. 3 is a sectional view of the untwisting machine and the synthetic resin extrusion molding machine, and Fig. 4 is It is a sectional view showing a covering state. a, ... coating layer, 1 ... PC strand coil,
2... PC strand, 2a... Single wire, 3... Heating furnace, 4... Untwisting machine, 5... Synthetic resin extrusion molding machine, 6... Cooling tank, 7... Winding stand, 8...
Reel, 14...mouthpiece, 15...crosshead,
16... Material extrusion screw, 17... Core bar, 1
8...Intake chamber.

Claims (1)

[Claims] 1 After heating the PC strand, which is made by twisting multiple single wires together, it is continuously fed into a twisting and spreading machine to
The individual wires of the PC strand are twisted so that they are separated from each other, and the twisted and expanded PC strand is passed through a synthetic resin extrusion molding machine, and a thermoplastic synthetic resin material with adhesive properties is heated and melted into each wire. The method of preventing PC strands is characterized by injecting the PC strands between them, returning them to their original twisted state, and sequentially extruding them from the center of the molding die of the molding machine to form a synthetic resin coating layer on the inside and outside of the PC strands. Rust coating method.