A MODIFIED DECK CELL-GUIDE SYSTEM FOR DECK STOWAGE OF CONTAINERS ON CONTAINER SHIPS

Field of the invention:

The present invention relates to on board stowage systems for cargo containers on container vessels (ships) and more particularly to an improved deck cell-guide structure for an on board stowage system.

Background of the invention:

Cargo container ships are specially designed for container carriage wherein the containers are generally carried lengthwise thereby making fore and aft loading of the containers. The stresses resulting from the movement of the ship, stack interactions between containers stowed in adjacent stacks and wind pressure are the most essential factors that need to be critically considered for securing containers on board against tipping, slippage and collapse thereof. Conventionally, the stacked stowage methods are generally used for securing the containers thereby combining with various securing methods known in the art.

A conventional container stacking system 100 is shown in FIG. 1, wherein a plurality of “On deck” containers 110 are secured by a respective plurality of lashing bars 120 secured either from a hatch cover (140) or from a lashing bridge (130) as illustrated and twist-locks (not shown). Generally, a hold portion or an under deck portion 150 includes a plurality of cell guides to secure the containers 110 therein. However, such conventional systems are associated with one or more disadvantages such as continued/ inevitable loss of on-deck containers overboard in rough weather, use of large quantities of lashing gear, lashing gear maintenance and the like. Interaction forces/slamming between adjacent container stacks are large and there are limitations in loading flexibility of containers within a container stack with very strict restrictions as to weight of containers and also strict requirements for the weighwise pyramiding of weights within a stack. This requirement of pyramiding, i.e containers with

SUBSTITUTE SHEETS (RULE 26) greater weight at the bottom of the stack and sequentially loading lighter containers at higher levels - also reduces the total stackweight capacity of individual stacks- thus also limiting the overall cargo/container capacity of the entire vessel in terms of cargo weight. Moreover, the job of checking correct application of lashing gears is a tedious work and consumes a lot of time as it essentially involves large number of lashings. Also, the job of checking container lashings becomes extremely difficult in extreme climate conditions such as heavy weather.

Another example of conventional hatch coverless/open-top container stacking system 200 is shown in FIG. 2. The container stacking system 200 includes a plurality of cell guides 210 that extend from a bottom of a hold 220 all the way through what would be hatch cover level above a deck level 230 to the required height. However, such conventional hatch coverless/open-top container stacking systems 200 have one or more of the following disadvantages. Firstly, such systems 200 involve extra steel weight which is quite substantial wherein much of the weight is especially “on deck”. Secondly, these systems 200 face problems in loading over-length containers thereby making them slightly impractical for the practical use. Thirdly, these systems 200 are also associated with problems such as excessive water ingress. Lastly, these systems 200 have limitations to stack-heights and stack-weights due to exceeding the permissible load density of tank tops and excessive weight on the lower tier of containers. Also, the “travel time” per container “move” is substantially increased since the container has to be moved up or down vertically along the entire height of the cell-guide while loading or discharging.

However, use of cell guides for securing the containers on board is well-known in the art. There are various efforts seen in the art in this regard. For example, Japanese Patent No. JP 995000174265 to Mitsubishi Heavy Ind Ltd. describes the cell guide for mounting a container on a hatch cover of a container ship. The use of lashing system is eliminated in this document wherein an elected pillar is provided between hatch openings in a deck of a container ship, and the containers are stacked on a hatch cover while they are guided between a movable cell guide and a fixed cell guide. In this system, the movable cell guide is removed through the parallel movement from the hatch cover through a connection mechanism when the hatch cover is opened/ closed. However, the mounting of these movable cell-guides is limited to mounting on deck side of the ship. Also, movable cell-guides are not very practical and also involve several problems which are intrinsic to the use of moving parts.

Alternatively, the Japanese patent no JP 2002173080 to Mitsubishi Heavy Ind Ltd provides a container loading device that increases container loading weight and reduces container loading man-hours by mounting the cell guides both on a hold part and a deck part to support the container weight on the deck part, to interrupt water to the body part and to improve maintainability of the container by perfectly interrupting water to the body part and abolish drainage inside the body part for improving operability in operating a containership. In this container loading device, both end parts of the container are engaged with cell guides standingly mounted on the deck part and the body part of a hull for loading. The cell guides are sectioned at a middle part in height direction. The hatch cover, on which the container on the deck part is loaded, is arranged at the sectioned portion. The recessed part, of which an interfering part with the hatch cover is notched at the middle part of the cell guide, is formed on the hatch cover and covered by a water interrupting member protruding from a cell guide support. However, this system is not without limitation . Firstly, in such systems the water ingress into holds takes place from the hatch covers which require additional protection. Secondly, severe stresses are generally developed on the areas near deck cell guides after loading of the containers. Such systems essentially require modification of the hatch covers thereby offering substantial limitations over use of standard hatch covers. Also, the “travel time” per container “move” is substantially increased since the container has to be moved up or down vertically along the entire height of the cell-guide while loading or discharging.

Accordingly, there exists a need for an improved deck cell-guide system for deck stowage of containers on container ships that overcomes all the drawbacks of the prior art.

Summary of the invention

The present invention provides an improved and modified deck cell-guide system that is robust and effective in operation thereby having no moving parts therein. The improved deck cell- guide system facilitates minimal possible modification to the existing container ship structures in addition to facilitating minimal possible changes in operations of the existing ships. The improved system also permits use of standard hatch covers without requiring any modification therein.

The modified deck cell guide system includes a plurality of modified deck cell guides positioned also with a respective plurality of twist-locks in conjunction with a support structure. Each modified deck cell guide has a fore length and an aft length that facilitate a transverse support to an on deck container. Each modified deck cell guide has a predefined gap between a hatch coaming and a lower part thereof. The predefined gap facilitates sliding out and lifting of a hatch cover from beneath deck cell guides. The predefined gap is preferably 6 feet in accordance with the present invention. The predefined gap enables the hatch cover to be slid off in an athwartship direction after being lifted off the hatch coaming. On larger vessels this gap may be made larger to facilitate the loading and discharging of containers directly from below the lower end of the modified deck cell-guides. These modified deck cell guides may be start at a height several container heights above the hatch cover level depending on the height of the allowable deck stack and the lashing bridge. The deck cell guides may be connected directly to the lashing bridges.

In an embodiment, the modified deck cell guide system includes a semi-automatic twist-lock operating cable that avoids contact with the support structure during loading and discharging of the container. In one embodiment, the modified deck cell guide is an equal angle steel flat bar/angle bar with a gap between lower end of deck cell guide and hatch cover. In one more embodiment, the lower part of the modified deck cell guide is elevated above the hatch coaming. In an alternative embodiment, the twist-locks are secured on an upper stack of the containers and the modified deck cell guides are secured on a lower stack of the containers with or without twist- locks- This is feasible only for smaller vessels. In another alternative embodiment, the modified deck cell guides respectively include an insertion guide on their lower end as well as their usual top ends that avoids snagging of the container during discharging operation thereof. The insertion guides facilitate easy discharge of the containers below a lower level of the modified deck cell guides. In still another embodiment, the deck cell guides include a predefined gap from the support structure to the container for insertion of an emergency operating tool therein. This gap in deck cell guides prevent damage to the twist- locks during loading/discharge of the containers. In yet another embodiment on larger vessels, the modified deck cell guide system includes an outboard positioning mechanism having a plurality of outboard rows having modified deck cell guides positioned thereon in order to reduce use of lashings for inboard stacks of the containers. The number of these outer modified deck cell guides may vary according to ship size. On smaller vessels modified deck cell guides may be used on all rows. In further embodiment, the modified deck cell guides include a plurality of lightening holes that enable access to the twist-locks In another embodiment several designs of fully automatic twistocks may be used and the gap between container stack and cell guide interface adjusted to allow enough “play” to enable use of these types of automatic twistlocks. In case twistlocks are used throughout the entire stow then the modified cell guides may be designed to only provide lateral (transverse) support - and not longitudinal support. Container stresses and vessel accelerations are largest in the lateral (transverse) direction. The longitudinal support provided by twistlocks in this embodiment are sufficient to provide support against longitudinal accelerations which are far less in magnitude than lateral (transverse) accelerations.

Brief description of drawings as shown below:

The above mentioned and other features, aspects and advantages of the present invention will become better understood with regard to following description, appended claims and accompanying drawings, wherein like reference numerals refer to similar parts throughout the several figures where

FIG. 1 illustrates a prior art container stacking system for "On deck" containers that are secured by a plurality of lashing bars and twist-locks;

FIG. 2 illustrates a prior art hatch coverless/open-top container stacking system;

FIG. 3 shows a modified deck cell guide system (MODC, hereinafter) constructed in accordance with the present invention wherein the fore-and-aft length of said MODC provides only transverse restraint;

FIG. 4A shows a profile view of the MODC adapted for having easy access to twist-locks; FIG. 4B shows a preferred method of securing the containers using MODCs and twist-locks in combination;

FIG. 4c shows a perspective view of the MODC adapted for having easy access to twist-locks thereby facilitating an ability to enable use of standard hatch covers which do not require any modification wherein the standard hatch covers require to be lifted off the hatch coaming then moved transversely below the level of the MODCs before being lifted off;

FIG. 5 is an alternative embodiment of MODC with regard to use of advanced twist-locks such as fully automated twist-locks (FA/Ls, hereinafter) and remotely accessed twist-locks (RATs, hereinafter);

FIG. 6 shows an outboard positioning mechanism of MODCs with regard to use on larger vessels;

FIG. 7 shows an arrangement for the MODCs adapted for the vessels wherein said MODCs are not in vertical alignment with hold cell guides;

FIG. 8 shows an arrangement of lightening holes adapted for accessing twistlocks between the support structure part of MODC and container.

FIG. 9 shows an arrangement of MODCs starting at a height above the hatch covers to enable loading/discharging of containers from below the MODC level. This arrangement is preferable on larger ships with larger number of deck container stack. This will reduce “travel time” of container loading/discharging as well as enable the MODCs to provide support at a greater height along the deck container stack. Thus providing more effective support and utilising lower amount of steel weight. The MODCs will also provide an interruption to interaction/slamming forces between adjacent stacks of containers. Detailed Description of the invention:

Although specific terms are used in the following description for sake of clarity, these terms are intended to refer only to particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention. The invention described herein is explained using specific exemplary details or better understanding. However, the invention disclosed can be worked on by a person skilled in the art without the use of these specific details.

References in the specification to "one embodiment" or " an embodiment" means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

References in the specification to “preferred embodiment/ s” means that a particular feature, structure, characteristic, or function described in detail thereby omitting known constructions and functions for clear description of the present invention.

Accordingly, the present invention provides a modified deck cell-guide system (MODC, hereinafter) along with twist-locks together in the same stack as opposed to usual practice of only either cell guide or lashing bar/ twist-lock combination known in the prior art. The MODCs of the present invention enable fore and aft length of the MODCs to be modified so as to specifically provide transverse support to the containers and not longitudinal support. The MODC create a predefined gap between a hatch coaming and a lower end of deck cell guide to primarily facilitate “sliding out” of the hatch cover from beneath deck cell-guides after the hatch cover is lifted off the hatch coaming followed by lifting thereof. On larger vessels the MODCs will be required to start at a greater height above the hatch coamings to enable loading/discharging of containers below the lower end of the MODCs so as to reduce “travel time” as well as provide overall better productivity and lesser use of steel weight for the MODCs. The MODCs of the present invention are advantageously implemented on existing cell-guide systems such that preferably only three to four outboard rows may be fitted with MODCs and the “center” rows are left unaltered thereby giving consideration to reduced lashing to the remaining inboard rows. The use of MODCs facilitates existing container vessels to be retrofitted with minimum modification in structure and change in operation thereof.

The present invention provides improved deck cell-guide system having at least partial implementation of MODCs therein that leads to minimal structural change in the conventional structures, but still being effective in eliminating container losses during use/ operation as also potentially reduced use of lashings for the inboard rows. The aim of the MODCs in the context of the present invention is to replace and improve the function of conventional lashing bars and also to allow the normal stacking, removal and placing of standard hatch covers.

Now referring to FIG. 3, a modified deck cell guide (MODC, hereinafter) 300 constructed in accordance with the present invention is shown wherein a fore-and-aft length 310 of the MODC 300 is adapted to provide only transverse restraint. The fore-and-aft length 310 provides transverse support only to the containers in accordance with the present invention. The MODC 300 has a support structure 320 as illustrated. A twist-lock operating cable 330 which is used in manually operated Twist-locks is shown as being well clear of the support structure 320 so as to avoid contact with the support structure 320 during loading/discharging of the container 340. It is understood here that FA/Ls and RATs do not have any such extending parts/cables hence the distance/clearance from the support structure requires to be accordingly less in this one embodiment. Now referring to FIGS. 4A and 4B, use of MODC 410 for facilitating easy access for a plurality of twist-locks 420 is shown. In this one embodiment, a standard equal angle steel flat bar/equal angle bar 430 is used as cell-guides in the holds. The MODCs 410 provide only transverse support such that lower part of MODC 410 is elevated above a hatch coaming, by approximately 6 feet distance in this one embodiment, to enable sliding out of a hatch cover 440 below the level of MODCs 410 after being lifted off the hatch coaming before being lifted clear as required . This further enables the hatch cover 440 to be slid off athwartship as shown by the line- A-A, in either direction atwhartships, as shown in FIG. 4A. The hatch cover 440 facilitates easy access to a plurality of containers 450 positioned below the hatch cover 440 after being lifted off. A support framework 460 is preferably adapted to facilitate support to MODCs 410.

As shown in FIG. 4B- 4C, an upper stack of the containers on deck 450 is preferably secured with the twist-locks 420 and a lower stack of the containers 450 is preferably held in position with the MODCs 410 and twist-locks 420 combined as illustrated. The MODC 410 extends to about a predefined height H depending on the design height of the stack. A predefined gap G is maintained between the hatch coaming and lower end of MODCs 410, which is preferably maintained at a distance of about 6 feet in this one preferred embodiment. However, it is understood that the predefined height H and the predefined gap G may vary in other alternative embodiments of the present invention. On larger vessels the preferred embodiment would require a greater height H and preferred gap G to enable loading/discharge of containers below the MODCs in an athwartship direction.

Referring again to FIG. 4C, the MODCs 410 preferably have their lower ends 470 provided with insertion guides. The insertion guides require to be placed so as to avoid snagging of the containers 450 at the lower end of the MODCs 410 during discharging operation. The insertion guides on the lower ends 470 of the MODCs 410 also facilitate easy discharge of containers below the lower level of the MODCs 410.

Referring to FIG. 5, an alternative embodiment of MODCs 510 is shown with regard to use of advanced twist- locks such as FA/Ls and/or RATs, wherein there exists an opportunity to reduce a distance “D” as illustrated. The idea being that access to twist-locks is available. It is understood here that in an emergency, in case of a twist-lock malfunction, an emergency operating tool may be used in said gap D. The gap D between the fore-and-aft section of the container wall and the MODC support structure may be kept at an approximate distance of about 6 inches, if using FA/Ls or RATs. Further, it is understood that it would then require greater strengthening and support framework 520 in conjunction with MODCs 510, if the total fore and aft length of the cell guide is “L” as illustrated.

In this one embodiment, the forward and aft sections of the MODCs 510 are “free”, hence the release of a container 530 while discharging has no problem during operation when using FA/Ls or RATs. Also, unlike, semi-automatic and other twist-locks there are no parts that extend out of a boundary of the container 530 while using FA/Ls or RATs, which may damage the twist-lock while loading/discharge. Hence, no part of the twist-lock may get damaged with use of MODCs 510 of the present invention. However, it is understood here that in the view of the current doubt about the efficacy of FA/Ls, semi-automatic twist-locks or RATs may be preferably used for the containers 530 stowed above the MODCs 510.

Alternatively, in cases where the conventional twist-locks are used (semi or fully automatic twist-locks) which have extending operating cables (as shown in FIG. 3) having a part protruding from the boundary of the container wall, a sufficiently large gap is maintained with the use of the MODCs 510 so as to avoid damage of this protruding part of the twist- lock coming in contact with the MODC strengthening structure is required. The exact dimensions of the gap will vary depending on the height of stack to be secured and hence dimensions of the strengthening structure of the MODCs 510. However, it is understood here that over-length containers of length 40 feet and above would be loaded above the height of the MODCs 510 in the context of the present invention.

Referring to FIG. 6, an outboard positioning mechanism 600 of MODCs 610 adapted for larger vessels is shown wherein a predefined number of outboard rows Rl, R2 are positioned with MODCS 610. In this one particular embodiment, the outboard positioning mechanism 600 includes four outboard rows Rl, R2 that have MODCs 610 positioned thereon. However, it is understood here that the number of outboard rows Rl, R2 may vary in other alternative embodiments of the present invention depending on the size of the vessel and the outreach of shore gantry cranes. Further, it is understood that use of MODCs 610 on the outboard rows Rl, R2 substantially reduce lashings of inboard stacks of the containers. As well as eliminate the possibility of loss of containers overboard. Also shown are hatch covers 620.

Referring to FIG. 7, an arrangement for the MODCs 710 of the present invention is shown for the vessels wherein the MODC 710 is not in vertical alignment with hold cell guides 720. In such cases, MODC 710 is essentially positioned approximately at a predefined height HI. The height HI is preferably 10 feet or above the hatch coming level for enabling a container 730 to be moved along a direction D1 to first clear a lower end of the MODCs 740 followed by realignment thereof with the Hold cell-guides 720 for being moved along a direction D2 as illustrated. The lower end 740 of the MODCs 710 is also fitted with insertion guides (not shown) to enable the smooth discharging of the container 730 from the Hold and Tier 82.

Referring to FIG. 8, an arrangement for the MODCs 810 of the present invention is shown wherein a plurality of lightening holes 820 are introduced in said arrangement. This arrangement reduces the distance between container and athwart ships part of MODC 810. The lightening holes 820 are preferably configured on a support structure 830 as illustrated. The lightening holes 820 enable access to respective twist-locks in case of malfunctioning of said twist-locks.

Referring now to Fig.9. MODCs 910 the lower level of which is at a considerable height above the hatch coaming level and well above the Hold (under deck cell guides) 920 thus enabling containers 930 to be loaded/discharged athwartships below the MODC levels.

Referring now to FIGS. 1-9 in operation, the MODCs provide only transverse restraint to the containers as compared to conventional equal-angle cell-guides which support containers both longitudinally and transversely. However, standard equal angle deck cell guides may also be used without twist-locks with a gap between the MODC and hatch cover. The MODCs facilitate comfortable use of twist-locks that can be used in addition to the MODCs supported by deck structures throughout the entire deck stow. Accordingly, the present invention provides a system wherein both twistlocks and MODCs are used together. This is not possible with prior art. In operation, The MODCs may also be used in conjunction with not only twist-locks but also lashing bars to even further increase efficiency of the system of the present invention.

Further, the MODCs of the present invention provide a gap between the fore-and-aft end of the container and the support structure of the proposed MODC that enables the use twist-locks and removal thereof in case of malfunctioning. The exact dimensions of the gap are substantially dependent on the height of stack to be secured and type of twist-lock to be used and hence dimensions of the strengthening structure of the MODCs. In operation, the MODCs start from a height above the hatch cover so as to enable the “sliding out” of the hatch cover below the level of the MODCs in an athwarthship direction before the hatch cover is lifted off. On larger vessels with container stack heights greater than 4 to 5 containers high the lower level of the MODCs may be at a height so as to enable loading/discharging of containers in an athwartship direction below the MODC level so as to avoid “travel” all along the MODCs.

In operation, the MODCs of present invention eliminate the perpetual threat of losing containers at sea. The MODCs of present invention reduce lashing equipment on the decks of container ships which is by virtue of the ability of the MODCs to reduce lashings on inboard containers since the outboard rows are completely secured due to use of the MODCs. The MODCs of present invention provide faster turnaround as a result of the reduction of conventional lashings. The MODCs of present invention facilitates retrofitting of existing Container ships and without being restricted to new buildings as minimum modification in structure and changes in operation to existing conventional container ships are required. The MODCs of present invention offer savings in costs due to the reduced lashing gear and consequent savings in stevedore costs in addition to eliminating the threat of losing containers at sea. The MODCs of present invention facilitate use of existing hatch cover without any change in the existing designs thereof as the use of the MODCs does not require any modification in standard hatch covers. The MODCs of present invention provides an access to all deck twist-locks which enables efficient use of twist-locks to provide additional protection compared to the use of standard equal angle cell guides. The MODCs of present invention may actually be used as replacements for lashing bars only and do not require to extend the entire height of the deck container stack. The MODCs of present invention facilitate no restriction in the loading of over-length containers above the MODC height thereof. The MODCs of present invention also reduce stack interactions and slamming between adjacent container stacks as they provide a barrier and gap along the span of the MODCs to reduce direct contact between adjacent stacks. Stack slamming against each other and stack interactions have been purported to be a primary cause of container stack collapses since these interactions have been calculated to produce upto 300% higher loads as per Industry calculations. By reducing stack interactions, and providing greater transverse support the present invention will also increase the permissible stackweight of the deck container stack - thus increasing the overall cargo carrying capacity of the Vessel. The present invention will also provide greater flexibility with cargo planning in a vertical height along the deck stow since the greater support enables containers of greater weight to be stowed higher up on the Deck container stack. The present invention could be advantageously implemented with conventional systems to enhance safety. For example, on smaller ships where a shore gantry may extend considerably beyond the offshore ship side and enable the offshore hatch cover to be slid off outboard then all rows may use the MODCs of the present invention.

In operation, the MODCs of present invention may be selectively used on larger vessels wherein only the outboard few rows of the containers in such vessels may be implemented with MODCs of present invention. For example, in a vessel of 17 rows or more across only the outboard 3 or 4 rows require MODCs of the present invention. When the few outboard rows are completely secured the chances of losing containers is practically eliminated. The MODCs of the present invention also permit the lashing bars to be used in order to provide additional securing support to the containers.

The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and verifications are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention described herein.