US3083665A - Pontoon - Google Patents

Description

April 1953 R. B. STEIDLEY 3,083,665

PONTOON Filed 001;. 51, 1961 FIG 3 ROY B. STEIDLEY INVENTOR.

AGENT t e. s s as use a a ,e ics ra-s ame firs 9 9 a ti e' r t fillin as? is elififigi Fatented Apr. 2. was

skin bonded on the expanded cellular polystyrene, the 3,983,655 skin would add little if any strength since, upon being EG-NTGGN 2 t'llainis. ill. I114 --.5)

,nor, by means g (3a., Terminal T his invention relates to flotation equipment, and more specifically to a pontoon. Among their many uses, pontoons are employed for the support of piers, wha-rves, work and equipment platforms, gasoline and oil dispensing facilities, etc.

Although their origins are lost in antiquity, previously employed pontoons have been less than satisfactory in certa n regards, and their improvement has remained a desirability. Since the load-carrying ability of a pontoon is equal to the weight of the amount of water it displaces less its own weight, it is very desirable to keep the weight as low as possbile in a pontoon of given volume. The cost of each pontoon is, of course, an important considera tion and this becomes especially significant where, as is frequently the case, ontoons are used in large numbers. Low weignt, however, is no advantage where it is obtained by the sacrifice of strength. The use of lessened amounts ofi materials or materials which are light but of little strength results in a pontoon which has not the structural strength or integrity requisite to its bearing a full load imposed by the structure it supports and by the water. Similarly, low initial cost is of no avail where it is obtained at the sacrifice of durability. Until the present, unfortunately, strength and durability have strongly tended to be accompanied by excessive weight and/or high cost.

Many pontoons previously have been made of wood, which is initially heavy and quickly becomes heavier through becoming waterlogged. Problems exist in the sealing of the joints in a wooden pontoon, and the wood is soon deteriorated and consumed by marine organisms and fungi. Wooden pontoons with waterproof skins have been proposed. Although an improvement, these still are subject to puncture by blows from boats, etc., and thus retain the same disadvantages as a plain wooden pontoon once water is admitted to their interiors.

Other pontoons have been made of steel, which is excessively weighty and subject to chemical attack by the salt waterj and still others have been made of concrete. (3f attractively low initial cost, concrete pontoons are too easily cracked in transit or in service. Like a steel pontoon, they sink and are of no further usefulness once water has entered and filled then In an effort to achieve light weight combined with strength and relatively low cost, pontoons have been made ofi blocks of expanded, cellular, polystyrene materials. These have had the disadvantage of an inherent friability which causes them to spall and be rubbed away where in contact with a shifting pier, etc. Polystyrene pontoons, like other materials, become encrusted with bmnacles, and in many cases it is required that these be periodically removed. Because of its crumbly nature, a polystyrene pontoon is damaged by the removal 05 barnacles, for chunks of the pontoon material are pulled away in scraping and chipping oil the barnacles. ttempts have been made to cover expanded polystyrene pontoons with protective: skins. for the polystyrene does not bond efiectively with relatively inexpensive, rigid skin materials. The skin, where bonded to the buoyant block of polystyrene, ordinarily is flexible and stretchable, for polystyrene will bond with rubber and the like. Even if more expensive materials were employed, as would be necessary in providing a rigid Such skins have ordinarily been loose,

stressed by forces imparted to it through the polystyrene, it would merely shear or pull away the material to which it was bonded at the exterior surface of the polystyrene block.

in common with steel, a polystyrene pontoon is vulner able to the etlects of acids and corrosives which may be spilled on it through, fior example, the planks of a pier, and in addition is subject to attack by many organic solvents, etc.

it is a major object of the present invention to produce a pontoon of maximum efiiciency and durability, and this at minimum cost.

A related object is to provide a pontoon of given displacement which is of lighter weight but of fully adequate strength.

Another object is to provide a pontoon of superior esistance to the deteriorating effects of salt Water and which is not subject to deterioration or sinking upon being punctured and filled with salt water.

A further object is to provide a pontoon having a rigid skin and which remains virtually waterproof even upon puncture of the skin.

Yet another object is to provide a pontoon the exterior and interior of which are substantially immune to the etiects of acids, bases, salts, and solvents.

A still further object is to provide a pontoon construction which, while employing a more desirable and concurrently more expensive material, nonetheless is of superior economy.

Still another object is to provide a method of fabricating a plastic pontoon.

Additional objects and advantages will be apparent firom specification and claims and from the accompanying drawing illustrative of the invention.

in the drawing:

FIGURE 1 is a side view, in vertical section, of a pontoon constructed according to the invention and bearing a member or members of a pier or the like;

HGURE 2 is an enlarged sectional view of a portion of the glass fiber reinforcements oi the lid preparatory to introduction of the resin;

FIGURE 3 is a view similar to FEGURE l and showing an embodiment of the invention wherein the pontoon is more elongated and has employed therein a cross-wall; and

FIGURE 4 is an enlarged sectional view of the pontoon lid and side wall construction.

With reference now to FIGURE 1, the pontoon 10 floats in water and supports heavily loaded planks of a pier or other supported body .11. Although shown in vertical section, the pontoon 19 will be understood to be shown in the form of a rectangular parallelepiped with square bottom and of which one wall is omitted in the sectional view presented. Other forms including cylindrical, spherical, or any other desired shape are readily possible in construction of the pontoon 19 according to the invention. The form of a rectangular parallelepiped is preferred, however, for the greater stability ofi such a body in the water and for the linear relationship between the depth of partial submersion of the pontoon and its buoyant force.

The pontoon 153 is held in place by the downward force of the supported body ill and, where desired, by cleats 12 attached under the supported body 11 in framing relation to the top of the pontoon ill.

The pontoon it comprises a skin 13 made of a glass fiber reinforced resin. Because of the properties of other components, as more fully explained later, a polyester resin is employed, and this is of great advantage because J; ofits' relative cheapness combined with its rigidity, toughness, imperviousness to water, and durability when combined with the glass fibers. Where it is desired to increase the resistance of the pontoon to fire, approximately (by weight) of antimony oxide mixed with chlorinated paraifnl is added to the resin. The skin 13 has a bottom 14, three sides .15, 16, 17, and a fourth side (omit-fed from the view in vertical section) which together with the bottom 14 and sides 15, 16, 17 forms a hollow body. Each side wall has an upper edge such as 18, and all these edges are trimmed to lie in one plane. The skin 13 is substantially unstret chable and for lightness and economy is made as thin as conveniently possible. A thickness of;% inch is adequate for strength and is conveniently produced while using known technics; a thickness of over inch is undesirable in pontoons of ordinary siz'e since it is unnecessary for strength, increases weight, and adds to cost. For reasons which will become evident, the; side walls of the pontoon (see the walls 15, 16 prefei ably taper inwardly from their upper edges 18 to the bottom 14. A taper of two degrees is generally sufficient, and to this extent the pontoon deviates from therefctangular parallelepiped form.

A layer of polyurethane foamed material 19 covers and is bonded to the inner surface of the skin 13 throughout the bottom and sides of the hollow body formed by the skin. The foam itself thus forms a hollow body 19 lining the skin and having a bottom and side walls such as 21 whose upper edges were flush with the upper edges 18 of the corresponding side walls of the skin. The preferred foam may currently be purchased under the designation of Hitco 1.5R, 1.5 lb./ft. density, polyurethane plastic foam components, marketed by the H. I. Thompson Fiber Glass Company of Los Angeles, California. This product has been found superior because of its negligible shrinkage when poured, a factor of importance in obtaining a good bond between the foam and skin and in preventing inwardzdenting of the skin and other deformations which would accompany shrinkage. The foam is of closedcell structure, tough, rigid, not subject to crumbling or spelling under forces in shear or tension between itself and the skin; and firmly bonds itself to any surface when it expands and cures.

It is of importance that the entire skin 13 is not filled with the foanr19. v The foamedmaterial is of considerable cost per cubic foot and currently is considerably more expensive than expanded, cellular, polystyrene materials. Byleaving a large void in the pontoon interior, however, and 'using only the material actually required for ade quate strength, the cost is sharply reduced and is highly preferable to, for example, that of a solid block of expanded polystyrene. In a representative application, a pontoon of exterior dimensions of 48 x 48x 21 inches in height employs a foamed, hollow body whose bottom is 5 inches 'in thickness and whose sides are four inches thick; and this has been found completely adequate for supplying all needed strength. It is of importance that 4 supported body :11 and the upper edges of the sidewalls of the skin 13 and foam 19, and its outer surface lies in bearing relation to the supported body 11. The upper edges of the sidewalls of the foam 19, meanwhile, are in bearing relation to the lid 23 and hence, through the latter, to the supported body 11.

The lid 23 is of rigid construction to prevent its being dented or dished and must be of sufiicient strength to withstand torsional loads, imposed upon it by shifting rotations of the supported body 11, which tend to twist the pontoon 10 about its horizontal axis. The second skin or lid 23 is made of glass fiber reinforced resin and is of the order of twice the thickness of the first skin 13.

As shown in FIGURE 2, the lid 23 is reinforced by a layer of glass fiber cloth 26 placed next to the lid inner surface 24 and a glass fiber mat'27 adjacent the smooth outer surface 25. A mat which is to inch thick is preferred' and contains numerous glass fibers of uniform length, unwoven but randomly distributed to form a uniformly thick, highly porous sheeting :of fibers held in compacted condition by a resinous binder the same as or compatible with the construction resin. The latter, as in I the skin, is a polyester. A representative weight for the glass fiber mat 27 is 1 /2 -oz./ft.

the exterior surfaces of the sidewalls such as 21 and bottom 20 of theifoamed, hollow body '19 are securely bonded to the,overlying;skin 13. The inner surfaces of the side walls 21 of the foamed body, also of its bottom 20 is desired, are covered by and bonded to a thin, light, substantially non-stretchable material 22 of good strength under tension, Paper, which is relatively excellent in tensile strength, has been utilized for this purpose with good results;

The foamed, hollow body 19, exteriorly covered by the skin 13, is open at'its top; and this opening is covered and the hollow body closed by the lid 23, whose inner surface overlies and is sealingly bonded to the flush upper edges 30, 18 of the sidewalls of the foam 19 and skin 13. The lid 23 thus is at once a diaphragm for watertight closure of and formingthe top of the hollow body .19 and a second skin which is applied to the upper edges of the sidewalls ofth'e foam. The lid is disposed between the The glass cloth 26 is placed next to the inner surface of the lid 23 because it very greatly increases the resistance of the lid to forces imposed on the outer face 25 and tending to dish the lid inwardly. Since such forces are not imposed on the lid inner face 24, no glass cloth is required at the lid outer face 25.

In a modification shown in FIGURE 3, the pontoon 10A is elongated to such an extent that adequate rigidity of the lid 23A cannot be obtained without excessive thickening of thelid and consequent increases in weight. To avoid this undesirability, the lid 23A remains the same thickness as before, and a cross-wall 28 made of the polyurethane foamed material is provided which extends across the hollow interior of the pontoon 10A. The cross-wall 28 is integral with the hollow body 19A formed by the foam, is footed on the hollow body bottom 14A, and has an upper edge 29 flush with the side wall upper edges 30A. The cross-wall upper'edge 29 thus bears against and supports the middle of the lid 23A, to which it is bonded. The crosswall 28 has oppositely disposed faces which are covered with the paper or-the like thin, substantially non-stretchable sheet material 22A.

7 The means bonding the lid or second to the foamed material is the same as employed in the embodiment shown in FIGURE 1 and preferably is the same resin employed in construction of the first skin 13A and lid 23A. Powdered asbestos is added to the resin to form a thick paste. Care is employed to apply the resin paste in such manner and location as to seal the pontoon 10 for rendering it watertight.

The method of fabricating the pontoon 10 comprises providing a female mold of the desired outer dimensions of the pontoon. To provide for later release of the skin 13 from the mold, a water-soluble mold release compound, such. as polyvinyl alcohol, is spread over the mold inner surface. The skin 13 then is laid up by applying and rolling out, on the mold bottom and sidewalls, randomly oriented chopped glass fibers and the polyester resin. The skin 13 is curedbefore applying the foamed polyurethane, fcr application of the latter to the uncured skin results inshrinkage of the foam away from the skin and ing the sidewalls of the skin. More of the polyurethane foam components then are poured into the skin in the space between the skin and second mold walls. The amount employed is that which produces sufficient foam to cover the skin to the upper edges of the skin sidewalls.

Preparatory to insertion of the second mold and pouring the sidewall foaming material, however, the faces of the walls of the second mold are covered with paper or the like thin, strong sheet material, which is detachably attached to the mold. After pouring, the foam is allowed to rise and cure, whereupon the paper is detached from the second mold, which is removed. As it is firmly bonded to the foam, the paper remains in place; besides adding strength, it provides for easy removal of the second mold.

The foam-containing skin 13 then is removed from the female mold, this being facilitated 'by introducing compressed air between the skin and female mold to break loose the mold release compound. Any of the latter adhering to the mold and skin is washed away with water. The second mold is removed at a time prior to installing the lid.

Excess foam then is trimmed from the hollow body sidewalls 21 to make their upper edges flush with the skin upper edges 18.

The lid 23 next is made in form of a glass fiber reinforced resin plate of a size suitable for forming a Waterproof lid for the pontoon. It is desirable that the edges of the lid 23 lie flush with the outer faces :of the corresponding sidewalls of the skin 13. In fabricating the lid 23, the glass fiber mat is placed on a smooth work surface which is waxed or otherwise provided with a parting agent. The glass cloth 26 then is laid over the glass fiber mat 27 and the polyester resin is worked into them. After curing, the lid 23 is trimmed to size, then bonded in place on the pontoon 1G with a polyester resin paste. Care must be taken to provide a good coverage of the top edges 3%) of the foamed material walls, including the cross-wall 28 (where this is employed) to provide the largest possible bonding area between the lid and foamed material. FIG- URE 4 shows the bonding means 31 between the upper edge of the hollow body side wall 21 and the lid 23. The bonding means 31 also preferably extends between the upper edge 18 of the skin .16 and the lid 23. The illustrated employment of the bonding means 31 is typical at all points of contact of the lid 23 with the hollow, foamed body 19 both in the embodiment of the invention shown in FIGURE 1 and in the embodiment shown in FIG- URE 3.

The above-delineated method will be found superior in results to a method wherein the polyurethane foamed resin components are sprayed in place in the skin to form the foamed body sidewalls and bottom. Spraying results in loss of material and an undesirable increase of density of the resulting foam. Shrinkage also is severe, and the sprayed foarn shrinks to its air-exposed side, thus pulling with it and deforming the outer skin. Moreover, it is difficult if not impossible to obtain a uniform wall thickness when the foam is sprayed. In ensuring that all areas are of the required minimum thickness, other areas inevitably build up to several times the desired thickness. This wasteage of the relatively expensive foam defeats a primary purpose of the invention, that of best economy linked with efiiciency and durability.

The present method also excels over spraying or pouring the foam to cast it in the female mold, with subsequent laying up of the skin over the foam. This method is unsatisfactory because of the virtual impossibility of freeing the cured foam from the female mold without damage to the foam outer surface.

The saving of foamed material 19 by virtue of the pontoon interior void results in a great saving in cost. Meanwhile, the foam 19 is of such thickness as to be able to bear all the load imposable on the pontoon by displacement of water equal to the pontoons submerged volume. To make the pontoon even stronger would be 6 to add strength not needed; therefore, the interior void from which the superior economy of the pontoon stems in no wise subtracts from useable strength.

Because the chief load-bearing element is the foam 1%, it is possible to make the skin 13 of quite thin construction, again saving in both weight and cost. The skin 13 of course keeps the foam 19 dry and protects it from abrasion and puncture; but very importantly, it adds a stressable outer layer which greatly adds to the strength of the foam. Strength similarly is aded by the thin sheeting 22 covering the interior faces of the foamed walls. The glass fiber resin skin 13 and top 23 are immune to salt water and substantially all other materials which might be brought into contact with the pontoon, as by spillage through the planks of a pier 11 supported by the pontoon 10.

Even upon puncture of the pontoon skin 13, as by being rammed by a boat, water still cannot enter the interior void of the pontoon 10 so long as the foam 19 is not pierced throughout its thickness. The polyurethane foam .19 is of closed-cell construction, and water will not percolate through it; its absorbency of water, for practical purposes, is zero. Upon puncture of the skin 13, there fore, the foam 19 itself prevents the entry of water into the interior void. The foam .19 also is resistant to practically all chemicals in concentrations rapt ever to be encountered in service.

Actual puncture of both the skin 13 and foam 19 so as to allow up to complete filling of the inner void does not result in sinking of the pontoon 10 or loss of all useful buoyancy. The foam 15? itself supplies much buoyancy and not only maintains the pontoon 1t) afloat but keeps it in useful service.

Employing the lid 23 in a manner wherein it is merely squeezed between the foam l9 and the flat bottom of the object 11 supported requires only that the lid have compressive strength; thus, from this standpoint, it may be made as thin as may be desired. Torsional forces imposed IOII the pontoon 10 through the lid 23 require, however, that the lid thickness be increased over that of the thin skin, but even upon this increase the lid still is light in weight and favorable to frugality in the use of materials. Because of savings in this regard, but particularly in consequence of the savings in the amount of the foamed material '19 employed, the pontoon 10 can be more cheaply constructed than previous plastic pontoons in spite of the fact that it employs a more expensive foamed material.

While only one embodiment of the invention, together with modifications thereof, has been described in detail herein and shown in the accompanying drawing, it will be apparent that various further modifications are possible without departing from the scope of the invention.

I claim:

1. In combination with a supported body, a pontoon which is floated in water and which contributes to support of the body, said pontoon comprising:

polyurethane foamed material forming a hollow body having a bottom wall, side and end walls with upper edges, and an open top; glass fiber reinforced resin lid underlying the supported body and receiving thrust and torsional loads from the latter, the lid being of a given thickness and rigid under the torsional loads imposed by the supported body and lying in load-bearing relation between the latter and the upper edges of the hollow body side and end walls, the open top of the hollow body being closed by the lid; an adhesive bonding the lid on the upper edges of the hollow body side walls; and a glass fiber reinforced resin skin of the order of half the given thickness of the lid and bonded to and covering the hollow body exterior, the skin lying between the hollow body and the water in which the pontoon floats. I 2. The combination claimed in claim 1, the hollow 7 bqdy further having a polyurptllane foam cross-Wall integr'l therewith,- the; cross-wan bifig fcioted 611 the E0? fofii wall and bqrldedto the Iefigtlziwis middle of the lid, to which the cross-wall is in supporting flation.

Refrencs Cited in the file of this patefit UNITED STATES PATENTS Crosby D60. 28, 1945 Wiley "2 1 116 5, 1945 1 Sampson Fb. 13, 1951 0

Claims (1)

1. IN COMBINATION WITH A SUPPORTED BODY, A PONTOON WHCICH IS FLOATED IN WATER AND WHICH CONTRIBUTES TO SUPPORT OF THE BODY, SAID PONTOON COMPRISING: POLYURETHANE FOAMED MATERIAL FORMING A HOLLOW BODY HAVING A BOTTOM WALL, SIDE AND END WALLS WITH UPPER EDGES, AND AN OPEN TOP; A GLASS FIBER REINFORCED RESIN LID UNDERLYING THE SUPPORTED BODY AND RECEIVING THRUST AND TORSIONAL LOADS FROM THE LATTER, THE LID BEING OF A GIVEN THICKNESS AND RIGID UNDER THE TORSIONAL LOADS IMPOSED BY THE SUPPORTED BODY AND LYING IN LOAD-BEARING RELATION BETWEEN THE LATTER AND THE UPPER EDGES OF THE HOLLOW BODY SAID AND END WALLS, AND OPEN TOP OF THE HOLLOW BODY BEING CLOSED BY LID; AN ADHESIVE BONDING THE LID ON THE UPPER EDGES OF THE HOLLOW BODY SIDE WALLS; AND A GLASS FIBER REINFORCED RESIN SKIN OF THE ORDER OF HALF THE GIVEN THICKNESS OF THE LID AND BONDED TO AND COVERING THE HOLLOW BODY EXTERIOR, THE SKIN LYING BETWEEN THE HOLLOW BODY OF THE WATER IN WHICH THE PONTOON FLOATS.

Images