US3237221A - Buoyancy devices - Google Patents

Description

March 1, 1966 R. N. THOMSON BUOYANCY DEVICES 2 Sheets-Sheet 1 Filed Aug. 12, 1964 Inn/Jar Rickqr'c! as; Thomson .zomwwm March 1, 1966 R. N. THOMSON I BUOYANCY DEVICES 2 Sheets-Sheet 2 Filed Aug. 12, 1964 W m N. L WM Um United States Patent 33,802/63; Jan. 18, 1964, 2,302/64 8 Claims. (Cl. 98)

This invention relates to buoyancy devices, particularly buoyancy devices for linear articles such as hose, pipe or cable, hawser or mooring line. The invention is useful for hose for the off-shore loading and discharge of oil.

According to the present invention, a buoyancy device comprises two or more complementary thin shell portions of a substantially rigid synthetic resin composition shaped so that the shell portions may be assembled about part of an article to be buoyed up and adapted so that the assembled device encloses a substantial quantity of gas or other buoyant material.

According to one aspect of the present invention, a buoyancy device comprises two complementary thin shell portions of a substantially rigid synthetic resin composition, said shell portions in assembly defining an enclosed space, at least one shell portion having in its edge a pair of recesses, the recesses when the two shell portions are in assembly defining a pair of apertures, the space enclosed by the shell portions in assembly being partly filled with buoyant material, and the apertures in the shell and a portion of the enclosed space which remains unfilled with buoyant material providing a housing for part of an article to be buoyed up.

The buoyancy device may be of generally spherical, cylindrical, or other solid figure outline. The shell portions in any one device may be generally similar in size and shape, for example the shell portions may be generally hemispherical or semicylindrical.

In one preferred embodiment of the invention, the buoyancy device comprises two complementary thin shell portions wherein the respective edges of the two shell portions around at least part of the periphery thereof have a co-operative overlapping relationship. Preferably the edges overlap in a male and female relationship. The extent of overlapping may be small provided that it inhibits any relative movement of the two shell portions, other than that which tends to move the edges directly out of the overlapping relationship. The edge of one shell portion may be provided with a skirt standing out from the surface of shell, the other shell portion having an edge which fits closely within the skirt.

Preferably the interior of each shell portion is partly filled with light cellular material. The cellular material may be a foam such as a thermoplastic fooam having closed cells. Other suitable buoyant material is light expanded bead material such as expanded polystyrene bead material. The buoyant material preferably fills substantially all of the space within the shell portion except for an open channel which extends across the surface of the buoyant material between the two recesses in the edge of the shell portion. The cross-sectional area of the channel may be equal to or greater than the crosssectional area of each recess. The channel may be semicylindrical. The channel lines up with a corresponding channel in the surface of the buoyant material in the other shell portion.

In an alternative embodiment of the invention, each shell portion is provided with a closing plate of a substantially rigid synthetic resin composition. The shell portion and the closing plate sealed thereto enclose a substantial quantity of gas such as air or other buoyant material such as cellular material. The closing plate nor- 3,237,221 Patented Mar. 1, 1966 mally has a channel across its surface which extends between the two recesses in the edge of the shell portion. This channel lines up with a corresponding channel in the surface of the closing plate fitted to the other shell portion. Two shell portions with closing plates sealed thereto in combination form a buoyancy device having two sealed compartments and a housing extending through the device between the two compartments.

If cellular material is used in the interior of the device, it is preferably foam material such as rigid closed cell polyurethane foam. The foam may be foamed in situ in the shell portions or it may be fitted into the shell portions in a foamed state. If it is foamed in situ a lid having a protruding rib is normally placed across the mouth of the shell portion with the rib facing inwardly and extending between the recesses in the periphery of the shell portion. When foaming takes place the lid controls the expansion of the material and the rib defines the channel in the surface of the foamed material extending between the recesses. An adhesive coating may be applied on the shell portion before foaming to improve adhesion of the foam to the shell portion.

The shell portions are preferably formed of a thermoplastic synthetic resin composition by any conventional moulding technique such as vacuum-forming, blow moulding, injection moulding, or compression moulding. It is preferred to use vacuum-forming. Normally the synthetic resin composition is heat-softened before forming. Examples of the synthetic resin compositions which may be used are thermoplastic compositions based on vinyl polymers and polyolefines and copolymers of a diene with one or more monomers which are suitable for moulding. Particularly suitable compositions are substantially rigid compositions of polyvinyl chloride, polyethylene, polypropylene, polystyrene or an acrylonitrile/ butadiene/ styrene copolymer.

Preferably each shell portion has in its edge a pair of recesses which may be semicircular. The recesses may be diametrically opposed across the shell portion and may each have a radius substantially equal to the external radius of the part of the article to be buoyed up.

Each shell portion is preferably provided on its surface with at least two hooks having concave surfaces directed away from the edge of the shell portion. Each hook may be the end of a ridge formed by the surface of the shell relative to a groove or grooves sunk into the surface of the shell. The ridge may lie between the arms of a generally U-shaped or l-I-shaped groove sunk into the surface of the shell. A continuous rubber band may be stretched from a hook on one shell portion to a hook on another shell portion to hold the buoyancy device in the assembled condition.

Alternatively or in addition one or more grooves may be provided right around the buoyancy device in the surface of the shell portions and one or more continuous rubber bands may be stretched right around the device in the groove or grooves.

The rubber bands are preferably moulded synthetic rubber bands of approximately inch cross-sectional diameter. It is particularly preferred to useethylenepropylene copolymer or terpolymer or neoprene rubber compositions in the bands.

It will be understood that other means of holding the two shell portions together may be used in addition to, or as an alternative to, the above-described method.

The continuous rubber bands may be replaced by finite lengths of tape or cord of rubber or wire or other material which can be knotted or otherwise joined around the hooks or in the grooves. The hooks may be formed as projections from the surface of the shell in theabsence of grooves or in combination with shallow grooves. Clips may be moulded into one half shell and corresponding housings may be moulded into the other half shell. There are many other possible methods of holding the half shells together. The method described above using rubber bands or hooks is preferred since the bands are simple and quick to apply, requiring no threading or knotting, and are easily replaceable and interchangeable.

The size of the device varies according to the diameter and type of the article such as hose to be buoyed up, the number of the devices used per unit length of the article, and the overall weight of the article, its contents and the couplings employed. By way of example, a buoyancy device for hose may have an overall diameter of 30 inches, whereas a buoyancy device for a hawser may have a diameter of 10 inches.

The shell portions may be formed with a series of bead edges around the recesses which accommodate the article to be buoyed up. These bead edges are preferably in an outwardly decreasing stepped succession, each one differing in diameter from that adjacent to it. It is thus possible to adapt the device for an article of a certain diameter by cutting off the bead edges having a smaller diameter and thus leaving the diameter of the recess to be determined by the smallest remaining bead edge which has the chosen diameter. Alternatively the shell portion may be moulded with the recesses closed over and recesses of the appropriate diameter may then be cut out of the edge of the shell portion.

The advantages of the buoyancy device in accordance with this invention are that it is cheap, light, strong, not susceptible to rusting, and capable of withstanding impact with shipping or jetties. The device is easy to apply to a linear article such as hose since it does not have to be threaded onto the article but can be assembled about the article at any point. The rubber bands are simple to apply and the hooks flush with the surface of the shell are not liable to damage. The rubber bands sunk into the grooves are protected from damage. The cooperative overlapping relationship prevents lateral displacement of the shell portions.

The invention is illustrated in the accompanying drawings, in which FIGURE 1 is a perspective view of a spherical buoyancy device assembled about a length of hose showing the rubber bands in position.

FIGURE 2 is a simple plan view of a spherical buoyancy device similar to that shown in FIGURE 1, not showing rubber bands.

FIGURE 3 is a section along the line A-A of FIG- URE 2.

FIGURE 4 is a side elevation of a cylindrical buoyancy device assembled about a length of hawser, showing rubber bands in one position.

FIGURE 5 is a portion of a side elevation similar to FIGURE 4 showing an alternative disposition of the rubber bands.

FIGURE 6 is an end elevation of the buoyancy device of FIGURES 4 and 5.

As shown in FIGURES 1-3, a buoyancy device 1 assembled on a length of flexible hose 2 consists of two thin half shells 3, 4, of generally hemispherical shape partly filled with cellular material 5. Each half shell has in its equatorial edge 6 a pair of diametrically opposed semicircular recesses 7, 8, having a radius substantially equal to the external radius of the hose. Each recess is defined by one of a series of bead edges 9 which are formed on the half shell in a stepped succession. The device as shown in FIGURE 2 has five bead edges in the series. The device as shown in FIGURE 1 has 3 bead edges, the bead edges of smaller radius having been cut off.

The radius of the recess is thus defined by the bead edge of smallest radius which remains. This bead edge has a radius substantially equal to the external radius of the hose.

When the two half Shells 3, 4, are assembled in abutting relationship about the hose 2, the recesses 7, 8, in one half shell come into line with recesses 7, 8, in the other half shell and the recesses in combination form circular apertures through which the hose passes.

Each half shell is provided on its surface with four grooves 10, each approximating in plan to an inverted U sunk into the surface of the shell, the arms 11, 12, of the U extending to the equatorial edge 6 of the shell and the base 14 of the U lying towards the polar region 15 of the shell. The four grooves 10 are disposed around the half shell in pairs alternating with the recesses 7, 8. The portion of the surface of the half shell which lies between the arms of the U of each groove is not sunk and so relative to the groove it forms in effect a ridge 16 extending from the equatorial edge 6 towards the polar region 15. The end of the ridge 16 is defined by the base 14 of the groove. The face of the ridge 16 which lies closest to the polar region 15 is slightly concave so that the end of the ridge forms a hook 17.

When the device is assembled the arms 11, 12, of corresponding grooves on the two half shells are placed in line and a continuous rubber band 18 is stretched across from -a hook 17 on one half shell to the corresponding hook 17 on the other half shell. The rubber band 18 lies in the groove 10 and holds the two shells in contact. When four of these rubber bands 18 are in position in their respective sets of grooves 10 the device is held tightly assembled about the hose.

As shown in FLIGURE 3, the interior of the device IS partly filled with cellular material 5, suchas rigid polyurethane foam. A housing 19 is left through the centre of the device to accommodate the hose.

An alternative form of buoyancy device shown 1n FIGURES 4, 5, 6, assembled on a hawser 20 consists of two thin half shells 21, 22, of generally semi-cylindrical shape partly filled with cellular material.

Each half shell has in its periphery a pair of opposed semi-circular recesses 23, 24, coaxial with the half shell. The radius of the recess, which is substantially equal to or greater than the external radius of the hawser, is defined by a bead edge 25 formed on the half shell and projecting from it. When the two half shells 21, 22, are assembled about the hawser 20, the recesses 23, 24, in one half shell come into line with recesses 23, 24, on the other half shell and the recesses in combination form circular apertures through which the hawser passes The edge of one half shell 21 is provided with an integral skirt 26 standing out from the surface of the shell. The edge 27 of the other half shell 22 fits closely within the skirt as the male component in a male/ female relationship. The extent of overlapping is of the order of /2 inch.

Each half shell is provided with two parallel grooves 28, 29 sunk into the external surface of the half shell, the two grooves being equidistant from the midplane perpendicular to the axis of the shell and encircling the shell. The portion of the surface of each half-shell which hes between the grooves 28, 2? is not sunk except in the polar region 30 of the shell and relative to the grooves it forms in effect a ridge 31 extending from the edge of the half shell towards the polar region 30. The end of the ridge 31 is defined by the sunk polar region 30. The end face of the ridge 31 closest to the polar region 30 is slightly concave so that the end of the ridge 31 forms a hook 32. The grooves 28, 29 together with the sunk polar region 30 approximate in plan to an H sunk into the surface of the shell, two ridges 31 lying between the arms of the H.

The device is assembled by fitting the two half shells together about the hawser with the edges 26, 27 in overlapping relationship and the corresponding grooves 28, 29 in the two half shells aligned. A continuous rubber band 33 (denoted on FIGURE 4 by a plain band having a short length cut away and cross-hatched) may then be stretched across from a book. .32 on one half shelllto ahqolg 3 2, on

the other half shell. The rubber band lies in the grooves 28, 29 below the general level of the surface of the shell. When the two rubber bands 33 are in position, the device is held tightly in assembly by the rubber bands in combination with the overlapping edges.

As shown in FIGURE 5, the two rubber bands 34 may be stretched right around the device in the two sets of grooves 28, 29. This is convenient if one end of the hawser is accessible or if a number of rubber bands have previously been threa-ded on the hawser. The dimensions of the grooves 28, 29 and placing of the hooks 32 are planned so that the same size of rubber band may be used in either arrangements.

The device shown in FIGURES 1-3 may be improved by using half shells whose edges have a co-operative overlapping relationship similar to that of the half shells shown in FIGURE 4-6.

An example of a polyurethane composition which may be foamed in situ in the shell portions is as follows:

Parts by weight Daltolac 60 polyester resin 100 Suprasec D isocyanate 212 Tribetachloroethyl phosphate 30 Catalyst 1.5 Triethanolamine Water 2 Silicone L-520 3 Arcton 11 Daltolac 60 is a polyester resin, Suprasec D is a polyisocyanate and Arcton 11 is a refrigerant gas, all avail- .able from Imperial Chemical Industries Limited. Silicone L-520 is a silicone oil available from Union Carbide Company.

The rigid polyurethane foam produced has a bulk density of 2.4-2.5 lb. per cubic foot and water absorbtion limit of 1 to 3% by weight depending on the ratio of cut surfaces to volume.

When the polyurethane foam is foamed in situ a skin is formed across the surface of the foam which is defined by the moulding lid. If this skin is kept intact, the foam may have a water absorbtion limit of well below 1% The degree of water absorbtion which is permissible will depend on the particular use for which the device is intended. In certain applications a water absorption limit of 25% or more may be permissible.

Having now described my invention, what I claim is:

'1. A buoyancy device capable of assembly about part of an article to be buoyed up comprising two complemen tary thin shell portions of a substantially rigid synthetic resin composition, said shell portions in assembly defining an enclosed space, each shell portion having in its edge a pair of recesses, the four recesses when the two shell portions are in assembly defining a pair of apertures through the shell, each shell portion being provided on its surface with at least two hooks having concave surfaces directed away from the edge of the shell portion, each hook being the end of a ridge formed by the surface of the shell relative to a groove system sunk into the surface of the shell, corresponding hooks on the two shell portions being capable of receiving a continuous rubber band stretched from a hook on one shell portion to a hook on the other shell portion to hold the shell portions in assembly, the space enclosed by the shell portions in assembly being partly filled with buoyant material, and the apertures through the shell and a portion of the enclosed space which remains unfilled with buoyant material providing a housing for part of the article to be buoyed up.

2. A buoyancy device according to claim 1 wherein each shell portion is semi-cylindrical and is provided on its surface with two hooks having concave surfaces directed away from the edges of the shell portion, the hooks on each shell portion being the ends of ridges formed by the surface of the shell relative to a generally H-shaped groove sunk into the surface of said shell.

3. A buoyancy device according to claim 2 wherein the buoyant material is a thermoplastic foam having closed cells and said foam fills substantially all the space within each shell portion except for an open channel which extends across the surface of the thermoplastic foam between the two recesses in the edge of that shell portion, the recesses and the channels when the shell portions are in assembly providing a housing for a part of the article to be buoyed up.

4. A buoyancy device according to claim 1 wherein each shell portion is hemi-spherical and is provided on its surface with four hooks having concave surfaces directed away from the edge of the shell portion, each hook being the end of a ridge formed in the surface of the shell relative to a generally U-shaped groove sunk into the surface of the shell.

5. A buoyancy device according to claim 4 wherein the buoyant material is a thermoplastic foam having closed cells and said foam fills substantially all the space within each shell portion except for an open channel which extends across the surface of the thermoplastic foam between the two recesses in the edge of that shell portion, the recesses and the channels when said shell portions are in assembly providing a housing for the article to be buoyed up.

6. A buoyancy device capable of assembly about part of an article to be buoyed up comprising two complementary thin shell portions of a substantially rigid synthetic composition, said shell portions in assembly defining an enclosed space therein, at least one shell portion having on its outer edge a pair of recesses, said recesses when the two shell portions are in assembly defining a pair of apertures through said shell, each shell portion being provided on its surface with at least two hooks having concave surfaces directed away from the edge of the shell portion, each hook being the end of a ridge formed on the surface of the shell, corresponding hooks on the tWo shell portions being capable of receiving a continuous rubber band stretched from a hook in one shell portion to a hook on the other shell portion to hold the shell portions in assembly, the space enclosed by the shell portions in assembly being partly filled with buoyant material, and the apertures through the shell and a portion of the enclosed space which remains unfilled with buoyant material providing a housing for part of the article to be buoyed up.

7. A buoyancy device according to claim 6 which comprises two complementary thin shell portions wherein the respective edges of the two shell portions around at least a part of the periphery thereof have a cooperative overlapping male and female relationship, the edge of one shell portion being provided with a skirt standing out from the surface of the shell and the other shell portion having an edge which fits closely within said skirt.

8. A buoyancy device according to claim 6 wherein the buoyant material is a thermoplastic foam having closed cells and said foam fills substantially all the space within each shell portion except for an open channel which extends across the surface of the thermoplastic foam between the two recesses in the edge of that shell portion, the recesses and the channels when the shell portions are in assembly providing a housing for a part of the article to be buoyed up.

References Cited by the Examiner UNITED STATES PATENTS 2,395,892 3/1946 Lontz 9-8 2,911,658 11/1959 Stanley 9-8 3,074,083 1/ 1963 Schermer 9-8 3,094,096 6/1963 Florence 114-235 3,132,417 5/1964 Irwin 9-8 MILTON BUCHLER, Primary Examiner.

R. G. BESHA, A. E. CORRIGAN, Assistant Examiners.

Claims (1)

1. 6. A BUOYANCY DEVICE CAPABLE OF ASSEMBLY ABOUT PART OF AN ARTICLE TO BE BUOYED UP COMPRISING TWO COMPLEMENTARY THIN SHELL PORTIONS OF A SUBSTANTIALLY RIGID SYNTHETIC COMPOSITION, SAID SHELL PORTIONS IN ASSEMBLY DEFINING AN ENCLOSED SPACE THEREIN, AT LEAST ONE SHELL PORTION HAVING ON ITS OUTER EDGE A PAIR OF RECESSES, SAID RECESSES WHEN THE TWO SHELL PORTIONS ARE IN ASSEMBLY DEFINING A PAIR OF APERTURES THROUGH SAID SHELL, EACH SHELL PORTION BEING PROVIDED ON ITS SURFACE WITH AT LEAST TWO HOOKS HAVING CONCAVE SURFACES DIRECTED AWAY FROM THE EDGE OF THE SHELL PORTION, EACH HOOK BEING THE END OF A RIDGE FORMED ON THE SURFACE OF THE SHELL, CORRESPONDING HOOKS ON THE TWO SHELL PORTIONS BEING CAPABLE OF RECEIVING A CONTINUOUS RUBBER BAND STRETCHED FROM A HOOK IN ONE SHELL PORTION TO A HOOK ON THE OTHER SHELL PORTION TO HOLD THE SHELL PORTIONS IN ASSEMBLY, THE SPACE ENCLOSED BY THE SHELL PORTIONS IN ASSEMBLY BEING PARTLY FILLED WITH BUOYANT MATERIAL, AND THE APERTURES THROUGH THE SHELL AND A PORTION OF THE ENCLOSED SPACE WHICH REMAINS UNFILLED WITH BUOYANT MATERIAL PROVIDING A HOUSING FOR PART OF THE ARTICLE TO BE BUOYED UP.

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