The present invention relates to a slide support for a hatch cover employed aboard a cargo ship to cover the hatchway to a ship's cargo space, said slide support being adapted between the hatchway coaming and the hatch cover attached to either of these for the purpose of transmitting vertical forces from the ship's hatch cover to the ship's hull, and said slide support further comprising a slide piece holder integrally attached by, e.g., welding, and slide pieces insertable in said holder.

Hatch covers made from steel for use aboard ships are basically planar structures having an extremely high stiff- ness against deformations in the horizontal plane. By con¬ trast, to make cargo loading/unloading easier, the hatch¬ ways on the decks of modern ships are made so large in regard with the ship's deck area that the stiffness of remaining deck structures against deformations in the horizontal plane is reduced to a low value. Resultingly, when the hatchway on the ship's deck is closed watertight for the duration of the voyage with the help of, e.g., a steel hatch cover, relative movement in the form of sliding will occur between the hatch cover and the ship's hull under conditions of heavy sea or abrupt changes of course.

This relative movement causes multiple problems which are particularly accentuated when deck cargo such as containers is loaded on the hatch covers as is customary in modern cargo ships. The weight of the deck cargo on a single hatch cover may amount to hundreds of tons. Such deck cargo can impose under heavy sea so high dynamic forces that specific movement limiters are required for transmitting the forces from the hatch cover to the ship's hull. Limiters transmit- ting vertical forces are in the context of the present

invention called slide supports, and they are adapted in the above-described manner between the hatchway coaming and the edge of the hatch cover.

To facilitate relative movements between the hatch cover and the ship's hull, the slide supports are provided with a design that prevents them from receiving large horizontal stresses, but instead facilitates a sliding movement between the hatch cover and the ship's hull. Inasmuch as the vertical stresses imposed on the slide supports are extremely high, the sliding movement involves a high frictional force that causes heavy wear on the slide sur¬ faces. To reduce such wear, the shipbuilding industry has worked to find material combinations capable of enduring high surface pressure while simultaneously exhibiting a coefficient of friction which is as small as possible.

Conventional slide supports may comprise, e.g., a slide piece holder welded to the ship's hull (to the hatchway coaming) , whereby to the upper surface of the holder is milled an elongated recess into which a slide piece or a plurality thereof is inserted. The surface of the slide piece facing the hatch cover acts as a slide surface which may be covered with a number of different materials that exhibit improved sliding properties. One possibility is to use braided PTFE packing material which functions well as long as it stays intact. However, such a slide surface may become damaged even during an overseas passage, whereby its frictional resistance will increase significantly. Then, the horizontal force acting on the slide piece holder will also increase essentially, whereby the end of the recess milled to the holder is subjected to an extremely high shear stress which may cause complete destruction of the holder. A problem of such a slide piece holder particularly in malfunction situations is that the entire horizontal

force is concentrated on a small area which despite its high strength may still yield under the stress. Hence, the prior-art techniques have been hampered by the limitation that only materials of high mechanical strength and/or extremely low frictional resistance have be usable. Moreover, the fabrication of the slide piece holder has been difficult, because the milling of a single elongated recess of constant depth in a mechanical shop is a costly multistep process.

In regard to the state of the art additional reference is made to DE Pat. No. 39 04 602.

It is an object of the present invention to provide a novel type of slide support free from the above-described pro¬ blems. The slide support according to the invention is characterized in that the surface of the slide piece holder intended to hold the slide pieces is provided with at least two recesses for the slide pieces, essentially separated from each other so that at least one slide piece can be inserted in each recess.

By virtue of the invention, slide pieces of small size can be used, because no individual slide piece need bear the entire vertical load, but instead the load is distributed in a more uniform manner, whereby the use of slide materi¬ als of higher coefficient of friction, yet of sufficiently low frictional resistance, is possible. A further advantage of the smaller slide piece size is that slide surface can better accommodate angular alignment errors of the mating slide surfaces. Additionally, the load-bearing capacity of the slide surface may be set accurately by varying the number of slide pieces in the holder. Moreover, the use of a plurality of slide pieces achieves a uniform distribution of the load over the holder, whereby the holder end wall

alone will not be subjected to the entire horizontal force, but the force will be distributed between the intermediate walls separating the recesses. Finally, it must be noted that in series production the fabrication of the holder and slide pieces according to the invention offers better cost- efficiency over the prior art.

A preferred embodiment of the invention is characterized in that said recesses are essentially cylindrical and advanta- geously made by drilling. Then, the slide piece fitting m the recesses can be made by cutting from material bars which is a really advantageous method of fabricating the slide pieces.

Other preferred embodiments of the invention are disclosed in appended dependent claims 3-7 and the following descrip¬ tion part of this patent application text in which the invention is examined in greater detail with reference to the appended drawings, m which:

Figure 1 shows a supporting arrangement based on a slide support adapted between the ship's hatch cover and the coaming of the hatchway;

Figure 2 shows a top view of a conventional slide piece holder for a slide support;

Figure 3 shows a perspective view of a conventional slide support;

Figure 4 shows a top view of a slide piece holder according to the invention for a slide support;

Figure 5 shows a perspective view of a slide support according to the invention;

Figure 6 shows a top view of a preferred embodiment of a slide piece holder according to the invention for a slide support; and

Figure 7 shows a sectional view of the slide piece holder along line VII-VII in the diagram of Fig. 4.

Referring to Fig. 1, a typical location is shown for the slide support m a cargo ship. The slide support comprising a slide piece holder 1 and slide piece or pieces 2 is adapted between the coaming 3 of the hatchway and the hatch cover . Typically the hatch cover has attached thereto a backing piece 5 against which the slide support rests. The slide piece holder 1 of the slide support is in the lllus- trated case attached by welding to the hatchway coaming 3. The edge of the hatch cover 4 may also incorporate a seal 6 which in the unstowed position of the hatch cover can rest against the backing piece 7.

Referring to Fig. 2, the slide piece holder part of a slide support representing the state of the art is shown m a top view. To that surface of the slide piece holder which is intended to hold a slide piece 2 (Fig. 1) is machined by milling, for instance, an elongated rectangular recess 8. Into this recess is inserted at least one slide piece 2. In Fig. 3 only one slide piece 2 is shown inserted having a shape essentially conformant with the recess.

Referring to Fig. 4, a slide piece holder 1' according to the invention for a slide support is shown therein m a top view. It can be seen from the diagram that in this embodi¬ ment the conventionally used single, elongated, essentially rectangular recess is replaced by a plurality, m the present case, five recesses 8' . In the embodiment shown in Fig. 4, the recesses are essentially made cylindrical,

advantageously by drilling, and they are made essentially equidistantly spaced on the surface of the slide piece holder 1' . This is considered the most preferred embodiment of the invention. Shown m Fig. 7 is a sectional view elucidating the cross-sectional shape of the recess. The depth of the recess 8' can be, e.g., in the range 10-40 mm, most advantageously approx. 20 mm.

Referring to Fig. 5, shown therein is the slide piece holder 1' illustrated in Fig. 4, now with cylindrical slide pieces 2' inserted in the recesses. Such slide pieces may be fixed if necessary by means of screws or similar ele¬ ments. Alternatively, the slide pieces can be inserted with such a tight fit that they will stay m place without the need for additional fixing. Obviously, the slide pieces must be adapted to extend above the upper surface of the holder so much that a sufficient reserve for wear remains on their tops.

Referring to Fig. 6, shown therein is an alternative em¬ bodiment of a slide piece holder 1" according to the inven¬ tion now having the recesses 8" formed essentially square with round corners. Also this kind of a recess shape is easy to machine. Additionally, the recess may be formed into an eclipse, rectangle (with acute or rounded corners) and other shapes .

The material of the slide pieces 2' need not be discussed herein m greater detail. However, the present invention permits the use more cost-effective materials than those employed by the prior-art, because in the present em¬ bodiment the coefficient of friction of the slide pieces need not be made artificially "overly" small and the strength of slide pieces overdimensioned to endure under the stress of the mechanical horizontal forces.

To those skilled m the art it is obvious that the invention is not limited to the embodiments described above, but rather, can be varied within the scope of the invention which is defined in the appended claims. Accordingly, between the slide pieces and the slide piece holder can be inserted a balancing rubber element or similar material known from DE Pat. No. 39 04 602. While theoretically it would be possible to insert more than one slide piece in each recess, most probably this would not represent an advantageous embodiment. It is further possible that the drilled recesses/slide pieces are placed nonsymmetrically and/or formed to have mutually different sizes .