Patent Application
20180105231
The present invention relates to the equipment used for the lashing of containers. More specifically, the invention relates to a lashing bar made of a composite material formed through the filament winding process to provide light weight and capacity to withstand high tensile loads, and a method of manufacturing the same.
Generally, on-deck containers refer to the boxes used for the efficient and cost-saving storage and transport of cargo.
Recently, extra-large container ships were developed for the purpose of reducing the shipping costs of containers, and these ships will often carry some thousands of containers on deck stacked more than six tiers high.
As illustrated in the figure, the conventional containers (10) are clamped together using Twistlocks (11), which fasten the upper and lower tiers of the containers (10), and then lashing bars (13) and turnbuckles (15) are secured on deck with a crisscross lashing arrangement to reinforce the strength to withstand inclined and horizontal loads.
Lashing bars are generally used on container ships to prevent containers from shifting and tilting during transportation at sea, and they connect the corner fittings and turnbuckles of containers.
As shown in
The eye type lashing bar in
The knob type lashing bar in
Meanwhile, a ship at sea moves in several degrees of motion, such as roll, pitch, and heave, and is affected by accelerations along the x, y, and z axes relative to different motions. Such acceleration causes a force on containers, which acts as a lashing force.
Lashing bars are therefore subject to strict control in accordance with marine safety control regulations so that containers are secured on deck with adequate strength higher than the design limit to withstand roll, pitch, and high winds while the ship moves at sea, and only those products whose performance has been tested by supervisory authorities are permitted to be used to meet the aforementioned standard.
To ensure adherence to these regulations, commonly used lashing bars are made of high tensile strength alloy steels including SCR4, SCM4, and SNCM8. However, products longer than 5 m weight from 20 to 25 kg each, and even products as long as 2.5 to 3 m weight 10 to 15 kg. These products cause fatigue in operators, as well as accidents during transportation, installation, and dismantling, resulting in such problems as reduced efficiency and avoidance of work.
It is therefore an object of the present invention to provide a lashing bar made of a composite material fabricated through filament winding and a method of manufacturing the same for the manufacture of lashing bars made of a composite material formed with continuous filament fibers that provides higher tensile strength at a lower specific gravity than any high-tensile steel.
In order to solve the aforementioned problem, the present invention provides a lashing bar made of a composite material comprising a bar-shaped central portion encased in a composite material through the winding of continuous fibers around the outer circumference of a metal cylindrical core which constitutes the core of the central portion; an oval coupling portion formed at one end of the aforementioned bar-shaped central portion and having wound continuous fibers attached to the holes of hook-type thimbles made from metal; and a hook-shaped coupling portion formed at the other end of the aforementioned bar-shaped central portion and having wound continuous fibers attached to the holes of two ring-type thimbles made from metal.
In order to solve the aforementioned problem, the invention also provides a method of manufacturing lashing bars of a composite material comprising (1) a step in which a forming mold for the aforementioned lashing bar is assembled and loaded onto a filament winding machine; (2) a step in which continuous fibers are wound around the outer circumference of the aforementioned loaded lashing bar forming mold through the filament winding technique; and (3) a step in which the filament wound composite product is cured to form a lashing bar.
An advantage of the present invention providing a lashing bar and a method of manufacturing the same is that it enables the manufacture of container lashing bars with light weight and capacity to withstand high tensile loads by forming a composite material through filament winding with continuous fibers including glass, carbon, and aramid fibers, which provide four to six times the tensile strength of high-tensile special steels at a specific gravity 25 to 35% lower than that of special steels, and by providing metal parts in certain areas where loads are concentrated.
Therefore, a lashing bar manufactured through the invention offers the advantages of maximizing efficiency during transportation and installation by radically lowering weight to 30 to 50% of the average weight of conventional metal lashing bars, thereby reducing accident rates and resolving the problem of work avoidance, and of allowing semi-permanent use by utilizing the corrosion resistance of the composite material, thereby solving the problem of limited service life for conventional metal products due to corrosion.
The following is a detailed description of a preferred embodiment of the present invention with reference to the accompanying drawings.
To begin with, a method of manufacturing a lashing bar made of a composite material according to the present invention with reference to
According to this embodiment, the prepared parts consist of a cylindrical core (210), hook-type thimbles (220), and two ring-type thimbles (230).
The said cylindrical core (210) constitutes the core of the center portion and a metal pipe thick enough to resist bending when tension is applied during the winding of continuous fibers.
On one end of the cylindrical core (210) are assembled the hook-type thimbles (220) and on the other end are assembled one or two ring-type thimbles (230) facing each other.
In this embodiment, the aforementioned thimbles (220, 230) are made from metal and serve as a framework for the winding of continuous fibers during the lashing bar manufacturing process and later constitute the coupling portion of a lashing bar that can be coupled to the hooks of a container and put on other rings.
The parts thus assembled are loaded onto the filament winding machine as the lashing bar forming mold (200) and then help wind the continuous fibers (240) according to the filament winding program (step 120).
Generally, the filament winding process is a fabrication technique by which the continuous filaments of fiber-reinforced plastic (FRP) are wound around and attached onto the surface of a mandrel through the application of tension, heated and cured, and then removed from the mandrel. The technique is used in the manufacture of rotationally symmetrical structures such as cylindrical or spherical pressure vessels, tanks, and pipes.
In the present invention, as shown in
In aligning continuous fibers, as shown in the plan view of
Then, in the second alignment sub-step ({circle around (2)}), the continuous fibers (240) are aligned at degrees not exceeding ±15 to minimize the loss of tensile strength while the fibers are evenly distributed lengthwise along the cylindrical core (210).
Then, in the third alignment sub-step ({circle around (3)}, the continuous fibers (240) are aligned at ±40 to ±50 degrees to efficiently and adequately resist torsion loads that arise during installation.
In alignment order of {circle around (1)}→{circle around (2)}→{circle around (3)}, the winding of the continuous fibers (240) is to be repeated a certain number of times until the fibers are attached through the application of tension to the surface of the lashing bar forming mold (20).
The types of the continuous fibers (240) to be applied in the present invention are glass, carbon, aramid, and polyethylene fibers. The tensile strengths of these fibers are generally higher than the tensile strength of high-tensile steels as shown in Table 1 below.
While the continuous fibers (240) forming the aforementioned composite material are wound and attached by tension to the surface of the lashing bar forming mold (200), the product is mounted in a rotating curing oven and then cured (step 130). Then, the product is transferred to the stripping/finishing process by which sharp edges on the surface are removed in a finishing workshop equipped with a dust collector (step 140).
Next, the stripped/finished product is tested for its capacity to withstand tensile and torsion loads (step 150) and, when the product meets its requirements, it is packaged and shipped (step 160).
A lashing bar made of a composite material manufactured and finished through the aforementioned processes according to the present invention will have the shape shown in
As shown in
As shown in an enlarged view, the oval coupling portion (320) comprises a hook-type metal thimble (220) featuring a hole into which the continuous fiber composite material (240) is integrated.
In the middle of the bar-shaped central portion (310) is located the metal cylindrical core (210) and on its outer circumference, the continuous fiber composite material (240) is integrated.
While its two metal ring-type thimbles (230) face each other, the hook coupling portion (330) is coupled to the container hook (250) in between the thimbles, and the bolts (260) pass the holes on the thimbles (230) fastening these hooks. Meanwhile, the continuous fiber composite material (240) is integrated into the holes of the ring-type thimbles (230).
Therefore, the lashing bar made of a composite material manufactured through the present invention (300) provides light weight and capacity to withstand tensile loads.
The foregoing description illustrates an embodiment of the invention pertaining to the manufacturing of eye-type lashing bars, but it will become apparent to those skilled in the art having read this detailed description that they can manufacture knob-type lashing bars through the alignment of continuous fibers through the above-described process of assembling the lashing bar forming mold (200) using the cylindrical core (210) on which stoppers are formed lengthwise at certain intervals.
The disclosed embodiment of the present invention is given by way of illustration only, and various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
Therefore, such changes and modifications may be made without departing from the scope of the invention defined in claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2016-0045712 | Apr 2016 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2017/002838 | 3/16/2017 | WO | 00 |
