US2870730A

US2870730A - Salvage pontoon

Info

Publication number: US2870730A
Application number: US562703A
Authority: US
Inventors: Anthony I Bruno
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-02-01
Filing date: 1956-02-01
Publication date: 1959-01-27
Anticipated expiration: 1976-01-27

Description

1 A. l. BRUNO I 2,870,730

' SALVAGE PONTOON Filed Feb. 1, 1956 2 Sheets-Sheet 1 INVENTOR ANTHONY I. BRUNO ATTORNEYS A. l. BRUNO SALVAGE PONTOON Jan. 27, 1959 2 Sheets-Sheet 2 Filed Feb. 1, 1956 INVENTOR ANTHONY l. BRUNO BY f v /a ATTORNEYS Unite This invention relates to salvage pontoons for raising sunken crafts and other objects, and is more particularly concerned with pontoons in the form of bags or balloons and constructed of flexible material so that they may be completely collapsed when deflated.

In order to avoid the formation within the unit of excessive pressures generated by the decrease of external pressure on the unit as it rises, pontoons of the indicated type have heretofore been made either with normally closed outlet ports controlled by suitable means, such as, mechanical safety valves, or with open bottoms to permit free escape of the inflating medium under increased internal pressures. The methods heretofore devised for controlling the pressures on the normally closed type of pontoon have proved unsatisfactory because of the time element involved in discharging the necessary amount of air through a small opening to compensate for the decreased external pressure, and because the speed of rise of the pontoon might vary instantly. As a result of these conditions, the pressures within the unit are usually irregular and out of balance with the external pressures, and there is the danger that the internal pressures will vary so rapidly relative to the external pressures as to cause sudden excessive stresses on the lifting tackle, the parting or sudden snapping of the pontoon from its anchor, and eventual rupture of the pontoon itself.

While the pontoons which were provided with open bottoms avoided the above discussed disadvantages of the normally closed pontoon, they possessed other disadvantages that rendered them impractical for salvaging operations. is under water, any movement or pressure on the bag tending to tilt it from its true vertical axis, such as may occur for example, from the bag bumping against the side of a ship, or because of the form of the ship at the place where the bag is attached thereto, or from tides or currents, etc., will enable the air in the bag to instantly escape through the so inclined bottom opening-thereof which is of relatively large area. This sudden escape of the air destroys the pressure balance on the bag and the external pressure, which is now greater than the internal pressure, will tend to force the remainder of the inflating medium from the interior of the bag. As the bag is deprived of its buoyant medium it will be caused to sink inert towards the sea bottom. When conditions are such that an open bag or envelope is enabled to rise to the surface of the sea, it will, because of its extremely buoyant condition, be subject to movement by sea swells, waves, tides or current, which if sufficiently strong will cause the bag to move from side to side in pendulous fashion.

Here again as the bag is swung from its true vertical axis or position, the inclined open bottom will enable the air to escape thus rendering the pontoon incapable of maintaining the raised object afloat. This danger also exists when it is necessary to tow the raised craft either to drydock, or some other destination, since the movement of the pontoons against the water will cause the resisting pressure of the latter to tilt the pontoons thus causing a Thus, when an open bottom bag or envelope States Patent displacement of the bags from the true vertical axis or position and a consequent loss of the buoyant or inflating medium from within their interiors. It will thus be seen that in order that the open bottom pontoon be used successfully it must retain its true vertical axis or position at all times, an accomplishment which this type of bag is unlikely to perform because the ideal conditions necessary to that end are seldom enjoyed at sea and if so not for any great length of time.

The primary purpose of the present invention is to provide a pontoon which is free of the above discussed disadvantages of prior pontoons, and which is so constructed that it will provide a practical, efiicient and safe means for salvaging sunken objects throughout the entire periods of such operations from the time the unit is attached to the object to be raised, until the latter is safely drydocked or towed to other ultimate destination.

A further object of the invention is to provide an improved salvage pontoon which will be substantially unaffected in its operability by sea conditions or currents during the raising and supporting operations and which can be safely moved through the water at the speed of towing for substantial periods with great maneuverability and without danger of any loss of buoyancy.-

Another object of the invention is to provide an improved pontoon that can be safely raised without damage through the water and which when it reaches the surface can be made substantially unsinkable.

A still further object of the invention is to provide an improved pontoon which is capable of maintaining afloat a weight substantially greater ,than the weight it was capable of raising from the sea bed.

Other objectsas well as the advantages and novel de- A tails of construction of my improved pontoon, will become apparent from a perusal of the following description when read in connection with the accompanying drawings, which illustrate one method of carrying out the invention and in which:

Fig. 1 is a schematic view showing a pontoon of this invention attached to an object on the sea bottom and prior to the supply of an inflating medium to the pontoon;

Figs. 2 to 4 are views similar to Fig. 1, but show respectively, the appearance of the pontoon when an inflating medium has been supplied thereto, the manner in which pressures on the pontoon are balanced during the lifting of the object, and the arrangement of the parts thereof after the pontoon has reached the surface and been operated to support the object in such position;

Fig. 5 is an elevational view, partly in section, to show the details of construction of the pontoon;

Fig. 6 is a top plan view of the pontoon shown in Fig. 5;

Pi g. 7 is a bottom view of the bag of the pontoon shown in Fig. 5 and indicates in dotted outline the opening of the bottom wall thereof to equalize pressures on such bag during the rise thereof, as illustrated in Fig. 3; and

Fig. 8 is a vertical sectional view of the valve mechanisms for inflating the bag during its rise from the sea bottom and after it has reached the surface of the ocean.

In the drawings the inflatable bag or envelope of the pontoon is indicated generally by the reference numeral 10. This bag may be made of any suitable'light weighted, flexible, non-porous material capable of withstanding the ravages of salt water,-such as for example, a light sailing or marine canvas, treated with a suitable primer and then coated with natural or synthetic rubber, or a rubber coated fabric made of synthetic material. The bag 10 may have any desired shape suitable for the pur poses intended, but it is preferred to make it of generally cylindrical form, as shown in the drawings. The bag illustrated is composed of a plurality of layers 11 of rubber coated canvas to give "it the necessary strength for-salvaging operations? The-layers '11 are formed to i provide a cylindrically shaped body 12 and a top wall 13 which joins the body 12 ina smooth curve, as is shown more clearlyin Fig. 1=of-the drawings. At the-center of the top wall 13 is secured an-eye bolt 14 to which is connected the cable 15 by which the pontoon is lowered in' a deflated condition from a ship or operational pon toon to the object to be raised. The eye bolt 14-has a shank which extends through top Wall '13, and is suitably connected to the material of such top wall by appropriate washers and lock nuts known to the art which enable an air tight connection to be made and without danger of damage to the material of the wall in the use of the pontoon; Secured to the shank of eye bolt id as by means of'welded ,bars16 is-a circular ring 17 which rests on the outersurface of the top wall 13. The ring 17 serves'as a means for anchoring the upper ends of a'plurality ofcables 18, which extend radially'outwardly from such ring, over the curved juncture of top wall 13 and cylindrical'body 12, and then vertically down to a ring 19 located in adjacent spaced relation below the bottom end of the body 12. Each cable 18 is preferably a steel cable covered with or contained within a tube of plastic material in order to minimize as much as possible any damage which might be caused'by such cables to the material of top wall 13 and body12 of the bag during the rising and towing operations. The upper ends of the cables 18' are looped around and permanently connected to ring 17 by suitable fasteners known to the art. In a similar fashion the lower ends of cables 18 are secured to ring 19. It willbe noted from Fig. 5 of the drawings, that ring 19, which may be located about one foot below the bottom end of thebag body 12, is provided on its inner and outer peripheral edges with a plurality of aligned, inner and outer recesses or notches .20 and 21, respectively, Each pair of notches 2 21 are spaced from adjacent pairs of such notches and receive the lower looped end of a cable 18. The depth of the notches may be such that the looped end of the cables will be flush with or in back of the inner and outer peripheral surfaces of the ring 19.

The cables 18 at the bottom end of the bag body pass inwardly through grommets 22 provided around such bottom end. Secured to each cable above its associated grommet 22, is a non-slip nut 23 having an outside diameter greater than the diameter of the opening in the grommetso that it functions as a stop to prevent the bag from sliding upward on the cables 18 when inflated and rising It will thus be seen that cables 18, ring 19, grommets 22 and stops 23 coact to maintain these parts together with the bottom end of the bag body substantially in their assembled relation during the use of the pontoon, and to maintain the cylindrical configuration of the bag at its lower end. Inasmuch as the ring 19 is of a fixed diameter, substantially the same as the diameter of the bag body 12, the bottom section of thebag will be caused bysuch partsto have a fixed circumference especially when'the bag is provided with the inflating medium: The cylindrical shape of the bag is also maintainedby the cables 18 and a plurality of circular, verticallyspaced cables 24 arranged on the exterior surfaces of the bag body 12 and top wall 13 and similar in construction to cables 18. As indicated in the drawings, the

cables

18 and 24 are maintained in their proper relation on the bag, while permitting movement relative to each other, by a plurality of patches 25 and strips 26-;of material similar to the bag material and cemented securelyto the latter without binding the cables to either so'that they may move relatively freely thereto. As the cables at their crossings are unconnected it will be understood that while the bag is confined within the network formed thereby, the cables in the network may have relative movement subject to the confining influiii ence of the patches 25 and strips 26. Preferably the cables 18-overlie-thecables 24 so that when the. bagsis inflated the former will hold the latter securely in their proper positions. Preferably also, there are provided a sufiicient number of cables 18 and cables 24 on the upper wall 13 (note Fig. 6) so that together with the latter there is provided at the top of the bag a strong wall capable of resisting relativelyhigh internal pressures on the bag during its ascension and in effect forcing the gas when under such high pressures to escape through the bottom of the bag, as will hereinafterbe more fully explained. The upper end of the bag during its raising operations is also strengthened by an inner wall 30 which shall now be described.

The inner wall 30 is constituted of one or more layers of material similar to that forming the

exterior walls

12 and 13 of the bag so as to provide a light, flexible, non-porous wall having relatively great strength. As the inner wall, during the descending and raising operations of the pontoon, lines the upper portion of the bag 10, as is shown in Figs. 1 to 3 and 5,. it has a shape conforming to that of such portion of the bag. In other words, the inner wall 30 has a cylindrically shaped body portion similar to the upper part of the bag body 12, and a top portion similar to the top wall 13 of the bag. The bottom circular edge portion 31 of 'wall 3! is folded up and permanently secured by a suitable bonding material of known make capable of making an air-tight connection between the two walls; By reason of this manner of connecting wall 3010 the bag 10, the former may be readily turned inside out so'that it depends from its line of juncture with the bag body 12 to form with the upper part of bag 10 anair-tight cylindrically shaped chamber, as shown in Fig. 4. The length of the cylindrically shaped body portion of wall 30 is greater than the length of bag 10 from the line of juncture of such bagwith wall 3% to the bottom end of such bag, so that the cubic area of such chamber'is substantially greater than'the cubic area of the bag 16 when the latter is in a fully inflated condition.

When the'wall 31 is folded upwardly in the manner shown in Figs. 1 to 3 and 5, so that it forms the inner wall of the upper part of bag 10, it is maintained insuch position by the valve means by which the inflating medium is supplied to the chamber in such bag partly defined by such inner wall. As is shown more clearly in-Fig; 8 of the drawings, such valve means includes an internal air valve composed of a valve casing 32 which is secured to the edge of a circular opening in the wall 30 in'a known manner toform an airtight connection. The valve casing 32 has an inlet opening'33 which is closed by a valve member 34, and a permanently open'discharge opening 35. The valve member 34 is biased to closed position by a coiled spring 36 of such strength that it 'is capable of maintaining the opening 33 closed against pressures greater than that that can safely be supplied to the bag 10 when the wall 30 is in a lowered position as shown in Fig. 4. The Valve member 34 is retracted from the position shown in Fig. 8, by a tube 37 which threadedly en "E gages the edge of opening 33 and may be advancedtoa position where the transverse passages 38 in the lower end thereof bring the interior of the tube into communication with the interior chamber of the valve casing 32. The threaded fitting between the casing 32 and tube 37 is so close that it is substantially air-tight and all of the inflating medium supplied through tube 37 will pass through the casing 32 and out the opening 35 thereof into the interior of the bag 10. The tube 37 extends in threaded engagement through a fitting 39 secured to the edge of a circular opening, in the top wall 13 of the bag 10 in a known manner to form an air-tight connection. Like the. valve casing 32, the threaded engagementbetween fitting 39 and tube 37 is so close that it is air-tight and will not leak air or gas under pressures supplied to the bag when the wall 30'is in a lowered position'as shown It will be understood from the foregoing that when the inner wall is folded upwardly in the manner of Figs. 1 to 3 and 5, the valve casing 32 will come into alignment with the fitting 39 to enable the tube 37 to be readily brought into threaded engagement with the sides of the casing opening 33. The tube 37 is rotatably advanced until the valve member 34 is moved to a retracted position such that the passages 38 come into communication with the interior of the casing and thereby enable the inflating medium to be supplied to the interior of the bag 10. This folding of the inner wall 36 and the connection thereof to the top wall 13 of the bag by the aforesaid valve means is preferably done onboard the tender prior to preparing the bag to be lowered to the sea bottom. The parts remain in this condition during the raising of the object from the sea bottom. When the bag reaches the surface of the water after having raised the object, crew members in rowboats can readily turn the nutlike portion 40 of the tube 37 to unscrew the tube from the valve casing 32, thereby permitting the valve member 34 to close opening 33, and releasing the inner wall 30 from the top wall 13 of the bag. When air is caused to flow again, it will be fed by the tube 37 between the inner wall 30 and the top wall 13 of the bag thus causing wall 30 to be forced downwardly to assume the position shown in Fig. 4 and forcing the air out of the bag in a manner which shall be hereinafter explained.

The lower end of the body portion 12 of the bag is provided with a bottom closure which is closed when the pressure of the inflating medium within the bag balances the exterior pressures exerted on the bag by the water during the raising operation, and which immediately and automatically opens to restore such balance of pressures as soon as the pressure of the inflating medium rises above that of the surrounding water on the bag during the raising operations. As shown more clearly in Figs. 5 and 7, this bottom closure is composed of two

quadrispherical sections

45, 46, the horizontal curved edges of WhlCh are secured in an air-tight connection to the interior surface of the bottom edge portion of the bag body 12, and the transverse curved edges of which are in overlapping relation. In the construction shown, the transverse edge portion of section 45 is outside the transverse edge portion of section 46. The

sections

45 and 46 are made of a resilient material such as natural or synthetic rubber so that when internal forces within the bag tending to separate such transverse edges thereof, as indicated by the dotted lines in Fig. 7, to provide a transverse opening in the shape of a spherical segment, no longer bear on such sections, the latter shall because of their inherent resiliency automatically return to the closed overlapping position shown in Figs. 1, 2, 5 and 7. Preferably the

sections

45 and 46 at their junctures with the bag 10 are thickest and then taper gradually toward the middle of the transverse, overlapping edge portions thereof so that they automatically tend to open first at the center of the closed wall formed thereby under pressure from the inflating medium. In the closed, overlapped COHCliLlOH of the

sections

45 and 46 they are relatively air-tight to a predetermined balanced pressure within the bag 10 because of the elastic qualities thereof. This quality as well as the opening and closing operations of the sections are enhanced by providing further resilient means tending normally to maintain the sections in closed position and to yieldingly resist, without preventing, sudden opening of such sections under increased internal pressures. As shown more clearly in Figs. 5 and 7, such means include a plurality of spaced elastic, rubber bands 47 connected at one end to the transverse edge of section 45 and extending over the outer surface 6 of section 46 to the line of juncture of the latter section with the bag body 12. The other ends of the bands 47 are preferably bonded between the horizontal edge of section 46 and the material of bag body 12. In a similar fashion rubber bands 48 are connected at one end to the transverse edge of section 46, extend over the outer surface of section 45, and are secured at their other ends between the horizontal edge of section 45 and the material of bag body 12. Due to the fact that the transverse edge of section 46 is inside the transverse edge of section 45, the connection of bands 48 to section 46 is in back of the edge portion thereof overlapped by section 45 (note Fig. 5). When the bag is not under pressure the closed, semi-spherically shaped, wall formed by

sections

45 and 46 will extend through ring 15, but will not engage the interior surface of such ring. However, when the bag 10 is inflated to raise an object from the sea bottom, such semi-spherically shaped wall will expand outwardly until it comes into relatively tight engagement with the interior of ring 19 so that the latter will tend to confine the chord of the opening of

sections

45 and 46 to the length of. the inside diameter of such ring.

It is believed that it will be apparent from the foregoing description, that prior to the lowering of the pontoon to the object to be raised, the inner wall 30 will be folded upwardly, as shown in Fig. 5, and connected to the top wall 13 of the bag by the valve fittings, so that it will in elfect constitute an inner strengthening wall for the upper part of bag 10.

With the inner wall 30 so connected, the valve fit tings will be enabled to supply compressed air through the

walls

13 and 30 of the bag into the chamber defined by inner wall 30, the lower part of bag body 12 and the bottom wall formed by

sections

45, 46. The bag or balloon is lowered to the object to be raised in a deflated state by the cable 15 connected to the eye bolt 14. The coupling 49 suspended from the ring 19 by cables 50 and the hook which i connected to such coupling will have a combined weight suflicient to sink the pontoon even though there is some air in the deflated bag 10. When the pontoon reaches the ocean bottom it may be connected to the object to be raised in the manner shown in Fig. 1 of the drawings. An inflating medium, such as air, is then pumped into the bag 10 until the pontoon is buoyant enough to raise the object from the sea bottom (note Fig. 2). As the pontoon rises from the sea bottom, the lessening pressure of the surrounding water will cause the air within the bag to expand and increase in pressure. As soon as these internal and external pressures reach an imbalance sufficient to retract the

sections

45 and 46, these sections will move automatically to provide a wide enough opening capable of immediately discharging a bubble or amount of air sullicient to at once restore the balance of internal and external pressures (note Fig. 3). It will be understood that until this imbalance is reached the

sections

45 and 46 will remain closed to prevent any escape of air, but as soon as such imbalance is attained such sections will open an amount proportional to the amount of imbalance created. Since the

sections

45, 46 are weakest in the center of the closure wall formed thereby, the initial opening will be formed from a small slit in the center of such wall and will then increase in transverse directions under increased pressures until the length of the opening is equivalent to a chord having a length at least equal to the interior diameter of the ring 19 and such opening is capable of enabling almost the entire volume of the inflatable medium to escape instantaneously therethrough. Because of this construction, sudden stresses on the bag and lifting tackle are eliminated and the pressures are maintained in substantial equilibrium throughout the rise of the bag. As the bag only opens in response to an imbalance of stresses and throughout the remainder of the period of rise is in closed condition so that no air can escape, it does not effect the buoyancy of the pontoon if it should be tilted from its true vertical axis in the lifting operation.

When the pontoon reaches the surface of the ocean, the inner wall 30'is disconnected in the manner previously described and compressed air is forced into the bag between such' inner wall and the bag. The force of this air will cause the inner wall 30 to move downward forcing out through the section Hand 46 the air thatwas used to lift the object from the sea bottom. When the chamber now defined at its lower end by the inner wall 30, is fully inflated, the parts will be. arranged as shown in .Fig. 4 of the drawings. The chamber so formed will provide a perfectly sealed pontoon capable of containing a greater volume of air than the bag was capable of holding when arranged for the. lifting operation and therefore capable of sustaining afloat a greater weight than the pontoon lifted. It will be evident also that in this condition, the pontoon cannot be capsized or sunk by sea turbulence, tides or currents, and may be readily towed with entire safety. Provided in the top wall 13 of the bag is a suitable safety valve 43 of known construction capable of relieving the pressure of the air in the sealed pontoon defined at its lower end by the wall 30, when such pressure at any time is in danger of increasing to a point at which the pontoon might be ruptured. The inner end of the safety valve is preferably formed to minimize possible damage to wall Stlwhen it is folded upwardly against the top bag wall 13.

While I have heretofore described and illustrated a preferred embodiment of my invention, it will be apparent to those skilled in the art that various changes and modifications may be made Without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. A salvage pontoon comprising an envelope made of flexible, substantially non-stretchable material adapted to contain an inflating medium provided with an opening for escape of the inflating medium, and a wall composed of flexible, resilient material normally closing the area of said opening, said wall having its peripheral edge portions secured to said envelope around the edge of said opening and having within the area defined by said secured edge portions thereof cooperative edge portions providing a vent opening under pressure directly applied by the inflating medium in said envelope, said cooperative edge portions being normally closed by the inherent resiliency of said wall material when the internal and external pressures on said envelope are substantially in balance to prevent escape of the inflating medium therebetween and being automatically operable as soon as there occurs a condition of unbalance in the internal and external pressures on said envelope suflicient to overcome the inherent resiliency of said wall to instantly release sufficient of the inflating medium to promptly restore a balanced condition of such pressures.

2. A salvage pontoon for raising a submerged object comprising an envelope made of flexible material adapted to contain an inflating medium, said envelope having a closed upper part and being provided at its lower part with an opening for escape of the inflating medium, an inner wall joined at its periphery to the inner wall of said envelope along a line between the closed upper part and opening thereof and being configured to be foldable up against the upper part of said envelope during the object raising operation and to be foldable downwardly to form with the upper part of said envelope a completely sealed pontoon, means for supplying inflating medium to said envelope when said inner wall is folded upwardly, said envelope supplying means being connected to said envelope and affording communication to the chamber defined by said envelope and upwardly folded inner wall, and means connected to said envelope and communicating a; with the, space between said envelope and said inner wall above the line of juncture of said inner wall with said envelope for supplying inflating medium to the'sealed pontoon formed by said envelope and inner Wall.

3. Asalvage pontoon comprising an envelope made of flexible, substantially non-stretchable material adapted to contain an inflating medium provided with an opening at its bottom for escape of the inflating medium, a rigid ring located exteriorly of and below said envelope and spaced adjacently below such opening thereof, a network mounted on and within which the envelope is confined for supporting said ring in suspended relation below said envelope, said network and ring coacting to maintain the edge portion of said material forming such opening in theconfiguration of said ring, and a wall composed of flexible, resilient material normally closing the area of said opening and normally spaced inwardly from said ring,'said wall having its peripheral edge portions secured around the edge of said opening and being expandable downwardly and outwardly towards said ring under pressure directly applied by the inflating medium in said envelope, said wall having within the areas defined by such secured edge portions thereof and said ring cooperative edge portions providing a vent opening under such pressure, said'cooperative edge portions being normally closed by the inherent resiliency of said wall material when the internal and external pressures on said envelope are substantially in balance to prevent escape of the inflating medium therebetween and being automatically operable as soc-n as there occurs a condition of unbalance in the internal and external pressures on said envelope suflicient to overcome the inherent resiliency of said wall to instantly release suflicient of the inflating medium to promptly restore a balanced condition of such pressures, and said ring through its engagement by said wall limiting the size of the opening for release of the inflating medium.

4. A salvage pontoon comprising an envelope made of flexible, substantially non-stretchable material adapted to contain an inflating medium provided with an opening for escape of the inflating medium, and a wall composed of flexible, resilient material norm-ally closing the areaiof said opening and automatically operable as soon as .there occurs a condition of unbalance in the internaland external pressures on said envelope to instantly release suflicient of the inflating medium to promptly restore a balanced condition of such pressures, said wall comprising a plurality of sections secured in air-tight condition at their'outer peripheral edge portions to the edge portion of said material forming such opening and having transverse edge portions arranged in overlapping relation, the resilient material of which such sections are constituted normally maintaining such transverse edge portions in closed overlapping relation and yieldingly resisting movement of such transverse edge portions away from such overlapping relation.

5. A salvage pontoon comprising an envelope made of flexible, substantially non-stretchable material adapted to contain an inflating medium provided with anopening for escape of the inflating medium, and a wall composed of flexible, resilient material normally closing theareaof said opening and automatically operable as soon as there occurs a condition of unbalance in the internal and external pressures on said envelope to instantly. release suflicient of the inflating medium to promptly restore a balanced condition of such pressures, said wall being composed of rubber material and gradually diminishing in thickness from the edge portion of said material forming such opening to the central part of said wall, and a transversely extending normally closed opening provided in said wall and extending into the central portion thereof.

6. A salvage pontoon comprising an envelopemade of flexible, substantially non-stretchable material adapted to contain an inflating medium provided with an opening for escape of the inflating medium, and a wall composed or flexible, resilient material normally closing the area of said opening and automatically operable as soon as there occurs a condition of unbalance in the internal and external pressures on said envelope to instantly release suflicient of the inflating medium to promptly restore a balanced condition of such pressures, said wall comprising a plurality of sections secured in air-tight condition at their outer peripheral edge portions to the edge portion of said material forming such opening and having transverse edge portions arranged in overlapping relation, and means carried by said envelope and connected to said transverse edge portions and constructed and arranged to maintain such transverse edge portions in closed overlapping relation and to yieldingly resist movement of such transverse edge portions away from such overlapping relation.

7. A salvage pontoon comprising an envelope made of flexible, substantially non-stretchable material adapted to contain an inflating medium provided with an opening for escape of the inflating medium, and a wall composed of flexible, resilient material normally closing the area of said opening and automatically operable as soon as there occurs a condition of unbalance in the internal and external pressures on said envelope to instantly release sufficient of the inflating medium to promptly restore a balanced condition of such pressures, said wall com-prising a plurality of sections secured in air-tight condition at their outer peripheral edge portions to the edge portion of said material forming such opening and having transverse edge portions arranged in overlapping relation, and means for maintaining such transverse edge portions in closed overlapping relation and yieldingly resisting movement of such transverse edge portions away from such overlapping relation, said last mentioned means including a plurality of stretchable bands secured to the transverse edge portion of each section and extending over the outer surface of another section, the outer ends of such bands being secured to the edge portion of said material forming such opening.

8. A salvage pontoon comprising an envelope made of flexible, substantially non-stretchable material adapted to contain an inflating medium provided with an opening for escape of the inflating medium, and a wall composed of flexible, resilient material normally closing the area of said opening and automatically operable as soon as there occurs a condition of unbalance in the internal and external pressures on said envelope to instantly release suflicient of the inflating medium to promptly restore a balanced condition of such pressures, said wall comprising a pair of quadrispherically shaped sections secured in air-tight condition at their outer peripheral edge portions to the edge portion of said material forming such opening and having a transverse edge portions arranged in overlapping relation, and a plurality of rubber bands connected to such transverse edge portions and to such edge portion of said material and normally tending to maintain such transverse edge portions in closed, overlapping relation.

9. A salvage pontoon for raising a submerged object comprising an envelope made of flexible material adapted to contain an inflating medium provided with an opening for escape of the inflating medium, an inner wall joined at its periphery to the inner wall of said envelope and foldable up against the upper part of said envelope during the object raising operation and foldable downwardly to form with the upper part of said envelope a completely sealed pontoon, said inner Wall having a length greater than the length of said envelope from the line of juncture of said inner Wall therewith, to the edge portion of the envelope material forming said opening, and such sealed pontoon having a substantially greater capacity for the inflating medium than said envelope, means for supply ing inflating medium to said envelope when said inner wall is folded upwardly, said envelope supplying means being connected to said envelope and affording communication to the chamber defined by said envelope and upwardly folded inner wall, and means connected to said envelope and communicating with the space between said envelope and said inner wall above such line of juncture for supplying inflating medium to the sealed pontoon formed by said envelope and inner wall.

10. A salvage pontoon comprising an envelope made of flexible material adapted to contain an inflating medium provided with an opening for escape of the inflating medium, an inner wall joined at its periphery to the inner wall of said envelope and foldable up against the upper part of said envelope during the object raising operation and foldable downwardly to form with the upper part of said envelope a completely sealed pontoon after raising such pontoon, valve means including a normally closed valve provided on said inner wall, a valve member connected to a source of supply of inflating medium and extending through said envelope to enable it to feed such medium to the sealed pontoon formed by said envelope and inner wall, said valve member being engageable with said valve to secure said inner wall to said envelope when the former is folded up against the top of the latter and to actuate said valve to enable inflating medium to be supplied from said valve member to said envelope when said inner wall is so secured.

11. A salvage pontoon comprising an envelope made of flexible-material adapted to contain an inflating medium and having an upper part located above an opening for escape of the inflating medium, closure means composed of flexible, resilient material normally closing the area of said opening and automatically operable as soon as there occurs a conditionof unbalance in the internal and external pressures on said envelope to instantly release suflicient of the inflating medium to promptly restore a balanced condition of such pressures, and an inner wall joined at its periphery to the inner wall of said envelope and foldable upwardly to re-enforce such upper part of said envelope and foldable downwardly to re-enforce said closure means.

References Cited in the file of this patent UNITED STATES PATENTS 2,413,313 Cook Dec. 31, 1946 2,475,839 Jalbert July 12, 1949 2,492,800 Isom Dec. 27, 1949 2,635,574 Sturtevant vApr. 21, 1953 FOREIGN PATENTS 122,961 Germany Aug. 14, 1901