EP1055598B1

EP1055598B1 - On-deck container lashing equipment

Info

Publication number: EP1055598B1
Application number: EP00110294A
Authority: EP
Inventors: Tukasa Kobe Shipyard & Machinery Works Hasegawa
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1999-05-25
Filing date: 2000-05-23
Publication date: 2006-04-19
Anticipated expiration: 2020-05-23
Also published as: KR100462927B1; EP1055598A2; DK1055598T3; KR20010049384A; DE60027349D1; JP2000335480A; EP1055598A3; DE60027349T2; JP4015318B2

Description

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

1. Field of the Invention

The present invention relates to an equipment for lashing containers stacked on the deck of a ship.

2. Description of the Related Art

Generally, on a container ship, not only containers are stowed in a hold, but also containers 2 are stacked on a hatch cover top face 1 etc. as shown in FIG. 5(a).
These stacked containers 2 may shift due to the rolling of the ship as shown in FIG. 5(b). Therefore, the containers 2 are lashed as shown in FIGS. 6(a) and 7. When it is assumed that the containers 2 are not lashed as shown in FIG. 5(a) to explain the principle of strength calculation on the lashing of container, each of the containers 2 is subjected to a horizontal force f₁, f₂, f₃ and a vertical force v₁, v₂, v₃ by the oscillation (rolling) of the ship as shown in FIG. 5(b).
At this time, a racking force R₁ expressed by Eq. 1 is created on top of the lowest-tier container by the horizontal forces f₁, f₂ and f₃. Accordingly, the container is deformed into a diamond shape, and if the deformation exceeds an allowable strength of the container itself, the container is crushed. $R_{1} = f_{1} + f_{2} + (1 / 2) f_{3}$
The aforementioned horizontal forces f₁, f₂ and f₃ develop an overturning force V₂ at a corner of the container, and if the overturning force V₂ exceeds an allowable strength of container corner and an allowable tensile strength of an automatic twist lock 3, a breaking accident occurs.
Also, the vertical forces v₁, v₂ and v₃ develop a compressive force V₁ at a corner of the container, and if compressive force V₁ exceeds an allowable compressive strength of the container body, the container is crushed.
Therefore, as shown in FIG. 6, a lashing rod 6 and a turnbuckle 7 connected to the rod 6 via a joint a are installed between a lashing eye plate 4 on the hatch cover top face 1 and a container corner metal 5, which are located on a diagonal line, by which the container 2 is lashed. Thereby, the aforementioned racking force R₁ is reduced to R₁' expressed by Eq. 2 by the horizontal component Tcosθ of a tension T created on the lashing rod 6 and the turnbuckle 7, by which the container is prevented from being crushed. ${R^{'}}_{1} = R_{1} - T \cos θ$

where θ is a tension angle of the turnbuckle 7 (lashing angle) shown in FIG. 6(b).
The horizontal component Tcosθ of the tension T also acts in the direction such as to reduce the aforementioned container overturning force V₂, by which the container overturning force V₂ is decreased. The decreased container over turning force V₂' is given by Eq. 3 according to the ratio of a container height H to a container width B. $V$ ${_{2}}^{'} = V_{2} - T \cos θ \cdot (H / B)$
Also, the container compressive force V₁ is reduced to V₁' given by Eq. 4 by the tension T on the aforementioned lashing means. ${V_{1}}^{'} = V_{1} - T \cos θ \cdot (H / B) + T \sin θ$
Therefore, inmulti-tier stacking and heavy stacking of containers, the tension T of the rod 6 is increased, or container lashing bridge pillars 8 must be installed to raise the lashing positions of the containers 2 as shown in FIGS. 8 and 9.
If the lashing tension T is increased, however, the container compressive force V₁' tends to be increased by an increase in the vertical component Tsinθ of the tension T.
The results of calculation on the lashing means shown in FIGS. 8 and 9 are given in Table 1.
In this table, case A shows the results of calculation on the second-tier container lashing means shown in FIG. 8, and case B shows the results of calculation on the third-tier container lashing means shown in FIG. 9.

As can be seen from these calculation results, the stowage weight in case A is 111.0 tons (five tier stowage) and 92.75 tons (six tier stowage), and the stowage weight in case B is 133.6 tons (five tier stowage) and 111.5 tons (six tier stowage).

Table 1 Roll Condition GW=0.5 m

		Case A	Case B	Case C
5th tier stow Container Weight(LT)	1 st tier	26.75	32.4	39.3
	2nd tier	26.75	32.4	39.3
	3rd tier	26.75	32.4	39.3
	4th tier	26.75	32.4	39.3
	5th tier	4 4 4
	Total	111	133.6	161.2
Lashing tention: T		26.94ton	28.43ton	28.63ton
Racking Force: R1		10.98ton	13.75ton	15.18t(Limit)
V.comp.:V1		82.09t(Limit)	82.19t(Limit)	76.37ton

6th tier stow	1 st tier	17.75	21.5	23.5
Container	2nd tier	17.75	21.5	23.5
Weight(LT)	3rd tier	17.75	21.5	23.5
	4th tier	17.75	21.5	23.5
	5th tier	17.75	21.5	23.5
	6th tier	4	4	4
	Total	92.75	111.5	121.5
Lashing tention: T	24.07ton	11.71 ton	26.61 ton	23.1 ton
Racking Force: R1		11.71ton	10.76ton	15.19t(Limit)
V.comp.:V1		82.02t(Limit)	82.13t(Limit)	72.82 ton

From WO 96/30255 an on-deck arrangement of container lashing equipment is known. It comprises a plurality of lashing bridge pillars to be erected on the deck of a ship to lash containers stacked on the deck between the lashing bridge pillars and a lashing bridge with an upper horizontal walkway for the workers lashing the containers. Furthermore, it comprises a plurality of first attachment members (lashing eyes) for lashing mounted on the lashing bridge pillars, a plurality of first tightening members (lashing rods), one end (the lower end) of which is to be attached to a first lashing eye on the pillar and the other end (the upper end) is to be attached to an upper corner metal of a container to be lashed so that it is directed under a steep angle upwardly. For allowing a more stable and reliable stacking of containers in addition to the first lashing members it comprises a further plurality of second tightening members (lashing rods), one end of which is to be attached to a second lashing eye mounted on the pillars in substantially the same level as the first lashing eyes and the other end (the upper end) is to be attached to a lower corner metal of the container. Two standard heights of containers should be accommodated. Therefore, the height of the first and second lashing eyes on the pillars for the first and second lashing rods should be halfway between the two mentioned standard heights. The substantially horizontally extending lashing rods thus might extend slightly downwards when the container stack (or the lowermost container) has the lowest standard height (8.5 feet) or extend slightly upwards when the they have the greatest standard height (9.5 feet).

OBJECT AND SUMMARY OF THE INVENTION

The present invention has been made to solve the above problems with the conventional on-deck arrangement of container lashing equipment. Accordingly, an object of the present invention is to provide an on-deck arrangement of container lashing equipment in which in lashing containers stacked on the deck of a ship, the arrangement of tightening means is contrived so that a force component in the direction such as to pull up the container is created, whereby the container can be prevented from being crushed, and the tightening means can be made small in size and light in weight.
To achieve the above object, the on-deck arrangement of container lashing equipment in accordance with the present invention comprises a plurality of lashing bridge pillars for erection on the deck of a ship to lash containers stacked on the deck; a plurality of attachment members mounted on said lashing bridge pillars for lashing thereto; and a plurality of tightening members, an upper end of each being adapted to be attached to one of said attachment members, a lower end of each being adapted to be attached to a lower corner metal of a container stowed between the lashing bridge pillars whereby in use all tightening members that are attached between the pillars and the containers extend slantwise downward, toward said deck of the ship. The attachment members are positioned on said lashing bridge pillars such that a lashing angle that the tightening direction of each tightening member makes with the horizontal plane is set in the range of 5 to 35 degrees, thereby providing an increased force component in a direction acting to pull up the container. The lashing angle may preferably be in the range of 25 to 35 degrees.
Further, the on-deck arrangement of container lashing equipment in accordance with the present invention is preferably characterized in that the tightening member is composed of a lashing rod and a turnbuckle or only a turnbuckle.
In the above-described on-deck arrangement of container lashing equipment in accordance with the present invention, the tightening member whose one end (upper end) is attached to the attachment member for lashing mounted on the lashing bridge pillar erected on the deck of the ship extends slantwise downward, and the other end (lower end) of the tightening member is attached to the corner metal of the container. Therefore, due to the tightening action caused by the shrinkage of the tightening member, an upward component of the tightening force acts in the direction such as to pull up the container, so that the compressive force at the container corner, which has so far presented a problem, can be decreased, thereby preventing the container from being crushed.
If the lashing angle that the tightening direction of the tightening member makes with the horizontal plane is set in the range of 5 to 35 degrees, the length of the tightening member can be decreased significantly as compared with the case of the lashing angle of 45 degrees and larger of the conventional tightening member, by which a small-sized, lightweight tightening member can be provided.
Also, as the length of the tightening member is decreased as described above, the tightening member is composed of the turnbuckle only, and the lashing rod connected to the conventional turnbuckle via the joint is omitted. Thereby, the number of required parts is decreased, and the construction is simplified, so that lowered cost and reduced maintenance can be achieved.
As described above in detail, the on-deck container lashing equipment in accordance with the present invention achieves the following effects.

(1) The tightening member whose one end (upper end) is attached to the attachment member for lashing mounted on the lashing bridge pillar erected on the deck of the ship extends slantwise downward, and the other end (lower end) of the tightening member is attached to the corner metal of the container. Therefore, due to the tightening action caused by the shrinkage of the tightening member, an upward component of the tightening force acts in the direction such as to pull up the container , so that the compressive force at the container corner, which has so far presented a problem, can be decreased, thereby preventing the container from being crushed.
(2) If the lashing angle that the tightening direction of the tightening member makes with the horizontal plane is set in the range of 5 to 35 degrees, the length of the tightening member can be decreased significantly as compared with the case of the lashing angle of 45 degrees and larger of the conventional tightening member, by which a small-sized, lightweight tightening member can be provided.
(3) As the length of the tightening member is decreased as described above, the tightening member is composed of the turnbuckle only, and the lashing rod connected to the conventional turnbuckle via the joint is omitted. Thereby, the number of required parts is decreased, and the construction is simplifies, so that lowered cost and reduced maintenance can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an on-deck arrangement of container lashing equipment in accordance with a first embodiment of the present invention;
FIG. 2 is a front view showing a modification of the on-deck container lashing equipment shown in FIG. 1, FIG. 2(a) showing a state before containers are subjected to ship oscillation, and FIG. 2(b) showing a state aftercontainers have been subjectedto ship oscillation;
FIG. 3 is a front view of an on-deck container lashing equipment in accordance with a second embodiment of the present invention;
FIG. 4 is a perspective view showing an essential part of the equipment shown in FIG. 3;
FIG. 5 is a front view showing a state in which containers are stacked on the deck of a ship, FIG. 5(a) showing a state before the containers are subjected to ship oscillation, and FIG. 5(b) showing a state after the containers have been subjected to ship oscillation;
FIG. 6 is a front view showing a state in which the container shown in FIG. 5 is provided with a conventional lashing equipment, FIG. 6(a) showing a state before containers are subjected to ship oscillation, and FIG. 6 (b) showing a state after containers have been subjected to ship oscillation;
FIG. 7 is a perspective view of a container provided with the conventional lashing equipment shown in FIG. 6;
FIG. 8 is a front view showing an example of a conventional on-deck container lashing equipment; and
FIG. 9 is a front view showing another example of a conventional on-deck container lashing equipment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a front view of an on-deck arrangement of container lashing equipment in accordance with a first embodiment of the present invention, FIG. 2(a) is a front view showing a case where the equipment shown in FIG. 1 is applied to containers stacked on a hatch cover top face, and FIG. 2(b) is a front view schematically showing a state in which the containers shown in FIG. 2(a) are subjected to ship oscillation. FIG. 3 is a front view of an on-deck container lashing equipment in accordance with a second embodimentof the present invention, and FIG. 4 is an enlarged perspective view showing an essential part of the equipment shown in FIG. 3.
First, the first embodiment of the present invention will be described. As shown in FIG. 1, in order to lash containers 2 stacked on the deck of a ship, a plurality of lashing bridge pillars 8 are erected on the deck of the ship, and a lashing eye plate 4 is mounted on the pillar 8 as an attachment member for lashing.
To the lashing eye plate 4 is attached one end (upper end) of a lashing rod 6 and a turnbuckle 7, which constitute a tightening member extending slantwise downward, and the other end (lower end) of the lashing rod 6 and the turnbuckle 7 is attached to a corner metal 5 of the container 2 stowed between the lashing bridge pillars 8.
A lashing angle α, which the tightening direction of the turnbuckle 7 constituting the tightening member makes with the horizontal plane, is set in the range of 5 to 35 degrees, preferably in the range of 25 to 35 degrees. The lashing rod 6 and the turnbuckle 7, constituting the tightening member, are connected to one another via a joint a.
FIG. 2(a) shows the case where the above-described on-deck container lashing equipment is used to lash the containers 2 stacked on a hatch cover top face 1. The symbols in FIG. 2(a) are used as in the case of FIG. 1.
FIG. 2(b) shows the state in which the containers 2 shown in FIG. 2(a) are subjected to ship oscillation (rolling). In FIG. 2(b), the vertical component T"sinα of the tension T" acts advantageously on a compressive force V₁" as is expressed by Eq. 5. ${V_{1}}^{''} = V_{1} - T^{''} \cos α \cdot (H / B) - T^{''} \sin α$
Since the lashing angle α is set in the range of 5 to 35 degrees, which is far smaller than the conventional case of 45 degrees and larger, the horizontal component T"cosα of the tension T" can be increased, so that the racking force R₁ and the overturning force V₂ can be reduced to R₁" and V₂", respectively, expressed by Eq. 6. $\begin{array}{l} {R_{1}}^{''} = R_{1} - T^{''} \cos α \\ {V_{2}}^{''} = V_{2} - T^{''} \cos α \cdot (H / B) \end{array}$
An increase in container stowing weight due to the above-described lashing equipment is shown as case C in Table 1.
As a result, the stowage weight is 161.2 tons for five tier stowage and 121.5 tons for six tier stowage. That is, the lashing means shown in FIG. 1 can ensures a stowage weight 30% or more heavier than that of the conventional second-tier lashing means shown in FIG. 8.
In the on-deck arrangement of container lashing equipment of the above-described first embodiment, the lashing rod 6 and the turnbuckle 7, which serve as the tightening member whose one end (upper end) is attached to the lashing eye plate 4 serving as the attachment member for lashing on the lashing bridge pillar 8 erected on the deck of the ship, extend slantwise downward, and the other end (lower end) of the tightening member is attached to the corner metal 5 of the container 2. Therefore, due to the tightening action caused by the shrinkage of the tightening member, an upward component of the tightening force acts in the direction such as to pull up the container 2, so that the compressive force at the container corner, which has so far presented a problem, can be decreased, thereby preventing the container 2 from being crushed.
Since the lashing angle that the tightening direction of the tightening member makes with the horizontal plane is set in the range of 5 to 35 degrees, the length of the tightening member can be decreased significantly as compared with the case of the lashing angle of 45 degrees and larger of the conventional tightening member, by which a small-sized, lightweight tightening member can be provided.
The following is a description of an on-deck arrangement of container lashing equipment in accordance with a second embodiment of the present invention. FIG. 3 is a front view thereof, and FIG. 4 is a perspective view thereof. In this second embodiment as well, in order to lash containers 2 stacked on the deck of a ship, the plurality of lashing bridge pillars 8 are erected on the deck of the ship, and the lashing eye plate 4 is mounted on the pillar 8 as an attachment member for lashing.
To the lashing eye plate 4 is attached one end (upper end) of the turnbuckle 7 serving as a tightening member, which extends slantwise downward and the other end (lower end) of which is attached to the corner metal 5 of the container 2 stowed between the lashing bridge pillars 8. The lashing rod 6 and the joint a in the above-described first embodiment are omitted. That is, since the length of the tightening member is decreased significantly as compared with the conventional tightening member by setting the lashing angle in the range of 5 to 35 degrees, it is necessary only that a rod portion of the turnbuckle 7 be lengthened slightly.
Thus, the second embodiment also achieves the same operation and effects as those of the above-described first embodiment. Further, since the tightening member is composed of only the turnbuckle owing to the decreased length of the tightening member, the number of required parts is decreased, and the construction is simplified, so that lowered cost and reduced maintenance can be achieved.

Claims

On-deck arrangement of container lashing equipment comprising:
a plurality of lashing bridge pillars (8) for erection on the deck of a ship to lash containers stacked on the deck;

a plurality of attachment members (4) mounted on said lashing bridge pillars (8) for lashing thereto; and

a plurality of tightening members (6, 7; 7), an upper end of each being adapted to be attached to one of said attachment members (4), a lower end of each being adapted to be attached to a lower corner metal (5) of a container (2) stowed between the lashing bridge pillars (8), whereby in use all tightening members that are attached between the pillars (8) and the containers (2) extend slantwise downward, toward said deck of the ship,

wherein the attachment members (4) are positioned on said lashing bridge pillars (8) such that a lashing angle (α) that the tightening direction of each tightening member (6, 7; 7) makes with the horizontal plane is set in the range of 5 to 35 degrees, thereby providing a force component in a direction acting to pull up the container (2).
On-deck arrangement of container lashing equipment according to claim 1, wherein the lashing angle (α) is set in the range of 25 to 35 degrees.
On-deck arrangement of container lashing equipment according to claim 1 or 2, wherein the tightening members are composed of a lashing rod (6) and a turnbuckle (7).
On-deck arrangement of container lashing equipment according to claim 1 or 2, wherein the tightening members are composed of a turnbuckle (7) only.