US3735722A

US3735722A - Rigid disconnectable coupling for waterborne vessels

Info

Publication number: US3735722A
Application number: US00206434A
Authority: US
Inventors: A Hooper; E Frankel
Original assignee: INTERSTATE OIL TRANSPORT Co
Current assignee: MARITRANS OPERATING PARTNERS LP A OF DE LP; INTERSTATE OIL TRANSPORT Co
Priority date: 1971-12-09
Filing date: 1971-12-09
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29
Also published as: DE2225065C2; JPS4865694A; IT955460B; ES402144A1; GB1375264A; SE397182B; DE2225065A1; NL171970C; FR2139414A5; NL7206493A

Abstract

A combination of a pushed watercraft with a pushing watercraft, which is powered accordingly. A deep, through-going stern notch on the pushed watercraft, mating with and extending to about amidships of the pushing watercraft. Multiple, short, quick engaging-disengaging coupling apparatus on the pushed watercraft stern notch and pushing watercraft bow end, arranged for multiple point engagement between the watercraft. Short fore and aft dimensioning of the coupling apparatus for coupling and uncoupling of the watercraft with a minimum of relative longitudinal motion. Vertically ordered pluralities of the coupling apparatus enabling different relative draft engagements of the watercraft.

Description

[ 51 May 29,1973

Garcia..............................

[ RIGID DISCONNECTABLE COUPLING FOR WATERBORNE VESSELS [75] Inventors: Adrian S. Hooper, Devon, Pa.; Ernst G. Frankel, Chestnut Hill, Mass.

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PATENIE MAY 2 91973 SHEET u 0F 4 RIGID DISCONNECTABLE COUPLING FOR WATERBORNE VESSELS BACKGROUND OF THE INVENTION The invention relates generally to waterborne or ocean push towing, and more especially to a novel type of push towing system providing at least two widely spaced point coupling of, or more particularly multiple, short, simultaneously engaged point supports for, said push towing system. 4

The transporting of a barge, or train of barges, by pushing it, is much to be preferred to, and has large advantages over, the pulling of the barge or train of barges, as with a steel cable. The push tow integrated or thrust coupled tug-barge system, or self propelled tank barge, as utilized particularly for shipment of bulk or liquid cargoes, has far greater maneuverability than the pull tow arrangement, wherein the tow is a substantial distance or hawser length away from the tug. With the push tow, because the tug and barge are close coupled, the tow can be turned more quickly and through sharper angles, stopped and even reversed.

The enhanced maneuverability, and much more compact organization, of the push tow is of great importance, and is indeed critical, when the tow is transiting restricted waters, or is nearing a port or other crowded area the navigating of which requires many maneuvers in close quarters. Numerous other problems and difficulties with the trailing tow, including barge yawing, propeller wash, hawser fouling or breaking, and others wellknown to the art, are eliminated by resort to push or thrust coupling of the tow to the tug or propelling vessel.

Accordingly, various arrangements or systems have been proposed for such push tow or thrust coupling of watercraft or vessels.

According to one such system, it is proposed to provide a pivoted joint or articulated coupling of the tug and barge, in a manner such as exemplified by Fletcher, U.S. Pat. No. 3,512,495. However, i has been considered that such hinged or articulated hrust coupling of the tug and bargemay present problems for oceangoing operations, in that, particularly in rough seas, the pivoted coupling means are subject to forces or strains of such large proportions as to endanger the integrity of the articulated coupling between the vessels.

Accordingly, it has alternatively been proposed to provide a rigid coupled push tow system, and more particularly a push tow system utilizing and dominantly characterized by rib, strake, or similar longitudinal coupling or support means of continuous or full length design or construction, such continuous length or full length coupling or support means being illustrated in Breit Jr. U.S. Pat. No. 3,486,476 and Peterson U.S. Pat. No. 3,362,372.

The prior or long length mode of rigid coupling of the vessels is found most vulnerable, or most likely to break down, at the point of disengagement, because, then, when-as in rough seas-the tug may be lifted relative to the barge in heave or in pitching, great shear forces resulting from large twisting moments are imposed on a fraction of the connecting linkage, these resultant shear forces originating from huge moments or torques acting on the short lengths of the continuous ribs or strakes that remain interfitted, at that disengagement point.

The excessively large twisting moments that are then to be experiences can be calculated, and thus it has been proven that forces which must be expected in, and which push towing units must therefore be designed to withstand for, oceangoing operations, will readily and inevitably damage or break the prior rigid type couplings by shearing or twisting off the ends of their continuous length couplings. I

With such prior form of rigid type continuous longitudinal push tow coupling also, the interval of time needed for disengaging the continuous or full length connecting ribs or strakes is found to be relatively long, thus greatly increasing the probability of occurrence, during such prolonged period or time of disengaging, of relative pitching or heaving of the degree of severity that results in the mentioned intolerable moments and forces.

It will be appreciated that self propelled sea going vessels of the combined tug-barge tonnage are subject to inspection for suitable hull structure, suitable passenger accommodations, and safe conditions, and are subject to costly requirements as well as to specified complement of officers and crew.

It is a heretofore unsolvedproblem of the push towing art,then, to provide a thrust or push coupling of tug and barge qualifying for treatment of the propulsion and cargo units as separate units for inspection and certification purposes. Such problem critically involving the separability or disengagement time, of the push towing system, or tug-barge coupling.

Accordingly, a principal object of this invention is to provide a push towing system or push tow unit, qualifying (for inspection and certification purposes) the propulsion and cargo units thereof for treatment as separate vessels as they are today.

The criteria now laid down for such separate vessel classification are, among other things, that the push towing system shall have demonstrable operational capability of safely separating both vessels in a timely fashion under open and rough sea conditions.

The very great cost savings and other benefits to be realized by solving the stated problem, and attaining the invention object, will be readily apparent to those skilled in the art. In cost or money terms, the benefit or advantage is that a push towing tug and barge systemv,and particularly including that for safe disengagement in sea going operations, can be built for as little as 60% of the cost of a tanker of equivalent capacity.

This invention solves the foregoing problem, and provides a rigid type push tow system meeting prudent criteria for treatment of the tug and tow as separate units, and which, therefore, is demonstrably safe and practicable to operate under all expected conditions of sea and navigation.

BRIEF SUMMARY OF THE INVENTION The invention provides for the coupling together of waterborne or floating bodies, such as surface ships, submarines, tugs and barges or other vessels, in a rigid manner, that is, in a manner whereby relative motions between the coupled bodies or watercraft will not be possible. The fixed coupling hereof also provides for a multitude of relative displacements of the vessels being joined, with the floating watercraft or vessels being rigidly joinable subject to and irrespective of different relative drafts or floating or ballasting conditions of the pushed and pushing vessels.

Under the invention, the pushed vessel has an open or throughgoing deep recess or stem notch, which may have any contour permitting the pushing vessel bow end to be fully inserted therein.

On the sides of the forward portion or bow end of the pushing vessel, fitting into the stern notch, are mating coupling means or point supports shaped and proportioned for rigid interfitting with those on the sides of the notch, and whereby, upon their interfitting, the two vessels will be locked together in push towing or thrust coupled engagement.

The coupling means or point supports are provided in multiple, or two or more, mating assemblies or groups located on each side, or on the front and sides, of the bow end and stern notch. At least one such group is arranged on the forward portion of the stern notch and bow end. At least one other such group is arranged on the aft portion of the stern notch and bow end, with the pushing vessel elements thereof located at about amidships.

The multiple coupling means or point supports hereof are also placed in such a way that said forward andaft portion groups thereof engage and disengage at exactly the same instant, in the closing and withdrawal of the vessels to and from their push tow relation. In this way, the two vessels, when engaging or disengaging, are always connected in at least two fore and aft locations, these being the aforementioned fronts or forward portion sides of the stern notch and bow end, and aft portion sides of the stern notch, and about amidships sides of the tug.

The invention will be fully understood by reference to the following description, taken together with the accompanying drawing, in which FIG. 1 is an assembly view in perspective of a push tow system of the invention;

FIG. 2 shows a front end arrangement of the coupling means;

FIG. 3 shows a latch and bar embodiment of one assembly of the coupling means;

FIGS. 4A and 4B illustrate the capability of the invention coupling means for interengaging the push tow vessels in different embodiments and in different combinations of their relative displacement;

FIG. 5 is a top plan view illustrating the simultaneous engaging and disengaging of the multiple coupling means or point supports of the invention;

FIGS. 6A and 6B illustrate exemplary wear resistant and shock absorbing configurations of the invention coupling means;

FIG. 7 is a top plan view of a push towing system of the invention incorporating fenders;

FIG. 8 shows an exemplary tug-barge separating means of the invention;

FIGS. 9A and 9B are top plan and side elevation views diagramming the shear forces to which the coupling means of the invention are subject;

FIGS. 10A and 10B are like top plan and side elevation views of the prior art rigid type push tow coupling apparatus, in which are correspondingly diagrammed the shear forces calculated therefor; and

FIG. 11 is a diagrammatic representation in fore and aft dimension of a segmental cross section of rigid type, towing unit coupling means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The rigid coupled push tow system hereof comprises 5 as the pushed watercraft or vessel a powerless, carrying waterborne craft 20, which may be a barge. Barge 20 has a stern notch 2l which is deeply indenting and also throughgoing in the vertical direction, as shown.

In relation to the pushed vessel 20, the push or thrust imparting vessel 22 may within the invention be either a powerless carrying waterborne craft, as when the vessels form a train of rigidly coupled craft, or an independent powered waterborne craft, such as the tug shown.

Pushing vessel or tug 22 has a bow end 23 that penetrates and fits fully into the stern notch 21, that extending rearwardly, upon said full inserting, to amidships, or approximately so, of the tug 22.

The shape of the stern notch 21 need not conform to that of the bow end 23, and may vary randomly intermediate, and except as required for the interfitting positioning of, the coupling means to be described.

THE COUPLING MEANS Means are provided for rigid coupling of the pushed and pushing craft, and more particularly for at least two, axially displaced point contact of and support by rigid, interfitting coupling or vertical-thrust-supporting formations or members, upon the engaging of said pushing vessel or tug bow end and pushed vessel or barge stern notch, in or as said push towing system, or push tow unit.

The invention coupling means comprise at least one forward portion point support assembly or group, consisting of at least one vertical-thrust-bearing formation or member at a forward portion of one of said bow end and stem notch, and at least two, generally vertically ordered, vertical-thrust-bearing formations or members at a forward portion of the other of said bow end and stern notch.

The invention coupling means further comprise at least one aft portion point support assembly or group, consisting of at least one vertical-thrust-bearing formation or member at an aft portion of one of said bow and stern notch, and at least two, generally vertically ordered, vertical-thrust-bearing formations or members at an aft portion of the other of said bow end and stem notch.

The forward portion coupling means of the push tow system are respectively projected from both, or projected from one and recessed in the other, of said bow end and stem notch; and they are of mating, complementary shape and proportion.

The aft portion coupling means of the push tow system are respectively projected from both, or projected from one and recessed in the other, of said bow and stem notch; and they are also of mating, complementary shape and proportion.

In one preferred form the forward and/or aft portion coupling or point support formations or members comprise forwardly converging

wedge projections

24, 28 at the opposite sides of the tug bow end 23; and the mating, complimentary coupling or point supports means comprise similarly forwardly converging wedge recesses 25, 29 at the opposite sides of the barge stern notch 21. The forward portion projections 24 and recesses 25 are seen as located relatively close to the bow and notch fronts, or to the very point or stem of the bow end and point or apex of the stern notch, to comprise the described assembly or group of mating or complementary, forward portion coupling means or-members.

Alternatively, the forward coupling means may comprise forwardly and rearwardly projecting or either way projecting and recessed wedges or

other interfitting formations

26, 27 located directly at, or wrapped around, the point of the tug bow end 23, and apex of the stern notch 21, respectively, FIG.-2.

It is pointed out that the push tow coupling means hereof not only maybe projecting, receiving, or indenting on either of the pushed and pushing craft, but also may be correspondingly or oppositely so in the forward and aft portion, and as well in the either side, groups or assemblies thereof.

The invention coupling means may also take any other practicable, rigid interfitting, vertical-thrustbearing shape or form, including oval or round, FIG. 4,

and square or rectangular, FIG. 6. And they may be fashioned of pins, bars, shafts, and numerous other types of point support or short fore and aft dimensioned formations or members.

Further, the respective forward portion and rear portion coupling means may be located in-the same, FIG. 1, or different, FIG. 9A, horizontal planes, the latter arrangement having the advantage of preventing accidental engagement of the forward portion coupling means, as the wedge projections 24, into the aft portion means, as the wedge recesses 29.

The relative width, or lateral extent, of the fore and aft coupling means, considered transversely, of the tug or barge, may commonly or conveniently be as shown in FIG. 5, with the maximum width of the forward portion coupling means being equal to or less than the minimum width of .the' aft portion coupling means, whereby the forward portion coupling means, as the wedges 24, may advance to their point of entry to, or initial engagement with, their notches 25, having cleared the aft notches 29, and without interference either with the converging stern notch walls intermediate the aft and forward portion coupling formations.

The coupling or point support means or members hereof may be formed on or applied to the bow end and stem notch in any wise. The projecting and receiving or recessing means or formations may be passed or received through the hull or stern notch, or integrally or detachably mounted thereon, individually, as in FIG. 6, or in plurality, as via the mounting plates indicated in FIG. 1. And as already shown, the stern notch, as well as the bow end, may be provided with coupling projections, as at 27, FIG. 2, in combination with or alternative to recesses, as the recesses 25, 29 also heretofore considered.

In all forms, the coupling means hereof have interengaging formations, faces or surfaces of somewhat forward and rearward facing extent, as in the FIG. 1 embodiment the wedge front faces 24a, 28a, and recess front faces 25A, 29A, thereby providing means for limit-stopping the insertion, or closing to push-towengagement, of the bow end-stern notch.

THE DIFFERENT, RELATIVE DRAFT ENGAGEMENT GROUPING OF THE COUPLING MEANS In accordance with the invention, at least one of one, and a plurality or at least two of the other, coupling means of the mating, forward and aft portion groups are provided on one and the other of, and at the forward and aft portions of, the bow end and stern notch. And the plurality, or two or more, of the forward and aft portion coupling means groups are generally vertically ordered, or arranged in a generally up and down assembly, as best shown by the stern notch rear portion wedge recesses 29, FIG. 1, flat-indenting the otherwise rounded rear corners of the stern notch, and extending forwardly therein in a fore and aft axis-paralleling direction, FIG. 5. Such vertical ordering of, the at least two, enables their different interfitting heightwise with the at least one, coupling means, of the fore and aft groups, whereby different relative height engagements of the tug and barge may be had, accommodating their changing relative draft conditions to be experienced, as represented in FIGS. 4A and 4B. A rigid coupling is thus provided for a multitude of relative drafts.

In the wedgelike or forward converging, rearward opening configuration of FIGS. 1 and 2, the coupling means will also permit the push tow engagement subject even to the relative drafts of the two crafts not being that which perfectly levels or matches up the same, upon the closing or inserting of the tug bow end into the stern notch from the position shown in FIGS. 1 and 2 and at the left, FIG. 5, through the middle FIG. 5 position to the ultimate or fully inserted position at the right, FIG. 5.

THE SHEAR WlTI-ISTANDING CAPABILITY OF THE COUPLING MEANS The strength, or shear withstanding capability, of the invention coupling means is determined by the material selected therefor, and by their cross sectional areafThe shear withstanding, or vertical-thrust supporting, requirement of the coupling means is a function both of the displacement of the pushing vessel, or tug, and of the relative displacement of the pushing and pushed vessels, or tug and barge.

The required cross sectional area may be made up of any combination of length and height. Thus, with shortest length, will go longest depth, for the same strength cross section.

Illustrating the invention in this regard are FIG. 6A, showing the coupling means with a greater vertical, and FIG. 68, showing the same with a greater horizontal, cross sectional dimension.

It will be apparent that theconfiguration of the coupling means may limit their length, as when pins or other round elements are selected therefor.

Similarly, for the maximum flexibility or adjustability of relative vertical interfitting to accommodate different relative displacements of the vessels, the required strength or cross sectional area will be compounded of the relatively shortest height and longest length of coupling means.

Along with the selection therefor of strong, durable material, such as mild steel, to impart damage resistance and long life to the coupling means hereof, the same may be formed or faced at one or more or all exposed surfaces with hard rubber, oak or any other shock absorbing and wear resistant material, as diagrammatically shown at 43, FIG. 6A.

Or the fore and aft entry and exit ends in particular of the coupling means or point supports hereof may be made of or faced with rubber or other elastic material, whereby to limit or reduce stress or shock during initial contact between, or final separation of, said point supports.

The push tow coupling means hereof may also or alternatively be provided with shock absorbing mounting, as herein diagrammatically shown in FIG. 68, wherein the random section, projecting coupling means 44, secured through wall 45 of its bow end or stem notch as by pin and fastening 46, 47, is provided with the rubberlike mounting 48 extending behind the coupling means 44 and about its mounting pin 46, as shown.

THE FORE AND AFT DIMENSIONS OF THE COUPLING MEANS In accordance with the invention, the length, or effective fore and aft dimensioning, of the coupling means, is made a small fraction of the fore and aft dimensioning of the stern notch, and not greater than that which permits the disengagement of the towing system vessels within the predicted or expected time interval or period of consecutive ship motions. More particularly, the coupling means hereof are predeterminedly formed with a quite short lengthwise or fore and aft dimension or proportion. In its effective or axial length, such dimension may be, for example, on the order of, or about, 4 feet.

The described fore and aft dimensioning of the invention coupling means is of critical importance to the successful operation of a push tow subject to sea or other conditions generating ship motions. With the continuous or full length supports of the prior art rigid type coupling means, two minutes, say, are required to uncouple. During this prolonged, two minute interval, with a sea running, overwhelming shearing forces, generated by large heave of one vessel or the other, or by large relative vertical displacement of the vessels,is almost certain to occur.

With this invention, on the other hand, and more particularly with the short coupling means dimensioning hereinabove indicated, the uncoupling is accomplished in as short as a 3-to-5-second, or even shorter, interval. It will be apparent that for this brief disengagement period the ships or tugs captain is enabled by the invention to chose an interval between the passage of successive waves, when he may separate free from travelling wave induced motions. This safe, controlled disengagement of the vessels obviously cannot be attained under open ocean or rough seas conditions, with the prior, continuous length type of rigid push tow coupling means.

THE SIMULTANEOUS ENGAGEMENT OF THE COUPLING MEANS Under the invention, the forward portion and aft portion coupling means importantly are so relatively positioned, lengthwise or fore and aft wise of the bow end and stern notch, as to enter into and clear from their push tow engagement at exactly or substantially the same instant, in the coupling and uncoupling of the two units or vessels.

This simultaneous coupling-uncoupling aspect is illustrated in FIG. 5, wherein the forward portion and aft portion coupling means diagrammed at 56, 57 are shown in the intermediate, dash line position to identically approach, and in the right hand, solid line position to matchingly close, the inserted or push two engaged position; the forward and aft portion coupling means in THE MOMENT ARM OF THE COUPLING MEANS It is now appreciated in the push tow art that tendency to relative motions in the waves between the two push tow vessels, such as pitching or heaving, can produce huge moments acting on the vessels, becoming ship motions which in turn generate impossible or intolerable shearing forces on the coupling means. This invention proceeds in part from the discovery that these huge moments, when divided by a long arm between, and such as enabled by the provision hereunder of two or more simultaneous engaging-disengaging groups of,

the coupling means or point supports, are greatly reduced thereby to acceptably small shearing forces acting on the coupling means.

Accordingly under the invention, the depth of the stern notch 21, and extent of penetration of the bow end 23 thereinto, is that which provides a distance between the fore and aft coupling means sufficient to the moment arm which is desired or required, for the particular tow. The sufficient distance is, again, that which will act as a moment arm by which the moments due to wave action on the coupled vessels will be reduced to an acceptable level, or a level withstandable by said fore and aft portion coupling means.

Pursuant thereto, the mentioned axial spacing of, or fore and aft distance between, the forward portion and aft portion coupling means may, and often does, correspond to about one half the length of the pushing or penetrating vessel, or tug.

With reference again to the moment arm feature of the invention coupling means, the length of notch 21, and the spacing between the forward portion and aft portion coupling means, will be approximately equal to, or will approach, the length from the bow to amidships of the pushing craft. Or the forward and aft portion coupling means spacing will approximate the pushing vessels bow to amidships length less the distance that the forward portion coupling means may belocated aft of the pushing vessel's bow.

It is understood again, that, without the plural or multiple fore and aft portion coupling means or point supports hereof, when disengaging the two vessels in rough seas the shear forces, such as would be acting on the prior continuous or full length supports, are tremendously large, particularly during the final disengagement of the push tow vessels, when there is generated a shear, or coupling means breaking-off force, which is expressed as a twisting moment.

It will be apparent as well that unavoidable failure to withstand such huge twisting moment will too likely result in, or create unacceptable risk of, damage to, and threatening the seaworthiness of, the engaged hulls.

The stated impracticality, as for disengagement in open sea, of the continuous or full length push tow couplings as heretofore known, and the immense advantage to push towing of at least two point supporting, simultaneously engagingdisengaging, long moment arm coupling means of this invention can both be shown, or proven, by calculation. The following example compares the prior, continuous or full length coupling means arrangement, such as illustrated in Breit U.S. Pat. No. 3,486,476, with the coupling means arrangement of this invention, with respect to shearing forces and the withstanding thereof.

As an example, the disengagement of a 136.5 foot long tug, such as the tug Intrepid built by Main Iron Works, and a 546 foot long, 30,000 deadweight ton barge such as of the Ocean 250 class built by Bethlehem Steel Corporation at Beaumont, Texas, will be considered.

The pertinent characteristics of the above two vessels can be stated as follows:

TUG

Length overall 136.5 feet Breadth 36.8 feet Depth 19.0 feet Draft (amidships) 16.0 feet Displacement 1 150.0 long tons LCG (longitudinal position of the center of gravity) TPI (tons per inch of immersion) 1.6 feet forward of amidships 10.00 long tons BARGE Length overall 546.0 feet readth 85.0 feet Depth 40.0 feet Draft 32.0 feet Displacement 35000.0 long tons As hereinabove explained, it is prudent practice, or to be assured, that the two push-tow vessels can disengage safely under wind and sea conditions such as correspondto those encountered or expected in the Western North Atlantic, for example. Pertinent characteristics of such conditions may be, in such example:

Wind force (Beaufort scale): 7

Description of the wind: Moderate gale Wind velocity: 32 knots Wave height (significant): 26 feet Wave penod (spectral peak): 12.9 seconds Wave length (spectral peak): 740 feet A: Amplitude, Tug A Amplitude, Barge (wherein upwards and downwards) Hence, assuming the possibility of difference in phase angle of 180 (i.e., of one vessel being in its lowest position and the other being in its highest position), the maximum possible vertical distance between the centers of gravity of the two vessels floating independently can be 13 +6=l9 feet The maximum possible relative displacement would correspond, with the two vessels interlocked, to the case when the tug is lifted up on the stern or rear end of the barge out of water, such as occurring with the wave trough located under the tug, and the wave crest under about amidships, of the rigid system. In this case, of course, the tugs weight will produce or become the shear load on the prior or continuous type of rigid cou- I pling means.

Further, the shear load (of 1150 long tons) produced by the weight of the tug may be increased or added to by the dynamic action between the two interlocked vessels, as would originate mainly from the pitching and rolling of the system. The load imposed by the tug upon the barge (and vice versa) could increase,then, in the given example, to as much as about 1500 long tons. This resultant coupling shear load can be considered as acting at the center of gravity of the tug, and is indicated by the arrow L, FIG. 10A.

Such load produces, then, shearing forces of the prior art support guides, or rubbing strakes, as indicated by the arrow S, FIG. 10A.

Turning now to the calculation of the forces acting on the prior, continuous length coupling means, and assuming the aforesaid Breit U.S. Pat. No. 3,486,476 configuration of single, strake and channel, longitudinally continuous or full length, rigid coupling means, and assuming further the vessels having closed or opened to point of engagement or disengageement at which one foot of fore and aft extent of the lengthwise coupling means has been or remains inserted or interfitted, as represented in FIGS. 10A and 108.

With the indicated prior continuous or full length type of rigid coupling, at the engagement or disengagement instant when only 1 foot of the coupling means or rubbing strake has been or remains engaged in the channel therefor, the center of gravity of the tug is positioned about 28 feet aft of the engagement, as shown, FIG. 108.

Accordingly, the resultant of the weight and dynamic forces, which is acting at the center of gravity of the tug, produces a moment about the point of engagement equal to:

M (Load) X (arm) 1500 long tons X 28 feet =42000 long tons X feet Half of this resultant moment will act as a shearing 'moment on each engaged portion of rubbing strake.

That is, half moments will be'applied to each of the 11 foot extension (or effective length) rubbing strakes that are in contact on each side of the vessel, in the example. Thus on each such strake the moment is M 21000 long tons X feet.

Assuming that mild steel will be the construction material of the rubbing strake, with an allowable stress in shear of Tallow 12000 psi,

111... Mm... (3a l.8b)/a b b the shorter side or effective length of the cross section (given as 1 foot or 12 inches) Then in the given case:

T,,,,,,,, M,,,,,,, (3a 1.8 x 12 /e 12 12,000 21,000 x 2,240 x 12 (3a 21.6))/(l44 a) which reduces finally to a 1974/2 987 inches 987/12 5 82 feet.

The required cross sectional area per 1 foot length of rubbing strake is, then:

a X b 987 X 12 11,844 square inches per foot.

The prior art requirement has just been shown to be, then, of a rubbing strake of solid steel which is 987 inches or 82 feet high. This is, of course, impossible; the tugs depth being only 19 feet, the physical dimension of the tug and barge obviously could not comport a rubbing strake of such size.

Considering now the shear loads acting on the coupling means or point supports of the push-towing system of this invention. In the present system, during, say, disengagement, at the instant when only one foot of horizontal projection of, say, forward and aft supports remain engaged, such as represented in FIGS. 9A and 9B, the center of gravity of the tug (the point, again, where the resultant load is applied) is positioned between the two groups of coupling means, or point supports, and more particularly about 2 feet forward of the after group of supports, FIG. 9B, the distance between forward and aft supports being 54 feet.

The load of 1,500 long tons (in the given example) will thus be distributed in the following manner between the two groups of supports:

The forward supports will take a load of F 2/54 1500 55.6 long tons, FIG. 9A. The after supports will take a load of F 52/54 1500 1444.4 long tons, FIG. 9A.

With respect both to the forward and to the aft groups of coupling means, the loads will act as shear forces on the point or thrust supports.

Assuming mild steel, again, as the construction material for the supports, whereby allow 12,000 (P and given that A is the required cross sectional area (in square inches) per foot of all the supports on each side of the vessel, either aft or forward F the shear load in long tons acting on the supports then the necessary cross sectional area, FIG. 1 l, for the engaged portion (one foot extension) of the steel supports will be:

Forward supports:

55.0 (LT) 2240 AFWDZFLWD: lbs

sq. 1n.

=about 5 sq. inches Aft supports:

sq.1n.

=abou1; sq. inches AAFT= FAFT From the foregoing it will be seen that if all of the aft load or shear force were to be withstood by a single invention support, that, in solid (mild) steel, would be required to have a width or height of about 12 inches, or one foot, to provide the required cross sectional area of 135 square inches, per foot of extension.

And given that the aft coupling means in the above example comprise two supports on either side of either of the tug and barge, the height required for each of the two aft supports will be seen to be reduced to but 6 inches, or one half foot.

Thus it is seen that the impossible prior requirement in the stated example of some 87 times more cross sectional area, or an 82 foot high support, has been reduced by the invention to practicable forward and aft coupling means or supports of but one half foot or 6 inches height.

The foregoing calculation demonstrates, then, that the prior continuous length type of rigid coupling system fails to solve the heretofore described shear problem, is not suitable for disengagement in rough seas, and cannot be built to acceptable specifications, in any form in which it can be constructed. Whereas the two (or more) point system of the present invention, by its herein shown requirement of but 135 square inches versus the prior required 1 1,844 square inches of cross sectional area per foot of longitudinal extension, is seen to be suitable, and more particularly to meet prudent safety considerations for, the mentioned rough seas disengagement.

THE DRAWING AND/OR LOCKING TOGETHER MEANS To assist the drawing together, or to prevent the sliding apart, of the joined floating bodies, or push tow vessels, and in addition or alternatively to the thrust of the tug propellers 49, steel cables 30, FIG. 1, as may be tensioned by a winch 31, may be carried on one and passed over bitts or the like 32 on the other of the pushtow system units or vessels.

Within the invention, any other type of locking device may be employed for the push-tow locking up purpose, such ashydraulic retractable pins, clamps, or mechanical couplings.

In the embodiment of FIG. 3, for example, a bar 33 spans the stern notch 21 and is engaged or clamped by a jaw 34 fixed on flatted bar 35 and pivoted therewith by a piston rod 36 between the solid line closed and dash line open positions. Link 37 actuated by rod 36 with jaw 34 through pin 38 serves upon retraction to swing the forward wall 37a of movable pivot bar 35 whereby to rotate the same to the horizontal, and whereby bar 35 may then be drawn rearwardly in slot 39 proportioned to receive the flatted bar section, and so to maintain jaw 34 in the open position. The last closing movement of link 37 is to lock jaw 34 and thereby the tow by biasing pin 40 into locking engagement in stern notch 41 and the first opening movement of link 37 is to release pin 40 for retraction from notch 41 subject to its upward biasing by spring 42.

THE DISENGAGING MEANS Any suitable means, including of course the stern thrust of the tug propellers 49, may be utilized for disengagement of the push towing system. As one alternative to the tug engines, a push-pull pneumatic or hydraulic ram 50, FIG. 1, may be provided at the bow of the tug. Such rarn or similar device 50 may, as well known in the art, be constructed and arranged to enable controllable, forced engagement and disengagement between the towing system vessels. As contemplated by the invention, the push-pull power of the ram or similar device 50 is such that it will provide a safe and fast means for emergency disengagement under any loading and sea conditions.

As another alternative, one or more nozzle means or assemblies SLFIG. 8, may be provided on the point or stem of the tug bow end for directing pressure fluid or water jets at the then matingly contoured apex 52 of the stern notch, the jets pressuring the cavity between the nozzles 51 and notch end 52 by the provision therewith of seals 53 in one and in fluid tight arrangement with the other of said nozzles and notch end to either side of the water jets 51.

It will be understood that cams, or other linkages may be used to create the horizontal separation forces.

Whatever the disengaging means that may be employed with the invention, it will be appreciated that the complete disengagement of the coupled vessels, from the fully engaged to the wholly separated position, proceeds in an immediate, swift, certain, one-sure-step manner, and thereby always without harm to the coupling means or point supports hereof. This is due, again, to the two or more point provision of the thrust or shear supports as hereinabove described, and is especially assured by the selection for the coupling means of the described fore and aft guiding wedge, or laterally retracting pin, configurations.

THE F ENDERING MEANS Under the invention also, fendering means 54, 55, FIG. 7, which may be of usual construction, may be provided, as at the corners of the stern notch and point of the bow end, and more particularly constructed and arranged, as thereby, to prevent the engagement of the vessels prior and subsequent to, and otherwise than by, the inte'rfitting of the coupling means.

Reinforcing means 56 may also be provided between the stern notch recessing 29, FIG. 1, which means may be fixed or movable, and of any shape or material suitable to their wear resisting, coupling means engaging and disengaging assisting purpose.

THE APPLICABILITY AND VERSATILITY OF THE PUSH TOW SYSTEM be used for general service. More particularly, any tug and barge, or combination of such craft, can be adapted to the system without change in line or form, or hull contour. In other words, the multiple supports hereof need merely be added or applied to the preexisting hull structure of the pushed and pushing vessels of the push tow system.

Hence, the invention is accommodated by but minor changes in configuration of existing barges, so that a tug also so configured has universal use, as opposed to being married" to one, specially designed or configured barge. Accordingly, its adapting hereto does not preclude such tug from engaging in other services normally performed by tugs, and existing tugs can be modifled, without undue design and construction complications, to suit the invention.

Further, even under the most severe weather, and extreme relative loading of the coupled crafts, a relative horizontal speed when disengaging of one knot between them can be easily maintained with or without auxiliary decoupling means, or force. As a result, it has been found, decoupling time can or will be about one (I) second for a multiple support system whose supports extend as much as four (4) feet horizontally.

Under this invention,then, the horizontal extent of the supports may be less than four (4) feet. No twisting of the invention supports can occur, for the reason that all forward and aft'supports engage or disengage simultaneously.

The elimination of the requirement of moving parts or complicated machinery or fittings to effect engagement or disengagement will be recognized as a distinct advantage, from all of the speed, safety, and cost points of view, which is not shared by prior forms or'systems of push tow coupling.

We claim:

l. A multiple point coupled, rigid, waterborne push towing unit comprising, in combination:

a waterborne pushed craft;

a deep throughgoing stern notch in said waterborne pushed craft;

a waterborne pushing craft;

a seaworthy bow end on said waterborne pushing craft; the conformation of said stern notch relative to that of said bow end being such asto enable said pushing craftbow end to be inserted into said pushed craft stern notch; f,

at least one, vertical-thrust-bearing, towing unit coupling means at a forward portion of one of said how end and stem notch; at least two, generally vertically ordered, verticalthrust-bearing, towing unit coupling means at a forward portion of the other of said bow end and stern notch;

said forward portion towing unit coupling means defining interfitting formations respectively projecting as to one and receiving as to the other of said bow end and stem notch;

said projecting-receiving forward portion towing unit coupling means being of mating, complementary shape and proportion,

whereby upon said inserting said forward portion towing unit coupling means are rigidly interfitted at one point of supporting contact between said pushed and pushing craft;

said generally vertical ordering of said at least two forward portion towing unit coupling means enabling said rigid interfitting of said at least two forward portion towing unit coupling means with said at least one mating forward portion towing unit coupling means in at least two different relative draft engagements of said pushed and pushing craft; at least one, vertical-thrust-bearing, towing unit coupling means on the opposite sides of and at an aft portion of one of said bow end and stern notch; at least two, generally vertically ordered, verticalthrust-bearing, towing unit coupling means on the opposite sides of and at an aft portion of the other of said bow end and stem notch; said aft portion towing unit coupling means defining respectively interfitting formations projecting as to one and receiving as to the other of said bow end and stern notch; said aft portion towing unit coupling means being of mating, complementary shape and proportion, whereby upon said inserting said aft portion towing unit coupling means are rigidly interfitted at at least one other point of supporting contact between said pushed and pushing craft; said generally vertical ordering of said at least two aft portion towing unit coupling means enabling said rigid interfitting of said at least two aft portion towing unit coupling means with said at least one mating, aft portion towing unit coupling means in at least two different relative draft engagements of said pushed and pushing craft; the actual spacing of said forward and aft portion coupling means being such as to position said aft portion coupling means a sufficient distance astern of said forward portion coupling means to provide a moment arm reducing shearing forces to a level withstandable by said forward and aft portion coupling means; the relative spacing of said forward and aft portion coupling means being such that, upon the closing to and withdrawal from said inserted, push towing engagement of said bow end and stem notch, the bringing thereby of said forward and aft portion coupling means to and from said at least two point, rigidly interfitted, supporting contact is substantially simultaneous; and the fore and aft dimensioning of said forward and aft portion coupling means being a small fraction of the fore and aft dimensioning of said stern notch, and being not greater than that which enables their said bringing to and from said at least two point, rigidly interfitted supporting contact within the expected time interval of consecutive ship motions. 2. A waterborne push towing unit according to claim wherein said aft portion coupling means on said bow end of said pushing craft are located in the proximity of the center of gravity of said pushing craft. 3. A waterborne push towing unit according to claim 1, wherein the fore and aft dimensioning of said forward and aft portion coupling means is a small fraction of the fore and aft spacing between said forward and aft portion coupling means.

4. A waterborne push towing unit according to claim 1, wherein said foward and aft portion coupling means 16 are arranged for their forward and aft interfitting in the same horizontal plane.

5. A waterborne push towing unit according to claim 1, wherein said forward and aft portion coupling means are arranged for their forward and aft interfitting in different horizontal planes.

6. A waterborne push towing unit according to claim 1, wherein port and starboard of said coupling means are arranged for interfitting in the same horizontal planes.

7. A waterborne push towing unit according to claim 1, wherein port and starboard of said coupling means are arranged for interfitting in different horizontal planes.

8. A waterborne push towing unit according to claim 1, wherein said forward and aft portion coupling means are provided in such vertically ordered multiplicity and vertical dimensioning as permits their said interfitting independently both of the relative drafts and of the relative trims of said pushed and pushing craft.

9. A waterborne push towing unit according to claim 1, and fendering means on at least one of and for engaging between said stern notch and bow end, said fendering means projecting to prevent the engagement of said waterborne craft in their said closing to and withdrawal from said inserted, push towing engagement prior or subsequent to and otherwise than by said interfitting of said coupling means.

10. A waterborne push towing unit according to claim 1, wherein mating of said coupling means have at least somewhat front and rear facing portions whereby to limit-stop said insertion of said bow end into said stern notch.

11. A waterborne push towing unit according to claim 1, and means for drawing said waterborne pushed and pushing craft together in their said inserted, push towing engagement.

12. A waterborne push towing unit according to claim 11, wherein said drawing together means comprise cables on one and cable fastenings on the other of said waterborne craft.

13. A waterborne push towing unit according to claim 1, and means for locking said waterborne pushed and pushing craft together in their said inserted, push towing engagement.

14. A waterborne push towing unit according to claim 13, wherein said locking together means comprise said coupling means.

15. A waterborne push towing unit according to claim 14, wherein said coupling means comprise a transverse bar on'one and bar clamping and releasing means on the other of said bow end and stem notch.

16. A waterborne push towing unit according to claim 1, and means for disengaging said pushed and pushing waterborne craft.

17. A waterborne push towing unit according to claim 16, wherein said disengaging means comprises an hydraulic ram.

18. A waterborne push towing unit according to claim 16, wherein said disengaging means comprise forwardly directed pressure fluid ejecting means at said bow end, and means for fluid sealing said stern notch engagement with said bow end to either side of said pressure fluid ejecting means.

19. A waterborne push towing unit according to claim 1, wherein said forward portion coupling means are located at the point of said bow end and apex of said stern notch.

20. A waterborne push towing unit according to claim 1, wherein said forward portion coupling means are laterally projecting and receiving at the opposite sides of one and the other of said bow end and stern notch.

. claim 1, wherein said aft portion coupling means on said stern notch comprise recesses opening tothe rear of said waterborne pushed craft.

24. A waterborne push towing unit according to claim 23, and means fendering the corners of said stern notch intermediate said recesses.

25. A waterborne push towing unit according to claim 1, wherein at least some of said coupling means have shock absorbing wear resistant facing.

26. A waterborne push towing unit according to claim 1, wherein at least some of said coupling means have shock absorbing mounting.

27. A waterborne push towing unit according to claim 1, wherein the effective fore and aft dimensioning of said coupling means is not greater than about 4 feet.

28. A waterborne push towing unit according to claim 1, wherein the fore and aft dimensioning of the said coupling means is such as to enable their said engaging and disengaging within a time interval of not greater than about 1 second, subject to a relative speed between the push tow vessels of not more than about one knot.

Claims

1. A multiple point coupled, rigid, waterborne push towing unit comprising, in combination: a waterborne pushed craft; a deep throughgoing stern notch in said waterborne pushed craft; a waterborne pushing craft; a seaworthy bow end on said waterborne pushing craft; the conformation of said stern notch relative to that of said bow end being such as to enable said pushing craft bow end to be inserted into said pushed craft stern notch; at least one, vertical-thrust-bearing, towing unit coupling means at a forward portion of one of said bow end and stern notch; at least two, generally vertically ordered, vertical-thrustbearing, towing unit coupling means at a forward portion of the other of said bow end and stern notch; said forward portion towing unit coupling means defining interfitting formations respectively projecting as to one and receiving as to the other of said bow end and stern notch; said projecting-receiving forward portion towing unit coupling means being of mating, complementary shape and proportion, whereby upon said inserting said forward portion towing unit coupling means are rigidly interfitted at one point of supporting contact between said pushed and pushing craft; said generally vertical ordering of said at least two forward portion towing unit coupling means enabling said rigid interfitting of said at least two forward portion towing unit coupling means with said at least one mating forward portion towing unit coupling means in at least two different relative draft engagements of said pushed and pushing craft; at least one, vertical-thrust-bearing, towing unit coupling means on the opposite sides of and at an aft portion of one of said bow end and stern notch; at least two, generally vertically ordered, vertical-thrustbearing, towing unit coupling means on the opposite sides of and at an aft portion of the other of said bow end and stern notch; said aft portion towing unit coupling means defining respectively interfitting formations projecting as to one and receiving as to the other of said bow end and stern notch; said aft portion towing unit coupling means being of mating, complementary shape and proportion, whereby upon said inserting said aft portion towing unit coupling means are rigidly interfitted at at least one other point of supporting contact between said pushed and pushing craft; said generally vertical ordering of said at least two aft portion towing unit coupling means enabling said rigid interfitting of said at least two aft portion towing unit coupling means with said at least one mating, aft portion towing unit coupling means in at least two different relative draft engagements of said pushed and pushing craft; the actual spacing of said forward and aft portion coupling means being such as to position said aft portion coupling means a sufficient distance astern of said forward portion coupling means to provide a moment arm reducing shearing forces to a level withstandable by said forward and aft portion coupling means; the relative spacing of said forward and aft portion coupling means being such that, upon the closing to and withdrawal from said Inserted, push towing engagement of said bow end and stern notch, the bringing thereby of said forward and aft portion coupling means to and from said at least two point, rigidly interfitted, supporting contact is substantially simultaneous; and the fore and aft dimensioning of said forward and aft portion coupling means being a small fraction of the fore and aft dimensioning of said stern notch, and being not greater than that which enables their said bringing to and from said at least two point, rigidly interfitted supporting contact within the expected time interval of consecutive ship motions.

2. A waterborne push towing unit according to claim 1, wherein said aft portion coupling means on said bow end of said pushing craft are located in the proximity of the center of gravity of said pushing craft.

3. A waterborne push towing unit according to claim 1, wherein the fore and aft dimensioning of said forward and aft portion coupling means is a small fraction of the fore and aft spacing between said forward and aft portion coupling means.

4. A waterborne push towing unit according to claim 1, wherein said foward and aft portion coupling means are arranged for their forward and aft interfitting in the same horizontal plane.

15. A waterborne push towing unit according to claim 14, wherein said coupling means comprise a transverse bar on one and bar clamping and releasing means on the other of said bow end and stern notch.

21. A waterborne push towing unit according to claim 1, wherein said coupling means are projecting and receiving formations having any combination of wedge shaped, round, square, rectangular, oval, or random configurations.

22. A waterborne push towing unit according to claim 1, wherein at least some of said coupling means are forwardly converging wedge shape projecting and receiving formations.

23. A waterborne push towing unit according to claim 1, wherein said aft portion coupling means on said stern notch comprise recesses opening to the rear of said waterborne pushed craft.