US3800723A

US3800723A - Barge

Info

Publication number: US3800723A
Application number: US00236727A
Authority: US
Inventors: J Collins
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-03-21
Filing date: 1972-03-21
Publication date: 1974-04-02
Anticipated expiration: 1991-04-02

Abstract

The present invention relates to a barge, a barge structure, and to novel hatch-covers that cover the cargo-hold; the disclosed hatch-covers being stackable atop each other for compactness when the barge is being loaded or unloaded.

Description

United States Patent 11 1 Collins Apr. 2, 1974 [54] BARGE 2,923,266 2/1960 Mercier 114/201 4 4 [76] lnventor: John w. Collins, 7111 Starl1ghtC1r., 3 Z132 22:2 132 Huntington Beach, Calif- 92647 3,078,938 2/1963 1361mm, Sr 114 69 3,656,446 4 1972 flgfiernan.,. 114 77 R [22] 1972 3,742,889 7 1973 Weise 111:: 114 65 R [21] FOREIGN PATENTS OR APPLICATIONS 1,063,920 8/1959 Germany 114/201 114/69, 114/201 R 1,010,971 6 1952 France 114/77 R [51] Int. Cl B63b 35/28 [58] Field of Search.... 114/26, 201, 203, 63, 68, Primary Examiner Duane Reg:r

77 R; 49/501 Assistant Examiner-Galen L. Barefoot Re erences Cited Attorney, Agent, or Firm-Grover A. Frater UNITED STATES PATENTS ABSTRACT 3,152,570 10/1964 Dyer 114/69 1,777,380 10/1930 Ewem et alm "4/201 The present 1nvent1on relates to a barge, a barge struc- 2,042,932 6/1936 Fogh 114/72 t a d o vel hatch-covers that cover the cargo- 3,423,878 1/1969 Kimmel v 49/501 hold; the disclosed hatch-covers being stackable atop 2,457,841 1/1949 Smith et 114/72 each other for compactness when the barge is being l Taylor w 1 1 loaded or unloaded 3,407,771 10/1968 Takezawa et a]. 114/77 R 2,021,629 11/1935 Leigh 114/26 5 Claims, 11 Drawing Figures 4 1 BARGE BACKGROUND It has been known for a long time, that transportation by water is much more economical than transportation by other means; and this economic advantage increases greatly when the cargo to be transported is extremely heavy or is extremely bulky. Examples of such cargoes are iron-ore, coal, gravel, sand, grains, cotton, chemicals, molasses, liquid-chlorine, sulphuric acid, wine, edible oils, railroad cars, automobiles, etc. At times, it is desirable to ship certain cargoes in a heated or in a refrigerated condition. I

It has been desirable in many cases, as for deep sea transportation, to use self-powered ships for carrying such cargoes; but more often, particularly for inland waterways, it is advantageous to use so-called barges that are not self-powered; but are moved about by means of tugboats. In the past, such tugboats towed a single barge behind them; but the trend has been toward lashing together a large number of barges to form a tow that is towed behind more-powerful tugboats whose diesel engines may generate up to about 3,000 horsepower.

However, it was found that the screws of the tugboat set up a prop wash wherein eratic water-currents ad: versely affected the tows, and made them difficult to control. Therefore, the tugs were placed at the back of the tows; and pushed the barges ahead of them, in this way establishing better control.

The size of the barges, and the size of the tows, depend to a great extent upon the river conditions; i.e., the river width, the current, the curves, the water velocity, the amount of boat traffic, etc. As a result, tows have varied to as many as forty barges combined into a single tow; the overall load reaching as high as 67,000 tons. The tows usually move about 2-to-l0 knots it generally being undesirable to move faster than this, because the waves that are set up by the tow may damage the river bank and structures thereon.

Barges have taken a number of different forms, depending upon their use, and upon the environment in which they are to be used. In general, the barges are made as broad as possible in order to provide lateral stability; this depending, of course, upon the water roughness to which the barge would be subjected. Also,

in general, the greater the ratio between the barges length and width, the faster the barge may be moved or, conversely, the less power is needed to move it. Moreover, barges generally have a flat bottom in order that they have as shallow a draft as possible; and it is interesting to note that the moving-draft is appreciably smaller than the standing-draft.

Thus, barges have received much thought and many designs. Unfortunately, even the latest barges have a large number of unsolved problems. Among these are the floatation problem, the collision-damage problem, the problem of the cargo-space shaping, and the problem of leakage. These problems will be further discussed in the following passages; and apparatus for their solution will be presented.

One common class of barge is made 35 feet wide and about 200'feet long. Such a barge conventionally constructed would weigh about 400 tons. The invention provides a way to make a barge of equal volumetric ca-' pacity at a weight of about 300 tons or less. That means that a barge made according to the invention can carry a hundred tons or more additional payload or, altematively, can carry the old payload to much shallower waters. The cost of constructing a barge according to the invention is also reduced by savings both in material costs and in fabrication costs.

In this connection, the special hatch covers provided by the invention make possible a cover weight saving of between 15 and 20 tons per barge and cost saving in both material and labor. The lesser weight provides another important advantage in that-the difficulty, and the danger, involved in handling the covers is greatly reduced.

OBJECTIVES AND DRAWINGS It is the principal objective of the present invention to provide an improved barge.

It is another objective of the invention to provide an improved barge that is practically sinkproof.

It is still another objective of the invention to provide an improvedbarge that limits leakage.

It is a further objective of the invention to provide an improved barge that minimizes collision-damage.

It is a still further objective of the invention to provide an improved barge with a pre-designed shape for the cargo space.

Another very important objective is to reduce the weight of barges, by as much as one hundred tons in a barge of standard size, whereby larger payloads can be carried and huge cost is reduced.

That these objectives and others are attained will be recognized from a study of the following description taken in conjunction with the drawings in which FIG. 1 shows a pictorial view of the overall barge, comprising a plurality of sections.

FIG. 2 shows a cross-sectional view of a body section of a box-type barge.

FIG. 3 shows a cross-sectional view of a body section of a hopper-type barge.

FIG. 4 shows a partially cross-sectional, partially exploded view of a hatch-cover.

FIG. 5 shows a cross-sectional view of joined sheets.

FIG. 6 shows a partial cross-sectional pictorial view of a normal stiffener.

FIG. 7 shows a partial cross-sectional pictorial view of a lifting-bracket stiffener.

FIG. 8 shows a cross-sectional view of the sealing/interlocking strips.

FIG. 9 shows a simple structure for producing the sealing/interlocking strips.

FIG. 10 shows a partial longitudinal view of several stacked hatch-covers.

FIG. 11 shows a partial transverse view of several stacked hatch-covers.

SYNOPSIS Broadly speaking, the present invention relates to a barge that has a double-wall hull, a double-wall coaming, double-wall hatch-covers, and double-wall hatchcover doors. A suitable plastic is positioned between the double-walls; providing a number of advantages over prior art structures. The advantages produce an improved barge that is more damage resistant, more leakproof, more sinkproof, provides thermal insulation for the cargo, and is less heavy than prior barges of similar capacity.

THE OVERALL BARGE FIG. 1 shows a pictorial view of a typical barge designed in accordance with the teachings of the present invention, the disclosed barge being primarily for the use on rivers such, for example, as the Mississippi River. Barge 10 is typically about 200 feet long, about 35 feet wide, and about 12 feet high excluding a 3- foot high coaming 11 and the hatch-covers 12 which are typically 9 feet by 20 feet.

The hatch-covers 12 are indicated to be arched. to a radius of about 48 feet; and to have hatch-cover doors 13 that typically are 75 inches long and about 51 inches wide, and fit into suitable openings of the hatchcovers 12. If desired, the hatch-cover door 13 may be equipped with a hinge arrangement along on edge thereof; so that the doors may be swung open, rather than having to be completely lifted from the hatchcover openings. Thus, the cargo-hold may be reached by either opening the hatch-covers 12; or by opening or removing the hatch-cover doors l3 depending upon the size of the object, the size of grab bucket, the type of crane, etc. that is to enter or to be removed from the cargo-hold.

Barge .10 is indicated to comprise about five bodysections 14 that are 36 feet long, and are affixed to each other; alternatively, l0 body-sections having 20- foot lengths may be used, etc. The affixed 8-foot headpieces 15 of the barge are preferably somewhat streamlined to minimize water drag.

A plurality of longitudinal bumper-strips 16 are affixed to the side of the barge, for protection against damage due to minor collisions or scrapings; and a plurality of cleats 17 are suitably positioned along the deck of the barge, for mooring, for receiving a tow-cable or a binding cable, etc.

TYPICAL CROSS-SECTION OF A BOX-TYPE BARGE SECTION FIG. 2 shows a cross-sectional view of a typical boxtype body-section 14 of the barge. First of all, it should be noted that the inner walls 18 of the cargo-hold are substantially perpendicular; as this vertical wallorientation is optimal for most cargoes that are to be loaded and removed from above. The double-wall hull 19 may be about 3 feet thick, and may be formed of about one-quarter inch plates; the double-wall hull bottom 22 being about 1 foot thick, and being formed of one-half inch plates inside, and about one-quarter plates outside.

The space between the hull-walls and the hull-bottom is filled with a plastic 24 that is both relatively strong and relatively light, (e.g., polystyrene). The plastic 24 may be either foamed into place in a manner that is well-known in the art; may be inserted in block form, the blocks having been suitably sized and shaped; may comprise expanded beads; etc. For convenience, the plastic will be designated as floatation means, even though as will be discussed later it has additional fnnctions. The entire plastic structure may then be integralized with the hull be means of a suitable adhesive,

such as an epoxy.

In this way, each barge-section is completed ex cept for its end-walls; and a desired number of bodysections are then assembled in a juxtaposed relation, to form a strong limited-leakage damage-resistant barge.

ADVANTAGES OF DISCLOSED CONSTRUCTION Due to the use of the floatation means discussed above, several advantages are obtained. First of all, when the barge is fully assembled (as by welding or a similar process) only a limited amount of water can enter the double-wall hull in case of a leak; the floatation-means being such that it fills all but an extremely small percentage of the hull-space.

It is the usual practice to build a barge with a plurality of transverse-frames; and to affix longitudinal hullplates to the transverse-frames. As the barge is used, minor collisions and the like cause most of the hullplates to be bent inwardly between the stronger transverse-frames; so that the side of the barge tends to become scalloped. These scallops appreciably increase the water drag; and thus lower the speed, and increase the needed towing power.

However, due to the strength of the floatation means, it is practically non-compressible. This means that if the barge rams into a dock, another barge, a boat, or the like, the resultant force is distributed among the barges outer hull-wall 25, the floatation means, 24, and the barges inner-hull 18. Therefore, there is less force-concentration; and plate bending is minimized.

A third advantage of the disclosed construction is that the plastic is a good thermal insulator; so that it tends to keep the barges cargo at its original temperature regardless of whether the original cargo temperature was warm or cold.

THE COAMING FIG. 2 also shows the coaming 11 to have a doublewall construction; and to also be filled with a floatation means as discussed above. The coaming must, of course, be strong enough to support the hatch-covers as indicated in FIG. 1.

TYPICAL CROSS-SECTION OF A HOPPER-TYPE BARGE SECTION FIG. 3 shows a cross-sectional view of a typical hopper-type barge section; this designation indicating that the inner hull-walls 26 are sloping, rather than being vertical. The reason for this sloping-angle is as follows. Certain cargoes (sand, etc.) are often loaded and unloaded by a water-fluidizing method; and a hopper-type cargo-hold tends to concentrate the sand at central locations that are more conveniently unloaded than when the sand is permitted to concentrate at the comers of a vertical inner hull-wall.

The hull-walls of the hopper-type body-section of FIG. 3 are similar to those of the box-type bodysections; except that the sloping inner hull-walls 26 should be somewhat stronger, since cargoes such as sand and the like place a somewhat greater force on the sloping inner-hull-walls.

THE HATCH COVERS As indicated in FIG. 1, the disclosed barge has a plurality of arched hatch-covers 12 that protect the cargo; and FIG. 4 shows a partially-pictorial partiallyexploded view of a hatch-cover 12. As shown, the hatch-cover 12 has a double-wall construction that comprises two spaced-apart sheets; an upper archsheet 30 and a lower arch-sheet 31. A plastic is sandwiched between the two sheets and 31 to form a bonded sandwich-like arched hatch-cover panel 32.

THE HATCH-COVER SIDE-BEAM ASSEMBLY Referring back to FIG. 4, it will be seen that in order for the hatch-cover 12 to be able to rest firmly on the coaming 11, each longitudinal edge of the hatch-cover 12 comprises a side-beam assembly 35 affixed thereto; the side-beam assembly 35 being adapted to have its lower edge 36 resting on. the top of the coaming l l, and to have its upper edge 37 provided with a suitable number of lifting brackets 38.

As indicated in the cutaway view of FIG. 4, the sidebeam assembly 35 has a spine 40 that extends for the entire length of the side-beam assembly 35, the spine 40 having a plurality of stiffeners 41 suitably spaced along, and affixed to, the spine 40. As indicated, except for a selected number of special stiffeners (which will be discussed later) the normal stiffeners 41 act primarily to vertically stiffen the side-beam assembly 35; and their inner and outer edges form planar formations to which an interior 9 of an exterior skin 42 which may be integral with spine 40 may be affixed.

As indicated in FIGS. 4 and 6, the upper portion of the inner skins 42 has an upward and inwardly extending support that is suitably angled to support the longitudinal edge 43 of its associated hatch-cover panel 32. The upper portion of the exterior skin 42 also has a similar support 46. The two supports 45 and 46, being affixed to the side-beam assembly 35, thus form a continuous or a segmented U-shaped channel for supporting the longitudinal edge 43 of the hatch-cover panel 32; and when supports 45 and 46 are affixed to the hatch-cover panel 32, they thus provide a unitary hatch-cover 12. Y

The hatch-cover doors 13 indicated in FIG. 4 are also preferable of a double-wall construction having a plastic center-portion.

THE LIFTING BRACKETS It was pointed out above that selected ones of the stiffeners have an additional function; and this function is to provide the lifting-brackets for lifting the hatchcovers 12 off the coaming 11 when this lifting action is desired. Lifting-brackets 38 may be provided as follows.

Referring to FIG. 7, it will be seen that the liftingbracket stiffeners 41 have a rectangular Z-like crosssection the transverse-bars 50 of the Z-shape coacting to provide the desired vertical stiffening effect in the manner as the previously-described regular stiffeners; whereas the longitudinal bar 51 of the Z-shape has an opening 52 (typically 2-3 inches long) through the top thereof, so that a lifting-hook (not shown) may be fitted to the aperture 52. Lifting-brackets 38 are provided with shoulders 53, whose function will be discussed later.

In this way, the lifting-bracket stiffeners, the regular stiffeners, the spine, the panel-supports, and the interior and exterior skins, form a rigid side-beam assembly for the hatch-covers l2; and thus form a unitary hatchcover that may be seated onto, or be lifted off, the coaming l 1.

THE HATCH-COVER SEALING/INTERLOCKING STRIP Several hatch-cover problems may now be solved simultaneously. The first problem is that of weathersealing the transverse-edges 55 of the hatch-cover panels 32 shown in FIG. 4.

The second problem is as follows. While the hatchcovers have sufficient weight to hold them in place during the expected weather and river conditions, it is desirable to lock the hatch-covers together in order to prevent them from sliding. One simple way to do this is shown in FIG. 8, which indicates a longitudinal crosssectional view of a hatch-cover panel 32; and shows the two transverse edges 55 of the panel 32, as well as showing the transverse-edges 55 of a juxtaposed panel 32.

As indicated in FIG. 8, one interlocking-strip 56 has an upwardly-curving trough 58; whereas the other interlock-strip 57 has a downwardly-curving trough 59; one adjacent upwardly-extending trough and one adjacent downwardly extending trough interlocking with each other to interlock the hatch-covers 12 against relative movement. This arrangement forms a nearly water-tight joint between hatches and a trough or gutter for fast removal of rain and sea water.

One easy way to produce the above interlockingtrough construction is shown in FIG. 9. This comprises a two-piece sheet-metal configuration 60 that is assembled as indicated; the assembly 60 is then cut apart at the dotted line 61. Each half of the cut-apart sheetmetal configuration is then affixed to an end 55 of a hatch-cover panel 32 as indicated in FIG. 8; providing the dual-function sealing/interlocking strip illustrated in FIGS. 4 and 8.

HATCH-COVER STACKING As indicated in FIG. 4, a lifting-bracket 38 is placed near each end of the hatch-cover side-beam assembly 35; a typical spacing being about 55 inches from the end. In order to be able to stack the hatch-covers 12 on top of each other for compact storage during loading and/or unloading operations, each side-beam assembly 35 has a pair of receiving-slots (see FIG. 4) about 6 inches long, positioned in the lower surface of the side-beam. assembly 35. Thus, when the hatchcovers 12 are placed atop each other, the upwardlyextending lifting-brackets 38 will protrude through respective receiving-slots 65 into the interior of the sidebeam assembly 35.

However, it has been found impracticable to locate the slots 65 in direct vertical alignment with the liftingbrackets 38; so lifting-brackets 38 and the receivingslots .65 are staggered in the following manner. Half of the hatch-covers 12 have their lifting-brackets 38 spaced about 48 inches from the end of the side-beam assembly, while their receiving-slots 65 are spaced about 55 inches from the end of the side-bar assembly 35 as indicated in FIG. 4. The other half of the hatch-covers 12 have their lifting-bracket and slot spacing reversed; that is, the lifting-brackets 38 are located about 55 inches from the ends of the side-beam assemblies, and the slots are placed about 48 inches from the end of the side-beam assemblies.

The operation of this bracket and slot reversal will become apparent from FIG. 10. This shows a longitudinal schematic representation of several stacked hatchcovers 12; shown in a manner to illustrate the effect of staggering the brackets 38 and the slots 65. It will be seen, from FIG. 10, that the resultant staggered arrangement permits the hatch-covers 12 to be stacked atop each other'without marring the protruding liftingbrackets 38, which are received by the slots 65 into the interior of the side-beam assembly.

FIG. 11 shows a transverse schematic representation of several stacked hatch-covers 12; and indicates how the lifting-brackets 38 are received into the side-beam assemblies 35 when the hatch-covers 12 are stacked atop each other; each successively-higher hatch-cover 12 having its side-beam assembly resting upon the shoulder 65 of the next-lower lifting-bracket 38.

I claim:

1. A barge comprising:

a plurality of juxtaposed body-sections, each said body-section having a double-wall hull;

plastic floatation means positioned within said double-wall hull of said body-sections;

a pair of affixed head sections, each said headsections having a double-wall hull;

plastic floatation means positioned within said double-wall hull of said head-section;

a plurality of hatch-covers adapted to cover the cargo-hold of said barge, said hatch-covers being of double-wall construction;

plastic floatation means positioned within aaid double-walls of said hatch-covers;

said hatch-covers comprising an arched hatch-cover panel of a double-wall construction;

plastic floatation means positioned within said double-walls of said hatch-cover panel;

said hatch-covers having a side-beam assembly positioned along each of their longitudinal edges;

said side-beam assembly comprising a spine and a plurality of stiffeners positioned along said spine;

selected ones of said stiffeners having supportchannel means for supporting the longitudinaledge of said hatch-cover panel;

a given number of stiffeners being adapted to serve as lifting-brackets; and

means for protecting said lifting-brackets when said hatchcovers are stacked atop each other.

2. A barge comprising:

a plastic floatation means positioned within said double-wall hull of said body-sections;

plastic floatation means positioned within said double-walls of said hatch-covers;

a given number of stiffeners being adapted to serve as lifting-brackets; and said side-beam assembly having a corresponding number of receiving-slots adapted to receive said liftingbrackets when said hatch-covers are stacked atop each other.

3. I The invention of claim 2 wherein said liftingbrackets and said receiving-slots are staggered relative to each other.

4. A barge comprising:

A. a plurality of affixed juxtaposed body-sections, each of said body-sections having a double-wall hull; plastic-floatation means positioned within said double-wall hull of said body-sections;

B. a pair of affixed end-sections, each of said endsections having a double-wall hull; plastic floatation means positioned within said double-wall hull of said end-sections;

C. a coaming extending above the deck of said barge, said coaming being of double-wall construction; plastic floatation means positioned within said double-wall construction of said coaming;

D. a plurality of hatch-covers adapted to rest on said coaming to cover the cargo-hold of said barge, said hatch-covers being of double-wall construction; plastic floatation means positioned within said double-wall construction of said hatch-covers;

B. said hatch-covers comprising an arched hatchcover panel of double-wall construction; plastic floatation means positioned within said double-wall construction of said hatch-cover panels;

F. said hatch-covers further comprising a side-beam assembly positioned along each of their longitudinal edges; said side-beam assemblies comprising a spine and a plurality of stiffeners positioned along said spines;

G. said stiffeners having support-channel means for supporting the longitudinal-edge of said hatchcover panels;

H. a given number of said stiffeners being adapted to serve as lifting-brackets;

l. said side-beam assemblies having a corresponding number of receiving-slots adapted to receive said lifting-brackets when said hatch-covers are stacked atop each other;

J. said hatch-covers having a sealing/interlocking strip positioned along each transverse-edge thereof;

K. said sealing/interlocking strips comprising vertically-extending troughs, the trough of one of said strips extending upwardly, and the trough of the other of said strips extending downwardly; adjacent troughs of juxtaposed hatch-covers interlocking with each other.

5. The apparatus of claim 4 wherein said liftingbrackets and said receiving-slots of one hatch-cover are staggered relative to the lifting-brackets and the receiving-slots of another hatch-cover.

Claims

1. A barge comprising: a plurality of juxtaposed body-sections, each said body-section having a double-wall hull; plastic floatation means positioned within said double-wall hull of said body-sections; a pair of affixed head sections, each said head-sections having a double-wall hull; plastic floatation means positioned within said double-wall hull of said head-section; a plurality of hatch-covers adapted to cover the cargo-hold of said barge, said hatch-covers being of double-wall construction; plastic floatation means positioned within aaid double-walls of said hatch-covers; said hatch-covers comprising an arched harch-cover panel of a double-wall construction; plastic floatation means positioned within said double-walls of said hatch-cover panel; said hatch-covers having a side-beam assembly positioned along each of their longitudinal edges; said side-beam assembly comprising a spine and a plurality of stiffeners positioned along said spine; selected ones of said stiffeners having support-channel means for supporting the longitudinal-edge of said hatch-cover panel; a given number of stiffeners being adapted to serve as liftingbrackets; and means for protecting said lifting-brackets when said hatchcovers are stacked atop each other.

2. A barge comprising: a plurality of juxtaposed body-sections, each said body-section having a double-wall hull; a plastic floatation means positioned within said double-wall hull of said body-sections; a pair of affixed head sections, each said head-sections having a double-wall hull; plastic floatation means positioned within said double-wall hull of said head-section; a plurality of hatch-covers adapted to cover the cargo-hold of said barge, said hatch-covers being of double-wall construction; plastic floatation means positioned within said double-walls of said hatch-covers; said hatch-covers comprising an arched hatch-cover panel of a double-wall construction; plastic floatation means positioned within said double-walls of said hatch-cover panel; said hatch-covers having a side-beam assembly positioned along each of their longitudinal edges; said side-beam assembly comprising a spine and a plurality of stiffeners positioned along said spine; selected ones of said stiffeners having support-channel means for supporting the longitudinal-edge of said hatch-cover panel; a given number of stiffeners being adapted to serve as lifting-brackets; and said side-beam assembly having a corresponding number of receiving-slots adapted to receive said lifting-brackets when said hatch-covers are stacked atop each other.

3. The invention of claim 2 wherein said lifting-brackets and said receiving-slots are staggered relative to each other.

4. A barge comprising: A. a plurality of affixed juxtaposed body-seCtions, each of said body-sections having a double-wall hull; plastic-floatation means positioned within said double-wall hull of said body-sections; B. a pair of affixed end-sections, each of said end-sections having a double-wall hull; plastic floatation means positioned within said double-wall hull of said end-sections; C. a coaming extending above the deck of said barge, said coaming being of double-wall construction; plastic floatation means positioned within said double-wall construction of said coaming; D. a plurality of hatch-covers adapted to rest on said coaming to cover the cargo-hold of said barge, said hatch-covers being of double-wall construction; plastic floatation means positioned within said double-wall construction of said hatch-covers; E. said hatch-covers comprising an arched hatch-cover panel of double-wall construction; plastic floatation means positioned within said double-wall construction of said hatch-cover panels; F. said hatch-covers further comprising a side-beam assembly positioned along each of their longitudinal edges; said side-beam assemblies comprising a spine and a plurality of stiffeners positioned along said spines; G. said stiffeners having support-channel means for supporting the longitudinal-edge of said hatch-cover panels; H. a given number of said stiffeners being adapted to serve as lifting-brackets; I. said side-beam assemblies having a corresponding number of receiving-slots adapted to receive said lifting-brackets when said hatch-covers are stacked atop each other; J. said hatch-covers having a sealing/interlocking strip positioned along each transverse-edge thereof; K. said sealing/interlocking strips comprising vertically-extending troughs, the trough of one of said strips extending upwardly, and the trough of the other of said strips extending downwardly; adjacent troughs of juxtaposed hatch-covers interlocking with each other.

5. The apparatus of claim 4 wherein said lifting-brackets and said receiving-slots of one hatch-cover are staggered relative to the lifting-brackets and the receiving-slots of another hatch-cover.