EP0121681B1

EP0121681B1 - Apparatus for securing on-deck containers

Info

Publication number: EP0121681B1
Application number: EP84101351A
Authority: EP
Inventors: Eugene Martin Kelly; Robert Benton Barnett
Original assignee: Sea Land Service Inc
Current assignee: Sea Land Service Inc
Priority date: 1983-03-14
Filing date: 1984-02-10
Publication date: 1987-08-19
Also published as: KR840008135A; YU45584A; NO159915C; DK117084A; DK117084D0; BR8400927A; KR890004945B1; YU46141B; JPS59176185A; DE3465449D1; DK159535C; EP0121681A1; NO159915B; JPH0229559B2; ES8600140A1; DK159535B; ES530541A0; NO840958L

Description

This invention relates to a securing structure for securing stacks of containers on the deck of a containership and especially on the hatch covers of such deck, said securing structure comprising a plurality of container-engaging means on said deck for engagement with each of the containers in the lowermost tier of containers;
at least two spaced tower assemblies mounted on said deck to define container stowage bays, said tower assemblies having vertical tower members connected by cross-members at levels substantially corresponding to the level of the container bottoms in each subsequent tier;
a plurality of supporting structures pivotally mounted on each said cross-member, each of said supporting structures being capable of pivotal movement between an upright position between adjacent tower members and an extended position projecting from the respective tower assemblies into a storage bay; and
support means provided on each said supporting structure and position such that a subsequent container in a stack rests thereon when said supporting structure is in said extended position with said support means resting on a lower container, each said support means having upwardly projecting means for engaging existing apertures in the bottom of a subsequent container for preventing horizontal movement thereof; and
locking means carried on each of said supporting structures located adjacent the bottom of the uppermost tier of containers for engaging the existing apertures in the lower portion of the uppermost container of a stack to prevent vertical movement of the stack.
The advent of the container has pointed the way to potentially great savings in time and labor in handling cargos. Realizing that potential, however, has required the development of specialized apparatus for transporting and handling containers. The most dramatic development has been the evolution of the containership, with attendant port facilities designed specifically for rapid handling of containerized cargo. Such ships not only carry containers in their holds, but also containers may be stacked on deck, permitting maximum utilization of available space.
On-deck containers present several problems. First, the stacks of containers must be fixed securely in position, to prevent their movement-and resulting damage - during the pitching and rolling to be expected during an ocean voyage. Second, the means employed to secure the containers must be easy to use, to permit rapid loading and unloading; otherwise, the potential for savings of time and effort will be lost. Third, a securing apparatus should not unduly raise the ship's center of gravity. Ideally, the securing apparatus should be lightweight and low to the deck, allowing containers to be stacked to the maximum height consistent with ship stability; short of the ideal, every effort should be made to keep the apparatus as low as possible. Fourth, the apparatus must be reliable and maintenance-free. In an environment where containers, hatch covers, and other equipment typically are handled by cranes, the apparatus cannot be prone to damage or downtime.
The original and still almost exclusively employed method for securing containers is by lashing. The bottom container of a stack is placed on deck - or, more specifically on a hatch cover, as hatch covers form the most convenient deck area for storage - with its corners engaged by castings, which restrain side-to-side movement. Vertical locating apertures are fitted in the corners of the container top and bottom, and horizontal locating apertures similarly are located in the corners of the ends and sides. Dowels placed in the vertical locating apertures atop one container engage similar apertures in the bottom of a subsequent container, to prevent side-to-side movement. The entire stack is then held in place by lashings fitted with turnbuckles and the like. Obviously, rigging such lashings is highly labor intensive and consumes valuable dockside time. Also, lashings require frequent inspection and maintenance during a voyage and must be replaced frequently.
Some of the disadvantages of lashings are overcome by providing stacking frames in lieu of lashings. Most such apparatus is bulky and must be moved into place by cranes, however, considerably lengthening the time required to on- load and off-load a ship. In addition, the frames commonly in use result in a higher stack of containers, often raising the ship's center of gravity unacceptably. For example, one typical stacking frame system results in a container stack about 0,36 m higher than the stack would be if lashed in place. Even such a seemingly small difference in center of gravity can result in the ship becoming marginally unstable; in such a situation, there is no choice but to leave cargo behind.
Another system employs fixed cell guides on deck. Such guides must be located so that containers fit snugly against guide rails. Because containers usually are stacked on hatch covers, however, the cell guides must overlap onto them, resulting in considerable difficulty in removing. the hatch covers. One is faced with a choice of employing fixed cell guides and accepting a high level of damage during hatch cover removal, or employing removable cell guides, which require additional time during loading and unloading to erect and dismantle the guide systems.
A system disclosed in US-A-3,680,518, attempts to solve these problems by providing apparatus comprising pillars located adjacent the hatch covers, carrying swinging arms with pins which engage the container locating apertures. A pivot arm is provided for each container in a stack, including the top one. This system possesses two major disadvantages. First, it does not overcome the problem encountered by cell guides in that the swinging arms, even in their retracted position, are vulnerable to damage during removal of a hatch cover. One can imagine the difficulty of lifting a heavy hatch cover past successive rows of projecting apparatus; the slightest shift in the wind or the smallest mistake by the crane operator will result in the hatch cover swinging and smashing against a projecting arm mechanism, crushing it. This system inherently is prone to high downtime due to damage. Also, the necessity for a pivoting arm apparatus atop the uppermost container raises the ship's center of gravity. An effective system should avoid placing heavy apparatus at such a great distance from the deck.
Further from US-A-3 481 298 there is known a securing structure of the general type indicated at the outset. In this known securing structure the supporting structures cannot be nested completely between adjacent tower members. Consequently, part of the pivoting arms and actuating mechanism of said supporting structures is exposed and extremely vulnerable under actual operating conditions. This is because the hatch covers that must be raised between the tower assemblies in order to gain access to the below deck cargo are enormously large and heavy with the largest center hatch covers being approx. 14 m long and 8 m wide and weighing about 22 t. Any movement of the hatch cover by wind, or movement of the ship from wave action can brush the hatch covers against the towers, and shear off the exposed operating mechanisms. Loading and unloading operations must be carried out in all types of weather conditions since the company cannot afford to keep the ship idle at port. The ships are normally loaded and unloaded within 24 hours and back under way again.
When loading and unloading containers, swinging a fully loaded container (approx. 30 t) against an exposed operating mechanism can damage both the mechanism and the container since the side walls of the containers are relatively fragile with their strength being carried in the reinforcing frame of the container, not the side walls.
This results in unacceptable cargo losses and ship downtime as the arms are repaired.
Further in the known securing structure each supporting structure comprises a beam having a height of approx. 20 cm said beams being interposed between subsequent tiers of containers and thus considerably raising the center of gravity for the ship.
Further from US-A-3 820 664 there is known a securing structure wherein the supporting means again comprise beams of considerable -height leading to a high center of gravity. Moreover, in this known securing system the entire weight of all the containers has to be supported by the tower assemblies. Consequently, the load requirements are more than doubled as compared to a securing structure wherein the containers are vertically stacked on the ships deck and on the hatch covers respectively. However, such extra massive tower assemblies further reduce the load carrying capacity of the vessel.
Proceeding on the basis of the prior art concept according to US-A-3 481 298 it is the object of this invention to further improve the known securing structure so as to improve the load carrying capacity of the container ship provided with such structure and to simultaneously reduce the risk of any more serious damage to the supporting structure when handling adjacent hatch covers.
In the securing structure described at the outset this object according to the invention is accomplished in that said supporting structures are completely nested between adjacent tower members in their upright position, and in that said supporting structures are cantilevered platforms and in that said support means are plates carried on each said platform.
Advantageous, but inessential details of the inventive concept have been made the subject matter of the dependent claims.
Further details and advantages of the inventive securing structure will be apparent from the accompanying drawings in which,

FIGURE 1 is a pictorial of the invention in use on a containership;
FIGURE 2 is a detailed pictorial of a cantilevered platform;
FIGURE 3 is a detailed pictorial of inner and outer intermediate tier pivot arms;
FIGURE 4 is a detailed pictorial of inner and outer upper tier pivot arms;
FIGURE 5 is a detailed pictorial of the mounting arrangement and rotary actuator of a pivot arm;
FIGURE 6 is a detailed view of the locking dowel and mounting block.

Detailed Description of a Preferred Embodiment

A typical installation embodying the present invention 10 is shown in Figure 1. Normally, on-deck containers are stacked on hatch covers, although they may be stacked on any open area of deck. Several hatch covers, mounted athwart- ships side-by-side, provide access to a hold section. Thus, containers are loaded into the hold, the hatch covers replaced, and then containers are stacked on the hatch covers and secured. The typical installation shown in Figure 1 employs three hatch covers. The outboard covers accommodate two container stacks each, while the center cover accommodates three stacks. The resulting arrangement of containers can be visualized in two dimensions. Vertically, the containers form stacks; horizontally, they form tiers - a first tier and subsequent tiers (one or more intermediate tiers and an upper tier). The example is shown with but one assembly installed, but, of course, a containership fully fitted out with the present invention would have similar installations at each container stowage area.
Containers 12 have locating apertures 13 in each corner of the top, bottom, sides, and ends. Hatch covers 14 carry castings 17, which are L-shaped container guides, and deck-mounted dowels 16 positioned to engage the locating apertures on the underside of the lowermost container in each stack. These dowels and guides position the containers and prevent side-to-side movement. As an alternative to such dowels, the industry often employs twist-lock devices for engaging container apertures. The two devices are equivalent in function. The use of the term "dowel" herein encompasses twist-locks and all similar, equivalent devices.
Tower assemblies 18 stand immediately fore and aft of hatch coamings 15. Constructional details may be modified to suit individual circumstances, but it is preferred that each assembly be an integral unit extending the width of the hatches. Each assembly includes vertical towers 21 tied together by cross-members 20, and ladders 22 may be provided for ease of access to the containers. As shown, each assembly includes four towers, two located at the outer extremity of the outboard hatches and two between the ends of the center hatch and the outboard hatches. Two sets of cross-members join the towers, located with their top surfaces slightly below the tops of the first and second tiers of containers, as explained below. The tower assemblies thus define three storage bays corresponding to the three hatches. It is preferred to use conventional structural steel for the tower assemblies, welded to the deck.
Cantilevered platforms 26 are carried on the upper surfaces of cross-members 20, as best seen in Figures 1 and 2. Each platform generally includes a series of pivot arms 28, joined by beams 34. A plate 30, carrying one or more upwardly projecting dowels 32 is mounted at the projecting end of each pivot arm. One platform is mounted on each cross-member, so that the total number of platforms depends upon the tower assembly design. The installation of Figure 1 has six platforms, as shown. Mounting details are discussed hereafter, but it should be noted that platforms pivot between an extended position 26a (Fig. 1) in which the platform projects into the container stowage bay, and an upright position 26b, in which the platform is nested into the space between adjacent vertical towers, completely behind the face of the tower assembly. It also should be noted that the installation shown in Figure 1 depicts a single installation of the present invention; in a complete installation for a containership, some tower assemblies will be located between two adjacent container stowage areas; -then, the tower assemblies would be dimensioned to carry cantilevered platforms extending both fore and aft into the respective stowage bays.
Before considering the construction of the cantilevered platform in detail, it is helpful to consider the operation of the invention generally. Figure 1 shows the apparatus in several stages of operation. Before any containers are stowed, as seen in the center bay of Figure 1, the cantilevered platforms are held in an upright position 26b. Here, the entire platform is behind the front face of the tower assembly. The first tier of containers is shown stowed in the leftmost bay of Figure 1. These containers are engaged by castings 17 and dowels 16 to hold them in position. After the first tier is loaded, the adjacent cantilevered platforms are lowered to their extended positions 26a. In this position, the projecting portions of plates 30 lie atop the containers, with dowels 32 vertically aligned with hatch cover dowels 16. As each subsequent tier of containers is loaded, the vertical locating apertures on the underside of each container engage dowels 32 carried on the cantilevered platforms, retaining each container in side-to-side position. It should be noted that no cantilevered platforms overlap the upper surface of the uppermost tier of containers. Rather, the cantilevered platform 26c upon which the uppermost tier rests, seen in the rightmost bay of Figure 1, includes means, discussed below, for securing the uppermost container in each stack without the necessity of an additional cantilevered platform.
The pivot arms 28 take several forms, based upon common constructional features, as seen, for example, in Fig. 3a. The arm is built around an extension member 42, formed from a section of box beam. Two pieces of flange stock are fixed to the sides of the extension member to form a shoulder 40 extending rearward of the extension member. A shaft aperture 38 is formed in that portion of the shoulder to the rear of the extension member. The forward end of the extension member carries a rectangular plate 30, overlapping the upper surface of the extension and projecting forward from it. One or more dowels 32 (as explained below) project upwardly from the upper surface of plate 30. Design of these dowels may be altered to adapt to different locating aperture designs, but it is preferred that each dowel have a lower portion of rectangular cross-section followed by a portion having the form of a truncated pyramid. Constructional details of the pivot arm may be selected to fit particular circumstances, but it is preferred to use structural steel members, welded together, with the total distance from the vertical center line of the shaft aperture to the center line of the dowel being about 28 inches.
Based upon these common features, four types of pivot arms are employed, classified according to their location on the tower assembly. The first distinction is whether the particular arm is used in conjunction with an intermediate tier of containers (e.g., platform 26a, Fig. 1) or the upper tier (e.g., platform 26c, Fig. 1). The second distinction is whether the particular pivot arm is located at the end of or inboard on the platform (see Fig. 2). Thus Fig. 3a shows an intermediate tier outer arm 28a and Fig. 3b shows an intermediate tier inner arm 28b; Fig. 4a shows an upper tier outer arm 29a, Fig. 4b shows an upper tier inner arm 29b.
The only difference between inner and outer arms is that each outer arm (28a or 29a) carries only one dowel 32, while each inner arm (28b or 29b) carries two dowels. The plates 30 carried on inner arms are, of course, wider than those on outer arms, to accommodate the extra dowel. This design stems from the need for inner arms to accommodate two containers resting on each plate, as can be seen in Fig. 1. The dowels 32 are identical for each type of arm; the difference appears only in the number of dowels and the width of the plate.
Upper tier pivot arms 29a and 29b (Figs. 4a, 4b, and 6) add an important feature. In addition to dowels 32, each plate 30 also carries a mounting block 50. This block is mounted to the rear of the dowel and has an aperture 51 passing through it from front to rear, parallel to the long axis of the pivot arm. It is preferred that the forward face of the mounting block be sloped rearward to assist in locating a container on the vertical dowel 32. The mounting block receives and carries locking dowel 44, which engages the horizontal locating aperture of a container (located at the bottom corners of the end of the container) to hold it in vertical position. The forward portion of this dowel, which engages the container, has a square cross-section; the dowel then flares outward to a rear portion of circular cross-section, adapted to be carried in the mounting block. Once the dowel is inserted in the mounting block, it is held in position by a retaining pin 46, which may be a piece of right-angled round stock, inserted into a transverse bore 47 formed in the rear portion of the dowel. (See Fig. 6). The position of the bore is chosen to insure that the locking dowel projects sufficiently forward from the mounting block to perform its locating function on container 12 (shown in phantom on Fig. 6). For ease of handling, a chain 48, joining the retaining pin to the locking dowel, and a handle 49 at the rearward end of the locating dowel, may be provided.
As with the lower tier arms, two forms of the upper tier arms are employed (Figs. 4a and 4b). Upper tier outer arms 29a carry one dowel and one mounting block each (Fig. 4a), while upper tier inner arms 29b each carry two dowels and a double mounting block 53 (Fig. 4b).
Each pivot arm pivots on a hinge 52 secured to a cross member 20. Best seen in Figures 2 and 5, two vertical members project upward from the hinge base to fit within the pivot arm shoulder 40. A hinge shaft 55 (Fig. 2), secured by cotter pins or other suitable means, joins the pivot arm to the hinge, leaving the pivot arm free to rotate between upright and extended positions.
Pivotal movement of the cantilevered platform is accomplished by hydraulic rotary actuators 36. One actuator is provided for each platform, mounted on an inner pivot arm (Fig. 2). For pivot arms which carry actuators, the arm and hinge are joined by an actuator shaft 54, elongated to carry the actuator (Fig. 5). One end of a torque arm 56 is suitably attached to the face of the actuator, and its other end is fixed between the U-shaped flanges of an anchor 58 mounted on the cross-member. The actuator may be keyed or otherwise suitably attached to shaft 54, and the torque arm may be bolted to the actuator and connected to anchor 58 by a pin 60. It is preferred that both the anchor and the hinge base be welded to the cross member; the hinge base additionally may be through-bolted, as shown. The rotary actuator may be, for example, a Bird Johnson Model HS-15-280 Rotary Actuator, readily available to the art.
Operation of the apparatus proceeds as follows. As described, the first tier of containers is loaded and is retained in place by castings 17 and on-deck dowels 16. During loading, all cantilevered platforms are held in their upright positions, preventing any possibility of damage to the platforms from impact with a container. Then, the first level of cantilevered platforms is lowered to their extended positions. As is apparent, the cross-members 20 must be located substantially equal to the level of the bottom of each subsequent tier of containers, so that when plates 30 lie atop the containers, the pivot arms are substantially level. Dowels 32 are then in vertical alignment with on-deck dowels 16, so that as the second tier of containers is loaded and engages the dowels, subsequent containers in a stack are located exactly atop one another. This process is repeated until the uppermost tier of containers is loaded. Although Figure 1 shows an installation for stacking containers three tiers high, other installations could stack containers more or less high, employing the present invention. After the uppermost tier is loaded, locking dowels 44 are inserted through mounting blocks 50 into the horizontal locating apertures in each container. With retaining pins 46 in place, the uppermost container, and thus the entire stack, is restrained from vertical movement.
The present invention solves a long-felt need of the container shipping industry in a manner superior to that of the prior art. First, containers are securely held in position, preventing damage. Second, the system is easy to use. The present invention permits securing to proceed as rapidly as containers can be on-loaded. Moreover, no maintenance of the apparatus is required to retain the containers in a secure condition during a voyage. Third, the apparatus minimizes the.raising of the ship's center of gravity. Because no machinery is needed atop the uppermost tier of containers, the apparatus maintains stability to the greatest possible degree. Fourth, the apparatus itself is durable and inherently free from problems. Because the cantilevered platforms can be retracted completely behind the face of the tower assembly, containers can be handled and hatch covers removed and replaced without fear of damaging the apparatus.
Those skilled in the art will be able to vary the details of the present invention to suit particular circumstances. For example, the apparatus easily can be adapted to installations requiring containers stacked in excess of three high. Similarly, different ship widths can be accommodated by varying the number of container bays and the number of stacks held within each bay. These and other variations are possible without departing from the present invention, defined by the claims, appended hereto.

Claims

1. A securing structure for securing stacks of containers on the deck of a containership and especially on the hatch covers (14) of such deck, said securing structure comprising a plurality of container-engaging means (16, 17) on said deck for engagement with each of the containers (12) in the lowermost tier of containers;

at least two spaced tower assemblies (18) mounted on said deck to define container stowage bays, said tower assemblies (18) having vertical tower members (21) connected by cross-members (20) at levels substantially corresponding to the level of the container bottoms in each subsequent tier;

a plurality of supporting structures (26) pivotally mounted on each said cross-member, each of said supporting structures (26) being capable of pivotal movement between an upright position between adjacent tower members (21) and an extended position projecting from the respective tower assemblies into a storage bay; and

support means (30) provided on each said supporting structure (26) and positioned such that a subsequent container (12) in a stack rests thereon when said supporting structure (26) is in said extended position with said support means (30) resting on a lower container, each said support means (30) having upwardly projecting means

(32) for engaging existing apertures (13) in the bottom of a subsequent container (12) for preventing horizontal movement thereof; and locking means (44) carried on each of said supporting structures (26) located adjacent the bottom of the uppermost tier of containers (12) for engaging the existing apertures (13) in the lower portion of the uppermost container (12) of a stack to prevent vertical movement of the stack, said securing structure (10) being characterized in that said supporting structures (26) are completely nested between adjacent tower members (21) in their upright position, and

in that said supporting structures (26) are canti-. levered platforms (26) and

in that said support means (30) are plates (30) carried on each said platform (26).

2. The securing structure of claim 1, wherein that locking means comprises locking dowels (44) carried on each of said platforms (26c) located adjacent the bottom of the uppermost tier of containers (12) for engaging the existing apertures (13) in the lower portion of the uppermost container (12) of a stack.

3. The securing structure of claim 1 further comprising powered means (36) for moving said platforms (26) between said upright and extended positions (26a, 26b).

4. The securing structure of claim 1, wherein each of said platforms (26) comprises:

at least two arms (28), each said pivot arm (28) including an extension member (42);

a shoulder (40) fixed to the rear of said extension member (42) and adapted for mounting to a hinge (52);

with said plate (30) being fixed to the upper surface of the forward end of said extension member (42) and projecting beyond the same and at least one beam (34) joining said pivot arms (28) and wherein each said pivot arm (29a, 29b) located on one of those said platforms (26c) located adjacent the bottom of the uppermost container (12) of a stack further includes:

a mounting block (50, 53) fixed to said plate (30) behind said upwardly projecting means (32) and having a longitudinal aperture (51) formed therethrough and

a locking dowel (44) carried in said block (50, 53) for engaging an existing container bottom horizontal locating aperture (13).