US 3857249 A
Underwater cofferdams which can be secured to a hull by pressure differentials established by other than through-hull venting are described. One embodiment utilizes surface venting in combination with water extraction by a pump, while another embodiment utilizes an evacuated flask.
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Description (OCR text may contain errors)
United States Patent [1 1 Kelly et al.
[451 Dec. 31, 1974 COFFERDAM  Inventors: Thomas E. Kelly, 20110 SW. 316th St., Homestead, Fla. 33030; James K. Shelton, 1915 Monroe Ave., Panama City, Fla. 32401 22 Filed: Mar. 22, 1973 21 Appl. No.: 344,003
 US. Cl... 61/68, 114/227  Int. Cl. B63c ll/34  Field of Search 61/68, 69, 69 A; 114/227  References Cited UNITED STATES PATENTS 808,638 1/1906 Cunningham et al 61/68 1,060,177 4/1913 Flugeltaub 1,072,569 9/1913 Cady 61/69 3,104,532 9/1963 Severinsson 61/53 3,640,079 2/1972 Theresien et al. 61/69 FOREIGN PATENTS OR APPLICATIONS 1,221,773 2/1971 Great Britain 114/227 Primary Examiner-Jacob Shapiro Attorney, Agent, or Firm -Richard S. Sciascia; Don D. Doty; Harvey A. David  ABSTRACT Underwater cofferdams which can be secured to a hull by pressure differentials established by other than through-hull venting are described. One embodiment utilizes surface venting in combination with water extraction by a pump, while another embodiment utilizes an evacuated flask.
3 Claims, 4 Drawing Figures Oding 114/227 PATENTEB DECS 1 I974 NIV/II/ COFFERDAM The invention described herein may be manufactured and used by or for the Government of the United States of America for Governmental purposes without the payment of any royalties thereon or therefor.
FIELD OF THE INVENTION- This invention relates to underwater repair apparatus, and more particularly, to improvements in cofferdams which are used to exclude water from a work site or damaged area, for example, on the hull of a ship. It is often necessary, or at least desirable, to provide an external barrier against the intrusion of water into a ships hull during repair work which would otherwise result in communication between the interior and exterior of the underwater portions of a hull. For example, it may be necessary to open or remove a through-hull induction valve or seacock for repairs, or it may be desired that an additional water intake line be established. Alternatively, a collision, galvanic action, storm, or other event may have resulted in a rupture, opened seam, popped rivet, or the like for which a temporary repair should be made.
DISCUSSION OF THE PRIOR ART Various cofferdam devices have been devised and proposed for the aforementioned purposes, many of which rely upon the differential in pressures without and within the submerged portions of a floating vessel hull to hold the applied device in sealing engagement therewith. Of course, the pressure differentials are greatest at the lowermost regions of the hull and decrease to negligible values as the waterline is approached. Accordingly, such pressure differentials are really effective for holding cofferdams only at the deeper draft sections of a hull. In any event, with a common simple cofferdam, it has been the practice either to utilize an existing opening or fissure in the hull, or to create an opening therethrough, to establish communication between the hull interior and the cofferdam so that ambient water pressure will hold the cofferdam in place. The creation of otherwise unnecessary openings in the hull is, of course, not a good practice.
In addition to making or using openings through the hull, it has been proposed to remove water from the cofferdam by means of pumps, ejectors, or the like, to establish the desired pressure differential.
Other devices than simple cofferdams, e.g., submarine crew rescue bells or chambers and ship salvage apparatus, of which US. Pat. Nos. 2,536,103; 2,715,379; 3,640,079; and 3,702,597 are representative, utilize hydrostatic pressure to hold the respective devices against a ship hull. In the operation of these devices, wherein it is undesirable or untimely to pierce the hull during the attaching procedure, the removal of water from an enclosed space adjacent the hull is accomplished by suitable pumps or ejectors. Each of these devices, however, are designed to be used substantially in a predetermined position. That is to say, each of the devices has an upright position in which it is used and the pump means and piping for removing water therefrom to produce a holding force is fixedly located for operation in that position. In the case of cofferdams, it is not infrequent that the location of use is such as to require inversion of the cofferdam, or at least positioning in any one of many possible attitudes which would preclude removal of substantially all water from the cofferdam cavity with a pump means which has a fixed intake location.
SUMMARY OF THE INVENTION The present invention aims to overcome most or all of the foregoing shortcomings and disadvantages, as well as others, of the prior art through the provision of a cofferdam which has a number of novel characteristic features. Among these features are included, either singly or in combination, the use of removable water extraction and vacuum inducing means, the use of a weighted, flexible intake hose within the cofferdam cavity, and the use of a vent hose extending from the cofferdam to the water surface.
With the foregoing in mind, it is a principal object of this invention to provide an improved cofferdam that can be readily applied to the surface of an underwater structure such as a hull or the like, and be hydrostatically held thereon without requiring any opening through the structure to a zone of atmospheric pressure.
Another object is the provision of a cofferdam device I which can be used in conjunction with an internal seal formed by a flexible, waterproof mat to effect a temporary repair of a hull puncture, leak, or the like.
Yet another object is the provision of a cofferdam which can be used in any attitude without need of adjustment or special attention to positioning of parts.
Still another object of the invention is to provide an improved cofferdam that can be secured in place by pressure differentials in excess of hydrostatic pressure alone.
Other objects and many of the attendant advantages will be readily appreciated as the subject invention becomes better understood by reference to the following detailed description, when considered in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectional view of an improved cofferdam embodying the invention;
FIG. 2 is a sectional view taken substantially along line 22 of FIG. 1;
FIG. 3 is a fragmentary sectional view illustrating a manner of use of the cofferdam of FIG. I; and
FIG. 4 is a vertical sectional view of another embodiment of cofferdam.
DESCRIPTION OF THE PREFERRED EMBODIMENT In the form of the invention illustrated in FIGS. 1 and 2, there is provided an improved cofferdam for use in making underwater repairs to a ship hull, underwater habitat, or the like. The improved cofferdam, generally indicated at 10, comprises a hollow, or cavity defining, body 12 which may be formed of any suitable rigid material, such as metal or fiberglass reinforced plastic. Body 12 may be of any configuration which is suitable for application to a desired section or area of a hull 14. In the embodiment being described, however, body 12 is characterized as having a cylindrical side wall 12a and a flat, circular end wall 12b. Provided along the free edge of cylindrical wall 12a is an annular, transverse flange 16, which carries a resiliently compressible sealing gasket 18 formed of rubber or the like. Flange 16 and/or gasket 18 may, if necessary, be shaped or configured to present surfaces complimentary to'the curvature of the hull section 14 to which cofferdam 10 is applied. In most instances, however, hull curvatures have such a generous radius that the compressibility of gasket 18 is sufficient to effect a good seal without the need for specially shaped gaskets or flanges.
The cavity or, interior 20 of cofferdam 10 is adapted to be selectively placed in free communication with atmospheric pressure above the surface S of water in which hull 14 is located. To this end, a pipe 22, a valve 24, and a suitable noncollapsing hose 26 are provided, with pipe 22 opening to the interior 20 of cofferdam l and the upper end 26a of hose 26 opening to the atmosphere above surface S. Upper end 26a of hose 26 may be secured to hull 14 if the latter extends above the water surface at a convenient location. Alternatively, end 26a may be supported above the water surface S by a suitable float means 28. Valve 24 may be opened or closed to vent or seal the cofferdam as will be later explained in more detail regarding operation of the device.
Mounted on end wall 12b of cofferdam is a fluid extraction means in the form of a pump 34, the inlet side of which is connected via a union 36, pipe 38, a valve 40, and a pipe 42 through end wall 12b to the interior 20 of the cofferdam. Connected to the inner end of pipe 42 is a flexible intake hose 44, the distal end of which carries a weight 46 that causes the hose to hang.
downwardly within the interior of the cofferdam. The outlet side of pump 34 is connected through pipe 48, valve 50, and pipe. 52 to the surrounding water medium.
Pump 34 may be either motor or hand powered, but in the present example is provided with a handle 34a for manual operation. The housing of pump 34 is provided with a plurality of radially extending ears 34b which cooperate with lugs 54 on wall 12b to releasably secure the pump to that wall. When union 36 s uncoupled, the housing of pump 34 can be rotated to disengage ears 34b from lugs 54 so that the pump may be detached from body 12 of the cofferdam.
Cofferdams are used for different purposes, keeping in mind that the main function is to remove and exclude water from a predetermined area on the outside of a section of hull 14. Sometimes the purpose is to permit the removal, repair, or installation of a water line opening through the hull 14. In some instances where there already exists an opening through the hull 14, the cofferdam to be used can be vented to atmospheric pressure through the existing hull opening. In other instances, there is no existing opening through the hull 14, nor is it desirable to place such an opening through the hull. For example, in a circumstance where it is'desirable to weld a fitting, such as a padeye or the like, to the innersurface of hull 14, it may be desirable to exclude water from the opposite side of the hull section to be worked on so that the hull plate can be more readily brought to welding temperature. In any event, the improved cofferdam 10 is especially useful where attachment of the cofferdam must be made without an opening through hull 14.
MODE OF OPERATION In using cofferdam 10, a diver will position it against hull 14 in the desired location, the cofferdam being full of water to facilitate its transport to that location, and
valves 24, 40, and 50 being in a closed condition. With a the cofferdam appropriately positioned, the diver will then open valve 24, thereby venting the interior 20 of the cofferdam to atmospheric pressure via hose 26. Because of the venting action, interior 20 of cofferdam 10 will go to atmospheric pressure, whereas the exterior of the cofferdam will be subjected to the hydrostatic pressure of the surrounding water medium at the water depth where the work is being performed. The existing pressure differential between the surrounding water medium and the interior 20 of the cofferdam will effectively hold the cofferdam against ship hull 14 with no further attachments being necessary.
With cofferdam 10 so held in place by pressure differential, the diver may open valves 40 and 50 and commence operation of pump 34. Operation of pump 34 serves to remove water from the interior 20 of the cofferdam, the water being replaced by air which is forced by atmospheric pressure through hose 26, valve 24, and pipe 22 into the interior of the cofferdam. Because of the flexible but noncollapsing nature of hose 44, and the effect of weight 46 thereon, hose 44 will assume a position in which practically all water can be effectively pumped out of cofferdam 10 irrespective of the position thereof on hull 14. Accordingly, cofferdam 10 is suitable for application on hull sides, hull bottoms, and the like, and the diver need not take care as to orientation of the device.
When all or most of the water has been removed from interior 20, the diver may close vent valve 24 and continue operation of pump 34. This will serve to remove air from inside the cofferdam, expelling it through pipe 52 to the surrounding water medium, and thereby further increasing the pressure differential between the exterior and the interior of the cofferdam. This increased pressure differential will increase the holding force with which the cofferdam is secured to ship hull 14. When continued operation of pump 34 is no longer effective, the diver may secure or close valve 40, and if desired valve 50, and then may remove pump 34 by rotating ears 34b from under lugs 54, after first having disconnected union 36. Pump 34 may then be used in connection with the application of other cofferdams, as also may hose 26.
After cofferdam 10 is secured to hull 14, and pumped dry, work such as welding, drilling, and the like may be done from the interior of ship hull 14. If the hull becomes pierced in such work, the air pressure within the cofferdam will return to atmospheric pressure, but the cofferdam will remain in place due to the hydrostatic pressure acting thereon. After the work is completed the cofferdam may be removed by simply opening valve 40 to admit water to the interior of the cofferdam until the pressures without and within are equalized,
whereupon the cofferdam will fall free.
lm some instances it is desirable to utilize a cofferdam to render a temporary repair of a leak in a hull due to a collision, broken fitting, or the like. FIG. 3 illustrates such an opening 14a in a hull 14. It is well known that a simple cofferdam may be placed against hull 14 over opening 14a, and that the interior, being vented to the interior, of the huli, will be at a lower pressure than the surrounding water medium so that the cofferdam will thereby be held in place over the opening. it is usual, however, in the case of such an emergency repair, that it is desirable for the vessel to be moved to a more suitable place for permanent repairs and such movement through the water often displaces the cofferdam from its position over the opening. The improved cofferdam l0 overcomes this problem because of its ability to be placed in communication with the atmosphere through hose 26, and also to be pumped out through the agency of pump 34.
Cofferdam is used to make an emergency repair of an opening such as 14a in the following manner. The cofferdam 10 is placed over opening 14a where it is held in the manner of a simple cofferdam by initial venting action through that opening, which creates a pressure differential sufficient to hold the cofferdam device in place while the hull 14 is stationary. It will be understood that, at the time of being so positioned, the valves 24, 40, and 50 are closed. Thereafter, a flexible, water and air impervious mat 60 is placed on the inside surface of hull 14 in covering relation to opening 14a. A diver then opens valve 24, as well as valves and 50 with pump 34 in place. Pump 34 is then operated to remove water from interior 20, which water is replaced by air at atmospheric pressure entering via hose 26. When all or most of the water has been evacuated from cofferdam device 10, the diver closes valve 24 and continues operation of pump 34. Such continued operation removes the air from the interior 20, thereby increasing the pressure effective in holding the cofferdam against hull 14. When operation of pump 34 is no longer effective to increase the pressure differential, valves 40 and 50 are closed, union 36 disconnected, and pump 34 re- 3 moved from the device. The cofferdam l0 and mat 60 will be held tightly on opposite sides of hull 14 by a force considerably in excess of hydrostatic pressure alone, and will permit movement of hull 14 through the water without displacement of the cofferdam 10.
A variation of improved cofferdam is indicated generally at 70 in FIG. 4, and comprises a hollow body 72, which is conveniently formed of a molded fiberglass plastic material, lightweight metal, or the like. In this embodiment, which is primarily intended to be used as an emergency patch that can be quickly and conveniently applied to a hull section 14' without the need of any vent or pressure hoses to the surface. The hollow body is preferably streamlined to minimize drag and presents a small cross-sectional profile. A resilient sealing gasket 74 is carried on the broad peripheral edge of body 72, as shown. Mounted on the exterior of body 72 is a vacuum bottle or flask 76, which flask has been previously evacuated so that the interior thereof is at a pressure substantially below atmospheric pressure. Flask 76 is connected via a valve 78 and conduit 80 to the interior 82 of body 72. When cofferdam 70 is to be applied, it is carried below by a diver who places it against the desired area of hull section 14, and then opens valve 78. Opening of valve 78 places flask 76 in communication with interior 82, whereupon the latter is subjected to a reduction in pressure.
The resulting reduction in pressure in interior 82 of cofferdam 70 causes the latter to adhere tightly to hull section 14'. Because the interior 82 will be full of water just prior to opening valve 78, and because water does not expand upon reduction in pressure, only a very small amount of water will be drawn into flask 76, and substantially the entire vacuum or negative pressure therein will be retained. Therefore. the device 70 may be left in place with valve 78 opened, and any small leaks past gasket 74 will be accommodated by a corresponding small amount of water being drawn into flask 76.
In some instances it may be desirable to remove flask 76 after the device is secured to the hull section 14', in which instances valve 78 may be closed, and flask 76 disconnected therefrom.
It will be understood that in those instances of use wherein hull section 14' has an opening therethrough which is to be sealed by cofferdam 70, a flexible, waterproof mat, such as mat 60 of FIG. 3, would be applied to the side of hull section 14 opposite the cofferdam device and in covering relation to the opening. Thereafter, valve 78 will be opened to produce the required reduction in pressure within interior 82 of the cofferdam device for securing thereof to the hull section.
Obviously, other embodiments and modifications of the subject invention will readily come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing description and the drawing. It is, therefore, to be understood that this invention is not to be limited thereto and that said modifications and embodiments are intended to be included within the scope of the appended claims.
What is claimed is:
1. A cofferdam device for exluding water from a predetermined area of an underwater surface, said device comprising in combination:
a cup-shaped body having sidewalls and an end wall defining a cavity having one side open;
gasket means, attached to the edges of said side walls, for effecting a sealing engagement of said device to said underwater surface with the latter closing said cavity;
a vent hose having its upper end in open communication with atmospheric pressure above the surface of said water;
a first valve, connected between said hose and said body, said first valve being operative to selectively place said cavity into or out of communication with said atmospheric pressure;
a pump having intake and discharge connections;
lug means for removably securing said pump to said end wall;
a second valve;
union means for separably connecting one side of said second valve to said intake connection of said Pump;
a flexible hose disposed into said cavity, said hose having one end connected to said second valve and having its other end free for movement within said cavity; and
a weight attached to said free end of said hose whereby said free end is adapted to be positioned at the lowermost portions of said cavity irrespective of the orientation of said body.
2. A cofferdam device as defined in claim 1, and further characterized by:
lugs extending from said body;
ears extending from said pump; and
said lugs and ears being in cooperating engagement to removably secure said pump to said body, whereby said pump can be detached by rotation thereof to disengage said ears from said lugs 3. A cofferdam device as defined in claim 1, and further comprising:
float means, connected to said upper end of said vent hose, for supporting said vent hose with said upper end above said surface of the water.
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