US2977920A

US2977920A - Floating dry docks

Info

Publication number: US2977920A
Application number: US645937A
Authority: US
Inventors: Christopher J Foster
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-03-14
Filing date: 1957-03-14
Publication date: 1961-04-04
Anticipated expiration: 1978-04-04

Description

docked on the rest thereof.

States Patent Christopher J. Foster, 44 Whitehall St.-, Sands Point, N.Y.

Filed Mar. 14, 1957, Ser. No. 645,937

7 Claims. (Cl. 114-46) My invention relates to an improvement in floating drydocks and has for its object to provide a self-docking floating drydock of great economy of structure. The invention relates especially to the Rennie type of floating drydock having continuous steel wings spanning a series of detachable pontoons, one ofwhich may readily be It is established by the prior art that the introduction of a central air space or buoyancy chamber into-adry- 'dock' having a rectangular pontoon body is an expensive luxury, as the bulkheads therefor and bracing of the chamber materially add to the weight of the dock center. Ordinarily, in a pontoon of rectangular crosssection having such a chamber, no benefitby way of reducing the size or strength of the parts can be obtained-v by decreasing the transverse stresses encountered, at the time the wings are first pumpedout; because the transverse bending moments-with the" ship raised, control the design of the conventional dock, and the-addition of a heavy central buoyancy chamber will materially increaseflthe transverse bending moments with the ship raised. Now, however, I have discovered that in a Rennie type of dock, where the continuous steel wingsare provided with heavy continuous bottoms, the weight of the wings, wing seats and fastenings oppose the ship momentto such a degree that the combined transverse stresses at the timethe wings are first pumped out with the pontoons still full ice The ensuing parallelogrammic section of the pontoon insures a substantial freeboard at the center of the pontoon while it cuts the bilge water left in the pontoon into half of that of the conventional dock. Due to the combination of square pontoon ends, which lie at the sides of the completed dock, lower than the center of the dock with a center buoyancy chamber, and the required wing Width as well as the dock-width substantially reduced, my preferred self docking floating drydock weighs only 25% of its lifting capacity, which is an economy of structure never before achieved. As my invention comprises a new combination of old elements from which new and useful results flow, -I do not claim only the combination of continuous sidewalls and detachable parallelogrammic pontoons with center buoyancy chambers as my invention, but I also claim as a method the several steps necessary to achieve said novel and useful results. In the. drawing- Fig. I is a'longitudinal elevation showing the center pontoon docked onthe remaining two pontoons. Fig.

I 10,- divides each pontoon into two pumping compartments are the controlling factors; and I have also discovered that theouse of. a-central buoyancy chamber, within'rectangular pontoons further reduces the controlling stresses in such a dock when the wings are first pumped out. This efiectis produced in two wayszi-The additional buoyancy causes the dock tofioat higher. and thereby reducesthe water pressure on the outside of the dock, and the" buoyancy chamber provides a substantial'cen tral lift instead of having a central ship Jload supported controlling factors in the conventional Rennie'dock with rectangular pontoons are thecombined transverse stresses when thezwings are first pumped out, a considerable economy of structure isachieved by the introduction of a center'buoyancy chamber in ,this'type'of-dock Further, the detachableppontoon is rendered laterallystable by the buoyancy chamber, and noheavy longitudinal bulk-, heads arerequired for lateral stability ,in'my preferredpontoon, which also for-;allipracticakpiurposes is renderedunsinkable when separated from the dock. In my ponor chambers 17, which chambers communicate with the Wingcompartments 19, through the communication openings 21,-. that are cut through the wing bottoms 14. A deck 5 near the tops of each wingv partitions oifa safety hold 20, the buoyancy of which will prevent an accidental sinking of the dock. The center pontoon 3, in Fig. I is shown docked when raised on special blocking7, while the ship8 shown in Fig. II is docked when raised on the regular blocking 9. For longitudinal stability of the dock,u the continuous wings, which I, for economyreasons prefer tomake rectangular in cross section are par t-itionedoif by bulkheads 6, that end at the safety deck 5. i The pontoons are shown fastened to the continuous wings by the bolts 15, and the two pumping compartments of the pontoon are divided at their bottom by shallow swash bulkheads 11, that are provided with the swing check valves 12, which open only towards the sides 3 of the dock and close towards the central chamber 18; sothat if the dock should careen or heel, the flow of water from the high side of thedock through the bulkhead on that SideltOWflTds thelow side of-the dock is prevented; this 'is-refiected in a considerable saving in the wing thickness, without a reduction in the stabilityof the loaded self docking, and the buoyancy chamber is provided with called to the fact that .the outside water line 16 is subt'o'on construction-ifor very, wide dock-,-;,where swash bulkheads: are 'required ito prevent a suddenof; waterjust when the ship has been lifted-clear out :of the; water andthe" metaceutric' height ofLship and dock is suddenly reduced to 'a; minimum,. I-' prefer to iinstalli a shallow Serial No. 633383, permitting :thewater to drain .;towards;

swash bulkhead," just high enoughtowutor top the inside water plane while. the ship bottom-. is still, sub; 7

' merged; This 1 shallow swash bulkhead "is supplied-with check valves'such shown in my copending application 70.

dock. 1 a a 7 Figures II and III indicate that the width of the .buoy- T V Y ancy chamber does not exceedone-fifthof the entirethepumps that are locatedat'the sides: ofthe ..docls',- 1 width oflthe doclg and that; each pumping chamber 17 stantially, higher than the ship bottom when the shipin the dock is still substantially submerged s'o that the stabilizingeffect of'the ships waterplane is still in effect when the partial' swash"bulkhead 11 cuts the free waterline 16 in halfithus adding to the'stability of the dock and ship, 'when' they pass through the critical zone,

wherethe water planes of the-wings alone stabilize' the beside the buoyancy chamber is twice as large, having twice the width of the central chamber. Hence the lifting capacity of the dock is four times its weight, and the weight of the dock, due to the buoyancy of the chain-j ber 18, is only 25% of the lifting capacity thereof.-

It is to be noted that portions 22 of the bottom of the chambers 17 slope downward from the central chamber 18 towards the sides of the dock, beneath the wings 2; and portions of the deck 23 slope downward from the central chamber 18 towards the wings; and these sloping portions 23 of the deck are substantially parallel to the sloping portions 22 of the bottom. Hence, when the dock has been sunk and the ship is in place between the wings, and the dock is pumped out so that the ship rises, and the level of the water in the chambers 17 sinks towards portions 22 of the bottom, the water in the chambers 17 tends to flow downward and sideways towards the spaces under the walls, and concentrate in such spaces. The advantage of the buoyancy chamber is therefore greatest, and the Water in the chambers 17 is largest in volume and heaviest adjacent the sides under the walls 2, and has a very marked balancing efiect on the dock and the load of the ship; and immensely increases the stability of the dock as the ship is lifted entirely out of the water and the deck of the dock is entirely above the level thereof.

Figures II and III indicate that the shortest dimension of each pontoon extends along the sides of the dock when the pontoon is in position, and the longest dimension extends transversely of the clock. I prefer to call the longest dimensions of the pontoons the sides thereof, because the pontoons are disposed side by side when assembled; and the shorter dimensions may therefore be regarded as the ends of each pontoon; although these ends extend along the sides of the completed dock. From this it follows that the buoyancy of the central dock forming pumping chambers, said walls being in communication with said pumping chambers at the ends of each pontoon, the central chamber being such size that the buoyancy effect thereof is greater than the submerged weight of the pontoon but smaller than the submerged weight of the pontoon and the portions of the wings super-imposed thereon, the bottom of each pontoon slop ing downward from the sides of the central chamber towards the ends of the pontoon under the wing walls thereon and being lowest directly under said wing walls.

3. In a self-docking floating dry dock, a row of pontoons arranged side by side longitudinally of the dock,

' continuous wing walls supported on the ends of said chamber is larger than the submerged weight of the 1011- t toon, but smaller than the combined weight of the pontoon and the weight of the wing portions superposed thereon; that is, the central buoyancy chamber will support the pontoon afloat even when it is filled with Water, but the dock will sink when the pontoon and wings are both filled. r I do not wish to be understood to limit my claims. to the shown structure as it is evident that alterations and modifications may be made in the adaptation of my invention without departing from the scope and spirit thereof. r

I claim: x v 1. In a self-docking floating dry dock, a row of pontoons arranged side by side longitudinally of the dock, continuous wing walls supported on the ends of said pontoons, said endsbeing directly under said walls, detachable means for securing the pontoons to the walls, each pontoon having a relatively shallow central buoyancy chamber, the spaces between the said buoyancy chamber pontoons, said ends being directly under said walls, detachable means for securing the pontoons to the walls, each pontoon having a central buoyancy chamber, the spaces between the said buoyancy chamber and the ends of said pontoons at the sides of the dock forming pumping chambers, said walls being in communication with said pumping chambers at the ends of each pontoon, the central chamber being such size that the buoyancy effect thereof isi'greater than the submerged weight of the pontoon but smaller than the submerged weight of the pontoon and the portions of-the wings super-imposed thereon, the bottom of each pontoon sloping downward from the sides of the central chamber towards the ends of the pontoon under the wing walls thereon and being lowest directly under said walls, said buoyancy cham' bers having swash bulkheads extending longitudinally of the dock along the sloping bottom, each bulkhead having one-way valves therein which open only towards the side of the dock.

4. A self-docking dry dock comprising hollow wing walls and a row of separated hollow pontoons substantially rectangularin cross-section arranged side by side longitudinally of said dock, the ends of said pontoons been directly under said wing walls, each pontoon 'having a central buoyancy chamber and spaces forming pumping chambers between the buoyancy chamber and saidwalls, said pumping chambers being in communication with the interior of said walls, the bottom of said pumping chambers sloping downward towards the sides walls and a row of separated hollow pontoons substanand the ends of said pontoons at the sides of the dock forming pumping chambers, said walls being in communication with said pumping chambers at the ends of each pontoon, the central chamber being such size that the buoyancy eifect thereof is greater than the sub merged weight of, the pontoon but smaller than the submerged weight of the pontoon and the portions of the wings superimposed thereon, the dock having a deck a pontoon having a relatively: shallow central buoyancy chamber, the=spaces between the said buoyancy cham-,

her and the ends, ofzsaidpontoons 'at the sides .of :the'

tially rectangular in cross-section arranged side by side longitudinally of said dock, the ends of said pontoons be ing directly under said side walls, each pontoon having a central buoyancy chamber and spaces forming pumping chambers between the buoyancy chamber and said walls, saidpumping chambers being in communication with'the interior of said walls, the bottom of said pumping chambers sloping downward towards the sides of t the dock, and being lowest under said walls, said pumppumpingchambers sloping downward towardsthe sides,

ing chambers having swash bulkheads on said sloping bottoms extending longitudinally of said dock, the width of said buoyancy chamber being substantially one-fifth of the width of saidtdock, each bulkhead having one-way valves therein which open only towards the side-of thedock.-' 1 .7 Y

6. A-self-docking dry dock comprising hollow wing walls and a row of separated hollow pontoons substantially rectangular in cross-section arranged side by side longitudinally of said dock, the ends of said pontoons being directly under said side walls, each pontoon having a central-buoyancy chamber and spaces forming pumping chambers between the buoyancychamber and said walls, saidpumping chambers being in COlIllTlllIIlQfi tion with the interior of saidwalls, the-bottom of; said ofthe'idock, andnbeingilowest'under said walls, said;

ans 52mph, 4

pumping chambers having swash bulkheads on said sloping bottoms extending longitudinally of said dock, each' bulkhead having one-Way valves therein which open only towards the side of the dock, the width of said buoyancy chamber being substantially one-fifth of the width of said dock, and the pumping chambers extending over the remainder of the Width of the dock, so that the lifting capacity of the dock is greatly increased.

7. In a self-docking floating dry dock, a row of pontoons arranged side by side longitudinally of the dock, continuous wing Walls supported on the ends of said pontoons, said ends being directly under said Walls, detachable means for securing the pontoons to the walls, each pontoon having a central buoyancy chamber, the spaces between said buoyancy chamber and the ends of said pontoons at the sides of the dock forming pumping chamhers, low bulkheads in each pumping chamber extending longitudinally of the dock, each bulkhead having valves opening only towards the sides, the pontoons having substantially constant depth from end to end, said Walls being in communication with said pumping chambers at the ends of each pontoon, the central chamber being of such size that the buoyancy efiect thereof is greater than the submerged Weight of the pontoon, but smaller than the submerged Weight of the pontoon and the portions of the Wings superimposed thereon.

: References Cited in the file of this patent UNITED STATES PATENTS