Among other reasons, a gasket is accordingly needed to prevent seawater from entering the payload cargo space. This countermeasure is important not only to protect the cargo, but also to secure the stability and safety of the ship. In a conventional continuous-section gasket, the resilience of the gasket so vital to the function of the seal is attained by providing the continuous section with one or more lumens that run in the interior of the section along its longitudinal direc- tion. Typically, the lumens have a cross section shaped ellipsoidal, triangular or a combination of the same, however, with an essentially wide-open channel disregarding some minor inward elevations of a smooth contour on its internal surface.

Accordingly, the function of continuous-section gaskets becomes problematic when, under a sealing contact established by the compression of the gasket against its mating surface, there occurs a lateral displacement between the gasket and the mating surface (as the hatch cover in high seas moves relative to the hatch coaming and, on the other hand, to the mating edge of the adjoin- ing cover section). Herein, the gasket follows the movement of the mating surface, whereby the gasket will be heavily compressed against the edge of the gasket fitting pocket. As the edge or corner of the gasket fitting pocket is typically rather sharp, a damage to the continuous-section gasket may result.

Additionally, such a lateral movement causes a substantial change in the cross- sectional shape of the continuous-section gasket as compared to deformation under direct compression. Generally, a lateral deformation of the gasket compromises its performance and the water-tightness of the hatch cover seals.

It is an object of the present invention to provide a novel type of continuous- section gasket free from the above-described problems. A continuous-section gasket according to the invention is characterized in that the internal wall of at least one lumen of the gasket has formed thereto at least one continuous elevation extending toward the center of the lumen and running in the longi- tudinal direction of the gasket so as to act as a fender ridge for the internal top surface of the gasket lumen when the gasket performs as a seal under compression.

By virtue of the invention, any lateral movements (orthogonal to the longitudinal axis of the gasket) under a compressive sealing load are resisted by the longi- tudinal projection or fender ridge made into the lumen of the continuous-section gasket through the supporting action rendered by the projection to the external top surface of the gasket that is pressed against the mating surface of the hatch coaming, whereby the amplitude of the lateral displacement of the continuous-section gasket is reduced. More specifically, the continuous-section gasket according to the invention is prevented from becoming compressed with as large a force as conventional gaskets against the inner corner of the gasket fitting pocket, thus providing a reduced risk of damage to the gasket and a longer life thereof. Further, the gasket subjected to compression and simulta- neous lateral displacement retains its original cross-sectional shape in an enhanced manner, thus offering superior sealing performance and water- tightness over conventional gasket embodiments. The improved contouring of the gasket lumen does not cause any practical increase in the manufacturing costs of the gasket. Moreover, conventional continuous-section gaskets may be readily replaced by gaskets according to the invention, thus bringing about an

upgrade to the gasket arrangements already installed aboard ships in service.

In the following, the invention is examined in greater detail with reference to a preferred embodiment illustrated in the appended drawings, in which: FIG. 1 shows a cross-sectional view of a conventional continuous-section gasket when uncompressed; FIG. 2 shows the gasket of FIG. 1 now under compression; FIG. 3 shows the gasket of FIGS. 1 and 2 now under compression and subjected to a lateral displacement of the sealed hatch cover; FIG. 4 shows a cross-sectional view of an embodiment of the continuous- section gasket according to the invention uncompressed; FIG. 5 shows the gasket of FIG. 4 now under compression; and FIG. 6 shows the gasket of FIGS. 4 and 5 now under compression and subjected to a lateral displacement of the sealed hatch cover.

Referring to the diagrams, a continuous-section gasket 1 is shown fitted in a pocket 2 that is typically welded to the hatch cover. The interior of the continuous-section gasket 1 is formed by an open lumen 4 that runs conti- nuously in the longitudinal direction of the gasket and may have, e. g., an ellipsoidal or triangular shape (as in FIG. 1) or a more general combination shape of the kind.

In FIG. 1 is shown a continuous-section gasket in its uncompressed state.

When the hatch covers are closed, the gasket becomes compressed against a mating surface 3 (formed on the hatch coaming or an adjoining hatch cover

section), whereby the gasket is compressed and laterally widened over the edges of the gasket fitting pocket as illustrated in FIG. 2. With the bending of the ship's hull at sea, the gasket is subjected to both a lateral displacement and a relative vertical motion between the gasket 1 and its mating surface 3 (see FIG. 3). The lateral displacement causes first a deformation of the gasket and, with an increasing amplitude of the movement, a sliding motion of the gasket over the mating surface 3. Herein, the gasket 1 is subjected to harsh compres- sion against the edge of the gasket fitting pocket 2 (denoted by arrow 5 in the diagram). This stress may cause a severe damage to the gasket.

In FIG. 4 is shown a continuous-section gasket 1'according to the invention that is fitted in the same fashion into the gasket pocket and similarly has a lumen 4 made thereto. Obviously, the lumen extends continuously in the longitudinal direction of the gasket over the entire length of the gasket.

According to the invention, the lumen 4 includes a fender ridge 6 that bulges into the lumen from its interior surface and in the manner shown in FIG. 5 forms an elevation capable of supporting the internal top surface of the gasket lumen under the compressive load of the closed hatch cover. Accordingly, the fender ridge 4 is dimensioned so as to back up the internal top surface of the gasket lumen under load. In this fashion is assured that the external surface of the gasket 1', which faces the mating surface 3, cannot yield as much under load as the external surface of a conventional gasket. Resultingly, the continuous- section gasket 1'can retain its initial shape in an improved manner that also prevents its deformation under the lateral displacement caused by heavy seas which is a problematic situation for a gasket of a conventional cross section.

The gasket is herein additionally protected from damage by compression against the inner edge 5 of the gasket fitting pocket 2.

The continuous-section gaskets 1'can be produced by injection moulding through the openings of a die, which means that the contouring of different kinds of the fender ridges 6 and the lumens 4 running in the longitudinal

direction of the gasket section is uncomplicated and does not essentially increase the manufacturing costs of the gasket.

To those versed in the art it is obvious that the invention is not limited to the exemplifying embodiments described above, but rather, can be varied within the scope and spirit of the appended claims. To this end, the number of ridges 5 in the interior of the gasket lumen 4 may be varied (from one to plural) as well as the size, shape and location thereof can be modified depending on the con- tour and other properties required from the gasket. The material of the conti- nuous-section gasket 1'can be rubber or any other elastic material.